feat(settings): add enable_sub_agents toggle to LLMAgentSettings (#2948)

Co-authored-by: openhands <openhands@all-hands.dev>

Author: xingyaoww

openhands-sdk/openhands/sdk/settings/model.py

@@ -646,6 +646,17 @@ class LLMAgentSettings(BaseModel):
             ).model_dump()
         },
     )
+    enable_sub_agents: bool = Field(
+        default=False,
+        description="Enable sub-agent delegation via TaskToolSet.",
+        json_schema_extra={
+            SETTINGS_METADATA_KEY: SettingsFieldMetadata(
+                label="Enable sub-agents",
+                prominence=SettingProminence.MAJOR,
+                variant="llm",
+            ).model_dump()
+        },
+    )
     mcp_config: MCPConfig | None = Field(
         default=None,
         description="MCP server configuration for the agent.",

openhands-tools/openhands/tools/preset/default.py

@@ -35,11 +35,14 @@ def register_default_tools(enable_browser: bool = True) -> None:
 
 def get_default_tools(
     enable_browser: bool = True,
+    enable_sub_agents: bool = False,
 ) -> list[Tool]:
     """Get the default set of tool specifications for the standard experience.
 
     Args:
         enable_browser: Whether to include browser tools.
+        enable_sub_agents: Whether to include the TaskToolSet for
+            sub-agent delegation.
     """
     register_default_tools(enable_browser=enable_browser)
 
@@ -57,6 +60,10 @@ def get_default_tools(
         from openhands.tools.browser_use import BrowserToolSet
 
         tools.append(Tool(name=BrowserToolSet.name))
+    if enable_sub_agents:
+        from openhands.tools.task import TaskToolSet
+
+        tools.append(Tool(name=TaskToolSet.name))
     return tools
 
 

tests/sdk/test_settings.py

@@ -56,12 +56,20 @@ def test_llm_agent_settings_export_schema_groups_sections() -> None:
 
     # -- general section (top-level scalar fields) --
     general_fields = {f.key: f for f in sections["general"].fields}
-    assert set(general_fields) == {"agent", "tools", "mcp_config"}
+    assert set(general_fields) == {
+        "agent",
+        "tools",
+        "enable_sub_agents",
+        "mcp_config",
+    }
     assert general_fields["agent"].default == "CodeActAgent"
     assert general_fields["agent"].prominence is SettingProminence.MAJOR
     assert general_fields["tools"].value_type == "array"
     assert general_fields["tools"].default == []
     assert general_fields["tools"].prominence is SettingProminence.MAJOR
+    assert general_fields["enable_sub_agents"].value_type == "boolean"
+    assert general_fields["enable_sub_agents"].default is False
+    assert general_fields["enable_sub_agents"].prominence is SettingProminence.MAJOR
 
     # -- llm section --
     llm_fields = {f.key: f for f in sections["llm"].fields}
@@ -237,7 +245,7 @@ def test_export_agent_settings_schema_emits_variant_tagged_sections() -> None:
     general = by_keyvariant.get(("general", None))
     assert general is not None
     general_keys = {f.key for f in general.fields}
-    assert general_keys == {"agent", "tools", "mcp_config"}
+    assert general_keys == {"agent", "tools", "enable_sub_agents", "mcp_config"}
     # No agent_kind field — each variant has its own settings page and
     # injects the discriminator on save.
     assert "agent_kind" not in general_keys