fix(health): report unhealthy memory vector store as degraded

Keep an unhealthy MemoryVectorStore instance available for health reporting instead of discarding it as disabled. This lets health checks report a degraded/down vector-store state while preserving focused regression coverage for initializer behavior.

src/app_initializer.py

@@ -68,8 +68,10 @@ def initialize_managers(base_dir: str, rag_manager=None) -> Dict[str, Any]:
                     logger.info(f"Rebuilt memory vector index from {len(existing)} existing entries")
             logger.info("MemoryVectorStore initialized")
         else:
+            # Keep the unhealthy object (do NOT reset to None): consumers gate on
+            # `.healthy`, and service_health.chromadb_health() needs a present
+            # object to report DEGRADED/DOWN instead of DISABLED ("not configured").
             logger.warning("MemoryVectorStore DEGRADED: ChromaDB vector memory unavailable")
-            memory_vector = None
     except Exception as e:
         logger.warning(f"MemoryVectorStore DEGRADED: {e}")
         memory_vector = None

tests/test_app_initializer_memory_vector_degraded.py

@@ -0,0 +1,71 @@
+"""Regression: a present-but-unhealthy MemoryVectorStore must survive initialization.
+
+When MemoryVectorStore._initialize() fails (ChromaDB unavailable / embeddings not
+installed) it swallows the exception and leaves `.healthy == False` — the object
+exists but is unhealthy. app_initializer.initialize_managers() previously reset that
+object to ``None`` in the ``else`` branch, so service_health.chromadb_health() saw
+``memory_vector is None`` and reported the vector memory as DISABLED ("not
+configured") instead of DEGRADED/DOWN ("initialization failed") — losing the
+diagnostic distinction the /api/diagnostics/services probe is built to surface.
+
+This test fails before the fix (memory_vector is None) and passes after it.
+"""
+from unittest.mock import MagicMock
+
+import src.app_initializer as app_init
+import src.memory_vector as memory_vector_mod
+import src.service_health as sh
+
+
+class _UnhealthyVectorStore:
+    """Stand-in for a MemoryVectorStore whose init failed: present but inert."""
+    healthy = False
+
+    def count(self):
+        return 0
+
+    def search(self, *a, **k):
+        return []
+
+
+def _neutralize_collaborators(monkeypatch):
+    """Stub out everything initialize_managers() builds except the vector store,
+    so the test isolates the memory_vector health-handling branch."""
+    for name in [
+        "MemoryManager", "SkillsManager", "SessionManager", "UploadHandler",
+        "PersonalDocsManager", "APIKeyManager", "PresetManager",
+        "MemoryProviderRegistry", "NativeMemoryProvider", "ChatProcessor",
+        "ResearchHandler", "ChatHandler", "ModelDiscovery",
+    ]:
+        monkeypatch.setattr(app_init, name, lambda *a, **k: MagicMock())
+    monkeypatch.setattr(app_init, "set_session_manager", lambda *a, **k: None)
+    monkeypatch.setattr(app_init, "update_search_config", lambda *a, **k: None)
+    monkeypatch.setattr(app_init, "create_directories", lambda: None)
+
+
+def test_failed_memory_vector_init_is_kept_not_discarded(monkeypatch, tmp_path):
+    _neutralize_collaborators(monkeypatch)
+    # initialize_managers does `from src.memory_vector import MemoryVectorStore`
+    # at call time, so patch it on the source module.
+    monkeypatch.setattr(
+        memory_vector_mod, "MemoryVectorStore",
+        lambda *a, **k: _UnhealthyVectorStore(),
+    )
+
+    result = app_init.initialize_managers(str(tmp_path), rag_manager=None)
+
+    mv = result["memory_vector"]
+    assert mv is not None, "unhealthy MemoryVectorStore was discarded (reported as DISABLED, not DEGRADED/DOWN)"
+    assert mv.healthy is False
+
+
+def test_chromadb_health_reports_down_for_unhealthy_vector_store():
+    # Pins the downstream taxonomy the fix feeds: a present-but-unhealthy vector
+    # store (rag absent) is DOWN, not DISABLED; with a healthy rag it is DEGRADED;
+    # only when both are absent is it DISABLED.
+    store = _UnhealthyVectorStore()
+    healthy_rag = MagicMock(healthy=True)
+
+    assert sh.chromadb_health(None, None)["status"] == sh.DISABLED
+    assert sh.chromadb_health(None, store)["status"] == sh.DOWN
+    assert sh.chromadb_health(healthy_rag, store)["status"] == sh.DEGRADED