Real-time trade feed client for Polymarket (RTDS — Real-Time Data Socket).

Connects to wss://ws-live-data.polymarket.com and forwards every trade on Polymarket to a callback PID as {:polymarket_rtds, :trade, payload}. The payload is the raw map sent by Polymarket; normalization (typed structs, snake_case keys) is left to the caller — typically by feeding the same map shape into Polymarket.Activity.normalize/1.

The surface is deliberately narrow:

• No backpressure / batching / debouncing. Every trade event is forwarded as a separate Erlang message. Busy markets can produce 5–20 events/second and a slow callback can flood. If this is a problem, debounce in the callback or migrate to a future demand-driven (GenStage/Broadway) shape.
• Reconnects on transient drops, stays closed on deliberate close. A network drop reconnects (with exponential backoff so a hard-down endpoint does not storm); a deliberate close — e.g. the callback PID dying — stays closed. This module is not embedded in a Supervisor here — callers that want crash-and-restart guarantees should add their own supervisor.
• No topic generalization. Only the global trades feed ({"topic": "activity", "type": "trades"}) is subscribed. New Polymarket RTDS topics (resolutions, liquidity events) are not modeled.
• No payload normalization. Forwarded payloads are the raw maps from Polymarket. Pair with Polymarket.Activity.normalize/1 if you need typed structs.
• Callback is PID-only. The {module, function} callback form is not supported.

Usage

{:ok, _pid} = Polymarket.RTDS.start_link(callback: self())

receive do
  {:polymarket_rtds, :trade, payload} ->
    IO.inspect(payload, label: "rtds trade")
end

Trade payload fields (raw, from Polymarket)

• proxyWallet — trader's wallet address.
• pseudonym — trader's display name.
• side — "BUY" or "SELL".
• outcome — "Yes", "No", or named outcome.
• price — execution price (number).
• size — trade size (number).
• asset — outcome token id (decimal string).
• conditionId — market condition id (hex).
• eventSlug — market slug.
• title — human-readable market name.
• transactionHash — on-chain tx hash.
• timestamp — Unix timestamp.

Options

• :callback (required) — PID to receive trade events.
• :url — Override the WebSocket URL (default "wss://ws-live-data.polymarket.com").
• :ping_interval — PING frame interval in milliseconds (default 5_000).
• :name — Optional process name passed to WebSockex.start_link/4.