Apply the dial delay the same way at boot and after a disconnect, tell socket create and setblocking failures apart, and cap the delay so the wait always elapses

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>

.claude/settings.json

@@ -0,0 +1,16 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "d=\"${CLAUDE_PROJECT_DIR:-.}\"; [ -x \"$d/venv/bin/python\" ] || { mkdir -p \"$d/.temp\"; env -u VIRTUAL_ENV \"$d/script/setup\" >\"$d/.temp/setup.log\" 2>&1 || echo '{\"systemMessage\":\"script/setup failed; see .temp/setup.log\"}'; }",
+            "statusMessage": "Setting up dev environment (script/setup)...",
+            "timeout": 900
+          }
+        ]
+      }
+    ]
+  }
+}

.github/actions/cache-clang-tidy-idedata/action.yml

@@ -0,0 +1,50 @@
+name: Cache clang-tidy idedata
+description: >
+  Cache the clang-tidy idedata and the headers it references under .temp
+  (headers only, about 30MB per env). Run after restore-python and cache-esp-idf.
+inputs:
+  environment:
+    description: 'clang-tidy environment (e.g. esp32-idf-tidy).'
+    required: true
+runs:
+  using: composite
+  steps:
+    - name: Compute cache key
+      id: key
+      shell: bash
+      run: |
+        . venv/bin/activate
+        [ -n "${{ inputs.environment }}" ] || { echo "::error::cache-clang-tidy-idedata: 'environment' input is empty"; exit 1; }
+        hash=$(python -c 'import sys; sys.path.insert(0, "script"); from clang_tidy_hash import idedata_cache_hash; print(idedata_cache_hash("${{ inputs.environment }}"))')
+        pyver=$(python -c 'import platform; print(platform.python_version())')
+        # Generating idedata is what installs ESP-IDF; never skip it over a missing
+        # install. This also skips the save, so a dev run that installs ESP-IDF
+        # warms the idedata cache on the next run.
+        if [ -d ~/.esphome-idf/frameworks ]; then
+          echo "skip=false" >> "$GITHUB_OUTPUT"
+        else
+          echo "ESP-IDF install missing, not using the clang-tidy idedata cache"
+          echo "skip=true" >> "$GITHUB_OUTPUT"
+        fi
+        echo "key=${{ runner.os }}-tidy-idedata-${{ inputs.environment }}-$hash-py$pyver" >> "$GITHUB_OUTPUT"
+        {
+          echo "path<<EOF"
+          printf '%s\n' '.temp/idedata-*.json' '.temp/idedata-*.hash'
+          printf '.temp/**/*.%s\n' h hpp hh hxx inc inl ipp tpp
+          echo "EOF"
+        } >> "$GITHUB_OUTPUT"
+    # Mirror cache-esp-idf: write on dev, restore-only on PRs. The post-step
+    # save only runs when the job succeeded, so a failed generation is never saved.
+    # Extend the extension list if a component ships extensionless headers.
+    - name: Cache clang-tidy idedata (write on dev)
+      if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write')) && steps.key.outputs.skip != 'true'
+      uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ${{ steps.key.outputs.path }}
+        key: ${{ steps.key.outputs.key }}
+    - name: Cache clang-tidy idedata (restore-only off dev)
+      if: github.ref != 'refs/heads/dev' && !contains(github.event.pull_request.labels.*.name, 'ci-cache-write') && steps.key.outputs.skip != 'true'
+      uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      with:
+        path: ${{ steps.key.outputs.path }}
+        key: ${{ steps.key.outputs.key }}

.github/actions/cache-esp-idf/action.yml

@@ -26,6 +26,9 @@ runs:
       # The native-IDF version is pinned in code, not in any file that feeds the
       # other cache keys, so resolve it explicitly. Keying on it means the cache
       # invalidates on a version bump (actions/cache never overwrites a key).
+      # Also key on the Python version: the cached IDF venv links to the
+      # runner's toolcache interpreter and is reinstalled every run after a
+      # runner image bump.
       id: version
       shell: bash
       run: |
@@ -36,19 +39,32 @@ runs:
           version=$(python -c 'from esphome.components.esp32 import ESP_IDF_FRAMEWORK_VERSION_LOOKUP as L; print(L["recommended"])')
         fi
         echo "version=$version" >> "$GITHUB_OUTPUT"
+        echo "python-version=$(python -c 'import platform; print(platform.python_version())')" >> "$GITHUB_OUTPUT"
     # Mirror the adjacent PlatformIO cache: only dev-branch runs write the
     # shared cache (so it lives in the default-branch scope readable by all
     # PRs), and PRs are restore-only -- they never push multi-GB artifacts into
-    # their own scope / the repo quota (e.g. on a version-bump PR).
+    # their own scope / the repo quota (e.g. on a version-bump PR). The
+    # ci-cache-write label lets a PR write into its own scope to test the hit path;
+    # that costs about 1GB of the repo cache quota per run, so remove it when done.
+    # -slim: bump when prune-esp-idf changes what it removes; a key is never overwritten.
     - name: Cache ESP-IDF install (write on dev)
-      if: github.ref == 'refs/heads/dev' && inputs.restore-only != 'true'
+      if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write')) && inputs.restore-only != 'true'
       uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
       with:
         path: ~/.esphome-idf
-        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}
+        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}-py${{ steps.version.outputs.python-version }}-slim
     - name: Cache ESP-IDF install (restore-only off dev)
-      if: github.ref != 'refs/heads/dev' || inputs.restore-only == 'true'
+      if: github.ref != 'refs/heads/dev' && !contains(github.event.pull_request.labels.*.name, 'ci-cache-write') || inputs.restore-only == 'true'
       uses: actions/cache/restore@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
       with:
         path: ~/.esphome-idf
-        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}
+        key: ${{ runner.os }}-esphome-idf-${{ steps.version.outputs.version }}-py${{ steps.version.outputs.python-version }}-slim
+    # Install explicitly so the prune below sees the toolchains on a cache miss
+    # too, instead of the install happening inside the first build step.
+    - name: Install ESP-IDF
+      shell: bash
+      run: |
+        . venv/bin/activate
+        python -c 'from esphome.espidf.framework import check_esp_idf_install; check_esp_idf_install("${{ steps.version.outputs.version }}")'
+    - name: Prune ESP-IDF install
+      uses: ./.github/actions/prune-esp-idf

.github/actions/prune-esp-idf/action.yml

@@ -0,0 +1,34 @@
+name: Prune ESP-IDF install
+description: >
+  Remove the picolibc sysroots (1.1GB of the 3.9GB install) from the native
+  ESP-IDF toolchains; IDF 5.x links newlib. Skipped when an IDF 6 install is
+  present, which links picolibc (see esp32/__init__.py).
+runs:
+  using: composite
+  steps:
+    - name: Prune picolibc
+      shell: bash
+      run: |
+        shopt -s nullglob
+        prefix="${ESPHOME_ESP_IDF_PREFIX:-$HOME/.esphome-idf}"
+        prefix="${prefix/#\~/$HOME}"
+        for fw in "$prefix"/frameworks/*/; do
+          case "$(basename "$fw")" in
+            [6-9].*) echo "IDF $(basename "$fw") installed, keeping picolibc"; exit 0 ;;
+          esac
+        done
+        n=0
+        for dir in "$prefix"/tools/*-esp-elf/*/*-esp-elf/picolibc; do
+          echo "Removing $dir ($(du -sh "$dir" | cut -f1))"
+          rm -rf "$dir"
+          n=$((n + 1))
+        done
+        # The marker rides along in the cache entry so a restored slim tree stays quiet.
+        if [ "$n" -gt 0 ]; then
+          touch "$prefix/.picolibc-pruned"
+        elif [ -d "$prefix/tools" ] && [ ! -f "$prefix/.picolibc-pruned" ]; then
+          echo "::warning::no picolibc sysroots matched under $prefix/tools"
+        fi
+        if [ -d "$prefix" ]; then
+          du -sh "$prefix"
+        fi

.github/actions/restore-python/action.yml

@@ -32,7 +32,7 @@ runs:
       # detects the activated venv via ``VIRTUAL_ENV`` so the venv layout
       # downstream jobs rely on is preserved.
       if: steps.cache-venv.outputs.cache-hit != 'true'
-      uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+      uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
       with:
         enable-cache: true
         # Pull request saves land in per-PR scopes nothing else can
@@ -49,7 +49,7 @@ runs:
         python -m venv venv
         source venv/bin/activate
         python --version
-        uv pip install -r requirements.txt -r requirements_test.txt
+        uv pip install -r requirements.txt -r requirements_dev.txt -r requirements_test.txt
         uv pip install -e .
     - name: Create Python virtual environment
       if: steps.cache-venv.outputs.cache-hit != 'true' && runner.os == 'Windows'
@@ -58,5 +58,5 @@ runs:
         python -m venv venv
         source ./venv/Scripts/activate
         python --version
-        uv pip install -r requirements.txt -r requirements_test.txt
+        uv pip install -r requirements.txt -r requirements_dev.txt -r requirements_test.txt
         uv pip install -e .

.github/scripts/auto-label-pr/detectors.js

@@ -70,6 +70,7 @@ async function isStackedPr(github, context) {
 async function detectMergeBranch(github, context) {
   const labels = new Set();
   const baseRef = context.payload.pull_request.base.ref;
+  const defaultBranch = context.payload.repository.default_branch;
 
   if (baseRef === 'release') {
     labels.add('merging-to-release');
@@ -78,7 +79,7 @@ async function detectMergeBranch(github, context) {
   } else if (await isStackedPr(github, context)) {
     // GitHub manages the merge order for a stack, so these are not blocked.
     labels.add('stacked-pr');
-  } else if (baseRef !== 'dev') {
+  } else if (baseRef !== defaultBranch) {
     // A chain built by hand: it must not merge until its base branch does.
     labels.add('chained-pr');
   }

.github/scripts/auto-label-pr/tests/detectors.test.js

@@ -43,14 +43,14 @@ const WITHOUT_SCHEMA = 'CODEOWNERS = ["@esphome/core"]';
 
 // Builds a fresh context for detectMergeBranch tests instead of mutating the
 // shared CONTEXT fixture above (which other describe blocks rely on).
-function makeMergeContext(baseRef, { stack } = {}) {
+function makeMergeContext(baseRef, { stack, defaultBranch = 'dev' } = {}) {
   const pull_request = { number: 1, base: { ref: baseRef } };
   if (stack !== undefined) {
     pull_request.stack = stack;
   }
   return {
     repo: { owner: 'esphome', repo: 'esphome' },
-    payload: { pull_request }
+    payload: { pull_request, repository: { default_branch: defaultBranch } }
   };
 }
 
@@ -136,6 +136,21 @@ describe('detectMergeBranch', () => {
     assert.deepEqual(Array.from(labels).sort(), ['chained-pr']);
     assert.equal(state.calls, 1);
   });
+
+  it('base ref matches default branch adds no labels', async () => {
+    const { github } = makeStackGithub({ stack: null });
+    const context = makeMergeContext('other', { defaultBranch: 'other' });
+    const labels = await detectMergeBranch(github, context);
+    assert.deepEqual(Array.from(labels).sort(), []);
+  });
+
+  it('base ref dev when the default branch is main adds chained-pr', async () => {
+    const { github } = makeStackGithub({ stack: null });
+    const context = makeMergeContext('dev', { defaultBranch: 'main' });
+    const labels = await detectMergeBranch(github, context);
+    assert.deepEqual(Array.from(labels).sort(), ['chained-pr']);
+  });
+
 });
 
 // ---------------------------------------------------------------------------

.github/workflows/ci-api-proto.yml

@@ -29,7 +29,7 @@ jobs:
       - name: Set up uv
         # ``--system`` (below) installs into the setup-python interpreter;
         # no venv is created or restored by this workflow.
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
         with:
           enable-cache: true
           # Pull-request-only workflow: a save could never be shared and
@@ -41,10 +41,32 @@ jobs:
           version: "0.11.15"
 
       - name: Install apt dependencies
+        # PR-only workflow, so nothing on dev could seed a shared apt cache
+        # entry; the cached apt action would save one copy per PR. Plain apt
+        # with every call bounded: the apt.conf.d timeouts make a dead
+        # mirror fail over in seconds, and timeout runs under sudo so it can
+        # kill apt-get itself. Install without update first: image lists are
+        # fresh, and the index refresh is what a congested mirror makes slow.
+        timeout-minutes: 15
         run: |
-          sudo apt update
-          sudo apt-cache show protobuf-compiler
-          sudo apt install -y protobuf-compiler
+          sudo tee /etc/apt/apt.conf.d/99ci-acquire-timeouts >/dev/null <<'EOF'
+          Acquire::Retries "1";
+          Acquire::http::Timeout "15";
+          Acquire::https::Timeout "15";
+          EOF
+          # Common path: the image's package lists are fresh enough.
+          if sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 90 \
+              apt-get install -y protobuf-compiler; then
+            protoc --version
+            exit 0
+          fi
+          # Rescue path: refresh the lists once with a generous bound; the
+          # apt config already fails a stalled mirror over quickly.
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 10 30 \
+            dpkg --configure -a || true
+          sudo timeout -k 15 300 apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 300 \
+            apt-get install -y protobuf-compiler
           protoc --version
       - name: Install python dependencies
         run: uv pip install --system aioesphomeapi -c requirements.txt -r requirements_dev.txt

.github/workflows/ci-docker.yml

@@ -67,7 +67,7 @@ jobs:
         with:
           python-version: "3.12"
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@37fe631027851001ddb9b187196cc803df7f5f0e # v4.3.0
 
       - name: Determine tag and whether to push
         id: tag
@@ -119,16 +119,22 @@ jobs:
       # pushed image) keeps it working for fork PRs, which never push to ghcr.io.
       - name: Export image for compile-test
         if: matrix.os == 'ubuntu-24.04' && matrix.build_type == 'docker'
-        run: docker save "ghcr.io/esphome/esphome-amd64:${{ steps.tag.outputs.tag }}" | gzip > compile-test-image.tar.gz
+        # zstd over gzip: docker save is on the critical path for every
+        # compile-test job, and zstd -T0 is multithreaded (export 50s -> 9s).
+        # docker load auto-detects the format; its time is layer extraction,
+        # not decompression, so it is unchanged. shell: bash adds pipefail so
+        # a failed docker save cannot upload a truncated artifact.
+        shell: bash
+        run: docker save "ghcr.io/esphome/esphome-amd64:${{ steps.tag.outputs.tag }}" | zstd -T0 -3 > compile-test-image.tar.zst
 
       - name: Upload compile-test image artifact
         if: matrix.os == 'ubuntu-24.04' && matrix.build_type == 'docker'
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
-          # The tar is already gzipped, so upload it as-is. archive: false skips
-          # the redundant zip and makes the file name the artifact name (the
-          # `name` input is ignored in that mode).
-          path: compile-test-image.tar.gz
+          # The tar is already compressed, so upload it as-is. archive: false
+          # skips the redundant zip and makes the file name the artifact name
+          # (the `name` input is ignored in that mode).
+          path: compile-test-image.tar.zst
           retention-days: 1
           archive: false
 
@@ -153,7 +159,7 @@ jobs:
         with:
           python-version: "3.12"
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@37fe631027851001ddb9b187196cc803df7f5f0e # v4.3.0
 
       - name: Log in to the GitHub container registry
         uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
@@ -182,8 +188,6 @@ jobs:
       contents: read  # actions/checkout to load the test configs
     strategy:
       fail-fast: false
-      # Modest cap so this smoke test leaves room on the shared runner pool.
-      max-parallel: 8
       matrix:
         # One entry per distinct toolchain. ESP32 variants (c3/c6/s2/s3/p4)
         # share a toolchain bundle, so esp32 is exercised on the base variant
@@ -208,9 +212,9 @@ jobs:
       - name: Download image artifact
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
-          name: compile-test-image.tar.gz
+          name: compile-test-image.tar.zst
       - name: Load image
-        run: docker load --input compile-test-image.tar.gz
+        run: docker load --input compile-test-image.tar.zst
       - name: Compile ${{ matrix.id }}
         run: |
           docker run --rm \

.github/workflows/ci.yml

@@ -49,7 +49,7 @@ jobs:
         # detects the activated venv via ``VIRTUAL_ENV`` so downstream jobs
         # that ``. venv/bin/activate`` see an identical layout.
         if: steps.cache-venv.outputs.cache-hit != 'true'
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
         with:
           enable-cache: true
           # Pull request saves land in per-PR scopes nothing else can
@@ -68,6 +68,22 @@ jobs:
           uv pip install -r requirements.txt -r requirements_dev.txt -r requirements_test.txt
           uv pip install -e .
 
+  seed-apt-cache:
+    name: Seed apt package cache
+    runs-on: ubuntu-24.04
+    # PR-branch cache saves are invisible to other PRs, so dev/beta/release
+    # pushes seed the one shared entry PR jobs restore. The key is derived
+    # only from the package list and version; keep both identical in every
+    # step that restores it. In ci-status needs so a broken seed fails dev.
+    if: github.event_name == 'push'
+    timeout-minutes: 10
+    steps:
+      - name: Install apt packages (cached)
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
+        with:
+          packages: libsdl2-dev ccache
+          version: 1.1
+
   determine-jobs:
     name: Determine which jobs to run
     runs-on: ubuntu-24.04
@@ -76,6 +92,7 @@ jobs:
     outputs:
       core-ci: ${{ steps.determine.outputs.core-ci }}
       integration-tests: ${{ steps.determine.outputs.integration-tests }}
+      integration-run-all: ${{ steps.determine.outputs.integration-run-all }}
       integration-test-buckets: ${{ steps.determine.outputs.integration-test-buckets }}
       clang-tidy: ${{ steps.determine.outputs.clang-tidy }}
       clang-tidy-mode: ${{ steps.determine.outputs.clang-tidy-mode }}
@@ -96,6 +113,12 @@ jobs:
       component-test-batches: ${{ steps.determine.outputs.component-test-batches }}
       validate-only-components: ${{ steps.determine.outputs.validate-only-components }}
       benchmarks: ${{ steps.determine.outputs.benchmarks }}
+      # "true" when this run is a pull request into one of the release
+      # branches. Those pull requests are batches of changes already tested on
+      # their original dev pull requests, so several jobs below trade coverage
+      # for turnaround time on them. Matched exactly, not by prefix, so an
+      # ordinary branch named e.g. "release-notes" is not caught by it.
+      release-pr: ${{ github.base_ref == 'beta' || github.base_ref == 'release' }}
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -130,6 +153,9 @@ jobs:
           # Extract individual fields
           echo "core-ci=$(echo "$output" | jq -r '.core_ci')" >> $GITHUB_OUTPUT
           echo "integration-tests=$(echo "$output" | jq -r '.integration_tests')" >> $GITHUB_OUTPUT
+          # A missing key must fail here, not silently disable the junit upload
+          run_all=$(echo "$output" | jq -r 'if has("integration_run_all") then .integration_run_all else error("integration_run_all missing") end')
+          echo "integration-run-all=${run_all}" >> $GITHUB_OUTPUT
           echo "integration-test-buckets=$(echo "$output" | jq -c '.integration_test_buckets')" >> $GITHUB_OUTPUT
           echo "clang-tidy=$(echo "$output" | jq -r '.clang_tidy')" >> $GITHUB_OUTPUT
           echo "clang-tidy-mode=$(echo "$output" | jq -r '.clang_tidy_mode')" >> $GITHUB_OUTPUT
@@ -179,6 +205,7 @@ jobs:
           . venv/bin/activate
           script/ci-custom.py
           script/build_codeowners.py --check
+          script/build_alias_registry.py --check
           script/build_language_schema.py --check
           script/generate-esp32-boards.py --check
           script/generate-rp2-boards.py --check
@@ -213,7 +240,7 @@ jobs:
     runs-on: ubuntu-latest
     needs:
       - determine-jobs
-    if: github.event_name == 'pull_request' && !startsWith(github.base_ref, 'beta') && !startsWith(github.base_ref, 'release') && needs.determine-jobs.outputs.core-ci == 'true'
+    if: github.event_name == 'pull_request' && needs.determine-jobs.outputs.release-pr == 'false' && needs.determine-jobs.outputs.core-ci == 'true'
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -322,7 +349,8 @@ jobs:
 
   integration-tests:
     name: Run integration tests (${{ matrix.bucket.name }})
-    runs-on: ubuntu-latest
+    # Must match seed-apt-cache's image: the apt cache key has no OS in it.
+    runs-on: ubuntu-24.04
     needs:
       - common
       - determine-jobs
@@ -331,32 +359,41 @@ jobs:
       fail-fast: false
       matrix:
         bucket: ${{ fromJson(needs.determine-jobs.outputs.integration-test-buckets) }}
+    env:
+      # What the cache steps persist; libdeps is excluded (keyed per xdist
+      # worker and env, it never crosses runs).
+      INTEGRATION_PIO_CACHE_PATH: |
+        ~/.esphome-integration-tests/platformio/platforms
+        ~/.esphome-integration-tests/platformio/packages
+        ~/.esphome-integration-tests/platformio/appstate.json
+        ~/.esphome-integration-tests/platformio/.cache
+        ~/.esphome-integration-tests/platformio/.esphome.pio.stamp.json
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
-      - name: Install ccache
-        # Speeds up the host compiles: tests in a bucket compile overlapping
-        # component sets, so later tests reuse earlier tests' objects.
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -y --no-install-recommends ccache
-      - name: Restore ccache (restore-only)
-        # esphome stores the PlatformIO ccache under the machine-global cache
-        # dir (see _ccache_env() in esphome/platformio/toolchain.py). The
-        # bucket-name prefix prefers a same-bucket seed; the bare prefix falls
-        # back to any seed when the bucket layout differs from dev.
-        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+      - name: Install apt packages (cached)
+        # ccache speeds up the host compiles. A cache hit never touches apt
+        # (mirror outages cannot hang the job); the timeout bounds the cold
+        # path. Packages and version must match seed-apt-cache exactly;
+        # libsdl2-dev is unused here and carried only for cache-key parity.
+        timeout-minutes: 10
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
         with:
-          path: ~/.cache/esphome/platformio-ccache
-          key: integration-ccache-${{ matrix.bucket.name }}-${{ github.sha }}
-          restore-keys: |
-            integration-ccache-${{ matrix.bucket.name }}-
-            integration-ccache-
+          packages: libsdl2-dev ccache
+          version: 1.1
       - name: Set up Python 3.13
         id: python
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
         with:
           python-version: "3.13"
+      - name: Restore integration PlatformIO cache
+        # Native platform + toolchain installed by shared_platformio_cache in
+        # tests/integration/conftest.py; a miss self-heals, so no restore-keys.
+        id: pio-cache
+        uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
+        with:
+          path: ${{ env.INTEGRATION_PIO_CACHE_PATH }}
+          key: integration-pio-v1-${{ runner.os }}-py${{ steps.python.outputs.python-version }}-${{ hashFiles('requirements.txt', 'tests/integration/fixtures/cache_init.yaml', 'esphome/components/host/__init__.py') }}
       - name: Restore Python virtual environment
         id: cache-venv
         uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
@@ -366,7 +403,7 @@ jobs:
       - name: Set up uv
         # Only needed on cache miss to populate the venv.
         if: steps.cache-venv.outputs.cache-hit != 'true'
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
         with:
           enable-cache: true
           # Pull request saves land in per-PR scopes nothing else can
@@ -394,20 +431,36 @@ jobs:
         run: |
           . venv/bin/activate
           mapfile -t test_files < <(echo "$BUCKET_TESTS" | jq -r '.[]')
+          if [ "${#test_files[@]}" -eq 0 ]; then
+            echo "::error::Empty integration test bucket; pytest would collect the whole tree"
+            exit 1
+          fi
           echo "Bucket ${{ matrix.bucket.name }}: running ${#test_files[@]} integration tests"
-          pytest -vv --no-cov --tb=native --durations=30 -n auto "${test_files[@]}"
+          pytest -vv --no-cov --tb=native --durations=30 -n auto --dist worksteal \
+            --junitxml=junit-integration.xml "${test_files[@]}"
+      - name: Upload junit timings
+        # Consumed by sync-integration-durations.yml through
+        # script/update_integration_test_durations.py; only full matrix dev
+        # runs produce usable data.
+        if: github.ref == 'refs/heads/dev' && needs.determine-jobs.outputs.integration-run-all == 'true'
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
+        with:
+          name: junit-integration-${{ strategy.job-index }}
+          path: junit-integration.xml
+          if-no-files-found: error
+          # A full cron period of margin for the weekly refresh
+          retention-days: 14
       - name: Print ccache statistics
         # esphome stores the PlatformIO ccache under the machine-global cache
         # dir (see _ccache_env() in esphome/platformio/toolchain.py).
         run: CCACHE_DIR="$HOME/.cache/esphome/platformio-ccache" ccache -s
-      - name: Save ccache
-        # Pull request saves land in per-PR scopes nothing else can reuse;
-        # dev pushes seed the shared copy instead.
-        if: github.event_name != 'pull_request'
+      - name: Save integration PlatformIO cache
+        # Bucket 0 only; the others would race the same immutable key.
+        if: success() && (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write')) && strategy.job-index == 0 && steps.pio-cache.outputs.cache-hit != 'true'
         uses: actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
-          path: ~/.cache/esphome/platformio-ccache
-          key: integration-ccache-${{ matrix.bucket.name }}-${{ github.sha }}
+          path: ${{ env.INTEGRATION_PIO_CACHE_PATH }}
+          key: ${{ steps.pio-cache.outputs.cache-primary-key }}
 
   import-time:
     name: Check import esphome.__main__ time
@@ -440,12 +493,28 @@ jobs:
   benchmarks:
     name: Run CodSpeed benchmarks
     runs-on: ubuntu-24.04
+    timeout-minutes: 30
     needs:
       - common
       - determine-jobs
     if: >-
-      (github.event_name == 'push' && github.ref_name == 'dev') ||
-      (github.event_name == 'pull_request' && needs.determine-jobs.outputs.benchmarks == 'true')
+      github.repository == 'esphome/esphome' && (
+        (github.event_name == 'push' && github.ref_name == 'dev') ||
+        (
+          github.event_name == 'pull_request' &&
+          needs.determine-jobs.outputs.release-pr == 'false' &&
+          needs.determine-jobs.outputs.benchmarks == 'true'
+        )
+      )
+    # CodSpeed benchmarks require a CodSpeed account linked to the repository to run
+    # (https://codspeed.io) -- disabled on forks that aren't esphome/esphome itself.
+    #
+    # Pull requests into beta and release are skipped as well. CodSpeed compares a
+    # pull request against the newest commit of its base branch that has a benchmark
+    # run of its own, and only dev is benchmarked. A release pull request therefore
+    # falls back to dev's latest run, so every speed-up merged into dev since the
+    # release branched is reported as a regression in the release. The changes there
+    # have already been benchmarked on their original dev pull requests.
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -459,14 +528,60 @@ jobs:
       - name: Build benchmarks
         id: build
         run: |
+          # pipefail: without it a failed build is masked by the grep/cut
+          # pipeline below, leaving BINARY empty and silently dropping every
+          # C++ benchmark from the run while the job still reports success.
+          set -o pipefail
           . venv/bin/activate
-          export BENCHMARK_LIB_CONFIG=$(python script/setup_codspeed_lib.py)
-          # --build-only prints BUILD_BINARY=<path> to stdout
-          BINARY=$(script/cpp_benchmark.py --all --build-only | grep '^BUILD_BINARY=' | tail -1 | cut -d= -f2-)
+          BENCHMARK_LIB_CONFIG=$(python script/setup_codspeed_lib.py)
+          export BENCHMARK_LIB_CONFIG
+          # --build-only prints BUILD_BINARY=<path> to stdout; the grep is
+          # non-fatal so a missing marker reaches the check below instead of
+          # tripping errexit at this assignment
+          BINARY=$(script/cpp_benchmark.py --all --build-only | { grep '^BUILD_BINARY=' || true; } | tail -1 | cut -d= -f2-)
+          if [ -z "$BINARY" ]; then
+            echo "::error::Benchmark build did not report a binary path"
+            exit 1
+          fi
           echo "binary=$BINARY" >> $GITHUB_OUTPUT
 
+      - name: Bound apt fetches and pre-install libc6-dbg
+        # The CodSpeed runner installs valgrind + libc6-dbg via its own
+        # unbounded apt-get update; per-invocation apt options cannot reach
+        # it. The apt.conf.d timeouts below bound every later apt call in
+        # this job, the runner's included. Pre-installing libc6-dbg lets the
+        # runner skip apt once its valgrind cache is restored (it checks
+        # ``dpkg -s libc6-dbg``, so the cache action's unregistered restores
+        # would not count). Install without update first: image lists are
+        # fresh, and the index refresh is what a congested mirror makes
+        # slow. Best effort; the job timeout is the last backstop.
+        timeout-minutes: 15
+        continue-on-error: true
+        run: |
+          sudo tee /etc/apt/apt.conf.d/99ci-acquire-timeouts >/dev/null <<'EOF'
+          Acquire::Retries "1";
+          Acquire::http::Timeout "15";
+          Acquire::https::Timeout "15";
+          EOF
+          if dpkg -s libc6-dbg >/dev/null 2>&1; then
+            echo "libc6-dbg already installed"
+            exit 0
+          fi
+          # Common path: the image's package lists are fresh enough.
+          if sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 90 \
+              apt-get install -y libc6-dbg; then
+            exit 0
+          fi
+          # Rescue path: refresh the lists once with a generous bound; the
+          # apt config already fails a stalled mirror over quickly.
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 10 30 \
+            dpkg --configure -a || true
+          sudo timeout -k 15 300 apt-get update
+          sudo DEBIAN_FRONTEND=noninteractive timeout -k 15 300 \
+            apt-get install -y libc6-dbg
+
       - name: Run CodSpeed benchmarks
-        uses: CodSpeedHQ/action@0ca9cbbf4623b599a6c3ed4fc8a922942705d9f1 # v5.0.2
+        uses: CodSpeedHQ/action@373d6868929f444bc08d901fd0eb0ad52a8875ea # v5.2.1
         with:
           run: |
             . venv/bin/activate
@@ -549,24 +664,29 @@ jobs:
           fetch-depth: 2
 
       - name: Restore Python
+        id: restore-python
         uses: ./.github/actions/restore-python
         with:
           python-version: ${{ env.DEFAULT_PYTHON }}
           cache-key: ${{ needs.common.outputs.cache-key }}
 
+      # Key on the exact Python version as well: LibreTiny creates a venv under
+      # ~/.platformio/penv whose interpreter is a symlink into the runner's
+      # hosted toolcache, so a cache saved on an older runner image breaks once
+      # a new image ships a newer patch release and drops the old interpreter.
       - name: Cache platformio
         if: github.ref == 'refs/heads/dev' && matrix.pio_cache_key
         uses: actions/cache@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
           path: ~/.platformio
-          key: platformio-${{ matrix.pio_cache_key }}-${{ hashFiles('platformio.ini') }}
+          key: platformio-${{ matrix.pio_cache_key }}-${{ steps.restore-python.outputs.python-version }}-${{ hashFiles('platformio.ini') }}
 
       - name: Cache platformio
         if: github.ref != 'refs/heads/dev' && matrix.pio_cache_key
         uses: actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
         with:
           path: ~/.platformio
-          key: platformio-${{ matrix.pio_cache_key }}-${{ hashFiles('platformio.ini') }}
+          key: platformio-${{ matrix.pio_cache_key }}-${{ steps.restore-python.outputs.python-version }}-${{ hashFiles('platformio.ini') }}
 
       - name: Cache ESP-IDF install
         if: matrix.cache_idf
@@ -574,6 +694,12 @@ jobs:
         with:
           framework: arduino
 
+      - name: Cache clang-tidy idedata
+        if: matrix.cache_idf
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: esp32-arduino-tidy
+
       - name: Cache nRF Connect SDK install
         if: matrix.cache_sdk_nrf
         uses: ./.github/actions/cache-sdk-nrf
@@ -623,6 +749,10 @@ jobs:
           # Also cache libdeps, store them in a ~/.platformio subfolder
           PLATFORMIO_LIBDEPS_DIR: ~/.platformio/libdeps
 
+      - name: Prune ESP-IDF install before cache save
+        if: matrix.cache_idf && (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
       - name: Suggested changes
         run: script/ci-suggest-changes ${{ matrix.ignore_errors && '|| true' || '' }}
         # yamllint disable-line rule:line-length
@@ -655,6 +785,11 @@ jobs:
       - name: Cache ESP-IDF install
         uses: ./.github/actions/cache-esp-idf
 
+      - name: Cache clang-tidy idedata
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: esp32-idf-tidy
+
       - name: Register problem matchers
         run: |
           echo "::add-matcher::.github/workflows/matchers/gcc.json"
@@ -689,6 +824,10 @@ jobs:
           # Also cache libdeps, store them in a ~/.platformio subfolder
           PLATFORMIO_LIBDEPS_DIR: ~/.platformio/libdeps
 
+      - name: Prune ESP-IDF install before cache save
+        if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
       - name: Suggested changes
         run: script/ci-suggest-changes
         if: always()
@@ -734,6 +873,11 @@ jobs:
       - name: Cache ESP-IDF install
         uses: ./.github/actions/cache-esp-idf
 
+      - name: Cache clang-tidy idedata
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: esp32-idf-tidy
+
       - name: Register problem matchers
         run: |
           echo "::add-matcher::.github/workflows/matchers/gcc.json"
@@ -768,6 +912,10 @@ jobs:
           # Also cache libdeps, store them in a ~/.platformio subfolder
           PLATFORMIO_LIBDEPS_DIR: ~/.platformio/libdeps
 
+      - name: Prune ESP-IDF install before cache save
+        if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
       - name: Suggested changes
         run: script/ci-suggest-changes
         if: always()
@@ -791,16 +939,19 @@ jobs:
             name: Run script/clang-tidy for ESP32 S3
             # yamllint disable-line rule:line-length
             options: --environment esp32s3-idf-tidy --grep SOC_TEMP_SENSOR_SUPPORTED --grep USE_ESP32_VARIANT_ESP32S3 --grep USE_LOGGER_USB_CDC
+            tidy_environment: esp32s3-idf-tidy
           - id: clang-tidy
             name: Run script/clang-tidy for ESP32 P4
             # P4 has no native Wi-Fi/BLE; those run over the hosted co-processor,
             # so their code paths differ -- lint them under the P4 build too.
             # yamllint disable-line rule:line-length
             options: --environment esp32p4-idf-tidy --grep USE_ESP32_VARIANT_ESP32P4 --grep USE_ESP32_HOSTED --grep USE_WIFI --grep USE_BLE
+            tidy_environment: esp32p4-idf-tidy
           - id: clang-tidy
             name: Run script/clang-tidy for ESP32 C6
             # yamllint disable-line rule:line-length
             options: --environment esp32c6-idf-tidy --grep SOC_LP_I2C_SUPPORTED --grep USE_ESP32_VARIANT_ESP32C6 --grep USE_OPENTHREAD --grep USE_ZIGBEE
+            tidy_environment: esp32c6-idf-tidy
 
     steps:
       - name: Check out code from GitHub
@@ -818,6 +969,11 @@ jobs:
       - name: Cache ESP-IDF install
         uses: ./.github/actions/cache-esp-idf
 
+      - name: Cache clang-tidy idedata
+        uses: ./.github/actions/cache-clang-tidy-idedata
+        with:
+          environment: ${{ matrix.tidy_environment }}
+
       - name: Register problem matchers
         run: |
           echo "::add-matcher::.github/workflows/matchers/gcc.json"
@@ -851,6 +1007,10 @@ jobs:
             script/clang-tidy --fix --changed ${{ matrix.options }}
           fi
 
+      - name: Prune ESP-IDF install before cache save
+        if: (github.ref == 'refs/heads/dev' || contains(github.event.pull_request.labels.*.name, 'ci-cache-write'))
+        uses: ./.github/actions/prune-esp-idf
+
       - name: Suggested changes
         run: script/ci-suggest-changes
         if: always()
@@ -871,7 +1031,6 @@ jobs:
       ESPHOME_SDK_NRF_PREFIX: ~/.esphome-sdk-nrf
     strategy:
       fail-fast: false
-      max-parallel: ${{ (startsWith(github.base_ref, 'beta') || startsWith(github.base_ref, 'release')) && 32 || 16 }}
       matrix:
         batch: ${{ fromJson(needs.determine-jobs.outputs.component-test-batches) }}
     steps:
@@ -883,12 +1042,17 @@ jobs:
       - name: List components
         run: echo ${{ matrix.batch.components }}
 
-      - name: Install apt packages
-        # Not cached: this job is pull-request-only, so a cache save could
-        # never be shared and would only consume quota.
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -y --no-install-recommends libsdl2-dev ccache
+      - name: Install apt packages (cached)
+        # A cache hit (seeded on dev by seed-apt-cache) never touches apt,
+        # so mirror outages cannot hang this PR-only job; the timeout bounds
+        # the cold path. Packages and version must match seed-apt-cache
+        # exactly. The action has no --no-install-recommends; same package
+        # set this job used before #17463.
+        timeout-minutes: 10
+        uses: awalsh128/cache-apt-pkgs-action@553a35bb8ebd9fcabcb1c9451aa4c98e1b4ca8a9 # v1.6.3
+        with:
+          packages: libsdl2-dev ccache
+          version: 1.1
 
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
@@ -953,7 +1117,7 @@ jobs:
           # - This catches pin conflicts and other issues in directly changed code
           # - Grouped tests use --testing-mode to allow config merging (disables some checks)
           # - Dependencies are safe to group since they weren't modified in this PR
-          if [[ "${{ github.base_ref }}" == beta* ]] || [[ "${{ github.base_ref }}" == release* ]]; then
+          if [[ "${{ needs.determine-jobs.outputs.release-pr }}" == "true" ]]; then
             directly_changed_csv=""
             echo "Testing components: $components_csv"
             echo "Target branch: ${{ github.base_ref }} - grouping all components"
@@ -1090,7 +1254,7 @@ jobs:
         # install step (order-of-magnitude faster on cold boots,
         # with its own wheel cache). actions/setup-python still
         # provides the interpreter.
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
         with:
           enable-cache: true
           # Pull request saves land in per-PR scopes nothing else can
@@ -1423,6 +1587,7 @@ jobs:
     # this check.
     needs:
       - common
+      - seed-apt-cache
       - determine-jobs
       - ci-custom
       - pylint

.github/workflows/codeql.yml

@@ -56,7 +56,7 @@ jobs:
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/init@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
         with:
           languages: ${{ matrix.language }}
           build-mode: ${{ matrix.build-mode }}
@@ -84,6 +84,6 @@ jobs:
           exit 1
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@5595ccaf912efad79be6eef63a5619ff05969be3 # v4.37.6
+        uses: github/codeql-action/analyze@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
         with:
           category: "/language:${{matrix.language}}"

.github/workflows/lock.yml

@@ -14,4 +14,4 @@ jobs:
     permissions:
       issues: write         # issues.lock on closed issues
       pull-requests: write  # issues.lock on closed pull requests
-    uses: esphome/workflows/.github/workflows/lock.yml@9f6577fd37b5cf773ab1b9be929714a0dcd15661  # 2026.7.0
+    uses: esphome/workflows/.github/workflows/lock.yml@0fdd5e311b7e744069166696072a1a9cbc5fbeb6  # 2026.8.1

.github/workflows/release-nightly.yml

@@ -0,0 +1,38 @@
+---
+name: Nightly Dev Release
+
+# Works out the dated dev tag and starts the release workflow with it, so that
+# the release run is named after the tag it builds. A workflow run name is
+# fixed when the run starts and cannot read a file or the current date.
+
+on:
+  schedule:
+    - cron: "0 2 * * *"
+
+permissions:
+  contents: read  # actions/checkout to read the version from esphome/const.py
+
+jobs:
+  trigger:
+    name: Start release build
+    if: github.repository == 'esphome/esphome'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read  # actions/checkout to read the version from esphome/const.py
+      actions: write  # gh workflow run starts release.yml
+    steps:
+      - name: Check out the repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Start the release workflow
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          VERSION=$(sed -n -E "s/^__version__\s+=\s+\"(.+)\"$/\1/p" esphome/const.py)
+          if [[ -z "$VERSION" ]]; then
+            echo "::error::Could not read __version__ from esphome/const.py"
+            exit 1
+          fi
+          TAG="${VERSION}$(date --utc '+%Y%m%d')"
+          echo "Starting release build for ${TAG}"
+          gh workflow run release.yml --ref "${GITHUB_REF_NAME}" --field tag="${TAG}"

.github/workflows/release.yml

@@ -1,12 +1,23 @@
 ---
 name: Publish Release
 
+# Releases (production and beta) are named after the version they publish.
+# Dev builds are named after the dated dev tag, which is passed in by the
+# nightly workflow because a run name cannot compute it itself.
+run-name: ${{ github.event.inputs.tag || github.event.release.tag_name || format('Manual build ({0})', github.ref_name) }}
+
 on:
   workflow_dispatch:
+    inputs:
+      tag:
+        description: >-
+          Tag to build. Only supported on dev, where the nightly workflow
+          uses it. Leave empty to build the version from esphome/const.py
+          with today's date appended.
+        required: false
+        default: ""
   release:
     types: [published]
-  schedule:
-    - cron: "0 2 * * *"
 
 permissions:
   contents: read  # actions/checkout for all jobs; deploy jobs add their own scopes when they need to write
@@ -23,6 +34,8 @@ jobs:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - name: Get tag
         id: tag
+        env:
+          INPUT_TAG: ${{ github.event.inputs.tag }}
         # yamllint disable rule:line-length
         run: |
           if [[ "${{ github.event_name }}" = "release" ]]; then
@@ -34,12 +47,23 @@ jobs:
               ENVIRONMENT="production"
             fi
           else
-            TAG=$(cat esphome/const.py | sed -n -E "s/^__version__\s+=\s+\"(.+)\"$/\1/p")
-            today="$(date --utc '+%Y%m%d')"
-            TAG="${TAG}${today}"
             BRANCH=${GITHUB_REF#refs/heads/}
+            # The nightly workflow passes the finished tag so that the run name
+            # matches what is built. Without it, work it out here.
+            TAG="${INPUT_TAG}"
+            if [[ -n "$TAG" && "$BRANCH" != "dev" ]]; then
+              echo "::error::The tag input is only supported on dev. A build from ${BRANCH} has to use the tag worked out here, which carries the branch name, so that it cannot publish over the dev, beta, latest or stable images."
+              exit 1
+            fi
+            if [[ -z "$TAG" ]]; then
+              TAG=$(cat esphome/const.py | sed -n -E "s/^__version__\s+=\s+\"(.+)\"$/\1/p")
+              today="$(date --utc '+%Y%m%d')"
+              TAG="${TAG}${today}"
+              if [[ "$BRANCH" != "dev" ]]; then
+                TAG="${TAG}-${BRANCH}"
+              fi
+            fi
             if [[ "$BRANCH" != "dev" ]]; then
-              TAG="${TAG}-${BRANCH}"
               BRANCH_BUILD="true"
               ENVIRONMENT=""
             else
@@ -99,7 +123,7 @@ jobs:
           python-version: "3.12"
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@37fe631027851001ddb9b187196cc803df7f5f0e # v4.3.0
 
       - name: Log in to docker hub
         uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
@@ -178,7 +202,7 @@ jobs:
           merge-multiple: true
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+        uses: docker/setup-buildx-action@37fe631027851001ddb9b187196cc803df7f5f0e # v4.3.0
 
       - name: Log in to docker hub
         if: matrix.registry == 'dockerhub'

.github/workflows/stale.yml

@@ -16,7 +16,7 @@ jobs:
     # No GITHUB_TOKEN permissions: the reusable workflow mints an ESPHome
     # GitHub App token so the labels, comments and closures come from
     # esphome[bot] instead of github-actions[bot].
-    uses: esphome/workflows/.github/workflows/stale.yml@61fd37a044cad4e9aa4303027b2a61b6a34da855  # main
+    uses: esphome/workflows/.github/workflows/stale.yml@a1c1485ab46ef41a84a6a9d8abd7fa4b7628fd70  # main
     secrets:
       ESPHOME_GITHUB_APP_PRIVATE_KEY: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
     with:

.github/workflows/sync-device-classes.yml

@@ -47,7 +47,7 @@ jobs:
         # setup-python interpreter so subsequent ``prek`` /
         # ``script/run-in-env.py`` steps find the deps without a
         # ``uv run`` prefix.
-        uses: astral-sh/setup-uv@c771a70e6277c0a99b617c7a806ffedaca235ff9 # v9.0.0
+        uses: astral-sh/setup-uv@20cfd1bf945f4377ade1205e4dbc17946fc9a30d # v10.0.1
         with:
           enable-cache: true
           # Pin uv version so the action does not have to fetch the

.github/workflows/sync-integration-durations.yml

@@ -0,0 +1,98 @@
+---
+name: Refresh integration test durations
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: "45 5 * * 1"
+
+# Repo writes (branch push, PR open) happen via the App token minted below,
+# so the workflow's GITHUB_TOKEN does not need any write scopes.
+permissions:
+  contents: read
+  actions: read  # gh api / gh run download for the CI junit artifacts
+
+jobs:
+  sync:
+    name: Refresh integration test durations
+    runs-on: ubuntu-latest
+    if: github.repository == 'esphome/esphome'
+    steps:
+      - name: Generate a token
+        id: generate-token
+        uses: actions/create-github-app-token@bcd2ba49218906704ab6c1aa796996da409d3eb1 # v3.2.0
+        with:
+          client-id: ${{ vars.ESPHOME_GITHUB_APP_CLIENT_ID }}
+          private-key: ${{ secrets.ESPHOME_GITHUB_APP_PRIVATE_KEY }}
+          permission-contents: write       # push the sync branch
+          permission-pull-requests: write  # open or refresh the sync PR
+
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Setup Python
+        uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
+        with:
+          python-version: "3.13"
+
+      - name: Refresh from the newest usable dev run
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          # Only full matrix dev runs upload junit-integration-* artifacts
+          # (see the integration-tests job); the merge script re-checks
+          # coverage regardless.
+          # Newest-first candidates via their bucket-0 artifact. Fork PRs run
+          # their own ci.yml, so name and branch are spoofable; require
+          # same-repo. Assignment failures trip set -e and fail loudly.
+          candidates=$(
+            gh api "repos/${GITHUB_REPOSITORY}/actions/artifacts?name=junit-integration-0&per_page=100" \
+              --jq '.artifacts[] | select(.expired | not) | .workflow_run
+                    | select(.head_branch == "dev" and .head_repository_id != null
+                             and .head_repository_id == .repository_id)
+                    | .id'
+          )
+          # Green runs first, then the rest newest first; a run missing a
+          # bucket fails the coverage check and the next one is tried
+          green=""
+          rest=""
+          for id in ${candidates}; do
+            conclusion=$(gh api "repos/${GITHUB_REPOSITORY}/actions/runs/${id}" --jq '.conclusion // ""')
+            if [ "${conclusion}" = "success" ]; then
+              green="${green} ${id}"
+            elif [ -n "${conclusion}" ]; then
+              rest="${rest} ${id}"
+            fi
+          done
+          # helpers.py imports colorama; the script needs nothing else
+          pip install colorama
+          for id in ${green} ${rest}; do
+            rm -rf /tmp/junit
+            if ! gh run download "${id}" --repo "${GITHUB_REPOSITORY}" -p "junit-integration-*" -D /tmp/junit; then
+              echo "::warning::Could not download artifacts for run ${id}; trying the next"
+              continue
+            fi
+            status=0
+            python script/update_integration_test_durations.py /tmp/junit || status=$?
+            if [ "${status}" -eq 0 ]; then
+              echo "Refreshed from run ${id}"
+              exit 0
+            fi
+            # Only EXIT_LOW_COVERAGE (3) from the script advances to the next run
+            [ "${status}" -eq 3 ] || exit 1
+            echo "::warning::Run ${id} covers too few test files; trying the next"
+          done
+          echo "::error::No dev CI run with usable junit artifacts in range; the feed is starved"
+          exit 1
+
+      - name: Commit changes
+        uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v8.1.1
+        with:
+          commit-message: "[ci] Refresh integration test durations"
+          committer: esphome[bot] <115708604+esphome[bot]@users.noreply.github.com>
+          author: esphome[bot] <115708604+esphome[bot]@users.noreply.github.com>
+          branch: sync/integration-durations
+          delete-branch: true
+          title: "[ci] Refresh integration test durations"
+          body-path: .github/PULL_REQUEST_TEMPLATE.md
+          token: ${{ steps.generate-token.outputs.token }}

.pre-commit-config.yaml

@@ -11,7 +11,7 @@ ci:
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
     # Ruff version.
-    rev: v0.16.0
+    rev: v0.16.3
     hooks:
       # Run the linter.
       - id: ruff

AGENTS.md

@@ -57,6 +57,12 @@ This document provides essential context for AI models interacting with this pro
         - Function-local constants: `lower_snake_case`
         - Protected/private fields: `lower_snake_case_with_trailing_underscore_`
         - Favor descriptive names over abbreviations
+        - Enumerator names: prefix every value of an `enum class` with the enum name converted to
+          `UPPER_SNAKE_CASE` (e.g. `UARTFlushResult::UART_FLUSH_RESULT_SUCCESS`). Never use bare
+          names like `SUCCESS`, `FAILURE`, `OK`, or `FAIL`: platform SDK headers define macros with
+          these common names (for example the Realtek SDKs used by LibreTiny define
+          `#define SUCCESS 0` in `basic_types.h`), and the preprocessor replaces the enumerator
+          before the compiler sees it, breaking the build and clang-tidy on those platforms.
 
 *   **Python Idioms:**
     *   **Assignment expressions (PEP 572):** Prefer the walrus operator (`:=`) wherever it removes a redundant lookup or a throwaway temporary. The most common case in component code is presence-checking a config key and then indexing it separately — fetch once with `.get()` and bind in the condition instead:
@@ -757,3 +763,13 @@ The project uses English for non-code content. When drafting documentation, code
 PR descriptions, and similar text, avoid technical jargon. Instead, express concepts in plain English,
 using standard technical terms only when required. Ensure the text is readily comprehensible to a wide
 audience, including non-native English speakers.
+
+## 10. Code Comments
+
+Code comments on individual lines should be used only where necessary to flag issues that may not be obvious
+on a simple reading of the code. Keep them short (e.g. 1 or 2 lines).
+
+Function and method comment blocks may include more detail as required to make
+calling contracts clear and document parameter usage, but should still be kept concise.
+
+Avoid redundancy and repetition; comments should never simply restate what the code already says.

CODEOWNERS

@@ -238,6 +238,7 @@ esphome/components/hlw8032/* @rici4kubicek
 esphome/components/hm3301/* @freekode
 esphome/components/hmac_md5/* @dwmw2
 esphome/components/hmac_sha256/* @dwmw2
+esphome/components/hoermann_hcp/* @zweckj
 esphome/components/homeassistant/* @esphome/core @OttoWinter
 esphome/components/homeassistant/number/* @landonr
 esphome/components/homeassistant/switch/* @Links2004
@@ -349,6 +350,7 @@ esphome/components/mipi_spi/* @clydebarrow
 esphome/components/mitsubishi/* @RubyBailey
 esphome/components/mitsubishi_cn105/* @crnjan
 esphome/components/mixer/speaker/* @kahrendt
+esphome/components/mk2pvrouter/* @FredM67
 esphome/components/mlx90393/* @functionpointer
 esphome/components/mlx90614/* @jesserockz
 esphome/components/mmc5603/* @benhoff
@@ -380,6 +382,7 @@ esphome/components/nextion/switch/* @senexcrenshaw
 esphome/components/nextion/text_sensor/* @senexcrenshaw
 esphome/components/nfc/* @jesserockz @kbx81
 esphome/components/noblex/* @AGalfra
+esphome/components/noise/* @esphome/core
 esphome/components/npi19/* @bakerkj
 esphome/components/nrf52/* @tomaszduda23
 esphome/components/number/* @esphome/core
@@ -465,6 +468,7 @@ esphome/components/sen21231/* @shreyaskarnik
 esphome/components/sen5x/* @martgras
 esphome/components/sen6x/* @martgras @mebner86 @tuct
 esphome/components/sendspin/* @kahrendt
+esphome/components/sendspin/image/* @kahrendt
 esphome/components/sendspin/media_player/* @kahrendt
 esphome/components/sendspin/media_source/* @kahrendt
 esphome/components/sendspin/sensor/* @kahrendt
@@ -473,6 +477,7 @@ esphome/components/sensirion_common/* @martgras
 esphome/components/sensor/* @esphome/core
 esphome/components/serial_proxy/* @kbx81
 esphome/components/sfa30/* @ghsensdev
+esphome/components/sfa40/* @NoQuarrel
 esphome/components/sgp40/* @SenexCrenshaw
 esphome/components/sgp4x/* @martgras @SenexCrenshaw
 esphome/components/sha256/* @esphome/core
@@ -573,6 +578,7 @@ esphome/components/tuya/select/* @bearpawmaxim
 esphome/components/tuya/sensor/* @jesserockz
 esphome/components/tuya/switch/* @jesserockz
 esphome/components/tuya/text_sensor/* @dentra
+esphome/components/tuya/water_heater/* @iago-veiga
 esphome/components/uart/* @esphome/core
 esphome/components/uart/button/* @ssieb
 esphome/components/uart/event/* @eoasmxd

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         = 2026.8.0-dev
+PROJECT_NUMBER         = 2026.9.0-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

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==1.9.4
+RUN uv pip install --no-cache-dir esphome-device-builder==1.13.1
 
 RUN \
     platformio settings set enable_telemetry No \

docker/generate_tags.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 import argparse
+import os
 import re
 
 CHANNEL_DEV = "dev"
@@ -64,7 +65,10 @@ def main():
 
     suffix = f"-{args.suffix}" if args.suffix else ""
 
-    image_name = f"esphome/esphome{suffix}"
+    repository = (
+        (os.environ.get("GITHUB_REPOSITORY") or "esphome/esphome").strip().lower()
+    )
+    image_name = f"{repository}{suffix}"
 
     print(f"channel={channel}")
 

esphome/__main__.py

@@ -10,7 +10,7 @@ from pathlib import Path
 import re
 import sys
 import time
-from typing import Protocol
+from typing import TYPE_CHECKING, Protocol
 
 # Note: Do not import modules from esphome.components here, as this would
 # cause them to be loaded before external components are processed, resulting
@@ -21,7 +21,6 @@ from esphome.const import (
     ARGUMENT_HELP_DEVICE,
     BUNDLE_EXTENSION,
     CONF_API,
-    CONF_AUTH,
     CONF_BAUD_RATE,
     CONF_BROKER,
     CONF_DEASSERT_RTS_DTR,
@@ -29,6 +28,7 @@ from esphome.const import (
     CONF_DISCOVER_IP,
     CONF_ESPHOME,
     CONF_LEVEL,
+    CONF_LOG,
     CONF_LOG_TOPIC,
     CONF_LOGGER,
     CONF_MDNS,
@@ -42,7 +42,7 @@ from esphome.const import (
     CONF_PORT,
     CONF_SUBSTITUTIONS,
     CONF_TOPIC,
-    CONF_USERNAME,
+    CONF_VERSION,
     CONF_WEB_SERVER,
     CONF_WIFI,
     ENV_NOGITIGNORE,
@@ -71,6 +71,9 @@ from esphome.util import (
     safe_print,
 )
 
+if TYPE_CHECKING:
+    import threading
+
 # Keep expensive imports (zeroconf, writer, yaml_util, etc.) out of this
 # module's top level. Every `esphome` invocation — including fast paths
 # like `esphome version` — pays the cost of what's imported here before
@@ -273,8 +276,8 @@ def _unresolved_default_error(purpose: Purpose, defaults: list[str]) -> str:
         if purpose == Purpose.LOGGING and not has_api():
             return (
                 "Cannot view logs over the network: no 'api:' component is "
-                "configured. Network log streaming requires the native API; add "
-                "an 'api:' component, enable MQTT logging, or view logs over USB."
+                "configured. Add an 'api:' component, enable MQTT logging, add a "
+                "'web_server:' component, or view logs over USB."
             )
         if purpose == Purpose.UPLOADING and not has_ota():
             return (
@@ -314,9 +317,12 @@ def choose_upload_log_host(
                 ]
                 resolved.append(choose_prompt(options, purpose=purpose))
             elif device == "OTA":
+                # Logs can stream over a network transport via the native API
+                # or the web_server HTTP SSE feed.
+                network_logging = has_api() or has_web_server_logging()
                 # ensure IP adresses are used first
                 if is_ip_address(CORE.address) and (
-                    (purpose == Purpose.LOGGING and has_api())
+                    (purpose == Purpose.LOGGING and network_logging)
                     or (purpose == Purpose.UPLOADING and has_ota())
                 ):
                     resolved.extend(_resolve_with_cache(CORE.address, purpose))
@@ -328,7 +334,11 @@ def choose_upload_log_host(
                     if has_mqtt_logging():
                         resolved.append("MQTT")
 
-                    if has_api() and has_non_ip_address() and has_resolvable_address():
+                    if (
+                        network_logging
+                        and has_non_ip_address()
+                        and has_resolvable_address()
+                    ):
                         resolved.extend(_ota_hostnames_for_default(purpose))
 
                 elif purpose == Purpose.UPLOADING:
@@ -390,7 +400,7 @@ def choose_upload_log_host(
             mqtt_config = CORE.config[CONF_MQTT]
             options.append((f"MQTT ({mqtt_config[CONF_BROKER]})", "MQTT"))
 
-        if has_api():
+        if has_api() or has_web_server_logging():
             add_ota_options()
 
     elif purpose == Purpose.UPLOADING and has_ota():
@@ -483,6 +493,21 @@ def has_web_server_ota() -> bool:
     )
 
 
+def has_web_server_logging() -> bool:
+    """Check if logs can be streamed over the web_server HTTP SSE endpoint.
+
+    The ``web_server`` component exposes a ``/events`` Server-Sent Events
+    stream that carries ``event: log`` frames. This requires version 2+ (the
+    v1 UI has no ``/events`` endpoint) and the ``log`` option enabled (default).
+    """
+    web_conf = CORE.config.get(CONF_WEB_SERVER)
+    if web_conf is None:
+        return False
+    if web_conf.get(CONF_VERSION, 2) == 1:
+        return False
+    return web_conf.get(CONF_LOG, True)
+
+
 def has_mqtt_ip_lookup() -> bool:
     """Check if MQTT is available and IP lookup is supported."""
     if CONF_MQTT not in CORE.config:
@@ -545,11 +570,48 @@ def has_name_add_mac_suffix() -> bool:
 
 
 def mqtt_get_ip(
-    config: ConfigType, username: str, password: str, client_id: str
+    config: ConfigType,
+    username: str,
+    password: str,
+    client_id: str,
+    stop_event: "threading.Event | None" = None,
 ) -> list[str]:
     from esphome import mqtt
 
-    return mqtt.get_esphome_device_ip(config, username, password, client_id)
+    return mqtt.get_esphome_device_ip(
+        config, username, password, client_id, stop_event=stop_event
+    )
+
+
+def _add_network_device(device: str, network_devices: list[str]) -> None:
+    """Append a device to the list, expanding it through ``CORE.address_cache``.
+
+    If the hostname is already in the address cache (e.g. populated by mDNS
+    discovery), substitute the cached IPs so aioesphomeapi doesn't open its
+    own Zeroconf to re-resolve it. Duplicates are dropped.
+    """
+    if CORE.address_cache and (cached := CORE.address_cache.get_addresses(device)):
+        network_devices.extend(addr for addr in cached if addr not in network_devices)
+    elif device not in network_devices:
+        network_devices.append(device)
+
+
+def _split_network_devices(devices: list[str]) -> tuple[list[str], bool]:
+    """Split the device list into direct addresses and an MQTT-lookup flag.
+
+    Direct addresses are expanded through ``CORE.address_cache`` and deduped
+    the same way ``_resolve_network_devices`` does; MQTT/MQTTIP magic strings
+    are not resolved, only reported via the returned bool so the caller can
+    defer the broker lookup.
+    """
+    network_devices: list[str] = []
+    has_mqtt_lookup = False
+    for device in devices:
+        if get_port_type(device) in _MQTT_PORT_TYPES:
+            has_mqtt_lookup = True
+        else:
+            _add_network_device(device, network_devices)
+    return network_devices, has_mqtt_lookup
 
 
 def _resolve_network_devices(
@@ -582,40 +644,44 @@ def _resolve_network_devices(
         if port_type in _MQTT_PORT_TYPES:
             # Only resolve MQTT once, even if multiple MQTT entries
             if not mqtt_resolved:
-                try:
-                    mqtt_ips = mqtt_get_ip(
-                        config, args.username, args.password, args.client_id
-                    )
-                    # pylint can't infer mqtt_get_ip's return through its
-                    # lazy ``from esphome import mqtt`` import, so it flags
-                    # the genexpr below.
-                    network_devices.extend(
-                        addr
-                        for addr in mqtt_ips  # pylint: disable=not-an-iterable
-                        if addr not in network_devices
-                    )
-                except EsphomeError as err:
-                    _LOGGER.warning(
-                        "MQTT IP discovery failed (%s), will try other devices if available",
-                        err,
-                    )
+                mqtt_ips = _mqtt_get_ip_or_warn(
+                    config, args.username, args.password, args.client_id
+                )
+                network_devices.extend(
+                    addr for addr in mqtt_ips if addr not in network_devices
+                )
                 mqtt_resolved = True
             continue
 
-        # If the hostname is already in the address cache (e.g. populated by
-        # mDNS discovery), substitute the cached IPs so aioesphomeapi doesn't
-        # open its own Zeroconf to re-resolve it.
-        if CORE.address_cache and (cached := CORE.address_cache.get_addresses(device)):
-            network_devices.extend(
-                addr for addr in cached if addr not in network_devices
-            )
-        elif device not in network_devices:
-            # Regular network address or IP - add if not already present
-            network_devices.append(device)
+        _add_network_device(device, network_devices)
 
     return network_devices
 
 
+def _mqtt_get_ip_or_warn(
+    config: ConfigType,
+    username: str,
+    password: str,
+    client_id: str,
+    stop_event: "threading.Event | None" = None,
+) -> list[str]:
+    """Look up the device IP via MQTT, returning [] with a warning on failure.
+
+    This owns the failure policy for MQTT IP discovery on paths that have
+    other addresses to fall back on: a broker problem must not abort the
+    operation. Also used as the deferred resolver handed to ``run_logs``,
+    where it runs in a worker thread.
+    """
+    try:
+        return mqtt_get_ip(config, username, password, client_id, stop_event=stop_event)
+    except EsphomeError as err:
+        _LOGGER.warning(
+            "MQTT IP discovery failed (%s), will try other devices if available",
+            err,
+        )
+        return []
+
+
 def run_miniterm(config: ConfigType, port: str, args) -> int:
     from datetime import datetime
 
@@ -696,9 +762,11 @@ def _wrap_to_code(name, comp, yaml_util):
     async def wrapped(conf):
         cg.add(cg.LineComment(f"{name}:"))
         if comp.config_schema is not None:
-            conf_str = yaml_util.dump(conf)
+            # sort_keys: voluptuous fills defaults in set order, so an
+            # unsorted dump would churn main.cpp and relink every run
+            conf_str = yaml_util.dump(conf, sort_keys=True)
             conf_str = conf_str.replace("//", "")
-            # remove tailing \ to avoid multi-line comment warning
+            # remove trailing \ to avoid multi-line comment warning
             conf_str = conf_str.replace("\\\n", "\n")
             cg.add(cg.LineComment(indent(conf_str)))
         await coro(conf)
@@ -789,7 +857,20 @@ def compile_program(args: ArgsProtocol, config: ConfigType) -> int:
         toolchain.create_factory_bin()
         toolchain.create_ota_bin()
         toolchain.create_elf_copy()
-        toolchain.get_idedata()
+        from esphome.build_helpers.idedata import IDEDATA_BEST_EFFORT_ERRORS
+
+        try:
+            if toolchain.get_idedata() is None:
+                _LOGGER.warning("No idedata was generated for this build")
+        except IDEDATA_BEST_EFFORT_ERRORS as err:
+            # The firmware already built; an idedata failure must not fail
+            # a successful build.
+            _LOGGER.warning(
+                "Could not generate idedata: %s (IDE, clang-tidy, and "
+                "memory-analysis data will be unavailable for this build)",
+                err,
+            )
+            _LOGGER.debug("Idedata failure detail", exc_info=True)
     else:
         from esphome.platformio import toolchain
 
@@ -1291,25 +1372,23 @@ def _upload_via_native_api(
 def _upload_via_web_server(
     config: ConfigType, network_devices: list[str], binary: Path
 ) -> tuple[int, str | None]:
-    web_conf = config.get(CONF_WEB_SERVER)
-    if not web_conf:
-        raise EsphomeError(
-            f"Cannot upload via web_server OTA: the {CONF_WEB_SERVER} component "
-            f"is not configured."
-        )
-
-    remote_port = int(web_conf[CONF_PORT])
-    auth = web_conf.get(CONF_AUTH) or {}
-    username = auth.get(CONF_USERNAME)
-    password = auth.get(CONF_PASSWORD)
-
     from esphome import web_server_ota
+    from esphome.web_server_helpers import get_web_server_connection
 
+    remote_port, username, password = get_web_server_connection(config)
     return web_server_ota.run_ota(
         network_devices, remote_port, username, password, binary
     )
 
 
+def _show_logs_via_web_server(config: ConfigType, network_devices: list[str]) -> int:
+    from esphome import web_server_logs
+    from esphome.web_server_helpers import get_web_server_connection
+
+    port, username, password = get_web_server_connection(config)
+    return web_server_logs.run_logs(network_devices, port, username, password)
+
+
 # Layout of esp_partition_info_t on flash. Each entry is 32 bytes, leading with a
 # 16-bit little-endian magic. ESP-IDF defines ESP_PARTITION_MAGIC = 0x50AA (stored as
 # bytes 0xAA, 0x50) for partition entries and ESP_PARTITION_MAGIC_MD5 = 0xEBEB for the
@@ -1418,17 +1497,37 @@ def show_logs(config: ConfigType, args: ArgsProtocol, devices: list[str]) -> int
         return run_miniterm(config, port, args)
 
     # Check if we should use API for logging
-    # Resolve MQTT magic strings to actual IP addresses
-    if has_api() and (
-        network_devices := _resolve_network_devices(devices, config, args)
-    ):
-        from esphome.api_client import run_logs
+    if has_api():
+        network_devices, has_mqtt_lookup = _split_network_devices(devices)
+        mqtt_resolver = None
+        if has_mqtt_lookup:
+            if network_devices:
+                # Addresses are already known, so don't block startup on the
+                # MQTT broker lookup; hand it to run_logs as a deferred
+                # resolver that runs in the background and feeds discovered
+                # addresses into the running log client, keeping MQTT as a
+                # fallback for when the known addresses are stale (e.g. DHCP
+                # reassigned the IP).
+                mqtt_resolver = functools.partial(
+                    _mqtt_get_ip_or_warn,
+                    config,
+                    args.username,
+                    args.password,
+                    args.client_id,
+                )
+            else:
+                # The MQTT lookup is the only way to find the device; resolve
+                # it up front since the client needs an address to start with.
+                network_devices = _resolve_network_devices(devices, config, args)
+        if network_devices:
+            from esphome.api_client import run_logs
 
-        return run_logs(
-            config,
-            network_devices,
-            subscribe_states=_should_subscribe_states(args),
-        )
+            return run_logs(
+                config,
+                network_devices,
+                subscribe_states=_should_subscribe_states(args),
+                mqtt_resolver=mqtt_resolver,
+            )
 
     if port_type in (PortType.NETWORK, PortType.MQTT) and has_mqtt_logging():
         from esphome import mqtt
@@ -1437,6 +1536,13 @@ def show_logs(config: ConfigType, args: ArgsProtocol, devices: list[str]) -> int
             config, args.topic, args.username, args.password, args.client_id
         )
 
+    # Fall back to the web_server HTTP SSE log stream for devices that have
+    # web_server: but no api: (the logging counterpart to web_server OTA).
+    if has_web_server_logging() and (
+        network_devices := _resolve_network_devices(devices, config, args)
+    ):
+        return _show_logs_via_web_server(config, network_devices)
+
     raise EsphomeError("No remote or local logging method configured (api/mqtt/logger)")
 
 
@@ -1564,20 +1670,26 @@ def command_compile(args: ArgsProtocol, config: ConfigType) -> int | None:
     if exit_code != 0:
         return exit_code
     if CORE.is_host:
-        if CORE.using_toolchain_esp_idf:
-            from esphome.espidf import toolchain
-
-            program_path = str(toolchain.get_elf_path())
-        else:
-            from esphome.platformio.toolchain import get_idedata
-
-            program_path = str(get_idedata(config).firmware_elf_path)
-        _LOGGER.info("Successfully compiled program to path '%s'", program_path)
+        _LOGGER.info(
+            "Successfully compiled program to path '%s'", _host_program_path(config)
+        )
     else:
         _LOGGER.info("Successfully compiled program.")
     return 0
 
 
+def _host_program_path(config: ConfigType) -> str:
+    """Return the compiled host ELF path."""
+    if CORE.using_toolchain_esp_idf:
+        from esphome.espidf import toolchain
+
+        return str(toolchain.get_elf_path())
+    from esphome.platformio.toolchain import get_idedata
+
+    # Memoized by compile_program's own call; this is a dict lookup
+    return str(get_idedata(config).firmware_elf_path)
+
+
 def command_upload(args: ArgsProtocol, config: ConfigType) -> int | None:
     # Get devices, resolving special identifiers like OTA
     devices = choose_upload_log_host(
@@ -1622,14 +1734,7 @@ def command_run(args: ArgsProtocol, config: ConfigType) -> int | None:
         return exit_code
     _LOGGER.info("Successfully compiled program.")
     if CORE.is_host:
-        if CORE.using_toolchain_esp_idf:
-            from esphome.espidf import toolchain
-
-            program_path = str(toolchain.get_elf_path())
-        else:
-            from esphome.platformio.toolchain import get_idedata
-
-            program_path = str(get_idedata(config).firmware_elf_path)
+        program_path = _host_program_path(config)
         _LOGGER.info("Running program from path '%s'", program_path)
         return run_external_process(program_path)
 
@@ -1941,7 +2046,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
     new_name = args.name
     for c in new_name:
         if c not in ALLOWED_NAME_CHARS:
-            print(
+            safe_print(
                 color(
                     AnsiFore.BOLD_RED,
                     f"'{c}' is an invalid character for names. Valid characters are: "
@@ -1954,7 +2059,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
 
     yaml = yaml_util.load_yaml(CORE.config_path)
     if CONF_ESPHOME not in yaml or CONF_NAME not in yaml[CONF_ESPHOME]:
-        print(
+        safe_print(
             color(
                 AnsiFore.BOLD_RED, "Complex YAML files cannot be automatically renamed."
             )
@@ -2001,7 +2106,9 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
             )
             > 1
         ):
-            print(color(AnsiFore.BOLD_RED, "Too many matches in YAML to safely rename"))
+            safe_print(
+                color(AnsiFore.BOLD_RED, "Too many matches in YAML to safely rename")
+            )
             return 1
 
         new_raw = re.sub(
@@ -2019,7 +2126,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
     # ``kitchen``; running ``esphome rename weird-file.yaml kitchen``
     # would otherwise just re-flash the same hostname).
     if new_name == old_name:
-        print(
+        safe_print(
             color(
                 AnsiFore.BOLD_RED,
                 f"'{new_name}' is already the device's name.",
@@ -2029,7 +2136,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
 
     new_path: Path = CORE.config_dir / (new_name + ".yaml")
     if new_path.resolve() == CORE.config_path.resolve():
-        print(
+        safe_print(
             color(
                 AnsiFore.BOLD_RED,
                 f"'{new_name}' is already the device's name.",
@@ -2037,7 +2144,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
         )
         return 1
     if new_path.exists():
-        print(
+        safe_print(
             color(
                 AnsiFore.BOLD_RED,
                 f"Cannot rename: {new_path} already exists. "
@@ -2045,7 +2152,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
             )
         )
         return 1
-    print(
+    safe_print(
         f"Updating {color(AnsiFore.CYAN, str(CORE.config_path))} to {color(AnsiFore.CYAN, str(new_path))}"
     )
     print()
@@ -2054,7 +2161,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
 
     rc = run_external_process(*ESPHOME_COMMAND, "config", str(new_path))
     if rc != 0:
-        print(color(AnsiFore.BOLD_RED, "Rename failed. Reverting changes."))
+        safe_print(color(AnsiFore.BOLD_RED, "Rename failed. Reverting changes."))
         new_path.unlink()
         return 1
 
@@ -2080,7 +2187,7 @@ def command_rename(args: ArgsProtocol, config: ConfigType) -> int | None:
     if CORE.config_path != new_path:
         CORE.config_path.unlink()
 
-    print(color(AnsiFore.BOLD_GREEN, "SUCCESS"))
+    safe_print(color(AnsiFore.BOLD_GREEN, "SUCCESS"))
     print()
     return 0
 
@@ -2507,6 +2614,49 @@ def parse_args(argv):
     return parser.parse_args(arguments)
 
 
+def _warn_if_source_tree_mismatch() -> None:
+    """Warn when the checkout the user is standing in is not the one being run.
+
+    An editable install records one absolute path, so a venv shared between git
+    worktrees (or reused after a checkout is copied or renamed) keeps importing
+    the tree it was installed from. Every command then silently runs, and
+    compiles, sources the user is not looking at. Only fires inside a checkout,
+    so ordinary installs never see it.
+    """
+    try:
+        cwd = Path.cwd()
+    except OSError:
+        return  # working directory is gone; a diagnostic must not break startup
+    for candidate in (cwd, *cwd.parents):
+        if (candidate / "esphome" / "__main__.py").is_file():
+            standing_in = candidate.resolve()
+            break
+    else:
+        return  # not inside a checkout; nothing to compare against
+
+    running = Path(__file__).resolve().parent.parent
+    # Both sides are resolved, so on a case-sensitive filesystem this matches
+    # plain equality. samefile() compares device and inode, which additionally
+    # covers a case-insensitive filesystem (macOS) reaching one directory by
+    # differently cased paths. Falls back to equality if either path is gone.
+    try:
+        same = standing_in.samefile(running)
+    except OSError:
+        same = standing_in == running
+    if same:
+        return
+
+    _LOGGER.warning(
+        "Running ESPHome from a different checkout than the one you are in:\n"
+        "  running from: %s\n"
+        "  you are in:   %s\n"
+        "The installed esphome resolves to the first, so its sources are used.\n"
+        "Run 'python -m esphome' from the second to use that one instead.",
+        running,
+        standing_in,
+    )
+
+
 def run_esphome(argv):
     from esphome.address_cache import AddressCache
 
@@ -2525,6 +2675,7 @@ def run_esphome(argv):
         args.log_level = "CRITICAL"
 
     setup_log(log_level=args.log_level)
+    _warn_if_source_tree_mismatch()
 
     if args.command in PRE_CONFIG_ACTIONS:
         try:
@@ -2582,10 +2733,14 @@ def run_esphome(argv):
     # Skipped when -s overrides are passed, since the cache was written
     # against the previous substitution set.
     config: ConfigType | None = None
-    cache_eligible = (
+    cache_write_eligible = (
         args.command in ("upload", "logs") and not command_line_substitutions
     )
-    if cache_eligible:
+    # An explicit --toolchain must re-run the per-platform validators, so
+    # gate only the cache read; the refresh below saves the result unless
+    # the sidecar records a different toolchain.
+    cache_read_eligible = cache_write_eligible and args.toolchain is None
+    if cache_read_eligible:
         from esphome.compiled_config import load_compiled_config
 
         config = load_compiled_config(conf_path)
@@ -2595,7 +2750,8 @@ def run_esphome(argv):
                 conf_path.name,
             )
 
-    if config is None:
+    cache_missed = config is None
+    if cache_missed:
         from esphome.config import read_config
 
         config = read_config(
@@ -2604,26 +2760,22 @@ def run_esphome(argv):
             # Snapshot only needed by `esphome config --no-defaults`.
             snapshot_user_config=getattr(args, "no_defaults", False),
         )
-        # Refresh the cache so the next upload/logs hits the fast path
-        # instead of re-running read_config. Skip when the storage
-        # sidecar is absent (no compile has run): the cache would
-        # never be loaded back, so writing secrets to disk is wasted.
-        if cache_eligible and config is not None:
-            from esphome.compiled_config import save_compiled_config
-            from esphome.storage_json import ext_storage_path
-
-            if ext_storage_path(conf_path.name).exists():
-                save_compiled_config(config)
-    if config is None:
-        return 2
+        if config is None:
+            return 2
     CORE.config = config
 
-    # Fallback for platforms whose validators didn't set the toolchain
-    # (only the esp32 component reads esp32.framework.toolchain). All
-    # other platforms only support PlatformIO today.
+    # The cache fast path skips validation, and legacy sidecars lack the
+    # toolchain field. Must run before the cache refresh below.
     if CORE.toolchain is None:
         CORE.toolchain = Toolchain.PLATFORMIO
 
+    # Refresh the cache so the next upload/logs hits the fast path
+    # instead of re-running read_config.
+    if cache_write_eligible and cache_missed:
+        from esphome.compiled_config import save_compiled_config_and_sidecar
+
+        save_compiled_config_and_sidecar(config)
+
     if args.command not in POST_CONFIG_ACTIONS:
         safe_print(f"Unknown command {args.command}")
         return 1

esphome/api_client.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import asyncio
 from contextlib import suppress
 import logging
+import threading
 from typing import TYPE_CHECKING, Any
 import warnings
 
@@ -20,6 +21,8 @@ from esphome.stacktrace import LogLineProcessor
 from esphome.util import safe_print
 
 if TYPE_CHECKING:
+    from collections.abc import Callable
+
     from aioesphomeapi.api_pb2 import (
         SubscribeLogsResponse,  # pylint: disable=no-name-in-module
     )
@@ -32,8 +35,18 @@ async def async_run_logs(
     config: dict[str, Any],
     addresses: list[str],
     subscribe_states: bool = True,
+    mqtt_resolver: Callable[[threading.Event], list[str]] | None = None,
 ) -> None:
-    """Run the logs command in the event loop."""
+    """Run the logs command in the event loop.
+
+    If ``mqtt_resolver`` is given, it is called in a worker thread (paho-mqtt
+    has no asyncio support on Windows) concurrently with the connection
+    attempts to ``addresses``, and any addresses it discovers are fed into
+    the running client. It owns its own failure handling (returning [] when
+    discovery fails) and must honor the ``threading.Event`` it is passed so
+    teardown is not delayed by the lookup's wait window; the initial broker
+    connect itself is only bounded by the socket timeout.
+    """
     from datetime import datetime
 
     conf = config["api"]
@@ -60,6 +73,41 @@ async def async_run_logs(
     # Decoder resolution policy lives in LogLineProcessor.
     processor = LogLineProcessor(config, CORE.target_platform)
 
+    mqtt_task: asyncio.Task[None] | None = None
+    mqtt_stop_event = threading.Event()
+
+    def _cancel_mqtt_discovery() -> None:
+        """Stop the broker lookup once a connection has been established.
+
+        Its answer is only useful while still disconnected: after that it
+        either duplicates the connected address or arrives too late to
+        matter, so don't keep an idle broker session open for it.
+        """
+        mqtt_stop_event.set()
+        if mqtt_task is not None and not mqtt_task.done():
+            mqtt_task.cancel()
+
+    async def _resolve_mqtt_addresses() -> None:
+        """Discover the device address via the MQTT broker in the background."""
+        try:
+            mqtt_ips = await asyncio.to_thread(mqtt_resolver, mqtt_stop_event)
+            if not mqtt_ips:
+                _LOGGER.debug(
+                    "MQTT discovery %s",
+                    "aborted" if mqtt_stop_event.is_set() else "found no addresses",
+                )
+                return
+            if cli.add_addresses(mqtt_ips):
+                _LOGGER.info("Discovered address(es) via MQTT: %s", ", ".join(mqtt_ips))
+            else:
+                _LOGGER.debug(
+                    "MQTT-discovered address(es) already known: %s", ", ".join(mqtt_ips)
+                )
+        except Exception:  # pylint: disable=broad-except
+            # A background task failure would otherwise stay invisible for
+            # the whole session and only re-raise at teardown
+            _LOGGER.exception("MQTT address discovery failed")
+
     def on_log(msg: SubscribeLogsResponse) -> None:
         """Handle a new log message."""
         time_ = datetime.now().astimezone()
@@ -98,20 +146,53 @@ async def async_run_logs(
         # A top-level ``deep_sleep:`` block means the device is only awake
         # briefly; cap the reconnect backoff so a wake window is not missed.
         deep_sleep="deep_sleep" in config,
+        on_connect=_cancel_mqtt_discovery if mqtt_resolver is not None else None,
     )
     try:
+        # Don't start (or keep) the broker lookup if a connection already
+        # succeeded; the stop event doubles as the not-needed-anymore latch
+        # and get_esphome_device_ip returns immediately when it is set.
+        if mqtt_resolver is not None and not mqtt_stop_event.is_set():
+            mqtt_task = asyncio.create_task(_resolve_mqtt_addresses())
         await asyncio.Event().wait()
     finally:
-        await stop()
+        try:
+            if mqtt_task is not None:
+                # Unblock the worker thread first so it can't hold up
+                # loop.shutdown_default_executor() for the full lookup timeout.
+                mqtt_stop_event.set()
+                # Give the worker a moment to exit through its own error
+                # handling; cancelling first would race out a late failure.
+                done, _ = await asyncio.wait([mqtt_task], timeout=1.0)
+                if not done:
+                    mqtt_task.cancel()
+                # return_exceptions keeps a CancelledError from the cancel()
+                # above from re-raising here and jumping over the stop() below.
+                # The task handles Exception itself, so only a BaseException
+                # escape (e.g. SystemExit from the worker) can land here.
+                (result,) = await asyncio.gather(mqtt_task, return_exceptions=True)
+                if isinstance(result, BaseException) and not isinstance(
+                    result, asyncio.CancelledError
+                ):
+                    _LOGGER.error("MQTT address discovery failed", exc_info=result)
+        finally:
+            # Must run even if a second cancellation lands mid-cleanup above
+            await stop()
 
 
 def run_logs(
     config: dict[str, Any],
     addresses: list[str],
     subscribe_states: bool = True,
+    mqtt_resolver: Callable[[threading.Event], list[str]] | None = None,
 ) -> None:
     """Run the logs command."""
     with suppress(KeyboardInterrupt):
         asyncio.run(
-            async_run_logs(config, addresses, subscribe_states=subscribe_states)
+            async_run_logs(
+                config,
+                addresses,
+                subscribe_states=subscribe_states,
+                mqtt_resolver=mqtt_resolver,
+            )
         )

esphome/arduino/library.py

@@ -0,0 +1,531 @@
+"""Arduino-core backend for the shared PlatformIO library converter.
+
+Bundled names build straight from the framework tree; everything else goes
+through ``esphome.platformio.library``. Mirrors ``lib_ldf_mode=off``: each
+library builds its own archive; all include dirs join one global path.
+
+Deviations from PlatformIO: flat-layout libraries get the recursive default
+source filter; ``dot_a_linkage`` is honored; bundled libraries never run a
+manifest ``extraScript``; manifest ``-I`` flags join the global include path;
+``precompiled``/``ldflags`` properties are refused by name.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+import logging
+from pathlib import Path
+import re
+
+from esphome.core import CORE, EsphomeError, Library
+from esphome.helpers import walk_files
+from esphome.platformio.extra_script import apply_extra_script
+from esphome.platformio.library import (
+    DEFAULT_BUILD_INCLUDE_DIR,
+    DEFAULT_BUILD_SRC_FILTER,
+    ESPHOME_DATA_KEY,
+    ESPHOME_DATA_LINK_FLAGS_KEY,
+    LIBRARY_HEADER_SUFFIXES,
+    SRC_FILE_EXTENSIONS,
+    ConvertedLibrary,
+    IncompatiblePlatform,
+    InvalidLibrary,
+    LibraryBackend,
+    _url_or_none,
+    check_library_data,
+    collect_filtered_files,
+    convert_libraries,
+    ensure_list,
+    is_lib_ignored,
+    lex_build_flags,
+    lib_ignore_set,
+    normalize_dependencies,
+    parse_library_json,
+    parse_library_properties,
+    warn_properties_depends,
+)
+
+_LOGGER = logging.getLogger(__name__)
+
+
+@dataclass
+class ArduinoLibrary:
+    """One resolved library, ready for the ninja generator."""
+
+    name: str
+    sources: list[Path] = field(default_factory=list)
+    include_dirs: list[Path] = field(default_factory=list)
+    # Extra compile flags private to this library's own sources
+    flags: list[str] = field(default_factory=list)
+    # PlatformIO's build.libArchive / Arduino's dot_a_linkage: when False the
+    # objects go to the linker directly (symbols nothing references survive)
+    lib_archive: bool = True
+    # Link inputs the library contributes (-L dirs / -l libs, e.g. from
+    # precompiled vendor blobs) and -Wl, options for the firmware link
+    link_dirs: list[Path] = field(default_factory=list)
+    link_libs: list[str] = field(default_factory=list)
+    link_flags: list[str] = field(default_factory=list)
+
+
+# Source-like suffixes the case-sensitive suffix map rejects
+_UNMAPPED_SOURCE_SUFFIXES = frozenset(
+    {s.lower() for s in SRC_FILE_EXTENSIONS} | {".ino"}
+)
+
+# Filename-plain names: an allowlist excludes separators, drive colons,
+# and dot-only names by shape
+_SAFE_LIBRARY_NAME_RE = re.compile(r"[A-Za-z0-9_][A-Za-z0-9_. +-]*\Z")
+
+
+def _is_safe_library_name(name: object) -> bool:
+    """Whether a name may be joined under the framework's libraries dir."""
+    return isinstance(name, str) and _SAFE_LIBRARY_NAME_RE.fullmatch(name) is not None
+
+
+def _manifest_build(name: str, data: object) -> dict:
+    """The manifest's ``build`` section; malformed manifests fail by name."""
+    build = data.get("build", {}) if isinstance(data, dict) else None
+    if not isinstance(build, dict):
+        raise EsphomeError(f"Library {name} has a malformed manifest")
+    return build
+
+
+def _resolve_src_dir(name: str, read_path: Path, build: dict) -> str:
+    """Resolve PIO's source dir: manifest srcDir, else src/Src, else the root."""
+    if "srcDir" not in build:
+        return next((d for d in ("src", "Src") if (read_path / d).is_dir()), ".")
+    # A declared srcDir (falsy included) that does not resolve is a manifest error
+    src_dir = build["srcDir"]
+    if not (isinstance(src_dir, str) and src_dir and (read_path / src_dir).is_dir()):
+        raise EsphomeError(
+            f"Library {name} declares srcDir {src_dir!r} which does not exist"
+        )
+    return src_dir
+
+
+def _reject_unsupported_link_fields(name: str, data: dict) -> None:
+    # PIO honors these; ignoring them would fail at link with no stated
+    # cause. Property values are strings, so "false" is not a declaration.
+    precompiled = data.get("precompiled")
+    if precompiled and str(precompiled).strip().lower() != "false":
+        raise EsphomeError(
+            f"Library {name} declares precompiled, which this backend does not support"
+        )
+    if data.get("ldflags"):
+        raise EsphomeError(
+            f"Library {name} declares ldflags, which this backend does not support"
+        )
+
+
+def _resolve_lib_archive(name: str, data: dict, build: dict) -> bool:
+    """build.libArchive, else dot_a_linkage (an Arduino IDE property PIO
+    ignores; a deliberate extra), else archive."""
+
+    # Strict parse: bool("false") is True
+    def _parse(key: str, raw: object) -> bool:
+        if isinstance(raw, bool):
+            return raw
+        value = str(raw).strip().lower()
+        if value in ("true", "false"):
+            return value == "true"
+        raise EsphomeError(f"Library {name} has a malformed {key} value {raw!r}")
+
+    if "libArchive" in build:
+        return _parse("libArchive", build["libArchive"])
+    if "dot_a_linkage" in data:
+        return _parse("dot_a_linkage", data["dot_a_linkage"])
+    return True
+
+
+def _classify_build_flags(
+    name: str, read_path: Path, lib: ArduinoLibrary, flag_tokens: list[str]
+) -> list[str]:
+    """Route the lexed build.flags into the library's flag lists.
+
+    Returns the ``-I`` arguments for the include-dir resolution.
+    """
+    include_flags: list[str] = []
+    for tok in flag_tokens:
+        if tok.startswith("-I"):
+            include_flags.append(tok[2:])
+        elif tok.startswith("-L"):
+            link_dir = (read_path / tok[2:]).resolve()
+            if not link_dir.is_dir():
+                # Kept (the linker ignores missing -L dirs); the warning
+                # names the culprit before a bare "cannot find -lfoo"
+                _LOGGER.warning(
+                    "Library %s declares library dir %s which does not exist",
+                    name,
+                    tok[2:],
+                )
+            lib.link_dirs.append(link_dir)
+        elif tok.startswith("-l"):
+            lib.link_libs.append(tok[2:])
+        elif tok.startswith("-Wl,"):
+            lib.link_flags.append(tok)
+        else:
+            lib.flags.append(tok)
+    return include_flags
+
+
+def _resolve_include_dirs(
+    name: str,
+    read_path: Path,
+    lib: ArduinoLibrary,
+    build: dict,
+    src_dir: str,
+    include_flags: list[str],
+) -> None:
+    include_dir = build.get("includeDir", DEFAULT_BUILD_INCLUDE_DIR)
+    if not isinstance(include_dir, str):
+        raise EsphomeError(f"Library {name} has a malformed includeDir")
+    for d, explicit in [
+        (include_dir, "includeDir" in build),
+        (src_dir, False),  # _resolve_src_dir already validated it
+        *((flag, True) for flag in include_flags),
+    ]:
+        if (path := (read_path / d)).is_dir():
+            lib.include_dirs.append(path.resolve())
+        elif explicit:
+            # Warn-and-drop (unlike srcDir): a missing include dir is
+            # harmless until a header is needed, and the compile names it
+            _LOGGER.warning(
+                "Library %s declares include dir %s which does not exist", name, d
+            )
+
+
+def _collect_lib_sources(
+    name: str,
+    read_path: Path,
+    lib: ArduinoLibrary,
+    src_dir: str,
+    src_filter: list[str],
+) -> None:
+    sources: list[Path] = []
+    dropped: list[str] = []
+    saw_header = False
+    for f in collect_filtered_files(read_path / src_dir, src_filter):
+        path = Path(f)
+        suffix = path.suffix
+        if suffix in SRC_FILE_EXTENSIONS:
+            # resolve() per file: srcFilter patterns may escape src_dir
+            sources.append(path.resolve())
+        elif suffix.lower() in _UNMAPPED_SOURCE_SUFFIXES:
+            # A source-like suffix the case-sensitive map rejects (.CPP,
+            # .ino) is a dropped compilation unit; headers fall through
+            dropped.append(path.name)
+        elif suffix.lower() in LIBRARY_HEADER_SUFFIXES:
+            saw_header = True
+    lib.sources = sorted(sources)
+    if dropped:
+        _LOGGER.warning(
+            "Library %s: %d file(s) with unmapped source suffixes are not compiled: %s",
+            name,
+            len(dropped),
+            ", ".join(sorted(dropped)),
+        )
+    if not lib.sources and not saw_header:
+        # Matched headers mean header-only; a filter matching nothing is
+        # a manifest/tree problem (a truly empty tree raises elsewhere)
+        _LOGGER.warning("Library %s: no source files matched", name)
+
+
+def _library_info(name: str, read_path: Path, data: dict) -> ArduinoLibrary:
+    """Resolve one library's sources, include dirs, and flags (PIO semantics)."""
+    build = _manifest_build(name, data)
+    _reject_unsupported_link_fields(name, data)
+    src_dir = _resolve_src_dir(name, read_path, build)
+    src_filter = ensure_list(build.get("srcFilter", DEFAULT_BUILD_SRC_FILTER))
+    if not all(isinstance(entry, str) for entry in src_filter):
+        raise EsphomeError(f"Library {name} has a malformed srcFilter")
+    lib = ArduinoLibrary(name=name, lib_archive=_resolve_lib_archive(name, data, build))
+    # PlatformIO shell-lexes each build.flags entry
+    include_flags = _classify_build_flags(
+        name, read_path, lib, lex_build_flags(build.get("flags", []), f"library {name}")
+    )
+    _resolve_include_dirs(name, read_path, lib, build, src_dir, include_flags)
+    _collect_lib_sources(name, read_path, lib, src_dir, src_filter)
+    return lib
+
+
+def _bundled_library(framework_path: Path, name: str) -> ArduinoLibrary:
+    """A library bundled with the Arduino core, read from the framework tree.
+
+    ``library.json`` wins over ``library.properties`` when both exist, as in
+    PlatformIO's LibBuilderFactory; only the JSON manifest can carry a
+    ``build`` section (srcDir, srcFilter, flags).
+    """
+    lib_dir = framework_path / "libraries" / name
+    manifest_json = lib_dir / "library.json"
+    if manifest_json.is_file():
+        try:
+            data = parse_library_json(manifest_json)
+        except ValueError as err:  # JSONDecodeError
+            raise EsphomeError(
+                f"Bundled library {name} has a corrupt library.json ({err}); "
+                "the framework install may be incomplete (run 'esphome clean-all')"
+            ) from err
+    elif (manifest := lib_dir / "library.properties").is_file():
+        data = parse_library_properties(manifest)
+    else:
+        # Debug, not warning: the legacy manifest-less layout is legal and
+        # the 3.1.2 core ships one such library (FSTools), so a warning
+        # would be unactionable noise on every build using it
+        _LOGGER.debug("Bundled library %s has no manifest; using defaults", name)
+        data = {}
+    if isinstance(data, dict):
+        # Bundled manifest deps are never walked; make the skip visible
+        if data.get("dependencies"):
+            _LOGGER.warning(
+                "Bundled library %s declares dependencies, which are not "
+                "resolved automatically; add them with add_library() if needed",
+                name,
+            )
+        warn_properties_depends(name, data)
+        build = data.get("build")
+        if isinstance(build, dict) and build.get("extraScript"):
+            # Scripts only run on the converted path; building without
+            # the script's flags would miscompile
+            raise EsphomeError(
+                f"Bundled library {name} declares an extraScript, which is "
+                "not run for bundled libraries"
+            )
+    lib = _library_info(name, lib_dir, data)
+    _assert_tree_has_code(
+        name,
+        lib_dir,
+        "the framework install may be incomplete (run 'esphome clean-all')",
+    )
+    return lib
+
+
+def _assert_tree_has_code(name: str, root: Path, hint: str) -> None:
+    """An empty or half-extracted tree can never link; fail by name (a
+    warning would scroll away and resurface as undefined symbols)."""
+    if not any(
+        Path(p).suffix in SRC_FILE_EXTENSIONS
+        or Path(p).suffix.lower() in LIBRARY_HEADER_SUFFIXES
+        for p in walk_files(root)
+    ):
+        raise EsphomeError(f"Library {name} has no sources or headers; {hint}")
+
+
+def _external_short_name(name: str) -> str:
+    """The short library name of a requested spec.
+
+    "owner/Name" and plain names take the last path segment; "Name=<url>"
+    takes the declared name. Git tails (".git", "#ref") are stripped like
+    the walk's URL normalization; the comparand is a manifest dependency
+    name, never a spec.
+    """
+    head, sep, tail = name.partition("=")
+    if sep and "://" in tail:
+        return head
+    short = name.rsplit("/", maxsplit=1)[-1]
+    return short.partition("#")[0].removesuffix(".git")
+
+
+def _check_unfulfilled_provides(
+    provided_requests: set[str], satisfied: set[str], still_requested: set[str]
+) -> None:
+    """Fail by name when a walk-skipped dependency was never added.
+
+    An unfulfilled provides() promise only surfaces as undefined symbols
+    at link. The walk records across re-resolutions, so a name no final
+    manifest still requests is stale state, never a failure.
+    """
+    if missing := sorted((provided_requests & still_requested) - satisfied):
+        raise EsphomeError(
+            "provides() skipped these dependencies but nothing added them: "
+            f"{', '.join(missing)}; the build is missing libraries"
+        )
+
+
+def resolve_libraries(
+    framework_path: Path, *, pio_platform: str, board_mcu: str, cache_key: str
+) -> list[ArduinoLibrary]:
+    """Resolve every ``cg.add_library()`` entry into an :class:`ArduinoLibrary`.
+
+    ``pio_platform``/``board_mcu`` filter manifests the way PlatformIO would
+    for that core (e.g. ``espressif8266``/``esp8266``); ``cache_key`` keys the
+    shared converter's download cache.
+
+    The returned list is not topologically sorted, so the caller must link
+    the archives inside one ``--start-group``/``--end-group`` pair (the
+    bundled-first grouping is incidental).
+    """
+    bundled: list[ArduinoLibrary] = []
+    external: list[Library] = []
+    # PlatformIO's lib_ignore covers framework-bundled libraries too; the
+    # shared converter only filters the registry/git ones.
+    lib_ignore = lib_ignore_set()
+    # Exact directory names keep membership case-sensitive everywhere
+    # (an is_dir() probe would match "wire" on macOS/Windows and build
+    # the bundled Wire twice)
+    libraries_dir = framework_path / "libraries"
+    if not libraries_dir.is_dir():
+        # A registry fallback would fail later with a misleading
+        # package-not-found error per bundled name
+        raise EsphomeError(
+            f"{libraries_dir} is missing; the framework install may be "
+            "incomplete (run 'esphome clean-all')"
+        )
+    bundled_dir_names = frozenset(p.name for p in libraries_dir.iterdir() if p.is_dir())
+
+    def _provided(name: object) -> bool:
+        return _is_safe_library_name(name) and name in bundled_dir_names
+
+    for library in CORE.platformio_libraries.values():
+        if is_lib_ignored(library.name, lib_ignore):
+            continue
+        # Bundled only for a bare name with a matching framework dir; pinned
+        # or unmatched names resolve from the registry, as under PlatformIO.
+        if not library.repository and not library.version and _provided(library.name):
+            # Bundled manifest deps are not walked; _bundled_library warns
+            bundled.append(_bundled_library(framework_path, library.name))
+        else:
+            external.append(library)
+
+    converted: list[ArduinoLibrary] = []
+    bundled_names = {lib.name for lib in bundled}
+    converted_manifest_names: set[str] = set()
+    # Bundled candidates skipped on purpose (platform filter); the
+    # provides() reconciliation must count them as satisfied
+    knowingly_skipped: set[str] = set()
+    # Dependency names of the manifests actually emitted; a walk recording
+    # for a since-re-resolved manifest must not fail the reconciliation
+    final_dep_names: set[str] = set()
+    # Ordered set of bundled dependency names to add once conversion is done
+    pending_bundled: dict[str, None] = {}
+    # Deps matching a separately-requested external are already in the build
+    # (a duplicate archive means duplicate-symbol link errors)
+    external_short_names = {
+        _external_short_name(lib.name) for lib in external if lib.name
+    }
+
+    def _add_bundled_dependencies(component: ConvertedLibrary) -> None:
+        # A version-less bare name ("Hash") is a core-bundled library the
+        # shared converter cannot resolve from the registry
+        for dep in normalize_dependencies(
+            component.data.get("dependencies"), component.name
+        ):
+            # normalize_dependencies guarantees a non-empty str name
+            name = dep["name"]
+            final_dep_names.add(name)
+            if "/" in name:
+                owner, _, pkg = name.partition("/")
+                if _is_safe_library_name(owner) and _is_safe_library_name(pkg):
+                    # Owner-qualified; the converter resolves it from the registry
+                    continue
+            if not _is_safe_library_name(name):
+                # The name becomes a path component; never join a traversal
+                _LOGGER.warning(
+                    "Ignoring malformed dependency entry %r of library %s",
+                    dep,
+                    component.name,
+                )
+                continue
+            if name in external_short_names:
+                if _provided(name):
+                    # A bundled copy is suppressed; a coincidental name
+                    # collision would surface as link errors
+                    _LOGGER.warning(
+                        "Dependency %s of %s is assumed satisfied by a "
+                        "requested external library; the bundled copy is "
+                        "not added",
+                        name,
+                        component.name,
+                    )
+                else:
+                    _LOGGER.debug(
+                        "Dependency %s of %s assumed satisfied by a requested "
+                        "external library",
+                        name,
+                        component.name,
+                    )
+                continue
+            if name in bundled_names or is_lib_ignored(name, lib_ignore):
+                continue
+            if _url_or_none(dep.get("version")) is not None:
+                # A URL names one specific source; never add the bundled copy
+                continue
+            if dep.get("owner") or not _provided(name):
+                # Only owner-less framework-tree names take the bundled
+                # copy (PIO's process_dependencies); the walk reports drops
+                continue
+            try:
+                # framework=None: the walk already warned for non-platform
+                # causes; debug keeps one fault from warning twice (pinned
+                # by test_nonplatform_rejection_warns_once_through_real_converter)
+                check_library_data(dep, pio_platform, None)
+            except IncompatiblePlatform as err:
+                # A knowing skip (platform filter), not a broken promise
+                knowingly_skipped.add(name)
+                _LOGGER.debug("Skip bundled candidate %s: %s", name, err)
+                continue
+            except InvalidLibrary as err:
+                # Malformed manifest data never counts as satisfied; the
+                # walk owns the warning (see the warns-once test above)
+                _LOGGER.debug("Skip malformed bundled candidate %s: %s", name, err)
+                continue
+            # Deferred: a later manifest name may satisfy this
+            pending_bundled.setdefault(name)
+
+    def _emit(component: ConvertedLibrary) -> None:
+        apply_extra_script(
+            component, board_mcu=lambda: board_mcu, pio_platform=pio_platform
+        )
+        _assert_tree_has_code(
+            component.get_require_name(),
+            component.source_dir,
+            "the download may be incomplete (run 'esphome clean-all')",
+        )
+        if isinstance(manifest_name := component.data.get("name"), str):
+            converted_manifest_names.add(manifest_name)
+        lib = _library_info(
+            component.get_require_name(), component.source_dir, component.data
+        )
+        # Extra-script LINKFLAGS travel outside build.flags; dropping
+        # them would link wrong with no stated cause
+        lib.link_flags.extend(
+            component.data.get(ESPHOME_DATA_KEY, {}).get(
+                ESPHOME_DATA_LINK_FLAGS_KEY, []
+            )
+        )
+        converted.append(lib)
+        _add_bundled_dependencies(component)
+
+    backend = LibraryBackend(
+        platform=pio_platform,
+        framework="arduino",
+        emit=_emit,
+        cache_key=cache_key,
+        # The walk must not resolve bundled names from the registry;
+        # _add_bundled_dependencies adds them after emit
+        provides=_provided,
+    )
+    if external:
+        convert_libraries(external, backend)
+    for name in pending_bundled:
+        if name in converted_manifest_names:
+            # The converted library is this one; the bundled copy would
+            # double the archive. Warn like the external_short_names twin.
+            _LOGGER.warning(
+                "Dependency %s is assumed satisfied by a converted library's "
+                "manifest name; the bundled copy is not added",
+                name,
+            )
+            continue
+        bundled_names.add(name)
+        bundled.append(_bundled_library(framework_path, name))
+
+    _check_unfulfilled_provides(
+        backend.provided_requests,
+        bundled_names
+        | converted_manifest_names
+        | external_short_names
+        | knowingly_skipped,
+        final_dep_names,
+    )
+
+    return bundled + converted

esphome/arduino8266/__init__.py

@@ -0,0 +1,9 @@
+"""Native (PlatformIO-free) build support for the ESP8266 Arduino core.
+
+This package downloads the Arduino ESP8266 core and the xtensa-lx106
+toolchain, generates a ninja build for them plus the ESPHome sources, and
+drives the build directly — the ESP8266 equivalent of ``esphome.espidf``.
+
+Deliberately importable without the esp8266 component to avoid circular
+imports; the component wires these modules in via lazy imports.
+"""

esphome/arduino8266/framework.py

@@ -0,0 +1,164 @@
+"""Download and install the Arduino ESP8266 core, toolchain, and ninja.
+
+Artifacts land in a machine-global cache (shared across projects, like the
+ESP-IDF install in ``esphome.espidf.framework``):
+
+    <cache>/arduino8266/frameworks/<version>/   framework-arduinoespressif8266
+    <cache>/arduino8266/toolchains/<version>/   toolchain-xtensa (gcc 10.3)
+
+Packages come from the PlatformIO registry (identical bits to the PlatformIO
+backend); ``ESPHOME_ARDUINO8266_*_MIRRORS`` overrides the URLs. ninja comes
+from PATH or the ninja PyPI wheel.
+"""
+
+from __future__ import annotations
+
+import os
+from pathlib import Path
+from typing import NamedTuple
+
+from esphome.build_helpers.ccache import ccache_defaults_env
+from esphome.build_helpers.ninja import find_ninja
+from esphome.build_helpers.tools_cache import ARDUINO8266_TOOLS_CACHE, tools_cache_path
+from esphome.core import EsphomeError, Version
+from esphome.framework_helpers import str_to_lst_of_str
+from esphome.platformio.registry import install_package, prefetch_packages
+
+FRAMEWORK_PACKAGE = "framework-arduinoespressif8266"
+TOOLCHAIN_PACKAGE = "toolchain-xtensa"
+# gcc 10.3, the toolchain Arduino core 3.x builds with; the build
+# generator's compile flags are tuned to it.
+TOOLCHAIN_VERSION = "2.100300.220621"
+
+ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS = str_to_lst_of_str(
+    os.environ.get("ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS", "")
+)
+ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS = str_to_lst_of_str(
+    os.environ.get("ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS", "")
+)
+
+
+def get_arduino8266_tools_path() -> Path:
+    # Machine-global so all projects share one install; see
+    # espidf.framework.get_idf_tools_path for the location rationale.
+    return tools_cache_path(*ARDUINO8266_TOOLS_CACHE)
+
+
+# 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)
+MIN_FRAMEWORK_VERSION = Version(3, 1, 1)
+
+
+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.
+    """
+    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)
+        raise EsphomeError(
+            f"Arduino core {ver} uses an older package encoding than this "
+            "helper implements (newer than 2.6.2)"
+        )
+    return f"3.{ver.major}{ver.minor:02d}{ver.patch:02d}.0"
+
+
+def get_framework_path(package_version: str) -> Path:
+    return get_arduino8266_tools_path() / "frameworks" / package_version
+
+
+def get_toolchain_path() -> Path:
+    return get_arduino8266_tools_path() / "toolchains" / TOOLCHAIN_VERSION
+
+
+class InstalledPaths(NamedTuple):
+    """Locations of the installed framework, toolchain, and ninja binary."""
+
+    framework: Path
+    toolchain: Path
+    ninja: Path
+
+
+def check_and_install(framework_version: Version) -> InstalledPaths:
+    """Ensure framework, toolchain, and ninja are installed; return their paths."""
+    if framework_version < MIN_FRAMEWORK_VERSION:
+        # Config validation enforces this too; keep the module honest when
+        # called directly.
+        raise EsphomeError(
+            f"The native toolchain requires the Arduino core "
+            f">= {MIN_FRAMEWORK_VERSION}, got {framework_version}"
+        )
+    # Probe the cheap local dependency before ~110 MB of downloads
+    ninja_path = find_ninja()
+    package_version = framework_package_version(framework_version)
+    framework_path = get_framework_path(package_version)
+    downloads_dir = get_arduino8266_tools_path() / "downloads"
+    toolchain_path = get_toolchain_path()
+    # One spec per package: the prefetch and the installs must agree
+    specs = (
+        (
+            FRAMEWORK_PACKAGE,
+            package_version,
+            framework_path,
+            ESPHOME_ARDUINO8266_FRAMEWORK_MIRRORS,
+            ("cores/esp8266", "tools/sdk", "libraries"),
+        ),
+        (
+            TOOLCHAIN_PACKAGE,
+            TOOLCHAIN_VERSION,
+            toolchain_path,
+            ESPHOME_ARDUINO8266_TOOLCHAIN_MIRRORS,
+            # xtensa-lx106-elf pins the target: every gcc package has a bin/
+            ("bin", "xtensa-lx106-elf"),
+        ),
+    )
+    # Fetch both archives at once; the installs below verify and extract
+    prefetch_packages([spec[:4] for spec in specs], downloads_dir)
+    for name, version, dest, mirrors, expect in specs:
+        install_package(name, version, dest, mirrors, downloads_dir, expect=expect)
+    return InstalledPaths(
+        framework=framework_path, toolchain=toolchain_path, ninja=ninja_path
+    )
+
+
+def toolchain_tool(toolchain_path: Path, name: str) -> Path:
+    """Path to one toolchain tool (gcc, g++, ar, size, addr2line, ...).
+
+    The single owner of the ``bin/xtensa-lx106-elf-<name>`` layout and the
+    Windows suffix, so a toolchain package bump touches one spot.
+    """
+    suffix = ".exe" if os.name == "nt" else ""
+    return toolchain_path / "bin" / f"xtensa-lx106-elf-{name}{suffix}"
+
+
+def get_build_env(toolchain_path: Path, ccache: str | None) -> dict[str, str]:
+    env = os.environ.copy()
+    # Drop empty entries: a trailing separator from an absent PATH would
+    # make the shell search the current directory for tools
+    parts = [
+        str(toolchain_path / "bin"),
+        *filter(None, env.get("PATH", "").split(os.pathsep)),
+    ]
+    env["PATH"] = os.pathsep.join(parts)
+    env.update(ccache_env(ccache))
+    return env
+
+
+def ccache_env(ccache: str | None) -> dict[str, str]:
+    """Return ccache settings for the build subprocess (not os.environ).
+
+    ``ccache`` is the pre-resolved binary (resolve_ccache_path), or None
+    when disabled. Values the user already set in the environment are
+    respected.
+    """
+    if ccache is None:
+        return {}
+    return ccache_defaults_env(get_arduino8266_tools_path() / "ccache")

esphome/build_gen/build_tool.py

@@ -0,0 +1,108 @@
+"""Tiny cross-platform build steps invoked from the generated ninja file.
+
+Plain script (not ``python -m``): it runs from ninja with whatever Python
+started esphome and must not depend on the package being importable.
+
+Subcommands:
+    ar <ar-binary> <archive> <rspfile>   remove stale archive, then ``ar rcs``
+    copy <src> <dst>                     copy a file
+
+The ar rspfile carries one object path per line (the generating rule must
+use ``$in_newline``, never ``$in``).
+"""
+
+from pathlib import Path
+import shutil
+import subprocess
+import sys
+
+
+def _read_rspfile(rspfile: str) -> list[str]:
+    r"""The object paths listed in ``rspfile``, unquoted.
+
+    GNU ar treats backslashes in response files as escapes (corrupts
+    Windows paths), so the caller expands the list into argv; strip the
+    simple surrounding quote ninja adds to special paths, then undo
+    ninja's POSIX escape for an embedded quote ('a'\\''b.o' -> a'b.o).
+    """
+    return [
+        line[1:-1].replace("'\\''", "'")
+        if len(line) >= 2 and line[0] == line[-1] and line[0] in "'\""
+        else line
+        for line in Path(rspfile).read_text(encoding="utf-8").splitlines()
+        if line
+    ]
+
+
+def _run_ar(ar: str, archive: str, rspfile: str) -> int:
+    # Remove first: ``ar rcs`` replaces members but never drops ones whose
+    # source was removed from the build, which would leak stale objects.
+    Path(archive).unlink(missing_ok=True)
+    objects = _read_rspfile(rspfile)
+    if not objects:
+        # An empty archive would "succeed" here and fail far away at link
+        print(f"ar: no objects listed in {rspfile} for {archive}", file=sys.stderr)
+        return 1
+    # Batch by argv length: expanding the rspfile gives back the Windows
+    # 32767-char command-line limit it existed to avoid. "rcs" creates,
+    # "qs" appends; the s keeps the symbol index explicit on every ar.
+    op = "rcs"
+    ok = False
+    try:
+        while objects:
+            batch = [objects.pop(0)]
+            batch_len = len(batch[0])
+            while objects and batch_len + len(objects[0]) < 25000:
+                batch_len += len(objects[0]) + 1
+                batch.append(objects.pop(0))
+            rc = subprocess.run(
+                [ar, op, archive, *batch], check=False, close_fds=False
+            ).returncode
+            if rc != 0:
+                return rc
+            op = "qs"
+        ok = True
+        return 0
+    finally:
+        if not ok:
+            # Any failure (bad exit, missing ar binary, interrupt) must not
+            # leave a truncated archive behind
+            Path(archive).unlink(missing_ok=True)
+
+
+def _run_copy(src: str, dst: str) -> int:
+    try:
+        shutil.copyfile(src, dst)
+    except OSError as err:
+        # Never leave a partially written output (e.g. a firmware image);
+        # SameFileError means dst IS src, where unlinking destroys the input
+        if not isinstance(err, shutil.SameFileError):
+            Path(dst).unlink(missing_ok=True)
+        print(f"copy: {src} -> {dst} failed: {err}", file=sys.stderr)
+        return 1
+    return 0
+
+
+# mode -> (handler, expected operand count); surplus argv means a
+# mis-specified ninja rule and must error, not silently drop operands
+_MODES = {"ar": (_run_ar, 3), "copy": (_run_copy, 2)}
+
+
+def main() -> int:
+    mode = sys.argv[1] if len(sys.argv) > 1 else ""
+    if entry := _MODES.get(mode):
+        handler, argc = entry
+        args = sys.argv[2:]
+        if len(args) != argc:
+            print(
+                f"build_tool {mode}: expected {argc} arguments, got {len(args)}",
+                file=sys.stderr,
+            )
+            return 1
+        return handler(*args)
+    print(f"unknown build_tool mode: {mode}", file=sys.stderr)
+    return 1
+
+
+if __name__ == "__main__":  # pragma: no cover
+    sys.exit(main())

esphome/build_gen/espidf.py

@@ -1,11 +1,18 @@
 """ESP-IDF direct build generator for ESPHome."""
 
 import json
+import logging
 from pathlib import Path
 
-from esphome.components.esp32 import get_esp32_variant, idf_version
+from esphome.components.esp32 import (
+    get_esp32_variant,
+    get_excluded_builtin_components,
+    get_managed_component_require_names,
+    idf_version,
+)
 import esphome.config_validation as cv
 from esphome.core import CORE
+from esphome.espidf import variant_to_idf_target
 from esphome.framework_helpers import (
     get_project_compile_flags,
     get_project_cxx_compile_flags,
@@ -13,6 +20,8 @@ from esphome.framework_helpers import (
 )
 from esphome.helpers import mkdir_p, write_file_if_changed
 
+_LOGGER = logging.getLogger(__name__)
+
 # Replaces the IDF default C++ standard (-std=gnu++2b appended to
 # CXX_COMPILE_OPTIONS by project.cmake's __build_init) with the one set via
 # cg.set_cpp_standard(). Emitted between include(project.cmake) and project(),
@@ -26,11 +35,12 @@ idf_build_set_property(CXX_COMPILE_OPTIONS "${{esphome_cxx_compile_options}}")""
 
 
 def get_available_components() -> list[str] | None:
-    """Get list of built-in ESP-IDF components from project_description.json.
+    """List the built-in ESP-IDF components from ``project_description.json``.
 
-    Excludes ``src``, IDF-managed components (``managed_components/``), and
-    converted PIO libs (``pio_components/``). Returns ``None`` if the build
-    dir or ``project_description.json`` isn't ready yet.
+    Only components below its ``idf_path/components`` count, which leaves out
+    ``src``, IDF-managed components, converted PIO libs and project local
+    ones such as the Arduino ``component_stubs``. Returns ``None`` if the
+    build dir or ``project_description.json`` isn't ready yet.
     """
     if CORE.build_path is None:
         return None
@@ -41,41 +51,44 @@ def get_available_components() -> list[str] | None:
     try:
         with project_desc.open(encoding="utf-8") as f:
             data = json.load(f)
-
-        component_info = data.get("build_component_info", {})
-
-        result = []
-        for name, info in component_info.items():
-            # Exclude our own src component
-            if name == "src":
-                continue
-
-            # Exclude IDF-managed and converted-PIO components (external).
-            comp_dir = info.get("dir", "")
-            if "managed_components" in comp_dir or "pio_components" in comp_dir:
-                continue
-
-            result.append(name)
-
-        return result
-    except (json.JSONDecodeError, OSError):
+        root = (Path(data["idf_path"]) / "components").resolve()
+        result = [
+            name
+            for name, info in data.get("build_component_info", {}).items()
+            if (comp_dir := info.get("dir"))
+            and Path(comp_dir).resolve().is_relative_to(root)
+        ]
+    except (json.JSONDecodeError, KeyError, OSError) as err:
+        _LOGGER.debug("Could not read %s: %s", project_desc, err)
         return None
+    if not result:
+        _LOGGER.warning("No ESP-IDF components found under %s", root)
+    return result
 
 
 def has_discovered_components() -> bool:
-    """Check if we have discovered components from a previous configure."""
-    return get_available_components() is not None
+    """Check if a previous configure discovered any built-in components."""
+    return bool(get_available_components())
 
 
-def get_project_cmakelists(minimal: bool = False) -> str:
+def _cmake_quote(value: str) -> str:
+    """Quote a cmake arg value for a set() line. add_cmake_arg rejects
+    whitespace, quotes, and '$', so only backslashes need escaping."""
+    escaped = value.replace("\\", "\\\\")
+    return f'"{escaped}"'
+
+
+def get_project_cmakelists(
+    minimal: bool = False, builtin_components: list[str] | None = None
+) -> str:
     """Generate the top-level CMakeLists.txt for ESP-IDF project.
 
     When ``minimal`` is true, omit ``ESPHOME_PROJECT_BUILTIN_COMPONENTS``
     since ``project_description.json`` may be stale on the first write.
+    ``builtin_components`` supplies the discovered list (from the cache)
+    instead of reading it from ``project_description.json``.
     """
-    # Get IDF target from ESP32 variant (e.g., ESP32S3 -> esp32s3)
-    variant = get_esp32_variant()
-    idf_target = variant.lower().replace("-", "")
+    idf_target = variant_to_idf_target(get_esp32_variant())
 
     # esp_idf_size 2.x (bundled with IDF >=6.0) made NG the default and
     # removed the --ng flag; on 1.x (IDF 5.5) --ng is required to get
@@ -109,6 +122,15 @@ def get_project_cmakelists(minimal: bool = False) -> str:
         else ""
     )
 
+    # CMake variables registered via cg.add_cmake_arg(). Emitted before
+    # include(project.cmake) so values like EXCLUDE_COMPONENTS are already
+    # set when project.cmake seeds the component list, and on minimal
+    # (discovery) writes too so excluded components never register.
+    cmake_args = "\n".join(
+        f"set({name} {_cmake_quote(value)})"
+        for name, value in sorted(CORE.cmake_args.items())
+    )
+
     # Per-project list exposed as a CMake variable so converted PIO libs
     # can reference ${ESPHOME_PROJECT_MANAGED_COMPONENTS} without baking
     # project-specific names into their cached CMakeLists.
@@ -119,8 +141,6 @@ def get_project_cmakelists(minimal: bool = False) -> str:
     # runs as a separate CMake script invocation that doesn't load the
     # project's top-level CMakeLists; without this, ${ESPHOME_PROJECT_
     # MANAGED_COMPONENTS} in a converted-lib REQUIRES expands to empty).
-    from esphome.components.esp32 import get_managed_component_require_names
-
     managed_components_property = "\n".join(
         f"idf_build_set_property(ESPHOME_PROJECT_MANAGED_COMPONENTS {name} APPEND)"
         for name in get_managed_component_require_names()
@@ -131,12 +151,24 @@ def get_project_cmakelists(minimal: bool = False) -> str:
     # component's REQUIRES including real IDF components). Referenced by
     # src/CMakeLists and by each converted PIO lib's CMakeLists. Skipped
     # on minimal writes because project_description.json may be stale.
+    # Excluded components are dropped here as well: a stale
+    # project_description.json from a build without exclusions may still
+    # list them, and requiring an excluded component pulls it back into
+    # the build (IDF requirement expansion overrides EXCLUDE_COMPONENTS).
+    # Derived from the EXCLUDE_COMPONENTS cmake arg emitted above so the
+    # two can never disagree within one generated file.
     builtin_components_property = (
         ""
         if minimal
         else "\n".join(
             f"idf_build_set_property(ESPHOME_PROJECT_BUILTIN_COMPONENTS {name} APPEND)"
-            for name in sorted(get_available_components() or [])
+            for name in sorted(
+                set(
+                    builtin_components
+                    if builtin_components is not None
+                    else get_available_components() or []
+                ).difference(CORE.cmake_args.get("EXCLUDE_COMPONENTS", "").split(";"))
+            )
         )
     )
 
@@ -163,6 +195,8 @@ set(CMAKE_NINJA_FORCE_RESPONSE_FILE 1)
 set(IDF_TARGET {idf_target})
 set(EXTRA_COMPONENT_DIRS ${{CMAKE_SOURCE_DIR}}/src)
 
+{cmake_args}
+
 include($ENV{{IDF_PATH}}/tools/cmake/project.cmake)
 
 {cpp_standard_options}
@@ -248,7 +282,9 @@ target_link_options(${{COMPONENT_LIB}} PUBLIC
 """
 
 
-def write_project(minimal: bool = False) -> None:
+def write_project(
+    minimal: bool = False, builtin_components: list[str] | None = None
+) -> None:
     """Write ESP-IDF project files."""
     mkdir_p(CORE.build_path)
     mkdir_p(CORE.relative_src_path())
@@ -256,7 +292,7 @@ def write_project(minimal: bool = False) -> None:
     # Write top-level CMakeLists.txt
     write_file_if_changed(
         CORE.relative_build_path("CMakeLists.txt"),
-        get_project_cmakelists(minimal=minimal),
+        get_project_cmakelists(minimal=minimal, builtin_components=builtin_components),
     )
 
     # Write component CMakeLists.txt in src/
@@ -264,3 +300,13 @@ def write_project(minimal: bool = False) -> None:
         CORE.relative_src_path("CMakeLists.txt"),
         get_component_cmakelists(),
     )
+
+    # Snapshot the exclusion set so has_outdated_files() can trigger a
+    # discovery reconfigure when it changes. Excluded components never
+    # register in project_description.json, so re-including one (e.g. a
+    # config gains mqtt) requires a fresh discovery pass before the
+    # ESPHOME_PROJECT_BUILTIN_COMPONENTS property can list it.
+    write_file_if_changed(
+        CORE.relative_build_path("exclude_components.esphomeinternal"),
+        ";".join(get_excluded_builtin_components()),
+    )

esphome/build_gen/platformio.py

@@ -63,6 +63,17 @@ def get_ini_content():
     # Add extra script for C++ flags
     CORE.add_platformio_option("extra_scripts", [f"pre:{CXX_FLAGS_FILE_NAME}"])
 
+    # Add CMake args. A user-supplied value (str or list) is deliberately
+    # replaced; this option was always overwritten at FINAL priority.
+    if CORE.cmake_args:
+        CORE.add_platformio_option(
+            "board_build.cmake_extra_args",
+            " ".join(
+                f"-D{name}={value}" for name, value in sorted(CORE.cmake_args.items())
+            ),
+            replace=True,
+        )
+
     content = "[platformio]\n"
     content += f"description = ESPHome {__version__}\n"
 

esphome/build_helpers/__init__.py

@@ -0,0 +1 @@
+"""Build helpers shared by the native (non-PlatformIO) toolchains."""

esphome/build_helpers/ccache.py

@@ -0,0 +1,92 @@
+"""Shared ccache policy for build backends: env-knob parsing, binary
+resolution, and default ``CCACHE_*`` values."""
+
+from __future__ import annotations
+
+import logging
+import os
+from pathlib import Path
+
+from esphome.framework_helpers import strip_win_long_path_prefix, tool_version_runs
+from esphome.helpers import FALSY_ENV_STRINGS, TRUTHY_ENV_STRINGS
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def _ccache_runs(ccache: str) -> bool:
+    """Return True when the ``ccache`` found on PATH actually runs."""
+    return tool_version_runs(
+        ccache,
+        "Ignoring ccache at %s because it failed to run; compiling without ccache",
+    )
+
+
+def parse_enable_env(name: str) -> bool | None:
+    """Strictly parse an on/off environment knob; None when unset or invalid.
+
+    ``bool(str)`` truthiness would flip ``no``/``off`` to enabled, so only
+    1/true/yes/on and 0/false/no/off count; anything else warns and reads
+    as unset so the caller's default policy applies.
+    """
+    raw = os.environ.get(name)
+    if raw is None:
+        return None
+    lowered = raw.strip().lower()
+    if not lowered:
+        # ENV KNOB= (Docker/CI) has always read as a disable
+        return False
+    if lowered in TRUTHY_ENV_STRINGS:
+        return True
+    if lowered in FALSY_ENV_STRINGS:
+        return False
+    _LOGGER.warning("Ignoring unrecognized %s=%r; use 1 or 0", name, raw)
+    return None
+
+
+def resolve_ccache_path() -> str | None:
+    """The ccache binary to wrap compiles with, or None when disabled.
+
+    An explicit ``ESPHOME_CCACHE_ENABLE=1`` skips the runnability probe; the
+    Windows extended-length prefix is stripped before probing (#18399).
+    """
+    import shutil
+
+    explicit = parse_enable_env("ESPHOME_CCACHE_ENABLE")
+    if explicit is False:
+        return None
+    ccache = shutil.which("ccache")
+    if ccache is None:
+        if explicit:
+            _LOGGER.warning(
+                "ESPHOME_CCACHE_ENABLE is set but no ccache binary is on PATH; "
+                "compiling without ccache"
+            )
+        return None
+    ccache = strip_win_long_path_prefix(ccache)
+    if not explicit and not _ccache_runs(ccache):
+        return None
+    return ccache
+
+
+def ccache_defaults_env(cache_dir: Path) -> dict[str, str]:
+    """Default ``CCACHE_*`` values for a build subprocess (not os.environ).
+
+    Values the user already set in the environment are respected. Depend
+    mode is on: both native backends emit depfiles (-MMD / CMake), which
+    keeps cache-miss overhead low.
+    """
+    from esphome.core import CORE
+
+    # An unset build_path means the env was built before preload; fail loudly
+    # rather than silently drop CCACHE_BASEDIR.
+    if CORE.build_path is None:
+        raise ValueError(
+            "CORE.build_path must be set before constructing the build environment"
+        )
+    defaults = {
+        "CCACHE_DIR": str(cache_dir),
+        "CCACHE_NOHASHDIR": "true",
+        "CCACHE_DEPEND": "1",
+        "CCACHE_BASEDIR": str(Path(CORE.build_path).resolve()),
+    }
+    return {k: v for k, v in defaults.items() if k not in os.environ}

esphome/build_helpers/idedata.py

@@ -1,10 +1,10 @@
-"""Derive idedata from an ESP-IDF native-toolchain ``compile_commands.json``.
+"""Derive idedata from a native (non-PlatformIO) build's ``compile_commands.json``.
 
-PlatformIO exposes a curated ``pio run -t idedata`` JSON; the native ESP-IDF
-toolchain has no such command, but its CMake build emits
-``build/compile_commands.json`` (CMAKE_EXPORT_COMPILE_COMMANDS). This module
-turns that file into the same fields consumers (IDE integration, clang-tidy)
-expect:
+PlatformIO exposes a curated ``pio run -t idedata`` JSON; the native
+toolchains have no such command, but each build produces a
+``compile_commands.json`` (CMAKE_EXPORT_COMPILE_COMMANDS for ESP-IDF, ninja's
+compdb tool otherwise). This module turns that file into the same fields
+consumers (IDE integration, clang-tidy) expect:
 
     {cc_path, cxx_path, cxx_flags, defines, includes: {build, toolchain}}
 """
@@ -18,6 +18,19 @@ from pathlib import Path
 import shlex
 import subprocess
 
+from esphome.core import EsphomeError
+from esphome.helpers import write_file
+
+# Everything idedata generation may raise after a successful link; idedata
+# is a bonus artifact, so consumers warn instead of failing the build
+IDEDATA_BEST_EFFORT_ERRORS = (
+    EsphomeError,
+    LookupError,
+    OSError,
+    RuntimeError,
+    ValueError,
+)
+
 _LOGGER = logging.getLogger(__name__)
 
 # C++ translation-unit suffixes used to identify ESPHome source files.
@@ -30,12 +43,8 @@ _ESPHOME_SRC_MARKER = "/src/esphome/"
 
 
 def _is_esphome_src(file: str) -> bool:
-    """Whether ``file`` is an ESPHome C++ translation unit.
-
-    ``compile_commands.json`` ``file`` paths use the OS-native separator, so on
-    Windows they contain backslashes; normalize to ``/`` before testing the
-    marker, otherwise no source matches and the build-include union is empty.
-    """
+    """Whether ``file`` is an ESPHome C++ translation unit; normalized to
+    ``/`` first since Windows compile DBs use backslashes."""
     return _ESPHOME_SRC_MARKER in file.replace("\\", "/") and file.endswith(
         _CXX_SUFFIXES
     )
@@ -106,11 +115,8 @@ def _expand_response_files(tokens: list[str], directory: Path) -> list[str]:
 
 
 def _pick_entry(entries: list[dict]) -> dict:
-    """Pick a representative ESPHome C++ translation unit.
-
-    All ESPHome sources share the same component flags/defines, so any one of
-    them yields the cxx_path / cxx_flags / defines we need.
-    """
+    """Pick a representative ESPHome C++ TU; all share the same component
+    flags/defines."""
     for entry in entries:
         if _is_esphome_src(entry["file"]):
             return entry
@@ -120,25 +126,46 @@ def _pick_entry(entries: list[dict]) -> dict:
     raise ValueError("no C++ translation unit found in compile_commands.json")
 
 
-def _parse_entry(entry: dict) -> tuple[str, list[str], list[str], list[str]]:
+# Compiler launchers that may prefix a compile command; a closed launcher
+# denylist beats enumerating compiler names, an open set.
+_LAUNCHER_STEMS = frozenset({"ccache", "sccache", "distcc", "icecc", "buildcache"})
+
+
+def _is_launcher(token: str) -> bool:
+    return Path(token).stem.lower() in _LAUNCHER_STEMS
+
+
+def parse_entry(
+    entry: dict, launcher: str | None = None
+) -> tuple[str, list[str], list[str], list[str]]:
     """Parse one compile_commands entry -> (cxx_path, defines, includes, cxx_flags)."""
     directory = Path(entry["directory"])
     tokens = _expand_response_files(_split_command(entry["command"]), directory)
 
     def _include(raw: str) -> str:
-        # Include paths in compile_commands are interpreted relative to the
-        # entry's ``directory`` (e.g. build-local ``-Iconfig``); resolve them
-        # so the cached idedata is usable regardless of the consumer's cwd.
-        # Emit forward slashes (``normpath`` yields ``\`` on Windows) so the
-        # paths match the absolute, already-forward-slash entries in the JSON.
+        # Resolve against the entry's ``directory`` so cached idedata works
+        # from any cwd; emit forward slashes to match the JSON's own entries
         raw = raw.strip()
         if raw and not Path(raw).is_absolute():
             raw = os.path.normpath(directory / raw)
         return raw.replace("\\", "/")
 
+    # A launcher-wrapped command ("ccache g++ ...") names the compiler second
+    if launcher is not None and tokens[:1] == [launcher]:
+        tokens = tokens[1:]
+    if not tokens:
+        # An empty command, or one that was only the launcher; fail by name
+        raise ValueError(f"empty compile command for {entry.get('file')}")
+    if _is_launcher(tokens[0]) and len(tokens) > 1 and not tokens[1].startswith("-"):
+        # Stale DB built with a launcher this run no longer configures; the
+        # real compiler is the next token
+        _LOGGER.warning("Stripping unconfigured launcher %s", tokens[0])
+        tokens = tokens[1:]
     # token0 is the compiler path; the rest of the command already uses forward
     # slashes on Windows, so normalize it too for a consistent idedata file.
     cxx_path = tokens[0].replace("\\", "/")
+    # Enforced here so no caller can record ccache as the compiler
+    reject_launcher_compiler(cxx_path)
     defines: list[str] = []
     includes: list[str] = []
     cxx_flags: list[str] = []
@@ -168,7 +195,7 @@ def _parse_entry(entry: dict) -> tuple[str, list[str], list[str], list[str]]:
     return cxx_path, defines, includes, cxx_flags
 
 
-def _get_toolchain_includes(cxx_path: str) -> list[str]:
+def get_toolchain_includes(cxx_path: str) -> list[str]:
     """Query the compiler for its builtin ``#include <...>`` search dirs."""
     result = subprocess.run(
         [cxx_path, "-E", "-x", "c++", "-", "-v"],
@@ -219,26 +246,128 @@ def _cc_path_from_cxx(cxx_path: str) -> str:
     return f"{stem}{suffix}"
 
 
-def idedata_from_build(compile_commands: Path) -> dict:
+def _cache_usable(cached: object) -> bool:
+    """Check a cached idedata dict against the guarantees of the write path.
+
+    Caches written by older versions predate the launcher rejection and the
+    include-union shape; serving one would bypass both. The dict check also
+    keeps "in" from substring-matching a bare JSON string.
+    """
+    if not isinstance(cached, dict) or "cc_path" not in cached:
+        return False
+    cxx_path = cached.get("cxx_path")
+    if not isinstance(cxx_path, str) or _is_launcher(cxx_path):
+        return False
+    includes = cached.get("includes")
+    return isinstance(includes, dict) and isinstance(includes.get("build"), list)
+
+
+def load_or_build_idedata(
+    compile_commands: Path,
+    elf_path: Path,
+    cache: Path,
+    launcher: str | None = None,
+) -> dict | None:
+    """Return idedata for a compile_commands.json build, cached on mtime.
+
+    Shared by the native ESP-IDF and ESP8266 Arduino toolchains. Returns None
+    when the compile DB doesn't exist yet (nothing was built). ``launcher``
+    is the compiler-launcher path (ccache) the build was generated with, if
+    any; commands in the compile DB are prefixed with it.
+    """
+    if not compile_commands.is_file():
+        _LOGGER.debug("No %s yet; skipping idedata generation", compile_commands)
+        return None
+
+    if cache.is_file() and cache.stat().st_mtime >= compile_commands.stat().st_mtime:
+        try:
+            cached = json.loads(cache.read_text(encoding="utf-8"))
+        except (ValueError, OSError) as err:
+            # A recurring cause (interrupted write, disk full) would otherwise
+            # look like unexplained slow builds
+            _LOGGER.warning("Discarding unreadable idedata cache %s: %s", cache, err)
+        else:
+            if _cache_usable(cached):
+                # Re-stamp so a relocated build dir cannot serve a stale ELF path
+                cached["prog_path"] = str(elf_path)
+                return cached
+            _LOGGER.debug("Regenerating idedata: cache %s fails validation", cache)
+
+    data = idedata_from_build(compile_commands, launcher)
+    data["prog_path"] = str(elf_path)
+    cache.parent.mkdir(parents=True, exist_ok=True)
+    # Atomic so a crash mid-write cannot leave a truncated cache
+    write_file(cache, json.dumps(data, indent=2) + "\n")
+    return data
+
+
+def reject_launcher_compiler(cxx_path: str) -> None:
+    """Reject a compile DB naming a launcher (ccache) as the compiler; it
+    must never be probed, cached, or consumed."""
+    if _is_launcher(cxx_path):
+        raise EsphomeError(
+            f"compile_commands.json names the launcher {cxx_path} as the "
+            "compiler; the compile database is unusable"
+        )
+
+
+def idedata_from_build(compile_commands: Path, launcher: str | None = None) -> dict:
     """Parse compile_commands.json into the idedata fields consumers expect.
 
-    A single ESP-IDF compile entry only carries its own component's REQUIRES
-    include set, but consumers (clang-tidy) analyze ESPHome headers that
-    transitively pull in other components. So take cxx_path / cxx_flags /
-    defines from a representative ESPHome TU, but union the include dirs across
-    all ESPHome TUs to get a project-wide superset (as PlatformIO's idedata
-    provides).
+    A single compile entry only carries the include set its own translation
+    unit was built with (per-component under ESP-IDF), but consumers
+    (clang-tidy) analyze ESPHome headers that transitively pull in other
+    components. So take cxx_path / cxx_flags / defines from a representative
+    ESPHome TU, but union the include dirs across all ESPHome TUs to get a
+    project-wide superset (as PlatformIO's idedata provides).
     """
     entries = json.loads(Path(compile_commands).read_text(encoding="utf-8"))
-    cxx_path, defines, _, cxx_flags = _parse_entry(_pick_entry(entries))
+    if not isinstance(entries, list) or not all(isinstance(e, dict) for e in entries):
+        # A TypeError here would escape IDEDATA_BEST_EFFORT_ERRORS
+        raise EsphomeError(f"{compile_commands} is not a compile-command list")
 
-    build_includes: dict[str, None] = {}
+    representative = _pick_entry(entries)
+    cxx_path, defines, rep_includes, cxx_flags = parse_entry(representative, launcher)
+
+    # Seed with the representative's includes so it is not parsed twice
+    has_esphome_tu = _is_esphome_src(representative["file"])
+    build_includes: dict[str, None] = dict.fromkeys(
+        rep_includes if has_esphome_tu else ()
+    )
+
+    def _shape(entry: dict) -> str:
+        # directory + command minus TU-specific paths: same shape means the
+        # same include set, so tokenize once per shape. Response-file
+        # commands never dedupe (the .rsp contents differ per object)
+        command = entry["command"]
+        directory = entry.get("directory", "")
+        if "@" in command:
+            return f"unique:{directory}|{entry.get('output') or command}"
+        stripped = command.replace(entry.get("file", ""), "").replace(
+            entry.get("output", ""), ""
+        )
+        return f"{directory}|{stripped}"
+
+    seen_shapes = {_shape(representative)}
     for entry in entries:
-        if not _is_esphome_src(entry["file"]):
+        if entry is representative or not _is_esphome_src(entry["file"]):
             continue
-        for inc in _parse_entry(entry)[2]:
+        has_esphome_tu = True
+        if (shape := _shape(entry)) in seen_shapes:
+            _LOGGER.debug("Include union: %s shares a command shape", entry["file"])
+            continue
+        seen_shapes.add(shape)
+        for inc in parse_entry(entry, launcher)[2]:
             build_includes.setdefault(inc, None)
 
+    if not has_esphome_tu:
+        # An arbitrary fallback TU breaks clang-tidy/IDE consumers, and a
+        # warning would be cached into permanence; call sites downgrade this
+        raise EsphomeError(
+            f"No ESPHome translation unit found in {compile_commands}; "
+            "refusing to cache unusable idedata"
+        )
+
     return {
         "cc_path": _cc_path_from_cxx(cxx_path),
         "cxx_path": cxx_path,
@@ -246,6 +375,6 @@ def idedata_from_build(compile_commands: Path) -> dict:
         "defines": defines,
         "includes": {
             "build": list(build_includes),
-            "toolchain": _get_toolchain_includes(cxx_path),
+            "toolchain": get_toolchain_includes(cxx_path),
         },
     }

esphome/build_helpers/ninja.py

@@ -0,0 +1,92 @@
+"""Platform-neutral helpers for ninja-driven native builds."""
+
+from __future__ import annotations
+
+import logging
+import os
+from pathlib import Path
+import re
+import shutil
+
+from esphome.core import EsphomeError
+from esphome.framework_helpers import strip_win_long_path_prefix, tool_version_runs
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def _ninja_runs(binary: str) -> bool:
+    """Whether the ninja found on PATH actually runs (see tool_version_runs)."""
+    return tool_version_runs(
+        binary,
+        "Ignoring ninja at %s because it failed to run; "
+        "falling back to the bundled wheel",
+    )
+
+
+def find_ninja() -> Path:
+    """Locate the ninja binary: a runnable PATH hit first, else the ninja
+    PyPI wheel."""
+    if binary := shutil.which("ninja"):
+        binary = strip_win_long_path_prefix(binary)
+        if _ninja_runs(binary):
+            return Path(binary)
+    import_error: ImportError | None = None
+    try:
+        import ninja
+    except ImportError as err:
+        import_error = err
+        wheel_binary = None
+    else:
+        wheel_binary = Path(ninja.BIN_DIR) / (
+            "ninja.exe" if os.name == "nt" else "ninja"
+        )
+    if wheel_binary is None or not wheel_binary.is_file():
+        raise EsphomeError(
+            "ninja not found on PATH or in the ninja package; reinstall the "
+            "esphome Python environment"
+        ) from import_error
+    return wheel_binary
+
+
+def escape(value: Path | str) -> str:
+    """Escape a path or token for a ninja file."""
+    return str(value).replace("$", "$$").replace(":", "$:").replace(" ", "$ ")
+
+
+def quote_arg(tok: str) -> str:
+    """Quote with the CreateProcess argv rule (as ``subprocess.list2cmdline``):
+    backslash runs double only before a quote. Windows-only; ``$`` must
+    already be doubled for ninja.
+    """
+    quoted = re.sub(r'(\\*)"', lambda m: m.group(1) * 2 + '\\"', tok)
+    quoted = re.sub(r"(\\+)\Z", lambda m: m.group(1) * 2, quoted)
+    return f'"{quoted}"'
+
+
+# Force-quote any token containing a character outside the shlex.quote-style
+# safe set: ninja hands POSIX commands to /bin/sh -c, so bare (, ;, <, *, `
+# and friends would be re-parsed as shell syntax.
+_NEEDS_QUOTE = re.compile(r"[^\w@%+=:,./-]")
+
+
+def shell_token(tok: str, force: bool = False) -> str:
+    """Re-quote a lexed token for the platform shell; ``force`` always quotes.
+
+    Single quotes on POSIX (/bin/sh), the argv rule on Windows
+    (CreateProcess). ``$`` is doubled first because ninja expands it before
+    the command reaches the shell.
+    """
+    tok = tok.replace("$", "$$")  # ninja would expand a bare $ to nothing
+    if not (force or not tok or _NEEDS_QUOTE.search(tok)):
+        return tok
+    # An empty token must become '' / "" or it vanishes from the argv
+    if os.name == "nt":
+        return quote_arg(tok)
+    # shlex.quote's rule; inlined because the $-doubled token must not be
+    # re-examined for safe characters
+    return "'" + tok.replace("'", "'\"'\"'") + "'"
+
+
+def quote_path(value: Path | str) -> str:
+    """Force-quote a path for the ninja command line (shell/CreateProcess)."""
+    return shell_token(str(value), force=True)

esphome/build_helpers/size_summary.py

@@ -0,0 +1,24 @@
+"""The PlatformIO-format size bar shared by the native toolchains."""
+
+from __future__ import annotations
+
+
+def format_bar(used: int, total: int) -> str:
+    """Match PlatformIO's ``_format_availale_bytes`` (sic, pioupload.py) exactly."""
+    pct_raw = used / total if total else 0
+    blocks = 10
+    filled = min(int(round(blocks * pct_raw)), blocks)
+    progress = "=" * filled
+    return (
+        f"[{progress:<{blocks}}] {pct_raw: 6.1%} "
+        f"(used {used:d} bytes from {total:d} bytes)"
+    )
+
+
+def print_size_line(label: str, used: int, total: int) -> None:
+    """One PlatformIO-format summary line (``RAM``/``Flash``).
+
+    The label padding is part of the format: ``script/ci_memory_impact_extract.py``
+    matches these lines verbatim.
+    """
+    print(f"{label + ':':<7}{format_bar(used, total)}")

esphome/build_helpers/tools_cache.py

@@ -0,0 +1,36 @@
+"""Machine-global tools cache location shared by the native backends."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+
+def tools_cache_path(env_var: str, subdir: str) -> Path:
+    """A backend's machine-global tools directory, with an env override.
+
+    A blank/whitespace override is treated as unset: ``Path("")`` resolves
+    to the CWD, which ``clean-all`` would then delete.
+    """
+    import platformdirs
+
+    from esphome.helpers import get_str_env
+
+    if prefix := get_str_env(env_var, "").strip():
+        # resolve(): symlinked prefixes otherwise trip idf.py's
+        # venv-mismatch warning on every build
+        return Path(prefix).expanduser().resolve()
+    # appauthor=False keeps the Windows path short (no vendor segment);
+    # deep IDF trees run into MAX_PATH otherwise
+    return (
+        Path(platformdirs.user_cache_dir("esphome", appauthor=False)) / subdir
+    ).resolve()
+
+
+# (env override, cache subdir) per native backend. writer.clean_all wipes
+# every entry via tools_cache_path, so listing a cache here is the single
+# step that registers it for removal; the backends' own path getters use
+# the same named pairs so the two cannot drift.
+IDF_TOOLS_CACHE = ("ESPHOME_ESP_IDF_PREFIX", "idf")
+SDK_NRF_TOOLS_CACHE = ("ESPHOME_SDK_NRF_PREFIX", "sdk-nrf")
+ARDUINO8266_TOOLS_CACHE = ("ESPHOME_ARDUINO8266_PREFIX", "arduino8266")
+TOOLS_CACHE_SPECS = (IDF_TOOLS_CACHE, SDK_NRF_TOOLS_CACHE, ARDUINO8266_TOOLS_CACHE)

esphome/codegen.py

@@ -25,6 +25,7 @@ from esphome.cpp_generator import (  # noqa: F401
     add,
     add_build_flag,
     add_build_unflag,
+    add_cmake_arg,
     add_cxx_build_flag,
     add_define,
     add_global,
@@ -77,6 +78,7 @@ from esphome.cpp_types import (  # noqa: F401
     StringRef,
     arduino_json_ns,
     bool_,
+    char,
     const_char_ptr,
     double,
     esphome_ns,

esphome/compiled_config.py

@@ -1,26 +1,193 @@
 """Validated-config cache for the upload/logs fast path.
 
-compile dumps the validated config to <data_dir>/storage/<file>.validated.yaml;
+compile dumps the validated config to <data_dir>/storage/<file>.validated.json;
 the next upload/logs for that YAML reuses it instead of running the full
-read_config pipeline. YAML round-trip (yaml_util.dump/load_yaml) keeps
-!lambda/!include/IDs/paths intact; mtime gates staleness.
+read_config pipeline. The cache is deliberately lossy: only ``!lambda``
+bodies survive typed (``Lambda``); IDs, time periods, MAC/IP addresses,
+paths, UUIDs and enums store the same string form the YAML dumper
+produced for them. JSON additionally coerces non-str dict keys to
+strings; validated configs only use string keys (every schema key
+validator is ``cv.string``). mtime gates staleness.
 """
 
 from __future__ import annotations
 
+import json
 import logging
 from pathlib import Path
+from typing import Any
 
-from esphome.core import CORE
+from esphome.const import __version__ as ESPHOME_VERSION
+from esphome.core import CORE, EsphomeError, Lambda
 from esphome.helpers import write_file
-from esphome.storage_json import StorageJSON, ext_storage_path
+from esphome.storage_json import StorageJSON, ext_storage_path, storage_path
 from esphome.types import ConfigType
 
 _LOGGER = logging.getLogger(__name__)
 
+# Bump when the on-disk shape changes; a mismatched version falls back
+# to read_config. The envelope also stamps the writing esphome version:
+# after an upgrade the cache holds the previous release's validation, so
+# it falls back once and the re-save self-heals.
+_CACHE_VERSION = 1
+_LAMBDA_KEY = "__esphome_lambda__"
+
 
 def compiled_config_path(config_filename: str) -> Path:
     """Path to the cached validated config alongside the storage sidecar."""
+    return CORE.data_dir / "storage" / f"{config_filename}.validated.json"
+
+
+def save_compiled_config(config: ConfigType) -> None:
+    """Write the validated-config cache. Always-write so mtime stays fresh.
+
+    Mode 0600 because config validation resolved !secret inline.
+    Failures are non-fatal: the fast path falls back to read_config.
+    """
+    try:
+        # The legacy YAML cache holds inline-resolved secrets and nothing
+        # reads it anymore; drop it even when the write below fails. A
+        # failed removal leaves resolved secrets on disk, so it warns.
+        try:
+            _legacy_compiled_config_path(CORE.config_filename).unlink(missing_ok=True)
+        except OSError as err:
+            _LOGGER.warning(
+                "Could not remove the legacy validated-config cache: %s", err
+            )
+        rendered = json.dumps(
+            {"v": _CACHE_VERSION, "esphome": ESPHOME_VERSION, "config": config},
+            separators=(",", ":"),
+            default=_json_default,
+        )
+        write_file(compiled_config_path(CORE.config_filename), rendered, private=True)
+    except TypeError as err:
+        # Structural, not transient: this config can never cache (e.g. a
+        # non-basic dict key), so every upload/logs pays the slow path.
+        _LOGGER.warning("Cannot cache the validated config: %s", err)
+    except Exception as err:  # noqa: BLE001  # pylint: disable=broad-except
+        # Likely persistent (permissions, full disk): every upload/logs
+        # pays the slow path until it clears, so surface it.
+        _LOGGER.warning("Skipping compiled config cache write: %s", err)
+
+
+def save_compiled_config_and_sidecar(config: ConfigType) -> None:
+    """Refresh the cache from the upload/logs fallback (CORE.config must be set).
+
+    The cache is only written when a complete sidecar is on disk:
+    load_compiled_config can't use it otherwise, and it holds resolved
+    secrets.
+    """
+    if _refresh_sidecar():
+        save_compiled_config(config)
+
+
+def _refresh_sidecar() -> bool:
+    """Ensure a complete sidecar is on disk; True when one is.
+
+    Writes one (without claiming a build) when missing or wizard-only.
+    Failures are non-fatal; the next upload/logs pays the slow path again.
+    """
+    try:
+        path = storage_path()
+        try:
+            old = StorageJSON.load_strict(path)
+        except Exception as err:  # noqa: BLE001  # pylint: disable=broad-except
+            # Present but unreadable: it may hold a real build's metadata,
+            # and a fresh rewrite would also stop the next compile from
+            # cleaning a possibly incoherent build tree.
+            _LOGGER.warning(
+                "Not caching: storage sidecar %s is unreadable (%s)", path, err
+            )
+            return False
+        if old is not None and old.can_apply_to_core():
+            if (
+                old.toolchain is not None
+                and CORE.toolchain is not None
+                and old.toolchain != CORE.toolchain.value
+            ):
+                # Platforms normalize toolchain-sensitive keys differently;
+                # never cache a config validated under a different toolchain
+                # than the compile's
+                _LOGGER.debug(
+                    "Not caching: config validated with toolchain %r but the "
+                    "last compile used %r",
+                    CORE.toolchain.value,
+                    old.toolchain,
+                )
+                return False
+            # Compile-written; nothing to refresh.
+            return True
+        if CORE.build_path is not None and CORE.build_path.exists():
+            # An unvalidated build tree: its absent or mismatched sidecar
+            # is what makes the next compile wipe it, so don't vouch for
+            # a build this run never saw.
+            _LOGGER.warning(
+                "Not caching: build tree %s has no matching sidecar; "
+                "'esphome compile' will settle it",
+                CORE.build_path,
+            )
+            return False
+        new = StorageJSON.from_esphome_core(CORE, old, claim_build=False)
+        if not new.can_apply_to_core():
+            _LOGGER.warning("Not caching: rebuilt storage sidecar is still incomplete")
+            return False
+        new.save(path)
+        return True
+    except (OSError, EsphomeError) as err:
+        # write_file wraps OSError into EsphomeError. Persistent
+        # (unwritable storage dir), so surface that every upload/logs
+        # pays the slow path.
+        _LOGGER.warning("Could not refresh the storage sidecar: %s", err)
+    except Exception:  # noqa: BLE001  # pylint: disable=broad-except
+        # A structural bug; keep the traceback so it isn't mistaken
+        # for the I/O failure above.
+        _LOGGER.warning(
+            "Unexpected error refreshing the storage sidecar", exc_info=True
+        )
+    return False
+
+
+def load_compiled_config(conf_path: Path) -> ConfigType | None:
+    """Load the cached validated config and apply storage metadata to CORE.
+
+    Returns None (caller falls back to read_config) when the cache is
+    missing, older than the source YAML, unparseable, a different cache
+    version, or the sidecar is incomplete. The loaded config carries no
+    source ranges; callers must not feed it into read_config/write_cpp.
+    """
+    cache_path = compiled_config_path(conf_path.name)
+    if not _cache_is_fresh(cache_path, conf_path):
+        return None
+
+    try:
+        envelope = json.loads(
+            cache_path.read_text(encoding="utf-8"), object_hook=_decode_object
+        )
+    except (OSError, ValueError) as err:
+        _LOGGER.debug("Ignoring unreadable compiled config cache: %s", err)
+        return None
+
+    if (
+        not isinstance(envelope, dict)
+        or envelope.get("v") != _CACHE_VERSION
+        or envelope.get("esphome") != ESPHOME_VERSION
+        or not isinstance(config := envelope.get("config"), dict)
+    ):
+        _LOGGER.debug("Ignoring compiled config cache with a foreign envelope")
+        return None
+
+    storage = StorageJSON.load(ext_storage_path(conf_path.name))
+    if storage is None or not storage.can_apply_to_core():
+        _LOGGER.debug("Ignoring compiled config cache: sidecar missing or incomplete")
+        return None
+    storage.apply_to_core()
+    return config
+
+
+# Remove before 2027.8: by then every maintained install has saved the
+# JSON cache at least once and dropped its legacy YAML file.
+def _legacy_compiled_config_path(config_filename: str) -> Path:
+    """Path of the pre-JSON YAML cache; only ever removed."""
     return CORE.data_dir / "storage" / f"{config_filename}.validated.yaml"
 
 
@@ -32,52 +199,21 @@ def _cache_is_fresh(cache_path: Path, source_path: Path) -> bool:
         return False
 
 
-def save_compiled_config(config: ConfigType) -> None:
-    """Write the validated-config cache. Always-write so mtime stays fresh.
+def _json_default(value: Any) -> Any:
+    """Mirror ESPHomeDumper's representers: Lambda stays typed, the rest
+    stringify (IDs, time periods, MAC/IP addresses, paths, UUIDs, enums).
 
-    Mode 0600 because show_secrets=True resolves !secret inline.
-    Failures are non-fatal: the fast path falls back to read_config.
+    IncludeFile/Extend/Remove have no JSON mirror and would stringify
+    wrong, but none survive validation (config.py's packages merge and
+    the substitution pass consume them) so no guard is spent on them.
     """
-    from esphome import yaml_util
-
-    try:
-        rendered = yaml_util.dump(config, show_secrets=True)
-        write_file(compiled_config_path(CORE.config_filename), rendered, private=True)
-    except Exception as err:  # noqa: BLE001  # pylint: disable=broad-except
-        _LOGGER.debug("Skipping compiled config cache write: %s", err)
+    if isinstance(value, Lambda):
+        return {_LAMBDA_KEY: value.value}
+    return str(value)
 
 
-def load_compiled_config(conf_path: Path) -> ConfigType | None:
-    """Load the cached validated config and apply storage metadata to CORE.
-
-    Returns None (caller falls back to read_config) when the cache is
-    missing, older than the source YAML, unparseable, or the sidecar
-    is incomplete.
-    """
-    cache_path = compiled_config_path(conf_path.name)
-    if not _cache_is_fresh(cache_path, conf_path):
-        return None
-
-    from esphome import yaml_util
-
-    try:
-        # Fast path never validates or generates code - no source ranges
-        # needed (see load_yaml). Callers must not feed this config into
-        # read_config/write_cpp: the esp_range consumers in config.py and
-        # cpp_generator.py are isinstance-guarded and would degrade
-        # silently (wrong error/lambda locations) instead of raising.
-        config = yaml_util.load_yaml(
-            cache_path, clear_secrets=False, track_document_range=False
-        )
-    except Exception:  # noqa: BLE001  # pylint: disable=broad-except
-        return None
-
-    storage = StorageJSON.load(ext_storage_path(conf_path.name))
-    if storage is None:
-        return None
-    # apply_to_core assumes a real compile wrote the sidecar; wizard-only
-    # sidecars leave both of these unset and can't drive upload/logs.
-    if not storage.core_platform and not storage.target_platform:
-        return None
-    storage.apply_to_core()
-    return config
+def _decode_object(obj: dict[str, Any]) -> Any:
+    """Revive the Lambda sentinel; every other mapping passes through."""
+    if len(obj) == 1 and isinstance(value := obj.get(_LAMBDA_KEY), str):
+        return Lambda(value)
+    return obj

esphome/component_aliases.py

@@ -0,0 +1,10 @@
+"""Component alias registry.
+
+Generated by script/build_alias_registry.py - do not edit manually.
+See the component-alias section of esphome/loader.py.
+"""
+
+# alias -> (canonical component, removal version or None)
+COMPONENT_ALIASES: dict[str, tuple[str, str | None]] = {
+    "rp2040": ("rp2", "2027.7.0"),
+}

esphome/components/a01nyub/sensor.py

@@ -6,6 +6,7 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_METER,
 )
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@MrSuicideParrot"]
 DEPENDENCIES = ["uart"]
@@ -35,7 +36,7 @@ FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await sensor.new_sensor(config)
     await cg.register_component(var, config)
     await uart.register_uart_device(var, config)

esphome/components/a02yyuw/sensor.py

@@ -6,6 +6,7 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_MILLIMETER,
 )
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@TH-Braemer"]
 DEPENDENCIES = ["uart"]
@@ -35,7 +36,7 @@ FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await sensor.new_sensor(config)
     await cg.register_component(var, config)
     await uart.register_uart_device(var, config)

esphome/components/a4988/stepper.py

@@ -3,6 +3,7 @@ import esphome.codegen as cg
 from esphome.components import stepper
 import esphome.config_validation as cv
 from esphome.const import CONF_DIR_PIN, CONF_ID, CONF_SLEEP_PIN, CONF_STEP_PIN
+from esphome.types import ConfigType
 
 a4988_ns = cg.esphome_ns.namespace("a4988")
 A4988 = a4988_ns.class_("A4988", stepper.Stepper, cg.Component)
@@ -17,7 +18,7 @@ CONFIG_SCHEMA = stepper.STEPPER_SCHEMA.extend(
 ).extend(cv.COMPONENT_SCHEMA)
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await stepper.register_stepper(var, config)

esphome/components/absolute_humidity/sensor.py

@@ -9,6 +9,7 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_GRAMS_PER_CUBIC_METER,
 )
+from esphome.types import ConfigType
 
 absolute_humidity_ns = cg.esphome_ns.namespace("absolute_humidity")
 AbsoluteHumidityComponent = absolute_humidity_ns.class_(
@@ -43,7 +44,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await sensor.new_sensor(config)
     await cg.register_component(var, config)
 

esphome/components/ac_dimmer/output.py

@@ -4,6 +4,7 @@ from esphome.components import output
 import esphome.config_validation as cv
 from esphome.const import CONF_ID, CONF_METHOD, CONF_MIN_POWER
 from esphome.core import CORE
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@glmnet"]
 
@@ -48,7 +49,13 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
+    if CORE.is_esp32:
+        from esphome.components.esp32 import include_builtin_idf_component
+
+        # Re-enable the gptimer driver (excluded by default to save compile time)
+        include_builtin_idf_component("esp_driver_gptimer")
+
     if CORE.is_esp8266:
         # ac_dimmer uses setTimer1Callback which requires the waveform generator
         from esphome.components.esp8266.const import require_waveform

esphome/components/adalight/__init__.py

@@ -4,6 +4,9 @@ from esphome.components.light.effects import register_addressable_effect
 from esphome.components.light.types import AddressableLightEffect
 import esphome.config_validation as cv
 from esphome.const import CONF_NAME, CONF_UART_ID
+from esphome.core import ID
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["uart"]
 
@@ -21,7 +24,7 @@ CONFIG_SCHEMA = cv.Schema({})
     "Adalight",
     {cv.GenerateID(CONF_UART_ID): cv.use_id(uart.UARTComponent)},
 )
-async def adalight_light_effect_to_code(config, effect_id):
+async def adalight_light_effect_to_code(config: ConfigType, effect_id: ID) -> MockObj:
     effect = cg.new_Pvariable(effect_id, config[CONF_NAME])
     await uart.register_uart_device(effect, config)
     return effect

esphome/components/adc/__init__.py

@@ -1,3 +1,5 @@
+from typing import Any
+
 from esphome import pins
 import esphome.codegen as cg
 from esphome.components.esp32 import (
@@ -11,11 +13,13 @@ from esphome.components.esp32 import (
     VARIANT_ESP32P4,
     VARIANT_ESP32S2,
     VARIANT_ESP32S3,
+    VARIANT_ESP32S31,
     get_esp32_variant,
 )
 import esphome.config_validation as cv
 from esphome.const import CONF_ANALOG, CONF_INPUT, CONF_NUMBER, PLATFORM_ESP8266
 from esphome.core import CORE
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@esphome/core"]
 
@@ -153,6 +157,17 @@ ESP32_VARIANT_ADC1_PIN_TO_CHANNEL = {
         9: adc_channel_t.ADC_CHANNEL_8,
         10: adc_channel_t.ADC_CHANNEL_9,
     },
+    # https://github.com/espressif/esp-idf/blob/master/components/soc/esp32s31/include/soc/adc_channel.h
+    VARIANT_ESP32S31: {
+        42: adc_channel_t.ADC_CHANNEL_0,
+        43: adc_channel_t.ADC_CHANNEL_1,
+        44: adc_channel_t.ADC_CHANNEL_2,
+        45: adc_channel_t.ADC_CHANNEL_3,
+        46: adc_channel_t.ADC_CHANNEL_4,
+        47: adc_channel_t.ADC_CHANNEL_5,
+        48: adc_channel_t.ADC_CHANNEL_6,
+        49: adc_channel_t.ADC_CHANNEL_7,
+    },
 }
 
 # pin to adc2 channel mapping
@@ -222,15 +237,27 @@ ESP32_VARIANT_ADC2_PIN_TO_CHANNEL = {
         19: adc_channel_t.ADC_CHANNEL_8,
         20: adc_channel_t.ADC_CHANNEL_9,
     },
+    # https://github.com/espressif/esp-idf/blob/master/components/soc/esp32s31/include/soc/adc_channel.h
+    VARIANT_ESP32S31: {
+        50: adc_channel_t.ADC_CHANNEL_0,
+        51: adc_channel_t.ADC_CHANNEL_1,
+        52: adc_channel_t.ADC_CHANNEL_2,
+        53: adc_channel_t.ADC_CHANNEL_3,
+        54: adc_channel_t.ADC_CHANNEL_4,
+        55: adc_channel_t.ADC_CHANNEL_5,
+        56: adc_channel_t.ADC_CHANNEL_6,
+        57: adc_channel_t.ADC_CHANNEL_7,
+    },
 }
 
 
-def validate_adc_pin(value):
+def validate_adc_pin(value: Any) -> ConfigType | str:
     if str(value).upper() == "VCC":
         if CORE.is_rp2:
             return pins.internal_gpio_input_pin_schema(29)
         return cv.only_on([PLATFORM_ESP8266])("VCC")
 
+    # Deprecated in favour of the `internal_temperature` platform, remove before 2027.2.0
     if str(value).upper() == "TEMPERATURE":
         return cv.only_on_rp2("TEMPERATURE")
 

esphome/components/adc/adc_sensor_common.cpp

@@ -3,7 +3,7 @@
 
 namespace esphome::adc {
 
-static const char *const TAG = "adc.common";
+static const char *const TAG = "adc";
 
 const LogString *sampling_mode_to_str(SamplingMode mode) {
   switch (mode) {

esphome/components/adc/adc_sensor_esp32.cpp

@@ -6,7 +6,7 @@
 
 namespace esphome::adc {
 
-static const char *const TAG = "adc.esp32";
+static const char *const TAG = "adc";
 
 adc_oneshot_unit_handle_t ADCSensor::shared_adc_handles[2] = {nullptr, nullptr};
 
@@ -74,9 +74,7 @@ void ADCSensor::setup() {
   if (this->calibration_handle_ == nullptr) {
     adc_cali_handle_t handle = nullptr;
 
-#if USE_ESP32_VARIANT_ESP32C3 || USE_ESP32_VARIANT_ESP32C5 || USE_ESP32_VARIANT_ESP32C6 || \
-    USE_ESP32_VARIANT_ESP32C61 || USE_ESP32_VARIANT_ESP32H2 || USE_ESP32_VARIANT_ESP32P4 || USE_ESP32_VARIANT_ESP32S3
-    // RISC-V variants (except C2) and S3 use curve fitting calibration
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED)
     adc_cali_curve_fitting_config_t cali_config = {};  // Zero initialize first
 #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 3, 0)
     cali_config.chan = this->channel_;
@@ -94,7 +92,7 @@ void ADCSensor::setup() {
       ESP_LOGW(TAG, "Curve fitting calibration failed with error %d, will use uncalibrated readings", err);
       this->setup_flags_.calibration_complete = false;
     }
-#else  // ESP32, ESP32-S2, and ESP32-C2 use line fitting calibration
+#elif defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
     adc_cali_line_fitting_config_t cali_config = {
       .unit_id = this->adc_unit_,
       .atten = this->attenuation_,
@@ -112,7 +110,11 @@ void ADCSensor::setup() {
       ESP_LOGW(TAG, "Line fitting calibration failed with error %d, will use uncalibrated readings", err);
       this->setup_flags_.calibration_complete = false;
     }
-#endif  // ESP32C3 || ESP32C5 || ESP32C6 || ESP32C61 || ESP32H2 || ESP32P4 || ESP32S3
+#else   // No calibration scheme available
+    (void) handle;
+    ESP_LOGD(TAG, "No calibration scheme for this variant, readings are uncalibrated");
+    this->setup_flags_.calibration_complete = false;
+#endif
   }
 
   this->setup_flags_.init_complete = true;
@@ -121,23 +123,28 @@ void ADCSensor::setup() {
 void ADCSensor::dump_config() {
   LOG_SENSOR("", "ADC Sensor", this);
   LOG_PIN("  Pin: ", this->pin_);
-  ESP_LOGCONFIG(
-      TAG,
-      "  Channel:       %d\n"
-      "  Unit:          %s\n"
-      "  Attenuation:   %s\n"
-      "  Samples:       %i\n"
-      "  Sampling mode: %s\n"
-      "  Setup Status:\n"
-      "    Handle Init:  %s\n"
-      "    Config:       %s\n"
-      "    Calibration:  %s\n"
-      "    Overall Init: %s",
-      this->channel_, LOG_STR_ARG(adc_unit_to_str(this->adc_unit_)),
-      this->autorange_ ? "Auto" : LOG_STR_ARG(attenuation_to_str(this->attenuation_)), this->sample_count_,
-      LOG_STR_ARG(sampling_mode_to_str(this->sampling_mode_)),
-      this->setup_flags_.handle_init_complete ? "OK" : "FAILED", this->setup_flags_.config_complete ? "OK" : "FAILED",
-      this->setup_flags_.calibration_complete ? "OK" : "FAILED", this->setup_flags_.init_complete ? "OK" : "FAILED");
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED) || defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
+  const char *calibration_status = this->setup_flags_.calibration_complete ? "OK" : "FAILED";
+#else
+  const char *calibration_status = "N/A";  // This variant has no calibration scheme
+#endif
+  ESP_LOGCONFIG(TAG,
+                "  Channel:       %d\n"
+                "  Unit:          %s\n"
+                "  Attenuation:   %s\n"
+                "  Samples:       %i\n"
+                "  Sampling mode: %s\n"
+                "  Setup Status:\n"
+                "    Handle Init:  %s\n"
+                "    Config:       %s\n"
+                "    Calibration:  %s\n"
+                "    Overall Init: %s",
+                this->channel_, LOG_STR_ARG(adc_unit_to_str(this->adc_unit_)),
+                this->autorange_ ? "Auto" : LOG_STR_ARG(attenuation_to_str(this->attenuation_)), this->sample_count_,
+                LOG_STR_ARG(sampling_mode_to_str(this->sampling_mode_)),
+                this->setup_flags_.handle_init_complete ? "OK" : "FAILED",
+                this->setup_flags_.config_complete ? "OK" : "FAILED", calibration_status,
+                this->setup_flags_.init_complete ? "OK" : "FAILED");
 
   LOG_UPDATE_INTERVAL(this);
 }
@@ -184,12 +191,11 @@ float ADCSensor::sample_fixed_attenuation_() {
     } else {
       ESP_LOGW(TAG, "ADC calibration conversion failed with error %d, disabling calibration", err);
       if (this->calibration_handle_ != nullptr) {
-#if USE_ESP32_VARIANT_ESP32C3 || USE_ESP32_VARIANT_ESP32C5 || USE_ESP32_VARIANT_ESP32C6 || \
-    USE_ESP32_VARIANT_ESP32C61 || USE_ESP32_VARIANT_ESP32H2 || USE_ESP32_VARIANT_ESP32P4 || USE_ESP32_VARIANT_ESP32S3
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED)
         adc_cali_delete_scheme_curve_fitting(this->calibration_handle_);
-#else   // Other ESP32 variants use line fitting calibration
+#elif defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
         adc_cali_delete_scheme_line_fitting(this->calibration_handle_);
-#endif  // ESP32C3 || ESP32C5 || ESP32C6 || ESP32C61 || ESP32H2 || ESP32P4 || ESP32S3
+#endif
         this->calibration_handle_ = nullptr;
       }
     }
@@ -217,10 +223,9 @@ float ADCSensor::sample_autorange_() {
     // Need to recalibrate for the new attenuation
     if (this->calibration_handle_ != nullptr) {
       // Delete old calibration handle
-#if USE_ESP32_VARIANT_ESP32C3 || USE_ESP32_VARIANT_ESP32C5 || USE_ESP32_VARIANT_ESP32C6 || \
-    USE_ESP32_VARIANT_ESP32C61 || USE_ESP32_VARIANT_ESP32H2 || USE_ESP32_VARIANT_ESP32P4 || USE_ESP32_VARIANT_ESP32S3
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED)
       adc_cali_delete_scheme_curve_fitting(this->calibration_handle_);
-#else
+#elif defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
       adc_cali_delete_scheme_line_fitting(this->calibration_handle_);
 #endif
       this->calibration_handle_ = nullptr;
@@ -229,8 +234,7 @@ float ADCSensor::sample_autorange_() {
     // Create new calibration handle for this attenuation
     adc_cali_handle_t handle = nullptr;
 
-#if USE_ESP32_VARIANT_ESP32C3 || USE_ESP32_VARIANT_ESP32C5 || USE_ESP32_VARIANT_ESP32C6 || \
-    USE_ESP32_VARIANT_ESP32C61 || USE_ESP32_VARIANT_ESP32H2 || USE_ESP32_VARIANT_ESP32P4 || USE_ESP32_VARIANT_ESP32S3
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED)
     adc_cali_curve_fitting_config_t cali_config = {};
 #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 3, 0)
     cali_config.chan = this->channel_;
@@ -242,7 +246,7 @@ float ADCSensor::sample_autorange_() {
     err = adc_cali_create_scheme_curve_fitting(&cali_config, &handle);
     ESP_LOGVV(TAG, "Autorange atten=%d: Calibration handle creation %s (err=%d)", atten,
               (err == ESP_OK) ? "SUCCESS" : "FAILED", err);
-#else
+#elif defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
     adc_cali_line_fitting_config_t cali_config = {
       .unit_id = this->adc_unit_,
       .atten = atten,
@@ -264,10 +268,9 @@ float ADCSensor::sample_autorange_() {
     if (err != ESP_OK) {
       ESP_LOGW(TAG, "ADC read failed in autorange with error %d", err);
       if (handle != nullptr) {
-#if USE_ESP32_VARIANT_ESP32C3 || USE_ESP32_VARIANT_ESP32C5 || USE_ESP32_VARIANT_ESP32C6 || \
-    USE_ESP32_VARIANT_ESP32C61 || USE_ESP32_VARIANT_ESP32H2 || USE_ESP32_VARIANT_ESP32P4 || USE_ESP32_VARIANT_ESP32S3
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED)
         adc_cali_delete_scheme_curve_fitting(handle);
-#else
+#elif defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
         adc_cali_delete_scheme_line_fitting(handle);
 #endif
       }
@@ -286,10 +289,9 @@ float ADCSensor::sample_autorange_() {
         ESP_LOGVV(TAG, "Autorange atten=%d: UNCALIBRATED FALLBACK - raw=%d -> %.6fV (3.3V ref)", atten, raw, voltage);
       }
       // Clean up calibration handle
-#if USE_ESP32_VARIANT_ESP32C3 || USE_ESP32_VARIANT_ESP32C5 || USE_ESP32_VARIANT_ESP32C6 || \
-    USE_ESP32_VARIANT_ESP32C61 || USE_ESP32_VARIANT_ESP32H2 || USE_ESP32_VARIANT_ESP32P4 || USE_ESP32_VARIANT_ESP32S3
+#if defined(ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED)
       adc_cali_delete_scheme_curve_fitting(handle);
-#else
+#elif defined(ADC_CALI_SCHEME_LINE_FITTING_SUPPORTED)
       adc_cali_delete_scheme_line_fitting(handle);
 #endif
     } else {

esphome/components/adc/adc_sensor_esp8266.cpp

@@ -13,7 +13,7 @@ ADC_MODE(ADC_VCC)
 
 namespace esphome::adc {
 
-static const char *const TAG = "adc.esp8266";
+static const char *const TAG = "adc";
 
 void ADCSensor::setup() {
 #ifndef USE_ADC_SENSOR_VCC

esphome/components/adc/adc_sensor_libretiny.cpp

@@ -5,7 +5,7 @@
 
 namespace esphome::adc {
 
-static const char *const TAG = "adc.libretiny";
+static const char *const TAG = "adc";
 
 void ADCSensor::setup() {
 #ifndef USE_ADC_SENSOR_VCC

esphome/components/adc/adc_sensor_rp2.cpp

@@ -17,7 +17,26 @@
 
 namespace esphome::adc {
 
-static const char *const TAG = "adc.rp2";
+static const char *const TAG = "adc";
+
+// The on-die temperature sensor sits on the last ADC channel: input 4 on RP2040
+// and RP2350A, but input 8 on RP2350B, which has eight external channels rather
+// than four.
+//
+// This deliberately does not use the SDK's ADC_TEMPERATURE_CHANNEL_NUM. That
+// derives from NUM_ADC_CHANNELS, which <pico.h> settles from a board header, and
+// arduino-pico supplies a fixed B-die one for every RP2350 build. The real die
+// is only declared later, by the variant's pins_arduino.h, so the SDK constant
+// reads 8 on A-die boards. PICO_RP2350A itself is correct by the time this file
+// is compiled, on both arduino-pico and pico-sdk builds.
+#if defined(PICO_RP2350) && !defined(PICO_RP2350A)
+#error "PICO_RP2350A is not defined, so the RP2350 die is unknown and the temperature ADC channel cannot be chosen"
+#endif
+#if defined(PICO_RP2350) && !PICO_RP2350A
+static constexpr uint8_t TEMPERATURE_ADC_INPUT = 8;
+#else
+static constexpr uint8_t TEMPERATURE_ADC_INPUT = 4;
+#endif
 
 void ADCSensor::setup() {
   static bool initialized = false;
@@ -52,7 +71,7 @@ float ADCSensor::sample() {
   if (this->is_temperature_) {
     adc_set_temp_sensor_enabled(true);
     delay(1);
-    adc_select_input(4);
+    adc_select_input(TEMPERATURE_ADC_INPUT);
 
     for (uint8_t sample = 0; sample < this->sample_count_; sample++) {
       raw = adc_read();

esphome/components/adc/adc_sensor_zephyr.cpp

@@ -7,7 +7,7 @@
 
 namespace esphome::adc {
 
-static const char *const TAG = "adc.zephyr";
+static const char *const TAG = "adc";
 
 void ADCSensor::setup() {
   if (!adc_is_ready_dt(this->channel_)) {

esphome/components/adc/sensor.py

@@ -3,6 +3,7 @@ import logging
 import esphome.codegen as cg
 from esphome.components import sensor, voltage_sampler
 from esphome.components.esp32 import (
+    VARIANT_ESP32S31,
     get_esp32_variant,
     include_builtin_idf_component,
     require_adc_oneshot_iram,
@@ -52,10 +53,18 @@ _attenuation = cv.enum(ATTENUATION_MODES, lower=True)
 _sampling_mode = cv.enum(SAMPLING_MODES, lower=True)
 
 
-def validate_config(config):
+def validate_config(config: ConfigType) -> ConfigType:
     if config[CONF_RAW] and config.get(CONF_ATTENUATION, None) == "auto":
         raise cv.Invalid("Automatic attenuation cannot be used when raw output is set")
 
+    # The S31 ADC supports a single attenuation level (SOC_ADC_ATTEN_NUM is 1)
+    if (
+        CORE.is_esp32
+        and get_esp32_variant() == VARIANT_ESP32S31
+        and config.get(CONF_ATTENUATION, "0db") != "0db"
+    ):
+        raise cv.Invalid("ESP32-S31 only supports 'attenuation: 0db'")
+
     if config.get(CONF_ATTENUATION, None) == "auto" and config.get(CONF_SAMPLES, 1) > 1:
         raise cv.Invalid(
             "Automatic attenuation cannot be used when multisampling is set"
@@ -67,6 +76,13 @@ def validate_config(config):
         # Alter value here so `config` command prints the recommended change
         config[CONF_ATTENUATION] = _attenuation("12db")
 
+    # Remove before 2027.2.0
+    if config[CONF_PIN] == "TEMPERATURE":
+        _LOGGER.warning(
+            "[adc] `pin: TEMPERATURE` is deprecated, use the `internal_temperature` "
+            "sensor platform instead. Will be removed in 2027.2.0"
+        )
+
     return config
 
 
@@ -113,7 +129,7 @@ CONFIG_SCHEMA = cv.All(
 CONF_ADC_CHANNEL_ID = "adc_channel_id"
 
 
-def _overlay_io_channels():
+def _overlay_io_channels() -> str:
     channel_count = CORE.data[CONF_ADC_CHANNEL_ID]
     entries = ", ".join(f"<&adc {channel_id}>" for channel_id in range(channel_count))
     return f"""
@@ -125,7 +141,7 @@ def _overlay_io_channels():
             """
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await sensor.register_sensor(var, config)
@@ -133,6 +149,7 @@ async def to_code(config):
     if config[CONF_PIN] == "VCC":
         cg.add_define("USE_ADC_SENSOR_VCC")
     elif config[CONF_PIN] == "TEMPERATURE":
+        # Remove before 2027.2.0
         cg.add(var.set_is_temperature())
     elif not CORE.is_nrf52 or config[CONF_PIN][CONF_NUMBER] not in EXTRA_ADC:
         pin = await cg.gpio_pin_expression(config[CONF_PIN])

esphome/components/adc128s102/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import spi
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["spi"]
 MULTI_CONF = True
@@ -17,7 +18,7 @@ CONFIG_SCHEMA = cv.Schema(
 ).extend(spi.spi_device_schema(cs_pin_required=True))
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await spi.register_spi_device(var, config)

esphome/components/adc128s102/sensor/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import sensor, voltage_sampler
 import esphome.config_validation as cv
 from esphome.const import CONF_CHANNEL, CONF_ID
+from esphome.types import ConfigType
 
 from .. import ADC128S102, adc128s102_ns
 
@@ -28,7 +29,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(
         config[CONF_ID],
         config[CONF_CHANNEL],

esphome/components/addressable_light/display.py

@@ -11,6 +11,7 @@ from esphome.const import (
     CONF_UPDATE_INTERVAL,
     CONF_WIDTH,
 )
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@justfalter"]
 
@@ -38,7 +39,7 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     wrapped_light = await cg.get_variable(config[CONF_ADDRESSABLE_LIGHT_ID])
     cg.add(var.set_width(config[CONF_WIDTH]))

esphome/components/ade7880/sensor.py

@@ -36,6 +36,7 @@ from esphome.const import (
     UNIT_WATT,
     UNIT_WATT_HOURS,
 )
+from esphome.cpp_generator import MockObj
 from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
@@ -243,7 +244,7 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-async def neutral_channel(config):
+async def neutral_channel(config: ConfigType) -> MockObj:
     var = cg.new_Pvariable(config[CONF_ID])
 
     current = config[CONF_CURRENT]
@@ -257,7 +258,7 @@ async def neutral_channel(config):
     return var
 
 
-async def power_channel(config):
+async def power_channel(config: ConfigType) -> MockObj:
     var = cg.new_Pvariable(config[CONF_ID])
 
     for sensor_type in POWER_SENSOR_TYPES:
@@ -280,7 +281,7 @@ async def power_channel(config):
     return var
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/ade7953_base/__init__.py

@@ -23,6 +23,8 @@ from esphome.const import (
     UNIT_VOLT_AMPS_REACTIVE,
     UNIT_WATT,
 )
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@angelnu"]
 
@@ -163,7 +165,7 @@ ADE7953_CONFIG_SCHEMA = cv.Schema(
 ).extend(cv.polling_component_schema("60s"))
 
 
-async def register_ade7953(var, config):
+async def register_ade7953(var: MockObj, config: ConfigType) -> None:
     await cg.register_component(var, config)
 
     if irq_pin_config := config.get(CONF_IRQ_PIN):

esphome/components/ade7953_i2c/sensor.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import ade7953_base, i2c
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 AUTO_LOAD = ["ade7953_base"]
@@ -20,7 +21,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await i2c.register_i2c_device(var, config)
     await ade7953_base.register_ade7953(var, config)

esphome/components/ade7953_spi/sensor.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import ade7953_base, spi
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["spi"]
 AUTO_LOAD = ["ade7953_base"]
@@ -20,7 +21,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await spi.register_spi_device(var, config)
     await ade7953_base.register_ade7953(var, config)

esphome/components/ads1115/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import i2c
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 MULTI_CONF = True
@@ -24,7 +25,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/ads1115/sensor/__init__.py

@@ -11,6 +11,7 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_VOLT,
 )
+from esphome.types import ConfigType
 
 from .. import CONF_ADS1115_ID, ADS1115Component, ads1115_ns
 
@@ -86,7 +87,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await sensor.register_sensor(var, config)
     await cg.register_component(var, config)

esphome/components/ads1118/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import spi
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@solomondg1"]
 DEPENDENCIES = ["spi"]
@@ -23,7 +24,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await spi.register_spi_device(var, config)

esphome/components/ads1118/sensor/__init__.py

@@ -11,6 +11,7 @@ from esphome.const import (
     UNIT_CELSIUS,
     UNIT_VOLT,
 )
+from esphome.types import ConfigType
 
 from .. import ADS1118, CONF_ADS1118_ID, ads1118_ns
 
@@ -86,7 +87,7 @@ CONFIG_SCHEMA = cv.typed_schema(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await sensor.new_sensor(config)
     await cg.register_component(var, config)
     await cg.register_parented(var, config[CONF_ADS1118_ID])

esphome/components/ags10/sensor.py

@@ -17,6 +17,9 @@ from esphome.const import (
     UNIT_OHM,
     UNIT_PARTS_PER_BILLION,
 )
+from esphome.core import ID
+from esphome.cpp_generator import MockObj, TemplateArgsType
+from esphome.types import ConfigType
 
 CONF_RESISTANCE = "resistance"
 
@@ -62,7 +65,7 @@ CONFIG_SCHEMA = (
 FINAL_VALIDATE_SCHEMA = i2c.final_validate_device_schema("ags10", max_frequency="15khz")
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)
@@ -94,7 +97,12 @@ AGS10_NEW_I2C_ADDRESS_SCHEMA = cv.maybe_simple_value(
     AGS10_NEW_I2C_ADDRESS_SCHEMA,
     synchronous=True,
 )
-async def ags10newi2caddress_to_code(config, action_id, template_arg, args):
+async def ags10newi2caddress_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])
     address = await cg.templatable(config[CONF_ADDRESS], args, cg.uint8)
@@ -126,7 +134,12 @@ AGS10_SET_ZERO_POINT_SCHEMA = cv.Schema(
     AGS10_SET_ZERO_POINT_SCHEMA,
     synchronous=True,
 )
-async def ags10setzeropoint_to_code(config, action_id, template_arg, args):
+async def ags10setzeropoint_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])
     mode = await cg.templatable(

esphome/components/aht10/sensor.py

@@ -12,6 +12,7 @@ from esphome.const import (
     UNIT_CELSIUS,
     UNIT_PERCENT,
 )
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 
@@ -50,7 +51,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/aic3204/audio_dac.py

@@ -4,6 +4,9 @@ from esphome.components import i2c
 from esphome.components.audio_dac import AudioDac
 import esphome.config_validation as cv
 from esphome.const import CONF_ID, CONF_MODE
+from esphome.core import ID
+from esphome.cpp_generator import MockObj, TemplateArgsType
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@kbx81"]
 DEPENDENCIES = ["i2c"]
@@ -39,7 +42,12 @@ SET_AUTO_MUTE_ACTION_SCHEMA = cv.maybe_simple_value(
     SET_AUTO_MUTE_ACTION_SCHEMA,
     synchronous=True,
 )
-async def aic3204_set_volume_to_code(config, action_id, template_arg, args):
+async def aic3204_set_volume_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     paren = await cg.get_variable(config[CONF_ID])
     var = cg.new_Pvariable(action_id, template_arg, paren)
 
@@ -49,7 +57,7 @@ async def aic3204_set_volume_to_code(config, action_id, template_arg, args):
     return var
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/airthings_ble/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import ble_device_base
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 AUTO_LOAD = ["ble_device_base"]
 CODEOWNERS = ["@jeromelaban"]
@@ -21,6 +22,6 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await ble_device_base.register_ble_device(var, config)

esphome/components/airthings_wave_base/__init__.py

@@ -20,6 +20,8 @@ from esphome.const import (
     UNIT_PERCENT,
     UNIT_VOLT,
 )
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@ncareau", "@jeromelaban"]
 
@@ -78,7 +80,7 @@ BASE_SCHEMA = (
 )
 
 
-async def wave_base_to_code(var, config):
+async def wave_base_to_code(var: MockObj, config: ConfigType) -> None:
     await cg.register_component(var, config)
 
     await ble_client.register_ble_node(var, config)

esphome/components/airthings_wave_mini/sensor.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import airthings_wave_base
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 DEPENDENCIES = airthings_wave_base.DEPENDENCIES
 
@@ -20,6 +21,6 @@ CONFIG_SCHEMA = airthings_wave_base.BASE_SCHEMA.extend(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await airthings_wave_base.wave_base_to_code(var, config)

esphome/components/airthings_wave_plus/sensor.py

@@ -83,7 +83,7 @@ CONFIG_SCHEMA = cv.All(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await airthings_wave_base.wave_base_to_code(var, config)
 

esphome/components/alpha3/sensor.py

@@ -20,6 +20,7 @@ from esphome.const import (
     UNIT_VOLT,
     UNIT_WATT,
 )
+from esphome.types import ConfigType
 
 alpha3_ns = cg.esphome_ns.namespace("alpha3")
 Alpha3 = alpha3_ns.class_("Alpha3", ble_client.BLEClientNode, cg.PollingComponent)
@@ -68,7 +69,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await ble_client.register_ble_node(var, config)

esphome/components/am2315c/sensor.py

@@ -11,6 +11,7 @@ from esphome.const import (
     UNIT_CELSIUS,
     UNIT_PERCENT,
 )
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 
@@ -40,7 +41,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/am2320/sensor.py

@@ -11,6 +11,7 @@ from esphome.const import (
     UNIT_CELSIUS,
     UNIT_PERCENT,
 )
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 
@@ -42,7 +43,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/am43/cover/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import ble_client, cover
 import esphome.config_validation as cv
 from esphome.const import CONF_PIN
+from esphome.types import ConfigType
 
 CODEOWNERS = ["@buxtronix"]
 DEPENDENCIES = ["ble_client"]
@@ -27,7 +28,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await cover.new_cover(config)
     cg.add(var.set_pin(config[CONF_PIN]))
     cg.add(var.set_invert_position(config[CONF_INVERT_POSITION]))

esphome/components/am43/sensor/__init__.py

@@ -11,6 +11,7 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_PERCENT,
 )
+from esphome.types import ConfigType
 
 AUTO_LOAD = ["am43"]
 CODEOWNERS = ["@buxtronix"]
@@ -42,7 +43,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await ble_client.register_ble_node(var, config)

esphome/components/analog_threshold/binary_sensor.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import binary_sensor, sensor
 import esphome.config_validation as cv
 from esphome.const import CONF_SENSOR_ID, CONF_THRESHOLD
+from esphome.types import ConfigType
 
 analog_threshold_ns = cg.esphome_ns.namespace("analog_threshold")
 
@@ -32,7 +33,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await binary_sensor.new_binary_sensor(config)
     await cg.register_component(var, config)
 

esphome/components/animation/__init__.py

@@ -13,8 +13,13 @@
 import esphome.components.image as espImage
 import esphome.config_validation as cv
 
+from . import image as animation_image
 from .image import ANIMATION_CONFIG_SCHEMA, setup_animation
 
+# The deprecated top-level `animation:` shim gets the same batched
+# downloads as the `image:` platform form.
+PREFETCH_FILES = animation_image.PREFETCH_FILES
+
 AUTO_LOAD = ["image", "file"]
 CODEOWNERS = ["@syndlex"]
 DEPENDENCIES = ["display"]

esphome/components/animation/image.py

@@ -1,13 +1,20 @@
 from esphome import automation
 import esphome.codegen as cg
 from esphome.components.const import CONF_LOOP
+from esphome.components.file import image as file_image
 from esphome.components.file.image import image_schema, write_image
 from esphome.components.image import Image_, validate_settings
 import esphome.config_validation as cv
 from esphome.const import CONF_ID, CONF_REPEAT
+from esphome.core import ID
+from esphome.cpp_generator import MockObj, TemplateArgsType
 from esphome.types import ConfigType
 
 CODEOWNERS = ["@syndlex"]
+
+# The animation platform shares the file platform's remote file handling,
+# including its batch-download hook.
+PREFETCH_FILES = file_image.PREFETCH_FILES
 AUTO_LOAD = ["file"]
 DEPENDENCIES = ["display"]
 
@@ -74,7 +81,12 @@ SET_FRAME_SCHEMA = cv.Schema(
 @automation.register_action(
     "animation.set_frame", SetFrameAction, SET_FRAME_SCHEMA, synchronous=True
 )
-async def animation_action_to_code(config, action_id, template_arg, args):
+async def animation_action_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     paren = await cg.get_variable(config[CONF_ID])
     var = cg.new_Pvariable(action_id, template_arg, paren)
 

esphome/components/anova/climate.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import ble_client, climate
 import esphome.config_validation as cv
 from esphome.const import CONF_UNIT_OF_MEASUREMENT
+from esphome.types import ConfigType
 
 UNITS = {
     "f": "f",
@@ -28,7 +29,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await climate.new_climate(config)
     await cg.register_component(var, config)
     await ble_client.register_ble_node(var, config)

esphome/components/apds9306/sensor.py

@@ -1,6 +1,8 @@
 # Based on this datasheet:
 # https://www.mouser.ca/datasheet/2/678/AVGO_S_A0002854364_1-2574547.pdf
 
+from typing import Any
+
 import esphome.codegen as cg
 from esphome.components import i2c, sensor
 import esphome.config_validation as cv
@@ -11,6 +13,8 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_LUX,
 )
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 
@@ -55,7 +59,7 @@ AMBIENT_LIGHT_GAINS = {
 }
 
 
-def _validate_measurement_rate(value):
+def _validate_measurement_rate(value: Any) -> MockObj:
     value = cv.positive_time_period_milliseconds(value)
     return cv.enum(MEASUREMENT_RATES, int=True)(value.total_milliseconds)
 
@@ -85,7 +89,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = await sensor.new_sensor(config)
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/apds9960/__init__.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import i2c
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.types import ConfigType
 
 DEPENDENCIES = ["i2c"]
 MULTI_CONF = True
@@ -57,7 +58,7 @@ CONFIG_SCHEMA = (
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
     await cg.register_component(var, config)
     await i2c.register_i2c_device(var, config)

esphome/components/apds9960/binary_sensor.py

@@ -2,6 +2,7 @@ import esphome.codegen as cg
 from esphome.components import binary_sensor
 import esphome.config_validation as cv
 from esphome.const import CONF_DIRECTION, DEVICE_CLASS_MOVING
+from esphome.types import ConfigType
 
 from . import APDS9960, CONF_APDS9960_ID
 
@@ -19,7 +20,7 @@ CONFIG_SCHEMA = binary_sensor.binary_sensor_schema(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     hub = await cg.get_variable(config[CONF_APDS9960_ID])
     var = await binary_sensor.new_binary_sensor(config)
     func = getattr(hub, f"set_{config[CONF_DIRECTION]}_direction_binary_sensor")

esphome/components/apds9960/sensor.py

@@ -7,6 +7,7 @@ from esphome.const import (
     STATE_CLASS_MEASUREMENT,
     UNIT_PERCENT,
 )
+from esphome.types import ConfigType
 
 from . import APDS9960, CONF_APDS9960_ID
 
@@ -27,7 +28,7 @@ CONFIG_SCHEMA = sensor.sensor_schema(
 )
 
 
-async def to_code(config):
+async def to_code(config: ConfigType) -> None:
     hub = await cg.get_variable(config[CONF_APDS9960_ID])
     var = await sensor.new_sensor(config)
     func = getattr(hub, f"set_{config[CONF_TYPE]}_sensor")

esphome/components/api/__init__.py

@@ -1,11 +1,22 @@
-import base64
 import logging
+import re
+from typing import Any
 
 from esphome import automation
 from esphome.automation import Condition
 import esphome.codegen as cg
+from esphome.components.const import CONF_DESCRIPTION, CONF_HOST
 from esphome.components.logger import request_log_listener
-from esphome.config_helpers import get_logger_level
+
+# ENCRYPTION_SCHEMA and validate_encryption_key are re-exported for external
+# components and downstream consumers that import them from api
+from esphome.components.noise import (  # noqa: F401
+    ENCRYPTION_SCHEMA,
+    decode_encryption_key,
+    encryption_schema,
+    validate_encryption_key,
+)
+from esphome.config_helpers import filter_source_files_from_defines, get_logger_level
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_ACTION,
@@ -13,6 +24,8 @@ from esphome.const import (
     CONF_CAPTURE_RESPONSE,
     CONF_DATA,
     CONF_DATA_TEMPLATE,
+    CONF_DELAY,
+    CONF_ENABLE_IPV6,
     CONF_ENCRYPTION,
     CONF_EVENT,
     CONF_ID,
@@ -31,12 +44,19 @@ from esphome.const import (
     CONF_TAG,
     CONF_THEN,
     CONF_TRIGGER_ID,
+    CONF_TYPE,
     CONF_VARIABLES,
 )
 from esphome.core import CORE, ID, CoroPriority, EsphomeError, coroutine_with_priority
 from esphome.cpp_generator import MockObj, TemplateArgsType
+import esphome.final_validate as fv
+from esphome.helpers import fnv1_hash
 from esphome.types import ConfigFragmentType, ConfigType
 
+# Compat alias: downstream consumers (e.g. device-builder) referenced the
+# schema by its old private name before it moved to the noise component
+_encryption_schema = encryption_schema
+
 _LOGGER = logging.getLogger(__name__)
 
 DOMAIN = "api"
@@ -45,9 +65,15 @@ CODEOWNERS = ["@esphome/core"]
 
 
 def AUTO_LOAD(config: ConfigType) -> list[str]:
-    """Conditionally auto-load json only when capture_response is used."""
+    """Conditionally auto-load noise (encryption) and json (capture_response)."""
     base = ["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
+    if not config or CONF_ENCRYPTION in config:
+        base = base + ["noise"]
+
     # Check if any homeassistant.action/homeassistant.service has capture_response: true
     # This flag is set during config validation in _validate_response_config
     if not config or CORE.data.get(DOMAIN, {}).get(CONF_CAPTURE_RESPONSE, False):
@@ -105,10 +131,12 @@ SERVICE_ARG_FALLBACK_TYPES: dict[str, MockObj] = {
 }
 CONF_BATCH_DELAY = "batch_delay"
 CONF_CUSTOM_SERVICES = "custom_services"
+CONF_EXAMPLE = "example"
 CONF_HOMEASSISTANT_SERVICES = "homeassistant_services"
 CONF_HOMEASSISTANT_STATES = "homeassistant_states"
 CONF_LISTEN_BACKLOG = "listen_backlog"
 CONF_MAX_SEND_QUEUE = "max_send_queue"
+CONF_OUTGOING_CONNECTION = "outgoing_connection"
 CONF_STATE_SUBSCRIPTION_ONLY = "state_subscription_only"
 
 
@@ -129,20 +157,6 @@ def _register_provisioning_source(config: ConfigType) -> ConfigType:
     return config
 
 
-def validate_encryption_key(value):
-    value = cv.string_strict(value)
-    try:
-        decoded = base64.b64decode(value, validate=True)
-    except ValueError as err:
-        raise cv.Invalid("Invalid key format, please check it's using base64") from err
-
-    if len(decoded) != 32:
-        raise cv.Invalid("Encryption key must be base64 and 32 bytes long")
-
-    # Return original data for roundtrip conversion
-    return value
-
-
 CONF_SUPPORTS_RESPONSE = "supports_response"
 
 # Enum values in api::enums namespace
@@ -217,19 +231,35 @@ def _auto_detect_supports_response(config: ConfigType) -> ConfigType:
     return config
 
 
-def _validate_supports_response(value):
+def _validate_supports_response(value: Any) -> str:
     """Validate supports_response after auto-detection has set the value."""
     return cv.enum(SUPPORTS_RESPONSE_OPTIONS, lower=True)(value)
 
 
+# ESP8266 copies every string of an action into a stack buffer sized by codegen; keep it small
+ESP8266_ACTION_STRINGS_MAX_TOTAL = 384
+
+VARIABLE_SCHEMA = cv.Schema(
+    {
+        cv.Required(CONF_TYPE): cv.one_of(*SERVICE_ARG_NATIVE_TYPES, lower=True),
+        cv.Optional(CONF_DESCRIPTION): cv.string_strict,
+        cv.Optional(CONF_EXAMPLE): cv.string_strict,
+    }
+)
+
+# Accepts the plain `name: type` shorthand or the full mapping form
+validate_variable = cv.maybe_simple_value(VARIABLE_SCHEMA, key=CONF_TYPE)
+
+
 ACTIONS_SCHEMA = automation.validate_automation(
     {
         cv.GenerateID(CONF_TRIGGER_ID): cv.declare_id(UserServiceTrigger),
         cv.Exclusive(CONF_SERVICE, group_of_exclusion=CONF_ACTION): cv.valid_name,
         cv.Exclusive(CONF_ACTION, group_of_exclusion=CONF_ACTION): cv.valid_name,
+        cv.Optional(CONF_DESCRIPTION): cv.string_strict,
         cv.Optional(CONF_VARIABLES, default={}): cv.Schema(
             {
-                cv.validate_id_name: cv.one_of(*SERVICE_ARG_NATIVE_TYPES, lower=True),
+                cv.validate_id_name: validate_variable,
             }
         ),
         # No default - auto-detected by _auto_detect_supports_response
@@ -249,18 +279,6 @@ ACTIONS_SCHEMA = automation.validate_automation(
     ),
 )
 
-ENCRYPTION_SCHEMA = cv.Schema(
-    {
-        cv.Optional(CONF_KEY): cv.sensitive(validate_encryption_key),
-    }
-)
-
-
-def _encryption_schema(config):
-    if config is None:
-        config = {}
-    return ENCRYPTION_SCHEMA(config)
-
 
 def _consume_api_sockets(config: ConfigType) -> ConfigType:
     """Register socket needs for API component."""
@@ -270,9 +288,53 @@ def _consume_api_sockets(config: ConfigType) -> ConfigType:
     # (not max_connections, which is the upper limit rarely reached)
     socket.consume_sockets(3, "api")(config)
     socket.consume_sockets(1, "api", socket.SocketType.TCP_LISTEN)(config)
+    if CONF_OUTGOING_CONNECTION in config:
+        socket.consume_sockets(1, "api_outgoing_connection")(config)
     return config
 
 
+def _validate_outgoing_connection(config: ConfigType) -> ConfigType:
+    if CONF_OUTGOING_CONNECTION not in config:
+        return config
+    # Platform default check here for a friendly early error; an explicit
+    # lwip_tcp selection on other platforms is caught against the resolved
+    # implementation in _validate_outgoing_socket_implementation
+    if CORE.is_esp8266 or CORE.is_rp2:
+        raise cv.Invalid(
+            "outgoing_connection is not supported on this platform because its "
+            "socket layer cannot make outgoing connections",
+            path=[CONF_OUTGOING_CONNECTION],
+        )
+    if CONF_ENCRYPTION not in config:
+        raise cv.Invalid(
+            "outgoing_connection requires 'encryption' so the peer is verified by key",
+            path=[CONF_OUTGOING_CONNECTION],
+        )
+    return config
+
+
+_OUTGOING_CONNECTION_SCHEMA = cv.Schema(
+    {
+        cv.Optional(CONF_HOST): cv.ipaddress,
+        cv.Optional(CONF_PORT, default=6054): cv.port,
+        # Bounded to half the device's uint32 millisecond range so the wait
+        # always elapses under a wrapping clock
+        cv.Optional(CONF_DELAY, default="60s"): cv.All(
+            cv.positive_time_period_milliseconds,
+            cv.Range(max=cv.TimePeriod(milliseconds=2147483647)),
+        ),
+    }
+)
+
+
+def _outgoing_connection_schema(config: ConfigType | None) -> ConfigType:
+    # A bare `outgoing_connection:` block is valid; without a host the device
+    # dials the remembered last dial-back client
+    if config is None:
+        config = {}
+    return _OUTGOING_CONNECTION_SCHEMA(config)
+
+
 CONFIG_SCHEMA = cv.All(
     cv.Schema(
         {
@@ -296,7 +358,8 @@ CONFIG_SCHEMA = cv.All(
                 CONF_SERVICES, group_of_exclusion=CONF_ACTIONS
             ): ACTIONS_SCHEMA,
             cv.Exclusive(CONF_ACTIONS, group_of_exclusion=CONF_ACTIONS): ACTIONS_SCHEMA,
-            cv.Optional(CONF_ENCRYPTION): _encryption_schema,
+            cv.Optional(CONF_ENCRYPTION): encryption_schema,
+            cv.Optional(CONF_OUTGOING_CONNECTION): _outgoing_connection_schema,
             cv.Optional(CONF_BATCH_DELAY, default="100ms"): cv.All(
                 cv.positive_time_period_milliseconds,
                 cv.Range(max=cv.TimePeriod(milliseconds=65535)),
@@ -353,11 +416,131 @@ CONFIG_SCHEMA = cv.All(
         }
     ).extend(cv.COMPONENT_SCHEMA),
     cv.rename_key(CONF_SERVICES, CONF_ACTIONS),
+    _validate_outgoing_connection,
     _consume_api_sockets,
     _register_provisioning_source,
 )
 
 
+def _has_action_metadata(actions: list[ConfigType]) -> bool:
+    # Empty strings count as unset, matching _action_strings
+    return any(
+        conf.get(CONF_DESCRIPTION)
+        or any(
+            var_.get(CONF_DESCRIPTION) or var_.get(CONF_EXAMPLE)
+            for var_ in conf[CONF_VARIABLES].values()
+        )
+        for conf in actions
+    )
+
+
+def _action_strings(conf: ConfigType, has_metadata: bool) -> list[str | None]:
+    """Strings of one action in the table order UserServiceStatic (user_services.h) expects."""
+    # An empty description or example is treated as unset
+    strings: list[str | None] = [conf[CONF_ACTION]]
+    if has_metadata:
+        strings.append(conf.get(CONF_DESCRIPTION) or None)
+    for name, var_ in conf[CONF_VARIABLES].items():
+        strings.append(name)
+        if has_metadata:
+            strings += [
+                var_.get(CONF_DESCRIPTION) or None,
+                var_.get(CONF_EXAMPLE) or None,
+            ]
+    return strings
+
+
+def _action_strings_size(strings: list[str | None]) -> int:
+    """Bytes needed to copy every string out of flash, each with its terminator."""
+    return sum(
+        len(string.encode("utf-8")) + 1 for string in strings if string is not None
+    )
+
+
+def _validate_esp8266_action_strings(config: ConfigType) -> ConfigType:
+    if not CORE.is_esp8266:
+        return config
+    actions = config.get(CONF_ACTIONS, [])
+    has_metadata = _has_action_metadata(actions)
+    for conf in actions:
+        size = _action_strings_size(_action_strings(conf, has_metadata))
+        if size > ESP8266_ACTION_STRINGS_MAX_TOTAL:
+            raise cv.Invalid(
+                f"Action '{conf[CONF_ACTION]}' has {size} bytes of name, variable name, "
+                f"description and example text; ESP8266 allows at most "
+                f"{ESP8266_ACTION_STRINGS_MAX_TOTAL} bytes per action"
+            )
+    return config
+
+
+def _validate_outgoing_socket_implementation(config: ConfigType) -> ConfigType:
+    """A raw lwip_tcp socket can be selected explicitly on any platform."""
+    if CONF_OUTGOING_CONNECTION not in config:
+        return config
+    from esphome.components import socket
+
+    socket_conf = fv.full_config.get().get("socket") or {}
+    if (
+        impl := socket_conf.get(socket.CONF_IMPLEMENTATION)
+    ) in socket.IMPLEMENTATIONS_WITHOUT_CONNECT:
+        raise cv.Invalid(
+            f"outgoing_connection is not supported with the {impl} socket "
+            "implementation because it cannot make outgoing connections",
+            path=[CONF_OUTGOING_CONNECTION],
+        )
+    return config
+
+
+def _validate_outgoing_host_ipv6(config: ConfigType) -> ConfigType:
+    """An IPv6 host can never be parsed, so never dialed, without IPv6."""
+    if (
+        (outgoing := config.get(CONF_OUTGOING_CONNECTION)) is None
+        or (host := outgoing.get(CONF_HOST)) is None
+        or host.version != 6
+    ):
+        return config
+    network_conf = fv.full_config.get().get("network") or {}
+    if not network_conf.get(CONF_ENABLE_IPV6):
+        raise cv.Invalid(
+            "outgoing_connection host is an IPv6 address but IPv6 is not "
+            "enabled; set 'network: enable_ipv6: true'",
+            path=[CONF_OUTGOING_CONNECTION, CONF_HOST],
+        )
+    return config
+
+
+FINAL_VALIDATE_SCHEMA = cv.All(
+    _validate_esp8266_action_strings,
+    _validate_outgoing_socket_implementation,
+    _validate_outgoing_host_ipv6,
+)
+
+
+def _add_action_strings(
+    index: int, strings: list[str | None], interned: dict[str, MockObj]
+) -> MockObj:
+    """Emit the PROGMEM string table for one action.
+
+    Each string is its own PROGMEM array because on ESP8266 .rodata is RAM, and identical
+    strings are shared between actions through `interned`.
+    """
+    entries: list[MockObj] = []
+    for string in strings:
+        if string is None:
+            entries.append(cg.nullptr)
+            continue
+        if (var := interned.get(string)) is None:
+            var = interned[string] = cg.progmem_array(
+                ID(f"api_action_str{len(interned)}", is_declaration=True, type=cg.char),
+                string,
+            )
+        entries.append(var)
+    return cg.progmem_array(
+        ID(f"api_action{index}_strings", is_declaration=True, type=cg.const_char_ptr),
+        entries,
+    )
+
+
 @coroutine_with_priority(CoroPriority.WEB)
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
@@ -377,8 +560,10 @@ async def to_code(config: ConfigType) -> None:
     cg.add_define("MAX_API_CONNECTIONS", config[CONF_MAX_CONNECTIONS])
     cg.add_define("API_MAX_SEND_QUEUE", config[CONF_MAX_SEND_QUEUE])
 
+    actions = config.get(CONF_ACTIONS, [])
+    has_user_actions = bool(actions) or config[CONF_CUSTOM_SERVICES]
     # Set USE_API_USER_DEFINED_ACTIONS if any services are enabled
-    if config.get(CONF_ACTIONS) or config[CONF_CUSTOM_SERVICES]:
+    if has_user_actions:
         cg.add_define("USE_API_USER_DEFINED_ACTIONS")
 
     # Set USE_API_CUSTOM_SERVICES if external components need dynamic service registration
@@ -391,10 +576,17 @@ async def to_code(config: ConfigType) -> None:
     if config[CONF_HOMEASSISTANT_STATES]:
         cg.add_define("USE_API_HOMEASSISTANT_STATES")
 
-    if actions := config.get(CONF_ACTIONS, []):
+    scratch_size = 0
+    if actions:
+        # Metadata is compiled in for every action once any action declares it, because the
+        # string table layout is fixed by the define rather than per action
+        has_metadata = _has_action_metadata(actions)
+        if has_metadata:
+            cg.add_define("USE_API_USER_DEFINED_ACTION_METADATA")
+        interned_strings: dict[str, MockObj] = {}
         # Collect all triggers first, then register all at once with initializer_list
-        triggers: list[cg.Pvariable] = []
-        for conf in actions:
+        triggers: list[cg.MockObj] = []
+        for index, conf in enumerate(actions):
             func_args: list[tuple[MockObj, str]] = []
             service_template_args: list[MockObj] = []  # User service argument types
 
@@ -427,22 +619,23 @@ async def to_code(config: ConfigType) -> None:
                 conf.get(CONF_THEN, [])
             )
 
-            service_arg_names: list[str] = []
             for name, var_ in conf[CONF_VARIABLES].items():
-                if has_non_synchronous and var_ in SERVICE_ARG_FALLBACK_TYPES:
-                    native = SERVICE_ARG_FALLBACK_TYPES[var_]
+                var_type = var_[CONF_TYPE]
+                if has_non_synchronous and var_type in SERVICE_ARG_FALLBACK_TYPES:
+                    native = SERVICE_ARG_FALLBACK_TYPES[var_type]
                 else:
-                    native = SERVICE_ARG_NATIVE_TYPES[var_]
+                    native = SERVICE_ARG_NATIVE_TYPES[var_type]
                 service_template_args.append(native)
                 func_args.append((native, name))
-                service_arg_names.append(name)
+            strings = _action_strings(conf, has_metadata)
+            table = _add_action_strings(index, strings, interned_strings)
+            if CORE.is_esp8266:
+                scratch_size = max(scratch_size, _action_strings_size(strings))
             # Template args: supports_response mode, then user service arg types
             templ = cg.TemplateArguments(supports_response, *service_template_args)
+            # Key is hashed here because the name is not readable at runtime on ESP8266
             trigger = cg.new_Pvariable(
-                conf[CONF_TRIGGER_ID],
-                templ,
-                conf[CONF_ACTION],
-                service_arg_names,
+                conf[CONF_TRIGGER_ID], templ, table, fnv1_hash(conf[CONF_ACTION])
             )
             triggers.append(trigger)
             auto = await automation.build_automation(trigger, func_args, conf)
@@ -464,6 +657,9 @@ async def to_code(config: ConfigType) -> None:
                 cg.add(auto.add_actions([unregister_action]))
         # Register all services at once - single allocation, no reallocations
         cg.add(var.initialize_user_services(triggers))
+    if CORE.is_esp8266 and has_user_actions:
+        # Stack buffer that list-entities copies PROGMEM strings into, sized for the largest action
+        cg.add_define("API_USER_ACTION_STRINGS_SCRATCH_SIZE", max(scratch_size, 1))
 
     if CONF_ON_CLIENT_CONNECTED in config:
         cg.add_define("USE_API_CLIENT_CONNECTED_TRIGGER")
@@ -483,7 +679,7 @@ 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 = base64.b64decode(key)
+            decoded = decode_encryption_key(key)
             cg.add(var.set_noise_psk(list(decoded)))
             cg.add_define("USE_API_NOISE_PSK_FROM_YAML")
         else:
@@ -497,19 +693,56 @@ async def to_code(config: ConfigType) -> None:
             # and plaintext disabled. Only a factory reset can remove it.
             cg.add_define("USE_API_PLAINTEXT")
         cg.add_define("USE_API_NOISE")
-        cg.add_library("esphome/noise-c", "0.1.11")
-        # 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")
     else:
         cg.add_define("USE_API_PLAINTEXT")
 
+    if (outgoing := config.get(CONF_OUTGOING_CONNECTION)) is not None:
+        cg.add_define("USE_API_OUTGOING_CONNECTION")
+        if (host := outgoing.get(CONF_HOST)) is not None:
+            cg.add_define("API_OUTGOING_CONNECTION_HOST", str(host))
+        cg.add_define("API_OUTGOING_CONNECTION_PORT", outgoing[CONF_PORT])
+        cg.add_define("API_OUTGOING_CONNECTION_DELAY", outgoing[CONF_DELAY])
+
     cg.add_define("USE_API")
     cg.add_global(api_ns.using)
 
 
 KEY_VALUE_SCHEMA = cv.Schema({cv.string: cv.templatable(cv.string_strict)})
 
+_ID_CALL_PROG = re.compile(r"\bid\s*\(")
+
+
+# Remove before 2027.3.0: untagged strings that look like lambda source keep
+# being compiled as lambdas during the deprecation window
+def _coerce_implicit_lambda(value: Any) -> Any:
+    if not isinstance(value, str):
+        return value
+    if cv.looks_like_returning_lambda(value):
+        _LOGGER.warning(
+            "[api] The 'variables' value '%s' looks like a lambda but is "
+            "missing the !lambda tag. It is compiled as a lambda for now but "
+            "will be sent as literal text from 2027.3.0. Add !lambda to keep "
+            "it evaluated; literal text belongs under 'data:'.",
+            value,
+        )
+        # cv.templatable runs returning_lambda on the coerced Lambda
+        return cv.lambda_(value)
+    if _ID_CALL_PROG.search(value):
+        # lambda source without a return: issue 5394's mistake class
+        _LOGGER.warning(
+            "[api] The 'variables' value '%s' is sent as literal text; wrap "
+            "it in !lambda 'return ...;' to evaluate it instead.",
+            value,
+        )
+    return value
+
+
+# Static strings or !lambda values. cv.templatable stays introspectable for
+# schema tooling; removing the shim leaves KEY_VALUE_SCHEMA.
+VARIABLES_SCHEMA = cv.Schema(
+    {cv.string: cv.All(_coerce_implicit_lambda, cv.templatable(cv.string_strict))}
+)
+
 
 def _validate_response_config(config: ConfigType) -> ConfigType:
     # Validate dependencies:
@@ -546,9 +779,7 @@ HOMEASSISTANT_ACTION_ACTION_SCHEMA = cv.All(
             ),
             cv.Optional(CONF_DATA, default={}): KEY_VALUE_SCHEMA,
             cv.Optional(CONF_DATA_TEMPLATE, default={}): KEY_VALUE_SCHEMA,
-            cv.Optional(CONF_VARIABLES, default={}): cv.Schema(
-                {cv.string: cv.returning_lambda}
-            ),
+            cv.Optional(CONF_VARIABLES, default={}): VARIABLES_SCHEMA,
             cv.Optional(CONF_RESPONSE_TEMPLATE): cv.templatable(cv.string),
             cv.Optional(CONF_CAPTURE_RESPONSE, default=False): cv.boolean,
             cv.Optional(CONF_ON_SUCCESS): automation.validate_automation(single=True),
@@ -581,7 +812,7 @@ async def homeassistant_service_to_code(
     action_id: ID,
     template_arg: cg.TemplateArguments,
     args: TemplateArgsType,
-):
+) -> MockObj:
     cg.add_define("USE_API_HOMEASSISTANT_SERVICES")
     serv = await cg.get_variable(config[CONF_ID])
     var = cg.new_Pvariable(action_id, template_arg, serv, False)
@@ -609,6 +840,8 @@ async def homeassistant_service_to_code(
     cg.add(var.init_variables(len(config[CONF_VARIABLES])))
     for key, value in config[CONF_VARIABLES].items():
         templ = await cg.templatable(value, args, None)
+        if isinstance(templ, str):
+            templ = cg.FlashStringLiteral(templ)
         cg.add(var.add_variable(cg.FlashStringLiteral(key), templ))
 
     if on_error := config.get(CONF_ON_ERROR):
@@ -647,7 +880,7 @@ async def homeassistant_service_to_code(
     return var
 
 
-def validate_homeassistant_event(value):
+def validate_homeassistant_event(value: Any) -> str:
     value = cv.string(value)
     if not value.startswith("esphome."):
         raise cv.Invalid(
@@ -663,7 +896,7 @@ HOMEASSISTANT_EVENT_ACTION_SCHEMA = cv.Schema(
         cv.Required(CONF_EVENT): validate_homeassistant_event,
         cv.Optional(CONF_DATA, default={}): KEY_VALUE_SCHEMA,
         cv.Optional(CONF_DATA_TEMPLATE, default={}): KEY_VALUE_SCHEMA,
-        cv.Optional(CONF_VARIABLES, default={}): KEY_VALUE_SCHEMA,
+        cv.Optional(CONF_VARIABLES, default={}): VARIABLES_SCHEMA,
     }
 )
 
@@ -676,7 +909,12 @@ HOMEASSISTANT_EVENT_ACTION_SCHEMA = cv.Schema(
     HOMEASSISTANT_EVENT_ACTION_SCHEMA,
     synchronous=True,
 )
-async def homeassistant_event_to_code(config, action_id, template_arg, args):
+async def homeassistant_event_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     cg.add_define("USE_API_HOMEASSISTANT_SERVICES")
     serv = await cg.get_variable(config[CONF_ID])
     var = cg.new_Pvariable(action_id, template_arg, serv, True)
@@ -704,6 +942,8 @@ async def homeassistant_event_to_code(config, action_id, template_arg, args):
     cg.add(var.init_variables(len(config[CONF_VARIABLES])))
     for key, value in config[CONF_VARIABLES].items():
         templ = await cg.templatable(value, args, None)
+        if isinstance(templ, str):
+            templ = cg.FlashStringLiteral(templ)
         cg.add(var.add_variable(cg.FlashStringLiteral(key), templ))
 
     return var
@@ -724,7 +964,12 @@ HOMEASSISTANT_TAG_SCANNED_ACTION_SCHEMA = cv.maybe_simple_value(
     HOMEASSISTANT_TAG_SCANNED_ACTION_SCHEMA,
     synchronous=True,
 )
-async def homeassistant_tag_scanned_to_code(config, action_id, template_arg, args):
+async def homeassistant_tag_scanned_to_code(
+    config: ConfigType,
+    action_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     cg.add_define("USE_API_HOMEASSISTANT_SERVICES")
     serv = await cg.get_variable(config[CONF_ID])
     var = cg.new_Pvariable(action_id, template_arg, serv, True)
@@ -740,7 +985,7 @@ CONF_SUCCESS = "success"
 CONF_ERROR_MESSAGE = "error_message"
 
 
-def _validate_api_respond_data(config):
+def _validate_api_respond_data(config: ConfigType) -> ConfigType:
     """Set flag during validation so AUTO_LOAD can include json component."""
     if CONF_DATA in config:
         CORE.data.setdefault(DOMAIN, {})[CONF_CAPTURE_RESPONSE] = True
@@ -824,18 +1069,33 @@ API_CONNECTED_CONDITION_SCHEMA = cv.Schema(
 @automation.register_condition(
     "api.connected", APIConnectedCondition, API_CONNECTED_CONDITION_SCHEMA
 )
-async def api_connected_to_code(config, condition_id, template_arg, args):
+async def api_connected_to_code(
+    config: ConfigType,
+    condition_id: ID,
+    template_arg: cg.TemplateArguments,
+    args: TemplateArgsType,
+) -> MockObj:
     var = cg.new_Pvariable(condition_id, template_arg)
     templ = await cg.templatable(config[CONF_STATE_SUBSCRIPTION_ONLY], args, cg.bool_)
     cg.add(var.set_state_subscription_only(templ))
     return var
 
 
+# user_services.cpp is only needed when user defined actions exist; the
+# frame helpers are fully #ifdef'd on the protocol defines set in to_code
+# (both are set when encryption is configured without a key).
+_define_filter = filter_source_files_from_defines(
+    {
+        "user_services.cpp": "USE_API_USER_DEFINED_ACTIONS",
+        "api_frame_helper_noise.cpp": "USE_API_NOISE",
+        "api_frame_helper_plaintext.cpp": "USE_API_PLAINTEXT",
+        "api_outgoing_connection.cpp": "USE_API_OUTGOING_CONNECTION",
+    }
+)
+
+
 def FILTER_SOURCE_FILES() -> list[str]:
-    """Filter out api_pb2_dump.cpp when proto message dumping is not enabled,
-    user_services.cpp when no services are defined, and protocol-specific
-    implementations based on encryption configuration."""
-    files_to_filter: list[str] = []
+    files_to_filter = _define_filter()
 
     # api_pb2_dump.cpp is only needed when HAS_PROTO_MESSAGE_DUMP is defined
     # This is a particularly large file that still needs to be opened and read
@@ -846,21 +1106,4 @@ def FILTER_SOURCE_FILES() -> list[str]:
     if get_logger_level() != "VERY_VERBOSE":
         files_to_filter.append("api_pb2_dump.cpp")
 
-    # user_services.cpp is only needed when services are defined
-    config = CORE.config.get(DOMAIN, {})
-    if config and not config.get(CONF_ACTIONS) and not config[CONF_CUSTOM_SERVICES]:
-        files_to_filter.append("user_services.cpp")
-
-    # Filter protocol-specific implementations based on encryption configuration
-    encryption_config = config.get(CONF_ENCRYPTION) if config else None
-
-    # If encryption is not configured at all, we only need plaintext
-    if encryption_config is None:
-        files_to_filter.append("api_frame_helper_noise.cpp")
-    # If encryption is configured with a key, we only need noise
-    elif encryption_config.get(CONF_KEY):
-        files_to_filter.append("api_frame_helper_plaintext.cpp")
-    # If encryption is configured but no key is provided, we need both
-    # (this allows a plaintext client to provide a noise key)
-
     return files_to_filter

esphome/components/api/api.proto

@@ -19,6 +19,7 @@ service APIConnection {
   rpc device_info (DeviceInfoRequest) returns (DeviceInfoResponse) {
     option (needs_authentication) = false;
   }
+  rpc device_capabilities (DeviceCapabilitiesRequest) returns (DeviceCapabilitiesResponse) {}
   rpc list_entities (ListEntitiesRequest) returns (void) {}
   rpc subscribe_states (SubscribeStatesRequest) returns (void) {}
   rpc subscribe_logs (SubscribeLogsRequest) returns (void) {}
@@ -111,6 +112,11 @@ message HelloRequest {
   string client_info = 1;
   uint32 api_version_major = 2;
   uint32 api_version_minor = 3;
+
+  // Set by clients that can accept connections the device opens to them
+  // (see api: outgoing_connection:). The device remembers this client's
+  // address as the target to dial when no such client is connected.
+  bool outgoing_connection_target = 4 [(field_ifdef) = "USE_API_OUTGOING_CONNECTION"];
 }
 
 // Confirmation of successful connection request.
@@ -231,6 +237,7 @@ enum SerialProxyPortType {
 message SerialProxyInfo {
   string name = 1;                    // Human-readable port name
   SerialProxyPortType port_type = 2;  // Port type (RS232, RS485)
+  uint32 configured_line_states = 3;  // Bitmask of SerialProxyLineStateFlags this instance can drive
 }
 
 // DeviceInfoResponse max_data_length values:
@@ -243,6 +250,12 @@ message SerialProxyInfo {
 //   model = 127 (core/config.BOARD_MAX_LENGTH, validated in platform schemas)
 //   project_name/project_version = 127 (core/config.PROJECT_MAX_LENGTH)
 //   suggested_area = 120 (core/config.FRIENDLY_NAME_MAX_LEN via AREA_SCHEMA)
+//
+// Some fields below are marked "Superseded by DeviceCapabilitiesResponse". They
+// have moved to that message as of API 1.15, but are still sent here so that
+// older clients keep working. Do NOT mark them (deprecated) until the removal
+// release: in this repo (deprecated) makes the generator drop the field
+// entirely, so the device would stop sending it.
 message DeviceInfoResponse {
   option (id) = 10;
   option (source) = SOURCE_SERVER;
@@ -280,6 +293,8 @@ message DeviceInfoResponse {
 
   // Deprecated in API version 1.9
   uint32 legacy_bluetooth_proxy_version = 11 [deprecated=true, (field_ifdef) = "USE_BLUETOOTH_PROXY"];
+
+  // Superseded by DeviceCapabilitiesResponse.bluetooth_proxy as of API 1.15.
   uint32 bluetooth_proxy_feature_flags = 15 [(field_ifdef) = "USE_BLUETOOTH_PROXY"];
 
   string manufacturer = 12 [(max_data_length) = 20, (force) = true];
@@ -288,11 +303,14 @@ message DeviceInfoResponse {
 
   // Deprecated in API version 1.10
   uint32 legacy_voice_assistant_version = 14 [deprecated=true, (field_ifdef) = "USE_VOICE_ASSISTANT"];
+
+  // Superseded by DeviceCapabilitiesResponse.voice_assistant as of API 1.15.
   uint32 voice_assistant_feature_flags = 17 [(field_ifdef) = "USE_VOICE_ASSISTANT"];
 
   string suggested_area = 16 [(max_data_length) = 120, (force) = true, (field_ifdef) = "USE_AREAS"];
 
   // The Bluetooth mac address of the device. For example "AC:BC:32:89:0E:AA"
+  // Superseded by DeviceCapabilitiesResponse.bluetooth_proxy.mac_address as of API 1.15.
   string bluetooth_mac_address = 18 [(max_data_length) = 17, (force) = true, (field_ifdef) = "USE_BLUETOOTH_PROXY"];
 
   // Supports receiving and saving api encryption key
@@ -305,16 +323,80 @@ message DeviceInfoResponse {
   AreaInfo area = 22 [(field_ifdef) = "USE_AREAS"];
 
   // Indicates if Z-Wave proxy support is available and features supported
+  // Superseded by DeviceCapabilitiesResponse.zwave_proxy as of API 1.15.
   uint32 zwave_proxy_feature_flags = 23 [(field_ifdef) = "USE_ZWAVE_PROXY"];
+  // Superseded by DeviceCapabilitiesResponse.zwave_proxy as of API 1.15.
   uint32 zwave_home_id = 24 [(field_ifdef) = "USE_ZWAVE_PROXY"];
 
   // Serial proxy instance metadata
+  // Superseded by DeviceCapabilitiesResponse.serial_proxies as of API 1.15.
   repeated SerialProxyInfo serial_proxies = 25 [(field_ifdef) = "USE_SERIAL_PROXY", (fixed_array_size_define) = "SERIAL_PROXY_COUNT"];
 
   // Device is unprovisioned and accepts Noise handshakes with the well-known
   // all-zeros PSK, so the api encryption key can be provisioned without being
   // sent in plaintext (protects against passive sniffing, not active MITM)
   bool api_encryption_provisionable = 26 [(field_ifdef) = "USE_API_NOISE"];
+
+  // Device is built with the api outgoing_connection option and can open
+  // the TCP connection to a dial-back target itself
+  bool api_outgoing_connection_supported = 27 [(field_ifdef) = "USE_API_OUTGOING_CONNECTION"];
+}
+
+// ==================== DEVICE CAPABILITIES ====================
+
+// Asks the device which optional features it supports.
+//
+// This message exists so that DeviceInfoResponse does not have to keep growing
+// a flat list of feature flags. DeviceInfoResponse is served before
+// authentication, so it is limited to identity information. Capabilities are
+// only served on an authenticated connection (encrypted as well, when
+// encryption is configured).
+//
+// Clients that see api_version >= 1.15 should read these values from
+// DeviceCapabilitiesResponse and ignore the matching DeviceInfoResponse fields.
+// Older clients keep reading DeviceInfoResponse, which still carries the same
+// values, so this is not a breaking change.
+message DeviceCapabilitiesRequest {
+  option (id) = 149;
+  option (source) = SOURCE_CLIENT;
+  // Empty
+}
+
+// Each feature gets its own sub-message so that it can gain fields over time
+// without crowding the top-level field numbering.
+//
+// Note: a sub-message whose fields are all at their default value is not sent
+// at all, so the presence of a sub-message is not a reliable test for "this
+// feature is compiled in". Clients should test a value inside it, for example
+// a non-zero feature_flags, exactly as they do today with DeviceInfoResponse.
+
+message BluetoothProxyCapabilities {
+  // Bitmask of the features this proxy supports
+  uint32 feature_flags = 1;
+  // The Bluetooth mac address of the device. For example "AC:BC:32:89:0E:AA"
+  string mac_address = 2 [(max_data_length) = 17, (force) = true];
+}
+
+message VoiceAssistantCapabilities {
+  // Bitmask of the features this voice assistant supports
+  uint32 feature_flags = 1;
+}
+
+message ZWaveProxyCapabilities {
+  // Bitmask of the features this proxy supports
+  uint32 feature_flags = 1;
+  uint32 home_id = 2;
+}
+
+message DeviceCapabilitiesResponse {
+  option (id) = 150;
+  option (source) = SOURCE_SERVER;
+
+  BluetoothProxyCapabilities bluetooth_proxy = 1 [(field_ifdef) = "USE_BLUETOOTH_PROXY"];
+  VoiceAssistantCapabilities voice_assistant = 2 [(field_ifdef) = "USE_VOICE_ASSISTANT"];
+  ZWaveProxyCapabilities zwave_proxy = 3 [(field_ifdef) = "USE_ZWAVE_PROXY"];
+  repeated SerialProxyInfo serial_proxies = 4
+      [(field_ifdef) = "USE_SERIAL_PROXY", (fixed_array_size_define) = "SERIAL_PROXY_COUNT"];
 }
 
 message ListEntitiesRequest {
@@ -930,8 +1012,12 @@ message GetTimeResponse {
   option (no_delay) = true;
 
   fixed32 epoch_seconds = 1;
-  string timezone = 2;
-  ParsedTimezone parsed_timezone = 3;
+  // Deprecated in 2026.9.0: clients still send this string for older firmware,
+  // but new firmware only reads parsed_timezone. Clients older than Home
+  // Assistant 2026.3.0 that send only the string leave the device on its
+  // codegen-configured timezone (or UTC).
+  string timezone = 2 [deprecated = true];
+  ParsedTimezone parsed_timezone = 3 [(track_presence) = true];
 }
 
 // ==================== USER-DEFINES SERVICES ====================
@@ -957,6 +1043,8 @@ message ListEntitiesServicesArgument {
   option (ifdef) = "USE_API_USER_DEFINED_ACTIONS";
   string name = 1;
   ServiceArgType type = 2;
+  string description = 3 [(field_ifdef) = "USE_API_USER_DEFINED_ACTION_METADATA"];
+  string example = 4 [(field_ifdef) = "USE_API_USER_DEFINED_ACTION_METADATA"];
 }
 message ListEntitiesServicesResponse {
   option (id) = 41;
@@ -967,6 +1055,7 @@ message ListEntitiesServicesResponse {
   fixed32 key = 2 [(force) = true];
   repeated ListEntitiesServicesArgument args = 3 [(fixed_vector) = true];
   SupportsResponseType supports_response = 4;
+  string description = 5 [(field_ifdef) = "USE_API_USER_DEFINED_ACTION_METADATA"];
 }
 message ExecuteServiceArgument {
   option (ifdef) = "USE_API_USER_DEFINED_ACTIONS";
@@ -1577,7 +1666,8 @@ message ListEntitiesMediaPlayerResponse {
   bool disabled_by_default = 6;
   EntityCategory entity_category = 7;
 
-  bool supports_pause = 8;
+  // Deprecated in ESPHome 2026.9.0; use feature_flags instead.
+  bool supports_pause = 8 [deprecated = true];
 
   repeated MediaPlayerSupportedFormat supported_formats = 9;
 
@@ -1688,7 +1778,7 @@ enum BluetoothDeviceRequestType {
 message BluetoothDeviceRequest {
   option (id) = 68;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   BluetoothDeviceRequestType request_type = 2;
@@ -1699,7 +1789,7 @@ message BluetoothDeviceRequest {
 message BluetoothDeviceConnectionResponse {
   option (id) = 69;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   bool connected = 2;
@@ -1710,7 +1800,7 @@ message BluetoothDeviceConnectionResponse {
 message BluetoothGATTGetServicesRequest {
   option (id) = 70;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
 }
@@ -1754,7 +1844,7 @@ message BluetoothGATTService {
 message BluetoothGATTGetServicesResponse {
   option (id) = 71;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   repeated BluetoothGATTService services = 2;
@@ -1763,7 +1853,7 @@ message BluetoothGATTGetServicesResponse {
 message BluetoothGATTGetServicesDoneResponse {
   option (id) = 72;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
 }
@@ -1771,7 +1861,7 @@ message BluetoothGATTGetServicesDoneResponse {
 message BluetoothGATTReadRequest {
   option (id) = 73;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1780,7 +1870,7 @@ message BluetoothGATTReadRequest {
 message BluetoothGATTReadResponse {
   option (id) = 74;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1792,7 +1882,7 @@ message BluetoothGATTReadResponse {
 message BluetoothGATTWriteRequest {
   option (id) = 75;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1804,7 +1894,7 @@ message BluetoothGATTWriteRequest {
 message BluetoothGATTReadDescriptorRequest {
   option (id) = 76;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1813,7 +1903,7 @@ message BluetoothGATTReadDescriptorRequest {
 message BluetoothGATTWriteDescriptorRequest {
   option (id) = 77;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1824,7 +1914,7 @@ message BluetoothGATTWriteDescriptorRequest {
 message BluetoothGATTNotifyRequest {
   option (id) = 78;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1834,7 +1924,7 @@ message BluetoothGATTNotifyRequest {
 message BluetoothGATTNotifyDataResponse {
   option (id) = 79;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1845,13 +1935,13 @@ message BluetoothGATTNotifyDataResponse {
 message SubscribeBluetoothConnectionsFreeRequest {
   option (id) = 80;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 }
 
 message BluetoothConnectionsFreeResponse {
   option (id) = 81;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint32 free = 1;
   uint32 limit = 2;
@@ -1864,7 +1954,7 @@ message BluetoothConnectionsFreeResponse {
 message BluetoothGATTErrorResponse {
   option (id) = 82;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1874,7 +1964,7 @@ message BluetoothGATTErrorResponse {
 message BluetoothGATTWriteResponse {
   option (id) = 83;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1883,7 +1973,7 @@ message BluetoothGATTWriteResponse {
 message BluetoothGATTNotifyResponse {
   option (id) = 84;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 handle = 2;
@@ -1892,7 +1982,7 @@ message BluetoothGATTNotifyResponse {
 message BluetoothDevicePairingResponse {
   option (id) = 85;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   bool paired = 2;
@@ -1902,7 +1992,7 @@ message BluetoothDevicePairingResponse {
 message BluetoothDeviceUnpairingResponse {
   option (id) = 86;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   bool success = 2;
@@ -1918,7 +2008,7 @@ message UnsubscribeBluetoothLEAdvertisementsRequest {
 message BluetoothDeviceClearCacheResponse {
   option (id) = 88;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   bool success = 2;
@@ -2550,6 +2640,22 @@ message ZWaveProxyRequest {
   bytes data = 2;
 }
 
+enum ZWaveProxyStatus {
+  ZWAVE_PROXY_STATUS_OK = 0;             // Request completed successfully
+  ZWAVE_PROXY_STATUS_IN_USE = 1;         // Denied: another client is already subscribed
+  ZWAVE_PROXY_STATUS_NOT_SUPPORTED = 2;  // Request type not supported
+}
+
+// Acknowledges a ZWaveProxyRequest (subscribe/unsubscribe). Sent since API 1.16.
+message ZWaveProxyRequestResponse {
+  option (id) = 151;
+  option (source) = SOURCE_SERVER;
+  option (ifdef) = "USE_ZWAVE_PROXY";
+
+  ZWaveProxyRequestType type = 1;  // Which request type this responds to
+  ZWaveProxyStatus status = 2;     // Result status
+}
+
 // ==================== INFRARED ====================
 // Note: Feature and capability flag enums are defined in
 // esphome/components/infrared/infrared.h
@@ -2693,12 +2799,18 @@ message SerialProxyGetModemPinsResponse {
 
   uint32 instance = 1;          // Instance index (0-based)
   uint32 line_states = 2;       // Bitmask of SerialProxyLineStateFlags
+  SerialProxyStatus status = 3; // INVALID_ARGUMENT if the instance index is out of range (since API 1.16)
 }
 
 enum SerialProxyRequestType {
   SERIAL_PROXY_REQUEST_TYPE_SUBSCRIBE = 0;   // Subscribe to receive data from this serial proxy instance
   SERIAL_PROXY_REQUEST_TYPE_UNSUBSCRIBE = 1; // Unsubscribe from this serial proxy instance
   SERIAL_PROXY_REQUEST_TYPE_FLUSH = 2;       // Flush the serial port (block until all TX data is sent)
+  // Values below are only valid in SerialProxyRequestResponse.type, identifying which
+  // operation is being acknowledged. Sending them in SerialProxyRequest.type is an
+  // error the device answers with INVALID_ARGUMENT.
+  SERIAL_PROXY_REQUEST_TYPE_CONFIGURE = 3;      // Acknowledges a SerialProxyConfigureRequest
+  SERIAL_PROXY_REQUEST_TYPE_SET_MODEM_PINS = 4; // Acknowledges a SerialProxySetModemPinsRequest
 }
 
 enum SerialProxyStatus {
@@ -2707,6 +2819,8 @@ enum SerialProxyStatus {
   SERIAL_PROXY_STATUS_ERROR = 2;           // Driver or hardware error
   SERIAL_PROXY_STATUS_TIMEOUT = 3;         // Timed out before TX completed
   SERIAL_PROXY_STATUS_NOT_SUPPORTED = 4;   // Request type not supported by this instance
+  SERIAL_PROXY_STATUS_PORT_IN_USE = 5;     // Denied: another client holds the port
+  SERIAL_PROXY_STATUS_INVALID_ARGUMENT = 6; // Invalid instance index or parameter value
 }
 
 // Generic request message for simple serial proxy operations
@@ -2719,7 +2833,9 @@ message SerialProxyRequest {
   SerialProxyRequestType type = 2;      // Request type
 }
 
-// Response to a SerialProxyRequest (e.g. flush completion or failure)
+// Acknowledges a serial proxy operation; the type field identifies which
+// operation is being acknowledged. Flush has been acknowledged since the
+// message was introduced; all other acknowledgements are sent since API 1.16.
 message SerialProxyRequestResponse {
   option (id) = 147;
   option (source) = SOURCE_SERVER;
@@ -2735,7 +2851,7 @@ message SerialProxyRequestResponse {
 message BluetoothSetConnectionParamsRequest {
   option (id) = 145;
   option (source) = SOURCE_CLIENT;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   uint32 min_interval = 2;  // units of 1.25ms
@@ -2747,7 +2863,7 @@ message BluetoothSetConnectionParamsRequest {
 message BluetoothSetConnectionParamsResponse {
   option (id) = 146;
   option (source) = SOURCE_SERVER;
-  option (ifdef) = "USE_BLUETOOTH_PROXY";
+  option (ifdef) = "USE_BLUETOOTH_PROXY_CONNECTIONS";
 
   uint64 address = 1;
   int32 error = 2;

esphome/components/api/api_buffer.cpp

@@ -1,13 +1,20 @@
 #include "api_buffer.h"
+#include <new>
 
 namespace esphome::api {
 
-void APIBuffer::grow_(size_t n) {
-  auto new_data = make_buffer(n);
+bool APIBuffer::grow_(size_t n) {
+  // nothrow (no zero-fill) so OOM is reportable; plain new aborts instead
+  // (NEW_OOM_ABORT on ESP8266 Arduino, exception stub on ESP-IDF).
+  // RAMAllocator is no fit here: unique_ptr needs delete[]-compatible memory.
+  std::unique_ptr<uint8_t[]> new_data(new (std::nothrow) uint8_t[n]);
+  if (new_data == nullptr)
+    return false;
   if (this->size_)
     std::memcpy(new_data.get(), this->data_.get(), this->size_);
   this->data_ = std::move(new_data);
   this->capacity_ = n;
+  return true;
 }
 
 }  // namespace esphome::api

esphome/components/api/api_buffer.h

@@ -9,16 +9,6 @@
 
 namespace esphome::api {
 
-/// Helper to use make_unique_for_overwrite where available (skips zero-fill),
-/// falling back to make_unique on older GCC (ESP8266, LibreTiny).
-inline std::unique_ptr<uint8_t[]> make_buffer(size_t n) {
-#if defined(USE_ESP8266) || defined(USE_LIBRETINY)
-  return std::make_unique<uint8_t[]>(n);
-#else
-  return std::make_unique_for_overwrite<uint8_t[]>(n);
-#endif
-}
-
 /// Byte buffer that skips zero-initialization on resize().
 ///
 /// std::vector<uint8_t>::resize() zero-fills new bytes via memset. For the
@@ -36,23 +26,23 @@ inline std::unique_ptr<uint8_t[]> make_buffer(size_t n) {
 class APIBuffer {
  public:
   void clear() { this->size_ = 0; }
-  inline void reserve(size_t n) ESPHOME_ALWAYS_INLINE {
-    if (n > this->capacity_)
-      this->grow_(n);
-  }
-  inline void resize(size_t n) ESPHOME_ALWAYS_INLINE {
-    this->reserve(n);
-    this->size_ = n;  // no zero-fill
-  }
+  /// Returns false if allocation fails; the buffer is left unchanged.
+  [[nodiscard]] inline bool reserve(size_t n) ESPHOME_ALWAYS_INLINE { return n <= this->capacity_ || this->grow_(n); }
+  /// Returns false if allocation fails; the buffer is left unchanged. No zero-fill.
+  [[nodiscard]] inline bool resize(size_t n) ESPHOME_ALWAYS_INLINE { return this->reserve_and_resize(n, n); }
   /// Reserve capacity for max(reserve_size, new_size) bytes, then set size to new_size.
   /// Single grow_ check regardless of argument order.
-  inline void reserve_and_resize(size_t reserve_size, size_t new_size) ESPHOME_ALWAYS_INLINE {
-    this->reserve(std::max(reserve_size, new_size));
+  /// Returns false if allocation fails; the buffer is left unchanged.
+  [[nodiscard]] inline bool reserve_and_resize(size_t reserve_size, size_t new_size) ESPHOME_ALWAYS_INLINE {
+    if (!this->reserve(std::max(reserve_size, new_size)))
+      return false;
     this->size_ = new_size;
+    return true;
   }
   uint8_t *data() { return this->data_.get(); }
   const uint8_t *data() const { return this->data_.get(); }
   size_t size() const { return this->size_; }
+  size_t capacity() const { return this->capacity_; }
   bool empty() const { return this->size_ == 0; }
   uint8_t &operator[](size_t i) { return this->data_[i]; }
   const uint8_t &operator[](size_t i) const { return this->data_[i]; }
@@ -64,7 +54,7 @@ class APIBuffer {
   }
 
  protected:
-  void grow_(size_t n);
+  bool grow_(size_t n);
   std::unique_ptr<uint8_t[]> data_;
   size_t size_{0};
   size_t capacity_{0};

esphome/components/api/api_connection.cpp

@@ -1,6 +1,6 @@
 #include "api_connection.h"
 #ifdef USE_API
-#include "api_connection_buffer.h"  // for encode_to_buffer / get_batch_delay_ms_ inlines
+#include "api_connection_buffer.h"  // for the APIServer-dependent APIConnection inlines
 #ifdef USE_API_NOISE
 #include "api_frame_helper_noise.h"
 #endif
@@ -23,6 +23,7 @@
 #include "esphome/core/application.h"
 #include "esphome/core/entity_base.h"
 #include "esphome/core/hal.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include "esphome/core/version.h"
 #ifdef USE_PROVISIONING
@@ -88,6 +89,13 @@ static_assert(ESPHOME_DEVICE_NAME_MAX_LEN <= 31, "Update max_data_length for nam
 static_assert(ESPHOME_FRIENDLY_NAME_MAX_LEN <= 120, "Update max_data_length for friendly_name in api.proto");
 
 static const char *const TAG = "api.connection";
+
+#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_WARN
+void log_dropped_message(const char *tag, int line, const LogString *what) {
+  esp_log_printf_(ESPHOME_LOG_LEVEL_WARN, tag, line, ESPHOME_LOG_FORMAT("%s dropped, TCP buffer full"),
+                  LOG_STR_ARG(what));
+}
+#endif
 #ifdef USE_CAMERA
 static const int CAMERA_STOP_STREAM = 5000;
 #endif
@@ -152,11 +160,6 @@ APIConnection::APIConnection(std::unique_ptr<socket::Socket> sock, APIServer *pa
 #else
 #error "No frame helper defined"
 #endif
-#ifdef USE_CAMERA
-  if (camera::Camera::instance() != nullptr) {
-    this->image_reader_ = std::unique_ptr<camera::CameraImageReader>{camera::Camera::instance()->create_image_reader()};
-  }
-#endif
 }
 
 void APIConnection::start() {
@@ -409,15 +412,15 @@ void APIConnection::finalize_iterator_sync_() {
 }
 
 void APIConnection::process_iterator_batch_(ComponentIterator &iterator) {
-  size_t initial_size = this->deferred_batch_.size();
-  size_t max_batch = MAX_INITIAL_PER_BATCH;
-  while (!iterator.completed() && (this->deferred_batch_.size() - initial_size) < max_batch) {
-    iterator.advance();
-  }
+  // Budget by remaining batch capacity so a pass cannot overfill the batch;
+  // stops early on a refused send and resumes next loop pass
+  size_t batch_size = this->deferred_batch_.size();
+  if (batch_size < MAX_INITIAL_BATCH_SIZE)
+    iterator.try_advance(MAX_INITIAL_BATCH_SIZE - batch_size);
 
-  // If the batch is full, process it immediately
-  // Note: iterator.advance() already calls schedule_batch_() via schedule_message_()
-  if (this->deferred_batch_.size() >= max_batch) {
+  // Flush immediately once enough is queued (not guaranteed every pass);
+  // partial batches go out via the batch timer or finalize_iterator_sync_()
+  if (this->deferred_batch_.size() >= MAX_INITIAL_BATCH_SIZE) {
     this->process_batch_();
   }
 }
@@ -440,7 +443,7 @@ void APIConnection::on_disconnect_response() {
 uint16_t APIConnection::fill_and_encode_entity_state(EntityBase *entity, StateResponseProtoMessage &msg,
                                                      CalculateSizeFn size_fn, MessageEncodeFn encode_fn,
                                                      APIConnection *conn, uint32_t remaining_size) {
-  msg.key = entity->get_entity_key();
+  msg.key = entity->get_object_id_hash();
 #ifdef USE_DEVICES
   msg.device_id = entity->get_device_id();
 #endif
@@ -451,7 +454,7 @@ uint16_t APIConnection::fill_and_encode_entity_info(EntityBase *entity, InfoResp
                                                     CalculateSizeFn size_fn, MessageEncodeFn encode_fn,
                                                     APIConnection *conn, uint32_t remaining_size) {
   // Set common fields that are shared by all entity types
-  msg.key = entity->get_entity_key();
+  msg.key = entity->get_object_id_hash();
 
   if (entity->has_own_name()) {
     msg.name = entity->get_name();
@@ -1096,7 +1099,6 @@ uint16_t APIConnection::try_send_media_player_info(EntityBase *entity, APIConnec
   auto *media_player = static_cast<media_player::MediaPlayer *>(entity);
   ListEntitiesMediaPlayerResponse msg;
   auto traits = media_player->get_traits();
-  msg.supports_pause = traits.get_supports_pause();
   msg.feature_flags = traits.get_feature_flags();
   for (auto &supported_format : traits.get_supported_formats()) {
     msg.supported_formats.emplace_back();
@@ -1132,6 +1134,7 @@ void APIConnection::try_send_camera_image_() {
   if (!this->image_reader_)
     return;
 
+  const auto *cam = camera::Camera::instance();
   // Send as many chunks as possible without blocking
   while (this->image_reader_->available()) {
     if (!this->helper_->can_write_without_blocking())
@@ -1141,11 +1144,11 @@ void APIConnection::try_send_camera_image_() {
     bool done = this->image_reader_->available() == to_send;
 
     CameraImageResponse msg;
-    msg.key = camera::Camera::instance()->get_entity_key();
+    msg.key = cam->get_object_id_hash();
     msg.set_data(this->image_reader_->peek_data_buffer(), to_send);
     msg.done = done;
 #ifdef USE_DEVICES
-    msg.device_id = camera::Camera::instance()->get_device_id();
+    msg.device_id = cam->get_device_id();
 #endif
 
     if (!this->send_message(msg)) {
@@ -1161,15 +1164,19 @@ void APIConnection::try_send_camera_image_() {
 void APIConnection::set_camera_state(std::shared_ptr<camera::CameraImage> image) {
   if (!this->flags_.state_subscription)
     return;
-  if (!this->image_reader_)
+  if (this->image_reader_ && this->image_reader_->available())
     return;
-  if (this->image_reader_->available())
+  if (!image->was_requested_by(esphome::camera::API_REQUESTER) && !image->was_requested_by(esphome::camera::IDLE))
     return;
-  if (image->was_requested_by(esphome::camera::API_REQUESTER) || image->was_requested_by(esphome::camera::IDLE)) {
-    this->image_reader_->set_image(std::move(image));
-    // Try to send immediately to reduce latency
-    this->try_send_camera_image_();
+  if (!this->image_reader_) {
+    // Created on the first image this connection will send, so connections
+    // that never receive one never pay for a reader. Only a registered
+    // camera's listener can reach this, so instance() is non-null here.
+    this->image_reader_ = std::unique_ptr<camera::CameraImageReader>{camera::Camera::instance()->create_image_reader()};
   }
+  this->image_reader_->set_image(std::move(image));
+  // Try to send immediately to reduce latency
+  this->try_send_camera_image_();
 }
 uint16_t APIConnection::try_send_camera_info(EntityBase *entity, APIConnection *conn, uint32_t remaining_size) {
   auto *camera = static_cast<camera::Camera *>(entity);
@@ -1196,31 +1203,28 @@ void APIConnection::on_get_time_response(const GetTimeResponse &value) {
   if (homeassistant::global_homeassistant_time != nullptr) {
     homeassistant::global_homeassistant_time->set_epoch_time(value.epoch_seconds);
 #if defined(USE_HOMEASSISTANT_TIMEZONE) && defined(USE_TIME_TIMEZONE)
-    if (!value.timezone.empty()) {
-      // Check if the sender provided pre-parsed timezone data.
-      // If std_offset is non-zero or DST rules are present, the parsed data was populated.
-      // For UTC (all zeros), string parsing produces the same result, so the fallback is equivalent.
+    // Apply only if the sender provided pre-parsed timezone data (Home Assistant 2026.3.0
+    // and newer); field presence distinguishes a genuine all-zero UTC timezone from an
+    // absent field. Older clients send only the deprecated timezone string, which is no
+    // longer decoded; for them the device keeps its codegen-configured timezone.
+    if (value.has_parsed_timezone) {
       const auto &pt = value.parsed_timezone;
-      if (pt.std_offset_seconds != 0 || pt.dst_start.type != enums::DST_RULE_TYPE_NONE) {
-        time::ParsedTimezone tz{};
-        tz.std_offset_seconds = pt.std_offset_seconds;
-        tz.dst_offset_seconds = pt.dst_offset_seconds;
-        tz.dst_start.time_seconds = pt.dst_start.time_seconds;
-        tz.dst_start.day = static_cast<uint16_t>(pt.dst_start.day);
-        tz.dst_start.type = static_cast<time::DSTRuleType>(pt.dst_start.type);
-        tz.dst_start.month = static_cast<uint8_t>(pt.dst_start.month);
-        tz.dst_start.week = static_cast<uint8_t>(pt.dst_start.week);
-        tz.dst_start.day_of_week = static_cast<uint8_t>(pt.dst_start.day_of_week);
-        tz.dst_end.time_seconds = pt.dst_end.time_seconds;
-        tz.dst_end.day = static_cast<uint16_t>(pt.dst_end.day);
-        tz.dst_end.type = static_cast<time::DSTRuleType>(pt.dst_end.type);
-        tz.dst_end.month = static_cast<uint8_t>(pt.dst_end.month);
-        tz.dst_end.week = static_cast<uint8_t>(pt.dst_end.week);
-        tz.dst_end.day_of_week = static_cast<uint8_t>(pt.dst_end.day_of_week);
-        time::set_global_tz(tz);
-      } else {
-        homeassistant::global_homeassistant_time->set_timezone(value.timezone.c_str(), value.timezone.size());
-      }
+      time::ParsedTimezone tz{};
+      tz.std_offset_seconds = pt.std_offset_seconds;
+      tz.dst_offset_seconds = pt.dst_offset_seconds;
+      tz.dst_start.time_seconds = pt.dst_start.time_seconds;
+      tz.dst_start.day = static_cast<uint16_t>(pt.dst_start.day);
+      tz.dst_start.type = static_cast<time::DSTRuleType>(pt.dst_start.type);
+      tz.dst_start.month = static_cast<uint8_t>(pt.dst_start.month);
+      tz.dst_start.week = static_cast<uint8_t>(pt.dst_start.week);
+      tz.dst_start.day_of_week = static_cast<uint8_t>(pt.dst_start.day_of_week);
+      tz.dst_end.time_seconds = pt.dst_end.time_seconds;
+      tz.dst_end.day = static_cast<uint16_t>(pt.dst_end.day);
+      tz.dst_end.type = static_cast<time::DSTRuleType>(pt.dst_end.type);
+      tz.dst_end.month = static_cast<uint8_t>(pt.dst_end.month);
+      tz.dst_end.week = static_cast<uint8_t>(pt.dst_end.week);
+      tz.dst_end.day_of_week = static_cast<uint8_t>(pt.dst_end.day_of_week);
+      time::set_global_tz(tz);
     }
 #endif
   }
@@ -1235,6 +1239,7 @@ void APIConnection::on_subscribe_bluetooth_le_advertisements_request(
 void APIConnection::on_unsubscribe_bluetooth_le_advertisements_request() {
   bluetooth_proxy::global_bluetooth_proxy->unsubscribe_api_connection(this);
 }
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
 void APIConnection::on_bluetooth_device_request(const BluetoothDeviceRequest &msg) {
   bluetooth_proxy::global_bluetooth_proxy->bluetooth_device_request(msg);
 }
@@ -1268,13 +1273,15 @@ void APIConnection::on_subscribe_bluetooth_connections_free_request() {
   }
 }
 
+void APIConnection::on_bluetooth_set_connection_params_request(const BluetoothSetConnectionParamsRequest &msg) {
+  bluetooth_proxy::global_bluetooth_proxy->bluetooth_set_connection_params(msg);
+}
+#endif
+
 void APIConnection::on_bluetooth_scanner_set_mode_request(const BluetoothScannerSetModeRequest &msg) {
   bluetooth_proxy::global_bluetooth_proxy->bluetooth_scanner_set_mode(
       msg.mode == enums::BluetoothScannerMode::BLUETOOTH_SCANNER_MODE_ACTIVE);
 }
-void APIConnection::on_bluetooth_set_connection_params_request(const BluetoothSetConnectionParamsRequest &msg) {
-  bluetooth_proxy::global_bluetooth_proxy->bluetooth_set_connection_params(msg);
-}
 #endif
 
 #ifdef USE_VOICE_ASSISTANT
@@ -1373,7 +1380,12 @@ void APIConnection::on_z_wave_proxy_frame(const ZWaveProxyFrame &msg) {
 }
 
 void APIConnection::on_z_wave_proxy_request(const ZWaveProxyRequest &msg) {
-  zwave_proxy::global_zwave_proxy->zwave_proxy_request(this, msg.type);
+  ZWaveProxyRequestResponse resp{};
+  resp.type = msg.type;
+  resp.status = zwave_proxy::global_zwave_proxy->zwave_proxy_request(this, msg.type);
+  if (!this->send_message(resp)) {
+    API_LOG_MSG_DROPPED(TAG, "Z-Wave proxy response");
+  }
 }
 #endif
 
@@ -1532,19 +1544,60 @@ void APIConnection::on_infrared_rf_transmit_raw_timings_request(const InfraredRF
 #endif
 
 #if defined(USE_IR_RF) || defined(USE_RADIO_FREQUENCY)
-void APIConnection::send_infrared_rf_receive_event(const InfraredRFReceiveEvent &msg) { this->send_message(msg); }
+void APIConnection::send_infrared_rf_receive_event(const InfraredRFReceiveEvent &msg) {
+  if (!this->send_message(msg)) {
+    // V: fires per decoded frame with no subscription gate, so a warning
+    // would flood the congested link it reports on.
+    ESP_LOGV(TAG, "IR/RF event dropped, TCP buffer full");
+  }
+}
 #endif
 
 #ifdef USE_SERIAL_PROXY
+static enums::SerialProxyStatus serial_proxy_result_to_status(serial_proxy::SerialProxyResult result) {
+  switch (result) {
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_OK:
+      return enums::SERIAL_PROXY_STATUS_OK;
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_ASSUMED_SUCCESS:
+      return enums::SERIAL_PROXY_STATUS_ASSUMED_SUCCESS;
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_PORT_IN_USE:
+      return enums::SERIAL_PROXY_STATUS_PORT_IN_USE;
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_INVALID_ARGUMENT:
+      return enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT;
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_TIMEOUT:
+      return enums::SERIAL_PROXY_STATUS_TIMEOUT;
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_NOT_SUPPORTED:
+      return enums::SERIAL_PROXY_STATUS_NOT_SUPPORTED;
+    case serial_proxy::SerialProxyResult::SERIAL_PROXY_RESULT_ERROR:
+      return enums::SERIAL_PROXY_STATUS_ERROR;
+  }
+  return enums::SERIAL_PROXY_STATUS_ERROR;  // Unreachable; all enum values handled above
+}
+
+static void send_serial_proxy_ack(APIConnection *conn, uint32_t instance, enums::SerialProxyRequestType type,
+                                  enums::SerialProxyStatus status) {
+  SerialProxyRequestResponse resp{};
+  resp.instance = instance;
+  resp.type = type;
+  resp.status = status;
+  if (!conn->send_message(resp)) {
+    API_LOG_MSG_DROPPED(TAG, "Serial proxy response");
+  }
+}
+
 void APIConnection::on_serial_proxy_configure_request(const SerialProxyConfigureRequest &msg) {
   auto &proxies = App.get_serial_proxies();
   if (msg.instance >= proxies.size()) {
     ESP_LOGW(TAG, "Serial proxy instance %" PRIu32 " out of range (max %" PRIu32 ")", msg.instance,
              static_cast<uint32_t>(proxies.size()));
+    send_serial_proxy_ack(this, msg.instance, enums::SERIAL_PROXY_REQUEST_TYPE_CONFIGURE,
+                          enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT);
     return;
   }
-  proxies[msg.instance]->configure(this, msg.baudrate, msg.flow_control, static_cast<uint8_t>(msg.parity),
-                                   msg.stop_bits, msg.data_size);
+  serial_proxy::SerialProxyResult result = proxies[msg.instance]->configure(
+      this, msg.baudrate, msg.flow_control, static_cast<uint8_t>(msg.parity), msg.stop_bits, msg.data_size);
+  send_serial_proxy_ack(this, msg.instance, enums::SERIAL_PROXY_REQUEST_TYPE_CONFIGURE,
+                        serial_proxy_result_to_status(result));
 }
 
 void APIConnection::on_serial_proxy_write_request(const SerialProxyWriteRequest &msg) {
@@ -1560,62 +1613,71 @@ void APIConnection::on_serial_proxy_set_modem_pins_request(const SerialProxySetM
   auto &proxies = App.get_serial_proxies();
   if (msg.instance >= proxies.size()) {
     ESP_LOGW(TAG, "Serial proxy instance %" PRIu32 " out of range", msg.instance);
+    send_serial_proxy_ack(this, msg.instance, enums::SERIAL_PROXY_REQUEST_TYPE_SET_MODEM_PINS,
+                          enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT);
     return;
   }
-  proxies[msg.instance]->set_modem_pins(this, msg.line_states);
+  serial_proxy::SerialProxyResult result = proxies[msg.instance]->set_modem_pins(this, msg.line_states);
+  send_serial_proxy_ack(this, msg.instance, enums::SERIAL_PROXY_REQUEST_TYPE_SET_MODEM_PINS,
+                        serial_proxy_result_to_status(result));
 }
 
 void APIConnection::on_serial_proxy_get_modem_pins_request(const SerialProxyGetModemPinsRequest &msg) {
   auto &proxies = App.get_serial_proxies();
-  if (msg.instance >= proxies.size()) {
-    ESP_LOGW(TAG, "Serial proxy instance %" PRIu32 " out of range", msg.instance);
-    return;
-  }
   SerialProxyGetModemPinsResponse resp{};
   resp.instance = msg.instance;
-  resp.line_states = proxies[msg.instance]->get_modem_pins();
-  this->send_message(resp);
+  if (msg.instance >= proxies.size()) {
+    ESP_LOGW(TAG, "Serial proxy instance %" PRIu32 " out of range", msg.instance);
+    // Pre-1.16 clients do not read the status field and would take this error
+    // for a successful "both pins deasserted" answer; let them time out as before
+    if (!this->client_supports_api_version(1, 16)) {
+      return;
+    }
+    resp.status = enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT;
+  } else {
+    resp.line_states = proxies[msg.instance]->get_modem_pins();
+  }
+  if (!this->send_message(resp)) {
+    API_LOG_MSG_DROPPED(TAG, "Serial proxy response");
+  }
 }
 
 void APIConnection::on_serial_proxy_request(const SerialProxyRequest &msg) {
   auto &proxies = App.get_serial_proxies();
   if (msg.instance >= proxies.size()) {
     ESP_LOGW(TAG, "Serial proxy instance %" PRIu32 " out of range", msg.instance);
+    send_serial_proxy_ack(this, msg.instance, msg.type, enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT);
     return;
   }
+  auto *proxy = proxies[msg.instance];
+  enums::SerialProxyStatus status;
   switch (msg.type) {
     case enums::SERIAL_PROXY_REQUEST_TYPE_SUBSCRIBE:
     case enums::SERIAL_PROXY_REQUEST_TYPE_UNSUBSCRIBE:
-      proxies[msg.instance]->serial_proxy_request(this, msg.type);
+      status = serial_proxy_result_to_status(proxy->serial_proxy_request(this, msg.type));
       break;
-    case enums::SERIAL_PROXY_REQUEST_TYPE_FLUSH: {
-      SerialProxyRequestResponse resp{};
-      resp.instance = msg.instance;
-      resp.type = enums::SERIAL_PROXY_REQUEST_TYPE_FLUSH;
-      switch (proxies[msg.instance]->flush_port()) {
-        case uart::UARTFlushResult::UART_FLUSH_RESULT_SUCCESS:
-          resp.status = enums::SERIAL_PROXY_STATUS_OK;
-          break;
-        case uart::UARTFlushResult::UART_FLUSH_RESULT_ASSUMED_SUCCESS:
-          resp.status = enums::SERIAL_PROXY_STATUS_ASSUMED_SUCCESS;
-          break;
-        case uart::UARTFlushResult::UART_FLUSH_RESULT_TIMEOUT:
-          resp.status = enums::SERIAL_PROXY_STATUS_TIMEOUT;
-          break;
-        case uart::UARTFlushResult::UART_FLUSH_RESULT_FAILED:
-          resp.status = enums::SERIAL_PROXY_STATUS_ERROR;
-          break;
-      }
-      this->send_message(resp);
+    case enums::SERIAL_PROXY_REQUEST_TYPE_FLUSH:
+      status = serial_proxy_result_to_status(proxy->flush_port(this));
+      break;
+    case enums::SERIAL_PROXY_REQUEST_TYPE_CONFIGURE:
+    case enums::SERIAL_PROXY_REQUEST_TYPE_SET_MODEM_PINS:
+      // Response-only discriminators; never valid in a request
+      ESP_LOGW(TAG, "Response-only serial proxy request type: %" PRIu32, static_cast<uint32_t>(msg.type));
+      status = enums::SERIAL_PROXY_STATUS_INVALID_ARGUMENT;
       break;
-    }
     default:
       ESP_LOGW(TAG, "Unknown serial proxy request type: %" PRIu32, static_cast<uint32_t>(msg.type));
+      status = enums::SERIAL_PROXY_STATUS_NOT_SUPPORTED;
       break;
   }
+  send_serial_proxy_ack(this, msg.instance, msg.type, status);
 }
 
-void APIConnection::send_serial_proxy_data(const SerialProxyDataReceived &msg) { this->send_message(msg); }
+void APIConnection::send_serial_proxy_data(const SerialProxyDataReceived &msg) {
+  if (!this->send_message(msg)) {
+    ESP_LOGV(TAG, "Serial proxy data dropped, TCP buffer full");
+  }
+}
 #endif
 
 #ifdef USE_INFRARED
@@ -1727,15 +1789,17 @@ void APIConnection::complete_authentication_() {
 bool APIConnection::send_hello_response_(const HelloRequest &msg) {
   // Copy client name with truncation if needed (set_client_name handles truncation)
   this->helper_->set_client_name(msg.client_info.c_str(), msg.client_info.size());
-  this->client_api_version_major_ = msg.api_version_major;
-  this->client_api_version_minor_ = msg.api_version_minor;
+  this->client_api_version_major_ =
+      static_cast<uint8_t>(std::min<uint32_t>(msg.api_version_major, std::numeric_limits<uint8_t>::max()));
+  this->client_api_version_minor_ =
+      static_cast<uint8_t>(std::min<uint32_t>(msg.api_version_minor, std::numeric_limits<uint8_t>::max()));
   char peername[socket::SOCKADDR_STR_LEN];
-  ESP_LOGV(TAG, "Hello from client: '%s' | %s | API Version %" PRIu16 ".%" PRIu16, this->helper_->get_client_name(),
+  ESP_LOGV(TAG, "Hello from client: '%s' | %s | API Version %u.%u", this->helper_->get_client_name(),
            this->helper_->get_peername_to(peername), this->client_api_version_major_, this->client_api_version_minor_);
 
   HelloResponse resp;
   resp.api_version_major = 1;
-  resp.api_version_minor = 14;
+  resp.api_version_minor = 16;
   // Send only the version string - the client only logs this for debugging and doesn't use it otherwise
   resp.server_info = ESPHOME_VERSION_REF;
   resp.name = StringRef(App.get_name());
@@ -1746,7 +1810,9 @@ bool APIConnection::send_hello_response_(const HelloRequest &msg) {
     // Acknowledge the hello so the client can read the server name, then request
     // disconnect with the reason. Authentication is intentionally not completed.
     this->log_client_(ESPHOME_LOG_LEVEL_WARN, LOG_STR("Provisioning closed; rejecting connection"));
-    this->send_message(resp);
+    if (!this->send_message(resp)) {
+      API_LOG_MSG_DROPPED(TAG, "Hello response");
+    }
     DisconnectRequest req;
     req.reason = enums::DISCONNECT_REASON_PROVISIONING_CLOSED;
     return this->send_message(req);
@@ -1756,6 +1822,19 @@ bool APIConnection::send_hello_response_(const HelloRequest &msg) {
   // Auto-authenticate - password auth was removed in ESPHome 2026.1.0
   this->complete_authentication_();
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  // With a PSK set only key-verified transports reach hello: plaintext and
+  // zero-PSK are rejected, and pre-activation sessions are force-closed
+  if (msg.outgoing_connection_target && !this->flags_.outgoing_connection_target) {
+    if (this->parent_->get_noise_ctx().has_psk()) {
+      this->flags_.outgoing_connection_target = true;
+      this->parent_->on_outgoing_target_client(this);
+    } else {
+      this->log_client_(ESPHOME_LOG_LEVEL_WARN, LOG_STR("Dial-back target refused; no key active"));
+    }
+  }
+#endif
+
   return this->send_message(resp);
 }
 
@@ -1771,9 +1850,8 @@ bool APIConnection::send_device_info_response_() {
 #ifdef USE_AREAS
   resp.suggested_area = StringRef(App.get_area());
 #endif
-  // Stack buffer for MAC address (XX:XX:XX:XX:XX:XX\0 = 18 bytes)
-  char mac_address[18];
-  uint8_t mac[6];
+  char mac_address[MAC_ADDRESS_PRETTY_BUFFER_SIZE];
+  uint8_t mac[MAC_ADDRESS_SIZE];
   get_mac_address_raw(mac);
   format_mac_addr_upper(mac, mac_address);
   resp.mac_address = StringRef(mac_address);
@@ -1849,8 +1927,7 @@ bool APIConnection::send_device_info_response_() {
 #endif
 #ifdef USE_BLUETOOTH_PROXY
   resp.bluetooth_proxy_feature_flags = bluetooth_proxy::global_bluetooth_proxy->get_feature_flags();
-  // Stack buffer for Bluetooth MAC address (XX:XX:XX:XX:XX:XX\0 = 18 bytes)
-  char bluetooth_mac[18];
+  char bluetooth_mac[MAC_ADDRESS_PRETTY_BUFFER_SIZE];
   bluetooth_proxy::global_bluetooth_proxy->get_bluetooth_mac_address_pretty(bluetooth_mac);
   resp.bluetooth_mac_address = StringRef(bluetooth_mac);
 #endif
@@ -1869,6 +1946,7 @@ bool APIConnection::send_device_info_response_() {
     auto &info = resp.serial_proxies[serial_proxy_index++];
     info.name = StringRef(proxy->get_name());
     info.port_type = proxy->get_port_type();
+    info.configured_line_states = proxy->get_configured_modem_pins();
   }
 #endif
 #ifdef USE_API_NOISE
@@ -1879,6 +1957,9 @@ bool APIConnection::send_device_info_response_() {
   // one) so this advertisement survives the plaintext removal in 2027.2.0.
   resp.api_encryption_provisionable = !this->parent_->get_noise_ctx().has_psk();
 #endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  resp.api_outgoing_connection_supported = true;
+#endif
 #endif
 #ifdef USE_DEVICES
   size_t device_index = 0;
@@ -1904,6 +1985,36 @@ bool APIConnection::send_device_info_response_() {
 
   return this->send_message(resp);
 }
+bool APIConnection::send_device_capabilities_response_() {
+  // These are the same values DeviceInfoResponse still reports for older clients. Keep the blocks
+  // below in sync with send_device_info_response_() until those copies are removed.
+  DeviceCapabilitiesResponse resp;
+#ifdef USE_BLUETOOTH_PROXY
+  resp.bluetooth_proxy.feature_flags = bluetooth_proxy::global_bluetooth_proxy->get_feature_flags();
+  char bluetooth_mac[MAC_ADDRESS_PRETTY_BUFFER_SIZE];
+  bluetooth_proxy::global_bluetooth_proxy->get_bluetooth_mac_address_pretty(bluetooth_mac);
+  resp.bluetooth_proxy.mac_address = StringRef(bluetooth_mac);
+#endif
+#ifdef USE_VOICE_ASSISTANT
+  resp.voice_assistant.feature_flags = voice_assistant::global_voice_assistant->get_feature_flags();
+#endif
+#ifdef USE_ZWAVE_PROXY
+  resp.zwave_proxy.feature_flags = zwave_proxy::global_zwave_proxy->get_feature_flags();
+  resp.zwave_proxy.home_id = zwave_proxy::global_zwave_proxy->get_home_id();
+#endif
+#ifdef USE_SERIAL_PROXY
+  size_t serial_proxy_index = 0;
+  for (auto const &proxy : App.get_serial_proxies()) {
+    if (serial_proxy_index >= SERIAL_PROXY_COUNT)
+      break;
+    auto &info = resp.serial_proxies[serial_proxy_index++];
+    info.name = StringRef(proxy->get_name());
+    info.port_type = proxy->get_port_type();
+    info.configured_line_states = proxy->get_configured_modem_pins();
+  }
+#endif
+  return this->send_message(resp);
+}
 void APIConnection::on_hello_request(const HelloRequest &msg) {
   if (!this->send_hello_response_(msg)) {
     this->on_fatal_error();
@@ -1925,6 +2036,11 @@ void APIConnection::on_device_info_request() {
     this->on_fatal_error();
   }
 }
+void APIConnection::on_device_capabilities_request() {
+  if (!this->send_device_capabilities_response_()) {
+    this->on_fatal_error();
+  }
+}
 
 #ifdef USE_API_HOMEASSISTANT_STATES
 void APIConnection::on_home_assistant_state_response(const HomeAssistantStateResponse &msg) {
@@ -2003,7 +2119,9 @@ void APIConnection::send_execute_service_response(uint32_t call_id, bool success
   resp.call_id = call_id;
   resp.success = success;
   resp.error_message = error_message;
-  this->send_message(resp);
+  if (!this->send_message(resp)) {
+    API_LOG_MSG_DROPPED(TAG, "Action response");
+  }
 }
 #ifdef USE_API_USER_DEFINED_ACTION_RESPONSES_JSON
 void APIConnection::send_execute_service_response(uint32_t call_id, bool success, StringRef error_message,
@@ -2014,12 +2132,34 @@ void APIConnection::send_execute_service_response(uint32_t call_id, bool success
   resp.error_message = error_message;
   resp.response_data = response_data;
   resp.response_data_len = response_data_len;
-  this->send_message(resp);
+  if (!this->send_message(resp)) {
+    API_LOG_MSG_DROPPED(TAG, "Action response");
+  }
 }
 #endif  // USE_API_USER_DEFINED_ACTION_RESPONSES_JSON
 #endif  // USE_API_USER_DEFINED_ACTION_RESPONSES
 #endif
 
+#ifdef USE_API_HOMEASSISTANT_SERVICES
+bool APIConnection::send_homeassistant_action(const HomeassistantActionRequest &call) {
+  if (!this->flags_.service_call_subscription)
+    return false;
+  if (!this->send_message(call)) {
+    API_LOG_MSG_DROPPED(TAG, "Action request");
+  }
+  return true;
+}
+#endif  // USE_API_HOMEASSISTANT_SERVICES
+
+#ifdef USE_HOMEASSISTANT_TIME
+void APIConnection::send_time_request() {
+  GetTimeRequest req;
+  if (!this->send_message(req)) {
+    API_LOG_MSG_DROPPED(TAG, "Time request");
+  }
+}
+#endif  // USE_HOMEASSISTANT_TIME
+
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES
 void APIConnection::on_homeassistant_action_response(const HomeassistantActionResponse &msg) {
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES_JSON
@@ -2047,7 +2187,7 @@ bool APIConnection::send_noise_encryption_set_key_response_(const NoiseEncryptio
   }
 #endif
 
-  psk_t psk{};
+  noise::psk_t psk{};
   if (msg.key_len == 0) {
     if (this->parent_->clear_noise_psk(true)) {
       resp.success = true;
@@ -2056,7 +2196,7 @@ bool APIConnection::send_noise_encryption_set_key_response_(const NoiseEncryptio
     }
   } else if (base64_decode(msg.key, msg.key_len, psk.data(), psk.size()) != psk.size()) {
     ESP_LOGW(TAG, "Invalid encryption key length");
-  } else if (APINoiseContext::is_all_zeros(psk)) {
+  } else if (noise::NoiseContext::is_all_zeros(psk)) {
     // Accepting the reserved provisioning PSK would report success without
     // enabling encryption (or silently clear an existing key)
     ESP_LOGW(TAG, "Rejecting all-zero encryption key");
@@ -2094,11 +2234,14 @@ bool APIConnection::try_to_clear_buffer_slow_(bool log_out_of_space) {
   if (this->helper_->can_write_without_blocking())
     return true;
   if (log_out_of_space) {
-    ESP_LOGV(TAG, "Cannot send message because of TCP buffer space");
+    // VV: refusals are either reported by the sending call site (naming what
+    // was lost) or retried without loss (the deferred batch), so this generic
+    // line only duplicates them.
+    ESP_LOGVV(TAG, "Cannot send message because of TCP buffer space");
   }
   return false;
 }
-bool APIConnection::send_message_(uint32_t payload_size, uint8_t message_type, MessageEncodeFn encode_fn,
+bool APIConnection::send_message_(uint32_t payload_size, uint16_t message_type, MessageEncodeFn encode_fn,
                                   const void *msg) {
 #ifdef HAS_PROTO_MESSAGE_DUMP
   // Skip dump for log messages (recursive logging risk) and camera frames (high-frequency noise)
@@ -2112,10 +2255,17 @@ bool APIConnection::send_message_(uint32_t payload_size, uint8_t message_type, M
     this->log_send_message_(proto_msg->message_name(), proto_msg->dump_to(dump_buf));
   }
 #endif
+  if (!this->prepare_first_message_buffer(payload_size)) [[unlikely]] {
+    this->fatal_out_of_memory_();
+    return false;
+  }
   auto &shared_buf = this->parent_->get_shared_buffer_ref();
-  this->prepare_first_message_buffer(shared_buf, payload_size);
   size_t write_start = shared_buf.size();
-  shared_buf.resize(write_start + payload_size);
+#ifdef ESPHOME_DEBUG_API
+  assert(shared_buf.capacity() >= write_start + payload_size);
+#endif
+  // Capacity reserved above, cannot fail
+  (void) shared_buf.resize(write_start + payload_size);
   ProtoWriteBuffer buffer{&shared_buf, write_start};
   encode_fn(msg, buffer PROTO_ENCODE_DEBUG_INIT(&shared_buf));
   return this->send_buffer(ProtoWriteBuffer{&shared_buf}, message_type);
@@ -2127,7 +2277,7 @@ uint16_t APIConnection::encode_to_buffer_slow(uint32_t calculated_size, MessageE
                                               APIConnection *conn, uint32_t remaining_size) {
   return encode_to_buffer(calculated_size, encode_fn, msg, conn, remaining_size);
 }
-bool APIConnection::send_buffer(ProtoWriteBuffer buffer, uint8_t message_type) {
+bool APIConnection::send_buffer(ProtoWriteBuffer buffer, uint16_t message_type) {
   const bool is_log_message = (message_type == SubscribeLogsResponse::MESSAGE_TYPE);
 
   if (!this->try_to_clear_buffer(!is_log_message)) {
@@ -2151,30 +2301,42 @@ void APIConnection::on_no_setup_connection() {
   this->on_fatal_error();
   this->log_client_(ESPHOME_LOG_LEVEL_DEBUG, LOG_STR("no connection setup"));
 }
+void APIConnection::fatal_out_of_memory_() {
+  this->fatal_error_with_log_(LOG_STR("Out of memory"), APIError::OUT_OF_MEMORY);
+}
 void APIConnection::on_fatal_error() {
   // Don't close socket here - keep it open so getpeername() works for logging
   // Socket will be closed when client is removed from the list in APIServer::loop()
   this->flags_.remove = true;
 }
 
-bool APIConnection::schedule_message_front_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size) {
+bool APIConnection::schedule_message_front_(EntityBase *entity, uint16_t message_type, uint8_t estimated_size) {
   this->deferred_batch_.add_item_front(entity, message_type, estimated_size);
   return this->schedule_batch_();
 }
 
-bool APIConnection::send_message_smart_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,
+bool APIConnection::send_message_smart_(EntityBase *entity, uint16_t message_type, uint8_t estimated_size,
                                         uint8_t aux_data_index) {
   if (this->should_send_immediately_(message_type) && this->helper_->can_write_without_blocking()) {
-    auto &shared_buf = this->parent_->get_shared_buffer_ref();
-    this->prepare_first_message_buffer(shared_buf, estimated_size);
+    // No local for the shared buffer here: keeping it live across
+    // dispatch_message_ costs a register and spills message_type into the
+    // batching path's dedup loop (measured on x86 GCC -Os)
+    if (!this->prepare_first_message_buffer(estimated_size)) [[unlikely]] {
+      this->fatal_out_of_memory_();
+      return false;
+    }
     DeferredBatch::BatchItem item{entity, message_type, estimated_size, aux_data_index};
     if (this->dispatch_message_(item, MAX_BATCH_PACKET_SIZE, true) &&
-        this->send_buffer(ProtoWriteBuffer{&shared_buf}, message_type)) {
+        this->send_buffer(ProtoWriteBuffer{&this->parent_->get_shared_buffer_ref()}, message_type)) {
 #ifdef HAS_PROTO_MESSAGE_DUMP
       this->log_batch_item_(item);
 #endif
       return true;
     }
+    // An OOM during the immediate attempt marks the connection for removal;
+    // don't queue more work (schedule_message_'s push_back may allocate again)
+    if (this->flags_.remove) [[unlikely]]
+      return false;
   }
   return this->schedule_message_(entity, message_type, estimated_size, aux_data_index);
 }
@@ -2224,7 +2386,11 @@ void APIConnection::process_batch_() {
     total_estimated_size = MAX_BATCH_PACKET_SIZE;
   }
 
-  this->prepare_first_message_buffer(shared_buf, header_padding, total_estimated_size);
+  if (!this->prepare_first_message_buffer(header_padding, total_estimated_size)) [[unlikely]] {
+    this->fatal_out_of_memory_();
+    this->clear_batch_();
+    return;
+  }
 
   // Fast path for single message - buffer already allocated above
   if (num_items == 1) {
@@ -2239,8 +2405,10 @@ void APIConnection::process_batch_() {
 #endif
       this->clear_batch_();
     } else if (payload_size == 0) {
-      // Message too large to fit in available space
-      ESP_LOGW(TAG, "Message too large to send: type=%u", item.message_type);
+      // payload_size == 0 with remove set means encoding hit OOM and the
+      // connection is being dropped; warn only for a genuinely oversized message
+      if (!this->flags_.remove)
+        ESP_LOGW(TAG, "Message too large to send: type=%u", item.message_type);
       this->clear_batch_();
     }
     return;
@@ -2303,8 +2471,10 @@ void APIConnection::process_batch_multi_(APIBuffer &shared_buf, size_t num_items
 
   if (items_processed > 0) {
     // Add footer space for the last message (for Noise protocol MAC)
-    if (footer_size > 0) {
-      shared_buf.resize(shared_buf.size() + footer_size);
+    if (footer_size > 0 && !shared_buf.resize(shared_buf.size() + footer_size)) [[unlikely]] {
+      this->fatal_out_of_memory_();
+      this->clear_batch_();
+      return;
     }
 
     // Send all collected messages

esphome/components/api/api_connection.h

@@ -25,6 +25,7 @@
 #include "esphome/components/esp8266/crash_handler.h"
 #endif
 #include "esphome/core/entity_base.h"
+#include "esphome/core/log.h"
 #include "esphome/core/string_ref.h"
 
 #include <functional>
@@ -40,13 +41,23 @@ namespace esphome::api {
 // Forward-declared to break the api_server.h cycle; full-type inlines are in api_connection_buffer.h.
 class APIServer;
 
+// One shared flash string for every refused-frame warning: send_message()
+// fails as soon as the TCP buffer is full, and each caller only pays for its
+// short name. The guard drops the helper and its arguments below WARN.
+#if ESPHOME_LOG_LEVEL >= ESPHOME_LOG_LEVEL_WARN
+void log_dropped_message(const char *tag, int line, const LogString *what);
+#define API_LOG_MSG_DROPPED(tag, what) esphome::api::log_dropped_message(tag, __LINE__, LOG_STR(what))
+#else
+#define API_LOG_MSG_DROPPED(tag, what)
+#endif
+
 // Keepalive timeout in milliseconds
 static constexpr uint32_t KEEPALIVE_TIMEOUT_MS = 60000;
-// Maximum number of entities to process in a single batch during initial state/info sending
-static constexpr size_t MAX_INITIAL_PER_BATCH = 34;
+// Deferred batch size cap during initial state/info sync
+static constexpr size_t MAX_INITIAL_BATCH_SIZE = 34;
 // Verify MAX_MESSAGES_PER_BATCH (defined in api_frame_helper.h) can hold the initial batch
-static_assert(MAX_MESSAGES_PER_BATCH >= MAX_INITIAL_PER_BATCH,
-              "MAX_MESSAGES_PER_BATCH must be >= MAX_INITIAL_PER_BATCH");
+static_assert(MAX_MESSAGES_PER_BATCH >= MAX_INITIAL_BATCH_SIZE,
+              "MAX_MESSAGES_PER_BATCH must be >= MAX_INITIAL_BATCH_SIZE");
 
 #ifdef USE_BENCHMARK
 class APIConnection;
@@ -169,12 +180,7 @@ class APIConnection final : public APIServerConnectionBase {
   // Returns whether this client has subscribed to Home Assistant actions; the message
   // is only handed to the send path when subscribed. A true return does not guarantee
   // delivery - it lets the caller warn when no connected client has the subscription.
-  bool send_homeassistant_action(const HomeassistantActionRequest &call) {
-    if (!this->flags_.service_call_subscription)
-      return false;
-    this->send_message(call);
-    return true;
-  }
+  bool send_homeassistant_action(const HomeassistantActionRequest &call);
 #ifdef USE_API_HOMEASSISTANT_ACTION_RESPONSES
   void on_homeassistant_action_response(const HomeassistantActionResponse &msg);
 #endif  // USE_API_HOMEASSISTANT_ACTION_RESPONSES
@@ -183,6 +189,7 @@ class APIConnection final : public APIServerConnectionBase {
   void on_subscribe_bluetooth_le_advertisements_request(const SubscribeBluetoothLEAdvertisementsRequest &msg);
   void on_unsubscribe_bluetooth_le_advertisements_request();
 
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
   void on_bluetooth_device_request(const BluetoothDeviceRequest &msg);
   void on_bluetooth_gatt_read_request(const BluetoothGATTReadRequest &msg);
   void on_bluetooth_gatt_write_request(const BluetoothGATTWriteRequest &msg);
@@ -191,15 +198,13 @@ class APIConnection final : public APIServerConnectionBase {
   void on_bluetooth_gatt_get_services_request(const BluetoothGATTGetServicesRequest &msg);
   void on_bluetooth_gatt_notify_request(const BluetoothGATTNotifyRequest &msg);
   void on_subscribe_bluetooth_connections_free_request();
-  void on_bluetooth_scanner_set_mode_request(const BluetoothScannerSetModeRequest &msg);
   void on_bluetooth_set_connection_params_request(const BluetoothSetConnectionParamsRequest &msg);
+#endif
+  void on_bluetooth_scanner_set_mode_request(const BluetoothScannerSetModeRequest &msg);
 
 #endif
 #ifdef USE_HOMEASSISTANT_TIME
-  void send_time_request() {
-    GetTimeRequest req;
-    this->send_message(req);
-  }
+  void send_time_request();
 #endif
 
 #ifdef USE_VOICE_ASSISTANT
@@ -266,6 +271,7 @@ class APIConnection final : public APIServerConnectionBase {
   void on_disconnect_request(const DisconnectRequest &msg);
   void on_ping_request();
   void on_device_info_request();
+  void on_device_capabilities_request();
   void on_list_entities_request() { this->begin_iterator_(ActiveIterator::LIST_ENTITIES); }
   void on_subscribe_states_request() {
     this->flags_.state_subscription = true;
@@ -320,8 +326,10 @@ class APIConnection final : public APIServerConnectionBase {
   bool is_marked_for_removal() const { return this->flags_.remove; }
   uint8_t get_log_subscription_level() const { return this->flags_.log_subscription; }
 
-  // Get client API version for feature detection
-  bool client_supports_api_version(uint16_t major, uint16_t minor) const {
+  // Get client API version for feature detection.
+  // Stored versions saturate at 255 (see send_hello_response_), so requesting
+  // a minimum above that can never match.
+  bool client_supports_api_version(uint8_t major, uint8_t minor) const {
     return this->client_api_version_major_ > major ||
            (this->client_api_version_major_ == major && this->client_api_version_minor_ >= minor);
   }
@@ -334,7 +342,9 @@ class APIConnection final : public APIServerConnectionBase {
   // Function pointer type for type-erased size calculation
   using CalculateSizeFn = uint32_t (*)(const void *);
 
-  template<typename T> bool send_message(const T &msg) {
+  /// 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 {
@@ -342,22 +352,13 @@ class APIConnection final : public APIServerConnectionBase {
     }
   }
 
-  void prepare_first_message_buffer(APIBuffer &shared_buf, size_t header_padding, size_t total_size) {
-    shared_buf.clear();
-    // Reserve space for header padding + message + footer
-    // - Header padding: space for protocol headers (7 bytes for Noise, 6 for Plaintext)
-    // - Footer: space for MAC (16 bytes for Noise, 0 for Plaintext)
-    // Reserve full size but only set initial size to header padding
-    // so message encoding starts at the correct position
-    shared_buf.reserve_and_resize(total_size, header_padding);
-  }
+  /// Clear the shared write buffer and reserve space for the first message.
+  /// Returns false if the allocation fails (out of memory).
+  /// Defined in api_connection_buffer.h (needs APIServer complete).
+  [[nodiscard]] bool prepare_first_message_buffer(size_t header_padding, size_t total_size);
 
   // Convenience overload - computes frame overhead internally
-  void prepare_first_message_buffer(APIBuffer &shared_buf, size_t payload_size) {
-    const uint8_t header_padding = this->helper_->frame_header_padding();
-    const uint8_t footer_size = this->helper_->frame_footer_size();
-    this->prepare_first_message_buffer(shared_buf, header_padding, payload_size + header_padding + footer_size);
-  }
+  [[nodiscard]] bool prepare_first_message_buffer(size_t payload_size);
 
   bool try_to_clear_buffer(bool log_out_of_space) {
     if (this->flags_.remove)
@@ -366,7 +367,7 @@ class APIConnection final : public APIServerConnectionBase {
       return true;
     return this->try_to_clear_buffer_slow_(log_out_of_space);
   }
-  bool send_buffer(ProtoWriteBuffer buffer, uint8_t message_type);
+  bool send_buffer(ProtoWriteBuffer buffer, uint16_t message_type);
 
   const char *get_name() const { return this->helper_->get_client_name(); }
   /// Get peer name (IP address) into caller-provided buffer, returns buf for convenience
@@ -374,6 +375,21 @@ class APIConnection final : public APIServerConnectionBase {
     return this->helper_->get_peername_to(buf);
   }
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  /// Outgoing connection: send our server hello immediately so the peer can
+  /// pick the matching key. Outgoing connections are only dialed when a PSK
+  /// is set, so the helper is always the noise helper. Call after start().
+  void mark_outgoing() {
+    if (this->flags_.remove) {
+      return;  // start() failed; the connection is already being torn down
+    }
+    APIError err = static_cast<APINoiseFrameHelper *>(this->helper_.get())->send_server_hello_first();
+    if (err != APIError::OK) {
+      this->fatal_error_with_log_(LOG_STR("Server hello failed"), err);
+    }
+  }
+#endif
+
  protected:
   bool try_to_clear_buffer_slow_(bool log_out_of_space);
 
@@ -385,10 +401,11 @@ class APIConnection final : public APIServerConnectionBase {
   bool send_disconnect_response_();
   bool send_ping_response_();
   bool send_device_info_response_();
+  bool send_device_capabilities_response_();
 #ifdef USE_API_NOISE
   bool send_noise_encryption_set_key_response_(const NoiseEncryptionSetKeyRequest &msg);
 #endif
-#ifdef USE_BLUETOOTH_PROXY
+#ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
   bool send_subscribe_bluetooth_connections_free_response_();
 #endif
 #ifdef USE_VOICE_ASSISTANT
@@ -414,7 +431,7 @@ class APIConnection final : public APIServerConnectionBase {
   }
 
   // Non-template buffer management for send_message
-  bool send_message_(uint32_t payload_size, uint8_t message_type, MessageEncodeFn encode_fn, const void *msg);
+  bool send_message_(uint32_t payload_size, uint16_t message_type, MessageEncodeFn encode_fn, const void *msg);
 
   // Core batch encoding logic. ALWAYS_INLINE so encode_fn devirtualizes at hot call sites.
   // Defined in api_connection_buffer.h (needs APIServer complete).
@@ -655,10 +672,9 @@ class APIConnection final : public APIServerConnectionBase {
 
     struct BatchItem {
       EntityBase *entity;                       // 4 bytes - Entity pointer
-      uint8_t message_type;                     // 1 byte - Message type for protocol and dispatch
+      uint16_t message_type;                    // 2 bytes - Message type for protocol and dispatch
       uint8_t estimated_size;                   // 1 byte - Estimated message size (max 255 bytes)
       uint8_t aux_data_index{AUX_DATA_UNUSED};  // 1 byte - For events: index into entity's event_types
-      // 1 byte padding
     };
 
     std::vector<BatchItem> items;
@@ -668,7 +684,7 @@ class APIConnection final : public APIServerConnectionBase {
     // connections that do, buffers are released after initial sync anyway
 
     // Add item to the batch (with deduplication)
-    void add_item(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,
+    void add_item(EntityBase *entity, uint16_t message_type, uint8_t estimated_size,
                   uint8_t aux_data_index = AUX_DATA_UNUSED) {
       // Dedup: O(n) scan but optimized for RAM over performance
       // Skip deduplication for events - they are edge-triggered, every occurrence matters
@@ -684,7 +700,7 @@ class APIConnection final : public APIServerConnectionBase {
       this->items.push_back({entity, message_type, estimated_size, aux_data_index});
     }
     // Add item to the front of the batch (for high priority messages like ping)
-    void add_item_front(EntityBase *entity, uint8_t message_type, uint8_t estimated_size) {
+    void add_item_front(EntityBase *entity, uint16_t message_type, uint8_t estimated_size) {
       // Swap to front avoids expensive vector::insert which shifts all elements
       this->items.push_back({entity, message_type, estimated_size, AUX_DATA_UNUSED});
       if (this->items.size() > 1) {
@@ -744,18 +760,23 @@ class APIConnection final : public APIServerConnectionBase {
     uint8_t batch_first_message : 1;          // For batch buffer allocation
     uint8_t should_try_send_immediately : 1;  // True after initial states are sent
     uint8_t may_have_remaining_data : 1;      // Read loop hit limit, retry without ready check
+#ifdef USE_API_OUTGOING_CONNECTION
+    uint8_t outgoing_connection_target : 1;  // Client declared itself a dial-back target in its hello
+#endif
 #ifdef HAS_PROTO_MESSAGE_DUMP
     uint8_t log_only_mode : 1;
 #endif
   } flags_{};  // 2 bytes total
 
-  // 2-byte types immediately after flags_ (no padding between them)
-  uint16_t client_api_version_major_{0};
-  uint16_t client_api_version_minor_{0};
+  // 2-byte type immediately after flags_ (no padding between them)
+  uint16_t batch_message_type_{0};  // Current message type during batch encoding
   // 1-byte types to fill remaining space before next 4-byte boundary
+  // Client API versions are clamped to 255 on receive (see send_hello_response_)
+  uint8_t client_api_version_major_{0};
+  uint8_t client_api_version_minor_{0};
   ActiveIterator active_iterator_{ActiveIterator::NONE};
-  uint8_t batch_message_type_{0};  // Current message type during batch encoding
-  // Total: 2 (flags) + 2 + 2 + 1 + 1 = 8 bytes, aligned to 4-byte boundary
+  // Total: 2 (flags) + 2 + 1 + 1 + 1 + 1 (batch_header_size_ below) = 8 bytes,
+  // aligned to 4-byte boundary
 
   // Actual header size used by encode_to_buffer for the current message.
   // Read by process_batch_multi_ to pass into MessageInfo.
@@ -804,7 +825,7 @@ class APIConnection final : public APIServerConnectionBase {
   // 2. It's an EventResponse (events are edge-triggered - every occurrence matters)
   // 3. OR: User has opted into immediate sending (should_try_send_immediately = true
   //    AND batch_delay = 0)
-  inline bool should_send_immediately_(uint8_t message_type) const {
+  inline bool should_send_immediately_(uint16_t message_type) const {
     return (
 #ifdef USE_UPDATE
         message_type == UpdateStateResponse::MESSAGE_TYPE ||
@@ -818,11 +839,11 @@ class APIConnection final : public APIServerConnectionBase {
   // Helper method to send a message either immediately or via batching
   // Tries immediate send if should_send_immediately_() returns true and buffer has space
   // Falls back to batching if immediate send fails or isn't applicable
-  bool send_message_smart_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,
+  bool send_message_smart_(EntityBase *entity, uint16_t message_type, uint8_t estimated_size,
                            uint8_t aux_data_index = DeferredBatch::AUX_DATA_UNUSED);
 
   // Helper function to schedule a deferred message with known message type
-  bool schedule_message_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size,
+  bool schedule_message_(EntityBase *entity, uint16_t message_type, uint8_t estimated_size,
                          uint8_t aux_data_index = DeferredBatch::AUX_DATA_UNUSED) {
     this->deferred_batch_.add_item(entity, message_type, estimated_size, aux_data_index);
     return this->schedule_batch_();
@@ -830,7 +851,7 @@ class APIConnection final : public APIServerConnectionBase {
 
   // Helper function to schedule a high priority message at the front of the batch
   // Out-of-line: callers (on_shutdown, check_keepalive_) are cold paths
-  bool schedule_message_front_(EntityBase *entity, uint8_t message_type, uint8_t estimated_size);
+  bool schedule_message_front_(EntityBase *entity, uint16_t message_type, uint8_t estimated_size);
 
   // Helper function to log client messages with name and peername
   void log_client_(int level, const LogString *message);
@@ -841,6 +862,9 @@ class APIConnection final : public APIServerConnectionBase {
     this->on_fatal_error();
     this->log_warning_(message, err);
   }
+  // Shared cold path for buffer allocation failures — noinline keeps the
+  // OOM handling out of the hot send paths
+  void __attribute__((noinline)) fatal_out_of_memory_();
 };
 
 }  // namespace esphome::api

esphome/components/api/api_connection_buffer.h

@@ -3,8 +3,8 @@
 #include "esphome/core/defines.h"
 #ifdef USE_API
 
-// Inline APIConnection methods that need APIServer complete. Include this
-// instead of api_connection.h when calling encode_to_buffer or get_batch_delay_ms_.
+// Inline APIConnection members that need APIServer complete. Include this
+// instead of api_connection.h when calling them.
 
 #include "api_connection.h"
 #include "api_server.h"
@@ -41,7 +41,10 @@ inline uint16_t ESPHOME_ALWAYS_INLINE APIConnection::encode_to_buffer(uint32_t c
     return 0;
 
   auto &shared_buf = conn->parent_->get_shared_buffer_ref();
-  shared_buf.resize(shared_buf.size() + to_add);
+  if (!shared_buf.resize(shared_buf.size() + to_add)) [[unlikely]] {
+    conn->fatal_out_of_memory_();
+    return 0;
+  }
   ProtoWriteBuffer buffer{&shared_buf, shared_buf.size() - calculated_size};
   encode_fn(msg, buffer PROTO_ENCODE_DEBUG_INIT(&shared_buf));
 
@@ -50,5 +53,22 @@ inline uint16_t ESPHOME_ALWAYS_INLINE APIConnection::encode_to_buffer(uint32_t c
 
 inline uint32_t APIConnection::get_batch_delay_ms_() const { return this->parent_->get_batch_delay(); }
 
+inline bool APIConnection::prepare_first_message_buffer(size_t header_padding, size_t total_size) {
+  auto &shared_buf = this->parent_->get_shared_buffer_ref();
+  shared_buf.clear();
+  // Reserve space for header padding + message + footer
+  // - Header padding: space for protocol headers (7 bytes for Noise, 6 for Plaintext)
+  // - Footer: space for MAC (16 bytes for Noise, 0 for Plaintext)
+  // Reserve full size but only set initial size to header padding
+  // so message encoding starts at the correct position
+  return shared_buf.reserve_and_resize(total_size, header_padding);
+}
+
+inline bool APIConnection::prepare_first_message_buffer(size_t payload_size) {
+  const uint8_t header_padding = this->helper_->frame_header_padding();
+  const uint8_t footer_size = this->helper_->frame_footer_size();
+  return this->prepare_first_message_buffer(header_padding, payload_size + header_padding + footer_size);
+}
+
 }  // namespace esphome::api
 #endif

esphome/components/api/api_frame_helper.cpp

@@ -172,7 +172,7 @@ APIError APIFrameHelper::write_raw_iov_(const struct iovec *iov, int iovcnt, uin
 
   // Queue unsent data into overflow buffer
   if (!this->overflow_buf_.enqueue_iov(iov, iovcnt, total_write_len, static_cast<uint16_t>(sent))) {
-    HELPER_LOG("Overflow buffer full, dropping connection");
+    HELPER_LOG("Overflow buffer full or out of memory, dropping connection");
     this->state_ = State::FAILED;
     return APIError::SOCKET_WRITE_FAILED;
   }

esphome/components/api/api_frame_helper.h

@@ -18,7 +18,7 @@
 namespace esphome::api {
 
 // uncomment to log raw packets
-//#define HELPER_LOG_PACKETS
+// #define HELPER_LOG_PACKETS
 
 // Maximum message size limits to prevent OOM on constrained devices
 // Handshake messages are limited to a small size for security
@@ -36,7 +36,7 @@ static constexpr uint16_t MAX_MESSAGE_SIZE = 32768;  // 32 KiB for ESP32 and oth
 static constexpr uint16_t RX_BUF_NULL_TERMINATOR = 1;
 
 // Maximum number of messages to batch in a single write operation
-// Must be >= MAX_INITIAL_PER_BATCH in api_connection.h (enforced by static_assert there)
+// Must be >= MAX_INITIAL_BATCH_SIZE in api_connection.h (enforced by static_assert there)
 static constexpr size_t MAX_MESSAGES_PER_BATCH = 34;
 
 // Max client name length (e.g., "Home Assistant 2026.1.0.dev0" = 28 chars)
@@ -49,16 +49,16 @@ struct ReadPacketBuffer {
 };
 
 // Packed message info structure to minimize memory usage
-// Note: message_type is uint8_t — all current protobuf message types fit in 8 bits.
-// The noise wire format encodes types as 16-bit, but the high byte is always 0.
-// If message types ever exceed 255, this and encrypt_noise_message_ must be updated.
+// message_type matches the wire formats: noise carries a fixed 16-bit type
+// field, plaintext a type varint. The proto codegen caps message IDs at 16383
+// so the plaintext type varint fits the 2 bytes budgeted in HEADER_PADDING.
 struct MessageInfo {
   uint16_t offset;        // Offset in buffer where message starts
   uint16_t payload_size;  // Size of the message payload
-  uint8_t message_type;   // Message type (0-255)
+  uint16_t message_type;  // Message type (0-16383)
   uint8_t header_size;    // Actual header size used (avoids recomputation in write path)
 
-  MessageInfo(uint8_t type, uint16_t off, uint16_t size, uint8_t hdr)
+  MessageInfo(uint16_t type, uint16_t off, uint16_t size, uint8_t hdr)
       : offset(off), payload_size(size), message_type(type), header_size(hdr) {}
 };
 
@@ -149,7 +149,7 @@ class APIFrameHelper {
   // holding data too long waiting for Nagle's timer causes buffer exhaustion
   // and dropped messages.
   //
-  // ESP32 (TCP_SND_BUF=4×MSS+) / RP2040 (8×MSS) / LibreTiny (4×MSS): 4 logs per cycle
+  // ESP32 (TCP_SND_BUF=4×MSS+) / RP2040 (4×MSS) / LibreTiny (4×MSS): 4 logs per cycle
   // ESP8266 (2×MSS): 3 logs per cycle (tightest buffers)
   //
   // Flow (ESP32/RP2040/LT): Log 1 (Nagle on) -> Log 2 -> Log 3 -> Log 4 (NODELAY, flush)
@@ -173,7 +173,7 @@ class APIFrameHelper {
   }
   // Write a single protobuf message - the hot path (87-100% of all writes).
   // Caller must ensure state is DATA before calling.
-  virtual APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) = 0;
+  virtual APIError write_protobuf_packet(uint16_t type, ProtoWriteBuffer buffer) = 0;
   // Write multiple protobuf messages in a single batched operation.
   // Caller must ensure state is DATA and messages is not empty.
   // messages contains (message_type, offset, length) for each message in the buffer.
@@ -187,15 +187,15 @@ class APIFrameHelper {
   // Distinguishes protocols via frame_footer_size_ (noise always has a non-zero MAC
   // footer, plaintext has footer=0). If a protocol with a plaintext footer is ever
   // added, this should become a virtual method.
-  uint8_t frame_header_size(uint16_t payload_size, uint8_t message_type) const {
+  uint8_t frame_header_size(uint16_t payload_size, uint16_t message_type) const {
 #if defined(USE_API_NOISE) && defined(USE_API_PLAINTEXT)
     return this->frame_footer_size_
                ? this->frame_header_padding_
-               : static_cast<uint8_t>(1 + ProtoSize::varint16(payload_size) + ProtoSize::varint8(message_type));
+               : static_cast<uint8_t>(1 + ProtoSize::varint16(payload_size) + ProtoSize::varint16(message_type));
 #elif defined(USE_API_NOISE)
     return this->frame_header_padding_;
 #else  // USE_API_PLAINTEXT only
-    return static_cast<uint8_t>(1 + ProtoSize::varint16(payload_size) + ProtoSize::varint8(message_type));
+    return static_cast<uint8_t>(1 + ProtoSize::varint16(payload_size) + ProtoSize::varint16(message_type));
 #endif
   }
   // Get the frame footer size required by this protocol
@@ -282,7 +282,8 @@ class APIFrameHelper {
     DATA = 5,
     CLOSED = 6,
     FAILED = 7,
-    EXPLICIT_REJECT = 8,  // Noise only
+    EXPLICIT_REJECT = 8,        // Noise only
+    CLIENT_HELLO_OUTGOING = 9,  // Noise only: like CLIENT_HELLO but the server hello already went out (outgoing conn)
   };
 
   // Fast inline state check for read_packet/write_protobuf_messages hot path.
@@ -312,7 +313,7 @@ class APIFrameHelper {
   // Values 1..LOG_NAGLE_COUNT count log messages in the current Nagle batch.
   // After LOG_NAGLE_COUNT logs, we flush by re-enabling NODELAY and resetting to 0.
   // ESP8266 has the tightest TCP send buffer (2×MSS) and needs conservative batching.
-  // ESP32 (4×MSS+), RP2040 (8×MSS), and LibreTiny (4×MSS) can coalesce more.
+  // ESP32 (4×MSS+), RP2040 (4×MSS), and LibreTiny (4×MSS) can coalesce more.
 #ifdef USE_ESP8266
   static constexpr uint8_t LOG_NAGLE_COUNT = 2;
 #else

esphome/components/api/api_frame_helper_noise.cpp

@@ -2,9 +2,9 @@
 #ifdef USE_API
 #ifdef USE_API_NOISE
 #include "api_connection.h"  // For ClientInfo struct
+#include "esphome/components/noise/noise.h"
 #include "esphome/core/application.h"
 #include "esphome/core/entity_base.h"
-#include "esphome/core/hal.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include "proto.h"
@@ -17,6 +17,14 @@
 
 namespace esphome::api {
 
+using noise::noise_err_to_logstr;
+
+// api_frame_helper.h keeps its own MAX_HANDSHAKE_SIZE because that header is
+// also compiled in plaintext-only builds without the noise component; keep
+// the two definitions from drifting apart.
+static_assert(MAX_HANDSHAKE_SIZE == noise::MAX_HANDSHAKE_SIZE,
+              "api and noise component handshake size limits must match");
+
 static const char *const TAG = "api.noise";
 #ifdef USE_ESP8266
 static constexpr char PROLOGUE_INIT[] PROGMEM = "NoiseAPIInit";
@@ -51,45 +59,6 @@ static constexpr size_t API_MAX_LOG_BYTES = 168;
 #define LOG_PACKET_RECEIVED(buffer) ((void) 0)
 #endif
 
-/// Convert a noise error code to a readable error
-const LogString *noise_err_to_logstr(int err) {
-  if (err == NOISE_ERROR_NO_MEMORY)
-    return LOG_STR("NO_MEMORY");
-  if (err == NOISE_ERROR_UNKNOWN_ID)
-    return LOG_STR("UNKNOWN_ID");
-  if (err == NOISE_ERROR_UNKNOWN_NAME)
-    return LOG_STR("UNKNOWN_NAME");
-  if (err == NOISE_ERROR_MAC_FAILURE)
-    return LOG_STR("MAC_FAILURE");
-  if (err == NOISE_ERROR_NOT_APPLICABLE)
-    return LOG_STR("NOT_APPLICABLE");
-  if (err == NOISE_ERROR_SYSTEM)
-    return LOG_STR("SYSTEM");
-  if (err == NOISE_ERROR_REMOTE_KEY_REQUIRED)
-    return LOG_STR("REMOTE_KEY_REQUIRED");
-  if (err == NOISE_ERROR_LOCAL_KEY_REQUIRED)
-    return LOG_STR("LOCAL_KEY_REQUIRED");
-  if (err == NOISE_ERROR_PSK_REQUIRED)
-    return LOG_STR("PSK_REQUIRED");
-  if (err == NOISE_ERROR_INVALID_LENGTH)
-    return LOG_STR("INVALID_LENGTH");
-  if (err == NOISE_ERROR_INVALID_PARAM)
-    return LOG_STR("INVALID_PARAM");
-  if (err == NOISE_ERROR_INVALID_STATE)
-    return LOG_STR("INVALID_STATE");
-  if (err == NOISE_ERROR_INVALID_NONCE)
-    return LOG_STR("INVALID_NONCE");
-  if (err == NOISE_ERROR_INVALID_PRIVATE_KEY)
-    return LOG_STR("INVALID_PRIVATE_KEY");
-  if (err == NOISE_ERROR_INVALID_PUBLIC_KEY)
-    return LOG_STR("INVALID_PUBLIC_KEY");
-  if (err == NOISE_ERROR_INVALID_FORMAT)
-    return LOG_STR("INVALID_FORMAT");
-  if (err == NOISE_ERROR_INVALID_SIGNATURE)
-    return LOG_STR("INVALID_SIGNATURE");
-  return LOG_STR("UNKNOWN");
-}
-
 /// Initialize the frame helper, returns OK if successful.
 APIError APINoiseFrameHelper::init() {
   APIError err = init_common_();
@@ -99,7 +68,10 @@ APIError APINoiseFrameHelper::init() {
 
   // init prologue
   size_t old_size = prologue_.size();
-  prologue_.resize(old_size + PROLOGUE_INIT_LEN);
+  if (!prologue_.resize(old_size + PROLOGUE_INIT_LEN)) [[unlikely]] {
+    state_ = State::FAILED;
+    return APIError::OUT_OF_MEMORY;
+  }
 #ifdef USE_ESP8266
   memcpy_P(prologue_.data() + old_size, PROLOGUE_INIT, PROLOGUE_INIT_LEN);
 #else
@@ -109,6 +81,13 @@ APIError APINoiseFrameHelper::init() {
   state_ = State::CLIENT_HELLO;
   return APIError::OK;
 }
+#ifdef USE_API_OUTGOING_CONNECTION
+APIError APINoiseFrameHelper::send_server_hello_first() {
+  // The peer needs our name and MAC to pick the key before its first message
+  this->state_ = State::CLIENT_HELLO_OUTGOING;
+  return this->send_server_hello_frame_();
+}
+#endif
 #ifdef USE_API_PLAINTEXT
 APIError APINoiseFrameHelper::init_from_handoff(const uint8_t *header, uint8_t header_len) {
   APIError err = this->init();
@@ -194,9 +173,9 @@ APIError APINoiseFrameHelper::loop() {
  */
 APIError APINoiseFrameHelper::try_read_frame_() {
   // read header
-  if (rx_header_buf_len_ < 3) {
+  if (rx_header_buf_len_ < noise::FRAME_HEADER_SIZE) {
     // no header information yet
-    uint8_t to_read = 3 - rx_header_buf_len_;
+    uint8_t to_read = static_cast<uint8_t>(noise::FRAME_HEADER_SIZE) - rx_header_buf_len_;
     ssize_t received = this->socket_->read(&rx_header_buf_[rx_header_buf_len_], to_read);
     APIError err = handle_socket_read_result_(received);
     if (err != APIError::OK) {
@@ -208,7 +187,7 @@ APIError APINoiseFrameHelper::try_read_frame_() {
       return APIError::WOULD_BLOCK;
     }
 
-    if (rx_header_buf_[0] != 0x01) {
+    if (rx_header_buf_[0] != noise::FRAME_INDICATOR) {
       state_ = State::FAILED;
       HELPER_LOG("Bad indicator byte %u", rx_header_buf_[0]);
       return APIError::BAD_INDICATOR;
@@ -233,7 +212,10 @@ APIError APINoiseFrameHelper::try_read_frame_() {
   // During handshake, rx_buf_.size() is used in prologue construction, so
   // the buffer must be exactly msg_size to avoid prologue mismatch.)
   uint16_t alloc_size = msg_size + (is_data ? RX_BUF_NULL_TERMINATOR : 0);
-  this->rx_buf_.resize(alloc_size);
+  if (!this->rx_buf_.resize(alloc_size)) [[unlikely]] {
+    state_ = State::FAILED;
+    return APIError::OUT_OF_MEMORY;
+  }
 
   if (rx_buf_len_ < msg_size) {
     // more data to read
@@ -278,6 +260,9 @@ APIError APINoiseFrameHelper::state_action_() {
       HELPER_LOG("Bad state for method: %d", (int) this->state_);
       return APIError::BAD_STATE;
     case State::CLIENT_HELLO:
+#ifdef USE_API_OUTGOING_CONNECTION
+    case State::CLIENT_HELLO_OUTGOING:
+#endif
       return this->state_action_client_hello_();
     case State::SERVER_HELLO:
       return this->state_action_server_hello_();
@@ -300,18 +285,26 @@ APIError APINoiseFrameHelper::state_action_client_hello_() {
   // Resize for: existing prologue + 2 size bytes + frame data
   size_t old_size = this->prologue_.size();
   size_t rx_size = this->rx_buf_.size();
-  this->prologue_.resize(old_size + 2 + rx_size);
+  if (!this->prologue_.resize(old_size + 2 + rx_size)) [[unlikely]] {
+    state_ = State::FAILED;
+    return APIError::OUT_OF_MEMORY;
+  }
   this->prologue_[old_size] = (uint8_t) (rx_size >> 8);
   this->prologue_[old_size + 1] = (uint8_t) rx_size;
   if (rx_size > 0) {
     std::memcpy(this->prologue_.data() + old_size + 2, this->rx_buf_.data(), rx_size);
   }
 
+#ifdef USE_API_OUTGOING_CONNECTION
+  if (this->state_ == State::CLIENT_HELLO_OUTGOING) {
+    // Server hello already went out at handoff
+    return this->start_handshake_();
+  }
+#endif
   state_ = State::SERVER_HELLO;
   return APIError::OK;
 }
-APIError APINoiseFrameHelper::state_action_server_hello_() {
-  // send server hello
+APIError APINoiseFrameHelper::send_server_hello_frame_() {
   const auto &name = App.get_name();
   char mac[MAC_ADDRESS_BUFFER_SIZE];
   get_mac_address_into_buffer(mac);
@@ -335,28 +328,31 @@ APIError APINoiseFrameHelper::state_action_server_hello_() {
   // node mac, terminated by null byte
   std::memcpy(msg + mac_offset, mac, MAC_ADDRESS_BUFFER_SIZE);
 
-  APIError aerr = write_frame_(msg, total_size);
+  return write_frame_(msg, total_size);
+}
+APIError APINoiseFrameHelper::state_action_server_hello_() {
+  APIError aerr = this->send_server_hello_frame_();
   if (aerr != APIError::OK)
     return aerr;
-
-  // start handshake
-  aerr = init_handshake_();
+  return this->start_handshake_();
+}
+APIError APINoiseFrameHelper::start_handshake_() {
+  APIError aerr = init_handshake_();
   if (aerr != APIError::OK)
     return aerr;
-
   state_ = State::HANDSHAKE;
   return APIError::OK;
 }
 APIError APINoiseFrameHelper::state_action_handshake_() {
-  int action = noise_handshakestate_get_action(this->handshake_);
-  if (action == NOISE_ACTION_READ_MESSAGE) {
+  noise::NoiseResponderHandshake::Action action = this->handshake_.action();
+  if (action == noise::NoiseResponderHandshake::Action::ACTION_READ) {
     return this->state_action_handshake_read_();
-  } else if (action == NOISE_ACTION_WRITE_MESSAGE) {
+  } else if (action == noise::NoiseResponderHandshake::Action::ACTION_WRITE) {
     return this->state_action_handshake_write_();
   }
   // bad state for action
   this->state_ = State::FAILED;
-  HELPER_LOG("Bad action for handshake: %d", action);
+  HELPER_LOG("Bad action for handshake: %d", (int) action);
   return APIError::HANDSHAKESTATE_BAD_STATE;
 }
 APIError APINoiseFrameHelper::state_action_handshake_read_() {
@@ -368,20 +364,16 @@ APIError APINoiseFrameHelper::state_action_handshake_read_() {
   if (this->rx_buf_.empty()) {
     this->send_explicit_handshake_reject_(LOG_STR("Empty handshake message"));
     return APIError::BAD_HANDSHAKE_ERROR_BYTE;
-  } else if (this->rx_buf_[0] != 0x00) {
+  } else if (this->rx_buf_[0] != noise::HANDSHAKE_STATUS_OK) {
     HELPER_LOG("Bad handshake error byte: %u", this->rx_buf_[0]);
     this->send_explicit_handshake_reject_(LOG_STR("Bad handshake error byte"));
     return APIError::BAD_HANDSHAKE_ERROR_BYTE;
   }
 
-  NoiseBuffer mbuf;
-  noise_buffer_init(mbuf);
-  noise_buffer_set_input(mbuf, this->rx_buf_.data() + 1, this->rx_buf_.size() - 1);
-  int err = noise_handshakestate_read_message(this->handshake_, &mbuf, nullptr);
+  int err = this->handshake_.read_message(this->rx_buf_.data() + 1, this->rx_buf_.size() - 1);
   if (err != 0) {
     // Special handling for MAC failure
-    this->send_explicit_handshake_reject_(err == NOISE_ERROR_MAC_FAILURE ? LOG_STR("Handshake MAC failure")
-                                                                         : LOG_STR("Handshake error"));
+    this->send_explicit_handshake_reject_(noise::reject_reason_for(err));
     return this->handle_noise_error_(err, LOG_STR("noise_handshakestate_read_message"),
                                      APIError::HANDSHAKESTATE_READ_FAILED);
   }
@@ -390,18 +382,16 @@ APIError APINoiseFrameHelper::state_action_handshake_read_() {
 }
 APIError APINoiseFrameHelper::state_action_handshake_write_() {
   uint8_t buffer[65];
-  NoiseBuffer mbuf;
-  noise_buffer_init(mbuf);
-  noise_buffer_set_output(mbuf, buffer + 1, sizeof(buffer) - 1);
+  size_t msg_len = 0;
 
-  int err = noise_handshakestate_write_message(this->handshake_, &mbuf, nullptr);
+  int err = this->handshake_.write_message(buffer + 1, sizeof(buffer) - 1, msg_len);
   APIError aerr = this->handle_noise_error_(err, LOG_STR("noise_handshakestate_write_message"),
                                             APIError::HANDSHAKESTATE_WRITE_FAILED);
   if (aerr != APIError::OK)
     return aerr;
-  buffer[0] = 0x00;  // success
+  buffer[0] = noise::HANDSHAKE_STATUS_OK;
 
-  aerr = this->write_frame_(buffer, mbuf.size + 1);
+  aerr = this->write_frame_(buffer, msg_len + 1);
   if (aerr != APIError::OK)
     return aerr;
   return this->check_handshake_finished_();
@@ -409,33 +399,22 @@ APIError APINoiseFrameHelper::state_action_handshake_write_() {
 void APINoiseFrameHelper::send_explicit_handshake_reject_(const LogString *reason) {
   // Max reject message: "Bad handshake packet len" (24) + 1 (failure byte) = 25 bytes
   uint8_t data[32];
-  data[0] = 0x01;  // failure
-
-#ifdef USE_STORE_LOG_STR_IN_FLASH
-  // On ESP8266 with flash strings, we need to use PROGMEM-aware functions
-  size_t reason_len = strlen_P(reinterpret_cast<PGM_P>(reason));
-  reason_len = std::min(reason_len, sizeof(data) - 1);
-  if (reason_len > 0) {
-    memcpy_P(data + 1, reinterpret_cast<PGM_P>(reason), reason_len);
-  }
-#else
-  // Normal memory access
-  const char *reason_str = LOG_STR_ARG(reason);
-  size_t reason_len = strlen(reason_str);
-  reason_len = std::min(reason_len, sizeof(data) - 1);
-  if (reason_len > 0) {
-    // NOLINTNEXTLINE(bugprone-not-null-terminated-result) - binary protocol, not a C string
-    std::memcpy(data + 1, reason_str, reason_len);
-  }
-#endif
-
-  size_t data_size = reason_len + 1;
+  static_assert(sizeof(data) >= noise::MAC_FAILURE_PAYLOAD_SIZE,
+                "reject buffer must fit the MAC failure wire contract");
+  size_t data_size = noise::format_reject_payload(data, sizeof(data), reason);
 
   // temporarily remove failed state
   auto orig_state = state_;
   state_ = State::EXPLICIT_REJECT;
-  write_frame_(data, data_size);
-  state_ = orig_state;
+  APIError aerr = write_frame_(data, data_size);
+  if (aerr != APIError::OK) {
+    // Best effort; the reject reason is a diagnosis aid, not a protocol step
+    ESP_LOGW(TAG, "Sending handshake reject failed: %d", (int) aerr);
+  }
+  if (state_ == State::EXPLICIT_REJECT) {
+    // write_frame_ may have moved the state to FAILED; keep that decision
+    state_ = orig_state;
+  }
 }
 APIError APINoiseFrameHelper::read_packet(ReadPacketBuffer *buffer) {
   APIError aerr = this->check_data_state_();
@@ -490,14 +469,12 @@ APIError APINoiseFrameHelper::read_packet(ReadPacketBuffer *buffer) {
 }
 // Encrypt a single noise message in place and return the encrypted frame length.
 // Returns APIError::OK on success.
-APIError APINoiseFrameHelper::encrypt_noise_message_(uint8_t *buf_start, uint16_t payload_size, uint8_t message_type,
+APIError APINoiseFrameHelper::encrypt_noise_message_(uint8_t *buf_start, uint16_t payload_size, uint16_t message_type,
                                                      uint16_t &encrypted_len_out) {
-  // Write noise header
-  buf_start[0] = 0x01;  // indicator
-  // buf_start[1], buf_start[2] to be set after encryption
+  // The noise frame header is written after encryption, when the size is known
 
   // Write message header (to be encrypted)
-  constexpr uint8_t msg_offset = 3;
+  constexpr uint8_t msg_offset = noise::FRAME_HEADER_SIZE;
   buf_start[msg_offset] = static_cast<uint8_t>(message_type >> 8);      // type high byte
   buf_start[msg_offset + 1] = static_cast<uint8_t>(message_type);       // type low byte
   buf_start[msg_offset + 2] = static_cast<uint8_t>(payload_size >> 8);  // data_len high byte
@@ -515,26 +492,27 @@ APIError APINoiseFrameHelper::encrypt_noise_message_(uint8_t *buf_start, uint16_
   if (aerr != APIError::OK)
     return aerr;
 
-  // Fill in the encrypted size
-  buf_start[1] = static_cast<uint8_t>(mbuf.size >> 8);
-  buf_start[2] = static_cast<uint8_t>(mbuf.size);
+  // Fill in the frame header now that the encrypted size is known
+  noise::write_frame_header(buf_start, static_cast<uint16_t>(mbuf.size));
 
-  encrypted_len_out = static_cast<uint16_t>(3 + mbuf.size);  // indicator + size + encrypted data
+  encrypted_len_out = static_cast<uint16_t>(noise::FRAME_HEADER_SIZE + mbuf.size);
   return APIError::OK;
 }
 
-APIError APINoiseFrameHelper::write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) {
+APIError APINoiseFrameHelper::write_protobuf_packet(uint16_t type, ProtoWriteBuffer buffer) {
 #ifdef ESPHOME_DEBUG_API
   assert(this->state_ == State::DATA);
 #endif
 
+  APIBuffer *buf = buffer.get_buffer();
   // Resize buffer to include footer space for Noise MAC
-  if (this->frame_footer_size_)
-    buffer.get_buffer()->resize(buffer.get_buffer()->size() + this->frame_footer_size_);
+  if (this->frame_footer_size_ && !buf->resize(buf->size() + this->frame_footer_size_)) [[unlikely]] {
+    state_ = State::FAILED;
+    return APIError::OUT_OF_MEMORY;
+  }
 
-  uint16_t payload_size =
-      static_cast<uint16_t>(buffer.get_buffer()->size() - HEADER_PADDING - this->frame_footer_size_);
-  uint8_t *buf_start = buffer.get_buffer()->data();
+  uint16_t payload_size = static_cast<uint16_t>(buf->size() - HEADER_PADDING - this->frame_footer_size_);
+  uint8_t *buf_start = buf->data();
   uint16_t encrypted_len;
   APIError aerr = this->encrypt_noise_message_(buf_start, payload_size, type, encrypted_len);
   if (aerr != APIError::OK)
@@ -568,21 +546,19 @@ APIError APINoiseFrameHelper::write_protobuf_messages(ProtoWriteBuffer buffer, s
 }
 
 APIError APINoiseFrameHelper::write_frame_(const uint8_t *data, uint16_t len) {
-  uint8_t header[3];
-  header[0] = 0x01;  // indicator
-  header[1] = (uint8_t) (len >> 8);
-  header[2] = (uint8_t) len;
+  uint8_t header[noise::FRAME_HEADER_SIZE];
+  noise::write_frame_header(header, len);
 
   if (len == 0) {
-    return this->write_raw_buf_(header, 3);
+    return this->write_raw_buf_(header, noise::FRAME_HEADER_SIZE);
   }
   struct iovec iov[2];
   iov[0].iov_base = header;
-  iov[0].iov_len = 3;
+  iov[0].iov_len = noise::FRAME_HEADER_SIZE;
   iov[1].iov_base = const_cast<uint8_t *>(data);
   iov[1].iov_len = len;
 
-  return this->write_raw_iov_(iov, 2, 3 + len);
+  return this->write_raw_iov_(iov, 2, noise::FRAME_HEADER_SIZE + len);
 }
 
 /** Initiate the data structures for the handshake.
@@ -590,42 +566,12 @@ 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;
-  memset(&nid_, 0, sizeof(nid_));
-  // const char *proto = "Noise_NNpsk0_25519_ChaChaPoly_SHA256";
-  // err = noise_protocol_name_to_id(&nid_, proto, strlen(proto));
-  nid_.pattern_id = NOISE_PATTERN_NN;
-  nid_.cipher_id = NOISE_CIPHER_CHACHAPOLY;
-  nid_.dh_id = NOISE_DH_CURVE25519;
-  nid_.prefix_id = NOISE_PREFIX_STANDARD;
-  nid_.hybrid_id = NOISE_DH_NONE;
-  nid_.hash_id = NOISE_HASH_SHA256;
-  nid_.modifier_ids[0] = NOISE_MODIFIER_PSK0;
-
-  err = noise_handshakestate_new_by_id(&handshake_, &nid_, NOISE_ROLE_RESPONDER);
-  APIError aerr =
-      handle_noise_error_(err, LOG_STR("noise_handshakestate_new_by_id"), APIError::HANDSHAKESTATE_SETUP_FAILED);
+  int err = this->handshake_.init(this->ctx_.get_psk(), 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;
-
-  const auto &psk = this->ctx_.get_psk();
-  err = noise_handshakestate_set_pre_shared_key(handshake_, psk.data(), psk.size());
-  aerr = handle_noise_error_(err, LOG_STR("noise_handshakestate_set_pre_shared_key"),
-                             APIError::HANDSHAKESTATE_SETUP_FAILED);
-  if (aerr != APIError::OK)
-    return aerr;
-
-  err = noise_handshakestate_set_prologue(handshake_, prologue_.data(), prologue_.size());
-  aerr = handle_noise_error_(err, LOG_STR("noise_handshakestate_set_prologue"), APIError::HANDSHAKESTATE_SETUP_FAILED);
-  if (aerr != APIError::OK)
-    return aerr;
-  // set_prologue copies it into handshakestate, so we can get rid of it now
+  // init copies the prologue into the handshakestate, so we can get rid of it now
   prologue_.release();
-
-  err = noise_handshakestate_start(handshake_);
-  aerr = handle_noise_error_(err, LOG_STR("noise_handshakestate_start"), APIError::HANDSHAKESTATE_SETUP_FAILED);
-  if (aerr != APIError::OK)
-    return aerr;
   return APIError::OK;
 }
 
@@ -634,15 +580,17 @@ APIError APINoiseFrameHelper::check_handshake_finished_() {
   assert(state_ == State::HANDSHAKE);
 #endif
 
-  int action = noise_handshakestate_get_action(handshake_);
-  if (action == NOISE_ACTION_READ_MESSAGE || action == NOISE_ACTION_WRITE_MESSAGE)
+  noise::NoiseResponderHandshake::Action action = this->handshake_.action();
+  if (action == noise::NoiseResponderHandshake::Action::ACTION_READ ||
+      action == noise::NoiseResponderHandshake::Action::ACTION_WRITE)
     return APIError::OK;
-  if (action != NOISE_ACTION_SPLIT) {
+  if (action != noise::NoiseResponderHandshake::Action::ACTION_SPLIT) {
     state_ = State::FAILED;
-    HELPER_LOG("Bad action for handshake: %d", action);
+    HELPER_LOG("Bad action for handshake: %d", (int) action);
     return APIError::HANDSHAKESTATE_BAD_STATE;
   }
-  int err = noise_handshakestate_split(handshake_, &send_cipher_, &recv_cipher_);
+  // split() also frees the handshake state
+  int err = this->handshake_.split(send_cipher_, recv_cipher_);
   APIError aerr =
       handle_noise_error_(err, LOG_STR("noise_handshakestate_split"), APIError::HANDSHAKESTATE_SPLIT_FAILED);
   if (aerr != APIError::OK)
@@ -651,17 +599,11 @@ APIError APINoiseFrameHelper::check_handshake_finished_() {
   this->frame_footer_size_ = noise_cipherstate_get_mac_length(send_cipher_);
 
   HELPER_LOG("Handshake complete!");
-  noise_handshakestate_free(handshake_);
-  handshake_ = nullptr;
   state_ = State::DATA;
   return APIError::OK;
 }
 
 APINoiseFrameHelper::~APINoiseFrameHelper() {
-  if (handshake_ != nullptr) {
-    noise_handshakestate_free(handshake_);
-    handshake_ = nullptr;
-  }
   if (send_cipher_ != nullptr) {
     noise_cipherstate_free(send_cipher_);
     send_cipher_ = nullptr;
@@ -672,16 +614,6 @@ APINoiseFrameHelper::~APINoiseFrameHelper() {
   }
 }
 
-extern "C" {
-// declare how noise generates random bytes (here with a good HWRNG based on the RF system)
-void noise_rand_bytes(void *output, size_t len) {
-  if (!esphome::random_bytes(reinterpret_cast<uint8_t *>(output), len)) {
-    ESP_LOGE(TAG, "Acquiring random bytes failed; rebooting");
-    arch_restart();
-  }
-}
-}
-
 }  // namespace esphome::api
 #endif  // USE_API_NOISE
 #endif  // USE_API

esphome/components/api/api_frame_helper_noise.h

@@ -3,7 +3,7 @@
 #ifdef USE_API
 #ifdef USE_API_NOISE
 #include "noise/protocol.h"
-#include "api_noise_context.h"
+#include "esphome/components/noise/noise_handshake.h"
 
 namespace esphome::api {
 
@@ -14,9 +14,9 @@ class APINoiseFrameHelper final : public APIFrameHelper {
   // Pos 1-2: encrypted payload size (16-bit big-endian)
   // Pos 3-6: encrypted type (16-bit) + data_len (16-bit)
   // Pos 7+: actual payload data
-  static constexpr uint8_t HEADER_PADDING = 1 + 2 + 2 + 2;  // indicator + size + type + data_len
+  static constexpr uint8_t HEADER_PADDING = noise::FRAME_HEADER_SIZE + 2 + 2;  // frame header + type + data_len
 
-  APINoiseFrameHelper(std::unique_ptr<socket::Socket> socket, APINoiseContext &ctx)
+  APINoiseFrameHelper(std::unique_ptr<socket::Socket> socket, noise::NoiseContext &ctx)
       : APIFrameHelper(std::move(socket)), ctx_(ctx) {
     frame_header_padding_ = HEADER_PADDING;
   }
@@ -28,10 +28,16 @@ class APINoiseFrameHelper final : public APIFrameHelper {
   // Seeds the already-read header bytes and pumps the handshake state machine
   // until it would block.
   APIError init_from_handoff(const uint8_t *header, uint8_t header_len);
+#endif
+#ifdef USE_API_OUTGOING_CONNECTION
+  // Send the server hello immediately so the peer can pick the key before
+  // its PSK-mixed message. Call after init(); the mode is tracked in state_
+  // so the helper does not grow.
+  APIError send_server_hello_first();
 #endif
   APIError loop() override;
   APIError read_packet(ReadPacketBuffer *buffer) override;
-  APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) override;
+  APIError write_protobuf_packet(uint16_t type, ProtoWriteBuffer buffer) override;
   APIError write_protobuf_messages(ProtoWriteBuffer buffer, std::span<const MessageInfo> messages) override;
 
  protected:
@@ -39,12 +45,14 @@ class APINoiseFrameHelper final : public APIFrameHelper {
   APIError state_action_();
   APIError state_action_client_hello_();
   APIError state_action_server_hello_();
+  APIError send_server_hello_frame_();
+  APIError start_handshake_();
   APIError state_action_handshake_();
   APIError state_action_handshake_read_();
   APIError state_action_handshake_write_();
   APIError try_read_frame_();
   APIError write_frame_(const uint8_t *data, uint16_t len);
-  APIError encrypt_noise_message_(uint8_t *buf_start, uint16_t payload_size, uint8_t message_type,
+  APIError encrypt_noise_message_(uint8_t *buf_start, uint16_t payload_size, uint16_t message_type,
                                   uint16_t &encrypted_len_out);
   APIError init_handshake_();
   APIError check_handshake_finished_();
@@ -52,25 +60,22 @@ class APINoiseFrameHelper final : public APIFrameHelper {
   APIError handle_handshake_frame_error_(APIError aerr);
   APIError handle_noise_error_(int err, const LogString *func_name, APIError api_err);
 
-  // Pointers first (4 bytes each)
-  NoiseHandshakeState *handshake_{nullptr};
+  // Pointers first (4 bytes each; the handshake wrapper holds one pointer)
+  noise::NoiseResponderHandshake handshake_;
   NoiseCipherState *send_cipher_{nullptr};
   NoiseCipherState *recv_cipher_{nullptr};
 
   // Reference to noise context (4 bytes on 32-bit)
-  APINoiseContext &ctx_;
+  noise::NoiseContext &ctx_;
 
   // Buffer for noise handshake prologue (released after handshake)
   APIBuffer prologue_;
 
-  // NoiseProtocolId (size depends on implementation)
-  NoiseProtocolId nid_;
-
   // Group small types together
   // Fixed-size header buffer for noise protocol:
   // 1 byte for indicator + 2 bytes for message size (16-bit value, not varint)
   // Note: Maximum message size is UINT16_MAX (65535), with a limit of 128 bytes during handshake phase
-  uint8_t rx_header_buf_[3];
+  uint8_t rx_header_buf_[noise::FRAME_HEADER_SIZE];
   uint8_t rx_header_buf_len_ = 0;
   // 4 bytes total, no padding
 };

esphome/components/api/api_frame_helper_plaintext.cpp

@@ -5,6 +5,7 @@
 #include "esphome/core/hal.h"
 #include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
+#include "api_pb2.h"
 #include "proto.h"
 #include <cstring>
 #include <cinttypes>
@@ -171,7 +172,10 @@ APIError APIPlaintextFrameHelper::try_read_frame_() {
 
   // Reserve space for body (+ null terminator so protobuf StringRef fields
   // can be safely null-terminated in-place after decode)
-  this->rx_buf_.resize(this->rx_header_parsed_len_ + RX_BUF_NULL_TERMINATOR);
+  if (!this->rx_buf_.resize(this->rx_header_parsed_len_ + RX_BUF_NULL_TERMINATOR)) [[unlikely]] {
+    state_ = State::FAILED;
+    return APIError::OUT_OF_MEMORY;
+  }
 
   if (rx_buf_len_ < rx_header_parsed_len_) {
     // more data to read
@@ -252,24 +256,21 @@ ESPHOME_ALWAYS_INLINE static inline void encode_varint_16(uint16_t value, uint8_
   *p = static_cast<uint8_t>(value);
 }
 
-// Encode an 8-bit varint (1-2 bytes) using pre-computed length.
-ESPHOME_ALWAYS_INLINE static inline void encode_varint_8(uint8_t value, uint8_t varint_len, uint8_t *p) {
-  if (varint_len == 2) {
-    *p++ = static_cast<uint8_t>(value | 0x80);
-    *p = static_cast<uint8_t>(value >> 7);
-  } else {
-    *p = value;
-  }
-}
+// The generator rejects message IDs above MAX_MESSAGE_TYPE, so the type varint
+// can never outgrow the 2 bytes HEADER_PADDING budgets for it. Without this
+// bound, write_plaintext_header's header_offset would underflow for the first
+// message in a batch and the header write would land outside the buffer.
+static_assert(1 + 3 + ProtoSize::varint16(MAX_MESSAGE_TYPE) <= APIPlaintextFrameHelper::HEADER_PADDING,
+              "HEADER_PADDING cannot fit the type varint of the largest message ID");
 
 // Write plaintext header into pre-allocated padding before payload.
 // padding_size: bytes reserved before payload (HEADER_PADDING for first/single msg,
 //               actual header size for contiguous batch messages).
 // Returns the total header length (indicator + varints).
 ESPHOME_ALWAYS_INLINE static inline uint8_t write_plaintext_header(uint8_t *buf_start, uint16_t payload_size,
-                                                                   uint8_t message_type, uint8_t padding_size) {
+                                                                   uint16_t message_type, uint8_t padding_size) {
   uint8_t size_varint_len = ProtoSize::varint16(payload_size);
-  uint8_t type_varint_len = ProtoSize::varint8(message_type);
+  uint8_t type_varint_len = ProtoSize::varint16(message_type);
   uint8_t total_header_len = 1 + size_varint_len + type_varint_len;
 
   // The header is right-justified within the padding so it sits immediately before payload.
@@ -292,12 +293,12 @@ ESPHOME_ALWAYS_INLINE static inline uint8_t write_plaintext_header(uint8_t *buf_
 
   // Encode varints directly into buffer using pre-computed lengths
   encode_varint_16(payload_size, size_varint_len, buf_start + header_offset + 1);
-  encode_varint_8(message_type, type_varint_len, buf_start + header_offset + 1 + size_varint_len);
+  encode_varint_16(message_type, type_varint_len, buf_start + header_offset + 1 + size_varint_len);
 
   return total_header_len;
 }
 
-APIError APIPlaintextFrameHelper::write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) {
+APIError APIPlaintextFrameHelper::write_protobuf_packet(uint16_t type, ProtoWriteBuffer buffer) {
 #ifdef ESPHOME_DEBUG_API
   assert(this->state_ == State::DATA);
 #endif

esphome/components/api/api_frame_helper_plaintext.h

@@ -10,7 +10,8 @@ class APIPlaintextFrameHelper final : public APIFrameHelper {
   // Plaintext header structure (worst case):
   // Pos 0: indicator (0x00)
   // Pos 1-3: payload size varint (up to 3 bytes)
-  // Pos 4-5: message type varint (up to 2 bytes)
+  // Pos 4-5: message type varint (up to 2 bytes; covers message IDs up to
+  //          16383, enforced by the proto codegen)
   // Pos 6+: actual payload data
   static constexpr uint8_t HEADER_PADDING = 1 + 3 + 2;  // indicator + size varint + type varint
 
@@ -21,7 +22,7 @@ class APIPlaintextFrameHelper final : public APIFrameHelper {
   APIError init() override;
   APIError loop() override;
   APIError read_packet(ReadPacketBuffer *buffer) override;
-  APIError write_protobuf_packet(uint8_t type, ProtoWriteBuffer buffer) override;
+  APIError write_protobuf_packet(uint16_t type, ProtoWriteBuffer buffer) override;
   APIError write_protobuf_messages(ProtoWriteBuffer buffer, std::span<const MessageInfo> messages) override;
 #ifdef USE_API_NOISE
   // After try_read_frame_ returned PROTOCOL_SWITCH_TO_NOISE: copy out the

esphome/components/api/api_noise_context.h

@@ -1,37 +0,0 @@
-#pragma once
-#include <array>
-#include <cstdint>
-#include "esphome/core/defines.h"
-
-namespace esphome::api {
-
-#ifdef USE_API_NOISE
-using psk_t = std::array<uint8_t, 32>;
-
-class APINoiseContext {
- public:
-  // The all-zeros PSK is reserved: it marks the device as unprovisioned and
-  // doubles as the well-known provisioning PSK that unprovisioned devices
-  // accept for Noise handshakes (passive-sniffing protection only, no
-  // authentication). It is never a valid real key.
-  static bool is_all_zeros(const psk_t &psk) {
-    uint8_t acc = 0;
-    for (uint8_t b : psk) {
-      acc |= b;
-    }
-    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_; }
-
- protected:
-  psk_t psk_{};
-  bool has_psk_{false};
-};
-#endif  // USE_API_NOISE
-
-}  // namespace esphome::api