Remove default system prompt, fix media_start token and update readme

README.md

@@ -29,6 +29,11 @@ pipeline_tag: image-text-to-text
 <b>📰&nbsp;&nbsp;<a href="https://www.kimi.com/blog/kimi-k2-5.html">Tech Blog</a></b>
 </p>
 
+## 0. Changelog
+- 2026.1.29: 
+    - The default system prompt might cause confusion to users and unexpected behaviours, so we remove it.
+    - The token `<|media_start|>` is incorrect; it has been replaced with `<|media_begin|>` in the chat template.
+
 ## 1. Model Introduction
 
 Kimi K2.5 is an open-source, native multimodal agentic model built through continual pretraining on approximately 15 trillion mixed visual and text tokens atop Kimi-K2-Base. It seamlessly integrates vision and language understanding with advanced agentic capabilities, instant and thinking modes, as well as conversational and agentic paradigms.

chat_template.jinja

@@ -5,7 +5,7 @@
     {%- elif c is not none -%}
       {% for content in c -%}
         {% if content['type'] == 'image' or content['type'] == 'image_url' -%}
-          <|media_start|>image<|media_content|><|media_pad|><|media_end|>
+          <|media_begin|>image<|media_content|><|media_pad|><|media_end|>
         {% elif content['type'] == 'video' or content['type']== 'video_url'-%}
           <|kimi_k25_video_placeholder|>
         {% else -%}
@@ -57,10 +57,6 @@
     <|im_system|>tool_declare<|im_middle|>{{ tools | tojson(separators=(',', ':')) }}<|im_end|>
   {%- endif -%}
 {%- endif -%}
-
-{%- if messages|length == 0 or messages[0]['role'] != 'system' -%}
-  <|im_system|>system<|im_middle|>You are Kimi, an AI assistant created by Moonshot AI.<|im_end|>
-{%- endif -%}
   
 {%- for message in hist_msgs -%}
   {{set_roles(message)}}