Has model selection been removed from Microsoft 365 Copilot?

It appears that GPT 5.5 has returned to the Copilot Chat model selector, with two visible options: GPT 5.5 Quick response and GPT 5.5 Deep response.

Microsoft Learn confirms that Copilot Chat offers Auto, Quick response, and Think deeper modes. Quick response prioritizes speed, while Think deeper uses deeper reasoning for more complex requests. Auto lets Copilot route the request dynamically.

However, Microsoft Learn does not yet document the exact technical mapping behind these GPT 5.5 labels in Copilot Chat.

Depending on admin settings, Anthropic models can also be enabled so models such as Claude Opus appear in the selector.

This is different in Copilot Studio, where model selection is more explicit: makers can choose the primary AI model for agent orchestration, with model categories.