diff --git a/src/lib/components/chat/Chat.svelte b/src/lib/components/chat/Chat.svelte
index dee368c489..4b3b83f146 100644
--- a/src/lib/components/chat/Chat.svelte
+++ b/src/lib/components/chat/Chat.svelte
@@ -2744,23 +2744,23 @@
 	};
 
 	const responseCompletionEventHandler = (data, message) => {
-		message.output = applyResponseStreamEvent(message.output ?? [], data);
+		const output = Array.isArray(data?.output)
+			? data.output
+			: applyResponseStreamEvent(message.output ?? [], data);
+
+		const updatedMessage = {
+			...message,
+			output
+		};
 
 		if (data?.type === 'response.output_text.delta') {
-			const value = data.delta ?? '';
-			if (!(message.content == '' && value == '\n')) {
-				message.content += value;
-
-				if (navigator.vibrate && ($settings?.hapticFeedback ?? false)) {
-					navigator.vibrate(5);
-				}
-				dispatchCallOverlayAudio(message);
+			if (navigator.vibrate && ($settings?.hapticFeedback ?? false)) {
+				navigator.vibrate(5);
 			}
-		} else if (data?.type === 'response.completed' || data?.type?.endsWith('.done')) {
-			message.content = getOutputText(message.output) || message.content;
+			dispatchCallOverlayAudio(updatedMessage);
 		}
 
-		history.messages[message.id] = message;
+		history.messages[message.id] = updatedMessage;
 		history = history;
 	};
 
diff --git a/src/lib/components/chat/Messages/ResponseMessage.svelte b/src/lib/components/chat/Messages/ResponseMessage.svelte
index a493a42a5b..2e9488ae6c 100644
--- a/src/lib/components/chat/Messages/ResponseMessage.svelte
+++ b/src/lib/components/chat/Messages/ResponseMessage.svelte
@@ -121,13 +121,17 @@
 	export let messageId;
 	export let selectedModels = [];
 
-	let message: MessageType = structuredClone(history.messages[messageId]);
+	let messageSource = history.messages[messageId];
+	let message: MessageType = structuredClone(messageSource);
 	$: if (history.messages) {
 		const source = history.messages[messageId];
 		if (source) {
-			// Fast path: O(1) check on the fields that change most often (content during streaming, done at end)
-			// Avoids 2x O(n) JSON.stringify calls that are always true during streaming anyway
-			if (
+			// Fast path for the fields that change most often while streaming.
+			// Responses streams update output even when legacy content is unchanged.
+			if (source !== messageSource) {
+				messageSource = source;
+				message = structuredClone(source);
+			} else if (
 				message.content !== source.content ||
 				message.done !== source.done ||
 				message.output?.length !== source.output?.length