diff --git a/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts b/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts
index eb97433..6eb7f9a 100644
--- a/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts
+++ b/packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts
@@ -35,6 +35,8 @@ interface ActiveSession {
   abort: AbortController;
   gate: ApprovalGate;
   sdkSessionId?: string;
+  /** Whether text was already streamed via stream_event deltas (to avoid duplicate from assistant message). */
+  hasStreamedText?: boolean;
 }
 
 @Injectable()
@@ -165,7 +167,7 @@ export class ClaudeAgentSdkEngine implements AgentEnginePort {
               }
             }
 
-            const events = this.mapSdkMessage(message);
+            const events = this.mapSdkMessage(message, params.sessionId);
             for (const event of events) {
               pushEvent(event);
             }
@@ -296,7 +298,7 @@ export class ClaudeAgentSdkEngine implements AgentEnginePort {
       });
 
       for await (const msg of sdkQuery) {
-        const events = this.mapSdkMessage(msg);
+        const events = this.mapSdkMessage(msg, sessionId);
         for (const event of events) {
           yield event;
         }
@@ -351,8 +353,9 @@ export class ClaudeAgentSdkEngine implements AgentEnginePort {
     return CommandRiskLevel.READ_ONLY;
   }
 
-  private mapSdkMessage(message: any): EngineStreamEvent[] {
+  private mapSdkMessage(message: any, sessionId: string): EngineStreamEvent[] {
     const events: EngineStreamEvent[] = [];
+    const session = this.activeSessions.get(sessionId);
 
     // Log every SDK message type for debugging
     if (message.type === 'stream_event') {
@@ -371,21 +374,26 @@ export class ClaudeAgentSdkEngine implements AgentEnginePort {
         const delta = streamEvent.delta;
         if (delta?.type === 'text_delta' && delta.text) {
           events.push({ type: 'text', content: delta.text });
+          if (session) session.hasStreamedText = true;
         } else if (delta?.type === 'thinking_delta' && delta.thinking) {
           events.push({ type: 'thinking', content: delta.thinking });
+          if (session) session.hasStreamedText = true;
         }
       }
       // Ignore content_block_start/stop/message_start/message_stop — they are structural
     } else if (message.type === 'assistant') {
-      // Complete assistant message — extract ALL content blocks.
-      // Text/thinking blocks are emitted here as fallback since the SDK
-      // may not always send stream_event deltas (depends on SDK version/config).
+      // Complete assistant message — extract content blocks.
+      // Skip text/thinking if already streamed via stream_event deltas to avoid duplication.
+      const alreadyStreamed = session?.hasStreamedText ?? false;
+      // Reset flag for next assistant turn
+      if (session) session.hasStreamedText = false;
+
       const content = message.message?.content;
       if (Array.isArray(content)) {
         for (const block of content) {
-          if (block.type === 'text' && block.text) {
+          if (block.type === 'text' && block.text && !alreadyStreamed) {
             events.push({ type: 'text', content: block.text });
-          } else if (block.type === 'thinking' && block.thinking) {
+          } else if (block.type === 'thinking' && block.thinking && !alreadyStreamed) {
             events.push({ type: 'thinking', content: block.thinking });
           } else if (block.type === 'tool_use') {
             events.push({