fix(desktop): detect stale backend for projects.create

Probe the projects.* RPC surface, block create with a clear update hint,
and avoid the raw "unknown method" toast. Includes i18n for en, zh, ja,
and zh-hant.

Fixes NousResearch/hermes-agent#54999

apps/desktop/src/i18n/en.ts

@@ -1330,6 +1330,8 @@ export const en: Translations = {
       copyPath: 'Copy path',
       removeFromSidebar: 'Hide from sidebar',
       createFailed: 'Could not create project',
+      staleBackend:
+        'Update the Hermes backend to create projects — your backend is older than this desktop app (Settings → Updates → Backend).',
       deleteConfirm: 'This removes the saved project from Hermes. Files, git repos, and worktrees stay untouched.',
       startWork: 'New worktree',
       newWorktreeTitle: 'New worktree',

apps/desktop/src/i18n/ja.ts

@@ -1450,6 +1450,8 @@ export const ja = defineLocale({
       copyPath: 'パスをコピー',
       removeFromSidebar: 'サイドバーから削除',
       createFailed: 'プロジェクトを作成できませんでした',
+      staleBackend:
+        'プロジェクトを作成するには Hermes バックエンドを更新してください。バックエンドがこのデスクトップアプリより古いです（設定 → 更新 → バックエンド）。',
       deleteConfirm:
         'Hermes から保存済みプロジェクトを削除します。ファイル・git リポジトリ・ワークツリーはそのまま残ります。',
       startWork: '新しいワークツリー',

apps/desktop/src/i18n/types.ts

@@ -1076,6 +1076,7 @@ export interface Translations {
       copyPath: string
       removeFromSidebar: string
       createFailed: string
+      staleBackend: string
       deleteConfirm: string
       startWork: string
       newWorktreeTitle: string

apps/desktop/src/i18n/zh-hant.ts

@@ -1403,6 +1403,8 @@ export const zhHant = defineLocale({
       copyPath: '複製路徑',
       removeFromSidebar: '從側邊欄移除',
       createFailed: '無法建立專案',
+      staleBackend:
+        '請更新 Hermes 後端以建立專案——目前後端比桌面應用舊（設定 → 更新 → 後端）。',
       deleteConfirm: '這會從 Hermes 中移除已儲存的專案。檔案、git 儲存庫和工作樹維持不變。',
       startWork: '新增工作樹',
       newWorktreeTitle: '新增工作樹',

apps/desktop/src/i18n/zh.ts

@@ -1510,6 +1510,8 @@ export const zh: Translations = {
       copyPath: '复制路径',
       removeFromSidebar: '从侧边栏移除',
       createFailed: '无法创建项目',
+      staleBackend:
+        '请更新 Hermes 后端以创建项目——当前后端比桌面应用旧（设置 → 更新 → 后端）。',
       deleteConfirm: '这会从 Hermes 中移除已保存的项目。文件、git 仓库和工作树保持不变。',
       startWork: '新建工作树',
       newWorktreeTitle: '新建工作树',

apps/desktop/src/lib/gateway-rpc.ts

@@ -0,0 +1,6 @@
+/** True when a JSON-RPC call failed because the backend predates the method. */
+export function isMissingRpcMethod(error: unknown): boolean {
+  const message = error instanceof Error ? error.message : String(error)
+
+  return /method not found|-32601|unknown method|no such method/i.test(message)
+}

apps/desktop/src/store/projects.ts

@@ -4,8 +4,11 @@ import { liveSessionProjectId, type SidebarProjectTree } from '@/app/chat/sideba
 import type { HermesGitBranch } from '@/global'
 import { desktopDefaultCwd, selectDesktopPaths, writeDesktopFileText } from '@/lib/desktop-fs'
 import { desktopGit } from '@/lib/desktop-git'
+import { isMissingRpcMethod } from '@/lib/gateway-rpc'
 import { persistentAtom } from '@/lib/persisted'
+import { translateNow } from '@/i18n'
 import { activeGateway, ensureActiveGatewayOpen } from '@/store/gateway'
+import { notify } from '@/store/notifications'
 import { setSidebarAgentsGrouped } from '@/store/layout'
 import { requestFreshSession } from '@/store/profile'
 import { $selectedStoredSessionId, $sessions, workspaceCwdForNewSession } from '@/store/session'
@@ -26,6 +29,24 @@ export const $activeProjectId = atom<null | string>(null)
 export const $projectTree = atom<SidebarProjectTree[]>([])
 export const $projectTreeLoading = atom(false)
 
+// False when the connected backend predates the projects.* JSON-RPC surface
+// (same semver label, older install). Null until the first probe.
+export const $projectsRpcAvailable = atom<boolean | null>(null)
+
+function markProjectsRpcSuccess(): void {
+  $projectsRpcAvailable.set(true)
+}
+
+function markProjectsRpcFailure(err: unknown): void {
+  if (isMissingRpcMethod(err)) {
+    $projectsRpcAvailable.set(false)
+  }
+}
+
+function projectsStaleBackendError(): Error {
+  return new Error(translateNow('sidebar.projects.staleBackend'))
+}
+
 // Client-side cache eviction (Apollo-style optimistic layer): ids the user just
 // deleted/archived. The backend tree is a snapshot that still lists them until
 // its next refresh, so the render-time overlay strips these so the tree matches
@@ -216,7 +237,9 @@ function applyPayload(payload: ProjectsPayload): void {
 export async function refreshProjects(): Promise<void> {
   try {
     applyPayload(await gatewayRequest<ProjectsPayload>('projects.list'))
-  } catch {
+    markProjectsRpcSuccess()
+  } catch (err) {
+    markProjectsRpcFailure(err)
     // Backend may not be ready; keep the last known list.
   }
 }
@@ -254,7 +277,10 @@ export async function refreshProjectTree(): Promise<void> {
         $removedSessionIds.set(pending)
       }
     }
-  } catch {
+
+    markProjectsRpcSuccess()
+  } catch (err) {
+    markProjectsRpcFailure(err)
     // Backend may not be ready; keep the last known tree.
   } finally {
     $projectTreeLoading.set(false)
@@ -410,17 +436,34 @@ function projectInfoToTreeNode(project: ProjectInfo): SidebarProjectTree {
 }
 
 export async function createProject(input: CreateProjectInput): Promise<ProjectInfo | null> {
-  const res = await gatewayRequest<{ project: ProjectInfo | null }>('projects.create', {
-    name: input.name,
-    folders: input.folders ?? [],
-    primary_path: input.primaryPath,
-    slug: input.slug,
-    description: input.description,
-    icon: input.icon,
-    color: input.color,
-    board_slug: input.boardSlug,
-    use: input.use ?? false
-  })
+  if ($projectsRpcAvailable.get() === false) {
+    throw projectsStaleBackendError()
+  }
+
+  let res: { project: ProjectInfo | null }
+
+  try {
+    res = await gatewayRequest<{ project: ProjectInfo | null }>('projects.create', {
+      name: input.name,
+      folders: input.folders ?? [],
+      primary_path: input.primaryPath,
+      slug: input.slug,
+      description: input.description,
+      icon: input.icon,
+      color: input.color,
+      board_slug: input.boardSlug,
+      use: input.use ?? false
+    })
+  } catch (err) {
+    if (isMissingRpcMethod(err)) {
+      $projectsRpcAvailable.set(false)
+      throw projectsStaleBackendError()
+    }
+
+    throw err
+  }
+
+  markProjectsRpcSuccess()
 
   // Not optimistic (the create awaits the RPC first, so there's nothing to roll
   // back): apply the server's row into the cached list + tree at once, so it
@@ -593,6 +636,15 @@ export interface ProjectDialogState {
 export const $projectDialog = atom<null | ProjectDialogState>(null)
 
 export function openProjectCreate(): void {
+  if ($projectsRpcAvailable.get() === false) {
+    notify({
+      kind: 'warning',
+      message: translateNow('sidebar.projects.staleBackend')
+    })
+
+    return
+  }
+
   $projectDialog.set({ mode: 'create' })
 }