On February 23, 2026, Flow Mainnet experienced an outage that temporarily halted block production. The network entered a safe state after detecting inconsistent results between nodes during preparations for a scheduled height coordinated upgrade. As designed, the protocol stopped sealing new blocks to protect network integrity. No user funds were impacted or at risk.
The issue has since been resolved and normal operations have resumed.
In preparation for a scheduled height coordinated upgrade, a new software version was rolled out to one execution node ahead of the coordinated update. That node generated results which did not match those produced by the other execution nodes.
At the same time, one verification node was running an older software version. Running an older verification node version by itself would not have caused an outage. However, in this specific situation, the combination of an execution node and a verification node operating on mismatched versions contributed to inconsistent approvals being produced.
The consensus safety mechanism detected that the required agreement conditions for sealing a block were not met and halted block production to prevent inconsistent state from being finalized. While this safety mechanism worked as intended, it resulted in temporary network downtime until the mismatch was identified and corrected.
The version mismatches were identified and corrected, and nodes were aligned to the expected software versions. Once consistency was restored, block production resumed. Performance returned to normal as consensus node operators completed their updates.
To reduce the likelihood of similar incidents in the future, the following actions are being implemented:
Network reliability and safety remain our top priorities. In this case, the protocol’s safety mechanisms correctly prevented inconsistent state from being finalized. The improvements outlined above will further strengthen Flow Mainnet’s resilience and upgrade processes going forward.