fix(chat): group run output and hide empty messages

docs/chat-chain-changes/2026-11-05-empty-assistant-bubbles.md

@@ -0,0 +1,12 @@
+---
+date: 2026-11-05
+pr: pending
+feature: Empty assistant bubbles during tool activity
+impact: Whitespace-only assistant messages are hidden, and assistant text within a turn is displayed together with a completion marker. Stream data and tool activity are unchanged.
+---
+
+Tool cycles can leave assistant messages containing only whitespace. The chat
+list excludes these empty bubbles while retaining the underlying streamed data,
+so later text can still be appended to the same message.
+Assistant messages within a turn are combined for display; tool rows remain
+available below the combined text, and a separator marks the end of the turn.

packages/client/src/components/hermes/chat/MessageList.vue

@@ -19,6 +19,7 @@ import { ref, computed, nextTick, onBeforeUnmount, onMounted, watch } from "vue"
 import { useI18n } from "vue-i18n";
 import VirtualMessageList from "./VirtualMessageList.vue";
 import MessageItem from "./MessageItem.vue";
+import { groupRunMessages } from "./groupRunMessages";
 import { LIVE_CHAT_MAX_LOADED_MESSAGES, useChatStore, type Message } from "@/stores/hermes/chat";
 import thinkingImage from "@/assets/thinking.gif";
 import { useToolTraceVisibility } from "@/composables/useToolTraceVisibility";
@@ -100,10 +101,15 @@ const emptyState = computed(() => ({
 
 const displayMessages = computed(() => {
   const currentToolIds = new Set(currentToolCalls.value.map((tool) => tool.id));
-  return chatStore.messages.filter((m) => {
+  const messages = chatStore.messages.filter((m) => {
     if (m.role === "tool") {
       return toolTraceVisible.value && !!m.toolName && !(chatStore.isRunActive && currentToolIds.has(m.id));
     }
+    // Tool cycles can produce whitespace-only assistant deltas. Keep them in
+    // the store for subsequent deltas, but don't render an empty bubble.
+    if (m.role === "assistant" && !m.content?.trim() && !m.reasoning?.trim() && !m.attachments?.length) {
+      return false;
+    }
     if (
       m.role === "assistant" &&
       m.isStreaming &&
@@ -115,6 +121,7 @@ const displayMessages = computed(() => {
     }
     return true;
   });
+  return groupRunMessages(messages, chatStore.isRunActive || !!chatStore.abortState);
 });
 
 function forkDividerId(sessionId: string): string {
@@ -484,7 +491,8 @@ defineExpose({
         </div>
       </template>
       <template #item="{ message: msg }">
-        <div v-if="msg.systemType === 'fork-divider' && forkLineage" class="fork-divider" role="separator">
+        <div v-if="msg.systemType === 'run-end'" class="run-end" role="separator">{{ t('chat.runOutputEnded') }}</div>
+        <div v-else-if="msg.systemType === 'fork-divider' && forkLineage" class="fork-divider" role="separator">
           <div class="fork-divider-line" aria-hidden="true"></div>
           <div class="fork-divider-pill">
             <span class="fork-divider-icon" aria-hidden="true">
@@ -867,6 +875,13 @@ defineExpose({
 <style scoped lang="scss">
 @use "@/styles/variables" as *;
 
+.run-end {
+  margin: 20px auto;
+  text-align: center;
+  color: var(--color-text-3);
+  font-size: 12px;
+}
+
 .message-list-shell {
   flex: 1;
   min-height: 0;

packages/client/src/components/hermes/chat/groupRunMessages.ts

@@ -0,0 +1,45 @@
+import type { Message } from '@/stores/hermes/chat'
+
+// Group only within an uninterrupted turn. Tool rows remain available after
+// the combined answer; user, command and system messages are hard boundaries.
+export function groupRunMessages(messages: Message[], runActive: boolean): Message[] {
+  const result: Message[] = []
+  let assistants: Message[] = []
+  let tools: Message[] = []
+  let marker: string | null = null
+
+  function flush(completed: boolean) {
+    if (assistants.length) {
+      const first = assistants[0]
+      result.push({
+        ...first,
+        id: assistants[assistants.length - 1].id,
+        content: assistants.map(m => m.content).filter(text => text.trim()).join('\n\n'),
+        reasoning: assistants.map(m => m.reasoning).filter(Boolean).join('\n\n') || undefined,
+        attachments: assistants.flatMap(m => m.attachments || []),
+        isStreaming: assistants.some(m => m.isStreaming),
+      })
+    }
+    result.push(...tools)
+    if (completed && assistants.length) {
+      result.push({ id: `run-end-${assistants[0].id}`, role: 'system', content: '', timestamp: assistants[assistants.length - 1].timestamp, systemType: 'run-end' })
+    }
+    assistants = []
+    tools = []
+    marker = null
+  }
+
+  for (const message of messages) {
+    if (message.role !== 'assistant' && message.role !== 'tool') {
+      flush(true)
+      result.push(message)
+      continue
+    }
+    if (marker && message.runMarker && marker !== message.runMarker) flush(true)
+    marker ||= message.runMarker || null
+    if (message.role === 'assistant') assistants.push(message)
+    else tools.push(message)
+  }
+  flush(!runActive)
+  return result
+}

packages/client/src/i18n/locales/en.ts

@@ -459,6 +459,7 @@ export default {
 
   // Chat
   chat: {
+    runOutputEnded: 'Run output ended',
     messageLoadFailed: 'Could not load this conversation. Please retry.',
     contextRemaining: 'remaining',
     contextClickToEdit: 'Click to edit context length',

packages/client/src/i18n/locales/zh.ts

@@ -459,6 +459,7 @@ export default {
 
   // 对话
   chat: {
+    runOutputEnded: '本轮输出结束',
     messageLoadFailed: '会话加载失败，请重试。',
     contextRemaining: '剩余',
     contextClickToEdit: '点击编辑上下文长度',

packages/client/src/stores/hermes/chat.ts

@@ -63,7 +63,7 @@ export interface Message {
   // 不含 <think> 包裹标签；内容自身可以为多段纯文本。
   reasoning?: string
   queued?: boolean
-  systemType?: 'command' | 'error' | 'fork-divider'
+  systemType?: 'command' | 'error' | 'fork-divider' | 'run-end'
   commandAction?: string
   commandData?: Record<string, unknown>
   finishReason?: string | null

tests/client/chat-group-run-messages.test.ts

@@ -0,0 +1,22 @@
+import { describe, expect, it } from 'vitest'
+import { groupRunMessages } from '../../packages/client/src/components/hermes/chat/groupRunMessages'
+import type { Message } from '../../packages/client/src/stores/hermes/chat'
+
+const message = (id: string, role: Message['role'], content = ''): Message => ({ id, role, content, timestamp: 1 })
+
+describe('groupRunMessages', () => {
+  it('groups text across tool calls and marks completion only when the run ends', () => {
+    const input = [message('u', 'user', 'question'), message('a', 'assistant', 'first'), message('t', 'tool'), message('b', 'assistant', 'second')]
+    const active = groupRunMessages(input, true)
+    expect(active.map(m => m.role)).toEqual(['user', 'assistant', 'tool'])
+    expect(active[1]).toMatchObject({ id: 'b', content: 'first\n\nsecond' })
+    const finished = groupRunMessages(input, false)
+    expect(finished.at(-1)?.systemType).toBe('run-end')
+  })
+
+  it('keeps separate user turns and explicit run markers separate', () => {
+    const input = [message('u', 'user'), { ...message('a', 'assistant', 'one'), runMarker: '1' }, { ...message('b', 'assistant', 'two'), runMarker: '2' }, message('u2', 'user'), message('c', 'assistant', 'three')]
+    expect(groupRunMessages(input, false).filter(m => m.role === 'assistant').map(m => m.content)).toEqual(['one', 'two', 'three'])
+    expect(groupRunMessages(input, false).filter(m => m.systemType === 'run-end')).toHaveLength(3)
+  })
+})

tests/e2e/chat-rendering-smoke.spec.ts

@@ -82,6 +82,62 @@ test('streams a run and renders markdown, code, math and mermaid without leaking
   expect(api.unexpectedRequests).toEqual([])
 })
 
+test('does not render empty assistant bubbles between tool calls', async ({ page }) => {
+  await authenticate(page, TEST_ACCESS_KEY, 'research')
+  await mockHermesApi(page)
+  await mockChatSocket(page)
+  await page.goto('/#/hermes/chat')
+  await sendChatMessage(page, 'run tools')
+  const { sessionId } = await waitForRunSessionId(page)
+
+  await page.evaluate((sid) => {
+    const socket = (window as any).__PW_CHAT_SOCKET__.latest
+    const common = { session_id: sid, run_id: 'blank-bubbles' }
+    socket.__trigger('run.started', { ...common, event: 'run.started' })
+    for (let i = 0; i < 3; i++) {
+      socket.__trigger('message.delta', { ...common, event: 'message.delta', delta: '\n  ' })
+      socket.__trigger('tool.started', { ...common, event: 'tool.started', tool_call_id: `tool-${i}`, tool: 'terminal' })
+      socket.__trigger('tool.completed', { ...common, event: 'tool.completed', tool_call_id: `tool-${i}`, output: 'done' })
+    }
+  }, sessionId)
+  await expect(page.locator('.message.assistant')).toHaveCount(0)
+
+  await page.evaluate((sid) => {
+    const socket = (window as any).__PW_CHAT_SOCKET__.latest
+    socket.__trigger('message.delta', { event: 'message.delta', session_id: sid, run_id: 'blank-bubbles', delta: '\n' })
+    socket.__trigger('message.delta', { event: 'message.delta', session_id: sid, run_id: 'blank-bubbles', delta: 'Visible answer' })
+  }, sessionId)
+  await expect(page.locator('.message.assistant')).toHaveCount(1)
+  await expect(page.locator('.message.assistant')).toContainText('Visible answer')
+})
+
+test('groups assistant output across tool calls until the run ends', async ({ page }) => {
+  await authenticate(page, TEST_ACCESS_KEY, 'research')
+  await mockHermesApi(page)
+  await mockChatSocket(page)
+  await page.goto('/#/hermes/chat')
+  await sendChatMessage(page, 'inspect')
+  const { sessionId } = await waitForRunSessionId(page)
+  await page.evaluate((sid) => {
+    const socket = (window as any).__PW_CHAT_SOCKET__.latest
+    const common = { session_id: sid, run_id: 'grouped-run' }
+    socket.__trigger('run.started', { ...common, event: 'run.started' })
+    socket.__trigger('message.delta', { ...common, event: 'message.delta', delta: 'First update' })
+    socket.__trigger('tool.started', { ...common, event: 'tool.started', tool_call_id: 't1', tool: 'terminal' })
+    socket.__trigger('tool.completed', { ...common, event: 'tool.completed', tool_call_id: 't1', output: 'done' })
+    socket.__trigger('message.delta', { ...common, event: 'message.delta', delta: 'Second update' })
+  }, sessionId)
+  const assistant = page.locator('.message.assistant')
+  await expect(assistant).toHaveCount(1)
+  await expect(assistant).toContainText('First update')
+  await expect(assistant).toContainText('Second update')
+  await expect(page.locator('.run-end')).toHaveCount(0)
+  await page.evaluate((sid) => {
+    (window as any).__PW_CHAT_SOCKET__.latest.__trigger('run.completed', { event: 'run.completed', session_id: sid, run_id: 'grouped-run' })
+  }, sessionId)
+  await expect(page.locator('.run-end')).toHaveText('Run output ended')
+})
+
 test('opens the session model dialog and the session search from the chat header', async ({ page }) => {
   await authenticate(page, TEST_ACCESS_KEY, 'research')
   await mockHermesApi(page, { sessions: [sampleSession] })