A ReplayContract.Subject over a file backend: slot n is the file /replay-<n>.txt, seeded x, and the effect is edit("x", "xy"), which shows a second application (xyy). seed writes a slot's file straight to the target, as setup and as another writer; observe reads it from the target; applied counts a transactional target's applied keys.
Performs effect slot under context through the target's guarded code path - building its key with context.effectKey - and returns its outcome as JSON, or the guard's Left.
Performs effect slot under context through the target's guarded code path - building its key with context.effectKey - and returns its outcome as JSON, or the guard's Left.