I have 20 custom CI checks and every single one exists because of a bug that shipped
Not linting. Not types. Twenty bespoke check-*.mjs scripts, each written the day after something broke in a way no normal test could have caught. The pattern is always the same: a decision recorded in prose, and a call site that reads fine.
A sample, all real:
A cron schedule inside a block comment. The retainer billing job was scheduled in SQL wrapped in /* */. It never ran. Meanwhile the in-app automation health panel advertised the job as active, with the impact line "Retainers will not bill automatically." So a freelancer set up a monthly retainer and it silently never invoiced. The part that makes this a guard rather than a fix: grep cron.schedule finds the commented-out version and looks reassuring. A machine has to tell executed SQL from documented SQL.
A Postgres COMMENT nobody could read. A migration retired a column and documented it perfectly: "read by nothing. Do not add a reader." Two readers were added anyway, months apart. Both call sites look completely ordinary — client.deal_value is a real field on a real type — while the knowledge that it's dead lives 300 lines into a SQL file nobody opens. One of the two silently forecast zero pipeline in the 90-day cash-flow panel on every workspace. So now no file under src/ may read a column whose COMMENT says DEAD.
An HTML entity inside a JS string. A page shipped 'You’re confirmed' inside a ternary. React escapes it, so the screen a buyer sees immediately after agreeing to pay a deposit read the markup out loud. In JSX text those same nine characters are correct. That's what makes it a defect class instead of a typo: the distinction is invisible while typing and invisible in review.
An endpoint documented nowhere. A token-authenticated ingest function shipped live and appeared in no OpenAPI spec. That's OWASP API9:2023, not a docs nit — an undocumented endpoint gets no contract test, no review, and can't be deprecated on purpose.
The meta-lesson I keep relearning: a comment addressed to a future human is decoration. If a decision matters, something has to read it.
