What would you pre-register before running an experiment, and why bother?

An answer that works

The quantity, the comparison, the noise floor measured on the baseline first, and the threshold that makes me stop — plus an explicit list of the moves I am not allowed to make afterwards, such as changing the eval set or dropping seeds. The point is the timestamp: it is a promise made by someone not yet invested to the person who will be invested in six weeks and will find sincere reasons why the disappointing number does not count.