"ERESOLVE unable to resolve dependency tree"

What it means

Two of your packages want different versions of a shared package (often React), and npm refuses to guess.

Why AI tools cause it

AI tools install packages from older tutorials alongside newer ones. A library that only supports React 18 meets a project on React 19, for example.

The fix

1. Read the error. It names the package that wants the older version (look for "Could not resolve dependency" and "peer").
2. Best fix: upgrade that package to a version that supports your setup (npm install <package>@latest).
3. If there's no compatible version yet, install with npm install --legacy-peer-deps. To make your host do the same, add a .npmrc file containing legacy-peer-deps=true and commit it.

Treat option 3 as a workaround: it hides the warning, and the package may still misbehave.

Paste this into your AI

npm install fails with ERESOLVE. Here is the full error: . Tell me which package conflicts with which, whether a newer compatible version exists, and the safest fix.

Still broken?

Delete node_modules and package-lock.json, then run npm install again so the lock file is rebuilt cleanly. Commit the new lock file.