Guard reasoning deltas after visible output

frontend/app/app/api/chat/route.ts

@@ -484,20 +484,28 @@ function writeRuntimeEvent(
 	if (event.type === "run_queued") {
 		if (streamState) streamState.phase = "queued";
 		if (streamState && event.run_id) streamState.runId = event.run_id;
-		writer.write({
-			type: "reasoning-delta",
-			id: "reasoning-1",
-			delta: "\n当前会话已有任务在执行，本轮正在排队。",
-		});
+		writeReasoningDelta(
+			writer,
+			{
+				type: "reasoning-delta",
+				id: "reasoning-1",
+				delta: "\n当前会话已有任务在执行，本轮正在排队。",
+			},
+			streamState,
+		);
 	}
 	if (event.type === "run_started") {
 		if (streamState) streamState.phase = "running";
 		if (streamState && event.run_id) streamState.runId = event.run_id;
-		writer.write({
-			type: "reasoning-delta",
-			id: "reasoning-1",
-			delta: "\n后端已开始执行本轮任务。",
-		});
+		writeReasoningDelta(
+			writer,
+			{
+				type: "reasoning-delta",
+				id: "reasoning-1",
+				delta: "\n后端已开始执行本轮任务。",
+			},
+			streamState,
+		);
 	}
 	if (event.type === "server_heartbeat") {
 		const elapsed =
@@ -505,11 +513,15 @@ function writeRuntimeEvent(
 				? `，已等待 ${formatDuration(event.elapsed_ms)}`
 				: "";
 		const phase = streamState?.phase === "queued" ? "仍在排队" : "后端仍在处理";
-		writer.write({
-			type: "reasoning-delta",
-			id: "reasoning-1",
-			delta: `\n${phase}${elapsed}。`,
-		});
+		writeReasoningDelta(
+			writer,
+			{
+				type: "reasoning-delta",
+				id: "reasoning-1",
+				delta: `\n${phase}${elapsed}。`,
+			},
+			streamState,
+		);
 	}
 	if (event.type === "content_delta" && event.delta) {
 		if (!streamState?.textStarted) {
@@ -531,11 +543,15 @@ function writeRuntimeEvent(
 				: `index:${event.tool_call_index}`);
 		if (key && !streamState?.announcedToolCallKeys.has(key)) {
 			streamState?.announcedToolCallKeys.add(key);
-			writer.write({
-				type: "reasoning-delta",
-				id: "reasoning-1",
-				delta: `\n准备调用 ${event.tool_name ?? "工具"}。`,
-			});
+			writeReasoningDelta(
+				writer,
+				{
+					type: "reasoning-delta",
+					id: "reasoning-1",
+					delta: `\n准备调用 ${event.tool_name ?? "工具"}。`,
+				},
+				streamState,
+			);
 		}
 	}
 	if (event.type === "final_text_start") {
@@ -576,11 +592,15 @@ function writeRuntimeEvent(
 		});
 	}
 	if (event.type === "tool_delta" && event.tool_call_id && event.delta) {
-		writer.write({
-			type: "reasoning-delta",
-			id: "reasoning-1",
-			delta: `\n${event.tool_name ?? "tool"} 输出中...`,
-		});
+		writeReasoningDelta(
+			writer,
+			{
+				type: "reasoning-delta",
+				id: "reasoning-1",
+				delta: `\n${event.tool_name ?? "tool"} 输出中...`,
+			},
+			streamState,
+		);
 	}
 	if (event.type === "tool_result" && event.tool_call_id) {
 		const preview = event.metadata?.output_preview;
@@ -597,6 +617,15 @@ function writeRuntimeEvent(
 	}
 }
 
+function writeReasoningDelta(
+	writer: UIMessageStreamWriter<UIMessage>,
+	part: Parameters<UIMessageStreamWriter<UIMessage>["write"]>[0],
+	streamState?: StreamState,
+) {
+	if (streamState?.reasoningEnded) return;
+	writer.write(part);
+}
+
 function formatClawResponse(payload: ClawChatResponse) {
 	if (payload.error) return payload.error;
 	return payload.final_output ?? "";