fix: closed document stays active & leaks into new chats (#1160) (#1238)

* fix: closed document no longer stays active and leaks into new chats (#1160)

Closing a document tab calls _detachDocFromSession: a doc with content is
PATCHed to session_id="" (unlinked, session_id -> NULL, is_active stays True),
an empty one is DELETEd. But the in-memory active-document pointer
(tool_implementations._active_document_id) was never cleared on either path.

The chat doc-injection last-resort looks up that pointer by id and injects it
when `not cand.session_id or cand.session_id == session`. An unlinked doc has
session_id NULL, so the stale pointer re-surfaced a closed document in later,
unrelated chats — the agent kept reading/suggesting edits to a doc the user
had closed.

Fix: add clear_active_document(doc_id) and call it when a document is unlinked
(PATCH session_id="") or deleted, so the pointer no longer resurrects a closed
document. clear_active_document only clears when the id matches (or no id), so a
different active doc is left untouched.

Covered by tests/test_active_document_clear.py (4 cases).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test: add route-level regression for #1160 (detach/delete clears active doc)

Per review: prove the actual API path, not just the helper. Drives
PATCH /api/document/{id} (session_id="") and DELETE /api/document/{id}
through TestClient against a temp SQLite DB under real owner routing, and
asserts get_active_document() is cleared (and untouched when a different
document is closed).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test: make #1160 route regression hang-proof and dev-DB-independent

The route test could hang in other environments: it set DATABASE_URL at import
time, which is ignored if core.database was already imported, so it fell back to
the real dev DB and could contend for its locks (maintainer saw it hang, exit
124).

Rebind to a DEDICATED temporary SQLite engine (NullPool) and patch the document
route module's SessionLocal to it via an autouse fixture — so the test never
touches the dev DB and is independent of import order. Runs in ~0.3s.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test: drive #1160 route regression without TestClient (fixes local hang)

The route test used Starlette TestClient (middleware app + threadpool), which
hung in the maintainer's environment. Rework it to call the async route handlers
directly — extracted from the router — with a minimal fake request against a
temp-SQLite-patched SessionLocal. Same real coverage (handler + DB + owner
routing), but it completes reliably (~0.3s) with no TestClient/threadpool.

Verified the maintainer's exact batch now passes:
  pytest tests/test_document_close_clears_active_route.py \
         tests/test_active_document_clear.py \
         tests/test_document_tool_owner_scope.py  -> 14 passed

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

routes/document_routes.py

@@ -593,6 +593,15 @@ def setup_document_routes(session_manager, upload_handler=None) -> APIRouter:
             if req.session_id is not None:
                 # Empty string = unlink from session
                 doc.session_id = req.session_id if req.session_id else None
+                if not req.session_id:
+                    # Tab closed / doc detached from its session — drop the
+                    # in-memory active-doc pointer so the last-resort injection
+                    # path doesn't re-surface this doc in a later chat (#1160).
+                    try:
+                        from src.tool_implementations import clear_active_document
+                        clear_active_document(doc_id)
+                    except Exception:
+                        pass
             db.commit()
             db.refresh(doc)
             return _doc_to_dict(doc)
@@ -615,6 +624,13 @@ def setup_document_routes(session_manager, upload_handler=None) -> APIRouter:
                 raise HTTPException(404, "Document not found")
             _verify_doc_owner(db, doc, user)
             doc.is_active = False
+            # Closed/deleted — drop the in-memory active-doc pointer so it isn't
+            # re-injected into a later, unrelated chat (#1160).
+            try:
+                from src.tool_implementations import clear_active_document
+                clear_active_document(doc_id)
+            except Exception:
+                pass
             db.commit()
             return {"status": "deleted", "id": doc_id}
         except HTTPException: