Layer-2 networks move fast—and occasionally hit the brakes. On 2 October 2026, the Arbitrum Security Council completed an emergency action that temporarily paused activation of new Stylus contracts on Arbitrum One and Nova, and installed a permissionless guard for One-Step Proof settlement under BoLD on Arbitrum One. [1]
Arbitrum is an Ethereum “rollup”—a chain that processes transactions off Ethereum’s main layer then posts data back for security. Stylus lets developers deploy contracts compiled to WebAssembly (WASM), not only the usual Ethereum Virtual Machine (EVM) / Solidity path.
What happened?
According to the Arbitrum Foundation’s Security Council forum post, the upgrade completed at about 11:30 EST on 2 October 2026. The bundle did two things: [1]
- Stylus pause: raised the WASM activation gas parameter (
ArbOwner.setWasmActivationGas(2^64 - 1)) so new Stylus activations become prohibitively expensive on One and Nova. - BoLD OSP guard: added a permissionless pause capability for One-Step Proof settlement of Arbitrum One on Ethereum if conflicting answers appear where only one should be valid.
Official docs confirm: you cannot activate new or expired Stylus contracts while the pause holds; already-active Stylus contracts keep running until they expire; Solidity / EVM deployment and execution are unaffected. [2]
Why did the Council act?
The Foundation says AI-assisted tooling has increased sophisticated attacks on hand-crafted WASM programmes that bypass the standard Stylus compiler toolchain—programmes designed to degrade chain performance for everyone else. Separately, the BoLD guard is framed as a precautionary response to a class of publicly detectable one-step-proof issues, so settlement can be halted while a fix is prepared. [1]
Key official characterisation: known Stylus bugs reviewed so far primarily affect chain liveness (denial-of-service-class risk), and do not put user funds at risk—that is the Foundation’s statement about findings to date, not an independent guarantee. [1][2]
Impact on builders and users
- No new Stylus activations (including new versions that need activation). [1][2]
- Active Stylus contracts continue; keepalive renewals before expiry remain available per docs. [2]
- EVM / Solidity unaffected. [1][2]
- If the BoLD guard pauses settlement, Arbitrum One can keep processing, but unconfirmed messages to Ethereum (such as withdrawals) would wait until resumed. [1]
The Foundation says it will work with the ArbitrumDAO on how and when to reopen activations. [1][2]
What we don’t know
- How long the Stylus pause will last; next steps are TBD with the DAO. [1]
- Whether future findings could change the “funds not at risk” characterisation of known issues. [1]
- Exact production timelines for any permanent Stylus hardening beyond this temporary configuration change. [1]
The Bottom Line
Arbitrum’s Security Council has temporarily blocked new Stylus activations on One and Nova while leaving existing Stylus and all EVM activity running, and added a BoLD settlement guard on One. Official posts frame known Stylus issues as liveness risks, not theft of funds—treat that as the Foundation’s current claim, and the pause as temporary pending DAO next steps.
Sources
- Arbitrum Foundation forum, Security Council Emergency Action – 2/10/2026, 2 October 2026 — https://forum.arbitrum.foundation/t/security-council-emergency-action-2-10-2026/31530
- Arbitrum Docs, Temporary pause on new Stylus activations — https://docs.arbitrum.io/notices/stylus-activation-pause-notice
