Zone of pain
Alternative name for Instability and abstractness.
The Zone of Pain is the lower-left of Robert Martin's Instability and Abstractness map. Incoming coupling dominates, while the public surface is mostly concrete. That combination creates design pressure when many callers share the contract, but it does not mean every internal change breaks them. AtlasArc shows the position, Distance, raw Fan-in, and concrete caller evidence so you can decide whether the surface is deliberately stable or needs a narrower seam.