Subagent Mcp

Independent harnesses. One Codex orchestrator.

When one model plans a change, implements it, and reviews it, the reviewer shares the author's context and blind spots. It can end up confirming its own plan instead of testing it.

Subagent MCP keeps Codex as the main agent and final decision-maker while delegating bounded work to external agent runtimes. Each runtime is a model paired with its native harness, so Codex can get implementation or review from an independent model with different context and assumptions.

That expands Codex's effective sub-agent pool and can use provider quota you already have. Subagent MCP never enables, purchases, auto-reloads, or silently opts into usage credits or paid overage.

Adapters translate every native harness into the same lifecycle: delegate, observe, steer, and close. The core hard-codes no provider role or model name.

Stable: 1.0.30 targets Windows. The MCP, package, localhost UI, and Claude Code and DeepSeek native-harness integrations are ready.

Runtime status

• Claude Code — Ready. Uses the native Claude Code harness, provider-native model and reasoning settings, subscription OAuth identity, and live no-overage evidence before accepting its output. Project/local context and exact auto-compaction-trigger attestation remain explicit capability gaps.
• DeepSeek Harness — Ready. Uses its native ACP transport and harness-published model catalog for bounded tasks. Resume after an MCP restart, exact provider quota evidence, interactive input, and declared MCP remain explicit capability gaps. A provider-retired model route fails terminally and is never replaced without the user's explicit selection.
• Grok Build — Ready for read-only review. The Windows adapter uses cached native login only and allows no credits, paid overage, or model fallback. Version 1.0.30 advertises and accepts repo_read only. Bounded writing remains In development and workspace_write requests fail before a native process starts. Other explicit gaps are terminal/test/Git execution, network/web/browser, MCP/plugins/hooks, nested agents, native worktrees, restart recovery, macOS/Linux support, and exact pre-request quota.

Runtime behavior comes from adapters rather than provider-specific branches in the core.

Quick start

1. Install

Install uv if needed, then register the exact isolated release and start its background UI:

winget install --id=astral-sh.uv -e
codex mcp add subagent-mcp -- uvx --isolated --from subagent-harness-mcp==1.0.30 subagent-harness-mcp serve
uvx --isolated --from subagent-harness-mcp==1.0.30 subagent-harness-mcp ui --background

Start a new Codex task after registration.

2. Configure runtimes

Open http://127.0.0.1:8765 in a browser. If the background UI was stopped, start the same exact release again:

uvx --isolated --from subagent-harness-mcp==1.0.30 subagent-harness-mcp ui --background

The settings and read-only activity UI stays on the fixed loopback port and does not depend on an active MCP connection.

If a runtime shows Sign in required, click Sign in. Its native harness opens the operating system's default browser; Subagent MCP never asks for or stores credentials. Complete login there, then click Refresh. A status check never opens a browser by itself.

Current and recent activity is listed by external agent. Select a row to inspect its model, native harness, workspace, permissions, write set, current stage, lifecycle, elapsed time, and redacted terminal result. Prompts, transcripts, hidden thinking, and raw provider events are never displayed.

3. Delegate

Ask Codex in plain language:

Use Subagent MCP to ask an external agent to review this change, then evaluate its findings independently.