# `npm error code ERESOLVE: unable to resolve dependency tree`

**Where it appears:** Terminal

**What it means:** Two packages in your project are asking for incompatible versions of another package.

## Likely causes

- Adding an older library that hasn't updated its peer dependency list for React 19 or Next.js.
- Pinning a package version that clashes with what another installed package expects.

## Message for your agent

```text
npm failed with ERESOLVE. Read which two packages conflict, pick compatible versions (or a modern alternative) and explain the fix before changing package.json.
```

**Prevention:** Prefer maintained packages from your stack skills instead of unmaintained add-ons.

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Source: [Agentic Makers](https://agenticmakers.app/en/help/errors/npm-eresolve-unable-to-resolve-dependency-tree) · License: CC BY 4.0