Vertex AI generative models return 404 NOT_FOUND (Publisher Model ... was not found) despite previously working

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1

Hello, I’m experiencing a persistent 404 NOT_FOUND error when calling Vertex AI generative models (Gemini) from my project. The error started occurring suddenly after working correctly for ~2 months, without any code changes on my side.

Error Detail (Python / Google GenAI):

google.genai.errors.ClientError: 404 NOT_FOUND. {'error': {'code': 404, 'message': 'Publisher Model `projects(PII Removed by Staff)gemini-2.5-flash-preview-09-2025` was not found or your project does not have access to it. Please ensure you are using a valid model version. ...', 'status': 'NOT_FOUND'}}

Steps to Reproduce:

  1. Code that was working for ~2 months now starts returning this error

  2. Model name: gemini-2.5-flash-preview-09-2025

  3. Billing enabled, Vertex AI API enabled

  4. Verified IAM roles include Vertex AI User for the service account

  5. Tried from multiple regions and SDK versions

Observations:

  • This error appears even with correct setup and models that were previously working.

  • It seems like either the model is no longer accessible or there’s a backend provisioning / model availability issue.

2

`client.models.list()` also returns 404 with `/v1/publishers/google/models was not found on this server.`

3

Hello @Pulkit_Agarwal

From Gemini API:

Preview

Points to a preview model that may be used in production. Preview models will typically have billing enabled, may come with more restrictive rate limits, and will be deprecated with at least 2 weeks’ notice.

For example: gemini-2.5-flash-preview-09-2025.

Personally, I no longer have it on any of my projects.

Using the link from the Gemini 2.5 Flash (preview) Model Page does not redirect to Vertex AI with the model ready for use, it’s just not there (for me).

You may have to use other models like gemini-2.5-flash.

Concerning client.models.list(), are your libs up to date? Also, you may be interested in looking into Vertex AI Method List.