In issue 12848, we resolved to change the outset property to inset. This property controls endpoints of segments created as a result of the rule-break property. The initial value for the interior points is currently -50% allowing the gap decoration to bleed halfway into the gap in the crossing direction. See below:

     column-rule-color: blue;
     column-rule-style: solid;
     column-rule-width: 5px;      

     row-rule-color: red;
     row-rule-style: solid;
     row-rule-width: 5px;

     rule-break: intersection;

I am opening this issue because I believe this should be reconsidered and in favor of setting the initial value to 0px. For one, just changing the rule-break property doesn't make it immediately clear what this property controls. Today, one would have to change the inset property to 0 to see the effect of changing the rule-break behavior:

In addition, we're also introducing an auto keyword to become the default value for rule break. This will allow us have different default behaviors for different layout types with the goal of preserving reading order across these layout types. rule-break: auto alone is not sufficient to achieve this. In multi-col, to preserve reading order when using `column-wrap we'd want the column gap decoration not to bleed into the cross gap initially. See: