diff --git a/src/hooks/epub/useEPUBHighlighting.ts b/src/hooks/epub/useEPUBHighlighting.ts
index d186670..a9a7dc8 100644
--- a/src/hooks/epub/useEPUBHighlighting.ts
+++ b/src/hooks/epub/useEPUBHighlighting.ts
@@ -44,7 +44,9 @@ export function useEPUBHighlighting({
   renderedTextMapsRef,
 }: UseEpubHighlightingParams): UseEpubHighlightingResult {
   // Cache the per-segment word→region map so we don't re-align on every whisper
-  // tick. Keyed by the segment + resolved region + alignment.
+  // tick. Keyed by the segment + resolved region + the aligned word texts, so a
+  // corrected/rebuilt alignment (even with an identical word count) misses the
+  // cache instead of reusing stale spans.
   const wordRangeCacheRef = useRef<{ key: string; spans: Array<AlignmentCharSpan | null> } | null>(null);
 
   const clearWordHighlights = useCallback(() => {
@@ -122,6 +124,9 @@ export function useEPUBHighlighting({
       resolved.startOffset,
       resolved.endOffset,
       words.length,
+      // Word texts (not timings) drive the span mapping, so include them: a
+      // re-aligned segment with the same count still invalidates the cache.
+      words.map((word) => word.text).join('
'),
     ].join('::');
     if (wordRangeCacheRef.current?.key !== cacheKey) {
       wordRangeCacheRef.current = {
@@ -166,10 +171,14 @@ export function useEPUBHighlighting({
 
   const setRenderedTextMaps = useCallback((maps: EpubRenderedTextMap[]) => {
     renderedTextMapsRef.current = maps;
+    // Remapped content can change a region's text under an unchanged cache key,
+    // so drop the word-span cache whenever the text maps are replaced.
+    wordRangeCacheRef.current = null;
   }, [renderedTextMapsRef]);
 
   const resetHighlightState = useCallback(() => {
     renderedTextMapsRef.current = [];
+    wordRangeCacheRef.current = null;
     clearHighlights();
   }, [clearHighlights, renderedTextMapsRef]);
 
diff --git a/src/lib/client/html/highlight.ts b/src/lib/client/html/highlight.ts
index 23779df..668e4dc 100644
--- a/src/lib/client/html/highlight.ts
+++ b/src/lib/client/html/highlight.ts
@@ -66,6 +66,9 @@ interface SentenceState {
   // Normalized text of the wrap (chars joined), tokenized to align each spoken
   // word against the rendered words.
   text: string;
+  // Locale captured when the sentence was highlighted, reused for locale-aware
+  // word segmentation when mapping the alignment (matters for CJK/Thai, etc.).
+  language?: string;
   // For an alignment we've already seen: each word's [start, end) char span
   // within `text`/`chars` (null entries = words that aligned to no token).
   alignment: TTSSentenceAlignment | null;
@@ -318,6 +321,7 @@ export function highlightHtmlSentence(
     sentence,
     chars,
     text,
+    language,
     alignment: null,
     wordRanges: null,
   };
@@ -349,7 +353,7 @@ export function highlightHtmlWord(
   // rendered words and won't jump to a later/duplicate word.
   if (sentenceState.alignment !== alignment || !sentenceState.wordRanges) {
     sentenceState.alignment = alignment;
-    sentenceState.wordRanges = locateAlignmentWordSpans(words, sentenceState.text);
+    sentenceState.wordRanges = locateAlignmentWordSpans(words, sentenceState.text, sentenceState.language);
   }
 
   const range = sentenceState.wordRanges[wordIndex];