Payroll Ninja

Private, real-time streaming payroll on Monad via Unlink.

Wages stream continuously into dedicated ZK-private buckets — taxes, retirement, health, utilities, take-home — all invisible on-chain. Bills pay themselves. The employer's identity and payroll amounts are fully private after a single lump-sum deposit.

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Architecture

Employer Unlink wallet
  └─ private send every cycle ──► Employee Master account (ZK, hidden)
                                      └─ private routing ──► Taxes bucket
                                                         ──► Retirement bucket
                                                         ──► Health bucket
                                                         ──► Utilities bucket
                                                         ──► Net (take-home) bucket

Scheduler detects due bills
  └─ executor calls biller via x402 ──► Biller address receives USDCm
  └─ Utilities bucket ──(Unlink withdraw)──► Executor EOA (reimbursement)

Components

Component	Stack	Port
App	Next.js 14, wagmi, RainbowKit, Unlink React SDK	3000
Executor	Node.js 24, Hono, Unlink Node SDK	3001
Electric biller	Node.js, Hono, x402	3002
Insurance biller	Node.js, Hono, x402	3003

Smart Contracts (Monad testnet)

PayrollManager.sol — optional on-chain registry. Not in the active payment path; wages flow entirely through Unlink.

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Privacy model

Event	Visible on-chain	Hidden
Employer lump-sum deposit	EOA address + amount (once)	Which account credited
Per-cycle wages	Nothing — ZK private send	Everything
Bucket routing	Nothing — ZK private sends	Everything
x402 bill payment	Executor EOA + biller address + amount	Which employee
Bill reimbursement	Amount + executor EOA	Source bucket / employee

The only public trace is the employer's initial deposit. Every payroll cycle and all bucket routing is invisible.

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Key technical decisions

Unlink as the privacy primitive

All payments happen inside the Unlink ZK pool on Monad testnet. Both employer and employee wallets are managed server-side by the executor (mnemonic stored in SQLite). The executor operates autonomously — no user interaction after one-time setup.

• Employer wallet: one account (Master), holds payroll float
• Employee wallet: 6 accounts (Master + 5 buckets), derived from same mnemonic
• Account derivation: BIP-39 mnemonic → deterministic keypairs → same unlink1... addresses across browser and executor

x402 for machine-to-machine bill payments

x402 is used for executor → biller flow. When a bill is due, the executor calls the biller's HTTP endpoint. The biller returns 402 Payment Required with payTo: billerAddress. wrapFetchWithPaymentFromConfig signs a Permit2 authorization (off-chain) and retries. The molandak facilitator verifies on-chain. The executor is then reimbursed from the employee's private Utilities bucket.

Scheduler

setInterval(30s) — checks for due employees and bills. Timestamps advanced in DB before execution (idempotency). On restart, already-advanced timestamps prevent double-payment.

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Token addresses

Token	Address
USDCm (Monad testnet)	0xc4fB617E4E4CfbdEb07216dFF62B4E46a2D6FdF6
Unlink pool	0x0813da0a10328e5ed617d37e514ac2f6fa49a254
Permit2	0x000000000022D473030F116dDEE9F6B43aC78BA3

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Running locally

Prerequisites: Node.js 24 (via Volta), Bun, a Monad testnet wallet with MON and USDCm.

1. Configure

# Fill in EXECUTOR_PRIVATE_KEY and EXECUTOR_ADDRESS
cp .env.example .env   # or edit .env directly

2. Executor (Terminal 1)

cd executor
npm install   # installs deps including better-sqlite3
volta run --node 24 node --env-file=../.env --import=tsx/esm index.ts

3. App (Terminal 2)

cd app
bun install
bun run dev

4. Billers (Terminal 3, optional — needed for bill payment demo)

cd executor
volta run --node 24 node --env-file=../.env --import=tsx/esm biller/electric.ts &
volta run --node 24 node --env-file=../.env --import=tsx/esm biller/insurance.ts

Open http://localhost:3000.

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E2E test (no frontend required)

cd executor

# Terminal 1: start executor
volta run --node 24 node --env-file=../.env --import=tsx/esm index.ts

# Terminal 2: run test
volta run --node 24 node --env-file=../.env --import=tsx/esm scripts/test.ts

The test creates real Unlink wallets, deposits USDCm into the employer's Unlink wallet, registers both parties with the executor, and triggers a full payroll cycle (employer → employee Master → 5 private bucket sends).

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Faucets

Asset	URL
MON (gas)	https://faucet.monad.xyz
USDCm	https://faucet.unlink.xyz

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Built with

• Monad — high-performance EVM L1
• Unlink — ZK private transfers
• x402 — HTTP payment protocol
• Hono — lightweight Node.js server
• Next.js — React framework
• wagmi + RainbowKit — wallet connection