diff --git a/tests/tools/test_delegate.py b/tests/tools/test_delegate.py
index e1e119d919..762654a259 100644
--- a/tests/tools/test_delegate.py
+++ b/tests/tools/test_delegate.py
@@ -903,6 +903,45 @@ class TestDelegationProviderIntegration(unittest.TestCase):
                 self.assertEqual(call.kwargs.get("override_api_key"), "sk-or-batch")
                 self.assertEqual(call.kwargs.get("override_api_mode"), "chat_completions")
 
+    @patch("tools.delegate_tool._load_config")
+    @patch("tools.delegate_tool._resolve_delegation_credentials")
+    def test_delegation_acp_runtime_reaches_child_agent(self, mock_creds, mock_cfg):
+        """Resolved ACP runtime command/args must be forwarded to child agents."""
+        mock_cfg.return_value = {
+            "max_iterations": 45,
+            "model": "copilot-model",
+            "provider": "copilot-acp",
+        }
+        mock_creds.return_value = {
+            "model": "copilot-model",
+            "provider": "copilot-acp",
+            "base_url": "acp://copilot",
+            "api_key": "copilot-acp",
+            "api_mode": "chat_completions",
+            "command": "custom-copilot",
+            "args": ["--stdio-custom"],
+        }
+        parent = _make_mock_parent(depth=0)
+
+        with patch("tools.delegate_tool._build_child_agent") as mock_build, \
+             patch("tools.delegate_tool._run_single_child") as mock_run:
+            mock_child = MagicMock()
+            mock_build.return_value = mock_child
+            mock_run.return_value = {
+                "task_index": 0, "status": "completed",
+                "summary": "Done", "api_calls": 1, "duration_seconds": 1.0
+            }
+
+            delegate_task(goal="ACP delegation test", parent_agent=parent)
+
+            _, kwargs = mock_build.call_args
+            self.assertEqual(kwargs.get("override_provider"), "copilot-acp")
+            self.assertEqual(kwargs.get("override_base_url"), "acp://copilot")
+            self.assertEqual(kwargs.get("override_api_key"), "copilot-acp")
+            self.assertEqual(kwargs.get("override_api_mode"), "chat_completions")
+            self.assertEqual(kwargs.get("override_acp_command"), "custom-copilot")
+            self.assertEqual(kwargs.get("override_acp_args"), ["--stdio-custom"])
+
     @patch("tools.delegate_tool._load_config")
     @patch("tools.delegate_tool._resolve_delegation_credentials")
     def test_model_only_no_provider_inherits_parent_credentials(self, mock_creds, mock_cfg):
diff --git a/tools/delegate_tool.py b/tools/delegate_tool.py
index 22b132f2c4..1db6c08622 100644
--- a/tools/delegate_tool.py
+++ b/tools/delegate_tool.py
@@ -768,6 +768,7 @@ def delegate_task(
     children = []
     try:
         for i, t in enumerate(task_list):
+            task_acp_args = t.get("acp_args") if "acp_args" in t else None
             child = _build_child_agent(
                 task_index=i, goal=t["goal"], context=t.get("context"),
                 toolsets=t.get("toolsets") or toolsets, model=creds["model"],
@@ -775,8 +776,10 @@ def delegate_task(
                 override_provider=creds["provider"], override_base_url=creds["base_url"],
                 override_api_key=creds["api_key"],
                 override_api_mode=creds["api_mode"],
-                override_acp_command=t.get("acp_command") or acp_command,
-                override_acp_args=t.get("acp_args") or acp_args,
+                override_acp_command=t.get("acp_command") or acp_command or creds.get("command"),
+                override_acp_args=task_acp_args if task_acp_args is not None else (
+                    acp_args if acp_args is not None else creds.get("args")
+                ),
             )
             # Override with correct parent tool names (before child construction mutated global)
             child._delegate_saved_tool_names = _parent_tool_names