fix(delegation): honor provider override for subagents

Clear inherited provider preference filters when delegation.provider is set so delegated children do not route back to the parent provider. Add a regression test for cross-provider delegation with parent OpenRouter filters.

Closes #10653

tests/tools/test_delegate.py

@@ -980,6 +980,48 @@ class TestDelegationProviderIntegration(unittest.TestCase):
             self.assertNotEqual(kwargs["base_url"], parent.base_url)
             self.assertNotEqual(kwargs["api_key"], parent.api_key)
 
+    @patch("tools.delegate_tool._load_config")
+    @patch("tools.delegate_tool._resolve_delegation_credentials")
+    def test_provider_override_clears_parent_openrouter_filters(
+        self, mock_creds, mock_cfg
+    ):
+        """Delegated provider should not inherit parent provider-preference filters."""
+        mock_cfg.return_value = {
+            "max_iterations": 45,
+            "model": "google/gemini-3-flash-preview",
+            "provider": "openrouter",
+        }
+        mock_creds.return_value = {
+            "model": "google/gemini-3-flash-preview",
+            "provider": "openrouter",
+            "base_url": "https://openrouter.ai/api/v1",
+            "api_key": "sk-or-key",
+            "api_mode": "chat_completions",
+        }
+        parent = _make_mock_parent(depth=0)
+        parent.providers_allowed = ["anthropic/claude-3.5-sonnet"]
+        parent.providers_ignored = ["openai/gpt-4o-mini"]
+        parent.providers_order = ["google/gemini-2.5-pro"]
+        parent.provider_sort = "price"
+
+        with patch("run_agent.AIAgent") as MockAgent:
+            mock_child = MagicMock()
+            mock_child.run_conversation.return_value = {
+                "final_response": "done",
+                "completed": True,
+                "api_calls": 1,
+            }
+            MockAgent.return_value = mock_child
+
+            delegate_task(goal="Cross-provider test", parent_agent=parent)
+
+            _, kwargs = MockAgent.call_args
+            self.assertEqual(kwargs["provider"], "openrouter")
+            self.assertIsNone(kwargs["providers_allowed"])
+            self.assertIsNone(kwargs["providers_ignored"])
+            self.assertIsNone(kwargs["providers_order"])
+            self.assertIsNone(kwargs["provider_sort"])
+
     @patch("tools.delegate_tool._load_config")
     @patch("tools.delegate_tool._resolve_delegation_credentials")
     def test_direct_endpoint_credentials_reach_child_agent(self, mock_creds, mock_cfg):

tools/delegate_tool.py

@@ -1032,6 +1032,23 @@ def _build_child_agent(
     # fallback_model parameter (which handles both list and dict forms).
     parent_fallback = getattr(parent_agent, "_fallback_chain", None) or None
 
+    # Inherit the parent's OpenRouter provider-preference filters by default
+    # (so subagents routed to the same provider honour the same routing
+    # constraints).  BUT: when `delegation.provider` is set the user is
+    # explicitly asking the child to run on a different provider, and
+    # parent-level OpenRouter filters (e.g. `only=["Anthropic"]`) would
+    # silently force the child back onto the parent's provider. Clear the
+    # filters in that case so the delegated provider is honoured.
+    child_providers_allowed = getattr(parent_agent, "providers_allowed", None)
+    child_providers_ignored = getattr(parent_agent, "providers_ignored", None)
+    child_providers_order = getattr(parent_agent, "providers_order", None)
+    child_provider_sort = getattr(parent_agent, "provider_sort", None)
+    if override_provider:
+        child_providers_allowed = None
+        child_providers_ignored = None
+        child_providers_order = None
+        child_provider_sort = None
+
     child = AIAgent(
         base_url=effective_base_url,
         api_key=effective_api_key,
@@ -1056,10 +1073,10 @@ def _build_child_agent(
         thinking_callback=child_thinking_cb,
         session_db=getattr(parent_agent, "_session_db", None),
         parent_session_id=getattr(parent_agent, "session_id", None),
-        providers_allowed=parent_agent.providers_allowed,
-        providers_ignored=parent_agent.providers_ignored,
-        providers_order=parent_agent.providers_order,
-        provider_sort=parent_agent.provider_sort,
+        providers_allowed=child_providers_allowed,
+        providers_ignored=child_providers_ignored,
+        providers_order=child_providers_order,
+        provider_sort=child_provider_sort,
         tool_progress_callback=child_progress_cb,
         iteration_budget=None,  # fresh budget per subagent
     )