Doug Field, the former VP of Mac hardware who left Apple to become Tesla’s chief vehicle engineer, has returned to Cupertino. Apple confirmed the news to Daring Fireball’s John Gruber, who separately reports that Field is now working on the company’s secretive “Project Titan” self-driving car program.

Field ran Tesla’s vehicle production and engineering, but CEO Elon Musk took over responsibility for production this year after the company failed to meet its initial first-quarter goal for the Model 3. Field then took a leave of absence in May, and subsequently left the company altogether in June.

Project Titan has reportedly been scaled back considerably from its initial scope, with hundreds of people leaving the division as Apple is said to focus on seeking carmaker partners for its self-driving software. Gruber speculates that Field’s return to Titan suggests Apple could still have an interest in producing vehicles itself, while cautioning that employees do move between the two companies regularly.