Greenroom gives a Rails application the parts that turn a Scientist experiment into evidence. An experiment stays inactive until a census job starts a recorder, so a team can merge agent-written code early and run nothing new. The recorder counts the rows, the comparisons, the mismatches, and the candidate errors. At the end of the run it sends one aggregate event and a limited number of sample events. A sample carries an identifier and a digest, and never the value itself.