Use Antigravity CLI with crystl

Updated September 18, 2026

Antigravity CLI is Google’s terminal coding agent and the successor to Gemini CLI. Its binary is called agy, not antigravity, which is worth knowing before you go looking for it.

crystl reads its conversations, reports its turn ends, and resumes it. The one thing it does not do is intercept its approvals. That is covered below and it is the difference most worth understanding before you leave one running.

1. Install Antigravity CLI

curl -fsSL https://antigravity.google/cli/install.sh | bash

The installer drops the binary at ~/.local/bin/agy and adds that directory to your shell profile’s PATH. Pass --skip-path if you would rather do the PATH part yourself.

2. Sign in

agy

It looks for a saved session in your Apple Keychain first, and opens a browser to sign in if it does not find one.

You can use a Gemini API key instead: set modelProvider to gemini in ~/.gemini/antigravity-cli/settings.json and export GEMINI_API_KEY.

3. Check it runs on its own

agy --version

If your shell says agy: command not found after installing, the PATH line went into a profile your shell does not read. Add it to ~/.zshrc and open a new terminal.

4. Launch it in crystl

Type it in a shard:

agy

or spawn one:

crystl shard create --gem myapp --agent antigravity --prompt "audit the error handling"

crystl passes an opening task with -i, which is the flag agy takes for an initial message.

What crystl can do with it

  • Turn ends are reported. crystl shards shows ✓ declared done or ❓ asked a question rather than a flat idle, and vigil and crystl wait done read that signal.
  • Conversations are readable and resumable. Transcripts land in history search and the chat dock, and resuming runs agy --conversation <id>.

What it does not do

Approvals stay in Antigravity’s own terminal. crystl does not intercept them, whatever your auto-approval mode says. Answer them in the shard. This is the one to plan around: a mode you set expecting unattended work does not apply to this agent, and an agy shard left alone can sit waiting on its own prompt.

Session ids arrive late. crystl reads Antigravity’s conversation id from its transcript when a shard closes, rather than from a hook at session start. Everything still works; the id just is not known as early as it is for Claude Code and Codex.

Settings

The antigravity tab under settings, agents enables it and shows whether crystl’s hook entries are installed.

Read the scope note on that page before enabling it. Antigravity’s hook config is global to your machine, not per project, so crystl’s entries are written once and apply to every agy session. crystl’s hook exits immediately when a session is not a crystl shard, so other sessions are unaffected in practice, but the file is still installed globally.

Model sizes

Antigravity takes a model with --model. Run agy models to list the slugs it accepts, and paste a slug rather than a display label. The default crystl uses is gemini-3.1-pro-high.

crystl agent profile set --agent antigravity --small gemini-3.5-flash-high --standard gemini-3.1-pro-low --large gemini-3.1-pro-high

There is no gemini-3.1-pro-medium. Pro ships high and low only, which trips people up when filling in three sizes. See model sizes.

Troubleshooting

agy: command not found in a shard. The installer writes its PATH line under bash conventions. macOS uses zsh, so add ~/.local/bin to ~/.zshrc and open a new shard.

A shard is quiet and nothing is waiting in crystl. Look in the terminal itself. Its approvals never leave it.

Other agent setup