Microsoft Brings GPT-5.5 Instant to Microsoft 365 Copilot and Copilot Studio

Microsoft rolled out OpenAI's GPT-5.5 Instant model to Microsoft 365 Copilot and Copilot Studio, replacing GPT-5.3 Instant. GPT-5.5 Instant reduces hallucinated claims by 52.5% on high-stakes prompts involving medicine, law, and finance, and lowers inaccurate responses by 37.3% in previously flagged conversations. The model improves contextual understanding by referencing previous conversations and attached files, and includes smart-switching to deeper reasoning for complex prompts. Microsoft 365 Copilot licensed users get priority access; non-licensed users get standard access. The model is also available in Copilot Studio as 'GPT-5.5 Chat' and in Microsoft Foundry for developers. CEO Satya Nadella confirmed the rollout in a LinkedIn post.