I was attracted to this leaf by a crackling noise, where I discovered this wasp chewing into the leaf. She then busily turned herself, chewed, turned herself, and when I saw her arched abdomen, I guessed she was laying eggs. Only after I looked at the photos did I notice the green, living larva of something that she has exposed with her mandibles, which I assume will allow her larvae, their main meal once they hatch?
Almost certainly a Paralastor, but I cannot see the wing veins quite clearly enough. Eumeninae usually nest in soil or hollows, or build mud nests provisioned with caterpillars - so that could be what the larva visible in your photos is.