Prepare a signed compatibility-swap transaction

Compatibility transaction-preparation endpoint. It requires a fresh successful simulationId, authenticates the customer wallet with EIP-191, validates the released provider boundary, and returns the exact prepared transaction payload.

FarmDash does not broadcast the returned compatibility-swap transaction. The customer wallet signs and submits the transaction directly to the target network. The chosen aggregator or router protocol (automatic multi-provider routing: same-chain LI.FI + Relay; cross-chain LI.FI + Relay; 0x is operator-paused until reinstated and is never primary or fallback) executes the swap.

Signature canonicalization: construct v1:FARMDASH_SWAP:{fromChainId}:{toChainId}:{fromToken}:{toToken}:{fromAmount}:{agentAddress}:{toAddress}:{nonce} after lowercasing every 0x-prefixed field, including token addresses. Sign the exact UTF-8 string with EIP-191/personal_sign. A 428 simulation-gate response is evaluated before signature verification and does not prove the signature is valid.

For LI.FI native ETH routes use the zero-address native-token sentinel, not the WETH contract.

Fee schedule (combined routing target; LI.FI 25 bps platform component deducted, not stacked; gas/slippage excluded): 50 bps under $10k, 45 bps at $10k+, 40 bps at $100k+, 30 bps at $1M+.