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Starknet, an Ethereum layer-2 (L2) scaling network, has released a detailed post-mortem report regarding the temporary mainnet downtime that occurred on Monday. The report identifies the root cause of the disruption as a specific discrepancy in the network state between the blockifier execution layer and the proving layer. This discrepancy interfered with the network’s ability to process transactions correctly, leading to a temporary halt in standard operations while the team worked to address the underlying state error.
The proving layer, which is designed to verify that the execution layer is functioning accurately, performed its role by flagging the error. By identifying the discrepancy, the proving layer ensured that faulty transactions were not committed to the ledger, thereby preventing incorrect data from reaching finality. Although the safety mechanism worked, the nature of the error required a block reorganization to restore the network to a consistent state. This process resulted in approximately 18 minutes of network activity being reverted, meaning transactions within that window were rolled back.
Following the resolution of the state discrepancy, the Starknet team announced that the network has returned to normal functionality. This incident highlights the technical challenges inherent in managing the complex interactions between execution and verification layers within a decentralized scaling environment. The recovery process emphasizes the importance of the proving layer as a safeguard against execution errors, even when such errors lead to brief periods of downtime and the necessity of re-synchronizing the blockchain state.
Context
The outage on Monday represents one of several disruptions Starknet has encountered throughout 2025. The network has faced various technical challenges as it continues to evolve its scaling capabilities. The most significant of these prior incidents occurred in September 2025, following the implementation of a major protocol upgrade known as Grinta. That particular event resulted in a major outage that lasted for more than five hours, representing a substantial period of inactivity for the mainnet.
According to a previous post-mortem report, the September disruption was caused by a sequencer bug. Sequencers are vital components of the blockchain architecture, as they are responsible for ordering transactions. During the September outage, block production was completely halted, necessitating a complex recovery process to bring the network back online. To restore functionality, the team had to execute two separate chain reorganizations, which are significant technical maneuvers used to correct the state of the blockchain after a failure.
These prior reorganizations forced approximately one hour of network activity to be reverted or rolled back. This required users to resubmit transactions that had been initiated during the affected period. These recurring issues in 2025, ranging from sequencer bugs to execution layer discrepancies, illustrate the difficulties of maintaining high uptime for next-generation blockchain networks. Each disruption has required different corrective measures, from simple block reorganizations to multi-hour halts in production, as the development team works to stabilize the multi-layered technology stack that supports the Starknet ecosystem.
Impact
The immediate impact of the Monday downtime was the loss of 18 minutes of transaction history due to the necessary block reorganization. For users and decentralized applications interacting with the network at that time, this meant that transactions were not finalized and had to be accounted for once the network returned to its normal state. While the proving layer successfully prevented the commitment of faulty transactions, the resulting rollback is a reminder of the operational risks associated with early-stage layer-2 scaling solutions.
When compared to the disruptions earlier in 2025, the impact of the recent event was relatively contained in terms of duration. The September outage, lasting over five hours, had a much broader impact on network availability and user confidence. During that event, the total halt in block production prevented any new activity from being recorded, and the subsequent one-hour reversion of activity was significantly longer than the 18-minute window affected this Monday. The need for users to resubmit transactions after such reorganizations adds a layer of manual effort and potential uncertainty to the network’s operation.
The recurring nature of these events throughout the year suggests that while the network can recover, the underlying complexity of the blockifier and sequencer systems remains a source of potential instability. The fact that the proving layer caught the recent error is a positive sign for the network’s security architecture, but the resulting downtime still affects the overall reliability of the platform. Each incident of this nature requires the team to analyze discrepancies between different layers of the stack, ensuring that the execution of code matches the intended state before transactions are permanently recorded on the ledger.
Outlook
The outlook for Starknet involves addressing the technical vulnerabilities identified in the recent post-mortem report to prevent further discrepancies between its execution and proving layers. The Monday incident was rooted in how the blockifier handled specific combinations of function calls and state-writing, a technical nuance that the team must now account for in future updates. By refining the interaction between these layers, the goal is to reduce the likelihood of future block reorganizations and the associated need to revert network activity.
The sequence of disruptions in 2025, including the major September outage following the Grinta upgrade, provides a roadmap for necessary protocol improvements. The transition from a five-hour outage caused by a sequencer bug to a more localized discrepancy that was quickly caught by the proving layer suggests that the network’s safety mechanisms are becoming more robust. However, the goal remains to achieve a state where block production is continuous and reorganizations are non-existent, ensuring that user transactions are finalized without the risk of being rolled back.
As the network maintains its current normal functionality, the focus will likely remain on hardening the infrastructure that supports transaction ordering and execution. The lessons learned from the 18-minute reversion on Monday and the one-hour reversion in September are critical for the long-term stability of the Ethereum layer-2 scaling space. Future developments will need to focus on ensuring that the multi-layered technology stack—comprising the blockifier, the sequencer, and the proving layer—can operate in perfect synchronization, even during complex protocol upgrades or high-stress periods of network activity.
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