name: build
description: "Run the production build including type-checking, and collect build metrics (duration, bundle size, route count, errors). Use as Phase 4 of the deployment pipeline or when verifying a project builds cleanly for production."

Type Check & Build

Run the production build, which typically includes type-checking.

Detect

Look for build commands in package.json scripts or project config:

Why This Is Separate from Unit Tests

Many test runners (Vitest/esbuild, Jest/babel) skip type-checking for speed. The production build catches type errors that tests silently ignore. This is a real gap — never skip this phase, even if all unit tests pass.

Example: a function parameter typed as string that receives number | undefined will pass Vitest (esbuild strips types) but fail next build or tsc --noEmit.

Run

Execute the detected build command. For TypeScript projects, if the build tool doesn't include type-checking, run tsc --noEmit separately first.

Collect

• Build duration
• Any type/compilation errors (file, line, message)
• Bundle/output size:
  bash du -sh .next/ # Next.js du -sh dist/ # Vite du -sh target/release/ # Rust
• Route count, page count, or equivalent metrics from build output
• Exit code

Stop Conditions

STOP if: Build fails. Fix type errors or compilation issues before proceeding.