The four V4 swap actions are read only as the parameter structs deployed on mainnet and Sepolia. ethers decoded the newer v4-periphery structs, which add minHopPriceX36, as the deployed ones without an error, and the newer multi-hop exact-in struct showed the offset of its hop-price array as the swap amount. A decode now counts only when encoding it again gives back the same bytes. A swap action that fails that marks its step "V4 Swap (could not be decoded)", and a side of the swap that its SETTLE or TAKE did not name reads "Unknown (could not be decoded)" instead of another step's token and figure. The README records both. Model: opus-5-5