Build logs, lessons, and the reasoning behind decisions
Good documentation doesn't say what the code does. It says why it was written that way, and which bug ordered it.
Not by running tests — by reading every line of my own backend as if a stranger wrote it, and writing down everything that looked off.
A bug that wasn't in the code at all — it was in the data. And how I proved it hadn't happened anywhere else.
The institute owner didn't want a shortcut into the app. He wanted the whole thing answerable in the chat — and that changed how I designed the feature.