Tracked Windows update
KB5129195 known issues and fixes
September 2026 out-of-band cumulative update for Windows 11 24H2 and 25H2. Fixes the tracked Plan9 sharing failure and only the 8-channel/3D subset of the USB audio issue.
- Release date
- Windows versions
- Windows 11 24H2, Windows 11 25H2
- OS builds
- 26200.9457, 26100.9457
- Official source
- KB5129195 — Microsoft Support
- Last verified
This is a directory of TraceCheck's tracked records, not a complete list of every vendor issue. Zero tracked records does not establish that an update is problem-free.
TraceCheck cross-reference
What role does this KB play?
Keep the update linked to the failure separate from the update linked to its resolution. These roles come from the cited issue records.
| Issue | This KB's role | Evidence |
|---|---|---|
| USB Audio Class 1.0 Code 10 / no sound after KB5124008 | Partial fixing update | Source: Microsoft |
| Claude Cowork / WSL host folders missing after KB5124008 | Resolving update | Microsoft [1] · Microsoft [2] |
An originating update identifies the documented association; it does not establish the technical root cause. A resolving update applies to its listed Windows versions. This historical index does not identify today's latest update.
Known issues
Mitigated Tracked software issue
USB Audio Class 1.0 Code 10 / no sound after KB5124008
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 issues
Resolved Resolution recorded 2026-09-14
Claude Cowork / WSL host folders missing after KB5124008
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
Compatibility reports
No separate unconfirmed compatibility reports are currently tracked.
Related fixes and workarounds
Update for the 8-channel / 3D audio subset
FACT Official fix · vendor fix
KB5129195 corrects the multichannel subset on Windows 11 24H2/25H2. Other documented startup, no-sound and control symptoms remain outside this partial resolution. The cited update is historical; select the applicable current update for the device.
Partial fix — remaining symptoms are unresolved
Applies to: Windows 11 24H2, Windows 11 25H2.
Risk: medium (TraceCheck editorial assessment, not a vendor success rate)
Install the applicable Windows update for Plan9 sharing
FACT Official fix · vendor fix
Microsoft documents KB5129195 or subsequent updates for Windows 11 24H2/25H2. Use the current applicable cumulative update. Previous Group Policy mitigation also requires the vendor re-enable/install/restart procedure. Other host versions need their own packages.
Documented symptom resolution
Applies to: Windows 11 24H2, Windows 11 25H2.
Risk: medium (TraceCheck editorial assessment, not a vendor success rate)
Fixing update: KB5129195 · Microsoft [1] · Microsoft [2]
Read Microsoft's instructions ↗Read Microsoft's instructions ↗
Evidence
- KB5129195 — Microsoft Support
Microsoft · Vendor documentation
Supports: Release date, Windows 11 24H2/25H2 applicability and OS builds. This KB is a historical record, not a claim about the latest update.
Change history
No earlier verified state transitions are recorded.