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Base said its June 25 and 26 mainnet outages lasted roughly 116 minutes and 20 minutes respectively, and that both were triggered by the same sequencer block-building bug. The flaw allowed a stale journal state to persist after a failed transaction, producing a block with an invalid state transition. Funds were not affected and the integrity of the chain was not compromised.
Why it matters
Two production halts inside a 48-hour window, traced to one shared bug, are an unusual concentration for a network processing base-layer throughput for Coinbase-linked flows. The post-mortem frames funds and chain integrity as intact, but the failure mode, an invalid state transition slipping through block production, is a category operators take seriously because downstream reorg handling and sequencer failover paths sit close to it.
Market impact
Base says the bug has been fixed and that it plans to strengthen protocol fuzz testing, load testing, monitoring and network recovery mechanisms. For builders and bridges sitting on top of Base, the watch item is whether the upgraded test coverage catches the next class of stale-state bugs before they reach mainnet, not the two specific incidents themselves.
Source: [Postmortem: June 25th Block Production Outage — Base Engineering Blog](https://blog.base.dev/postmortem-june-25th-block-production-outage)
Frequently asked questions
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How long did each Base mainnet outage last?
Base said the June 25 outage lasted about 116 minutes and the June 26 outage lasted about 20 minutes.
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What caused both Base outages?
Both were triggered by the same sequencer block-building bug, which allowed a stale journal state to persist after a failed transaction and produced a block with an invalid state transition.
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Were user funds affected by the Base outages?
Base said funds were not affected and the integrity of the chain was not compromised.
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Has the Base sequencer bug been fixed?
Base said the bug has been fixed and outlined stronger protocol fuzz testing, load testing, monitoring and network recovery mechanisms as follow-up work.
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Why do two outages in 48 hours matter if funds were safe?
Two production halts inside 48 hours from a shared root cause is an unusual concentration for a Layer-2 processing Coinbase-linked throughput, and the failure mode sits close to downstream reorg and sequencer failover paths.
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