Architecture

How Bitcoin, the Lightning Network, RGB, the Utexo execution layer, the Bridge, and Swap fit together as a unified stablecoin settlement stack.

Utexo is built on a layered stack. Each layer has a distinct and non-overlapping role. Together they deliver the properties that make Bitcoin-native stablecoin settlement viable for production payment systems: deterministic costs, settlement privacy, and Bitcoin-backed security. The Bridge and Swap layers extend this stack outward — connecting external EVM-based networks and enabling non-custodial BTC/USDT exchange on Bitcoin.

Stack Overview

Layer	Role	What Utexo Uses It For
Bitcoin	Settlement anchor and finality	Double-spend prevention, dispute resolution, irreversible state
Lightning Network	Off-chain execution and value transfer	High-throughput payments, near-instant finality, predictable latency
RGB	Asset issuance and client-side validation	Stablecoin creation, privacy-preserving transfers, Bitcoin-secured ownership
Utexo	Execution and coordination layer	Routing, liquidity, fee management, SDK/API abstraction
Bridge	USDT Cross-chain connectivity	Atomic, non-custodial inbound and outbound transfers between Ethereum, Tron, and the RGB layer
Swap	Cross-chain swap	Non-custodial BTC ↔ USDT swaps on Bitcoin and Lightning via the HotPot intent protocol

In the Utexo model, ownership proofs are validated locally by users’ wallets (client-side validation), while actual payments occur through bidirectional Lightning channels. There is no global state to synchronise. Each transaction is a direct peer-to-peer exchange verified by cryptographic commitments.

Bitcoin

Bitcoin serves as the settlement and finality anchor for the entire Utexo system.

It handles correctness, finality and dispute resolution, acting as the foundational layer that grants irreversible settlement and strong security. This allows Utexo to decouple settlement guarantees from execution cost volatility.

What this means in practice:

• Individual payments, asset transfers, and balances are not recorded on-chain. Only compact cryptographic commitments derived from Utexo activity are anchored to Bitcoin in the form of UTXOs, indistinguishable from other ordinary metadata.
• By anchoring state commitments to Bitcoin via RGB, Utexo ensures that execution taking place off-chain cannot be arbitrarily rewritten or manipulated without detection.
• This model minimises on-chain footprint while preserving the ability to prove that off-chain execution followed the agreed rules, remaining accountable to a globally verifiable settlement layer.

If off-chain execution were to fail, stall, or behave maliciously, participants retain the ability to fall back to Bitcoin-backed guarantees. This approach allows Utexo to scale payment activity without compromising on the long-term trust model that Bitcoin provides.

Lightning Network

The Lightning Network provides the off-chain execution environment for Utexo payments.

Utexo adds pooled liquidity and routing access through its APIs, so applications do not need to manage channels directly. All channel management, rebalancing, and routing are handled internally.

What this means in practice:

• Payments settle off-chain in milliseconds with near-instant finality.
• Utexo pre-funds channels and manages liquidity so that routing never fails due to insufficient capacity.
• Fixed latency and predictable fees make payment behaviour deterministic for application developers.

RGB

RGB is the smart contract and asset issuance protocol running on top of Bitcoin that enables Utexo to issue and transfer USDT natively on-chain.

RGB uses a client-side validation model: contract state is maintained locally by the asset owner, not broadcast to a public ledger. Ownership proofs are committed to Bitcoin UTXOs without revealing transfer details on-chain.

What this means in practice:

• Asset transfers are private by default. There is no public ledger of individual RGB transfers.
• USDT issued via RGB is a real Bitcoin-layer asset with Bitcoin-backed finality, not a wrapped token on a separate chain.
• The RGB protocol enforces asset supply integrity: issuance, transfer, and destruction are cryptographically verifiable by any participant holding the relevant contract history.

Utexo Execution Layer

The Utexo execution layer is the payment execution environment for USDT. It sits above Bitcoin, Lightning, and RGB and provides the coordination logic that makes the stack usable at the application level.

Role in the stack:

• Routes payments through Lightning channels with pre-funded liquidity.
• Manages RGB asset state and channel balances internally.
• Abstracts away the complexity of Lightning channel management, RGB state transitions, and fee estimation.

Performance characteristics:

• By combining RGB’s client-side validation architecture with Lightning’s routing network, Utexo achieves transaction times of around 200 ms latency, comparable to Visa speeds.
• Utexo makes Bitcoin usable as a stablecoin settlement network for high-throughput, private-by-default payments that behave predictably regardless of network conditions.

Integration surface:

• REST API and SDK for application-level integration
• Abstracts all channel management, routing, and liquidity operations internally
• No protocol-specific knowledge required in application code

Bridge

The Utexo Bridge connects external EVM-based networks to the Bitcoin RGB layer, enabling atomic, non-custodial USDT transfers in both directions. It is built around Arbitrum as the single EVM settlement hub, with USDT from Ethereum, Tron, and Solana supported transparently via the USDT0 / LayerZero protocol. Bridged USDT is represented on Bitcoin as RGB USDT — a real on-chain asset with Bitcoin-backed settlement guarantees.

The Bridge is composed of five coordinated components:

1. Bridge orchestrator that tracks all in-flight transfers; stateless chain-specific.
2. Connectors that monitor smart contracts and issue on-chain transactions; three independent.
3. Federated Signer Nodes, each running inside an AWS Nitro Enclave, that jointly sign transactions using a 2-of-3 threshold — ensuring no single node can act unilaterally.
4. RGB Multisig Bridge that coordinates multi-party custody of RGB assets with its own 2-of-3 cosigner threshold
5. BTC Relay that streams Bitcoin block headers into the TEE for in-enclave SPV verification.

For full component details, supported networks, transfer flow, and security properties, see Bridge.

Swap

The Utexo Swap enables cross-chain swaps, with BTC ↔ USDT exchange directly on Bitcoin, also on Solana, Ethereum, Tron powered by the HotPot intent protocol. It provides internal BTC/USDT execution for settlement, treasury management, and payments — reducing reliance on centralised venues for rebalancing and conversion.

How it works:

Swap uses an intent-based execution model with two participants: the user, who initiates the swap, and a resolver, who executes it.

1. Quote — The user requests a quote for their desired currency pair and amount via the HotPot Quote API. The API returns a time-limited execution estimate with all pricing information.
2. Intent creation — The user creates a structured intent specifying their addresses and the agreed quote identifier, representing their intention to execute the swap under the quoted conditions.
3. Signing — The user signs the intent off-chain, cryptographically authorising resolvers to execute the swap according to the quoted conditions.
4. Execution — HotPot notifies the winning resolver, who deposits assets into a per-swap escrow contract. Funds are only released once fulfillment is verified on-chain. The swap either completes in full or reverts — there is no partial execution risk.

Key properties:

Property	Description
Non-custodial	Users maintain control of assets throughout the swap process
Atomic settlement	Swaps complete in full or revert safely — no partial fills
Smart routing	Best-execution path across all available liquidity
Privacy-preserving	Front-running is prevented by design via off-chain signed intents
Instant finality	Trades settle with predictable fees on Bitcoin

For full component details, supported networks, transfer flow and security properties, see Swap.

Further Reading

The Problem

Why existing payment infrastructure fails and what Utexo solves.

What is Utexo

Product overview and integration paths.

Bridge

Full Bridge component reference, supported networks, and security model.

Swap

Cross-chain BTC/USDT exchange on Bitcoin.