fix: discover sessions from persisted messages (#5938)

* fix(session): discover sessions from persisted messages

Use indexed chat-row existence instead of stale derived message_count metadata during startup discovery, then repair the bounded in-memory counts so lazy hydration remains correct. Keep truly empty sessions excluded and cover stale-low and stale-high counts with real SQLite.

* test(session): isolate discovery database

* test(session): use manager database metadata

core/session_manager.py

@@ -14,6 +14,8 @@ import logging
 from datetime import datetime, timezone, timedelta
 from typing import Dict, Optional
 
+from sqlalchemy import func
+
 from .database import Session as DbSession, ChatMessage as DbChatMessage, Document as DbDocument, SessionLocal, utcnow_naive
 from .models import Session, ChatMessage
 from src.attachment_refs import persistable_message_content
@@ -92,14 +94,28 @@ class SessionManager:
         try:
             db_sessions = db.query(DbSession).filter(
                 DbSession.archived == False,
-                DbSession.message_count > 0,
+                DbSession.messages.any(),
             ).order_by(DbSession.last_accessed.desc()).limit(100).all()
 
+            # message_count is derived metadata and can drift after interrupted
+            # or legacy writes. Count only the bounded discovery set so startup
+            # remains metadata-only while lazy hydration sees an authoritative
+            # positive count for every discovered non-empty session.
+            message_counts = {}
+            if db_sessions:
+                message_counts = dict(
+                    db.query(DbChatMessage.session_id, func.count(DbChatMessage.id))
+                    .filter(DbChatMessage.session_id.in_([row.id for row in db_sessions]))
+                    .group_by(DbChatMessage.session_id)
+                    .all()
+                )
+
             loaded_count = 0
             for db_session in db_sessions:
                 try:
                     session = self._db_to_session_meta(db_session)
                     if session is not None:
+                        session.message_count = message_counts[db_session.id]
                         self.sessions[db_session.id] = session
                         loaded_count += 1
                 except Exception as e:

tests/test_session_discovery_message_count.py

@@ -0,0 +1,62 @@
+"""Real-SQLite regressions for session discovery with stale derived counts."""
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import NullPool
+
+import core.session_manager as session_manager
+
+
+def _make_manager(db_path, monkeypatch):
+    engine = create_engine(
+        f"sqlite:///{db_path}",
+        connect_args={"check_same_thread": False},
+        poolclass=NullPool,
+    )
+    session_manager.DbSession.metadata.create_all(bind=engine)
+    session_local = sessionmaker(
+        bind=engine,
+        autoflush=False,
+        autocommit=False,
+    )
+    monkeypatch.setattr(session_manager, "SessionLocal", session_local)
+    return session_manager.SessionManager(), session_manager
+
+
+def test_discovery_uses_persisted_rows_and_repairs_cached_count(tmp_path, monkeypatch):
+    from core.models import ChatMessage
+
+    manager, session_manager = _make_manager(
+        tmp_path / "session-discovery.db", monkeypatch
+    )
+    for session_id in ("stale-low", "empty", "stale-high"):
+        manager.create_session(
+            session_id=session_id,
+            name=session_id,
+            endpoint_url="http://example.invalid",
+            model="test-model",
+            rag=False,
+            owner="tester",
+        )
+    manager.add_message("stale-low", ChatMessage("user", "persisted message"))
+
+    db = session_manager.SessionLocal()
+    try:
+        db.query(session_manager.DbSession).filter(
+            session_manager.DbSession.id == "stale-low"
+        ).update({"message_count": 0})
+        db.query(session_manager.DbSession).filter(
+            session_manager.DbSession.id == "stale-high"
+        ).update({"message_count": 7})
+        db.commit()
+    finally:
+        db.close()
+
+    restarted = session_manager.SessionManager()
+
+    assert set(restarted.sessions) == {"stale-low"}
+    assert restarted.sessions["stale-low"].history == []
+    assert restarted.sessions["stale-low"].message_count == 1
+
+    hydrated = restarted.get_session("stale-low")
+    assert [message.content for message in hydrated.history] == ["persisted message"]