Read the plan file $1 and interview me in detail using the AskUserQuestion about literally anything: technical implementation, UI & UX, concerns, tradeoffs, etc. but make sure the questions are not obvious.
Be very in-depth and continue interviewing me continually until it's complete, then write the spec to the file.
/goal Do not stop asking questions until you're satisfied the plan is unambiguous, covers all important aspects of the feature such as performance, security, architecture, design, etc.