Bridge USDC to your OP Stack Rollup

Locate Bridge Contracts

In the Conduit UI, navigate to the Apps section. Click on Your Apps and select Bridged USDC. You’ll find the Installation Details in the bottom-right corner, including contract addresses for:

• Bridged USDC (Rollup)
• USDC (Settlement Layer)
• Bridge (Rollup)
• Bridge (Settlement Layer)
• Rollup Factory (Rollup)

Export these addresses as environment variables:

$
export ROLLUP_USDC_TOKEN_ADDRESS=<Bridged USDC>

$
export ROLLUP_USDC_BRIDGE_ADDRESS=<Bridge (Rollup)>

$
export SETTLEMENT_USDC_BRIDGE_ADDRESS=<Bridge (Settlement Layer)>

Set settlement layer variables

Pick your settlement layer and export the Settlement USDC Token Address and the RPC URL as environment variables:

$
export SETTLEMENT_USDC_TOKEN_ADDRESS=0x....

$
export SETTLEMENT_RPC_URL=https://...

Configure Foundry with your wallet

We need to sign the transactions with a private key. Refer to Foundry’s Key Management Best Practices for production use.

The following steps will utilize the --private-key flag and the $PRIVATE_KEY environment variable. Set the environment variable with the following command:

$
export PRIVATE_KEY=...

If you’re using a different method, replace --private-key $PRIVATE_KEY with the appropriate flag in the commands below.

Fund your wallet

Make sure your wallet is funded with the native token and USDC on the settlement layer. If you are bridging onto a Testnet you can claim some testnet USDC here: Circle Testnet Faucet.

Approve

Set the amount you want to bridge

$
export AMOUNT=100

Approve the Optimism bridge contract on the settlement layer to transfer your USDC:

$
cast send $SETTLEMENT_USDC_TOKEN_ADDRESS "approve(address,uint256)" $SETTLEMENT_USDC_BRIDGE_ADDRESS $AMOUNT --rpc-url $SETTLEMENT_RPC_URL --private-key $PRIVATE_KEY

Bridge

Bridge USDC to your rollup:

$
cast send $SETTLEMENT_USDC_BRIDGE_ADDRESS "sendMessage(address,uint256,uint32)" $(cast wallet address $PRIVATE_KEY) $AMOUNT 100000 --rpc-url $SETTLEMENT_RPC_URL --private-key $PRIVATE_KEY

Approve

Approve the rollup bridge contract to transfer your USDC:

$
cast send $ROLLUP_USDC_TOKEN_ADDRESS "approve(address,uint256)" $ROLLUP_USDC_BRIDGE_ADDRESS $AMOUNT --rpc-url $ROLLUP_RPC_URL --private-key $PRIVATE_KEY

Bridge

Send USDC from your rollup back to the Settlement Layer:

$
cast send $ROLLUP_USDC_BRIDGE_ADDRESS "sendMessage(address,uint256,uint32)" $(cast wallet address $PRIVATE_KEY) $AMOUNT 100000 --rpc-url $ROLLUP_RPC_URL --private-key $PRIVATE_KEY