Parse JSON and filter by field

I’m logging a JSON which is being shown as a detected field log in Grafana:

Screenshot of detected fields

Now I want to filter the logs by level name, but I can’t figure out how…

I thought something like this would work, but doesn’t, no results are returned:

{app="hello"} | json | line_format "{{.log}}" | levelname="ERROR"

What am I missing?

I think you need a json stage after the line_format stage @pe3