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Build errors guide

Vercel build failed on pull request?

The fix is rarely “just rerun deploy.” Most Vercel deployment failed compile error TypeScript incidents are PR-quality failures: invented types, missing imports, Next.js dynamic import mistakes, circular dependencies, or code that only ever ran in `next dev`. The reliable answer is to force every PR through a real build and test path before merge.

Run the real build

If you want to prevent failing builds on Vercel, run `npm run build` locally before push and again in CI on every PR.

Catch TypeScript drift

AI agents love making up types and ignoring imports. A TypeScript compile error in GitHub Action is usually better discovered before the branch ever hits Vercel.

Verify in a sandbox

When repos are flaky, use an ephemeral sandbox for PR verification so you can verify code actually runs on GitHub in a clean environment.

The failure patterns behind most bad PR deploys

Search intent

vercel build failed on pull request

Usually means the PR was never forced through the same production build path before merge: TypeScript drift, missing imports, circular dependencies, bad dynamic imports, or unused imports that local dev tolerated but Next.js build rejected.

Search intent

vercel deployment failed compile error typescript

This is the classic vibe-coding failure mode: invented types, stale imports, widened any-casts, or server/client boundary mistakes that survive local clicking but fail under full compile.

Search intent

next js circular dependency vercel build failed

Circular imports often hide until bundling. If the app only breaks on Vercel or CI, check dependency cycles first, especially around shared config, re-export barrels, and server-only utilities.

Search intent

unused imports breaking nextjs build

Unused imports are rarely the root cause alone, but they often travel with stale type references, misnamed exports, or code paths that changed without a clean compile pass.

How to catch build failures before merge

  • Check: Run `npm run build` or `pnpm build` locally before push, not just `next dev`.
  • Check: Run `pnpm exec tsc --noEmit` or the repo’s TypeScript check explicitly to catch compile-only drift.
  • Check: Fail the PR if `npm run build` fails in CI; do not rely on Vercel to be the first full build.
  • Check: Detect circular imports with a dependency graph tool before merge on larger Next.js repos.
  • Check: Verify the PR in an ephemeral sandbox when the repo needs full install, build, and test isolation.
  • Check: Treat Vercel build errors as review signals, not deployment noise.

When local build is not enough

Teams searching for “run npm run build in ephemeral sandbox”, “run GitHub PR in Docker sandbox”, or “automated playground for testing pull requests” are really asking for the same thing: a clean execution environment that proves the branch builds and tests without local-machine contamination. That is where a sandbox-backed coding agent or verification worker fits.

Product page

Run build and fix loops in an ephemeral sandbox

Critique’s Coding Agent API runs OpenCode in E2B, so PRs can be compiled, tested, patched, and turned into draft PRs with a clean environment on every run.

Open coding agent API

Buyer guide

Use review as the forcing function for real builds

The point is not just to comment on diffs. The point is to make compile, test, and merge quality a PR-level control instead of waiting for deployment to fail.

Open review guide

FAQ

How do I run Vercel build locally before push?

Run the same package-manager install and build command your PR uses in CI. For most Next.js repos that means install dependencies cleanly, then run `npm run build`, `pnpm build`, or `vercel build` if the project depends on Vercel-specific config. Local clicking in `next dev` is not enough.

How do I test Vercel build on a GitHub PR?

At minimum, run the production build in CI on every PR. Better: run the build plus the critical test suite in an ephemeral sandbox so the PR is verified under a clean filesystem and dependency install instead of the contributor’s local machine.

How do I catch circular imports in Next.js?

Use a dependency graph tool in CI, and pay extra attention to barrel exports, shared util folders, and server-only modules imported into client trees. Circular imports often show up as mysterious build or runtime failures only after bundling.

What causes a Next.js dynamic import TypeScript error?

Most failures come from incorrect default-vs-named export assumptions, importing server-only modules into client code, or returning a component type that does not match what `dynamic()` expects.

How do I auto-fix TypeScript errors on a PR?

Use a coding agent or sandboxed fixer only after the PR is forced through the real compile path. Otherwise the agent is guessing. The reliable loop is: run build, capture exact errors, patch, rerun build, then open or update the PR with proof.

Why run npm run build in an ephemeral sandbox?

Because it proves the PR builds in a clean environment with no local-machine contamination. That is the fastest way to verify code actually runs on GitHub before Vercel or production is embarrassed by the merge.