Show HN: StarkZap – Gasless Bitcoin Payments SDK for TypeScript

StarkZap is an open-source TypeScript SDK for adding Bitcoin-backed asset transfers, balances, lending & borrowing and staking to web, mobile, or server apps. The goal is to let developers integrate programmable Bitcoin assets without requiring users to install wallets, manage seed phrases, or hold gas tokens. Under the hood it runs on Starknet and supports WBTC, tBTC, LBTC, SolvBTC, and other Bitcoin-backed ERC20 tokens.

```import { StarkZap, StarkSigner, Amount, fromAddress, getPresets } from "starkzap";

const sdk = new StarkZap({ network: "sepolia" }); const wallet = await sdk.connectWallet({ account: { signer: new StarkSigner("0xYOUR_PRIVATE_KEY") } });

await wallet.ensureReady({ deploy: "if_needed" });

const { STRK } = getPresets(wallet.getChainId()); const balance = await wallet.balanceOf(STRK);

if (balance.gte(Amount.parse("10", STRK))) { const tx = await wallet.transfer(STRK, [ { to: fromAddress("0xRECIPIENT"), amount: Amount.parse("10", STRK) } ]); await tx.wait(); console.log(tx.explorerUrl); } ```

Key properties: - Gas sponsorship via paymaster (users don’t need gas tokens) - Multiple auth strategies (email/social via Privy, passkeys via Cartridge) - Batch transfers and contract calls in a single atomic transaction - Works in Node, browser, and React Native

The SDK abstracts account management, fee handling, and wallet popups. This won’t make sense for every app (e.g., if you only need fiat checkout). It’s for existing apps that want programmable onchain assets without the wallet UX.

Would appreciate feedback on the API design and whether this abstraction makes sense.