Source
Home win
Forecast
62%
Backtesting.Paper Trading.Evaluation.Routing.
Get the CLI
npm install -g arena-prediction-cliBacktesting
Early access
In early access: write a rule and Arena will run it over markets that have settled, then run it forward so the record is real. No look-ahead, no cherry-picked windows, and a verdict that is allowed to be no.
fade NBA favourites when the line moves 3¢ or more in the last hour before tip-off
Illustrative sample, not a real backtest · 640 settled games
Key moments
+5.8¢
Games 24 to 54, 22 wins
Rose from −10.7¢ to +5.8¢.
−4.9¢
Games 55 to 155, 58 losses
Fell from +5.8¢ to −4.9¢.
+1.8¢
Games 156 to 640, 282 wins
Rose from −4.9¢ to +1.8¢.
- Settled games
- 640
- 56% won
- Edge per contract
- +1.8¢
- mean, after fees
- 95% interval
- −2.0¢ to +5.6¢
- crosses zero
- Verdict
- Not an edge yet
- run it forward
- 01
Describe the rule
A JSON spec, or your own probabilities for each game. Game-winner markets in seven leagues.
- 02
Test it on the settled record
Markets that have resolved, with the edge reported as an interval, not a win rate.
- 03
Run it forward
Trade the same picks in the sandbox at live prices, and the eval board grades each as it settles. It goes on the public board only if you ask.
Design
How a run reads
A saved backtest or eval becomes a workflow you can read left to right. It shows where the forecast came from, the model, the rule, what it did and how it scored. The workflow below is an example.
Model
Your model
Stated probability
Rule
At least 55%
Take the side
55%
Action
Picks
Two markets
- Allocate
- $250.00
- Take
- +35%
- Stop
- -15%
- KC ML
- BOS ML
Result
Result
Recorded
- P&L
- +$14.20
- Brier
- 0.22
The line
What moved it
One line per outcome through a game. Each play that moves the price is pinned on the line of the team it concerns, and the note under the chart names the play, when it happened and what that price did.
- Home99%
- Away1%
Q1Q2Q3Q4
7:15 PMFinal 10:21 PM
Key moments
Home69%
Touchdown, Home
Q1 6:187:40 PM
Home 7, Away 0.
Rose from 55% to 69%.
Away37%
Field goal, Away
Q2 9:318:13 PM
Home 7, Away 3.
Rose from 30% to 37%.
Away58%
Touchdown, Away
Q3 4:079:24 PM
Home 7, Away 10.
Rose from 41% to 58%.
Home84%
Touchdown, Home
Q4 4:3610:08 PM
Home 14, Away 10.
Rose from 44% to 84%.
Historical data
Point-in-time
Arena keeps the history a backtest needs: the markets it lists, recorded as they trade, the facts those markets settle on, and the AI models’ graded picks. Everything is stored point-in-time: each row keeps the time it became known, taken from the source’s own dates for older history, so a backtest will only see what could have been known then. Backtesting is in early access, and none of this is offered as a download.
| Data | Coverage | From |
|---|---|---|
| Markets | ||
| Market listings | Recorded from July 2021. | Jul 2021 |
| Settlements | Recorded from July 2021. | Jul 2021 |
| Price candles | Being added from July 2021 across the whole window. No finished stretch yet. | Jul 2021 |
| Imported trades and fills | Recorded from November 2022 through March 4, 2026. | Nov 2022 |
| Earlier trade history | Recorded from September 17, 2026. Earlier days, back to June 30, 2021, are being added. | Sep 2026 |
| Daily exchange trade files | Recorded from August 2026, for every market on the exchange, not only Arena’s games. | Aug 2026 |
| Order books and trades on the games Arena lists | Recorded from September 28, 2026. | Sep 2026 |
| Graded record | ||
| AI model picks, graded | Recorded from June 2026; stated probabilities scored from September 2026. | Jun 2026 |
| Economics | ||
| Weekly gas prices | Recorded from 1990. | 1990 |
| US economic series, with revisions | Recorded from 2018, each revision kept. | 2018 |
| Sports | ||
| International football results | Recorded from 1872 to 1970; the years since are being added. | 1872 |
| NFL scores and closing lines | The 1999 to 2002 seasons and this season recorded; the seasons in between are being added. | 1999 |
| Club soccer results | This season recorded from August 2026, and some leagues’ 2010–11 season; the seasons in between are being added. | Aug 2026 |
| College football scores and lines | The 2013 season and this season recorded; the seasons in between are being added. | 2013 |
| Weather | ||
| Weather at settlement stations | Daily reports, forecasts and observations recorded from September 2026. | Sep 2026 |
| Elections | ||
| 2026 elections: polls, race ratings, early vote | Polls, race ratings and early vote recorded from September 2026; campaign finance filings from 2025. | Sep 2026 |
Planned, not held yet: baseball; Treasury yield, air-travel and weather archives; page-view counts; past election results and election-night counts.
- Recorded around each game
- Order books and trades on the games Arena lists, from six hours before the start until two hours after the final. Where an exchange’s book can only be polled, busy days are sampled.
- Kept as it was known
- Economic series keep every revision since 2018, and market rules keep each wording from September 2026 on, so a test will see what was published on the day, not the later correction.
- Graded against the result
- The AI models’ picks are graded against the real outcome, and since September 2026 a pick can state a probability, which is scored too. Your own paper trades held to the end are graded the same way, and stay private unless you make your profile public.
Agents
Early access
Tell an agent what you want. It builds the strategy, tests it against Arena’s markets, and runs it around the clock on infrastructure we host. What exists today is the CLI and the MCP server; hosting is what early access is for.
- 01
Say what you want
In plain English, to Claude Code, Cursor or any agent with the Arena CLI or MCP server.
- 02
It builds and tests the strategy
Against every settled market on record, and tells you straight whether the idea is an edge.
- 03
It runs it, hosted
Around the clock on infrastructure we host, on paper. The record goes on the public board only if you ask.
Signals
Noticeable orders · Unusual
Large trades on Kalshi and Polymarket as they print, within seconds. Follow one on paper, or trade against it.
Sample printsNot live data
YesChiefs ML$62,40063¢
YesBTC ≥ $65.5k$90,20057¢
NoLakers ML$148,10041¢
NoFed cut in Sept$57,50033¢
YesYankees ML$71,80052¢
NoETH ≥ $1.9k$81,90047¢