Valve failure analysis

Engine: audi 1.8T 20V

what can cause this failure this's supertech valve kit with everything else OEM in the head the engine just ran for 5 minutes and this happened what could be the problem?

Could you please post a close detail picture of the broken end of the valve stem?

Exactly which valves are they - intake or exhaust, material, solid or sodium filled, etc - the greater the information you can provide, the better. There is no way such failures are acceptable, but apparently there were issues with some nitrided stainless steel exhaust valves failing in a similar manner.

What the engine rpm at the time, or shortly before?

[edit] You may find this of interest - https://www.youtube.com/watch?v=CvrVLa5iR40