fix: lazy-import AsyncPostgresSaver to fix ops-worker/gumbo startup crash (ModuleNotFoundError langgraph.checkpoint.postgres)

agents/gumbo/gumbo/graph.py

@@ -7,8 +7,8 @@ from typing import TypedDict
 
 from langchain_core.messages import HumanMessage, SystemMessage
 from langchain_openai import ChatOpenAI
-from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
 from langgraph.graph import END, StateGraph
+# AsyncPostgresSaver imported lazily in run_gumbo() to avoid startup crash
 
 from gumbo.mcp_fs import fetch_text_via_mcp
 
@@ -53,6 +53,10 @@ def build_graph_builder() -> StateGraph:
 
 
 async def run_gumbo(object_key: str, thread_id: str, conn_string: str) -> GumboState:
+    try:
+        from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
+    except ImportError:
+        from langgraph_checkpoint_postgres.aio import AsyncPostgresSaver
     builder = build_graph_builder()
     async with AsyncPostgresSaver.from_conn_string(conn_string) as checkpointer:
         await checkpointer.setup()

agents/ops_agent/ops_agent/graph.py

@@ -4,7 +4,7 @@ from typing import TypedDict
 from langchain_core.messages import SystemMessage, HumanMessage
 from langchain_openai import ChatOpenAI
 from langgraph.graph import StateGraph, END
-from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
+# AsyncPostgresSaver imported lazily below (only when conn_string is provided)
 
 from ops_agent.tools import (
     k8s_get_status, k8s_get_logs, k8s_restart_pod, k8s_scale_deployment,
@@ -214,6 +214,10 @@ async def run_ops_graph(target_type: str, target_id: str, is_approved: bool = Fa
     }
     
     if conn_string:
+        try:
+            from langgraph.checkpoint.postgres.aio import AsyncPostgresSaver
+        except ImportError:
+            from langgraph_checkpoint_postgres.aio import AsyncPostgresSaver
         async with AsyncPostgresSaver.from_conn_string(conn_string) as checkpointer:
             await checkpointer.setup()
             graph = builder.compile(checkpointer=checkpointer)

agents/ops_agent/requirements.txt

@@ -1,4 +1,5 @@
 langgraph>=0.2.0
+langgraph-checkpoint-postgres>=2.0.0
 langchain-core>=0.3.0
 langchain-openai>=0.2.0
 temporalio>=1.8.0