Microsoft announced on Thursday that OpenAI’s GPT-5.5 Instant model is now available in Microsoft 365 Copilot and Copilot Studio, just two days after OpenAI released the model as the new default for ChatGPT users.
CEO Satya Nadella confirmed the rollout in a LinkedIn post, writing, “Great to bring GPT 5.5 Instant to M365 Copilot today. With quicker, clearer, and more accurate responses, you can get to useful answers with less back and forth.”
What GPT-5.5 Instant Brings to Enterprise Users
The upgrade replaces GPT-5.3 Instant, which had been integrated into Microsoft 365 Copilot since March 2026. According to OpenAI, the new model produced 52.5% fewer hallucinated claims than its predecessor on high-stakes prompts in medicine, law, and finance, and saw a 37.3% reduction in inaccurate responses on conversations users had previously flagged for errors.
GPT-5.5 Instant also features improved context handling, with the ability to reference past conversations and files to deliver more relevant answers. The model includes a “smart-switching” capability that can trigger deeper reasoning when a prompt is particularly complex.
Microsoft’s Broader AI Integration Strategy
The Microsoft 365 Copilot integration follows the company’s earlier rollout of GPT-5.5’s full reasoning model into its Copilot ecosystem in late April, which enhanced multi-step task execution across GitHub, Microsoft 365, and Azure Foundry. Users can select specific models or allow an auto mode to choose the most appropriate model for each request.
OpenAI released GPT-5.5 Instant on May 5 as the new default ChatGPT model for all users, with the previous GPT-5.3 Instant remaining available to paid subscribers for three months before being retired. The rapid two-day turnaround from OpenAI’s consumer launch to Microsoft’s enterprise deployment underscores the tight integration between the two companies as they compete with Google’s Gemini across both consumer and enterprise AI markets.
