# 2026-07-20 — Desktop mascot ("Cluck")

**Status:** Planned

## Why

The web control room is an OS-style desktop shell (icons, floating
windows, taskbar) but has no ambient, always-visible signal of what the
system is doing — you have to open a window to see a chat streaming, a
knowledge-graph write, or a critical signal land. The user asked for a
pixel-art chicken mascot that roams the desktop, is draggable and
interactable (Sims-style radial right-click menu with nested actions), and
is itself a tamagotchi (egg → chick → adult, nameable, persistent) that
visibly reacts to real app activity. This plan is scaffolding: every piece
(sprites, autonomous behaviors, menu actions, environment reactions) is a
data-driven registry so each can be extended independently later without
touching the engine code.

The MBSE subsystem model for this feature (Mission, Requirements,
Structural/Behavioral/Interfaces views, Verification) lives at
[docs/mascot/README.md](../docs/mascot/README.md) — read it first for the
full rationale and diagrams; this document is the concrete file-by-file
implementation plan derived from it.

**Design decisions already made with the user:**
- Renders **above windows** (desktop-pet style) — mascot layer `z-45`,
  radial menu `z-[60]` (must beat the desktop's own right-click menu,
  which is `z-50`).
- Art is **code-drawn pixel art** — string pixel-grids + a palette map in
  TypeScript, rendered to a small canvas, no binary sprite assets.
- Movement is **gravity + ground** — walks along the desktop surface's
  bottom edge (= the taskbar's top edge), flutter-falls when dropped
  mid-air.

## Verified codebase facts this plan builds on

- `web/src/lib/components/desktop-shell/Desktop.svelte` — the surface div
  (`relative min-h-0 flex-1 overflow-hidden`) hosts layered children: icon
  layer `z-0`, `TaskLauncher` wrapper `z-10`, `WindowLayer` `z-40` — every
  wrapper is `pointer-events-none` with interactive children re-enabling
  `pointer-events-auto`. The desktop's own right-click menu is `fixed
  z-50`, dismissed via `<svelte:window onclick={closeMenu}>` + Escape.
  Bare-surface clicks are gated with `e.currentTarget === e.target`.
- Drag pattern to copy: `desktop-shell/DesktopIcon.svelte` —
  `pointerdown` + `el.setPointerCapture(e.pointerId)`, a 5px movement
  threshold distinguishes a click from a drag, move/up listeners attached
  to the element itself (not `window`), position blended via `$derived`
  between rest and drag-in-progress values.
- Game loop convention: `GraphBackground.svelte` drives its canvas with
  `setTimeout(() => draw(performance.now()), 33)` (~30fps), **not**
  `requestAnimationFrame` — the code comment there explains some embedding
  contexts report `document.hidden=true` and suspend rAF, which would
  freeze the animation; `setTimeout` keeps ticking. Follow this for the
  mascot loop, and clamp `dt` to 100ms so a throttled/backgrounded tab
  doesn't produce a physics-breaking huge step on resume.
- Persistence convention: hyphenated `oikos-*` localStorage keys
  (`oikos-desktop-icons`, `oikos-theme`, `oikos-windows`). Window layout
  uses wmkit's `persist(wm, { key: 'oikos-windows', debounce: 300,
  autoRestore: true })` — mirror the 300ms debounce for `oikos-mascot`;
  never write on every animation frame, only on discrete state
  transitions (behavior change, drag end, stage change, rename).
- Runes idiom for cross-component client state: a `.svelte.ts` module with
  module-level `$state` plus exported getter/mutator functions —
  `web/src/lib/stores/theme.svelte.ts` is the canonical example
  (`let current: Theme = $state(initialTheme)`, `getTheme()`,
  `setTheme()`, `toggleTheme()`).
- Awareness sources, all plain Svelte stores already in the codebase:
  - `web/src/lib/stores/events.ts` — `liveEvents: Writable<OikosEvent[]>`
    (newest-first, capped at 200), fed by a ref-counted SSE subscription
    `subscribeEvents()`. `OikosEvent.type` families: `approval.*`,
    `signal.*`, `execution.*`, `health.changed`; `severity: 'info' |
    'warning' | 'critical'`.
  - `web/src/lib/stores/chat.ts` — `streaming: Writable<boolean>`.
  - `web/src/lib/stores/activity.ts` — `activityLog` is a **derived**
    store recomputed wholesale from `messages`/`planSteps`/`currentTask`
    on every emission, **not an append-only log** — detecting a "new"
    entry (e.g. `type === 'knowledge'`) requires diffing entry `id`s
    against the previous emission, not just reacting to the store firing.
  - `web/src/lib/stores/context.ts` — `summary: Writable<DashboardSummary
    | null>`, `openSignalCount(summary)`.
- No `@keyframes`, no `requestAnimationFrame`, no sprite/pixel-art code
  exists anywhere in the repo today — this is greenfield within the
  established canvas-loop convention above.

## File layout

All new, under `web/src/lib/mascot/`:

```
types.ts            PixelGrid, AnimName, MascotStage, BehaviorId, Stimulus, RadialAction
palette.ts           Record<char, cssColor>; '.' = transparent
sprites.ts            SPRITES: Record<MascotStage, Partial<Record<AnimName, AnimDef>>> + resolveAnim() fallback
render.ts             drawFrame(ctx, grid, palette, flip) — stateless canvas painter
state.svelte.ts       Tamagotchi model: module $state + mutators, debounced persist, versioned schema
behavior.ts           FSM: BEHAVIORS registry + stepMascot(rt, model, now, dt)
stimuli.ts            Stimulus bus: REACTIONS registry + attachStimuli(emit), ref-counted
actions.ts            MASCOT_ACTIONS radial tree + registerMascotAction()
Mascot.svelte         canvas sprite, 30fps loop, pointer drag/click/contextmenu
MascotLayer.svelte    pointer-events-none absolute inset-0 z-45 overlay; hosts Mascot + RadialMenu + bubble
RadialMenu.svelte     round nested menu, fixed z-[60]
NameDialog.svelte     naming prompt (hatch + rename)
```

**Integration — 2 lines in `Desktop.svelte`:** import `MascotLayer` and
render `<MascotLayer />` inside the surface `<div>`, after `<WindowLayer
/>`, so its `absolute inset-0` shares the surface's coordinate space and
its ground line lands exactly at the surface's bottom edge (the taskbar's
top edge).

## Sprite system (`types.ts`, `palette.ts`, `sprites.ts`, `render.ts`)

Frames are human-editable string pixel-grids indexing a palette, e.g.:

```ts
export type PixelGrid = string[]   // rows of same-length strings, one char per pixel
export interface AnimDef { frames: PixelGrid[]; fps: number; loop: boolean }
export type AnimName =
  | 'egg-idle' | 'egg-wiggle' | 'egg-crack' | 'hatch'
  | 'idle' | 'blink' | 'walk' | 'peck' | 'flap' | 'sleep'
  | 'dragged' | 'fall-flutter' | 'land'
  | 'react-eureka' | 'react-alarm' | 'react-think' | 'react-happy'
```

- Grids: egg 12×12, chick 14×14, adult 16×16, all bottom-anchored inside a
  fixed 20×20 logical canvas so feet land on the ground line consistently
  across stages.
- `SPRITES: Record<MascotStage, Partial<Record<AnimName, AnimDef>>>` is
  the registry; `resolveAnim(stage, name)` falls back to that stage's
  `idle` and finally a 1-frame placeholder, so a missing animation never
  crashes the renderer.
- Canvas is sized to the logical grid; screen scale is pure CSS (`width:
  20*SCALE px; image-rendering: pixelated`), `ctx.imageSmoothingEnabled =
  false` set once. Horizontal facing flip via `ctx.translate(w,0);
  ctx.scale(-1,1)` — no mirrored frame data needed.
- Initial animation set (2–4 frames each): egg-idle/egg-wiggle/egg-crack/
  hatch; idle/blink/walk/peck/flap/sleep; dragged/fall-flutter/land;
  react-think/react-eureka/react-alarm/react-happy.
- Frame index = `floor((now - animStart) / 1000 * fps)`, wrapped if
  `loop`.

## Behavior engine (`behavior.ts`)

```ts
export interface MascotRuntime {
  x: number; y: number            // sprite bottom-center, surface coords
  vx: number; vy: number
  facing: 1 | -1
  behavior: BehaviorId            // 'egg' | 'idle' | 'wander' | 'peck' | 'sleep' | 'dragged' | 'falling' | 'react'
  behaviorUntil: number
  anim: AnimName
  animStart: number
  reactAnim: AnimName | null
  bounds: { w: number; h: number }
}

export interface BehaviorDef {
  id: BehaviorId
  anim: (rt: MascotRuntime, model: MascotModel) => AnimName
  enter?: (rt: MascotRuntime) => void
  tick: (rt: MascotRuntime, dt: number, now: number) => void
  next: (rt: MascotRuntime, now: number) => BehaviorId | null
  weight?: number         // idle-selectable when > 0; undefined/0 = not auto-picked
  minMs: number; maxMs: number
}
export const BEHAVIORS: Record<BehaviorId, BehaviorDef>
export function stepMascot(rt: MascotRuntime, model: MascotModel, now: number, dt: number): void
export function forceBehavior(rt: MascotRuntime, id: BehaviorId, opts?: { anim?: AnimName; durationMs?: number }): void
```

- **Ground/gravity**: `GROUND_Y = bounds.h`. When above ground and not
  dragged, behavior is `falling`: `vy += GRAVITY * dt`, capped at a slow
  flutter terminal velocity, anim `fall-flutter` with occasional `flap`;
  on reaching ground, snap `y`, brief `land`, then `idle`.
- **Wander**: constant `vx = facing * ~40px/s`, flip `facing` at the
  surface margins.
- **Idle selection**: when `now > behaviorUntil` and the current
  behavior's `next()` returns null, roll a weighted random pick over
  `BEHAVIORS` entries that declare `weight` — starting weights: idle 3,
  wander 4, peck 2, sleep 1.
- **Non-self-selecting behaviors** (`dragged`, `falling`, `react`) have no
  `weight` and are entered only via `forceBehavior()` — pointer code calls
  it for `dragged`, gravity logic for `falling`, the stimulus bus for
  `react`.
- **Egg stage**: `behavior` locked to `'egg'` (periodic `egg-wiggle`,
  `egg-crack` as `hatchProgress` nears 1); dragging is still allowed (the
  egg can be picked up and moved).
- Loop lives in `Mascot.svelte`: `setTimeout(() => tick(performance.now()),
  33)` inside an `$effect`, cleared on teardown, `dt` clamped to 100ms.

## Tamagotchi model (`state.svelte.ts`)

```ts
export type MascotStage = 'egg' | 'chick' | 'adult'
export interface MascotModel {
  version: 1
  stage: MascotStage
  name: string | null
  hatchProgress: number       // 0..1, egg stage only
  happiness: number           // 0..100, slow decay, boosted by pet/feed
  xp: number                  // chick -> adult growth hook
  hatchedAt: number | null
  lastPos: { x: number } | null
  lastSeen: number            // for capped offline egg-incubation progress
}
export const HATCH_MS = 3 * 60_000   // active time to hatch (demo-friendly)
export const ADULT_XP = 200
export function grantXp(n: number): void
export function feed(): void
export function pet(): void
export function setName(name: string): void
export function tickLifecycle(dt: number): void   // called ~1x/sec, not per frame
export function advanceStageIfReady(): void
```

- `load()` parses `localStorage['oikos-mascot']`, checks `version`, falls
  back to `defaultModel()` on mismatch/corruption. `migrate(raw):
  MascotModel` is a stub switch on `version` for future schema changes —
  v1 has no migrations to perform, the stub just documents where they go.
- Every mutator calls a shared `schedulePersist()` — a 300ms trailing
  debounce, plus a `beforeunload` flush so a quick reload doesn't lose a
  rename. `lastPos.x` is written only on behavior transitions and
  drag-end, never per frame.
- Multi-tab races (two tabs both writing `oikos-mascot`) are
  last-writer-wins — accepted for this scaffolding, not solved; a future
  pass could listen to the `storage` event if it becomes a real problem.

## Radial menu (`actions.ts`, `RadialMenu.svelte`)

```ts
export interface RadialAction {
  id: string
  label: string
  icon?: Component                          // lucide, same convention as the desktop menu
  visible?: (model: MascotModel) => boolean // e.g. Rename only once hatched
  children?: RadialAction[]
  action?: (ctx: MascotActionCtx) => void   // leaf only
}
export const MASCOT_ACTIONS: RadialAction[]
export function registerMascotAction(a: RadialAction, parentId?: string): void
```

v1 tree: **Interact** [Pet, Feed → [Seeds, Worm]], **Care** [Sleep, Wake],
**Identity** [Rename], **Debug** [Force hatch/stage, Reset].

- Rendered by `MascotLayer.svelte` as `fixed`, positioned at the
  chicken's screen center, **`z-[60]`** (must beat the desktop context
  menu's `z-50`, comfortably above `WindowLayer`'s `z-40`).
- Layout: items on a circle (radius ≈ 70px) via polar `transform`s around
  the menu's anchor point. Open animation: buttons start scale-0 at
  center and transition to their polar position with `transform 120ms
  cubic-bezier(.2,1.4,.4,1)`, staggered ~20ms per item — pure CSS, no
  keyframes, reads as snappy/springy per the "snappy" requirement.
- **Nesting**: selecting a node with `children` swaps the ring's contents
  to those children plus a center "back" button; track the breadcrumb as
  a local `$state<RadialAction[][]>` stack.
- Dismissal mirrors the desktop menu's existing pattern:
  `<svelte:window onclick={close}>`, Escape pops one level then closes on
  the next press; the menu's own clicks `stopPropagation()`. Clamp the
  ring's screen position so it never renders off-viewport (relevant near
  screen edges/corners).
- Opened from `Mascot.svelte`'s `oncontextmenu`:
  `e.preventDefault(); e.stopPropagation();` then tell `MascotLayer` to
  open at the sprite's center (the surface's own `onSurfaceContextMenu`
  already gates on `currentTarget === target`, so this is defensive, not
  strictly required — but keep it for clarity).

## Stimulus / reaction system (`stimuli.ts`)

```ts
export interface ReactionDef {
  id: string
  anim: AnimName
  priority: number
  cooldownMs: number
  durationMs: number
  interruptsSleep?: boolean
  effect?: () => void          // e.g. grantXp(5) on eureka
}
export const REACTIONS: Record<string, ReactionDef>
export function attachStimuli(emit: (r: ReactionDef) => void): () => void   // ref-counted, owns subscribeEvents()
```

Initial wiring:

| Source | Trigger | Reaction |
|---|---|---|
| `chat.ts` `streaming` | `false → true` edge, held while `true` | `thinking` (`react-think`, priority 1) |
| `activity.ts` `activityLog` | new entry with `type === 'knowledge'`, detected by diffing entry ids against the last-seen set (see note above — the store is recomputed wholesale) | `eureka` (`react-eureka`, priority 2, cooldown 10s, `effect: grantXp(5)`) |
| `events.ts` `liveEvents` | new head event (`id > lastSeen`) with `severity === 'critical'` or `type` starting `signal.` | `alarmed` (`react-alarm`, priority 3, cooldown 15s, `interruptsSleep: true`) |
| `events.ts` `liveEvents` | new head event, `type` starting `execution.`, success-ish | `happy` (`react-happy`, priority 1, cooldown 20s) |

- `attachStimuli` calls `subscribeEvents()` itself and folds its
  unsubscribe into the returned teardown, so the mascot keeps the SSE
  stream open (ref-counted alongside any page that also subscribes) only
  while mounted.
- On first emission of `liveEvents`, just record the head event id — do
  not replay history as reactions on mount.
- Dispatch: `emit(reaction)` checks the cooldown map and
  `priority >= currentReactPriority` (or current behavior isn't
  `dragged`), then calls `forceBehavior(rt, 'react', { anim,
  durationMs })`. `dragged` always wins over any reaction; `sleep` is
  broken only when `interruptsSleep` is true.

## Implementation order (sized for one PR each)

1. `types.ts`, `palette.ts`, `sprites.ts` (egg + chick idle/walk only),
   `render.ts` — pure data/functions, no UI yet.
2. `state.svelte.ts` model + debounced persistence — verify by hand via
   devtools console before wiring any UI.
3. `behavior.ts` FSM (egg/idle/wander/falling/dragged) + `Mascot.svelte` +
   `MascotLayer.svelte`, insert into `Desktop.svelte`. **First visible
   milestone** — an egg sits on the ground and can be dragged.
4. Hatch flow: `tickLifecycle` wired into the loop, egg→chick transition +
   `NameDialog.svelte`, remaining animations, `peck`/`sleep` behaviors.
5. `actions.ts` + `RadialMenu.svelte` (nested rings, open animation,
   dismissal).
6. `stimuli.ts` + the four reaction animations + the wiring table above.
7. Adult stage sprites + XP threshold; polish (speech/name bubble, a
   squash frame on `land`).
8. A short "how to add an animation / behavior / action / reaction" doc
   comment at the top of `sprites.ts`, `behavior.ts`, `actions.ts`, and
   `stimuli.ts` respectively (this plan's registry tables above become
   those comments, condensed).

## Verification checklist

Run `npm run dev` in `web/`, then in the browser:

- Egg renders on the ground at the surface bottom, wiggles occasionally,
  and is at the same `x` after a reload (`oikos-mascot` in localStorage —
  confirm it is *not* being written on every frame while merely idling or
  walking, only on discrete transitions).
- Dragging the egg up and releasing triggers a flutter-fall back down with
  no tunneling below the taskbar; dragging past the surface's left/right
  edges clamps rather than escaping the viewport.
- The debug "force hatch" action transitions egg → chick, opens the name
  dialog, and the chosen name persists across a reload.
- The chick wanders and flips its sprite at the surface edges, pecks, and
  sleeps on its own; a plain click (below the 5px drag threshold) triggers
  a pet/hop reaction and grants a little xp.
- Right-clicking the chicken opens the radial menu centered on it — and
  right-clicking bare desktop elsewhere still opens the *original* desktop
  menu, unaffected. The nested Feed submenu opens; Escape pops one level
  then closes on the next press; clicking outside the menu closes it;
  the menu stays fully on-screen when the chicken is near a corner.
- With a maximized window open, the chicken visibly walks above it; window
  drag/resize/close still work normally when the chicken merely passes
  under the cursor (not when it's directly over a button being clicked —
  known, accepted overlap per the "renders above windows" decision).
- Sending a chat message and watching it stream triggers the `thinking`
  animation for the duration; simulate (or trigger for real) a
  knowledge-graph write and confirm `eureka` fires once and respects its
  cooldown on a second write; simulate a critical signal and confirm
  `alarmed` fires even while the chicken is asleep.
- Resizing the browser viewport re-grounds the chicken and keeps it
  within the new bounds.
- Both the Terracotta and Carbon themes keep the pixel palette legible.
- `npm run build` passes with no new errors or warnings beyond the
  pre-existing baseline.

## Risks

- Z-index ordering is easy to get subtly wrong: radial menu must be
  `z-[60]` to beat the desktop context menu's `z-50`; the mascot layer
  itself is `z-45` (above `WindowLayer`'s `z-40`, below both menus).
- The mascot rendering above windows means it can occlude/steal clicks on
  window chrome directly beneath it — accepted per the "above windows"
  decision; mitigate by keeping the pointer hitbox tight to the canvas
  element only (no oversized invisible padding).
- `activityLog` is a derived store recomputed wholesale on every
  emission, not an append-only log — any "new entry" detection must diff
  entry ids between emissions, never assume the store only ever grows by
  appending.
- `setTimeout`-driven loops can receive large `dt` spikes after tab
  throttling/backgrounding resumes — clamp `dt` before feeding it into
  physics or lifecycle ticking.