Update app.py

app.py

@@ -2,7 +2,7 @@ import os
 import sqlite3
 import json
 import openai
-from langgraph.graph import StateGraph
+from langgraph.graph import StateGraph, START
 from typing import TypedDict, Optional
 
 # Set your OpenAI API key from environment variable
@@ -125,6 +125,8 @@ def execution_agent(state: SQLExecutionState) -> SQLExecutionState:
 graph.add_node("SQL Execution", execution_agent)
 
 # ------------------ Define Execution Flow ------------------
+# Adding an edge from the reserved START node to the first agent establishes the entrypoint.
+graph.add_edge(START, "Query Understanding")
 graph.add_edge("Query Understanding", "Query Validation")
 graph.add_edge("Query Validation", "Query Optimization")
 graph.add_edge("Query Optimization", "SQL Execution")