The volume field (data[i][5]) is always 0 for Index tokens, such as NIFTY 50 (token: 99926000) across all intervals (ONE_MINUTE, FIVE_MINUTE, etc.).
POST https://apiconnect.angelone.in/rest/secure/angelbroking/historical/v1/getCandleData
This issue only affects INDEX tokens like 99926000 (NIFTY) etc.
Equity tokens like 12713 (RELIANCE) are working fine and return proper volume data.
Confirmed via direct cURL.