.tip

Four tax implementations, three date helpers and ninety files in utils. Each was written by an agent that started with an empty picture of the codebase and built whatever it needed right in front of it.

Tax is computed in billing/tax.ts and nowhere else.
Dates go through lib/format/date.ts.
Search for an existing helper before writing one.

Keeping it current takes a minute per feature, and nothing else stops the duplication as well.