# Desktop Design System

Conventions for the Electron desktop app (`apps/desktop`). Read this before
adding a component, overlay, or style. The rule of thumb: **one source per
concern, tokens over literals, flat over boxed.** If you reach for a raw color,
a one-off shadow, a bespoke button, or a hardcoded `px-*` on a control — stop,
there's already a primitive for it.

This file owns the visual and interaction contract. Read
[`AGENTS.md`](./AGENTS.md) for architecture, state, resolver, transport, and
testing rules.

This doc contains two kinds of content, maintained differently:

- **Principles** (flatness, intent, feedback, motion, cancellation) are durable.
  They hold as components come and go.
- **Named contracts** (tokens, `Button` variants, primitive names) are the
  design system's current API. They are maintained *with* the code: if you
  change a primitive, token, or variant, update its entry here **in the same
  change** — a stale name in this file is a bug, exactly like a stale type.

When a rule and the code disagree, fix whichever is wrong rather than forking a
one-off at the call site.

## Principles

1. **Flat, not boxed.** No card-in-card, no divider borders inside a panel.
   Group with whitespace and a single hairline, never nested rounded boxes.
2. **Borderless elevation for floating panels.** Overlays float on
   `shadow-nous` + a `--stroke-nous` hairline, not thick framed boxes. In-panel
   structure may use token hairlines sparingly.
3. **One primitive per concern.** One `Button`, one set of control variants,
   one `SearchField`, one `Loader`, one `ErrorState`. Migrate onto them; don't
   fork.
4. **Tokens, not literals.** Reference CSS vars (`--ui-*`, `--shadow-nous`,
   `--theme-*`), never raw hex / ad-hoc rgba in components.
5. **Style lives in the primitive.** Variants and sizes own padding, radius,
   color, chrome. Call sites pass a `variant`/`size`, not `className` overrides
   that re-specify those.
6. **Intent before automation.** Surface useful actions and previews, but do not
   open panes, move focus, or navigate because a tool happened to produce
   something.
7. **Immediate feedback.** Direct manipulation updates the view first. Network
   or disk persistence reconciles afterward and rolls back visibly on failure.

## Information architecture

- **Chat is the home surface.** The transcript and composer stay primary; tools,
  previews, files, review, and terminal complement the conversation.
- **Pages are durable destinations.** Chat, Skills, Messaging, and Artifacts
  remain in shell chrome. Do not hide a distinct product noun inside an
  unrelated page.
- **Route overlays are short tasks.** Settings, Command Center, Cron, Profiles,
  Agents, and Starmap render as `OverlayView` cards and return to the previous
  route on close. Model/session pickers and dialogs layer above the current
  surface; they are not navigation stacks.
- **Panes are working context.** Preview, files, review, and terminal remain
  attached to the current task. Their state survives temporary hiding and chat
  switches where the underlying tool is meant to persist.
- **One action, one home.** A command may have keyboard, palette, and visible
  affordances, but they invoke the same action and state. Do not fork behavior
  per entry point.
- **Projects own workspace cwd.** Use Sidebar → Projects for local folders and
  worktrees; do not reintroduce a per-session/right-sidebar folder-picker flow.

Navigation must preserve context. A background session finishing, a tool result
arriving, or a project refresh may update badges and cached data; it must not
replace the foreground transcript or steal focus.

## Surfaces & elevation

Floating panels (base `Dialog`, route overlays, boot/install/update surfaces,
model-picker, onboarding, prompt overlays, notifications) use:

```
shadow-nous           /* downward-weighted, layered contact→ambient falloff */
border-(--stroke-nous) /* currentColor hairline, theme-adaptive */
```

Both are CSS vars in `src/styles.css` — tune in one place, everything inherits.
Don't add per-overlay `shadow-[…]` or `border-(--ui-stroke-secondary)`
one-offs; if elevation needs to change, change the token.

Menus and popovers use their own shared `shadow-md` +
`--ui-stroke-secondary` primitive treatment. Drag affordances may use tokenized
dashed targets and local blur. These are semantic surface classes, not licenses
for call-site shadow or border inventions.

## Stroke & color tokens

| Token | Use |
| --- | --- |
| `--ui-stroke-primary…quaternary` | hairlines, in descending strength |
| `--ui-stroke-tertiary` | the default in-panel divider / list hairline |
| `--stroke-nous` | the overlay hairline (pairs with `shadow-nous`) |
| `--ui-text-primary / -secondary / -tertiary` | text hierarchy |
| `--ui-bg-quaternary` | soft control fill (secondary button) |
| `--chrome-action-hover` | hover fill for quiet controls |
| `--theme-primary`, `--ui-accent` | brand/accent |

Never hardcode `border-gray-*`, `bg-white`, `text-black`, etc. The white tile in
`BrandMark` is the one sanctioned literal (the mark needs a fixed backdrop).

## Buttons — one component

`src/components/ui/button.tsx` is the single source. Pick a `variant` + `size`;
do **not** pass `h-*`, `px-*`, `py-*`, or icon-size overrides.

**Variants:** `default` (primary), `destructive`, `secondary` (soft fill —
the default non-primary look), `outline` (transparent + 1px inset ring, no
fill/shadow), `ghost`, `link`, `text` (boxless quiet inline — "Cancel",
"Clear"), `textStrong` (bold underlined inline affordance — "Change",
"Open logs").

**Sizes:** `default`, `xs`, `sm`, `lg`, `inline` (flush, zero box — for buttons
that sit inside a heading/sentence; replaces `h-auto px-0 py-0`), `micro`
(status-stack/table-footers), and the icon family `icon` / `icon-xs` /
`icon-sm` / `icon-lg` / `icon-titlebar`.

Notes:
- Text buttons are square (no radius) and sized by padding + line-height (no
  fixed heights). Only icon buttons carry the shared 4px radius.
- SVGs inherit `size-3.5` (`size-3` at `xs`). Don't re-set icon size.
- Polymorph with `asChild` when the button must render as a link/Slot.

## Form controls

- **`controlVariants`** (`src/components/ui/control.ts`) is the shared shape for
  `Input` / `Textarea` / `SelectTrigger`. New text-entry controls compose it.
- **`SearchField`** — borderless, underline-on-focus, auto-width. The only
  search input. Don't build boxed search bars; don't wrap it in a bordered tile.
  Empty lists hide their search field.
- **`SegmentedControl`** — the choice control for small mutually-exclusive sets
  (color mode, tool-call display, usage period). Replaces radio piles and
  pill rows.
- **`Switch`** (`size="xs"`) — bare, with `aria-label`. No bordered text wrapper.

## Layout

- **Gutters:** `PAGE_INSET_X` (`src/app/layout-constants.ts`) for page side
  padding; `PAGE_INSET_NEG_X` to bleed a child to the edge. Don't hardcode
  `px-6`/`px-8` on pages.
- **Master/detail overlays:** `OverlaySplitLayout` + `OverlaySidebar` /
  `OverlayMain`. Cron, profiles, etc. ride this — don't rebuild a titlebar
  shell.
- **Rows:** `ListRow` (settings `primitives.tsx`) for label/description/action
  rows. Flat, flush-left; no per-row indentation that fights flush headers.
- **No dividers between rows** unless the list genuinely needs them; prefer
  spacing. When you do need one, it's a single `--ui-stroke-tertiary` hairline.

## Feedback & empty/error/loading states

- **Loading:** `Loader` (`src/components/ui/loader.tsx`) — animated math/ascii
  curves (`lemniscate-bloom` for long ops). Never ship the literal text
  "Loading…".
- **Errors:** `ErrorState` + the canonical `ErrorIcon` (no bg chip). One look
  for the React boundary, in-dialog errors, and the boot-failure banner. Pass
  nodes for title/description so Radix `DialogTitle`/`Description` can flow
  through for a11y.
- **Logs:** `LogView` — no bg, hairline border, tight padding, small mono.
  Every place we surface raw logs uses it.
- **Empty:** `EmptyState` for plain page bodies; `PanelEmpty` for overlay
  master/detail empties with an icon and action. Don't hand-roll a third
  centered empty.

## Chat, tools & boot surfaces

- The transcript and composer are built on `@assistant-ui/react`. Extend the
  existing components under `src/components/assistant-ui` and
  `src/app/chat/composer`; do not fork a second markdown, message, tool-call, or
  approval renderer for one feature.
- A tool result may expose an inline action that opens a preview. It must not
  open the rail automatically.
- Install, onboarding, connecting, boot failure, and reauthentication are
  distinct states with shared visual primitives. Preserve their recovery
  semantics when unifying appearance.
- Respect `AppShell` overlay ownership. Persistent terminal/content layers,
  route overlays, dialogs, and boot surfaces must not compete through ad-hoc
  z-index literals.

## Iconography & brand

- **Tabler** is the default component/chrome set. Import its curated aliases and
  `iconSize` scale from `src/lib/icons.ts`; do not import icon packages directly
  in feature code.
- **`Codicon`** is the compact editor/tool/status vocabulary. Use
  `src/components/ui/codicon.tsx`, including `codiconIcon()` where a
  Tabler-shaped component is required.
- Pick the vocabulary by semantic context and reuse the existing icon for an
  action. Do not introduce a third icon set or mix styles within one control
  group.
- **`BrandMark`** (`src/components/brand-mark.tsx`) is the brand glyph — the
  `nous-girl` mark on a white tile, softly rounded, identical in light/dark.
  It replaced scattered Sparkles glyphs in updates / onboarding / about. Use it
  for hero/brand moments; don't reintroduce decorative star/sparkle icons.

## Motion

- Quick, functional transitions (~100ms on controls). Respect
  `prefers-reduced-motion` for anything beyond a fade.
- Choreographed exits (e.g. onboarding's "matrix" fade-down) stagger per-element
  then settle the surface — the outer container's fade is *delayed* so it
  doesn't swallow the inner animation. Don't let a global fade race the detail.
- Motion follows state; it never delays state. Selection, drag targets, cancel,
  and pressed feedback paint in the current frame.
- Do not animate layout geometry with `transition-all` on a hot interaction.
  Name the properties, avoid backdrop-filter repaints during movement, and
  remove animation before masking a performance problem.

## Direct manipulation & performance

The app should feel instant under real load — long transcripts, several panes,
live streams. Design toward that:

- Direct manipulation paints first; persistence reconciles after and rolls back
  visibly on failure.
- Keep interaction feedback cheap: hot-path state stays local or narrowly
  derived, not wired into heavy trees; pointer work coalesces per frame.
- One drop region has one visual owner, and drop targets speak one affordance
  language across files, sessions, tabs, and panes. Overlapping targets resolve
  to the active one instead of stacking overlays.
- Forgiving geometry beats pixel-perfect triggers; edge actions live near their
  edge, not clustered in the center.
- Expensive stateful surfaces stay mounted when hidden. Visibility is not
  lifecycle.

Prove speed with realistic content. A fast empty-state demo says nothing about a
long transcript or a busy terminal.

## Keyboard & cancellation

- Keyboard ownership follows focus. The focused surface wins its keys; shell
  shortcuts must not steal a terminal's or editor's bindings.
- Register global shortcuts through the shared layer, not ad-hoc listeners.
- One cancel gesture does one thing: cancel the active interaction, or close the
  topmost dismissable surface — never both, never the control underneath.
- Cancellation is synchronous in the UI even if cleanup is async: overlays,
  cursors, and pending gesture state clear at once.
- Flows that deliberately cannot be dismissed (install/onboarding, destructive
  confirmation) must make that explicit.

## i18n

- Every user-facing string goes through `useI18n()` (`src/i18n/context.tsx`).
  No literals in JSX.
- **Update all locales together** — `en`, `ja`, `zh`, `zh-hant`. A string change
  in `en.ts` that skips the others is a regression (drifted punctuation,
  stale labels). Keep trailing-punctuation and tone consistent across all four.

## State (TypeScript)

The detailed state contract lives in the scoped
[`AGENTS.md`](./AGENTS.md). Visual code follows these essentials:

- Shared/cross-component state → small **nanostores**, not prop-drilling.
  Each feature owns its atoms; shared atoms live in `src/store`.
- Rendering components subscribe with `useStore`; non-render actions read with
  `$atom.get()`.
- Subscribe to derived coarse facts instead of high-frequency source atoms when
  the component does not render the full value.
- Colocated action modules over god hooks. A hook owns one narrow job.
- Keep persistence beside the atom that owns it. Route roots stay thin.
- Prefer `interface` for public props; extend React primitives
  (`React.ComponentProps<'button'>`, `Omit<…>`).

## Affordances

- `cursor-pointer` at the primitive level (Button, dropdown/select) — don't
  hardcode it per call site.
- Global focus-ring reset; titlebar actions have no active-background state.
- `Esc` closes every dismissable overlay/dialog (install/onboarding excluded);
  close is an x-icon, not the word "Close".

## Before you add something — checklist

- [ ] Reuse a primitive (`Button`, `SearchField`, `SegmentedControl`,
      `ListRow`, `Loader`, `ErrorState`, `LogView`) instead of forking one?
- [ ] Tokens (`--ui-*`, `shadow-nous`, `--stroke-nous`) — zero raw colors /
      one-off shadows?
- [ ] No `className` overriding a primitive's padding / size / radius / chrome?
- [ ] Overlay uses `shadow-nous` + `border-(--stroke-nous)`, no hard border?
- [ ] Flat — no card-in-card, no gratuitous row dividers?
- [ ] No automatic navigation, focus steal, or pane opening from background
      events?
- [ ] Direct manipulation paints immediately and rolls back cleanly on failure?
- [ ] Hot interactions avoid broad subscriptions, layout thrash, and
      `transition-all`?
- [ ] Keyboard ownership and single-action `Esc` behavior are correct?
- [ ] All four locales updated for any new/changed string?
- [ ] `cursor-pointer`, focus ring, and `Esc`-to-close behave?
- [ ] Touched a primitive, token, or variant? Its named-contract entry in this
      file is updated in the same change.
