The critical problem is not the instrumentation, but the way how BugJail works: it doesn't dumb the raw events to disk, instead it reconstructs relational model of the program execution. This requires resolving raw low level events against schema of types/methods/fields/etc. With JS the schema is dynamic, so now the already hard 'reverse-engineering' has moving target. Not impossible, just hard.

And thanks for the pointer to GraalJS/Truffle, I'll have look and perhaps that provides great way for doing the instrumentation side.