this gap is exactly 0.145 um accordingly to klayout. when i look at it in magic, it complains that there is a DRC error

Diffusion contact spacing to poly < 0.145um (CO.7 - CO.6)

@Ethan Mahintorabi: I replied in the issue tracker for magic on github where this was posted.

Ah cool sorry for the interruption. I'll check there first next time

That's okay; Arya didn't cross-reference it. Anyway, the gist of it was: Don't confuse magic's DRC rules for magic derived layers with rules for GDS mask layers. In this case, magic's rule is 0.145um but the referenced rule is "CO.7 - CO.6": The GF rule for contact to poly spacing (CO.7) is 0.15um. Magic's rule is relative to magic's layer and is computed by accounting for the 0.005um minimum metal overlap of contact (rule CO.6) that is part of magic's derived layer for the contact area. So the moral of the story is that if you do layout with klayout, you should probably just run the klayout DRC checker, because it's easier than trying to figure out how magic's layers and rules map to GDS mask layers and rules.

Is it OK to submit for tapeout designs which pass KLayout DRC, but not Magic ones? Will such designs be accepted by precheck?

sorry for the confusion, should've updated this thread with a link