diff --git a/esphome/build_gen/arduino8266.py b/esphome/build_gen/arduino8266.py
index cbe7fec81f..251b6e19eb 100644
--- a/esphome/build_gen/arduino8266.py
+++ b/esphome/build_gen/arduino8266.py
@@ -1313,6 +1313,9 @@ def write_project(paths: InstalledPaths, ccache: str | None) -> bool:
                 pch_dep = f"{gch} esphome_pch.probe"
             src_cxx_override = ("$srccxxflags", pch_dep)
             mark_pch_emitted()
+    else:
+        # Strict CI must not read "no pch at all" as success
+        pch_degraded("pch disabled by ESPHOME_PCH_ENABLE")
     src_objs = _ninja_compile_edges(
         lines,
         _collect_sources(src_dir),
diff --git a/esphome/build_gen/espidf.py b/esphome/build_gen/espidf.py
index 79f032238a..7feb6c4c4e 100644
--- a/esphome/build_gen/espidf.py
+++ b/esphome/build_gen/espidf.py
@@ -323,6 +323,7 @@ def prepare_pch() -> None:
     if not pch_enabled():
         # Self-cleaning escape hatch: drop any previously built .gch
         pch.discard_pch(CORE.relative_build_path("build"))
+        pch.pch_degraded("pch disabled by ESPHOME_PCH_ENABLE")
         return
     sdkconfig_path = CORE.relative_build_path(f"sdkconfig.{CORE.name}")
     try:
diff --git a/esphome/build_helpers/pch.py b/esphome/build_helpers/pch.py
index 233bd43cb9..d886d37b0e 100644
--- a/esphome/build_helpers/pch.py
+++ b/esphome/build_helpers/pch.py
@@ -148,7 +148,11 @@ def ccache_pch_env() -> dict[str, str]:
 def pch_extra_scripts() -> list[str]:
     """The extra_scripts entries a PlatformIO platform registers for the
     pch; empty when disabled (the script itself has no enable check)."""
-    return ["post:pch.py"] if pch_enabled() else []
+    if not pch_enabled():
+        # Strict CI must not read "no pch at all" as success
+        pch_degraded("pch disabled by ESPHOME_PCH_ENABLE")
+        return []
+    return ["post:pch.py"]
 
 
 def pch_header_text(include_headers: Iterable[str]) -> str:
diff --git a/esphome/platformio/pch.py.script b/esphome/platformio/pch.py.script
index 7a3b8884d2..4c737460b7 100644
--- a/esphome/platformio/pch.py.script
+++ b/esphome/platformio/pch.py.script
@@ -160,10 +160,15 @@ def _read_stamp(path: Path) -> str:
 
 def _setup_pch() -> bool | None:
     if projenv is None:
-        # Expected under -t nobuild (nothing compiles), so not a degrade
-        # even in strict mode; anything else still leaves a trail
         print(f"ESPHome: projenv unavailable ({_projenv_error}); skipping pch")
-        return True
+        try:
+            from SCons.Script import COMMAND_LINE_TARGETS
+
+            # Expected under -t nobuild (nothing compiles); a missing
+            # projenv on a real compile must not pass strict
+            return "nobuild" in [str(t) for t in COMMAND_LINE_TARGETS]
+        except Exception:  # noqa: BLE001 -- no SCons: cannot tell, stay lenient
+            return True
     # Project root: SCons compiles run here, so the relative -include
     # resolves; an absolute path would break cross-device ccache sharing.
     proj_dir = Path(env.subst("$PROJECT_DIR"))  # noqa: F821
diff --git a/tests/unit_tests/build_gen/test_espidf.py b/tests/unit_tests/build_gen/test_espidf.py
index 450a2b673c..1c97de14d5 100644
--- a/tests/unit_tests/build_gen/test_espidf.py
+++ b/tests/unit_tests/build_gen/test_espidf.py
@@ -869,6 +869,61 @@ def test_prepare_pch_signal_kill_is_transient(tmp_path: Path) -> None:
     assert len(calls) == 2
 
 
+def test_prepare_pch_signal_kill_strict_raises(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    from esphome.build_gen.espidf import prepare_pch
+    from esphome.core import EsphomeError
+
+    monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
+    dev = _make_pch_device(tmp_path, "dev_ks")
+    CORE.build_path = dev
+    with (
+        patch.object(CORE, "name", "test"),
+        patch(
+            "esphome.build_helpers.pch.subprocess.run",
+            side_effect=lambda cmd, **kw: subprocess.CompletedProcess(cmd, -9, "", ""),
+        ),
+        pytest.raises(EsphomeError, match="killed by signal"),
+    ):
+        prepare_pch()
+
+
+def test_prepare_pch_strict_raises_when_disabled(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """Strict must not read a disabled pch as success."""
+    from esphome.build_gen.espidf import prepare_pch
+    from esphome.core import EsphomeError
+
+    monkeypatch.setenv("ESPHOME_PCH_ENABLE", "0")
+    monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
+    dev = _make_pch_device(tmp_path, "dev_ds")
+    CORE.build_path = dev
+    with (
+        patch.object(CORE, "name", "test"),
+        pytest.raises(EsphomeError, match="disabled"),
+    ):
+        prepare_pch()
+
+
+def test_prepare_pch_missing_sdkconfig_strict_raises(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    from esphome.build_gen.espidf import prepare_pch
+    from esphome.core import EsphomeError
+
+    monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
+    dev = _make_pch_device(tmp_path, "dev_ss")
+    (dev / "sdkconfig.test").unlink()
+    CORE.build_path = dev
+    with (
+        patch.object(CORE, "name", "test"),
+        pytest.raises(EsphomeError, match="sdkconfig unreadable"),
+    ):
+        prepare_pch()
+
+
 def test_prepare_pch_without_compile_commands(tmp_path: Path) -> None:
     """Stale checksum but no configured TU yet: no compile, no sidecars."""
     from esphome.build_gen.espidf import prepare_pch
diff --git a/tests/unit_tests/build_helpers/test_pch.py b/tests/unit_tests/build_helpers/test_pch.py
index 1d8423eb1c..3b5650fae8 100644
--- a/tests/unit_tests/build_helpers/test_pch.py
+++ b/tests/unit_tests/build_helpers/test_pch.py
@@ -242,3 +242,14 @@ def test_pch_degraded_raises_only_in_strict(
     monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
     with pytest.raises(EsphomeError, match="reason"):
         pch.pch_degraded("reason")
+
+
+def test_pch_extra_scripts_strict_raises_when_disabled(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    from esphome.core import EsphomeError
+
+    monkeypatch.setenv("ESPHOME_PCH_ENABLE", "0")
+    monkeypatch.setenv("ESPHOME_PCH_STRICT", "1")
+    with pytest.raises(EsphomeError, match="disabled"):
+        pch.pch_extra_scripts()