Alpaca

US equities, options, and crypto via Alpaca. Connect with one line.

Alpaca is a commission-free US broker with a clean REST + WebSocket API, a free paper sandbox, and equity / option / crypto coverage. Usable from the core library via hz.connect("alpaca", ...).

Connect

python

import horizon as hz

ex = hz.connect("alpaca",
    paper=True,                    # False for live
    api_key="APCA-...",
    api_secret="...",
)
ex.buy("AAPL", qty=10, limit=180.0)
print(ex.positions())
ex.close()

Kwargs

Kwarg	Type	Default	Notes
`paper`	`bool`	`True`	Paper sandbox vs. live. Fail-safe default.
`api_key`	`str \\| None`	`None`	Falls back to secrets / env (`ALPACA_API_KEY`).
`api_secret`	`str \\| None`	`None`	Falls back to secrets / env (`ALPACA_SECRET_KEY`).
`secrets`	`Secrets \\| None`	`None`	Credential resolver (see Secrets).
`http_client`	`HttpClient \\| None`	Rate-limited default	Inject for tests or custom retry.
`budget_usd`	`float`	`0.0`	Optional hard cap on notional the venue will accept.

Credentials are resolved in order: explicit kwarg → secrets.get("alpaca.api_key") → environment variable. Use whichever fits your deployment.

Install

bash

pip install -e ".[equity]"          # alpaca-py + ib_async + pandas-ta
# add validate for stats inference (scipy + sklearn)
pip install -e ".[equity,validate]"
# add options for the options chain / IV path
pip install -e ".[equity,options,validate]"

Bracket / OCO / OTO order

python

from horizon.types import OrderAction

action = OrderAction.place(
    market_id="AAPL", side="buy", quantity=10, price=180.0,
    order_class="bracket",
    take_profit_price=190.0,
    stop_loss_price=175.0,
)
ex.venue.submit(action)

The venue rejects a bracket / OCO with a missing leg before anything hits Alpaca. Details: Alpaca pro docs.

Options chain

python

chain = ex.venue.options_chain(
    "AAPL", expiry="2026-06-19", option_type="call",
    strike_gte=175.0, strike_lte=200.0,
)
for row in chain:
    print(row["symbol"], row.get("impliedVolatility"))

Pair with horizon.stats.iv_rank / iv_hv_spread for an end-to-end research workflow.

Status

REST submit / cancel / amend: shipped.
Bracket / OCO / OTO as one ticket: shipped.
Options chain snapshot: shipped (Alpaca.options_chain).
Polling drain_fills(): shipped.
WebSocket order stream + quote feed: see horizon.data.live.alpaca_ws.
Rate-limited HTTP, exponential backoff, audit chain integration: shipped.
Multi-leg options combos / spreads: follow-up.

Examples

examples/alpaca_research.py — historical bars → horizon.stats inference → backtest.
examples/alpaca_paper_trading.py — full live loop against the paper sandbox.

Full integration details, wire formats, error mapping: Alpaca (professionals).