{
  "id": "msg_compaction_x",
  "type": "message",
  "role": "assistant",
  "model": "claude-sonnet-4-5",
  "content": [
    {"type": "compaction", "content": "summary text", "encrypted_content": "EpwBCioIDxgC_opaque_payload"}
  ],
  "stop_reason": "end_turn",
  "stop_sequence": null,
  "usage": {"input_tokens": 1, "output_tokens": 12}
}