microsoft/playwright · error · Error

Could not start the session "${sessionName}"

Error message

Could not start the session "${sessionName}"

What it means

Thrown by Registry.loadEntry when Registry._loadSessionEntry returns no entry for the requested session file (sessionName + '.session' could not be read/parsed from the daemon profiles dir). It means the named session does not exist or its file is unreadable.

Source

Thrown at packages/playwright-core/src/tools/cli-client/registry.ts:85

  entry(clientInfo: ClientInfo, sessionName: string): SessionFile | undefined {
    const key = clientKey(clientInfo);
    const entries = this._files.get(key) || [];
    return entries.find(entry => entry.config.name === sessionName);
  }

  entries(clientInfo: ClientInfo): SessionFile[] {
    return this._files.get(clientKey(clientInfo)) || [];
  }

  entryMap(): Map<string, SessionFile[]> {
    return this._files;
  }

  async loadEntry(clientInfo: ClientInfo, sessionName: string): Promise<SessionFile> {
    const entry = await Registry._loadSessionEntry(clientInfo.daemonProfilesDir, sessionName + '.session');
    if (!entry)
      throw new Error(`Could not start the session "${sessionName}"`);

    const key = clientKey(clientInfo);
    let list = this._files.get(key);
    if (!list) {
      list = [];
      this._files.set(key, list);
    }
    const oldIndex = list.findIndex(e => e.config.name === sessionName);
    if (oldIndex !== -1)
      list.splice(oldIndex, 1);
    list.push(entry);
    return entry;
  }

  private static async _loadSessionEntry(daemonDir: string, file: string): Promise<SessionFile | undefined> {
    try {
      const fileName = path.join(daemonDir, file);
      const data = await fs.promises.readFile(fileName, 'utf-8');

View on GitHub (pinned to c8fc3bf8d3)

Solutions

1. Create the session first with: playwright-cli -s=<name> open.
2. Verify the session file exists under the daemon profiles dir (clientInfo.daemonProfilesDir).
3. Drop the -s flag to operate on the 'default' session, or list sessions to confirm the name.

Example fix

# before
playwright-cli -s=ci screenshot        # session 'ci' missing -> throws

# after
playwright-cli -s=ci open               # create/launch the session
playwright-cli -s=ci screenshot         # now works

import fs from 'fs';
import path from 'path';
function sessionExists(daemonProfilesDir: string, name: string): boolean {
  return fs.existsSync(path.join(daemonProfilesDir, name + '.session'));
}
if (!sessionExists(info.daemonProfilesDir, name)) {
  // run `playwright-cli -s=<name> open` instead of failing

function isMissingSessionError(e: unknown): boolean {
  return e instanceof Error && e.message.startsWith('Could not start the session');
}

try {
  await session.run(clientInfo, args);
} catch (e) {
  if (isMissingSessionError(e)) {
    await Session.startDaemon(clientInfo, { session: name } as any, 'open');
    await session.run(clientInfo, args); // retry after open
  } else throw e;
}

When it happens

Trigger: Calling a session-scoped command (e.g. playwright-cli -s=myname <cmd>) when 'myname' has never been opened, was deleted, or its .session file is corrupt.

Common situations: Typo in the -s flag; running on a different machine / user account where the daemon profiles dir has no such session; the session file was hand-deleted; downgrading left the file unreadable.

Related errors

• Client is v${clientInfo.version}, session '${this.name}' is
• Browser '${this.name}' is not open. Run playwright-cli${t
• --data must be in "mime/type=value" format, got: ${entry}
• Command is required
• No trace opened. Run 'npx playwright trace open <file>' firs

AI-assisted analysis of microsoft/playwright@c8fc3bf8d3 (2026-08-12). Data as JSON: /api/errors/db90ddd98db3b954. Report an issue: GitHub.