Google Vertex AI

Configure Gemini on Google Vertex AI in GoModel, including ADC and service-account authentication, regions, and native vs OpenAI-compatible routing.

This page covers Gemini hosted on Google Vertex AI. For Gemini through Google AI Studio API keys, see the Google Gemini guide.

Vertex needs a GCP project, a region where the model is available, and either Application Default Credentials or a service-account JSON key. GoModel routes to Vertex’s native Gemini publisher endpoint by default; switch to the OpenAI-compatible endpoint when you need its compatibility behavior.

Vertex authentication is enterprise-oriented and may become paid or licensed in a future release.

Configure

VERTEX_PROJECT=my-gcp-project
VERTEX_LOCATION=us-central1
VERTEX_AUTH_TYPE=gcp_adc       # default; ADC via gcloud, GKE Workload Identity, or metadata server
VERTEX_API_MODE=native         # or openai_compatible

Or in config.yaml:

providers:
  vertex:
    type: vertex
    auth_type: gcp_adc
    vertex_project: my-gcp-project
    vertex_location: us-central1
    api_mode: native

Service-account authentication

VERTEX_AUTH_TYPE=gcp_service_account
VERTEX_SERVICE_ACCOUNT_FILE=/secrets/service-account.json
# or VERTEX_SERVICE_ACCOUNT_JSON / VERTEX_SERVICE_ACCOUNT_JSON_BASE64

Multiple regions or accounts

Use suffixed env vars to register additional Vertex providers:

VERTEX_US_PROJECT=prod-ai
VERTEX_US_LOCATION=us-central1
VERTEX_US_AUTH_TYPE=gcp_adc

VERTEX_EU_PROJECT=prod-ai
VERTEX_EU_LOCATION=europe-west4
VERTEX_EU_AUTH_TYPE=gcp_service_account
VERTEX_EU_SERVICE_ACCOUNT_FILE=/secrets/vertex-eu.json

This registers vertex-us and vertex-eu.

Base URLs and modes

Default bases are derived from project and location:

• OpenAI-compatible: .../projects/{project}/locations/{location}/endpoints/openapi
• native Gemini: .../projects/{project}/locations/{location}/publishers/google

Vertex embeddings use Vertex AI native prediction regardless of VERTEX_API_MODE. In native mode (the default) the image endpoints are served through the publisher endpoints (Imagen via predict, Gemini image models via generateContent); in openai_compatible mode image generation forwards to the OpenAI-compatible endpoint and image edits are rejected. Vertex does not expose Gemini Files or OpenAI-compatible batch operations.

Image input

Mode	OpenAI-style image_url
native (default)	inline data: URLs only — remote https://... URLs are rejected
openai_compatible	OpenAI-style remote URLs pass through to Vertex’s OpenAI-compatible endpoint

Not yet integrated

• Automatic fetching of remote image_url values in native mode.
• Vertex Files and batch prediction APIs.

References

• Vertex AI OpenAI compatibility
• Gemini API in Vertex AI
• Application Default Credentials