fix: stabilize background operations and large embedding results

backend/app/retrieval/activity.py

@@ -0,0 +1,30 @@
+"""Process-local retrieval activity, shared by search, RAG and Agent callers."""
+import asyncio
+from functools import wraps
+
+active = 0
+completed = 0
+failed = 0
+cancelled = 0
+
+
+def track_search(operation):
+    @wraps(operation)
+    async def wrapped(self, request):
+        global active, completed, failed, cancelled
+        if request.mode == 'fts':
+            return await operation(self, request)
+        active += 1
+        try:
+            result = await operation(self, request)
+            completed += 1
+            return result
+        except asyncio.CancelledError:
+            cancelled += 1
+            raise
+        except Exception:
+            failed += 1
+            raise
+        finally:
+            active -= 1
+    return wrapped

backend/app/retrieval/engine.py

@@ -10,6 +10,7 @@ from __future__ import annotations
 from datetime import datetime, timezone
 
 from app import repository
+from app.retrieval.activity import track_search
 from app.contracts import (
     Citation,
     PageMeta,
@@ -52,6 +53,7 @@ class RetrievalEngine:
         # remain authoritative, including monkeypatches on the singleton.
         self._routed_defaults = (embedding, vector_store) if route_embeddings else None
 
+    @track_search
     async def search(self, request: SearchRequest) -> SearchResponse:
         if request.mode == SearchMode.fts:
             return self._search_fts(request)

backend/app/retrieval/routed_vectors.py

@@ -20,6 +20,7 @@ from typing import Protocol
 
 from app.database.db import connect, transaction
 from app.errors import ApiError
+from app.operation_logs import log_event
 from app.retrieval.vectorstore import VectorHit
 from app.retrieval.provenance import record_embedding
 from app.retrieval.hybrid import rrf_fuse
@@ -101,6 +102,8 @@ async def embed_remote(texts: list[str], *, accept_local=False, strict=False, lo
             source=result.source,
         )
     except Exception as exc:
+        log_event('vectors', 'embedding.failed', level='ERROR' if strict else 'WARNING', error=exc,
+                  count=len(texts), fallback='none' if strict else 'local_index')
         # Avoid logging provider exceptions containing credentials or note text.
         record_embedding(fallback_reason="REMOTE_EMBEDDING_UNAVAILABLE")
         logger.warning("Remote embedding unavailable (%s); using local index", type(exc).__name__)