The series was first announced in May 2023 as a spinoff of The Librarians in development at The CW, before being picked up for a two-season, twelve-episode order at TNT in August 2024.

The show was originally scheduled to premiere on The CW in October 2024, but was pulled from the schedule before eventually airing on TNT in May 2025.

Christian Kane reprises his role as Jacob Stone from The Librarians, appearing as a guest star to link the spin-off to the original series' continuity.

The character of Elaine Astolat is revealed to be a former knight of Camelot whose history was erased by a vengeful Lancelot, tying the new series' mythology back to Arthurian lore established in the franchise.

The role of Lancelot connects across the franchise: Matt Frewer played the character living as the 21st-century 'Dulaque' in The Librarians as the season's main antagonist, with Jerry O'Connell portraying his younger self, while Philip Rosch plays Lancelot in The Next Chapter.

The series is filmed on location in Belgrade, Serbia, with the Military Museum entrance of the Belgrade Fortress used as the exterior of the fictional 'Belgrade Castle' that houses the Library Annex, while interiors are shot in a Serbian studio.

Production relies heavily on Serbian extras and post-production work is largely handled in Serbia as well.

By May 2025, filming had already begun on the show's second season, even as the first season was just premiering.