diff --git a/.eslintrc.cjs b/.eslintrc.cjs
index e2d4240257..3160c30b5e 100644
--- a/.eslintrc.cjs
+++ b/.eslintrc.cjs
@@ -84,7 +84,7 @@ module.exports = {
       ],
       excludedFiles: [
         // @babel/register is the require() hook, so it will always be CJS-based
-        "packages/babel-register/**/*.js",
+        "packages/babel-register/**/*.{js,ts}",
       ],
       rules: {
         "no-restricted-globals": ["error", ...cjsGlobals],
diff --git a/Gulpfile.mjs b/Gulpfile.mjs
index bffce65ecf..ba431b72cc 100644
--- a/Gulpfile.mjs
+++ b/Gulpfile.mjs
@@ -61,7 +61,7 @@ function mapSrcToLib(srcPath) {
 function mapToDts(packageName) {
   return packageName.replace(
     /(?<=\\|\/|^)(packages|eslint|codemods)(?=\\|\/)/,
-    "dts"
+    "dts/$1"
   );
 }
 
diff --git a/codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.js b/codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.ts
similarity index 100%
rename from codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.js
rename to codemods/babel-plugin-codemod-object-assign-to-object-spread/src/index.ts
diff --git a/codemods/babel-plugin-codemod-optional-catch-binding/src/index.js b/codemods/babel-plugin-codemod-optional-catch-binding/src/index.ts
similarity index 100%
rename from codemods/babel-plugin-codemod-optional-catch-binding/src/index.js
rename to codemods/babel-plugin-codemod-optional-catch-binding/src/index.ts
diff --git a/eslint/babel-eslint-plugin-development-internal/src/index.js b/eslint/babel-eslint-plugin-development-internal/src/index.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development-internal/src/index.js
rename to eslint/babel-eslint-plugin-development-internal/src/index.ts
diff --git a/eslint/babel-eslint-plugin-development-internal/src/rules/dry-error-messages.js b/eslint/babel-eslint-plugin-development-internal/src/rules/dry-error-messages.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development-internal/src/rules/dry-error-messages.js
rename to eslint/babel-eslint-plugin-development-internal/src/rules/dry-error-messages.ts
diff --git a/eslint/babel-eslint-plugin-development-internal/src/rules/report-error-message-format.js b/eslint/babel-eslint-plugin-development-internal/src/rules/report-error-message-format.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development-internal/src/rules/report-error-message-format.js
rename to eslint/babel-eslint-plugin-development-internal/src/rules/report-error-message-format.ts
diff --git a/eslint/babel-eslint-plugin-development/src/index.js b/eslint/babel-eslint-plugin-development/src/index.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/index.js
rename to eslint/babel-eslint-plugin-development/src/index.ts
diff --git a/eslint/babel-eslint-plugin-development/src/rules/no-deprecated-clone.js b/eslint/babel-eslint-plugin-development/src/rules/no-deprecated-clone.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/rules/no-deprecated-clone.js
rename to eslint/babel-eslint-plugin-development/src/rules/no-deprecated-clone.ts
diff --git a/eslint/babel-eslint-plugin-development/src/rules/no-undefined-identifier.js b/eslint/babel-eslint-plugin-development/src/rules/no-undefined-identifier.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/rules/no-undefined-identifier.js
rename to eslint/babel-eslint-plugin-development/src/rules/no-undefined-identifier.ts
diff --git a/eslint/babel-eslint-plugin-development/src/rules/plugin-name.js b/eslint/babel-eslint-plugin-development/src/rules/plugin-name.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/rules/plugin-name.js
rename to eslint/babel-eslint-plugin-development/src/rules/plugin-name.ts
diff --git a/eslint/babel-eslint-plugin-development/src/utils/get-export-name.js b/eslint/babel-eslint-plugin-development/src/utils/get-export-name.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/utils/get-export-name.js
rename to eslint/babel-eslint-plugin-development/src/utils/get-export-name.ts
diff --git a/eslint/babel-eslint-plugin-development/src/utils/get-reference-origin.js b/eslint/babel-eslint-plugin-development/src/utils/get-reference-origin.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/utils/get-reference-origin.js
rename to eslint/babel-eslint-plugin-development/src/utils/get-reference-origin.ts
diff --git a/eslint/babel-eslint-plugin-development/src/utils/is-babel-plugin-factory.js b/eslint/babel-eslint-plugin-development/src/utils/is-babel-plugin-factory.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/utils/is-babel-plugin-factory.js
rename to eslint/babel-eslint-plugin-development/src/utils/is-babel-plugin-factory.ts
diff --git a/eslint/babel-eslint-plugin-development/src/utils/is-from-babel-types.js b/eslint/babel-eslint-plugin-development/src/utils/is-from-babel-types.ts
similarity index 100%
rename from eslint/babel-eslint-plugin-development/src/utils/is-from-babel-types.js
rename to eslint/babel-eslint-plugin-development/src/utils/is-from-babel-types.ts
diff --git a/eslint/babel-eslint-plugin/src/index.js b/eslint/babel-eslint-plugin/src/index.ts
similarity index 100%
rename from eslint/babel-eslint-plugin/src/index.js
rename to eslint/babel-eslint-plugin/src/index.ts
diff --git a/eslint/babel-eslint-plugin/src/rules/new-cap.js b/eslint/babel-eslint-plugin/src/rules/new-cap.ts
similarity index 100%
rename from eslint/babel-eslint-plugin/src/rules/new-cap.js
rename to eslint/babel-eslint-plugin/src/rules/new-cap.ts
diff --git a/eslint/babel-eslint-plugin/src/rules/no-invalid-this.js b/eslint/babel-eslint-plugin/src/rules/no-invalid-this.ts
similarity index 100%
rename from eslint/babel-eslint-plugin/src/rules/no-invalid-this.js
rename to eslint/babel-eslint-plugin/src/rules/no-invalid-this.ts
diff --git a/eslint/babel-eslint-plugin/src/rules/no-unused-expressions.js b/eslint/babel-eslint-plugin/src/rules/no-unused-expressions.ts
similarity index 100%
rename from eslint/babel-eslint-plugin/src/rules/no-unused-expressions.js
rename to eslint/babel-eslint-plugin/src/rules/no-unused-expressions.ts
diff --git a/eslint/babel-eslint-plugin/src/rules/object-curly-spacing.js b/eslint/babel-eslint-plugin/src/rules/object-curly-spacing.ts
similarity index 100%
rename from eslint/babel-eslint-plugin/src/rules/object-curly-spacing.js
rename to eslint/babel-eslint-plugin/src/rules/object-curly-spacing.ts
diff --git a/eslint/babel-eslint-plugin/src/rules/semi.js b/eslint/babel-eslint-plugin/src/rules/semi.ts
similarity index 98%
rename from eslint/babel-eslint-plugin/src/rules/semi.js
rename to eslint/babel-eslint-plugin/src/rules/semi.ts
index 5c4fa9cfea..1d96632e68 100644
--- a/eslint/babel-eslint-plugin/src/rules/semi.js
+++ b/eslint/babel-eslint-plugin/src/rules/semi.ts
@@ -47,7 +47,7 @@ function isOneLinerBlock(context, node) {
   );
 }
 
-function report(context, node, missing) {
+function report(context, node, missing?) {
   const lastToken = context.getSourceCode().getLastToken(node);
 
   let message,
diff --git a/packages/babel-core/src/config/plugin.ts b/packages/babel-core/src/config/plugin.ts
index 2f958faa70..1ac360fc8f 100644
--- a/packages/babel-core/src/config/plugin.ts
+++ b/packages/babel-core/src/config/plugin.ts
@@ -2,13 +2,13 @@ import type { PluginObject } from "./validation/plugins";
 
 export default class Plugin {
   key: string | undefined | null;
-  manipulateOptions: ((options: unknown, parserOpts: unknown) => void) | void;
-  post: Function | void;
-  pre: Function | void;
+  manipulateOptions?: (options: unknown, parserOpts: unknown) => void;
+  post?: Function;
+  pre?: Function;
   visitor: {};
 
-  parserOverride: Function | void;
-  generatorOverride: Function | void;
+  parserOverride?: Function;
+  generatorOverride?: Function;
 
   options: {};
 
diff --git a/packages/babel-generator/src/buffer.ts b/packages/babel-generator/src/buffer.ts
index 50e393306a..cbbaef52e0 100644
--- a/packages/babel-generator/src/buffer.ts
+++ b/packages/babel-generator/src/buffer.ts
@@ -38,7 +38,7 @@ export default class Buffer {
    * Get the final string output from the buffer, along with the sourcemap if one exists.
    */
 
-  get(): any {
+  get() {
     this._flush();
 
     const map = this._map;
diff --git a/packages/babel-generator/src/generators/jsx.ts b/packages/babel-generator/src/generators/jsx.ts
index c265fb5570..0bb50ff781 100644
--- a/packages/babel-generator/src/generators/jsx.ts
+++ b/packages/babel-generator/src/generators/jsx.ts
@@ -67,7 +67,7 @@ export function JSXElement(this: Printer, node: t.JSXElement) {
   if (open.selfClosing) return;
 
   this.indent();
-  for (const child of node.children as Array<any>) {
+  for (const child of node.children) {
     this.print(child, node);
   }
   this.dedent();
@@ -109,7 +109,7 @@ export function JSXFragment(this: Printer, node: t.JSXFragment) {
   this.print(node.openingFragment, node);
 
   this.indent();
-  for (const child of node.children as Array<any>) {
+  for (const child of node.children) {
     this.print(child, node);
   }
   this.dedent();
diff --git a/packages/babel-generator/src/generators/statements.ts b/packages/babel-generator/src/generators/statements.ts
index 981234adf5..3150857fee 100644
--- a/packages/babel-generator/src/generators/statements.ts
+++ b/packages/babel-generator/src/generators/statements.ts
@@ -267,7 +267,7 @@ export function VariableDeclaration(
   let hasInits = false;
   // don't add whitespace to loop heads
   if (!isFor(parent)) {
-    for (const declar of node.declarations as Array<any>) {
+    for (const declar of node.declarations) {
       if (declar.init) {
         // has an init so let's split it up over multiple lines
         hasInits = true;
diff --git a/packages/babel-generator/src/index.ts b/packages/babel-generator/src/index.ts
index 5346c24460..104f8325bc 100644
--- a/packages/babel-generator/src/index.ts
+++ b/packages/babel-generator/src/index.ts
@@ -246,7 +246,7 @@ export default function generate(
   ast: t.Node,
   opts?: GeneratorOptions,
   code?: string | { [filename: string]: string },
-): any {
+) {
   const gen = new Generator(ast, opts, code);
   return gen.generate();
 }
diff --git a/packages/babel-generator/src/printer.ts b/packages/babel-generator/src/printer.ts
index b27bfa0395..bbdcc5b1ba 100644
--- a/packages/babel-generator/src/printer.ts
+++ b/packages/babel-generator/src/printer.ts
@@ -375,7 +375,7 @@ class Printer {
    *  `undefined` will be returned and not `foo` due to the terminator.
    */
 
-  startTerminatorless(isLabel: boolean = false): any {
+  startTerminatorless(isLabel: boolean = false) {
     if (isLabel) {
       this._noLineTerminator = true;
       return null;
diff --git a/packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.js b/packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.ts
similarity index 78%
rename from packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.js
rename to packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.ts
index 951accfbe6..c498d70369 100644
--- a/packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.js
+++ b/packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.ts
@@ -1,15 +1,17 @@
 import explode from "@babel/helper-explode-assignable-expression";
 import { assignmentExpression, sequenceExpression } from "@babel/types";
+import type { Visitor } from "@babel/traverse";
 
-export default function (opts: { build: Function, operator: string }): Object {
+export default function (opts: { build: Function; operator: string }) {
   const { build, operator } = opts;
 
-  return {
+  const visitor: Visitor = {
     AssignmentExpression(path) {
       const { node, scope } = path;
       if (node.operator !== operator + "=") return;
 
       const nodes = [];
+      // @ts-expect-error todo(flow->ts)
       const exploded = explode(node.left, nodes, this, scope);
       nodes.push(
         assignmentExpression(
@@ -28,4 +30,5 @@ export default function (opts: { build: Function, operator: string }): Object {
       }
     },
   };
+  return visitor;
 }
diff --git a/packages/babel-helper-builder-react-jsx/package.json b/packages/babel-helper-builder-react-jsx/package.json
index 7455f39c8e..12c5d642f2 100644
--- a/packages/babel-helper-builder-react-jsx/package.json
+++ b/packages/babel-helper-builder-react-jsx/package.json
@@ -17,6 +17,9 @@
     "@babel/helper-annotate-as-pure": "workspace:^",
     "@babel/types": "workspace:^"
   },
+  "devDependencies": {
+    "@babel/traverse": "workspace:^"
+  },
   "engines": {
     "node": ">=6.9.0"
   },
diff --git a/packages/babel-helper-builder-react-jsx/src/index.js b/packages/babel-helper-builder-react-jsx/src/index.ts
similarity index 93%
rename from packages/babel-helper-builder-react-jsx/src/index.js
rename to packages/babel-helper-builder-react-jsx/src/index.ts
index b8c54f2867..e9f436afb6 100644
--- a/packages/babel-helper-builder-react-jsx/src/index.js
+++ b/packages/babel-helper-builder-react-jsx/src/index.ts
@@ -24,17 +24,19 @@ import {
   thisExpression,
 } from "@babel/types";
 import annotateAsPure from "@babel/helper-annotate-as-pure";
+import type { Visitor } from "@babel/traverse";
 
 type ElementState = {
-  tagExpr: Object, // tag node
-  tagName: ?string, // raw string tag name
-  args: Array<Object>, // array of call arguments
-  call?: Object, // optional call property that can be set to override the call expression returned
-  pure: boolean, // true if the element can be marked with a #__PURE__ annotation
+  tagExpr: any; // tag node,
+  tagName: string | undefined | null; // raw string tag name,
+  args: Array<any>; // array of call arguments,
+  call?: any; // optional call property that can be set to override the call expression returned,
+  pure: boolean; // true if the element can be marked with a #__PURE__ annotation
+  callee?: any;
 };
 
 export default function (opts) {
-  const visitor = {};
+  const visitor: Visitor = {};
 
   visitor.JSXNamespacedName = function (path) {
     if (opts.throwIfNamespace) {
@@ -81,6 +83,7 @@ You can set \`throwIfNamespace: false\` to bypass this warning.`,
       if (node.name === "this" && isReferenced(node, parent)) {
         return thisExpression();
       } else if (isValidIdentifier(node.name, false)) {
+        // @ts-expect-error todo(flow->ts) avoid type unsafe mutations
         node.type = "Identifier";
       } else {
         return stringLiteral(node.name);
@@ -152,6 +155,7 @@ You can set \`throwIfNamespace: false\` to bypass this warning.`,
     if (isIdentifier(tagExpr)) {
       tagName = tagExpr.name;
     } else if (isLiteral(tagExpr)) {
+      // @ts-expect-error todo(flow->ts) NullLiteral
       tagName = tagExpr.value;
     }
 
diff --git a/packages/babel-helper-create-class-features-plugin/src/index.ts b/packages/babel-helper-create-class-features-plugin/src/index.ts
index df7046213e..6e242a58c7 100644
--- a/packages/babel-helper-create-class-features-plugin/src/index.ts
+++ b/packages/babel-helper-create-class-features-plugin/src/index.ts
@@ -19,6 +19,7 @@ import {
   isLoose,
 } from "./features";
 import { assertFieldTransformed } from "./typescript";
+import type { ParserOptions } from "@babel/parser";
 
 export { FEATURES, enableFeature, injectInitialization };
 
@@ -38,7 +39,7 @@ interface Options {
   feature: number;
   loose?: boolean;
   // same as PluginObject.manipulateOptions
-  manipulateOptions: (options: unknown, parserOpts: unknown) => void;
+  manipulateOptions: (options: unknown, parserOpts: ParserOptions) => void;
   // TODO(flow->ts): change to babel api
   api?: { assumption: (key?: string) => boolean | undefined };
 }
diff --git a/packages/babel-helper-define-map/src/index.js b/packages/babel-helper-define-map/src/index.ts
similarity index 87%
rename from packages/babel-helper-define-map/src/index.js
rename to packages/babel-helper-define-map/src/index.ts
index 60c69cbf91..591cd78193 100644
--- a/packages/babel-helper-define-map/src/index.js
+++ b/packages/babel-helper-define-map/src/index.ts
@@ -18,7 +18,7 @@ import {
   toKeyAlias,
 } from "@babel/types";
 
-function toKind(node: Object) {
+function toKind(node: any) {
   if (isClassMethod(node) || isObjectMethod(node)) {
     if (node.kind === "get" || node.kind === "set") {
       return node.kind;
@@ -30,18 +30,12 @@ function toKind(node: Object) {
 
 const has = Function.prototype.call.bind(Object.prototype.hasOwnProperty);
 
-export function push(
-  mutatorMap: Object,
-  node: Object,
-  kind: string,
-  file,
-  scope?,
-): Object {
+export function push(mutatorMap: any, node: any, kind: string, file, scope?) {
   const alias = toKeyAlias(node);
 
   //
 
-  let map = {};
+  let map = {} as any;
   if (has(mutatorMap, alias)) map = mutatorMap[alias];
   mutatorMap[alias] = map;
 
@@ -79,6 +73,7 @@ export function push(
   } else if (isObjectMethod(node) || isClassMethod(node)) {
     value = functionExpression(
       null,
+      // @ts-expect-error todo(flow->ts) TSParameterProperty is not assignable to parameter of type 'Identifier | RestElement | Pattern'.
       node.params,
       node.body,
       node.generator,
@@ -110,7 +105,7 @@ export function push(
   return map;
 }
 
-export function hasComputed(mutatorMap: Object): boolean {
+export function hasComputed(mutatorMap: any): boolean {
   for (const key of Object.keys(mutatorMap)) {
     if (mutatorMap[key]._computed) {
       return true;
@@ -119,7 +114,7 @@ export function hasComputed(mutatorMap: Object): boolean {
   return false;
 }
 
-export function toComputedObjectFromClass(obj: Object): Object {
+export function toComputedObjectFromClass(obj: any) {
   const objExpr = arrayExpression([]);
 
   for (let i = 0; i < obj.properties.length; i++) {
@@ -134,7 +129,7 @@ export function toComputedObjectFromClass(obj: Object): Object {
   return objExpr;
 }
 
-export function toClassObject(mutatorMap: Object): Object {
+export function toClassObject(mutatorMap: any) {
   const objExpr = objectExpression([]);
 
   Object.keys(mutatorMap).forEach(function (mutatorMapKey) {
@@ -160,7 +155,7 @@ export function toClassObject(mutatorMap: Object): Object {
   return objExpr;
 }
 
-export function toDefineObject(mutatorMap: Object): Object {
+export function toDefineObject(mutatorMap: any) {
   Object.keys(mutatorMap).forEach(function (key) {
     const map = mutatorMap[key];
     if (map.value) map.writable = booleanLiteral(true);
diff --git a/packages/babel-helper-module-transforms/src/normalize-and-load-metadata.ts b/packages/babel-helper-module-transforms/src/normalize-and-load-metadata.ts
index 35e1b02b17..0fac804b8f 100644
--- a/packages/babel-helper-module-transforms/src/normalize-and-load-metadata.ts
+++ b/packages/babel-helper-module-transforms/src/normalize-and-load-metadata.ts
@@ -482,8 +482,7 @@ function getLocalExportMetadata(
       (initializeReexports || !child.node.source)
     ) {
       if (child.node.declaration) {
-        // todo: flow->ts babel-types node field types
-        const declaration = child.get("declaration") as NodePath;
+        const declaration = child.get("declaration");
         const ids = declaration.getOuterBindingIdentifierPaths();
         Object.keys(ids).forEach(name => {
           if (name === "__esModule") {
diff --git a/packages/babel-helper-plugin-test-runner/src/index.js b/packages/babel-helper-plugin-test-runner/src/index.ts
similarity index 100%
rename from packages/babel-helper-plugin-test-runner/src/index.js
rename to packages/babel-helper-plugin-test-runner/src/index.ts
diff --git a/packages/babel-helper-plugin-utils/src/index.js b/packages/babel-helper-plugin-utils/src/index.ts
similarity index 82%
rename from packages/babel-helper-plugin-utils/src/index.js
rename to packages/babel-helper-plugin-utils/src/index.ts
index 5347c2470f..53c7caaa0f 100644
--- a/packages/babel-helper-plugin-utils/src/index.js
+++ b/packages/babel-helper-plugin-utils/src/index.ts
@@ -1,4 +1,19 @@
-export function declare(builder) {
+export function declare<
+  Args extends
+    | [any]
+    | [any, any?]
+    | [any, any?, any?]
+    | [any, any]
+    | [any, any, any?]
+    | [any, any, any],
+  Builder extends (...args: Args) => any,
+>(
+  builder: Builder,
+  // todo(flow->ts) maybe add stricter type for returned function
+  // reason any is there to not expose exact implementation details in type
+  // example of issue with this packages/babel-preset-typescript/src/index.ts
+): Builder extends (...args: infer A) => any ? (...args: A) => any : never {
+  // @ts-ignore
   return (api, options, dirname) => {
     let clonedApi;
 
@@ -10,6 +25,7 @@ export function declare(builder) {
       clonedApi[name] = apiPolyfills[name](clonedApi);
     }
 
+    // @ts-ignore
     return builder(clonedApi ?? api, options || {}, dirname);
   };
 }
@@ -101,12 +117,9 @@ function throwVersionError(range, version) {
     Error.stackTraceLimit = limit;
   }
 
-  throw Object.assign(
-    err,
-    ({
-      code: "BABEL_VERSION_UNSUPPORTED",
-      version,
-      range,
-    }: any),
-  );
+  throw Object.assign(err, {
+    code: "BABEL_VERSION_UNSUPPORTED",
+    version,
+    range,
+  } as any);
 }
diff --git a/packages/babel-helper-remap-async-to-generator/src/index.js b/packages/babel-helper-remap-async-to-generator/src/index.ts
similarity index 96%
rename from packages/babel-helper-remap-async-to-generator/src/index.js
rename to packages/babel-helper-remap-async-to-generator/src/index.ts
index 88197fdcf5..47926f221d 100644
--- a/packages/babel-helper-remap-async-to-generator/src/index.js
+++ b/packages/babel-helper-remap-async-to-generator/src/index.ts
@@ -30,8 +30,11 @@ const awaitVisitor = {
 };
 
 export default function (
-  path: NodePath,
-  helpers: { wrapAsync: Object, wrapAwait: Object },
+  path: NodePath<any>,
+  helpers: {
+    wrapAsync: any;
+    wrapAwait?: any;
+  },
   noNewArrows?: boolean,
 ) {
   path.traverse(awaitVisitor, {
diff --git a/packages/babel-helper-wrap-function/src/index.js b/packages/babel-helper-wrap-function/src/index.ts
similarity index 85%
rename from packages/babel-helper-wrap-function/src/index.js
rename to packages/babel-helper-wrap-function/src/index.ts
index eac5c924f5..2c87622567 100644
--- a/packages/babel-helper-wrap-function/src/index.js
+++ b/packages/babel-helper-wrap-function/src/index.ts
@@ -9,6 +9,7 @@ import {
   isRestElement,
   returnStatement,
 } from "@babel/types";
+import type * as t from "@babel/types";
 
 const buildAnonymousExpressionWrapper = template.expression(`
   (function () {
@@ -37,7 +38,10 @@ const buildDeclarationWrapper = template(`
   }
 `);
 
-function classOrObjectMethod(path: NodePath, callId: Object) {
+function classOrObjectMethod(
+  path: NodePath<t.ClassMethod | t.ClassPrivateMethod | t.ObjectMethod>,
+  callId: any,
+) {
   const node = path.node;
   const body = node.body;
 
@@ -57,12 +61,12 @@ function classOrObjectMethod(path: NodePath, callId: Object) {
   node.generator = false;
 
   // Unwrap the wrapper IIFE's environment so super and this and such still work.
-  path
-    .get("body.body.0.argument.callee.arguments.0")
-    .unwrapFunctionEnvironment();
+  (
+    path.get("body.body.0.argument.callee.arguments.0") as NodePath
+  ).unwrapFunctionEnvironment();
 }
 
-function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
+function plainFunction(path: NodePath<any>, callId: any, noNewArrows: boolean) {
   const node = path.node;
   const isDeclaration = path.isFunctionDeclaration();
   const functionId = node.id;
@@ -109,6 +113,7 @@ function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
     path.replaceWith(container[0]);
     path.insertAfter(container[1]);
   } else {
+    // @ts-expect-error todo(flow->ts) separate `wrapper` for `isDeclaration` and `else` branches
     const retFunction = container.callee.body.body[1].argument;
     if (!functionId) {
       nameFunction({
@@ -120,6 +125,7 @@ function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
 
     if (!retFunction || retFunction.id || node.params.length) {
       // we have an inferred function id or params so we need this wrapper
+      // @ts-expect-error todo(flow->ts) separate `wrapper` for `isDeclaration` and `else` branches
       path.replaceWith(container);
     } else {
       // we can omit this wrapper as the conditions it protects for do not apply
@@ -130,7 +136,7 @@ function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
 
 export default function wrapFunction(
   path: NodePath,
-  callId: Object,
+  callId: any,
   // TODO(Babel 8): Consider defaulting to false for spec compliancy
   noNewArrows: boolean = true,
 ) {
diff --git a/packages/babel-node/src/_babel-node.js b/packages/babel-node/src/_babel-node.ts
similarity index 94%
rename from packages/babel-node/src/_babel-node.js
rename to packages/babel-node/src/_babel-node.ts
index 7331d99943..3e2fee2b3e 100644
--- a/packages/babel-node/src/_babel-node.js
+++ b/packages/babel-node/src/_babel-node.ts
@@ -67,6 +67,7 @@ program.option(
 program.option("-w, --plugins [string]", "", collect);
 program.option("-b, --presets [string]", "", collect);
 
+declare const PACKAGE_JSON: { name: string; version: string };
 program.version(PACKAGE_JSON.version);
 program.usage("[options] [ -e script | script.js ] [arguments]");
 program.parse(process.argv);
@@ -144,17 +145,26 @@ if (program.eval || program.print) {
   let code = program.eval;
   if (!code || code === true) code = program.print;
 
+  // @ts-expect-error todo(flow->ts)
   global.__filename = "[eval]";
+  // @ts-expect-error todo(flow->ts)
   global.__dirname = process.cwd();
 
+  // @ts-expect-error todo(flow->ts)
   const module = new Module(global.__filename);
+  // @ts-expect-error todo(flow->ts)
   module.filename = global.__filename;
+  // @ts-expect-error todo(flow->ts)
   module.paths = Module._nodeModulePaths(global.__dirname);
 
+  // @ts-expect-error todo(flow->ts)
   global.exports = module.exports;
+  // @ts-expect-error todo(flow->ts)
   global.module = module;
+  // @ts-expect-error todo(flow->ts)
   global.require = module.require.bind(module);
 
+  // @ts-expect-error todo(flow->ts)
   const result = _eval(code, global.__filename);
   if (program.print) {
     const output = typeof result === "string" ? result : inspect(result);
diff --git a/packages/babel-node/src/babel-node.js b/packages/babel-node/src/babel-node.ts
similarity index 100%
rename from packages/babel-node/src/babel-node.js
rename to packages/babel-node/src/babel-node.ts
diff --git a/packages/babel-plugin-external-helpers/src/index.js b/packages/babel-plugin-external-helpers/src/index.ts
similarity index 100%
rename from packages/babel-plugin-external-helpers/src/index.js
rename to packages/babel-plugin-external-helpers/src/index.ts
diff --git a/packages/babel-plugin-proposal-async-generator-functions/src/for-await.js b/packages/babel-plugin-proposal-async-generator-functions/src/for-await.ts
similarity index 96%
rename from packages/babel-plugin-proposal-async-generator-functions/src/for-await.js
rename to packages/babel-plugin-proposal-async-generator-functions/src/for-await.ts
index 16f08dca15..163eb5f6f3 100644
--- a/packages/babel-plugin-proposal-async-generator-functions/src/for-await.js
+++ b/packages/babel-plugin-proposal-async-generator-functions/src/for-await.ts
@@ -61,6 +61,7 @@ export default function (path, { getAsyncIterator }) {
   });
 
   // remove async function wrapper
+  // @ts-expect-error todo(flow->ts) improve type annotation for buildForAwait
   template = template.body.body;
 
   const isLabeledParent = t.isLabeledStatement(parent);
diff --git a/packages/babel-plugin-proposal-async-generator-functions/src/index.js b/packages/babel-plugin-proposal-async-generator-functions/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-async-generator-functions/src/index.js
rename to packages/babel-plugin-proposal-async-generator-functions/src/index.ts
diff --git a/packages/babel-plugin-proposal-class-properties/src/index.js b/packages/babel-plugin-proposal-class-properties/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-class-properties/src/index.js
rename to packages/babel-plugin-proposal-class-properties/src/index.ts
diff --git a/packages/babel-plugin-proposal-class-static-block/package.json b/packages/babel-plugin-proposal-class-static-block/package.json
index 51be46c443..cf678a74cb 100644
--- a/packages/babel-plugin-proposal-class-static-block/package.json
+++ b/packages/babel-plugin-proposal-class-static-block/package.json
@@ -28,7 +28,9 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^",
+    "@babel/types": "workspace:^"
   },
   "homepage": "https://babel.dev/docs/en/next/babel-plugin-proposal-class-static-block",
   "engines": {
diff --git a/packages/babel-plugin-proposal-class-static-block/src/index.js b/packages/babel-plugin-proposal-class-static-block/src/index.ts
similarity index 83%
rename from packages/babel-plugin-proposal-class-static-block/src/index.js
rename to packages/babel-plugin-proposal-class-static-block/src/index.ts
index 5bc560fc77..ff43aa8cf5 100644
--- a/packages/babel-plugin-proposal-class-static-block/src/index.js
+++ b/packages/babel-plugin-proposal-class-static-block/src/index.ts
@@ -6,11 +6,13 @@ import {
   FEATURES,
 } from "@babel/helper-create-class-features-plugin";
 
+import type * as t from "@babel/types";
+import type { NodePath } from "@babel/traverse";
 /**
  * Generate a uid that is not in `denyList`
  *
  * @param {*} scope
- * @param {Set<string>} a deny list that the generated uid should avoid
+ * @param {Set<string>} denyList a deny list that the generated uid should avoid
  * @returns
  */
 function generateUid(scope, denyList: Set<string>) {
@@ -41,9 +43,9 @@ export default declare(({ types: t, template, assertVersion }) => {
       // Run on ClassBody and not on class so that if @babel/helper-create-class-features-plugin
       // is enabled it can generte optimized output without passing from the intermediate
       // private fields representation.
-      ClassBody(classBody: NodePath<Class>) {
+      ClassBody(classBody: NodePath<t.ClassBody>) {
         const { scope } = classBody;
-        const privateNames = new Set();
+        const privateNames = new Set<string>();
         const body = classBody.get("body");
         for (const path of body) {
           if (path.isPrivate()) {
@@ -60,7 +62,9 @@ export default declare(({ types: t, template, assertVersion }) => {
           path.replaceWith(
             t.classPrivateProperty(
               staticBlockRef,
-              template.expression.ast`(() => { ${path.node.body} })()`,
+              template.expression.ast`(() => { ${
+                (path.node as t.StaticBlock).body
+              } })()`,
               [],
               /* static */ true,
             ),
diff --git a/packages/babel-plugin-proposal-decorators/package.json b/packages/babel-plugin-proposal-decorators/package.json
index fea778a988..2173a299e3 100644
--- a/packages/babel-plugin-proposal-decorators/package.json
+++ b/packages/babel-plugin-proposal-decorators/package.json
@@ -30,6 +30,7 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^",
     "babel-plugin-polyfill-es-shims": "^0.6.0",
     "object.getownpropertydescriptors": "^2.1.1"
   },
diff --git a/packages/babel-plugin-proposal-decorators/src/index.js b/packages/babel-plugin-proposal-decorators/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-decorators/src/index.js
rename to packages/babel-plugin-proposal-decorators/src/index.ts
diff --git a/packages/babel-plugin-proposal-decorators/src/transformer-legacy.js b/packages/babel-plugin-proposal-decorators/src/transformer-legacy.ts
similarity index 90%
rename from packages/babel-plugin-proposal-decorators/src/transformer-legacy.js
rename to packages/babel-plugin-proposal-decorators/src/transformer-legacy.ts
index 5b8dd8d202..ca16608bbb 100644
--- a/packages/babel-plugin-proposal-decorators/src/transformer-legacy.js
+++ b/packages/babel-plugin-proposal-decorators/src/transformer-legacy.ts
@@ -1,18 +1,19 @@
 // Fork of https://github.com/loganfsmyth/babel-plugin-proposal-decorators-legacy
 
 import { template, types as t } from "@babel/core";
+import type { Visitor } from "@babel/traverse";
 
 const buildClassDecorator = template(`
   DECORATOR(CLASS_REF = INNER) || CLASS_REF;
-`);
+`) as (replacements: { DECORATOR; CLASS_REF; INNER }) => t.ExpressionStatement;
 
 const buildClassPrototype = template(`
   CLASS_REF.prototype;
-`);
+`) as (replacements: { CLASS_REF }) => t.ExpressionStatement;
 
 const buildGetDescriptor = template(`
     Object.getOwnPropertyDescriptor(TARGET, PROPERTY);
-`);
+`) as (replacements: { TARGET; PROPERTY }) => t.ExpressionStatement;
 
 const buildGetObjectInitializer = template(`
     (TEMP = Object.getOwnPropertyDescriptor(TARGET, PROPERTY), (TEMP = TEMP ? TEMP.value : undefined), {
@@ -23,7 +24,7 @@ const buildGetObjectInitializer = template(`
             return TEMP;
         }
     })
-`);
+`) as (replacements: { TEMP; TARGET; PROPERTY }) => t.ExpressionStatement;
 
 const WARNING_CALLS = new WeakSet();
 
@@ -241,6 +242,7 @@ export default {
         replacement,
         t.exportNamedDeclaration(null, [
           t.exportSpecifier(
+            // @ts-expect-error todo(flow->ts) might be add more specific return type for decoratedClassToExpression
             t.cloneNode(replacement.declarations[0].id),
             t.identifier("default"),
           ),
@@ -263,7 +265,7 @@ export default {
     // class decorators, and a second pass to process method decorators.
     const decoratedClass =
       applyEnsureOrdering(path) ||
-      applyClassDecorators(path, state) ||
+      applyClassDecorators(path) ||
       applyMethodDecorators(path, state);
 
     if (decoratedClass) path.replaceWith(decoratedClass);
@@ -280,12 +282,17 @@ export default {
 
     path.replaceWith(
       t.callExpression(state.addHelper("initializerDefineProperty"), [
+        // @ts-expect-error todo(flow->ts) typesafe NodePath.get
         t.cloneNode(path.get("left.object").node),
         t.stringLiteral(
+          // @ts-expect-error todo(flow->ts) typesafe NodePath.get
           path.get("left.property").node.name ||
+            // @ts-expect-error todo(flow->ts) typesafe NodePath.get
             path.get("left.property").node.value,
         ),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("right.arguments")[0].node),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("right.arguments")[1].node),
       ]),
     );
@@ -297,6 +304,7 @@ export default {
 
     // If the class properties plugin isn't enabled, this line will add an unused helper
     // to the code. It's not ideal, but it's ok since the configuration is not valid anyway.
+    // @ts-expect-error todo(flow->ts) check that `callee` is Identifier
     if (path.node.callee.name !== state.addHelper("defineProperty").name) {
       return;
     }
@@ -305,9 +313,11 @@ export default {
       t.callExpression(state.addHelper("initializerDefineProperty"), [
         t.cloneNode(path.get("arguments")[0].node),
         t.cloneNode(path.get("arguments")[1].node),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("arguments.2.arguments")[0].node),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("arguments.2.arguments")[1].node),
       ]),
     );
   },
-};
+} as Visitor<any>;
diff --git a/packages/babel-plugin-proposal-do-expressions/src/index.js b/packages/babel-plugin-proposal-do-expressions/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-do-expressions/src/index.js
rename to packages/babel-plugin-proposal-do-expressions/src/index.ts
diff --git a/packages/babel-plugin-proposal-dynamic-import/src/index.js b/packages/babel-plugin-proposal-dynamic-import/src/index.ts
similarity index 94%
rename from packages/babel-plugin-proposal-dynamic-import/src/index.js
rename to packages/babel-plugin-proposal-dynamic-import/src/index.ts
index a9f9285fa8..2a499d1bfe 100644
--- a/packages/babel-plugin-proposal-dynamic-import/src/index.js
+++ b/packages/babel-plugin-proposal-dynamic-import/src/index.ts
@@ -16,6 +16,8 @@ the @babel/plugin-syntax-dynamic-import plugin and let your
 bundler handle dynamic imports.
 `;
 
+declare const PACKAGE_JSON: { name: string; version: string };
+
 export default declare(api => {
   api.assertVersion(7);
 
diff --git a/packages/babel-plugin-proposal-export-default-from/src/index.js b/packages/babel-plugin-proposal-export-default-from/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-export-default-from/src/index.js
rename to packages/babel-plugin-proposal-export-default-from/src/index.ts
diff --git a/packages/babel-plugin-proposal-export-namespace-from/src/index.js b/packages/babel-plugin-proposal-export-namespace-from/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-export-namespace-from/src/index.js
rename to packages/babel-plugin-proposal-export-namespace-from/src/index.ts
diff --git a/packages/babel-plugin-proposal-function-bind/src/index.js b/packages/babel-plugin-proposal-function-bind/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-function-bind/src/index.js
rename to packages/babel-plugin-proposal-function-bind/src/index.ts
diff --git a/packages/babel-plugin-proposal-function-sent/src/index.js b/packages/babel-plugin-proposal-function-sent/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-function-sent/src/index.js
rename to packages/babel-plugin-proposal-function-sent/src/index.ts
diff --git a/packages/babel-plugin-proposal-json-strings/src/index.js b/packages/babel-plugin-proposal-json-strings/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-json-strings/src/index.js
rename to packages/babel-plugin-proposal-json-strings/src/index.ts
diff --git a/packages/babel-plugin-proposal-logical-assignment-operators/src/index.js b/packages/babel-plugin-proposal-logical-assignment-operators/src/index.ts
similarity index 94%
rename from packages/babel-plugin-proposal-logical-assignment-operators/src/index.js
rename to packages/babel-plugin-proposal-logical-assignment-operators/src/index.ts
index dd5ea53681..da1eeaea35 100644
--- a/packages/babel-plugin-proposal-logical-assignment-operators/src/index.js
+++ b/packages/babel-plugin-proposal-logical-assignment-operators/src/index.ts
@@ -34,6 +34,7 @@ export default declare(api => {
               lhs.property = t.assignmentExpression(
                 "=",
                 t.cloneNode(memo),
+                // @ts-expect-error todo(flow->ts): property can be t.PrivateName
                 property,
               );
             }
diff --git a/packages/babel-plugin-proposal-nullish-coalescing-operator/src/index.js b/packages/babel-plugin-proposal-nullish-coalescing-operator/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-nullish-coalescing-operator/src/index.js
rename to packages/babel-plugin-proposal-nullish-coalescing-operator/src/index.ts
diff --git a/packages/babel-plugin-proposal-numeric-separator/package.json b/packages/babel-plugin-proposal-numeric-separator/package.json
index cf3c955843..3a74a449fb 100644
--- a/packages/babel-plugin-proposal-numeric-separator/package.json
+++ b/packages/babel-plugin-proposal-numeric-separator/package.json
@@ -25,7 +25,9 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^",
+    "@babel/types": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"
diff --git a/packages/babel-plugin-proposal-numeric-separator/src/index.js b/packages/babel-plugin-proposal-numeric-separator/src/index.ts
similarity index 74%
rename from packages/babel-plugin-proposal-numeric-separator/src/index.js
rename to packages/babel-plugin-proposal-numeric-separator/src/index.ts
index 3fc6c4a405..dfa9943255 100644
--- a/packages/babel-plugin-proposal-numeric-separator/src/index.js
+++ b/packages/babel-plugin-proposal-numeric-separator/src/index.ts
@@ -1,5 +1,7 @@
 import { declare } from "@babel/helper-plugin-utils";
 import syntaxNumericSeparator from "@babel/plugin-syntax-numeric-separator";
+import type { NodePath } from "@babel/traverse";
+import type * as t from "@babel/types";
 
 /**
  * Given a bigIntLiteral or NumericLiteral, remove numeric
@@ -7,9 +9,11 @@ import syntaxNumericSeparator from "@babel/plugin-syntax-numeric-separator";
  *
  * @param {NodePath<BigIntLiteral | NumericLiteral>} { node }: A Babel AST node path
  */
-function remover({ node }: NodePath<BigIntLiteral | NumericLiteral>) {
+function remover({ node }: NodePath<t.BigIntLiteral | t.NumericLiteral>) {
   const { extra } = node;
+  // @ts-expect-error todo(flow->ts)
   if (extra?.raw?.includes("_")) {
+    // @ts-expect-error todo(flow->ts)
     extra.raw = extra.raw.replace(/_/g, "");
   }
 }
diff --git a/packages/babel-plugin-proposal-optional-catch-binding/src/index.js b/packages/babel-plugin-proposal-optional-catch-binding/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-optional-catch-binding/src/index.js
rename to packages/babel-plugin-proposal-optional-catch-binding/src/index.ts
diff --git a/packages/babel-plugin-proposal-optional-chaining/package.json b/packages/babel-plugin-proposal-optional-chaining/package.json
index 570f7a8ef2..2498966ec0 100644
--- a/packages/babel-plugin-proposal-optional-chaining/package.json
+++ b/packages/babel-plugin-proposal-optional-chaining/package.json
@@ -27,7 +27,8 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/helper-plugin-test-runner": "workspace:^",
-    "@babel/plugin-transform-block-scoping": "workspace:^"
+    "@babel/plugin-transform-block-scoping": "workspace:^",
+    "@babel/traverse": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"
diff --git a/packages/babel-plugin-proposal-optional-chaining/src/index.js b/packages/babel-plugin-proposal-optional-chaining/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-optional-chaining/src/index.js
rename to packages/babel-plugin-proposal-optional-chaining/src/index.ts
diff --git a/packages/babel-plugin-proposal-optional-chaining/src/transform.js b/packages/babel-plugin-proposal-optional-chaining/src/transform.ts
similarity index 92%
rename from packages/babel-plugin-proposal-optional-chaining/src/transform.js
rename to packages/babel-plugin-proposal-optional-chaining/src/transform.ts
index 05ae81bdb4..5ba92765f1 100644
--- a/packages/babel-plugin-proposal-optional-chaining/src/transform.js
+++ b/packages/babel-plugin-proposal-optional-chaining/src/transform.ts
@@ -1,4 +1,5 @@
 import { types as t, template } from "@babel/core";
+import type { NodePath } from "@babel/traverse";
 import {
   skipTransparentExprWrapperNodes,
   skipTransparentExprWrappers,
@@ -48,7 +49,7 @@ export function transform(
   {
     pureGetters,
     noDocumentAll,
-  }: { pureGetters: boolean, noDocumentAll: boolean },
+  }: { pureGetters: boolean; noDocumentAll: boolean },
 ) {
   const { scope } = path;
   // maybeWrapped points to the outermost transparent expression wrapper
@@ -69,7 +70,7 @@ export function transform(
   // Replace `function (a, x = a.b?.c) {}` to `function (a, x = (() => a.b?.c)() ){}`
   // so the temporary variable can be injected in correct scope
   if (scope.path.isPattern() && needsMemoize(optionalPath)) {
-    path.replaceWith(template.ast`(() => ${path.node})()`);
+    path.replaceWith(template.ast`(() => ${path.node})()` as t.Statement);
     // The injected optional chain will be queued and eventually transformed when visited
     return;
   }
@@ -83,15 +84,19 @@ export function transform(
     }
 
     if (optionalPath.isOptionalMemberExpression()) {
+      // @ts-expect-error todo(flow->ts) avoid changing more type
       optionalPath.node.type = "MemberExpression";
+      // @ts-expect-error todo(flow->ts)
       optionalPath = skipTransparentExprWrappers(optionalPath.get("object"));
     } else if (optionalPath.isOptionalCallExpression()) {
+      // @ts-expect-error todo(flow->ts) avoid changing more type
       optionalPath.node.type = "CallExpression";
+      // @ts-expect-error todo(flow->ts)
       optionalPath = skipTransparentExprWrappers(optionalPath.get("callee"));
     }
   }
 
-  let replacementPath = path;
+  let replacementPath: NodePath<any> = path;
   if (parentPath.isUnaryExpression({ operator: "delete" })) {
     replacementPath = parentPath;
     isDeleteOperation = true;
@@ -145,7 +150,7 @@ export function transform(
         // Otherwise, we need to memoize the context object, and change the call into a Function#call.
         // `a.?b.?()` translates roughly to `(_b = _a.b) != null && _b.call(_a)`
         const { object } = chain;
-        let context = scope.maybeGenerateMemoised(object);
+        let context: t.Expression = scope.maybeGenerateMemoised(object);
         if (context) {
           chain.object = t.assignmentExpression("=", context, object);
         } else if (t.isSuper(object)) {
@@ -194,6 +199,7 @@ export function transform(
         t.logicalExpression("&&", nonNullishCheck, replacement),
       );
       replacementPath = skipTransparentExprWrappers(
+        // @ts-expect-error todo(flow->ts)
         replacementPath.get("right"),
       );
     } else {
@@ -207,6 +213,7 @@ export function transform(
         t.conditionalExpression(nullishCheck, returnValue, replacement),
       );
       replacementPath = skipTransparentExprWrappers(
+        // @ts-expect-error todo(flow->ts)
         replacementPath.get("alternate"),
       );
     }
diff --git a/packages/babel-plugin-proposal-optional-chaining/src/util.js b/packages/babel-plugin-proposal-optional-chaining/src/util.ts
similarity index 95%
rename from packages/babel-plugin-proposal-optional-chaining/src/util.js
rename to packages/babel-plugin-proposal-optional-chaining/src/util.ts
index 7f98ccb2fc..4bb72bc55b 100644
--- a/packages/babel-plugin-proposal-optional-chaining/src/util.js
+++ b/packages/babel-plugin-proposal-optional-chaining/src/util.ts
@@ -1,3 +1,4 @@
+import type { NodePath } from "@babel/traverse";
 import { isTransparentExprWrapper } from "@babel/helper-skip-transparent-expression-wrappers";
 /**
  * Test if a NodePath will be cast to boolean when evaluated.
@@ -58,7 +59,7 @@ export function willPathCastToBoolean(path: NodePath): boolean {
 export function findOutermostTransparentParent(path: NodePath): NodePath {
   let maybeWrapped = path;
   path.findParent(p => {
-    if (!isTransparentExprWrapper(p)) return true;
+    if (!isTransparentExprWrapper(p.node)) return true;
     maybeWrapped = p;
   });
   return maybeWrapped;
diff --git a/packages/babel-plugin-proposal-partial-application/src/index.js b/packages/babel-plugin-proposal-partial-application/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-partial-application/src/index.js
rename to packages/babel-plugin-proposal-partial-application/src/index.ts
diff --git a/packages/babel-plugin-proposal-pipeline-operator/src/buildOptimizedSequenceExpression.js b/packages/babel-plugin-proposal-pipeline-operator/src/buildOptimizedSequenceExpression.ts
similarity index 100%
rename from packages/babel-plugin-proposal-pipeline-operator/src/buildOptimizedSequenceExpression.js
rename to packages/babel-plugin-proposal-pipeline-operator/src/buildOptimizedSequenceExpression.ts
diff --git a/packages/babel-plugin-proposal-pipeline-operator/src/fsharpVisitor.js b/packages/babel-plugin-proposal-pipeline-operator/src/fsharpVisitor.ts
similarity index 100%
rename from packages/babel-plugin-proposal-pipeline-operator/src/fsharpVisitor.js
rename to packages/babel-plugin-proposal-pipeline-operator/src/fsharpVisitor.ts
diff --git a/packages/babel-plugin-proposal-pipeline-operator/src/hackVisitor.js b/packages/babel-plugin-proposal-pipeline-operator/src/hackVisitor.ts
similarity index 100%
rename from packages/babel-plugin-proposal-pipeline-operator/src/hackVisitor.js
rename to packages/babel-plugin-proposal-pipeline-operator/src/hackVisitor.ts
diff --git a/packages/babel-plugin-proposal-pipeline-operator/src/index.js b/packages/babel-plugin-proposal-pipeline-operator/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-pipeline-operator/src/index.js
rename to packages/babel-plugin-proposal-pipeline-operator/src/index.ts
diff --git a/packages/babel-plugin-proposal-pipeline-operator/src/minimalVisitor.js b/packages/babel-plugin-proposal-pipeline-operator/src/minimalVisitor.ts
similarity index 100%
rename from packages/babel-plugin-proposal-pipeline-operator/src/minimalVisitor.js
rename to packages/babel-plugin-proposal-pipeline-operator/src/minimalVisitor.ts
diff --git a/packages/babel-plugin-proposal-pipeline-operator/src/smartVisitor.js b/packages/babel-plugin-proposal-pipeline-operator/src/smartVisitor.ts
similarity index 100%
rename from packages/babel-plugin-proposal-pipeline-operator/src/smartVisitor.js
rename to packages/babel-plugin-proposal-pipeline-operator/src/smartVisitor.ts
diff --git a/packages/babel-plugin-proposal-private-methods/src/index.js b/packages/babel-plugin-proposal-private-methods/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-private-methods/src/index.js
rename to packages/babel-plugin-proposal-private-methods/src/index.ts
diff --git a/packages/babel-plugin-proposal-private-property-in-object/src/index.js b/packages/babel-plugin-proposal-private-property-in-object/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-private-property-in-object/src/index.js
rename to packages/babel-plugin-proposal-private-property-in-object/src/index.ts
diff --git a/packages/babel-plugin-proposal-record-and-tuple/src/index.js b/packages/babel-plugin-proposal-record-and-tuple/src/index.ts
similarity index 97%
rename from packages/babel-plugin-proposal-record-and-tuple/src/index.js
rename to packages/babel-plugin-proposal-record-and-tuple/src/index.ts
index 0a63de2e31..ac57361166 100644
--- a/packages/babel-plugin-proposal-record-and-tuple/src/index.js
+++ b/packages/babel-plugin-proposal-record-and-tuple/src/index.ts
@@ -20,6 +20,7 @@ import { types as t } from "@babel/core";
 import { addNamed, isModule } from "@babel/helper-module-imports";
 import { OptionValidator } from "@babel/helper-validator-option";
 
+declare const PACKAGE_JSON: { name: string; version: string };
 const v = new OptionValidator(PACKAGE_JSON.name);
 
 export default declare((api, options) => {
diff --git a/packages/babel-plugin-proposal-throw-expressions/src/index.js b/packages/babel-plugin-proposal-throw-expressions/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-throw-expressions/src/index.js
rename to packages/babel-plugin-proposal-throw-expressions/src/index.ts
diff --git a/packages/babel-plugin-proposal-unicode-property-regex/src/index.js b/packages/babel-plugin-proposal-unicode-property-regex/src/index.ts
similarity index 100%
rename from packages/babel-plugin-proposal-unicode-property-regex/src/index.js
rename to packages/babel-plugin-proposal-unicode-property-regex/src/index.ts
diff --git a/packages/babel-plugin-syntax-decimal/src/index.js b/packages/babel-plugin-syntax-decimal/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-decimal/src/index.js
rename to packages/babel-plugin-syntax-decimal/src/index.ts
diff --git a/packages/babel-plugin-syntax-decorators/src/index.js b/packages/babel-plugin-syntax-decorators/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-decorators/src/index.js
rename to packages/babel-plugin-syntax-decorators/src/index.ts
diff --git a/packages/babel-plugin-syntax-do-expressions/src/index.js b/packages/babel-plugin-syntax-do-expressions/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-do-expressions/src/index.js
rename to packages/babel-plugin-syntax-do-expressions/src/index.ts
diff --git a/packages/babel-plugin-syntax-export-default-from/src/index.js b/packages/babel-plugin-syntax-export-default-from/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-export-default-from/src/index.js
rename to packages/babel-plugin-syntax-export-default-from/src/index.ts
diff --git a/packages/babel-plugin-syntax-flow/src/index.js b/packages/babel-plugin-syntax-flow/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-flow/src/index.js
rename to packages/babel-plugin-syntax-flow/src/index.ts
diff --git a/packages/babel-plugin-syntax-function-bind/src/index.js b/packages/babel-plugin-syntax-function-bind/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-function-bind/src/index.js
rename to packages/babel-plugin-syntax-function-bind/src/index.ts
diff --git a/packages/babel-plugin-syntax-function-sent/src/index.js b/packages/babel-plugin-syntax-function-sent/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-function-sent/src/index.js
rename to packages/babel-plugin-syntax-function-sent/src/index.ts
diff --git a/packages/babel-plugin-syntax-import-assertions/src/index.js b/packages/babel-plugin-syntax-import-assertions/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-import-assertions/src/index.js
rename to packages/babel-plugin-syntax-import-assertions/src/index.ts
diff --git a/packages/babel-plugin-syntax-jsx/src/index.js b/packages/babel-plugin-syntax-jsx/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-jsx/src/index.js
rename to packages/babel-plugin-syntax-jsx/src/index.ts
diff --git a/packages/babel-plugin-syntax-module-blocks/src/index.js b/packages/babel-plugin-syntax-module-blocks/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-module-blocks/src/index.js
rename to packages/babel-plugin-syntax-module-blocks/src/index.ts
diff --git a/packages/babel-plugin-syntax-partial-application/src/index.js b/packages/babel-plugin-syntax-partial-application/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-partial-application/src/index.js
rename to packages/babel-plugin-syntax-partial-application/src/index.ts
diff --git a/packages/babel-plugin-syntax-pipeline-operator/src/index.js b/packages/babel-plugin-syntax-pipeline-operator/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-pipeline-operator/src/index.js
rename to packages/babel-plugin-syntax-pipeline-operator/src/index.ts
diff --git a/packages/babel-plugin-syntax-record-and-tuple/src/index.js b/packages/babel-plugin-syntax-record-and-tuple/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-record-and-tuple/src/index.js
rename to packages/babel-plugin-syntax-record-and-tuple/src/index.ts
diff --git a/packages/babel-plugin-syntax-throw-expressions/src/index.js b/packages/babel-plugin-syntax-throw-expressions/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-throw-expressions/src/index.js
rename to packages/babel-plugin-syntax-throw-expressions/src/index.ts
diff --git a/packages/babel-plugin-syntax-typescript/src/index.js b/packages/babel-plugin-syntax-typescript/src/index.ts
similarity index 100%
rename from packages/babel-plugin-syntax-typescript/src/index.js
rename to packages/babel-plugin-syntax-typescript/src/index.ts
diff --git a/packages/babel-plugin-transform-arrow-functions/package.json b/packages/babel-plugin-transform-arrow-functions/package.json
index a2d74f1c89..f760580a42 100644
--- a/packages/babel-plugin-transform-arrow-functions/package.json
+++ b/packages/babel-plugin-transform-arrow-functions/package.json
@@ -25,7 +25,8 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/helper-plugin-test-runner": "workspace:^",
-    "@babel/traverse": "workspace:^"
+    "@babel/traverse": "workspace:^",
+    "@babel/types": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"
diff --git a/packages/babel-plugin-transform-arrow-functions/src/index.js b/packages/babel-plugin-transform-arrow-functions/src/index.ts
similarity index 84%
rename from packages/babel-plugin-transform-arrow-functions/src/index.js
rename to packages/babel-plugin-transform-arrow-functions/src/index.ts
index 98ac9f4d62..4138442337 100644
--- a/packages/babel-plugin-transform-arrow-functions/src/index.js
+++ b/packages/babel-plugin-transform-arrow-functions/src/index.ts
@@ -1,5 +1,6 @@
 import { declare } from "@babel/helper-plugin-utils";
-import type NodePath from "@babel/traverse";
+import type { NodePath } from "@babel/traverse";
+import type * as t from "@babel/types";
 
 export default declare((api, options) => {
   api.assertVersion(7);
@@ -10,9 +11,7 @@ export default declare((api, options) => {
     name: "transform-arrow-functions",
 
     visitor: {
-      ArrowFunctionExpression(
-        path: NodePath<BabelNodeArrowFunctionExpression>,
-      ) {
+      ArrowFunctionExpression(path: NodePath<t.ArrowFunctionExpression>) {
         // In some conversion cases, it may have already been converted to a function while this callback
         // was queued up.
         if (!path.isArrowFunctionExpression()) return;
diff --git a/packages/babel-plugin-transform-async-to-generator/src/index.js b/packages/babel-plugin-transform-async-to-generator/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-async-to-generator/src/index.js
rename to packages/babel-plugin-transform-async-to-generator/src/index.ts
diff --git a/packages/babel-plugin-transform-block-scoped-functions/src/index.js b/packages/babel-plugin-transform-block-scoped-functions/src/index.ts
similarity index 91%
rename from packages/babel-plugin-transform-block-scoped-functions/src/index.js
rename to packages/babel-plugin-transform-block-scoped-functions/src/index.ts
index 79b9b27e2b..1e39245223 100644
--- a/packages/babel-plugin-transform-block-scoped-functions/src/index.js
+++ b/packages/babel-plugin-transform-block-scoped-functions/src/index.ts
@@ -5,7 +5,7 @@ export default declare(api => {
   api.assertVersion(7);
 
   function statementList(key, path) {
-    const paths: Array = path.get(key);
+    const paths = path.get(key);
 
     for (const path of paths) {
       const func = path.node;
@@ -16,6 +16,7 @@ export default declare(api => {
       ]);
 
       // hoist it up above everything else
+      // @ts-expect-error todo(flow->ts): avoid mutations
       declar._blockHoist = 2;
 
       // todo: name this
diff --git a/packages/babel-plugin-transform-block-scoping/src/index.ts b/packages/babel-plugin-transform-block-scoping/src/index.ts
index f3ffbef6d0..a57ad115c1 100644
--- a/packages/babel-plugin-transform-block-scoping/src/index.ts
+++ b/packages/babel-plugin-transform-block-scoping/src/index.ts
@@ -920,7 +920,7 @@ class BlockScoping {
    * later on.
    */
 
-  checkLoop(): any {
+  checkLoop() {
     const state: LoopVisitorState = {
       hasBreakContinue: false,
       ignoreLabeless: false,
diff --git a/packages/babel-plugin-transform-computed-properties/src/index.js b/packages/babel-plugin-transform-computed-properties/src/index.ts
similarity index 94%
rename from packages/babel-plugin-transform-computed-properties/src/index.js
rename to packages/babel-plugin-transform-computed-properties/src/index.ts
index 9fa5c5c964..e523cd5e88 100644
--- a/packages/babel-plugin-transform-computed-properties/src/index.js
+++ b/packages/babel-plugin-transform-computed-properties/src/index.ts
@@ -32,7 +32,7 @@ export default declare((api, options) => {
 
   function pushAssign(objId, prop, body) {
     if (prop.kind === "get" && prop.kind === "set") {
-      pushMutatorDefine(objId, prop, body);
+      pushMutatorDefine(objId, prop);
     } else {
       body.push(
         t.expressionStatement(
@@ -43,6 +43,7 @@ export default declare((api, options) => {
               prop.key,
               prop.computed || t.isLiteral(prop.key),
             ),
+            // @ts-expect-error todo(flow->ts): double-check type error
             getValue(prop),
           ),
         ),
@@ -65,12 +66,12 @@ export default declare((api, options) => {
     }
 
     body.push(
-      ...buildMutatorMapAssign({
+      ...(buildMutatorMapAssign({
         MUTATOR_MAP_REF: getMutatorId(),
         KEY: t.cloneNode(key),
         VALUE: getValue(prop),
         KIND: t.identifier(prop.kind),
-      }),
+      }) as t.Statement[]),
     );
   }
 
@@ -122,7 +123,7 @@ export default declare((api, options) => {
         exit(path, state) {
           const { node, parent, scope } = path;
           let hasComputed = false;
-          for (const prop of (node.properties: Array<Object>)) {
+          for (const prop of node.properties) {
             hasComputed = prop.computed === true;
             if (hasComputed) break;
           }
@@ -194,6 +195,7 @@ export default declare((api, options) => {
             );
           }
 
+          // @ts-expect-error todo(flow->ts) `void` should not be used as variable
           if (single) {
             path.replaceWith(single);
           } else {
diff --git a/packages/babel-plugin-transform-destructuring/package.json b/packages/babel-plugin-transform-destructuring/package.json
index 9c3b9a5f74..531df29ad6 100644
--- a/packages/babel-plugin-transform-destructuring/package.json
+++ b/packages/babel-plugin-transform-destructuring/package.json
@@ -24,7 +24,8 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"
diff --git a/packages/babel-plugin-transform-destructuring/src/index.js b/packages/babel-plugin-transform-destructuring/src/index.ts
similarity index 96%
rename from packages/babel-plugin-transform-destructuring/src/index.js
rename to packages/babel-plugin-transform-destructuring/src/index.ts
index 7af938dbeb..959e8fbf2e 100644
--- a/packages/babel-plugin-transform-destructuring/src/index.js
+++ b/packages/babel-plugin-transform-destructuring/src/index.ts
@@ -1,5 +1,6 @@
 import { declare } from "@babel/helper-plugin-utils";
 import { types as t } from "@babel/core";
+import type { Scope } from "@babel/traverse";
 
 export default declare((api, options) => {
   api.assertVersion(7);
@@ -23,7 +24,7 @@ export default declare((api, options) => {
    */
 
   function variableDeclarationHasPattern(node) {
-    for (const declar of (node.declarations: Array)) {
+    for (const declar of node.declarations) {
       if (t.isPattern(declar.id)) {
         return true;
       }
@@ -36,7 +37,7 @@ export default declare((api, options) => {
    */
 
   function hasRest(pattern) {
-    for (const elem of (pattern.elements: Array)) {
+    for (const elem of pattern.elements) {
       if (t.isRestElement(elem)) {
         return true;
       }
@@ -49,7 +50,7 @@ export default declare((api, options) => {
    */
 
   function hasObjectRest(pattern) {
-    for (const elem of (pattern.properties: Array)) {
+    for (const elem of pattern.properties) {
       if (t.isRestElement(elem)) {
         return true;
       }
@@ -77,6 +78,15 @@ export default declare((api, options) => {
   };
 
   class DestructuringTransformer {
+    private blockHoist: any;
+    private operator: any;
+    arrays: any;
+    private nodes: any;
+    private scope: Scope;
+    private kind: any;
+    private iterableIsArray: any;
+    private arrayLikeIsIterable: any;
+    private addHelper: any;
     constructor(opts) {
       this.blockHoist = opts.blockHoist;
       this.operator = opts.operator;
@@ -118,6 +128,7 @@ export default declare((api, options) => {
       const declar = t.variableDeclaration("var", [
         t.variableDeclarator(t.cloneNode(id), t.cloneNode(init)),
       ]);
+      // @ts-expect-error todo(flow->ts): avoid mutations
       declar._blockHoist = this.blockHoist;
       return declar;
     }
@@ -135,7 +146,7 @@ export default declare((api, options) => {
       }
     }
 
-    toArray(node, count) {
+    toArray(node, count?) {
       if (
         this.iterableIsArray ||
         (t.isIdentifier(node) && this.arrays[node.name])
@@ -208,6 +219,7 @@ export default declare((api, options) => {
           keys.push(t.cloneNode(key));
           hasTemplateLiteral = true;
         } else if (t.isLiteral(key)) {
+          // @ts-expect-error todo(flow->ts) NullLiteral
           keys.push(t.stringLiteral(String(key.value)));
         } else {
           keys.push(t.cloneNode(key));
@@ -222,7 +234,7 @@ export default declare((api, options) => {
           t.cloneNode(objRef),
         ]);
       } else {
-        let keyExpression = t.arrayExpression(keys);
+        let keyExpression: t.Expression = t.arrayExpression(keys);
 
         if (!allLiteral) {
           keyExpression = t.callExpression(
@@ -342,7 +354,7 @@ export default declare((api, options) => {
         return false;
       }
 
-      for (const elem of (pattern.elements: Array)) {
+      for (const elem of pattern.elements) {
         // deopt on holes
         if (!elem) return false;
 
@@ -350,7 +362,7 @@ export default declare((api, options) => {
         if (t.isMemberExpression(elem)) return false;
       }
 
-      for (const elem of (arr.elements: Array)) {
+      for (const elem of arr.elements) {
         // deopt on spread elements
         if (t.isSpreadElement(elem)) return false;
 
diff --git a/packages/babel-plugin-transform-dotall-regex/src/index.js b/packages/babel-plugin-transform-dotall-regex/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-dotall-regex/src/index.js
rename to packages/babel-plugin-transform-dotall-regex/src/index.ts
diff --git a/packages/babel-plugin-transform-duplicate-keys/src/index.js b/packages/babel-plugin-transform-duplicate-keys/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-duplicate-keys/src/index.js
rename to packages/babel-plugin-transform-duplicate-keys/src/index.ts
diff --git a/packages/babel-plugin-transform-exponentiation-operator/src/index.js b/packages/babel-plugin-transform-exponentiation-operator/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-exponentiation-operator/src/index.js
rename to packages/babel-plugin-transform-exponentiation-operator/src/index.ts
diff --git a/packages/babel-plugin-transform-flow-comments/src/index.js b/packages/babel-plugin-transform-flow-comments/src/index.ts
similarity index 98%
rename from packages/babel-plugin-transform-flow-comments/src/index.js
rename to packages/babel-plugin-transform-flow-comments/src/index.ts
index db926052c3..d1190fefe0 100644
--- a/packages/babel-plugin-transform-flow-comments/src/index.js
+++ b/packages/babel-plugin-transform-flow-comments/src/index.ts
@@ -19,6 +19,13 @@ export default declare(api => {
     optional = false,
     comments = generateComment(ofPath, optional),
     keepType = false,
+  }: {
+    ofPath?;
+    toPath?;
+    where?: string;
+    optional?;
+    comments?;
+    keepType?;
   }) {
     if (!toPath?.node) {
       toPath = ofPath.getPrevSibling();
@@ -67,7 +74,7 @@ export default declare(api => {
     });
   }
 
-  function generateComment(path, optional) {
+  function generateComment(path, optional?) {
     let comment = path
       .getSource()
       .replace(/\*-\//g, "*-ESCAPED/")
diff --git a/packages/babel-plugin-transform-flow-strip-types/src/index.js b/packages/babel-plugin-transform-flow-strip-types/src/index.ts
similarity index 98%
rename from packages/babel-plugin-transform-flow-strip-types/src/index.js
rename to packages/babel-plugin-transform-flow-strip-types/src/index.ts
index 5d293ae474..6b5ec02a25 100644
--- a/packages/babel-plugin-transform-flow-strip-types/src/index.js
+++ b/packages/babel-plugin-transform-flow-strip-types/src/index.ts
@@ -33,7 +33,7 @@ export default declare((api, opts) => {
         let directiveFound = false;
 
         if (comments) {
-          for (const comment of (comments: Array<Object>)) {
+          for (const comment of comments) {
             if (FLOW_DIRECTIVE.test(comment.value)) {
               directiveFound = true;
 
diff --git a/packages/babel-plugin-transform-for-of/src/index.js b/packages/babel-plugin-transform-for-of/src/index.ts
similarity index 98%
rename from packages/babel-plugin-transform-for-of/src/index.js
rename to packages/babel-plugin-transform-for-of/src/index.ts
index 882ff9b82b..91d99c4880 100644
--- a/packages/babel-plugin-transform-for-of/src/index.js
+++ b/packages/babel-plugin-transform-for-of/src/index.ts
@@ -157,7 +157,7 @@ export default declare((api, options) => {
       KEY: iterationKey,
       NAME: right,
       ARR: node.right,
-    });
+    }) as t.For;
 
     t.inherits(loop, node);
     t.ensureBlock(loop);
@@ -171,8 +171,10 @@ export default declare((api, options) => {
     const left = node.left;
     if (t.isVariableDeclaration(left)) {
       left.declarations[0].init = iterationValue;
+      // @ts-expect-error todo(flow->ts):
       loop.body.body.unshift(left);
     } else {
+      // @ts-expect-error todo(flow->ts):
       loop.body.body.unshift(
         t.expressionStatement(
           t.assignmentExpression("=", left, iterationValue),
diff --git a/packages/babel-plugin-transform-for-of/src/no-helper-implementation.js b/packages/babel-plugin-transform-for-of/src/no-helper-implementation.ts
similarity index 99%
rename from packages/babel-plugin-transform-for-of/src/no-helper-implementation.js
rename to packages/babel-plugin-transform-for-of/src/no-helper-implementation.ts
index c867a5d096..d84143b6e3 100644
--- a/packages/babel-plugin-transform-for-of/src/no-helper-implementation.js
+++ b/packages/babel-plugin-transform-for-of/src/no-helper-implementation.ts
@@ -115,7 +115,7 @@ function pushComputedPropsLoose(path, file) {
     INDEX: scope.generateUidIdentifier("i"),
     ID: id,
     INTERMEDIATE: intermediate,
-  });
+  }) as t.Statement;
 
   //
   const isLabeledParent = t.isLabeledStatement(parent);
diff --git a/packages/babel-plugin-transform-function-name/src/index.js b/packages/babel-plugin-transform-function-name/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-function-name/src/index.js
rename to packages/babel-plugin-transform-function-name/src/index.ts
diff --git a/packages/babel-plugin-transform-instanceof/src/index.js b/packages/babel-plugin-transform-instanceof/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-instanceof/src/index.js
rename to packages/babel-plugin-transform-instanceof/src/index.ts
diff --git a/packages/babel-plugin-transform-jscript/src/index.js b/packages/babel-plugin-transform-jscript/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-jscript/src/index.js
rename to packages/babel-plugin-transform-jscript/src/index.ts
diff --git a/packages/babel-plugin-transform-literals/src/index.js b/packages/babel-plugin-transform-literals/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-literals/src/index.js
rename to packages/babel-plugin-transform-literals/src/index.ts
diff --git a/packages/babel-plugin-transform-member-expression-literals/src/index.js b/packages/babel-plugin-transform-member-expression-literals/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-member-expression-literals/src/index.js
rename to packages/babel-plugin-transform-member-expression-literals/src/index.ts
diff --git a/packages/babel-plugin-transform-modules-amd/src/index.js b/packages/babel-plugin-transform-modules-amd/src/index.ts
similarity index 97%
rename from packages/babel-plugin-transform-modules-amd/src/index.js
rename to packages/babel-plugin-transform-modules-amd/src/index.ts
index 737ef30a14..71b0b7585c 100644
--- a/packages/babel-plugin-transform-modules-amd/src/index.js
+++ b/packages/babel-plugin-transform-modules-amd/src/index.ts
@@ -70,7 +70,7 @@ export default declare((api, options) => {
           state.rejectId = rejectId;
         }
 
-        let result = t.identifier("imported");
+        let result: t.Node = t.identifier("imported");
         if (!noInterop) result = wrapInterop(path, result, "namespace");
 
         path.replaceWith(
@@ -105,6 +105,7 @@ export default declare((api, options) => {
           }
 
           let moduleName = getModuleName(this.file.opts, options);
+          // @ts-expect-error todo(flow->ts): do not reuse variables
           if (moduleName) moduleName = t.stringLiteral(moduleName);
 
           const { meta, headers } = rewriteModuleStatementsAndPrepareHeader(
diff --git a/packages/babel-plugin-transform-modules-commonjs/src/index.js b/packages/babel-plugin-transform-modules-commonjs/src/index.ts
similarity index 99%
rename from packages/babel-plugin-transform-modules-commonjs/src/index.js
rename to packages/babel-plugin-transform-modules-commonjs/src/index.ts
index e33768c1cc..c142c2d230 100644
--- a/packages/babel-plugin-transform-modules-commonjs/src/index.js
+++ b/packages/babel-plugin-transform-modules-commonjs/src/index.ts
@@ -169,6 +169,7 @@ export default declare((api, options) => {
           }
 
           let moduleName = getModuleName(this.file.opts, options);
+          // @ts-expect-error todo(flow->ts): do not reuse variables
           if (moduleName) moduleName = t.stringLiteral(moduleName);
 
           const { meta, headers } = rewriteModuleStatementsAndPrepareHeader(
diff --git a/packages/babel-plugin-transform-modules-systemjs/src/index.js b/packages/babel-plugin-transform-modules-systemjs/src/index.ts
similarity index 98%
rename from packages/babel-plugin-transform-modules-systemjs/src/index.js
rename to packages/babel-plugin-transform-modules-systemjs/src/index.ts
index b9407d8c1e..6a573f487b 100644
--- a/packages/babel-plugin-transform-modules-systemjs/src/index.js
+++ b/packages/babel-plugin-transform-modules-systemjs/src/index.ts
@@ -37,7 +37,7 @@ ERROR: Dynamic import() transformation must be enabled using the
 //todo: use getExportSpecifierName in `helper-module-transforms` when this library is refactored to NodePath usage.
 
 export function getExportSpecifierName(
-  node: Node,
+  node: t.Node,
   stringSpecifiers: Set<string>,
 ): string {
   if (node.type === "Identifier") {
@@ -61,15 +61,14 @@ export function getExportSpecifierName(
   }
 }
 
-type PluginState = {|
-  contextIdent: string,
-
+type PluginState = {
+  contextIdent: string;
   // List of names that should only be printed as string literals.
   // i.e. `import { "any unicode" as foo } from "some-module"`
   // `stringSpecifiers` is Set(1) ["any unicode"]
   // In most cases `stringSpecifiers` is an empty Set
-  stringSpecifiers: Set<string>,
-|};
+  stringSpecifiers: Set<string>;
+};
 
 function constructExportCall(
   path,
@@ -333,7 +332,7 @@ export default declare((api, options) => {
           const exportNames = [];
           const exportValues = [];
 
-          const body: Array<Object> = path.get("body");
+          const body: Array<any> = path.get("body");
 
           for (const path of body) {
             if (path.isFunctionDeclaration()) {
@@ -563,6 +562,7 @@ export default declare((api, options) => {
           });
 
           let moduleName = getModuleName(this.file.opts, options);
+          // @ts-expect-error todo(flow->ts): do not reuse variables
           if (moduleName) moduleName = t.stringLiteral(moduleName);
 
           hoistVariables(
diff --git a/packages/babel-plugin-transform-modules-umd/src/index.js b/packages/babel-plugin-transform-modules-umd/src/index.ts
similarity index 98%
rename from packages/babel-plugin-transform-modules-umd/src/index.js
rename to packages/babel-plugin-transform-modules-umd/src/index.ts
index 37a244b56c..ff8ef645f3 100644
--- a/packages/babel-plugin-transform-modules-umd/src/index.js
+++ b/packages/babel-plugin-transform-modules-umd/src/index.ts
@@ -147,6 +147,7 @@ export default declare((api, options) => {
           const browserGlobals = globals || {};
 
           let moduleName = getModuleName(this.file.opts, options);
+          // @ts-expect-error todo(flow->ts): do not reuse variables
           if (moduleName) moduleName = t.stringLiteral(moduleName);
 
           const { meta, headers } = rewriteModuleStatementsAndPrepareHeader(
@@ -202,6 +203,7 @@ export default declare((api, options) => {
                     interop,
                   ),
                 );
+                // @ts-expect-error todo(flow->ts)
                 header.loc = meta.loc;
                 headers.push(header);
               }
diff --git a/packages/babel-plugin-transform-named-capturing-groups-regex/src/index.js b/packages/babel-plugin-transform-named-capturing-groups-regex/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-named-capturing-groups-regex/src/index.js
rename to packages/babel-plugin-transform-named-capturing-groups-regex/src/index.ts
diff --git a/packages/babel-plugin-transform-new-target/src/index.js b/packages/babel-plugin-transform-new-target/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-new-target/src/index.js
rename to packages/babel-plugin-transform-new-target/src/index.ts
diff --git a/packages/babel-plugin-transform-object-assign/src/index.js b/packages/babel-plugin-transform-object-assign/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-object-assign/src/index.js
rename to packages/babel-plugin-transform-object-assign/src/index.ts
diff --git a/packages/babel-plugin-transform-object-set-prototype-of-to-assign/src/index.js b/packages/babel-plugin-transform-object-set-prototype-of-to-assign/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-object-set-prototype-of-to-assign/src/index.js
rename to packages/babel-plugin-transform-object-set-prototype-of-to-assign/src/index.ts
diff --git a/packages/babel-plugin-transform-object-super/src/index.js b/packages/babel-plugin-transform-object-super/src/index.ts
similarity index 96%
rename from packages/babel-plugin-transform-object-super/src/index.js
rename to packages/babel-plugin-transform-object-super/src/index.ts
index c810a49d22..b375f575f9 100644
--- a/packages/babel-plugin-transform-object-super/src/index.js
+++ b/packages/babel-plugin-transform-object-super/src/index.ts
@@ -3,6 +3,7 @@ import ReplaceSupers from "@babel/helper-replace-supers";
 import { types as t } from "@babel/core";
 
 function replacePropertySuper(path, getObjectRef, file) {
+  // @ts-expect-error todo(flow->ts):
   const replaceSupers = new ReplaceSupers({
     getObjectRef: getObjectRef,
     methodPath: path,
diff --git a/packages/babel-plugin-transform-parameters/src/index.js b/packages/babel-plugin-transform-parameters/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-parameters/src/index.js
rename to packages/babel-plugin-transform-parameters/src/index.ts
diff --git a/packages/babel-plugin-transform-parameters/src/params.js b/packages/babel-plugin-transform-parameters/src/params.ts
similarity index 99%
rename from packages/babel-plugin-transform-parameters/src/params.js
rename to packages/babel-plugin-transform-parameters/src/params.ts
index aac3e64bb4..d9bfd15af9 100644
--- a/packages/babel-plugin-transform-parameters/src/params.js
+++ b/packages/babel-plugin-transform-parameters/src/params.ts
@@ -45,8 +45,8 @@ const iifeVisitor = {
 export default function convertFunctionParams(
   path,
   ignoreFunctionLength,
-  shouldTransformParam,
-  replaceRestElement,
+  shouldTransformParam?,
+  replaceRestElement?,
 ) {
   const params = path.get("params");
 
diff --git a/packages/babel-plugin-transform-parameters/src/rest.js b/packages/babel-plugin-transform-parameters/src/rest.ts
similarity index 99%
rename from packages/babel-plugin-transform-parameters/src/rest.js
rename to packages/babel-plugin-transform-parameters/src/rest.ts
index 2d2f422d3c..196c11f82d 100644
--- a/packages/babel-plugin-transform-parameters/src/rest.js
+++ b/packages/babel-plugin-transform-parameters/src/rest.ts
@@ -289,7 +289,7 @@ export default function convertFunctionRest(path) {
 
   // There are only "shorthand" references
   if (!state.deopted && !state.references.length) {
-    for (const { path, cause } of (state.candidates: Array)) {
+    for (const { path, cause } of state.candidates) {
       const clonedArgsId = t.cloneNode(argsId);
       switch (cause) {
         case "indexGetter":
diff --git a/packages/babel-plugin-transform-property-literals/src/index.js b/packages/babel-plugin-transform-property-literals/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-property-literals/src/index.js
rename to packages/babel-plugin-transform-property-literals/src/index.ts
diff --git a/packages/babel-plugin-transform-property-mutators/src/index.js b/packages/babel-plugin-transform-property-mutators/src/index.ts
similarity index 95%
rename from packages/babel-plugin-transform-property-mutators/src/index.js
rename to packages/babel-plugin-transform-property-mutators/src/index.ts
index ee419c7e44..3ed962f38f 100644
--- a/packages/babel-plugin-transform-property-mutators/src/index.js
+++ b/packages/babel-plugin-transform-property-mutators/src/index.ts
@@ -12,7 +12,7 @@ export default declare(api => {
       ObjectExpression(path, file) {
         const { node } = path;
         let hasAny = false;
-        for (const prop of (node.properties: Array)) {
+        for (const prop of node.properties) {
           if (prop.kind === "get" || prop.kind === "set") {
             hasAny = true;
             break;
diff --git a/packages/babel-plugin-transform-proto-to-assign/src/index.js b/packages/babel-plugin-transform-proto-to-assign/src/index.ts
similarity index 88%
rename from packages/babel-plugin-transform-proto-to-assign/src/index.js
rename to packages/babel-plugin-transform-proto-to-assign/src/index.ts
index 2c2a111df2..7a78893091 100644
--- a/packages/babel-plugin-transform-proto-to-assign/src/index.js
+++ b/packages/babel-plugin-transform-proto-to-assign/src/index.ts
@@ -12,6 +12,7 @@ export default declare(api => {
     const left = node.left;
     return (
       t.isMemberExpression(left) &&
+      // @ts-expect-error todo(flow->ts): property can be t.PrivateName
       t.isLiteral(t.toComputedKey(left, left.property), { value: "__proto__" })
     );
   }
@@ -56,7 +57,12 @@ export default declare(api => {
 
         if (isProtoAssignmentExpression(expr)) {
           path.replaceWith(
-            buildDefaultsCallExpression(expr, expr.left.object, file),
+            buildDefaultsCallExpression(
+              expr,
+              // todo(flow->ts) isProtoAssignmentExpression actually checks that
+              (expr.left as t.MemberExpression).object,
+              file,
+            ),
           );
         }
       },
diff --git a/packages/babel-plugin-transform-react-constant-elements/src/index.js b/packages/babel-plugin-transform-react-constant-elements/src/index.ts
similarity index 98%
rename from packages/babel-plugin-transform-react-constant-elements/src/index.js
rename to packages/babel-plugin-transform-react-constant-elements/src/index.ts
index 873b15a4d4..2beafc4965 100644
--- a/packages/babel-plugin-transform-react-constant-elements/src/index.js
+++ b/packages/babel-plugin-transform-react-constant-elements/src/index.ts
@@ -249,7 +249,8 @@ export default declare((api, options) => {
         const id = path.scope.generateUidBasedOnNode(name);
         targetScope.push({ id: t.identifier(id) });
 
-        let replacement = template.expression.ast`
+        let replacement: t.Expression | t.JSXExpressionContainer = template
+          .expression.ast`
           ${t.identifier(id)} || (${t.identifier(id)} = ${path.node})
         `;
         if (
diff --git a/packages/babel-plugin-transform-react-display-name/src/index.js b/packages/babel-plugin-transform-react-display-name/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-react-display-name/src/index.js
rename to packages/babel-plugin-transform-react-display-name/src/index.ts
diff --git a/packages/babel-plugin-transform-react-inline-elements/src/index.js b/packages/babel-plugin-transform-react-inline-elements/src/index.ts
similarity index 93%
rename from packages/babel-plugin-transform-react-inline-elements/src/index.js
rename to packages/babel-plugin-transform-react-inline-elements/src/index.ts
index 925d46032c..46199b940b 100644
--- a/packages/babel-plugin-transform-react-inline-elements/src/index.js
+++ b/packages/babel-plugin-transform-react-inline-elements/src/index.ts
@@ -48,9 +48,11 @@ export default declare(api => {
       let hasKey = false;
       if (t.isObjectExpression(props)) {
         const keyIndex = props.properties.findIndex(prop =>
+          // @ts-expect-error todo(flow->ts) key does not exist on SpeadElement
           t.isIdentifier(prop.key, { name: "key" }),
         );
         if (keyIndex > -1) {
+          // @ts-expect-error todo(flow->ts) value does not exist on ObjectMethod
           state.args.splice(2, 0, props.properties[keyIndex].value);
           props.properties.splice(keyIndex, 1);
           hasKey = true;
diff --git a/packages/babel-plugin-transform-react-jsx-compat/src/index.js b/packages/babel-plugin-transform-react-jsx-compat/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-react-jsx-compat/src/index.js
rename to packages/babel-plugin-transform-react-jsx-compat/src/index.ts
diff --git a/packages/babel-plugin-transform-react-jsx-development/src/index.js b/packages/babel-plugin-transform-react-jsx-development/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-react-jsx-development/src/index.js
rename to packages/babel-plugin-transform-react-jsx-development/src/index.ts
diff --git a/packages/babel-plugin-transform-react-jsx-self/src/index.js b/packages/babel-plugin-transform-react-jsx-self/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-react-jsx-self/src/index.js
rename to packages/babel-plugin-transform-react-jsx-self/src/index.ts
diff --git a/packages/babel-plugin-transform-react-jsx-source/src/index.js b/packages/babel-plugin-transform-react-jsx-source/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-react-jsx-source/src/index.js
rename to packages/babel-plugin-transform-react-jsx-source/src/index.ts
diff --git a/packages/babel-plugin-transform-react-pure-annotations/src/index.js b/packages/babel-plugin-transform-react-pure-annotations/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-react-pure-annotations/src/index.js
rename to packages/babel-plugin-transform-react-pure-annotations/src/index.ts
diff --git a/packages/babel-plugin-transform-regenerator/src/index.js b/packages/babel-plugin-transform-regenerator/src/index.ts
similarity index 63%
rename from packages/babel-plugin-transform-regenerator/src/index.js
rename to packages/babel-plugin-transform-regenerator/src/index.ts
index 3c776e3d8f..a9af30f526 100644
--- a/packages/babel-plugin-transform-regenerator/src/index.js
+++ b/packages/babel-plugin-transform-regenerator/src/index.ts
@@ -1,2 +1,3 @@
+// eslint-disable-next-line @babel/development/plugin-name
 import regeneratorTransform from "regenerator-transform";
 export default regeneratorTransform.default;
diff --git a/packages/babel-plugin-transform-reserved-words/src/index.js b/packages/babel-plugin-transform-reserved-words/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-reserved-words/src/index.js
rename to packages/babel-plugin-transform-reserved-words/src/index.ts
diff --git a/packages/babel-plugin-transform-shorthand-properties/src/index.js b/packages/babel-plugin-transform-shorthand-properties/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-shorthand-properties/src/index.js
rename to packages/babel-plugin-transform-shorthand-properties/src/index.ts
diff --git a/packages/babel-plugin-transform-spread/src/index.ts b/packages/babel-plugin-transform-spread/src/index.ts
index ee3ed8bbcd..ec68db00ff 100644
--- a/packages/babel-plugin-transform-spread/src/index.ts
+++ b/packages/babel-plugin-transform-spread/src/index.ts
@@ -167,7 +167,7 @@ export default declare((api, options) => {
 
         const callee = calleePath.node as t.MemberExpression;
 
-        if (calleePath.isMemberExpression()) {
+        if (t.isMemberExpression(callee)) {
           const temp = scope.maybeGenerateMemoised(callee.object);
           if (temp) {
             callee.object = t.assignmentExpression("=", temp, callee.object);
diff --git a/packages/babel-plugin-transform-sticky-regex/src/index.js b/packages/babel-plugin-transform-sticky-regex/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-sticky-regex/src/index.js
rename to packages/babel-plugin-transform-sticky-regex/src/index.ts
diff --git a/packages/babel-plugin-transform-strict-mode/src/index.js b/packages/babel-plugin-transform-strict-mode/src/index.ts
similarity index 87%
rename from packages/babel-plugin-transform-strict-mode/src/index.js
rename to packages/babel-plugin-transform-strict-mode/src/index.ts
index 9be2ae2f15..8f3ae8b024 100644
--- a/packages/babel-plugin-transform-strict-mode/src/index.js
+++ b/packages/babel-plugin-transform-strict-mode/src/index.ts
@@ -11,7 +11,7 @@ export default declare(api => {
       Program(path) {
         const { node } = path;
 
-        for (const directive of (node.directives: Array<Object>)) {
+        for (const directive of node.directives) {
           if (directive.value.value === "use strict") return;
         }
 
diff --git a/packages/babel-plugin-transform-template-literals/src/index.js b/packages/babel-plugin-transform-template-literals/src/index.ts
similarity index 97%
rename from packages/babel-plugin-transform-template-literals/src/index.js
rename to packages/babel-plugin-transform-template-literals/src/index.ts
index 5b588900d3..d3fdc6e678 100644
--- a/packages/babel-plugin-transform-template-literals/src/index.js
+++ b/packages/babel-plugin-transform-template-literals/src/index.ts
@@ -61,7 +61,7 @@ export default declare((api, options) => {
         // Flag variable to check if contents of strings and raw are equal
         let isStringsRawEqual = true;
 
-        for (const elem of (quasi.quasis: Array)) {
+        for (const elem of quasi.quasis) {
           const { raw, cooked } = elem.value;
           const value =
             cooked == null
@@ -103,7 +103,7 @@ export default declare((api, options) => {
         const expressions = path.get("expressions");
 
         let index = 0;
-        for (const elem of (path.node.quasis: Array)) {
+        for (const elem of path.node.quasis) {
           if (elem.value.cooked) {
             nodes.push(t.stringLiteral(elem.value.cooked));
           }
diff --git a/packages/babel-plugin-transform-typeof-symbol/src/index.js b/packages/babel-plugin-transform-typeof-symbol/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-typeof-symbol/src/index.js
rename to packages/babel-plugin-transform-typeof-symbol/src/index.ts
diff --git a/packages/babel-plugin-transform-unicode-escapes/src/index.js b/packages/babel-plugin-transform-unicode-escapes/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-unicode-escapes/src/index.js
rename to packages/babel-plugin-transform-unicode-escapes/src/index.ts
diff --git a/packages/babel-plugin-transform-unicode-regex/src/index.js b/packages/babel-plugin-transform-unicode-regex/src/index.ts
similarity index 100%
rename from packages/babel-plugin-transform-unicode-regex/src/index.js
rename to packages/babel-plugin-transform-unicode-regex/src/index.ts
diff --git a/packages/babel-preset-env/package.json b/packages/babel-preset-env/package.json
index d70ab28728..5fe461c19b 100644
--- a/packages/babel-preset-env/package.json
+++ b/packages/babel-preset-env/package.json
@@ -97,7 +97,8 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/core-7.12": "npm:@babel/core@7.12.9",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"
diff --git a/packages/babel-preset-env/src/index.ts b/packages/babel-preset-env/src/index.ts
index 86de8f790f..53bf3998fc 100644
--- a/packages/babel-preset-env/src/index.ts
+++ b/packages/babel-preset-env/src/index.ts
@@ -336,7 +336,7 @@ option \`forceAllTransforms: true\` instead.
       ? forceAllTransforms
       : forceAllTransforms || hasUglifyTarget
   )
-    ? {}
+    ? ({} as Targets)
     : targets;
 
   const include = transformIncludesAndExcludes(optionsInclude);
diff --git a/packages/babel-preset-flow/src/index.js b/packages/babel-preset-flow/src/index.ts
similarity index 100%
rename from packages/babel-preset-flow/src/index.js
rename to packages/babel-preset-flow/src/index.ts
diff --git a/packages/babel-preset-flow/src/normalize-options.js b/packages/babel-preset-flow/src/normalize-options.ts
similarity index 92%
rename from packages/babel-preset-flow/src/normalize-options.js
rename to packages/babel-preset-flow/src/normalize-options.ts
index 9d79c4395b..77da4803a5 100644
--- a/packages/babel-preset-flow/src/normalize-options.js
+++ b/packages/babel-preset-flow/src/normalize-options.ts
@@ -1,7 +1,7 @@
 import { OptionValidator } from "@babel/helper-validator-option";
 const v = new OptionValidator("@babel/preset-flow");
 
-export default function normalizeOptions(options = {}) {
+export default function normalizeOptions(options: any = {}) {
   let { all } = options;
   const { allowDeclareFields } = options;
 
diff --git a/packages/babel-preset-react/src/index.js b/packages/babel-preset-react/src/index.ts
similarity index 100%
rename from packages/babel-preset-react/src/index.js
rename to packages/babel-preset-react/src/index.ts
diff --git a/packages/babel-preset-react/src/normalize-options.js b/packages/babel-preset-react/src/normalize-options.ts
similarity index 98%
rename from packages/babel-preset-react/src/normalize-options.js
rename to packages/babel-preset-react/src/normalize-options.ts
index 9061f07276..fcf4bfaa57 100644
--- a/packages/babel-preset-react/src/normalize-options.js
+++ b/packages/babel-preset-react/src/normalize-options.ts
@@ -4,7 +4,7 @@ import {
 } from "@babel/helper-validator-option";
 const v = new OptionValidator("@babel/preset-react");
 
-export default function normalizeOptions(options = {}) {
+export default function normalizeOptions(options: any = {}) {
   if (process.env.BABEL_8_BREAKING) {
     if ("useSpread" in options) {
       throw new Error(
diff --git a/packages/babel-preset-typescript/src/index.js b/packages/babel-preset-typescript/src/index.ts
similarity index 100%
rename from packages/babel-preset-typescript/src/index.js
rename to packages/babel-preset-typescript/src/index.ts
diff --git a/packages/babel-preset-typescript/src/normalize-options.js b/packages/babel-preset-typescript/src/normalize-options.ts
similarity index 97%
rename from packages/babel-preset-typescript/src/normalize-options.js
rename to packages/babel-preset-typescript/src/normalize-options.ts
index 9d93723a58..419c18adb9 100644
--- a/packages/babel-preset-typescript/src/normalize-options.js
+++ b/packages/babel-preset-typescript/src/normalize-options.ts
@@ -1,7 +1,7 @@
 import { OptionValidator } from "@babel/helper-validator-option";
 const v = new OptionValidator("@babel/preset-typescript");
 
-export default function normalizeOptions(options = {}) {
+export default function normalizeOptions(options = {} as any) {
   let { allowNamespaces = true, jsxPragma, onlyRemoveTypeImports } = options;
 
   const TopLevelOptions = {
diff --git a/packages/babel-register/src/browser.js b/packages/babel-register/src/browser.ts
similarity index 100%
rename from packages/babel-register/src/browser.js
rename to packages/babel-register/src/browser.ts
diff --git a/packages/babel-register/src/cache.js b/packages/babel-register/src/cache.ts
similarity index 98%
rename from packages/babel-register/src/cache.js
rename to packages/babel-register/src/cache.ts
index 8e3f812b3d..80495ae782 100644
--- a/packages/babel-register/src/cache.js
+++ b/packages/babel-register/src/cache.ts
@@ -11,7 +11,7 @@ const DEFAULT_FILENAME = path.join(
   `.babel.${babel.version}.${babel.getEnv()}.json`,
 );
 const FILENAME: string = process.env.BABEL_CACHE_PATH || DEFAULT_FILENAME;
-let data: Object = {};
+let data: any = {};
 
 let cacheDirty = false;
 
@@ -112,7 +112,7 @@ due to a permission issue. Cache is disabled.`,
  * Retrieve data from cache.
  */
 
-export function get(): Object {
+export function get(): any {
   return data;
 }
 
diff --git a/packages/babel-register/src/node.js b/packages/babel-register/src/node.ts
similarity index 91%
rename from packages/babel-register/src/node.js
rename to packages/babel-register/src/node.ts
index 6d627a6574..f7990885f0 100644
--- a/packages/babel-register/src/node.js
+++ b/packages/babel-register/src/node.ts
@@ -9,7 +9,7 @@ import path from "path";
 import Module from "module";
 
 const maps = {};
-let transformOpts = {};
+let transformOpts: any = {};
 let piratesRevert = null;
 
 function installSourceMapSupport() {
@@ -52,7 +52,7 @@ function compile(code, filename) {
 
   let cacheKey = `${JSON.stringify(opts)}:${babel.version}`;
 
-  const env = babel.getEnv(false);
+  const env = babel.getEnv("");
 
   if (env) cacheKey += `:${env}`;
 
@@ -87,18 +87,22 @@ function compile(code, filename) {
 }
 
 let compiling = false;
+// @ts-expect-error field is missing in type definitions
 const internalModuleCache = Module._cache;
 
 function compileHook(code, filename) {
   if (compiling) return code;
 
+  // @ts-expect-error field is missing in type definitions
   const globalModuleCache = Module._cache;
   try {
     compiling = true;
+    // @ts-expect-error field is missing in type definitions
     Module._cache = internalModuleCache;
     return compile(code, filename);
   } finally {
     compiling = false;
+    // @ts-expect-error field is missing in type definitions
     Module._cache = globalModuleCache;
   }
 }
@@ -116,7 +120,7 @@ function escapeRegExp(string) {
   return string.replace(/[|\\{}()[\]^$+*?.]/g, "\\$&");
 }
 
-export default function register(opts?: Object = {}) {
+export default function register(opts: any = {}) {
   // Clone to avoid mutating the arguments object with the 'delete's below.
   opts = {
     ...opts,
diff --git a/packages/babel-register/src/nodeWrapper.js b/packages/babel-register/src/nodeWrapper.ts
similarity index 94%
rename from packages/babel-register/src/nodeWrapper.js
rename to packages/babel-register/src/nodeWrapper.ts
index 13a7157b0d..1839dfc7e4 100644
--- a/packages/babel-register/src/nodeWrapper.js
+++ b/packages/babel-register/src/nodeWrapper.ts
@@ -5,6 +5,7 @@
  * and allows register to transform these modules if they are loaded externally.
  */
 
+// @ts-ignore todo(flow->ts) convert to esm
 const Module = require("module");
 
 const globalModuleCache = Module._cache;
diff --git a/packages/babel-standalone/src/preset-stage-3.ts b/packages/babel-standalone/src/preset-stage-3.ts
index b7d84d0251..d8a8bfcb46 100644
--- a/packages/babel-standalone/src/preset-stage-3.ts
+++ b/packages/babel-standalone/src/preset-stage-3.ts
@@ -1,7 +1,8 @@
 import * as babelPlugins from "./generated/plugins";
 
 export default (_: any, { loose = false } = {}) => {
-  const plugins = [
+  // todo(flow->ts) improve types
+  const plugins: any[] = [
     babelPlugins.syntaxImportAssertions,
     babelPlugins.proposalClassStaticBlock,
   ];
diff --git a/packages/babel-traverse/src/path/evaluation.ts b/packages/babel-traverse/src/path/evaluation.ts
index de673dd007..89541ccd78 100644
--- a/packages/babel-traverse/src/path/evaluation.ts
+++ b/packages/babel-traverse/src/path/evaluation.ts
@@ -139,8 +139,8 @@ function _evaluate(path: NodePath, state) {
     path.isMemberExpression() &&
     !path.parentPath.isCallExpression({ callee: path.node })
   ) {
-    const property = path.get("property") as NodePath;
-    const object = path.get("object") as NodePath;
+    const property = path.get("property");
+    const object = path.get("object");
 
     if (object.isLiteral() && property.isIdentifier()) {
       // @ts-expect-error todo(flow->ts): instead of typeof - would it be better to check type of ast node?
@@ -353,8 +353,7 @@ function _evaluate(path: NodePath, state) {
 
     if (callee.isMemberExpression()) {
       const object = callee.get("object");
-      // todo: improve babel-types
-      const property = callee.get("property") as NodePath;
+      const property = callee.get("property");
 
       // Math.min(1, 2)
       if (
diff --git a/packages/babel-traverse/src/scope/index.ts b/packages/babel-traverse/src/scope/index.ts
index 056dc22078..93aa941016 100644
--- a/packages/babel-traverse/src/scope/index.ts
+++ b/packages/babel-traverse/src/scope/index.ts
@@ -1091,7 +1091,7 @@ export default class Scope {
    * Walks the scope tree and gathers all declarations of `kind`.
    */
 
-  getAllBindingsOfKind(...kinds: string[]): any {
+  getAllBindingsOfKind(...kinds: string[]): Record<string, Binding> {
     const ids = Object.create(null);
 
     for (const kind of kinds) {
diff --git a/scripts/generators/tsconfig.js b/scripts/generators/tsconfig.js
index 413f4e3e75..974170cc4c 100644
--- a/scripts/generators/tsconfig.js
+++ b/scripts/generators/tsconfig.js
@@ -16,7 +16,12 @@ function getTsPkgs(subRoot) {
       dir: path.resolve(root, subRoot, name),
       relative: `./${subRoot}/${name}`,
     }))
-    .filter(({ dir }) => fs.existsSync(path.join(dir, "src", "index.ts")));
+    .filter(
+      ({ dir }) =>
+        // babel-register is special-cased because its entry point is a js file
+        dir.includes("babel-register") ||
+        fs.existsSync(path.join(dir, "src", "index.ts"))
+    );
 }
 
 const tsPkgs = [
diff --git a/tsconfig.json b/tsconfig.json
index edf6a89408..2ba274f749 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,9 +6,12 @@
     "./packages/babel-core/src/**/*.ts",
     "./packages/babel-generator/src/**/*.ts",
     "./packages/babel-helper-annotate-as-pure/src/**/*.ts",
+    "./packages/babel-helper-builder-binary-assignment-operator-visitor/src/**/*.ts",
+    "./packages/babel-helper-builder-react-jsx/src/**/*.ts",
     "./packages/babel-helper-compilation-targets/src/**/*.ts",
     "./packages/babel-helper-create-class-features-plugin/src/**/*.ts",
     "./packages/babel-helper-create-regexp-features-plugin/src/**/*.ts",
+    "./packages/babel-helper-define-map/src/**/*.ts",
     "./packages/babel-helper-explode-assignable-expression/src/**/*.ts",
     "./packages/babel-helper-fixtures/src/**/*.ts",
     "./packages/babel-helper-function-name/src/**/*.ts",
@@ -18,6 +21,9 @@
     "./packages/babel-helper-module-imports/src/**/*.ts",
     "./packages/babel-helper-module-transforms/src/**/*.ts",
     "./packages/babel-helper-optimise-call-expression/src/**/*.ts",
+    "./packages/babel-helper-plugin-test-runner/src/**/*.ts",
+    "./packages/babel-helper-plugin-utils/src/**/*.ts",
+    "./packages/babel-helper-remap-async-to-generator/src/**/*.ts",
     "./packages/babel-helper-replace-supers/src/**/*.ts",
     "./packages/babel-helper-simple-access/src/**/*.ts",
     "./packages/babel-helper-skip-transparent-expression-wrappers/src/**/*.ts",
@@ -25,24 +31,119 @@
     "./packages/babel-helper-transform-fixture-test-runner/src/**/*.ts",
     "./packages/babel-helper-validator-identifier/src/**/*.ts",
     "./packages/babel-helper-validator-option/src/**/*.ts",
+    "./packages/babel-helper-wrap-function/src/**/*.ts",
     "./packages/babel-helpers/src/**/*.ts",
     "./packages/babel-highlight/src/**/*.ts",
     "./packages/babel-plugin-bugfix-safari-id-destructuring-collision-in-function-expression/src/**/*.ts",
     "./packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/src/**/*.ts",
+    "./packages/babel-plugin-external-helpers/src/**/*.ts",
     "./packages/babel-plugin-proposal-async-do-expressions/src/**/*.ts",
+    "./packages/babel-plugin-proposal-async-generator-functions/src/**/*.ts",
+    "./packages/babel-plugin-proposal-class-properties/src/**/*.ts",
+    "./packages/babel-plugin-proposal-class-static-block/src/**/*.ts",
+    "./packages/babel-plugin-proposal-decorators/src/**/*.ts",
+    "./packages/babel-plugin-proposal-do-expressions/src/**/*.ts",
+    "./packages/babel-plugin-proposal-dynamic-import/src/**/*.ts",
+    "./packages/babel-plugin-proposal-export-default-from/src/**/*.ts",
+    "./packages/babel-plugin-proposal-export-namespace-from/src/**/*.ts",
+    "./packages/babel-plugin-proposal-function-bind/src/**/*.ts",
+    "./packages/babel-plugin-proposal-function-sent/src/**/*.ts",
+    "./packages/babel-plugin-proposal-json-strings/src/**/*.ts",
+    "./packages/babel-plugin-proposal-logical-assignment-operators/src/**/*.ts",
+    "./packages/babel-plugin-proposal-nullish-coalescing-operator/src/**/*.ts",
+    "./packages/babel-plugin-proposal-numeric-separator/src/**/*.ts",
     "./packages/babel-plugin-proposal-object-rest-spread/src/**/*.ts",
+    "./packages/babel-plugin-proposal-optional-catch-binding/src/**/*.ts",
+    "./packages/babel-plugin-proposal-optional-chaining/src/**/*.ts",
+    "./packages/babel-plugin-proposal-partial-application/src/**/*.ts",
+    "./packages/babel-plugin-proposal-pipeline-operator/src/**/*.ts",
+    "./packages/babel-plugin-proposal-private-methods/src/**/*.ts",
+    "./packages/babel-plugin-proposal-private-property-in-object/src/**/*.ts",
+    "./packages/babel-plugin-proposal-record-and-tuple/src/**/*.ts",
+    "./packages/babel-plugin-proposal-throw-expressions/src/**/*.ts",
+    "./packages/babel-plugin-proposal-unicode-property-regex/src/**/*.ts",
     "./packages/babel-plugin-syntax-async-do-expressions/src/**/*.ts",
+    "./packages/babel-plugin-syntax-decimal/src/**/*.ts",
+    "./packages/babel-plugin-syntax-decorators/src/**/*.ts",
+    "./packages/babel-plugin-syntax-do-expressions/src/**/*.ts",
+    "./packages/babel-plugin-syntax-export-default-from/src/**/*.ts",
+    "./packages/babel-plugin-syntax-flow/src/**/*.ts",
+    "./packages/babel-plugin-syntax-function-bind/src/**/*.ts",
+    "./packages/babel-plugin-syntax-function-sent/src/**/*.ts",
+    "./packages/babel-plugin-syntax-import-assertions/src/**/*.ts",
+    "./packages/babel-plugin-syntax-jsx/src/**/*.ts",
+    "./packages/babel-plugin-syntax-module-blocks/src/**/*.ts",
+    "./packages/babel-plugin-syntax-partial-application/src/**/*.ts",
+    "./packages/babel-plugin-syntax-pipeline-operator/src/**/*.ts",
+    "./packages/babel-plugin-syntax-record-and-tuple/src/**/*.ts",
+    "./packages/babel-plugin-syntax-throw-expressions/src/**/*.ts",
+    "./packages/babel-plugin-syntax-typescript/src/**/*.ts",
+    "./packages/babel-plugin-transform-arrow-functions/src/**/*.ts",
+    "./packages/babel-plugin-transform-async-to-generator/src/**/*.ts",
+    "./packages/babel-plugin-transform-block-scoped-functions/src/**/*.ts",
     "./packages/babel-plugin-transform-block-scoping/src/**/*.ts",
     "./packages/babel-plugin-transform-classes/src/**/*.ts",
+    "./packages/babel-plugin-transform-computed-properties/src/**/*.ts",
+    "./packages/babel-plugin-transform-destructuring/src/**/*.ts",
+    "./packages/babel-plugin-transform-dotall-regex/src/**/*.ts",
+    "./packages/babel-plugin-transform-duplicate-keys/src/**/*.ts",
+    "./packages/babel-plugin-transform-exponentiation-operator/src/**/*.ts",
+    "./packages/babel-plugin-transform-flow-comments/src/**/*.ts",
+    "./packages/babel-plugin-transform-flow-strip-types/src/**/*.ts",
+    "./packages/babel-plugin-transform-for-of/src/**/*.ts",
+    "./packages/babel-plugin-transform-function-name/src/**/*.ts",
+    "./packages/babel-plugin-transform-instanceof/src/**/*.ts",
+    "./packages/babel-plugin-transform-jscript/src/**/*.ts",
+    "./packages/babel-plugin-transform-literals/src/**/*.ts",
+    "./packages/babel-plugin-transform-member-expression-literals/src/**/*.ts",
+    "./packages/babel-plugin-transform-modules-amd/src/**/*.ts",
+    "./packages/babel-plugin-transform-modules-commonjs/src/**/*.ts",
+    "./packages/babel-plugin-transform-modules-systemjs/src/**/*.ts",
+    "./packages/babel-plugin-transform-modules-umd/src/**/*.ts",
+    "./packages/babel-plugin-transform-named-capturing-groups-regex/src/**/*.ts",
+    "./packages/babel-plugin-transform-new-target/src/**/*.ts",
+    "./packages/babel-plugin-transform-object-assign/src/**/*.ts",
+    "./packages/babel-plugin-transform-object-set-prototype-of-to-assign/src/**/*.ts",
+    "./packages/babel-plugin-transform-object-super/src/**/*.ts",
+    "./packages/babel-plugin-transform-parameters/src/**/*.ts",
+    "./packages/babel-plugin-transform-property-literals/src/**/*.ts",
+    "./packages/babel-plugin-transform-property-mutators/src/**/*.ts",
+    "./packages/babel-plugin-transform-proto-to-assign/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-constant-elements/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-display-name/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-inline-elements/src/**/*.ts",
     "./packages/babel-plugin-transform-react-jsx/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-jsx-compat/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-jsx-development/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-jsx-self/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-jsx-source/src/**/*.ts",
+    "./packages/babel-plugin-transform-react-pure-annotations/src/**/*.ts",
+    "./packages/babel-plugin-transform-regenerator/src/**/*.ts",
+    "./packages/babel-plugin-transform-reserved-words/src/**/*.ts",
     "./packages/babel-plugin-transform-runtime/src/**/*.ts",
+    "./packages/babel-plugin-transform-shorthand-properties/src/**/*.ts",
     "./packages/babel-plugin-transform-spread/src/**/*.ts",
+    "./packages/babel-plugin-transform-sticky-regex/src/**/*.ts",
+    "./packages/babel-plugin-transform-strict-mode/src/**/*.ts",
+    "./packages/babel-plugin-transform-template-literals/src/**/*.ts",
+    "./packages/babel-plugin-transform-typeof-symbol/src/**/*.ts",
     "./packages/babel-plugin-transform-typescript/src/**/*.ts",
+    "./packages/babel-plugin-transform-unicode-escapes/src/**/*.ts",
+    "./packages/babel-plugin-transform-unicode-regex/src/**/*.ts",
     "./packages/babel-preset-env/src/**/*.ts",
+    "./packages/babel-preset-flow/src/**/*.ts",
+    "./packages/babel-preset-react/src/**/*.ts",
+    "./packages/babel-preset-typescript/src/**/*.ts",
+    "./packages/babel-register/src/**/*.ts",
     "./packages/babel-standalone/src/**/*.ts",
     "./packages/babel-template/src/**/*.ts",
     "./packages/babel-traverse/src/**/*.ts",
-    "./packages/babel-types/src/**/*.ts"
+    "./packages/babel-types/src/**/*.ts",
+    "./eslint/babel-eslint-plugin/src/**/*.ts",
+    "./eslint/babel-eslint-plugin-development/src/**/*.ts",
+    "./eslint/babel-eslint-plugin-development-internal/src/**/*.ts",
+    "./codemods/babel-plugin-codemod-object-assign-to-object-spread/src/**/*.ts",
+    "./codemods/babel-plugin-codemod-optional-catch-binding/src/**/*.ts"
   ],
   "compilerOptions": {
     "paths": {
@@ -58,6 +159,12 @@
       "@babel/helper-annotate-as-pure": [
         "./packages/babel-helper-annotate-as-pure/src"
       ],
+      "@babel/helper-builder-binary-assignment-operator-visitor": [
+        "./packages/babel-helper-builder-binary-assignment-operator-visitor/src"
+      ],
+      "@babel/helper-builder-react-jsx": [
+        "./packages/babel-helper-builder-react-jsx/src"
+      ],
       "@babel/helper-compilation-targets": [
         "./packages/babel-helper-compilation-targets/src"
       ],
@@ -67,6 +174,9 @@
       "@babel/helper-create-regexp-features-plugin": [
         "./packages/babel-helper-create-regexp-features-plugin/src"
       ],
+      "@babel/helper-define-map": [
+        "./packages/babel-helper-define-map/src"
+      ],
       "@babel/helper-explode-assignable-expression": [
         "./packages/babel-helper-explode-assignable-expression/src"
       ],
@@ -94,6 +204,15 @@
       "@babel/helper-optimise-call-expression": [
         "./packages/babel-helper-optimise-call-expression/src"
       ],
+      "@babel/helper-plugin-test-runner": [
+        "./packages/babel-helper-plugin-test-runner/src"
+      ],
+      "@babel/helper-plugin-utils": [
+        "./packages/babel-helper-plugin-utils/src"
+      ],
+      "@babel/helper-remap-async-to-generator": [
+        "./packages/babel-helper-remap-async-to-generator/src"
+      ],
       "@babel/helper-replace-supers": [
         "./packages/babel-helper-replace-supers/src"
       ],
@@ -115,6 +234,9 @@
       "@babel/helper-validator-option": [
         "./packages/babel-helper-validator-option/src"
       ],
+      "@babel/helper-wrap-function": [
+        "./packages/babel-helper-wrap-function/src"
+      ],
       "@babel/helpers": [
         "./packages/babel-helpers/src"
       ],
@@ -127,36 +249,303 @@
       "@babel/plugin-bugfix-v8-spread-parameters-in-optional-chaining": [
         "./packages/babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining/src"
       ],
+      "@babel/plugin-external-helpers": [
+        "./packages/babel-plugin-external-helpers/src"
+      ],
       "@babel/plugin-proposal-async-do-expressions": [
         "./packages/babel-plugin-proposal-async-do-expressions/src"
       ],
+      "@babel/plugin-proposal-async-generator-functions": [
+        "./packages/babel-plugin-proposal-async-generator-functions/src"
+      ],
+      "@babel/plugin-proposal-class-properties": [
+        "./packages/babel-plugin-proposal-class-properties/src"
+      ],
+      "@babel/plugin-proposal-class-static-block": [
+        "./packages/babel-plugin-proposal-class-static-block/src"
+      ],
+      "@babel/plugin-proposal-decorators": [
+        "./packages/babel-plugin-proposal-decorators/src"
+      ],
+      "@babel/plugin-proposal-do-expressions": [
+        "./packages/babel-plugin-proposal-do-expressions/src"
+      ],
+      "@babel/plugin-proposal-dynamic-import": [
+        "./packages/babel-plugin-proposal-dynamic-import/src"
+      ],
+      "@babel/plugin-proposal-export-default-from": [
+        "./packages/babel-plugin-proposal-export-default-from/src"
+      ],
+      "@babel/plugin-proposal-export-namespace-from": [
+        "./packages/babel-plugin-proposal-export-namespace-from/src"
+      ],
+      "@babel/plugin-proposal-function-bind": [
+        "./packages/babel-plugin-proposal-function-bind/src"
+      ],
+      "@babel/plugin-proposal-function-sent": [
+        "./packages/babel-plugin-proposal-function-sent/src"
+      ],
+      "@babel/plugin-proposal-json-strings": [
+        "./packages/babel-plugin-proposal-json-strings/src"
+      ],
+      "@babel/plugin-proposal-logical-assignment-operators": [
+        "./packages/babel-plugin-proposal-logical-assignment-operators/src"
+      ],
+      "@babel/plugin-proposal-nullish-coalescing-operator": [
+        "./packages/babel-plugin-proposal-nullish-coalescing-operator/src"
+      ],
+      "@babel/plugin-proposal-numeric-separator": [
+        "./packages/babel-plugin-proposal-numeric-separator/src"
+      ],
       "@babel/plugin-proposal-object-rest-spread": [
         "./packages/babel-plugin-proposal-object-rest-spread/src"
       ],
+      "@babel/plugin-proposal-optional-catch-binding": [
+        "./packages/babel-plugin-proposal-optional-catch-binding/src"
+      ],
+      "@babel/plugin-proposal-optional-chaining": [
+        "./packages/babel-plugin-proposal-optional-chaining/src"
+      ],
+      "@babel/plugin-proposal-partial-application": [
+        "./packages/babel-plugin-proposal-partial-application/src"
+      ],
+      "@babel/plugin-proposal-pipeline-operator": [
+        "./packages/babel-plugin-proposal-pipeline-operator/src"
+      ],
+      "@babel/plugin-proposal-private-methods": [
+        "./packages/babel-plugin-proposal-private-methods/src"
+      ],
+      "@babel/plugin-proposal-private-property-in-object": [
+        "./packages/babel-plugin-proposal-private-property-in-object/src"
+      ],
+      "@babel/plugin-proposal-record-and-tuple": [
+        "./packages/babel-plugin-proposal-record-and-tuple/src"
+      ],
+      "@babel/plugin-proposal-throw-expressions": [
+        "./packages/babel-plugin-proposal-throw-expressions/src"
+      ],
+      "@babel/plugin-proposal-unicode-property-regex": [
+        "./packages/babel-plugin-proposal-unicode-property-regex/src"
+      ],
       "@babel/plugin-syntax-async-do-expressions": [
         "./packages/babel-plugin-syntax-async-do-expressions/src"
       ],
+      "@babel/plugin-syntax-decimal": [
+        "./packages/babel-plugin-syntax-decimal/src"
+      ],
+      "@babel/plugin-syntax-decorators": [
+        "./packages/babel-plugin-syntax-decorators/src"
+      ],
+      "@babel/plugin-syntax-do-expressions": [
+        "./packages/babel-plugin-syntax-do-expressions/src"
+      ],
+      "@babel/plugin-syntax-export-default-from": [
+        "./packages/babel-plugin-syntax-export-default-from/src"
+      ],
+      "@babel/plugin-syntax-flow": [
+        "./packages/babel-plugin-syntax-flow/src"
+      ],
+      "@babel/plugin-syntax-function-bind": [
+        "./packages/babel-plugin-syntax-function-bind/src"
+      ],
+      "@babel/plugin-syntax-function-sent": [
+        "./packages/babel-plugin-syntax-function-sent/src"
+      ],
+      "@babel/plugin-syntax-import-assertions": [
+        "./packages/babel-plugin-syntax-import-assertions/src"
+      ],
+      "@babel/plugin-syntax-jsx": [
+        "./packages/babel-plugin-syntax-jsx/src"
+      ],
+      "@babel/plugin-syntax-module-blocks": [
+        "./packages/babel-plugin-syntax-module-blocks/src"
+      ],
+      "@babel/plugin-syntax-partial-application": [
+        "./packages/babel-plugin-syntax-partial-application/src"
+      ],
+      "@babel/plugin-syntax-pipeline-operator": [
+        "./packages/babel-plugin-syntax-pipeline-operator/src"
+      ],
+      "@babel/plugin-syntax-record-and-tuple": [
+        "./packages/babel-plugin-syntax-record-and-tuple/src"
+      ],
+      "@babel/plugin-syntax-throw-expressions": [
+        "./packages/babel-plugin-syntax-throw-expressions/src"
+      ],
+      "@babel/plugin-syntax-typescript": [
+        "./packages/babel-plugin-syntax-typescript/src"
+      ],
+      "@babel/plugin-transform-arrow-functions": [
+        "./packages/babel-plugin-transform-arrow-functions/src"
+      ],
+      "@babel/plugin-transform-async-to-generator": [
+        "./packages/babel-plugin-transform-async-to-generator/src"
+      ],
+      "@babel/plugin-transform-block-scoped-functions": [
+        "./packages/babel-plugin-transform-block-scoped-functions/src"
+      ],
       "@babel/plugin-transform-block-scoping": [
         "./packages/babel-plugin-transform-block-scoping/src"
       ],
       "@babel/plugin-transform-classes": [
         "./packages/babel-plugin-transform-classes/src"
       ],
+      "@babel/plugin-transform-computed-properties": [
+        "./packages/babel-plugin-transform-computed-properties/src"
+      ],
+      "@babel/plugin-transform-destructuring": [
+        "./packages/babel-plugin-transform-destructuring/src"
+      ],
+      "@babel/plugin-transform-dotall-regex": [
+        "./packages/babel-plugin-transform-dotall-regex/src"
+      ],
+      "@babel/plugin-transform-duplicate-keys": [
+        "./packages/babel-plugin-transform-duplicate-keys/src"
+      ],
+      "@babel/plugin-transform-exponentiation-operator": [
+        "./packages/babel-plugin-transform-exponentiation-operator/src"
+      ],
+      "@babel/plugin-transform-flow-comments": [
+        "./packages/babel-plugin-transform-flow-comments/src"
+      ],
+      "@babel/plugin-transform-flow-strip-types": [
+        "./packages/babel-plugin-transform-flow-strip-types/src"
+      ],
+      "@babel/plugin-transform-for-of": [
+        "./packages/babel-plugin-transform-for-of/src"
+      ],
+      "@babel/plugin-transform-function-name": [
+        "./packages/babel-plugin-transform-function-name/src"
+      ],
+      "@babel/plugin-transform-instanceof": [
+        "./packages/babel-plugin-transform-instanceof/src"
+      ],
+      "@babel/plugin-transform-jscript": [
+        "./packages/babel-plugin-transform-jscript/src"
+      ],
+      "@babel/plugin-transform-literals": [
+        "./packages/babel-plugin-transform-literals/src"
+      ],
+      "@babel/plugin-transform-member-expression-literals": [
+        "./packages/babel-plugin-transform-member-expression-literals/src"
+      ],
+      "@babel/plugin-transform-modules-amd": [
+        "./packages/babel-plugin-transform-modules-amd/src"
+      ],
+      "@babel/plugin-transform-modules-commonjs": [
+        "./packages/babel-plugin-transform-modules-commonjs/src"
+      ],
+      "@babel/plugin-transform-modules-systemjs": [
+        "./packages/babel-plugin-transform-modules-systemjs/src"
+      ],
+      "@babel/plugin-transform-modules-umd": [
+        "./packages/babel-plugin-transform-modules-umd/src"
+      ],
+      "@babel/plugin-transform-named-capturing-groups-regex": [
+        "./packages/babel-plugin-transform-named-capturing-groups-regex/src"
+      ],
+      "@babel/plugin-transform-new-target": [
+        "./packages/babel-plugin-transform-new-target/src"
+      ],
+      "@babel/plugin-transform-object-assign": [
+        "./packages/babel-plugin-transform-object-assign/src"
+      ],
+      "@babel/plugin-transform-object-set-prototype-of-to-assign": [
+        "./packages/babel-plugin-transform-object-set-prototype-of-to-assign/src"
+      ],
+      "@babel/plugin-transform-object-super": [
+        "./packages/babel-plugin-transform-object-super/src"
+      ],
+      "@babel/plugin-transform-parameters": [
+        "./packages/babel-plugin-transform-parameters/src"
+      ],
+      "@babel/plugin-transform-property-literals": [
+        "./packages/babel-plugin-transform-property-literals/src"
+      ],
+      "@babel/plugin-transform-property-mutators": [
+        "./packages/babel-plugin-transform-property-mutators/src"
+      ],
+      "@babel/plugin-transform-proto-to-assign": [
+        "./packages/babel-plugin-transform-proto-to-assign/src"
+      ],
+      "@babel/plugin-transform-react-constant-elements": [
+        "./packages/babel-plugin-transform-react-constant-elements/src"
+      ],
+      "@babel/plugin-transform-react-display-name": [
+        "./packages/babel-plugin-transform-react-display-name/src"
+      ],
+      "@babel/plugin-transform-react-inline-elements": [
+        "./packages/babel-plugin-transform-react-inline-elements/src"
+      ],
       "@babel/plugin-transform-react-jsx": [
         "./packages/babel-plugin-transform-react-jsx/src"
       ],
+      "@babel/plugin-transform-react-jsx-compat": [
+        "./packages/babel-plugin-transform-react-jsx-compat/src"
+      ],
+      "@babel/plugin-transform-react-jsx-development": [
+        "./packages/babel-plugin-transform-react-jsx-development/src"
+      ],
+      "@babel/plugin-transform-react-jsx-self": [
+        "./packages/babel-plugin-transform-react-jsx-self/src"
+      ],
+      "@babel/plugin-transform-react-jsx-source": [
+        "./packages/babel-plugin-transform-react-jsx-source/src"
+      ],
+      "@babel/plugin-transform-react-pure-annotations": [
+        "./packages/babel-plugin-transform-react-pure-annotations/src"
+      ],
+      "@babel/plugin-transform-regenerator": [
+        "./packages/babel-plugin-transform-regenerator/src"
+      ],
+      "@babel/plugin-transform-reserved-words": [
+        "./packages/babel-plugin-transform-reserved-words/src"
+      ],
       "@babel/plugin-transform-runtime": [
         "./packages/babel-plugin-transform-runtime/src"
       ],
+      "@babel/plugin-transform-shorthand-properties": [
+        "./packages/babel-plugin-transform-shorthand-properties/src"
+      ],
       "@babel/plugin-transform-spread": [
         "./packages/babel-plugin-transform-spread/src"
       ],
+      "@babel/plugin-transform-sticky-regex": [
+        "./packages/babel-plugin-transform-sticky-regex/src"
+      ],
+      "@babel/plugin-transform-strict-mode": [
+        "./packages/babel-plugin-transform-strict-mode/src"
+      ],
+      "@babel/plugin-transform-template-literals": [
+        "./packages/babel-plugin-transform-template-literals/src"
+      ],
+      "@babel/plugin-transform-typeof-symbol": [
+        "./packages/babel-plugin-transform-typeof-symbol/src"
+      ],
       "@babel/plugin-transform-typescript": [
         "./packages/babel-plugin-transform-typescript/src"
       ],
+      "@babel/plugin-transform-unicode-escapes": [
+        "./packages/babel-plugin-transform-unicode-escapes/src"
+      ],
+      "@babel/plugin-transform-unicode-regex": [
+        "./packages/babel-plugin-transform-unicode-regex/src"
+      ],
       "@babel/preset-env": [
         "./packages/babel-preset-env/src"
       ],
+      "@babel/preset-flow": [
+        "./packages/babel-preset-flow/src"
+      ],
+      "@babel/preset-react": [
+        "./packages/babel-preset-react/src"
+      ],
+      "@babel/preset-typescript": [
+        "./packages/babel-preset-typescript/src"
+      ],
+      "@babel/register": [
+        "./packages/babel-register/src"
+      ],
       "@babel/standalone": [
         "./packages/babel-standalone/src"
       ],
@@ -168,6 +557,21 @@
       ],
       "@babel/types": [
         "./packages/babel-types/src"
+      ],
+      "@babel/eslint-plugin": [
+        "./eslint/babel-eslint-plugin/src"
+      ],
+      "@babel/eslint-plugin-development": [
+        "./eslint/babel-eslint-plugin-development/src"
+      ],
+      "@babel/eslint-plugin-development-internal": [
+        "./eslint/babel-eslint-plugin-development-internal/src"
+      ],
+      "@babel/plugin-codemod-object-assign-to-object-spread": [
+        "./codemods/babel-plugin-codemod-object-assign-to-object-spread/src"
+      ],
+      "@babel/plugin-codemod-optional-catch-binding": [
+        "./codemods/babel-plugin-codemod-optional-catch-binding/src"
       ]
     }
   }
diff --git a/yarn.lock b/yarn.lock
index 6f16fac72c..8a82ef2fe0 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -466,6 +466,7 @@ __metadata:
   resolution: "@babel/helper-builder-react-jsx@workspace:packages/babel-helper-builder-react-jsx"
   dependencies:
     "@babel/helper-annotate-as-pure": "workspace:^"
+    "@babel/traverse": "workspace:^"
     "@babel/types": "workspace:^"
   languageName: unknown
   linkType: soft
@@ -1231,6 +1232,8 @@ __metadata:
     "@babel/helper-plugin-test-runner": "workspace:^"
     "@babel/helper-plugin-utils": "workspace:^"
     "@babel/plugin-syntax-class-static-block": ^7.14.5
+    "@babel/traverse": "workspace:^"
+    "@babel/types": "workspace:^"
   peerDependencies:
     "@babel/core": ^7.12.0
   languageName: unknown
@@ -1245,6 +1248,7 @@ __metadata:
     "@babel/helper-plugin-test-runner": "workspace:^"
     "@babel/helper-plugin-utils": "workspace:^"
     "@babel/plugin-syntax-decorators": "workspace:^"
+    "@babel/traverse": "workspace:^"
     babel-plugin-polyfill-es-shims: ^0.6.0
     object.getownpropertydescriptors: ^2.1.1
   peerDependencies:
@@ -1452,6 +1456,8 @@ __metadata:
     "@babel/helper-plugin-test-runner": "workspace:^"
     "@babel/helper-plugin-utils": "workspace:^"
     "@babel/plugin-syntax-numeric-separator": ^7.10.4
+    "@babel/traverse": "workspace:^"
+    "@babel/types": "workspace:^"
   peerDependencies:
     "@babel/core": ^7.0.0-0
   languageName: unknown
@@ -1537,6 +1543,7 @@ __metadata:
     "@babel/helper-skip-transparent-expression-wrappers": "workspace:^"
     "@babel/plugin-syntax-optional-chaining": ^7.8.3
     "@babel/plugin-transform-block-scoping": "workspace:^"
+    "@babel/traverse": "workspace:^"
   peerDependencies:
     "@babel/core": ^7.0.0-0
   languageName: unknown
@@ -2067,6 +2074,7 @@ __metadata:
     "@babel/helper-plugin-test-runner": "workspace:^"
     "@babel/helper-plugin-utils": "workspace:^"
     "@babel/traverse": "workspace:^"
+    "@babel/types": "workspace:^"
   peerDependencies:
     "@babel/core": ^7.0.0-0
   languageName: unknown
@@ -2223,6 +2231,7 @@ __metadata:
     "@babel/core": "workspace:^"
     "@babel/helper-plugin-test-runner": "workspace:^"
     "@babel/helper-plugin-utils": "workspace:^"
+    "@babel/traverse": "workspace:^"
   peerDependencies:
     "@babel/core": ^7.0.0-0
   languageName: unknown
@@ -3316,6 +3325,7 @@ __metadata:
     "@babel/plugin-transform-unicode-escapes": "workspace:^"
     "@babel/plugin-transform-unicode-regex": "workspace:^"
     "@babel/preset-modules": ^0.1.5
+    "@babel/traverse": "workspace:^"
     "@babel/types": "workspace:^"
     babel-plugin-polyfill-corejs2: ^0.3.0
     babel-plugin-polyfill-corejs3: ^0.4.0