KB5121003 rolls back with error 0x800f0845 on some Windows 11 HP laptops (August 22, 2026)
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What the failure looks like
The sequence in the thread does not vary. Windows Update downloads KB5121003 and asks for a restart. The laptop reboots to the HP logo and sits there long enough that the owner assumes the machine is dead. Automatic Repair then takes over, undoes the update and returns Windows to OS Build 26200.8875. Windows Update records the attempt with error 0x800f0845.
A memory-training screen appears during the boot that follows each failed attempt. Nothing published as of August 22, 2026 ties that screen to the update, so I am keeping it as an observation rather than a cause.
Nothing else about the laptop looks broken. The owner ran the two commands that usually explain a failed update, and both came back clean, which is covered further down.
TL;DR
On Windows 11 Home 25H2, the August security update KB5121003 refuses to install on a batch of HP OmniBook X Flip laptops, hanging at the vendor logo before Automatic Repair rolls it back, according to a Microsoft Q&A thread opened on August 22, 2026. Windows Update reports error 0x800f0845 and the machine stays on OS Build 26200.8875 instead of the 26200.9168 that KB5121003 is supposed to deliver, per the update's own notes (Microsoft Support, August 11, 2026). As of August 22, 2026 there is no Microsoft known issue for this install failure and no published workaround.
- The loop is the same every time: download, restart, a long wait on the HP logo, Automatic Repair, rollback to OS Build 26200.8875.
- Windows Update logs error 0x800f0845, and the machine stays on OS Build 26200.8875 rather than the 26200.9168 that KB5121003 installs.
- DISM /Online /Cleanup-image /Restorehealth completed successfully and sfc /scannow found no integrity violations, so the usual corruption checks clear the machine rather than explain it.
- The reported hardware is narrow: HP OmniBook X Flip 16-inch 2-in-1, model 16-cc0003dx, AMD Ryzen AI 5 430, 16 GB RAM, Windows 11 Home 25H2.
- Microsoft's known issues list for KB5121003 covers the RGB-driver game crashes and an Arm64 launch failure in Teams and the new Outlook, not install failures.
The machine and the build numbers
One machine is described in detail, which matters because that detail is what lets another owner tell whether they are looking at the same fault. Here is what is on the record.
| Item | Detail |
|---|---|
| Model | HP OmniBook X Flip 16-inch 2-in-1, 16-cc0003dx |
| Processor | AMD Ryzen AI 5 430 |
| Memory | 16 GB |
| Edition | Windows 11 Home 25H2 |
| Build after rollback | 26200.8875 |
| Build KB5121003 should deliver | 26200.9168 |
| Update error | 0x800f0845 |
What Microsoft has published about KB5121003
Microsoft's page for KB5121003 lists the update's known issues. On August 11, 2026 that list covered games becoming unresponsive on systems with RGB lighting drivers, naming ARC Raiders, MARVEL Tokon: Fighting Souls and THE FINALS, plus a launch failure in Teams and the new Outlook on Arm64 devices. Install failures are not on the list.
The same page notes that KB5121003 ships servicing stack update KB5123304, which Microsoft says "improves Windows update installation reliability". That is the component whose job is to make an installation like this one complete. On these laptops it did not.
So the honest status as of August 22, 2026 is a documented user report with a repeatable pattern, no Microsoft acknowledgement, and no fix.
What the standard repair commands rule out
The two commands most help desks run first both came back clean on the affected laptop. DISM /Online /Cleanup-image /Restorehealth completed successfully. sfc /scannow found no integrity violations. That is information, not a dead end: the component store and the protected system files are intact, and whatever stops KB5121003 from installing is not visible to either tool.
It also means the advice that circulates for update error codes, run DISM and sfc then retry, has already been tried on this hardware and did not change the outcome. Repeating it costs another long boot and another Automatic Repair pass.
What you can do today
If a laptop is stuck in this loop, this is the order I would work in as of August 22, 2026.
1. Confirm the build. Press Windows and R, type winver, press Enter. OS Build 26200.8875 on a machine that has tried KB5121003 means the update rolled back rather than installed.
2. Read the exact code. Settings > Windows Update > Update history shows the failed entry and its error code. 0x800f0845 is the code on the record for this model, and it is the first thing anyone looking at the machine will ask for.
3. Run the two repair commands once, from an elevated Command Prompt: DISM /Online /Cleanup-image /Restorehealth, then sfc /scannow. If they report and repair something, retry the update once. If they come back clean, as they did in the thread, stop retrying.
4. Do not uninstall anything. Nothing installed, so there is nothing to remove, and the security content of KB5121003 stays missing until the install succeeds. That gap is the reason this is worth chasing rather than shrugging off.
5. Add your model, edition, build and error code to the Microsoft Q&A thread. One report on one laptop reads as a local fault. Several reports on the same model are what moves a problem onto Microsoft's known issues list, which is where a workaround and a fix build would appear.
If you would rather not run any of that by hand, Get XLAnt.
Frequently asked questions
Is there a Microsoft known issue for this install failure?
Not as of August 22, 2026. Microsoft's KB5121003 page lists the RGB-driver game crashes and the Arm64 Teams and Outlook launch failure, and install failures are not among them. Until an entry exists there is no official workaround and no fix build to wait for.