Bernstein MCP Server

bernstein-mcp

Stateless, read-only MCP endpoint at https://mcp.bernstein.run that verifies bernstein run receipts and hash chains. No account, no key, nothing stored, nothing fetched.

claude mcp add --transport http bernstein https://mcp.bernstein.run/mcp

What it does

Same walk as bernstein verify-receipt, reachable from any MCP client or the paste form at /verify. A verdict's page address is the receipt's own digest.

Trust model

Pass the receipt file's contents as a string: an already parsed object cannot tell 1 from 1.0, and the reference hashes the original spelling.

Signed verdicts

Every verdict comes back as a DSSE envelope (signed_verdict) signed with this deployment's Ed25519 key: the payload is a JCS-canonical statement naming the receipt by digest, the verdict, every check, and an appraisal block in the EAR status vocabulary (affirming / contraindicated / none). Keep it next to the receipt; anyone can re-check it offline against the public key at /.well-known/bernstein-mcp/keys.json (kid = RFC 7638 thumbprint). The signature covers the DSSE PAE of application/vnd.bernstein.verdict+json, the same construction the receipt itself uses. It attests that this verifier reached this verdict for these bytes at this time — nothing about the receipt's producer.

Session receipts

bernstein-attest turns a Claude Code or Codex CLI session into a signed run receipt that this server verifies.

npx bernstein-attest init          # registers hooks for both agents (user scope); --claude-code / --codex / --project to narrow
bernstein-attest link              # verify link + one Markdown line for a PR description
bernstein-attest verify .bernstein/receipts/<session>.json

Codex runs project hooks only after they are trusted once with /hooks in an interactive session; codex exec skips untrusted hooks without printing anything. With --project, Claude Code hooks go to .claude/settings.local.json and Codex hooks to .codex/hooks.json; both name the bundle under your home directory, so keep .codex/hooks.json out of version control.

Recorded per tool call: tool name, hashes of its input and output, success flag, repo-relative path for files the call wrote (hash only for paths outside the project), the program name of a shell command (first token, path stripped, at most 32 characters). Not recorded: prompts, model output, command text, file contents, absolute paths. The receipt is sealed at the end of every turn that recorded something new, and every 2 000 rows; the file lives in .bernstein/receipts/ and can be committed with the change it describes. Because later turns reseal the same file, run npx bernstein-attest link right before committing it so the link you paste names the current bytes.

Limits

Correctness

vectors/ holds eight golden vectors generated by the Python reference (scripts/gen_vectors.py against the pinned bernstein source). The TypeScript verifier must reproduce each vector's verdict, every check, the binding bytes and the receipt digest byte for byte (test/vectors.test.ts). vectors/session/ holds three frozen session receipts written by bernstein-attest (scripts/gen-session-vectors.mjs).

Development

npm install
npm test          # no-fetch guard + vitest
npm run typecheck
npm run dev       # wrangler dev

src/ may not call fetch, eval or new Function; CI fails otherwise. Deploying: see DEPLOY.md. Licence: Apache-2.0.