spreadsheets are still one of the most common ways teams encode business logic. pricing models, revenue plans, reconciliations, forecasts, data checks, and ad hoc operational tools often start in a workbook because the shape is flexible and everyone can inspect it. that creates an awkward automation problem: the logic is structured like a workbook, but most programmatic workflows either drive a browser grid or rewrite the model in application code. that is especially brittle for coding agents. a screenshot can show a grid, but it cannot give the agent a stable contract for formulas, structural edits, persistence, validation, or post-write readback. i maintain an open-source typescript project called bilig . the public package is @bilig/headless , a node-facing workbook runtime for programmatic spreadsheet automation. this post is the practical argument for the API boundary. it is not a claim that the project is a finished excel clone.…