# Gemini CLI and Antigravity

> Review changed Gemini CLI and Antigravity extensions, skills, and MCP servers before launch through the Guard launcher shim.

Canonical: https://hol.org/guard/docs/guard/gemini-harness · Updated: 2026-10-23 · Applies to: Guard 3.x

Use this guide when Gemini CLI or Antigravity loads local extensions, skills, or MCP server declarations and you want Guard to review changed surfaces before launch.

Guard ships two separate adapters for these tools, with separate ids:

| Tool | Id | Executable |
| --- | --- | --- |
| Gemini CLI | `gemini` | `gemini` |
| Antigravity | `antigravity` | `antigravity` |

Both use the `approval-center` tier and the same protection path: a launcher shim and a scan before launch. Neither adapter writes hooks into the tool's config.

## What Guard detects

### Gemini CLI

The Gemini adapter reads the `.gemini` directory under your home directory and under the workspace:

- `.gemini/settings.json` for MCP servers and hooks
- `.gemini/extensions/*/gemini-extension.json`
- `.gemini/skills`
- skills under `<workspace>/.agents/skills`

For each extension manifest Guard records:

- the extension name
- the publisher when present
- the optional `contextFileName`
- embedded MCP server definitions under `mcpServers`

### Antigravity

The Antigravity adapter reads:

- the Antigravity user `settings.json`, from `~/Library/Application Support/Antigravity/User` on macOS, `~/.config/Antigravity/User` on Linux, and `AppData/Roaming/Antigravity/User` under your home directory on Windows
- `<workspace>/.vscode/settings.json`, when it carries Antigravity settings
- `.gemini/antigravity/mcp_config.json` under your home directory and the workspace
- `.gemini/antigravity/skills` under your home directory and the workspace
- the extension index at `~/.antigravity/extensions/extensions.json`

Guard records installed extensions, MCP servers from each of those files, and skill documents.

## How protection attaches

`hol-guard install gemini` and `hol-guard install antigravity` write one launcher shim each, `guard-gemini` and `guard-antigravity`, into `~/.hol-guard/bin`. The shim, and `hol-guard run`, run Guard's pre-launch check and then start the real tool.

That makes the shim and `hol-guard run` the whole protection path. Launching `gemini` or `antigravity` directly skips the check, and Guard does not watch tool calls while the tool runs.

## Approval model

Both tools use the `approval-center` tier:

- Guard scans extensions, MCP registrations, and skills before launch
- blocked changes go to the local approval center
- `hol-guard approvals` resolves the same requests from the terminal

Neither tool exposes a native approval surface that Guard can answer.

## Install and launch flow

For Gemini CLI:

```bash
hol-guard detect gemini --json
hol-guard install gemini --dry-run
hol-guard install gemini
hol-guard run gemini --dry-run
hol-guard run gemini
hol-guard approvals
```

For Antigravity, use the same commands with `antigravity`:

```bash
hol-guard detect antigravity --json
hol-guard install antigravity
hol-guard run antigravity --dry-run
hol-guard run antigravity
```

To check or remove either one:

```bash
hol-guard apps test gemini --json
hol-guard uninstall gemini
hol-guard apps test antigravity --json
hol-guard uninstall antigravity
```

## Known limits

- Gemini CLI: prompt submission and file reads and writes are not observable.
- Antigravity: shell commands are not observable. Guard covers extensions and MCP registrations through the scan at launch time.
- Gemini CLI: hooks declared in `settings.json` are recorded as artifacts, but Guard does not install its own.

## Recommended validation loop

Use a home directory or workspace with a real extension or MCP registration installed, then confirm:

1. `hol-guard detect <id> --json` lists the extension manifest, skills, and MCP servers
2. the first dry run records a receipt
3. a changed extension or MCP entry routes to the approval center when policy blocks

## Next guides

- [OpenCode harness](https://hol.org/guard/docs/guard/opencode-harness)
- [Harness support matrix](https://hol.org/guard/docs/guard/harness-support)
- [Approval center and audit trail](https://hol.org/guard/docs/guard/approval-center-and-audit)
- [Testing and validation](https://hol.org/guard/docs/guard/testing-and-validation)