{"service":"flow-fill","method":"POST","what":"Pay-for-improvement execution (Path C, live): Flow measures your swap's improvement over the baseline route at a pinned block, you pay the fee via x402, and the executable route package is released. You then swap wallet-to-DEX yourself — Flow never holds funds.","terms":{"fee":"25% of the measured improvement","cap_bps":10,"currency":"USDC on Base (x402 v2 exact)","custody":"none"},"body":{"tokenIn":"0x… token address","tokenOut":"0x… token address","amountIn":"atomic units as a string"},"flow":"POST unpaid → 402 challenge priced from YOUR measured improvement, carrying the quote commitment → retry with an X-PAYMENT header, the quote's blockNumber, and the commitment echoed back → 200 with the route package, its terms object, the measurement evidence, and the commitment + settlement receipt pair.","commitment":"Every fill quote carries a commitment: { routeHash, expires_at, min_output, fee_quote }. routeHash is a SHA-256 over the route package's core (venue, router, calldata params, expected output, min output, block pin; expires_at is a Base block number). Echo it back as `commitment` on the paid retry: the fill settles only when the delivered package's routeHash matches the commitment and the commitment is unexpired — a mismatch or an expired commitment is a 409 BEFORE settlement, never a settled surprise. A settled response echoes commitment.routeHash together with payment.transaction; that pair is your proof, and your refund claim.","refund_rule":"Refundable, from the ops wallet, on claim within 7 days presenting the quote commitment + the settlement tx, when: (a) the package was never delivered after settlement, (b) the commitment expired before delivery, or (c) the delivered package's routeHash ≠ the commitment. NOT refundable: the buyer received the committed package in-window and chose not to swap — that is the disclosed term. Claims verified against Flow's own delivery records; refunds are ops-wallet transactions and are never counted as negative revenue in the public ledger — they are recorded as refunds.","docs":"https://flow-kg4x.vercel.app/llms.txt"}