Codegree conditions for cycle decompositions and Euler tours in 3-uniform hypergraphs

We show that 3-graphs whose codegree is at least (2/3 + o(1))n can be decomposed into tight cycles and admit Euler tours, subject to the trivial necessary divisibility conditions. We also provide a construction showing that our bounds are best possible up to the o(1) term. All together, our results answer in the negative some recent questions of Glock, Joos, Kühn and Osthus.