openpyxl is great at what it does, but it’s a file-format library rather than a workbook runtime.

It can insert columns, for example, but it doesn’t maintain dependencies such as formulas, tables, charts, or defined names when doing so. It also doesn’t evaluate formulas.

Nobie runs the workbook like Excel would: it evaluates formulas, maintains workbook semantics through edits, renders the result, and reads and writes the file.

Roughly speaking, Nobie is to an Excel workbook what V8 is to JavaScript. openpyxl is closer to a parser and serializer.

agents do a lot better when they can "run" the excel workbook and understand the impact of inputs, and how pixels look when layering on things like conditional formats.