baton-mcp

🏃 BATON

Hand off AI work — with a receipt.

An AI did the work. How does the next person — or the next AI — know it actually works, not just that the build passed? BATON seals a unit of AI work into a portable capsule, and an independent verifier replays it and issues a server-signed Verification Receipt. The receiver trusts observed evidence, not a claim.

Never trust an agent handoff without a receipt.

BATON is a standard MCP (Model Context Protocol) server — any MCP-capable tool (Claude Code, Codex CLI, Gemini CLI, Cursor …) connects with one URL. The producer and the verifier can be different models, machines, and people.

Why this, and not the dozen orchestration tools?

Running Claude + Codex + Gemini together (swarms, rooms, agent messaging) is a crowded space. BATON isn't that. The one thing almost nobody does: bind the handoff artifact to independent execution evidence as a single, forgeable-proof trust unit. That's the receipt.

Claude did the work
   ↓  baton_pass  → sealed capsule (BTN-H-…)
Codex / a teammate receives it
   ↓  baton_verify → replay in a clean env, observe the real flow
   ↓
🕸️ VERIFIED — signed receipt: who verified · what was observed · in what env · with what artifacts
   ↓
trust  (or reject)

The real buyer isn't "me switching Claude→Codex" (just re-read the repo). It's outsourcer→in-house, leaver→joiner, KO team→US team — where "an AI made this, does it really work?" is a question worth paying to answer.

The receipt (the differentiator)

baton_verify doesn't return a ✅ sticker. It returns a signed record:

{
  "kind": "baton.verification-receipt/v1",
  "capsule": "BTN-H-…",              // the handoff this verifies
  "verifier": "receiver-spider",    // WHO verified — independent of the producer
  "environment": { "os": "ubuntu-24.04", "node": "24.2" },
  "observed": [{ "claim": "payment succeeds", "observed": true,
                 "detail": "POST /pay 200 + order row +1" }],
  "artifacts": ["playwright.trace.zip", "network.har"],
  "verdict": "verified",
  "signature": "…hmac-sha256…"       // server-signed → tamper the verdict, break the sig
}

Flip verdict to "verified" without re-signing and the badge is refused. A passing build never earns verified on its own — only observed E2E does (this is what catches a silent upsert that returns 200 but writes nothing).

Tools

Group	Tools	What it does
Handoff	baton_pass baton_receive baton_diff baton_revoke	Seal a work capsule into a code (BTN-H-…), hand it over, diff versions. Body encrypted with a code-derived key — the server never sees plaintext
Verify	baton_verify baton_verify_plan + spider_* ×6	Independent verifier replays and issues the signed receipt. No observation, no 🕸️
Relay (supporting)	baton_create_room baton_join baton_send baton_inbox baton_who baton_leave	Live sessions from different people/models talk in an invite-code room (BTN-R-…)

Design principles (from the security review)

• Code-derived encryption. The server stores only ciphertext + code_hash. Without the code, even the operator can't read the plaintext — the proof of "we can't lock you in."
• Signed receipts. Verdicts are HMAC-signed server-side (BATON_RECEIPT_SECRET); no client can forge verified.
• Prompt-injection containment. Inbound capsules/messages are returned fenced as untrusted data; secrets are auto-masked before storage.
• Codes are ≥128-bit secrets, one-time codes redeem atomically, alias-spoofing blocked.
• A passing build ≠ working behavior. verified requires observed side effects, never static analysis alone.

Run

npm install
npm test                                      # 15/15 E2E groups pass
node src/server.js                            # stdio (local / any CLI)
BATON_HTTP=1 PORT=8080 node src/server.js      # remote Streamable HTTP

Register (remote)

claude mcp add --transport http baton https://baton-mcp-production.up.railway.app/mcp

Billing/gating is off by default (dogfooding phase). Set BATON_BILLING=on to re-enable quotas/seats. See USAGE.md for the full guide.

Storage

MVP uses SQLite (better-sqlite3) — self-host single binary. The hosted service drops a Postgres adapter into the narrow interface in src/store.js.

License

MIT