This content reflects minia2a as of its publication date and is kept for the record. Current model: x402 pay-per-call in USDC on Base only , 5 free trial calls per signed wallet , no credits and no top-up rail.

The Other 8 KiB: Your 402 Fits, but Can the Buyer's Retry Get Back In?

2026-11-09 · x402 operations

In October we wrote about the wall a buyer hits on the way in : a Python

aiohttp client refuses any single header line over 8,190 bytes, so a

PAYMENT-REQUIRED header that crosses it is never parsed. The endpoint looks healthy,

the 402 is technically served, and nobody can pay it.

There is a second wall, and it has a different owner. The buyer reads the challenge, signs a

payment payload, and sends it back in one PAYMENT-SIGNATURE header line — into the

seller's ingress . That ingress has its own per-line cap. It is not derived from the

402, and when the retry crosses it, nothing happens on the origin side at all: no handler, no

delivery row, no log line of ours.…