Antigravity CLI

Antigravity CLI (agy) is the command-line companion to Google Antigravity, a Gemini-based agent. Unlike the Antigravity IDE, agy has a native plugin system (agy plugin install) and a hook surface, so context-mode ships as a first-class agy plugin. A single command registers the MCP server, a routing rule, a routing skill, and bounded PreToolUse/PostToolUse/Stop hooks that steer data-heavy tool output into the sandbox — the model writes a program that processes the data and prints only the answer.

Install

The plugin install is a single agy command, but the plugin's MCP server and hooks run the global context-mode binary, so npm install -g context-mode is a prerequisite.

npm install -g context-mode

agy plugin install https://github.com/mksglu/context-mode/tree/main/configs/antigravity-cli

Hook scope

context-mode wires only the surfaces that have a verified mapping on agy:

• PreToolUse — bounded routing enforcement on the mapped high-flood tools (run_command, view_file, grep_search, web_fetch, read_url_content). Other tools are not PreToolUse-routed.
• PostToolUse — capture-only. Records executed tool calls into the session database. agy's PostToolUse payload carries no tool-output text, so byte accounting for output is unavailable on this surface, but the tool call, project, and error state are still captured.
• Stop — best-effort, capture-only session-end marker. It is registered, but agy did not emit it in probes, so treat it as best-effort.

PreCompact, SessionStart, PreInvocation, and PostInvocation are not wired.

Where agy reads its config

agy reads its global MCP profile from ~/.gemini/config/mcp_config.json — not the Antigravity IDE's ~/.gemini/antigravity/mcp_config.json — and its hooks from ~/.gemini/config/hooks.json. The plugin install instead registers everything under its plugin profile at ~/.gemini/config/plugins/context-mode/. It shares the ~/.gemini/ session root with the rest of the Gemini family; the session database is keyed by project hash to prevent collisions.

Alternative (MCP only, no plugin)

If you cannot use the plugin install, register the MCP server manually by adding context-mode to ~/.gemini/config/mcp_config.json under mcpServers. This path ships no hooks, so routing enforcement is advisory only.

{
  "mcpServers": {
    "context-mode": {
      "command": "context-mode",
      "env": {
        "CONTEXT_MODE_PLATFORM": "antigravity-cli"
      }
    }
  }
}

Verify

Confirm the install with the doctor. It checks language runtimes, the FTS5 knowledge base, MCP registration, and hook registration, then reports anything that needs attention.

context-mode doctor

A clean run means the MCP server is reachable and the hooks are wired.

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