Show spawned agent model and effort in TUI (#14273)

- include the requested sub-agent model and reasoning effort in the
spawn begin event\n- render that metadata next to the spawned agent name
and role in the TUI transcript

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/tui/src/chatwidget/tests.rs

@@ -58,9 +58,12 @@ use codex_protocol::protocol::AgentMessageDeltaEvent;
 use codex_protocol::protocol::AgentMessageEvent;
 use codex_protocol::protocol::AgentReasoningDeltaEvent;
 use codex_protocol::protocol::AgentReasoningEvent;
+use codex_protocol::protocol::AgentStatus;
 use codex_protocol::protocol::ApplyPatchApprovalRequestEvent;
 use codex_protocol::protocol::BackgroundEventEvent;
 use codex_protocol::protocol::CodexErrorInfo;
+use codex_protocol::protocol::CollabAgentSpawnBeginEvent;
+use codex_protocol::protocol::CollabAgentSpawnEndEvent;
 use codex_protocol::protocol::CreditsSnapshot;
 use codex_protocol::protocol::Event;
 use codex_protocol::protocol::EventMsg;
@@ -1838,6 +1841,7 @@ async fn make_chatwidget_manual(
         plan_stream_controller: None,
         last_copyable_output: None,
         running_commands: HashMap::new(),
+        pending_collab_spawn_requests: HashMap::new(),
         suppressed_exec_calls: HashSet::new(),
         skills_all: Vec::new(),
         skills_initial_state: None,
@@ -2011,6 +2015,48 @@ fn lines_to_single_string(lines: &[ratatui::text::Line<'static>]) -> String {
     s
 }
 
+#[tokio::test]
+async fn collab_spawn_end_shows_requested_model_and_effort() {
+    let (mut chat, mut rx, _ops) = make_chatwidget_manual(None).await;
+    let sender_thread_id = ThreadId::new();
+    let spawned_thread_id = ThreadId::new();
+
+    chat.handle_codex_event(Event {
+        id: "spawn-begin".into(),
+        msg: EventMsg::CollabAgentSpawnBegin(CollabAgentSpawnBeginEvent {
+            call_id: "call-spawn".to_string(),
+            sender_thread_id,
+            prompt: "Explore the repo".to_string(),
+            model: "gpt-5".to_string(),
+            reasoning_effort: ReasoningEffortConfig::High,
+        }),
+    });
+    chat.handle_codex_event(Event {
+        id: "spawn-end".into(),
+        msg: EventMsg::CollabAgentSpawnEnd(CollabAgentSpawnEndEvent {
+            call_id: "call-spawn".to_string(),
+            sender_thread_id,
+            new_thread_id: Some(spawned_thread_id),
+            new_agent_nickname: Some("Robie".to_string()),
+            new_agent_role: Some("explorer".to_string()),
+            prompt: "Explore the repo".to_string(),
+            status: AgentStatus::PendingInit,
+        }),
+    });
+
+    let cells = drain_insert_history(&mut rx);
+    let rendered = cells
+        .iter()
+        .map(|lines| lines_to_single_string(lines))
+        .collect::<Vec<_>>()
+        .join("\n");
+
+    assert!(
+        rendered.contains("Spawned Robie [explorer] (gpt-5 high)"),
+        "expected spawn line to include agent metadata and requested model, got {rendered:?}"
+    );
+}
+
 fn status_line_text(chat: &ChatWidget) -> Option<String> {
     chat.status_line_text()
 }