The CI job that failed every push after the monorepo move

The symptom

A failure email on every push to main. The backend and Docker jobs were green; the red one was Frontend (Next.js), and it died in 10 seconds, before installing anything:

Run actions/setup-node@v4
Error: Some specified paths were not resolved, unable to cache dependencies.

The cause

The job was written when the frontend was the repo — and the monorepo migration never updated it. Two stale assumptions:

defaults: { run: { working-directory: frontend } }
- uses: actions/setup-node@v4
  with:
    cache: 'npm'
    cache-dependency-path: frontend/package-lock.json   # ← doesn't exist anymore
- run: npm ci                                            # ← in frontend/, no workspace lockfile

After the move, the lockfile lives at the repo root (it's an npm workspaces lockfile covering packages/* + frontend). So setup-node couldn't find frontend/package-lock.json to key the cache on, and npm ci from inside frontend/ has no lockfile to install from.

The fix

Re-point everything at the workspace root:

- uses: actions/setup-node@v4
  with:
    node-version: '24'
    cache: 'npm'
    cache-dependency-path: package-lock.json          # root lockfile
 
- run: npm install --no-package-lock                  # workspace root; resolves linux
                                                      # native prebuilts npm ci can't
- run: npm run lint  --workspace frontend
- run: npm test      --workspace frontend             # advisory (see below)
  continue-on-error: true
- run: npm run build --workspace frontend             # the gate

npm install --no-package-lock is the same install the Vercel build needed — it resolves the linux native prebuilts (@next/swc, @tailwindcss/oxide, lightningcss) that aren't pinned in the macOS-generated lockfile, where npm ci would install none of them. The vitest suite is temporarily advisory: it can't resolve vitest from a hoisted @testing-library/jest-dom under workspaces — a separate fix — so it shouldn't block the job; next build is the real gate. Result: the frontend job goes green, and the email storm stops.

The takeaway

When you turn a single-app repo into a monorepo, the CI is the easiest thing to forget — every working-directory, lockfile cache path, and npm ci quietly assumed the app was the repo root. They don't error until a push hits CI, and then they error on every push. Re-point them at the workspace root the same day you move the code.

Commit: 6fa4994.