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Get an alert the moment a big order hits the mempool, before it is in a block. Subscribe to trading with confirmed: false to stream pending exchange transactions. Pair it with the confirmed trading feed to know when the trade actually lands.
Mempool messages are guesses, not facts. A pending transaction can be dropped, replaced, reordered, or reverted. Never treat a mempool alert as a settled trade — always confirm against trading.

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What you need

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Alert on pending, confirm on landing

Subscribe to both feeds. Alert on the pending frame, then match it to the confirmed event by transaction_hash. Both arrive on the trading channel, so you tell them apart by the confirmed flag on the frame. 
import { Radion } from "@radion-app/sdk";

const radion = new Radion({ apiKey: process.env.RADION_API_KEY });
const pending = new Map<string, number>();

radion.realtime.onChannel("trading", (event) => {
  if (!event.confirmed) {
    const call = event.data.call;
    if (!call?.notional_usd || call.notional_usd < 10_000) return;
    pending.set(event.data.transaction_hash, call.notional_usd);
    console.log(
      `pending $${call.notional_usd} order — ${event.data.transaction_hash}`
    );
    return;
  }

  const hash = event.data.transactionHash;
  if (pending.has(hash)) {
    console.log(`landed — ${hash}`);
    pending.delete(hash);
  }
});

radion.realtime.subscribe({
  id: "pending",
  channel: "trading",
  confirmed: false,
});
radion.realtime.subscribe({
  id: "confirmed",
  channel: "trading",
  confirmed: true,
  filters: { min_usd: 10_000 },
});

await radion.realtime.connect();

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How the size filter differs

  • On the confirmed trading feed, min_usd measures the filled amount.
  • On the pending feed (confirmed: false), the call.notional_usd field is the pending order size. It may only partly fill or never land.
So filter the pending side in your own code (as above), and let min_usd narrow the confirmed side.

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Read the pending frame

The call object holds decoded calldata: method, market_ids, token_ids, wallets, notional_usd, and an orders array (each order is { maker, taker, token_id, side, maker_amount, taker_amount }). call is null when the calldata is not a known Polymarket call. See Mempool for the full frame and filter reach.

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Next steps

Mempool reference

Frame shape, the call object, and filter limits.

Copy-trade a whale

Mirror a wallet’s trades in real time.
Last modified on July 5, 2026