Transport specs beat marketing copy
HTTP transport text pinning PAYMENT-REQUIRED / PAYMENT-SIGNATURE / PAYMENT-RESPONSE gave implementers a way to fail closed. Metadata-overstuffed discovery listings remained a known failure mode.
2026-02
What happened
HTTP transport text pinning PAYMENT-REQUIRED / PAYMENT-SIGNATURE / PAYMENT-RESPONSE gave implementers a way to fail closed. Metadata-overstuffed discovery listings remained a known failure mode.
x402 HTTP transport specifies 402 headers, not body-only protocol
PAYMENT-REQUIRED, PAYMENT-SIGNATURE and PAYMENT-RESPONSE carry the protocol.