Some users may have been unable to send messages in Microsoft 365 Copilot chat

Title: Some users may have been unable to send messages in Microsoft 365 Copilot chat User impact: Users may have been unable to send messages in Copilot chat. More info: Impacted experiences included Copilot chat through the Copilot web app, the Copilot app on Windows, Microsoft Teams, Outlook, and Microsoft 365 desktop apps. Final status: We’ve determined that a recent Copilot service update inadvertently increased traffic beyond expected levels, resulting in impact. We’ve confirmed that reverting the update successfully mitigated the impact and restored the service. Scope of impact: Some users attempting to send messages in Copilot chat through the Copilot web app, the Copilot app on Windows, Microsoft Teams, Outlook, and Microsoft 365 desktop apps may have been impacted. Start time: Monday, October 19, 2026, at 7:20 AM UTC End time: Monday, October 19, 2026, at 9:20 AM UTC Root cause: A recent Copilot service update inadvertently increased traffic beyond expected levels, resulting in impact. Next steps: - We're reviewing our update procedures to better identify similar issues during our development and testing cycles. This is the final update for the event.

Title: Some users may be unable to send messages in Microsoft 365 Copilot chat User impact: Users may be unable to send messages in Copilot chat. More info: Impacted experiences include Copilot chat through the Copilot web app, the Copilot app on Windows, Microsoft Teams, Outlook, and Microsoft 365 desktop apps. Current status: We’ve identified that a section of the Copilot service infrastructure that facilitates access is performing below acceptable thresholds. We’ve identified a service change that may be contributing to the impact and have reverted the change in an attempt to mitigate the issue. In parallel, we’re reviewing service telemetry and error data to confirm the root cause. Scope of impact: Some users attempting to send messages in Copilot chat through the Copilot web app, the Copilot app on Windows, Microsoft Teams, Outlook, and Microsoft 365 desktop apps are impacted. This information may be updated as our investigation continues. Next update by: Monday, October 19, 2026, at 11:30 AM UTC