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The Operator Queue acts as the verification gateway between confirmed Bitcoin network transactions and Nexio smart contract execution. The Operator Queue is a Protocol Layer component that validates Bitcoin-side activity before triggering on-chain events. It acts as the verification gateway between confirmed Bitcoin transactions and smart contract execution. This ensures every uBTC or yBTC mint, burn, or redemption corresponds exactly to a verified Bitcoin transaction. Without it, the on-chain state could desync from the custody reality.

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How The Operator Queue Works

Many borrowers and lenders choose to operate through approved custodians. **The Operator Queue treats native Taproot vault flows and custodial flows identically: **deposits originate from (and redemptions return to) whitelisted custodian sub-accounts, and every transaction still passes through the same proof-gating and attestation checks. This preserves 1:1 backing, auditability, and deterministic mint/burn logic while allowing institutions to use their existing key-management and segregated cold-storage setups. The Operator Queue verifies Nexio transactions (e.g. tge burning/minting of uBTC/yBTC) and executes the corresponding action, as follows:
  1. A BTC deposit or repayment occurs on Bitcoin.
  2. The Operator Queue (relayer network) continuously observes the Bitcoin mempool and confirmed blocks for vault-related transactions.
  3. After detecting a relevant deposit or repayment, it waits for the required number of Bitcoin confirmations before submitting attested transaction metadata on-chain.
  4. A 2-of-3 FROST signer quorum then co-signs the corresponding PSBT, authorizing the mint, burn, or Series accounting update.
This ensures that every on-chain state change precisely matches a verified Bitcoin transaction. 9thimage Jp

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Security Model

The Operator Queue requires multiple approved parties to co-sign attestations (2-of-3 threshold) before they are accepted, ensuring no single actor can alter the system’s state. All vault spends use Taproot key-path spends, which aggregate multiple signer keys into a single Schnorr signature. On-chain, these appear as single-sig transactions but still enforce 2-of-3 multisig verification off-chain. This keeps transactions small, private, and cost-efficient, while batching and dynamic fee management (RBF/CPFP) ensure confirmations finalize quickly. In the event of dishonest behavior, operators can be slashed or permanently excluded.

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Example: Operator Queue

A lender deposits 5 BTC into a Series vault. The Series vault is a Taproot vault on the Bitcoin network, meaning the receipt of funds is public. The Operator Queue confirms receipt and generates a proof, which is submitted to Nexio’s smart contract that, in turn, mints 5 uBTC to the lender’s address. If the Bitcoin transaction is invalid or double-spent, no mint occurs.