diff --git a/crates/language_models/src/provider/open_ai.rs b/crates/language_models/src/provider/open_ai.rs
index 2879b01ff3..9eac58c880 100644
--- a/crates/language_models/src/provider/open_ai.rs
+++ b/crates/language_models/src/provider/open_ai.rs
@@ -473,6 +473,7 @@ pub fn into_open_ai(
         } else {
             None
         },
+        prompt_cache_key: request.thread_id,
         tools: request
             .tools
             .into_iter()
diff --git a/crates/open_ai/src/open_ai.rs b/crates/open_ai/src/open_ai.rs
index a6fd03a296..919b1d9ebf 100644
--- a/crates/open_ai/src/open_ai.rs
+++ b/crates/open_ai/src/open_ai.rs
@@ -244,6 +244,8 @@ pub struct Request {
     pub parallel_tool_calls: Option<bool>,
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub tools: Vec<ToolDefinition>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub prompt_cache_key: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]