did i commit to a wrong build ?

The rim is not at fault. Some random sharp pointy object cut your tire. Find the hole. Patch it. Inflate. Ride and enjoy. 819's are great hoops.

Edit: Kenda Navigator? Is this a new tire? I can't find any information regarding it.

haha, sorry for the typo error, its kenda Nevegal UST. my bad!

So a rim is to blame for a cut in the tire

Sounds like the "slit" is larger than the sealant can seal (about 1/8" is max) so you can get a patch kit and fix the existing tire or get a new tire...the rims have nothing to do with it.

819's are plenty strong for your weight.....you simply cut your tire on something. Sh!t happens.....replace the tire and get back out there!

alright, patching up the tire now. thanks guys.

ps: do i need to re-apply the sealant after patching the tire from the inside?

Sealant is a UST tire....

is a matter of choice. A UST tire will hold air just fine without sealant. But, as you've just discovered, there can be a need for it. You can still get punctures in UST tires. For the most part sealant in a UST tire is just good insurance. In your case however the pucture or cut was just too large for the sealant to handle. So your choice on that one. Where I live we don't run tires, tubeless or tubed, without some sort of sealant. At certain times of the year we've got thorns called "goat heads" that have 4 spikes on them arranged in such a way that when they fall to the groud there is always one spike sticking straight up. They'll puncture anything from a standard tire to a heavy duty dual ply down hill tire in a heart beat. So unless we want to walk, carry a half dozen tubes on every ride, or are just feeling lucky (read stupid!), sealant is used.

Your choice, but from the sound of it, a good tire sealant would be a good idea for you.

Good Dirt