Mobile Fixed-Shell Scroll and Focus Recovery
Growing mobile App content and constrained viewports now retain a real vertical escape path, while the frame pipeline reveals focused controls inside the nearest content scroller without moving Home, the App bar, or the Dock.
# Mobile Fixed-Shell Scroll and Focus Recovery
This release gives the public mobile fixed shell a recovery path for growing content and constrained height while preserving the fixed Home desktop composition, top App bar, and bottom Dock.
## Real scroll ownership
- The active non-Home App window now has a dormant vertical overflow fallback. It becomes a usable path only when its content truly grows, so default viewport geometry and layout dimensions remain unchanged.
- Existing internal scrollers in Knowledge, Videos, Resources, Games, Blog, About, and Chat can hand remaining movement to the active window at their boundary. Article reading keeps the detail body as its exclusive scroll owner, preventing nested scrolling from returning.
- Quick Transfer login, room entry, and room content retain their existing security flow. Only vertical chaining and focus padding change; session, encryption, and upload protocols do not.
## Focus recovery
- A mobile App `focusin` is measured through the single frame pipeline. It finds the nearest genuinely scrollable ancestor and the current visible height, then mutates only that container's `scrollTop`.
- On Home, only the account popover may use this recovery path. The normal Home composition, document, App bar, and Dock are never moved by focus recovery.
- Transfer continues to use its own focused-control recovery without creating a second native VisualViewport listener.
## Verification boundary
Controlled Headless Chrome exercises growing content, a constrained 390×500 viewport, native 2× page scale, and the established exact viewport matrix. It verifies the real scroll owner, focused-control visibility, a zero document scroll position, and unchanged default composition. This does not emulate a real iOS or Android on-screen keyboard; complete address-bar, safe-area, rotation, and keyboard avoidance remain a follow-up. No production data, release, or deployment is involved.
