It's both, and the answer has changed in 2026. Microsoft has its own AI models now, but Copilot still runs on other companies' models too.
Microsoft AI, led by Mustafa Suleyman, began releasing in-house models in August 2025 (MAI-1-preview and MAI-Voice-1). At its Build conference in early June 2026, it announced seven MAI models covering reasoning, code, image, voice and transcription, led by MAI-Thinking-1 and MAI-Code-1-Flash. MAI-Code-1-Flash is the default model for individual VS Code users in GitHub Copilot. Reporting in July 2026 said Microsoft was moving some Copilot features in Excel and Outlook from OpenAI and Anthropic models to its own, though these still handle only a small share of requests.
Copilot is not just ChatGPT with a new name. Microsoft also uses Anthropic's Claude in parts of Copilot, and it holds a large stake in OpenAI, so OpenAI models remain part of the product. Earlier in the decade, nearly all of Microsoft's AI ran on OpenAI models, which is why the question makes sense.
The model names and the shift away from OpenAI come from trade press and Microsoft's own announcements, and some details (like the exact share of requests) are still moving. Microsoft's own product pages will show which model powers which feature.
🕒 As of October 2026
