[OnePlus 3T ROMs, Kernels, Recoveries, & Other Deve] mad-murdock:
Boy, what did i start here. But you should finish what you started, right? Also it might be insightful or at least entertaining to others monitoring this thread.

So, dear [MENTION=5365221]myfreexp[/MENTION], I try to go from top to bottom and try to point out your issues. Not quoting, because too much work on a phone.

- it is the same, since there is only one important command - apart from unlocking - but for the sake of discussion let's pretend it's not the same. Also the fastboot command is pretty well documented if I remember correctly.

- a basic misunderstanding you have is that the flash command might very well be unsuccessful, but the boot command works (at least it boots). The boot command only starts a recovery or kernel one time temporary. Usually used by kernel developers to test their new kernels without really flashing it. If it doesn't work, just reboot and your old, stable kernel is still there.

In this case the boot command is used as a simple way to bring you from fastboot to recovery.

That's why an output of your flash command might share some light, as I believe you might have never really flashed the recovery. Why it gets stuck on boot is another great question we might answer in the upcoming days.

- another way for getting from fastboot to recovery is holding down the volume button while rebooting (with the command). As is default for all Qualcomm and many other devices for ages.

- your quote >>>"Either I'm seeing the TWRP splash screen forever (after "fastboot boot twrp.img"), or I'm thrown back into stock recovery (after "fastboot reboot")."<<< proofs pretty much that you never flashed the recovery in the first place. I hope after explanations above you see now, why.

- my guess is, once you figure out why flashing doesn't work you also figure out why booting the image won't work.

- you wipe the device once you unlock it. It's the idea of another party being able to do with your device whatever they like but for the price of losing all already stored private data. Fits well into Google's secure-but-open philosophy. I never meant wipe via recovery.

- why not try another version? Just to see if that is booting. Can't go wrong, can it? If you did a file compare on your downloads, good, but we have no clue yet why flashing and booting doesn't work. Try the one from op and tell me if you get the same result. I promise nothing will go wrong if you just start it

- wow, you got the recovery not from this post? It was just mentioned today, go to post #550 and download the recovery from there. Let's see if I can copy and paste the md5.

Yes, I can. The md5 of your recovery, from over there or from here, should be a96a334f1a5d7a1e76158ce291e6cab2 - if it's not that might be the answer. I can and will say nothing to the other forum you downloaded it from.

- on a side note, bragging how good you are with computers while having issues with basic tasks always leaves a awkward impression.

- about driver issues, cannot help you there. Never using Windows for flashing and never would advice anyone to do so. If it works, yeah, congrats. If it doesn't, who knows, might be Windows related, might be not, get a boot stick and make sure to eliminate all possible Windows issues. Anyway, just my 2 cent. Cannot help there.

- my educated guess for your situation right now - and I might be 100% wrong - you downloaded a borked recovery from another source, flash didn't work since validity check failed, boot did work, but crashed, since invalid. Since everyone here assumed it's "our" recovery, this got never discovered.

Let's find out, I think I covered everything. And while there was some criticism inside my post, I hope you value the majority of helpful insight information. Good luck.

Update: after reading this again, yeah, probably a broken image. You never tried to flash anything else for a strange reason and always thought the flash worked. Try recovery from here and you are probably done. Easy solution, complicated way. But again, just an educated guess