chore: switch to module ESNext + moduleResolution bundler (#2095)

test/conformance/package.json

@@ -25,9 +25,6 @@
         "lint": "eslint src/ && prettier --ignore-path ../../.prettierignore --check .",
         "lint:fix": "eslint src/ --fix && prettier --ignore-path ../../.prettierignore --write .",
         "check": "npm run typecheck && npm run lint",
-        "start": "npm run server",
-        "server": "tsx watch --clear-screen=false scripts/cli.ts server",
-        "client": "tsx scripts/cli.ts client",
         "test:conformance:client": "conformance client --command 'node --import tsx ./src/everythingClient.ts' --suite core --expected-failures ./expected-failures.yaml",
         "test:conformance:client:all": "conformance client --command 'node --import tsx ./src/everythingClient.ts' --suite all --expected-failures ./expected-failures.yaml",
         "test:conformance:client:run": "node --import tsx ./src/everythingClient.ts",

test/conformance/src/everythingClient.ts

@@ -22,9 +22,9 @@ import {
 } from '@modelcontextprotocol/client';
 import * as z from 'zod/v4';
 
-import { ConformanceOAuthProvider } from './helpers/conformanceOAuthProvider.js';
-import { logger } from './helpers/logger.js';
-import { handle401, withOAuthRetry } from './helpers/withOAuthRetry.js';
+import { ConformanceOAuthProvider } from './helpers/conformanceOAuthProvider';
+import { logger } from './helpers/logger';
+import { handle401, withOAuthRetry } from './helpers/withOAuthRetry';
 
 /**
  * Fixed client metadata URL for CIMD conformance tests.

test/conformance/src/helpers/withOAuthRetry.ts

@@ -1,7 +1,7 @@
 import type { FetchLike, Middleware } from '@modelcontextprotocol/client';
 import { auth, extractWWWAuthenticateParams, UnauthorizedError } from '@modelcontextprotocol/client';
 
-import { ConformanceOAuthProvider } from './conformanceOAuthProvider.js';
+import { ConformanceOAuthProvider } from './conformanceOAuthProvider';
 
 export const handle401 = async (
     response: Response,

test/e2e/coverage.test.ts

@@ -13,7 +13,7 @@ import { fileURLToPath } from 'node:url';
 
 import { expect, test } from 'vitest';
 
-import { REQUIREMENTS } from './requirements.js';
+import { REQUIREMENTS } from './requirements';
 
 const E2E_DIR = path.dirname(fileURLToPath(import.meta.url));
 

test/e2e/helpers/index.ts

@@ -19,10 +19,10 @@ import type { EventStore, JSONRPCMessage, McpServer, Server } from '@modelcontex
 import { InMemoryTransport, ReadBuffer, serializeMessage, WebStandardStreamableHTTPServerTransport } from '@modelcontextprotocol/server';
 import { StdioServerTransport } from '@modelcontextprotocol/server/stdio';
 
-import type { Transport } from '../types.js';
-import { startLegacySseHost } from './sse-host.js';
-import type { SnifferOptions } from './wire-sniffer.js';
-import { sniffTransport } from './wire-sniffer.js';
+import type { Transport } from '../types';
+import { startLegacySseHost } from './sse-host';
+import type { SnifferOptions } from './wire-sniffer';
+import { sniffTransport } from './wire-sniffer';
 
 export type ServerFactory = () => McpServer | Server;
 

test/e2e/helpers/verifies.ts

@@ -17,9 +17,9 @@
 
 import { describe, test } from 'vitest';
 
-import { REQUIREMENTS } from '../requirements.js';
-import type { TestArgs } from '../types.js';
-import { ALL_SPEC_VERSIONS, ALL_TRANSPORTS } from '../types.js';
+import { REQUIREMENTS } from '../requirements';
+import type { TestArgs } from '../types';
+import { ALL_SPEC_VERSIONS, ALL_TRANSPORTS } from '../types';
 
 type TestBody = (args: TestArgs) => Promise<void>;
 

test/e2e/helpers/wire-sniffer.test.ts

@@ -1,7 +1,7 @@
 import { LATEST_PROTOCOL_VERSION } from '@modelcontextprotocol/server';
 import { describe, expect, it } from 'vitest';
 
-import { assertWireMessage } from './wire-sniffer.js';
+import { assertWireMessage } from './wire-sniffer';
 
 const req = (method: string, params?: unknown, id = 1) => ({
     jsonrpc: '2.0' as const,

test/e2e/requirements.ts

@@ -7,7 +7,7 @@
  * the behavior).
  */
 
-import type { Requirement } from './types.js';
+import type { Requirement } from './types';
 
 /** Transports with a persistent server instance / standalone notification stream. */
 const STATEFUL_TRANSPORTS = ['inMemory', 'stdio', 'streamableHttp', 'sse'] as const;

test/e2e/scenarios/client-auth.test.ts

@@ -43,9 +43,9 @@ import { importSPKI, jwtVerify } from 'jose';
 import { expect, vi } from 'vitest';
 import { z } from 'zod/v4';
 
-import { hostPerSession } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { hostPerSession } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 const ISSUER = 'https://auth.example.com';
 const MCP_URL = 'http://in-process/mcp';

test/e2e/scenarios/completion.test.ts

@@ -12,9 +12,9 @@ import { completable, McpServer, ProtocolError, ProtocolErrorCode, ResourceTempl
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { wire } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { wire } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 const COLORS = ['red', 'green', 'blue', 'rebeccapurple'] as const;
 const FILE_PATHS = ['README.md', 'src/index.ts', 'src/types.ts'] as const;

test/e2e/scenarios/custom-methods.test.ts

@@ -15,9 +15,9 @@ import { McpServer, ProtocolErrorCode, Server } from '@modelcontextprotocol/serv
 import { expect, vi } from 'vitest';
 import { z } from 'zod/v4';
 
-import { wire } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { wire } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 verifies('custom-methods:server-handler:roundtrip', async ({ transport }: TestArgs) => {
     const SearchParams = z.object({ query: z.string(), limit: z.number().int().default(5) });

test/e2e/scenarios/dynamic.test.ts

@@ -12,9 +12,9 @@ import { McpServer, ProtocolErrorCode, Server } from '@modelcontextprotocol/serv
 import { expect, vi } from 'vitest';
 import { z } from 'zod/v4';
 
-import { wire } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { wire } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 const newClient = () => new Client({ name: 'c', version: '0' });
 

test/e2e/scenarios/elicitation.test.ts

@@ -22,9 +22,9 @@ import {
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { tapWire, wire } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { tapWire, wire } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 /** Client with form-mode elicitation support. */
 const formClient = () => new Client({ name: 'c', version: '0' }, { capabilities: { elicitation: { form: {} } } });

test/e2e/scenarios/errors.test.ts

@@ -24,9 +24,9 @@ import {
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { hostPerSession, tapWire, wire } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { hostPerSession, tapWire, wire } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 const newClient = () => new Client({ name: 'c', version: '0' });
 

test/e2e/scenarios/flow.test.ts

@@ -24,10 +24,10 @@ import { McpServer, ProtocolErrorCode, Server, specTypeSchemas, UrlElicitationRe
 import { expect, vi } from 'vitest';
 import { z } from 'zod/v4';
 
-import { hostPerSession, hostResumable, wire } from '../helpers/index.js';
-import { startLegacySseHost } from '../helpers/sse-host.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { hostPerSession, hostResumable, wire } from '../helpers/index';
+import { startLegacySseHost } from '../helpers/sse-host';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 verifies('flow:compat:dual-transport-server', async (_args: TestArgs) => {
     // One deployment, one server factory, both transports: the modern Streamable HTTP

test/e2e/scenarios/handler-context.test.ts

@@ -15,9 +15,9 @@ import { McpServer } from '@modelcontextprotocol/server';
 import { expect, vi } from 'vitest';
 import { z } from 'zod/v4';
 
-import { hostPerSession, wire } from '../helpers/index.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { hostPerSession, wire } from '../helpers/index';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 verifies('mcpserver:context:log-from-handler', async ({ transport }: TestArgs) => {
     let releaseHandler!: () => void;

test/e2e/scenarios/hosting-auth.test.ts

@@ -31,8 +31,8 @@ import { McpServer, WebStandardStreamableHTTPServerTransport } from '@modelconte
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 const VALID_TOKEN = 'analytics-dashboard-access-token';
 

test/e2e/scenarios/hosting-express.test.ts

@@ -30,9 +30,9 @@ import express from 'express';
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { startExpressMinimal, startExpressWithHostValidation } from '../helpers/express.js';
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { startExpressMinimal, startExpressWithHostValidation } from '../helpers/express';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 const RESOURCE_METADATA_URL = 'https://mcp.example.com/.well-known/oauth-protected-resource';
 const VALID_TOKEN = 'analytics-dashboard-token';

test/e2e/scenarios/hosting-fastify.test.ts

@@ -19,8 +19,8 @@ import type { FastifyInstance, FastifyRequest } from 'fastify';
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 function forecastServer(): McpServer {
     const s = new McpServer({ name: 'forecast-server', version: '0.3.0' });

test/e2e/scenarios/hosting-hono.test.ts

@@ -20,8 +20,8 @@ import type { Hono } from 'hono';
 import { expect } from 'vitest';
 import { z } from 'zod/v4';
 
-import { verifies } from '../helpers/verifies.js';
-import type { TestArgs } from '../types.js';
+import { verifies } from '../helpers/verifies';
+import type { TestArgs } from '../types';
 
 function recipeServer(): McpServer {
     const s = new McpServer({ name: 'recipe-server', version: '1.2.0' });