Microsoft has said that extra work caused by AI‑driven bug‑finding tools has delayed the release of Exchange Server Subscription Edition Cumulative Update 1 (CU1). Redmond’s Exchange team posted on Thursday that customers have asked when the update will be available, noting that the original timeline of the first half of 2026 was later pushed to the second half of 2026. Exchange Server Subscription Edition is the subscription version of Microsoft’s email server, and a cumulative update includes all recent bug fixes plus additional changes. The development team is reviewing reported issues, verifying that they are real security vulnerabilities, reproducing them, applying fixes, testing for regressions, and planning monthly releases. Microsoft attributes the delay to its focus on security, a stance taken after a suspected Chinese‑linked attack on Exchange that drew criticism from the U.S. government. The team said it is integrating monthly security patches into its internal CU1 build and will release the update once a stable point is reached and there is a month without urgent security payloads. Releasing CU1 without a concurrent security update would require administrators to apply two major patches, increasing testing burden. Microsoft did not provide a specific release date and said it will announce the update when ready.