Migrating from Gemini API to Vertex (enterprise agent platform)

Hello all - running some test scripts to try and migrate to the enterprise agent platform but hitting auth walls? Can some from google update my allowlist or am I missing something obvious?

Allowlist request: gemini-3-pro-image-preview & gemini-3.1-flash-image-preview on Vertex

We are formally requesting allowlist access for two preview image models on Vertex AI(google enterprise now) so we can complete an in-progress
migration from the AI Studio Gemini API to Vertex AI.

Request

Field Value
Models gemini-3-pro-image-preview, gemini-3.1-flash-image-preview
GCP Project ID bevai-26
Region us-central1

Environment

  • Billing: enabled (paid Workspace account, $300 free-trial credit active)
  • Vertex AI API: enabled (aiplatform.googleapis.com)
  • Authentication: Application Default Credentials, verified working — a control call to gemini-2.5-flash (GA) succeeds
    end-to-end from this project
  • IAM: requester holds roles/aiplatform.user

Use case

We operate a production beverage-product imagery platform (bevai.io) that currently calls
gemini-3-pro-image-preview via the AI Studio Gemini API for image generation and multi-turn image refinement across ~15
application routes (keyframe generation/refinement, storyboard prompt assistance, brand moodboard analysis, product
mockup refinement). We are migrating to Vertex AI to (1) use the GCP free-trial credit, (2) gain enterprise
data-residency controls, and (3) align with the recommended production auth path (service-account/ADC instead of API
keys).

We are requesting gemini-3.1-flash-image-preview alongside the Pro variant so we can offer a faster/lower-cost tier for
high-volume use cases where 4K quality and 14-reference-image support are not required.

Error encountered

{
“error”: {
“code”: 404,
“message”: “Publisher Model
projects/bevai-26/locations/us-central1/publishers/google/models/gemini-3-pro-image-preview was not found or your project
does not have access to it.”,
“status”: “NOT_FOUND”
}
}

Same 404 returned for gemini-3.1-flash-image-preview. Control call to gemini-2.5-flash from the same project, region,
and credentials returns 200.

Happy to provide any additional information needed. Thanks!

Hi
@Bev_Dev , can you share your project ID via the DMs with me?