This was resolved with the Ostrów agreement -- Jogaila became Grand Prince of Lithuania , while Vytautas retained the rights of an overlord . This was resolved with the Ostrów Agreement -- Jogaila became the Grand Duke of Lithuania while Vytautas retained rights of an overlord . This was solved with the Ostrów agreement -- Vytautas became Grand Duke of Lithuania , while Jogaila retained the rights of an overlord .