Code that accesses deeply nested attributes like result.solution.root and then operates on the internals (indexing, type assertions) is reaching through abstraction layers. This signals the logic belongs in the lower layer that owns those objects.

Adds a new section to the usethis-python-code skill (v1.3 → v1.4) covering:

• Procedure for identifying and resolving deep nesting by moving logic down or adding interfaces
• Concrete example contrasting the anti-pattern with the preferred approach
• Common mistakes: extracting to local variables (hides but doesn't fix), adding type assertions at the wrong layer, adding thin wrappers instead of moving logic

# Bad: caller knows internal structure of result.solution
flat = result.solution.root
idx = flat.index(step_name)
predecessor = flat[idx - 1] if idx > 0 else None

# Good: lower layer encapsulates the logic
predecessor = result.get_predecessor(step_name)