OpenAI's GPT‑5.6 named preferred model for Microsoft 365 Copilot

OpenAI launched its new flagship model series GPT‑5.6 and announced it will be the "preferred model" powering Microsoft 365 Copilot across Word, Excel, PowerPoint, Copilot Chat and Cowork. The model is offered in three variants—Sol, Terra and Luna—designed for high‑performance reasoning, balanced cost‑efficiency and high‑volume workloads respectively. Alongside the model rollout, OpenAI introduced ChatGPT Work, a workspace that combines ChatGPT with its Codex coding platform to automate end‑to‑end enterprise tasks.

The move deepens the OpenAI‑Microsoft partnership after earlier speculation of a split, with Microsoft previously switching the Copilot default to Anthropic’s Claude. The switch back to OpenAI reaffirms the companies’ collaborative roadmap, while Microsoft continues a dual‑track strategy that includes its own MAI models and direct API access to OpenAI’s services. Under their amended 2026 agreement, Microsoft remains OpenAI’s primary cloud provider and Azure continues to host OpenAI products.