---
marp: true
title: 04 Prague / EIP-7702 prep
---

# 04 Prague and EIP-7702: get ready

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## EIP-7702 in one slide
- New tx type **0x04** (set-code tx) with an `authorization_list`
- Each tuple `[chain_id, address, nonce, y_parity, r, s]` is signed by an EOA
- EOA code becomes the **delegation indicator** `0xef0100 || address` (23 bytes)
- Calls to the EOA run the delegate's code **in the EOA's context** (its storage, balance)
- Delegating to `address(0)` clears it
- Source: https://eips.ethereum.org/EIPS/eip-7702

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## Why builders care
- **Batching**: approve + swap / pay in one tx
- **Sponsorship**: someone else pays gas
- **Privilege de-escalation**: session keys with limits
- Persistent until changed; not a one-off script

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## Status (checked 2026-10-21)
- Ethereum: live since Pectra, activation epoch 364032 (https://eips.ethereum.org/EIPS/eip-7600)
- XDC devnet: 7702 active since block 3,000,600 (xdc.dev, "EIP-7702 is available on devnet now")
- XDC Apothem (51): Prague at block **84,333,000** (XDPoSChain v3.0.0-testnet-1 release notes, github.com/XinFinOrg/XDPoSChain/releases)
- XDC mainnet (50): no Prague block announced yet; stays Cancun → prep now, ship later

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## Security points from the EIP
- Delegate must authenticate callers (`msg.sender == address(this)` or a signature)
- Signed payloads need **nonce, target, calldata, value, gas** (replay / griefing)
- Front-running of initialization: no initcode, verify setup data is signed by the EOA
- Storage collisions when switching delegates → namespaced storage (ERC-7201)
- `tx.origin == msg.sender` no longer means "top-level EOA call"

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## Prep checklist for existing XDC contracts
- Grep for `tx.origin` checks and `extcodesize == 0` "is EOA" checks
- Do not assume an EOA cannot have code or run logic on receive
- Test with Foundry: `evm_version = "prague"`, `vm.signAndAttachDelegation`
- Local chain: `anvil --hardfork prague`, `cast send --auth <impl>`

→ Lab 3