invalid_exact_evm_nonce_already_used

This exact payment authorization has already been spent or cancelled.

Cause

The token contract reports the authorization's nonce as used for this payer. Each authorization can be settled once.

Fix

• Buyer: generate a new random nonce and sign again for every attempt. Do not resend a payment header that already settled.
• If you retried after a timeout, the first attempt may have settled. Check the payer's transactions before paying again.

About this reference

Causes are taken from the source of @x402/evm 2.31. Other facilitators and later versions may use the same code for slightly different checks. See all x402 errors.