TxSentinel

TxSentinel is a deterministic, pre-sign transaction policy firewall for autonomous agents and Agentic Wallets.

Before an agent signs an onchain action, it sends the proposed transaction, the user's policy limits, and simulation evidence to TxSentinel. The policy engine evaluates spending limits, fees, slippage, recipients, approvals, simulation results, and contract verification before any transaction is signed or broadcast.

Every request returns an explainable ALLOW, HOLD, or DENY decision with a risk score, rule-level evidence, an action digest, and a deterministic SHA-256 receipt. ALLOW permits the wallet to continue, HOLD requires human review, and DENY stops execution.

TxSentinel never receives private keys, signs transactions, or broadcasts user transactions. Policies belong to the user and can be versioned or replaced. The seller controls the x402 payment asset, price, and receiving address, while the buyer authorizes payment through OKX Wallet.

The live product provides two integration paths:

• Free preflight API for testing and integration

• Paid production API using the official OKX x402 Express, Core, and EVM packages

Policy checks run offchain before wallet signing for speed and privacy. A PolicyAnchor contract on X Layer Testnet provides tamper-evident policy and receipt anchoring without exposing private transaction data.

A real x402 settlement has been completed on X Layer Testnet using OKX Wallet and the official facilitator flow.

I built and deployed the complete TxSentinel MVP during the hackathon.

Completed:

• Live pre-sign policy console and public REST API

• Three deterministic outcomes: ALLOW, HOLD, and DENY

• User-defined policies with versioned policy digests

• Spend, fee, slippage, recipient, approval, simulation, and contract-verification controls

• Deterministic SHA-256 decision receipts

• Official OKX x402 Express, Core, and EVM integration

• Browser buyer flow with quote, OKX Wallet connection, balance validation, EIP-3009 signing, retry, and settlement receipt

• Real x402 testnet settlement of 0.01 USD₮0 on X Layer Testnet

• PolicyAnchor smart contract deployed on X Layer Testnet

• Support for USD₮0, USDG, and USDC test assets

• ASP candidate TxSentinel #6828 submitted for OKX.AI listing review (still under reviewing till 21 JUL)

• 30 automated policy, HTTP, validation, contract, and x402 integration tests

• Bilingual documentation, static architecture diagrams, API documentation, evidence report, screenshots, and narrated demo

• Public v1.0.0 Genesis release

Verified x402 settlement:

0x78865316d773400a223c0e76aced95c25def2fba3f0335b79ba64ff70354f68d

Release:

https://github.com/FeeeeelixWong/txsentinel-okx/releases/tag/v1.0.0-genesis

Technical evidence:

https://github.com/FeeeeelixWong/txsentinel-okx/blob/main/EVIDENCE.md

TxSentinel is bootstrapped and self-funded. I have not raised external equity, institutional, or token funding for this project.

I independently cover the current development, infrastructure, testing, and deployment costs. The initial business model is usage-based API revenue through x402 pay-per-policy-check access, with future enterprise plans for agent wallet platforms and automation teams.