Which mechanism ensures a TTask terminates during a timeout in RAD Studio?

No built-in mechanism in RAD Studio System.Threading.TTask forces a task to terminate when a wait timeout expires. A timeout on the waiting side only stops the waiter; the task continues to run on the thread pool until it finishes or cooperates with cancellation.

Confirmed facts

• TTask.WaitFor / TTask.Wait with a timeout returns a TTaskStatus such as Running when the timeout elapses. It does not abort or kill the task.
• ITask.Cancel and TCancellationTokenSource.Cancel only signal intent. The worker thread must observe the signal and exit voluntarily.
• TThread.ForceTerminate on a thread pool worker used by TTask is unsafe and unsupported. It can corrupt memory, deadlock, and leak resources, and it is not a supported way to stop a TTask.

Supported pattern for a timeout trigger

The reliable pattern is cooperative cancellation coordinated with the wait timeout:

1. Create a TCancellationTokenSource before starting the work.
2. Start the task with the token and have the body poll cancellation points, e.g. Token.IsCancellationRequested or Token.ThrowIfCancellationRequested, and avoid long uninterruptible blocks.
3. Call WaitFor with the desired timeout. If the result is not Completed, call Source.Cancel to signal the task.
4. Wait again briefly for graceful exit, then proceed. Do not rely on WaitFor to stop the task.

var
  Src: TCancellationTokenSource;
  Task: ITask;
begin
  Src := TCancellationTokenSource.Create;
  Task := TTask.Run(
    procedure
    begin
      while not Src.Token.IsCancellationRequested do
      begin
        // work chunk
        Src.Token.ThrowIfCancellationRequested;
      end;
    end,
    Src.Token);
  if Task.WaitFor(5000) = TTaskStatus.Running then
    Src.Cancel;
end;

This ensures the waiter is released on timeout while giving the task a chance to unwind cleanly.

One diagnostic detail changes the recommendation: is the code inside the TTask owned by you and able to include cancellation checks, or is it third-party code with no cooperative points? Without cooperative points, safe termination is not achievable with TTask.