diff --git a/aider/watch.py b/aider/watch.py
index e69de29bb..8d913bf31 100644
--- a/aider/watch.py
+++ b/aider/watch.py
@@ -0,0 +1,56 @@
+from pathlib import Path
+from typing import Set
+from watchfiles import watch
+
+def is_source_file(path: Path) -> bool:
+    """
+    Check if a file is a source file that uses # or // style comments.
+    This includes Python, JavaScript, TypeScript, C, C++, etc.
+    """
+    COMMENT_STYLE_EXTENSIONS = {
+        # # style comments
+        '.py', '.r', '.rb', '.pl', '.pm', '.sh', '.bash', '.yaml', '.yml',
+        # // style comments
+        '.js', '.ts', '.jsx', '.tsx', '.cpp', '.c', '.h', '.hpp', '.java',
+        '.swift', '.kt', '.cs', '.go', '.rs', '.php'
+    }
+    return path.suffix.lower() in COMMENT_STYLE_EXTENSIONS
+
+def watch_source_files(directory: str) -> Set[str]:
+    """
+    Watch for changes to source files in the given directory and its subdirectories.
+    Returns a set of changed file paths whenever changes are detected.
+    """
+    root = Path(directory)
+    
+    # Create a filter function that only accepts source files
+    def filter_func(change_type, path):
+        return is_source_file(Path(path))
+
+    # Watch the directory for changes
+    for changes in watch(root, watch_filter=filter_func):
+        # Convert the changes to a set of unique file paths
+        changed_files = {str(Path(change[1])) for change in changes}
+        yield changed_files
+
+def main():
+    """Example usage of the file watcher"""
+    import sys
+    
+    if len(sys.argv) != 2:
+        print("Usage: python watch.py <directory>")
+        sys.exit(1)
+        
+    directory = sys.argv[1]
+    print(f"Watching source files in {directory}...")
+    
+    try:
+        for changed_files in watch_source_files(directory):
+            print("\nChanged files:")
+            for file in sorted(changed_files):
+                print(f"  {file}")
+    except KeyboardInterrupt:
+        print("\nStopped watching files")
+
+if __name__ == "__main__":
+    main()