diff --git a/codex-rs/tui/src/app/tests.rs b/codex-rs/tui/src/app/tests.rs
index 45de2c5c24..3e5d3f741b 100644
--- a/codex-rs/tui/src/app/tests.rs
+++ b/codex-rs/tui/src/app/tests.rs
@@ -1366,65 +1366,87 @@ async fn open_agent_picker_marks_loaded_threads_open() -> Result<()> {
     Ok(())
 }
 
-#[tokio::test]
-async fn attach_live_thread_for_selection_rejects_empty_non_ephemeral_fallback_threads()
--> Result<()> {
-    let mut app = make_test_app().await;
-    let mut app_server = crate::start_embedded_app_server_for_picker(app.chat_widget.config_ref())
-        .await
-        .expect("embedded app server");
-    let started = app_server
-        .start_thread(app.chat_widget.config_ref())
-        .await?;
-    let thread_id = started.session.thread_id;
-    app.agent_navigation.upsert(
-        thread_id,
-        Some("Scout".to_string()),
-        Some("worker".to_string()),
-        /*is_closed*/ false,
-    );
+#[test]
+fn attach_live_thread_for_selection_rejects_empty_non_ephemeral_fallback_threads() -> Result<()> {
+    const WORKER_THREADS: usize = 1;
+    const TEST_STACK_SIZE_BYTES: usize = 8 * 1024 * 1024;
 
-    let err = app
-        .attach_live_thread_for_selection(&mut app_server, thread_id)
-        .await
-        .expect_err("empty fallback should not attach as a blank replay-only thread");
+    let runtime = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(WORKER_THREADS)
+        .thread_stack_size(TEST_STACK_SIZE_BYTES)
+        .enable_all()
+        .build()?;
 
-    assert_eq!(
-        err.to_string(),
-        format!("Agent thread {thread_id} is not yet available for replay or live attach.")
-    );
-    assert!(!app.thread_event_channels.contains_key(&thread_id));
-    Ok(())
+    runtime.block_on(async {
+        let config = {
+            let app = make_test_app().await;
+            app.chat_widget.config_ref().clone()
+        };
+        let mut app_server = crate::start_embedded_app_server_for_picker(&config)
+            .await
+            .expect("embedded app server");
+        let started = app_server.start_thread(&config).await?;
+        let thread_id = started.session.thread_id;
+        let mut app = make_test_app().await;
+        app.agent_navigation.upsert(
+            thread_id,
+            Some("Scout".to_string()),
+            Some("worker".to_string()),
+            /*is_closed*/ false,
+        );
+
+        let err = app
+            .attach_live_thread_for_selection(&mut app_server, thread_id)
+            .await
+            .expect_err("empty fallback should not attach as a blank replay-only thread");
+
+        assert_eq!(
+            err.to_string(),
+            format!("Agent thread {thread_id} is not yet available for replay or live attach.")
+        );
+        assert!(!app.thread_event_channels.contains_key(&thread_id));
+        Ok(())
+    })
 }
 
-#[tokio::test]
-async fn attach_live_thread_for_selection_rejects_unmaterialized_fallback_threads() -> Result<()> {
-    let mut app = make_test_app().await;
-    let mut app_server = crate::start_embedded_app_server_for_picker(app.chat_widget.config_ref())
-        .await
-        .expect("embedded app server");
-    let mut ephemeral_config = app.chat_widget.config_ref().clone();
-    ephemeral_config.ephemeral = true;
-    let started = app_server.start_thread(&ephemeral_config).await?;
-    let thread_id = started.session.thread_id;
-    app.agent_navigation.upsert(
-        thread_id,
-        Some("Scout".to_string()),
-        Some("worker".to_string()),
-        /*is_closed*/ false,
-    );
+#[test]
+fn attach_live_thread_for_selection_rejects_unmaterialized_fallback_threads() -> Result<()> {
+    const WORKER_THREADS: usize = 1;
+    const TEST_STACK_SIZE_BYTES: usize = 8 * 1024 * 1024;
 
-    let err = app
-        .attach_live_thread_for_selection(&mut app_server, thread_id)
-        .await
-        .expect_err("ephemeral fallback should not attach as a blank live thread");
+    let runtime = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(WORKER_THREADS)
+        .thread_stack_size(TEST_STACK_SIZE_BYTES)
+        .enable_all()
+        .build()?;
 
-    assert_eq!(
-        err.to_string(),
-        format!("Agent thread {thread_id} is not yet available for replay or live attach.")
-    );
-    assert!(!app.thread_event_channels.contains_key(&thread_id));
-    Ok(())
+    runtime.block_on(async {
+        let mut app = make_test_app().await;
+        let mut app_server =
+            crate::start_embedded_app_server_for_picker(app.chat_widget.config_ref()).await?;
+        let mut ephemeral_config = app.chat_widget.config_ref().clone();
+        ephemeral_config.ephemeral = true;
+        let started = app_server.start_thread(&ephemeral_config).await?;
+        let thread_id = started.session.thread_id;
+        app.agent_navigation.upsert(
+            thread_id,
+            Some("Scout".to_string()),
+            Some("worker".to_string()),
+            /*is_closed*/ false,
+        );
+
+        let err = app
+            .attach_live_thread_for_selection(&mut app_server, thread_id)
+            .await
+            .expect_err("ephemeral fallback should not attach as a blank live thread");
+
+        assert_eq!(
+            err.to_string(),
+            format!("Agent thread {thread_id} is not yet available for replay or live attach.")
+        );
+        assert!(!app.thread_event_channels.contains_key(&thread_id));
+        Ok(())
+    })
 }
 
 #[tokio::test]