Alpaca TS Alpha Sdk

Building on @alpacahq/alpaca-ts-alpha

This is a map, not the territory. It gives you the mental model, the idioms agents most often get wrong, and where to look — it deliberately omits the full API surface. Whenever you need specifics (exact method names, parameters, response fields), open the package README and grep the API reference: the README is ~2750 lines and its second half is an auto-generated, per-method reference. Do not guess method signatures from this file alone — confirm in the README or the source.

Where the source of truth lives

Paths are relative to the package root — the repo root when developing here, or node_modules/@alpacahq/alpaca-ts-alpha/ when installed (src/ ships in the published tarball).

When unsure where a method lives, prefer the programmatic lookups (below) over guessing, then confirm against the README.

Mental model: a two-layer facade

The Alpaca client bundles every Trading and Market Data API behind one constructor, reached via the .trading and .marketData namespaces.

1. Generated (always present, uniform). Every generated REST method is reachable raw at alpaca.<group>.<resource>.<method>(...) — e.g. alpaca.trading.assets.getV2Assets(), alpaca.marketData.stocks.stockBars(...). Nothing is ever hidden.
2. Ergonomic (additive, never replaces layer 1). Hand-written conveniences sit on top: order builders, normalized market-data accessors, pagination, workflow helpers. The raw method each one wraps is still available.

The rule: if there's no ergonomic helper for what you need, the raw generated method is always there. You never have to choose between them.

Setup essentials

import { Alpaca } from "@alpacahq/alpaca-ts-alpha";

const alpaca = new Alpaca({
  keyId: process.env.APCA_API_KEY_ID,
  secret: process.env.APCA_API_SECRET_KEY,
  paper: true, // DEFAULT. set false for LIVE trading — a deliberate flag.
});

• Credentials resolve from env vars when omitted: APCA_API_KEY_ID, APCA_API_SECRET_KEY, APCA_API_OAUTH_TOKEN. Explicit values win.
• Never pass apiKey as a plain string — Alpaca needs two distinct headers and will reject a single value (the SDK throws a guided error). Use OAuth via accessToken, or auth.apiKeyAuth({ keyId, secret }) for lazy credentials.
• OAuth-only clients cannot open WebSocket streams (streaming needs key/secret).

Idioms agents get wrong (read these before writing code)

• Money & quantities are numeric strings (wire-truthful, no float loss). Convert for display/compute with the values helpers (values.toNumber, values.toNumberOr, values.formatMoney); for exact math keep the string and feed a decimal library. Never parseFloat blindly for arithmetic.
• Timeframes are branded. Don't hand-write "1minute" (the API rejects it). Build with TimeFrame.Day / timeFrame(15, TimeFrameUnit.Minute) → the branded TimeFrameString the facade bar methods require.
• Orders: prefer the ergonomic builders on alpaca.trading.orders (market, limit, stop, stopLimit, trailingStop, bracket, oco, oto) — they drop the postOrder({ postOrderRequest }) wrapper and enforce required fields per kind at compile time. For uncovered shapes (e.g. multi-leg mleg) use orders.submit(input) or the raw postOrder.
• Pagination is built in. iterate* lazily yields across all pages; collect* / collect*BySymbol eagerly return them — never thread page tokens by hand. For big back-fills pass SymbolCollectOptions (maxPerSymbol, concurrency, chunkSize) to bound memory / parallelize.
• REST and streaming share one shape. The normalized accessors (getStockBars, getCryptoTrades, …; single-symbol *For(symbol) variants; chart-ready get*Candles) return the SAME Bar/Trade/Quote type the streams emit — backfill over REST then append live updates without remapping. The raw generated map responses (e.g. marketData.stocks.stockBars) keep Alpaca's compact wire keys ({ o, h, l, c, v, … }) and may carry ISO-string timestamps; prefer the normalized accessors or marketDataShapes.toBar etc.
• Errors are typed. Non-2xx rejects with ApiError and status-specific subclasses (AuthError 401, PermissionError 403, NotFoundError 404, ValidationError 400/422, RateLimitError 429). Branch on the subclass, not magic numbers. Always log err.requestId (Alpaca's X-Request-ID) — it can't be looked up later. Network/abort failures reject with FetchError.
• Resilience is opt-in but conservative. timeoutMs, retry (maxRetries > 0 to enable; non-idempotent POSTs are never auto-retried), rateLimit (the Alpaca client enables a safe ~200/min default; raw Api classes do not), and userAgent are all top-level client options.
• REST-only builds: import from @alpacahq/alpaca-ts-alpha/rest to keep ws/@msgpack/msgpack out of the module graph. Stream factories and submitAndWait throw from this entrypoint — import the root package for streams. On edge/browser runtimes (Cloudflare Workers/workerd, Vercel Edge, Deno, browsers) the root import auto-resolves to this REST-only build via the package exports conditions, so streaming is unavailable there (ws can't run on edge) but REST works without the Class extends value [object Module] crash.
• ESM & CJS dual package: don't load the SDK through both import and require in one process if you rely on instanceof against its classes (e.g. ApiError) — you may compare against two copies.

Streaming (quick shape)

WebSocket clients are typed EventEmitters: register listeners, then connect(). They auto-authenticate, reconnect with backoff, and re-subscribe.

const stocks = alpaca.marketData.stockStream({ feed: "iex" }); // iex | sip | delayed_sip
stocks.onBar((bar) => {/* canonical Bar */});
stocks.onConnect(() => stocks.subscribeForBars(["AAPL", "MSFT"]));
stocks.connect();

cryptoStream(), optionStream(), newsStream(), and the trading alpaca.trading.stream() (order/account updates) share the same surface. The submitAndWait workflow helper places an order and resolves on its terminal state over the trading-updates stream.

Discovering anything programmatically

import { findCapabilities, findErgonomic } from "@alpacahq/alpaca-ts-alpha";

findCapabilities("getAccount"); // generated: which Api / accessor hosts it
findErgonomic("market");        // ergonomic: is there a helper, and where

capabilities / ergonomicCapabilities / streamingCapabilities are the full maps. Use these (or grep the README ## API reference) to answer "where does X live?" instead of guessing.

Testing integrations

@alpacahq/alpaca-ts-alpha/testing is a network-free harness: createMockAlpaca([...]) returns a ready client backed by canned responses matched by method + path; use it so unit tests never hit Alpaca.

When you're unsure

Don't stop at this file. Open README.md and read the relevant ## section, or grep the ## API reference for the exact method, or read the src/ module in the table above. This skill points the way; the README and source are authoritative.