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AXIOMAXIOM

Builder mcp@v2
Builder id https://dragoscv.github.io/axiom/spec/builder/mcp@v2
Used in runDetails.builder.id of plan@v2 provenance; predicate.verifier.id of the apply attestation
Legacy URI https://axiom.dev/builder/mcp@v2 — what 2.x produced; same builder, so a verifier treats both as equal
Status stable

What the id asserts

Section titled “What the id asserts”

A statement carrying this id was produced by the AXIOM code in packages/canon (statement builders), packages/plan (compilation) and packages/apply (verifyTree), shipped as @codai/axiom-mcp, the axiom standalone binary or the dragoscv/axiom/action GitHub Action. It runs with:

  • no clock in anything hashed — timestamps appear only in optional runDetails.metadata;
  • no network unless --allow-net was given for ref sources (the digest still pins them);
  • an explicit root allowlist — there is no cwd fallback;
  • fail-closed checks — a predicate that cannot run is error, which blocks apply.

The exact versions are in the statement itself: runDetails.builder.version (a package → version record) or predicate.verifier.version.

Trust

Section titled “Trust”

The id says which software made the claim, not who ran it. Bind the claim to an identity by:

  • Sigstore: CI uploads with id-token: write; gh attestation verify --repo <owner>/<repo> checks the workflow identity that signed it.
  • Ed25519 DSSE: axiom keys sign / axiom journal attest --sign, verified against .axiom/trust/keys.json (Signing).

Re-running the build is always possible: compilation and verification are deterministic, so axiom plan compile + axiom plan verify --tree reproduce the claim from the Plan and the tree.

@v2 names the builder contract, not the npm version: it stays @v2 across AXIOM 3.x because the statements it builds have the same shape.