diff --git a/examples/tool_permission_callback.py b/examples/tool_permission_callback.py
new file mode 100644
index 0000000..a520755
--- /dev/null
+++ b/examples/tool_permission_callback.py
@@ -0,0 +1,166 @@
+#!/usr/bin/env python3
+"""Example: Tool Permission Callbacks.
+
+This example demonstrates how to use tool permission callbacks to control
+which tools Claude can use and modify their inputs.
+"""
+
+import asyncio
+import json
+from claude_code_sdk import (
+    ClaudeCodeOptions,
+    ClaudeSDKClient,
+    ToolPermissionCallback,
+    ToolPermissionResponse,
+    ToolPermissionContext,
+    TextBlock,
+    AssistantMessage,
+    ResultMessage,
+)
+
+
+# Track tool usage for demonstration
+tool_usage_log = []
+
+
+async def my_permission_callback(
+    tool_name: str,
+    input_data: dict,
+    context: ToolPermissionContext
+) -> ToolPermissionResponse:
+    """Control tool permissions based on tool type and input."""
+    
+    # Log the tool request
+    tool_usage_log.append({
+        "tool": tool_name,
+        "input": input_data,
+        "suggestions": context.suggestions
+    })
+    
+    print(f"\n🔧 Tool Permission Request: {tool_name}")
+    print(f"   Input: {json.dumps(input_data, indent=2)}")
+    
+    # Always allow read operations
+    if tool_name in ["Read", "Glob", "Grep"]:
+        print(f"   ✅ Automatically allowing {tool_name} (read-only operation)")
+        return ToolPermissionResponse(
+            allow=True,
+            reason="Read operations are always allowed"
+        )
+    
+    # Deny write operations to system directories
+    if tool_name in ["Write", "Edit", "MultiEdit"]:
+        file_path = input_data.get("file_path", "")
+        if file_path.startswith("/etc/") or file_path.startswith("/usr/"):
+            print(f"   ❌ Denying write to system directory: {file_path}")
+            return ToolPermissionResponse(
+                allow=False,
+                reason=f"Cannot write to system directory: {file_path}"
+            )
+        
+        # Redirect writes to a safe directory
+        if not file_path.startswith("/tmp/") and not file_path.startswith("./"):
+            safe_path = f"./safe_output/{file_path.split('/')[-1]}"
+            print(f"   ⚠️  Redirecting write from {file_path} to {safe_path}")
+            modified_input = input_data.copy()
+            modified_input["file_path"] = safe_path
+            return ToolPermissionResponse(
+                allow=True,
+                input=modified_input,
+                reason=f"Redirected to safe path: {safe_path}"
+            )
+    
+    # Check dangerous bash commands
+    if tool_name == "Bash":
+        command = input_data.get("command", "")
+        dangerous_commands = ["rm -rf", "sudo", "chmod 777", "dd if=", "mkfs"]
+        
+        for dangerous in dangerous_commands:
+            if dangerous in command:
+                print(f"   ❌ Denying dangerous command: {command}")
+                return ToolPermissionResponse(
+                    allow=False,
+                    reason=f"Dangerous command pattern detected: {dangerous}"
+                )
+        
+        # Allow but log the command
+        print(f"   ✅ Allowing bash command: {command}")
+        return ToolPermissionResponse(
+            allow=True,
+            reason="Command appears safe"
+        )
+    
+    # For all other tools, ask the user
+    print(f"   ❓ Unknown tool: {tool_name}")
+    print(f"      Input: {json.dumps(input_data, indent=6)}")
+    user_input = input("   Allow this tool? (y/N): ").strip().lower()
+    
+    return ToolPermissionResponse(
+        allow=user_input in ("y", "yes"),
+        reason=f"User {'approved' if user_input in ('y', 'yes') else 'denied'}"
+    )
+
+
+async def main():
+    """Run example with tool permission callbacks."""
+    
+    print("=" * 60)
+    print("Tool Permission Callback Example")
+    print("=" * 60)
+    print("\nThis example demonstrates how to:")
+    print("1. Allow/deny tools based on type")
+    print("2. Modify tool inputs for safety")
+    print("3. Log tool usage")
+    print("4. Prompt for unknown tools")
+    print("=" * 60)
+    
+    # Configure options with our callback
+    options = ClaudeCodeOptions(
+        tool_permission_callback=my_permission_callback,
+        # Use default permission mode to ensure callbacks are invoked
+        permission_mode="default",
+        cwd="."  # Set working directory
+    )
+    
+    # Create client and send a query that will use multiple tools
+    async with ClaudeSDKClient(options) as client:
+        print("\n📝 Sending query to Claude...")
+        await client.query(
+            "Please do the following:\n"
+            "1. List the files in the current directory\n"
+            "2. Create a simple Python hello world script at hello.py\n"
+            "3. Run the script to test it"
+        )
+        
+        print("\n📨 Receiving response...")
+        message_count = 0
+        
+        async for message in client.receive_response():
+            message_count += 1
+            
+            if isinstance(message, AssistantMessage):
+                # Print Claude's text responses
+                for block in message.content:
+                    if isinstance(block, TextBlock):
+                        print(f"\n💬 Claude: {block.text}")
+            
+            elif isinstance(message, ResultMessage):
+                print(f"\n✅ Task completed!")
+                print(f"   Duration: {message.duration_ms}ms")
+                if message.total_cost_usd:
+                    print(f"   Cost: ${message.total_cost_usd:.4f}")
+                print(f"   Messages processed: {message_count}")
+    
+    # Print tool usage summary
+    print("\n" + "=" * 60)
+    print("Tool Usage Summary")
+    print("=" * 60)
+    for i, usage in enumerate(tool_usage_log, 1):
+        print(f"\n{i}. Tool: {usage['tool']}")
+        print(f"   Input: {json.dumps(usage['input'], indent=6)}")
+        if usage['suggestions']:
+            print(f"   Suggestions: {usage['suggestions']}")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())
\ No newline at end of file
diff --git a/src/claude_code_sdk/__init__.py b/src/claude_code_sdk/__init__.py
index f2b9bdb..a1f0831 100644
--- a/src/claude_code_sdk/__init__.py
+++ b/src/claude_code_sdk/__init__.py
@@ -14,6 +14,9 @@ from .types import (
     AssistantMessage,
     ClaudeCodeOptions,
     ContentBlock,
+    HookCallback,
+    HookContext,
+    HookMatcher,
     McpServerConfig,
     Message,
     PermissionMode,
@@ -21,6 +24,9 @@ from .types import (
     SystemMessage,
     TextBlock,
     ThinkingBlock,
+    ToolPermissionCallback,
+    ToolPermissionContext,
+    ToolPermissionResponse,
     ToolResultBlock,
     ToolUseBlock,
     UserMessage,
@@ -48,6 +54,13 @@ __all__ = [
     "ToolUseBlock",
     "ToolResultBlock",
     "ContentBlock",
+    # Tool callbacks
+    "ToolPermissionCallback",
+    "ToolPermissionContext",
+    "ToolPermissionResponse",
+    "HookCallback",
+    "HookContext",
+    "HookMatcher",
     # Errors
     "ClaudeSDKError",
     "CLIConnectionError",
diff --git a/src/claude_code_sdk/_internal/client.py b/src/claude_code_sdk/_internal/client.py
index 6b5331f..763f7da 100644
--- a/src/claude_code_sdk/_internal/client.py
+++ b/src/claude_code_sdk/_internal/client.py
@@ -19,6 +19,22 @@ class InternalClient:
     def __init__(self) -> None:
         """Initialize the internal client."""
 
+    def _convert_hooks_to_internal_format(
+        self, hooks: dict[str, list]
+    ) -> dict[str, list[dict[str, Any]]]:
+        """Convert HookMatcher format to internal Query format."""
+        internal_hooks = {}
+        for event, matchers in hooks.items():
+            internal_hooks[event] = []
+            for matcher in matchers:
+                # Convert HookMatcher to internal dict format
+                internal_matcher = {
+                    "matcher": matcher.matcher if hasattr(matcher, 'matcher') else None,
+                    "hooks": matcher.hooks if hasattr(matcher, 'hooks') else []
+                }
+                internal_hooks[event].append(internal_matcher)
+        return internal_hooks
+
     async def process_query(
         self,
         prompt: str | AsyncIterable[dict[str, Any]],
@@ -41,8 +57,8 @@ class InternalClient:
         query = Query(
             transport=chosen_transport,
             is_streaming_mode=is_streaming,
-            can_use_tool=None,  # TODO: Add support for can_use_tool callback
-            hooks=None,  # TODO: Add support for hooks
+            can_use_tool=options.tool_permission_callback,
+            hooks=self._convert_hooks_to_internal_format(options.hooks) if options.hooks else None,
         )
 
         try:
diff --git a/src/claude_code_sdk/_internal/query.py b/src/claude_code_sdk/_internal/query.py
index cf0b6d8..9a8a336 100644
--- a/src/claude_code_sdk/_internal/query.py
+++ b/src/claude_code_sdk/_internal/query.py
@@ -184,15 +184,35 @@ class Query:
                 if not self.can_use_tool:
                     raise Exception("canUseTool callback is not provided")
 
-                response_data = await self.can_use_tool(
+                # Import here to avoid circular dependency
+                from ..types import ToolPermissionContext, ToolPermissionResponse
+
+                context = ToolPermissionContext(
+                    signal=None,  # TODO: Add abort signal support
+                    suggestions=permission_request.get("permission_suggestions", [])
+                )
+
+                response = await self.can_use_tool(
                     permission_request["tool_name"],
                     permission_request["input"],
-                    {
-                        "signal": None,  # TODO: Add abort signal support
-                        "suggestions": permission_request.get("permission_suggestions"),
-                    },
+                    context
                 )
 
+                # Convert ToolPermissionResponse to expected dict format
+                if isinstance(response, ToolPermissionResponse):
+                    response_data = {
+                        "allow": response.allow
+                    }
+                    if response.input is not None:
+                        response_data["input"] = response.input
+                    if response.reason is not None:
+                        response_data["reason"] = response.reason
+                elif isinstance(response, dict):
+                    # Support returning dict directly for compatibility
+                    response_data = response
+                else:
+                    raise TypeError(f"Tool permission callback must return ToolPermissionResponse or dict, got {type(response)}")
+
             elif subtype == "hook_callback":
                 hook_callback_request: SDKHookCallbackRequest = request_data  # type: ignore[assignment]
                 # Handle hook callback
diff --git a/src/claude_code_sdk/client.py b/src/claude_code_sdk/client.py
index 330d947..bc865eb 100644
--- a/src/claude_code_sdk/client.py
+++ b/src/claude_code_sdk/client.py
@@ -100,6 +100,22 @@ class ClaudeSDKClient:
         self._query: Any | None = None
         os.environ["CLAUDE_CODE_ENTRYPOINT"] = "sdk-py-client"
 
+    def _convert_hooks_to_internal_format(
+        self, hooks: dict[str, list]
+    ) -> dict[str, list[dict[str, Any]]]:
+        """Convert HookMatcher format to internal Query format."""
+        internal_hooks = {}
+        for event, matchers in hooks.items():
+            internal_hooks[event] = []
+            for matcher in matchers:
+                # Convert HookMatcher to internal dict format
+                internal_matcher = {
+                    "matcher": matcher.matcher if hasattr(matcher, 'matcher') else None,
+                    "hooks": matcher.hooks if hasattr(matcher, 'hooks') else []
+                }
+                internal_hooks[event].append(internal_matcher)
+        return internal_hooks
+
     async def connect(
         self, prompt: str | AsyncIterable[dict[str, Any]] | None = None
     ) -> None:
@@ -128,8 +144,8 @@ class ClaudeSDKClient:
         self._query = Query(
             transport=self._transport,
             is_streaming_mode=True,  # ClaudeSDKClient always uses streaming mode
-            can_use_tool=None,  # TODO: Add support for can_use_tool callback
-            hooks=None,  # TODO: Add support for hooks
+            can_use_tool=self.options.tool_permission_callback,
+            hooks=self._convert_hooks_to_internal_format(self.options.hooks) if self.options.hooks else None,
         )
 
         # Start reading messages and initialize
diff --git a/src/claude_code_sdk/types.py b/src/claude_code_sdk/types.py
index 1f61ec6..7b200af 100644
--- a/src/claude_code_sdk/types.py
+++ b/src/claude_code_sdk/types.py
@@ -1,15 +1,66 @@
 """Type definitions for Claude SDK."""
 
+from collections.abc import Awaitable, Callable
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, Literal, TypedDict
 
-from typing_extensions import NotRequired  # For Python < 3.11 compatibility
+try:
+    from typing import NotRequired  # Python 3.11+
+except ImportError:
+    from typing_extensions import NotRequired  # For Python < 3.11 compatibility
 
 # Permission modes
 PermissionMode = Literal["default", "acceptEdits", "plan", "bypassPermissions"]
 
 
+# Tool callback types
+@dataclass
+class ToolPermissionContext:
+    """Context information for tool permission callbacks."""
+
+    signal: Any | None = None  # Future: abort signal support
+    suggestions: list[str] = field(default_factory=list)  # Permission suggestions from CLI
+
+
+@dataclass
+class ToolPermissionResponse:
+    """Response from tool permission callback."""
+
+    allow: bool
+    input: dict[str, Any] | None = None  # Optional: modified input parameters
+    reason: str | None = None  # Optional: reason for decision
+
+
+ToolPermissionCallback = Callable[
+    [str, dict[str, Any], ToolPermissionContext],
+    Awaitable[ToolPermissionResponse | dict[str, Any]]
+]
+
+
+# Hook callback types
+@dataclass
+class HookContext:
+    """Context information for hook callbacks."""
+
+    signal: Any | None = None  # Future: abort signal support
+
+
+HookCallback = Callable[
+    [dict[str, Any], str | None, HookContext],  # input, tool_use_id, context
+    Awaitable[dict[str, Any]]  # response data
+]
+
+
+# Hook matcher configuration
+@dataclass
+class HookMatcher:
+    """Hook matcher configuration."""
+
+    matcher: dict[str, Any] | None = None  # Matcher criteria
+    hooks: list[HookCallback] = field(default_factory=list)  # Callbacks to invoke
+
+
 # MCP Server config
 class McpStdioServerConfig(TypedDict):
     """MCP stdio server configuration."""
@@ -142,6 +193,12 @@ class ClaudeCodeOptions:
         default_factory=dict
     )  # Pass arbitrary CLI flags
 
+    # Tool permission callback
+    tool_permission_callback: ToolPermissionCallback | None = None
+
+    # Hook configurations
+    hooks: dict[str, list[HookMatcher]] | None = None
+
 
 # SDK Control Protocol
 class SDKControlInterruptRequest(TypedDict):
diff --git a/tests/test_tool_callbacks.py b/tests/test_tool_callbacks.py
new file mode 100644
index 0000000..b51d0f0
--- /dev/null
+++ b/tests/test_tool_callbacks.py
@@ -0,0 +1,373 @@
+"""Tests for tool permission callbacks and hook callbacks."""
+
+import asyncio
+from unittest.mock import AsyncMock, Mock
+import pytest
+
+from claude_code_sdk import (
+    ClaudeCodeOptions,
+    ToolPermissionCallback,
+    ToolPermissionResponse,
+    ToolPermissionContext,
+    HookCallback,
+    HookContext,
+    HookMatcher,
+)
+from claude_code_sdk._internal.query import Query
+from claude_code_sdk._internal.transport import Transport
+
+
+class MockTransport(Transport):
+    """Mock transport for testing."""
+    
+    def __init__(self):
+        self.written_messages = []
+        self.messages_to_read = []
+        self._connected = False
+    
+    async def connect(self) -> None:
+        self._connected = True
+    
+    async def close(self) -> None:
+        self._connected = False
+    
+    async def write(self, data: str) -> None:
+        self.written_messages.append(data)
+    
+    async def end_input(self) -> None:
+        pass
+    
+    def read_messages(self):
+        async def _read():
+            for msg in self.messages_to_read:
+                yield msg
+        return _read()
+    
+    def is_ready(self) -> bool:
+        return self._connected
+
+
+class TestToolPermissionCallbacks:
+    """Test tool permission callback functionality."""
+    
+    @pytest.mark.asyncio
+    async def test_permission_callback_allow(self):
+        """Test callback that allows tool execution."""
+        callback_invoked = False
+        
+        async def allow_callback(
+            tool_name: str, 
+            input_data: dict, 
+            context: ToolPermissionContext
+        ) -> ToolPermissionResponse:
+            nonlocal callback_invoked
+            callback_invoked = True
+            assert tool_name == "TestTool"
+            assert input_data == {"param": "value"}
+            return ToolPermissionResponse(allow=True, reason="Test allow")
+        
+        transport = MockTransport()
+        query = Query(
+            transport=transport,
+            is_streaming_mode=True,
+            can_use_tool=allow_callback,
+            hooks=None
+        )
+        
+        # Simulate control request
+        request = {
+            "type": "control_request",
+            "request_id": "test-1",
+            "request": {
+                "subtype": "can_use_tool",
+                "tool_name": "TestTool",
+                "input": {"param": "value"},
+                "permission_suggestions": []
+            }
+        }
+        
+        await query._handle_control_request(request)
+        
+        # Check callback was invoked
+        assert callback_invoked
+        
+        # Check response was sent
+        assert len(transport.written_messages) == 1
+        response = transport.written_messages[0]
+        assert '"allow": true' in response
+        assert '"reason": "Test allow"' in response
+    
+    @pytest.mark.asyncio
+    async def test_permission_callback_deny(self):
+        """Test callback that denies tool execution."""
+        async def deny_callback(
+            tool_name: str, 
+            input_data: dict, 
+            context: ToolPermissionContext
+        ) -> ToolPermissionResponse:
+            return ToolPermissionResponse(
+                allow=False, 
+                reason="Security policy violation"
+            )
+        
+        transport = MockTransport()
+        query = Query(
+            transport=transport,
+            is_streaming_mode=True,
+            can_use_tool=deny_callback,
+            hooks=None
+        )
+        
+        request = {
+            "type": "control_request",
+            "request_id": "test-2",
+            "request": {
+                "subtype": "can_use_tool",
+                "tool_name": "DangerousTool",
+                "input": {"command": "rm -rf /"},
+                "permission_suggestions": ["deny"]
+            }
+        }
+        
+        await query._handle_control_request(request)
+        
+        # Check response
+        assert len(transport.written_messages) == 1
+        response = transport.written_messages[0]
+        assert '"allow": false' in response
+        assert '"reason": "Security policy violation"' in response
+    
+    @pytest.mark.asyncio
+    async def test_permission_callback_input_modification(self):
+        """Test callback that modifies tool input."""
+        async def modify_callback(
+            tool_name: str, 
+            input_data: dict, 
+            context: ToolPermissionContext
+        ) -> ToolPermissionResponse:
+            # Modify the input to add safety flag
+            modified_input = input_data.copy()
+            modified_input["safe_mode"] = True
+            return ToolPermissionResponse(
+                allow=True,
+                input=modified_input,
+                reason="Modified for safety"
+            )
+        
+        transport = MockTransport()
+        query = Query(
+            transport=transport,
+            is_streaming_mode=True,
+            can_use_tool=modify_callback,
+            hooks=None
+        )
+        
+        request = {
+            "type": "control_request",
+            "request_id": "test-3",
+            "request": {
+                "subtype": "can_use_tool",
+                "tool_name": "WriteTool",
+                "input": {"file_path": "/etc/passwd"},
+                "permission_suggestions": []
+            }
+        }
+        
+        await query._handle_control_request(request)
+        
+        # Check response includes modified input
+        assert len(transport.written_messages) == 1
+        response = transport.written_messages[0]
+        assert '"allow": true' in response
+        assert '"safe_mode": true' in response
+        assert '"reason": "Modified for safety"' in response
+    
+    @pytest.mark.asyncio
+    async def test_permission_callback_dict_return(self):
+        """Test callback can return dict for backwards compatibility."""
+        async def dict_callback(
+            tool_name: str, 
+            input_data: dict, 
+            context: ToolPermissionContext
+        ) -> dict:
+            # Return dict directly instead of ToolPermissionResponse
+            return {
+                "allow": True,
+                "reason": "Dict response"
+            }
+        
+        transport = MockTransport()
+        query = Query(
+            transport=transport,
+            is_streaming_mode=True,
+            can_use_tool=dict_callback,
+            hooks=None
+        )
+        
+        request = {
+            "type": "control_request",
+            "request_id": "test-4",
+            "request": {
+                "subtype": "can_use_tool",
+                "tool_name": "TestTool",
+                "input": {},
+                "permission_suggestions": []
+            }
+        }
+        
+        await query._handle_control_request(request)
+        
+        # Check response
+        assert len(transport.written_messages) == 1
+        response = transport.written_messages[0]
+        assert '"allow": true' in response
+        assert '"reason": "Dict response"' in response
+    
+    @pytest.mark.asyncio
+    async def test_callback_exception_handling(self):
+        """Test that callback exceptions are properly handled."""
+        async def error_callback(
+            tool_name: str, 
+            input_data: dict, 
+            context: ToolPermissionContext
+        ) -> ToolPermissionResponse:
+            raise ValueError("Callback error")
+        
+        transport = MockTransport()
+        query = Query(
+            transport=transport,
+            is_streaming_mode=True,
+            can_use_tool=error_callback,
+            hooks=None
+        )
+        
+        request = {
+            "type": "control_request",
+            "request_id": "test-5",
+            "request": {
+                "subtype": "can_use_tool",
+                "tool_name": "TestTool",
+                "input": {},
+                "permission_suggestions": []
+            }
+        }
+        
+        await query._handle_control_request(request)
+        
+        # Check error response was sent
+        assert len(transport.written_messages) == 1
+        response = transport.written_messages[0]
+        assert '"subtype": "error"' in response
+        assert "Callback error" in response
+
+
+class TestHookCallbacks:
+    """Test hook callback functionality."""
+    
+    @pytest.mark.asyncio
+    async def test_hook_execution(self):
+        """Test that hooks are called at appropriate times."""
+        hook_calls = []
+        
+        async def test_hook(
+            input_data: dict,
+            tool_use_id: str | None,
+            context: HookContext
+        ) -> dict:
+            hook_calls.append({
+                "input": input_data,
+                "tool_use_id": tool_use_id
+            })
+            return {"processed": True}
+        
+        transport = MockTransport()
+        
+        # Create hooks configuration
+        hooks = {
+            "tool_use_start": [
+                {
+                    "matcher": {"tool": "TestTool"},
+                    "hooks": [test_hook]
+                }
+            ]
+        }
+        
+        query = Query(
+            transport=transport,
+            is_streaming_mode=True,
+            can_use_tool=None,
+            hooks=hooks
+        )
+        
+        # During initialization, hook callbacks are registered
+        await query.initialize()
+        
+        # Find the registered callback ID
+        callback_id = None
+        for cid in query.hook_callbacks:
+            if query.hook_callbacks[cid] == test_hook:
+                callback_id = cid
+                break
+        
+        assert callback_id is not None
+        
+        # Simulate hook callback request
+        request = {
+            "type": "control_request",
+            "request_id": "test-hook-1",
+            "request": {
+                "subtype": "hook_callback",
+                "callback_id": callback_id,
+                "input": {"test": "data"},
+                "tool_use_id": "tool-123"
+            }
+        }
+        
+        await query._handle_control_request(request)
+        
+        # Check hook was called
+        assert len(hook_calls) == 1
+        assert hook_calls[0]["input"] == {"test": "data"}
+        assert hook_calls[0]["tool_use_id"] == "tool-123"
+        
+        # Check response
+        assert len(transport.written_messages) > 0
+        last_response = transport.written_messages[-1]
+        assert '"processed": true' in last_response
+
+
+class TestClaudeCodeOptionsIntegration:
+    """Test that callbacks work through ClaudeCodeOptions."""
+    
+    def test_options_with_callbacks(self):
+        """Test creating options with callbacks."""
+        async def my_callback(
+            tool_name: str,
+            input_data: dict,
+            context: ToolPermissionContext
+        ) -> ToolPermissionResponse:
+            return ToolPermissionResponse(allow=True)
+        
+        async def my_hook(
+            input_data: dict,
+            tool_use_id: str | None,
+            context: HookContext
+        ) -> dict:
+            return {}
+        
+        options = ClaudeCodeOptions(
+            tool_permission_callback=my_callback,
+            hooks={
+                "tool_use_start": [
+                    HookMatcher(
+                        matcher={"tool": "Bash"},
+                        hooks=[my_hook]
+                    )
+                ]
+            }
+        )
+        
+        assert options.tool_permission_callback == my_callback
+        assert "tool_use_start" in options.hooks
+        assert len(options.hooks["tool_use_start"]) == 1
+        assert options.hooks["tool_use_start"][0].hooks[0] == my_hook
\ No newline at end of file