Merge remote-tracking branch 'origin/dev' into declcfg-migrate

# Conflicts: # esphome/pins.py
[core][gpio_expander] Add a shared expander pin class and pin codegen helpers (#20866 )
2026-10-23 06:15:58 +00:00 · 2026-10-18 14:51:26 -10:00 · 2026-10-18 14:48:35 -10:00 · 2026-10-18 14:47:37 -10:00 · 2026-10-18 14:47:19 -10:00 · 2026-10-18 14:46:57 -10:00
6373 changed files with 276854 additions and 71465 deletions
@@ -0,0 +1,116 @@
+---
+name: code-review
+description: Review guidance for ESPHome pull requests. Use this when reviewing a pull request that changes ESPHome Python, C++, or component code, to check it against the project's coding conventions, embedded-systems memory rules, testing requirements, and breaking-change policy.
+---
+
+# Reviewing ESPHome pull requests
+
+ESPHome parses YAML into C++ firmware for memory-constrained microcontrollers
+(ESP32, ESP8266, RP2040, LibreTiny). Review changes with that in mind: RAM and
+flash are scarce, and code runs unattended for months.
+
+`AGENTS.md` in the repository root is the full contributor guide and the
+authority when it disagrees with this summary. The developer documentation at
+https://developers.esphome.io explains the component lifecycle and the reasoning
+behind these rules. This skill lists the concrete things worth flagging in a
+review; read `AGENTS.md` for the detail behind any item.
+
+Only raise findings that the diff actually introduces or changes. Do not ask for
+drive-by cleanup of pre-existing code the PR did not touch.
+
+## Memory and embedded constraints (highest value)
+
+Heap allocation after `setup()` is treated as a reliability bug, not a
+performance nit, because it fragments a small shared heap. Flag:
+
+- New heap allocation on a hot path or after setup that could be avoided.
+- `std::vector` where the size is known at compile time (use `std::array`, or
+  `StaticVector<T, N>` when a `push_back` API is needed) or fixed at runtime
+  init (use `FixedVector<T>`).
+- Listener / child-entity registration lists stored as `std::vector`; these have
+  a compile-time-known count and should use `cg.slot_counter()` plus
+  `StaticVector`.
+- `std::vector<uint8_t>` for a byte buffer that never grows: prefer
+  `std::unique_ptr<uint8_t[]>` or `std::array`.
+- `std::map` / `std::set` / `std::unordered_map` for small datasets (1-16
+  elements): a `std::vector` of a small struct with linear search is lighter.
+- `std::deque` anywhere: it allocates 512-byte blocks and should be avoided.
+- `std::string` storing a value set once from config: prefer `StringRef` (the
+  literal already lives in flash).
+- `std::string` / `std::to_string` / string-returning helpers on hot paths where
+  a buffer or view API exists.
+
+## C++ conventions
+
+- Include what you use: a file referencing a symbol must include the header that
+  declares it, even if it currently arrives transitively. New or changed uses of
+  a symbol need the matching include.
+- Prefix all member access with `this->`.
+- Naming: `lower_snake_case` for functions/methods/variables, `UpperCamelCase`
+  for classes/structs/enums, `UPPER_SNAKE_CASE` for namespace-scope constants,
+  trailing underscore on protected/private fields.
+- `enum class` values must be prefixed with the enum name in `UPPER_SNAKE_CASE`
+  (e.g. `UARTFlushResult::UART_FLUSH_RESULT_SUCCESS`). Bare names like `SUCCESS`,
+  `FAIL`, or `OK` collide with SDK macros on some platforms and break the build.
+- Prefer `const`/`enum` over `#define`; `#define` is only for conditional
+  compilation and code-generation sizes.
+- Never call `millis()` in a `loop()` body; use
+  `App.get_loop_component_start_time()`. A rate-limit gate below ~16 ms (the loop
+  period) does nothing.
+- Pick the timing primitive by cadence: gated `loop()` under 250 ms,
+  `set_interval` at 500 ms and above.
+- Do not override a base method to return the value it already returns (e.g.
+  `get_setup_priority()` returning `setup_priority::DATA`).
+- Wrap string literals passed as printf `%s` args in `LOG_STR_LITERAL()`.
+- Required, invariant dependencies should be constructor parameters, not setters.
+- Callback registration methods must be templated (`template<typename F>`), not
+  typed as `std::function`, so lightweight forwarders avoid a heap allocation.
+- Two-space indent, `using` over `typedef`, wrap at 120 columns.
+
+## Python conventions
+
+- Type-annotate every new function signature (params and return), new dataclass
+  fields, and new module-level variables. Import `ConfigType` from
+  `esphome.types`.
+- Use the walrus operator to avoid a double lookup, e.g.
+  `if (blah := config.get(CONF_BLAH)) is not None:`.
+- Reuse existing validators from `config_validation.py` (`cv.rename_key`,
+  `cv.has_exactly_one_key`, etc.) via `cv.All(...)` instead of hand-rolling.
+- `esphome/const.py` is frozen: no new `CONF_` constants there. Define them in
+  the component's own `.py`, or in `esphome/components/const/__init__.py` when
+  shared. The same constant defined in three or more component files fails CI.
+- State that must persist during code generation goes in `CORE.data` namespaced
+  under the component `DOMAIN` (a `@dataclass`), not module-level mutable globals.
+- Prefer callback-based triggers via `build_callback_automation()`; only use a
+  `Trigger<Ts...>` subclass when the forwarder needs mutable state.
+
+## Testing and coverage
+
+- New and changed lines and branches need test coverage, including defensive
+  early-returns, error paths, and no-op guards. A mocked-out function is not
+  covered; exercise the real call path too.
+- Component YAML tests live in `tests/components/<component>/`. Never define
+  buses (uart, i2c, spi, modbus) directly in a test file: pull them from
+  `tests/test_build_components/common/` through dict-style `packages:` so CI can
+  group builds. List-style packages or top-level merge keys block grouping.
+- Config-only checks use the `validate.*.yaml` prefix; compiled checks use
+  `test.*.yaml`.
+
+## Breaking changes and public API
+
+- Base classes under `esphome/core/` and documented config options are public
+  API. Undocumented `public` members of a component are internal.
+- A breaking change needs justification, a migration path in the PR description,
+  and a deprecation window where feasible (`ESPDEPRECATED` in C++,
+  `cv.rename_key(..., removed_in=...)` in Python). Changing a codegen-injected
+  lambda signature is not a breaking change.
+
+## Process and PR hygiene
+
+- PR titles start with a `[tag]` prefix: the component name (e.g. `[uart] ...`)
+  or `[core]` for shared code.
+- Prose in docs, comments, and commit messages should be plain English. Keep
+  inline comments short and only where the code is not self-explanatory; do not
+  restate what the code says.
+- Verify the PR fills out `.github/PULL_REQUEST_TEMPLATE.md` and adds
+  `CODEOWNERS` entries for a new component.
@@ -0,0 +1,123 @@
+---
+name: hardware-test
+description: Test an ESPHome change on real boards over USB. Use this whenever a task asks to test, verify, reproduce, bench, A/B or soak a pull request, a branch or a crash on hardware, or mentions flashing, serial logs, esphome upload, a captive portal or fallback AP test, or results to post on a PR. Covers finding the serial ports, building from the right checkout, flashing each chip family (including the LibreTiny kits that stock tools cannot flash), bounded log capture, proven test flows and how to report results.
+allowed-tools: Read, Write, Edit, Bash, Glob, Grep
+---
+
+# Hardware testing
+
+The goal of a hardware test is evidence a reviewer can trust: which build ran on which board, what was
+driven, what the logs show, and the same flow on a `dev` build when a quirk could be pre-existing.
+`$SKILL` below is this directory (`.agents/skills/hardware-test`).
+
+## Ground rules
+
+1. **Serial ports cannot be shared.** One bounded capture per port, stopped before any flash on that
+   port, never an open-ended `esphome logs`. Stop a capture with `pkill -f "[s]erial_capture.py <port> "`,
+   naming the port so a capture on another board survives; the bracket keeps the pattern from matching
+   the shell that runs it. Never run `esphome logs` in a
+   `while true` loop: the loop respawns it and holds the port.
+2. **Credentials stay local.** Put a `secrets.yaml` next to the scratch configs and reference it with
+   `!secret`. Never paste a config with credentials into a PR, never commit scratch configs or logs.
+3. **Build from the tree under test.** `python -m esphome` puts the current directory first on
+   `sys.path`, so run it with the checkout or worktree as the working directory and pass the yaml by
+   its absolute path. A venv `esphome` entry point may import an installed snapshot instead of the
+   checkout. Confirm with `python -c 'import esphome; print(esphome.__file__)'`, and for an A/B grep
+   the build's `src/` for the change before trusting any number.
+4. **PR build and baseline build get different `name:` values.** Builds share
+   `.esphome/build/<name>`, so the same name means `esphome upload` can flash the wrong binary. Saved
+   Wi-Fi credentials are keyed by the name too, so a test that must start unprovisioned gets a fresh
+   name every run.
+5. **Flash and RAM deltas are measured against the PR's merge base** (`git merge-base origin/dev HEAD`
+   checked out in a throwaway worktree), with the baseline commit named in the table. When a delta
+   looks odd, diff symbol sizes (`nm -S -C --size-sort` from the matching toolchain) before quoting it.
+6. **Prove a quirk is pre-existing before blaming the PR:** run the identical flow on a `dev` build in
+   the same session and say so in the results.
+7. **Pipe safely.** Set `PYTHONUNBUFFERED=1` on any `esphome run` or `esphome logs` whose output is
+   piped, or lines land minutes late. Bound every long command with `timeout` (coreutils) or
+   `perl -e 'alarm shift; exec @ARGV' <seconds> <command>` on macOS without it.
+
+## Workflow
+
+1. **Find the boards:** `python $SKILL/scripts/ports.py` (any Python with pyserial, for example the
+   ESPHome venv). Port names follow the USB hub port and change on every replug, so never reuse a name
+   from an earlier session. CH340 adapters (D1 mini, BW15 kit, BK7238, CB3S) all look the same; tell
+   them apart with a 10 s capture using `serial_capture.py --reset` (ESP8266 prints its ROM banner at
+   74880 baud, LibreTiny boards print `[LT]` and ESPHome lines, BK7238 prints its bootloader version).
+   `ports.py --wait 2e8a` blocks until a Pico re-enumerates.
+2. **Make a scratch directory** outside the checkout, with `secrets.yaml` and the templates you need.
+   One yaml per board per variant, file name equal to `name:`.
+3. **Compile** in the right tree:
+   `(cd <worktree> && PYTHONUNBUFFERED=1 timeout 1500 python -m esphome compile <abs yaml> > <name>-compile.log 2>&1)`.
+   Keep the RAM and flash lines at the end. Two ESP-IDF or two LibreTiny builds at the same time race
+   over tool caches; run them one at a time.
+4. **Flash** per chip family (table below). Stop the capture on that port first.
+5. **Capture** with `serial_capture.py PORT SECONDS OUT` in the background, then poll the file with
+   `grep` in an `until ... sleep 2` loop with a cap. USB CDC boards (Pico, nRF52, native USB ESP32)
+   drop the port on reboot; the script reopens it until its deadline.
+6. **Drive** the test: a second board running a client config, `curl`, an aioesphomeapi script that
+   presses a template button and subscribes to logs, MQTT publishes, or `interval:` and `on_boot:`
+   automations in the config itself.
+7. **Analyze** with `grep -a -c` counts over the capture and keep an `-events.txt` extract of the lines
+   that matter. Decode crashes with the platform's `addr2line` (see `reference/boards.md`).
+8. **Report** on the PR as a table: build SHA, board and framework, what was driven, counts, result,
+   plus the `dev` control row and the exact flow in a `<details>` block. No credentials, no port names,
+   no IP addresses.
+
+## Flashing by chip family
+
+| Board | Flash | Log |
+|---|---|---|
+| ESP8266 D1 mini (CH340) | `python -m esphome upload <yaml> --device <port>` | `serial_capture.py` at 115200; `esphome logs` on some CH340s emits garbage after the RTS reset. A failed esptool write can wedge the adapter until the board is replugged. `esptool erase_flash` before a test that needs an unprovisioned device: the preference sector survives a reflash |
+| ESP32 devkit (CP2102 or CH340) | `esphome upload --device <port>`, ESP-IDF or Arduino | `serial_capture.py`. Default Wi-Fi light sleep delays API driven actions by seconds; judge timing from device logs. `power_save_mode: none` for OTA overlap tests |
+| ESP32-S3, C3, C6, H2 native USB | `esphome upload --device /dev/cu.usbmodem*` | `logger: hardware_uart: USB_SERIAL_JTAG`. The USB console can wedge when the app takes over the console (0 bytes, esptool `No serial data received`); replug, or watch through `esphome logs --device <name>.local` |
+| Pico W / Pico 2 W | `esphome upload --device <port>` (1200 baud touch); first flash ever via BOOTSEL and `--device /Volumes/RPI-RP2` or `RP2350` | port re-enumerates after upload: `ports.py --wait 2e8a` then capture |
+| BW15 kit (RTL8720CF, rtl87xx) | `~/.platformio/penv/.libretiny/bin/python $SKILL/scripts/flash_rtl87xx_kit.py flash write -d <port> <build>/.pioenvs/<name>/*.uf2`. Plain `esphome upload` and plain ltchiptool time out because opening the port asserts DTR/RTS and holds the chip in reset | `serial_capture.py --released`, never `esphome logs` |
+| BK7238 / CB3S (bk72xx, RTS on CEN) | `~/.platformio/penv/.libretiny/bin/python $SKILL/scripts/flash_bk72xx.py flash write -d <port> <uf2>` (about 75 s) | logs are on UART2 by default; `logger: hardware_uart: UART1` puts them on the flashing adapter. Opening the port resets the chip, so keep one capture open for the whole test |
+| LN882H | ltchiptool forces 1 Mbaud for writes; weak adapters need `LN882H_YM_BAUDRATE` patched to 115200 in the penv's `ln882htool.py`; short BOOT to GND while the tool connects | OTA after the first flash |
+| nRF52840 Dongle (PCA10059) | Nordic `nrfutil nrf5sdk-tools dfu usb-serial` on the bootloader port, or `dfu: true` in the config so the 1200 baud touch pin-resets into the bootloader; adafruit-nrfutil is refused | app has two CDC ports, ESPHome log on the second |
+| Adafruit-style nRF52 (UF2 bootloader) | `UF2BOOT` volume or adafruit-nrfutil; `dfu: true` works through GPREGRET | single CDC port |
+| Any reachable device | `esphome upload <yaml> --device <ip or name.local>`; `--file <bin>` for a prebuilt image | `esphome logs --device <ip>` bounded with `timeout` |
+
+ESP-IDF OTA image: `.esphome/build/<name>/build/firmware.ota.bin`. LibreTiny OTA port is 8892.
+
+## Scripts in `$SKILL/scripts`
+
+- `ports.py`: list ports with VID:PID, product, serial and a board guess; `--wait VID[:PID]`,
+  `--product NAME`, `--serial SN` (one specific board, whatever path it comes back under) and
+  `--serial-of PORT` (the serial number behind a path).
+- `serial_capture.py PORT SECONDS OUT [--baud] [--released] [--reset] [--append]`: bounded timestamped
+  capture, ANSI stripped, `LOG_SECRET` text written as `<secret>`, reopens a vanished port, exits at the
+  deadline. OUT is truncated unless `--append` is given, so counts over it cover one run.
+- `flash_rtl87xx_kit.py`: ltchiptool wrapper for the BW15 kit whose CH340 drives CEN (RTS) and the boot
+  strap (DTR). `flash read` needs the family `realtek-ambz2`; `flash write` does not.
+- `flash_bk72xx.py`: ltchiptool wrapper for BK72xx boards whose RTS drives CEN.
+- `wifisave_hammer.sh KIND DUT_PORT DUT_YAML DUT_TREE CLIENT_PORT CLIENT_YAML CLIENT_TREE [SETTLE]`:
+  the fallback AP plus captive portal hammer end to end (compile, flash, capture, counts) with the
+  templates below. KIND is `esp`, `pico`, `bw15` or `bk`. It ends with `RESULT PASS` (exit 0),
+  `RESULT FAIL` (exit 3: a crash, a reboot after the AP came up, or the device never joined the network),
+  `RESULT INVALID`
+  (exit 2: a precondition was missed, the stimulus was insufficient, or a capture did not last the run)
+  or exits 1 when a build, flash or port step failed.
+
+## Templates in `$SKILL/templates`
+
+- `dut-fallback-ap.yaml` (package): a device that never finds its network, falls back to its AP and
+  serves the captive portal. `example-dut.yaml` is the per-run file with the platform block.
+- `client-wifisave.yaml` (package): joins that AP, posts N bogus `/wifisave` requests, then the real
+  credentials from `!secret`. `example-client.yaml` is the per-run file. `bogus_saves: "1"` gives a
+  plain provisioning check.
+
+## When something looks wrong
+
+- A capture stopped early or a line is missing: check the timestamps before trusting it.
+- The client never joins the AP: another board may still run an AP with the same SSID, or the device
+  booted with saved credentials because the name was reused. One AP device at a time on the bench.
+- Builds come out byte-identical between branches: the wrong tree was imported (rule 3).
+- Multicast from the host never arrives on some access points: test it device to device. Broadcast
+  is lossy under Wi-Fi power save, unicast is not. Throttle UDP floods to a fixed packet rate.
+- `api:` reboots a board after 15 min without a client: `reboot_timeout: 0s` on `api:` and `mqtt:` for
+  soak tests.
+
+`reference/boards.md` has per-chip facts and crash decoding; `reference/recipes.md` has the proven
+flows. Add new findings there.
@@ -0,0 +1,138 @@
+# Board facts
+
+Ports are not listed on purpose: they follow the USB hub port and change on every replug. Run
+`scripts/ports.py`.
+
+## ESP8266 (D1 mini, NodeMCU, CH340 or CP2102)
+
+- Opening the port usually resets the board through DTR, but not always; `serial_capture.py --reset`
+  pulses RTS to capture from boot. 74880 baud shows the ROM boot messages (`rst cause`, `boot mode`).
+- `esphome logs` on some CH340s emits thousands of duplicated garbage lines right after the RTS reset;
+  a plain pyserial capture at 115200 is reliable.
+- A failed esptool write can wedge the adapter (`termios` error 22, or an open that hangs) until replug.
+- The preference sector survives a reflash: a provisioned API key or saved Wi-Fi credentials stay
+  active. `esptool erase_flash` gives a clean device.
+- `Panic core_esp8266_main.cpp:191 __yield` with `ctx: sys` means a yield from lwIP context (a web
+  handler, an lwIP callback). Decode stacks with
+  `xtensa-lx106-elf-addr2line -e <build>/.pioenvs/<name>/firmware.elf -f -C -i <addr...>` from the
+  toolchain under `~/.platformio/packages/toolchain-xtensa/bin/` (PlatformIO builds) or the ESPHome
+  cache directory (native toolchain builds).
+- Constant data lives in RAM unless marked `PROGMEM`; with 80 KB of RAM a few hundred bytes are worth a
+  row in the PR.
+- AsyncMqttClient drops inbound topics over 128 characters; topics of 255 or more wrap a counter and
+  stall the link until the broker drops TCP.
+
+## ESP32 classic devkit
+
+- Takes ESP-IDF and Arduino. Default Wi-Fi light sleep delays API driven actions by up to 6 s; judge
+  timings from device logs, not from the host. `power_save_mode: none` for OTA overlap tests (an IDF web
+  upload of 739 KB took 107 s with power save and 45 s without).
+- Receives only a few percent of IPv6 multicast on some access points with power save on; a raw lwIP
+  socket loses the same, so that is the AP or driver, not a PR.
+- Decode with `xtensa-esp32-elf-addr2line` from the IDF tools directory against
+  `<build>/.pioenvs/<name>/firmware.elf` (PlatformIO) or `<build>/build/<name>.elf` (IDF native).
+- Clean reboot between runs with the capture stopped: `esptool --after hard_reset chip_id`.
+- Trigger a forced crash only after the app is marked valid (45 s after boot is plenty), never on an
+  image still pending OTA rollback.
+- Signed OTA testing: build with `esp32.framework.advanced.signed_ota_verification.verification_keys`
+  under a different name, sign with `python -m espsecure sign_data --version 2 --keyfile
+  tests/components/esp32/dummy_signing_key.pem`, upload with `esphome upload --file`. The verifier
+  refuses unsigned images afterwards, so restore with a signed plain build.
+
+## ESP32-S3, C3, C6, H2 with native USB
+
+- `/dev/cu.usbmodem*`, esptool works, `logger: hardware_uart: USB_SERIAL_JTAG`.
+- The USB console can die at the moment the app takes over the console during a reboot (log stops after
+  `Disabling RNG early entropy source`, then 0 bytes, esptool reports `No serial data received`). Only a
+  USB replug fixes it. Fallback: `esphome logs --device <name>.local` (API log stream, which drops lines
+  while Wi-Fi is off).
+- The ESP32-P4 before silicon revision 3 is bricked by rev3-only firmware (boot loop at bootloader entry).
+
+## RP2040 / RP2350 (Pico W, Pico 2 W)
+
+- The CDC port re-enumerates after every reboot and after `esphome upload` (1200 baud touch). Re-detect
+  with `ports.py --wait 2e8a` before capturing; `serial_capture.py` reopens on its own if the port
+  vanishes mid-capture.
+- First flash ever: BOOTSEL, then `esphome upload --device /Volumes/RPI-RP2` (or `RP2350`).
+- arduino-pico creates the lwIP netif in `WiFi.begin()`, so any IGMP join during component setup fails;
+  joins must wait for `network::is_connected()`.
+- Parallel Pico builds race on package extraction after a PlatformIO package wipe; one at a time.
+- An RTS pulse from pyserial does not reset the board; reboot with `App.safe_reboot()` or the touch.
+
+## BW15 kit (RTL8720CF, LibreTiny rtl87xx)
+
+- The kit's CH340 wires RTS to CEN and DTR to PA00 (boot strap). A plain pyserial open asserts both and
+  holds the chip in reset, which is why `esphome upload`, plain `ltchiptool` and `esphome logs` all fail
+  ("Timeout while linking", or silence). `scripts/flash_rtl87xx_kit.py` sets DTR high and RTS released
+  on every open, pulses RTS once so the ROM answers `ping`, and after the command drops DTR and pulses
+  RTS to boot the app. Run it with the PlatformIO LibreTiny penv Python.
+- `flash write -d <port> <uf2>` takes no family argument; `flash read -d <port> -s 0 -l <len>
+  realtek-ambz2 <out>` does.
+- Capture with `serial_capture.py --released`. The ESPHome log is on the flashing UART already.
+- The macOS CH340 driver only pushes DTR/RTS to the wire once a session has driven them, so the first
+  plain open after a replug streams logs and the second is silent; always open with the lines released.
+- Driver quirks seen on `dev`: `WiFi.begin` can refuse the real network on the first try after bogus
+  credentials (it connects after two cooldowns); right after connecting while the AP is still up the
+  driver can bus-fault in `rtw_is_adapter_up` (`R0 = 0xdeadbeef`) and reboot; the AP restarts on every
+  STA retry, so stations cannot stay joined; `WiFi.begin` fails synchronously for an absent network and
+  lands in a cooldown at once; connecting blocks the loop 2.5 to 4.1 s.
+- Decode faults with `arm-none-eabi-addr2line -e <build>/.pioenvs/<name>/raw_firmware.elf -f -C -i <PC>`
+  from `~/.platformio/packages/toolchain-gccarmnoneeabi/bin/` (`raw_firmware.elf`, not `firmware.elf`).
+  Fault dumps print PC, LR and R0 to R3.
+- The AmebaZ2 SDK sets `LWIP_TCPIP_CORE_LOCKING 0`.
+
+## BK7238, WB3S, CB3S (BK7231N) (LibreTiny bk72xx, CH340, RTS on CEN)
+
+- Stock ltchiptool closes and reopens the port after its reset, and pyserial raises both lines on open,
+  holding CEN low through the BootROM window. `scripts/flash_bk72xx.py` opens with both released and
+  pulses the reset right before the link checks. A write takes about 75 s. Only a CEN or power reset
+  reaches the downloader; no software reboot does.
+- ESPHome logs on UART2 by default; `logger: hardware_uart: UART1` puts them on the flashing adapter.
+- Opening the port resets the chip (bootloader banner on every open, even with DTR/RTS low), so keep one
+  capture open for the whole test and never reopen mid-phase.
+- Callbacks run on the `async_tcp` task and log lines can lose a byte. Wi-Fi connect takes tens of ms;
+  radio enable 160 to 278 ms, disable about 200 ms.
+
+## BW16 kit (RTL8720DN, AmebaD)
+
+- The kit's own USB-C (CH340) is on LOG_UART and flashes fine. Its two-transistor circuit resets while
+  RTS alone is asserted and straps BURN while DTR alone is; both asserted does nothing. ROM entry is
+  esptool's classic sequence (`dtr:false,rts:true` 100 ms, `dtr:true,rts:false` 400 ms, both false); the
+  first pulse after a replug can be lost, retry up to three times.
+- Any reopen resets the chip, 460800 is flaky, 115200 is solid: one open per session, in-place baud
+  changes only. The ROM and the loader NAK continuously while idle, so ACK scans must drain first.
+- The AmebaD core has no mDNS responder (`mdns: disabled: true`).
+
+## LN882H
+
+- ltchiptool forces 1 Mbaud for writes; adapters that cannot hold it fail with "Timeout while linking"
+  or die mid-write. Patch `LN882H_YM_BAUDRATE` in the penv's `ltchiptool/soc/ln882h/util/ln882htool.py`
+  to 115200 (lost on reprovision). Weak 3.3 V from the adapter: feed the module's 5 V pad instead. Short
+  BOOT to GND while the tool connects. OTA afterwards.
+- `USE_WIFI_AP_EXCLUSIVE` (one radio mode at a time) exists only on LN882x; compile-check changes there.
+
+## nRF52840
+
+- Nordic PCA10059 dongle: the factory Open DFU bootloader enumerates as `1915:521F` on its own port
+  name; the app as `2FE3:0100` with two CDC ports, ESPHome log on the second. Only Nordic
+  `nrfutil nrf5sdk-tools` works (`pkg generate --hw-version 52 --sd-req 0x00 --application-version 1
+  --application zephyr.hex app.zip`, then `dfu usb-serial -pkg app.zip -p <port>`); ESPHome downloads
+  it on the first build. GPREGRET does not enter the bootloader; a pin reset through P0.19 does, which
+  `dfu: true` wires up on this board. A pulsing red LED means bootloader; the side RESET button
+  re-enters it.
+- Makerdiary MDK USB dongle: UF2 bootloader without SoftDevice, app at 0x1000, `UF2BOOT` volume,
+  adafruit-nrfutil, GPREGRET 0x57 works. RGB LED active low (red P0.23, green P0.22, blue P0.24),
+  button P0.18.
+
+## ESP Thread Border Router board v1.2 (S3 host + H2 RCP)
+
+- S3 host on USB JTAG serial, H2 RCP on its own USB. Spinel UART1 from the host: `rx_pin: GPIO17`,
+  `tx_pin: GPIO18`, RCP reset `GPIO7` active low, 460800. The config needs `network: enable_ipv6: true`.
+- The shipped H2 firmware fails `CheckRadioCapabilities` with IDF 5.5; build `examples/openthread/ot_rcp`
+  for esp32h2 with ESPHome's own IDF (`IDF_PATH` at the cached framework, its penv and tools,
+  `IDF_PYTHON_CHECK_CONSTRAINTS=no`) and flash with esptool at 0x0, 0x8000 and 0x10000.
+- A crash-looping S3 pulses the H2 reset every boot, so the H2 cannot be flashed and the S3 will not
+  enter its bootloader over USB. Hold S3 BOOT, tap S3 RST, flash the H2, release, then replug both.
+- `dns-sd -L <name> _meshcop._udp local.` shows the `omr` prefix; it disappears when routing is dead.
+  Keep one capture per chip; never reset the H2 over USB mid-test unless that is the test (the host
+  logs `Unexpected RCP reset: RESET_OTHER` and recovers).
@@ -0,0 +1,117 @@
+# Proven test flows
+
+Each flow names the pull requests it was used on, so their result tables show what to post.
+
+## Captive portal `/wifisave` hammer (#20802, #20784)
+
+Reproduces a `/wifisave` arriving during the STA cooldown, and proves a fix on every board.
+Device under test: `templates/example-dut.yaml` (bogus network, `ap:` with `ap_timeout: 15s`,
+`captive_portal:`). Client: `templates/example-client.yaml` on an ESP32 or a D1 mini; it joins the
+device's AP, posts 15 bogus saves 3 s apart, then the real credentials. With the portal up the cooldown
+is 30 s, so nearly every save lands inside one. Driver: `scripts/wifisave_hammer.sh`. Settle 40 s on
+ESP boards, 90 s on the BW15 (its first attempt on the real network fails, see boards.md).
+
+Counts that matter: `Requested WiFi Settings Change` (saves received), `Exiting cooldown early`, crash
+markers, boots (`Log initialized`), and the client's `bogus save status 200` and `real save status 200`.
+A healthy run: every save answered 200, one cooldown exit per save (two on the BW15, whose retry enters
+the adapter restart), no panic, and the real credentials connect the device within about 10 s.
+
+Fault injection for AP start failures: wrap `this->ap_setup_ = this->wifi_start_ap_(this->ap_)` in
+`setup_ap_config_()` with an `HWTEST_AP_FAIL_COUNT` build flag
+(`esphome: platformio_options: build_flags: -DHWTEST_AP_FAIL_COUNT=2`), raise the portal's "Captive
+portal started" from LOGV to LOGI, and after provisioning curl the device's STA address: connection
+refused proves the portal's server is gone.
+
+## `reboot_timeout` with a fallback AP (#9958)
+
+Only one board runs the AP at a time, or stations join the wrong one. AP probe: bogus network,
+`ap: {ssid, password, ap_timeout: 5s}`, `reboot_timeout: 60s`, `logger: level: VERBOSE` (ESP32 and
+ESP8266 log `AP client connected MAC=` at verbose), `on_boot: logger.log: BOOT`. Station probes:
+`reboot_timeout: 0s`, `interval: 150s` running `wifi.disable`, `delay: 20s`, `wifi.enable` (60 s cycles
+are too short to cover the due moment). Pass pattern: "Can't connect; rebooting" exactly 60 s after boot
+with no station joined, no reboot for minutes while one is, then a reboot within a second of the last
+disconnect. The BW15 restarts its AP on every STA retry and cannot be tested this way.
+
+## MQTT (#20433, #17935, #20762, #20767, #20768)
+
+A local mosquitto with `allow_anonymous true`, `log_type all` and `log_dest file`: the broker log gives
+each subscription's QoS, the device address (`New client connected from <ip> as <name>-<mac>`) and exact
+subscribe counts. Kill and restart mosquitto to exercise `on_disconnect` (reason 0) and resubscription.
+Keep `reboot_timeout: 0s` on `api:` and `mqtt:`. The ESP-IDF outbox swings free heap about 2 kB right
+after bulk subscribe and unsubscribe; read the heap seconds later over several rounds before calling a
+leak. Spawned subscriptions need about 2.5 s to reach the broker before the next publish.
+`esphome logs --device MQTT` only uses the MQTT transport when the config has no `api:`. Driver pattern: a
+paho script publishes and polls the serial capture file.
+
+## UDP, multicast, sockets (#20556 to #20559, #20585, #20590)
+
+A listener on port 9 needs no privileges on macOS. Test multicast device to device; host to device
+multicast never arrives on some access points, and `239.255.x.x` groups are unreliable even to a stock
+listener. Broadcast to boards is lossy under power save, unicast is not. Flood at a fixed packet rate
+(the host hits `ENOBUFS` unthrottled); 1500 packets per second survived on every board. A forced Wi-Fi
+reconnect on the Pico keeps IGMP membership. Set a long loop interval from `wifi.on_connect`
+(`App.set_loop_interval(20000)`), not `on_boot`, or Wi-Fi connect crawls. The `logger.log` action
+rejects `%.*s`; use a lambda.
+
+## OTA overlap and lock (#20588), OTA timeouts (#19041), deflate (#19037)
+
+All overlap orders (a web upload during a native OTA and the reverse) must be refused; the lock release
+after an interrupted web upload waits about 14 s (ESP8266) or 7 s (ESP-IDF) for disconnect detection. A
+refused web client on `web_server_idf` never gets the busy reply; the connection drops at reboot.
+`pkill -f "a\|b"` does not alternate; use two pkills.
+
+## DHCP lease cache (#17767)
+
+Cycle 20 s awake, `deep_sleep.enter 30s`, wake, 20 s, `App.safe_reboot()`, logging `millis()` at the
+`wifi.connected` condition. An RTS hardware reset must fall back to DHCP; a software reboot and a deep
+sleep wake must apply the cache. `esphome run --no-logs` silently skipped the upload on one board; use
+`upload` then `logs`.
+
+## HDMI-CEC two-board wire (#9189)
+
+Two boards on one wire: promiscuous mode, a 0x8F request answered with 0x90 0x00, a `destination:`
+filter on the reply handler, template buttons for each target plus lambdas calling
+`send(source, dest, span)` as another initiator. Healthy numbers: device-side turnaround 15 to 22 ms,
+round trip 144 to 156 ms. Press buttons over the API; judge timings from device logs (ESP32 light sleep
+lags the press).
+
+## LD2450 polygon zones (#20154)
+
+To make a target "leave" without anyone moving, set the radar's Zone-1 numbers over the target and
+switch the zone type to `Filter` (the count drops to 0 within 0.5 s); set it back to `Disabled` after.
+Writing those numbers blocks the ld2450 loop about 50 ms.
+
+## Scheduler and loop wake A/B (#20356)
+
+An external component whose template button arms an SDK `os_timer` (50 ms, one shot) on the ESP8266;
+the callback runs in SYS context, records `millis()` and calls `set_timeout` or `defer`; the timeout
+logs the elapsed time and loop count delta. Drive with an aioesphomeapi script (`subscribe_logs` plus
+`button_command`). Build the same yaml twice with different names, one per tree.
+
+## Noise handshake and OTA encryption on the ESP8266 (#19062, #19233)
+
+Host side timing is useless on a weak link; use an on-device bench with the minimum of five runs over
+two boots. Provision a key with `noise_encryption_set_key` through aioesphomeapi and upload with
+`espota2.run_ota(host, 8266, None, bin, noise_psk=key)` when the key is not in the yaml.
+
+## ESP-NOW on the ESP8266 (#14407)
+
+The NONOS SDK only delivers broadcast ESP-NOW frames while the station is associated or a soft-AP is
+up; a hidden, open, client-less soft-AP (60 s beacon, DHCP stopped) makes broadcasts arrive. In AP-only
+mode the device transmits from the soft-AP MAC.
+
+## Wi-Fi Easy Connect (DPP) enrollee (#17934)
+
+Only an Android phone configures: Settings, network details, Add device, Share Wi-Fi (the Wi-Fi list's
+QR scanner makes the phone an enrollee). Render the URI with the `qrcode` module and open the PNG.
+`esp32: framework: log_level: DEBUG` plus `sdkconfig_options: CONFIG_WPA_DEBUG_PRINT: y` prints the
+supplicant state machine.
+
+## Thread border router (#18104)
+
+See boards.md for the ESP Thread BR board. Check that the H2 answers Spinel before blaming a PR.
+
+## nRF52840 dongle boards (#19009, #20814)
+
+Test config: the two LEDs as inverted GPIO outputs, the button as an inverted pull-up binary sensor, a
+10 s alive interval. To retest the nrfutil download path, move the cached `sdk-nrf/nrfutil` aside first.
@@ -0,0 +1,51 @@
+"""ltchiptool for boards whose RTS drives CEN: reset and link on one open port.
+
+Stock ltchiptool closes and reopens the port after its DTR/RTS reset, and
+pyserial raises both lines on open, holding CEN low through the BootROM's
+listen window. Open with both lines released and pulse the reset right
+before the LinkChecks instead.
+"""
+
+import sys
+
+import bk7231tools.serial.main as bk_main
+from ltchiptool.__main__ import cli
+from ltchiptool.soc.bk72xx.flash import BK72XXFlash
+from serial import Serial
+
+
+class ReleasedSerial(Serial):
+    def __init__(self, port=None, **kwargs):
+        super().__init__(None, **kwargs)
+        self.dtr = False
+        self.rts = False
+        self.port = port
+        self.open()
+
+
+bk_main.Serial = ReleasedSerial
+
+_connect = BK72XXFlash.flash_connect
+
+
+def flash_hw_reset(self) -> None:
+    self._reset_pending = True
+
+
+def flash_connect(self) -> None:
+    pending = getattr(self, "_reset_pending", False)
+    if self.bk and self.conn.linked and not pending:
+        return
+    self.flash_build_protocol()
+    if pending:
+        self._reset_pending = False
+        self.bk.hw_reset()
+        self.conn.linked = False  # the chip rebooted, so link again below
+    _connect(self)
+
+
+BK72XXFlash.flash_hw_reset = flash_hw_reset
+BK72XXFlash.flash_connect = flash_connect
+
+sys.argv = ["ltchiptool", *sys.argv[1:]]
+cli()
@@ -0,0 +1,87 @@
+"""ltchiptool for the BW15 kit whose CH340 drives CEN (RTS) and PA00 (DTR).
+
+A plain open asserts both lines and holds the chip in reset. Here every open keeps DTR high and RTS
+released; the first open pulses RTS so the ROM comes up; after the command DTR low plus an RTS pulse
+boots the app. The exit status is ltchiptool's; 2 means the flash succeeded but the app was not
+booted (boot pulse failed, or no -d PORT to send it to), so the board sits in the ROM until reset.
+
+Usage: python flash_rtl87xx_kit.py flash write -d <port> firmware.uf2
+"""
+
+import sys
+import time
+
+import serial
+
+_first = [True]
+_orig_open = serial.Serial.open
+
+
+def _open(self):
+    self.dtr = True  # PA00 high: ROM download mode on the next reset
+    self.rts = False  # CEN released
+    _orig_open(self)
+    if _first[0]:
+        _first[0] = False
+        self.rts = True
+        time.sleep(0.1)
+        self.rts = False
+        time.sleep(0.3)  # reset into the ROM
+        self.reset_input_buffer()
+
+
+serial.Serial.open = _open
+
+from ltchiptool.__main__ import cli_entrypoint  # noqa: E402
+
+
+def port_argument(argv: list[str]) -> str | None:
+    for i, a in enumerate(argv):
+        if a in ("-d", "--device") and i + 1 < len(argv):
+            return argv[i + 1]
+        if a.startswith(("-d=", "--device=")):
+            return a.split("=", 1)[1]
+        if a.startswith("-d") and len(a) > 2:
+            return a[2:]
+    return None
+
+
+def boot_app(port: str) -> None:
+    s = serial.Serial(port=None)
+    s.port = port
+    s.dtr = False
+    s.rts = False
+    _orig_open(s)
+    s.rts = True
+    time.sleep(0.1)
+    s.rts = False
+    s.close()
+
+
+def main() -> int:
+    rc = 1
+    try:
+        result = cli_entrypoint.main(args=sys.argv[1:], standalone_mode=False)
+        rc = int(result) if isinstance(result, int) else 0
+    finally:
+        port = port_argument(sys.argv)
+        if not port:
+            print(
+                "[flash_rtl87xx_kit] no -d PORT given, the application was not booted",
+                file=sys.stderr,
+            )
+            if rc == 0:
+                rc = 2
+        else:
+            try:
+                boot_app(port)
+                print("[flash_rtl87xx_kit] application booted")
+            except (serial.SerialException, OSError) as err:
+                print(f"[flash_rtl87xx_kit] boot pulse failed: {err}", file=sys.stderr)
+                if rc == 0:
+                    rc = 2  # flashed, but the board is still in the ROM: press reset
+    return rc
+
+
+if __name__ == "__main__":
+    sys.exit(main())
@@ -0,0 +1,123 @@
+"""List the boards on USB, or wait for one to enumerate.
+
+  ports.py                          table: port, vid:pid, product, serial number, guess
+  ports.py --wait 2e8a              print the first port with VID 0x2e8a once it appears (default 60 s)
+  ports.py --wait 1a86:7523 --timeout 30
+  ports.py --product "USB Serial"   first port whose USB product string matches (case-insensitive)
+  ports.py --wait 2e8a --serial SN  the port of one specific board, whatever name it comes back under
+  ports.py --serial-of PORT         print the USB serial number behind a port name
+
+Run with a Python that has pyserial (any ESPHome venv). Port names follow the hub port on macOS, so
+re-run this after every replug instead of trusting a name from an earlier session.
+"""
+
+import argparse
+import sys
+import time
+
+from serial.tools import list_ports
+
+GUESS = [
+    (
+        (0x1A86, 0x7523),
+        "CH340: D1 mini, BW15 kit, BK7238/CB3S or LN882H adapter; identify by the boot banner",
+    ),
+    ((0x1A86, 0x55D3), "CH343: ESP32-P4 devkit console"),
+    ((0x1A86, 0x55D4), "CH343: ESP32 devkit"),
+    ((0x1A86, None), "WCH CH34x USB serial bridge"),
+    ((0x10C4, 0xEA60), "CP2102: classic ESP32 devkit (esp32dev)"),
+    (
+        (0x303A, 0x1001),
+        "Espressif USB JTAG serial: S3/C3/C6/H2 native USB (logger hardware_uart USB_SERIAL_JTAG)",
+    ),
+    (
+        (0x2E8A, None),
+        "Raspberry Pi Pico W / Pico 2 W CDC; the port vanishes and comes back on every reboot",
+    ),
+    ((0x1915, 0x521F), "nRF52840 Dongle (PCA10059) in the Open DFU bootloader"),
+    (
+        (0x2FE3, 0x0100),
+        "nRF52840 Dongle running a Zephyr app; two CDC ports, ESPHome log on the second",
+    ),
+    ((0x1915, 0xCAFE), "Makerdiary nRF52840 MDK dongle running a Zephyr app"),
+    ((0x239A, None), "Adafruit style nRF52 board (UF2 bootloader family)"),
+]
+
+
+def guess(vid: int, pid: int) -> str:
+    for (gv, gp), text in GUESS:
+        if vid == gv and (gp is None or pid == gp):
+            return text
+    return ""
+
+
+def parse_id(text: str) -> tuple[int, int | None]:
+    vid, _, pid = text.partition(":")
+    return int(vid, 16), (int(pid, 16) if pid else None)
+
+
+def matches(
+    port, vid: int | None, pid: int | None, product: str | None, serial: str | None
+) -> bool:
+    if vid is not None and (port.vid != vid or (pid is not None and port.pid != pid)):
+        return False
+    if product and (port.product or "").lower() != product.lower():
+        return False
+    return not serial or (port.serial_number or "") == serial
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(
+        description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
+    )
+    ap.add_argument(
+        "--wait",
+        metavar="VID[:PID]",
+        help="block until a matching port appears, print it",
+    )
+    ap.add_argument("--product", help="USB product string to match")
+    ap.add_argument("--serial", help="USB serial number to match")
+    ap.add_argument(
+        "--serial-of", metavar="PORT", help="print the USB serial number of PORT"
+    )
+    ap.add_argument("--timeout", type=float, default=60)
+    args = ap.parse_args()
+
+    if args.serial_of:
+        for p in list_ports.comports():
+            if p.device == args.serial_of and p.serial_number:
+                print(p.serial_number)
+                return 0
+        print(f"no USB serial number for {args.serial_of}", file=sys.stderr)
+        return 1
+
+    vid = pid = None
+    if args.wait:
+        vid, pid = parse_id(args.wait)
+
+    if args.wait or args.product or args.serial:
+        deadline = time.time() + args.timeout
+        while True:
+            for p in sorted(list_ports.comports(), key=lambda p: p.device):
+                if p.vid and matches(p, vid, pid, args.product, args.serial):
+                    print(p.device)
+                    return 0
+            if time.time() >= deadline:
+                print("no matching port", file=sys.stderr)
+                return 1
+            time.sleep(1)
+
+    rows = [p for p in list_ports.comports() if p.vid]
+    if not rows:
+        print("no USB serial ports")
+        return 1
+    for p in sorted(rows, key=lambda p: p.device):
+        print(
+            f"{p.device:32} {p.vid:04x}:{p.pid:04x}  {p.product or '?':34} "
+            f"{p.serial_number or '':18} {guess(p.vid, p.pid)}"
+        )
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
@@ -0,0 +1,157 @@
+"""Bounded, timestamped serial capture that always exits and closes the port.
+
+  serial_capture.py PORT SECONDS OUTFILE [--baud 115200] [--released] [--reset] [--append]
+
+  default      open with DTR/RTS as pyserial leaves them (asserted); fine for ESP devkits and the Pico.
+  --released   drive DTR and RTS low before opening: the BW15 and BK7238 CH340 kits strap the boot pin
+               (DTR) and reset (RTS), so a plain open holds the chip in reset.
+  --reset      pulse reset after opening (DTR low, RTS high 100 ms, RTS low) to capture a fresh boot.
+  --baud       115200 by default; 74880 shows the ESP8266 ROM boot messages.
+  --append     keep what OUTFILE already holds; by default it is truncated so counts cover this run only.
+
+Exit status 1 when nothing was received (wrong port name, or a port another capture still holds).
+Text ESPHome marks as secret (LOG_SECRET, the Wi-Fi password) is written as <secret>.
+Lines are written as [HH:MM:SS]text with ANSI colour stripped and flushed one by one, so a shell
+loop can grep the file while the capture runs. If the port is missing or disappears (USB CDC boards
+re-enumerate on reboot) the script retries until the deadline, and follows the board by its USB serial
+number when it comes back under another device path.
+
+Never run an open-ended serial session: every capture has a deadline, and a flash on the same port
+needs the capture stopped first (pkill -f "[s]erial_capture.py" does not match the killing shell).
+"""
+
+import argparse
+import contextlib
+import pathlib
+import re
+import sys
+import time
+
+import serial
+from serial.tools import list_ports
+
+ANSI = re.compile(rb"\x1b\[[0-9;]*[A-Za-z]")
+# ESPHome's LOG_SECRET span (a Wi-Fi password); a span cut off before its end marker is secret to the end
+SECRET = re.compile(rb"\x1b\[8m.*?(?:\x1b\[28m|$)", re.DOTALL)
+PORT_ERRORS = (serial.SerialException, OSError)
+
+
+def identify(port: str) -> tuple[str | None, int]:
+    """USB serial number of the port and its position among that device's ports (a dongle has two)."""
+    ports = sorted(list_ports.comports(), key=lambda p: p.device)
+    serial_number = next((p.serial_number for p in ports if p.device == port), None)
+    siblings = [
+        p.device for p in ports if serial_number and p.serial_number == serial_number
+    ]
+    return serial_number, siblings.index(port) if port in siblings else 0
+
+
+def current_path(port: str, serial_number: str | None, index: int) -> str:
+    """The port's current device path: a USB CDC board can come back under a new name after a reboot."""
+    if serial_number:
+        ports = sorted(list_ports.comports(), key=lambda p: p.device)
+        siblings = [p.device for p in ports if p.serial_number == serial_number]
+        if index < len(siblings):
+            return siblings[index]
+    return port
+
+
+def open_port(args: argparse.Namespace, path: str) -> serial.Serial:
+    s = serial.Serial(port=None, baudrate=args.baud, timeout=0.2)
+    s.port = path
+    if args.released:
+        s.dtr = False
+        s.rts = False
+    s.open()
+    if args.reset:
+        try:
+            s.dtr = False
+            s.rts = True
+            time.sleep(0.1)
+            s.rts = False
+            s.reset_input_buffer()
+        except PORT_ERRORS:
+            s.close()
+            raise
+    return s
+
+
+def write_line(out, tag: bytes, data: bytes) -> None:
+    stamp = time.strftime("[%H:%M:%S]").encode()
+    out.write(stamp + tag + ANSI.sub(b"", SECRET.sub(b"<secret>", data)) + b"\n")
+    out.flush()
+
+
+def note(out, text: str) -> None:
+    write_line(out, b"[capture] ", text.encode())
+
+
+def capture(args: argparse.Namespace, out) -> int:
+    """Returns the number of bytes received."""
+    deadline = time.time() + args.seconds
+    buf = b""
+    s = None
+    received = 0
+    serial_number, index = None, 0
+    while time.time() < deadline:
+        if s is None:
+            path = current_path(args.port, serial_number, index)
+            try:
+                s = open_port(args, path)
+                args.reset = False  # only reset on the first open
+                if serial_number is None:
+                    serial_number, index = identify(path)
+                if path != args.port:
+                    note(out, f"reopened as {path}")
+            except PORT_ERRORS as err:
+                note(out, f"open failed: {err}")
+                time.sleep(1)
+                continue
+        try:
+            data = s.read(4096)
+        except PORT_ERRORS as err:
+            if buf:  # keep the cut-off line apart from the next boot's first line
+                write_line(out, b"[partial]", buf)
+                buf = b""
+            note(out, f"port lost: {err}")
+            with contextlib.suppress(*PORT_ERRORS):
+                s.close()
+            s = None
+            time.sleep(1)
+            continue
+        if not data:
+            continue
+        received += len(data)
+        buf += data
+        while b"\n" in buf:
+            line, buf = buf.split(b"\n", 1)
+            write_line(out, b"", line.rstrip(b"\r"))
+    if buf:
+        write_line(out, b"[partial]", buf)
+    if s is not None:
+        s.close()
+    return received
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(
+        description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
+    )
+    ap.add_argument("port")
+    ap.add_argument("seconds", type=float)
+    ap.add_argument("outfile")
+    ap.add_argument("--baud", type=int, default=115200)
+    ap.add_argument("--released", action="store_true")
+    ap.add_argument("--reset", action="store_true")
+    ap.add_argument("--append", action="store_true")
+    args = ap.parse_args()
+    with pathlib.Path(args.outfile).open("ab" if args.append else "wb") as out:
+        received = capture(args, out)
+    if received == 0:
+        print(f"[capture] nothing received from {args.port}", file=sys.stderr)
+        return 1
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
@@ -0,0 +1,133 @@
+#!/bin/bash
+# wifisave_hammer.sh: the device under test (DUT) falls back to its AP; a client board joins it and posts
+# /wifisave repeatedly, then the real credentials. Compiles, flashes, captures both serial logs and
+# prints counts. Configs come from templates/example-dut.yaml and templates/example-client.yaml.
+#
+# Usage: wifisave_hammer.sh DUT_KIND DUT_PORT DUT_YAML DUT_TREE CLIENT_PORT CLIENT_YAML CLIENT_TREE [SETTLE_S]
+#   DUT_KIND    esp (esphome upload), pico (upload, then re-find the CDC port by USB serial number),
+#               bw15 (flash_rtl87xx_kit.py) or bk (flash_bk72xx.py)
+#   *_YAML      absolute path; the file name without .yaml must equal the config's `name`
+#   *_TREE      checkout or worktree whose esphome code must build that yaml (cwd for python -m esphome)
+#   SETTLE_S    seconds to keep capturing after the client reports the real save (default 40; BW15 wants 90)
+# Env: PY (python with esphome; default DUT_TREE/venv/bin/python, else python3 on PATH; an explicit PY must exist), LTPY
+#      (LibreTiny penv python with ltchiptool; default ~/.platformio/penv/.libretiny/bin/python)
+# Output next to each yaml: NAME-compile.log, NAME-upload.log, NAME-serial.log, NAME-capture.err, and DUT NAME-events.txt
+# (addresses redacted so the extract can go on a PR; the serial logs themselves stay local).
+# Exit status: 0 RESULT PASS (no crash marker or reboot after the AP came up, the device joined the network,
+# and real stimulus: saves answered and a cooldown exit); 3 RESULT FAIL (the counts show
+# a failure); 2 RESULT INVALID (a precondition or the stimulus was missed, or a capture did not last the run);
+# 1 when a build, flash or port step fails (nothing is reported).
+set -u
+SKILL=$(cd "$(dirname "$0")/.." && pwd)
+KIND=$1; DPORT=$2; DYAML=$3; DTREE=$4; CPORT=$5; CYAML=$6; CTREE=$7; SETTLE=${8:-40}
+if [ -n "${PY:-}" ]; then [ -x "$PY" ] || { echo "[hammer] FAILED: PY=$PY is not executable"; exit 1; }
+else PY=$DTREE/venv/bin/python; [ -x "$PY" ] || PY=$(command -v python3) || { echo "[hammer] FAILED: no python found, set PY"; exit 1; }; fi
+LTPY=${LTPY:-$HOME/.platformio/penv/.libretiny/bin/python}
+DDIR=$(dirname "$DYAML"); DNAME=$(basename "$DYAML" .yaml)
+CDIR=$(dirname "$CYAML"); CNAME=$(basename "$CYAML" .yaml)
+DLOG=$DDIR/$DNAME-serial.log; CLOG=$CDIR/$CNAME-serial.log
+INVALID=""
+AP_WAIT=120; UPLOAD_WAIT=300; SAVE_WAIT=240
+# Crash signatures (extended regex), not bare words: "aborting connection attempt" is a normal Wi-Fi retry line
+CRASH_RE='Panic |abort\(\)|Fatal exception|Exception \(|Guru Meditation|HardFault|Bus Fault|Backtrace:|Soft WDT reset|wdt reset|Brownout|rst cause:[24]'
+# Boot banners and port losses are counted apart: a Pico reboot shows as a port loss (and maybe a banner too),
+# while on a UART board a port loss comes from the adapter or the hub, not the chip
+BANNER_RE='Log initialized'; LOSS_RE='\[capture\] port lost'
+DUT_CAPTURE=$((AP_WAIT + UPLOAD_WAIT + SAVE_WAIT + SETTLE + 60)); CLIENT_CAPTURE=$((SAVE_WAIT + SETTLE + 60))
+
+bound() { local t=$1; shift; if command -v timeout >/dev/null; then timeout "$t" "$@"; else perl -e 'alarm shift; exec @ARGV' "$t" "$@"; fi; }
+count() { LC_ALL=C grep -a -c "$1" "$2"; }
+wait_for() { # wait_for FILE PATTERN SECONDS -> prints elapsed, status 1 on timeout
+  local n=0; until LC_ALL=C grep -a -q "$2" "$1"; do sleep 2; n=$((n+2)); [ $n -ge "$3" ] && { echo "$n"; return 1; }; done; echo "$n"; }
+# Only this run's captures: another capture on the host (a soak on a third board) must survive
+stop_tails() { pkill -f "[s]erial_capture.py $DPORT " 2>/dev/null; pkill -f "[s]erial_capture.py $CPORT " 2>/dev/null; sleep 1; }
+fail() { echo "[hammer] FAILED: $1"; stop_tails; exit 1; }
+port_never_opened() { # an open failure and no line that is not a capture note: the port, not the firmware
+  LC_ALL=C grep -a -q '\[capture\] open failed' "$1" && ! LC_ALL=C grep -a -q -v '^\[[0-9:]*\]\[capture\]' "$1"; }
+compile() { # compile YAML TREE
+  (cd "$2" && PYTHONUNBUFFERED=1 bound 1500 "$PY" -m esphome compile "$1" > "${1%.yaml}-compile.log" 2>&1); local rc=$?
+  echo "[hammer] compile $(basename "$1"): rc=$rc"; return $rc; }
+esp_upload() { # esp_upload YAML PORT TREE
+  (cd "$3" && bound $UPLOAD_WAIT "$PY" -m esphome upload "$1" --device "$2" > "${1%.yaml}-upload.log" 2>&1)
+  local ok; ok=$(count 'Successfully uploaded' "${1%.yaml}-upload.log"); echo "[hammer] upload $(basename "$1"): ok=$ok"; [ "$ok" -ge 1 ]; }
+
+stop_tails
+compile "$DYAML" "$DTREE" || fail "DUT build failed, see $DDIR/$DNAME-compile.log"
+compile "$CYAML" "$CTREE" || fail "client build failed, see $CDIR/$CNAME-compile.log"
+
+TAILOPT=""
+case $KIND in
+  esp) esp_upload "$DYAML" "$DPORT" "$DTREE" || fail "DUT upload failed" ;;
+  pico)
+    SN=$("$PY" "$SKILL/scripts/ports.py" --serial-of "$DPORT") || fail "no USB serial number for $DPORT"
+    esp_upload "$DYAML" "$DPORT" "$DTREE" || fail "DUT upload failed"
+    # The Pico drops its CDC port on reboot and may already be back: take whatever path this board has now;
+    # the capture follows the serial number if the path changes again
+    DPORT=$("$PY" "$SKILL/scripts/ports.py" --wait 2e8a --serial "$SN" --timeout 60) || fail "pico did not re-enumerate"
+    echo "[hammer] pico port after upload: $DPORT"; sleep 2 ;;
+  bw15|bk)
+    UF2=$(ls "$DDIR/.esphome/build/$DNAME/.pioenvs/$DNAME/"*.uf2 2>/dev/null | head -1)
+    [ -n "$UF2" ] || fail "no uf2 under $DDIR/.esphome/build/$DNAME"
+    echo "[hammer] uf2: ${UF2##*/}"
+    W=$SKILL/scripts/flash_rtl87xx_kit.py; [ "$KIND" = bk ] && W=$SKILL/scripts/flash_bk72xx.py
+    (cd "$DDIR" && bound 400 "$LTPY" "$W" flash write -d "$DPORT" "$UF2" > "$DDIR/$DNAME-upload.log" 2>&1); rc=$?
+    echo "[hammer] $KIND flash: rc=$rc"; [ $rc -eq 0 ] || fail "DUT flash failed, see $DDIR/$DNAME-upload.log"
+    TAILOPT="--released" ;;
+  *) echo "unknown DUT_KIND $KIND"; exit 1 ;;
+esac
+
+: > "$DLOG"; ("$PY" "$SKILL/scripts/serial_capture.py" "$DPORT" $DUT_CAPTURE "$DLOG" $TAILOPT 2> "${DLOG%-serial.log}-capture.err" &)
+if ! n=$(wait_for "$DLOG" "Captive portal\|Starting fallback AP" $AP_WAIT); then
+  [ -s "$DLOG" ] || fail "the DUT capture produced nothing (the capture itself failed), see ${DLOG%-serial.log}-capture.err"
+  port_never_opened "$DLOG" && fail "could not open $DPORT (held by another process, or the wrong port), see $DLOG"
+  fail "DUT never raised its AP within ${n}s, see $DLOG"
+fi
+echo "[hammer] DUT fallback AP after ${n}s"; sleep 2
+# reboots are counted from here; the first banner may predate the capture
+BANNER_BASE=$(count "$BANNER_RE" "$DLOG"); LOSS_BASE=$(count "$LOSS_RE" "$DLOG")
+
+esp_upload "$CYAML" "$CPORT" "$CTREE" || fail "client upload failed"
+: > "$CLOG"; ("$PY" "$SKILL/scripts/serial_capture.py" "$CPORT" $CLIENT_CAPTURE "$CLOG" 2> "${CLOG%-serial.log}-capture.err" &)
+if n=$(wait_for "$CLOG" "real save status\|posting the real" $SAVE_WAIT); then
+  echo "[hammer] client posted the real credentials after ${n}s; settling ${SETTLE}s"; sleep "$SETTLE"
+else
+  [ -s "$CLOG" ] || fail "the client capture produced nothing (the capture itself failed), see ${CLOG%-serial.log}-capture.err"
+  port_never_opened "$CLOG" && fail "could not open $CPORT (held by another process, or the wrong port), see $CLOG"
+  INVALID="client never reached the real save within ${n}s"; echo "[hammer] WARNING: $INVALID"
+fi
+
+# A verdict needs complete evidence: both captures must have lasted the run and logged no error of their own
+for spec in "$DPORT:${DLOG%-serial.log}-capture.err" "$CPORT:${CLOG%-serial.log}-capture.err"; do
+  port=${spec%%:*}; err=${spec#*:}
+  pgrep -f "[s]erial_capture.py $port " >/dev/null || INVALID="${INVALID:+$INVALID; }the capture on $port ended before the run did, see $err"
+  [ -s "$err" ] && INVALID="${INVALID:+$INVALID; }the capture on $port reported an error, see $err"
+done
+CRASHES=$(LC_ALL=C grep -a -c -E "$CRASH_RE" "$DLOG")
+BANNERS=$(( $(count "$BANNER_RE" "$DLOG") - BANNER_BASE )); LOSSES=$(( $(count "$LOSS_RE" "$DLOG") - LOSS_BASE ))
+if [ "$KIND" = pico ]; then
+  REBOOTS=$BANNERS; [ "$LOSSES" -gt "$REBOOTS" ] && REBOOTS=$LOSSES  # one reboot can show as both, so take the larger
+else
+  REBOOTS=$BANNERS; [ "$LOSSES" -gt 0 ] && INVALID="${INVALID:+$INVALID; }the DUT port dropped $LOSSES time(s) mid-run (adapter or hub, not the chip)"
+fi
+STA=$(LC_ALL=C grep -a 'IP Address:' "$DLOG" | grep -v -c '192\.168\.4\.'); REAL=$(LC_ALL=C grep -a -o 'real save status [-0-9]*' "$CLOG" | tail -1 | awk '{print $4}')
+SAVES=$(count 'Requested WiFi Settings Change' "$DLOG"); EXITS=$(count 'cooldown early' "$DLOG"); ANSWERED=$(count 'bogus save status 200' "$CLOG")
+echo "[hammer] $DNAME: saves requested $SAVES, cooldown exits $EXITS, crash markers $CRASHES, after the AP came up: boot banners $BANNERS, port losses $LOSSES, reboots $REBOOTS; STA addresses $STA"
+FAILED=$(count 'bogus save status -1' "$CLOG")
+echo "[hammer] $CNAME: bogus saves answered $ANSWERED, failed $FAILED, real save status ${REAL:-none}"
+# Only whole messages, matched where the message starts, so a credential line or an odd SSID never gets in
+LC_ALL=C grep -a -E "^\[[0-9:]+\](\[[A-Z]\]\[[a-z_]+:[0-9]+\]: *(Exiting cooldown early|Starting fallback AP|Captive portal|Requested WiFi Settings Change|Retry phase|Connected\$|IP Address: )|\[capture\] port lost|($CRASH_RE))" "$DLOG" | LC_ALL=C tr -cd '\11\12\15\40-\176' | sed -E 's/(IP Address: )[^ ]+/\1<redacted>/' | cut -c1-110 | head -80 > "$DDIR/$DNAME-events.txt"
+echo "[hammer] events: $DDIR/$DNAME-events.txt"
+stop_tails
+[ -z "$INVALID" ] || { echo "[hammer] RESULT INVALID: $INVALID"; exit 2; }
+# Provisioning is proven by the device joining the network; the client's answer to the real save can time
+# out because the device leaves the AP before replying, so its status is information only
+if [ "$CRASHES" -gt 0 ] || [ "$REBOOTS" -gt 0 ] || [ "$STA" -lt 1 ]; then
+  echo "[hammer] RESULT FAIL: crash markers $CRASHES, reboots $REBOOTS, STA addresses $STA, real save status ${REAL:-none}"; exit 3
+fi
+# A pass needs the stimulus the flow is about: at least half the configured bogus saves answered and one cooldown exit
+CONFIGURED=$(LC_ALL=C grep -a -E '^[[:space:]]*bogus_saves:' "$CYAML" | head -1 | tr -dc '0-9'); CONFIGURED=${CONFIGURED:-15}
+if [ "$EXITS" -lt 1 ] || [ $((ANSWERED * 2)) -lt "$CONFIGURED" ]; then
+  echo "[hammer] RESULT INVALID: insufficient stimulus (bogus saves answered $ANSWERED of $CONFIGURED, cooldown exits $EXITS)"; exit 2
+fi
+[ "$FAILED" -eq 0 ] || echo "[hammer] WARNING: $FAILED of $CONFIGURED bogus saves got no answer"
+echo "[hammer] RESULT PASS"; exit 0
@@ -0,0 +1,77 @@
+# Package for the client board: it joins the device under test's AP (priority 10), posts
+# `bogus_saves` bogus /wifisave requests `save_interval` apart, then posts the real credentials once.
+# Include from a per-run yaml that holds the platform block and the substitutions (example-client.yaml);
+# real_ssid and real_psk come from the scratch directory's secrets.yaml and must be URL safe.
+# Set bogus_saves to 1 for a plain provisioning check. Log lines the driver script counts:
+#   "bogus save N", "bogus save status 200", "posting the real credentials", "real save status 200"
+# The hammer is a single-mode script, so a reconnect to the AP (the device under test rebooted) does not
+# start a second series on top of the first.
+substitutions:
+  ap_password: hwtestpass
+  bogus_saves: "15"
+  save_interval: 3s
+  bogus_ssid: hwtest-no-such-network
+  bogus_psk: nosuchpassword
+
+esphome:
+  name: ${name}
+
+logger:
+  level: DEBUG
+
+http_request:
+  id: http
+  verify_ssl: false
+  timeout: 10s
+
+wifi:
+  id: wifi_id
+  networks:
+    - ssid: ${ap_ssid}
+      password: ${ap_password}
+      priority: 10
+    - ssid: ${real_ssid}
+      password: ${real_psk}
+  on_connect:
+    - lambda: |-
+        char b[40];
+        ESP_LOGI("test", "connected, ip %s", id(wifi_id).get_ip_addresses()[0].str_to(b));
+    - if:
+        condition:
+          lambda: |-
+            char b[40];
+            return strncmp(id(wifi_id).get_ip_addresses()[0].str_to(b), "192.168.4.", 10) == 0;
+        then:
+          - script.execute: hammer
+
+script:
+  - id: hammer
+    mode: single
+    then:
+      - delay: 3s
+      - logger.log: "hammering /wifisave with bogus credentials"
+      - repeat:
+          count: ${bogus_saves}
+          then:
+            - lambda: ESP_LOGI("test", "bogus save %u", (unsigned) iteration + 1);
+            - http_request.get:
+                url: "http://192.168.4.1/wifisave?ssid=${bogus_ssid}&psk=${bogus_psk}"
+                capture_response: true
+                on_response:
+                  - lambda: ESP_LOGI("test", "bogus save status %d", response->status_code);
+                on_error:
+                  - lambda: ESP_LOGW("test", "bogus save status -1");
+            - delay: ${save_interval}
+      - logger.log: "posting the real credentials"
+      - http_request.get:
+          url: "http://192.168.4.1/wifisave?ssid=${real_ssid}&psk=${real_psk}"
+          capture_response: true
+          on_response:
+            - lambda: ESP_LOGI("test", "real save status %d", response->status_code);
+          on_error:
+            - lambda: ESP_LOGW("test", "real save status -1");
+
+interval:
+  - interval: 5s
+    then:
+      - lambda: ESP_LOGI("test", "alive %u s", (unsigned) (millis() / 1000));
@@ -0,0 +1,31 @@
+# Package for a device under test that never finds its network, falls back to its AP and serves the
+# captive portal. Include it from a per-run yaml that holds the platform block and the substitutions
+# (see example-dut.yaml). Bump `name` on every run: saved credentials are keyed by it, and a reused
+# name boots straight onto the real network and never raises the AP.
+substitutions:
+  ap_password: hwtestpass
+  ap_timeout: 15s
+  bogus_ssid: hwtest-no-such-network
+  bogus_psk: nosuchpassword
+
+esphome:
+  name: ${name}
+
+logger:
+  level: DEBUG
+
+wifi:
+  networks:
+    - ssid: ${bogus_ssid}
+      password: ${bogus_psk}
+  ap:
+    ssid: ${ap_ssid}
+    password: ${ap_password}
+    ap_timeout: ${ap_timeout}
+
+captive_portal:
+
+interval:
+  - interval: 5s
+    then:
+      - lambda: ESP_LOGI("test", "alive %u s", (unsigned) (millis() / 1000));
@@ -0,0 +1,18 @@
+# Client board for the /wifisave hammer. Copy into a scratch directory next to a secrets.yaml;
+# ap_ssid must match the device under test, real_ssid and real_psk must be URL safe.
+substitutions:
+  name: hwtest-client-1
+  ap_ssid: hwtest-ap
+  real_ssid: !secret wifi_ssid
+  real_psk: !secret wifi_password
+  bogus_saves: "15"
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+# esp8266: {board: d1_mini}
+
+packages:
+  hwtest: !include client-wifisave.yaml
@@ -0,0 +1,16 @@
+# Device under test for the /wifisave hammer. Copy into a scratch directory, keep the file name equal
+# to `name`, pick one platform block, bump `name` every run.
+substitutions:
+  name: hwtest-dut-1
+  ap_ssid: hwtest-ap
+
+esp8266:
+  board: d1_mini
+
+# esp32: {board: esp32dev, framework: {type: esp-idf}}
+# rtl87xx: {board: bw15}
+# bk72xx: {board: generic-bk7238}   # plus logger: {hardware_uart: UART1}, BK72xx logs on UART2 by default
+# rp2040: {board: rpipico2w}
+
+packages:
+  hwtest: !include dut-fallback-ap.yaml
@@ -0,0 +1,16 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "d=\"${CLAUDE_PROJECT_DIR:-.}\"; [ -x \"$d/venv/bin/python\" ] || { mkdir -p \"$d/.temp\"; env -u VIRTUAL_ENV \"$d/script/setup\" >\"$d/.temp/setup.log\" 2>&1 || echo '{\"systemMessage\":\"script/setup failed; see .temp/setup.log\"}'; }",
+            "statusMessage": "Setting up dev environment (script/setup)...",
+            "timeout": 900
+          }
+        ]
+      }
+    ]
+  }
+}
@@ -0,0 +1 @@
+../.agents/skills
@@ -31,7 +31,4 @@ RUN \
    platformio settings set enable_telemetry No \
    && platformio settings set check_platformio_interval 1000000

-COPY script/platformio_install_deps.py platformio.ini ./
-RUN ./platformio_install_deps.py platformio.ini --libraries --platforms --tools
-
 WORKDIR /workspaces
@@ -9,6 +9,29 @@ body:
        If you have a feature request or enhancement, please [request them here instead][fr].

        [fr]: https://github.com/orgs/esphome/discussions
+  - type: markdown
+    attributes:
+      value: |
+        ## Use of AI in bug reports
+
+        AI tools are good at carrying out well-defined tasks, but they are not good at troubleshooting.
+        Please do NOT paste an AI-generated wall of text into the issue template - if the AI hasn't solved
+        your problem, its wild guesses are not likely to help.
+
+        Please DO include your own words and observations, compile/boot logs, and
+        especially a minimal reproducible example of your YAML configuration that demonstrates the problem.
+
+        It is however quite acceptable to use AI to translate your *own* report,
+        if you aren't a competent English speaker.
+
+        If you really think it will be useful to include an AI's analysis, preferably wrap it in a `<details>` block which will be collapsed by default.
+
+        If you are using AI to help solve a problem, rather than asking it to speculate about what the problem is,
+        it can be more useful to ask it to create a step-by-step troubleshooting procedure.
+        AI is also useful for generating boilerplate code, such as a minimal reproducible example of your YAML
+        configuration that demonstrates the problem.
+
+        Used properly, AI can be a useful tool to help you solve your problem, but don't let it get in the way.
  - type: textarea
    validations:
      required: true
@@ -42,7 +42,7 @@ runs:

    - name: Build and push to ghcr by digest
      id: build-ghcr
-      uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7.3.0
+      uses: docker/build-push-action@c3c9e263c25d99ce0380d002d59b67737d91b0dc # v7.4.0
      env:
        DOCKER_BUILD_SUMMARY: false
        DOCKER_BUILD_RECORD_UPLOAD: false
@@ -67,7 +67,7 @@ runs:

    - name: Build and push to dockerhub by digest
      id: build-dockerhub
-      uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7.3.0
+      uses: docker/build-push-action@c3c9e263c25d99ce0380d002d59b67737d91b0dc # v7.4.0
      env:
        DOCKER_BUILD_SUMMARY: false
        DOCKER_BUILD_RECORD_UPLOAD: false
@@ -0,0 +1,39 @@
+name: Cache Arduino ESP8266
+description: >
+  Resolve the pinned Arduino core and xtensa toolchain versions and cache the
+  native ESP8266 install (~110 MB framework + toolchain; no ccache store, the
+  seed job saves before any compile runs). Exports
+  ESPHOME_ARDUINO8266_PREFIX to the job so every later step installs into
+  the cached path; the Python venv must already be restored. Mirrors
+  cache-esp-idf: only dev-branch pushes write the shared cache, everything
+  else restores.
+runs:
+  using: composite
+  steps:
+    - name: Resolve the native toolchain cache key
+      # Versions are pinned in code, not a hashable file; resolve them so a
+      # bump changes the cache key. Assignment form so errexit catches a
+      # resolver failure.
+      id: version
+      shell: bash
+      run: |
+        # One owner for the install prefix: exported here and referenced by
+        # the cache steps below via env, so the caller's install and the
+        # cached path cannot diverge.
+        echo "ESPHOME_ARDUINO8266_PREFIX=$HOME/.esphome-arduino8266" >> "$GITHUB_ENV"
+        . venv/bin/activate
+        key=$(python -c 'from esphome.components.esp8266 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION as f; from esphome.arduino8266.framework import FRAMEWORK_RELEASES, TOOLCHAIN_VERSION as t; print(f"{FRAMEWORK_RELEASES[f].tag}-{t}")')
+        [ -n "$key" ] || exit 1
+        echo "key=$key" >> "$GITHUB_OUTPUT"
+    - name: Cache the native toolchain (write on dev)
+      if: github.ref == 'refs/heads/dev'
+      uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ${{ env.ESPHOME_ARDUINO8266_PREFIX }}
+        key: ${{ runner.os }}-esp8266-native-${{ steps.version.outputs.key }}
+    - name: Restore the native toolchain (off dev)
+      if: github.ref != 'refs/heads/dev'
+      uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ${{ env.ESPHOME_ARDUINO8266_PREFIX }}
+        key: ${{ runner.os }}-esp8266-native-${{ steps.version.outputs.key }}
@@ -0,0 +1,50 @@
+name: Cache clang-tidy idedata
+description: >
+  Cache the clang-tidy idedata and the headers it references under .temp
+  (headers only, about 30MB per env). Run after restore-python and cache-esp-idf.
+inputs:
+  environment:
+    description: 'clang-tidy environment (e.g. esp32-idf-tidy).'
+    required: true
+runs:
+  using: composite
+  steps:
+    - name: Compute cache key
+      id: key
+      shell: bash
+      run: |
+        . venv/bin/activate
+        [ -n "${{ inputs.environment }}" ] || { echo "::error::cache-clang-tidy-idedata: 'environment' input is empty"; exit 1; }
+        hash=$(python -c 'import sys; sys.path.insert(0, "script"); from clang_tidy_hash import idedata_cache_hash; print(idedata_cache_hash("${{ inputs.environment }}"))')
+        pyver=$(python -c 'import platform; print(platform.python_version())')
+        # Generating idedata is what installs ESP-IDF; never skip it over a missing
+        # install. This also skips the save, so a dev run that installs ESP-IDF
+        # warms the idedata cache on the next run.
+        if [ -d ~/.esphome-idf/frameworks ]; then
+          echo "skip=false" >> "$GITHUB_OUTPUT"
+        else
+          echo "ESP-IDF install missing, not using the clang-tidy idedata cache"
+          echo "skip=true" >> "$GITHUB_OUTPUT"
+        fi
+        echo "key=${{ runner.os }}-tidy-idedata-${{ inputs.environment }}-$hash-py$pyver" >> "$GITHUB_OUTPUT"
+        {
+          echo "path<<EOF"
+          printf '%s\n' '.temp/idedata-*.json' '.temp/idedata-*.hash'
+          printf '.temp/**/*.%s\n' h hpp hh hxx inc inl ipp tpp
+          echo "EOF"
+        } >> "$GITHUB_OUTPUT"
+    # Mirror cache-esp-idf: write on dev, restore-only on PRs. The post-step
+    # save only runs when the job succeeded, so a failed generation is never saved.
+    # Extend the extension list if a component ships extensionless headers.
+    - name: Cache clang-tidy idedata (write on dev)
+      if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write')) && steps.key.outputs.skip != 'true'
+      uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ${{ steps.key.outputs.path }}
+        key: ${{ steps.key.outputs.key }}
+    - name: Cache clang-tidy idedata (restore-only off dev)
+      if: github.ref != 'refs/heads/dev' && !contains(github.event.pull_request.labels.*.name, 'ci-cache-write') && steps.key.outputs.skip != 'true'
+      uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ${{ steps.key.outputs.path }}
+        key: ${{ steps.key.outputs.key }}
@@ -26,6 +26,9 @@ runs:
      # The native-IDF version is pinned in code, not in any file that feeds the
      # other cache keys, so resolve it explicitly. Keying on it means the cache
      # invalidates on a version bump (actions/cache never overwrites a key).
+      # Also key on the Python version: the cached IDF venv links to the
+      # runner's toolcache interpreter and is reinstalled every run after a
+      # runner image bump.
      id: version
      shell: bash
      run: |
@@ -36,19 +39,32 @@ runs:
          version=$(python -c 'from esphome.components.esp32 import ESP_IDF_FRAMEWORK_VERSION_LOOKUP as L; print(L["recommended"])')
        fi
        echo "version=$version" >> "$GITHUB_OUTPUT"
+        echo "python-version=$(python -c 'import platform; print(platform.python_version())')" >> "$GITHUB_OUTPUT"
    # Mirror the adjacent PlatformIO cache: only dev-branch runs write the
    # shared cache (so it lives in the default-branch scope readable by all
    # PRs), and PRs are restore-only -- they never push multi-GB artifacts into
-    # their own scope / the repo quota (e.g. on a version-bump PR).
+    # their own scope / the repo quota (e.g. on a version-bump PR). The
+    # ci-cache-write label lets a PR write into its own scope to test the hit path;
+    # that costs about 1GB of the repo cache quota per run, so remove it when done.
+    # -slim: bump when prune-esp-idf changes what it removes; a key is never overwritten.
    - name: Cache ESP-IDF install (write on dev)
-      if: github.ref == 'refs/heads/dev' && inputs.restore-only != 'true'
+      if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write')) && inputs.restore-only != 'true'
      uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
      with:
        path: ~/.esphome-idf
-        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}
+        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}-py${{ steps.version.outputs.python-version }}-slim
    - name: Cache ESP-IDF install (restore-only off dev)
-      if: github.ref != 'refs/heads/dev' || inputs.restore-only == 'true'
+      if: github.ref != 'refs/heads/dev' && !contains(github.event.pull_request.labels.*.name, 'ci-cache-write') || inputs.restore-only == 'true'
      uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
      with:
        path: ~/.esphome-idf
-        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}
+        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}-py${{ steps.version.outputs.python-version }}-slim
+    # Install explicitly so the prune below sees the toolchains on a cache miss
+    # too, instead of the install happening inside the first build step.
+    - name: Install ESP-IDF
+      shell: bash
+      run: |
+        . venv/bin/activate
+        python -c 'from esphome.espidf.framework import check_esp_idf_install; check_esp_idf_install("${{ steps.version.outputs.version }}")'
+    - name: Prune ESP-IDF install
+      uses: ./.github/actions/prune-esp-idf
@@ -0,0 +1,34 @@
+name: Prune ESP-IDF install
+description: >
+  Remove the picolibc sysroots (1.1GB of the 3.9GB install) from the native
+  ESP-IDF toolchains; IDF 5.x links newlib. Skipped when an IDF 6 install is
+  present, which links picolibc (see esp32/__init__.py).
+runs:
+  using: composite
+  steps:
+    - name: Prune picolibc
+      shell: bash
+      run: |
+        shopt -s nullglob
+        prefix="${ESPHOME_ESP_IDF_PREFIX:-$HOME/.esphome-idf}"
+        prefix="${prefix/#\~/$HOME}"
+        for fw in "$prefix"/frameworks/*/; do
+          case "$(basename "$fw")" in
+            [6-9].*) echo "IDF $(basename "$fw") installed, keeping picolibc"; exit 0 ;;
+          esac
+        done
+        n=0
+        for dir in "$prefix"/tools/*-esp-elf/*/*-esp-elf/picolibc; do
+          echo "Removing $dir ($(du -sh "$dir" | cut -f1))"
+          rm -rf "$dir"
+          n=$((n + 1))
+        done
+        # The marker rides along in the cache entry so a restored slim tree stays quiet.
+        if [ "$n" -gt 0 ]; then
+          touch "$prefix/.picolibc-pruned"
+        elif [ -d "$prefix/tools" ] && [ ! -f "$prefix/.picolibc-pruned" ]; then
+          echo "::warning::no picolibc sysroots matched under $prefix/tools"
+        fi
+        if [ -d "$prefix" ]; then
+          du -sh "$prefix"
+        fi
@@ -32,7 +32,7 @@ runs:
      # detects the activated venv via ``VIRTUAL_ENV`` so the venv layout
      # downstream jobs rely on is preserved.
      if: steps.cache-venv.outputs.cache-hit != 'true'
-      uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+      uses: astral-sh/setup-uv@1c37ad07a6a961277cf70c0d37d6f313000f5884 # v10.3.0
      with:
        enable-cache: true
        # Pull request saves land in per-PR scopes nothing else can
@@ -49,7 +49,7 @@ runs:
        python -m venv venv
        source venv/bin/activate
        python --version
-        uv pip install -r requirements.txt -r requirements_test.txt
+        uv pip install -r requirements.txt -r requirements_dev.txt -r requirements_test.txt
        uv pip install -e .
    - name: Create Python virtual environment
      if: steps.cache-venv.outputs.cache-hit != 'true' && runner.os == 'Windows'
@@ -58,5 +58,5 @@ runs:
        python -m venv venv
        source ./venv/Scripts/activate
        python --version
-        uv pip install -r requirements.txt -r requirements_test.txt
+        uv pip install -r requirements.txt -r requirements_dev.txt -r requirements_test.txt
        uv pip install -e .
@@ -70,6 +70,7 @@ async function isStackedPr(github, context) {
 async function detectMergeBranch(github, context) {
  const labels = new Set();
  const baseRef = context.payload.pull_request.base.ref;
+  const defaultBranch = context.payload.repository.default_branch;

  if (baseRef === 'release') {
    labels.add('merging-to-release');
@@ -78,7 +79,7 @@ async function detectMergeBranch(github, context) {
  } else if (await isStackedPr(github, context)) {
    // GitHub manages the merge order for a stack, so these are not blocked.
    labels.add('stacked-pr');
-  } else if (baseRef !== 'dev') {
+  } else if (baseRef !== defaultBranch) {
    // A chain built by hand: it must not merge until its base branch does.
    labels.add('chained-pr');
  }
@@ -53,7 +53,7 @@ module.exports = async ({ github, context }) => {
  });
  const currentLabels = currentLabelsData.map(label => label.name);
  const managedLabels = currentLabels.filter(label =>
-    label.startsWith('component: ') || MANAGED_LABELS.includes(label)
+    label.startsWith('component: ') || label.startsWith('platform: ') || MANAGED_LABELS.includes(label)
  );

  // Check for mega-PR early - if present, skip most automatic labeling
@@ -42,8 +42,8 @@ function generateReviewMessages(finalLabels, originalLabelCount, deprecatedInfo,
    let message = `${TOO_BIG_MARKER}\n### 📦 Pull Request Size\n\n`;

    message +=
-      `Hey @${prAuthor}, thanks for the contribution! Just a heads up, ` +
-      `this PR is on the large side `;
+      `Hey @${prAuthor}, thanks for the contribution. This PR is on the ` +
+      `large side `;

    if (tooManyLabels && tooManyChanges) {
      message +=
@@ -57,16 +57,31 @@ function generateReviewMessages(finalLabels, originalLabelCount, deprecatedInfo,
    }

    message += `, which makes it harder for maintainers to review.\n\n`;
+    let condition;
+    if (tooManyLabels && tooManyChanges) {
+      condition =
+        `is at most ${TOO_BIG_THRESHOLD} lines (excluding tests) and touches ` +
+        `at most ${MAX_LABELS} components/areas`;
+    } else if (tooManyLabels) {
+      condition = `touches at most ${MAX_LABELS} components/areas`;
+    } else {
+      condition = `is at most ${TOO_BIG_THRESHOLD} lines (excluding tests)`;
+    }
    message +=
-      `Smaller, focused PRs tend to be reviewed much faster since they ` +
-      `fit into the short gaps between other maintainer work; large ones ` +
-      `often have to wait for a rare long uninterrupted block of time. ` +
-      `If you can break this up into smaller pieces that can be reviewed ` +
-      `independently, it will almost certainly land faster overall.\n\n`;
+      `**This PR will not be reviewed until it ${condition}.** We know ` +
+      `that is not what you want to hear after this much work, and we want ` +
+      `to be upfront so you do not wait for a review that is not coming: ` +
+      `please split the change. The label is removed automatically once ` +
+      `the PR ${condition}.\n\n`;
    message +=
-      `Before putting more time in, it's also worth popping into ` +
-      `\`#devs\` on [Discord](https://esphome.io/chat) so we can help ` +
-      `you scope things and flag anything already in flight.\n\n`;
+      `There is no exception you can request. Rarely, a maintainer agrees in ` +
+      `\`#devs\` on [Discord](https://esphome.io/chat) to review a change that ` +
+      `genuinely cannot be split as one piece and adds the \`mega-pr\` label, ` +
+      `but that is rare enough that you should plan on splitting rather than ` +
+      `wait for it. Smaller, focused PRs are picked up much faster because ` +
+      `they fit into the short gaps between other maintainer work. For a new ` +
+      `component, the first PR brings the hub and a single platform (for ` +
+      `example \`sensor\`); each further platform is its own PR on top of it.\n\n`;
    message +=
      `For more details (including how to split the work up), see: ` +
      `https://developers.esphome.io/contributing/submitting-your-work/` +
@@ -214,6 +229,7 @@ async function handleMaintainerAccessComment(github, context, maintainerAccess)
 }

 module.exports = {
+  generateReviewMessages,
  handleReviews,
  handleMaintainerAccessComment
 };
@@ -43,14 +43,14 @@ const WITHOUT_SCHEMA = 'CODEOWNERS = ["@esphome/core"]';

 // Builds a fresh context for detectMergeBranch tests instead of mutating the
 // shared CONTEXT fixture above (which other describe blocks rely on).
-function makeMergeContext(baseRef, { stack } = {}) {
+function makeMergeContext(baseRef, { stack, defaultBranch = 'dev' } = {}) {
  const pull_request = { number: 1, base: { ref: baseRef } };
  if (stack !== undefined) {
    pull_request.stack = stack;
  }
  return {
    repo: { owner: 'esphome', repo: 'esphome' },
-    payload: { pull_request }
+    payload: { pull_request, repository: { default_branch: defaultBranch } }
  };
 }

@@ -136,6 +136,21 @@ describe('detectMergeBranch', () => {
    assert.deepEqual(Array.from(labels).sort(), ['chained-pr']);
    assert.equal(state.calls, 1);
  });
+
+  it('base ref matches default branch adds no labels', async () => {
+    const { github } = makeStackGithub({ stack: null });
+    const context = makeMergeContext('other', { defaultBranch: 'other' });
+    const labels = await detectMergeBranch(github, context);
+    assert.deepEqual(Array.from(labels).sort(), []);
+  });
+
+  it('base ref dev when the default branch is main adds chained-pr', async () => {
+    const { github } = makeStackGithub({ stack: null });
+    const context = makeMergeContext('dev', { defaultBranch: 'main' });
+    const labels = await detectMergeBranch(github, context);
+    assert.deepEqual(Array.from(labels).sort(), ['chained-pr']);
+  });
+
 });

 // ---------------------------------------------------------------------------
@@ -0,0 +1,38 @@
+const { describe, it } = require('node:test');
+const assert = require('node:assert/strict');
+const { generateReviewMessages } = require('../reviews');
+
+const MAX_LABELS = 15;
+const TOO_BIG_THRESHOLD = 1000;
+
+function tooBigMessage(labelCount, additions) {
+  const files = [{ filename: 'esphome/components/a/a.cpp', additions, deletions: 0 }];
+  const messages = generateReviewMessages(['too-big'], labelCount, null, files, additions, 0, 'someone', MAX_LABELS, TOO_BIG_THRESHOLD);
+  assert.equal(messages.length, 1);
+  return messages[0];
+}
+
+describe('too-big review message', () => {
+  it('names the line cap when the PR is too long', () => {
+    const message = tooBigMessage(3, 1500);
+    assert.match(message, /will not be reviewed until it is at most 1000 lines \(excluding tests\)\./);
+    assert.match(message, /removed automatically once the PR is at most 1000 lines/);
+    assert.doesNotMatch(message, /components\/areas\./);
+  });
+
+  it('names the area cap when the PR touches too many areas but is short', () => {
+    const message = tooBigMessage(20, 200);
+    assert.match(message, /will not be reviewed until it touches at most 15 components\/areas\./);
+    assert.doesNotMatch(message, /until it is at most 1000 lines/);
+  });
+
+  it('names both caps when both are exceeded', () => {
+    const message = tooBigMessage(20, 1500);
+    assert.match(message, /is at most 1000 lines \(excluding tests\) and touches at most 15 components\/areas\./);
+  });
+
+  it('tells new-component authors to bring one platform first', () => {
+    assert.match(tooBigMessage(3, 1500), /hub and a single platform/);
+    assert.match(tooBigMessage(3, 1500), /mega-pr/);
+  });
+});
@@ -0,0 +1 @@
+../.agents/skills
@@ -28,7 +28,7 @@ jobs:

      - name: Generate a token
        id: generate-token
-        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
        with:
          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
@@ -29,7 +29,7 @@ jobs:
      - name: Set up uv
        # ``--system`` (below) installs into the setup-python interpreter;
        # no venv is created or restored by this workflow.
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@1c37ad07a6a961277cf70c0d37d6f313000f5884 # v10.3.0
        with:
          enable-cache: true
          # Pull-request-only workflow: a save could never be shared and
@@ -41,10 +41,32 @@ jobs:
          version: "0.11.15"

      - name: Install apt dependencies
+        # PR-only workflow, so nothing on dev could seed a shared apt cache
+        # entry; the cached apt action would save one copy per PR. Plain apt
+        # with every call bounded: the apt.conf.d timeouts make a dead
+        # mirror fail over in seconds, and timeout runs under sudo so it can
+        # kill apt-get itself. Install without update first: image lists are
+        # fresh, and the index refresh is what a congested mirror makes slow.
+        timeout-minutes: 15
        run: |
-          sudo apt update
-          sudo apt-cache show protobuf-compiler
-          sudo apt install -y protobuf-compiler
+          sudo tee /etc/apt/apt.conf.d/99ci-acquire-timeouts >/dev/null <<'EOF'
+          Acquire::Retries "1";
+          Acquire::http::Timeout "15";
+          Acquire::https::Timeout "15";
+          EOF
+          # Common path: the image's package lists are fresh enough.
+          if sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 90 \
+              apt-get install -y protobuf-compiler; then
+            protoc --version
+            exit 0
+          fi
+          # Rescue path: refresh the lists once with a generous bound; the
+          # apt config already fails a stalled mirror over quickly.
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 10 30 \
+            dpkg --configure -a || true
+          sudo timeout -k 15 300 apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 300 \
+            apt-get install -y protobuf-compiler
          protoc --version
      - name: Install python dependencies
        run: uv pip install --system aioesphomeapi -c requirements.txt -r requirements_dev.txt
@@ -75,7 +97,7 @@ jobs:
        run: git diff
      - if: failure()
        name: Archive artifacts
-        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
          name: generated-proto-files
          path: |
@@ -12,15 +12,14 @@ on:
      - ".github/workflows/ci-docker.yml"
      - "requirements*.txt"
      - "pyproject.toml"
-      - "platformio.ini"
      - "esphome/idf_component.yml"
-      - "script/platformio_install_deps.py"
      # Core, build pipeline, toolchain, and target-platform changes can change
      # how a toolchain is set up or built, so re-run the per-toolchain compile
      # smoke test when they change.
      - "esphome/core/**"
      - "esphome/writer.py"
      - "esphome/build_gen/**"
+      - "esphome/build_helpers/**"
      - "esphome/espidf/**"
      - "esphome/platformio/**"
      - "esphome/components/bk72xx/**"
@@ -67,7 +66,7 @@ jobs:
        with:
          python-version: "3.12"
      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@594f3bf4285d9ea8dc53c9a0c9c4092420091003 # v4.4.0

      - name: Determine tag and whether to push
        id: tag
@@ -119,16 +118,22 @@ jobs:
      # pushed image) keeps it working for fork PRs, which never push to ghcr.io.
      - name: Export image for compile-test
        if: matrix.os == 'ubuntu-24.04' && matrix.build_type == 'docker'
-        run: docker save "ghcr.io/esphome/esphome-amd64:${{ steps.tag.outputs.tag }}" | gzip > compile-test-image.tar.gz
+        # zstd over gzip: docker save is on the critical path for every
+        # compile-test job, and zstd -T0 is multithreaded (export 50s -> 9s).
+        # docker load auto-detects the format; its time is layer extraction,
+        # not decompression, so it is unchanged. shell: bash adds pipefail so
+        # a failed docker save cannot upload a truncated artifact.
+        shell: bash
+        run: docker save "ghcr.io/esphome/esphome-amd64:${{ steps.tag.outputs.tag }}" | zstd -T0 -3 > compile-test-image.tar.zst

      - name: Upload compile-test image artifact
        if: matrix.os == 'ubuntu-24.04' && matrix.build_type == 'docker'
-        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
-          # The tar is already gzipped, so upload it as-is. archive: false skips
-          # the redundant zip and makes the file name the artifact name (the
-          # `name` input is ignored in that mode).
-          path: compile-test-image.tar.gz
+          # The tar is already compressed, so upload it as-is. archive: false
+          # skips the redundant zip and makes the file name the artifact name
+          # (the `name` input is ignored in that mode).
+          path: compile-test-image.tar.zst
          retention-days: 1
          archive: false

@@ -153,7 +158,7 @@ jobs:
        with:
          python-version: "3.12"
      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@594f3bf4285d9ea8dc53c9a0c9c4092420091003 # v4.4.0

      - name: Log in to the GitHub container registry
        uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
@@ -182,8 +187,6 @@ jobs:
      contents: read  # actions/checkout to load the test configs
    strategy:
      fail-fast: false
-      # Modest cap so this smoke test leaves room on the shared runner pool.
-      max-parallel: 8
      matrix:
        # One entry per distinct toolchain. ESP32 variants (c3/c6/s2/s3/p4)
        # share a toolchain bundle, so esp32 is exercised on the base variant
@@ -193,6 +196,7 @@ jobs:
        # the default.
        id:
          - esp8266-arduino
+          - esp8266-arduino-native
          - esp32-arduino-platformio
          - esp32-arduino-esp-idf
          - esp32-idf-platformio
@@ -206,14 +210,15 @@ jobs:
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
      - name: Download image artifact
-        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
        with:
-          name: compile-test-image.tar.gz
+          name: compile-test-image.tar.zst
      - name: Load image
-        run: docker load --input compile-test-image.tar.gz
+        run: docker load --input compile-test-image.tar.zst
      - name: Compile ${{ matrix.id }}
        run: |
          docker run --rm \
            -v "${{ github.workspace }}/docker/test_configs:/config" \
+            -e ESPHOME_LDGEN_STRICT=1 \
            "ghcr.io/esphome/esphome-amd64:${{ needs.check-docker.outputs.tag }}" \
            compile "${{ matrix.id }}.yaml"
@@ -49,7 +49,7 @@ jobs:
        # detects the activated venv via ``VIRTUAL_ENV`` so downstream jobs
        # that ``. venv/bin/activate`` see an identical layout.
        if: steps.cache-venv.outputs.cache-hit != 'true'
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@1c37ad07a6a961277cf70c0d37d6f313000f5884 # v10.3.0
        with:
          enable-cache: true
          # Pull request saves land in per-PR scopes nothing else can
@@ -68,6 +68,22 @@ jobs:
          uv pip install -r requirements.txt -r requirements_dev.txt -r requirements_test.txt
          uv pip install -e .

+  seed-apt-cache:
+    name: Seed apt package cache
+    runs-on: ubuntu-24.04
+    # PR-branch cache saves are invisible to other PRs, so dev/beta/release
+    # pushes seed the one shared entry PR jobs restore. The key is derived
+    # only from the package list and version; keep both identical in every
+    # step that restores it. In ci-status needs so a broken seed fails dev.
+    if: github.event_name == 'push'
+    timeout-minutes: 10
+    steps:
+      - name: Install apt packages (cached)
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
+        with:
+          packages: libsdl2-dev libmbedtls-dev ccache
+          version: 1.2
+
  determine-jobs:
    name: Determine which jobs to run
    runs-on: ubuntu-24.04
@@ -76,6 +92,7 @@ jobs:
    outputs:
      core-ci: ${{ steps.determine.outputs.core-ci }}
      integration-tests: ${{ steps.determine.outputs.integration-tests }}
+      integration-run-all: ${{ steps.determine.outputs.integration-run-all }}
      integration-test-buckets: ${{ steps.determine.outputs.integration-test-buckets }}
      clang-tidy: ${{ steps.determine.outputs.clang-tidy }}
      clang-tidy-mode: ${{ steps.determine.outputs.clang-tidy-mode }}
@@ -85,6 +102,8 @@ jobs:
      device-builder: ${{ steps.determine.outputs.device-builder }}
      esp32-platformio: ${{ steps.determine.outputs.esp32-platformio }}
      esp32-platformio-components: ${{ steps.determine.outputs.esp32-platformio-components }}
+      esp8266-native: ${{ steps.determine.outputs.esp8266-native }}
+      esp8266-native-components: ${{ steps.determine.outputs.esp8266-native-components }}
      changed-components: ${{ steps.determine.outputs.changed-components }}
      changed-components-with-tests: ${{ steps.determine.outputs.changed-components-with-tests }}
      directly-changed-components-with-tests: ${{ steps.determine.outputs.directly-changed-components-with-tests }}
@@ -96,6 +115,12 @@ jobs:
      component-test-batches: ${{ steps.determine.outputs.component-test-batches }}
      validate-only-components: ${{ steps.determine.outputs.validate-only-components }}
      benchmarks: ${{ steps.determine.outputs.benchmarks }}
+      # "true" when this run is a pull request into one of the release
+      # branches. Those pull requests are batches of changes already tested on
+      # their original dev pull requests, so several jobs below trade coverage
+      # for turnaround time on them. Matched exactly, not by prefix, so an
+      # ordinary branch named e.g. "release-notes" is not caught by it.
+      release-pr: ${{ github.base_ref == 'beta' || github.base_ref == 'release' }}
    steps:
      - name: Check out code from GitHub
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -130,6 +155,9 @@ jobs:
          # Extract individual fields
          echo "core-ci=$(echo "$output" | jq -r '.core_ci')" >> $GITHUB_OUTPUT
          echo "integration-tests=$(echo "$output" | jq -r '.integration_tests')" >> $GITHUB_OUTPUT
+          # A missing key must fail here, not silently disable the junit upload
+          run_all=$(echo "$output" | jq -r 'if has("integration_run_all") then .integration_run_all else error("integration_run_all missing") end')
+          echo "integration-run-all=${run_all}" >> $GITHUB_OUTPUT
          echo "integration-test-buckets=$(echo "$output" | jq -c '.integration_test_buckets')" >> $GITHUB_OUTPUT
          echo "clang-tidy=$(echo "$output" | jq -r '.clang_tidy')" >> $GITHUB_OUTPUT
          echo "clang-tidy-mode=$(echo "$output" | jq -r '.clang_tidy_mode')" >> $GITHUB_OUTPUT
@@ -139,6 +167,8 @@ jobs:
          echo "device-builder=$(echo "$output" | jq -r '.device_builder')" >> $GITHUB_OUTPUT
          echo "esp32-platformio=$(echo "$output" | jq -r '.esp32_platformio')" >> $GITHUB_OUTPUT
          echo "esp32-platformio-components=$(echo "$output" | jq -r '.esp32_platformio_components')" >> $GITHUB_OUTPUT
+          echo "esp8266-native=$(echo "$output" | jq -r '.esp8266_native')" >> $GITHUB_OUTPUT
+          echo "esp8266-native-components=$(echo "$output" | jq -r '.esp8266_native_components')" >> $GITHUB_OUTPUT
          echo "changed-components=$(echo "$output" | jq -c '.changed_components')" >> $GITHUB_OUTPUT
          echo "changed-components-with-tests=$(echo "$output" | jq -c '.changed_components_with_tests')" >> $GITHUB_OUTPUT
          echo "directly-changed-components-with-tests=$(echo "$output" | jq -c '.directly_changed_components_with_tests')" >> $GITHUB_OUTPUT
@@ -157,6 +187,33 @@ jobs:
          path: .temp/components_graph.json
          key: components-graph-${{ hashFiles('esphome/components/**/*.py') }}

+  seed-esp8266-native-cache:
+    name: Seed the esp8266 native toolchain cache
+    runs-on: ubuntu-24.04
+    needs:
+      - common
+    # PR-branch cache saves are invisible to other PRs, so dev pushes seed
+    # the shared entry the component matrix, the memory impact jobs and
+    # test-esp8266-native restore. Only dev: the composite action saves
+    # nowhere else, so a beta/release push would download the toolchain and
+    # discard it.
+    if: github.event_name == 'push' && github.ref == 'refs/heads/dev'
+    timeout-minutes: 15
+    steps:
+      - name: Check out code from GitHub
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Restore Python
+        uses: ./.github/actions/restore-python
+        with:
+          python-version: ${{ env.DEFAULT_PYTHON }}
+          cache-key: ${{ needs.common.outputs.cache-key }}
+      - name: Cache the native toolchain
+        uses: ./.github/actions/cache-arduino8266
+      - name: Install the native toolchain
+        run: |
+          . venv/bin/activate
+          python -c "from esphome.arduino8266.framework import check_and_install; from esphome.components.esp8266 import RECOMMENDED_ARDUINO_FRAMEWORK_VERSION; check_and_install(RECOMMENDED_ARDUINO_FRAMEWORK_VERSION)"
+
  ci-custom:
    name: Run script/ci-custom
    runs-on: ubuntu-24.04
@@ -179,6 +236,7 @@ jobs:
          . venv/bin/activate
          script/ci-custom.py
          script/build_codeowners.py --check
+          script/build_alias_registry.py --check
          script/build_language_schema.py --check
          script/generate-esp32-boards.py --check
          script/generate-rp2-boards.py --check
@@ -213,15 +271,24 @@ jobs:
    runs-on: ubuntu-latest
    needs:
      - determine-jobs
-    if: github.event_name == 'pull_request' && !startsWith(github.base_ref, 'beta') && !startsWith(github.base_ref, 'release') && needs.determine-jobs.outputs.core-ci == 'true'
+    if: github.event_name == 'pull_request' && needs.determine-jobs.outputs.release-pr == 'false' && needs.determine-jobs.outputs.core-ci == 'true'
    steps:
      - name: Check out code from GitHub
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Read prek version from requirements_test.txt
+        id: prek
+        # requirements_test.txt is the only place the version is pinned, so a
+        # Dependabot bump there is picked up here without a second edit.
+        run: |
+          if ! version=$(sed -nE 's/^prek==([^[:space:]#]+).*/\1/p' requirements_test.txt) || [ -z "$version" ]; then
+            echo "::error::No prek== pin found in requirements_test.txt."
+            exit 1
+          fi
+          echo "version=$version" >> "$GITHUB_OUTPUT"
      - name: Run prek
-        uses: j178/prek-action@4e14d07f9231acabce116ccfca13b13dd9755ece # v3.0.0
+        uses: j178/prek-action@1382ad72dea72f9d53832f2bcb65b3e87a947204 # v3.0.1
        with:
-          # Keep in sync with requirements_test.txt.
-          prek-version: "0.4.11"
+          prek-version: ${{ steps.prek.outputs.version }}
          # This job only runs on pull requests, so nothing ever populates
          # the cache on dev. Every run would miss and then write a per-pull
          # request copy, which is what the old seed-cache job existed to
@@ -232,7 +299,7 @@ jobs:
      # Pushes any fixes the hooks made back to the pull request. This step
      # must keep its default name: the GitHub App that performs the push
      # locates the workflow run by that name.
-      - uses: pre-commit-ci/lite-action@5d6cc0eb514c891a40562a58a8e71576c5c7fb43 # v1.1.0
+      - uses: pre-commit-ci/lite-action@062bca0919bc9d6e66755cc05074b70c77e111fc # v1.2.0
        if: always()
        with:
          msg: apply automatic formatting fixes
@@ -285,7 +352,7 @@ jobs:
          . venv/bin/activate
          pytest -vv --cov-report=xml --tb=native --durations=30 -n auto tests --ignore=tests/integration/
      - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
+        uses: codecov/codecov-action@303a32d7a59b442fa8d48b6a1cc6825c09c847a5 # v7.1.1
      - name: Save Python virtual environment cache
        if: github.ref == 'refs/heads/dev'
        uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
@@ -314,7 +381,7 @@ jobs:
      - name: Check out code from GitHub
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
      - name: Report empty upload to Codecov
-        uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
+        uses: codecov/codecov-action@303a32d7a59b442fa8d48b6a1cc6825c09c847a5 # v7.1.1
        with:
          run_command: empty-upload
          force: true
@@ -322,41 +389,48 @@ jobs:

  integration-tests:
    name: Run integration tests (${{ matrix.bucket.name }})
-    runs-on: ubuntu-latest
+    # Must match seed-apt-cache's image: the apt cache key has no OS in it.
+    runs-on: ubuntu-24.04
    needs:
      - common
      - determine-jobs
    if: needs.determine-jobs.outputs.integration-tests == 'true'
+    # A hung test is failed by pytest's --timeout below; this bounds the rest
+    timeout-minutes: 60
    strategy:
      fail-fast: false
      matrix:
        bucket: ${{ fromJson(needs.determine-jobs.outputs.integration-test-buckets) }}
+    env:
+      # Registry libraries (noise-c, libsodium, ArduinoJson, lvgl) the host builds
+      # download, shared per xdist worker by tests/integration/conftest.py
+      INTEGRATION_LIBRARY_CACHE_PATH: ~/.esphome-integration-tests/pio_components
    steps:
      - name: Check out code from GitHub
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - name: Install ccache
-        # Speeds up the host compiles: tests in a bucket compile overlapping
-        # component sets, so later tests reuse earlier tests' objects.
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -y --no-install-recommends ccache
-      - name: Restore ccache (restore-only)
-        # esphome stores the PlatformIO ccache under the machine-global cache
-        # dir (see _ccache_env() in esphome/platformio/toolchain.py). The
-        # bucket-name prefix prefers a same-bucket seed; the bare prefix falls
-        # back to any seed when the bucket layout differs from dev.
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      - name: Install apt packages (cached)
+        # ccache speeds up the host compiles. A cache hit never touches apt
+        # (mirror outages cannot hang the job); the timeout bounds the cold
+        # path. Packages and version must match seed-apt-cache exactly.
+        # libsdl2-dev is needed by the headless display tests, which capture
+        # screenshots.
+        timeout-minutes: 10
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
        with:
-          path: ~/.cache/esphome/platformio-ccache
-          key: integration-ccache-${{ matrix.bucket.name }}-${{ github.sha }}
-          restore-keys: |
-            integration-ccache-${{ matrix.bucket.name }}-
-            integration-ccache-
+          packages: libsdl2-dev libmbedtls-dev ccache
+          version: 1.2
      - name: Set up Python 3.13
        id: python
        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
        with:
          python-version: "3.13"
+      - name: Restore integration library cache
+        # A miss or a changed pin self-heals with a download, so no restore-keys
+        id: library-cache
+        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ${{ env.INTEGRATION_LIBRARY_CACHE_PATH }}
+          key: integration-libraries-v1-${{ runner.os }}-${{ hashFiles('esphome/components/json/__init__.py', 'esphome/components/noise/__init__.py', 'esphome/components/lvgl/__init__.py', 'esphome/components/improv_base/__init__.py') }}
      - name: Restore Python virtual environment
        id: cache-venv
        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
@@ -366,7 +440,7 @@ jobs:
      - name: Set up uv
        # Only needed on cache miss to populate the venv.
        if: steps.cache-venv.outputs.cache-hit != 'true'
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@1c37ad07a6a961277cf70c0d37d6f313000f5884 # v10.3.0
        with:
          enable-cache: true
          # Pull request saves land in per-PR scopes nothing else can
@@ -394,20 +468,47 @@ jobs:
        run: |
          . venv/bin/activate
          mapfile -t test_files < <(echo "$BUCKET_TESTS" | jq -r '.[]')
+          if [ "${#test_files[@]}" -eq 0 ]; then
+            echo "::error::Empty integration test bucket; pytest would collect the whole tree"
+            exit 1
+          fi
          echo "Bucket ${{ matrix.bucket.name }}: running ${#test_files[@]} integration tests"
-          pytest -vv --no-cov --tb=native --durations=30 -n auto "${test_files[@]}"
+          # A hung test fails after 30 min: the 15 min shared build lock wait plus a cold compile
+          pytest -vv --no-cov --tb=native --durations=30 -n auto --dist worksteal --timeout=1800 \
+            --junitxml=junit-integration.xml "${test_files[@]}"
+      - name: Upload test artifacts
+        # Tests that compare rendered output write the image they actually got here, so a
+        # failure can be looked at without reproducing the whole build locally.
+        if: failure()
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: integration-test-artifacts-${{ matrix.bucket.name }}
+          path: test_artifacts/
+          if-no-files-found: ignore
+          retention-days: 7
+      - name: Upload junit timings
+        # Consumed by sync-integration-durations.yml through
+        # script/update_integration_test_durations.py; only full matrix dev
+        # runs produce usable data.
+        if: github.ref == 'refs/heads/dev' && needs.determine-jobs.outputs.integration-run-all == 'true'
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: junit-integration-${{ strategy.job-index }}
+          path: junit-integration.xml
+          if-no-files-found: error
+          # A full cron period of margin for the weekly refresh
+          retention-days: 14
      - name: Print ccache statistics
-        # esphome stores the PlatformIO ccache under the machine-global cache
-        # dir (see _ccache_env() in esphome/platformio/toolchain.py).
-        run: CCACHE_DIR="$HOME/.cache/esphome/platformio-ccache" ccache -s
-      - name: Save ccache
-        # Pull request saves land in per-PR scopes nothing else can reuse;
-        # dev pushes seed the shared copy instead.
-        if: github.event_name != 'pull_request'
+        # esphome stores the host build's ccache under the machine-global
+        # cache dir (see get_build_env() in esphome/host/toolchain.py).
+        run: CCACHE_DIR="$HOME/.cache/esphome/host/ccache" ccache -s
+      - name: Save integration library cache
+        # Bucket 0 only; the others would race the same immutable key.
+        if: success() && (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write')) && strategy.job-index == 0 && steps.library-cache.outputs.cache-hit != 'true'
        uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
        with:
-          path: ~/.cache/esphome/platformio-ccache
-          key: integration-ccache-${{ matrix.bucket.name }}-${{ github.sha }}
+          path: ${{ env.INTEGRATION_LIBRARY_CACHE_PATH }}
+          key: ${{ steps.library-cache.outputs.cache-primary-key }}

  import-time:
    name: Check import esphome.__main__ time
@@ -430,7 +531,7 @@ jobs:
          script/check_import_time.py --check --har importtime.har
      - name: Upload waterfall HAR
        if: always()
-        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
          name: import-time-waterfall
          path: importtime.har
@@ -440,12 +541,28 @@ jobs:
  benchmarks:
    name: Run CodSpeed benchmarks
    runs-on: ubuntu-24.04
+    timeout-minutes: 30
    needs:
      - common
      - determine-jobs
    if: >-
-      (github.event_name == 'push' && github.ref_name == 'dev') ||
-      (github.event_name == 'pull_request' && needs.determine-jobs.outputs.benchmarks == 'true')
+      github.repository == 'esphome/esphome' && (
+        (github.event_name == 'push' && github.ref_name == 'dev') ||
+        (
+          github.event_name == 'pull_request' &&
+          needs.determine-jobs.outputs.release-pr == 'false' &&
+          needs.determine-jobs.outputs.benchmarks == 'true'
+        )
+      )
+    # CodSpeed benchmarks require a CodSpeed account linked to the repository to run
+    # (https://codspeed.io) -- disabled on forks that aren't esphome/esphome itself.
+    #
+    # Pull requests into beta and release are skipped as well. CodSpeed compares a
+    # pull request against the newest commit of its base branch that has a benchmark
+    # run of its own, and only dev is benchmarked. A release pull request therefore
+    # falls back to dev's latest run, so every speed-up merged into dev since the
+    # release branched is reported as a regression in the release. The changes there
+    # have already been benchmarked on their original dev pull requests.
    steps:
      - name: Check out code from GitHub
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -459,14 +576,60 @@ jobs:
      - name: Build benchmarks
        id: build
        run: |
+          # pipefail: without it a failed build is masked by the grep/cut
+          # pipeline below, leaving BINARY empty and silently dropping every
+          # C++ benchmark from the run while the job still reports success.
+          set -o pipefail
          . venv/bin/activate
-          export BENCHMARK_LIB_CONFIG=$(python script/setup_codspeed_lib.py)
-          # --build-only prints BUILD_BINARY=<path> to stdout
-          BINARY=$(script/cpp_benchmark.py --all --build-only | grep '^BUILD_BINARY=' | tail -1 | cut -d= -f2-)
+          BENCHMARK_LIB_CONFIG=$(python script/setup_codspeed_lib.py)
+          export BENCHMARK_LIB_CONFIG
+          # --build-only prints BUILD_BINARY=<path> to stdout; the grep is
+          # non-fatal so a missing marker reaches the check below instead of
+          # tripping errexit at this assignment
+          BINARY=$(script/cpp_benchmark.py --all --build-only | { grep '^BUILD_BINARY=' || true; } | tail -1 | cut -d= -f2-)
+          if [ -z "$BINARY" ]; then
+            echo "::error::Benchmark build did not report a binary path"
+            exit 1
+          fi
          echo "binary=$BINARY" >> $GITHUB_OUTPUT

+      - name: Bound apt fetches and pre-install libc6-dbg
+        # The CodSpeed runner installs valgrind + libc6-dbg via its own
+        # unbounded apt-get update; per-invocation apt options cannot reach
+        # it. The apt.conf.d timeouts below bound every later apt call in
+        # this job, the runner's included. Pre-installing libc6-dbg lets the
+        # runner skip apt once its valgrind cache is restored (it checks
+        # ``dpkg -s libc6-dbg``, so the cache action's unregistered restores
+        # would not count). Install without update first: image lists are
+        # fresh, and the index refresh is what a congested mirror makes
+        # slow. Best effort; the job timeout is the last backstop.
+        timeout-minutes: 15
+        continue-on-error: true
+        run: |
+          sudo tee /etc/apt/apt.conf.d/99ci-acquire-timeouts >/dev/null <<'EOF'
+          Acquire::Retries "1";
+          Acquire::http::Timeout "15";
+          Acquire::https::Timeout "15";
+          EOF
+          if dpkg -s libc6-dbg >/dev/null 2>&1; then
+            echo "libc6-dbg already installed"
+            exit 0
+          fi
+          # Common path: the image's package lists are fresh enough.
+          if sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 90 \
+              apt-get install -y libc6-dbg; then
+            exit 0
+          fi
+          # Rescue path: refresh the lists once with a generous bound; the
+          # apt config already fails a stalled mirror over quickly.
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 10 30 \
+            dpkg --configure -a || true
+          sudo timeout -k 15 300 apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 300 \
+            apt-get install -y libc6-dbg
+
      - name: Run CodSpeed benchmarks
-        uses: CodSpeedHQ/action@4296e51e7041e24dadb86d1d6e8b9320d223dbe8 # v5.0.3
+        uses: CodSpeedHQ/action@f842b9a3ffe213dbb81768fd7f7eeb4dfcf1c369 # v5.4.2
        with:
          run: |
            . venv/bin/activate
@@ -520,7 +683,7 @@ jobs:
        include:
          - id: clang-tidy
            name: Run script/clang-tidy for ESP8266
-            options: --environment esp8266-arduino-tidy --grep USE_ESP8266
+            options: --environment esp8266-arduino-tidy --grep USE_ESP8266 --grep USE_SOCKET_IMPL_LWIP_TCP --grep USE_SHD_FIRMWARE_DATA
            pio_cache_key: tidyesp8266
          - id: clang-tidy
            name: Run script/clang-tidy for ESP32 Arduino
@@ -533,12 +696,16 @@ jobs:
            ignore_errors: false
          - id: clang-tidy
            name: Run script/clang-tidy for RP2
-            options: --environment rp2-tidy --grep USE_RP2
+            options: --environment rp2-tidy --grep USE_RP2 --grep USE_BLE_SCAN_RESPONSE_MERGER
            pio_cache_key: tidyrp2
+          - id: clang-tidy
+            name: Run script/clang-tidy for host
+            options: --environment host-tidy --grep USE_HOST
+            pio_cache_key: tidyhost
          - id: clang-tidy
            name: Run script/clang-tidy for LibreTiny
            environments: bk72xx-tidy ln882h-tidy rtl87xxb-tidy rtl87xxc-tidy
-            options: --grep USE_LIBRETINY --grep USE_BK72XX --grep USE_RTL87XX --grep USE_LN882X
+            options: --grep USE_LIBRETINY --grep USE_BK72XX --grep USE_RTL87XX --grep USE_LN882X --grep USE_LN882H_BLE --grep USE_SOCKET_IMPL_LWIP_SOCKETS
            pio_cache_key: tidylibretiny

    steps:
@@ -547,26 +714,41 @@ jobs:
        with:
          # Need history for HEAD~1 to work for checking changed files
          fetch-depth: 2
+      - name: Install apt packages (cached)
+        if: matrix.pio_cache_key == 'tidyhost'
+        # libsdl2-dev is needed by the sdl component on the host, libmbedtls-dev
+        # by dsmr and dlms_meter. Packages and version must match seed-apt-cache
+        # exactly.
+        timeout-minutes: 10
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
+        with:
+          packages: libsdl2-dev libmbedtls-dev ccache
+          version: 1.2

      - name: Restore Python
+        id: restore-python
        uses: ./.github/actions/restore-python
        with:
          python-version: ${{ env.DEFAULT_PYTHON }}
          cache-key: ${{ needs.common.outputs.cache-key }}

+      # Key on the exact Python version as well: LibreTiny creates a venv under
+      # ~/.platformio/penv whose interpreter is a symlink into the runner's
+      # hosted toolcache, so a cache saved on an older runner image breaks once
+      # a new image ships a newer patch release and drops the old interpreter.
      - name: Cache platformio
        if: github.ref == 'refs/heads/dev' && matrix.pio_cache_key
        uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
        with:
          path: ~/.platformio
-          key: platformio-${{ matrix.pio_cache_key }}-${{ hashFiles('platformio.ini') }}
+          key: platformio-${{ matrix.pio_cache_key }}-${{ steps.restore-python.outputs.python-version }}-${{ hashFiles('platformio.ini') }}

      - name: Cache platformio
        if: github.ref != 'refs/heads/dev' && matrix.pio_cache_key
        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
        with:
          path: ~/.platformio
-          key: platformio-${{ matrix.pio_cache_key }}-${{ hashFiles('platformio.ini') }}
+          key: platformio-${{ matrix.pio_cache_key }}-${{ steps.restore-python.outputs.python-version }}-${{ hashFiles('platformio.ini') }}

      - name: Cache ESP-IDF install
        if: matrix.cache_idf
@@ -574,6 +756,12 @@ jobs:
        with:
          framework: arduino

+      - name: Cache clang-tidy idedata
+        if: matrix.cache_idf
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: esp32-arduino-tidy
+
      - name: Cache nRF Connect SDK install
        if: matrix.cache_sdk_nrf
        uses: ./.github/actions/cache-sdk-nrf
@@ -623,6 +811,10 @@ jobs:
          # Also cache libdeps, store them in a ~/.platformio subfolder
          PLATFORMIO_LIBDEPS_DIR: ~/.platformio/libdeps

+      - name: Prune ESP-IDF install before cache save
+        if: matrix.cache_idf && (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
      - name: Suggested changes
        run: script/ci-suggest-changes ${{ matrix.ignore_errors && '|| true' || '' }}
        # yamllint disable-line rule:line-length
@@ -655,6 +847,11 @@ jobs:
      - name: Cache ESP-IDF install
        uses: ./.github/actions/cache-esp-idf

+      - name: Cache clang-tidy idedata
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: esp32-idf-tidy
+
      - name: Register problem matchers
        run: |
          echo "::add-matcher::.github/workflows/matchers/gcc.json"
@@ -689,6 +886,10 @@ jobs:
          # Also cache libdeps, store them in a ~/.platformio subfolder
          PLATFORMIO_LIBDEPS_DIR: ~/.platformio/libdeps

+      - name: Prune ESP-IDF install before cache save
+        if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
      - name: Suggested changes
        run: script/ci-suggest-changes
        if: always()
@@ -709,14 +910,20 @@ jobs:
      matrix:
        include:
          - id: clang-tidy
-            name: Run script/clang-tidy for ESP32 IDF 1/3
-            options: --environment esp32-idf-tidy --split-num 3 --split-at 1
+            name: Run script/clang-tidy for ESP32 IDF 1/5
+            options: --environment esp32-idf-tidy --split-num 5 --split-at 1
          - id: clang-tidy
-            name: Run script/clang-tidy for ESP32 IDF 2/3
-            options: --environment esp32-idf-tidy --split-num 3 --split-at 2
+            name: Run script/clang-tidy for ESP32 IDF 2/5
+            options: --environment esp32-idf-tidy --split-num 5 --split-at 2
          - id: clang-tidy
-            name: Run script/clang-tidy for ESP32 IDF 3/3
-            options: --environment esp32-idf-tidy --split-num 3 --split-at 3
+            name: Run script/clang-tidy for ESP32 IDF 3/5
+            options: --environment esp32-idf-tidy --split-num 5 --split-at 3
+          - id: clang-tidy
+            name: Run script/clang-tidy for ESP32 IDF 4/5
+            options: --environment esp32-idf-tidy --split-num 5 --split-at 4
+          - id: clang-tidy
+            name: Run script/clang-tidy for ESP32 IDF 5/5
+            options: --environment esp32-idf-tidy --split-num 5 --split-at 5

    steps:
      - name: Check out code from GitHub
@@ -734,6 +941,11 @@ jobs:
      - name: Cache ESP-IDF install
        uses: ./.github/actions/cache-esp-idf

+      - name: Cache clang-tidy idedata
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: esp32-idf-tidy
+
      - name: Register problem matchers
        run: |
          echo "::add-matcher::.github/workflows/matchers/gcc.json"
@@ -768,6 +980,10 @@ jobs:
          # Also cache libdeps, store them in a ~/.platformio subfolder
          PLATFORMIO_LIBDEPS_DIR: ~/.platformio/libdeps

+      - name: Prune ESP-IDF install before cache save
+        if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
      - name: Suggested changes
        run: script/ci-suggest-changes
        if: always()
@@ -790,17 +1006,20 @@ jobs:
          - id: clang-tidy
            name: Run script/clang-tidy for ESP32 S3
            # yamllint disable-line rule:line-length
-            options: --environment esp32s3-idf-tidy --grep SOC_TEMP_SENSOR_SUPPORTED --grep USE_ESP32_VARIANT_ESP32S3 --grep USE_LOGGER_USB_CDC
+            options: --environment esp32s3-idf-tidy --grep SOC_TEMP_SENSOR_SUPPORTED --grep USE_ESP32_VARIANT_ESP32S3 --grep USE_LOGGER_USB_CDC --grep SOC_I2S_SUPPORTS_TDM --grep USE_OPENTHREAD
+            tidy_environment: esp32s3-idf-tidy
          - id: clang-tidy
            name: Run script/clang-tidy for ESP32 P4
            # P4 has no native Wi-Fi/BLE; those run over the hosted co-processor,
            # so their code paths differ -- lint them under the P4 build too.
            # yamllint disable-line rule:line-length
-            options: --environment esp32p4-idf-tidy --grep USE_ESP32_VARIANT_ESP32P4 --grep USE_ESP32_HOSTED --grep USE_WIFI --grep USE_BLE
+            options: --environment esp32p4-idf-tidy --grep USE_ESP32_VARIANT_ESP32P4 --grep CONFIG_IDF_TARGET_ESP32P4 --grep USE_ESP32_HOSTED --grep USE_WIFI --grep USE_BLE
+            tidy_environment: esp32p4-idf-tidy
          - id: clang-tidy
            name: Run script/clang-tidy for ESP32 C6
            # yamllint disable-line rule:line-length
            options: --environment esp32c6-idf-tidy --grep SOC_LP_I2C_SUPPORTED --grep USE_ESP32_VARIANT_ESP32C6 --grep USE_OPENTHREAD --grep USE_ZIGBEE
+            tidy_environment: esp32c6-idf-tidy

    steps:
      - name: Check out code from GitHub
@@ -818,6 +1037,11 @@ jobs:
      - name: Cache ESP-IDF install
        uses: ./.github/actions/cache-esp-idf

+      - name: Cache clang-tidy idedata
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: ${{ matrix.tidy_environment }}
+
      - name: Register problem matchers
        run: |
          echo "::add-matcher::.github/workflows/matchers/gcc.json"
@@ -851,6 +1075,10 @@ jobs:
            script/clang-tidy --fix --changed ${{ matrix.options }}
          fi

+      - name: Prune ESP-IDF install before cache save
+        if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
      - name: Suggested changes
        run: script/ci-suggest-changes
        if: always()
@@ -871,7 +1099,6 @@ jobs:
      ESPHOME_SDK_NRF_PREFIX: ~/.esphome-sdk-nrf
    strategy:
      fail-fast: false
-      max-parallel: ${{ (startsWith(github.base_ref, 'beta') || startsWith(github.base_ref, 'release')) && 32 || 16 }}
      matrix:
        batch: ${{ fromJson(needs.determine-jobs.outputs.component-test-batches) }}
    steps:
@@ -883,12 +1110,17 @@ jobs:
      - name: List components
        run: echo ${{ matrix.batch.components }}

-      - name: Install apt packages
-        # Not cached: this job is pull-request-only, so a cache save could
-        # never be shared and would only consume quota.
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -y --no-install-recommends libsdl2-dev ccache
+      - name: Install apt packages (cached)
+        # A cache hit (seeded on dev by seed-apt-cache) never touches apt,
+        # so mirror outages cannot hang this PR-only job; the timeout bounds
+        # the cold path. Packages and version must match seed-apt-cache
+        # exactly. The action has no --no-install-recommends; same package
+        # set this job used before #17463.
+        timeout-minutes: 10
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
+        with:
+          packages: libsdl2-dev libmbedtls-dev ccache
+          version: 1.2

      - name: Check out code from GitHub
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -913,6 +1145,11 @@ jobs:
        uses: ./.github/actions/cache-sdk-nrf
        with:
          restore-only: true
+      - name: Cache the native ESP8266 toolchain
+        # Only batches whose test platforms include esp8266; never saves
+        # here, it reuses the install the dev seed job cached.
+        if: matrix.batch.needs_arduino8266
+        uses: ./.github/actions/cache-arduino8266
      - name: Validate and compile components with intelligent grouping
        run: |
          . venv/bin/activate
@@ -953,7 +1190,7 @@ jobs:
          # - This catches pin conflicts and other issues in directly changed code
          # - Grouped tests use --testing-mode to allow config merging (disables some checks)
          # - Dependencies are safe to group since they weren't modified in this PR
-          if [[ "${{ github.base_ref }}" == beta* ]] || [[ "${{ github.base_ref }}" == release* ]]; then
+          if [[ "${{ needs.determine-jobs.outputs.release-pr }}" == "true" ]]; then
            directly_changed_csv=""
            echo "Testing components: $components_csv"
            echo "Target branch: ${{ github.base_ref }} - grouping all components"
@@ -1011,9 +1248,28 @@ jobs:

          if [ -n "$compile_csv" ]; then
            # Run compilation with grouping and isolation
-            python3 script/test_build_components.py -e compile -c "$compile_csv" -f --isolate "$directly_changed_csv"
+            # The bootloader has no ESPHome code and these builds never
+            # flash; the check_idf_py batch keeps the full build so the
+            # native sub-build and the equivalence check stay covered.
+            skip_flag="--skip-bootloader"
+            if [[ "${{ matrix.batch.check_idf_py }}" == "true" ]]; then
+              skip_flag=""
+            fi
+            python3 script/test_build_components.py -e compile -c "$compile_csv" -f --isolate "$directly_changed_csv" $skip_flag
+            if [[ "${{ matrix.batch.check_idf_py }}" == "true" ]]; then
+              # The real idf.py must find nothing to configure or build in a
+              # tree built above; catches drift on ESP-IDF bumps.
+              echo "Checking the native ESP-IDF build matches idf.py"
+              python3 script/check_idf_py_equivalence.py
+            fi
          else
            echo "All components in this batch are validate-only -- skipping compile stage."
+            if [[ "${{ matrix.batch.check_idf_py }}" == "true" ]]; then
+              # determine-jobs and this step disagree on what compiles; fail
+              # rather than let the check run nowhere.
+              echo "::error::This batch was picked for the idf.py check but compiled nothing"
+              exit 1
+            fi
          fi

      - name: Print ccache statistics
@@ -1053,7 +1309,7 @@ jobs:

          # compile validates config first, so a separate config pass is
          # redundant for this smoke test. ESP-IDF framework via PlatformIO:
-          python3 script/test_build_components.py -e compile -t esp32-idf -c "$TEST_COMPONENTS" -f --toolchain platformio
+          python3 script/test_build_components.py -e compile -t esp32-idf -c "$TEST_COMPONENTS" -f --toolchain platformio --fail-on-no-tests

          echo ""
          echo "ESP-IDF-via-PlatformIO build passed! Starting Arduino smoke test..."
@@ -1062,6 +1318,125 @@ jobs:
          # Arduino framework via PlatformIO (only components with an esp32-ard test are built):
          python3 script/test_build_components.py -e compile -t esp32-ard -c "$TEST_COMPONENTS" -f --toolchain platformio

+  test-esp8266-native:
+    name: Test esp8266 components with the native toolchain
+    runs-on: ubuntu-24.04
+    needs:
+      - common
+      - determine-jobs
+    if: github.event_name == 'pull_request' && needs.determine-jobs.outputs.esp8266-native == 'true'
+    env:
+      # Computed by script/determine-jobs.py (ESP8266_NATIVE_TEST_COMPONENTS)
+      TEST_COMPONENTS: ${{ needs.determine-jobs.outputs.esp8266-native-components }}
+    steps:
+      - name: Check out code from GitHub
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Restore Python
+        uses: ./.github/actions/restore-python
+        with:
+          python-version: ${{ env.DEFAULT_PYTHON }}
+          cache-key: ${{ needs.common.outputs.cache-key }}
+
+      - name: Cache the native toolchain
+        uses: ./.github/actions/cache-arduino8266
+
+      - name: Run native toolchain compile test
+        run: |
+          . venv/bin/activate
+
+          echo "Testing components: $TEST_COMPONENTS"
+          echo ""
+
+          # ESP8266 Arduino built directly (no PlatformIO); compile validates
+          # config first, so a separate config pass is redundant.
+          python3 script/test_build_components.py -e compile -t esp8266-ard -c "$TEST_COMPONENTS" -f --toolchain arduino --fail-on-no-tests
+
+  test-esp8266-native-windows:
+    name: Compile esp8266 with the native toolchain on Windows (ccache ${{ matrix.ccache }})
+    runs-on: windows-latest
+    needs:
+      - common
+      - determine-jobs
+    if: github.event_name == 'pull_request' && needs.determine-jobs.outputs.esp8266-native == 'true'
+    # A hung compiler must fail the job, not hold the runner for six hours.
+    timeout-minutes: 40
+    strategy:
+      fail-fast: false
+      matrix:
+        # Both ways the build runs on Windows: ESPHome Desktop bundles
+        # ccache and puts it on PATH, a pip install has none.
+        ccache: ["1", "0"]
+    env:
+      ESPHOME_CCACHE_ENABLE: ${{ matrix.ccache }}
+      # The test script prints characters the cp1252 console cannot encode
+      PYTHONUTF8: "1"
+      # The exact static build ESPHome Desktop ships
+      CCACHE_URL: https://github.com/ccache/ccache/releases/download/v4.14/ccache-4.14-windows-x86_64.zip
+      CCACHE_SHA256: 2568347a697e103ca1b073981c704ad76fb2507d066c38dba038dd73399d968f
+    steps:
+      - name: Check out code from GitHub
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Restore Python
+        uses: ./.github/actions/restore-python
+        with:
+          python-version: ${{ env.DEFAULT_PYTHON }}
+          cache-key: ${{ needs.common.outputs.cache-key }}
+
+      - name: Install ccache
+        if: matrix.ccache == '1'
+        shell: pwsh
+        run: |
+          $dir = Join-Path $env:RUNNER_TEMP "ccache"
+          New-Item -ItemType Directory -Force $dir | Out-Null
+          $zip = Join-Path $dir "ccache.zip"
+          Invoke-WebRequest -Uri $env:CCACHE_URL -OutFile $zip
+          $hash = (Get-FileHash $zip -Algorithm SHA256).Hash.ToLower()
+          if ($hash -ne $env:CCACHE_SHA256) {
+            Write-Host "::error::ccache archive sha256 $hash does not match $env:CCACHE_SHA256"
+            exit 1
+          }
+          Expand-Archive -Path $zip -DestinationPath $dir
+          $bin = Get-ChildItem -Path $dir -Recurse -Filter ccache.exe | Select-Object -First 1
+          Add-Content -Path $env:GITHUB_PATH -Value $bin.DirectoryName
+          & $bin.FullName --version
+
+      - name: Compile
+        shell: pwsh
+        # One component test: web_server brings wifi, api and the async web
+        # server libraries, the shape of a typical ESP8266 device
+        run: |
+          . .\venv\Scripts\Activate.ps1
+          $arguments = "script/test_build_components.py", "-e", "compile", "-t", "esp8266-ard", "-c", "web_server", "--base-only", "--toolchain", "arduino", "--fail-on-no-tests"
+          $p = Start-Process -FilePath python -ArgumentList $arguments -NoNewWindow -PassThru
+          # Reading the handle keeps ExitCode available after the process exits
+          $null = $p.Handle
+          if (-not $p.WaitForExit(25 * 60 * 1000)) {
+            Write-Host "::error::The compile did not finish in 25 minutes; processes still running:"
+            Get-CimInstance Win32_Process |
+              Where-Object { $_.CommandLine -match 'xtensa|ccache|ninja|esphome' } |
+              Select-Object ProcessId, ParentProcessId, CreationDate, CommandLine |
+              Format-List | Out-String -Width 4096 | Write-Host
+            Get-Process |
+              Where-Object { $_.Name -match 'cc1|ccache|ninja|xtensa|python' } |
+              Select-Object Id, Name, CPU, WorkingSet64 |
+              Format-Table | Out-String | Write-Host
+            taskkill /PID $p.Id /T /F
+            exit 1
+          }
+          exit $p.ExitCode
+
+      - name: Show ccache statistics
+        # Also after a failed or killed compile: the counters say whether
+        # ccache was ever reached
+        if: always() && matrix.ccache == '1'
+        shell: pwsh
+        # The build keeps its store under the esphome tools cache
+        run: |
+          $env:CCACHE_DIR = Join-Path $env:LOCALAPPDATA "esphome\Cache\arduino8266\ccache"
+          ccache -s
+
  device-builder:
    name: Test downstream esphome/device-builder
    runs-on: ubuntu-24.04
@@ -1090,7 +1465,7 @@ jobs:
        # install step (order-of-magnitude faster on cold boots,
        # with its own wheel cache). actions/setup-python still
        # provides the interpreter.
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@1c37ad07a6a961277cf70c0d37d6f313000f5884 # v10.3.0
        with:
          enable-cache: true
          # Pull request saves land in per-PR scopes nothing else can
@@ -1149,31 +1524,27 @@ jobs:
            echo "::warning::ci_memory_impact_extract.py not found on target branch, skipping memory impact analysis"
          fi

-      # Check if test files exist on the target branch for the requested
-      # components and platform. When a PR adds new test files for a platform,
-      # the target branch won't have them yet, so skip instead of failing.
-      # This check must be done here (not in determine-jobs.py) because
-      # determine-jobs runs on the PR branch and cannot see what the target
-      # branch has.
+      # The build below uses --base-only, so skip unless the target branch has
+      # test.<platform>.yaml for every requested component (test-*.yaml
+      # variants alone compile nothing, and a partial set would compare a
+      # smaller target build against the PR build). Checked here, not in
+      # determine-jobs.py, because determine-jobs runs on the PR branch and
+      # cannot see the target branch.
      - name: Check for test files on target branch
        id: check-tests
        if: steps.check-script.outputs.skip != 'true'
        run: |
          components='${{ toJSON(fromJSON(needs.determine-jobs.outputs.memory_impact).components) }}'
          platform="${{ fromJSON(needs.determine-jobs.outputs.memory_impact).platform }}"
-          found=false
+          missing=""
          for component in $(echo "$components" | jq -r '.[]'); do
-            # Check for test files matching the platform (test.platform.yaml or test-*.platform.yaml)
-            for f in tests/components/${component}/test*.${platform}.yaml; do
-              if [ -f "$f" ]; then
-                found=true
-                break 2
-              fi
-            done
+            if [ ! -f "tests/components/${component}/test.${platform}.yaml" ]; then
+              missing="${missing} ${component}"
+            fi
          done
-          if [ "$found" = false ]; then
+          if [ -n "$missing" ]; then
            echo "skip=true" >> $GITHUB_OUTPUT
-            echo "::warning::No test files found on target branch for platform ${platform}, skipping memory impact analysis"
+            echo "::warning::No test.${platform}.yaml on target branch for${missing}, skipping memory impact analysis"
          else
            echo "skip=false" >> $GITHUB_OUTPUT
          fi
@@ -1231,12 +1602,9 @@ jobs:
          python-version: ${{ env.DEFAULT_PYTHON }}
          cache-key: ${{ needs.common.outputs.cache-key }}

-      - name: Cache platformio
-        if: steps.check-script.outputs.skip != 'true' && steps.check-tests.outputs.skip != 'true' && steps.cache-memory-analysis.outputs.cache-hit != 'true'
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-        with:
-          path: ~/.platformio
-          key: platformio-memory-${{ fromJSON(needs.determine-jobs.outputs.memory_impact).platform }}-${{ hashFiles('platformio.ini') }}
+      - name: Cache the native ESP8266 toolchain
+        if: steps.check-script.outputs.skip != 'true' && steps.check-tests.outputs.skip != 'true' && steps.cache-memory-analysis.outputs.cache-hit != 'true' && fromJSON(needs.determine-jobs.outputs.memory_impact).needs_arduino8266
+        uses: ./.github/actions/cache-arduino8266

      - name: Build, compile, and analyze memory
        if: steps.check-script.outputs.skip != 'true' && steps.check-tests.outputs.skip != 'true' && steps.cache-memory-analysis.outputs.cache-hit != 'true'
@@ -1296,7 +1664,7 @@ jobs:
          fi

      - name: Upload memory analysis JSON
-        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
          name: memory-analysis-target
          path: memory-analysis-target.json
@@ -1321,11 +1689,9 @@ jobs:
        with:
          python-version: ${{ env.DEFAULT_PYTHON }}
          cache-key: ${{ needs.common.outputs.cache-key }}
-      - name: Cache platformio
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
-        with:
-          path: ~/.platformio
-          key: platformio-memory-${{ fromJSON(needs.determine-jobs.outputs.memory_impact).platform }}-${{ hashFiles('platformio.ini') }}
+      - name: Cache the native ESP8266 toolchain
+        if: fromJSON(needs.determine-jobs.outputs.memory_impact).needs_arduino8266
+        uses: ./.github/actions/cache-arduino8266
      - name: Build, compile, and analyze memory
        id: extract
        run: |
@@ -1361,7 +1727,7 @@ jobs:
            --platform "$platform"

      - name: Upload memory analysis JSON
-        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
          name: memory-analysis-pr
          path: memory-analysis-pr.json
@@ -1391,13 +1757,13 @@ jobs:
          python-version: ${{ env.DEFAULT_PYTHON }}
          cache-key: ${{ needs.common.outputs.cache-key }}
      - name: Download target analysis JSON
-        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
        with:
          name: memory-analysis-target
          path: ./memory-analysis
        continue-on-error: true
      - name: Download PR analysis JSON
-        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
        with:
          name: memory-analysis-pr
          path: ./memory-analysis
@@ -1423,6 +1789,8 @@ jobs:
    # this check.
    needs:
      - common
+      - seed-apt-cache
+      - seed-esp8266-native-cache
      - determine-jobs
      - ci-custom
      - pylint
@@ -1438,6 +1806,8 @@ jobs:
      - clang-tidy-esp32-variants
      - test-build-components-split
      - test-esp32-platformio
+      - test-esp8266-native
+      - test-esp8266-native-windows
      - device-builder
      - memory-impact-target-branch
      - memory-impact-pr-branch
@@ -35,7 +35,7 @@ jobs:

      - name: Generate a token
        id: generate-token
-        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
        with:
          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
@@ -56,7 +56,7 @@ jobs:

      # Initializes the CodeQL tools for scanning.
      - name: Initialize CodeQL
-        uses: github/codeql-action/init@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/init@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
        with:
          languages: ${{ matrix.language }}
          build-mode: ${{ matrix.build-mode }}
@@ -84,6 +84,6 @@ jobs:
          exit 1

      - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/analyze@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
        with:
          category: "/language:${{matrix.language}}"
@@ -15,7 +15,7 @@ jobs:
    steps:
      - name: Generate a token
        id: generate-token
-        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
        with:
          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
@@ -125,14 +125,20 @@ jobs:
            }

            async function getEsphomeAndComponentChanges(github, owner, repo, prNumber) {
-                const changedFiles = await github.rest.pulls.listFiles({
-                    owner: owner,
-                    repo: repo,
-                    pull_number: prNumber,
-                });
+                const changedFiles = await github.paginate(
+                    github.rest.pulls.listFiles,
+                    {
+                        owner: owner,
+                        repo: repo,
+                        pull_number: prNumber,
+                        per_page: 100,
+                    }
+                );

-                const esphomeChanges = changedFiles.data
-                    .filter(file => file.filename !== "esphome/core/defines.h" && file.filename.startsWith('esphome/'))
+                // Files used only for development and CI, which do not affect use as an external component
+                const ignoredFiles = ["esphome/core/defines.h", "esphome/idf_component.yml"];
+                const esphomeChanges = changedFiles
+                    .filter(file => !ignoredFiles.includes(file.filename) && file.filename.startsWith('esphome/'))
                    .map(file => {
                        const match = file.filename.match(/esphome\/([^/]+)/);
                        return match ? match[1] : null;
@@ -144,7 +150,7 @@ jobs:
                }

                const uniqueEsphomeChanges = [...new Set(esphomeChanges)];
-                const componentChanges = changedFiles.data
+                const componentChanges = changedFiles
                    .filter(file => file.filename.startsWith('esphome/components/'))
                    .map(file => {
                        const match = file.filename.match(/esphome\/components\/([^/]+)\//);
@@ -14,4 +14,4 @@ jobs:
    permissions:
      issues: write         # issues.lock on closed issues
      pull-requests: write  # issues.lock on closed pull requests
-    uses: esphome/workflows/.github/workflows/lock.yml@9f6577fd37b5cf773ab1b9be929714a0dcd15661  # 2026.7.0
+    uses: esphome/workflows/.github/workflows/lock.yml@cc3e76de337dc59bc1cba8da58d963cd23b873f1  # 2026.9.0
@@ -123,7 +123,7 @@ jobs:
          python-version: "3.12"

      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@594f3bf4285d9ea8dc53c9a0c9c4092420091003 # v4.4.0

      - name: Log in to docker hub
        uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
@@ -162,7 +162,7 @@ jobs:
      #     version: ${{ needs.init.outputs.tag }}

      - name: Upload digests
-        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
        with:
          name: digests-${{ matrix.platform.arch }}
          path: /tmp/digests
@@ -195,14 +195,14 @@ jobs:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1

      - name: Download digests
-        uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
        with:
          pattern: digests-*
          path: /tmp/digests
          merge-multiple: true

      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@594f3bf4285d9ea8dc53c9a0c9c4092420091003 # v4.4.0

      - name: Log in to docker hub
        if: matrix.registry == 'dockerhub'
@@ -245,7 +245,7 @@ jobs:
    steps:
      - name: Generate a token
        id: generate-token
-        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
        with:
          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
@@ -16,16 +16,18 @@ jobs:
    # No GITHUB_TOKEN permissions: the reusable workflow mints an ESPHome
    # GitHub App token so the labels, comments and closures come from
    # esphome[bot] instead of github-actions[bot].
-    uses: esphome/workflows/.github/workflows/stale.yml@61fd37a044cad4e9aa4303027b2a61b6a34da855  # main
+    uses: esphome/workflows/.github/workflows/stale.yml@4fbce13026c393d6eb6b247e394dcd9ef1af76c2  # main
    secrets:
      ESPHOME_GITHUB_APP_PRIVATE_KEY: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
    with:
      # Live only on dev: a workflow_dispatch from any other branch is a dry run
      dry-run: ${{ github.ref != 'refs/heads/dev' }}
      days-before-stale: 90
+      days-before-stale-conflicting: 30
      days-before-close: 7
      stale-label: stale
      exempt-label: not-stale
+      conflict-label: has-conflicts
      ignored-users: esphbot,codecov-commenter
      stale-pr-message: >
        There hasn't been any activity on this pull request recently. This
@@ -33,9 +35,21 @@ jobs:
        and will be closed if no further activity occurs within 7 days.

        If you are the author of this PR, please leave a comment if you want
-        to keep it open. Also, please rebase your PR onto the latest dev
+        to keep it open. Also, please merge the latest dev branch into your
        branch to ensure that it's up to date with the latest changes.

+        Thank you for your contribution!
+      conflict-pr-message: >
+        This pull request has merge conflicts. Please merge the latest dev
+        branch into your branch to resolve them.
+      stale-conflicting-pr-message: >
+        The merge conflicts on this pull request have not been resolved for
+        30 days, so it has been marked as stale and will be closed if they
+        are not resolved within 7 days.
+
+        Please merge the latest dev branch into your branch. Once the pull
+        request is mergeable again the stale label is removed.
+
        Thank you for your contribution!
      stale-issue-message: >
        There hasn't been any activity on this issue recently. Due to the
@@ -7,10 +7,6 @@ on:
 permissions:
  pull-requests: read  # issues.listLabelsOnIssue to detect blocking labels (needs-docs, needs-developer-docs, merge-after-release, chained-pr)

-concurrency:
-  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
-  cancel-in-progress: true
-
 jobs:
  check:
    name: Check blocking labels
@@ -0,0 +1,96 @@
+# Keeps pre-commit hook revs in sync with the requirements files.
+#
+# Dependabot only bumps the pins in requirements*.txt. Some of those tools
+# are pinned again as hook revs in .pre-commit-config.yaml. This workflow
+# runs script/sync_dependency_versions.py against the pull request branch
+# and pushes a commit with the revs updated.
+
+name: Sync dependency versions
+
+on:
+  # pull_request_target rather than pull_request so the App secret is
+  # available on Dependabot pull requests (pull_request runs opened by
+  # Dependabot only see Dependabot secrets). The job below only touches
+  # branches in this repository and only ever executes the script from the
+  # base branch checkout, so fork code never runs with the token.
+  pull_request_target:
+    types: [opened, synchronize, reopened]
+    branches:
+      - dev
+    paths:
+      - requirements_dev.txt
+      - requirements_test.txt
+      - .pre-commit-config.yaml
+      - script/sync_dependency_versions.py
+
+# The push to the pull request branch uses the App token minted below, so
+# the workflow's GITHUB_TOKEN does not need any scopes.
+permissions: {}
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  sync:
+    name: Sync pinned versions
+    runs-on: ubuntu-latest
+    # Same-repository branches only: a push to a fork is not possible with
+    # this token, and it keeps untrusted heads out of a privileged job.
+    if: >-
+      github.repository == 'esphome/esphome'
+      && github.event.pull_request.head.repo.full_name == github.repository
+    steps:
+      - name: Generate a token
+        id: generate-token
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
+        with:
+          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
+          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
+          # A push made with the workflow's own GITHUB_TOKEN would not start
+          # CI on the new commit; a push with the App token does.
+          permission-contents: write  # git push of the sync commit to the pull request branch
+
+      - name: Check out base branch
+        # Provides the script that runs below. Deliberately the base branch
+        # so the pull request cannot change what executes here.
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: ${{ github.event.pull_request.base.sha }}
+          persist-credentials: false
+
+      - name: Check out pull request branch
+        # No allow-unsafe-pr-checkout here on purpose: checkout v7 only
+        # refuses heads that live in a different repository, and the job
+        # condition above already limits runs to same-repository branches.
+        # Leaving it off keeps that refusal as a backstop for fork heads.
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: ${{ github.event.pull_request.head.ref }}
+          path: pull-request
+          token: ${{ steps.generate-token.outputs.token }}
+
+      - name: Set up Python
+        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        with:
+          python-version: "3.12"
+
+      - name: Install yamlrocks
+        # The script edits YAML through yamlrocks. Take the pin from the
+        # base branch requirements so this workflow has no copy of its own.
+        run: pip install "$(grep -E '^yamlrocks==' requirements_test.txt | cut -d'#' -f1)"
+
+      - name: Sync pinned versions
+        run: python script/sync_dependency_versions.py --root pull-request
+
+      - name: Push changes
+        working-directory: pull-request
+        run: |
+          if git diff --quiet; then
+            echo "All pinned versions already match the requirements files."
+            exit 0
+          fi
+          git config user.name "esphome[bot]"
+          git config user.email "115708604+esphome[bot]@users.noreply.github.com"
+          git commit -am "Sync pinned tool versions with requirements files"
+          git push
@@ -19,7 +19,7 @@ jobs:
    steps:
      - name: Generate a token
        id: generate-token
-        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
        with:
          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
@@ -47,7 +47,7 @@ jobs:
        # setup-python interpreter so subsequent ``prek`` /
        # ``script/run-in-env.py`` steps find the deps without a
        # ``uv run`` prefix.
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@1c37ad07a6a961277cf70c0d37d6f313000f5884 # v10.3.0
        with:
          enable-cache: true
          # Pin uv version so the action does not have to fetch the
@@ -0,0 +1,98 @@
+---
+name: Refresh integration test durations
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "45 5 * * 1"
+
+# Repo writes (branch push, PR open) happen via the App token minted below,
+# so the workflow's GITHUB_TOKEN does not need any write scopes.
+permissions:
+  contents: read
+  actions: read  # gh api / gh run download for the CI junit artifacts
+
+jobs:
+  sync:
+    name: Refresh integration test durations
+    runs-on: ubuntu-latest
+    if: github.repository == 'esphome/esphome'
+    steps:
+      - name: Generate a token
+        id: generate-token
+        uses: actions/create-github-app-token@64ab729a6294000f5aa4a4bc0b73d1f32bc45510 # v3.3.0
+        with:
+          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
+          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
+          permission-contents: write       # push the sync branch
+          permission-pull-requests: write  # open or refresh the sync PR
+
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Setup Python
+        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        with:
+          python-version: "3.13"
+
+      - name: Refresh from the newest usable dev run
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          # Only full matrix dev runs upload junit-integration-* artifacts
+          # (see the integration-tests job); the merge script re-checks
+          # coverage regardless.
+          # Newest-first candidates via their bucket-0 artifact. Fork PRs run
+          # their own ci.yml, so name and branch are spoofable; require
+          # same-repo. Assignment failures trip set -e and fail loudly.
+          candidates=$(
+            gh api "repos/${GITHUB_REPOSITORY}/actions/artifacts?name=junit-integration-0&per_page=100" \
+              --jq '.artifacts[] | select(.expired | not) | .workflow_run
+                    | select(.head_branch == "dev" and .head_repository_id != null
+                             and .head_repository_id == .repository_id)
+                    | .id'
+          )
+          # Green runs first, then the rest newest first; a run missing a
+          # bucket fails the coverage check and the next one is tried
+          green=""
+          rest=""
+          for id in ${candidates}; do
+            conclusion=$(gh api "repos/${GITHUB_REPOSITORY}/actions/runs/${id}" --jq '.conclusion // ""')
+            if [ "${conclusion}" = "success" ]; then
+              green="${green} ${id}"
+            elif [ -n "${conclusion}" ]; then
+              rest="${rest} ${id}"
+            fi
+          done
+          # helpers.py imports colorama; the script needs nothing else
+          pip install colorama
+          for id in ${green} ${rest}; do
+            rm -rf /tmp/junit
+            if ! gh run download "${id}" --repo "${GITHUB_REPOSITORY}" -p "junit-integration-*" -D /tmp/junit; then
+              echo "::warning::Could not download artifacts for run ${id}; trying the next"
+              continue
+            fi
+            status=0
+            python script/update_integration_test_durations.py /tmp/junit || status=$?
+            if [ "${status}" -eq 0 ]; then
+              echo "Refreshed from run ${id}"
+              exit 0
+            fi
+            # Only EXIT_LOW_COVERAGE (3) from the script advances to the next run
+            [ "${status}" -eq 3 ] || exit 1
+            echo "::warning::Run ${id} covers too few test files; trying the next"
+          done
+          echo "::error::No dev CI run with usable junit artifacts in range; the feed is starved"
+          exit 1
+
+      - name: Commit changes
+        uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v8.1.1
+        with:
+          commit-message: "[ci] Refresh integration test durations"
+          committer: esphome[bot] <115708604+esphome[bot]@users.noreply.github.com>
+          author: esphome[bot] <115708604+esphome[bot]@users.noreply.github.com>
+          branch: sync/integration-durations
+          delete-branch: true
+          title: "[ci] Refresh integration test durations"
+          body-path: .github/PULL_REQUEST_TEMPLATE.md
+          token: ${{ steps.generate-token.outputs.token }}
@@ -137,6 +137,8 @@ config/
 !tests/component_tests/**/config/
 tests/build/
 tests/.esphome/
+# Output kept by failing tests for inspection; uploaded by CI
+test_artifacts/
 /.temp-clang-tidy.cpp
 /.temp/
 .pio/
@@ -1,7 +1,6 @@
 ---
 # See https://pre-commit.com for more information
 # See https://pre-commit.com/hooks.html for more hooks
-
 ci:
  autoupdate_commit_msg: 'pre-commit: autoupdate'
  autoupdate_schedule: off  # Disabled until ruff versions are synced between deps and pre-commit
@@ -11,7 +10,7 @@ ci:
 repos:
  - repo: https://github.com/astral-sh/ruff-pre-commit
    # Ruff version.
-    rev: v0.16.0
+    rev: v0.17.0
    hooks:
      # Run the linter.
      - id: ruff
@@ -19,7 +18,7 @@ repos:
      # Run the formatter.
      - id: ruff-format
  - repo: https://github.com/PyCQA/flake8
-    rev: 7.3.0
+    rev: 7.4.1
    hooks:
      - id: flake8
        additional_dependencies:
@@ -37,12 +36,12 @@ repos:
      - id: end-of-file-fixer
      - id: trailing-whitespace
  - repo: https://github.com/asottile/pyupgrade
-    rev: v3.21.2
+    rev: v3.22.0
    hooks:
      - id: pyupgrade
        args: [--py312-plus]
  - repo: https://github.com/adrienverge/yamllint.git
-    rev: v1.37.1
+    rev: v1.38.0
    hooks:
      - id: yamllint
        exclude: ^(\.clang-format|\.clang-tidy)$
@@ -44,6 +44,16 @@ This document provides essential context for AI models interacting with this pro

 ## 4. Coding Conventions & Style Guide

+**Read the developer documentation before writing a component.** https://developers.esphome.io covers the
+component lifecycle, the main loop, and the reasoning behind the rules below in far more depth than this
+file does, and it is the authority when they disagree. The most useful starting points:
+
+*   https://developers.esphome.io/architecture/components/ - component lifecycle, `setup()`, `loop()`,
+    setup priorities, and how a component is registered.
+*   https://developers.esphome.io/architecture/components/advanced/ - choosing between `loop()`,
+    `set_interval`, `set_timeout` and `defer`; waking the loop from another thread; the RAM cost of each.
+*   https://developers.esphome.io/contributing/code/ - contribution rules, public API and breaking changes.
+
 *   **Formatting:**
    *   **Python:** Uses `ruff` and `flake8` for linting and formatting. Configuration is in `pyproject.toml`.
    *   **C++:** Uses `clang-format` for formatting. Configuration is in `.clang-format`.
@@ -57,6 +67,7 @@ This document provides essential context for AI models interacting with this pro
        - Function-local constants: `lower_snake_case`
        - Protected/private fields: `lower_snake_case_with_trailing_underscore_`
        - Favor descriptive names over abbreviations
+        - Device components are named brand plus model (`siemens_ira211`), without a protocol-family prefix
        - Enumerator names: prefix every value of an `enum class` with the enum name converted to
          `UPPER_SNAKE_CASE` (e.g. `UARTFlushResult::UART_FLUSH_RESULT_SUCCESS`). Never use bare
          names like `SUCCESS`, `FAILURE`, `OK`, or `FAIL`: platform SDK headers define macros with
@@ -133,6 +144,9 @@ This document provides essential context for AI models interacting with this pro

 *   **C++ Preprocessor Directives:**
    *   **Avoid `#define` for constants:** Using `#define` for constants is discouraged and should be replaced with `const` variables or enums.
+    *   **A constant with a compile-time initializer is `static constexpr`,** not `static const`, at namespace scope
+        and inside functions; `static const` is only for a value computed at run time. A function-local
+        `static constexpr` table is a static constant to clang-tidy, so it is `UPPER_SNAKE_CASE` too.
    *   **Use `#define` only for:**
        - Conditional compilation (`#ifdef`, `#ifndef`)
        - Compile-time sizes calculated during Python code generation (e.g., configuring `std::array` or `StaticVector` dimensions via `cg.add_define()`)
@@ -142,6 +156,95 @@ This document provides essential context for AI models interacting with this pro
    *   **Indentation:** Use spaces (two per indentation level), not tabs
    *   **Type aliases:** Prefer `using type_t = int;` over `typedef int type_t;`
    *   **Line length:** Wrap lines at no more than 120 characters
+    *   **Timing in `loop()`:** Never call `millis()` in a `loop()` body. The current tick's timestamp is
+        already cached - use `App.get_loop_component_start_time()` (from `esphome/core/application.h`).
+        Only reach for `millis()` when you genuinely need sub-tick resolution inside a long operation.
+    *   **The main loop runs every 16 ms.** A rate-limit gate shorter than that does nothing: the check
+        passes on essentially every pass of the loop, so it costs a comparison and buys nothing. Pick an
+        interval comfortably coarser than 16 ms, or drop the gate entirely and accept running every loop.
+        ```cpp
+        // Bad - a 10ms gate against a 16ms loop never holds anything back
+        static constexpr uint32_t POLL_INTERVAL_MS = 10;
+        const uint32_t now = millis();
+        if (now - this->last_poll_ < POLL_INTERVAL_MS)
+          return;
+        this->last_poll_ = now;
+        ```
+        ```cpp
+        // Good - an interval that actually rate limits, off the cached timestamp
+        static constexpr uint32_t POLL_INTERVAL_MS = 100;
+        const uint32_t now = App.get_loop_component_start_time();
+        if (now - this->last_poll_ < POLL_INTERVAL_MS)
+          return;
+        this->last_poll_ = now;
+        ```
+        Pick the primitive by cadence: under 250 ms use a gated `loop()`; 500 ms and above use
+        `set_interval`. Full reasoning, including why `set_interval` costs more below 500 ms:
+        https://developers.esphome.io/architecture/components/advanced/#quick-rule-of-thumb
+    *   **Repeating work:** use `set_interval`, never a `set_timeout` that re-arms itself; every re-arm
+        rebuilds the callback and re-queues a scheduler item, and the period drifts.
+    *   **Scheduler ids:** name a timer only when it must be cancelled or replaced, and use a
+        `static constexpr uint32_t` id, never a string. Ids are per component instance and cannot clash with other
+        components, so number them from 0 and keep all of a component's ids together in one place.
+        ```cpp
+        static constexpr uint32_t READ_TIMEOUT_ID = 0;
+        this->set_timeout(READ_TIMEOUT_ID, 50, [this]() { this->read_(); });
+        ```
+    *   **Don't override a default with the same value:** if a base class method already returns what you
+        want, do not override it. `Component::get_setup_priority()` returns `setup_priority::DATA`, so a
+        component that wants `DATA` should simply leave it alone.
+        ```cpp
+        // Bad - this is exactly what the base class already does
+        float get_setup_priority() const override { return setup_priority::DATA; }
+        ```
+    *   **Constant data lives in RAM on ESP8266** unless marked `PROGMEM`: `const` tables, class-scope
+        constant arrays, and in-class `std::array` initializers (a `.rodata` template plus a copy). Mark the
+        table `PROGMEM` and read it with `progmem_memcpy()` or `progmem_read_byte()` (`esphome/core/hal.h`);
+        for a table of structs copy the whole entry out and return the copy, never a pointer into flash.
+        On other platforms they are a plain `memcpy` and dereference, so no `#ifdef` is needed. Declare log tags with
+        `ESPHOME_LOG_TAG(TAG, "name")`, pass status text as `LOG_STR`, e.g.
+        `this->mark_failed(LOG_STR(ESP_LOG_MSG_COMM_FAIL))`, and give an action whose payload is a byte array
+        a `TEMPLATABLE_BYTES` field so a static code stays in flash.
+    *   **Fixed sets of names** (status words, model names): a `PROGMEM_STRING_TABLE` (`esphome/core/progmem.h`),
+        logged with `get_log_str` and `LOG_STR_ARG`, copied out with `ESPHOME_strncpy_P` before `publish_state`.
+        A `dump_config` helper that picks a name returns `const LogString *` from `LOG_STR(...)`.
+    *   **CRCs and bit tricks** come from `esphome/core/helpers.h` (`crc8`, `crc16`, `reverse_bits`, `encode_uint16`);
+        pick the helper's polynomial and bit-order arguments instead of writing a CRC loop.
+    *   **An unset float is `NAN`**, not `optional<float>`; the optional costs 4 to 8 bytes of padding per member.
+    *   **`PollingComponent` first runs `update()`** after a random share of the interval; call `this->update()` at the
+        end of `setup()` when the entities need a state at boot.
+    *   **A multi-step command sequence** leaves the step pending when the answer is malformed, so the existing
+        resend and give-up logic handles it; never advance on an answer that was only logged.
+    *   **Entities that each watch a register field:** one class taking register, shift, mask and match from a Python
+        tuple table, in typed `StaticVector`s sized by `cg.slot_counter`; not a template per bit, not a virtual
+        listener base (a second vptr per entity).
+    *   **A global feature define** says the code is compiled in, not that this instance uses it: keep the
+        per-instance check (`if (this->aux_device_ == ...)`) inside the `#ifdef`.
+    *   **Model-specific code** sits behind a define the Python side emits only for configs that use that model
+        (`cg.add_define("USE_SELEC_METER_EM4M")`), so the other models' builds leave it out; the runtime model check
+        stays inside the `#ifdef`.
+    *   **Failures after `setup()`:** `mark_failed()` is for `setup()` only. A runtime read or write failure
+        sets `status_set_warning()` and the next success clears it; writes skip work when `is_failed()`.
+    *   **`dump_config()` already prints the failure reason:** for a failed component, core prints
+        `<component> is marked FAILED: <reason>` right after the component's `dump_config()`, using the reason
+        passed to `mark_failed()`. So `dump_config()` never checks `is_failed()` to log a failure, and no
+        `error_code_` member exists only to pick that message. Pass the reason where setup fails instead:
+        `this->mark_failed(LOG_STR(ESP_LOG_MSG_COMM_FAIL))` for a failed bus transfer, a short specific reason
+        otherwise (`LOG_STR("Wrong chip ID")`). Core also logs it at that moment, so no `ESP_LOGE` repeats it
+        before `mark_failed()`; keep a separate line only when it prints a value read at run time, such as the
+        chip ID that did not match. Only the first reason is kept, so do not call `status_set_error()` before
+        `mark_failed()` and do not mark the component failed again after a helper already did.
+    *   **Fixed platform facts compile to nothing:** gate on `#ifdef USE_ESP8266` and friends, not on a
+        runtime check of something the build already knows.
+    *   **Logging string literals:** wrap literals passed as `%s` arguments in `LOG_STR_LITERAL()` so they
+        can be stored in flash rather than RAM.
+        ```cpp
+        // Bad
+        ESP_LOGV(TAG, "Key %u %s", key, pressed ? "pressed" : "released");
+
+        // Good
+        ESP_LOGV(TAG, "Key %u %s", key, pressed ? LOG_STR_LITERAL("pressed") : LOG_STR_LITERAL("released"));
+        ```
    *   **Constructor parameters vs setters:** Component properties that are both **required** and **invariant**
        (never change after construction) should be constructor parameters rather than set via setter methods.
        This makes the dependency explicit and prevents use of the object in an incompletely-initialized state.
@@ -179,8 +282,13 @@ This document provides essential context for AI models interacting with this pro
        ```

    *   **Component Metadata:**
+        - `DOMAIN`: Required in every component's `__init__.py`, set to the component's own name as a plain
+          string (e.g. `DOMAIN = "my_component"`). Other code refers to the component through it, e.g.
+          `from esphome.components.my_component import DOMAIN`. Keep it in alphabetical order with the other
+          metadata constants. CI (`lint_component_domain`) fails without it.
        - `DEPENDENCIES`: List of required components
-        - `AUTO_LOAD`: Components to automatically load
+        - `AUTO_LOAD`: Components to automatically load. Not a way to put entities under the component's
+          own key; see "Entities of a hub" below.
        - `CONFLICTS_WITH`: Incompatible components
        - `CODEOWNERS`: GitHub usernames responsible for maintenance
        - `MULTI_CONF`: Whether multiple instances are allowed
@@ -192,6 +300,7 @@ This document provides essential context for AI models interacting with this pro
        import esphome.config_validation as cv
        from esphome.const import CONF_KEY, CONF_ID

+        DOMAIN = "my_component"
        CONF_PARAM = "param"  # A constant that does not yet exist in esphome/const.py

        my_component_ns = cg.esphome_ns.namespace("my_component")
@@ -271,6 +380,55 @@ This document provides essential context for AI models interacting with this pro
              var = await switch.new_switch(config)
          ```

+        - **Entities of a hub:** a new component's entities go in platform files (`sensor.py`,
+          `binary_sensor.py`, ...) that take the hub's id, never under the hub's own key with their platforms
+          added to `AUTO_LOAD` to make that work. Auto loading a platform because the C++ uses its type is
+          fine. See https://developers.esphome.io/architecture/components/#exposing-multiple-entities.
+          ```yaml
+          # Bad - entities under the hub's key
+          my_hub:
+            connected:
+              name: Connected
+
+          # Good - the hub, then one platform entry that holds its entities
+          my_hub:
+            id: hub1
+          binary_sensor:
+            - platform: my_hub
+              my_hub_id: hub1  # optional with a single hub
+              connected:
+                name: Connected
+          ```
+
+        - **Optional child entities of a hub:** bind the config once with `sensor.sub_sensors(config)` (or
+          `sub_binary_sensors`, `sub_text_sensors`, `sub_buttons`, `sub_switches`, `sub_numbers`,
+          `sub_selects` in their domains), adding `parent=hub` for entities that derive from `Parented<T>`,
+          then make one call per key, even when there is only one. A call creates the entity only when its key
+          is configured, passes it to the setter and returns it (or `None`); extra arguments such as
+          `min_value` or `options` go on the call. Always name the setter explicitly on the object that owns
+          it, never with `getattr` and an f-string, and keep that variable short (`var` for the component
+          itself, `hub` for one fetched with `cg.get_variable`) so the calls fit on one line. Loops whose
+          setter also takes an index, such as `set_gate_threshold(x, n)`, stay as they are.
+          ```python
+          # my_hub/sensor.py
+          async def to_code(config):
+              hub = await cg.get_variable(config[CONF_MY_HUB_ID])
+              sensors = sensor.sub_sensors(config)
+              await sensors(CONF_TEMPERATURE, hub.set_temperature_sensor)
+              await sensors(CONF_HUMIDITY, hub.set_humidity_sensor)
+
+
+          # my_hub/button.py
+          async def to_code(config):
+              hub = await cg.get_variable(config[CONF_MY_HUB_ID])
+              buttons = button.sub_buttons(config, parent=hub)
+              await buttons(CONF_RESTART, hub.set_restart_button)
+          ```
+
+        - **Pins and referenced components:** set them with `await cg.add_pin(var.set_cs_pin, config[CONF_CS_PIN])`
+          and `await cg.add_variable(var.set_bus, config[CONF_BUS_ID])`; both skip a `None` value, so pass
+          `config.get(KEY)` for an optional key, and return what they created. Use `cg.register_parented` for `set_parent`.
+
 *   **Automations (Triggers, Actions, Conditions):**

    Automations have three building blocks: **Triggers** (fire when something happens), **Actions** (do something), and **Conditions** (check if something is true).
@@ -314,6 +472,25 @@ This document provides essential context for AI models interacting with this pro
                )
        ```

+        When the callback's parameters differ from the automation's arguments, or the trigger should only
+        fire for some values, pass `params`, `forward` and `when`; the helper then generates a capture-less
+        lambda (stored inline, nothing allocated). Name the parent with `automation.parent_ref(var)` and build
+        `forward` from `MockObj` calls, not f-strings of C++:
+        ```python
+        parent = automation.parent_ref(var)
+        index = cg.RawExpression("index")
+        await automation.build_callback_automation(
+            var,
+            "add_on_state_callback",
+            [(cg.StringRef, "x"), (cg.size_t, "i")],
+            conf,
+            params=[(cg.size_t, "index")],
+            forward=[cg.StringRef(parent.option_at(index)), index],
+        )
+        ```
+        `build_parent_callback_automation`, `build_trigger_callback`, `build_callback_automations` and
+        `build_trigger_automations` cover the other shapes; see their docstrings in `esphome/automation.py`.
+
        **C++ -- no trigger class needed.** The callback registration method must be templatized to accept both `std::function` and lightweight forwarder structs (which avoid heap allocation):
        ```cpp
        class MyComponent : public Component {
@@ -380,7 +557,31 @@ This document provides essential context for AI models interacting with this pro
          MyComponent *parent_;
        };
        ```
-        Register with `@automation.register_action("my_component.do_something", MyAction, schema, synchronous=True)`. Use `synchronous=True` for actions that run to completion inside `play()` without deferring. Use `synchronous=False` if the action may suspend/defer execution (e.g. `delay`, `wait_until`, `script.wait`) or store trigger arguments for later use.
+        Register it without writing a builder:
+        ```python
+        automation.register_simple_action(
+            "my_component.do_something", MyAction, schema, synchronous=True
+        )
+        ```
+        The constructor receives the object named by `config[CONF_ID]`. Use `register_bare_action` for a
+        no-argument constructor, `register_parented_action` for a class deriving from `Parented<T>`, and
+        the `@automation.register_action(...)` decorator only when the builder must also set fields.
+
+        Use `synchronous=True` for actions that run to completion inside `play()` without deferring. Use `synchronous=False` if the action may suspend/defer execution (e.g. `delay`, `wait_until`, `script.wait`) or store trigger arguments for later use.
+
+        **Actions that only forward templatable values to their parent need no C++ class.** Register them
+        with `register_apply_action`; do not write a `TEMPLATABLE_VALUE` class or a builder for this shape.
+        ```python
+        automation.register_apply_action(
+            "my_component.set_gains",
+            schema,
+            automation.ApplyField(CONF_KP, "set_kp", cg.float_),
+            automation.ApplyField(CONF_KI, "set_ki", cg.float_),
+        )
+        ```
+        The `ApplyField`, `ApplyCall` and `register_apply_action` docstrings in `esphome/automation.py` cover
+        the rest; `cover.control` and `cover.template.publish` are in-tree examples. `TEMPLATABLE_VALUE` with
+        `cg.templatable` stays for actions whose `play()` has real logic beyond forwarding values.

    *   **Conditions:**
        ```cpp
@@ -392,11 +593,29 @@ This document provides essential context for AI models interacting with this pro
          MyComponent *parent_;
        };
        ```
-        Register with `@automation.register_condition("my_component.is_active", MyCondition, schema)`.
+        Register with `automation.register_simple_condition("my_component.is_active", MyCondition, schema)`;
+        `register_bare_condition`, `register_parented_condition` and the decorator follow the action rules.
+
+        **Conditions that only test their parent need no C++ class either.** Register them with
+        `register_apply_condition`; the expression is applied to the parent, and an `ApplyCall` compares
+        against config values.
+        ```python
+        automation.register_apply_condition("my_component.is_active", schema, "is_active()")
+        automation.register_apply_condition(
+            "my_component.state_is",
+            schema,
+            automation.ApplyCall("state == {}", ((CONF_STATE, cg.bool_),)),
+        )
+        ```
+        `cover.is_open`, `rtttl.is_playing` and `component.is_idle` are in-tree examples.

 *   **Type Hints:** Type-hint all function signatures, including test functions and config validators (e.g. `def validate_x(config: ConfigType) -> ConfigType:`, `def test_x() -> None:`). Import `ConfigType` from `esphome.types`.
+    An intentionally empty body (an unused `register_dumper` builder, for example) gets a one-line docstring, not `pass`.

 *   **Configuration Validation:**
+    *   **One schema per model:** when a component's options depend on a `model` key, use `cv.typed_schema({...},
+        key=CONF_MODEL, default_type=...)` with each model's own keys and defaults, not one schema plus a validator
+        that rejects keys and fills defaults afterwards.
    *   **Reuse existing validators:** Before writing a custom validator, check for an existing one in `config_validation.py` and compose it in `cv.All(...)` rather than duplicating logic across components. For example, rename a config key with `cv.rename_key(CONF_OLD, CONF_NEW, removed_in="2026.6.0")`, and reject mutually-exclusive keys with `cv.has_at_most_one_key(...)` / `cv.has_exactly_one_key(...)`. See how `api` composes `cv.has_exactly_one_key` + `cv.rename_key`.
    *   **Common Validators:** `cv.int_`, `cv.float_`, `cv.string`, `cv.boolean`, `cv.int_range(min=0, max=100)`, `cv.positive_int`, `cv.percentage`.
    *   **Complex Validation:** `cv.All(cv.string, cv.Length(min=1, max=50))`, `cv.Any(cv.int_, cv.string)`.
@@ -430,6 +649,18 @@ This document provides essential context for AI models interacting with this pro
 *   **Testing:**
    *   **Python:** Run unit tests with `pytest`.
    *   **C++:** Use `clang-tidy` for static analysis.
+    *   **C++ unit tests:** gtests in `tests/components/<component>/*.cpp`, run with
+        `script/cpp_unit_test.py <component>`; see `tests/components/README.md`. Set the loop clock in a test
+        with `LoopBlockingGuard{nullptr, nullptr, now_ms}`; the runner resets it before every test.
+    *   **Integration tests:** `tests/integration/` runs real firmware on the host. Serial components prove
+        timeouts and recovery with the `uart_mock` fixture (`tests/integration/test_uart_mock_*.py`). Its
+        `responses` match on content every time they see it; to answer a repeated request differently, use an
+        `on_tx` lambda with a static counter and `inject_to_rx_buffer` (see `uart_mock_ld2412_requery_after_giveup.yaml`).
+    *   **Keep build-test variants few:** one `test.<platform>.yaml` per platform the code actually differs
+        on. A variant per board for platform-identical code only adds CI time.
+    *   **A test that needs a shared component in a particular state** (`esp32_ble` security settings, an option
+        that PSRAM rejects) cannot be grouped: the merged block wins and the whole batch fails. Add the component to
+        `ISOLATED_COMPONENTS` in `script/analyze_component_buses.py`, or move the option to a `test-<variant>` file.
    *   **Component Tests:** YAML-based compilation tests are located in `tests/`. The structure is as follows:
        ```
        tests/
@@ -476,6 +707,7 @@ This document provides essential context for AI models interacting with this pro
            name: My Sensor
        ```
        Components that define buses directly are flagged as "NEEDS MIGRATION" and cannot be grouped, increasing CI build time.
+        `!extend` and `!remove` in a `test.*.yaml` also make the component ungroupable; add a standalone entity with its own id instead.

    *   **Testing All Components Together:** To verify that all components can be tested together without ID conflicts or configuration issues, use:
        ```bash
@@ -502,6 +734,7 @@ This document provides essential context for AI models interacting with this pro
    4.  **Lint:** Run `prek` to ensure code is compliant.
    5.  **Commit:** Commit your changes. There is no strict format for commit messages.
    6.  **Pull Request:** Submit a PR against the `dev` branch. The Pull Request title must start with a `[tag]` prefix. For component work, use the component name (e.g., `[display] Fix bug`, `[abc123] Add new component`); for changes to shared/core code that isn't tied to a single component, use `[core]` (e.g., `[core] Add validator`). Update documentation, examples, and add `CODEOWNERS` entries as needed. Pull requests should always be made using the `.github/PULL_REQUEST_TEMPLATE.md` template - fill out all sections completely without removing any parts of the template.
+    7.  **Comments:** When commenting on GitHub PRs or issues, don't tag contributors, especially bots. Avoid referring to list items (e.g. from reviews) with the form #nn - this will be interpreted by GitHub as a reference to issue or PR nn. Keep comments short and exclude irrelevant details, backstories, restatement of previous comments and anything that is already obvious to the reader.

 *   **Documentation Contributions:**
    *   Documentation is hosted in the separate `esphome/esphome.io` repository.
@@ -562,6 +795,36 @@ This document provides essential context for AI models interacting with this pro
           Use `cg.add_define("MAX_SERVICES", count)` to set the size from Python configuration.
           Like `std::array` but with vector-like API (`push_back()`, `size()`) and no STL reallocation code.

+           **Listener and child-entity registration lists are the most common case, and the most commonly
+           missed.** A `register_*()` method called once per child at code generation time has a count that
+           is known at compile time, so it should never be a `std::vector`. Use `cg.slot_counter()`: it
+           returns a function that each consumer calls once per slot it will occupy, and after every
+           `to_code` has run it emits the define with the final count. When nothing registers, no define is
+           emitted and the storage plus its registration method compile out entirely.
+           ```python
+           # hub component's __init__.py
+           _request_listener_slot = cg.slot_counter("MY_COMPONENT_LISTENER_COUNT")
+
+
+           async def register_listener(hub: MockObj, var: MockObj) -> None:
+               _request_listener_slot()
+               cg.add(hub.register_listener(var))
+           ```
+           When several instances each own a list declared at the same size (one per hub of a
+           `MULTI_CONF` component), pass the owning object as the key, `_request_listener_slot(str(hub))`;
+           the define is then the largest count any one key requested instead of the total.
+           ```cpp
+           #ifdef MY_COMPONENT_LISTENER_COUNT
+             void register_listener(MyComponentListener *listener);
+           #endif
+            protected:
+           #ifdef MY_COMPONENT_LISTENER_COUNT
+             StaticVector<MyComponentListener *, MY_COMPONENT_LISTENER_COUNT> listeners_;
+           #endif
+           ```
+           Request slots from `to_code`, not from a job that runs after `CoroPriority.FINAL` - a late
+           request raises rather than silently undercounting.
+
        3. **Runtime-known sizes:** Use `FixedVector` from `esphome/core/helpers.h` when the size is only known at runtime initialization.
           ```cpp
           // Bad - generates STL realloc code (_M_realloc_insert)
@@ -599,9 +862,27 @@ This document provides essential context for AI models interacting with this pro
           ```
           Linear search on small datasets (1-16 elements) is often faster than hashing/tree overhead, but this depends on lookup frequency and access patterns. For frequent lookups in hot code paths, the O(1) vs O(n) complexity difference may still matter even for small datasets. `std::vector` with simple structs is usually fine—it's the heavy containers (`map`, `set`, `unordered_map`) that should be avoided for small datasets unless profiling shows otherwise.

-        5. **Avoid `std::deque`:** It allocates in 512-byte blocks regardless of element size, guaranteeing at least 512 bytes of RAM usage immediately. This is a major source of crashes on memory-constrained devices.
+        5. **Strings set once from configuration:** Use `StringRef` (`esphome/core/string_ref.h`) rather than
+           `std::string`. Code generation passes a string literal that lives in flash for the life of the
+           program, so storing a `std::string` copies it onto the heap for nothing. `StringRef` is a
+           non-owning pointer plus length; it does not copy, and it must only ever refer to storage that
+           outlives it (a string literal, or a buffer owned elsewhere).
+           ```cpp
+           // Bad - heap copy of a literal that is already in flash
+           void set_keys(std::string keys) { this->keys_ = std::move(keys); }
+           std::string keys_;
+           ```
+           ```cpp
+           // Good - no allocation
+           void set_keys(const char *keys) { this->keys_ = StringRef(keys); }
+           StringRef keys_;
+           ```

-        6. **Detection:** Look for these patterns in compiler output:
+        6. **Avoid `std::deque`:** It allocates in 512-byte blocks regardless of element size, guaranteeing at least 512 bytes of RAM usage immediately. This is a major source of crashes on memory-constrained devices.
+
+        7. **Never use `new (std::nothrow)`:** On ESP-IDF exceptions are disabled, so a failed nothrow allocation aborts instead of returning `nullptr`. Use `RAMAllocator` from `esphome/core/helpers.h`; CI rejects `std::nothrow`.
+
+        8. **Detection:** Look for these patterns in compiler output:
           - Large code sections with STL symbols (vector, map, set)
           - `alloc`, `realloc`, `dealloc` in symbol names
           - `_M_realloc_insert`, `_M_default_append` (vector reallocation)
@@ -745,7 +1026,7 @@ This document provides essential context for AI models interacting with this pro
        cv.rename_key(
            CONF_OLD_KEY, CONF_NEW_KEY, removed_in="2026.6.0", component="my_component"
        ),
-        cv.Schema({ ... }),
+        cv.Schema({...}),
    )
    ```
    For other deprecations, warn manually during validation:
@@ -763,3 +1044,13 @@ The project uses English for non-code content. When drafting documentation, code
 PR descriptions, and similar text, avoid technical jargon. Instead, express concepts in plain English,
 using standard technical terms only when required. Ensure the text is readily comprehensible to a wide
 audience, including non-native English speakers.
+
+## 10. Code Comments
+
+Code comments on individual lines should be used only where necessary to flag issues that may not be obvious
+on a simple reading of the code. Keep them short (e.g. 1 or 2 lines).
+
+Function and method comment blocks may include more detail as required to make
+calling contracts clear and document parameter usage, but should still be kept concise.
+
+Avoid redundancy and repetition; comments should never simply restate what the code already says.
@@ -30,6 +30,9 @@ esphome/components/airthings_ble/* @jeromelaban
 esphome/components/airthings_wave_base/* @jeromelaban @ncareau
 esphome/components/airthings_wave_mini/* @ncareau
 esphome/components/airthings_wave_plus/* @jeromelaban @precurse
+esphome/components/airton/* @Procsiab
+esphome/components/airton/select/* @Procsiab
+esphome/components/airton/switch/* @Procsiab
 esphome/components/alarm_control_panel/* @grahambrown11 @hwstar
 esphome/components/alpha3/* @jan-hofmeier
 esphome/components/am2315c/* @swoboda1337
@@ -39,12 +42,17 @@ esphome/components/am43/sensor/* @buxtronix
 esphome/components/analog_threshold/* @ianchi
 esphome/components/animation/* @syndlex
 esphome/components/anova/* @buxtronix
+esphome/components/apc1/* @ademuri
+esphome/components/apc_proteous/* @clydebarrow
 esphome/components/apds9306/* @aodrenah
+esphome/components/apds9930/* @iyesin
 esphome/components/api/* @esphome/core
 esphome/components/aqi/* @freekode @jasstrong @ximex
+esphome/components/aranet/* @patrickod
 esphome/components/as5600/* @ammmze
 esphome/components/as5600/sensor/* @ammmze
 esphome/components/as7341/* @mrgnr
+esphome/components/as734x/* @latonita @mrgnr
 esphome/components/async_tcp/* @esphome/core
 esphome/components/at581x/* @X-Ryl669
 esphome/components/atc_mithermometer/* @ahpohl
@@ -65,6 +73,7 @@ esphome/components/bedjet/climate/* @jhansche
 esphome/components/bedjet/fan/* @jhansche
 esphome/components/bedjet/sensor/* @javawizard @jhansche
 esphome/components/beken_spi_led_strip/* @Mat931
+esphome/components/bh1745/* @latonita
 esphome/components/bh1750/* @OttoWinter
 esphome/components/bh1900nux/* @B48D81EFCC
 esphome/components/binary_sensor/* @esphome/core
@@ -100,6 +109,10 @@ esphome/components/bmp581_i2c/* @danielkent-net @kahrendt
 esphome/components/bmp581_spi/* @danielkent-net @kahrendt
 esphome/components/bp1658cj/* @Cossid
 esphome/components/bp5758d/* @Cossid
+esphome/components/bq25186/* @Rapsssito
+esphome/components/bq27220/* @rggammon
+esphome/components/bq76972/* @limpkin
+esphome/components/bridge/* @kbx81
 esphome/components/bthome_mithermometer/* @nagyrobi
 esphome/components/button/* @esphome/core
 esphome/components/bytebuffer/* @clydebarrow
@@ -111,6 +124,8 @@ esphome/components/captive_portal/* @esphome/core
 esphome/components/cc1101/* @gabest11 @lygris
 esphome/components/ccs811/* @habbie
 esphome/components/cd74hc4067/* @asoehlke
+esphome/components/cdc_acm_uart/* @kbx81
+esphome/components/cdc_acm_uart/bridge/* @kbx81
 esphome/components/ch422g/* @clydebarrow @jesterret
 esphome/components/ch423/* @dwmw2
 esphome/components/chsc6x/* @kkosik20
@@ -122,6 +137,7 @@ esphome/components/combination/* @Cat-Ion @kahrendt
 esphome/components/const/* @esphome/core
 esphome/components/coolix/* @glmnet
 esphome/components/copy/* @OttoWinter
+esphome/components/counter/* @clydebarrow
 esphome/components/cover/* @esphome/core
 esphome/components/cs5460a/* @balrog-kun
 esphome/components/cse7761/* @berfenger
@@ -131,6 +147,7 @@ esphome/components/cst816/* @clydebarrow
 esphome/components/cst9220/* @clydebarrow
 esphome/components/ct_clamp/* @jesserockz
 esphome/components/current_based/* @djwmarcx
+esphome/components/d01/* @ch604
 esphome/components/dac7678/* @NickB1
 esphome/components/daikin_arc/* @MagicBear
 esphome/components/daikin_brc/* @hagak
@@ -143,15 +160,22 @@ esphome/components/delonghi/* @grob6000
 esphome/components/dew_point/* @CFlix
 esphome/components/dfplayer/* @glmnet
 esphome/components/dfrobot_sen0395/* @niklasweber
+esphome/components/dfrobot_sen0465_base/* @tzabbi
+esphome/components/dfrobot_sen0465_i2c/* @tzabbi
+esphome/components/dfrobot_sen0465_uart/* @tzabbi
+esphome/components/dfrobot_sen0609/* @remcom
 esphome/components/dht/* @OttoWinter
 esphome/components/display_menu_base/* @numo68
 esphome/components/dlms_meter/* @latonita @PolarGoose @SimonFischer04 @Tomer27cz
 esphome/components/dps310/* @kbx81
 esphome/components/ds1307/* @badbadc0ffee
+esphome/components/ds1603l/* @JakeLC15
 esphome/components/ds2484/* @mrk-its
 esphome/components/ds248x/* @tomwellnitz
+esphome/components/ds3231/* @linkedupbits
 esphome/components/dsmr/* @glmnet @PolarGoose
 esphome/components/duty_time/* @dudanov
+esphome/components/ecocomfort2/* @gledian
 esphome/components/ee895/* @Stock-M
 esphome/components/ektf2232/touchscreen/* @jesserockz
 esphome/components/emc2101/* @ellull
@@ -168,6 +192,7 @@ esphome/components/es7243e/* @kbx81
 esphome/components/es8156/* @kbx81
 esphome/components/es8311/* @kahrendt @kroimon
 esphome/components/es8388/* @P4uLT
+esphome/components/es9038q2m_katana/* @GioMez
 esphome/components/esp32/* @esphome/core
 esphome/components/esp32_ble/* @bdraco @jesserockz @Rapsssito
 esphome/components/esp32_ble_client/* @bdraco @jesserockz
@@ -177,27 +202,34 @@ esphome/components/esp32_camera_web_server/* @ayufan
 esphome/components/esp32_can/* @Sympatron
 esphome/components/esp32_hosted/* @swoboda1337
 esphome/components/esp32_hosted/update/* @swoboda1337
-esphome/components/esp32_improv/* @jesserockz
+esphome/components/esp32_power_management/* @rwrozelle
 esphome/components/esp32_rmt/* @jesserockz
 esphome/components/esp32_rmt_led_strip/* @jesserockz
 esphome/components/esp8266/* @esphome/core
 esphome/components/esp_ldo/* @clydebarrow
+esphome/components/espectre/* @francescopace
+esphome/components/esphome/ota/* @esphome/core
 esphome/components/espnow/* @jesserockz
 esphome/components/espnow/packet_transport/* @EasilyBoredEngineer
 esphome/components/ethernet_info/* @gtjadsonsantos
 esphome/components/event/* @nohat
+esphome/components/exponential_moving_average/* @clydebarrow
 esphome/components/exposure_notifications/* @OttoWinter
 esphome/components/ezo/* @ssieb
 esphome/components/ezo_pmp/* @carlos-sarmiento
+esphome/components/ezsp_proxy_tap/* @kbx81 @puddly
 esphome/components/factory_reset/* @anatoly-savchenkov
 esphome/components/fastled_base/* @OttoWinter
 esphome/components/feedback/* @ianchi
 esphome/components/file/* @esphome/core
+esphome/components/filter_lifetime/* @tuct
 esphome/components/fingerprint_grow/* @alexborro @loongyh @OnFreund
 esphome/components/font/* @clydebarrow @esphome/core
+esphome/components/friedrich/* @rwrozelle
 esphome/components/fs3000/* @kahrendt
 esphome/components/ft5x06/* @clydebarrow
 esphome/components/ft63x6/* @gpambrozio
+esphome/components/fusb302b/* @remcom
 esphome/components/gcja5/* @gcormier
 esphome/components/gdk101/* @Szewcson
 esphome/components/gl_r01_i2c/* @pkejval
@@ -219,9 +251,14 @@ esphome/components/gt911/* @clydebarrow @jesserockz
 esphome/components/haier/* @paveldn
 esphome/components/haier/binary_sensor/* @paveldn
 esphome/components/haier/button/* @paveldn
+esphome/components/haier/select/* @paveldn
 esphome/components/haier/sensor/* @paveldn
 esphome/components/haier/switch/* @paveldn
 esphome/components/haier/text_sensor/* @paveldn
+esphome/components/haier_tundra/* @fauxpark
+esphome/components/haier_tundra/button/* @fauxpark
+esphome/components/haier_tundra/switch/* @fauxpark
+esphome/components/haier_water_heater/* @TheLexus
 esphome/components/havells_solar/* @sourabhjaiswal
 esphome/components/hbridge/fan/* @WeekendWarrior
 esphome/components/hbridge/light/* @DotNetDann
@@ -230,6 +267,7 @@ esphome/components/hc8/* @omartijn
 esphome/components/hdc2010/* @optimusprimespace @ssieb
 esphome/components/hdc2080/* @G-Pereira @jesserockz
 esphome/components/hdc302x/* @joshuasing
+esphome/components/hdmi_cec/* @JosVanEijndhoven
 esphome/components/he60r/* @clydebarrow
 esphome/components/heatpumpir/* @rob-deutsch
 esphome/components/hitachi_ac424/* @sourabhjaiswal
@@ -240,8 +278,12 @@ esphome/components/hmac_md5/* @dwmw2
 esphome/components/hmac_sha256/* @dwmw2
 esphome/components/hoermann_hcp/* @zweckj
 esphome/components/homeassistant/* @esphome/core @OttoWinter
+esphome/components/homeassistant/button/* @jesserockz
+esphome/components/homeassistant/light/* @egormanga
 esphome/components/homeassistant/number/* @landonr
+esphome/components/homeassistant/select/* @jesserockz
 esphome/components/homeassistant/switch/* @Links2004
+esphome/components/homeassistant/text/* @jesserockz
 esphome/components/honeywell_hih_i2c/* @Benichou34
 esphome/components/honeywellabp/* @RubyBailey
 esphome/components/honeywellabp2_i2c/* @jpfaff
@@ -253,6 +295,7 @@ esphome/components/http_request/ota/* @oarcher
 esphome/components/http_request/update/* @jesserockz
 esphome/components/htu31d/* @betterengineering
 esphome/components/hub75/* @stuartparmenter
+esphome/components/husb238/* @latonita
 esphome/components/hydreon_rgxx/* @functionpointer
 esphome/components/hyt271/* @Philippe12
 esphome/components/i2c/* @esphome/core
@@ -260,9 +303,13 @@ esphome/components/i2c_device/* @gabest11
 esphome/components/i2s_audio/* @jesserockz
 esphome/components/i2s_audio/microphone/* @jesserockz
 esphome/components/i2s_audio/speaker/* @jesserockz @kahrendt
+esphome/components/i2s_clockless_led_strip/* @j9brown
 esphome/components/iaqcore/* @yozik04
+esphome/components/icm20689/* @lboue
+esphome/components/icnt86/* @danepowell
 esphome/components/ili9xxx/* @clydebarrow @nielsnl68
 esphome/components/improv_base/* @esphome/core
+esphome/components/improv_ble/* @jesserockz
 esphome/components/improv_serial/* @esphome/core
 esphome/components/ina226/* @latonita @Sergio303
 esphome/components/ina260/* @mreditor97
@@ -275,6 +322,7 @@ esphome/components/inkplate/* @jesserockz @JosipKuci
 esphome/components/integration/* @OttoWinter
 esphome/components/internal_temperature/* @Mat931
 esphome/components/interval/* @esphome/core
+esphome/components/ir_rf_base/* @bdraco @kbx81
 esphome/components/ir_rf_proxy/* @kbx81
 esphome/components/it8951/* @koosoli @limengdu @Passific
 esphome/components/jsn_sr04t/* @Mafus1
@@ -286,9 +334,11 @@ esphome/components/kuntze/* @ssieb
 esphome/components/lc709203f/* @ilikecake
 esphome/components/lcd_menu/* @numo68
 esphome/components/ld2410/* @regevbr @sebcaps
+esphome/components/ld2410s/* @NovakIrs
 esphome/components/ld2412/* @Rihan9
 esphome/components/ld2420/* @descipher
 esphome/components/ld2450/* @hareeshmu
+esphome/components/ld2460/* @jesusvallejo
 esphome/components/ld24xx/* @kbx81
 esphome/components/ld6002b/* @hepter
 esphome/components/ledc/* @OttoWinter
@@ -297,6 +347,10 @@ esphome/components/libretiny_pwm/* @kuba2k2
 esphome/components/light/* @esphome/core
 esphome/components/lightwaverf/* @max246
 esphome/components/lilygo_t5_47/touchscreen/* @jesserockz
+esphome/components/lis2dw12/* @latonita
+esphome/components/lis2dw12_i2c/* @latonita
+esphome/components/lis2dw12_spi/* @latonita
+esphome/components/lis3dh/* @zebble
 esphome/components/lm75b/* @beormund
 esphome/components/ln882h_ble/* @Bl00d-B0b
 esphome/components/ln882h_ble_tracker/* @Bl00d-B0b
@@ -304,6 +358,7 @@ esphome/components/ln882x/* @lamauny
 esphome/components/lock/* @esphome/core
 esphome/components/logger/* @esphome/core
 esphome/components/logger/select/* @clydebarrow
+esphome/components/lp5562/* @DennisGaida
 esphome/components/lps22/* @nagisa
 esphome/components/lsm6ds/* @clydebarrow
 esphome/components/ltr390/* @latonita @sjtrny
@@ -314,7 +369,9 @@ esphome/components/m5stack_8angle/* @rnauber
 esphome/components/mapping/* @clydebarrow
 esphome/components/matrix_keypad/* @ssieb
 esphome/components/max17043/* @blacknell
+esphome/components/max17048/* @B48D81EFCC
 esphome/components/max31865/* @DAVe3283
+esphome/components/max31888/* @JiriPrchal
 esphome/components/max44009/* @berfenger
 esphome/components/max6956/* @looping40
 esphome/components/max7219digit/* @rspaargaren
@@ -333,7 +390,6 @@ esphome/components/mcp4461/* @p1ngb4ck
 esphome/components/mcp4728/* @berfenger
 esphome/components/mcp47a1/* @jesserockz
 esphome/components/mcp9600/* @mreditor97
-esphome/components/mcp9808/* @k7hpn
 esphome/components/md5/* @esphome/core
 esphome/components/mdns/* @esphome/core
 esphome/components/media_player/* @jesserockz
@@ -342,14 +398,18 @@ esphome/components/micro_wake_word/* @jesserockz @kahrendt
 esphome/components/micronova/* @edenhaus @jorre05
 esphome/components/microphone/* @jesserockz @kahrendt
 esphome/components/mics_4514/* @jesserockz
+esphome/components/mics_5524/* @nliaudat
 esphome/components/midea/* @dudanov
 esphome/components/midea_ir/* @dudanov
+esphome/components/midea_portasplit/* @Fexiven
 esphome/components/mipi_dsi/* @clydebarrow
 esphome/components/mipi_rgb/* @clydebarrow
 esphome/components/mipi_spi/* @clydebarrow
+esphome/components/mistral_ir/* @lerhum
 esphome/components/mitsubishi/* @RubyBailey
 esphome/components/mitsubishi_cn105/* @crnjan
 esphome/components/mixer/speaker/* @kahrendt
+esphome/components/mk2pvrouter/* @FredM67
 esphome/components/mlx90393/* @functionpointer
 esphome/components/mlx90614/* @jesserockz
 esphome/components/mmc5603/* @benhoff
@@ -372,6 +432,9 @@ esphome/components/mpl3115a2/* @kbickar
 esphome/components/mpu6886/* @fabaff
 esphome/components/ms8607/* @e28eta
 esphome/components/msa3xx/* @latonita
+esphome/components/mt6701/* @slimcdk
+esphome/components/mt6701_i2c/* @slimcdk
+esphome/components/mt6701_spi/* @slimcdk
 esphome/components/nau7802/* @cujomalainey
 esphome/components/network/* @esphome/core
 esphome/components/nextion/* @edwardtfn @senexcrenshaw
@@ -381,8 +444,11 @@ esphome/components/nextion/switch/* @senexcrenshaw
 esphome/components/nextion/text_sensor/* @senexcrenshaw
 esphome/components/nfc/* @jesserockz @kbx81
 esphome/components/noblex/* @AGalfra
+esphome/components/noise/* @esphome/core
 esphome/components/npi19/* @bakerkj
 esphome/components/nrf52/* @tomaszduda23
+esphome/components/ns2009/* @tchilov
+esphome/components/ns2009/touchscreen/* @tchilov
 esphome/components/number/* @esphome/core
 esphome/components/one_wire/* @ssieb
 esphome/components/online_image/* @clydebarrow @guillempages
@@ -393,10 +459,12 @@ esphome/components/ota/* @esphome/core
 esphome/components/output/* @esphome/core
 esphome/components/packet_transport/* @clydebarrow
 esphome/components/pca6416a/* @Mat931
+esphome/components/pca9505/* @ajfriesen @ssieb
 esphome/components/pca9554/* @bdraco @clydebarrow @hwstar
 esphome/components/pcf85063/* @brogon
 esphome/components/pcf8563/* @KoenBreeman
 esphome/components/pcm5122/* @remcom
+esphome/components/pd_pioneer_ir/* @martinsah
 esphome/components/pi4ioe5v6408/* @jesserockz
 esphome/components/pid/* @OttoWinter
 esphome/components/pipsolar/* @andreashergert1984
@@ -414,6 +482,8 @@ esphome/components/pn7150_i2c/* @jesserockz @kbx81
 esphome/components/pn7160/* @jesserockz @kbx81
 esphome/components/pn7160_i2c/* @jesserockz @kbx81
 esphome/components/pn7160_spi/* @jesserockz @kbx81
+esphome/components/pn71xx/* @jesserockz @kbx81
+esphome/components/power_management/* @rwrozelle
 esphome/components/power_supply/* @esphome/core
 esphome/components/preferences/* @esphome/core
 esphome/components/provisioning/* @esphome/core
@@ -421,6 +491,7 @@ esphome/components/psram/* @esphome/core
 esphome/components/pulse_meter/* @cstaahl @stevebaxter @TrentHouliston
 esphome/components/pvvx_mithermometer/* @pasiz
 esphome/components/pylontech/* @functionpointer
+esphome/components/pzem6l24/* @nuttytree
 esphome/components/qmi8658/* @clydebarrow
 esphome/components/qmp6988/* @andrewpc
 esphome/components/qr_code/* @wjtje
@@ -433,6 +504,8 @@ esphome/components/rc522/* @glmnet
 esphome/components/rc522_i2c/* @glmnet
 esphome/components/rc522_spi/* @glmnet
 esphome/components/rd03d/* @jasstrong
+esphome/components/remko_ar715/* @naKruul
+esphome/components/renogy_inverter_ble/* @emilioaray-dev
 esphome/components/resampler/speaker/* @kahrendt
 esphome/components/restart/* @esphome/core
 esphome/components/rf_bridge/* @jesserockz
@@ -446,11 +519,15 @@ esphome/components/rp2040_pwm/* @jesserockz
 esphome/components/rp2_ble_tracker/* @bdraco
 esphome/components/rpi_dpi_rgb/* @clydebarrow
 esphome/components/rtl87xx/* @kuba2k2
+esphome/components/rtsp_server/* @max246
 esphome/components/rtttl/* @glmnet @ximex
 esphome/components/runtime_image/* @clydebarrow @guillempages @kahrendt
 esphome/components/runtime_stats/* @bdraco
+esphome/components/rx8025t/* @remcom
+esphome/components/rx8111/* @techdregs
 esphome/components/rx8130/* @beormund
 esphome/components/safe_mode/* @jsuanet @kbx81 @paulmonigatti
+esphome/components/samsung/* @jorofi
 esphome/components/scd4x/* @martgras @sjtrny
 esphome/components/script/* @esphome/core
 esphome/components/sdl/* @bdm310 @clydebarrow
@@ -470,18 +547,23 @@ esphome/components/sendspin/image/* @kahrendt
 esphome/components/sendspin/media_player/* @kahrendt
 esphome/components/sendspin/media_source/* @kahrendt
 esphome/components/sendspin/sensor/* @kahrendt
+esphome/components/sendspin/switch/* @kahrendt
 esphome/components/sendspin/text_sensor/* @kahrendt
 esphome/components/sensirion_common/* @martgras
 esphome/components/sensor/* @esphome/core
 esphome/components/serial_proxy/* @kbx81
 esphome/components/sfa30/* @ghsensdev
+esphome/components/sfa40/* @NoQuarrel
 esphome/components/sgp40/* @SenexCrenshaw
 esphome/components/sgp4x/* @martgras @SenexCrenshaw
+esphome/components/sh1122_base/* @pl4nkton
+esphome/components/sh1122_spi/* @pl4nkton
 esphome/components/sha256/* @esphome/core
 esphome/components/shelly_dimmer/* @edge90 @rnauber
 esphome/components/sht3xd/* @mrtoy-me
 esphome/components/sht4x/* @sjtrny
 esphome/components/shutdown/* @esphome/core @jsuanet
+esphome/components/siemens_ira211/* @fonix232
 esphome/components/sigma_delta_output/* @Cat-Ion
 esphome/components/sim800l/* @glmnet
 esphome/components/sm10bit_base/* @Cossid
@@ -491,12 +573,14 @@ esphome/components/sm2335/* @Cossid
 esphome/components/sml/* @alengwenus
 esphome/components/smt100/* @piechade
 esphome/components/sn74hc165/* @jesserockz
+esphome/components/snapshot/* @clydebarrow
 esphome/components/socket/* @esphome/core
 esphome/components/sonoff_d1/* @anatoly-savchenkov
 esphome/components/sound_level/* @kahrendt
 esphome/components/spa06_base/* @danielkent-net
 esphome/components/spa06_i2c/* @danielkent-net
 esphome/components/spa06_spi/* @danielkent-net
+esphome/components/spd2010/* @grischard
 esphome/components/speaker/* @jesserockz @kahrendt
 esphome/components/speaker/media_player/* @kahrendt @synesthesiam
 esphome/components/speaker_source/* @kahrendt
@@ -526,6 +610,7 @@ esphome/components/st7735/* @SenexCrenshaw
 esphome/components/st7789v/* @kbx81
 esphome/components/st7920/* @marsjan155
 esphome/components/statsd/* @Links2004
+esphome/components/stcc4/* @j9brown
 esphome/components/stts22h/* @B48D81EFCC
 esphome/components/substitutions/* @esphome/core
 esphome/components/sun/* @OttoWinter
@@ -536,29 +621,38 @@ esphome/components/sx126x/* @swoboda1337
 esphome/components/sx127x/* @swoboda1337
 esphome/components/sy6970/* @linkedupbits
 esphome/components/syslog/* @clydebarrow
+esphome/components/systa_bus/* @Mat931
 esphome/components/t6615/* @tylermenezes
+esphome/components/tas2780/* @remcom
+esphome/components/tas58xx/* @mrtoy-me @remcom
 esphome/components/tc74/* @sethgirvan
+esphome/components/tca8418/* @zebble
 esphome/components/tca9548a/* @andreashergert1984
 esphome/components/tca9555/* @mobrembski
 esphome/components/tcl112/* @glmnet
+esphome/components/tcp_uart/* @Bascht74
 esphome/components/tee501/* @Stock-M
-esphome/components/teleinfo/* @0hax
+esphome/components/teleinfo/* @0hax @FredM67
 esphome/components/tem3200/* @bakerkj
 esphome/components/template/alarm_control_panel/* @grahambrown11 @hwstar
 esphome/components/template/datetime/* @rfdarter
 esphome/components/template/event/* @nohat
 esphome/components/template/fan/* @ssieb
 esphome/components/text/* @mauritskorse
+esphome/components/tfluna/* @candrews
 esphome/components/thermopro_ble/* @sittner
 esphome/components/thermostat/* @kbx81
 esphome/components/time/* @esphome/core
 esphome/components/tinyusb/* @kbx81
+esphome/components/tinyusb_keyboard/* @frederikbolding
 esphome/components/tlc5947/* @rnauber
 esphome/components/tlc5971/* @IJIJI
 esphome/components/tm1621/* @Philippe12
 esphome/components/tm1637/* @glmnet
 esphome/components/tm1638/* @skykingjwc
 esphome/components/tm1651/* @mrtoy-me
+esphome/components/tmc2209/* @remcom
+esphome/components/tmc22xx/* @remcom
 esphome/components/tmp102/* @timsavage
 esphome/components/tmp1075/* @sybrenstuvel
 esphome/components/tmp117/* @Azimath
@@ -575,15 +669,19 @@ esphome/components/tuya/select/* @bearpawmaxim
 esphome/components/tuya/sensor/* @jesserockz
 esphome/components/tuya/switch/* @jesserockz
 esphome/components/tuya/text_sensor/* @dentra
+esphome/components/tuya/water_heater/* @iago-veiga
 esphome/components/uart/* @esphome/core
 esphome/components/uart/button/* @ssieb
 esphome/components/uart/event/* @eoasmxd
 esphome/components/uart/packet_transport/* @clydebarrow
+esphome/components/uart_mux/* @kbx81
+esphome/components/uart_tcp/* @Bascht74
 esphome/components/udp/* @clydebarrow
 esphome/components/ufire_ec/* @pvizeli
 esphome/components/ufire_ise/* @pvizeli
 esphome/components/ufm01/* @ljungqvist
 esphome/components/ultrasonic/* @ssieb @swoboda1337
+esphome/components/unicode/* @esphome/core
 esphome/components/update/* @jesserockz
 esphome/components/uponor_smatrix/* @kroimon
 esphome/components/usb_cdc_acm/* @kbx81
@@ -594,10 +692,11 @@ esphome/components/vbus/* @ssieb
 esphome/components/veml3235/* @kbx81
 esphome/components/veml7700/* @latonita
 esphome/components/version/* @esphome/core
+esphome/components/vevor_dtx/* @Bofr5555
 esphome/components/voice_assistant/* @jesserockz @kahrendt
 esphome/components/wake_on_lan/* @clydebarrow @willwill2will54
 esphome/components/watchdog/* @oarcher
-esphome/components/water_heater/* @dhoeben
+esphome/components/water_heater/* @esphome/core
 esphome/components/waveshare_epaper/* @clydebarrow
 esphome/components/waveshare_io_ch32v003/* @latonita
 esphome/components/web_server/ota/* @esphome/core
@@ -606,7 +705,7 @@ esphome/components/web_server_idf/* @dentra
 esphome/components/weikai/* @DrCoolZic
 esphome/components/weikai_i2c/* @DrCoolZic
 esphome/components/weikai_spi/* @DrCoolZic
-esphome/components/whirlpool/* @glmnet
+esphome/components/whirlpool/* @arpena @glmnet
 esphome/components/whynter/* @aeonsablaze
 esphome/components/wiegand/* @ssieb
 esphome/components/wireguard/* @droscy @lhoracek @thomas0bernard
@@ -623,9 +722,11 @@ esphome/components/wts01/* @alepee
 esphome/components/x9c/* @EtienneMD
 esphome/components/xdb401/* @RT530
 esphome/components/xgzp68xx/* @gcormier
+esphome/components/xiaomi_body_scale/* @dckiller51
 esphome/components/xiaomi_hhccjcy10/* @fariouche
 esphome/components/xiaomi_lywsd02mmc/* @juanluss31
 esphome/components/xiaomi_lywsd03mmc/* @ahpohl
+esphome/components/xiaomi_mccgq02hl/* @ahpohl @morph027
 esphome/components/xiaomi_mhoc303/* @drug123
 esphome/components/xiaomi_mhoc401/* @vevsvevs
 esphome/components/xiaomi_rtcgq02lm/* @jesserockz
@@ -634,6 +735,7 @@ esphome/components/xl9535/* @mreditor97
 esphome/components/xpt2046/touchscreen/* @nielsnl68 @numo68
 esphome/components/xxtea/* @clydebarrow
 esphome/components/zephyr/* @tomaszduda23
+esphome/components/zephyr_coredump/* @tomaszduda23
 esphome/components/zephyr_mcumgr/ota/* @tomaszduda23
 esphome/components/zephyr_pwm/* @wiomoc
 esphome/components/zhlt01/* @cfeenstra1024
@@ -48,7 +48,7 @@ PROJECT_NAME           = ESPHome
 # could be handy for archiving the generated documentation or if some version
 # control system is used.

-PROJECT_NUMBER         = 2026.9.0-dev
+PROJECT_NUMBER         = 2026.11.0-dev

 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
@@ -23,7 +23,8 @@ For this repository there are two trusted inputs by design:
 1. **The configuration.** Anyone who can supply or edit a YAML config is trusted
   (see below).
 2. **Authenticated peers of a running device** — clients holding the device's
-   API encryption key / password, OTA password, or web server credentials.
+   API/OTA encryption key, API password, OTA password, or web server
+   credentials.

 The security boundary is therefore **unauthenticated network traffic vs. those
 trusted inputs.** A bug that lets an unauthenticated attacker cross it is a
@@ -76,8 +77,8 @@ These *are* security bugs in this repo, and we want to hear about them privately
  captive portal, etc.) **without** valid credentials.
 - Authentication or encryption bypass on the device — reaching API calls, OTA
  updates, or the web server without the configured key/password.
- Flaws that weaken the device's API encryption (Noise), OTA, or web server auth
-  below their documented guarantees.
+- Flaws that weaken the device's API or OTA encryption (Noise), OTA auth, or
+  web server auth below their documented guarantees.

 ## The web server is an open HTTP API by design

@@ -121,6 +122,54 @@ and any memory-safety or protocol bug in the server reachable without credential
 This section documents the current design and scope; it is not a judgment that the
 design is optimal or that it will not change.

+## OTA update encryption
+
+The `esphome` OTA platform optionally encrypts updates with the same Noise
+`NNpsk0` pattern the native API uses; one key protects the device. A device
+whose `api:` block has an encryption key, static in the YAML or provisioned at
+runtime, compiles in the transport and offers it on every OTA connection once
+it holds a key, so an uploader presenting that key gets the guarantees below
+even without an `ota: encryption:` block; only that block makes the device
+require encryption. The guarantees are: the firmware image is confidential in
+transit, the uploader is authenticated by the pre-shared key, and the plaintext
+negotiation preceding the handshake is bound into the handshake prologue, so
+stripping or tampering with it fails the first MAC. With `ota: encryption:`
+configured both ends fail closed with no override: the device refuses
+plaintext uploads, and the CLI refuses to send plaintext when a key is
+configured. Without that block the CLI tries a static api key when the device
+offers and, until 2027.3.0, falls back to plaintext with a warning when the
+offer is missing or the handshake fails; a runtime provisioned key never
+reaches the CLI, so those uploads stay plaintext.
+
+Defeating any of that without the key is in scope: a device that requires
+encryption accepting a plaintext or downgraded upload, getting past the MAC,
+or recovering image contents from captured traffic.
+
+The following are **not** vulnerabilities, by design:
+
+- Plaintext OTA on a device with no `ota: encryption:` block, including one
+  that offers encryption because it has an api key. That is the documented
+  default, authenticated (if at all) by the OTA password. An uploader that
+  takes the offer skips the password; the key authenticates it. With a
+  runtime provisioned key and no `provisioning:` window, whoever provisions
+  the key gains that upload path too; validation warns about the pair.
+- The CLI plaintext fallback until 2027.3.0: without `ota: encryption:` an
+  active attacker who strips the offer or breaks the handshake can make a
+  keyed CLI upload plaintext, with the pre-existing plaintext exposure. A
+  device that requires encryption still refuses that upload.
+- The enablement window: firmware built with a static api key already offers
+  encryption, so turning on `ota: encryption:` is itself an encrypted upload.
+  Older firmware needs one last plaintext upload of an offering build, with
+  the pre-existing plaintext exposure.
+- The web OTA `/update` endpoint alongside encryption. With the `web_server`
+  or `prometheus` component the shared listener is always up, so the endpoint
+  stays reachable and validation warns about that combination;
+  `captive_portal:` alone brings the listener up only for the fallback AP
+  window, which is the intended recovery path, so that is not warned about.
+- CLI retry behavior on transport or MAC failures; every attempt renegotiates
+  a fresh handshake with fresh ephemerals, so retrying does not weaken
+  authentication.
+
 ## Explicitly out of scope

 - Local attackers who already have shell access on the host that runs `esphome`.
@@ -22,16 +22,13 @@ RUN \
    -r /requirements.txt

 # Install the ESPHome Device Builder dashboard.
-RUN uv pip install --no-cache-dir esphome-device-builder==1.9.6
+RUN uv pip install --no-cache-dir esphome-device-builder==1.24.0

 RUN \
    platformio settings set enable_telemetry No \
    && platformio settings set check_platformio_interval 1000000 \
    && mkdir -p /piolibs

-COPY script/platformio_install_deps.py platformio.ini /
-RUN /platformio_install_deps.py /platformio.ini --libraries
-
 ARG BUILD_VERSION

 LABEL \
@@ -21,10 +21,14 @@ export PLATFORMIO_PLATFORMS_DIR="${pio_cache_base}/platforms"
 export PLATFORMIO_PACKAGES_DIR="${pio_cache_base}/packages"
 export PLATFORMIO_CACHE_DIR="${pio_cache_base}/cache"

-# Keep the native toolchain installs on the persistent cache root, not the
-# container's ephemeral user cache dir (re-downloaded on every restart).
+# Keep the native toolchain installs and compiler caches on the persistent
+# cache root, not the container's user cache dir: it is lost on every
+# restart, and not writable when the container runs as a non-root user.
 export ESPHOME_ESP_IDF_PREFIX="$(dirname "${pio_cache_base}")/idf"
 export ESPHOME_SDK_NRF_PREFIX="$(dirname "${pio_cache_base}")/sdk-nrf"
+export ESPHOME_ARDUINO8266_PREFIX="$(dirname "${pio_cache_base}")/arduino8266"
+export ESPHOME_HOST_PREFIX="$(dirname "${pio_cache_base}")/host"
+export ESPHOME_PLATFORMIO_CCACHE_DIR="$(dirname "${pio_cache_base}")/platformio-ccache"

 # If /build is mounted, use that as the build path
 # otherwise use path in /config (so that builds aren't lost on container restart)
@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 import argparse
+import os
 import re

 CHANNEL_DEV = "dev"
@@ -64,7 +65,10 @@ def main():

    suffix = f"-{args.suffix}" if args.suffix else ""

-    image_name = f"esphome/esphome{suffix}"
+    repository = (
+        (os.environ.get("GITHUB_REPOSITORY") or "esphome/esphome").strip().lower()
+    )
+    image_name = f"{repository}{suffix}"

    print(f"channel={channel}")

@@ -4,7 +4,6 @@
 # Home Assistant Add-on: ESPHome
 # Sends discovery information to Home Assistant.
 # ==============================================================================
-declare config
 declare port

 # We only disable it when disabled explicitly
@@ -19,14 +18,17 @@ port=$(bashio::addon.ingress_port)
 # Wait for the ESPHome Device Builder to become available
 bashio::net.wait_for "${port}" "127.0.0.1" 300

-config=$(\
-    bashio::var.json \
-        host "127.0.0.1" \
-        port "^${port}" \
-)
+# Send one discovery message; the config is a JSON string built with bashio::var.json.
+send_discovery() {
+    local service=$1
+    local config=$2
+    if bashio::discovery "${service}" "${config}" > /dev/null; then
+        bashio::log.info "Successfully send ${service} discovery information to Home Assistant."
+    else
+        bashio::log.error "${service} discovery message to Home Assistant failed!"
+    fi
+}

-if bashio::discovery "esphome" "${config}" > /dev/null; then
-    bashio::log.info "Successfully send discovery information to Home Assistant."
-else
-    bashio::log.error "Discovery message to Home Assistant failed!"
-fi
+send_discovery "esphome" "$(bashio::var.json host "127.0.0.1" port "^${port}")"
+# The Device Builder MCP server, consumed by Home Assistant's mcp integration.
+send_discovery "mcp" "$(bashio::var.json url "http://127.0.0.1:${port}/api/mcp")"
@@ -15,10 +15,14 @@ export PLATFORMIO_PLATFORMS_DIR="${pio_cache_base}/platforms"
 export PLATFORMIO_PACKAGES_DIR="${pio_cache_base}/packages"
 export PLATFORMIO_CACHE_DIR="${pio_cache_base}/cache"

-# Keep the native toolchain installs on the persistent /data volume, not the
-# container's ephemeral user cache dir (wiped on every add-on update/restart).
+# Keep the native toolchain installs and compiler caches on the persistent
+# /data volume, not the container's ephemeral user cache dir (wiped on every
+# add-on update/restart).
 export ESPHOME_ESP_IDF_PREFIX=/data/cache/idf
 export ESPHOME_SDK_NRF_PREFIX=/data/cache/sdk-nrf
+export ESPHOME_ARDUINO8266_PREFIX=/data/cache/arduino8266
+export ESPHOME_HOST_PREFIX=/data/cache/host
+export ESPHOME_PLATFORMIO_CCACHE_DIR=/data/cache/platformio-ccache

 if bashio::config.true 'leave_front_door_open'; then
    export DISABLE_HA_AUTHENTICATION=true
@@ -5,3 +5,15 @@ bk72xx:
  board: generic-bk7231n-qfn32-tuya

 logger:
+
+wifi:
+  ssid: MySSID
+  password: password1
+  ap:
+
+# mqtt and captive_portal together pull in AsyncTCP and ESPAsyncWebServer;
+# a stray ESP32 AsyncTCP copy on the library search path breaks this build
+captive_portal:
+
+mqtt:
+  broker: 192.168.178.84
@@ -0,0 +1,8 @@
+esphome:
+  name: docker-test-esp8266-native
+
+esp8266:
+  board: d1_mini
+  toolchain: arduino
+
+logger:
@@ -3,5 +3,7 @@ esphome:

 esp8266:
  board: d1_mini
+  # The PlatformIO path stays covered whatever the default is
+  toolchain: platformio

 logger:
@@ -7,6 +7,7 @@ import importlib
 import logging
 import os
 from pathlib import Path
+import platform
 import re
 import sys
 import time
@@ -16,8 +17,8 @@ from typing import TYPE_CHECKING, Protocol
 # cause them to be loaded before external components are processed, resulting
 # in the built-in version being used instead of the external component one.
 from esphome import const, platform_hooks
+from esphome.build_helpers.native import analysis_backend, native_backend
 from esphome.const import (
-    ALLOWED_NAME_CHARS,
    ARGUMENT_HELP_DEVICE,
    BUNDLE_EXTENSION,
    CONF_API,
@@ -26,14 +27,15 @@ from esphome.const import (
    CONF_DEASSERT_RTS_DTR,
    CONF_DISABLED,
    CONF_DISCOVER_IP,
+    CONF_ENCRYPTION,
    CONF_ESPHOME,
+    CONF_KEY,
    CONF_LEVEL,
    CONF_LOG,
    CONF_LOG_TOPIC,
    CONF_LOGGER,
    CONF_MDNS,
    CONF_MQTT,
-    CONF_NAME,
    CONF_NAME_ADD_MAC_SUFFIX,
    CONF_OTA,
    CONF_PASSWORD,
@@ -46,19 +48,24 @@ from esphome.const import (
    CONF_WEB_SERVER,
    CONF_WIFI,
    ENV_NOGITIGNORE,
+    KEY_CORE,
    KEY_ESP32,
+    KEY_TARGET_PLATFORM,
    KEY_VARIANT,
+    PLATFORM_HOST,
    SECRETS_FILES,
+    ErrorFormat,
    Toolchain,
 )
 from esphome.core import CORE, EsphomeError, coroutine
 from esphome.enum import StrEnum
-from esphome.helpers import get_bool_env, indent, is_ip_address
+from esphome.helpers import IS_MACOS, get_bool_env, indent, is_ip_address
 from esphome.log import AnsiFore, color, setup_log
 from esphome.stacktrace import LogLineProcessor
 from esphome.types import ConfigType
 from esphome.upload_targets import PortType, get_port_type
 from esphome.util import (
+    ESPHOME_COMMAND,
    PICOTOOL_PACKAGE,
    FlashImage,
    detect_rp2040_bootsel,
@@ -66,6 +73,7 @@ from esphome.util import (
    get_serial_ports,
    is_picotool_usb_permission_error,
    list_yaml_files,
+    read_secret_line,
    run_external_command,
    run_external_process,
    safe_print,
@@ -82,7 +90,6 @@ if TYPE_CHECKING:

 _LOGGER = logging.getLogger(__name__)

-ESPHOME_COMMAND = [sys.executable, "-m", "esphome"]

 # Maximum buffer size for serial log reading to prevent unbounded memory growth
 SERIAL_BUFFER_MAX_SIZE = 65536
@@ -147,6 +154,7 @@ class ArgsProtocol(Protocol):
    file: str | None
    no_logs: bool
    only_generate: bool
+    skip_bootloader: bool
    show_secrets: bool
    dashboard: bool
    configuration: str
@@ -475,12 +483,9 @@ def has_ota() -> bool:

 def has_native_ota() -> bool:
    """Check if native API OTA upload is available (``platform: esphome``)."""
-    if CONF_OTA not in CORE.config:
-        return False
-    return any(
-        ota_item.get(CONF_PLATFORM) == CONF_ESPHOME
-        for ota_item in CORE.config[CONF_OTA]
-    )
+    from esphome.espota2 import esphome_ota_items
+
+    return bool(esphome_ota_items(CORE.config))


 def has_web_server_ota() -> bool:
@@ -762,9 +767,11 @@ def _wrap_to_code(name, comp, yaml_util):
    async def wrapped(conf):
        cg.add(cg.LineComment(f"{name}:"))
        if comp.config_schema is not None:
-            conf_str = yaml_util.dump(conf)
+            # sort_keys: voluptuous fills defaults in set order, so an
+            # unsorted dump would churn main.cpp and relink every run
+            conf_str = yaml_util.dump(conf, sort_keys=True)
            conf_str = conf_str.replace("//", "")
-            # remove tailing \ to avoid multi-line comment warning
+            # remove trailing \ to avoid multi-line comment warning
            conf_str = conf_str.replace("\\\n", "\n")
            cg.add(cg.LineComment(indent(conf_str)))
        await coro(conf)
@@ -813,7 +820,9 @@ def write_cpp_file() -> int:
        from esphome.build_gen import espidf

        espidf.write_project()
-    else:
+    elif not CORE.using_native_toolchain:
+        # Other native builds generate their project at compile time;
+        # never write a platformio.ini for them
        from esphome.build_gen import platformio

        platformio.write_project()
@@ -822,6 +831,14 @@ def write_cpp_file() -> int:


 def compile_program(args: ArgsProtocol, config: ConfigType) -> int:
+    if CORE.skip_bootloader and not (CORE.is_esp32 and CORE.using_toolchain_esp_idf):
+        # Debug only: an orchestrator cannot see YAML toolchain overrides,
+        # so this is its expected no-op, and a full build is safe.
+        _LOGGER.debug(
+            "--skip-bootloader ignored: only supported on ESP32 with the "
+            "esp-idf toolchain"
+        )
+        CORE.skip_bootloader = False
    # Keep this gate here, NOT in config validation: device-builder needs
    # `esphome config` to keep succeeding with placeholders so onboarding can run.
    if CONF_WIFI in config:
@@ -831,7 +848,7 @@ def compile_program(args: ArgsProtocol, config: ConfigType) -> int:

    # Keep this here, NOT in codegen: config-hash and --only-generate must keep
    # working on machines that cannot run the toolchain.
-    if CORE.is_esp8266:
+    if CORE.is_esp8266 and CORE.using_toolchain_platformio:
        from esphome.components.esp8266 import check_rosetta

        check_rosetta()
@@ -852,10 +869,20 @@ def compile_program(args: ArgsProtocol, config: ConfigType) -> int:
            return rc

        # Create factory.bin, ota.bin, and firmware.elf copy
-        toolchain.create_factory_bin()
+        if not toolchain.create_factory_bin():
+            # A build whose factory image could not be produced must not
+            # exit 0; downloads would serve an image from an older build.
+            return 1
        toolchain.create_ota_bin()
        toolchain.create_elf_copy()
-        toolchain.get_idedata()
+        from esphome.build_helpers.idedata import warn_if_idedata_missing
+
+        warn_if_idedata_missing(toolchain.get_idedata)
+    elif CORE.using_native_toolchain:
+        raise EsphomeError(
+            f"Toolchain '{CORE.toolchain.value}' resolved but no platform "
+            "backend claimed the build"
+        )
    else:
        from esphome.platformio import toolchain

@@ -958,12 +985,16 @@ def upload_using_esptool(

    if file is not None:
        flash_images = [FlashImage(path=file, offset="0x0")]
-    elif CORE.using_toolchain_esp_idf:
-        from esphome.espidf import toolchain
-
-        flash_images = [
-            FlashImage(path=toolchain.get_factory_firmware_path(), offset="0x0")
-        ]
+    elif (native := native_backend()) is not None:
+        # Every native backend supplies its own 0x0 flash image (bootloader
+        # and partitions included where the target needs them)
+        image = native.get_factory_firmware_path()
+        if not image.is_file():
+            hint = getattr(native, "missing_image_hint", lambda: None)()
+            raise EsphomeError(
+                hint or f"{image} does not exist; compile the configuration first"
+            )
+        flash_images = [FlashImage(path=image, offset="0x0")]
    else:
        from esphome.platformio import toolchain

@@ -1202,14 +1233,28 @@ def upload_program(
    config: ConfigType, args: ArgsProtocol, devices: list[str]
 ) -> tuple[int, str | None]:
    host = devices[0]
+    port_type = get_port_type(host)
+    ota_key = getattr(args, "ota_key", None)
+    if ota_key and port_type in (PortType.SERIAL, PortType.BOOTSEL):
+        _LOGGER.warning(
+            "The presented OTA key only applies to network uploads; ignored for %s",
+            host,
+        )
+
    platform_upload = platform_hooks.get_platform_hook(
        CORE.target_platform, "upload_program"
    )
    if platform_upload is not None and platform_upload(config, args, host):
+        if ota_key and port_type not in (PortType.SERIAL, PortType.BOOTSEL):
+            # A platform's own network path (nrf52 mcumgr) has no key handshake
+            _LOGGER.warning(
+                "The presented OTA key only applies to the %s OTA platform; "
+                "ignored for %s",
+                CONF_ESPHOME,
+                host,
+            )
        return 0, host

-    port_type = get_port_type(host)
-
    # MQTT and MQTTIP are also OTA paths; MQTTIP gets resolved to a real IP later by
    # _resolve_network_devices(). Only SERIAL and BOOTSEL are non-OTA upload paths.
    is_partition_table = getattr(args, "partition_table", False)
@@ -1252,6 +1297,8 @@ def upload_program(
    network_devices = _resolve_network_devices(devices, config, args)

    if chosen_platform == CONF_WEB_SERVER:
+        if ota_key:
+            raise EsphomeError(OTA_KEY_PLATFORM_ERROR)
        if is_partition_table or is_bootloader:
            raise EsphomeError(
                f"{option_string} is only supported with the esphome OTA platform; "
@@ -1265,6 +1312,17 @@ def upload_program(
    return _upload_via_native_api(config, network_devices, args)


+def _ota_upload_platforms(config: ConfigType) -> dict[str, None]:
+    """The network OTA platforms the config provides, one entry each, in
+    config order; the web_server final-validate hook merges duplicates."""
+    return {
+        ota_platform: None
+        for ota_item in config.get(CONF_OTA, [])
+        if (ota_platform := ota_item.get(CONF_PLATFORM))
+        in (CONF_ESPHOME, CONF_WEB_SERVER)
+    }
+
+
 def _choose_ota_platform(config: ConfigType, requested: str | None) -> str:
    """Pick the OTA platform to use, optionally honoring ``--ota-platform``.

@@ -1272,22 +1330,12 @@ def _choose_ota_platform(config: ConfigType, requested: str | None) -> str:
    The native API uses challenge-response auth with MD5/SHA256 hashing of a
    server-issued nonce, so the password is never sent over the wire; the
    ``web_server`` path uses HTTP Basic auth which transmits credentials in
-    cleartext over the LAN. (The native path also supports gzip compression
-    on ESP8266, where flash space is tight; on ESP32/RP2040/LibreTiny the
-    backend reports ``supports_compression() == false`` and the firmware is
-    sent uncompressed regardless of which platform is used.) Falls back to
+    cleartext over the LAN. (The native path also compresses the upload:
+    gzip on ESP8266 and RP2040, which inflate it at reboot, and a deflate
+    stream on ESP32/LibreTiny, which inflate it as it arrives.) Falls back to
    ``web_server`` only when that is the only available platform.
    """
-    # Use a dict (insertion-ordered) instead of a list so error messages and
-    # membership checks see one entry per platform even if the user has
-    # multiple ``ota:`` items of the same platform; the web_server OTA
-    # platform's final-validate hook merges duplicates anyway.
-    available: dict[str, None] = {}
-    for ota_item in config.get(CONF_OTA, []):
-        platform = ota_item.get(CONF_PLATFORM)
-        if platform in (CONF_ESPHOME, CONF_WEB_SERVER):
-            available[platform] = None
-
+    available = _ota_upload_platforms(config)
    if not available:
        raise EsphomeError(
            f"Cannot upload Over the Air as the {CONF_OTA} configuration is not "
@@ -1308,19 +1356,53 @@ def _choose_ota_platform(config: ConfigType, requested: str | None) -> str:
    return CONF_WEB_SERVER


+def _esphome_ota_conf(config: ConfigType) -> ConfigType | None:
+    """The validated esphome OTA platform block, if configured."""
+    from esphome.espota2 import esphome_ota_items
+
+    return next(iter(esphome_ota_items(config)), None)
+
+
 def _upload_via_native_api(
    config: ConfigType, network_devices: list[str], args: ArgsProtocol
 ) -> tuple[int, str | None]:
-    ota_conf: ConfigType = {}
-    for ota_item in config.get(CONF_OTA, []):
-        if ota_item.get(CONF_PLATFORM) == CONF_ESPHOME:
-            ota_conf = ota_item
-            break
+    ota_conf = _esphome_ota_conf(config) or {}

    from esphome import espota2
+    from esphome.components.noise import static_encryption_key

    remote_port = int(ota_conf[CONF_PORT])
    password = ota_conf.get(CONF_PASSWORD)
+    # Fail closed: an encryption block whose key did not resolve must never
+    # fall back to a plaintext upload
+    noise_psk = None
+    old_noise_psk = None
+    plaintext_fallback = False
+    allow_plaintext_upload = False
+    if ota_key := getattr(args, "ota_key", None):
+        # The user presents a key the device still runs instead of the
+        # configured one (a key change in progress); an explicit key never
+        # downgrades to plaintext
+        noise_psk = ota_key
+    elif (encryption_conf := ota_conf.get(CONF_ENCRYPTION)) is not None:
+        noise_psk = encryption_conf.get(CONF_KEY)
+        allow_plaintext_upload = bool(
+            encryption_conf.get(espota2.CONF_ALLOW_PLAINTEXT_UPLOAD)
+        )
+        if not noise_psk:
+            raise EsphomeError(
+                "OTA encryption is configured but no key was resolved; "
+                "set the key under 'ota: encryption:' or 'api: encryption:'"
+            )
+        # Ensure the key is a string, as required by the underlying OTA implementation.
+        # It arrives here as a SensitiveStr which aioesphomeapi rejects.
+        noise_psk = str(noise_psk)
+        if old_key := encryption_conf.get(espota2.CONF_OLD_KEY):
+            old_noise_psk = str(old_key)
+    elif api_key := static_encryption_key(config.get(CONF_API) or {}):
+        # Remove before 2027.3.0: the api key is tried, falling back to plaintext
+        noise_psk = str(api_key)
+        plaintext_fallback = True

    def check_partition_access(option_string: str) -> None:
        if not ota_conf.get("allow_partition_access"):
@@ -1341,6 +1423,12 @@ def _upload_via_native_api(
        ota_type = espota2.OTA_TYPE_UPDATE_PARTITION_TABLE
    elif getattr(args, "bootloader", False):
        check_partition_access("--bootloader")
+        if (
+            getattr(args, "file", None) is None
+            and (native := native_backend())
+            and (hint := getattr(native, "missing_image_hint", lambda: None)())
+        ):
+            raise EsphomeError(hint)
        binary = CORE.bootloader_bin
        ota_type = espota2.OTA_TYPE_UPDATE_BOOTLOADER
    if getattr(args, "file", None) is not None:
@@ -1351,15 +1439,45 @@ def _upload_via_native_api(
    if ota_type == espota2.OTA_TYPE_UPDATE_BOOTLOADER:
        _validate_bootloader_binary(binary)

-    return espota2.run_ota(network_devices, remote_port, password, binary, ota_type)
+    return espota2.run_ota(
+        network_devices,
+        remote_port,
+        password,
+        binary,
+        ota_type,
+        noise_psk,
+        plaintext_fallback=plaintext_fallback,
+        allow_plaintext_upload=allow_plaintext_upload,
+        old_noise_psk=old_noise_psk,
+    )
+
+
+def _old_key_notice(config: ConfigType) -> None:
+    """After `run`, whose image was just built from this config; a plain
+    `upload` may send a stale image that still carries the previous key."""
+    from esphome import espota2
+
+    for item in espota2.esphome_ota_items(config):
+        if (item.get(CONF_ENCRYPTION) or {}).get(espota2.CONF_OLD_KEY):
+            _LOGGER.warning(espota2.OLD_KEY_REMOVE_NOTICE)


 def _upload_via_web_server(
    config: ConfigType, network_devices: list[str], binary: Path
 ) -> tuple[int, str | None]:
    from esphome import web_server_ota
+    from esphome.espota2 import esphome_ota_items
    from esphome.web_server_helpers import get_web_server_connection

+    if any(
+        ota_item.get(CONF_ENCRYPTION) is not None
+        for ota_item in esphome_ota_items(config)
+    ):
+        _LOGGER.warning(
+            "This config has OTA encryption, but the web_server OTA path sends "
+            "the image over plaintext HTTP; use the esphome OTA platform to "
+            "keep it confidential"
+        )
    remote_port, username, password = get_web_server_connection(config)
    return web_server_ota.run_ota(
        network_devices, remote_port, username, password, binary
@@ -1655,21 +1773,66 @@ def command_compile(args: ArgsProtocol, config: ConfigType) -> int | None:
    if exit_code != 0:
        return exit_code
    if CORE.is_host:
-        if CORE.using_toolchain_esp_idf:
-            from esphome.espidf import toolchain
-
-            program_path = str(toolchain.get_elf_path())
-        else:
-            from esphome.platformio.toolchain import get_idedata
-
-            program_path = str(get_idedata(config).firmware_elf_path)
-        _LOGGER.info("Successfully compiled program to path '%s'", program_path)
+        _LOGGER.info("Successfully compiled program to path '%s'", CORE.firmware_bin)
    else:
        _LOGGER.info("Successfully compiled program.")
    return 0


+ENV_OTA_KEY = "ESPHOME_OTA_KEY"
+OTA_KEY_PLATFORM_ERROR = (
+    f"--prompt-ota-key and {ENV_OTA_KEY} only apply to the {CONF_ESPHOME} OTA "
+    "platform; to flash by serial instead, name the port with --device"
+)
+
+
+def _read_ota_key(args: ArgsProtocol, config: ConfigType) -> None:
+    """Take the key to present to the device for this upload, from the
+    prompt or from ESPHOME_OTA_KEY, before any compile so the prompt is
+    not buried in build output."""
+    prompt = getattr(args, "prompt_ota_key", False)
+    env_key = getattr(args, "env_ota_key", None)
+    if not prompt and env_key is None:
+        return
+    if CORE.data.get(KEY_CORE, {}).get(KEY_TARGET_PLATFORM) == PLATFORM_HOST:
+        _LOGGER.warning("A host program runs locally; the presented OTA key is ignored")
+        return
+    # The HTTP path has no key handshake; decide before prompting or
+    # compiling. A serial target is a serial flash: the key is not even
+    # asked for, and --ota-platform means nothing to it. Every entry must
+    # be serial: a missing port is skipped and the next entry may be a host
+    devices = getattr(args, "device", None) or []
+    serial_target = bool(devices) and all(
+        device == "SERIAL"
+        or get_port_type(device) in (PortType.SERIAL, PortType.BOOTSEL)
+        for device in devices
+    )
+    chosen = (
+        _choose_ota_platform(config, getattr(args, "ota_platform", None))
+        if not serial_target and _ota_upload_platforms(config)
+        else None
+    )
+    if chosen == CONF_WEB_SERVER:
+        raise EsphomeError(OTA_KEY_PLATFORM_ERROR)
+    from esphome.components.noise import validate_encryption_key
+    from esphome.config_validation import Invalid
+
+    if serial_target:
+        _LOGGER.warning(
+            "The presented OTA key only applies to network uploads; ignored for %s",
+            ", ".join(devices),
+        )
+        return
+    key = read_secret_line("OTA encryption key: ") if prompt else env_key
+    try:
+        validate_encryption_key(key)
+    except Invalid as err:
+        raise EsphomeError(f"Invalid OTA encryption key: {err}") from err
+    args.ota_key = key
+
+
 def command_upload(args: ArgsProtocol, config: ConfigType) -> int | None:
+    _read_ota_key(args, config)
    # Get devices, resolving special identifiers like OTA
    devices = choose_upload_log_host(
        default=args.device,
@@ -1705,6 +1868,19 @@ def command_logs(args: ArgsProtocol, config: ConfigType) -> int | None:


 def command_run(args: ArgsProtocol, config: ConfigType) -> int | None:
+    if (
+        CORE.skip_bootloader
+        and CORE.is_esp32
+        and CORE.using_toolchain_esp_idf
+        and any(
+            get_port_type(device) == PortType.SERIAL for device in (args.device or [])
+        )
+    ):
+        # Fail before the compile: the result could never flash over serial.
+        # Elsewhere the flag is ignored, so serial stays fine there.
+        _LOGGER.error("--skip-bootloader builds cannot be flashed over serial")
+        return 1
+    _read_ota_key(args, config)
    exit_code = write_cpp(config)
    if exit_code != 0:
        return exit_code
@@ -1713,14 +1889,7 @@ def command_run(args: ArgsProtocol, config: ConfigType) -> int | None:
        return exit_code
    _LOGGER.info("Successfully compiled program.")
    if CORE.is_host:
-        if CORE.using_toolchain_esp_idf:
-            from esphome.espidf import toolchain
-
-            program_path = str(toolchain.get_elf_path())
-        else:
-            from esphome.platformio.toolchain import get_idedata
-
-            program_path = str(get_idedata(config).firmware_elf_path)
+        program_path = str(CORE.firmware_bin)
        _LOGGER.info("Running program from path '%s'", program_path)
        return run_external_process(program_path)

@@ -1737,6 +1906,7 @@ def command_run(args: ArgsProtocol, config: ConfigType) -> int | None:
    exit_code, successful_device = upload_program(config, args, devices)
    if exit_code == 0:
        _LOGGER.info("Successfully uploaded program.")
+        _old_key_notice(config)
    else:
        _LOGGER.warning("Failed to upload to %s", devices)
        return exit_code
@@ -1873,7 +2043,10 @@ def run_multiple_configs(
        safe_print()

        cmd = command_builder(f)
-        rc = run_external_process(*cmd)
+        # The parent already logged the Intel macOS warning; children skip it.
+        rc = run_external_process(
+            *cmd, env={**os.environ, _INTEL_MACOS_WARNED_ENV: "1"}
+        )

        if rc == 0:
            print_bar(f"[{color(AnsiFore.BOLD_GREEN, 'SUCCESS')}] {str(f)}")
@@ -1912,12 +2085,12 @@ def command_update_all(args: ArgsProtocol) -> int | None:
 def command_idedata(args: ArgsProtocol, config: ConfigType) -> int:
    import json

-    if CORE.using_toolchain_esp_idf:
-        # Native ESP-IDF derives idedata from the build's compile_commands.json,
-        # so the configuration must already be compiled.
-        from esphome.espidf import toolchain as espidf_toolchain
+    native_toolchain = native_backend()

-        idedata = espidf_toolchain.get_idedata()
+    if native_toolchain is not None:
+        # Native toolchains derive idedata from the build's
+        # compile_commands.json, so the configuration must already be compiled.
+        idedata = native_toolchain.get_idedata()
        if idedata is None:
            _LOGGER.error(
                "No idedata available; compile the configuration first",
@@ -1956,6 +2129,22 @@ def command_analyze_memory(args: ArgsProtocol, config: ConfigType) -> int:
    from esphome.analyze_memory.cli import MemoryAnalyzerCLI
    from esphome.analyze_memory.ram_strings import RamStringsAnalyzer

+    # Refuse an unsupported toolchain before paying for a full compile
+    analysis_toolchain = analysis_backend()
+    if analysis_toolchain is None and not CORE.using_toolchain_platformio:
+        _LOGGER.error(
+            "analyze-memory is not supported with the '%s' toolchain on %s; "
+            "re-run with --toolchain platformio",
+            CORE.toolchain.value if CORE.toolchain else "unresolved",
+            CORE.target_platform,
+        )
+        return 1
+    if (
+        check_supported := getattr(analysis_toolchain, "check_analysis_supported", None)
+    ) is not None:
+        # Raises with the reason; before the compile, not after it
+        check_supported()
+
    # Always compile to ensure fresh data (fast if no changes - just relinks)
    exit_code = write_cpp(config)
    if exit_code != 0:
@@ -1967,13 +2156,30 @@ def command_analyze_memory(args: ArgsProtocol, config: ConfigType) -> int:

    # Get idedata for analysis
    idedata = None
-    if CORE.using_toolchain_esp_idf:
-        from esphome.espidf import toolchain
+    if analysis_toolchain is not None:
+        objdump = analysis_toolchain.get_objdump_path()
+        readelf = analysis_toolchain.get_readelf_path()
+        for tool in (objdump, readelf):
+            if not tool.is_file():
+                # The analyzer would silently fall back to host
+                # binutils, which cannot read the target ELF
+                _LOGGER.error(
+                    "%s is missing; the toolchain install may be incomplete "
+                    "(recompile, or run 'esphome clean-all' if it persists)",
+                    tool,
+                )
+                return 1
+        objdump_path = str(objdump)
+        readelf_path = str(readelf)

-        objdump_path = str(toolchain.get_objdump_path())
-        readelf_path = str(toolchain.get_readelf_path())
-
-        firmware_elf = toolchain.get_elf_path()
+        firmware_elf = analysis_toolchain.get_elf_path()
+        if not firmware_elf.is_file():
+            # The analyzer swallows tool failures, so a missing ELF would
+            # produce an exit-0 zeroed report
+            _LOGGER.error(
+                "%s is missing; compile the configuration first", firmware_elf
+            )
+            return 1
    else:
        from esphome.platformio import toolchain

@@ -2027,155 +2233,9 @@ def command_analyze_memory(args: ArgsProtocol, config: ConfigType) -> int:


 def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
-    from esphome import yaml_util
+    from esphome.cli.rename import command_rename as run

-    new_name = args.name
-    for c in new_name:
-        if c not in ALLOWED_NAME_CHARS:
-            safe_print(
-                color(
-                    AnsiFore.BOLD_RED,
-                    f"'{c}' is an invalid character for names. Valid characters are: "
-                    f"{ALLOWED_NAME_CHARS} (lowercase, no spaces)",
-                )
-            )
-            return 1
-    # Load existing yaml file
-    raw_contents = CORE.config_path.read_text(encoding="utf-8")
-
-    yaml = yaml_util.load_yaml(CORE.config_path)
-    if CONF_ESPHOME not in yaml or CONF_NAME not in yaml[CONF_ESPHOME]:
-        safe_print(
-            color(
-                AnsiFore.BOLD_RED, "Complex YAML files cannot be automatically renamed."
-            )
-        )
-        return 1
-    old_name = yaml[CONF_ESPHOME][CONF_NAME]
-    match = re.match(r"^\$\{?([a-zA-Z0-9_]+)\}?$", old_name)
-    if match is None:
-        # Only swap the ``name:`` line that sits directly under the
-        # top-level ``esphome:`` block. A naked ``re.sub`` would
-        # also clobber any other ``name:`` line whose value happens
-        # to match (e.g. a sensor / output / wifi entry sharing the
-        # device's hostname), silently rewriting unrelated user
-        # configuration. The pattern anchors:
-        # - at the start of the line so ``friendly_name:``,
-        #   ``device_name:`` etc. don't match the trailing ``name:``
-        #   substring; and
-        # - at the end of the value (lookahead for whitespace +
-        #   comment + EOL) so ``old_name`` doesn't match as a
-        #   prefix of a longer value (``kitchen`` vs ``kitchen2``).
-        name_pattern = re.compile(
-            rf"^(\s*)name:\s+[\"']?{re.escape(old_name)}[\"']?(?=\s*(?:#|$))"
-        )
-        out_lines: list[str] = []
-        in_esphome_block = False
-        for line in raw_contents.splitlines(keepends=True):
-            if line and not line[0].isspace() and line.strip():
-                in_esphome_block = line.lstrip().startswith("esphome:")
-                out_lines.append(line)
-                continue
-            if in_esphome_block:
-                line = name_pattern.sub(rf'\1name: "{new_name}"', line, count=1)
-            out_lines.append(line)
-        new_raw = "".join(out_lines)
-    else:
-        old_name = yaml[CONF_SUBSTITUTIONS][match.group(1)]
-        if (
-            len(
-                re.findall(
-                    rf"^\s+{match.group(1)}:\s+[\"']?{old_name}[\"']?",
-                    raw_contents,
-                    flags=re.MULTILINE,
-                )
-            )
-            > 1
-        ):
-            safe_print(
-                color(AnsiFore.BOLD_RED, "Too many matches in YAML to safely rename")
-            )
-            return 1
-
-        new_raw = re.sub(
-            rf"^(\s+{match.group(1)}):\s+[\"']?{old_name}[\"']?",
-            f'\\1: "{new_name}"',
-            raw_contents,
-            flags=re.MULTILINE,
-        )
-
-    # ``new_name == old_name`` (after substitution resolution) is
-    # a no-op rewrite that would still queue a pointless re-flash.
-    # Catch it before the path-equality check below — covers the
-    # case where the config filename doesn't match the device name
-    # (e.g. ``weird-file.yaml`` whose ``esphome.name`` is
-    # ``kitchen``; running ``esphome rename weird-file.yaml kitchen``
-    # would otherwise just re-flash the same hostname).
-    if new_name == old_name:
-        safe_print(
-            color(
-                AnsiFore.BOLD_RED,
-                f"'{new_name}' is already the device's name.",
-            )
-        )
-        return 1
-
-    new_path: Path = CORE.config_dir / (new_name + ".yaml")
-    if new_path.resolve() == CORE.config_path.resolve():
-        safe_print(
-            color(
-                AnsiFore.BOLD_RED,
-                f"'{new_name}' is already the device's name.",
-            )
-        )
-        return 1
-    if new_path.exists():
-        safe_print(
-            color(
-                AnsiFore.BOLD_RED,
-                f"Cannot rename: {new_path} already exists. "
-                "Refusing to overwrite an existing configuration.",
-            )
-        )
-        return 1
-    safe_print(
-        f"Updating {color(AnsiFore.CYAN, str(CORE.config_path))} to {color(AnsiFore.CYAN, str(new_path))}"
-    )
-    print()
-
-    new_path.write_text(new_raw, encoding="utf-8")
-
-    rc = run_external_process(*ESPHOME_COMMAND, "config", str(new_path))
-    if rc != 0:
-        safe_print(color(AnsiFore.BOLD_RED, "Rename failed. Reverting changes."))
-        new_path.unlink()
-        return 1
-
-    cli_args = [
-        "run",
-        str(new_path),
-        "--no-logs",
-        "--device",
-        CORE.address,
-    ]
-
-    if args.dashboard:
-        cli_args.insert(0, "--dashboard")
-
-    try:
-        rc = run_external_process(*ESPHOME_COMMAND, *cli_args)
-    except KeyboardInterrupt:
-        rc = 1
-    if rc != 0:
-        new_path.unlink()
-        return 1
-
-    if CORE.config_path != new_path:
-        CORE.config_path.unlink()
-
-    safe_print(color(AnsiFore.BOLD_GREEN, "SUCCESS"))
-    print()
-    return 0
+    return run(args, config)


 PRE_CONFIG_ACTIONS = {
@@ -2210,6 +2270,15 @@ SIMPLE_CONFIG_ACTIONS = [
 ]


+def _add_skip_bootloader_arg(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        "--skip-bootloader",
+        help="Do not build the bootloader or the factory image; "
+        "the result can only be flashed over OTA.",
+        action="store_true",
+    )
+
+
 def _add_states_args(parser: argparse.ArgumentParser) -> None:
    """Add mutually exclusive ``--states``/``--no-states`` flags to a parser.

@@ -2233,6 +2302,25 @@ def _add_states_args(parser: argparse.ArgumentParser) -> None:
    )


+def _error_format(value: str) -> ErrorFormat:
+    try:
+        return ErrorFormat(value.lower())
+    except ValueError:
+        choices = ", ".join(ErrorFormat)
+        raise argparse.ArgumentTypeError(
+            f"invalid choice: '{value}' (choose from {choices})"
+        ) from None
+
+
+ARGUMENT_HELP_PROMPT_OTA_KEY = (
+    "Ask for the OTA encryption key to present to the device instead of using "
+    "the one in the configuration, for a device that still runs a previous key. "
+    "The key is read without echo, or as one line from stdin when that is not "
+    "a terminal; it is never taken from the command line. A calling program "
+    f"can hand the key over in the {ENV_OTA_KEY} environment variable instead."
+)
+
+
 def parse_args(argv):
    options_parser = argparse.ArgumentParser(add_help=False)
    options_parser.add_argument(
@@ -2290,7 +2378,19 @@ def parse_args(argv):
        metavar="{" + ",".join(t.value for t in Toolchain) + "}",
        help=(
            "Select toolchain for compiling. Overrides '<platform>.toolchain' in YAML. "
-            f"Default: {Toolchain.PLATFORMIO.value}."
+            "Default: the platform's native toolchain where it has one, else "
+            f"{Toolchain.PLATFORMIO.value}."
+        ),
+    )
+
+    options_parser.add_argument(
+        "--error-format",
+        type=_error_format,
+        metavar="{" + ",".join(f.value for f in ErrorFormat) + "}",
+        help=(
+            "How configuration errors are shown. 'yaml' shows them inside the "
+            "failing YAML; 'line' prints one 'file:line:column: error: message' "
+            "line per error. Default: $ESPHOME_ERROR_FORMAT, else 'yaml'."
        ),
    )

@@ -2350,6 +2450,7 @@ def parse_args(argv):
        help="Only generate source code, do not compile.",
        action="store_true",
    )
+    _add_skip_bootloader_arg(parser_compile)

    parser_upload = subparsers.add_parser(
        "upload",
@@ -2388,6 +2489,11 @@ def parse_args(argv):
        help="Upload as partition table (OTA).",
        action="store_true",
    )
+    parser_upload.add_argument(
+        "--prompt-ota-key",
+        action="store_true",
+        help=ARGUMENT_HELP_PROMPT_OTA_KEY,
+    )
    parser_upload.add_argument(
        "--bootloader",
        help="Upload as bootloader (OTA).",
@@ -2413,7 +2519,7 @@ def parse_args(argv):
        "-r",
        action="store_true",
        help="Reset the device before starting serial logs.",
-        default=os.getenv("ESPHOME_SERIAL_LOGGING_RESET"),
+        default=get_bool_env("ESPHOME_SERIAL_LOGGING_RESET"),
    )
    _add_states_args(parser_logs)

@@ -2446,6 +2552,7 @@ def parse_args(argv):
    parser_run.add_argument(
        "--no-logs", help="Disable starting logs.", action="store_true"
    )
+    _add_skip_bootloader_arg(parser_run)

    _add_states_args(parser_run)

@@ -2454,7 +2561,7 @@ def parse_args(argv):
        "-r",
        action="store_true",
        help="Reset the device before starting serial logs.",
-        default=os.getenv("ESPHOME_SERIAL_LOGGING_RESET"),
+        default=get_bool_env("ESPHOME_SERIAL_LOGGING_RESET"),
    )
    parser_run.add_argument(
        "--ota-platform",
@@ -2467,6 +2574,11 @@ def parse_args(argv):
            "(HTTP Basic auth) when that is the only configured platform."
        ),
    )
+    parser_run.add_argument(
+        "--prompt-ota-key",
+        action="store_true",
+        help=ARGUMENT_HELP_PROMPT_OTA_KEY,
+    )

    parser_clean = subparsers.add_parser(
        "clean-mqtt",
@@ -2595,9 +2707,18 @@ def parse_args(argv):
        args, unknown_args = parser.parse_known_args(arguments)
        if unknown_args:
            _LOGGER.warning("Ignored unrecognized arguments: %s", unknown_args)
-        return args
+    else:
+        args = parser.parse_args(arguments)

-    return parser.parse_args(arguments)
+    # Read here rather than as the option default, so a bad value is reported
+    # against the environment variable instead of --error-format
+    if args.error_format is None:
+        env_value = os.getenv("ESPHOME_ERROR_FORMAT", ErrorFormat.YAML.value)
+        try:
+            args.error_format = _error_format(env_value)
+        except argparse.ArgumentTypeError as err:
+            parser.error(f"ESPHOME_ERROR_FORMAT: {err}")
+    return args


 def _warn_if_source_tree_mismatch() -> None:
@@ -2643,12 +2764,34 @@ def _warn_if_source_tree_mismatch() -> None:
    )


+_INTEL_MACOS_REMOVAL = "2027.6.0"
+_INTEL_MACOS_WARNED_ENV = "ESPHOME_INTEL_MACOS_WARNED"
+
+
+def _warn_if_intel_macos() -> None:
+    """Warn that Intel (x86_64) Python on macOS loses support by _INTEL_MACOS_REMOVAL."""
+    if (
+        not IS_MACOS
+        or platform.machine() != "x86_64"
+        or _INTEL_MACOS_WARNED_ENV in os.environ
+    ):
+        return
+    _LOGGER.warning(
+        "Support for Intel Macs will end in ESPHome %s or earlier. The Python "
+        "packages ESPHome depends on have stopped publishing Intel macOS builds, "
+        "so future releases will not install on this machine. On an Apple "
+        "Silicon Mac, switch to a native arm64 Python.",
+        _INTEL_MACOS_REMOVAL,
+    )
+
+
 def run_esphome(argv):
    from esphome.address_cache import AddressCache

    args = parse_args(argv)
    CORE.dashboard = args.dashboard
    CORE.testing_mode = args.testing_mode
+    CORE.error_format = args.error_format

    # Create address cache from command-line arguments
    CORE.address_cache = AddressCache.from_cli_args(
@@ -2661,7 +2804,25 @@ def run_esphome(argv):
        args.log_level = "CRITICAL"

    setup_log(log_level=args.log_level)
+    # Taken out of the environment before any command runs, so no build
+    # tool inherits a key a calling program handed over
+    args.env_ota_key = os.environ.pop(ENV_OTA_KEY, None)
+    if args.command in ("upload", "run"):
+        # One key is one device's; several configs run in child processes
+        # that would never see it
+        if (args.env_ota_key is not None or args.prompt_ota_key) and len(
+            args.configuration
+        ) > 1:
+            raise EsphomeError(
+                f"--prompt-ota-key and {ENV_OTA_KEY} take one configuration; "
+                f"{len(args.configuration)} were given"
+            )
+    elif args.env_ota_key is not None:
+        _LOGGER.warning(
+            "%s is set but the %s command does not use it", ENV_OTA_KEY, args.command
+        )
    _warn_if_source_tree_mismatch()
+    _warn_if_intel_macos()

    if args.command in PRE_CONFIG_ACTIONS:
        try:
@@ -2705,6 +2866,7 @@ def run_esphome(argv):

    CORE.config_path = conf_path
    CORE.dashboard = args.dashboard
+    CORE.skip_bootloader = getattr(args, "skip_bootloader", False)
    if args.toolchain is not None:
        # CLI toolchain wins over esp32.toolchain in YAML.
        CORE.toolchain = args.toolchain
@@ -2719,10 +2881,14 @@ def run_esphome(argv):
    # Skipped when -s overrides are passed, since the cache was written
    # against the previous substitution set.
    config: ConfigType | None = None
-    cache_eligible = (
+    cache_write_eligible = (
        args.command in ("upload", "logs") and not command_line_substitutions
    )
-    if cache_eligible:
+    # An explicit --toolchain must re-run the per-platform validators, so
+    # gate only the cache read; the refresh below saves the result unless
+    # the sidecar records a different toolchain.
+    cache_read_eligible = cache_write_eligible and args.toolchain is None
+    if cache_read_eligible:
        from esphome.compiled_config import load_compiled_config

        config = load_compiled_config(conf_path)
@@ -2732,7 +2898,8 @@ def run_esphome(argv):
                conf_path.name,
            )

-    if config is None:
+    cache_missed = config is None
+    if cache_missed:
        from esphome.config import read_config

        config = read_config(
@@ -2741,26 +2908,22 @@ def run_esphome(argv):
            # Snapshot only needed by `esphome config --no-defaults`.
            snapshot_user_config=getattr(args, "no_defaults", False),
        )
-        # Refresh the cache so the next upload/logs hits the fast path
-        # instead of re-running read_config. Skip when the storage
-        # sidecar is absent (no compile has run): the cache would
-        # never be loaded back, so writing secrets to disk is wasted.
-        if cache_eligible and config is not None:
-            from esphome.compiled_config import save_compiled_config
-            from esphome.storage_json import ext_storage_path
-
-            if ext_storage_path(conf_path.name).exists():
-                save_compiled_config(config)
-    if config is None:
-        return 2
+        if config is None:
+            return 2
    CORE.config = config

-    # Fallback for platforms whose validators didn't set the toolchain
-    # (only the esp32 component reads esp32.framework.toolchain). All
-    # other platforms only support PlatformIO today.
+    # The cache fast path skips validation, and legacy sidecars lack the
+    # toolchain field. Must run before the cache refresh below.
    if CORE.toolchain is None:
        CORE.toolchain = Toolchain.PLATFORMIO

+    # Refresh the cache so the next upload/logs hits the fast path
+    # instead of re-running read_config.
+    if cache_write_eligible and cache_missed:
+        from esphome.compiled_config import save_compiled_config_and_sidecar
+
+        save_compiled_config_and_sidecar(config)
+
    if args.command not in POST_CONFIG_ACTIONS:
        safe_print(f"Unknown command {args.command}")
        return 1
@@ -148,6 +148,13 @@ class AddressCache:
                continue
            hostname, ips = arg.split("=", 1)
            # Normalize hostname for consistent lookups
-            normalized = normalize_hostname(hostname)
-            cache[normalized] = [ip.strip() for ip in ips.split(",")]
+            normalized = normalize_hostname(hostname.strip())
+            addresses = [ip for value in ips.split(",") if (ip := value.strip())]
+            if not normalized or not addresses:
+                _LOGGER.warning(
+                    "Invalid cache entry: %s (hostname and at least one address are required)",
+                    arg,
+                )
+                continue
+            cache[normalized] = addresses
        return cache
@@ -37,7 +37,7 @@ def find_elf_path(build_path: Path) -> Path | None:
    """
    name = build_path.name
    for candidate in (
-        # Native ESP-IDF: idf.py writes build/<name>.elf, which ESPHome copies
+        # Native ESP-IDF: the build writes build/<name>.elf, which ESPHome copies
        # to build/firmware.elf (see espidf.toolchain.create_elf_copy)
        build_path / "build" / "firmware.elf",
        # PlatformIO
@@ -68,12 +68,16 @@ def idedata_candidates(build_path: Path) -> list[Path]:
        The candidate idedata JSON paths, most specific first
    """
    name = build_path.name
+    data_dir = build_path.parent.parent / "idedata"
+    # Native backends suffix the cache by toolchain (<name>.arduino.json)
+    suffixed = sorted(data_dir.glob(f"{name}.*.json")) if data_dir.is_dir() else []
    return [
        # In .pioenvs for test builds
        build_path / ".pioenvs" / name / "idedata.json",
        # Both toolchains cache it in the data dir, which holds this build dir:
        # <data_dir>/idedata/<name>.json next to <data_dir>/build/<name>
        build_path.parent.parent / "idedata" / f"{name}.json",
+        *suffixed,
        # Regular builds, invoked from the config dir or from anywhere
        Path.cwd() / ".esphome" / "idedata" / f"{name}.json",
        Path.home() / ".esphome" / "idedata" / f"{name}.json",
@@ -23,9 +23,7 @@ from esphome.util import safe_print
 if TYPE_CHECKING:
    from collections.abc import Callable

-    from aioesphomeapi.api_pb2 import (
-        SubscribeLogsResponse,  # pylint: disable=no-name-in-module
-    )
+    from aioesphomeapi.api_pb2 import SubscribeLogsResponse  # pylint: disable=no-name-in-module


 _LOGGER = logging.getLogger(__name__)
@@ -0,0 +1,549 @@
+"""Arduino-core backend for the shared PlatformIO library converter.
+
+Bundled names build straight from the framework tree; everything else goes
+through ``esphome.platformio.library``. Mirrors ``lib_ldf_mode=off``: each
+library builds its own archive; all include dirs join one global path. The
+host build reuses it without a framework tree: nothing is bundled there and
+every name resolves from the registry.
+
+Deviations from PlatformIO: flat-layout libraries get the recursive default
+source filter; ``dot_a_linkage`` is honored; bundled libraries never run a
+manifest ``extraScript``; manifest ``-I`` flags join the global include path;
+``precompiled``/``ldflags`` properties are refused by name.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+import logging
+from pathlib import Path
+import re
+
+from esphome.core import CORE, EsphomeError, Library
+from esphome.helpers import walk_files
+from esphome.platformio.extra_script import apply_extra_script
+from esphome.platformio.library import (
+    DEFAULT_BUILD_INCLUDE_DIR,
+    DEFAULT_BUILD_SRC_FILTER,
+    ESPHOME_DATA_KEY,
+    ESPHOME_DATA_LINK_FLAGS_KEY,
+    LIBRARY_HEADER_SUFFIXES,
+    SRC_FILE_EXTENSIONS,
+    ConvertedLibrary,
+    IncompatiblePlatform,
+    InvalidLibrary,
+    LibraryBackend,
+    _url_or_none,
+    check_library_data,
+    collect_filtered_files,
+    convert_libraries,
+    ensure_list,
+    is_lib_ignored,
+    lex_build_flags,
+    lib_ignore_set,
+    normalize_dependencies,
+    parse_library_json,
+    parse_library_properties,
+    warn_properties_depends,
+)
+
+_LOGGER = logging.getLogger(__name__)
+
+
+@dataclass
+class ArduinoLibrary:
+    """One resolved library, ready for the ninja generator."""
+
+    name: str
+    sources: list[Path] = field(default_factory=list)
+    include_dirs: list[Path] = field(default_factory=list)
+    # Extra compile flags private to this library's own sources
+    flags: list[str] = field(default_factory=list)
+    # PlatformIO's build.libArchive / Arduino's dot_a_linkage: when False the
+    # objects go to the linker directly (symbols nothing references survive)
+    lib_archive: bool = True
+    # Link inputs the library contributes (-L dirs / -l libs, e.g. from
+    # precompiled vendor blobs) and -Wl, options for the firmware link
+    link_dirs: list[Path] = field(default_factory=list)
+    link_libs: list[str] = field(default_factory=list)
+    link_flags: list[str] = field(default_factory=list)
+
+
+# Source-like suffixes the case-sensitive suffix map rejects
+_UNMAPPED_SOURCE_SUFFIXES = frozenset(
+    {s.lower() for s in SRC_FILE_EXTENSIONS} | {".ino"}
+)
+
+# Filename-plain names: an allowlist excludes separators, drive colons,
+# and dot-only names by shape
+_SAFE_LIBRARY_NAME_RE = re.compile(r"[A-Za-z0-9_][A-Za-z0-9_. +-]*\Z")
+
+
+def _is_safe_library_name(name: object) -> bool:
+    """Whether a name may be joined under the framework's libraries dir."""
+    return isinstance(name, str) and _SAFE_LIBRARY_NAME_RE.fullmatch(name) is not None
+
+
+def _manifest_build(name: str, data: object) -> dict:
+    """The manifest's ``build`` section; malformed manifests fail by name."""
+    build = data.get("build", {}) if isinstance(data, dict) else None
+    if not isinstance(build, dict):
+        raise EsphomeError(f"Library {name} has a malformed manifest")
+    return build
+
+
+def _resolve_src_dir(name: str, read_path: Path, build: dict) -> str:
+    """Resolve PIO's source dir: manifest srcDir, else src/Src, else the root."""
+    if "srcDir" not in build:
+        return next((d for d in ("src", "Src") if (read_path / d).is_dir()), ".")
+    # A declared srcDir (falsy included) that does not resolve is a manifest error
+    src_dir = build["srcDir"]
+    if not (isinstance(src_dir, str) and src_dir and (read_path / src_dir).is_dir()):
+        raise EsphomeError(
+            f"Library {name} declares srcDir {src_dir!r} which does not exist"
+        )
+    return src_dir
+
+
+def _reject_unsupported_link_fields(name: str, data: dict) -> None:
+    # PIO honors these; ignoring them would fail at link with no stated
+    # cause. Property values are strings, so "false" is not a declaration.
+    precompiled = data.get("precompiled")
+    if precompiled and str(precompiled).strip().lower() != "false":
+        raise EsphomeError(
+            f"Library {name} declares precompiled, which this backend does not support"
+        )
+    if data.get("ldflags"):
+        raise EsphomeError(
+            f"Library {name} declares ldflags, which this backend does not support"
+        )
+
+
+def _resolve_lib_archive(name: str, data: dict, build: dict) -> bool:
+    """build.libArchive, else dot_a_linkage (an Arduino IDE property PIO
+    ignores; a deliberate extra), else archive."""
+
+    # Strict parse: bool("false") is True
+    def _parse(key: str, raw: object) -> bool:
+        if isinstance(raw, bool):
+            return raw
+        value = str(raw).strip().lower()
+        if value in ("true", "false"):
+            return value == "true"
+        raise EsphomeError(f"Library {name} has a malformed {key} value {raw!r}")
+
+    if "libArchive" in build:
+        return _parse("libArchive", build["libArchive"])
+    if "dot_a_linkage" in data:
+        return _parse("dot_a_linkage", data["dot_a_linkage"])
+    return True
+
+
+def _classify_build_flags(
+    name: str, read_path: Path, lib: ArduinoLibrary, flag_tokens: list[str]
+) -> list[str]:
+    """Route the lexed build.flags into the library's flag lists.
+
+    Returns the ``-I`` arguments for the include-dir resolution.
+    """
+    include_flags: list[str] = []
+    for tok in flag_tokens:
+        if tok.startswith("-I"):
+            include_flags.append(tok[2:])
+        elif tok.startswith("-L"):
+            link_dir = (read_path / tok[2:]).resolve()
+            if not link_dir.is_dir():
+                # Kept (the linker ignores missing -L dirs); the warning
+                # names the culprit before a bare "cannot find -lfoo"
+                _LOGGER.warning(
+                    "Library %s declares library dir %s which does not exist",
+                    name,
+                    tok[2:],
+                )
+            lib.link_dirs.append(link_dir)
+        elif tok.startswith("-l"):
+            lib.link_libs.append(tok[2:])
+        elif tok.startswith("-Wl,"):
+            lib.link_flags.append(tok)
+        else:
+            lib.flags.append(tok)
+    return include_flags
+
+
+def _resolve_include_dirs(
+    name: str,
+    read_path: Path,
+    lib: ArduinoLibrary,
+    build: dict,
+    src_dir: str,
+    include_flags: list[str],
+) -> None:
+    include_dir = build.get("includeDir", DEFAULT_BUILD_INCLUDE_DIR)
+    if not isinstance(include_dir, str):
+        raise EsphomeError(f"Library {name} has a malformed includeDir")
+    for d, explicit in [
+        (include_dir, "includeDir" in build),
+        (src_dir, False),  # _resolve_src_dir already validated it
+        *((flag, True) for flag in include_flags),
+    ]:
+        if (path := (read_path / d)).is_dir():
+            lib.include_dirs.append(path.resolve())
+        elif explicit:
+            # Warn-and-drop (unlike srcDir): a missing include dir is
+            # harmless until a header is needed, and the compile names it
+            _LOGGER.warning(
+                "Library %s declares include dir %s which does not exist", name, d
+            )
+
+
+def _collect_lib_sources(
+    name: str,
+    read_path: Path,
+    lib: ArduinoLibrary,
+    src_dir: str,
+    src_filter: list[str],
+) -> None:
+    sources: list[Path] = []
+    dropped: list[str] = []
+    saw_header = False
+    for f in collect_filtered_files(read_path / src_dir, src_filter):
+        path = Path(f)
+        suffix = path.suffix
+        if suffix in SRC_FILE_EXTENSIONS:
+            # resolve() per file: srcFilter patterns may escape src_dir
+            sources.append(path.resolve())
+        elif suffix.lower() in _UNMAPPED_SOURCE_SUFFIXES:
+            # A source-like suffix the case-sensitive map rejects (.CPP,
+            # .ino) is a dropped compilation unit; headers fall through
+            dropped.append(path.name)
+        elif suffix.lower() in LIBRARY_HEADER_SUFFIXES:
+            saw_header = True
+    lib.sources = sorted(sources)
+    if dropped:
+        _LOGGER.warning(
+            "Library %s: %d file(s) with unmapped source suffixes are not compiled: %s",
+            name,
+            len(dropped),
+            ", ".join(sorted(dropped)),
+        )
+    if not lib.sources and not saw_header:
+        # Matched headers mean header-only; a filter matching nothing is
+        # a manifest/tree problem (a truly empty tree raises elsewhere)
+        _LOGGER.warning("Library %s: no source files matched", name)
+
+
+def _library_info(name: str, read_path: Path, data: dict) -> ArduinoLibrary:
+    """Resolve one library's sources, include dirs, and flags (PIO semantics)."""
+    build = _manifest_build(name, data)
+    _reject_unsupported_link_fields(name, data)
+    src_dir = _resolve_src_dir(name, read_path, build)
+    src_filter = ensure_list(build.get("srcFilter", DEFAULT_BUILD_SRC_FILTER))
+    if not all(isinstance(entry, str) for entry in src_filter):
+        raise EsphomeError(f"Library {name} has a malformed srcFilter")
+    lib = ArduinoLibrary(name=name, lib_archive=_resolve_lib_archive(name, data, build))
+    # PlatformIO shell-lexes each build.flags entry
+    include_flags = _classify_build_flags(
+        name, read_path, lib, lex_build_flags(build.get("flags", []), f"library {name}")
+    )
+    _resolve_include_dirs(name, read_path, lib, build, src_dir, include_flags)
+    _collect_lib_sources(name, read_path, lib, src_dir, src_filter)
+    return lib
+
+
+def _bundled_library(framework_path: Path, name: str) -> ArduinoLibrary:
+    """A library bundled with the Arduino core, read from the framework tree.
+
+    ``library.json`` wins over ``library.properties`` when both exist, as in
+    PlatformIO's LibBuilderFactory; only the JSON manifest can carry a
+    ``build`` section (srcDir, srcFilter, flags).
+    """
+    lib_dir = framework_path / "libraries" / name
+    manifest_json = lib_dir / "library.json"
+    if manifest_json.is_file():
+        try:
+            data = parse_library_json(manifest_json)
+        except ValueError as err:  # JSONDecodeError
+            raise EsphomeError(
+                f"Bundled library {name} has a corrupt library.json ({err}); "
+                "the framework install may be incomplete (run 'esphome clean-all')"
+            ) from err
+    elif (manifest := lib_dir / "library.properties").is_file():
+        data = parse_library_properties(manifest)
+    else:
+        # Debug, not warning: the legacy manifest-less layout is legal and
+        # the 3.1.2 core ships one such library (FSTools), so a warning
+        # would be unactionable noise on every build using it
+        _LOGGER.debug("Bundled library %s has no manifest; using defaults", name)
+        data = {}
+    if isinstance(data, dict):
+        # Bundled manifest deps are never walked; make the skip visible
+        if data.get("dependencies"):
+            _LOGGER.warning(
+                "Bundled library %s declares dependencies, which are not "
+                "resolved automatically; add them with add_library() if needed",
+                name,
+            )
+        warn_properties_depends(name, data)
+        build = data.get("build")
+        if isinstance(build, dict) and build.get("extraScript"):
+            # Scripts only run on the converted path; building without
+            # the script's flags would miscompile
+            raise EsphomeError(
+                f"Bundled library {name} declares an extraScript, which is "
+                "not run for bundled libraries"
+            )
+    lib = _library_info(name, lib_dir, data)
+    _assert_tree_has_code(
+        name,
+        lib_dir,
+        "the framework install may be incomplete (run 'esphome clean-all')",
+    )
+    return lib
+
+
+def _assert_tree_has_code(name: str, root: Path, hint: str) -> None:
+    """An empty or half-extracted tree can never link; fail by name (a
+    warning would scroll away and resurface as undefined symbols)."""
+    if not any(
+        Path(p).suffix in SRC_FILE_EXTENSIONS
+        or Path(p).suffix.lower() in LIBRARY_HEADER_SUFFIXES
+        for p in walk_files(root)
+    ):
+        raise EsphomeError(f"Library {name} has no sources or headers; {hint}")
+
+
+def _external_short_name(name: str) -> str:
+    """The short library name of a requested spec.
+
+    "owner/Name" and plain names take the last path segment; "Name=<url>"
+    takes the declared name. Git tails (".git", "#ref") are stripped like
+    the walk's URL normalization; the comparand is a manifest dependency
+    name, never a spec.
+    """
+    head, sep, tail = name.partition("=")
+    if sep and "://" in tail:
+        return head
+    short = name.rsplit("/", maxsplit=1)[-1]
+    return short.partition("#")[0].removesuffix(".git")
+
+
+def _check_unfulfilled_provides(
+    provided_requests: set[str], satisfied: set[str], still_requested: set[str]
+) -> None:
+    """Fail by name when a walk-skipped dependency was never added.
+
+    An unfulfilled provides() promise only surfaces as undefined symbols
+    at link. The walk records across re-resolutions, so a name no final
+    manifest still requests is stale state, never a failure.
+    """
+    if missing := sorted((provided_requests & still_requested) - satisfied):
+        raise EsphomeError(
+            "provides() skipped these dependencies but nothing added them: "
+            f"{', '.join(missing)}; the build is missing libraries"
+        )
+
+
+def resolve_libraries(
+    framework_path: Path | None,
+    *,
+    pio_platform: str,
+    board_mcu: str,
+    cache_key: str,
+    framework: str | None = "arduino",
+    manifest_optional: bool = False,
+) -> list[ArduinoLibrary]:
+    """Resolve every ``cg.add_library()`` entry into an :class:`ArduinoLibrary`.
+
+    ``pio_platform``/``board_mcu`` filter manifests the way PlatformIO would
+    for that core (e.g. ``espressif8266``/``esp8266``); ``cache_key`` keys the
+    shared converter's download cache. ``framework`` is the manifest
+    framework token the compatibility check warns about; None skips it.
+    A None ``framework_path`` means no core-bundled libraries exist (the
+    host build): every name resolves from the registry.
+    ``manifest_optional`` accepts libraries without a manifest, built with
+    PlatformIO's default layout.
+
+    The returned list is not topologically sorted, so the caller must link
+    the archives inside one ``--start-group``/``--end-group`` pair (the
+    bundled-first grouping is incidental).
+    """
+    bundled: list[ArduinoLibrary] = []
+    external: list[Library] = []
+    # PlatformIO's lib_ignore covers framework-bundled libraries too; the
+    # shared converter only filters the registry/git ones.
+    lib_ignore = lib_ignore_set()
+    bundled_dir_names: frozenset[str] = frozenset()
+    if framework_path is not None:
+        # Exact directory names keep membership case-sensitive everywhere
+        # (an is_dir() probe would match "wire" on macOS/Windows and build
+        # the bundled Wire twice)
+        libraries_dir = framework_path / "libraries"
+        if not libraries_dir.is_dir():
+            # A registry fallback would fail later with a misleading
+            # package-not-found error per bundled name
+            raise EsphomeError(
+                f"{libraries_dir} is missing; the framework install may be "
+                "incomplete (run 'esphome clean-all')"
+            )
+        bundled_dir_names = frozenset(
+            p.name for p in libraries_dir.iterdir() if p.is_dir()
+        )
+
+    def _provided(name: object) -> bool:
+        return _is_safe_library_name(name) and name in bundled_dir_names
+
+    for library in CORE.platformio_libraries.values():
+        if is_lib_ignored(library.name, lib_ignore):
+            continue
+        # Bundled only for a bare name with a matching framework dir; pinned
+        # or unmatched names resolve from the registry, as under PlatformIO.
+        if not library.repository and not library.version and _provided(library.name):
+            # Bundled manifest deps are not walked; _bundled_library warns
+            bundled.append(_bundled_library(framework_path, library.name))
+        else:
+            external.append(library)
+
+    converted: list[ArduinoLibrary] = []
+    bundled_names = {lib.name for lib in bundled}
+    converted_manifest_names: set[str] = set()
+    # Bundled candidates skipped on purpose (platform filter); the
+    # provides() reconciliation must count them as satisfied
+    knowingly_skipped: set[str] = set()
+    # Dependency names of the manifests actually emitted; a walk recording
+    # for a since-re-resolved manifest must not fail the reconciliation
+    final_dep_names: set[str] = set()
+    # Ordered set of bundled dependency names to add once conversion is done
+    pending_bundled: dict[str, None] = {}
+    # Deps matching a separately-requested external are already in the build
+    # (a duplicate archive means duplicate-symbol link errors)
+    external_short_names = {
+        _external_short_name(lib.name) for lib in external if lib.name
+    }
+
+    def _add_bundled_dependencies(component: ConvertedLibrary) -> None:
+        # A version-less bare name ("Hash") is a core-bundled library the
+        # shared converter cannot resolve from the registry
+        for dep in normalize_dependencies(
+            component.data.get("dependencies"), component.name
+        ):
+            # normalize_dependencies guarantees a non-empty str name
+            name = dep["name"]
+            final_dep_names.add(name)
+            if "/" in name:
+                owner, _, pkg = name.partition("/")
+                if _is_safe_library_name(owner) and _is_safe_library_name(pkg):
+                    # Owner-qualified; the converter resolves it from the registry
+                    continue
+            if not _is_safe_library_name(name):
+                # The name becomes a path component; never join a traversal
+                _LOGGER.warning(
+                    "Ignoring malformed dependency entry %r of library %s",
+                    dep,
+                    component.name,
+                )
+                continue
+            if name in external_short_names:
+                if _provided(name):
+                    # A bundled copy is suppressed; a coincidental name
+                    # collision would surface as link errors
+                    _LOGGER.warning(
+                        "Dependency %s of %s is assumed satisfied by a "
+                        "requested external library; the bundled copy is "
+                        "not added",
+                        name,
+                        component.name,
+                    )
+                else:
+                    _LOGGER.debug(
+                        "Dependency %s of %s assumed satisfied by a requested "
+                        "external library",
+                        name,
+                        component.name,
+                    )
+                continue
+            if name in bundled_names or is_lib_ignored(name, lib_ignore):
+                continue
+            if _url_or_none(dep.get("version")) is not None:
+                # A URL names one specific source; never add the bundled copy
+                continue
+            if dep.get("owner") or not _provided(name):
+                # Only owner-less framework-tree names take the bundled
+                # copy (PIO's process_dependencies); the walk reports drops
+                continue
+            try:
+                # framework=None: the walk already warned for non-platform
+                # causes; debug keeps one fault from warning twice (pinned
+                # by test_nonplatform_rejection_warns_once_through_real_converter)
+                check_library_data(dep, pio_platform, None)
+            except IncompatiblePlatform as err:
+                # A knowing skip (platform filter), not a broken promise
+                knowingly_skipped.add(name)
+                _LOGGER.debug("Skip bundled candidate %s: %s", name, err)
+                continue
+            except InvalidLibrary as err:
+                # Malformed manifest data never counts as satisfied; the
+                # walk owns the warning (see the warns-once test above)
+                _LOGGER.debug("Skip malformed bundled candidate %s: %s", name, err)
+                continue
+            # Deferred: a later manifest name may satisfy this
+            pending_bundled.setdefault(name)
+
+    def _emit(component: ConvertedLibrary) -> None:
+        apply_extra_script(
+            component, board_mcu=lambda: board_mcu, pio_platform=pio_platform
+        )
+        _assert_tree_has_code(
+            component.get_require_name(),
+            component.source_dir,
+            "the download may be incomplete (run 'esphome clean-all')",
+        )
+        if isinstance(manifest_name := component.data.get("name"), str):
+            converted_manifest_names.add(manifest_name)
+        lib = _library_info(
+            component.get_require_name(), component.source_dir, component.data
+        )
+        # Extra-script LINKFLAGS travel outside build.flags; dropping
+        # them would link wrong with no stated cause
+        lib.link_flags.extend(
+            component.data.get(ESPHOME_DATA_KEY, {}).get(
+                ESPHOME_DATA_LINK_FLAGS_KEY, []
+            )
+        )
+        converted.append(lib)
+        _add_bundled_dependencies(component)
+
+    backend = LibraryBackend(
+        platform=pio_platform,
+        framework=framework,
+        emit=_emit,
+        cache_key=cache_key,
+        # The walk must not resolve bundled names from the registry;
+        # _add_bundled_dependencies adds them after emit
+        provides=_provided,
+        manifest_optional=manifest_optional,
+    )
+    if external:
+        convert_libraries(external, backend)
+    for name in pending_bundled:
+        if name in converted_manifest_names:
+            # The converted library is this one; the bundled copy would
+            # double the archive. Warn like the external_short_names twin.
+            _LOGGER.warning(
+                "Dependency %s is assumed satisfied by a converted library's "
+                "manifest name; the bundled copy is not added",
+                name,
+            )
+            continue
+        bundled_names.add(name)
+        bundled.append(_bundled_library(framework_path, name))
+
+    _check_unfulfilled_provides(
+        backend.provided_requests,
+        bundled_names
+        | converted_manifest_names
+        | external_short_names
+        | knowingly_skipped,
+        final_dep_names,
+    )
+
+    return bundled + converted
@@ -0,0 +1,9 @@
+"""Native (PlatformIO-free) build support for the ESP8266 Arduino core.
+
+This package downloads the Arduino ESP8266 core and the xtensa-lx106
+toolchain, generates a ninja build for them plus the ESPHome sources, and
+drives the build directly — the ESP8266 equivalent of ``esphome.espidf``.
+
+Deliberately importable without the esp8266 component to avoid circular
+imports; the component wires these modules in via lazy imports.
+"""
@@ -0,0 +1,207 @@
+"""Download and install the Arduino ESP8266 core, toolchain, and ninja.
+
+Artifacts land in a machine-global cache (shared across projects, like the
+ESP-IDF install in ``esphome.espidf.framework``):
+
+    <cache>/arduino8266/frameworks/<tag>/   the Arduino core
+    <cache>/arduino8266/toolchains/<tag>/   xtensa-lx106-elf gcc 10.3
+
+Both come from esphome-libs releases pinned below;
+``ESPHOME_ARDUINO8266_*_MIRRORS`` overrides the URLs, with ``{VERSION}``
+standing for the release tag. ninja comes from PATH or the ninja PyPI wheel.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+from typing import NamedTuple
+
+from esphome.build_helpers.ccache import ccache_env
+from esphome.build_helpers.ninja import find_ninja
+from esphome.build_helpers.tools_cache import ARDUINO8266_TOOLS_CACHE, tools_cache_path
+from esphome.core import EsphomeError, Version
+from esphome.framework_helpers import str_to_lst_of_str
+from esphome.platformio.registry import (
+    Download,
+    PackageSpec,
+    Resolver,
+    get_systype,
+    install_packages,
+    prefetch_packages,
+)
+
+FRAMEWORK_PACKAGE = "arduino-esp8266"
+_FRAMEWORK_RELEASES = "https://github.com/esphome-libs/arduino-esp8266/releases/"
+
+
+class FrameworkRelease(NamedTuple):
+    tag: str
+    sha256: str
+    size: int
+
+    def download(self) -> Download:
+        archive = f"{FRAMEWORK_PACKAGE}-{self.tag}.tar.gz"
+        url = f"{_FRAMEWORK_RELEASES}download/{self.tag}/{archive}"
+        return Download(url, self.sha256, self.size)
+
+
+# Arduino core version -> its build in esphome-libs/arduino-esp8266
+FRAMEWORK_RELEASES: dict[Version, FrameworkRelease] = {
+    Version(3, 1, 2): FrameworkRelease(
+        "3.1.2-esphome.3",
+        "3af533a85163804e164500a5b254dc23b922080e25ecb7dc37b3dd8ac84651db",
+        37185650,
+    ),
+}
+
+TOOLCHAIN_PACKAGE = "toolchain-xtensa-lx106-elf"
+# gcc 10.3, the toolchain Arduino core 3.x builds with; the build
+# generator's compile flags are tuned to it.
+TOOLCHAIN_VERSION = "10.3.0-esphome.3"
+_TOOLCHAIN_RELEASES = (
+    "https://github.com/esphome-libs/xtensa-lx106-elf-toolchain/releases/"
+)
+# Registry system tag -> (sha256, size) of that host's archive
+TOOLCHAIN_BUILDS: dict[str, tuple[str, int]] = {
+    "darwin_arm64": (
+        "ad0ea929238d9b527c43e0d20257acc2a5680bdb0d2b1cf8f2c99169786217e9",
+        60747260,
+    ),
+    "darwin_x86_64": (
+        "997090cac80c8eb59604ec52b73fb3568e5f2d9b2971f83c3f2a5c545c9c949c",
+        64065752,
+    ),
+    "linux_aarch64": (
+        "403f14d0d5755682fcd6eaea1e4c457a1d8cad30690e52fb0c804d8db266b908",
+        67487067,
+    ),
+    "linux_x86_64": (
+        "64f21fa3ba736b363dc8c234dbbb39e005e574e33de08a78e9a00c55a64ae706",
+        68343668,
+    ),
+    "windows_amd64": (
+        "1e62abf8df041ce5158f5770dffef955f2f981ce7f7adee88fcd5a8197705aa6",
+        67536405,
+    ),
+}
+
+ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS = str_to_lst_of_str(
+    os.environ.get("ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS", "")
+)
+ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS = str_to_lst_of_str(
+    os.environ.get("ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS", "")
+)
+
+
+def get_arduino8266_tools_path() -> Path:
+    # Machine-global so all projects share one install; see
+    # espidf.framework.get_idf_tools_path for the location rationale.
+    return tools_cache_path(*ARDUINO8266_TOOLS_CACHE)
+
+
+def framework_release(version: Version) -> FrameworkRelease:
+    if (release := FRAMEWORK_RELEASES.get(version)) is None:
+        raise EsphomeError(
+            f"'toolchain: arduino' has no build of Arduino core {version}; "
+            f"available: {', '.join(str(v) for v in FRAMEWORK_RELEASES)}. "
+            "Use one of those or 'toolchain: platformio'"
+        )
+    return release
+
+
+def get_framework_path(tag: str) -> Path:
+    return get_arduino8266_tools_path() / "frameworks" / tag
+
+
+def get_toolchain_path() -> Path:
+    return get_arduino8266_tools_path() / "toolchains" / TOOLCHAIN_VERSION
+
+
+def toolchain_download() -> Download:
+    """The toolchain archive for the current host."""
+    systype = get_systype()
+    if (build := TOOLCHAIN_BUILDS.get(systype)) is None:
+        raise EsphomeError(
+            f"There is no ESP8266 toolchain for this system ({systype}); "
+            f"supported systems are {', '.join(sorted(TOOLCHAIN_BUILDS))}. "
+            "Either set 'toolchain: platformio' under 'esp8266:', or point "
+            "ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS at a toolchain archive"
+        )
+    sha256, size = build
+    archive = f"{TOOLCHAIN_PACKAGE}-{TOOLCHAIN_VERSION}-{systype}.tar.gz"
+    url = f"{_TOOLCHAIN_RELEASES}download/{TOOLCHAIN_VERSION}/{archive}"
+    return Download(url, sha256, size)
+
+
+class InstalledPaths(NamedTuple):
+    """Locations of the installed framework, toolchain, and ninja binary."""
+
+    framework: Path
+    toolchain: Path
+    ninja: Path
+
+
+def check_and_install(framework_version: Version) -> InstalledPaths:
+    """Ensure framework, toolchain, and ninja are installed; return their paths."""
+    release = framework_release(framework_version)
+    # Probe the cheap local dependency before ~110 MB of downloads
+    ninja_path = find_ninja()
+    framework_path = get_framework_path(release.tag)
+    downloads_dir = get_arduino8266_tools_path() / "downloads"
+    toolchain_path = get_toolchain_path()
+    # One spec per package: the prefetch and the installs must agree
+    specs = (
+        PackageSpec(
+            FRAMEWORK_PACKAGE,
+            release.tag,
+            framework_path,
+            ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS,
+            ("cores/esp8266", "tools/sdk", "libraries"),
+        ),
+        PackageSpec(
+            TOOLCHAIN_PACKAGE,
+            TOOLCHAIN_VERSION,
+            toolchain_path,
+            ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS,
+            # xtensa-lx106-elf pins the target: every gcc package has a bin/
+            ("bin", "xtensa-lx106-elf"),
+        ),
+    )
+    # Resolved only when a download is needed, so an installed toolchain
+    # keeps working on a host without a build; a mirror override wins
+    resolvers: dict[str, Resolver] = {}
+    if not ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS:
+        resolvers[FRAMEWORK_PACKAGE] = release.download
+    if not ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS:
+        resolvers[TOOLCHAIN_PACKAGE] = toolchain_download
+    # Fetch both archives at once; the installs verify and extract them.
+    # One spec list for both, so the two phases cannot drift.
+    prefetch_packages(specs, downloads_dir, resolvers)
+    install_packages(specs, downloads_dir, resolvers)
+    return InstalledPaths(
+        framework=framework_path, toolchain=toolchain_path, ninja=ninja_path
+    )
+
+
+def toolchain_tool(toolchain_path: Path, name: str) -> Path:
+    """Path to one toolchain tool (gcc, g++, ar, size, addr2line, ...).
+
+    The single owner of the ``bin/xtensa-lx106-elf-<name>`` layout and the
+    Windows suffix, so a toolchain package bump touches one spot.
+    """
+    suffix = ".exe" if os.name == "nt" else ""
+    return toolchain_path / "bin" / f"xtensa-lx106-elf-{name}{suffix}"
+
+
+def get_build_env(toolchain_path: Path, ccache: str | None) -> dict[str, str]:
+    env = os.environ.copy()
+    # Drop empty entries: a trailing separator from an absent PATH would
+    # make the shell search the current directory for tools
+    parts = [
+        str(toolchain_path / "bin"),
+        *filter(None, env.get("PATH", "").split(os.pathsep)),
+    ]
+    env["PATH"] = os.pathsep.join(parts)
+    env.update(ccache_env(ccache, ARDUINO8266_TOOLS_CACHE))
+    return env
@@ -0,0 +1,212 @@
+"""Native Arduino ESP8266 build driver (the PlatformIO ``run`` equivalent)."""
+
+from __future__ import annotations
+
+import logging
+from pathlib import Path
+import subprocess
+from typing import TYPE_CHECKING
+
+from esphome.build_helpers.ccache import resolve_absolute_ccache_path
+from esphome.build_helpers.native import warn_ignored_platformio_options
+from esphome.build_helpers.ninja import refresh_compile_commands
+from esphome.const import (
+    CONF_COMPILE_PROCESS_LIMIT,
+    CONF_ESPHOME,
+    KEY_CORE,
+    KEY_FRAMEWORK_VERSION,
+)
+from esphome.core import CORE
+from esphome.types import ConfigType
+
+if TYPE_CHECKING:
+    from esphome.arduino8266.framework import InstalledPaths
+
+_LOGGER = logging.getLogger(__name__)
+
+# ESP8266 user RAM (matches upload.maximum_ram_size in every board manifest)
+_MAX_RAM_SIZE = 81920
+
+
+_RAM_SECTIONS = (".data", ".rodata", ".bss")
+_FLASH_SECTIONS = (".irom0.text", ".text", ".text1", ".data", ".rodata")
+
+
+def get_build_dir() -> Path:
+    return CORE.relative_pioenvs_path(CORE.name)
+
+
+def get_elf_path() -> Path:
+    return get_build_dir() / "firmware.elf"
+
+
+def _toolchain_tool(name: str) -> Path:
+    # Imported here, not at module scope: the serial upload/logs fast path
+    # resolves this module for its artifact paths alone, and framework
+    # pulls in the whole package-download stack
+    from esphome.arduino8266 import framework
+
+    return framework.toolchain_tool(framework.get_toolchain_path(), name)
+
+
+def get_factory_firmware_path() -> Path:
+    """The image to serial-flash at 0x0 (same bytes as firmware.bin: the
+    8266 factory copy exists for artifact-contract parity, not content)."""
+    return get_build_dir() / "firmware.factory.bin"
+
+
+def get_addr2line_path() -> Path:
+    return _toolchain_tool("addr2line")
+
+
+def get_objdump_path() -> Path:
+    return _toolchain_tool("objdump")
+
+
+def get_readelf_path() -> Path:
+    return _toolchain_tool("readelf")
+
+
+def run_compile(config: ConfigType, verbose: bool) -> int:
+    from esphome.arduino8266 import framework
+    from esphome.build_gen import arduino8266 as build_gen
+    from esphome.core.config import NATIVE_ARDUINO_CONSUMED_PIO_OPTIONS
+
+    warn_ignored_platformio_options(NATIVE_ARDUINO_CONSUMED_PIO_OPTIONS)
+    paths = framework.check_and_install(CORE.data[KEY_CORE][KEY_FRAMEWORK_VERSION])
+    # Resolved once: the probe is not free and three consumers need it
+    ccache = resolve_absolute_ccache_path()
+    ninja_changed = build_gen.write_project(paths, ccache)
+
+    build_dir = get_build_dir()
+    env = framework.get_build_env(paths.toolchain, ccache)
+    refresh_compile_commands(paths.ninja, build_dir, env, ninja_changed)
+
+    cmd = [str(paths.ninja)]
+    if verbose:
+        cmd.append("-v")
+    if jobs := config[CONF_ESPHOME].get(CONF_COMPILE_PROCESS_LIMIT):
+        cmd += ["-j", str(jobs)]
+    # Explicit targets: a generator defect that drops them fails loudly
+    # instead of a green no-op run leaving stale artifacts in place
+    targets = ["firmware.factory.bin", "firmware.ota.bin"]
+    cmd += targets
+
+    # cwd, not -C: drops ninja's "Entering directory" banner
+    _LOGGER.debug("Running: %s", " ".join(cmd))
+    rc = subprocess.run(
+        cmd, cwd=build_dir, env=env, check=False, close_fds=False
+    ).returncode
+    if rc != 0:
+        return rc
+
+    # ninja already refused missing targets; existence covers a rule that
+    # ran but wrote elsewhere
+    build_dir_artifacts = (
+        get_elf_path(),
+        build_dir / "firmware.bin",
+        get_factory_firmware_path(),
+        build_dir / "firmware.ota.bin",
+    )
+    for artifact in build_dir_artifacts:
+        if not artifact.is_file():
+            _LOGGER.error("Build produced no %s", artifact)
+            return 1
+
+    if not _print_size_summary(build_dir, paths):
+        # Cause already warned; name the consequence for CI harnesses
+        _LOGGER.warning("Firmware size summary unavailable for this build")
+    from esphome.build_helpers.idedata import warn_if_idedata_missing
+
+    warn_if_idedata_missing(lambda: get_idedata(ccache))
+    return 0
+
+
+def _parse_app_size(build_dir: Path, paths: InstalledPaths) -> int | None:
+    """Read the app flash budget (irom0_0_seg length) from the linker script."""
+    from esphome.build_gen.arduino8266 import get_flash_ld_path
+    from esphome.components.esp8266.build_surgery import segment_length
+
+    # Warnings, not debug: without the app size the Flash summary line is
+    # dropped and CI's memory-impact extraction loses its flash metric.
+    ld_path = get_flash_ld_path(build_dir, paths)
+    try:
+        ld_text = ld_path.read_text(encoding="utf-8")
+    except (OSError, UnicodeDecodeError) as err:
+        # A corrupt script degrades the same way, never aborts the build
+        _LOGGER.warning("Cannot read linker script for the Flash summary: %s", err)
+        return None
+    if not (app_size := segment_length(ld_text, "irom0_0_seg")):
+        _LOGGER.warning("No usable irom0_0_seg in %s; skipping Flash summary", ld_path)
+        return None
+    return app_size
+
+
+def _print_size_summary(build_dir: Path, paths: InstalledPaths) -> bool:
+    """Print the RAM/Flash lines ``ci_memory_impact_extract.py`` parses;
+    False when skipped."""
+    from esphome.arduino8266.framework import toolchain_tool
+    from esphome.build_helpers.size_summary import print_size_line
+
+    try:
+        result = subprocess.run(
+            [
+                str(toolchain_tool(paths.toolchain, "size")),
+                "-A",
+                "-d",
+                str(build_dir / "firmware.elf"),
+            ],
+            capture_output=True,
+            text=True,
+            check=True,
+            close_fds=False,
+        )
+    except (OSError, subprocess.CalledProcessError) as err:
+        # The summary is a bonus artifact like idedata; a truncated
+        # toolchain extraction must not discard an already-linked build
+        _LOGGER.warning("Could not summarize firmware size: %s", err)
+        return False
+    # -d prints decimal sizes; anything else trips the missing-sections guard
+    sections = {
+        parts[0]: int(parts[1])
+        for line in result.stdout.splitlines()
+        if (parts := line.split())[:1] and parts[0].startswith(".") and len(parts) >= 2
+        if parts[1].isdigit()
+    }
+    if missing := set(_RAM_SECTIONS + _FLASH_SECTIONS) - set(sections):
+        # A defaulted 0 would print a confidently wrong total for CI's metric
+        _LOGGER.warning(
+            "Size output is missing section(s) %s; skipping the size summary",
+            ", ".join(sorted(missing)),
+        )
+        return False
+    # Resolve the flash budget before printing: a RAM line without its
+    # Flash line would skew CI's memory-impact extraction
+    app_size = _parse_app_size(build_dir, paths)
+    if not app_size:
+        return False
+    ram = sum(sections[s] for s in _RAM_SECTIONS)
+    flash = sum(sections[s] for s in _FLASH_SECTIONS)
+    print_size_line("RAM", ram, _MAX_RAM_SIZE)
+    print_size_line("Flash", flash, app_size)
+    return True
+
+
+def get_idedata(ccache: str | None = None) -> dict | None:
+    """Derive idedata from the build's compile_commands.json (same
+    contract as ``espidf.toolchain.get_idedata``)."""
+    from esphome.build_helpers.idedata import load_or_build_idedata
+
+    # A disabled ccache resolves to None without spawning anything, so
+    # re-resolving here costs nothing when the caller has no answer
+    launcher = ccache or resolve_absolute_ccache_path()
+    return load_or_build_idedata(
+        get_build_dir() / "compile_commands.json",
+        get_elf_path(),
+        # Suffixed so a platformio->arduino->platformio round trip on one
+        # config never serves the other toolchain's cache shape
+        CORE.relative_internal_path("idedata", f"{CORE.name}.arduino.json"),
+        # The compile DB's commands carry the same ccache prefix the ninja
+        # rules were generated with
+        launcher=str(launcher) if launcher else None,
+    )
@@ -0,0 +1,108 @@
+"""Tiny cross-platform build steps invoked from the generated ninja file.
+
+Plain script (not ``python -m``): it runs from ninja with whatever Python
+started esphome and must not depend on the package being importable.
+
+Subcommands:
+    ar <ar-binary> <archive> <rspfile>   remove stale archive, then ``ar rcs``
+    copy <src> <dst>                     copy a file
+
+The ar rspfile carries one object path per line (the generating rule must
+use ``$in_newline``, never ``$in``).
+"""
+
+from pathlib import Path
+import shutil
+import subprocess
+import sys
+
+
+def _read_rspfile(rspfile: str) -> list[str]:
+    r"""The object paths listed in ``rspfile``, unquoted.
+
+    GNU ar treats backslashes in response files as escapes (corrupts
+    Windows paths), so the caller expands the list into argv; strip the
+    simple surrounding quote ninja adds to special paths, then undo
+    ninja's POSIX escape for an embedded quote ('a'\\''b.o' -> a'b.o).
+    """
+    return [
+        line[1:-1].replace("'\\''", "'")
+        if len(line) >= 2 and line[0] == line[-1] and line[0] in "'\""
+        else line
+        for line in Path(rspfile).read_text(encoding="utf-8").splitlines()
+        if line
+    ]
+
+
+def _run_ar(ar: str, archive: str, rspfile: str) -> int:
+    # Remove first: ``ar rcs`` replaces members but never drops ones whose
+    # source was removed from the build, which would leak stale objects.
+    Path(archive).unlink(missing_ok=True)
+    objects = _read_rspfile(rspfile)
+    if not objects:
+        # An empty archive would "succeed" here and fail far away at link
+        print(f"ar: no objects listed in {rspfile} for {archive}", file=sys.stderr)
+        return 1
+    # Batch by argv length: expanding the rspfile gives back the Windows
+    # 32767-char command-line limit it existed to avoid. "rcs" creates,
+    # "qs" appends; the s keeps the symbol index explicit on every ar.
+    op = "rcs"
+    ok = False
+    try:
+        while objects:
+            batch = [objects.pop(0)]
+            batch_len = len(batch[0])
+            while objects and batch_len + len(objects[0]) < 25000:
+                batch_len += len(objects[0]) + 1
+                batch.append(objects.pop(0))
+            rc = subprocess.run(
+                [ar, op, archive, *batch], check=False, close_fds=False
+            ).returncode
+            if rc != 0:
+                return rc
+            op = "qs"
+        ok = True
+        return 0
+    finally:
+        if not ok:
+            # Any failure (bad exit, missing ar binary, interrupt) must not
+            # leave a truncated archive behind
+            Path(archive).unlink(missing_ok=True)
+
+
+def _run_copy(src: str, dst: str) -> int:
+    try:
+        shutil.copyfile(src, dst)
+    except OSError as err:
+        # Never leave a partially written output (e.g. a firmware image);
+        # SameFileError means dst IS src, where unlinking destroys the input
+        if not isinstance(err, shutil.SameFileError):
+            Path(dst).unlink(missing_ok=True)
+        print(f"copy: {src} -> {dst} failed: {err}", file=sys.stderr)
+        return 1
+    return 0
+
+
+# mode -> (handler, expected operand count); surplus argv means a
+# mis-specified ninja rule and must error, not silently drop operands
+_MODES = {"ar": (_run_ar, 3), "copy": (_run_copy, 2)}
+
+
+def main() -> int:
+    mode = sys.argv[1] if len(sys.argv) > 1 else ""
+    if entry := _MODES.get(mode):
+        handler, argc = entry
+        args = sys.argv[2:]
+        if len(args) != argc:
+            print(
+                f"build_tool {mode}: expected {argc} arguments, got {len(args)}",
+                file=sys.stderr,
+            )
+            return 1
+        return handler(*args)
+    print(f"unknown build_tool mode: {mode}", file=sys.stderr)
+    return 1
+
+
+if __name__ == "__main__":  # pragma: no cover
+    sys.exit(main())
@@ -1,17 +1,29 @@
 """ESP-IDF direct build generator for ESPHome."""

 import json
+import logging
 from pathlib import Path
+import re
+import textwrap

-from esphome.components.esp32 import get_esp32_variant, idf_version
+from esphome.build_helpers import pch
+from esphome.components.esp32 import (
+    get_esp32_variant,
+    get_excluded_builtin_components,
+    get_managed_component_require_names,
+    idf_version,
+)
 import esphome.config_validation as cv
 from esphome.core import CORE
+from esphome.espidf import variant_to_idf_target
 from esphome.framework_helpers import (
    get_project_compile_flags,
    get_project_cxx_compile_flags,
    get_project_link_flags,
 )
-from esphome.helpers import mkdir_p, write_file_if_changed
+from esphome.helpers import get_bool_env, mkdir_p, write_file_if_changed
+
+_LOGGER = logging.getLogger(__name__)

 # Replaces the IDF default C++ standard (-std=gnu++2b appended to
 # CXX_COMPILE_OPTIONS by project.cmake's __build_init) with the one set via
@@ -24,13 +36,91 @@ list(FILTER esphome_cxx_compile_options EXCLUDE REGEX "^-std=")
 list(APPEND esphome_cxx_compile_options "-std={standard}")
 idf_build_set_property(CXX_COMPILE_OPTIONS "${{esphome_cxx_compile_options}}")"""

+# Drops the app archive from ldgen's inputs so app-only edits skip the
+# sections.ld regeneration. Safe: no mapping fragment references it
+# (run_compile re-checks each build). Filters only the top-level call;
+# the prior definition stays reachable with an underscore prefix.
+_LDGEN_OVERRIDE = """\
+if(COMMAND __ldgen_get_lib_deps_of_target)
+    set_property(GLOBAL PROPERTY ESPHOME_LDGEN_ARMED 1)
+    function(__ldgen_get_lib_deps_of_target target out_list_var)
+        if(NOT COMMAND ___ldgen_get_lib_deps_of_target)
+            message(FATAL_ERROR "ESPHome ldgen override lost the original "
+                "implementation; set ESPHOME_LDGEN_FULL_DEPS=1 and rebuild.")
+        endif()
+        ___ldgen_get_lib_deps_of_target(${target} ${out_list_var})
+        if(out_list_var STREQUAL "ldgen_libraries")
+            set_property(GLOBAL PROPERTY ESPHOME_LDGEN_FILTERED 1)
+            list(LENGTH ${out_list_var} esphome_ldgen_before)
+            list(REMOVE_ITEM ${out_list_var} idf::src __idf_src)
+            list(LENGTH ${out_list_var} esphome_ldgen_after)
+            if(esphome_ldgen_before EQUAL esphome_ldgen_after)
+                message(@SEVERITY@ "ESPHome ldgen app archive exclusion matched "
+                    "nothing; app edits will regenerate sections.ld.")
+            endif()
+        endif()
+        set(${out_list_var} "${${out_list_var}}" PARENT_SCOPE)
+    endfunction()
+else()
+    message(@MISSING@ "ESPHome ldgen override target not found; "
+        "app edits will regenerate sections.ld.")
+endif()"""
+
+# lwip sources that compile to empty objects with the option off (their own
+# #if guard). (option, regex valid for both Python and CMake); a source is
+# only dropped when its option is defined and off, so a renamed option
+# keeps it.
+LWIP_EMPTY_SOURCES: tuple[tuple[str, str], ...] = (
+    ("CONFIG_LWIP_PPP_SUPPORT", "/netif/ppp/"),
+    ("CONFIG_LWIP_IPV6", "/core/ipv6/"),
+    ("CONFIG_LWIP_AUTOIP", "/core/ipv4/autoip[.]c$"),
+    ("CONFIG_LWIP_STATS", "/core/stats[.]c$"),
+)
+# Drift guard only: keep every lwip source.
+LWIP_FULL_SOURCES_ENV = "ESPHOME_LWIP_FULL_SOURCES"
+
+# Drops the empty objects after project(), once the lwip target exists.
+_LWIP_EMPTY_SOURCES_FILTER = f"""\
+idf_build_get_property(esphome_build_components BUILD_COMPONENTS)
+if(lwip IN_LIST esphome_build_components AND NOT DEFINED ENV{{{LWIP_FULL_SOURCES_ENV}}})
+    idf_component_get_property(esphome_lwip_lib lwip COMPONENT_LIB)
+    get_target_property(esphome_lwip_srcs ${{esphome_lwip_lib}} SOURCES)
+@FILTERS@
+    set_property(TARGET ${{esphome_lwip_lib}} PROPERTY SOURCES ${{esphome_lwip_srcs}})
+endif()"""
+
+
+def lwip_empty_source_gate(option: str, regex: str) -> str:
+    return (
+        f"    if(DEFINED {option} AND NOT {option})\n"
+        f'        list(FILTER esphome_lwip_srcs EXCLUDE REGEX "{regex}")\n'
+        "    endif()"
+    )
+
+
+def _lwip_empty_sources_filter() -> str:
+    gates = "\n".join(lwip_empty_source_gate(*entry) for entry in LWIP_EMPTY_SOURCES)
+    return _LWIP_EMPTY_SOURCES_FILTER.replace("@FILTERS@", gates)
+
+
+# Runs after project() so the walk has happened; catches the remaining
+# silent path where the top-level out-var was renamed.
+_LDGEN_OVERRIDE_CHECK = """\
+get_property(esphome_ldgen_armed GLOBAL PROPERTY ESPHOME_LDGEN_ARMED)
+get_property(esphome_ldgen_filtered GLOBAL PROPERTY ESPHOME_LDGEN_FILTERED)
+if(esphome_ldgen_armed AND NOT esphome_ldgen_filtered)
+    message(@SEVERITY@ "ESPHome ldgen override never filtered the app "
+        "archive; app edits will regenerate sections.ld.")
+endif()"""
+

 def get_available_components() -> list[str] | None:
-    """Get list of built-in ESP-IDF components from project_description.json.
+    """List the built-in ESP-IDF components from ``project_description.json``.

-    Excludes ``src``, IDF-managed components (``managed_components/``), and
-    converted PIO libs (``pio_components/``). Returns ``None`` if the build
-    dir or ``project_description.json`` isn't ready yet.
+    Only components below its ``idf_path/components`` count, which leaves out
+    ``src``, IDF-managed components, converted PIO libs and project local
+    ones such as the Arduino ``component_stubs``. Returns ``None`` if the
+    build dir or ``project_description.json`` isn't ready yet.
    """
    if CORE.build_path is None:
        return None
@@ -41,45 +131,157 @@ def get_available_components() -> list[str] | None:
    try:
        with project_desc.open(encoding="utf-8") as f:
            data = json.load(f)
-
-        component_info = data.get("build_component_info", {})
-
-        result = []
-        for name, info in component_info.items():
-            # Exclude our own src component
-            if name == "src":
-                continue
-
-            # Exclude IDF-managed and converted-PIO components (external).
-            comp_dir = info.get("dir", "")
-            if "managed_components" in comp_dir or "pio_components" in comp_dir:
-                continue
-
-            result.append(name)
-
-        return result
-    except (json.JSONDecodeError, OSError):
+        root = (Path(data["idf_path"]) / "components").resolve()
+        result = [
+            name
+            for name, info in data.get("build_component_info", {}).items()
+            if (comp_dir := info.get("dir"))
+            and Path(comp_dir).resolve().is_relative_to(root)
+        ]
+    except (json.JSONDecodeError, KeyError, OSError) as err:
+        _LOGGER.debug("Could not read %s: %s", project_desc, err)
        return None
+    if not result:
+        _LOGGER.warning("No ESP-IDF components found under %s", root)
+    return result


 def has_discovered_components() -> bool:
-    """Check if we have discovered components from a previous configure."""
-    return get_available_components() is not None
+    """Check if a previous configure discovered any built-in components."""
+    return bool(get_available_components())


-def get_project_cmakelists(minimal: bool = False) -> str:
+def _cmake_quote(value: str) -> str:
+    """Quote a cmake arg value for a set() line. add_cmake_arg rejects
+    whitespace, quotes, and '$', so only backslashes need escaping."""
+    escaped = value.replace("\\", "\\\\")
+    return f'"{escaped}"'
+
+
+# CONFIG_APP_BUILD_BOOTLOADER is hidden and force-selected, so it can only be
+# cleared at the CMake level (the same state IDF's RAM-app build type uses).
+# The macro is IDF's __build_process_project_includes plus a few added lines;
+# the flag is ignored and the bootloader builds as usual if IDF changes it.
+IDF_BOOTLOADER_OVERRIDE = """\
+# ESPHome bootloader skip switch; see esphome/espidf/toolchain.py.
+if(ESPHOME_SKIP_BOOTLOADER)
+    macro(__build_process_project_includes)
+        idf_build_get_property(sdkconfig_cmake SDKCONFIG_CMAKE)
+        include(${sdkconfig_cmake})
+        set(CONFIG_APP_BUILD_BOOTLOADER "")
+        # bt's CMakeLists reads the lowercase idf_target that the (now
+        # skipped) bootloader project_include leaks; keep it defined, or
+        # its empty TARGET_SRC_NAME sends file(GLOB_RECURSE) across /.
+        idf_build_get_property(idf_target IDF_TARGET)
+        # partition_table's V1 ECDSA signing reads this key, which the
+        # skipped bootloader project_include also sets.
+        get_filename_component(SECURE_BOOT_SIGNING_KEY "${CONFIG_SECURE_BOOT_SIGNING_KEY}" ABSOLUTE BASE_DIR "${project_dir}")
+        idf_build_get_property(build_properties __BUILD_PROPERTIES)
+        foreach(build_property ${build_properties})
+            idf_build_get_property(val ${build_property})
+            set(${build_property} "${val}")
+        endforeach()
+        idf_build_get_property(build_component_targets __BUILD_COMPONENT_TARGETS)
+        foreach(component_target ${build_component_targets})
+            __component_get_property(dir ${component_target} COMPONENT_DIR)
+            __component_get_property(_name ${component_target} COMPONENT_NAME)
+            set(COMPONENT_NAME ${_name})
+            set(COMPONENT_DIR ${dir})
+            set(COMPONENT_PATH ${dir})
+            if(EXISTS ${COMPONENT_DIR}/project_include.cmake)
+                include(${COMPONENT_DIR}/project_include.cmake)
+            endif()
+        endforeach()
+    endmacro()
+endif()
+"""
+
+# The lines the override adds to IDF's macro; idf_macro_matches() below
+# strips them before comparing with the live macro.
+BOOTLOADER_OVERRIDE_ADDED_LINES = (
+    'set(CONFIG_APP_BUILD_BOOTLOADER "")',
+    "idf_build_get_property(idf_target IDF_TARGET)",
+    (
+        "get_filename_component(SECURE_BOOT_SIGNING_KEY"
+        ' "${CONFIG_SECURE_BOOT_SIGNING_KEY}" ABSOLUTE BASE_DIR "${project_dir}")'
+    ),
+)
+
+_MACRO = re.compile(
+    r"macro\(__build_process_project_includes\)(.*?)endmacro\(\)", re.DOTALL
+)
+
+
+def _normalized_macro(text: str) -> list[str] | None:
+    """The macro body as comment-free, whitespace-collapsed lines."""
+    if (match := _MACRO.search(text)) is None:
+        return None
+    return [
+        re.sub(r"\s+", " ", line)
+        for raw in match.group(1).splitlines()
+        if (line := raw.split("#", 1)[0].strip())
+    ]
+
+
+_EXPECTED_MACRO = [
+    line
+    for line in _normalized_macro(IDF_BOOTLOADER_OVERRIDE)
+    if line not in BOOTLOADER_OVERRIDE_ADDED_LINES
+]
+
+
+def idf_macro_matches(idf_path: Path) -> bool:
+    """Whether IDF's macro still matches the copy the override replays."""
+    build_cmake = idf_path / "tools" / "cmake" / "build.cmake"
+    live = _normalized_macro(build_cmake.read_text(encoding="utf-8"))
+    return live == _EXPECTED_MACRO
+
+
+def _cmake_args_for_write(minimal: bool) -> dict[str, str]:
+    """The cg.add_cmake_arg() values for one project write.
+
+    The discovery (minimal) write lets every built-in component register so
+    the list it finds, cached per target, serves any exclusion set; the full
+    write drops the excluded names from that list and passes all of them to
+    IDF. Names outside the framework's components directory (managed
+    components) stay excluded on the discovery write too, since the list
+    only holds built-in ones. A checkout supplied through IDF_PATH caches
+    nothing, so its discovery keeps every exclusion.
+    """
+    from esphome.espidf.toolchain import _esphome_manages_idf, _get_idf_path
+
+    args = dict(CORE.cmake_args)
+    if (
+        not minimal
+        or not _esphome_manages_idf()
+        or not (excluded := args.get("EXCLUDE_COMPONENTS"))
+    ):
+        return args
+    root = _get_idf_path() / "components"
+    outside = [name for name in excluded.split(";") if not (root / name).is_dir()]
+    if outside:
+        args["EXCLUDE_COMPONENTS"] = ";".join(outside)
+    else:
+        del args["EXCLUDE_COMPONENTS"]
+    return args
+
+
+def get_project_cmakelists(
+    minimal: bool = False, builtin_components: list[str] | None = None
+) -> str:
    """Generate the top-level CMakeLists.txt for ESP-IDF project.

    When ``minimal`` is true, omit ``ESPHOME_PROJECT_BUILTIN_COMPONENTS``
    since ``project_description.json`` may be stale on the first write.
+    ``builtin_components`` supplies the discovered list (from the cache)
+    instead of reading it from ``project_description.json``.
    """
-    # Get IDF target from ESP32 variant (e.g., ESP32S3 -> esp32s3)
-    variant = get_esp32_variant()
-    idf_target = variant.lower().replace("-", "")
+    idf_target = variant_to_idf_target(get_esp32_variant())

-    # esp_idf_size 2.x (bundled with IDF >=6.0) made NG the default and
-    # removed the --ng flag; on 1.x (IDF 5.5) --ng is required to get
-    # --format=raw because the legacy mode doesn't support it.
+    # esp_idf_size 2.x (IDF >=6.0) made NG the default and removed --ng;
+    # 1.x (IDF 5.5) needs --ng for --format=json2. 1.x json2 also lacks
+    # total_size, hence the ELF fallback in espidf/size_summary.py; both
+    # go away together when 1.x support is dropped.
    size_ng_flag = "--ng" if idf_version() < cv.Version(6, 0, 0) else ""

    # Project-wide compile options: -D defines and -W warning flags (skip
@@ -109,6 +311,30 @@ def get_project_cmakelists(minimal: bool = False) -> str:
        else ""
    )

+    # Stops the ~3s sections.ld regeneration on app-only edits; see
+    # _LDGEN_OVERRIDE. ESPHOME_LDGEN_FULL_DEPS=1 restores stock behavior;
+    # ESPHOME_LDGEN_STRICT=1 (CI) fails the configure when an IDF bump
+    # breaks the override instead of degrading to stock deps.
+    if get_bool_env("ESPHOME_LDGEN_FULL_DEPS"):
+        ldgen_override = ""
+        ldgen_override_check = ""
+    else:
+        strict = get_bool_env("ESPHOME_LDGEN_STRICT")
+        severity = "FATAL_ERROR" if strict else "WARNING"
+        missing = "FATAL_ERROR" if strict else "STATUS"
+        ldgen_override = _LDGEN_OVERRIDE.replace("@SEVERITY@", severity).replace(
+            "@MISSING@", missing
+        )
+        ldgen_override_check = _LDGEN_OVERRIDE_CHECK.replace("@SEVERITY@", severity)
+
+    # CMake variables registered via cg.add_cmake_arg(). Emitted before
+    # include(project.cmake) so values like EXCLUDE_COMPONENTS are already
+    # set when project.cmake seeds the component list.
+    cmake_args = "\n".join(
+        f"set({name} {_cmake_quote(value)})"
+        for name, value in sorted(_cmake_args_for_write(minimal).items())
+    )
+
    # Per-project list exposed as a CMake variable so converted PIO libs
    # can reference ${ESPHOME_PROJECT_MANAGED_COMPONENTS} without baking
    # project-specific names into their cached CMakeLists.
@@ -119,8 +345,6 @@ def get_project_cmakelists(minimal: bool = False) -> str:
    # runs as a separate CMake script invocation that doesn't load the
    # project's top-level CMakeLists; without this, ${ESPHOME_PROJECT_
    # MANAGED_COMPONENTS} in a converted-lib REQUIRES expands to empty).
-    from esphome.components.esp32 import get_managed_component_require_names
-
    managed_components_property = "\n".join(
        f"idf_build_set_property(ESPHOME_PROJECT_MANAGED_COMPONENTS {name} APPEND)"
        for name in get_managed_component_require_names()
@@ -131,12 +355,24 @@ def get_project_cmakelists(minimal: bool = False) -> str:
    # component's REQUIRES including real IDF components). Referenced by
    # src/CMakeLists and by each converted PIO lib's CMakeLists. Skipped
    # on minimal writes because project_description.json may be stale.
+    # Excluded components are dropped here as well: the discovery list
+    # (cached per target) still holds them, and requiring an excluded
+    # component pulls it back into the build (IDF requirement expansion
+    # overrides EXCLUDE_COMPONENTS).
+    # Derived from the EXCLUDE_COMPONENTS cmake arg emitted above so the
+    # two can never disagree within one generated file.
    builtin_components_property = (
        ""
        if minimal
        else "\n".join(
            f"idf_build_set_property(ESPHOME_PROJECT_BUILTIN_COMPONENTS {name} APPEND)"
-            for name in sorted(get_available_components() or [])
+            for name in sorted(
+                set(
+                    builtin_components
+                    if builtin_components is not None
+                    else get_available_components() or []
+                ).difference(CORE.cmake_args.get("EXCLUDE_COMPONENTS", "").split(";"))
+            )
        )
    )

@@ -163,8 +399,13 @@ set(CMAKE_NINJA_FORCE_RESPONSE_FILE 1)
 set(IDF_TARGET {idf_target})
 set(EXTRA_COMPONENT_DIRS ${{CMAKE_SOURCE_DIR}}/src)

+{cmake_args}
+
 include($ENV{{IDF_PATH}}/tools/cmake/project.cmake)

+{IDF_BOOTLOADER_OVERRIDE}
+{ldgen_override}
+
 {cpp_standard_options}

 {cxx_compile_options}
@@ -177,12 +418,31 @@ include($ENV{{IDF_PATH}}/tools/cmake/project.cmake)

 project({CORE.name})

-# Emit raw JSON size data for ESPHome to read post-build.
+{ldgen_override_check}
+
+{_lwip_empty_sources_filter()}
+
+# Emit per-memory-type JSON size data for ESPHome to read post-build.
+# json2 stays small; raw dumps every symbol (~2s on a large map) and
+# this command runs inside the link edge, blocking everything downstream.
+# IDF's size target depends on the map, so ninja has to know the link
+# writes it for size to build in the same run as all. IDF declares the
+# map itself since espressif/esp-idf#19201 (and in cmakev2), and ninja
+# rejects two rules for one output, so declare it here only when IDF has
+# not. add_custom_command(OUTPUT) marks its outputs GENERATED.
+get_source_file_property(esphome_map_declared
+    ${{CMAKE_BINARY_DIR}}/${{CMAKE_PROJECT_NAME}}.map GENERATED)
+if(esphome_map_declared)
+    set(esphome_map_byproducts)
+else()
+    set(esphome_map_byproducts BYPRODUCTS ${{CMAKE_BINARY_DIR}}/${{CMAKE_PROJECT_NAME}}.map)
+endif()
 add_custom_command(
    TARGET ${{CMAKE_PROJECT_NAME}}.elf POST_BUILD
-    COMMAND ${{PYTHON}} -m esp_idf_size {size_ng_flag} --format=raw
+    COMMAND ${{PYTHON}} -m esp_idf_size {size_ng_flag} --format=json2
            -o ${{CMAKE_BINARY_DIR}}/esp_idf_size.json
            ${{CMAKE_PROJECT_NAME}}.map
+    ${{esphome_map_byproducts}}
    WORKING_DIRECTORY ${{CMAKE_BINARY_DIR}}
    VERBATIM
 )
@@ -245,10 +505,75 @@ idf_component_register(
 target_link_options(${{COMPONENT_LIB}} PUBLIC
    {link_opts_str}
 )
+{_pch_cmake_block()}"""
+
+
+# Where CMake puts the .gch of the src component; ccache reads the checksum
+# next to it in place of the .gch
+_PCH_SUM_PATH = "build/esp-idf/src/CMakeFiles/__idf_src.dir/cmake_pch.hxx.gch.sum"
+# Where the Windows gate records its choice
+_PCH_CHOICE_VAR = "ESPHOME_PCH"
+
+
+def _pch_cmake_block() -> str:
+    """The CMake block that precompiles the core headers for the C++ sources
+    of the src component; empty when disabled."""
+    if not pch.pch_enabled():
+        return ""
+    headers = "\n".join(
+        f'    "$<$<COMPILE_LANGUAGE:CXX>:${{CMAKE_CURRENT_SOURCE_DIR}}/{header}>"'
+        for header in pch.PCH_DEFAULT_HEADERS
+    )
+    block = f"""target_precompile_headers(${{COMPONENT_LIB}} PRIVATE
+{headers}
+)"""
+    if not pch.pch_needs_gcc_check():
+        return f"\n# ESPHome precompiled header\n{block}\n"
+    # Before the first configure only CMake knows the compiler version
+    return f"""
+# ESPHome precompiled header, unless GCC bug 14940 keeps it from loading
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND ({pch.PCH_WINDOWS_CMAKE_OLD_GCC}))
+  message(STATUS "ESPHome: GCC ${{CMAKE_CXX_COMPILER_VERSION}} cannot load a precompiled header on Windows; compiling without it")
+  set({_PCH_CHOICE_VAR} OFF CACHE BOOL "ESPHome precompiled header in use" FORCE)
+else()
+  set({_PCH_CHOICE_VAR} ON CACHE BOOL "ESPHome precompiled header in use" FORCE)
+{textwrap.indent(block, "  ")}
+endif()
 """


-def write_project(minimal: bool = False) -> None:
+def _read_if_exists(path: Path) -> str:
+    return path.read_text(encoding="utf-8") if path.is_file() else ""
+
+
+def write_pch_checksum() -> None:
+    """Write the checksum ccache uses in place of the .gch: the core headers,
+    the framework version, the sdkconfig and the managed component versions."""
+    from esphome.espidf.toolchain import get_cmake_cache_value
+
+    if not pch.pch_enabled():
+        return
+    # The gate's choice, cached by configure
+    if pch.pch_needs_gcc_check() and get_cmake_cache_value(_PCH_CHOICE_VAR) != "ON":
+        return
+    pch.log_pch_in_use()
+    checksum = pch.pch_checksum(
+        CORE.relative_src_path(),
+        pch.PCH_DEFAULT_HEADERS,
+        (
+            str(idf_version()),
+            _read_if_exists(CORE.relative_build_path(f"sdkconfig.{CORE.name}")),
+            _read_if_exists(CORE.relative_build_path("dependencies.lock")),
+        ),
+    )
+    path = CORE.relative_build_path(_PCH_SUM_PATH)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    write_file_if_changed(path, checksum + "\n")
+
+
+def write_project(
+    minimal: bool = False, builtin_components: list[str] | None = None
+) -> None:
    """Write ESP-IDF project files."""
    mkdir_p(CORE.build_path)
    mkdir_p(CORE.relative_src_path())
@@ -256,7 +581,7 @@ def write_project(minimal: bool = False) -> None:
    # Write top-level CMakeLists.txt
    write_file_if_changed(
        CORE.relative_build_path("CMakeLists.txt"),
-        get_project_cmakelists(minimal=minimal),
+        get_project_cmakelists(minimal=minimal, builtin_components=builtin_components),
    )

    # Write component CMakeLists.txt in src/
@@ -264,3 +589,12 @@ def write_project(minimal: bool = False) -> None:
        CORE.relative_src_path("CMakeLists.txt"),
        get_component_cmakelists(),
    )
+
+    # Snapshot the exclusion set so has_outdated_files() can trigger a
+    # reconfigure when it changes. The ESPHOME_PROJECT_BUILTIN_COMPONENTS
+    # property drops excluded names, so re-including one (e.g. a config
+    # gains mqtt) needs a reconfigure to rebuild it from the discovery list.
+    write_file_if_changed(
+        CORE.relative_build_path("exclude_components.esphomeinternal"),
+        ";".join(get_excluded_builtin_components()),
+    )
@@ -0,0 +1,303 @@
+"""Native ninja build generator for the host platform.
+
+Emits ``build.ninja`` under ``.pioenvs/<name>/``: every source in the
+generated ``src/`` tree plus the resolved registry libraries compiles with
+the machine's compiler and links into ``program``, the name PlatformIO's
+native platform produced. Build flags route the way SCons's ``ParseFlags``
+did under PlatformIO: ``-D``/``-I``/``-std=``/``-W`` shapes reach the
+compile lines only, ``-l``/``-L``/``-Wl,`` the link line only, everything
+else both.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterable
+import logging
+import os
+from pathlib import Path
+import subprocess
+import sys
+from typing import TYPE_CHECKING
+
+from esphome.build_helpers.ninja import escape as _e, quote_path as _q, shell_token
+from esphome.build_helpers.ninja_gen import (
+    PATH_ARG_FLAGS,
+    Flag,
+    anchor_path_flag,
+    ar_rule_lines,
+    collect_sources,
+    compile_edges,
+    compile_rule_lines,
+    library_edges,
+    pch_edges,
+    pch_rule_lines,
+    tool_lines,
+)
+from esphome.build_helpers.pch import PCH_DEFAULT_HEADERS, pch_enabled
+from esphome.core import CORE, EsphomeError
+from esphome.framework_helpers import get_project_cxx_compile_flags
+from esphome.helpers import mkdir_p, write_file_if_changed
+from esphome.host.toolchain import PROGRAM_NAME, HostCompilers, find_tool, get_build_dir
+from esphome.platformio.library import lex_build_flags
+
+if TYPE_CHECKING:
+    from esphome.arduino.library import ArduinoLibrary
+
+_LOGGER = logging.getLogger(__name__)
+
+# The PlatformIO platform the host built under; registry manifests declare
+# compatibility against it, as lib_compat_mode=strict checked before
+PIO_PLATFORM = "native"
+# Namespaces the shared library download cache (pio_components/host/)
+LIBRARY_CACHE_KEY = "host"
+
+# Flag shapes that only the compiler understands; dropped from the link line
+_COMPILE_ONLY_PREFIXES = ("-D", "-U", "-I", "-std=", "-W", *PATH_ARG_FLAGS)
+# Flag shapes that only the linker consumes; inert on a -c compile line
+_LINK_ONLY_PREFIXES = ("-l", "-L", "-Wl,")
+# Link-only flags whose argument is the next token
+_LINK_ONLY_ARG_FLAGS = ("-framework", "-Xlinker", "-z")
+
+
+def parse_flags(entries: Iterable[str], owner: str) -> list[Flag]:
+    """Lex build flag entries into flags, each with its argument.
+
+    Entries are a set, so their order is not the user's: a flag and the
+    argument it takes as the next token must share one entry.
+    """
+    flags: list[Flag] = []
+    for entry in entries:
+        it = iter(lex_build_flags(entry, owner))
+        for tok in it:
+            if tok not in PATH_ARG_FLAGS and tok not in _LINK_ONLY_ARG_FLAGS:
+                flags.append((tok,))
+                continue
+            arg = next(it, None)
+            # A path never starts with "-"; that is the next flag
+            if arg is None or (tok in PATH_ARG_FLAGS and arg.startswith("-")):
+                raise EsphomeError(
+                    f"{owner} build flags have '{tok}' with no argument; write "
+                    f"the flag and its argument as one entry"
+                )
+            flags.append((tok, arg))
+    return flags
+
+
+def split_flags(flags: list[Flag]) -> tuple[list[Flag], list[Flag]]:
+    """Route build flags to the compile and link lines."""
+    compile_flags: list[Flag] = []
+    link_flags: list[Flag] = []
+    for flag in flags:
+        name = flag[0]
+        if len(flag) > 1:
+            (compile_flags if name in PATH_ARG_FLAGS else link_flags).append(flag)
+        elif name.startswith(_LINK_ONLY_PREFIXES):
+            # Checked before the compile prefixes: -Wl, would match -W
+            link_flags.append(flag)
+        elif name.startswith(_COMPILE_ONLY_PREFIXES):
+            compile_flags.append(flag)
+        else:
+            # -g, -O, -f*, -m*, -pthread, --coverage: both lines, as SCons
+            compile_flags.append(flag)
+            link_flags.append(flag)
+    return compile_flags, link_flags
+
+
+def _is_std(flag: Flag) -> bool:
+    return flag[0].startswith("-std=")
+
+
+def _is_cxx_std(flag: Flag) -> bool:
+    return _is_std(flag) and "++" in flag[0]
+
+
+def _anchored_flags(entries: Iterable[str], owner: str) -> list[Flag]:
+    build_path = Path(CORE.build_path)
+    return [
+        anchor_path_flag(flag, build_path)
+        for flag in parse_flags(sorted(entries), owner)
+    ]
+
+
+def _flag_lists() -> tuple[list[str], list[str], list[str]]:
+    """The C, C++, and link flag lists (raw tokens), build_unflags applied.
+
+    ``cg.set_cpp_standard`` wins over any ``-std=`` in the build flags for
+    C++ compiles, as PlatformIO's unflag of every other standard did; C
+    compiles never see a C++ standard.
+    """
+    # The funnel warns and drops empty glued arguments (-D "") itself
+    compile_flags, link_flags = split_flags(
+        _anchored_flags(CORE.build_flags, "esphome")
+    )
+    cflags = [f for f in compile_flags if not _is_cxx_std(f)]
+    cxx_std = CORE.cpp_standard
+    cxxflags = [f for f in compile_flags if not (cxx_std and _is_std(f))]
+    if cxx_std:
+        cxxflags.insert(0, (f"-std={cxx_std}",))
+    cxxflags += [(tok,) for tok in get_project_cxx_compile_flags()]
+
+    # A flag is removed whole, with its argument, as PlatformIO did
+    unflags = set(_anchored_flags(CORE.build_unflags, "esphome build_unflags"))
+    # An unflag that hits nothing (a typo, or -DUSE_FOO against
+    # -DUSE_FOO=1) must be visible, since the user believes the flag is
+    # gone while it still drives the build
+    if unmatched := sorted(unflags - set(cflags) - set(cxxflags) - set(link_flags)):
+        _LOGGER.warning(
+            "build_unflags entries matched no build flag: %s",
+            ", ".join(" ".join(flag) for flag in unmatched),
+        )
+
+    def keep(flags: list[Flag]) -> list[str]:
+        return [tok for flag in flags if flag not in unflags for tok in flag]
+
+    return keep(cflags), keep(cxxflags), keep(link_flags)
+
+
+def _resolve_host_libraries() -> list[ArduinoLibrary]:
+    """Every ``cg.add_library()`` entry, fetched from the registry.
+
+    The host has no framework, so nothing is bundled and no framework
+    compatibility check applies; the platform check keeps the strict
+    manifest gate PlatformIO's native platform enforced. Manifest-less
+    libraries (a bare git checkout) build with PlatformIO's default
+    layout, as they did under its native platform.
+    """
+    if not CORE.platformio_libraries:
+        return []
+    from esphome.arduino.library import resolve_libraries
+
+    return resolve_libraries(
+        None,
+        pio_platform=PIO_PLATFORM,
+        board_mcu="host",
+        cache_key=LIBRARY_CACHE_KEY,
+        framework=None,
+        manifest_optional=True,
+    )
+
+
+def _file_macro_maps(build_dir: Path) -> list[str]:
+    """Flags that keep ``__FILE__`` relative to the build path.
+
+    PlatformIO compiled ``src/x.cpp`` from the build path, and tools name
+    things after that spelling (CodSpeed's benchmark ids). Here a source
+    reaches the compiler by its absolute path, or relative to the build
+    directory when ccache rewrites it.
+    """
+    build_path = Path(CORE.build_path)
+    prefixes = (build_path, Path(os.path.relpath(build_path, build_dir)))
+    return [
+        shell_token(f"-fmacro-prefix-map={prefix}{os.sep}=", force=True)
+        for prefix in prefixes
+    ]
+
+
+def _compiler_version(cxx: tuple[str, ...]) -> str:
+    """What the compiler says it is: its path can stay the same across an
+    update (the macOS shims in /usr/bin)."""
+    result = subprocess.run(
+        [*cxx, "--version"], capture_output=True, text=True, check=False
+    )
+    return result.stdout
+
+
+def write_project(compilers: HostCompilers, ccache: str | None) -> bool:
+    """Write the ninja build for the current configuration.
+
+    ``ccache`` is the caller's already-resolved binary (None when disabled).
+    Returns True when ``build.ninja`` changed, so the caller can skip work
+    derived purely from it (the compile database) on unchanged builds.
+    """
+    build_dir = get_build_dir()
+    mkdir_p(build_dir)
+    src_dir = CORE.relative_src_path()
+    if not src_dir.is_dir():
+        # Generated project state, not install state: clean-all would not help
+        raise EsphomeError(f"Generated source directory {src_dir} is missing")
+
+    cflags, cxxflags, link_flags = _flag_lists()
+    libraries = _resolve_host_libraries()
+
+    include_dirs = [src_dir]
+    for lib in libraries:
+        include_dirs += lib.include_dirs
+    includes = [f"-I{_q(d)}" for d in include_dirs]
+    includes += _file_macro_maps(build_dir)
+
+    # SCons's link line: $LINKFLAGS $SOURCES $_LIBDIRFLAGS $_LIBFLAGS, so
+    # -L and -l trail the objects while every other link token leads
+    lib_dirs = [Path(t[2:]) for t in link_flags if t.startswith("-L")]
+    libs = [t for t in link_flags if t.startswith("-l")]
+    linkflags = [shell_token(t) for t in link_flags if not t.startswith(("-L", "-l"))]
+    for lib in libraries:
+        lib_dirs += lib.link_dirs
+        libs += [f"-l{name}" for name in lib.link_libs]
+        linkflags += [shell_token(f) for f in lib.link_flags]
+
+    # PlatformIO's ASPPCOM passes only -D/-I user flags to assembly
+    asflags = [t for t in cflags if t.startswith(("-D", "-I"))]
+
+    lines = [
+        *tool_lines(compilers.cc, compilers.cxx, ccache),
+        *compile_rule_lines(ccache),
+        *pch_rule_lines(),
+        "rule link",
+        "  command = $cxx -o $out $linkflags @$out.rsp $archives $libdirflags $libflags",
+        "  rspfile = $out.rsp",
+        "  rspfile_content = $in_newline",
+        "  description = LINK $out",
+    ]
+    if any(lib.sources and lib.lib_archive for lib in libraries):
+        # Resolved only when an archive is built, so a system without
+        # binutils still links a library-free configuration
+        lines += ar_rule_lines(find_tool("AR", ("ar",)))
+    lines += [
+        "",
+        f"cflags = {' '.join([*map(shell_token, cflags), *includes])}",
+        f"cxxflags = {' '.join([*map(shell_token, cxxflags), *includes])}",
+        f"asflags = {' '.join([*map(shell_token, asflags), *includes])}",
+        f"linkflags = {' '.join(linkflags)}",
+        f"libdirflags = {' '.join(f'-L{_q(d)}' for d in lib_dirs)}",
+        f"libflags = {' '.join(shell_token(lib) for lib in libs)}",
+        "",
+    ]
+
+    archives, direct_objs = library_edges(lines, libraries)
+
+    src_cxx_override = pch_edges(
+        lines,
+        build_dir,
+        src_dir,
+        PCH_DEFAULT_HEADERS,
+        # The arguments of a CXX override come before the flags
+        [*compilers.cxx[1:], *cxxflags],
+        (),
+        (compilers.cxx[0], _compiler_version(compilers.cxx)) if pch_enabled() else (),
+        compilers.cxx,
+    )
+    src_objs = compile_edges(
+        lines,
+        collect_sources(src_dir),
+        src_dir,
+        "src",
+        cxx_override=src_cxx_override,
+    )
+    if not src_objs:
+        raise EsphomeError(f"No source files found under {src_dir}")
+
+    # Archives are not topologically sorted; GNU ld needs the group to
+    # resolve references between them. ld64 loads archives iteratively and
+    # rejects the option, so macOS lists them bare.
+    archive_tokens = [shell_token(a) for a in archives]
+    if archive_tokens and sys.platform != "darwin":
+        archive_tokens = ["-Wl,--start-group", *archive_tokens, "-Wl,--end-group"]
+    lines.append(
+        f"build {PROGRAM_NAME}: link {' '.join(src_objs + direct_objs)} | "
+        f"{' '.join(_e(a) for a in archives)}"
+    )
+    lines.append(f"  archives = {' '.join(archive_tokens)}")
+    lines.append(f"default {PROGRAM_NAME}")
+    lines.append("")
+
+    return write_file_if_changed(build_dir / "build.ninja", "\n".join(lines))
@@ -1,6 +1,8 @@
+from esphome.build_helpers.pch import pch_script_enabled
 from esphome.const import __version__
 from esphome.core import CORE
 from esphome.helpers import mkdir_p, read_file, write_file_if_changed
+from esphome.platformio.toolchain import copy_pch_script
 from esphome.writer import find_begin_end

 INI_AUTO_GENERATE_BEGIN = "; ========== AUTO GENERATED CODE BEGIN ==========="
@@ -62,6 +64,19 @@ def get_ini_content():

    # Add extra script for C++ flags
    CORE.add_platformio_option("extra_scripts", [f"pre:{CXX_FLAGS_FILE_NAME}"])
+    if pch_script_enabled():
+        CORE.add_platformio_option("extra_scripts", ["post:pch.py"])
+
+    # Add CMake args. A user-supplied value (str or list) is deliberately
+    # replaced; this option was always overwritten at FINAL priority.
+    if CORE.cmake_args:
+        CORE.add_platformio_option(
+            "board_build.cmake_extra_args",
+            " ".join(
+                f"-D{name}={value}" for name, value in sorted(CORE.cmake_args.items())
+            ),
+            replace=True,
+        )

    content = "[platformio]\n"
    content += f"description = ESPHome {__version__}\n"
@@ -95,6 +110,8 @@ def write_project():

    # Write extra script for C++ specific flags
    write_cxx_flags_script()
+    if pch_script_enabled():
+        copy_pch_script()


 CXX_FLAGS_FILE_NAME = "cxx_flags.py"
@@ -0,0 +1 @@
+"""Build helpers shared by the native (non-PlatformIO) toolchains."""
@@ -0,0 +1,131 @@
+"""Shared ccache policy for build backends: env-knob parsing, binary
+resolution, and default ``CCACHE_*`` values."""
+
+from __future__ import annotations
+
+import logging
+import os
+from pathlib import Path
+
+from esphome.framework_helpers import strip_win_long_path_prefix, tool_version_runs
+from esphome.helpers import FALSY_ENV_STRINGS, TRUTHY_ENV_STRINGS
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def _ccache_runs(ccache: str) -> bool:
+    """Return True when the ``ccache`` found on PATH actually runs."""
+    return tool_version_runs(
+        ccache,
+        "Ignoring ccache at %s because it failed to run; compiling without ccache",
+    )
+
+
+def parse_enable_env(name: str) -> bool | None:
+    """Strictly parse an on/off environment knob; None when unset or invalid.
+
+    ``bool(str)`` truthiness would flip ``no``/``off`` to enabled, so only
+    1/true/yes/on and 0/false/no/off count; anything else warns and reads
+    as unset so the caller's default policy applies.
+    """
+    raw = os.environ.get(name)
+    if raw is None:
+        return None
+    lowered = raw.strip().lower()
+    if not lowered:
+        # ENV KNOB= (Docker/CI) has always read as a disable
+        return False
+    if lowered in TRUTHY_ENV_STRINGS:
+        return True
+    if lowered in FALSY_ENV_STRINGS:
+        return False
+    _LOGGER.warning("Ignoring unrecognized %s=%r; use 1 or 0", name, raw)
+    return None
+
+
+def resolve_ccache_path() -> str | None:
+    """The ccache binary to wrap compiles with, or None when disabled.
+
+    An explicit ``ESPHOME_CCACHE_ENABLE=1`` skips the runnability probe; the
+    Windows extended-length prefix is stripped before probing (#18399).
+    """
+    import shutil
+
+    explicit = parse_enable_env("ESPHOME_CCACHE_ENABLE")
+    if explicit is False:
+        return None
+    ccache = shutil.which("ccache")
+    if ccache is None:
+        if explicit:
+            _LOGGER.warning(
+                "ESPHOME_CCACHE_ENABLE is set but no ccache binary is on PATH; "
+                "compiling without ccache"
+            )
+        return None
+    ccache = strip_win_long_path_prefix(ccache)
+    if not explicit and not _ccache_runs(ccache):
+        return None
+    return ccache
+
+
+def resolve_absolute_ccache_path() -> str | None:
+    """``resolve_ccache_path`` for the ninja backends, which run their
+    commands from the build directory, where a relative path is lost."""
+    from esphome.build_helpers.ninja import absolute_tool
+
+    ccache = resolve_ccache_path()
+    return absolute_tool(ccache) if ccache else None
+
+
+def ccache_defaults_env(cache_dir: Path) -> dict[str, str]:
+    """Default ``CCACHE_*`` values for a build subprocess (not os.environ).
+
+    Values the user already set in the environment are respected. Depend
+    mode is on: both native backends emit depfiles (-MMD / CMake), which
+    keeps cache-miss overhead low.
+    """
+    from esphome.core import CORE
+
+    # An unset build_path means the env was built before preload; fail loudly
+    # rather than silently drop CCACHE_BASEDIR.
+    if CORE.build_path is None:
+        raise ValueError(
+            "CORE.build_path must be set before constructing the build environment"
+        )
+    defaults = {
+        # ccache expands $VAR in its settings; $$ is a literal $
+        "CCACHE_DIR": str(cache_dir).replace("$", "$$"),
+        "CCACHE_NOHASHDIR": "true",
+        "CCACHE_DEPEND": "1",
+        "CCACHE_BASEDIR": str(Path(CORE.build_path).resolve()).replace("$", "$$"),
+    }
+    return {k: v for k, v in defaults.items() if k not in os.environ}
+
+
+def effective_ccache_basedir() -> str:
+    """The prefix ccache strips from hashed paths: a usable user
+    CCACHE_BASEDIR, else the resolved build path."""
+    from esphome.core import CORE
+
+    raw = os.environ.get("CCACHE_BASEDIR")
+    if raw is not None and Path(raw).is_absolute() and len(Path(raw).parts) > 1:
+        return raw
+    return str(Path(CORE.build_path).resolve())
+
+
+def ccache_env(ccache: str | None, tools_cache: tuple[str, str]) -> dict[str, str]:
+    """The ccache settings for a build subprocess (not os.environ).
+
+    ``ccache`` is the pre-resolved binary (resolve_ccache_path), or None when
+    disabled; ``tools_cache`` is the backend's tools cache spec, which holds
+    its ccache dir. The pch settings include ``time_macros``: a cached
+    object can keep an older ``__DATE__`` or ``__TIME__``.
+    """
+    if ccache is None:
+        return {}
+    from esphome.build_helpers.pch import ccache_pch_env
+    from esphome.build_helpers.tools_cache import tools_cache_path
+
+    env = ccache_defaults_env(tools_cache_path(*tools_cache) / "ccache")
+    env.update(ccache_pch_env())
+    return env
@@ -0,0 +1,406 @@
+"""Derive idedata from a native (non-PlatformIO) build's ``compile_commands.json``.
+
+PlatformIO exposes a curated ``pio run -t idedata`` JSON; the native
+toolchains have no such command, but each build produces a
+``compile_commands.json`` (CMAKE_EXPORT_COMPILE_COMMANDS for ESP-IDF, ninja's
+compdb tool otherwise). This module turns that file into the same fields
+consumers (IDE integration, clang-tidy) expect:
+
+    {cc_path, cxx_path, cxx_flags, defines, includes: {build, toolchain}}
+"""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+import json
+import logging
+import os
+from pathlib import Path
+import shlex
+import subprocess
+
+from esphome.core import EsphomeError
+from esphome.helpers import write_file
+
+_LOGGER = logging.getLogger(__name__)
+
+# Everything idedata generation may raise after a successful link; idedata
+# is a bonus artifact, so consumers warn instead of failing the build
+IDEDATA_BEST_EFFORT_ERRORS = (
+    EsphomeError,
+    LookupError,
+    OSError,
+    RuntimeError,
+    ValueError,
+)
+
+
+def warn_if_idedata_missing(get_idedata: Callable[[], dict | None]) -> None:
+    """Run an idedata generator, downgrading any failure to a warning:
+    the firmware already built."""
+    try:
+        if get_idedata() is None:
+            _LOGGER.warning("No idedata was generated for this build")
+    except IDEDATA_BEST_EFFORT_ERRORS as err:
+        _LOGGER.warning(
+            "Could not generate idedata: %s (IDE, clang-tidy, and "
+            "memory-analysis data will be unavailable for this build)",
+            err,
+        )
+        _LOGGER.debug("Idedata failure detail", exc_info=True)
+
+
+# C++ translation-unit suffixes used to identify ESPHome source files.
+_CXX_SUFFIXES = (".cpp", ".cc")
+# Suffixes of input/output files that appear bare on the command line (and so
+# must not be mistaken for compiler flags).
+_INPUT_FILE_SUFFIXES = (*_CXX_SUFFIXES, ".c", ".o", ".S", ".s")
+# Path marker identifying an ESPHome source translation unit.
+_ESPHOME_SRC_MARKER = "/src/esphome/"
+
+
+def _is_esphome_src(file: str) -> bool:
+    """Whether ``file`` is an ESPHome C++ translation unit; normalized to
+    ``/`` first since Windows compile DBs use backslashes."""
+    return _ESPHOME_SRC_MARKER in file.replace("\\", "/") and file.endswith(
+        _CXX_SUFFIXES
+    )
+
+
+def _split_command(command: str) -> list[str]:
+    r"""Tokenize a compile_commands.json / response-file command string.
+
+    On Windows, tokenize per Windows ``argv`` rules via ``CommandLineToArgvW``.
+    ESP-IDF's compile_commands.json there mixes two backslash conventions in one
+    string: literal path separators in the compiler path (``C:\Users\...g++.exe``,
+    no quote follows) and shell quote-escaping in -D defines (``-DVER=\"1.2.3\"``).
+    Only the real Windows parser — where a backslash escapes solely a following
+    quote — handles both, and it is the exact tokenizer the compiler is launched
+    with. ``shlex`` cannot: POSIX mode eats the path separators, and disabling
+    its escape mangles the defines.
+    """
+    if os.name != "nt":
+        return shlex.split(command)
+
+    import ctypes
+    from ctypes import wintypes
+
+    # CommandLineToArgvW("") returns the current process name, not []; guard it
+    # so an empty response file tokenizes the same as it would via shlex.
+    if not command.strip():
+        return []
+
+    CommandLineToArgvW = ctypes.windll.shell32.CommandLineToArgvW
+    CommandLineToArgvW.argtypes = [wintypes.LPCWSTR, ctypes.POINTER(ctypes.c_int)]
+    CommandLineToArgvW.restype = ctypes.POINTER(wintypes.LPWSTR)
+    argc = ctypes.c_int()
+    argv = CommandLineToArgvW(command, ctypes.byref(argc))
+    if not argv:  # pragma: no cover
+        raise ctypes.WinError()
+    try:
+        return [argv[i] for i in range(argc.value)]
+    finally:
+        ctypes.windll.kernel32.LocalFree(argv)
+
+
+def _expand_response_files(tokens: list[str], directory: Path) -> list[str]:
+    """Inline any ``@response-file`` arguments (paths relative to ``directory``).
+
+    GCC response files embed flags that must be expanded so GCC-only flags
+    inside them (e.g. ``-mlongcalls``) can be filtered downstream; left as
+    ``@file`` clang would read them and choke.
+    """
+    out: list[str] = []
+    for tok in tokens:
+        if tok.startswith("@"):
+            rf = Path(tok[1:])
+            if not rf.is_absolute():
+                rf = directory / rf
+            try:
+                out.extend(
+                    _expand_response_files(
+                        _split_command(rf.read_text(encoding="utf-8")), directory
+                    )
+                )
+                continue
+            except OSError as err:
+                # Keep the literal token if the file can't be read, but log it
+                # so the (otherwise opaque) downstream clang failure is traceable.
+                _LOGGER.warning("Could not read response file %s: %s", rf, err)
+        out.append(tok)
+    return out
+
+
+def _pick_entry(entries: list[dict]) -> dict:
+    """Pick a representative ESPHome C++ TU; all share the same component
+    flags/defines."""
+    for entry in entries:
+        if _is_esphome_src(entry["file"]):
+            return entry
+    for entry in entries:
+        if entry["file"].endswith(_CXX_SUFFIXES):
+            return entry
+    raise ValueError("no C++ translation unit found in compile_commands.json")
+
+
+# Compiler launchers that may prefix a compile command; a closed launcher
+# denylist beats enumerating compiler names, an open set.
+_LAUNCHER_STEMS = frozenset({"ccache", "sccache", "distcc", "icecc", "buildcache"})
+
+
+def _is_launcher(token: str) -> bool:
+    return Path(token).stem.lower() in _LAUNCHER_STEMS
+
+
+def is_joined_include(tok: str) -> bool:
+    """The joined ``-includefoo.h`` spelling; excludes clang's -include-pch."""
+    return (
+        tok.startswith("-include")
+        and tok != "-include"
+        and not tok.startswith("-include-")
+    )
+
+
+def parse_entry(
+    entry: dict, launcher: str | None = None
+) -> tuple[str, list[str], list[str], list[str]]:
+    """Parse one compile_commands entry -> (cxx_path, defines, includes, cxx_flags)."""
+    directory = Path(entry["directory"])
+    tokens = _expand_response_files(_split_command(entry["command"]), directory)
+
+    def _include(raw: str) -> str:
+        # Resolve against the entry's ``directory`` so cached idedata works
+        # from any cwd; emit forward slashes to match the JSON's own entries
+        raw = raw.strip()
+        if raw and not Path(raw).is_absolute():
+            raw = os.path.normpath(directory / raw)
+        return raw.replace("\\", "/")
+
+    # A launcher-wrapped command ("ccache g++ ...") names the compiler second
+    if launcher is not None and tokens[:1] == [launcher]:
+        tokens = tokens[1:]
+    if not tokens:
+        # An empty command, or one that was only the launcher; fail by name
+        raise ValueError(f"empty compile command for {entry.get('file')}")
+    if _is_launcher(tokens[0]) and len(tokens) > 1 and not tokens[1].startswith("-"):
+        # Stale DB built with a launcher this run no longer configures; the
+        # real compiler is the next token
+        _LOGGER.warning("Stripping unconfigured launcher %s", tokens[0])
+        tokens = tokens[1:]
+    # token0 is the compiler path; the rest of the command already uses forward
+    # slashes on Windows, so normalize it too for a consistent idedata file.
+    cxx_path = tokens[0].replace("\\", "/")
+    # Enforced here so no caller can record ccache as the compiler
+    reject_launcher_compiler(cxx_path)
+    defines: list[str] = []
+    includes: list[str] = []
+    cxx_flags: list[str] = []
+
+    it = iter(tokens[1:])
+    for tok in it:
+        if tok in ("-c", "-o"):
+            next(it, None)  # drop the flag and its argument (input/output)
+        elif tok.startswith("-D"):
+            # ``.strip()`` handles tokens like ``-D CONFIGURED=1`` (a single
+            # quoted arg with a space after -D) that some flags arrive as.
+            defines.append(tok[2:].strip() if len(tok) > 2 else next(it, "").strip())
+        elif tok.startswith("-I"):
+            includes.append(_include(tok[2:] if len(tok) > 2 else next(it, "")))
+        elif tok == "-isystem":
+            includes.append(_include(next(it, "")))
+        elif tok.startswith("-isystem"):
+            includes.append(_include(tok[len("-isystem") :]))
+        elif tok in ("-MT", "-MF", "-MQ"):
+            next(it, None)  # dependency-file flag + its argument
+        elif tok.startswith(("-MD", "-MMD", "-MP", "-MM")):
+            pass  # dependency-generation flags, no argument
+        elif tok.endswith(_INPUT_FILE_SUFFIXES):
+            pass  # input/output files
+        else:
+            cxx_flags.append(tok)
+    return cxx_path, defines, includes, cxx_flags
+
+
+def get_toolchain_includes(cxx_path: str) -> list[str]:
+    """Query the compiler for its builtin ``#include <...>`` search dirs."""
+    result = subprocess.run(
+        [cxx_path, "-E", "-x", "c++", "-", "-v"],
+        input="",
+        text=True,
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+        check=False,
+        close_fds=False,
+    )
+    includes: list[str] = []
+    capture = False
+    for line in result.stderr.splitlines():
+        if "#include <...> search starts here:" in line:
+            capture = True
+            continue
+        if "End of search list." in line:
+            break
+        if capture:
+            includes.append(line.strip())
+    if result.returncode != 0 or not includes:
+        raise RuntimeError(
+            f"Could not query builtin include dirs from {cxx_path} "
+            f"(return code {result.returncode}); stderr:\n{result.stderr.strip()}"
+        )
+    return includes
+
+
+def _cc_path_from_cxx(cxx_path: str) -> str:
+    """Derive the C compiler path from the C++ compiler path.
+
+    compile_commands.json only names the C++ compiler, but consumers reach the
+    rest of the toolchain (objdump, readelf, addr2line) by rewriting the tail of
+    ``cc_path``, so they need the ``gcc``-suffixed name.
+    """
+    stem, suffix = (
+        (cxx_path[: -len(".exe")], ".exe")
+        if cxx_path.endswith(".exe")
+        else (cxx_path, "")
+    )
+    # Rewrite the program name only when it is g++ itself, or a toolchain
+    # prefixed one such as xtensa-esp32-elf-g++ -> xtensa-esp32-elf-gcc.
+    # Requiring a separator before the "g++" keeps names that merely end in
+    # those three characters intact: "clang++" must not become "clangcc".
+    head = stem[: -len("g++")]
+    if stem.endswith("g++") and (not head or head.endswith(("-", "/", "\\"))):
+        stem = f"{head}gcc"
+    return f"{stem}{suffix}"
+
+
+def _cache_usable(cached: object) -> bool:
+    """Check a cached idedata dict against the guarantees of the write path.
+
+    Caches written by older versions predate the launcher rejection and the
+    include-union shape; serving one would bypass both. The dict check also
+    keeps "in" from substring-matching a bare JSON string.
+    """
+    if not isinstance(cached, dict) or "cc_path" not in cached:
+        return False
+    cxx_path = cached.get("cxx_path")
+    if not isinstance(cxx_path, str) or _is_launcher(cxx_path):
+        return False
+    includes = cached.get("includes")
+    return isinstance(includes, dict) and isinstance(includes.get("build"), list)
+
+
+def load_or_build_idedata(
+    compile_commands: Path,
+    elf_path: Path,
+    cache: Path,
+    launcher: str | None = None,
+) -> dict | None:
+    """Return idedata for a compile_commands.json build, cached on mtime.
+
+    Shared by the native ESP-IDF and ESP8266 Arduino toolchains. Returns None
+    when the compile DB doesn't exist yet (nothing was built). ``launcher``
+    is the compiler-launcher path (ccache) the build was generated with, if
+    any; commands in the compile DB are prefixed with it.
+    """
+    if not compile_commands.is_file():
+        _LOGGER.debug("No %s yet; skipping idedata generation", compile_commands)
+        return None
+
+    if cache.is_file() and cache.stat().st_mtime >= compile_commands.stat().st_mtime:
+        try:
+            cached = json.loads(cache.read_text(encoding="utf-8"))
+        except (ValueError, OSError) as err:
+            # A recurring cause (interrupted write, disk full) would otherwise
+            # look like unexplained slow builds
+            _LOGGER.warning("Discarding unreadable idedata cache %s: %s", cache, err)
+        else:
+            if _cache_usable(cached):
+                # Re-stamp so a relocated build dir cannot serve a stale ELF path
+                cached["prog_path"] = str(elf_path)
+                return cached
+            _LOGGER.debug("Regenerating idedata: cache %s fails validation", cache)
+
+    data = idedata_from_build(compile_commands, launcher)
+    data["prog_path"] = str(elf_path)
+    cache.parent.mkdir(parents=True, exist_ok=True)
+    # Atomic so a crash mid-write cannot leave a truncated cache
+    write_file(cache, json.dumps(data, indent=2) + "\n")
+    return data
+
+
+def reject_launcher_compiler(cxx_path: str) -> None:
+    """Reject a compile DB naming a launcher (ccache) as the compiler; it
+    must never be probed, cached, or consumed."""
+    if _is_launcher(cxx_path):
+        raise EsphomeError(
+            f"compile_commands.json names the launcher {cxx_path} as the "
+            "compiler; the compile database is unusable"
+        )
+
+
+def idedata_from_build(compile_commands: Path, launcher: str | None = None) -> dict:
+    """Parse compile_commands.json into the idedata fields consumers expect.
+
+    A single compile entry only carries the include set its own translation
+    unit was built with (per-component under ESP-IDF), but consumers
+    (clang-tidy) analyze ESPHome headers that transitively pull in other
+    components. So take cxx_path / cxx_flags / defines from a representative
+    ESPHome TU, but union the include dirs across all ESPHome TUs to get a
+    project-wide superset (as PlatformIO's idedata provides).
+    """
+    entries = json.loads(Path(compile_commands).read_text(encoding="utf-8"))
+    if not isinstance(entries, list) or not all(isinstance(e, dict) for e in entries):
+        # A TypeError here would escape IDEDATA_BEST_EFFORT_ERRORS
+        raise EsphomeError(f"{compile_commands} is not a compile-command list")
+
+    representative = _pick_entry(entries)
+    cxx_path, defines, rep_includes, cxx_flags = parse_entry(representative, launcher)
+
+    # Seed with the representative's includes so it is not parsed twice
+    has_esphome_tu = _is_esphome_src(representative["file"])
+    build_includes: dict[str, None] = dict.fromkeys(
+        rep_includes if has_esphome_tu else ()
+    )
+
+    def _shape(entry: dict) -> str:
+        # directory + command minus TU-specific paths: same shape means the
+        # same include set, so tokenize once per shape. Response-file
+        # commands never dedupe (the .rsp contents differ per object)
+        command = entry["command"]
+        directory = entry.get("directory", "")
+        if "@" in command:
+            return f"unique:{directory}|{entry.get('output') or command}"
+        stripped = command.replace(entry.get("file", ""), "").replace(
+            entry.get("output", ""), ""
+        )
+        return f"{directory}|{stripped}"
+
+    seen_shapes = {_shape(representative)}
+    for entry in entries:
+        if entry is representative or not _is_esphome_src(entry["file"]):
+            continue
+        has_esphome_tu = True
+        if (shape := _shape(entry)) in seen_shapes:
+            _LOGGER.debug("Include union: %s shares a command shape", entry["file"])
+            continue
+        seen_shapes.add(shape)
+        for inc in parse_entry(entry, launcher)[2]:
+            build_includes.setdefault(inc, None)
+
+    if not has_esphome_tu:
+        # An arbitrary fallback TU breaks clang-tidy/IDE consumers, and a
+        # warning would be cached into permanence; call sites downgrade this
+        raise EsphomeError(
+            f"No ESPHome translation unit found in {compile_commands}; "
+            "refusing to cache unusable idedata"
+        )
+
+    return {
+        "cc_path": _cc_path_from_cxx(cxx_path),
+        "cxx_path": cxx_path,
+        "cxx_flags": cxx_flags,
+        "defines": defines,
+        "includes": {
+            "build": list(build_includes),
+            "toolchain": get_toolchain_includes(cxx_path),
+        },
+    }
@@ -0,0 +1,74 @@
+"""Resolution of the native (non-PlatformIO) build backend for a config.
+
+Kept deliberately light: the serial upload and logs fast path resolves a
+backend for its artifact paths alone, so importing this must not pull in a
+platform component package or the backend itself.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Collection
+import importlib
+import logging
+from types import ModuleType
+
+from esphome.const import Toolchain
+from esphome.core import CORE, EsphomeError
+
+_LOGGER = logging.getLogger(__name__)
+
+# Native build backend per (target platform, toolchain)
+NATIVE_TOOLCHAIN_MODULES = {
+    ("esp32", Toolchain.ESP_IDF): "esphome.espidf.toolchain",
+    ("esp8266", Toolchain.ARDUINO): "esphome.arduino8266.toolchain",
+    ("host", Toolchain.HOST): "esphome.host.toolchain",
+}
+
+
+def native_backend() -> ModuleType | None:
+    """The native build backend module for the resolved toolchain."""
+    if not CORE.using_native_toolchain:
+        return None
+    key = (CORE.target_platform, CORE.toolchain)
+    if (module_path := NATIVE_TOOLCHAIN_MODULES.get(key)) is None:
+        # Degrading to the PlatformIO path would build with the wrong backend
+        raise EsphomeError(
+            f"Toolchain '{CORE.toolchain.value}' has no native build backend "
+            f"module for platform {CORE.target_platform}"
+        )
+    return importlib.import_module(module_path)
+
+
+# Binutils and the linked image for memory analysis, for toolchains that build
+# without PlatformIO but have no native build backend (which supplies them)
+ANALYSIS_TOOLCHAIN_MODULES = {
+    ("nrf52", Toolchain.SDK_NRF): "esphome.components.nrf52.toolchain",
+}
+
+
+def analysis_backend() -> ModuleType | None:
+    """The module giving objdump, readelf and the ELF of a non-PlatformIO build.
+
+    None means PlatformIO's idedata supplies them (or nothing can).
+    """
+    if (native := native_backend()) is not None:
+        return native
+    module_path = ANALYSIS_TOOLCHAIN_MODULES.get((CORE.target_platform, CORE.toolchain))
+    return importlib.import_module(module_path) if module_path else None
+
+
+def warn_ignored_platformio_options(consumed: Collection[str]) -> None:
+    """Warn for component-added platformio options a native build drops.
+
+    User-supplied keys were already routed or warned about by
+    ``core/config.py``; what survives into ``CORE.platformio_options`` came
+    from ``cg.add_platformio_option`` calls in components.
+    """
+    for key in sorted(CORE.platformio_options or {}):
+        if key not in consumed:
+            _LOGGER.warning(
+                "platformio_options->%s is ignored when building with the "
+                "native '%s' toolchain",
+                key,
+                CORE.toolchain.value,
+            )
@@ -0,0 +1,182 @@
+"""Platform-neutral helpers for ninja-driven native builds."""
+
+from __future__ import annotations
+
+import json
+import logging
+import os
+from pathlib import Path
+import re
+import shutil
+import subprocess
+
+from esphome.core import EsphomeError
+from esphome.framework_helpers import strip_win_long_path_prefix, tool_version_runs
+from esphome.helpers import write_file_if_changed
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def _ninja_runs(binary: str) -> bool:
+    """Whether the ninja found on PATH actually runs (see tool_version_runs)."""
+    return tool_version_runs(
+        binary,
+        "Ignoring ninja at %s because it failed to run; "
+        "falling back to the bundled wheel",
+    )
+
+
+# Compile rule names the generators emit; ninja's compdb tool is asked for
+# exactly these, so a renamed rule fails the build instead of stranding idedata
+COMPILE_RULES = ("c", "cxx", "aspp", "asm")
+
+
+def absolute_tool(tool: str | Path) -> str:
+    """A tool path that still resolves from the build directory.
+
+    ``shutil.which`` returns a relative path for a relative PATH entry, and
+    ninja runs the commands from ``.pioenvs/<name>``. Symlinks are kept:
+    ccache's compiler links depend on the name they are called by.
+    """
+    return strip_win_long_path_prefix(str(Path(tool).absolute()))
+
+
+def find_ninja() -> Path:
+    """Locate the ninja binary: a runnable PATH hit first, else the ninja
+    PyPI wheel."""
+    if binary := shutil.which("ninja"):
+        binary = absolute_tool(binary)
+        if _ninja_runs(binary):
+            return Path(binary)
+    import_error: ImportError | None = None
+    try:
+        import ninja
+    except ImportError as err:
+        import_error = err
+        wheel_binary = None
+    else:
+        wheel_binary = Path(ninja.BIN_DIR) / (
+            "ninja.exe" if os.name == "nt" else "ninja"
+        )
+    if wheel_binary is None or not wheel_binary.is_file():
+        raise EsphomeError(
+            "ninja not found on PATH or in the ninja package; reinstall the "
+            "esphome Python environment"
+        ) from import_error
+    return wheel_binary
+
+
+def escape(value: Path | str) -> str:
+    """Escape a path or token for a ninja file.
+
+    ninja has no escape for ``|`` or a line break in a path, so those fail
+    here by name instead of producing a build file ninja misreads.
+    """
+    text = str(value)
+    if bad := next((c for c in "|\r\n" if c in text), None):
+        raise EsphomeError(
+            f"Path {text!r} contains {bad!r}, which a ninja build file cannot "
+            "express; rename the file or directory"
+        )
+    return text.replace("$", "$$").replace(":", "$:").replace(" ", "$ ")
+
+
+def quote_arg(tok: str) -> str:
+    """Quote with the CreateProcess argv rule (as ``subprocess.list2cmdline``):
+    backslash runs double only before a quote. Windows-only; ``$`` must
+    already be doubled for ninja.
+    """
+    quoted = re.sub(r'(\\*)"', lambda m: m.group(1) * 2 + '\\"', tok)
+    quoted = re.sub(r"(\\+)\Z", lambda m: m.group(1) * 2, quoted)
+    return f'"{quoted}"'
+
+
+# Force-quote any token containing a character outside the shlex.quote-style
+# safe set: ninja hands POSIX commands to /bin/sh -c, so bare (, ;, <, *, `
+# and friends would be re-parsed as shell syntax.
+_NEEDS_QUOTE = re.compile(r"[^\w@%+=:,./-]")
+
+
+def shell_token(tok: str, force: bool = False) -> str:
+    """Re-quote a lexed token for the platform shell; ``force`` always quotes.
+
+    Single quotes on POSIX (/bin/sh), the argv rule on Windows
+    (CreateProcess). ``$`` is doubled first because ninja expands it before
+    the command reaches the shell.
+    """
+    tok = tok.replace("$", "$$")  # ninja would expand a bare $ to nothing
+    if not (force or not tok or _NEEDS_QUOTE.search(tok)):
+        return tok
+    # An empty token must become '' / "" or it vanishes from the argv
+    if os.name == "nt":
+        return quote_arg(tok)
+    # shlex.quote's rule; inlined because the $-doubled token must not be
+    # re-examined for safe characters
+    return "'" + tok.replace("'", "'\"'\"'") + "'"
+
+
+def quote_path(value: Path | str) -> str:
+    """Force-quote a path for the ninja command line (shell/CreateProcess)."""
+    return shell_token(str(value), force=True)
+
+
+def refresh_compile_commands(
+    ninja_path: Path, build_dir: Path, env: dict[str, str], ninja_changed: bool
+) -> None:
+    """Regenerate the compile DB (a pure function of build.ninja) when stale.
+
+    Freshness rides a stamp: the DB itself is written through
+    write_file_if_changed (its mtime feeds the idedata cache), so a
+    regeneration with identical content would stay "stale" forever. An
+    interrupted previous run may have rewritten the manifest without
+    regenerating the DB, hence the mtime comparison.
+    """
+    compdb = build_dir / "compile_commands.json"
+    compdb_stamp = build_dir / ".compile_commands.stamp"
+    ninja_file = build_dir / "build.ninja"
+    if (
+        ninja_changed
+        or not compdb.is_file()
+        or not compdb_stamp.is_file()
+        or compdb_stamp.stat().st_mtime < ninja_file.stat().st_mtime
+    ):
+        write_compile_commands(ninja_path, build_dir, env)
+        compdb_stamp.touch()
+
+
+def write_compile_commands(
+    ninja_path: Path, build_dir: Path, env: dict[str, str]
+) -> None:
+    compdb = build_dir / "compile_commands.json"
+    result = subprocess.run(
+        [str(ninja_path), "-C", str(build_dir), "-t", "compdb", *COMPILE_RULES],
+        env=env,
+        capture_output=True,
+        text=True,
+        check=False,
+        close_fds=False,
+    )
+    if result.returncode != 0:
+        # Drop any stale database so consumers (IDE integration, clang-tidy,
+        # the memory analyzer) can't silently read outdated data
+        compdb.unlink(missing_ok=True)
+        raise EsphomeError(f"Could not generate compile_commands.json: {result.stderr}")
+    try:
+        entries = json.loads(result.stdout)
+    except ValueError as err:
+        compdb.unlink(missing_ok=True)
+        raise EsphomeError(
+            f"ninja produced an unparsable compile database: {err} "
+            f"(output starts {result.stdout[:120]!r})"
+        ) from err
+    if not entries:
+        # compdb exits 0 with [] for unknown rule names; a renamed compile
+        # rule must fail the build, not silently strand every consumer
+        compdb.unlink(missing_ok=True)
+        raise EsphomeError(
+            "ninja produced an empty compile database; the generator's rule "
+            "names no longer match"
+        )
+    # write_file_if_changed keeps the mtime stable on no-op builds so the
+    # idedata cache stays valid
+    write_file_if_changed(compdb, result.stdout)
@@ -0,0 +1,288 @@
+"""The parts of a ``build.ninja`` every native backend emits the same way.
+
+Rule names match ``SOURCE_KIND_FOR_SUFFIX`` values (c, cxx, asm, aspp) and
+``ninja.COMPILE_RULES``, which the compile database is asked for.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Collection, Sequence
+import logging
+import os
+from pathlib import Path
+import sys
+from typing import TYPE_CHECKING
+
+from esphome.build_helpers.idedata import is_joined_include
+from esphome.build_helpers.ninja import (
+    escape as _e,
+    quote_path as _q,
+    shell_token as _shell_token,
+)
+from esphome.build_helpers.pch import (
+    PCH_GCH_NAME,
+    PCH_SUM_NAME,
+    log_pch_in_use,
+    pch_consumer_flags,
+    pch_identity,
+    pch_usable,
+    write_pch_headers,
+)
+from esphome.framework_helpers import strip_win_long_path_prefix
+from esphome.helpers import write_file_if_changed
+from esphome.platformio.library import SOURCE_KIND_FOR_SUFFIX
+
+if TYPE_CHECKING:
+    from esphome.arduino.library import ArduinoLibrary
+
+_LOGGER = logging.getLogger(__name__)
+
+_BUILD_TOOL = Path(__file__).parent.parent / "build_gen" / "build_tool.py"
+
+
+def collect_sources(root: Path, exclude: Collection[str] = frozenset()) -> list[Path]:
+    return sorted(
+        p
+        for p in root.rglob("*")
+        if p.suffix in SOURCE_KIND_FOR_SUFFIX and p.name not in exclude
+    )
+
+
+def common_parent(paths: list[Path]) -> Path:
+    return Path(os.path.commonpath([str(p.parent) for p in paths]))
+
+
+def _command(words: Sequence[Path | str]) -> str:
+    program, *args = words
+    return " ".join([_q(program), *(_shell_token(str(a)) for a in args)])
+
+
+def tool_lines(
+    cc: Sequence[Path | str], cxx: Sequence[Path | str], ccache: str | None
+) -> list[str]:
+    """The file header: the compilers and the helper tools as variables.
+
+    A compiler is its program followed by any arguments it always takes.
+    """
+    return [
+        "# Auto-generated by ESPHome",
+        "ninja_required_version = 1.5",
+        f"cc = {_command(cc)}",
+        f"cxx = {_command(cxx)}",
+        # The NSIS launcher starts Python with a \\?\ extended-length path
+        # that cmd.exe cannot spawn; same strip every other emitted binary
+        # path gets
+        f"python = {_q(strip_win_long_path_prefix(sys.executable))}",
+        f"buildtool = {_q(_BUILD_TOOL)}",
+        *([f"ccache = {_q(ccache)}"] if ccache else []),
+        "",
+    ]
+
+
+def compile_rule_lines(ccache: str | None) -> list[str]:
+    """The compile rules; ``$own_includes`` is empty unless an edge sets it.
+
+    ``ccache`` is the launcher ``tool_lines`` was given; the same test here
+    keeps the variable and the rules in step. It is spliced in rather than
+    left as an empty variable: a leading space on the command line makes
+    CreateProcess fail on Windows.
+    """
+    launcher = "$ccache " if ccache else ""
+    return [
+        "rule c",
+        f"  command = {launcher}$cc -MMD -MF $out.d $own_includes $cflags $flags -c $in -o $out",
+        "  depfile = $out.d",
+        "  deps = gcc",
+        "  description = CC $out",
+        "rule cxx",
+        f"  command = {launcher}$cxx -MMD -MF $out.d $own_includes $cxxflags $flags -c $in -o $out",
+        "  depfile = $out.d",
+        "  deps = gcc",
+        "  description = CXX $out",
+        "rule aspp",
+        f"  command = {launcher}$cc -MMD -MF $out.d -x assembler-with-cpp $own_includes $asflags $flags -c $in -o $out",
+        "  depfile = $out.d",
+        "  deps = gcc",
+        "  description = AS $out",
+        # Plain assembler, as SCons's ASCOM: no preprocessor, so no
+        # depfile and no $flags (defines/includes) either
+        "rule asm",
+        f"  command = {launcher}$cc -x assembler $asflags -c $in -o $out",
+        "  description = AS $out",
+    ]
+
+
+def pch_rule_lines() -> list[str]:
+    """The precompiled header rule, for a generator that emits one."""
+    return [
+        # No $ccache: the .gch embeds build dir paths
+        "rule pch",
+        "  command = $cxx -MMD -MF $out.d -x c++-header $cxxflags $flags -c $in -o $out",
+        "  depfile = $out.d",
+        "  deps = gcc",
+        "  description = PCH $out",
+    ]
+
+
+def pch_edges(
+    lines: list[str],
+    build_dir: Path,
+    src_dir: Path,
+    headers: Sequence[str],
+    cxxflags: Sequence[str],
+    src_flags: Sequence[str],
+    identity: Sequence[str],
+    cxx: Sequence[Path | str],
+) -> tuple[str, str] | None:
+    """Emit the precompiled header for the C++ src edges.
+
+    ``headers`` are folded into one prefix header, ``src_flags`` are the
+    flags every src edge carries, ``identity`` names what else the compile
+    depends on, the compiler included, and ``cxx`` is what the host rule
+    asks. Returns the ``cxx_override`` for ``compile_edges``, or None
+    without a pch.
+    """
+    if not pch_usable(cxx):
+        return None
+    if any(
+        tok == "-include" or tok.startswith("--include") or is_joined_include(tok)
+        for tok in cxxflags
+    ):
+        # $cxxflags expands first and GCC only loads a .gch for the first
+        # -include
+        _LOGGER.warning(
+            "A -include in the compiler flags prevents the precompiled header from "
+            "loading; compiling without it"
+        )
+        return None
+    log_pch_in_use()
+    source = write_pch_headers(build_dir, headers)
+    write_file_if_changed(
+        build_dir / PCH_SUM_NAME,
+        pch_identity([*cxxflags, *src_flags], src_dir, tuple(headers), identity) + "\n",
+    )
+    gch = _e(PCH_GCH_NAME)
+    # The checksum file changes with anything the .gch depends on
+    lines.append(f"build {gch}: pch {_e(source)} | {_e(PCH_SUM_NAME)}")
+    if src_flags:
+        lines.append(f"  flags = {' '.join(src_flags)}")
+    lines.append(f"srccxxflags = {' '.join([*src_flags, *pch_consumer_flags()])}")
+    return ("$srccxxflags", gch)
+
+
+def ar_rule_lines(ar: Path | str) -> list[str]:
+    return [
+        "rule ar",
+        f"  command = $python $buildtool ar {_q(ar)} $out $out.rsp",
+        "  rspfile = $out.rsp",
+        "  rspfile_content = $in_newline",
+        "  description = AR $out",
+    ]
+
+
+def compile_edges(
+    lines: list[str],
+    sources: list[Path],
+    root: Path,
+    group: str,
+    flags: str = "",
+    own_includes: str = "",
+    cxx_override: tuple[str, str] | None = None,
+) -> list[str]:
+    """Emit compile edges for ``sources``; return the object paths.
+
+    ``cxx_override`` is a (flags, implicit-dep) pair applied to C++ edges
+    only, replacing ``flags`` (used for the precompiled header).
+    """
+    objects = []
+    for src in sources:
+        rel = src.relative_to(root).as_posix()
+        obj = f"obj/{group}/{rel}.o"
+        escaped_obj = _e(obj)
+        kind = SOURCE_KIND_FOR_SUFFIX[src.suffix]
+        override = cxx_override if kind == "cxx" else None
+        implicit = f" | {override[1]}" if override else ""
+        lines.append(f"build {escaped_obj}: {kind} {_e(src)}{implicit}")
+        if own_includes:
+            lines.append(f"  own_includes = {own_includes}")
+        if edge_flags := override[0] if override else flags:
+            lines.append(f"  flags = {edge_flags}")
+        # Escaped once here: the returned paths only ever appear in build
+        # statements (archive/link inputs), which use ninja escaping
+        objects.append(escaped_obj)
+    return objects
+
+
+def library_edges(
+    lines: list[str], libraries: list[ArduinoLibrary], extra_flags: str = ""
+) -> tuple[list[str], list[str]]:
+    """Emit every library's compile and archive edges.
+
+    ``extra_flags`` (raw ninja text) precede each library's own flags.
+
+    Returns the archive names and the objects that link directly. A
+    library's own include dirs lead its compile lines, as PlatformIO searched
+    them first: the include path is one global list, so another library's
+    header of the same name would shadow them.
+    """
+    archives: list[str] = []
+    direct_objs: list[str] = []
+    for lib in libraries:
+        if not lib.sources:
+            # Header-only libraries are legitimate; the log makes an empty
+            # srcFilter or broken tree traceable before link errors do
+            _LOGGER.debug(
+                "Library %s has no source files; contributing includes only",
+                lib.name,
+            )
+            continue
+        objs = compile_edges(
+            lines,
+            lib.sources,
+            common_parent(lib.sources),
+            f"lib/{lib.name}",
+            flags=" ".join(filter(None, [extra_flags, *map(_shell_token, lib.flags)])),
+            own_includes=" ".join(f"-I{_q(d)}" for d in lib.include_dirs),
+        )
+        if not lib.lib_archive:
+            # libArchive: false / dot_a_linkage=false: hand the objects to
+            # the linker directly so unreferenced-but-required symbols
+            # (exception handlers, weak overrides) survive
+            direct_objs.extend(objs)
+            continue
+        archive = f"lib{lib.name}.a"
+        lines.append(f"build {_e(archive)}: ar {' '.join(objs)}")
+        archives.append(archive)
+    return archives, direct_objs
+
+
+# One build flag: the flag, plus its argument when that is a separate token
+Flag = tuple[str, ...]
+
+# Flags whose path operand is the next token; gcc also takes it glued on
+PATH_ARG_FLAGS = ("-include", "-imacros", "-isystem", "-iquote", "-idirafter")
+# Flags whose path operand is glued on
+PATH_PREFIXES = ("-I", "-L", *PATH_ARG_FLAGS)
+
+
+def _anchor(path: str, base: Path) -> str:
+    if not path or Path(path).is_absolute():
+        return path
+    return str(base / path)
+
+
+def anchor_path_flag(flag: Flag, base: Path) -> Flag:
+    """Anchor a flag's relative path operand at ``base``.
+
+    PlatformIO ran the compiler from the build path; ninja runs it from
+    ``.pioenvs/<name>``, where a relative operand would point elsewhere.
+    """
+    name, *args = flag
+    if args:
+        if name in PATH_ARG_FLAGS:
+            return (name, _anchor(args[0], base))
+        return flag
+    for prefix in PATH_PREFIXES:
+        if name.startswith(prefix):
+            return (prefix + _anchor(name[len(prefix) :], base),)
+    return flag
@@ -0,0 +1,248 @@
+"""Shared precompiled header policy for the build backends."""
+
+from __future__ import annotations
+
+from collections.abc import Iterable, Sequence
+import hashlib
+import logging
+import os
+from pathlib import Path
+import posixpath
+import re
+import subprocess
+import sys
+
+from esphome.build_helpers.ccache import effective_ccache_basedir, parse_enable_env
+from esphome.const import PLATFORM_NRF52
+from esphome.helpers import write_file_if_changed
+
+_LOGGER = logging.getLogger(__name__)
+
+# The header and its sidecars live in the build directory
+PCH_HEADER_NAME = "esphome_pch.h"
+PCH_GCH_NAME = f"{PCH_HEADER_NAME}.gch"
+# ccache hashes this instead of the .gch; also the freshness stamp
+PCH_SUM_NAME = f"{PCH_GCH_NAME}.sum"
+# The include list the .gch is compiled from
+PCH_SOURCE_NAME = "esphome_pch_src.h"
+
+# GCC can skip a .gch without a diagnostic and read the header of the same
+# name, so that header is an error. Other tools get the include list.
+PCH_GUARD_TEXT = f"""\
+#if defined(__GNUC__) && !defined(__clang__) && !defined(__INTELLISENSE__)
+#error "The precompiled header was not loaded"
+#else
+#include "{PCH_SOURCE_NAME}"
+#endif
+"""
+
+# The cc1plus wrapper the PlatformIO script writes on arm64 macOS
+PCH_CC1_DIR = "pch_cc1"
+
+# What the PlatformIO script leaves in the project root, for cleanup
+PCH_ARTIFACT_NAMES = (PCH_HEADER_NAME, PCH_GCH_NAME, PCH_SUM_NAME, PCH_SOURCE_NAME)
+PCH_ARTIFACT_DIRS = (PCH_CC1_DIR,)
+
+# The core headers every backend precompiles
+PCH_DEFAULT_HEADERS = ("esphome/core/pch_prefix.h",)
+
+# PlatformIO platforms that do not take the pch script
+PCH_SCRIPT_EXCLUDED_PLATFORMS = frozenset(
+    {
+        PLATFORM_NRF52,
+    }
+)
+
+# What ccache needs to cache compiles that load a .gch
+_CCACHE_PCH_SLOPPINESS = ("pch_defines", "time_macros")
+
+# Both include forms: an angle include resolving under src/ enters the digest
+_INCLUDE_RE = re.compile(rb'^\s*#\s*include\s+["<]([^">]+)[">]', re.MULTILINE)
+
+
+def pch_enabled() -> bool:
+    """Precompiled-header knob: default on, ``ESPHOME_PCH_ENABLE=0`` opts out."""
+    return parse_enable_env("ESPHOME_PCH_ENABLE") is not False
+
+
+def pch_forced() -> bool:
+    """``ESPHOME_PCH_ENABLE=1``: wanted even where the host rule says no."""
+    return parse_enable_env("ESPHOME_PCH_ENABLE") is True
+
+
+# GCC bug 14940: before these releases the Windows loader maps a .gch only
+# at its saved address. First fixed release per major, 16 on always fixed;
+# PCH_WINDOWS_CMAKE_OLD_GCC and the pch_usable message spell the same table
+PCH_WINDOWS_GCC_FIXED = {14: (14, 4), 15: (15, 3)}
+PCH_WINDOWS_GCC_FIXED_DEFAULT = (16, 0)
+# The same rule for CMake, which alone knows the version before configure
+PCH_WINDOWS_CMAKE_OLD_GCC = (
+    "CMAKE_CXX_COMPILER_VERSION VERSION_LESS 14.4 OR "
+    "(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 15 AND "
+    "CMAKE_CXX_COMPILER_VERSION VERSION_LESS 15.3)"
+)
+
+
+def gcc_relocates_pch_on_windows(version: Sequence[int]) -> bool:
+    """Whether a GCC of this version loads a .gch on Windows."""
+    if not version:
+        return False
+    fixed = PCH_WINDOWS_GCC_FIXED.get(version[0], PCH_WINDOWS_GCC_FIXED_DEFAULT)
+    return tuple(version[:2]) >= fixed
+
+
+# GCC ends the first --version line with its version; clang names itself
+_VERSION_RE = re.compile(r"\d+(?:\.\d+)+")
+
+
+def gcc_version(cxx: Sequence[Path | str]) -> tuple[int, ...] | None:
+    """The GCC version from ``--version``: () when it cannot be read, None
+    for a compiler that is not GCC."""
+    try:
+        result = subprocess.run(
+            [*cxx, "--version"], capture_output=True, text=True, check=False
+        )
+    except OSError as err:
+        _LOGGER.debug("Cannot run %s: %s", cxx[0], err)
+        return ()
+    banner = result.stdout.partition("\n")[0]
+    if "clang" in banner.lower():
+        return None
+    found = _VERSION_RE.findall(banner)
+    return tuple(int(part) for part in found[-1].split(".")) if found else ()
+
+
+def pch_needs_gcc_check() -> bool:
+    """Windows host with the knob unset: the compiler version decides."""
+    return sys.platform == "win32" and parse_enable_env("ESPHOME_PCH_ENABLE") is None
+
+
+def pch_usable(cxx: Sequence[Path | str]) -> bool:
+    """The knob plus the host rule; ``ESPHOME_PCH_ENABLE=1`` skips the rule."""
+    if not pch_enabled():
+        return False
+    if not pch_needs_gcc_check():
+        return True
+    version = gcc_version(cxx)
+    if version is None or gcc_relocates_pch_on_windows(version):
+        return True
+    _LOGGER.info(
+        "GCC %s cannot load a precompiled header on Windows (GCC bug 14940, "
+        "fixed in 14.4, 15.3 and 16); compiling without it "
+        "(set ESPHOME_PCH_ENABLE=1 to force)",
+        ".".join(map(str, version)) or "of unknown version",
+    )
+    return False
+
+
+def pch_consumer_flags() -> list[str]:
+    """Flags a C++ src compile loads the pch with. The -include stays
+    relative: an absolute path would enter the ccache key."""
+    return ["-Winvalid-pch", "-Werror=invalid-pch", "-include", PCH_HEADER_NAME]
+
+
+def ccache_pch_env() -> dict[str, str]:
+    """What ccache needs to cache compiles that load a .gch, added to what
+    the user already set."""
+    if not pch_enabled():
+        return {}
+    sloppiness = [
+        item.strip()
+        for item in os.environ.get("CCACHE_SLOPPINESS", "").split(",")
+        if item.strip()
+    ]
+    sloppiness += [item for item in _CCACHE_PCH_SLOPPINESS if item not in sloppiness]
+    env = {"CCACHE_SLOPPINESS": ",".join(sloppiness)}
+    if "CCACHE_PCH_EXTSUM" not in os.environ:
+        env["CCACHE_PCH_EXTSUM"] = "true"
+    return env
+
+
+def pch_script_enabled() -> bool:
+    """Whether this PlatformIO build takes the pch script."""
+    from esphome.core import CORE
+
+    return pch_enabled() and CORE.target_platform not in PCH_SCRIPT_EXCLUDED_PLATFORMS
+
+
+def pch_header_text(include_headers: Iterable[str]) -> str:
+    """The prefix-header source: exactly these includes, in order."""
+    return "".join(f'#include "{name}"\n' for name in include_headers)
+
+
+def write_pch_headers(build_dir: Path, include_headers: Iterable[str]) -> Path:
+    """Write the guard header and the include list; return the latter,
+    which is what the .gch compiles from."""
+    write_file_if_changed(build_dir / PCH_HEADER_NAME, PCH_GUARD_TEXT)
+    source = build_dir / PCH_SOURCE_NAME
+    write_file_if_changed(source, pch_header_text(include_headers))
+    return source
+
+
+def _include_closure(src_dir: Path, roots: Iterable[str]) -> dict[str, bytes]:
+    """Include closure of ``roots``: src-relative name -> contents.
+
+    Resolution mirrors the compiler (includer's dir, then src root). No
+    #ifdef evaluation: including too much is the safe direction. Headers
+    outside ``src_dir`` are covered by the version strings of the caller.
+    """
+    seen: dict[str, bytes] = {}
+    stack: list[tuple[str, str]] = [(name, "") for name in roots]
+    while stack:
+        name, from_dir = stack.pop()
+        for candidate in (f"{from_dir}/{name}" if from_dir else name, name):
+            rel = posixpath.normpath(candidate)
+            if not rel.startswith("..") and (src_dir / rel).is_file():
+                break
+        else:
+            continue
+        if rel in seen:
+            continue
+        data = seen[rel] = (src_dir / rel).read_bytes()
+        parent = posixpath.dirname(rel)
+        stack.extend((inc.decode(), parent) for inc in _INCLUDE_RE.findall(data))
+    return seen
+
+
+def pch_checksum(
+    src_dir: Path, include_headers: Iterable[str], extra: Iterable[str]
+) -> str:
+    """Digest of the prefix header's include closure plus ``extra``."""
+    digest = hashlib.sha256()
+    closure = _include_closure(src_dir, include_headers)
+    for name in sorted(closure):
+        digest.update(name.encode())
+        digest.update(closure[name])
+        digest.update(b"\0")
+    for item in extra:
+        digest.update(item.encode())
+        digest.update(b"\0")
+    return digest.hexdigest()
+
+
+def pch_identity(
+    tokens: Iterable[str],
+    src_dir: Path,
+    include_headers: tuple[str, ...],
+    extra: Iterable[str],
+) -> str:
+    """The .sum digest: include closure, header text, ``extra`` and the
+    compile flags with the build path stripped, as ccache does."""
+    from esphome.core import CORE
+
+    flags = (
+        " ".join(tokens)
+        .replace(str(CORE.build_path), "")
+        .replace(effective_ccache_basedir(), "")
+    )
+    # The closure is sorted, so header order only enters via the text
+    return pch_checksum(
+        src_dir, include_headers, (pch_header_text(include_headers), *extra, flags)
+    )
+
+
+_DISABLE_HINT = " (set ESPHOME_PCH_ENABLE=0 to disable)"
+
+
+def log_pch_in_use() -> None:
+    _LOGGER.info("Compiling with a precompiled header%s", _DISABLE_HINT)
@@ -0,0 +1,24 @@
+"""The PlatformIO-format size bar shared by the native toolchains."""
+
+from __future__ import annotations
+
+
+def format_bar(used: int, total: int) -> str:
+    """Match PlatformIO's ``_format_availale_bytes`` (sic, pioupload.py) exactly."""
+    pct_raw = used / total if total else 0
+    blocks = 10
+    filled = min(int(round(blocks * pct_raw)), blocks)
+    progress = "=" * filled
+    return (
+        f"[{progress:<{blocks}}] {pct_raw: 6.1%} "
+        f"(used {used:d} bytes from {total:d} bytes)"
+    )
+
+
+def print_size_line(label: str, used: int, total: int) -> None:
+    """One PlatformIO-format summary line (``RAM``/``Flash``).
+
+    The label padding is part of the format: ``script/ci_memory_impact_extract.py``
+    matches these lines verbatim.
+    """
+    print(f"{label + ':':<7}{format_bar(used, total)}")
@@ -0,0 +1,180 @@
+"""Run a native build tool (cmake, ninja) and relay its output.
+
+Output is read from a pipe so it can be filtered here: a child that inherits
+our stdout writes straight to the file descriptor, past any Python wrapper.
+"""
+
+from __future__ import annotations
+
+import codecs
+from contextlib import suppress
+import logging
+import os
+from pathlib import Path
+import re
+import shutil
+import subprocess
+import sys
+from typing import Any, TextIO
+
+from esphome.util import ANSI_ESCAPE, RedirectText, shlex_quote
+
+_LOGGER = logging.getLogger(__name__)
+
+# Windows code page identifier for UTF-8, as used by ``chcp 65001``.
+UTF8_CODEPAGE = 65001
+
+# Same pattern idf.py uses to spot ninja status lines (``is_progression``).
+_PROGRESS = re.compile(r"^\[\d+/\d+\]|.*\(\d+ \%\)$")
+_READ_SIZE = 65536
+
+
+def _get_kernel32() -> Any | None:
+    """Return the Windows kernel32 module, or None on any other platform."""
+    if sys.platform != "win32":
+        return None
+    import ctypes
+
+    return ctypes.windll.kernel32
+
+
+class Utf8Console:
+    """Keep an attached Windows console on UTF-8 while a build tool runs.
+
+    esp_idf_size draws its table with Unicode box characters, and CMake
+    re-decodes a child's output with the console code page, which garbles the
+    table on any page but UTF-8. A console already on UTF-8 is left alone so
+    an overlapping build never records UTF-8 as the page to go back to.
+    """
+
+    def __init__(self, kernel32: Any | None) -> None:
+        self._kernel32 = kernel32
+        self._codepages: tuple[int, int] | None = None
+
+    def __enter__(self) -> None:
+        kernel32 = self._kernel32
+        if kernel32 is None:
+            return
+        old_in = kernel32.GetConsoleCP()
+        old_out = kernel32.GetConsoleOutputCP()
+        # Both calls return 0 when no console is attached.
+        if not old_in or not old_out:
+            return
+        if old_in == UTF8_CODEPAGE and old_out == UTF8_CODEPAGE:
+            return
+        # Record first so a switch that fails part way is still undone.
+        self._codepages = (old_in, old_out)
+        kernel32.SetConsoleCP(UTF8_CODEPAGE)
+        kernel32.SetConsoleOutputCP(UTF8_CODEPAGE)
+
+    def __exit__(self, *exc_info: object) -> None:
+        if self._codepages is None:
+            return
+        old_in, old_out = self._codepages
+        self._codepages = None
+        self._kernel32.SetConsoleCP(old_in)
+        self._kernel32.SetConsoleOutputCP(old_out)
+
+
+def _fit_terminal(text: str) -> str:
+    """Elide the middle of ``text`` to fit the terminal, as idf.py does.
+
+    A width of 0 (a pipe, the dashboard) leaves the text whole.
+    """
+    width = shutil.get_terminal_size((0, 0)).columns
+    if not width:
+        return text
+    if width <= 3:
+        return "." * width
+    if len(text) >= width:
+        keep = (width - 3) // 2
+        return f"{text[:keep]}...{text[len(text) - keep :]}"
+    return text
+
+
+class ToolOutput(RedirectText):
+    """RedirectText that can collapse ninja status lines into one line.
+
+    With ``progress`` each ``[n/m]`` line overwrites the previous one, the
+    way idf.py shows a build.
+    """
+
+    def __init__(
+        self, out: TextIO, filter_lines: list[str] | None, progress: bool
+    ) -> None:
+        super().__init__(out, filter_lines=filter_lines)
+        self._progress = progress
+        self._on_progress_line = False
+
+    def _splits_lines(self) -> bool:
+        return self._progress or super()._splits_lines()
+
+    def _emit_line(self, line: str) -> None:
+        if self._progress and _PROGRESS.match(line):
+            if not self._is_filtered(line):
+                text = _fit_terminal(line.strip("\r\n"))
+                self._write_color_replace(f"\r{text}\x1b[K")
+                self._on_progress_line = True
+            return
+        self._end_progress_line()
+        super()._emit_line(line)
+
+    def _end_progress_line(self) -> None:
+        if self._on_progress_line:
+            self._on_progress_line = False
+            self._write_color_replace(os.linesep)
+
+    def drain(self) -> None:
+        super().drain()
+        # Called from cleanup, so a broken stream must not hide the exit code.
+        with suppress(OSError, ValueError):
+            self._end_progress_line()
+            self._out.flush()
+
+
+def run_build_tool(
+    cmd: list[str],
+    *,
+    cwd: Path,
+    env: dict[str, str],
+    filter_lines: list[str] | None = None,
+    progress: bool = False,
+    log_path: Path | None = None,
+) -> int:
+    """Run ``cmd`` and relay stdout and stderr, merged, to our stdout.
+
+    ``log_path`` also gets the full, unfiltered output without color codes, as
+    idf.py wrote its logs (its hint patterns expect plain text). Returns the
+    exit code.
+    """
+    _LOGGER.debug("Running: %s", " ".join(shlex_quote(arg) for arg in cmd))
+    _LOGGER.debug("  in directory: %s", cwd)
+    output = ToolOutput(sys.stdout, filter_lines, progress)
+    decoder = codecs.getincrementaldecoder("utf-8")(errors="replace")
+    if log_path is not None:
+        log_path.parent.mkdir(parents=True, exist_ok=True)
+    with (
+        Path(log_path or os.devnull).open("w", encoding="utf-8", newline="") as log,
+        Utf8Console(_get_kernel32()),
+        subprocess.Popen(
+            cmd,
+            cwd=cwd,
+            env=env,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+            close_fds=False,
+        ) as proc,
+    ):
+        try:
+            # read1 returns as soon as anything is available, so output
+            # streams while the tool runs.
+            while chunk := proc.stdout.read1(_READ_SIZE):
+                text = decoder.decode(chunk)
+                log.write(ANSI_ESCAPE.sub("", text))
+                output.write(text)
+            if tail := decoder.decode(b"", final=True):
+                log.write(ANSI_ESCAPE.sub("", tail))
+                output.write(tail)
+        finally:
+            output.drain()
+    return proc.returncode
@@ -0,0 +1,46 @@
+"""Machine-global tools cache location shared by the native backends."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+
+def tools_cache_path(env_var: str, subdir: str) -> Path:
+    """A backend's machine-global tools directory, with an env override.
+
+    A blank/whitespace override is treated as unset: ``Path("")`` resolves
+    to the CWD, which ``clean-all`` would then delete.
+    """
+    import platformdirs
+
+    from esphome.helpers import get_str_env
+
+    if prefix := get_str_env(env_var, "").strip():
+        # resolve(): a symlinked prefix would otherwise record a second
+        # spelling of the same paths in the build tree
+        return Path(prefix).expanduser().resolve()
+    # appauthor=False keeps the Windows path short (no vendor segment);
+    # deep IDF trees run into MAX_PATH otherwise
+    return (
+        Path(platformdirs.user_cache_dir("esphome", appauthor=False)) / subdir
+    ).resolve()
+
+
+# (env override, cache subdir) per native backend. writer.clean_all wipes
+# every entry via tools_cache_path, so listing a cache here is the single
+# step that registers it for removal; the backends' own path getters use
+# the same named pairs so the two cannot drift.
+IDF_TOOLS_CACHE = ("ESPHOME_ESP_IDF_PREFIX", "idf")
+SDK_NRF_TOOLS_CACHE = ("ESPHOME_SDK_NRF_PREFIX", "sdk-nrf")
+ARDUINO8266_TOOLS_CACHE = ("ESPHOME_ARDUINO8266_PREFIX", "arduino8266")
+# The host backend installs nothing; the entry only holds its ccache dir
+HOST_TOOLS_CACHE = ("ESPHOME_HOST_PREFIX", "host")
+# PlatformIO installs into its own dirs; the entry is its ccache dir itself
+PLATFORMIO_CCACHE = ("ESPHOME_PLATFORMIO_CCACHE_DIR", "platformio-ccache")
+TOOLS_CACHE_SPECS = (
+    IDF_TOOLS_CACHE,
+    SDK_NRF_TOOLS_CACHE,
+    ARDUINO8266_TOOLS_CACHE,
+    HOST_TOOLS_CACHE,
+    PLATFORMIO_CCACHE,
+)
@@ -102,25 +102,21 @@ _KNOWN_FILE_EXTENSIONS = frozenset(
 )


-# Matches !secret references in YAML text.  An optional surrounding
-# quote pair around the key is allowed and ignored: YAML treats
-# ``!secret 'foo'`` and ``!secret foo`` as the same key.  This is
-# intentionally a simple regex scan rather than a YAML parse — it may
-# match inside comments or multi-line strings, which is the conservative
-# direction (include more secrets rather than fewer).
-_SECRET_RE = re.compile(r"""!secret\s+['"]?([^\s'"]+)""")
-
-
 def _find_used_secret_keys(yaml_files: list[Path]) -> set[str]:
    """Scan YAML files for ``!secret <key>`` references."""
    keys: set[str] = set()
    for fpath in yaml_files:
        try:
            text = fpath.read_text(encoding="utf-8")
-        except (OSError, UnicodeDecodeError):
+        except (OSError, UnicodeDecodeError) as err:
+            _LOGGER.warning(
+                "Could not scan %s for !secret references (%s); the bundled "
+                "secret set may be incomplete",
+                fpath,
+                err,
+            )
            continue
-        for match in _SECRET_RE.finditer(text):
-            keys.add(match.group(1))
+        keys |= yaml_util.find_secret_references(text)
    return keys


@@ -422,6 +418,18 @@ class ConfigBundleCreator:
        must ship every candidate so the remote build can pick any one.
        """
        discovered = yaml_util.discover_user_yaml_files(self._config_path)
+        if discovered.load_errors:
+            _LOGGER.warning(
+                "Bundle may be incomplete; could not load all configuration files: %s",
+                "; ".join(discovered.load_errors),
+            )
+        if discovered.unresolved:
+            _LOGGER.warning(
+                "Bundle may be incomplete; %d !include path(s) use "
+                "substitutions and cannot be captured: %s",
+                len(discovered.unresolved),
+                ", ".join(discovered.unresolved),
+            )
        self._secrets_paths.update(discovered.secrets)
        # A !secret inside a file this re-parse does not reach (for example
        # a git-fetched package the builder re-fetches) still resolves
@@ -0,0 +1,2 @@
+"""Commands of the esphome command line, one module each, imported by
+__main__ only when they run so that startup stays light."""
@@ -0,0 +1,164 @@
+"""``esphome rename``."""
+
+from __future__ import annotations
+
+import argparse
+from pathlib import Path
+import re
+
+from esphome import yaml_edit, yaml_util
+from esphome.const import (
+    ALLOWED_NAME_CHARS,
+    CONF_ESPHOME,
+    CONF_NAME,
+    CONF_SUBSTITUTIONS,
+)
+from esphome.core import CORE, EsphomeError
+from esphome.log import AnsiFore, color
+from esphome.types import ConfigType
+from esphome.util import ESPHOME_COMMAND, run_external_process, safe_print
+
+
+def _revert(new_path: Path, why: str) -> int:
+    """Say why the rename stopped and take the new file back; an orphan the
+    next attempt would trip over is reported."""
+    safe_print(color(AnsiFore.BOLD_RED, f"Rename failed: {why}"))
+    try:
+        new_path.unlink(missing_ok=True)
+    except OSError as err:
+        safe_print(color(AnsiFore.BOLD_RED, f"Could not remove {new_path}: {err}"))
+    return 1
+
+
+def command_rename(args: argparse.Namespace, config: ConfigType) -> int | None:
+    """Rename the device: a new file with the name line rewritten, validated
+    and installed, then the old file removed."""
+    new_name = args.name
+    for c in new_name:
+        if c not in ALLOWED_NAME_CHARS:
+            safe_print(
+                color(
+                    AnsiFore.BOLD_RED,
+                    f"'{c}' is an invalid character for names. Valid characters are: "
+                    f"{ALLOWED_NAME_CHARS} (lowercase, no spaces)",
+                )
+            )
+            return 1
+
+    yaml = yaml_util.load_yaml(CORE.config_path)
+
+    def name_edit() -> tuple[str, yaml_edit.LineEdit]:
+        """The name and the line to rewrite: the name's own line, or the
+        substitution's line it comes from, as a plain value in this file."""
+        esphome_conf = yaml.get(CONF_ESPHOME)
+        if not isinstance(esphome_conf, dict) or CONF_NAME not in esphome_conf:
+            raise EsphomeError(f"no '{CONF_ESPHOME}: {CONF_NAME}:' in the file")
+        old_name = str(esphome_conf[CONF_NAME])
+        mapping, field = esphome_conf, CONF_NAME
+        if match := re.match(r"^\$\{?([a-zA-Z0-9_]+)\}?$", old_name):
+            mapping, field = yaml.get(CONF_SUBSTITUTIONS), match.group(1)
+            if not isinstance(mapping, dict) or field not in mapping:
+                raise EsphomeError(f"the substitution '{field}' is not in the file")
+            old_name = str(mapping[field])
+        # Only read here; the rewritten text goes to a new file, so the
+        # source may live anywhere the config path points to
+        source = yaml_edit.source_of(mapping, field)
+        if source is None or source[0].resolve() != CORE.config_path.resolve():
+            raise EsphomeError(f"'{field}' was not read from {CORE.config_path}")
+        doc, line_no = source
+        text = yaml_edit.line_at(doc, line_no)
+        if (line_match := yaml_edit.field_line_re(field, old_name).match(text)) is None:
+            raise EsphomeError(f"'{field}' is not a plain value on {doc}:{line_no + 1}")
+        # The new value is always quoted, whatever the old line had
+        return old_name, yaml_edit.LineEdit(
+            doc, line_no, text, yaml_edit.rewrite(line_match, new_name, '"')
+        )
+
+    try:
+        old_name, edit = name_edit()
+    except EsphomeError as err:
+        safe_print(
+            color(
+                AnsiFore.BOLD_RED,
+                f"Complex YAML files cannot be automatically renamed: {err}",
+            )
+        )
+        return 1
+
+    # ``new_name == old_name`` (after substitution resolution) is
+    # a no-op rewrite that would still queue a pointless re-flash.
+    # Catch it before the path-equality check below — covers the
+    # case where the config filename doesn't match the device name
+    # (e.g. ``weird-file.yaml`` whose ``esphome.name`` is
+    # ``kitchen``; running ``esphome rename weird-file.yaml kitchen``
+    # would otherwise just re-flash the same hostname).
+    if new_name == old_name:
+        safe_print(
+            color(
+                AnsiFore.BOLD_RED,
+                f"'{new_name}' is already the device's name.",
+            )
+        )
+        return 1
+
+    new_path: Path = CORE.config_dir / (new_name + ".yaml")
+    if new_path.resolve() == CORE.config_path.resolve():
+        safe_print(
+            color(
+                AnsiFore.BOLD_RED,
+                f"'{new_name}' is already the device's name.",
+            )
+        )
+        return 1
+    if new_path.exists():
+        safe_print(
+            color(
+                AnsiFore.BOLD_RED,
+                f"Cannot rename: {new_path} already exists. "
+                "Refusing to overwrite an existing configuration.",
+            )
+        )
+        return 1
+    safe_print(
+        f"Updating {color(AnsiFore.CYAN, str(CORE.config_path))} to {color(AnsiFore.CYAN, str(new_path))}"
+    )
+    print()
+
+    try:
+        yaml_edit.write_keeping_mode(
+            new_path,
+            yaml_edit.rewritten_text(yaml_edit.read_text(CORE.config_path), [edit]),
+            like=CORE.config_path,
+        )
+    except EsphomeError as err:
+        return _revert(new_path, str(err))
+
+    if run_external_process(*ESPHOME_COMMAND, "config", str(new_path)) != 0:
+        return _revert(new_path, "the new configuration does not validate")
+
+    cli_args = [
+        "run",
+        str(new_path),
+        "--no-logs",
+        "--device",
+        CORE.address,
+    ]
+
+    if args.dashboard:
+        cli_args.insert(0, "--dashboard")
+
+    try:
+        rc = run_external_process(*ESPHOME_COMMAND, *cli_args)
+    except KeyboardInterrupt:
+        rc = 1
+    if rc != 0:
+        return _revert(
+            new_path,
+            "the install did not finish; the device may already run the new name",
+        )
+
+    CORE.config_path.unlink()
+
+    safe_print(color(AnsiFore.BOLD_GREEN, "SUCCESS"))
+    print()
+    return 0
@@ -25,32 +25,42 @@ from esphome.cpp_generator import (  # noqa: F401
    add,
    add_build_flag,
    add_build_unflag,
+    add_cmake_arg,
    add_cxx_build_flag,
    add_define,
    add_global,
    add_library,
    add_platformio_option,
+    extern_progmem_array,
    get_variable,
    get_variable_with_full_id,
+    is_static_pointer,
    is_template,
    new_Pvariable,
    new_variable,
    process_lambda,
    progmem_array,
+    progmem_string,
    safe_exp,
    set_cpp_standard,
+    shared_progmem_array,
+    shared_progmem_string,
    statement,
    static_const_array,
+    static_function,
    templatable,
    variable,
    with_local_variable,
 )
 from esphome.cpp_helpers import (  # noqa: F401
+    add_pin,
+    add_variable,
    build_registry_entry,
    build_registry_list,
    extract_registry_entry_config,
    get_slot_count,
    gpio_pin_expression,
+    new_bus_component,
    past_safe_mode,
    register_component,
    register_parented,
@@ -63,7 +73,6 @@ from esphome.cpp_types import (  # noqa: F401
    Application,
    Component,
    ComponentPtr,
-    Controller,
    EntityBase,
    EntityCategory,
    ESPTime,
@@ -77,6 +86,7 @@ from esphome.cpp_types import (  # noqa: F401
    StringRef,
    arduino_json_ns,
    bool_,
+    char,
    const_char_ptr,
    double,
    esphome_ns,
@@ -18,9 +18,9 @@ from pathlib import Path
 from typing import Any

 from esphome.const import __version__ as ESPHOME_VERSION
-from esphome.core import CORE, Lambda
+from esphome.core import CORE, EsphomeError, Lambda
 from esphome.helpers import write_file
-from esphome.storage_json import StorageJSON, ext_storage_path
+from esphome.storage_json import StorageJSON, ext_storage_path, storage_path
 from esphome.types import ConfigType

 _LOGGER = logging.getLogger(__name__)
@@ -65,7 +65,86 @@ def save_compiled_config(config: ConfigType) -> None:
        # non-basic dict key), so every upload/logs pays the slow path.
        _LOGGER.warning("Cannot cache the validated config: %s", err)
    except Exception as err:  # noqa: BLE001  # pylint: disable=broad-except
-        _LOGGER.debug("Skipping compiled config cache write: %s", err)
+        # Likely persistent (permissions, full disk): every upload/logs
+        # pays the slow path until it clears, so surface it.
+        _LOGGER.warning("Skipping compiled config cache write: %s", err)
+
+
+def save_compiled_config_and_sidecar(config: ConfigType) -> None:
+    """Refresh the cache from the upload/logs fallback (CORE.config must be set).
+
+    The cache is only written when a complete sidecar is on disk:
+    load_compiled_config can't use it otherwise, and it holds resolved
+    secrets.
+    """
+    if _refresh_sidecar():
+        save_compiled_config(config)
+
+
+def _refresh_sidecar() -> bool:
+    """Ensure a complete sidecar is on disk; True when one is.
+
+    Writes one (without claiming a build) when missing or wizard-only.
+    Failures are non-fatal; the next upload/logs pays the slow path again.
+    """
+    try:
+        path = storage_path()
+        try:
+            old = StorageJSON.load_strict(path)
+        except Exception as err:  # noqa: BLE001  # pylint: disable=broad-except
+            # Present but unreadable: it may hold a real build's metadata,
+            # and a fresh rewrite would also stop the next compile from
+            # cleaning a possibly incoherent build tree.
+            _LOGGER.warning(
+                "Not caching: storage sidecar %s is unreadable (%s)", path, err
+            )
+            return False
+        if old is not None and old.can_apply_to_core():
+            if (
+                old.toolchain is not None
+                and CORE.toolchain is not None
+                and old.toolchain != CORE.toolchain.value
+            ):
+                # Platforms normalize toolchain-sensitive keys differently;
+                # never cache a config validated under a different toolchain
+                # than the compile's
+                _LOGGER.debug(
+                    "Not caching: config validated with toolchain %r but the "
+                    "last compile used %r",
+                    CORE.toolchain.value,
+                    old.toolchain,
+                )
+                return False
+            # Compile-written; nothing to refresh.
+            return True
+        if CORE.build_path is not None and CORE.build_path.exists():
+            # An unvalidated build tree: its absent or mismatched sidecar
+            # is what makes the next compile wipe it, so don't vouch for
+            # a build this run never saw.
+            _LOGGER.warning(
+                "Not caching: build tree %s has no matching sidecar; "
+                "'esphome compile' will settle it",
+                CORE.build_path,
+            )
+            return False
+        new = StorageJSON.from_esphome_core(CORE, old, claim_build=False)
+        if not new.can_apply_to_core():
+            _LOGGER.warning("Not caching: rebuilt storage sidecar is still incomplete")
+            return False
+        new.save(path)
+        return True
+    except (OSError, EsphomeError) as err:
+        # write_file wraps OSError into EsphomeError. Persistent
+        # (unwritable storage dir), so surface that every upload/logs
+        # pays the slow path.
+        _LOGGER.warning("Could not refresh the storage sidecar: %s", err)
+    except Exception:  # noqa: BLE001  # pylint: disable=broad-except
+        # A structural bug; keep the traceback so it isn't mistaken
+        # for the I/O failure above.
+        _LOGGER.warning(
+            "Unexpected error refreshing the storage sidecar", exc_info=True
+        )
+    return False


 def load_compiled_config(conf_path: Path) -> ConfigType | None:
@@ -98,11 +177,8 @@ def load_compiled_config(conf_path: Path) -> ConfigType | None:
        return None

    storage = StorageJSON.load(ext_storage_path(conf_path.name))
-    if storage is None:
-        return None
-    # apply_to_core assumes a real compile wrote the sidecar; wizard-only
-    # sidecars leave both of these unset and can't drive upload/logs.
-    if not storage.core_platform and not storage.target_platform:
+    if storage is None or not storage.can_apply_to_core():
+        _LOGGER.debug("Ignoring compiled config cache: sidecar missing or incomplete")
        return None
    storage.apply_to_core()
    return config
@@ -0,0 +1,11 @@
+"""Component alias registry.
+
+Generated by script/build_alias_registry.py - do not edit manually.
+See the component-alias section of esphome/loader.py.
+"""
+
+# alias -> (canonical component, removal version or None)
+COMPONENT_ALIASES: dict[str, tuple[str, str | None]] = {
+    "esp32_improv": ("improv_ble", "2027.4.0"),
+    "rp2040": ("rp2", "2027.7.0"),
+}
@@ -1 +1,2 @@
 CODEOWNERS = ["@MrSuicideParrot"]
+DOMAIN = "a01nyub"
@@ -6,18 +6,16 @@

 namespace esphome::a01nyub {

-static const char *const TAG = "a01nyub.sensor";
+ESPHOME_LOG_TAG(TAG, "a01nyub.sensor");

 void A01nyubComponent::loop() {
-  uint8_t data;
-  while (this->available() > 0) {
-    this->read_byte(&data);
+  this->read_available([this](uint8_t data) {
    if (this->buffer_.empty() && (data != 0xff))
-      continue;
+      return;
    buffer_.push_back(data);
    if (this->buffer_.size() == 4)
      this->check_buffer_();
-  }
+  });
 }

 void A01nyubComponent::check_buffer_() {
@@ -6,6 +6,7 @@ from esphome.const import (
    STATE_CLASS_MEASUREMENT,
    UNIT_METER,
 )
+from esphome.types import ConfigType

 CODEOWNERS = ["@MrSuicideParrot"]
 DEPENDENCIES = ["uart"]
@@ -35,7 +36,7 @@ FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
 )


-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
    var = await sensor.new_sensor(config)
    await cg.register_component(var, config)
    await uart.register_uart_device(var, config)
@@ -1 +1,2 @@
 CODEOWNERS = ["@TH-Braemer"]
+DOMAIN = "a02yyuw"
@@ -6,18 +6,16 @@

 namespace esphome::a02yyuw {

-static const char *const TAG = "a02yyuw.sensor";
+ESPHOME_LOG_TAG(TAG, "a02yyuw.sensor");

 void A02yyuwComponent::loop() {
-  uint8_t data;
-  while (this->available() > 0) {
-    this->read_byte(&data);
+  this->read_available([this](uint8_t data) {
    if (this->buffer_.empty() && (data != 0xff))
-      continue;
+      return;
    buffer_.push_back(data);
    if (this->buffer_.size() == 4)
      this->check_buffer_();
-  }
+  });
 }

 void A02yyuwComponent::check_buffer_() {
@@ -6,6 +6,7 @@ from esphome.const import (
    STATE_CLASS_MEASUREMENT,
    UNIT_MILLIMETER,
 )
+from esphome.types import ConfigType

 CODEOWNERS = ["@TH-Braemer"]
 DEPENDENCIES = ["uart"]
@@ -35,7 +36,7 @@ FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
 )


-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
    var = await sensor.new_sensor(config)
    await cg.register_component(var, config)
    await uart.register_uart_device(var, config)
@@ -0,0 +1 @@
+DOMAIN = "a4988"
@@ -3,7 +3,7 @@

 namespace esphome::a4988 {

-static const char *const TAG = "a4988.stepper";
+ESPHOME_LOG_TAG(TAG, "a4988.stepper");

 void A4988::setup() {
  if (this->sleep_pin_ != nullptr) {
@@ -3,6 +3,7 @@ import esphome.codegen as cg
 from esphome.components import stepper
 import esphome.config_validation as cv
 from esphome.const import CONF_DIR_PIN, CONF_ID, CONF_SLEEP_PIN, CONF_STEP_PIN
+from esphome.types import ConfigType

 a4988_ns = cg.esphome_ns.namespace("a4988")
 A4988 = a4988_ns.class_("A4988", stepper.Stepper, cg.Component)
@@ -17,16 +18,11 @@ CONFIG_SCHEMA = stepper.STEPPER_SCHEMA.extend(
 ).extend(cv.COMPONENT_SCHEMA)


-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
    var = cg.new_Pvariable(config[CONF_ID])
    await cg.register_component(var, config)
    await stepper.register_stepper(var, config)

-    step_pin = await cg.gpio_pin_expression(config[CONF_STEP_PIN])
-    cg.add(var.set_step_pin(step_pin))
-    dir_pin = await cg.gpio_pin_expression(config[CONF_DIR_PIN])
-    cg.add(var.set_dir_pin(dir_pin))
-
-    if sleep_pin_config := config.get(CONF_SLEEP_PIN):
-        sleep_pin = await cg.gpio_pin_expression(sleep_pin_config)
-        cg.add(var.set_sleep_pin(sleep_pin))
+    await cg.add_pin(var.set_step_pin, config[CONF_STEP_PIN])
+    await cg.add_pin(var.set_dir_pin, config[CONF_DIR_PIN])
+    await cg.add_pin(var.set_sleep_pin, config.get(CONF_SLEEP_PIN))
@@ -1 +1,2 @@
 CODEOWNERS = ["@DAVe3283"]
+DOMAIN = "absolute_humidity"
@@ -3,7 +3,7 @@

 namespace esphome::absolute_humidity {

-static const char *const TAG{"absolute_humidity.sensor"};
+ESPHOME_LOG_TAG(TAG, "absolute_humidity.sensor");

 void AbsoluteHumidityComponent::setup() {
  this->temperature_sensor_->add_on_state_callback([this](float state) {
				`@@ -0,0 +1 @@`
				`"""Build helpers shared by the native (non-PlatformIO) toolchains."""`