> ## Documentation Index
> Fetch the complete documentation index at: https://mathematicalcompany.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Horizon Exchanges
> Horizon's exchange model: prediction markets, crypto, stocks, and multi-exchange support.
Horizon supports ten exchange backends that all implement the same `Exchange` trait. You can trade on a single exchange or multiple exchanges simultaneously.
## Verification Status
Different exchanges have received different levels of audit. **Verification status** below reflects how rigorously each backend has been compared against its reference implementation or live API behavior.
| Exchange | Status | Notes |
| -------------- | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Paper** | ✅ Verified | In-process simulation, exhaustively unit-tested |
| **Polymarket** | ✅ Verified | Byte-for-byte HMAC parity with `py_clob_client` (regression-tested), live API endpoints confirmed, EOA + Gnosis Safe both supported |
| Hyperliquid | 🟡 Fixes pushed | msgpack ordering, cloid format, spot offset, error handling, cancelByCloid all fixed in v0.8.7. Needs live verification. |
| Kalshi | 🟡 Fixes pushed | Modern host + RSA-PSS auth + fixed-point dollar field format in v0.8.7. Needs live verification. |
| Coinbase | 🟡 Fixes pushed | ES256 JWT auth + correct list-orders endpoint in v0.8.7. Needs live verification. |
| Limitless | 🟡 Fixes pushed | Polymarket fork — same salt/field name fixes applied in v0.8.7. Needs live verification. |
| Alpaca | 🟡 Fixes pushed | v0.8.8: switched fill polling to `/v2/account/activities/FILL` (the previous `/v2/orders?status=filled` query was invalid and never returned fills). Added `client_order_id` for idempotent retries, fixed limit-price formatter to preserve precision for sub-dollar stocks, added `Day` TIF, signed-qty parsing for short positions, per-order status check on cancel-all. Needs live verification. |
| IBKR | 🟡 Fixes pushed | v0.8.8: dropped fabricated `paper-api.ibkr.com` host (paper accounts use the same host), fixed positions endpoint to include the required `{pageId}` segment, added multi-step order-confirmation loop, account-id filtering on `cancel_all` and fill polling (was previously cross-account), commission string parsing (`"1.00 USD"`), epoch-ms timestamp via `trade_time_r`, contract multiplier inference for options, `/iserver/auth/ssodh/init` on session timeout, `acctId` in order body. Needs live verification — and remember the bearer token must come from IBKR's `private_key_jwt` SSO flow or a local Client Portal Gateway. |
| Robinhood | ⚠ Unverified | Code paths exist, never byte-for-byte audited (Bearer token may need replacement with Ed25519 for newer Crypto API) |
For live trading with real money, **Polymarket** is the only fully verified backend. The 🟡 exchanges have all critical bugs fixed and should now work in principle, but have not been tested against real accounts. Test in paper or with small size first.
## Prediction Markets
Local simulated exchange with tick-based matching. No credentials needed. Default for development.
Largest prediction market on Polygon. EIP-712 signed orders via the CLOB API.
US-regulated (CFTC) prediction market. REST API with bearer token auth.
Base chain prediction market. REST client for on-chain trading.
## Traditional & Crypto
Commission-free stock and ETF trading. Paper and live modes.
Crypto exchange with deep liquidity. HMAC-SHA256 auth via Advanced Trade API.
Commission-free crypto trading via REST API.
Decentralized perpetuals + spot on its own L1 chain. Wallet-based EIP-712 auth.
Multi-asset broker: stocks, options, futures, and ForecastEx prediction markets. Bridges equities/options and prediction market trading.
## Exchange Model
All exchanges implement a common trait:
```rust theme={null}
trait Exchange {
fn submit_order(&self, request: &OrderRequest) -> Result;
fn cancel_order(&self, order_id: &str) -> Result<()>;
fn cancel_all(&self) -> Result;
fn cancel_for_market(&self, market_id: &str) -> Result;
fn drain_fills(&self) -> Vec;
fn fetch_positions(&self) -> Result>;
}
```
The Engine wraps exchanges in an `ExchangeBackend` enum for dispatch without trait objects:
```
ExchangeBackend::Paper(PaperExchange)
ExchangeBackend::Polymarket(PolymarketExchange)
ExchangeBackend::Kalshi(KalshiExchange)
ExchangeBackend::Alpaca(AlpacaExchange)
ExchangeBackend::Coinbase(CoinbaseExchange)
ExchangeBackend::Hyperliquid(HyperliquidExchange)
ExchangeBackend::Robinhood(RobinhoodExchange)
ExchangeBackend::IBKR(IBKRExchange)
```
## Single vs Multi-Exchange
### Single exchange (default)
```python theme={null}
# Paper (implicit)
hz.run(name="simple", markets=["test"], pipeline=[...])
# Single live exchange
hz.run(
name="poly_mm",
exchange=hz.Polymarket(private_key="0x..."),
mode="live",
...
)
```
### Multi-exchange
```python theme={null}
hz.run(
name="cross_venue",
exchanges=[
hz.Polymarket(private_key="0x..."),
hz.InteractiveBrokers(paper=True),
hz.Coinbase(),
],
mode="live",
...
)
```
See [Multi-Exchange](/multi-exchange) for details on routing, netting, and cross-venue strategies.
## Fill Model
All exchanges use a **pull model** for fills:
| Exchange | Fill Source | Method |
| --------------- | -------------------------------------- | --------------------------------------------- |
| **Paper** | `tick(market_id, mid_price)` | Matches orders against mid price |
| **Polymarket** | `drain_fills()` → `poll_fills_async()` | Polls `/trades` endpoint |
| **Kalshi** | `drain_fills()` → `poll_fills_async()` | Polls `/portfolio/fills` endpoint |
| **Alpaca** | `drain_fills()` → `poll_fills_async()` | Polls `/v2/orders?status=filled` |
| **Coinbase** | `drain_fills()` → `poll_fills_async()` | Polls `/orders/historical/fills` |
| **Robinhood** | `drain_fills()` → `poll_fills_async()` | Polls `/crypto/trading/orders/?status=filled` |
| **IBKR** | `drain_fills()` → `poll_fills_async()` | Polls `/iserver/account/trades` |
| **Hyperliquid** | `drain_fills()` → `poll_fills_async()` | Polls `/info` with `userFillsByTime` |
The strategy loop calls `poll_fills()` each cycle for live exchanges, and `tick()` for paper exchanges.
## Order Routing
When you submit an order via `hz.run()`, it's automatically routed to the correct exchange based on the `market.exchange` field:
* Markets resolved as `"polymarket"` → routed to the Polymarket backend
* Markets resolved as `"kalshi"` → routed to the Kalshi backend
* Markets with `"alpaca"` → routed to the Alpaca backend
* Markets with `"ibkr"` → routed to the IBKR backend
* Markets with `"coinbase"` → routed to the Coinbase backend
* Markets with `"robinhood"` → routed to the Robinhood backend
* Markets with `"hyperliquid"` → routed to the Hyperliquid backend
* Markets with `"paper"` or empty exchange → routed to the primary exchange
You can also explicitly specify the exchange when using the Engine directly:
```python theme={null}
engine.submit_order(request, exchange="polymarket")
engine.submit_quotes("market_id", quotes, Side.Yes, exchange="kalshi")
```
## Side Mapping
| Exchange | Side Used | Notes |
| ----------- | ---------------------- | -------------------------------------- |
| Polymarket | `Side.Yes` / `Side.No` | Binary prediction contracts |
| Kalshi | `Side.Yes` / `Side.No` | Binary prediction contracts |
| Limitless | `Side.Yes` / `Side.No` | Binary prediction contracts |
| Alpaca | `Side.Long` | Equities — no Yes/No concept |
| Coinbase | `Side.Long` | Crypto — no Yes/No concept |
| Hyperliquid | `Side.Long` | Perps/spot — no Yes/No concept |
| Robinhood | `Side.Long` | Crypto — no Yes/No concept |
| IBKR | `Side.Long` | Multi-asset — no Yes/No concept |
| Paper | Any | Copies the side from the order request |
## Exchange Fields on Types
Orders, Fills, and Positions all carry an `exchange` field indicating which exchange they belong to:
```python theme={null}
order.exchange # "polymarket", "kalshi", "alpaca", "coinbase", "hyperliquid", "robinhood", "ibkr", or "paper"
fill.exchange # "polymarket", "kalshi", "alpaca", "coinbase", "hyperliquid", "robinhood", "ibkr", or "paper"
position.exchange # "polymarket", "kalshi", "alpaca", "coinbase", "hyperliquid", "robinhood", "ibkr", or "paper"
```