Anthropic

The anthropic provider translates OpenAI-format requests to the Anthropic Messages API and back.

Configuration

[providers.anthropic]
kind = "anthropic"
api_key = "${ANTHROPIC_API_KEY}"
models = ["claude-sonnet-4-20250514", "claude-haiku-4-20250514"]

Translation

CrabLLM handles the full translation between OpenAI and Anthropic formats:

• System messages — extracted from the messages array and sent as the Anthropic system parameter.
• Stop reasons — mapped between formats (end_turn to stop, etc.).
• Tool calling — fully supported. Tool definitions, tool use responses, and tool result messages are all translated.
• Streaming — Anthropic's event stream (message_start, content_block_delta, etc.) is translated to OpenAI-format SSE chunks.

Usage

Send requests in OpenAI format as usual:

curl http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-20250514",
    "messages": [
      {"role": "system", "content": "You are a helpful assistant."},
      {"role": "user", "content": "Hello!"}
    ]
  }'

Limitations

Embeddings, image generation, and audio endpoints are not supported by the Anthropic API.