---
name: principle-migrate-callers-then-delete-legacy-apis
description: "Apply when introducing a new internal API while old callers still exist. Migrate callers and delete the old API in the same wave instead of preserving compatibility layers."
disable-model-invocation: true
title: principle-migrate-callers-then-delete-legacy-apis
canonical_url: https://skilld.dev/gh/cursor/plugins/principle-migrate-callers-then-delete-legacy-apis
last_updated: 2026-09-26T18:49:30.000Z
---

> **Skill from skilld.dev.** Follow the instructions below for this session. You do not need to install anything.
>
> If the user asked to install this Skill, run `npx skilld install cursor/plugins/principle-migrate-callers-then-delete-legacy-apis`. Install writes the Skill files into the project, so every session loads them.

# Migrate Callers Then Delete Legacy APIs

When we decide a new API is the right design, migrate callers and remove the old API in the same refactor wave instead of preserving compatibility layers.

**Rule:**
- Do not keep legacy API paths only because internal callers still exist
- Inventory callers, migrate them, and delete the old API immediately
- Treat temporary adapters as exceptional and time-boxed, not default architecture
- Update tests to assert the new contract, and delete tests that only protect pre-refactor implementation details

**When this applies:**
- No external users depend on backward compatibility
- The project can absorb coordinated breaking changes
- The new API is part of a simplification or refactor initiative

Keeping both old and new APIs creates dual-path complexity, slows cleanup, and makes the codebase feel append-only.