MCX margin_calculator + get_margin return HTTP 401 / 'Object reference not set' while NFO works

[gurusura]

Summary

Both margin_calculator() and get_margin() return HTTP 401 (wrapped server-side as {"Status": 500, "Error": "Object reference not set to an instance of an object."}) whenever exchange_code="MCX" is passed. The same SDK + API key + session token works correctly for NFO. MCX trading is fully active on the account (place_order for MCX options/futures works, MCX historical data works, capital is allocated to commodity segment on iDirect web).

Environment

• breeze-connect version: 1.0.64 (also reproduced on the latest from PyPI)
• Python 3.12 on Linux
• Account: live MCX trading active, ~₹98K allocated to commodity segment on iDirect web
• Same session token works for NFO calls in the same Python process

Reproduction

import os
from breeze_connect import BreezeConnect

b = BreezeConnect(api_key=os.environ["BREEZE_API_KEY"])
b.generate_session(api_secret=os.environ["BREEZE_API_SECRET"],
                   session_token=os.environ["BREEZE_SESSION_TOKEN"])

# === Control: NFO margin_calculator — HTTP 200 ===
nfo_leg = {
    "stock_code": "NIFTY", "exchange_code": "NFO", "product": "options",
    "expiry_date": "2026-04-28T07:00:00.000Z", "right": "call",
    "strike_price": "24050", "action": "buy", "quantity": "75",
    "price": "0", "cover_order_flow": "N", "fresh_order_type": "N",
    "cover_limit_rate": "0", "cover_sltp_price": "0",
    "fresh_limit_rate": "0", "open_quantity": "0",
}
print(b.margin_calculator(list_of_positions=[nfo_leg], exchange_code="NFO"))
# {'Success': {'margin_calulation': [...], ...}, 'Status': 200, 'Error': None}

# === MCX margin_calculator — HTTP 401 ===
mcx_leg = {**nfo_leg, "stock_code": "CRUDEOIL", "exchange_code": "MCX",
           "expiry_date": "2026-05-14T07:00:00.000Z",
           "strike_price": "9000", "quantity": "10"}
print(b.margin_calculator(list_of_positions=[mcx_leg], exchange_code="MCX"))
# {'Status': 500, 'Error': 'Object reference not set to an instance of an object.'}

# === Control: account-level get_margin — HTTP 200 ===
print(b.get_margin())
# {'Success': {'cash_limit': 293374.73, 'amount_allocated': 287938.67, ...},
#  'Status': 200, 'Error': None}

# === MCX get_margin — HTTP 401 ===
print(b.get_margin(exchange_code="MCX"))
# {'Status': 500, 'Error': 'Object reference not set to an instance of an object.'}

What's been tested (rules out parameter-shape issues)

12 distinct parameter combinations on margin_calculator for MCX, all return identical 401:

Field	Variations tried
Product field name	product=options, product_type=options, product_type=futureplus_options, product_type=futures
Expiry format	ISO 8601 (T07:00:00.000Z), T06:00:00.000Z, DD-MMM-YYYY (14-May-2026), strike_date instead of expiry_date
Quantity field	quantity="10" (lot size) vs lots="1"
Stock code	CRUDEOIL vs CRUDEOILM (mini)
Style	Options-style (right="call", strike="9000") vs futures-style (right="others", strike="0")

The 401 returns BEFORE any param validation runs, so the .NET ref error is the gateway's fallback message rather than a real null dereference.

Expected behaviour

margin_calculator and get_margin should accept exchange_code="MCX" for accounts with active MCX trading entitlement, the same way they accept "NFO" today.

Workaround

Falling back to a static SPAN approximation for required margin and to account-level get_margin() (no exchange_code) for available capital. Functional but loses per-exchange precision.

Notes

• This is not reported on this repo or on r/algotrading / StackOverflow / forum.icicidirect.com as of April 2026. May be a recent server-side regression.
• Happy to provide additional logs (request headers, full response body) if useful — please let me know what's safe to share publicly.