Silicon has a high affinity for Oxygen so you might get O silylation: by analogy with
bis(trimethylsilyl)acetamide (see https://en.wikipedia.org/wiki/Bis(trimethylsilyl)acetamide) here, with NEt3 as a base.
NH2CONH2 + 4TMSCl + 4NEt3 -> (Me3Si)2N(COTMS)=NTMS + 4HNEt3Cl: that is the silylation occurs on Oxygen after tautomerisation and then the remaining NHs are replaced by TMS.