New 2021 Child Tax Credit Issue for Divorced Parent

So from what I understand the new $3,000 Child Tax Credit goes into effect for 2021.  The credit is around $3,000 for kids 7-18, and will be paid out at a rate of $250 per month from July to December, and the remainder will be a credit on your 2021 taxes.  Here is my situation.  My Ex and I alternate each year on who claims our child as a dependent.  BUT.... All tax stimulus payments are sent to whoever claimed the child in 2020.  So in year 2021, they will send HER the $250/month, since she claimed him in 2020, but for the tax year 2021 I will be claiming him as a dependent, but I won't receive any of the advance payments.

How will this work?  Will I be out of luck, for half of my child credit deduction?  Will she have to pay back the advance payments she received for the 2021 credit, since she will not be claiming him in 2021?

I'm worried the IRS , when I claim my child for 2021 tax year,  will automatically assume I received $1,500 in advance tax credit payments, when in fact it was sent to HER.  And NO.... she will not forward any of the money to me or make any kind of repayments.