fix(web): prevent speech result duplication on mobile browsers (#187)

web/src/components/live-demo.tsx

@@ -126,8 +126,6 @@ export function LiveDemo() {
     const [detectedLanguage, setDetectedLanguage] = useState<string>("en-US");
     const recognitionRef = useRef<SpeechRecognition | null>(null);
     const isListeningRef = useRef(false);
-    // Track the index up to which results have been processed to prevent duplicates on mobile
-    const processedResultIndexRef = useRef(0);
 
     // Keep ref in sync with state for use in event handlers
     useEffect(() => {
@@ -165,33 +163,19 @@ export function LiveDemo() {
         };
 
         recognition.onresult = (event: SpeechRecognitionEvent) => {
-            // Get the base index - on some browsers (especially mobile), resultIndex
-            // may be 0 but the array contains all previous results. We need to
-            // track which results we've already processed to avoid duplicates.
-            const startIndex = Math.max(event.resultIndex, processedResultIndexRef.current);
+            // On mobile browsers, the Web Speech API returns all previous results in the array
+            // with resultIndex staying at 0. Only process the LAST result which is the new one.
+            // This prevents the exponential duplication bug where text repeats like:
+            // "Hey Hey how Hey how are Hey how are you..."
+            const lastResultIndex = event.results.length - 1;
+            const result = event.results[lastResultIndex];
+            const transcript = result[0].transcript;
 
-            let interim = "";
-            let final = "";
-
-            // Only process new results (from startIndex to end)
-            for (let i = startIndex; i < event.results.length; i++) {
-                const transcript = event.results[i][0].transcript;
-                if (event.results[i].isFinal) {
-                    final += transcript + " ";
-                } else {
-                    interim += transcript;
-                }
-            }
-
-            // Update processed index to the end of current results
-            // Any results before this have been handled
-            processedResultIndexRef.current = event.results.length;
-
-            if (final) {
-                setTranscript((prev) => prev + final);
+            if (result.isFinal) {
+                setTranscript((prev) => prev + transcript + " ");
                 setInterimTranscript("");
             } else {
-                setInterimTranscript(interim);
+                setInterimTranscript(transcript);
             }
         };
 
@@ -218,7 +202,6 @@ export function LiveDemo() {
         if (recognitionRef.current) {
             setTranscript("");
             setInterimTranscript("");
-            processedResultIndexRef.current = 0; // Reset processed result index
             try {
                 recognitionRef.current.start();
             } catch (e) {