[ci] Trigger CodSpeed benchmarks on host platform changes (#15995)

script/determine-jobs.py

@@ -402,8 +402,11 @@ def should_run_benchmarks(branch: str | None = None) -> bool:
     Benchmarks run when any of the following conditions are met:
 
     1. Core C++ files changed (esphome/core/*)
-    2. A directly changed component has benchmark files (no dependency expansion)
+    2. The host platform changed (esphome/components/host/*) — benchmarks
-    3. Benchmark infrastructure changed (tests/benchmarks/*, script/cpp_benchmark.py,
+       are built and run on the host platform, so its implementations of
+       ``millis()``/``micros()``/etc. affect every benchmark
+    3. A directly changed component has benchmark files (no dependency expansion)
+    4. Benchmark infrastructure changed (tests/benchmarks/*, script/cpp_benchmark.py,
        script/build_helpers.py, script/setup_codspeed_lib.py)
 
     Unlike unit tests, benchmarks do NOT expand to dependent components.
@@ -420,6 +423,10 @@ def should_run_benchmarks(branch: str | None = None) -> bool:
     if core_changed(files):
         return True
 
+    # Host platform supplies the runtime that benchmarks execute on
+    if any(f.startswith("esphome/components/host/") for f in files):
+        return True
+
     # Check if benchmark infrastructure changed
     if any(
         f.startswith("tests/benchmarks/") or f in BENCHMARK_INFRASTRUCTURE_FILES

tests/script/test_determine_jobs.py

@@ -1842,6 +1842,22 @@ def test_should_run_benchmarks_core_header_change() -> None:
         assert determine_jobs.should_run_benchmarks() is True
 
 
+def test_should_run_benchmarks_host_platform_change() -> None:
+    """Test benchmarks trigger on host platform changes.
+
+    Benchmarks build and run on the host platform, so changes to its
+    millis()/micros()/etc. implementations affect every benchmark.
+    """
+    for host_file in [
+        "esphome/components/host/core.cpp",
+        "esphome/components/host/__init__.py",
+    ]:
+        with patch.object(determine_jobs, "changed_files", return_value=[host_file]):
+            assert determine_jobs.should_run_benchmarks() is True, (
+                f"Expected benchmarks to run for {host_file}"
+            )
+
+
 def test_should_run_benchmarks_benchmark_infra_change() -> None:
     """Test benchmarks trigger on benchmark infrastructure changes."""
     for infra_file in [