Kalshi–Polymarket Snipper Bot

A real-time cross-market snipper bot that monitors Kalshi and Polymarket in parallel to decide which token (direction) will win. By watching both platforms’ order books and prices live, the bot identifies favorable sides (e.g. UP vs DOWN on Bitcoin 15m markets) and can place orders accordingly.

What it does

• Monitors cross markets in real time – Kalshi and Polymarket feeds for the same or related events (e.g. Bitcoin 15-minute up/down).
• Decides winning direction – Uses dual best bid/ask and last-trade data from both venues to infer which side (token) is favored.
• Trading – Can place limit orders on Kalshi and/or Polymarket based on the monitored signals (e.g. buy UP when ask is below threshold).

Setup

cp .env.sample .env
# Edit .env: set KALSHI_API_KEY and either KALSHI_PRIVATE_KEY_PATH or KALSHI_PRIVATE_KEY_PEM
npm install

Scripts

• npm start – Run the main Kalshi + Polymarket monitor (dual price feed and direction logic).
• npm run auto-redeem – Run the auto-redeem/copytrade script.
• npm run build – Compile TypeScript to dist/.

Environment

Kalshi

Variable	Description
KALSHI_API_KEY	Your Kalshi API key id.
KALSHI_PRIVATE_KEY_PATH	Path to your RSA private key .pem file.
KALSHI_PRIVATE_KEY_PEM	Alternatively, the PEM string (e.g. from a secret manager).
KALSHI_DEMO	Set to true to use the demo API.
KALSHI_BASE_PATH	Optional override for API base URL.

Monitor (cross-market direction)

Variable	Description
KALSHI_MONITOR_INTERVAL_MS	Poll interval in ms (default 2000).
KALSHI_MONITOR_TICKER	Optional market ticker; if unset, uses first open KXBTC15M market.

The monitor exposes dual Kalshi + Polymarket prices (DualMarketPrices); use startDualPriceMonitor and formatDualPricesLine from ./monitor to build buy logic (e.g. buy UP when up ask < threshold).

Polymarket (orders)

Variable	Description
POLYMARKET_PRIVATE_KEY	Required to place orders.
POLYMARKET_PROXY	Proxy wallet / config.
POLYMARKET_TICK_SIZE / COPYTRADE_TICK_SIZE	Optional tick size.
POLYMARKET_NEG_RISK / COPYTRADE_NEG_RISK	Optional neg-risk flag.
POLYMARKET_CLOB_URL / CLOB_API_URL, POLYMARKET_CHAIN_ID / CHAIN_ID	Optional API overrides.
POLYMARKET_CREDENTIAL_PATH	Optional path to JSON with key, secret, passphrase.

Real-time cross-market monitor

Monitor best bid/ask for UP (YES) and DOWN (NO) on both Kalshi and Polymarket so the bot can decide which direction (token) will win.

Example

npm start
# [KXBTC15M-26FEB021130-30] UP   bid=0.54 ask=0.56  |  DOWN bid=0.44 ask=0.46  |  last=0.56  @ ...

In code: use the dual monitor for cross-market prices and implement logic that chooses UP or DOWN based on both venues.

Order placement (Kalshi + Polymarket)

Both platforms support limit buy orders.

Kalshi

• Function: placeOrder(ticker, side, count, priceCents) from ./bot.
• Parameters: ticker (e.g. KXBTC15M-24JAN15), side ("yes" | "no"), count (contracts), priceCents (1–99).
• Env: KALSHI_API_KEY, KALSHI_PRIVATE_KEY_PEM or KALSHI_PRIVATE_KEY_PATH; for bot: KALSHI_BOT_SIDE, KALSHI_BOT_PRICE_CENTS, KALSHI_BOT_CONTRACTS, KALSHI_BOT_DRY_RUN.

Polymarket

• Function: placePolymarketOrder(tokenId, price, size, options?) from ./polymarket-order.
• Parameters: tokenId (CLOB token ID), price (0–1), size (shares). Optional options: { tickSize?, negRisk? }.
• Env: POLYMARKET_PRIVATE_KEY, POLYMARKET_PROXY; optional tick size, neg-risk, CLOB URL, chain ID, credential path.

The arb script places one Kalshi order and one Polymarket order in parallel when cross-market conditions are in range (src/arb.ts, env ARB_*, ARB_POLY_SIZE).

Docs

• Kalshi API
• Kalshi TypeScript SDK
• Kalshi WebSockets