PR #428 added a General Settings zoom slider after the desktop shortcut work already introduced a native-first app zoom controller. Keeping both paths would create double scaling and stale UI state, so the slider now routes through the existing controller and store state while the app shell no longer applies a second CSS zoom.
Constraint: UI zoom is device-local display state and should not be written into shared user settings.
Rejected: Keep cc-haha-ui-zoom plus AppShell style.zoom | it conflicts with shortcut zoom and multiplies visual scale.
Rejected: Persist zoom through /api/settings/user | it would sync display-specific state across machines.
Confidence: high
Scope-risk: moderate
Directive: Keep app zoom behind desktop/src/lib/appZoom.ts; do not add another storage key or DOM zoom application point without migration and shortcut sync tests.
Tested: cd desktop && bun run test -- --run src/lib/appZoom.test.ts src/hooks/useKeyboardShortcuts.test.tsx src/stores/settingsStore.test.ts src/__tests__/generalSettings.test.tsx src/lib/persistenceMigrations.test.ts src/lib/doctorRepair.test.ts
Tested: bun run check:desktop
Not-tested: Real Windows/Linux desktop runtime smoke.
The desktop shell needed predictable zoom controls across macOS,
Windows, and Linux without depending on browser defaults. This adds a
small app zoom controller that persists a bounded zoom factor, maps the
IDE-style primary-modifier shortcuts, and uses native Tauri webview zoom
when available with a browser fallback for H5/dev runs.
Constraint: Issue #407 requested IDE-style zoom shortcuts across macOS, Windows, and Linux
Rejected: Enable Tauri built-in zoom hotkeys only | it would not cover browser/H5 fallback or app-owned persistence consistently
Confidence: high
Scope-risk: narrow
Directive: Keep app zoom bounded and validated before applying persisted localStorage values
Tested: bun run verify; browser smoke on http://127.0.0.1:45679/ with Meta+= and Meta+0
Not-tested: Manual Windows/Linux desktop runtime smoke
