diff --git a/Dockerfile b/Dockerfile
index 1751362..5b4a588 100755
--- a/Dockerfile
+++ b/Dockerfile
@@ -31,7 +31,9 @@ ENV FUNCTION_COMMAND="python"
 # Args to start the evaluation function with
 ENV FUNCTION_ARGS="-m,evaluation_function.main"
 
-# The transport to use for the RPC server
-ENV FUNCTION_RPC_TRANSPORT="ipc"
+# Use file-based communication interface instead of RPC
+# This handles larger payloads better (shimmy writes input to file, reads output from file)
+# shimmy will append input/output file paths as the last two arguments
+ENV FUNCTION_INTERFACE="file"
 
 ENV LOG_LEVEL="debug"
diff --git a/evaluation_function/main.py b/evaluation_function/main.py
index 9375f86..ae972f4 100644
--- a/evaluation_function/main.py
+++ b/evaluation_function/main.py
@@ -1,18 +1,127 @@
+"""
+Main entry point for the FSA evaluation function.
+
+Supports two communication modes with shimmy:
+1. File-based (recommended for large payloads): shimmy passes input/output file paths as args
+2. RPC/IPC (default): Uses lf_toolkit's server for stdio/IPC communication
+"""
+
+import sys
+import json
+from typing import Any, Dict
 
 from lf_toolkit import create_server, run
+from lf_toolkit.evaluation import Params, Result as LFResult
 
 from .evaluation import evaluation_function
 from .preview import preview_function
 
+
+def handle_file_based_communication(input_path: str, output_path: str) -> None:
+    """
+    Handle file-based communication with shimmy.
+    
+    Reads input JSON from input_path, processes it, and writes result to output_path.
+    This is used when shimmy is configured with --interface file.
+    
+    Args:
+        input_path: Path to the input JSON file
+        output_path: Path to write the output JSON file
+    """
+    # Read input from file
+    with open(input_path, 'r', encoding='utf-8') as f:
+        input_data = json.load(f)
+    
+    # Extract command and request data
+    command = input_data.get('command', 'eval')
+    request_id = input_data.get('$id')
+    
+    # Build response structure
+    response_data: Dict[str, Any] = {}
+    if request_id is not None:
+        response_data['$id'] = request_id
+    response_data['command'] = command
+    
+    try:
+        if command == 'eval':
+            # Extract evaluation inputs
+            response = input_data.get('response')
+            answer = input_data.get('answer')
+            params_dict = input_data.get('params', {})
+            
+            # Create params object
+            params = Params(**params_dict) if params_dict else Params()
+            
+            # Call evaluation function
+            result = evaluation_function(response, answer, params)
+            
+            # Convert result to dict
+            if hasattr(result, 'to_dict'):
+                response_data['result'] = result.to_dict()
+            elif isinstance(result, dict):
+                response_data['result'] = result
+            else:
+                response_data['result'] = {'is_correct': False, 'feedback': str(result)}
+                
+        elif command == 'preview':
+            # Extract preview inputs
+            response = input_data.get('response')
+            params_dict = input_data.get('params', {})
+            
+            params = Params(**params_dict) if params_dict else Params()
+            
+            # Call preview function
+            result = preview_function(response, params)
+            
+            if hasattr(result, 'to_dict'):
+                response_data['result'] = result.to_dict()
+            elif isinstance(result, dict):
+                response_data['result'] = result
+            else:
+                response_data['result'] = {'preview': str(result)}
+                
+        else:
+            response_data['result'] = {
+                'is_correct': False,
+                'feedback': f'Unknown command: {command}'
+            }
+            
+    except Exception as e:
+        response_data['result'] = {
+            'is_correct': False,
+            'feedback': f'Error processing request: {str(e)}'
+        }
+    
+    # Write output to file
+    with open(output_path, 'w', encoding='utf-8') as f:
+        json.dump(response_data, f, ensure_ascii=False)
+
+
 def main():
-    """Run the IPC server with the evaluation and preview functions.
     """
+    Run the evaluation function.
+    
+    Detects communication mode based on command-line arguments:
+    - If 2+ args provided: File-based communication (last 2 args are input/output paths)
+    - Otherwise: RPC/IPC server mode using lf_toolkit
+    """
+    # Check for file-based communication
+    # shimmy passes input and output file paths as the last two arguments
+    if len(sys.argv) >= 3:
+        input_path = sys.argv[-2]
+        output_path = sys.argv[-1]
+        
+        # Verify they look like file paths (basic check)
+        if not input_path.startswith('-') and not output_path.startswith('-'):
+            handle_file_based_communication(input_path, output_path)
+            return
+    
+    # Fall back to RPC/IPC server mode
     server = create_server()
-
     server.eval(evaluation_function)
     server.preview(preview_function)
-
     run(server)
 
+
 if __name__ == "__main__":
     main()
\ No newline at end of file