pi-anthropic-vertex

Anthropic Claude models on Google Cloud Vertex AI for pi.

Built-in support is coming. There is an open PR to add a native anthropic-vertex provider to pi, which would make this extension unnecessary. Multiple issues have requested this: #5082, #5300, #4449, #1155. If you want this to land, leave a 👍 on the PR. Until then, this extension is the only shipped solution.

This extension started from a comment on #1155.

Compatibility

Extension	pi
0.1.13	0.81.1
0.1.12	0.80.10
0.1.11	0.80.3
0.1.10	0.80.0 - 0.80.2
0.1.9	0.78.0 - 0.79.4
0.1.8	0.75.5 - 0.78.0
0.1.7	0.75.4
0.1.6	0.75.1
0.1.5	0.74.1
0.1.4	0.72.0 - 0.73.1
0.1.3	0.72.0 - 0.73.0
0.1.2	0.67.1 - 0.71.0
0.1.0	0.66.1

Prerequisites

• Google Cloud project with Vertex AI API enabled
• Claude models enabled in Model Garden
• gcloud CLI installed and authenticated

How it works

This extension injects an AnthropicVertex client into pi's built-in anthropic-messages streaming implementation. All message transformation, prompt caching, tool call normalization, thinking block replay, partial JSON streaming, and usage tracking are handled by pi's battle-tested internals, nothing is reimplemented.

Other Vertex AI extensions (pi-vertex-claude, pi-vertex, pi-anthropic-vertex) reimplement the Anthropic streaming protocol from scratch at 500–1500 lines, losing features like prompt caching, tool call adjacency enforcement, aborted message filtering, and partial JSON parsing. This extension delegates to pi's built-in at ~160 lines and inherits everything for free.

Model definitions are pulled at runtime from pi's built-in Anthropic provider via getModels("anthropic"), so new Claude models are picked up automatically when pi updates.

Install

pi install npm:@twogiants/pi-anthropic-vertex

Or install from git:

pi install git:github.com/twoGiants/pi-anthropic-vertex

Setup

Authenticate with Google Cloud:

gcloud auth application-default login

Set your project and region:

export GOOGLE_CLOUD_PROJECT=your-project-id
export GOOGLE_CLOUD_LOCATION=us-east5  # optional, defaults to us-east5

The extension also recognizes ANTHROPIC_VERTEX_PROJECT_ID and GOOGLE_CLOUD_PROJECT_ID for project resolution, and CLOUD_ML_REGION for region. This allows it to work with existing Claude Code setups without additional configuration.

Usage

pi --provider anthropic-vertex --model claude-opus-4-6
pi --provider anthropic-vertex --model claude-sonnet-4-6

All Claude models available on Vertex AI are registered automatically.

License

MIT