Merge branch 'dev' into noise-spare-ephemeral

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

.github/workflows/ci.yml

@@ -244,11 +244,20 @@ jobs:
     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
         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

.github/workflows/sync-dependency-versions.yml

@@ -0,0 +1,94 @@
+# 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]
+    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@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        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

.pre-commit-config.yaml

@@ -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: v0.16.3
+    rev: v0.16.6
     hooks:
       # Run the linter.
       - id: ruff
@@ -42,7 +41,7 @@ repos:
       - 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)$

AGENTS.md

@@ -553,6 +553,7 @@ file does, and it is the authority when they disagree. The most useful starting
     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.
@@ -839,7 +840,7 @@ file does, and it is the authority when they disagree. The most useful starting
         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:

Doxyfile

@@ -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         = 2026.9.0b3
+PROJECT_NUMBER         = 2026.10.0-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

esphome/api_client.py

@@ -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__)

esphome/components/api/__init__.py

@@ -13,6 +13,7 @@ from esphome.components.logger import request_log_listener
 from esphome.components.noise import (  # noqa: F401
     ENCRYPTION_SCHEMA,
     decode_encryption_key,
+    enable_spare_ephemeral,
     encryption_schema,
     new_psk_progmem,
     validate_encryption_key,
@@ -603,6 +604,7 @@ async def to_code(config: ConfigType) -> None:
             # and plaintext disabled. Only a factory reset can remove it.
             cg.add_define("USE_API_PLAINTEXT")
         cg.add_define("USE_API_NOISE")
+        enable_spare_ephemeral()
     else:
         cg.add_define("USE_API_PLAINTEXT")
 

esphome/components/api/api_connection.h

@@ -316,9 +316,16 @@ class APIConnection final : public APIServerConnectionBase {
   void on_noise_encryption_set_key_request(const NoiseEncryptionSetKeyRequest &msg);
 #endif
 
+  // How long a new connection holds off the spare ephemeral refill
+  static constexpr uint32_t CONNECT_GRACE_MS = 1000;
   bool is_authenticated() {
     return static_cast<ConnectionState>(this->flags_.connection_state) == ConnectionState::AUTHENTICATED;
   }
+  // Unauthenticated and within its grace period; an older unauthenticated
+  // connection is a stale half open client and no longer counts
+  bool is_still_connecting(uint32_t now) {
+    return !this->is_authenticated() && now - this->last_traffic_ < CONNECT_GRACE_MS;
+  }
   bool is_connection_setup() {
     return static_cast<ConnectionState>(this->flags_.connection_state) == ConnectionState::CONNECTED ||
            this->is_authenticated();

esphome/components/api/api_server.cpp

@@ -143,6 +143,15 @@ void APIServer::loop() {
     this->accept_new_connections_();
   }
 
+  // Checked once per pass for the refill and for the clients below
+  const bool connected = network::is_connected();
+#ifdef USE_NOISE_SPARE_EPHEMERAL
+  // Only the flag test is inline; refilling is the rare path
+  if (connected && !noise::has_spare_ephemeral()) {
+    this->refill_spare_ephemeral_();
+  }
+#endif
+
   if (this->api_connection_count_ == 0) {
     // Check reboot timeout - done in loop to avoid scheduler heap churn
     // (cancelled scheduler items sit in heap memory until their scheduled time).
@@ -159,8 +168,7 @@ void APIServer::loop() {
   }
 
   // Process clients and remove disconnected ones in a single pass
-  // Check network connectivity once for all clients
-  if (!network::is_connected()) {
+  if (!connected) {
     // Network is down - disconnect all clients
     for (auto &client : this->active_clients()) {
       client->on_fatal_error();
@@ -188,6 +196,21 @@ void APIServer::loop() {
   }
 }
 
+#ifdef USE_NOISE_SPARE_EPHEMERAL
+// Called with the network up; refill only while no api client is still
+// connecting (an OTA handshake is not visible here and just pays the refill
+// it triggered).
+void APIServer::refill_spare_ephemeral_() {
+  const uint32_t now = App.get_loop_component_start_time();
+  for (auto &client : this->active_clients()) {
+    if (client->is_still_connecting(now)) {
+      return;
+    }
+  }
+  noise::prepare_spare_ephemeral();
+}
+#endif
+
 void APIServer::remove_client_(uint8_t client_index) {
   auto &client = this->clients_[client_index];
 

esphome/components/api/api_server.h

@@ -5,7 +5,7 @@
 #include "api_buffer.h"
 // Must precede clients_ so APIConnection is complete for default_delete (libc++).
 #include "api_connection.h"
-#ifdef USE_API_NOISE
+#if defined(USE_API_NOISE) || defined(USE_NOISE_SPARE_EPHEMERAL)
 // Only present in the build when the noise component is loaded
 #include "esphome/components/noise/noise.h"
 #endif
@@ -363,6 +363,9 @@ class APIServer final : public Component,
   uint8_t provisioning_source_{0};
 #endif
 
+#ifdef USE_NOISE_SPARE_EPHEMERAL
+  void refill_spare_ephemeral_();
+#endif
 #ifdef USE_API_NOISE
   noise::NoiseContext noise_ctx_;
 #ifndef USE_API_NOISE_PSK_FROM_YAML

esphome/components/debug/sensor.py

@@ -23,11 +23,7 @@ from esphome.const import (
 )
 from esphome.types import ConfigType
 
-from . import (  # noqa: F401  pylint: disable=unused-import
-    CONF_DEBUG_ID,
-    FILTER_SOURCE_FILES,
-    DebugComponent,
-)
+from . import CONF_DEBUG_ID, FILTER_SOURCE_FILES, DebugComponent  # noqa: F401  pylint: disable=unused-import
 
 DEPENDENCIES = ["debug"]
 

esphome/components/debug/text_sensor.py

@@ -9,11 +9,7 @@ from esphome.const import (
 )
 from esphome.types import ConfigType
 
-from . import (  # noqa: F401  pylint: disable=unused-import
-    CONF_DEBUG_ID,
-    FILTER_SOURCE_FILES,
-    DebugComponent,
-)
+from . import CONF_DEBUG_ID, FILTER_SOURCE_FILES, DebugComponent  # noqa: F401  pylint: disable=unused-import
 
 DEPENDENCIES = ["debug"]
 

esphome/components/esp32/const.py

@@ -3,18 +3,11 @@ import esphome.codegen as cg
 # Re-exported for the many esp32-side users; defined in esphome.const
 # and esphome.espidf so the upload/logs fast path can use them without
 # importing this package.
-from esphome.const import (  # noqa: F401  # pylint: disable=unused-import
-    KEY_ESP32,
-    KEY_FLASH_SIZE,
-    KEY_IDF_VERSION,
-    KEY_VARIANT,
-)
+from esphome.const import KEY_ESP32, KEY_FLASH_SIZE, KEY_IDF_VERSION, KEY_VARIANT  # noqa: F401  # pylint: disable=unused-import
 
 # Back compat for external components only; in-tree callers import it
 # from esphome.espidf directly.
-from esphome.espidf import (  # noqa: F401  # pylint: disable=unused-import
-    variant_to_idf_target,
-)
+from esphome.espidf import variant_to_idf_target  # noqa: F401  # pylint: disable=unused-import
 
 KEY_BOARD = "board"
 KEY_SDKCONFIG_OPTIONS = "sdkconfig_options"

esphome/components/mipi_dsi/mipi_dsi.cpp

@@ -35,8 +35,8 @@ void MipiDsi::setup() {
       .bus_id = 0,  // index from 0, specify the DSI host to use
       .num_data_lanes =
           this->lanes_,  // Number of data lanes to use, can't set a value that exceeds the chip's capability
-      .phy_clk_src = MIPI_DSI_PHY_CLK_SRC_DEFAULT,  // Clock source for the DPHY
-      .lane_bit_rate_mbps = this->lane_bit_rate_,   // Bit rate of the data lanes, in Mbps
+      // phy_clk_src left at 0 to enable runtime auto-select.
+      .lane_bit_rate_mbps = this->lane_bit_rate_,  // Bit rate of the data lanes, in Mbps
   };
   auto err = esp_lcd_new_dsi_bus(&bus_config, &this->bus_handle_);
   if (err != ESP_OK) {

esphome/components/nextion/display.py

@@ -14,12 +14,7 @@ from esphome.const import (
 )
 from esphome.core import CORE, TimePeriod
 
-from . import (  # noqa: F401  pylint: disable=unused-import
-    FILTER_SOURCE_FILES,
-    Nextion,
-    nextion_ns,
-    nextion_ref,
-)
+from . import FILTER_SOURCE_FILES, Nextion, nextion_ns, nextion_ref  # noqa: F401  pylint: disable=unused-import
 from .base_component import (
     CONF_AUTO_WAKE_ON_TOUCH,
     CONF_COMMAND_SPACING,

esphome/components/noise/__init__.py

@@ -86,6 +86,11 @@ def encryption_schema(config: ConfigType | None) -> ConfigType:
     return ENCRYPTION_SCHEMA(config)
 
 
+def enable_spare_ephemeral() -> None:
+    """Compile the spare ephemeral key slot; the component that refills it calls this."""
+    cg.add_define("USE_NOISE_SPARE_EPHEMERAL")
+
+
 async def to_code(config: ConfigType) -> None:
     cg.add_define("USE_NOISE")
     cg.add_library("esphome/noise-c", "0.1.26")

esphome/components/noise/noise.cpp

@@ -1,12 +1,14 @@
 #include "noise.h"
 #ifdef USE_NOISE
 #include "esphome/core/hal.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 #include <algorithm>
 #include <cstring>
 
 #include <noise/protocol.h>
+#include <sodium.h>
 
 #ifdef USE_ESP8266
 #include <pgmspace.h>
@@ -24,6 +26,39 @@ void NoiseContext::load_psk(psk_t &out) const {
   progmem_memcpy(out.data(), this->psk_, out.size());
 }
 
+#ifdef USE_NOISE_SPARE_EPHEMERAL
+static constexpr size_t PRIVATE_KEY_SIZE = SPARE_EPHEMERAL_KEY_SIZE;
+static constexpr size_t PUBLIC_KEY_SIZE = SPARE_EPHEMERAL_KEY_SIZE;
+uint8_t spare_ephemeral[SPARE_EPHEMERAL_SIZE];  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+
+void prepare_spare_ephemeral() {
+  uint8_t *private_key = spare_ephemeral;
+  uint8_t *public_key = spare_ephemeral + PRIVATE_KEY_SIZE;
+  // Same steps as noise-c's curve25519 keygen; the clamp sets the ready bit,
+  // a failure wipes the slot so the handshake generates its own key
+  if (!random_bytes(private_key, PRIVATE_KEY_SIZE)) {
+    sodium_memzero(spare_ephemeral, sizeof(spare_ephemeral));
+    return;
+  }
+  private_key[0] &= 0xF8;
+  private_key[PRIVATE_KEY_SIZE - 1] = (private_key[PRIVATE_KEY_SIZE - 1] & 0x7F) | 0x40;
+  if (crypto_scalarmult_curve25519_base(public_key, private_key) != 0) {
+    sodium_memzero(spare_ephemeral, sizeof(spare_ephemeral));
+  }
+}
+
+int consume_spare_ephemeral(NoiseHandshakeState *state) {
+  if (!has_spare_ephemeral()) {
+    return 0;
+  }
+  // noise-c keeps its own copy, so the slot is wiped either way
+  int err = noise_handshakestate_set_local_ephemeral(state, spare_ephemeral, PRIVATE_KEY_SIZE,
+                                                     spare_ephemeral + PRIVATE_KEY_SIZE, PUBLIC_KEY_SIZE);
+  sodium_memzero(spare_ephemeral, sizeof(spare_ephemeral));
+  return err;
+}
+#endif  // USE_NOISE_SPARE_EPHEMERAL
+
 const LogString *noise_err_to_logstr(int err) {
   if (err == NOISE_ERROR_NO_MEMORY)
     return LOG_STR("NO_MEMORY");

esphome/components/noise/noise.h

@@ -6,6 +6,9 @@
 #include <cstdint>
 #include "esphome/core/log.h"
 
+// noise-c handshake state; the full definition lives in <noise/protocol.h>
+using NoiseHandshakeState = struct NoiseHandshakeState_s;
+
 namespace esphome::noise {
 
 using psk_t = std::array<uint8_t, 32>;
@@ -38,6 +41,26 @@ class NoiseContext {
 /// Convert a noise error code to a readable error
 const LogString *noise_err_to_logstr(int err);
 
+#ifdef USE_NOISE_SPARE_EPHEMERAL
+// One responder ephemeral key pair generated ahead of time (about 60 ms on
+// ESP8266), refilled by the api server while idle and consumed by the next
+// handshake of any noise transport; an empty slot means the handshake
+// generates its own key. The private key stays in RAM until consumed; it is
+// not wiped on shutdown.
+// Private key then public key; zero when empty
+static constexpr size_t SPARE_EPHEMERAL_KEY_SIZE = 32;
+static constexpr size_t SPARE_EPHEMERAL_SIZE = 2 * SPARE_EPHEMERAL_KEY_SIZE;
+extern uint8_t spare_ephemeral[SPARE_EPHEMERAL_SIZE];  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+// Polled every api loop tick, so it must inline. A clamped X25519 private key
+// always has bit 254 set, so that byte doubles as the ready flag.
+inline bool has_spare_ephemeral() { return (spare_ephemeral[SPARE_EPHEMERAL_KEY_SIZE - 1] & 0x40) != 0; }
+/// Fill the slot; blocks for the base point multiply
+void prepare_spare_ephemeral();
+/// Hand the slot's key pair to a handshake that has not started and wipe the
+/// slot; 0 when the slot was empty or the key was taken, else the noise-c error
+int consume_spare_ephemeral(NoiseHandshakeState *state);
+#endif
+
 // Shared wire format for the noise transports (api and ota): every frame is
 // FRAME_INDICATOR, a 16-bit big-endian payload length, then the payload.
 // Handshake payloads start with a status byte; transport payloads end with

esphome/components/noise/noise_handshake.cpp

@@ -57,6 +57,13 @@ int NoiseResponderHandshake::init(const NoiseContext &ctx, const uint8_t *prolog
     HANDSHAKE_STEP_LOG("noise_handshakestate_set_prologue", err);
     return this->fail_init_(err);
   }
+#ifdef USE_NOISE_SPARE_EPHEMERAL
+  err = consume_spare_ephemeral(this->handshake_);
+  // Not fatal: the handshake generates its own key instead
+  if (err != 0) {
+    HANDSHAKE_STEP_LOG("noise_handshakestate_set_local_ephemeral", err);
+  }
+#endif
   err = noise_handshakestate_start(this->handshake_);
   if (err != 0) {
     HANDSHAKE_STEP_LOG("noise_handshakestate_start", err);

esphome/components/noise/noise_handshake.h

@@ -37,7 +37,8 @@ class NoiseResponderHandshake {
   NoiseResponderHandshake &operator=(const NoiseResponderHandshake &) = delete;
 
   /// Create and start the handshake with the context's PSK and the prologue.
-  /// A repeated call frees the previous handshake state and starts over.
+  /// A repeated call frees the previous handshake state and starts over. A
+  /// spare ephemeral key, when one is ready, is used instead of generating.
   [[nodiscard]] int init(const NoiseContext &ctx, const uint8_t *prologue, size_t prologue_len);
   /// ACTION_FAILED is the catch-all: returned before init(), after split()
   /// has released the state, and when noise-c reports a failed handshake.

esphome/components/sendspin/__init__.py

@@ -307,7 +307,7 @@ async def to_code(config: ConfigType) -> None:
         player_cfg = data.player_config
         sample_rate = player_cfg[CONF_SAMPLE_RATE]
 
-        codecs = player_cfg[CONF_CODECS]
+        codecs = [CODECS[codec] for codec in player_cfg[CONF_CODECS]]
 
         def _audio_format(codec: MockObj, channels: int) -> cg.StructInitializer:
             return cg.StructInitializer(

esphome/components/wifi/__init__.py

@@ -66,13 +66,14 @@ from esphome.const import (
 )
 from esphome.core import (
     CORE,
+    ID,
     CoroPriority,
     EsphomeError,
     HexInt,
     coroutine_with_priority,
 )
 import esphome.final_validate as fv
-from esphome.types import ConfigType
+from esphome.types import ConfigType, TemplateArgsType
 
 from . import wpa2_eap
 
@@ -208,6 +209,7 @@ WiFiEnabledCondition = wifi_ns.class_("WiFiEnabledCondition", Condition)
 WiFiAPActiveCondition = wifi_ns.class_("WiFiAPActiveCondition", Condition)
 WiFiEnableAction = wifi_ns.class_("WiFiEnableAction", automation.Action)
 WiFiDisableAction = wifi_ns.class_("WiFiDisableAction", automation.Action)
+WiFiRoamAction = wifi_ns.class_("WiFiRoamAction", automation.Action)
 WiFiConfigureAction = wifi_ns.class_(
     "WiFiConfigureAction", automation.Action, cg.Component
 )
@@ -820,6 +822,18 @@ async def wifi_disable_to_code(config, action_id, template_arg, args):
     return cg.new_Pvariable(action_id, template_arg)
 
 
+@automation.register_action(
+    "wifi.roam", WiFiRoamAction, cv.Schema({}), synchronous=True
+)
+async def wifi_roam_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> cg.MockObj:
+    return cg.new_Pvariable(action_id, template_arg)
+
+
 KEEP_SCAN_RESULTS_KEY = "wifi_keep_scan_results"
 RUNTIME_POWER_SAVE_KEY = "wifi_runtime_power_save"
 RUNTIME_ROAMING_SUPPRESSION_KEY = "wifi_runtime_roaming_suppression"

esphome/components/wifi/automation.h

@@ -31,6 +31,11 @@ template<typename... Ts> class WiFiDisableAction final : public Action<Ts...> {
   void play(const Ts &...x) override { global_wifi_component->disable(); }
 };
 
+template<typename... Ts> class WiFiRoamAction final : public Action<Ts...> {
+ public:
+  void play(const Ts &...x) override { global_wifi_component->force_roam_check(); }
+};
+
 template<typename... Ts> class WiFiConfigureAction final : public Action<Ts...>, public Component {
  public:
   TEMPLATABLE_VALUE(std::string, ssid)

esphome/components/wifi/wifi_component.cpp

@@ -846,17 +846,18 @@ void WiFiComponent::loop() {
           this->notify_connect_state_listeners_();
 #endif
 
-          // Post-connect roaming: check for better AP
-          if (this->post_connect_roaming_) {
-            if (this->is_roaming_scan_active()) {
-              if (this->scan_done_) {
-                this->process_roaming_scan_();
-              }
-              // else: scan in progress, wait
-            } else if (this->roaming_state_ == RoamingState::IDLE && this->roaming_attempts_ < ROAMING_MAX_ATTEMPTS &&
-                       now - this->roaming_last_check_ >= ROAMING_CHECK_INTERVAL && !this->roaming_suppressed_()) {
-              this->check_roaming_(now);
+          // Post-connect roaming: check for better AP. A scan may have been started by an
+          // explicit force_roam_check() even when post_connect_roaming_ is disabled, so the
+          // scan must always be consumed here to avoid leaving roaming_state_ stuck.
+          if (this->is_roaming_scan_active()) {
+            if (this->scan_done_) {
+              this->process_roaming_scan_();
             }
+            // else: scan in progress, wait
+          } else if (this->post_connect_roaming_ && this->roaming_state_ == RoamingState::IDLE &&
+                     this->roaming_attempts_ < ROAMING_MAX_ATTEMPTS &&
+                     now - this->roaming_last_check_ >= ROAMING_CHECK_INTERVAL && !this->roaming_suppressed_()) {
+            this->check_roaming_(now);
           }
         }
         break;
@@ -2463,6 +2464,17 @@ void WiFiComponent::notify_scan_results_listeners_() {
 }
 #endif  // USE_WIFI_SCAN_RESULTS_LISTENERS
 
+void WiFiComponent::force_roam_check() {
+  if (!this->is_connected() || this->roaming_state_ != RoamingState::IDLE || this->roaming_suppressed_()) {
+    ESP_LOGD(TAG, "Roam check requested, but not able to check now");
+    return;
+  }
+  // Reset the attempt counter so a prior run of failed roams doesn't block this explicit request
+  // Note that this re-arms automatic roaming if enabled.
+  this->roaming_attempts_ = 0;
+  this->check_roaming_(millis());
+}
+
 void WiFiComponent::check_roaming_(uint32_t now) {
   // Guard: not for hidden networks (may not appear in scan)
   const WiFiAP *selected = this->get_selected_sta_();
@@ -2484,7 +2496,11 @@ void WiFiComponent::check_roaming_(uint32_t now) {
 
   ESP_LOGD(TAG, "Roam scan (%d dBm, attempt %u/%u)", rssi, this->roaming_attempts_, ROAMING_MAX_ATTEMPTS);
   this->roaming_state_ = RoamingState::SCANNING;
-  this->wifi_scan_start_(this->passive_scan_);
+  if (!this->wifi_scan_start_(this->passive_scan_)) {
+    // Scan failed to start (e.g. busy) - don't get stuck in SCANNING forever
+    ESP_LOGD(TAG, "Roam scan failed to start");
+    this->roaming_state_ = RoamingState::IDLE;
+  }
 }
 
 void WiFiComponent::process_roaming_scan_() {

esphome/components/wifi/wifi_component.h

@@ -565,6 +565,12 @@ class WiFiComponent final : public Component {
   void set_keep_scan_results(bool keep_scan_results) { this->keep_scan_results_ = keep_scan_results; }
   void set_post_connect_roaming(bool enabled) { this->post_connect_roaming_ = enabled; }
 
+  /** Force an immediate post-connect roaming check, bypassing the periodic interval and the
+   * per-connection attempt limit. Does nothing (besides a debug log) if not connected, if a
+   * roam scan or connect is already in progress, or if roaming is currently suppressed.
+   */
+  void force_roam_check();
+
 #ifdef USE_WIFI_CONNECT_TRIGGER
   Trigger<> *get_connect_trigger() { return &this->connect_trigger_; }
 #endif

esphome/const.py

@@ -4,7 +4,7 @@ from enum import Enum
 
 from esphome.enum import StrEnum
 
-__version__ = "2026.9.0b3"
+__version__ = "2026.10.0-dev"
 
 ALLOWED_NAME_CHARS = "abcdefghijklmnopqrstuvwxyz0123456789-_"
 VALID_SUBSTITUTIONS_CHARACTERS = (

esphome/core/defines.h

@@ -231,6 +231,7 @@
 #define USE_IMPROV_SERIAL_NEXT_URL
 #define USE_MD5
 #define USE_NOISE
+#define USE_NOISE_SPARE_EPHEMERAL
 #define USE_SHA256
 #ifndef USE_RP2  // no MQTT backend or esp_wireguard library on RP2
 #define USE_MQTT

esphome/happy_eyeballs.py

@@ -69,10 +69,7 @@ def _make_create_connection() -> Callable[..., socket.socket]:
 
     from aiohappyeyeballs import start_connection
     from urllib3.exceptions import LocationParseError
-    from urllib3.util.connection import (  # noqa: PLC2701
-        _set_socket_options,
-        allowed_gai_family,
-    )
+    from urllib3.util.connection import _set_socket_options, allowed_gai_family  # noqa: PLC2701
     from urllib3.util.timeout import _DEFAULT_TIMEOUT  # noqa: PLC2701
 
     from esphome import async_thread

requirements.txt

@@ -10,11 +10,11 @@ tzlocal==5.4.4    # from time
 tzdata>=2026.3  # from time
 pyserial==3.5
 platformio==6.1.19
-esptool==5.3.1
+esptool==5.4.0
 click==8.3.3
 aioesphomeapi==46.3.0
 aiohappyeyeballs==2.7.1  # Happy Eyeballs for requests downloads; already pulled in by aioesphomeapi
-zeroconf==0.151.2
+zeroconf==0.151.3
 puremagic==2.2.0
 ruamel.yaml==0.19.1 # dashboard_import
 ruamel.yaml.clib==0.2.15 # dashboard_import
@@ -27,9 +27,9 @@ bleak==3.0.2
 smpclient==7.2.0
 requests==2.34.2
 py7zr==1.1.3
-platformdirs==4.11.5  # native esp-idf toolchain global cache dir
-ninja==1.13.0  # native esp8266 arduino toolchain build driver
-filelock==3.32.4  # inter-process locks (PlatformIO cache heal, git clone cache); >=3.32 for FileLock(fallback_to_soft=...), older versions silently drop the kwarg
+platformdirs==4.11.7  # native esp-idf toolchain global cache dir
+ninja==1.13.2  # native esp8266 arduino toolchain build driver
+filelock==3.32.5  # inter-process locks (PlatformIO cache heal, git clone cache); >=3.32 for FileLock(fallback_to_soft=...), older versions silently drop the kwarg
 
 # esp-idf >= 5.0 requires this
 pyparsing >= 3.3.2

requirements_dev.txt

@@ -1,4 +1,4 @@
 # Useful stuff when working in a development environment
-clang-format==13.0.1  # also change in .pre-commit-config.yaml and Dockerfile when updating
+clang-format==13.0.1  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py
 clang-tidy==22.1.8
-yamllint==1.38.0  # also change in .pre-commit-config.yaml when updating
+yamllint==1.38.0  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py

requirements_test.txt

@@ -1,8 +1,9 @@
 pylint==4.0.8
-flake8==7.3.0  # also change in .pre-commit-config.yaml when updating
-ruff==0.16.5  # also change in .pre-commit-config.yaml when updating
-pyupgrade==3.21.2  # also change in .pre-commit-config.yaml when updating
-prek==0.5.0  # also change in .github/workflows/ci.yml when updating
+flake8==7.3.0  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py
+ruff==0.16.6  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py
+pyupgrade==3.21.2  # .pre-commit-config.yaml rev synced by script/sync_dependency_versions.py
+prek==0.5.2  # .github/workflows/ci.yml reads this pin
+yamlrocks==0.6.1  # used by script/sync_dependency_versions.py
 
 # Unit tests
 pytest==9.1.1

script/git-hooks/post-checkout

@@ -14,7 +14,31 @@ top=$(git rev-parse --show-toplevel 2>/dev/null) || exit 0
 [ -x "$top/venv/bin/python" ] && exit 0
 [ -x "$top/script/setup" ] || exit 0
 
+# Every worktree shares the hooks directory of the checkout it was created
+# from, and the script/setup run below is the one from whichever branch was just
+# checked out. Older branches install their own pre-commit hook without checking
+# for a worktree: that moves the shared hook aside as pre-commit.legacy and
+# replaces it with one tied to this worktree's virtual environment, so commits
+# break in every checkout. To rule that out, the hooks directory is copied
+# before script/setup runs and put back exactly as it was afterwards, including
+# removing any file script/setup added.
+hooks=$(git rev-parse --path-format=absolute --git-path hooks 2>/dev/null) || exit 0
+snap=$(mktemp -d "$hooks/.post-checkout.XXXXXX") || exit 0
+cp -p "$hooks"/* "$snap"/ 2>/dev/null
+
 # Clear VIRTUAL_ENV so a checkout made from a shell with an environment already
 # activated still gets its own, rather than having the active one repointed at
 # this working tree.
-exec env -u VIRTUAL_ENV "$top/script/setup"
+env -u VIRTUAL_ENV "$top/script/setup"
+status=$?
+
+for f in "$hooks"/*; do
+  [ -e "$snap/${f##*/}" ] || rm -f "$f"
+done
+# Files are moved rather than copied so a hook that is still running, such as
+# this one, is swapped out atomically instead of being rewritten in place.
+for f in "$snap"/*; do
+  cmp -s "$f" "$hooks/${f##*/}" 2>/dev/null || mv -f "$f" "$hooks/${f##*/}"
+done
+rm -rf "$snap"
+exit $status

script/helpers.py

@@ -1104,6 +1104,10 @@ def get_components_per_integration_fixture() -> dict[str, set[str]]:
 
 
 _TEST_FUNC_RE = re.compile(r"async def (test_\w+)")
+# Any usage form (decorator, pytestmark assignment or list element); only
+# test_*.py files are scanned, so the marker docs elsewhere cannot false-hit
+_SHARED_YAML_USE_RE = re.compile(r"\bmark\.shared_yaml")
+_SHARED_YAML_ARG_RE = re.compile(r"\(\s*[\"'](\w+)[\"']\s*\)")
 
 
 @cache
@@ -1123,6 +1127,19 @@ def get_fixture_to_test_files() -> dict[str, frozenset[str]]:
         for func in _TEST_FUNC_RE.findall(content):
             base_name = func.replace("test_", "").partition("[")[0]
             result.setdefault(base_name, set()).add(rel_path)
+        # Shared fixtures are named by marker, not by a test function; each
+        # decorator must carry a string literal or its fixture would silently
+        # map to no tests
+        for use in _SHARED_YAML_USE_RE.finditer(content):
+            arg = _SHARED_YAML_ARG_RE.match(content, use.end())
+            if arg is None:
+                line = content.count("\n", 0, use.start()) + 1
+                raise ValueError(
+                    f"{rel_path}:{line}: shared_yaml marker must take a "
+                    "single-line string literal so CI test selection can map "
+                    "its fixture"
+                )
+            result.setdefault(arg.group(1), set()).add(rel_path)
 
     return {k: frozenset(v) for k, v in result.items()}
 

script/sync_dependency_versions.py

@@ -0,0 +1,164 @@
+#!/usr/bin/env python3
+"""Keep pre-commit hook revs in sync with the requirements files.
+
+Dependabot only bumps the ``package==version`` pins in ``requirements*.txt``.
+Some of those tools are pinned a second time as hook ``rev`` values in
+``.pre-commit-config.yaml``. This script treats the requirements files as
+the source of truth and rewrites the revs to match, editing the config
+through yamlrocks so comments and layout survive.
+
+Run without arguments to apply the changes in place, or with ``--check`` to
+only report drift (exit status 1 when anything is out of sync).
+"""
+
+from __future__ import annotations
+
+import argparse
+from dataclasses import dataclass
+from pathlib import Path
+import re
+import sys
+from typing import Any
+
+import yamlrocks
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+PRECOMMIT_CONFIG = ".pre-commit-config.yaml"
+
+
+class SyncError(Exception):
+    """A pin could not be located in a requirements file or the config."""
+
+
+@dataclass(frozen=True)
+class SyncTarget:
+    """A requirements pin and the pre-commit repo whose rev mirrors it."""
+
+    package: str
+    requirements_file: str
+    repo: str
+
+
+SYNC_TARGETS: tuple[SyncTarget, ...] = (
+    SyncTarget(
+        "ruff", "requirements_test.txt", "https://github.com/astral-sh/ruff-pre-commit"
+    ),
+    SyncTarget("flake8", "requirements_test.txt", "https://github.com/PyCQA/flake8"),
+    SyncTarget(
+        "pyupgrade", "requirements_test.txt", "https://github.com/asottile/pyupgrade"
+    ),
+    SyncTarget(
+        "clang-format",
+        "requirements_dev.txt",
+        "https://github.com/pre-commit/mirrors-clang-format",
+    ),
+    SyncTarget(
+        "yamllint",
+        "requirements_dev.txt",
+        "https://github.com/adrienverge/yamllint.git",
+    ),
+)
+
+
+def read_requirement_version(requirements: str, package: str) -> str | None:
+    """Return the ``==`` pin for ``package`` or None when it is not pinned."""
+    pattern = re.compile(
+        rf"^{re.escape(package)}==(?P<version>[^\s#]+)",
+        re.MULTILINE | re.IGNORECASE,
+    )
+    match = pattern.search(requirements)
+    return match.group("version") if match else None
+
+
+def find_repo_entry(doc: Any, repo: str) -> Any:
+    """Return the single ``- repo:`` block for ``repo`` in a pre-commit doc."""
+    try:
+        entries = [entry for entry in doc["repos"] if entry["repo"] == repo]
+    except KeyError as err:
+        raise SyncError(f"malformed pre-commit config, missing key {err}") from None
+    if len(entries) != 1:
+        raise SyncError(
+            f"expected exactly one block for repo {repo}, found {len(entries)}"
+        )
+    return entries[0]
+
+
+def current_rev(entry: Any, repo: str) -> tuple[str, str]:
+    """Split the block's rev into its tag prefix (``v`` or empty) and version."""
+    if "rev" not in entry:
+        raise SyncError(f"repo {repo} has no rev")
+    rev = entry["rev"]
+    if not isinstance(rev, str):
+        # A rev such as ``1.0`` parses as a number and cannot be compared or
+        # rewritten safely; quote it in the config instead.
+        raise SyncError(f"rev of repo {repo} is not a string: {rev!r}")
+    prefix = "v" if rev.startswith("v") else ""
+    return prefix, rev.removeprefix("v")
+
+
+def sync(root: Path, *, write: bool) -> list[str]:
+    """Bring every hook rev in line with its requirements pin.
+
+    Returns one description per rev that was (or, when ``write`` is False,
+    would be) changed. Raises SyncError when a pin cannot be found, which
+    means SYNC_TARGETS has gone stale and needs updating by hand.
+    """
+    config_path = root / PRECOMMIT_CONFIG
+    doc = yamlrocks.loads(config_path.read_bytes(), option=yamlrocks.OPT_ROUND_TRIP)
+    requirements: dict[str, str] = {}
+    changes: list[str] = []
+    for target in SYNC_TARGETS:
+        if target.requirements_file not in requirements:
+            requirements[target.requirements_file] = (
+                root / target.requirements_file
+            ).read_text()
+        version = read_requirement_version(
+            requirements[target.requirements_file], target.package
+        )
+        if version is None:
+            raise SyncError(
+                f"{target.requirements_file}: no '{target.package}==' pin found"
+            )
+
+        entry = find_repo_entry(doc, target.repo)
+        prefix, current = current_rev(entry, target.repo)
+        if current == version:
+            continue
+        changes.append(f"{target.package}: {current} -> {version}")
+        entry["rev"] = f"{prefix}{version}"
+
+    if changes and write:
+        config_path.write_bytes(doc.to_yaml())
+    return changes
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(description=__doc__.splitlines()[0])
+    parser.add_argument(
+        "--check",
+        action="store_true",
+        help="report drift without modifying any file; exit 1 if out of sync",
+    )
+    parser.add_argument(
+        "--root",
+        type=Path,
+        default=REPO_ROOT,
+        help="repository checkout to operate on (default: this checkout)",
+    )
+    args = parser.parse_args(argv)
+
+    try:
+        changes = sync(args.root, write=not args.check)
+    except SyncError as err:
+        print(f"error: {err}", file=sys.stderr)
+        return 1
+
+    for change in changes:
+        print(change)
+    if args.check and changes:
+        return 1
+    return 0
+
+
+if __name__ == "__main__":  # pragma: no cover
+    sys.exit(main())

tests/components/noise/__init__.py

@@ -1,3 +1,4 @@
+import esphome.codegen as cg
 from tests.testing_helpers import ComponentManifestOverride
 
 
@@ -5,3 +6,10 @@ def override_manifest(manifest: ComponentManifestOverride) -> None:
     # to_code must run: it defines USE_NOISE and adds the noise-c library
     # the component sources under test need.
     manifest.enable_codegen()
+    real_to_code = manifest.to_code
+
+    async def to_code_testing(config):
+        await real_to_code(config)
+        cg.add_define("USE_NOISE_SPARE_EPHEMERAL")
+
+    manifest.to_code = to_code_testing

tests/components/noise/test_noise_handshake.cpp

@@ -157,6 +157,74 @@ TEST(NoiseResponderHandshakeTest, FullHandshakeAndTransportRoundTrip) {
   noise_cipherstate_free(recv_cipher);
 }
 
+// Drive one full NNpsk0 handshake between a fresh initiator and responder;
+// responder_e receives the ephemeral public key the responder put on the
+// wire (the clear text start of its message, taken before the initiator
+// consumes the buffer in place)
+static void run_handshake(NoiseResponderHandshake &responder, uint8_t responder_e[SPARE_EPHEMERAL_KEY_SIZE]) {
+  const psk_t psk = make_psk(7);
+  ASSERT_EQ(responder.init(ctx_for(psk), PROLOGUE, sizeof(PROLOGUE)), 0);
+  Initiator initiator(psk, PROLOGUE, sizeof(PROLOGUE));
+  uint8_t msg[MAX_HANDSHAKE_SIZE];
+  size_t msg_len = initiator.write_message(msg, sizeof(msg));
+  ASSERT_EQ(responder.read_message(msg, msg_len), 0);
+  size_t reply_len = 0;
+  ASSERT_EQ(responder.write_message(msg, sizeof(msg), reply_len), 0);
+  ASSERT_GE(reply_len, SPARE_EPHEMERAL_KEY_SIZE);
+  std::memcpy(responder_e, msg, SPARE_EPHEMERAL_KEY_SIZE);
+  ASSERT_EQ(initiator.read_message(msg, reply_len), 0);
+  ASSERT_EQ(responder.action(), Action::ACTION_SPLIT);
+}
+
+TEST(SpareEphemeralTest, EmptySlotLeavesHandshakeToGenerate) {
+  ASSERT_FALSE(has_spare_ephemeral());
+  NoiseResponderHandshake responder;
+  uint8_t responder_e[SPARE_EPHEMERAL_KEY_SIZE];
+  run_handshake(responder, responder_e);
+  EXPECT_FALSE(has_spare_ephemeral());
+}
+
+TEST(SpareEphemeralTest, ConsumeHandsTheKeyToANewState) {
+  prepare_spare_ephemeral();
+  ASSERT_TRUE(has_spare_ephemeral());
+  const NoiseProtocolId nid = {
+      .prefix_id = NOISE_PREFIX_STANDARD,
+      .pattern_id = NOISE_PATTERN_NN,
+      .modifier_ids = {NOISE_MODIFIER_PSK0},
+      .dh_id = NOISE_DH_CURVE25519,
+      .cipher_id = NOISE_CIPHER_CHACHAPOLY,
+      .hash_id = NOISE_HASH_SHA256,
+      .hybrid_id = NOISE_DH_NONE,
+  };
+  NoiseHandshakeState *state = nullptr;
+  ASSERT_EQ(noise_handshakestate_new_by_id(&state, &nid, NOISE_ROLE_RESPONDER), 0);
+  const psk_t psk = make_psk(7);
+  ASSERT_EQ(noise_handshakestate_set_pre_shared_key(state, psk.data(), psk.size()), 0);
+  ASSERT_EQ(noise_handshakestate_set_prologue(state, PROLOGUE, sizeof(PROLOGUE)), 0);
+  EXPECT_EQ(consume_spare_ephemeral(state), 0);
+  EXPECT_FALSE(has_spare_ephemeral());
+  noise_handshakestate_free(state);
+}
+
+TEST(SpareEphemeralTest, SlotKeyIsOnTheWireAndConsumedOnce) {
+  prepare_spare_ephemeral();
+  ASSERT_TRUE(has_spare_ephemeral());
+  uint8_t expected_pub[SPARE_EPHEMERAL_KEY_SIZE];
+  std::memcpy(expected_pub, spare_ephemeral + SPARE_EPHEMERAL_KEY_SIZE, sizeof(expected_pub));
+
+  NoiseResponderHandshake first;
+  uint8_t responder_e[SPARE_EPHEMERAL_KEY_SIZE];
+  run_handshake(first, responder_e);
+  // The spare, not a generated key, went out; and it went out once
+  EXPECT_EQ(std::memcmp(responder_e, expected_pub, sizeof(expected_pub)), 0);
+  EXPECT_FALSE(has_spare_ephemeral());
+
+  NoiseResponderHandshake second;
+  run_handshake(second, responder_e);
+  EXPECT_NE(std::memcmp(responder_e, expected_pub, sizeof(expected_pub)), 0);
+  EXPECT_FALSE(has_spare_ephemeral());
+}
+
 TEST(NoiseResponderHandshakeTest, ReInitRestartsHandshake) {
   // The documented retry shape: a repeated init() frees the previous state
   // and starts over. The first message under the new key authenticating

tests/components/sendspin/common-media_source.yaml

@@ -9,4 +9,3 @@ media_source:
     static_delay_adjustable: true
     fixed_delay: 480us
     decode_memory: internal
-    codecs: [pcm, opus, flac]

tests/components/wifi/common.yaml

@@ -14,6 +14,7 @@ esphome:
           condition: wifi.ap_active
           then:
             - logger.log: "WiFi AP is active!"
+      - wifi.roam
 
 wifi:
   networks:

tests/integration/README.md

@@ -21,6 +21,13 @@ The `yaml_config` fixture automatically loads YAML configurations based on the t
 - The fixture file must exist or the test will fail with a clear error message
 - The fixture automatically injects a dynamic port number into the API configuration
 
+Tests marked `@pytest.mark.shared_yaml("name")` load `fixtures/name.yaml` instead
+of the test-named file and compile it in a shared, hash-keyed build directory, so
+the whole group pays one full compile and each test only a relink. The marker
+argument must be a single-line string literal (CI test selection maps fixtures to
+test files by scanning for it), and marked tests must hand the `yaml_config`
+content to `run_compiled` unmodified.
+
 ### Key Fixtures
 
 - `run_compiled` - Combines write, compile, and run operations into a single context manager

tests/integration/conftest.py

@@ -4,17 +4,22 @@ from __future__ import annotations
 
 import asyncio
 from collections.abc import AsyncGenerator, Callable, Generator
-from contextlib import AbstractAsyncContextManager, asynccontextmanager
+from contextlib import AbstractAsyncContextManager, asynccontextmanager, suppress
 import fcntl
+from functools import cache
+import hashlib
 import logging
 import os
 from pathlib import Path
 import platform
+import re
+import shutil
 import signal
 import socket
 import subprocess
 import sys
 import tempfile
+import time
 from typing import TextIO
 
 from aioesphomeapi import APIClient, APIConnectionError, LogParser, ReconnectLogic
@@ -23,7 +28,13 @@ import pytest_asyncio
 
 import esphome.config
 from esphome.core import CORE
-from esphome.helpers import get_usable_cpu_count
+from esphome.helpers import (
+    get_usable_cpu_count,
+    read_file,
+    rmtree,
+    write_file,
+    write_file_if_changed,
+)
 from esphome.platformio.toolchain import get_idedata
 
 from .const import (
@@ -56,6 +67,21 @@ import pty  # not available on Windows
 pytest.register_assert_rewrite("tests.integration.entity_utils")
 
 
+def pytest_configure(config: pytest.Config) -> None:
+    config.addinivalue_line(
+        "markers",
+        "shared_yaml(name): load fixtures/<name>.yaml and compile it in a shared, "
+        "hash-keyed incremental build directory",
+    )
+
+
+FIXTURES_DIR = Path(__file__).parent / "fixtures"
+REPO_ROOT = Path(__file__).resolve().parent.parent.parent
+
+# CI caches parts of this path; keep in sync with ci.yml integration-tests.
+INTEGRATION_TESTS_ROOT = Path.home() / ".esphome-integration-tests"
+
+
 def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
     """Get environment variables for PlatformIO with shared cache."""
     env = os.environ.copy()
@@ -78,7 +104,7 @@ def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
         )
     # Compile with THIS tree's esphome sources, not wherever the venv's editable
     # install points (which may be a different git worktree or checkout).
-    repo_root = str(Path(__file__).resolve().parent.parent.parent)
+    repo_root = str(REPO_ROOT)
     existing = env.get("PYTHONPATH")
     env["PYTHONPATH"] = f"{repo_root}{os.pathsep}{existing}" if existing else repo_root
     return env
@@ -88,8 +114,7 @@ def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
 def shared_platformio_cache() -> Generator[Path]:
     """Initialize a shared PlatformIO cache for all integration tests."""
     # Use a dedicated directory for integration tests to avoid conflicts.
-    # CI caches parts of this path; keep in sync with ci.yml integration-tests.
-    test_cache_dir = Path.home() / ".esphome-integration-tests"
+    test_cache_dir = INTEGRATION_TESTS_ROOT
     cache_dir = test_cache_dir / "platformio"
 
     # Use a lock file in the home directory to ensure only one process initializes the cache
@@ -112,7 +137,9 @@ def shared_platformio_cache() -> Generator[Path]:
                 init_dir = Path(tmpdir)
                 fixture_path = Path(__file__).parent / "fixtures" / "cache_init.yaml"
                 config_path = init_dir / "cache_init.yaml"
-                config_path.write_text(fixture_path.read_text())
+                config_path.write_text(
+                    fixture_path.read_text(encoding="utf-8"), encoding="utf-8"
+                )
 
                 # Run compilation to populate the cache
                 # We must succeed here to avoid race conditions where multiple
@@ -162,13 +189,6 @@ def integration_test_dir() -> Generator[Path]:
         yield Path(tmpdir)
 
 
-@pytest.fixture
-def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
-    """Host preferences persist per device name; give the test its own so a
-    provisioned key never leaks into another run."""
-    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))
-
-
 @pytest.fixture
 def reserved_tcp_port() -> Generator[tuple[int, socket.socket]]:
     """Reserve an unused TCP port by holding the socket open."""
@@ -188,21 +208,29 @@ def unused_tcp_port(reserved_tcp_port: tuple[int, socket.socket]) -> int:
     return reserved_tcp_port[0]
 
 
+@pytest.fixture(autouse=True)
+def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> Path:
+    """Give every test its own host prefs dir; prefs are keyed only by device
+    name, which tests sharing a fixture also share."""
+    prefdir = tmp_path / "prefs"
+    monkeypatch.setenv("ESPHOME_PREFDIR", str(prefdir))
+    return prefdir
+
+
 @pytest_asyncio.fixture
 async def yaml_config(request: pytest.FixtureRequest, unused_tcp_port: int) -> str:
     """Load YAML configuration based on test name."""
-    # Get the test function name
-    test_name: str = request.node.name
-    # Extract the base test name (remove test_ prefix and any parametrization)
-    base_name = test_name.replace("test_", "").partition("[")[0]
+    shared_name = _shared_yaml_name(request)
+    # Base test name: test_ prefix and any parametrization stripped
+    base_name = shared_name or request.node.name.replace("test_", "").partition("[")[0]
 
     # Load the fixture file
-    fixture_path = Path(__file__).parent / "fixtures" / f"{base_name}.yaml"
+    fixture_path = FIXTURES_DIR / f"{base_name}.yaml"
     if not fixture_path.exists():
         raise FileNotFoundError(f"Fixture file not found: {fixture_path}")
 
     loop = asyncio.get_running_loop()
-    content = await loop.run_in_executor(None, fixture_path.read_text)
+    content = await loop.run_in_executor(None, read_file, fixture_path)
 
     # Replace the port in the config if it contains api section
     if "api:" in content:
@@ -226,11 +254,13 @@ async def yaml_config(request: pytest.FixtureRequest, unused_tcp_port: int) -> s
 
     # Replace external component path placeholder if present
     if "EXTERNAL_COMPONENT_PATH" in content:
-        external_components_path = str(
-            Path(__file__).parent / "fixtures" / "external_components"
-        )
+        external_components_path = str(FIXTURES_DIR / "external_components")
         content = content.replace("EXTERNAL_COMPONENT_PATH", external_components_path)
 
+    if shared_name is not None:
+        # _compile verifies the marked test compiles this content unmodified
+        request.node._shared_yaml_content = content
+
     return content
 
 
@@ -240,24 +270,218 @@ async def write_yaml_config(
 ) -> AsyncGenerator[ConfigWriter]:
     """Write YAML configuration to a file."""
     # Get the test name for default filename
-    test_name = request.node.name
-    base_name = test_name.replace("test_", "").split("[")[0]
+    base_name = request.node.name.replace("test_", "").partition("[")[0]
 
     async def _write_config(content: str, filename: str | None = None) -> Path:
         if filename is None:
             filename = f"{base_name}.yaml"
         config_path = integration_test_dir / filename
         loop = asyncio.get_running_loop()
-        await loop.run_in_executor(None, config_path.write_text, content)
+        await loop.run_in_executor(None, write_file, config_path, content)
         return config_path
 
     yield _write_config
 
 
+# Deliberately not CI-cached (ci.yml caches only platformio/ subpaths); stale
+# dirs for a fixture are pruned when its content hash changes.
+SHARED_BUILDS_ROOT = INTEGRATION_TESTS_ROOT / "builds"
+
+# In the dir name (not just the hash) so pruning stays inside this checkout
+_REPO_KEY = hashlib.sha256(str(REPO_ROOT).encode()).hexdigest()[:8]
+
+# Give a contended shared build lock time for a full cold compile ahead of us
+_SHARED_LOCK_TIMEOUT_S = 900
+_SHARED_LOCK_POLL_S = 0.1
+_SHARED_LOCK_REPORT_S = 30
+
+# Reclaims dirs orphaned by fixture renames or deleted checkouts
+_STALE_BUILD_MAX_AGE_S = 30 * 24 * 3600
+
+# ELF path per shared build dir; constant once compiled, so resolve it only once
+_shared_elf_paths: dict[Path, Path] = {}
+
+# Dirs this process already swept; pruning is session-scoped work
+_pruned_dirs: set[Path] = set()
+
+
+def _shared_yaml_name(request: pytest.FixtureRequest) -> str | None:
+    """Name passed to the shared_yaml marker, or None when unmarked."""
+    marker = request.node.get_closest_marker("shared_yaml")
+    if marker is None:
+        return None
+    # Exactly one \w+ positional arg: the name doubles as a build dir
+    # component, and CI test selection (script/helpers.py) parses the same shape
+    if (
+        len(marker.args) != 1
+        or marker.kwargs
+        or not re.fullmatch(r"\w+", str(marker.args[0]))
+    ):
+        raise ValueError(
+            "shared_yaml marker requires exactly one \\w+ fixture name literal"
+        )
+    return marker.args[0]
+
+
+def _shared_build_prefix(name: str) -> str:
+    return f"{name}-{_REPO_KEY}-"
+
+
+@cache
+def _shared_build_dir(name: str) -> Path:
+    """Dir keyed by checkout and fixture source, before per-test injections."""
+    key = hashlib.sha256((FIXTURES_DIR / f"{name}.yaml").read_bytes()).hexdigest()[:16]
+    return SHARED_BUILDS_ROOT / (_shared_build_prefix(name) + key)
+
+
+def _read_stamp(stamp: Path, shared_dir: Path) -> Path | None:
+    """ELF path recorded by the last completed compile, or None."""
+    try:
+        text = stamp.read_text(encoding="utf-8").strip()
+    except FileNotFoundError:
+        return None
+    except OSError as err:
+        print(f"Cannot read {stamp}: {err}")
+        return None
+    if not text:
+        print(f"Ignoring empty stamp {stamp}")
+        return None
+    built = Path(text)
+    # Never trust a stamp pointing outside its own build dir as an unlink target
+    if shared_dir.resolve() in built.resolve().parents:
+        return built
+    print(f"Ignoring stamp {stamp} pointing outside {shared_dir}")
+    return None
+
+
+def _unused_since(stale: Path, cutoff: float) -> bool:
+    """Whether a build dir looks untouched since cutoff; unknown counts as used."""
+    # Newest of the .built stamp (rewritten by every completed compile) and the
+    # dir itself (freshened by a worker claiming the dir before locking)
+    newest: float | None = None
+    for probe in (stale / ".built", stale):
+        try:
+            mtime = probe.stat().st_mtime
+        except FileNotFoundError:
+            continue
+        except NotADirectoryError:
+            return True  # a stray file where a dir should be; reclaimable
+        except OSError as err:
+            print(f"Cannot age-probe {stale}: {err}")
+            return False  # unknown never authorizes deletion
+        newest = mtime if newest is None else max(newest, mtime)
+    return newest is not None and newest < cutoff
+
+
+def _prune_stale_builds(name: str, keep: Path) -> None:
+    """Remove outdated build dirs (blocking, run in executor): this checkout's
+    other dirs for the fixture, plus anything untouched for 30 days. Tolerates
+    other workers pruning the same dirs concurrently."""
+    cutoff = time.time() - _STALE_BUILD_MAX_AGE_S
+    prefix = _shared_build_prefix(name)
+    for stale in SHARED_BUILDS_ROOT.iterdir():
+        if stale == keep:
+            continue
+        same_fixture = stale.name.startswith(prefix)
+        if not same_fixture and not _unused_since(stale, cutoff):
+            continue
+        # Creating .lock bumps the dir mtime, so remember whether the re-probe
+        # under the lock can trust it
+        lock_preexisting = (stale / ".lock").exists()
+        try:
+            lock_file = (stale / ".lock").open("w")
+        except FileNotFoundError:
+            continue  # pruned by another worker meanwhile
+        except NotADirectoryError:
+            print(f"Removing stray file {stale}")
+            stale.unlink(missing_ok=True)
+            continue
+        except OSError as err:
+            print(f"Cannot prune {stale}: {err}")
+            continue
+        with lock_file:
+            try:
+                fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except BlockingIOError:
+                continue  # still in use by another run
+            # Re-probe under the lock: a worker freshens its dir before
+            # locking, so a just-claimed dir no longer looks unused. A dir
+            # whose .lock we just created cannot be held by anyone, and our
+            # own open bumped its mtime, so its pre-open probe stands
+            if (
+                lock_preexisting
+                and not same_fixture
+                and not _unused_since(stale, cutoff)
+            ):
+                continue
+            # rmtree tolerates races; a leftover partial tree only costs a
+            # rebuild, since the ELF is deleted before every compile
+            try:
+                rmtree(stale)
+            except OSError as err:
+                print(f"Failed to prune {stale}: {err}")
+
+
+async def _run_esphome_compile(
+    config_path: Path, cwd: Path, env: dict[str, str]
+) -> None:
+    """Run `esphome compile`, retrying up to 3 times on a segfault."""
+    max_retries = 3
+    for attempt in range(max_retries):
+        # Compile using subprocess, inheriting stdout/stderr to show progress
+        proc = await asyncio.create_subprocess_exec(
+            sys.executable,
+            "-m",
+            "esphome",
+            "compile",
+            str(config_path),
+            cwd=cwd,
+            stdout=None,  # Inherit stdout
+            stderr=None,  # Inherit stderr
+            stdin=asyncio.subprocess.DEVNULL,
+            # Start in a new process group to isolate signal handling
+            start_new_session=True,
+            env=env,
+            close_fds=False,
+        )
+        await proc.wait()
+
+        if proc.returncode == 0:
+            break
+        if proc.returncode == -11 and attempt < max_retries - 1:
+            # Segfault (-11 = SIGSEGV), retry
+            print(
+                f"Compilation segfaulted (attempt {attempt + 1}/{max_retries}), retrying..."
+            )
+            await asyncio.sleep(1)  # Brief pause before retry
+            continue
+        raise RuntimeError(
+            f"Failed to compile {config_path}, return code: {proc.returncode}. "
+            f"Run with 'pytest -s' to see compilation output."
+        )
+
+
+def _resolve_compiled_binary(config_path: Path) -> Path:
+    """Load the config to learn the compiled ELF path (blocking, run in executor)."""
+    CORE.reset()  # Reset CORE state between test runs
+    CORE.config_path = config_path
+    config = esphome.config.read_config(
+        {"command": "compile", "config": str(config_path)}
+    )
+    if config is None:
+        raise RuntimeError(f"Failed to read config from {config_path}")
+    idedata = get_idedata(config)
+    binary_path = Path(idedata.firmware_elf_path)
+    if not binary_path.exists():
+        raise RuntimeError(f"Compiled binary not found at {binary_path}")
+    return binary_path
+
+
 @pytest_asyncio.fixture
 async def compile_esphome(
     integration_test_dir: Path,
     shared_platformio_cache: Path,
+    request: pytest.FixtureRequest,
 ) -> AsyncGenerator[CompileFunction]:
     """Compile an ESPHome configuration and return the binary path."""
 
@@ -265,66 +489,96 @@ async def compile_esphome(
         # Use the shared PlatformIO cache for faster compilation
         # This avoids re-downloading dependencies for each test
         env = _get_platformio_env(shared_platformio_cache)
-
-        # Retry compilation up to 3 times if we get a segfault
-        max_retries = 3
-        for attempt in range(max_retries):
-            # Compile using subprocess, inheriting stdout/stderr to show progress
-            proc = await asyncio.create_subprocess_exec(
-                sys.executable,
-                "-m",
-                "esphome",
-                "compile",
-                str(config_path),
-                cwd=integration_test_dir,
-                stdout=None,  # Inherit stdout
-                stderr=None,  # Inherit stderr
-                stdin=asyncio.subprocess.DEVNULL,
-                # Start in a new process group to isolate signal handling
-                start_new_session=True,
-                env=env,
-                close_fds=False,
-            )
-            await proc.wait()
-
-            if proc.returncode == 0:
-                # Success!
-                break
-            if proc.returncode == -11 and attempt < max_retries - 1:
-                # Segfault (-11 = SIGSEGV), retry
-                print(
-                    f"Compilation segfaulted (attempt {attempt + 1}/{max_retries}), retrying..."
-                )
-                await asyncio.sleep(1)  # Brief pause before retry
-                continue
-            # Other error or final retry
-            raise RuntimeError(
-                f"Failed to compile {config_path}, return code: {proc.returncode}. "
-                f"Run with 'pytest -s' to see compilation output."
-            )
-
-        # Load the config to get idedata (blocking call, must use executor)
         loop = asyncio.get_running_loop()
 
-        def _read_config_and_get_binary():
-            CORE.reset()  # Reset CORE state between test runs
-            CORE.config_path = config_path
-            config = esphome.config.read_config(
-                {"command": "compile", "config": str(config_path)}
+        name = _shared_yaml_name(request)
+        if name is None:
+            await _run_esphome_compile(config_path, integration_test_dir, env)
+            return await loop.run_in_executor(
+                None, _resolve_compiled_binary, config_path
             )
-            if config is None:
-                raise RuntimeError(f"Failed to read config from {config_path}")
 
-            # Get the compiled binary path
-            idedata = get_idedata(config)
-            return Path(idedata.firmware_elf_path)
-
-        binary_path = await loop.run_in_executor(None, _read_config_and_get_binary)
-
-        if not binary_path.exists():
-            raise RuntimeError(f"Compiled binary not found at {binary_path}")
-
-        return binary_path
+        # Shared fixture: build in a hash-keyed dir so tests sharing a config
+        # pay one full compile and later only a main.cpp (port) rebuild + relink
+        shared_dir = _shared_build_dir(name)
+        shared_dir.mkdir(parents=True, exist_ok=True)
+        # Freshen the dir before locking so a concurrent age sweep, which
+        # re-probes under the lock, never reaps a dir a worker just claimed;
+        # if a peer reaped it already, the guarded lock open recreates it
+        with suppress(FileNotFoundError):
+            os.utime(shared_dir)
+        if shared_dir not in _pruned_dirs:
+            _pruned_dirs.add(shared_dir)
+            await loop.run_in_executor(None, _prune_stale_builds, name, shared_dir)
+        shared_config = shared_dir / f"{name}.yaml"
+        private_binary = integration_test_dir / f"{name}.elf"
+        content = await loop.run_in_executor(None, read_file, config_path)
+        if content != getattr(request.node, "_shared_yaml_content", None):
+            # The dir is keyed by the fixture source; a mutated config would be
+            # cached under a hash that does not describe it
+            raise RuntimeError(
+                "shared_yaml tests must compile the yaml_config content unmodified"
+            )
+        # flock serializes concurrent xdist workers; closing the fd releases it.
+        # Hand-rolled rather than filelock.FileLock: non-blocking retries keep
+        # the wait cancellable, while a blocking acquire in an executor thread
+        # would survive test cancellation holding the fd
+        try:
+            lock_file = (shared_dir / ".lock").open("w")
+        except FileNotFoundError:
+            # A peer run pruning divergent hashes reaped the dir between our
+            # mkdir and this open; recreate it and pay a full rebuild
+            shared_dir.mkdir(parents=True, exist_ok=True)
+            lock_file = (shared_dir / ".lock").open("w")
+        with lock_file:
+            start = time.monotonic()
+            last_report = start
+            while True:
+                try:
+                    fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
+                    break
+                except BlockingIOError:
+                    now = time.monotonic()
+                    if now - start > _SHARED_LOCK_TIMEOUT_S:
+                        raise RuntimeError(
+                            f"Timed out waiting for the {shared_dir} lock"
+                        ) from None
+                    if now - last_report >= _SHARED_LOCK_REPORT_S:
+                        last_report = now
+                        print(
+                            f"Waited {now - start:.0f}s for another worker's "
+                            f"build of {shared_dir.name}"
+                        )
+                    await asyncio.sleep(_SHARED_LOCK_POLL_S)
+            # .built carries the ELF path of the last completed compile, so
+            # later workers skip the config re-read in _resolve_compiled_binary
+            stamp = shared_dir / ".built"
+            if (built := _shared_elf_paths.get(shared_dir)) is None:
+                built = await loop.run_in_executor(None, _read_stamp, stamp, shared_dir)
+            # Delete the ELF before compiling: whatever exists afterwards is
+            # this compile's output, so no staleness check is ever needed.
+            # With no usable stamp, sweep any leftover at the known layout
+            if built is not None:
+                built.unlink(missing_ok=True)
+            else:
+                # Layout-agnostic: ESPHOME_BUILD_PATH can move the build tree
+                for leftover in shared_dir.rglob("program"):
+                    if leftover.is_file():
+                        leftover.unlink()
+            await loop.run_in_executor(
+                None, write_file_if_changed, shared_config, content
+            )
+            await _run_esphome_compile(shared_config, shared_dir, env)
+            if built is None or not built.exists():
+                built = await loop.run_in_executor(
+                    None, _resolve_compiled_binary, shared_config
+                )
+            _shared_elf_paths[shared_dir] = built
+            await loop.run_in_executor(None, write_file, stamp, str(built))
+            # Copy out before unlocking: another worker may relink firmware.elf
+            # while this test is still running its private copy
+            await loop.run_in_executor(None, shutil.copy2, built, private_binary)
+        return private_binary
 
     yield _compile
 

tests/integration/fixtures/sensor_filters_batch_window.yaml

@@ -1,58 +0,0 @@
-esphome:
-  name: test-batch-window-filters
-
-host:
-api:
-  batch_delay: 0ms  # Disable batching to receive all state updates
-logger:
-  level: DEBUG
-
-# Template sensor that we'll use to publish values
-sensor:
-  - platform: template
-    name: "Source Sensor"
-    id: source_sensor
-    accuracy_decimals: 2
-
-  # Batch window filters (window_size == send_every) - use streaming filters
-  - platform: copy
-    source_id: source_sensor
-    name: "Min Sensor"
-    id: min_sensor
-    filters:
-      - min:
-          window_size: 5
-          send_every: 5
-          send_first_at: 1
-
-  - platform: copy
-    source_id: source_sensor
-    name: "Max Sensor"
-    id: max_sensor
-    filters:
-      - max:
-          window_size: 5
-          send_every: 5
-          send_first_at: 1
-
-  - platform: copy
-    source_id: source_sensor
-    name: "Moving Avg Sensor"
-    id: moving_avg_sensor
-    filters:
-      - sliding_window_moving_average:
-          window_size: 5
-          send_every: 5
-          send_first_at: 1
-
-# Button to trigger publishing test values
-button:
-  - platform: template
-    name: "Publish Values Button"
-    id: publish_button
-    on_press:
-      - lambda: |-
-          // Publish 10 values: 1.0, 2.0, ..., 10.0
-          for (int i = 1; i <= 10; i++) {
-            id(source_sensor).publish_state(float(i));
-          }

tests/integration/fixtures/uart_mock_modbus_client_read_write.yaml

@@ -1,111 +0,0 @@
-esphome:
-  name: uart-mock-modbus-cli-rw
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-# Two virtual buses looped back to each other: the client's transmissions reach the server and the
-# server's replies reach the client. auto_start so forwarding is active before the button fires.
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_client
-              data: !lambda return data;
-  - id: virtual_uart_client
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-
-globals:
-  - id: stored_1
-    type: uint16_t
-    initial_value: "0"
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_client
-    id: virtual_modbus_client
-    role: client
-    turnaround_time: 10ms
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    registers:
-      # Writable + readable register: the read publishes what it returns, so the test can confirm the
-      # write half of the 0x17 ran before the read half (Modbus 6.17).
-      - address: 0x01
-        value_type: U_WORD
-        read_lambda: |-
-          id(srv_read_1).publish_state(id(stored_1));
-          return id(stored_1);
-        write_lambda: |-
-          id(stored_1) = x;
-          id(srv_write_1).publish_state(x);
-          return true;
-      # Read-only register, returned together with 0x01 by the 2-register read half.
-      - address: 0x02
-        value_type: U_WORD
-        read_lambda: return 0x00AA;
-
-sensor:
-  # Server-side observations.
-  - platform: template
-    name: "srv_write_1"
-    id: srv_write_1
-  - platform: template
-    name: "srv_read_1"
-    id: srv_read_1
-  # Client-side read-back: the values the client's on_response received.
-  - platform: template
-    name: "client_read_0"
-    id: client_read_0
-  - platform: template
-    name: "client_read_1"
-    id: client_read_1
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    on_press:
-      # FC 0x17: write reg 0x0001 = 0x1234, then read regs 0x0001..0x0002 back in the same transaction.
-      - modbus_client.read_write_multiple_registers:
-          address: 0x01
-          read_address: 0x0001
-          read_count: 2
-          write_address: 0x0001
-          values: [0x1234]
-          on_response:
-            then:
-              - lambda: |-
-                  // values is the read-back block: reg 0x0001 (must be the just-written 0x1234) and reg 0x0002.
-                  if (values.size() >= 2) {
-                    id(client_read_0).publish_state(values[0]);
-                    id(client_read_1).publish_state(values[1]);
-                  }

tests/integration/fixtures/uart_mock_modbus_custom_pdu.yaml

@@ -1,88 +0,0 @@
-esphome:
-  name: uart-mock-modbus-custom-pdu
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-  - id: virtual_uart_controller
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_controller
-    id: virtual_modbus_controller
-    role: client
-    turnaround_time: 10ms
-
-modbus_controller:
-  - address: 1
-    modbus_id: virtual_modbus_controller
-    id: modbus_controller_1
-    update_interval: 1s
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    id: modbus_server_1
-    registers:
-      - address: 0x01
-        value_type: U_WORD
-        read_lambda: return 259;
-
-sensor:
-  # Plain read to confirm the controller <-> server link is up.
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "plain_read"
-    address: 0x01
-    register_type: holding
-    value_type: U_WORD
-  # Custom PDU: read holding register 0x0001, count 1. The PDU is
-  # {function code, address hi, address lo, count hi, count lo}; the device
-  # address and CRC are added by the hub. The lambda parses the response payload
-  # (the register value, big-endian).
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "custom_read"
-    custom_pdu: [0x03, 0x00, 0x01, 0x00, 0x01]
-    lambda: |-
-      if (data.size() < 2) return {};
-      return (float) ((data[0] << 8) | data[1]);
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    # This test does not have anything to start (mock is autostart)

tests/integration/fixtures/uart_mock_modbus_deprecated_write_buffer.yaml

@@ -1,106 +0,0 @@
-esphome:
-  name: uart-mock-modbus-dep-buffer
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-  - id: virtual_uart_controller
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-
-globals:
-  - id: reg10
-    type: uint16_t
-    initial_value: "0"
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_controller
-    id: virtual_modbus_controller
-    role: client
-    turnaround_time: 10ms
-
-modbus_controller:
-  - address: 1
-    modbus_id: virtual_modbus_controller
-    id: modbus_controller_1
-    update_interval: 1s
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    id: modbus_server_1
-    registers:
-      - address: 0x10
-        value_type: U_WORD
-        read_lambda: return id(reg10);
-        write_lambda: |-
-          id(reg10) = x;
-          return true;
-
-# A number whose write_lambda uses the DEPRECATED buffer parameter (fills `payload` with a legacy raw
-# frame as words: device address + function code + data) instead of the new item->write_* API. The write
-# must still land with its legacy semantics, and the one-time deprecation warning must fire only once per
-# entity no matter how many writes happen.
-number:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "buf_number"
-    id: buf_number
-    address: 0x10
-    register_type: holding
-    value_type: U_WORD
-    min_value: 0
-    max_value: 1000
-    step: 1
-    write_lambda: |-
-      // Legacy raw frame as words: [addr 0x01 | fc 0x06], register 0x0010, value.
-      payload.push_back(0x0106);
-      payload.push_back(0x0010);
-      payload.push_back((uint16_t) x);
-      return {};
-
-# Reports the server-side register so the test can observe that the deprecated buffer write landed.
-sensor:
-  - platform: template
-    name: "written_value"
-    id: written_value
-    update_interval: 0.5s
-    lambda: "return id(reg10);"
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    # The test drives the writes via number_command; the mock is autostart.

tests/integration/fixtures/uart_mock_modbus_lambda_invert.yaml

@@ -1,95 +0,0 @@
-esphome:
-  name: uart-mock-modbus-lambda-invert
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-  - id: virtual_uart_controller
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-
-globals:
-  - id: reg40
-    type: uint16_t
-    initial_value: "5"
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_controller
-    id: virtual_modbus_controller
-    role: client
-    turnaround_time: 10ms
-
-modbus_controller:
-  - address: 1
-    modbus_id: virtual_modbus_controller
-    id: modbus_controller_1
-    update_interval: 1s
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    id: modbus_server_1
-    registers:
-      - address: 0x40
-        value_type: U_WORD
-        read_lambda: return id(reg40);
-        write_lambda: id(reg40) = x; return true;
-
-# An active-low holding switch: the write_lambda inverts the wire value, but the entity must still
-# report the REQUESTED state. assumed_state keeps the register unpolled, so the published state comes
-# only from write_state() - turning ON writes 0x0000 yet the switch shows ON.
-switch:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "invert_switch"
-    register_type: holding
-    address: 0x40
-    assumed_state: true
-    write_lambda: |-
-      return !x;
-
-sensor:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "reg_40"
-    address: 0x40
-    register_type: holding
-    value_type: U_WORD
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    # This test does not have anything to start (mock is autostart)

tests/integration/fixtures/uart_mock_modbus_lambda_write.yaml

@@ -1,97 +0,0 @@
-esphome:
-  name: uart-mock-modbus-lambda-write
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-  - id: virtual_uart_controller
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-
-globals:
-  - id: reg30
-    type: uint16_t
-    initial_value: "0"
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_controller
-    id: virtual_modbus_controller
-    role: client
-    turnaround_time: 10ms
-
-modbus_controller:
-  - address: 1
-    modbus_id: virtual_modbus_controller
-    id: modbus_controller_1
-    update_interval: 1s
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    id: modbus_server_1
-    registers:
-      - address: 0x30
-        value_type: U_WORD
-        read_lambda: return id(reg30);
-        write_lambda: id(reg30) = x; return true;
-
-# A COIL-type switch (assumed_state, write-only) whose write_lambda ignores its own coil type and instead
-# drives a HOLDING-REGISTER write on the mock server through the entity itself: `item` IS the command, so
-# item->write_single_register() sends a register write from a coil entity (cross-type). Returning nothing
-# (an empty optional) tells the write path the lambda already dispatched the frame - no default coil write.
-switch:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "cross_switch"
-    register_type: coil
-    address: 0x00
-    assumed_state: true
-    write_lambda: |-
-      item->write_single_register(0x30, x ? 1234 : 0);
-      return {};
-
-sensor:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "reg_30"
-    address: 0x30
-    register_type: holding
-    value_type: U_WORD
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    # This test does not have anything to start (mock is autostart)

tests/integration/fixtures/uart_mock_modbus_loopback.yaml

@@ -0,0 +1,233 @@
+esphome:
+  name: uart-mock-modbus-loopback
+
+host:
+api:
+logger:
+  level: VERBOSE
+
+external_components:
+  - source:
+      type: local
+      path: EXTERNAL_COMPONENT_PATH
+
+# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
+# The actual UART bus used is the uart_mock component below
+uart:
+  baud_rate: 115200
+  port: /dev/null
+
+# Shared loopback fixture (see the shared_yaml markers in the test file);
+# register spaces are disjoint so each test only observes its own entities.
+uart_mock:
+  - id: virtual_uart_server
+    baud_rate: 9600
+    auto_start: true
+    debug:
+    on_tx:
+      - then:
+          - uart_mock.inject_rx:
+              id: virtual_uart_controller
+              data: !lambda return data;
+  - id: virtual_uart_controller
+    baud_rate: 9600
+    auto_start: true
+    debug:
+    on_tx:
+      - then:
+          - uart_mock.inject_rx:
+              id: virtual_uart_server
+              data: !lambda return data;
+
+globals:
+  - id: reg10
+    type: uint16_t
+    initial_value: "100"
+  - id: reg11
+    type: uint16_t
+    initial_value: "200"
+  - id: reg12
+    type: uint16_t
+    initial_value: "300"
+  - id: reg13
+    type: uint16_t
+    initial_value: "0xABCD"
+  - id: reg30
+    type: uint16_t
+    initial_value: "0"
+  - id: reg40
+    type: uint16_t
+    initial_value: "5"
+  - id: reg50
+    type: uint16_t
+    initial_value: "0"
+
+modbus:
+  - uart_id: virtual_uart_server
+    id: virtual_modbus_server
+    role: server
+  - uart_id: virtual_uart_controller
+    id: virtual_modbus_controller
+    role: client
+    turnaround_time: 10ms
+
+modbus_controller:
+  - address: 1
+    modbus_id: virtual_modbus_controller
+    id: modbus_controller_1
+    update_interval: 1s
+
+modbus_server:
+  - address: 1
+    modbus_id: virtual_modbus_server
+    registers:
+      - address: 0x01
+        value_type: U_WORD
+        read_lambda: return 259;
+      - address: 0x10
+        value_type: U_WORD
+        read_lambda: return id(reg10);
+        write_lambda: id(reg10) = x; return true;
+      - address: 0x11
+        value_type: U_WORD
+        read_lambda: return id(reg11);
+        write_lambda: id(reg11) = x; return true;
+      - address: 0x12
+        value_type: U_WORD
+        read_lambda: return id(reg12);
+        write_lambda: id(reg12) = x; return true;
+      - address: 0x13
+        value_type: U_WORD
+        read_lambda: return id(reg13);
+      - address: 0x30
+        value_type: U_WORD
+        read_lambda: return id(reg30);
+        write_lambda: id(reg30) = x; return true;
+      - address: 0x40
+        value_type: U_WORD
+        read_lambda: return id(reg40);
+        write_lambda: id(reg40) = x; return true;
+      - address: 0x50
+        value_type: U_WORD
+        read_lambda: return id(reg50);
+        write_lambda: id(reg50) = x; return true;
+
+# Byte-based offset: 2 bytes -> register 0x11 (the old code folded it in as a
+# register count, hitting 0x12). assumed_state keeps the switch write-only.
+switch:
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "offset_switch"
+    register_type: holding
+    address: 0x10
+    offset: 2
+    assumed_state: true
+  # Reading switch, byte offset 6 -> register 0x13; the pre-fix resolution (0x16)
+  # would draw ILLEGAL_DATA_ADDRESS and never publish.
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "read_offset_switch"
+    register_type: holding
+    address: 0x10
+    offset: 6
+    bitmask: 0x1
+  # Coil switch whose write_lambda dispatches a holding-register write via `item`;
+  # returning an empty optional suppresses the default coil write.
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "cross_switch"
+    register_type: coil
+    address: 0x00
+    assumed_state: true
+    write_lambda: |-
+      item->write_single_register(0x30, x ? 1234 : 0);
+      return {};
+  # Active-low: the write_lambda inverts the wire value but the entity must still
+  # report the requested state (assumed_state keeps the register unpolled).
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "invert_switch"
+    register_type: holding
+    address: 0x40
+    assumed_state: true
+    write_lambda: |-
+      return !x;
+
+# Uses the deprecated buffer parameter (legacy raw frame as words); the write
+# must land and the deprecation warning must fire only once per entity.
+number:
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "buf_number"
+    id: buf_number
+    address: 0x50
+    register_type: holding
+    value_type: U_WORD
+    min_value: 0
+    max_value: 1000
+    step: 1
+    write_lambda: |-
+      // Legacy raw frame as words: [addr 0x01 | fc 0x06], register 0x0050, value.
+      payload.push_back(0x0106);
+      payload.push_back(0x0050);
+      payload.push_back((uint16_t) x);
+      return {};
+
+sensor:
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "plain_read"
+    address: 0x01
+    register_type: holding
+    value_type: U_WORD
+  # Custom PDU: read holding register 0x0001; device address and CRC are added
+  # by the hub. The lambda parses the big-endian register value.
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "custom_read"
+    custom_pdu: [0x03, 0x00, 0x01, 0x00, 0x01]
+    lambda: |-
+      if (data.size() < 2) return {};
+      return (float) ((data[0] << 8) | data[1]);
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "reg_10"
+    address: 0x10
+    register_type: holding
+    value_type: U_WORD
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "reg_11"
+    address: 0x11
+    register_type: holding
+    value_type: U_WORD
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "reg_12"
+    address: 0x12
+    register_type: holding
+    value_type: U_WORD
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "reg_30"
+    address: 0x30
+    register_type: holding
+    value_type: U_WORD
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_1
+    name: "reg_40"
+    address: 0x40
+    register_type: holding
+    value_type: U_WORD
+  # Reports the server-side register so the test can observe that the deprecated buffer write landed.
+  - platform: template
+    name: "written_value"
+    id: written_value
+    update_interval: 0.5s
+    lambda: "return id(reg50);"
+
+button:
+  - platform: template
+    name: "Start Scenario"
+    id: start_scenario_btn
+    # Nothing to start (mock is autostart); tests drive entities directly

tests/integration/fixtures/uart_mock_modbus_mesh.yaml

@@ -1,5 +1,5 @@
 esphome:
-  name: uart-mock-modbus-server-contro
+  name: uart-mock-modbus-mesh
 
 host:
 api:
@@ -17,13 +17,14 @@ uart:
   baud_rate: 115200
   port: /dev/null
 
+# Shared 3-bus mesh (see the shared_yaml markers): addr 1 = typed read-only
+# registers, addr 5 = the read/write 0x17 target, addr 2/3 on the second
+# server hub. auto_start everywhere: the controller polls at boot, so the
+# forwarding must already be live or early requests generate warnings.
+# Every test presses Start Scenario, so all merged actions fire in every test.
 uart_mock:
   - id: virtual_uart_server
     baud_rate: 9600
-    # auto_start must be true for loopback fixtures: the modbus controller
-    # polls on its update_interval immediately at boot, so the uart_mock
-    # forwarding must already be active or early requests are lost and
-    # generate modbus warnings.
     auto_start: true
     debug:
     on_tx:
@@ -31,35 +32,68 @@ uart_mock:
           - uart_mock.inject_rx:
               id: virtual_uart_controller
               data: !lambda return data;
-  - id: virtual_uart_controller
+          - uart_mock.inject_rx:
+              id: virtual_uart_server_2
+              data: !lambda return data;
+  - id: virtual_uart_server_2
     baud_rate: 9600
-    auto_start: true # See comment on virtual_uart_server above
+    auto_start: true
     debug:
     on_tx:
       - then:
           - uart_mock.inject_rx:
               id: virtual_uart_server
               data: !lambda return data;
+          - uart_mock.inject_rx:
+              id: virtual_uart_controller
+              data: !lambda return data;
+  - id: virtual_uart_controller
+    baud_rate: 9600
+    auto_start: true
+    debug:
+    on_tx:
+      - then:
+          - uart_mock.inject_rx:
+              id: virtual_uart_server
+              data: !lambda return data;
+          - uart_mock.inject_rx:
+              id: virtual_uart_server_2
+              data: !lambda return data;
+
+globals:
+  - id: stored_1
+    type: uint16_t
+    initial_value: "0"
 
 modbus:
   - uart_id: virtual_uart_server
     id: virtual_modbus_server
     role: server
+  - uart_id: virtual_uart_server_2
+    id: virtual_modbus_server_2
+    role: server
   - uart_id: virtual_uart_controller
-    id: virtual_modbus_controller
+    id: virtual_modbus_client
     role: client
     turnaround_time: 10ms
 
 modbus_controller:
   - address: 1
-    modbus_id: virtual_modbus_controller
+    modbus_id: virtual_modbus_client
     id: modbus_controller_1
     update_interval: 1s
+  - address: 2
+    modbus_id: virtual_modbus_client
+    id: modbus_controller_2
+    update_interval: 1s
+  - address: 3
+    modbus_id: virtual_modbus_client
+    id: modbus_controller_3
+    update_interval: 1s
 
 modbus_server:
   - address: 1
     modbus_id: virtual_modbus_server
-    id: modbus_server_1
     registers:
       - address: 0x01
         value_type: U_WORD
@@ -103,6 +137,34 @@ modbus_server:
       - address: 0x28
         value_type: FP32_R
         read_lambda: return 3.14;
+  - address: 5
+    modbus_id: virtual_modbus_server
+    registers:
+      # Writable + readable register: srv_write_1 plus the client's read-back
+      # confirm the write half of the 0x17 ran before the read half (Modbus 6.17).
+      - address: 0x01
+        value_type: U_WORD
+        read_lambda: return id(stored_1);
+        write_lambda: |-
+          id(stored_1) = x;
+          id(srv_write_1).publish_state(x);
+          return true;
+      # Read-only register, returned together with 0x01 by the 2-register read half.
+      - address: 0x02
+        value_type: U_WORD
+        read_lambda: return 0x00AA;
+  - address: 2
+    modbus_id: virtual_modbus_server_2
+    registers:
+      - address: 0x01
+        value_type: U_WORD
+        read_lambda: return 919;
+  - address: 3
+    modbus_id: virtual_modbus_server_2
+    registers:
+      - address: 0x01
+        value_type: U_WORD
+        read_lambda: return 929;
 
 sensor:
   - platform: modbus_controller
@@ -195,9 +257,46 @@ sensor:
     address: 0x28
     register_type: holding
     value_type: FP32_R
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_2
+    name: "multi_reg_a"
+    address: 0x01
+    register_type: holding
+    value_type: U_WORD
+  - platform: modbus_controller
+    modbus_controller_id: modbus_controller_3
+    name: "multi_reg_b"
+    address: 0x01
+    register_type: holding
+    value_type: U_WORD
+  # client_read_write observations, server- and client-side.
+  - platform: template
+    name: "srv_write_1"
+    id: srv_write_1
+  - platform: template
+    name: "client_read_0"
+    id: client_read_0
+  - platform: template
+    name: "client_read_1"
+    id: client_read_1
 
 button:
   - platform: template
     name: "Start Scenario"
     id: start_scenario_btn
-    # This test does not have anything to start (mock is autostart)
+    on_press:
+      # FC 0x17: write reg 0x0001 = 0x1234, then read regs 0x0001..0x0002 back in the same transaction.
+      - modbus_client.read_write_multiple_registers:
+          address: 5
+          read_address: 0x0001
+          read_count: 2
+          write_address: 0x0001
+          values: [0x1234]
+          on_response:
+            then:
+              - lambda: |-
+                  // values is the read-back block: reg 0x0001 (must be the just-written 0x1234) and reg 0x0002.
+                  if (values.size() >= 2) {
+                    id(client_read_0).publish_state(values[0]);
+                    id(client_read_1).publish_state(values[1]);
+                  }

tests/integration/fixtures/uart_mock_modbus_register_offset.yaml

@@ -1,138 +0,0 @@
-esphome:
-  name: uart-mock-modbus-reg-offset
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-  - id: virtual_uart_controller
-    baud_rate: 9600
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-
-globals:
-  - id: reg10
-    type: uint16_t
-    initial_value: "100"
-  - id: reg11
-    type: uint16_t
-    initial_value: "200"
-  - id: reg12
-    type: uint16_t
-    initial_value: "300"
-  - id: reg13
-    type: uint16_t
-    initial_value: "0xABCD"
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_controller
-    id: virtual_modbus_controller
-    role: client
-    turnaround_time: 10ms
-
-modbus_controller:
-  - address: 1
-    modbus_id: virtual_modbus_controller
-    id: modbus_controller_1
-    update_interval: 1s
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    id: modbus_server_1
-    registers:
-      - address: 0x10
-        value_type: U_WORD
-        read_lambda: return id(reg10);
-        write_lambda: id(reg10) = x; return true;
-      - address: 0x11
-        value_type: U_WORD
-        read_lambda: return id(reg11);
-        write_lambda: id(reg11) = x; return true;
-      - address: 0x12
-        value_type: U_WORD
-        read_lambda: return id(reg12);
-        write_lambda: id(reg12) = x; return true;
-      - address: 0x13
-        value_type: U_WORD
-        read_lambda: return id(reg13);
-        write_lambda: id(reg13) = x; return true;
-
-# A holding-register switch at 0x10 with a 2-BYTE offset. offset is byte-based, so the write must target
-# register 0x10 + 2/2 = 0x11. The old (pre-fix) behavior folded offset into the address as a register
-# count, hitting 0x12 instead. assumed_state keeps the switch write-only so it does not read any register.
-switch:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "offset_switch"
-    register_type: holding
-    address: 0x10
-    offset: 2
-    assumed_state: true
-  # A holding-register switch that READS its state. Byte offset 6 -> register 0x10 + 6/2 = 0x13. Post-fix
-  # the switch itself resolves to 0x13 (the even byte offset folds into the address as whole registers) and
-  # joins the 0x10..0x13 range, so no separate 0x13 sensor is needed. Pre-fix the whole byte offset folds
-  # into the address (0x16), where the server answers ILLEGAL_DATA_ADDRESS and the switch never publishes.
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "read_offset_switch"
-    register_type: holding
-    address: 0x10
-    offset: 6
-    bitmask: 0x1
-
-sensor:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "reg_10"
-    address: 0x10
-    register_type: holding
-    value_type: U_WORD
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "reg_11"
-    address: 0x11
-    register_type: holding
-    value_type: U_WORD
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "reg_12"
-    address: 0x12
-    register_type: holding
-    value_type: U_WORD
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    # This test does not have anything to start (mock is autostart)

tests/integration/fixtures/uart_mock_modbus_server.yaml

@@ -1,124 +0,0 @@
-esphome:
-  name: uart-mock-modbus-server-test
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_dev
-    baud_rate: 9600
-    rx_full_threshold: 120
-    rx_timeout: 2
-    auto_start: false
-    debug:
-    injections:
-      - delay: 100ms
-        inject_rx: [0x01, 0x03, 0x00, 0x03, 0x00, 0x01, 0x74, 0x0A] #  Read holding register 3 on device 1 (basic_read)
-      - delay: 100ms
-        #  Read holding register 7 on device 2
-        #  Reply from device 2
-        #  Read holding register 5 on device 1 (read_after_peer_response)
-        inject_rx:
-          [
-            0x02,
-            0x03,
-            0x00,
-            0x07,
-            0x00,
-            0x01,
-            0x35,
-            0xF8,
-            0x02,
-            0x03,
-            0x02,
-            0x00,
-            0xF0,
-            0xFC,
-            0x00,
-            0x01,
-            0x03,
-            0x00,
-            0x05,
-            0x00,
-            0x01,
-            0x94,
-            0x0B,
-          ]
-      - delay: 100ms
-        inject_rx: [0x02, 0x03, 0x00, 0x07, 0x00, 0x01, 0x35, 0xF8] #  Read holding register 7 on device 2, with no response
-      - delay: 100ms
-        #  Read holding register 7 on device 2, with no response
-        #  Read holding register A on device 1 (read_after_peer_timeout)
-        inject_rx:
-          [
-            0x02,
-            0x03,
-            0x00,
-            0x07,
-            0x00,
-            0x01,
-            0x35,
-            0xF8,
-            0x01,
-            0x03,
-            0x00,
-            0x0A,
-            0x00,
-            0x01,
-            0xA4,
-            0x08,
-          ]
-
-modbus:
-  uart_id: virtual_uart_dev
-  role: server
-
-modbus_server:
-  - address: 1
-    registers:
-      - address: 0x03
-        value_type: U_WORD
-        read_lambda: |-
-          id(basic_read).publish_state(1);
-          return 1;
-      - address: 0x05
-        value_type: U_WORD
-        read_lambda: |-
-          id(read_after_peer_response).publish_state(1);
-          return 1;
-      - address: 0x0A
-        value_type: U_WORD
-        read_lambda: |-
-          id(read_after_peer_timeout).publish_state(1);
-          return 1;
-
-sensor:
-  - platform: template
-    name: "basic_read"
-    id: basic_read
-  - platform: template
-    name: "read_after_peer_response"
-    id: read_after_peer_response
-  - platform: template
-    name: "read_after_peer_timeout"
-    id: read_after_peer_timeout
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    on_press:
-      - lambda: "id(virtual_uart_dev).start_scenario();"

tests/integration/fixtures/uart_mock_modbus_server_controller_multiple.yaml

@@ -1,116 +0,0 @@
-esphome:
-  name: uart-mock-modbus-server-mult
-
-host:
-api:
-logger:
-  level: VERBOSE
-
-external_components:
-  - source:
-      type: local
-      path: EXTERNAL_COMPONENT_PATH
-
-# Dummy uart entry to satisfy modbus's DEPENDENCIES = ["uart"]
-# The actual UART bus used is the uart_mock component below
-uart:
-  baud_rate: 115200
-  port: /dev/null
-
-uart_mock:
-  - id: virtual_uart_server
-    baud_rate: 9600
-    # auto_start must be true for loopback fixtures: the modbus controller
-    # polls on its update_interval immediately at boot, so the uart_mock
-    # forwarding must already be active or early requests are lost and
-    # generate modbus warnings.
-    auto_start: true
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-          - uart_mock.inject_rx:
-              id: virtual_uart_server_2
-              data: !lambda return data;
-  - id: virtual_uart_server_2
-    baud_rate: 9600
-    auto_start: true # See comment on virtual_uart_server above
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-          - uart_mock.inject_rx:
-              id: virtual_uart_controller
-              data: !lambda return data;
-  - id: virtual_uart_controller
-    baud_rate: 9600
-    auto_start: true # See comment on virtual_uart_server above
-    debug:
-    on_tx:
-      - then:
-          - uart_mock.inject_rx:
-              id: virtual_uart_server
-              data: !lambda return data;
-          - uart_mock.inject_rx:
-              id: virtual_uart_server_2
-              data: !lambda return data;
-
-modbus:
-  - uart_id: virtual_uart_server
-    id: virtual_modbus_server
-    role: server
-  - uart_id: virtual_uart_server_2
-    id: virtual_modbus_server_2
-    role: server
-  - uart_id: virtual_uart_controller
-    id: virtual_modbus_client
-    role: client
-    turnaround_time: 10ms
-
-modbus_controller:
-  - address: 1
-    modbus_id: virtual_modbus_client
-    update_interval: 1s
-    id: modbus_controller_1
-  - address: 2
-    modbus_id: virtual_modbus_client
-    update_interval: 1s
-    id: modbus_controller_2
-
-modbus_server:
-  - address: 1
-    modbus_id: virtual_modbus_server
-    registers:
-      - address: 0x01
-        value_type: U_WORD
-        read_lambda: return 919;
-  - address: 2
-    modbus_id: virtual_modbus_server_2
-    registers:
-      - address: 0x01
-        value_type: U_WORD
-        read_lambda: return 929;
-
-sensor:
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_1
-    name: "reg_u_word"
-    address: 0x01
-    register_type: holding
-    value_type: U_WORD
-  - platform: modbus_controller
-    modbus_controller_id: modbus_controller_2
-    name: "reg_u_word_2"
-    address: 0x01
-    register_type: holding
-    value_type: U_WORD
-
-button:
-  - platform: template
-    name: "Start Scenario"
-    id: start_scenario_btn
-    # This test does not have anything to start (mock is autostart)

tests/integration/fixtures/uart_mock_modbus_server_injected.yaml

@@ -1,5 +1,5 @@
 esphome:
-  name: uart-mock-modbus-srv-rw
+  name: uart-mock-modbus-srv-injected
 
 host:
 api:
@@ -17,6 +17,8 @@ uart:
   baud_rate: 115200
   port: /dev/null
 
+# Shared server-role fixture (see the shared_yaml markers in the test file);
+# the injections concatenate and each test waits only on its own sensors.
 uart_mock:
   - id: virtual_uart_dev
     baud_rate: 9600
@@ -25,18 +27,31 @@ uart_mock:
     auto_start: false
     debug:
     injections:
-      # FC 0x17 Read/Write Multiple Registers on device 1:
-      #   write reg 0x0001 = 0x1234 (qty 1), then read regs 0x0001..0x0002 (qty 2).
-      # Per Modbus 6.17 the write is performed before the read, so reg 0x0001 must
-      # read back the just-written 0x1234 in the same request.
+      - delay: 100ms
+        inject_rx: [0x01, 0x03, 0x00, 0x03, 0x00, 0x01, 0x74, 0x0A] #  Read holding register 3 on device 1 (basic_read)
+      - delay: 100ms
+        #  Read holding register 7 on device 2, its reply, then read holding
+        #  register 5 on device 1 (read_after_peer_response)
+        inject_rx: [0x02, 0x03, 0x00, 0x07, 0x00, 0x01, 0x35, 0xF8,
+                    0x02, 0x03, 0x02, 0x00, 0xF0, 0xFC,
+                    0x00, 0x01, 0x03, 0x00, 0x05, 0x00, 0x01, 0x94, 0x0B]
+      - delay: 100ms
+        inject_rx: [0x02, 0x03, 0x00, 0x07, 0x00, 0x01, 0x35, 0xF8] #  Read holding register 7 on device 2, with no response
+      - delay: 100ms
+        #  Read holding register 7 on device 2 with no response, then read
+        #  holding register A on device 1 (read_after_peer_timeout)
+        inject_rx: [0x02, 0x03, 0x00, 0x07, 0x00, 0x01, 0x35, 0xF8,
+                    0x01, 0x03, 0x00, 0x0A, 0x00, 0x01, 0xA4, 0x08]
+      # FC 0x17 on device 1: write reg 0x0001 = 0x1234 then read 0x0001..0x0002;
+      # per Modbus 6.17 the write runs first, so 0x0001 must read back 0x1234.
       - delay: 100ms
         inject_rx:
           [0x01, 0x17, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x01, 0x02, 0x12, 0x34, 0x49, 0xD8]
-      # FC 0x17: write reg 0x0003 = 0x5678 (qty 1), then read reg 0x0003 (qty 1) -
+      # FC 0x17: write reg 0x0006 = 0x5678 (qty 1), then read reg 0x0006 (qty 1) -
       # a write and read targeting a different register block.
       - delay: 100ms
         inject_rx:
-          [0x01, 0x17, 0x00, 0x03, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x02, 0x56, 0x78, 0x9B, 0x10]
+          [0x01, 0x17, 0x00, 0x06, 0x00, 0x01, 0x00, 0x06, 0x00, 0x01, 0x02, 0x56, 0x78, 0x8B, 0x55]
 
 globals:
   - id: stored_1
@@ -70,8 +85,18 @@ modbus_server:
         read_lambda: |-
           id(rw_read_2).publish_state(0x00AA);
           return 0x00AA;
-      # Second writable + readable register, targeted by the second request.
       - address: 0x03
+        value_type: U_WORD
+        read_lambda: |-
+          id(basic_read).publish_state(1);
+          return 1;
+      - address: 0x05
+        value_type: U_WORD
+        read_lambda: |-
+          id(read_after_peer_response).publish_state(1);
+          return 1;
+      # Second writable + readable register, targeted by the second FC 0x17 request.
+      - address: 0x06
         value_type: U_WORD
         read_lambda: |-
           id(rw_read_3).publish_state(id(stored_3));
@@ -80,8 +105,22 @@ modbus_server:
           id(stored_3) = x;
           id(rw_write_3).publish_state(x);
           return true;
+      - address: 0x0A
+        value_type: U_WORD
+        read_lambda: |-
+          id(read_after_peer_timeout).publish_state(1);
+          return 1;
 
 sensor:
+  - platform: template
+    name: "basic_read"
+    id: basic_read
+  - platform: template
+    name: "read_after_peer_response"
+    id: read_after_peer_response
+  - platform: template
+    name: "read_after_peer_timeout"
+    id: read_after_peer_timeout
   - platform: template
     name: "rw_write_1"
     id: rw_write_1

tests/integration/host_prefs.py

@@ -1,7 +1,7 @@
 """Helpers for manipulating the host platform's preferences file.
 
 ESPHome's host platform stores preferences in
-``~/.esphome/prefs/<app_name>.prefs`` using a simple binary layout that
+``$ESPHOME_PREFDIR/<app_name>.prefs`` using a simple binary layout that
 mirrors ``HostPreferences::sync()``:
 ``[uint32_t key][uint8_t len][uint8_t data[len]]`` per entry.
 
@@ -11,13 +11,21 @@ boot (e.g. forcing safe mode) or to clear stale state between runs.
 
 from __future__ import annotations
 
+import os
 from pathlib import Path
 import struct
 
 
 def host_prefs_path(device_name: str) -> Path:
-    """Return the on-disk prefs file path for a host-platform device."""
-    return Path.home() / ".esphome" / "prefs" / f"{device_name}.prefs"
+    """Return the on-disk prefs file path for a host-platform device.
+
+    Requires ESPHOME_PREFDIR, which the autouse isolated_preferences fixture
+    sets; refusing the ~/.esphome/prefs fallback keeps tests off real user
+    data if the fixture is ever bypassed."""
+    prefdir = os.environ.get("ESPHOME_PREFDIR")
+    if not prefdir:
+        raise RuntimeError("ESPHOME_PREFDIR is not set; refusing the real prefs dir")
+    return Path(prefdir) / f"{device_name}.prefs"
 
 
 def clear_host_prefs(device_name: str) -> None:

tests/integration/integration_test_durations.json

@@ -1,143 +1,154 @@
 {
-  "tests/integration/test_action_concurrent_reentry.py": 57.91,
-  "tests/integration/test_addressable_light_transition.py": 21.25,
-  "tests/integration/test_alarm_control_panel_state_transitions.py": 70.71,
-  "tests/integration/test_api_action_metadata.py": 66.6,
-  "tests/integration/test_api_action_responses.py": 36.1,
-  "tests/integration/test_api_action_timeout.py": 68.86,
-  "tests/integration/test_api_conditional_memory.py": 15.48,
-  "tests/integration/test_api_custom_services.py": 18.77,
-  "tests/integration/test_api_get_time_response_timezone.py": 21.08,
-  "tests/integration/test_api_homeassistant.py": 65.59,
-  "tests/integration/test_api_homeassistant_action_no_subscriber.py": 18.44,
-  "tests/integration/test_api_homeassistant_binary_sensor_initial_state.py": 15.05,
-  "tests/integration/test_api_list_entities_backpressure.py": 13.88,
-  "tests/integration/test_api_message_size_batching.py": 29.98,
-  "tests/integration/test_api_reboot_timeout.py": 16.05,
-  "tests/integration/test_api_string_lambda.py": 15.31,
-  "tests/integration/test_api_vv_logging.py": 19.28,
-  "tests/integration/test_api_zero_psk_provisioning.py": 31.5,
-  "tests/integration/test_areas_and_devices.py": 24.95,
-  "tests/integration/test_automation_wait_actions.py": 20.92,
-  "tests/integration/test_automations.py": 35.19,
-  "tests/integration/test_batch_delay_zero_rapid_transitions.py": 17.99,
-  "tests/integration/test_binary_sensor_autorepeat_filter.py": 20.39,
-  "tests/integration/test_binary_sensor_invalidate_state.py": 18.41,
-  "tests/integration/test_blocking_warning_log_time_not_charged_to_next_operation.py": 24.69,
-  "tests/integration/test_build_info.py": 18.7,
-  "tests/integration/test_camera_mock.py": 16.23,
-  "tests/integration/test_climate_control_action.py": 21.14,
-  "tests/integration/test_climate_custom_modes.py": 20.74,
-  "tests/integration/test_continuation_actions.py": 16.81,
-  "tests/integration/test_cover_control_action.py": 20.34,
-  "tests/integration/test_crc8_helper.py": 9.36,
-  "tests/integration/test_device_id_in_state.py": 44.67,
-  "tests/integration/test_duplicate_entities.py": 23.58,
-  "tests/integration/test_entity_icon.py": 34.35,
-  "tests/integration/test_fan_turn_on_action.py": 24.23,
-  "tests/integration/test_fnv1_hash_object_id.py": 16.21,
-  "tests/integration/test_fnv1a_hash.py": 13.38,
-  "tests/integration/test_gpio_expander_cache.py": 13.06,
-  "tests/integration/test_host_logger_thread_safety.py": 23.66,
-  "tests/integration/test_host_mode_basic.py": 8.01,
-  "tests/integration/test_host_mode_batch_delay.py": 21.0,
-  "tests/integration/test_host_mode_climate_basic_state.py": 22.14,
-  "tests/integration/test_host_mode_climate_control.py": 19.39,
-  "tests/integration/test_host_mode_empty_string_options.py": 21.76,
-  "tests/integration/test_host_mode_entity_fields.py": 29.61,
-  "tests/integration/test_host_mode_fan_preset.py": 20.01,
-  "tests/integration/test_host_mode_many_entities.py": 39.08,
-  "tests/integration/test_host_mode_many_entities_multiple_connections.py": 23.92,
-  "tests/integration/test_host_mode_noise_encryption.py": 42.42,
-  "tests/integration/test_host_mode_reconnect.py": 3.41,
-  "tests/integration/test_host_mode_sensor.py": 22.96,
-  "tests/integration/test_host_ota.py": 29.5,
-  "tests/integration/test_host_preferences.py": 16.06,
-  "tests/integration/test_host_preferences_suspend_resume.py": 18.71,
-  "tests/integration/test_improv_serial_uart.py": 20.22,
-  "tests/integration/test_large_message_batching.py": 26.56,
-  "tests/integration/test_legacy_area.py": 22.72,
-  "tests/integration/test_legacy_climate_compat.py": 14.13,
-  "tests/integration/test_legacy_fan_compat.py": 14.33,
-  "tests/integration/test_light_automations.py": 18.81,
-  "tests/integration/test_light_binary_effect_off_phase.py": 8.38,
-  "tests/integration/test_light_calls.py": 21.88,
-  "tests/integration/test_light_constant_brightness.py": 59.45,
-  "tests/integration/test_light_control_action.py": 31.91,
-  "tests/integration/test_light_dim_relative_action.py": 14.43,
-  "tests/integration/test_light_effect_zero_brightness.py": 25.05,
-  "tests/integration/test_light_initial_state.py": 18.97,
-  "tests/integration/test_light_toggle_action.py": 17.44,
-  "tests/integration/test_lock_automations.py": 18.9,
-  "tests/integration/test_logger_buffered_recursion_guard.py": 18.2,
-  "tests/integration/test_loop_disable_enable.py": 63.35,
-  "tests/integration/test_loop_interval_decoupling.py": 17.7,
-  "tests/integration/test_loop_interval_default_not_pulled_forward.py": 21.56,
-  "tests/integration/test_micros_to_millis.py": 15.89,
-  "tests/integration/test_multi_click_trigger.py": 17.23,
-  "tests/integration/test_multi_device_preferences.py": 19.4,
-  "tests/integration/test_noise_encryption_key_protection.py": 72.59,
-  "tests/integration/test_object_id_api_verification.py": 19.22,
-  "tests/integration/test_object_id_friendly_name_no_mac_suffix.py": 16.77,
-  "tests/integration/test_object_id_no_friendly_name.py": 45.8,
-  "tests/integration/test_online_image_auto_detects_image_bmp_mime.py": 86.73,
-  "tests/integration/test_online_image_auto_detects_redirected_image_bmp_mime.py": 40.4,
-  "tests/integration/test_online_image_bmp.py": 37.24,
-  "tests/integration/test_oversized_payloads.py": 55.75,
-  "tests/integration/test_preference_key_stability.py": 25.49,
-  "tests/integration/test_runtime_stats.py": 29.81,
-  "tests/integration/test_safe_mode_loop_runs.py": 6.26,
-  "tests/integration/test_scheduler_blocking_warning.py": 37.98,
-  "tests/integration/test_scheduler_bulk_cleanup.py": 18.67,
-  "tests/integration/test_scheduler_defer_cancel.py": 18.46,
-  "tests/integration/test_scheduler_defer_cancel_regular.py": 16.34,
-  "tests/integration/test_scheduler_defer_fifo_simple.py": 18.26,
-  "tests/integration/test_scheduler_defer_stress.py": 17.74,
-  "tests/integration/test_scheduler_heap_stress.py": 3.89,
-  "tests/integration/test_scheduler_internal_id_no_collision.py": 20.01,
-  "tests/integration/test_scheduler_interval_reschedule.py": 16.29,
-  "tests/integration/test_scheduler_interval_zero_coerced.py": 16.09,
-  "tests/integration/test_scheduler_null_name.py": 14.69,
-  "tests/integration/test_scheduler_numeric_id_test.py": 17.08,
-  "tests/integration/test_scheduler_pool.py": 19.88,
-  "tests/integration/test_scheduler_rapid_cancellation.py": 4.42,
-  "tests/integration/test_scheduler_recursive_timeout.py": 4.3,
-  "tests/integration/test_scheduler_removed_item_race.py": 15.49,
-  "tests/integration/test_scheduler_self_keyed.py": 25.77,
-  "tests/integration/test_scheduler_simultaneous_callbacks.py": 14.84,
-  "tests/integration/test_scheduler_string_test.py": 15.42,
-  "tests/integration/test_script_array_params.py": 12.73,
-  "tests/integration/test_script_delay_params.py": 12.69,
-  "tests/integration/test_script_queued.py": 20.38,
-  "tests/integration/test_script_queued_idle_loop.py": 25.06,
-  "tests/integration/test_script_wait_on_boot.py": 15.67,
-  "tests/integration/test_select_stringref_trigger.py": 19.48,
-  "tests/integration/test_sensor_filters_delta.py": 27.62,
-  "tests/integration/test_sensor_filters_ring_buffer.py": 20.27,
-  "tests/integration/test_sensor_filters_sliding_window.py": 56.28,
-  "tests/integration/test_sensor_filters_value_list.py": 20.6,
-  "tests/integration/test_sensor_timeout_filter.py": 22.21,
-  "tests/integration/test_socket_wake_gate_tcp.py": 16.37,
-  "tests/integration/test_status_flags.py": 29.68,
-  "tests/integration/test_strftime_to.py": 17.42,
-  "tests/integration/test_syslog.py": 18.39,
-  "tests/integration/test_template_alarm_control_panel_many_sensors.py": 25.61,
-  "tests/integration/test_template_text_save.py": 19.16,
-  "tests/integration/test_text_command.py": 16.43,
-  "tests/integration/test_text_sensor_raw_state.py": 17.19,
-  "tests/integration/test_uart_mock_ld2410.py": 37.0,
-  "tests/integration/test_uart_mock_ld2412.py": 40.82,
-  "tests/integration/test_uart_mock_ld2420.py": 32.7,
-  "tests/integration/test_uart_mock_ld2450.py": 32.84,
-  "tests/integration/test_uart_mock_modbus.py": 548.87,
-  "tests/integration/test_udp.py": 16.67,
-  "tests/integration/test_use_address_runtime.py": 27.26,
-  "tests/integration/test_valve_control_action.py": 24.58,
-  "tests/integration/test_varint_five_byte_device_id.py": 22.5,
-  "tests/integration/test_wait_until_mid_loop_timing.py": 22.05,
-  "tests/integration/test_wait_until_on_boot.py": 10.37,
-  "tests/integration/test_wait_until_ordering.py": 18.23,
-  "tests/integration/test_wait_until_reentrant_restart.py": 19.35,
-  "tests/integration/test_wake_loop_forces_phase_b.py": 17.83,
-  "tests/integration/test_water_heater_template.py": 25.7
+  "tests/integration/test_action_concurrent_reentry.py": 30.48,
+  "tests/integration/test_addressable_light_transition.py": 42.1,
+  "tests/integration/test_alarm_control_panel_state_transitions.py": 35.76,
+  "tests/integration/test_api_action_metadata.py": 22.35,
+  "tests/integration/test_api_action_responses.py": 30.31,
+  "tests/integration/test_api_action_timeout.py": 34.73,
+  "tests/integration/test_api_conditional_memory.py": 18.35,
+  "tests/integration/test_api_custom_services.py": 15.99,
+  "tests/integration/test_api_get_time_response_timezone.py": 24.21,
+  "tests/integration/test_api_homeassistant.py": 33.77,
+  "tests/integration/test_api_homeassistant_action_no_subscriber.py": 20.8,
+  "tests/integration/test_api_homeassistant_binary_sensor_initial_state.py": 23.55,
+  "tests/integration/test_api_list_entities_backpressure.py": 23.04,
+  "tests/integration/test_api_message_size_batching.py": 27.31,
+  "tests/integration/test_api_reboot_timeout.py": 29.32,
+  "tests/integration/test_api_string_lambda.py": 14.9,
+  "tests/integration/test_api_vv_logging.py": 26.25,
+  "tests/integration/test_api_zero_psk_provisioning.py": 38.19,
+  "tests/integration/test_areas_and_devices.py": 27.52,
+  "tests/integration/test_automation_wait_actions.py": 24.25,
+  "tests/integration/test_automations.py": 36.02,
+  "tests/integration/test_batch_delay_zero_rapid_transitions.py": 18.46,
+  "tests/integration/test_binary_sensor_autorepeat_filter.py": 17.47,
+  "tests/integration/test_binary_sensor_invalidate_state.py": 14.79,
+  "tests/integration/test_blocking_warning_log_time_not_charged_to_next_operation.py": 21.52,
+  "tests/integration/test_build_info.py": 21.42,
+  "tests/integration/test_camera_mock.py": 17.02,
+  "tests/integration/test_climate_control_action.py": 26.56,
+  "tests/integration/test_climate_custom_modes.py": 18.82,
+  "tests/integration/test_continuation_actions.py": 20.39,
+  "tests/integration/test_cover_control_action.py": 19.91,
+  "tests/integration/test_crc8_helper.py": 16.73,
+  "tests/integration/test_device_id_in_state.py": 58.41,
+  "tests/integration/test_duplicate_entities.py": 30.76,
+  "tests/integration/test_entity_icon.py": 25.34,
+  "tests/integration/test_fan_turn_on_action.py": 23.64,
+  "tests/integration/test_fnv1_hash_object_id.py": 25.44,
+  "tests/integration/test_fnv1a_hash.py": 20.85,
+  "tests/integration/test_gpio_expander_cache.py": 14.42,
+  "tests/integration/test_host_logger_thread_safety.py": 21.31,
+  "tests/integration/test_host_mode_basic.py": 2.65,
+  "tests/integration/test_host_mode_batch_delay.py": 22.21,
+  "tests/integration/test_host_mode_climate_basic_state.py": 27.12,
+  "tests/integration/test_host_mode_climate_control.py": 21.57,
+  "tests/integration/test_host_mode_empty_string_options.py": 27.17,
+  "tests/integration/test_host_mode_entity_fields.py": 30.1,
+  "tests/integration/test_host_mode_fan_preset.py": 17.55,
+  "tests/integration/test_host_mode_many_entities.py": 38.98,
+  "tests/integration/test_host_mode_many_entities_multiple_connections.py": 23.82,
+  "tests/integration/test_host_mode_noise_encryption.py": 39.84,
+  "tests/integration/test_host_mode_reconnect.py": 13.1,
+  "tests/integration/test_host_mode_sensor.py": 22.17,
+  "tests/integration/test_host_ota.py": 92.05,
+  "tests/integration/test_host_preferences.py": 20.29,
+  "tests/integration/test_host_preferences_suspend_resume.py": 15.02,
+  "tests/integration/test_improv_serial_uart.py": 30.15,
+  "tests/integration/test_large_message_batching.py": 25.84,
+  "tests/integration/test_legacy_area.py": 21.24,
+  "tests/integration/test_legacy_climate_compat.py": 17.34,
+  "tests/integration/test_legacy_fan_compat.py": 22.6,
+  "tests/integration/test_light_automations.py": 29.13,
+  "tests/integration/test_light_binary_effect_off_phase.py": 33.99,
+  "tests/integration/test_light_calls.py": 26.81,
+  "tests/integration/test_light_constant_brightness.py": 25.0,
+  "tests/integration/test_light_control_action.py": 25.57,
+  "tests/integration/test_light_dim_relative_action.py": 21.4,
+  "tests/integration/test_light_effect_zero_brightness.py": 19.65,
+  "tests/integration/test_light_initial_state.py": 17.58,
+  "tests/integration/test_light_toggle_action.py": 28.28,
+  "tests/integration/test_lock_automations.py": 23.3,
+  "tests/integration/test_logger_buffered_recursion_guard.py": 22.96,
+  "tests/integration/test_loop_disable_enable.py": 16.18,
+  "tests/integration/test_loop_interval_decoupling.py": 25.19,
+  "tests/integration/test_loop_interval_default_not_pulled_forward.py": 20.59,
+  "tests/integration/test_lvgl_headless_render.py": 87.78,
+  "tests/integration/test_micros_to_millis.py": 18.73,
+  "tests/integration/test_multi_click_trigger.py": 24.2,
+  "tests/integration/test_multi_device_preferences.py": 20.52,
+  "tests/integration/test_noise_encryption_key_protection.py": 19.1,
+  "tests/integration/test_object_id_api_verification.py": 26.24,
+  "tests/integration/test_object_id_friendly_name_no_mac_suffix.py": 14.88,
+  "tests/integration/test_object_id_no_friendly_name.py": 61.27,
+  "tests/integration/test_online_image_auto_detects_image_bmp_mime.py": 82.32,
+  "tests/integration/test_online_image_auto_detects_redirected_image_bmp_mime.py": 46.03,
+  "tests/integration/test_online_image_bmp.py": 34.21,
+  "tests/integration/test_oversized_payloads.py": 62.75,
+  "tests/integration/test_preference_key_stability.py": 26.8,
+  "tests/integration/test_runtime_stats.py": 28.26,
+  "tests/integration/test_safe_mode_loop_runs.py": 18.14,
+  "tests/integration/test_scheduler_blocking_warning.py": 28.7,
+  "tests/integration/test_scheduler_bulk_cleanup.py": 20.73,
+  "tests/integration/test_scheduler_defer_cancel.py": 22.99,
+  "tests/integration/test_scheduler_defer_cancel_regular.py": 21.97,
+  "tests/integration/test_scheduler_defer_fifo_simple.py": 24.15,
+  "tests/integration/test_scheduler_defer_stress.py": 23.11,
+  "tests/integration/test_scheduler_heap_stress.py": 20.2,
+  "tests/integration/test_scheduler_internal_id_no_collision.py": 23.75,
+  "tests/integration/test_scheduler_interval_reschedule.py": 15.32,
+  "tests/integration/test_scheduler_interval_zero_coerced.py": 20.1,
+  "tests/integration/test_scheduler_null_name.py": 17.43,
+  "tests/integration/test_scheduler_numeric_id_test.py": 25.51,
+  "tests/integration/test_scheduler_pool.py": 24.22,
+  "tests/integration/test_scheduler_rapid_cancellation.py": 24.01,
+  "tests/integration/test_scheduler_recursive_timeout.py": 22.94,
+  "tests/integration/test_scheduler_removed_item_race.py": 23.07,
+  "tests/integration/test_scheduler_self_keyed.py": 18.43,
+  "tests/integration/test_scheduler_simultaneous_callbacks.py": 21.99,
+  "tests/integration/test_scheduler_string_test.py": 17.27,
+  "tests/integration/test_script_array_params.py": 4.59,
+  "tests/integration/test_script_delay_params.py": 22.46,
+  "tests/integration/test_script_queued.py": 25.24,
+  "tests/integration/test_script_queued_idle_loop.py": 5.04,
+  "tests/integration/test_script_wait_on_boot.py": 21.77,
+  "tests/integration/test_sdl_headless_screenshot.py": 19.23,
+  "tests/integration/test_select_stringref_trigger.py": 19.31,
+  "tests/integration/test_sensor_filters_delta.py": 25.92,
+  "tests/integration/test_sensor_filters_ring_buffer.py": 22.39,
+  "tests/integration/test_sensor_filters_sliding_window.py": 57.93,
+  "tests/integration/test_sensor_filters_value_list.py": 20.32,
+  "tests/integration/test_sensor_timeout_filter.py": 25.35,
+  "tests/integration/test_snapshot_display.py": 19.7,
+  "tests/integration/test_socket_wake_gate_tcp.py": 14.5,
+  "tests/integration/test_status_flags.py": 33.83,
+  "tests/integration/test_strftime_to.py": 17.64,
+  "tests/integration/test_syslog.py": 24.49,
+  "tests/integration/test_template_alarm_control_panel_many_sensors.py": 24.81,
+  "tests/integration/test_template_climate_basic.py": 15.28,
+  "tests/integration/test_template_climate_custom_modes.py": 25.07,
+  "tests/integration/test_template_climate_nonoptimistic.py": 24.25,
+  "tests/integration/test_template_climate_on_control_ordering.py": 24.09,
+  "tests/integration/test_template_climate_publish_all_fields.py": 17.78,
+  "tests/integration/test_template_climate_sensor_push.py": 17.42,
+  "tests/integration/test_template_climate_set_actions.py": 23.63,
+  "tests/integration/test_template_climate_two_point_temperature.py": 25.19,
+  "tests/integration/test_template_text_save.py": 17.88,
+  "tests/integration/test_text_command.py": 22.71,
+  "tests/integration/test_text_sensor_raw_state.py": 25.17,
+  "tests/integration/test_uart_mock_ld2410.py": 58.15,
+  "tests/integration/test_uart_mock_ld2412.py": 61.14,
+  "tests/integration/test_uart_mock_ld2420.py": 33.87,
+  "tests/integration/test_uart_mock_ld2450.py": 26.06,
+  "tests/integration/test_uart_mock_modbus.py": 391.79,
+  "tests/integration/test_udp.py": 7.38,
+  "tests/integration/test_use_address_runtime.py": 24.09,
+  "tests/integration/test_valve_control_action.py": 23.22,
+  "tests/integration/test_varint_five_byte_device_id.py": 17.93,
+  "tests/integration/test_wait_until_mid_loop_timing.py": 22.26,
+  "tests/integration/test_wait_until_on_boot.py": 17.46,
+  "tests/integration/test_wait_until_ordering.py": 11.89,
+  "tests/integration/test_wait_until_reentrant_restart.py": 22.88,
+  "tests/integration/test_wake_loop_forces_phase_b.py": 16.6,
+  "tests/integration/test_water_heater_template.py": 19.66
 }

tests/integration/test_api_zero_psk_provisioning.py

@@ -24,7 +24,6 @@ from .types import (
     RunCompiledFunction,
 )
 
-pytestmark = pytest.mark.usefixtures("isolated_preferences")
 NEW_KEY = PROVISIONING_PSK
 
 

tests/integration/test_host_preferences_suspend_resume.py

@@ -41,15 +41,6 @@ async def _poll_until_exists(path: Path) -> None:
         await asyncio.sleep(0.05)
 
 
-@pytest.fixture(autouse=True)
-def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path) -> Path:
-    """Keep host preferences per-test so this test never touches the real
-    ~/.esphome/prefs and never races other tests over ESPHOME_PREFDIR."""
-    prefdir = tmp_path / "prefs"
-    monkeypatch.setenv("ESPHOME_PREFDIR", str(prefdir))
-    return prefdir / f"{DEVICE_NAME}.prefs"
-
-
 @pytest.mark.asyncio
 async def test_host_preferences_suspend_resume(
     yaml_config: str,
@@ -58,7 +49,7 @@ async def test_host_preferences_suspend_resume(
     isolated_preferences: Path,
 ) -> None:
     """Test that a running syncer flushes, a suspended one doesn't, and resume restores flushing."""
-    pref_file = isolated_preferences
+    pref_file = isolated_preferences / f"{DEVICE_NAME}.prefs"
 
     loop = asyncio.get_running_loop()
     saved_in_memory = loop.create_future()

tests/integration/test_light_initial_state.py

@@ -11,14 +11,6 @@ from .state_utils import InitialStateHelper, require_entity
 from .types import APIClientConnectedFactory, RunCompiledFunction
 
 
-@pytest.fixture(autouse=True)
-def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
-    """Keep host preferences per-test so RESTORE_AND_ON never loads a stale value left
-    behind by a previous run (host preferences otherwise persist to ~/.esphome/prefs,
-    keyed only by device name)."""
-    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))
-
-
 @pytest.mark.asyncio
 async def test_light_initial_state(
     yaml_config: str,

tests/integration/test_uart_mock_modbus.py

@@ -173,6 +173,7 @@ async def test_uart_mock_modbus_no_threshold(
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_server_injected")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_server(
     yaml_config: str,
@@ -203,6 +204,7 @@ async def test_uart_mock_modbus_server(
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_server_injected")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_server_read_write(
     yaml_config: str,
@@ -231,8 +233,8 @@ async def test_uart_mock_modbus_server_read_write(
             "rw_write_1": 4660,  # 0x1234 written to reg 0x0001
             "rw_read_1": 4660,  # reg 0x0001 reads back the just-written value
             "rw_read_2": 170,  # 0x00AA read from reg 0x0002 in the same request
-            "rw_write_3": 22136,  # 0x5678 written to reg 0x0003
-            "rw_read_3": 22136,  # reg 0x0003 reads back the just-written value
+            "rw_write_3": 22136,  # 0x5678 written to reg 0x0006
+            "rw_read_3": 22136,  # reg 0x0006 reads back the just-written value
         }
     )
 
@@ -241,7 +243,8 @@ async def test_uart_mock_modbus_server_read_write(
         api_client_connected() as client,
     ):
         await tracker.setup_and_start_scenario(client)
-        await tracker.await_all(futures)
+        # The FC 0x17 injections fire last, behind four earlier 100ms delays
+        await tracker.await_all(futures, timeout=4.0)
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
@@ -296,6 +299,7 @@ async def test_uart_mock_modbus_server_read_write_invalid(
     )
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_mesh")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_server_controller(
     yaml_config: str,
@@ -485,6 +489,7 @@ async def test_uart_mock_modbus_server_controller_bits(
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_mesh")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_server_controller_multiple(
     yaml_config: str,
@@ -495,7 +500,7 @@ async def test_uart_mock_modbus_server_controller_multiple(
 
     line_callback, error_log_lines, warning_log_lines = _make_modbus_line_callback()
 
-    expected_values = {"reg_u_word": 919, "reg_u_word_2": 929}
+    expected_values = {"multi_reg_a": 919, "multi_reg_b": 929}
     tracker = SensorTracker(list(expected_values.keys()))
     futures = tracker.expect_all(expected_values)
 
@@ -706,6 +711,7 @@ async def test_uart_mock_modbus_shared_address(
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_loopback")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_custom_pdu(
     yaml_config: str,
@@ -932,6 +938,7 @@ async def test_uart_mock_modbus_broadcast_write(
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_mesh")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_client_read_write(
     yaml_config: str,
@@ -947,9 +954,7 @@ async def test_uart_mock_modbus_client_read_write(
     """
     line_callback, error_log_lines, warning_log_lines = _make_modbus_line_callback()
 
-    tracker = SensorTracker(
-        ["srv_write_1", "srv_read_1", "client_read_0", "client_read_1"]
-    )
+    tracker = SensorTracker(["srv_write_1", "client_read_0", "client_read_1"])
     futures = tracker.expect_all(
         {
             "srv_write_1": 4660,  # server wrote 0x1234 to reg 0x0001
@@ -967,6 +972,7 @@ async def test_uart_mock_modbus_client_read_write(
         _assert_no_modbus_errors(error_log_lines, warning_log_lines)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_loopback")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_register_offset(
     yaml_config: str,
@@ -1022,6 +1028,7 @@ async def test_uart_mock_modbus_register_offset(
         )
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_loopback")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_lambda_write(
     yaml_config: str,
@@ -1058,6 +1065,7 @@ async def test_uart_mock_modbus_lambda_write(
         await tracker.await_change(wrote_30, "reg_30", timeout=4.0)
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_loopback")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_lambda_invert(
     yaml_config: str,
@@ -1113,6 +1121,7 @@ async def test_uart_mock_modbus_lambda_invert(
         )
 
 
+@pytest.mark.shared_yaml("uart_mock_modbus_loopback")
 @pytest.mark.asyncio
 async def test_uart_mock_modbus_deprecated_write_buffer(
     yaml_config: str,

tests/script/test_helpers.py

@@ -2122,6 +2122,34 @@ def test_get_cpp_changed_components_independent_of_cwd(
     ) == ["time"]
 
 
+def test_fixture_map_includes_shared_yaml_markers() -> None:
+    """Fixtures named only by shared_yaml markers must map to their test file."""
+    helpers.get_fixture_to_test_files.cache_clear()
+    mapping = helpers.get_fixture_to_test_files()
+    for fixture in (
+        "uart_mock_modbus_loopback",
+        "uart_mock_modbus_mesh",
+        "uart_mock_modbus_server_injected",
+    ):
+        assert mapping[fixture] == frozenset(
+            {"tests/integration/test_uart_mock_modbus.py"}
+        )
+
+
+def test_no_orphan_integration_fixtures() -> None:
+    """Every fixture must reach CI test selection; an orphan selects nothing."""
+    helpers.get_fixture_to_test_files.cache_clear()
+    mapping = helpers.get_fixture_to_test_files()
+    fixtures_dir = (Path(__file__).parent.parent / "integration" / "fixtures").resolve()
+    fixtures = list(fixtures_dir.glob("*.yaml"))
+    assert fixtures, f"no fixtures found under {fixtures_dir}"
+    # cache_init is covered via INTEGRATION_TESTS_TRIGGER_FILES instead
+    orphans = [
+        f.stem for f in fixtures if f.stem != "cache_init" and f.stem not in mapping
+    ]
+    assert not orphans, f"fixtures invisible to CI test selection: {orphans}"
+
+
 def test_lpt_partition_balances_skewed_weights() -> None:
     """Heavy items spread across groups instead of clustering."""
     items = [f"i{n}" for n in range(6)]

tests/script/test_sync_dependency_versions.py

@@ -0,0 +1,219 @@
+"""Unit tests for script/sync_dependency_versions.py."""
+
+from pathlib import Path
+import subprocess
+import sys
+
+import pytest
+import yamlrocks
+
+sys.path.insert(0, str((Path(__file__).parent / ".." / ".." / "script").resolve()))
+
+import sync_dependency_versions as sync_mod  # noqa: E402
+
+PRECOMMIT = """\
+# See https://pre-commit.com for more information
+repos:
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    # Ruff version.
+    rev: v0.1.0
+    hooks:
+      - id: ruff
+  - repo: https://github.com/PyCQA/flake8
+    rev: 7.0.0
+    hooks:
+      - id: flake8
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v3.0.0
+    hooks:
+      - id: pyupgrade
+  - repo: https://github.com/pre-commit/mirrors-clang-format
+    rev: v13.0.1
+    hooks:
+      - id: clang-format
+  - repo: https://github.com/adrienverge/yamllint.git
+    rev: v1.0.0
+    hooks:
+      - id: yamllint
+  - repo: local
+    hooks:
+      - id: pylint
+"""
+
+REQ_TEST = """\
+pylint==4.0.8
+flake8==7.1.0
+ruff==0.2.0  # comment
+pyupgrade==3.0.0
+"""
+
+REQ_DEV = """\
+clang-format==13.0.1
+yamllint==1.0.0
+"""
+
+RUFF_REPO = "https://github.com/astral-sh/ruff-pre-commit"
+DUPLICATE_RUFF_BLOCK = f"  - repo: {RUFF_REPO}\n    rev: v0.3.0\n    hooks: []\n"
+
+EXPECTED_DRIFT = ["ruff: 0.1.0 -> 0.2.0", "flake8: 7.0.0 -> 7.1.0"]
+EXPECTED_PRECOMMIT = PRECOMMIT.replace("rev: v0.1.0", "rev: v0.2.0").replace(
+    "rev: 7.0.0", "rev: 7.1.0"
+)
+
+
+@pytest.fixture
+def root(tmp_path: Path) -> Path:
+    """A fake checkout where ruff (v-prefixed) and flake8 (bare) have drifted."""
+    (tmp_path / ".pre-commit-config.yaml").write_text(PRECOMMIT)
+    (tmp_path / "requirements_test.txt").write_text(REQ_TEST)
+    (tmp_path / "requirements_dev.txt").write_text(REQ_DEV)
+    return tmp_path
+
+
+def _load(text: str) -> object:
+    return yamlrocks.loads(text.encode(), option=yamlrocks.OPT_ROUND_TRIP)
+
+
+@pytest.mark.parametrize(
+    ("requirements", "expected"),
+    [
+        ("prek==0.5.1  # comment\n", "0.5.1"),
+        ("Prek==0.5.1\n", "0.5.1"),
+        ("other==1.0\nprek==0.5.1\n", "0.5.1"),
+        ("prek>=0.5.1\n", None),
+        ("prek-extra==0.5.1\n", None),
+        ("", None),
+    ],
+)
+def test_read_requirement_version(requirements: str, expected: str | None) -> None:
+    assert sync_mod.read_requirement_version(requirements, "prek") == expected
+
+
+def test_find_repo_entry() -> None:
+    entry = sync_mod.find_repo_entry(_load(PRECOMMIT), RUFF_REPO)
+    assert entry["rev"] == "v0.1.0"
+
+
+@pytest.mark.parametrize(
+    ("text", "message"),
+    [
+        ("hooks: []\n", "missing key 'repos'"),
+        ("repos:\n  - rev: 1.0.0\n", "missing key 'repo'"),
+        (PRECOMMIT + DUPLICATE_RUFF_BLOCK, "found 2"),
+        ("repos:\n  - repo: other\n    rev: 1.0.0\n", "found 0"),
+    ],
+)
+def test_find_repo_entry_errors(text: str, message: str) -> None:
+    with pytest.raises(sync_mod.SyncError, match=message):
+        sync_mod.find_repo_entry(_load(text), RUFF_REPO)
+
+
+@pytest.mark.parametrize(
+    ("rev", "expected"),
+    [("v0.1.0", ("v", "0.1.0")), ("7.0.0", ("", "7.0.0")), ("'1.0'", ("", "1.0"))],
+)
+def test_current_rev(rev: str, expected: tuple[str, str]) -> None:
+    doc = _load(f"repos:\n  - repo: {RUFF_REPO}\n    rev: {rev}\n")
+    assert sync_mod.current_rev(doc["repos"][0], RUFF_REPO) == expected
+
+
+@pytest.mark.parametrize(
+    ("block", "message"),
+    [("    hooks: []\n", "has no rev"), ("    rev: 1.0\n", "not a string: 1.0")],
+)
+def test_current_rev_errors(block: str, message: str) -> None:
+    doc = _load(f"repos:\n  - repo: {RUFF_REPO}\n{block}")
+    with pytest.raises(sync_mod.SyncError, match=message):
+        sync_mod.current_rev(doc["repos"][0], RUFF_REPO)
+
+
+def test_sync_reports_without_writing(root: Path) -> None:
+    assert sync_mod.sync(root, write=False) == EXPECTED_DRIFT
+    assert (root / ".pre-commit-config.yaml").read_text() == PRECOMMIT
+
+
+def test_sync_writes_keeps_layout_and_is_idempotent(root: Path) -> None:
+    assert sync_mod.sync(root, write=True) == EXPECTED_DRIFT
+    assert (root / ".pre-commit-config.yaml").read_text() == EXPECTED_PRECOMMIT
+    assert sync_mod.sync(root, write=True) == []
+
+
+def test_sync_does_not_touch_a_config_that_matches(root: Path) -> None:
+    (root / ".pre-commit-config.yaml").write_text(EXPECTED_PRECOMMIT)
+    before = (root / ".pre-commit-config.yaml").stat().st_mtime_ns
+    assert sync_mod.sync(root, write=True) == []
+    assert (root / ".pre-commit-config.yaml").stat().st_mtime_ns == before
+
+
+def test_sync_missing_requirement_pin(root: Path) -> None:
+    (root / "requirements_dev.txt").write_text("")
+    with pytest.raises(sync_mod.SyncError, match="no 'clang-format==' pin"):
+        sync_mod.sync(root, write=True)
+
+
+def test_sync_propagates_config_errors(root: Path) -> None:
+    (root / ".pre-commit-config.yaml").write_text(PRECOMMIT + DUPLICATE_RUFF_BLOCK)
+    with pytest.raises(sync_mod.SyncError, match="found 2"):
+        sync_mod.sync(root, write=True)
+
+
+def test_main_check_reports_drift(
+    root: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    assert sync_mod.main(["--check", "--root", str(root)]) == 1
+    assert capsys.readouterr().out.splitlines() == EXPECTED_DRIFT
+    assert (root / ".pre-commit-config.yaml").read_text() == PRECOMMIT
+
+
+def test_main_writes_then_check_is_clean(
+    root: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    assert sync_mod.main(["--root", str(root)]) == 0
+    assert capsys.readouterr().out.splitlines() == EXPECTED_DRIFT
+    assert sync_mod.main(["--check", "--root", str(root)]) == 0
+    assert capsys.readouterr().out == ""
+
+
+def test_main_reports_sync_error(
+    root: Path, capsys: pytest.CaptureFixture[str]
+) -> None:
+    (root / "requirements_dev.txt").write_text("")
+    assert sync_mod.main(["--root", str(root)]) == 1
+    assert (
+        "error: requirements_dev.txt: no 'clang-format==' pin"
+        in capsys.readouterr().err
+    )
+
+
+def test_main_defaults_to_repo_root(monkeypatch: pytest.MonkeyPatch) -> None:
+    seen: dict[str, object] = {}
+
+    def fake_sync(root: Path, *, write: bool) -> list[str]:
+        seen["root"] = root
+        seen["write"] = write
+        return []
+
+    monkeypatch.setattr(sync_mod, "sync", fake_sync)
+    assert sync_mod.main([]) == 0
+    assert seen == {"root": sync_mod.REPO_ROOT, "write": True}
+
+
+def test_repository_is_in_sync() -> None:
+    """The real checkout must match; a failure here means a rev has drifted.
+
+    Also proves every SYNC_TARGETS entry still resolves in the real files.
+    """
+    assert sync_mod.sync(sync_mod.REPO_ROOT, write=False) == []
+
+
+def test_cli_entry_point(root: Path) -> None:
+    """Run the script the way the workflow does, as a subprocess."""
+    script = Path(sync_mod.__file__)
+    result = subprocess.run(
+        [sys.executable, str(script), "--check", "--root", str(root)],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+    assert result.returncode == 1
+    assert result.stdout.splitlines() == EXPECTED_DRIFT