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After you have spun up your sequencer and batcher, you need to attach a proposer to post your L2 state roots data back onto L1 so we can prove withdrawal validity. The proposer is a critical component that enables trustless L2-to-L1 messaging and creates the authoritative view of L2 state from L1’s perspective.
Step 4 of 5: This tutorial is designed to be followed step-by-step. Each step builds on the previous one.
Automated Setup AvailableFor a complete working setup with all components, check out the automated approach in the code directory.
This guide assumes you already have a functioning sequencer, batcher, and the necessary L1 contracts deployed using op-deployer. If you haven’t set up your sequencer and batcher yet, please refer to the sequencer guide and batcher guide first. To see configuration info for the proposer, check out the configuration page.

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Understanding the proposer’s role

The proposer (op-proposer) serves as a crucial bridge between your L2 chain and L1. Its primary responsibilities include:
  • State commitment: Proposing L2 state roots to L1 at regular intervals
  • Withdrawal enablement: Providing the necessary commitments for users to prove and finalize withdrawals
The proposer creates dispute games via the DisputeGameFactory contract.

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Prerequisites

Before setting up your proposer, ensure you have: Running infrastructure:
  • An operational sequencer node
  • Access to a L1 RPC endpoint
Network information:
  • Your L2 chain ID and network configuration
  • L1 network details (chain ID, RPC endpoints)
For setting up the proposer, we recommend using Docker as it provides a consistent and isolated environment. Building from source is also available as an option.
If you prefer containerized deployment, you can use the official Docker images and do the following:
1

Set up directory structure and copy configuration files

# Create a proposer directory inside rollup
cd ../    # Go back to rollup directory if you're in batcher
mkdir proposer
cd proposer
# inside the proposer directory, copy the state.json file from the op-deployer setup
# Copy configuration files from deployer
cp ../deployer/.deployer/state.json .

# Extract the DisputeGameFactory address
GAME_FACTORY_ADDRESS=$(cat state.json | jq -r '.opChainDeployments[0].disputeGameFactoryProxyAddress')
echo "DisputeGameFactory Address: $GAME_FACTORY_ADDRESS"
2

Create environment variables file

OP Stack Standard VariablesThe proposer uses OP Stack standard environment variables following the OP Stack conventions. These are prefixed with OP_PROPOSER_ for proposer-specific settings.
# Create .env file with your actual values
cat > .env << 'EOF'
#  L1 Configuration - Replace with your actual RPC URLs
OP_PROPOSER_L1_RPC_URL=https://sepolia.infura.io/v3/YOUR_ACTUAL_INFURA_KEY

# L2 Configuration - Should match your sequencer setup
OP_PROPOSER_ROLLUP_RPC=http://op-node:8547

# Contract addresses - Extract from your op-deployer output
OP_PROPOSER_GAME_FACTORY_ADDRESS=YOUR_ACTUAL_GAME_FACTORY_ADDRESS

# Private key - Replace with your actual private key
OP_PROPOSER_PRIVATE_KEY=YOUR_ACTUAL_PRIVATE_KEY

# OP Stack proposer configuration (optional - defaults provided)
OP_PROPOSER_PROPOSAL_INTERVAL=3600s
OP_PROPOSER_GAME_TYPE=0
OP_PROPOSER_POLL_INTERVAL=20s
OP_PROPOSER_ALLOW_NON_FINALIZED=true
OP_PROPOSER_WAIT_NODE_SYNC=true
EOF
Important: Replace ALL placeholder values (YOUR_ACTUAL_*) with your real configuration values.
3

Create docker-compose.yml

If you get “failed to dial address” errors, ensure your proposer is in the same Docker network as your sequencer.Common fixes:
  • Add networks: - sequencer-node_default to your proposer’s docker-compose.yml
  • Use service names like op-geth:8545 and op-node:8547 in your .env file
  • Verify your sequencer network name with docker network ls

services:
  op-proposer:
    image: us-docker.pkg.dev/oplabs-tools-artifacts/images/op-proposer:v1.10.0
    volumes:
      - .:/workspace
    working_dir: /workspace
    ports:
      - "8560:8560"
    env_file:
      - .env
    command: >
      op-proposer
      --rpc.port=8560
      --log.level=info
      --log.format=json
    restart: unless-stopped
    networks:
      - sequencer-node_default

networks:
  sequencer-node_default:
    external: false
4

Start the proposer service

# Make sure your sequencer network exists
docker network create op-stack 2>/dev/null || true

# Start the proposer
docker-compose up -d

# View logs
docker-compose logs -f op-proposer
5

Verify proposer is running

# Check container status
docker-compose ps
6

Final directory structure

rollup/
├── deployer/            # From previous step
│   └── .deployer/      # Contains state.json
├── sequencer/          # From previous step
├── batcher/           # From previous step
└── proposer/         # You are here
    ├── state.json    # Copied from deployer
    ├── .env          # Environment variables
    └── docker-compose.yml # Docker configuration
Your proposer is now operational and will continuously submit state roots to L1!

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What’s Next?

Perfect! Your proposer is submitting state roots to L1. The final step is to set up the challenger to monitor and respond to disputes.

Spin up challenger →

Next: Configure and start op-challenger to monitor disputes and maintain your rollup’s security.

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