Google Vertex AI

Use Vertex AI-hosted Gemini models with Nexus — GCP OAuth2 auth with project/location routing.

The Vertex AI provider connects to Google Cloud's Vertex AI platform. It uses the same Gemini API format but with OAuth2 Bearer token authentication and project/location-based URL routing.

Installation

import "github.com/xraph/nexus/providers/vertex"

Quick Start

// With service account credentials (recommended)
creds, _ := os.ReadFile("service-account.json")
provider := vertex.New(
    vertex.WithProjectID("my-project"),
    vertex.WithLocation("us-central1"),
    vertex.WithCredentialsJSON(creds),
)

gw := nexus.New(
    nexus.WithProvider(provider),
)

Options

Option	Description
`vertex.WithProjectID(id)`	Google Cloud project ID
`vertex.WithLocation(loc)`	GCP region (default: `us-central1`)
`vertex.WithAccessToken(token)`	Static OAuth2 access token
`vertex.WithCredentialsJSON(json)`	Service account JSON for automatic token management
`vertex.WithBaseURL(url)`	Override the full base URL directly

Capabilities

Capability	Supported
Chat	Yes
Streaming	Yes
Embeddings	Yes
Vision	Yes
Tools	Yes
Thinking	No

Authentication

Vertex AI uses Google Cloud OAuth2 instead of API keys:

// Option 1: Service account JSON (auto-refreshing tokens)
creds, _ := os.ReadFile("service-account.json")
provider := vertex.New(
    vertex.WithProjectID("my-project"),
    vertex.WithCredentialsJSON(creds),
)

// Option 2: Static access token (e.g., from gcloud auth)
provider := vertex.New(
    vertex.WithProjectID("my-project"),
    vertex.WithAccessToken(os.Getenv("GCLOUD_ACCESS_TOKEN")),
)

Models

Model	Context	Max Output	Input Price	Output Price
`gemini-2.0-flash`	1M	8,192	$0.10/M	$0.40/M
`gemini-1.5-pro`	2M	8,192	$1.25/M	$5.00/M
`text-embedding-004`	2,048	—	$0.025/M	—