diff --git a/metagpt/provider/openai_api.py b/metagpt/provider/openai_api.py
index 1d2057e50..bd9c02231 100644
--- a/metagpt/provider/openai_api.py
+++ b/metagpt/provider/openai_api.py
@@ -114,9 +114,6 @@ class OpenAILLM(BaseLLM):
                 elif hasattr(chunk.choices[0], "usage"):
                     # The usage of some services is an attribute of chunk.choices[0], such as Moonshot
                     usage = CompletionUsage(**chunk.choices[0].usage)
-                elif "openrouter.ai" in self.config.base_url and chunk_has_usage:
-                    # due to it get token cost from api
-                    usage = chunk.usage
                 has_finished = True
 
         log_llm_stream("\n")
diff --git a/metagpt/utils/mmdc_playwright.py b/metagpt/utils/mmdc_playwright.py
index e7e6e3b2e..53d2c4a2b 100644
--- a/metagpt/utils/mmdc_playwright.py
+++ b/metagpt/utils/mmdc_playwright.py
@@ -81,10 +81,13 @@ async def mermaid_to_file(mermaid_code, output_file_without_suffix, width=2048,
             if "svg" in suffixes:
                 svg_xml = await page.evaluate(
                     """() => {
-                    const svg = document.querySelector('svg');
-                    const xmlSerializer = new XMLSerializer();
-                    return xmlSerializer.serializeToString(svg);
-                }"""
+                        const svg = document.querySelector('svg');
+                        if (!svg) {
+                            throw new Error('SVG element not found');
+                        }
+                        const xmlSerializer = new XMLSerializer();
+                        return xmlSerializer.serializeToString(svg);
+                    }"""
                 )
                 logger.info(f"Generating {output_file_without_suffix}.svg..")
                 with open(f"{output_file_without_suffix}.svg", "wb") as f:
diff --git a/requirements.txt b/requirements.txt
index 5344ffb8c..36cf4350e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -81,4 +81,6 @@ volcengine-python-sdk[ark]~=1.0.94 # Solution for installation error in Windows:
 gymnasium==0.29.1
 boto3~=1.34.69
 spark_ai_python~=0.3.30
-agentops
\ No newline at end of file
+agentops
+tree_sitter~=0.23.2
+tree_sitter_python~=0.23.2