Add support for the new vscode.lm.registerMcpServerDefinitionProvider API

packages/plugin-ext/package.json

@@ -5,6 +5,7 @@
   "main": "lib/common/index.js",
   "typings": "lib/common/index.d.ts",
   "dependencies": {
+    "@theia/ai-mcp": "1.62.0",
     "@theia/bulk-edit": "1.62.0",
     "@theia/callhierarchy": "1.62.0",
     "@theia/console": "1.62.0",

packages/plugin-ext/src/common/lm-protocol.ts

@@ -0,0 +1,137 @@
+// *****************************************************************************
+// Copyright (C) 2025 EclipseSource.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License v. 2.0 which is available at
+// http://www.eclipse.org/legal/epl-2.0.
+//
+// This Source Code may also be made available under the following Secondary
+// Licenses when the conditions for such availability set forth in the Eclipse
+// Public License v. 2.0 are satisfied: GNU General Public License, version 2
+// with the GNU Classpath Exception which is available at
+// https://www.gnu.org/software/classpath/license.html.
+//
+// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
+// *****************************************************************************
+
+import { UriComponents } from './uri-components';
+
+/**
+ * Protocol interfaces for MCP server definition providers.
+ */
+
+export interface McpStdioServerDefinitionDto {
+    /**
+     * The human-readable name of the server.
+     */
+    readonly label: string;
+
+    /**
+     * The working directory used to start the server.
+     */
+    cwd?: UriComponents;
+
+    /**
+     * The command used to start the server. Node.js-based servers may use
+     * `process.execPath` to use the editor's version of Node.js to run the script.
+     */
+    command: string;
+
+    /**
+     * Additional command-line arguments passed to the server.
+     */
+    args?: string[];
+
+    /**
+     * Optional additional environment information for the server. Variables
+     * in this environment will overwrite or remove (if null) the default
+     * environment variables of the editor's extension host.
+     */
+    env?: Record<string, string | number | null>;
+
+    /**
+     * Optional version identification for the server. If this changes, the
+     * editor will indicate that tools have changed and prompt to refresh them.
+     */
+    version?: string;
+
+}
+
+/**
+ * McpHttpServerDefinition represents an MCP server available using the
+ * Streamable HTTP transport.
+ */
+export interface McpHttpServerDefinitionDto {
+    /**
+     * The human-readable name of the server.
+     */
+    readonly label: string;
+
+    /**
+     * The URI of the server. The editor will make a POST request to this URI
+     * to begin each session.
+     */
+    uri: UriComponents;
+
+    /**
+     * Optional additional heads included with each request to the server.
+     */
+    headers?: Record<string, string>;
+
+    /**
+     * Optional version identification for the server. If this changes, the
+     * editor will indicate that tools have changed and prompt to refresh them.
+     */
+    version?: string;
+}
+
+/**
+ * Definitions that describe different types of Model Context Protocol servers,
+ * which can be returned from the {@link McpServerDefinitionProvider}.
+ */
+export type McpServerDefinitionDto = McpStdioServerDefinitionDto | McpHttpServerDefinitionDto;
+export const isMcpHttpServerDefinitionDto = (definition: McpServerDefinitionDto): definition is McpHttpServerDefinitionDto => 'uri' in definition;
+/**
+ * Main side of the MCP server definition registry.
+ */
+export interface McpServerDefinitionRegistryMain {
+    /**
+     * Register an MCP server definition provider.
+     */
+    $registerMcpServerDefinitionProvider(handle: number, name: string): void;
+
+    /**
+     * Unregister an MCP server definition provider.
+     */
+    $unregisterMcpServerDefinitionProvider(handle: number): void;
+
+    /**
+     * Notify that server definitions have changed.
+     */
+    $onDidChangeMcpServerDefinitions(handle: number): void;
+
+    /**
+     * Get server definitions from a provider.
+     */
+    $getServerDefinitions(handle: number): Promise<McpServerDefinitionDto[]>;
+
+    /**
+     * Resolve a server definition.
+     */
+    $resolveServerDefinition(handle: number, server: McpServerDefinitionDto): Promise<McpServerDefinitionDto | undefined>;
+}
+
+/**
+ * Extension side of the MCP server definition registry.
+ */
+export interface McpServerDefinitionRegistryExt {
+    /**
+     * Request server definitions from a provider.
+     */
+    $provideServerDefinitions(handle: number): Promise<McpServerDefinitionDto[]>;
+
+    /**
+     * Resolve a server definition from a provider.
+     */
+    $resolveServerDefinition(handle: number, server: McpServerDefinitionDto): Promise<McpServerDefinitionDto | undefined>;
+}

packages/plugin-ext/src/common/plugin-api-rpc.ts

@@ -127,6 +127,7 @@ import { AccessibilityInformation } from '@theia/core/lib/common/accessibility';
 import { TreeDelta } from '@theia/test/lib/common/tree-delta';
 import { TestItemDTO, TestOutputDTO, TestRunDTO, TestRunProfileDTO, TestRunRequestDTO, TestStateChangeDTO } from './test-types';
 import { ArgumentProcessor } from './commands';
+import { McpServerDefinitionRegistryMain, McpServerDefinitionRegistryExt } from './lm-protocol';
 
 export interface PreferenceData {
     [scope: number]: any;
@@ -2346,7 +2347,8 @@ export const PLUGIN_RPC_CONTEXT = {
     TELEMETRY_MAIN: createProxyIdentifier<TelemetryMain>('TelemetryMain'),
     LOCALIZATION_MAIN: createProxyIdentifier<LocalizationMain>('LocalizationMain'),
     TESTING_MAIN: createProxyIdentifier<TestingMain>('TestingMain'),
-    URI_MAIN: createProxyIdentifier<UriMain>('UriMain')
+    URI_MAIN: createProxyIdentifier<UriMain>('UriMain'),
+    MCP_SERVER_DEFINITION_REGISTRY_MAIN: createProxyIdentifier<McpServerDefinitionRegistryMain>('McpServerDefinitionRegistryMain')
 };
 
 export const MAIN_RPC_CONTEXT = {
@@ -2389,7 +2391,8 @@ export const MAIN_RPC_CONTEXT = {
     TABS_EXT: createProxyIdentifier<TabsExt>('TabsExt'),
     TELEMETRY_EXT: createProxyIdentifier<TelemetryExt>('TelemetryExt)'),
     TESTING_EXT: createProxyIdentifier<TestingExt>('TestingExt'),
-    URI_EXT: createProxyIdentifier<UriExt>('UriExt')
+    URI_EXT: createProxyIdentifier<UriExt>('UriExt'),
+    MCP_SERVER_DEFINITION_REGISTRY_EXT: createProxyIdentifier<McpServerDefinitionRegistryExt>('McpServerDefinitionRegistryExt')
 };
 
 export interface TasksExt {

packages/plugin-ext/src/common/plugin-protocol.ts

@@ -104,6 +104,7 @@ export interface PluginPackageContribution {
     notebooks?: PluginPackageNotebook[];
     notebookRenderer?: PluginNotebookRendererContribution[];
     notebookPreload?: PluginPackageNotebookPreload[];
+    mcpServerDefinitionProviders?: PluginPackageMcpServerDefinitionProviderContribution[];
 }
 
 export interface PluginPackageNotebook {
@@ -126,6 +127,12 @@ export interface PluginPackageNotebookPreload {
     entrypoint: string;
 }
 
+export interface PluginPackageMcpServerDefinitionProviderContribution {
+    id: string;
+    label: string;
+    description?: string;
+}
+
 export interface PluginPackageAuthenticationProvider {
     id: string;
     label: string;

packages/plugin-ext/src/hosted/node/plugin-host-module.ts

@@ -36,6 +36,7 @@ import { WebviewsExtImpl } from '../../plugin/webviews';
 import { TerminalServiceExtImpl } from '../../plugin/terminal-ext';
 import { InternalSecretsExt, SecretsExtImpl } from '../../plugin/secrets-ext';
 import { setupPluginHostLogger } from './plugin-host-logger';
+import { LmExtImpl } from '../../plugin/lm-ext';
 
 export default new ContainerModule(bind => {
     const channel = new IPCChannel();
@@ -63,6 +64,7 @@ export default new ContainerModule(bind => {
     bind(SecretsExtImpl).toSelf().inSingletonScope();
     bind(PreferenceRegistryExtImpl).toSelf().inSingletonScope();
     bind(DebugExtImpl).toSelf().inSingletonScope();
+    bind(LmExtImpl).toSelf().inSingletonScope();
     bind(EditorsAndDocumentsExtImpl).toSelf().inSingletonScope();
     bind(WorkspaceExtImpl).toSelf().inSingletonScope();
     bind(MessageRegistryExt).toSelf().inSingletonScope();

packages/plugin-ext/src/main/browser/lm-main.ts

@@ -0,0 +1,137 @@
+// *****************************************************************************
+// Copyright (C) 2025 EclipseSource
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License v. 2.0 which is available at
+// http://www.eclipse.org/legal/epl-2.0.
+//
+// This Source Code may also be made available under the following Secondary
+// Licenses when the conditions for such availability set forth in the Eclipse
+// Public License v. 2.0 are satisfied: GNU General Public License, version 2
+// with the GNU Classpath Exception which is available at
+// https://www.gnu.org/software/classpath/license.html.
+//
+// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
+// *****************************************************************************
+
+import { interfaces } from '@theia/core/shared/inversify';
+import { RPCProtocol } from '../../common/rpc-protocol';
+import {
+    McpServerDefinitionRegistryMain,
+    McpServerDefinitionRegistryExt,
+    McpServerDefinitionDto,
+    isMcpHttpServerDefinitionDto,
+} from '../../common/lm-protocol';
+import { MAIN_RPC_CONTEXT } from '../../common/plugin-api-rpc';
+import { MCPServerManager, MCPServerDescription } from '@theia/ai-mcp/lib/common';
+
+export class McpServerDefinitionRegistryMainImpl implements McpServerDefinitionRegistryMain {
+    private readonly proxy: McpServerDefinitionRegistryExt;
+    private readonly providers = new Map<number, string>();
+    private readonly mcpServerManager: MCPServerManager | undefined;
+
+    constructor(
+        rpc: RPCProtocol,
+        container: interfaces.Container
+    ) {
+        this.proxy = rpc.getProxy(MAIN_RPC_CONTEXT.MCP_SERVER_DEFINITION_REGISTRY_EXT);
+        try {
+            this.mcpServerManager = container.get(MCPServerManager);
+        } catch {
+            // MCP Server Manager is optional
+            this.mcpServerManager = undefined;
+        }
+    }
+
+    $registerMcpServerDefinitionProvider(handle: number, name: string): void {
+        this.providers.set(handle, name);
+        // Trigger initial load of server definitions
+        this.loadServerDefinitions(handle);
+    }
+
+    $unregisterMcpServerDefinitionProvider(handle: number): void {
+        if (!this.mcpServerManager) {
+            console.warn('MCP Server Manager not available - MCP server definitions will not be loaded');
+            return;
+        }
+        const provider = this.providers.get(handle);
+        if (!provider) {
+            console.warn(`No MCP Server provider found for handle '${handle}' - MCP server definitions will not be loaded`);
+            return;
+        }
+        this.mcpServerManager.removeServer(provider);
+        this.providers.delete(handle);
+    }
+
+    $onDidChangeMcpServerDefinitions(handle: number): void {
+        // Reload server definitions when provider reports changes
+        this.loadServerDefinitions(handle);
+    }
+
+    async $getServerDefinitions(handle: number): Promise<McpServerDefinitionDto[]> {
+        try {
+            return await this.proxy.$provideServerDefinitions(handle);
+        } catch (error) {
+            console.error('Error getting MCP server definitions:', error);
+            return [];
+        }
+    }
+
+    async $resolveServerDefinition(handle: number, server: McpServerDefinitionDto): Promise<McpServerDefinitionDto | undefined> {
+        try {
+            return await this.proxy.$resolveServerDefinition(handle, server);
+        } catch (error) {
+            console.error('Error resolving MCP server definition:', error);
+            return server;
+        }
+    }
+
+    private async loadServerDefinitions(handle: number): Promise<void> {
+        if (!this.mcpServerManager) {
+            console.warn('MCP Server Manager not available - MCP server definitions will not be loaded');
+            return;
+        }
+
+        try {
+            const definitions = await this.$getServerDefinitions(handle);
+
+            for (const definition of definitions) {
+                const resolved = await this.$resolveServerDefinition(handle, definition);
+                if (resolved) {
+                    const mcpServerDescription = this.convertToMcpServerDescription(resolved);
+                    this.mcpServerManager.addOrUpdateServer(mcpServerDescription);
+                }
+            }
+        } catch (error) {
+            console.error('Error loading MCP server definitions:', error);
+        }
+    }
+
+    private convertToMcpServerDescription(definition: McpServerDefinitionDto): MCPServerDescription {
+        if (isMcpHttpServerDefinitionDto(definition)) {
+            // For HTTP servers, we would need to create a bridge or adapter
+            // For now, we'll create a placeholder stdio server that could proxy to HTTP
+            console.warn(`HTTP transport not yet supported for MCP server '${definition.label}'. Skipping.`);
+            throw new Error(`HTTP transport not yet supported for MCP server '${definition.label}'`);
+        }
+
+        // Convert env values to strings, filtering out null values
+        let convertedEnv: Record<string, string> | undefined;
+        if (definition.env) {
+            convertedEnv = {};
+            for (const [key, value] of Object.entries(definition.env)) {
+                if (value !== null) {
+                    convertedEnv[key] = String(value);
+                }
+            }
+        }
+
+        return {
+            name: definition.label,
+            command: definition.command!,
+            args: definition.args,
+            env: convertedEnv,
+            autostart: false, // Extensions should manage their own server lifecycle
+        };
+    }
+}

packages/plugin-ext/src/main/browser/main-context.ts

@@ -67,6 +67,7 @@ import { TestingMainImpl } from './test-main';
 import { UriMainImpl } from './uri-main';
 import { LoggerMainImpl } from './logger-main';
 import { MonacoEditorProvider } from '@theia/monaco/lib/browser/monaco-editor-provider';
+import { McpServerDefinitionRegistryMainImpl } from './lm-main';
 
 export function setUpPluginApi(rpc: RPCProtocol, container: interfaces.Container): void {
     const loggerMain = new LoggerMainImpl(container);
@@ -213,4 +214,7 @@ export function setUpPluginApi(rpc: RPCProtocol, container: interfaces.Container
 
     const uriMain = new UriMainImpl(rpc, container);
     rpc.set(PLUGIN_RPC_CONTEXT.URI_MAIN, uriMain);
+
+    const mcpServerDefinitionRegistryMain = new McpServerDefinitionRegistryMainImpl(rpc, container);
+    rpc.set(PLUGIN_RPC_CONTEXT.MCP_SERVER_DEFINITION_REGISTRY_MAIN, mcpServerDefinitionRegistryMain);
 }