Base sequencer bug caused back-to-back network outages, post-mortem finds

Coinbase's layer-2 network Base suffered two outages last week due to a sequencer bug that allowed stale journal state to persist after a failed transaction. The first outage lasted 116 minutes, the second 20 minutes.

• A bug in Base's sequencer block-building logic caused two outages on June 25-26, lasting 116 and 20 minutes.
• The bug allowed stale journal state to persist after a transaction validation failure, halting block production.
• A 'race condition' after the system reset caused the second outage by preventing sequencers from catching up.
• Base plans to improve fuzz testing and build graceful recovery so validator nodes don't need manual restarts.
• This is not Base's first sequencer outage -- similar issues occurred in September 2024 and August 2025.

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