Copilot.exe crashes due to Microsoft.UI.Xaml.dll (October 18, 2025) #10848
Description
Describe the bug
Summary:
On October 18, 2025 at 22:14 and 22:15 JST, Copilot.exe (version 1.25095.165.0) crashed twice due to Microsoft.UI.Xaml.dll (version 3.1.7.0). The issue was recorded in both Event Viewer and Reliability Monitor.
Event Viewer details:
- Faulting application: Copilot.exe
- Version: 1.25095.165.0
- Faulting module: Microsoft.UI.Xaml.dll (version 3.1.7.0)
- Exception code: 0xc000027b
- Fault offset: 0x000000000039cde5
- Application path: C:\Program Files\WindowsApps\Microsoft.Copilot_1.25095.165.0_x64__8wekyb3d8bbwe\Copilot.exe
- Module path: C:\Program Files\WindowsApps\Microsoft.WindowsAppRuntime.1.7_7000.652.1806.0_x64__8wekyb3d8bbwe\Microsoft.UI.Xaml.dll
- Report IDs: 9dc667c7-8c0d-4ad3-a984-57e8566fba41 and e913863c-b9be-420c-81a4-55ada4312596
Reliability Monitor details:
- Problem event name: MoAppCrash
- Faulting module: StackHash12_76b
- Exception code: 8000ffff
- OS version: 10.0.26200.2
- Bucket ID: 333c85dec68b8f88cb560ed288193270
Additional note:
The affected DLL (Microsoft.UI.Xaml.dll) was last modified on October 17, 2025 at 08:29:55 JST, indicating it was reinstalled or redeployed prior to the crash. Since the crash occurred after this timestamp, it is likely that the newly deployed DLL itself contains a defect or incompatibility worth investigating.
During the crash events, the entire Windows environment became nearly unresponsive for several minutes. Window contents stopped rendering properly, and UI drawing was significantly delayed or frozen. This suggests that the fault may have affected system-wide rendering components beyond the Copilot process.
Environment details:
- OS version: Windows 11 Pro, Version 25H2, Build 26200.6899
- System language: Japanese (ja-JP)
- Region: Japan (JST)
Steps to reproduce the bug
The exact trigger is unknown, and the issue cannot be reproduced reliably through specific actions. However, the following conditions were observed:
- Launch Copilot from the Start menu or taskbar.
- Wait for the interface to load and begin interacting with the UI.
- No specific input is required; within a few minutes, the application crashes.
- During the crash, the entire Windows environment becomes nearly unresponsive.
- Window contents stop rendering, and UI drawing freezes across multiple applications.
Note: The crash does not occur consistently, and no clear pattern has been identified. It appears to be caused by internal conditions or DLL behavior rather than user interaction.
Expected behavior
Copilot.exe was expected to launch normally and remain responsive throughout usage. The UI should have rendered consistently without freezing or delays. No system-wide impact was expected; other windows and applications should have continued to function and display properly. The application should not crash or trigger rendering failures in the Windows environment.
Screenshots
No response
NuGet package version
None
Packaging type
Packaged (MSIX)
Windows version
No response
IDE
No response
Additional context
The crash caused a temporary system-wide rendering freeze. For several minutes, window contents stopped updating and UI responsiveness was severely degraded across multiple applications. Additionally, the affected DLL (Microsoft.UI.Xaml.dll) had been last modified on October 17, 2025—prior to the crash events on October 18—suggesting that the issue may stem from the newly deployed version itself.
Windows version: 11, 25H2 (not listed in dropdown)