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# Why modelId is deprecated in the Vercel API and how to select models for cost control

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Yoav Aviram (@yobo) · 2026-03-12 · ♥ 1

The API documentation says `modelId` is deprecated. The UI still lets you choose which model to work with.

## Questions
- Which model is the `API` working with by default?
- Why do we not get a choice in the `API`?
- What if we want to save on cost and don’t need the best model?


Jacob Paris (@jacobparis) · 2026-03-12

`modelId` was deprecated when v0 switched from specific models to the v0 Agent, which calls different models under the hood. Later, v0 rolled out 3 different agents (mini, pro, and max) which are primarily based on haiku, sonnet, and opus respectively. When this happened, the API was not updated to restore the modelId functionality

It currently corresponds to pro, which uses sonnet

I will ping the v0 team and see if we can get the option restored


Yoav Aviram (@yobo) · 2026-03-12 · ♥ 1

Thanks you!