diff --git a/script/helpers.py b/script/helpers.py
index 2fcfe3e1f9..2ac59c71b0 100644
--- a/script/helpers.py
+++ b/script/helpers.py
@@ -1104,8 +1104,8 @@ def get_components_per_integration_fixture() -> dict[str, set[str]]:
 
 
 _TEST_FUNC_RE = re.compile(r"async def (test_\w+)")
-_SHARED_YAML_RE = re.compile(r"@pytest\.mark\.shared_yaml\([\"'](\w+)[\"']\)")
-_SHARED_YAML_DECORATOR_RE = re.compile(r"@pytest\.mark\.shared_yaml\(")
+_SHARED_YAML_RE = re.compile(r"pytest\.mark\.shared_yaml\([\"'](\w+)[\"']\)")
+_SHARED_YAML_USE_RE = re.compile(r"pytest\.mark\.shared_yaml\(")
 
 
 @cache
@@ -1127,7 +1127,7 @@ def get_fixture_to_test_files() -> dict[str, frozenset[str]]:
             result.setdefault(base_name, set()).add(rel_path)
         # Shared fixtures are named by marker, not by a test function
         names = _SHARED_YAML_RE.findall(content)
-        if len(names) != len(_SHARED_YAML_DECORATOR_RE.findall(content)):
+        if len(names) != len(_SHARED_YAML_USE_RE.findall(content)):
             # A wrapped or non-literal marker would silently drop the mapping
             # and CI would select no tests for that fixture
             raise ValueError(
diff --git a/tests/integration/conftest.py b/tests/integration/conftest.py
index fc84637317..fe50ae391e 100644
--- a/tests/integration/conftest.py
+++ b/tests/integration/conftest.py
@@ -342,7 +342,10 @@ def _read_stamp(stamp: Path, shared_dir: Path) -> Path | None:
         return None
     built = Path(text)
     # Never trust a stamp pointing outside its own build dir as an unlink target
-    return built if shared_dir in built.parents else None
+    if shared_dir.resolve() in built.resolve().parents:
+        return built
+    warnings.warn(f"Ignoring stamp {stamp} pointing outside {shared_dir}", stacklevel=2)
+    return None
 
 
 def _unused_since(stale: Path, cutoff: float) -> bool:
@@ -376,6 +379,9 @@ def _prune_stale_builds(name: str, keep: Path) -> None:
         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:
@@ -392,8 +398,14 @@ def _prune_stale_builds(name: str, keep: Path) -> None:
             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
-            if not same_fixture and not _unused_since(stale, cutoff):
+            # 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
diff --git a/tests/integration/host_prefs.py b/tests/integration/host_prefs.py
index 82569a5d66..5f526dce5f 100644
--- a/tests/integration/host_prefs.py
+++ b/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.
 
@@ -19,11 +19,13 @@ import struct
 def host_prefs_path(device_name: str) -> Path:
     """Return the on-disk prefs file path for a host-platform device.
 
-    Honors ESPHOME_PREFDIR, which the autouse isolated_preferences fixture
-    sets, so seeds land where the binary will look."""
+    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")
-    base = Path(prefdir) if prefdir else Path.home() / ".esphome" / "prefs"
-    return base / f"{device_name}.prefs"
+    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: