fix: align IDs with metadatas in ChromaSearchStrategy

ChromaSync.queryChroma() returns deduplicated sqlite_ids but the
metadatas array contains multiple entries per observation (narrative +
facts). The filterByRecency() method was iterating over metadatas and
using the index to access ids, causing array out-of-bounds access.

The fix builds a Map from sqlite_id to metadata, then iterates over
the deduplicated ids array to ensure proper alignment.

Symptoms before fix:
- Semantic search returning incorrect/empty results
- Search only working with near-exact queries
- Recent items (same day) not being found

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/worker/search/strategies/ChromaSearchStrategy.ts

@@ -167,6 +167,13 @@ export class ChromaSearchStrategy extends BaseSearchStrategy implements SearchSt
 
   /**
    * Filter results by recency (90-day window)
+   *
+   * IMPORTANT: ChromaSync.queryChroma() returns deduplicated `ids` (unique sqlite_ids)
+   * but the `metadatas` array may contain multiple entries per sqlite_id (e.g., one
+   * observation can have narrative + multiple facts as separate Chroma documents).
+   *
+   * This method iterates over the deduplicated `ids` and finds the first matching
+   * metadata for each ID to avoid array misalignment issues.
    */
   private filterByRecency(chromaResults: {
     ids: number[];
@@ -174,10 +181,19 @@ export class ChromaSearchStrategy extends BaseSearchStrategy implements SearchSt
   }): Array<{ id: number; meta: ChromaMetadata }> {
     const cutoff = Date.now() - SEARCH_CONSTANTS.RECENCY_WINDOW_MS;
 
-    return chromaResults.metadatas
-      .map((meta, idx) => ({
-        id: chromaResults.ids[idx],
-        meta
+    // Build a map from sqlite_id to first metadata for efficient lookup
+    const metadataByIdMap = new Map<number, ChromaMetadata>();
+    for (const meta of chromaResults.metadatas) {
+      if (meta?.sqlite_id !== undefined && !metadataByIdMap.has(meta.sqlite_id)) {
+        metadataByIdMap.set(meta.sqlite_id, meta);
+      }
+    }
+
+    // Iterate over deduplicated ids and get corresponding metadata
+    return chromaResults.ids
+      .map(id => ({
+        id,
+        meta: metadataByIdMap.get(id) as ChromaMetadata
       }))
       .filter(item => item.meta && item.meta.created_at_epoch > cutoff);
   }

tests/worker/search/strategies/chroma-search-strategy.test.ts

@@ -295,6 +295,87 @@ describe('ChromaSearchStrategy', () => {
       expect(result.usedChroma).toBe(false); // Error occurred
       expect(result.results.observations).toHaveLength(0);
     });
+
+    it('should correctly align IDs with metadatas when Chroma returns duplicate sqlite_ids (multiple docs per observation)', async () => {
+      // BUG SCENARIO: One observation (id=100) has 3 documents in Chroma (narrative + 2 facts)
+      // Another observation (id=200) has 1 document
+      // Chroma returns 4 metadatas but after deduplication we have 2 unique IDs
+      // The metadatas MUST be deduplicated/aligned to match the unique IDs
+      const recentEpoch = Date.now() - 1000 * 60 * 60 * 24; // 1 day ago
+
+      mockChromaSync.queryChroma = mock(() => Promise.resolve({
+        // After deduplication in ChromaSync.queryChroma, ids should be [100, 200]
+        // But metadatas array has 4 elements - THIS IS THE BUG
+        ids: [100, 200],  // Deduplicated
+        distances: [0.3, 0.4, 0.5, 0.6],  // Original 4 distances
+        metadatas: [
+          // Original 4 metadatas - not aligned with deduplicated ids!
+          { sqlite_id: 100, doc_type: 'observation', created_at_epoch: recentEpoch },
+          { sqlite_id: 100, doc_type: 'observation', created_at_epoch: recentEpoch },
+          { sqlite_id: 100, doc_type: 'observation', created_at_epoch: recentEpoch },
+          { sqlite_id: 200, doc_type: 'observation', created_at_epoch: recentEpoch }
+        ]
+      }));
+
+      // Mock that returns observations when called with correct IDs
+      const mockObs100 = { ...mockObservation, id: 100 };
+      const mockObs200 = { ...mockObservation, id: 200, title: 'Second observation' };
+      mockSessionStore.getObservationsByIds = mock((ids: number[]) => {
+        // Should receive [100, 200]
+        return ids.map(id => id === 100 ? mockObs100 : mockObs200);
+      });
+
+      const options: StrategySearchOptions = {
+        query: 'test query',
+        searchType: 'observations'
+      };
+
+      const result = await strategy.search(options);
+
+      // The strategy should correctly identify BOTH observations
+      // Before the fix: idx=2 and idx=3 would access ids[2] and ids[3] which are undefined
+      expect(result.usedChroma).toBe(true);
+      expect(mockSessionStore.getObservationsByIds).toHaveBeenCalled();
+
+      // Verify the correct IDs were passed to SQLite hydration
+      const calledWith = mockSessionStore.getObservationsByIds.mock.calls[0][0];
+      expect(calledWith).toContain(100);
+      expect(calledWith).toContain(200);
+      expect(calledWith.length).toBe(2); // Should have exactly 2 unique IDs
+    });
+
+    it('should handle misaligned arrays gracefully without undefined access', async () => {
+      // Edge case: metadatas array longer than ids array
+      // This simulates the actual bug condition
+      const recentEpoch = Date.now() - 1000 * 60 * 60 * 24;
+
+      mockChromaSync.queryChroma = mock(() => Promise.resolve({
+        ids: [100],  // Only 1 ID after deduplication
+        distances: [0.3, 0.4, 0.5],  // 3 distances
+        metadatas: [
+          { sqlite_id: 100, doc_type: 'observation', created_at_epoch: recentEpoch },
+          { sqlite_id: 100, doc_type: 'observation', created_at_epoch: recentEpoch },
+          { sqlite_id: 100, doc_type: 'observation', created_at_epoch: recentEpoch }
+        ]  // 3 metadatas for same observation
+      }));
+
+      mockSessionStore.getObservationsByIds = mock(() => [mockObservation]);
+
+      const options: StrategySearchOptions = {
+        query: 'test query',
+        searchType: 'observations'
+      };
+
+      // Before fix: This would try to access ids[1], ids[2] which are undefined
+      // causing incorrect filtering or crashes
+      const result = await strategy.search(options);
+
+      expect(result.usedChroma).toBe(true);
+      // Should still find the one observation correctly
+      expect(mockSessionStore.getObservationsByIds).toHaveBeenCalled();
+      const calledWith = mockSessionStore.getObservationsByIds.mock.calls[0][0];
+      expect(calledWith).toEqual([100]);
+    });
   });
 
   describe('strategy name', () => {