1) Je saurai que tu es ici.

2) Je saurai que tu as été ici.

3) Je saurai que tu fus ici.

4) Je serai heureuse que tu sois ici.

5) Je serai heureuse que tu aies été ici.

So I couldn’t give you a rule, but it looks to me that you shouldn’t modify the tense in thhe second part of the sentence.

Edit : the 3) really sounds strange to me ; it might be because of the rare use of passé simple in french, but still, it might even be incorrect. It would take someone with a deeper knowledge of french rules (i’m french, but mathematician and informatician 🙂 ).