# Application shell

Panel toggles, floating drawers, project/right-panel tabs, the session sidebar and native application menus.

## Agent conventions

- Session rows keep actions inline until their measured title, badges, and controls no longer fit. Keep responsive action styles in `styles/components/session-row-actions.css`; hidden inline controls remain measurable but inert, and an open overflow menu stays mounted until dismissal.
- A subsession that starts working is revealed only below the session active in that instance (`revealWorkingSubsession`); other families stay collapsed. A collapsed parent's own expander chevron carries its descendants' most urgent visible state (input steady, working/compacting pulsing, idle steady green) with counted states in its label (`session-child-activity.ts`); idle follows the existing badge visibility, unseen-subagent preference and seen/fade lifecycle, and never outranks input or work. Never add a separate badge, and an expanded parent's chevron stays plain. Automatic reveals are transient: excluded from restorable expansion state until the user toggles or explicitly reveals the row, and a manual collapse dismisses the branch for subsessions running at that moment. Styles live in `styles/components/session-child-activity.css`.
- Session hierarchy geometry lives in `styles/components/session-tree.css`; connector axes follow the parent expander at every depth, including selection mode, RTL and touch layouts.
- Session search/filter mode uses flat per-session results with an optional subsession switch; filters, sorting, worktree badges and selection use each result's own identity. Normal browsing retains the session hierarchy.
- Project and right-panel tabs share `components/tab-scroll.tsx` and `styles/components/tab-scroll.css`. Keep their native scrollbar above upright content without mirrored transforms, negative border overlaps or permanent compositing hints. Validate shared scrollbar styling and adjoining edges at fractional zoom in the browser and isolated Electron renderer fixtures (`tests/browser/tab-chrome.test.ts`).
- Built-in right-panel tabs are constructed directly in `right-panel/core-runtime.tsx` (never add a first-party plugin loader for them); external sandboxed panels keep their independent consent/loading path.
- Embedded floating session drawers use `instance/shell/HostedDrawer.tsx` so their SUID modal roots are direct children of the existing geometry host. A Solid Portal wrapper must not become an ARIA-hidden ancestor of visible controls. Preserve SUID's modal stacking, sibling isolation, focus policy, Escape/backdrop handling and scroll restoration; validate with `tests/browser/drawer-accessibility.test.ts` rather than overriding ARIA or disabling modal enforcement.
- Floating-panel outside-pointer dismissal must leave ARIA menus, listboxes and dialogs to their own selection/dismissal handlers: their portals are outside the drawer DOM, and closing the drawer on pointerdown destroys a menu before touch pointerup selects its action. Keep this guard shared in the shell, not in individual menu actions; validate the real session Delete confirmation with `tests/browser/session-delete.test.ts`.
- Each side panel has exactly one open/close control: `instance/shell/ShellPanelToggle.tsx` (`PanelLeft`/`PanelRight`, `.icon-toggle` with `aria-expanded`/`aria-controls`), absolutely placed at the shell's outer header corners (`--space-xs` from the window edge) in `.session-shell-frame`, outside the drawer host so modal sibling isolation never hides it, and above floating drawers. The frame is an isolated stacking context: toggles stay above in-frame drawers but below body-portaled dialogs, scrims and utility windows. Both toggles precede the shell content in tab order and use the fixed View-menu labels (`window.menu.leftPanel`/`rightPanel`) with `aria-expanded`, never an Open/Close label flip. They are strictly fixed: no horizontal or vertical movement between docked, floating and closed states in any layout; the sidebar header, right-panel tab bar (both edges when floating) and the conversation header (`data-{left,right}-toggle-reserve`) reserve their footprint instead. Every header's action row (session list header row, right-panel `.tab-strip-shortcuts`, conversation side groups and status indicators, with or without the title row) and the toggles centre on one shared line, `--panel-header-action-center` in `styles/tokens.css`; never measure per-state offsets. The session list header holds a single action row; never add a keyboard-shortcut footer below the session list. Opening one floating drawer closes the other; the outside-pointer handler ignores the toggles. Styles live in `styles/panels/shell-panel-toggles.css`; validate with `tests/browser/shell-navigation.test.ts`.
- The session sidebar header ends with Back/Forward (`ArrowLeft`/`ArrowRight`, mirrored in RTL; history wording "Back"/"Forward" with conversation tooltips, distinct from the palette's Previous/Next Session list cycling) over a browser-like in-memory history per project tab and window (`stores/session-navigation-history.ts`, `instance/shell/useSessionNavigationHistory.ts`, at most 50 entries). It records every displayed conversation whatever selected it; Info and the no-session draft are not entries (Back first returns to the cursor entry). Navigating moves the cursor and selects through the ordinary `handleSessionSelect` path without pushing; a new selection truncates the forward stack; unavailable/deleted sessions are skipped and determine the disabled states. Do not add keyboard shortcuts or persistence to this history.
- Native Electron/Tauri application menus follow the UI locale: renderers translate `NATIVE_MENU_LABEL_KEYS` (`lib/native/menu-labels.ts`) and send them with the View menu state. Hosts keep English until a renderer reports labels, keep the last locale for windows without one, and escape `&` outside macOS. Electron takes its defaults from `lib/native/menu-labels-en.ts`; Tauri's `menu_labels.rs` defaults are checked against the English messages by `menu-labels.test.ts`. Tauri retitles retained items in place; Electron rebuilds its menu on a label change. About CodeNomad runs the `open-about` command (Settings → Info), falling back to a native panel only when no application window can receive it.