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When a routing rule sends a request to a provider that speaks a different format than the caller, the gateway translates it both ways. Your OpenAI code can call an Anthropic model, and your Anthropic code can call an OpenAI model, with no change on your side.

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How it works

Set up a routing rule that targets a provider in the other format, for example routing OpenAI-format traffic to an anthropic provider. From then on, the gateway:
  • Translates the request from the OpenAI Responses API to the Anthropic Messages API, or the reverse.
  • Translates the response back into the format your client expects.
  • Translates streaming events the same way, so streaming keeps working.

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What’s translated

The common shape of a chat request carries over in both directions:
  • Messages and the system prompt.
  • The max-tokens setting.
  • Tools, tool choice, and tool results.
  • Streaming, temperature, and top-p.
Settings with no counterpart in the target format are dropped rather than approximated. Anthropic’s top_k is one, so a translated request runs without it.

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Endpoints

Image generation is a passthrough to an OpenAI-format provider, so it isn’t translated and can’t be routed to an anthropic upstream. Streaming image generation, the gpt-image partial-images mode, isn’t supported: send the request without stream. Keys, usage limits, model access, and guardrails apply on all three endpoints.

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Limits

  • Content types beyond text are not translated. A request carrying an image or document block across formats fails rather than being silently sent without it.
  • The provider-specific tools in the OpenAI Responses API, web search, file search, and code interpreter, have no Anthropic counterpart and are not translated.
  • The azure_openai format is wire-compatible with openai, so traffic between them is never translated.
Media that isn’t translated between formats is still captured in the trace. The limit is on converting it between provider wire formats, not on recording it. Which models a key may request is separate from translation: model access rules run on the name the client asked for, before routing.