Add Antigravity CLI plugin support (Google IO 2026)

[danieljustus]

Feature Request: Antigravity CLI Plugin

Context

Google announced Antigravity CLI on May 19, 2026 at Google I/O as the successor to Gemini CLI (announcement, product blog). It is a Go-based terminal client that replaces Gemini CLI, sharing the same unified Antigravity agent harness as Antigravity 2.0 and Antigravity IDE.

Users migrating from Gemini CLI to Antigravity CLI (Gemini CLI stops serving on June 18, 2026) will need a dedicated OpenUsage plugin to track their usage.

What OpenUsage currently has

Plugin	Product	Status
plugins/antigravity	Original Antigravity desktop (legacy)	✅ Existing
plugins/gemini	Gemini CLI (being sunset)	✅ Existing
PR #474	Antigravity IDE 2.0 (new)	🟡 Open PR
❌ Antigravity CLI	New CLI (this request)	Not covered

None of the existing plugins cover Antigravity CLI. The original Antigravity plugin uses LS probing + OAuth tokens for the desktop app, and PR #474 targets the IDE — both are architecturally distinct from the CLI.

How Gemini CLI tracks usage (reference)

The existing plugins/gemini plugin works by:

1. Reading ~/.gemini/settings.json for auth type config
2. Reading ~/.gemini/oauth_creds.json for OAuth tokens
3. Hitting cloudcode-pa.googleapis.com/v1internal:loadCodeAssist to get user tier/subscription info
4. Hitting cloudcode-pa.googleapis.com/v1internal:retrieveUserQuota for per-model quota data
5. Using Google Cloud Resource Manager API for project discovery

What we know about Antigravity CLI

• Built in Go (not Node.js like Gemini CLI)
• Shares the same agent harness as Antigravity 2.0 (source)
• Common settings shared across Antigravity CLI and Antigravity 2.0
• Supports Antigravity plugins (the new name for Extensions)
• Conversations can be imported from CLI to Antigravity 2.0

Suggested implementation approach

Since Antigravity CLI uses the same Google backend (Cloud Code API) as Gemini CLI, a similar approach should work, but with different auth/config paths:

1. Auth / config paths — Antigravity CLI likely stores its config/auth in ~/.antigravity/ (to be confirmed — may use the same Google OAuth flow with a different client ID)
2. API endpoints — Likely the same cloudcode-pa.googleapis.com endpoints for quota and user info, or potentially new antigravity.googleapis.com endpoints
3. Subscription plan — Display user tier (Free/Pro/Ultra) from userTier.name (similar to how the existing Antigravity plugin handles this in PR fix Antigravity local DB import loading error #392/fix(antigravity): prefer userTier.name over legacy planInfo.planName #369)
4. Model tracking — Track Gemini Pro quota, Gemini Flash quota, and Claude quota (same pools as the existing Antigravity plugin, per plugins/antigravity/plugin.json)

Open questions / research needed

• Where does Antigravity CLI store authentication tokens? (~/.antigravity/ or shared with Antigravity 2.0?)
• Does it reuse the same Google OAuth client or have its own?
• Does it expose a local API socket (like Gemini CLI) or use direct HTTP API calls?
• What does the quota endpoint response look like for Antigravity CLI vs Gemini CLI?
• Does it use new antigravity.googleapis.com endpoints or the existing cloudcode-pa.googleapis.com ones?

Resources

• Antigravity CLI announcement: https://developers.googleblog.com/an-important-update-transitioning-gemini-cli-to-antigravity-cli/
• Antigravity CLI product blog: https://antigravity.google/blog/introducing-google-antigravity-cli
• Gemini CLI deprecation: June 18, 2026
• Existing Gemini CLI plugin: plugins/gemini/plugin.js
• Existing Antigravity plugin: plugins/antigravity/plugin.js
• PR Add Antigravity IDE plugin #474 (Antigravity IDE): Add Antigravity IDE plugin #474
• Antigravity CLI docs: https://antigravity.google/docs/cli (presumed URL)

I would be happy to help test or contribute to this plugin once a path forward is identified.