Sui Mainnet Halts Three Times After Upgrade Bugs

Three Halts Hit Mainnet During Recovery Efforts

The first outage began on May 28 at 07:15 PDT and lasted approximately six hours, with the more detailed technical explanation placing the duration at roughly six and a half hours before enough validators adopted an emergency patch. The emergency patch restored network operations, but it was not a complete fix and carried a small but real probability of allowing the same crash to happen again.

That risk materialized during the second outage on May 29, when validators upgraded to the emergency patch and another cancellation-path issue appeared. The second disruption paused block production for approximately 3.5 hours. By Friday morning, the core team had prepared a more robust long-term fix, and validators restarted to install it.

The third failure was separate from the gas-charging bug. It began at 13:57 PDT on May 29 during an epoch transition while validators were rolling out the long-term fix. Sui’s distributed key generation protocol, which establishes randomness at the start of each epoch, requires a minimum level of validator participation. Validator restarts temporarily pushed participation below that threshold, causing randomness to disable itself as designed.

The bug was that the disabled randomness state was never written to disk. When validators came back online, they continued expecting randomness to function even though it was unavailable. Transactions requiring randomness queued up, and the end-of-epoch process waited indefinitely because it must clear the transaction queue before closing.

During the third halt, validators processed only system transactions, while normal user transactions could not be confirmed. Token transfers, swaps, DeFi deposits and DeFi withdrawals were affected. The third disruption lasted approximately 5.5 hours, while another timeline described it as nearly six hours. The network advanced to epoch 1143 at 19:32 PDT before normal operations resumed, although validator participation remained degraded afterward.

Sui Network said on May 30, 2026: “Sui mainnet is back online and transactions are flowing normally.”

Funds Were Not at Risk, Foundation Says

The permanent fix addressed both the gas-charging underflow and the randomness state persistence bug. Engineers also added a mechanism allowing validators to force-close a stuck epoch at a coordinated point, and that mechanism was used once to exit the affected epoch and restore normal operations.

The Sui Foundation said no user funds were at risk at any point during the incident. The Sui Foundation also said no previously confirmed transactions were rolled back, meaning the outage stopped new activity but did not reverse settled transactions.

The post-incident explanation said AI agents with access to validator logs and production metrics helped accelerate diagnosis by allowing more engineers to participate in live debugging. The team identified end-of-epoch resilience, gas-charging code quality and better failure containment as areas needing deeper investment after the outages.

The affected network carried approximately $527.91 million in total value locked and approximately $459.25 million in stablecoin market capitalization during the outage period. DeFi activity, including liquidity provision, lending and stablecoin transfers, was interrupted while validators processed only system transactions.

SUI’s crypto price came under pressure after the outages, with COIN360 data showing SUI traded at $0.878 on June 1, 2026, down 15.62% over seven days. Another market snapshot placed SUI at $0.876 after the weekend selloff, while SUI dropped 7.27% on May 28 alone.