Merge branch 'pch-strict-ci' into host-pch

.github/workflows/ci-docker.yml

@@ -210,7 +210,7 @@ jobs:
           - host
         # Strict by default so a new matrix id cannot silently join in the
         # degrade-quietly mode the knob exists to catch; the knob is inert
-        # where no pch code runs (esp32-*-platformio, nrf52, host).
+        # where no pch code runs (esp32-*-platformio, nrf52).
         # Opt-outs: libretiny GCC rejects its own pch until a toolchain bump.
         include:
           - id: bk72xx-arduino

esphome/components/host/__init__.py

@@ -1,3 +1,4 @@
+from esphome.build_helpers.pch import pch_enabled, pch_extra_scripts
 import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome.const import (
@@ -10,7 +11,7 @@ from esphome.const import (
     ThreadModel,
 )
 from esphome.core import CORE
-from esphome.platformio.toolchain import copy_ccache_script
+from esphome.platformio.toolchain import copy_ccache_script, copy_pch_script
 from esphome.types import ConfigType
 
 from .const import KEY_HOST
@@ -18,6 +19,9 @@ from .const import KEY_HOST
 # force import gpio to register pin schema
 from .gpio import host_pin_to_code  # noqa: F401
 
+# Guarded wrapper: build_src_flags reaches C/assembly edges too
+HOST_PCH_PREFIX = "esphome/core/pch_prefix.h"
+
 CODEOWNERS = ["@esphome/core", "@clydebarrow"]
 AUTO_LOAD = ["network", "preferences"]
 IS_TARGET_PLATFORM = True
@@ -55,9 +59,18 @@ async def to_code(config: ConfigType) -> None:
     cg.add_platformio_option("platform", "platformio/native")
     cg.add_platformio_option("lib_ldf_mode", "off")
     cg.add_platformio_option("lib_compat_mode", "strict")
-    cg.add_platformio_option("extra_scripts", ["pre:ccache.py"])
+    cg.add_platformio_option("extra_scripts", ["pre:ccache.py", *pch_extra_scripts()])
+    if pch_enabled():
+        # Curated prefix for the pch (the script folds it plus defines.h):
+        # host has no framework force-includes, and the per-TU cost is the
+        # STL closure behind the core headers. Measured -43% compile CPU.
+        # Gated so ESPHOME_PCH_ENABLE=0 restores the strict view. When the
+        # .gch fails to build or load, the force-include stays and every TU
+        # parses the closure as text: correct, but slower than no pch.
+        cg.add_platformio_option("build_src_flags", f"-include {HOST_PCH_PREFIX}")
 
 
 # Called by writer.py
 def copy_files() -> None:
     copy_ccache_script()
+    copy_pch_script()

esphome/core/pch_prefix.h

@@ -0,0 +1,8 @@
+#pragma once
+// Curated precompiled-header prefix for backends that force-include it via
+// build_src_flags (the pch script folds it into the .gch). Guarded because
+// build_src_flags also reaches C and assembly src edges.
+#ifdef __cplusplus
+#include "esphome/core/application.h"
+#include "esphome/core/automation.h"
+#endif

esphome/writer.py

@@ -247,6 +247,7 @@ def copy_src_tree():
         Path(
             "esphome/core/ring_buffer.h"
         ),  # moved to components/ring_buffer/, removed in 2026.11.0
+        Path("esphome/core/pch_prefix.h"),  # build machinery, not user API
     }
     include_l = []
     for target, _ in source_files_l:

tests/unit_tests/test_host_pch_prefix.py

@@ -0,0 +1,21 @@
+"""The host pch prefix must keep resolving; a rename would silently
+collapse the precompiled set to defines.h with strict CI still green."""
+
+from pathlib import Path
+import re
+
+from esphome.components.host import HOST_PCH_PREFIX
+
+REPO = Path(__file__).parents[2]
+
+
+def test_host_pch_prefix_resolves() -> None:
+    prefix = REPO / HOST_PCH_PREFIX
+    assert prefix.is_file()
+    body = prefix.read_text()
+    includes = re.findall(r'#include "([^"]+)"', body)
+    assert includes, "prefix wrapper folds nothing"
+    for name in includes:
+        assert (REPO / name).is_file(), f"{name} does not resolve"
+    # The C guard is what keeps build_src_flags safe on C/assembly edges
+    assert "#ifdef __cplusplus" in body