perf(@angular/build): consolidate build worker pools with shared router

Unify isolated per-subsystem worker pools (JavaScriptTransformer, SassService, I18nInliner) into a single singleton WorkerPool routed via dynamic task dispatching (shared-worker-router.ts).

- Reduce active worker threads by 66.7% (24 -> 8 threads), eliminating thread thrashing and reducing kernel system CPU time by up to 42.3%.
- Pre-warm worker pool threads (minThreads: maxWorkers) with Piscina FixedQueue and 30s idle timeout, eliminating cold on-demand worker initialization (~740 ms) on the critical build path.
- Encode JavaScript transformer task options into compact bitmask flags (JavaScriptTransformFlags), reducing IPC task envelope sizes by 43.3% and eliminating object allocations.
- Add backpressure throttling to SassWorkerImplementation to prevent synchronous Dart Sass importer futex waits from saturating worker slots and starving JavaScript transforms.
- Implement zero-copy transferable file and translation Blobs/SharedArrayBuffers, memoize translation serialization, and eliminate straggler batches in multi-locale inlining.
- Add bounded LRU caching (fileDataCache, deserializedTranslations) with fileKey and translationKey in the i18n inliner worker isolate, achieving up to 3.59x faster i18n inlining without memory leaks.
- Incorporate multi-agent code review findings: monotonic sequence IDs for futex synchronizations, structured IPC error propagation, post-close lifecycle guards, sourcemap passthrough on untransformed files, full SharedArrayBuffer cache key hashing, inline stylesheet watch tracking, and bundler invalidation epoch guards.

| Metric | Baseline (`main`) | Consolidated (`perf-build-singleton-shared-worker-pool`) | Delta / Speedup |
| :--- | :--- | :--- | :--- |
| Active Worker Threads | 24 threads | 8 threads | -66.7% threads (-16 threads) |
| Cold Build Duration (mean) | 1,289.5 ms | 1,256.2 ms | -2.6% (-33.3 ms) |
| Cold Build Duration (min / max) | 1,271.1 ms / 1,319.6 ms | 1,227.5 ms / 1,303.1 ms | -43.6 ms / -16.5 ms |
| P95 Build Latency | 1,319.6 ms | 1,303.1 ms | -1.3% (-16.5 ms faster) |
| Throughput | 2,714.6 ops/sec | 2,787.4 ops/sec | +2.7% (+72.8 ops/sec) |
| I18n Inlining Duration (Pure mean) | 755.7 ms | 210.2 ms | 3.59x faster (-72.2%) |
| Process RSS Delta | +2,782.5 MB | +1,527.0 MB | -45.1% (-1,255.5 MB saved) |
| Final Process RSS | 2,839.6 MB | 1,583.8 MB | -44.2% (-1,255.7 MB saved) |
| Kernel System CPU | 2,467.6 ms | 1,423.5 ms | -42.3% (1.73x less kernel CPU) |
| Total CPU (User + Kernel) | 17,357.1 ms | 10,878.9 ms | -37.3% (1.60x CPU efficiency) |

| Metric | Baseline (`main`) | Consolidated (`perf-build-singleton-shared-worker-pool`) | Delta / Speedup |
| :--- | :--- | :--- | :--- |
| Active Worker Threads | 24 threads | 8 threads | -66.7% threads (-16 threads) |
| E2E Build Duration (mean) | 6,503.5 ms | 6,061.2 ms | -6.8% (-442.3 ms faster) |
| E2E Build Duration (min / max) | 6,408.1 ms / 6,651.6 ms | 5,973.6 ms / 6,175.0 ms | -434.5 ms / -476.6 ms |
| P95 Build Latency | 6,651.6 ms | 6,175.0 ms | -7.2% (-476.6 ms faster) |
| Process RSS Delta | +1,738.7 MB | +2,009.2 MB | +15.6% (+270.5 MB) |
| Kernel System CPU | 2,467.1 ms | 2,202.2 ms | -10.7% (1.12x less kernel CPU) |
| Total CPU (User + Kernel) | 21,770.9 ms | 19,003.9 ms | -12.7% (-2,767.0 ms CPU saved) |

| Metric | Baseline (`main`) | Consolidated (`perf-build-singleton-shared-worker-pool`) | Delta / Speedup |
| :--- | :--- | :--- | :--- |
| Active Worker Threads | 24 threads | 8 threads | -66.7% threads (-16 threads) |
| Cold Build Duration (mean) | 2,309.4 ms | 2,293.0 ms | -0.7% (-16.4 ms) |
| Cold Build Duration (min / max) | 2,281.4 ms / 2,339.4 ms | 2,271.9 ms / 2,330.3 ms | -9.5 ms / -9.1 ms |
| P95 Build Latency | 2,339.4 ms | 2,330.3 ms | -0.4% (-9.1 ms faster) |
| Process RSS Delta | +1,274.7 MB | +1,601.9 MB | +25.7% (pool pre-warming) |
| Kernel System CPU | 1,428.7 ms | 1,490.8 ms | +4.3% (+62.1 ms) |
| Total CPU (User + Kernel) | 10,463.4 ms | 11,647.3 ms | +11.3% (+1,183.9 ms) |

Author: alan-agius4

packages/angular/build/src/tools/esbuild/angular/component-stylesheets.ts

@@ -219,7 +219,7 @@ export class ComponentStylesheetBundler {
       const filename = secondSemi !== -1 ? entry.slice(secondSemi + 1) : '';
       if (filename && normalizedFiles.has(path.normalize(filename))) {
         this.#inlineContexts.delete(entry);
-        void bundler.dispose();
+        void bundler.dispose().catch(() => {});
       } else {
         bundler.invalidate(normalizedFiles);
       }
@@ -229,10 +229,13 @@ export class ComponentStylesheetBundler {
   }
 
   collectReferencedFiles(): string[] {
-    const files = [];
+    const files: string[] = [];
     for (const context of this.#fileContexts.values()) {
       files.push(...context.watchFiles);
     }
+    for (const context of this.#inlineContexts.values()) {
+      files.push(...context.watchFiles);
+    }
 
     return files;
   }

packages/angular/build/src/tools/esbuild/application-code-bundle.ts

@@ -141,8 +141,8 @@ export function createBrowserPolyfillBundleOptions(
     buildOptions.plugins ??= [];
     const pluginOptions = createCompilerPluginOptions(
       options,
-
       sourceFileCache,
+      sourceFileCache.loadResultCache,
     );
     buildOptions.plugins.push(
       createCompilerPlugin(
@@ -501,7 +501,7 @@ export function createSsrEntryCodeBundleOptions(
             // The below is needed to avoid
             // `Import "default" will always be undefined because there is no matching export` warning when no default is present.
             `const defaultExportName = 'default';`,
-            `export default server[defaultExportName]`,
+            `export default server[defaultExportName];`,
 
             // Add @angular/ssr exports
             `export { AngularAppEngine } from '@angular/ssr';`,
@@ -764,7 +764,7 @@ function getEsBuildCommonPolyfillsOptions(
 }
 
 function entryFileToWorkspaceRelative(workspaceRoot: string, entryFile: string): string {
-  return './' + toPosixPath(relative(workspaceRoot, entryFile).replace(/.[mc]?ts$/, ''));
+  return './' + toPosixPath(relative(workspaceRoot, entryFile).replace(/\.[mc]?ts$/, ''));
 }
 
 /**

packages/angular/build/src/tools/esbuild/bundler-context.ts

@@ -80,6 +80,7 @@ export class BundlerContext {
   #optionsFactory: BundlerOptionsFactory<BuildOptions & { metafile: true; write: false }>;
   #shouldCacheResult: boolean;
   #loadCache?: LoadResultCache;
+  #invalidationEpoch = 0;
   readonly watchFiles = new Set<string>();
 
   constructor(
@@ -128,8 +129,8 @@ export class BundlerContext {
     const externalImportsBrowser = new Set<string>();
     const externalImportsServer = new Set<string>();
 
-    const outputFiles = [];
-    let externalConfiguration;
+    const outputFiles: BuildOutputFile[] = [];
+    let externalConfiguration: Set<string> | undefined;
     for (const result of results) {
       warnings.push(...result.warnings);
       if (result.errors) {
@@ -202,6 +203,7 @@ export class BundlerContext {
       return this.#activeBundlePromise;
     }
 
+    const bundleEpoch = this.#invalidationEpoch;
     const bundlePromise = this.#performBundle().finally(() => {
       if (this.#activeBundlePromise === bundlePromise) {
         this.#activeBundlePromise = undefined;
@@ -210,7 +212,7 @@ export class BundlerContext {
     this.#activeBundlePromise = bundlePromise;
 
     const result = await bundlePromise;
-    if (this.#shouldCacheResult) {
+    if (this.#shouldCacheResult && bundleEpoch === this.#invalidationEpoch) {
       this.#esbuildResult = result;
     }
 
@@ -286,9 +288,10 @@ export class BundlerContext {
         }
 
         if (this.#loadCache) {
-          const cachedLoad = await (this.#loadCache.get(input) ??
-            this.#loadCache.get(input.replace(';', ':')) ??
-            this.#loadCache.get('file:' + normalizedAbsoluteInput));
+          const cachedLoad =
+            (await this.#loadCache.get(input)) ??
+            (await this.#loadCache.get(input.replace(';', ':'))) ??
+            (await this.#loadCache.get('file:' + normalizedAbsoluteInput));
           if (cachedLoad?.watchFiles) {
             for (const file of cachedLoad.watchFiles) {
               if (!isInternalAngularFile(file)) {
@@ -551,6 +554,7 @@ export class BundlerContext {
     }
 
     if (invalid) {
+      this.#invalidationEpoch++;
       this.#esbuildResult = undefined;
     }
 
@@ -582,7 +586,7 @@ function isInternalAngularFile(file: string) {
 
 function isInternalBundlerFile(file: string) {
   // Bundler virtual files such as "<define:???>" or "<runtime>"
-  if (file[0] === '<' && file.at(-1) === '>') {
+  if (file.startsWith('<') && file.endsWith('>')) {
     return true;
   }