diff --git a/scripts/release.py b/scripts/release.py
index a76dc642c27..084e960f495 100755
--- a/scripts/release.py
+++ b/scripts/release.py
@@ -45,6 +45,7 @@ ACP_REGISTRY_MANIFEST = REPO_ROOT / "acp_registry" / "agent.json"
 
 # Auto-extracted from noreply emails + manual overrides
 AUTHOR_MAP = {
+    "phanvanhoa@gmail.com": "theAgenticBuilder",  # PR #14180 salvage (route delegate_task progress lines through _safe_print so ACP stdio JSON-RPC frames stay clean)
     "cypher@augmentl.com": "Nickperillo",  # PR #8008 salvage (Discord channel-name matching + flush pending sends on shutdown)
     "tenoryang@outlook.com": "MarioYounger",  # PR #9028 salvage (bash/sh heredoc approval, NFKC homograph fold, execute_code CREDS/BEARER/APIKEY env filter)
     "peet.wannasarnmetha@gmail.com": "peetwan",  # PR #51841 salvage (loopback ws-ping tuning + token-frame coalescing + loop heartbeat; #48445/#50005)
diff --git a/tests/tools/test_delegate_toolset_scope.py b/tests/tools/test_delegate_toolset_scope.py
index 175cd8f6485..fd90dc1b561 100644
--- a/tests/tools/test_delegate_toolset_scope.py
+++ b/tests/tools/test_delegate_toolset_scope.py
@@ -8,7 +8,7 @@ arbitrary toolsets.
 
 from types import SimpleNamespace
 
-from tools.delegate_tool import _strip_blocked_tools
+from tools.delegate_tool import _strip_blocked_tools, _emit_parent_console
 
 
 class TestToolsetIntersection:
@@ -63,3 +63,44 @@ class TestToolsetIntersection:
         scoped = [t for t in requested if t in parent_toolsets]
 
         assert scoped == []
+
+
+class TestEmitParentConsole:
+    """Progress lines (e.g. ``✓ [N/M] …``) must route through the parent's
+    configured ``_safe_print`` in headless stdio hosts (ACP, gateway) so
+    they don't land on stdout and corrupt JSON-RPC frames. Regression for a
+    bug where delegate_task completion lines pushed to stdout caused
+    ``Failed to parse JSON message: ✓ [3/3] …`` errors in the ACP adapter."""
+
+    def test_routes_through_parent_safe_print_when_available(self, capsys):
+        captured_lines = []
+        parent = SimpleNamespace(_safe_print=lambda line: captured_lines.append(line))
+
+        _emit_parent_console(parent, "  ✓ [1/3] Research done  (11.55s)")
+
+        assert captured_lines == ["  ✓ [1/3] Research done  (11.55s)"]
+        stdout_stderr = capsys.readouterr()
+        assert stdout_stderr.out == ""
+        assert stdout_stderr.err == ""
+
+    def test_falls_back_to_stdout_when_no_safe_print(self, capsys):
+        parent = SimpleNamespace()
+        _emit_parent_console(parent, "  ✓ [1/3] fallback path")
+        captured = capsys.readouterr()
+        assert "fallback path" in captured.out
+
+    def test_falls_back_to_stdout_when_safe_print_raises(self, capsys):
+        def raiser(_line):
+            raise RuntimeError("boom")
+
+        parent = SimpleNamespace(_safe_print=raiser)
+        _emit_parent_console(parent, "  ✓ [2/3] fallback on exception")
+        captured = capsys.readouterr()
+        assert "fallback on exception" in captured.out
+
+    def test_non_callable_safe_print_is_ignored(self, capsys):
+        """Defensive: if _safe_print is set but not callable, fall back."""
+        parent = SimpleNamespace(_safe_print="not-a-function")
+        _emit_parent_console(parent, "  ✓ [3/3] non-callable guard")
+        captured = capsys.readouterr()
+        assert "non-callable guard" in captured.out
diff --git a/tools/delegate_tool.py b/tools/delegate_tool.py
index 49a76318254..7bd510d7f5f 100644
--- a/tools/delegate_tool.py
+++ b/tools/delegate_tool.py
@@ -800,6 +800,24 @@ def _strip_blocked_tools(toolsets: List[str]) -> List[str]:
     return [t for t in toolsets if t not in blocked_toolset_names]
 
 
+def _emit_parent_console(parent_agent, line: str) -> None:
+    """Emit a human-readable progress line to the parent's console.
+
+    Routes through ``parent_agent._safe_print`` when available so headless
+    stdio hosts (ACP, gateway API) can redirect non-protocol output to
+    stderr via their configured ``_print_fn``. A bare ``print()`` would
+    otherwise land on stdout and corrupt JSON-RPC framing.
+    """
+    printer = getattr(parent_agent, "_safe_print", None)
+    if callable(printer):
+        try:
+            printer(line)
+            return
+        except Exception:
+            pass
+    print(line)
+
+
 def _build_child_progress_callback(
     task_index: int,
     goal: str,
@@ -2610,9 +2628,9 @@ def delegate_task(
                             try:
                                 spinner_ref.print_above(completion_line)
                             except Exception:
-                                print(f"  {completion_line}")
+                                _emit_parent_console(parent_agent, f"  {completion_line}")
                         else:
-                            print(f"  {completion_line}")
+                            _emit_parent_console(parent_agent, f"  {completion_line}")
 
                         # Update spinner text to show remaining count
                         if spinner_ref and remaining > 0: