Task: Merge duplicated implementations into one

Usage: /routine-dup-unifier [package-or-path]

Find two (or more) live copies of the same logic inside one package, prove they are semantically the same, keep the best one, repoint all callers, delete the rest, and ship via /ship.

Contract

Read .agents/skills/routine-shared/contract.md first — preconditions, scope resolution, verify gates, ship protocol, budget, universal STOPs. Floor even without it: never ship red; one finding per ship; anything in a DO_NOT_DO.md is a hard STOP.

Workflow

1. Scope

Resolve scope per the contract. Duplication is a within-one-package concern here; never widen scope mid-run.

2. Discover

Agent-driven search — Grep for repeated names, similar signatures, and shared distinctive string literals (error messages, format strings, regexes); read sibling directories that grew in parallel (helpers/utils files, per-screen copies of formatting or validation logic). Optional accelerator with no new dependency: npx --yes jscpd --min-tokens 50 <pkg>/src --output <pkg>/tmp/ (output stays in the gitignored tmp/).

3. Prove it

• Read every copy end to end — name similarity is not proof.
• Semantics must be identical, or differ only in ways trivially covered by a parameter that keeps the survivor simpler than the sum of the copies.
• The intended survivor is test-covered for the behavior all callers rely on; if not, write those tests first (they are part of the finding).

4. Fix

Keep the better copy (better tested, more used, better placed). Port any unique behavior from the losers, repoint every caller, delete the losers, and move over any tests that pinned loser-only behavior worth keeping. Re-run the package's dead-code detector (yarn lint:deadcode / make deadcode) to confirm nothing was orphaned.

5. Verify

Owning package's full gate per the contract.

6. Ship

Compose /ship for this one unification. Loop within budget.

What NOT to do

• Never merge across packages. Packages are independent by repo rule (no new cross-package imports). Cross-package duplication goes in the summary as a report, nothing more.
• If unification requires an abstraction more complex than either original (config objects, strategy callbacks, mode flags), skip the finding — a slightly duplicated simple thing beats a unified complicated one.
• Never delete a copy before every caller is repointed and green.
• The deliberate clean-room reimplementations noted in .pm/DO_NOT_DO.md (e.g. fava-slim vs vendored fava) are not duplication findings.

Arguments

$ARGUMENTS