> ## Documentation Index
> Fetch the complete documentation index at: https://docs.routeur.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Cross-venue pairs

> The same question on Kalshi and Polymarket, and how to compare them.

When a Kalshi market and a Polymarket market are proven related, the pair is a **cross-venue pair**. Most useful are `equivalent` pairs: the same question, which should cost the same on both venues.

## Three ways in

| To                                      | Use                                                       |
| --------------------------------------- | --------------------------------------------------------- |
| List every proven pair                  | `GET /v1/cross-venue?relation=equivalent`                 |
| See the pairs priced furthest apart now | `GET /v1/insights`, field `spreads`                       |
| Find a market's counterpart             | `GET /v1/markets/{venue}/{id}/relations?cross_venue=true` |

Events do this for you as well: when both venues list the same event, `GET /v1/events` returns it once, with a `twin` and both venues' asks on each outcome.

## Reading a pair

Pairs are stated from the **left** market's side:

| `relation`    | Meaning                                       |
| ------------- | --------------------------------------------- |
| `equivalent`  | Both resolve the same way in every outcome.   |
| `subset`      | If the left resolves Yes, the right does too. |
| `superset`    | If the right resolves Yes, the left does too. |
| `contradicts` | Both cannot resolve Yes.                      |
| `overlaps`    | Their outcomes intersect without containment. |

Each pair carries `evidence`: the structured facts the proof rests on, such as the matched game, team and line.

```bash theme={null}
curl "https://api.routeur.app/v1/cross-venue?relation=equivalent&limit=20" \
  -H "X-API-Key: $ROUTEUR_API_KEY"
```

## What gets matched

Cross-venue proofs need the same real-world quantity **and** the same settlement scope on both sides. Today that covers sports: winners, totals and spreads for games matched across the two venues. Numeric ladders on economic data and crypto prices, and one-winner events such as elections, are proven within each venue, and are being extended across venues.

<Tip>
  A gap between two equivalent markets is only money if both books have size and fees leave something. [Leads](/concepts/leads) do that arithmetic for you, and [Compare a market across venues](/cookbook/compare-venues) shows how to rank gaps yourself.
</Tip>