diff --git a/web/app/components/apps/__tests__/app-card.spec.tsx b/web/app/components/apps/__tests__/app-card.spec.tsx
index 97e841264e..13df967e71 100644
--- a/web/app/components/apps/__tests__/app-card.spec.tsx
+++ b/web/app/components/apps/__tests__/app-card.spec.tsx
@@ -352,6 +352,18 @@ describe('AppCard', () => {
       expect(screen.getByTestId('app-type-icon')).toBeInTheDocument()
     })
 
+    it('should render the sandbox corner mark when the app uses sandboxed runtime', () => {
+      renderAppCard({ runtime_type: 'sandboxed' })
+
+      expect(screen.getByText('app.sandboxBadge')).toBeInTheDocument()
+    })
+
+    it('should not render the sandbox corner mark for classic runtime apps', () => {
+      renderAppCard({ runtime_type: 'classic' })
+
+      expect(screen.queryByText('app.sandboxBadge')).not.toBeInTheDocument()
+    })
+
     it('should call getRedirection when the main card button is clicked', () => {
       const { app } = renderAppCard()
 
diff --git a/web/app/components/apps/app-card.tsx b/web/app/components/apps/app-card.tsx
index bebeab17f9..434da40243 100644
--- a/web/app/components/apps/app-card.tsx
+++ b/web/app/components/apps/app-card.tsx
@@ -31,6 +31,7 @@ import {
 import { toast } from '@/app/components/base/ui/toast'
 import { Tooltip, TooltipContent, TooltipTrigger } from '@/app/components/base/ui/tooltip'
 import { UserAvatarList } from '@/app/components/base/user-avatar-list'
+import CornerMark from '@/app/components/plugins/card/base/corner-mark'
 import { NEED_REFRESH_APP_LIST_KEY } from '@/config'
 import { useAppContext } from '@/context/app-context'
 import { useGlobalPublicStore } from '@/context/global-public-context'
@@ -441,11 +442,18 @@ const AppCard = ({ app, onRefresh, onlineUsers = [] }: AppCardProps) => {
       .filter(user => !!user.id)
   }, [onlineUsers])
 
+  const isSandboxApp = app.runtime_type === 'sandboxed'
+
   return (
     <>
       <div
         className="group relative col-span-1 inline-flex h-[160px] flex-col rounded-xl border-[1px] border-solid border-components-card-border bg-components-card-bg shadow-sm transition-all duration-200 ease-in-out hover:shadow-lg"
       >
+        {isSandboxApp && (
+          <div className="pointer-events-none">
+            <CornerMark text={t('sandboxBadge', { ns: 'app' })} />
+          </div>
+        )}
         <button
           type="button"
           onClick={() => getRedirection(isCurrentWorkspaceEditor, app, push)}
diff --git a/web/app/components/plugins/card/base/corner-mark.tsx b/web/app/components/plugins/card/base/corner-mark.tsx
index 4996944767..02bcc136ce 100644
--- a/web/app/components/plugins/card/base/corner-mark.tsx
+++ b/web/app/components/plugins/card/base/corner-mark.tsx
@@ -4,7 +4,7 @@ const CornerMark = ({ text }: { text: string }) => {
   return (
     <div className="absolute right-0 top-0 flex pl-[13px]">
       <LeftCorner className="text-background-section" />
-      <div className="h-5 rounded-tr-xl bg-background-section pr-2 leading-5 text-text-tertiary system-2xs-medium-uppercase">{text}</div>
+      <div className="h-5 rounded-tr-xl bg-background-section pr-2 !leading-5 text-text-tertiary system-2xs-medium-uppercase">{text}</div>
     </div>
   )
 }
diff --git a/web/app/components/workflow/skill/editor/skill-editor/plugins/__tests__/file-picker-block.spec.tsx b/web/app/components/workflow/skill/editor/skill-editor/plugins/__tests__/file-picker-block.spec.tsx
new file mode 100644
index 0000000000..d39cc90b71
--- /dev/null
+++ b/web/app/components/workflow/skill/editor/skill-editor/plugins/__tests__/file-picker-block.spec.tsx
@@ -0,0 +1,132 @@
+import type { LexicalEditor } from 'lexical'
+import { LexicalComposer } from '@lexical/react/LexicalComposer'
+import { useLexicalComposerContext } from '@lexical/react/LexicalComposerContext'
+import { ContentEditable } from '@lexical/react/LexicalContentEditable'
+import { LexicalErrorBoundary } from '@lexical/react/LexicalErrorBoundary'
+import { RichTextPlugin } from '@lexical/react/LexicalRichTextPlugin'
+import { act, render, screen, waitFor } from '@testing-library/react'
+import { $createParagraphNode, $createTextNode, $getRoot } from 'lexical'
+import * as React from 'react'
+import FilePickerBlock from '../file-picker-block'
+
+vi.mock('@/app/components/workflow/skill/hooks/file-tree/data/use-skill-asset-tree', () => ({
+  useSkillAssetTreeData: () => ({
+    data: { children: [] },
+    isLoading: false,
+    error: null,
+  }),
+}))
+
+const mockDOMRect = {
+  x: 100,
+  y: 100,
+  width: 100,
+  height: 20,
+  top: 100,
+  right: 200,
+  bottom: 120,
+  left: 100,
+  toJSON: () => ({}),
+}
+
+beforeAll(() => {
+  Range.prototype.getClientRects = vi.fn(() => {
+    const rectList = [mockDOMRect] as unknown as DOMRectList
+    Object.defineProperty(rectList, 'length', { value: 1 })
+    Object.defineProperty(rectList, 'item', { value: (index: number) => (index === 0 ? mockDOMRect : null) })
+    return rectList
+  })
+  Range.prototype.getBoundingClientRect = vi.fn(() => mockDOMRect as DOMRect)
+})
+
+type Captures = {
+  editor: LexicalEditor | null
+}
+
+const CONTENT_EDITABLE_TEST_ID = 'file-picker-block-ce'
+
+const CaptureEditor = ({ captures }: { captures: Captures }) => {
+  const [editor] = useLexicalComposerContext()
+
+  React.useEffect(() => {
+    captures.editor = editor
+  }, [captures, editor])
+
+  return null
+}
+
+const MinimalEditor = ({ captures }: { captures: Captures }) => {
+  const initialConfig = React.useMemo(() => ({
+    namespace: `file-picker-block-test-${Math.random().toString(16).slice(2)}`,
+    onError: (e: Error) => {
+      throw e
+    },
+  }), [])
+
+  return (
+    <LexicalComposer initialConfig={initialConfig}>
+      <RichTextPlugin
+        contentEditable={<ContentEditable data-testid={CONTENT_EDITABLE_TEST_ID} />}
+        placeholder={null}
+        ErrorBoundary={LexicalErrorBoundary}
+      />
+      <CaptureEditor captures={captures} />
+      <FilePickerBlock />
+    </LexicalComposer>
+  )
+}
+
+async function waitForEditor(captures: Captures): Promise<LexicalEditor> {
+  await waitFor(() => {
+    expect(captures.editor).not.toBeNull()
+  })
+  return captures.editor as LexicalEditor
+}
+
+async function setEditorText(editor: LexicalEditor, text: string): Promise<void> {
+  await act(async () => {
+    editor.update(() => {
+      const root = $getRoot()
+      root.clear()
+      const paragraph = $createParagraphNode()
+      const textNode = $createTextNode(text)
+      paragraph.append(textNode)
+      root.append(paragraph)
+      textNode.selectEnd()
+    })
+  })
+}
+
+async function flushNextTick(): Promise<void> {
+  await act(async () => {
+    await new Promise<void>(resolve => setTimeout(resolve, 0))
+  })
+}
+
+describe('FilePickerBlock', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  // Regression coverage for the slash-triggered picker lifecycle.
+  describe('Typeahead Menu', () => {
+    it('should keep the file picker panel rendered when slash opens the menu', async () => {
+      const captures: Captures = { editor: null }
+
+      render(<MinimalEditor captures={captures} />)
+
+      const editor = await waitForEditor(captures)
+
+      await setEditorText(editor, '/')
+
+      expect(await screen.findByText('workflow.skillEditor.referenceFiles')).toBeInTheDocument()
+
+      await flushNextTick()
+
+      await waitFor(() => {
+        expect(screen.getByText('workflow.skillEditor.referenceFiles')).toBeInTheDocument()
+        expect(screen.getByText('workflow.skillSidebar.empty')).toBeInTheDocument()
+      })
+    })
+  })
+})
diff --git a/web/app/components/workflow/skill/editor/skill-editor/plugins/file-reference-block/__tests__/component.spec.tsx b/web/app/components/workflow/skill/editor/skill-editor/plugins/file-reference-block/__tests__/component.spec.tsx
new file mode 100644
index 0000000000..b363789d4d
--- /dev/null
+++ b/web/app/components/workflow/skill/editor/skill-editor/plugins/file-reference-block/__tests__/component.spec.tsx
@@ -0,0 +1,91 @@
+import type { AppAssetTreeView } from '@/types/app-asset'
+import { act, fireEvent, render, screen, waitFor } from '@testing-library/react'
+import * as React from 'react'
+import { useSelectOrDelete } from '@/app/components/base/prompt-editor/hooks'
+import FileReferenceBlock from '../component'
+
+const mockEditor = {
+  isEditable: vi.fn(() => true),
+  update: vi.fn(),
+}
+
+const mockRef = { current: null as HTMLDivElement | null }
+const mockNodeMap = new Map<string, AppAssetTreeView>()
+const mockWorkflowStoreState = {
+  activeTabId: null,
+  fileMetadata: new Map(),
+}
+
+vi.mock('@lexical/react/LexicalComposerContext', () => ({
+  useLexicalComposerContext: () => [mockEditor],
+}))
+
+vi.mock('@/app/components/base/prompt-editor/hooks', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('@/app/components/base/prompt-editor/hooks')>()
+  return {
+    ...actual,
+    useSelectOrDelete: vi.fn(),
+  }
+})
+
+vi.mock('@/app/components/workflow/skill/hooks/file-tree/data/use-skill-asset-tree', () => ({
+  useSkillAssetNodeMap: () => ({
+    data: mockNodeMap,
+    isLoading: false,
+  }),
+  useSkillAssetTreeData: () => ({
+    data: { children: [] },
+    isLoading: false,
+    error: null,
+  }),
+}))
+
+vi.mock('@/app/components/workflow/store', () => ({
+  useStore: (selector: (state: typeof mockWorkflowStoreState) => unknown) => selector(mockWorkflowStoreState),
+}))
+
+vi.mock('../preview-context', () => ({
+  useFilePreviewContext: (selector: (context: { enabled: boolean }) => boolean) => selector({ enabled: false }),
+}))
+
+describe('FileReferenceBlock', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    mockEditor.isEditable.mockReturnValue(true)
+    mockRef.current = null
+    mockNodeMap.clear()
+    mockNodeMap.set('file-1', {
+      id: 'file-1',
+      name: 'contract.pdf',
+      path: '/contract.pdf',
+      node_type: 'file',
+      children: [],
+      extension: 'pdf',
+      size: 0,
+    })
+    vi.mocked(useSelectOrDelete).mockReturnValue([mockRef, false])
+  })
+
+  // Click-triggered popover should remain visible after opening from the inline file block.
+  describe('Picker Popover', () => {
+    it('should keep the picker panel visible after pressing the inline file reference', async () => {
+      render(
+        <FileReferenceBlock
+          nodeKey="node-1"
+          resourceId="file-1"
+        />,
+      )
+
+      await act(async () => {
+        fireEvent.mouseDown(screen.getByText('contract.pdf'))
+      })
+
+      expect(await screen.findByText('workflow.skillEditor.referenceFiles')).toBeInTheDocument()
+
+      await waitFor(() => {
+        expect(screen.getByText('workflow.skillEditor.referenceFiles')).toBeInTheDocument()
+        expect(screen.getByText('workflow.skillSidebar.empty')).toBeInTheDocument()
+      })
+    })
+  })
+})
diff --git a/web/i18n/en-US/app.json b/web/i18n/en-US/app.json
index 33f0295918..8eaf0671ff 100644
--- a/web/i18n/en-US/app.json
+++ b/web/i18n/en-US/app.json
@@ -221,6 +221,7 @@
   "publishApp.title": "Who can access web app",
   "removeOriginal": "Delete the original app",
   "roadmap": "See our roadmap",
+  "sandboxBadge": "Sandbox",
   "showMyCreatedAppsOnly": "Created by me",
   "skills.comingSoon": "Workspace skills coming soon. Stay tuned.",
   "skills.title": "Skills",