feat: detect MCP server status and show warning in status bar

Add check_mcp_status Tauri command that detects whether the MCP server
is installed, Claude CLI is missing, or config needs setup. The status
bar shows a warning badge (MCP ⚠) when not installed, clickable to
trigger install. Also available via command palette "Install MCP Server".

Replaces useMcpRegistration with useMcpStatus which combines detection
and registration in a single hook.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/hooks/useAppCommands.ts

@@ -64,6 +64,8 @@ interface AppCommandsConfig {
   onRestoreGettingStarted?: () => void
   isGettingStartedHidden?: boolean
   vaultCount?: number
+  mcpStatus?: string
+  onInstallMcp?: () => void
 }
 
 /** Sets up keyboard shortcuts, command registry, menu events, and keyboard navigation. */
@@ -172,6 +174,8 @@ export function useAppCommands(config: AppCommandsConfig): CommandAction[] {
     onRestoreGettingStarted: config.onRestoreGettingStarted,
     isGettingStartedHidden: config.isGettingStartedHidden,
     vaultCount: config.vaultCount,
+    mcpStatus: config.mcpStatus,
+    onInstallMcp: config.onInstallMcp,
   })
 
   useKeyboardNavigation({

src/hooks/useCommandRegistry.ts

@@ -19,6 +19,8 @@ interface CommandRegistryConfig {
   entries: VaultEntry[]
   modifiedCount: number
   conflictCount?: number
+  mcpStatus?: string
+  onInstallMcp?: () => void
 
   onQuickOpen: () => void
   onCreateNote: () => void
@@ -193,6 +195,7 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
     onCheckForUpdates,
     onCreateType,
     onRemoveActiveVault, onRestoreGettingStarted, isGettingStartedHidden, vaultCount,
+    mcpStatus, onInstallMcp,
   } = config
 
   const hasActiveNote = activeTabPath !== null
@@ -252,6 +255,7 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
       { id: 'remove-vault', label: 'Remove Vault from List', group: 'Settings', keywords: ['vault', 'remove', 'disconnect', 'hide'], enabled: (vaultCount ?? 0) > 1 && !!onRemoveActiveVault, execute: () => onRemoveActiveVault?.() },
       { id: 'restore-getting-started', label: 'Restore Getting Started Vault', group: 'Settings', keywords: ['vault', 'restore', 'demo', 'getting started', 'reset'], enabled: !!isGettingStartedHidden && !!onRestoreGettingStarted, execute: () => onRestoreGettingStarted?.() },
       { id: 'check-updates', label: 'Check for Updates', group: 'Settings', keywords: ['update', 'version', 'upgrade', 'release'], enabled: true, execute: () => onCheckForUpdates?.() },
+      { id: 'install-mcp', label: 'Install MCP Server', group: 'Settings', keywords: ['mcp', 'claude', 'ai', 'tools', 'install'], enabled: mcpStatus === 'not_installed' && !!onInstallMcp, execute: () => onInstallMcp?.() },
 
       // Type-aware: "New [Type]" and "List [Type]"
       ...buildTypeCommands(vaultTypes, onCreateNoteOfType, onSelect),
@@ -269,5 +273,6 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
     onGoBack, onGoForward, canGoBack, canGoForward,
     vaultTypes, themes, activeThemeId, onSwitchTheme, onCreateTheme, onOpenTheme,
     onRemoveActiveVault, onRestoreGettingStarted, isGettingStartedHidden, vaultCount,
+    mcpStatus, onInstallMcp,
   ])
 }

src/hooks/useMcpStatus.test.ts

@@ -0,0 +1,151 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { renderHook, act, waitFor } from '@testing-library/react'
+import { useMcpStatus } from './useMcpStatus'
+
+vi.mock('@tauri-apps/api/core', () => ({
+  invoke: vi.fn(),
+}))
+
+vi.mock('../mock-tauri', () => ({
+  isTauri: () => false,
+  mockInvoke: vi.fn(),
+}))
+
+const { mockInvoke } = await import('../mock-tauri') as { mockInvoke: ReturnType<typeof vi.fn> }
+
+describe('useMcpStatus', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('starts in checking state and resolves to installed', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('installed')
+      if (cmd === 'register_mcp_tools') return Promise.resolve('updated')
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    const { result } = renderHook(() => useMcpStatus('/vault', onToast))
+
+    expect(result.current.mcpStatus).toBe('checking')
+
+    await waitFor(() => {
+      expect(result.current.mcpStatus).toBe('installed')
+    })
+  })
+
+  it('resolves to not_installed when check returns not_installed', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('not_installed')
+      if (cmd === 'register_mcp_tools') return Promise.reject(new Error('fail'))
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    const { result } = renderHook(() => useMcpStatus('/vault', onToast))
+
+    await waitFor(() => {
+      expect(result.current.mcpStatus).toBe('not_installed')
+    })
+  })
+
+  it('resolves to no_claude_cli when check returns no_claude_cli', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('no_claude_cli')
+      if (cmd === 'register_mcp_tools') return Promise.reject(new Error('no cli'))
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    const { result } = renderHook(() => useMcpStatus('/vault', onToast))
+
+    await waitFor(() => {
+      expect(result.current.mcpStatus).toBe('no_claude_cli')
+    })
+  })
+
+  it('install action calls register_mcp_tools and updates status', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('not_installed')
+      if (cmd === 'register_mcp_tools') return Promise.resolve('registered')
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    const { result } = renderHook(() => useMcpStatus('/vault', onToast))
+
+    await waitFor(() => {
+      expect(result.current.mcpStatus).toBe('installed')
+    })
+
+    // Reset to test install action directly
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('not_installed')
+      if (cmd === 'register_mcp_tools') return Promise.resolve('registered')
+      return Promise.resolve(null)
+    })
+
+    await act(async () => {
+      await result.current.installMcp()
+    })
+
+    expect(result.current.mcpStatus).toBe('installed')
+    expect(onToast).toHaveBeenCalledWith('MCP server installed successfully')
+  })
+
+  it('install action shows error toast on failure', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('not_installed')
+      if (cmd === 'register_mcp_tools') return Promise.reject(new Error('disk full'))
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    const { result } = renderHook(() => useMcpStatus('/vault', onToast))
+
+    await waitFor(() => {
+      expect(result.current.mcpStatus).toBe('not_installed')
+    })
+
+    await act(async () => {
+      await result.current.installMcp()
+    })
+
+    expect(result.current.mcpStatus).toBe('not_installed')
+    expect(onToast).toHaveBeenCalledWith(expect.stringContaining('MCP install failed'))
+  })
+
+  it('shows toast when registered for the first time', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('installed')
+      if (cmd === 'register_mcp_tools') return Promise.resolve('registered')
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    renderHook(() => useMcpStatus('/vault', onToast))
+
+    await waitFor(() => {
+      expect(onToast).toHaveBeenCalledWith('Laputa registered as MCP tool for Claude Code')
+    })
+  })
+
+  it('does not show toast when already registered', async () => {
+    mockInvoke.mockImplementation((cmd: string) => {
+      if (cmd === 'check_mcp_status') return Promise.resolve('installed')
+      if (cmd === 'register_mcp_tools') return Promise.resolve('updated')
+      return Promise.resolve(null)
+    })
+
+    const onToast = vi.fn()
+    renderHook(() => useMcpStatus('/vault', onToast))
+
+    await waitFor(() => {
+      expect(mockInvoke).toHaveBeenCalledWith('register_mcp_tools', { vaultPath: '/vault' })
+    })
+
+    // 'updated' should not trigger a toast
+    expect(onToast).not.toHaveBeenCalledWith('Laputa registered as MCP tool for Claude Code')
+  })
+})

src/hooks/useMcpStatus.ts

@@ -0,0 +1,72 @@
+import { useCallback, useEffect, useRef, useState } from 'react'
+import { invoke } from '@tauri-apps/api/core'
+import { isTauri, mockInvoke } from '../mock-tauri'
+
+export type McpStatus = 'checking' | 'installed' | 'not_installed' | 'no_claude_cli'
+
+function tauriCall<T>(command: string, args?: Record<string, unknown>): Promise<T> {
+  return isTauri() ? invoke<T>(command, args) : mockInvoke<T>(command, args)
+}
+
+/**
+ * Detects MCP server status on vault open and provides an install action.
+ *
+ * Combines the old `useMcpRegistration` functionality (auto-register on vault
+ * switch) with new status detection for the status bar indicator.
+ */
+export function useMcpStatus(
+  vaultPath: string,
+  onToast: (msg: string) => void,
+) {
+  const [status, setStatus] = useState<McpStatus>('checking')
+  const registeredRef = useRef<string | null>(null)
+  const onToastRef = useRef(onToast)
+  useEffect(() => { onToastRef.current = onToast })
+
+  // Check MCP status on vault open / vault switch
+  useEffect(() => {
+    let cancelled = false
+    setStatus('checking') // eslint-disable-line react-hooks/set-state-in-effect -- reset to checking on vault switch
+
+    tauriCall<string>('check_mcp_status')
+      .then((result) => {
+        if (!cancelled) setStatus(result as McpStatus)
+      })
+      .catch(() => {
+        if (!cancelled) setStatus('not_installed')
+      })
+
+    return () => { cancelled = true }
+  }, [vaultPath])
+
+  // Auto-register on vault switch (preserves old useMcpRegistration behavior)
+  useEffect(() => {
+    if (registeredRef.current === vaultPath) return
+    registeredRef.current = vaultPath
+
+    tauriCall<string>('register_mcp_tools', { vaultPath })
+      .then((result) => {
+        if (result === 'registered') {
+          onToastRef.current('Laputa registered as MCP tool for Claude Code')
+        }
+        setStatus('installed')
+      })
+      .catch(() => {
+        // Non-critical — status check will show the right state
+      })
+  }, [vaultPath])
+
+  const install = useCallback(async () => {
+    setStatus('checking')
+    try {
+      await tauriCall<string>('register_mcp_tools', { vaultPath })
+      setStatus('installed')
+      onToastRef.current('MCP server installed successfully')
+    } catch (e) {
+      setStatus('not_installed')
+      onToastRef.current(`MCP install failed: ${e}`)
+    }
+  }, [vaultPath])
+
+  return { mcpStatus: status, installMcp: install }
+}