diff --git a/CHANGELOG.md b/CHANGELOG.md
index f095e92..5cd9cc3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@ Follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) · versioned wi
 ## [Unreleased]
 
 ### Changed
+- **TTS preview namespace migration.** Backend voice selection, Fish emotion tags, preview synthesis, stream fallback,
+  and performance-history helpers now use a private scope with explicit compatibility exports and a `window.TTVC.tts` API.
 - **Settings namespace migration.** Settings state, backend catalogs, help rendering, and provider configuration now use
   a private scope with live compatibility accessors and a `window.TTVC.settings` API.
 - **Character library namespace migration.** SQLite-backed character persistence, identity merging, image updates, and
diff --git a/VERSION b/VERSION
index 01d9cc8..27ec546 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.24.74
+1.24.75
diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index 107ef27..a4a9b0c 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -64,6 +64,7 @@ Done incrementally as global-scope ordered files (no ES-module change needed) 
 - ✅ Studio navigation and DOM-borrowing coordination use a private scope with explicit compatibility exports.
 - ✅ Character library persistence and rendering use a private scope with explicit identity/image compatibility exports.
 - ✅ Settings state and backend configuration use a private scope with live compatibility accessors and a namespace API.
+- ✅ TTS preview and performance-history helpers use a private scope with explicit preview/history compatibility exports.
 - ✅ `static/css/resource-diagnostics.css` — isolated Performance/resource diagnostic panel styles.
 - ✅ `static/css/background-jobs.css` — isolated background-job history and retry-panel styles.
 - ✅ `static/css/voice-design.css` — isolated Voice Design form, samples, and preview-match styles.
diff --git a/static/index.html b/static/index.html
index 07e2654..e9eb80b 100644
--- a/static/index.html
+++ b/static/index.html
@@ -10,7 +10,7 @@
   <meta name="format-detection" content="telephone=no">
   <meta name="color-scheme" content="light dark">
   <meta name="theme-color" content="#2563EB">
-  <meta name="app-version" content="1.24.74">
+  <meta name="app-version" content="1.24.75">
   <link rel="manifest" href="/manifest.webmanifest">
   <link rel="icon" href="/static/icon.svg" type="image/svg+xml">
   <link rel="apple-touch-icon" href="/static/icon.svg">
@@ -27,12 +27,12 @@
 
   <!-- ── Core styles (local — no CDN dependency for first paint) ────────── -->
   <link rel="stylesheet" href="/static/vendor/mdi/materialdesignicons.min.css">
-  <link rel="stylesheet" href="/static/style.css?v=1.24.74">
-  <link rel="stylesheet" href="/static/css/resource-diagnostics.css?v=1.24.74">
-  <link rel="stylesheet" href="/static/css/background-jobs.css?v=1.24.74">
-  <link rel="stylesheet" href="/static/css/voice-design.css?v=1.24.74">
-  <link rel="stylesheet" href="/static/css/rehearser.css?v=1.24.74">
-  <link rel="stylesheet" href="/static/css/audiobook.css?v=1.24.74">
+  <link rel="stylesheet" href="/static/style.css?v=1.24.75">
+  <link rel="stylesheet" href="/static/css/resource-diagnostics.css?v=1.24.75">
+  <link rel="stylesheet" href="/static/css/background-jobs.css?v=1.24.75">
+  <link rel="stylesheet" href="/static/css/voice-design.css?v=1.24.75">
+  <link rel="stylesheet" href="/static/css/rehearser.css?v=1.24.75">
+  <link rel="stylesheet" href="/static/css/audiobook.css?v=1.24.75">
 
 
   <!-- ── Flag icons — non-blocking (loaded async, icons appear after JS) ── -->
@@ -397,7 +397,7 @@ window.toggleNavTree = function(treeId, chevronId) {
 </script>
 
 <!-- loader.js: fetches sections → loads JS modules → removes skeleton -->
-<script src="/static/loader.js?v=1.24.74"></script>
+<script src="/static/loader.js?v=1.24.75"></script>
 
 </body>
 </html>
diff --git a/static/js/tts-preview.js b/static/js/tts-preview.js
index 4f270cf..ca679a4 100644
--- a/static/js/tts-preview.js
+++ b/static/js/tts-preview.js
@@ -1,5 +1,7 @@
 // ── TTS preview ───────────────────────────────────────────────────────────
 
+(function (root) {
+
 function backendVoiceId(value) {
   return typeof value === 'string' ? value : (value?.id || value?.voice || value?.name || JSON.stringify(value));
 }
@@ -292,6 +294,7 @@ function _fishTagsSync() {
     if (ta) { ta.value = FISH_TAG_SAMPLE_TEXT; ta.focus(); }
   });
 })();
+
 function _ttsApplyEmotionTag(text, emotionValue) {
   const backend = $('tts-backend-select')?.value || '';
   if (!_ttsIsFishBackend(backend) || !emotionValue) return text;
@@ -973,3 +976,26 @@ function renderPerfHistory() {
   renderPerfHistory();
 })();
 
+Object.assign(root, {
+  backendVoiceId, shouldFilterBackendVoices, shouldReplaceWithLibraryVoices,
+  activeLibraryVoiceIds, cleanReferenceText, selectedPreviewLibraryVoice,
+  previewVoiceWarnings, updatePreviewVoiceMatchPanel, synthesizeSelectedReferenceText,
+  _ttsIsFishBackend, FISH_EMOTION_TAGS, FISH_TAG_SAMPLE_TEXT, _fishInsertTag,
+  _fishTagsRender, _fishTagsSync, _ttsApplyEmotionTag, _ttsStreamHealth,
+  effectiveTtsPlaybackMode, isTtsStreamAvailable, createTtsStreamUrl,
+  _ttsPreviewFetchWithRetry, _ttsBackendForVoice, fetchTtsPreviewBlob,
+  _textWords, _textSimilarity, _voiceRoundtripCheck, createTtsAudioSource,
+  previewBlob, PREVIEW_SAMPLE_TEXT, _onPreviewGenerated, _TRYOUT_SPEED_KEY,
+  PERF_HISTORY_KEY, PERF_HISTORY_MAX, PERF_HISTORY_SORT, perfHistoryLoad,
+  perfHistorySave, perfHistoryAdd, perfSparklineSvg, perfHistoryVoiceLookup,
+  perfHistoryVoiceMeta, perfHistoryExtraFields, perfHistoryGenderLabel,
+  perfHistoryDeviceLabel, perfHistoryDeviceHtml, perfHistoryAvatarHtml,
+  perfHistorySortValue, perfHistoryCompare, perfHistoryHeadButton, renderPerfHistory,
+});
+root.TTVC = root.TTVC || {};
+root.TTVC.tts = root.TTVC.tts || {};
+Object.assign(root.TTVC.tts, {
+  preview: { synthesize: synthesizeSelectedReferenceText, createAudio: createTtsAudioSource },
+  history: { load: perfHistoryLoad, save: perfHistorySave, render: renderPerfHistory },
+});
+})(window);