[T-Mobile HTC One (M7)] 850csi:
Hello all,

If you're like me, you also feel that the GPE version of the HTC One is a better Nexus than the Nexus 5 - but you're on T-Mobile, and the ATT/original GPE versions are no bueno since no one has figured out a way to unlock that AWS band. I'm aware that there are a variety of GPE conversion guides out there, but I didn't find one dealing with our particular device on 1.55 hboot. Not that anything is drastically different, but I was thinking this 30,000 foot overview might help other novices out there like me who might have trouble piecing everything together. I managed to do this last night despite having very little experience with Android modding. I'm not going to do a detailed step-by-step because there are far better guides detailing what each of these steps requires. I just wanted to provide a roadmap or place to start. I give some credit to [MENTION=418428]funks[/MENTION], because his post here helped me figure out what I was doing. I relied on various other guides and of course had to get the RUU from somewhere. Thanks also to the rumrunner team of course.

***This is for informational purposes only; I take no responsibility for anything that might happen to your device. I'm only posting what worked with mine, and before attempting to do any of this you should read up on some of the basics having to do with Android flashing***

Prerequisites (I did this entirely with Windows 7)

HTC Sync installed -> Uninstalled

ADB/Fastboot

Settings: USB Debugging enabled/security lock disabled/app verification off/allow unknown sources/fast boot disabled

Windows: No antiviruses/firewall completely disabled.

Step 1 - Unlock Bootloader

I pretty much used HTC Dev for this. It was fairly straightforward. Used fastboot.

Step 2 - Install Custom Recovery

I flashed TWRP 2.6.3.3, but I recommend using 2.6.3.0 if you're going to change the MID.

Step 3 - Root

You have to do this via the 'TWRP' method in the SuperSU installer. Basically you push SuperSU to your phone and install it from TWRP. Make sure supersu is set to automatically grant root requests.

Step 4 - S-OFF*

Download rumrunner 0.5 Universal, follow their instructions, and let it go to work. If you did the above correctly, you should be S-OFF when it's done.

From this point forward, I'd recommend looking at this thread here.

Step 5 - Change MID (may not be necessary)

I have read conflicting posts over whether it's necessary to go PN07130 -> PN07120 in order to get a fully stock GPE experience. The 4.4.2 OTA appeared to include our MID in its text file, so it seems like the answer is probably no (see this post here). I did it anyways because it's easy. There are a variety of relatively low-risk ways to do this; I used Aroma to do it, but I had to flash TWRP 2.6.3.0 first because it wouldn't work in 2.6.3.3. YMMV. Part of the reason I changed my MID is I used an older RUU that didn't support PN07130 (I wanted to see my device get/apply OTAs).

Step 6 - Change CID

You'll use fastboot to do change your CID to GOOGL001

Step 7 - Flash RUU

If you'd like, you can even go pre-rooted - see the link above step 5.

...and that was it. Everything worked like a charm. I used a 4.2.2 RUU, so my phone applied 3 updates, and I'm now running 4.4.2 with no issues at all. I will update this thread if anything comes up. I'm also interested in whether the stock GPE baseband will properly utlize the UMTS AWS band in our T-Mobile phones that it typically does not have access to. I will likely flash the T-Mobile radio at some point, and will update this thread accordingly. I hope this helps someone.

I also installed the Google Experience Launcher because I think it's pretty awesome [5 home screens was always massive overkill for me].

*If you have trouble getting rumrunner to work in Windows (particularly some kind of package download issue), see [MENTION=418428]funks[/MENTION] post here. S/he had to use Linux to get it to work. I had no issues with W7.