Next.js CI on GitHub Actions

next build recompiles every page even when one component changed.

Why it happens

The .next/cache directory holds the incremental build cache and is discarded between runs.

What to change

1. Cache .next/cache keyed on the lockfile plus source hash
2. Turn on Turbopack builds where your app supports them
3. Split typecheck and lint into parallel jobs so they do not serialise the build
4. Use a 4 vCPU runner with NVMe — Next builds are heavily I/O bound

Next.js on runnerhut

jobs:
  build:
    runs-on: runnerhut-4vcpu-ubuntu-2404
    steps:
      - uses: actions/checkout@v4
      - uses: actions/cache@v4
        with:
          path: .next/cache
          key: next-${{ hashFiles('**/package-lock.json') }}-${{ github.sha }}
          restore-keys: next-${{ hashFiles('**/package-lock.json') }}-
      - run: npm ci && npm run build

The only runnerhut-specific line is `runs-on: runnerhut-4vcpu-ubuntu-2404`. Everything else is standard GitHub Actions — the same actions, the same secrets and the same permissions model you use today.