Version:           4.7.3 (using KDE 4.7.3) 
OS:                Linux

If you set automatic window tabbing, new windows should automatically be tabbed with existing windows of the same application.

However, if you have two activities running, X and Y, and Y has the app running but X doesn't, if you are currently in X and run the app, it'll appear in Y instead of X.

As a result, you don't _see_ the window unless you switch activities, which is non-intuitive.

Reproducible: Didn't try

Steps to Reproduce:
1. Create and run two activities, X and Y.
2. Turn on auto tab similar apps in system settings.
3. Switch to activity Y. Open an app. The app is now part of activity Y.
4. Switch to activity X. Open an app.

Actual Results:  
The app will open in activity Y.

Expected Results:  
It should open in activity X.

It's technically correct behavior, but only because it seems that automatic window tabbing isn't yet semantically aware.