diff --git a/codex-rs/Cargo.lock b/codex-rs/Cargo.lock
index 0d8522a67b..a2e49fc506 100644
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -853,6 +853,7 @@ dependencies = [
  "pretty_assertions",
  "serde",
  "serde_json",
+ "serial_test",
  "tempfile",
  "tokio",
  "toml",
diff --git a/codex-rs/app-server/Cargo.toml b/codex-rs/app-server/Cargo.toml
index 5efbefd6b0..c1efb2ef93 100644
--- a/codex-rs/app-server/Cargo.toml
+++ b/codex-rs/app-server/Cargo.toml
@@ -47,6 +47,7 @@ base64 = { workspace = true }
 core_test_support = { workspace = true }
 os_info = { workspace = true }
 pretty_assertions = { workspace = true }
+serial_test = { workspace = true }
 tempfile = { workspace = true }
 toml = { workspace = true }
 wiremock = { workspace = true }
diff --git a/codex-rs/app-server/tests/suite/login.rs b/codex-rs/app-server/tests/suite/login.rs
index 220769b7d6..d4d6374bc4 100644
--- a/codex-rs/app-server/tests/suite/login.rs
+++ b/codex-rs/app-server/tests/suite/login.rs
@@ -13,6 +13,7 @@ use codex_app_server_protocol::LoginChatGptResponse;
 use codex_app_server_protocol::LogoutChatGptResponse;
 use codex_app_server_protocol::RequestId;
 use codex_login::login_with_api_key;
+use serial_test::serial;
 use tempfile::TempDir;
 use tokio::time::timeout;
 
@@ -94,6 +95,8 @@ async fn logout_chatgpt_removes_auth() {
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+// Serialize tests that launch the login server since it binds to a fixed port.
+#[serial(login_port)]
 async fn login_and_cancel_chatgpt() {
     let codex_home = TempDir::new().unwrap_or_else(|e| panic!("create tempdir: {e}"));
     create_config_toml(codex_home.path()).unwrap_or_else(|err| panic!("write config.toml: {err}"));
@@ -208,6 +211,8 @@ async fn login_chatgpt_rejected_when_forced_api() {
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+// Serialize tests that launch the login server since it binds to a fixed port.
+#[serial(login_port)]
 async fn login_chatgpt_includes_forced_workspace_query_param() {
     let codex_home = TempDir::new().unwrap_or_else(|e| panic!("create tempdir: {e}"));
     create_config_toml_forced_workspace(codex_home.path(), "ws-forced")