Show and tell: Codex supervising Reasonix workers through MCP + ACP

[rixzkiye]

I built codex-reasonix-mcp, an open-source MCP bridge that keeps Codex as the supervisor while Reasonix acts as a sandboxed implementation worker.

The design goal is not agent routing. Codex owns the immutable task contract, review, steering, and finalization decision. Reasonix runs the implementation loop in an isolated Git worktree through an ACP Goal session. The bridge returns bounded diffs and evidence instead of unbounded terminal transcripts.

The MCP surface is deliberately small:

• reasonix_delegate starts or resumes a contract-bound worker asynchronously.
• reasonix_control handles steering, interactions, cancellation, up to two repair rounds, and finalization.
• reasonix_inspect returns bounded status, diff, verification, evidence, risks, usage, and events.

Security properties include repository-derived workspace identity, planner-off verification, Delivery plus Goal mode verification, scoped permissions, network off by default, secret checks, argv-only verification, explicit-file staging, and exactly one atomic worker commit. The bridge never pushes or merges.

Current status: 0.1.0-rc.3 is a prerelease for Node.js 22+ on Linux, macOS, and WSL. It requires a compatible Reasonix build containing the merged ACP supervisor work from DeepSeek-Reasonix PR #7097. Stable v1 will wait for an official compatible Reasonix release.

Install with an exact pin:

codex mcp add reasonix-worker -- npx -y codex-reasonix-mcp@0.1.0-rc.3

When using a locally built Reasonix binary:

codex mcp add reasonix-worker --env REASONIX_BIN=/absolute/path/to/reasonix -- npx -y codex-reasonix-mcp@0.1.0-rc.3

Run the no-model compatibility check first:

REASONIX_BIN=/absolute/path/to/reasonix npx -y codex-reasonix-mcp@0.1.0-rc.3 doctor

Links:

• Source
• npm package
• v0.1.0-rc.3 release

Feedback is especially welcome on the task-contract shape, bounded evidence model, and supervisor versus worker ownership boundary.

Disclosure: I maintain the linked project and npm package.