The Not callable: nil error happens on a stub VM (frames=[], sp=0) during
cek_resume with 12 CEK kont frames. The error is from a reactive signal
subscriber (reset! current ...) that triggers during run vm after resume.
The subscriber callback goes through CEK via cek_call_or_suspend and the
CEK continuation tries to call nil.
This is a reactive subscriber notification issue, not a perform/resume
frame management issue. The VM frames are correctly restored — the error
happens during a synchronous reset! call within the resumed VM execution.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>