I'm wondering if anyone has more information than me. I'm interested in building a second road bike. I use a carbon flatbar cockpit (typically Canyon, but I could also use Specialized Roval or Syncros). These flat bar cockpits fit 1 1/8" steerer tubes. My build will be 1X with SRAM AXS components (I have most of the parts already). I'm open to different bike brands, but I'd like a frameset that has a standard 1 1/8" steerer tube. Here is what I already know about what's currently out there.

Canyon: Newer Ultimate and Aeroad uses either the proprietary cockpit OR CP0030 which is a 1 1/4" steerer tube. There aren't any carbon flatbar cockpits that fit that. I could use a separate stem and flat bar, but then my computer mount options are less slick.
Scott: 2018-2020 Addict has a 1 1/8" steerer tube but newer models don't. However, same situation as Canyon, on newer Scott framesets, I can use their stem, and add a flat handlebar to that.
Specialized: I wasn't able to get information about the steerer tube diameter for the Tarmac SL7 or SL8. I know the SL6 doesn't use the thru-axles I'd like to use, so SL6 is out. Does anyone have more info about handlebar options for the SL7 or SL8 frameset?
Winspace: I'm not opposed to a Chinese frameset, but I'm not sure if Winspace has their assembly issues ironed out (bottom bracket, seatpost wedge, etc).

My frame size appears to be XS or XXS depending on the brand. I'd like a standover of approximately 730mm, but could go up to 740mm if I had to. My Canyon Ultimate was a 748mm standover, size XS, and it fit, but was the absolute highest I could work with.

I'm open to other brands... so if anyone has information that could help me, could you please reply?

The oversized steerer used on Canyon bikes doesn't keep you from using a flat bar. The handlebar diameter isn't any different, just the stem/steerer diameter

I explained in the original post that the one piece flat bar cockpits I like to use require a 1 1/8" steerer tube. I could of course use a separate stem/handlebar combo, but then my options for a computer mount are not as sleek. You can't use this cockpit with anything other than a 1 1/8" steerer tube.

https://www.canyon.com/en-us/outlet-...12_pv_farbe=BK

With few exceptions, almost everything currently available will fit that.

Look up the specs on each bike, since there are exceptions and you're not lazy.

One and one eighth is the standard stem size across nearly every road and mountain bike stem and has been for years. Many bikes use a tapered fork, but that'll change your fork and headset choice, not your stem selection.

2025 Scott Addict is not 1 1/8", and Canyon Ultimate and Aeroad are either proprietary or 1 1/4". Specialized does not state the steerer tube diameter in the specs for their Tarmac. This is why I posted on this forum, to see if anyone had useful expertise other than saying "go look it up."

Contact Specialized and see if they can get you the specs for the steerer tubes used on those Tarmac models' fork options. They should have a customer service email or such on their website. I've done that with Trek a few times and got timely replies (2 business days max).

You have cited a couple exceptions that use larger steerers. Exceptions means there are a lot that are the traditional 1 1/8".

When I build up a frame, I focus on fit over what cockpit I am going to use. It makes more sense to me to focus on frames that have the geometry I want instead of focusing on using an integrated stem and bar, and building backwards from there.

You said you could use a separate stem and bar...well yeah that would be super simple. Needing to find a spot for an accessory on the bar seems like a no brainer solution.

But anyways, perhaps you prioritize geometry. Fit and ride feel for steering and handling seem like something that would be better to focus on.