Microsoft 365 Alert – Service Degradation – Microsoft Copilot (Microsoft 365) – Some users may be unable to open or use custom Copilot agents in Microsoft 365 Copilot and receive an error – ONGOING

13/07/2026 08:12:00 AM

NHSmail Reference: INC46877071

Microsoft Reference: CP1425545

Issue Status: ONGOING

Issue Description: Users may be unable to open or use custom Copilot agents and receive an error.

More info: Impacted users report receiving an error stating “Something went wrong” or “Client error: Cannot read properties of undefined” and may encounter client crashes when attempting to open custom Copilot agents that were created through the Agent Builder in Microsoft 365 Copilot. User reports indicate that custom agents may still be accessible through Microsoft Teams.

Current Update: 13/07/2026 09:22:00 AM – Microsoft has identified that Microsoft Copilot (Microsoft 365) receives incomplete data while loading the agent experience, causing the app to fail and render correctly. They are validating deployment of a newer build that contains the fix and, if successful, plan to roll it out to the affected environment to mitigate impact.

Scope of impact: Some users who are attempting to open or use custom Copilot agents that were created through the Agent Builder in Microsoft 365 Copilot may be impacted. This information may be updated as our investigation continues.

Root cause: A recent service change caused Microsoft Copilot (Microsoft 365) to receive incomplete data when loading the agent experience. As a result, the app couldn’t render the affected experience correctly for some users.

Next update by: Monday, July 13, 2026, at 7:00 PM UTC