# A402 (Atomic Service Channels)

> A research-stage payment architecture (arXiv, Mar 2026) that binds crypto payments to verifiable service execution for machine-to-machine commerce. It is positioned explicitly as addressing x402's lack of end-to-end atomicity across execution, payment, and delivery.

## At a glance

| Field | Value |
| --- | --- |
| Name | a402 |
| Layer | payment-execution |
| Category | onchain |
| Status | proposed |
| Created by | Li et al. (academic research) |
| Launched | — |
| Rails | Ethereum, Bitcoin |
| Settlement | Off-chain Atomic Service Channels, aggregated and settled on-chain via a TEE-based liquidity vault. |
| Reversible | no |
| Human in loop | none |
| D2C fit | weak |
| B2B fit | moderate |
| Spec | https://arxiv.org/abs/2603.01179 |
| Last verified | 2026-09-02 |

## How it works

A402 is a **trust-minimized payment architecture** proposed to fix a specific gap the authors identify in x402: x402 sequences payment, service execution, and response delivery through a facilitator but does **not enforce end-to-end atomicity** across the three.

- **Atomic Service Channels (ASCs).** A402 extends payment channels so that each payment is explicitly bound to a service request and its result delivery, offloading on-chain payments into off-chain channels for real-time, high-frequency micropayments.
- **Exec–Pay–Deliver invariant.** Within an ASC, an atomic exchange protocol built on **TEE-assisted adaptor signatures** guarantees a payment is finalized *if and only if* the request is correctly executed and the result is delivered.
- **TEE Liquidity Vault.** A trusted-execution-environment vault privately manages ASC lifecycles and aggregates many settlements into a single on-chain transaction that reveals only aggregated balances.

The authors report an implementation evaluated against x402 on both Bitcoin and Ethereum, claiming order-of-magnitude performance and on-chain-cost improvements. This entry is marked **proposed**: it is a published research design, not a production deployment, and its claims should be read as the paper's rather than as settled ecosystem fact.

## Tradeoffs

- Research-stage: a published architecture with a prototype, not a production system with real deployments.
- Security guarantees depend on trusted execution environments (TEEs) and remote attestation — a hardware-trust assumption x402 does not require.
- Meaningfully more complex than a plain HTTP-402 flow, trading simplicity for atomicity and privacy.
- Reported performance and cost advantages are the authors' own measurements and are not yet independently corroborated at scale.

## Security & limitations

- The Exec–Pay–Deliver guarantee rests on TEE integrity; a TEE compromise or attestation failure undermines the atomicity claim.
- Correctness of the adaptor-signature construction is load-bearing for the atomic exchange.
- As with any channel protocol, force-close and dispute paths must be sound to prevent fund lock-up or theft.

## Fits together with

- x402

## Sources

1. [A402: Binding Cryptocurrency Payments to Service Execution for Agentic Commerce](https://arxiv.org/abs/2603.01179) — arXiv (Li et al.), 2026-03
2. [A402 (DOI)](https://doi.org/10.48550/arXiv.2603.01179) — arXiv, 2026-03

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_Source: payful.ai — independent editorial reference. Verified 2026-09-02._