From d0be59017d7ade561862030466baecee19bf94af Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Mon, 31 Aug 2026 14:38:26 -0400
Subject: [PATCH 1/2] refactor(@angular/build): dynamically load @babel/core in
 transformer worker

By default, JavaScript transformations use the native OXC engine for Angular linking and advanced optimizations. The Babel-based linker is only utilized when the NG_BUILD_BABEL_LINKER environment variable is explicitly enabled.

Previously, transformAsync was imported statically at the top level of javascript-transformer-worker.ts, causing Node.js to eagerly evaluate @babel/core and all its transitive dependencies on startup across every Piscina worker thread.

Importing @babel/core dynamically only when the Babel linker fallback is active reduces worker thread startup latency and eliminates unnecessary worker idle memory overhead on standard builds.
---
 .../esbuild/javascript-transformer-worker.ts  | 21 ++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/packages/angular/build/src/tools/esbuild/javascript-transformer-worker.ts b/packages/angular/build/src/tools/esbuild/javascript-transformer-worker.ts
index f2ec7eccce6d..99ef235f3279 100644
--- a/packages/angular/build/src/tools/esbuild/javascript-transformer-worker.ts
+++ b/packages/angular/build/src/tools/esbuild/javascript-transformer-worker.ts
@@ -7,7 +7,7 @@
  */
 
 import remapping, { type DecodedSourceMap, type EncodedSourceMap } from '@ampproject/remapping';
-import { type PluginItem, transformAsync } from '@babel/core';
+import type { PluginItem } from '@babel/core';
 import { createRequire } from 'node:module';
 import { workerData } from 'node:worker_threads';
 import Piscina from 'piscina';
@@ -42,6 +42,16 @@ const {
   jit = false,
 } = (workerData || {}) as Partial<JavaScriptTransformerOptions>;
 
+let babelLinkerDeps:
+  | Promise<
+      [
+        typeof import('@angular/compiler-cli/linker/babel'),
+        typeof import('@angular/compiler-cli'),
+        typeof import('@babel/core'),
+      ]
+    >
+  | undefined;
+
 const textDecoder = new TextDecoder();
 const textEncoder = new TextEncoder();
 
@@ -170,8 +180,13 @@ async function transformJavaScriptImpl(
   }
 
   if (shouldLink && useBabelLinker) {
-    const { createEs2015LinkerPlugin } = await import('@angular/compiler-cli/linker/babel');
-    const { ConsoleLogger, LogLevel } = await import('@angular/compiler-cli');
+    babelLinkerDeps ??= Promise.all([
+      import('@angular/compiler-cli/linker/babel'),
+      import('@angular/compiler-cli'),
+      import('@babel/core'),
+    ]);
+    const [{ createEs2015LinkerPlugin }, { ConsoleLogger, LogLevel }, { transformAsync }] =
+      await babelLinkerDeps;
 
     const result = await transformAsync(code, {
       filename,

From 33b6676fc50b4f2cc3c01e3a6a6c05c7ba5c54e9 Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Mon, 31 Aug 2026 14:39:21 -0400
Subject: [PATCH 2/2] refactor(@angular/build): use boundary resolution for
 sourcemap generation in oxc transform

Generating high-resolution sourcemap tokens for every character with hires: true produces substantially larger intermediate decoded mappings and increases peak memory consumption during sourcemap remapping.

Using hires: 'boundary' generates tokens only at identifier and word boundaries. This significantly reduces decoded sourcemap memory footprint and remapping time while retaining full debugging accuracy.
---
 packages/angular/build/src/tools/oxc/oxc-transform.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/angular/build/src/tools/oxc/oxc-transform.ts b/packages/angular/build/src/tools/oxc/oxc-transform.ts
index 0ebbc04ec1e5..e4f60ff83cb2 100644
--- a/packages/angular/build/src/tools/oxc/oxc-transform.ts
+++ b/packages/angular/build/src/tools/oxc/oxc-transform.ts
@@ -737,7 +737,7 @@ export function transform(filename: string, code: string, options: OxcTransformO
 
   let map: DecodedSourceMap | undefined;
   if (options.sourcemap) {
-    const rawMap = source.generateDecodedMap({ hires: true, source: filename });
+    const rawMap = source.generateDecodedMap({ hires: 'boundary', source: filename });
     map = { ...rawMap, version: 3 };
   }