diff --git a/integration_tests/test_edit_integration.py b/integration_tests/test_edit_integration.py
new file mode 100644
index 0000000..f53a724
--- /dev/null
+++ b/integration_tests/test_edit_integration.py
@@ -0,0 +1,102 @@
+import subprocess
+import time
+import sys
+import os
+
+
+def run_integration_test():
+    print("🚀 Starting Integration Test for 'edit' tool...")
+
+    # Ensure current directory is in PYTHONPATH for the subprocess
+    env = os.environ.copy()
+    env["PYTHONPATH"] = os.getcwd() + ":" + env.get("PYTHONPATH", "")
+
+    # Create a test file
+    test_filename = "test_edit_integration.txt"
+    with open(test_filename, "w") as f:
+        f.write("Line 1\nLine 2\nLine 3\n")
+
+    # Start the mini-copilot process
+    process = subprocess.Popen(
+        [sys.executable, "-m", "mini_copilot.main"],
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        text=True,
+        bufsize=1,
+        cwd=os.getcwd(),
+        env=env,
+    )
+
+    try:
+        # 1. Wait for prompt
+        print("Waiting for prompt...")
+        output = ""
+        start_time = time.time()
+        while time.time() - start_time < 30:
+            char = process.stdout.read(1)
+            if not char:
+                break
+            output += char
+            if "> " in output:
+                print("✅ Prompt detected.")
+                break
+
+        if "> " not in output:
+            print(f"❌ Timed out waiting for prompt. Last output: {output}")
+            return False
+
+        # 2. Trigger tool
+        print(f"Sending message to trigger 'edit' tool on {test_filename}...")
+        edit_request = f"Edit the file {test_filename}. Change 'Line 2' to 'Line Two'.\n"
+        process.stdin.write(edit_request)
+        process.stdin.flush()
+
+        # 3. Look for tool execution
+        print("Monitoring for tool invocation and response...")
+        found_tool = False
+        found_success = False
+        start_time = time.time()
+        output = ""
+        while time.time() - start_time < 60:
+            char = process.stdout.read(1)
+            if not char:
+                break
+            output += char
+            sys.stdout.write(char)
+            sys.stdout.flush()
+
+            if f"Successfully edited {test_filename}" in output:
+                found_tool = True
+                
+            # If the assistant replies and we found the tool message, we are good
+            if found_tool and "> " in output:
+                found_success = True
+                break
+
+        if found_tool:
+            # Verify file content
+            with open(test_filename, "r") as f:
+                content = f.read()
+            if "Line Two" in content and "Line 2" not in content:
+                print(f"\n✅ File content verified: {test_filename}")
+                print("\n🎉 Integration Test PASSED!")
+                return True
+            else:
+                print(f"\n❌ File content mismatch. Content: {content}")
+                return False
+        else:
+            print("\n❌ Integration Test FAILED (Tool not triggered or response not found).")
+            return False
+
+    finally:
+        process.terminate()
+        if os.path.exists(test_filename):
+            os.remove(test_filename)
+
+
+if __name__ == "__main__":
+    if run_integration_test():
+        sys.exit(0)
+    else:
+        sys.exit(1)
diff --git a/mini_copilot/main.py b/mini_copilot/main.py
index 18331da..3b4b950 100644
--- a/mini_copilot/main.py
+++ b/mini_copilot/main.py
@@ -21,6 +21,7 @@ def completer(text, state):
 from mini_copilot.github_api import chat, get_copilot_token
 from mini_copilot.web_search import web_search
 from mini_copilot.exec_tool import exec_command as exec
+from tools.edit_tool import EditTool
 from mini_copilot.commands.auth import handle_login_command
 from mini_copilot.commands.model import handle_model_command
 from mini_copilot.commands.search_provider import handle_search_provider_command
@@ -78,7 +79,29 @@ def completer(text, state):
         },
     },
 }
-TOOLS = [WEB_SEARCH_TOOL, EXEC_COMMAND_TOOL]
+
+EDIT_TOOL = {
+    "type": "function",
+    "function": {
+        "name": "edit",
+        "description": "Apply a unified diff edit to a file on the local system.",
+        "parameters": {
+            "type": "object",
+            "properties": {
+                "file_path": {
+                    "type": "string",
+                    "description": "The path to the file to edit.",
+                },
+                "edit_content": {
+                    "type": "string",
+                    "description": "The unified diff content to apply.",
+                },
+            },
+            "required": ["file_path", "edit_content"],
+        },
+    },
+}
+TOOLS = [WEB_SEARCH_TOOL, EXEC_COMMAND_TOOL, EDIT_TOOL]
 
 
 def load_github_token():
@@ -199,6 +222,23 @@ def main():
                                 "content": output,
                             }
                         )
+
+                    if function_name == "edit":
+                        file_path = function_args.get("file_path")
+                        edit_content = function_args.get("edit_content")
+
+                        result = EditTool.edit(file_path, edit_content)
+                        with open(file_path, "w") as f:
+                            f.write(result)
+
+                        messages.append(
+                            {
+                                "tool_call_id": tool_call["id"],
+                                "role": "tool",
+                                "name": function_name,
+                                "content": f"Successfully edited {file_path}",
+                            }
+                        )
                 response_message = chat(
                     messages, copilot_token, current_model, tools=TOOLS
                 )