diff --git a/codex-rs/tui/src/app_server_session.rs b/codex-rs/tui/src/app_server_session.rs
index 0280628e29..ee6e92666f 100644
--- a/codex-rs/tui/src/app_server_session.rs
+++ b/codex-rs/tui/src/app_server_session.rs
@@ -1944,7 +1944,7 @@ fn new_thread_reasoning_overrides(config: &Config) -> Option<HashMap<String, ser
     let mut overrides = config_request_overrides_from_config(config).unwrap_or_default();
     let summary = config
         .model_reasoning_summary
-        .unwrap_or(codex_protocol::config_types::ReasoningSummary::Detailed);
+        .unwrap_or(codex_protocol::config_types::ReasoningSummary::None);
     overrides.insert(
         "model_reasoning_summary".to_string(),
         serde_json::Value::String(summary.to_string()),
diff --git a/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs b/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
index 40c65d9c4e..d57115a686 100644
--- a/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
+++ b/codex-rs/tui/src/app_server_session/reasoning_defaults_tests.rs
@@ -10,14 +10,24 @@ use serde_json::json;
 #[tokio::test]
 async fn embedded_reasoning_defaults_reach_responses() -> Result<()> {
     for (settings, summary, stream_options) in [
-        ("", json!("detailed"), json!(null)),
+        ("", json!(null), json!(null)),
         (
             "[features]\nconcurrent_reasoning_summaries = false",
-            json!("detailed"),
+            json!(null),
             json!(null),
         ),
         (
             "[features]\nconcurrent_reasoning_summaries = true",
+            json!(null),
+            json!(null),
+        ),
+        (
+            "model_reasoning_summary = 'detailed'",
+            json!("detailed"),
+            json!(null),
+        ),
+        (
+            "model_reasoning_summary = 'detailed'\n[features]\nconcurrent_reasoning_summaries = true",
             json!("detailed"),
             json!({"reasoning_summary_delivery": "sequential_cutoff"}),
         ),
@@ -102,12 +112,19 @@ stream_max_retries = 0
 }
 
 #[tokio::test]
-async fn new_tui_threads_request_summaries_unless_explicitly_disabled() {
+async fn new_tui_threads_disable_summaries_unless_explicitly_enabled() {
     let temp_dir = tempfile::tempdir().expect("tempdir");
     for (config_text, expected_summary, expected_concurrent) in [
-        ("", "detailed", false),
+        ("", "none", false),
         (
             "[features]\nconcurrent_reasoning_summaries = true",
+            "none",
+            false,
+        ),
+        ("model_reasoning_summary = 'auto'", "auto", false),
+        ("model_reasoning_summary = 'detailed'", "detailed", false),
+        (
+            "model_reasoning_summary = 'detailed'\n[features]\nconcurrent_reasoning_summaries = true",
             "detailed",
             true,
         ),