microsoft/playwright · error · Error

Unknown command: ${args._[0]}

Error message

Unknown command: ${args._[0]}

What it means

Thrown by runCommandOnSnapshot() when the first positional argument (args._[0]) is not a key in the commands map. After a trace snapshot page is served in a headless browser, the CLI dispatches a sub-command against it; an unrecognized sub-command name is rejected here. The command list is imported from the cli-daemon commands module.

Source

Thrown at packages/playwright-core/src/tools/trace/traceSnapshot.ts:203

  const browser = await playwright.chromium.launch({ headless: true });
  const context = await browser.newContext();
  const page = await context.newPage();
  await page.goto(server.url);
  await page.waitForURL(url => new URL(url).pathname.startsWith('/snapshot/'));

  const backend = new BrowserBackend({
    snapshot: { mode: 'full' },
    skillMode: true,
  }, context, browserTools);
  await backend.initialize({ cwd: process.cwd(), clientName: 'playwright-cli' });

  try {
    if (!browserArgs.length)
      browserArgs = ['snapshot'];
    const args = minimist(browserArgs, { string: ['_'] });
    const command = commands[args._[0]];
    if (!command)
      throw new Error(`Unknown command: ${args._[0]}`);
    const { toolName, toolParams } = parseCommand(command, args as Record<string, string> & { _: string[] });
    const result = await backend.callTool(toolName, toolParams);
    const text = result.content[0]?.type === 'text' ? result.content[0].text : undefined;
    if (text)
      console.log(text);
    if (result.isError) {
      console.error('Command failed.');
      process.exitCode = 1;
    }
  } catch (e) {
    console.error((e as Error).message);
    process.exitCode = 1;
  } finally {
    await server.stop().catch(e => console.error(e));
    await gracefullyCloseAll();
  }
}

View on GitHub (pinned to c8fc3bf8d3)

Solutions

1. Check the registered command names for your installed Playwright version and use an exact match.
2. If you only want to view the snapshot, omit the extra positional argument (the default is 'snapshot').
3. Upgrade or downgrade Playwright to the version whose command set you are targeting.

Example fix

// before
npx playwright trace snapshot 5 slect option
// after
npx playwright trace snapshot 5 select option

import { commands } from '../cli-daemon/commands';
function assertKnownCommand(name: string) {
  if (!(name in commands)) {
    throw new Error(`Unknown command: ${name}. Known: ${Object.keys(commands).join(', ')}`);
  }
}

function isKnownCommand(name: string): name is keyof typeof commands {
  return name in commands;
}

When it happens

Trigger: Running `npx playwright trace snapshot <actionId> <subcommand>` where <subcommand> is not one of the registered snapshot sub-commands (e.g. a typo like 'slect' instead of 'select').

Common situations: Typo in the sub-command; using a command name from a different/newer Playwright version not present in the installed one; passing a flag in the command position by mistake.

Related errors

• No trace opened. Run 'npx playwright trace open <file>' firs
• Trace file not found: ${filePath}
• Cannot find .trace file
• Invalid viewport size format: use "width,height", for exampl
• Invalid geolocation format, should be "lat,long". For exampl

AI-assisted analysis of microsoft/playwright@c8fc3bf8d3 (2026-08-12). Data as JSON: /api/errors/db29212b2826a368. Report an issue: GitHub.