diff --git a/apps/desktop/src/components/pane-shell/tree/floating-adoption.test.ts b/apps/desktop/src/components/pane-shell/tree/floating-adoption.test.ts
new file mode 100644
index 00000000000..4020b03ddce
--- /dev/null
+++ b/apps/desktop/src/components/pane-shell/tree/floating-adoption.test.ts
@@ -0,0 +1,92 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+// A `placement: 'floating'` pane must never enter the layout tree. Adoption is
+// what turns a contribution into a track (and therefore into something that
+// steals width from a zone), so this exercises the real `adoptContributedPanes`
+// path via `watchContributedPanes` rather than asserting on the filter itself.
+
+describe('floating panes stay out of the layout tree', () => {
+  beforeEach(() => {
+    window.localStorage.clear()
+    vi.resetModules()
+  })
+
+  afterEach(() => {
+    vi.resetModules()
+  })
+
+  async function setup() {
+    const tree = await import('@/components/pane-shell/tree/store')
+    const model = await import('@/components/pane-shell/tree/model')
+    const { registry } = await import('@/contrib/registry')
+
+    registry.register({ id: 'workspace', area: 'panes', title: 'chat', data: { placement: 'main' }, render: () => null })
+
+    tree.declareDefaultTree(model.group(['workspace'], { id: 'grp-main' }))
+
+    return { model, registry, tree }
+  }
+
+  it('does not adopt a floating pane, while still adopting a docked one', async () => {
+    const { model, registry, tree } = await setup()
+
+    registry.register({
+      id: 'hud',
+      area: 'panes',
+      title: 'HUD',
+      data: { placement: 'floating', anchor: 'top-right', width: '240px' },
+      render: () => null
+    })
+    registry.register({
+      id: 'files',
+      area: 'panes',
+      title: 'Files',
+      data: { placement: 'right' },
+      render: () => null
+    })
+
+    tree.watchContributedPanes()
+
+    const ids = model.allPaneIds(tree.$layoutTree.get()!)
+
+    expect(ids).not.toContain('hud')
+    // Control: a normal placement DOES get adopted through the same pass, so
+    // the exclusion is specific to 'floating', not a broken adoption run.
+    expect(ids).toContain('files')
+  })
+
+  it('keeps the main zone unsplit when only a floating pane registers', async () => {
+    const { model, registry, tree } = await setup()
+
+    registry.register({
+      id: 'hud',
+      area: 'panes',
+      title: 'HUD',
+      data: { placement: 'floating' },
+      render: () => null
+    })
+
+    tree.watchContributedPanes()
+
+    const root = tree.$layoutTree.get()!
+
+    // Still the single group it was declared as — no track was created.
+    expect(root.type).toBe('group')
+    expect(model.allPaneIds(root)).toEqual(['workspace'])
+  })
+
+  it('survives a registry change without ever adopting the floating pane', async () => {
+    const { model, registry, tree } = await setup()
+
+    registry.register({ id: 'hud', area: 'panes', data: { placement: 'floating' }, render: () => null })
+    tree.watchContributedPanes()
+
+    // A later registration re-runs adoption via the registry subscription.
+    registry.register({ id: 'terminal', area: 'panes', data: { placement: 'bottom' }, render: () => null })
+
+    const ids = model.allPaneIds(tree.$layoutTree.get()!)
+
+    expect(ids).toContain('terminal')
+    expect(ids).not.toContain('hud')
+  })
+})
diff --git a/apps/desktop/src/components/pane-shell/tree/renderer/floating-panes.test.tsx b/apps/desktop/src/components/pane-shell/tree/renderer/floating-panes.test.tsx
new file mode 100644
index 00000000000..b5e97640dfa
--- /dev/null
+++ b/apps/desktop/src/components/pane-shell/tree/renderer/floating-panes.test.tsx
@@ -0,0 +1,203 @@
+/**
+ * Live-behavior test for FloatingPanes: mounts the REAL component into a real
+ * DOM and drives real pointer/resize events. This is the closest thing to
+ * "running it" without an Electron main process — it exercises the rendered
+ * element's computed geometry, not the pure geometry module (that's
+ * floating-rect.test.ts).
+ */
+
+import { act, type ReactNode } from 'react'
+import { createRoot, type Root } from 'react-dom/client'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { registry } from '@/contrib/registry'
+
+import { FloatingPanes } from './floating-panes'
+
+let root: null | Root = null
+let container: HTMLDivElement | null = null
+let disposers: (() => void)[] = []
+
+function render(ui: ReactNode) {
+  container = document.createElement('div')
+  document.body.append(container)
+  root = createRoot(container)
+
+  act(() => {
+    root!.render(ui)
+  })
+}
+
+const card = () => document.querySelector<HTMLElement>('[data-floating-pane="hud"]')
+
+const grab = () => card()!.querySelector('header')!
+
+/** jsdom has no real pointer events; PointerEvent falls back to MouseEvent. */
+function pointer(target: Element, type: string, x: number, y: number) {
+  const event = new MouseEvent(type, { bubbles: true, clientX: x, clientY: y })
+
+  Object.defineProperty(event, 'pointerId', { value: 1 })
+
+  act(() => {
+    target.dispatchEvent(event)
+  })
+}
+
+function resizeWindow(width: number, height: number) {
+  Object.defineProperty(window, 'innerWidth', { configurable: true, value: width, writable: true })
+  Object.defineProperty(window, 'innerHeight', { configurable: true, value: height, writable: true })
+
+  act(() => {
+    window.dispatchEvent(new Event('resize'))
+  })
+}
+
+function registerHud(data: Record<string, unknown>) {
+  disposers.push(
+    registry.register({
+      area: 'panes',
+      data,
+      id: 'hud',
+      render: () => <p data-testid="hud-body">live</p>,
+      title: 'HUD'
+    })
+  )
+}
+
+describe('FloatingPanes (live DOM)', () => {
+  beforeEach(() => {
+    window.localStorage.clear()
+    resizeWindow(1440, 900)
+    // setPointerCapture / releasePointerCapture don't exist in jsdom.
+    Element.prototype.setPointerCapture = vi.fn()
+    Element.prototype.releasePointerCapture = vi.fn()
+  })
+
+  afterEach(() => {
+    if (root) {
+      act(() => root!.unmount())
+    }
+
+    container?.remove()
+    root = null
+    container = null
+    disposers.forEach(dispose => dispose())
+    disposers = []
+  })
+
+  it('mounts a fixed card in the anchored corner with the pane body inside', () => {
+    registerHud({ anchor: 'top-right', height: '132px', placement: 'floating', width: '224px' })
+    render(<FloatingPanes />)
+
+    const el = card()!
+
+    expect(el).toBeTruthy()
+    expect(el.className).toContain('fixed')
+    // 1440 - 224 - 12 margin = 1204; titlebar 34 + 12 = 46.
+    expect(el.style.left).toBe('1204px')
+    expect(el.style.top).toBe('46px')
+    expect(el.style.width).toBe('224px')
+    expect(document.querySelector('[data-testid="hud-body"]')?.textContent).toBe('live')
+  })
+
+  it('renders nothing for a non-floating placement', () => {
+    registerHud({ placement: 'right', width: '224px' })
+    render(<FloatingPanes />)
+
+    expect(card()).toBeNull()
+  })
+
+  it('moves with a real pointer drag on the header', () => {
+    registerHud({ anchor: 'top-left', height: '132px', placement: 'floating', width: '224px' })
+    render(<FloatingPanes />)
+
+    expect(card()!.style.left).toBe('12px')
+
+    pointer(grab(), 'pointerdown', 100, 100)
+    pointer(grab(), 'pointermove', 260, 240)
+    pointer(grab(), 'pointerup', 260, 240)
+
+    expect(card()!.style.left).toBe('172px')
+    expect(card()!.style.top).toBe('186px')
+  })
+
+  it('persists the dragged position across a remount', () => {
+    registerHud({ anchor: 'top-left', height: '132px', placement: 'floating', width: '224px' })
+    render(<FloatingPanes />)
+
+    pointer(grab(), 'pointerdown', 100, 100)
+    pointer(grab(), 'pointermove', 300, 300)
+    pointer(grab(), 'pointerup', 300, 300)
+
+    const moved = card()!.style.left
+
+    act(() => root!.unmount())
+    container!.remove()
+    render(<FloatingPanes />)
+
+    expect(card()!.style.left).toBe(moved)
+  })
+
+  it('rides the right edge when the window shrinks', () => {
+    registerHud({ anchor: 'top-right', height: '132px', placement: 'floating', width: '224px' })
+    render(<FloatingPanes />)
+
+    expect(card()!.style.left).toBe('1204px')
+
+    resizeWindow(1000, 700)
+
+    // Tracks the edge: 1000 - 224 - 12 = 764.
+    expect(card()!.style.left).toBe('764px')
+  })
+
+  it('never lets a drag push the card under the titlebar', () => {
+    registerHud({ anchor: 'top-left', height: '132px', placement: 'floating', width: '224px' })
+    render(<FloatingPanes />)
+
+    pointer(grab(), 'pointerdown', 100, 100)
+    pointer(grab(), 'pointermove', 100, -900)
+    pointer(grab(), 'pointerup', 100, -900)
+
+    expect(Number.parseFloat(card()!.style.top)).toBeGreaterThanOrEqual(34)
+  })
+
+  it('collapses to the header and drops the body, and does not drag from the button', () => {
+    registerHud({ anchor: 'top-left', height: '132px', placement: 'floating', width: '224px' })
+    render(<FloatingPanes />)
+
+    const before = card()!.style.left
+    const toggle = card()!.querySelector('button')!
+
+    // The button is inside the drag handle — [data-floating-no-drag] must
+    // stop it starting a drag.
+    pointer(toggle, 'pointerdown', 100, 100)
+    pointer(grab(), 'pointermove', 400, 400)
+    pointer(grab(), 'pointerup', 400, 400)
+
+    expect(card()!.style.left).toBe(before)
+
+    act(() => {
+      toggle.click()
+    })
+
+    expect(document.querySelector('[data-testid="hud-body"]')).toBeNull()
+    expect(card()!.style.height).toBe('')
+  })
+
+  it('renders one card per floating contribution', () => {
+    registerHud({ anchor: 'top-left', placement: 'floating', width: '224px' })
+    disposers.push(
+      registry.register({
+        area: 'panes',
+        data: { anchor: 'bottom-right', placement: 'floating', width: '200px' },
+        id: 'hud2',
+        render: () => null,
+        title: 'HUD 2'
+      })
+    )
+
+    render(<FloatingPanes />)
+
+    expect(document.querySelectorAll('[data-floating-pane]').length).toBe(2)
+  })
+})
diff --git a/apps/desktop/src/components/pane-shell/tree/renderer/floating-panes.tsx b/apps/desktop/src/components/pane-shell/tree/renderer/floating-panes.tsx
new file mode 100644
index 00000000000..338a2f17b9c
--- /dev/null
+++ b/apps/desktop/src/components/pane-shell/tree/renderer/floating-panes.tsx
@@ -0,0 +1,206 @@
+/**
+ * Floating panes — the tree's non-tiling placement.
+ *
+ * `placement: 'floating'` opts a pane OUT of the layout tree: it never becomes
+ * a track, never takes width from a zone, and never appears in a tab strip.
+ * The tree renders it as a fixed card above itself, draggable by its header,
+ * with position + collapse persisted per pane id. The geometry rules live in
+ * floating-rect.ts.
+ */
+
+import { useStore } from '@nanostores/react'
+import { type PointerEvent as ReactPointerEvent, useCallback, useEffect, useRef, useState } from 'react'
+
+import { HUD_SURFACE } from '@/app/floating-hud'
+import { TITLEBAR_HEIGHT } from '@/app/shell/titlebar'
+import { Codicon } from '@/components/ui/codicon'
+import { ContribBoundary } from '@/contrib/react/boundary'
+import { useContributions } from '@/contrib/react/use-contributions'
+import type { Contribution } from '@/contrib/types'
+import { readJson, writeJson } from '@/lib/storage'
+import { cn } from '@/lib/utils'
+
+import { $hiddenTreePanes } from '../store'
+
+import {
+  anchoredRect,
+  clampFloatingRect,
+  FLOATING_PLACEMENT,
+  floatingPx,
+  type FloatingRect,
+  type FloatingViewport,
+  reflowRect
+} from './floating-rect'
+import { paneChrome } from './track-model'
+
+const POSITIONS_KEY = 'hermes.desktop.floatingPanes.v1'
+
+const DEFAULT_SIZE = { width: 240, height: 180 }
+
+interface StoredRect {
+  x: number
+  y: number
+  collapsed?: boolean
+}
+
+const readStored = (): Record<string, StoredRect> => readJson<Record<string, StoredRect>>(POSITIONS_KEY) ?? {}
+
+const viewportNow = (): FloatingViewport => ({
+  width: window.innerWidth,
+  height: window.innerHeight,
+  top: TITLEBAR_HEIGHT
+})
+
+function FloatingPane({ pane }: { pane: Contribution }) {
+  const chrome = paneChrome(pane)
+  const anchor = chrome.anchor ?? 'top-right'
+
+  const size = {
+    width: floatingPx(chrome.width, DEFAULT_SIZE.width),
+    height: floatingPx(chrome.height, DEFAULT_SIZE.height)
+  }
+
+  const [rect, setRect] = useState<FloatingRect>(() => {
+    const stored = readStored()[pane.id]
+    const spawned = anchoredRect(anchor, size, viewportNow())
+
+    return stored ? { ...spawned, x: stored.x, y: stored.y } : spawned
+  })
+
+  const [collapsed, setCollapsed] = useState(() => readStored()[pane.id]?.collapsed ?? false)
+
+  const drag = useRef<{ x: number; y: number } | null>(null)
+  const viewport = useRef<FloatingViewport>(viewportNow())
+
+  const persist = useCallback(
+    (next: FloatingRect, nextCollapsed: boolean) => {
+      writeJson(POSITIONS_KEY, { ...readStored(), [pane.id]: { x: next.x, y: next.y, collapsed: nextCollapsed } })
+    },
+    [pane.id]
+  )
+
+  // Track the viewport so an edge-anchored pane rides its edge on resize.
+  // The previous-size read lives in the handler (not a useEffect body): it's
+  // window geometry, not a mirrored reactive value.
+  const handleResize = useCallback(() => {
+    const next = viewportNow()
+
+    setRect(current => reflowRect(current, anchor, viewport.current, next))
+    viewport.current = next
+  }, [anchor])
+
+  useEffect(() => {
+    window.addEventListener('resize', handleResize)
+
+    return () => window.removeEventListener('resize', handleResize)
+  }, [handleResize])
+
+  const onPointerDown = useCallback((event: ReactPointerEvent<HTMLElement>) => {
+    if ((event.target as HTMLElement).closest('[data-floating-no-drag]')) {
+      return
+    }
+
+    event.currentTarget.setPointerCapture(event.pointerId)
+    drag.current = { x: event.clientX, y: event.clientY }
+    event.preventDefault()
+  }, [])
+
+  const onPointerMove = useCallback((event: ReactPointerEvent<HTMLElement>) => {
+    const from = drag.current
+
+    if (!from) {
+      return
+    }
+
+    drag.current = { x: event.clientX, y: event.clientY }
+
+    setRect(current =>
+      clampFloatingRect(
+        { ...current, x: current.x + event.clientX - from.x, y: current.y + event.clientY - from.y },
+        viewport.current
+      )
+    )
+  }, [])
+
+  const onPointerUp = useCallback(
+    (event: ReactPointerEvent<HTMLElement>) => {
+      if (!drag.current) {
+        return
+      }
+
+      drag.current = null
+      event.currentTarget.releasePointerCapture?.(event.pointerId)
+      setRect(current => {
+        persist(current, collapsed)
+
+        return current
+      })
+    },
+    [collapsed, persist]
+  )
+
+  const toggleCollapsed = () =>
+    setCollapsed(current => {
+      persist(rect, !current)
+
+      return !current
+    })
+
+  return (
+    <div
+      className={cn('pointer-events-auto fixed z-45 flex flex-col overflow-hidden', HUD_SURFACE)}
+      data-floating-pane={pane.id}
+      style={{
+        left: rect.x,
+        top: rect.y,
+        width: size.width,
+        height: collapsed ? undefined : size.height
+      }}
+    >
+      {/* Header IS the drag handle — the floating equivalent of a tab strip. */}
+      <header
+        className="flex shrink-0 cursor-grab items-center justify-between gap-2 px-2.5 py-1.5 text-[0.6875rem] text-(--ui-text-secondary) select-none"
+        onPointerDown={onPointerDown}
+        onPointerMove={onPointerMove}
+        onPointerUp={onPointerUp}
+        style={{ touchAction: 'none' }}
+      >
+        <span className="truncate font-medium">{pane.title ?? pane.id}</span>
+        <button
+          className="rounded p-0.5 text-(--ui-text-quaternary) transition-colors hover:text-(--ui-text-primary)"
+          data-floating-no-drag=""
+          onClick={toggleCollapsed}
+          type="button"
+        >
+          <Codicon name={collapsed ? 'chevron-down' : 'chevron-up'} size="0.75rem" />
+        </button>
+      </header>
+
+      {!collapsed && (
+        <div className="min-h-0 flex-1 overflow-auto">
+          <ContribBoundary id={pane.id}>{pane.render?.()}</ContribBoundary>
+        </div>
+      )}
+    </div>
+  )
+}
+
+/** Every `placement: 'floating'` contribution, rendered above the tree. */
+export function FloatingPanes() {
+  const panes = useContributions('panes')
+  const hidden = useStore($hiddenTreePanes)
+
+  const floating = panes.filter(pane => paneChrome(pane).placement === FLOATING_PLACEMENT && !hidden.has(pane.id))
+
+  if (floating.length === 0) {
+    return null
+  }
+
+  return (
+    <>
+      {floating.map(pane => (
+        <FloatingPane key={`${pane.source ?? 'core'}:${pane.id}`} pane={pane} />
+      ))}
+    </>
+  )
+}
diff --git a/apps/desktop/src/components/pane-shell/tree/renderer/floating-rect.test.ts b/apps/desktop/src/components/pane-shell/tree/renderer/floating-rect.test.ts
new file mode 100644
index 00000000000..dec110531fe
--- /dev/null
+++ b/apps/desktop/src/components/pane-shell/tree/renderer/floating-rect.test.ts
@@ -0,0 +1,86 @@
+import { describe, expect, it } from 'vitest'
+
+import { anchoredRect, clampFloatingRect, floatingPx, reflowRect } from './floating-rect'
+
+const viewport = { width: 1440, height: 900, top: 34 }
+const size = { width: 240, height: 180 }
+
+describe('anchoredRect', () => {
+  it('spawns in the named corner, inset by the margin', () => {
+    expect(anchoredRect('top-right', size, viewport)).toMatchObject({ x: 1188, y: 46 })
+    expect(anchoredRect('top-left', size, viewport)).toMatchObject({ x: 12, y: 46 })
+    expect(anchoredRect('bottom-right', size, viewport)).toMatchObject({ x: 1188, y: 708 })
+    expect(anchoredRect('bottom-left', size, viewport)).toMatchObject({ x: 12, y: 708 })
+  })
+
+  it('never spawns over the reserved top chrome', () => {
+    for (const anchor of ['top-left', 'top-right', 'bottom-left', 'bottom-right'] as const) {
+      expect(anchoredRect(anchor, size, { width: 320, height: 120, top: 34 }).y).toBeGreaterThanOrEqual(34)
+    }
+  })
+})
+
+describe('clampFloatingRect', () => {
+  it('keeps a grabbable sliver on screen at either horizontal edge', () => {
+    expect(clampFloatingRect({ ...size, x: 5000, y: 100 }, viewport).x).toBe(1392)
+    expect(clampFloatingRect({ ...size, x: -5000, y: 100 }, viewport).x).toBe(-192)
+  })
+
+  it('hard-bounds the top so the drag handle is always reachable', () => {
+    expect(clampFloatingRect({ ...size, x: 100, y: -500 }, viewport).y).toBe(34)
+    expect(clampFloatingRect({ ...size, x: 100, y: 5000 }, viewport).y).toBe(852)
+  })
+
+  it('pins to the top-left rather than inverting when larger than the viewport', () => {
+    const tiny = { width: 200, height: 100, top: 34 }
+    const rect = clampFloatingRect({ x: 0, y: 0, width: 400, height: 400 }, tiny)
+
+    expect(rect.x).toBeLessThanOrEqual(tiny.width)
+    expect(rect.y).toBe(34)
+  })
+
+  it('leaves an in-bounds rect untouched', () => {
+    const rect = { ...size, x: 400, y: 200 }
+
+    expect(clampFloatingRect(rect, viewport)).toEqual(rect)
+  })
+})
+
+describe('reflowRect', () => {
+  const shrunk = { width: 1000, height: 700, top: 34 }
+
+  it('rides the right edge when right-anchored', () => {
+    const start = anchoredRect('top-right', size, viewport)
+
+    expect(reflowRect(start, 'top-right', viewport, shrunk).x).toBe(748)
+  })
+
+  it('rides the bottom edge when bottom-anchored', () => {
+    const start = anchoredRect('bottom-left', size, viewport)
+
+    expect(reflowRect(start, 'bottom-left', viewport, shrunk).y).toBe(508)
+  })
+
+  it('holds position when left/top-anchored, but still clamps into view', () => {
+    const start = { ...size, x: 40, y: 60 }
+
+    expect(reflowRect(start, 'top-left', viewport, shrunk)).toMatchObject({ x: 40, y: 60 })
+    expect(reflowRect({ ...size, x: 1300, y: 60 }, 'top-left', viewport, shrunk).x).toBe(952)
+  })
+
+  it('is identity for an in-bounds rect when the viewport did not change', () => {
+    const rect = { ...size, x: 300, y: 300 }
+
+    expect(reflowRect(rect, 'top-right', viewport, viewport)).toEqual(rect)
+  })
+})
+
+describe('floatingPx', () => {
+  it('accepts authored px strings and raw numbers, falling back otherwise', () => {
+    expect(floatingPx('216px', 240)).toBe(216)
+    expect(floatingPx(300, 240)).toBe(300)
+    expect(floatingPx(undefined, 240)).toBe(240)
+    expect(floatingPx('auto', 240)).toBe(240)
+    expect(floatingPx(Number.NaN, 240)).toBe(240)
+  })
+})
diff --git a/apps/desktop/src/components/pane-shell/tree/renderer/floating-rect.ts b/apps/desktop/src/components/pane-shell/tree/renderer/floating-rect.ts
new file mode 100644
index 00000000000..f09947e8132
--- /dev/null
+++ b/apps/desktop/src/components/pane-shell/tree/renderer/floating-rect.ts
@@ -0,0 +1,109 @@
+/**
+ * Floating-pane geometry — pure, so the clamping/anchoring rules are testable
+ * without a DOM.
+ *
+ * A floating pane is NOT a track in the layout tree: it never takes width from
+ * a zone. It's a fixed-position card the tree renders above itself. Its whole
+ * contract is "stay a sane rect inside the viewport", which is this module.
+ */
+
+/** Corner a floating pane spawns from (and re-anchors to on reset). */
+export type FloatingAnchor = 'bottom-left' | 'bottom-right' | 'top-left' | 'top-right'
+
+export interface FloatingRect {
+  x: number
+  y: number
+  width: number
+  height: number
+}
+
+export interface FloatingViewport {
+  width: number
+  height: number
+  /** Chrome reserved at the top (the 34px titlebar) — panes never cover it. */
+  top: number
+}
+
+/** Keep this much of the card on screen when clamping, so it stays grabbable. */
+const MIN_VISIBLE = 48
+
+/** Gap between a spawned pane and the viewport edge it anchors to. */
+export const FLOATING_MARGIN = 12
+
+/** The one non-tiling placement — see renderer/floating-panes.tsx. */
+export const FLOATING_PLACEMENT = 'floating'
+
+export const clamp = (n: number, lo: number, hi: number): number => Math.min(Math.max(n, lo), hi)
+
+/**
+ * Clamp a rect into the viewport. Horizontal keeps `MIN_VISIBLE` px on screen
+ * from either edge (a card can hang off the right, never vanish); vertical is
+ * hard-bounded by the reserved chrome so the drag handle is always reachable.
+ *
+ * Both axes clamp `lo` before `hi`, so a card wider/taller than the viewport
+ * pins to the top-left rather than inverting.
+ */
+export function clampFloatingRect(rect: FloatingRect, viewport: FloatingViewport): FloatingRect {
+  const maxX = Math.max(MIN_VISIBLE - rect.width, viewport.width - MIN_VISIBLE)
+  const maxY = Math.max(viewport.top, viewport.height - MIN_VISIBLE)
+
+  return {
+    ...rect,
+    x: clamp(rect.x, Math.min(MIN_VISIBLE - rect.width, maxX), maxX),
+    y: clamp(rect.y, viewport.top, maxY)
+  }
+}
+
+/** Spawn position for an anchor — the corner, inset by `FLOATING_MARGIN`. */
+export function anchoredRect(
+  anchor: FloatingAnchor,
+  size: { width: number; height: number },
+  viewport: FloatingViewport
+): FloatingRect {
+  const right = anchor === 'bottom-right' || anchor === 'top-right'
+  const bottom = anchor === 'bottom-left' || anchor === 'bottom-right'
+
+  const rect = {
+    ...size,
+    x: right ? viewport.width - size.width - FLOATING_MARGIN : FLOATING_MARGIN,
+    y: bottom ? viewport.height - size.height - FLOATING_MARGIN : viewport.top + FLOATING_MARGIN
+  }
+
+  return clampFloatingRect(rect, viewport)
+}
+
+/**
+ * Re-clamp on viewport resize. A pane anchored to a right/bottom edge TRACKS
+ * that edge (shrinking the window keeps it in the corner) instead of being
+ * dragged inward only when it would fall off — matching how the pet and every
+ * OS HUD behave.
+ */
+export function reflowRect(
+  rect: FloatingRect,
+  anchor: FloatingAnchor,
+  previous: FloatingViewport,
+  next: FloatingViewport
+): FloatingRect {
+  const right = anchor === 'bottom-right' || anchor === 'top-right'
+  const bottom = anchor === 'bottom-left' || anchor === 'bottom-right'
+
+  return clampFloatingRect(
+    {
+      ...rect,
+      x: right ? rect.x + (next.width - previous.width) : rect.x,
+      y: bottom ? rect.y + (next.height - previous.height) : rect.y
+    },
+    next
+  )
+}
+
+/** Parse an authored CSS px length (`'216px'`, `216`) with a fallback. */
+export function floatingPx(value: number | string | undefined, fallback: number): number {
+  if (typeof value === 'number') {
+    return Number.isFinite(value) ? value : fallback
+  }
+
+  const parsed = Number.parseFloat(value ?? '')
+
+  return Number.isFinite(parsed) ? parsed : fallback
+}
diff --git a/apps/desktop/src/components/pane-shell/tree/renderer/index.tsx b/apps/desktop/src/components/pane-shell/tree/renderer/index.tsx
index ddb466b9f26..3145f563d3d 100644
--- a/apps/desktop/src/components/pane-shell/tree/renderer/index.tsx
+++ b/apps/desktop/src/components/pane-shell/tree/renderer/index.tsx
@@ -29,6 +29,7 @@ import { $layoutTree, trackActiveTreeGroup } from '../store'
 import { ZoneEditor } from '../zone-editor'
 
 import { TreeEditBar } from './edit-bar'
+import { FloatingPanes } from './floating-panes'
 import { NarrowOverlays } from './narrow-overlays'
 import { TreeNode } from './tree-node'
 
@@ -73,6 +74,8 @@ export function LayoutTreeRoot({ children }: { children?: ReactNode }) {
       `}</style>
       <TreeNode node={tree} root rootRow={tree.type === 'split' && tree.orientation === 'row'} />
       <NarrowOverlays />
+      {/* Non-tiling panes: fixed cards above the tree, outside every zone. */}
+      <FloatingPanes />
       <TreeEditBar />
       <ZoneEditor />
       {children}
diff --git a/apps/desktop/src/components/pane-shell/tree/renderer/track-model.ts b/apps/desktop/src/components/pane-shell/tree/renderer/track-model.ts
index b3785b38476..7dd10012aa3 100644
--- a/apps/desktop/src/components/pane-shell/tree/renderer/track-model.ts
+++ b/apps/desktop/src/components/pane-shell/tree/renderer/track-model.ts
@@ -15,6 +15,7 @@ import type { GroupNode, LayoutNode } from '../model'
 import { allPaneIds } from '../model'
 
 import type { DoubleTapContext } from './drag-session'
+import type { FloatingAnchor } from './floating-rect'
 
 export const MIN_PANE_PX = 80
 
@@ -34,13 +35,20 @@ export interface PaneSizing {
 }
 
 /** Chrome behavior flags a pane contributes. Read via `paneChrome`. */
-interface PaneChrome {
+interface PaneChrome extends PaneSizing {
   /** Leaves the grid on narrow viewports; revealed as an edge overlay. */
   collapsible?: boolean
   /** Extra ids accepted from PANE_TOGGLE_REVEAL_EVENT (the real app's pane
    *  ids, e.g. `chat-sidebar` for `sessions`). */
   revealAliases?: string[]
+  /** Tiling role in the tree, or `'floating'` — the one NON-tiling placement:
+   *  the pane is excluded from the tree entirely and rendered as a fixed card
+   *  above it (see renderer/floating-panes.tsx). A floating pane takes no
+   *  space from any zone, has no tab, and can't be docked or split. */
   placement?: string
+  /** Spawn corner for `placement: 'floating'` (default `'top-right'`). The
+   *  pane also TRACKS that corner's edges when the window resizes. */
+  anchor?: FloatingAnchor
   /** No Close in the tab menu — the one surface the app can't lose (the
    *  main workspace). Session tiles share `placement: 'main'` but close. */
   uncloseable?: boolean
diff --git a/apps/desktop/src/components/pane-shell/tree/store.ts b/apps/desktop/src/components/pane-shell/tree/store.ts
index b07f4eb4424..f40427156c6 100644
--- a/apps/desktop/src/components/pane-shell/tree/store.ts
+++ b/apps/desktop/src/components/pane-shell/tree/store.ts
@@ -38,6 +38,7 @@ import {
   splitGroupZone as splitGroupZoneOp,
   type SplitNode
 } from './model'
+import { FLOATING_PLACEMENT } from './renderer/floating-rect'
 import { rootChildSide } from './renderer/track-model'
 
 // v2: v1 trees were saved against placeholder panes with index-order zone
@@ -837,7 +838,14 @@ function adoptContributedPanes(): void {
   }
 
   const dismissed = $dismissedPanes.get()
-  const missing = panes.filter(c => !inTree.has(c.id) && !dismissed.has(c.id))
+
+  // `placement: 'floating'` opts OUT of the tree entirely — those panes render
+  // as fixed cards above it (renderer/floating-panes.tsx). Adopting one would
+  // turn it into a track that steals width from a zone, which is the whole
+  // thing floating exists to avoid.
+  const missing = panes.filter(
+    c => !inTree.has(c.id) && !dismissed.has(c.id) && placementOf(c.id) !== FLOATING_PLACEMENT
+  )
 
   if (missing.length === 0) {
     return
diff --git a/apps/desktop/src/sdk/index.ts b/apps/desktop/src/sdk/index.ts
index 285f843dcc2..8d28af45238 100644
--- a/apps/desktop/src/sdk/index.ts
+++ b/apps/desktop/src/sdk/index.ts
@@ -125,6 +125,12 @@ export { type RouteContribution, ROUTES_AREA, SIDEBAR_NAV_AREA, type SidebarNavC
 export type { StatusbarItem } from '@/app/shell/statusbar-controls'
 
 export type { TitlebarTool } from '@/app/shell/titlebar-controls'
+/** Pane placement roles. `'floating'` is the one NON-tiling value: the pane is
+ *  excluded from the layout tree and rendered as a fixed, draggable card above
+ *  it — it takes no width from any zone, has no tab, and can't be docked.
+ *  Pair it with `anchor` (spawn corner, default `'top-right'`) plus
+ *  `width`/`height`. */
+export type { FloatingAnchor } from '@/components/pane-shell/tree/renderer/floating-rect'
 export { StatusDot, type StatusTone } from '@/components/status-dot'
 export { Badge } from '@/components/ui/badge'
 export { Button } from '@/components/ui/button'
@@ -177,6 +183,9 @@ export { Tabs, TabsList, TabsTrigger } from '@/components/ui/tabs'
 export { Textarea } from '@/components/ui/textarea'
 export { Tip, Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from '@/components/ui/tooltip'
 export type { GatewayEventListener } from '@/contrib/events'
+
+// -- contracts ----------------------------------------------------------------
+
 export type {
   HermesPlugin,
   PluginContext,
@@ -184,9 +193,6 @@ export type {
   PluginRestOptions,
   PluginStorage
 } from '@/contrib/plugin'
-
-// -- contracts ----------------------------------------------------------------
-
 /** Mount-scoped contribution: while the rendering component is mounted, its
  *  children render in the target area's slot; unmount disposes it. Use for
  *  page-owned chrome (a page's titlebar control leaves with the page) —
@@ -215,12 +221,12 @@ export { type KeybindContribution, KEYBINDS_AREA } from '@/lib/keybinds/actions'
  *  authors) + its translucent tag fill — so plugin-rendered identities read
  *  the same hue as everywhere else. */
 export { profileColor, profileColorSoft } from '@/lib/profile-color'
+
+export const PANES_AREA = 'panes'
 /** The shared client itself, for invalidation OUTSIDE React (e.g. a
  *  `ctx.socket` frame invalidating a query). Inside components keep using
  *  `useQueryClient`. */
 export { queryClient } from '@/lib/query-client'
-
-export const PANES_AREA = 'panes'
 export const STATUSBAR_AREAS = { left: 'statusBar.left', right: 'statusBar.right' } as const
 export const TITLEBAR_AREAS = { center: 'titleBar.center', left: 'titleBar.left', right: 'titleBar.right' } as const