feat: zod v4 with backwards compatibility for v3.25+

.prettierignore

@@ -7,4 +7,6 @@ node_modules
 **/build
 **/dist
 .github/CODEOWNERS
-pnpm-lock.yaml
+pnpm-lock.yaml
+# vendored code
+src/_vendor/

README.md

@@ -58,7 +58,7 @@ Let's create a simple MCP server that exposes a calculator tool and some data. S
 import { McpServer, ResourceTemplate } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import express from 'express';
-import { z } from 'zod';
+import * as z from 'zod/v4'; // or import * as z from 'zod/v3';
 
 // Create an MCP server
 const server = new McpServer({
@@ -477,7 +477,7 @@ MCP servers can request LLM completions from connected clients that support samp
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import express from 'express';
-import { z } from 'zod';
+import * as z from 'zod/v4'; // or import * as z from 'zod/v3';
 
 const mcpServer = new McpServer({
     name: 'tools-with-sample-server',
@@ -561,7 +561,7 @@ For most use cases where session management isn't needed:
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import express from 'express';
-import { z } from 'zod';
+import * as z from 'zod/v4'; // or import * as z from 'zod/v3';
 
 const app = express();
 app.use(express.json());
@@ -796,7 +796,7 @@ A simple server demonstrating resources, tools, and prompts:
 
 ```typescript
 import { McpServer, ResourceTemplate } from '@modelcontextprotocol/sdk/server/mcp.js';
-import { z } from 'zod';
+import * as z from 'zod/v4'; // or import * as z from 'zod/v3';
 
 const server = new McpServer({
     name: 'echo-server',
@@ -866,7 +866,7 @@ A more complex example showing database integration:
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import sqlite3 from 'sqlite3';
 import { promisify } from 'util';
-import { z } from 'zod';
+import * as z from 'zod/v4'; // or import * as z from 'zod/v3';
 
 const server = new McpServer({
     name: 'sqlite-explorer',
@@ -961,7 +961,7 @@ If you want to offer an initial set of tools/prompts/resources, but later add ad
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
 import express from 'express';
-import { z } from 'zod';
+import * as z from 'zod/v4'; // or import * as z from 'zod/v3';
 
 const server = new McpServer({
     name: 'Dynamic Example',

eslint.config.mjs

@@ -15,6 +15,25 @@ export default tseslint.config(
             '@typescript-eslint/no-unused-vars': ['error', { argsIgnorePattern: '^_' }]
         }
     },
+    {
+        files: ['src/_vendor/**/*.ts'],
+        rules: {
+            '@typescript-eslint/ban-ts-comment': 'off',
+            '@typescript-eslint/no-unused-vars': 'off',
+            '@typescript-eslint/no-explicit-any': 'off',
+            '@typescript-eslint/no-empty-object-type': 'off',
+            '@typescript-eslint/no-wrapper-object-types': 'off',
+            'no-fallthrough': 'off',
+            'no-case-declarations': 'off',
+            'no-useless-escape': 'off'
+        }
+    },
+    {
+        files: ['src/server/mcp.zodv3.test.ts'],
+        rules: {
+            '@typescript-eslint/ban-ts-comment': 'off'
+        }
+    },
     {
         files: ['src/client/**/*.ts', 'src/server/**/*.ts'],
         ignores: ['**/*.test.ts'],

jest.config.js

@@ -10,5 +10,6 @@ export default {
         '^pkce-challenge$': '<rootDir>/src/__mocks__/pkce-challenge.ts'
     },
     transformIgnorePatterns: ['/node_modules/(?!eventsource)/'],
-    testPathIgnorePatterns: ['/node_modules/', '/dist/']
+    testPathIgnorePatterns: ['/node_modules/', '/dist/'],
+    modulePathIgnorePatterns: ['<rootDir>/dist/']
 };