Antigravity MCP Server

MCP (Model Context Protocol) server for Google Antigravity CLI (agy) integration. Lets any MCP client (Claude Code, Claude Desktop, Cursor, etc.) delegate tasks to Antigravity's agentic CLI — with model selection (Gemini, Claude, GPT-OSS), conversation resume, and workspace controls.

For the why behind it, read the project write-up on trishchuk.com. It covers how I use Claude Code or Cursor as the lead engineer and hand bounded work to Antigravity: long tasks delegated to the Gemini 4 Orchestrator in an isolated git worktree, read-only plans and reviews from a different model family, and large-context digests. It also has a table for choosing the right tool, the costs and isolation limits to know before delegating, and where Google's multi-agent tooling is heading.

Requirements

• Node.js >= 18

• Antigravity CLI installed (agy --version works) and authenticated (run agy once interactively and sign in with your Google account)

Related MCP server: antigravity-mcp

Installation

npm install -g @trishchuk/antigravity-mcp-server

додай Or run from source:

pnpm install && pnpm build

MCP client configuration

{
  "mcpServers": {
    "antigravity": {
      "command": "npx",
      "args": ["-y", "@trishchuk/antigravity-mcp-server"],
      "env": {
        "AGY_MCP_CWD": "/path/to/your/project"
      }
    }
  }
}

For Claude Code:

claude mcp add antigravity -- npx -y @trishchuk/antigravity-mcp-server

Tools

Background, batch and delegate tools default to --dangerously-skip-permissions because print mode cannot answer interactive permission prompts; pass skipPermissions: false to opt out. An explicit mode turns that default off (the mode is the permission policy), and mode: "plan" with skipPermissions: true is rejected.

Models

The model parameter takes a display label (Gemini 4 Hydrogen (High)), a full ID (gemini-4-hydrogen-high), or a base ID plus effort (model: "gemini-4-hydrogen", effort: "xhigh"). A base label with effort is rejected by the CLI. As of Antigravity CLI v1.5.9 (availability depends on your plan — list-models shows the live list):

agy --effort accepts low | medium | high | xhigh | max, but each model supports only the subset above (no current model accepts max); a suffixed ID such as gemini-4-hydrogen-high only accepts its own level. Orchestrator has a fixed thinking level and rejects effort.

Omit model and the server passes no --model flag, so the CLI's own default applies ("model" in ~/.gemini/antigravity-cli/settings.json). The label this server uses in its examples and hints is Gemini 4 Hydrogen (High) — see DEFAULT_MODEL in src/constants.ts.

Delegating long tasks

delegate-antigravity hands a multi-step implementation task to Antigravity and returns immediately:

{
  "task": "Add rate limiting to the /api routes",
  "autoTest": "pnpm test",
  "acceptanceCriteria": ["429 after 100 req/min"]
}

• Creates a git worktree on a fresh agy/<random> branch under ~/.agy-mcp/delegations/ and runs agy detached there (survives the MCP call and server restarts).

• Without model, picks the Orchestrator (Carbon if your plan has it, else Argon); otherwise falls back to Gemini 4 Hydrogen (High).

• Captures --output-format stream-json: action: "status" shows steps, tool calls, the last command and the latest text; action: "continue" with a message sends a follow-up turn into the same conversation and worktree; action: "result" returns the agent's final report, outcome (finished_reason), token usage and the diff against the base commit (cleanup: true removes the worktree and branch).

• Per-turn timeout defaults to 2 hours (timeout: 0 = none). stop signals the whole process group (signal: SIGTERM by default, SIGKILL for a run that ignores it).

Sessions and conversation resume

ask-antigravity supports multi-turn conversations:

{
  "prompt": "Analyze src/auth.ts for security issues",
  "sessionId": "auth-review"
}

{
  "prompt": "Now suggest fixes for the issues you found",
  "sessionId": "auth-review"
}

How it works: in text output agy doesn't print its conversation ID to stdout, so the server passes --log-file to a temp file and parses the ID from it (Created conversation <uuid> / conversationID="<uuid>"). The next call with the same sessionId resumes via agy --conversation <uuid>.

You can also pass a native conversationId directly, or continueLatest: true for agy --continue.

Session storage is in-memory (lost on server restart). Configure with:

• AGY_SESSION_TTL_MS — session TTL (default 24h)

• AGY_MAX_SESSIONS — max stored sessions (default 50)

• AGY_MCP_CWD — default working directory for agy runs. Resolution order: workingDir → AGY_MCP_CWD → the project root of an @path in your prompt (ask, digest, delegate) → the server's launch directory

Safety

• skipPermissions: true maps to --dangerously-skip-permissions — agy auto-approves all tool/command permission requests. Use deliberately.

• sandbox: true maps to --sandbox — terminal restrictions enabled.

• Since CLI 1.5.7 headless runs start in Auto mode where it is available, which edits files without asking. plan-antigravity, review-changes, digest-antigravity and brainstorm therefore pass --settings '{"agentMode":"","permissions":{"allow":[]}}': Default mode, plus your allow-rules suspended for that run (otherwise a pre-approved command such as git checkout still executes). A headless run cannot answer permission prompts, so writes and shell commands are auto-denied; reading files works and the answer still reaches stdout. (--mode plan is not used because it writes the answer into a plan artifact instead.)

• mode maps to --mode accept-edits | auto | plan; Auto is not available on every account.

• A delegation worktree isolates git state, not the filesystem: with skipPermissions (the default for background work) the agent can read and write outside it and run any command.

• digest-antigravity never sends credential-like files (.env*, .npmrc, private keys, *.pem, …) and does not follow symlinks while walking directories.

• Cancelling a tool call from the client stops the agy / git processes it started; background and delegated tasks keep running until you stop them.

• An explicit workingDir / cd that does not exist is an error — the server never falls back to another directory.

• Otherwise agy uses your configured permission rules (/permissions in interactive agy).

Development

pnpm build          # tsc
pnpm lint           # tsc --noEmit
pnpm test           # build + node --test
pnpm format         # prettier

License

MIT