# chat-bison

Calls to the model chat-bison on Vertex AI stopped working on April 21, 2025.

- API: Vertex AI (aiplatform.googleapis.com)
- Model: chat-bison
- Kind: Model retirement
- Takes effect: April 21, 2025
- Calls after that day: fail
- Calls it hits: `model chat-bison`
- Source: [Deprecations page](https://cloud.google.com/vertex-ai/generative-ai/docs/learn/model-versions)
- Page: https://www.okapi.bot/models/vertex-ai/chat-bison/

## What to use instead

Move to gemini-3.8-flash. gemini-2.5-flash-lite, named first, stopped working on 2026-10-20.