SearchHost.exe crash loop (combase.dll 0xc0000602 / Windows.UI.Xaml.dll 0xc0000409) after build 26220.9836 — taskbar search box completely unresponsive

兴睿 邓 0 Reputation points
2026-11-02T05:33:06.53+00:00

Environment

Windows 11 25H2, Build 26220.9836 (Beta channel, Ring=External, BranchName=Beta, IsBuildFlightingEnabled=1) BuildLabEx: 26100.6.amd64fre.ge_release_flt.260716-1700 Update installed: 2026-11-01 21:37:56 (Windows 11 Insider Preview Quality Update 26220.9836)

Symptom

After installing build 26220.9836, clicking the taskbar search box (or pressing Win+S) does nothing. The search flyout never appears. SearchHost.exe crashes immediately on every launch and enters a continuous crash loop (one crash every 8–20 seconds). Sometimes the process survives but creates zero top-level windows, so the search UI never renders.

Crash signatures (Application Error, Event ID 1000 — 249 occurrences in 24 hours)

Primary (224 occurrences):

Faulting application name: SearchHost.exe, version: 2610.12001.100.6000, time stamp: 0x6ad3c7e0 Faulting module name: combase.dll, version: 10.0.26100.9836, time stamp: 0x21696719 Exception code: 0xc0000602 (STATUS_FAIL_FAST_EXCEPTION) Fault offset: 0x00000000001746f0 Faulting application path: C:\WINDOWS\SystemApps\MicrosoftWindows.Client.CBS_cw5n1h2txyewy\SearchHost.exe Faulting package full name: MicrosoftWindows.Client.CBS_1000.26100.494.0_x64__cw5n1h2txyewy Faulting package-relative application ID: CortanaUI

Secondary (11 occurrences):

Faulting module name: Windows.UI.Xaml.dll, version: 10.0.26100.9836 Exception code: 0xc0000409 (__fastfail(7)), Exception data: 0000000000000007 Fault offset: 0x000000000032ed0e

Activation failure (Microsoft-Windows-TWinUI/Operational, Event ID 5961, 56+ occurrences):

Activation for MicrosoftWindows.Client.CBS_cw5n1h2txyewy!CortanaUI failed. Error code: Unknown HResult Error code: 0x80040904. Activation phase: COM App activation

Timeline 2026-11-01 21:37:56 — build 26220.9836 install completes 2026-11-01 22:18:59 — first SearchHost.exe crash (41 minutes after the update) 2026-10-11 to 2026-11-01 — three full weeks, ZERO SearchHost.exe crashes in the Application log Since then — continuous crash loop

What I have already verified (to save everyone time) The crash happens extremely early: WER LoadedModule snapshot at crash time shows only 19 modules, all Microsoft-signed system DLLs, no third-party modules. The crash occurs before dui70.dll is even loaded. The exact same Windows.UI.Xaml.dll binary (SHA256 D76D7B180BE58315D033A17A246A455CA95AC040DFD5E15BE9ED5518A3555F76, hard-linked from WinSxS component amd64_microsoft-windows-directui_10.0.26100.9836) loads and works correctly in TextInputHost.exe, ShellExperienceHost.exe, StartMenuExperienceHost.exe and ApplicationFrameHost.exe. Only SearchHost.exe fails. FESearchHost.exe, which shares the same EntryPoint (CortanaUI.App), crashes with the same signature. The update replaced 74 files inside the MicrosoftWindows.Client.CBS package on 2026-11-01 20:53:53 (SearchHost.exe, FESearchHost.exe, SearchUx.UI.dll, resources.pri, OSClient.NET.dll, OSClient.UWP.dll, etc.), while the package Identity version stayed at 1000.26100.494.0. Package signature is valid, ACLs are repaired successfully on every re-registration, and Get-AppxPackage reports Status=Ok for all framework packages (Microsoft.UI.Xaml.CBS 9.2603.18001.0, WindowsAppRuntime.CBS.1.6, etc.). WSearch service is Running/Automatic; no search-related group policies are set; no third-party shell modifiers; no IFEO/AppInit_DLLs entries. 12 WER reports archived (AppCrash_SearchHost.exe_75be5253b15048cf44e47c4efa96dc4c3c359da_6d7586b4_*). Full WER reports and a CSV of all 249 crash events are available on request. The 26220.9836 release notes page has no Known issues section, and the Windows 11 25H2 release health page has no Search/SearchHost entries — this does not appear to be a tracked issue yet.

Steps to reproduce Install build 26220.9836 (Beta channel) on Windows 11 25H2. Click the taskbar search box, or press Win+S. Nothing happens.

Expected: the search flyout opens. Actual: no response; SearchHost.exe enters a crash loop (visible under Event Viewer → Windows Logs → Application → Error, Event ID 1000).

Question

Is this a known regression in build 26220.9836? Is there a workaround (e.g., re-registering the CBS package, resetting search) that actually stops the crash loop, or is the only fix to wait for the next Beta build / roll back?

Windows Insider program | Windows Insider preview | Search
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  1. Kai-H 30,565 Reputation points Microsoft External Staff Moderator
    2026-11-02T10:29:40.4166667+00:00

    Hi, 兴睿 邓

    Thanks for the detailed write-up, it really helps. The update swapped out the files inside the MicrosoftWindows.Client.CBS package but kept the old package version number, and that mismatch is the most likely reason SearchHost fails during COM activation. Re-registering the package won't fix it because the broken files are part of the build itself. I can't find this listed anywhere as a known issue for this build yet, either in the release notes or on forums.

    Here are some suggestions you can try:

    Repair the build without losing anything. Go to Settings > System > Recovery and click Reinstall now under "Fix problems using Windows Update." It reinstalls the same build and keeps your apps and files, so the CBS package gets a clean, matching copy.

    Uninstall the update if the repair doesn't help. Go to Settings > Windows Update > Update history > Uninstall updates and remove the 26220.9836 quality update (KB5127935). If it isn't listed there, use Settings > System > Recovery > Go back, which is only available for about 10 days after the update. Then pause updates until the next Beta flight comes out.

    Check whether it's tied to your user profile. Create a new local account and try Win+S there. If search works in the new account, it's recommended that you move to that profile instead of rolling back.

    Send it to Microsoft through Feedback Hub (Win+F > Desktop Environment > Search) and attach a couple of your WER reports. That's the fastest way to get it in front of the Insider team.

    In the meantime, you can still search your files from File Explorer, and PowerToys Command Palette works well as a stand-in for the search box.

    Was this answer helpful?

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