fix: support cjs

package.json

@@ -6,6 +6,7 @@
   "author": "Anthropic, PBC (https://anthropic.com)",
   "homepage": "https://modelcontextprotocol.io",
   "bugs": "https://github.com/modelcontextprotocol/typescript-sdk/issues",
+  "type": "module",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/modelcontextprotocol/typescript-sdk.git"
@@ -26,8 +27,7 @@
   "typesVersions": {
     "*": {
       "*": [
-        "./dist/esm/*",
-        "./dist/cjs/*"
+        "./dist/esm/*"
       ]
     }
   },
@@ -35,8 +35,10 @@
     "dist"
   ],
   "scripts": {
-    "build": "tsup",
-    "prepack": "tsup",
+    "build": "npm run build:esm && npm run build:cjs",
+    "build:esm": "tsc -p tsconfig.prod.json && echo '{\"type\": \"module\"}' > dist/esm/package.json",
+    "build:cjs": "tsc -p tsconfig.cjs.json && echo '{\"type\": \"commonjs\"}' > dist/cjs/package.json",
+    "prepack": "npm run build:esm && npm run build:cjs",
     "lint": "eslint src/",
     "test": "jest",
     "start": "npm run server",
@@ -49,7 +51,6 @@
     "zod": "^3.23.8"
   },
   "devDependencies": {
-    "tsup": "^8.3.5",
     "@eslint/js": "^9.8.0",
     "@types/content-type": "^1.1.8",
     "@types/eslint__js": "^8.42.3",

tsconfig.cjs.json

@@ -0,0 +1,9 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "outDir": "./dist/cjs"
+  },
+  "exclude": ["**/*.test.ts"]
+}

tsconfig.prod.json

@@ -1,6 +1,7 @@
 {
   "extends": "./tsconfig.json",
-  "exclude": [
-    "**/*.test.ts",
-  ]
+  "compilerOptions": {
+    "outDir": "./dist/esm"
+  },
+  "exclude": ["**/*.test.ts"]
 }

tsup.config.ts

@@ -1,25 +0,0 @@
-import { defineConfig, Options } from "tsup";
-
-const commonConfig: Options = {
-  clean: true,
-  dts: true,
-  splitting: false,
-  tsconfig: "tsconfig.prod.json",
-};
-
-export default defineConfig([
-  {
-    ...commonConfig,
-    entry: ["src/**/*"],
-    bundle: false,
-    outDir: "dist/cjs",
-    format: ["cjs"],
-  },
-  {
-    ...commonConfig,
-    entry: ["src/**/*"],
-    bundle: false,
-    outDir: "dist/esm",
-    format: ["esm"],
-  },
-]);