Technical Debt vs Diff Debt, and Why I Stopped Treating Them as the Same Thing

Short summary

The author introduces "diff debt"—code merged without anyone truly understanding it, increasingly common as AI generates large, confident-looking diffs that get rubber-stamped. Unlike technical debt (a deliberate shortcut you understand), diff debt is invisible until something breaks and nobody can explain why. The fix isn't refactoring but ensuring reviewers actually understand changes before merging, keeping diffs small, and requiring walkthroughs of AI-generated code.

• •Diff debt = code merged without human understanding, distinct from deliberate technical debt
• •AI-generated diffs look mergeable but reviewing them hasn't gotten faster, creating invisible liabilities
• •Fix: make approval mean "I understood this," keep diffs small, require walkthroughs for AI-authored changes

Generated with AI, which can make mistakes.