Base Post-Mortem Blames Sequencer Bug For Two Outages

A sequencer bug triggered two outages on Coinbase’s layer-2 network Base last week, according to a Saturday post mortem. The engineering team found a flaw in sequencer block-building logic that let “stale journal state” persist after a failed transaction validation. An invalid transaction failed during execution as expected, but it didn’t clear the journal state tracking accessed accounts and storage slots, jamming the system.

Since Base runs on a single sequencer, one bug can halt the entire network. This has also caused outages on other layer-2s like Arbitrum, OP Mainnet and zkSync Era. Thursday’s outage lasted 116 minutes, and Friday’s lasted 20 minutes, both completely stopping new block production.

Fix Took Longer Than Expected

The team patched the sequencers to properly update journal state during execution. But the fix took longer than planned due to unrelated infrastructure issues. A “race condition” after the system reset also stopped sequencers from catching up, triggering the second outage.

Not Base’s First Sequencer Issue

Going forward, the team plans to boost fuzz testing and build “graceful recovery” so validator nodes won’t need manual restarts. This isn’t new for Base, which saw a 17-minute outage in September 2024 and a roughly 30-minute one in August 2025. Base remains the second-largest layer-2 by total value secured, just under $11 billion.