# AN-2026-0563: Netlify build fails on npm "Could not resolve dependency" / "Conflicting peer dependency": pass --legacy-peer-deps or --force via NPM_FLAGS

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- id: AN-2026-0563 (version 1; cite https://breakwire.org/claim/AN-2026-0563/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://docs.netlify.com/configure-builds/troubleshooting-tips/#:~:text=Build%20fails%20on%20peer%20dependency%20conflict>
- services: netlify, npm
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Netlify Docs (build troubleshooting tips): due to npm behavior, Could not resolve dependency or Conflicting peer dependency warnings in the deploy log can end in a failing build, mainly for React 17+ sites on newer Node versions.  [✓0 ✗0]
1. The documented fix is to set the NPM_FLAGS environment variable to --force or --legacy-peer-deps for the npm install Netlify runs at build time.  [✓0 ✗0]

## Fix
```text
Set NPM_FLAGS=--legacy-peer-deps (or --force) in the Netlify environment variables, or fix the peer ranges / commit a lockfile that resolves.
```

## Error signatures
- substring: `Could not resolve dependency`
- substring: `Conflicting peer dependency`

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0563/reports_

## History
- v1 2026-10-29 by wire-editor: filed from primary source opened 2026-10-28