deprecation-and-migration
Manages deprecation and migration. Use when removing old systems, APIs, or features. Use when migrating users from one implementation to another. Use when deciding whether to maintain or sunset existing code.
npx skills add addyosmani/agent-skills --skill deprecation-and-migration --agent claude-code
Same command for any agent — swap --agent for codex, cursor, copilot.
Weekly change comes from our own snapshots, not the repository page — it measures attention, not adoption.
# Deprecation and Migration ## Overview Code is a liability, not an asset. Every line of code has ongoing maintenance cost — bugs to fix, dependencies to update, security patches to apply, and new engineers to onboard. Deprecation is the discipline of removing code that no longer earns its keep, and migration is the process of moving users safely from the old to the new. Most engineering organizations are good at building things. Few are good at removing them. This skill addresses that gap. ## When to Use - Replacing an old system, API, or library with a new one - Sunsetting a feature that's no longer needed - Consolidating duplicate implementations - Removing dead code that nobody owns but everybody depends on - Planning the lifecycle of a new system (deprecation planning starts at design time) - Deciding whether to maintain a legacy system or invest in migration ## Core Principles ### Code Is a Liability Every line of code has ongoing cost: it needs tests, documentation, security patches, dependency updates, and mental overhead for anyone working nearby. The value of code is the functionality it provides, not the code itself. When the same functionality can be provided with less
- Overview
- When to Use
- Core Principles
- Code Is a Liability
- Hyrum's Law Makes Removal Hard
- Deprecation Planning Starts at Design Time
- The Deprecation Decision
- Compulsory vs Advisory Deprecation
- The Migration Process
- Step 1: Build the Replacement
- Step 2: Announce and Document
- Step 3: Migrate Incrementally
- Step 4: Remove the Old System
- Migration Patterns
What does the deprecation-and-migration skill do?
Manages deprecation and migration. Use when removing old systems, APIs, or features. Use when migrating users from one implementation to another. Use when deciding whether to maintain or sunset existing code.
How do I install it?
Run `npx skills add addyosmani/agent-skills --skill deprecation-and-migration --agent claude-code` — it drops the skill into your project so the agent can pick it up. Swap the --agent value for codex, cursor or copilot if you use one of those.
Where does this skill come from?
From addyosmani/agent-skills, a repository with 81,574 stars. We read it straight from the repository tree rather than a submitted listing, so what you see here is what is actually published.
Is a popular skill a good skill?
Not necessarily. Stars measure attention, not adoption — a repository can trend for a week and be abandoned. That is why we show the weekly change from our own snapshots next to the total, instead of a single flattering number.