fix(delegate): default inherit_mcp_toolsets=true, drop version bump

Follow-up on helix4u's PR #14211:
- Flip default to true: narrowing toolsets=['web','browser'] expresses
  'I want these extras', not 'silently strip MCP'. Parent MCP tools
  (registered at runtime) should survive narrowing by default.
- Drop _config_version bump (22->23); additive nested key under
  delegation.* is handled by _deep_merge, no migration needed.
- Update tests to reflect new default behavior.

cli-config.yaml.example

@@ -776,7 +776,7 @@ delegation:
   # max_concurrent_children: 3                # Max parallel child agents (default: 3)
   # max_spawn_depth: 1                        # Tree depth cap (1-3, default: 1 = flat). Raise to 2 or 3 to allow orchestrator children to spawn their own workers.
   # orchestrator_enabled: true                # Kill switch for role="orchestrator" children (default: true).
-  # inherit_mcp_toolsets: true                # When explicit child toolsets are narrowed, also keep the parent's MCP toolsets (default: false).
+  # inherit_mcp_toolsets: true                # When explicit child toolsets are narrowed, also keep the parent's MCP toolsets (default: true). Set false for strict intersection.
   # model: "google/gemini-3-flash-preview"    # Override model for subagents (empty = inherit parent)
   # provider: "openrouter"                    # Override provider for subagents (empty = inherit parent)
   #                                           # Resolves full credentials (base_url, api_key) automatically.

hermes_cli/config.py

@@ -713,9 +713,11 @@ DEFAULT_CONFIG = {
         "base_url": "",    # direct OpenAI-compatible endpoint for subagents
         "api_key": "",     # API key for delegation.base_url (falls back to OPENAI_API_KEY)
         # When delegate_task narrows child toolsets explicitly, preserve any
-        # MCP toolsets the parent already has enabled. Off by default so
-        # narrowed child toolsets stay strict unless the operator opts in.
-        "inherit_mcp_toolsets": False,
+        # MCP toolsets the parent already has enabled. On by default so
+        # narrowing (e.g. toolsets=["web","browser"]) expresses "I want these
+        # extras" without silently stripping MCP tools the parent already has.
+        # Set to false for strict intersection.
+        "inherit_mcp_toolsets": True,
         "max_iterations": 50,  # per-subagent iteration cap (each subagent gets its own budget,
                                # independent of the parent's max_iterations)
         "reasoning_effort": "",  # reasoning effort for subagents: "xhigh", "high", "medium",
@@ -927,7 +929,7 @@ DEFAULT_CONFIG = {
     },
 
     # Config schema version - bump this when adding new required fields
-    "_config_version": 23,
+    "_config_version": 22,
 }
 
 # =============================================================================

tests/tools/test_delegate.py

@@ -1059,35 +1059,7 @@ class TestChildCredentialPoolResolution(unittest.TestCase):
             self.assertEqual(mock_child._credential_pool, mock_pool)
 
     @patch("tools.delegate_tool._load_config", return_value={})
-    def test_build_child_agent_does_not_preserve_mcp_toolsets_by_default(self, mock_cfg):
-        parent = _make_mock_parent()
-        parent.enabled_toolsets = ["web", "browser", "mcp-MiniMax"]
-
-        with patch("run_agent.AIAgent") as MockAgent:
-            mock_child = MagicMock()
-            MockAgent.return_value = mock_child
-
-            _build_child_agent(
-                task_index=0,
-                goal="Test narrowed toolsets",
-                context=None,
-                toolsets=["web", "browser"],
-                model=None,
-                max_iterations=10,
-                parent_agent=parent,
-                task_count=1,
-            )
-
-        self.assertEqual(
-            MockAgent.call_args[1]["enabled_toolsets"],
-            ["web", "browser"],
-        )
-
-    @patch(
-        "tools.delegate_tool._load_config",
-        return_value={"inherit_mcp_toolsets": True},
-    )
-    def test_build_child_agent_can_preserve_parent_mcp_toolsets(self, mock_cfg):
+    def test_build_child_agent_preserves_mcp_toolsets_by_default(self, mock_cfg):
         parent = _make_mock_parent()
         parent.enabled_toolsets = ["web", "browser", "mcp-MiniMax"]
 
@@ -1111,6 +1083,34 @@ class TestChildCredentialPoolResolution(unittest.TestCase):
             ["web", "browser", "mcp-MiniMax"],
         )
 
+    @patch(
+        "tools.delegate_tool._load_config",
+        return_value={"inherit_mcp_toolsets": False},
+    )
+    def test_build_child_agent_strict_intersection_when_opted_out(self, mock_cfg):
+        parent = _make_mock_parent()
+        parent.enabled_toolsets = ["web", "browser", "mcp-MiniMax"]
+
+        with patch("run_agent.AIAgent") as MockAgent:
+            mock_child = MagicMock()
+            MockAgent.return_value = mock_child
+
+            _build_child_agent(
+                task_index=0,
+                goal="Test narrowed toolsets",
+                context=None,
+                toolsets=["web", "browser"],
+                model=None,
+                max_iterations=10,
+                parent_agent=parent,
+                task_count=1,
+            )
+
+        self.assertEqual(
+            MockAgent.call_args[1]["enabled_toolsets"],
+            ["web", "browser"],
+        )
+
 
 class TestChildCredentialLeasing(unittest.TestCase):
     def test_run_single_child_acquires_and_releases_lease(self):

tools/delegate_tool.py

@@ -379,7 +379,7 @@ def _get_orchestrator_enabled() -> bool:
 def _get_inherit_mcp_toolsets() -> bool:
     """Whether narrowed child toolsets should keep the parent's MCP toolsets."""
     cfg = _load_config()
-    return is_truthy_value(cfg.get("inherit_mcp_toolsets"), default=False)
+    return is_truthy_value(cfg.get("inherit_mcp_toolsets"), default=True)
 
 
 def _is_mcp_toolset_name(name: str) -> bool: