# API Breaking Change Detector (agent skill)

> API Breaking Change Detector is an agent skill (a SKILL.md file) from github/awesome-copilot. Cross-references C# Web API controllers/DTOs against their TypeScript/JavaScript consumers (React, Angular, Vue, Svelte, Node.js, or hand-written/auto-generated HTTP clients like Fetch, Axios. It works with Claude Code and GitHub Copilot and has 40,416 GitHub stars across a repository of 7 listed skills.

Cross-references C# Web API controllers/DTOs against their TypeScript/JavaScript consumers (React, Angular, Vue, Svelte, Node.js, or hand-written/auto-generated HTTP clients like Fetch, Axios, NSwag) to catch contract drift in both directions: backend changes that break client applications (renamed/removed JSON keys, new required parameters, status code shifts) and frontend code sending fields the backend no longer reads. Works directly against source code, not exported OpenAPI spec files.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/github/awesome-copilot |
| Skill path | skills/api-breaking-change-detector/SKILL.md |
| Skill name | api-breaking-change-detector |
| GitHub stars | 40,416 |
| Installs on skills.sh | not listed |
| License | MIT |
| Skills in repo | 7 |
| Plugin marketplace | no |
| Official | yes |
| Works with | Claude Code, GitHub Copilot |
| Category | Design & frontend |
| Last commit | Oct 26, 2026 |

## When it triggers

- Use when the user asks to check for breaking API changes, verify frontend/backend contract sync, or audit a DTO/controller change against its TypeScript/JS consumers before merging.

## Add this skill

### Claude Code

```sh
git clone --depth 1 https://github.com/github/awesome-copilot.git
cp -r awesome-copilot/skills/api-breaking-change-detector ~/.claude/skills/api-breaking-change-detector   # personal, or .claude/skills in a project
```

In the Claude apps, zip the skill folder and upload it under Customize > Skills > + > Upload a skill (code execution must be on).

### ChatGPT / Codex

```sh
git clone --depth 1 https://github.com/github/awesome-copilot.git
cp -r awesome-copilot/skills/api-breaking-change-detector .agents/skills/api-breaking-change-detector   # repo; ~/.agents/skills for all projects
```

### Cursor

```sh
git clone --depth 1 https://github.com/github/awesome-copilot.git
cp -r awesome-copilot/skills/api-breaking-change-detector .cursor/skills/api-breaking-change-detector   # project; ~/.cursor/skills for all projects
```

Sources (checked 2026-10-07): https://code.claude.com/docs/en/skills, https://support.claude.com/en/articles/12512180-using-skills-in-claude, https://learn.chatgpt.com/docs/build-skills, https://cursor.com/docs/context/skills

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Canonical page: https://appsgit.com/skills/github-api-breaking-change-detector
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