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

# Trades stream mapping

> How each upstream WebSocket channel maps to the unified OpenPX `trades` stream.

Subscribe inputs and receive frames for the unified **trades** WebSocket channel,
crosswalked against the upstream AsyncAPI specs cached under `schema/upstream/`.

Every source entry is one of three types — **direct** (taken from upstream), **synthetic** (constructed by OpenPX), or **omitted** (not exposed upstream).

## Coverage

| Exchange   | Direct | Synthetic | Omitted |
| ---------- | ------ | --------- | ------- |
| kalshi     | 3      | 3         | 1       |
| polymarket | 2      | 5         | 0       |

## Subscribe payload

| Field       | kalshi source                            | polymarket source                           | Notes                                                                                                                                                                                                                                                                                          |
| ----------- | ---------------------------------------- | ------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `market_id` | `#/components/messages/subscribeCommand` | `#/components/messages/subscriptionRequest` | **kalshi:** Kalshi auto-subscribes the `trade` channel alongside `orderbook_delta` on every `subscribe(market_ticker)` call. **polymarket:** Polymarket `assets_ids[*]`. The market channel emits `last_trade_price` for the asset; trades on the *user* channel surface as fills, not trades. |
| `outcome`   | *omitted*                                | *synthetic*                                 | **kalshi:** Trade frames carry `side` and `taker_side`; outcome (YES/NO) is implicit per Kalshi binary market. **polymarket:** Populated only when `register_outcomes(yes_token, no_token)` was called. Otherwise `ActivityTrade.outcome` is `None`.                                           |

## Receive messages

| Variant | kalshi source                 | polymarket source                      | Notes                                                                                                                                                                                                                                                                                                                               |
| ------- | ----------------------------- | -------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `Trade` | `#/components/messages/trade` | `#/components/messages/lastTradePrice` | **kalshi:** Public Kalshi trade frame — exchange-side fills (any maker/taker pair). Mapped to `ActivityTrade \{ source_channel: "kalshi_public_trade" \}`. **polymarket:** Polymarket `last_trade_price` carries the most recent trade for an asset. Mapped to `ActivityTrade \{ source_channel: "polymarket_last_trade_price" \}`. |

## Session events

| Variant       | kalshi source                         | polymarket source | Notes |
| ------------- | ------------------------------------- | ----------------- | ----- |
| `Connected`   | *synthetic*                           | *synthetic*       |       |
| `Reconnected` | *synthetic*                           | *synthetic*       |       |
| `Lagged`      | *synthetic*                           | *synthetic*       |       |
| `Error`       | `#/components/messages/errorResponse` | *synthetic*       |       |

## Source specs

* **kalshi** · [`schema/upstream/kalshi.asyncapi.yaml`](https://github.com/openpx-trade/openpx/blob/main/schema/upstream/kalshi.asyncapi.yaml)
* **polymarket** · [`schema/upstream/polymarket.asyncapi.json`](https://github.com/openpx-trade/openpx/blob/main/schema/upstream/polymarket.asyncapi.json)

> Tables are auto-generated from `schema/mappings/`. CI fails if any `direct` ref no longer resolves in the cached upstream AsyncAPI spec; the daily upstream-refresh PR surfaces drift here.