How the blind-send guard works

The flow is intentionally small enough for a real builder to validate in minutes, not days.

Funnel

• External discovery: read https://api.nishvault.com/.well-known/x402.
• External landing or quickstart: understand the route and why a live preflight matters.
• External start-here decision: map the runtime shape to the right public entrypoint without paying yet.
• External examples view: map the guard to a real transaction workflow before funding a wallet.
• External unpaid 402: hit POST /simulate/transaction-preflight once without payment and confirm payment_required.
• External paid request: retry with an x402-capable Base mainnet buyer wallet.
• External wallet-credit: confirm the seller-side USDC credit with the fresh artifact bundle.

Why the unpaid 402 matters

It is the cheapest intent signal. A crawler will keep poking discovery. A serious builder eventually wants to see the protected route respond with a real unpaid challenge.