Native OpenXR on Horizon OS

A Quest app written in C or C++ talks to the headset through OpenXR and to the phone-class OS underneath through Android. Most of what breaks sits in that seam: a manifest that is legal for sideloading and illegal for the Store, a loader version that crashes instead of degrading, a frame loop that stops drawing the moment focus is lost.

Read references/project-playbook.md for project discovery, target/version contracts, engine handoff, a vertical slice and an audit. Read references/mixed-reality.md for feature/permission decisions, tracking/room lifecycle, colocation and camera or AI input.

For a whole-product roadmap or stage audit, use quest-lifecycle; a single technical task stays with this owner. If absent, identify the current stage, its evidence and the next prerequisite inline.

Step 0 — is this project even on this lane?