diff --git a/lightrag/operate.py b/lightrag/operate.py
index 5f824af0..521e8b03 100644
--- a/lightrag/operate.py
+++ b/lightrag/operate.py
@@ -2832,9 +2832,11 @@ async def extract_entities(
         cache_keys_collector = []
 
         # Get initial extraction
+        # Format system prompt once without input_text for OpenAI prompt caching
         entity_extraction_system_prompt = PROMPTS[
             "entity_extraction_system_prompt"
-        ].format(**{**context_base, "input_text": content})
+        ].format(**context_base)
+        # Format user prompts with input_text for each chunk
         entity_extraction_user_prompt = PROMPTS["entity_extraction_user_prompt"].format(
             **{**context_base, "input_text": content}
         )
diff --git a/lightrag/prompt.py b/lightrag/prompt.py
index bf514fe8..cfa5b76f 100644
--- a/lightrag/prompt.py
+++ b/lightrag/prompt.py
@@ -62,14 +62,16 @@ You are a Knowledge Graph Specialist responsible for extracting entities and rel
 ---Real Data to be Processed---
 <Input>
 Entity_types: [{entity_types}]
+"""
+
+PROMPTS["entity_extraction_user_prompt"] = """---Task---
+Extract entities and relationships from the following input text.
+
+---Input Text---
 Text:
 ```
 {input_text}
 ```
-"""
-
-PROMPTS["entity_extraction_user_prompt"] = """---Task---
-Extract entities and relationships from the input text to be processed.
 
 ---Instructions---
 1.  **Strict Adherence to Format:** Strictly adhere to all format requirements for entity and relationship lists, including output order, field delimiters, and proper noun handling, as specified in the system prompt.