Advice on claims processing

Here's the situation. U.S. (obviously, because what other industrialized nation has to deal with this ****).

I'm on a HDHP (High Deductible Health Plan). I pay 100% of my costs up to the deductible (let's say $100), and after my deductible my insurance covers 100% of the costs (presumably up to Stop Loss? I don't remember, doesn't matter for this).

My deductible resets on Jan 1, in this case Jan 1, 2026 (presumably 00:00:00.001, or something like that). After that I called and refilled my high cost specialty prescription (technically on or after Jan 2, let's say) and it was processed and I received it a few days later -- we'll say Jan 9th, 2026.

The cost of this specialty prescription is just about the same as my deductible. This year, it was slightly less than the deductible, let's say $99.

This year, the pharmacy that fills my rx accidentally billed it to my insurance for the previous year, sometime in December 2025. I made the order after Jan 1, it wasn't filled or submitted to insurance until after that, it was just a mistake on their end. However since that time, I've accrued many other prescriptions and medical costs.

The question is essentially, does my insurance **HAVE** to process the claims in the order they occurred. That is, if my specialty rx was filled on Jan 7th, and then I went to the ER on Feb 1st, does the insurance need to process and apply $99 to my deductible before figuring in the cost of the ER visit, resulting in a $99 bill to me from the specialty pharmacy and a $1 to the ER, and any costs beyond that taken care of by my insurance under the HDHP.

There's more details, but I'm being obviously a little vague and deliberately changing dates and amounts in case this becomes a more... litigious issue.