The Regression That Only Exists in the Field
Decide what you would build from the brief alone. Everything below it is available, but the exercise stops working if you open it first.
Field data shows interaction responsiveness got clearly worse after a release. Local profiling on the same interactions shows no change. Find it.
Adding CPU throttling locally, reproducing something that looks like the regression, fixing that, and shipping. Throttling makes everything slower, so almost any interaction will look bad enough to explain the numbers, and there is always a plausible expensive function to optimise. The fix ships, the field metric does not move, and the team now believes the metric is unreliable. Throttling is a way to test a hypothesis you already have from segmentation; used as a way to *find* a regression it manufactures a suspect on demand.