diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 2fe33cf531..86a711e436 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -332,6 +332,10 @@ impl ModelClient {
     pub fn get_reasoning_summary(&self) -> ReasoningSummaryConfig {
         self.summary
     }
+
+    pub fn get_auth(&self) -> Option<CodexAuth> {
+        self.auth.clone()
+    }
 }
 
 #[derive(Debug, Deserialize, Serialize)]
diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index bd553c6ff7..397246a7de 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -1022,6 +1022,7 @@ async fn submission_loop(
                 let effective_effort = effort.unwrap_or(prev.client.get_reasoning_effort());
                 let effective_summary = summary.unwrap_or(prev.client.get_reasoning_summary());
 
+                let auth = prev.client.get_auth();
                 // Build updated config for the client
                 let mut updated_config = (*config).clone();
                 updated_config.model = effective_model.clone();
@@ -1029,7 +1030,7 @@ async fn submission_loop(
 
                 let client = ModelClient::new(
                     Arc::new(updated_config),
-                    None,
+                    auth,
                     provider,
                     effective_effort,
                     effective_summary,