Address review: marker scan covers every usage form including multiline pytestmark lists

AGENTS.md

@@ -44,6 +44,16 @@ This document provides essential context for AI models interacting with this pro
 
 ## 4. Coding Conventions & Style Guide
 
+**Read the developer documentation before writing a component.** https://developers.esphome.io covers the
+component lifecycle, the main loop, and the reasoning behind the rules below in far more depth than this
+file does, and it is the authority when they disagree. The most useful starting points:
+
+*   https://developers.esphome.io/architecture/components/ - component lifecycle, `setup()`, `loop()`,
+    setup priorities, and how a component is registered.
+*   https://developers.esphome.io/architecture/components/advanced/ - choosing between `loop()`,
+    `set_interval`, `set_timeout` and `defer`; waking the loop from another thread; the RAM cost of each.
+*   https://developers.esphome.io/contributing/code/ - contribution rules, public API and breaking changes.
+
 *   **Formatting:**
     *   **Python:** Uses `ruff` and `flake8` for linting and formatting. Configuration is in `pyproject.toml`.
     *   **C++:** Uses `clang-format` for formatting. Configuration is in `.clang-format`.
@@ -142,6 +152,47 @@ This document provides essential context for AI models interacting with this pro
     *   **Indentation:** Use spaces (two per indentation level), not tabs
     *   **Type aliases:** Prefer `using type_t = int;` over `typedef int type_t;`
     *   **Line length:** Wrap lines at no more than 120 characters
+    *   **Timing in `loop()`:** Never call `millis()` in a `loop()` body. The current tick's timestamp is
+        already cached - use `App.get_loop_component_start_time()` (from `esphome/core/application.h`).
+        Only reach for `millis()` when you genuinely need sub-tick resolution inside a long operation.
+    *   **The main loop runs every 16 ms.** A rate-limit gate shorter than that does nothing: the check
+        passes on essentially every pass of the loop, so it costs a comparison and buys nothing. Pick an
+        interval comfortably coarser than 16 ms, or drop the gate entirely and accept running every loop.
+        ```cpp
+        // Bad - a 10ms gate against a 16ms loop never holds anything back
+        static constexpr uint32_t POLL_INTERVAL_MS = 10;
+        const uint32_t now = millis();
+        if (now - this->last_poll_ < POLL_INTERVAL_MS)
+          return;
+        this->last_poll_ = now;
+        ```
+        ```cpp
+        // Good - an interval that actually rate limits, off the cached timestamp
+        static constexpr uint32_t POLL_INTERVAL_MS = 100;
+        const uint32_t now = App.get_loop_component_start_time();
+        if (now - this->last_poll_ < POLL_INTERVAL_MS)
+          return;
+        this->last_poll_ = now;
+        ```
+        Pick the primitive by cadence: under 250 ms use a gated `loop()`; 500 ms and above use
+        `set_interval`. Full reasoning, including why `set_interval` costs more below 500 ms:
+        https://developers.esphome.io/architecture/components/advanced/#quick-rule-of-thumb
+    *   **Don't override a default with the same value:** if a base class method already returns what you
+        want, do not override it. `Component::get_setup_priority()` returns `setup_priority::DATA`, so a
+        component that wants `DATA` should simply leave it alone.
+        ```cpp
+        // Bad - this is exactly what the base class already does
+        float get_setup_priority() const override { return setup_priority::DATA; }
+        ```
+    *   **Logging string literals:** wrap literals passed as `%s` arguments in `LOG_STR_LITERAL()` so they
+        can be stored in flash rather than RAM.
+        ```cpp
+        // Bad
+        ESP_LOGV(TAG, "Key %u %s", key, pressed ? "pressed" : "released");
+
+        // Good
+        ESP_LOGV(TAG, "Key %u %s", key, pressed ? LOG_STR_LITERAL("pressed") : LOG_STR_LITERAL("released"));
+        ```
     *   **Constructor parameters vs setters:** Component properties that are both **required** and **invariant**
         (never change after construction) should be constructor parameters rather than set via setter methods.
         This makes the dependency explicit and prevents use of the object in an incompletely-initialized state.
@@ -562,6 +613,33 @@ This document provides essential context for AI models interacting with this pro
            Use `cg.add_define("MAX_SERVICES", count)` to set the size from Python configuration.
            Like `std::array` but with vector-like API (`push_back()`, `size()`) and no STL reallocation code.
 
+           **Listener and child-entity registration lists are the most common case, and the most commonly
+           missed.** A `register_*()` method called once per child at code generation time has a count that
+           is known at compile time, so it should never be a `std::vector`. Use `cg.slot_counter()`: it
+           returns a function that each consumer calls once per slot it will occupy, and after every
+           `to_code` has run it emits the define with the final count. When nothing registers, no define is
+           emitted and the storage plus its registration method compile out entirely.
+           ```python
+           # hub component's __init__.py
+           _request_listener_slot = cg.slot_counter("MY_COMPONENT_LISTENER_COUNT")
+
+
+           async def register_listener(hub: MockObj, var: MockObj) -> None:
+               _request_listener_slot()
+               cg.add(hub.register_listener(var))
+           ```
+           ```cpp
+           #ifdef MY_COMPONENT_LISTENER_COUNT
+             void register_listener(MyComponentListener *listener);
+           #endif
+            protected:
+           #ifdef MY_COMPONENT_LISTENER_COUNT
+             StaticVector<MyComponentListener *, MY_COMPONENT_LISTENER_COUNT> listeners_;
+           #endif
+           ```
+           Request slots from `to_code`, not from a job that runs after `CoroPriority.FINAL` - a late
+           request raises rather than silently undercounting.
+
         3. **Runtime-known sizes:** Use `FixedVector` from `esphome/core/helpers.h` when the size is only known at runtime initialization.
            ```cpp
            // Bad - generates STL realloc code (_M_realloc_insert)
@@ -599,9 +677,25 @@ This document provides essential context for AI models interacting with this pro
            ```
            Linear search on small datasets (1-16 elements) is often faster than hashing/tree overhead, but this depends on lookup frequency and access patterns. For frequent lookups in hot code paths, the O(1) vs O(n) complexity difference may still matter even for small datasets. `std::vector` with simple structs is usually fine—it's the heavy containers (`map`, `set`, `unordered_map`) that should be avoided for small datasets unless profiling shows otherwise.
 
-        5. **Avoid `std::deque`:** It allocates in 512-byte blocks regardless of element size, guaranteeing at least 512 bytes of RAM usage immediately. This is a major source of crashes on memory-constrained devices.
+        5. **Strings set once from configuration:** Use `StringRef` (`esphome/core/string_ref.h`) rather than
+           `std::string`. Code generation passes a string literal that lives in flash for the life of the
+           program, so storing a `std::string` copies it onto the heap for nothing. `StringRef` is a
+           non-owning pointer plus length; it does not copy, and it must only ever refer to storage that
+           outlives it (a string literal, or a buffer owned elsewhere).
+           ```cpp
+           // Bad - heap copy of a literal that is already in flash
+           void set_keys(std::string keys) { this->keys_ = std::move(keys); }
+           std::string keys_;
+           ```
+           ```cpp
+           // Good - no allocation
+           void set_keys(const char *keys) { this->keys_ = StringRef(keys); }
+           StringRef keys_;
+           ```
 
-        6. **Detection:** Look for these patterns in compiler output:
+        6. **Avoid `std::deque`:** It allocates in 512-byte blocks regardless of element size, guaranteeing at least 512 bytes of RAM usage immediately. This is a major source of crashes on memory-constrained devices.
+
+        7. **Detection:** Look for these patterns in compiler output:
            - Large code sections with STL symbols (vector, map, set)
            - `alloc`, `realloc`, `dealloc` in symbol names
            - `_M_realloc_insert`, `_M_default_append` (vector reallocation)

script/helpers.py

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

tests/integration/README.md

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

tests/integration/conftest.py

@@ -4,17 +4,22 @@ from __future__ import annotations
 
 import asyncio
 from collections.abc import AsyncGenerator, Callable, Generator
-from contextlib import AbstractAsyncContextManager, asynccontextmanager
+from contextlib import AbstractAsyncContextManager, asynccontextmanager, suppress
 import fcntl
+from functools import cache
+import hashlib
 import logging
 import os
 from pathlib import Path
 import platform
+import re
+import shutil
 import signal
 import socket
 import subprocess
 import sys
 import tempfile
+import time
 from typing import TextIO
 
 from aioesphomeapi import APIClient, APIConnectionError, LogParser, ReconnectLogic
@@ -23,7 +28,13 @@ import pytest_asyncio
 
 import esphome.config
 from esphome.core import CORE
-from esphome.helpers import get_usable_cpu_count
+from esphome.helpers import (
+    get_usable_cpu_count,
+    read_file,
+    rmtree,
+    write_file,
+    write_file_if_changed,
+)
 from esphome.platformio.toolchain import get_idedata
 
 from .const import (
@@ -56,6 +67,21 @@ import pty  # not available on Windows
 pytest.register_assert_rewrite("tests.integration.entity_utils")
 
 
+def pytest_configure(config: pytest.Config) -> None:
+    config.addinivalue_line(
+        "markers",
+        "shared_yaml(name): load fixtures/<name>.yaml and compile it in a shared, "
+        "hash-keyed incremental build directory",
+    )
+
+
+FIXTURES_DIR = Path(__file__).parent / "fixtures"
+REPO_ROOT = Path(__file__).resolve().parent.parent.parent
+
+# CI caches parts of this path; keep in sync with ci.yml integration-tests.
+INTEGRATION_TESTS_ROOT = Path.home() / ".esphome-integration-tests"
+
+
 def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
     """Get environment variables for PlatformIO with shared cache."""
     env = os.environ.copy()
@@ -78,7 +104,7 @@ def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
         )
     # Compile with THIS tree's esphome sources, not wherever the venv's editable
     # install points (which may be a different git worktree or checkout).
-    repo_root = str(Path(__file__).resolve().parent.parent.parent)
+    repo_root = str(REPO_ROOT)
     existing = env.get("PYTHONPATH")
     env["PYTHONPATH"] = f"{repo_root}{os.pathsep}{existing}" if existing else repo_root
     return env
@@ -88,8 +114,7 @@ def _get_platformio_env(cache_dir: Path) -> dict[str, str]:
 def shared_platformio_cache() -> Generator[Path]:
     """Initialize a shared PlatformIO cache for all integration tests."""
     # Use a dedicated directory for integration tests to avoid conflicts.
-    # CI caches parts of this path; keep in sync with ci.yml integration-tests.
-    test_cache_dir = Path.home() / ".esphome-integration-tests"
+    test_cache_dir = INTEGRATION_TESTS_ROOT
     cache_dir = test_cache_dir / "platformio"
 
     # Use a lock file in the home directory to ensure only one process initializes the cache
@@ -112,7 +137,9 @@ def shared_platformio_cache() -> Generator[Path]:
                 init_dir = Path(tmpdir)
                 fixture_path = Path(__file__).parent / "fixtures" / "cache_init.yaml"
                 config_path = init_dir / "cache_init.yaml"
-                config_path.write_text(fixture_path.read_text())
+                config_path.write_text(
+                    fixture_path.read_text(encoding="utf-8"), encoding="utf-8"
+                )
 
                 # Run compilation to populate the cache
                 # We must succeed here to avoid race conditions where multiple
@@ -181,21 +208,29 @@ def unused_tcp_port(reserved_tcp_port: tuple[int, socket.socket]) -> int:
     return reserved_tcp_port[0]
 
 
+@pytest.fixture(autouse=True)
+def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> Path:
+    """Give every test its own host prefs dir; prefs are keyed only by device
+    name, which tests sharing a fixture also share."""
+    prefdir = tmp_path / "prefs"
+    monkeypatch.setenv("ESPHOME_PREFDIR", str(prefdir))
+    return prefdir
+
+
 @pytest_asyncio.fixture
 async def yaml_config(request: pytest.FixtureRequest, unused_tcp_port: int) -> str:
     """Load YAML configuration based on test name."""
-    # Get the test function name
-    test_name: str = request.node.name
-    # Extract the base test name (remove test_ prefix and any parametrization)
-    base_name = test_name.replace("test_", "").partition("[")[0]
+    shared_name = _shared_yaml_name(request)
+    # Base test name: test_ prefix and any parametrization stripped
+    base_name = shared_name or request.node.name.replace("test_", "").partition("[")[0]
 
     # Load the fixture file
-    fixture_path = Path(__file__).parent / "fixtures" / f"{base_name}.yaml"
+    fixture_path = FIXTURES_DIR / f"{base_name}.yaml"
     if not fixture_path.exists():
         raise FileNotFoundError(f"Fixture file not found: {fixture_path}")
 
     loop = asyncio.get_running_loop()
-    content = await loop.run_in_executor(None, fixture_path.read_text)
+    content = await loop.run_in_executor(None, read_file, fixture_path)
 
     # Replace the port in the config if it contains api section
     if "api:" in content:
@@ -219,11 +254,13 @@ async def yaml_config(request: pytest.FixtureRequest, unused_tcp_port: int) -> s
 
     # Replace external component path placeholder if present
     if "EXTERNAL_COMPONENT_PATH" in content:
-        external_components_path = str(
-            Path(__file__).parent / "fixtures" / "external_components"
-        )
+        external_components_path = str(FIXTURES_DIR / "external_components")
         content = content.replace("EXTERNAL_COMPONENT_PATH", external_components_path)
 
+    if shared_name is not None:
+        # _compile verifies the marked test compiles this content unmodified
+        request.node._shared_yaml_content = content
+
     return content
 
 
@@ -233,24 +270,218 @@ async def write_yaml_config(
 ) -> AsyncGenerator[ConfigWriter]:
     """Write YAML configuration to a file."""
     # Get the test name for default filename
-    test_name = request.node.name
-    base_name = test_name.replace("test_", "").split("[")[0]
+    base_name = request.node.name.replace("test_", "").partition("[")[0]
 
     async def _write_config(content: str, filename: str | None = None) -> Path:
         if filename is None:
             filename = f"{base_name}.yaml"
         config_path = integration_test_dir / filename
         loop = asyncio.get_running_loop()
-        await loop.run_in_executor(None, config_path.write_text, content)
+        await loop.run_in_executor(None, write_file, config_path, content)
         return config_path
 
     yield _write_config
 
 
+# Deliberately not CI-cached (ci.yml caches only platformio/ subpaths); stale
+# dirs for a fixture are pruned when its content hash changes.
+SHARED_BUILDS_ROOT = INTEGRATION_TESTS_ROOT / "builds"
+
+# In the dir name (not just the hash) so pruning stays inside this checkout
+_REPO_KEY = hashlib.sha256(str(REPO_ROOT).encode()).hexdigest()[:8]
+
+# Give a contended shared build lock time for a full cold compile ahead of us
+_SHARED_LOCK_TIMEOUT_S = 900
+_SHARED_LOCK_POLL_S = 0.1
+_SHARED_LOCK_REPORT_S = 30
+
+# Reclaims dirs orphaned by fixture renames or deleted checkouts
+_STALE_BUILD_MAX_AGE_S = 30 * 24 * 3600
+
+# ELF path per shared build dir; constant once compiled, so resolve it only once
+_shared_elf_paths: dict[Path, Path] = {}
+
+# Dirs this process already swept; pruning is session-scoped work
+_pruned_dirs: set[Path] = set()
+
+
+def _shared_yaml_name(request: pytest.FixtureRequest) -> str | None:
+    """Name passed to the shared_yaml marker, or None when unmarked."""
+    marker = request.node.get_closest_marker("shared_yaml")
+    if marker is None:
+        return None
+    # Exactly one \w+ positional arg: the name doubles as a build dir
+    # component, and CI test selection (script/helpers.py) parses the same shape
+    if (
+        len(marker.args) != 1
+        or marker.kwargs
+        or not re.fullmatch(r"\w+", str(marker.args[0]))
+    ):
+        raise ValueError(
+            "shared_yaml marker requires exactly one \\w+ fixture name literal"
+        )
+    return marker.args[0]
+
+
+def _shared_build_prefix(name: str) -> str:
+    return f"{name}-{_REPO_KEY}-"
+
+
+@cache
+def _shared_build_dir(name: str) -> Path:
+    """Dir keyed by checkout and fixture source, before per-test injections."""
+    key = hashlib.sha256((FIXTURES_DIR / f"{name}.yaml").read_bytes()).hexdigest()[:16]
+    return SHARED_BUILDS_ROOT / (_shared_build_prefix(name) + key)
+
+
+def _read_stamp(stamp: Path, shared_dir: Path) -> Path | None:
+    """ELF path recorded by the last completed compile, or None."""
+    try:
+        text = stamp.read_text(encoding="utf-8").strip()
+    except FileNotFoundError:
+        return None
+    except OSError as err:
+        print(f"Cannot read {stamp}: {err}")
+        return None
+    if not text:
+        print(f"Ignoring empty stamp {stamp}")
+        return None
+    built = Path(text)
+    # Never trust a stamp pointing outside its own build dir as an unlink target
+    if shared_dir.resolve() in built.resolve().parents:
+        return built
+    print(f"Ignoring stamp {stamp} pointing outside {shared_dir}")
+    return None
+
+
+def _unused_since(stale: Path, cutoff: float) -> bool:
+    """Whether a build dir looks untouched since cutoff; unknown counts as used."""
+    # Newest of the .built stamp (rewritten by every completed compile) and the
+    # dir itself (freshened by a worker claiming the dir before locking)
+    newest: float | None = None
+    for probe in (stale / ".built", stale):
+        try:
+            mtime = probe.stat().st_mtime
+        except FileNotFoundError:
+            continue
+        except NotADirectoryError:
+            return True  # a stray file where a dir should be; reclaimable
+        except OSError as err:
+            print(f"Cannot age-probe {stale}: {err}")
+            return False  # unknown never authorizes deletion
+        newest = mtime if newest is None else max(newest, mtime)
+    return newest is not None and newest < cutoff
+
+
+def _prune_stale_builds(name: str, keep: Path) -> None:
+    """Remove outdated build dirs (blocking, run in executor): this checkout's
+    other dirs for the fixture, plus anything untouched for 30 days. Tolerates
+    other workers pruning the same dirs concurrently."""
+    cutoff = time.time() - _STALE_BUILD_MAX_AGE_S
+    prefix = _shared_build_prefix(name)
+    for stale in SHARED_BUILDS_ROOT.iterdir():
+        if stale == keep:
+            continue
+        same_fixture = stale.name.startswith(prefix)
+        if not same_fixture and not _unused_since(stale, cutoff):
+            continue
+        # Creating .lock bumps the dir mtime, so remember whether the re-probe
+        # under the lock can trust it
+        lock_preexisting = (stale / ".lock").exists()
+        try:
+            lock_file = (stale / ".lock").open("w")
+        except FileNotFoundError:
+            continue  # pruned by another worker meanwhile
+        except NotADirectoryError:
+            print(f"Removing stray file {stale}")
+            stale.unlink(missing_ok=True)
+            continue
+        except OSError as err:
+            print(f"Cannot prune {stale}: {err}")
+            continue
+        with lock_file:
+            try:
+                fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except BlockingIOError:
+                continue  # still in use by another run
+            # Re-probe under the lock: a worker freshens its dir before
+            # locking, so a just-claimed dir no longer looks unused. A dir
+            # whose .lock we just created cannot be held by anyone, and our
+            # own open bumped its mtime, so its pre-open probe stands
+            if (
+                lock_preexisting
+                and not same_fixture
+                and not _unused_since(stale, cutoff)
+            ):
+                continue
+            # rmtree tolerates races; a leftover partial tree only costs a
+            # rebuild, since the ELF is deleted before every compile
+            try:
+                rmtree(stale)
+            except OSError as err:
+                print(f"Failed to prune {stale}: {err}")
+
+
+async def _run_esphome_compile(
+    config_path: Path, cwd: Path, env: dict[str, str]
+) -> None:
+    """Run `esphome compile`, retrying up to 3 times on a segfault."""
+    max_retries = 3
+    for attempt in range(max_retries):
+        # Compile using subprocess, inheriting stdout/stderr to show progress
+        proc = await asyncio.create_subprocess_exec(
+            sys.executable,
+            "-m",
+            "esphome",
+            "compile",
+            str(config_path),
+            cwd=cwd,
+            stdout=None,  # Inherit stdout
+            stderr=None,  # Inherit stderr
+            stdin=asyncio.subprocess.DEVNULL,
+            # Start in a new process group to isolate signal handling
+            start_new_session=True,
+            env=env,
+            close_fds=False,
+        )
+        await proc.wait()
+
+        if proc.returncode == 0:
+            break
+        if proc.returncode == -11 and attempt < max_retries - 1:
+            # Segfault (-11 = SIGSEGV), retry
+            print(
+                f"Compilation segfaulted (attempt {attempt + 1}/{max_retries}), retrying..."
+            )
+            await asyncio.sleep(1)  # Brief pause before retry
+            continue
+        raise RuntimeError(
+            f"Failed to compile {config_path}, return code: {proc.returncode}. "
+            f"Run with 'pytest -s' to see compilation output."
+        )
+
+
+def _resolve_compiled_binary(config_path: Path) -> Path:
+    """Load the config to learn the compiled ELF path (blocking, run in executor)."""
+    CORE.reset()  # Reset CORE state between test runs
+    CORE.config_path = config_path
+    config = esphome.config.read_config(
+        {"command": "compile", "config": str(config_path)}
+    )
+    if config is None:
+        raise RuntimeError(f"Failed to read config from {config_path}")
+    idedata = get_idedata(config)
+    binary_path = Path(idedata.firmware_elf_path)
+    if not binary_path.exists():
+        raise RuntimeError(f"Compiled binary not found at {binary_path}")
+    return binary_path
+
+
 @pytest_asyncio.fixture
 async def compile_esphome(
     integration_test_dir: Path,
     shared_platformio_cache: Path,
+    request: pytest.FixtureRequest,
 ) -> AsyncGenerator[CompileFunction]:
     """Compile an ESPHome configuration and return the binary path."""
 
@@ -258,66 +489,96 @@ async def compile_esphome(
         # Use the shared PlatformIO cache for faster compilation
         # This avoids re-downloading dependencies for each test
         env = _get_platformio_env(shared_platformio_cache)
-
-        # Retry compilation up to 3 times if we get a segfault
-        max_retries = 3
-        for attempt in range(max_retries):
-            # Compile using subprocess, inheriting stdout/stderr to show progress
-            proc = await asyncio.create_subprocess_exec(
-                sys.executable,
-                "-m",
-                "esphome",
-                "compile",
-                str(config_path),
-                cwd=integration_test_dir,
-                stdout=None,  # Inherit stdout
-                stderr=None,  # Inherit stderr
-                stdin=asyncio.subprocess.DEVNULL,
-                # Start in a new process group to isolate signal handling
-                start_new_session=True,
-                env=env,
-                close_fds=False,
-            )
-            await proc.wait()
-
-            if proc.returncode == 0:
-                # Success!
-                break
-            if proc.returncode == -11 and attempt < max_retries - 1:
-                # Segfault (-11 = SIGSEGV), retry
-                print(
-                    f"Compilation segfaulted (attempt {attempt + 1}/{max_retries}), retrying..."
-                )
-                await asyncio.sleep(1)  # Brief pause before retry
-                continue
-            # Other error or final retry
-            raise RuntimeError(
-                f"Failed to compile {config_path}, return code: {proc.returncode}. "
-                f"Run with 'pytest -s' to see compilation output."
-            )
-
-        # Load the config to get idedata (blocking call, must use executor)
         loop = asyncio.get_running_loop()
 
-        def _read_config_and_get_binary():
-            CORE.reset()  # Reset CORE state between test runs
-            CORE.config_path = config_path
-            config = esphome.config.read_config(
-                {"command": "compile", "config": str(config_path)}
+        name = _shared_yaml_name(request)
+        if name is None:
+            await _run_esphome_compile(config_path, integration_test_dir, env)
+            return await loop.run_in_executor(
+                None, _resolve_compiled_binary, config_path
             )
-            if config is None:
-                raise RuntimeError(f"Failed to read config from {config_path}")
 
-            # Get the compiled binary path
-            idedata = get_idedata(config)
-            return Path(idedata.firmware_elf_path)
-
-        binary_path = await loop.run_in_executor(None, _read_config_and_get_binary)
-
-        if not binary_path.exists():
-            raise RuntimeError(f"Compiled binary not found at {binary_path}")
-
-        return binary_path
+        # Shared fixture: build in a hash-keyed dir so tests sharing a config
+        # pay one full compile and later only a main.cpp (port) rebuild + relink
+        shared_dir = _shared_build_dir(name)
+        shared_dir.mkdir(parents=True, exist_ok=True)
+        # Freshen the dir before locking so a concurrent age sweep, which
+        # re-probes under the lock, never reaps a dir a worker just claimed;
+        # if a peer reaped it already, the guarded lock open recreates it
+        with suppress(FileNotFoundError):
+            os.utime(shared_dir)
+        if shared_dir not in _pruned_dirs:
+            _pruned_dirs.add(shared_dir)
+            await loop.run_in_executor(None, _prune_stale_builds, name, shared_dir)
+        shared_config = shared_dir / f"{name}.yaml"
+        private_binary = integration_test_dir / f"{name}.elf"
+        content = await loop.run_in_executor(None, read_file, config_path)
+        if content != getattr(request.node, "_shared_yaml_content", None):
+            # The dir is keyed by the fixture source; a mutated config would be
+            # cached under a hash that does not describe it
+            raise RuntimeError(
+                "shared_yaml tests must compile the yaml_config content unmodified"
+            )
+        # flock serializes concurrent xdist workers; closing the fd releases it.
+        # Hand-rolled rather than filelock.FileLock: non-blocking retries keep
+        # the wait cancellable, while a blocking acquire in an executor thread
+        # would survive test cancellation holding the fd
+        try:
+            lock_file = (shared_dir / ".lock").open("w")
+        except FileNotFoundError:
+            # A peer run pruning divergent hashes reaped the dir between our
+            # mkdir and this open; recreate it and pay a full rebuild
+            shared_dir.mkdir(parents=True, exist_ok=True)
+            lock_file = (shared_dir / ".lock").open("w")
+        with lock_file:
+            start = time.monotonic()
+            last_report = start
+            while True:
+                try:
+                    fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
+                    break
+                except BlockingIOError:
+                    now = time.monotonic()
+                    if now - start > _SHARED_LOCK_TIMEOUT_S:
+                        raise RuntimeError(
+                            f"Timed out waiting for the {shared_dir} lock"
+                        ) from None
+                    if now - last_report >= _SHARED_LOCK_REPORT_S:
+                        last_report = now
+                        print(
+                            f"Waited {now - start:.0f}s for another worker's "
+                            f"build of {shared_dir.name}"
+                        )
+                    await asyncio.sleep(_SHARED_LOCK_POLL_S)
+            # .built carries the ELF path of the last completed compile, so
+            # later workers skip the config re-read in _resolve_compiled_binary
+            stamp = shared_dir / ".built"
+            if (built := _shared_elf_paths.get(shared_dir)) is None:
+                built = await loop.run_in_executor(None, _read_stamp, stamp, shared_dir)
+            # Delete the ELF before compiling: whatever exists afterwards is
+            # this compile's output, so no staleness check is ever needed.
+            # With no usable stamp, sweep any leftover at the known layout
+            if built is not None:
+                built.unlink(missing_ok=True)
+            else:
+                # Layout-agnostic: ESPHOME_BUILD_PATH can move the build tree
+                for leftover in shared_dir.rglob("program"):
+                    if leftover.is_file():
+                        leftover.unlink()
+            await loop.run_in_executor(
+                None, write_file_if_changed, shared_config, content
+            )
+            await _run_esphome_compile(shared_config, shared_dir, env)
+            if built is None or not built.exists():
+                built = await loop.run_in_executor(
+                    None, _resolve_compiled_binary, shared_config
+                )
+            _shared_elf_paths[shared_dir] = built
+            await loop.run_in_executor(None, write_file, stamp, str(built))
+            # Copy out before unlocking: another worker may relink firmware.elf
+            # while this test is still running its private copy
+            await loop.run_in_executor(None, shutil.copy2, built, private_binary)
+        return private_binary
 
     yield _compile
 

tests/integration/fixtures/sensor_filters_batch_window.yaml

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

tests/integration/fixtures/uart_mock_modbus_client_read_write.yaml

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

tests/integration/fixtures/uart_mock_modbus_custom_pdu.yaml

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

tests/integration/fixtures/uart_mock_modbus_deprecated_write_buffer.yaml

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

tests/integration/fixtures/uart_mock_modbus_lambda_invert.yaml

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

tests/integration/fixtures/uart_mock_modbus_lambda_write.yaml

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

tests/integration/fixtures/uart_mock_modbus_loopback.yaml

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

tests/integration/fixtures/uart_mock_modbus_mesh.yaml

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

tests/integration/fixtures/uart_mock_modbus_register_offset.yaml

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

tests/integration/fixtures/uart_mock_modbus_server.yaml

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

tests/integration/fixtures/uart_mock_modbus_server_controller_multiple.yaml

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

tests/integration/fixtures/uart_mock_modbus_server_injected.yaml

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

tests/integration/host_prefs.py

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

tests/integration/integration_test_durations.json

@@ -1,142 +1,143 @@
 {
-  "tests/integration/test_action_concurrent_reentry.py": 45.23,
-  "tests/integration/test_addressable_light_transition.py": 74.47,
-  "tests/integration/test_alarm_control_panel_state_transitions.py": 74.1,
-  "tests/integration/test_api_action_metadata.py": 62.1,
-  "tests/integration/test_api_action_responses.py": 71.08,
-  "tests/integration/test_api_action_timeout.py": 21.64,
-  "tests/integration/test_api_conditional_memory.py": 13.72,
-  "tests/integration/test_api_custom_services.py": 24.16,
-  "tests/integration/test_api_get_time_response_timezone.py": 23.48,
-  "tests/integration/test_api_homeassistant.py": 37.87,
-  "tests/integration/test_api_homeassistant_action_no_subscriber.py": 14.38,
-  "tests/integration/test_api_list_entities_backpressure.py": 26.85,
-  "tests/integration/test_api_message_size_batching.py": 33.36,
-  "tests/integration/test_api_reboot_timeout.py": 13.63,
-  "tests/integration/test_api_string_lambda.py": 25.04,
-  "tests/integration/test_api_vv_logging.py": 16.6,
-  "tests/integration/test_api_zero_psk_provisioning.py": 43.14,
-  "tests/integration/test_areas_and_devices.py": 25.98,
-  "tests/integration/test_automation_wait_actions.py": 21.91,
-  "tests/integration/test_automations.py": 42.43,
-  "tests/integration/test_batch_delay_zero_rapid_transitions.py": 16.65,
-  "tests/integration/test_binary_sensor_autorepeat_filter.py": 28.67,
-  "tests/integration/test_binary_sensor_invalidate_state.py": 23.69,
-  "tests/integration/test_blocking_warning_log_time_not_charged_to_next_operation.py": 22.99,
-  "tests/integration/test_build_info.py": 24.96,
-  "tests/integration/test_camera_mock.py": 14.47,
-  "tests/integration/test_climate_control_action.py": 31.07,
-  "tests/integration/test_climate_custom_modes.py": 28.59,
-  "tests/integration/test_continuation_actions.py": 14.96,
-  "tests/integration/test_cover_control_action.py": 26.14,
-  "tests/integration/test_crc8_helper.py": 10.92,
-  "tests/integration/test_device_id_in_state.py": 64.97,
-  "tests/integration/test_duplicate_entities.py": 30.81,
-  "tests/integration/test_entity_icon.py": 32.85,
-  "tests/integration/test_fan_turn_on_action.py": 24.91,
-  "tests/integration/test_fnv1_hash_object_id.py": 12.54,
-  "tests/integration/test_fnv1a_hash.py": 21.8,
-  "tests/integration/test_gpio_expander_cache.py": 5.2,
-  "tests/integration/test_host_logger_thread_safety.py": 21.7,
-  "tests/integration/test_host_mode_basic.py": 13.62,
-  "tests/integration/test_host_mode_batch_delay.py": 14.56,
-  "tests/integration/test_host_mode_climate_basic_state.py": 30.95,
-  "tests/integration/test_host_mode_climate_control.py": 29.06,
-  "tests/integration/test_host_mode_empty_string_options.py": 27.22,
-  "tests/integration/test_host_mode_entity_fields.py": 30.95,
-  "tests/integration/test_host_mode_fan_preset.py": 14.44,
-  "tests/integration/test_host_mode_many_entities.py": 54.13,
-  "tests/integration/test_host_mode_many_entities_multiple_connections.py": 32.17,
-  "tests/integration/test_host_mode_noise_encryption.py": 42.77,
-  "tests/integration/test_host_mode_reconnect.py": 4.06,
-  "tests/integration/test_host_mode_sensor.py": 13.47,
-  "tests/integration/test_host_ota.py": 21.4,
-  "tests/integration/test_host_preferences.py": 25.43,
-  "tests/integration/test_host_preferences_suspend_resume.py": 19.2,
-  "tests/integration/test_improv_serial_uart.py": 31.52,
-  "tests/integration/test_large_message_batching.py": 15.64,
-  "tests/integration/test_legacy_area.py": 22.63,
-  "tests/integration/test_legacy_climate_compat.py": 26.13,
-  "tests/integration/test_legacy_fan_compat.py": 24.05,
-  "tests/integration/test_light_automations.py": 30.86,
-  "tests/integration/test_light_binary_effect_off_phase.py": 23.19,
-  "tests/integration/test_light_calls.py": 32.35,
-  "tests/integration/test_light_constant_brightness.py": 29.89,
-  "tests/integration/test_light_control_action.py": 29.06,
-  "tests/integration/test_light_dim_relative_action.py": 29.61,
-  "tests/integration/test_light_effect_zero_brightness.py": 18.68,
-  "tests/integration/test_light_initial_state.py": 24.49,
-  "tests/integration/test_light_toggle_action.py": 26.46,
-  "tests/integration/test_lock_automations.py": 23.28,
-  "tests/integration/test_logger_buffered_recursion_guard.py": 24.29,
-  "tests/integration/test_loop_disable_enable.py": 45.28,
-  "tests/integration/test_loop_interval_decoupling.py": 28.35,
-  "tests/integration/test_loop_interval_default_not_pulled_forward.py": 21.97,
-  "tests/integration/test_micros_to_millis.py": 20.79,
-  "tests/integration/test_multi_click_trigger.py": 26.2,
-  "tests/integration/test_multi_device_preferences.py": 16.87,
-  "tests/integration/test_noise_encryption_key_protection.py": 77.05,
-  "tests/integration/test_object_id_api_verification.py": 73.51,
-  "tests/integration/test_object_id_friendly_name_no_mac_suffix.py": 62.33,
-  "tests/integration/test_object_id_no_friendly_name.py": 43.47,
-  "tests/integration/test_online_image_auto_detects_image_bmp_mime.py": 32.21,
-  "tests/integration/test_online_image_auto_detects_redirected_image_bmp_mime.py": 56.86,
-  "tests/integration/test_online_image_bmp.py": 50.9,
-  "tests/integration/test_oversized_payloads.py": 53.2,
-  "tests/integration/test_preference_key_stability.py": 26.09,
-  "tests/integration/test_runtime_stats.py": 18.34,
-  "tests/integration/test_safe_mode_loop_runs.py": 10.07,
-  "tests/integration/test_scheduler_blocking_warning.py": 40.91,
-  "tests/integration/test_scheduler_bulk_cleanup.py": 23.14,
-  "tests/integration/test_scheduler_defer_cancel.py": 24.54,
-  "tests/integration/test_scheduler_defer_cancel_regular.py": 13.48,
-  "tests/integration/test_scheduler_defer_fifo_simple.py": 26.86,
-  "tests/integration/test_scheduler_defer_stress.py": 27.23,
-  "tests/integration/test_scheduler_heap_stress.py": 24.02,
-  "tests/integration/test_scheduler_internal_id_no_collision.py": 24.57,
-  "tests/integration/test_scheduler_interval_reschedule.py": 13.12,
-  "tests/integration/test_scheduler_interval_zero_coerced.py": 22.91,
-  "tests/integration/test_scheduler_null_name.py": 23.46,
-  "tests/integration/test_scheduler_numeric_id_test.py": 24.54,
-  "tests/integration/test_scheduler_pool.py": 25.0,
-  "tests/integration/test_scheduler_rapid_cancellation.py": 14.68,
-  "tests/integration/test_scheduler_recursive_timeout.py": 25.35,
-  "tests/integration/test_scheduler_removed_item_race.py": 26.19,
-  "tests/integration/test_scheduler_self_keyed.py": 23.43,
-  "tests/integration/test_scheduler_simultaneous_callbacks.py": 22.16,
-  "tests/integration/test_scheduler_string_test.py": 15.22,
-  "tests/integration/test_script_array_params.py": 14.67,
-  "tests/integration/test_script_delay_params.py": 15.65,
-  "tests/integration/test_script_queued.py": 24.93,
-  "tests/integration/test_script_queued_idle_loop.py": 5.04,
-  "tests/integration/test_script_wait_on_boot.py": 13.08,
-  "tests/integration/test_select_stringref_trigger.py": 29.6,
-  "tests/integration/test_sensor_filters_delta.py": 28.01,
-  "tests/integration/test_sensor_filters_ring_buffer.py": 25.04,
-  "tests/integration/test_sensor_filters_sliding_window.py": 71.5,
-  "tests/integration/test_sensor_filters_value_list.py": 16.94,
-  "tests/integration/test_sensor_timeout_filter.py": 29.48,
-  "tests/integration/test_socket_wake_gate_tcp.py": 20.36,
-  "tests/integration/test_status_flags.py": 37.42,
-  "tests/integration/test_strftime_to.py": 22.61,
-  "tests/integration/test_syslog.py": 16.34,
-  "tests/integration/test_template_alarm_control_panel_many_sensors.py": 29.81,
-  "tests/integration/test_template_text_save.py": 25.43,
-  "tests/integration/test_text_command.py": 23.34,
-  "tests/integration/test_text_sensor_raw_state.py": 69.57,
-  "tests/integration/test_uart_mock_ld2410.py": 37.95,
-  "tests/integration/test_uart_mock_ld2412.py": 93.22,
-  "tests/integration/test_uart_mock_ld2420.py": 43.24,
-  "tests/integration/test_uart_mock_ld2450.py": 31.75,
-  "tests/integration/test_uart_mock_modbus.py": 667.4,
-  "tests/integration/test_udp.py": 9.38,
-  "tests/integration/test_use_address_runtime.py": 37.05,
-  "tests/integration/test_valve_control_action.py": 24.47,
-  "tests/integration/test_varint_five_byte_device_id.py": 25.03,
-  "tests/integration/test_wait_until_mid_loop_timing.py": 23.73,
-  "tests/integration/test_wait_until_on_boot.py": 9.16,
-  "tests/integration/test_wait_until_ordering.py": 13.3,
-  "tests/integration/test_wait_until_reentrant_restart.py": 25.23,
-  "tests/integration/test_wake_loop_forces_phase_b.py": 23.34,
-  "tests/integration/test_water_heater_template.py": 17.67
+  "tests/integration/test_action_concurrent_reentry.py": 57.91,
+  "tests/integration/test_addressable_light_transition.py": 21.25,
+  "tests/integration/test_alarm_control_panel_state_transitions.py": 70.71,
+  "tests/integration/test_api_action_metadata.py": 66.6,
+  "tests/integration/test_api_action_responses.py": 36.1,
+  "tests/integration/test_api_action_timeout.py": 68.86,
+  "tests/integration/test_api_conditional_memory.py": 15.48,
+  "tests/integration/test_api_custom_services.py": 18.77,
+  "tests/integration/test_api_get_time_response_timezone.py": 21.08,
+  "tests/integration/test_api_homeassistant.py": 65.59,
+  "tests/integration/test_api_homeassistant_action_no_subscriber.py": 18.44,
+  "tests/integration/test_api_homeassistant_binary_sensor_initial_state.py": 15.05,
+  "tests/integration/test_api_list_entities_backpressure.py": 13.88,
+  "tests/integration/test_api_message_size_batching.py": 29.98,
+  "tests/integration/test_api_reboot_timeout.py": 16.05,
+  "tests/integration/test_api_string_lambda.py": 15.31,
+  "tests/integration/test_api_vv_logging.py": 19.28,
+  "tests/integration/test_api_zero_psk_provisioning.py": 31.5,
+  "tests/integration/test_areas_and_devices.py": 24.95,
+  "tests/integration/test_automation_wait_actions.py": 20.92,
+  "tests/integration/test_automations.py": 35.19,
+  "tests/integration/test_batch_delay_zero_rapid_transitions.py": 17.99,
+  "tests/integration/test_binary_sensor_autorepeat_filter.py": 20.39,
+  "tests/integration/test_binary_sensor_invalidate_state.py": 18.41,
+  "tests/integration/test_blocking_warning_log_time_not_charged_to_next_operation.py": 24.69,
+  "tests/integration/test_build_info.py": 18.7,
+  "tests/integration/test_camera_mock.py": 16.23,
+  "tests/integration/test_climate_control_action.py": 21.14,
+  "tests/integration/test_climate_custom_modes.py": 20.74,
+  "tests/integration/test_continuation_actions.py": 16.81,
+  "tests/integration/test_cover_control_action.py": 20.34,
+  "tests/integration/test_crc8_helper.py": 9.36,
+  "tests/integration/test_device_id_in_state.py": 44.67,
+  "tests/integration/test_duplicate_entities.py": 23.58,
+  "tests/integration/test_entity_icon.py": 34.35,
+  "tests/integration/test_fan_turn_on_action.py": 24.23,
+  "tests/integration/test_fnv1_hash_object_id.py": 16.21,
+  "tests/integration/test_fnv1a_hash.py": 13.38,
+  "tests/integration/test_gpio_expander_cache.py": 13.06,
+  "tests/integration/test_host_logger_thread_safety.py": 23.66,
+  "tests/integration/test_host_mode_basic.py": 8.01,
+  "tests/integration/test_host_mode_batch_delay.py": 21.0,
+  "tests/integration/test_host_mode_climate_basic_state.py": 22.14,
+  "tests/integration/test_host_mode_climate_control.py": 19.39,
+  "tests/integration/test_host_mode_empty_string_options.py": 21.76,
+  "tests/integration/test_host_mode_entity_fields.py": 29.61,
+  "tests/integration/test_host_mode_fan_preset.py": 20.01,
+  "tests/integration/test_host_mode_many_entities.py": 39.08,
+  "tests/integration/test_host_mode_many_entities_multiple_connections.py": 23.92,
+  "tests/integration/test_host_mode_noise_encryption.py": 42.42,
+  "tests/integration/test_host_mode_reconnect.py": 3.41,
+  "tests/integration/test_host_mode_sensor.py": 22.96,
+  "tests/integration/test_host_ota.py": 29.5,
+  "tests/integration/test_host_preferences.py": 16.06,
+  "tests/integration/test_host_preferences_suspend_resume.py": 18.71,
+  "tests/integration/test_improv_serial_uart.py": 20.22,
+  "tests/integration/test_large_message_batching.py": 26.56,
+  "tests/integration/test_legacy_area.py": 22.72,
+  "tests/integration/test_legacy_climate_compat.py": 14.13,
+  "tests/integration/test_legacy_fan_compat.py": 14.33,
+  "tests/integration/test_light_automations.py": 18.81,
+  "tests/integration/test_light_binary_effect_off_phase.py": 8.38,
+  "tests/integration/test_light_calls.py": 21.88,
+  "tests/integration/test_light_constant_brightness.py": 59.45,
+  "tests/integration/test_light_control_action.py": 31.91,
+  "tests/integration/test_light_dim_relative_action.py": 14.43,
+  "tests/integration/test_light_effect_zero_brightness.py": 25.05,
+  "tests/integration/test_light_initial_state.py": 18.97,
+  "tests/integration/test_light_toggle_action.py": 17.44,
+  "tests/integration/test_lock_automations.py": 18.9,
+  "tests/integration/test_logger_buffered_recursion_guard.py": 18.2,
+  "tests/integration/test_loop_disable_enable.py": 63.35,
+  "tests/integration/test_loop_interval_decoupling.py": 17.7,
+  "tests/integration/test_loop_interval_default_not_pulled_forward.py": 21.56,
+  "tests/integration/test_micros_to_millis.py": 15.89,
+  "tests/integration/test_multi_click_trigger.py": 17.23,
+  "tests/integration/test_multi_device_preferences.py": 19.4,
+  "tests/integration/test_noise_encryption_key_protection.py": 72.59,
+  "tests/integration/test_object_id_api_verification.py": 19.22,
+  "tests/integration/test_object_id_friendly_name_no_mac_suffix.py": 16.77,
+  "tests/integration/test_object_id_no_friendly_name.py": 45.8,
+  "tests/integration/test_online_image_auto_detects_image_bmp_mime.py": 86.73,
+  "tests/integration/test_online_image_auto_detects_redirected_image_bmp_mime.py": 40.4,
+  "tests/integration/test_online_image_bmp.py": 37.24,
+  "tests/integration/test_oversized_payloads.py": 55.75,
+  "tests/integration/test_preference_key_stability.py": 25.49,
+  "tests/integration/test_runtime_stats.py": 29.81,
+  "tests/integration/test_safe_mode_loop_runs.py": 6.26,
+  "tests/integration/test_scheduler_blocking_warning.py": 37.98,
+  "tests/integration/test_scheduler_bulk_cleanup.py": 18.67,
+  "tests/integration/test_scheduler_defer_cancel.py": 18.46,
+  "tests/integration/test_scheduler_defer_cancel_regular.py": 16.34,
+  "tests/integration/test_scheduler_defer_fifo_simple.py": 18.26,
+  "tests/integration/test_scheduler_defer_stress.py": 17.74,
+  "tests/integration/test_scheduler_heap_stress.py": 3.89,
+  "tests/integration/test_scheduler_internal_id_no_collision.py": 20.01,
+  "tests/integration/test_scheduler_interval_reschedule.py": 16.29,
+  "tests/integration/test_scheduler_interval_zero_coerced.py": 16.09,
+  "tests/integration/test_scheduler_null_name.py": 14.69,
+  "tests/integration/test_scheduler_numeric_id_test.py": 17.08,
+  "tests/integration/test_scheduler_pool.py": 19.88,
+  "tests/integration/test_scheduler_rapid_cancellation.py": 4.42,
+  "tests/integration/test_scheduler_recursive_timeout.py": 4.3,
+  "tests/integration/test_scheduler_removed_item_race.py": 15.49,
+  "tests/integration/test_scheduler_self_keyed.py": 25.77,
+  "tests/integration/test_scheduler_simultaneous_callbacks.py": 14.84,
+  "tests/integration/test_scheduler_string_test.py": 15.42,
+  "tests/integration/test_script_array_params.py": 12.73,
+  "tests/integration/test_script_delay_params.py": 12.69,
+  "tests/integration/test_script_queued.py": 20.38,
+  "tests/integration/test_script_queued_idle_loop.py": 25.06,
+  "tests/integration/test_script_wait_on_boot.py": 15.67,
+  "tests/integration/test_select_stringref_trigger.py": 19.48,
+  "tests/integration/test_sensor_filters_delta.py": 27.62,
+  "tests/integration/test_sensor_filters_ring_buffer.py": 20.27,
+  "tests/integration/test_sensor_filters_sliding_window.py": 56.28,
+  "tests/integration/test_sensor_filters_value_list.py": 20.6,
+  "tests/integration/test_sensor_timeout_filter.py": 22.21,
+  "tests/integration/test_socket_wake_gate_tcp.py": 16.37,
+  "tests/integration/test_status_flags.py": 29.68,
+  "tests/integration/test_strftime_to.py": 17.42,
+  "tests/integration/test_syslog.py": 18.39,
+  "tests/integration/test_template_alarm_control_panel_many_sensors.py": 25.61,
+  "tests/integration/test_template_text_save.py": 19.16,
+  "tests/integration/test_text_command.py": 16.43,
+  "tests/integration/test_text_sensor_raw_state.py": 17.19,
+  "tests/integration/test_uart_mock_ld2410.py": 37.0,
+  "tests/integration/test_uart_mock_ld2412.py": 40.82,
+  "tests/integration/test_uart_mock_ld2420.py": 32.7,
+  "tests/integration/test_uart_mock_ld2450.py": 32.84,
+  "tests/integration/test_uart_mock_modbus.py": 548.87,
+  "tests/integration/test_udp.py": 16.67,
+  "tests/integration/test_use_address_runtime.py": 27.26,
+  "tests/integration/test_valve_control_action.py": 24.58,
+  "tests/integration/test_varint_five_byte_device_id.py": 22.5,
+  "tests/integration/test_wait_until_mid_loop_timing.py": 22.05,
+  "tests/integration/test_wait_until_on_boot.py": 10.37,
+  "tests/integration/test_wait_until_ordering.py": 18.23,
+  "tests/integration/test_wait_until_reentrant_restart.py": 19.35,
+  "tests/integration/test_wake_loop_forces_phase_b.py": 17.83,
+  "tests/integration/test_water_heater_template.py": 25.7
 }

tests/integration/test_api_zero_psk_provisioning.py

@@ -24,12 +24,6 @@ NEW_KEY = base64.b64encode(b"n" * 32)
 KEY_ACTIVATION_DELAY = 0.5
 
 
-@pytest.fixture(autouse=True)
-def isolated_preferences(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
-    """Keep host preferences per-test so every run starts unprovisioned."""
-    monkeypatch.setenv("ESPHOME_PREFDIR", str(tmp_path / "prefs"))
-
-
 @pytest.mark.asyncio
 async def test_api_zero_psk_provisioning(
     yaml_config: str,

tests/integration/test_host_preferences_suspend_resume.py

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

tests/integration/test_light_initial_state.py

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

tests/integration/test_uart_mock_modbus.py

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

tests/script/test_helpers.py

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