Precompile a curated core-header prefix on host

.github/workflows/ci-docker.yml

@@ -206,7 +206,7 @@ jobs:
         # platforms where it must work. Excluded: bk72xx/rtl87xx/ln882x
         # (libretiny GCC rejects its own pch until a toolchain bump),
         # esp32-*-platformio (no pch; the toolchain is being dropped),
-        # nrf52 and host (no pch)
+        # nrf52 (no pch)
         include:
           - id: esp8266-arduino
             pch_strict: "1"
@@ -218,6 +218,8 @@ jobs:
             pch_strict: "1"
           - id: rp2040-arduino
             pch_strict: "1"
+          - id: host
+            pch_strict: "1"
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
       - name: Download image artifact

esphome/components/host/__init__.py

@@ -1,3 +1,4 @@
+from esphome.build_helpers.pch import 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
@@ -55,9 +56,18 @@ 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()])
+    # Curated prefix for the pch (the script folds these plus defines.h):
+    # host has no framework force-includes, and the per-TU cost is the STL
+    # closure behind these core headers. Measured -43% compile CPU.
+    # macOS system clang cannot load a GCC .gch; the load probe falls back.
+    cg.add_platformio_option(
+        "build_src_flags",
+        "-include esphome/core/application.h -include esphome/core/automation.h",
+    )
 
 
 # Called by writer.py
 def copy_files() -> None:
     copy_ccache_script()
+    copy_pch_script()