Docs: document BUILD_POOL_TIMEOUT; Refactor: extract production build helpers

- Add BUILD_POOL_TIMEOUT to Build Performance Options for thread-loader pool timeout tuning
- Extract duplicated parallel/sequential production build logic into a helper

Validated with prettier, eslint, and production build

Author: PeterDaveHello

.github/copilot-instructions.md

@@ -29,6 +29,8 @@ Always reference these instructions first and fall back to search or bash comman
   - Options: `0|false|none`, `gzip` (or `brotli` if explicitly desired)
   - Affects only `.cache/webpack` size/speed; does not change final artifacts
 - BUILD_WATCH_ONCE (dev): When set, `npm run dev` runs a single build and exits (useful for timing)
+ - BUILD_POOL_TIMEOUT: Override thread-loader production pool timeout (ms)
+   - Default: `2000`. Increase if workers recycle too aggressively on slow machines/CI
 
 Performance defaults: esbuild handles JS/CSS minification; in development CSS is injected via style-loader;
 in production CSS is extracted via MiniCssExtractPlugin; thread-loader is enabled by default in both dev and prod.

build.mjs

@@ -511,59 +511,32 @@ async function finishOutput(outputDirSuffix, sourceBuildDir = outdir) {
 
 async function build() {
   await deleteOldDir()
+  function createWebpackBuildPromise(isWithoutKatex, isWithoutTiktoken, minimal, tmpDir, suffix) {
+    return new Promise((resolve, reject) =>
+      runWebpack(isWithoutKatex, isWithoutTiktoken, minimal, tmpDir, async (err, stats) => {
+        if (err || (stats && typeof stats.hasErrors === 'function' && stats.hasErrors())) {
+          console.error(err || stats.toString())
+          reject(err || new Error('webpack error'))
+          return
+        }
+        await finishOutput(suffix, tmpDir)
+        resolve()
+      }),
+    )
+  }
   if (isProduction && !isAnalyzing) {
     const tmpFull = `${outdir}/.tmp-full`
     const tmpMin = `${outdir}/.tmp-min`
     if (parallelBuild) {
       await Promise.all([
-        new Promise((resolve, reject) =>
-          runWebpack(true, true, true, tmpMin, async (err, stats) => {
-            if (err || stats.hasErrors()) {
-              console.error(err || stats.toString())
-              reject(err || new Error('webpack error'))
-              return
-            }
-            await finishOutput('-without-katex-and-tiktoken', tmpMin)
-            resolve()
-          }),
-        ),
-        new Promise((resolve, reject) =>
-          runWebpack(false, false, false, tmpFull, async (err, stats) => {
-            if (err || stats.hasErrors()) {
-              console.error(err || stats.toString())
-              reject(err || new Error('webpack error'))
-              return
-            }
-            await finishOutput('', tmpFull)
-            resolve()
-          }),
-        ),
+        createWebpackBuildPromise(true, true, true, tmpMin, '-without-katex-and-tiktoken'),
+        createWebpackBuildPromise(false, false, false, tmpFull, ''),
       ])
       await fs.rm(tmpFull, { recursive: true, force: true })
       await fs.rm(tmpMin, { recursive: true, force: true })
     } else {
-      await new Promise((resolve, reject) =>
-        runWebpack(true, true, true, tmpMin, async (err, stats) => {
-          if (err || stats.hasErrors()) {
-            console.error(err || stats.toString())
-            reject(err || new Error('webpack error'))
-            return
-          }
-          await finishOutput('-without-katex-and-tiktoken', tmpMin)
-          resolve()
-        }),
-      )
-      await new Promise((resolve, reject) =>
-        runWebpack(false, false, false, tmpFull, async (err, stats) => {
-          if (err || stats.hasErrors()) {
-            console.error(err || stats.toString())
-            reject(err || new Error('webpack error'))
-            return
-          }
-          await finishOutput('', tmpFull)
-          resolve()
-        }),
-      )
+      await createWebpackBuildPromise(true, true, true, tmpMin, '-without-katex-and-tiktoken')
+      await createWebpackBuildPromise(false, false, false, tmpFull, '')
       await fs.rm(tmpFull, { recursive: true, force: true })
       await fs.rm(tmpMin, { recursive: true, force: true })
     }