Cherry-pick: perf(protocol): serve the MCP client and its transports from @frontmcp/protocol/client

eslint.config.mjs

@@ -63,6 +63,7 @@ export default [
             '@frontmcp/uipack',
             '@frontmcp/uipack/*',
             '@frontmcp/protocol',
+            '@frontmcp/protocol/client',
             '@frontmcp/testing',
             '@frontmcp/observability',
             '^#(mcp-.+|crypto-.+|async-.+|event-.+|langchain-.+|sse-.+|express-.+|server-.+|stdio-.+|env|runtime-context|path|client|import-computed|js-yaml|semver|uipack-render)$',

libs/protocol/README.md

@@ -1,6 +1,6 @@
 # @frontmcp/protocol
 
-FrontMCP's single point of contact with the upstream [`@modelcontextprotocol/sdk`](https://www.npmjs.com/package/@modelcontextprotocol/sdk): it re-exports the MCP protocol types, server, client and transports that the other `@frontmcp/*` packages use. This is an internal package, published only so those packages can depend on it. Don't import it from application code: import MCP types from [`@frontmcp/sdk`](https://www.npmjs.com/package/@frontmcp/sdk), and use `McpClient` from [`@frontmcp/testing`](https://www.npmjs.com/package/@frontmcp/testing) when a test needs a raw client.
+FrontMCP's single point of contact with the upstream [`@modelcontextprotocol/sdk`](https://www.npmjs.com/package/@modelcontextprotocol/sdk): it re-exports the MCP protocol types, server, client and transports that the other `@frontmcp/*` packages use. The client and its transports come from the `@frontmcp/protocol/client` subpath, so a server, or a browser or Worker bundle of one, doesn't load them. This is an internal package, published only so those packages can depend on it. Don't import it from application code: import MCP types from [`@frontmcp/sdk`](https://www.npmjs.com/package/@frontmcp/sdk), and use `McpClient` from [`@frontmcp/testing`](https://www.npmjs.com/package/@frontmcp/testing) when a test needs a raw client.
 
 [![npm](https://img.shields.io/npm/v/@frontmcp/protocol.svg)](https://www.npmjs.com/package/@frontmcp/protocol) [![License](https://img.shields.io/npm/l/@frontmcp/protocol.svg)](https://github.com/agentfront/frontmcp/blob/main/LICENSE)
 
@@ -10,13 +10,13 @@ You don't install it yourself: `@frontmcp/sdk` depends on it. It needs Node.js 2
 
 ## What it exports
 
-| Area                | Contents                                                                                                         |
-| ------------------- | ---------------------------------------------------------------------------------------------------------------- |
-| Protocol types      | Everything in `@modelcontextprotocol/sdk/types.js`: requests, results, notifications, schemas, `McpError`        |
-| Protocol 2026-07-28 | `MCP_20260728_META`, `MCP_20260728_ERROR_CODES`, `CacheableResult`, `DiscoverResult`, `InputRequiredResult`, …   |
-| Server              | `McpServer`, `StreamableHTTPServerTransport`, `WebStandardStreamableHTTPServerTransport`, `StdioServerTransport` |
-| Client              | `Client`, `StreamableHTTPClientTransport`, `SSEClientTransport`, `StdioClientTransport`                          |
-| Other               | `InMemoryTransport`, `Transport`, `RequestHandlerExtra`, `AuthInfo`                                              |
+| Area                                 | Contents                                                                                                         |
+| ------------------------------------ | ---------------------------------------------------------------------------------------------------------------- |
+| Protocol types                       | Everything in `@modelcontextprotocol/sdk/types.js`: requests, results, notifications, schemas, `McpError`        |
+| Protocol 2026-07-28                  | `MCP_20260728_META`, `MCP_20260728_ERROR_CODES`, `CacheableResult`, `DiscoverResult`, `InputRequiredResult`, …   |
+| Server                               | `McpServer`, `StreamableHTTPServerTransport`, `WebStandardStreamableHTTPServerTransport`, `StdioServerTransport` |
+| Client (`@frontmcp/protocol/client`) | `Client`, `StreamableHTTPClientTransport`, `SSEClientTransport`, `StdioClientTransport`                          |
+| Other                                | `InMemoryTransport`, `Transport`, `RequestHandlerExtra`, `AuthInfo`                                              |
 
 The browser build swaps in browser versions of the server and Streamable HTTP modules through the package's `imports` map. The stdio transports need Node.js: in a browser or worker build they throw when constructed.
 

libs/protocol/package.json

@@ -82,6 +82,17 @@
         "types": "./dist/index.d.ts",
         "default": "./dist/esm/index.mjs"
       }
+    },
+    "./client": {
+      "development": "./src/clients.ts",
+      "require": {
+        "types": "./dist/clients.d.ts",
+        "default": "./dist/clients.js"
+      },
+      "import": {
+        "types": "./dist/clients.d.ts",
+        "default": "./dist/esm/clients.mjs"
+      }
     }
   },
   "devDependencies": {

libs/protocol/project.json

@@ -31,7 +31,8 @@
           "libs/protocol/src/browser-stdio-server.ts",
           "libs/protocol/src/client.ts",
           "libs/protocol/src/lazy-client.ts",
-          "libs/protocol/src/lazy-mcp-streamable-http.ts"
+          "libs/protocol/src/lazy-mcp-streamable-http.ts",
+          "libs/protocol/src/clients.ts"
         ],
         "assets": ["libs/protocol/README.md", "libs/protocol/CHANGELOG.md", "LICENSE", "libs/protocol/package.json"],
         "esbuildOptions": {
@@ -79,7 +80,8 @@
           "libs/protocol/src/browser-stdio-server.ts",
           "libs/protocol/src/client.ts",
           "libs/protocol/src/lazy-client.ts",
-          "libs/protocol/src/lazy-mcp-streamable-http.ts"
+          "libs/protocol/src/lazy-mcp-streamable-http.ts",
+          "libs/protocol/src/clients.ts"
         ],
         "esbuildOptions": {
           "minifyWhitespace": true,

libs/protocol/src/__tests__/exports.spec.ts

@@ -12,6 +12,7 @@ import * as browserStreamableHttp from '../browser-mcp-streamable-http';
 import * as browserServerTypes from '../browser-server-types';
 import { StdioClientTransport as BrowserStdioClientTransport } from '../browser-stdio-client';
 import { StdioServerTransport as BrowserStdioServerTransport } from '../browser-stdio-server';
+import * as clients from '../clients';
 import { InMemoryTransport } from '../in-memory';
 import * as protocol from '../index';
 import { Server as NodeServer } from '../node-mcp-server';
@@ -38,8 +39,13 @@ describe('@frontmcp/protocol exports', () => {
     expect(protocol.LATEST_PROTOCOL_VERSION).toBe(LATEST_PROTOCOL_VERSION);
     expect(protocol.PROTOCOL_2026_07_28).toBe('2026-07-28');
     expect(protocol.StdioServerTransport).toBe(SdkStdioServerTransport);
-    expect(typeof protocol.Client).toBe('function');
-    expect(typeof protocol.StreamableHTTPClientTransport).toBe('function');
+  });
+
+  it('serves the MCP client and its transports from the client subpath, not the root', () => {
+    for (const name of ['Client', 'StreamableHTTPClientTransport', 'SSEClientTransport', 'StdioClientTransport']) {
+      expect(typeof (clients as Record<string, unknown>)[name]).toBe('function');
+      expect(name in protocol).toBe(false);
+    }
   });
 
   it('gives browsers stand-ins that say what is not available', () => {

libs/protocol/src/clients.ts

@@ -0,0 +1,2 @@
+// `@frontmcp/protocol/client`: the MCP client and its transports, kept out of the root that every server and server bundle loads.
+export * from '#client';

libs/protocol/src/index.ts

@@ -19,9 +19,6 @@ export * from './auth-types';
 // Shared protocol types (Transport, RequestHandlerExtra)
 export * from './shared';
 
-// MCP Client
-export * from '#client';
-
 // Stdio transport
 export * from './stdio';
 

libs/sdk/project.json

@@ -45,6 +45,7 @@
             "@frontmcp/auth",
             "@frontmcp/guard",
             "@frontmcp/protocol",
+            "@frontmcp/protocol/*",
             "@frontmcp/observability",
             "@opentelemetry/api",
             "@opentelemetry/sdk-trace-base",
@@ -89,6 +90,7 @@
             "@frontmcp/auth",
             "@frontmcp/guard",
             "@frontmcp/protocol",
+            "@frontmcp/protocol/*",
             "@frontmcp/observability",
             "@opentelemetry/api",
             "@opentelemetry/sdk-trace-base",
@@ -133,6 +135,7 @@
             "@frontmcp/auth",
             "@frontmcp/guard",
             "@frontmcp/protocol",
+            "@frontmcp/protocol/*",
             "@frontmcp/observability",
             "@opentelemetry/api",
             "@opentelemetry/sdk-trace-base",

libs/sdk/src/agent/__tests__/agent-context-wiring.spec.ts

@@ -2,12 +2,12 @@ import 'reflect-metadata';
 
 import { z } from '@frontmcp/lazy-zod';
 import {
-  Client,
   LoggingMessageNotificationSchema,
   MCP_20260728_META,
   type CallToolResult,
   type Progress,
 } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 
 import {
   createTestFetchServer,

libs/sdk/src/agent/__tests__/agent-streaming.spec.ts

@@ -7,7 +7,8 @@
 import 'reflect-metadata';
 
 import { z } from '@frontmcp/lazy-zod';
-import { Client, type CallToolResult, type Progress } from '@frontmcp/protocol';
+import { type CallToolResult, type Progress } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 
 import {
   createTestFetchServer,

libs/sdk/src/direct/__tests__/connect.spec.ts

@@ -89,8 +89,8 @@ const mockMcpClient = {
   getPrompt: jest.fn().mockResolvedValue({ messages: [] }),
 };
 
-jest.mock('@frontmcp/protocol', () => ({
-  ...jest.requireActual('@frontmcp/protocol'),
+jest.mock('@frontmcp/protocol/client', () => ({
+  ...jest.requireActual('@frontmcp/protocol/client'),
   Client: jest.fn().mockImplementation(() => mockMcpClient),
 }));
 
@@ -120,7 +120,7 @@ describe('connect utilities', () => {
 
     it('should use default clientInfo when not provided', async () => {
       const { connect } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       await connect(config);
@@ -133,7 +133,7 @@ describe('connect utilities', () => {
 
     it('should pass custom clientInfo to MCP client', async () => {
       const { connect } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       await connect(config, {
@@ -242,7 +242,7 @@ describe('connect utilities', () => {
 
     it('should pass capabilities to MCP client', async () => {
       const { connect } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       // Note: ClientCapabilities uses 'roots', not 'tools' (tools is a ServerCapability)
@@ -262,7 +262,7 @@ describe('connect utilities', () => {
   describe('connectOpenAI', () => {
     it('should use OpenAI client info', async () => {
       const { connectOpenAI } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       await connectOpenAI(config);
@@ -295,7 +295,7 @@ describe('connect utilities', () => {
   describe('connectClaude', () => {
     it('should use Claude client info', async () => {
       const { connectClaude } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       await connectClaude(config);
@@ -307,7 +307,7 @@ describe('connect utilities', () => {
   describe('connectLangChain', () => {
     it('should use LangChain client info', async () => {
       const { connectLangChain } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       await connectLangChain(config);
@@ -319,7 +319,7 @@ describe('connect utilities', () => {
   describe('connectVercelAI', () => {
     it('should use Vercel AI client info', async () => {
       const { connectVercelAI } = await import('../connect');
-      const { Client } = await import('@frontmcp/protocol');
+      const { Client } = await import('@frontmcp/protocol/client');
       const config = createTestConfig();
 
       await connectVercelAI(config);

libs/sdk/src/direct/__tests__/direct-client.spec.ts

@@ -79,14 +79,14 @@ const mockMcpClient = {
 
 // MockClient defined inside the mock factory to avoid hoisting issues
 // (jest.mock is hoisted, but accessing outer variables before they're defined causes errors)
-jest.mock('@frontmcp/protocol', () => ({
-  ...jest.requireActual('@frontmcp/protocol'),
+jest.mock('@frontmcp/protocol/client', () => ({
+  ...jest.requireActual('@frontmcp/protocol/client'),
   Client: jest.fn().mockImplementation(() => mockMcpClient),
 }));
 
 // Import the mocked Client to use in tests for assertions
 
-const { Client: MockClient } = require('@frontmcp/protocol');
+const { Client: MockClient } = require('@frontmcp/protocol/client');
 
 describe('DirectClientImpl', () => {
   // Minimal mock scope

libs/sdk/src/direct/direct-client.ts

@@ -5,7 +5,6 @@
  */
 
 import {
-  Client,
   ElicitRequestSchema,
   ResourceUpdatedNotificationSchema,
   type CallToolResult,
@@ -20,6 +19,7 @@ import {
   type ReadResourceResult,
   type ServerCapabilities,
 } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 import { fileExists, pathResolve, randomUUID } from '@frontmcp/utils';
 
 import { listAllPages } from '../common/utils/list-all-pages.utils';

libs/sdk/src/remote-mcp/mcp-client.service.ts

@@ -5,9 +5,6 @@
 
 import { decodeJwtPayloadSafe } from '@frontmcp/auth';
 import {
-  Client,
-  SSEClientTransport,
-  StreamableHTTPClientTransport,
   type AuthInfo,
   type CallToolResult,
   type GetPromptResult,
@@ -18,6 +15,7 @@ import {
   type Tool,
   type Transport,
 } from '@frontmcp/protocol';
+import { Client, SSEClientTransport, StreamableHTTPClientTransport } from '@frontmcp/protocol/client';
 
 import { type FrontMcpLogger } from '../common';
 import { listAllPages } from '../common/utils/list-all-pages.utils';

libs/sdk/src/remote-mcp/mcp-client.types.ts

@@ -6,7 +6,6 @@
 import {
   type AuthInfo,
   type CallToolResult,
-  type Client,
   type GetPromptResult,
   type Prompt,
   type ReadResourceResult,
@@ -16,6 +15,7 @@ import {
   type Tool,
   type Transport,
 } from '@frontmcp/protocol';
+import { type Client } from '@frontmcp/protocol/client';
 
 // ═══════════════════════════════════════════════════════════════════
 // CONNECTION TYPES

libs/sdk/src/skill/__tests__/skill-filter.flow.spec.ts

@@ -1,6 +1,7 @@
 import 'reflect-metadata';
 
-import { Client, InMemoryTransport, type ReadResourceResult } from '@frontmcp/protocol';
+import { InMemoryTransport, type ReadResourceResult } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 
 import {
   createTestFetchServer,

libs/sdk/src/transport/__tests__/in-memory-server.initialize.spec.ts

@@ -4,7 +4,7 @@
  */
 import 'reflect-metadata';
 
-import { Client } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 
 import { App, LogLevel, Tool, ToolContext } from '../../common';
 import { FrontMcpInstance } from '../../front-mcp/front-mcp';

libs/sdk/src/transport/in-memory-server.ts

@@ -63,7 +63,7 @@ export interface InMemoryServerResult {
  *
  * @example
  * ```typescript
- * import { Client } from '@frontmcp/protocol';
+ * import { Client } from '@frontmcp/protocol/client';
  * import { FrontMcpInstance, createInMemoryServer } from '@frontmcp/sdk';
  *
  * // Create a FrontMCP instance

libs/sdk/src/transport/index.ts

@@ -54,7 +54,7 @@ export type {
  * @example
  * ```typescript
  * import { createInMemoryServer } from '@frontmcp/sdk';
- * import { Client } from '@frontmcp/protocol';
+ * import { Client } from '@frontmcp/protocol/client';
  *
  * const { clientTransport, setAuthInfo, close } = await createInMemoryServer(scope, {
  *   authInfo: { token: 'jwt-token' }

libs/sdk/tsconfig.lib.json

@@ -21,7 +21,8 @@
       "@frontmcp/ui/*": ["libs/ui/dist/*/index.d.ts"],
       "@frontmcp/auth": ["libs/auth/dist/index.d.ts"],
       "@frontmcp/guard": ["libs/guard/dist/index.d.ts"],
-      "@frontmcp/protocol": ["libs/protocol/dist/index.d.ts"]
+      "@frontmcp/protocol": ["libs/protocol/dist/index.d.ts"],
+      "@frontmcp/protocol/client": ["libs/protocol/dist/clients.d.ts"]
     }
   },
   "include": ["src/**/*.ts"],

libs/testing/src/raw-client/index.ts

@@ -2,6 +2,6 @@
  * Raw MCP protocol client re-exports for low-level e2e testing.
  * For programmatic access, prefer connect()/connectOpenAI() from @frontmcp/sdk.
  */
-export { Client as McpClient } from '@frontmcp/protocol';
-export { StdioClientTransport as McpStdioClientTransport } from '@frontmcp/protocol';
+export { Client as McpClient } from '@frontmcp/protocol/client';
+export { StdioClientTransport as McpStdioClientTransport } from '@frontmcp/protocol/client';
 export { isTcpPortListening } from './port-probe';

libs/testing/tsconfig.lib.json

@@ -13,7 +13,8 @@
       "@frontmcp/sdk/*": ["libs/sdk/dist/*/index.d.ts"],
       "@frontmcp/ui": ["libs/ui/dist/index.d.ts"],
       "@frontmcp/ui/*": ["libs/ui/dist/*/index.d.ts"],
-      "@frontmcp/protocol": ["libs/protocol/dist/index.d.ts"]
+      "@frontmcp/protocol": ["libs/protocol/dist/index.d.ts"],
+      "@frontmcp/protocol/client": ["libs/protocol/dist/clients.d.ts"]
     }
   },
   "include": ["src/**/*.ts"],

plugins/plugin-approval/src/__tests__/approval.refusal-result.spec.ts

@@ -7,7 +7,8 @@
  */
 import 'reflect-metadata';
 
-import { Client, type CallToolResult } from '@frontmcp/protocol';
+import { type CallToolResult } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 import { App, createInMemoryServer, FrontMcpInstance, LogLevel, Tool, ToolContext } from '@frontmcp/sdk';
 
 import { ApprovalPlugin } from '../index';

plugins/plugin-codecall/src/__tests__/codecall-access-control.flow.spec.ts

@@ -8,7 +8,8 @@
  */
 import 'reflect-metadata';
 
-import { Client, type CallToolResult } from '@frontmcp/protocol';
+import { type CallToolResult } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 import {
   Adapter,
   App,

plugins/plugin-codecall/src/__tests__/codecall-direct-call.flow.spec.ts

@@ -11,7 +11,8 @@
 import 'reflect-metadata';
 
 import { z } from '@frontmcp/lazy-zod';
-import { Client, type CallToolResult } from '@frontmcp/protocol';
+import { type CallToolResult } from '@frontmcp/protocol';
+import { Client } from '@frontmcp/protocol/client';
 import { App, createInMemoryServer, FrontMcpInstance, LogLevel, Tool, ToolContext } from '@frontmcp/sdk';
 
 import CodeCallPlugin from '../codecall.plugin';