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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.

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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

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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

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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.

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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. Vertex does not expose Gemini Files or OpenAI-compatible batch operations.

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Image input

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

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Not yet integrated

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

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References