pi-provider-vertex-anthropic

A Pi provider plugin that gives you access to Claude models through Google Cloud Vertex AI. Use your existing GCP billing, stay within your organisation's cloud perimeter, and take advantage of regional deployments -- all from inside Pi.

Features

• 10 Claude models from Opus 4.6 down to Haiku 3, including extended thinking
• Streaming via Vertex AI's streamRawPredict endpoint with full SSE support
• Prompt caching with automatic ephemeral cache control
• Multiple auth strategies -- service account, Application Default Credentials, or the gcloud CLI
• Interactive /login wizard that walks you through project, region, and API setup
• Cross-tool env vars -- uses the same variables as Claude Code, with Opencode fallbacks

Prerequisites

• A Google Cloud project with the Vertex AI API enabled
• One of the following authentication methods:
  • Google Cloud CLI (gcloud) installed and authenticated
  • A service account key (via GOOGLE_APPLICATION_CREDENTIALS)
  • Application Default Credentials (gcloud auth application-default login)

Installation

Install using the Pi extension manager:

pi install npm:pi-provider-vertex-anthropic

The provider registers automatically and will be available the next time you start Pi.

Configuration

Interactive setup

Run /login inside Pi to walk through authentication, project selection, region selection, and API enablement in one step. Credentials are persisted to ~/.pi/agent/auth.json.

Environment variables

You can also configure the provider entirely through environment variables. The plugin checks them in the order shown below, picking the first one it finds.

Project ID

Priority	Variable	Used by
1	ANTHROPIC_VERTEX_PROJECT_ID	Claude Code
2	GOOGLE_CLOUD_PROJECT	Opencode, standard GCP tooling
3	(persisted from /login)

Region

Priority	Variable	Used by
1	CLOUD_ML_REGION	Claude Code
2	VERTEX_LOCATION	Opencode
3	VERTEXAI_LOCATION	Opencode (alternative)
4	(persisted from /login)
5	us-east5 (default)

Authentication

Priority	Method	Details
1	Service account	Set GOOGLE_APPLICATION_CREDENTIALS to your key file path
2	Application Default Credentials	Run gcloud auth application-default login
3	Google Cloud CLI	Run gcloud auth login

[!TIP] For local development, gcloud auth login is the easiest way to get started. For CI or headless environments, use a service account key via GOOGLE_APPLICATION_CREDENTIALS.

Pi settings

To set a Vertex model as your default, add to ~/.pi/agent/settings.json:

{
  "packages": ["npm:pi-provider-vertex-anthropic"],
  "defaultProvider": "vertex-anthropic",
  "defaultModel": "claude-sonnet-4-5@20250929",
  "enabledModels": [
    "vertex-anthropic/claude-opus-4-6",
    "vertex-anthropic/claude-sonnet-4-5@20250929",
    "vertex-anthropic/claude-haiku-4-5@20251001"
  ]
}

Available models

Model	ID	Thinking	Max output
Claude Opus 4.6	claude-opus-4-6	Yes	64k
Claude Opus 4.5	claude-opus-4-5@20251101	Yes	64k
Claude Sonnet 4.5	claude-sonnet-4-5@20250929	Yes	64k
Claude Haiku 4.5	claude-haiku-4-5@20251001	Yes	64k
Claude 3.5 Sonnet v2	claude-3-5-sonnet-v2@20241022	No	8k
Claude 3.5 Sonnet	claude-3-5-sonnet@20240620	No	8k
Claude 3.5 Haiku	claude-3-5-haiku@20241022	No	8k
Claude 3 Opus	claude-3-opus@20240229	No	4k
Claude 3 Sonnet	claude-3-sonnet@20240229	No	4k
Claude 3 Haiku	claude-3-haiku@20240307	No	4k

All models support 200k context, text + image input, and prompt caching.

Development

# Install dependencies
npm install

# Type-check
npm run typecheck

# Run tests
npm run test:run

# Watch mode
npm test

Project structure

src/
  index.ts          Extension entry point, provider registration, /login flow
  vertex-api.ts     SSE streaming against Vertex AI's streamRawPredict
  messages.ts       Message transformation and Anthropic API conversion
  auth.ts           Token acquisition (service account, ADC, gcloud CLI)
  config.ts         Environment variable resolution and endpoint building
  models.ts         Model definitions and provider constants
  pre-register.ts   Synchronous model ID collection for pre-registration
  shell.ts          Safe shell execution (spawn with args arrays)