Arbitrum Elara Upgrade: Expanding Stylus Limits and Adding Orbit Compliance Filters

Arbitrum deployed ArbOS 61, codename "Elara," on mainnet August 20, 2026. The upgrade ships three state-level changes: a compliance-filter primitive for Orbit chains, priority-fee routing, and a fourfold expansion of the Stylus contract size limit — from 24 KB to 96 KB. For developers shipping on Arbitrum One or building dedicated chains, each change alters deployment constraints and attack surface in measurable ways.

Stylus Contract Size: 24 KB → 96 KB

The most immediate developer-facing mutation. Stylus — Arbitrum's framework for compiling Rust, C, and C++ into WASM-based contracts — previously enforced a 24 KB ceiling on deployed bytecode. That limit forced aggressive code splitting or dependency pruning for anything non-trivial.

ArbOS 61 raises the cap to 96 KB. Quadruple the space. This is a direct expansion of the contract's on-chain footprint and changes the calculus for monolithic vs. modular architectures on Stylus. Larger single contracts mean fewer cross-contract calls, fewer external delegatecall hops, and fewer reentrancy surfaces introduced by design. The tradeoff: a larger bytecode blob increases the gas cost of contract deployment and widens the static analysis surface for auditors.

If you maintain Stylus contracts that were previously split across multiple proxies to stay under 24 KB, re-evaluate whether consolidation is now viable. Fewer deployed artifacts reduce composability risk but increase per-contract complexity. Audit scope shifts accordingly.

Compliance Filters: A New State Gate for Orbit Chains

Elara introduces optional transaction-blocking for operators of dedicated Arbitrum chains — private or consortium Orbit deployments. The mechanism allows operators to maintain restricted address lists and reject transactions (transfers, contract calls) originating from flagged addresses. Integration points exist for third-party compliance providers such as TRM Labs and Chainalysis.

This filter is disabled on Arbitrum One and Arbitrum Nova. Public chain users see zero change in execution semantics. The feature targets enterprise operators who need deterministic transaction gating at the sequencer level.

From a security architecture standpoint, this is a state-level access control primitive injected into the transaction pipeline. It does not alter EVM opcodes or contract-level execution. It operates upstream — at the sequencer or block-building layer — before transactions reach the state transition function. The invariant here: on public Arbitrum networks, no address filtering occurs. On dedicated chains, the operator controls the filter list. There is no on-chain governance mechanism for this feature; it is an off-chain operator configuration.

For developers building on Orbit chains, understand that transaction rejection now happens before your contract code ever executes. If your application assumes all submitted transactions reach the EVM, that assumption no longer holds on filtered Orbit chains. Design accordingly — particularly for time-sensitive DeFi primitives where transaction ordering and inclusion guarantees matter.

Priority-Fee Support

Elara adds priority-fee functionality, enabling transactions to signal urgency levels. This aligns Arbitrum's fee market closer to Ethereum's EIP-1559 model, where base fees and priority tips create a two-dimensional fee structure.

The practical impact: on dedicated chains, operators gain finer control over transaction sequencing. On public Arbitrum networks, this gives users and MEV-aware protocols a mechanism to express ordering preferences through fee signaling rather than relying solely on first-come-first-served sequencing.

What to Verify Now

• Stylus deployments: Audit any contract previously constrained by the 24 KB limit. Check if consolidation is safe and whether larger bytecode introduces new attack surface.
• Orbit chain operators: If you run a dedicated chain, decide whether compliance filtering is required. Understand that enabling it changes transaction inclusion guarantees at the sequencer level.
• Cross-chain integrations: If your protocol bridges to or from Orbit chains, confirm whether the target chain has filtering enabled. A transaction that succeeds on Arbitrum One may be rejected on a filtered Orbit chain — not at the contract level, but before execution.
• Priority-fee logic: Review any gas estimation or transaction submission code. Hardcoded gas strategies may need updating to account for the new priority-fee dimension.

Elara is not a consensus-layer change. It is an operating system upgrade — ArbOS, the execution environment that sits between the sequencer and the EVM. State transitions on Arbitrum One remain deterministic and unchanged for end users. But the contract size expansion and the compliance filter primitive represent two distinct vectors of capability growth: one for developers, one for operators. Know which applies to your deployment.