Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat

A post-incident report has been published.

A post-incident report has been published.

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may have been unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations weren’t deleted and were temporarily unavailable within conversation history. Some reports indicated that this issue typically occurred when users with an active Copilot Chat left and then reopened the chat. Final status: We’ve completed deployment of the fixes and have received confirmation from a subset of affected customers that the issue is resolved. To ensure you’re using the latest build, please close and reopen the web interface or, if using the app, close and restart it. Scope of impact: Some users were sporadically missing recent portions of their conversation history with Copilot Chat. Start time: Wednesday, October 14, 2026, at 3:55 PM UTC End time: Wednesday, November 4, 2026, at 9:27 PM UTC Root cause: Microsoft 365 Copilot Chat keeps a cached copy of recent conversation activity so that history loads quickly when a user returns to a conversation. Each conversation is stored durably, and the cached copy is held in the part of our service infrastructure that handles the user's requests. During this event, two conditions combined so that some requests loaded an earlier cached copy of a conversation that didn't yet include its most recent exchanges. First, resource limitations in portions of the infrastructure supporting conversation history meant that some updates to the cached copy couldn't be completed in their usual location. Second, requests that load conversation history weren't always routed in the same way as requests that add new messages. As a result, a user returning to a conversation could sometimes be directed to a location holding an older copy of their history. Next steps: - For a more comprehensive list of next steps and actions, please refer to the Post Incident Report document. We've provided a Post-Incident Report for this incident.

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: Our secondary fix has completed across the affected regions, and we're continuing to apply targeted adjustments to address any peripheral errors resulting from the previously identified resource limitations. Meantime, we've observed a withstanding reduction in the errors related to inconsistent message routing, and we expect the impact to users is largely resolved at this time. We're reaching out to a sample of reporting users to seek validation that conversation history is displaying as expected and the impact is fully remediated. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Root cause: A latent request routing configuration issue is impacting users' ability to view recent portions of their conversation history with Copilot Chat. Next update by: Thursday, November 5, 2026, at 2:00 AM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: Deployment of the secondary fix to the remaining regions is nearing completion, and we've observed a precipitous decrease in the errors related to inconsistent message routing, suggesting the impact is largely resolved. We're observing some instances wherein the incorrect routing information persists, so we're continuing our previously described workstream to clear the cached error responses and ensure new requests can use the corrected routing information. In parallel, we're continuing to make targeted adjustments to address any peripheral errors resulting from the previously identified resource limitations within portions of the infrastructure supporting conversation history. This will help us ensure withstanding recovery. After these actions are complete, we’ll closely monitor the service environment during peak business hours and reach out to a sample of reporting users to validate that conversation history is displaying as expected and the impact is fully remediated. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Root cause: A latent request routing configuration issue is impacting users' ability to view recent portions of their conversation history with Copilot Chat. Next update by: Wednesday, November 4, 2026, at 2:00 AM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We’ve deployed the secondary fix to nearly all affected regions to correct inconsistent message routing, and related errors have decreased significantly. Deployment to the remaining regions is ongoing. We’re also clearing cached error responses so that new requests can use the corrected routing information. Separately, we’ve identified resource limitations within portions of the infrastructure supporting conversation history and are making adjustments to address the resulting errors. After these actions are complete, we’ll monitor to validate that conversation history is displaying as expected. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Tuesday, November 3, 2026, at 2:00 AM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We’ve successfully applied the targeted change to improve our infrastructure balancing processes and are monitoring the environment to validate that this change has been successful. In addition, we’re deploying a secondary change to address errors in the environment that have caused inconsistent message routing. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Monday, November 2, 2026, at 8:30 PM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We're continuing our analysis related to how recent conversation activity is synchronized within our service as part of our effort to fully understand the cause of this issue and implement a withstanding solution. In parallel, we're applying a targeted change to improve our infrastructure balancing processes related to the service components which support this synchronization. We expect this change will be completed by the time of our next scheduled update, at which time we'll validate its effectiveness and assess what additional mitigation actions may be required. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Saturday, October 31, 2026, at 11:00 PM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: Our investigation has identified specific geographic regions in our broader service infrastructure where the majority of failures are occurring. We're continuing our analysis related to how recent conversation activity is synchronized within our service as part of this effort. In parallel, we're continuing to review reported cases to confirm whether this accounts for all instances of impact, which will help guide our next steps toward remediation. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Saturday, October 31, 2026, at 1:00 AM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We're continuing our analysis of diagnostic data and service logs provided by affected users to disambiguate reported behaviors, identify any apparent patterns, and isolate the conditions which may be contributing to the issue so we can assess our next troubleshooting actions. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Friday, October 30, 2026, at 6:00 PM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We're continuing to make steady progress in our investigation. We're analyzing diagnostic data and service logs collected from affected users to identify patterns and isolate the conditions contributing to the issue. This analysis is helping us narrow the investigation and determine the most effective path toward remediation. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Friday, October 30, 2026, at 3:00 AM UTC

We're analyzing newly provided diagnostic data from affected users alongside our service logs to help isolate the source of the issue. This quick update is designed to give the latest information on this issue.

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We're working to trace how impacted conversation history requests are moving through each layer of our service to identify any potential inconsistences in routing behavior. We're also reviewing recent diagnostic data from affected users, which will inform our next steps toward remediation. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Thursday, October 29, 2026, at 11:00 PM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: Our review of support cases and service telemetry has identified an issue with how some Copilot Chat requests are directed to our service infrastructure. Requests from the same user can intermittently be sent to different parts of our infrastructure, so a conversation may sometimes load an earlier version of its history that doesn't include the latest exchanges. We're working to determine why these requests aren't being consistently directed, so that we can develop a fix that ensures users always see their complete conversation history. Scope of impact: Some users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Thursday, October 29, 2026, at 9:00 PM UTC

Title: Users may be unable to view recent portions of their conversation history with Microsoft 365 Copilot Chat User impact: Users may be unable to view recent portions of their conversation history with Copilot Chat. More info: The affected conversations have not been deleted and are temporarily unavailable within conversation history. Some reports indicate that this issue typically occurs when users with an active Copilot Chat leave and then reopen the chat. Current status: We're reviewing support cases to further our understanding of the current impact scenario and to determine our next troubleshooting steps. Scope of impact: Your organization is affected by this event, and users are sporadically missing recent portions of their conversation history with Copilot Chat. This section may be updated as the investigation progresses. Next update by: Thursday, October 29, 2026, at 7:00 PM UTC

Title: We're looking into a potential problem impacting Microsoft 365 Copilot Chat User impact: We're checking for potential impact to your users. Current status: We're investigating a potential issue with Microsoft 365 Copilot Chat and checking for impact to your organization. We'll provide an update within 30 minutes.