What probably matters to youSection of the release
What
The prompt suggesting fullscreen mode is rendered as a first-class dialog rather than an ad hoc surface. Dismissing it records the dismissal, and if you typed something first it queues a 12-second feedback notification. Eligibility is a long list of negative checks plus a cap on how many times you have already seen it; setting CLAUDE_CODE_FORCE_FULLSCREEN_UPSELL shows it regardless.
Evidence
fullscreen-upsell-done
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
