Fuel Fast Bridge

The Fuel Fast Bridge enables users to securely transfer crypto assets between EVM compatible chains (Base, Ethereum) and the Fuel network in 10 seconds or less. This is a dramatic improvement over the canonical bridge's 30 minute deposits and 1 day withdrawals.

Designed for seamless integration, the Fast Bridge operates transparently within applications like o2 Exchange. Users interact directly with the app while cross chain transfers happen automatically in the background, eliminating the need to manage bridging manually.

Universal Wrapped Assets

When assets are bridged to Fuel, they are represented as Universal Wrapped (UW) assets. These are wrapped versions of the original tokens that maintain 1:1 backing with their source assets locked in the bridge contracts.

Why Universal Wrapped Assets?

Universal wrapped assets provide a unified representation of bridged tokens on Fuel, regardless of their origin chain. This approach offers several advantages:

• Chain Abstraction: A single UW asset can represent the same token from multiple source chains
• Liquidity Consolidation: All bridged versions of an asset share the same liquidity pools
• Simplified Trading: Users don't need to worry about which chain their assets originally came from

Current Status

The Fast Bridge is currently live on mainnet with outposts deployed on:

• Base (live)
• Ethereum (live)
• BSC, Arbitrum, and Optimism (coming soon)

Its primary use case is currently onboarding o2 traders, with a broader rollout to the entire Fuel ecosystem planned in the future. Additional chains and Layer 2s will be added based on demand and strategic priorities.

Overview

The Fast Bridge operates through a sophisticated multi-signature architecture that ensures security while maintaining speed. Assets deposited on EVM chains are validated by multiple independent signers before being made available on Fuel, and withdrawals follow a similar verification process.

flowchart TD
    %% Users
    User([User])

    %% EVM Chains subgraphs
    subgraph ETHChain[Ethereum]
        ETH((Multisig))
    end

    subgraph OPChain[Optimism]
        OP((Multisig))
    end

    subgraph BASEChain[Base]
        BASE((Multisig))
    end

    %% Offchain subgraph
    subgraph Offchain[Offchain]
        Servers[Relayer Instances]
        Watchtower[WatchTower Service For Monitoring]
    end

    %% Fuel Ignition subgraph
    subgraph FuelIgnition[Fuel Ignition]
        AssetRegistry[(Asset Registry)]
        WrappedMinter[(WrappedAsset Minter)]
    end

    Recipient([Recipient])

    %% User deposits
    User -->|Deposit| ETH
    User -->|Deposit| OP
    User -->|Deposit| BASE

    %% Chains emit events
    ETH -->|Emit event| Servers
    OP -->|Emit event| Servers
    BASE -->|Emit event| Servers

    %% Server ↔ Watchtower
    Servers <--> Watchtower

    %% Offchain to Asset Registry
    Servers --> AssetRegistry

    %% Onchain minting
    AssetRegistry --> WrappedMinter -->|Wrapped Asset| Recipient

    %% Monitoring connection
    WrappedMinter -.- Watchtower

Key Components:

• EVM Chain Outposts: Multisig contracts on Base, Ethereum, and other EVM chains that hold deposited assets
• Server Instances: Offchain signers and proposers that validate cross chain events
• WatchTower Service: Monitoring system ensuring all events are captured and processed
• Asset Registry & WrappedAsset Minter: Onchain contracts on Fuel that manage asset creation and redemption

How the Fast Bridge Works

The Fast Bridge architecture consists of smart contracts on both the EVM and Fuel sides, coordinated by offchain relayers that monitor and facilitate cross chain operations.

Architecture Components

EVM (Source Chains)

Component	Purpose	Key Capabilities
Messenger Contract	Deposit Management	Whitelisted deposits, per token caps, emergency pause, upgradeable
Outpost Contract	Withdrawal Execution	Multisig approvals, signature collection, auto execution, asset release

Fuel (Destination Chain)

Component	Purpose	Key Capabilities
FastBridge Contract	Deposit Gateway	Multisig approvals, signature validation, quorum release
AssetRegistry Contract	Token Registry	Central registry, token registration, mint/burn routing
WrappedAssetMinter Contract	Asset Minting	Mints wrapped assets, burns on withdrawal, decimal conversion
GasOracle Contract	Fee Management	Gas price storage, fee calculation, price feed updates

Offchain Infrastructure

Component	Purpose	Key Capabilities
Indexers	Event Monitoring	WebSocket listeners, Envio primary, Sentio fallback, pipeline feed
Relayer	Transaction Coordination	Event monitoring, transaction batching, approval submission, multisig coordination
Monitoring	Observability	Prometheus metrics, JSON logs, latency tracking, error alerting

Deposit Flow (EVM → Fuel)

1. User Initiates Deposit: User calls deposit() on the Messenger contract

2. Contract Validation: The Messenger contract performs checks:

   • Token is whitelisted
   • Deposit cap (if any) isn't exceeded

3. Event Emission & Indexing: Deposit event is emitted and picked up by:

   • WebSocket (real-time)
   • Envio (fallback)

4. Relayer Processing: Relayer creates a deposit approval payload and sends it to FastBridge contract on Fuel

5. Multisig & Minting: Once the multisig threshold is satisfied, AssetRegistry contract instructs WrappedAssetMinter to mint the wrapped assets for the user on Fuel

Withdrawal Flow (Fuel → EVM)

1. User Initiates Withdrawal: User calls the withdrawal function on AssetRegistry (includes gas fee)

2. Fee Calculation: GasOracle supplies the current fee for the target chain

3. Event Emission & Indexing: FastBridgeWithdrawalEvent is emitted and indexed by:

   • Envio (primary)
   • Sentio (fallback)

4. Relayer Processing: Relayer reads the event, builds a withdrawal hash, and sends signer approvals to the Outpost contract on the destination EVM chain

5. Auto Execution: When the required number of signatures is collected, Outpost auto executes the token transfer to the user's address