Microsoft Update Breaks Outlook and Teams on Arm Devices

A Windows security update distributed by Microsoft in August 2026 is causing serious application failures on some devices that use the Arm architecture. It has been confirmed that the new Outlook and Microsoft Teams fail to launch or close immediately after launching. The company acknowledged the issue on September 1 and published information on the Windows release health dashboard. According to reporting by Richard Speed of The Register, a separate issue in which custom cursor settings are reset has also been reported alongside this bug.

Overview of the Launch Failure Caused by the

August Update

The source of the problem is Windows security update KB5121003, distributed on or after August 11, 2026. On Arm-based devices that have applied this update, there have been a series of cases where the new Outlook for Windows and Microsoft Teams fail to launch properly. In a notice published by Microsoft, it states:

After installing Windows security updates released on or after August 11, 2026 (KB5121003), Microsoft Teams and the new Outlook for Windows might fail to launch or might close unexpectedly on ARM-based devices, such as Surface Pro 11 and Surface Laptop 7

The company explains that no impact has been confirmed on the classic version of Outlook (Classic Outlook) or other applications such as Word and Excel. It notes that the issue tends to occur more prominently in environments that have not yet applied updates via the Microsoft Store, such as newly deployed PCs or PCs immediately after reimaging. According to The Register, Microsoft has not yet provided a detailed explanation of the root cause.

This incident is significant in that it has surfaced as Arm-based Windows becomes more widespread. In recent years, Microsoft has strengthened its optimization for Arm, centered on Copilot+ PCs. A situation in which Outlook and Teams, which are central to business operations, become simultaneously unusable has a major impact on productivity. In corporate environments especially, these applications function as the foundation for communication. If the launch failure is prolonged, concerns about business continuity will arise.

Impact Limited to Arm Devices

The impact is limited to Arm-based devices. Specifically, Microsoft’s own hardware such as Surface Pro 11 and Surface Laptop 7 is cited as examples. These models are equipped with Qualcomm SoCs and are positioned as representative implementations of Windows on Arm.

The affected OS versions include Windows 11 24H2 and 25H2, as well as Windows 11 26H1. 26H1 is an extremely new version that requires specific silicon such as Qualcomm’s Snapdragon X2, and its distribution in the market is limited. The fact that the test population for Arm-based Windows is smaller than that for the x86 version may be behind why this bug was overlooked.

Microsoft adds that it is “more likely to occur on new PCs or reimaged PCs.” This is thought to be because components distributed via the Microsoft Store have not been updated to the latest version at the factory-shipped state or immediately after initial setup. In existing environments where Store updates have already been applied, the necessary dependencies may have already been resolved. In corporate mass-deployment kitting processes, the timing of Store updates becomes an operational issue.

There have been past cases where Windows updates caused failures only on a specific architecture. The Arm version has a different execution path from the x86 version, including a mix of emulation layers and native compilation. Both Outlook and Teams in this case rely heavily on WebView and Edge-based components, and it is possible that the consistency of dependent libraries was broken during the process of making them Arm-native. However, this is speculation by the editorial team, and Microsoft has not disclosed the technical cause.

Temporary Workaround Using AI Gaming Feature

The workaround presented by Microsoft is the installation of a component that at first glance appears unrelated. The company states that the Outlook and Teams launch failure can be mitigated by installing version 1.0.19.0 or later of the Auto Super Resolution Package from the Microsoft Store.

The Auto Super Resolution Package is originally an AI-powered gaming feature provided for Copilot+ PCs. According to Microsoft, it is positioned as a package aimed at “making supported games run more smoothly and in higher detail with AI.” It is unclear why components related to frame generation and super-resolution processing for games would be involved in launching an email client and a business chat app. It is possible that they share a common graphics stack, AI runtime, or system libraries for Arm.

The distribution via the Store is also distinctive. It is provided as a Store app update, through a different channel from OS-level security updates like KB5121003. For this reason, in corporate environments that only manage Windows Update, Store updates may be outside the scope of management by WSUS or Intune. In environments where administrators have intentionally disabled the Store, applying the workaround itself may be difficult.

Microsoft has not specified a timeline for a permanent fix. For the time being, applying this package is the official mitigation. Users need to launch the Microsoft Store and manually obtain the package from library updates. Even if automatic updates are enabled, it may take time to be reflected, so manual checking is recommended if urgency is high.

Separate Custom Cursor Bug

Separately from the Arm-related launch failure, another bug caused by a preview update distributed on August 27, 2026 has been confirmed. Custom mouse pointer settings are reset to the Windows default state. Microsoft has also published its investigation findings on this issue.

Our investigation indicates that this issue is caused by code components used in non-English Windows installations. In impacted locales, these settings will fail to load, causing a default to be used instead.

According to the company, it is caused by code components used in non-English Windows installations. In affected locales, pointer settings fail to load and fall back to default values. Even if a user tries to manually restore the settings, they will not be applied because the loading process itself fails.

The targets are Windows 11 24H2 and 25H2. Unlike the Arm-specific issue, this is an event dependent on language settings and may affect a broader range of users. For users who customize pointer size and color from an accessibility perspective, this is an issue that directly affects visibility and operability. If a company deploys unified accessibility settings, an unintended reset will lead to increased support load.

The two bugs have different causes and scopes, but they share the common point of originating from August update programs. This means that separate regressions have occurred in different distribution categories — security updates and preview updates. This is a situation that calls into question the reliability of Microsoft’s update programs.

Consecutive Issues Diverging from a

Quality-First Stance

The series of bugs is creating a gap with Microsoft’s stated commitment to quality. Pavan Davuluri, who leads Windows, emphasized a commitment to quality in early 2026. While feature improvements such as making the taskbar movable have attracted attention, updates that prevent applications from launching and reset user settings undermine stability as a foundation.

The quality of Windows updates has been the subject of repeated debate in the past. As reported in Microsoft Secure Boot Remained Vulnerable for 13 Years, there are areas where fundamental fixes have not been made for a long time, while cases where new features or security fixes trigger other bugs, as in this instance, are endless. As demonstrated by Microsoft Defender Privilege Escalation Vulnerability “RoguePlanet” Disclosed, the increasing complexity of security-related components may cause unexpected interactions on emerging architectures such as Arm.

Windows on Arm is a strategically important area for Microsoft. Copilot+ PCs equipped with the Snapdragon X series are positioned as next-generation PCs that run AI processing locally. The stable operation of core Microsoft 365 applications such as Outlook and Teams on Arm is a prerequisite for that strategy. The fact that this failure is characterized as “more likely to occur on new PCs” directly impacts new buyers of Arm devices.

In addition, as shown by Behind the Scenes of the Microsoft AARD Code $280 Million Settlement, Microsoft’s platform strategy has in the past also led to controversy over compatibility and display controls. The workaround using the Auto Super Resolution Package highlights the high degree of internal coupling within the platform, where a gaming AI feature has become a dependency for business applications. As long as dependencies between components remain opaque, administrators and developers cannot predict the scope of impact.

The focus going forward will be on through which distribution channel and how quickly Microsoft will provide a permanent fix. The mitigation via the Store package is only a temporary measure, and a revised version of KB5121003 itself or a comprehensive solution in a cumulative update is required. For organizations considering enterprise adoption of Arm devices, the need to include Arm hardware in the update verification process has once again become clear.

Editorial Opinion

In the short term, we expect the operational burden of update management to increase for companies and educational institutions that operate Arm-based Windows. A decision will be required on whether to defer the application of KB5121003 or to enforce distribution of the Auto Super Resolution Package via the Store. We assess that a review of the verification flow, including Store updates, will be essential, especially in the kitting process for new PCs. The cursor bug caused by the preview update also provides reason for caution in deployments in non-English environments. From a long-term perspective, we see this as a phase in which the reliability of Windows on Arm itself is being tested. The spread of next-generation hardware such as Copilot+ PCs and devices equipped with Snapdragon X2 depends on the maturity of OS and application support for Arm native. If incidents where Outlook and Teams, which are central to business operations, become unable to launch continue, IT departments may become more conservative about transitioning to Arm. Whether Microsoft treats Arm as a first-class target in its quality assurance system will be tested.

References

• “Microsoft update disarms Outlook and Teams on Arm PCs”, by Richard Speed — The Register, 2026-09-02T12:30:00.000Z (ARR)
• Source URL: https://www.theregister.com/os-platforms/2026/09/02/microsoft-update-disarms-outlook-and-teams-on-arm-pcs/5293849