Microsoft is rolling out Anthropic's Claude Code to thousands of employees across its core engineering divisions - Windows, Office, Surface, Teams - while continuing to sell GitHub Copilot to enterprise customers. The internal adoption now extends beyond developers to designers and project managers prototyping ideas without coding experience.
The deployment covers Microsoft's CoreAI team (led by former Meta engineering chief Jay Parikh) and the Experiences + Devices division. Software engineers are expected to use both Claude Code and GitHub Copilot, then provide comparative feedback. Claude Code has also been approved across all repositories for Business and Industry Copilot teams.
This follows Microsoft's June 2025 adoption of Claude Sonnet 4 in its developer division, and making Claude models the default for paid GitHub Copilot users months later. The company spent approximately $500M on Anthropic products in 2024, making it one of Anthropic's largest customers.
What's driving the internal preference: Claude Code's agentic features - full repository analysis, terminal execution, and multi-file edits - outperform Copilot for complex workflows. This matters for enterprise architects evaluating coding assistants: the architecture differences are significant enough that Microsoft's own engineers prefer Claude for real work.
Microsoft is now counting Anthropic model sales toward Azure quotas - unusual for non-homegrown products - and made Claude Sonnet 4.5, Haiku 4.5, and Opus 4.1 available in public preview via Azure Foundry last week. The C# SDK for Anthropic's Model Context Protocol launched simultaneously, enabling Claude integration in Copilot Studio and VS Code.
The paradox: Microsoft maintains OpenAI as its "primary partner" while broadly deploying a competitor's tool internally. Frank Shaw, Microsoft's communications chief, frames this as standard market research: "Companies regularly test and trial competing products to gain a better understanding of the market landscape."
For CTOs evaluating coding assistants: Microsoft's internal choice signals which capabilities matter for production environments. Anthropic's enterprise market share grew from 18% to 29% year-over-year, driven by 300,000+ business customers. The question isn't whether to test alternatives to your current tooling - it's which trade-offs your teams will accept.
Microsoft may eventually sell Claude Code directly to Azure customers. For now, the internal deployment is the signal worth watching.