Zcash has released new software in preparation for its first system-wide software upgrade.
The first version of zcashd that supports Overwinter will be 1.1.0, which is planned for release in April. This release will set the Overwinter activation block height on the main network, currently targeted for June 25th, 2018. Once activated, the main chain will start enforcing the new consensus rules. Due to the nature of the code, which will be enacted via a mechanism called a hard fork, all users will be required to make the shift.
According to a blog post announcing the new software, Overwinter will include "versioning, replay protection for network upgrades, performance improvements for transparent transactions, a new feature of transaction expiry and more."
However, while the software implements new Overwinter rules, a further upgrade will be required when the precise block number has been finalized, the release states.
According to zcash forum posts, the zcash team has delayed the release of Overwinter several times, citing a need for extra time to review the software and fix bugs discovered during testing.
As of Feb. 27, an employee wrote on the forum that the team's "manual testing of the release candidate" was still in progress.