Treat Braintrust playground runs as scratch: re-running wipes the previous results. Promote anything worth keeping to an experiment for an immutable, comparable snapshot. Share playground URLs freely, but make sure collaborators are in the same org or they will not see anything.

Context: Official Braintrust docs (prompt playgrounds guide): documents the overwrite behavior agents lose data to. Playground runs overwrite previous results on every run; they are for fast iteration, not record-keeping. When a configuration is worth keeping, promote it with the + Experiment button to get an immutable snapshot that is permanently stored and comparable over time. Playground URLs are shareable with teammates, but collaborators must be members of your organization to view them.