drift-detection

# Drift-Detection ## Overview **Drift is divergence on a timescale longer than one work session.** Twenty individually-reasonable commits can compose into a system whose mental model no longer matches the code. Per-commit gates (`docs-as-definition-of-done`) cannot catch it because no single commit violates a rule — the violation is the **cumulative pattern**. **Core principle:** drift accumulates silently. Detecting it requires a periodic full-system scan, not per-edit vigilance. The scan produces a finite list of drift indicators; each becomes a candidate for immediate fix or a `method-evolution` step. See [`../../docs/ldd/convergence.md`](../../docs/ldd/convergence.md) §4 for the drift taxonomy. ## When to Use Invoke on a **periodic cadence**, not per-commit: - Weekly on active projects (bundled with release-candidate review) - Before a major version bump or breaking-API release - After onboarding/offboarding a contributor (someone leaves; check for orphaned mental models) - After a long sprint of many small commits in one area - Before a documentation overhaul (know what's wrong before you rewrite) - After a refactor that touched >20 files Do **not** use: - On every commit (that's `docs-as-definition-of-done`'s job; this skill is slower and more expensive) - On small projects with few contributors (drift is a large-codebase / many-contributor pathology) - During active development (it generates noise, you'll ignore it; run it at stable points) ## The Seven Drift...