asyncapi: '2.6.0'
id: 'urn:com:backpack:exchange:streams'
info:
  title: Backpack Exchange WebSocket Streams API
  version: '2024-01-16'
  description: |
    Real-time market data and account event streams for Backpack Exchange.

    Clients connect to a single WebSocket endpoint and manage many streams over
    that connection by sending `SUBSCRIBE` / `UNSUBSCRIBE` JSON frames. Each
    inbound data message is wrapped in an envelope of the form
    `{ "stream": "<name>", "data": <payload> }`.

    Public streams (ticker, depth, kline, trade, bookTicker, markPrice,
    openInterest, liquidation) require no authentication. Private streams are
    prefixed with `account.` and require an ED25519 signature in the subscribe
    parameters using the `subscribe` instruction.

    All timestamps are in microseconds, except for the K-Line `t`/`T` start and
    close times (ISO 8601) and the RFQ `w`/`W` submission and expiry times
    (milliseconds).

    Keep-alive: the server sends a WebSocket `Ping` every 60 seconds; the
    client must reply with a `Pong` within 120 seconds or the connection is
    closed. On server shutdown a `Close` frame is sent with a 30 second grace
    period and the client should reconnect.
  contact:
    name: Backpack Exchange Support
    url: https://support.backpack.exchange/
  license:
    name: Proprietary
  termsOfService: https://backpack.exchange/refer/terms
  x-apis-json:
    aid: backpack:backpack-exchange-streams-api
    humanURL: https://docs.backpack.exchange/#tag/Streams
externalDocs:
  description: Backpack Exchange Streams documentation
  url: https://docs.backpack.exchange/#tag/Streams

defaultContentType: application/json

servers:
  production:
    url: ws.backpack.exchange
    protocol: wss
    description: Backpack Exchange production WebSocket endpoint.

channels:
  'bookTicker.{symbol}':
    description: Best bid/ask updates pushed in real time as the top of book changes.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeBookTicker
      summary: Receive best bid/ask updates for a symbol.
      message:
        $ref: '#/components/messages/BookTickerEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'depth.{symbol}':
    description: |
      Incremental order book depth updates. Each event contains absolute
      values at the listed levels; a level with quantity `0` is removed.
      A REST snapshot from `/api/v1/depth` is required to seed local state.
      Updates are sequential — `U` must equal previous `u + 1`.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeDepth
      summary: Receive realtime incremental depth updates.
      message:
        $ref: '#/components/messages/DepthEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'depth.{aggregation}.{symbol}':
    description: |
      Aggregated depth stream variant. Updates are buffered and emitted on a
      fixed interval (200ms, 600ms, or 1000ms) instead of in real time.
    parameters:
      aggregation:
        description: Aggregation window for the depth stream.
        schema:
          type: string
          enum: ['200ms', '600ms', '1000ms']
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeDepthAggregated
      summary: Receive depth updates aggregated over a fixed window.
      message:
        $ref: '#/components/messages/DepthEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'kline.{interval}.{symbol}':
    description: |
      Candlestick (K-Line) updates. Pushed up to once per second while the
      candle is open; a final message with `X: true` is sent when the candle
      closes.
    parameters:
      interval:
        description: K-line interval.
        schema:
          type: string
          enum:
            - 1s
            - 1m
            - 3m
            - 5m
            - 15m
            - 30m
            - 1h
            - 2h
            - 4h
            - 6h
            - 8h
            - 12h
            - 1d
            - 3d
            - 1w
            - 1month
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeKline
      summary: Receive candlestick OHLCV updates for a symbol.
      message:
        $ref: '#/components/messages/KlineEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  liquidation:
    description: Public liquidation events across all markets and liquidation types.
    subscribe:
      operationId: subscribeLiquidation
      summary: Receive liquidation events.
      message:
        $ref: '#/components/messages/LiquidationEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'markPrice.{symbol}':
    description: |
      Mark price stream for futures markets. Includes estimated funding rate,
      index price, and next funding timestamp (omitted on prediction markets).
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeMarkPrice
      summary: Receive mark price updates for a symbol.
      message:
        $ref: '#/components/messages/MarkPriceEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'openInterest.{symbol}':
    description: Open interest updates pushed every 60 seconds.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeOpenInterest
      summary: Receive open interest updates for a symbol.
      message:
        $ref: '#/components/messages/OpenInterestEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'ticker.{symbol}':
    description: 24 hour rolling statistics pushed once per second for a single symbol.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeTicker
      summary: Receive 24h rolling ticker statistics.
      message:
        $ref: '#/components/messages/TickerEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  'trade.{symbol}':
    description: |
      Public trade prints for a single symbol. The trade ID is a sequential
      number scoped to the symbol. Trades produced by liquidations are
      included.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeTrade
      summary: Receive public trade prints for a symbol.
      message:
        $ref: '#/components/messages/TradeEnvelope'
    bindings:
      ws:
        bindingVersion: '0.1.0'

  account.orderUpdate:
    description: |
      Authenticated stream of order lifecycle updates across all symbols on
      the signing account. Event types include `orderAccepted`,
      `orderCancelled`, `orderExpired`, `orderFill`, `orderModified`,
      `triggerPlaced`, and `triggerFailed`.
    subscribe:
      operationId: subscribeOrderUpdateAll
      summary: Receive order updates for all symbols on the account.
      bindings:
        ws:
          bindingVersion: '0.1.0'
      message:
        $ref: '#/components/messages/OrderUpdateEnvelope'

  'account.orderUpdate.{symbol}':
    description: Authenticated stream of order lifecycle updates filtered to a single symbol.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeOrderUpdateSymbol
      summary: Receive order updates for a single symbol on the account.
      bindings:
        ws:
          bindingVersion: '0.1.0'
      message:
        $ref: '#/components/messages/OrderUpdateEnvelope'

  account.positionUpdate:
    description: |
      Authenticated stream of position lifecycle updates across all markets.
      On subscribe, the server sends current open positions with the `e`
      field omitted. Subsequent events use one of `positionAdjusted`,
      `positionOpened`, or `positionClosed`.
    subscribe:
      operationId: subscribePositionUpdateAll
      summary: Receive position updates for all markets on the account.
      bindings:
        ws:
          bindingVersion: '0.1.0'
      message:
        $ref: '#/components/messages/PositionUpdateEnvelope'

  'account.positionUpdate.{symbol}':
    description: Authenticated position update stream filtered to a single market.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribePositionUpdateSymbol
      summary: Receive position updates for a single market.
      bindings:
        ws:
          bindingVersion: '0.1.0'
      message:
        $ref: '#/components/messages/PositionUpdateEnvelope'

  account.rfqUpdate:
    description: |
      Authenticated stream of RFQ (Request for Quote) and Quote lifecycle
      events relevant to the signing account, both as taker and maker.
      Event types include `rfqActive`, `rfqAccepted`, `rfqRefreshed`,
      `rfqCancelled`, `rfqCandidate`, `rfqFilled`, `quoteAccepted`, and
      `quoteCancelled`.
    subscribe:
      operationId: subscribeRfqUpdateAll
      summary: Receive RFQ and quote lifecycle events for the account.
      bindings:
        ws:
          bindingVersion: '0.1.0'
      message:
        $ref: '#/components/messages/RfqUpdateEnvelope'

  'account.rfqUpdate.{symbol}':
    description: Authenticated RFQ update stream filtered to a single symbol.
    parameters:
      symbol:
        $ref: '#/components/parameters/symbol'
    subscribe:
      operationId: subscribeRfqUpdateSymbol
      summary: Receive RFQ and quote lifecycle events for a single symbol.
      bindings:
        ws:
          bindingVersion: '0.1.0'
      message:
        $ref: '#/components/messages/RfqUpdateEnvelope'

  subscriptionControl:
    description: |
      Control channel for client-initiated `SUBSCRIBE` and `UNSUBSCRIBE`
      frames sent over the same WebSocket connection. Private streams must
      include a `signature` array of
      `[verifyingKey, signature, timestamp, window]` base64-encoded values
      using the `subscribe` instruction.
    publish:
      operationId: sendSubscriptionControl
      summary: Send a SUBSCRIBE or UNSUBSCRIBE request.
      message:
        oneOf:
          - $ref: '#/components/messages/SubscribeRequest'
          - $ref: '#/components/messages/UnsubscribeRequest'
      bindings:
        ws:
          bindingVersion: '0.1.0'

components:
  parameters:
    symbol:
      description: Market symbol, e.g. `SOL_USDC`, `SOL_USDC_PERP`, `SOL_USDC_RFQ`.
      schema:
        type: string
        pattern: '^[A-Z0-9_]+$'

  messages:
    SubscribeRequest:
      name: SubscribeRequest
      title: Subscribe request
      summary: Subscribe to one or more streams.
      contentType: application/json
      payload:
        type: object
        required: [method, params]
        properties:
          method:
            type: string
            enum: [SUBSCRIBE]
          params:
            type: array
            description: Stream names to subscribe to.
            items:
              type: string
          signature:
            type: array
            minItems: 4
            maxItems: 4
            description: |
              Required for private streams. Tuple of
              `[verifyingKey, signature, timestamp, window]` where the
              first two are base64 encoded and timestamp/window are
              milliseconds. The signing string is
              `instruction=subscribe&timestamp=<ts>&window=<window>`.
            items:
              type: string

    UnsubscribeRequest:
      name: UnsubscribeRequest
      title: Unsubscribe request
      summary: Unsubscribe from one or more streams.
      contentType: application/json
      payload:
        type: object
        required: [method, params]
        properties:
          method:
            type: string
            enum: [UNSUBSCRIBE]
          params:
            type: array
            items:
              type: string

    BookTickerEnvelope:
      name: BookTickerEnvelope
      title: Book ticker envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/BookTickerEvent'

    DepthEnvelope:
      name: DepthEnvelope
      title: Depth envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/DepthEvent'

    KlineEnvelope:
      name: KlineEnvelope
      title: K-Line envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/KlineEvent'

    LiquidationEnvelope:
      name: LiquidationEnvelope
      title: Liquidation envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/LiquidationEvent'

    MarkPriceEnvelope:
      name: MarkPriceEnvelope
      title: Mark price envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/MarkPriceEvent'

    OpenInterestEnvelope:
      name: OpenInterestEnvelope
      title: Open interest envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/OpenInterestEvent'

    TickerEnvelope:
      name: TickerEnvelope
      title: Ticker envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/TickerEvent'

    TradeEnvelope:
      name: TradeEnvelope
      title: Trade envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/TradeEvent'

    OrderUpdateEnvelope:
      name: OrderUpdateEnvelope
      title: Order update envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/OrderUpdateEvent'

    PositionUpdateEnvelope:
      name: PositionUpdateEnvelope
      title: Position update envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/PositionUpdateEvent'

    RfqUpdateEnvelope:
      name: RfqUpdateEnvelope
      title: RFQ update envelope
      contentType: application/json
      payload:
        allOf:
          - $ref: '#/components/schemas/StreamEnvelope'
          - type: object
            properties:
              data:
                $ref: '#/components/schemas/RfqUpdateEvent'

  schemas:
    StreamEnvelope:
      type: object
      required: [stream, data]
      properties:
        stream:
          type: string
          description: Stream name the payload was emitted on.
        data:
          type: object
          description: Stream-specific event payload.

    BookTickerEvent:
      type: object
      properties:
        e:
          type: string
          const: bookTicker
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        a:
          type: string
          description: Inside ask price.
        A:
          type: string
          description: Inside ask quantity.
        b:
          type: string
          description: Inside bid price.
        B:
          type: string
          description: Inside bid quantity.
        u:
          type: string
          description: Update ID of the event.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.

    DepthEvent:
      type: object
      properties:
        e:
          type: string
          const: depth
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        a:
          type: array
          description: Ask updates. Each entry is `[price, quantity]`.
          items:
            type: array
            minItems: 2
            maxItems: 2
            items:
              type: string
        b:
          type: array
          description: Bid updates. Each entry is `[price, quantity]`.
          items:
            type: array
            minItems: 2
            maxItems: 2
            items:
              type: string
        U:
          type: integer
          format: int64
          description: First update ID in the event.
        u:
          type: integer
          format: int64
          description: Last update ID in the event.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.

    KlineEvent:
      type: object
      properties:
        e:
          type: string
          const: kline
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        t:
          type: string
          description: K-Line start time (ISO 8601).
        T:
          type: string
          description: K-Line close time (ISO 8601).
        o:
          type: string
          description: Open price.
        c:
          type: string
          description: Close price.
        h:
          type: string
          description: High price.
        l:
          type: string
          description: Low price.
        v:
          type: string
          description: Base asset volume.
        n:
          type: integer
          description: Number of trades.
        X:
          type: boolean
          description: True when this candle is closed.

    LiquidationEvent:
      type: object
      properties:
        e:
          type: string
          const: liquidation
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        q:
          type: string
          description: Quantity.
        p:
          type: string
          description: Price.
        S:
          type: string
          enum: [Bid, Ask]
          description: Side.
        s:
          type: string
          description: Symbol.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.

    MarkPriceEvent:
      type: object
      properties:
        e:
          type: string
          const: markPrice
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        p:
          type: string
          description: Mark price.
        f:
          type: string
          description: Estimated funding rate. Not present for prediction markets.
        i:
          type: string
          description: Index price. Not present for prediction markets.
        n:
          type: integer
          format: int64
          description: Next funding timestamp in milliseconds. Not present for prediction markets.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.

    OpenInterestEvent:
      type: object
      properties:
        e:
          type: string
          const: openInterest
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        o:
          type: string
          description: Open interest in contracts.

    TickerEvent:
      type: object
      properties:
        e:
          type: string
          const: ticker
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        o:
          type: string
          description: First price (24h open).
        c:
          type: string
          description: Last price.
        h:
          type: string
          description: High price.
        l:
          type: string
          description: Low price.
        v:
          type: string
          description: Base asset volume.
        V:
          type: string
          description: Quote asset volume.
        n:
          type: integer
          description: Number of trades.

    TradeEvent:
      type: object
      properties:
        e:
          type: string
          const: trade
          description: Event type.
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        p:
          type: string
          description: Price.
        q:
          type: string
          description: Quantity.
        b:
          type: string
          description: Buyer order ID.
        a:
          type: string
          description: Seller order ID.
        t:
          type: integer
          format: int64
          description: Sequential trade ID for the symbol.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.
        m:
          type: boolean
          description: True if the buyer is the maker.

    OrderUpdateEvent:
      type: object
      description: |
        Order lifecycle event. Many fields are conditional on order type or
        event type — see Backpack docs for full conditional rules.
      properties:
        e:
          type: string
          description: Event type.
          enum:
            - orderAccepted
            - orderCancelled
            - orderExpired
            - orderFill
            - orderModified
            - triggerPlaced
            - triggerFailed
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        c:
          type: integer
          format: int64
          description: Client order ID. Only present if set on the order.
        S:
          type: string
          enum: [Bid, Ask]
          description: Side.
        o:
          type: string
          description: Order type (e.g. LIMIT, MARKET).
        f:
          type: string
          description: Time in force (e.g. GTC, IOC, FOK).
        q:
          type: string
          description: Quantity. Only present if the order has a quantity set.
        Q:
          type: string
          description: Quantity in quote. Only present on reverse market orders.
        p:
          type: string
          description: Price. Only present on limit orders.
        P:
          type: string
          description: Trigger price. Only present on trigger orders.
        B:
          type: string
          description: Trigger by reference. Only present on trigger orders.
        a:
          type: string
          description: Take profit trigger price. Only present if set.
        b:
          type: string
          description: Stop loss trigger price. Only present if set.
        j:
          type: string
          description: Take profit limit price.
        k:
          type: string
          description: Stop loss limit price.
        d:
          type: string
          description: Take profit trigger by reference.
        g:
          type: string
          description: Stop loss trigger by reference.
        Y:
          type: string
          description: Trigger quantity. Only present on trigger orders.
        X:
          type: string
          description: Order state.
        R:
          type: string
          description: Order expiry reason. Only present on orderExpired events.
        i:
          type: string
          description: Order ID.
        t:
          type: integer
          format: int64
          description: Trade ID. Only present on orderFill events.
        l:
          type: string
          description: Fill quantity. Only present on orderFill events.
        z:
          type: string
          description: Cumulative executed quantity.
        Z:
          type: string
          description: Cumulative executed quantity in quote.
        L:
          type: string
          description: Fill price. Only present on orderFill events.
        m:
          type: boolean
          description: Whether the order was the maker side. Only on orderFill.
        n:
          type: string
          description: Fee. Only present on orderFill events.
        N:
          type: string
          description: Fee asset symbol. Only present on orderFill events.
        V:
          type: string
          description: Self trade prevention mode.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.
        O:
          type: string
          description: Origin of the update.
          enum:
            - USER
            - LIQUIDATION_AUTOCLOSE
            - ADL_AUTOCLOSE
            - COLLATERAL_CONVERSION
            - SETTLEMENT_AUTOCLOSE
            - BACKSTOP_LIQUIDITY_PROVIDER
        I:
          type: string
          description: Related order ID.
        H:
          type: integer
          format: int64
          description: Strategy ID.
        y:
          type: boolean
          description: Post only flag.

    PositionUpdateEvent:
      type: object
      properties:
        e:
          type: string
          description: |
            Event type. Omitted in the initial snapshot of current open
            positions sent on subscribe.
          enum:
            - positionAdjusted
            - positionOpened
            - positionClosed
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        s:
          type: string
          description: Symbol.
        b:
          type: number
          description: Break even price.
        B:
          type: number
          description: Entry price.
        f:
          type: number
          description: Initial margin fraction.
        M:
          type: number
          description: Mark price.
        m:
          type: number
          description: Maintenance margin fraction.
        q:
          type: number
          description: Net quantity. Positive for long, negative for short.
        Q:
          type: number
          description: Net exposure quantity, including open orders.
        n:
          type: number
          description: Net exposure notional.
        i:
          type: string
          description: Position ID.
        p:
          type: string
          description: Realized PnL.
        P:
          type: string
          description: Unrealized PnL.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.

    RfqUpdateEvent:
      type: object
      description: |
        RFQ / Quote lifecycle event. Field presence varies per event type —
        either `q` (base) or `Q` (quote quantity) is present, never both.
      properties:
        e:
          type: string
          description: Event type.
          enum:
            - rfqActive
            - rfqAccepted
            - rfqRefreshed
            - rfqCancelled
            - rfqCandidate
            - rfqFilled
            - quoteAccepted
            - quoteCancelled
        E:
          type: integer
          format: int64
          description: Event time in microseconds.
        R:
          type: integer
          format: int64
          description: RFQ ID.
        u:
          type: integer
          format: int64
          description: Quote ID.
        C:
          type: string
          description: Client ID (Client RFQ ID or Client Quote ID depending on context).
        s:
          type: string
          description: Symbol.
        S:
          type: string
          enum: [Bid, Ask]
          description: RFQ side.
        q:
          type: string
          description: Quantity in base asset. Present when RFQ is in base.
        Q:
          type: string
          description: Quantity in quote asset. Present when RFQ is in quote.
        p:
          type: string
          description: Price associated with the quote or fill event.
        w:
          type: integer
          format: int64
          description: Submission time in milliseconds.
        W:
          type: integer
          format: int64
          description: Expiry time in milliseconds.
        X:
          type: string
          description: RFQ or quote status.
          enum: [New, Cancelled, Filled]
        o:
          type: string
          description: System order type (e.g. CollateralConversion). Only on system-initiated RFQs.
        T:
          type: integer
          format: int64
          description: Engine timestamp in microseconds.

  securitySchemes:
    ed25519SubscribeSignature:
      type: apiKey
      in: user
      description: |
        ED25519 signature passed in the `signature` field of the SUBSCRIBE
        frame as `[verifyingKey, signature, timestamp, window]`. The signing
        string is
        `instruction=subscribe&timestamp=<timestamp>&window=<window>`.
        Required for any stream prefixed with `account.`.