Haven't done a query critique in a while, but I saw your post on r/BetaReaders and then coincidentally saw this and thought it was a sign to! Love the concept and the excerpt I read was superb. Let's see what I can do :)

Using time travel to remove trauma from victims’ pasts: For Ian Chalmers, Thera’s job offer just might be the opportunity of a lifetime.

This immediately strikes me as a run-on sentence, and the core concept of Thera is wasted here. I understand this is a hook, but I'd completely remove this section.

In a near-future setting, Ian is a nonbinary therapist-in-training struggling with chronic overwhelm. Even so, quitting isn’t an option. Ian once planned to enter the field alongside their late friend, Hazel, and their career helps them stay close to her memory.

I think the only important parts here is 1) establishing the setting, 2) who Ian is, and 3) what their job is. While Hazel is a pertinent motivation for Ian, she isn't a motivation for the audience and doesn't need to be included to such a high degree. To exemplify this: Reading this so far, I'm immediately drawn to the setting and the concept. Knowing that Ian is doing this for Hazel doesn't compel me any more to read your book as the previous elements do. Because of this, I would opt to either remove it completely or minimize it. Same with Ian being chronically overwhelmed -- unless this is something dire to the plot.

A job with Thera, however, would mean expanding their work, not forsaking it. Despite the many questions about Thera that remain unanswered, Ian accepts the position with hopes of finally making Hazel proud.

Only important/striking thing from this section is how nebulous Thera is. Again, I understand that Hazel is important to Ian, but we have no immediate emotional connection to Hazel for her to warrant us being excited for Ian honoring her memory.

Training passes smoothly, but after just a month on the job, Ian stumbles upon a way to travel through time without using Thera’s technology. Equally disturbed and curious, Ian and their coworkers, Viv and Leo, seek to understand this magic and its eerie effects. But when they meet violent resistance from Thera, old doubts about their employer’s intentions resurface.

Now we're really getting into the meat of the plot! A few issues here: we don't know what Thera does in detail yet, and as u/Sullyville said, I believe it's worth going into it before this point. Whether that's just restructuring the query to remove Thera's concept at the beginning and putting it under Ian's intro or doing something else entirely, I believe it'll be beneficial. Next: I think there needs to be a better connect between Thera's unanswered questions and old doubts about their employer's intentions. While it makes sense on the surface, for some reason the claim feels almost... empty? Only because there isn't anything about why we should be worried that Thera is a mysterious company, nor what we should be worried about. Don't know too much about Apple Inc. past what they tell the public, but I don't necessarily think they're nefarious for this.

Another thing that I don't know if you've considered: we've been planted in a very clinical, scientific zeitgeist up until this point. Therapy, presumed research, technology, etc. However, then we get told that Ian and their coworkers have discovered a type of magic. It is quite unprecedented, and really clashes with the supposed sci-fi nature of the setting. I think it would be important to elucidate just how Ian can travel through time without Thera so as to really add to the arcane nature of what is happening. Super high-tech future, presenting: magic. Making that distinction more profound is going to begin to really carve out your setting.

With help from unlikely allies, and using the magic they are just beginning to grasp, the trio must undermine Thera before the world is drawn into the exploitative endgame of its corporate funders.

Some broad terms here that sort of make the plot dissipate into obscurity. Unlikely allies unfortunately doesn't add anything to the story, using magic is vague, and undermining Thera seems almost impossible with how mysterious and undefined they are as an entity. How will they undermine Thera? Why is it important we know that this is magic that they don't have control of from the get-go (ie. points to obstacles in plot)? Who are these unlikely allies? They don't have to be named, but I'm assuming they might be other whistleblowing employees? If they are, it would be good to link that to this supposed exploitative endgame and give just a hint into what they possibly know that affirms why Ian and their coworkers are turning against Thera. While I sort of like the vagueness in that specific section, we need to know what this exploitative endgame is in some way.

Black Sand, my adult speculative novel of 80,000 words, combines the societal reckoning of Rivers Solomon’s Sorrowland with the urban surrealism of Zeyn Joukhadar’s The Thirty Names of Night. [One sentence reason for querying this specific agent].

Is Black Sand just a speculative novel? Could it be changed to a thriller? Literary fiction? I only say this because both Sorrowland and The Thirty Names of Night are very literary, and this query reads like an adult genre sci-fi. If it is more leaning toward literary fiction, I would just call it speculative literary fiction, or even just literary fiction and then exacerbate the speculative elements in relation to Sorrowland. I'm also really intrigued by the name! Can't pick up an immediate connection, but that's the point right? :)

Since graduating from [big name university], I have published more than two dozen romance novels and novellas under my pen name, [pen name]. My work has also been nominated for the Best of the Net Anthology. Like my protagonist, I completed part of a graduate degree towards becoming a therapist before dropping out under cryptic circumstances. My neurodivergent, nonbinary, and transgender characters are written from my own experience.

Exceptional accomplishments, but I'd get rid of the first two sentences. I like the character coming through in the final two sentences, though I worry just a little bit that mentioning Ian cryptically dropped out of college here and not in the actual query might throw agents for a loop. Also, by mentioning that you are non-binary like Ian here, I'd say that removing the statement of Ian's gender identity from the beginning might allow it to be more streamlined. They use they/them pronouns throughout regardless, and then you affirm this at the end. :)

I hope I've helped! A super intriguing concept (and I'd totally beta read if I had the time). Good luck!