Log in with an email, and your ordinary wallet becomes a smart account that treats every chain as one balance. Tap Save, and your USDC lands in an ERC-4626 vault on Arbitrum One earning live Aave V3 yield — even if the dollars started on a different chain. No bridges, no networks to pick, no gas token to hold.

Built for the Encode UXMAXX Hackathon — Universal Accounts Track (Particle Network). The cross-chain leg is handled entirely by the Particle Universal Account SDK in EIP-7702 mode; the on-chain savings vault is three EIP-2535 diamonds assembled from the Lattice framework, consumed as an installable dependency.

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Try it

Live app: https://everyield.vercel.app

Run locally — the frontend lives in app/:

cd app
bun install
bun dev            # http://localhost:3000

Set these five env vars (see app/.env.example) — from the Particle and Privy dashboards:

Variable	Source
NEXT_PUBLIC_PARTICLE_PROJECT_ID	dashboard.particle.network → project
NEXT_PUBLIC_PARTICLE_CLIENT_KEY	dashboard.particle.network → project
NEXT_PUBLIC_PARTICLE_APP_ID	dashboard.particle.network → Web app
NEXT_PUBLIC_PRIVY_APP_ID	dashboard.privy.io → app → Settings
NEXT_PUBLIC_PRIVY_CLIENT_ID	dashboard.privy.io → app → Settings

The vault contracts are already live on Arbitrum One (below) — the app reads and writes them as-is.

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Deployed contracts — Arbitrum One (chain 42161)

All three diamonds are Etherscan-verified at deploy; a Sourcify layer is available via make verify-mainnet. Addresses are the source of truth in deployments/42161.json.

Contract	Address
Vault (eyUSDC)	0x4aE34A2fA9efD143C0330c306dDF8808eE34815D
StrategyManager	0xcFf692A6cc69D868Bb1944d9269a233c01643Adc
AaveV3Adapter	0x9e104F4Ec391128Ad0cc101D2D1bB5Be6c02Dd02
Deployer	0xdadada4e8038641212262fd94e816d4a57cdc751

Deployed at block 485711716; total deploy cost 0.000572 ETH (38 txns). Underlying asset is Arbitrum native USDC (0xaf88d065e77c8cC2239327C5EDb3A432268e5831) supplied into Aave V3. A dress-rehearsal stack lives on Arbitrum Sepolia — deployments/421614.json.

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How it works

flowchart TD
    U["User<br/>(email login)"] --> P["Privy embedded wallet<br/>— an ordinary EOA"]
    P -->|"signs EIP-7702<br/>delegation"| UA["Particle Universal Account<br/>one balance across chains"]
    UA -->|"routes value cross-chain<br/>(e.g. Base to Arbitrum)"| VAULT

    subgraph ARB["Arbitrum One — Lattice diamonds"]
        VAULT["Vault diamond<br/>ERC-20 shares (eyUSDC) + ERC-4626 + VaultCore"]
        MGR["StrategyManager diamond<br/>+ EveryieldCrank facet"]
        ADP["AaveV3Adapter diamond"]
        VAULT <-->|"strategy hooks"| MGR
        MGR -->|"80% deploy / 20% idle"| ADP
        ADP --> AAVE["Aave V3 Pool (USDC)"]
    end

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1. Email in. Privy issues an embedded wallet — a normal EOA. Under EIP-7702, that same key signs an authorization delegating the account, so the embedded wallet is both signer and executor of every vault call.
2. One balance. The Particle Universal Account (SDK v2.0.3, useEIP7702: true) aggregates the user's assets across chains into a single spendable number and quotes an all-in fee before any signature.
3. One Save. A deposit is a batched approve + ERC-4626 deposit(assets, receiver) on the Arbitrum vault. If the dollars are on another chain, Particle routes them there — the contracts never bridge.
4. It earns. An operator crank rebalances the vault to an 80% Aave / 20% idle split and supplies the idle adapter balance into Aave V3. Shares (eyUSDC) accrue live yield; withdrawals are partial or full.

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Built on Lattice

Everyield is also a demonstration of Lattice as a framework you forge install and build on:

forge install dadadave80/lattice   # pinned at v0.2.0

Lattice's value is a three-layer Diamond (EIP-2535) facet pattern — facet → *Lib → interface. Everyield assembles three diamonds straight from the framework's deploy recipes:

• Vault — the Lattice VaultCore recipe: ERC-20 share facet (eyUSDC), ERC-4626 facet, and the VaultCore strategy-hook facet, reused (selector surgery and all) rather than copied.
• StrategyManager — the stock StrategyManager diamond with one extra facet cut in: our EveryieldCrank. It is a single external function (crankDeploy) that pushes the adapter's idle USDC into Aave — proof of how cheap it is to extend a Lattice diamond with app-specific logic.
• AaveV3Adapter — the framework's Aave V3 adapter, wired to the vault by EveryieldAaveInit.

The assembly and wiring is one broadcast: script/DeployEveryield.s.sol.

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Live rehearsal — real funds, on-chain

A full round trip on 2026-07-20 with real money, verifiable against the vault address above:

• $2.00 cross-chain deposit, Base → Arbitrum, through the 7702 account. All-in fee quoted $0.36, charged $0.36 — exactly as quoted.
• Crank produced the exact 80/20 split — 1,599,999 / 400,000 units (Aave / idle) on a 2,000,000-unit deposit.
• Yield accrued, then a full recall returned everything to idle with no principal loss.
• $1.00 partial withdrawal at exact share math, fee $0.14.

Every number is reproducible on-chain and pinned by the fork test below.

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What our fork test caught — in our own framework

Our Arbitrum-fork round trip caught a share-pricing composition bug in Lattice's own ERC4626Lib: its deposit/redeem price against idle-only assets while funds are deployed to a strategy, because the library binds to totalAssets internally and never sees the diamond's full-NAV VaultCore override. The fork test pins the exact behavior — a partial redeem of 10% of shares pays 10% of the idle buffer, not 10% of NAV:

// test/EveryieldFork.t.sol
assertApproxEqAbs(got, 2e6, 1, "partial redeem prices against idle-only totalAssets (20e6 * 10%)");

Rather than paper over it, the app engineers around it, fail-closed:

• Interaction-window guard — Save and Withdraw are enabled only when the vault is fully idle (idleAssets >= totalAssets); pre-first-read they stay disabled, never briefly open (app/lib/everyield.ts, OptimizingNotice).
• Full-NAV display pricing — positions are valued shares × totalAssets / totalSupply, never convertToAssets/previewRedeem (those bind to the idle-only path).

An upstream fix to ERC4626Lib is scoped for post-hackathon Lattice.

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Keeper & roadmap

The rebalance/deploy crank (make crank) and full recall (make exit) are operator-side by design for the hackathon — one command, explicit keystore auth. Roadmap: hand these to Chainlink Automation / Gelato, land the upstream ERC4626Lib fix, and support multiple vaults / strategies.

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Tests

Suite	What it covers	Run
Foundry — assembly	Three diamonds assemble and wire	forge test
Foundry — Arbitrum fork	Deposit → crank → earn → partial + full redeem, incl. the idle-only pricing pin	forge test (needs ARBITRUM_RPC_URL)
bun — calldata	approve+deposit batching, redeem(shares, owner, owner) encoding	cd app && bun test
bun — USD decoder	Hex/decimal fee decode, fail-closed to 0 on garbage	cd app && bun test
bun — feeDrifted	Re-confirm boundary: max(20% of prev, $0.25)	cd app && bun test

Toolchain: Next.js 16.2.10 (Turbopack), React 19.2.7, bun, Particle Universal Account SDK 2.0.3, Privy; Solidity 0.8.30 / Foundry.

Budget

~$2.10 total consumed of a $10 cap — deploy ~$1.50, Universal Account fees ~$0.50, keeper gas in cents.