jackwener/OpenCLI · error · CommandExecutionError

Browser session required

Error message

Browser session required

What it means

CommandExecutionError thrown when the reddit subscribe command is invoked without an active browser session. The command uses Strategy.COOKIE with browser:true, so it needs a logged-in browser page to run the /api/subscribe POST; without one, it fails fast instead of silently no-op'ing a write action.

Source

Thrown at clis/reddit/subscribe.js:18

import { CommandExecutionError } from '@jackwener/opencli/errors';
import { cli, Strategy } from '@jackwener/opencli/registry';
cli({
    site: 'reddit',
    name: 'subscribe',
    access: 'write',
    description: 'Subscribe or unsubscribe to a subreddit',
    domain: 'reddit.com',
    strategy: Strategy.COOKIE,
    browser: true,
    args: [
        { name: 'subreddit', type: 'string', required: true, positional: true, help: 'Subreddit name (e.g. python)' },
        { name: 'undo', type: 'boolean', default: false, help: 'Unsubscribe instead of subscribe' },
    ],
    columns: ['status', 'message'],
    func: async (page, kwargs) => {
        if (!page)
            throw new CommandExecutionError('Browser session required');
        await page.goto('https://www.reddit.com');
        const result = await page.evaluate(`(async () => {
      try {
        let sub = ${JSON.stringify(kwargs.subreddit)};
        if (sub.startsWith('r/')) sub = sub.slice(2);

        const undo = ${kwargs.undo ? 'true' : 'false'};
        const action = undo ? 'unsub' : 'sub';

        // Get modhash
        const meRes = await fetch('/api/me.json', { credentials: 'include' });
        const me = await meRes.json();
        const modhash = me?.data?.modhash || '';

        const res = await fetch('/api/subscribe', {
          method: 'POST',
          credentials: 'include',
          headers: { 'Content-Type': 'application/x-www-form-urlencoded' },

View on GitHub (pinned to 49907e53dc)

Solutions

  1. Launch the command in browser mode so a page handle is created (per the library's browser:true config)
  2. Log into reddit.com in that browser session first — subscribe is a write action requiring cookies
  3. If embedding, pass a valid Playwright/puppeteer page object instead of null/undefined
  4. Check that the browser runtime (Chromium etc.) is installed and the library can launch it

Example fix

// before
await redditSubscribe(page = null, { subreddit: 'python' }) // throws
// after
const page = await browser.newPage();
await loginReddit(page);
await redditSubscribe(page, { subreddit: 'python' });
Defensive patterns

Strategy: validation

Validate before calling

if (!page || typeof page.goto !== 'function') throw new Error('subscribe requires an active browser page');

Type guard

function hasBrowserPage(p){ return !!p && typeof p.goto === 'function' && typeof p.evaluate === 'function'; }

Try / catch

try { await cli.redditSubscribe(sub); }
catch (e) { if (e.message === 'Browser session required') { await launchAndLoginBrowser(); return cli.redditSubscribe(sub); } throw e; }

Prevention

When it happens

Trigger: Calling the subscribe command (subscribe/undo to a subreddit) in an environment where the browser-session-backed `page` argument is null/undefined — e.g. headless/no-browser mode, browser not launched, or calling func directly with page=null.

Common situations: Running the CLI in CI without a browser configured; browser login to reddit.com not completed; a wrapper invoking the command function with no page handle; browser launch failure upstream.

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/54e052591b2253e3. Report an issue: GitHub.