# imagen-4.0-fast-generate-preview-05-20

Calls to the model imagen-4.0-fast-generate-preview-05-20 on Vertex AI (us-central1-aiplatform.googleapis.com) stopped working on March 19, 2026.

## The error Vertex AI (us-central1-aiplatform.googleapis.com) returns once imagen-4.0-fast-generate-preview-05-20 is gone

HTTP 404

```json
{"error":{"code":404,"message":"Publisher model `projects/{project}/locations/{region}/publishers/google/models/imagen-4.0-fast-generate-preview-05-20` was not found or your project does not have access to it. Ensure you are using a valid model name and that the model is available in the specified region.","status":"NOT_FOUND"}}
```

## What to use instead

Update your model endpoints before March 19, 2026, using either imagen-4.0-generate-001 or gemini-2.5-flash-image.

- API: Vertex AI (us-central1-aiplatform.googleapis.com) (us-central1-aiplatform.googleapis.com)
- Model: imagen-4.0-fast-generate-preview-05-20
- Kind: Model retirement
- Announced: February 17, 2026
- Takes effect: March 19, 2026
- Calls after that day: fail
- Calls it hits: `model imagen-4.0-fast-generate-preview-05-20`
- Source: [Changelog](https://docs.cloud.google.com/vertex-ai/docs/release-notes)
- Verified: November 3, 2026, against Vertex AI (us-central1-aiplatform.googleapis.com)'s own pages
- Page: https://www.okapi.bot/models/vertex-ai-2/imagen-4.0-fast-generate-preview-05-20/

## Vertex AI (us-central1-aiplatform.googleapis.com)'s words

> | `imagen-4.0-fast-generate-preview-05-20` | `imagen-4.0-generate-001` or `gemini-2.5-flash-image` |

Okapi finds the calls this change hits in your repo and opens the pull request with the fix: https://github.com/apps/okapi-agent