diff --git a/package.json b/package.json
index 264c03c89..fa9d30573 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "clawx",
-    "version": "0.3.10-beta.1",
+    "version": "0.3.10-beta.2",
     "pnpm": {
         "onlyBuiltDependencies": [
             "@discordjs/opus",
diff --git a/src/pages/Chat/ChatInput.tsx b/src/pages/Chat/ChatInput.tsx
index cd7437a31..dbe8307eb 100644
--- a/src/pages/Chat/ChatInput.tsx
+++ b/src/pages/Chat/ChatInput.tsx
@@ -491,6 +491,7 @@ export function ChatInput({ onSend, onStop, disabled = false, sending = false, i
                 onPaste={handlePaste}
                 placeholder={disabled ? t('composer.gatewayDisconnectedPlaceholder') : ''}
                 disabled={disabled}
+                data-testid="chat-composer-input"
                 className="min-h-[40px] max-h-[200px] resize-none border-0 focus-visible:ring-0 focus-visible:ring-offset-0 shadow-none bg-transparent py-2.5 px-2 text-[15px] placeholder:text-muted-foreground/60 leading-relaxed"
                 rows={1}
               />
@@ -501,6 +502,7 @@ export function ChatInput({ onSend, onStop, disabled = false, sending = false, i
               onClick={sending ? handleStop : handleSend}
               disabled={sending ? !canStop : !canSend}
               size="icon"
+              data-testid="chat-composer-send"
               className={`shrink-0 h-10 w-10 rounded-full transition-colors ${
                 (sending || canSend)
                   ? 'bg-black/5 dark:bg-white/10 text-foreground hover:bg-black/10 dark:hover:bg-white/20'
diff --git a/src/pages/Chat/message-utils.ts b/src/pages/Chat/message-utils.ts
index 1df16eed8..4a490bbbb 100644
--- a/src/pages/Chat/message-utils.ts
+++ b/src/pages/Chat/message-utils.ts
@@ -25,6 +25,44 @@ function cleanUserText(text: string): string {
     .trim();
 }
 
+function normalizeProgressiveText(text: string | undefined): string {
+  return typeof text === 'string' ? text.replace(/\r\n/g, '\n').trim() : '';
+}
+
+function compactProgressiveParts(parts: string[]): string[] {
+  const compacted: string[] = [];
+
+  for (const part of parts) {
+    const current = normalizeProgressiveText(part);
+    if (!current) continue;
+
+    const previous = compacted.at(-1);
+    if (!previous) {
+      compacted.push(part);
+      continue;
+    }
+
+    const normalizedPrevious = normalizeProgressiveText(previous);
+    if (!normalizedPrevious) {
+      compacted[compacted.length - 1] = part;
+      continue;
+    }
+
+    if (current === normalizedPrevious || normalizedPrevious.startsWith(current)) {
+      continue;
+    }
+
+    if (current.startsWith(normalizedPrevious)) {
+      compacted[compacted.length - 1] = part;
+      continue;
+    }
+
+    compacted.push(part);
+  }
+
+  return compacted;
+}
+
 /**
  * Extract displayable text from a message's content field.
  * Handles both string content and array-of-blocks content.
@@ -49,7 +87,7 @@ export function extractText(message: RawMessage | unknown): string {
         }
       }
     }
-    const combined = parts.join('\n\n');
+    const combined = compactProgressiveParts(parts).join('\n\n');
     result = combined.trim().length > 0 ? combined : '';
   } else if (typeof msg.text === 'string') {
     // Fallback: try .text field
@@ -85,7 +123,7 @@ export function extractThinking(message: RawMessage | unknown): string | null {
     }
   }
 
-  const combined = parts.join('\n\n').trim();
+  const combined = compactProgressiveParts(parts).join('\n\n').trim();
   return combined.length > 0 ? combined : null;
 }
 
diff --git a/src/stores/chat.ts b/src/stores/chat.ts
index 4af9b507e..29c57b1c4 100644
--- a/src/stores/chat.ts
+++ b/src/stores/chat.ts
@@ -165,14 +165,178 @@ function saveImageCache(cache: Map<string, AttachedFileMeta>): void {
 
 const _imageCache = loadImageCache();
 
+function normalizeBlockText(text: string | undefined): string {
+  return typeof text === 'string' ? text.replace(/\r\n/g, '\n').trim() : '';
+}
+
+function compactProgressiveTextParts(parts: string[]): string[] {
+  const compacted: string[] = [];
+
+  for (const part of parts) {
+    const current = normalizeBlockText(part);
+    if (!current) continue;
+
+    const previous = compacted.at(-1);
+    if (!previous) {
+      compacted.push(part);
+      continue;
+    }
+
+    const normalizedPrevious = normalizeBlockText(previous);
+    if (!normalizedPrevious) {
+      compacted[compacted.length - 1] = part;
+      continue;
+    }
+
+    if (current === normalizedPrevious || normalizedPrevious.startsWith(current)) {
+      continue;
+    }
+
+    if (current.startsWith(normalizedPrevious)) {
+      compacted[compacted.length - 1] = part;
+      continue;
+    }
+
+    compacted.push(part);
+  }
+
+  return compacted;
+}
+
+function normalizeLiveContentBlocks(content: ContentBlock[]): ContentBlock[] {
+  const normalized: ContentBlock[] = [];
+
+  let textBuffer: string[] = [];
+  let thinkingBuffer: string[] = [];
+
+  const flushTextBuffer = () => {
+    for (const part of compactProgressiveTextParts(textBuffer)) {
+      normalized.push({ type: 'text', text: part });
+    }
+    textBuffer = [];
+  };
+
+  const flushThinkingBuffer = () => {
+    for (const part of compactProgressiveTextParts(thinkingBuffer)) {
+      normalized.push({ type: 'thinking', thinking: part });
+    }
+    thinkingBuffer = [];
+  };
+
+  for (const block of content) {
+    if (block.type === 'text' && block.text) {
+      textBuffer.push(block.text);
+      continue;
+    }
+
+    if (block.type === 'thinking' && block.thinking) {
+      thinkingBuffer.push(block.thinking);
+      continue;
+    }
+
+    flushTextBuffer();
+    flushThinkingBuffer();
+    normalized.push(block);
+  }
+
+  flushTextBuffer();
+  flushThinkingBuffer();
+
+  return normalized;
+}
+
+function normalizeStreamingMessage(message: unknown): unknown {
+  if (!message || typeof message !== 'object') return message;
+
+  const rawMessage = message as RawMessage;
+  const rawContent = rawMessage.content;
+  if (!Array.isArray(rawContent)) return rawMessage;
+
+  const normalizedContent = normalizeLiveContentBlocks(rawContent as ContentBlock[]);
+  const didChange = normalizedContent.some((block, index) => block !== rawContent[index])
+    || normalizedContent.length !== rawContent.length;
+
+  return didChange
+    ? { ...rawMessage, content: normalizedContent }
+    : rawMessage;
+}
+
+function normalizeComparableUserText(content: unknown): string {
+  return getMessageText(content)
+    .replace(/\s+/g, ' ')
+    .trim();
+}
+
+function getComparableAttachmentSignature(message: Pick<RawMessage, '_attachedFiles'>): string {
+  const files = (message._attachedFiles || [])
+    .map((file) => file.filePath || `${file.fileName}|${file.mimeType}|${file.fileSize}`)
+    .filter(Boolean)
+    .sort();
+  return files.join('::');
+}
+
+function matchesOptimisticUserMessage(
+  candidate: RawMessage,
+  optimistic: RawMessage,
+  optimisticTimestampMs: number,
+): boolean {
+  if (candidate.role !== 'user') return false;
+
+  const optimisticText = normalizeComparableUserText(optimistic.content);
+  const candidateText = normalizeComparableUserText(candidate.content);
+  const sameText = optimisticText.length > 0 && optimisticText === candidateText;
+
+  const optimisticAttachments = getComparableAttachmentSignature(optimistic);
+  const candidateAttachments = getComparableAttachmentSignature(candidate);
+  const sameAttachments = optimisticAttachments.length > 0 && optimisticAttachments === candidateAttachments;
+
+  const hasOptimisticTimestamp = Number.isFinite(optimisticTimestampMs) && optimisticTimestampMs > 0;
+  const hasCandidateTimestamp = candidate.timestamp != null;
+  const timestampMatches = hasOptimisticTimestamp && hasCandidateTimestamp
+    ? Math.abs(toMs(candidate.timestamp as number) - optimisticTimestampMs) < 5000
+    : false;
+
+  if (sameText && sameAttachments) return true;
+  if (sameText && (!optimisticAttachments || !candidateAttachments) && (timestampMatches || !hasCandidateTimestamp)) return true;
+  if (sameAttachments && (!optimisticText || !candidateText) && (timestampMatches || !hasCandidateTimestamp)) return true;
+  return false;
+}
+
+function snapshotStreamingAssistantMessage(
+  currentStream: RawMessage | null,
+  existingMessages: RawMessage[],
+  runId: string,
+): RawMessage[] {
+  if (!currentStream) return [];
+
+  const normalizedStream = normalizeStreamingMessage(currentStream) as RawMessage;
+  const streamRole = normalizedStream.role;
+  if (streamRole !== 'assistant' && streamRole !== undefined) return [];
+
+  const snapId = normalizedStream.id || `${runId || 'run'}-turn-${existingMessages.length}`;
+  if (existingMessages.some((message) => message.id === snapId)) return [];
+
+  return [{
+    ...normalizedStream,
+    role: 'assistant',
+    id: snapId,
+  }];
+}
+
+function getLatestOptimisticUserMessage(messages: RawMessage[], userTimestampMs: number): RawMessage | undefined {
+  return [...messages].reverse().find(
+    (message) => message.role === 'user' && (!message.timestamp || Math.abs(toMs(message.timestamp) - userTimestampMs) < 5000),
+  );
+}
+
 /** Extract plain text from message content (string or content blocks) */
 function getMessageText(content: unknown): string {
   if (typeof content === 'string') return content;
   if (Array.isArray(content)) {
-    return (content as Array<{ type?: string; text?: string }>)
+    const parts = (content as Array<{ type?: string; text?: string }>)
       .filter(b => b.type === 'text' && b.text)
-      .map(b => b.text!)
-      .join('\n');
+      .map(b => b.text!);
+    return compactProgressiveTextParts(parts).join('\n');
   }
   return '';
 }
@@ -1416,17 +1580,12 @@ export const useChatStore = create<ChatState>((set, get) => ({
       const userMsgAt = get().lastUserMessageAt;
       if (get().sending && userMsgAt) {
         const userMsMs = toMs(userMsgAt);
-        const hasRecentUser = enrichedMessages.some(
-          (m) => m.role === 'user' && m.timestamp && Math.abs(toMs(m.timestamp) - userMsMs) < 5000,
-        );
-        if (!hasRecentUser) {
-          const currentMsgs = get().messages;
-          const optimistic = [...currentMsgs].reverse().find(
-            (m) => m.role === 'user' && m.timestamp && Math.abs(toMs(m.timestamp) - userMsMs) < 5000,
-          );
-          if (optimistic) {
-            finalMessages = [...enrichedMessages, optimistic];
-          }
+        const optimistic = getLatestOptimisticUserMessage(get().messages, userMsMs);
+        const hasMatchingUser = optimistic
+          ? enrichedMessages.some((message) => matchesOptimisticUserMessage(message, optimistic, userMsMs))
+          : false;
+        if (optimistic && !hasMatchingUser) {
+          finalMessages = [...enrichedMessages, optimistic];
         }
       }
 
@@ -1890,7 +2049,7 @@ export const useChatStore = create<ChatState>((set, get) => ({
               const msgRole = (event.message as RawMessage).role;
               if (isToolResultRole(msgRole)) return s.streamingMessage;
             }
-            return event.message ?? s.streamingMessage;
+            return normalizeStreamingMessage(event.message ?? s.streamingMessage);
           })(),
           streamingTools: updates.length > 0 ? upsertToolStatuses(s.streamingTools, updates) : s.streamingTools,
         }));
@@ -1902,17 +2061,18 @@ export const useChatStore = create<ChatState>((set, get) => ({
         // Message complete - add to history and clear streaming
         const finalMsg = event.message as RawMessage | undefined;
         if (finalMsg) {
-          const updates = collectToolUpdates(finalMsg, resolvedState);
-          if (isToolResultRole(finalMsg.role)) {
+          const normalizedFinalMessage = normalizeStreamingMessage(finalMsg) as RawMessage;
+          const updates = collectToolUpdates(normalizedFinalMessage, resolvedState);
+          if (isToolResultRole(normalizedFinalMessage.role)) {
             // Resolve file path from the streaming assistant message's matching tool call
             const currentStreamForPath = get().streamingMessage as RawMessage | null;
-            const matchedPath = (currentStreamForPath && finalMsg.toolCallId)
-              ? getToolCallFilePath(currentStreamForPath, finalMsg.toolCallId)
+            const matchedPath = (currentStreamForPath && normalizedFinalMessage.toolCallId)
+              ? getToolCallFilePath(currentStreamForPath, normalizedFinalMessage.toolCallId)
               : undefined;
 
             // Mirror enrichWithToolResultFiles: collect images + file refs for next assistant msg
             const toolFiles: AttachedFileMeta[] = [
-              ...extractImagesAsAttachedFiles(finalMsg.content),
+              ...extractImagesAsAttachedFiles(normalizedFinalMessage.content),
             ];
             if (matchedPath) {
               for (const f of toolFiles) {
@@ -1922,7 +2082,7 @@ export const useChatStore = create<ChatState>((set, get) => ({
                 }
               }
             }
-            const text = getMessageText(finalMsg.content);
+            const text = getMessageText(normalizedFinalMessage.content);
             if (text) {
               const mediaRefs = extractMediaRefs(text);
               const mediaRefPaths = new Set(mediaRefs.map(r => r.filePath));
@@ -1938,22 +2098,7 @@ export const useChatStore = create<ChatState>((set, get) => ({
               // tool result. Without snapshotting here, the intermediate thinking+tool steps
               // would be overwritten by the next turn's deltas and never appear in the UI.
               const currentStream = s.streamingMessage as RawMessage | null;
-              const snapshotMsgs: RawMessage[] = [];
-              if (currentStream) {
-                const streamRole = currentStream.role;
-                if (streamRole === 'assistant' || streamRole === undefined) {
-                  // Use message's own id if available, otherwise derive a stable one from runId
-                  const snapId = currentStream.id
-                    || `${runId || 'run'}-turn-${s.messages.length}`;
-                  if (!s.messages.some(m => m.id === snapId)) {
-                    snapshotMsgs.push({
-                      ...(currentStream as RawMessage),
-                      role: 'assistant',
-                      id: snapId,
-                    });
-                  }
-                }
-              }
+              const snapshotMsgs = snapshotStreamingAssistantMessage(currentStream, s.messages, runId);
               return {
                 messages: snapshotMsgs.length > 0 ? [...s.messages, ...snapshotMsgs] : s.messages,
                 streamingText: '',
@@ -1967,9 +2112,9 @@ export const useChatStore = create<ChatState>((set, get) => ({
             });
             break;
           }
-          const toolOnly = isToolOnlyMessage(finalMsg);
-          const hasOutput = hasNonToolAssistantContent(finalMsg);
-          const msgId = finalMsg.id || (toolOnly ? `run-${runId}-tool-${Date.now()}` : `run-${runId}`);
+          const toolOnly = isToolOnlyMessage(normalizedFinalMessage);
+          const hasOutput = hasNonToolAssistantContent(normalizedFinalMessage);
+          const msgId = normalizedFinalMessage.id || (toolOnly ? `run-${runId}-tool-${Date.now()}` : `run-${runId}`);
           set((s) => {
             const nextTools = updates.length > 0 ? upsertToolStatuses(s.streamingTools, updates) : s.streamingTools;
             const streamingTools = hasOutput ? [] : nextTools;
@@ -1978,12 +2123,12 @@ export const useChatStore = create<ChatState>((set, get) => ({
             const pendingImgs = s.pendingToolImages;
             const msgWithImages: RawMessage = pendingImgs.length > 0
               ? {
-                ...finalMsg,
-                role: (finalMsg.role || 'assistant') as RawMessage['role'],
+                ...normalizedFinalMessage,
+                role: (normalizedFinalMessage.role || 'assistant') as RawMessage['role'],
                 id: msgId,
-                _attachedFiles: [...(finalMsg._attachedFiles || []), ...pendingImgs],
+                _attachedFiles: [...(normalizedFinalMessage._attachedFiles || []), ...pendingImgs],
               }
-              : { ...finalMsg, role: (finalMsg.role || 'assistant') as RawMessage['role'], id: msgId };
+              : { ...normalizedFinalMessage, role: (normalizedFinalMessage.role || 'assistant') as RawMessage['role'], id: msgId };
             const clearPendingImages = { pendingToolImages: [] as AttachedFileMeta[] };
 
             // Check if message already exists (prevent duplicates)
@@ -2044,15 +2189,15 @@ export const useChatStore = create<ChatState>((set, get) => ({
         // content ("Let me get that written down...") is preserved in the UI
         // rather than being silently discarded.
         const currentStream = get().streamingMessage as RawMessage | null;
-        if (currentStream && (currentStream.role === 'assistant' || currentStream.role === undefined)) {
-          const snapId = (currentStream as RawMessage).id
-            || `error-snap-${Date.now()}`;
-          const alreadyExists = get().messages.some(m => m.id === snapId);
-          if (!alreadyExists) {
-            set((s) => ({
-              messages: [...s.messages, { ...currentStream, role: 'assistant' as const, id: snapId }],
-            }));
-          }
+        const errorSnapshot = snapshotStreamingAssistantMessage(
+          currentStream,
+          get().messages,
+          `error-${runId || Date.now()}`,
+        );
+        if (errorSnapshot.length > 0) {
+          set((s) => ({
+            messages: [...s.messages, ...errorSnapshot],
+          }));
         }
 
         set({
diff --git a/src/stores/chat/helpers.ts b/src/stores/chat/helpers.ts
index 6f28cfbf2..2f9cab017 100644
--- a/src/stores/chat/helpers.ts
+++ b/src/stores/chat/helpers.ts
@@ -70,6 +70,169 @@ function saveImageCache(cache: Map<string, AttachedFileMeta>): void {
 
 const _imageCache = loadImageCache();
 
+function normalizeBlockText(text: string | undefined): string {
+  return typeof text === 'string' ? text.replace(/\r\n/g, '\n').trim() : '';
+}
+
+function compactProgressiveTextParts(parts: string[]): string[] {
+  const compacted: string[] = [];
+
+  for (const part of parts) {
+    const current = normalizeBlockText(part);
+    if (!current) continue;
+
+    const previous = compacted.at(-1);
+    if (!previous) {
+      compacted.push(part);
+      continue;
+    }
+
+    const normalizedPrevious = normalizeBlockText(previous);
+    if (!normalizedPrevious) {
+      compacted[compacted.length - 1] = part;
+      continue;
+    }
+
+    if (current === normalizedPrevious || normalizedPrevious.startsWith(current)) {
+      continue;
+    }
+
+    if (current.startsWith(normalizedPrevious)) {
+      compacted[compacted.length - 1] = part;
+      continue;
+    }
+
+    compacted.push(part);
+  }
+
+  return compacted;
+}
+
+function normalizeLiveContentBlocks(content: ContentBlock[]): ContentBlock[] {
+  const normalized: ContentBlock[] = [];
+  let textBuffer: string[] = [];
+  let thinkingBuffer: string[] = [];
+
+  const flushTextBuffer = () => {
+    for (const part of compactProgressiveTextParts(textBuffer)) {
+      normalized.push({ type: 'text', text: part });
+    }
+    textBuffer = [];
+  };
+
+  const flushThinkingBuffer = () => {
+    for (const part of compactProgressiveTextParts(thinkingBuffer)) {
+      normalized.push({ type: 'thinking', thinking: part });
+    }
+    thinkingBuffer = [];
+  };
+
+  for (const block of content) {
+    if (block.type === 'text' && block.text) {
+      textBuffer.push(block.text);
+      continue;
+    }
+
+    if (block.type === 'thinking' && block.thinking) {
+      thinkingBuffer.push(block.thinking);
+      continue;
+    }
+
+    flushTextBuffer();
+    flushThinkingBuffer();
+    normalized.push(block);
+  }
+
+  flushTextBuffer();
+  flushThinkingBuffer();
+
+  return normalized;
+}
+
+function normalizeStreamingMessage(message: unknown): unknown {
+  if (!message || typeof message !== 'object') return message;
+
+  const rawMessage = message as RawMessage;
+  const rawContent = rawMessage.content;
+  if (!Array.isArray(rawContent)) return rawMessage;
+
+  const normalizedContent = normalizeLiveContentBlocks(rawContent as ContentBlock[]);
+  const didChange = normalizedContent.some((block, index) => block !== rawContent[index])
+    || normalizedContent.length !== rawContent.length;
+
+  return didChange
+    ? { ...rawMessage, content: normalizedContent }
+    : rawMessage;
+}
+
+function normalizeComparableUserText(content: unknown): string {
+  return getMessageText(content)
+    .replace(/\s+/g, ' ')
+    .trim();
+}
+
+function getComparableAttachmentSignature(message: Pick<RawMessage, '_attachedFiles'>): string {
+  const files = (message._attachedFiles || [])
+    .map((file) => file.filePath || `${file.fileName}|${file.mimeType}|${file.fileSize}`)
+    .filter(Boolean)
+    .sort();
+  return files.join('::');
+}
+
+function matchesOptimisticUserMessage(
+  candidate: RawMessage,
+  optimistic: RawMessage,
+  optimisticTimestampMs: number,
+): boolean {
+  if (candidate.role !== 'user') return false;
+
+  const optimisticText = normalizeComparableUserText(optimistic.content);
+  const candidateText = normalizeComparableUserText(candidate.content);
+  const sameText = optimisticText.length > 0 && optimisticText === candidateText;
+
+  const optimisticAttachments = getComparableAttachmentSignature(optimistic);
+  const candidateAttachments = getComparableAttachmentSignature(candidate);
+  const sameAttachments = optimisticAttachments.length > 0 && optimisticAttachments === candidateAttachments;
+
+  const hasOptimisticTimestamp = Number.isFinite(optimisticTimestampMs) && optimisticTimestampMs > 0;
+  const hasCandidateTimestamp = candidate.timestamp != null;
+  const timestampMatches = hasOptimisticTimestamp && hasCandidateTimestamp
+    ? Math.abs(toMs(candidate.timestamp as number) - optimisticTimestampMs) < 5000
+    : false;
+
+  if (sameText && sameAttachments) return true;
+  if (sameText && (!optimisticAttachments || !candidateAttachments) && (timestampMatches || !hasCandidateTimestamp)) return true;
+  if (sameAttachments && (!optimisticText || !candidateText) && (timestampMatches || !hasCandidateTimestamp)) return true;
+  return false;
+}
+
+function snapshotStreamingAssistantMessage(
+  currentStream: RawMessage | null,
+  existingMessages: RawMessage[],
+  runId: string,
+): RawMessage[] {
+  if (!currentStream) return [];
+
+  const normalizedStream = normalizeStreamingMessage(currentStream) as RawMessage;
+  const streamRole = normalizedStream.role;
+  if (streamRole !== 'assistant' && streamRole !== undefined) return [];
+
+  const snapId = normalizedStream.id || `${runId || 'run'}-turn-${existingMessages.length}`;
+  if (existingMessages.some((message) => message.id === snapId)) return [];
+
+  return [{
+    ...normalizedStream,
+    role: 'assistant',
+    id: snapId,
+  }];
+}
+
+function getLatestOptimisticUserMessage(messages: RawMessage[], userTimestampMs: number): RawMessage | undefined {
+  return [...messages].reverse().find(
+    (message) => message.role === 'user' && (!message.timestamp || Math.abs(toMs(message.timestamp) - userTimestampMs) < 5000),
+  );
+}
+
 function upsertImageCacheEntry(filePath: string, file: Omit<AttachedFileMeta, 'filePath'>): void {
   _imageCache.set(filePath, { ...file, filePath });
   saveImageCache(_imageCache);
@@ -86,10 +249,10 @@ function withAttachedFileSource(
 function getMessageText(content: unknown): string {
   if (typeof content === 'string') return content;
   if (Array.isArray(content)) {
-    return (content as Array<{ type?: string; text?: string }>)
+    const parts = (content as Array<{ type?: string; text?: string }>)
       .filter(b => b.type === 'text' && b.text)
-      .map(b => b.text!)
-      .join('\n');
+      .map(b => b.text!);
+    return compactProgressiveTextParts(parts).join('\n');
   }
   return '';
 }
@@ -627,7 +790,7 @@ function extractTextFromContent(content: unknown): string {
       parts.push(block.text);
     }
   }
-  return parts.join('\n');
+  return compactProgressiveTextParts(parts).join('\n');
 }
 
 function summarizeToolOutput(text: string): string | undefined {
@@ -855,6 +1018,10 @@ export {
   upsertToolStatuses,
   hasNonToolAssistantContent,
   isToolOnlyMessage,
+  normalizeStreamingMessage,
+  matchesOptimisticUserMessage,
+  snapshotStreamingAssistantMessage,
+  getLatestOptimisticUserMessage,
   setHistoryPollTimer,
   hasErrorRecoveryTimer,
   setErrorRecoveryTimer,
diff --git a/src/stores/chat/history-actions.ts b/src/stores/chat/history-actions.ts
index 0d817ec73..7d88e08f4 100644
--- a/src/stores/chat/history-actions.ts
+++ b/src/stores/chat/history-actions.ts
@@ -5,11 +5,13 @@ import {
   clearHistoryPoll,
   enrichWithCachedImages,
   enrichWithToolResultFiles,
+  getLatestOptimisticUserMessage,
   getMessageText,
   hasNonToolAssistantContent,
   isInternalMessage,
   isToolResultRole,
   loadMissingPreviews,
+  matchesOptimisticUserMessage,
   toMs,
 } from './helpers';
 import { buildCronSessionHistoryPath, isCronSessionKey } from './cron-session-utils';
@@ -101,17 +103,12 @@ export function createHistoryActions(
         const userMsgAt = get().lastUserMessageAt;
         if (get().sending && userMsgAt) {
           const userMsMs = toMs(userMsgAt);
-          const hasRecentUser = enrichedMessages.some(
-            (m) => m.role === 'user' && m.timestamp && Math.abs(toMs(m.timestamp) - userMsMs) < 5000,
-          );
-          if (!hasRecentUser) {
-            const currentMsgs = get().messages;
-            const optimistic = [...currentMsgs].reverse().find(
-              (m) => m.role === 'user' && m.timestamp && Math.abs(toMs(m.timestamp) - userMsMs) < 5000,
-            );
-            if (optimistic) {
-              finalMessages = [...enrichedMessages, optimistic];
-            }
+          const optimistic = getLatestOptimisticUserMessage(get().messages, userMsMs);
+          const hasMatchingUser = optimistic
+            ? enrichedMessages.some((message) => matchesOptimisticUserMessage(message, optimistic, userMsMs))
+            : false;
+          if (optimistic && !hasMatchingUser) {
+            finalMessages = [...enrichedMessages, optimistic];
           }
         }
 
diff --git a/src/stores/chat/runtime-event-handlers.ts b/src/stores/chat/runtime-event-handlers.ts
index d0cfb1e29..6d2784557 100644
--- a/src/stores/chat/runtime-event-handlers.ts
+++ b/src/stores/chat/runtime-event-handlers.ts
@@ -12,7 +12,9 @@ import {
   isToolOnlyMessage,
   isToolResultRole,
   makeAttachedFile,
+  normalizeStreamingMessage,
   setErrorRecoveryTimer,
+  snapshotStreamingAssistantMessage,
   upsertToolStatuses,
 } from './helpers';
 import type { AttachedFileMeta, RawMessage } from './types';
@@ -65,7 +67,7 @@ export function handleRuntimeEventState(
                   return s.streamingMessage;
                 }
               }
-              return event.message ?? s.streamingMessage;
+              return normalizeStreamingMessage(event.message ?? s.streamingMessage);
             })(),
             streamingTools: updates.length > 0 ? upsertToolStatuses(s.streamingTools, updates) : s.streamingTools,
           }));
@@ -77,16 +79,17 @@ export function handleRuntimeEventState(
           // Message complete - add to history and clear streaming
           const finalMsg = event.message as RawMessage | undefined;
           if (finalMsg) {
-            const updates = collectToolUpdates(finalMsg, resolvedState);
-            if (isToolResultRole(finalMsg.role)) {
+            const normalizedFinalMessage = normalizeStreamingMessage(finalMsg) as RawMessage;
+            const updates = collectToolUpdates(normalizedFinalMessage, resolvedState);
+            if (isToolResultRole(normalizedFinalMessage.role)) {
               // Resolve file path from the streaming assistant message's matching tool call
               const currentStreamForPath = get().streamingMessage as RawMessage | null;
-              const matchedPath = (currentStreamForPath && finalMsg.toolCallId)
-                ? getToolCallFilePath(currentStreamForPath, finalMsg.toolCallId)
+              const matchedPath = (currentStreamForPath && normalizedFinalMessage.toolCallId)
+                ? getToolCallFilePath(currentStreamForPath, normalizedFinalMessage.toolCallId)
                 : undefined;
 
               // Mirror enrichWithToolResultFiles: collect images + file refs for next assistant msg
-              const toolFiles: AttachedFileMeta[] = extractImagesAsAttachedFiles(finalMsg.content)
+              const toolFiles: AttachedFileMeta[] = extractImagesAsAttachedFiles(normalizedFinalMessage.content)
                 .map((file) => (file.source ? file : { ...file, source: 'tool-result' }));
               if (matchedPath) {
                 for (const f of toolFiles) {
@@ -96,7 +99,7 @@ export function handleRuntimeEventState(
                   }
                 }
               }
-              const text = getMessageText(finalMsg.content);
+              const text = getMessageText(normalizedFinalMessage.content);
               if (text) {
                 const mediaRefs = extractMediaRefs(text);
                 const mediaRefPaths = new Set(mediaRefs.map(r => r.filePath));
@@ -112,22 +115,7 @@ export function handleRuntimeEventState(
                 // tool result. Without snapshotting here, the intermediate thinking+tool steps
                 // would be overwritten by the next turn's deltas and never appear in the UI.
                 const currentStream = s.streamingMessage as RawMessage | null;
-                const snapshotMsgs: RawMessage[] = [];
-                if (currentStream) {
-                  const streamRole = currentStream.role;
-                  if (streamRole === 'assistant' || streamRole === undefined) {
-                    // Use message's own id if available, otherwise derive a stable one from runId
-                    const snapId = currentStream.id
-                      || `${runId || 'run'}-turn-${s.messages.length}`;
-                    if (!s.messages.some(m => m.id === snapId)) {
-                      snapshotMsgs.push({
-                        ...(currentStream as RawMessage),
-                        role: 'assistant',
-                        id: snapId,
-                      });
-                    }
-                  }
-                }
+                const snapshotMsgs = snapshotStreamingAssistantMessage(currentStream, s.messages, runId);
                 return {
                   messages: snapshotMsgs.length > 0 ? [...s.messages, ...snapshotMsgs] : s.messages,
                   streamingText: '',
@@ -141,9 +129,9 @@ export function handleRuntimeEventState(
               });
               break;
             }
-            const toolOnly = isToolOnlyMessage(finalMsg);
-            const hasOutput = hasNonToolAssistantContent(finalMsg);
-            const msgId = finalMsg.id || (toolOnly ? `run-${runId}-tool-${Date.now()}` : `run-${runId}`);
+            const toolOnly = isToolOnlyMessage(normalizedFinalMessage);
+            const hasOutput = hasNonToolAssistantContent(normalizedFinalMessage);
+            const msgId = normalizedFinalMessage.id || (toolOnly ? `run-${runId}-tool-${Date.now()}` : `run-${runId}`);
             set((s) => {
               const nextTools = updates.length > 0 ? upsertToolStatuses(s.streamingTools, updates) : s.streamingTools;
               const streamingTools = hasOutput ? [] : nextTools;
@@ -152,12 +140,12 @@ export function handleRuntimeEventState(
               const pendingImgs = s.pendingToolImages;
               const msgWithImages: RawMessage = pendingImgs.length > 0
                 ? {
-                  ...finalMsg,
-                  role: (finalMsg.role || 'assistant') as RawMessage['role'],
+                  ...normalizedFinalMessage,
+                  role: (normalizedFinalMessage.role || 'assistant') as RawMessage['role'],
                   id: msgId,
-                  _attachedFiles: [...(finalMsg._attachedFiles || []), ...pendingImgs],
+                  _attachedFiles: [...(normalizedFinalMessage._attachedFiles || []), ...pendingImgs],
                 }
-                : { ...finalMsg, role: (finalMsg.role || 'assistant') as RawMessage['role'], id: msgId };
+                : { ...normalizedFinalMessage, role: (normalizedFinalMessage.role || 'assistant') as RawMessage['role'], id: msgId };
               const clearPendingImages = { pendingToolImages: [] as AttachedFileMeta[] };
 
               // Check if message already exists (prevent duplicates)
@@ -218,15 +206,15 @@ export function handleRuntimeEventState(
           // content ("Let me get that written down...") is preserved in the UI
           // rather than being silently discarded.
           const currentStream = get().streamingMessage as RawMessage | null;
-          if (currentStream && (currentStream.role === 'assistant' || currentStream.role === undefined)) {
-            const snapId = (currentStream as RawMessage).id
-              || `error-snap-${Date.now()}`;
-            const alreadyExists = get().messages.some(m => m.id === snapId);
-            if (!alreadyExists) {
-              set((s) => ({
-                messages: [...s.messages, { ...currentStream, role: 'assistant' as const, id: snapId }],
-              }));
-            }
+          const errorSnapshot = snapshotStreamingAssistantMessage(
+            currentStream,
+            get().messages,
+            `error-${runId || Date.now()}`,
+          );
+          if (errorSnapshot.length > 0) {
+            set((s) => ({
+              messages: [...s.messages, ...errorSnapshot],
+            }));
           }
 
           set({
@@ -291,7 +279,7 @@ export function handleRuntimeEventState(
             console.warn(`[handleChatEvent] Unknown event state "${resolvedState}", treating message as streaming delta. Event keys:`, Object.keys(event));
             const updates = collectToolUpdates(event.message, 'delta');
             set((s) => ({
-              streamingMessage: event.message ?? s.streamingMessage,
+              streamingMessage: normalizeStreamingMessage(event.message ?? s.streamingMessage),
               streamingTools: updates.length > 0 ? upsertToolStatuses(s.streamingTools, updates) : s.streamingTools,
             }));
           }
diff --git a/src/stores/gateway.ts b/src/stores/gateway.ts
index dcb2b9bba..910f336f4 100644
--- a/src/stores/gateway.ts
+++ b/src/stores/gateway.ts
@@ -97,6 +97,9 @@ function maybeLoadSessions(
   state: { loadSessions: () => Promise<void> },
   force = false,
 ): void {
+  const { status } = useGatewayStore.getState();
+  if (status.gatewayReady === false) return;
+
   const now = Date.now();
   if (!force && now - lastLoadSessionsAt < LOAD_SESSIONS_MIN_INTERVAL_MS) return;
   lastLoadSessionsAt = now;
diff --git a/tests/e2e/chat-task-visualizer.spec.ts b/tests/e2e/chat-task-visualizer.spec.ts
index 3d1373480..d3d97667d 100644
--- a/tests/e2e/chat-task-visualizer.spec.ts
+++ b/tests/e2e/chat-task-visualizer.spec.ts
@@ -16,7 +16,7 @@ function stableStringify(value: unknown): string {
 const seededHistory = [
   {
     role: 'user',
-    content: [{ type: 'text', text: '[Mon 2026-04-06 15:18 GMT+8] 分析 Velaria 当前未提交改动' }],
+    content: [{ type: 'text', text: '[Mon 2026-04-06 15:18 GMT+8] Analyze Velaria uncommitted changes' }],
     timestamp: Date.now(),
   },
   {
@@ -57,7 +57,7 @@ const seededHistory = [
       type: 'toolCall',
       id: 'yield-call',
       name: 'sessions_yield',
-      arguments: { message: '我让 coder 去拆 ~/Velaria 当前未提交改动的核心块了，等它回来我直接给你结论。' },
+      arguments: { message: 'I asked coder to break down the core blocks of ~/Velaria uncommitted changes; will give you the conclusion when it returns.' },
     }],
     timestamp: Date.now(),
   },
@@ -69,12 +69,12 @@ const seededHistory = [
       type: 'text',
       text: JSON.stringify({
         status: 'yielded',
-        message: '我让 coder 去拆 ~/Velaria 当前未提交改动的核心块了，等它回来我直接给你结论。',
+        message: 'I asked coder to break down the core blocks of ~/Velaria uncommitted changes; will give you the conclusion when it returns.',
       }, null, 2),
     }],
     details: {
       status: 'yielded',
-      message: '我让 coder 去拆 ~/Velaria 当前未提交改动的核心块了，等它回来我直接给你结论。',
+      message: 'I asked coder to break down the core blocks of ~/Velaria uncommitted changes; will give you the conclusion when it returns.',
     },
     isError: false,
     timestamp: Date.now(),
@@ -94,7 +94,7 @@ status: completed successfully`,
   },
   {
     role: 'assistant',
-    content: [{ type: 'text', text: '我让 coder 分析完了，下面是结论。' }],
+    content: [{ type: 'text', text: 'Coder has finished the analysis, here are the conclusions.' }],
     _attachedFiles: [
       {
         fileName: 'CHECKLIST.md',
@@ -112,7 +112,7 @@ status: completed successfully`,
 const childTranscriptMessages = [
   {
     role: 'user',
-    content: [{ type: 'text', text: '分析 ~/Velaria 当前未提交改动的核心内容' }],
+    content: [{ type: 'text', text: 'Analyze the core content of ~/Velaria uncommitted changes' }],
     timestamp: Date.now(),
   },
   {
@@ -143,7 +143,7 @@ const childTranscriptMessages = [
   },
   {
     role: 'assistant',
-    content: [{ type: 'text', text: '已完成分析，最关键的有 4 块。' }],
+    content: [{ type: 'text', text: 'Analysis complete, there are 4 key blocks.' }],
     timestamp: Date.now(),
   },
 ];
@@ -229,10 +229,145 @@ test.describe('ClawX chat execution graph', () => {
       await expect(
         page.locator('[data-testid="chat-execution-graph"] [data-testid="chat-execution-step"]').getByText('exec', { exact: true }),
       ).toBeVisible();
-      await expect(page.locator('[data-testid="chat-execution-graph"]').getByText('我让 coder 去拆 ~/Velaria 当前未提交改动的核心块了，等它回来我直接给你结论。')).toBeVisible();
+      await expect(page.locator('[data-testid="chat-execution-graph"]').getByText('I asked coder to break down the core blocks of ~/Velaria uncommitted changes; will give you the conclusion when it returns.')).toBeVisible();
       await expect(page.getByText('CHECKLIST.md')).toHaveCount(0);
     } finally {
       await closeElectronApp(app);
     }
   });
+
+  test('does not duplicate the in-flight user prompt or cumulative streaming content', async ({ launchElectronApp }) => {
+    const app = await launchElectronApp({ skipSetup: true });
+
+    try {
+      await installIpcMocks(app, {
+        gatewayStatus: { state: 'running', port: 18789, pid: 12345 },
+        gatewayRpc: {
+          [stableStringify(['sessions.list', {}])]: {
+            success: true,
+            result: {
+              sessions: [{ key: PROJECT_MANAGER_SESSION_KEY, displayName: 'main' }],
+            },
+          },
+          [stableStringify(['chat.history', { sessionKey: PROJECT_MANAGER_SESSION_KEY, limit: 200 }])]: {
+            success: true,
+            result: {
+              messages: [],
+            },
+          },
+        },
+        hostApi: {
+          [stableStringify(['/api/gateway/status', 'GET'])]: {
+            ok: true,
+            data: {
+              status: 200,
+              ok: true,
+              json: { state: 'running', port: 18789, pid: 12345 },
+            },
+          },
+          [stableStringify(['/api/agents', 'GET'])]: {
+            ok: true,
+            data: {
+              status: 200,
+              ok: true,
+              json: {
+                success: true,
+                agents: [{ id: 'main', name: 'main' }],
+              },
+            },
+          },
+        },
+      });
+
+      await app.evaluate(async ({ app: _app }) => {
+        const { ipcMain } = process.mainModule!.require('electron') as typeof import('electron');
+        const sendPayloads: Array<{ message?: string; sessionKey?: string }> = [];
+        ipcMain.removeHandler('gateway:rpc');
+        ipcMain.handle('gateway:rpc', async (_event: unknown, method: string, payload: unknown) => {
+          if (method === 'sessions.list') {
+            return {
+              success: true,
+              result: {
+                sessions: [{ key: 'agent:main:main', displayName: 'main' }],
+              },
+            };
+          }
+          if (method === 'chat.history') {
+            return {
+              success: true,
+              result: { messages: [] },
+            };
+          }
+          if (method === 'chat.send') {
+            if (payload && typeof payload === 'object') {
+              const p = payload as { message?: string; sessionKey?: string };
+              sendPayloads.push({ message: p.message, sessionKey: p.sessionKey });
+            }
+            return {
+              success: true,
+              result: { runId: 'mock-run' },
+            };
+          }
+          return { success: true, result: {} };
+        });
+        (globalThis as typeof globalThis & { __clawxSendPayloads?: Array<{ message?: string; sessionKey?: string }> }).__clawxSendPayloads = sendPayloads;
+      });
+
+      const page = await getStableWindow(app);
+      try {
+        await page.reload();
+      } catch (error) {
+        if (!String(error).includes('ERR_FILE_NOT_FOUND')) {
+          throw error;
+        }
+      }
+
+      await expect(page.getByTestId('main-layout')).toBeVisible();
+      await page.getByTestId('chat-composer-input').fill('Open browser, search for tech news, and take a screenshot');
+      await page.getByTestId('chat-composer-send').click();
+
+      await expect(page.getByText('Open browser, search for tech news, and take a screenshot')).toHaveCount(1);
+      await expect.poll(async () => {
+        return await app.evaluate(() => {
+          const sendPayloads = (globalThis as typeof globalThis & {
+            __clawxSendPayloads?: Array<{ message?: string; sessionKey?: string }>;
+          }).__clawxSendPayloads || [];
+          return sendPayloads.length;
+        });
+      }).toBe(1);
+
+      await app.evaluate(async ({ BrowserWindow }) => {
+        const win = BrowserWindow.getAllWindows()[0];
+        win?.webContents.send('gateway:notification', {
+          method: 'agent',
+          params: {
+            runId: 'mock-run',
+            sessionKey: 'agent:main:main',
+            state: 'delta',
+            message: {
+              role: 'assistant',
+              content: [
+                { type: 'thinking', thinking: 'thinking 1' },
+                { type: 'thinking', thinking: 'thinking 1 2' },
+                { type: 'thinking', thinking: 'thinking 1 2 3' },
+                { type: 'text', text: '1' },
+                { type: 'text', text: '1 2' },
+                { type: 'text', text: '1 2 3' },
+              ],
+            },
+          },
+        });
+      });
+
+      await expect(page.getByText('Open browser, search for tech news, and take a screenshot')).toHaveCount(1);
+      await expect(page.getByText(/^thinking 1 2 3$/)).toHaveCount(1);
+      await expect(page.getByText(/^thinking 1 2$/)).toHaveCount(0);
+      await expect(page.getByText(/^thinking 1$/)).toHaveCount(0);
+      await expect(page.getByText(/^1 2 3$/)).toHaveCount(1);
+      await expect(page.getByText(/^1 2$/)).toHaveCount(0);
+      await expect(page.getByText(/^1$/)).toHaveCount(0);
+    } finally {
+      await closeElectronApp(app);
+    }
+  });
 });
diff --git a/tests/unit/chat-history-actions.test.ts b/tests/unit/chat-history-actions.test.ts
index 31aa46c8c..ac9e3bca5 100644
--- a/tests/unit/chat-history-actions.test.ts
+++ b/tests/unit/chat-history-actions.test.ts
@@ -41,11 +41,40 @@ vi.mock('@/stores/chat/helpers', () => ({
   clearHistoryPoll: (...args: unknown[]) => clearHistoryPoll(...args),
   enrichWithCachedImages: (...args: unknown[]) => enrichWithCachedImages(...args),
   enrichWithToolResultFiles: (...args: unknown[]) => enrichWithToolResultFiles(...args),
+  getLatestOptimisticUserMessage: (messages: Array<{ role: string; timestamp?: number }>, userTimestampMs: number) =>
+    [...messages].reverse().find(
+      (message) => message.role === 'user'
+        && (!message.timestamp || Math.abs(toMs(message.timestamp) - userTimestampMs) < 5000),
+    ),
   getMessageText: (...args: unknown[]) => getMessageText(...args),
   hasNonToolAssistantContent: (...args: unknown[]) => hasNonToolAssistantContent(...args),
   isInternalMessage: (...args: unknown[]) => isInternalMessage(...args),
   isToolResultRole: (...args: unknown[]) => isToolResultRole(...args),
   loadMissingPreviews: (...args: unknown[]) => loadMissingPreviews(...args),
+  matchesOptimisticUserMessage: (
+    candidate: { role: string; timestamp?: number; content?: unknown; _attachedFiles?: Array<{ filePath?: string; fileName?: string; mimeType?: string; fileSize?: number }> },
+    optimistic: { role: string; timestamp?: number; content?: unknown; _attachedFiles?: Array<{ filePath?: string; fileName?: string; mimeType?: string; fileSize?: number }> },
+    optimisticTimestampMs: number,
+  ) => {
+    if (candidate.role !== 'user') return false;
+    const normalizeText = (content: unknown) => (typeof content === 'string' ? content : '')
+      .replace(/^\[(?:Mon|Tue|Wed|Thu|Fri|Sat|Sun)\s+\d{4}-\d{2}-\d{2}\s+\d{2}:\d{2}\s+[^\]]+\]\s*/i, '')
+      .replace(/\s+/g, ' ')
+      .trim();
+    const candidateText = normalizeText(candidate.content);
+    const optimisticText = normalizeText(optimistic.content);
+    const candidateAttachments = (candidate._attachedFiles || []).map((file) => file.filePath || `${file.fileName}|${file.mimeType}|${file.fileSize}`).sort().join('::');
+    const optimisticAttachments = (optimistic._attachedFiles || []).map((file) => file.filePath || `${file.fileName}|${file.mimeType}|${file.fileSize}`).sort().join('::');
+    const hasCandidateTimestamp = candidate.timestamp != null;
+    const timestampMatches = hasCandidateTimestamp
+      ? Math.abs(toMs(candidate.timestamp as number) - optimisticTimestampMs) < 5000
+      : false;
+
+    if (candidateText && optimisticText && candidateText === optimisticText && candidateAttachments === optimisticAttachments) return true;
+    if (candidateText && optimisticText && candidateText === optimisticText && (!hasCandidateTimestamp || timestampMatches)) return true;
+    if (candidateAttachments && optimisticAttachments && candidateAttachments === optimisticAttachments && (!hasCandidateTimestamp || timestampMatches)) return true;
+    return false;
+  },
   toMs: (...args: unknown[]) => toMs(...args as Parameters<typeof toMs>),
 }));
 
@@ -527,4 +556,45 @@ describe('chat history actions', () => {
     ]);
     expect(h.read().messages[0]?._attachedFiles?.[0]?.preview).toBe('data:image/png;base64,abc');
   });
+
+  it('does not append an optimistic duplicate when history already includes the user message without timestamp', async () => {
+    const { createHistoryActions } = await import('@/stores/chat/history-actions');
+    const h = makeHarness({
+      currentSessionKey: 'agent:main:main',
+      sending: true,
+      lastUserMessageAt: 1_773_281_732_000,
+      messages: [
+        {
+          role: 'user',
+          content: '[Fri 2026-03-13 10:00 GMT+8] Open browser, search for tech news, and take a screenshot',
+          timestamp: 1_773_281_732,
+        },
+      ],
+    });
+    const actions = createHistoryActions(h.set as never, h.get as never);
+
+    invokeIpcMock.mockResolvedValueOnce({
+      success: true,
+      result: {
+        messages: [
+          {
+            role: 'user',
+            content: 'Open browser, search for tech news, and take a screenshot',
+          },
+          {
+            role: 'assistant',
+            content: 'Processing',
+            timestamp: 1_773_281_733,
+          },
+        ],
+      },
+    });
+
+    await actions.loadHistory(true);
+
+    expect(h.read().messages.map((message) => message.content)).toEqual([
+      'Open browser, search for tech news, and take a screenshot',
+      'Processing',
+    ]);
+  });
 });
diff --git a/tests/unit/chat-runtime-event-handlers.test.ts b/tests/unit/chat-runtime-event-handlers.test.ts
index 97dee04f5..9921af308 100644
--- a/tests/unit/chat-runtime-event-handlers.test.ts
+++ b/tests/unit/chat-runtime-event-handlers.test.ts
@@ -20,7 +20,9 @@ const makeAttachedFile = vi.fn((ref: { filePath: string; mimeType: string }, sou
   filePath: ref.filePath,
   source,
 }));
+const normalizeStreamingMessage = vi.fn((message: unknown) => message);
 const setErrorRecoveryTimer = vi.fn();
+const snapshotStreamingAssistantMessage = vi.fn((currentStream: unknown) => currentStream ? [currentStream] : []);
 const upsertToolStatuses = vi.fn((_current, updates) => updates);
 
 vi.mock('@/stores/chat/helpers', () => ({
@@ -37,7 +39,9 @@ vi.mock('@/stores/chat/helpers', () => ({
   isToolOnlyMessage: (...args: unknown[]) => isToolOnlyMessage(...args),
   isToolResultRole: (...args: unknown[]) => isToolResultRole(...args),
   makeAttachedFile: (...args: unknown[]) => makeAttachedFile(...args),
+  normalizeStreamingMessage: (...args: unknown[]) => normalizeStreamingMessage(...args),
   setErrorRecoveryTimer: (...args: unknown[]) => setErrorRecoveryTimer(...args),
+  snapshotStreamingAssistantMessage: (...args: unknown[]) => snapshotStreamingAssistantMessage(...args),
   upsertToolStatuses: (...args: unknown[]) => upsertToolStatuses(...args),
 }));
 
@@ -84,6 +88,8 @@ describe('chat runtime event handlers', () => {
     vi.resetAllMocks();
     hasErrorRecoveryTimer.mockReturnValue(false);
     collectToolUpdates.mockReturnValue([]);
+    normalizeStreamingMessage.mockImplementation((message: unknown) => message);
+    snapshotStreamingAssistantMessage.mockImplementation((currentStream: unknown) => currentStream ? [currentStream as Record<string, unknown>] : []);
     upsertToolStatuses.mockImplementation((_current, updates) => updates);
   });
 
@@ -228,6 +234,100 @@ describe('chat runtime event handlers', () => {
     expect(h.read().streamingMessage).toEqual(incoming);
   });
 
+  it('normalizes cumulative text and thinking blocks while streaming', async () => {
+    const { handleRuntimeEventState } = await import('@/stores/chat/runtime-event-handlers');
+    const h = makeHarness({ streamingMessage: null });
+    normalizeStreamingMessage.mockReturnValue({
+      role: 'assistant',
+      content: [
+        { type: 'thinking', thinking: 'thinking 1 2 3' },
+        { type: 'text', text: '1 2 3' },
+      ],
+    });
+
+    handleRuntimeEventState(h.set as never, h.get as never, {
+      message: {
+        role: 'assistant',
+        content: [
+          { type: 'thinking', thinking: 'thinking 1' },
+          { type: 'thinking', thinking: 'thinking 1 2' },
+          { type: 'thinking', thinking: 'thinking 1 2 3' },
+          { type: 'text', text: '1' },
+          { type: 'text', text: '1 2' },
+          { type: 'text', text: '1 2 3' },
+        ],
+      },
+    }, 'delta', 'run-stream');
+
+    expect(h.read().streamingMessage).toEqual({
+      role: 'assistant',
+      content: [
+        { type: 'thinking', thinking: 'thinking 1 2 3' },
+        { type: 'text', text: '1 2 3' },
+      ],
+    });
+  });
+
+  it('snapshots normalized streaming content when tool results arrive', async () => {
+    const { handleRuntimeEventState } = await import('@/stores/chat/runtime-event-handlers');
+    normalizeStreamingMessage.mockImplementation((message: unknown) => {
+      const msg = message as { role: string; id: string; content: unknown[] };
+      return {
+        ...msg,
+        content: [
+          { type: 'thinking', thinking: 'thinking 1 2 3' },
+          { type: 'tool_use', id: 'call-1', name: 'read', input: { filePath: '/tmp/demo.md' } },
+          { type: 'text', text: '1 2 3' },
+        ],
+      };
+    });
+    snapshotStreamingAssistantMessage.mockImplementation((currentStream: unknown) => {
+      const msg = currentStream as { role: string; id: string; content: unknown[] };
+      return [{
+        ...msg,
+        content: [
+          { type: 'thinking', thinking: 'thinking 1 2 3' },
+          { type: 'tool_use', id: 'call-1', name: 'read', input: { filePath: '/tmp/demo.md' } },
+          { type: 'text', text: '1 2 3' },
+        ],
+      }];
+    });
+    const h = makeHarness({
+      streamingMessage: {
+        role: 'assistant',
+        id: 'streaming-assistant',
+        content: [
+          { type: 'thinking', thinking: 'thinking 1' },
+          { type: 'thinking', thinking: 'thinking 1 2 3' },
+          { type: 'tool_use', id: 'call-1', name: 'read', input: { filePath: '/tmp/demo.md' } },
+          { type: 'text', text: '1' },
+          { type: 'text', text: '1 2 3' },
+        ],
+      },
+    });
+
+    handleRuntimeEventState(h.set as never, h.get as never, {
+      message: {
+        role: 'toolResult',
+        toolCallId: 'call-1',
+        toolName: 'read',
+        content: [{ type: 'text', text: 'done' }],
+      },
+    }, 'final', 'run-normalize');
+
+    expect(h.read().messages).toEqual([
+      {
+        role: 'assistant',
+        id: 'streaming-assistant',
+        content: [
+          { type: 'thinking', thinking: 'thinking 1 2 3' },
+          { type: 'tool_use', id: 'call-1', name: 'read', input: { filePath: '/tmp/demo.md' } },
+          { type: 'text', text: '1 2 3' },
+        ],
+      },
+    ]);
+  });
+
   it('clears runtime state on aborted event', async () => {
     const { handleRuntimeEventState } = await import('@/stores/chat/runtime-event-handlers');
     const h = makeHarness({
diff --git a/tests/unit/task-visualization.test.ts b/tests/unit/task-visualization.test.ts
index 1b8523e7d..81a9f26f3 100644
--- a/tests/unit/task-visualization.test.ts
+++ b/tests/unit/task-visualization.test.ts
@@ -203,6 +203,31 @@ describe('deriveTaskSteps', () => {
     ]);
   });
 
+  it('collapses cumulative streaming thinking details into the newest version', () => {
+    const steps = deriveTaskSteps({
+      messages: [],
+      streamingMessage: {
+        role: 'assistant',
+        content: [
+          { type: 'thinking', thinking: 'thinking 1' },
+          { type: 'thinking', thinking: 'thinking 1 2' },
+          { type: 'thinking', thinking: 'thinking 1 2 3' },
+        ],
+      },
+      streamingTools: [],
+      sending: true,
+      pendingFinal: false,
+      showThinking: true,
+    });
+
+    expect(steps).toEqual([
+      expect.objectContaining({
+        id: 'stream-thinking',
+        detail: 'thinking 1 2 3',
+      }),
+    ]);
+  });
+
   it('builds a branch for spawned subagents', () => {
     const messages: RawMessage[] = [
       {