Antigravity Skill

Claude Code is one model.
Antigravity gives it a second opinion from another.

A single model agreeing with itself is not a review. The Antigravity skill wires Google Antigravity — the agy CLI, running Gemini 3.5 Flash with High Reasoning — into Claude Code as a callable second-opinion agent. When Claude is about to guess, push back, or commit to a design call, you can ask another model family to weigh in without leaving the session.

It is the Gemini sibling to the existing codex skill: same shape, different model behind it.

What It's For

Use the skill when you want an independent take, not a second pass from the same model:

• a bug that survived Claude's fix
• an architecture decision where the trade-off matters more than the answer
• a stack trace nobody on this side of the model can read clearly
• a moment where you are about to accept a guess instead of a verification

Skip it for routine questions Claude can answer alone, and for anything that needs deep local codebase context agy does not have.

How It Works

Trigger phrases inside Claude Code:

• "frag antigravity ..."
• "ask antigravity ..."
• /antigravity ...

Claude Code invokes a thin wrapper script — agy.ps1 on Windows, agy.sh on macOS/Linux — which calls agy over a real PTY, captures the response, and returns it to the conversation. No extra terminal, no copy-paste between tools.

The first call performs a 30-second health check against agy and caches the result for 24 hours, so subsequent calls go straight to the answer.

Requirements

1. Claude Code with skills enabled (~/.claude/skills/ exists).
2. Antigravity CLI (agy):
   • Windows: irm https://antigravity.google/cli/install.ps1 | iex
   • macOS / Linux: curl -fsSL https://antigravity.google/cli/install.sh | bash
3. One-time interactive login in a normal terminal (not from inside Claude Code):

   agy
   

   This kicks off the Google OAuth flow; the token lands in the system keyring.

Install

git clone https://github.com/offbyone1/antigravity-skill ~/.claude/skills/antigravity

That is the whole install. Claude Code picks the skill up automatically.

Usage

Inside Claude Code:

frag antigravity: is this migration safe under concurrent writes?

Or with the slash command:

/antigravity review this rate-limit code for race conditions

The skill structures the call, runs agy, and returns the response to the conversation. Treat the answer as a second opinion, not ground truth — verify against the actual code before acting on it.

Direct invocation

You can also call the wrappers directly:

Windows (PowerShell)

& "$env:USERPROFILE\.claude\skills\antigravity\agy.ps1" -Prompt "your question"

macOS / Linux (Bash)

bash "$HOME/.claude/skills/antigravity/agy.sh" "your question"

Both accept an optional timeout (default 300 s):

& "$env:USERPROFILE\.claude\skills\antigravity\agy.ps1" -Prompt "..." -TimeoutSeconds 600

bash "$HOME/.claude/skills/antigravity/agy.sh" "..." 600

Exit Codes

The wrappers exit cleanly with codes Claude Code can route on:

Code	Meaning	Resolution
0	OK	Answer on stdout
2	agy not installed	Run the install command above
3	agy installed, login missing or unresponsive	Run agy interactively, complete OAuth
4	Timeout	Increase -TimeoutSeconds or shorten the prompt

Why the PTY Wrapper

agy 1.0.0 has no clean headless mode. agy --print writes directly to the console buffer instead of stdout, which means a normal pipe redirect captures nothing. The wrappers work around this by allocating a real PTY:

• Windows (agy.ps1): spawns a hidden PowerShell with Start-Transcript, then parses the transcript file.
• macOS / Linux (agy.sh): uses script(1) to allocate a PTY and parses the resulting log.

The --dangerously-skip-permissions flag is set so tool approvals in print mode do not block the call.

Model

• Default: Gemini 3.5 Flash (High Reasoning)
• No CLI switch for model selection — agy decides

Files

File	Purpose
SKILL.md	Skill manifest Claude Code reads — when to trigger, how to call
agy.ps1	Windows PowerShell wrapper
agy.sh	macOS / Linux Bash wrapper
README.md	This file
LICENSE	MIT

License

MIT — see LICENSE.