Routing
Model Fallbacks
Provide alternate model IDs when a model cannot serve a request.
Set model to the preferred ID and models to an array of fallback IDs.
The models field can also be used without model.
The API tries fallback models after the primary model, following OpenRouter semantics.
Provider filters still decide which hosts are eligible.
See recorded case chat_models_fallback in tests/fixtures/chat-completions/chat_models_fallback.json.