diff --git a/scripts/cache.ts b/scripts/cache.ts
index d8917d837b3..2024dd479cc 100644
--- a/scripts/cache.ts
+++ b/scripts/cache.ts
@@ -2,7 +2,7 @@ import fsp from 'fs/promises';
 
 import { hashElement } from 'folder-hash';
 
-import { exists } from './common';
+import { exists } from './common.js';
 
 export class Cache {
   folder: string;
diff --git a/scripts/ci/codegen/createGitHubReleases.ts b/scripts/ci/codegen/createGitHubReleases.ts
index ba18bf7eb41..2b73735b7e5 100644
--- a/scripts/ci/codegen/createGitHubReleases.ts
+++ b/scripts/ci/codegen/createGitHubReleases.ts
@@ -1,9 +1,9 @@
-import { ensureGitHubToken, getOctokit, OWNER, run, setVerbose, toAbsolutePath } from '../../common';
-import { isPreRelease } from '../../release/versionsHistory';
-import type { Language } from '../../types';
-import { cloneRepository } from '../utils';
+import { ensureGitHubToken, getOctokit, OWNER, run, setVerbose, toAbsolutePath } from '../../common.js';
+import { isPreRelease } from '../../release/versionsHistory.js';
+import type { Language } from '../../types.js';
+import { cloneRepository } from '../utils.js';
 
-import { commitStartRelease } from './text';
+import { commitStartRelease } from './text.js';
 
 async function createGitHubRelease(lang: Language): Promise<void> {
   // **Full Changelog**:
diff --git a/scripts/ci/codegen/waitForAllReleases.ts b/scripts/ci/codegen/waitForAllReleases.ts
index fc2d6f2bc9a..f0111caf3cb 100644
--- a/scripts/ci/codegen/waitForAllReleases.ts
+++ b/scripts/ci/codegen/waitForAllReleases.ts
@@ -1,11 +1,11 @@
 import type { components } from '@octokit/openapi-types';
 
-import { exists, getOctokit, run, setVerbose, toAbsolutePath } from '../../common';
-import { getClientsConfigField, getLanguageFolder } from '../../config';
-import { getTargetBranch } from '../../release/common';
-import type { Language } from '../../types';
+import { exists, getOctokit, run, setVerbose, toAbsolutePath } from '../../common.js';
+import { getClientsConfigField, getLanguageFolder } from '../../config.js';
+import { getTargetBranch } from '../../release/common.js';
+import type { Language } from '../../types.js';
 
-import { commitStartRelease } from './text';
+import { commitStartRelease } from './text.js';
 
 type Run = {
   language: Language;
diff --git a/scripts/cli/index.ts b/scripts/cli/index.ts
index b1f7dec0929..65c2b16f7e8 100644
--- a/scripts/cli/index.ts
+++ b/scripts/cli/index.ts
@@ -6,14 +6,14 @@ import { CI, CLIENTS, LANGUAGES, run, setVerbose, toAbsolutePath } from '../comm
 import { getLanguageFolder } from '../config.js';
 import { ctsGenerateMany } from '../cts/generate.js';
 import { runCts } from '../cts/runCts.js';
-import { startTestServer } from '../cts/testServer';
+import { startTestServer } from '../cts/testServer/index.js';
 import { docsGenerateMany } from '../docs/generate.js';
 import { formatter } from '../formatter.js';
 import { generate } from '../generate.js';
 import { playground } from '../playground.js';
 import { createReleasePR } from '../release/createReleasePR.js';
 import { generateVersionsHistory } from '../release/versionsHistory.js';
-import { buildSpecs } from '../specs';
+import { buildSpecs } from '../specs/index.js';
 import type { Language } from '../types.js';
 
 import { existsSync } from 'node:fs';
diff --git a/scripts/common.ts b/scripts/common.ts
index bf17469231e..28ebc98dd8c 100644
--- a/scripts/common.ts
+++ b/scripts/common.ts
@@ -9,11 +9,11 @@ import { remove } from 'fs-extra';
 import clientsConfig from '../config/clients.config.json' assert { type: 'json' };
 import releaseConfig from '../config/release.config.json' assert { type: 'json' };
 
-import { Cache } from './cache';
-import { getDockerImage } from './config';
-import { generateOpenapitools } from './pre-gen';
+import { Cache } from './cache.js';
+import { getDockerImage } from './config.js';
+import { generateOpenapitools } from './pre-gen/index.js';
 import { getGitAuthor } from './release/common.js';
-import { buildSpecs } from './specs';
+import { buildSpecs } from './specs/index.js';
 import { createSpinner } from './spinners.js';
 import type { Generator, GeneratorMode, Language, RunOptions } from './types.js';
 
diff --git a/scripts/config.ts b/scripts/config.ts
index f3c814d04c0..1a4bda1f16a 100644
--- a/scripts/config.ts
+++ b/scripts/config.ts
@@ -1,6 +1,6 @@
 import clientsConfig from '../config/clients.config.json' assert { type: 'json' };
 
-import { CI } from './common';
+import { CI } from './common.js';
 import type { Language, LanguageConfig } from './types.js';
 
 export function getClientsConfigField(
diff --git a/scripts/cts/runCts.ts b/scripts/cts/runCts.ts
index ee72387d62c..9caa155ae45 100644
--- a/scripts/cts/runCts.ts
+++ b/scripts/cts/runCts.ts
@@ -5,9 +5,9 @@ import { getTestOutputFolder } from '../config.js';
 import { createSpinner } from '../spinners.js';
 import type { Language } from '../types.js';
 
-import { startTestServer } from './testServer';
 import { printBenchmarkReport } from './testServer/benchmark.js';
 import { assertChunkWrapperValid } from './testServer/chunkWrapper.js';
+import { startTestServer } from './testServer/index.js';
 import { assertValidReplaceAllObjects } from './testServer/replaceAllObjects.js';
 import { assertValidTimeouts } from './testServer/timeout.js';
 import { assertValidWaitForApiKey } from './testServer/waitFor.js';
diff --git a/scripts/cts/testServer/apiKey.ts b/scripts/cts/testServer/apiKey.ts
index 00ea0ed28e1..f2a05f30a16 100644
--- a/scripts/cts/testServer/apiKey.ts
+++ b/scripts/cts/testServer/apiKey.ts
@@ -3,7 +3,7 @@ import type { Server } from 'http';
 import { expect } from 'chai';
 import type { Express, Request, Response } from 'express';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 // Checks that the client sends a different API key after the first request.
 function addRoutes(app: Express): void {
diff --git a/scripts/cts/testServer/benchmark.ts b/scripts/cts/testServer/benchmark.ts
index 430d94824b7..815d90636db 100644
--- a/scripts/cts/testServer/benchmark.ts
+++ b/scripts/cts/testServer/benchmark.ts
@@ -6,9 +6,9 @@ import chalk from 'chalk';
 import type { Express } from 'express';
 import express from 'express';
 
-import { CI, toAbsolutePath } from '../../common';
+import { CI, toAbsolutePath } from '../../common.js';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 const benchmarkStatus: Record<
   string,
diff --git a/scripts/cts/testServer/chunkWrapper.ts b/scripts/cts/testServer/chunkWrapper.ts
index 25640e7a787..b69d36a5c18 100644
--- a/scripts/cts/testServer/chunkWrapper.ts
+++ b/scripts/cts/testServer/chunkWrapper.ts
@@ -4,7 +4,7 @@ import { expect } from 'chai';
 import type { Express } from 'express';
 import express from 'express';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 const chunkWrapperState: Record<string, any> = {};
 
diff --git a/scripts/cts/testServer/gzip.ts b/scripts/cts/testServer/gzip.ts
index bf033bce73c..5ea6d828b6e 100644
--- a/scripts/cts/testServer/gzip.ts
+++ b/scripts/cts/testServer/gzip.ts
@@ -4,9 +4,9 @@ import zlib from 'node:zlib';
 import crc32 from 'crc/crc32';
 import type { Express } from 'express';
 
-import { retryHandler } from './timeout';
+import { retryHandler } from './timeout.js';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 function addRoutes(app: Express): void {
   app.get('/1/test/retry/:lang', retryHandler(0, 'ok test server response'));
diff --git a/scripts/cts/testServer/index.ts b/scripts/cts/testServer/index.ts
index 1ffa3bc72b9..5bc595f9f2e 100644
--- a/scripts/cts/testServer/index.ts
+++ b/scripts/cts/testServer/index.ts
@@ -3,17 +3,17 @@ import type { Server } from 'http';
 import type { Express } from 'express';
 import express from 'express';
 
-import { createSpinner } from '../../spinners';
-import type { CTSType } from '../runCts';
+import { createSpinner } from '../../spinners.js';
+import type { CTSType } from '../runCts.js';
 
-import { apiKeyServer } from './apiKey';
-import { benchmarkServer } from './benchmark';
-import { chunkWrapperServer } from './chunkWrapper';
-import { gzipServer } from './gzip';
-import { replaceAllObjectsServer } from './replaceAllObjects';
-import { timeoutServer } from './timeout';
-import { timeoutServerBis } from './timeoutBis';
-import { waitForApiKeyServer } from './waitFor';
+import { apiKeyServer } from './apiKey.js';
+import { benchmarkServer } from './benchmark.js';
+import { chunkWrapperServer } from './chunkWrapper.js';
+import { gzipServer } from './gzip.js';
+import { replaceAllObjectsServer } from './replaceAllObjects.js';
+import { timeoutServer } from './timeout.js';
+import { timeoutServerBis } from './timeoutBis.js';
+import { waitForApiKeyServer } from './waitFor.js';
 
 export async function startTestServer(suites: Record<CTSType, boolean>): Promise<() => Promise<void>> {
   const toStart: Array<Promise<Server>> = [];
diff --git a/scripts/cts/testServer/replaceAllObjects.ts b/scripts/cts/testServer/replaceAllObjects.ts
index 42afbebe4be..33278723e1e 100644
--- a/scripts/cts/testServer/replaceAllObjects.ts
+++ b/scripts/cts/testServer/replaceAllObjects.ts
@@ -4,7 +4,7 @@ import { expect } from 'chai';
 import type { Express } from 'express';
 import express from 'express';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 const raoState: Record<
   string,
diff --git a/scripts/cts/testServer/timeout.ts b/scripts/cts/testServer/timeout.ts
index 61c710a55ab..1309dd8c7e7 100644
--- a/scripts/cts/testServer/timeout.ts
+++ b/scripts/cts/testServer/timeout.ts
@@ -3,7 +3,7 @@ import type { Server } from 'http';
 import { expect } from 'chai';
 import type express from 'express';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 const timeoutState: Record<string, { timestamp: number[]; duration: number[]; hangCount: number }> = {};
 
diff --git a/scripts/cts/testServer/timeoutBis.ts b/scripts/cts/testServer/timeoutBis.ts
index 21b494dbde6..d9b6bd8ffc5 100644
--- a/scripts/cts/testServer/timeoutBis.ts
+++ b/scripts/cts/testServer/timeoutBis.ts
@@ -2,9 +2,9 @@ import type { Server } from 'http';
 
 import type express from 'express';
 
-import { retryHandler } from './timeout';
+import { retryHandler } from './timeout.js';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 function addRoutes(app: express.Express): void {
   // this endpoint is also defined in the gzip server but without the timeout
diff --git a/scripts/cts/testServer/waitFor.ts b/scripts/cts/testServer/waitFor.ts
index 68f68e4b6ed..b4909bb441c 100644
--- a/scripts/cts/testServer/waitFor.ts
+++ b/scripts/cts/testServer/waitFor.ts
@@ -3,7 +3,7 @@ import type { Server } from 'http';
 import { expect } from 'chai';
 import type { Express } from 'express';
 
-import { setupServer } from '.';
+import { setupServer } from './index.js';
 
 const retryCount: Record<
   string,
diff --git a/scripts/generate.ts b/scripts/generate.ts
index 04beefe3652..65dc26141cf 100644
--- a/scripts/generate.ts
+++ b/scripts/generate.ts
@@ -1,7 +1,7 @@
 import { callGenerator, setupAndGen } from './common.js';
 import { getLanguageFolder } from './config.js';
 import { formatter } from './formatter.js';
-import { removeExistingCodegen } from './pre-gen';
+import { removeExistingCodegen } from './pre-gen/index.js';
 import type { Generator } from './types.js';
 
 async function preGen(gen: Generator): Promise<void> {
diff --git a/scripts/specs/__tests__/snippets.test.ts b/scripts/specs/__tests__/snippets.test.ts
index 818b11fdb4b..0f4038c52fc 100644
--- a/scripts/specs/__tests__/snippets.test.ts
+++ b/scripts/specs/__tests__/snippets.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vitest';
 
-import { transformCodeSamplesToGuideMethods } from '../snippets';
-import { SnippetSamples } from '../types';
+import { transformCodeSamplesToGuideMethods } from '../snippets.js';
+import { SnippetSamples } from '../types.js';
 
 describe('init', () => {
   it('parses a multi line import', () => {
diff --git a/scripts/specs/types.ts b/scripts/specs/types.ts
index ce118331e63..25b0c7a3c7a 100644
--- a/scripts/specs/types.ts
+++ b/scripts/specs/types.ts
@@ -1,4 +1,4 @@
-import type { Language } from '../types';
+import type { Language } from '../types.js';
 
 export type BaseBuildSpecsOptions = {
   outputFormat: 'json' | 'yml';
diff --git a/scripts/tsconfig.json b/scripts/tsconfig.json
index 83692f53b9f..f6deb3d7d68 100644
--- a/scripts/tsconfig.json
+++ b/scripts/tsconfig.json
@@ -1,7 +1,7 @@
 {
   "extends": "../config/base.tsconfig.json",
   "compilerOptions": {
-    "module": "esnext",
+    "module": "nodenext",
     "target": "esnext",
     "typeRoots": ["../node_modules/@types"],
     "types": ["node"],
diff --git a/scripts/types.ts b/scripts/types.ts
index 2b900487548..c5236c59d38 100644
--- a/scripts/types.ts
+++ b/scripts/types.ts
@@ -1,6 +1,6 @@
 import type config from '../config/clients.config.json';
 
-import type { CodeSamples } from './specs/types';
+import type { CodeSamples } from './specs/types.js';
 
 /**
  * Config.