EVM: decode a multicall or a Universal Router execute

⚠️ DANGEROUS: use at your own risk. Code that handles keys and signs transactions should always be read and audited by you before you trust it with real funds. Used incorrectly, it can destroy your money.

Task: one transaction carries several calls packed as bytes[]. Decode the outer call, then each inner one. No tool recurses for you: it is a pipeline of abi-decode steps, each one given the layout you read from the contract's source. Part of the EVM contract recipes.

Fixtures are raw Ethereum mainnet JSON-RPC responses in fixtures/evm-mainnet/ (requests in PROVENANCE.md).

Uniswap Universal Router execute(bytes,bytes[],uint256)

02a is a mainnet Universal Router swap. The outer call: a command string (one byte per command), one input per command, and a deadline:

jq -r .result.input recipes/fixtures/evm-mainnet/02a-swap-tx.json | abi-decode --sig 'execute(bytes,bytes[],uint256)' | jq -c '{commands: .args[0].value, inputs: (.args[1].value | length), deadline: .args[2].value}'

Command 0x0a is PERMIT2_PERMIT and 0x10 is V4_SWAP in Uniswap's Commands.sol (read from their source, not from a tool). The PERMIT2_PERMIT input is a PermitSingle plus its signature: ((token, amount, expiration, nonce), spender, sigDeadline), signature:

jq -r .result.input recipes/fixtures/evm-mainnet/02a-swap-tx.json | abi-decode --sig 'execute(bytes,bytes[],uint256)' | jq -r '.args[1].value[0]' | abi-decode --types '(((address,uint160,uint48,uint48),address,uint256),bytes)' | jq -c '.args[0].value'

That signature is checked offline in evm-permit2-signing-request.md. The V4_SWAP input is (bytes actions, bytes[] params):

jq -r .result.input recipes/fixtures/evm-mainnet/02a-swap-tx.json | abi-decode --sig 'execute(bytes,bytes[],uint256)' | jq -r '.args[1].value[1]' | abi-decode --types '(bytes,bytes[])' | jq -c '{actions: .args[0].value, params: (.args[1].value | length)}'

NOT BUILT: naming Universal Router command bytes or Uniswap v4 action bytes, and decoding each v4 action's parameter struct. You can decode each params element with --types once you have the struct layout from Uniswap's Actions.sol and router source; that step is not shown or tested here.

A plain multicall(bytes[])

The same pattern for the common multicall(bytes[]). The calldata here is constructed with abi-encode from two inner calls (no fixture); each inner call is decoded against the signatures you supply:

abi-encode --raw 'multicall(bytes[])' "[\"$(abi-encode --raw 'approve(address,uint256)' 0x000000000022d473030f116ddee9f6b43ac78ba3 1000)\",\"$(abi-encode --raw 'transfer(address,uint256)' 0x264bd8291fae1d75db2c5f573b07faa6715997b5 5050510000)\"]" | abi-decode --sig 'multicall(bytes[])' | jq -r '.args[0].value[]' | while read -r c; do abi-decode --sig 'approve(address,uint256)' --sig 'transfer(address,uint256)' "$c" | jq -c '{signature, args: [.args[].value]}'; done

An inner call with an unknown selector prints no_match; look it up with evm-unknown-selector.md.