OoOoAhAHHead

Just tried the above test (started world in 1.12 with seed 7989069131527685205, closing and opening world in 1.13 pre5 with the current launcher) and it opened without issue and everything appeared to work as expected.

mr wobst have you tried using the old launcher? just curious!

fyi the issue persists in 1.13 pre-3 I also tried turning off the console, that did not help. However if I load minecraft with the old launcher it runs PERFECTLY!

TLDR; try the old launcher.

http://s3.amazonaws.com/Minecraft.Download/launcher/Minecraft.jar

I was getting a LInux live installation USB ready and had a portable install on the usb I was going to use .. for giggles I tried it and it loaded the world fine!

So perhaps the problem lies with the new launcher somehow? Perhaps the console? Good luck with that!

Later I'll try this on Linux. Michal are you using Ubuntu? 16.04?

Interesting. I can open another (much more populated) save based on the same seed. New chunks are being generated as expected if I move beyond previously generated chunks. File too large to attach, you can dl here:

https://drive.google.com/open?id=1AEJ6rFX8V_55Dhetmkki8_rULKKkPNbj

fwiw I can confirm. Log attached.

Thanks for your help. I left it loading for about an hour, no luck. Please find launcher log attached.

this is a faster way to recreate the error:

create 1.12.2 world with this seed:

7989069131527685205

save and open in 1.13 pre2

AWESOME THANK YOU MR WOBST! high five