perf(ci)

scripts/ci-workflow.spec.ts

@@ -98,9 +98,9 @@ describe('CI workflow', () => {
     ))
     expect(buildCommands.map(step => step.run)).toContain('pnpm run check:ci:windows-blocking')
 
-    // windows-coverage uses the lower 4-partition profile.
+    // windows-coverage runs the 6-partition profile.
     expect(windowsCoverage.name).toBe('windows node 24 / coverage')
-    expect(windowsCoverage.env).toMatchObject({ DSH_COVERAGE_PARTITIONS: '4' })
+    expect(windowsCoverage.env).toMatchObject({ DSH_COVERAGE_PARTITIONS: '6' })
     const coverageSteps = windowsCoverage.steps as unknown[]
     const coverageCommands = coverageSteps.filter((step): step is Record<string, unknown> & { run: string } => (
       isRecord(step) && typeof step.run === 'string'

scripts/coverage-exempt.ts

@@ -34,6 +34,14 @@ export const coverageExemptHeavySuites: readonly CoverageExemptSuite[] = [
     filter: 'packages/typert/generator/tests/',
     exclude: 'packages/typert/generator/tests/**',
   },
+  // Spawns the full-corpus transform gate in a child process (Node's ESM
+  // loader is its oracle), so no measured file executes in-process; the
+  // sibling in-process suites carry the package's src coverage. As a single
+  // 499–513 s case it dominated one native Windows coverage partition.
+  {
+    filter: 'packages/experimental/webworker-runtime/tests/compile/transform-corpus.spec.ts',
+    exclude: 'packages/experimental/webworker-runtime/tests/compile/transform-corpus.spec.ts',
+  },
   // Real child-process fixtures over scripts/ sources, which coverage never measures.
   { filter: 'scripts/install-lefthook.spec.ts', exclude: 'scripts/install-lefthook.spec.ts' },
   { filter: 'scripts/oxlint-contract.spec.ts', exclude: 'scripts/oxlint-contract.spec.ts' },