March 1 (UPI) -- Kate Hudson's ex-husband wants to challenge his custody agreement with the 37-year-old actress.
Hudson and Robinson, who share joint custody of Ryder, agreed to undergo an evaluation to determine what living and visitation arrangements are best for their son. The court ordered the actress to pay for the assessment, which requires a $7,500 deposit.
Hudson and Robinson also gave permission for the court to access their health and mental health records. In addition, the pair agreed to undergo drug, alcohol and psychological testing if deemed necessary.
"When they finalized their divorce, they agreed to joint custody," a source told InTouch Weekly. "Chris now wants full custody of Ryder. This has been an ongoing issue for months now, and they are still battling it out behind closed doors."
Hudson, who also shares 5-year-old son Bingham with ex-fiancé Matthew Bellamy, split from Robinson in 2006 after more than five years of marriage. She told People in December that her elder son is growing up fast.
"Ryder's a great kid, But, you know, he's 12. So it's all changing and starting. It's a beautiful time," the star said.
"I think I'm going to be good [during his teenage years]. I think I might -- knock on wood -- but I think he's going to do just fine. So I couldn't be prouder," she added.