In #2230, the CSSWG resolved to make min-width/min-height: auto always compute to itself (though per #2230 (comment) , this was only with regards to flex and grid items).

What should happen for other elements? Right now the spec doesn't say (so it implies that it'd still compute to itself everywhere, which I don't think matches reality)... Previously it was defined as computing to 0 for these elements.

Suggestion: how about we say the resolved value of this auto keyword should be 0 for any non-grid/flex item. (This is basically what we've got implemented in Firefox, for non-grid/flex items -- i.e. we store auto internally in the computed style, and then we check the styles.) I'm guessing that might be what other engines do, too, though I don't know for sure (CC @rossen @cbiesinger)