ChatGPT and Claude did not experience a complete system downtime, but due to ongoing failures with Microsoft 365, both of these AI assistants lost access to users' Microsoft work data.

The problem lies with the Microsoft 365 connectors, which allow the assistant to access Outlook emails, Teams chats, and SharePoint files. Since this data is stored on Microsoft's servers, any failure of these servers on Thursday would result in the connectors stopping working.

The status page for OpenAI shows that the error rate of its Microsoft 365 connector has increased, and there is a warning that new connections may fail, as well as that related tools might not function properly.

Anthropic also reported similar issues with Claude, including Claude, for, and Outlook plugins, and linked these to Microsoft's recent incident. Anthropic stated that its API and Claude Code are running normally, while claude.ai experienced a decline in performance, but it did not specify whether this was related to the incident.

Microsoft stated that this failure was caused by an overload of the software responsible for handling secure connections, rather than a cyberattack.

If the main applications stop responding, users should check the status pages of each company.