diff --git a/src/claude_agent_sdk/_internal/query.py b/src/claude_agent_sdk/_internal/query.py
index c30fc159..e6a1cb5f 100644
--- a/src/claude_agent_sdk/_internal/query.py
+++ b/src/claude_agent_sdk/_internal/query.py
@@ -15,6 +15,7 @@
 )
 
 from ..types import (
+    PermissionMode,
     PermissionResultAllow,
     PermissionResultDeny,
     SDKControlPermissionRequest,
@@ -521,7 +522,7 @@ async def interrupt(self) -> None:
         """Send interrupt control request."""
         await self._send_control_request({"subtype": "interrupt"})
 
-    async def set_permission_mode(self, mode: str) -> None:
+    async def set_permission_mode(self, mode: PermissionMode) -> None:
         """Change permission mode."""
         await self._send_control_request(
             {
diff --git a/src/claude_agent_sdk/client.py b/src/claude_agent_sdk/client.py
index 18ab818d..ed4574ed 100644
--- a/src/claude_agent_sdk/client.py
+++ b/src/claude_agent_sdk/client.py
@@ -8,7 +8,14 @@
 
 from . import Transport
 from ._errors import CLIConnectionError
-from .types import ClaudeAgentOptions, HookEvent, HookMatcher, Message, ResultMessage
+from .types import (
+    ClaudeAgentOptions,
+    HookEvent,
+    HookMatcher,
+    Message,
+    PermissionMode,
+    ResultMessage,
+)
 
 
 class ClaudeSDKClient:
@@ -213,13 +220,14 @@ async def interrupt(self) -> None:
             raise CLIConnectionError("Not connected. Call connect() first.")
         await self._query.interrupt()
 
-    async def set_permission_mode(self, mode: str) -> None:
+    async def set_permission_mode(self, mode: PermissionMode) -> None:
         """Change permission mode during conversation (only works with streaming mode).
 
         Args:
             mode: The permission mode to set. Valid options:
                 - 'default': CLI prompts for dangerous tools
                 - 'acceptEdits': Auto-accept file edits
+                - 'plan': Plan mode for planning tasks
                 - 'bypassPermissions': Allow all tools (use with caution)
 
         Example:
diff --git a/src/claude_agent_sdk/types.py b/src/claude_agent_sdk/types.py
index 9c09345f..57f35fea 100644
--- a/src/claude_agent_sdk/types.py
+++ b/src/claude_agent_sdk/types.py
@@ -701,8 +701,7 @@ class SDKControlInitializeRequest(TypedDict):
 
 class SDKControlSetPermissionModeRequest(TypedDict):
     subtype: Literal["set_permission_mode"]
-    # TODO: Add PermissionMode
-    mode: str
+    mode: PermissionMode
 
 
 class SDKHookCallbackRequest(TypedDict):