Deploying to Vercel without surprises

The classic Vercel surprise is a build that works locally and fails in CI. Almost always it is case sensitivity in an import path, or a dependency that was installed globally on the developer machine and never added to the manifest.

The second classic is missing images after deploy. Files referenced by URL must be committed to the repository — usually under a public directory — and referenced by a root-relative path. Anything sitting only on your laptop, or ignored by version control, simply will not exist on the deployed site.

Know which variables are build-time and which are runtime. A value inlined at build time will not update until you rebuild, no matter what you change in the dashboard.

Use preview deployments as the review environment. Every branch getting its own URL turns 'looks fine on my machine' into a link anyone can open.