Qui doen't contract before a vowel

Question

Qu'est-ce que tu penses?
but,
Qui est-ce qui vient ce soir?

Just wondering why 'Qui', which ends in a vowel, wouldn't contract when the following word begins with a vowel, as does the example with 'Que'?

Accepted Answer

Hi Lewis,
 In answer to your question logically, it is probably to differentiate the meanings which would be lost if you could elide both vowels - 
Qu'est-ce -que ...? = What is ...?
Qui est-ce que ...? = Who is ...?
Hope this helps.

Answer

Only words ending in "e" contract.

Answer

Mainly it's words ending in "e", but also "la" and "si".
The rules are explained here:
https://french.kwiziq.com/revision/glossary/contraction/l-elision-elision

Answer

But si does not contract if the following vowel is an "e". It only contracts in cases such as si+il = s'il or s+ils = s'ils.
If you want a more complete summary on elisions, you can check, e.g.,here:https://www.lawlessfrench.com/pronunciation/elision/