Windows intelligence
Investigate an update failure by matching the symptom, Windows version and affected feature. Separate the update that introduced a documented issue from the remedy that applies to your environment.
Windows failure investigation
Start with the failure you can observe. This check connects the recorded symptom, Windows version and affected feature to the matching evidence. It does not scan or diagnose your PC.
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TraceCheck analysis
A search for a KB can produce both failure reports and success reports. These can describe different features on the same release. Start with the symptom and environment, then determine the update's role in that specific record.
| Update | Recorded as an originating update | Recorded as a correction |
|---|---|---|
| KB5129195 | No originating relationship in this inventory |
|
| KB5124008 |
| |
| KB5120998 | No correction relationship in this inventory | |
| KB5121003 | No correction relationship in this inventory | |
| KB5065426 | No originating relationship in this inventory |
|
| KB5063878 | No correction relationship in this inventory |
In our 24H2/25H2 records, KB5124008 is the correction for the ARM Teams / new Outlook launch issue, while it is an originating update for Plan9 sharing and USB Audio Class 1.0 failures. “This KB fixed my PC” and “this KB broke my PC” therefore do not contradict each other. They answer different questions. Verify which application or device fails before drawing a conclusion from the KB.
ARM app launch record · Plan9 sharing record · USB audio record
KB5129195 is mapped as a complete correction for Plan9 sharing on 24H2/25H2, but as a partial correction for the USB audio issue on those versions. For audio, the recorded correction concerns 8-channel / 3D modes. A device that still fails to start with Code 10 is not evidence that this narrower correction promised to fix every audio symptom. This distinction changes the next step: check the symptom subset instead of repeatedly applying a package for a different failure.
Read the two correction scopes
Manually starting Explorer can recover a desktop session in the documented black-screen case. A session becoming usable does not establish that the underlying change was permanently corrected. Keep the result separate from the vendor's mitigated status, and check the version-specific KIR guidance with the administrator of a managed PC.
These checks are our interpretation of the cited records. They help decide which record deserves investigation; they do not establish the cause on an individual device.
Check: Distinguish a desktop session that fails to load after sign-in from a black wallpaper, a blank display before sign-in or a failed remote connection.
When the evidence does not fit: Microsoft primarily observed this in AVD hosts using FSLogix. A different environment does not rule it out, but this record alone cannot establish that your black screen is the same issue.
Microsoft [1] · Microsoft [2]Check: Confirm the USB Audio Class with the device documentation. Record whether startup fails or only 8-channel / 3D playback fails; the documented update addresses only the latter subset.
When the evidence does not fit: The documented issue is limited to USB Audio Class 1.0. Code 10 or no sound on another device is insufficient to identify this issue.
Microsoft [1] · Microsoft [2] · Microsoft [3] · Microsoft [4]Check: Check architecture and the exact Outlook edition. Compare the Windows update date and Store-package version before selecting the update or Store workaround.
When the evidence does not fit: This record concerns ARM devices and Teams / new Outlook. It does not establish a cause for an x64 PC, classic Outlook or a different application.
Microsoft [1] · Microsoft [2] · Microsoft [3]Check: Confirm that the guest starts and the missing mount is a Plan9 host share. Check whether an administrator previously applied the temporary Group Policy mitigation.
When the evidence does not fit: Standard Hyper-V VMs without Plan9 sharing are outside the documented issue. A VM that fails to boot is a different symptom from a running guest with missing shares.
Microsoft [1] · Microsoft [2]Check: Confirm the application uses NDI and compare the originating update with when the failure started. The linked Windows 11 correction is not a Windows 10 package.
When the evidence does not fit: This record concerns NDI streaming. It cannot establish the cause of generic network latency, an unrelated video stream or a game frame-rate problem.
Source: MicrosoftA reproducible description helps distinguish an unresolved issue from a similar-looking failure. Before changing anything, record the Windows version and build, the installed update history, the exact failure and when it started. Add the feature-specific detail from the checks above. For example, “USB Audio Class 1.0, stereo works, 8-channel playback fails” is more useful than “sound broken after update.”
Compare the version, symptom and feature together. If one is unknown, collect that fact before treating a remedy as applicable. A source-confirmed issue establishes a documented failure; update timing on one PC alone does not prove causation.
After a documented remedy, retry the operation that originally failed and record the result. If the record describes a partial correction or workaround, retain that boundary even when the immediate symptom disappears. If the environment falls outside the cited scope, use the device or application vendor's current support guidance rather than importing an unrelated fix.
The tool saves a brief with the selected applicability, scoped remedy descriptions and source-review date. Complete it locally with your own observations. Keep private logs and identifying information out of public correction requests.
Mitigated Tracked software issue
Some Windows 11 devices fail to load the desktop after sign-in following KB5120998 or later updates. Microsoft primarily observed this on Azure Virtual Desktop hosts using FSLogix. Workarounds are documented; a full resolution remains pending in the reviewed vendor entry.
Windows 11 24H2 · KB5120998; Windows 11 25H2 · KB5120998; Windows 11 26H1; Windows 11 26H2
Mitigated Tracked software issue
Microsoft tracks a USB Audio Class 1.0 failure affecting startup, sound and controls. The current vendor state is mitigated. On Windows 11 24H2/25H2, KB5129195 fixes the 8-channel/3D audio subset; it does not establish that Code 10 or every no-sound symptom is resolved.
15 documented versions across Windows 11, Windows 10, Windows Server · Affected environments
Recorded update fix: Partial — remaining symptoms unresolved · Windows 11 24H2, Windows 11 25H2 · Check instructions
Resolved Resolution recorded 2026-09-08
Microsoft confirmed launch failures or unexpected exits in Teams and the new Outlook on ARM devices after the August 2026 security update. New or freshly imaged PCs without Store updates are more likely to be affected. Windows 11 24H2/25H2 updates from KB5124008 onward resolve this documented issue.
Windows 11 26H1; Windows 11 25H2 · KB5121003; Windows 11 24H2 · KB5121003
Recorded update fix: Documented symptom resolution · Windows 11 24H2, Windows 11 25H2 · Check instructions
Resolved Resolution recorded 2026-09-14
Microsoft confirmed a Plan9 host-folder sharing failure in HCS-managed Linux VMs after the September 2026 Windows security update. Claude Cowork and WSL are named examples. For Windows 11 24H2/25H2, KB5129195 and subsequent updates resolve the issue; ordinary Hyper-V VMs without Plan9 are outside this documented scope.
6 documented versions across Windows 11, Windows 10 · Affected environments
Recorded update fix: Documented symptom resolution · Windows 11 24H2, Windows 11 25H2 · Check instructions
Resolved Resolution recorded 2025-09-09
Microsoft documented uneven NDI audio/video after KB5063878, including in OBS and NDI Tools. The Windows 11 24H2 fix is KB5065426 or a later cumulative update; use the latest applicable update for your device.
Windows 11 24H2 · KB5063878; Windows 10 22H2; Windows 10 21H2
Recorded update fix: Documented symptom resolution · Windows 11 24H2 · Check instructions
Released
Windows 11 24H2, Windows 11 25H2 · Build 26200.9457, 26100.9457
0 tracked known issues · 1 linked resolution
1 partial fix — remaining symptoms unresolved
Released
Windows 11 24H2, Windows 11 25H2 · Build 26200.9445, 26100.9445
2 tracked known issues · 2 linked resolutions
Released
Windows 11 24H2, Windows 11 25H2 · Build 26200.9278, 26100.9278
1 tracked known issue · 0 linked resolutions
Released
Windows 11 24H2, Windows 11 25H2 · Build 26200.9168, 26100.9168
1 tracked known issue · 1 linked resolution
Released
Windows 11 24H2 · Build 26100.6584
0 tracked known issues · 1 linked resolution
Released
Windows 11 24H2 · Build 26100.4946
1 tracked known issue · 1 linked resolution
Microsoft records mitigation with a future resolution still pending.
The reviewed 24H2 entry is mitigated and describes a partial September 14 fix. Its opened date is later than that update, so no earlier confirmed state is invented.
Microsoft records resolution with the September 14 updates and later.
Microsoft opened the Plan9 sharing record. This is an acknowledgement timestamp, not the first device occurrence.
Microsoft records the September 8 Windows update resolution.
Microsoft opened the ARM application launch record.
Microsoft records the Windows 11 24H2 issue as resolved by KB5065426.
Microsoft opened the issue in release health.