feat: respect mcpEnabled setting to prevent automatic MCP server initialization

- Add conditional initialization in ClineProvider based on mcpEnabled setting
- Update McpHub constructor to accept autoInitialize parameter
- Add enableServers() and disableServers() methods for dynamic control
- Handle mcpEnabled toggle in webview message handler
- Update tests to cover new behavior

Fixes #6014

Author: roomote

src/core/webview/ClineProvider.ts

@@ -148,19 +148,34 @@ export class ClineProvider
 			await this.postStateToWebview()
 		})
 
-		// Initialize MCP Hub through the singleton manager
-		McpServerManager.getInstance(this.context, this)
-			.then((hub) => {
-				this.mcpHub = hub
-				this.mcpHub.registerClient()
-			})
-			.catch((error) => {
-				this.log(`Failed to initialize MCP Hub: ${error}`)
-			})
+		// Initialize MCP Hub through the singleton manager only if mcpEnabled
+		this.initializeMcpIfEnabled()
 
 		this.marketplaceManager = new MarketplaceManager(this.context)
 	}
 
+	private async initializeMcpIfEnabled() {
+		try {
+			// Get the mcpEnabled setting from global state
+			const mcpEnabled = this.contextProxy.getValue("mcpEnabled") ?? true
+
+			if (mcpEnabled) {
+				// Initialize MCP Hub through the singleton manager
+				const hub = await McpServerManager.getInstance(this.context, this, true)
+				this.mcpHub = hub
+				this.mcpHub.registerClient()
+			} else {
+				this.log("MCP is disabled, skipping MCP Hub initialization")
+				// Still create the hub instance but don't initialize servers
+				const hub = await McpServerManager.getInstance(this.context, this, false)
+				this.mcpHub = hub
+				this.mcpHub.registerClient()
+			}
+		} catch (error) {
+			this.log(`Failed to initialize MCP Hub: ${error}`)
+		}
+	}
+
 	// Adds a new Cline instance to clineStack, marking the start of a new task.
 	// The instance is pushed to the top of the stack (LIFO order).
 	// When the task is completed, the top instance is removed, reactivating the previous task.

src/core/webview/webviewMessageHandler.ts

@@ -880,6 +880,17 @@ export const webviewMessageHandler = async (
 		case "mcpEnabled":
 			const mcpEnabled = message.bool ?? true
 			await updateGlobalState("mcpEnabled", mcpEnabled)
+
+			// Enable or disable MCP servers based on the setting
+			const mcpHubInstance = provider.getMcpHub()
+			if (mcpHubInstance) {
+				if (mcpEnabled) {
+					await mcpHubInstance.enableServers()
+				} else {
+					await mcpHubInstance.disableServers()
+				}
+			}
+
 			await provider.postStateToWebview()
 			break
 		case "enableMcpServerCreation":

src/services/mcp/McpHub.ts

@@ -135,13 +135,16 @@ export class McpHub {
 	private refCount: number = 0 // Reference counter for active clients
 	private configChangeDebounceTimers: Map<string, NodeJS.Timeout> = new Map()
 
-	constructor(provider: ClineProvider) {
+	constructor(provider: ClineProvider, autoInitialize: boolean = true) {
 		this.providerRef = new WeakRef(provider)
 		this.watchMcpSettingsFile()
 		this.watchProjectMcpFile().catch(console.error)
 		this.setupWorkspaceFoldersWatcher()
-		this.initializeGlobalMcpServers()
-		this.initializeProjectMcpServers()
+
+		if (autoInitialize) {
+			this.initializeGlobalMcpServers()
+			this.initializeProjectMcpServers()
+		}
 	}
 	/**
 	 * Registers a client (e.g., ClineProvider) using this hub.
@@ -1643,4 +1646,38 @@ export class McpHub {
 		}
 		this.disposables.forEach((d) => d.dispose())
 	}
+
+	/**
+	 * Enable MCP servers by initializing them
+	 */
+	async enableServers(): Promise<void> {
+		if (this.connections.length > 0) {
+			console.log("MCP servers are already initialized")
+			return
+		}
+
+		console.log("Enabling MCP servers...")
+		await this.initializeGlobalMcpServers()
+		await this.initializeProjectMcpServers()
+		await this.notifyWebviewOfServerChanges()
+	}
+
+	/**
+	 * Disable MCP servers by disconnecting all connections
+	 */
+	async disableServers(): Promise<void> {
+		console.log("Disabling MCP servers...")
+
+		// Disconnect all servers
+		const allConnections = [...this.connections]
+		for (const conn of allConnections) {
+			await this.deleteConnection(conn.server.name, conn.server.source)
+		}
+
+		// Clear connections array
+		this.connections = []
+
+		// Notify webview of changes
+		await this.notifyWebviewOfServerChanges()
+	}
 }

src/services/mcp/McpServerManager.ts

@@ -17,7 +17,11 @@ export class McpServerManager {
 	 * Creates a new instance if one doesn't exist.
 	 * Thread-safe implementation using a promise-based lock.
 	 */
-	static async getInstance(context: vscode.ExtensionContext, provider: ClineProvider): Promise<McpHub> {
+	static async getInstance(
+		context: vscode.ExtensionContext,
+		provider: ClineProvider,
+		autoInitialize: boolean = true,
+	): Promise<McpHub> {
 		// Register the provider
 		this.providers.add(provider)
 
@@ -36,7 +40,7 @@ export class McpServerManager {
 			try {
 				// Double-check instance in case it was created while we were waiting
 				if (!this.instance) {
-					this.instance = new McpHub(provider)
+					this.instance = new McpHub(provider, autoInitialize)
 					// Store a unique identifier in global state to track the primary instance
 					await context.globalState.update(this.GLOBAL_STATE_KEY, Date.now().toString())
 				}

src/services/mcp/__tests__/McpHub.spec.ts

@@ -65,6 +65,19 @@ vi.mock("vscode", () => ({
 	Disposable: {
 		from: vi.fn(),
 	},
+	Uri: {
+		file: vi.fn((path) => ({
+			scheme: "file",
+			authority: "",
+			path,
+			query: "",
+			fragment: "",
+			fsPath: path,
+			with: vi.fn(),
+			toJSON: vi.fn(),
+		})),
+	},
+	RelativePattern: vi.fn((base, pattern) => ({ base, pattern })),
 }))
 vi.mock("fs/promises")
 vi.mock("../../../core/webview/ClineProvider")
@@ -1226,4 +1239,144 @@ describe("McpHub", () => {
 			)
 		})
 	})
+
+	describe("Conditional initialization", () => {
+		it("should not initialize servers when autoInitialize is false", async () => {
+			// Clear existing mocks
+			vi.clearAllMocks()
+
+			// Create McpHub with autoInitialize = false
+			const mcpHubNoInit = new McpHub(mockProvider as ClineProvider, false)
+
+			// Verify no connections were created
+			expect(mcpHubNoInit.connections.length).toBe(0)
+
+			// Verify fs.readFile was not called for server initialization
+			expect(fs.readFile).not.toHaveBeenCalled()
+		})
+
+		it("should initialize servers when autoInitialize is true", async () => {
+			// Clear existing mocks
+			vi.clearAllMocks()
+
+			// Mock the config file read
+			vi.mocked(fs.readFile).mockResolvedValue(
+				JSON.stringify({
+					mcpServers: {
+						"test-server": {
+							type: "stdio",
+							command: "node",
+							args: ["test.js"],
+						},
+					},
+				}),
+			)
+
+			// Create McpHub with autoInitialize = true
+			const mcpHubInit = new McpHub(mockProvider as ClineProvider, true)
+
+			// Wait a bit for async initialization
+			await new Promise((resolve) => setTimeout(resolve, 100))
+
+			// Verify fs.readFile was called for initialization
+			expect(fs.readFile).toHaveBeenCalled()
+		})
+
+		it("should enable servers after creation when enableServers is called", async () => {
+			// Clear existing mocks
+			vi.clearAllMocks()
+
+			// Mock the config file read
+			vi.mocked(fs.readFile).mockResolvedValue(
+				JSON.stringify({
+					mcpServers: {
+						"test-server": {
+							type: "stdio",
+							command: "node",
+							args: ["test.js"],
+						},
+					},
+				}),
+			)
+
+			// Mock StdioClientTransport
+			const mockTransport = {
+				start: vi.fn().mockResolvedValue(undefined),
+				close: vi.fn().mockResolvedValue(undefined),
+				stderr: {
+					on: vi.fn(),
+				},
+				onerror: null,
+				onclose: null,
+			}
+
+			const stdioModule = await import("@modelcontextprotocol/sdk/client/stdio.js")
+			const StdioClientTransport = stdioModule.StdioClientTransport as ReturnType<typeof vi.fn>
+			StdioClientTransport.mockImplementation(() => mockTransport)
+
+			// Mock Client
+			const clientModule = await import("@modelcontextprotocol/sdk/client/index.js")
+			const Client = clientModule.Client as ReturnType<typeof vi.fn>
+			Client.mockImplementation(() => ({
+				connect: vi.fn().mockResolvedValue(undefined),
+				close: vi.fn().mockResolvedValue(undefined),
+				getInstructions: vi.fn().mockReturnValue("test instructions"),
+				request: vi.fn().mockResolvedValue({ tools: [], resources: [], resourceTemplates: [] }),
+			}))
+
+			// Create McpHub without auto-initialization
+			const mcpHubNoInit = new McpHub(mockProvider as ClineProvider, false)
+
+			// Verify no connections initially
+			expect(mcpHubNoInit.connections.length).toBe(0)
+
+			// Enable servers
+			await mcpHubNoInit.enableServers()
+
+			// Verify connections were created
+			expect(mcpHubNoInit.connections.length).toBeGreaterThan(0)
+		})
+
+		it("should disable all servers when disableServers is called", async () => {
+			// Create McpHub with some connections
+			mcpHub.connections = [
+				{
+					server: {
+						name: "test-server-1",
+						source: "global",
+					} as any,
+					client: {
+						close: vi.fn().mockResolvedValue(undefined),
+					} as any,
+					transport: {
+						close: vi.fn().mockResolvedValue(undefined),
+					} as any,
+				},
+				{
+					server: {
+						name: "test-server-2",
+						source: "project",
+					} as any,
+					client: {
+						close: vi.fn().mockResolvedValue(undefined),
+					} as any,
+					transport: {
+						close: vi.fn().mockResolvedValue(undefined),
+					} as any,
+				},
+			]
+
+			// Disable servers
+			await mcpHub.disableServers()
+
+			// Verify all connections were closed
+			expect(mcpHub.connections.length).toBe(0)
+			expect(mockProvider.postMessageToWebview).toHaveBeenCalledWith(
+				expect.objectContaining({
+					type: "mcpServers",
+					mcpServers: [],
+				}),
+			)
+		})
+	})
 })