Minimal smart account for delegated EOAs (EIP-7702), targeting ERC-4337 EntryPoint v0.8 and v0.9.

An EOA delegates its code to HermesDelegateV1 and gains smart-account capabilities — call batching, gas abstraction through ERC-4337, typed-data authorization, ERC-1271/ERC-7739 signature verification — while keeping its address and an EOA-like signature lifecycle. The delegate holds no mutable storage: the only mutable state lives in the HermesV1 manager singleton (a per-account nonce), so re-delegation never leaves stale storage behind.

All execution goes through the single standard ERC-7821 entry point execute(bytes32 mode, bytes executionData), with two supported modes. The three authorization schemes map onto them:

• No-opData mode (0x01000000000000000000…) — executionData is abi.encode(Call[]); authorized by msg.sender (the account itself or a trusted EntryPoint).
• opData mode (0x01000000000078210001…) — executionData is abi.encode(Call[], opData), where opData is the EOA's signature; msg.sender-agnostic.

Notes on the design:

• Standard execution surface. Exposing ERC-7821 (execute + supportsExecutionMode) lets standard tooling drive the account — e.g. an EIP-5792 wallet_sendCalls batch routes through the no-opData mode.
• Validation/execution coupling (4337). validateUserOp rejects any userOp whose callData does not target execute, and the no-opData mode only authorizes a trusted EntryPoint (or self). EntryPoint's protocol guarantees validation runs before execution, so no transient flag is needed.
• Fully-typed signing. The opData path is authorized by a canonical EIP-712 struct, so eth_signTypedData_v4 wallets render every target, value and calldata at signing time — no opaque hashes.
• EOA-like signature lifecycle. Signatures have no expiry; a pending signature is cancelled by consuming its nonce, exactly like replacing a pending EOA transaction. The nonce is consumed before any external call, so a signature cannot be replayed by reentering from a target.
• Re-delegation safety. The EIP-712 domain uses the implementation address as salt, pinning every signature to the specific delegate version. Re-delegating the EOA to different code invalidates all outstanding signatures.
• Defensive ERC-1271 (ERC-7739). Contract-signature checks use ERC-7739 nested rehashing — the two standard forms TypedDataSign (typed data) and PersonalSign (an EIP-191 mimic) — built on OpenZeppelin's audited ERC7739Utils. The request is re-nested under this account's EIP-712 domain (including the impl-pinning salt), so a signature for one account, domain or protocol never validates here while the signed content stays human-readable. The empty-signature probe (hash = 0x7739…7739) returns the ERC-7739 detection magic 0x77390001.
• Discoverable domain. ERC-5267 eip712Domain() exposes the full domain (including the non-standard salt), so signers/tooling can reconstruct the signing domain on-chain instead of hardcoding it per deployment.
• EntryPoints. Two canonical EntryPoints are trusted as callers — v0.8 (0x4337084D9E255Ff0702461CF8895CE9E3b5Ff108) and v0.9 (0x433709009B8330FDa32311DF1C2AFA402eD8D009) — at the same addresses on all supported chains. entryPoint() reports v0.9 for discovery and isSupportedEntryPoint probes the set. v0.7 is intentionally excluded: its userOpHash is a plain keccak rather than an EIP-712 typed hash. Each EntryPoint binds its own address as the EIP-712 verifyingContract, so a userOp signature never replays across the two.

Toolchain: Hardhat, Solidity 0.8.35 (viaIR, Prague EVM), TypeChain, ethers v6.

yarn install
yarn compile          # hardhat compile (+ ABI export to reports/abi)
yarn hardhat test     # full suite on the in-process Hardhat network
yarn coverage         # solidity-coverage
yarn size             # contract size report
REPORT_GAS=true yarn hardhat test   # gas report to reports/gas

Against a local node:

yarn lh               # start a Hardhat node on 127.0.0.1:8545
yarn test:lh          # run the tests against it

Tests live in test/: HermesDelegateV1.test.ts covers the three flows, ERC-1271 and the EIP-712 encoding against reference implementations; GasComparison.test.ts benchmarks the execution paths.

Apache License 2.0.