SocketModeClient.disconnect() takes ~5 seconds to close on 3.0.1

package.json

{
  "name": "slack-repro",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "type": "module",
  "dependencies": {
    "@slack/socket-mode": "3.0.1"
  }
}

slack-shutdown.mjs

// Repro: what a Ctrl+C actually costs when disconnecting a Slack socket-mode
// client. Connects, waits for Ctrl+C, disconnects, and stamps every step.
//
//   SLACK_APP_TOKEN=xapp-… node slack-shutdown.mjs [--ping-timeout 1000]
//
// The client is built exactly like packages/channel-slack/src/connection.ts
// builds it (same options; --ping-timeout sets the SDK's clientPingTimeout,
// whose default is 5000 ms, to try other values). Install the version aivi
// pins next to this file: npm i @slack/[email protected]
//
// What the stamps say:
//   - the SDK's own lines (close frame sent/received, pong watchdog) arrive
//     through the routed logger, stamped with ms since start and since signal;
//   - `disconnect() resolved after Xms` is what aivi's teardown awaits;
//   - `event loop drained` is when the process is finally free to exit — the
//     gap after `resolved` is SDK handles (timers, sockets) holding a process
//     that already finished its work.
// A second Ctrl+C exits at once, like serve's.
import { SocketModeClient } from '@slack/socket-mode';

const appToken = process.env.SLACK_APP_TOKEN;
if (!appToken) {
  console.error('no SLACK_APP_TOKEN in the environment');
  process.exit(1);
}

const pingAt = process.argv.indexOf('--ping-timeout');
const pingTimeout = pingAt > 0 ? Number(process.argv[pingAt + 1]) : undefined;

const began = Date.now();
let signalAt = 0;
const at = () => `${String(Date.now() - began).padStart(6)}ms`;
const since = () => (signalAt ? ` (+${Date.now() - signalAt}ms from signal)` : '');
const line = level => (msg, ...rest) =>
  console.log(`${at()} ${level.padEnd(5)} ${msg}${rest.length ? ` ${rest.map(String).join(' ')}` : ''}`);

// Every SDK log line, routed here with a stamp: the close handshake, the pong
// watchdog, all of it, in order, with times.
const logger = {
  debug: line('debug'),
  info: line('info'),
  warn: line('WARN'),
  error: line('ERROR'),
  setLevel: () => {},
  getLevel: () => 'debug',
  setName: () => {},
};

const client = new SocketModeClient({
  appToken,
  clientOptions: { retryConfig: { retries: 0 } },
  logger,
  ...(Number.isFinite(pingTimeout) ? { clientPingTimeout: pingTimeout } : {}),
});

const pingLabel = Number.isFinite(pingTimeout) ? `clientPingTimeout=${pingTimeout}ms` : 'clientPingTimeout=default 5000ms';
console.log(`${at()} connect: start() (${pingLabel})`);
await client.start();
console.log(`${at()} connected — press Ctrl+C`);

process.on('beforeExit', () => console.log(`${at()} event loop drained — free to exit${since()}`));
process.on('exit', () => console.log(`${at()} process exit${since()}`));

let stopping = false;
process.once('SIGINT', async () => {
  if (stopping) {
    console.log(`${at()} second SIGINT — process.exit(1) now`);
    process.exit(1);
  }
  stopping = true;
  signalAt = Date.now();
  const readyStates = ['CONNECTING', 'OPEN', 'CLOSING', 'CLOSED'];
  const state = readyStates[client.websocket?.readyState ?? -1] ?? 'absent';
  console.log(`${at()} SIGINT — websocket is ${state}; calling disconnect() and awaiting it`);
  const started = Date.now();
  await client.disconnect();
  console.log(`${at()} disconnect() resolved after ${Date.now() - started}ms${since()}`);
  console.log(`${at()} our work is done; anything after this is the SDK's handles keeping the process alive`);
});

Logs

     0ms debug The logLevel given to WebClient was ignored as you also gave logger
     1ms debug initialized
     1ms debug The Socket Mode client has successfully initialized
     1ms connect: start() (clientPingTimeout=default 5000ms)
     1ms debug Starting Socket Mode session ...
     1ms debug Going to retrieve a new WSS URL ...
     1ms debug apiCall('apps.connections.open') start
     2ms debug http request url: https://slack.com/api/apps.connections.open
     2ms debug http request body: {}
     2ms debug http request headers: {"User-Agent":"@slack:socket-mode/3.0.1 @slack:web-api/8.1.1 node/26.10.0 darwin/25.5.0","Accept":"application/json","Authorization":"[[REDACTED]]","Content-Type":"application/x-www-form-urlencoded"}
   221ms debug http response received
   223ms debug http request result: {"ok":true,"url":"wss://wss-primary.slack.com/link/?ticket=redacted&app_id=redacted","response_metadata":{"scopes":{"0":"connections:write"},"acceptedScopes":{"0":"connections:write"}}}
   223ms debug apiCall('apps.connections.open') end
   223ms debug Initiating new WebSocket connection.
   480ms debug WebSocket open event received (connection established)!
   480ms debug Started monitoring pings to and pongs from Slack.
   489ms debug Received a message on the WebSocket: {"type":"hello","num_connections":1,"debug_info":{"host":"applink-1","build_number":27,"approximate_connection_time":18060},"connection_info":{"app_id":"redacted"}}
   490ms connected — press Ctrl+C
^C  3890ms SIGINT — websocket is OPEN; calling disconnect() and awaiting it
  3891ms debug Manually disconnecting this Socket Mode client
  3891ms debug Sending close frame (status=1000).
 10482ms WARN  A pong wasn't received from the server before the timeout of 5000ms!
 10483ms debug Terminating WebSocket (close frame sent but no response, force-terminating).
 10483ms debug isActive(): websocket not instantiated!
 10483ms disconnect() resolved after 6593ms (+6593ms from signal)
 10483ms our work is done; anything after this is the SDK's handles keeping the process alive
 10483ms event loop drained — free to exit (+6593ms from signal)
 10483ms process exit (+6593ms from signal)