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Every run-creating endpoint accepts an optional model field. When omitted, runs use the default model, currently anthropic/claude-sonnet-5-5. The resolved model is echoed on every run object as model. The accepted ids are listed on Supported Models.

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Choosing a model

The model field is accepted on POST /v1/runs, POST /v1/realtime/runs, POST /v1/agents, and POST /v1/agents/{agent_id}/edits. On agent create and edit, it selects the model the builder uses. Model selection applies to that run only. It is not stored as an agent or conversation preference, and follow-up runs in the same conversation may use a different model.

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Errors

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Model lifecycle

Superseded models are flagged legacy: true but remain fully supported, at unchanged pricing. The flag is presentational: it is what moves a model under the Older versions row in the product model picker (see How the list is ordered), and it is the Legacy status on Supported Models. It is not a deprecation notice and does not change how a request is served. Removing a model from CREAO CLI is announced in the changelog before removal. After removal, requests for it return MODEL_NOT_SUPPORTED. Runs recorded with a retired model keep their historical model value.