[api] Cover repeated and sub message fields in the decode case tests

Repeated fields encode their elements through one encode_element() hook instead of two
isinstance ladders, the fixed32 precomputed tag path owns its own guard, the generated
switches drop the dead default case, StringRef takes the byte pointer directly, the
three hand written tag expressions in proto.h go through proto_tag(), and stale comments
about the previous decode design go. The compiled functions are unchanged.

.github/workflows/ci.yml

@@ -374,8 +374,9 @@ jobs:
       - name: Install apt packages (cached)
         # ccache speeds up the host compiles. A cache hit never touches apt
         # (mirror outages cannot hang the job); the timeout bounds the cold
-        # path. Packages and version must match seed-apt-cache exactly;
-        # libsdl2-dev is unused here and carried only for cache-key parity.
+        # path. Packages and version must match seed-apt-cache exactly.
+        # libsdl2-dev is needed by the headless display tests, which capture
+        # screenshots.
         timeout-minutes: 10
         uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
         with:
@@ -438,6 +439,16 @@ jobs:
           echo "Bucket ${{ matrix.bucket.name }}: running ${#test_files[@]} integration tests"
           pytest -vv --no-cov --tb=native --durations=30 -n auto --dist worksteal \
             --junitxml=junit-integration.xml "${test_files[@]}"
+      - name: Upload test artifacts
+        # Tests that compare rendered output write the image they actually got here, so a
+        # failure can be looked at without reproducing the whole build locally.
+        if: failure()
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: integration-test-artifacts-${{ matrix.bucket.name }}
+          path: test_artifacts/
+          if-no-files-found: ignore
+          retention-days: 7
       - name: Upload junit timings
         # Consumed by sync-integration-durations.yml through
         # script/update_integration_test_durations.py; only full matrix dev

.gitignore

@@ -137,6 +137,8 @@ config/
 !tests/component_tests/**/config/
 tests/build/
 tests/.esphome/
+# Output kept by failing tests for inspection; uploaded by CI
+test_artifacts/
 /.temp-clang-tidy.cpp
 /.temp/
 .pio/

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.

CODEOWNERS

@@ -496,6 +496,7 @@ esphome/components/sm2335/* @Cossid
 esphome/components/sml/* @alengwenus
 esphome/components/smt100/* @piechade
 esphome/components/sn74hc165/* @jesserockz
+esphome/components/snapshot/* @clydebarrow
 esphome/components/socket/* @esphome/core
 esphome/components/sonoff_d1/* @anatoly-savchenkov
 esphome/components/sound_level/* @kahrendt

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         = 2026.9.0-dev
+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

THREAT_MODEL.md

@@ -125,30 +125,47 @@ design is optimal or that it will not change.
 ## OTA update encryption
 
 The `esphome` OTA platform optionally encrypts updates with the same Noise
-`NNpsk0` pattern the native API uses; one key protects the device. With an
-`encryption:` block configured the guarantees are: the firmware image is
-confidential in transit, the uploader is authenticated by the pre-shared key,
-and the plaintext negotiation preceding the handshake is bound into the
-handshake prologue, so stripping or tampering with it fails the first MAC.
-Both ends fail closed with no override: a device built with a key refuses
+`NNpsk0` pattern the native API uses; one key protects the device. A device
+whose `api:` block has an encryption key, static in the YAML or provisioned at
+runtime, compiles in the transport and offers it on every OTA connection once
+it holds a key, so an uploader presenting that key gets the guarantees below
+even without an `ota: encryption:` block; only that block makes the device
+require encryption. The guarantees are: the firmware image is confidential in
+transit, the uploader is authenticated by the pre-shared key, and the plaintext
+negotiation preceding the handshake is bound into the handshake prologue, so
+stripping or tampering with it fails the first MAC. With `ota: encryption:`
+configured both ends fail closed with no override: the device refuses
 plaintext uploads, and the CLI refuses to send plaintext when a key is
-configured.
+configured. Without that block the CLI tries a static api key when the device
+offers and, until 2027.3.0, falls back to plaintext with a warning when the
+offer is missing or the handshake fails; a runtime provisioned key never
+reaches the CLI, so those uploads stay plaintext.
 
-Defeating any of that without the key is in scope: a keyed device accepting a
-plaintext or downgraded upload, getting past the MAC, or recovering image
-contents from captured traffic.
+Defeating any of that without the key is in scope: a device that requires
+encryption accepting a plaintext or downgraded upload, getting past the MAC,
+or recovering image contents from captured traffic.
 
 The following are **not** vulnerabilities, by design:
 
-- Plaintext OTA on a device with no `encryption:` block. That is the
-  documented default, authenticated (if at all) by the OTA password.
-- The enablement window: turning encryption on takes one last upload of the
-  encryption-enabled firmware over the existing plaintext channel, with the
-  pre-existing plaintext exposure.
-- The web OTA `/update` endpoint alongside encryption. The `web_server`
-  component keeps it always reachable, and `captive_portal:` auto-loads it
-  for the fallback AP window; validation warns about both combinations, and
-  the operator keeps the recovery path.
+- Plaintext OTA on a device with no `ota: encryption:` block, including one
+  that offers encryption because it has an api key. That is the documented
+  default, authenticated (if at all) by the OTA password. An uploader that
+  takes the offer skips the password; the key authenticates it. With a
+  runtime provisioned key and no `provisioning:` window, whoever provisions
+  the key gains that upload path too; validation warns about the pair.
+- The CLI plaintext fallback until 2027.3.0: without `ota: encryption:` an
+  active attacker who strips the offer or breaks the handshake can make a
+  keyed CLI upload plaintext, with the pre-existing plaintext exposure. A
+  device that requires encryption still refuses that upload.
+- The enablement window: firmware built with a static api key already offers
+  encryption, so turning on `ota: encryption:` is itself an encrypted upload.
+  Older firmware needs one last plaintext upload of an offering build, with
+  the pre-existing plaintext exposure.
+- The web OTA `/update` endpoint alongside encryption. With the `web_server`
+  or `prometheus` component the shared listener is always up, so the endpoint
+  stays reachable and validation warns about that combination;
+  `captive_portal:` alone brings the listener up only for the fallback AP
+  window, which is the intended recovery path, so that is not warned about.
 - CLI retry behavior on transport or MAC failures; every attempt renegotiates
   a fresh handshake with fresh ephemerals, so retrying does not weaken
   authentication.

docker/Dockerfile

@@ -22,7 +22,7 @@ RUN \
     -r /requirements.txt
 
 # Install the ESPHome Device Builder dashboard.
-RUN uv pip install --no-cache-dir esphome-device-builder==1.13.1
+RUN uv pip install --no-cache-dir esphome-device-builder==1.14.4
 
 RUN \
     platformio settings set enable_telemetry No \

esphome/__main__.py

@@ -1335,12 +1335,14 @@ def _upload_via_native_api(
             break
 
     from esphome import espota2
+    from esphome.components.noise import static_encryption_key
 
     remote_port = int(ota_conf[CONF_PORT])
     password = ota_conf.get(CONF_PASSWORD)
     # Fail closed: an encryption block whose key did not resolve must never
     # fall back to a plaintext upload
     noise_psk = None
+    plaintext_fallback = False
     if (encryption_conf := ota_conf.get(CONF_ENCRYPTION)) is not None:
         noise_psk = encryption_conf.get(CONF_KEY)
         if not noise_psk:
@@ -1351,6 +1353,10 @@ def _upload_via_native_api(
         # Ensure the key is a string, as required by the underlying OTA implementation.
         # It arrives here as a SensitiveStr which aioesphomeapi rejects.
         noise_psk = str(noise_psk)
+    elif api_key := static_encryption_key(config.get(CONF_API) or {}):
+        # Remove before 2027.3.0: the api key is tried, falling back to plaintext
+        noise_psk = str(api_key)
+        plaintext_fallback = True
 
     def check_partition_access(option_string: str) -> None:
         if not ota_conf.get("allow_partition_access"):
@@ -1382,7 +1388,13 @@ def _upload_via_native_api(
         _validate_bootloader_binary(binary)
 
     return espota2.run_ota(
-        network_devices, remote_port, password, binary, ota_type, noise_psk
+        network_devices,
+        remote_port,
+        password,
+        binary,
+        ota_type,
+        noise_psk,
+        plaintext_fallback=plaintext_fallback,
     )
 
 

esphome/arduino8266/framework.py

@@ -44,8 +44,7 @@ def get_arduino8266_tools_path() -> Path:
     return tools_cache_path(*ARDUINO8266_TOOLS_CACHE)
 
 
-# 3.1.1 rather than 3.1.0: the registry has no package for 3.1.0, and the
-# encoder below cannot name 3.0.0/3.0.1 either (see its docstring)
+# 3.1.1 rather than 3.1.0: the registry has no packages for 3.0.0, 3.0.1 or 3.1.0
 MIN_FRAMEWORK_VERSION = Version(3, 1, 1)
 
 
@@ -53,20 +52,16 @@ def framework_package_version(ver: Version) -> str:
     """Map an Arduino core version to its registry package version (3.1.2 ->
     3.30102.0; the leading 3 is the package major).
 
-    Exact registry names only for cores > 2.6.2 and >= 3.0.2; callers floor
-    at MIN_FRAMEWORK_VERSION.
+    Exact registry names for 3.x cores; callers floor at MIN_FRAMEWORK_VERSION.
     """
     if ver.major > 3:
         raise EsphomeError(
             f"Arduino core {ver} is not supported yet; "
             "the newest known core series is 3.x"
         )
-    if ver <= Version(2, 6, 2):
-        # Cores <= 2.6.2 use the older 1.x/2.x package-major encodings (same
-        # boundary as _format_framework_arduino_version's era guard)
+    if ver.major < 3:
         raise EsphomeError(
-            f"Arduino core {ver} uses an older package encoding than this "
-            "helper implements (newer than 2.6.2)"
+            f"Arduino core {ver} is not supported; ESPHome requires core 3.x"
         )
     return f"3.{ver.major}{ver.minor:02d}{ver.patch:02d}.0"
 

esphome/components/api/__init__.py

@@ -14,6 +14,7 @@ from esphome.components.noise import (  # noqa: F401
     ENCRYPTION_SCHEMA,
     decode_encryption_key,
     encryption_schema,
+    new_psk_progmem,
     validate_encryption_key,
 )
 from esphome.config_helpers import filter_source_files_from_defines, get_logger_level
@@ -589,8 +590,7 @@ async def to_code(config: ConfigType) -> None:
 
     if (encryption_config := config.get(CONF_ENCRYPTION, None)) is not None:
         if key := encryption_config.get(CONF_KEY):
-            decoded = decode_encryption_key(key)
-            cg.add(var.set_noise_psk(list(decoded)))
+            cg.add(var.set_noise_psk(new_psk_progmem(config[CONF_ID], key)))
             cg.add_define("USE_API_NOISE_PSK_FROM_YAML")
         else:
             # No key provided, but encryption desired

esphome/components/api/api_connection.cpp

@@ -2161,7 +2161,10 @@ void APIConnection::on_homeassistant_action_response(const HomeassistantActionRe
 bool APIConnection::send_noise_encryption_set_key_response_(const NoiseEncryptionSetKeyRequest &msg) {
   NoiseEncryptionSetKeyResponse resp;
   resp.success = false;
-
+#ifdef USE_API_NOISE_PSK_FROM_YAML
+  // A yaml key cannot be changed at runtime, so no decode or save path is built
+  ESP_LOGW(TAG, "Key set in YAML");
+#else
 #ifdef USE_PROVISIONING
   // Refuse to set a key once the provisioning window has closed (defense in depth;
   // such connections are already rejected at hello).
@@ -2196,6 +2199,7 @@ bool APIConnection::send_noise_encryption_set_key_response_(const NoiseEncryptio
     }
 #endif
   }
+#endif  // USE_API_NOISE_PSK_FROM_YAML
 
   return this->send_message(resp);
 }

esphome/components/api/api_connection.h

@@ -345,11 +345,7 @@ class APIConnection final : public APIServerConnectionBase {
   /// Returns false as soon as the TCP buffer is full. Marked nodiscard so we
   /// have no silent failures: every caller must handle (or log) a refusal.
   template<typename T> [[nodiscard]] bool send_message(const T &msg) {
-    if constexpr (T::ESTIMATED_SIZE == 0) {
-      return this->send_message_(0, T::MESSAGE_TYPE, &encode_msg_noop, &msg);
-    } else {
-      return this->send_message_(msg.calculate_size(), T::MESSAGE_TYPE, &proto_encode_msg<T>, &msg);
-    }
+    return this->send_message_(T::calc_size_msg(&msg), T::MESSAGE_TYPE, &T::encode_msg, &msg);
   }
 
   /// Clear the shared write buffer and reserve space for the first message.
@@ -405,16 +401,6 @@ class APIConnection final : public APIServerConnectionBase {
   void process_state_subscriptions_();
 #endif
 
-  // Size thunk — converts void* back to concrete type for direct calculate_size() call
-  template<typename T> static uint32_t calc_size(const void *msg) {
-    return static_cast<const T *>(msg)->calculate_size();
-  }
-
-  // Shared no-op encode thunk for empty messages (ESTIMATED_SIZE == 0)
-  static uint8_t *encode_msg_noop(const void *, ProtoWriteBuffer &buf PROTO_ENCODE_DEBUG_PARAM) {
-    return buf.get_pos();
-  }
-
   // Non-template buffer management for send_message
   bool send_message_(uint32_t payload_size, uint16_t message_type, MessageEncodeFn encode_fn, const void *msg);
 
@@ -433,11 +419,7 @@ class APIConnection final : public APIServerConnectionBase {
   // Hot paths (state/info) go through fill_and_encode_entity_state/info instead.
   // batch_message_type_ is already set by dispatch_message_ before reaching here.
   template<typename T> static uint16_t encode_message_to_buffer(T &msg, APIConnection *conn, uint32_t remaining_size) {
-    if constexpr (T::ESTIMATED_SIZE == 0) {
-      return encode_to_buffer_slow(0, &encode_msg_noop, &msg, conn, remaining_size);
-    } else {
-      return encode_to_buffer_slow(msg.calculate_size(), &proto_encode_msg<T>, &msg, conn, remaining_size);
-    }
+    return encode_to_buffer_slow(T::calc_size_msg(&msg), &T::encode_msg, &msg, conn, remaining_size);
   }
 
   // Non-template core — fills state fields and encodes
@@ -449,7 +431,7 @@ class APIConnection final : public APIServerConnectionBase {
   template<typename T>
   static uint16_t fill_and_encode_entity_state(EntityBase *entity, T &msg, APIConnection *conn,
                                                uint32_t remaining_size) {
-    return fill_and_encode_entity_state(entity, msg, &calc_size<T>, &proto_encode_msg<T>, conn, remaining_size);
+    return fill_and_encode_entity_state(entity, msg, &T::calc_size_msg, &T::encode_msg, conn, remaining_size);
   }
 
   // Non-template core — fills info fields, allocates buffers, and encodes
@@ -461,7 +443,7 @@ class APIConnection final : public APIServerConnectionBase {
   template<typename T>
   static uint16_t fill_and_encode_entity_info(EntityBase *entity, T &msg, APIConnection *conn,
                                               uint32_t remaining_size) {
-    return fill_and_encode_entity_info(entity, msg, &calc_size<T>, &proto_encode_msg<T>, conn, remaining_size);
+    return fill_and_encode_entity_info(entity, msg, &T::calc_size_msg, &T::encode_msg, conn, remaining_size);
   }
 
   // Non-template core — fills device_class, then delegates to fill_and_encode_entity_info
@@ -475,8 +457,8 @@ class APIConnection final : public APIServerConnectionBase {
   static uint16_t fill_and_encode_entity_info_with_device_class(EntityBase *entity, T &msg,
                                                                 StringRef &device_class_field, APIConnection *conn,
                                                                 uint32_t remaining_size) {
-    return fill_and_encode_entity_info_with_device_class(entity, msg, device_class_field, &calc_size<T>,
-                                                         &proto_encode_msg<T>, conn, remaining_size);
+    return fill_and_encode_entity_info_with_device_class(entity, msg, device_class_field, &T::calc_size_msg,
+                                                         &T::encode_msg, conn, remaining_size);
   }
 
 #ifdef USE_VOICE_ASSISTANT

esphome/components/api/api_frame_helper_noise.cpp

@@ -548,7 +548,7 @@ APIError APINoiseFrameHelper::write_frame_(const uint8_t *data, uint16_t len) {
  * @return 0 on success, -1 on error (check errno)
  */
 APIError APINoiseFrameHelper::init_handshake_() {
-  int err = this->handshake_.init(this->ctx_.get_psk(), prologue_.data(), prologue_.size());
+  int err = this->handshake_.init(this->ctx_, prologue_.data(), prologue_.size());
   APIError aerr = handle_noise_error_(err, LOG_STR("noise_handshake_init"), APIError::HANDSHAKESTATE_SETUP_FAILED);
   if (aerr != APIError::OK)
     return aerr;

esphome/components/api/api_server.cpp

@@ -41,13 +41,13 @@ void APIServer::setup() {
   ControllerRegistry::register_controller(this);
 
 #ifdef USE_API_NOISE
+  // Always reserve the slot: flash preferences are positional on esp8266, so
+  // a yaml key build must keep the layout of a runtime key build
   uint32_t hash = 88491486UL;
-
   this->noise_pref_ = global_preferences->make_preference<SavedNoisePsk>(hash, true);
-
 #ifndef USE_API_NOISE_PSK_FROM_YAML
-  // Only load saved PSK if not set from YAML
-  if (this->load_and_apply_noise_psk_()) {
+  // A cleared record loads fine but holds no key
+  if (this->load_and_apply_noise_psk_() && this->noise_ctx_.has_psk()) {
     ESP_LOGD(TAG, "Loaded saved Noise PSK");
   }
 #endif
@@ -550,6 +550,7 @@ const std::vector<APIServer::HomeAssistantStateSubscription> &APIServer::get_sta
 #endif
 
 #ifdef USE_API_NOISE
+#ifndef USE_API_NOISE_PSK_FROM_YAML
 bool APIServer::update_noise_psk_(const SavedNoisePsk &new_psk, const LogString *save_log_msg,
                                   const LogString *fail_log_msg, bool make_active) {
   if (!this->noise_pref_.save(&new_psk)) {
@@ -583,22 +584,19 @@ bool APIServer::update_noise_psk_(const SavedNoisePsk &new_psk, const LogString
 }
 
 bool APIServer::load_and_apply_noise_psk_() {
-  SavedNoisePsk saved{};
-  if (!this->noise_pref_.load(&saved))
+  // Load into a temp so a failed read cannot disturb the key in use
+  SavedNoisePsk loaded{};
+  if (!this->noise_pref_.load(&loaded))
     return false;
-  this->set_noise_psk(saved.psk);
+  this->saved_psk_ = loaded;
+  // An unprovisioned device stores the reserved all-zeros key, which is no key
+  const bool has_key = !noise::NoiseContext::is_all_zeros(this->saved_psk_.psk);
+  this->noise_ctx_.set_psk(has_key ? this->saved_psk_.psk.data() : nullptr);
   return true;
 }
 
 bool APIServer::save_noise_psk(noise::psk_t psk, bool make_active) {
-#ifdef USE_API_NOISE_PSK_FROM_YAML
-  // When PSK is set from YAML, this function should never be called
-  // but if it is, reject the change
-  ESP_LOGW(TAG, "Key set in YAML");
-  return false;
-#else
-  auto &old_psk = this->noise_ctx_.get_psk();
-  if (std::equal(old_psk.begin(), old_psk.end(), psk.begin())) {
+  if (this->saved_psk_.psk == psk) {
     ESP_LOGW(TAG, "New PSK matches old");
     return true;
   }
@@ -614,15 +612,8 @@ bool APIServer::save_noise_psk(noise::psk_t psk, bool make_active) {
   }
 #endif
   return result;
-#endif
 }
 bool APIServer::clear_noise_psk(bool make_active) {
-#ifdef USE_API_NOISE_PSK_FROM_YAML
-  // When PSK is set from YAML, this function should never be called
-  // but if it is, reject the change
-  ESP_LOGW(TAG, "Key set in YAML");
-  return false;
-#else
   SavedNoisePsk empty_psk{};
   bool result = this->update_noise_psk_(empty_psk, LOG_STR("Noise PSK cleared"), LOG_STR("Failed to clear Noise PSK"),
                                         make_active);
@@ -634,8 +625,8 @@ bool APIServer::clear_noise_psk(bool make_active) {
   }
 #endif
   return result;
-#endif
 }
+#endif  // USE_API_NOISE_PSK_FROM_YAML
 #endif
 
 #ifdef USE_HOMEASSISTANT_TIME

esphome/components/api/api_server.h

@@ -76,9 +76,14 @@ class APIServer final : public Component,
   APIBuffer &get_shared_buffer_ref() { return shared_write_buffer_; }
 
 #ifdef USE_API_NOISE
+#ifndef USE_API_NOISE_PSK_FROM_YAML
+  // Runtime key changes exist for the provisioning path only (not lambdas);
+  // with a yaml key they compile out
   bool save_noise_psk(noise::psk_t psk, bool make_active = true);
   bool clear_noise_psk(bool make_active = true);
-  void set_noise_psk(noise::psk_t psk) { this->noise_ctx_.set_psk(psk); }
+#endif
+  /// psk points at 32 bytes that live in flash for the life of the program
+  void set_noise_psk(const uint8_t *psk) { this->noise_ctx_.set_psk(psk); }
   noise::NoiseContext &get_noise_ctx() { return this->noise_ctx_; }
 #endif  // USE_API_NOISE
 
@@ -275,10 +280,12 @@ class APIServer final : public Component,
 #endif
 
 #ifdef USE_API_NOISE
+#ifndef USE_API_NOISE_PSK_FROM_YAML
   bool update_noise_psk_(const SavedNoisePsk &new_psk, const LogString *save_log_msg, const LogString *fail_log_msg,
                          bool make_active);
   // Load saved PSK from preferences and apply it. Returns true on success.
   bool load_and_apply_noise_psk_();
+#endif  // USE_API_NOISE_PSK_FROM_YAML
 #endif  // USE_API_NOISE
 #ifdef USE_API_HOMEASSISTANT_STATES
   // Helper methods to reduce code duplication
@@ -358,6 +365,9 @@ class APIServer final : public Component,
 
 #ifdef USE_API_NOISE
   noise::NoiseContext noise_ctx_;
+#ifndef USE_API_NOISE_PSK_FROM_YAML
+  SavedNoisePsk saved_psk_{};  // backs noise_ctx_ for a runtime provisioned key
+#endif
   ESPPreferenceObject noise_pref_;
 #endif  // USE_API_NOISE
 };

esphome/components/api/proto.cpp

@@ -214,73 +214,74 @@ void ProtoDecodableMessage::decode(const uint8_t *buffer, size_t length) {
   const uint8_t *ptr = buffer;
   const uint8_t *end = buffer + length;
 
-  while (ptr < end) {
-    // Parse field header - ptr < end guarantees len >= 1
+  // Single-byte varints dominate, so that case advances the cursor inline.
+  auto read_varint = [&](proto_varint_value_t &value) ESPHOME_ALWAYS_INLINE {
+    if (ptr == end)
+      return false;
+    if (*ptr < 0x80) [[likely]] {
+      value = *ptr++;
+      return true;
+    }
     auto res = ProtoVarInt::parse_non_empty(ptr, end - ptr);
-    if (!res.has_value()) {
+    if (!res.has_value())
+      return false;
+    value = res.value;
+    ptr += res.consumed;
+    return true;
+  };
+
+  while (ptr < end) {
+    proto_varint_value_t tag_value;
+    if (!read_varint(tag_value)) {
       ESP_LOGV(TAG, "Invalid field start at offset %ld", (long) (ptr - buffer));
       return;
     }
 
-    uint32_t tag = static_cast<uint32_t>(res.value);
+    uint32_t tag = static_cast<uint32_t>(tag_value);
     uint32_t field_type = tag & WIRE_TYPE_MASK;
-    uint32_t field_id = tag >> 3;
-    ptr += res.consumed;
+    // Length-delimited fields move this past the length prefix
+    const uint8_t *data = ptr;
+    proto_varint_value_t scalar;
 
-    switch (field_type) {
-      case WIRE_TYPE_VARINT: {  // VarInt
-        res = ProtoVarInt::parse(ptr, end - ptr);
-        if (!res.has_value()) {
-          ESP_LOGV(TAG, "Invalid VarInt at offset %ld", (long) (ptr - buffer));
-          return;
-        }
-        if (!this->decode_varint(field_id, res.value)) {
-          ESP_LOGV(TAG, "Cannot decode VarInt field %" PRIu32 " with value %" PRIu64 "!", field_id,
-                   static_cast<uint64_t>(res.value));
-        }
-        ptr += res.consumed;
-        break;
-      }
-      case WIRE_TYPE_LENGTH_DELIMITED: {  // Length-delimited
-        res = ProtoVarInt::parse(ptr, end - ptr);
-        if (!res.has_value()) {
-          ESP_LOGV(TAG, "Invalid Length Delimited at offset %ld", (long) (ptr - buffer));
-          return;
-        }
-        uint32_t field_length = static_cast<uint32_t>(res.value);
-        ptr += res.consumed;
-        if (field_length > static_cast<size_t>(end - ptr)) {
-          ESP_LOGV(TAG, "Out-of-bounds Length Delimited at offset %ld", (long) (ptr - buffer));
-          return;
-        }
-        if (!this->decode_length(field_id, ProtoLengthDelimited(ptr, field_length))) {
-          ESP_LOGV(TAG, "Cannot decode Length Delimited field %" PRIu32 "!", field_id);
-        }
-        ptr += field_length;
-        break;
-      }
-      case WIRE_TYPE_FIXED32: {  // 32-bit
-        if (end - ptr < 4) {
-          ESP_LOGV(TAG, "Out-of-bounds Fixed32-bit at offset %ld", (long) (ptr - buffer));
-          return;
-        }
-        uint32_t val;
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-        // Protobuf fixed32 is little-endian — direct load on LE platforms
-        memcpy(&val, ptr, 4);
-#else
-        val = encode_uint32(ptr[3], ptr[2], ptr[1], ptr[0]);
-#endif
-        if (!this->decode_32bit(field_id, Proto32Bit(val))) {
-          ESP_LOGV(TAG, "Cannot decode 32-bit field %" PRIu32 " with value %" PRIu32 "!", field_id, val);
-        }
-        ptr += 4;
-        break;
-      }
-      default:
-        ESP_LOGV(TAG, "Invalid field type %" PRIu32 " at offset %ld", field_type, (long) (ptr - buffer));
+    if (field_type == WIRE_TYPE_VARINT) [[likely]] {
+      if (!read_varint(scalar)) {
+        ESP_LOGV(TAG, "Invalid VarInt at offset %ld", (long) (ptr - buffer));
         return;
+      }
+    } else {
+      switch (field_type) {
+        case WIRE_TYPE_LENGTH_DELIMITED: {
+          proto_varint_value_t length_value;
+          if (!read_varint(length_value)) {
+            ESP_LOGV(TAG, "Invalid Length Delimited at offset %ld", (long) (ptr - buffer));
+            return;
+          }
+          uint32_t field_length = static_cast<uint32_t>(length_value);
+          if (field_length > static_cast<size_t>(end - ptr)) {
+            ESP_LOGV(TAG, "Out-of-bounds Length Delimited at offset %ld", (long) (ptr - buffer));
+            return;
+          }
+          data = ptr;
+          scalar = field_length;
+          ptr += field_length;
+          break;
+        }
+        case WIRE_TYPE_FIXED32: {
+          if (end - ptr < 4) {
+            ESP_LOGV(TAG, "Out-of-bounds Fixed32-bit at offset %ld", (long) (ptr - buffer));
+            return;
+          }
+          // Byte loads instead of memcpy: ESP-IDF passes -fno-builtin-memcpy, which made this a call
+          scalar = encode_uint32(ptr[3], ptr[2], ptr[1], ptr[0]);
+          ptr += 4;
+          break;
+        }
+        default:
+          ESP_LOGV(TAG, "Invalid field type %" PRIu32 " at offset %ld", field_type, (long) (ptr - buffer));
+          return;
+      }
     }
+    this->decode_field(tag, data, scalar);
   }
 }
 

esphome/components/api/proto.h

@@ -170,40 +170,43 @@ class ProtoVarInt {
 class ProtoMessage;
 class ProtoSize;
 
-class ProtoLengthDelimited {
+/// Case label for decode_field(): the wire tag of a field, so a field that arrives with another wire
+/// type matches no case.
+constexpr uint32_t proto_tag(uint32_t field_id, uint32_t wire_type) { return (field_id << 3) | wire_type; }
+
+/// One decoded field: the payload pointer and a scalar holding the varint or fixed32 value, or the
+/// length of a length-delimited field. The wire type in the tag says which applies; accessors do not check.
+class ProtoFieldValue {
  public:
-  explicit ProtoLengthDelimited(const uint8_t *value, size_t length) : value_(value), length_(length) {}
-  std::string as_string() const { return std::string(reinterpret_cast<const char *>(this->value_), this->length_); }
+  ProtoFieldValue(const uint8_t *data, proto_varint_value_t scalar) : data_(data), scalar_(scalar) {}
 
-  // Direct access to raw data without string allocation
-  const uint8_t *data() const { return this->value_; }
-  size_t size() const { return this->length_; }
+  proto_varint_value_t as_varint() const { return this->scalar_; }
+  // A bool is sent as 0 or 1, so the low word is enough and saves a second compare with 64 bit varints
+  bool as_bool() const { return static_cast<uint32_t>(this->scalar_) != 0; }
 
-  /// Decode the length-delimited data into a message instance.
+  // Length-delimited accessors
+  const uint8_t *data() const { return this->data_; }
+  size_t size() const { return static_cast<size_t>(this->scalar_); }
+  std::string as_string() const { return std::string(reinterpret_cast<const char *>(this->data_), this->size()); }
+  /// Decode the length-delimited payload into a message instance.
   /// Template preserves concrete type so decode() resolves statically.
-  template<typename T> void decode_to_message(T &msg) const;
+  template<typename T> void decode_to_message(T &msg) const { msg.decode(this->data_, this->size()); }
 
- protected:
-  const uint8_t *const value_;
-  const size_t length_;
-};
-
-class Proto32Bit {
- public:
-  explicit Proto32Bit(uint32_t value) : value_(value) {}
-  uint32_t as_fixed32() const { return this->value_; }
-  int32_t as_sfixed32() const { return static_cast<int32_t>(this->value_); }
+  // Fixed32 accessors
+  uint32_t as_fixed32() const { return static_cast<uint32_t>(this->scalar_); }
+  int32_t as_sfixed32() const { return static_cast<int32_t>(this->as_fixed32()); }
   float as_float() const {
     union {
       uint32_t raw;
       float value;
     } s{};
-    s.raw = this->value_;
+    s.raw = this->as_fixed32();
     return s.value;
   }
 
- protected:
-  const uint32_t value_;
+ private:
+  const uint8_t *data_;
+  proto_varint_value_t scalar_;
 };
 
 // NOTE: Proto64Bit class removed - wire type 1 (64-bit fixed) not supported
@@ -252,7 +255,7 @@ class ProtoWriteBuffer {
    *
    * Following https://protobuf.dev/programming-guides/encoding/#structure
    */
-  void encode_field_raw(uint32_t field_id, uint32_t type) { this->encode_varint_raw((field_id << 3) | type); }
+  void encode_field_raw(uint32_t field_id, uint32_t type) { this->encode_varint_raw(proto_tag(field_id, type)); }
   /// Single-pass encode for repeated submessage elements.
   /// Thin template wrapper; all buffer work is in the non-template core.
   template<typename T> void encode_sub_message(uint32_t field_id, const T &value);
@@ -287,19 +290,31 @@ class ProtoWriteBuffer {
   uint8_t *pos_;
 };
 
+// A four byte unaligned store is a memcpy call on ESP-IDF (-fno-builtin-memcpy) and on ARM cores without
+// unaligned access (Cortex-M0+, ARM9), so those targets share one outlined byte store helper per fixed32
+// field. Elsewhere the write inlines to a single store, or on ESP8266 to a few stores that measured
+// faster than a call, so it stays inline.
+#if defined(USE_ESP32) || (defined(__arm__) && !defined(__ARM_FEATURE_UNALIGNED))
+#define PROTO_OUTLINE_FOR_SIZE __attribute__((noinline))
+#define PROTO_FIXED32_BYTE_STORES true
+#else
+#define PROTO_OUTLINE_FOR_SIZE inline
+#define PROTO_FIXED32_BYTE_STORES false
+#endif
+
 // Varint encoding thresholds — used by both proto_encode_* free functions and ProtoSize.
 constexpr uint32_t VARINT_MAX_1_BYTE = 1 << 7;   // 128
 constexpr uint32_t VARINT_MAX_2_BYTE = 1 << 14;  // 16384
 
-/// Static encode helpers for generated encode() functions.
-/// Generated code hoists buffer.pos_ into a local uint8_t *__restrict__ pos,
-/// then calls these methods which take pos by reference. No struct, no overhead.
-/// For sub-messages, pos is synced back to buffer before the call and reloaded after.
+/// Static encode helpers for the generated encode bodies. Each takes the write cursor by value and
+/// returns it advanced, so outlined calls at -Os chain through the return register instead of a
+/// stack slot. Helpers without a _force suffix skip fields holding the proto3 default.
 class ProtoEncode {
  public:
   /// Write a multi-byte varint directly through a pos pointer.
   template<typename T>
-  static inline void encode_varint_raw_loop(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, T value) {
+  [[nodiscard]] static inline uint8_t *encode_varint_raw_loop(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                              T value) {
     do {
       PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
       *pos++ = static_cast<uint8_t>(value | 0x80);
@@ -307,48 +322,49 @@ class ProtoEncode {
     } while (value > 0x7F);
     PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
     *pos++ = static_cast<uint8_t>(value);
+    return pos;
   }
-  static inline void ESPHOME_ALWAYS_INLINE encode_varint_raw(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                             uint32_t value) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  encode_varint_raw(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint32_t value) {
     if (value < VARINT_MAX_1_BYTE) [[likely]] {
       PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
       *pos++ = static_cast<uint8_t>(value);
-      return;
+      return pos;
     }
-    encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, value);
+    return encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, value);
   }
   /// Encode a varint that is expected to be 1-2 bytes (e.g. zigzag RSSI, small lengths).
-  static inline void ESPHOME_ALWAYS_INLINE encode_varint_raw_short(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                                   uint32_t value) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  encode_varint_raw_short(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint32_t value) {
     if (value < VARINT_MAX_1_BYTE) [[likely]] {
       PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
       *pos++ = static_cast<uint8_t>(value);
-      return;
+      return pos;
     }
     if (value < VARINT_MAX_2_BYTE) [[likely]] {
       PROTO_ENCODE_CHECK_BOUNDS(pos, 2);
       *pos++ = static_cast<uint8_t>(value | 0x80);
       *pos++ = static_cast<uint8_t>(value >> 7);
-      return;
+      return pos;
     }
-    encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, value);
+    return encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, value);
   }
-  static inline void ESPHOME_ALWAYS_INLINE encode_varint_raw_64(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                                uint64_t value) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  encode_varint_raw_64(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint64_t value) {
     if (value < VARINT_MAX_1_BYTE) [[likely]] {
       PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
       *pos++ = static_cast<uint8_t>(value);
-      return;
+      return pos;
     }
-    encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, value);
+    return encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, value);
   }
   /// Encode a 48-bit MAC address (stored in a uint64) as varint.
   /// Real MAC addresses occupy the full 48 bits (OUI in upper 24), so the
   /// fast path -- any non-zero bit in the top 6 of 48 -- emits exactly 7 bytes
   /// with no per-byte branch. Falls back to the general loop otherwise.
   /// Caller must guarantee value fits in 48 bits (checked in debug builds).
-  static inline void ESPHOME_ALWAYS_INLINE encode_varint_raw_48bit(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                                   uint64_t value) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  encode_varint_raw_48bit(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint64_t value) {
 #ifdef ESPHOME_DEBUG_API
     assert(value < (1ULL << (MAC_ADDRESS_SIZE * 8)) && "encode_varint_raw_48bit: value exceeds 48 bits");
 #endif
@@ -363,38 +379,39 @@ class ProtoEncode {
       pos[4] = static_cast<uint8_t>((value >> 28) | 0x80);
       pos[5] = static_cast<uint8_t>((value >> 35) | 0x80);
       pos[6] = static_cast<uint8_t>(value >> 42);
-      pos += 7;
-      return;
+      return pos + 7;
     }
-    encode_varint_raw_64(pos PROTO_ENCODE_DEBUG_ARG, value);
+    return encode_varint_raw_64(pos PROTO_ENCODE_DEBUG_ARG, value);
   }
-  static inline void ESPHOME_ALWAYS_INLINE encode_field_raw(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                            uint32_t field_id, uint32_t type) {
-    encode_varint_raw(pos PROTO_ENCODE_DEBUG_ARG, (field_id << 3) | type);
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  encode_field_raw(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, uint32_t type) {
+    return encode_varint_raw(pos PROTO_ENCODE_DEBUG_ARG, proto_tag(field_id, type));
   }
   /// Write a single precomputed tag byte. Tag must be < 128.
-  static inline void ESPHOME_ALWAYS_INLINE write_raw_byte(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                          uint8_t b) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  write_raw_byte(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint8_t b) {
     PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
     *pos++ = b;
+    return pos;
   }
   /// Reserve one byte for later backpatch (e.g., sub-message length).
   /// Advances pos past the reserved byte without writing a value.
-  static inline void ESPHOME_ALWAYS_INLINE reserve_byte(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  reserve_byte(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM) {
     PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
-    pos++;
+    return pos + 1;
   }
   /// Write raw bytes to the buffer (no tag, no length prefix).
-  static inline void ESPHOME_ALWAYS_INLINE encode_raw(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                      const void *data, size_t len) {
+  [[nodiscard]] static inline uint8_t *ESPHOME_ALWAYS_INLINE
+  encode_raw(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, const void *data, size_t len) {
     PROTO_ENCODE_CHECK_BOUNDS(pos, len);
     std::memcpy(pos, data, len);
-    pos += len;
+    return pos + len;
   }
   /// Encode tag + 1-byte length + raw string data. For strings with max_data_length < 128.
   /// Tag must be a single-byte varint (< 128). Always encodes (no zero check).
-  static inline void encode_short_string_force(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint8_t tag,
-                                               const StringRef &ref) {
+  [[nodiscard]] static inline uint8_t *encode_short_string_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                                 uint8_t tag, const StringRef &ref) {
 #ifdef ESPHOME_DEBUG_API
     assert(ref.size() < 128 && "encode_short_string_force: string exceeds max_data_length < 128");
 #endif
@@ -402,137 +419,187 @@ class ProtoEncode {
     pos[0] = tag;
     pos[1] = static_cast<uint8_t>(ref.size());
     std::memcpy(pos + 2, ref.c_str(), ref.size());
-    pos += 2 + ref.size();
+    return pos + 2 + ref.size();
   }
-  /// Write a precomputed tag byte + 32-bit value in one operation.
-  static inline void ESPHOME_ALWAYS_INLINE write_tag_and_fixed32(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                                 uint8_t tag, uint32_t value) {
+  /// Unaligned little-endian store; __builtin_memcpy stays inline even under -fno-builtin-memcpy.
+  static inline void ESPHOME_ALWAYS_INLINE write_fixed32_le(uint8_t *__restrict__ pos, uint32_t value) {
+    if constexpr (PROTO_FIXED32_BYTE_STORES) {
+      // Spelled out so the outlined helper does not itself become a memcpy call
+      pos[0] = static_cast<uint8_t>(value);
+      pos[1] = static_cast<uint8_t>(value >> 8);
+      pos[2] = static_cast<uint8_t>(value >> 16);
+      pos[3] = static_cast<uint8_t>(value >> 24);
+    } else {
+      const uint32_t le = convert_little_endian(value);
+      __builtin_memcpy(pos, &le, 4);
+    }
+  }
+  /// Write a precomputed tag byte + 32-bit value. Outlined on embedded: one copy beats inline stores per field.
+  [[nodiscard]] static PROTO_OUTLINE_FOR_SIZE uint8_t *write_tag_and_fixed32(
+      uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint8_t tag, uint32_t value) {
     PROTO_ENCODE_CHECK_BOUNDS(pos, 5);
     pos[0] = tag;
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    std::memcpy(pos + 1, &value, 4);
-#else
-    pos[1] = static_cast<uint8_t>(value & 0xFF);
-    pos[2] = static_cast<uint8_t>((value >> 8) & 0xFF);
-    pos[3] = static_cast<uint8_t>((value >> 16) & 0xFF);
-    pos[4] = static_cast<uint8_t>((value >> 24) & 0xFF);
-#endif
-    pos += 5;
+    write_fixed32_le(pos + 1, value);
+    return pos + 5;
   }
-  static inline void encode_string(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   const char *string, size_t len, bool force = false) {
-    if (len == 0 && !force)
-      return;
-    encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 2);  // type 2: Length-delimited string
+  [[nodiscard]] static inline uint8_t *encode_string_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, const char *string, size_t len) {
+    pos = encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 2);  // type 2: Length-delimited string
     // NOLINTNEXTLINE(readability-inconsistent-ifelse-braces) -- false positive on [[likely]] attribute
     if (len < VARINT_MAX_1_BYTE) [[likely]] {
       PROTO_ENCODE_CHECK_BOUNDS(pos, 1 + len);
       *pos++ = static_cast<uint8_t>(len);
     } else {
-      encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, len);
+      pos = encode_varint_raw_loop(pos PROTO_ENCODE_DEBUG_ARG, len);
       PROTO_ENCODE_CHECK_BOUNDS(pos, len);
     }
     std::memcpy(pos, string, len);
-    pos += len;
+    return pos + len;
   }
-  static inline void encode_string(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   const std::string &value, bool force = false) {
-    encode_string(pos PROTO_ENCODE_DEBUG_ARG, field_id, value.data(), value.size(), force);
+  [[nodiscard]] static inline uint8_t *encode_string(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                     uint32_t field_id, const char *string, size_t len) {
+    if (len == 0)
+      return pos;
+    return encode_string_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, string, len);
   }
-  static inline void encode_string(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   const StringRef &ref, bool force = false) {
-    encode_string(pos PROTO_ENCODE_DEBUG_ARG, field_id, ref.c_str(), ref.size(), force);
+  [[nodiscard]] static inline uint8_t *encode_string_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, const std::string &value) {
+    return encode_string_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, value.data(), value.size());
   }
-  static inline void encode_bytes(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                  const uint8_t *data, size_t len, bool force = false) {
-    encode_string(pos PROTO_ENCODE_DEBUG_ARG, field_id, reinterpret_cast<const char *>(data), len, force);
+  [[nodiscard]] static inline uint8_t *encode_string(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                     uint32_t field_id, const StringRef &ref) {
+    return encode_string(pos PROTO_ENCODE_DEBUG_ARG, field_id, ref.c_str(), ref.size());
   }
-  static inline void encode_uint32(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   uint32_t value, bool force = false) {
-    if (value == 0 && !force)
-      return;
-    encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 0);
-    encode_varint_raw(pos PROTO_ENCODE_DEBUG_ARG, value);
+  [[nodiscard]] static inline uint8_t *encode_string_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, const StringRef &ref) {
+    return encode_string_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, ref.c_str(), ref.size());
   }
-  static inline void encode_uint64(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   uint64_t value, bool force = false) {
-    if (value == 0 && !force)
-      return;
-    encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 0);
-    encode_varint_raw_64(pos PROTO_ENCODE_DEBUG_ARG, value);
+  [[nodiscard]] static inline uint8_t *encode_bytes(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                    uint32_t field_id, const uint8_t *data, size_t len) {
+    return encode_string(pos PROTO_ENCODE_DEBUG_ARG, field_id, reinterpret_cast<const char *>(data), len);
   }
-  static inline void encode_bool(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, bool value,
-                                 bool force = false) {
-    if (!value && !force)
-      return;
-    encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 0);
+  [[nodiscard]] static inline uint8_t *encode_bytes_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                          uint32_t field_id, const uint8_t *data, size_t len) {
+    return encode_string_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, reinterpret_cast<const char *>(data), len);
+  }
+  [[nodiscard]] static inline uint8_t *encode_uint32_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, uint32_t value) {
+    pos = encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 0);
+    return encode_varint_raw(pos PROTO_ENCODE_DEBUG_ARG, value);
+  }
+  [[nodiscard]] static inline uint8_t *encode_uint32(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                     uint32_t field_id, uint32_t value) {
+    if (value == 0)
+      return pos;
+    return encode_uint32_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, value);
+  }
+  [[nodiscard]] static inline uint8_t *encode_uint64_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, uint64_t value) {
+    pos = encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 0);
+    return encode_varint_raw_64(pos PROTO_ENCODE_DEBUG_ARG, value);
+  }
+  [[nodiscard]] static inline uint8_t *encode_uint64(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                     uint32_t field_id, uint64_t value) {
+    if (value == 0)
+      return pos;
+    return encode_uint64_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, value);
+  }
+  [[nodiscard]] static inline uint8_t *encode_bool_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                         uint32_t field_id, bool value) {
+    pos = encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 0);
     PROTO_ENCODE_CHECK_BOUNDS(pos, 1);
     *pos++ = value ? 0x01 : 0x00;
+    return pos;
   }
-  static inline void encode_fixed32(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                    uint32_t value, bool force = false) {
-    if (value == 0 && !force)
-      return;
-    encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 5);
+  [[nodiscard]] static inline uint8_t *encode_bool(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                   uint32_t field_id, bool value) {
+    if (!value)
+      return pos;
+    return encode_bool_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, value);
+  }
+  /// Tag + fixed32 for multi-byte tags; single-byte tags use write_tag_and_fixed32.
+  [[nodiscard]] static PROTO_OUTLINE_FOR_SIZE uint8_t *encode_fixed32_force(
+      uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, uint32_t value) {
+    pos = encode_field_raw(pos PROTO_ENCODE_DEBUG_ARG, field_id, 5);
     PROTO_ENCODE_CHECK_BOUNDS(pos, 4);
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    std::memcpy(pos, &value, 4);
-    pos += 4;
-#else
-    *pos++ = (value >> 0) & 0xFF;
-    *pos++ = (value >> 8) & 0xFF;
-    *pos++ = (value >> 16) & 0xFF;
-    *pos++ = (value >> 24) & 0xFF;
-#endif
+    write_fixed32_le(pos, value);
+    return pos + 4;
+  }
+  [[nodiscard]] static inline uint8_t *encode_fixed32(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                      uint32_t field_id, uint32_t value) {
+    if (value == 0)
+      return pos;
+    return encode_fixed32_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, value);
   }
   // NOTE: Wire type 1 (64-bit fixed: double, fixed64, sfixed64) is intentionally
   // not supported to reduce overhead on embedded systems. All ESPHome devices are
   // 32-bit microcontrollers where 64-bit operations are expensive. If 64-bit support
   // is needed in the future, the necessary encoding/decoding functions must be added.
-  static inline void encode_float(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, float value,
-                                  bool force = false) {
-    uint32_t raw = float_to_raw(value);
-    if (raw == 0 && !force)
-      return;
-    encode_fixed32(pos PROTO_ENCODE_DEBUG_ARG, field_id, raw);
+  [[nodiscard]] static inline uint8_t *encode_float(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                    uint32_t field_id, float value) {
+    return encode_fixed32(pos PROTO_ENCODE_DEBUG_ARG, field_id, float_to_raw(value));
   }
-  static inline void encode_int32(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, int32_t value,
-                                  bool force = false) {
+  [[nodiscard]] static inline uint8_t *encode_float_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                          uint32_t field_id, float value) {
+    return encode_fixed32_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, float_to_raw(value));
+  }
+  [[nodiscard]] static inline uint8_t *encode_int32_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                          uint32_t field_id, int32_t value) {
     if (value < 0) {
       // negative int32 is always 10 byte long
-      encode_uint64(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint64_t>(value), force);
-      return;
+      return encode_uint64_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint64_t>(value));
     }
-    encode_uint32(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint32_t>(value), force);
+    return encode_uint32_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint32_t>(value));
   }
-  static inline void encode_int64(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id, int64_t value,
-                                  bool force = false) {
-    encode_uint64(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint64_t>(value), force);
+  [[nodiscard]] static inline uint8_t *encode_int32(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                    uint32_t field_id, int32_t value) {
+    if (value == 0)
+      return pos;
+    return encode_int32_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, value);
   }
-  static inline void encode_sint32(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   int32_t value, bool force = false) {
-    encode_uint32(pos PROTO_ENCODE_DEBUG_ARG, field_id, encode_zigzag32(value), force);
+  [[nodiscard]] static inline uint8_t *encode_int64(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                    uint32_t field_id, int64_t value) {
+    return encode_uint64(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint64_t>(value));
   }
-  static inline void encode_sint64(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, uint32_t field_id,
-                                   int64_t value, bool force = false) {
-    encode_uint64(pos PROTO_ENCODE_DEBUG_ARG, field_id, encode_zigzag64(value), force);
+  [[nodiscard]] static inline uint8_t *encode_int64_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                          uint32_t field_id, int64_t value) {
+    return encode_uint64_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, static_cast<uint64_t>(value));
   }
-  /// Sub-message encoding: sync pos to buffer, delegate, get pos from return value.
+  [[nodiscard]] static inline uint8_t *encode_sint32(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                     uint32_t field_id, int32_t value) {
+    return encode_uint32(pos PROTO_ENCODE_DEBUG_ARG, field_id, encode_zigzag32(value));
+  }
+  [[nodiscard]] static inline uint8_t *encode_sint32_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, int32_t value) {
+    return encode_uint32_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, encode_zigzag32(value));
+  }
+  [[nodiscard]] static inline uint8_t *encode_sint64(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                     uint32_t field_id, int64_t value) {
+    return encode_uint64(pos PROTO_ENCODE_DEBUG_ARG, field_id, encode_zigzag64(value));
+  }
+  [[nodiscard]] static inline uint8_t *encode_sint64_force(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                           uint32_t field_id, int64_t value) {
+    return encode_uint64_force(pos PROTO_ENCODE_DEBUG_ARG, field_id, encode_zigzag64(value));
+  }
+  /// Sub-message encoding: sync pos to buffer, delegate, read the cursor back.
   template<typename T>
-  static inline void encode_sub_message(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM, ProtoWriteBuffer &buffer,
-                                        uint32_t field_id, const T &value) {
+  [[nodiscard]] static inline uint8_t *encode_sub_message(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                          ProtoWriteBuffer &buffer, uint32_t field_id, const T &value) {
     buffer.set_pos(pos);
     buffer.encode_sub_message(field_id, value);
-    pos = buffer.get_pos();
+    return buffer.get_pos();
   }
   template<typename T>
-  static inline void encode_optional_sub_message(uint8_t *__restrict__ &pos PROTO_ENCODE_DEBUG_PARAM,
-                                                 ProtoWriteBuffer &buffer, uint32_t field_id, const T &value) {
+  [[nodiscard]] static inline uint8_t *encode_optional_sub_message(uint8_t *__restrict__ pos PROTO_ENCODE_DEBUG_PARAM,
+                                                                   ProtoWriteBuffer &buffer, uint32_t field_id,
+                                                                   const T &value) {
     buffer.set_pos(pos);
     buffer.encode_optional_sub_message(field_id, value);
-    pos = buffer.get_pos();
+    return buffer.get_pos();
   }
 };
+#undef PROTO_OUTLINE_FOR_SIZE
+#undef PROTO_FIXED32_BYTE_STORES
 
 #ifdef HAS_PROTO_MESSAGE_DUMP
 /**
@@ -624,11 +691,12 @@ class DumpBuffer {
 
 class ProtoMessage {
  public:
-  // Non-virtual defaults for messages with no fields.
-  // Concrete message classes hide these with their own implementations.
-  // All call sites use templates to preserve the concrete type, so virtual
-  // dispatch is not needed. This eliminates per-message vtable entries for
-  // encode/calculate_size, saving ~1.3 KB of flash across all message types.
+  // Non-virtual defaults for messages with no fields; generated classes hide all four. The
+  // static encode_msg/calc_size_msg take const void * so &T::encode_msg needs no thunk.
+  static uint8_t *encode_msg(const void *self, ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) {
+    return buffer.get_pos();
+  }
+  static uint32_t calc_size_msg(const void *self) { return 0; }
   uint8_t *encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const { return buffer.get_pos(); }
   uint32_t calculate_size() const { return 0; }
 #ifdef HAS_PROTO_MESSAGE_DUMP
@@ -663,10 +731,10 @@ class ProtoDecodableMessage : public ProtoMessage {
 
  protected:
   ~ProtoDecodableMessage() = default;
-  virtual bool decode_varint(uint32_t field_id, proto_varint_value_t value) { return false; }
-  virtual bool decode_length(uint32_t field_id, ProtoLengthDelimited value) { return false; }
-  virtual bool decode_32bit(uint32_t field_id, Proto32Bit value) { return false; }
-  // NOTE: decode_64bit removed - wire type 1 not supported
+  /// Store one decoded field; \p scalar is the varint or fixed32 value, or the length of the
+  /// length-delimited payload at \p data. An unknown field or wrong wire type matches no case and is skipped.
+  /// Three register arguments keep the decode loop free of spills.
+  virtual void decode_field(uint32_t tag, const uint8_t *data, proto_varint_value_t scalar) {}
 };
 
 class ProtoSize {
@@ -792,7 +860,7 @@ class ProtoSize {
    * @return The number of bytes needed to encode the field ID and wire type
    */
   static constexpr uint32_t field(uint32_t field_id, uint32_t type) {
-    uint32_t tag = (field_id << 3) | (type & WIRE_TYPE_MASK);
+    uint32_t tag = proto_tag(field_id, type & WIRE_TYPE_MASK);
     return varint(tag);
   }
 
@@ -876,24 +944,14 @@ class ProtoSize {
 
 // Implementation of methods that depend on ProtoSize being fully defined
 
-// Encode thunk — converts void* back to concrete type for direct encode() call
-template<typename T> uint8_t *proto_encode_msg(const void *msg, ProtoWriteBuffer &buf PROTO_ENCODE_DEBUG_PARAM) {
-  return static_cast<const T *>(msg)->encode(buf PROTO_ENCODE_DEBUG_ARG);
-}
-
 // Thin template wrapper; delegates to non-template core in proto.cpp.
 template<typename T> inline void ProtoWriteBuffer::encode_sub_message(uint32_t field_id, const T &value) {
-  this->encode_sub_message(field_id, &value, &proto_encode_msg<T>);
+  this->encode_sub_message(field_id, &value, &T::encode_msg);
 }
 
 // Thin template wrapper; delegates to non-template core.
 template<typename T> inline void ProtoWriteBuffer::encode_optional_sub_message(uint32_t field_id, const T &value) {
-  this->encode_optional_sub_message(field_id, value.calculate_size(), &value, &proto_encode_msg<T>);
-}
-
-// Template decode_to_message - preserves concrete type so decode() resolves statically
-template<typename T> void ProtoLengthDelimited::decode_to_message(T &msg) const {
-  msg.decode(this->value_, this->length_);
+  this->encode_optional_sub_message(field_id, T::calc_size_msg(&value), &value, &T::encode_msg);
 }
 
 template<typename T> const char *proto_enum_to_string(T value);

esphome/components/climate/__init__.py

@@ -125,6 +125,19 @@ CLIMATE_SWING_MODES = {
 
 validate_climate_swing_mode = cv.enum(CLIMATE_SWING_MODES, upper=True)
 
+ClimateAction = climate_ns.enum("ClimateAction")
+CLIMATE_ACTIONS = {
+    "OFF": ClimateAction.CLIMATE_ACTION_OFF,
+    "COOLING": ClimateAction.CLIMATE_ACTION_COOLING,
+    "HEATING": ClimateAction.CLIMATE_ACTION_HEATING,
+    "IDLE": ClimateAction.CLIMATE_ACTION_IDLE,
+    "DRYING": ClimateAction.CLIMATE_ACTION_DRYING,
+    "FAN": ClimateAction.CLIMATE_ACTION_FAN,
+    "DEFROSTING": ClimateAction.CLIMATE_ACTION_DEFROSTING,
+}
+
+validate_climate_action = cv.enum(CLIMATE_ACTIONS, upper=True)
+
 CONF_MIN_HUMIDITY = "min_humidity"
 CONF_MAX_HUMIDITY = "max_humidity"
 CONF_TARGET_HUMIDITY = "target_humidity"

esphome/components/climate/climate.cpp

@@ -368,8 +368,8 @@ optional<ClimateDeviceRestoreState> Climate::restore_state_() {
 }
 
 void Climate::save_state_(const ClimateTraits &traits) {
-#if (defined(USE_ESP32) || (defined(USE_ESP8266) && USE_ARDUINO_VERSION_CODE >= VERSION_CODE(3, 0, 0))) && \
-    !defined(CLANG_TIDY)
+#if (defined(USE_ESP32) || defined(USE_ESP8266)) && !defined(CLANG_TIDY)
+#pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wclass-memaccess"
 #define TEMP_IGNORE_MEMACCESS
 #endif

esphome/components/cm1106/cm1106.cpp

@@ -100,7 +100,6 @@ bool CM1106Component::cm1106_write_command_(const uint8_t *command, size_t comma
 void CM1106Component::dump_config() {
   ESP_LOGCONFIG(TAG, "CM1106:");
   LOG_SENSOR("  ", "CO2", this->co2_sensor_);
-  this->check_uart_settings(9600);
   if (this->is_failed()) {
     ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
   }

esphome/components/cm1106/sensor.py

@@ -46,6 +46,14 @@ CONFIG_SCHEMA = (
     .extend(uart.UART_DEVICE_SCHEMA)
 )
 
+FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
+    "cm1106",
+    baud_rate=9600,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
+)
+
 
 async def to_code(config: ConfigType) -> None:
     """Code generation entry point."""

esphome/components/cse7761/cse7761.cpp

@@ -58,7 +58,6 @@ void CSE7761Component::dump_config() {
     ESP_LOGE(TAG, ESP_LOG_MSG_COMM_FAIL);
   }
   LOG_UPDATE_INTERVAL(this);
-  this->check_uart_settings(38400, 1, uart::UART_CONFIG_PARITY_EVEN, 8);
 }
 
 void CSE7761Component::update() {

esphome/components/cse7761/sensor.py

@@ -68,7 +68,13 @@ CONFIG_SCHEMA = (
 )
 
 FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
-    "cse7761", baud_rate=38400, require_rx=True, require_tx=True
+    "cse7761",
+    baud_rate=38400,
+    require_rx=True,
+    require_tx=True,
+    data_bits=8,
+    parity="EVEN",
+    stop_bits=1,
 )
 
 

esphome/components/cse7766/cse7766.cpp

@@ -255,7 +255,6 @@ void CSE7766Component::dump_config() {
   LOG_SENSOR("  ", "Apparent Power", this->apparent_power_sensor_);
   LOG_SENSOR("  ", "Reactive Power", this->reactive_power_sensor_);
   LOG_SENSOR("  ", "Power Factor", this->power_factor_sensor_);
-  this->check_uart_settings(4800, 1, uart::UART_CONFIG_PARITY_EVEN);
 }
 
 }  // namespace esphome::cse7766

esphome/components/cse7766/sensor.py

@@ -84,7 +84,12 @@ CONFIG_SCHEMA = (
     .extend(cv.COMPONENT_SCHEMA)
 )
 FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
-    "cse7766", baud_rate=4800, parity="EVEN", require_rx=True
+    "cse7766",
+    baud_rate=4800,
+    require_rx=True,
+    data_bits=8,
+    parity="EVEN",
+    stop_bits=1,
 )
 
 

esphome/components/daly_bms/__init__.py

@@ -26,6 +26,14 @@ CONFIG_SCHEMA = (
     .extend(cv.polling_component_schema("30s"))
 )
 
+FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
+    "daly_bms",
+    baud_rate=9600,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
+)
+
 
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])

esphome/components/daly_bms/daly_bms.cpp

@@ -22,10 +22,7 @@ static const uint8_t DALY_REQUEST_TEMPERATURE = 0x96;
 
 void DalyBmsComponent::setup() { this->next_request_ = 1; }
 
-void DalyBmsComponent::dump_config() {
-  ESP_LOGCONFIG(TAG, "Daly BMS:");
-  this->check_uart_settings(9600);
-}
+void DalyBmsComponent::dump_config() { ESP_LOGCONFIG(TAG, "Daly BMS:"); }
 
 void DalyBmsComponent::update() {
   this->trigger_next_ = true;

esphome/components/debug/debug_component.cpp

@@ -22,9 +22,9 @@ void DebugComponent::dump_config() {
   LOG_SENSOR("  ", "Free space on heap", this->free_sensor_);
   LOG_SENSOR("  ", "Largest free heap block", this->block_sensor_);
   LOG_SENSOR("  ", "CPU frequency", this->cpu_frequency_sensor_);
-#if defined(USE_ESP8266) && USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 5, 2)
+#ifdef USE_ESP8266
   LOG_SENSOR("  ", "Heap fragmentation", this->fragmentation_sensor_);
-#endif  // defined(USE_ESP8266) && USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 5, 2)
+#endif  // USE_ESP8266
 #endif  // USE_SENSOR
 
   char device_info_buffer[DEVICE_INFO_BUFFER_SIZE];

esphome/components/debug/debug_component.h

@@ -35,7 +35,7 @@ class DebugComponent final : public PollingComponent {
 #ifdef USE_SENSOR
   void set_free_sensor(sensor::Sensor *free_sensor) { free_sensor_ = free_sensor; }
   void set_block_sensor(sensor::Sensor *block_sensor) { block_sensor_ = block_sensor; }
-#if (defined(USE_ESP8266) && USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 5, 2)) || defined(USE_ESP32)
+#if defined(USE_ESP8266) || defined(USE_ESP32)
   void set_fragmentation_sensor(sensor::Sensor *fragmentation_sensor) { fragmentation_sensor_ = fragmentation_sensor; }
 #endif
 #if defined(USE_ESP32) || defined(USE_LIBRETINY)
@@ -61,7 +61,7 @@ class DebugComponent final : public PollingComponent {
 
   sensor::Sensor *free_sensor_{nullptr};
   sensor::Sensor *block_sensor_{nullptr};
-#if (defined(USE_ESP8266) && USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 5, 2)) || defined(USE_ESP32)
+#if defined(USE_ESP8266) || defined(USE_ESP32)
   sensor::Sensor *fragmentation_sensor_{nullptr};
 #endif
 #if defined(USE_ESP32) || defined(USE_LIBRETINY)

esphome/components/debug/debug_esp8266.cpp

@@ -159,12 +159,10 @@ void DebugComponent::update_platform_() {
     // NOLINTNEXTLINE(readability-static-accessed-through-instance)
     this->block_sensor_->publish_state(ESP.getMaxFreeBlockSize());
   }
-#if USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 5, 2)
   if (this->fragmentation_sensor_ != nullptr) {
     // NOLINTNEXTLINE(readability-static-accessed-through-instance)
     this->fragmentation_sensor_->publish_state(ESP.getHeapFragmentation());
   }
-#endif
 
 #endif
 }

esphome/components/debug/sensor.py

@@ -52,12 +52,9 @@ CONFIG_SCHEMA = {
     ),
     cv.Optional(CONF_FRAGMENTATION): cv.All(
         cv.Any(
-            cv.All(
-                cv.only_on_esp8266,
-                cv.require_framework_version(esp8266_arduino=cv.Version(2, 5, 2)),
-            ),
+            cv.only_on_esp8266,
             cv.only_on_esp32,
-            msg="This feature is only available on ESP8266 (Arduino 2.5.2+) and ESP32",
+            msg="This feature is only available on ESP8266 and ESP32",
         ),
         sensor.sensor_schema(
             unit_of_measurement=UNIT_PERCENT,

esphome/components/dfplayer/__init__.py

@@ -60,7 +60,12 @@ CONFIG_SCHEMA = cv.All(
     ).extend(uart.UART_DEVICE_SCHEMA)
 )
 FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
-    "dfplayer", baud_rate=9600, require_tx=True
+    "dfplayer",
+    baud_rate=9600,
+    require_tx=True,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
 )
 
 

esphome/components/dfplayer/dfplayer.cpp

@@ -277,9 +277,6 @@ void DFPlayer::loop() {
     }
   }
 }
-void DFPlayer::dump_config() {
-  ESP_LOGCONFIG(TAG, "DFPlayer:");
-  this->check_uart_settings(9600);
-}
+void DFPlayer::dump_config() { ESP_LOGCONFIG(TAG, "DFPlayer:"); }
 
 }  // namespace esphome::dfplayer

esphome/components/esp32_ble/ble.cpp

@@ -100,21 +100,38 @@ void ESP32BLE::disable() {
 #ifdef USE_ESP32_BLE_ADVERTISING
 void ESP32BLE::advertising_start() {
   this->advertising_init_();
-  if (!this->is_active())
+  this->advertising_ref_count_++;
+  this->advertising_refresh();
+}
+
+void ESP32BLE::advertising_stop() {
+  if (this->advertising_ref_count_ == 0)
     return;
-  this->advertising_->start();
+  this->advertising_ref_count_--;
+  this->advertising_refresh();
+}
+
+void ESP32BLE::advertising_refresh() {
+  if (this->advertising_ == nullptr || !this->is_active())
+    return;
+  // Advertise while any component still needs it, otherwise stop
+  if (this->advertising_ref_count_ == 0) {
+    this->advertising_->stop();
+  } else {
+    this->advertising_->start();
+  }
 }
 
 void ESP32BLE::advertising_set_service_data(const std::vector<uint8_t> &data) {
   this->advertising_init_();
   this->advertising_->set_service_data(data);
-  this->advertising_start();
+  this->advertising_refresh();
 }
 
 void ESP32BLE::advertising_set_manufacturer_data(const std::vector<uint8_t> &data) {
   this->advertising_init_();
   this->advertising_->set_manufacturer_data(data);
-  this->advertising_start();
+  this->advertising_refresh();
 }
 
 void ESP32BLE::advertising_set_service_data_and_name(std::span<const uint8_t> data, bool include_name) {
@@ -136,7 +153,7 @@ void ESP32BLE::advertising_set_service_data_and_name(std::span<const uint8_t> da
     this->advertising_->set_service_data(data);
   }
 
-  this->advertising_start();
+  this->advertising_refresh();
 }
 
 void ESP32BLE::advertising_register_raw_advertisement_callback(std::function<void(bool)> &&callback) {
@@ -147,13 +164,13 @@ void ESP32BLE::advertising_register_raw_advertisement_callback(std::function<voi
 void ESP32BLE::advertising_add_service_uuid(ESPBTUUID uuid) {
   this->advertising_init_();
   this->advertising_->add_service_uuid(uuid);
-  this->advertising_start();
+  this->advertising_refresh();
 }
 
 void ESP32BLE::advertising_remove_service_uuid(ESPBTUUID uuid) {
   this->advertising_init_();
   this->advertising_->remove_service_uuid(uuid);
-  this->advertising_start();
+  this->advertising_refresh();
 }
 #endif
 
@@ -575,6 +592,10 @@ void ESP32BLE::loop_handle_state_transition_not_active_() {
     }
 
     this->state_ = BLE_COMPONENT_STATE_ACTIVE;
+#ifdef USE_ESP32_BLE_ADVERTISING
+    // Requests made before the stack was up (or before it was re-enabled) take effect now
+    this->advertising_refresh();
+#endif
   }
 }
 

esphome/components/esp32_ble/ble.h

@@ -114,7 +114,17 @@ class ESP32BLE final : public Component {
   void set_name(const char *name) { this->name_ = name; }
 
 #ifdef USE_ESP32_BLE_ADVERTISING
+  /** Request advertising on behalf of a component.
+   *
+   * Requests are reference counted: advertising runs until every component that called
+   * advertising_start() has released it again with advertising_stop(). Each component must
+   * pair its calls, so nothing advertises until something actually asks for it.
+   */
   void advertising_start();
+  /// Release a request made with advertising_start(); advertising stops at the last release.
+  void advertising_stop();
+  /// Apply the current payload and request count: advertise while requested, otherwise stop.
+  void advertising_refresh();
   void advertising_set_service_data(const std::vector<uint8_t> &data);
   void advertising_set_manufacturer_data(const std::vector<uint8_t> &data);
   void advertising_set_appearance(uint16_t appearance) { this->appearance_ = appearance; }
@@ -226,6 +236,9 @@ class ESP32BLE final : public Component {
   // 1-byte aligned members (grouped together to minimize padding)
   BLEComponentState state_{BLE_COMPONENT_STATE_OFF};  // 1 byte (uint8_t enum)
   bool enable_on_boot_{};                             // 1 byte
+#ifdef USE_ESP32_BLE_ADVERTISING
+  uint8_t advertising_ref_count_{0};  // 1 byte, number of components requesting advertising
+#endif
 
 #ifdef ESPHOME_ESP32_BLE_EXTENDED_AUTH_PARAMS
   optional<esp_ble_auth_req_t> auth_req_mode_;

esphome/components/esp32_ble_beacon/esp32_ble_beacon.cpp

@@ -67,6 +67,8 @@ void ESP32BLEBeacon::setup() {
       this->on_advertise_();
     }
   });
+  // A beacon always needs the device to advertise, and never releases the request
+  global_ble->advertising_start();
 }
 
 void ESP32BLEBeacon::on_advertise_() {

esphome/components/esp32_ble_server/__init__.py

@@ -596,6 +596,18 @@ async def to_code(config):
     cg.add(var.set_parent(parent))
     cg.add(parent.advertising_set_appearance(config[CONF_APPEARANCE]))
     cg.add(var.set_max_clients(config[CONF_MAX_CLIENTS]))
+    # Only advertise for the server itself when the configuration gives clients something to
+    # find. A server that is auto-loaded purely to host a runtime service (esp32_improv) stays
+    # silent until that service asks for advertising.
+    cg.add(
+        var.set_advertising_required(
+            CONF_MANUFACTURER_DATA in config
+            or any(
+                not uuid_is(service_config[CONF_UUID], DEVICE_INFORMATION_SERVICE_UUID)
+                for service_config in config[CONF_SERVICES]
+            )
+        )
+    )
     if CONF_MANUFACTURER_DATA in config:
         cg.add(var.set_manufacturer_data(config[CONF_MANUFACTURER_DATA]))
     for service_config in config[CONF_SERVICES]:

esphome/components/esp32_ble_server/ble_server.cpp

@@ -81,6 +81,7 @@ void BLEServer::loop() {
       if (this->device_information_service_->is_running()) {
         this->state_ = RUNNING;
         this->restart_advertising_();
+        this->request_advertising_();
         ESP_LOGD(TAG, "BLE server setup successfully");
       } else if (this->device_information_service_->is_created()) {
         this->device_information_service_->start();
@@ -98,6 +99,20 @@ void BLEServer::restart_advertising_() {
   }
 }
 
+void BLEServer::request_advertising_() {
+  if (!this->advertising_required_ || this->advertising_requested_)
+    return;
+  this->advertising_requested_ = true;
+  this->parent_->advertising_start();
+}
+
+void BLEServer::release_advertising_() {
+  if (!this->advertising_requested_)
+    return;
+  this->advertising_requested_ = false;
+  this->parent_->advertising_stop();
+}
+
 BLEService *BLEServer::create_service(ESPBTUUID uuid, bool advertise, uint16_t num_handles) {
 #if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_VERBOSE
   char uuid_buf[esp32_ble::UUID_STR_LEN];
@@ -170,7 +185,7 @@ void BLEServer::gatts_event_handler(esp_gatts_cb_event_t event, esp_gatt_if_t ga
       this->add_client_(param->connect.conn_id);
       // Resume advertising so additional clients can discover and connect
       if (this->client_count_ < this->max_clients_) {
-        this->parent_->advertising_start();
+        this->parent_->advertising_refresh();
       }
       this->dispatch_callbacks_(CallbackType::ON_CONNECT, param->connect.conn_id);
       break;
@@ -178,7 +193,7 @@ void BLEServer::gatts_event_handler(esp_gatts_cb_event_t event, esp_gatt_if_t ga
     case ESP_GATTS_DISCONNECT_EVT: {
       ESP_LOGD(TAG, "BLE Client disconnected");
       this->remove_client_(param->disconnect.conn_id);
-      this->parent_->advertising_start();
+      this->parent_->advertising_refresh();
       this->dispatch_callbacks_(CallbackType::ON_DISCONNECT, param->disconnect.conn_id);
       break;
     }
@@ -226,6 +241,8 @@ void BLEServer::remove_client_(uint16_t conn_id) {
 }
 
 void BLEServer::ble_before_disabled_event_handler() {
+  // Advertising is re-requested once the server is running again after BLE is re-enabled
+  this->release_advertising_();
   // Delete all clients
   this->client_count_ = 0;
   // Delete all services

esphome/components/esp32_ble_server/ble_server.h

@@ -38,6 +38,13 @@ class BLEServer final : public Component, public Parented<ESP32BLE> {
     this->restart_advertising_();
   }
 
+  /** Whether this server needs the device to advertise so clients can find and connect to it.
+   *
+   * False for a server that only hosts services created at runtime (e.g. esp32_improv), which
+   * request advertising themselves for as long as they need it.
+   */
+  void set_advertising_required(bool required) { this->advertising_required_ = required; }
+
   void set_max_clients(uint8_t max_clients) { this->max_clients_ = max_clients; }
   uint8_t get_max_clients() const { return this->max_clients_; }
 
@@ -82,6 +89,8 @@ class BLEServer final : public Component, public Parented<ESP32BLE> {
   };
 
   void restart_advertising_();
+  void request_advertising_();
+  void release_advertising_();
 
   int8_t find_client_index_(uint16_t conn_id) const;
   void add_client_(uint16_t conn_id);
@@ -93,6 +102,8 @@ class BLEServer final : public Component, public Parented<ESP32BLE> {
   std::vector<uint8_t> manufacturer_data_{};
   esp_gatt_if_t gatts_if_{0};
   bool registered_{false};
+  bool advertising_required_{true};
+  bool advertising_requested_{false};
 
   uint16_t clients_[USE_ESP32_BLE_MAX_CONNECTIONS]{};
   uint8_t client_count_{0};

esphome/components/esp32_hosted/__init__.py

@@ -37,6 +37,25 @@ CONF_HANDSHAKE_PIN = "handshake_pin"
 CONF_SDIO_FREQUENCY = "sdio_frequency"
 CONF_SPI_MODE = "spi_mode"
 
+# ESP-NOW-over-hosted shim (esp_now_hosted.cpp). esp-hosted proxies esp_wifi.h
+# but not esp_now.h (espressif/esp-hosted-mcu#19), and esp_wifi_remote injects
+# the esp_now.h header on the ESP32-P4 host with no implementation, leaving the
+# esp_now_* symbols undefined at link. On a P4 host, esp_now_hosted.cpp DEFINES
+# those symbols and forwards each call to the co-processor over esp-hosted's
+# CustomRpc "peer data transfer" channel, so ESPHome's `espnow` component links
+# and runs unchanged (proven on a Tab5, 2026-07-20). The .cpp is guarded to
+# CONFIG_IDF_TARGET_ESP32P4 so it compiles to nothing on hosts with a native
+# ESP-NOW stack. CustomRpc needs these two host-side Kconfig options. Host
+# registers 3 handlers (RESP, RECV, SEND); the coprocessor registers 1 (REQ);
+# we ask for 8 to leave room for other CustomRpc extensions alongside.
+#
+# The coprocessor must run the matching custom firmware (a parallel effort in
+# esphome/esp-hosted-firmware). esp_now_hosted_rpc.h here is the canonical copy
+# of the wire contract and MUST stay byte-identical to the copy that coprocessor
+# firmware uses — the packed structs are the on-wire layout, so any divergence
+# silently corrupts every ESP-NOW frame.
+_MAX_CUSTOM_MSG_HANDLERS = 8
+
 # Shared fields for both transport modes
 BASE_SCHEMA = cv.Schema(
     {
@@ -262,6 +281,23 @@ async def to_code(config: ConfigType) -> None:
     else:
         _configure_spi(config)
 
+    # ESP-NOW-over-hosted shim: only the radio-less ESP32-P4 host needs it (see
+    # the note by _MAX_CUSTOM_MSG_HANDLERS). Enabled for every P4 host, not
+    # gated on the `espnow` component being present: the shim is tiny and the
+    # esp_now_* symbols/CustomRpc calls it defines require these Kconfig options
+    # to link whenever esp_now_hosted.cpp compiles (which is on any P4 host), so
+    # coupling the two keeps the build consistent. When `espnow` is absent the
+    # symbols are simply unused and never register a callback at runtime.
+    if esp32.get_esp32_variant() == esp32.VARIANT_ESP32P4:
+        add_define("USE_ESP_NOW_HOSTED")
+        # esp-hosted's CustomRpc ("peer data transfer") path — off by default.
+        esp32.add_idf_sdkconfig_option(
+            "CONFIG_ESP_HOSTED_ENABLE_PEER_DATA_TRANSFER", True
+        )
+        esp32.add_idf_sdkconfig_option(
+            "CONFIG_ESP_HOSTED_MAX_CUSTOM_MSG_HANDLERS", _MAX_CUSTOM_MSG_HANDLERS
+        )
+
     # Place the transport mempool in PSRAM. Required on memory-tight host
     # configurations (e.g. P4 with a large LVGL UI) where the internal-RAM
     # mempool allocation fails at boot with `sdio_mempool_create` assert.

esphome/components/esp32_hosted/esp_now_hosted.cpp

@@ -0,0 +1,467 @@
+/*
+ * esp_now_hosted — host-side shim implementing <esp_now.h> over esp-hosted
+ * CustomRpc, so ESPHome's `espnow` component can run on a radio-less host
+ * (e.g. the ESP32-P4) whose radio lives on an esp-hosted co-processor.
+ *
+ * A radio-less host has no native ESP-NOW. esp_wifi_remote INJECTS the full
+ * esp_now.h header (types + declarations) but ships NO implementation, so every
+ * esp_now_* symbol is an undefined reference at link time. This translation
+ * unit provides those definitions; each forwards to the co-processor over
+ * CustomRpc (see esphome/esp-hosted-firmware for the matching coprocessor
+ * handlers). No esp-hosted or esp_wifi_remote source is patched, and there is no
+ * duplicate-symbol clash because nothing else defines these symbols here.
+ *
+ * See esp_now_hosted_rpc.h for the wire protocol.
+ */
+
+#include "sdkconfig.h"
+
+// Only build the shim on the radio-less host. On chips with a native ESP-NOW
+// stack (S3, C6, …) the real symbols exist and this file must stay empty to
+// avoid duplicate definitions.
+#if defined(CONFIG_IDF_TARGET_ESP32P4)
+
+#include <cstring>
+
+#include "freertos/FreeRTOS.h"
+#include "freertos/semphr.h"
+
+#include "esp_idf_version.h"
+#include "esp_log.h"
+#include "esp_timer.h"
+
+#include <esp_now.h>         // injected declarations we are now DEFINING
+#include <esp_wifi_types.h>  // wifi_pkt_rx_ctrl_t, wifi_tx_info_t
+
+// esp_hosted_misc.h (host) ships WITHOUT an extern "C" guard, so including it
+// from C++ would give its declarations C++ linkage and the real C symbols in
+// libesp_hosted would go unresolved at link. Wrap it. (Verified vs
+// esp_hosted 2.12.9.)
+extern "C" {
+#include "esp_hosted_misc.h"  // esp_hosted_{send_custom_data,register_custom_callback}
+}
+
+#include "esp_now_hosted_rpc.h"
+
+namespace {
+
+const char *const TAG = "esp_now_hosted";
+
+// One outstanding request at a time. ESPHome drives esp_now_* from the main
+// loop; the matching response and the async RECV/SEND events all arrive on the
+// single esp-hosted RPC RX thread. Serializing requests keeps the shared
+// response slot race-free; a sequence number stops a late/stale response from
+// being mistaken for ours.
+SemaphoreHandle_t g_req_mutex = nullptr;
+SemaphoreHandle_t g_resp_sem = nullptr;  // given when the matching RESP lands
+bool g_setup_done = false;               // set only after setup fully succeeds
+uint8_t g_seq = 0;
+volatile uint8_t g_expect_seq = 0;
+volatile int32_t g_resp_status = 0;
+uint8_t g_resp_ret[16];
+volatile uint16_t g_resp_ret_len = 0;
+
+// Written from the main loop (register/unregister/deinit), read from the
+// esp-hosted RX thread (on_recv/on_send). volatile for the same reason the
+// g_resp_* globals are: force the RX thread to observe an updated pointer
+// (e.g. a nulling by esp_now_deinit) rather than a cached one.
+volatile esp_now_recv_cb_t g_recv_cb = nullptr;
+volatile esp_now_send_cb_t g_send_cb = nullptr;
+
+// Local mirror of the co-processor's peer table. ESPHome's espnow component
+// calls esp_now_is_peer_exist() on the main loop for every received frame
+// (twice) and every send; forwarding each as a blocking RPC round-trip stalls
+// the loop. The shim is the only path that mutates the co-processor peer table
+// (add/del/deinit all go through here), so this mirror is authoritative and
+// esp_now_is_peer_exist() can answer from it with no round-trip.
+//
+// esp_now_* are public C symbols: any component or user lambda may call them,
+// and although ESPHome's espnow touches peers only from the main loop today
+// (its RX/TX callbacks merely enqueue), the shim cannot rely on that. A short
+// spinlock keeps the mirror consistent from any task/core, matching native
+// esp_now_*'s own internal thread-safety. The critical sections are a bounded
+// (<=20-entry) scan, so they stay tiny. ESP_NOW_MAX_TOTAL_PEER_NUM is 20.
+constexpr size_t ESP_NOW_HOSTED_MAX_PEERS = 20;
+uint8_t g_peer_cache[ESP_NOW_HOSTED_MAX_PEERS][6];
+size_t g_peer_count = 0;
+portMUX_TYPE g_peer_lock = portMUX_INITIALIZER_UNLOCKED;
+
+// Caller must hold g_peer_lock.
+int peer_cache_find_locked(const uint8_t *mac) {
+  for (size_t i = 0; i < g_peer_count; i++) {
+    if (memcmp(g_peer_cache[i], mac, 6) == 0)
+      return static_cast<int>(i);
+  }
+  return -1;
+}
+
+bool peer_cache_contains(const uint8_t *mac) {
+  portENTER_CRITICAL(&g_peer_lock);
+  const bool found = peer_cache_find_locked(mac) >= 0;
+  portEXIT_CRITICAL(&g_peer_lock);
+  return found;
+}
+
+void peer_cache_add(const uint8_t *mac) {
+  portENTER_CRITICAL(&g_peer_lock);
+  if (peer_cache_find_locked(mac) < 0 && g_peer_count < ESP_NOW_HOSTED_MAX_PEERS)
+    memcpy(g_peer_cache[g_peer_count++], mac, 6);
+  portEXIT_CRITICAL(&g_peer_lock);
+}
+
+void peer_cache_remove(const uint8_t *mac) {
+  portENTER_CRITICAL(&g_peer_lock);
+  const int idx = peer_cache_find_locked(mac);
+  if (idx >= 0) {
+    g_peer_count--;
+    if (static_cast<size_t>(idx) != g_peer_count)  // move the last entry into the gap
+      memcpy(g_peer_cache[idx], g_peer_cache[g_peer_count], 6);
+  }
+  portEXIT_CRITICAL(&g_peer_lock);
+}
+
+void peer_cache_clear() {
+  portENTER_CRITICAL(&g_peer_lock);
+  g_peer_count = 0;
+  portEXIT_CRITICAL(&g_peer_lock);
+}
+
+// ── CustomRpc event handlers (run on the esp-hosted RPC RX thread) ──────────
+// Keep them short and non-blocking. In particular they MUST NOT call back into
+// any esp_now_* shim function: that would try to take g_req_mutex / wait on the
+// RX thread that delivers the response, and deadlock.
+
+void on_resp(uint32_t /*msg_id*/, const uint8_t *data, size_t len, void * /*ctx*/) {
+  if (len < sizeof(esp_now_hosted_resp_t)) {
+    ESP_LOGW(TAG, "RESP too short: %u bytes", static_cast<unsigned>(len));
+    return;
+  }
+  const auto *r = reinterpret_cast<const esp_now_hosted_resp_t *>(data);
+  if (r->seq != g_expect_seq) {  // late response from a timed-out request (expected)
+    ESP_LOGV(TAG, "dropping stale RESP seq %u (want %u)", r->seq, g_expect_seq);
+    return;
+  }
+  g_resp_status = r->status;
+  uint16_t rl = r->ret_len;
+  if (rl > sizeof(g_resp_ret)) {
+    // Larger than any real opcode return — a likely wire-format drift signal.
+    ESP_LOGW(TAG, "RESP ret_len %u exceeds buffer, clamping (wire drift?)", rl);
+    rl = sizeof(g_resp_ret);
+  }
+  if (len >= sizeof(esp_now_hosted_resp_t) + rl) {
+    memcpy(g_resp_ret, r->ret, rl);
+  } else {
+    // Truncated frame: fail closed. Never hand the caller stale bytes left in
+    // g_resp_ret by a previous response, and don't let request() report a
+    // zeroed payload as success — override the status to an error.
+    ESP_LOGW(TAG, "RESP truncated: claims %u ret bytes, frame too short", rl);
+    rl = 0;
+    g_resp_status = ESP_ERR_INVALID_RESPONSE;
+  }
+  g_resp_ret_len = rl;
+  xSemaphoreGive(g_resp_sem);
+}
+
+void on_recv(uint32_t /*msg_id*/, const uint8_t *data, size_t len, void * /*ctx*/) {
+  // Read the volatile pointer once: esp_now_unregister_recv_cb()/deinit() (via
+  // the espnow component's disable()) can null it on the main loop between the
+  // guard and the call, which would otherwise turn the call into a null-deref.
+  const esp_now_recv_cb_t cb = g_recv_cb;
+  if (cb == nullptr)
+    return;
+  if (len < sizeof(esp_now_hosted_recv_evt_t)) {
+    ESP_LOGW(TAG, "RECV too short: %u bytes", static_cast<unsigned>(len));
+    return;
+  }
+  const auto *e = reinterpret_cast<const esp_now_hosted_recv_evt_t *>(data);
+  if (len < sizeof(esp_now_hosted_recv_evt_t) + e->data_len) {
+    ESP_LOGW(TAG, "RECV data_len %u exceeds frame", e->data_len);
+    return;
+  }
+
+  // ESPHome dereferences info->rx_ctrl->{rssi,timestamp}; give it a real one.
+  wifi_pkt_rx_ctrl_t rx_ctrl;
+  memset(&rx_ctrl, 0, sizeof(rx_ctrl));
+  rx_ctrl.rssi = e->rssi;
+  rx_ctrl.channel = e->channel;
+  rx_ctrl.timestamp = static_cast<uint32_t>(esp_timer_get_time());
+
+  esp_now_recv_info_t info;
+  info.src_addr = const_cast<uint8_t *>(e->src_addr);
+  info.des_addr = const_cast<uint8_t *>(e->des_addr);
+  info.rx_ctrl = &rx_ctrl;
+  cb(&info, e->data, static_cast<int>(e->data_len));
+}
+
+void on_send(uint32_t /*msg_id*/, const uint8_t *data, size_t len, void * /*ctx*/) {
+  // Read the volatile pointer once (see on_recv): disable()/deinit() can null it
+  // on the main loop concurrently with this RX-thread callback.
+  const esp_now_send_cb_t cb = g_send_cb;
+  if (cb == nullptr)
+    return;
+  if (len < sizeof(esp_now_hosted_send_evt_t)) {
+    ESP_LOGW(TAG, "SEND evt too short: %u bytes", static_cast<unsigned>(len));
+    return;
+  }
+  const auto *e = reinterpret_cast<const esp_now_hosted_send_evt_t *>(data);
+#if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 5, 0)
+  // IDF >= 5.5: esp_now_send_cb_t takes esp_now_send_info_t (== wifi_tx_info_t),
+  // whose des_addr is a POINTER (not an inline array). Point it at the event's
+  // MAC (valid for this callback) — do NOT memcpy into it (that writes NULL and
+  // faults). ESPHome reads only info->des_addr.
+  esp_now_send_info_t si;
+  memset(&si, 0, sizeof(si));
+  si.des_addr = const_cast<uint8_t *>(e->des_addr);
+  cb(&si, static_cast<esp_now_send_status_t>(e->status));
+#else
+  cb(e->des_addr, static_cast<esp_now_send_status_t>(e->status));
+#endif
+}
+
+esp_err_t ensure_setup() {
+  // Gate on g_setup_done, not on g_req_mutex: a failure part-way through (a
+  // semaphore that did not allocate, a callback that did not register) must not
+  // leave a later call thinking setup completed. Semaphore creation is guarded
+  // so a retry after a partial failure does not leak the earlier handles.
+  if (g_setup_done)
+    return ESP_OK;
+  if (g_req_mutex == nullptr)
+    g_req_mutex = xSemaphoreCreateMutex();
+  if (g_resp_sem == nullptr)
+    g_resp_sem = xSemaphoreCreateBinary();
+  if (g_req_mutex == nullptr || g_resp_sem == nullptr)
+    return ESP_ERR_NO_MEM;
+  esp_err_t err;
+  if ((err = esp_hosted_register_custom_callback(ESP_NOW_HOSTED_MSG_RESP, on_resp, nullptr)) != ESP_OK)
+    return err;
+  if ((err = esp_hosted_register_custom_callback(ESP_NOW_HOSTED_MSG_RECV, on_recv, nullptr)) != ESP_OK)
+    return err;
+  if ((err = esp_hosted_register_custom_callback(ESP_NOW_HOSTED_MSG_SEND, on_send, nullptr)) != ESP_OK)
+    return err;
+  g_setup_done = true;
+  return ESP_OK;
+}
+
+// Send one request envelope. With wait=true (default) block until the matching
+// response (or timeout); with wait=false return as soon as the frame is handed
+// to the transport (fire-and-forget, used by esp_now_send).
+//
+// `tail` is an optional second chunk written straight after `payload`. Callers
+// with a fixed header plus a bulk body (esp_now_send) pass the two separately
+// so they never need a build buffer of their own: both chunks are laid into the
+// request buffer here, under g_req_mutex, which keeps concurrent callers from
+// racing and saves a full copy of the body on every transmit.
+esp_err_t request(uint8_t opcode, const void *payload, uint16_t plen, void *ret, uint16_t ret_cap, uint16_t *ret_len,
+                  bool wait = true, const void *tail = nullptr, uint16_t tail_len = 0) {
+  esp_err_t err = ensure_setup();
+  if (err != ESP_OK)
+    return err;
+  if (plen > ESP_NOW_HOSTED_MAX_PAYLOAD || tail_len > ESP_NOW_HOSTED_MAX_PAYLOAD - plen)
+    return ESP_ERR_INVALID_SIZE;
+  const uint16_t total_len = static_cast<uint16_t>(plen + tail_len);
+
+  if (xSemaphoreTake(g_req_mutex, portMAX_DELAY) != pdTRUE)
+    return ESP_FAIL;
+
+  static uint8_t buf[sizeof(esp_now_hosted_req_t) + ESP_NOW_HOSTED_MAX_PAYLOAD];  // guarded by g_req_mutex
+  auto *req = reinterpret_cast<esp_now_hosted_req_t *>(buf);
+  req->opcode = opcode;
+  req->seq = ++g_seq;
+  req->payload_len = total_len;
+  if (plen != 0)
+    memcpy(req->payload, payload, plen);
+  if (tail_len != 0)
+    memcpy(req->payload + plen, tail, tail_len);
+  g_expect_seq = req->seq;
+
+  xSemaphoreTake(g_resp_sem, 0);  // drain any stale signal before sending
+  err = esp_hosted_send_custom_data(ESP_NOW_HOSTED_MSG_REQ, buf, sizeof(esp_now_hosted_req_t) + total_len);
+  if (err != ESP_OK) {
+    xSemaphoreGive(g_req_mutex);
+    return err;
+  }
+  if (!wait) {
+    // Fire-and-forget (esp_now_send): the co-processor enqueues the frame and
+    // reports the real TX result later via the async SEND event, exactly like
+    // native esp_now_send. Returning here keeps the main loop off the ~100 ms+
+    // RPC round-trip. The matching RESP is ignored (seq won't match the next
+    // waited request, so on_resp drops it).
+    xSemaphoreGive(g_req_mutex);
+    return ESP_OK;
+  }
+  if (xSemaphoreTake(g_resp_sem, pdMS_TO_TICKS(ESP_NOW_HOSTED_TIMEOUT_MS)) != pdTRUE) {
+    ESP_LOGW(TAG, "opcode %u timed out", opcode);
+    xSemaphoreGive(g_req_mutex);
+    return ESP_ERR_TIMEOUT;
+  }
+
+  const int32_t status = g_resp_status;
+  if (ret != nullptr && ret_cap != 0) {
+    uint16_t n = g_resp_ret_len < ret_cap ? g_resp_ret_len : ret_cap;
+    memcpy(ret, const_cast<const uint8_t *>(g_resp_ret), n);
+    if (ret_len != nullptr)
+      *ret_len = n;
+  }
+  xSemaphoreGive(g_req_mutex);
+  return static_cast<esp_err_t>(status);
+}
+
+}  // namespace
+
+// ── The <esp_now.h> surface, defined for the radio-less host ────────────────
+extern "C" {
+
+esp_err_t esp_now_init(void) { return request(ESP_NOW_HOSTED_OP_INIT, nullptr, 0, nullptr, 0, nullptr); }
+
+esp_err_t esp_now_deinit(void) {
+  g_recv_cb = nullptr;
+  g_send_cb = nullptr;
+  peer_cache_clear();  // the co-processor drops all peers on deinit
+  return request(ESP_NOW_HOSTED_OP_DEINIT, nullptr, 0, nullptr, 0, nullptr);
+}
+
+esp_err_t esp_now_get_version(uint32_t *version) {
+  uint32_t v = 0;
+  uint16_t rl = 0;
+  esp_err_t err = request(ESP_NOW_HOSTED_OP_GET_VERSION, nullptr, 0, &v, sizeof(v), &rl);
+  if (version != nullptr)
+    *version = v;
+  return err;
+}
+
+esp_err_t esp_now_register_recv_cb(esp_now_recv_cb_t cb) {
+  // Only arm the callback once the CustomRpc handlers are actually registered,
+  // so a failed setup leaves g_recv_cb null rather than falsely "registered".
+  esp_err_t err = ensure_setup();
+  if (err != ESP_OK)
+    return err;
+  g_recv_cb = cb;
+  return ESP_OK;
+}
+esp_err_t esp_now_unregister_recv_cb(void) {
+  g_recv_cb = nullptr;
+  return ESP_OK;
+}
+esp_err_t esp_now_register_send_cb(esp_now_send_cb_t cb) {
+  esp_err_t err = ensure_setup();
+  if (err != ESP_OK)
+    return err;
+  g_send_cb = cb;
+  return ESP_OK;
+}
+esp_err_t esp_now_unregister_send_cb(void) {
+  g_send_cb = nullptr;
+  return ESP_OK;
+}
+
+static esp_err_t add_or_mod_peer(uint8_t opcode, const esp_now_peer_info_t *peer, bool wait) {
+  if (peer == nullptr)
+    return ESP_ERR_ESPNOW_ARG;
+  esp_now_hosted_peer_t p;
+  memset(&p, 0, sizeof(p));
+  memcpy(p.peer_addr, peer->peer_addr, 6);
+  memcpy(p.lmk, peer->lmk, 16);
+  p.channel = peer->channel;
+  p.ifidx = static_cast<uint8_t>(peer->ifidx);
+  p.encrypt = peer->encrypt ? 1 : 0;
+  return request(opcode, &p, sizeof(p), nullptr, 0, nullptr, wait);
+}
+esp_err_t esp_now_add_peer(const esp_now_peer_info_t *peer) {
+  // Fire-and-forget (wait=false): adding a peer is a blocking RPC round-trip,
+  // and ESPHome's espnow calls it on the main loop when a device joins the mesh
+  // — under co-processor load that stalls the UI (peer-churn stutter). Issue it
+  // without waiting and mirror it locally. Safe against a following
+  // esp_now_send to the same peer: both ride the same in-order CustomRpc
+  // channel (mutex-serialized on the host) and the co-processor processes REQs
+  // FIFO, so ADD_PEER is applied before the SEND. Trade-off: a co-processor-side
+  // failure (e.g. peer table full) is no longer reported synchronously — the
+  // same limitation as esp_now_send — but ESPHome only adds peers it validated.
+  esp_err_t err = add_or_mod_peer(ESP_NOW_HOSTED_OP_ADD_PEER, peer, /*wait=*/false);
+  if (err == ESP_OK)
+    peer_cache_add(peer->peer_addr);  // keep the local mirror in sync
+  return err;
+}
+esp_err_t esp_now_mod_peer(const esp_now_peer_info_t *peer) {
+  // mod_peer changes a peer's parameters, not its existence, so the cache is
+  // unaffected. Kept synchronous — it is not on any hot path (espnow never
+  // calls it), so the extra round-trip does not matter and the status is useful.
+  return add_or_mod_peer(ESP_NOW_HOSTED_OP_MOD_PEER, peer, /*wait=*/true);
+}
+
+esp_err_t esp_now_del_peer(const uint8_t *peer_addr) {
+  if (peer_addr == nullptr)
+    return ESP_ERR_ESPNOW_ARG;
+  // Fire-and-forget for the same reason as add_peer (peer churn on the main
+  // loop). Removal is order-independent, so this is strictly safe.
+  esp_err_t err = request(ESP_NOW_HOSTED_OP_DEL_PEER, peer_addr, 6, nullptr, 0, nullptr, /*wait=*/false);
+  if (err == ESP_OK)
+    peer_cache_remove(peer_addr);  // keep the local mirror in sync
+  return err;
+}
+
+bool esp_now_is_peer_exist(const uint8_t *peer_addr) {
+  if (peer_addr == nullptr)
+    return false;
+  // Answered from the local mirror — no RPC round-trip. ESPHome's espnow calls
+  // this on the main loop for every received frame and every send, so a
+  // blocking round-trip here would stall rendering under mesh traffic.
+  return peer_cache_contains(peer_addr);
+}
+
+esp_err_t esp_now_send(const uint8_t *peer_addr, const uint8_t *data, size_t len) {
+  if (len > ESP_NOW_HOSTED_MAX_FRAME)
+    return ESP_ERR_ESPNOW_ARG;
+  if (data == nullptr && len != 0)  // native esp_now_send treats this as an arg error
+    return ESP_ERR_ESPNOW_ARG;
+  // Only the small fixed header is built here; the caller's frame goes over as
+  // the request tail, so request() lays both into its own buffer under
+  // g_req_mutex. esp_now_send is a public C symbol and may be called from any
+  // task, and a shared build buffer here would let two callers corrupt each
+  // other's frame. Passing the body through also drops a full-frame copy per
+  // transmit, on the path this shim exists to keep quick.
+  uint8_t hdr[sizeof(esp_now_hosted_send_req_t)];
+  auto *s = reinterpret_cast<esp_now_hosted_send_req_t *>(hdr);
+  s->has_addr = peer_addr != nullptr ? 1 : 0;
+  if (peer_addr != nullptr)
+    memcpy(s->peer_addr, peer_addr, 6);
+  else
+    memset(s->peer_addr, 0, 6);
+  s->data_len = static_cast<uint16_t>(len);
+  // Fire-and-forget (wait=false): native esp_now_send returns once the frame is
+  // queued, with the real TX result delivered later through the send callback.
+  // The co-processor mirrors that — it acks enqueue immediately and reports the
+  // outcome via the async SEND event (on_send -> on_send_report). Waiting for
+  // the RPC RESP here would block the main loop for the full round-trip on
+  // every transmit.
+  return request(ESP_NOW_HOSTED_OP_SEND, hdr, sizeof(hdr), nullptr, 0, nullptr, /*wait=*/false, data,
+                 static_cast<uint16_t>(len));
+}
+
+esp_err_t esp_now_set_pmk(const uint8_t *pmk) {
+  if (pmk == nullptr)
+    return ESP_ERR_ESPNOW_ARG;
+  return request(ESP_NOW_HOSTED_OP_SET_PMK, pmk, 16, nullptr, 0, nullptr);
+}
+
+// Remainder of the <esp_now.h> surface. Not used by ESPHome's espnow component
+// today; provided so the whole header links and future callers get a defined
+// (if unimplemented) symbol rather than a link error. Wire them through
+// CustomRpc if a use case appears.
+esp_err_t esp_now_get_peer(const uint8_t * /*peer_addr*/, esp_now_peer_info_t * /*peer*/) {
+  return ESP_ERR_NOT_SUPPORTED;
+}
+esp_err_t esp_now_fetch_peer(bool /*from_head*/, esp_now_peer_info_t * /*peer*/) { return ESP_ERR_NOT_SUPPORTED; }
+esp_err_t esp_now_get_peer_num(esp_now_peer_num_t * /*num*/) { return ESP_ERR_NOT_SUPPORTED; }
+esp_err_t esp_now_set_wake_window(uint16_t /*window*/) {
+  return ESP_ERR_NOT_SUPPORTED;  // power-save wake window is not forwarded; don't claim success
+}
+esp_err_t esp_now_set_peer_rate_config(const uint8_t * /*peer_addr*/, esp_now_rate_config_t * /*cfg*/) {
+  return ESP_ERR_NOT_SUPPORTED;
+}
+esp_err_t esp_wifi_config_espnow_rate(wifi_interface_t /*ifx*/, wifi_phy_rate_t /*rate*/) {
+  return ESP_ERR_NOT_SUPPORTED;
+}
+
+}  // extern "C"
+
+#endif  // CONFIG_IDF_TARGET_ESP32P4

esphome/components/esp32_hosted/esp_now_hosted_rpc.h

@@ -0,0 +1,128 @@
+/*
+ * esp_now_hosted — ESP-NOW-over-CustomRpc wire protocol.
+ *
+ * Shared, byte-for-byte-identical contract between:
+ *   - the host shim         (esphome/components/esp32_hosted/esp_now_hosted.cpp)
+ *   - the coprocessor firmware (esphome/esp-hosted-firmware)
+ *
+ * It rides esp-hosted's CustomRpc channel (RPC ID 388, "peer data transfer",
+ * available since esp-hosted v2.8.1), teaching the radio-less host <-> radio
+ * co-processor link to carry esp_now.h, which esp-hosted itself does not proxy
+ * (Espressif issue espressif/esp-hosted-mcu#19).
+ *
+ * KEEP THE TWO COPIES IN SYNC. The canonical copy lives here; the coprocessor
+ * firmware uses a verbatim copy. Both sides are little-endian, so these packed
+ * structs are wire-compatible with no byte-swapping.
+ */
+
+#ifndef ESP_NOW_HOSTED_RPC_H
+#define ESP_NOW_HOSTED_RPC_H
+
+#ifdef __cplusplus
+#include <cstdint>
+#else
+#include <stdint.h>
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* ── CustomRpc message IDs (any uint32_t except 0xFFFFFFFF) ──────────────────
+ * One REQ handler slot on the device; three event handler slots on the host.
+ * The bytes spell "now" + index, a private range unlikely to clash with other
+ * CustomRpc users (e.g. the stock peer_data_transfer example's 1..6).         */
+#define ESP_NOW_HOSTED_MSG_REQ 0x6E6F7701u  /* host   -> device : request envelope */
+#define ESP_NOW_HOSTED_MSG_RESP 0x6E6F7702u /* device -> host   : reply to a REQ   */
+#define ESP_NOW_HOSTED_MSG_RECV 0x6E6F7703u /* device -> host   : async RX frame   */
+#define ESP_NOW_HOSTED_MSG_SEND 0x6E6F7704u /* device -> host   : async TX status  */
+
+/* ── Request opcodes ────────────────────────────────────────────────────── */
+enum {
+  ESP_NOW_HOSTED_OP_INIT = 1,          /* esp_now_init + register device recv/send cbs */
+  ESP_NOW_HOSTED_OP_DEINIT = 2,        /* unregister cbs + esp_now_deinit             */
+  ESP_NOW_HOSTED_OP_ADD_PEER = 3,      /* payload: esp_now_hosted_peer_t              */
+  ESP_NOW_HOSTED_OP_DEL_PEER = 4,      /* payload: 6-byte peer MAC                    */
+  ESP_NOW_HOSTED_OP_IS_PEER_EXIST = 5, /* payload: 6-byte MAC; ret: 1 byte bool       */
+  ESP_NOW_HOSTED_OP_SEND = 6,          /* payload: esp_now_hosted_send_req_t          */
+  ESP_NOW_HOSTED_OP_GET_VERSION = 7,   /* ret: uint32 version                        */
+  ESP_NOW_HOSTED_OP_SET_PMK = 8,       /* payload: 16-byte PMK                        */
+  ESP_NOW_HOSTED_OP_MOD_PEER = 9,      /* payload: esp_now_hosted_peer_t              */
+};
+
+/* Largest ESP-NOW payload we forward. ESP-NOW v2 (IDF >= 5.4) is 1470 B; well
+ * under esp-hosted's 8166 B CustomRpc cap, so the shim never truncates.        */
+#define ESP_NOW_HOSTED_MAX_FRAME 1470u
+/* Envelope slack for the largest opcode payload (a SEND req wrapping a frame). */
+#define ESP_NOW_HOSTED_MAX_PAYLOAD (ESP_NOW_HOSTED_MAX_FRAME + 16u)
+/* Host request/response round-trip timeout over the transport. Generous:
+ * normal RTT is sub-millisecond, but Wi-Fi/BLE contention on the co-processor
+ * can stall the RX thread.                                                     */
+#define ESP_NOW_HOSTED_TIMEOUT_MS 2000
+
+/* ── Envelopes ──────────────────────────────────────────────────────────── */
+
+/* These payloads are shared verbatim with the C co-processor firmware, so they
+ * use C's `typedef struct {...} name;` idiom rather than C++ `using` aliases,
+ * which would not compile there. Silence clang-tidy's modernize-use-using for
+ * the shared struct block. */
+// NOLINTBEGIN(modernize-use-using)
+typedef struct {
+  uint8_t opcode;       /* one of ESP_NOW_HOSTED_OP_*                        */
+  uint8_t seq;          /* wraps 0..255; echoed in the response for matching */
+  uint16_t payload_len; /* bytes of opcode-specific payload that follow      */
+  uint8_t payload[];    /* flexible                                          */
+} __attribute__((packed)) esp_now_hosted_req_t;
+
+typedef struct {
+  uint8_t opcode;   /* echoes the request opcode                         */
+  uint8_t seq;      /* echoes the request seq                            */
+  int32_t status;   /* esp_err_t from the native call on the co-processor */
+  uint16_t ret_len; /* bytes of return payload that follow               */
+  uint8_t ret[];    /* flexible (e.g. version u32, is_peer_exist bool)   */
+} __attribute__((packed)) esp_now_hosted_resp_t;
+
+/* ── Opcode payloads ────────────────────────────────────────────────────── */
+
+/* esp_now_peer_info_t minus the host-only `priv` pointer, which is meaningless
+ * across the transport and never set by ESPHome's espnow component.           */
+typedef struct {
+  uint8_t peer_addr[6];
+  uint8_t lmk[16];
+  uint8_t channel; /* 0 = current channel                              */
+  uint8_t ifidx;   /* wifi_interface_t (0=STA, 1=AP)                    */
+  uint8_t encrypt; /* bool                                             */
+} __attribute__((packed)) esp_now_hosted_peer_t;
+
+typedef struct {
+  uint8_t has_addr; /* 0 => peer_addr is NULL (broadcast to all peers)   */
+  uint8_t peer_addr[6];
+  uint16_t data_len;
+  uint8_t data[]; /* flexible, up to ESP_NOW_HOSTED_MAX_FRAME          */
+} __attribute__((packed)) esp_now_hosted_send_req_t;
+
+/* ── Async events (device -> host) ──────────────────────────────────────── */
+
+/* Reconstructed on the host into an esp_now_recv_info_t + a minimal
+ * wifi_pkt_rx_ctrl_t. ESPHome's espnow reads info->src_addr, info->des_addr,
+ * info->rx_ctrl->rssi and info->rx_ctrl->timestamp.                           */
+typedef struct {
+  uint8_t src_addr[6];
+  uint8_t des_addr[6];
+  int8_t rssi;
+  uint8_t channel;
+  uint16_t data_len;
+  uint8_t data[]; /* flexible                                          */
+} __attribute__((packed)) esp_now_hosted_recv_evt_t;
+
+typedef struct {
+  uint8_t des_addr[6];
+  uint8_t status; /* esp_now_send_status_t (0 = success)               */
+} __attribute__((packed)) esp_now_hosted_send_evt_t;
+// NOLINTEND(modernize-use-using)
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ESP_NOW_HOSTED_RPC_H */

esphome/components/esp32_improv/esp32_improv_component.cpp

@@ -112,6 +112,7 @@ void ESP32ImprovComponent::loop() {
       this->state_callback_.call(this->state_, this->error_state_);
 #endif
     }
+    this->release_advertising_();
     this->incoming_data_.clear();
     return;
   }
@@ -143,8 +144,9 @@ void ESP32ImprovComponent::loop() {
           ESP_LOGV(TAG, "Starting with device name advertising");
           this->advertising_device_name_ = true;
           this->last_name_adv_time_ = App.get_loop_component_start_time();
+          // Set the payload before requesting, so advertising starts exactly once
           esp32_ble::global_ble->advertising_set_service_data_and_name(std::span<const uint8_t>{}, true);
-          esp32_ble::global_ble->advertising_start();
+          this->request_advertising_();
 
           // Set initial state based on whether we have an authorizer
           this->set_state_(this->get_initial_state_(), false);
@@ -326,6 +328,8 @@ void ESP32ImprovComponent::stop() {
   this->set_timeout("end-service", STOP_ADVERTISING_DELAY, [this] {
     if (this->state_ == improv::STATE_STOPPED || this->service_ == nullptr)
       return;
+    // Release first so removing the service UUID does not restart advertising on the way out
+    this->release_advertising_();
     this->service_->stop();
     this->set_state_(improv::STATE_STOPPED);
   });
@@ -520,6 +524,20 @@ void ESP32ImprovComponent::update_advertising_type_() {
   }
 }
 
+void ESP32ImprovComponent::request_advertising_() {
+  if (this->advertising_requested_)
+    return;
+  this->advertising_requested_ = true;
+  esp32_ble::global_ble->advertising_start();
+}
+
+void ESP32ImprovComponent::release_advertising_() {
+  if (!this->advertising_requested_)
+    return;
+  this->advertising_requested_ = false;
+  esp32_ble::global_ble->advertising_stop();
+}
+
 improv::State ESP32ImprovComponent::get_initial_state_() const {
 #ifdef USE_BINARY_SENSOR
   // If we have an authorizer, start in awaiting authorization state

esphome/components/esp32_improv/esp32_improv_component.h

@@ -104,8 +104,11 @@ class ESP32ImprovComponent final : public Component, public improv_base::ImprovB
   bool status_indicator_state_{false};
   uint32_t last_name_adv_time_{0};
   bool advertising_device_name_{false};
+  bool advertising_requested_{false};
   void set_status_indicator_state_(bool state);
   void update_advertising_type_();
+  void request_advertising_();
+  void release_advertising_();
 
   void set_state_(improv::State state, bool update_advertising = true);
   void set_error_(improv::Error error);

esphome/components/esp8266/__init__.py

@@ -35,7 +35,7 @@ from esphome.platformio.toolchain import copy_ccache_script
 from esphome.storage_json import StorageJSON
 from esphome.types import ConfigType
 
-from .boards import BOARDS, ESP8266_LD_SCRIPTS, board_ld_script
+from .boards import BOARDS, board_ld_script
 from .const import (
     CONF_EARLY_PIN_INIT,
     CONF_ENABLE_SERIAL,
@@ -43,8 +43,6 @@ from .const import (
     CONF_RESTORE_FROM_FLASH,
     KEY_BOARD,
     KEY_ESP8266,
-    KEY_FLASH_SIZE,
-    KEY_LDSCRIPT,
     KEY_PIN_INITIAL_STATES,
     KEY_SERIAL1_REQUIRED,
     KEY_SERIAL_REQUIRED,
@@ -133,10 +131,6 @@ def _format_framework_arduino_version(ver: cv.Version) -> str:
     # format the given arduino (https://github.com/esp8266/Arduino/releases) version to
     # a PIO platformio/framework-arduinoespressif8266 value
     # List of package versions: https://api.registry.platformio.org/v3/packages/platformio/tool/framework-arduinoespressif8266
-    if ver <= cv.Version(2, 4, 1):
-        return f"~1.{ver.major}{ver.minor:02d}{ver.patch:02d}.0"
-    if ver <= cv.Version(2, 6, 2):
-        return f"~2.{ver.major}{ver.minor:02d}{ver.patch:02d}.0"
     # Same encoding the native toolchain uses for its package download, so a
     # version bump cannot drift between the two paths.
     from esphome.arduino8266.framework import framework_package_version
@@ -159,11 +153,9 @@ def _format_framework_arduino_version(ver: cv.Version) -> str:
 #  - https://github.com/esp8266/Arduino/releases
 #  - https://api.registry.platformio.org/v3/packages/platformio/tool/framework-arduinoespressif8266
 RECOMMENDED_ARDUINO_FRAMEWORK_VERSION = cv.Version(3, 1, 2)
-# The platformio/espressif8266 version to use for arduino 2 framework versions
+# The platformio/espressif8266 version to use for arduino 3 framework versions
 #  - https://github.com/platformio/platform-espressif8266/releases
 #  - https://api.registry.platformio.org/v3/packages/platformio/platform/espressif8266
-ARDUINO_2_PLATFORM_VERSION = cv.Version(2, 6, 3)
-# for arduino 3 framework versions
 ARDUINO_3_PLATFORM_VERSION = cv.Version(3, 2, 0)
 # for arduino 4 framework versions
 ARDUINO_4_PLATFORM_VERSION = cv.Version(4, 2, 1)
@@ -188,6 +180,14 @@ def _arduino_check_versions(value: ConfigType) -> ConfigType:
         version = cv.Version.parse(cv.version_number(value[CONF_VERSION]))
         source = value.get(CONF_SOURCE, None)
 
+    if version < cv.Version(3, 0, 0):
+        raise cv.Invalid(
+            f"Arduino framework {version} is no longer supported; ESPHome requires "
+            f"C++20, which needs Arduino core 3.x. Use the recommended version "
+            f"({RECOMMENDED_ARDUINO_FRAMEWORK_VERSION}).",
+            path=[CONF_VERSION],
+        )
+
     value[CONF_VERSION] = str(version)
     value[CONF_SOURCE] = source or _format_framework_arduino_version(version)
 
@@ -195,12 +195,8 @@ def _arduino_check_versions(value: ConfigType) -> ConfigType:
     if platform_version is None:
         if version >= cv.Version(3, 1, 0):
             platform_version = _parse_platform_version(str(ARDUINO_4_PLATFORM_VERSION))
-        elif version >= cv.Version(3, 0, 0):
-            platform_version = _parse_platform_version(str(ARDUINO_3_PLATFORM_VERSION))
-        elif version >= cv.Version(2, 5, 0):
-            platform_version = _parse_platform_version(str(ARDUINO_2_PLATFORM_VERSION))
         else:
-            platform_version = _parse_platform_version(str(cv.Version(1, 8, 0)))
+            platform_version = _parse_platform_version(str(ARDUINO_3_PLATFORM_VERSION))
     value[CONF_PLATFORM_VERSION] = platform_version
 
     if version != RECOMMENDED_ARDUINO_FRAMEWORK_VERSION:
@@ -289,29 +285,11 @@ def check_rosetta() -> None:
         )
 
 
-def _choose_ld_script(board: str, ver: cv.Version) -> str | None:
-    """The flash ld to pin for this board and core, or None for cores
-    without ld-script support."""
-    board_data = BOARDS[board]
-    ld_scripts = ESP8266_LD_SCRIPTS[board_data[KEY_FLASH_SIZE]]
-    if ver <= cv.Version(2, 3, 0):
-        # No ld script support
-        return None
-    if ver <= cv.Version(2, 4, 2):
-        # Old ld script path; the modern per-board override names do not
-        # exist in this core's SDK, so the override cannot be honored.
-        # Substituting the size default would move _FS_end and the
-        # preferences sector, wiping flash-backed state on flash.
-        if KEY_LDSCRIPT in board_data:
-            raise EsphomeError(
-                f"Board {board} requires its {board_data[KEY_LDSCRIPT]} "
-                f"flash layout, which Arduino core {ver} cannot honor; "
-                "use a core newer than 2.4.2"
-            )
-        return ld_scripts[0]
+def _choose_ld_script(board: str) -> str:
+    """The flash ld to pin for this board."""
     # A per-board override preserves a layout the board shipped with
     # (see d1_wroom_02 in boards.py)
-    return board_ld_script(board_data)
+    return board_ld_script(BOARDS[board])
 
 
 @coroutine_with_priority(CoroPriority.PLATFORM)
@@ -435,10 +413,9 @@ async def to_code(config: ConfigType) -> None:
     )
 
     if config[CONF_BOARD] in BOARDS:
-        ld_script = _choose_ld_script(config[CONF_BOARD], ver)
-
-        if ld_script is not None:
-            cg.add_platformio_option("board_build.ldscript", ld_script)
+        cg.add_platformio_option(
+            "board_build.ldscript", _choose_ld_script(config[CONF_BOARD])
+        )
 
     CORE.add_job(add_pin_initial_states_array)
     CORE.add_job(finalize_waveform_config)

esphome/components/esphome/ota/__init__.py

@@ -2,12 +2,12 @@ import logging
 
 import esphome.codegen as cg
 from esphome.components.noise import (
-    decode_encryption_key,
     encryption_schema,
-    is_reserved_key,
+    new_psk_progmem,
+    static_encryption_key,
 )
 from esphome.components.ota import BASE_OTA_SCHEMA, OTAComponent, ota_to_code
-from esphome.config_helpers import merge_config
+from esphome.config_helpers import filter_source_files_from_defines, merge_config
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_API,
@@ -31,7 +31,6 @@ import esphome.final_validate as fv
 from esphome.types import ConfigType
 
 CONF_ALLOW_PARTITION_ACCESS = "allow_partition_access"
-CONF_CAPTIVE_PORTAL = "captive_portal"
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -41,11 +40,10 @@ DEPENDENCIES = ["network"]
 
 
 def AUTO_LOAD(config: ConfigType) -> list[str]:
-    """Auto-load noise only when encryption is configured."""
+    """Auto-load noise only when encryption is configured; the api key offer
+    inherits it from the api component."""
     base = ["sha256", "socket"]
-    # A falsy config is a tooling probe for the maximal set (None from
-    # dependency resolution, {} from the components-graph platform probe);
-    # a validated config always carries defaults, never empty
+    # A falsy config is a tooling probe for the maximal set
     if not config or CONF_ENCRYPTION in config:
         return base + ["noise"]
     return base
@@ -132,12 +130,56 @@ def ota_esphome_final_validate(config: ConfigType) -> None:
         _validate_no_password_with_encryption(ota_conf)
         if (encryption_conf := ota_conf.get(CONF_ENCRYPTION)) is not None:
             _resolve_encryption_key(encryption_conf, api_conf)
-    if any(
-        conf.get(CONF_PLATFORM) == CONF_WEB_SERVER for conf in full_ota_conf
-    ) and any(
-        CONF_ENCRYPTION in conf for conf in merged_ota_esphome_configs_by_port.values()
+        elif CONF_PASSWORD in ota_conf and static_encryption_key(api_conf) is not None:
+            _LOGGER.warning(
+                "'%s' %s wastes significant flash and RAM (about 3.5 KB and 60 "
+                "bytes plus the password on the heap): the device already offers "
+                "encryption with the '%s' %s %s, which authenticates any uploader "
+                "that takes it, and a password only matters for uploaders without "
+                "encryption support; remove '%s' and add '%s' under '%s' so "
+                "uploads use the key and encryption is required",
+                CONF_OTA,
+                CONF_PASSWORD,
+                CONF_API,
+                CONF_ENCRYPTION,
+                CONF_KEY,
+                CONF_PASSWORD,
+                CONF_ENCRYPTION,
+                CONF_OTA,
+            )
+        elif (
+            CONF_PASSWORD in ota_conf
+            and CONF_ENCRYPTION in api_conf
+            and not api_conf[CONF_ENCRYPTION].get(CONF_KEY)
+        ):
+            # The CLI still needs the password; whoever provisions the key skips it
+            _LOGGER.warning(
+                "The '%s' %s %s provisioned at runtime also authenticates OTA "
+                "uploads once provisioned; '%s' %s then only guards plaintext "
+                "uploads. Whoever provisions the key can upload firmware "
+                "without the password, so add a 'provisioning:' block to limit "
+                "when that is possible",
+                CONF_API,
+                CONF_ENCRYPTION,
+                CONF_KEY,
+                CONF_OTA,
+                CONF_PASSWORD,
+            )
+    # web_server and prometheus keep the shared listener up; the captive
+    # portal's copy only exists on the fallback AP and is the recovery path
+    if (
+        (CONF_WEB_SERVER in full_conf or "prometheus" in full_conf)
+        and any(conf.get(CONF_PLATFORM) == CONF_WEB_SERVER for conf in full_ota_conf)
+        and any(
+            CONF_ENCRYPTION in conf
+            for conf in merged_ota_esphome_configs_by_port.values()
+        )
     ):
-        _warn_web_server_ota(full_conf)
+        _LOGGER.warning(
+            "OTA encryption does not cover the %s OTA platform; its "
+            "plaintext /update endpoint accepts the same image",
+            CONF_WEB_SERVER,
+        )
 
     full_conf[CONF_OTA] = new_ota_conf
     fv.full_config.set(full_conf)
@@ -152,33 +194,11 @@ def ota_esphome_final_validate(config: ConfigType) -> None:
         )
 
 
-def _warn_web_server_ota(full_conf: ConfigType) -> None:
-    """The web_server ota platform accepts the same image over plaintext HTTP
-    with basic auth, bypassing the encryption; warn rather than fail so the
-    operator keeps the recovery path."""
-    if CONF_CAPTIVE_PORTAL in full_conf and CONF_WEB_SERVER not in full_conf:
-        # The captive_portal auto-load: the endpoint only exists while the
-        # fallback AP is active
-        _LOGGER.warning(
-            "OTA encryption does not cover the %s OTA platform (auto-loaded "
-            "by captive_portal); the plaintext /update endpoint stays "
-            "reachable while the fallback AP is active",
-            CONF_WEB_SERVER,
-        )
-    else:
-        _LOGGER.warning(
-            "OTA encryption does not cover the %s OTA platform; its "
-            "plaintext /update endpoint accepts the same image",
-            CONF_WEB_SERVER,
-        )
-
-
 def _resolve_encryption_key(encryption_conf: ConfigType, api_conf: ConfigType) -> None:
     """Resolve the one encryption key per device into the ota block.
 
     An explicit ota key must match the api key, a bare block inherits it,
-    a runtime provisioned api key cannot be inherited, and the all-zeros
-    provisioning sentinel is rejected (the device treats it as no key).
+    a runtime provisioned api key cannot be inherited.
     """
     api_key = api_conf.get(CONF_ENCRYPTION, {}).get(CONF_KEY)
     if ota_key := encryption_conf.get(CONF_KEY):
@@ -201,11 +221,6 @@ def _resolve_encryption_key(encryption_conf: ConfigType, api_conf: ConfigType) -
         )
     else:
         encryption_conf[CONF_KEY] = api_key
-    if is_reserved_key(encryption_conf[CONF_KEY]):
-        raise cv.Invalid(
-            f"The all-zeros {CONF_KEY} is reserved and provides no protection; "
-            f"generate a real key with: openssl rand -base64 32"
-        )
 
 
 # Also called on merged same-port configs in final validate, where schemas
@@ -267,15 +282,9 @@ CONFIG_SCHEMA = cv.All(
 FINAL_VALIDATE_SCHEMA = ota_esphome_final_validate
 
 
-def FILTER_SOURCE_FILES() -> list[str]:
-    """Filter out the noise transport when no ota entry configures encryption."""
-    for ota_conf in CORE.config.get(CONF_OTA, []):
-        if (
-            ota_conf.get(CONF_PLATFORM) == CONF_ESPHOME
-            and ota_conf.get(CONF_ENCRYPTION) is not None
-        ):
-            return []
-    return ["ota_esphome_noise.cpp"]
+FILTER_SOURCE_FILES = filter_source_files_from_defines(
+    {"ota_esphome_noise.cpp": "USE_OTA_ENCRYPTION"}
+)
 
 
 @coroutine_with_priority(CoroPriority.OTA_UPDATES)
@@ -296,11 +305,24 @@ async def to_code(config: ConfigType) -> None:
     if config.get(CONF_ALLOW_PARTITION_ACCESS):
         cg.add_define("USE_OTA_PARTITIONS")
 
-    if (encryption_conf := config.get(CONF_ENCRYPTION)) is not None:
-        # A missing key was resolved from the api component in final validate.
-        key = encryption_conf[CONF_KEY]
+    # One key per device: an api encryption block supplies it (static or
+    # runtime) and offers; the ota block only adds the requirement
+    api_conf = CORE.config.get(CONF_API) or {}
+    encryption_conf = config.get(CONF_ENCRYPTION)
+    own_key = None
+    if encryption_conf is not None and static_encryption_key(api_conf) is None:
+        own_key = encryption_conf[CONF_KEY]
+    if own_key is not None:
         cg.add_define("USE_OTA_ENCRYPTION")
-        cg.add(var.set_noise_psk(list(decode_encryption_key(key))))
+        cg.add(var.set_noise_psk(new_psk_progmem(config[CONF_ID], own_key)))
+    elif CONF_ENCRYPTION in api_conf:
+        cg.add_define("USE_OTA_ENCRYPTION")
+        cg.add_define("USE_OTA_ENCRYPTION_FROM_API")
+        if static_encryption_key(api_conf) is None:
+            # The key arrives at runtime, so the offer has to look for it
+            cg.add_define("USE_OTA_ENCRYPTION_PROVISIONED")
+    if encryption_conf is not None:
+        cg.add_define("USE_OTA_ENCRYPTION_REQUIRED")
 
     # Build flag so lwip_fast_select.c (a .c file that can't include defines.h) sees it.
     cg.add_build_flag("-DUSE_OTA_PLATFORM_ESPHOME")

esphome/components/esphome/ota/ota_esphome.cpp

@@ -1,4 +1,7 @@
 #include "ota_esphome.h"
+#ifdef USE_OTA_ENCRYPTION_FROM_API
+#include "esphome/components/api/api_server.h"
+#endif
 #ifdef USE_OTA
 #ifdef USE_OTA_PASSWORD
 #include "esphome/components/sha256/sha256.h"
@@ -26,6 +29,16 @@
 namespace esphome {
 
 static const char *const TAG = "esphome.ota";
+
+#ifdef USE_OTA_ENCRYPTION
+const noise::NoiseContext &ESPHomeOTAComponent::noise_context_() const {
+#ifdef USE_OTA_ENCRYPTION_FROM_API
+  return api::global_api_server->get_noise_ctx();
+#else
+  return this->noise_ctx_;
+#endif
+}
+#endif
 static constexpr uint16_t OTA_BLOCK_SIZE = 8192;
 static constexpr uint32_t OTA_SOCKET_TIMEOUT_HANDSHAKE = 20000;  // milliseconds for initial handshake
 static constexpr uint32_t OTA_SOCKET_TIMEOUT_DATA = 90000;       // milliseconds for data transfer
@@ -97,18 +110,30 @@ void ESPHomeOTAComponent::dump_config() {
   ESP_LOGCONFIG(TAG,
                 "Over-The-Air updates:\n"
                 "  Address: %s:%u\n"
-                "  Version: %d",
-                network::get_use_address_to(addr_buf), this->port_, USE_OTA_VERSION);
+                "  Version: %d"
+#ifdef USE_OTA_ENCRYPTION
+                "\n  Encryption: %s"
+#endif
+                ,
+                network::get_use_address_to(addr_buf), this->port_, USE_OTA_VERSION
+#ifdef USE_OTA_ENCRYPTION_REQUIRED
+                ,
+                LOG_STR_LITERAL("required")
+#elif defined(USE_OTA_ENCRYPTION_PROVISIONED)
+                // A runtime provisioned key may not exist yet
+                ,
+                this->noise_context_().has_psk() ? LOG_STR_LITERAL("offered, plaintext accepted")
+                                                 : LOG_STR_LITERAL("offered once the api key is provisioned")
+#elif defined(USE_OTA_ENCRYPTION)
+                ,
+                LOG_STR_LITERAL("offered, plaintext accepted")
+#endif
+  );
 #ifdef USE_OTA_PASSWORD
   if (!this->password_.empty()) {
     ESP_LOGCONFIG(TAG, "  Password configured");
   }
 #endif
-#ifdef USE_OTA_ENCRYPTION
-  if (this->noise_ctx_.has_psk()) {
-    ESP_LOGCONFIG(TAG, "  Encryption configured");
-  }
-#endif
 #ifdef USE_OTA_PARTITIONS
   ESP_LOGCONFIG(TAG,
                 "  Partition access allowed\n"
@@ -154,10 +179,22 @@ static constexpr uint8_t CLIENT_FEATURE_SUPPORTS_COMPRESSION = 0x01;
 static constexpr uint8_t CLIENT_FEATURE_SUPPORTS_SHA256_AUTH = 0x02;
 static constexpr uint8_t CLIENT_FEATURE_SUPPORTS_EXTENDED_PROTOCOL = 0x04;
 static constexpr uint8_t CLIENT_FEATURE_SUPPORTS_NOISE = 0x08;
+// Noise needs the extended protocol: the prologue binds the 2-byte feature ack
+static constexpr uint8_t CLIENT_NOISE_FEATURES =
+    CLIENT_FEATURE_SUPPORTS_NOISE | CLIENT_FEATURE_SUPPORTS_EXTENDED_PROTOCOL;
 static constexpr uint8_t SERVER_FEATURE_SUPPORTS_COMPRESSION = 0x01;
 static constexpr uint8_t SERVER_FEATURE_SUPPORTS_PARTITION_ACCESS = 0x02;
 static constexpr uint8_t SERVER_FEATURE_SUPPORTS_NOISE = 0x04;
 
+inline bool ESPHomeOTAComponent::extended_proto_() const {
+#ifdef USE_OTA_ENCRYPTION_REQUIRED
+  // FEATURE_READ already refused every client without the extended protocol
+  return true;
+#else
+  return (this->ota_features_ & CLIENT_FEATURE_SUPPORTS_EXTENDED_PROTOCOL) != 0;
+#endif
+}
+
 void ESPHomeOTAComponent::handle_handshake_() {
   /// Handle the OTA handshake and authentication.
   ///
@@ -241,12 +278,9 @@ void ESPHomeOTAComponent::handle_handshake_() {
       this->ota_features_ = this->handshake_buf_[0];
       ESP_LOGV(TAG, "Features: 0x%02X", this->ota_features_);
 
-#ifdef USE_OTA_ENCRYPTION
-      // Fail closed: with a PSK configured the client must negotiate encryption
-      // (which requires the extended protocol); refuse plaintext uploads.
-      static constexpr uint8_t NOISE_REQUIRED_FEATURES =
-          CLIENT_FEATURE_SUPPORTS_NOISE | CLIENT_FEATURE_SUPPORTS_EXTENDED_PROTOCOL;
-      if (this->noise_ctx_.has_psk() && (this->ota_features_ & NOISE_REQUIRED_FEATURES) != NOISE_REQUIRED_FEATURES) {
+#ifdef USE_OTA_ENCRYPTION_REQUIRED
+      // `ota: encryption:` requires the client to negotiate encryption
+      if ((this->ota_features_ & CLIENT_NOISE_FEATURES) != CLIENT_NOISE_FEATURES) {
         ESP_LOGW(TAG, "Client does not support encryption");
         this->send_error_and_cleanup_(ota::OTA_RESPONSE_ERROR_ENCRYPTION_REQUIRED);
         return;
@@ -261,18 +295,21 @@ void ESPHomeOTAComponent::handle_handshake_() {
       // Compose the feature-ack response. When the client negotiates the extended protocol we emit
       // a 2-byte response (marker + server feature flags); otherwise we emit the single-byte
       // legacy response.
-      this->extended_proto_ = (this->ota_features_ & CLIENT_FEATURE_SUPPORTS_EXTENDED_PROTOCOL) != 0;
-      if (this->extended_proto_) {
+      if (this->extended_proto_()) {
         static_assert(HANDSHAKE_BUF_SIZE >= 2, "handshake_buf_ must hold the 2-byte extended-protocol feature ack");
         this->handshake_buf_[0] = ota::OTA_RESPONSE_FEATURE_FLAGS;
         this->handshake_buf_[1] = (supports_compression ? SERVER_FEATURE_SUPPORTS_COMPRESSION : 0);
 #ifdef USE_OTA_PARTITIONS
         this->handshake_buf_[1] |= SERVER_FEATURE_SUPPORTS_PARTITION_ACCESS;
 #endif
-#ifdef USE_OTA_ENCRYPTION
-        if (this->noise_ctx_.has_psk()) {
+#ifdef USE_OTA_ENCRYPTION_PROVISIONED
+        // A runtime provisioned key may not exist yet
+        if (this->noise_context_().has_psk()) {
           this->handshake_buf_[1] |= SERVER_FEATURE_SUPPORTS_NOISE;
         }
+#elif defined(USE_OTA_ENCRYPTION)
+        // A yaml key always exists: validation rejects the all-zeros key
+        this->handshake_buf_[1] |= SERVER_FEATURE_SUPPORTS_NOISE;
 #endif
       } else {
         this->handshake_buf_[0] =
@@ -284,15 +321,15 @@ void ESPHomeOTAComponent::handle_handshake_() {
     case OTAState::FEATURE_ACK: {
       static constexpr size_t STANDARD_PROTO_ACK_SIZE = 1;
       static constexpr size_t EXTENDED_PROTO_ACK_SIZE = 2;
-      const size_t ack_size = this->extended_proto_ ? EXTENDED_PROTO_ACK_SIZE : STANDARD_PROTO_ACK_SIZE;
+      const size_t ack_size = this->extended_proto_() ? EXTENDED_PROTO_ACK_SIZE : STANDARD_PROTO_ACK_SIZE;
       if (!this->try_write_(ack_size, LOG_STR("ack feature"))) {
         return;
       }
 #ifdef USE_OTA_ENCRYPTION
-      // With a PSK configured the rest of the session runs inside the noise
-      // transport; the client sends the first handshake frame next, so there
-      // is nothing to do until data arrives.
-      if (this->noise_ctx_.has_psk()) {
+      // Latch the offer actually sent: a key activating between the two
+      // states must not start a session the client never expects
+      if ((this->handshake_buf_[1] & SERVER_FEATURE_SUPPORTS_NOISE) != 0 &&
+          (this->ota_features_ & CLIENT_NOISE_FEATURES) == CLIENT_NOISE_FEATURES) {
         // handshake_buf_ still holds the feature ack composed above; a
         // would-block re-entry lands here without rebuilding it
         if (!this->noise_start_session_(this->handshake_buf_[1])) {
@@ -412,7 +449,7 @@ void ESPHomeOTAComponent::handle_data_() {
   // Acknowledge auth OK - 1 byte
   this->data_write_byte_(ota::OTA_RESPONSE_AUTH_OK);
 
-  if (this->extended_proto_) {
+  if (this->extended_proto_()) {
     // Read ota type, 1 byte
     if (!this->data_readall_(buf, 1)) {
       this->log_read_error_(LOG_STR("OTA type"));

esphome/components/esphome/ota/ota_esphome.h

@@ -44,8 +44,9 @@ class ESPHomeOTAComponent final : public ota::OTAComponent {
   }
 #endif  // USE_OTA_PASSWORD
 
-#ifdef USE_OTA_ENCRYPTION
-  void set_noise_psk(noise::psk_t psk) { this->noise_ctx_.set_psk(psk); }
+#if defined(USE_OTA_ENCRYPTION) && !defined(USE_OTA_ENCRYPTION_FROM_API)
+  /// psk points at 32 bytes that live in flash for the life of the program
+  void set_noise_psk(const uint8_t *psk) { this->noise_ctx_.set_psk(psk); }
 #endif
 
   /// Manually set the port OTA should listen on
@@ -85,9 +86,12 @@ class ESPHomeOTAComponent final : public ota::OTAComponent {
     bool writing{false};    // a produced handshake frame is still being flushed
     uint8_t frame_buf[noise::FRAME_HEADER_SIZE + 1 + noise::MAX_HANDSHAKE_SIZE];
   };
+  // The api server's live context when the api has encryption, else our own
+  const noise::NoiseContext &noise_context_() const;
   bool noise_start_session_(uint8_t server_feature_flags);
   bool handle_noise_handshake_();
   bool noise_try_read_frame_();
+  size_t noise_frame_payload_len_(const uint8_t *header, size_t min_len, size_t max_len);
   bool noise_try_write_frame_();
   void noise_send_reject_(const LogString *reason);
   ssize_t noise_decrypt_(uint8_t *buf, size_t len);
@@ -144,7 +148,9 @@ class ESPHomeOTAComponent final : public ota::OTAComponent {
   std::unique_ptr<uint8_t[]> auth_buf_;
 #endif  // USE_OTA_PASSWORD
 #ifdef USE_OTA_ENCRYPTION
+#ifndef USE_OTA_ENCRYPTION_FROM_API
   noise::NoiseContext noise_ctx_;
+#endif
   std::unique_ptr<NoiseSession> noise_;
 #endif  // USE_OTA_ENCRYPTION
 
@@ -166,6 +172,8 @@ class ESPHomeOTAComponent final : public ota::OTAComponent {
                 "OTA_BUFFER_SIZE must fit a full encrypted data frame");
 #endif
   static constexpr uint8_t MAGIC_BYTES[5] = {0x6C, 0x26, 0xF7, 0x5C, 0x45};
+  // Derived from the feature byte; storing it would pad the trailing bytes
+  bool extended_proto_() const;
 #ifdef USE_OTA_PARTITIONS
   uint32_t running_app_offset_{0};
   size_t running_app_size_{0};
@@ -179,7 +187,6 @@ class ESPHomeOTAComponent final : public ota::OTAComponent {
   uint8_t auth_buf_pos_{0};
   uint8_t auth_type_{0};  // Store auth type to know which hasher to use
 #endif                    // USE_OTA_PASSWORD
-  bool extended_proto_{false};
 };
 
 }  // namespace esphome

esphome/components/esphome/ota/ota_esphome_noise.cpp

@@ -3,6 +3,7 @@
 #ifdef USE_OTA_ENCRYPTION
 #include "esphome/components/noise/noise.h"
 #include "esphome/components/ota/ota_backend.h"
+#include "esphome/core/hal.h"
 #include "esphome/core/log.h"
 
 #include <cstring>
@@ -40,24 +41,17 @@ ESPHomeOTAComponent::NoiseSession::~NoiseSession() {
  *   "NoiseOTAInit" | magic(5) | OK,version | client_features | FEATURE_FLAGS,server_flags
  */
 bool ESPHomeOTAComponent::noise_start_session_(uint8_t server_feature_flags) {
+  // A provisioned key cleared between the offer and here is not guarded: the
+  // session runs on the zero key load_psk fills in and fails the client's MAC.
+  // Default-init: the frame buffer is written before it is read
   // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
-  this->noise_ = std::unique_ptr<NoiseSession>(new (std::nothrow) NoiseSession());
-  if (this->noise_ == nullptr) {
-    ESP_LOGW(TAG, "Session allocation failed");
-    this->cleanup_connection_();
-    return false;
-  }
-
+  this->noise_ = std::unique_ptr<NoiseSession>(new (std::nothrow) NoiseSession);
   static constexpr size_t PROLOGUE_ACK_LEN = 2;  // OTA_RESPONSE_OK + version
   static constexpr size_t PROLOGUE_CLIENT_FEATURES_LEN = 1;
   static constexpr size_t PROLOGUE_FEATURE_ACK_LEN = 2;  // OTA_RESPONSE_FEATURE_FLAGS + server flags
   uint8_t prologue[OTA_NOISE_PROLOGUE_INIT_LEN + sizeof(MAGIC_BYTES) + PROLOGUE_ACK_LEN + PROLOGUE_CLIENT_FEATURES_LEN +
                    PROLOGUE_FEATURE_ACK_LEN];
-#ifdef USE_ESP8266
-  memcpy_P(prologue, OTA_NOISE_PROLOGUE_INIT, OTA_NOISE_PROLOGUE_INIT_LEN);
-#else
-  std::memcpy(prologue, OTA_NOISE_PROLOGUE_INIT, OTA_NOISE_PROLOGUE_INIT_LEN);
-#endif
+  progmem_memcpy(prologue, OTA_NOISE_PROLOGUE_INIT, OTA_NOISE_PROLOGUE_INIT_LEN);
   uint8_t *p = prologue + OTA_NOISE_PROLOGUE_INIT_LEN;
   // Magic bytes, already validated in MAGIC_READ
   std::memcpy(p, MAGIC_BYTES, sizeof(MAGIC_BYTES));
@@ -71,9 +65,13 @@ bool ESPHomeOTAComponent::noise_start_session_(uint8_t server_feature_flags) {
   *p++ = ota::OTA_RESPONSE_FEATURE_FLAGS;
   *p++ = server_feature_flags;
 
-  int err = this->noise_->handshake.init(this->noise_ctx_.get_psk(), prologue, sizeof(prologue));
+  // The caller only starts a session when the context holds a key
+  int err = this->noise_ == nullptr ? NOISE_ERROR_NO_MEMORY
+                                    : this->noise_->handshake.init(this->noise_context_(), prologue, sizeof(prologue));
   if (err != 0) {
-    ESP_LOGW(TAG, "Handshake init: %s", LOG_STR_ARG(noise::noise_err_to_logstr(err)));
+    // Raw noise codes throughout: the name table would cost flash in builds
+    // where only the OTA uses noise
+    ESP_LOGW(TAG, "Session init: %d", err);
     this->cleanup_connection_();
     return false;
   }
@@ -105,14 +103,16 @@ bool ESPHomeOTAComponent::handle_noise_handshake_() {
         s.frame_pos = 0;
         s.frame_len = 0;
         if (s.frame_buf[noise::FRAME_HEADER_SIZE] != noise::HANDSHAKE_STATUS_OK) {
-          ESP_LOGW(TAG, "Bad handshake error byte: %u", s.frame_buf[noise::FRAME_HEADER_SIZE]);
+          ESP_LOGW(TAG, "Client rejected the handshake: %u", s.frame_buf[noise::FRAME_HEADER_SIZE]);
           this->cleanup_connection_();
           return false;
         }
         int err = s.handshake.read_message(s.frame_buf + noise::FRAME_HEADER_SIZE + 1, payload_len - 1);
         if (err != 0) {
-          ESP_LOGW(TAG, "Handshake read: %s", LOG_STR_ARG(noise::noise_err_to_logstr(err)));
-          this->noise_send_reject_(noise::reject_reason_for(err));
+          // A MAC failure here almost always means the uploader has a different key
+          const LogString *reason = noise::reject_reason_for(err);
+          ESP_LOGW(TAG, "Handshake read: %s (%d)", LOG_STR_ARG(reason), err);
+          this->noise_send_reject_(reason);
           this->cleanup_connection_();
           return false;
         }
@@ -123,7 +123,7 @@ bool ESPHomeOTAComponent::handle_noise_handshake_() {
         int err =
             s.handshake.write_message(s.frame_buf + noise::FRAME_HEADER_SIZE + 1, noise::MAX_HANDSHAKE_SIZE, msg_len);
         if (err != 0) {
-          ESP_LOGW(TAG, "Handshake write: %s", LOG_STR_ARG(noise::noise_err_to_logstr(err)));
+          ESP_LOGW(TAG, "Handshake write: %d", err);
           this->cleanup_connection_();
           return false;
         }
@@ -138,7 +138,7 @@ bool ESPHomeOTAComponent::handle_noise_handshake_() {
       case noise::NoiseResponderHandshake::Action::ACTION_SPLIT: {
         int err = s.handshake.split(s.send_cipher, s.recv_cipher);
         if (err != 0) {
-          ESP_LOGW(TAG, "Handshake split: %s", LOG_STR_ARG(noise::noise_err_to_logstr(err)));
+          ESP_LOGW(TAG, "Handshake split: %d", err);
           this->cleanup_connection_();
           return false;
         }
@@ -154,33 +154,41 @@ bool ESPHomeOTAComponent::handle_noise_handshake_() {
   }
 }
 
+/// Payload length from a frame header, or 0 (logged) when the indicator or
+/// the length is out of range. Callers pass min_len >= 1 so 0 is never valid.
+size_t ESPHomeOTAComponent::noise_frame_payload_len_(const uint8_t *header, size_t min_len, size_t max_len) {
+  const size_t payload_len = encode_uint16(header[1], header[2]);
+  if (header[0] != noise::FRAME_INDICATOR || payload_len < min_len || payload_len > max_len) {
+    ESP_LOGW(TAG, "Bad frame: 0x%02X, %zu bytes", header[0], payload_len);
+    return 0;
+  }
+  return payload_len;
+}
+
 /// Non-blocking read of one handshake frame into the session buffer.
 bool ESPHomeOTAComponent::noise_try_read_frame_() {
   NoiseSession &s = *this->noise_;
-  while (s.frame_pos < noise::FRAME_HEADER_SIZE) {
-    ssize_t read = this->client_->read(s.frame_buf + s.frame_pos, noise::FRAME_HEADER_SIZE - s.frame_pos);
-    if (!this->handle_read_error_(read, LOG_STR("read noise header"))) {
-      return false;
+  while (true) {
+    // The header first, then the body once the header says how long it is
+    const uint16_t want = s.frame_len == 0 ? noise::FRAME_HEADER_SIZE : s.frame_len;
+    if (s.frame_pos < want) {
+      ssize_t read = this->client_->read(s.frame_buf + s.frame_pos, want - s.frame_pos);
+      if (!this->handle_read_error_(read, LOG_STR("read noise"))) {
+        return false;
+      }
+      s.frame_pos += read;
+      continue;
     }
-    s.frame_pos += read;
-  }
-  if (s.frame_len == 0) {
-    const uint16_t payload_len = encode_uint16(s.frame_buf[1], s.frame_buf[2]);
-    if (s.frame_buf[0] != noise::FRAME_INDICATOR || payload_len < 1 || payload_len > 1 + noise::MAX_HANDSHAKE_SIZE) {
-      ESP_LOGW(TAG, "Bad handshake frame: 0x%02X, %u bytes", s.frame_buf[0], payload_len);
+    if (s.frame_len != 0) {
+      return true;
+    }
+    const size_t payload_len = this->noise_frame_payload_len_(s.frame_buf, 1, 1 + noise::MAX_HANDSHAKE_SIZE);
+    if (payload_len == 0) {
       this->cleanup_connection_();
       return false;
     }
     s.frame_len = noise::FRAME_HEADER_SIZE + payload_len;
   }
-  while (s.frame_pos < s.frame_len) {
-    ssize_t read = this->client_->read(s.frame_buf + s.frame_pos, s.frame_len - s.frame_pos);
-    if (!this->handle_read_error_(read, LOG_STR("read noise frame"))) {
-      return false;
-    }
-    s.frame_pos += read;
-  }
-  return true;
 }
 
 /// Non-blocking write of the pending session-buffer frame.
@@ -214,7 +222,7 @@ ssize_t ESPHomeOTAComponent::noise_decrypt_(uint8_t *buf, size_t len) {
   noise_buffer_set_inout(mbuf, buf, len, len);
   int err = noise_cipherstate_decrypt(this->noise_->recv_cipher, &mbuf);
   if (err != 0) {
-    ESP_LOGW(TAG, "Decrypt: %s", LOG_STR_ARG(noise::noise_err_to_logstr(err)));
+    ESP_LOGW(TAG, "Decrypt: %d", err);
     return -1;
   }
   return mbuf.size;
@@ -229,9 +237,8 @@ ssize_t ESPHomeOTAComponent::noise_read_frame_blocking_(uint8_t *buf, size_t min
   if (!this->readall_(header, sizeof(header))) {
     return -1;
   }
-  const size_t ciphertext_len = encode_uint16(header[1], header[2]);
-  if (header[0] != noise::FRAME_INDICATOR || ciphertext_len < min_ciphertext || ciphertext_len > max_ciphertext) {
-    ESP_LOGW(TAG, "Bad frame: 0x%02X, %zu bytes", header[0], ciphertext_len);
+  const size_t ciphertext_len = this->noise_frame_payload_len_(header, min_ciphertext, max_ciphertext);
+  if (ciphertext_len == 0) {
     return -1;
   }
   if (!this->readall_(buf, ciphertext_len)) {
@@ -267,7 +274,7 @@ bool ESPHomeOTAComponent::noise_write_byte_(uint8_t byte) {
   noise_buffer_set_inout(mbuf, frame + noise::FRAME_HEADER_SIZE, 1, 1 + noise::MAC_SIZE);
   int err = noise_cipherstate_encrypt(this->noise_->send_cipher, &mbuf);
   if (err != 0) {
-    ESP_LOGW(TAG, "Encrypt: %s", LOG_STR_ARG(noise::noise_err_to_logstr(err)));
+    ESP_LOGW(TAG, "Encrypt: %d", err);
     return false;
   }
   noise::write_frame_header(frame, mbuf.size);

esphome/components/espnow/__init__.py

@@ -3,6 +3,7 @@ from typing import Any
 from esphome import automation, core
 import esphome.codegen as cg
 from esphome.components import wifi
+from esphome.components.esp32 import VARIANT_ESP32P4, get_esp32_variant
 from esphome.components.udp import CONF_ON_RECEIVE
 import esphome.config_validation as cv
 from esphome.const import (
@@ -17,6 +18,7 @@ from esphome.const import (
 )
 from esphome.core import CORE, HexInt
 from esphome.cpp_generator import MockObj, TemplateArgsType
+import esphome.final_validate as fv
 from esphome.types import ConfigType
 
 CODEOWNERS = ["@jesserockz"]
@@ -132,6 +134,24 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
+def _validate_variant(config: ConfigType) -> ConfigType:
+    # ESP-NOW rides the Wi-Fi PHY. Radio-less esp32 variants have no native
+    # ESP-NOW; only the ESP32-P4 has a path, via the esp32_hosted shim that
+    # supplies the esp_now_* symbols. Fail here with a clear message instead of
+    # letting the build reach an "undefined reference to esp_now_*" link error.
+    variant = get_esp32_variant()
+    if wifi.variant_has_wifi(variant):
+        return config
+    if variant != VARIANT_ESP32P4:
+        raise cv.Invalid(f"ESP-NOW is not supported on {variant} (no Wi-Fi radio)")
+    if "esp32_hosted" not in fv.full_config.get():
+        raise cv.Invalid(f"ESP-NOW on {variant} requires the esp32_hosted component")
+    return config
+
+
+FINAL_VALIDATE_SCHEMA = _validate_variant
+
+
 async def _trigger_to_code(config: ConfigType) -> MockObj:
     if address := config.get(CONF_ADDRESS):
         address = address.parts

esphome/components/hc8/hc8.cpp

@@ -96,7 +96,6 @@ void HC8Component::dump_config() {
                 "  Warmup time: %" PRIu32 " s",
                 this->warmup_seconds_);
   LOG_SENSOR("  ", "CO2", this->co2_sensor_);
-  this->check_uart_settings(9600);
 }
 
 }  // namespace esphome::hc8

esphome/components/hc8/sensor.py

@@ -47,6 +47,9 @@ FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
     baud_rate=9600,
     require_rx=True,
     require_tx=True,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
 )
 
 

esphome/components/he60r/he60r.cpp

@@ -38,7 +38,6 @@ CoverTraits HE60rCover::get_traits() {
 
 void HE60rCover::dump_config() {
   LOG_COVER("", "HE60R Cover", this);
-  this->check_uart_settings(1200, 1, uart::UART_CONFIG_PARITY_EVEN, 8);
   ESP_LOGCONFIG(TAG,
                 "  Open Duration: %.1fs\n"
                 "  Close Duration: %.1fs",

esphome/components/hrxl_maxsonar_wr/hrxl_maxsonar_wr.cpp

@@ -68,8 +68,6 @@ void HrxlMaxsonarWrComponent::check_buffer_() {
 void HrxlMaxsonarWrComponent::dump_config() {
   ESP_LOGCONFIG(TAG, "HRXL MaxSonar WR Sensor:");
   LOG_SENSOR("  ", "Distance", this);
-  // As specified in the sensor's data sheet
-  this->check_uart_settings(9600, 1, esphome::uart::UART_CONFIG_PARITY_NONE, 8);
 }
 
 }  // namespace esphome::hrxl_maxsonar_wr

esphome/components/hrxl_maxsonar_wr/sensor.py

@@ -23,6 +23,14 @@ CONFIG_SCHEMA = sensor.sensor_schema(
     state_class=STATE_CLASS_MEASUREMENT,
 ).extend(uart.UART_DEVICE_SCHEMA)
 
+FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
+    "hrxl_maxsonar_wr",
+    baud_rate=9600,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
+)
+
 
 async def to_code(config: ConfigType) -> None:
     var = await sensor.new_sensor(config)

esphome/components/hydreon_rgxx/hydreon_rgxx.cpp

@@ -11,7 +11,6 @@ static const char *const PROTOCOL_NAMES[] = {HYDREON_RGXX_PROTOCOL_LIST(, HYDREO
 static const char *const IGNORE_STRINGS[] = {HYDREON_RGXX_IGNORE_LIST(, HYDREON_RGXX_COMMA)};
 
 void HydreonRGxxComponent::dump_config() {
-  this->check_uart_settings(9600, 1, esphome::uart::UART_CONFIG_PARITY_NONE, 8);
   ESP_LOGCONFIG(TAG, "hydreon_rgxx:");
   if (this->is_failed()) {
     ESP_LOGE(TAG, "Connection with hydreon_rgxx failed!");

esphome/components/hydreon_rgxx/sensor.py

@@ -130,6 +130,14 @@ CONFIG_SCHEMA = cv.All(
     _validate,
 )
 
+FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
+    "hydreon_rgxx",
+    baud_rate=9600,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
+)
+
 
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])

esphome/components/kamstrup_kmp/kamstrup_kmp.cpp

@@ -26,8 +26,6 @@ void KamstrupKMPComponent::dump_config() {
     LOG_SENSOR("  ", "Custom Sensor", this->custom_sensors_[i]);
     ESP_LOGCONFIG(TAG, "    Command: 0x%04X", this->custom_commands_[i]);
   }
-
-  this->check_uart_settings(1200, 2, uart::UART_CONFIG_PARITY_NONE, 8);
 }
 
 void KamstrupKMPComponent::update() {

esphome/components/kamstrup_kmp/sensor.py

@@ -102,7 +102,13 @@ CONFIG_SCHEMA = (
 )
 
 FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
-    "kamstrup_kmp", baud_rate=1200, require_rx=True, require_tx=True
+    "kamstrup_kmp",
+    baud_rate=1200,
+    require_rx=True,
+    require_tx=True,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=2,
 )
 
 

esphome/components/mdns/__init__.py

@@ -192,6 +192,8 @@ async def to_code(config: ConfigType) -> None:
     if CORE.using_arduino:
         if CORE.is_esp8266:
             cg.add_library("ESP8266mDNS", None)
+            # No MDNS global in the build; mdns_esp8266.cpp owns a guarded MDNSResponder
+            cg.add_build_flag("-DNO_GLOBAL_MDNS")
         elif CORE.is_rp2:
             cg.add_library("LEAmDNS", None)
 

esphome/components/mdns/mdns_esp8266.cpp

@@ -13,8 +13,47 @@
 
 namespace esphome::mdns {
 
+// Main-loop calls into LEAmDNS that send (update() and close(); begin(), addService() and
+// the scheduled restart never reach a send) can yield inside UdpContext::sendTimeout(); a
+// packet arriving then re-enters LEAmDNS from lwIP on the same UdpContext and both sides
+// free the same tx pbufs (#18760). Received packets stay queued during such a call and are
+// processed from the main loop afterwards.
+class GuardedMDNSResponder : public ::esp8266::MDNSImplementation::MDNSResponder {
+ public:
+  void update_guarded() { this->run_guarded_(&GuardedMDNSResponder::update); }
+  void close_guarded() { this->run_guarded_(&GuardedMDNSResponder::close); }
+
+ private:
+  void run_guarded_(bool (GuardedMDNSResponder::*fn)()) {
+    UdpContext *ctx = this->m_pUDPContext;
+    if (ctx == nullptr) {
+      (this->*fn)();
+      return;
+    }
+    // Set every time: a restart replaces the context together with its stock handler. Only
+    // begin() and the scheduled netif callback restart, never update() or close(), so the
+    // context cannot change underneath this call.
+    ctx->onRx([this]() {
+      if (!this->in_loop_call_) {
+        this->_callProcess();
+      }
+    });
+    this->in_loop_call_ = true;
+    (this->*fn)();
+    // close() releases the context; a yield in here queues further packets for this loop too
+    while (this->m_pUDPContext != nullptr && this->m_pUDPContext->next()) {
+      this->_parseMessage();
+    }
+    this->in_loop_call_ = false;
+  }
+
+  volatile bool in_loop_call_{false};
+};
+
+static GuardedMDNSResponder mdns_responder;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
+
 static void register_esp8266(MDNSComponent *, StaticVector<MDNSService, MDNS_SERVICE_COUNT> &services) {
-  MDNS.begin(App.get_name().c_str());
+  mdns_responder.begin(App.get_name().c_str());
 
   for (const auto &service : services) {
     // Strip the leading underscore from the proto and service_type. While it is
@@ -30,10 +69,10 @@ static void register_esp8266(MDNSComponent *, StaticVector<MDNSService, MDNS_SER
       service_type++;
     }
     uint16_t port = service.port.value();
-    MDNS.addService(FPSTR(service_type), FPSTR(proto), port);
+    mdns_responder.addService(FPSTR(service_type), FPSTR(proto), port);
     for (const auto &record : service.txt_records) {
-      MDNS.addServiceTxt(FPSTR(service_type), FPSTR(proto), FPSTR(MDNS_STR_ARG(record.key)),
-                         FPSTR(MDNS_STR_ARG(record.value)));
+      mdns_responder.addServiceTxt(FPSTR(service_type), FPSTR(proto), FPSTR(MDNS_STR_ARG(record.key)),
+                                   FPSTR(MDNS_STR_ARG(record.value)));
     }
   }
 }
@@ -52,7 +91,7 @@ void MDNSComponent::start_polling_window_() {
     if (wifi->is_roaming() || (!wifi->is_connected() && !wifi->is_ap_active()))
       return;
 #endif
-    MDNS.update();
+    mdns_responder.update_guarded();
   });
   this->set_timeout(MDNS_POLL_STOP_ID, MDNS_POLL_WINDOW_MS, [this]() { this->cancel_interval(MDNS_POLL_ID); });
 }
@@ -81,7 +120,7 @@ void MDNSComponent::on_ip_state(const network::IPAddresses &ips, const network::
 #endif
 
 void MDNSComponent::on_shutdown() {
-  MDNS.close();
+  mdns_responder.close_guarded();
   delay(10);
 }
 

esphome/components/mhz19/mhz19.cpp

@@ -143,8 +143,6 @@ void MHZ19Component::dump_config() {
   ESP_LOGCONFIG(TAG, "MH-Z19:");
   LOG_SENSOR("  ", "CO2", this->co2_sensor_);
   LOG_SENSOR("  ", "Temperature", this->temperature_sensor_);
-  this->check_uart_settings(9600);
-
   if (this->abc_boot_logic_ == MHZ19_ABC_ENABLED) {
     ESP_LOGCONFIG(TAG, "  Automatic baseline calibration enabled on boot");
   } else if (this->abc_boot_logic_ == MHZ19_ABC_DISABLED) {

esphome/components/mhz19/sensor.py

@@ -80,6 +80,14 @@ CONFIG_SCHEMA = (
     .extend(uart.UART_DEVICE_SCHEMA)
 )
 
+FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
+    "mhz19",
+    baud_rate=9600,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
+)
+
 
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])

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/mk2pvrouter/mk2pvrouter.cpp

@@ -163,10 +163,7 @@ void Mk2PVRouter::publish_value_(const char *tag, const char *val) {
 #endif
 }
 
-void Mk2PVRouter::dump_config() {
-  ESP_LOGCONFIG(TAG, "Mk2PVRouter:");
-  this->check_uart_settings(BAUD_RATE, 1, uart::UART_CONFIG_PARITY_EVEN, 7);
-}
+void Mk2PVRouter::dump_config() { ESP_LOGCONFIG(TAG, "Mk2PVRouter:"); }
 
 #ifdef MK2PVROUTER_LISTENER_COUNT
 void Mk2PVRouter::register_mk2pvrouter_listener(Mk2PVRouterListener *listener) {

esphome/components/mk2pvrouter/mk2pvrouter.h

@@ -43,7 +43,6 @@ class Mk2PVRouter final : public Component, public uart::UARTDevice {
 
  protected:
   static constexpr size_t CRC_SUFFIX_LEN = 1;
-  static constexpr uint32_t BAUD_RATE = 9600;
 
   enum class State : uint8_t {
     WAITING_FOR_START,

esphome/components/nextion/nextion_upload_arduino.cpp

@@ -209,14 +209,8 @@ bool Nextion::upload_tft(uint32_t baud_rate, bool exit_reparse) {
   http_client.setTimeout(this->tft_upload_http_timeout_);
 
   bool begin_status = false;
-#if USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 7, 0)
   http_client.setFollowRedirects(HTTPC_STRICT_FOLLOW_REDIRECTS);
-#elif USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 6, 0)
-  http_client.setFollowRedirects(true);
-#endif
-#if USE_ARDUINO_VERSION_CODE >= VERSION_CODE(2, 6, 0)
   http_client.setRedirectLimit(3);
-#endif
   begin_status = http_client.begin(*this->get_wifi_client_(), this->tft_url_.c_str());
   if (!begin_status) {
     this->connection_state_.is_updating_ = false;

esphome/components/noise/__init__.py

@@ -4,7 +4,9 @@ from typing import Any
 
 import esphome.codegen as cg
 import esphome.config_validation as cv
-from esphome.const import CONF_KEY
+from esphome.const import CONF_ENCRYPTION, CONF_KEY
+from esphome.core import ID
+from esphome.cpp_generator import MockObj
 from esphome.types import ConfigType
 
 CODEOWNERS = ["@esphome/core"]
@@ -23,6 +25,14 @@ def validate_encryption_key(value: Any) -> str:
 
     if len(decoded) != 32:
         raise cv.Invalid("Encryption key must be base64 and 32 bytes long")
+    if not any(decoded):
+        # The device treats the all-zeros key as no key at all (it is the
+        # provisioning sentinel), so it must never reach a build
+        raise cv.Invalid(
+            f"The all-zeros {CONF_KEY} is reserved and provides no protection; "
+            f"omit the {CONF_KEY} to provision it at runtime, or generate a real "
+            "key with: openssl rand -base64 32"
+        )
 
     # Return original data for roundtrip conversion
     return value
@@ -45,15 +55,6 @@ def decode_encryption_key(value: str) -> bytes:
     return decoded
 
 
-def is_reserved_key(value: str) -> bool:
-    """Whether the key is the reserved all-zeros provisioning sentinel.
-
-    The device treats it as no key configured, so consumers that require a
-    real key must reject it.
-    """
-    return not any(decode_encryption_key(value))
-
-
 ENCRYPTION_SCHEMA = cv.Schema(
     {
         cv.Optional(CONF_KEY): cv.sensitive(validate_encryption_key),
@@ -61,6 +62,21 @@ ENCRYPTION_SCHEMA = cv.Schema(
 )
 
 
+def static_encryption_key(conf: ConfigType) -> str | None:
+    """The build time key of a component config; None without one or when
+    the key is provisioned at runtime."""
+    return (conf.get(CONF_ENCRYPTION) or {}).get(CONF_KEY) or None
+
+
+def new_psk_progmem(parent_id: ID, key: str) -> MockObj:
+    """Emit the decoded key as a PROGMEM array; the component keeps a pointer
+    so the key never occupies RAM."""
+    return cg.progmem_array(
+        ID(f"{parent_id.id}_psk", is_declaration=True, type=cg.uint8),
+        list(decode_encryption_key(key)),
+    )
+
+
 def encryption_schema(config: ConfigType | None) -> ConfigType:
     # A bare `encryption:` block is valid; a missing key means the consumer
     # falls back to its keyless behavior (api provisioning, ota inheriting
@@ -72,12 +88,12 @@ def encryption_schema(config: ConfigType | None) -> ConfigType:
 
 async def to_code(config: ConfigType) -> None:
     cg.add_define("USE_NOISE")
-    cg.add_library("esphome/noise-c", "0.1.21")
+    cg.add_library("esphome/noise-c", "0.1.24")
     # noise-c depends on libsodium, but declaring it here too lets the
     # library manager see the full set up front instead of discovering
     # libsodium only after noise-c has downloaded, so the two can download
     # in parallel. The version must match noise-c's library.json.
-    cg.add_library("esphome/libsodium", "1.10021.4")
+    cg.add_library("esphome/libsodium", "1.10021.6")
     # Enable optimized memzero/memcmp in libsodium instead of volatile byte loops
     cg.add_build_flag("-DHAVE_WEAK_SYMBOLS=1")
     cg.add_build_flag("-DHAVE_INLINE_ASM=1")

esphome/components/noise/noise.cpp

@@ -1,5 +1,6 @@
 #include "noise.h"
 #ifdef USE_NOISE
+#include "esphome/core/hal.h"
 #include "esphome/core/log.h"
 
 #include <algorithm>
@@ -15,6 +16,14 @@ namespace esphome::noise {
 
 static const char *const TAG = "noise";
 
+void NoiseContext::load_psk(psk_t &out) const {
+  if (this->psk_ == nullptr) {
+    out.fill(0);
+    return;
+  }
+  progmem_memcpy(out.data(), this->psk_, out.size());
+}
+
 const LogString *noise_err_to_logstr(int err) {
   if (err == NOISE_ERROR_NO_MEMORY)
     return LOG_STR("NO_MEMORY");

esphome/components/noise/noise.h

@@ -23,16 +23,16 @@ class NoiseContext {
     }
     return acc == 0;
   }
-  void set_psk(psk_t psk) {
-    this->psk_ = psk;
-    this->has_psk_ = !is_all_zeros(psk);
-  }
-  const psk_t &get_psk() const { return this->psk_; }
-  bool has_psk() const { return this->has_psk_; }
+  /// psk points at 32 bytes that outlive the context (PROGMEM or caller owned
+  /// RAM); nullptr means no key. Runtime callers map the all-zeros key to
+  /// nullptr themselves; validation keeps it out of yaml.
+  void set_psk(const uint8_t *psk) { this->psk_ = psk; }
+  /// Copy the key out (flash-aware on ESP8266); all zeros when none is set.
+  void load_psk(psk_t &out) const;
+  bool has_psk() const { return this->psk_ != nullptr; }
 
  protected:
-  psk_t psk_{};
-  bool has_psk_{false};
+  const uint8_t *psk_{nullptr};
 };
 
 /// Convert a noise error code to a readable error

esphome/components/noise/noise_handshake.cpp

@@ -20,7 +20,7 @@ NoiseResponderHandshake::~NoiseResponderHandshake() {
   }
 }
 
-int NoiseResponderHandshake::init(const psk_t &psk, const uint8_t *prologue, size_t prologue_len) {
+int NoiseResponderHandshake::init(const NoiseContext &ctx, const uint8_t *prologue, size_t prologue_len) {
   if (this->handshake_ != nullptr) {
     noise_handshakestate_free(this->handshake_);
     this->handshake_ = nullptr;
@@ -44,6 +44,9 @@ int NoiseResponderHandshake::init(const psk_t &psk, const uint8_t *prologue, siz
     HANDSHAKE_STEP_LOG("noise_handshakestate_new_by_id", err);
     return err;
   }
+  // noise-c keeps its own copy, so the key only passes through the stack here
+  psk_t psk;
+  ctx.load_psk(psk);
   err = noise_handshakestate_set_pre_shared_key(this->handshake_, psk.data(), psk.size());
   if (err != 0) {
     HANDSHAKE_STEP_LOG("noise_handshakestate_set_pre_shared_key", err);

esphome/components/noise/noise_handshake.h

@@ -36,9 +36,9 @@ class NoiseResponderHandshake {
   NoiseResponderHandshake(const NoiseResponderHandshake &) = delete;
   NoiseResponderHandshake &operator=(const NoiseResponderHandshake &) = delete;
 
-  /// Create and start the handshake with the given PSK and prologue. A
-  /// repeated call frees the previous handshake state and starts over.
-  [[nodiscard]] int init(const psk_t &psk, const uint8_t *prologue, size_t prologue_len);
+  /// Create and start the handshake with the context's PSK and the prologue.
+  /// A repeated call frees the previous handshake state and starts over.
+  [[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.
   [[nodiscard]] Action action() const;

esphome/components/pm1006/pm1006.cpp

@@ -16,7 +16,6 @@ void PM1006Component::dump_config() {
   ESP_LOGCONFIG(TAG, "PM1006:");
   LOG_SENSOR("  ", "PM2.5", this->pm_2_5_sensor_);
   LOG_UPDATE_INTERVAL(this);
-  this->check_uart_settings(9600);
 }
 
 void PM1006Component::update() {

esphome/components/pm1006/sensor.py

@@ -48,6 +48,9 @@ def validate_interval_uart(config: ConfigType) -> None:
         baud_rate=9600,
         require_rx=True,
         require_tx=interval.total_milliseconds != SCHEDULER_DONT_RUN,
+        data_bits=8,
+        parity="NONE",
+        stop_bits=1,
     )(config)
 
 

esphome/components/pmsx003/pmsx003.cpp

@@ -46,8 +46,6 @@ void PMSX003Component::dump_config() {
   } else {
     ESP_LOGCONFIG(TAG, "  Mode: passive with sleep/wake cycles");
   }
-
-  this->check_uart_settings(9600);
 }
 
 void PMSX003Component::loop() {

esphome/components/pmsx003/sensor.py

@@ -302,7 +302,13 @@ CONFIG_SCHEMA = cv.All(
 def final_validate(config: ConfigType) -> None:
     require_tx = config[CONF_UPDATE_INTERVAL] > cv.time_period("0s")
     schema = uart.final_validate_device_schema(
-        "pmsx003", baud_rate=9600, require_rx=True, require_tx=require_tx
+        "pmsx003",
+        baud_rate=9600,
+        require_rx=True,
+        require_tx=require_tx,
+        data_bits=8,
+        parity="NONE",
+        stop_bits=1,
     )
     schema(config)
 

esphome/components/pylontech/__init__.py

@@ -41,6 +41,14 @@ CONFIG_SCHEMA = cv.All(
     .extend(uart.UART_DEVICE_SCHEMA)
 )
 
+FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
+    "pylontech",
+    baud_rate=115200,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
+)
+
 
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])

esphome/components/pylontech/pylontech.cpp

@@ -33,7 +33,6 @@ static const uint8_t ASCII_LF = 0x0A;
 PylontechComponent::PylontechComponent() {}
 
 void PylontechComponent::dump_config() {
-  this->check_uart_settings(115200, 1, esphome::uart::UART_CONFIG_PARITY_NONE, 8);
   ESP_LOGCONFIG(TAG, "pylontech:");
   if (this->is_failed()) {
     ESP_LOGE(TAG, "Connection with pylontech failed!");

esphome/components/remote_transmitter/__init__.py

@@ -4,11 +4,7 @@ from esphome import automation, pins
 import esphome.codegen as cg
 from esphome.components import esp32, esp32_rmt, remote_base
 from esphome.components.libretiny import get_libretiny_family
-from esphome.components.libretiny.const import (
-    FAMILY_BK7231N,
-    FAMILY_BK7238,
-    FAMILY_RTL8720C,
-)
+from esphome.components.libretiny.const import FAMILY_BK7238, FAMILY_RTL8720C
 from esphome.config_helpers import filter_source_files_from_platform
 import esphome.config_validation as cv
 from esphome.const import (
@@ -49,7 +45,9 @@ DigitalWriteAction = remote_transmitter_ns.class_(
 )
 
 
-_NON_BLOCKING_LIBRETINY_FAMILIES = (FAMILY_RTL8720C, FAMILY_BK7231N, FAMILY_BK7238)
+# Keep in sync with the USE_LIBRETINY_VARIANT_RTL8720C / REMOTE_TRANSMITTER_BK_PWM gates in
+# remote_transmitter.h, which decide where set_non_blocking() is declared
+_NON_BLOCKING_LIBRETINY_FAMILIES = (FAMILY_RTL8720C, FAMILY_BK7238)
 
 
 def _validate_non_blocking_platform(value: bool) -> bool:
@@ -59,9 +57,7 @@ def _validate_non_blocking_platform(value: bool) -> bool:
         return cv.boolean(value)
     if CORE.is_libretiny and get_libretiny_family() in _NON_BLOCKING_LIBRETINY_FAMILIES:
         return cv.boolean(value)
-    raise cv.Invalid(
-        "non_blocking is only supported on ESP32, RTL8720C, BK7231N and BK7238"
-    )
+    raise cv.Invalid("non_blocking is only supported on ESP32, RTL8720C and BK7238")
 
 
 MULTI_CONF = True

esphome/components/remote_transmitter/remote_transmitter.h

@@ -12,10 +12,11 @@
 #endif  // SOC_RMT_SUPPORTED
 #endif  // USE_ESP32
 
-// The BK7231N-style PWM block (hardware shadow-load duty updates) enables the ISR-driven
-// transmitter on these families; family-level proxy for the SDK's CFG_SOC_NAME gate.
-// See remote_transmitter_bk72xx.cpp.
-#if defined(USE_LIBRETINY_VARIANT_BK7231N) || defined(USE_LIBRETINY_VARIANT_BK7238)
+// Enables the ISR-driven transmitter on Beken. Gated on BK7238 alone: the shadow-load PWM
+// block is shared with BK7231N, but LibreTiny builds that family against an older BDK whose
+// PWM driver has no pwm_init_param()/pwm_start(). See remote_transmitter_bk72xx.cpp.
+// Keep in sync with _NON_BLOCKING_LIBRETINY_FAMILIES in __init__.py.
+#ifdef USE_LIBRETINY_VARIANT_BK7238
 #define REMOTE_TRANSMITTER_BK_PWM
 #endif
 

esphome/components/remote_transmitter/remote_transmitter_bk72xx.cpp

@@ -9,10 +9,13 @@
 // with the core's fixes for type-name collisions between the two
 #include <ArduinoPrivate.h>
 
-// Only the BK7231N-style PWM block (shadow registers with a hardware CFG_UPDATA load bit)
-// supports glitch-free per-edge duty updates; older SoCs compile the generic bit-bang
-// implementation (remote_transmitter.cpp) instead, and this file compiles to nothing.
-// REMOTE_TRANSMITTER_BK_PWM is set per-family in remote_transmitter.h.
+// Needs the BK7231N-style PWM block (shadow registers with a hardware CFG_UPDATA load bit)
+// for glitch-free per-edge duty updates, and an SDK exposing pwm_init_param()/pwm_start().
+// BK7231N has the block but LibreTiny builds it against an older BDK offering only the
+// sddev_control API (CMD_PWM_INIT_PARAM), so it stays on the generic bit-bang path until
+// someone can add and validate that path on real hardware. Every other Beken SoC lacks the
+// block. REMOTE_TRANSMITTER_BK_PWM is set per-family in remote_transmitter.h; when it is
+// unset this file compiles to nothing and remote_transmitter.cpp is used instead.
 
 namespace esphome::remote_transmitter {
 

esphome/components/remote_transmitter/remote_transmitter_libretiny_isr.cpp

@@ -3,11 +3,11 @@
 #include "esphome/core/hal.h"
 #include "esphome/core/log.h"
 
-// Envelope chain shared by the LibreTiny families that pace transmission from a hardware
-// timer interrupt: RTL8720C (gtimer) and the BK7231N-style PWM block (BKTIMER1). Everything
-// platform-specific sits behind five hooks implemented in the per-family files -- carrier
-// setup, duty writes, one-shot arming and timer stop. Families without a usable timer keep
-// the generic bit-bang implementation and compile none of this.
+// Envelope chain shared by the LibreTiny families that pace transmission from a hardware timer
+// interrupt: RTL8720C (gtimer) and BK7238 (BKTIMER1). Everything platform-specific sits behind
+// five hooks implemented in the per-family files -- carrier setup, duty writes, one-shot arming
+// and timer stop. Families without a usable timer keep the generic bit-bang implementation and
+// compile none of this.
 #if defined(USE_LIBRETINY_VARIANT_RTL8720C) || defined(REMOTE_TRANSMITTER_BK_PWM)
 
 namespace esphome::remote_transmitter {

esphome/components/sdl/__init__.py

@@ -1 +1,254 @@
+import esphome.codegen as cg
+
 CODEOWNERS = ["@clydebarrow"]
+
+SDL_KeyCode = cg.global_ns.enum("SDL_KeyCode")
+
+SDL_KEYS = (
+    "SDLK_UNKNOWN",
+    "SDLK_RETURN",
+    "SDLK_ESCAPE",
+    "SDLK_BACKSPACE",
+    "SDLK_TAB",
+    "SDLK_SPACE",
+    "SDLK_EXCLAIM",
+    "SDLK_QUOTEDBL",
+    "SDLK_HASH",
+    "SDLK_PERCENT",
+    "SDLK_DOLLAR",
+    "SDLK_AMPERSAND",
+    "SDLK_QUOTE",
+    "SDLK_LEFTPAREN",
+    "SDLK_RIGHTPAREN",
+    "SDLK_ASTERISK",
+    "SDLK_PLUS",
+    "SDLK_COMMA",
+    "SDLK_MINUS",
+    "SDLK_PERIOD",
+    "SDLK_SLASH",
+    "SDLK_0",
+    "SDLK_1",
+    "SDLK_2",
+    "SDLK_3",
+    "SDLK_4",
+    "SDLK_5",
+    "SDLK_6",
+    "SDLK_7",
+    "SDLK_8",
+    "SDLK_9",
+    "SDLK_COLON",
+    "SDLK_SEMICOLON",
+    "SDLK_LESS",
+    "SDLK_EQUALS",
+    "SDLK_GREATER",
+    "SDLK_QUESTION",
+    "SDLK_AT",
+    "SDLK_LEFTBRACKET",
+    "SDLK_BACKSLASH",
+    "SDLK_RIGHTBRACKET",
+    "SDLK_CARET",
+    "SDLK_UNDERSCORE",
+    "SDLK_BACKQUOTE",
+    "SDLK_a",
+    "SDLK_b",
+    "SDLK_c",
+    "SDLK_d",
+    "SDLK_e",
+    "SDLK_f",
+    "SDLK_g",
+    "SDLK_h",
+    "SDLK_i",
+    "SDLK_j",
+    "SDLK_k",
+    "SDLK_l",
+    "SDLK_m",
+    "SDLK_n",
+    "SDLK_o",
+    "SDLK_p",
+    "SDLK_q",
+    "SDLK_r",
+    "SDLK_s",
+    "SDLK_t",
+    "SDLK_u",
+    "SDLK_v",
+    "SDLK_w",
+    "SDLK_x",
+    "SDLK_y",
+    "SDLK_z",
+    "SDLK_CAPSLOCK",
+    "SDLK_F1",
+    "SDLK_F2",
+    "SDLK_F3",
+    "SDLK_F4",
+    "SDLK_F5",
+    "SDLK_F6",
+    "SDLK_F7",
+    "SDLK_F8",
+    "SDLK_F9",
+    "SDLK_F10",
+    "SDLK_F11",
+    "SDLK_F12",
+    "SDLK_PRINTSCREEN",
+    "SDLK_SCROLLLOCK",
+    "SDLK_PAUSE",
+    "SDLK_INSERT",
+    "SDLK_HOME",
+    "SDLK_PAGEUP",
+    "SDLK_DELETE",
+    "SDLK_END",
+    "SDLK_PAGEDOWN",
+    "SDLK_RIGHT",
+    "SDLK_LEFT",
+    "SDLK_DOWN",
+    "SDLK_UP",
+    "SDLK_NUMLOCKCLEAR",
+    "SDLK_KP_DIVIDE",
+    "SDLK_KP_MULTIPLY",
+    "SDLK_KP_MINUS",
+    "SDLK_KP_PLUS",
+    "SDLK_KP_ENTER",
+    "SDLK_KP_1",
+    "SDLK_KP_2",
+    "SDLK_KP_3",
+    "SDLK_KP_4",
+    "SDLK_KP_5",
+    "SDLK_KP_6",
+    "SDLK_KP_7",
+    "SDLK_KP_8",
+    "SDLK_KP_9",
+    "SDLK_KP_0",
+    "SDLK_KP_PERIOD",
+    "SDLK_APPLICATION",
+    "SDLK_POWER",
+    "SDLK_KP_EQUALS",
+    "SDLK_F13",
+    "SDLK_F14",
+    "SDLK_F15",
+    "SDLK_F16",
+    "SDLK_F17",
+    "SDLK_F18",
+    "SDLK_F19",
+    "SDLK_F20",
+    "SDLK_F21",
+    "SDLK_F22",
+    "SDLK_F23",
+    "SDLK_F24",
+    "SDLK_EXECUTE",
+    "SDLK_HELP",
+    "SDLK_MENU",
+    "SDLK_SELECT",
+    "SDLK_STOP",
+    "SDLK_AGAIN",
+    "SDLK_UNDO",
+    "SDLK_CUT",
+    "SDLK_COPY",
+    "SDLK_PASTE",
+    "SDLK_FIND",
+    "SDLK_MUTE",
+    "SDLK_VOLUMEUP",
+    "SDLK_VOLUMEDOWN",
+    "SDLK_KP_COMMA",
+    "SDLK_KP_EQUALSAS400",
+    "SDLK_ALTERASE",
+    "SDLK_SYSREQ",
+    "SDLK_CANCEL",
+    "SDLK_CLEAR",
+    "SDLK_PRIOR",
+    "SDLK_RETURN2",
+    "SDLK_SEPARATOR",
+    "SDLK_OUT",
+    "SDLK_OPER",
+    "SDLK_CLEARAGAIN",
+    "SDLK_CRSEL",
+    "SDLK_EXSEL",
+    "SDLK_KP_00",
+    "SDLK_KP_000",
+    "SDLK_THOUSANDSSEPARATOR",
+    "SDLK_DECIMALSEPARATOR",
+    "SDLK_CURRENCYUNIT",
+    "SDLK_CURRENCYSUBUNIT",
+    "SDLK_KP_LEFTPAREN",
+    "SDLK_KP_RIGHTPAREN",
+    "SDLK_KP_LEFTBRACE",
+    "SDLK_KP_RIGHTBRACE",
+    "SDLK_KP_TAB",
+    "SDLK_KP_BACKSPACE",
+    "SDLK_KP_A",
+    "SDLK_KP_B",
+    "SDLK_KP_C",
+    "SDLK_KP_D",
+    "SDLK_KP_E",
+    "SDLK_KP_F",
+    "SDLK_KP_XOR",
+    "SDLK_KP_POWER",
+    "SDLK_KP_PERCENT",
+    "SDLK_KP_LESS",
+    "SDLK_KP_GREATER",
+    "SDLK_KP_AMPERSAND",
+    "SDLK_KP_DBLAMPERSAND",
+    "SDLK_KP_VERTICALBAR",
+    "SDLK_KP_DBLVERTICALBAR",
+    "SDLK_KP_COLON",
+    "SDLK_KP_HASH",
+    "SDLK_KP_SPACE",
+    "SDLK_KP_AT",
+    "SDLK_KP_EXCLAM",
+    "SDLK_KP_MEMSTORE",
+    "SDLK_KP_MEMRECALL",
+    "SDLK_KP_MEMCLEAR",
+    "SDLK_KP_MEMADD",
+    "SDLK_KP_MEMSUBTRACT",
+    "SDLK_KP_MEMMULTIPLY",
+    "SDLK_KP_MEMDIVIDE",
+    "SDLK_KP_PLUSMINUS",
+    "SDLK_KP_CLEAR",
+    "SDLK_KP_CLEARENTRY",
+    "SDLK_KP_BINARY",
+    "SDLK_KP_OCTAL",
+    "SDLK_KP_DECIMAL",
+    "SDLK_KP_HEXADECIMAL",
+    "SDLK_LCTRL",
+    "SDLK_LSHIFT",
+    "SDLK_LALT",
+    "SDLK_LGUI",
+    "SDLK_RCTRL",
+    "SDLK_RSHIFT",
+    "SDLK_RALT",
+    "SDLK_RGUI",
+    "SDLK_MODE",
+    "SDLK_AUDIONEXT",
+    "SDLK_AUDIOPREV",
+    "SDLK_AUDIOSTOP",
+    "SDLK_AUDIOPLAY",
+    "SDLK_AUDIOMUTE",
+    "SDLK_MEDIASELECT",
+    "SDLK_WWW",
+    "SDLK_MAIL",
+    "SDLK_CALCULATOR",
+    "SDLK_COMPUTER",
+    "SDLK_AC_SEARCH",
+    "SDLK_AC_HOME",
+    "SDLK_AC_BACK",
+    "SDLK_AC_FORWARD",
+    "SDLK_AC_STOP",
+    "SDLK_AC_REFRESH",
+    "SDLK_AC_BOOKMARKS",
+    "SDLK_BRIGHTNESSDOWN",
+    "SDLK_BRIGHTNESSUP",
+    "SDLK_DISPLAYSWITCH",
+    "SDLK_KBDILLUMTOGGLE",
+    "SDLK_KBDILLUMDOWN",
+    "SDLK_KBDILLUMUP",
+    "SDLK_EJECT",
+    "SDLK_SLEEP",
+    "SDLK_APP1",
+    "SDLK_APP2",
+    "SDLK_AUDIOREWIND",
+    "SDLK_AUDIOFASTFORWARD",
+    "SDLK_SOFTLEFT",
+    "SDLK_SOFTRIGHT",
+    "SDLK_CALL",
+    "SDLK_ENDCALL",
+)
+
+SDL_KEYMAP = {key: getattr(SDL_KeyCode, key) for key in SDL_KEYS}

esphome/components/sdl/binary_sensor.py

@@ -7,262 +7,15 @@ from esphome.core import Lambda
 from esphome.cpp_generator import ExpressionStatement, RawExpression
 from esphome.types import ConfigType
 
-from .display import CONF_SDL_ID, Sdl
+from . import SDL_KEYMAP
+from .display import CONF_SDL_ID, Sdl, headless_final_validate
 
 CODEOWNERS = ["@bdm310"]
 
 STATE_ARG = "state"
 
-SDL_KeyCode = cg.global_ns.enum("SDL_KeyCode")
+FINAL_VALIDATE_SCHEMA = headless_final_validate("binary_sensor")
 
-SDL_KEYS = (
-    "SDLK_UNKNOWN",
-    "SDLK_RETURN",
-    "SDLK_ESCAPE",
-    "SDLK_BACKSPACE",
-    "SDLK_TAB",
-    "SDLK_SPACE",
-    "SDLK_EXCLAIM",
-    "SDLK_QUOTEDBL",
-    "SDLK_HASH",
-    "SDLK_PERCENT",
-    "SDLK_DOLLAR",
-    "SDLK_AMPERSAND",
-    "SDLK_QUOTE",
-    "SDLK_LEFTPAREN",
-    "SDLK_RIGHTPAREN",
-    "SDLK_ASTERISK",
-    "SDLK_PLUS",
-    "SDLK_COMMA",
-    "SDLK_MINUS",
-    "SDLK_PERIOD",
-    "SDLK_SLASH",
-    "SDLK_0",
-    "SDLK_1",
-    "SDLK_2",
-    "SDLK_3",
-    "SDLK_4",
-    "SDLK_5",
-    "SDLK_6",
-    "SDLK_7",
-    "SDLK_8",
-    "SDLK_9",
-    "SDLK_COLON",
-    "SDLK_SEMICOLON",
-    "SDLK_LESS",
-    "SDLK_EQUALS",
-    "SDLK_GREATER",
-    "SDLK_QUESTION",
-    "SDLK_AT",
-    "SDLK_LEFTBRACKET",
-    "SDLK_BACKSLASH",
-    "SDLK_RIGHTBRACKET",
-    "SDLK_CARET",
-    "SDLK_UNDERSCORE",
-    "SDLK_BACKQUOTE",
-    "SDLK_a",
-    "SDLK_b",
-    "SDLK_c",
-    "SDLK_d",
-    "SDLK_e",
-    "SDLK_f",
-    "SDLK_g",
-    "SDLK_h",
-    "SDLK_i",
-    "SDLK_j",
-    "SDLK_k",
-    "SDLK_l",
-    "SDLK_m",
-    "SDLK_n",
-    "SDLK_o",
-    "SDLK_p",
-    "SDLK_q",
-    "SDLK_r",
-    "SDLK_s",
-    "SDLK_t",
-    "SDLK_u",
-    "SDLK_v",
-    "SDLK_w",
-    "SDLK_x",
-    "SDLK_y",
-    "SDLK_z",
-    "SDLK_CAPSLOCK",
-    "SDLK_F1",
-    "SDLK_F2",
-    "SDLK_F3",
-    "SDLK_F4",
-    "SDLK_F5",
-    "SDLK_F6",
-    "SDLK_F7",
-    "SDLK_F8",
-    "SDLK_F9",
-    "SDLK_F10",
-    "SDLK_F11",
-    "SDLK_F12",
-    "SDLK_PRINTSCREEN",
-    "SDLK_SCROLLLOCK",
-    "SDLK_PAUSE",
-    "SDLK_INSERT",
-    "SDLK_HOME",
-    "SDLK_PAGEUP",
-    "SDLK_DELETE",
-    "SDLK_END",
-    "SDLK_PAGEDOWN",
-    "SDLK_RIGHT",
-    "SDLK_LEFT",
-    "SDLK_DOWN",
-    "SDLK_UP",
-    "SDLK_NUMLOCKCLEAR",
-    "SDLK_KP_DIVIDE",
-    "SDLK_KP_MULTIPLY",
-    "SDLK_KP_MINUS",
-    "SDLK_KP_PLUS",
-    "SDLK_KP_ENTER",
-    "SDLK_KP_1",
-    "SDLK_KP_2",
-    "SDLK_KP_3",
-    "SDLK_KP_4",
-    "SDLK_KP_5",
-    "SDLK_KP_6",
-    "SDLK_KP_7",
-    "SDLK_KP_8",
-    "SDLK_KP_9",
-    "SDLK_KP_0",
-    "SDLK_KP_PERIOD",
-    "SDLK_APPLICATION",
-    "SDLK_POWER",
-    "SDLK_KP_EQUALS",
-    "SDLK_F13",
-    "SDLK_F14",
-    "SDLK_F15",
-    "SDLK_F16",
-    "SDLK_F17",
-    "SDLK_F18",
-    "SDLK_F19",
-    "SDLK_F20",
-    "SDLK_F21",
-    "SDLK_F22",
-    "SDLK_F23",
-    "SDLK_F24",
-    "SDLK_EXECUTE",
-    "SDLK_HELP",
-    "SDLK_MENU",
-    "SDLK_SELECT",
-    "SDLK_STOP",
-    "SDLK_AGAIN",
-    "SDLK_UNDO",
-    "SDLK_CUT",
-    "SDLK_COPY",
-    "SDLK_PASTE",
-    "SDLK_FIND",
-    "SDLK_MUTE",
-    "SDLK_VOLUMEUP",
-    "SDLK_VOLUMEDOWN",
-    "SDLK_KP_COMMA",
-    "SDLK_KP_EQUALSAS400",
-    "SDLK_ALTERASE",
-    "SDLK_SYSREQ",
-    "SDLK_CANCEL",
-    "SDLK_CLEAR",
-    "SDLK_PRIOR",
-    "SDLK_RETURN2",
-    "SDLK_SEPARATOR",
-    "SDLK_OUT",
-    "SDLK_OPER",
-    "SDLK_CLEARAGAIN",
-    "SDLK_CRSEL",
-    "SDLK_EXSEL",
-    "SDLK_KP_00",
-    "SDLK_KP_000",
-    "SDLK_THOUSANDSSEPARATOR",
-    "SDLK_DECIMALSEPARATOR",
-    "SDLK_CURRENCYUNIT",
-    "SDLK_CURRENCYSUBUNIT",
-    "SDLK_KP_LEFTPAREN",
-    "SDLK_KP_RIGHTPAREN",
-    "SDLK_KP_LEFTBRACE",
-    "SDLK_KP_RIGHTBRACE",
-    "SDLK_KP_TAB",
-    "SDLK_KP_BACKSPACE",
-    "SDLK_KP_A",
-    "SDLK_KP_B",
-    "SDLK_KP_C",
-    "SDLK_KP_D",
-    "SDLK_KP_E",
-    "SDLK_KP_F",
-    "SDLK_KP_XOR",
-    "SDLK_KP_POWER",
-    "SDLK_KP_PERCENT",
-    "SDLK_KP_LESS",
-    "SDLK_KP_GREATER",
-    "SDLK_KP_AMPERSAND",
-    "SDLK_KP_DBLAMPERSAND",
-    "SDLK_KP_VERTICALBAR",
-    "SDLK_KP_DBLVERTICALBAR",
-    "SDLK_KP_COLON",
-    "SDLK_KP_HASH",
-    "SDLK_KP_SPACE",
-    "SDLK_KP_AT",
-    "SDLK_KP_EXCLAM",
-    "SDLK_KP_MEMSTORE",
-    "SDLK_KP_MEMRECALL",
-    "SDLK_KP_MEMCLEAR",
-    "SDLK_KP_MEMADD",
-    "SDLK_KP_MEMSUBTRACT",
-    "SDLK_KP_MEMMULTIPLY",
-    "SDLK_KP_MEMDIVIDE",
-    "SDLK_KP_PLUSMINUS",
-    "SDLK_KP_CLEAR",
-    "SDLK_KP_CLEARENTRY",
-    "SDLK_KP_BINARY",
-    "SDLK_KP_OCTAL",
-    "SDLK_KP_DECIMAL",
-    "SDLK_KP_HEXADECIMAL",
-    "SDLK_LCTRL",
-    "SDLK_LSHIFT",
-    "SDLK_LALT",
-    "SDLK_LGUI",
-    "SDLK_RCTRL",
-    "SDLK_RSHIFT",
-    "SDLK_RALT",
-    "SDLK_RGUI",
-    "SDLK_MODE",
-    "SDLK_AUDIONEXT",
-    "SDLK_AUDIOPREV",
-    "SDLK_AUDIOSTOP",
-    "SDLK_AUDIOPLAY",
-    "SDLK_AUDIOMUTE",
-    "SDLK_MEDIASELECT",
-    "SDLK_WWW",
-    "SDLK_MAIL",
-    "SDLK_CALCULATOR",
-    "SDLK_COMPUTER",
-    "SDLK_AC_SEARCH",
-    "SDLK_AC_HOME",
-    "SDLK_AC_BACK",
-    "SDLK_AC_FORWARD",
-    "SDLK_AC_STOP",
-    "SDLK_AC_REFRESH",
-    "SDLK_AC_BOOKMARKS",
-    "SDLK_BRIGHTNESSDOWN",
-    "SDLK_BRIGHTNESSUP",
-    "SDLK_DISPLAYSWITCH",
-    "SDLK_KBDILLUMTOGGLE",
-    "SDLK_KBDILLUMDOWN",
-    "SDLK_KBDILLUMUP",
-    "SDLK_EJECT",
-    "SDLK_SLEEP",
-    "SDLK_APP1",
-    "SDLK_APP2",
-    "SDLK_AUDIOREWIND",
-    "SDLK_AUDIOFASTFORWARD",
-    "SDLK_SOFTLEFT",
-    "SDLK_SOFTRIGHT",
-    "SDLK_CALL",
-    "SDLK_ENDCALL",
-)
-
-SDL_KEYMAP = {key: getattr(SDL_KeyCode, key) for key in SDL_KEYS}
 
 CONFIG_SCHEMA = (
     binary_sensor.binary_sensor_schema(BinarySensor)

esphome/components/sdl/display.py

@@ -4,6 +4,7 @@ from typing import Any
 
 import esphome.codegen as cg
 from esphome.components import display
+from esphome.components.snapshot import Snapshot, register_snapshot
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_DIMENSIONS,
@@ -16,14 +17,21 @@ from esphome.const import (
     CONF_Y,
     PLATFORM_HOST,
 )
+import esphome.final_validate as fv
 from esphome.types import ConfigType
 
+from . import SDL_KEYMAP
+
+AUTO_LOAD = ["snapshot"]
+
 sdl_ns = cg.esphome_ns.namespace("sdl")
-Sdl = sdl_ns.class_("Sdl", display.Display, cg.Component)
+Sdl = sdl_ns.class_("Sdl", display.Display, cg.Component, Snapshot)
 sdl_window_flags = cg.global_ns.enum("SDL_WindowFlags")
 
 
 CONF_CENTERED_ON_DISPLAY = "centered_on_display"
+CONF_HEADLESS = "headless"
+CONF_SNAPSHOT_KEY = "snapshot_key"
 CONF_SDL_OPTIONS = "sdl_options"
 CONF_SDL_ID = "sdl_id"
 CONF_WINDOW_OPTIONS = "window_options"
@@ -67,12 +75,29 @@ def _validate_position(config: dict) -> dict:
     raise cv.Invalid("Must specify either 'x' and 'y' or 'centered_on_display'")
 
 
+def _validate_headless(config: ConfigType) -> ConfigType:
+    if not config[CONF_HEADLESS]:
+        return config
+    if CONF_WINDOW_OPTIONS in config:
+        raise cv.Invalid(
+            f"'{CONF_WINDOW_OPTIONS}' has no effect when '{CONF_HEADLESS}' is set - there is no window"
+        )
+    if CONF_SNAPSHOT_KEY in config:
+        raise cv.Invalid(
+            f"'{CONF_SNAPSHOT_KEY}' cannot be used when '{CONF_HEADLESS}' is set - "
+            f"there is no keyboard. Use the 'snapshot.take' action instead"
+        )
+    return config
+
+
 CONFIG_SCHEMA = cv.All(
     display.FULL_DISPLAY_SCHEMA.extend(
         cv.Schema(
             {
                 cv.GenerateID(): cv.declare_id(Sdl),
                 cv.Optional(CONF_SDL_OPTIONS, default=""): get_sdl_options,
+                cv.Optional(CONF_HEADLESS, default=False): cv.boolean,
+                cv.Optional(CONF_SNAPSHOT_KEY): cv.enum(SDL_KEYMAP),
                 cv.Required(CONF_DIMENSIONS): cv.Any(
                     cv.dimensions,
                     cv.Schema(
@@ -99,16 +124,42 @@ CONFIG_SCHEMA = cv.All(
             }
         )
     ),
+    _validate_headless,
     cv.only_on(PLATFORM_HOST),
 )
 
 
+def headless_final_validate(platform: str) -> cv.Schema:
+    """Build a FINAL_VALIDATE_SCHEMA rejecting a platform whose sdl display is headless.
+
+    Mouse and keyboard platforms are driven by window events, so under a headless display they
+    would never report anything.
+    """
+
+    def validate_display(display_config: ConfigType) -> ConfigType:
+        if display_config.get(CONF_HEADLESS):
+            raise cv.Invalid(
+                f"The sdl {platform} platform needs a window, but its display has "
+                f"'{CONF_HEADLESS}' set"
+            )
+        return display_config
+
+    return cv.Schema(
+        {cv.Required(CONF_SDL_ID): fv.id_declaration_match_schema(validate_display)},
+        extra=cv.ALLOW_EXTRA,
+    )
+
+
 async def to_code(config: ConfigType) -> None:
     for option in config[CONF_SDL_OPTIONS].split():
         cg.add_build_flag(option)
     cg.add_build_flag("-DSDL_BYTEORDER=4321")
     var = cg.new_Pvariable(config[CONF_ID])
     await display.register_display(var, config)
+    await register_snapshot(var, config)
+    cg.add(var.set_headless(config[CONF_HEADLESS]))
+    if (key := config.get(CONF_SNAPSHOT_KEY)) is not None:
+        cg.add(var.set_snapshot_key(key))
 
     dimensions = config[CONF_DIMENSIONS]
     if isinstance(dimensions, dict):

esphome/components/sdl/sdl_esphome.cpp

@@ -2,8 +2,17 @@
 #include "sdl_esphome.h"
 #include "esphome/components/display/display_color_utils.h"
 
+#include <cstdlib>
+
 namespace esphome::sdl {
 
+namespace {
+
+// Key under which each window keeps a pointer back to its Sdl instance.
+constexpr const char *const WINDOW_DATA_KEY = "esphome_sdl";
+
+}  // namespace
+
 int Sdl::get_width() {
   switch (this->rotation_) {
     case display::DISPLAY_ROTATION_90_DEGREES:
@@ -28,17 +37,96 @@ int Sdl::get_height() {
   }
 }
 
-void Sdl::setup() {
-  SDL_Init(SDL_INIT_VIDEO);
-  this->window_ = SDL_CreateWindow(App.get_name().c_str(), this->pos_x_, this->pos_y_, this->width_, this->height_,
-                                   this->window_options_);
-  this->renderer_ = SDL_CreateRenderer(this->window_, -1, SDL_RENDERER_SOFTWARE);
-  SDL_RenderSetLogicalSize(this->renderer_, this->width_, this->height_);
+void Sdl::destroy_renderer_() {
+  // Reverse order of creation: the renderer refers to the window or surface it was made from.
+  if (this->shot_target_ != nullptr) {
+    SDL_DestroyTexture(this->shot_target_);
+    this->shot_target_ = nullptr;
+  }
+  if (this->texture_ != nullptr) {
+    SDL_DestroyTexture(this->texture_);
+    this->texture_ = nullptr;
+  }
+  if (this->renderer_ != nullptr) {
+    SDL_DestroyRenderer(this->renderer_);
+    this->renderer_ = nullptr;
+  }
+  if (this->window_ != nullptr) {
+    SDL_DestroyWindow(this->window_);
+    this->window_ = nullptr;
+  }
+  if (this->surface_ != nullptr) {
+    SDL_FreeSurface(this->surface_);
+    this->surface_ = nullptr;
+  }
+}
+
+bool Sdl::setup_failed_(const char *what) {
+  ESP_LOGE(TAG, "%s: %s", what, SDL_GetError());
+  // Give back whatever was created before the failure. Without this a half set up display leaves an
+  // empty window on screen for the life of the process, still registered as an event target.
+  this->destroy_renderer_();
+  return false;
+}
+
+bool Sdl::setup_renderer_() {
+  SDL_SetMainReady();
+  if (this->headless_) {
+    // SDL_INIT_VIDEO is deliberately not requested: a software renderer bound to a surface needs no
+    // video device, so this works on a machine with no display server at all.
+    if (SDL_Init(0) != 0)
+      return this->setup_failed_("SDL_Init failed");
+    this->surface_ = SDL_CreateRGBSurfaceWithFormat(0, this->width_, this->height_, 16, SDL_PIXELFORMAT_RGB565);
+    if (this->surface_ == nullptr)
+      return this->setup_failed_("Could not create offscreen surface");
+    this->renderer_ = SDL_CreateSoftwareRenderer(this->surface_);
+  } else {
+    if (SDL_Init(SDL_INIT_VIDEO) != 0)
+      return this->setup_failed_("SDL_Init failed");
+    this->window_ = SDL_CreateWindow(App.get_name().c_str(), this->pos_x_, this->pos_y_, this->width_, this->height_,
+                                     this->window_options_);
+    if (this->window_ == nullptr)
+      return this->setup_failed_("Could not create window");
+    // Lets loop() find the display an event belongs to, so one display does not act on another's
+    // input when several windows are open.
+    SDL_SetWindowData(this->window_, WINDOW_DATA_KEY, this);
+    this->renderer_ = SDL_CreateRenderer(this->window_, -1, SDL_RENDERER_SOFTWARE);
+  }
+  if (this->renderer_ == nullptr)
+    return this->setup_failed_("Could not create renderer");
+  if (SDL_RenderSetLogicalSize(this->renderer_, this->width_, this->height_) != 0)
+    return this->setup_failed_("Could not set renderer logical size");
   this->texture_ =
       SDL_CreateTexture(this->renderer_, SDL_PIXELFORMAT_RGB565, SDL_TEXTUREACCESS_STATIC, this->width_, this->height_);
-  SDL_SetTextureBlendMode(this->texture_, SDL_BLENDMODE_BLEND);
+  if (this->texture_ == nullptr)
+    return this->setup_failed_("Could not create texture");
+  // The texture has no alpha channel, so blending is pointless. Headless it would also force a
+  // different software blit path onto the 16 bit target surface.
+  if (SDL_SetTextureBlendMode(this->texture_, this->headless_ ? SDL_BLENDMODE_NONE : SDL_BLENDMODE_BLEND) != 0)
+    return this->setup_failed_("Could not set texture blend mode");
+  return true;
 }
+
+void Sdl::setup() {
+  if (!this->setup_renderer_()) {
+    this->mark_failed();
+    return;
+  }
+  if (this->headless_) {
+    // Nothing generates events, so there is nothing for loop() to do.
+    this->disable_loop();
+  } else if (this->snapshot_key_ != 0) {
+    this->add_key_listener(this->snapshot_key_, [this](bool down) {
+      if (down && !this->take_snapshot(nullptr)) {
+        ESP_LOGW(TAG, "snapshot key did not write a file");
+      }
+    });
+  }
+}
+
 void Sdl::update() {
+  if (this->texture_ == nullptr)
+    return;
   this->do_update_();
   if ((this->x_high_ < this->x_low_) || (this->y_high_ < this->y_low_))
     return;
@@ -51,12 +139,19 @@ void Sdl::update() {
 }
 
 void Sdl::redraw_(SDL_Rect &rect) {
+  // Nothing to present when headless - a snapshot blits the whole texture when it needs it, so
+  // doing it here as well would just burn CPU. draw_pixels_at() calls this on every partial
+  // update, so it is worth skipping.
+  if (this->headless_)
+    return;
   SDL_RenderCopy(this->renderer_, this->texture_, &rect, &rect);
   SDL_RenderPresent(this->renderer_);
 }
 
 void Sdl::draw_pixels_at(int x_start, int y_start, int w, int h, const uint8_t *ptr, display::ColorOrder order,
                          display::ColorBitness bitness, bool big_endian, int x_offset, int y_offset, int x_pad) {
+  if (this->texture_ == nullptr)
+    return;
   SDL_Rect rect{x_start, y_start, w, h};
   if (this->rotation_ != display::DISPLAY_ROTATION_0_DEGREES || bitness != display::COLOR_BITNESS_565 || big_endian) {
     Display::draw_pixels_at(x_start, y_start, w, h, ptr, order, bitness, big_endian, x_offset, y_offset, x_pad);
@@ -69,7 +164,7 @@ void Sdl::draw_pixels_at(int x_start, int y_start, int w, int h, const uint8_t *
 }
 
 void Sdl::draw_pixel_at(int x, int y, Color color) {
-  if (!this->get_clipping().inside(x, y))
+  if (this->texture_ == nullptr || !this->get_clipping().inside(x, y))
     return;
 
   if (this->rotation_ == display::DISPLAY_ROTATION_180_DEGREES) {
@@ -104,61 +199,148 @@ void Sdl::process_key(uint32_t keycode, bool down) {
     callback->second(down);
 }
 
+Sdl *Sdl::instance_for_window_(uint32_t window_id) {
+  SDL_Window *window = SDL_GetWindowFromID(window_id);
+  if (window == nullptr)
+    return nullptr;
+  return static_cast<Sdl *>(SDL_GetWindowData(window, WINDOW_DATA_KEY));
+}
+
+void Sdl::handle_event_(const SDL_Event &event) {
+  switch (event.type) {
+    case SDL_MOUSEBUTTONDOWN:
+    case SDL_MOUSEBUTTONUP:
+      if (event.button.button == 1) {
+        this->mouse_x = event.button.x;
+        this->mouse_y = event.button.y;
+        this->mouse_down = event.button.state != 0;
+      }
+      break;
+
+    case SDL_MOUSEMOTION:
+      if (event.motion.state & 1) {
+        this->mouse_x = event.motion.x;
+        this->mouse_y = event.motion.y;
+        this->mouse_down = true;
+      } else {
+        this->mouse_down = false;
+      }
+      break;
+
+    case SDL_KEYDOWN:
+      // Ignore auto-repeat, otherwise holding a key floods the listeners.
+      if (event.key.repeat != 0)
+        break;
+      ESP_LOGD(TAG, "keydown %d", event.key.keysym.sym);
+      this->process_key(event.key.keysym.sym, true);
+      break;
+
+    case SDL_KEYUP:
+      ESP_LOGD(TAG, "keyup %d", event.key.keysym.sym);
+      this->process_key(event.key.keysym.sym, false);
+      break;
+
+    case SDL_WINDOWEVENT:
+      switch (event.window.event) {
+        case SDL_WINDOWEVENT_SIZE_CHANGED:
+        case SDL_WINDOWEVENT_EXPOSED:
+        case SDL_WINDOWEVENT_RESIZED: {
+          SDL_Rect rect{0, 0, this->width_, this->height_};
+          this->redraw_(rect);
+          break;
+        }
+        default:
+          break;
+      }
+      break;
+
+    default:
+      break;
+  }
+}
+
 void Sdl::loop() {
   SDL_Event e;
-  if (SDL_PollEvent(&e)) {
-    switch (e.type) {
-      case SDL_QUIT:
-        exit(0);
+  // Take everything that is waiting, not one event per loop. A touch drag produces a burst of
+  // motion events, and consuming them one at a time lets the queue grow without bound, so the
+  // pointer ends up acting on input from further and further in the past. Draining collapses a
+  // burst to the position it ended at, which is the one the user is asking for anyway.
+  while (SDL_PollEvent(&e)) {
+    if (e.type == SDL_QUIT)
+      exit(0);
 
+    // Events carry the window they happened in, so send each one to the display that owns it.
+    uint32_t window_id;
+    switch (e.type) {
       case SDL_MOUSEBUTTONDOWN:
       case SDL_MOUSEBUTTONUP:
-        if (e.button.button == 1) {
-          this->mouse_x = e.button.x;
-          this->mouse_y = e.button.y;
-          this->mouse_down = e.button.state != 0;
-        }
+        window_id = e.button.windowID;
         break;
-
       case SDL_MOUSEMOTION:
-        if (e.motion.state & 1) {
-          this->mouse_x = e.button.x;
-          this->mouse_y = e.button.y;
-          this->mouse_down = true;
-        } else {
-          this->mouse_down = false;
-        }
+        window_id = e.motion.windowID;
         break;
-
       case SDL_KEYDOWN:
-        ESP_LOGD(TAG, "keydown %d", e.key.keysym.sym);
-        this->process_key(e.key.keysym.sym, true);
-        break;
-
       case SDL_KEYUP:
-        ESP_LOGD(TAG, "keyup %d", e.key.keysym.sym);
-        this->process_key(e.key.keysym.sym, false);
+        window_id = e.key.windowID;
         break;
-
       case SDL_WINDOWEVENT:
-        switch (e.window.event) {
-          case SDL_WINDOWEVENT_SIZE_CHANGED:
-          case SDL_WINDOWEVENT_EXPOSED:
-          case SDL_WINDOWEVENT_RESIZED: {
-            SDL_Rect rect{0, 0, this->width_, this->height_};
-            this->redraw_(rect);
-            break;
-          }
-          default:
-            break;
-        }
+        window_id = e.window.windowID;
         break;
-
       default:
+        // Anything else, including the touch events SDL reports alongside the mouse events it
+        // synthesises from them, is not used here.
         ESP_LOGV(TAG, "Event %d", e.type);
-        break;
+        continue;
+    }
+
+    Sdl *target = instance_for_window_(window_id);
+    if (target == nullptr) {
+      // Nothing to route this to: the window has gone, or it is not one of ours. Say so, otherwise
+      // input that stops working leaves no trace at all.
+      ESP_LOGV(TAG, "Event %d for unknown window %u", e.type, window_id);
+      continue;
+    }
+    target->handle_event_(e);
+  }
+}
+
+bool Sdl::capture_bgr(uint8_t *dest, size_t row_stride) {
+  if (this->texture_ == nullptr || this->renderer_ == nullptr) {
+    ESP_LOGE(TAG, "Snapshot requested but SDL is not set up");
+    return false;
+  }
+  if (this->shot_target_ == nullptr) {
+    this->shot_target_ = SDL_CreateTexture(this->renderer_, SDL_PIXELFORMAT_RGB565, SDL_TEXTUREACCESS_TARGET,
+                                           this->width_, this->height_);
+    if (this->shot_target_ == nullptr) {
+      ESP_LOGE(TAG, "Could not create capture texture: %s", SDL_GetError());
+      return false;
+    }
+    SDL_SetTextureBlendMode(this->shot_target_, SDL_BLENDMODE_NONE);
+  }
+
+  // Render into an offscreen target first. SDL_RenderReadPixels works in physical output pixels and
+  // ignores the logical size, so reading straight off a resizable window would read more pixels than
+  // there is room for.
+  // Every step is checked: a failed clear or copy would otherwise be read back as a blank or stale
+  // picture, written out, and reported as a snapshot that worked.
+  bool ok = false;
+  if (SDL_SetRenderTarget(this->renderer_, this->shot_target_) == 0) {
+    ok = SDL_SetRenderDrawColor(this->renderer_, 0, 0, 0, SDL_ALPHA_OPAQUE) == 0 &&
+         SDL_RenderClear(this->renderer_) == 0 &&
+         SDL_RenderCopy(this->renderer_, this->texture_, nullptr, nullptr) == 0 &&
+         SDL_RenderReadPixels(this->renderer_, nullptr, SDL_PIXELFORMAT_BGR24, dest, static_cast<int>(row_stride)) == 0;
+    if (SDL_SetRenderTarget(this->renderer_, nullptr) != 0) {
+      // Stuck rendering into shot_target_ from here on, so there's no point continuing.
+      ESP_LOGE(TAG, "Could not restore the render target: %s", SDL_GetError());
+      this->mark_failed();
+      return false;
     }
   }
+  if (!ok) {
+    ESP_LOGE(TAG, "Could not capture the screen: %s", SDL_GetError());
+  }
+  return ok;
 }
 
 }  // namespace esphome::sdl

esphome/components/sdl/sdl_esphome.h

@@ -1,10 +1,12 @@
 #pragma once
 
 #ifdef USE_HOST
+#include "esphome/core/automation.h"
 #include "esphome/core/component.h"
 #include "esphome/core/log.h"
 #include "esphome/core/application.h"
 #include "esphome/components/display/display.h"
+#include "esphome/components/snapshot/snapshot.h"
 #define SDL_MAIN_HANDLED
 #include "SDL.h"
 #include <map>
@@ -13,7 +15,7 @@ namespace esphome::sdl {
 
 constexpr static const char *const TAG = "sdl";
 
-class Sdl final : public display::Display {
+class Sdl final : public display::Display, public snapshot::Snapshot {
  public:
   display::DisplayType get_display_type() override { return display::DISPLAY_TYPE_COLOR; }
   void update() override;
@@ -32,6 +34,9 @@ class Sdl final : public display::Display {
     this->pos_x_ = pos_x;
     this->pos_y_ = pos_y;
   }
+  void set_headless(bool headless) { this->headless_ = headless; }
+  void set_snapshot_key(int32_t keycode) { this->snapshot_key_ = keycode; }
+
   int get_width() override;
   int get_height() override;
   float get_setup_priority() const override { return setup_priority::HARDWARE; }
@@ -51,20 +56,40 @@ class Sdl final : public display::Display {
   int get_width_internal() override { return this->width_; }
   int get_height_internal() override { return this->height_; }
   void redraw_(SDL_Rect &rect);
+  bool setup_renderer_();
+  /// Release the window, surface, renderer and textures, and forget them.
+  void destroy_renderer_();
+  /// Log an SDL failure during setup, release anything already created, and return false.
+  bool setup_failed_(const char *what);
+  int snapshot_width() override { return this->width_; }
+  int snapshot_height() override { return this->height_; }
+  bool capture_bgr(uint8_t *dest, size_t row_stride) override;
+  void handle_event_(const SDL_Event &event);
+  /// The display owning the given window, or nullptr if it is not one of ours.
+  static Sdl *instance_for_window_(uint32_t window_id);
+  SDL_Renderer *renderer_{};
+  SDL_Window *window_{};
+  SDL_Texture *texture_{};
+  // Offscreen render target used when headless. SDL_CreateSoftwareRenderer only borrows the
+  // surface, and the renderer goes back to using it as its output whenever the capture target is
+  // released, so it has to stay alive as long as the renderer does.
+  SDL_Surface *surface_{};
+  // Capture target, created on first snapshot.
+  SDL_Texture *shot_target_{};
+  std::map<int32_t, CallbackManager<void(bool)>> key_callbacks_{};
   int width_{};
   int height_{};
   uint32_t window_options_{0};
   int32_t pos_x_{SDL_WINDOWPOS_UNDEFINED};
   int32_t pos_y_{SDL_WINDOWPOS_UNDEFINED};
-  SDL_Renderer *renderer_{};
-  SDL_Window *window_{};
-  SDL_Texture *texture_{};
+  int32_t snapshot_key_{0};
   uint16_t x_low_{0};
   uint16_t y_low_{0};
   uint16_t x_high_{0};
   uint16_t y_high_{0};
-  std::map<int32_t, CallbackManager<void(bool)>> key_callbacks_{};
+  bool headless_{false};
 };
+
 }  // namespace esphome::sdl
 
 #endif

esphome/components/sdl/touchscreen/__init__.py

@@ -4,10 +4,12 @@ import esphome.config_validation as cv
 from esphome.const import CONF_ID
 from esphome.types import ConfigType
 
-from ..display import CONF_SDL_ID, Sdl, sdl_ns
+from ..display import CONF_SDL_ID, Sdl, headless_final_validate, sdl_ns
 
 SdlTouchscreen = sdl_ns.class_("SdlTouchscreen", touchscreen.Touchscreen)
 
+FINAL_VALIDATE_SCHEMA = headless_final_validate("touchscreen")
+
 
 CONFIG_SCHEMA = touchscreen.TOUCHSCREEN_SCHEMA.extend(
     {

esphome/components/seeed_mr60fda2/__init__.py

@@ -31,6 +31,7 @@ FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
     require_tx=True,
     require_rx=True,
     baud_rate=115200,
+    data_bits=8,
     parity="NONE",
     stop_bits=1,
 )

esphome/components/seeed_mr60fda2/seeed_mr60fda2.cpp

@@ -33,8 +33,6 @@ void MR60FDA2Component::dump_config() {
 
 // Initialisation functions
 void MR60FDA2Component::setup() {
-  this->check_uart_settings(115200);
-
   this->current_frame_locate_ = LOCATE_FRAME_HEADER;
   this->current_frame_id_ = 0;
   this->current_frame_len_ = 0;

esphome/components/serial_proxy/serial_proxy.cpp

@@ -130,17 +130,26 @@ SerialProxyResult SerialProxy::configure(api::APIConnection *api_connection, uin
     return SerialProxyResult::SERIAL_PROXY_RESULT_NOT_SUPPORTED;
   }
 
-  // Apply validated parameters
-  uart_comp->set_baud_rate(baudrate);
-  uart_comp->set_stop_bits(stop_bits);
-  uart_comp->set_data_bits(data_size);
-
-  // Map parity value to UARTParityOptions
+  // Skip a no-op reconfigure. Clients routinely re-send identical settings on every
+  // port open, and on a USB UART each apply is a CDC SET_LINE_CODING control transfer.
+  // Some bridges watch line-coding changes as a signalling channel (a magic baud
+  // sequence to enter a bootloader, say), so redundant applies are not harmless.
   static const uart::UARTParityOptions PARITY_MAP[] = {
       uart::UART_CONFIG_PARITY_NONE,
       uart::UART_CONFIG_PARITY_EVEN,
       uart::UART_CONFIG_PARITY_ODD,
   };
+  if (uart_comp->get_baud_rate() == baudrate && uart_comp->get_stop_bits() == stop_bits &&
+      uart_comp->get_data_bits() == data_size && uart_comp->get_parity() == PARITY_MAP[parity]) {
+    ESP_LOGV(TAG, "Settings unchanged, skipping reconfigure [%" PRIu32 "]", this->instance_index_);
+    return SerialProxyResult::SERIAL_PROXY_RESULT_OK;
+  }
+
+  // Apply validated parameters
+  uart_comp->set_baud_rate(baudrate);
+  uart_comp->set_stop_bits(stop_bits);
+  uart_comp->set_data_bits(data_size);
+
   uart_comp->set_parity(PARITY_MAP[parity]);
 
   // load_settings() is available on ESP8266 and ESP32 platforms

esphome/components/smt100/sensor.py

@@ -68,7 +68,13 @@ CONFIG_SCHEMA = (
 )
 
 FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
-    "smt100", baud_rate=9600, require_rx=True, require_tx=True
+    "smt100",
+    baud_rate=9600,
+    require_rx=True,
+    require_tx=True,
+    data_bits=8,
+    parity="NONE",
+    stop_bits=1,
 )
 
 

esphome/components/smt100/smt100.cpp

@@ -65,7 +65,6 @@ void SMT100Component::dump_config() {
   LOG_SENSOR(TAG, "Temperature", this->temperature_sensor_);
   LOG_SENSOR(TAG, "Moisture", this->moisture_sensor_);
   LOG_UPDATE_INTERVAL(this);
-  this->check_uart_settings(9600);
 }
 
 int SMT100Component::readline_(int readch, char *buffer, int len) {

esphome/components/snapshot/__init__.py

@@ -0,0 +1,76 @@
+"""Shared support for writing what a display is showing out to an image file.
+
+The component itself has no configuration. It provides the ``snapshot.take`` action and the C++
+base class behind it, so any display that can hand over its pixels - the in memory display in this
+component, or an SDL window - saves files the same way, under the same directory, with the same
+rules about names.
+"""
+
+from dataclasses import dataclass
+
+from esphome import automation
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ID
+from esphome.core import CORE, ID
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType, TemplateArgsType
+
+CODEOWNERS = ["@clydebarrow"]
+
+DOMAIN = "snapshot"
+
+CONF_FILENAME = "filename"
+
+snapshot_ns = cg.esphome_ns.namespace("snapshot")
+Snapshot = snapshot_ns.class_("Snapshot")
+SnapshotAction = snapshot_ns.class_("SnapshotAction", automation.Action)
+
+
+@automation.register_action(
+    "snapshot.take",
+    SnapshotAction,
+    automation.maybe_simple_id(
+        {
+            cv.GenerateID(): cv.use_id(Snapshot),
+            cv.Optional(CONF_FILENAME): cv.templatable(cv.string),
+        }
+    ),
+    synchronous=True,
+)
+async def snapshot_take_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
+    var = cg.new_Pvariable(action_id, template_arg)
+    await cg.register_parented(var, config[CONF_ID])
+    if (filename := config.get(CONF_FILENAME)) is not None:
+        cg.add(var.set_filename(await cg.templatable(filename, args, cg.std_string)))
+    return var
+
+
+@dataclass
+class SnapshotData:
+    directory_defined: bool = False
+
+
+def _get_data() -> SnapshotData:
+    if DOMAIN not in CORE.data:
+        CORE.data[DOMAIN] = SnapshotData()
+    return CORE.data[DOMAIN]
+
+
+async def register_snapshot(var: MockObj, config: ConfigType) -> None:
+    """Set up a component so that the snapshot action can write its picture to a file."""
+    data = _get_data()
+    # Only once, however many displays there are: two defines that say the same thing do not
+    # compare equal, so asking for this per display repeats the line in defines.h.
+    if not data.directory_defined:
+        data.directory_defined = True
+        cg.add_define(
+            "ESPHOME_SNAPSHOT_DIR",
+            (CORE.data_dir / "snapshots" / CORE.name).as_posix(),
+        )
+    cg.add(var.set_snapshot_prefix(str(config[CONF_ID])))

esphome/components/snapshot/display/__init__.py

@@ -0,0 +1,61 @@
+import esphome.codegen as cg
+from esphome.components import display
+import esphome.config_validation as cv
+from esphome.const import (
+    CONF_DIMENSIONS,
+    CONF_HEIGHT,
+    CONF_ID,
+    CONF_LAMBDA,
+    CONF_WIDTH,
+    PLATFORM_HOST,
+)
+from esphome.types import ConfigType
+
+from .. import Snapshot, register_snapshot, snapshot_ns
+
+# The base class and the file writing live in the parent component, which nothing else in a
+# configuration using only this platform would pull in.
+AUTO_LOAD = ["snapshot"]
+
+SnapshotDisplay = snapshot_ns.class_(
+    "SnapshotDisplay", display.DisplayBuffer, cg.Component, Snapshot
+)
+
+CONFIG_SCHEMA = cv.All(
+    display.FULL_DISPLAY_SCHEMA.extend(
+        cv.Schema(
+            {
+                cv.GenerateID(): cv.declare_id(SnapshotDisplay),
+                cv.Required(CONF_DIMENSIONS): cv.Any(
+                    cv.dimensions,
+                    cv.Schema(
+                        {
+                            cv.Required(CONF_WIDTH): cv.positive_not_null_int,
+                            cv.Required(CONF_HEIGHT): cv.positive_not_null_int,
+                        }
+                    ),
+                ),
+            }
+        )
+    ),
+    cv.only_on(PLATFORM_HOST),
+)
+
+
+async def to_code(config: ConfigType) -> None:
+    var = cg.new_Pvariable(config[CONF_ID])
+    await display.register_display(var, config)
+    await register_snapshot(var, config)
+
+    dimensions = config[CONF_DIMENSIONS]
+    if isinstance(dimensions, dict):
+        cg.add(var.set_dimensions(dimensions[CONF_WIDTH], dimensions[CONF_HEIGHT]))
+    else:
+        (width, height) = dimensions
+        cg.add(var.set_dimensions(width, height))
+
+    if lamb := config.get(CONF_LAMBDA):
+        lambda_ = await cg.process_lambda(
+            lamb, [(display.DisplayRef, "it")], return_type=cg.void
+        )
+        cg.add(var.set_writer(lambda_))

esphome/components/snapshot/display/snapshot_display.cpp

@@ -0,0 +1,80 @@
+#ifdef USE_HOST
+#include "snapshot_display.h"
+#include "esphome/components/display/display_color_utils.h"
+#include "esphome/core/log.h"
+
+#include <cstring>
+
+namespace esphome::snapshot {
+
+static const char *const TAG = "snapshot.display";
+
+namespace {
+
+/// Spread a channel that only goes up to `max` over the whole 0 to 255 range, so that the
+/// brightest value stays the brightest. This is the same arithmetic SDL uses, which is what makes
+/// a picture taken here come out identical to the same picture taken from an SDL window.
+constexpr uint8_t expand_channel(uint16_t value, uint16_t max) { return static_cast<uint8_t>(value * 255 / max); }
+
+constexpr uint16_t RED_MAX = 0x1F;
+constexpr uint16_t GREEN_MAX = 0x3F;
+constexpr uint16_t BLUE_MAX = 0x1F;
+
+}  // namespace
+
+void SnapshotDisplay::setup() {
+  this->init_internal_(static_cast<uint32_t>(this->width_) * this->height_ * 2);
+  if (this->buffer_ == nullptr) {
+    this->mark_failed(LOG_STR("Could not allocate display buffer"));
+  }
+}
+
+void SnapshotDisplay::dump_config() { LOG_DISPLAY("", "Snapshot", this); }
+
+void SnapshotDisplay::draw_absolute_pixel_internal(int x, int y, Color color) {
+  if (this->buffer_ == nullptr || x < 0 || x >= this->width_ || y < 0 || y >= this->height_)
+    return;
+  this->pixels_()[y * this->width_ + x] = display::ColorUtil::color_to_565(color, display::COLOR_ORDER_RGB);
+}
+
+void SnapshotDisplay::draw_pixels_at(int x_start, int y_start, int w, int h, const uint8_t *ptr,
+                                     display::ColorOrder order, display::ColorBitness bitness, bool big_endian,
+                                     int x_offset, int y_offset, int x_pad) {
+  if (this->buffer_ == nullptr)
+    return;
+  // Anything that is not already laid out the way the buffer is, or that would reach outside it,
+  // goes through the base class, which turns it into one call per pixel with the bounds checked.
+  const bool copyable = this->rotation_ == display::DISPLAY_ROTATION_0_DEGREES &&
+                        bitness == display::COLOR_BITNESS_565 && !big_endian && x_start >= 0 && y_start >= 0 &&
+                        x_start + w <= this->width_ && y_start + h <= this->height_;
+  if (!copyable) {
+    DisplayBuffer::draw_pixels_at(x_start, y_start, w, h, ptr, order, bitness, big_endian, x_offset, y_offset, x_pad);
+    return;
+  }
+  const size_t stride = static_cast<size_t>(x_offset) + w + x_pad;
+  const uint8_t *src = ptr + (stride * y_offset + x_offset) * 2;
+  for (int y = 0; y != h; y++) {
+    memcpy(&this->pixels_()[(y_start + y) * this->width_ + x_start], src + y * stride * 2, w * 2);
+  }
+}
+
+bool SnapshotDisplay::capture_bgr(uint8_t *dest, size_t row_stride) {
+  if (this->buffer_ == nullptr) {
+    ESP_LOGE(TAG, "Snapshot requested but there is no buffer to read");
+    return false;
+  }
+  const uint16_t *src = this->pixels_();
+  for (int y = 0; y != this->height_; y++) {
+    uint8_t *out = dest + y * row_stride;
+    for (int x = 0; x != this->width_; x++) {
+      const uint16_t pixel = *src++;
+      *out++ = expand_channel(pixel & BLUE_MAX, BLUE_MAX);
+      *out++ = expand_channel((pixel >> 5) & GREEN_MAX, GREEN_MAX);
+      *out++ = expand_channel(pixel >> 11, RED_MAX);
+    }
+  }
+  return true;
+}
+
+}  // namespace esphome::snapshot
+#endif

esphome/components/snapshot/display/snapshot_display.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#ifdef USE_HOST
+#include "esphome/components/display/display_buffer.h"
+#include "esphome/components/snapshot/snapshot.h"
+#include "esphome/core/component.h"
+
+namespace esphome::snapshot {
+
+/// A display with nowhere to show anything: it keeps the picture in memory, where the snapshot
+/// action can pick it up. That makes it a way to see what a configuration draws on a machine with
+/// no screen, and to check the result in a test.
+class SnapshotDisplay final : public display::DisplayBuffer, public Snapshot {
+ public:
+  void setup() override;
+  void update() override { this->do_update_(); }
+  void dump_config() override;
+  float get_setup_priority() const override { return setup_priority::HARDWARE; }
+  display::DisplayType get_display_type() override { return display::DISPLAY_TYPE_COLOR; }
+
+  void set_dimensions(uint16_t width, uint16_t height) {
+    this->width_ = width;
+    this->height_ = height;
+  }
+
+  void draw_pixels_at(int x_start, int y_start, int w, int h, const uint8_t *ptr, display::ColorOrder order,
+                      display::ColorBitness bitness, bool big_endian, int x_offset, int y_offset, int x_pad) override;
+
+ protected:
+  void draw_absolute_pixel_internal(int x, int y, Color color) override;
+  int get_width_internal() override { return this->width_; }
+  int get_height_internal() override { return this->height_; }
+
+  int snapshot_width() override { return this->width_; }
+  int snapshot_height() override { return this->height_; }
+  bool capture_bgr(uint8_t *dest, size_t row_stride) override;
+
+  /// The picture, one 16 bit RGB565 value per pixel, topmost row first. Owned by DisplayBuffer as
+  /// a byte pointer; this is the same memory seen as what is actually stored in it.
+  uint16_t *pixels_() { return reinterpret_cast<uint16_t *>(this->buffer_); }
+
+  int width_{};
+  int height_{};
+};
+
+}  // namespace esphome::snapshot
+
+#endif

esphome/components/snapshot/snapshot.cpp

@@ -0,0 +1,248 @@
+#ifdef USE_HOST
+#include "snapshot.h"
+#include "esphome/core/log.h"
+
+#include <fcntl.h>
+#include <strings.h>
+#include <unistd.h>
+#include <cctype>
+#include <cerrno>
+#include <cstdio>
+#include <cstring>
+#include <ctime>
+#include <filesystem>
+#include <memory>
+
+namespace esphome::snapshot {
+
+namespace {
+
+constexpr const char *const TAG = "snapshot";
+
+// Longest name we will build a path from. NAME_MAX is 255 and we may append a collision suffix.
+constexpr size_t MAX_NAME_LENGTH = 200;
+// Give up rather than spin forever if every candidate name is taken.
+constexpr unsigned MAX_NAME_ATTEMPTS = 1000;
+// A BMP file header followed by a BITMAPINFOHEADER, which is where the pixels start.
+constexpr size_t BMP_HEADER_SIZE = 54;
+constexpr size_t BMP_INFO_HEADER_SIZE = 40;
+constexpr int BMP_BITS_PER_PIXEL = 24;
+
+/// True if the name already ends in ".bmp". The comparison ignores case, so "shot.BMP" is left
+/// alone rather than turned into "shot.BMP.bmp".
+bool has_bmp_suffix(const std::string &name) {
+  return name.size() >= 4 && strcasecmp(name.c_str() + name.size() - 4, ".bmp") == 0;
+}
+
+/// Reduce a user supplied name to a single safe path component. Everything outside the allowed set
+/// is replaced, so "..", "/" and absolute paths cannot escape the snapshot directory.
+/// Returns an empty string if nothing usable is left.
+std::string sanitise_filename(const char *const name, bool *name_changed) {
+  std::string result;
+  bool all_dots = true;
+  bool changed = false;
+  for (const char *p = name; *p != '\0'; p++) {
+    if (result.size() >= MAX_NAME_LENGTH) {
+      changed = true;
+      break;
+    }
+    char c = *p;
+    if (!(std::isalnum(static_cast<unsigned char>(c)) || c == '.' || c == '_' || c == '-')) {
+      c = '_';
+      changed = true;
+    }
+    if (c != '.')
+      all_dots = false;
+    result.push_back(c);
+  }
+  if (all_dots) {
+    *name_changed = true;
+    return "";
+  }
+  if (!has_bmp_suffix(result))
+    result += ".bmp";
+  *name_changed = changed;
+  return result;
+}
+
+/// Insert "-<attempt>" before the file extension, e.g. "shot.bmp" -> "shot-1.bmp".
+std::string add_suffix(const std::string &name, unsigned attempt) {
+  char suffix[12];
+  snprintf(suffix, sizeof(suffix), "-%u", attempt);
+  auto dot = name.rfind('.');
+  if (dot == std::string::npos)
+    return name + suffix;
+  return name.substr(0, dot) + suffix + name.substr(dot);
+}
+
+/// Directory snapshots are written to. The environment variable lets a test redirect output
+/// without rebuilding, matching how the host platform handles ESPHOME_PREFDIR.
+const char *snapshot_dir() {
+  const char *dir = getenv("ESPHOME_SNAPSHOT_DIR");  // NOLINT(concurrency-mt-unsafe)
+  return dir != nullptr && dir[0] != '\0' ? dir : ESPHOME_SNAPSHOT_DIR;
+}
+
+/// Store a value in as many bytes, least significant first, and step the pointer past it.
+/// BMP is a little endian format whatever the machine writing it uses.
+void put_le(uint8_t *&dest, uint32_t value, size_t bytes) {
+  for (size_t i = 0; i != bytes; i++)
+    *dest++ = static_cast<uint8_t>(value >> (8 * i));
+}
+
+/// The number of bytes one row of `width` pixels takes up in the file. Rows are padded out to a
+/// multiple of four bytes.
+size_t bmp_row_size(int width) { return (static_cast<size_t>(width) * 3 + 3) & ~size_t{3}; }
+
+/// Write pixels out as a 24 bit BMP. The rows given start with the topmost and are `row_stride`
+/// bytes apart, which must leave room for a whole padded row; a BMP holds its rows the other way
+/// up, so they go out last first.
+bool write_bmp(FILE *file, const uint8_t *pixels, int width, int height, size_t row_stride) {
+  const size_t row_size = bmp_row_size(width);
+  const size_t pixel_bytes = row_size * height;
+
+  uint8_t header[BMP_HEADER_SIZE];
+  uint8_t *pos = header;
+  *pos++ = 'B';
+  *pos++ = 'M';
+  put_le(pos, static_cast<uint32_t>(BMP_HEADER_SIZE + pixel_bytes), 4);
+  put_le(pos, 0, 4);  // reserved
+  put_le(pos, BMP_HEADER_SIZE, 4);
+  put_le(pos, BMP_INFO_HEADER_SIZE, 4);
+  put_le(pos, static_cast<uint32_t>(width), 4);
+  put_le(pos, static_cast<uint32_t>(height), 4);
+  put_le(pos, 1, 2);  // one plane
+  put_le(pos, BMP_BITS_PER_PIXEL, 2);
+  put_le(pos, 0, 4);  // not compressed
+  put_le(pos, static_cast<uint32_t>(pixel_bytes), 4);
+  put_le(pos, 0, 4);  // pixels per metre across, unspecified
+  put_le(pos, 0, 4);  // pixels per metre down, unspecified
+  put_le(pos, 0, 4);  // no palette
+  put_le(pos, 0, 4);  // so no palette entry matters more than another
+
+  if (fwrite(header, 1, sizeof(header), file) != sizeof(header))
+    return false;
+  for (int y = height - 1; y >= 0; y--) {
+    if (fwrite(pixels + static_cast<size_t>(y) * row_stride, 1, row_size, file) != row_size)
+      return false;
+  }
+  return true;
+}
+
+/// Reserve a name in the snapshot directory and write the picture to it.
+/// With `exact` set the given name is the only one tried; otherwise a number is added on
+/// collision. Returns true if a file was written.
+bool write_snapshot_file(const uint8_t *pixels, int width, int height, size_t row_stride, const std::string &name,
+                         bool exact) {
+  const std::string dir = snapshot_dir();
+  std::error_code ec;
+  std::filesystem::create_directories(dir, ec);
+  if (ec) {
+    ESP_LOGE(TAG, "Could not create snapshot directory %s: %s", dir.c_str(), ec.message().c_str());
+    return false;
+  }
+
+  // O_EXCL guarantees we never write over a file that is already there.
+  std::string path;
+  int fd = -1;
+  for (unsigned attempt = 0; attempt < MAX_NAME_ATTEMPTS; attempt++) {
+    path = dir + "/" + (attempt == 0 ? name : add_suffix(name, attempt));
+    fd = ::open(path.c_str(), O_WRONLY | O_CREAT | O_EXCL | O_NOFOLLOW, 0644);
+    if (fd >= 0)
+      break;
+    if (errno != EEXIST) {
+      ESP_LOGE(TAG, "Could not create %s: %s", path.c_str(), strerror(errno));
+      return false;
+    }
+    if (exact) {
+      // The caller asked for this exact name, so silently writing somewhere else would be worse
+      // than failing - a test asserting on the path would pick up a stale file.
+      ESP_LOGE(TAG, "Snapshot %s already exists, not overwriting", path.c_str());
+      return false;
+    }
+  }
+  if (fd < 0) {
+    ESP_LOGE(TAG, "Could not find an unused name for %s in %s", name.c_str(), dir.c_str());
+    return false;
+  }
+
+  FILE *file = fdopen(fd, "wb");
+  if (file == nullptr) {
+    ESP_LOGE(TAG, "Could not open %s: %s", path.c_str(), strerror(errno));
+    ::close(fd);
+    ::unlink(path.c_str());
+    return false;
+  }
+  bool ok = write_bmp(file, pixels, width, height, row_stride);
+  int saved_errno = ok ? 0 : errno;
+  // Closing can fail in its own right - the last of the data is still on its way out.
+  if (fclose(file) != 0) {
+    if (ok)
+      saved_errno = errno;
+    ok = false;
+  }
+  if (!ok) {
+    ESP_LOGE(TAG, "Could not write %s: %s", path.c_str(), strerror(saved_errno));
+    // Leave no truncated file behind - it would block a retry under the same name.
+    ::unlink(path.c_str());
+    return false;
+  }
+  ESP_LOGI(TAG, "Snapshot written to %s", path.c_str());
+  return true;
+}
+
+}  // namespace
+
+// helper function since ESP_LOGW is disallowed in a header file
+void Snapshot::log_action_failed() { ESP_LOGW(TAG, "snapshot.take did not write a file"); }
+
+bool Snapshot::take_snapshot(const char *filename) {
+  const int width = this->snapshot_width();
+  const int height = this->snapshot_height();
+  if (width <= 0 || height <= 0) {
+    ESP_LOGE(TAG, "Snapshot requested but the display is %dx%d", width, height);
+    return false;
+  }
+
+  std::string name;
+  bool exact = false;
+  if (filename != nullptr) {
+    bool name_changed = false;
+    name = sanitise_filename(filename, &name_changed);
+    exact = !name.empty();
+    if (name_changed) {
+      ESP_LOGW(TAG, "Requested snapshot name '%s' is not an acceptable file name, using '%s' instead", filename,
+               name.empty() ? "a name made from the time" : name.c_str());
+    }
+  }
+  if (name.empty()) {
+    struct timespec now {};
+    if (clock_gettime(CLOCK_REALTIME, &now) != 0)
+      now = {};
+    struct tm tm_buf {};
+    if (localtime_r(&now.tv_sec, &tm_buf) == nullptr)
+      tm_buf = {};
+    char stamp[32]{};
+    // ::strftime to be sure of the one from <ctime>; display has an unrelated member of that name
+    if (::strftime(stamp, sizeof(stamp), "%Y%m%d-%H%M%S", &tm_buf) == 0)
+      snprintf(stamp, sizeof(stamp), "unknown-time");
+    char buffer[MAX_NAME_LENGTH];
+    int written =
+        snprintf(buffer, sizeof(buffer), "%s-%s-%03ld.bmp", this->snapshot_prefix_, stamp, now.tv_nsec / 1000000);
+    if (written < 0 || static_cast<size_t>(written) >= sizeof(buffer)) {
+      ESP_LOGW(TAG, "Could not build a timestamped snapshot name, using a fallback");
+      snprintf(buffer, sizeof(buffer), "snapshot.bmp");
+    }
+    name = buffer;
+  }
+
+  // Rows are padded out to a multiple of four bytes, as the file wants them, so each one can be
+  // written straight from the buffer. Zeroed on allocation, which is what the padding must be.
+  const size_t row_stride = bmp_row_size(width);
+  auto pixels = std::make_unique<uint8_t[]>(row_stride * height);
+  if (!this->capture_bgr(pixels.get(), row_stride))
+    return false;
+  return write_snapshot_file(pixels.get(), width, height, row_stride, name, exact);
+}
+
+}  // namespace esphome::snapshot
+#endif