diff --git a/apps/desktop/src/lib/desktop-fs.test.ts b/apps/desktop/src/lib/desktop-fs.test.ts
new file mode 100644
index 00000000000..23c9ea8faf4
--- /dev/null
+++ b/apps/desktop/src/lib/desktop-fs.test.ts
@@ -0,0 +1,100 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { $connection } from '@/store/session'
+
+import {
+  desktopGitRoot,
+  readDesktopDir,
+  readDesktopFileDataUrl,
+  readDesktopFileText,
+  selectDesktopPaths,
+  setDesktopFsRemotePicker
+} from './desktop-fs'
+
+const readDir = vi.fn(async () => ({ entries: [{ name: 'local', path: '/local', isDirectory: true }] }))
+const readFileText = vi.fn(async () => ({ path: '/local/file.txt', text: 'local', byteSize: 5 }))
+const readFileDataUrl = vi.fn(async () => 'data:text/plain;base64,bG9jYWw=')
+const gitRoot = vi.fn(async () => '/local')
+const selectPaths = vi.fn(async () => ['/local'])
+const api = vi.fn(async ({ path }: { path: string }) => {
+  if (path.startsWith('/api/fs/list?')) return { entries: [{ name: 'remote', path: '/remote', isDirectory: true }] }
+  if (path.startsWith('/api/fs/read-text?')) return { path: '/remote/file.txt', text: 'remote', byteSize: 6 }
+  if (path.startsWith('/api/fs/read-data-url?')) return { dataUrl: 'data:text/plain;base64,cmVtb3Rl' }
+  if (path.startsWith('/api/fs/git-root?')) return { root: '/remote' }
+  throw new Error(`unexpected path ${path}`)
+})
+
+function stubBridge() {
+  vi.stubGlobal('window', {
+    hermesDesktop: {
+      api,
+      gitRoot,
+      readDir,
+      readFileDataUrl,
+      readFileText,
+      selectPaths
+    }
+  })
+}
+
+describe('desktop filesystem facade', () => {
+  beforeEach(() => {
+    stubBridge()
+    $connection.set(null)
+  })
+
+  afterEach(() => {
+    vi.unstubAllGlobals()
+    vi.clearAllMocks()
+    $connection.set(null)
+    setDesktopFsRemotePicker(null)
+  })
+
+  it('uses local Electron filesystem methods in local mode', async () => {
+    $connection.set({ mode: 'local' } as never)
+
+    await expect(readDesktopDir('/work')).resolves.toEqual({ entries: [{ name: 'local', path: '/local', isDirectory: true }] })
+    await expect(readDesktopFileText('/work/file.txt')).resolves.toMatchObject({ text: 'local' })
+    await expect(readDesktopFileDataUrl('/work/file.txt')).resolves.toBe('data:text/plain;base64,bG9jYWw=')
+    await expect(desktopGitRoot('/work')).resolves.toBe('/local')
+    await expect(selectDesktopPaths({ directories: true })).resolves.toEqual(['/local'])
+
+    expect(readDir).toHaveBeenCalledWith('/work')
+    expect(readFileText).toHaveBeenCalledWith('/work/file.txt')
+    expect(readFileDataUrl).toHaveBeenCalledWith('/work/file.txt')
+    expect(gitRoot).toHaveBeenCalledWith('/work')
+    expect(selectPaths).toHaveBeenCalledWith({ directories: true })
+    expect(api).not.toHaveBeenCalled()
+  })
+
+  it('routes filesystem reads through authenticated backend REST in remote mode', async () => {
+    $connection.set({ mode: 'remote' } as never)
+
+    await expect(readDesktopDir('/home/user/project')).resolves.toMatchObject({ entries: [{ name: 'remote' }] })
+    await expect(readDesktopFileText('/home/user/project/a b.txt')).resolves.toMatchObject({ text: 'remote' })
+    await expect(readDesktopFileDataUrl('/home/user/project/a b.txt')).resolves.toBe('data:text/plain;base64,cmVtb3Rl')
+    await expect(desktopGitRoot('/home/user/project')).resolves.toBe('/remote')
+
+    expect(api).toHaveBeenCalledWith({ path: '/api/fs/list?path=%2Fhome%2Fuser%2Fproject' })
+    expect(api).toHaveBeenCalledWith({ path: '/api/fs/read-text?path=%2Fhome%2Fuser%2Fproject%2Fa%20b.txt' })
+    expect(api).toHaveBeenCalledWith({ path: '/api/fs/read-data-url?path=%2Fhome%2Fuser%2Fproject%2Fa%20b.txt' })
+    expect(api).toHaveBeenCalledWith({ path: '/api/fs/git-root?path=%2Fhome%2Fuser%2Fproject' })
+    expect(readDir).not.toHaveBeenCalled()
+    expect(readFileText).not.toHaveBeenCalled()
+    expect(readFileDataUrl).not.toHaveBeenCalled()
+    expect(gitRoot).not.toHaveBeenCalled()
+  })
+
+  it('uses the registered in-app picker in remote mode', async () => {
+    const remoteSelect = vi.fn(async () => ['/remote/project'])
+    $connection.set({ mode: 'remote' } as never)
+    setDesktopFsRemotePicker({ selectPaths: remoteSelect })
+
+    await expect(selectDesktopPaths({ defaultPath: '/remote', directories: true, multiple: false })).resolves.toEqual([
+      '/remote/project'
+    ])
+
+    expect(remoteSelect).toHaveBeenCalledWith({ defaultPath: '/remote', directories: true, multiple: false })
+    expect(selectPaths).not.toHaveBeenCalled()
+  })
+})
diff --git a/apps/desktop/src/lib/desktop-fs.ts b/apps/desktop/src/lib/desktop-fs.ts
new file mode 100644
index 00000000000..d49394130b5
--- /dev/null
+++ b/apps/desktop/src/lib/desktop-fs.ts
@@ -0,0 +1,84 @@
+import { $connection } from '@/store/session'
+
+import type { HermesConnection, HermesReadDirResult, HermesReadFileTextResult, HermesSelectPathsOptions } from '@/global'
+
+export interface DesktopFsRemotePicker {
+  selectPaths: (options?: HermesSelectPathsOptions) => Promise<string[]>
+}
+
+let remotePicker: DesktopFsRemotePicker | null = null
+
+export function setDesktopFsRemotePicker(next: DesktopFsRemotePicker | null) {
+  remotePicker = next
+}
+
+function connectionCacheKey(connection: HermesConnection | null) {
+  if (!connection) {
+    return 'local:'
+  }
+  return `${connection.mode || 'local'}:${connection.profile || ''}:${connection.baseUrl || ''}`
+}
+
+export function desktopFsCacheKey() {
+  return connectionCacheKey($connection.get())
+}
+
+function isRemoteMode() {
+  return $connection.get()?.mode === 'remote'
+}
+
+function fsPath(endpoint: string, filePath: string) {
+  return `/api/fs/${endpoint}?path=${encodeURIComponent(filePath)}`
+}
+
+function bridge() {
+  const desktop = window.hermesDesktop
+  if (!desktop) {
+    throw new Error('Hermes Desktop bridge is unavailable')
+  }
+  return desktop
+}
+
+export async function readDesktopDir(path: string): Promise<HermesReadDirResult> {
+  const desktop = bridge()
+  if (!isRemoteMode()) {
+    return desktop.readDir(path)
+  }
+  return desktop.api<HermesReadDirResult>({ path: fsPath('list', path) })
+}
+
+export async function readDesktopFileText(path: string): Promise<HermesReadFileTextResult> {
+  const desktop = bridge()
+  if (!isRemoteMode()) {
+    return desktop.readFileText(path)
+  }
+  return desktop.api<HermesReadFileTextResult>({ path: fsPath('read-text', path) })
+}
+
+export async function readDesktopFileDataUrl(path: string): Promise<string> {
+  const desktop = bridge()
+  if (!isRemoteMode()) {
+    return desktop.readFileDataUrl(path)
+  }
+
+  const result = await desktop.api<string | { dataUrl?: string }>({ path: fsPath('read-data-url', path) })
+  return typeof result === 'string' ? result : result.dataUrl || ''
+}
+
+export async function desktopGitRoot(path: string): Promise<string | null> {
+  const desktop = bridge()
+  if (!isRemoteMode()) {
+    return desktop.gitRoot ? desktop.gitRoot(path) : null
+  }
+
+  const result = await desktop.api<{ root: string | null }>({ path: fsPath('git-root', path) })
+  return result.root
+}
+
+export async function selectDesktopPaths(options?: HermesSelectPathsOptions): Promise<string[]> {
+  const desktop = bridge()
+  if (!isRemoteMode()) {
+    return desktop.selectPaths(options)
+  }
+  return remotePicker ? remotePicker.selectPaths(options) : []
+}