Add EIP-7702 Batch Delegation Support

[TobiWo]

Description

Summary

Each validator operation (consolidation, withdrawal, exit, credential switch) currently requires an individual EIP-1559 transaction to the system contract. For users managing 50+ validators, this means dozens of transactions split across multiple batches, each requiring separate nonce management, receipt monitoring, and retry logic. Additionally, the EIP-7002 spec notes that EOA callers always overpay system contract fees.

Proposal

Add an optional EIP-7702 code path that delegates the user's EOA to a BatchDelegator contract, enabling all validator requests to be submitted in a single type 0x04 transaction.

Key benefits:

• Atomicity — all operations in a batch succeed or fail together
• Gas savings — one base transaction cost instead of one per validator
• Predictable fees — same-block inclusion avoids inter-block fee escalation
• Fee overpayment elimination — BatchDelegator can staticcall the fee getter to pay exact amounts
• Simplified orchestration — single transaction to monitor instead of N individual replacements
• Reduced Ledger interaction — one auth tuple + one signature instead of N signatures

Scope

Component	Description
BatchDelegator contract	Solidity contract with executeBatch(), deployed per network. Requires audit.
Transaction construction	Type 0x04 transactions with authorizationList and ABI-encoded batch calldata
Signer support	WalletSigner via ethers.js authorize(). LedgerSigner supported at hardware level but subject to Ledger's delegate contract whitelist.
Dual-path orchestration	New single-tx path alongside existing multi-batch path
CLI	--eip7702 flag or auto-detection of existing delegation

Constraints

• EIP-7825 (Fusaka) introduces a ~16.78M per-transaction gas cap, limiting batch size to ~80 requests per transaction
• Ledger devices enforce a whitelist for delegate contracts — custom contracts require Ledger approval
• BatchDelegator needs a security audit before mainnet use

Approach

1. PoC for WalletSigner on hoodi
2. Validate gas savings and UX empirically
3. Investigate Ledger whitelist process for custom delegate contracts in parallel
4. Existing EOA path remains the default fallback

References

• EIP-7702 Specification
• EIP-7002 Specification
• EIP-7825 Specification
• Ledger Pectra Upgrade Blog Post

Additional information

No response

[yorickdowne]

Feedback from stakely. They use this with a Ledger and 400 tx per batch, so someone doesn't have to click Ledger buttons thousands of times. The fee is low for all 400, then in the next block it increases.

Quote

Even though the contract fee increases significantly after the submission, the cost remains the same for all validators included in the same transaction.
For example:

First batch of 400 validators (total fee ≈ 0.000003 ETH):
https://hoodi.etherscan.io/tx/0x524d7c6172ea0270ec3546dd15ccfeb49604fb25963b7e294210cbcecee2de73

Second batch of 400 validators (total fee ≈ 0.504 ETH):
https://hoodi.etherscan.io/tx/0x0316a773a5690854c05a0631533018f0e61b00a170a8b82ed831f2c02e2579ab