deployments-cicd

What this skill does

# Vercel Deployments & CI/CD

You are an expert in Vercel deployment workflows — `vercel deploy`, `vercel promote`, `vercel rollback`, `vercel inspect`, `vercel build`, and CI/CD pipeline integration with GitHub Actions, GitLab CI, and Bitbucket Pipelines.

## Deployment Commands

### Preview Deployment

```bash
# Deploy from project root (creates preview URL)
vercel

# Equivalent explicit form
vercel deploy
```

Preview deployments are created automatically for every push to a non-production branch when using Git integration. They provide a unique URL for testing.

### Production Deployment

```bash
# Deploy directly to production
vercel --prod
vercel deploy --prod

# Force a new deployment (skip cache)
vercel --prod --force
```

### Build Locally, Deploy Build Output

```bash
# Build locally (uses development env vars by default)
vercel build

# Build with production env vars
vercel build --prod

# Deploy only the build output (no remote build)
vercel deploy --prebuilt
vercel deploy --prebuilt --prod
```

**When to use `--prebuilt`:** Custom CI pipelines where you control the build step, need build caching at the CI level, or need to run tests between build and deploy.

### Promote & Rollback

```bash
# Promote a preview deployment to production
vercel promote <deployment-url-or-id>

# Rollback to the previous production deployment
vercel rollback

# Rollback to a specific deployment
vercel rollback <deployment-url-or-id>
```

**Promote vs deploy --prod:** `promote` is instant — it re-points the production alias without rebuilding. Use it when a preview deployment has been validated and is ready for production.

### Inspect Deployments

```bash
# View deployment details (build info, functions, metadata)
vercel inspect <deployment-url>

# List recent deployments
vercel ls

# View logs for a deployment
vercel logs <deployment-url>
vercel logs <deployment-url> --follow
```

## CI/CD Integration

### Required Environment Variables

Every CI pipeline needs these three variables:

```bash
VERCEL_TOKEN=<your-token>        # Personal or team token
VERCEL_ORG_ID=<org-id>           # From .vercel/project.json
VERCEL_PROJECT_ID=<project-id>   # From .vercel/project.json
```

Set these as secrets in your CI provider. Never commit them to source control.

### GitHub Actions

```yaml
name: Deploy to Vercel
on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Install Vercel CLI
        run: npm install -g vercel

      - name: Pull Vercel Environment
        run: vercel pull --yes --environment=production --token=${{ secrets.VERCEL_TOKEN }}

      - name: Build
        run: vercel build --prod --token=${{ secrets.VERCEL_TOKEN }}

      - name: Deploy
        run: vercel deploy --prebuilt --prod --token=${{ secrets.VERCEL_TOKEN }}
```

### OIDC Federation (Secure Backend Access)

Vercel OIDC federation is for **secure backend access** — letting your deployed Vercel functions authenticate with third-party services (AWS, GCP, HashiCorp Vault) without storing long-lived secrets. It does **not** replace `VERCEL_TOKEN` for CLI deployments.

**What OIDC does:** Your Vercel function requests a short-lived OIDC token from Vercel at runtime, then exchanges it with an external provider's STS/token endpoint for scoped credentials.

**What OIDC does not do:** Authenticate the Vercel CLI in CI pipelines. All `vercel pull`, `vercel build`, and `vercel deploy` commands still require `--token=${{ secrets.VERCEL_TOKEN }}`.

**When to use OIDC:**
- Serverless functions that need to call AWS APIs (S3, DynamoDB, SQS)
- Functions authenticating to GCP services via Workload Identity Federation
- Any runtime service-to-service auth where you want to avoid storing static secrets in Vercel env vars

### GitLab CI

```yaml
deploy:
  image: node:20
  stage: deploy
  script:
    - npm install -g vercel
    - vercel pull --yes --environment=production --token=$VERCEL_TOKEN
    - vercel build --prod --token=$VERCEL_TOKEN
    - vercel deploy --prebuilt --prod --token=$VERCEL_TOKEN
  only:
    - main
```

### Bitbucket Pipelines

```yaml
pipelines:
  branches:
    main:
      - step:
          name: Deploy to Vercel
          image: node:20
          script:
            - npm install -g vercel
            - vercel pull --yes --environment=production --token=$VERCEL_TOKEN
            - vercel build --prod --token=$VERCEL_TOKEN
            - vercel deploy --prebuilt --prod --token=$VERCEL_TOKEN
```

## Common CI Patterns

### Preview Deployments on PRs

```yaml
# GitHub Actions
on:
  pull_request:
    types: [opened, synchronize]

jobs:
  preview:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm install -g vercel
      - run: vercel pull --yes --environment=preview --token=${{ secrets.VERCEL_TOKEN }}
      - run: vercel build --token=${{ secrets.VERCEL_TOKEN }}
      - id: deploy
        run: echo "url=$(vercel deploy --prebuilt --token=${{ secrets.VERCEL_TOKEN }})" >> $GITHUB_OUTPUT
      - name: Comment PR
        uses: actions/github-script@v7
        with:
          script: |
            github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: `Preview: ${{ steps.deploy.outputs.url }}`
            })
```

### Promote After Tests Pass

```yaml
jobs:
  deploy-preview:
    # ... deploy preview ...
    outputs:
      url: ${{ steps.deploy.outputs.url }}

  e2e-tests:
    needs: deploy-preview
    runs-on: ubuntu-latest
    steps:
      - run: npx playwright test --base-url=${{ needs.deploy-preview.outputs.url }}

  promote:
    needs: [deploy-preview, e2e-tests]
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'
    steps:
      - run: npm install -g vercel
      - run: vercel promote ${{ needs.deploy-preview.outputs.url }} --token=${{ secrets.VERCEL_TOKEN }}
```

## Global CLI Flags for CI

| Flag | Purpose |
|------|---------|
| `--token <token>` | Authenticate (required in CI) |
| `--yes` / `-y` | Skip confirmation prompts |
| `--scope <team>` | Execute as a specific team |
| `--cwd <dir>` | Set working directory |

## Best Practices

1. **Always use `--prebuilt` in CI** — separates build from deploy, enables build caching and test gates
2. **Use `vercel pull` before build** — ensures correct env vars and project settings
3. **Prefer `promote` over re-deploy** — instant, no rebuild, same artifact
4. **Use OIDC federation for runtime backend access** — lets Vercel functions auth to AWS/GCP without static secrets (does not replace `VERCEL_TOKEN` for CLI)
5. **Pin the Vercel CLI version in CI** — `npm install -g vercel@latest` can break unexpectedly
6. **Add `--yes` flag in CI** — prevents interactive prompts from hanging pipelines

## Deployment Strategy Matrix

| Scenario | Strategy | Commands |
|----------|----------|----------|
| Standard team workflow | Git-push deploy | Push to main/feature branches |
| Custom CI/CD (Actions, CircleCI) | Prebuilt deploy | `vercel build && vercel deploy --prebuilt` |
| Monorepo with Turborepo | Affected + remote cache | `turbo run build --affected --remote-cache` |
| Preview for every PR | Default behavior | Auto-creates preview URL per branch |
| Promote preview to production | CLI promotion | `vercel promote <url>` |
| Atomic deploys with DB migrations | Two-phase | Run migration → verify → `vercel promote` |
| Edge-first architecture | Edge Functions | Set `runtime: 'edge'` in route config |

## Common Build Errors

| Error | Cause | Fix |
|-------|-------|-----|
| `ERR_PNPM_OUTDATED_LOCKFILE` | Lockfile doesn't match package.json | Run `pnpm install`, commit lockfile |
| `NEXT_NOT_FOUND` | Root directory misconfigured | Set `rootDirectory` in Project Settings |
| `Invalid next.config.js` | Config syntax error | Validate config locally with `next build` |
| `functions/api/*.js` mismatch | W