Anthropic

The anthropic provider speaks the native Anthropic Messages API. Use it for Claude models on Anthropic's own endpoint, or for any proxy that serves the same API shape.

model:
  provider: anthropic
  id: claude-sonnet-5

With no base_url, requests go to https://api.anthropic.com and the key is read from ANTHROPIC_API_KEY. Point api_key_env at a different env var if your key lives elsewhere; the mechanics are in Providers.

model:
  provider: anthropic
  id: claude-sonnet-5
  base_url: https://my-litellm-proxy.internal   # any Messages-API-compatible endpoint
  api_key_env: PROXY_API_KEY

One behavior worth knowing: this dialect caps output at 4096 tokens per call. The Messages API requires an explicit maximum and the framework deliberately has no config field for it, so we picked a fixed value. If a run needs longer single responses, put a rewriting proxy such as LiteLLM behind base_url; the reasoning is in what is deliberately not configurable.