Zcash stopped producing blocks at 05:27:48 UTC on June 3 at block height 3,364,601, with no new blocks generated for more than four hours. Under normal conditions, the network produces a block roughly every 75 seconds, so the outage represented a delay of nearly 200 blocks and left on-chain transactions effectively frozen.
Network stall followed an emergency soft fork
The halt came one day after Zcash activated an emergency coordinated upgrade. The soft fork was triggered at about 02:00 UTC on June 2 at block height 3,363,426, after independent security researcher Taylor Hornby found a critical vulnerability in the Orchard shielded pool during an audit commissioned by Shielded Labs. Miners then paused all Orchard-related transactions, and Orchard functionality was disrupted for about 24 hours.
The fix was described as a two-step process. The first step was the soft fork already deployed. A second step is expected to use a hard fork to update the zero-knowledge proof circuit and fully restore Orchard. The Zcash team also alerted maintainers of other protocols that use Orchard, while the full scope of impact has yet to be determined.
Mining pool coordination drew immediate scrutiny
The report pointed to failed mining pool coordination as the direct cause behind the block production halt. Foundry, ViaBTC, F2Pool, and Antpool together control more than 81.6% of ZEC hash power, leaving the network heavily dependent on a small group of operators. If those major pools do not align on software versions or block parameters during an emergency upgrade, the whole chain can stall.
Foundry is a key part of that concentration. It launched an institutional Zcash mining pool in April and quickly captured nearly one-third of new production. That level of concentration may be manageable under normal conditions, but it becomes a clear fault line when urgent coordination is required.
Governance strains add to the technical crisis
The outage also landed against a backdrop of governance instability. According to the source material, the core development team at ECC, or Electric Coin Company, resigned collectively in January 2026. Josh Swihart publicly accused the Bootstrap board of drifting away from Zcash’s original mission, and ZEC fell more than 20% in a single day at that time. Former developers later formed a new structure, but this incident has renewed questions about whether the project can coordinate miners and protocol upgrades during periods of stress.
Price action has reflected that split in interpretation. During the public repair process, ZEC briefly moved above $600. Even so, the operational picture remains clear: block production stopped, Orchard was restricted, and coordination across the network became a visible point of failure.