diff --git a/backend/open_webui/utils/middleware.py b/backend/open_webui/utils/middleware.py
index e11830d4f9..6c18eb26ba 100644
--- a/backend/open_webui/utils/middleware.py
+++ b/backend/open_webui/utils/middleware.py
@@ -5223,7 +5223,12 @@ async def streaming_chat_response_handler(response, ctx):
                                                 reasoning_detail_items,
                                             )
                                             await save_current_response_stream()
-                                            data = None
+                                            # Providers such as OpenRouter send reasoning_details
+                                            # alongside the reasoning text: only drop the event when
+                                            # the details were all there was to report, otherwise the
+                                            # reasoning delta never reaches the client.
+                                            if not reasoning_content:
+                                                data = None
 
                                     if value:
                                         if (
diff --git a/src/lib/components/chat/Messages/structuredOutput.ts b/src/lib/components/chat/Messages/structuredOutput.ts
index 96d5bd869f..d4ebe0493e 100644
--- a/src/lib/components/chat/Messages/structuredOutput.ts
+++ b/src/lib/components/chat/Messages/structuredOutput.ts
@@ -462,9 +462,12 @@ function ensureOutputItem(
 	fallback?: OutputItem
 ): OutputItem {
 	while (output.length <= outputIndex) {
-		output.push(
-			fallback ?? { type: 'message', status: 'in_progress', role: 'assistant', content: [] }
-		);
+		// Only the addressed slot gets the event's item; filler slots must not reuse its id.
+		const item =
+			output.length === outputIndex && fallback
+				? { ...fallback }
+				: { type: 'message', status: 'in_progress', role: 'assistant', content: [] };
+		output.push(item);
 	}
 	output[outputIndex] = { ...output[outputIndex] };
 	return output[outputIndex];