On August 7, 2025, Microsoft began rolling out GPT-5 to Microsoft 365 Copilot and Copilot Studio. The headline: faster, more reliable reasoning in the apps people use every day, like Outlook, Teams, Word, Excel, PowerPoint, plus new options for makers building agents in Copilot Studio.

OpenAI’s brief on GPT-5 supports this. Compared to the prior generation, GPT-5 is designed to reason more effectively with fewer errors, reduce hallucinations, and accomplish more with less thinking time. In evaluations, GPT-5 produced materially fewer factual mistakes than earlier models when web reasoning was needed.

What changes for end users:

• Sharper summaries and drafts in context: Expect tighter meeting recaps in Teams, clearer email drafts in Outlook, and more precise “write & refine” loops in Word, especially on ambiguous requests where prior models struggled. 

• Better analysis helpers in Excel/Power BI workflows: GPT-5’s reasoning upgrades mean more reliable explanations of trends and assumptions when you ask “why did this move?” or “what’s driving variance?”, not just the chart, but a defendable narrative.

• Fewer follow-ups to fix basics: GPT-5 is tuned to make fewer factual slips and require less back-and-forth to land on the right structure or next step. 

What changes for builders (Copilot Studio):

• Model selection with GPT-5: Makers can pick GPT-5 for new or existing agents. Microsoft notes it’s rolling through early release rings before broad availability, so timing can differ by tenant/environment. 

• Same governance, better brains: You still ground agents on your data (Graph, SharePoint, Dataverse, websites/APIs) and keep tenant boundaries, RBAC, audit logs, the model upgrade doesn’t change those controls. (Microsoft’s Copilot model swaps happen behind the scenes; admins choose where GPT-5 is allowed.) 

Why this upgrade matters:

• Reasoning > autocomplete:  GPT-5 is built to plan steps, check itself, and explain the “why,” which is what knowledge work actually needs. 

• Reliability:  OpenAI reports 45% fewer factual errors than GPT-4o on real-world web tasks, and even bigger gains in high-effort reasoning. That translates to fewer edits and faster reviews. 

• Everyday impact: Microsoft’s messaging positions GPT-5 as a work upgrade inside Outlook, Teams, Word, and Excel, rather than a separate chatbot experience. 

GPT-5 makes Microsoft 365 Copilot more capable at real work. We recommend that you start by upgrading a couple of high-leverage workflows (email triage, meeting notes, executive briefs, or forecast analysis), measure the gains, and then scale to agents in Copilot Studio.

If you want help mapping your first GPT-5 pilot (use cases, guardrails, metrics), we'd be happy to share a playbook that gets you from idea to measurable win - just reach out!