Dev Builds PrivacyStage, a Mac Virtual Camera That Hides Apps Mid-Screen-Share, Using Claude Code
Reasonable-Bass9893 · reddit · 2026-10-10
A developer used Claude Code over 6 months to build PrivacyStage, a Mac menu-bar app that replaces screen sharing with a virtual camera, letting you hide or show individual apps mid-call—filtering happens in macOS's compositor via ScreenCaptureKit, so hidden apps never enter the captured frames.
Key technical lessons:
- Getting frames into the sandboxed CMIO camera extension: shared files, App Groups and POSIX shared memory all failed; the working approach passes global IOSurface IDs via Darwin notifications.
- The blank-camera-in-Google-Meet bug: log show revealed Safari's GPU process rejecting every frame (FigSampleBufferSerialization err=-19646) and restarting the camera every 30s—caused by extra metadata on the video format. Claude also caught a zsh log alias shadowing /usr/bin/log.
- Full-screen leaks: hiding by window ID broke under native full-screen (new window created); switching to per-app exclusion fixed it.
Limitations: 1080p30, per-app (not per-window) hiding, video only. 7-day trial, then a one-time $6.99.
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