Cedulon

Audit layer for agent-to-agent spend: signed trade manifest, fail-closed policy, signed spend receipt (SCITT-anchorable).

Cedulon is not a payment rail. It sits above x402 and AP2.

The packages are on npm and the MCP server is in the MCP Registry, but nothing here touches money: no real wallets and no network rails, only mock fixtures. cedulon_spend settles on a mock rail and says so in its own description.

Core packages carry zero runtime dependencies; the MCP server package depends only on the official MCP SDK.

Requirements

Node.js 22 or newer (20+ for the libraries; scripts use Node type stripping)
npm 10 or newer

Install and run (clean clone)

Terminal

npm install
npx tsc --noEmit
npm run test:all
npm run demo

npm run tamper is expected to exit non-zero (tampered bytes fail verify).

npm run demo:unguarded shows the unprotected hole: 100/100 allows.

npm run audit must exit 0 (audit: balanced).

npm run demo:bypass must exit non-zero: audit: 1 settlement without receipt → FAIL.

npm run demo:bypasses prints four FAIL lines (missing receipt, wrong amount, null-ref, garbage chain head) and exits 0 only when every bypass is caught; a missed bypass makes it exit non-zero.

npm run demo:live reconciles a real Base Sepolia USDC window instead of a fixture. Read-only: it needs an RPC URL in CEDULON_RPC_URL and no wallet, key, or transaction. Against an account whose receipts you do not hold, every settlement the chain reports comes back as a gap.

A third party can reproduce this without trusting us: docs/RUN_AS_VERIFIER.md.

Five-minute path, including the MCP host config: docs/QUICKSTART.md.

MCP server

Cedulon can run as a local stdio MCP server. The host talks JSON-RPC on stdin/stdout. The five tools are thin wrappers over the existing packages; they do not reimplement policy, receipts, or audit.

Tool	Arguments	Result
`cedulon_spend`	`amount` (string), `currency`, `payee`, `nonce`, optional `tool`	Allow → signed receipt JSON. Deny → `{ ok: false, reason }` (for example `limit-amount`).
`cedulon_audit`	optional `extract` (a signed rail extract you were presented with: `body`, `signature`, `publicKeyPem`), the trust roots (`trust`, `issuerTrust`, `witnessTrust`, `payeeTrust`, `manifest`, `manifestTrust`), optional `extraSettlements[]` (`ref`, `amount`, `currency`, `timestampMs`; refused beside `extract`)	`{ ok, summary, findings, warnings, guarantee, counts }`, plus `scope` when the audit ran over a presented extract; `counts` is the class every receipt and row landed in. Balanced books print `audit: balanced`.
`cedulon_verify_receipt`	`receipt` object, or `coseHex` + `publicKeyPem`, optional countersignature fields	`{ ok, receipt, countersignature }`
`cedulon_export_ledger`	none	Receipts + checkpoint + extract in the `demo:export` JSON shape
`cedulon_status`	none	`{ version, policy, receiptCount, chainHead }`

Claude Desktop / Claude Code / Cursor. Nothing to clone and nothing to build:

config.json

{
  "mcpServers": {
    "cedulon": {
      "command": "npx",
      "args": ["-y", "@cedulon/mcp-server"]
    }
  }
}

In Claude Code that config is one command:

Terminal

claude mcp add cedulon -- npx -y @cedulon/mcp-server

Policy limits come from the environment: CEDULON_MAX_AMOUNT, CEDULON_MAX_CUMULATIVE, CEDULON_MAX_PAYMENTS, CEDULON_WINDOW_MS, CEDULON_ALLOWED_PAYEES, CEDULON_ALLOWED_CURRENCIES, CEDULON_ALLOWED_TOOLS, CEDULON_PAYER. Set CEDULON_STATE_PATH to keep the receipt chain across restarts; without it the ledger lives in memory.

Working inside this repository instead, against the sources:

Terminal

npm run mcp

The server is listed in the MCP Registry as io.github.dogrucanemek-alt/cedulon; server.json is the entry it is published from.

npm run mcpb builds an .mcpb bundle — a zip holding the server and its dependencies, which a desktop host installs in one click, with the policy caps exposed as settings. It installs the released npm package rather than packing the working tree, so the bundle holds what npm would have given you, and the version must already be released. The result lands in build/ and is a release artifact, not source. Released bundles are attached to the matching GitHub release, with the bundle's SHA-256 in the release notes; v0.13.0 carries cedulon-0.13.0.mcpb, and v0.12.0 the one before it.

smithery.yaml is the older ecosystem format and is not submitted; Smithery's current instructions take an HTTPS endpoint or an .mcpb bundle.

There is also a Dockerfile, for hosts and directories that build the repository rather than install the package:

Terminal

docker build -t cedulon .
docker run -i --rm cedulon

The protocol is the container's stdin/stdout, so it needs -i. It needs no credentials: the server settles on a mock rail and holds no wallet.

Layout

Code

packages/core           policy engine + Decision Token (workspace dep on @cedulon/cose)
packages/cose           deterministic CBOR + COSE_Sign1 (Ed25519)
packages/manifest       signed trade manifest
packages/receipts       spend receipt (COSE default, JSON legacy)
packages/checkpoint     epoch checkpoints + in-process transparency log
packages/audit          rail-extract completeness checker
packages/mcp-guard      MCP tools/call wrapper (mock)
packages/mcp-server     stdio MCP server (official SDK)
packages/x402-adapter   HTTP 402 adapter + mock rail extract
packages/base-extract   read-only Base Sepolia USDC → RailExtract
examples/demo           runaway, dispute, bypass, audit CLI
spec/                   draft-dogru-cedulon-09 (posted 6 September 2026),
                        -08, -07, -06, -05, -04, -03, -02, -01, -00;
                        draft-dogru-cedulon-decision-profile-03 (posted
                        6 September 2026), -02, -01, -00: decisions against effects
                        on the same reconciler; and the direction seeds
                        draft-dogru-cedulon-reattestation-00 and
                        draft-dogru-cedulon-streaming-00
THREAT_MODEL.md
docs/RUN_AS_VERIFIER.md

Brand names come from packages/core/src/brand.ts only.

How to cite

Citation metadata is in CITATION.cff. The archived -00 release is published as https://doi.org/10.5281/zenodo.22099792. The posted decision profile, draft-dogru-cedulon-decision-profile-03, is deposited on its own as https://doi.org/10.5281/zenodo.22337734 (all versions; the posted -03 text is https://doi.org/10.5281/zenodo.22550761)

Privacy Policy

https://cedulon.com/privacy.html

The MCP server runs on your machine and makes no network requests. It collects nothing, because there is no endpoint of ours to collect it. packages/mcp-server/README.md states what it holds while it runs and what it writes if you ask it to.

License

Apache-2.0