Well seems like the world gen was the problem, started another fort within another world where I changed a bit the order of the mods and it seems that this time they were available on embark... So I don't know what happened before, still works fine.

Tough cap mushrooms spawn in cavern layers 2 and 3. However, it is possible for an embark to not have enough water for plants to spawn in a cavern layer. Tough cap mushrooms cannot be requested in trade because only edible plants are available in embark and trade menus. However, their spawn should be available.

Tried to start a fortres today, and it seems like tough cap mushroom were not spawning anywhere on the map. Couldn't ask merchant to bring some and couldn't bring from embark... I had to give myself some thanks to DF hacks, and everything else seems to be working fine despite the lack of spawn.

Vegan Leather kek

This is cool, thanks! Makes me want to make an underground mushroom village.

Just uploaded a fix for that, thanks for finding it. At least now I know that the game does not report errors when a reaction requests a material that doesn't exist.

Yes I found that it grabbed any nearby plant and returned "Tanned Hide" and a "seed". Sorry for the delayed response.

That shouldn't be possible, the reaction for mushroom leather is written to only use a plant with the tough cap structural material. Does it accept any other plant for the reaction, or only cave wheat?

It is a great idea. However I just was running the reaction and it took a cave wheat and returned me a "Tanned Hide" and a "seed". I don't think it is fully working.

brilliant mod idea!

Cool idea. Now if only I could add it to an existing save game!