📦Bundlers
Overview of Bundlers in the ERC-4337 architecture.
Bundlers are the relayers of ERC-4337. They collect UserOperations, simulate them for validity, and package them into a call to the EntryPoint contract on-chain.
They are a critical part of the infrastructure that makes Account Abstraction work without consensus-layer changes.
🧠 What Do Bundlers Do?
Monitor the alt mempool for
UserOperationsSimulate operations using EntryPoint’s
simulateValidationGroup valid ops into bundles
Submit via
handleOps()to the EntryPointPay gas and earn fees (like a miner)
🔍 Why Are They Needed?
Ethereum’s base protocol doesn’t natively support UserOperation-style logic. Bundlers:
Act like “miners for smart wallets”
Provide validation guarantees for off-chain mempools
Allow modular signature and sponsorship logic without protocol changes
🏗️ EntryPoint Compatibility
All bundlers interact with a canonical EntryPoint contract, which is deployed at a fixed address per network (e.g. v0.6, v0.7, v0.8).
They must support:
handleOps()to process batchedUserOperationssimulateValidation()to precheck operations without state changes
🤑 Incentives
Bundlers receive:
Priority fees specified in each
UserOperationRefunds from the account or Paymaster for gas used
They compete similarly to miners, but operate entirely in the mempool layer.
🔐 Security Considerations
Bundlers must not include
UserOpsthat fail simulationThey should enforce ERC-7562 constraints on validation logic
A single bad UserOp can revert the whole bundle — simulate carefully
✅ Summary
Bundlers are essential to ERC-4337. They verify, package, and submit smart wallet transactions in a decentralized, incentive-aligned way. While they operate off-chain, their correctness directly impacts the security and UX of Account Abstraction flows.
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