refactor(gui): slot system standard — single register, four props shares, framework store seat

The definitive slot model for the web client, replacing the first-generation
define/register two-step, ScopedSlots whitelist faces, and binding handles:

- 'root' is the only a-priori slot (SlotsService built-in); the shell renders
  exactly ctx.slots.renderSlot('root', {}).
- register is the single API: children = slot declaration + render
  authorization + runtime spec in one options object; misconfiguration fails
  loud at load (duplicate declaration, undeclared contribution, one store
  handle under two scopes).
- Component props arrive in four auto-derived shares: PropsRuntime<K>
  (owner params + session/global standard kits via declare-merge),
  PropsRenderSlots<S>, PropsStore<H>, and the inject business face.
  sessionId is framework-supplied; hooks are framework-made only.
- Framework store seat: defineStore factories declare schema/actions/persist;
  read = useStore, write = baked actions only; store scope derives from the
  mounting entry; per-session persist keys and clearPersisted lifecycle.
- inject factories read the apply closure's own ctx (binding handles retired;
  root-ctx back door closed); SessionProvider is self-wired render-prop.
- Rendering sits behind the SlotRenderer install seam; runtime stays
  React-free; ownership ledger keyed to the single entry axis closes the
  stale-authority window (StaleAuthorizationError probes).

Docs: the slot type-chain note is refreshed in place as the slot system
standard RFC (bilingual pair re-recorded); the web client architecture RFC
defers its slot sections there; packages/client/AGENTS.md gains the slot and
props discipline; gui-testing/web-styling notes drop missions/ references.

Tests: suites rewritten to the standard (props fed directly, real store
engines via createXXXStore().create(), no render machinery); load-time
negative samples for declaration/authorization/store conflicts; verified by
real-host playwright run (three columns, empty state, collapse, keyed session
remount, cross-slot selection sharing).

docs(ui-sidebar): point contract reference at the committed slot standard RFC

missions/ is workspace-local and never committed; the README must not cite it.

packages/client/runtime/tests/client-apply.spec.ts

@@ -37,6 +37,9 @@ describe('runtime client apply', () => {
   it('mounts ctx.slots + ctx.sessions and wires the stream sinks into the manager', async () => {
     const bench = await mount()
     expect(bench.ctx.get('slots') !== undefined).toBe(true)
+    // The built-in 'root' declaration ships with this package's SlotsService
+    // (the SlotMap 'root' merge lives here since the slot-parity rework).
+    expect(bench.ctx.slots.spec('root')).toEqual({ kind: 'single', scope: 'root' })
     const sessions = bench.ctx.get('sessions')
     expect(sessions !== undefined).toBe(true)
     expect(bench.sinks).toBeDefined()

packages/client/runtime/tests/invariant.spec.ts

@@ -25,9 +25,11 @@ describe('runtime slots/changed invariant', () => {
     const ctx = await setup()
     expect(() => { emit(ctx, 'unrelated/event', 'x') }).not.toThrow()
     await ctx.plugin(SlotsService).await() // fiber must reach ACTIVE — the audit reads strict ctx.get
-    // A real define bumps the version first and re-emits through onMutate —
-    // the audit sees version > 0 and stays quiet.
-    expect(() => ctx.slots.define('t-single', { kind: 'single', scope: 'root' })).not.toThrow()
+    // A real registration bumps the version first and re-emits through
+    // onMutate — the audit sees version > 0 and stays quiet. (Erased call:
+    // the typed register face rides the wave-1 ui-slots types.)
+    const slots = ctx.slots as unknown as { register(options: object, component: unknown): () => void }
+    expect(() => slots.register({ name: 'root' }, () => null)).not.toThrow()
   })
 
   it('fails loud on a missing key and on an emission with no applied mutation', async () => {

packages/client/runtime/tests/sessions-service.spec.ts

@@ -1,10 +1,12 @@
 /**
- * SessionsService: list store projection (manager → {ids, byId} with derived
- * titles), scope-tree lifecycle (lazy mint / frozen survival / removed
- * teardown with watch deferral), binding identity, ancestry walk, create.
+ * SessionsService: list store projection (manager → {ids, byId, current}
+ * with derived titles), the migrated current-selection account (open
+ * validation, persisted mask semantics, cell resolution), scope-tree
+ * lifecycle (lazy mint / frozen survival / removed teardown with watch
+ * deferral), binding identity, ancestry walk, create.
  */
 import { Context } from 'cordis'
-import { describe, expect, it } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
 import type { SessionId } from '@deepseek-ai/dsh-client-connection/client'
 import { SessionsService, scopeOf } from '../src/client/sessions/service.ts'
 import { FakeApiClient, ok } from './fake-api.ts'
@@ -112,6 +114,95 @@ describe('scope tree', () => {
   })
 })
 
+describe('current selection (migrated from ui-layout, arbitrated into the list snapshot)', () => {
+  afterEach(() => { vi.unstubAllGlobals() })
+
+  it('open() writes list.current; unknown ids fail loud', async () => {
+    const b = bench()
+    await feedList(b, [{ id: 's1' }])
+    expect(b.svc.list.getSnapshot().current).toBeUndefined()
+    b.svc.open(sid('s1'))
+    expect(b.svc.list.getSnapshot().current).toBe('s1')
+    expect(() => { b.svc.open(sid('ghost')) }).toThrow(/unknown session ghost/)
+    expect(b.svc.list.getSnapshot().current).toBe('s1') // failed open leaves the selection alone
+  })
+
+  it('masks (not destroys) the selection while its session is off the list', async () => {
+    const b = bench()
+    await feedList(b, [{ id: 's1' }, { id: 's2' }])
+    b.svc.open(sid('s1'))
+    await feedList(b, [{ id: 's2' }]) // s1 removed → current falls to the empty state
+    expect(b.svc.list.getSnapshot().current).toBeUndefined()
+    await feedList(b, [{ id: 's1' }, { id: 's2' }]) // s1 returns → selection resurfaces
+    expect(b.svc.list.getSnapshot().current).toBe('s1')
+  })
+
+  it('persists the selection under dsh.sessions.current and rehydrates it into a fresh service', async () => {
+    const storage = new Map<string, string>()
+    vi.stubGlobal('localStorage', {
+      getItem: (k: string) => storage.get(k) ?? null,
+      setItem: (k: string, v: string) => { storage.set(k, v) },
+    })
+    const first = bench()
+    await feedList(first, [{ id: 's1' }])
+    first.svc.open(sid('s1'))
+    expect(storage.get('dsh.sessions.current')).toContain('s1')
+    // A fresh boot (same storage) recovers the selection once the list holds the session.
+    const second = bench()
+    await feedList(second, [{ id: 's1' }])
+    expect(second.svc.list.getSnapshot().current).toBe('s1')
+  })
+})
+
+describe('cell (render-layer session kit)', () => {
+  it('resolves an identity-stable {sessionId, useSession} pair; unknown ids yield undefined', async () => {
+    const b = bench()
+    await feedList(b, [{ id: 's1' }])
+    const cell = b.svc.cell('s1')
+    expect(cell).toBeDefined()
+    expect(cell?.sessionId).toBe('s1')
+    expect(cell?.useSession).toBe(b.svc.manager.get(sid('s1')).useSelector)
+    expect(b.svc.cell('s1')).toBe(cell)
+    expect(b.svc.cell('ghost')).toBeUndefined()
+  })
+
+  it('moves the watch like binding(): switching cells sweeps a deferred removal', async () => {
+    const b = bench()
+    await feedList(b, [{ id: 's1' }])
+    b.svc.cell('s1') // watched
+    await feedList(b, []) // removed while watched → deferred, scope survives
+    expect(b.svc.scope(sid('s1'))).toBeDefined()
+    await feedList(b, [{ id: 's2' }])
+    b.svc.cell('s2') // watch moves → sweep tears s1 down
+    expect(b.svc.scope(sid('s1'))).toBeUndefined()
+  })
+})
+
+describe('slot-store scope prune hook', () => {
+  it('notifies ctx.slots.pruneStoreScope when a scope dies (both teardown paths)', async () => {
+    const b = bench()
+    const pruneStoreScope = vi.fn()
+    b.ctx.reflect.provide('slots', { pruneStoreScope })
+    await feedList(b, [{ id: 's1' }, { id: 's2' }])
+    b.svc.scope(sid('s1'))
+    b.svc.binding(sid('s2')) // s2 watched
+    await feedList(b, []) // s1 unwatched → immediate drop; s2 watched → deferred
+    expect(pruneStoreScope).toHaveBeenCalledWith('s1')
+    expect(pruneStoreScope).not.toHaveBeenCalledWith('s2')
+    await feedList(b, [{ id: 's3' }])
+    b.svc.binding(sid('s3')) // watch moves → deferred sweep drops s2
+    expect(pruneStoreScope).toHaveBeenCalledWith('s2')
+  })
+
+  it('tolerates a slots-less boot (object-layer benches carry no slot service)', async () => {
+    const b = bench()
+    await feedList(b, [{ id: 's1' }])
+    b.svc.scope(sid('s1'))
+    await feedList(b, []) // teardown without ctx.slots must not throw
+    expect(b.svc.scope(sid('s1'))).toBeUndefined()
+  })
+})
+
 describe('ancestry', () => {
   it('walks parentId links root-first including self; broken links stop the walk', async () => {
     const b = bench()

packages/client/runtime/tests/slots-service.spec.ts

@@ -1,80 +1,379 @@
 /**
- * SlotsService: cordis Service wrapper semantics — core delegation, the
- * 'slots/changed' event bridge, and fiber-scoped registration disposal.
+ * SlotsService terminal-design account (design.md §11-3 main landing):
+ * built-in 'root', the three load-time throws (duplicate declaration /
+ * undeclared contribution / cross-scope store handle), the renderer install
+ * seam (double install / not installed / non-root key), store instance
+ * resolution and lifecycle on the ledger axis, and the entry-unload cascade.
  */
 import { Context } from 'cordis'
-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 import type { FC } from 'react'
+import type { SlotRendererHost } from '@deepseek-ai/dsh-client-ui-slots'
 import { SlotsService } from '../src/client/slots.ts'
 
-// Test-only slot keys (SlotMap is empty in this package; the service is generic over it).
+// Test-only slot keys (merged so the typed entries/spec faces accept them).
 declare module '@deepseek-ai/dsh-client-ui-slots' {
   interface SlotMap {
-    't-single': { kind: 'single'; scope: 'root'; props: object }
-    't-list': { kind: 'list'; scope: 'root'; props: object }
+    't.host': { kind: 'single'; scope: 'root' }
+    't.panel': { kind: 'single'; scope: 'session' }
+    't.rows': { kind: 'list'; scope: 'root' }
   }
 }
 
 const C: FC<object> = () => null
 
-async function boot(): Promise<Context> {
+/**
+ * Register/install/renderSlot through a type-erased view: the typed register
+ * face rides wave-1 ui-slots types (red until that wave lands); the runtime
+ * semantics under test are final.
+ */
+interface ErasedService {
+  register(options: object, component: unknown): () => void
+  install(renderer: object): void
+  renderSlot(key: string, owner: object): unknown
+}
+
+interface Bench {
+  ctx: Context
+  svc: SlotsService
+  erased: ErasedService
+}
+
+async function boot(): Promise<Bench> {
   const ctx = new Context()
   ctx.plugin(SlotsService)
   await ctx.fiber.await()
-  return ctx
+  // Service accessor (ctx.get reads the reflect store, which Service-class
+  // plugins do not write; the accessor is the product path).
+  const svc = ctx.slots
+  return { ctx, svc, erased: svc as unknown as ErasedService }
 }
 
-describe('SlotsService', () => {
-  it('proxies define/register/entries/spec/getVersion to the core', async () => {
-    const ctx = await boot()
-    ctx.slots.define('t-single', { kind: 'single', scope: 'root' })
-    expect(ctx.slots.spec('t-single')).toEqual({ kind: 'single', scope: 'root' })
-    const v0 = ctx.slots.getVersion('t-single')
-    ctx.slots.register('t-single', C)
-    expect(ctx.slots.entries('t-single')).toHaveLength(1)
-    expect(ctx.slots.getVersion('t-single')).toBeGreaterThan(v0)
-    expect(ctx.slots.core.spec('t-single')).toBeDefined()
+/** Engine-shaped instance stub (the arbitrated persist face: scope-keyed create + clearPersisted). */
+interface FakeInstance {
+  useSelector: () => undefined
+  actions: Record<string, never>
+  clearPersisted: ReturnType<typeof vi.fn>
+}
+
+/** Fake store handle factory (create-count and clearPersisted observable). */
+function fakeHandle() {
+  const created: FakeInstance[] = []
+  const handle = {
+    create: vi.fn((_scopeKey?: string): FakeInstance => {
+      const instance: FakeInstance = { useSelector: () => undefined, actions: {}, clearPersisted: vi.fn() }
+      created.push(instance)
+      return instance
+    }),
+  }
+  return { handle, created }
+}
+
+/**
+ * Install a capturing renderer, occupy 'root' (declaring `children` in the
+ * same call — 'root' is single, so the one occupant is also the declarer),
+ * and pull the host face out through renderSlot('root').
+ */
+function captureHost(bench: Bench, children?: object): SlotRendererHost {
+  let host: SlotRendererHost | undefined
+  bench.erased.install({
+    renderRoot: (h: SlotRendererHost) => { host = h; return 'rendered' },
+  })
+  bench.erased.register({ name: 'root', ...(children !== undefined ? { children } : {}) }, C)
+  bench.ctx.reflect.provide('sessions', fakeSessions())
+  bench.erased.renderSlot('root', {})
+  if (host === undefined) throw new Error('renderer never received the host')
+  return host
+}
+
+/** Minimal sessions face for the host seam (list observable + cell). */
+function fakeSessions() {
+  const state = { ids: [], byId: {}, current: undefined as string | undefined }
+  return {
+    list: { getSnapshot: () => state, subscribe: () => () => undefined },
+    cell: (id: string) => (id === 'known' ? { sessionId: id, useSession: () => undefined } : undefined),
+  }
+}
+
+describe("built-in 'root'", () => {
+  it('is declared at construction: spec readable, occupancy open, no plugin needed', async () => {
+    const bench = await boot()
+    expect(bench.svc.spec('root')).toEqual({ kind: 'single', scope: 'root' })
+    expect(() => bench.erased.register({ name: 'root' }, C)).not.toThrow()
+    expect(bench.svc.entries('root')).toHaveLength(1)
   })
 
-  it("re-emits every mutation as 'slots/changed' with the key", async () => {
-    const ctx = await boot()
-    const seen: string[] = []
-    ctx.on('slots/changed', (key) => { seen.push(key) })
-    ctx.slots.define('t-list', { kind: 'list', scope: 'root' })
-    ctx.slots.register('t-list', C, { id: 'a' })
-    expect(seen).toEqual(['t-list', 't-list'])
+  it('rejects a second declaration of root, attributing the built-in row', async () => {
+    const bench = await boot()
+    expect(() => bench.erased.register({
+      name: 'root', children: { 'root': { kind: 'single', scope: 'root' } },
+    }, C)).toThrow(/already declared.*built-in/)
+  })
+})
+
+describe('load-time validation', () => {
+  it('throws on contributing into an undeclared slot', async () => {
+    const bench = await boot()
+    expect(() => bench.erased.register({ name: 't.host' }, C)).toThrow(/slot "t.host" is not declared/)
   })
 
-  it('collects a plugin fiber\'s registrations when the fiber unloads (cascade)', async () => {
-    const ctx = await boot()
-    ctx.slots.define('t-single', { kind: 'single', scope: 'root' })
-    const fiber = ctx.plugin({
+  it('throws on a duplicate declaration, naming the slot and the prior declarant', async () => {
+    const bench = await boot()
+    bench.erased.register({ name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } } }, C)
+    bench.erased.register({
+      name: 't.host', children: { 't.rows': { kind: 'list', scope: 'root' } },
+    }, C)
+    expect(() => bench.erased.register({
+      name: 't.rows', id: 'r1', children: { 't.rows': { kind: 'list', scope: 'root' } },
+    }, C)).toThrow(/slot "t.rows" is already declared.*"t.host"/)
+  })
+
+  it('throws when one store handle is bound to two scopes', async () => {
+    const bench = await boot()
+    bench.erased.register({
+      name: 'root',
+      children: {
+        't.host': { kind: 'single', scope: 'root' },
+        't.panel': { kind: 'single', scope: 'session' },
+      },
+    }, C)
+    const { handle } = fakeHandle()
+    bench.erased.register({ name: 't.host', store: handle }, C)
+    expect(() => bench.erased.register({ name: 't.panel', store: handle }, C))
+      .toThrow(/one handle, one scope/)
+  })
+
+  it('commits nothing when the core rejects the entry (children stay undeclared)', async () => {
+    const bench = await boot()
+    bench.erased.register({ name: 'root' }, C) // 'root' single slot now occupied
+    expect(() => bench.erased.register({
+      name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } },
+    }, C)).toThrow(/already has a registration/)
+    // The failing call's declaration must not have landed.
+    expect(() => bench.erased.register({ name: 't.host' }, C)).toThrow(/is not declared/)
+  })
+})
+
+describe('renderer install seam', () => {
+  it('throws on renderSlot before install (boot-order guidance)', async () => {
+    const bench = await boot()
+    expect(() => bench.erased.renderSlot('root', {})).toThrow(/renderer not installed/)
+  })
+
+  it('throws on double install', async () => {
+    const bench = await boot()
+    bench.erased.install({ renderRoot: () => null })
+    expect(() => { bench.erased.install({ renderRoot: () => null }) }).toThrow(/already installed/)
+  })
+
+  it('throws on any non-root key (single ctx-level entry)', async () => {
+    const bench = await boot()
+    bench.erased.install({ renderRoot: () => null })
+    expect(() => bench.erased.renderSlot('t.host', {})).toThrow(/only renders 'root'/)
+  })
+
+  it("throws on renderSlot('root') before any root registration", async () => {
+    const bench = await boot()
+    bench.erased.install({ renderRoot: () => null })
+    expect(() => bench.erased.renderSlot('root', {})).toThrow(/no registration/)
+  })
+
+  it('renders through the installed renderer and returns its product', async () => {
+    const bench = await boot()
+    const renderRoot = vi.fn(() => 'tree')
+    bench.erased.install({ renderRoot })
+    bench.erased.register({ name: 'root' }, C)
+    bench.ctx.reflect.provide('sessions', fakeSessions())
+    expect(bench.erased.renderSlot('root', {})).toBe('tree')
+    expect(renderRoot).toHaveBeenCalledTimes(1)
+  })
+})
+
+describe('host face', () => {
+  it('serves entriesOf/specOf/isLive off the ledger and flips isLive on disposal', async () => {
+    const bench = await boot()
+    const host = captureHost(bench, { 't.host': { kind: 'single', scope: 'root' } })
+    const dispose = bench.erased.register({ name: 't.host' }, C)
+    const rootEntry = host.entriesOf('root')[0]
+    expect(rootEntry).toBeDefined()
+    expect(rootEntry?.component).toBe(C)
+    expect(host.specOf('root')).toEqual({ kind: 'single', scope: 'root' })
+    expect(host.specOf('t.host')).toEqual({ kind: 'single', scope: 'root' })
+    const childEntry = host.entriesOf('t.host')[0]
+    expect(host.isLive(childEntry as never)).toBe(true)
+    dispose()
+    expect(host.isLive(childEntry as never)).toBe(false)
+    expect(host.entriesOf('t.host')).toHaveLength(0)
+  })
+
+  it('exposes sessions list/current/cell (current riding the list snapshot)', async () => {
+    const bench = await boot()
+    const host = captureHost(bench)
+    expect(host.sessions.list.getSnapshot()).toMatchObject({ ids: [] })
+    expect(host.sessions.current.getSnapshot()).toBeUndefined()
+    expect(host.sessions.cell('known')).toMatchObject({ sessionId: 'known' })
+    expect(host.sessions.cell('ghost')).toBeUndefined()
+  })
+})
+
+describe('store instance axis', () => {
+  /** Boot with 'root' occupied and the three test children declared. */
+  async function storeBench() {
+    const bench = await boot()
+    const host = captureHost(bench, {
+      't.host': { kind: 'single', scope: 'root' },
+      't.rows': { kind: 'list', scope: 'root' },
+      't.panel': { kind: 'single', scope: 'session' },
+    })
+    return { bench, host }
+  }
+
+  it('resolves one instance per (handle x root scope) shared across entries', async () => {
+    const { bench, host } = await storeBench()
+    const { handle } = fakeHandle()
+    bench.erased.register({ name: 't.host', store: handle }, C)
+    bench.erased.register({ name: 't.rows', id: 'a', store: handle }, C)
+    const [hostEntry] = host.entriesOf('t.host')
+    const [rowEntry] = host.entriesOf('t.rows')
+    const a = host.storeOf(hostEntry as never, undefined)
+    const b = host.storeOf(rowEntry as never, undefined)
+    expect(a).toBeDefined()
+    expect(a).toBe(b) // shared handle, same scope key = same instance
+    expect(handle.create).toHaveBeenCalledTimes(1)
+    expect(handle.create).toHaveBeenCalledWith() // root scope: keyless create
+  })
+
+  it('resolves per-session instances keyed by session id, created with the scope key', async () => {
+    const { bench, host } = await storeBench()
+    const { handle } = fakeHandle()
+    bench.erased.register({ name: 't.panel', store: handle }, C)
+    const [entry] = host.entriesOf('t.panel')
+    const s1 = host.storeOf(entry as never, 's1')
+    const s2 = host.storeOf(entry as never, 's2')
+    expect(s1).not.toBe(s2)
+    expect(host.storeOf(entry as never, 's1')).toBe(s1) // cached per key
+    expect(handle.create).toHaveBeenCalledWith('s1')
+    expect(handle.create).toHaveBeenCalledWith('s2')
+    expect(() => host.storeOf(entry as never, undefined)).toThrow(/requires a session id/)
+  })
+
+  it('mints a fresh handle per register for the factory (exclusive) form', async () => {
+    const { bench, host } = await storeBench()
+    const factory = vi.fn(() => fakeHandle().handle)
+    bench.erased.register({ name: 't.host', store: factory }, C)
+    bench.erased.register({ name: 't.rows', id: 'a', store: factory }, C)
+    expect(factory).toHaveBeenCalledTimes(2)
+    const a = host.storeOf(host.entriesOf('t.host')[0] as never, undefined)
+    const b = host.storeOf(host.entriesOf('t.rows')[0] as never, undefined)
+    expect(a).not.toBe(b) // two mints, two instances
+  })
+
+  it('drops instances with the last holding entry and refuses stale resolution', async () => {
+    const { bench, host } = await storeBench()
+    const { handle } = fakeHandle()
+    const d1 = bench.erased.register({ name: 't.host', store: handle }, C)
+    bench.erased.register({ name: 't.rows', id: 'a', store: handle }, C)
+    const rowEntry = host.entriesOf('t.rows')[0]
+    const hostEntry = host.entriesOf('t.host')[0]
+    const shared = host.storeOf(rowEntry as never, undefined)
+    d1() // one holder left: record (and instance) survive
+    expect(host.storeOf(rowEntry as never, undefined)).toBe(shared)
+    expect(() => host.storeOf(hostEntry as never, undefined)).not.toThrow() // handle still live via the row entry
+    // Note: dropping the row entry would sever the last reference; stale
+    // resolution is covered through the cascade spec below.
+  })
+
+  it('pruneStoreScope clears persisted state per dead session, including never-materialized ones', async () => {
+    const { bench, host } = await storeBench()
+    const { handle, created } = fakeHandle()
+    bench.erased.register({ name: 't.panel', store: handle }, C)
+    const [entry] = host.entriesOf('t.panel')
+    const s1 = host.storeOf(entry as never, 's1')
+    expect(s1).toBe(created[0]) // the resolved instance is the fake the handle minted
+    bench.svc.pruneStoreScope('s1')
+    expect(created[0]?.clearPersisted).toHaveBeenCalledTimes(1)
+    expect(host.storeOf(entry as never, 's1')).not.toBe(s1) // instance dropped, next resolve mints anew
+    // Never-rendered dead session: a transient instance is created just to clear storage.
+    const before = created.length
+    bench.svc.pruneStoreScope('s-never')
+    expect(created.length).toBe(before + 1)
+    expect(created[created.length - 1]?.clearPersisted).toHaveBeenCalledTimes(1)
+  })
+})
+
+describe('entry-unload cascade', () => {
+  it('kills declared children, their contributions, and the ledger rows with the entry', async () => {
+    const bench = await boot()
+    let host: SlotRendererHost | undefined
+    bench.erased.install({
+      renderRoot: (h: SlotRendererHost) => { host = h; return 'rendered' },
+    })
+    bench.ctx.reflect.provide('sessions', fakeSessions())
+    // The declarer here is NOT the root occupant: root stays occupied by a
+    // separate entry so disposing the declarer only kills its children.
+    const disposeRoot = bench.erased.register({ name: 'root' }, C)
+    bench.erased.renderSlot('root', {})
+    if (host === undefined) throw new Error('renderer never received the host')
+    disposeRoot()
+    const disposeDeclarer = bench.erased.register({
+      name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } },
+    }, C)
+    bench.erased.register({ name: 't.host' }, C)
+    const [childEntry] = host.entriesOf('t.host')
+    expect(childEntry).toBeDefined()
+
+    disposeDeclarer()
+    expect(bench.svc.spec('t.host')).toBeUndefined() // ledger row gone
+    expect(host.specOf('t.host')).toBeUndefined() // outlets now render empty
+    expect(bench.svc.entries('t.host')).toHaveLength(0) // contribution cleared
+    expect(host.isLive(childEntry as never)).toBe(false) // stale bindings will throw upstream
+    // The freed key is re-declarable by a new entry (no residue).
+    expect(() => bench.erased.register({
+      name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } },
+    }, C)).not.toThrow()
+  })
+
+  it('cascades through cordis fiber disposal (plugin unload = full cleanup)', async () => {
+    const bench = await boot()
+    bench.erased.register({
+      name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } },
+    }, C)
+    const fiber = bench.ctx.plugin({
       name: 'occupant',
       inject: ['slots'],
       apply: (pluginCtx: Context) => {
-        pluginCtx.slots.register('t-single', C)
+        ;(pluginCtx.slots as unknown as ErasedService).register({ name: 't.host' }, C)
       },
     })
     await fiber.await()
-    expect(ctx.slots.entries('t-single')).toHaveLength(1)
+    expect(bench.svc.entries('t.host')).toHaveLength(1)
     await fiber.dispose()
-    expect(ctx.slots.entries('t-single')).toHaveLength(0)
-    // The slot definition (registered from root) survives; a new occupant may register.
-    expect(() => ctx.slots.register('t-single', C)).not.toThrow()
+    expect(bench.svc.entries('t.host')).toHaveLength(0)
+    expect(bench.svc.spec('t.host')).toBeDefined() // declarer still live; slot stays declared
   })
 
-  it('proxies specDynamic/subscribe/getVersion through the core', async () => {
-    const ctx = await boot()
-    ctx.slots.define('t-list', { kind: 'list', scope: 'root' })
-    expect(ctx.slots.specDynamic('t-list')).toEqual({ kind: 'list', scope: 'root' })
-    expect(ctx.slots.specDynamic('never-defined')).toBeUndefined()
-    let notified = 0
-    const unsubscribe = ctx.slots.subscribe('t-list', () => { notified += 1 })
-    ctx.slots.register('t-list', C, { id: 'row' })
-    await new Promise(resolve => setTimeout(resolve, 0)) // microtask-batched flush
-    expect(notified).toBeGreaterThan(0)
-    expect(ctx.slots.getVersion('t-list')).toBeGreaterThan(0)
-    unsubscribe()
+  it('disposer is idempotent (stale second call is a no-op)', async () => {
+    const bench = await boot()
+    const dispose = bench.erased.register({
+      name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } },
+    }, C)
+    dispose()
+    expect(() => { dispose() }).not.toThrow()
+    expect(() => bench.erased.register({
+      name: 'root', children: { 't.host': { kind: 'single', scope: 'root' } },
+    }, C)).not.toThrow()
+  })
+})
+
+describe('event bridge', () => {
+  it("re-emits entry writes and child declarations as 'slots/changed'", async () => {
+    const bench = await boot()
+    const seen: string[] = []
+    bench.ctx.on('slots/changed', (key) => { seen.push(key) })
+    bench.erased.register({
+      name: 'root', children: { 't.rows': { kind: 'list', scope: 'root' } },
+    }, C)
+    bench.erased.register({ name: 't.rows', id: 'a' }, C)
+    expect(seen).toEqual(['root', 't.rows', 't.rows'])
   })
-
 })