Microsoft is expanding its collaboration with Anthropic, a key rival of OpenAI. Starting Wednesday, the tech giant will integrate Anthropic’s AI models into its AI assistant, Copilot, which was previously powered mainly by OpenAI.

This move marks another step toward gradually ending what was once an exclusive partnership, coming just weeks after Microsoft signed a deal to incorporate Anthropic’s AI into Office 365 applications such as Word, Excel, and Outlook.

Business users of Copilot will now have the option to choose between OpenAI’s advanced reasoning model and Anthropic’s Claude Opus 4.1 and Claude Sonnet 4 to assist with specific tasks, including in-depth research and the development of customized AI tools and enterprise-level agents. Opus 4.1 is engineered for complex reasoning, coding, and detailed architectural planning, while Sonnet 4 is better suited for routine development tasks, large-scale data processing, and content creation.