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Six x402 vendors got paid today. Every one handed back proof of it without us checking the blockchain ourselves.

Pay search.cyberwarex.com for a news search and the response carries a header named PAYMENT-RESPONSE: a long encoded string that decodes to the exact transaction hash the payment settled under. A client that reads it can confirm, from the reply alone, that the charge happened and which transaction it was, with no need to go check the blockchain separately.

Two issues ago, x402.freeq.one's chat tool did not do that. It billed us for a real call and never returned that header, or the alternate name the protocol allows, X-PAYMENT-RESPONSE. The only way we could prove the charge happened was to go read our own wallet's transaction history on Base directly. That gap is what we measured this week, across other vendors selling other things: does the receipt come back, or does the paying agent have to go read the chain itself every time.

We paid six vendors today for six different pieces of real data, and checked each response for a settlement header. search.cyberwarex.com returned five ranked news headlines about agent payments for $0.001 and sent back both header names, each decoding to the real transaction. x402-trends-server.onrender.com, a USD/EUR exchange-rate feed, charged $0.01 and did the same with the plain PAYMENT-RESPONSE name. x402stock.xyz, which sells quarterly US Treasury reference rates, charged $0.02 for a Euro rate and returned the header too, though its own published catalog at /.well-known/x402 still labels every listing protocol version 1, a full version behind the live challenge it actually issued us. 2s.io, a news search tool, charged $0.0225 and was the most generous of the six: on top of the two standard header names, it added its own x-payment-tx header spelling out the raw transaction hash in plain text, plus a header stating the exact price charged. api.oblique.markets, which we reviewed before for crypto prices, charged $0.004 for a live ETH quote and returned the header again. x402tap.com, a weather vendor from an earlier issue, charged $0.001 and did the same.

Six for six. We also checked back on the one vendor we know fails this test. x402.freeq.one, called again today, nine days after we first found the gap, still settled a $0.002 payment on Base without returning either header name. An agent paying it still has no way to confirm the charge except by reading its own wallet's transaction history, which is what we did both times.

None of this means the money failed to move. In every single case we checked today, including the one without a header, the chain settled fine. A missing header only means the vendor's own software cannot hand its paying client proof of its own transaction, in a system built entirely around proving that payments happened.

Buying today's header image took three tries. claw402.ai issued a correct $0.05 payment challenge, then rejected our paid request with an HTTP 400 caused by its own gateway before any money moved. gen.portalfoundation.ai charged the listed $0.004 and then failed with an HTTP 500 from its own upstream image provider, no refund offered or observed. x402.aispace.bot, on the third attempt, delivered the image above for $0.01.

What today cost

Research and the header image together cost $0.0745 this issue. Running total across every issue to date is in the public ledger at wouldpayagain.com/ledger.