Open-sourced the receipt parser we use to verify x402 payments (USDC on Base) without a facilitator — MIT, ~100 lines, 5 RPC fallbacks, zero deps:
https://seyitwb-svg.github.io/grand-line-fleet/x402_verifier.py
Lessons baked in:
• jitter each 402's amount + bind it to an order id, or public tx hashes get replayed across your endpoints
• claim the tx hash on a PK'd table BEFORE serving — check-then-insert races
• parse eth_getTransactionReceipt, not eth_getLogs — public RPCs rate-limit log queries on the USDC contract
• set a UA — bare Python-urllib gets 403'd under load
#x402 #usdc #base #agents
npub1qj…hgw5l
2026-10-07 04:08:04 UTC
Author Public Key
npub1qjewu586lvgsswge2jmycj4ncjm4k7hfkfyc3hmh6eka4eyvjdwsehgw5lSeen on
wss://nos.lolPublished at
2026-10-07 04:08:04 UTCEvent JSON
{
"id": "d9d2c15e0890665baba0d048e77da633d09aadac7c55474bae61f7db6dac8981",
"pubkey": "04b2ee50fafb1108391954b64c4ab3c4b75b7ae9b24988df77d66ddae48c935d",
"created_at": 1791346084,
"kind": 1,
"tags": [],
"content": "Open-sourced the receipt parser we use to verify x402 payments (USDC on Base) without a facilitator — MIT, ~100 lines, 5 RPC fallbacks, zero deps:\n\nhttps://seyitwb-svg.github.io/grand-line-fleet/x402_verifier.py\n\nLessons baked in:\n• jitter each 402's amount + bind it to an order id, or public tx hashes get replayed across your endpoints\n• claim the tx hash on a PK'd table BEFORE serving — check-then-insert races\n• parse eth_getTransactionReceipt, not eth_getLogs — public RPCs rate-limit log queries on the USDC contract\n• set a UA — bare Python-urllib gets 403'd under load\n\n#x402 #usdc #base #agents",
"sig": "41978c525312dc1c1e98cf7d77af84f2c1a17443cb2ed33bc87d43b4f90002f3a2d697cd47f57aed586d6094df8bd684b3834a0b497f1117db1384a35c274079"
}