feat(ui-slots): bind inject hooks compartments into use<Name> selector hooks

Registrant-private reactive facts previously reached components as raw
observables that each component subscribed by hand (InputBar notices/
lexicon via uSES, SettingsRoot via a version/subscribe/getter triple).
The inject face now carries a reserved hooks compartment of bare
sources; the renderer binds each into a use<Name> selector hook through
the same machinery as the provide channel, so components consume
useNotices/useLexicon/useSections and never see a subscription
primitive. InputBar and SettingsRoot are the first two consumers.

packages/client/AGENTS.md

@@ -11,10 +11,10 @@ The [slot system standard](../../.agents/notes/implemented/architecture/2026-07-
 1. **One API**: a plugin composes UI only through `ctx.slots.register({ name, children?, store?, inject? }, Component)`. There is no separate slot-definition call, no whitelist face object, no face-minting helper. The shell alone renders `'root'`.
 2. **children = declaration + authorization**: the slots your component renders are exactly the keys of your register call's `children` object (spec values: `kind`/`scope`). Rendering a slot you didn't declare, or declaring one someone else declared, fails at load — do not work around it; the conflict is the design speaking. Slot names mirror the composition path: `<domain>.<entry>.<hole>` (e.g. `'conversation.chat.toolview'`).
 3. **Component props are the four shares, all derived**: `PropsRuntime<K>` (SlotMap: owner params + `useSession`/`sessionId` on session scope + global `useSessions`/`useWorkspaces`) & `PropsRenderSlots<S>` (children keys) & `PropsStore<H>` (store factory) & the inject face. Never hand-write a member a share already derives; never re-type a share locally.
-4. **Hooks are framework-made only**: `useSession`, `useSessions`, `useWorkspaces`, `useStore`, `renderSlot` are the five seats. Business code never creates a hook or selector as a prop value — pass plain data and callbacks. (Component-internal behavioral hooks that subscribe to nothing external are fine.)
+4. **Hooks are framework-made only**: `useSession`, `useSessions`, `useWorkspaces`, `useStore`, `renderSlot` are the five standing seats, plus the `use<Name>` hooks the renderer binds from provide contributions and inject `hooks` compartments. Business code never creates a hook or selector as a prop value — pass plain data and callbacks. (Component-internal behavioral hooks that subscribe to nothing external are fine.)
 5. **Live data has exactly three channels**: parent knows it → owner props at the renderSlot site; only the component knows it → local state; shared across entries or survives remounts → a store declared at register. Derived data is a pure function over framework-hook data (`useMemo`), never its own subscription.
 6. **Stores: read `props.useStore`, write `props.actions.*`** — the declared actions are the complete mutation surface. Write the store as an exported `createXXXStore()` factory (module-level handles are forbidden — de-facto singletons); share by passing one handle to several registers inside `apply`. Production code never calls the factory or `.create()` outside `apply`; tests do (that is the sanctioned zero-machinery path).
-7. **inject returns plain data and callbacks** from the apply closure's own ctx — no hooks, no ReactNode producers, no whole-service objects. Its capability boundary is the plugin's declared `inject` topology; there is no wider ctx to reach for.
+7. **inject returns plain data and callbacks** from the apply closure's own ctx — no hand-made hooks, no ReactNode producers, no whole-service objects. A registrant-private reactive fact rides the reserved `hooks` compartment (bare observables the renderer binds to `use<Name>`; components never see the sources). Its capability boundary is the plugin's declared `inject` topology; there is no wider ctx to reach for.
 
 ## Export discipline (client plugin packages)
 

packages/client/ui-conversation/src/client/apply.ts

@@ -135,13 +135,15 @@ export function apply(ctx: Context): void {
       'conversation.input.model': { kind: 'single', scope: 'session' },
     },
     inject: (sessionId: SessionId): ComposerBarInjected => {
+      const shell = inputHub.shell(sessionId)
       return {
-        keyboard: inputHub.keyboard(sessionId),
+        keyboard: shell,
         stop: () => {
           scopedConversation(sessions, sessionId).cancel().catch(() => {
             // Stop failure surfaces via snapshot.promptError; nothing to restore.
           })
         },
+        hooks: { notices: shell.notices, lexicon: shell.lexicon },
       }
     },
   }, InputBar)

packages/client/ui-conversation/src/client/contract/slots.ts

@@ -1,11 +1,11 @@
 /** Conversation slot declarations and their composed component props. */
 import type { ReactNode, RefObject } from 'react'
 import type {
-  MaybeSnapshotSelectorHook, PropsRenderSlots, PropsRuntime, PropsStore, SnapshotSelectorHook,
+  InjectFace, MaybeSnapshotSelectorHook, PropsRenderSlots, PropsRuntime, PropsStore, SnapshotSelectorHook,
 } from '@deepseek-ai/dsh-client-ui-slots'
-import type { ConversationSnapshot, PendingInteraction, SessionId, ToolCallBlock, WorkspaceId } from '@deepseek-ai/dsh-client-runtime/client'
+import type { ConversationSnapshot, ObservableSnapshot, PendingInteraction, SessionId, ToolCallBlock, WorkspaceId } from '@deepseek-ai/dsh-client-runtime/client'
 import type {} from '@deepseek-ai/dsh-client-ui-layout/client'
-import type { ComposerKeyboard, InputActions, InputState } from '../input/contract.ts'
+import type { ComposerKeyboard, InputActions, InputNotice, InputState } from '../input/contract.ts'
 import type { createChatStore } from '../stores.ts'
 import type { CallId, SelectionTarget, ViewTab } from './views.ts'
 
@@ -220,6 +220,13 @@ export interface ComposerBarInjected {
   keyboard: ComposerKeyboard
   /** Cancel the in-flight turn. */
   stop: () => void
+  /** Registrant hooks compartment: the renderer binds these to useNotices/useLexicon. */
+  hooks: {
+    /** Latest surfaced notice (null after none; seq keys re-render of repeats). */
+    notices: ObservableSnapshot<InputNotice | null>
+    /** Hot plain-text reference lexicon for the decoration scan (decision 21). */
+    lexicon: ObservableSnapshot<ReadonlyMap<'/' | '@', readonly string[]>>
+  }
 }
 
 /**
@@ -231,11 +238,11 @@ export interface InputControlOwnerProps {
   locked: boolean
 }
 
-/** Full composer-bar component props: standard kit & owner share & control-seat render share & injected share. */
+/** Full composer-bar component props: standard kit & owner share & control-seat render share & injected share (hooks compartment bound). */
 export type ComposerBarProps =
   PropsRuntime<'conversation.composer.bar'>
   & PropsRenderSlots<'conversation.input.plan' | 'conversation.input.model'>
-  & ComposerBarInjected
+  & InjectFace<ComposerBarInjected>
 
 /**
  * Composer chain currency: what ConversationRoot dispatches at its

packages/client/ui-conversation/src/client/input/contract.ts

@@ -5,7 +5,7 @@
  * conversation wiring layer alone sees the full SessionInput. InputMachine
  * (machine.ts) is package-private and never exported.
  */
-import type { ClientContext, ObservableSnapshot, SnapshotStore } from '@deepseek-ai/dsh-client-runtime/client'
+import type { ClientContext, SnapshotStore } from '@deepseek-ai/dsh-client-runtime/client'
 import type {
   ArbitrateKey, ArbitrateOutcome, CommandClaim, ConsumeTokenRequest, PickOutcome,
   ReferenceInsert, SubmitOutcome, TokenSpan,
@@ -77,8 +77,6 @@ export interface InputNotice {
  * satisfies it structurally.
  */
 export interface ComposerKeyboard {
-  /** Latest surfaced notice store (null after none). */
-  readonly notices: SnapshotStore<InputNotice | null>
   /** Live machine state for event-handler reads (render reads go through useInput). */
   readonly snapshot: InputState
   /** Draft write with the DOM-observed edit shape (narrows occurrence math). */
@@ -99,8 +97,6 @@ export interface ComposerKeyboard {
   space(): boolean
   /** Dismiss the popupSelect shell (any interaction outside the box). */
   dismissPopup(): void
-  /** Hot plain-text reference lexicon source for the decoration scan (decision 21; empty Map without a pipeline). */
-  readonly lexicon: ObservableSnapshot<ReadonlyMap<'/' | '@', readonly string[]>>
 }
 
 /** One queued-message row projected from the session/queued frames (T9 supplies the store). */

packages/client/ui-conversation/src/client/skeleton/InputBar.tsx

@@ -1,11 +1,12 @@
 /** The default composer body: the 'conversation.composer.bar' slot entry
  * (decision 20). Machine state arrives through the standard provide channel
  * (useInput + inputActions); the keyboard/DOM command face and stop arrive
- * through this entry's own inject; layout-phase inputs (variant, placeholder,
+ * through this entry's own inject, whose hooks compartment binds
+ * useNotices/useLexicon; layout-phase inputs (variant, placeholder,
  * region-slot content) ride the owner props. Session facts
  * (running/removed/promptError) are self-selected via useSession. */
 
-import { useEffect, useRef, useState, useSyncExternalStore } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import type { ChangeEvent, KeyboardEvent, MouseEvent, ReactNode } from 'react'
 import clsx from 'clsx'
 import { IconPlusOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
@@ -27,20 +28,12 @@ const READONLY_OPTIONS: readonly { id: string; label: string }[] = [
 ]
 
 export function InputBar({
-  useSession, useInput, inputActions, keyboard, stop, renderSlot,
+  useSession, useInput, inputActions, keyboard, stop, renderSlot, useNotices, useLexicon,
   variant, placeholder, accessory, overlay, leftItems, rightItems, onAdd, addLabel = 'Add attachment',
 }: InputBarProps) {
   const input = useInput(s => s)
-  const noticeStore = keyboard.notices
-  const notice = useSyncExternalStore(
-    (fn: () => void) => noticeStore.subscribe(fn),
-    () => noticeStore.getSnapshot(),
-  )
-  const lexiconStore = keyboard.lexicon
-  const lexicon = useSyncExternalStore(
-    (fn: () => void) => lexiconStore.subscribe(fn),
-    () => lexiconStore.getSnapshot(),
-  )
+  const notice = useNotices(s => s)
+  const lexicon = useLexicon(s => s)
   const promptError = useSession(s => s.promptError)
   const running = useSession(s => s.running)
   const disabled = useSession(s => s.removed)

packages/client/ui-conversation/tests/input-bar.spec.tsx

@@ -91,6 +91,8 @@ function bench(over?: BenchOptions) {
     useInput: bindSnapshotSelector(shell.state),
     inputActions: shell.actions,
     keyboard: shell,
+    useNotices: bindSnapshotSelector(shell.notices),
+    useLexicon: bindSnapshotSelector(shell.lexicon),
     stop,
     renderSlot,
     variant: over?.variant ?? 'composer',

packages/client/ui-conversation/tests/input-matrix.spec.tsx

@@ -42,6 +42,8 @@ function mountBar(shell: SessionInputShell, over?: { running?: boolean; disabled
     useInput: bindSnapshotSelector(shell.state),
     inputActions: shell.actions,
     keyboard: shell,
+    useNotices: bindSnapshotSelector(shell.notices),
+    useLexicon: bindSnapshotSelector(shell.lexicon),
     renderSlot: (() => null) as InputBarProps['renderSlot'],
     stop: vi.fn(),
     variant: 'composer',

packages/client/ui-conversation/tests/input-scenarios.spec.tsx

@@ -128,6 +128,8 @@ async function scopedBench(register?: (slash: SlashService) => void) {
     useInput: bindSnapshotSelector(shell.state),
     inputActions: shell.actions,
     keyboard: shell,
+    useNotices: bindSnapshotSelector(shell.notices),
+    useLexicon: bindSnapshotSelector(shell.lexicon),
     renderSlot: (() => null) as InputBarProps['renderSlot'],
     stop: vi.fn(),
     variant: 'composer',

packages/client/ui-conversation/tests/skeleton.spec.tsx

@@ -118,6 +118,8 @@ function mount(
           useInput={useInput}
           inputActions={inputActions}
           keyboard={wiring}
+          useNotices={bindSnapshotSelector(wiring.notices)}
+          useLexicon={bindSnapshotSelector(wiring.lexicon)}
           stop={stop}
           renderSlot={(() => null) as InputBarProps['renderSlot']}
           {...bar}

packages/client/ui-settings/src/client/SettingsRoot.tsx

@@ -7,10 +7,10 @@
  * aria-labelledby the title node; close: visually-hidden slot text). Modal
  * open state and the active section id are component-local viewing state.
  */
-import { useCallback, useEffect, useId, useRef, useState, useSyncExternalStore } from 'react'
+import { useCallback, useEffect, useId, useRef, useState } from 'react'
 import clsx from 'clsx'
 import { IconCloseOutline16, IconDataOutline16, IconSettingsOutline16 } from '@deepseek-ai/dsh-client-ui-primitives'
-import type { SettingsRootComponentProps } from './contract/slots.ts'
+import type { SettingsRootComponentProps, SettingsSectionRow } from './contract/slots.ts'
 import css from './SettingsRoot.module.css'
 
 /** Nav glyph by section id; unknown ids fall back to the settings gear. */
@@ -20,7 +20,7 @@ function navIcon(id: string) {
 }
 
 type PanelProps = {
-  rows: ReturnType<SettingsRootComponentProps['sections']>
+  rows: readonly SettingsSectionRow[]
   renderSlot: SettingsRootComponentProps['renderSlot']
   onClose: () => void
 }
@@ -92,18 +92,14 @@ function SettingsPanel({ rows, renderSlot, onClose }: PanelProps) {
  * @returns the settings shell element tree.
  */
 export function SettingsRoot(props: SettingsRootComponentProps) {
-  const { wide, subscribeSections, sectionsVersion, sections, renderSlot } = props
+  const { wide, useSections, renderSlot } = props
   const [open, setOpen] = useState(false)
   const close = useCallback(() => { setOpen(false) }, [])
 
   // The ledger tick keeps the nav rows fresh: registrants re-register with
   // freshly localized text on locale change, and the trigger/header/close
   // seats re-render through their own outlets' subscriptions.
-  // uSES over the ledger version: same-version notifications dedupe to no
-  // render, and a registration landing between render and effect
-  // subscription cannot be missed.
-  useSyncExternalStore(subscribeSections, sectionsVersion)
-  const rows = sections()
+  const rows = useSections(s => s)
 
   return (
     <>

packages/client/ui-settings/src/client/contract/slots.ts

@@ -7,7 +7,7 @@
  * setting never means editing the shell; copy that belongs to no single
  * feature (chrome, the General section) is owned by ui-settings-general.
  */
-import type { PropsRenderSlots, PropsRuntime } from '@deepseek-ai/dsh-client-ui-slots'
+import type { HostObservable, InjectFace, PropsRenderSlots, PropsRuntime } from '@deepseek-ai/dsh-client-ui-slots'
 // Type-only: pulls ui-sidebar's SlotMap merge (the 'sidebar.settings' entry)
 // into every program that sees this contract.
 import type {} from '@deepseek-ai/dsh-client-ui-sidebar/client'
@@ -72,26 +72,32 @@ export interface SettingsSectionOwnerProps {
   children?: never
 }
 
+/** One nav row projected from a settings.section registration's options. */
+export interface SettingsSectionRow {
+  id: string
+  order: number
+  label: string
+}
+
 /**
  * Registrant-private injected share of the settings shell (assembled in
- * apply): ledger projections only — the shell reads no locale state.
+ * apply): the ledger's nav-row projection as a hooks-compartment source —
+ * the shell reads no locale state and subscribes through the bound hook.
  */
 export type SettingsRootInjected = {
-  /** Read the settings.section ledger version (nav invalidation). */
-  sectionsVersion: () => number
-  /** Subscribe to settings.section ledger changes. */
-  subscribeSections: (listener: () => void) => () => void
-  /** Project the settings.section ledger into nav rows (id/order/label). */
-  sections: () => readonly { id: string; order: number; label: string }[]
+  hooks: {
+    /** settings.section ledger projected into ordered nav rows. */
+    sections: HostObservable<readonly SettingsSectionRow[]>
+  }
 }
 
 /**
  * Full component props of the settings shell root: the sidebar owner share
- * (wide/rail state) plus the declared render shares and the injected face.
- * No store is registered — modal open state and active section id are
- * component-local viewing state.
+ * (wide/rail state) plus the declared render shares and the injected face
+ * (hooks compartment bound to useSections). No store is registered — modal
+ * open state and active section id are component-local viewing state.
  */
 export type SettingsRootComponentProps =
   PropsRuntime<'sidebar.settings'>
   & PropsRenderSlots<'settings.trigger' | 'settings.header' | 'settings.close' | 'settings.section'>
-  & SettingsRootInjected
+  & InjectFace<SettingsRootInjected>

packages/client/ui-settings/src/client/index.ts

@@ -10,12 +10,12 @@
  */
 import type { ClientContext } from '@deepseek-ai/dsh-client-runtime/client'
 import { deferRegistration } from '@deepseek-ai/dsh-client-ui-slots'
-import type { SettingsRootInjected } from './contract/slots.ts'
+import type { SettingsRootInjected, SettingsSectionRow } from './contract/slots.ts'
 import { SettingsRoot } from './SettingsRoot.tsx'
 
 export type {
   SettingsHeaderOwnerProps, SettingsRootComponentProps, SettingsRootInjected,
-  SettingsSectionOwnerProps, SettingsTriggerOwnerProps,
+  SettingsSectionOwnerProps, SettingsSectionRow, SettingsTriggerOwnerProps,
 } from './contract/slots.ts'
 
 /**
@@ -32,17 +32,31 @@ export const inject = ['slots']
  * @param ctx - client root context.
  */
 export function apply(ctx: ClientContext): void {
+  // Ledger → nav-row projection as an observable source (uSES contract:
+  // getSnapshot returns the cached rows until the ledger version moves).
+  let rowsVersion = -1
+  let rows: readonly SettingsSectionRow[] = []
   const injected = (): SettingsRootInjected => ({
-    sectionsVersion: () => ctx.slots.getVersion('settings.section'),
-    subscribeSections: listener => ctx.slots.subscribe('settings.section', listener),
-    sections: () => ctx.slots.entries('settings.section')
-      .map(e => ({
-        /* v8 ignore next -- list-slot registration requires id (SlotCore rejects an entry without one) */
-        id: e.options.id ?? '',
-        order: e.options.order ?? 0,
-        label: e.options.label ?? '',
-      }))
-      .sort((a, b) => a.order - b.order),
+    hooks: {
+      sections: {
+        getSnapshot: () => {
+          const version = ctx.slots.getVersion('settings.section')
+          if (version !== rowsVersion) {
+            rowsVersion = version
+            rows = ctx.slots.entries('settings.section')
+              .map(e => ({
+                /* v8 ignore next -- list-slot registration requires id (SlotCore rejects an entry without one) */
+                id: e.options.id ?? '',
+                order: e.options.order ?? 0,
+                label: e.options.label ?? '',
+              }))
+              .sort((a, b) => a.order - b.order)
+          }
+          return rows
+        },
+        subscribe: listener => ctx.slots.subscribe('settings.section', listener),
+      },
+    },
   })
   ctx.effect(() => {
     const deferred = deferRegistration(ctx.slots, 'sidebar.settings', SettingsRoot, () =>

packages/client/ui-settings/tests/apply.spec.ts

@@ -60,22 +60,25 @@ describe('ui-settings apply', () => {
     const b = await bench()
     declare(b.slots)
     await b.ctx.plugin({ inject: [...inject], apply }).await()
-    const injected = injectedOf(b.slots)
+    const { sections } = injectedOf(b.slots).hooks
     // The shell ships no sections of its own — registrants fill the ledger.
-    expect(injected.sections()).toEqual([])
+    expect(sections.getSnapshot()).toEqual([])
     b.slots.register({ name: 'settings.section', id: 'z', order: 20, label: 'Z' } as never, () => null)
     // No order and no label: both projection defaults apply.
     b.slots.register({ name: 'settings.section', id: 'a' } as never, () => null)
-    expect(injected.sections()).toEqual([
+    const rows = sections.getSnapshot()
+    expect(rows).toEqual([
       { id: 'a', order: 0, label: '' },
       { id: 'z', order: 20, label: 'Z' },
     ])
-    expect(injected.sectionsVersion()).toBe(b.slots.getVersion('settings.section'))
+    // Snapshot identity is stable until the ledger moves (uSES contract).
+    expect(sections.getSnapshot()).toBe(rows)
     const listener = vi.fn()
-    const off = injected.subscribeSections(listener)
+    const off = sections.subscribe(listener)
     b.slots.register({ name: 'settings.section', id: 'b', order: 1, label: 'B' } as never, () => null)
     await Promise.resolve()
     expect(listener).toHaveBeenCalled()
+    expect(sections.getSnapshot()).not.toBe(rows)
     off()
   })
 

packages/client/ui-settings/tests/settings-root.spec.tsx

@@ -1,5 +1,6 @@
 // @vitest-environment jsdom
 import { afterEach, describe, expect, it, vi } from 'vitest'
+import { useEffect, useState } from 'react'
 import { act, cleanup, fireEvent, render, screen } from '@testing-library/react'
 import type { SettingsRootComponentProps } from '../src/client/contract/slots.ts'
 import { SettingsRoot } from '../src/client/SettingsRoot.tsx'
@@ -22,9 +23,9 @@ function mount({
     { id: 'models', order: 10, label: 'Models' },
   ],
 }: { wide?: boolean; rows?: Row[] } = {}) {
-  // Mutable row store standing in for the ledger; bump() plays a change.
+  // Mutable row source standing in for the bound useSections hook; bump()
+  // plays a ledger change through the same observable contract.
   let current = rows
-  let version = 0
   const listeners = new Set<() => void>()
   const renderSlot = vi.fn(
     ((key: string, _owner: unknown, opts?: { only?: string }) => {
@@ -38,19 +39,21 @@ function mount({
     useSessions: unusedHook,
     useWorkspaces: unusedHook,
     wide,
-    sectionsVersion: () => version,
-    subscribeSections: (listener) => {
-      listeners.add(listener)
-      return () => { listeners.delete(listener) }
+    useSections: (select) => {
+      const [, force] = useState(0)
+      useEffect(() => {
+        const listener = () => { force(n => n + 1) }
+        listeners.add(listener)
+        return () => { listeners.delete(listener) }
+      }, [])
+      return select(current)
     },
-    sections: () => current,
     renderSlot,
   }
   const view = render(<SettingsRoot {...props} />)
   const bump = (next: Row[]) => {
     act(() => {
       current = next
-      version += 1
       for (const fn of [...listeners]) fn()
     })
   }

packages/client/ui-slots/src/index.ts

@@ -14,6 +14,7 @@
  * consumer merges keys in and the intersection is what keeps them string-typed.
  * The rule fires on the empty-map view, not on real redundancy. */
 import type { ReactNode } from 'react'
+import type { HostObservable } from './renderer.ts'
 import type { BoundActions, HandleOf, PropsStore, SnapshotSelectorHook, StoreDecl } from './store.ts'
 
 export * from './store.ts'
@@ -214,11 +215,40 @@ export type PropsRenderSlots<S extends keyof SlotMap & string> = {
  */
 export type SlotComponent<P> = (props: P) => ReactNode
 
+/**
+ * Registrant hooks compartment: bare observable sources (getSnapshot +
+ * subscribe pairs) supplied under the reserved `hooks` key of an inject
+ * face. The registrant-private twin of the `sessions.provide` hooks
+ * compartment: the renderer binds each source into a `use<Name>` selector
+ * hook, so the sources never reach the component and plugin-private reactive
+ * facts ride the same subscription machinery as the standard kit instead of
+ * hand-rolled component subscriptions.
+ */
+export type HooksSources = Record<string, HostObservable<unknown>>
+
+/**
+ * Selector-hook share synthesized from a hooks compartment: each source
+ * `name` becomes a `use<Name>` selector hook over its snapshot type.
+ */
+export type PropsHooks<HS extends HooksSources> = {
+  [N in keyof HS & string as `use${Capitalize<N>}`]:
+  SnapshotSelectorHook<HS[N] extends HostObservable<infer T> ? T : never>
+}
+
+/**
+ * The component-side view of an inject face: the reserved `hooks`
+ * compartment (when declared) arrives as bound `use<Name>` selector hooks;
+ * every other member passes through verbatim.
+ */
+export type InjectFace<I extends object> =
+  I extends { hooks: infer HS extends HooksSources } ? Omit<I, 'hooks'> & PropsHooks<HS> : I
+
 /**
  * The four-share component props intersection: runtime share (SlotMap) +
  * child-render share (children declaration) + store share (declared handle) +
- * the registrant's injected business face. Each share derives from its single
- * source of truth; components reference this composition, never re-type it.
+ * the registrant's injected business face (its hooks compartment bound, see
+ * {@link InjectFace}). Each share derives from its single source of truth;
+ * components reference this composition, never re-type it.
  */
 export type ComposedProps<
   K extends keyof SlotMap & string,
@@ -226,7 +256,7 @@ export type ComposedProps<
   H,
   I extends object,
   M = never,
-> = PropsRuntime<K> & PropsRenderSlots<S> & PropsStore<H> & I & MatchedShare<SlotMap[K], M>
+> = PropsRuntime<K> & PropsRenderSlots<S> & PropsStore<H> & InjectFace<I> & MatchedShare<SlotMap[K], M>
 
 /**
  * Inject factory parameter list, derived from the registration's declaration:

packages/client/web-react/src/scoped-slots.tsx

@@ -5,8 +5,8 @@
 import { Component, useSyncExternalStore, type FC, type ReactNode } from 'react'
 import {
   SlotOwnershipError, StaleAuthorizationError,
-  type ChainRenderOpts, type RenderOpts, type SessionMaybeProvideInfo, type SessionProvideInfo,
-  type SlotRenderer, type SlotRendererHost, type SlotScope, type StoredEntry,
+  type ChainRenderOpts, type HostObservable, type RenderOpts, type SessionMaybeProvideInfo,
+  type SessionProvideInfo, type SlotRenderer, type SlotRendererHost, type SlotScope, type StoredEntry,
 } from '@deepseek-ai/dsh-client-ui-slots'
 import {
   HostContext, SessionMaybeProvider, SessionProvider, SlotAssemblyError, maybeObservableHook,
@@ -96,7 +96,26 @@ function runInject(entry: StoredEntry, info: SessionMaybeProvideInfo | undefined
   const args: unknown[] = []
   if (info !== undefined) args.push(info.sessionId)
   if (actions !== undefined) args.push(actions)
-  return (inject as (...args: unknown[]) => InjectedProps)(...args)
+  return bindInjectHooks((inject as (...args: unknown[]) => InjectedProps)(...args))
+}
+
+/**
+ * Bind an inject face's reserved `hooks` compartment (bare observable
+ * sources, see HooksSources) into `use<Name>` selector hooks — the
+ * registrant-private twin of the provide-bundle binding in standardKit.
+ * Runs once per cached inject result; hook identity rides observableHook's
+ * per-source cache.
+ */
+function bindInjectHooks(face: InjectedProps): InjectedProps {
+  const sources = face['hooks']
+  if (sources === undefined) return face
+  const { hooks: _hooks, ...rest } = face
+  const bound: InjectedProps = rest
+  for (const [name, source] of Object.entries(sources as Record<string, HostObservable<unknown>>)) {
+    const hookName = `use${name[0]?.toUpperCase() ?? ''}${name.slice(1)}`
+    bound[hookName] = observableHook(source)
+  }
+  return bound
 }
 
 function cachedRootInject(entry: StoredEntry, actions: object | undefined): InjectedProps {

packages/client/web-react/tests/scoped-slots.spec.tsx

@@ -748,6 +748,25 @@ describe('inject: execution point, parameter derivation, cache granularity', ()
     expect(inject).toHaveBeenCalledWith()
   })
 
+  it('binds the inject hooks compartment into use<Name> selector hooks (sources never reach the component)', () => {
+    const h = makeHost()
+    h.declare('k.single', SINGLE_ROOT)
+    const badge = observable('cold')
+    const seen: Record<string, unknown>[] = []
+    h.add('k.single', {
+      component: (props: { useBadge?: <S>(sel: (s: string) => S) => S; hooks?: unknown; plain?: string }) => {
+        seen.push({ hooks: props.hooks, plain: props.plain, read: props.useBadge!(s => s) })
+        return null
+      },
+      inject: () => ({ plain: 'kept', hooks: { badge } }),
+    })
+    mountRoot(h, { 'k.single': SINGLE_ROOT }, renderSlot => renderSlot('k.single', {}))
+    // The raw compartment is consumed by the binding; the plain member passes through.
+    expect(seen.at(-1)).toEqual({ hooks: undefined, plain: 'kept', read: 'cold' })
+    act(() => { badge.set('hot') })
+    expect(seen.at(-1)!['read']).toBe('hot')
+  })
+
   it('session inject receives sessionId and caches per (entry x session): switch-back reuses', () => {
     const h = makeHost()
     h.declare('k.session', SINGLE_SESSION)