An autopsy found that a sequencer error was responsible for two outages of Coinbase’s Layer 2 network last week.

Base engineering team he said in Saturday’s autopsy, they identified a bug in the sequencer’s block building logic that allowed a “stale log state” to persist after transaction validation failed.

“The block constructor received an invalid transaction that failed as expected, but erroneously did not clear the log state of the accounts and memory locations that were accessed,” the team said.

Base layer 2 network runs a single sequencer, which means one mistake can stop everything. It is a centralized blockchain component that decides the order of transactions and is responsible for failures on other Layer 2 chains, including Arbitrum, OP Mainnet, and zkSync Era.

On Thursday and Friday, the Base mainnet experienced two interruptions in block production, the first lasting 116 minutes and the second 20 minutes.

There was a complete stoppage of recent Layer 2 blocks, and the sequencer and validator nodes were unable to move beyond the invalid block until sequencing was restored.

The team fixed the crashes by patching the sequencers to ensure the log state was updated correctly during execution.

However, mitigation took longer than expected “due to infrastructure conditions unrelated to the original fault,” they said.

After the system was reset, a “race condition” also occurred that prevented the sequencers from catching up, causing a second crash.

Related: Coinbase resumes block production after a 2-hour break

In the future, Base’s engineering team plans to improve the protocol’s “fuzzy testing,” which involves bombarding the system with enormous amounts of random, garbled or unexpected input to find errors, and building in “seamless recovery” so that validator nodes don’t need to be manually restarted during future incidents.

This is not the first failure of the Base

This is not the first sequencer failure at Base, which in September 2024 stopped block production for 17 minutes, and in August 2025 for about half an hour.

Base is the second largest Layer 2 network in terms of total secured value, which is just under $11 billion. According to to L2beat.

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