diff --git a/backend/app/services/llm/deepseek_client.py b/backend/app/services/llm/deepseek_client.py
index 0e0a7f3..22ed427 100644
--- a/backend/app/services/llm/deepseek_client.py
+++ b/backend/app/services/llm/deepseek_client.py
@@ -116,14 +116,17 @@ class DeepSeekClient(BaseLLMClient):
             with self._client.stream("POST", "/chat/completions", json=payload) as response:
                 response.raise_for_status()
                 for line in response.iter_lines():
-                    if not line or line.startswith(b":"):
+                    if not line:
                         continue
 
-                    line_str = line.decode("utf-8").strip()
-                    if not line_str.startswith("data: "):
+                    line = line.strip()
+                    if line.startswith(":"):
                         continue
 
-                    data_str = line_str[6:]
+                    if not line.startswith("data: "):
+                        continue
+
+                    data_str = line[6:]
                     if data_str == "[DONE]":
                         break