X_EXERCISE_INPUT_THREW
Means
an exercise entry's input threw
Typical cause
the input function of a defineExercise() entry threw before the pass could call its primitive — the throw is apps/web/exercise.ts's, never the handler's
Fix
x exercise <name> --json — after the entry's input in apps/web/exercise.ts returns a value (it runs as the seated actor, inside the call's request), or { off: '<why>' }