At two hundred sections you can hold the system in your head. At six hundred you need a checklist. At two thousand four hundred the checklist is a fiction — nobody is measuring padding on the four hundredth review of the month, and everyone involved knows it.
Why does review stop working?#
Because it depends on attention, and attention is the resource that runs out first. A reviewer who has looked at nine sections today will catch a broken layout and miss a 20px gap where the system says 24px. That is not carelessness; it is what sustained visual comparison actually costs.
Make the wrong value unavailable#
The fix is to shrink the space of possible mistakes. If spacing can only be one of seven values, a 20px gap is not a thing a contributor can accidentally produce — the token does not exist and the build fails.
| Property | Open system | Closed system |
|---|---|---|
| Spacing | Any px value | 7 steps |
| Type size | Any px value | 9 steps |
| Radius | Any px value | 6 steps |
| Colour | Any hex | Semantic tokens only |
| Shadow | Any value | 4 elevations |
Nobody has asked for an eighth spacing step in fourteen months. When someone does, that is a design conversation worth having — which is exactly the conversation an open system never surfaces, because the deviation just ships.
What constraints cannot catch#
Composition. Every value can be on-system and the section can still be ugly, unbalanced or wrong for its slot. That is where human review earns its cost, and it is the only thing our review checklist covers now.