diff --git a/.eslintrc.cjs b/.eslintrc.cjs
index 1ada9b291ecc..e2d424025744 100644
--- a/.eslintrc.cjs
+++ b/.eslintrc.cjs
@@ -67,10 +67,8 @@ module.exports = {
         "jest/no-standalone-expect": "off",
         "jest/no-test-callback": "off",
         "jest/valid-describe": "off",
-        "import/extensions": [
-          "error",
-          { json: "always", js: "always", cjs: "always", mjs: "always" },
-        ],
+        "import/extensions": ["error", "always"],
+        "no-restricted-imports": ["error", { patterns: ["**/src/**"] }],
       },
     },
     {
diff --git a/Makefile b/Makefile
index 341cd136a90f..d17500b8631a 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@ NODE := $(YARN) node
 
 .PHONY: build build-dist watch lint fix clean test-clean test-only test test-ci publish bootstrap
 
-build: build-bundle
+build: build-no-bundle
 ifneq ("$(BABEL_COVERAGE)", "true")
 	$(MAKE) build-standalone
 endif
@@ -28,8 +28,15 @@ build-bundle: clean clean-lib
 	$(MAKE) build-flow-typings
 	$(MAKE) build-dist
 
-build-bundle-ci: bootstrap-only
-	$(MAKE) build-bundle
+build-no-bundle-ci: bootstrap-only
+	$(YARN) gulp build-dev
+	$(MAKE) build-flow-typings
+	$(MAKE) build-dist
+
+build-no-bundle: clean clean-lib
+	BABEL_ENV=development $(YARN) gulp build-dev
+	$(MAKE) build-flow-typings
+	$(MAKE) build-dist
 
 generate-tsconfig:
 	$(NODE) scripts/generators/tsconfig.js
@@ -46,7 +53,7 @@ build-typescript-legacy-typings:
 
 build-standalone: build-babel-standalone
 
-build-standalone-ci: build-bundle-ci
+build-standalone-ci: build-no-bundle-ci
 	$(MAKE) build-standalone
 
 build-babel-standalone:
@@ -61,12 +68,6 @@ build-plugin-transform-runtime-dist:
 	cd packages/babel-plugin-transform-runtime; \
 	$(NODE) scripts/build-dist.js
 
-build-no-bundle: clean clean-lib
-	BABEL_ENV=development $(YARN) gulp build-dev
-	# Ensure that build artifacts for types are created during local
-	# development too.
-	$(MAKE) build-flow-typings
-
 watch: build-no-bundle
 	BABEL_ENV=development $(YARN) gulp watch
 
diff --git a/eslint/babel-eslint-tests/test/integration/parser-override.js b/eslint/babel-eslint-tests/test/integration/parser-override.js
index 1091c40671a1..5c5632485b1c 100644
--- a/eslint/babel-eslint-tests/test/integration/parser-override.js
+++ b/eslint/babel-eslint-tests/test/integration/parser-override.js
@@ -34,6 +34,7 @@ describe("parserOverride", () => {
   const babel7node12 = parseInt(process.versions.node) < 12 ? it.skip : it;
   babel7node12("works when parsing in a worker", async () => {
     const require = createRequire(import.meta.url);
+    // eslint-disable-next-line import/extensions
     const babelESLintWorker = require("@babel/eslint-parser/experimental-worker");
 
     const { ast } = babelESLintWorker.parseForESLint(`27`, {
diff --git a/jest.config.js b/jest.config.js
index 276e156144d9..b60fa636a815 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -1,4 +1,5 @@
 const supportsESM = parseInt(process.versions.node) >= 12;
+const isPublishBundle = process.env.IS_PUBLISH;
 
 module.exports = {
   collectCoverageFrom: [
@@ -23,6 +24,9 @@ module.exports = {
     "<rootDir>/build/",
     "<rootDir>/.history/", // local directory for VSCode Extension - https://marketplace.visualstudio.com/items?itemName=xyz.local-history
     "_browser\\.js",
+    // Some tests require internal files of bundled packages, which are not available
+    // in production builds. They are marked using the .skip-bundled.js extension.
+    ...(isPublishBundle ? ["\\.skip-bundled\\.js$"] : []),
   ],
   testEnvironment: "node",
   setupFilesAfterEnv: ["<rootDir>/test/testSetupFile.js"],
diff --git a/packages/babel-parser/test/unit/tokenizer/types.js b/packages/babel-parser/test/unit/tokenizer/types.skip-bundled.js
similarity index 90%
rename from packages/babel-parser/test/unit/tokenizer/types.js
rename to packages/babel-parser/test/unit/tokenizer/types.skip-bundled.js
index f242441bd588..0cbcaa8d6fd6 100644
--- a/packages/babel-parser/test/unit/tokenizer/types.js
+++ b/packages/babel-parser/test/unit/tokenizer/types.skip-bundled.js
@@ -1,4 +1,4 @@
-import { tt, tokenOperatorPrecedence } from "../../../src/tokenizer/types.js";
+import { tt, tokenOperatorPrecedence } from "../../../lib/tokenizer/types.js";
 
 describe("token types", () => {
   it("should check if the binOp for relational === in", () => {
diff --git a/packages/babel-parser/test/unit/util/identifier.js b/packages/babel-parser/test/unit/util/identifier.skip-bundled.js
similarity index 96%
rename from packages/babel-parser/test/unit/util/identifier.js
rename to packages/babel-parser/test/unit/util/identifier.skip-bundled.js
index c6c25ec942da..6a9b3f7b20fb 100644
--- a/packages/babel-parser/test/unit/util/identifier.js
+++ b/packages/babel-parser/test/unit/util/identifier.skip-bundled.js
@@ -1,7 +1,7 @@
 import {
   isKeyword,
   keywordRelationalOperator,
-} from "../../../src/util/identifier.js";
+} from "../../../lib/util/identifier.js";
 
 describe("identifier", () => {
   describe("isKeyword", () => {
diff --git a/packages/babel-parser/test/unit/util/location.js b/packages/babel-parser/test/unit/util/location.skip-bundled.js
similarity index 93%
rename from packages/babel-parser/test/unit/util/location.js
rename to packages/babel-parser/test/unit/util/location.skip-bundled.js
index 9c8fb79b37a4..463463c88921 100644
--- a/packages/babel-parser/test/unit/util/location.js
+++ b/packages/babel-parser/test/unit/util/location.skip-bundled.js
@@ -1,4 +1,4 @@
-import { getLineInfo } from "../../../src/util/location.js";
+import { getLineInfo } from "../../../lib/util/location.js";
 
 describe("getLineInfo", () => {
   const input = "a\nb\nc\nd\ne\nf\ng\nh\ni";
diff --git a/packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/test/util.test.js b/packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/test/util.skip-bundled.js
similarity index 96%
rename from packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/test/util.test.js
rename to packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/test/util.skip-bundled.js
index f6e9282e42fa..ed7576030378 100644
--- a/packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/test/util.test.js
+++ b/packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/test/util.skip-bundled.js
@@ -1,5 +1,5 @@
 import { parseSync, traverse } from "@babel/core";
-import { shouldTransform } from "../src/util.ts";
+import { shouldTransform } from "../lib/util.js";
 
 function getPath(input, parserOpts = {}) {
   let targetPath;
diff --git a/packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/test/util.test.js b/packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/test/util.skip-bundled.js
similarity index 98%
rename from packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/test/util.test.js
rename to packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/test/util.skip-bundled.js
index 89bc17afb5d7..e475940c0b31 100644
--- a/packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/test/util.test.js
+++ b/packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/test/util.skip-bundled.js
@@ -1,5 +1,5 @@
 import { parseSync, traverse } from "@babel/core";
-import { shouldTransform } from "../src/util.ts";
+import { shouldTransform } from "../lib/util.js";
 
 function getPath(input, parserOpts = {}) {
   let targetPath;
diff --git a/packages/babel-plugin-proposal-optional-chaining/test/util.test.js b/packages/babel-plugin-proposal-optional-chaining/test/util.skip-bundled.js
similarity index 97%
rename from packages/babel-plugin-proposal-optional-chaining/test/util.test.js
rename to packages/babel-plugin-proposal-optional-chaining/test/util.skip-bundled.js
index d2b8a3d83331..ee3289dcc530 100644
--- a/packages/babel-plugin-proposal-optional-chaining/test/util.test.js
+++ b/packages/babel-plugin-proposal-optional-chaining/test/util.skip-bundled.js
@@ -1,4 +1,4 @@
-import { willPathCastToBoolean } from "../src/util.js";
+import { willPathCastToBoolean } from "../lib/util.js";
 import { parseSync, traverse } from "@babel/core";
 
 function getPath(input, parserOpts) {
diff --git a/packages/babel-preset-react/test/normalize-options.spec.js b/packages/babel-preset-react/test/normalize-options.skip-bundled.js
similarity index 98%
rename from packages/babel-preset-react/test/normalize-options.spec.js
rename to packages/babel-preset-react/test/normalize-options.skip-bundled.js
index b3e1b8dee390..5932ed4b6d73 100644
--- a/packages/babel-preset-react/test/normalize-options.spec.js
+++ b/packages/babel-preset-react/test/normalize-options.skip-bundled.js
@@ -1,4 +1,5 @@
-import normalizeOptions from "../src/normalize-options.js";
+import normalizeOptions from "../lib/normalize-options.js";
+
 describe("normalize options", () => {
   (process.env.BABEL_8_BREAKING ? describe : describe.skip)("Babel 8", () => {
     it("should throw on unknown options", () => {
diff --git a/packages/babel-preset-typescript/test/normalize-options.spec.js b/packages/babel-preset-typescript/test/normalize-options.skip-bundled.js
similarity index 98%
rename from packages/babel-preset-typescript/test/normalize-options.spec.js
rename to packages/babel-preset-typescript/test/normalize-options.skip-bundled.js
index 710c9dc797c6..205409af007e 100644
--- a/packages/babel-preset-typescript/test/normalize-options.spec.js
+++ b/packages/babel-preset-typescript/test/normalize-options.skip-bundled.js
@@ -1,4 +1,5 @@
-import normalizeOptions from "../src/normalize-options.js";
+import normalizeOptions from "../lib/normalize-options.js";
+
 describe("normalize options", () => {
   (process.env.BABEL_8_BREAKING ? describe : describe.skip)("Babel 8", () => {
     it("should throw on unknown options", () => {