x402 Deferred-Scheme Handshake Validator

Validates a Cloudflare deferred x402 scheme handshake: 402 offer field shape (scheme:"deferred", id, termsUrl), RFC 9421 HTTP Message Signature covered-component coverage (@method, @target-uri, content-digest), and settlement-reference id continuity across a call sequence (uniqueness, no internal duplicates). Cryptographic signature verification reuses verify_webbotauth_signature (art-129); rollup/batch settlement arithmetic is owned by reconcile_x402_batch_settlement (art-61); this node validates the offer and handshake shape only. Scheme registry is a plugin surface and is not hard-coded.

Tool URL: https://ainumbers.co/chaingraph/art-394-x402-deferred-handshake-validator.html