Monorepos: multiple Vercel projects from one repository

A monorepo holding several independently-deployable apps maps to several separate Vercel projects, each one connected to the same Git repository but configured with its own root directory (apps/marketing-site, say) telling Vercel which subfolder that particular project actually builds from. Each project gets its own deployment history, its own custom domain, its own environment variables — genuinely independent from the others, despite sharing one repository and one Git history.

Without configuration, every push to the repository would trigger a build for every project, even ones whose code didn't actually change — wasteful, and exactly the problem CI/CD's own monorepo lesson covers for a general pipeline, just needing its own Vercel-specific mechanism here. An "Ignored Build Step" script runs before a build starts and can exit early (skipping the build entirely) if the specific files that project cares about weren't touched by the current commit — tools like Turborepo's own turbo-ignore helper automate detecting this based on the monorepo's dependency graph, rather than a team manually maintaining a list of "which paths affect which project."

When shared-ui changes, every app depending on it genuinely needs rebuilding — this is exactly why naive "ignore unless files in my own folder changed" logic is wrong for a real monorepo: a change to a shared package affects every consumer, and the ignore-script tooling above needs to understand the actual dependency graph (which Turborepo and similar tools track explicitly) rather than just watching one folder in isolation.

A monorepo's real advantage — atomic commits that touch a shared package and every app depending on it together, in one single commit/PR — only holds if the deployment tooling respects that same dependency graph. Treating each app's Vercel project as if it were connected to a completely separate repository (ignoring the shared-package relationship) would silently reintroduce exactly the cross-repository coordination problem a monorepo was adopted to avoid in the first place.