Distinguish an Avalanche X-Chain mint authority from spendable tokens
A raw X-Chain UTXO set can contain both fungible balances and a mint authority for the same asset. Summing every matching asset ID without decoding the output type gives a misleading inventory.
Classify the inner feature-extension output
Decode the transferable output wrapper to obtain the asset ID and the nested output. A secp256k1 mint output encodes locktime, threshold and owner addresses. Its serialized fields contain no fungible amount to add to a balance. A transfer output additionally carries its amount.
SECP256K1MintOutput type 0x00000006 mint authority
SECP256K1TransferOutput type 0x00000007 token amount and owners
Keep a separate issuance-authority register
A wallet with a 900-unit transfer output and one mint output holds 900 spendable units subject to its ownership conditions. Separately report which key threshold can exercise issuance and which outpoint grants it. When a mint operation spends the authority, inspect the newly produced mint output and its owners before treating the old signer group as current.