fix: improve stdout/stderr handling in delegate_task function

- Saved and restored stdout/stderr to prevent redirection issues in child threads, ensuring consistent output during task delegation.
- Enhanced reliability of output handling in concurrent execution scenarios.

tools/delegate_tool.py

@@ -21,6 +21,7 @@ import io
 import json
 import logging
 import os
+import sys
 import time
 from concurrent.futures import ThreadPoolExecutor, as_completed
 from typing import Any, Dict, List, Optional
@@ -253,6 +254,11 @@ def delegate_task(
         completed_count = 0
         spinner_ref = getattr(parent_agent, '_delegate_spinner', None)
 
+        # Save stdout/stderr before the executor — redirect_stdout in child
+        # threads races on sys.stdout and can leave it as devnull permanently.
+        _saved_stdout = sys.stdout
+        _saved_stderr = sys.stderr
+
         with ThreadPoolExecutor(max_workers=MAX_CONCURRENT_CHILDREN) as executor:
             futures = {}
             for i, t in enumerate(task_list):
@@ -300,6 +306,10 @@ def delegate_task(
                     except Exception:
                         pass
 
+        # Restore stdout/stderr in case redirect_stdout race left them as devnull
+        sys.stdout = _saved_stdout
+        sys.stderr = _saved_stderr
+
         # Sort by task_index so results match input order
         results.sort(key=lambda r: r["task_index"])