The Problem With EOAs
Every Ethereum wallet today is an Externally Owned Account (EOA) — a private key that signs transactions. This creates a hard UX ceiling: no gas abstraction, no batched transactions, no social recovery.
What ERC-4337 Actually Does
ERC-4337 introduces UserOperation — a pseudo-transaction signed by a smart contract wallet, bundled by a Bundler, and validated on-chain by the EntryPoint contract.
Key components:
- EntryPoint (
0x0000000071727De22E5E9d8BAf0edAc6f37da032) — singleton validation contract - Smart Contract Wallet — your wallet is now a contract with programmable validation
- Bundler — collects UserOps off-chain and submits batched transactions
- Paymaster — optional contract that sponsors gas
Architecture Implications
When building custody infrastructure for AA wallets, you must:
- Probe
entryPoint()on wallet contracts to detect AA (not just code size check) - Handle both v0.6 and v0.7 EntryPoint addresses
- Account for
UserOperationvalidation in your security model
What This Means For Your Stack
If you're building on Fireblocks or BitGo today, neither natively supports ERC-4337 UserOps yet. You'll need a proxy layer that translates UserOps into standard transactions the custody provider can sign.
This is solvable — but plan for it before you're mid-deployment.