Engineering
How a hard part was actually built, including the attempts that failed first.
Written and covered by tests, not yet observed in a live run
- In an Excel number format, a bare letter is a dateA workbook passed every structural check, seventeen parts, well-formed XML, no index out of range, and Excel still repaired it on open. The defect was one line and three letters.2026-09-13
- An XLSX engine that reopens its own outputWriting a spreadsheet is easy. Proving that what you wrote is a spreadsheet requires a second library.2026-09-10
- A fix that reproduced its own defectThe negation list was matched as a substring. The word for “a” contains the word for “not”, and a requested deck quietly disappeared.2026-09-10
- One tool contract across three providersThree vendor CLIs, three stream formats, one vocabulary of phases, and a rule that the adapter never summarises.2026-09-10
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