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Announcing Windows Server vNext Preview Build 29621
Hello Windows Server Insiders! Today we are pleased to release a new build of the next Windows Server Long-Term Servicing Channel (LTSC) Preview that contains both the Desktop Experience and Server Core installation options for Datacenter and Standard editions and Azure Edition (for VM evaluation only). Branding remains Windows Server 2025 in this preview - when reporting issues please refer to Windows Server vNext preview. Build 29531 established a new Server preview baseline build. Please perform a clean install of Build 29531 (or later) using the installation media linked below. Please note: Upgrades from Windows Server vNext preview builds older than 29531 are not supported. We encourage all Windows Server vNext preview users to perform a clean install using 29531 or later to successfully upgrade to future Windows Server vNext preview builds. While upgrades from earlier Windows Server previews (Build 26525 and older) are not technically blocked by setup.exe, a number of known issues have been identified related to upgrades necessitating the establishment of a new baseline build for our Server vNext Preview Program. The new baseline build (29531) will not be Flighted due to upgrade issues. Flighting support resumed with preview build 29550 or later. What's New [NEW] We're excited to announce Trusted Launch for virtual machines (TVMs) on Windows Server—a security feature you can enable when creating Generation 2 VMs. This initial preview supports TVMs with Secure Boot, vTPM, and vTPM state protection (at rest), managed via PowerShell. ⚠ Not supported in this release: Moving TVMs to another server TVMs in failover clusters or Hyper-V Replica Boot integrity verification TVMs in Windows Admin Center (WAC) Instructions 1. Install the latest ServerInsider preview build. 2. Enable Hyper-V (restarts the server): Install-WindowsFeature -Name Hyper-V -IncludeManagementTools -Restart 3. Set the registry keys: New-Item -Path "HKLM:\SOFTWARE\Microsoft\AszIgvmAgent" -Force New-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\AszIgvmAgent" -Name "TvmWinServer" -Value 1 -PropertyType DWord -Force 4. Enable Trusted Launch: Enable-WindowsOptionalFeature -Online -FeatureName "IsolatedGuestVm" -NoRestart 5. Verify IGVmAgent is running (should show Running): Get-Service -Name "IGVmAgent" If it isn't running, report the issue with the IGVmAgent and IGVmSystem Operational logs (Event Viewer → Applications and Services Logs → Microsoft → Windows). 6. Create an external virtual switch (if needed): (Get-VMSwitch | Where-Object { $_.SwitchType -eq "External" }).Name 7. Create the TVM. With an existing Gen 2 VHDX: New-VM -Name <VMName> -Generation 2 -GuestStateIsolationType TrustedLaunch -SwitchName <switch> -VHDPath <path to vhdx> -Path <config path> Or with a new VHD, then attach a Gen 2–compatible guest OS ISO: New-VM -Name <VMName> -SwitchName <switch> -NewVHDPath <new VHD path> -NewVHDSizeBytes 40GB -Generation 2 -GuestStateIsolationType TrustedLaunch -Path <config path> Add-VMDvdDrive -VMName <VMName> -Path <Guest OS ISO path> Ensure the DVD drive is first in the firmware boot order so the VM boots from it. 8. Verify isolation type (should return TrustedLaunch): (Get-VM -Name <VMName>).GuestStateIsolationType 9. Verify guest state protection: Stop the IGVmAgent service and restart the VM—without IGVmAgent running, a Trusted launch VM with guest state protection won't start. Quick Machine Recovery available in Windows Server vNext Insider Previews. Quick machine recovery (QMR) is now available for Server vNext Insiders to test. This feature enables the recovery of Windows Server devices when they encounter boot critical errors that prevent them from booting. QMR can automatically search for cloud‑based remediations to recover from widespread boot failures significantly reducing the burden on IT administrators when multiple devices are impacted. This supports the goals of the Windows Resiliency Initiative by enabling applicable fixes to be delivered through trusted Windows Update to restore affected devices, helping reduce downtime and minimize manual recovery efforts across enterprise environments. This feature is currently enabled in the latest Server vNext Insider builds for customers to experience test mode. A Group Policy option to enable or disable the feature will be introduced in upcoming builds to provide additional administrative control. To simulate the quick machine recovery experience, use the following commands from an elevated command prompt: Enable test mode: reagentc.exe /SetRecoveryTestmode Configure Windows to boot to Windows Recovery Environment on the next boot: reagentc.exe /BootToRe Reboot your device. The system goes through autoremediation of a simulated crash safely and reboots back to Windows Server. For more information, please review Quick machine recovery (QMR) and Windows Resiliency Initiative. When providing feedback using Feedback hub, please select QMR from the Recovery and Uninstall category in the app. NVMe-over-Fabrics (NVMe-oF) extends the NVMe protocol—originally designed for local PCIe-attached SSDs—across a network fabric. Instead of using legacy SCSI-based protocols such as iSCSI or Fibre Channel, NVMe-oF allows a host to communicate directly with remote NVMe controllers using the same NVMe command set used for local devices. In this Insider build, Windows Server supports: NVMe-oF over TCP (NVMe/TCP), allowing NVMe-oF to run over standard Ethernet networks without specialized hardware. NVMe-oF over RDMA (NVMe/RDMA), enabling low-latency, high-throughput NVMe access over RDMA-capable networks (for example, RoCE or iWARP) using supported RDMA NICs. For more information, please visit: Introducing the Windows NVMe-oF Initiator Preview in Windows Server Insiders Builds | Microsoft Community Hub ReFS Boot is enabled for Windows Server vNext preview builds. Known Limitations ReFS Boot systems create a minimum 2GB WinRE partition. When WinRE cannot be updated due to space constraints, the system may disable WinRE. Disabling WinRE does not remove the partition. If the WinRE partition is deleted and the boot volume is extended over it, this operation is unrecoverable without a clean install. For more information, please visit: Resilient File System (ReFS) overview | Microsoft Learn Feedback Hub app is available for Server Desktop users!  The app should automatically update with the latest version, but if it does not, simply Check for updates in the app’s settings tab. Known Issues A race condition in the TLS hybrid key exchange implementation may cause the LSASS service to crash when hybrid groups are negotiated by a TLS server. To avoid this issue until the fix is released, please disable hybrid groups (X25519_MLKEM768, SecP256r1_MLKEM768, SecP384r1_MLKEM1024) using TLS cmdlets or Group Policy, as outlined here. Server Core Upgrades and AppCompat FOD: Enabling AppCompat FOD after reinstall may fail due to legacy 3rd-party license compatibility issues on Server Core devices. Server Core users may be unable to install the latest AppCompat FOD after upgrading to build 29574. This appears to be limited to Server Core installations with 3rd-party application licenses that fail compatibility checks after upgrade. This will be addressed in a future build. Upgrading from older builds of Windows Server vNext previews (26525 or older) are not supported. Please perform a clean install of build 29531 or later. Users may experience failures when attempting to upgrade from earlier previews (build 26525 and older). VMs may fail to upgrade or start after upgrade from older preview builds impacting live migration and failover cluster scenarios. Download Windows Server Insider Preview (microsoft.com) Flighting: The label for this flight may incorrectly reference Windows 11. However, when selected, the package installed is the Windows Server vNext update. Please ignore the label and proceed with installing your flight. This issue will be addressed in a future release. Available Downloads Downloads to certain countries may not be available. See Microsoft suspends new sales in Russia - Microsoft On the Issues. Windows Server Long-Term Servicing Channel Preview in ISO format in 18 languages, and in VHDX format in English only.  Windows Server Datacenter Azure Edition Preview in ISO and VHDX format, English only. Microsoft Server Languages and Optional Features Preview  Keys: Keys are valid for preview builds only  Server Standard: MFY9F-XBN2F-TYFMP-CCV49-RMYVH Datacenter: 2KNJJ-33Y9H-2GXGX-KMQWH-G6H67 Azure Edition does not accept a key. Symbols:  Available on the public symbol server – see Using the Microsoft Symbol Server.  Expiration: This Windows Server Preview will expire September 15, 2026. How to Download Registered Insiders may navigate directly to the Windows Server Insider Preview download page. If you have not yet registered as an Insider, see GETTING STARTED WITH SERVER on the Windows Insiders for Business portal. We value your feedback! The most important part of the release cycle is to hear what's working and what needs to be improved, so your feedback is extremely valued. Please use the new Feedback Hub app for Windows Server if you are running a Desktop version of Server. If you are using a Core edition, or if you are unable to use the Feedback Hub app, you can use your registered Windows 10 or Windows 11 Insider device and use the Feedback Hub application.  In the app, choose the Windows Server category and then the appropriate subcategory for your feedback. In the title of the Feedback, please indicate the build number you are providing feedback on as shown below to ensure that your issue is attributed to the right version:      [Server #####] Title of my feedback See Give Feedback on Windows Server via Feedback Hub for specifics. The Windows Server Insiders space on the Microsoft Tech Communities supports preview builds of the next version of Windows Server. Use the forum to collaborate, share and learn from experts.  For versions that have been released to general availability in market, try the Windows Server for IT Pro forum or contact Support for Business. Diagnostic and Usage Information Microsoft collects this information over the internet to help keep Windows secure and up to date, troubleshoot problems, and make product improvements. Microsoft server operating systems can be configured to turn diagnostic data off, send Required diagnostic data, or send Optional diagnostic data. During previews, Microsoft asks that you change the default setting to Optional to provide the best automatic feedback and help us improve the final product. Administrators can change the level of information collection through Settings. For details, see http://aka.ms/winserverdata. Also see the Microsoft Privacy Statement. Terms of Use This is pre-release software - it is provided for use "as-is" and is not supported in production environments. Users are responsible for installing any updates that may be made available from Windows Update. All pre-release software made available to you via the Windows Server Insider program is governed by the Insider Terms of Use.
StaceyCL_RM
Jul 13, 2026 Place Windows Server Insiders
156Views
1like
0Comments
Follow up to Azure Host OS Article
When will there be a follow up to the Azure Host OS article? It would be great to learn more about how the NT kernel is being used inside Microsoft outside of standard Windows. This is the article: Azure Host OS
Steskalj
Jul 11, 2026 Place Windows Server Insiders
53Views
0likes
1Comment
Problems to join Debian/Ubuntu machines to a domain
Is not posible to join Debian/Ubuntu machines to a domain based on Windows Server 2025 (using realm at least) this is the error: ! Couldn't set password for computer account: XXXX$: Message stream modified adcli: joining domain xxxx.local failed: Couldn't set password for computer account: XXXX$: Message stream modified ! Failed to join the domain realm: Couldn't join realm: Failed to join the domain Domain is discoverable vía realm: root@lnms01:/home/administrator# realm discover xxxx.local xxxx.local type: kerberos realm-name: XXXX.LOCAL domain-name: xxxx.local configured: no server-software: active-directory client-software: sssd required-package: sssd-tools required-package: sssd required-package: libnss-sss Tested on WS2025 build 26227 and Linux 6.1.0-21-amd64 x86_64, Linux 6.6.31+rpt-rpi-v8 aarch64 and Linux 6.8.0-31-generic x86_64. Those 3 versions of Linux joined to another doman based con Windows Server 2022 without issues.
ejc2_
Jul 06, 2026 Place Windows Server Insiders
11KViews
0likes
8Comments
in-place upgrade fails from b29574 to latest vnext b29595
Hi all, is anyone facing the same issue IPU fails on a fresh b29574 upgrading to latest using WU? provided more information in feedback hub. Thanks for sharing your experience. as a next attempt I will mount ISO and upgrade. mind b29574 was the base bare metal installation so no previous IPUs involved. related feedback https://aka.ms/AA11g03n Tested Upgrade Paths Baseline TargetOS Result 29574 29595 fails 29574 29602 fails 29595 29602 fails Installed roles: - Hyper-V Specialities: tried SysWOW64 removal but failed to do so https://aka.ms/AA11eyy5 OS Drive is ReFS, potientially related https://aka.ms/AA11eyy8 <?xml version="1.0" encoding="utf-16"?> <SetupDiag xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="https://docs.microsoft.com/en-us/windows/deployment/upgrade/setupdiag"> <Version>1.7.0.0</Version> <ProfileName>FindRollbackFailure</ProfileName> <ProfileGuid>3A43C9B5-05B3-4F7C-A955-88F991BB5A48</ProfileGuid> <FailureData>0xc1900101-0x20017 Error: SetupDiag reports rollback failure found.Last Phase = FinalizeLast Operation = Cleanup external drivers after installationError = 0xC1900101-0x20017</FailureData> <FailureData>LogEntry: </FailureData> <FailureData>Refer to "https://docs.microsoft.com/en-us/windows/desktop/Debug/system-error-codes" for error information.</FailureData> <FailureDetails>RollbackErrorCode = 0xC1900101, ExtendedCode = 0x20017, LastOperation = Cleanup external drivers after installation, LastPhase = Finalize</FailureDetails> <Setup360Result>0xc1900101</Setup360Result> <Setup360Extended>0x20017</Setup360Extended> <SetupPhaseInfo> <PhaseName>Finalize</PhaseName> <PhaseStartTime>06/06/2026 13:16:53</PhaseStartTime> <PhaseEndTime>06/06/2026 13:17:35</PhaseEndTime> <PhaseTimeDelta>0:00:00:42.0000000</PhaseTimeDelta> <CompletedSuccessfully>true</CompletedSuccessfully> </SetupPhaseInfo> <SetupOperationInfo> <OperationName>Cleanup external drivers after installation</OperationName> <OperationStartTime>06/06/2026 13:17:35</OperationStartTime> <OperationEndTime>06/06/2026 13:17:35</OperationEndTime> <OperationTimeDelta>0:00:00:00.0000000</OperationTimeDelta> <CompletedSuccessfully>true</CompletedSuccessfully> </SetupOperationInfo> </SetupDiag> also noticing uncommon links in root as if I were using FAT32.
Karl-WE
Jun 30, 2026 Place Windows Server Insiders
227Views
0likes
8Comments
Server flighting not being offered on 29595 on 3 VMs
Hi, I'm on not getting build 29602 offered as a flight through Windows update on any of my VMs and I can figure out why, it has not been offered in the last couple of builds. Is anyone else experiencing this or have any ideas of how to fix this? Optional diagnostics are on and they are connected to my account under insider setting in Windows update settings. I am just not getting offered the build flight. Thanks Kevin
kevdog98
Jun 24, 2026 Place Windows Server Insiders
93Views
2likes
2Comments
Windows Server vNext cannot be activated
Error Code 0xC004F012 when trying to activate WS vNext Datacenter with Key 2KNJJ-33Y9H-2GXGX-KMQWH-G6H67. vbscript is removed, implying the future removal of this component from the OS. It appears that Windows Activation relies on vbscript. I would wish for a native PowerShell support / module instead of vbscript. Is this something that is on the roadmap?
Solved
Karl-WE
Jun 23, 2026 Place Windows Server Insiders
165Views
0likes
4Comments
Announcing Windows Server vNext Preview Build 29602
Hello Windows Server Insiders! Today we are pleased to release a new build of the next Windows Server Long-Term Servicing Channel (LTSC) Preview that contains both the Desktop Experience and Server Core installation options for Datacenter and Standard editions and Azure Edition (for VM evaluation only). Branding remains Windows Server 2025 in this preview - when reporting issues please refer to Windows Server vNext preview. Build 29531 established a new Server preview baseline build. Please perform a clean install of Build 29531 (or later) using the installation media linked below. Please note: Upgrades from Windows Server vNext preview builds older than 29531 are not supported. We encourage all Windows Server vNext preview users to perform a clean install using 29531 or later to successfully upgrade to future Windows Server vNext preview builds. While upgrades from earlier Windows Server previews (Build 26525 and older) are not technically blocked by setup.exe, a number of known issues have been identified related to upgrades necessitating the establishment of a new baseline build for our Server vNext Preview Program. The new baseline build (29531) will not be Flighted due to upgrade issues. Flighting support resumed with preview build 29550 or later. What's New Quick Machine Recovery available in Windows Server vNext Insider Previews. Quick machine recovery (QMR) is now available for Server vNext Insiders to test. This feature enables the recovery of Windows Server devices when they encounter boot critical errors that prevent them from booting. QMR can automatically search for cloud‑based remediations to recover from widespread boot failures significantly reducing the burden on IT administrators when multiple devices are impacted. This supports the goals of the Windows Resiliency Initiative by enabling applicable fixes to be delivered through trusted Windows Update to restore affected devices, helping reduce downtime and minimize manual recovery efforts across enterprise environments. This feature is currently enabled in the latest Server vNext Insider builds for customers to experience test mode. A Group Policy option to enable or disable the feature will be introduced in upcoming builds to provide additional administrative control. To simulate the quick machine recovery experience, use the following commands from an elevated command prompt: 1. Enable test mode: reagentc.exe /SetRecoveryTestmode 2. Configure Windows to boot to Windows Recovery Environment on the next boot: reagentc.exe /BootToRe 3. Reboot your device.The system goes through autoremediation of a simulated crash safely and reboots back to Windows Server. For more information, please review Quick machine recovery (QMR) and Windows Resiliency Initiative. When providing feedback using Feedback hub, please select QMR from the Recovery and Uninstall category in the app. NVMe-over-Fabrics (NVMe-oF) extends the NVMe protocol—originally designed for local PCIe-attached SSDs—across a network fabric. Instead of using legacy SCSI-based protocols such as iSCSI or Fibre Channel, NVMe-oF allows a host to communicate directly with remote NVMe controllers using the same NVMe command set used for local devices. In this Insider build, Windows Server supports: NVMe-oF over TCP (NVMe/TCP), allowing NVMe-oF to run over standard Ethernet networks without specialized hardware. NVMe-oF over RDMA (NVMe/RDMA), enabling low-latency, high-throughput NVMe access over RDMA-capable networks (for example, RoCE or iWARP) using supported RDMA NICs. For more information, please visit: Introducing the Windows NVMe-oF Initiator Preview in Windows Server Insiders Builds | Microsoft Community Hub ReFS Boot is enabled for Windows Server vNext preview builds. Known Limitations ReFS Boot systems create a minimum 2GB WinRE partition. When WinRE cannot be updated due to space constraints, the system may disable WinRE. Disabling WinRE does not remove the partition. If the WinRE partition is deleted and the boot volume is extended over it, this operation is unrecoverable without a clean install. For more information, please visit: Resilient File System (ReFS) overview | Microsoft Learn Feedback Hub app is available for Server Desktop users!  The app should automatically update with the latest version, but if it does not, simply Check for updates in the app’s settings tab. Known Issues [NEW] A race condition in the TLS hybrid key exchange implementation may cause the LSASS service to crash when hybrid groups are negotiated by a TLS server. To avoid this issue until the fix is released, please disable hybrid groups (X25519_MLKEM768, SecP256r1_MLKEM768, SecP384r1_MLKEM1024) using TLS cmdlets or Group Policy, as outlined here. Server Core Upgrades and AppCompat FOD: Enabling AppCompat FOD after reinstall may fail due to legacy 3rd-party license compatibility issues on Server Core devices. Server Core users may be unable to install the latest AppCompat FOD after upgrading to build 29574. This appears to be limited to Server Core installations with 3rd-party application licenses that fail compatibility checks after upgrade. This will be addressed in a future build. Upgrading from older builds of Windows Server vNext previews (26525 or older) are not supported. Please perform a clean install of build 29531 or later. Users may experience failures when attempting to upgrade from earlier previews (build 26525 and older). VMs may fail to upgrade or start after upgrade from older preview builds impacting live migration and failover cluster scenarios. Download Windows Server Insider Preview (microsoft.com) Flighting: The label for this flight may incorrectly reference Windows 11. However, when selected, the package installed is the Windows Server vNext update. Please ignore the label and proceed with installing your flight. This issue will be addressed in a future release. Available Downloads Downloads to certain countries may not be available. See Microsoft suspends new sales in Russia - Microsoft On the Issues. Windows Server Long-Term Servicing Channel Preview in ISO format in 18 languages, and in VHDX format in English only.  Windows Server Datacenter Azure Edition Preview in ISO and VHDX format, English only. Microsoft Server Languages and Optional Features Preview  Keys: Keys are valid for preview builds only  Server Standard: MFY9F-XBN2F-TYFMP-CCV49-RMYVH Datacenter: 2KNJJ-33Y9H-2GXGX-KMQWH-G6H67 Azure Edition does not accept a key. Symbols:  Available on the public symbol server – see Using the Microsoft Symbol Server.  Expiration: This Windows Server Preview will expire September 15, 2026. How to Download Registered Insiders may navigate directly to the Windows Server Insider Preview download page. If you have not yet registered as an Insider, see GETTING STARTED WITH SERVER on the Windows Insiders for Business portal. We value your feedback! The most important part of the release cycle is to hear what's working and what needs to be improved, so your feedback is extremely valued. Please use the new Feedback Hub app for Windows Server if you are running a Desktop version of Server. If you are using a Core edition, or if you are unable to use the Feedback Hub app, you can use your registered Windows 10 or Windows 11 Insider device and use the Feedback Hub application.  In the app, choose the Windows Server category and then the appropriate subcategory for your feedback. In the title of the Feedback, please indicate the build number you are providing feedback on as shown below to ensure that your issue is attributed to the right version:      [Server #####] Title of my feedback See Give Feedback on Windows Server via Feedback Hub for specifics. The Windows Server Insiders space on the Microsoft Tech Communities supports preview builds of the next version of Windows Server. Use the forum to collaborate, share and learn from experts.  For versions that have been released to general availability in market, try the Windows Server for IT Pro forum or contact Support for Business. Diagnostic and Usage Information Microsoft collects this information over the internet to help keep Windows secure and up to date, troubleshoot problems, and make product improvements. Microsoft server operating systems can be configured to turn diagnostic data off, send Required diagnostic data, or send Optional diagnostic data. During previews, Microsoft asks that you change the default setting to Optional to provide the best automatic feedback and help us improve the final product. Administrators can change the level of information collection through Settings. For details, see http://aka.ms/winserverdata. Also see the Microsoft Privacy Statement. Terms of Use This is pre-release software - it is provided for use "as-is" and is not supported in production environments. Users are responsible for installing any updates that may be made available from Windows Update. All pre-release software made available to you via the Windows Server Insider program is governed by the Insider Terms of Use.
StaceyCL_RM
Jun 08, 2026 Place Windows Server Insiders
1.2KViews
2likes
0Comments
CXL Memory Expansion on WinServer 2025
I'm looking to find out if on window server 2025 is CXL Type 3 in memory expansion mode is validated "GA" and if so which cxl devices. I'm having issues finding this information. Anyone know and able to share?
isheaffer
May 15, 2026 Place Windows Server Insiders
154Views
0likes
2Comments
Windows NVMe-oF Initiator connect error
Hi everyone, I am trying to test the new Windows NVMe-oF Initiator within build 29550.1000 but I am not able to connect to a remote storage array - getting the error "IOCTL_NVMEOF_CONNECT_CONTROLLER failed with error code 0x1f" (see screenshot). Any idea what does this error mean or what can be wrong?
pkovar
Mar 26, 2026 Place Windows Server Insiders
178Views
0likes
1Comment
ISSUE: Windows Server 2025 - OneDrive Shell Folder does not work in File Explorer
Dear Windows Server Insider team, I am seeing this issue for a longer time now and hoped it would be resolved. Will be repeating my tests with 26311 soon and updating this thread by then. I consider this issue of low to medium importance. If this goes live it can harm especially Windows Server based VDI which usually using OneDrive and FSLogix Containers. This one is just tested in easy complexity with OneDrive for Home Use, but I expect it can also affect OneDrive for Business. Overall, I would rate this an UX limitation with an available workaround for advanced users. Thanks! https://aka.ms/AAt80nr
Solved
Karl-WE
Mar 25, 2026 Place Windows Server Insiders
1.3KViews
1like
5Comments