Bridging Architecture

Lombard is a direct route from Bitcoin to every chain it supports. LBTC and BTC.b mint natively from BTC on each supported chain, with no bridging step involved. Bridging is how tokens that are already minted move from one chain to another.

Every cross-chain transfer goes through a dual-verification system: independent approval from both the bridge infrastructure and the Security Consortium, providing a significantly higher security bar than single-layer bridges. Since September 2026, transfers between chains route through Ethereum, and Ethereum is the only bridge destination from the deprecated chains listed below.

Routing Through Ethereum

Cross-chain transfers follow a hub and spoke model anchored on Ethereum:

• Native minting is unchanged. LBTC and BTC.b mint directly from BTC on every supported chain. Hub and spoke only describes how already-minted tokens move between chains.
• Ethereum is the bridge hub. Every other supported chain has a single bridge lane to and from Ethereum.
• Transfers between two non-Ethereum chains route through Ethereum. Chains do not bridge directly to each other.

Fewer bridge contracts and message paths mean a smaller surface to secure and monitor, and let security budget and engineering resources concentrate on the lanes that carry the most value. Ethereum is also where LBTC and BTC.b liquidity runs deepest and integrations run widest.

Deprecated Chains (September 2026)

Native minting and redemption for LBTC and BTC.b are deprecated on TAC, Sonic, Katana, Berachain and Starknet, effective September 16, 2026. From TAC, Sonic, Katana and Berachain, the only remaining bridge route is to Ethereum, until December 10, 2026. The lock and mint bridge between Ethereum and Starknet remains in place. For BTC.b, Ethereum is the only valid destination: BTC.b does not bridge from Katana back to Avalanche or to any other chain.

Details, timeline and step-by-step instructions are on the Chain Support Update page.

How Bridging Works

When you transfer LBTC or BTC.b from one chain to another, the process involves burning tokens on the source chain and minting equivalent tokens on the destination chain. This burn-and-mint model ensures total supply consistency, the same amount of LBTC or BTC.b exists regardless of how it is distributed across chains.

Dual Verification

Every bridge transfer must be approved by two independent systems before completion:

1. Bridge Infrastructure, Chainlink CCIP validates the transfer through its own decentralized oracle networks
2. Security Consortium, The Lombard Consortium independently verifies and co-signs the transfer using its supermajority threshold (10 of 14 members)

Both approvals are required. If either system rejects the transfer, it does not proceed. This means an attacker would need to simultaneously compromise the bridge validators and a supermajority of the Consortium, a far higher bar than compromising either system alone.

Transfers between Ethereum and Sui use the Sui Bridge, which is secured by Sui’s own validator set. See Bridge Infrastructure below.

Bridge Infrastructure

Chainlink CCIP is the exclusive external bridge for EVM-compatible chains and Solana. Sui connects to Ethereum through the Sui Bridge.

LBTC Supported Chains

LBTC mints natively from BTC on every chain in this table. The bridge method describes how already-minted LBTC moves between that chain and Ethereum. CCIP lanes are listed in the Chainlink CCIP token directory ; every lane uses a burn-and-mint token pool.

Native minting and redemption deprecated since September 16, 2026:

BTC.b Supported Chains

BTC.b mints natively from BTC on every chain in this table. CCIP lanes are listed in the Chainlink CCIP token directory .

Deprecated, bridge to Ethereum only until December 10, 2026:

BTC.b is not deployed on Solana or Sui.

Bridge Transfer Flow

A cross-chain LBTC transfer follows these steps:

Timing

Bridge transfer times vary by route and bridge infrastructure:

• CCIP transfers, Typically complete within 10-30 minutes depending on source and destination chain finality
• Sui Bridge transfers, Typically 5-15 minutes, followed by a claim step on Sui to convert wLBTC to LBTC

Fees

Bridge transfers may incur gas fees on both the source and destination chains. Bridge protocol fees vary by route and provider. Lombard does not charge additional fees for cross-chain transfers beyond the underlying infrastructure costs.

Security Considerations

• Dual verification ensures no single system failure can result in unauthorized minting
• Rate limiting on bridge contracts prevents large-scale attacks even if signatures are compromised
• Pausable contracts allow the protocol to halt bridge operations if anomalous activity is detected
• Independent monitoring through Hexagate provides real-time alerts on bridge contract behavior
• Chainlink CCIP Risk Management Network provides an additional layer of independent validation on every CCIP route, monitoring for anomalous cross-chain activity
• Institutional-grade infrastructure backs CCIP, including an extensively audited codebase and certifications such as SOC 2 Type 2 and ISO/IEC 27001:2022

Next Steps

• Smart Contracts, View deployed bridge contracts on each chain
• Security Model, How bridging fits into the overall security architecture
• Infrastructure, Overview of Lombard’s infrastructure layer