TypeError: Cannot create property 'lastIndex' on string when using playwrightConfigOptions.grep in browserstack.yml

[amir-ziaei]

Given configuration:

platforms:
  - os: OS X
     ...
    playwrightConfigOptions:
      grep: '@myTag'

The following error happens:

Error: 2025-11-06 14:21:58 - info: [GrpcClient] PlaywrightConfig request successful
TypeError: Cannot create property 'lastIndex' on string '@myTag'

This prevents filtering Playwright tests by tags or grep in general. I cannot use the workaround of passing the grep directly to the command line because the following pattern would not be possible:

platforms:
  - os: OS X
     ...
    playwrightConfigOptions:
      grep: '@slow'
  - os: OS X
     ...
    playwrightConfigOptions:
      grep: '@fast'