classifiers

At a 0.05% base rate, a classifier that is right 99% of the time on safe messages still flags about twenty people who are fine for every one in danger. Build a ladder of responses that each fit their error rate.

A large-scale design question where every error is someone's real harm: harmful content left up, or legitimate speech taken down. Strong answers tier by severity and confidence, keep humans in the hard cases, and measure both kinds of error per language.