Originally published on hexisteme notes.
Three features shipped in one session. All three had dedicated unit tests. All the tests passed. None of the three ever ran in the live app.
Not "had a bug." Not "worked but looked wrong." Never executed — the argument that would have activated each feature was never populated on any live path. The app fell back to its default rendering, crashed nowhere, logged nothing.
The part worth writing down isn't the first incident. It's the second and third, which happened after I had diagnosed the first and added a dedicated test file for this exact failure mode. Knowing the pattern did not stop the pattern — so the fix cannot be vigilance.
Setting: a solo-built SwiftUI iOS app that scores restaurant reviews for trustworthiness, with implementation fanned out to LLM subagents that each own a slice of files.
