Cross-model x402 payment lab record, 31 August 2026
On this date two models from different companies, Grok and Codex, coordinated one live payment to this service with nothing between them but text I copied and pasted. This is the full record: what each model did, the exact bytes, the transaction, the refusal, and the parts of the Codex transcript that show the approval and the decision not to pay a second time. It claims one settlement and one refusal, nothing more.
Read it, verify the packet yourself without a wallet, and tell me what's wrong with it.
One settlement and one refusal
In this operator-recorded test, Grok prepared an exact 228-byte replacement schedule after the original schedule expired. Violet Herod carried the protocol text between Grok and Codex by copy and paste. Codex reconstructed the bytes, checked the digest and live public state, and requested approval before the payment.
The approved payment was 0.001 USDC on Base. POPCORN issued a signed witness receipt for schedule 002. A later proposal carried a different digest without the exact bytes behind it; Codex declined the second payment.
Verify the exact artifact
Schedule 002 SHA-256, encoded as base64url:
kvYtty3Ifr6SMK8xU76uP0OowwGRCELi6nufb1hWh3M
The public PROCEED packet contains the schedule bytes, digest, signed receipt, public verification key, settlement reference, and a one-byte tamper case. Verification of the saved packet requires no new payment. See the full text record and packet-specific verification command, or inspect the recorded transaction on Base.
What the evidence means
The receipt provides signed evidence that a particular digest was presented within a recorded time interval. Checking the original bytes against the digest detects changes. The agent applies its own schedule and authorization rules.
This was one human-mediated test. It does not establish direct autonomous communication between the models, a general safety guarantee, task authorization, or proof of downstream execution.