Type a customer name and see which version of a prompt they get, and whether the new one earns its promotion.
When a team changes the wording of a prompt, two questions follow. Which customers are seeing the new version, and is it actually better? Both are easy to get wrong: a split that reshuffles on every request means one customer sees both versions and the comparison measures nothing.
Type a customer or company name. The page works out which of the two versions that name gets, shows that the answer is the same every time it is asked, and shows the same name landing somewhere else in a different experiment. There is no table of assignments anywhere. The arm is worked out from the name itself, so it survives a restart and can be recalculated later from a log.
Then six hundred customers go through both versions for real, each one answering a question with a known correct answer, and the results are put in front of a gate that decides whether the new version ships. The page shows the gate refusing on a small sample even though the numbers already look convincing, and agreeing later on the full sample, with the odds that the difference is chance.