If you use content-distribution keyword, like "space-between" on a flexbox or grid, and the content overflows the container, it defaults to unsafely centering the content.

But you can't specify safe alignment with a content-distribution keyword! So there's just no way for an author to deal with this, except guess at the screen sizes where it might overflow and use an MQ to change it to something safe.

I propose that we specify that the distribution keywords that currently fall back to "center" instead fall back to "safe center".

(If UAs would just implement the "smart" overflow behavior - be unsafe unless it would push content into the unscrollable area - we'd be fine as-is. But nobody's doing that, grrr.)