Arbitrum activates ArbOS 61 Elara with optional compliance filters for Orbit chains

Arbitrum flipped the switch on its ArbOS 61 “Elara” upgrade on August 20 at 17:00 UTC, rolling out a bundle of infrastructure changes across both Arbitrum One and Arbitrum Nova. The most eyebrow-raising feature: optional protocol-level transaction screening baked directly into the network’s architecture.

Before anyone starts drafting outrage tweets, a key distinction matters here. The compliance-filtering tools are disabled by default on Arbitrum One and Nova. They’re designed exclusively for operators of dedicated Orbit chains, Arbitrum’s customizable Layer 3 networks, who face regulatory obligations in their specific jurisdictions.

What Elara actually changes

Stylus, Arbitrum’s framework that lets developers write smart contracts in languages like Rust and C++ instead of just Solidity, got a significant capacity boost. The compressed contract code size limit jumped from 24 KB to 96 KB on Arbitrum One. That’s a fourfold expansion, meaning developers can deploy substantially more complex applications without running into size constraints that previously forced awkward workarounds like splitting contracts across multiple deployments.

Beyond Stylus, Elara introduces customizable priority fees for Orbit chain operators. The upgrade also ships an alternative data-availability interface for dedicated chains and modifies base-fee administration across the network. On the housekeeping side, Elara fixes gas-refund logic errors that surfaced during earlier testing phases, cleaning up technical debt carried over from the previous ArbOS 51 “Dia” release.

All node operators were required to upgrade their systems to Nitro version 3.11.3 or higher before activation. Running anything older than that after the switch means your node is effectively out of consensus.

The compliance question

Arbitrum One and Nova, the networks that the vast majority of users interact with, have these filters turned off. The feature exists as an opt-in tool for Orbit chain operators who are building application-specific chains and need to satisfy regulators in their operating jurisdictions.

The ArbitrumDAO approved the upgrade through its constitutional governance process, meaning ARB token holders voted on these changes before they went live. The proposal first hit the Arbitrum Sepolia testnet on June 29, giving roughly seven weeks of testing before mainnet deployment.