Yes, Jamie Fraser unequivocally believes Claire Randall is from the future.
Jamie's Acceptance of Claire's Extraordinary Truth
Jamie's belief in Claire's incredible claim emerges during a pivotal moment in their relationship. In Outlander season 1, episode 11, titled "The Devil's Mark," Claire finally confides in Jamie about her true origins, revealing that she is, in fact, from the future.
Despite the monumental and seemingly impossible nature of her confession, Jamie accepts her story. The narrative highlights that while he may not fully comprehend the mechanics or implications of time travel, he firmly believes in Claire's words. This acceptance marks a significant turning point in their bond and showcases the depth of his trust in her.
Prior to this profound revelation, Claire had been grappling with her loyalties and emotions, torn between her burgeoning love for Jamie and her past life with Frank. Jamie's unwavering belief in her, even in the face of such an astounding disclosure, underscores his profound devotion and their unique connection.