A new feature delivered in Sui’s v1.72 release revealed an edge case in the Layer 1 blockchain’s gas-charging logic that shut down the mainnet three times on May 28 and 29, with each patch triggering or exposing the next outage, the Sui Foundation said in a post-mortem published Sunday.
The first outage began around 7 a.m. PT on Thursday and lasted for nearly seven hours.
According to the foundation, this stemmed from a rare issue in the way the network charged gas for paid transactions with a mix of the new address balance feature and traditional coin objects. The bug caused validators to crash with an overflow error when a transaction was canceled for insufficient funds, but the gas destruction routine still tried to spend those same funds.
Think of a coin as a digital bank note. A user’s SUI balance is not a single number: it is a stack of separate “notes”, each with its own identifier, which can be moved or combined. The wallet can hold three coins worth 60, 30 and 10 SUI rather than a single balance of 100 SUI. To pay for something, the network combines the tickets it needs.
Validators are computers (and the operators behind them) that manage the network by processing transactions, voting on which ones are valid, and keeping the chain alive.
The core team restored the network around 1:30 p.m. PT with what it called an “interim fix” that fixed the most common version of the bug but had “a known issue with a low probability of causing an outage.” The team accepted this risk to quickly restore the main network while a more robust patch was developed.
The known risk materialized the next morning. A second outage began around 5 a.m. PT on Friday when a transaction triggered a hidden variation of the same bug, in which the insufficient funds error was replaced with another cancellation reason, bypassing the interim fix. The core team completed a more robust fix and validators adopted it around 9:40 a.m. PT.
The third stop was an extension of the second. When validators restarted to install the robust patch, validator participation in the protocol that bootstraps the network’s on-chain randomness fell below the required threshold and randomness turned off as expected.
(On-chain randomness is a protocol that the network uses to produce a number that no one can predict or falsify, even though each validator must agree on the same value. Applications that rely on randomness – lotteries, some games, random NFT currencies – cannot function without it.)
A latent bug then failed to maintain this disabled state on disk, leaving validators unaware on the next reboot that randomness had been disabled. The next epoch change paused for almost six hours as chance-dependent transactions piled up in a paused queue.
No user funds were at risk during the outages and no committed transactions were canceled, the foundation said.
SUI fell about 8% during the cascade to a low of $0.90 and was trading near $0.90 on Monday, leaving the token down about 19% for the week, according to CoinDesk data.
These events represent Sui’s third major reliability incident since its mainnet launched in 2023, following a two-hour transaction scheduling bug in November 2024 and a six-hour consensus divergence in January 2026.
