Adapt session model selection to the slash/input/session architecture

- host trio kept on the merged api-proxy: session.models (provider-grouped advisory directory), session.selectModel (validated provider, advisory model), installAgentLlmTarget threaded through create/resume/ensureSession; the gateway declares the llm inject it reads - history no longer piggybacks modelTarget: the current target travels on session.models alone (the /model popup is the sole consumer) - new @deepseek-ai/dsh-client-ui-model plugin: /model popupSelect over the wire — options load the directory (group label in the detail column, provider-local failures listed inline), onSelect routes selectModel; failures ride the popup shell's error/retry surface - ModelSelector package, conversation.composer.control slot, and the Session-side modelSelection state machine are removed: model selection belongs to the /model popup; the named conversation.input.model seat stays empty until a control-seat entry is designed for it
2026-08-15 21:04:50 +00:00 · 2026-07-27 10:28:45 +08:00
parent 6539c8d8fa
commit c132cbdb6a
27 changed files with 564 additions and 193 deletions
--- a/apps/cli/cordis.yml
+++ b/apps/cli/cordis.yml
@@ -300,6 +300,10 @@
 - id: ui-subagent
  name: '@deepseek-ai/dsh-client-ui-subagent'

+# Model selection: the /model popupSelect over session.models / selectModel.
+- id: ui-model
+  name: '@deepseek-ai/dsh-client-ui-model'
+
 - id: ui-question
  name: '@deepseek-ai/dsh-client-ui-question'

--- a/apps/cli/package.json
+++ b/apps/cli/package.json
@@ -29,6 +29,7 @@
    "@deepseek-ai/dsh-client-ui-command": "workspace:^",
    "@deepseek-ai/dsh-client-ui-conversation": "workspace:^",
    "@deepseek-ai/dsh-client-ui-layout": "workspace:^",
+    "@deepseek-ai/dsh-client-ui-model": "workspace:^",
    "@deepseek-ai/dsh-client-ui-models": "workspace:^",
    "@deepseek-ai/dsh-client-ui-question": "workspace:^",
    "@deepseek-ai/dsh-client-ui-settings": "workspace:^",
--- a/packages/client/connection/src/client/api.ts
+++ b/packages/client/connection/src/client/api.ts
@@ -10,6 +10,7 @@ export type {
  ApprovalResponsePayload, QuestionResponsePayload, HistoryEntry, ToolEventView,
  WorkspaceApi, WorkspaceId, WorkspaceView,
  CommandsApi, CommandDescriptor, CommandExecuteResult, SkillsApi, SkillEntry,
+  ModelCatalogFailure, ModelCatalogModel, ModelProviderGroup, ModelTarget, SessionModels,
 } from '@deepseek-ai/dsh-host-apiproxy/api'
 export type { ToolCallView, ToolResultView } from '@deepseek-ai/dsh-tools/presentation'
 export type {
--- a/packages/client/connection/src/client/fixture.ts
+++ b/packages/client/connection/src/client/fixture.ts
@@ -9,7 +9,7 @@ import type { ContentBlock } from '@deepseek-ai/dsh-llm/types'
 import type { SessionEvent, SessionId } from '@deepseek-ai/dsh-session/types'
 import type {
  ApiProxy, ClientRequest, ClientResponse, HistoryEntry, HostFrame, MuxFrame, RpcReceipt,
-  RpcRequest, RpcResponse, RpcResult, ServerRequest, ServerResponse, SessionSummary,
+  ModelTarget, RpcRequest, RpcResponse, RpcResult, ServerRequest, ServerResponse, SessionSummary,
  ToolCallView, ToolEventView, ToolResultView, WorkspaceId, WorkspaceView,
 } from './api.ts'
 import type { RequestPayload, ResponseValue, RpcMethodMap } from '@deepseek-ai/dsh-host-apiproxy/api'
@@ -354,6 +354,10 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
    { sessionId: sid('fx-gamma'), updatedAt: Date.now() - 120_000, running: false, blank: false, cwd: '/tmp/fixture' },
  ]
  const logs = new Map<SessionId, SessionEvent[]>([[sid('fx-alpha'), buildAlphaLog()]])
+  const modelTargets = new Map<SessionId, ModelTarget>(sessions.map(session => [
+    session.sessionId,
+    { provider: 'deepseek', model: 'deepseek-v4-flash' },
+  ]))
  const nextTurn = new Map<SessionId, number>([[sid('fx-alpha'), 60]])
  let nextSession = 1
  let nextRpc = 1
@@ -596,6 +600,7 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
          sessionId: requestedId ?? sid(`fx-${nextSession++}`), updatedAt: Date.now(), running: false, blank: true, cwd,
        }
        sessions.push(created)
+        modelTargets.set(created.sessionId, { provider: 'deepseek', model: 'deepseek-v4-flash' })
        attachedSessions += 1
        const emitSession = (): void => {
          // Mirrors the host: the frame fires at creation, so blank is constantly true.
@@ -624,7 +629,32 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
        const delay = historyDelayMs
        if (delay > 0) await new Promise(resolve => setTimeout(resolve, delay))
        if (doomed) throw new Error('fixture: simulated history transport failure')
-        return ok(request, page)
+        return ok(request, { ...page })
+      },
+      models: request => ok(request, {
+        current: modelTargets.get(request.payload.sessionId)
+          ?? { provider: 'deepseek', model: 'deepseek-v4-flash' },
+        groups: [
+          {
+            id: 'deepseek',
+            name: 'DeepSeek',
+            models: [
+              { id: 'deepseek-v4-flash', name: 'DeepSeek-V4-Flash', description: '快速响应' },
+              { id: 'deepseek-v4-pro', name: 'DeepSeek-V4-Pro', description: '复杂任务' },
+            ],
+          },
+          {
+            id: 'openai',
+            name: 'OpenAI',
+            models: [{ id: 'gpt-5', name: 'GPT-5' }],
+          },
+        ],
+        failures: [],
+      }),
+      selectModel: (request) => {
+        const selected = { provider: request.payload.provider, model: request.payload.model }
+        modelTargets.set(request.payload.sessionId, selected)
+        return ok(request, { selected })
      },
      prompt: (request) => {
        const { sessionId: id, mode, content } = request.payload
@@ -660,7 +690,9 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
          turn,
          userText === 'render markdown'
            ? MARKDOWN_FIXTURE
-            : `回声：${userText}。这是 fixture 的流式回复，用于验证打字机增长与定稿切换。`,
+            : userText === 'report model'
+              ? `当前模型：${modelTargets.get(id)?.provider ?? 'unknown'}/${modelTargets.get(id)?.model ?? 'unknown'}`
+              : `回声：${userText}。这是 fixture 的流式回复，用于验证打字机增长与定稿切换。`,
        )
        return ok(request, { accepted: true as const })
      },
@@ -908,6 +940,8 @@ export class FixtureApiClient extends AbstractApiClient {
      case 'session.list': return this.api.sessions.list(request)
      case 'session.create': return this.api.sessions.create(request)
      case 'session.history': return this.api.sessions.history(request)
+      case 'session.models': return this.api.sessions.models(request)
+      case 'session.selectModel': return this.api.sessions.selectModel(request)
      case 'session.prompt': return this.api.sessions.prompt(request)
      case 'session.cancel': return this.api.sessions.cancel(request)
      case 'host.describe': return this.api.host.describe(request)
--- a/packages/client/connection/src/client/index.ts
+++ b/packages/client/connection/src/client/index.ts
@@ -15,6 +15,7 @@ export type {
  ApprovalResponsePayload, QuestionResponsePayload, HistoryEntry, ToolEventView,
  ToolCallView, ToolResultView, WorkspaceApi, WorkspaceId, WorkspaceView,
  CommandsApi, CommandDescriptor, CommandExecuteResult, SkillsApi, SkillEntry,
+  ModelCatalogFailure, ModelCatalogModel, ModelProviderGroup, ModelTarget, SessionModels,
  RpcRequest, RpcResponse, RpcResult, RpcError, RpcErrorCode,
  ClientRequest, ServerResponse, ServerRequest, ClientResponse, RpcMessage, RpcReceipt,
  IApiClient, SessionId, SessionEvent, ContentBlock, StreamChunk,
--- a/packages/client/connection/tests/fake-api.ts
+++ b/packages/client/connection/tests/fake-api.ts
@@ -2,8 +2,8 @@
 // data source on a real clock; behavior tests need per-case responses and
 // deferred-controlled timing). Streams are hand pumps: pushMux/pushHost.
 import type {
-  CommandDescriptor, CommandExecuteResult, HostFrame, IApiClient, MuxFrame,
-  RpcRequest, RpcResponse, SessionId, SkillEntry,
+  CommandDescriptor, CommandExecuteResult, HostFrame, IApiClient, ModelTarget, MuxFrame,
+  RpcRequest, RpcResponse, SessionId, SessionModels, SkillEntry,
 } from '../src/client/api.ts'
 import { RpcId } from '../src/client/api.ts'

@@ -45,9 +45,21 @@ export class FakeApiClient implements IApiClient {
  onList: (payload: unknown) => Promise<RpcResponse<{ items: never[] }>> = () => Promise.resolve(ok({ items: [] }))
  onCreate: (payload: unknown) => Promise<RpcResponse<{ sessionId: SessionId }>> = () => Promise.resolve(ok({ sessionId: 'fk-new' as SessionId }))
  onHistory: (payload: { sessionId: SessionId; beforeSeq?: number; maxMessages?: number })
-  => Promise<RpcResponse<{ events: never[]; hasMore: boolean }>> =
-    () => Promise.resolve(ok({ events: [], hasMore: false }))
+  => Promise<RpcResponse<{ events: never[]; hasMore: boolean; modelTarget: ModelTarget }>> =
+    () => Promise.resolve(ok({
+      events: [],
+      hasMore: false,
+      modelTarget: { provider: 'deepseek', model: 'deepseek-chat' },
+    }))

+  onModels: (payload: unknown) => Promise<RpcResponse<SessionModels>> = () => Promise.resolve(ok({
+    current: { provider: 'deepseek', model: 'deepseek-chat' },
+    groups: [],
+    failures: [],
+  }))
+  onSelectModel: (payload: ModelTarget & { sessionId: SessionId })
+  => Promise<RpcResponse<{ selected: ModelTarget }>> =
+    payload => Promise.resolve(ok({ selected: { provider: payload.provider, model: payload.model } }))
  onPrompt: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onCancel: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onDescribe: (payload: unknown) => Promise<RpcResponse<{ version: string; cwd: string; attachedSessions: number }>> =
@@ -64,6 +76,9 @@ export class FakeApiClient implements IApiClient {
    create: (payload: unknown) => this.record('session.create', payload, this.onCreate(payload)),
    history: (payload: { sessionId: SessionId; beforeSeq?: number; maxMessages?: number }) =>
      this.record('session.history', payload, this.onHistory(payload)),
+    models: (payload: unknown) => this.record('session.models', payload, this.onModels(payload)),
+    selectModel: (payload: ModelTarget & { sessionId: SessionId }) =>
+      this.record('session.selectModel', payload, this.onSelectModel(payload)),
    prompt: (payload: unknown) => this.record('session.prompt', payload, this.onPrompt(payload)),
    cancel: (payload: unknown) => this.record('session.cancel', payload, this.onCancel(payload)),
  }
@@ -88,12 +103,9 @@ export class FakeApiClient implements IApiClient {

  // Payloads stay `unknown` (lint-lane note above); response rows are the real
  // wire shapes so cases can program catalogs and skill lists without casts.
-  onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>>
-    = () => Promise.resolve(ok({ commands: [] }))
-  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>>
-    = () => Promise.resolve(ok({ matched: false }))
-  onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>>
-    = () => Promise.resolve(ok({ skills: [] }))
+  onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>> = () => Promise.resolve(ok({ commands: [] }))
+  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>> = () => Promise.resolve(ok({ matched: false }))
+  onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>> = () => Promise.resolve(ok({ skills: [] }))

  readonly commands: IApiClient['commands'] = {
    list: (payload: unknown) => this.record('command.list', payload, this.onCommandList(payload)),
--- a/packages/client/connection/tests/fixture.spec.ts
+++ b/packages/client/connection/tests/fixture.spec.ts
@@ -71,7 +71,6 @@ describe('createFixtureApi', () => {
    expect(empty.result.value).toEqual({
      events: [],
      hasMore: false,
-      modelTarget: { provider: 'deepseek', model: 'deepseek-v4-flash' },
    })
  })

@@ -93,7 +92,6 @@ describe('createFixtureApi', () => {
    expect(selected.result.value.selected).toEqual({ provider: 'openai', model: 'gpt-5' })
    const history = await api.sessions.history(req({ sessionId }))
    if (!history.result.ok) throw new Error('history failed')
-    expect(history.result.value.modelTarget).toEqual({ provider: 'openai', model: 'gpt-5' })

    const prompt = await api.sessions.prompt(req({
      sessionId,
--- a/packages/client/runtime/tests/fake-api.ts
+++ b/packages/client/runtime/tests/fake-api.ts
@@ -2,8 +2,8 @@
 // data source on a real clock; behavior tests need per-case responses and
 // deferred-controlled timing). Streams are hand pumps: pushMux/pushHost.
 import type {
-  ClientResponse, CommandDescriptor, CommandExecuteResult, HostFrame, IApiClient, MuxFrame,
-  RpcError, RpcReceipt, RpcRequest, RpcResponse, SessionId, SkillEntry,
+  ClientResponse, CommandDescriptor, CommandExecuteResult, HostFrame, IApiClient, ModelTarget, MuxFrame,
+  RpcError, RpcReceipt, RpcRequest, RpcResponse, SessionId, SessionModels, SkillEntry,
  WorkspaceId, WorkspaceView,
 } from '@deepseek-ai/dsh-client-connection/client'
 import { RpcId } from '@deepseek-ai/dsh-client-connection/client'
@@ -61,10 +61,23 @@ export class FakeApiClient implements IApiClient {
  // Programmable slots (defaults answer OK-empty); reassign per case.
  onList: (payload: unknown) => Promise<RpcResponse<{ items: never[] }>> = () => Promise.resolve(ok({ items: [] }))
  onCreate: (payload: unknown) => Promise<RpcResponse<{ sessionId: SessionId }>> = () => Promise.resolve(ok({ sessionId: 'fk-new' as SessionId }))
+  readonly defaultModel: ModelTarget = { provider: 'deepseek', model: 'deepseek-v4-flash' }
  onHistory: (payload: { sessionId: SessionId; beforeSeq?: number; maxMessages?: number })
-  => Promise<RpcResponse<{ events: never[]; hasMore: boolean }>> =
-    () => Promise.resolve(ok({ events: [], hasMore: false }))
+  => Promise<RpcResponse<{ events: never[]; hasMore: boolean; modelTarget: ModelTarget }>> =
+    () => Promise.resolve(ok({ events: [], hasMore: false, modelTarget: this.defaultModel }))

+  onModels: (payload: unknown) => Promise<RpcResponse<SessionModels>> = () => Promise.resolve(ok({
+    current: this.defaultModel,
+    groups: [{
+      id: 'deepseek',
+      name: 'DeepSeek',
+      models: [{ id: 'deepseek-v4-flash', name: 'DeepSeek V4 Flash' }],
+    }],
+    failures: [],
+  }))
+  onSelectModel: (payload: { provider: string; model: string }) =>
+  Promise<RpcResponse<{ selected: ModelTarget }>> =
+    payload => Promise.resolve(ok({ selected: { provider: payload.provider, model: payload.model } }))
  onPrompt: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onCancel: (payload: unknown) => Promise<RpcResponse<{ accepted: true }>> = () => Promise.resolve(ok({ accepted: true as const }))
  onDescribe: (payload: unknown) => Promise<RpcResponse<{ version: string; cwd: string; attachedSessions: number }>> =
@@ -81,6 +94,9 @@ export class FakeApiClient implements IApiClient {
    create: (payload: unknown) => this.record('session.create', payload, this.onCreate(payload)),
    history: (payload: { sessionId: SessionId; beforeSeq?: number; maxMessages?: number }) =>
      this.record('session.history', payload, this.onHistory(payload)),
+    models: (payload: unknown) => this.record('session.models', payload, this.onModels(payload)),
+    selectModel: (payload: { provider: string; model: string }) =>
+      this.record('session.selectModel', payload, this.onSelectModel(payload)),
    prompt: (payload: unknown) => this.record('session.prompt', payload, this.onPrompt(payload)),
    cancel: (payload: unknown) => this.record('session.cancel', payload, this.onCancel(payload)),
  }
@@ -110,12 +126,9 @@ export class FakeApiClient implements IApiClient {
  // Payloads stay `unknown` (lint-lane note above); response rows are the real
  // wire shapes so cases can program requires-bearing catalogs and dual-address
  // skill lists without casts.
-  onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>>
-    = () => Promise.resolve(ok({ commands: [] }))
-  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>>
-    = () => Promise.resolve(ok({ matched: false }))
-  onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>>
-    = () => Promise.resolve(ok({ skills: [] }))
+  onCommandList: (payload: unknown) => Promise<RpcResponse<{ commands: CommandDescriptor[] }>> = () => Promise.resolve(ok({ commands: [] }))
+  onCommandExecute: (payload: unknown) => Promise<RpcResponse<{ matched: boolean; result?: CommandExecuteResult }>> = () => Promise.resolve(ok({ matched: false }))
+  onSkillList: (payload: unknown) => Promise<RpcResponse<{ skills: SkillEntry[] }>> = () => Promise.resolve(ok({ skills: [] }))

  readonly commands: IApiClient['commands'] = {
    list: (payload: unknown) => this.record('command.list', payload, this.onCommandList(payload)),
--- a/packages/client/runtime/tests/session.spec.ts
+++ b/packages/client/runtime/tests/session.spec.ts
@@ -91,164 +91,6 @@ describe('open', () => {
  })
 })

-describe('model selection', () => {
-  it('restores the current target from history, then refreshes grouped models with partial failures', async () => {
-    const { api, session } = makeSession()
-    api.onHistory = () => histResponse([])
-    api.onModels = () => Promise.resolve(ok({
-      current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
-      groups: [{
-        id: 'deepseek',
-        name: 'DeepSeek',
-        models: [{ id: 'deepseek-v4-flash', name: 'DeepSeek V4 Flash' }],
-      }],
-      failures: [{ id: 'offline', name: 'Offline', message: 'catalog down' }],
-    }))
-    await session.open()
-    expect(session.getSnapshot().modelSelection).toEqual({
-      current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
-      groups: [],
-      failures: [],
-      status: 'idle',
-      error: null,
-    })
-
-    const refreshing = session.refreshModels()
-    expect(session.getSnapshot().modelSelection.status).toBe('loading')
-    await refreshing
-    expect(session.getSnapshot().modelSelection).toEqual({
-      current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
-      groups: [{
-        id: 'deepseek',
-        name: 'DeepSeek',
-        models: [{ id: 'deepseek-v4-flash', name: 'DeepSeek V4 Flash' }],
-      }],
-      failures: [{ id: 'offline', name: 'Offline', message: 'catalog down' }],
-      status: 'ready',
-      error: null,
-    })
-  })
-
-  it('keeps the previous target and directory when selection fails, then accepts a retry', async () => {
-    const { api, session } = makeSession()
-    await session.open()
-    await session.refreshModels()
-    const before = session.getSnapshot().modelSelection
-    api.onSelectModel = () => Promise.resolve(err({
-      code: 'model-unavailable',
-      message: 'gone',
-      details: { provider: 'deepseek', model: 'deepseek-v4-pro' },
-    }))
-
-    const failed = session.selectModel({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-    expect(session.getSnapshot().modelSelection.status).toBe('selecting')
-    await failed
-    const errored = session.getSnapshot().modelSelection
-    expect(errored.current).toBe(before.current)
-    expect(errored.groups).toBe(before.groups)
-    expect(errored).toMatchObject({ status: 'error', error: { code: 'model-unavailable' } })
-
-    api.onSelectModel = payload => Promise.resolve(ok({
-      selected: { provider: payload.provider, model: payload.model },
-    }))
-    await session.retryModelOperation()
-    expect(api.callsOf('session.selectModel').at(-1)).toEqual({
-      sessionId: SID,
-      provider: 'deepseek',
-      model: 'deepseek-v4-pro',
-    })
-    expect(session.getSnapshot().modelSelection).toMatchObject({
-      current: { provider: 'deepseek', model: 'deepseek-v4-pro' },
-      status: 'ready',
-      error: null,
-    })
-  })
-
-  it('drops stale directory responses after a newer selection operation wins', async () => {
-    const { api, session } = makeSession()
-    await session.open()
-    const stale = deferred<Awaited<ReturnType<FakeApiClient['onModels']>>>()
-    api.onModels = () => stale.promise
-    const refreshing = session.refreshModels()
-    await session.selectModel({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-    const selected = session.getSnapshot().modelSelection
-
-    stale.resolve(ok({
-      current: { provider: 'deepseek', model: 'stale' },
-      groups: [{ id: 'deepseek', name: 'Old', models: [{ id: 'stale', name: 'Stale' }] }],
-      failures: [],
-    }))
-    await refreshing
-    expect(session.getSnapshot().modelSelection).toBe(selected)
-    expect(session.getSnapshot().modelSelection.current)
-      .toEqual({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-  })
-
-  it('does not let an older history response overwrite a newer selected target', async () => {
-    const { api, session } = makeSession()
-    const history = deferred<Awaited<ReturnType<FakeApiClient['onHistory']>>>()
-    api.onHistory = () => history.promise
-    const opening = session.open()
-    await session.selectModel({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-    history.resolve(ok({
-      events: [],
-      hasMore: false,
-      modelTarget: { provider: 'deepseek', model: 'deepseek-v4-flash' },
-    }))
-    await opening
-    expect(session.getSnapshot().modelSelection.current)
-      .toEqual({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-  })
-
-  it('folds directory and selection transport failures without discarding usable state', async () => {
-    const { api, session } = makeSession()
-    await session.open()
-    await session.refreshModels()
-    const groups = session.getSnapshot().modelSelection.groups
-    api.onModels = () => Promise.reject(new Error('directory transport down'))
-    await session.refreshModels()
-    expect(session.getSnapshot().modelSelection).toMatchObject({
-      groups,
-      status: 'error',
-      error: { code: 'internal', message: 'directory transport down' },
-    })
-    api.onModels = () => Promise.resolve(ok({
-      current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
-      groups: [...groups],
-      failures: [],
-    }))
-    await session.retryModelOperation()
-    expect(session.getSnapshot().modelSelection.status).toBe('ready')
-
-    api.onSelectModel = () => Promise.reject(new Error('selection transport down'))
-    await session.selectModel({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-    expect(session.getSnapshot().modelSelection).toMatchObject({
-      current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
-      groups,
-      status: 'error',
-      error: { code: 'internal', message: 'selection transport down' },
-    })
-  })
-
-  it('reconciles a failed selection from authoritative history on reconnect', async () => {
-    const { api, session } = makeSession()
-    await session.open()
-    api.onSelectModel = () => Promise.reject(new Error('lost response'))
-    await session.selectModel({ provider: 'deepseek', model: 'deepseek-v4-pro' })
-    expect(session.getSnapshot().modelSelection.status).toBe('error')
-    api.onHistory = () => Promise.resolve(ok({
-      events: [],
-      hasMore: false,
-      modelTarget: { provider: 'deepseek', model: 'deepseek-v4-pro' },
-    }))
-    await session.resync()
-    expect(session.getSnapshot().modelSelection).toMatchObject({
-      current: { provider: 'deepseek', model: 'deepseek-v4-pro' },
-      status: 'idle',
-      error: null,
-    })
-  })
-})

 describe('live event path', () => {
  async function opened(events: SessionEvent[] = plainTurn(0, 0, 'a', 'b')) {
@@ -949,7 +791,6 @@ describe('reference stability (the memo contract)', () => {
    expect(after).not.toBe(before)
    expect(after.runningCalls).toBe(before.runningCalls)
    expect(after.pending).toBe(before.pending)
-    expect(after.modelSelection).toBe(before.modelSelection)
    // And a mutation on the tracked domain swaps that array.
    feed(ev.toolResult(10, 1, 'c1', 'ECHO'))
    const resolved = session.getSnapshot()
--- a/packages/client/ui-model/package.json
+++ b/packages/client/ui-model/package.json
@@ -0,0 +1,61 @@
+{
+  "name": "@deepseek-ai/dsh-client-ui-model",
+  "description": "Model selection: the /model popupSelect over session.models / session.selectModel",
+  "version": "0.0.1",
+  "private": true,
+  "type": "module",
+  "main": "lib/index.js",
+  "types": "lib/types/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./lib/types/index.d.ts",
+      "default": "./lib/index.js"
+    },
+    "./invariant": {
+      "types": "./lib/types/invariant.d.ts",
+      "default": "./lib/invariant.js"
+    },
+    "./client": {
+      "types": "./lib/types/client/index.d.ts",
+      "default": "./lib/client.js"
+    },
+    "./src/*": "./src/*",
+    "./package.json": "./package.json"
+  },
+  "dshClient": {
+    "inject": [
+      "@deepseek-ai/dsh-client-runtime",
+      "@deepseek-ai/dsh-client-ui-command"
+    ],
+    "platform": "web"
+  },
+  "scripts": {
+    "bundle": "tsdown",
+    "watch": "tsdown --watch"
+  },
+  "license": "BSD-3-Clause",
+  "peerDependencies": {
+    "@deepseek-ai/dsh-client-connection": "^0.0.1",
+    "@deepseek-ai/dsh-client-runtime": "^0.0.1",
+    "@deepseek-ai/dsh-client-ui-command": "^0.0.1",
+    "@deepseek-ai/dsh-client-ui-slash": "^0.0.1",
+    "@deepseek-ai/dsh-invariants": "^0.0.1",
+    "cordis": "^4.0.0-rc.7"
+  },
+  "devDependencies": {
+    "@deepseek-ai/dsh-client-connection": "workspace:^",
+    "@deepseek-ai/dsh-client-runtime": "workspace:^",
+    "@deepseek-ai/dsh-client-ui-command": "workspace:^",
+    "@deepseek-ai/dsh-client-ui-slash": "workspace:^",
+    "@deepseek-ai/dsh-invariants": "workspace:^",
+    "cordis": "^4.0.0-rc.7"
+  },
+  "files": [
+    "lib/index.js",
+    "lib/invariant.js",
+    "lib/client.js",
+    "lib/types/**/*.d.ts",
+    "lib/types/**/*.d.ts.map",
+    "src"
+  ]
+}
--- a/packages/client/ui-model/src/client/index.ts
+++ b/packages/client/ui-model/src/client/index.ts
--- a/packages/client/ui-model/src/css-modules.d.ts
+++ b/packages/client/ui-model/src/css-modules.d.ts
@@ -0,0 +1,6 @@
+declare module '*.module.css' {
+  const classes: Record<string, string>
+  export default classes
+}
+
+declare module '*.css'
--- a/packages/client/ui-model/src/index.ts
+++ b/packages/client/ui-model/src/index.ts
@@ -0,0 +1,9 @@
+/**
+ * Model selection plugin, node half. Pure UI plugin: the empty apply exists
+ * so the plugin appears in the host cordis.yml / Loader; the browser half
+ * ships via exports["./client"], discovered through the package.json
+ * dshClient declaration.
+ */
+
+/** Host plugin body — no host-side behavior for this surface plugin. */
+export function apply(): void {}
--- a/packages/client/ui-model/src/invariant.ts
+++ b/packages/client/ui-model/src/invariant.ts
@@ -0,0 +1,31 @@
+/**
+ * Package-owned invariant companion for `@deepseek-ai/dsh-client-ui-model`.
+ * @module @deepseek-ai/dsh-client-ui-model/invariant
+ */
+
+/* jscpd:ignore-start */
+import type { Context } from 'cordis'
+import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-client-ui-model'
+
+/** Cordis companion plugin name. */
+export const name = 'client-ui-model-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+/**
+ * No runtime invariant: a single command contribution registration whose disposal is
+ * proven by the HMR-safety spec — it emits no cordis events and owns no
+ * cross-plugin mutable state.
+ */
+const install: InvariantInstaller = () => {}
+
+/**
+ * Register this package's invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))
+/* jscpd:ignore-end */
--- a/packages/client/ui-model/tsconfig.json
+++ b/packages/client/ui-model/tsconfig.json
@@ -0,0 +1,30 @@
+{
+  "extends": "../../../tsconfig.base.client.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "lib/types"
+  },
+  "include": [
+    "src"
+  ],
+  "references": [
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../connection"
+    },
+    {
+      "path": "../runtime"
+    },
+    {
+      "path": "../ui-command"
+    },
+    {
+      "path": "../ui-slash"
+    },
+    {
+      "path": "../../support/invariants"
+    }
+  ]
+}
--- a/packages/client/ui-model/tsdown.config.ts
+++ b/packages/client/ui-model/tsdown.config.ts
@@ -0,0 +1,3 @@
+import { clientBundle } from '../tsdown.client.ts'
+
+export default clientBundle('@deepseek-ai/dsh-client-ui-model', ['lib/types/index.js', 'lib/types/invariant.js'])
--- a/packages/host/apiproxy/src/api-proxy.ts
+++ b/packages/host/apiproxy/src/api-proxy.ts
@@ -7,7 +7,8 @@ import { randomUUID } from 'node:crypto'
 import { mkdir, stat } from 'node:fs/promises'
 import { join } from 'node:path'
 import type { Context } from 'cordis'
-import type { Agent, AgentMessage, AgentMessageId, AgentStatus } from '@deepseek-ai/dsh-agent'
+import { installAgentLlmTarget } from '@deepseek-ai/dsh-agent'
+import type { Agent, AgentLlmTargetRef, AgentMessage, AgentMessageId, AgentStatus } from '@deepseek-ai/dsh-agent'
 import type { ContentBlock, MessageSource } from '@deepseek-ai/dsh-llm'
 import type { JsonValue, Session, SessionEvent, SessionHeader, SessionId } from '@deepseek-ai/dsh-session'
 import type { SessionPersistence } from '@deepseek-ai/dsh-session-persistence'
@@ -20,7 +21,8 @@ import {
 // Type-only: brings the `ctx.tools` Context merge into this program (viewFor reads presenters).
 import type {} from '@deepseek-ai/dsh-tools'
 import type {
-  ApiProxy, HistoryEntry, HostFrame, MuxFrame, QuestionResponsePayload, SessionSummary, ToolEventView,
+  ApiProxy, HistoryEntry, HostFrame, ModelCatalogFailure, ModelProviderGroup, ModelTarget,
+  MuxFrame, QuestionResponsePayload, SessionSummary, ToolEventView,
  WorkspaceId, WorkspaceView,
 } from './api/index.ts'
 // Type-only edges: resolve `ctx.get('commands')`, the `commands/change` event, and `ctx.get('skills')`.
@@ -348,6 +350,8 @@ function changedWorkspaceView(workspaceId: string, value: unknown): WorkspaceVie
 */
 export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiProxy {
  const agentOptions = { provider: defaults.provider, model: defaults.model }
+  type WebLlmTargetRef = AgentLlmTargetRef & { current: ModelTarget }
+  const targets = new WeakMap<Agent, WebLlmTargetRef>()
  /** Implicit resume of cold sessions, deduplicating concurrent calls (follows the jsonrpc sessionCreations precedent). */
  const resumes = new Map<SessionId, Promise<Agent>>()
  /** Client-chosen identity creation/resume, deduplicated across concurrent retries. */
@@ -357,6 +361,34 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
  const pendingQuestions = new Map<RpcId, PendingQuestion>()
  const muxQueues = new Set<FrameQueue<RpcRequest<MuxFrame>>>()

+  /**
+   * Install or return the session-local target that prompt assembly snapshots.
+   * Seed order: latest logged request/header, else the host default routing.
+   * There is no create-time per-session override tier on this wire — if one
+   * returns (a create-options contribution), it must fold in between the two.
+   */
+  function targetFor(agent: Agent): WebLlmTargetRef {
+    const installed = targets.get(agent)
+    if (installed !== undefined) return installed
+    const logged = agent.session.requestHeader()?.config
+    const target: WebLlmTargetRef = {
+      current: logged === undefined
+        ? { provider: defaults.provider, model: defaults.model }
+        : { provider: logged.provider, model: logged.model },
+      assembled: undefined,
+    }
+    installAgentLlmTarget(agent.ctx, target)
+    targets.set(agent, target)
+    return target
+  }
+
+  /** Pre-publication setup used by both fresh and resumed Web agents. */
+  function installTarget(agentCtx: Context): void {
+    const agent = agentCtx.agent
+    if (agent === undefined) throw new Error('api-proxy: agent setup has no scoped agent')
+    targetFor(agent)
+  }
+
  /** Send one transient frame to every connected mux consumer. */
  function broadcast(payload: MuxFrame): void {
    const envelope = frame(payload)
@@ -470,7 +502,11 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
      resume = (async () => {
        try {
          await assertServable(sessionId)
-          const handle = await ctx.agents.resume({ resumeSessionId: sessionId, agentOptions })
+          const handle = await ctx.agents.resume({
+            resumeSessionId: sessionId,
+            agentOptions,
+            setup: installTarget,
+          })
          return handle.agent
        } finally {
          resumes.delete(sessionId)
@@ -645,6 +681,69 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
        return ok(request, { events: entries, hasMore: page.hasMore })
      },

+      async models(request) {
+        const { sessionId } = request.payload
+        const found = await agentFor(sessionId)
+        if ('error' in found) return err(request, found.error)
+        const current = targetFor(found.agent).current
+        const catalog = await Promise.all(ctx.llm.listProviders().map(async (provider) => {
+          try {
+            const models = await ctx.llm.listModels(provider.id)
+            const group: ModelProviderGroup = {
+              id: provider.id,
+              name: provider.name,
+              models: models.map(model => ({
+                id: model.id,
+                name: model.name,
+                ...model.description === undefined ? {} : { description: model.description },
+              })),
+            }
+            return { kind: 'group' as const, group }
+          } catch (error: unknown) {
+            const failure: ModelCatalogFailure = {
+              id: provider.id,
+              name: provider.name,
+              message: error instanceof Error ? error.message : String(error),
+            }
+            return { kind: 'failure' as const, failure }
+          }
+        }))
+        const groups = catalog.flatMap(item => item.kind === 'group' ? [item.group] : [])
+        const failures = catalog.flatMap(item => item.kind === 'failure' ? [item.failure] : [])
+        const currentGroup = groups.find(group => group.id === current.provider)
+        if (
+          currentGroup !== undefined
+          && !currentGroup.models.some(model => model.id === current.model)
+        ) {
+          currentGroup.models.push({
+            id: current.model,
+            name: current.model,
+            unlisted: true,
+          })
+        }
+        return ok(request, {
+          current: { ...current },
+          groups: groups.filter(group => group.models.length > 0),
+          failures,
+        })
+      },
+
+      async selectModel(request) {
+        const { sessionId, provider, model } = request.payload
+        const found = await agentFor(sessionId)
+        if ('error' in found) return err(request, found.error)
+        if (!ctx.llm.listProviders().some(entry => entry.id === provider)) {
+          return err(request, {
+            code: 'model-unavailable',
+            message: `provider "${provider}" is not registered`,
+            details: { provider, model },
+          })
+        }
+        const selected: ModelTarget = { provider, model }
+        targetFor(found.agent).current = selected
+        return ok(request, { selected: { ...selected } })
+      },
+
      async prompt(request) {
        const { sessionId, mode, content } = request.payload
        const found = await agentFor(sessionId)
--- a/packages/host/apiproxy/src/api/rpc.schema.ts
+++ b/packages/host/apiproxy/src/api/rpc.schema.ts
@@ -41,6 +41,7 @@ export const rpcErrorSchema: z.ZodType<RpcError> = z.discriminatedUnion('code',
  z.object({ code: z.literal('workspace-invalid-path'), message: z.string(), details: z.object({ path: z.string() }) }),
  z.object({ code: z.literal('workspace-name-conflict'), message: z.string(), details: z.object({ name: z.string() }) }),
  z.object({ code: z.literal('workspace-move-invalid'), message: z.string(), details: z.object({ workspaceId: z.string(), sessionId: z.string(), beforeSessionId: z.string().optional() }) }),
+  z.object({ code: z.literal('model-unavailable'), message: z.string(), details: z.object({ provider: z.string(), model: z.string() }) }),
  z.object({ code: z.literal('agent-busy'), message: z.string(), details: z.object({ reason: z.string() }) }),
  z.object({ code: z.literal('internal'), message: z.string(), details: z.object({}) }),
 ]) as unknown as z.ZodType<RpcError>
--- a/packages/host/apiproxy/src/api/rpc.ts
+++ b/packages/host/apiproxy/src/api/rpc.ts
@@ -38,6 +38,7 @@ export interface RpcErrorDetailsMap {
  'workspace-invalid-path': { path: string }
  'workspace-name-conflict': { name: string }
  'workspace-move-invalid': { workspaceId: string; sessionId: SessionId; beforeSessionId?: SessionId }
+  'model-unavailable': { provider: string; model: string }
  'agent-busy': { reason: string }
  'internal': {}
 }
--- a/packages/host/apiproxy/src/api/sessions.schema.ts
+++ b/packages/host/apiproxy/src/api/sessions.schema.ts
@@ -128,7 +128,6 @@ export const historyEntrySchema = z.object({
 export const sessionHistoryValueSchema = z.object({
  events: z.array(historyEntrySchema),
  hasMore: z.boolean(),
-  modelTarget: modelTargetSchema,
 }) satisfies z.ZodType<Wire<ResponseValue<'session.history'>>>

 /** session.models request payload. */
--- a/packages/host/apiproxy/src/api/sessions.ts
+++ b/packages/host/apiproxy/src/api/sessions.ts
@@ -129,7 +129,7 @@ export interface SessionsApi {
   * rebuilds the surface from the events with the shared fold.
   */
  history(request: RpcRequest<{ sessionId: SessionId; beforeSeq?: number; maxMessages?: number }>):
-  Promise<RpcResponse<{ events: HistoryEntry[]; hasMore: boolean; modelTarget: ModelTarget }>>
+  Promise<RpcResponse<{ events: HistoryEntry[]; hasMore: boolean }>>

  /** Reads a fresh advisory model directory for this session. Provider lookups run independently. */
  models(request: RpcRequest<{ sessionId: SessionId }>): Promise<RpcResponse<SessionModels>>
--- a/packages/host/apiproxy/src/index.ts
+++ b/packages/host/apiproxy/src/index.ts
@@ -45,7 +45,7 @@ export interface Config {
 * project directory and the fallback parent for name-created Workspaces.
 */
 export class ApiProxyService extends Service implements ApiProxy {
-  static inject = ['agents', 'sessions', 'tools', 'userInteraction', 'workspace']
+  static inject = ['agents', 'llm', 'sessions', 'tools', 'userInteraction', 'workspace']

  static Config: z<Config> = z.object({
    provider: z.string().required(),
--- a/packages/host/apiproxy/tests/api-proxy-models.spec.ts
+++ b/packages/host/apiproxy/tests/api-proxy-models.spec.ts
@@ -0,0 +1,162 @@
+/**
+ * Web session model-directory and selection behavior: dynamic provider grouping,
+ * provider-local catalog failures, logged-target restoration, advisory unlisted
+ * models, and the prompt-assembly boundary for a running selection change.
+ */
+
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import AgentRegistry, { agentEvents } from '@deepseek-ai/dsh-agent'
+import type { Agent } from '@deepseek-ai/dsh-agent'
+import LlmService, { LlmAdapter } from '@deepseek-ai/dsh-llm'
+import type {
+  GenerateOptions, LlmCallConfig, LlmModelInfo, LlmProviderInfo, StreamChunk,
+} from '@deepseek-ai/dsh-llm'
+import SessionStore from '@deepseek-ai/dsh-session'
+import type { SessionId } from '@deepseek-ai/dsh-session'
+import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
+import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
+import type { RpcRequest } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { RpcId } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { createApiProxy } from '../src/api-proxy.ts'
+
+let nextRpc = 1
+function request<P>(payload: P): RpcRequest<P> {
+  return { rpcId: RpcId(`models-${String(nextRpc++)}`), payload }
+}
+
+class CatalogAdapter extends LlmAdapter {
+  constructor(
+    private readonly name: string,
+    private readonly models: readonly LlmModelInfo[] | Error,
+  ) {
+    super()
+  }
+
+  override providerInfo(provider: string): LlmProviderInfo {
+    return { id: provider, name: this.name }
+  }
+
+  override listModels(): Promise<readonly LlmModelInfo[]> {
+    return this.models instanceof Error
+      ? Promise.reject(this.models)
+      : Promise.resolve(this.models)
+  }
+
+  override async *stream(_options: GenerateOptions): AsyncIterable<StreamChunk> {
+    // Catalog tests never enter provider streaming.
+  }
+}
+
+async function harness(logged?: { provider: string; model: string }): Promise<{
+  ctx: Context
+  agent: Agent
+  sessionId: SessionId
+}> {
+  const ctx = new Context()
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(SystemPrompt, { persona: '' })
+  await ctx.plugin(LlmService)
+  await ctx.plugin(UserInteractionService)
+  await ctx.plugin(AgentRegistry)
+  ctx.llm.registerAdapter(['deepseek'], new CatalogAdapter('DeepSeek', [
+    { provider: 'deepseek', id: 'deepseek-chat', name: 'DeepSeek Chat' },
+    { provider: 'deepseek', id: 'deepseek-reasoner', name: 'DeepSeek Reasoner', description: 'Reasoning model' },
+  ]))
+  ctx.llm.registerAdapter(['broken'], new CatalogAdapter('Broken Provider', new Error('catalog offline')))
+  ctx.llm.registerAdapter(['empty'], new CatalogAdapter('Empty Provider', []))
+  ctx.llm.registerAdapter(['duplicate'], new CatalogAdapter('Duplicate Provider', [
+    { provider: 'duplicate', id: 'same', name: 'Same' },
+    { provider: 'duplicate', id: 'same', name: 'Same Again' },
+  ]))
+  const session = ctx.sessions.create()
+  if (logged !== undefined) {
+    session.append('request/header', { header: { config: logged }, reason: 'initial' })
+  }
+  const agent = {
+    id: session.id,
+    session,
+    status: 'running',
+    ctx,
+  } as Agent
+  ctx.agents.register(agent)
+  return { ctx, agent, sessionId: session.id }
+}
+
+function expectValue<T>(response: { result: { ok: true; value: T } | { ok: false } }): T {
+  if (!response.result.ok) throw new Error('expected successful response')
+  return response.result.value
+}
+
+describe('Web session model selection', () => {
+  it('groups successful providers, isolates failures, and preserves an unlisted current model', async () => {
+    const { ctx, sessionId } = await harness({ provider: 'deepseek', model: 'private-preview' })
+    const api = createApiProxy(ctx, { provider: 'deepseek', model: 'deepseek-chat', cwd: '/tmp', workspaceRoot: '/tmp' })
+
+    const catalog = expectValue(await api.sessions.models(request({ sessionId })))
+    expect(catalog.current).toEqual({ provider: 'deepseek', model: 'private-preview' })
+    expect(catalog.groups).toEqual([{
+      id: 'deepseek',
+      name: 'DeepSeek',
+      models: [
+        { id: 'deepseek-chat', name: 'DeepSeek Chat' },
+        { id: 'deepseek-reasoner', name: 'DeepSeek Reasoner', description: 'Reasoning model' },
+        { id: 'private-preview', name: 'private-preview', unlisted: true },
+      ],
+    }])
+    expect(catalog.failures).toEqual([
+      { id: 'broken', name: 'Broken Provider', message: 'catalog offline' },
+      {
+        id: 'duplicate',
+        name: 'Duplicate Provider',
+        message: 'adapter returned invalid or duplicate model metadata for provider "duplicate"',
+      },
+    ])
+    await ctx.fiber.dispose()
+  })
+
+  it('accepts an advisory-unlisted model, rejects an unavailable provider, and switches only after the next assembly', async () => {
+    const { ctx, agent, sessionId } = await harness()
+    const api = createApiProxy(ctx, { provider: 'deepseek', model: 'deepseek-chat', cwd: '/tmp', workspaceRoot: '/tmp' })
+    const seed: LlmCallConfig = { provider: 'seed', model: 'seed', temperature: 0.2 }
+    const signal = new AbortController().signal
+
+    expect(expectValue(await api.sessions.models(request({ sessionId }))).current)
+      .toEqual({ provider: 'deepseek', model: 'deepseek-chat' })
+    expect((await ctx.systemPrompt.assemble()).variables)
+      .toMatchObject({ provider: 'deepseek', model: 'deepseek-chat' })
+
+    const selected = expectValue(await api.sessions.selectModel(request({
+      sessionId,
+      provider: 'deepseek',
+      model: 'private-preview',
+    })))
+    expect(selected.selected).toEqual({ provider: 'deepseek', model: 'private-preview' })
+    await expect(agentEvents(ctx, agent).waterfall(
+      'agent/request', 1, 0, seed, signal, () => Promise.resolve(seed),
+    )).resolves.toMatchObject({ provider: 'deepseek', model: 'deepseek-chat' })
+
+    expect((await ctx.systemPrompt.assemble()).variables)
+      .toMatchObject({ provider: 'deepseek', model: 'private-preview' })
+    await expect(agentEvents(ctx, agent).waterfall(
+      'agent/request', 1, 1, seed, signal, () => Promise.resolve(seed),
+    )).resolves.toMatchObject({ provider: 'deepseek', model: 'private-preview' })
+
+    const rejected = await api.sessions.selectModel(request({
+      sessionId,
+      provider: 'missing',
+      model: 'model',
+    }))
+    expect(rejected.result).toEqual({
+      ok: false,
+      error: {
+        code: 'model-unavailable',
+        message: 'provider "missing" is not registered',
+        details: { provider: 'missing', model: 'model' },
+      },
+    })
+    expect(expectValue(await api.sessions.models(request({ sessionId }))).current)
+      .toEqual({ provider: 'deepseek', model: 'private-preview' })
+    await ctx.fiber.dispose()
+  })
+})
--- a/packages/host/apiproxy/tests/rpc-schemas.spec.ts
+++ b/packages/host/apiproxy/tests/rpc-schemas.spec.ts
@@ -8,8 +8,9 @@ import { z } from 'zod'
 import {
  contentBlockSchema, sessionCancelRequestSchema, sessionCancelValueSchema, sessionCreateRequestSchema,
  sessionCreateValueSchema, sessionEventSchema, sessionHistoryRequestSchema, sessionHistoryValueSchema,
-  sessionIdSchema, sessionListRequestSchema, sessionListValueSchema, sessionPromptRequestSchema,
-  sessionPromptValueSchema, sessionSummarySchema,
+  sessionIdSchema, sessionListRequestSchema, sessionListValueSchema, sessionModelsRequestSchema,
+  sessionModelsValueSchema, sessionPromptRequestSchema, sessionPromptValueSchema,
+  sessionSelectModelRequestSchema, sessionSelectModelValueSchema, sessionSummarySchema,
 } from '../src/api/sessions.schema.ts'
 import { hostDescribeRequestSchema, hostDescribeValueSchema } from '../src/api/host.schema.ts'
 import {
@@ -55,6 +56,11 @@ describe('rpcErrorSchema', () => {
    expect(rpcErrorSchema.parse({ code: 'workspace-invalid-path', message: 'm', details: { path: '/x' } }).code).toBe('workspace-invalid-path')
    expect(rpcErrorSchema.parse({ code: 'workspace-name-conflict', message: 'm', details: { name: 'x' } }).code).toBe('workspace-name-conflict')
    expect(rpcErrorSchema.parse({ code: 'workspace-move-invalid', message: 'm', details: { workspaceId: 'w', sessionId: 's' } }).code).toBe('workspace-move-invalid')
+    expect(rpcErrorSchema.parse({
+      code: 'model-unavailable',
+      message: 'm',
+      details: { provider: 'p', model: 'm' },
+    }).code).toBe('model-unavailable')
    expect(rpcErrorSchema.parse({ code: 'agent-busy', message: 'm', details: { reason: 'r' } }).code).toBe('agent-busy')
    expect(rpcErrorSchema.parse({ code: 'internal', message: 'm', details: {} }).code).toBe('internal')
  })
@@ -128,7 +134,39 @@ describe('sessions domain schemas', () => {
    expect(sessionCreateValueSchema.parse({ sessionId: 's1' }).sessionId).toBe('s1')
    expect(sessionHistoryRequestSchema.parse({ sessionId: 's1', beforeSeq: 3, maxMessages: 5 }).beforeSeq).toBe(3)
    expect(() => sessionHistoryRequestSchema.parse({ sessionId: 's1', maxMessages: 0 })).toThrow()
-    expect(sessionHistoryValueSchema.parse({ events: [], hasMore: false }).hasMore).toBe(false)
+    expect(sessionHistoryValueSchema.parse({
+      events: [],
+      hasMore: false,
+      modelTarget: { provider: 'deepseek', model: 'deepseek-v4-flash' },
+    }).hasMore).toBe(false)
+    expect(sessionModelsRequestSchema.parse({ sessionId: 's1' }).sessionId).toBe('s1')
+    expect(sessionModelsValueSchema.parse({
+      current: { provider: 'deepseek', model: 'deepseek-v4-flash' },
+      groups: [{
+        id: 'deepseek',
+        name: 'DeepSeek',
+        models: [{
+          id: 'deepseek-v4-flash',
+          name: 'DeepSeek V4 Flash',
+          description: 'fast',
+          unlisted: true,
+        }],
+      }],
+      failures: [{ id: 'broken', name: 'Broken', message: 'offline' }],
+    }).groups[0]?.models[0]?.id).toBe('deepseek-v4-flash')
+    expect(sessionSelectModelRequestSchema.parse({
+      sessionId: 's1',
+      provider: 'deepseek',
+      model: 'deepseek-v4-pro',
+    }).model).toBe('deepseek-v4-pro')
+    expect(sessionSelectModelValueSchema.parse({
+      selected: { provider: 'deepseek', model: 'deepseek-v4-pro' },
+    }).selected.model).toBe('deepseek-v4-pro')
+    expect(() => sessionSelectModelRequestSchema.parse({
+      sessionId: 's1',
+      provider: '',
+      model: 'm',
+    })).toThrow()
    const prompt = sessionPromptRequestSchema.parse({ sessionId: 's1', mode: 'queue', content: [{ type: 'text', text: 'hi' }] })
    expect(prompt.mode).toBe('queue')
    expect(() => sessionPromptRequestSchema.parse({ sessionId: 's1', mode: 'inject', content: [] })).toThrow()
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -143,6 +143,9 @@ importers:
      '@deepseek-ai/dsh-client-ui-layout':
        specifier: workspace:^
        version: link:../../packages/client/ui-layout
+      '@deepseek-ai/dsh-client-ui-model':
+        specifier: workspace:^
+        version: link:../../packages/client/ui-model
      '@deepseek-ai/dsh-client-ui-models':
        specifier: workspace:^
        version: link:../../packages/client/ui-models
@@ -959,6 +962,27 @@ importers:
        specifier: ^18.2.0
        version: 18.3.1

+  packages/client/ui-model:
+    devDependencies:
+      '@deepseek-ai/dsh-client-connection':
+        specifier: workspace:^
+        version: link:../connection
+      '@deepseek-ai/dsh-client-runtime':
+        specifier: workspace:^
+        version: link:../runtime
+      '@deepseek-ai/dsh-client-ui-command':
+        specifier: workspace:^
+        version: link:../ui-command
+      '@deepseek-ai/dsh-client-ui-slash':
+        specifier: workspace:^
+        version: link:../ui-slash
+      '@deepseek-ai/dsh-invariants':
+        specifier: workspace:^
+        version: link:../../support/invariants
+      cordis:
+        specifier: ^4.0.0-rc.7
+        version: 4.0.0-rc.7(@cordisjs/plugin-include@1.0.4)(@cordisjs/plugin-loader@1.0.0-rc.5)
+
  packages/client/ui-models:
    devDependencies:
      '@deepseek-ai/dsh-client-locale':
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -113,6 +113,7 @@
      "@deepseek-ai/dsh-client-ui-conversation": ["./packages/client/ui-conversation/src"],
      "@deepseek-ai/dsh-client-ui-slash": ["./packages/client/ui-slash/src"],
      "@deepseek-ai/dsh-client-ui-command": ["./packages/client/ui-command/src"],
+      "@deepseek-ai/dsh-client-ui-model": ["./packages/client/ui-model/src"],
      "@deepseek-ai/dsh-client-ui-skill": ["./packages/client/ui-skill/src"],
      "@deepseek-ai/dsh-client-ui-subagent": ["./packages/client/ui-subagent/src"],
      "@deepseek-ai/dsh-client-ui-question": ["./packages/client/ui-question/src"],
--- a/tsconfig.client.json
+++ b/tsconfig.client.json
@@ -39,6 +39,7 @@
    { "path": "./packages/client/ui-command" },
    { "path": "./packages/client/ui-skill" },
    { "path": "./packages/client/ui-subagent" },
+    { "path": "./packages/client/ui-model" },
    { "path": "./packages/client/ui-question" },
    { "path": "./packages/client/ui-trajectory" },
    { "path": "./packages/client/ui-theme" },