diff --git a/packages/protobuf/package.json b/packages/protobuf/package.json
index e2e34ae3c..01989fb95 100644
--- a/packages/protobuf/package.json
+++ b/packages/protobuf/package.json
@@ -10,10 +10,9 @@
   },
   "scripts": {
     "clean": "rm -rf ./dist/*",
-    "build": "npm run build:cjs && npm run build:esm && npm run build:proxy",
+    "build": "npm run build:cjs && npm run build:esm",
     "build:cjs": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module commonjs --outDir ./dist/cjs --declaration --declarationDir ./dist/cjs && echo >./dist/cjs/package.json '{\"type\":\"commonjs\"}'",
     "build:esm": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module ES2015 --verbatimModuleSyntax --outDir ./dist/esm --declaration --declarationDir ./dist/esm",
-    "build:proxy": "node ../../scripts/gen-esm-proxy.mjs .",
     "bootstrap:featureset-defaults": "upstream-inject-feature-defaults src/private/feature-set.ts",
     "prebootstrap:wkt": "rm -rf .tmp && mkdir -p .tmp/google/protobuf && cp -rp src/google/protobuf/* .tmp/google/protobuf",
     "bootstrap:wkt": "protoc --es_out=src --es_opt=bootstrap_wkt=true,ts_nocheck=false,target=ts --proto_path $(upstream-include wkt) $(upstream-files wkt) && license-header src/google/protobuf",
@@ -25,11 +24,6 @@
   "main": "./dist/cjs/index.js",
   "exports": {
     ".": {
-      "node": {
-        "import": "./dist/proxy/index.js",
-        "require": "./dist/cjs/index.js"
-      },
-      "module": "./dist/esm/index.js",
       "import": "./dist/esm/index.js",
       "require": "./dist/cjs/index.js"
     }
diff --git a/packages/protobuf/src/create-descriptor-set.ts b/packages/protobuf/src/create-descriptor-set.ts
index d51d62385..38d91def6 100644
--- a/packages/protobuf/src/create-descriptor-set.ts
+++ b/packages/protobuf/src/create-descriptor-set.ts
@@ -55,7 +55,7 @@ import type { BinaryReadOptions, BinaryWriteOptions } from "./binary-format.js";
 import type { FeatureResolverFn } from "./private/feature-set.js";
 import { createFeatureResolver } from "./private/feature-set.js";
 import { LongType, ScalarType } from "./scalar.js";
-import { isMessage } from "./is-message";
+import { isMessage } from "./is-message.js";
 
 /**
  * Create a DescriptorSet, a convenient interface for working with a set of
diff --git a/packages/protobuf/src/create-registry-from-desc.ts b/packages/protobuf/src/create-registry-from-desc.ts
index 569a657bf..10ace8525 100644
--- a/packages/protobuf/src/create-registry-from-desc.ts
+++ b/packages/protobuf/src/create-registry-from-desc.ts
@@ -66,7 +66,7 @@ import type {
 import { createDescriptorSet } from "./create-descriptor-set.js";
 import type { Extension } from "./extension.js";
 import type { ExtensionFieldSource } from "./private/extensions.js";
-import { isMessage } from "./is-message";
+import { isMessage } from "./is-message.js";
 
 // well-known message types with specialized JSON representation
 const wkMessages = [
diff --git a/packages/protobuf/src/private/binary-format.ts b/packages/protobuf/src/private/binary-format.ts
index 132323343..069f700c4 100644
--- a/packages/protobuf/src/private/binary-format.ts
+++ b/packages/protobuf/src/private/binary-format.ts
@@ -27,7 +27,7 @@ import { assert } from "./assert.js";
 import { isFieldSet } from "./reflect.js";
 import type { ScalarValue } from "../scalar.js";
 import { LongType, ScalarType } from "../scalar.js";
-import { isMessage } from "../is-message";
+import { isMessage } from "../is-message.js";
 
 /* eslint-disable prefer-const,no-case-declarations,@typescript-eslint/no-explicit-any,@typescript-eslint/no-unsafe-argument,@typescript-eslint/no-unsafe-assignment,@typescript-eslint/no-unsafe-member-access,@typescript-eslint/no-unsafe-call,@typescript-eslint/no-unsafe-return */
 
diff --git a/packages/protobuf/src/private/field-wrapper.ts b/packages/protobuf/src/private/field-wrapper.ts
index 9c399e8fc..16facfbcf 100644
--- a/packages/protobuf/src/private/field-wrapper.ts
+++ b/packages/protobuf/src/private/field-wrapper.ts
@@ -16,7 +16,7 @@ import { Message } from "../message.js";
 import type { MessageType } from "../message-type.js";
 import type { DescExtension, DescField } from "../descriptor-set.js";
 import { ScalarType } from "../scalar.js";
-import { isMessage } from "../is-message";
+import { isMessage } from "../is-message.js";
 
 /* eslint-disable @typescript-eslint/no-explicit-any -- unknown fields are represented with any */
 
diff --git a/packages/protobuf/src/private/json-format.ts b/packages/protobuf/src/private/json-format.ts
index f5790e937..0ee056f52 100644
--- a/packages/protobuf/src/private/json-format.ts
+++ b/packages/protobuf/src/private/json-format.ts
@@ -45,7 +45,7 @@ import { scalarZeroValue } from "./scalars.js";
 import { isScalarZeroValue } from "./scalars.js";
 import type { ScalarValue } from "../scalar.js";
 import { LongType, ScalarType } from "../scalar.js";
-import { isMessage } from "../is-message";
+import { isMessage } from "../is-message.js";
 
 /* eslint-disable no-case-declarations,@typescript-eslint/no-unsafe-argument,@typescript-eslint/no-unsafe-assignment,@typescript-eslint/no-unsafe-member-access,@typescript-eslint/no-unsafe-call */
 
diff --git a/packages/protobuf/src/private/util-common.ts b/packages/protobuf/src/private/util-common.ts
index e3c0126fc..c2e1a5400 100644
--- a/packages/protobuf/src/private/util-common.ts
+++ b/packages/protobuf/src/private/util-common.ts
@@ -19,7 +19,7 @@ import type { MessageType } from "../message-type.js";
 import type { Util } from "./util.js";
 import { scalarEquals } from "./scalars.js";
 import { ScalarType } from "../scalar.js";
-import { isMessage } from "../is-message";
+import { isMessage } from "../is-message.js";
 
 /* eslint-disable @typescript-eslint/no-explicit-any,@typescript-eslint/no-unsafe-assignment,@typescript-eslint/no-unsafe-member-access,@typescript-eslint/no-unsafe-return,@typescript-eslint/no-unsafe-argument,no-case-declarations */
 
diff --git a/packages/protobuf/src/to-plain-message.ts b/packages/protobuf/src/to-plain-message.ts
index d4bac975f..fca3f9a5c 100644
--- a/packages/protobuf/src/to-plain-message.ts
+++ b/packages/protobuf/src/to-plain-message.ts
@@ -16,7 +16,7 @@
 
 import { Message } from "./message.js";
 import type { AnyMessage, PlainMessage } from "./message.js";
-import { isMessage } from "./is-message";
+import { isMessage } from "./is-message.js";
 
 /**
  * toPlainMessage returns a new object by stripping
diff --git a/packages/protoplugin/package.json b/packages/protoplugin/package.json
index f71bbd205..dc9c8fe07 100644
--- a/packages/protoplugin/package.json
+++ b/packages/protoplugin/package.json
@@ -10,10 +10,9 @@
   },
   "scripts": {
     "clean": "rm -rf ./dist/*",
-    "build": "npm run build:cjs && npm run build:esm && npm run build:proxy",
+    "build": "npm run build:cjs && npm run build:esm",
     "build:cjs": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module commonjs --outDir ./dist/cjs --declaration --declarationDir ./dist/cjs && echo >./dist/cjs/package.json '{\"type\":\"commonjs\"}'",
     "build:esm": "../../node_modules/typescript/bin/tsc --project tsconfig.json --module ES2015 --outDir ./dist/esm --declaration --declarationDir ./dist/esm",
-    "build:proxy": "node ../../scripts/gen-esm-proxy.mjs . ecmascript",
     "attw": "attw --pack"
   },
   "type": "module",
@@ -21,20 +20,10 @@
   "main": "./dist/cjs/index.js",
   "exports": {
     ".": {
-      "node": {
-        "import": "./dist/proxy/index.js",
-        "require": "./dist/cjs/index.js"
-      },
-      "module": "./dist/esm/index.js",
       "import": "./dist/esm/index.js",
       "require": "./dist/cjs/index.js"
     },
     "./ecmascript": {
-      "node": {
-        "import": "./dist/proxy/ecmascript/index.js",
-        "require": "./dist/cjs/ecmascript/index.js"
-      },
-      "module": "./dist/esm/ecmascript/index.js",
       "import": "./dist/esm/ecmascript/index.js",
       "require": "./dist/cjs/ecmascript/index.js"
     }
diff --git a/packages/protoplugin/src/ecmascript/generated-file.ts b/packages/protoplugin/src/ecmascript/generated-file.ts
index 1c0e7e7b8..c0bd31479 100644
--- a/packages/protoplugin/src/ecmascript/generated-file.ts
+++ b/packages/protoplugin/src/ecmascript/generated-file.ts
@@ -34,7 +34,7 @@ import {
   LiteralString,
   RefDescEnum,
   RefDescMessage,
-} from "./opaque-printables";
+} from "./opaque-printables.js";
 
 /**
  * All types that can be passed to GeneratedFile.print()
diff --git a/scripts/gen-esm-proxy.mjs b/scripts/gen-esm-proxy.mjs
deleted file mode 100644
index 249953fbe..000000000
--- a/scripts/gen-esm-proxy.mjs
+++ /dev/null
@@ -1,117 +0,0 @@
-// Copyright 2021-2024 Buf Technologies, Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
-import * as path from "node:path";
-import { exit, stderr, stdout, argv } from "node:process";
-
-const args = argv.slice(2);
-
-if (args.length === 0) {
-  stdout.write(`USAGE: ${path.basename(argv[1])} [...path]
-path: One or more subpath exports. A dot (.) is valid.
-
-Generates ESM wrappers for dual packages.
-
-Example:
-
-  ${path.basename(argv[1])} . foo
-
-Assumes that the following CJS artifacts exist: 
-  
-  dist/cjs
-  ├── index.d.ts
-  ├── index.js
-  └── foo
-      ├── index.d.ts
-      └── index.js
-
-Generates the following ESM wrappers:
-
-  dist/proxy
-  ├── index.d.ts
-  ├── index.js
-  └── foo
-      ├── index.d.ts
-      └── index.js
-
-package.json must contain:
-
-  "type": "module", 
-  "exports": {
-    ".": {
-      "require": "./dist/cjs/index.js",
-      "import": "./dist/proxy/index.js"
-    },
-    "./protocol": {
-      "require": "./dist/cjs/foo/index.js",
-      "import": "./dist/proxy/foo/index.js"
-    },
-
-Known limitations:
-- expects CJS files with a .js extension, not .cjs
-- does not support default exports
-- supports only simple subpath directory exports, assuming a index.js file
-- does not support export patterns
-`);
-  exit(1);
-}
-
-const cjsDist = "dist/cjs";
-const proxyDist = "dist/proxy";
-
-const packageType = readPackageJsonType();
-if (packageType !== "module") {
-  stderr.write(`package.json is missing "type": "module" field.\n`);
-  exit(1);
-}
-
-for (const subpath of args) {
-  const cjsPath = path.join(cjsDist, subpath, "index.js");
-  if (!existsSync(cjsPath)) {
-    stderr.write(
-      `CommonJS artifact for subpath "${subpath}" not found at expected path ${cjsPath}\n`,
-    );
-    exit(1);
-  }
-  const proxyDir = path.join(proxyDist, subpath);
-  if (!existsSync(proxyDir)) {
-    mkdirSync(proxyDir, { recursive: true });
-  }
-  const cjsImportPath = path.relative(proxyDir, cjsPath);
-  writeFileSync(
-    path.join(proxyDir, "index.js"),
-    `export * from "${cjsImportPath}";\n`,
-  );
-  writeFileSync(
-    path.join(proxyDir, "index.d.ts"),
-    `export * from "${cjsImportPath}";\n`,
-  );
-}
-
-/**
- * @return {"commonjs"|"module"}
- */
-function readPackageJsonType() {
-  const pkgString = readFileSync("package.json", "utf-8");
-  const pkg = JSON.parse(pkgString);
-  const t = pkg.type;
-  if (typeof t !== "string") {
-    return "commonjs";
-  }
-  if (t.toLowerCase() === "module") {
-    return "module";
-  }
-  return "commonjs";
-}