fix(tui): hold subagent cap until status reconciles

(cherry picked from commit 5f01dda291e8354e779cc9220f38754fe0c3786f)

crates/tui/src/tools/subagent/mod.rs

@@ -1249,11 +1249,13 @@ impl SubAgentManager {
                     return false;
                 }
                 // Exclude persisted agents with no task_handle (they're not actually running)
-                let Some(handle) = agent.task_handle.as_ref() else {
+                if agent.task_handle.is_none() {
                     return false;
-                };
-                // Exclude agents whose task has finished (status will be updated to Completed shortly)
-                !handle.is_finished()
+                }
+                // Keep recently finished handles counted until the terminal
+                // status update has reconciled. Otherwise a fanout burst can
+                // refill the cap before the UI/state catches up (#2211).
+                true
             })
             .count()
     }

crates/tui/src/tools/subagent/tests.rs

@@ -938,7 +938,7 @@ fn test_running_count_ignores_running_status_without_task_handle() {
 }
 
 #[tokio::test]
-async fn test_running_count_ignores_finished_task_handles() {
+async fn test_running_count_counts_running_agents_until_status_reconciles() {
     let mut manager = SubAgentManager::new(PathBuf::from("."), 1);
     let (input_tx, _input_rx) = mpsc::unbounded_channel();
     let mut agent = SubAgent::new(
@@ -953,17 +953,14 @@ async fn test_running_count_ignores_finished_task_handles() {
         "boot_test".to_string(),
     );
     agent.status = SubAgentStatus::Running;
-    let handle = tokio::spawn(async {});
-    handle.await.expect("dummy task should finish immediately");
-    agent.task_handle = Some(tokio::spawn(async {}));
-    if let Some(handle) = agent.task_handle.as_ref() {
-        while !handle.is_finished() {
-            tokio::task::yield_now().await;
-        }
+    let finished_handle = tokio::spawn(async {});
+    while !finished_handle.is_finished() {
+        tokio::task::yield_now().await;
     }
+    agent.task_handle = Some(finished_handle);
     manager.agents.insert(agent.id.clone(), agent);
 
-    assert_eq!(manager.running_count(), 0);
+    assert_eq!(manager.running_count(), 1);
 }
 
 #[test]