diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 86a711e4..35d2c92e 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -252,6 +252,14 @@ impl ModelClient {
                         .and_then(|v| v.to_str().ok())
                         .and_then(|s| s.parse::<u64>().ok());
 
+                    if status == StatusCode::UNAUTHORIZED {
+                        if let Some(a) = auth.as_ref() {
+                            let _ = a.refresh_token().await;
+                        }
+                        // Retry immediately with refreshed credentials.
+                        continue;
+                    }
+
                     // The OpenAI Responses endpoint returns structured JSON bodies even for 4xx/5xx
                     // errors. When we bubble early with only the HTTP status the caller sees an opaque
                     // "unexpected status 400 Bad Request" which makes debugging nearly impossible.
diff --git a/codex-rs/login/src/lib.rs b/codex-rs/login/src/lib.rs
index 327daa7e..d6fa4aef 100644
--- a/codex-rs/login/src/lib.rs
+++ b/codex-rs/login/src/lib.rs
@@ -62,6 +62,39 @@ impl CodexAuth {
         }
     }
 
+    pub async fn refresh_token(&self) -> Result<String, std::io::Error> {
+        let token_data = self
+            .get_current_token_data()
+            .ok_or(std::io::Error::other("Token data is not available."))?;
+        let token = token_data.refresh_token;
+
+        let refresh_response = try_refresh_token(token)
+            .await
+            .map_err(std::io::Error::other)?;
+
+        let updated = update_tokens(
+            &self.auth_file,
+            refresh_response.id_token,
+            refresh_response.access_token,
+            refresh_response.refresh_token,
+        )
+        .await?;
+
+        if let Ok(mut auth_lock) = self.auth_dot_json.lock() {
+            *auth_lock = Some(updated.clone());
+        }
+
+        let access = match updated.tokens {
+            Some(t) => t.access_token,
+            None => {
+                return Err(std::io::Error::other(
+                    "Token data is not available after refresh.",
+                ));
+            }
+        };
+        Ok(access)
+    }
+
     /// Loads the available auth information from the auth.json or
     /// OPENAI_API_KEY environment variable.
     pub fn from_codex_home(