The series was originally developed under the working title 'FBI: CIA' and was initially intended to launch via a backdoor pilot airing as an episode of FBI, but repeated delays pushed CBS to instead order it straight-to-series with a new script.

Showrunner duties changed hands multiple times during development: David Hudgins initially planned to be showrunner, but Warren Leight took over by July 2025, and both he and director/executive producer Eriq La Salle later departed the show during production, with Mike Weiss (FBI showrunner) expected to take over.

One of the show's creators and executive producers, David Chasteen, is a former CIA officer.

Eriq La Salle was originally set to direct the pilot, but after he left the series, the premiere episode ended up being directed by Ken Girotti instead.

Filming began in September 2025 in New York City, and production was temporarily put on hold after both Michael Michele and showrunner Warren Leight departed the series.

Tom Ellis said he originally read for the CIA case officer role as an American character, but Dick Wolf later changed the character at the last minute to be British, giving him dual British-American citizenship and a received pronunciation accent.

The second lead role of the FBI special agent was not cast until September 2025, when Nick Gehlfuss joined opposite Tom Ellis.

Michael Michele was originally cast as the chief of the CIA's New York station but left the series in November after production had begun, and her role was recast with Necar Zadegan.