--- a/src/diff-renderer.ts
+++ b/src/diff-renderer.ts
@@ -1217,6 +1217,18 @@
 	return output;
 }
 
+function graphemeSafeSpan(text: string, span: DiffSpan): DiffSpan {
+	let start = span.start;
+	let end = span.end;
+	for (const part of new Intl.Segmenter(undefined, { granularity: "grapheme" }).segment(text)) {
+		const next = part.index + part.segment.length;
+		if (start > part.index && start < next) start = part.index;
+		if (end > part.index && end < next) end = next;
+		if (part.index >= end) break;
+	}
+	return { start, end };
+}
+
 function applyInlineSpanHighlight(
 	plainText: string,
 	renderedText: string,
@@ -1235,6 +1247,7 @@
 				start: Math.max(0, Math.min(plainText.length, span.start)),
 				end: Math.max(0, Math.min(plainText.length, span.end)),
 			}))
+			.map((span) => graphemeSafeSpan(plainText, span))
 			.filter((span) => span.end > span.start),
 	);
 	if (sorted.length === 0) {