1000x cheaper than per-request protocols
Only the latest voucher matters. The escrow settles the delta.
Traditional (per-request)
$250.00
1,000,000 payments × $0.00025 each
1,000,000 on-chain transactions
SPX Protocol
$0.00025
1,000,000 payments → 1 settlement
1 on-chain transaction
How it works
Fund
Owner creates an escrow and deposits tokens. Sets an agent key and optional spending limits.
Sign
Agent signs cumulative vouchers off-chain. Each voucher supersedes the last. Free and instant.
Settle
Service submits the latest voucher on-chain. Escrow pays the delta. 1 million payments, 1 transaction.
Protocol Comparison
| SPX | x402 | Circle Nano | Stripe ACP | L402 | |
|---|---|---|---|---|---|
| Payments per TX | 1,000,000 | 1 | Batched | 1 | 1 |
| Cost / 1M payments | $0.00025 | $250 | Free* | $300K+ | ~$1,000 |
| Settlement | <1s | <1s | Batched | 2-3 days | <1s |
| Open Source | Yes | Yes | No | Yes | Yes |
| Chain | Solana | Multi | Off-chain | Fiat | Bitcoin |
* Circle Nanopayments is closed-source and centralized
Multi-Token
USDC, SOL, or any SPL token. One protocol for all.
Auditable
Fully on-chain, permissionless, open source. Every settlement is verifiable.
Instant
Vouchers signed in <1ms off-chain. Settlements confirm in <1s on Solana.
Multi-Escrow
Create labeled escrows per use-case. Each with its own agent and budget.
Fee Model
0.5% on settlement delta. No fee on the off-chain voucher flow.
Owner Control
Freeze, close, rotate agent keys, extend expiry. Full control always.