Eco's New Contribution to Chain Abstraction: Permit3

Eco has introduced Permit3, a cross-chain approval contract that the author describes as a promising iteration on Uniswap Labs' Permit2 and an effort to bring multichain UX forward. Permit3 lets a user sign one signature covering approvals for multiple tokens, applications and chains, such as approving Uniswap to spend WETH on Unichain and Aerodrome to spend USDC on Base. It uses Merkle trees so each chain only needs its own approvals plus a Merkle proof, and it uses a salt per operation, an "async nonce" system, instead of Permit2's linear nonces. The author notes that users must still manually approve tokens for Permit3 on every chain, and that Permit3 will need time before its safety is assured.