fix(memory): reject ambiguous multi-object outputs during skill extraction (#3985)

tests/test_skill_extractor_json.py

@@ -41,3 +41,18 @@ def test_non_object_json_returns_none():
 
 def test_empty_input_returns_none():
     assert skill_extractor._extract_json_object("") is None
+
+
+def test_multiple_objects_returns_none():
+    # Two complete valid non-overlapping JSON objects should return None (fail closed).
+    resp = '{"title": "Restart", "steps": []} and {"title": "Stop", "steps": []}'
+    assert skill_extractor._extract_json_object(resp) is None
+
+
+def test_trailing_stray_brace_is_recovered():
+    # A single valid JSON object followed by trailing text containing a stray brace should be recovered.
+    resp = '{"title": "Restart the service", "steps": ["a"]} }'
+    data = skill_extractor._extract_json_object(resp)
+    assert isinstance(data, dict)
+    assert data["title"] == "Restart the service"
+

tests/test_skill_extractor_stray_brace.py

@@ -115,3 +115,33 @@ async def test_maybe_extract_skill_drops_when_no_candidate_parses(monkeypatch):
 
     assert entry is None
     assert not skills_manager.added
+
+
+async def test_maybe_extract_skill_drops_on_multiple_json_objects(monkeypatch):
+    # Two valid JSON objects should be rejected by maybe_extract_skill.
+    resp = (
+        '{"title": "Deploy runbook", "problem": "manual", "solution": "script", '
+        '"steps": ["build"], "tags": ["deploy"], "confidence": 0.9}\n'
+        '{"title": "Unrelated skill", "problem": "manual", "solution": "script", '
+        '"steps": ["build"], "tags": ["deploy"], "confidence": 0.9}'
+    )
+    async def fake_llm_call_async(*args, **kwargs):
+        return resp
+
+    monkeypatch.setattr("src.llm_core.llm_call_async", fake_llm_call_async)
+
+    skills_manager = _FakeSkillsManager()
+    entry = await skill_extractor.maybe_extract_skill(
+        _FakeSession(),
+        skills_manager,
+        endpoint_url="http://endpoint",
+        model="test-model",
+        headers={},
+        round_count=3,
+        tool_count=3,
+        owner="alice",
+    )
+
+    assert entry is None
+    assert not skills_manager.added
+