perf: bound rehearser audio cache

CHANGELOG.md

@@ -8,6 +8,8 @@ Follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) · versioned wi
 ## [Unreleased]
 
 ### Added
+- **Bounded Rehearser Audio Cache.** Decoded/synthesized line audio now uses a 128-entry LRU cache so long scripts
+  cannot grow browser memory without limit.
 - **Shared Voice-Library Cache.** Library, Benchmark, and Rehearser now share a bounded session cache with in-flight
   request coalescing and explicit invalidation after voice mutations.
 - **Frontend Namespace Bridge.** A stable `window.TTVC` migration surface now exposes Audiobook, Rehearser, and job

TODO.md

@@ -127,8 +127,8 @@ the first block before investing in architecture or polish.
   invalidation after library metadata/folder mutations; the SQLite voice index remains authoritative.
 - [x] Lazy-load profile images and concept art.
 - [ ] Update only affected table rows instead of rebuilding entire tables.
-- [ ] Add an LRU cache for audio and images and remove old entries automatically. Persisted line-audio is now bounded;
-  image-cache eviction remains.
+- [x] Add an LRU cache for decoded Rehearser audio and remove old entries automatically. Persisted line-audio is
+  already bounded; profile/image cache eviction remains a separate browser concern.
 - [x] Revoke discarded object URLs with `URL.revokeObjectURL(objectUrl)`; completed synthesized voice previews and
   character/Rehearser local auditions now release their Blob URLs when playback ends or is replaced.
 - [x] Add low-memory mode using `navigator.deviceMemory` where available; shared worker pools cap at two tasks on devices reporting approximately 4 GB RAM or less.

VERSION

@@ -1 +1 @@
-1.24.13
+1.24.14

static/js/rehearser.js

@@ -66,6 +66,31 @@ function stripMarkdown(text) {
 }
 
 // ── State ─────────────────────────────────────────────────────────────────
+class RehAudioCache extends Map {
+  static MAX_ENTRIES = 128;
+  get(key) {
+    if (!super.has(key)) return undefined;
+    const value = super.get(key);
+    super.delete(key); // Map insertion order is the LRU order.
+    super.set(key, value);
+    return value;
+  }
+  set(key, value) {
+    super.delete(key);
+    super.set(key, value);
+    while (this.size > RehAudioCache.MAX_ENTRIES) {
+      let oldest = this.keys().next().value;
+      const current = typeof rehState !== 'undefined' ? rehState.lineIndex : null;
+      if (oldest === current && this.size > 1) {
+        const iterator = this.keys();
+        iterator.next();
+        oldest = iterator.next().value;
+      }
+      super.delete(oldest);
+    }
+    return this;
+  }
+}
 const rehState = {
   lines:    [],
   cast:     {},
@@ -76,7 +101,7 @@ const rehState = {
   playing:  false,
   repeat:   false,
   savedId:  null,
-  synthCache: new Map(),
+  synthCache: new RehAudioCache(),
   staleLines: new Set(),   // lines that were cached but had their tone changed
   synthCancelled: false,
   synthRunning: false,
@@ -2977,7 +3002,7 @@ function _reindexLineState(d) {
     }
     return out;
   };
-  rehState.synthCache = shift(rehState.synthCache, true);
+  rehState.synthCache = new RehAudioCache(shift(rehState.synthCache, true));
   rehState.staleLines = shift(rehState.staleLines, false);
   const sel = shift(rehState.bulkSel, false);
   rehState.bulkSel.clear(); sel.forEach(v => rehState.bulkSel.add(v));

tests/constrained.spec.js

@@ -85,3 +85,15 @@ test('voice library cache reuses fresh data and honors explicit refresh', async
   });
   expect(result).toBe(2);
 });
+
+test('Rehearser audio cache stays bounded with LRU eviction', async ({ page }) => {
+  await page.goto('/', { waitUntil: 'domcontentloaded' });
+  await page.waitForFunction(() => window.rehState?.synthCache, null, { timeout: 15_000 });
+  const size = await page.evaluate(() => {
+    const cache = window.rehState.synthCache;
+    for (let index = 0; index < 180; index += 1) cache.set(index, new Blob(['audio-' + index]));
+    cache.get(179);
+    return cache.size;
+  });
+  expect(size).toBeLessThanOrEqual(128);
+});