Arbitrum Sepolia testnet stops producing blocks after consensus failure at 204606366

Arbitrum Sepolia, Arbitrum's main testnet, stopped producing blocks after a consensus failure at block 204606366. The incident triggered a split between ARM and x86 node operators and disrupted activity from 6:44 AM to 9:02 PM. Engineers at Offchain Labs are deploying emergency mitigations while a longer-term Nitro update and new snapshot are planned.