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Arbitrum activated ArbOS 61 Elara on Aug. 20, adding optional protocol-level transaction screening, priority-fee support and an alternative data-availability interface for dedicated chains, while changing base-fee administration and expanding Stylus capacity on Arbitrum One.
The upgrade went live after approval through Arbitrum governance. The governance proposal included compliance and priority-fee capabilities in ArbOS 61 but left them intentionally disabled on Arbitrum One and Nova. The compliance filter is therefore not a new screening system for users of Arbitrum One; it is configurable tooling for owners of dedicated Arbitrum chains.
Chain Owners Control the Filter
Arbitrum's technical documentation says compliance filtering is off by default and that chain owners must explicitly configure and enable each component. An owner can select an external compliance provider, such as TRM Labs or Chainalysis, to produce a restricted-address list and can define rules covering transfers, contract calls and other interactions involving those addresses.
Enforcement operates at two levels. The sequencer simulates transactions and rejects those that violate the configured rules before they enter a block. For transactions submitted through the parent chain's Delayed Inbox, a sentinel can register the transaction hash with an onchain guardian so the state transition function forcibly fails it when it is included.
That second layer is designed to prevent a restricted user from bypassing the sequencer through Arbitrum's force-inclusion path. The documentation also says restricted addresses are stored as salted hashes rather than plaintext and recommends that chains wait at least 30 days after the ArbOS 61 release on Arbitrum One before adopting the feature.
Priority Fees Still Require Opt-In
Elara also gives dedicated-chain owners the ability to collect priority fees, or tips, but the feature ships disabled. Only the chain owner—typically an operator address or DAO—can turn collection on through the access-controlled `ArbOwner` precompile.
Collecting tips alone does not change transaction ordering. A chain must also update its sequencer logic to sort using the priority-fee field. On Arbitrum One, activating priority-fee collection still requires a separate constitutional DAO vote; Elara only installs the underlying capability.
For Arbitrum One's base fee, Elara introduces a `BaseFeeManager` contract that lets Offchain Labs adjust the minimum Layer 2 base fee within a DAO-approved range of 0.01 to 0.10 gwei. The delegation expires two years after mainnet activation, requires public notice through the Arbitrum forum and can be removed by the DAO. The upgrade does not itself raise fees.
The alternative data-availability API is also aimed at dedicated chains, allowing operators to connect providers without maintaining custom Nitro forks. Arbitrum One is not expected to use it because its transaction data settles on Ethereum. Elara separately raises the code-size limit for Stylus contracts from 24 KB to 96 KB; the change does not apply to Solidity contracts.