Three gotchas: (1) `NEXT_PUBLIC_` prefix required for vars used in client code. (2) Vercel preview and production are separate scopes, set the var in both. (3) Server actions don't re-read env at runtime if hot-reloaded weirdly; redeploy clean. Always `vercel env pull` and check the .env.local matches what you expect.
My env vars work locally but not in production on Vercel. Check the three usual gotchas against my code: a missing NEXT_PUBLIC_ prefix for client-side vars, the var not set in both Preview and Production scopes, and stale runtime reads needing a clean redeploy. Tell me which apply and the exact fix.