KB5124010 fixes a 0x139 Bluetooth audio crash on Windows 11, in preview (September 10, 2026)
Chapters
The fix list is the bug list
A release note that says an update resolves a crash is also an admission that the crash exists. Read the KB5124010 notes that way and they describe the Bluetooth experience a lot of people have been living with on Windows 11: accessories shown as connected after they had disconnected, a radio that is off while Settings says it is on, a Settings page that falls over while you manage audio devices, unreliable microphones on Bluetooth Classic Audio accessories, flaky LE Audio accessories, and a crash with error code 0x139 while audio is streaming.
The two verbatim lines are worth quoting. The notes say the update resolves an issue that could result in a crash, error code 0x139, while streaming Bluetooth audio, and an issue where the Bluetooth radio could be turned off but the radio control toggle on the Bluetooth and devices page in Settings appeared on. The second one explains a lot of failed troubleshooting: the switch in Settings was not telling the truth about the hardware.
| Item | Detail |
|---|---|
| Update | KB5124010, Release Preview Channel, September 10, 2026 |
| Builds | 26100.9539 (24H2), 26200.9539 (25H2), 26300.9539 (26H2) |
| Crash fixed | Error code 0x139 while streaming Bluetooth audio |
| Toggle fixed | Radio off while the control on the Bluetooth and devices page appeared on |
| Connection state | Accuracy of the state shown for accessories that have disconnected |
| Settings stability | The Bluetooth and devices page in Settings |
| Added | Shell volume flyout when adjusting a Bluetooth Classic Audio accessory's volume during voice calls |
| Rollout | Gradual and normal rollout phases, so availability varies by device |
TL;DR
Streaming Bluetooth audio on Windows 11 could crash with error code 0x139, and that is one of the defects Microsoft says it has corrected in KB5124010, the Release Preview update documented in Microsoft's Windows Insider release notes published on September 10, 2026. The same notes describe a Bluetooth radio that could be turned off while the toggle in Settings showed it on, plus fixes for accessory connection state and for the stability of the Bluetooth and devices page. None of it has reached general-availability PCs, which are still on September's KB5124008.
- KB5124010 went to the Release Preview Channel on September 10, 2026 for builds 26100.9539 (24H2), 26200.9539 (25H2) and 26300.9539 (26H2).
- Microsoft's wording: the update resolves an issue that could result in a crash, error code 0x139, while streaming Bluetooth audio.
- It also resolves a radio that could be off while the control on the Bluetooth and devices page in Settings appeared on, improves the reported connection state for accessories that have disconnected, and improves the stability of that Settings page.
- It adds the shell volume flyout when you change a Bluetooth Classic Audio accessory's volume during a voice call.
- It is a preview-stage servicing update on gradual and normal rollout, so the fixes are not on PCs running the general-availability September update, KB5124008, builds 26200.9445 and 26100.9445.
Who actually has these fixes
Only Release Preview machines, and not all of them at once. KB5124010 is served through gradual rollout and normal rollout phases, so availability varies by device even inside the channel. A PC in the Release Preview Channel on 26100.9539, 26200.9539 or 26300.9539 has the fixes. Everything else does not.
Ordinary PCs are running the September security update instead. Microsoft Support published KB5124008 on September 8, 2026, taking 25H2 to build 26200.9445 and 24H2 to 26100.9445, and none of the Bluetooth work above is in it. Its known issues list has a separate audio problem of its own, USB audio devices failing to start, along with Hyper-V host folder shares and Remote Desktop Services.
What Microsoft has not said
The notes do not say when this reaches general availability. There is no date, no target month and no statement about which of the fixes ride which future update. Release Preview content usually lands in a following monthly update, but I am not going to put a date on it that Microsoft has not published.
The notes also do not say what caused any of it. There is no root cause for the 0x139 crash, no list of affected Bluetooth chipsets or drivers, and no way to tell from the outside whether your particular headset is in scope. If your accessory misbehaves in exactly one of these ways, the honest position on September 10, 2026 is that a fix exists in preview and you cannot have it yet.
What you can do today
1. Check which build you are on. Run winver. 26100.9539, 26200.9539 or 26300.9539 means you have KB5124010. 26200.9445 or 26100.9445 means you are on the September security update and you do not.
2. Do not join the Release Preview Channel on a machine you depend on to earn a living. Running pre-release Windows to fix a Bluetooth accessory trades a known irritation for unknown ones.
3. When Bluetooth audio crashes a machine, write down the time, the accessory model and whether audio was streaming. Event Viewer keeps the crash record, and error code 0x139 is now a documented Windows defect rather than a mystery to chase.
4. Stop trusting the Bluetooth toggle in Settings while you are on the September update. Microsoft has now documented that it can show on while the radio is off, so check the device itself before you conclude the accessory is broken.
5. For anything that has to work this week, use a cable or a different accessory. There is no published workaround for these Bluetooth defects on a general-availability PC as of September 10, 2026.
Frequently asked questions
Can I get KB5124010 on a normal Windows 11 PC?
Not on September 10, 2026. It is a Release Preview Channel update for builds 26100.9539, 26200.9539 and 26300.9539, delivered through gradual and normal rollout. The only way to get it is to run pre-release Windows on that machine.