diff --git a/codex-rs/models-manager/src/model_info_overrides_tests.rs b/codex-rs/models-manager/src/model_info_overrides_tests.rs
index 1e5b5dcf4..392b0c846 100644
--- a/codex-rs/models-manager/src/model_info_overrides_tests.rs
+++ b/codex-rs/models-manager/src/model_info_overrides_tests.rs
@@ -32,8 +32,10 @@ async fn offline_model_info_without_tool_output_override() {
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn offline_model_info_with_tool_output_override() {
     let codex_home = TempDir::new().expect("create temp dir");
-    let mut config = ModelsManagerConfig::default();
-    config.tool_output_token_limit = Some(123);
+    let config = ModelsManagerConfig {
+        tool_output_token_limit: Some(123),
+        ..Default::default()
+    };
     let auth_manager =
         AuthManager::from_auth_for_testing(CodexAuth::create_dummy_chatgpt_auth_for_testing());
     let manager = ModelsManager::new(
diff --git a/codex-rs/models-manager/src/model_info_tests.rs b/codex-rs/models-manager/src/model_info_tests.rs
index 61dac6d7c..ec5b6ed85 100644
--- a/codex-rs/models-manager/src/model_info_tests.rs
+++ b/codex-rs/models-manager/src/model_info_tests.rs
@@ -5,8 +5,10 @@ use pretty_assertions::assert_eq;
 #[test]
 fn reasoning_summaries_override_true_enables_support() {
     let model = model_info_from_slug("unknown-model");
-    let mut config = ModelsManagerConfig::default();
-    config.model_supports_reasoning_summaries = Some(true);
+    let config = ModelsManagerConfig {
+        model_supports_reasoning_summaries: Some(true),
+        ..Default::default()
+    };
 
     let updated = with_config_overrides(model.clone(), &config);
     let mut expected = model;
@@ -19,8 +21,10 @@ fn reasoning_summaries_override_true_enables_support() {
 fn reasoning_summaries_override_false_does_not_disable_support() {
     let mut model = model_info_from_slug("unknown-model");
     model.supports_reasoning_summaries = true;
-    let mut config = ModelsManagerConfig::default();
-    config.model_supports_reasoning_summaries = Some(false);
+    let config = ModelsManagerConfig {
+        model_supports_reasoning_summaries: Some(false),
+        ..Default::default()
+    };
 
     let updated = with_config_overrides(model.clone(), &config);
 
@@ -30,8 +34,10 @@ fn reasoning_summaries_override_false_does_not_disable_support() {
 #[test]
 fn reasoning_summaries_override_false_is_noop_when_model_is_false() {
     let model = model_info_from_slug("unknown-model");
-    let mut config = ModelsManagerConfig::default();
-    config.model_supports_reasoning_summaries = Some(false);
+    let config = ModelsManagerConfig {
+        model_supports_reasoning_summaries: Some(false),
+        ..Default::default()
+    };
 
     let updated = with_config_overrides(model.clone(), &config);