x402 State Channel Demo

Channel side (left) — everything is real

1. Open channel — A real Soroban transaction deposits USDC into an on-chain escrow contract. A fee-bump relayer pays the XLM gas so the agent spends zero XLM. You can verify this tx on stellar.expert.
2. Pre-sign states — The agent pre-signs N ed25519 payment states offline (channelId || iteration || balances). Each signature authorizes one more unit of payment to the server. No network calls.
3. Purchase images — Each request hits the live NFT service at x402-nft.stellar.buzz with a signed channel payment header. The Cloudflare Worker verifies the ed25519 signature (sub-millisecond, no blockchain), generates the art, counter-signs the state, and returns a real SVG. Every image you see was paid for.
4. Close channel — A second real Soroban transaction submits the final mutually-signed state. The contract verifies both signatures and distributes the USDC: unused deposit back to the agent, earned amount to the merchant. Again, relayer pays gas.

Traditional side (right) — simulated Stellar timing

Standard x402 requires 1 on-chain transaction per API call. Each payment waits ~5 seconds for a Stellar ledger close before it settles. This side simulates that cadence — one image every ~5 seconds with locally-generated placeholder art. No actual transactions are submitted, but the timing reflects real Stellar throughput. For 100 images that's over 8 minutes of waiting.

Why channels win

The on-chain cost is fixed at 2 transactions regardless of how many images you buy. The per-image payment cost is just an ed25519 signature verification — pure math, no network, no gas. The more images you buy, the greater the advantage: the 2 on-chain transactions are amortized across all purchases while traditional x402 pays the ~5s ledger-close cost every time.