diff --git a/codex-rs/core/src/models_manager/collaboration_mode_presets.rs b/codex-rs/core/src/models_manager/collaboration_mode_presets.rs
index b7efe156f..aff111b1a 100644
--- a/codex-rs/core/src/models_manager/collaboration_mode_presets.rs
+++ b/codex-rs/core/src/models_manager/collaboration_mode_presets.rs
@@ -27,7 +27,7 @@ fn plan_preset() -> CollaborationModeMask {
     CollaborationModeMask {
         name: "Plan".to_string(),
         mode: Some(ModeKind::Plan),
-        model: Some("gpt-5.2-codex".to_string()),
+        model: None,
         reasoning_effort: Some(Some(ReasoningEffort::High)),
         developer_instructions: Some(Some(COLLABORATION_MODE_PLAN.to_string())),
     }
@@ -37,8 +37,8 @@ fn code_preset() -> CollaborationModeMask {
     CollaborationModeMask {
         name: "Code".to_string(),
         mode: Some(ModeKind::Code),
-        model: Some("gpt-5.2-codex".to_string()),
-        reasoning_effort: Some(Some(ReasoningEffort::Medium)),
+        model: None,
+        reasoning_effort: None,
         developer_instructions: Some(Some(COLLABORATION_MODE_CODE.to_string())),
     }
 }
@@ -47,7 +47,7 @@ fn pair_programming_preset() -> CollaborationModeMask {
     CollaborationModeMask {
         name: "Pair Programming".to_string(),
         mode: Some(ModeKind::PairProgramming),
-        model: Some("gpt-5.2-codex".to_string()),
+        model: None,
         reasoning_effort: Some(Some(ReasoningEffort::Medium)),
         developer_instructions: Some(Some(COLLABORATION_MODE_PAIR_PROGRAMMING.to_string())),
     }
@@ -57,7 +57,7 @@ fn execute_preset() -> CollaborationModeMask {
     CollaborationModeMask {
         name: "Execute".to_string(),
         mode: Some(ModeKind::Execute),
-        model: Some("gpt-5.2-codex".to_string()),
+        model: None,
         reasoning_effort: Some(Some(ReasoningEffort::High)),
         developer_instructions: Some(Some(COLLABORATION_MODE_EXECUTE.to_string())),
     }
diff --git a/codex-rs/tui/src/chatwidget.rs b/codex-rs/tui/src/chatwidget.rs
index 1252b792e..ce87b33ee 100644
--- a/codex-rs/tui/src/chatwidget.rs
+++ b/codex-rs/tui/src/chatwidget.rs
@@ -4662,8 +4662,10 @@ impl ChatWidget {
         if !config.features.enabled(Feature::CollaborationModes) {
             return None;
         }
-        let kind = config.experimental_mode?;
-        let mut mask = collaboration_modes::mask_for_kind(models_manager, kind)?;
+        let mut mask = match config.experimental_mode {
+            Some(kind) => collaboration_modes::mask_for_kind(models_manager, kind)?,
+            None => collaboration_modes::default_mask(models_manager)?,
+        };
         if let Some(model_override) = model_override {
             mask.model = Some(model_override.to_string());
         }
diff --git a/codex-rs/tui/src/chatwidget/tests.rs b/codex-rs/tui/src/chatwidget/tests.rs
index 9eff1b2f4..e76abdbd7 100644
--- a/codex-rs/tui/src/chatwidget/tests.rs
+++ b/codex-rs/tui/src/chatwidget/tests.rs
@@ -2273,6 +2273,44 @@ async fn collab_slash_command_opens_picker_and_updates_mode() {
     }
 }
 
+#[tokio::test]
+async fn collaboration_modes_defaults_to_code_on_startup() {
+    let codex_home = tempdir().expect("tempdir");
+    let cfg = ConfigBuilder::default()
+        .codex_home(codex_home.path().to_path_buf())
+        .cli_overrides(vec![(
+            "features.collaboration_modes".to_string(),
+            TomlValue::Boolean(true),
+        )])
+        .build()
+        .await
+        .expect("config");
+    let resolved_model = ModelsManager::get_model_offline(cfg.model.as_deref());
+    let otel_manager = test_otel_manager(&cfg, resolved_model.as_str());
+    let thread_manager = Arc::new(ThreadManager::with_models_provider(
+        CodexAuth::from_api_key("test"),
+        cfg.model_provider.clone(),
+    ));
+    let auth_manager = AuthManager::from_auth_for_testing(CodexAuth::from_api_key("test"));
+    let init = ChatWidgetInit {
+        config: cfg,
+        frame_requester: FrameRequester::test_dummy(),
+        app_event_tx: AppEventSender::new(unbounded_channel::<AppEvent>().0),
+        initial_user_message: None,
+        enhanced_keys_supported: false,
+        auth_manager,
+        models_manager: thread_manager.get_models_manager(),
+        feedback: codex_feedback::CodexFeedback::new(),
+        is_first_run: true,
+        model: Some(resolved_model.clone()),
+        otel_manager,
+    };
+
+    let chat = ChatWidget::new(init, thread_manager);
+    assert_eq!(chat.active_collaboration_mode_kind(), ModeKind::Code);
+    assert_eq!(chat.current_model(), resolved_model);
+}
+
 #[tokio::test]
 async fn experimental_mode_plan_applies_on_startup() {
     let codex_home = tempdir().expect("tempdir");