Letters of credit that settle themselves.
The buyer's stablecoin is locked in a Solana escrow before the goods ship. When an approved inspector verifies the shipping documents, the contract pays the seller automatically. If nobody proves shipment by the deadline, the buyer gets a refund.
- 01FundBuyer
Agree the terms and lock the payment in test USDC in an on-chain escrow. The seller can see it's there before shipping.
- 02ShipSeller
Ship the goods and submit the documents. Only their SHA-256 fingerprints go on-chain: a tamper-evident record.
- 03VerifyInspector
The designated verifier checks the shipment and signs an on-chain approval.
- 04ReleaseProgram
The contract pays the seller in the same transaction. No proof by the deadline? The buyer can take a refund.
What the chain can and can't know
A blockchain can't see a container leave a port. In this MVP a designated verifier (a shipping line, inspection company or oracle) signs an on-chain approval. The contract checks that the authorised verifier approved. It doesn't observe the physical shipment.
- ✓Enforced by code: the funds are locked, only the named inspector can release them, and the refund is only possible after the deadline.
- ✓Tamper-evident: document hashes on-chain, so changing one character is detectable.
- →Next: shipping-line data, electronic bills of lading, inspection companies and oracle attestations.
A programmable complement to the paper process
Letters of credit protect both sides of an international trade, but the process is document-heavy, and the seller is only paid after the documents are couriered and reviewed. Tradelock keeps the idea (pay on proof of shipment) and makes the escrow and release programmable.
Regulatory clarity is improving: the US GENIUS Act (July 2025) set up a federal framework for payment stablecoins, and the UK Electronic Trade Documents Act 2023 recognises electronic trade documents. That makes stablecoin trade settlement increasingly viable. It doesn't make this demo a legal letter of credit.
Why this belongs on Solana
The release rules are code, not a manual payment instruction. Nobody has to remember to pay.
Approval and payment are one transaction, confirmed in seconds rather than after a courier and a review queue.
Network fees are a fraction of a cent per transaction, so anchoring every document on-chain is cheap.
Dollar-denominated USDC, so neither side takes crypto price risk. This demo uses a devnet test token.
Funding, every document hash, the approval and the payout are all visible on Solana Explorer.
A neutral program holds the funds, so the parties don't need a shared private ledger to trust the escrow.
Switch between Buyer, Seller and Inspector with the “Viewing as” control.