fix(desktop): prevent empty blocks rendering in chat UI

- Guard empty thinking events from creating blank ThinkingBlock rows
- Skip empty assistant_text from history loading
- Hide ToolResultBlock when content is empty (non-error)
- Add component-level null returns as safety net

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cc-haha/desktop/src/components/chat/AssistantMessage.tsx

@@ -8,6 +8,8 @@ type Props = {
 }
 
 export function AssistantMessage({ content, isStreaming }: Props) {
+  if (!content.trim() && !isStreaming) return null
+
   const documentLayout = shouldUseDocumentLayout(content)
 
   return (

cc-haha/desktop/src/components/chat/ThinkingBlock.tsx

@@ -17,6 +17,8 @@ export function ThinkingBlock({ content, isActive = false }: { content: string;
   const firstLine = lines[0]?.replace(/\s+/g, ' ').trim() || ''
   const preview = firstLine.length > 80 ? firstLine.slice(0, 80) + '...' : firstLine
 
+  if (!content.trim() && !isActive) return null
+
   return (
     <div className="mb-1">
       <style>{thinkingStyles}</style>

cc-haha/desktop/src/components/chat/ToolResultBlock.tsx

@@ -23,6 +23,8 @@ export function ToolResultBlock({ content, isError, toolName, standalone = true
   if (!standalone) return null
 
   const text = extractText(content)
+  if (!text.trim() && !isError) return null
+
   const preview = text.slice(0, 200)
   const hasMore = text.length > 200
 

cc-haha/desktop/src/stores/chatStore.ts

@@ -634,6 +634,9 @@ export const useChatStore = create<ChatStore>((set, get) => ({
             updated[updated.length - 1] = { ...last, content: last.content + msg.text }
             return { messages: updated, chatState: 'thinking', activeThinkingId: last.id, streamingText: '' }
           }
+          if (!msg.text) {
+            return { chatState: 'thinking', streamingText: '' }
+          }
           const id = nextId()
           return {
             messages: [...base, { id, type: 'thinking', content: msg.text, timestamp: Date.now() }],
@@ -1037,7 +1040,9 @@ export function mapHistoryMessagesToUiMessages(
       continue
     }
     if (msg.type === 'assistant' && typeof msg.content === 'string') {
-      uiMessages.push({ id: msg.id || nextId(), type: 'assistant_text', content: msg.content, timestamp, model: msg.model })
+      if (msg.content.trim()) {
+        uiMessages.push({ id: msg.id || nextId(), type: 'assistant_text', content: msg.content, timestamp, model: msg.model })
+      }
       continue
     }
     if ((msg.type === 'assistant' || msg.type === 'tool_use') && Array.isArray(msg.content)) {