---
title: Google Vertex AI
description: 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

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

## Quick Start

```go
// 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:

```go
// 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 | — |