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Across Protocol

7.0/10

Intent-based optimistic bridge using UMA's Oracle — fast, capital-efficient, and strong on L2-to-L2 transfers.

Updated: February 16, 2026AI Model: claude-4-opusVersion 1

Overview

Across Protocol is a cross-chain bridge that uses an optimistic verification model powered by UMA's Optimistic Oracle. Rather than verifying every transaction through validators or multisigs before execution, Across uses an intent-based architecture: professional relayers fill user bridge requests instantly on the destination chain by fronting their own capital, and are reimbursed from a liquidity pool after an optimistic challenge window passes.

Developed by Risk Labs (the team behind UMA Protocol), Across launched in late 2022 and has grown into one of the top bridges for Ethereum L2-to-L2 transfers. Its V3 architecture, introduced in 2024, fully embraced an intents-based model that separates user experience from settlement mechanics, enabling near-instant bridging with competitive fees.

Across's design philosophy prioritizes capital efficiency and speed. By having relayers front liquidity and settling through optimistic verification, the protocol avoids the latency of waiting for cross-chain proofs while maintaining security through economic incentives and UMA's dispute resolution mechanism.

Security

Bridge Architecture

Across uses a two-layer security model. The fast path relies on competitive relayers who fill user bridge intents on the destination chain using their own capital. Settlement occurs on Ethereum mainnet through UMA's Optimistic Oracle — relayers submit claims that funds were correctly transferred, and these claims can be disputed during a challenge window (typically 2 hours). If disputed, UMA's decentralized oracle resolves the dispute through a Schelling-point voting mechanism among UMA token holders.

Audit History

Across has been audited by OpenZeppelin, Code4rena, and other security firms. The UMA Optimistic Oracle underlying the protocol has its own extensive audit history from Trail of Bits, OpenZeppelin, and others. The combined protocol stack has undergone 10+ audits. Across maintains a bug bounty program for ongoing vulnerability discovery.

Exploit Track Record

Across has not suffered a major exploit as of early 2026. The optimistic verification model limits exposure — relayers bear the immediate risk of fronting capital, and the dispute window provides a safety net against incorrect settlements. However, the protocol is younger and smaller than some competitors, which partially explains the clean record. The UMA Oracle underlying the protocol has also maintained a clean security track record through years of production use.

Technology

Verification Method

Across uses UMA's Optimistic Oracle for settlement verification. The process works as follows: (1) A user expresses a bridge intent on the source chain, (2) A relayer fills the intent on the destination chain, (3) The relayer submits a reimbursement claim to the Optimistic Oracle on Ethereum mainnet, (4) After a challenge window passes without dispute, the relayer is reimbursed from the protocol's liquidity pool. This optimistic model means most transactions are never actively verified — they settle unless someone proves fraud.

Supported Chains

Across supports Ethereum mainnet, Arbitrum, Optimism, Base, Polygon, ZkSync Era, Linea, and other major EVM L2s. The protocol is specifically optimized for the Ethereum L2 ecosystem rather than attempting to connect every chain. This focused approach allows deeper liquidity and better pricing on supported routes. As of 2025-2026, Across has expanded to 10+ chains.

Speed & Cost

Across is one of the fastest bridges available, with fill times often under 30 seconds for supported routes. Relayers compete to fill intents quickly, creating a market-driven speed optimization. Fees are highly competitive — typically 0.04-0.12% for major routes — driven by relayer competition and capital efficiency. The intent-based model eliminates the need for users to wait for cross-chain finality.

Decentralization

Validator Set

Across does not use a traditional validator set. Instead, it relies on three decentralized components: (1) competitive relayers who can be anyone willing to front capital, (2) UMA's Optimistic Oracle with its decentralized voter set for dispute resolution, and (3) liquidity providers in the protocol's pools. Relayer operations are permissionless but require significant capital, leading to practical concentration among professional market makers.

Governance

The ACX token provides governance over protocol parameters, fee structures, and liquidity pool configurations. Governance operates through snapshot voting and on-chain execution. Risk Labs maintains significant influence over protocol development. The relationship between ACX governance and UMA governance (the underlying oracle) creates a layered governance structure.

Trust Assumptions

Users trust that: (1) at least one honest relayer will fill their intent, (2) the UMA Optimistic Oracle will correctly resolve any disputes, and (3) the challenge window is sufficient for watchers to identify and dispute fraudulent claims. The optimistic model assumes fraud will be detected and challenged — if all watchers fail to dispute a fraudulent claim, funds could be stolen from the liquidity pool.

Adoption

Volume

Across processes $300M-$700M in monthly bridge volume, with strong concentration in Ethereum L2 routes. It consistently ranks among the top 3-5 bridges by volume. The protocol has processed over $15B in cumulative volume. L2-to-L2 transfers (e.g., Arbitrum to Optimism) represent a growing share of volume.

Market Share

Across holds approximately 15-25% of the Ethereum L2 bridge market by volume, competing directly with Stargate and native canonical bridges. It has gained market share consistently due to superior speed and pricing. In bridge aggregator integrations, Across frequently wins on best-route calculations.

Integrations

Across is integrated into major bridge aggregators including Socket/Bungee, LI.FI, and Jumper Exchange. It is also used as backend infrastructure by several wallets and DeFi protocols for cross-chain transfers. The protocol's API enables programmatic bridging for institutional users and automated systems.

Tokenomics

Token Overview

The ACX token launched in November 2022 with a total supply of 1 billion tokens. Distribution allocated 50% to the community treasury, 22.5% to Risk Labs and the team, 17.5% to early investors, and 10% to an initial airdrop. Vesting schedules span 2-4 years for team and investor allocations.

Fee Model

Across generates revenue through bridge fees charged to users — a percentage of the transfer amount that varies by route and congestion. These fees are split between relayers (who earn a portion for fronting capital), liquidity providers (who earn yield on their deposited assets), and the protocol treasury. The competitive relayer market keeps fees low but ensures capital is available.

Value Capture

ACX captures value through governance over the protocol treasury (which accrues fees) and potential future fee-sharing mechanisms. Liquidity providers can stake LP tokens to earn ACX rewards, creating a flywheel between liquidity provision and token demand. The protocol's growing volume and fee revenue provide a tangible value base, making ACX one of the more fundamentally grounded bridge tokens.

Risk Factors

  • Optimistic assumption risk: The security model assumes fraud will always be detected and disputed within the challenge window. Sophisticated attacks that evade watcher detection, or a failure of the UMA Oracle voting mechanism, could result in fund loss from liquidity pools.
  • Relayer centralization: While relaying is permissionless, the capital requirements create practical concentration among a small number of professional relayers. Relayer collusion or failure could temporarily halt bridge operations.
  • UMA Oracle dependency: Across's security is fundamentally dependent on UMA's Optimistic Oracle. A compromise or failure of the UMA voting system would directly impact Across settlement security.
  • L2 focus limits addressable market: Across's focus on Ethereum L2s means it misses volume from non-EVM chains and cross-ecosystem transfers. This strategic focus could become a limitation if non-EVM chains gain bridge volume.
  • Liquidity pool risk: Liquidity providers face the risk of pool depletion through fraudulent relayer claims that pass the optimistic challenge window. While this hasn't occurred, it remains a tail risk inherent to the design.

Conclusion

Across Protocol represents one of the most elegant bridge designs in crypto. The intent-based architecture with optimistic verification achieves a rare combination of speed, low cost, and reasonable security. By letting relayers front capital and settling optimistically through UMA's Oracle, Across avoids the latency of active verification while maintaining economic security guarantees.

The protocol's focus on the Ethereum L2 ecosystem has proven strategically sound — as L2 adoption accelerates, the demand for fast and cheap L2-to-L2 transfers has grown significantly. Across's competitive metrics in speed and pricing have earned it substantial market share and integration into major aggregators.

The primary trade-offs are the optimistic security assumptions (fraud must be detected to be prevented) and the dependency on UMA's Oracle infrastructure. These are reasonable trade-offs for the performance gains, but users should understand that Across's security model is fundamentally different from actively-verified bridges — it assumes honesty and penalizes dishonesty, rather than proving correctness before execution.

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