Flow Mainnet Network Issue

Update timeline

1. investigating Feb 24, 2026, 01:15 AM UTC

   Block sealing on Flow mainnet has stopped. We are investigating the issue.

2. identified Feb 24, 2026, 04:07 AM UTC

   Flow is still in maintenance as the team works to restore full operations. The issue was caused by an incomplete node update in preparation for tomorrow’s height coordinated upgrade, which triggered a consensus safety mechanism that halted block sealing. Flow engineers are actively working on a fix, and the next update will be shared at 10 PM PT.

3. monitoring Feb 24, 2026, 04:59 AM UTC

   The root cause of the issue has been resolved, and block production has resumed, though it is currently progressing slowly. Consensus node operators are actively upgrading their nodes, and once a majority of the consensus nodes in the network have completed the update, block sealing is expected to return to normal performance.

4. resolved Feb 24, 2026, 05:13 AM UTC

   The incident has been resolved and the network has resumed.

5. postmortem Feb 25, 2026, 01:43 AM UTC

   ### **Summary** 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. ### **What Happened** 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. ### **Resolution** 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. ### **Action Items** To reduce the likelihood of similar incidents in the future, the following actions are being implemented: 1. Height Coordinated Upgrade protections for verification nodesVerification nodes will soon adopt the upgrade enforcement behavior similar to execution nodes. If a verification node is not running the expected version after a coordinated upgrade, it will automatically crash and restart rather than continue participating. 2. CI and deployment safeguards for Cadence versionsA strengthening of the deployment process to ensure that node software upgrade cannot deploy a lower version of the node software. Automated checks will prevent accidental deployment of incorrect or older versions, reducing the risk of human error. ### **Closing** 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.