Spoiler-safe episode companion
What it is
A conversational character that discusses a video the viewer is watching and is structurally unable to reveal what has not yet played.
How it works
The guarantee is architectural, not instructional. The model is only ever given the portion of the episode that has already been shown, so a request for the ending cannot be satisfied — there is nothing in context to leak. A prompt instruction would have been talked around on day one.
What it taught me
Where a behaviour genuinely must not happen, remove the capability rather than asking the model to decline. Policies are negotiable; absent context is not.