Google Vertex AI

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.

Installation01

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

Quick Start02

// 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),
)

Options03

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

Capabilities04

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

Authentication05

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")),
)

Models06

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	—

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