diff --git a/apps/desktop/src/lib/gateway-rpc.test.ts b/apps/desktop/src/lib/gateway-rpc.test.ts
new file mode 100644
index 00000000000..6da30b87b76
--- /dev/null
+++ b/apps/desktop/src/lib/gateway-rpc.test.ts
@@ -0,0 +1,16 @@
+import { describe, expect, it } from 'vitest'
+
+import { isMissingRpcMethod } from './gateway-rpc'
+
+describe('isMissingRpcMethod', () => {
+  it('detects JSON-RPC method-not-found errors', () => {
+    expect(isMissingRpcMethod(new Error('unknown method: projects.create'))).toBe(true)
+    expect(isMissingRpcMethod(new Error('Method not found'))).toBe(true)
+    expect(isMissingRpcMethod(new Error('RPC failed: -32601'))).toBe(true)
+  })
+
+  it('ignores unrelated failures', () => {
+    expect(isMissingRpcMethod(new Error('Hermes gateway is not connected'))).toBe(false)
+    expect(isMissingRpcMethod(new Error('no such project'))).toBe(false)
+  })
+})
diff --git a/apps/desktop/src/store/projects.test.ts b/apps/desktop/src/store/projects.test.ts
index 9e80fe5b889..24bc2a6f854 100644
--- a/apps/desktop/src/store/projects.test.ts
+++ b/apps/desktop/src/store/projects.test.ts
@@ -5,15 +5,26 @@ import { $sidebarAgentsGrouped } from '@/store/layout'
 import {
   $activeProjectId,
   $projectScope,
+  $projectsRpcAvailable,
   $worktreeRefreshToken,
   ALL_PROJECTS,
   createProject,
   enterProject,
   exitProjectScope,
+  openProjectCreate,
   pickProjectFolder,
+  refreshProjects,
   refreshWorktrees
 } from './projects'
 
+vi.mock('@/i18n', () => ({
+  translateNow: (key: string) => key
+}))
+
+vi.mock('@/store/notifications', () => ({
+  notify: vi.fn()
+}))
+
 vi.mock('@/lib/desktop-fs', () => ({
   desktopDefaultCwd: vi.fn(),
   isDesktopFsRemoteMode: vi.fn(),
@@ -33,6 +44,8 @@ const selectDesktopPaths = vi.mocked(fs.selectDesktopPaths)
 
 const gw = await import('@/store/gateway')
 const activeGateway = vi.mocked(gw.activeGateway)
+const notifications = await import('@/store/notifications')
+const notify = vi.mocked(notifications.notify)
 
 describe('project scope', () => {
   beforeEach(() => {
@@ -115,6 +128,7 @@ describe('createProject', () => {
     vi.clearAllMocks()
     $sidebarAgentsGrouped.set(false)
     $activeProjectId.set(null)
+    $projectsRpcAvailable.set(null)
   })
 
   it('creates the project and flips into the grouped view so a blank slate shows it', async () => {
@@ -139,4 +153,44 @@ describe('createProject', () => {
     expect($sidebarAgentsGrouped.get()).toBe(true)
     expect($activeProjectId.get()).toBe('p_new')
   })
+
+  it('marks the backend stale and surfaces a friendly error when projects.create is missing', async () => {
+    activeGateway.mockReturnValue({
+      connectionState: 'open',
+      request: vi.fn().mockRejectedValue(new Error('unknown method: projects.create'))
+    } as never)
+
+    await expect(createProject({ folders: ['/srv/demo'], name: 'Demo' })).rejects.toThrow(
+      'sidebar.projects.staleBackend'
+    )
+    expect($projectsRpcAvailable.get()).toBe(false)
+  })
+})
+
+describe('projects RPC capability', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    $projectsRpcAvailable.set(null)
+  })
+
+  it('marks the backend stale when projects.list is missing', async () => {
+    activeGateway.mockReturnValue({
+      connectionState: 'open',
+      request: vi.fn().mockRejectedValue(new Error('unknown method: projects.list'))
+    } as never)
+
+    await refreshProjects()
+
+    expect($projectsRpcAvailable.get()).toBe(false)
+  })
+
+  it('blocks opening the create dialog once the backend is known stale', () => {
+    $projectsRpcAvailable.set(false)
+
+    openProjectCreate()
+
+    expect(notify).toHaveBeenCalledWith(
+      expect.objectContaining({ kind: 'warning', message: 'sidebar.projects.staleBackend' })
+    )
+  })
 })