Kalshi 15-Minute Bots: The Math Every Bot Has to Beat, Tested on 2,710 Bitcoin Windows

Search "Kalshi bot" and you'll find a lot of code: repositories that poll the 15-minute markets, bots for sale, and threads about a friend of a friend who's printing money. Most of the ideas come down to three trades. Before you run one, here's what each of them would have done on Kalshi's Bitcoin 15-minute markets from Aug. 29 to Sept. 27, 2026, fills and fees included.

Polymarket US lists the same 15-minute windows for bitcoin, ether, solana and XRP, plus a 5-minute version Kalshi doesn't →

A free live feed for your bot

Our 15-minute bitcoin board is a public JSON endpoint: https://predictionmarketspicks.com/api/tools/bitcoin-edge-15m. No key, open CORS, cached at the edge for seconds at a time, and rate-limited per IP (the limit comes back in the response headers). It returns the live window (snapshot.data.window: ticker, open, close, seconds remaining), Kalshi's book for it (snapshot.data.book: bid, ask, mid), the locked target (snapshot.data.strike), and live_call: the one call we publish, which is our own bot's position for the top-of-hour window, or the reason it sat out.

This reads the feed and prints the window, the market and the call. It places nothing:

const r = await fetch('https://predictionmarketspicks.com/api/tools/bitcoin-edge-15m')
const j = await r.json()
const { window: w, book, strike } = j.snapshot.data
console.log(w.ticker, `${w.seconds_remaining}s left`, `target ${strike}`)
console.log(`YES bid ${book.yes_bid}¢ / ask ${book.yes_ask}¢ / mid ${book.mid}¢`)
const c = j.live_call
console.log(c.state === 'call' ? `bot call: ${c.call.side} ${c.call.ticker}` : `bot: ${c.state}${c.no_call_reason ? ` (${c.no_call_reason})` : ''}`)

Building with an AI agent instead? The free PredictionMarketsPicks MCP server has a fifteen_min_board tool that returns every Kalshi 15-minute series, the live window and the same bot record: connect it here.

Our bot's record

The live tool behind the feed is Bitcoin Edge 15-Min. How we time the last minute is in the 12:30 rule vs. our tape, the strategy itself in the Kalshi 15-minute bitcoin strategy, and the settlement rules in how KXBTC15M settles.

First, what every bot is up against

The price is fair. Across 2,764 graded windows, every 10-cent price band won within about one point of its price: 8.1¢ contracts won 8.6% of the time, 46.2¢ won 45.8%, 91.9¢ won 91.4% (the full test). There's no lazy mispricing to scoop up.

The fee is at the fill, win or lose. Kalshi's taker fee is 7% × price × (1 − price) per contract:

Trade in and out of a window and you pay it twice. Run any size through the Kalshi fee calculator.

The spread is real. With five minutes left in a window, the Bitcoin book's median spread was 1¢. A bot that crosses it to get filled gives that up on every trade, before the fee.

Bot 1: buy the late favorite

The idea: with a minute or two left, the side priced 95¢ or more almost always wins. Buy it, collect the few cents.

What happened: we took every window where the favorite's midpoint was 95–99¢ closest to 90 seconds before the close, and bought it at the ask.

It won almost every time and still lost. The favorite wins about as often as its midpoint says, so paying the ask on top of that is a small loss, and the fee makes it a bigger one. It also means sitting in the final minute, when the 60-second settlement average is mostly locked in and the fastest traders are repricing faster than any retail bot can.

Bot 2: trade a fair-value model

The idea: estimate the true odds from where Bitcoin sits against the target, how much time is left and how fast it's moving, then buy whichever side the model says is cheap.

What happened: our own Bitcoin 15-minute model does exactly that. We took its reading with five minutes left in each window and traded whenever it disagreed with the market's midpoint by more than 3 points, taking the ask or the bid.

The market's own price was the better forecast (a lower Brier score is better), so trading against it lost money before the fee did anything. A better model could do better. But the bar isn't "beat a coin flip." It's "beat a price that is already fair, by more than the fee and the spread."

Bot 3: arbitrage another venue

The idea: Polymarket also lists 15-minute Bitcoin markets. When the two prices disagree, buy "up" on one and "down" on the other and lock in the gap.

What happened: Polymarket's international venue settles on a Chainlink 60-second average, not the CF Benchmarks index Kalshi uses. Across 663 identical windows from Sept. 21 to Sept. 27, 2026, the two settled opposite ways four times. Every one was a window Kalshi's settle decided by $5.10 or less: 3 of the 30 windows decided by under $5 split between the venues (the same-window test). On a split, both legs of your "arbitrage" can lose. Polymarket US settles on the same index as Kalshi, but it's a separate order book that publishes no volume, so the depth to fill both legs isn't there to measure. See Polymarket US fees for the per-contract cost.

If you build one anyway

• Read by series, not the whole exchange. GET /trade-api/v2/markets?series_ticker=KXBTC15M&status=open returns the open window. Querying every open market returns thousands of rows you don't want.
• Know the fields. floor_strike is the target, locked at the open. close_time is the close. On settled markets, result and expiration_value tell you what happened. Event tickers end in the Eastern close time: KXBTC15M-26SEP271945 closes at 7:45 PM ET.
• Go easy on the API. Kalshi drops some 15-minute reads under heavy parallel load. Read a few series at a time and retry.
• Price the fee into every signal, at the price you'll actually fill, and count it twice if you'll exit early.
• Grade yourself on profit, not win rate. Bot 1 won 97.8% of the time and lost money.
• Size small. The Kelly calculator will tell you that with no edge, the right size is zero.

Every series has a ticker-named page with the same builder notes, starting with Ethereum (KXETH15M), all on the Kalshi 15-minute markets board. How the 15-minute contract stacks up against Kalshi's hourly, daily and perp clocks: which Kalshi clock fits your view.

Building against a shorter clock? Every 5-minute window's result is on the 5-Minute Board, with a public results feed.