Microsoft adds GPT-5.5 'Thinking' and ChatGPT Images 2.0 to Microsoft 365 Copilot

Microsoft said on April 27 that GPT-5.5 Thinking is rolling out across Microsoft 365 Copilot in Copilot Chat, Word, Excel and PowerPoint. (techcommunity.microsoft.com) The same update adds ChatGPT Images 2.0 to Copilot in PowerPoint, with Copilot Chat listed as coming soon. Microsoft said the new models are meant for analysis, creation and more complex work. (techcommunity.microsoft.com) Microsoft has been moving these model upgrades into Copilot on a steady cadence. A March post added GPT-5.4 Thinking, and an August 2025 post said Microsoft aimed to bring OpenAI’s latest models to Microsoft 365 Copilot within 30 days. (techcommunity.microsoft.com 1) (techcommunity.microsoft.com 2) The product shift is no longer just about one model vendor. In March, Microsoft said its Researcher agent was adding “Critique” and “Council,” two multi-model systems that use models from Anthropic and OpenAI. (techcommunity.microsoft.com) Microsoft’s support documents now say Researcher can work with Claude models from Anthropic. A Microsoft Mechanics post said customers can use Anthropic and OpenAI models inside Microsoft 365 rather than switching providers. (support.microsoft.com) (techcommunity.microsoft.com) Microsoft paired the product update with a large customer example. In a Microsoft-published case study on April 27, Accenture said it is rolling out Microsoft 365 Copilot across about 743,000 employees, which Microsoft called its largest enterprise Copilot deployment to date. (news.microsoft.com) That case study included performance claims from Accenture’s 2025 internal data on 200,000 users. Microsoft said 97% of those employees reported completing routine tasks 15 times faster, and 53% reported significant productivity and efficiency gains. (news.microsoft.com) The practical change for Microsoft 365 buyers is that Copilot is turning into a routed system, with different models handling different jobs inside the same workplace software. Microsoft’s September 2025 post on “expanding model choice” framed that as adding Anthropic models while keeping OpenAI’s latest models in the product. (microsoft.com) The next test is whether customers treat those model swaps as a buying reason or just table stakes. Microsoft is shipping them as native Copilot features inside Office, not as separate tools employees have to go find. (techcommunity.microsoft.com)