The Sui Foundation has disclosed that the Sui blockchain’s mainnet was struck by three consecutive outages on May 28 and 29. According to the foundation, the disruptions resulted from an unexpected bug affecting gas fee collection, triggered by a new feature introduced in version 1.72. Launched in 2023, the Sui mainnet had already made headlines for previous critical incidents, raising new concerns about network stability.
First outage: Insufficient balance and gas fee clash
The initial outage began around 7:00 AM on May 28 and lingered for nearly seven hours. Foundation reports point to a conflict created by the recent “address-balance” feature, which collided with transactions involving traditional coin objects. Under this new structure, a user’s SUI balance is managed as separate digital “banknotes” of varying amounts, rather than a single figure. During operations, these “banknotes” are combined to facilitate payments.
This clash meant that if the selected coin objects for a transaction proved insufficient, the operation would be canceled. However, when attempting to collect the gas fee, an “underflow” error occurred in the software, causing the validators to automatically shut down the network.
Glossary: A coin object, as used in Sui and some blockchain projects, stores user balances as digital “banknotes” each with a unique identifier. Transactions combine these objects to reach the required amount.
Temporary patch and cascading issues
A provisional patch released by the core team at 1:30 PM resolved the initial network outage. Still, this hotfix came with a known risk: under certain rare conditions, the mainnet could stall again. The network was quickly restored, but soon the anticipated vulnerability materialized.
On May 29 at around 5:00 AM, a second disruption struck. This time a different bug, one not accounted for by the earlier patch, was triggered and once again disabled validators. The core engineers then developed a more comprehensive fix, which validators upgraded to at approximately 9:40 AM.
Third stoppage: On-chain randomness and pending transactions
The third outage arose when validators were restarted following the previous bug but encountered a protocol error within the chain’s random number generation system. Without enough validator participation, the randomness mechanism failed to activate.
As a result, operations dependent on randomness—such as random NFT minting—were left pending and the next epoch could not begin, creating a nearly six-hour standstill across the network.
Glossary: On-chain randomness provides unpredictable, tamper-proof random numbers for blockchains. It’s vital for fair NFT minting and some transparent on-chain games.
The Sui Foundation assured that user funds remained secure through all outages, emphasizing that no transactions were reversed and that timely, phased interventions by the team prevented additional mainnet disruptions.
Price impact and past troubles
Mirroring the technical setbacks, SUI’s price came under heavy pressure. After three days of successive outages, SUI had plummeted nearly 8 percent to $0.90, sending its weekly loss to 19 percent. CoinDesk data showed SUI holding steady at the $0.90 mark as the new week began.
These events represent the third major network incident in Sui’s relatively short history. Previously, an operations planning error caused a two-hour stoppage in November 2024; another incident in January 2026 involved a six-hour disruption due to consensus protocol issues.
