{"id":17678,"date":"2026-08-04T19:01:54","date_gmt":"2026-08-04T10:01:54","guid":{"rendered":"https:\/\/m365jp.net\/?p=17678"},"modified":"2026-08-04T19:11:01","modified_gmt":"2026-08-04T10:11:01","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-2","status":"publish","type":"post","link":"https:\/\/m365jp.net\/index.php\/2026-08-04-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-2","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 09:28:37<\/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, some users may be able to mitigate the impact by clearing their browser cookies and then retrying access to Microsoft Copilot Chat. <\/p>\n

Current status: We’ve identified that a recent service change introduced an issue affecting how browser authentication information is stored when accessing Microsoft Copilot Chat, which is causing some browser requests to become larger than expected and preventing users from accessing the service. We’re deploying a fix to address the issue and restore normal access, and we expect to provide a deployment timeline in 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 introduced an issue affecting how browser authentication information is stored when accessing Microsoft Copilot Chat, which is causing some browser requests to become larger than expected. <\/p>\n

Next update by: Tuesday, August 4, 2026, at 11:00 PM UTC<\/td>\n<\/tr>\n

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CW1447067 | Microsoft 365 Copilot Chat | Users may be unable to access Microsoft Copilot Chat in the browser a […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-17678","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts\/17678","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/comments?post=17678"}],"version-history":[{"count":0,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/posts\/17678\/revisions"}],"wp:attachment":[{"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/media?parent=17678"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/categories?post=17678"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/m365jp.net\/index.php\/wp-json\/wp\/v2\/tags?post=17678"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}