Brighton Central School District

Title: Users may be unable to access Microsoft 365 Copilot in the browser and may encounter a 400 Request Header error User impact: Users may be unable to access Copilot in the browser and may encounter a 400 Request Header error. More info: As a temporary workaround, affected users may be able to restore access to Microsoft Copilot by clearing their browser cookies and then trying again. Current status: We've received reports from a subset of affected users who have reported that they are unable to access Copilot in their browser and are encountering a 400 Request Header error. We've isolated that impact is caused by a recent service change that affects the way browser authentication information is stored for Copilot. This can cause some browser requests to exceed expected limits, which may prevent users from accessing the service. We've initiated deployment of a fix to address the browser authentication information misconfiguration, and we anticipate deployment to be completed by our next scheduled update. Scope of impact: Impact is specific to some users attempting to access Copilot in the browser. Start time: Friday, July 31, 2026, at 8:00 PM UTC Root cause: A recent service change that affects the way browser authentication information is stored for Copilot. This can cause some browser requests to exceed expected limits, which may prevent users from accessing the service. Next update by: Wednesday, August 5, 2026, at 7:00 PM UTC