Yellowpay

YellowPay is a multi-chain payment and yield platform built on Yellow Network's off-chain state channels. Users send instant, gasless payments to anyone using ENS names, DNS names, or wallet addresses — no gas fees, no block confirmations.

The standout feature is "pay from anywhere": pick any token on any supported chain, and LI.FI finds the best swap and bridge route to deliver the payment through Yellow Network in a single flow. The recipient gets funds instantly via an off-chain state channel transfer, regardless of the sender's starting chain or token.

The app is organized into five tabs. Pay handles both balance-mode (instant off-chain transfer from Yellow Network balance) and wallet-mode (any-token cross-chain payment via LI.FI). Fund lets users deposit from any chain into Yellow Network. Withdraw settles state channels back on-chain. Earn deposits into Aave V3 lending vaults on Ethereum, Base, and Polygon with live on-chain APY — vaults are discovered dynamically from Aave V3 reserve data. History tracks every transaction with type filtering and rich metadata.

YellowPay supports 7 chains in production (Ethereum, BNB Smart Chain, Polygon, World Chain, Base, Linea, XRPL EVM Sidechain), 8 assets (USDC, USDT, ETH, WETH, BNB, LINK, XRP, Beatwav), and full ENS integration including CCIP-Read for L2 names like base.eth and cb.id, avatar display, and text record lookups.

YellowPay is built with Next.js 15 (App Router, Turbopack) and TypeScript, using wagmi 2.14, RainbowKit 2.2, and viem 2.21 for wallet connection across 8 chains. Tailwind CSS 4 handles the dark-themed UI.

The core payment layer uses the @erc7824/nitrolite SDK (v0.5.3) to connect to Yellow Network via WebSocket. Authentication follows a 3-step EIP-712 flow: generate an ephemeral session keypair locally, request an auth challenge, then sign an EIP-712 message with the main wallet containing the session key, allowances, and a 24-hour expiry.

All subsequent RPC calls — transfers, channel management, balance queries — are signed with the session key using raw ECDSA via the SDK's createECDSAMessageSigner. A 30-second heartbeat keeps the WebSocket alive, and real-time balance updates arrive via server broadcasts.

The most notable integration is the 3-step "Any Token" payment mode. Step 1: LI.FI swap/bridge executes on-chain (any token, any chain → settlement token on target chain). Step 2: NitroliteClient deposits the output token into Yellow Network's custody contract (with automatic ERC20 approval). Step 3: an instant off-chain transfer sends funds to the recipient. React effects coordinate step transitions by watching the LI.FI transaction status polling hook — when the LI.FI transfer completes, the deposit fires automatically, and when deposit succeeds, the transfer executes.

LI.FI is integrated via a custom REST client calling li.quest/v1 directly — no npm SDK. This keeps the bundle small and avoids dependency version conflicts. The client handles quote fetching (debounced at 500ms to prevent API spam), chain/token enumeration, and transaction status polling at 5-second intervals.

The Earn feature reads Aave V3 reserve data on-chain using viem public clients for Ethereum, Base, and Polygon. APY is computed from the currentLiquidityRate field in RAY format (10^27) using daily compounding. Vaults are discovered dynamically from the settlement token registry — any token with an Aave V3 reserve on a supported chain automatically becomes a vault. Deposits and withdrawals route through LI.FI for cross-chain access, and position tracking combines aToken balanceOf on-chain reads with localStorage persistence for deposit amounts to calculate accrued yield.

ENS integration supports forward resolution (name → address), reverse resolution (address → name), CCIP-Read (ERC-3668) for L2 names, avatar loading via the ENS metadata HTTP service (avoids CORS issues with the standard on-chain approach), and text record display for recipient profiles.

Partner Technologies

a. Yellow Network

Full Nitrolite SDK lifecycle: WebSocket connection, EIP-712 session auth with ephemeral keypairs, state channel creation, instant off-chain transfers, channel resize (partial withdrawal), channel close (full settlement). Plus NitroliteClient on-chain custody deposits. The 3-step wallet payment (LI.FI → custody deposit → instant transfer) demonstrates a novel integration pattern for cross-chain funding of state channels.

b. ENS Creative

ENS names are the primary payment identifier across the app. Integration goes beyond basic resolution: CCIP-Read for L2 names (base.eth, cb.id), avatar display via the metadata service, text record lookups (description, Twitter, GitHub, URL), forward + reverse resolution, and ENS-aware sender identity display.

c. LI.FI DeFi

LI.FI powers three distinct features: (1) "Any Token" payments — swap/bridge any token into settlement currency for instant off-chain transfer, (2) cross-chain account funding — deposit from any chain into Yellow Network, (3) cross-chain Earn deposits — route tokens into Aave V3 vaults on remote chains. Custom REST client with debounced quoting and status polling.