Ken Stovitz is ending an 18-year run at CAA to become a partner in Overbrook Entertainment, the production company run by Will Smith and James Lassiter.

Along with agency president Richard Lovett, Stovitz has been Smith’s primary dealmaker since the actor’s breakthrough in “Six Degrees of Separation.” He has repped Smith and Lassiter’s production company for 15 years.

Stovitz gave notice late Monday. He began notifying other clients and will start at Overbrook as soon as the handoff process is completed.

Stovitz isn’t the first CAA agent to leave for a production partnership with a longtime client. It’s something of an unofficial tradition: Paula Wagner partnered with Tom Cruise; Michael Wimer with Roland Emmerich; Josh Donen with Sam Raimi; and Jack Rapke with Robert Zemeckis and Steve Starkey.

Stovitz becomes a partner as Overbrook continues to build itself as a film and TV supplier. Company has a first-look feature deal at Sony and is in pre-production at the studio on “Tonight, He Comes,” the Peter Berg-directed drama in which Smith will star alongside Charlize Theron. He and Lassiter will produce with Michael Mann and Akiva Goldsman. Overbrook is also producing the Neil LaBute-directed Screen Gems drama “Lakeview Terrace,” starring Samuel L. Jackson and Ashton Kutcher, and the production company entered into a deal with India-based UTV, which will bankroll modestly budgeted films that Smith and Lassiter will produce and co-own, with Sony distributing.

“Will and I have been searching for a partner to help us expand our company, and Ken’s knowledge of the business and our 15-year association with him at CAA will really help us attain our goals at Overbrook,” Lassiter said.

Stovitz first came to Hollywood as an attorney at Pillsbury, Madison & Sutro. After a short stint at ICM, he moved to CAA in 1989.

“I have been presented with the opportunity of a lifetime, to work with Will and James,” Stovitz said. “Although it is very hard for me to leave, I am very excited.”

CAA president Richard Lovett said of Stovitz’s move: “Ken has been a terrific colleague, agent and friend for many years. We are excited for him as he embarks on the next chapter of his career and look forward to continuing to work closely with him in his new role with Will and James.”