Ethereum Development Skill

Master Ethereum development including EVM internals, gas optimization, transaction mechanics, and client interactions.

Quick Start

# Invoke this skill for Ethereum development
Skill("ethereum-development", topic="gas", network="mainnet")

Topics Covered

1. EVM (Ethereum Virtual Machine)

Understand the execution environment:

• Stack Machine: 256-bit words, 1024 depth
• Memory: Linear byte array, expansion costs
• Storage: Persistent key-value, 32-byte slots
• Opcodes: Costs, effects, gas consumption

2. Gas Optimization

Reduce transaction costs:

• Storage Packing: Fit multiple values in one slot
• Calldata vs Memory: Choose efficiently
• Loop Optimization: Cache storage reads
• Custom Errors: Save gas on reverts

3. Transaction Mechanics

Master transaction lifecycle:

• Types: Legacy (0), Access List (1), EIP-1559 (2)
• Fee Estimation: Base fee, priority fee, max fee
• Nonce Management: Sequential ordering
• Receipts: Status, logs, gas used

4. Client Interactions

Work with Ethereum nodes:

• RPC Methods: eth_, debug_, trace_
• State Queries: Storage slots, code, balance
• Event Subscriptions: Filter logs, topics

Code Examples

Gas-Efficient Storage

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

contract Optimized {
    // Pack into single slot (32 bytes)
    struct User {
        uint128 balance;    // 16 bytes
        uint64 lastUpdate;  // 8 bytes
        uint32 nonce;       // 4 bytes
        bool active;        // 1 byte
        // 3 bytes padding
    }

    mapping(address => User) public users;
}

Read Storage Slot

import { createPublicClient, http, keccak256, encodePacked, pad } from 'viem';
import { mainnet } from 'viem/chains';

const client = createPublicClient({ chain: mainnet, transport: http() });

// Read mapping value: balances[address]
async function getBalance(contract: `0x${string}`, user: `0x${string}`) {
  const slot = keccak256(encodePacked(['address', 'uint256'], [user, 0n]));
  return await client.getStorageAt({ address: contract, slot });
}

EIP-1559 Transaction

import { createWalletClient, http, parseEther } from 'viem';

const client = createWalletClient({ transport: http() });

const hash = await client.sendTransaction({
  to: '0x...',
  value: parseEther('0.1'),
  type: 'eip1559',
  maxFeePerGas: parseGwei('30'),
  maxPriorityFeePerGas: parseGwei('2'),
});

Gas Optimization Cheatsheet

Technique	Savings	Example
Storage packing	~20k/slot	uint128 + uint128 in one slot
Calldata vs memory	~3/byte	Use calldata for read-only
Unchecked math	~80/op	unchecked { i++; }
Custom errors	~200+	error Unauthorized()
Short-circuit	Variable	Cheap checks first

Common Pitfalls

Pitfall	Issue	Solution
Storage in loops	Expensive reads	Cache in memory first
String storage	Uses multiple slots	Use bytes32 when possible
Zero value storage	Full refund gone	Don't rely on SSTORE refunds

Troubleshooting

"Transaction underpriced"

# Check current gas prices
cast gas-price --rpc-url $RPC
cast basefee --rpc-url $RPC

Set maxFeePerGas to at least 2x current base fee.

"Out of gas"

# Trace transaction to find issue
cast run --trace $TX_HASH --rpc-url $RPC

"Nonce too low"

# Get current nonce
cast nonce $ADDRESS --rpc-url $RPC

CLI Commands

# Foundry essentials
forge build --sizes          # Contract sizes
forge test --gas-report      # Gas consumption
forge snapshot               # Gas snapshots
cast storage $ADDR $SLOT     # Read storage
cast call $ADDR "fn()"       # Simulate call

Test Template

contract GasTest is Test {
    function test_GasOptimization() public {
        uint256 gasBefore = gasleft();
        target.optimizedFunction();
        uint256 gasUsed = gasBefore - gasleft();

        assertLt(gasUsed, 50000, "Too much gas used");
    }
}

Cross-References

• Bonded Agent: 02-ethereum-development
• Related Skills: solidity-development, web3-frontend

Version History

Version	Date	Changes
2.0.0	2025-01	Production-grade with viem, gas optimization
1.0.0	2024-12	Initial release