Microsoft Deepens Anthropic Ties: Claude Integrates into Office 365, OpenAI Sidelined

On March 9, 2026, Microsoft announced the deep integration of Anthropic's Claude agentic AI tool into Microsoft 365 Copilot. This announcement has sent shockwaves through the tech industry—the OpenAI, once considered Microsoft's core AI strategic partner, has been replaced by a competitor in the office productivity space for the first time.

From Copilot to "Multi-Copilot" Strategy

Microsoft stated in its announcement that users can now delegate work-related tasks to AI agents that can autonomously work across documents, emails, and other office tools. This means users no longer need to open documents one by one, copy and paste content—the AI can independently complete the entire workflow from information gathering to content generation.

Notably, Microsoft began exploring third-party AI integration into Microsoft 365 Copilot as early as January 2025. The tech giant at the time insisted OpenAI would continue as the primary partner for frontier models, but that commitment now appears to have been broken.

OpenAI "Demoted"

Industry observers point out that Microsoft's choice of Anthropic over OpenAI reflects intensifying competition in the AI agent赛道. Claude's performance in code generation and complex reasoning tasks has made it a popular choice for enterprise applications. While OpenAI's ChatGPT dominates the consumer market, it seemingly failed to meet Microsoft's expectations for deep customization in enterprise office scenarios.

Following this integration, Microsoft 365 Copilot will support both OpenAI and Anthropic models, but Claude's advantages in intelligent agent capabilities have earned it deeper system-level integration.

An "Unexpected Alliance" Between Microsoft and Anthropic

This isn't the first time Microsoft has publicly supported Anthropic. Just last week, Microsoft filed an amicus brief in federal court supporting Anthropic's request to block the U.S. Department of Defense from designating it a "national security risk." Microsoft stated in the brief that the Defense Department's decision directly impacts its collaboration with Anthropic.

Previously, Anthropic clashed with the U.S. government after rejecting Pentagon demands regarding AI use for "fully autonomous weapons or domestic mass surveillance." Microsoft's public support for Anthropic reflects both business considerations and a stance on AI ethics.

Reference: Indian Express, IT Pro, The New York Times