knockout · brianmhunt · Apr 22, 2026 · Apr 22, 2026
diff --git a/tko.io/package.json b/tko.io/package.json
@@ -7,10 +7,10 @@
     "postinstall": "patch-package",
     "prebuild": "bun ./scripts/generate-verified-behaviors.mjs && mkdir -p public/lib && cd ../builds/knockout && bun run build && cp dist/browser.min.js ../../tko.io/public/lib/ko.js && cd ../reference && bun run build && cp dist/browser.min.js ../../tko.io/public/lib/tko.js && cd ../../tko.io && bun ./scripts/bundle-tests.mjs",
     "predev": "bun run prebuild",
-    "dev": "ASTRO_TELEMETRY_DISABLED=1 astro dev",
-    "build": "ASTRO_TELEMETRY_DISABLED=1 astro build --force",
-    "preview": "ASTRO_TELEMETRY_DISABLED=1 astro preview",
-    "check": "ASTRO_TELEMETRY_DISABLED=1 astro check"
+    "dev": "ASTRO_TELEMETRY_DISABLED=1 bun --bun astro dev",
+    "build": "ASTRO_TELEMETRY_DISABLED=1 bun --bun astro build --force",
+    "preview": "ASTRO_TELEMETRY_DISABLED=1 bun --bun astro preview",
+    "check": "ASTRO_TELEMETRY_DISABLED=1 bun --bun astro check"
   },
   "keywords": ["tko", "knockout", "documentation"],
   "author": "",

diff --git a/tko.io/public/tests-frame.html b/tko.io/public/tests-frame.html
@@ -80,8 +80,9 @@
           runner.on('end', () => parent.postMessage({ type: 'end', slug, stats: runner.stats }, '*'))
           parent.postMessage({ type: 'start', slug, total: runner.total }, '*')
         } catch (err) {
-          document.getElementById('err').textContent = 'import failed: ' + (err?.message || err)
-          parent.postMessage({ type: 'import-error', slug, err: err?.message || String(err) }, '*')
+          const msg = err?.message || String(err)
+          document.getElementById('err').textContent = 'import failed: ' + msg
+          parent.postMessage({ type: 'import-error', slug, err: msg }, '*')
         }
       }
     </script>

diff --git a/tko.io/scripts/bundle-tests.mjs b/tko.io/scripts/bundle-tests.mjs
@@ -256,7 +256,14 @@ async function buildSourceBundles({ buildVersion, tsconfig, alias }) {
   const specs = await collectSpecs(scope)
   if (specs.length === 0) throw new Error('source-bundle scope matched no specs')
 
+  // Clean previous chunk-*.js emissions so removed specs / shifted
+  // dependency graphs don't leak stale hashed chunks into the new
+  // manifest. Wrappers + per-spec bundles regenerate from fresh
+  // entry points, so leaving them alone is fine.
   await fs.mkdir(sourceOutputDir, { recursive: true })
+  for await (const name of new Bun.Glob('chunk-*.js').scan({ cwd: sourceOutputDir })) {
+    await fs.unlink(path.join(sourceOutputDir, name))
+  }
   const { entryPoints, manifest } = await writeSpecWrappers(specs)
 
   await esbuild.build({
@@ -275,9 +282,21 @@ async function buildSourceBundles({ buildVersion, tsconfig, alias }) {
     logLevel: 'warning'
   })
 
+  // Enumerate the shared chunk files esbuild just emitted. The
+  // /tests page preloads these via <link rel="modulepreload"> in
+  // <head> so the browser HTTP cache is warm before iframes race
+  // to dynamic-import them — otherwise WebKit occasionally reports
+  // the opaque "Importing a module script failed." error. See
+  // tko.io/src/pages/tests.astro.
+  const chunks = []
+  for await (const name of new Bun.Glob('chunk-*.js').scan({ cwd: sourceOutputDir })) {
+    chunks.push(name)
+  }
+  chunks.sort()
+
   await fs.writeFile(
     path.join(sourceOutputDir, 'manifest.json'),
-    JSON.stringify({ specs: manifest }, null, 2),
+    JSON.stringify({ specs: manifest, chunks }, null, 2),
     'utf8'
   )
 

diff --git a/tko.io/src/pages/tests.astro b/tko.io/src/pages/tests.astro
@@ -1,4 +1,17 @@
 ---
+import { fileURLToPath } from 'node:url'
+
+// Read the source-mode chunk list at SSR time so the HTML ships
+// with <link rel="modulepreload"> for every shared chunk already
+// in <head>. The browser starts warming the HTTP cache during
+// initial parse — well before any JS runs — which side-steps the
+// concurrent-fetch race that makes WebKit occasionally fail spec
+// iframes with the opaque "Importing a module script failed."
+// error. `prebuild` always runs bundle-tests.mjs before Astro
+// builds the site, so manifest.json is guaranteed to exist.
+const manifestPath = fileURLToPath(new URL('../../public/tests/source/manifest.json', import.meta.url))
+const sourceChunks: string[] = (await Bun.file(manifestPath).json()).chunks ?? []
+
 // TKO Browser Test Runner — written in TKO itself.
 //
 // Two modes:
@@ -32,6 +45,8 @@
     <title>TKO · Browser Tests</title>
     <link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Lobster&display=swap" />
     <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/mocha@10/mocha.css" />
+    {sourceChunks.map(name => <link rel="modulepreload" href={`/tests/source/${name}`} />)}
+    <link rel="preload" as="script" href="/tests/source/setup.js" />
     <style>
       :root {
         --bg: #0b0d11;
@@ -362,7 +377,7 @@
         self.pkg     = ko.observable(safePkg)
         self.ver     = ko.observable(safeVer)
         self.grep    = ko.observable(qs.get('grep') || '')
-        // Pool for the parallel (non-focus) phase. Focus-needing
+        // Pool for the parallel-hidden run. Focus-needing
         // specs — flagged at bundle time via `manifest.specs[].needsFocus`
         // — always run serially in the visible #workarea so each
         // has sole system focus; Chromium only grants
@@ -520,6 +535,7 @@
         const res = await fetch('/tests/source/manifest.json')
         const manifest = await res.json()
         let specs = manifest.specs
+
         const grep = page.grep().trim()
         if (grep) {
           // Invalid regex patterns (e.g. bare `(`) throw from the
@@ -632,7 +648,11 @@
           })
         }
 
-        // Phase 1: parallel hidden specs.
+        // Parallel-hidden run: non-focus specs, `pool`-at-a-time
+        // inside the offscreen `hiddenHost`. The <link rel=modulepreload>
+        // tags in <head> warmed the HTTP cache, so iframes can
+        // race on dynamic import() without tripping WebKit's
+        // dependency-tree fetcher.
         async function hiddenWorker() {
           while (hiddenQueue.length) {
             const spec = hiddenQueue.shift()
@@ -642,7 +662,8 @@
         }
         await Promise.all(Array.from({ length: page.pool }, hiddenWorker))
 
-        // Phase 2: serial focus specs in the visible workarea.
+        // Serial-focus run: one focus-needing spec at a time in
+        // the visible #workarea so each has sole system focus.
         for (const spec of focusQueue) {
           await runOne(spec, { host: workarea, label: workareaLabel, grantFocus: true })
         }