Major AI platforms suffered disruptions this week alongside a widespread Microsoft outage. The affected tools included Anthropic’s Claude, OpenAI’s ChatGPT, and xAI’s Grok.
These disruptions coincided with a technical issue that hit Microsoft’s Exchange Online and several other Microsoft 365 services worldwide.
AI Tools Caught in the Disruption
All three major AI agents experienced problems during the outage. Outage-tracking site Downdetector also reported widespread service issues.
Additionally, Axios noted worldwide problems with Google’s Gemini. Claude’s own status page confirmed that its Opus 4.8 and Opus 5 models were affected. However, issues affecting Claude Mythos 5.1, Fable 5.1, and Opus 5 were later resolved.
The Root Cause
Microsoft traced the disruption to a core authentication configuration problem. This configuration is used by several internal services within the Exchange Online infrastructure. In simpler terms, the fault prevented authentication components from deploying correctly across part of the system. As a result, users struggled to sign in and access their services.
Microsoft engineers responded by conducting manual tests on individual servers. They then expanded remedial measures across the affected infrastructure gradually. The company acknowledged the fix would take time. It warned users to expect varying levels of disruption and email delays during recovery.
A Wide Blast Radius
xAI down
claude down
codex down pic.twitter.com/Y4HhZHUMsq— vittorio (@IterIntellectus) September 3, 2026
The authentication issue extended far beyond email alone. While Outlook received most attention, many other services failed too. The outage affected OneDrive for Business and SharePoint Online, and disrupted Microsoft Teams, Microsoft Purview, and Microsoft Defender XDR. Notably, Microsoft’s own Copilot AI assistant was among the affected tools.
Microsoft first acknowledged the Exchange Online issues on August 31. It later tracked the incident under the reference MO1465074. Downdetector recorded thousands of user reports at the height of the disruption. However, those figures reflect only submitted reports, not the total number affected.
Recovery and Resolution
Microsoft has confirmed the outage had been fully mitigated. The company said all affected services were restored. It noted the final Outlook impact occurred in less than one percent of its infrastructure. Microsoft added that it would continue monitoring telemetry to ensure services remained healthy going forward.
It’s pretty rare to see all four of the affected frontier models experiencing interruptions at the same time, even if they do go down occasionally. Claude has been doing well, boasting a 99.4% uptime for its services over the past 90 days, with its last notable hiccup being a three-hour “partial outage” on August 24. Meanwhile, OpenAI has reported an impressive 99.63% uptime for ChatGPT and a perfect 100 percent for ChatGPT Codex during that same timeframe. However, on August 31, ChatGPT’s “Work Mode” did experience a lengthy stretch of “elevated latency.”
