Using dp_exchange_webull

EXPERIMENTAL. Not run in production. Pin three-part. Maturity is per endpoint — read capabilities/0, not this banner.

Everything general is in dp_exchange_core's usage rules. This file is only what is specific to Webull.

Credentials are required for market data

There is no anonymous endpoint on this venue. Every OpenAPI call is signed, including the ones that look public, so get_price/2 needs credentials that the same call on Coinbase or Gemini does not:

{:ok, quote} = DpExchange.Webull.get_price("BTC-USD", credentials: %{
  app_key: "…", app_secret: "…"
})

capabilities/0 declares credential_benefit: :required — the first venue in the family to, and not the only one (dp_exchange_robinhood and dp_exchange_schwab declare it too). Branch on that rather than assuming market data is free; the alternative is finding out from a 401.

You keep the credentials. This package signs one request with them and holds nothing.

It is not only market data, and the fake enforces all of it

Every account and order call — get_balances/2, get_accounts/2, get_fees/2, get_transfers/2, get_transactions/2, get_positions/1, quantization/2, place_order/3, place_orders/3, preview_order/3, replace_order/4, cancel_order/3, get_order/3, get_orders/2 — and every options, watchlist, fundamentals, news and screener call — get_option_chain/2, get_option_expirations/2, list_watchlists/1, get_watchlist/2, create_watchlist/3, update_watchlist/2, delete_watchlist/2, get_financials/3, get_corporate_events/1, get_filings/2, get_news/1, get_screener/2 — refuses the same way market data does without a credential: {:error, {:missing_credentials, :webull}}, never {:ok, _}. Not {:refused, _} either — a missing local credential never reaches the venue at all (Core.Venue's :refused is the venue's own permanent word about a request it received), so this is Auth.headers/2's own return value, not an invented one.

DpExchange.Webull.Fake enforces this too, and it did not before. Before this fix, Fake.get_fees/2, Fake.get_accounts/2, Fake.get_balances/2, Fake.get_transfers/2, Fake.get_transactions/2, Fake.place_order/3, Fake.place_orders/3, Fake.preview_order/3, Fake.replace_order/4, Fake.cancel_order/3, Fake.get_order/3, Fake.get_orders/2, Fake.get_positions/1 and Fake.quantization/2 answered {:ok, _} regardless of whether credentials were supplied at all — several ignored the argument outright, and two checked only opts[:account_id], a different question. A consuming test suite that called any of these without credentials and asserted success was passing against behaviour the real venue does not have. If your own tests do this, they need updating; that is the point of the fix, not a regression in it. market_status/1 is the one exception — the real venue answers it with no credential either, and the fake still does too.

The same gap survived one round longer on the options, watchlist, fundamentals, news and screener callbacks, and is now closed as well: Fake.get_option_chain/2, Fake.get_option_expirations/2, Fake.list_watchlists/1, Fake.get_watchlist/2, Fake.create_watchlist/3, Fake.update_watchlist/2, Fake.delete_watchlist/2, Fake.get_financials/3, Fake.get_corporate_events/1, Fake.get_filings/2, Fake.get_news/1 and Fake.get_screener/2 all answered {:ok, _} with no credentials. The credential check now runs before each call's own argument validation, matching the real Rest order — so Fake.get_corporate_events() with neither a credential nor a :symbol is {:error, {:missing_credentials, :webull}}, not {:error, :symbol_required}. These were missed by the earlier sweep because dp_exchange_core's assertion 17 checks a fixed list of nine callback names that predates this surface and does not include any of them — passing that assertion is not evidence that the rest of your fake gates credentials.

Start it, and it brings its own rate limiter

children = [{DpExchange.Webull, credentials: my_credentials()}]

Passing credentials at start is what lets the package replay your subscriptions after a reconnect — see below. Without them, a reconnect cannot re-subscribe.

You never need to pass :limiter yourself. The supervision tree above starts and names its own rate limiter, and every call this package makes on your behalf — the reconnect replay, the 60-second blind resubscribe, and subscribe/2/unsubscribe/2/update_symbols/2 called with no :limiter in opts — is wired to it automatically. If you do pass one explicitly, it wins.

A shard's socket crash costs one shard, never your whole subscription

Each shard's MQTT-over-WebSocket connection is a linked child of Feed — not a supervised sibling you can restart independently. Feed traps exits, so a shard's socket dying abnormally does not take Feed down with it: only that shard's symbols drop out of coverage/1 and coverage_by_kind/1 (cleared immediately, not left to report :stream for a connection that no longer exists), you get a :link_down Core.Notice naming the crashed shard, and this package reopens it on its own — you never need to call subscribe/2 again.

Your app_secret and access_token will not appear in Feed's crash log. Feed keeps what you passed at start (or on a later subscribe/2) so it can replay your subscriptions after a reconnect — see above — and a crash of Feed logs its state via OTP's default crash report, which is where you would see it, because a crash report prints unredacted Logger metadata otherwise. The credential map is wrapped in a struct before it ever reaches state, so the crash line reads credentials: #DpExchange.Webull.Credentials<...> rather than the key pair itself. This does not extend to app_key on a live shard's socket — app_key is sent as a plaintext header (x-app-key) on every signed request this venue accepts by design, so it carries none of the confidentiality app_secret does, and a shard's own crash report still shows it.

What still costs you your whole subscription: Feed itself crashing — a bug outside the per-shard crash path, or anything that kills the Feed pid directly. DpExchange.Webull.Supervisor restarts Feed under :one_for_one, but from the static opts your supervision tree started it with; every subscribe/2, update_symbols/2 and subscribe_notices/1 call you made afterward is gone. Nothing inside this package can replay those calls — it never held onto the functions or the process that made them. If your consumer needs to survive a Feed restart unattended, monitor the Feed pid (or the DpExchange.Webull pid it sits under) yourself and re-issue subscribe/2 on :DOWN.

Subscribing is two protocols, and you see neither

Market data arrives over MQTT on a WebSocket. Subscriptions are HTTP calls. They are joined by a session identifier this package generates and gives to both.

:ok = DpExchange.Webull.subscribe(["BTC-USD"], credentials: creds, to: self())

The venue does not restore subscriptions after a reconnect. This package replays them for you, which is the whole reason you never have to notice a reconnect. That replay uses the credentials you supplied — at start, or on the subscribe call.

Three kinds arrive on the same subscription, not one

A subscribe asks the venue for its SNAPSHOT, QUOTE and TICK topics, and all three are forwarded to you: %DpExchange.Core.Types.Quote{} (a traded price), %DpExchange.Core.Types.TopOfBook{} (bid/ask) and %DpExchange.Core.Types.Trade{} (one print — the tape). Match on the struct, not on having subscribed once — a handler that only matches %Quote{} silently drops every top-of-book message and every trade rather than erroring.

receive do
  {:dp_exchange, :webull, %DpExchange.Core.Types.Quote{} = q} -> handle_price(q)
  {:dp_exchange, :webull, %DpExchange.Core.Types.TopOfBook{} = t} -> handle_book(t)
  {:dp_exchange, :webull, %DpExchange.Core.Types.Trade{} = t} -> handle_trade(t)
end

capabilities/0 declares streamable: [:quotes, :top_of_book, :trades] for exactly this reason. Trade.id is always nil on this venue — the streamed tape carries no per-print identifier, on this topic or on get_trades/2's REST tape, and nil says that truthfully rather than inventing one.

Unlike SNAPSHOT/QUOTE, TICK's presence in the default subscribe is read from the venue's own documentation and has not been confirmed against the live venue — see capabilities/0's measured_against. If the venue answers TICK differently than documented, that surfaces the same way any other subscribe refusal does.

Coverage means delivering, not accepted

On this venue there are three different moments: you asked, the HTTP subscribe returned 200, and data is arriving. coverage/1 reports only the third. A 200 on the subscribe does not mean the stream is flowing.

coverage/1 folds all three kinds above into one :stream per symbol. coverage_by_kind/1 splits them apart — a symbol can show :quotes healthy while :top_of_book or :trades has gone dark for it, or the reverse, and coverage/1 alone cannot tell you which:

DpExchange.Webull.coverage_by_kind(credentials: creds)
#=> %{
#=>   quotes: %{"BTC-USD" => :stream},
#=>   top_of_book: %{"BTC-USD" => :stream},
#=>   trades: %{"BTC-USD" => :stream}
#=> }

The venue's connection budget shapes what you can ask for

This package shards across at most five connections — the venue's own ceiling — because a single MQTT session caps at 100 subscribed tickers. It never exposes sockets, so you cannot cause a sixth: five shards of 100 is 500 symbols, and a larger universe on this venue needs a second App Key rather than a bigger number here. The one-minute retention is why reconnect backoff matters: reconnecting immediately after hitting the limit fails until the venue ages the old sessions out.

If two instances ever shared a session id, the venue would disconnect whichever connected first — each instance looking healthy in isolation. The id is generated per shard, inside this package, so this cannot happen.

UAT has REST but no stream

{:ok, quote} = DpExchange.Webull.get_price("BTC-USD", environment: :uat, credentials: creds)

environment: :uat gives authenticated REST against test data. There is no UAT broker — the hostname does not resolve — so:

DpExchange.Webull.subscribe(["BTC-USD"], environment: :uat)
#=> {:error, {:streaming_unavailable, :uat}}

It refuses rather than falling back to production, because a consumer testing against UAT that received production prices would be reading real market data believing it was fake.

Ask first if you need to branch:

if DpExchange.Webull.streaming?(environment: :uat), do: …

Production and UAT can run side by side — supervisor, feed and limiter names all derive from the environment, so the two neither collide nor share a rate-limit bucket.

:production is the default and a typo raises. environment: :uatt is an ArgumentError, not a quiet fallback: meaning UAT and getting production sends a real order to a real broker.

live?/1 answers the money question directly, resolving opts the same way every call here does, so a caller can confirm before a money-moving call rather than trust a default:

if DpExchange.Webull.live?(opts) do
  # confirm with a human before place_order/3 goes out
end

There is no aggregate trade volume on crypto — but there is on stocks

Not on the bars, not on the crypto snapshot's Quote.volume. On a crypto symbol that field is nil, never 0 — zero would look like a real measurement of no trading.

The stock snapshot is different: get_price/2 with category: "US_STOCK" or "US_ETF" carries a real volume, the day's aggregate rather than the last trade's size. capabilities/0 says reports_trade_volume: true because that path is real — a single package-wide boolean cannot say "true for equities, false for crypto," and false would be an under-declaration of a venue capability this package already reaches. Branch on opts[:category], not on the boolean alone, if the distinction matters to you: nil on a crypto call, a real aggregate on a stock or ETF call. Bars carry no volume on any category, and get_volume_profile/3 is the equity endpoint that splits traded volume by price and side.

That is a different claim from Trade.quantity — the streamed tape and get_trades/2 both report one print's own size, which the venue does publish. This package does not sum sizes into an aggregate figure of its own; that would be this package's arithmetic wearing the venue's name.

Eleven declared candle widths

1m 5m 15m 30m 1h 2h 4h 1d 1w 1M 1y — the full capabilities/0 historical_timeframes list, as of 2026-09-07. Two under-declarations were corrected to get here. Until 2026-09-06 this declared only the first eight, the crypto and event-contract default generalised to the whole venue, which was false for the equity, option and futures bars that have always served 1w and 1M too. 1y was then withheld for a real reason that stopped being true: dp_exchange_core 0.1.48's Timeframe.nameable/0 had no entry for it and Capabilities.new/1 raised on it. Core 0.1.57 names it, and the workaround outlived the gap by three releases — nothing fails when a documented workaround goes stale, which is exactly why a served width stayed hidden from consumers reading capabilities/0.

The crypto and event-contract bar endpoints serve 1m 5m 15m 30m 1h 2h 4h 1d and nothing wider. 1w is left off those endpoints deliberately: a weekly boundary depends on which weekday the venue starts its week, Core.Timeframe models no alignment rule for it, and a bar whose boundary cannot be verified is a bar that should not be stored. That reasoning is about a continuous, boundary-less crypto week — it does not apply to equities, which trade on a fixed calendar week the venue's own bar aligns to.

The equity, option and futures bar endpoints take three widths beyond those eight — 1w, 1M and 1y — because that is the timespan vocabulary those endpoints publish (Rest.get_stock_bars/5, tested against it). Core.Capabilities has one flat list for the whole package with no per-asset-class shape, so the declaration is the union every active path reaches rather than the crypto subset, and it is now derived from Rest.wide_timeframes/0 rather than a hand-maintained subtraction from it. Asking a crypto or event-contract category for 1w, 1M or 1y is still an error, never the nearest width it does serve — branch on opts[:category], not on the flat list alone, if you need to know which endpoint a width actually reaches.

Equity/ETF bars are adjusted at daily and above, not below

get_historical_prices/4 against US_STOCK/US_ETF: daily and longer widths are forward-adjusted for splits, minute widths are not — the vendor's own rule, and these are two different series, not the same one at two resolutions. adjusted?/1 answers it for a width before you fetch it, so stitching a daily series onto a minute one across a split does not join an adjusted half to an unadjusted one silently:

DpExchange.Webull.adjusted?("1d")  #=> true
DpExchange.Webull.adjusted?("1m")  #=> false

Timestamps come from the venue, or the call fails

A bar or quote the venue did not date returns {:error, :missing_venue_timestamp}. The local clock is never substituted — an undated bar stamped with your own clock is indistinguishable from a real one, which is how a gap becomes invisible.

What this package does not do yet

Read capabilities/0, not this paragraph. As of 2026-09-01 the order path, balances, accounts, transfers and order book are all implemented, along with options, futures, event contracts, fundamentals, screeners, news and watchlists. get_trade_history/2 and get_market_overview/1 are not — both still answer {:error, :not_supported}, as not-yet-ported rather than as an absence at the venue. What remains :unsupported is listed there and per endpoint.

The money-movement callbacks are the ones that will not arrive: Webull's published API moves no money. There is no payment-method endpoint at either scope, no bank registration, no crypto network list, no allowlist and no transfer between accounts — funding happens in Webull's own applications, which need a person.

Five markets, five sets of endpoints, five parameter sets

opts[:category] routes: US_CRYPTO, US_STOCK/US_ETF, US_OPTION, US_FUTURES, US_EVENT. They are not one endpoint with a filter — each is its own path with its own parameters, and this package sends only the ones that endpoint's page documents.

That matters because the sets differ in ways that look arbitrary and are not: futures bars take no real_time_required and no time range; the futures tape and depth take no session filter; the option snapshot takes no extended-hours block. A parameter an endpoint does not know is at best ignored and at worst a refusal, and neither tells you which happened.

The default depends on which endpoint you called. get_price/2, get_top_of_book/2, get_historical_prices/4 and get_symbols/1 default to US_CRYPTO, which is what this package served before it widened. get_order_book/2, get_trades/2, get_volume_profile/3 and get_fundamental/3 default to US_STOCK, because this venue publishes no crypto depth, tape or footprint endpoint for them to have defaulted to. Changing either default would silently re-route existing callers onto a different market.

Event contracts have two prices and four books

get_trades/2 and get_order_book/2 refuse US_EVENT, and that is deliberate. An event tick carries a yes_price and a no_price and a side of yes/no; Types.Trade has one price and a side of :buy/:sell. An event book returns four arrays; Types.OrderBook has two sides.

Use get_event_trades/2 and get_event_order_book/2, which return the venue's own rows. The nearest mapping would produce a number that looks right and belongs to the other instrument of a two-instrument market.

The venue notes that in a binary market a yes bid at X equals a no ask at 1−X. That identity is the venue's; this package does not derive one side from the other, because a derived level cannot be told from a quoted one.

Event bars do not say which side they are. The venue's schema names open, close, high, low and no side. Reconcile against get_event_trades/2, which does name both.

Options: a chain is rebuilt, and greeks do not exist here

get_option_chain/2 turns the venue's flat contract list into expiry × strike, both sides. A contract this package cannot address — no readable expiry, strike or right — is refused, naming the keys the venue actually sent. A dropped row leaves a chain with a hole in it that looks complete.

A strike listed with one side keeps a nil on the other. :underlying_price is nil: this endpoint lists contracts and does not quote the underlying, and pairing it with a price fetched separately is two observations at two times.

get_option_greeks/2 returns {:error, :not_supported} and it is the venue, not the package. No Webull endpoint publishes them, and computing them would need a rate and a volatility surface it does not publish either.

Fundamentals: twenty-three endpoints, one shape

get_fundamental/3 reaches any of them; fundamental_kinds/0 lists them. Every one takes symbol and category; :type and :count reach only the endpoints that document them and are dropped elsewhere.

get_financials/3 takes the contract's :balance_sheet, :income, :cash_flow or :indicators. A fundamentals kind that is real but is not a statement is refused — :company_profile exists and answering get_financials/3 with it would put a profile in a statement's shape.

fiscal_period is the venue's code translated through the venue's own legend (0=FY, 1=Q1 …). The raw integer stays in line_items, and a code outside the legend leaves the label nil rather than inventing one.

get_corporate_events/1 needs :symbol — these calendars are per issuer, not market-wide — and without :kind reads both calendars, which is two requests.

get_news/1 is generated, not reported. The vendor's own description is "invokes LLM to generate news summaries", so each summary is a model's paraphrase and source names the venue rather than a wire. If you quote it, you are quoting a summary.

A screener's rank is the position the venue returned the row in. Nothing is re-ranked: two venues' "top movers" answer different questions, and so do one venue's under two sorts.

Watchlists: three absences and a boolean

symbols is nil on a list_watchlists/1 row — that endpoint names watchlists and does not read membership, and [] would say the watchlist is empty. name is nil on get_watchlist/2, because the membership endpoint does not return it.

update_watchlist/2 refuses opts[:symbols]. This venue's update endpoint touches properties only; add_watchlist_instruments/3 and remove_watchlist_instruments/3 are the membership writes, and silently skipping the option would leave you believing the list changed.

Every watchlist write answers {"success": …} rather than an error status, so a false is a 200 that did nothing — reported here as {:refused, :watchlist_write_rejected}.

Creating with members is two requests. Where the add fails, the watchlist exists and is empty: {:error, {:watchlist_created_without_members, id, reason}} carries its id so you can deal with it.

A stop order needs :stop_price; a trailing stop needs :trailing_stop_step

place_order/3's request map takes the same field names for every instrument type, and which ones matter depends on :order_type:

A field a given order type does not use is dropped rather than sent — a :stop request built from a :limit template (with :price left over) will not carry a stray limit_price the venue's schema for STOP_LOSS does not have. Read the fields back the same way: get_order/2 and the struct place_order/3 hands back both carry :stop_price on a stop or stop-limit order, nil on anything else.

Which pairs of :order_type and :time_in_force this venue actually accepts differs by instrument — crypto's list is five pairs (MARKET/IOC, LIMIT and STOP_LOSS_LIMIT at DAY or GTC — no plain STOP_LOSS, no TRAILING_STOP_LOSS); equity, option and futures orders add STOP_LOSS and (equity only) TRAILING_STOP_LOSS; an event contract takes LIMIT only, at any of five time-in-force values. A pair outside the matrix is refused before the request is sent, naming both halves of what was wrong, rather than being sent and rejected by the venue.

Batch orders: fifty, equities, and one request

place_orders/3 is not place_order/3 in a loop — the venue accepts the batch as one request. Both of its limits are enforced before the request: 50 orders and equities only. A batch over the cap is refused rather than split, because splitting turns one atomic request into several.

The result is per order. The venue validates each and returns each; a batch where three of five were accepted is the normal shape. The vendor also notes the endpoint is not available to every client, so a refusal can mean the account is not entitled.

Tokens: a token that exists is not a token that works

create_token/1 returns one that is PENDING, and verification happens through an SMS code in the Webull app — which needs a person. check_token/2 is the only call that tells PENDING from EXPIRED from INVALID; all three fail identically at the next request and each has a different remedy.

oauth_token/3 is one endpoint doing two jobs on a different host, with a form body. opts[:code] exchanges, opts[:refresh_token] refreshes, and exactly one is required. Two expiries come back and they are not the same clock — rt_expires_in is the one that ends the session.

Every negative here is audited

docs/reference/webull/negative-claims.md lists each one with the source and date consulted. Three were wrong, all the same mistake: a true statement about the stock endpoint restated as a claim about the venue. It also records why the vendor's pages have to be rendered to be read — their parameter tables are built in JavaScript, and an inventory captured without them looks finished and cannot be implemented from.