Arbitrum Sepolia Nitro halts block production for hours

Arbitrum’s Sepolia testnet has stalled for several hours after a suspected issue in Nitro, the network’s execution engine. Arbitrum developers said block production was temporarily paused due to a potential block divergence tied to Nitro. On-chain data from the Arbitrum Sepolia explorer shows no new transactions processed for roughly 3–4 hours. The explorer indicates it is still “scanning new transactions,” but batch and transaction timestamps have not advanced, confirming the testnet is effectively frozen rather than merely delayed. Block divergence occurs when nodes disagree on chain state, breaking consensus and preventing further block production. Arbitrum said no action is required from infrastructure providers at this stage, but node operators should prepare to upgrade once a patched Nitro release is available. The outage mainly impacts developers using Arbitrum Sepolia for contract deployment and testing. Arbitrum advised pausing time-sensitive testing and using alternative environments until recovery. Importantly for traders, this is limited to the Sepolia testnet and does not affect the Arbitrum mainnet. No user funds are at risk, though the incident highlights reliability risk in core scaling/execution infrastructure. Arbitrum is actively investigating and expects a new Nitro version to restore normal block production on Arbitrum Sepolia.