- Sui’s v1.72 upgrade introduced two separate bugs that caused three mainnet outages.
- The first two halts stemmed from a gas-charging flaw tied to the new address balances.
- A separate randomness-state bug triggered the third outage after validators restarted.
Sui Foundation has released a detailed post-mortem explaining the three separate outages that halted the network on May 28 and May 29.
According to the foundation, two bugs introduced through the v1.72 software release caused the disruptions. The incidents shut down the Layer-1 blockchain three times in less than two days and triggered a sharp decline in the SUI token price.
SUI fell about 8% during the outage sequence to a low near $0.90. The token was trading around $0.90 on Monday and was down roughly 19% over the week.
The foundation said no user funds were at risk during any of the outages and no completed transactions were reversed.
New Feature Triggered Gas-Charging Failure
The first two outages were linked to a flaw in the network’s gas-charging system. Version 1.72 introduced “address balances,” a feature designed to let users pay transaction fees directly from account balances instead of relying entirely on coin objects.
The update also introduced new payment paths that combine address balances with traditional coin-based payments. The issue appeared when multiple transactions attempted to spend the same balance at the same time.
In certain cases, a transaction could be canceled because there were not enough funds available. However, part of the gas-processing system still attempted to charge those funds after the cancellation. That created a negative balance during settlement, causing validators to crash.
The first outage began around 7 a.m. PT on May 28 and lasted until about 1:30 p.m. PT. To restore the network quickly, developers deployed an interim fix. The team acknowledged at the time that the patch contained a known low-probability risk that could still halt the network. However, the risk materialized the next morning.
Emergency Patch Led to Second Halt
The second outage started around 5 a.m. PT on May 29. Sui said some transactions can fail for multiple reasons simultaneously. In one scenario, the insufficient-funds error that the patch was designed to catch was obscured by another cancellation error.
Because the original error was masked, the temporary fix failed to stop the same negative-balance condition from occurring again.
Validators crashed a second time with the same underlying underflow problem. Developers completed a more comprehensive repair, and enough validators upgraded to restore the network by roughly 9:40 a.m. PT.
Randomness Bug Caused Third Shutdown
The third outage was unrelated to the gas bug itself. After validators restarted to install the second fix, participation in the network’s randomness setup process fell below the required threshold.
The randomness system automatically disabled itself as designed. However, a separate bug prevented validators from saving that disabled state to disk. When validators restarted again, they incorrectly assumed the randomness process was still active.
Applications that relied on on-chain randomness could neither execute nor fail, causing transactions to accumulate in a paused queue. The network became stuck during the next epoch transition because it could not fully clear that queue.
The third halt started around 1:30 p.m. PT and lasted until approximately 7:20 p.m. PT. Developers fixed the persistence bug and added a new mechanism allowing validators to force-close a stalled epoch when necessary.
The foundation also revealed that AI-powered internal tools helped engineers diagnose the incidents faster by querying validator logs, analyzing production data, and assembling operational metrics during recovery efforts.
Related: Sui Mainnet Freezes Again, Raising Reliability Concerns
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