Why real mainnet now?

The internal rail proof is complete; this live surface now charges real Base mainnet USDC so revenue proof means actual wallet credit.

What should I verify before paying?

Verify discovery metadata, confirm one unpaid payment_required challenge, and inspect the proof and artifact index before a paid retry.

Buyer trust for the first agent-builder payment

Real Base mainnet USDC

This browser is marked as owner/self traffic.

Your visits from this browser will be reported separately so the external funnel does not mistake your own testing for outside demand.

Clear owner tag for this browser

This page is for a first-time outside buyer, especially a programmatic EVM agent builder, deciding whether the paid preflight is real enough to try once.

The cleanest no-wallet trust cut is now /first-unpaid-402. It exists to verify discovery plus the unpaid challenge before any wallet decision.

What you can verify before you pay

The focused first-check page is /first-unpaid-402.
The public seller origin is https://api.nishvault.com.
The x402 metadata is exposed at /.well-known/x402.
The browser-first unpaid challenge now lives on /first-unpaid-402 and requires no wallet.
The paid route is POST /simulate/transaction-preflight and returns an unpaid 402 Payment Required challenge before any wallet funding decision; if that response looks wrong, stop.
The public quickstart is available at /quickstart.
The integration surface is available at /integrations.
The example-flow surface is available at /examples.
The proof artifact index is available at /artifact-index.

First payment checklist

1. Read /.well-known/x402 and confirm the guard route, network, and price.
2. Trigger one unpaid POST to /simulate/transaction-preflight and confirm payment_required before you fund anything.
3. Fund a Base mainnet buyer wallet only if the unpaid challenge looks correct.
4. Run one buyer CLI command and keep the fresh artifact directory.
5. Verify the wallet-credit artifact before treating the flow as complete.

What the existing proof artifacts mean

They prove the seller rail and wallet-credit flow already worked internally.
They do not prove a net-new outside buyer yet.
The next real milestone is one fresh outside unpaid 402, then one fresh outside paid artifact with a new timestamp and tx hash.

FAQ

Why real mainnet now? The proof phase is complete; this live path now exists to collect real Base mainnet USDC for one pre-send guard check.
What do I get if I pay? One live JSON-RPC preflight result with call outcome, gas estimate, fee context, and settlement metadata.
What should I inspect after payment? The new paid artifact directory, the settlement tx hash, and the wallet-credit check output.
What if I only want to validate discovery? Stop after the unpaid 402 challenge; that is the no-risk public proof step.