diff --git a/desktop/src/components/chat/AskUserQuestion.tsx b/desktop/src/components/chat/AskUserQuestion.tsx
index 67006926..93694544 100644
--- a/desktop/src/components/chat/AskUserQuestion.tsx
+++ b/desktop/src/components/chat/AskUserQuestion.tsx
@@ -135,7 +135,7 @@ export function AskUserQuestion({ toolUseId, input, result }: Props) {
   if (!activeQuestion) return null
 
   return (
-    <div className={`mb-4 ml-10 rounded-[var(--radius-lg)] border overflow-hidden ${
+    <div className={`mb-4 rounded-[var(--radius-lg)] border overflow-hidden ${
       submitted
         ? 'border-[var(--color-outline-variant)]/40 bg-[var(--color-surface-container-low)] opacity-70'
         : 'border-[var(--color-secondary)] bg-[var(--color-surface-container-lowest)]'
diff --git a/desktop/src/components/chat/AssistantMessage.tsx b/desktop/src/components/chat/AssistantMessage.tsx
index 65ac2a74..0ed75e69 100644
--- a/desktop/src/components/chat/AssistantMessage.tsx
+++ b/desktop/src/components/chat/AssistantMessage.tsx
@@ -8,14 +8,23 @@ type Props = {
 }
 
 export function AssistantMessage({ content, isStreaming }: Props) {
+  const documentLayout = shouldUseDocumentLayout(content)
+
   return (
     <div className="group mb-5 flex justify-start">
       <div
         data-message-shell="assistant"
-        className="flex min-w-0 w-full max-w-[84%] flex-col items-start gap-2 sm:max-w-[80%] lg:max-w-[74%]"
+        data-layout={documentLayout ? 'document' : 'bubble'}
+        className={`flex min-w-0 flex-col items-start gap-2 ${
+          documentLayout
+            ? 'w-full max-w-full'
+            : 'w-full max-w-[88%] sm:max-w-[80%] lg:max-w-[72%]'
+        }`}
       >
-        <div className="rounded-[20px] rounded-tl-[8px] border border-[var(--color-border)]/60 bg-[var(--color-surface)] px-4 py-3 text-sm text-[var(--color-text-primary)] shadow-sm">
-          <MarkdownRenderer content={content} />
+        <div className={`rounded-[20px] rounded-tl-[8px] border border-[var(--color-border)]/60 bg-[var(--color-surface)] px-4 py-3 text-sm text-[var(--color-text-primary)] shadow-sm ${
+          documentLayout ? 'w-full' : 'max-w-full'
+        }`}>
+          <MarkdownRenderer content={content} variant={documentLayout ? 'document' : 'default'} />
           {!isStreaming && <InlineImageGallery text={content} />}
           {isStreaming && (
             <span className="ml-0.5 inline-block h-4 w-0.5 animate-shimmer bg-[var(--color-brand)] align-text-bottom" />
@@ -31,3 +40,18 @@ export function AssistantMessage({ content, isStreaming }: Props) {
     </div>
   )
 }
+
+function shouldUseDocumentLayout(content: string) {
+  const normalized = content.trim()
+  if (!normalized) return false
+
+  if (/```/.test(normalized)) return true
+  if (/^\s{0,3}(#{1,6}\s|[-*+]\s|\d+\.\s|>\s|\|.+\|)/m.test(normalized)) return true
+
+  const paragraphs = normalized
+    .split(/\n\s*\n/)
+    .map((chunk) => chunk.trim())
+    .filter(Boolean)
+
+  return paragraphs.length >= 2 || normalized.split('\n').filter((line) => line.trim()).length >= 8
+}
diff --git a/desktop/src/components/chat/MessageList.test.tsx b/desktop/src/components/chat/MessageList.test.tsx
index 9e46d5c8..a0b77b1d 100644
--- a/desktop/src/components/chat/MessageList.test.tsx
+++ b/desktop/src/components/chat/MessageList.test.tsx
@@ -371,10 +371,46 @@ describe('MessageList nested tool calls', () => {
     expect(userShell?.className).toContain('items-end')
     expect(assistantShell).toBeTruthy()
     expect(assistantShell?.className).toContain('items-start')
+    expect(assistantShell?.className).not.toContain('ml-10')
     expect(userActions?.getAttribute('data-align')).toBe('end')
     expect(assistantActions?.getAttribute('data-align')).toBe('start')
   })
 
+  it('uses the document column for markdown-heavy assistant replies', () => {
+    useChatStore.setState({
+      sessions: {
+        [ACTIVE_TAB]: makeSessionState({
+          messages: [
+            {
+              id: 'assistant-doc',
+              type: 'assistant_text',
+              content: [
+                '## 交付结果',
+                '',
+                '已完成以下内容：',
+                '',
+                '- 添加任务',
+                '- 删除任务',
+                '',
+                '```bash',
+                'npm run build',
+                '```',
+              ].join('\n'),
+              timestamp: 1,
+            },
+          ],
+        }),
+      },
+    })
+
+    render(<MessageList />)
+
+    const assistantShell = screen.getByText('交付结果').closest('[data-message-shell="assistant"]')
+    expect(assistantShell?.getAttribute('data-layout')).toBe('document')
+    expect(assistantShell?.className).toContain('w-full')
+    expect(assistantShell?.className).not.toContain('ml-10')
+  })
+
   it('opens a rewind preview modal for user messages', async () => {
     vi.spyOn(sessionsApi, 'rewind').mockResolvedValue({
       target: {
diff --git a/desktop/src/components/chat/PermissionDialog.tsx b/desktop/src/components/chat/PermissionDialog.tsx
index e1de3566..8e12ac17 100644
--- a/desktop/src/components/chat/PermissionDialog.tsx
+++ b/desktop/src/components/chat/PermissionDialog.tsx
@@ -127,7 +127,7 @@ export function PermissionDialog({ requestId, toolName, input, description }: Pr
   const allowRawToggle = !preview
 
   return (
-    <div className={`mb-4 ml-10 overflow-hidden rounded-[var(--radius-lg)] border ${
+    <div className={`mb-4 overflow-hidden rounded-[var(--radius-lg)] border ${
       isPending
         ? 'border-[var(--color-warning)] bg-[var(--color-surface-container-lowest)]'
         : 'border-[var(--color-outline-variant)]/40 bg-[var(--color-surface-container-low)] opacity-70'
diff --git a/desktop/src/components/chat/StreamingIndicator.tsx b/desktop/src/components/chat/StreamingIndicator.tsx
index 1cb38f47..a6a405ab 100644
--- a/desktop/src/components/chat/StreamingIndicator.tsx
+++ b/desktop/src/components/chat/StreamingIndicator.tsx
@@ -23,7 +23,7 @@ export function StreamingIndicator() {
   }
 
   return (
-    <div className="mb-2 ml-10 flex w-fit items-center gap-2 rounded-full border border-[var(--color-border)]/40 bg-[var(--color-surface-container-low)] px-3 py-1">
+    <div className="mb-2 flex w-fit items-center gap-2 rounded-full border border-[var(--color-border)]/40 bg-[var(--color-surface-container-low)] px-3 py-1">
       <span className="text-[var(--color-brand)] animate-shimmer text-xs">✦</span>
       <span className="text-xs font-medium text-[var(--color-text-secondary)]">{verb}...</span>
       {elapsedSeconds > 0 && (
diff --git a/desktop/src/components/chat/ThinkingBlock.tsx b/desktop/src/components/chat/ThinkingBlock.tsx
index dc97706e..3975525d 100644
--- a/desktop/src/components/chat/ThinkingBlock.tsx
+++ b/desktop/src/components/chat/ThinkingBlock.tsx
@@ -18,7 +18,7 @@ export function ThinkingBlock({ content, isActive = false }: { content: string;
   const preview = firstLine.length > 80 ? firstLine.slice(0, 80) + '...' : firstLine
 
   return (
-    <div className="mb-1 ml-10">
+    <div className="mb-1">
       <style>{thinkingStyles}</style>
       <button
         onClick={() => setExpanded((v) => !v)}
diff --git a/desktop/src/components/chat/ToolCallBlock.tsx b/desktop/src/components/chat/ToolCallBlock.tsx
index d2e32be6..8c0b5201 100644
--- a/desktop/src/components/chat/ToolCallBlock.tsx
+++ b/desktop/src/components/chat/ToolCallBlock.tsx
@@ -51,7 +51,7 @@ export function ToolCallBlock({ toolName, input, result, compact = false }: Prop
 
   return (
     <div className={`overflow-hidden rounded-lg border border-[var(--color-border)]/50 bg-[var(--color-surface-container-lowest)] ${
-      compact ? 'mb-0' : 'mb-2 ml-10'
+      compact ? 'mb-0' : 'mb-2'
     }`}>
       <button
         type="button"
diff --git a/desktop/src/components/chat/ToolCallGroup.tsx b/desktop/src/components/chat/ToolCallGroup.tsx
index f63b82a2..4277d620 100644
--- a/desktop/src/components/chat/ToolCallGroup.tsx
+++ b/desktop/src/components/chat/ToolCallGroup.tsx
@@ -128,7 +128,7 @@ function AgentToolGroup({
   }, [isStreaming])
 
   return (
-    <div className="mb-2 ml-10">
+    <div className="mb-2">
       <button
         type="button"
         onClick={() => setExpanded((value) => !value)}
@@ -201,7 +201,7 @@ function ToolCallGroupMulti({ toolCalls, resultMap, childToolCallsByParent, isSt
   }, [hasNestedToolCalls, isStreaming])
 
   return (
-    <div className="mb-2 ml-10">
+    <div className="mb-2">
       <button
         type="button"
         onClick={() => setExpanded((v) => !v)}
diff --git a/desktop/src/components/chat/ToolResultBlock.tsx b/desktop/src/components/chat/ToolResultBlock.tsx
index 16ef5be6..791ae1b1 100644
--- a/desktop/src/components/chat/ToolResultBlock.tsx
+++ b/desktop/src/components/chat/ToolResultBlock.tsx
@@ -27,7 +27,7 @@ export function ToolResultBlock({ content, isError, toolName, standalone = true
   const hasMore = text.length > 200
 
   return (
-    <div className={`mb-2 ml-10 overflow-hidden rounded-xl border ${
+    <div className={`mb-2 overflow-hidden rounded-xl border ${
       isError
         ? 'border-[var(--color-error)]/20'
         : 'border-[var(--color-outline-variant)]/20'