Trust402 — Lemma's verifiable x402 layer
A reference implementation by Lemma that layers verifiability onto the x402 payment protocol. Cryptographically proves not just that payment happened, but that the payment was legitimate — authorized, scoped, purposeful.
Definition
x402 alone answers "did payment settle"; the agent economy adds a second question: "did a properly authorized agent, within the granted scope, pay for the declared purpose?" Trust402 is the layer that answers the second question.
Three stages: (1) the delegator (human or higher agent) issues a payment authority as a commitment; (2) the delegated agent runs x402 settlement and proves the authority's validity in zero-knowledge; (3) the facilitator verifies the payment and the proof together at settlement time.
The developer integration path is four-stage: Explorer (trial), Builder (integration), Studio (operations), Pro (production). Interop is preserved with both EIP-3009 meta-transactions and facilitator services.
Lemma Oracle implementation
Trust402 sits on Lemma's underlying cryptographic infrastructure (docHash + commitment + ZK proof) and adds an x402-spec adapter. To existing x402 clients and servers, the difference is whether or not an additional X-PROOF HTTP header is understood.
Financial-institution autonomous agents, enterprise procurement automation, public-sector spending APIs — every domain where "the payment happened" alone fails to satisfy regulators and audits, and "the payment was legitimate" needs to be provable. Trust402 is the bridge.
Settling the audit and compliance question becomes a single read of the audit trail after the fact.