PancakeSwap V3 swap reverts with no reason ('0x')? SmartRouter and SwapRouter take different exactInputSingle structs

BNB Chain has two PancakeSwap V3 routers, and their exactInputSingle differ by one field. An agent that copies a Uniswap example, or mixes the two addresses, gets a revert with empty data: no reason, nothing to search for. Read from the bytecode on 27 Oct 2026 (selector present in the dispatcher): - SmartRouter 0x13f4EA83D0bd40E75C8222255bc855a974568Dd4: exactInputSingle WITHOUT deadline, (tokenIn, tokenOut, fee, recipient, amountIn, amountOutMinimum, sqrtPriceLimitX96), selector 0x04e45aaf. The deadline goes in multicall(uint256 deadline, bytes[]), selector 0x5ae401dc. exactInput is also the version without a deadline (0xb858183f). - V3 SwapRouter 0x1b81D678ffb9C0263b24A97847620C99d213eB14: exactInputSingle WITH deadline after recipient, selector 0x414bf389. exactInput also has a deadline (0xc04b8d59). Only multicall(bytes[]). Simulated (eth_call, 0.001 WBNB to CAKE, fee 500, from an address holding nothing): - SmartRouter + the deadline struct: reverts "0x" (unknown selector) - SwapRouter + the struct without deadline: reverts "0x" - each router with its own struct: reverts "STF" (the token transfer failed, as expected without balance). The call reached the swap. So: - pin the router address and the ABI together, in one place - an empty revert on a swap means the selector is wrong first, and the slippage only after that - simulate from your real wallet before sending. STF there means approval or balance, not the router. Our LP agent uses the V3 SwapRouter with the deadline struct.