src/fabledassistant/services/embeddings.py

@@ -153,17 +153,22 @@ async def semantic_search_notes(
     if not rows:
         return []
 
-    scored: list[tuple[float, Note]] = []
-    for ne, note in rows:
-        try:
-            sim = _cosine_similarity(query_vec, ne.embedding)
-        except Exception:
-            continue
-        if sim >= threshold:
-            scored.append((sim, note))
+    def _score() -> list[tuple[float, Note]]:
+        out: list[tuple[float, Note]] = []
+        for ne, note in rows:
+            try:
+                sim = _cosine_similarity(query_vec, ne.embedding)
+            except Exception:
+                continue
+            if sim >= threshold:
+                out.append((sim, note))
+        out.sort(key=lambda x: x[0], reverse=True)
+        return out[:limit]
 
-    scored.sort(key=lambda x: x[0], reverse=True)
-    return scored[:limit]
+    # Offload the O(rows) cosine scoring off the event loop so a large corpus
+    # doesn't stall other requests while ranking. Results are unchanged; the
+    # real scaling fix (ORDER BY / LIMIT in pgvector) is a separate effort.
+    return await asyncio.to_thread(_score)
 
 
 async def backfill_note_embeddings() -> None:

src/fabledassistant/services/knowledge.py

@@ -140,6 +140,14 @@ async def _semantic_knowledge_search(
     Exact keyword matches always rank above semantic-only matches so that
     searching for a name like "Weston" surfaces the note with that title
     before conceptually related notes.
+
+    BEST-EFFORT TOP-N, not exhaustive pagination: the ranked candidate set is
+    capped (keyword limit*2 + up to ~200 semantic), so `total` is the size of
+    that window, NOT the true match count, and matches beyond the cap are not
+    reachable by paging. Each page also recomputes the full merge (O(corpus)
+    per page). Acceptable for an interactive "best results" feed; a cached
+    ranked-id list or pgvector ORDER BY/LIMIT is the fix if exhaustive,
+    cheap pagination is ever needed.
     """
     # 1. Keyword search — title and body ILIKE
     keyword_notes: list[Note] = []