Codebase Hygiene (Duplicate Detection + Module Deepening)

Advisory and read-heavy. Diagnoses and proposes; does not refactor. Any actual change goes through BUILD with full gates.

Mode: DUPLICATE DETECTION

Semantic duplicates: functions serving the same purpose but implemented independently under different names. Copy-paste detectors catch syntactic duplicates; this finds "same intent, different implementation."

Method

0. Scope before you scan — take the user's named target; else git log --oneline for hot spots and weight recently-changed code — deepening pays off in proportion to future change.
1. Extract catalog — Grep/Glob for exported functions. Record name | file:line | signature.
2. Categorize by domain (cheap tier) — validation, formatting, path manipulation, HTTP shaping, date handling. Mechanical bucketing to shrink comparison space.
3. Drop categories with <3 functions — can't hide a meaningful duplication pattern.
4. Detect duplicates per category (capable tier) — read implementations, decide which share intent. Never use cheap tier for detection — it anchors on names and rubber-stamps "these look different."
5. Emit findings — group by confidence, highest first. Each finding: what is duplicated, why it matters, the fix, file:line evidence. Route through code-reviewer finding contract.

High-Risk Zones