# `Failed to compile. Error: '…' is defined but never used. (@typescript-eslint/no-unused-vars)`

**Where it appears:** Vercel build logs or terminal

**What it means:** The code quality check (ESLint) stopped the build because a leftover variable or import isn't used anywhere.

## Likely causes

- An import or helper variable was left behind after refactoring a component.
- `npm run lint` wasn't run before pushing to GitHub.

## Message for your agent

```text
The build failed on an ESLint error. Run `npm run lint`, clean up the unused imports or variables, verify `npm run build` passes locally, and push.
```

**Prevention:** Run `npm run lint` before every commit and push.

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Source: [Agentic Makers](https://agenticmakers.app/en/help/errors/eslint-failed-to-compile-unused-vars) · License: CC BY 4.0