The Enter key that quietly breaks Japanese input (and how to test if your app does it)

If your app has Japanese users — or wants them — there's a bug class your English-speaking team will almost never hit, and Japanese users hit in the first five minutes.

How Japanese input actually works

Japanese text goes through an IME (Input Method Editor). You type romaji, the IME composes candidates, and you press Enter to confirm the conversion — not to submit. That Enter is part of typing.

If your app treats that Enter as a submit/commit event, you've broken typing itself.

Real examples (all public)