event-contract-arbitrage: what it does, how to run it, where it stops

What it does

The README describes a web application for examining opportunity cost and spreads with fees included. You choose binary or multiple choice, enter contract prices from each market, optionally add principal and contract length, and it returns the positions and the profit, including an annualized ROI.

It adds gas-fee handling for Polymarket legs. A YouTube demo is linked from the README, and the site built from this code offers shareable calculation links and a free email alert signup.

The README's best-practices list is short and worth keeping: verify market conditions match exactly, consider liquidity for fill probability, account for gas on Polymarket, and double-check the numbers before executing.

• Binary and multiple-choice market arbitrage
• Cross-market detection from entered prices
• Contract length and annualized ROI
• Gas-fee input for Polymarket

Setup and license

The README documents UI usage only, not a local install. There is no license file, so the repository's reuse terms are unstated. Check with the author before redistributing a fork.

The README disclaimer states the tool is for informational purposes only and that the authors are not responsible for the accuracy of its data.

Venues and data

The UI supports Kalshi, Polymarket and Robinhood. The README says the math applies to any markets with identical outcome conditions, matching timeframes and compatible price structures.

There is no data feed. The roadmap lists three unchecked items: automated market condition matching, pulling market lists from Kalshi and Polymarket, and portfolio features such as alerts.

Where it falls short

With 27 stars and one primary author, this is a small project. Expect to read the code rather than rely on documentation if you fork it.

It neither discovers pairs nor executes. Its job ends when it tells you the two legs and the expected profit.

Who should use it

Developers who want the fee-inclusive arb formulas in code, or who want to self-host EventArb rather than depend on the public site. Everyone else can use eventarb.com directly.