diff --git a/packages/client/ui-tool/src/client/apply.ts b/packages/client/ui-tool/src/client/apply.ts
index a226c5116b..a2cc912d0d 100644
--- a/packages/client/ui-tool/src/client/apply.ts
+++ b/packages/client/ui-tool/src/client/apply.ts
@@ -1,5 +1,5 @@
 /** Register the Tool call tree, details renderer, and built-in atomic views. */
-import type { ConnectionHandle, HostDescriptionSource } from '@deepseek-ai/dsh-client-connection/client'
+import type { ConnectionHandle } from '@deepseek-ai/dsh-client-connection/client'
 import type { ClientContext } from '@deepseek-ai/dsh-client-runtime/client'
 import type {} from '@deepseek-ai/dsh-client-ui-conversation/client'
 import { ToolCallTree } from './tool/ToolCallTree.tsx'
@@ -16,19 +16,13 @@ import { webToolview } from './tool/toolviews/web-row.tsx'
 /** Required services: the slot registry and the Host description used for POSIX `~`. */
 export const inject = ['slots', 'connection']
 
-const absentHostDescription: HostDescriptionSource = {
-  getSnapshot: () => undefined,
-  subscribe: () => () => {},
-}
-
 /**
  * Mount the whole-Tool renderers and built-in atomic Tool registrations.
  * @param ctx - Client root context.
  */
 export function apply(ctx: ClientContext): void {
   const connection = ctx.get('connection') as ConnectionHandle
-  const hostDescription = connection.hostDescription ?? absentHostDescription
-  const toolInject = () => ({ hooks: { hostDescription } })
+  const toolInject = () => ({ hooks: { hostDescription: connection.hostDescription } })
   ctx.slots.inject('conversation.chat.node', () => ctx.slots.register({
     name: 'conversation.chat.node',
     key: 'tool-call',
diff --git a/packages/client/ui-tool/tests/assembly-surfaces.client.spec.tsx b/packages/client/ui-tool/tests/assembly-surfaces.client.spec.tsx
index 501d4c27b9..44a820a110 100644
--- a/packages/client/ui-tool/tests/assembly-surfaces.client.spec.tsx
+++ b/packages/client/ui-tool/tests/assembly-surfaces.client.spec.tsx
@@ -68,7 +68,11 @@ const LAYOUT_CHILDREN = {
 
 async function bench(nodes: ToolResultNode[]) {
   const runtime = await SlotTestRuntime.create()
-  runtime.provide('connection', { api: { settings: {} }, isLoopback: false })
+  runtime.provide('connection', {
+    api: { settings: {} },
+    isLoopback: false,
+    hostDescription: { getSnapshot: () => undefined, subscribe: () => () => {} },
+  })
   // ui-theme's Appearance row binds a durable scope through these two.
   runtime.provide('remote', { $on: () => () => {} })
   runtime.provide('settingsScope', { bind: () => stubSettingsScope().scope } as never)
diff --git a/packages/client/ui-tool/tests/chat-code-subcalls.client.spec.tsx b/packages/client/ui-tool/tests/chat-code-subcalls.client.spec.tsx
index cb4325a09e..d73c09013c 100644
--- a/packages/client/ui-tool/tests/chat-code-subcalls.client.spec.tsx
+++ b/packages/client/ui-tool/tests/chat-code-subcalls.client.spec.tsx
@@ -158,7 +158,11 @@ async function bench(snapshot: ConversationSnapshot) {
   }
   ctx.provide('workspaces', workspaces)
   ctx.provide('layout', layout)
-  ctx.provide('connection', { api: { settings: {} }, isLoopback: false } as never)
+  ctx.provide('connection', {
+    api: { settings: {} },
+    isLoopback: false,
+    hostDescription: { getSnapshot: () => undefined, subscribe: () => () => {} },
+  } as never)
   // ui-theme's Appearance row binds a durable scope through these two.
   ctx.provide('remote', { $on: () => () => {} } as never)
   ctx.provide('settingsScope', { bind: () => stubSettingsScope().scope } as never)
diff --git a/packages/client/ui-tool/tests/tool-details-render.client.tsx b/packages/client/ui-tool/tests/tool-details-render.client.tsx
index 5e70747b98..7d3ffefe7c 100644
--- a/packages/client/ui-tool/tests/tool-details-render.client.tsx
+++ b/packages/client/ui-tool/tests/tool-details-render.client.tsx
@@ -4,7 +4,6 @@ import type {
 } from '@deepseek-ai/dsh-client-runtime/client'
 import type { SessionProviderComponent, TranslateNS } from '@deepseek-ai/dsh-client-ui-slots'
 import type { DetailsSlotProps, DetailsToolOwnerProps } from '@deepseek-ai/dsh-client-ui-conversation/src/client/contract/slots.ts'
-import type { ToolDetailsProps } from '../src/client/contract/slots.ts'
 import { ToolDetails } from '../src/client/tool/ToolDetails.tsx'
 
 /** Framework session-area seat used by direct DetailsPanel tests. */
@@ -62,7 +61,7 @@ export function renderToolDetails(t: TranslateNS<'conversation'>): DetailsSlotPr
     return <ToolDetails
       block={details.block}
       cwd={details.cwd}
-      useHostDescription={(selector => selector(undefined)) as ToolDetailsProps['useHostDescription']}
+      useHostDescription={selector => selector(undefined)}
       t={t}
     />
   }
diff --git a/packages/client/ui-tool/tests/toolview-slot.client.spec.tsx b/packages/client/ui-tool/tests/toolview-slot.client.spec.tsx
index 09ec2f0d3f..bdfba88345 100644
--- a/packages/client/ui-tool/tests/toolview-slot.client.spec.tsx
+++ b/packages/client/ui-tool/tests/toolview-slot.client.spec.tsx
@@ -64,7 +64,11 @@ const LAYOUT_CHILDREN = {
  */
 async function bench(nodes: ToolResultNode[]) {
   const runtime = await SlotTestRuntime.create()
-  runtime.provide('connection', { api: { settings: {} }, isLoopback: false })
+  runtime.provide('connection', {
+    api: { settings: {} },
+    isLoopback: false,
+    hostDescription: { getSnapshot: () => undefined, subscribe: () => () => {} },
+  })
   // ui-theme's Appearance row binds a durable scope through these two.
   runtime.provide('remote', { $on: () => () => {} })
   runtime.provide('settingsScope', { bind: () => stubSettingsScope().scope } as never)
@@ -203,7 +207,11 @@ describe('keyed toolview hole through the real machinery', () => {
 describe('registrant declaration injection', () => {
   it('runs a registrant before ui-tool and waits on the actual toolview declaration', async () => {
     const runtime = await SlotTestRuntime.create()
-    runtime.provide('connection', { api: { settings: {} }, isLoopback: false })
+    runtime.provide('connection', {
+      api: { settings: {} },
+      isLoopback: false,
+      hostDescription: { getSnapshot: () => undefined, subscribe: () => () => {} },
+    })
     // ui-theme's Appearance row binds a durable scope through these two.
     runtime.provide('remote', { $on: () => () => {} })
     runtime.provide('settingsScope', { bind: () => stubSettingsScope().scope } as never)
diff --git a/packages/client/ui-workspace/src/client/index.ts b/packages/client/ui-workspace/src/client/index.ts
index b149121fff..93269c22c1 100644
--- a/packages/client/ui-workspace/src/client/index.ts
+++ b/packages/client/ui-workspace/src/client/index.ts
@@ -8,7 +8,7 @@
  * client half (see the contract module doc). Export discipline:
  * packages/client/AGENTS.md.
  */
-import type { ConnectionHandle, HostDescriptionSource } from '@deepseek-ai/dsh-client-connection/client'
+import type { ConnectionHandle } from '@deepseek-ai/dsh-client-connection/client'
 import type { HostObservable } from '@deepseek-ai/dsh-client-ui-slots'
 import type { ClientContext } from '@deepseek-ai/dsh-client-runtime/client'
 // Type-only: pulls the locale plugin's Context merge (ctx.locale).
@@ -45,11 +45,6 @@ const NS = 'workspace'
  */
 export const inject = ['slots', 'sessions', 'workspaces', 'locale', 'connection']
 
-const absentHostDescription: HostDescriptionSource = {
-  getSnapshot: () => undefined,
-  subscribe: () => () => {},
-}
-
 /**
  * Register the browser and picker once their slot declarations are on the
  * ledger. Inject factories return plain callbacks; data reads use the
@@ -58,7 +53,7 @@ const absentHostDescription: HostDescriptionSource = {
  */
 export function apply(ctx: ClientContext): void {
   const connection = ctx.get('connection') as ConnectionHandle
-  const hostDescription = connection.hostDescription ?? absentHostDescription
+  const hostDescription = connection.hostDescription
   ctx.effect(() => ctx.locale.register(NS, { zh, en }), 'ui-workspace: dictionaries')
 
   const searchSessions: WorkspaceBrowserInjected['searchSessions'] = async (query, signal) => {
diff --git a/packages/client/ui-workspace/tests/rename-assembly.client.spec.tsx b/packages/client/ui-workspace/tests/rename-assembly.client.spec.tsx
index 5359678050..c2e201469f 100644
--- a/packages/client/ui-workspace/tests/rename-assembly.client.spec.tsx
+++ b/packages/client/ui-workspace/tests/rename-assembly.client.spec.tsx
@@ -33,7 +33,7 @@ async function createRuntime(): Promise<SlotTestRuntime> {
   const runtime = await SlotTestRuntime.create()
   runtime.provide('connection', {
     hostDescription: { getSnapshot: () => undefined, subscribe: () => () => {} },
-  } as never)
+  })
   const locale = new LocaleRuntime(runtime.ctx)
   runtime.provide('locale', locale)
   runtime.slots.installLocale(locale)