Brokers

The system is broker-agnostic: the engine, strategies, scanners, execution, and optimizer all depend on two interfaces — Broker (trading) and MarketDataProvider (data) — never on a specific vendor. A broker is just an adapter that implements those. Today Alpaca is the one bundled adapter; others can be added without touching anything above the broker layer.

Supported

Alpaca (US equities)

Capability	Status
Historical bars (get_bars)	✅
Live bar stream (stream_bars)	✅ minute bars
Trade-update / fill stream (stream_trade_updates)	✅
Account & positions	✅
Market & bracket orders	✅
Open-order listing / cancel	✅
Close position(s)	✅
Market clock (hours gating)	✅
Paper and live	✅ (paper by default)

Implemented in src/brokers/alpaca/ — AlpacaBroker (trading) and AlpacaMarketData (data). This is the only place the alpaca SDK is imported.

Not yet supported

These aren't built, but the design has a clear seam for each:

• Crypto / other Alpaca asset classes — AlpacaBroker/AlpacaMarketData are equity-focused (StockHistoricalDataClient / StockDataStream). A crypto adapter would use Alpaca's crypto clients behind the same interfaces.
• Options, trailing-stop, and other order types — the Broker interface exposes the order types the engine uses (market, bracket); more can be added.
• Other brokerages (Interactive Brokers, Tradier, ...) — implement Broker.
• Other data vendors (Polygon, Databento, ...) — implement MarketDataProvider; you can mix a data vendor from one provider with order routing through another.

What it takes to add a broker

1. Create src/brokers/<vendor>/ implementing Broker (and optionally MarketDataProvider), mapping the SDK's objects to the project's vendor-neutral domain types (Position, OrderResult, AccountSnapshot, BarEvent, ...).
2. Construct it in main.build_data_and_broker().

That's the whole change — engine/, execution/, strategies/, scanners/, and the optimizer are untouched. See Broker abstraction for the interface contract and Extending for a worked example. Trade-update streaming is optional: a broker that can't stream account events just returns False from supports_trade_updates.