{
  "method": "sessionUpdate",
  "args": [
    {
      "sessionId": "test-session-id",
      "update": {
        "sessionUpdate": "agent_message_chunk",
        "messageId": "plan-2",
        "content": {
          "type": "text",
          "text": "### Fallback plan\n\n1. Use the completed item."
        },
        "_meta": {
          "codex": {
            "phase": "final_answer"
          }
        }
      }
    }
  ]
}