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The Sui blockchain froze for roughly six hours on Jan. 14, temporarily locking up an estimated $1 billion in on-chain assets after validators failed to agree on transaction ordering due to a consensus bug.
In a post-mortem published Friday, developers said the halt was triggered by an edge-case flaw in how consensus commits were processed — not by external attacks or traffic surges. While no funds were lost and the network resumed normal operations later that day, the incident marks the second major disruption since Sui’s 2023 launch.
According to the post-mortem, the Sui network outage stemmed from an edge-case bug in how consensus commits were processed by validators. The flaw caused different validators to reach conflicting conclusions when handling certain transactions submitted around the same time.
As Sui explained in the report, “an edge-case bug in the way consensus commits were processed caused validators to reach different conclusions when handling certain conflicting transactions,” — Sui development team, post-mortem report.
Because of this divergence, validators began producing incompatible checkpoint candidates. Under Sui’s consensus rules, checkpoints must reach stake-weighted agreement before being certified. When that threshold could not be met, the system halted automatically.
“When validators detected that a significant portion of the stake was signing conflicting checkpoint data, the network halted by design,” — Sui development team, post-mortem report.
This halt stopped block production and transaction execution, leading to widespread timeouts for transaction submissions. However, read-only queries continued to serve the last certified state, allowing users to view balances and historical data despite the Sui network outage.
Developers estimated that about $1 billion in on-chain value was temporarily inactive during the roughly six-hour disruption. Importantly, no certified transactions were reversed, and no forks occurred while the network was paused.
Once engineers identified the root cause of the Sui network outage, recovery efforts moved quickly. Validators first removed the incorrect consensus data and applied a fix to the faulty commit logic. They then replayed the chain from the point where consensus had diverged.
A canary deployment was initially rolled out by validators operated by , the core development company behind Sui. After the fix proved stable, the broader validator set upgraded their software and resumed checkpoint signing, allowing the network to return to normal operations later on Jan. 14.
“The incident confirmed that Sui’s safety-first design worked as intended by prioritizing consistency over uptime,” — Sui development team, post-mortem report.
The team acknowledged, however, that the length of the Sui network outage underscored the need to shorten recovery times in future incidents.
Planned improvements include better automation for validator operations, expanded testing to catch similar consensus edge cases before they reach mainnet, and earlier detection of checkpoint inconsistencies.
The Jan. 14 Sui network outage was the second major disruption for the layer-1 blockchain since its launch in 2023, following a shorter incident in late 2024. Despite the scale of the halt, market reaction was muted.
SUI’s price experienced limited volatility, suggesting investors viewed the issue as operational rather than a fundamental flaw in the network.
For developers and users, the episode highlighted both the strengths and trade-offs of Sui’s architecture. By halting automatically when consensus diverged, the network avoided finalizing conflicting states, but at the cost of several hours of downtime. The post-mortem framed this outcome as intentional.
By publicly detailing the Sui network outage, the team aimed to reinforce confidence in the protocol’s transparency and resilience. The report emphasized that user funds were never at risk and that the safeguards performed as designed, even under unexpected conditions.
As Sui continues to position itself among high-throughput layer-1 blockchains, the Jan. 14 Sui network outage is likely to remain a reference point for discussions about reliability, validator coordination, and the balance between safety and availability.
Whether the promised improvements reduce the risk of similar disruptions will be closely watched by developers, validators, and users alike.
