Built This Week/Builds

Builds

AI Trading Bot for Kalshi

A Kalshi bot that follows whale bets and crowd moves can pick winners (8 of 12 for us) and still lose money, because fees eat thin margins and everyone else is running the same signals.

Over the 2025 holiday break, Jordan built a full-stack trading bot for Kalshi, the prediction market. It scans every active market for whale bets, coordinated entries and volume spikes, then scores each trade. He showed it in Episode 26 (January 9, 2026), along with a real-money result: 8 wins out of 12 trades, and still about $7 down. He did not give an exact build time, only that he built it in his free time over the break.

Why we built it

Prediction markets were one of the big crazes of 2025. Kalshi and Polymarket grew fast, and brokerages and sportsbooks started talking about launching their own. Jordan had seen traders post huge wins, some of which looked like inside information, and wanted to see whether a bot could find an edge without it.

He also admits he is "not really a good gambler" and knows little about sports. He saw that as a plus: the bot would have to work from market behavior, not from his opinions about who would win.

The stack

  • Claude (Opus 4.5): the model behind the algorithm and the code.
  • Claude Code: agentic coding for the app.
  • Cursor: the editor, used alongside Claude Code.
  • Kalshi API: live market and trade data. Jordan picked Kalshi because Polymarket was not available to US traders and Kalshi has a complete API.

How we built it, step by step

  1. Pick the venue. Kalshi, for US access and its API.
  2. Pick markets that settle fast. Long-dated questions like the World Cup winner give no feedback while you build. Jordan filtered for markets about to expire, which mostly meant live sports.
  3. Build a live alert feed. The back end watches all active trades and flags three signals: whale trades (big dollar positions), coordinated entries (for example, seven traders piling into the same "yes"), and sudden volume spikes.
  4. Score every opportunity. A trading view shows a confidence score, ROI and a recommended bet size, with filters by category (sports, politics, crypto, economy, entertainment) and by signal. Jordan wanted 80 or higher before trading. On air, the best live score was 75.
  5. Make trading one tap away. Each trade gets a QR code that opens it on your phone.
  6. Trade small. He deposited $250, placed about 12 trades worth roughly $20 to $40 in total, and bet a fraction of each recommendation (around $9.20 when the bot said $92).

How it turned out

And of those 12 trades, I actually won eight of the 12. So I was actually at about 66% success rate in those trades.

— Jordan Metzner, Episode 26

He still lost money. At 11:34 he explains why:

And I think I lost money for two major reasons. One, the transaction fees are incredibly high, and when I'm taking low margin trades, of like low risk settlements, I found that the transaction fees kinda take away my margin.

— Jordan Metzner, Episode 26

The second reason is that it is "bots trading on bots." If everyone trades on what the crowd is doing, the signal gets priced in. Later in the episode, Jordan asked NotebookLM whether anyone wins consistently with a Kalshi bot. Its answer was arbitrage or providing liquidity, not betting on outcomes. Jordan thinks fees are too high for cross-platform arbitrage to pay off, and expects time arbitrage (trading before the scoreboard updates) to get patched. His verdict: the markets "sure feel like the house, and it sure feels like the house always wins." He planned to withdraw his money and take the $7 loss.

What we'd do differently

  • Put fees in the model from day one. They were not in the original algorithm, and they wiped out the gains on low-risk trades.
  • Don't expect consensus signals to last. Following whales and crowds gets arbitraged away. Jordan's takeaway is that the only real edge is inside information.
  • Stick to markets with clean outcomes. Sports settle cleanly. Jordan pointed to a political market where Polymarket disputed whether an event counted, which is a risk a bot cannot price.

Sam's view: the hard part is finding signals that actually drive earnings, but the build shows what you can do with AI even when the trades don't go your way, and someone with real betting experience could take the same tool further. If you are deciding which coding agent to build something like this with, see Claude Code vs OpenAI Codex.

FAQ

How do you build a Kalshi trading bot?

Jordan connected a full-stack app to Kalshi's API, pulled all active markets into a live feed, flagged whale bets, coordinated entries and volume spikes, and scored each trade with a confidence score. He built it with Claude Opus 4.5, Cursor and Claude Code.

Can a Kalshi trading bot make money?

Ours did not. It won 8 of 12 trades, about 66%, but ended about $7 down because transaction fees ate the margin on low-risk trades. Jordan's conclusion was that the only real edge is inside information.

Why use Kalshi instead of Polymarket for a bot?

Polymarket was not available to US traders, and Kalshi has a full API that the bot could connect to directly.

What markets work best for testing a prediction market bot?

Short-dated ones. Jordan focused on live sports because they settle quickly, which gives near-real-time feedback on the algorithm, and because sports have clear winners and losers.