A history recorded before the move (MLflow experiments) had nowhere to go, since runs were only made by running a flow. Each entry is stored as it ended: parameters completed and checked like a submit, cause "import", empty commit and code digest, metrics and artifacts written as given, nothing queued or announced. Run.external_id (new migration) makes a second import a no-op and is an export column so a row joins back. The request is all or nothing and capped at 200 entries; Client.import_runs pages a longer history.
Generic single-database configuration.