WebSocket API

Don't blindly reconnect on every disconnect. The close code tells you exactly what happened — treat each one differently:

import WebSocket from 'ws';

const URL = 'wss://apiv2.laevitas.ch/ws';
const API_KEY = process.env.LAEVITAS_API_KEY;
const SUBSCRIPTIONS = [
  'trades.spot.binance.BTCUSDT',
  'trades.perpetuals.binance.BTCUSDT',
  'open-interest.perpetuals.bybit.BTCUSDT',
  'funding-rate.perpetuals.bybit.BTCUSDT',
];

// Codes that mean "the same retry will fail the same way" — surface and stop.
const FATAL = new Set([4001, 4003, 4005, 4006]);

let attempt = 0;

function connect() {
  const ws = new WebSocket(URL, { headers: { apikey: API_KEY } });

  ws.on('open', () => {
    attempt = 0; // reset backoff on successful connect
    ws.send(JSON.stringify({ id: 1, method: 'subscribe', params: { channels: SUBSCRIPTIONS } }));
  });

  ws.on('message', (raw) => {
    const msg = JSON.parse(raw.toString());
    if (msg.channel) handleEvent(msg.channel, msg.data);
  });

  ws.on('close', (code, reason) => {
    console.log(`closed code=${code} reason=${reason}`);
    if (FATAL.has(code)) {
      console.error('Fatal close — not reconnecting. Fix the underlying issue.');
      return;
    }
    // Exponential backoff with jitter; cap at 30s.
    const base = Math.min(1000 * 2 ** attempt++, 30_000);
    const jitter = base * (0.8 + Math.random() * 0.4);
    setTimeout(connect, jitter);
  });

  ws.on('error', (err) => console.error('ws error:', err.message));
}

connect();

~30 lines. Handles all the failure modes documented above. Substitute SUBSCRIPTIONS with whatever you need; pass an X-Credit-Token header instead of apikey for x402 ws-pass auth.

1. POST to one of the pass routes — receive a 402 with USDC payment requirements (Base mainnet).
2. Sign and retry with the PAYMENT-SIGNATURE header. The server settles on-chain, grants your slot, and returns an x-credit-token JWT.
3. Connect to wss://apiv2.laevitas.ch/ws with that JWT in the X-Credit-Token header.
4. The server validates your wallet has an active slot. Disconnect and reconnect freely until expiry.
5. When the slot expires, your next connection attempt returns close code 4006. Buy another pass to resume.
6. If your connection is still open at the expiry timestamp, the server closes it with the same 4006 code — a long-lived connection cannot outlive its paid window.

For sustained heavy usage, the API subscription remains the most cost-effective option (rate-limit-free, full historical access, support included). Day passes are convenience pricing for short bursts — not a subscription replacement.