Trusting your spreadsheet starts with being able to trace what changed and reverse it when needed, whether the changes came from AI or your coworkers. Most AI can help with what's in front of you. The new Change History skill helps Copilot in Excel understand what happened before. We've all come back from vacation to a spreadsheet that looks nothing like the one we left behind. Change History can understand changes made by both people and AI, summarize what matters, and answer questions about how the workbook evolved. In this example, I ask Copilot what changed, which edit broke a formula, and then restore the last working version. You can try it yourself in any workbook stored in SharePoint/OneDrive... just ask Excel Copilot: “Summarize the changes made in the last two weeks.”