fix: use CASE instead of COALESCE for swapper_state to always update when provided

services/city-service/repo_city.py

@@ -3801,7 +3801,9 @@ async def node_heartbeat(
         
         # Update heartbeat
         swapper_state = metrics.get("swapper_state")
-        swapper_state_json = json.dumps(swapper_state) if swapper_state else None
+        # Always update swapper_state if provided (even if empty dict)
+        # Use empty JSON object as default if swapper_state is None
+        swapper_state_json = json.dumps(swapper_state) if swapper_state is not None else None
 
         await pool.execute("""
             UPDATE node_cache SET
@@ -3817,7 +3819,10 @@ async def node_heartbeat(
                 swapper_healthy = COALESCE($9::boolean, swapper_healthy),
                 swapper_models_loaded = COALESCE($10::integer, swapper_models_loaded),
                 swapper_models_total = COALESCE($11::integer, swapper_models_total),
-                swapper_state = COALESCE($12::jsonb, swapper_state)
+                swapper_state = CASE 
+                    WHEN $12::jsonb IS NOT NULL THEN $12::jsonb 
+                    ELSE swapper_state 
+                END
             WHERE node_id = $1
         """, 
             node_id,