Jessie Buckley and Riz Ahmed in Fingernails Photo: Courtesy of San Sebastian Film Festival
Among the additions is Fingernails, the second feature from Apples director Christos Nikou, which stars Riz Ahmed, Jessie Buckley, Luke Wilson, Jeremy Allen White and Annie Murphy. The festival says it is a "thought-provoking romantic drama about an institution that tests the presence of romantic love between couples".
Also joining the competition is backpacker drama The Royal Hotel, directed by Kitty Green (The Assistant), while Holiday director Isabella Eklöf brings her second feature Kalak about a Danish nurse who moves to Greenland.
Also competing for the Golden Shell is Custody director Xavier Legrand's The Successor about a designer who discovers a terrible secret in the wake of his father's death and Great Absence, directed by Kei Chikaura, which sees a young actor reconnect with his estranged father.
The additions are rounded out by A Journey in Spring, the debut feature from Taiwanese filmmakers Tzu-Hui Peng and Ping-Wen Wang, about a man mourning his wife's death.
The festival also announced a special screening, out of competition, of Thomas Lilti's A Real Job, which sees a PhD student take on a teaching job.