fix: remove stale session entry from sessions.json on idle-TTL eviction

gateway/run.py

@@ -14915,6 +14915,12 @@ def _sweep_idle_cached_agents(self) -> int:
                 "Agent cache idle-TTL evict: session=%s (idle=%.0fs)",
                 key, now - getattr(agent, "_last_activity_ts", now),
             )
+            # Remove from sessions.json so the stale entry doesn't route
+            # messages into an ended session until gateway restart.
+            try:
+                self.session_store.remove(key)
+            except Exception:
+                logger.debug("Failed to remove stale session entry for %s", key, exc_info=True)
             threading.Thread(
                 target=self._release_evicted_agent_soft,
                 args=(agent,),

gateway/session.py

@@ -1615,6 +1615,22 @@ def switch_session(self, session_key: str, target_session_id: str) -> Optional[S
 
         return new_entry
 
+    def remove(self, session_key: str) -> bool:
+        """Remove a session key from the routing index.
+
+        Called after idle-TTL eviction to prevent sessions.json from holding
+        stale entries that route messages into ended sessions.
+
+        Returns True if the key was present and removed, False otherwise.
+        """
+        with self._lock:
+            self._ensure_loaded_locked()
+            if session_key not in self._entries:
+                return False
+            del self._entries[session_key]
+            self._save()
+            return True
+
     def list_sessions(self, active_minutes: Optional[int] = None) -> List[SessionEntry]:
         """List all sessions, optionally filtered by activity."""
         with self._lock:

tests/gateway/test_session_store_stale_prune.py

@@ -179,3 +179,37 @@ def test_live_entry_survives_load(self, tmp_path):
         store._ensure_loaded()
 
         assert "active_key" in store._entries
+
+
+def test_session_store_remove():
+    """SessionStore.remove() should remove a key from the routing index.
+
+    Regression test for #54878: after idle-TTL eviction, sessions.json
+    held stale entries that routed messages into ended sessions.
+    """
+    import tempfile
+    from pathlib import Path
+    from gateway.session import SessionStore, SessionSource
+    from gateway.config import GatewayConfig, Platform
+
+    with tempfile.TemporaryDirectory() as tmp:
+        sessions_dir = Path(tmp) / "sessions"
+        config = GatewayConfig()
+        store = SessionStore(sessions_dir, config)
+
+        # Create a session entry via get_or_create
+        source = SessionSource(
+            platform=Platform.TELEGRAM,
+            chat_id="12345",
+            user_id="user1",
+        )
+        entry = store.get_or_create_session(source)
+        assert entry is not None
+
+        # Remove the key
+        removed = store.remove(entry.session_key)
+        assert removed is True
+
+        # Removing again should return False
+        removed2 = store.remove(entry.session_key)
+        assert removed2 is False