# StablecoinX

> Stablecoin payment platform: hosted checkout for accepting stablecoin payments, a merchant dashboard, ERC-4337 gas sponsorship (paymaster), and a non-custodial on-chain treasury. This surface (`harness.stablecoinx.com`) is the public StablecoinX platform — live on Ethereum, Base and Arbitrum, with a sandbox (testnet) mode for integration testing. Reachable without VPN.

A StablecoinX merchant account can be driven programmatically — auth, payment sessions, API keys, paymaster clients/allowlist, and webhooks — through the official StablecoinX MCP server at https://github.com/e2xlabs/stablecoinx-mcp (npm: https://www.npmjs.com/package/@stablecoinx/mcp). Install with `npx @stablecoinx/mcp setup`.

## Surfaces

- [Checkout / Pay](https://harness.stablecoinx.com/): hosted payment page. A payment session (`/session/:id`) renders the amount and accepts a stablecoin payment settled through an ERC-4337 smart account with sponsored gas.
- [Merchant dashboard](https://business.harness.stablecoinx.com/): create and manage payment sessions, API keys, webhooks, and paymaster clients/allowlist. See its [llms.txt](https://business.harness.stablecoinx.com/llms.txt).
- [Treasury dashboard](https://treasury.harness.stablecoinx.com/): non-custodial treasury — balances, yield positions, P&L, sponsored deposits/withdrawals. See its [llms.txt](https://treasury.harness.stablecoinx.com/llms.txt).
- [Paymaster test UI](https://paymaster-ui.harness.stablecoinx.com/): exercise sponsored UserOperations and ERC-20-paid gas against the public paymaster RPC. See its [llms.txt](https://paymaster-ui.harness.stablecoinx.com/llms.txt).

## APIs

- **Paymaster** — `https://paymaster.harness.stablecoinx.com` (ERC-4337 / ERC-7677 paymaster RPC + REST). OpenAPI: [/openapi.json](https://paymaster.harness.stablecoinx.com/openapi.json), [/openapi.yaml](https://paymaster.harness.stablecoinx.com/openapi.yaml), Swagger UI [/openapi](https://paymaster.harness.stablecoinx.com/openapi).
- **Treasury API** — `https://treasury-api.harness.stablecoinx.com` (read aggregation, history, P&L, deposit/withdraw quotes). OpenAPI: [/openapi.json](https://treasury-api.harness.stablecoinx.com/openapi.json), [/openapi.yaml](https://treasury-api.harness.stablecoinx.com/openapi.yaml), Swagger UI [/openapi](https://treasury-api.harness.stablecoinx.com/openapi).
- **Merchant API** — `https://api.harness.stablecoinx.com` (merchant account, sessions, keys, webhooks; thirdweb-authenticated). There is no public OpenAPI spec for the merchant API; the agent-facing interface is the StablecoinX MCP server above.

## Networks

The harness serves a sandbox testnet mode and live mainnet settlement, resolved server-side per the merchant account.

## Security

- Vulnerability disclosure: `tech@e2xlabs.com`. Machine-readable contact at [/.well-known/security.txt](https://harness.stablecoinx.com/.well-known/security.txt) (RFC 9116).
- Non-custodial: settlement happens on-chain via the payer's smart account; the checkout never holds funds.
- See [llms-full.txt](https://harness.stablecoinx.com/llms-full.txt) for the extended reference.