TL;DR: I use a teleprompter, which only works if the image on the screen is flipped left to right. No remote desktop or screen mirroring app does that. Not one. So I built one: a Windows app that streams my desktop to a tablet, mirrored. A couple of days to a working version with touch, a microphone and dictation already in it, and it kept growing from there. Two bugs took real work to find: an audio cable running at two different speeds, and Windows Explorer crashing on something my own app was doing. Claude Fable 5 wrote most of the code. I directed it and tested on real hardware and real calls. I used AI to help write this post too. The problem. A teleprompter is a sheet of glass angled in front of the camera lens. You read off the reflection while looking straight down the lens, so you’re looking at the people you’re talking to and into the camera at the same time. Glass only reflects, so whatever you feed it has to be mirrored first. Otherwise every line reads backwards. Nothing mirrors a live desktop. Not TeamViewer, AnyDesk, VNC, or scrcpy. Microsoft closed a request for it saying Windows does rotation, not flipping. The professional teleprompter rigs sidestep the whole thing by selling monitors that flip the image in their own electronics. The part that took me longest to name is that I didn’t want a teleprompter app. Those solve a different problem: you paste a script in and it scrolls. I wanted a second monitor. My real desktop, whatever happens to be open on it, live and flipped, the way a monitor plugged into the wall would show it. So we built that. Once the desktop was on the tablet with low enough latency to feel real, it kept growing, because every next idea had become cheap to try: touch going back the other way, the tablet’s mic working as a PC microphone, hold a key and dictate into whatever window I’m in. Where it got hard. The audio had a click in it. We fixed four separate genuine bugs and the click stayed. So I recorded thirty seconds of it, and what I noticed in the recording was that the clicks were perfectly evenly spaced. That ruled out the connection on its own, because network trouble doesn’t arrive on a schedule. Fable took it from there into real forensics and landed on the virtual audio cable: 48kHz on one side, 44.1kHz on the other, nothing converting between them, so it was quietly dropping samples to keep up. Then Explorer started crashing, with the same signature every time. We assumed the touch input, guarded against it, and it kept crashing. So we logged everything the app sent in the five seconds before each crash. The touch was innocent. What showed up three seconds before every single crash was our own feature, killing a Windows process so our keyboard could take its place. Windows did not appreciate that. Where it is now. It’s what I actually use. The desktop lands on a tablet under the glass, mirrored. A custom keyboard raises itself when I tap into a text field. Holding a key records and types the transcript into whatever has focus, through a local Whisper model rather than a cloud API. Two fingers scroll a window, because it turns out most terminal emulators never implemented touch panning. Nineteen unit tests gate every build before it ships to my tablet or phone. Why there’s no download or public repo. The repo is private and I’m not allowed to distribute it since it bundles VB-Audio’s VB-CABLE, the driver from the click bug above. That’s donationware: free to use, pay what you think it’s worth. Free to use isn’t free to redistribute though, and bundling it needs a license I don’t have. So no download and no repo. Get the cable itself from vb-audio.com , it’s worth the donation. Photos of the rig, the mirror doing its thing, and the full write-up: https://karimmesallam.com/posts/promptcast/ submitted by /u/LiftForLife90
Originally posted by u/LiftForLife90 on r/ClaudeCode