diff --git a/scripts/scraper/fbneo_hash_scraper.py b/scripts/scraper/fbneo_hash_scraper.py
index f21fdd75..2968d863 100644
--- a/scripts/scraper/fbneo_hash_scraper.py
+++ b/scripts/scraper/fbneo_hash_scraper.py
@@ -42,6 +42,8 @@ def _is_cache_fresh() -> bool:
         return False
     try:
         data = json.loads(CACHE_PATH.read_text(encoding="utf-8"))
+        if not data.get("bios_sets"):
+            return False
         fetched_at = datetime.fromisoformat(data["fetched_at"])
         return datetime.now(timezone.utc) - fetched_at < timedelta(hours=STALE_HOURS)
     except (json.JSONDecodeError, KeyError, ValueError):
@@ -178,6 +180,10 @@ def fetch_and_cache(force: bool = False) -> dict[str, Any]:
 
         log.info("parsing source tree")
         bios_sets = parse_fbneo_source_tree(str(CLONE_DIR))
+        if not bios_sets or not commit:
+            # An empty read was cached for a day and merged nothing, and
+            # the pipeline step reported OK.
+            raise RuntimeError(f"no BIOS set read at FBNeo {version} ({commit[:12]})")
 
         cache: dict[str, Any] = {
             "source": "finalburnneo/FBNeo",
diff --git a/scripts/scraper/mame_hash_scraper.py b/scripts/scraper/mame_hash_scraper.py
index f384b396..fc25d28d 100644
--- a/scripts/scraper/mame_hash_scraper.py
+++ b/scripts/scraper/mame_hash_scraper.py
@@ -62,7 +62,7 @@ def _load_cache() -> dict[str, Any] | None:
 
 
 def _is_stale(cache: dict[str, Any] | None) -> bool:
-    if cache is None:
+    if cache is None or not cache.get("bios_sets"):
         return True
     fetched_at = cache.get("fetched_at")
     if not fetched_at:
@@ -292,6 +292,11 @@ def _fetch_hashes(force: bool) -> dict[str, Any]:
         bios_sets = parse_mame_source_tree(str(_CLONE_DIR))
         version = _parse_version_tag(tag)
         commit = _get_commit()
+        if not bios_sets or not commit:
+            # An empty read was cached for a day and every profile entry
+            # came out "out of scope", so nothing was refreshed and the
+            # pipeline step reported OK.
+            raise RuntimeError(f"no BIOS root set read at {tag}")
 
         data: dict[str, Any] = {
             "source": "mamedev/mame",
diff --git a/tests/test_scraper_contract.py b/tests/test_scraper_contract.py
index 2a36aacf..4b2d961c 100644
--- a/tests/test_scraper_contract.py
+++ b/tests/test_scraper_contract.py
@@ -880,5 +880,66 @@ class OneNativeIdOneSystem(unittest.TestCase):
                 ids = {_norm_system_id(s) for s in data["systems"]}
                 self.assertEqual(wanted & ids & machines, wanted)
 
+
+class HashScraperRefusesAnEmptyRead(unittest.TestCase):
+    """A source tree that yields no BIOS set is never cached as a result.
+
+    Cached, it was served for a day: every profile entry came out "out of
+    scope", nothing was refreshed and pipeline steps 2a and 2a2 said OK.
+    """
+
+    def _fresh(self, sets: dict) -> dict:
+        from datetime import datetime, timezone  # noqa: PLC0415
+
+        return {"fetched_at": datetime.now(timezone.utc).isoformat(),
+                "commit": "abc", "bios_sets": sets}
+
+    def test_mame_raises_and_writes_no_cache(self):
+        from scraper import mame_hash_scraper as m  # noqa: PLC0415
+
+        with tempfile.TemporaryDirectory() as tmp:
+            cache = Path(tmp) / "mame-hashes.json"
+            with mock.patch.object(m, "_CACHE_PATH", cache), \
+                    mock.patch.object(m, "_get_release_tag", return_value="mame0289"), \
+                    mock.patch.object(m, "_sparse_clone"), \
+                    mock.patch.object(m, "_cleanup"), \
+                    mock.patch.object(m, "_get_commit", return_value="abc"), \
+                    mock.patch.object(m, "parse_mame_source_tree", return_value={}):
+                with self.assertRaises(RuntimeError):
+                    m._fetch_hashes(force=True)
+            self.assertFalse(cache.exists())
+
+    def test_mame_does_not_serve_an_empty_cache(self):
+        from scraper import mame_hash_scraper as m  # noqa: PLC0415
+
+        self.assertTrue(m._is_stale(self._fresh({})))
+        self.assertFalse(m._is_stale(self._fresh({"neogeo": {}})))
+
+    def test_fbneo_raises_and_writes_no_cache(self):
+        from scraper import fbneo_hash_scraper as f  # noqa: PLC0415
+
+        with tempfile.TemporaryDirectory() as tmp:
+            cache = Path(tmp) / "fbneo-hashes.json"
+            with mock.patch.object(f, "CACHE_PATH", cache), \
+                    mock.patch.object(f, "_sparse_clone"), \
+                    mock.patch.object(f, "_cleanup"), \
+                    mock.patch.object(f, "_extract_version", return_value=("v1.0.0.03", "abc")), \
+                    mock.patch.object(f, "parse_fbneo_source_tree", return_value={}):
+                with self.assertRaises(RuntimeError):
+                    f.fetch_and_cache(force=True)
+            self.assertFalse(cache.exists())
+
+    def test_fbneo_does_not_serve_an_empty_cache(self):
+        from scraper import fbneo_hash_scraper as f  # noqa: PLC0415
+
+        with tempfile.TemporaryDirectory() as tmp:
+            cache = Path(tmp) / "fbneo-hashes.json"
+            with mock.patch.object(f, "CACHE_PATH", cache):
+                cache.write_text(json.dumps(self._fresh({})))
+                self.assertFalse(f._is_cache_fresh())
+                cache.write_text(json.dumps(self._fresh({"neogeo": {}})))
+                self.assertTrue(f._is_cache_fresh())
+
+
 if __name__ == "__main__":
     unittest.main()