{"id":17690,"date":"2026-08-05T08:01:42","date_gmt":"2026-08-04T23:01:42","guid":{"rendered":"https:\/\/m365jp.net\/?p=17690"},"modified":"2026-08-05T08:15:19","modified_gmt":"2026-08-04T23:15:19","slug":"servicedegradation-cw1447067-microsoft-365-copilot-chat-users-may-be-unable-to-access-microsoft-copilot-chat-in-the-browser-and-may-encounter-a-400-request-header-error-4","status":"publish","type":"post","link":"https:\/\/m365jp.net\/index.php\/2026-08-05-servicedegradation-cw1447067-microsoft-365-copilot-chat-users-may-be-unable-to-access-microsoft-copilot-chat-in-the-browser-and-may-encounter-a-400-request-header-error-4","title":{"rendered":"[serviceDegradation] CW1447067 | Microsoft 365 Copilot Chat | Users may be unable to access Microsoft Copilot Chat in the browser and may encounter a 400 Request Header error"},"content":{"rendered":"
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CW1447067 | Microsoft 365 Copilot Chat | Users may be unable to access Microsoft Copilot Chat in the browser and may encounter a 400 Request Header error<\/th>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n\n\n\n\n\n\n\n\n\n\n
Status<\/th>\nserviceDegradation<\/td>\n<\/tr>\n
Classification<\/th>\nincident<\/td>\n<\/tr>\n
User Impact<\/th>\nUsers may be unable to access Microsoft Copilot Chat in the browser and may encounter a 400 Request Header error.<\/td>\n<\/tr>\n
Last Updated<\/th>\n08\/04\/2026 22:09:39<\/td>\n<\/tr>\n
Start Time<\/th>\n07\/31\/2026 20:00:00<\/td>\n<\/tr>\n
End Time<\/th>\n<\/td>\n<\/tr>\n
Latest Message<\/th>\nTitle: Users may be unable to access Microsoft Copilot Chat in the browser and may encounter a 400 Request Header error <\/p>\n

User impact: Users may be unable to access Microsoft Copilot Chat in the browser and may encounter a 400 Request Header error. <\/p>\n

More info: As a temporary workaround, affected users may be able to restore access to Microsoft Copilot Chat by clearing their browser cookies and then trying again. <\/p>\n

Current status: Our fix deployment to address the browser authentication information misconfiguration is ongoing, and we anticipate deployment to be completed by our next scheduled update. <\/p>\n

Scope of impact: Impact is specific to some users attempting to access Microsoft Copilot Chat in the browser. <\/p>\n

Start time: Friday, July 31, 2026, at 8:00 PM UTC <\/p>\n

Root cause: A recent service change that affects the way browser authentication information is stored for Microsoft Copilot Chat. This can cause some browser requests to exceed expected limits, which may prevent users from accessing the service. <\/p>\n

Next update by: Wednesday, August 5, 2026, at 7:00 PM UTC<\/td>\n<\/tr>\n

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