diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index cb3f68c7..7d91d1c8 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -24,6 +24,7 @@ lib/<component>/
 * The directory name must match the driver name (e.g. `mcp23009e`, `wsen-hids`)
 * The main class must be exposed in `__init__.py`
 * Drivers must be self-contained (no cross-driver dependencies)
+* Every driver is automatically checked against the upstream firmware manifest by `tests/test_frozen_manifest.py`. If a driver is intentionally **not** frozen (experimental, not yet integrated, etc.), add a `lib/<driver>/.not-frozen` marker file (it may be empty; optionally include a one-line reason) — the test will skip it and display the reason if present.
 
 ## Coding conventions
 
diff --git a/lib/gc9a01/.not-frozen b/lib/gc9a01/.not-frozen
new file mode 100644
index 00000000..196258f1
--- /dev/null
+++ b/lib/gc9a01/.not-frozen
@@ -0,0 +1 @@
+Pending freeze, see #368.
diff --git a/lib/im34dt05/.not-frozen b/lib/im34dt05/.not-frozen
new file mode 100644
index 00000000..b3f88e4a
--- /dev/null
+++ b/lib/im34dt05/.not-frozen
@@ -0,0 +1 @@
+Not yet integrated into the firmware manifest.
diff --git a/tests/test_frozen_manifest.py b/tests/test_frozen_manifest.py
new file mode 100644
index 00000000..fa56890d
--- /dev/null
+++ b/tests/test_frozen_manifest.py
@@ -0,0 +1,98 @@
+"""Verify each driver under lib/ is declared in the upstream frozen manifest.
+
+Catches silent regressions where a driver is accidentally removed from, or
+forgotten in, the STEAM32_WB55RG board manifest in `steamicc/micropython-steami`.
+"""
+
+import ast
+import os
+from pathlib import Path
+from urllib.error import HTTPError, URLError
+from urllib.request import urlopen
+
+import pytest
+
+LIB_DIR = Path(__file__).parent.parent / "lib"
+
+# Keep this branch in sync with MICROPYTHON_BRANCH in env.mk.
+MANIFEST_URL = os.environ.get(
+    "STEAMI_FIRMWARE_MANIFEST_URL",
+    "https://raw.githubusercontent.com/steamicc/micropython-steami/"
+    "stm32-steami-rev1d-final/ports/stm32/boards/STEAM32_WB55RG/manifest.py",
+)
+
+STEAMI_LIBRARY = "micropython-steami-lib"
+
+
+def _extract_required_drivers(source):
+    """Parse a board manifest and return the set of driver names required
+    from `micropython-steami-lib`. Uses the AST so the check is resilient to
+    quoting, spacing, and extra keyword arguments."""
+    tree = ast.parse(source)
+    required = set()
+    for node in ast.walk(tree):
+        if not (isinstance(node, ast.Call) and isinstance(node.func, ast.Name)):
+            continue
+        if node.func.id != "require":
+            continue
+        library = None
+        for kw in node.keywords:
+            if kw.arg == "library" and isinstance(kw.value, ast.Constant):
+                library = kw.value.value
+        if library != STEAMI_LIBRARY:
+            continue
+        if node.args and isinstance(node.args[0], ast.Constant):
+            name = node.args[0].value
+            if isinstance(name, str):
+                required.add(name)
+    return required
+
+
+@pytest.fixture(scope="session")
+def frozen_drivers():
+    """Fetch the upstream manifest once per session and return the set of
+    driver names required from micropython-steami-lib."""
+    try:
+        with urlopen(MANIFEST_URL, timeout=10) as resp:
+            content = resp.read().decode("utf-8")
+    except HTTPError as exc:
+        pytest.fail(
+            f"unexpected HTTP {exc.code} while fetching {MANIFEST_URL}: "
+            f"{exc.reason}. The branch or path may have moved — update "
+            f"MANIFEST_URL in tests/test_frozen_manifest.py."
+        )
+    except (URLError, TimeoutError, OSError) as exc:
+        pytest.skip(f"cannot fetch upstream manifest: {exc}")
+    return _extract_required_drivers(content)
+
+
+def _discover_driver_dirs():
+    return sorted(d for d in LIB_DIR.iterdir() if d.is_dir())
+
+
+_driver_dirs = _discover_driver_dirs()
+
+
+@pytest.mark.parametrize(
+    "driver_dir",
+    _driver_dirs,
+    ids=[d.name for d in _driver_dirs],
+)
+def test_driver_is_frozen_in_firmware_mock(driver_dir, frozen_drivers):
+    """Each driver under lib/ must be required in the upstream firmware manifest.
+
+    To intentionally ship a driver outside the firmware, add an empty
+    `lib/<driver>/.not-frozen` marker (optionally containing a one-line reason).
+    """
+    not_frozen = driver_dir / ".not-frozen"
+    if not_frozen.exists():
+        reason = not_frozen.read_text(encoding="utf-8").strip() or "marked .not-frozen"
+        pytest.skip(f"{driver_dir.name}: {reason}")
+
+    assert driver_dir.name in frozen_drivers, (
+        f"{driver_dir.name} is not required in the frozen manifest "
+        f"({MANIFEST_URL}). Add "
+        f'require("{driver_dir.name}", library="micropython-steami-lib") '
+        f"to the upstream manifest, or add a lib/{driver_dir.name}/.not-frozen "
+        f"marker if the driver is intentionally not shipped."
+    )