My developers frequently need to jump into a completely unknown stack. And even if they didn't, I still expect the senior developers to reason and make decision

My developers frequently need to jump into a completely unknown stack. And even if they didn't, I still expect the senior developers to reason and make decisions about things out of their comfort zone. I'm not asking them to rewrite WordPress in Elixir, or implement vEB trees in C - I'm giving them simple tasks where they are given a codebase to work with, and the task assumes zero knowledge about it, and they have time to prepare.