diff --git a/src/openultrasast/learning/families.py b/src/openultrasast/learning/families.py
index b077e6a..c414991 100644
--- a/src/openultrasast/learning/families.py
+++ b/src/openultrasast/learning/families.py
@@ -99,6 +99,7 @@ def load_families(path: Path | None = None, *, require_all: bool = True) -> Fami
         raise FamiliesError(f"{source}: version is required")
     families: list[Family] = []
     claimed: dict[str, str] = {}
+    claimed_mechanisms: dict[str, str] = {}
     for entry in payload.get("family", []):
         if not isinstance(entry, dict):
             raise FamiliesError(f"{source}: every [[family]] entry must be a table")
@@ -109,6 +110,12 @@ def load_families(path: Path | None = None, *, require_all: bool = True) -> Fami
             if cwe in claimed:
                 raise FamiliesError(f"{source}: {cwe} is claimed by both {claimed[cwe]!r} and {family.id!r}")
             claimed[cwe] = family.id
+        for mechanism in sorted(family.mechanisms):
+            if mechanism in claimed_mechanisms:
+                raise FamiliesError(
+                    f"{source}: mechanism {mechanism} is claimed by both {claimed_mechanisms[mechanism]!r} and {family.id!r}"
+                )
+            claimed_mechanisms[mechanism] = family.id
         families.append(family)
     _check_parents(source, families)
     if require_all and tuple(family.id for family in families) != FAMILY_IDS:
diff --git a/tests/test_hunter_curated_tools.py b/tests/test_hunter_curated_tools.py
index 1263fdd..1b373dd 100644
--- a/tests/test_hunter_curated_tools.py
+++ b/tests/test_hunter_curated_tools.py
@@ -65,6 +65,8 @@ def test_obligations_lists_what_a_function_owes_without_dumping_code(repo: Path)
     assert "identity_constraint" in {str(row["missing"]) for row in rows}
     assert all("text" not in row and "content" not in row for row in rows)
     assert obligations(repo, path="app.py", function="helper") == []
+    with pytest.raises(PathEscapesRepo):
+        obligations(repo, path="../outside.py", function="leaky")
 
 
 def test_flows_lists_adjudicated_source_to_sink_records_for_one_function(repo: Path) -> None:
diff --git a/tests/test_learning_endpoint.py b/tests/test_learning_endpoint.py
index 7bc80f0..160b86a 100644
--- a/tests/test_learning_endpoint.py
+++ b/tests/test_learning_endpoint.py
@@ -67,6 +67,18 @@ def test_resolution_order_override_then_scripted_then_openrouter_then_none(monke
     assert resolve_chat_endpoint(ResolvedConfig()) is None
 
 
+def test_a_provider_that_refuses_to_build_degrades_to_no_endpoint(monkeypatch: pytest.MonkeyPatch) -> None:
+    from openultrasast.learning.endpoint import resolve_chat_endpoint
+
+    _endpoint_env(monkeypatch, OPENROUTER_API_KEY="or-key")
+
+    def _refuse() -> provider.OpenRouterChatClient:
+        raise provider.OpenRouterError("no key after all")
+
+    monkeypatch.setattr(provider.OpenRouterChatClient, "from_env", staticmethod(_refuse))
+    assert resolve_chat_endpoint(ResolvedConfig()) is None  # a caller degrades; nothing raises into a scan
+
+
 def test_the_config_can_point_the_chat_endpoint_somewhere_else(monkeypatch: pytest.MonkeyPatch, tmp_path: Any) -> None:
     from openultrasast.config import load_config
     from openultrasast.learning.endpoint import resolve_chat_endpoint, resolve_models
diff --git a/tests/test_learning_families.py b/tests/test_learning_families.py
index c57e288..24a9e66 100644
--- a/tests/test_learning_families.py
+++ b/tests/test_learning_families.py
@@ -88,6 +88,10 @@ def test_relation_answers_same_lateral_fabricated_and_parent_child_when_declared
         (GOOD.replace('cwes = ["CWE-89"]', 'cwes = ["CWE-89", "CWE-89"]'), "CWE-89"),
         (GOOD.replace('description = "x"\n', ""), "description"),
         (GOOD + '\n[[family]]\nid = "path"\ndescription = "y"\ncwes = ["CWE-89"]\nmechanisms = []\nverifier = "canary"\n', "CWE-89"),
+        (
+            GOOD + '\n[[family]]\nid = "path"\ndescription = "y"\ncwes = []\nmechanisms = ["source_reaches_sink"]\nverifier = "canary"\n',
+            "source_reaches_sink",
+        ),
         (GOOD.replace('version = "1"\n', ""), "version"),
         (GOOD + '\n[[family]]\nid = "path"\nparent = "nope"\ndescription = "y"\ncwes = []\nmechanisms = []\nverifier = "none"\n', "nope"),
     ],
@@ -99,6 +103,7 @@ def test_relation_answers_same_lateral_fabricated_and_parent_child_when_declared
         "duplicate_cwe",
         "no_description",
         "cwe_claimed_twice",
+        "mechanism_claimed_twice",
         "no_version",
         "unknown_parent",
     ],
diff --git a/tests/test_typescript_grammar.py b/tests/test_typescript_grammar.py
index 3153cb3..393133b 100644
--- a/tests/test_typescript_grammar.py
+++ b/tests/test_typescript_grammar.py
@@ -46,4 +46,6 @@ def test_every_vendored_typescript_pair_parses_on_both_sides() -> None:
             elif not ir.parse_ok:
                 failed.append(f"{case.name}:{side}")
     assert unsupported == []
-    assert len(failed) <= len(cases) // 4, failed  # a parse failure is a walker gap, not a missing grammar
+    # One excerpt is a truncated destructuring parameter list, so it is not valid TypeScript on its own;
+    # that is a corpus defect for the re-harvest, not a grammar gap. Pinned exactly so a regression shows.
+    assert failed == ["lensops-kubernetesmanagement-fe4910:vuln", "lensops-kubernetesmanagement-fe4910:fixed"], failed