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The most-requested integration on Predexon. You pick a profitable wallet, watch every fill it does, and mirror those fills into your own account at a fraction of the size. You’ll build:
  1. A WebSocket listener that fires on every trade by the target wallet
  2. A handler that translates target-wallet trades into your-account orders
  3. A scale-and-execute path via the Order Router (cross-venue compatible)
Endpoints used: 1 WebSocket channel + 2 Trading API endpoints. Runs on Dev plan or higher (WebSocket requires Dev+).

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Architecture

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Step 1 — Verify the target

Before mirroring, check they’re actually profitable. Pull the wallet profile: 
import os, requests, time, json
from websockets.sync.client import connect

DATA = "https://api.predexon.com"
TRADE = "https://trade.predexon.com"
WSS = "wss://wss.predexon.com/v1"
KEY = os.environ["PREDEXON_API_KEY"]
H = {"x-api-key": KEY}
TARGET = "0xSmartTraderAddressHere"
ACCOUNT_ID = "your-account-id"   # set up via builder-guide

profile = requests.get(f"{DATA}/v2/polymarket/wallet/{TARGET}", headers=H).json()
print(f"Profit: ${profile['realized_profit_usd']:,.0f}  ROI: {profile['roi']:.1%}")
assert profile["realized_profit_usd"] > 50_000, "Target isn't profitable enough"
Re-run this check daily — wallets degrade.

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Step 2 — Subscribe to their trades

The trades channel takes a users filter. You’ll receive every fill they take in real time, on both V1 and V2 Polymarket contracts. 
def subscribe():
    return json.dumps({
        "action": "subscribe",
        "platform": "polymarket",
        "version": 1,
        "type": "orders",
        "filters": {"users": [TARGET]},
    })

with connect(f"{WSS}/{KEY}") as ws:
    ws.send(subscribe())
    for raw in ws:
        msg = json.loads(raw)
        if msg.get("type") != "event":
            continue
        handle_trade(msg["data"])

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Step 3 — Scale and mirror

The hardest part of copy-trading is sizing. Mirror their trade as a fraction of their original size, capped by your venue balance. 
SIZE_RATIO = 0.10              # mirror 10% of their size
MAX_PER_TRADE_USD = 500

def handle_trade(trade):
    # only mirror trades initiated by the target wallet (not against them)
    if trade["user"].lower() != TARGET.lower():
        return
    # only follow buys; let me close on my own logic
    if trade["side"] != "BUY":
        return

    target_shares = float(trade["shares_normalized"])
    target_price = float(trade["price"])
    notional = target_shares * target_price

    # scale
    mirror_shares = target_shares * SIZE_RATIO
    mirror_notional = mirror_shares * target_price
    if mirror_notional > MAX_PER_TRADE_USD:
        mirror_shares = MAX_PER_TRADE_USD / target_price

    # the target trades on Polymarket — mirror directly on the same token_id
    resp = requests.post(
        f"{TRADE}/api/accounts/{ACCOUNT_ID}/orders",
        headers={**H, "Content-Type": "application/json"},
        json={
            "venue": "polymarket",
            "market": {"tokenId": trade["token_id"]},
            "side": "buy",
            "type": "market",       # or "limit" at target_price * 1.005
            "size": f"{mirror_shares:.2f}",
        },
    ).json()
    print(f"Mirrored: {trade['token_id']}  shares={mirror_shares:.2f}  → {resp.get('status')}")
The example above mirrors on the same venue (Polymarket → Polymarket) which is the most reliable copy-trading path. If you want to mirror cross-venue (e.g. target trades Polymarket, you trade Kalshi at a tighter spread), resolve the condition_id to a canonical predexon_id via List Canonical Markets (filter by condition_id) and use the Order Router instead.

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Step 4 — Run it under supervision

Things that will go wrong in production:
FailureMitigation
WebSocket disconnectWrap the loop with reconnect + resume. See Subscriptions.
Mirror order fails (insufficient balance)Catch the 400, alert yourself, top up the venue, don’t auto-retry.
Target sells before you fillUse market orders + smaller size; or accept the slippage as part of the cost.
Target wallet changes strategyRe-pull the wallet profile daily; pause mirroring if realized_profit drops.
You mirror a trade and they immediately reverseBuild a “follow exits too” version: also handle side: "SELL" to close mirrored positions.
For the simplest possible production version, also subscribe to the activity channel to mirror splits, merges, and redemptions.

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Variations

  • Multi-wallet copy-trading: subscribe with filters: {"users": [w1, w2, w3, ...]} and route each trade to the right end-user account in your DB.
  • Filtered copy-trading: only mirror trades above a notional threshold, or in specific market categories.
  • Cross-venue copy-trading: target trades on Polymarket, you mirror on Kalshi via canonical predexon_id — the router handles the venue switch automatically.
  • Agent-driven copy-trading: replace the WebSocket loop with the Agent Cookbook recipe 4, which polls and reasons about whether to mirror.

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Reference