diff --git a/src/main/assistant/assistant-database.test.ts b/src/main/assistant/assistant-database.test.ts
index 9b26959..c0ece7d 100644
--- a/src/main/assistant/assistant-database.test.ts
+++ b/src/main/assistant/assistant-database.test.ts
@@ -393,11 +393,17 @@ describe('AssistantDatabase', () => {
       name: '产品发布 2',
       description: '更新后的项目',
       rootPath: 'C:\\Release',
-      defaultWorkMode: 'execute'
+      defaultWorkMode: 'execute',
+      runtimeSelection: {
+        provider: 'continue'
+      }
     })
     expect(updated).toMatchObject({
       name: '产品发布 2',
-      defaultWorkMode: 'execute'
+      defaultWorkMode: 'execute',
+      runtimeSelection: {
+        provider: 'continue'
+      }
     })
     database.setProjectArchived(project.id, true)
     expect(database.listProjects()).toHaveLength(1)
diff --git a/src/renderer/src/App.test.tsx b/src/renderer/src/App.test.tsx
index 15feb27..56c2a35 100644
--- a/src/renderer/src/App.test.tsx
+++ b/src/renderer/src/App.test.tsx
@@ -3357,9 +3357,16 @@ describe('App', () => {
     expect(within(dialog).getByLabelText('根目录')).toHaveValue(
       project.rootPath
     )
+    expect(
+      within(dialog).getByLabelText('新对话默认 Runtime')
+    ).toHaveValue('model')
     fireEvent.change(within(dialog).getByLabelText('说明'), {
       target: { value: '更新后的说明' }
     })
+    fireEvent.change(
+      within(dialog).getByLabelText('新对话默认 Runtime'),
+      { target: { value: 'continue' } }
+    )
     fireEvent.click(
       within(dialog).getByRole('button', { name: '保存项目' })
     )
@@ -3368,7 +3375,11 @@ describe('App', () => {
         project.id,
         expect.objectContaining({
           description: '更新后的说明',
-          rootPath: project.rootPath
+          rootPath: project.rootPath,
+          runtimeSelection: {
+            provider: 'continue',
+            profileId: modelProfileId
+          }
         })
       )
     )
@@ -3403,6 +3414,49 @@ describe('App', () => {
     )
   })
 
+  it('uses the project default Runtime for new conversations', async () => {
+    vi.mocked(api.projects.list).mockResolvedValueOnce([
+      {
+        ...project,
+        runtimeSelection: {
+          provider: 'opencode',
+          profileId: modelProfileId
+        }
+      }
+    ])
+    vi.mocked(api.conversations.list).mockResolvedValueOnce([
+      {
+        id: '00000000-0000-4000-8000-000000000220',
+        projectId,
+        runtimeSelection: {
+          provider: 'model',
+          profileId: modelProfileId
+        },
+        title: '已有对话',
+        updatedAt: 1,
+        messages: []
+      }
+    ])
+    render(<App />)
+
+    await screen.findAllByText('已有对话')
+    fireEvent.click(
+      screen.getByRole('button', { name: /新建对话/u })
+    )
+
+    await waitFor(() =>
+      expect(api.agent.getStatus).toHaveBeenLastCalledWith({
+        provider: 'opencode',
+        profileId: modelProfileId
+      })
+    )
+    expect(
+      screen.getByRole('button', {
+        name: /OpenCode · 默认模型/u
+      })
+    ).toBeInTheDocument()
+  })
+
   it('uses a message icon for conversation navigation', async () => {
     render(<App />)
 
diff --git a/src/renderer/src/App.tsx b/src/renderer/src/App.tsx
index 885f832..1eccea3 100644
--- a/src/renderer/src/App.tsx
+++ b/src/renderer/src/App.tsx
@@ -818,6 +818,16 @@ function getDefaultRuntimeSelection(
   }
 }
 
+function getProjectDefaultRuntimeSelection(
+  project: AssistantProject | undefined,
+  settings: RuntimeSettings
+): AgentRuntimeSelection {
+  const selection = project?.runtimeSelection
+  return !selection || selection.provider === 'auto'
+    ? getDefaultRuntimeSelection(settings)
+    : repairAgentRuntimeSelection(selection, settings)
+}
+
 function getRuntimeSelectionLabel(
   selection: AgentRuntimeSelection | undefined,
   settings: RuntimeSettings | undefined,
@@ -1798,11 +1808,17 @@ function App(): React.JSX.Element {
     if (!runtimeSettings || !conversationStoreReady) {
       return
     }
-    const defaultSelection = getDefaultRuntimeSelection(runtimeSettings)
     const timeout = setTimeout(() => {
       setConversations((current) => {
         let changed = false
         const next = current.map((conversation) => {
+          const project = projects.find(
+            (candidate) => candidate.id === conversation.projectId
+          )
+          const defaultSelection = getProjectDefaultRuntimeSelection(
+            project,
+            runtimeSettings
+          )
           const selection =
             !conversation.runtimeSelection ||
             conversation.runtimeSelection.provider === 'auto'
@@ -1828,7 +1844,7 @@ function App(): React.JSX.Element {
       })
     }, 0)
     return () => clearTimeout(timeout)
-  }, [conversationStoreReady, runtimeSettings])
+  }, [conversationStoreReady, projects, runtimeSettings])
 
   useEffect(() => {
     const selection = activeRuntimeSelectionRef.current
@@ -1914,7 +1930,7 @@ function App(): React.JSX.Element {
       const conversation = createConversation(
         projectId,
         runtimeSettings
-          ? getDefaultRuntimeSelection(runtimeSettings)
+          ? getProjectDefaultRuntimeSelection(project, runtimeSettings)
           : undefined,
         tRef.current('conversation.greeting')
       )
@@ -3520,7 +3536,7 @@ function App(): React.JSX.Element {
       const created = createConversation(
         projectId,
         runtimeSettings
-          ? getDefaultRuntimeSelection(runtimeSettings)
+          ? getProjectDefaultRuntimeSelection(project, runtimeSettings)
           : undefined,
         t('conversation.greeting')
       )
@@ -3540,7 +3556,7 @@ function App(): React.JSX.Element {
     const conversation = createConversation(
       project.id,
       runtimeSettings
-        ? getDefaultRuntimeSelection(runtimeSettings)
+        ? getProjectDefaultRuntimeSelection(project, runtimeSettings)
         : undefined,
       t('conversation.greeting')
     )
@@ -3635,7 +3651,7 @@ function App(): React.JSX.Element {
         const created = createConversation(
           next.id,
           runtimeSettings
-            ? getDefaultRuntimeSelection(runtimeSettings)
+            ? getProjectDefaultRuntimeSelection(next, runtimeSettings)
             : undefined,
           t('conversation.greeting')
         )
@@ -3767,7 +3783,10 @@ function App(): React.JSX.Element {
     const replacement = createConversation(
       activeProjectId || undefined,
       runtimeSettings
-        ? getDefaultRuntimeSelection(runtimeSettings)
+        ? getProjectDefaultRuntimeSelection(
+            activeProject,
+            runtimeSettings
+          )
         : undefined,
       t('conversation.greeting')
     )
@@ -4531,7 +4550,10 @@ function App(): React.JSX.Element {
     const conversation = createConversation(
       activeProjectId || undefined,
       runtimeSettings
-        ? getDefaultRuntimeSelection(runtimeSettings)
+        ? getProjectDefaultRuntimeSelection(
+            activeProject,
+            runtimeSettings
+          )
         : undefined,
       t('conversation.greeting')
     )
@@ -4602,6 +4624,7 @@ function App(): React.JSX.Element {
 
         <ProjectSwitcher
           activeProjectId={activeProjectId}
+          runtimeSettings={runtimeSettings}
           onArchive={archiveProject}
           onCreate={createProject}
           onDelete={deleteProject}
diff --git a/src/renderer/src/ProjectSwitcher.tsx b/src/renderer/src/ProjectSwitcher.tsx
index 919c8ea..5fa6adb 100644
--- a/src/renderer/src/ProjectSwitcher.tsx
+++ b/src/renderer/src/ProjectSwitcher.tsx
@@ -17,11 +17,14 @@ import {
   interactiveWorkModes,
   normalizeInteractiveWorkMode
 } from '../../shared/assistant-contracts'
+import type { RuntimeSettings } from '../../shared/contracts'
+import type { AgentRuntimeSelection } from '../../shared/runtime-selection-contracts'
 import { trapTabFocus } from './dialog-focus'
 
 type ProjectSwitcherProps = {
   projects: AssistantProject[]
   activeProjectId: string
+  runtimeSettings?: RuntimeSettings
   onArchive: (projectId: string) => Promise<void>
   onCreate: (input: ProjectCreateInput) => Promise<AssistantProject>
   onDelete: (projectId: string, confirmation: string) => Promise<void>
@@ -33,9 +36,47 @@ type ProjectSwitcherProps = {
   ) => Promise<AssistantProject>
 }
 
+function runtimeSelectionForProvider(
+  provider: 'model' | 'opencode' | 'continue',
+  settings: RuntimeSettings
+): AgentRuntimeSelection {
+  if (provider === 'model') {
+    return {
+      provider,
+      profileId: settings.defaultModelProfileId
+    }
+  }
+  const source =
+    provider === 'opencode'
+      ? settings.opencodeModelSource
+      : settings.continueModelSource
+  return {
+    provider,
+    ...(source.kind === 'profile' ? { profileId: source.profileId } : {})
+  }
+}
+
+function defaultRuntimeSelection(
+  settings: RuntimeSettings
+): AgentRuntimeSelection {
+  if (settings.provider === 'model') {
+    return runtimeSelectionForProvider('model', settings)
+  }
+  if (settings.provider === 'opencode') {
+    return runtimeSelectionForProvider('opencode', settings)
+  }
+  if (settings.provider === 'continue') {
+    return runtimeSelectionForProvider('continue', settings)
+  }
+  return settings.opencodeBaseUrl || settings.opencodeEmbedded
+    ? runtimeSelectionForProvider('opencode', settings)
+    : runtimeSelectionForProvider('model', settings)
+}
+
 export function ProjectSwitcher({
   projects,
   activeProjectId,
+  runtimeSettings,
   onArchive,
   onCreate,
   onDelete,
@@ -111,10 +152,17 @@ export function ProjectSwitcher({
     setSaving(true)
     setError(undefined)
     try {
+      const input =
+        draft.runtimeSelection || !runtimeSettings
+          ? draft
+          : {
+              ...draft,
+              runtimeSelection: defaultRuntimeSelection(runtimeSettings)
+            }
       if (dialogMode === 'settings' && activeProject) {
-        await onUpdate(activeProject.id, draft)
+        await onUpdate(activeProject.id, input)
       } else {
-        await onCreate(draft)
+        await onCreate(input)
       }
       closeDialog()
     } catch (reason) {
@@ -226,7 +274,10 @@ export function ProjectSwitcher({
               name: '',
               description: '',
               rootPath: '',
-              defaultWorkMode: 'ask'
+              defaultWorkMode: 'ask',
+              runtimeSelection: runtimeSettings
+                ? defaultRuntimeSelection(runtimeSettings)
+                : undefined
             })
             restoreFocusTarget.current = 'create'
             setDialogMode('create')
@@ -253,7 +304,12 @@ export function ProjectSwitcher({
               rootPath: activeProject.rootPath,
               defaultWorkMode: normalizeInteractiveWorkMode(
                 activeProject.defaultWorkMode
-              )
+              ),
+              runtimeSelection:
+                activeProject.runtimeSelection ??
+                (runtimeSettings
+                  ? defaultRuntimeSelection(runtimeSettings)
+                  : undefined)
             })
             restoreFocusTarget.current = 'settings'
             setDialogMode('settings')
@@ -373,6 +429,48 @@ export function ProjectSwitcher({
                 ))}
               </select>
             </label>
+            {runtimeSettings && (
+              <label>
+                <span>
+                  {t('projectSwitcher.dialog.fields.defaultRuntime')}
+                </span>
+                <select
+                  aria-label={t(
+                    'projectSwitcher.dialog.fields.defaultRuntime'
+                  )}
+                  onChange={(event) =>
+                    setDraft((current) => ({
+                      ...current,
+                      runtimeSelection: runtimeSelectionForProvider(
+                        event.target.value as
+                          | 'model'
+                          | 'opencode'
+                          | 'continue',
+                        runtimeSettings
+                      )
+                    }))
+                  }
+                  value={
+                    draft.runtimeSelection?.provider === 'auto'
+                      ? 'model'
+                      : (draft.runtimeSelection?.provider ??
+                        defaultRuntimeSelection(runtimeSettings)
+                          .provider)
+                  }
+                >
+                  <option value="model">
+                    {t(
+                      'projectSwitcher.dialog.runtimeOptions.direct'
+                    )}
+                  </option>
+                  <option value="opencode">OpenCode</option>
+                  <option value="continue">Continue</option>
+                </select>
+                <small>
+                  {t('projectSwitcher.dialog.defaultRuntimeHelp')}
+                </small>
+              </label>
+            )}
             {error && (
               <p className="project-create-card__error" role="alert">
                 {error}
diff --git a/src/renderer/src/i18n/locales/en-US/workspace.ts b/src/renderer/src/i18n/locales/en-US/workspace.ts
index 9b8521d..a4e088d 100644
--- a/src/renderer/src/i18n/locales/en-US/workspace.ts
+++ b/src/renderer/src/i18n/locales/en-US/workspace.ts
@@ -23,8 +23,14 @@ export const workspace = {
         name: 'Name',
         description: 'Description',
         rootPath: 'Root folder',
-        defaultMode: 'Default mode'
+        defaultMode: 'Default mode',
+        defaultRuntime: 'Default Runtime for new conversations'
       },
+      runtimeOptions: {
+        direct: 'Direct model'
+      },
+      defaultRuntimeHelp:
+        'Applies only to new conversations in this project. Existing conversations are unchanged.',
       channelManaged: 'GoodBuddy manages channel project names.',
       selectRoot: 'Select project root folder',
       danger: {
diff --git a/src/renderer/src/i18n/locales/zh-CN/workspace.ts b/src/renderer/src/i18n/locales/zh-CN/workspace.ts
index 93d5db1..85ad293 100644
--- a/src/renderer/src/i18n/locales/zh-CN/workspace.ts
+++ b/src/renderer/src/i18n/locales/zh-CN/workspace.ts
@@ -20,8 +20,14 @@ export const workspace = {
         name: '名称',
         description: '说明',
         rootPath: '根目录',
-        defaultMode: '默认模式'
+        defaultMode: '默认模式',
+        defaultRuntime: '新对话默认 Runtime'
       },
+      runtimeOptions: {
+        direct: '直连模型'
+      },
+      defaultRuntimeHelp:
+        '仅应用于此项目中新建的对话，不会更改已有对话。',
       channelManaged: '通道项目名称由 GoodBuddy 管理。',
       selectRoot: '选择项目根目录',
       danger: {