fix: handle empty allowed_tools and disallowed_tools correctly

src/claude_agent_sdk/_internal/transport/subprocess_cli.py

@@ -192,7 +192,7 @@ def _build_command(self) -> list[str]:
                 # Preset object - 'claude_code' preset maps to 'default'
                 cmd.extend(["--tools", "default"])
 
-        if self._options.allowed_tools:
+        if self._options.allowed_tools is not None:
             cmd.extend(["--allowedTools", ",".join(self._options.allowed_tools)])
 
         if self._options.max_turns:
@@ -201,7 +201,7 @@ def _build_command(self) -> list[str]:
         if self._options.max_budget_usd is not None:
             cmd.extend(["--max-budget-usd", str(self._options.max_budget_usd)])
 
-        if self._options.disallowed_tools:
+        if self._options.disallowed_tools is not None:
             cmd.extend(["--disallowedTools", ",".join(self._options.disallowed_tools)])
 
         if self._options.model:

src/claude_agent_sdk/types.py

@@ -717,15 +717,15 @@ class ClaudeAgentOptions:
     """Query options for Claude SDK."""
 
     tools: list[str] | ToolsPreset | None = None
-    allowed_tools: list[str] = field(default_factory=list)
+    allowed_tools: list[str] | None = None
     system_prompt: str | SystemPromptPreset | None = None
     mcp_servers: dict[str, McpServerConfig] | str | Path = field(default_factory=dict)
     permission_mode: PermissionMode | None = None
     continue_conversation: bool = False
     resume: str | None = None
     max_turns: int | None = None
     max_budget_usd: float | None = None
-    disallowed_tools: list[str] = field(default_factory=list)
+    disallowed_tools: list[str] | None = None
     model: str | None = None
     fallback_model: str | None = None
     # Beta features - see https://docs.anthropic.com/en/api/beta-headers

tests/test_types.py

@@ -87,11 +87,11 @@ class TestOptions:
     def test_default_options(self):
         """Test Options with default values."""
         options = ClaudeAgentOptions()
-        assert options.allowed_tools == []
+        assert options.allowed_tools is None
         assert options.system_prompt is None
         assert options.permission_mode is None
         assert options.continue_conversation is False
-        assert options.disallowed_tools == []
+        assert options.disallowed_tools is None
 
     def test_claude_code_options_with_tools(self):
         """Test Options with built-in tools."""