Tiny hard cocoon, maybe 3 mm long, in/on underside of mache (Valerianella locusta) leaf. Second one I've seen in last 2 or 3 days.
Maybe some kind of leafminer (Agromyzidae)?
4-5 mm long fly that hatched from puparium on mache leaf in this observation:
https://www.inaturalist.org/observations/196098756
The first three photos are alive; the last four are dead after putting in freezer.