peer-agents-mcp

MCP server that lets other AI coding tools (Codex, Claude, Cursor, etc.) call the Grok CLI and Antigravity CLI as peer reviewers and collaborators.

What it does

This server wraps the local grok and agy (Antigravity) CLIs behind a clean Model Context Protocol (MCP) interface.

Any MCP-capable agent can now:

• Send code changes, plans, errors, or questions to Grok or Antigravity
• Receive structured peer feedback
• Run multi-turn review/debug/planning sessions with session memory
• Get independent opinions by running both CLIs on the same task

The primary agent (Codex, Claude, etc.) stays in control. It simply delegates specific tasks to these peers when it wants a second (or different) opinion.

Core idea

Instead of one model doing everything, your main coding agent can use Grok and Antigravity as peers:

• Grok for most coding work (reviews, planning, debugging, implementation critique)
• Antigravity for large context, general knowledge, or multimodal tasks

Smart routing happens automatically based on the type of request.

Available tools

Additional session tools: peer_summarize, peer_transcript, peer_list_sessions, peer_reset, and peer_health.

All routed tools accept full file contents via the files parameter and diffs via diff. Never send summaries — send the actual content.

When to use sync vs async

Grok sync reviews of ordinary diffs typically take 3–6 minutes. The Grok child timeout is GROK_TURN_TIMEOUT_MS (default 6 minutes). Raising the child timeout does not raise the host MCP client wait. If the host gives up first, Codex never sees durationAdvisory / continuationHint / nativeSessionId in that tool response — use *_async.

The server does not silently convert sync tools into jobs.

Sync Grok/routed results may include additive durationAdvisory when the prompt was truncated, estimated tokens exceed ~20k (~80k chars), risk_level=high / focus=security, or a stub auto-continue was consumed. Example:

{
  "durationAdvisory": "Grok sync reviews of this size often take 3–6 minutes. If your MCP client times out sooner, use peer_review_diff_async / peer_turn_async and poll peer_job_status."
}

A truncated peer_review_diff still runs synchronously (tools-against-cwd instruction is prepended). Prefer peer_review_diff_async next time; do not treat truncation as a hard reject.

Long-running async jobs

Large implementation handoffs can exceed the MCP client's synchronous tool timeout. Use the async path instead of blocking on peer_turn:

1. Start work with peer_implement_async (cold start) or peer_turn_async (existing session).
2. Continue local work while the peer runs.
3. Poll peer_job_status every 30–60 seconds (avoid aggressive polling).
4. While status is running, optional progress may include textSnippet, lastThought, and eventCount (Grok streaming-json / agy stream-json).
5. When status is succeeded, read result and continue with peer_turn if needed.
6. Use peer_job_cancel to stop a queued/running job owned by this MCP process.

Terminal statuses: succeeded, failed, timed_out, cancelled, orphaned.

Idempotency: retries with the same idempotency_key return the same job (running or sticky terminal). After timed_out / cancelled / failed, use a new key to retry the work.

Jobs and completed results are stored under ~/.peer-agents/jobs/. Live provider processes do not survive MCP server restarts; non-terminal jobs are marked orphaned on hydrate (unless the session already committed the operation, which recovers as succeeded).

Terminal jobs older than 7 days are garbage-collected on hydrate (override with PEER_AGENTS_JOB_GC_MAX_AGE_MS) or via peer_jobs_gc.

Async jobs use a separate timeout from synchronous turns:

• PEER_AGENTS_JOB_TIMEOUT_MS — default 30 minutes (1800000)
• GROK_JOB_TIMEOUT_MS / ANTIGRAVITY_JOB_TIMEOUT_MS — optional per-provider overrides
• PEER_AGENTS_JOB_GC_MAX_AGE_MS — terminal job retention (default 7 days)
• PEER_AGENTS_GROK_TRANSPORT — headless (default) or acp for warm process pool
• PEER_AGENTS_GROK_ACP_MAX_CLIENTS — max concurrent ACP processes (default 4)
• PEER_AGENTS_GROK_ACP_IDLE_MS — ACP between-turns idle recycle (default max(5 min, GROK_TURN_TIMEOUT_MS + 60s)). Idle is not the job lifetime; in-flight session/prompt ignores it.

Keep the MCP server process alive for the duration of a job.

Grok transport: headless vs ACP

Prefer headless for one-shot reviews with strict sandboxing. Prefer acp when you run many follow-up peer_turns and want lower process-startup cost.

How other agents use it

Codex, Claude, or any other MCP client connects to this server over stdio. Once connected, the agent can call the peer tools exactly like any other tool.

Typical flow:

1. Your agent prepares a diff, error log, or task description.
2. It calls peer_review_diff, peer_plan, peer_debug, etc.
3. The server invokes the appropriate CLI(s) in headless mode.
4. The peer response comes back with a sessionId.
5. Your agent can follow up later with peer_turn using that sessionId.

This gives you persistent, contextual peer conversations without the primary agent having to manage CLI invocation itself.

Prerequisites

• Node.js ≥ 18
• The grok CLI (or set GROK_COMMAND)
• The agy CLI (Antigravity, or set ANTIGRAVITY_COMMAND)

Both CLIs must be authenticated and working on your machine.

Installation & usage

git clone https://github.com/Rakeen70210/peer-agents-mcp
cd peer-agents-mcp
npm install
npm run build

Run directly:

node dist/index.js

MCP client configuration

Add it to your client's MCP servers config (example for a typical stdio setup):

{
  "mcpServers": {
    "peer-agents": {
      "command": "node",
      "args": ["/absolute/path/to/peer-agents-mcp/dist/index.js"],
      "env": {
        "GROK_COMMAND": "/home/you/.grok/bin/grok",
        "ANTIGRAVITY_COMMAND": "/home/you/.local/bin/agy"
      }
    }
  }
}

Environment variables

• GROK_COMMAND — path to grok binary (default: grok)
• ANTIGRAVITY_COMMAND — path to agy binary (default: agy)
• GROK_ARGS / ANTIGRAVITY_ARGS — JSON array of extra CLI args
• ANTIGRAVITY_CONVERSATIONS_DIR — override agy conversation store used as fallback session-id capture (default: ~/.gemini/antigravity-cli/conversations)
• PEER_AGENTS_WORKTREE_DIR — parent directory for DIY Grok git worktrees (default: ~/.peer-agents/worktrees)
• PEER_AGENTS_STORAGE_DIR — where sessions are persisted (default: ~/.peer-agents/sessions)
• PEER_AGENTS_ENABLED_PROVIDERS — comma list whitelist of peer CLIs (grok, antigravity). Use antigravity alone when the host is Grok so peers never re-enter Grok.
• PEER_AGENTS_DISABLED_PROVIDERS — comma list blacklist (ignored if PEER_AGENTS_ENABLED_PROVIDERS is set)
• GROK_TURN_TIMEOUT_MS — Grok sync timeout for headless and ACP (default 6 minutes / 360000). Only source besides per-call timeoutMs. Grok does not read PEER_AGENTS_TURN_TIMEOUT_MS.
• PEER_AGENTS_TURN_TIMEOUT_MS — Antigravity sync fallback only (default 300s). Does not pin Grok. Unset it or set GROK_TURN_TIMEOUT_MS explicitly. Operators who want the old 120s Grok timeout must set GROK_TURN_TIMEOUT_MS=120000.
• ANTIGRAVITY_TURN_TIMEOUT_MS — optional Antigravity sync override (default 300s)
• PEER_AGENTS_GROK_ACP_IDLE_MS — ACP between-turns idle recycle (default max(5 min, GROK_TURN_TIMEOUT_MS + 60s)). In-flight session/prompt ignores idle (promptDepth). Not the 30-minute job lifetime.
• PEER_AGENTS_JOB_TIMEOUT_MS — async job timeout (default 30 minutes)
• GROK_JOB_TIMEOUT_MS / ANTIGRAVITY_JOB_TIMEOUT_MS — optional async per-provider overrides
• PEER_AGENTS_MAX_PROMPT_CHARS — safety limit on prompt size (default 120000); truncation prepends a tools-against-cwd instruction and continues the sync turn

Multi-turn peer sessions

Each routed call returns a sessionId. Use peer_turn to continue the conversation:

• Tell the peer what changed
• Attach new diffs or files
• Ask it to re-review or check your fixes

Sessions are persisted to disk, so they survive across restarts of the MCP server.

Grok and Antigravity multi-turn turns prefer native CLI resume when a conversation/session id was captured on the first turn; otherwise the MCP rehydrates recent transcript into the prompt.

Grok CLI integration (1.0.x+)

Grok peer turns use modern headless flags under the hood (callers do not pass these):

Antigravity CLI integration (agy 1.1.8+)

Antigravity peer turns use print mode under the hood (callers do not pass these flags):

agy still has no worktree, --prompt-file, or ACP transport. Sync turns stay --output-format json; only background jobs stream.

Design notes

• The server never modifies your repo itself — it only runs the CLIs you already have.
• User messages in session transcripts are labeled from the caller's perspective (commonly "Codex").
• Idempotency keys are supported so repeated calls with the same key are safe.
• Context quality hints are returned when the input looks too thin (missing files, diffs, etc.).
• Implementation handoffs default to an isolated git worktree (--cwd into it) so the peer does not clobber a dirty main tree.

License

MIT (or as specified in the repo).