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debridge

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@0xinit

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0xinit/cryptoskills

skills/debridge/SKILL.md

deBridge Solana SDK Development Guide

A comprehensive guide for building Solana programs with the deBridge Solana SDK - enabling decentralized cross-chain transfers of arbitrary messages and value between blockchains.

Overview

deBridge is a cross-chain infrastructure protocol enabling:

  • Cross-Chain Transfers: Bridge assets between Solana and 20+ EVM chains
  • Message Passing: Send arbitrary messages across blockchains
  • External Calls: Execute smart contract calls on destination chains
  • Sub-Second Settlement: ~2 second median settlement time
  • Capital Efficiency: Intent-based architecture with 4bps lowest spreads

Key Features

  • 26+ security audits (Halborn, Zokyo, Ackee Blockchain)
  • $200K bug bounty on Immunefi
  • 100% uptime since launch
  • Zero security incidents

Quick Start

Installation

Add the SDK to your Anchor/Solana program:

cargo add --git ssh://git@github.com/debridge-finance/debridge-solana-sdk.git debridge-solana-sdk

Or add to Cargo.toml:

[dependencies]
debridge-solana-sdk = { git = "ssh://git@github.com/debridge-finance/debridge-solana-sdk.git" }

Basic Setup (Anchor)

use anchor_lang::prelude::*;
use debridge_solana_sdk::prelude::*;

declare_id!("YourProgramId11111111111111111111111111111");

#[program]
pub mod my_bridge_program {
    use super::*;

    pub fn send_cross_chain(
        ctx: Context<SendCrossChain>,
        target_chain_id: [u8; 32],
        receiver: Vec<u8>,
        amount: u64,
    ) -> Result<()> {
        // Invoke deBridge send
        debridge_sending::invoke_debridge_send(
            debridge_sending::SendIx {
                target_chain_id,
                receiver,
                is_use_asset_fee: false,  // Use native SOL for fees
                amount,
                submission_params: None,
                referral_code: None,
            },
            ctx.remaining_accounts,
        )?;

        Ok(())
    }
}

#[derive(Accounts)]
pub struct SendCrossChain<'info> {
    #[account(mut)]
    pub sender: Signer<'info>,
    // Additional accounts passed via remaining_accounts
}

Core Concepts

1. Chain IDs

deBridge uses 32-byte chain identifiers for all supported networks:

use debridge_solana_sdk::chain_ids::*;

// Solana
let solana = SOLANA_CHAIN_ID;  // Solana mainnet

// EVM Chains
let ethereum = ETHEREUM_CHAIN_ID;     // Chain ID: 1
let polygon = POLYGON_CHAIN_ID;       // Chain ID: 137
let bnb = BNB_CHAIN_CHAIN_ID;         // Chain ID: 56
let arbitrum = ARBITRUM_CHAIN_ID;     // Chain ID: 42161
let avalanche = AVALANCHE_CHAIN_ID;   // Chain ID: 43114
let fantom = FANTOM_CHAIN_ID;         // Chain ID: 250
let heco = HECO_CHAIN_ID;             // Chain ID: 128

2. Program IDs

use debridge_solana_sdk::{DEBRIDGE_ID, SETTINGS_ID};

// Main deBridge program for sending/claiming
let debridge_program = DEBRIDGE_ID;

// Settings and confirmation storage program
let settings_program = SETTINGS_ID;

3. Fee Structure

deBridge supports multiple fee payment methods:

// Native Fee (SOL)
is_use_asset_fee: false  // Pay fees in SOL

// Asset Fee
is_use_asset_fee: true   // Pay fees in the bridged token

// Fee Constants
const BPS_DENOMINATOR: u64 = 10000;  // Basis points divisor

4. Flags

Control transfer behavior with flags:

use debridge_solana_sdk::flags::*;

// Available flags (bit positions)
const UNWRAP_ETH: u8 = 0;              // Unwrap to native ETH on destination
const REVERT_IF_EXTERNAL_FAIL: u8 = 1; // Revert if external call fails
const PROXY_WITH_SENDER: u8 = 2;       // Include sender in proxy call
const SEND_HASHED_DATA: u8 = 3;        // Send data as hash
const DIRECT_WALLET_FLOW: u8 = 31;     // Use direct wallet flow

// Setting flags on submission params
let mut flags = [0u8; 32];
flags.set_reserved_flag(UNWRAP_ETH);
flags.set_reserved_flag(REVERT_IF_EXTERNAL_FAIL);

Sending Cross-Chain Transfers

Basic Token Transfer

use debridge_solana_sdk::prelude::*;

pub fn send_tokens(
    ctx: Context<SendTokens>,
    amount: u64,
) -> Result<()> {
    debridge_sending::invoke_debridge_send(
        debridge_sending::SendIx {
            target_chain_id: chain_ids::ETHEREUM_CHAIN_ID,
            receiver: recipient_eth_address.to_vec(),
            is_use_asset_fee: false,
            amount,
            submission_params: None,
            referral_code: Some(12345),  // Optional referral
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

Transfer with Fixed Native Fee

pub fn send_with_native_fee(
    ctx: Context<Send>,
    target_chain_id: [u8; 32],
    receiver: Vec<u8>,
    amount: u64,
) -> Result<()> {
    // Get the fixed fee for the target chain
    let fee = debridge_sending::get_chain_native_fix_fee(
        &target_chain_id,
        ctx.remaining_accounts,
    )?;

    debridge_sending::invoke_debridge_send(
        debridge_sending::SendIx {
            target_chain_id,
            receiver,
            is_use_asset_fee: false,
            amount,
            submission_params: None,
            referral_code: None,
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

Transfer with Asset Fee

pub fn send_with_asset_fee(
    ctx: Context<Send>,
    target_chain_id: [u8; 32],
    receiver: Vec<u8>,
    amount: u64,
) -> Result<()> {
    // Check if asset fee is available for this chain
    let is_available = debridge_sending::is_asset_fee_available(
        &target_chain_id,
        ctx.remaining_accounts,
    )?;

    if !is_available {
        return Err(error!(ErrorCode::AssetFeeNotAvailable));
    }

    debridge_sending::invoke_debridge_send(
        debridge_sending::SendIx {
            target_chain_id,
            receiver,
            is_use_asset_fee: true,  // Use asset for fees
            amount,
            submission_params: None,
            referral_code: None,
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

Transfer with Exact Amount

pub fn send_exact_amount(
    ctx: Context<Send>,
    target_chain_id: [u8; 32],
    receiver: Vec<u8>,
    exact_receive_amount: u64,
) -> Result<()> {
    // Calculate total amount including fees
    let total_with_fees = debridge_sending::add_all_fees(
        exact_receive_amount,
        &target_chain_id,
        ctx.remaining_accounts,
    )?;

    debridge_sending::invoke_debridge_send(
        debridge_sending::SendIx {
            target_chain_id,
            receiver,
            is_use_asset_fee: true,
            amount: total_with_fees,
            submission_params: None,
            referral_code: None,
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

Transfer from PDA (Signed)

pub fn send_from_pda(
    ctx: Context<SendFromPda>,
    target_chain_id: [u8; 32],
    receiver: Vec<u8>,
    amount: u64,
    pda_seeds: Vec<Vec<u8>>,
) -> Result<()> {
    // Use signed variant for PDA-owned tokens
    debridge_sending::invoke_debridge_send_signed(
        debridge_sending::SendIx {
            target_chain_id,
            receiver,
            is_use_asset_fee: false,
            amount,
            submission_params: None,
            referral_code: None,
        },
        ctx.remaining_accounts,
        &pda_seeds,
    )?;

    Ok(())
}

Message Passing

Send messages without token transfers:

use debridge_solana_sdk::prelude::*;

pub fn send_message(
    ctx: Context<SendMessage>,
    target_chain_id: [u8; 32],
    receiver: Vec<u8>,
    message_data: Vec<u8>,
) -> Result<()> {
    // Create submission params with message
    let submission_params = debridge_sending::SendSubmissionParamsInput {
        execution_fee: 0,
        flags: [0u8; 32],
        fallback_address: receiver.clone(),
        external_call_shortcut: compute_keccak256(&message_data),
    };

    // Send message (zero amount)
    debridge_sending::invoke_send_message(
        debridge_sending::SendIx {
            target_chain_id,
            receiver,
            is_use_asset_fee: false,
            amount: 0,  // No token transfer
            submission_params: Some(submission_params),
            referral_code: None,
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

External Calls

Execute smart contract calls on destination chains:

Initialize External Call Buffer

pub fn init_external_call(
    ctx: Context<InitExternalCall>,
    target_chain_id: [u8; 32],
    external_call_data: Vec<u8>,
) -> Result<()> {
    let shortcut = compute_keccak256(&external_call_data);

    debridge_sending::invoke_init_external_call(
        debridge_sending::InitExternalCallIx {
            external_call_len: external_call_data.len() as u32,
            chain_id: target_chain_id,
            external_call_shortcut: shortcut,
            external_call: external_call_data,
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

Send with External Call

pub fn send_with_external_call(
    ctx: Context<SendWithExternalCall>,
    target_chain_id: [u8; 32],
    receiver: Vec<u8>,  // Target contract address
    amount: u64,
    external_call_data: Vec<u8>,
    execution_fee: u64,  // Fee for executor on destination
) -> Result<()> {
    let shortcut = compute_keccak256(&external_call_data);

    // Set flags for external call behavior
    let mut flags = [0u8; 32];
    flags.set_reserved_flag(flags::REVERT_IF_EXTERNAL_FAIL);

    let submission_params = debridge_sending::SendSubmissionParamsInput {
        execution_fee,
        flags,
        fallback_address: ctx.accounts.fallback.key().to_bytes().to_vec(),
        external_call_shortcut: shortcut,
    };

    debridge_sending::invoke_debridge_send(
        debridge_sending::SendIx {
            target_chain_id,
            receiver,
            is_use_asset_fee: false,
            amount,
            submission_params: Some(submission_params),
            referral_code: None,
        },
        ctx.remaining_accounts,
    )?;

    Ok(())
}

Claim Verification

Verify claims on the receiving side:

Validate Incoming Claims

use debridge_solana_sdk::check_claiming::*;

pub fn receive_tokens(ctx: Context<ReceiveTokens>) -> Result<()> {
    // Get and validate the parent claim instruction
    let claim_ix = ValidatedExecuteExtCallIx::try_from_current_ix()?;

    // Validate submission details
    let validation = SubmissionAccountValidation {
        receiver_validation: Some(ctx.accounts.receiver.key()),
        token_mint_validation: Some(ctx.accounts.token_mint.key()),
        source_chain_id_validation: Some(chain_ids::ETHEREUM_CHAIN_ID),
        ..Default::default()
    };

    claim_ix.validate_submission_account(
        &ctx.accounts.submission_account,
        &validation,
    )?;

    // Proceed with claim logic
    Ok(())
}

Get Submission Key

pub fn get_claim_info(ctx: Context<ClaimInfo>) -> Result<Pubkey> {
    let claim_ix = ValidatedExecuteExtCallIx::try_from_current_ix()?;
    let submission_key = claim_ix.get_submission_key()?;
    Ok(submission_key)
}

Fee Queries

Get Transfer Fees

// Get base transfer fee (in BPS)
let transfer_fee = debridge_sending::get_transfer_fee(
    ctx.remaining_accounts,
)?;

// Get transfer fee for specific chain
let chain_fee = debridge_sending::get_transfer_fee_for_chain(
    &target_chain_id,
    ctx.remaining_accounts,
)?;

// Get default native fix fee
let default_fee = debridge_sending::get_default_native_fix_fee(
    ctx.remaining_accounts,
)?;

// Get chain-specific native fix fee
let native_fee = debridge_sending::get_chain_native_fix_fee(
    &target_chain_id,
    ctx.remaining_accounts,
)?;

// Get asset fix fee for chain
let asset_fee = debridge_sending::try_get_chain_asset_fix_fee(
    &target_chain_id,
    ctx.remaining_accounts,
)?;

Calculate Total Amount with Fees

// Add transfer fee to amount
let with_transfer_fee = debridge_sending::add_transfer_fee(
    amount,
    ctx.remaining_accounts,
)?;

// Add all fees (transfer + execution + asset fees)
let total_amount = debridge_sending::add_all_fees(
    amount,
    &target_chain_id,
    ctx.remaining_accounts,
)?;

Chain Support Queries

// Check if chain is supported
let is_supported = debridge_sending::is_chain_supported(
    &target_chain_id,
    ctx.remaining_accounts,
)?;

// Get chain support info
let chain_info = debridge_sending::get_chain_support_info(
    &target_chain_id,
    ctx.remaining_accounts,
)?;

// Check if asset fee is available
let asset_fee_available = debridge_sending::is_asset_fee_available(
    &target_chain_id,
    ctx.remaining_accounts,
)?;

PDA Derivation

Bridge Account

use debridge_solana_sdk::keys::*;

// Find bridge PDA for a token mint
let (bridge_address, bump) = BridgePubkey::find_bridge_address(&token_mint);

// Create with known bump
let bridge_address = BridgePubkey::create_bridge_address(&token_mint, bump)?;

Chain Support Info

// Find chain support info PDA
let (chain_support_info, bump) = ChainSupportInfoPubkey::find_chain_support_info_address(
    &target_chain_id,
);

Asset Fee Info

// Find asset fee info PDA
let (asset_fee_info, bump) = AssetFeeInfoPubkey::find_asset_fee_info_address(
    &bridge_pubkey,
    &target_chain_id,
);

// Get default bridge fee address
let default_fee = AssetFeeInfoPubkey::default_bridge_fee_address();

External Call Storage

// Find external call storage PDA
let (storage, bump) = ExternalCallStoragePubkey::find_external_call_storage_address(
    &shortcut,
    &owner,
);

// Find external call meta PDA
let (meta, bump) = ExternalCallMetaPubkey::find_external_call_meta_address(
    &storage_account,
);

Required Accounts

The SDK requires specific accounts passed via remaining_accounts. The account order is important:

IndexAccountSignerWritableDescription
0BridgeNoYesBridge account for token
1Token MintNoNoSPL Token mint
2Staking WalletNoYesStaking rewards wallet
3Mint AuthorityNoNoToken mint authority
4Chain Support InfoNoNoTarget chain config
5Settings ProgramNoNodeBridge settings
6SPL Token ProgramNoNoToken program
7StateNoNoProtocol state
8deBridge ProgramNoNoMain deBridge program
...Additional accounts--Varies by operation

TypeScript Client Integration

Setup

import { Connection, Keypair, PublicKey, Transaction } from '@solana/web3.js';
import { Program, AnchorProvider, Wallet } from '@coral-xyz/anchor';

const connection = new Connection('https://api.mainnet-beta.solana.com');
const wallet = new Wallet(keypair);
const provider = new AnchorProvider(connection, wallet, {});

// deBridge Program IDs
const DEBRIDGE_PROGRAM_ID = new PublicKey('DEbrdGj3HsRsAzx6uH4MKyREKxVAfBydijLUF3ygsFfh');
const SETTINGS_PROGRAM_ID = new PublicKey('DeSetTwWhjZq6Pz9Kfdo1KoS5NqtsM6G8ERbX4SSCSft');

Build Send Transaction

import {
  TOKEN_PROGRAM_ID,
  getAssociatedTokenAddress
} from '@solana/spl-token';

async function buildSendTransaction(
  tokenMint: PublicKey,
  amount: bigint,
  targetChainId: Uint8Array,
  receiver: Uint8Array,
): Promise<Transaction> {
  // Derive required PDAs
  const [bridge] = PublicKey.findProgramAddressSync(
    [Buffer.from('BRIDGE'), tokenMint.toBuffer()],
    DEBRIDGE_PROGRAM_ID
  );

  const [chainSupportInfo] = PublicKey.findProgramAddressSync(
    [Buffer.from('CHAIN_SUPPORT_INFO'), targetChainId],
    SETTINGS_PROGRAM_ID
  );

  const [state] = PublicKey.findProgramAddressSync(
    [Buffer.from('STATE')],
    DEBRIDGE_PROGRAM_ID
  );

  // Build instruction with remaining accounts
  const instruction = await program.methods
    .sendViaDebridge(
      Array.from(targetChainId),
      Array.from(receiver),
      new BN(amount.toString()),
    )
    .remainingAccounts([
      { pubkey: bridge, isSigner: false, isWritable: true },
      { pubkey: tokenMint, isSigner: false, isWritable: false },
      // ... additional required accounts
    ])
    .instruction();

  return new Transaction().add(instruction);
}

Build External Call Data

import { ethers } from 'ethers';
import { keccak256 } from '@ethersproject/keccak256';

function buildExternalCallData(
  targetContract: string,
  functionSig: string,
  params: any[]
): { data: Uint8Array; shortcut: Uint8Array } {
  const iface = new ethers.Interface([functionSig]);
  const calldata = iface.encodeFunctionData(
    functionSig.split('(')[0].replace('function ', ''),
    params
  );

  const data = ethers.getBytes(calldata);
  const shortcut = ethers.getBytes(keccak256(data));

  return { data, shortcut };
}

// Example: ERC20 approve call
const { data, shortcut } = buildExternalCallData(
  '0xTargetContract...',
  'function approve(address spender, uint256 amount)',
  ['0xSpenderAddress...', ethers.parseEther('1000')]
);

Testing

Anchor Test Setup

# Anchor.toml
[provider]
cluster = "mainnet"  # Use mainnet for testing with real deBridge

[programs.mainnet]
my_program = "YourProgramId..."

Run Tests

# Full build and test
cd example_program && anchor build && anchor test

# Test only (skip rebuild)
anchor test --skip-build --skip-deploy

Local Testing Tips

  1. Use Mainnet Fork: deBridge infrastructure is on mainnet
  2. Mock Remaining Accounts: Create mock accounts for unit tests
  3. Test Fee Calculations: Verify fee amounts before sending

Build Features

The SDK supports different environments via Cargo features:

# Production (default) - uses hardcoded program IDs
debridge-solana-sdk = { git = "..." }

# Custom environment - uses env vars
debridge-solana-sdk = { git = "...", features = ["env"] }

Environment variables for custom networks:

  • DEBRIDGE_PROGRAM_PUBKEY: Custom deBridge program ID
  • DEBRIDGE_SETTINGS_PROGRAM_PUBKEY: Custom settings program ID

Resources

Skill Structure

debridge/
├── SKILL.md                          # This file
├── resources/
│   ├── sdk-api-reference.md          # Complete SDK API reference
│   ├── chain-ids.md                  # Supported chain identifiers
│   ├── program-ids.md                # Program IDs and PDAs
│   └── error-codes.md                # Error types and handling
├── examples/
│   ├── basic-transfer/               # Simple cross-chain transfer
│   ├── external-calls/               # External call execution
│   ├── message-passing/              # Message-only transfers
│   └── fee-configurations/           # Fee payment options
└── docs/
    └── troubleshooting.md            # Common issues and solutions

optimism

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Author

@0xinit

Stars

53

Repository

0xinit/cryptoskills

skills/optimism/SKILL.md

Optimism

Optimism is an EVM-equivalent Layer 2 using optimistic rollups. Transactions execute on L2 with data posted to Ethereum L1 for security. The OP Stack is the modular framework powering OP Mainnet, Base, Zora, Mode, and the broader Superchain. Smart contracts deploy identically to Ethereum — no custom compiler, no special opcodes.

What You Probably Got Wrong

  • OP Mainnet IS EVM-equivalent, not just EVM-compatible — Your Solidity contracts deploy without modification. No --legacy flag, no custom compiler. forge create and hardhat deploy work identically to Ethereum. If someone tells you to change your Solidity for "OP compatibility", they are wrong.
  • Gas has two components, not one — Every transaction pays L2 execution gas AND an L1 data fee for posting calldata/blobs to Ethereum. If you only estimate L2 gas via eth_estimateGas, your cost estimate will be wrong. The L1 data fee often dominates total cost. Use the GasPriceOracle predeploy at 0x420000000000000000000000000000000000000F.
  • L2→L1 withdrawals take 7 days, not minutes — L1→L2 deposits finalize in ~1-3 minutes. L2→L1 withdrawals require a 7-day challenge period (the "fault proof window"). Users must prove the withdrawal, wait 7 days, then finalize. Three separate transactions on L1. If your UX assumes instant bridging both ways, it is broken.
  • block.number returns the L2 block number, not L1 — On OP Mainnet, block.number is the L2 block number. To get the L1 block number, read the L1Block predeploy at 0x4200000000000000000000000000000000000015. L2 blocks are produced every 2 seconds.
  • msg.sender works normally — there is no tx.origin aliasing on L2 — Cross-domain messages from L1 to L2 alias the sender address (add 0x1111000000000000000000000000000000001111). But for normal L2 transactions, msg.sender behaves exactly like Ethereum. Only worry about aliasing when receiving L1→L2 messages in your contract.
  • Predeploy contracts live at fixed addresses starting with 0x4200... — These are NOT deployed by you. They exist at genesis. L2CrossDomainMessenger, L2StandardBridge, GasPriceOracle, L1Block, and others all live at hardcoded addresses in the 0x4200... range. Do not try to deploy them.
  • The sequencer is centralized but cannot steal funds — The sequencer orders transactions and proposes state roots. If it goes down, you cannot submit new transactions until it recovers (or until permissionless fault proofs allow forced inclusion). But the sequencer cannot forge invalid state — the fault proof system protects withdrawals.
  • EIP-4844 blob data changed the gas model — After the Ecotone upgrade (March 2024), OP Mainnet posts data using EIP-4844 blobs instead of calldata. This reduced L1 data fees by ~10-100x. The GasPriceOracle methods changed. If you are reading pre-Ecotone documentation, the fee formulas are outdated.
  • SuperchainERC20 is not a standard ERC20 — It is a cross-chain token standard for OP Stack chains that enables native interop between Superchain members. Tokens must implement ICrosschainERC20 with crosschainMint and crosschainBurn. Do not assume a regular ERC20 works across chains.

Quick Start

Chain Configuration

import { defineChain } from "viem";
import { optimism, optimismSepolia } from "viem/chains";

// OP Mainnet is built-in
// Chain ID: 10
// RPC: https://mainnet.optimism.io
// Explorer: https://optimistic.etherscan.io

// OP Sepolia is also built-in
// Chain ID: 11155420
// RPC: https://sepolia.optimism.io
// Explorer: https://sepolia-optimistic.etherscan.io

Environment Setup

# .env
PRIVATE_KEY=your_private_key_here
OP_MAINNET_RPC=https://mainnet.optimism.io
OP_SEPOLIA_RPC=https://sepolia.optimism.io
ETHERSCAN_API_KEY=your_optimistic_etherscan_api_key

Viem Client Setup

import { createPublicClient, createWalletClient, http } from "viem";
import { optimism } from "viem/chains";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(`0x${process.env.PRIVATE_KEY}`);

const publicClient = createPublicClient({
  chain: optimism,
  transport: http(process.env.OP_MAINNET_RPC),
});

const walletClient = createWalletClient({
  account,
  chain: optimism,
  transport: http(process.env.OP_MAINNET_RPC),
});

Chain Configuration

PropertyOP MainnetOP Sepolia
Chain ID1011155420
CurrencyETHETH
RPChttps://mainnet.optimism.iohttps://sepolia.optimism.io
Explorerhttps://optimistic.etherscan.iohttps://sepolia-optimistic.etherscan.io
Block time2 seconds2 seconds
Withdrawal period7 days~12 seconds (testnet)

Alternative RPCs

ProviderEndpoint
Alchemyhttps://opt-mainnet.g.alchemy.com/v2/<KEY>
Infurahttps://optimism-mainnet.infura.io/v3/<KEY>
QuickNodeCustom endpoint per project
Conduithttps://rpc.optimism.io

Deployment

OP Mainnet is EVM-equivalent. Deploy exactly as you would to Ethereum.

Foundry

# Deploy to OP Mainnet
forge create src/MyContract.sol:MyContract \
  --rpc-url $OP_MAINNET_RPC \
  --private-key $PRIVATE_KEY \
  --broadcast

# Deploy with constructor args
forge create src/MyToken.sol:MyToken \
  --rpc-url $OP_MAINNET_RPC \
  --private-key $PRIVATE_KEY \
  --constructor-args "MyToken" "MTK" 18 \
  --broadcast

# Deploy via script
forge script script/Deploy.s.sol:DeployScript \
  --rpc-url $OP_MAINNET_RPC \
  --private-key $PRIVATE_KEY \
  --broadcast \
  --verify \
  --etherscan-api-key $ETHERSCAN_API_KEY

Hardhat

// hardhat.config.ts
import { HardhatUserConfig } from "hardhat/config";
import "@nomicfoundation/hardhat-toolbox";

const config: HardhatUserConfig = {
  solidity: "0.8.24",
  networks: {
    optimism: {
      url: process.env.OP_MAINNET_RPC || "https://mainnet.optimism.io",
      accounts: [process.env.PRIVATE_KEY!],
    },
    optimismSepolia: {
      url: process.env.OP_SEPOLIA_RPC || "https://sepolia.optimism.io",
      accounts: [process.env.PRIVATE_KEY!],
    },
  },
  etherscan: {
    apiKey: {
      optimisticEthereum: process.env.ETHERSCAN_API_KEY!,
      optimisticSepolia: process.env.ETHERSCAN_API_KEY!,
    },
  },
};

export default config;

npx hardhat run scripts/deploy.ts --network optimism

Verification

Foundry

# Verify after deployment
forge verify-contract <DEPLOYED_ADDRESS> src/MyContract.sol:MyContract \
  --chain-id 10 \
  --etherscan-api-key $ETHERSCAN_API_KEY

# Verify with constructor args
forge verify-contract <DEPLOYED_ADDRESS> src/MyToken.sol:MyToken \
  --chain-id 10 \
  --etherscan-api-key $ETHERSCAN_API_KEY \
  --constructor-args $(cast abi-encode "constructor(string,string,uint8)" "MyToken" "MTK" 18)

Hardhat

npx hardhat verify --network optimism <DEPLOYED_ADDRESS> "MyToken" "MTK" 18

Blockscout

OP Mainnet also has a Blockscout explorer at https://optimism.blockscout.com. Verification works via the standard Blockscout API — set the verifier URL in Foundry:

forge verify-contract <DEPLOYED_ADDRESS> src/MyContract.sol:MyContract \
  --verifier blockscout \
  --verifier-url https://optimism.blockscout.com/api/

Cross-Chain Messaging

The CrossDomainMessenger is the canonical way to send arbitrary messages between L1 and L2. It handles replay protection, sender authentication, and gas forwarding.

Architecture

L1 → L2 (Deposits):
  User → L1CrossDomainMessenger → OptimismPortal → L2CrossDomainMessenger → Target

L2 → L1 (Withdrawals):
  User → L2CrossDomainMessenger → L2ToL1MessagePasser → [7 day wait] → OptimismPortal → L1CrossDomainMessenger → Target

L1 → L2 Message (Deposit)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface IL1CrossDomainMessenger {
    function sendMessage(
        address _target,
        bytes calldata _message,
        uint32 _minGasLimit
    ) external payable;
}

contract L1Sender {
    IL1CrossDomainMessenger public immutable messenger;

    constructor(address _messenger) {
        messenger = IL1CrossDomainMessenger(_messenger);
    }

    /// @notice Send a message from L1 to a contract on L2.
    /// @param l2Target The L2 contract address to call.
    /// @param message The calldata to send to the L2 target.
    /// @param minGasLimit Minimum gas for L2 execution. Overestimate — unused gas is NOT refunded to L1.
    function sendToL2(
        address l2Target,
        bytes calldata message,
        uint32 minGasLimit
    ) external payable {
        messenger.sendMessage{value: msg.value}(l2Target, message, minGasLimit);
    }
}

L2 → L1 Message (Withdrawal)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface IL2CrossDomainMessenger {
    function sendMessage(
        address _target,
        bytes calldata _message,
        uint32 _minGasLimit
    ) external payable;

    function xDomainMessageSender() external view returns (address);
}

contract L2Sender {
    /// @dev L2CrossDomainMessenger predeploy address — same on all OP Stack chains
    IL2CrossDomainMessenger public constant MESSENGER =
        IL2CrossDomainMessenger(0x4200000000000000000000000000000000000007);

    function sendToL1(
        address l1Target,
        bytes calldata message,
        uint32 minGasLimit
    ) external payable {
        MESSENGER.sendMessage{value: msg.value}(l1Target, message, minGasLimit);
    }
}

Receiving Cross-Chain Messages

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

interface ICrossDomainMessenger {
    function xDomainMessageSender() external view returns (address);
}

contract L2Receiver {
    ICrossDomainMessenger public constant MESSENGER =
        ICrossDomainMessenger(0x4200000000000000000000000000000000000007);

    address public immutable l1Sender;

    constructor(address _l1Sender) {
        l1Sender = _l1Sender;
    }

    modifier onlyFromL1Sender() {
        require(
            msg.sender == address(MESSENGER) &&
            MESSENGER.xDomainMessageSender() == l1Sender,
            "Not authorized L1 sender"
        );
        _;
    }

    function handleMessage(uint256 value) external onlyFromL1Sender {
        // Process the cross-chain message
    }
}

Sender Aliasing

When an L1 contract sends a message to L2, the apparent msg.sender on L2 is the aliased address:

l2Sender = l1ContractAddress + 0x1111000000000000000000000000000000001111

The CrossDomainMessenger handles un-aliasing internally. If you bypass the messenger and send directly via OptimismPortal, you must account for aliasing yourself.

Predeploy Contracts

These contracts exist at genesis on every OP Stack chain. Do not deploy them — they are already there.

ContractAddressPurpose
L2ToL1MessagePasser0x4200000000000000000000000000000000000016Initiates L2→L1 withdrawals
L2CrossDomainMessenger0x4200000000000000000000000000000000000007Sends/receives cross-chain messages
L2StandardBridge0x4200000000000000000000000000000000000010Bridges ETH and ERC20 tokens
L2ERC721Bridge0x4200000000000000000000000000000000000014Bridges ERC721 tokens
GasPriceOracle0x420000000000000000000000000000000000000FL1 data fee calculation
L1Block0x4200000000000000000000000000000000000015Exposes L1 block info on L2
WETH90x4200000000000000000000000000000000000006Wrapped ETH
L1BlockNumber0x4200000000000000000000000000000000000013L1 block number (deprecated, use L1Block)
SequencerFeeVault0x4200000000000000000000000000000000000011Collects sequencer fees
BaseFeeVault0x4200000000000000000000000000000000000019Collects base fees
L1FeeVault0x420000000000000000000000000000000000001ACollects L1 data fees
GovernanceToken0x4200000000000000000000000000000000000042OP token on L2

Reading L1 Block Info

interface IL1Block {
    function number() external view returns (uint64);
    function timestamp() external view returns (uint64);
    function basefee() external view returns (uint256);
    function hash() external view returns (bytes32);
    function batcherHash() external view returns (bytes32);
    function l1FeeOverhead() external view returns (uint256);
    function l1FeeScalar() external view returns (uint256);
    function blobBaseFee() external view returns (uint256);
    function baseFeeScalar() external view returns (uint32);
    function blobBaseFeeScalar() external view returns (uint32);
}

// Usage
IL1Block constant L1_BLOCK = IL1Block(0x4200000000000000000000000000000000000015);
uint64 l1BlockNumber = L1_BLOCK.number();
uint256 l1BaseFee = L1_BLOCK.basefee();

Gas Model

Every OP Mainnet transaction pays two fees:

  1. L2 execution fee — Standard EVM gas, priced by L2 basefee + optional priority fee. Calculated identically to Ethereum.
  2. L1 data fee — Cost of posting the transaction's data to Ethereum L1 as calldata or blob data. This is the OP-specific component.

Post-Ecotone Formula (Current)

After the Ecotone upgrade (March 2024), L1 data fee uses a two-component formula based on calldata gas and blob gas:

l1DataFee = (l1BaseFeeScalar * l1BaseFee * 16 + l1BlobBaseFeeScalar * l1BlobBaseFee) * compressedTxSize / 1e6
  • l1BaseFee — Ethereum L1 base fee (from L1Block predeploy)
  • l1BlobBaseFee — EIP-4844 blob base fee (from L1Block predeploy)
  • l1BaseFeeScalar — System-configured scalar for calldata cost component
  • l1BlobBaseFeeScalar — System-configured scalar for blob cost component
  • compressedTxSize — Estimated compressed size of the signed transaction

GasPriceOracle

interface IGasPriceOracle {
    /// @notice Estimate L1 data fee for raw signed transaction bytes
    function getL1Fee(bytes memory _data) external view returns (uint256);

    /// @notice Get current L1 base fee (read from L1Block)
    function l1BaseFee() external view returns (uint256);

    /// @notice Ecotone: get blob base fee
    function blobBaseFee() external view returns (uint256);

    /// @notice Ecotone: get base fee scalar
    function baseFeeScalar() external view returns (uint32);

    /// @notice Ecotone: get blob base fee scalar
    function blobBaseFeeScalar() external view returns (uint32);

    /// @notice Check if Ecotone is active
    function isEcotone() external view returns (bool);

    /// @notice Check if Fjord is active
    function isFjord() external view returns (bool);

    /// @notice Fjord: estimate compressed size using FastLZ
    function getL1GasUsed(bytes memory _data) external view returns (uint256);
}

IGasPriceOracle constant GAS_ORACLE =
    IGasPriceOracle(0x420000000000000000000000000000000000000F);

Estimating Total Cost in TypeScript

import { createPublicClient, http, parseAbi } from "viem";
import { optimism } from "viem/chains";

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

const GAS_ORACLE = "0x420000000000000000000000000000000000000F" as const;

const gasPriceOracleAbi = parseAbi([
  "function getL1Fee(bytes memory _data) external view returns (uint256)",
  "function l1BaseFee() external view returns (uint256)",
  "function blobBaseFee() external view returns (uint256)",
  "function baseFeeScalar() external view returns (uint32)",
  "function blobBaseFeeScalar() external view returns (uint32)",
]);

async function estimateTotalCost(serializedTx: `0x${string}`) {
  const [l2GasEstimate, gasPrice, l1DataFee] = await Promise.all([
    client.estimateGas({ data: serializedTx }),
    client.getGasPrice(),
    client.readContract({
      address: GAS_ORACLE,
      abi: gasPriceOracleAbi,
      functionName: "getL1Fee",
      args: [serializedTx],
    }),
  ]);

  const l2ExecutionFee = l2GasEstimate * gasPrice;
  const totalFee = l2ExecutionFee + l1DataFee;

  return {
    l2ExecutionFee,
    l1DataFee,
    totalFee,
  };
}

Gas Optimization Tips

  • Minimize calldata: the L1 data fee scales with transaction data size. Fewer bytes = lower L1 fee.
  • Use 0 bytes when possible: zero bytes cost 4 gas in calldata vs 16 gas for non-zero bytes.
  • Batch operations: one large transaction costs less in L1 data fee overhead than many small ones.
  • After Ecotone, blob pricing makes L1 data fees much cheaper and more stable than pre-Ecotone calldata pricing.

Standard Bridge

The Standard Bridge enables ETH and ERC20 transfers between L1 and L2. It is a pair of contracts: L1StandardBridge on Ethereum and L2StandardBridge (predeploy) on OP Mainnet.

Bridge ETH: L1 → L2

interface IL1StandardBridge {
    /// @notice Bridge ETH to L2. Appears at recipient address on L2 after ~1-3 min.
    function depositETH(uint32 _minGasLimit, bytes calldata _extraData) external payable;

    /// @notice Bridge ETH to a different address on L2.
    function depositETHTo(
        address _to,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;
}

Bridge ETH: L2 → L1

interface IL2StandardBridge {
    /// @notice Initiate ETH withdrawal to L1. Requires prove + finalize after 7 days.
    function withdraw(
        address _l2Token,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;
}

// Withdraw ETH from L2 to L1
// _l2Token = 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000 (legacy ETH representation)
// Send ETH as msg.value, set _amount to the same value

Bridge ERC20: L1 → L2

interface IL1StandardBridge {
    /// @notice Bridge ERC20 to L2. Token must have a corresponding L2 representation.
    function depositERC20(
        address _l1Token,
        address _l2Token,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external;

    function depositERC20To(
        address _l1Token,
        address _l2Token,
        uint256 _amount,
        address _to,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external;
}

Bridge ERC20: L2 → L1

interface IL2StandardBridge {
    function withdraw(
        address _l2Token,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;

    function withdrawTo(
        address _l2Token,
        address _to,
        uint256 _amount,
        uint32 _minGasLimit,
        bytes calldata _extraData
    ) external payable;
}

Withdrawal Lifecycle (L2 → L1)

Every L2→L1 withdrawal requires three L1 transactions:

  1. Initiate — Call withdraw on L2StandardBridge or L2CrossDomainMessenger. Produces a withdrawal hash.
  2. Prove — After the L2 output root containing your withdrawal is proposed on L1 (~1 hour), call proveWithdrawalTransaction on OptimismPortal.
  3. Finalize — After the 7-day challenge period, call finalizeWithdrawalTransaction on OptimismPortal.
import { getWithdrawals, getL2Output } from "viem/op-stack";

// After initiating withdrawal on L2, get the receipt
const l2Receipt = await publicClient.getTransactionReceipt({ hash: l2TxHash });

// Build withdrawal proof (after output root is proposed, ~1 hour)
const output = await getL2Output(l1Client, {
  l2BlockNumber: l2Receipt.blockNumber,
  targetChain: optimism,
});

// Prove on L1
const proveHash = await walletClient.proveWithdrawal({
  output,
  withdrawal: withdrawals[0],
  targetChain: optimism,
});

// Wait 7 days, then finalize on L1
const finalizeHash = await walletClient.finalizeWithdrawal({
  withdrawal: withdrawals[0],
  targetChain: optimism,
});

SuperchainERC20

SuperchainERC20 is a cross-chain token standard enabling native token transfers between OP Stack chains in the Superchain. Tokens implementing this standard can move between chains without traditional bridge locking.

Interface

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";

/// @notice Interface for tokens that support cross-chain transfers within the Superchain.
interface ICrosschainERC20 {
    /// @notice Emitted when tokens are minted via a cross-chain transfer.
    event CrosschainMint(address indexed to, uint256 amount, address indexed sender);

    /// @notice Emitted when tokens are burned for a cross-chain transfer.
    event CrosschainBurn(address indexed from, uint256 amount, address indexed sender);

    /// @notice Mint tokens on this chain as part of a cross-chain transfer.
    /// @dev Only callable by the SuperchainTokenBridge.
    function crosschainMint(address _to, uint256 _amount) external;

    /// @notice Burn tokens on this chain to initiate a cross-chain transfer.
    /// @dev Only callable by the SuperchainTokenBridge.
    function crosschainBurn(address _from, uint256 _amount) external;
}

Implementation

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import {ICrosschainERC20} from "./ICrosschainERC20.sol";

/// @dev SuperchainTokenBridge predeploy address — same on all OP Stack chains
address constant SUPERCHAIN_TOKEN_BRIDGE = 0x4200000000000000000000000000000000000028;

contract MySuperchainToken is ERC20, ICrosschainERC20 {
    constructor() ERC20("MySuperchainToken", "MST") {
        _mint(msg.sender, 1_000_000 * 1e18);
    }

    function crosschainMint(address _to, uint256 _amount) external override {
        require(msg.sender == SUPERCHAIN_TOKEN_BRIDGE, "Only bridge");
        _mint(_to, _amount);
        emit CrosschainMint(_to, _amount, msg.sender);
    }

    function crosschainBurn(address _from, uint256 _amount) external override {
        require(msg.sender == SUPERCHAIN_TOKEN_BRIDGE, "Only bridge");
        _burn(_from, _amount);
        emit CrosschainBurn(_from, _amount, msg.sender);
    }
}

Cross-Chain Transfer Flow

  1. User calls SuperchainTokenBridge.sendERC20 on the source chain
  2. Bridge calls crosschainBurn on the token contract (burns on source)
  3. A cross-chain message is relayed to the destination chain
  4. Bridge calls crosschainMint on the destination chain's token contract (mints on destination)

OP Stack

The OP Stack is the modular, open-source framework for building L2 blockchains. OP Mainnet, Base, Zora, Mode, and others are all OP Stack chains forming the Superchain.

Key Components

ComponentDescription
op-nodeConsensus client — derives L2 blocks from L1 data
op-gethExecution client — modified go-ethereum
op-batcherPosts transaction data to L1 (calldata or blobs)
op-proposerProposes L2 output roots to L1
op-challengerRuns fault proof games to challenge invalid proposals

Superchain

The Superchain is a network of OP Stack chains sharing:

  • Bridge contracts on L1
  • Sequencer coordination
  • Governance via the Optimism Collective
  • Interoperability messaging

Current Superchain members include OP Mainnet, Base, Zora, Mode, Fraxtal, Metal, and others. All share the same upgrade path and security model.

Building a Custom OP Chain

Use the OP Stack to launch your own chain:

# Clone the optimism monorepo
git clone https://github.com/ethereum-optimism/optimism.git
cd optimism

# Install dependencies
pnpm install

# Configure your chain (edit deploy-config)
# Deploy L1 contracts
# Start op-node, op-geth, op-batcher, op-proposer

Refer to the OP Stack Getting Started Guide for complete chain deployment.

Governance

The Optimism Collective governs the protocol through a bicameral system:

  • Token House — OP token holders vote on protocol upgrades, incentive programs, and treasury allocations
  • Citizens' House — Soulbound "citizen" badges vote on retroactive public goods funding (RetroPGF)

OP Token

PropertyValue
Address (L2)0x4200000000000000000000000000000000000042
Address (L1)0x4200000000000000000000000000000000000042 is the L2 predeploy; L1 address is 0x4200000000000000000000000000000000000042 bridged
Total supply4,294,967,296 (2^32)
TypeGovernance only (no fee burn or staking yield)

Delegation

OP token holders delegate voting power to active governance participants:

import { parseAbi } from "viem";

const opTokenAbi = parseAbi([
  "function delegate(address delegatee) external",
  "function delegates(address account) external view returns (address)",
  "function getVotes(address account) external view returns (uint256)",
]);

const OP_TOKEN = "0x4200000000000000000000000000000000000042" as const;

// Delegate voting power
const hash = await walletClient.writeContract({
  address: OP_TOKEN,
  abi: opTokenAbi,
  functionName: "delegate",
  args: [delegateAddress],
});

Key Differences from Ethereum

FeatureEthereumOP Mainnet
Block time12 seconds2 seconds
Gas pricingSingle base feeL2 execution + L1 data fee
block.numberL1 block numberL2 block number
Finality~15 minutes (2 epochs)7 days for L2→L1 (challenge period)
SequencingDecentralized validatorsCentralized sequencer (OP Labs)
PREVRANDAOBeacon chain randomnessSequencer-set value (NOT random, do NOT use for randomness)
PUSH0Supported (Shanghai+)Supported
block.difficultyAlways 0 post-mergeAlways 0

Opcodes Differences

  • PREVRANDAO (formerly DIFFICULTY) — Returns the sequencer-set value, NOT true randomness. Never use for on-chain randomness. Use Chainlink VRF or a commit-reveal scheme.
  • ORIGIN / CALLER — Work normally for L2 transactions. For L1→L2 deposits, the origin is aliased (see Sender Aliasing).
  • All other opcodes behave identically to Ethereum.

Unsupported Features

  • No native account abstraction (EIP-4337) — Use third-party bundlers (Pimlico, Alchemy, Stackup).
  • No eth_getProof with pending block tag — Use latest instead.

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