Unable to use langchain[anthropic] package for redshift db. BadRequestError: Error code: 400 - {'type': 'error', 'error': {'type': 'invalid_request_error', 'message': 'messages: at least one message is required'}}

[shehroz010]

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Example Code

import os
import getpass
from langchain import hub
import redshift_connector
from sqlalchemy import create_engine
from typing_extensions import Annotated
from typing_extensions import TypedDict
from langchain.chat_models import init_chat_model
from langchain_community.utilities.sql_database import SQLDatabase

conn_params = {
    'host': host,
    'port': 5439,
    'database': database,
    'user': username,
    'password': password
}

conn = redshift_connector.connect(**conn_params)
engine = create_engine('redshift+redshift_connector://', creator=lambda: conn)

db = SQLDatabase(engine, include_tables=['clients', 'master_employee'])

if not os.environ.get("ANTHROPIC_API_KEY"):
    os.environ["ANTHROPIC_API_KEY"] = getpass.getpass("Enter API key for Anthropic: ")

llm = init_chat_model("claude-3-7-sonnet-latest", model_provider="anthropic")
query_prompt_template = hub.pull("langchain-ai/sql-query-system-prompt")

class State(TypedDict):
    question: str
    query: str
    result: str
    answer: str

class QueryOutput(TypedDict):
    query: Annotated[str, ..., "Syntactically valid SQL query."]

def write_query(state: State):
    prompt = query_prompt_template.invoke(
        {
            "dialect": db.dialect,
            "top_k": 10,
            "table_info": db.get_table_info(),
            "input": state["question"],
        }
    )
    structured_llm = llm.with_structured_output(QueryOutput)
    result = structured_llm.invoke(prompt)
    return prompt, {"query": result["query"]}

prompt, dataDict = write_query({"question": "what is the xirr of Scarlet Family for nifty 50 quaterly ?"})

Description

I am trying to use the connect my redshift db to a llm (Claude) using langchain and I m following this documentation:
https://python.langchain.com/docs/tutorials/sql_qa/
The code and steps given in the tutorial works fine for Open AI but as soon as i switch to Anthropic's version the same code provided in the tutorial doesn't work. It contantly throws an error

BadRequestError: Error code: 400 - {'type': 'error', 'error': {'type': 'invalid_request_error', 'message': 'messages: at least one message is required'}}

Is this a bug or am i doing it wrong as I haven't changed the main code apart from return statement of function write_query()

System Info

langchain==0.3.23
langchain-anthropic==0.3.10
langchain-community==0.3.21
langchain-core==0.3.51
langchain-openai==0.3.12
langchain-text-splitters==0.3.8
langchainhub==0.1.21

Platform = Windows 11
Python = 3.12

[shehroz010]

fixed