Deprecation And Migration
Most teams are better at building systems than removing them, which is how you end up maintaining three authentication flows and two logging libraries. This skill helps you decide whether to sunset old code, plan compulsory versus advisory deprecations, and actually migrate users without leaving zombie code that nobody owns but everybody depends on. The core insight is that code is a liability with ongoing maintenance costs, and Hyrum's Law means you can't just announce deprecation and expect users to switch. It includes the strangler pattern for gradual cutover, the churn rule (if you deprecate infrastructure, you migrate the users), and a decision framework for weighing migration cost against maintenance burden. Use this when replacing APIs, consolidating duplicate implementations, or deciding if that legacy service earns its keep.
- skills.sh installs
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- last updated
- Aug 21, 2026
Install
$ npx -y skills add addyosmani/agent-skills --skill deprecation-and-migration --agent claude-codeInstalls into .claude/skills of the current project.
Files
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
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- Repository
- github.com/addyosmani/agent-skills
- Category
- AI & Agent Building
- First seen
- Apr 16, 2026
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