Sailor Lend
Sailor Lend: Bitcoin-Backed Lending
Non-custodial Bitcoin-backed lending with stablecoin loans, debit cards, and bank transfers
The problem
Cross-chain borrowing and collateral handling required validation of high-risk fund movements.
My contribution
Tested borrowing, repayment, collateral release, and integration edge cases with engineering.
The outcome
Caught cross-chain issues before production and established repeatable validation coverage.
The Challenge
Sailor Lend lets users borrow against Bitcoin without KYC or giving up custody, relying on a trustless escrow built from NEAR's Omnibridge, Intents, and Chain Signatures with Bitcoin MPC wallets. This cross-chain, multi-component architecture meant a single defect in collateral handling, loan-to-value calculation, or fund movement could put real user assets at risk - raising the bar for QA well beyond a typical web app.
Approach & decisions
- Built end-to-end test coverage for the core borrow flow: BTC deposit to escrow, collateral valuation, loan disbursement, repayment, and collateral release
- Validated loan-to-value logic and liquidation thresholds across price movements to ensure the protocol stayed solvent under volatile conditions
- Tested the trustless Bitcoin escrow path (NEAR Omnibridge, Intents, Chain Signatures, MPC wallets) across happy paths and failure/edge cases
- Verified the debit card, global bank transfer, and DeFi earn (Rujira / ThorChain) integrations against expected balances and states
- Documented reproducible defects with clear severity and worked with engineering to confirm fixes before release