{
  "events": [
    {
      "type": "message_start",
      "message": {
        "type": "message",
        "model": "upstream-model",
        "usage": {
          "input_tokens": 0,
          "cache_creation_input_tokens": 0,
          "cache_read_input_tokens": 0,
          "output_tokens": 0,
          "claude_cache_creation_5_m_tokens": 0,
          "claude_cache_creation_1_h_tokens": 0
        },
        "role": "assistant",
        "id": "stream_fixed",
        "content": []
      }
    },
    {
      "type": "content_block_start",
      "index": 0,
      "content_block": {
        "type": "text",
        "text": ""
      }
    },
    {
      "type": "content_block_delta",
      "index": 0,
      "delta": {
        "type": "text_delta",
        "text": "Hello"
      }
    },
    {
      "type": "content_block_delta",
      "index": 0,
      "delta": {
        "type": "text_delta",
        "text": " world"
      }
    },
    {
      "type": "content_block_stop",
      "index": 0
    },
    {
      "type": "message_delta",
      "usage": {
        "input_tokens": 4,
        "cache_creation_input_tokens": 0,
        "cache_read_input_tokens": 0,
        "output_tokens": 2,
        "claude_cache_creation_5_m_tokens": 0,
        "claude_cache_creation_1_h_tokens": 0,
        "billing_usage": {
          "source": "gemini_chat",
          "semantic": "gemini",
          "gemini_usage_metadata": {
            "promptTokenCount": 4,
            "toolUsePromptTokenCount": 0,
            "candidatesTokenCount": 2,
            "totalTokenCount": 6,
            "thoughtsTokenCount": 0,
            "cachedContentTokenCount": 0,
            "promptTokensDetails": [],
            "toolUsePromptTokensDetails": [],
            "candidatesTokensDetails": []
          }
        }
      },
      "delta": {
        "stop_reason": "end_turn"
      }
    },
    {
      "type": "message_stop"
    }
  ]
}