Microsoft removes the COPILOT function from Excel and existing formulas return #NAME? on recalculation

Sources: primary, HN submission
Summary: Microsoft's support page states that the COPILOT function has been removed from Excel. The page describes it as a preview feature that was previously available only in the Frontier program and the Microsoft 365 Insider program. Cells holding the function keep their cached values until something triggers a recalculation, at which point they return #NAME?.
Why it matters: Preview formulas outlive the preview program in shared workbooks, so the breakage lands on whoever recalculates the file next rather than on the Insider who wrote it.