Deterministic but also very fragile. Excel _still_ doesn't have unit tests or linters. Someone can accidentally type a static number in place of a formula and

Deterministic but also very fragile. Excel _still_ doesn't have unit tests or linters. Someone can accidentally type a static number in place of a formula and it may stick there for years. Or Excel decides that a name of a gene is a date: https://www.theverge.com/2020/8/6/21355674/human-genes-rename-microsoft-excel-misreading-dates https://www.theverge.com/2020/8/6/21355674/human-genes-renam... Or Excel silently losing important health data: https://www.bbc.com/news/technology-54423988 https://www.bbc.com/news/technology-54423988 None of these would've happened with a vibe-coded bespoke tool. A basic elementary level unit test would've caught them instantly.