AMP: Arc Multi-Proposer Protocol with Bounded Inclusion Guarantees

AMP (Arc Multi-Proposer Protocol) is a consensus layer introduced by Circle for the Arc blockchain that replaces the traditional single-block-assembly model to eliminate unilateral validator control over transaction inclusion and ordering.

Key Mechanisms and Guarantees:

• Decoupled Roles: Dedicated proposer nodes collect user transactions into payloads and broadcast them to validators, who only run consensus on payload identifiers rather than full transaction data.
• Bounded Inclusion: Any payload attested by more than 2f validators (a super-majority) at height h must appear in the block finalized at height h+1, preventing censorship by the block assembler.
• Deterministic Ordering: A fixed ordering function sequences transactions across all finalized payloads, removing the assembler’s discretion to reorder or front-run transactions.
• MEV Mitigation: By stripping the block assembler of inclusion and ordering power, AMP curbs Maximal Extractable Value (MEV) strategies such as front-running and sandwich attacks, aligning blockchain behavior with traditional financial market regulations.
• Performance: The protocol removes the need for a shared mempool and decouples dissemination from agreement, aiming to increase throughput and resolve single-point-of-failure bottlenecks inherent in classic BFT protocols.

Published on arXiv:2605.23677v2 in May 2026, AMP is designed to compose with BFT algorithms like Tendermint that support vote extensions, ensuring that financial infrastructure adheres to regulatory standards for fairness and market integrity.

The material addresses a core fairness problem in blockchain-based financial systems: the validator or builder that assembles a block has unilateral control over which transactions are included and in what order. This gives rise to front-running, self-preferencing, sandwich attacks, and other forms of market manipulation that are closely analogous to prohibited conduct in regulated securities markets. The paper frames this not only as an economic inefficiency but as a market-integrity gap: without protocol-level rules, blockchain transaction markets lack the structural protections that traditional exchanges rely on.

Its central contribution is the AMP: Arc Multi-Proposer Protocol, which proposes to distribute block-construction authority across multiple proposers rather than concentrating it in a single builder. The key idea is to provide bounded inclusion guarantees, meaning the protocol constrains how much any one proposer can delay, exclude, or reorder transactions beyond a defined limit. By introducing a multi-proposer coordination structure, AMP aims to replace unilateral builder discretion with a more checkable, protocol-enforced ordering process, reducing the worst-case power of individual proposers over transaction inclusion.

This matters because it moves the solution to front-running and manipulation from ex post governance or regulation toward protocol-level market design. For DeFi, payment settlement, and other financial applications on blockchains, bounded inclusion can make transaction timing less exploitable, improve fairness for ordinary users, and give regulators a concrete technical mechanism to evaluate. More broadly, the work contributes to the emerging literature on fair sequencing, MEV mitigation, and decentralized market integrity.