The string you're referring to describes an official evaluation or retail build
Are you planning to upgrade your test environments soon? Let me know in the comments.
Expected new features in Server 2025:
- Build 26100 is part of the Germanium codebase, which debuted with Windows 11 version 24H2.
- Some Windows Server 2025 preview builds (from 2024–2025) used 260xx and 261xx kernels, but they were never designated “OEMRET.”