diff --git a/dockerfiles/Dockerfile.browser b/dockerfiles/Dockerfile.browser
index 701e8c54ac..f98bbb39e9 100644
--- a/dockerfiles/Dockerfile.browser
+++ b/dockerfiles/Dockerfile.browser
@@ -10,6 +10,7 @@ COPY babel.config.js lerna.json .eslintignore .eslintrc.js jest.config.js tsconf
 ADD min_packages.tar .
 COPY .rollup ./.rollup
 COPY bin ./bin
+COPY jest ./jest
 COPY packages ./packages
 
 RUN npm install
diff --git a/dockerfiles/Dockerfile.ci b/dockerfiles/Dockerfile.ci
index b8560c6d7b..83cbaf1b0d 100644
--- a/dockerfiles/Dockerfile.ci
+++ b/dockerfiles/Dockerfile.ci
@@ -12,6 +12,7 @@ COPY .rollup ./.rollup
 COPY bin ./bin
 COPY scripts ./scripts
 COPY test ./test
+COPY jest ./jest
 COPY packages ./packages
 
 RUN npm install --unsafe-perm
diff --git a/dockerfiles/Dockerfile.node b/dockerfiles/Dockerfile.node
index 187ec60a9d..4852f01a2e 100644
--- a/dockerfiles/Dockerfile.node
+++ b/dockerfiles/Dockerfile.node
@@ -10,6 +10,7 @@ COPY babel.config.js lerna.json .eslintignore .eslintrc.js jest.config.js tsconf
 ADD min_packages.tar .
 COPY .rollup ./.rollup
 COPY bin ./bin
+COPY jest ./jest
 COPY packages ./packages
 
 RUN npm install
diff --git a/jest.config.js b/jest.config.js
index 64bc93ba34..40bc65fde5 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -49,7 +49,9 @@ module.exports = {
       'plugin-simple-throttle',
       'plugin-console-breadcrumbs',
       'plugin-browser-session'
-    ]),
+    ], {
+      setupFiles: ['<rootDir>/jest/setup/mockEventTarget.js']
+    }),
     project('react native', [
       'react-native',
       'delivery-react-native',
diff --git a/jest/setup/mockEventTarget.js b/jest/setup/mockEventTarget.js
new file mode 100644
index 0000000000..784b0d699a
--- /dev/null
+++ b/jest/setup/mockEventTarget.js
@@ -0,0 +1,40 @@
+// copy the code from https://developer.mozilla.org/en-US/docs/Web/API/EventTarget#Simple_implementation_of_EventTarget
+var EventTarget = function () {
+  this.listeners = {}
+}
+
+EventTarget.prototype.listeners = null
+EventTarget.prototype.addEventListener = function (type, callback) {
+  if (!(type in this.listeners)) {
+    this.listeners[type] = []
+  }
+  this.listeners[type].push(callback)
+}
+
+EventTarget.prototype.removeEventListener = function (type, callback) {
+  if (!(type in this.listeners)) {
+    return
+  }
+  var stack = this.listeners[type]
+  for (var i = 0, l = stack.length; i < l; i++) {
+    if (stack[i] === callback) {
+      stack.splice(i, 1)
+      return
+    }
+  }
+}
+
+EventTarget.prototype.dispatchEvent = function (event) {
+  if (!(event.type in this.listeners)) {
+    return true
+  }
+  var stack = this.listeners[event.type].slice()
+
+  for (var i = 0, l = stack.length; i < l; i++) {
+    stack[i].call(this, event)
+  }
+  return !event.defaultPrevented
+}
+
+// make the EventTarget global
+global.EventTarget = EventTarget
diff --git a/packages/browser/package.json b/packages/browser/package.json
index 5e81bc2618..6cc6cf081e 100644
--- a/packages/browser/package.json
+++ b/packages/browser/package.json
@@ -1,8 +1,15 @@
 {
   "name": "@bugsnag/browser",
   "version": "8.1.2",
-  "main": "dist/bugsnag.js",
+  "main": "dist/notifier.js",
   "types": "types/bugsnag.d.ts",
+  "exports": {
+    ".": {
+      "types": "./types/bugsnag.d.ts",
+      "default": "./dist/notifier.js",
+      "import": "./dist/notifier.mjs"
+    }
+  },
   "description": "Bugsnag error reporter for browser JavaScript",
   "homepage": "https://www.bugsnag.com/",
   "repository": {
@@ -22,7 +29,8 @@
   "scripts": {
     "size": "../../bin/size dist/bugsnag.min.js",
     "clean": "rm -fr dist && mkdir dist",
-    "build": "npm run clean && npm run build:dist && npm run build:dist:min",
+    "build": "npm run clean && npm run build:npm",
+    "build:npm": "rollup --config rollup.config.npm.mjs",
     "build:dist": "cross-env NODE_ENV=production bash -c '../../bin/bundle src/notifier.js --standalone=Bugsnag | ../../bin/extract-source-map dist/bugsnag.js'",
     "build:dist:min": "cross-env NODE_ENV=production bash -c '../../bin/bundle src/notifier.js --standalone=Bugsnag | ../../bin/minify dist/bugsnag.min.js'",
     "cdn-upload": "../../bin/cdn-upload dist/*"
diff --git a/packages/browser/rollup.config.npm.mjs b/packages/browser/rollup.config.npm.mjs
new file mode 100644
index 0000000000..6235d5fe1a
--- /dev/null
+++ b/packages/browser/rollup.config.npm.mjs
@@ -0,0 +1,33 @@
+import createRollupConfig from "../../.rollup/index.mjs";
+
+export default createRollupConfig({
+  input: "src/notifier.ts",
+  external: [
+    "@bugsnag/core/client",
+    "@bugsnag/core/event",
+    "@bugsnag/core/session",
+    "@bugsnag/core/breadcrumb",
+    "@bugsnag/core/config",
+    "@bugsnag/core/types",
+    "@bugsnag/core/lib/es-utils/map",
+    "@bugsnag/core/lib/es-utils/keys",
+    "@bugsnag/core/lib/es-utils/assign",
+    "@bugsnag/plugin-window-onerror",
+    "@bugsnag/plugin-window-unhandled-rejection",
+    "@bugsnag/plugin-app-duration",
+    "@bugsnag/plugin-browser-device",
+    "@bugsnag/plugin-browser-context",
+    "@bugsnag/plugin-browser-request",
+    "@bugsnag/plugin-simple-throttle",
+    "@bugsnag/plugin-console-breadcrumbs",
+    "@bugsnag/plugin-network-breadcrumbs",
+    "@bugsnag/plugin-navigation-breadcrumbs",
+    "@bugsnag/plugin-interaction-breadcrumbs",
+    "@bugsnag/plugin-inline-script-content",
+    "@bugsnag/plugin-browser-session",
+    "@bugsnag/plugin-client-ip",
+    "@bugsnag/plugin-strip-query-string",
+    "@bugsnag/delivery-x-domain-request",
+    "@bugsnag/delivery-xml-http-request"
+  ],
+});
diff --git a/packages/browser/src/config.js b/packages/browser/src/config.js
deleted file mode 100644
index 12a003b5f1..0000000000
--- a/packages/browser/src/config.js
+++ /dev/null
@@ -1,35 +0,0 @@
-const { schema } = require('@bugsnag/core/config')
-const map = require('@bugsnag/core/lib/es-utils/map')
-const assign = require('@bugsnag/core/lib/es-utils/assign')
-
-module.exports = {
-  releaseStage: assign({}, schema.releaseStage, {
-    defaultValue: () => {
-      if (/^localhost(:\d+)?$/.test(window.location.host)) return 'development'
-      return 'production'
-    }
-  }),
-  appType: {
-    ...schema.appType,
-    defaultValue: () => 'browser'
-  },
-  logger: assign({}, schema.logger, {
-    defaultValue: () =>
-      // set logger based on browser capability
-      (typeof console !== 'undefined' && typeof console.debug === 'function')
-        ? getPrefixedConsole()
-        : undefined
-  })
-}
-
-const getPrefixedConsole = () => {
-  const logger = {}
-  const consoleLog = console.log
-  map(['debug', 'info', 'warn', 'error'], (method) => {
-    const consoleMethod = console[method]
-    logger[method] = typeof consoleMethod === 'function'
-      ? consoleMethod.bind(console, '[bugsnag]')
-      : consoleLog.bind(console, '[bugsnag]')
-  })
-  return logger
-}
diff --git a/packages/browser/src/config.ts b/packages/browser/src/config.ts
new file mode 100644
index 0000000000..fd9c49a335
--- /dev/null
+++ b/packages/browser/src/config.ts
@@ -0,0 +1,24 @@
+import { schema } from '@bugsnag/core/config'
+import assign from '@bugsnag/core/lib/es-utils/assign'
+import getPrefixedConsole from './get-prefixed-console'
+
+const config = {
+  releaseStage: assign({}, schema.releaseStage, {
+    defaultValue: () => {
+      if (/^localhost(:\d+)?$/.test(window.location.host)) return 'development'
+      return 'production'
+    }
+  }),
+  appType: assign({}, schema.appType, {
+    defaultValue: () => 'browser'
+  }),
+  logger: assign({}, schema.logger, {
+    defaultValue: () =>
+      // set logger based on browser capability
+      (typeof console !== 'undefined' && typeof console.debug === 'function')
+        ? getPrefixedConsole()
+        : undefined
+  })
+}
+
+export default config
diff --git a/packages/browser/src/get-prefixed-console.ts b/packages/browser/src/get-prefixed-console.ts
new file mode 100644
index 0000000000..2fcb2bc1b0
--- /dev/null
+++ b/packages/browser/src/get-prefixed-console.ts
@@ -0,0 +1,17 @@
+import map from '@bugsnag/core/lib/es-utils/map'
+
+type LoggerMethod = 'debug' | 'info' | 'warn' | 'error'
+
+const getPrefixedConsole = () => {
+  const logger: Record<string, unknown> = {}
+  const consoleLog = console.log
+  map(['debug', 'info', 'warn', 'error'], (method: LoggerMethod) => {
+    const consoleMethod = console[method]
+    logger[method] = typeof consoleMethod === 'function'
+      ? consoleMethod.bind(console, '[bugsnag]')
+      : consoleLog.bind(console, '[bugsnag]')
+  })
+  return logger
+}
+
+export default getPrefixedConsole
diff --git a/packages/browser/src/notifier.d.ts b/packages/browser/src/notifier.d.ts
deleted file mode 100644
index 844bfb518c..0000000000
--- a/packages/browser/src/notifier.d.ts
+++ /dev/null
@@ -1,2 +0,0 @@
-export { default } from '../types/bugsnag'
-export * from '../types/bugsnag'
diff --git a/packages/browser/src/notifier.js b/packages/browser/src/notifier.js
deleted file mode 100644
index dcb9fb1eda..0000000000
--- a/packages/browser/src/notifier.js
+++ /dev/null
@@ -1,110 +0,0 @@
-const name = 'Bugsnag JavaScript'
-const version = '__VERSION__'
-const url = 'https://github.com/bugsnag/bugsnag-js'
-
-const Client = require('@bugsnag/core/client')
-const Event = require('@bugsnag/core/event')
-const Session = require('@bugsnag/core/session')
-const Breadcrumb = require('@bugsnag/core/breadcrumb')
-
-const map = require('@bugsnag/core/lib/es-utils/map')
-const keys = require('@bugsnag/core/lib/es-utils/keys')
-const assign = require('@bugsnag/core/lib/es-utils/assign')
-
-// extend the base config schema with some browser-specific options
-const schema = assign({}, require('@bugsnag/core/config').schema, require('./config'))
-
-const pluginWindowOnerror = require('@bugsnag/plugin-window-onerror')
-const pluginUnhandledRejection = require('@bugsnag/plugin-window-unhandled-rejection')
-const pluginApp = require('@bugsnag/plugin-app-duration')
-const pluginDevice = require('@bugsnag/plugin-browser-device')
-const pluginContext = require('@bugsnag/plugin-browser-context')
-const pluginRequest = require('@bugsnag/plugin-browser-request')
-const pluginThrottle = require('@bugsnag/plugin-simple-throttle')
-const pluginConsoleBreadcrumbs = require('@bugsnag/plugin-console-breadcrumbs')
-const pluginNetworkBreadcrumbs = require('@bugsnag/plugin-network-breadcrumbs')
-const pluginNavigationBreadcrumbs = require('@bugsnag/plugin-navigation-breadcrumbs')
-const pluginInteractionBreadcrumbs = require('@bugsnag/plugin-interaction-breadcrumbs')
-const pluginInlineScriptContent = require('@bugsnag/plugin-inline-script-content')
-const pluginSession = require('@bugsnag/plugin-browser-session')
-const pluginIp = require('@bugsnag/plugin-client-ip')
-const pluginStripQueryString = require('@bugsnag/plugin-strip-query-string')
-
-// delivery mechanisms
-const dXDomainRequest = require('@bugsnag/delivery-x-domain-request')
-const dXMLHttpRequest = require('@bugsnag/delivery-xml-http-request')
-
-const Bugsnag = {
-  _client: null,
-  createClient: (opts) => {
-    // handle very simple use case where user supplies just the api key as a string
-    if (typeof opts === 'string') opts = { apiKey: opts }
-    if (!opts) opts = {}
-
-    const internalPlugins = [
-      // add browser-specific plugins
-      pluginApp,
-      pluginDevice(),
-      pluginContext(),
-      pluginRequest(),
-      pluginThrottle,
-      pluginSession,
-      pluginIp,
-      pluginStripQueryString,
-      pluginWindowOnerror(),
-      pluginUnhandledRejection(),
-      pluginNavigationBreadcrumbs(),
-      pluginInteractionBreadcrumbs(),
-      pluginNetworkBreadcrumbs(),
-      pluginConsoleBreadcrumbs,
-
-      // this one added last to avoid wrapping functionality before bugsnag uses it
-      pluginInlineScriptContent()
-    ]
-
-    // configure a client with user supplied options
-    const bugsnag = new Client(opts, schema, internalPlugins, { name, version, url })
-
-    // set delivery based on browser capability (IE 8+9 have an XDomainRequest object)
-    bugsnag._setDelivery(window.XDomainRequest ? dXDomainRequest : dXMLHttpRequest)
-
-    bugsnag._logger.debug('Loaded!')
-    bugsnag.leaveBreadcrumb('Bugsnag loaded', {}, 'state')
-
-    return bugsnag._config.autoTrackSessions
-      ? bugsnag.startSession()
-      : bugsnag
-  },
-  start: (opts) => {
-    if (Bugsnag._client) {
-      Bugsnag._client._logger.warn('Bugsnag.start() was called more than once. Ignoring.')
-      return Bugsnag._client
-    }
-    Bugsnag._client = Bugsnag.createClient(opts)
-    return Bugsnag._client
-  },
-  isStarted: () => {
-    return Bugsnag._client != null
-  }
-}
-
-map(['resetEventCount'].concat(keys(Client.prototype)), (m) => {
-  if (/^_/.test(m)) return
-  Bugsnag[m] = function () {
-    if (!Bugsnag._client) return console.log(`Bugsnag.${m}() was called before Bugsnag.start()`)
-    Bugsnag._client._depth += 1
-    const ret = Bugsnag._client[m].apply(Bugsnag._client, arguments)
-    Bugsnag._client._depth -= 1
-    return ret
-  }
-})
-
-module.exports = Bugsnag
-
-module.exports.Client = Client
-module.exports.Event = Event
-module.exports.Session = Session
-module.exports.Breadcrumb = Breadcrumb
-
-// Export a "default" property for compatibility with ESM imports
-module.exports.default = Bugsnag
diff --git a/packages/browser/src/notifier.ts b/packages/browser/src/notifier.ts
new file mode 100644
index 0000000000..f95b38e111
--- /dev/null
+++ b/packages/browser/src/notifier.ts
@@ -0,0 +1,124 @@
+import Client from '@bugsnag/core/client'
+// import Event from '@bugsnag/core/event'
+// import Session from '@bugsnag/core/session'
+// import Breadcrumb from '@bugsnag/core/breadcrumb'
+import { Config } from '@bugsnag/core/types'
+
+import map from '@bugsnag/core/lib/es-utils/map'
+import keys from '@bugsnag/core/lib/es-utils/keys'
+import assign from '@bugsnag/core/lib/es-utils/assign'
+
+// extend the base config schema with some browser-specific options
+import { schema as baseConfig } from '@bugsnag/core/config'
+import browserConfig from './config'
+
+import pluginWindowOnerror from '@bugsnag/plugin-window-onerror'
+import pluginUnhandledRejection from '@bugsnag/plugin-window-unhandled-rejection'
+import pluginApp from '@bugsnag/plugin-app-duration'
+import pluginDevice from '@bugsnag/plugin-browser-device'
+import pluginContext from '@bugsnag/plugin-browser-context'
+import pluginRequest from '@bugsnag/plugin-browser-request'
+import pluginThrottle from '@bugsnag/plugin-simple-throttle'
+import pluginConsoleBreadcrumbs from '@bugsnag/plugin-console-breadcrumbs'
+import pluginNetworkBreadcrumbs from '@bugsnag/plugin-network-breadcrumbs'
+import pluginNavigationBreadcrumbs from '@bugsnag/plugin-navigation-breadcrumbs'
+import pluginInteractionBreadcrumbs from '@bugsnag/plugin-interaction-breadcrumbs'
+import pluginInlineScriptContent from '@bugsnag/plugin-inline-script-content'
+import pluginSession from '@bugsnag/plugin-browser-session'
+import pluginIp from '@bugsnag/plugin-client-ip'
+import pluginStripQueryString from '@bugsnag/plugin-strip-query-string'
+
+// delivery mechanisms
+import dXDomainRequest from '@bugsnag/delivery-x-domain-request'
+import dXMLHttpRequest from '@bugsnag/delivery-xml-http-request'
+
+const name = 'Bugsnag JavaScript'
+const version = '__VERSION__'
+const url = 'https://github.com/bugsnag/bugsnag-js'
+
+const schema = assign({}, baseConfig, browserConfig)
+
+declare global {
+  interface Window {
+    XDomainRequest: unknown
+  }
+}
+
+type BrowserClient = Partial<Client> & {
+  _client: Client | null
+  createClient: (opts?: Config) => Client
+  start: (opts?: Config) => Client
+  isStarted: () => boolean
+  _setDelivery?: (handler: typeof dXDomainRequest | typeof dXMLHttpRequest) => void
+}
+
+const Bugsnag: BrowserClient = {
+  _client: null,
+  createClient: (opts) => {
+    // handle very simple use case where user supplies just the api key as a string
+    if (typeof opts === 'string') opts = { apiKey: opts }
+    if (!opts) opts = {} as unknown as Config
+
+    const internalPlugins = [
+      // add browser-specific plugins
+      pluginApp,
+      pluginDevice(),
+      pluginContext(),
+      pluginRequest(),
+      pluginThrottle,
+      pluginSession,
+      pluginIp,
+      pluginStripQueryString,
+      pluginWindowOnerror(),
+      pluginUnhandledRejection(),
+      pluginNavigationBreadcrumbs(),
+      pluginInteractionBreadcrumbs(),
+      pluginNetworkBreadcrumbs(),
+      pluginConsoleBreadcrumbs,
+
+      // this one added last to avoid wrapping functionality before bugsnag uses it
+      pluginInlineScriptContent()
+    ]
+
+    // configure a client with user supplied options
+    const bugsnag = new Client(opts, schema, internalPlugins, { name, version, url });
+
+    // set delivery based on browser capability (IE 8+9 have an XDomainRequest object)
+    (bugsnag as BrowserClient)._setDelivery?.(window.XDomainRequest ? dXDomainRequest : dXMLHttpRequest)
+
+    bugsnag._logger.debug('Loaded!')
+    bugsnag.leaveBreadcrumb('Bugsnag loaded', {}, 'state')
+
+    return bugsnag._config.autoTrackSessions
+      ? bugsnag.startSession()
+      : bugsnag
+  },
+  start: (opts) => {
+    if (Bugsnag._client) {
+      Bugsnag._client._logger.warn('Bugsnag.start() was called more than once. Ignoring.')
+      return Bugsnag._client
+    }
+    Bugsnag._client = Bugsnag.createClient(opts)
+    return Bugsnag._client
+  },
+  isStarted: () => {
+    return Bugsnag._client != null
+  }
+}
+
+type Method = keyof typeof Client.prototype
+
+map(['resetEventCount'].concat(keys(Client.prototype)) as Method[], (m) => {
+  if (/^_/.test(m)) return
+  Bugsnag[m] = function () {
+    if (!Bugsnag._client) return console.log(`Bugsnag.${m}() was called before Bugsnag.start()`)
+    Bugsnag._client._depth += 1
+    const ret = Bugsnag._client[m].apply(Bugsnag._client, arguments)
+    Bugsnag._client._depth -= 1
+    return ret
+  }
+})
+
+// export { Client, Event, Session, Breadcrumb, Bugsnag }
+
+export default Bugsnag
diff --git a/packages/browser/test/index.test.ts b/packages/browser/test/index.test.ts
index 7e39b8cb13..3834a9f5e3 100644
--- a/packages/browser/test/index.test.ts
+++ b/packages/browser/test/index.test.ts
@@ -1,4 +1,4 @@
-import BugsnagBrowserStatic, { Breadcrumb, BrowserConfig, Session } from '../src/notifier'
+import BugsnagBrowserStatic, { Breadcrumb, BrowserConfig, Session } from '../'
 
 const DONE = window.XMLHttpRequest.DONE
 
@@ -39,7 +39,7 @@ describe('browser notifier', () => {
   })
 
   function getBugsnag (): typeof BugsnagBrowserStatic {
-    const Bugsnag = require('../src/notifier') as typeof BugsnagBrowserStatic
+    const Bugsnag = require('../src/notifier').default
     return Bugsnag
   }
 
@@ -52,7 +52,7 @@ describe('browser notifier', () => {
         load: client => 10
       }]
     })
-    expect(Bugsnag.getPlugin('foobar')).toBe(10)
+    expect(Bugsnag.getPlugin?.('foobar')).toBe(10)
   })
 
   it('notifies handled errors', (done) => {
@@ -138,7 +138,7 @@ describe('browser notifier', () => {
   it('accepts all config options', (done) => {
     const Bugsnag = getBugsnag()
 
-    const completeConfig: Required<BrowserConfig> = {
+    const completeConfig: BrowserConfig = {
       apiKey: API_KEY,
       appVersion: '1.2.3',
       appType: 'worker',
@@ -148,7 +148,7 @@ describe('browser notifier', () => {
         unhandledRejections: true
       },
       onError: [
-        event => true
+        () => true
       ],
       onBreadcrumb: (b: Breadcrumb) => {
         return false
diff --git a/packages/browser/tsconfig.json b/packages/browser/tsconfig.json
new file mode 100644
index 0000000000..a5cb75c562
--- /dev/null
+++ b/packages/browser/tsconfig.json
@@ -0,0 +1,4 @@
+{
+  "extends": "../../tsconfig.json",
+  "include": ["src/**/*.ts"]
+}
diff --git a/packages/core/config.d.ts b/packages/core/config.d.ts
new file mode 100644
index 0000000000..cee871526c
--- /dev/null
+++ b/packages/core/config.d.ts
@@ -0,0 +1,115 @@
+export interface Schema {
+  apiKey: {
+    defaultValue: () => null
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  appVersion: {
+    defaultValue: () => undefined
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  appType: {
+    defaultValue: () => undefined
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  autoDetectErrors: {
+    defaultValue: () => true
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  enabledErrorTypes: {
+    defaultValue: () => { unhandledExceptions: boolean, unhandledRejections: boolean }
+    message: string
+    allowPartialObject: boolean
+    validate: (value: unknown) => boolean
+  }
+  onError: {
+    defaultValue: () => []
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  onSession: {
+    defaultValue: () => []
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  onBreadcrumb: {
+    defaultValue: () => []
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  endpoints: {
+    defaultValue: (endpoints: { notify: string, sessions: string } | undefined) => { notify: string | null, sessions: string | null }
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  autoTrackSessions: {
+    defaultValue: () => boolean
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  enabledReleaseStages: {
+    defaultValue: () => null
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  releaseStage: {
+    defaultValue: () => 'production'
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  maxBreadcrumbs: {
+    defaultValue: () => 25
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  enabledBreadcrumbTypes: {
+    defaultValue: () => ['navigation', 'request', 'process', 'log', 'user', 'state', 'error', 'manual']
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  context: {
+    defaultValue: () => undefined
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  user: {
+    defaultValue: () => {}
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  metadata: {
+    defaultValue: () => {}
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  logger: {
+    defaultValue: () => undefined
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  redactedKeys: {
+    defaultValue: () => ['password']
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  plugins: {
+    defaultValue: () => []
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  featureFlags: {
+    defaultValue: () => []
+    message: string
+    validate: (value: unknown) => boolean
+  }
+  reportUnhandledPromiseRejectionsAsHandled: {
+    defaultValue: () => false
+    message: string
+    validate: (value: unknown) => boolean
+  }
+}
+
+export const schema: Schema
diff --git a/packages/plugin-inline-script-content/package.json b/packages/plugin-inline-script-content/package.json
index af39d4b493..9d22fed43c 100644
--- a/packages/plugin-inline-script-content/package.json
+++ b/packages/plugin-inline-script-content/package.json
@@ -1,7 +1,15 @@
 {
   "name": "@bugsnag/plugin-inline-script-content",
   "version": "8.1.1",
-  "main": "inline-script-content.js",
+  "main": "dist/inline-script-content.js",
+  "types": "dist/types/inline-script-content.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/types/inline-script-content.d.ts",
+      "default": "./dist/inline-script-content.js",
+      "import": "./dist/inline-script-content.mjs"
+    }
+  },
   "description": "@bugsnag/js plugin to attach inline script content to error events",
   "homepage": "https://www.bugsnag.com/",
   "repository": {
@@ -14,7 +22,11 @@
   "files": [
     "*.js"
   ],
-  "scripts": {},
+  "scripts": {
+    "build": "npm run build:npm",
+    "build:npm": "rollup --config rollup.config.npm.mjs",
+    "clean": "rm -rf dist/*"
+  },
   "author": "Bugsnag",
   "license": "MIT",
   "devDependencies": {
diff --git a/packages/plugin-inline-script-content/rollup.config.npm.mjs b/packages/plugin-inline-script-content/rollup.config.npm.mjs
new file mode 100644
index 0000000000..a472a8a594
--- /dev/null
+++ b/packages/plugin-inline-script-content/rollup.config.npm.mjs
@@ -0,0 +1,6 @@
+import createRollupConfig from '../../.rollup/index.mjs'
+
+export default createRollupConfig({
+    input: 'src/inline-script-content.ts',
+    external: ['@bugsnag/core/lib/es-utils/map', '@bugsnag/core/lib/es-utils/reduce', '@bugsnag/core/lib/es-utils/filter']
+})
diff --git a/packages/plugin-inline-script-content/inline-script-content.js b/packages/plugin-inline-script-content/src/inline-script-content.ts
similarity index 72%
rename from packages/plugin-inline-script-content/inline-script-content.js
rename to packages/plugin-inline-script-content/src/inline-script-content.ts
index 26749c6a2f..826effeec8 100644
--- a/packages/plugin-inline-script-content/inline-script-content.js
+++ b/packages/plugin-inline-script-content/src/inline-script-content.ts
@@ -1,13 +1,33 @@
-const map = require('@bugsnag/core/lib/es-utils/map')
-const reduce = require('@bugsnag/core/lib/es-utils/reduce')
-const filter = require('@bugsnag/core/lib/es-utils/filter')
+import map from '@bugsnag/core/lib/es-utils/map'
+import reduce from '@bugsnag/core/lib/es-utils/reduce'
+import filter from '@bugsnag/core/lib/es-utils/filter'
+import type { Config, Plugin } from '@bugsnag/core/types'
+import type ClientWithInternals from 'packages/core/client'
 
 const MAX_LINE_LENGTH = 200
 const MAX_SCRIPT_LENGTH = 500000
 
-module.exports = (doc = document, win = window) => ({
+interface ExtendedConfig extends Config {
+  trackInlineScripts: boolean
+}
+
+interface ExtendedDocument extends Document {
+  attachEvent?: unknown
+}
+
+interface ValidationOption {
+  validate: (value: unknown) => boolean
+  defaultValue: () => unknown
+  message: string
+}
+
+interface ExtendedPlugin extends Plugin {
+  configSchema: Record<string, ValidationOption>
+}
+
+export default (doc: ExtendedDocument = document, win = window): ExtendedPlugin => ({
   load: (client) => {
-    if (!client._config.trackInlineScripts) return
+    if (!(client as ClientWithInternals<ExtendedConfig>)._config.trackInlineScripts) return
 
     const originalLocation = win.location.href
     let html = ''
@@ -28,15 +48,15 @@ module.exports = (doc = document, win = window) => ({
         html = getHtml()
         DOMContentLoaded = true
       }
-      try { prev.apply(this, arguments) } catch (e) {}
+      try { prev && prev.apply(this, arguments as unknown as Parameters<typeof prev>) } catch (e) {}
     }
 
-    let _lastScript = null
-    const updateLastScript = script => {
+    let _lastScript: HTMLOrSVGScriptElement | null = null
+    const updateLastScript = (script: HTMLOrSVGScriptElement | null) => {
       _lastScript = script
     }
 
-    const getCurrentScript = () => {
+    const getCurrentScript = (): HTMLOrSVGScriptElement | null => {
       let script = doc.currentScript || _lastScript
       if (!script && !DOMContentLoaded) {
         const scripts = doc.scripts || doc.getElementsByTagName('script')
@@ -45,7 +65,7 @@ module.exports = (doc = document, win = window) => ({
       return script
     }
 
-    const addSurroundingCode = lineNumber => {
+    const addSurroundingCode = (lineNumber: number) => {
       // get whatever html has rendered at this point
       if (!DOMContentLoaded || !html) html = getHtml()
       // simulate the raw html
@@ -62,12 +82,12 @@ module.exports = (doc = document, win = window) => ({
     client.addOnError(event => {
       // remove any of our own frames that may be part the stack this
       // happens before the inline script check as it happens for all errors
-      event.errors[0].stacktrace = filter(event.errors[0].stacktrace, f => !(/__trace__$/.test(f.method)))
+      event.errors[0].stacktrace = filter(event.errors[0].stacktrace, f => !(/__trace__$/.test(String(f.method))))
 
       const frame = event.errors[0].stacktrace[0]
 
       // remove hash and query string from url
-      const cleanUrl = (url) => url.replace(/#.*$/, '').replace(/\?.*$/, '')
+      const cleanUrl = (url: string) => url.replace(/#.*$/, '').replace(/\?.*$/, '')
 
       // if frame.file exists and is not the original location of the page, this can't be an inline script
       if (frame && frame.file && cleanUrl(frame.file) !== cleanUrl(originalLocation)) return
@@ -87,6 +107,7 @@ module.exports = (doc = document, win = window) => ({
           frame.code = addSurroundingCode(frame.lineNumber)
         }
       }
+      // @ts-expect-error second argument is private API
     }, true)
 
     // Proxy all the timer functions whose callback is their 0th argument.
@@ -105,6 +126,10 @@ module.exports = (doc = document, win = window) => ({
       )
     )
 
+    type ValidWindowProperties = 'EventTarget' | 'Window' | 'Node' | 'ChannelMergerNode' | 'EventSource' | 'FileReader' | 'HTMLUnknownElement' | 'IDBDatabase' | 'IDBRequest' | 'IDBTransaction' | 'MessagePort' | 'Notification' | 'Screen' | 'TextTrack' | 'TextTrackCue' | 'TextTrackList' | 'WebSocket' | 'Worker' | 'XMLHttpRequest' | 'XMLHttpRequestEventTarget' | 'XMLHttpRequestUpload'
+
+    type WindowProperties = keyof Pick<Window & typeof globalThis, ValidWindowProperties>
+
     // Proxy all the host objects whose prototypes have an addEventListener function
     map([
       'EventTarget', 'Window', 'Node', 'ApplicationCache', 'AudioTrackList', 'ChannelMergerNode',
@@ -112,7 +137,7 @@ module.exports = (doc = document, win = window) => ({
       'IDBRequest', 'IDBTransaction', 'KeyOperation', 'MediaController', 'MessagePort', 'ModalWindow',
       'Notification', 'SVGElementInstance', 'Screen', 'TextTrack', 'TextTrackCue', 'TextTrackList',
       'WebSocket', 'WebSocketWorker', 'Worker', 'XMLHttpRequest', 'XMLHttpRequestEventTarget', 'XMLHttpRequestUpload'
-    ], o => {
+    ] as WindowProperties[], o => {
       if (!win[o] || !win[o].prototype || !Object.prototype.hasOwnProperty.call(win[o].prototype, 'addEventListener')) return
       __proxy(win[o].prototype, 'addEventListener', original =>
         __traceOriginalScript(original, eventTargetCallbackAccessor)
@@ -122,7 +147,7 @@ module.exports = (doc = document, win = window) => ({
       )
     })
 
-    function __traceOriginalScript (fn, callbackAccessor, alsoCallOriginal = false) {
+    function __traceOriginalScript (fn: Function, callbackAccessor: EventTargetCallbackAccessor, alsoCallOriginal = false) {
       return function () {
         // this is required for removeEventListener to remove anything added with
         // addEventListener before the functions started being wrapped by Bugsnag
@@ -130,8 +155,8 @@ module.exports = (doc = document, win = window) => ({
         try {
           const cba = callbackAccessor(args)
           const cb = cba.get()
-          if (alsoCallOriginal) fn.apply(this, args)
-          if (typeof cb !== 'function') return fn.apply(this, args)
+          if (alsoCallOriginal) fn.apply(fn, args)
+          if (typeof cb !== 'function') return fn.apply(fn, args)
           if (cb.__trace__) {
             cba.replace(cb.__trace__)
           } else {
@@ -159,7 +184,7 @@ module.exports = (doc = document, win = window) => ({
           // WebDriverException: Message: Permission denied to access property "handleEvent"
         }
         // IE8 doesn't let you call .apply() on setTimeout/setInterval
-        if (fn.apply) return fn.apply(this, args)
+        if (fn.apply) return fn.apply(fn, args)
         switch (args.length) {
           case 1: return fn(args[0])
           case 2: return fn(args[0], args[1])
@@ -177,7 +202,7 @@ module.exports = (doc = document, win = window) => ({
   }
 })
 
-function __proxy (host, name, replacer) {
+function __proxy (host: any, name: string, replacer: (original: Function) => Function) {
   const original = host[name]
   if (!original) return original
   const replacement = replacer(original)
@@ -185,13 +210,19 @@ function __proxy (host, name, replacer) {
   return original
 }
 
-function eventTargetCallbackAccessor (args) {
+type NestedFunction = Function & { __trace__?: NestedFunction }
+
+type Argument = NestedFunction & {
+  handleEvent?: NestedFunction
+}
+
+function eventTargetCallbackAccessor (args: Argument[]) {
   const isEventHandlerObj = !!args[1] && typeof args[1].handleEvent === 'function'
   return {
     get: function () {
       return isEventHandlerObj ? args[1].handleEvent : args[1]
     },
-    replace: function (fn) {
+    replace: function (fn: Function) {
       if (isEventHandlerObj) {
         args[1].handleEvent = fn
       } else {
@@ -200,3 +231,5 @@ function eventTargetCallbackAccessor (args) {
     }
   }
 }
+
+type EventTargetCallbackAccessor = typeof eventTargetCallbackAccessor
diff --git a/packages/plugin-inline-script-content/test/inline-script-content.test.ts b/packages/plugin-inline-script-content/test/inline-script-content.test.ts
index afaff413de..b8b2b12e52 100644
--- a/packages/plugin-inline-script-content/test/inline-script-content.test.ts
+++ b/packages/plugin-inline-script-content/test/inline-script-content.test.ts
@@ -1,4 +1,4 @@
-import plugin from '../inline-script-content'
+import plugin from '../'
 
 import Client from '@bugsnag/core/client'
 import Event from '@bugsnag/core/event'
diff --git a/packages/plugin-inline-script-content/tsconfig.json b/packages/plugin-inline-script-content/tsconfig.json
new file mode 100644
index 0000000000..09758ceb4c
--- /dev/null
+++ b/packages/plugin-inline-script-content/tsconfig.json
@@ -0,0 +1,5 @@
+{
+    "extends": "../../tsconfig.json",
+    "include": ["src/**/*.ts"]
+}
+  
\ No newline at end of file
diff --git a/packages/plugin-interaction-breadcrumbs/package.json b/packages/plugin-interaction-breadcrumbs/package.json
index 3d11035d01..1549f67872 100644
--- a/packages/plugin-interaction-breadcrumbs/package.json
+++ b/packages/plugin-interaction-breadcrumbs/package.json
@@ -1,7 +1,15 @@
 {
   "name": "@bugsnag/plugin-interaction-breadcrumbs",
   "version": "8.1.1",
-  "main": "interaction-breadcrumbs.js",
+  "main": "dist/interaction-breadcrumbs.js",
+  "types": "dist/types/interaction-breadcrumbs.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/types/interaction-breadcrumbs.d.ts",
+      "default": "./dist/interaction-breadcrumbs.js",
+      "import": "./dist/interaction-breadcrumbs.mjs"
+    }
+  },
   "description": "@bugsnag/js plugin to record UI click events as breadcrumbs",
   "homepage": "https://www.bugsnag.com/",
   "repository": {
@@ -14,7 +22,11 @@
   "files": [
     "*.js"
   ],
-  "scripts": {},
+  "scripts": {
+    "build": "npm run build:npm",
+    "build:npm": "rollup --config rollup.config.npm.mjs",
+    "clean": "rm -rf dist/*"
+  },
   "author": "Bugsnag",
   "license": "MIT",
   "devDependencies": {
diff --git a/packages/plugin-interaction-breadcrumbs/rollup.config.npm.mjs b/packages/plugin-interaction-breadcrumbs/rollup.config.npm.mjs
new file mode 100644
index 0000000000..5683a04647
--- /dev/null
+++ b/packages/plugin-interaction-breadcrumbs/rollup.config.npm.mjs
@@ -0,0 +1,5 @@
+import createRollupConfig from '../../.rollup/index.mjs'
+
+export default createRollupConfig({
+    input: 'src/interaction-breadcrumbs.ts'
+})
diff --git a/packages/plugin-interaction-breadcrumbs/interaction-breadcrumbs.js b/packages/plugin-interaction-breadcrumbs/src/interaction-breadcrumbs.ts
similarity index 78%
rename from packages/plugin-interaction-breadcrumbs/interaction-breadcrumbs.js
rename to packages/plugin-interaction-breadcrumbs/src/interaction-breadcrumbs.ts
index 86c7b03086..d910565175 100644
--- a/packages/plugin-interaction-breadcrumbs/interaction-breadcrumbs.js
+++ b/packages/plugin-interaction-breadcrumbs/src/interaction-breadcrumbs.ts
@@ -1,10 +1,13 @@
+import { Plugin } from '@bugsnag/core'
+import type ClientWithInternals from 'packages/core/client'
+
 /*
  * Leaves breadcrumbs when the user interacts with the DOM
  */
-module.exports = (win = window) => ({
+export default (win = window): Plugin => ({
   load: (client) => {
     if (!('addEventListener' in win)) return
-    if (!client._isBreadcrumbTypeEnabled('user')) return
+    if (!(client as ClientWithInternals)._isBreadcrumbTypeEnabled('user')) return
 
     win.addEventListener('click', (event) => {
       let targetText, targetSelector
@@ -13,8 +16,8 @@ module.exports = (win = window) => ({
         targetSelector = getNodeSelector(event.target, win)
       } catch (e) {
         targetText = '[hidden]'
-        targetSelector = '[hidden]'
-        client._logger.error('Cross domain error when tracking click event. See docs: https://tinyurl.com/yy3rn63z')
+        targetSelector = '[hidden]';
+        (client as ClientWithInternals)._logger.error('Cross domain error when tracking click event. See docs: https://tinyurl.com/yy3rn63z')
       }
       client.leaveBreadcrumb('UI click', { targetText, targetSelector }, 'user')
     }, true)
@@ -23,7 +26,8 @@ module.exports = (win = window) => ({
 
 const trim = /^\s*([^\s][\s\S]{0,139}[^\s])?\s*/
 
-function getNodeText (el) {
+// TODO: Fix Type
+function getNodeText (el: any) {
   let text = el.textContent || el.innerText || ''
 
   if (!text && (el.type === 'submit' || el.type === 'button')) {
@@ -40,7 +44,8 @@ function getNodeText (el) {
 }
 
 // Create a label from tagname, id and css class of the element
-function getNodeSelector (el, win) {
+// TODO: Fix Type
+function getNodeSelector (el: any, win: Window): string {
   const parts = [el.tagName]
   if (el.id) parts.push('#' + el.id)
   if (el.className && el.className.length) parts.push(`.${el.className.split(' ').join('.')}`)
diff --git a/packages/plugin-interaction-breadcrumbs/test/interaction-breadcrumbs.test.ts b/packages/plugin-interaction-breadcrumbs/test/interaction-breadcrumbs.test.ts
index e2c198dec5..8ce1f00285 100644
--- a/packages/plugin-interaction-breadcrumbs/test/interaction-breadcrumbs.test.ts
+++ b/packages/plugin-interaction-breadcrumbs/test/interaction-breadcrumbs.test.ts
@@ -1,4 +1,4 @@
-import plugin from '../'
+import plugin from '../src/interaction-breadcrumbs'
 
 import Client from '@bugsnag/core/client'
 import Breadcrumb from '@bugsnag/core/breadcrumb'
diff --git a/packages/plugin-interaction-breadcrumbs/tsconfig.json b/packages/plugin-interaction-breadcrumbs/tsconfig.json
new file mode 100644
index 0000000000..09758ceb4c
--- /dev/null
+++ b/packages/plugin-interaction-breadcrumbs/tsconfig.json
@@ -0,0 +1,5 @@
+{
+    "extends": "../../tsconfig.json",
+    "include": ["src/**/*.ts"]
+}
+  
\ No newline at end of file
diff --git a/packages/plugin-navigation-breadcrumbs/package.json b/packages/plugin-navigation-breadcrumbs/package.json
index 29d32cf7e9..2561c83511 100644
--- a/packages/plugin-navigation-breadcrumbs/package.json
+++ b/packages/plugin-navigation-breadcrumbs/package.json
@@ -1,7 +1,15 @@
 {
   "name": "@bugsnag/plugin-navigation-breadcrumbs",
   "version": "8.1.1",
-  "main": "navigation-breadcrumbs.js",
+  "main": "dist/navigation-breadcrumbs.js",
+  "types": "dist/types/navigation-breadcrumbs.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/types/navigation-breadcrumbs.d.ts",
+      "default": "./dist/navigation-breadcrumbs.js",
+      "import": "./dist/navigation-breadcrumbs.mjs"
+    }
+  },
   "description": "@bugsnag/js plugin to record browser navigation as breadcrumbs",
   "homepage": "https://www.bugsnag.com/",
   "repository": {
@@ -14,6 +22,11 @@
   "files": [
     "*.js"
   ],
+  "scripts": {
+    "build": "npm run build:npm",
+    "build:npm": "rollup --config rollup.config.npm.mjs",
+    "clean": "rm -rf dist/*"
+  },
   "author": "Bugsnag",
   "license": "MIT",
   "devDependencies": {
diff --git a/packages/plugin-navigation-breadcrumbs/rollup.config.npm.mjs b/packages/plugin-navigation-breadcrumbs/rollup.config.npm.mjs
new file mode 100644
index 0000000000..e74dd35c57
--- /dev/null
+++ b/packages/plugin-navigation-breadcrumbs/rollup.config.npm.mjs
@@ -0,0 +1,5 @@
+import createRollupConfig from '../../.rollup/index.mjs'
+
+export default createRollupConfig({
+    input: 'src/navigation-breadcrumbs.ts'
+})
diff --git a/packages/plugin-navigation-breadcrumbs/navigation-breadcrumbs.js b/packages/plugin-navigation-breadcrumbs/src/navigation-breadcrumbs.ts
similarity index 59%
rename from packages/plugin-navigation-breadcrumbs/navigation-breadcrumbs.js
rename to packages/plugin-navigation-breadcrumbs/src/navigation-breadcrumbs.ts
index 873215dd83..10559b8053 100644
--- a/packages/plugin-navigation-breadcrumbs/navigation-breadcrumbs.js
+++ b/packages/plugin-navigation-breadcrumbs/src/navigation-breadcrumbs.ts
@@ -1,14 +1,29 @@
+import { Client, Plugin } from 'packages/core/types'
+
+interface PluginClient extends Client {
+  _isBreadcrumbTypeEnabled: (type: string) => boolean
+}
+
+type ExtendedHistory = History & {
+  replaceState: History['replaceState'] & { _restore?: () => void }
+  pushState: History['pushState'] & { _restore?: () => void }
+}
+
+type ExtendedWindow = Window & {
+  history: ExtendedHistory
+}
+
 /*
 * Leaves breadcrumbs when navigation methods are called or events are emitted
 */
-module.exports = (win = window) => {
-  const plugin = {
+export default (win = window): Plugin => {
+  const plugin: Plugin = {
     load: (client) => {
       if (!('addEventListener' in win)) return
-      if (!client._isBreadcrumbTypeEnabled('navigation')) return
+      if (!(client as PluginClient)._isBreadcrumbTypeEnabled('navigation')) return
 
       // returns a function that will drop a breadcrumb with a given name
-      const drop = name => () => client.leaveBreadcrumb(name, {}, 'navigation')
+      const drop = (name: string) => () => client.leaveBreadcrumb(name, {}, 'navigation')
 
       // simple drops – just names, no meta
       win.addEventListener('pagehide', drop('Page hidden'), true)
@@ -27,15 +42,15 @@ module.exports = (win = window) => {
       }, true)
 
       // the only way to know about replaceState/pushState is to wrap them… >_<
-      if (win.history.pushState) wrapHistoryFn(client, win.history, 'pushState', win, true)
-      if (win.history.replaceState) wrapHistoryFn(client, win.history, 'replaceState', win)
+      if (typeof win.history.pushState === 'function') wrapHistoryFn(client, win.history, 'pushState', win, true)
+      if (typeof win.history.replaceState === 'function') wrapHistoryFn(client, win.history, 'replaceState', win)
     }
   }
 
   if (process.env.NODE_ENV !== 'production') {
-    plugin.destroy = (win = window) => {
-      win.history.replaceState._restore()
-      win.history.pushState._restore()
+    plugin.destroy = (win: ExtendedWindow = window) => {
+      if (win.history.replaceState._restore) win.history.replaceState._restore()
+      if (win.history.pushState._restore) win.history.pushState._restore()
     }
   }
 
@@ -43,26 +58,27 @@ module.exports = (win = window) => {
 }
 
 if (process.env.NODE_ENV !== 'production') {
-  exports.destroy = (win = window) => {
-    win.history.replaceState._restore()
-    win.history.pushState._restore()
+  exports.destroy = (win: ExtendedWindow = window) => {
+    if (win.history.replaceState._restore) win.history.replaceState._restore()
+    if (win.history.pushState._restore) win.history.pushState._restore()
   }
 }
 
 // takes a full url like http://foo.com:1234/pages/01.html?yes=no#section-2 and returns
 // just the path and hash parts, e.g. /pages/01.html?yes=no#section-2
-const relativeLocation = (url, win) => {
-  const a = win.document.createElement('A')
+const relativeLocation = (url: string, win: Window) => {
+  const a = win.document.createElement('a')
   a.href = url
   return `${a.pathname}${a.search}${a.hash}`
 }
 
-const stateChangeToMetadata = (win, state, title, url) => {
+const stateChangeToMetadata = (win: Window, state: string, title: string, url?: string | URL | null) => {
   const currentPath = relativeLocation(win.location.href, win)
   return { title, state, prevState: getCurrentState(win), to: url || currentPath, from: currentPath }
 }
 
-const wrapHistoryFn = (client, target, fn, win, resetEventCount = false) => {
+type HistoryMethods = 'pushState' | 'replaceState'
+const wrapHistoryFn = (client: Client, target: ExtendedHistory, fn: HistoryMethods, win: Window, resetEventCount = false) => {
   const orig = target[fn]
   target[fn] = (state, title, url) => {
     client.leaveBreadcrumb(`History ${fn}`, stateChangeToMetadata(win, state, title, url), 'navigation')
@@ -70,14 +86,14 @@ const wrapHistoryFn = (client, target, fn, win, resetEventCount = false) => {
     if (resetEventCount && typeof client.resetEventCount === 'function') client.resetEventCount()
     // Internet Explorer will convert `undefined` to a string when passed, causing an unintended redirect
     // to '/undefined'. therefore we only pass the url if it's not undefined.
-    orig.apply(target, [state, title].concat(url !== undefined ? url : []))
+    orig.apply(target, [state, title].concat(url !== undefined ? url : []) as Parameters<History[HistoryMethods]>)
   }
   if (process.env.NODE_ENV !== 'production') {
     target[fn]._restore = () => { target[fn] = orig }
   }
 }
 
-const getCurrentState = (win) => {
+const getCurrentState = (win: Window) => {
   try {
     return win.history.state
   } catch (e) {}
diff --git a/packages/plugin-navigation-breadcrumbs/test/navigation-breadcrumbs.test.ts b/packages/plugin-navigation-breadcrumbs/test/navigation-breadcrumbs.test.ts
index 1b05070d53..0d2c34b9de 100644
--- a/packages/plugin-navigation-breadcrumbs/test/navigation-breadcrumbs.test.ts
+++ b/packages/plugin-navigation-breadcrumbs/test/navigation-breadcrumbs.test.ts
@@ -1,4 +1,4 @@
-import plugin from '../navigation-breadcrumbs'
+import plugin from '../src/navigation-breadcrumbs'
 
 import Client from '@bugsnag/core/client'
 
diff --git a/packages/plugin-navigation-breadcrumbs/tsconfig.json b/packages/plugin-navigation-breadcrumbs/tsconfig.json
new file mode 100644
index 0000000000..a4cc3029ff
--- /dev/null
+++ b/packages/plugin-navigation-breadcrumbs/tsconfig.json
@@ -0,0 +1,8 @@
+{
+    "extends": "../../tsconfig.json",
+    "include": ["src/**/*.ts"],
+    "compilerOptions": {
+        "types": ["node"]
+    }
+}
+  
\ No newline at end of file
diff --git a/packages/plugin-simple-throttle/rollup.config.npm.mjs b/packages/plugin-simple-throttle/rollup.config.npm.mjs
index 17c25ef1a6..bb2a0d724e 100644
--- a/packages/plugin-simple-throttle/rollup.config.npm.mjs
+++ b/packages/plugin-simple-throttle/rollup.config.npm.mjs
@@ -1,5 +1,6 @@
-import createRollupConfig from "../../.rollup/index.mjs";
+import createRollupConfig from '../../.rollup/index.mjs'
 
 export default createRollupConfig({
-  input: "src/throttle.ts"
-});
+    input: 'src/throttle.ts',
+    external: ['@bugsnag/core/lib/validators/int-range']
+})
diff --git a/packages/plugin-simple-throttle/src/throttle.ts b/packages/plugin-simple-throttle/src/throttle.ts
index b2aa3e3b81..234f9102b9 100644
--- a/packages/plugin-simple-throttle/src/throttle.ts
+++ b/packages/plugin-simple-throttle/src/throttle.ts
@@ -1,10 +1,26 @@
-import { Plugin } from '@bugsnag/core'
 import intRange from '@bugsnag/core/lib/validators/int-range'
+import { Client, Config, Logger, Plugin } from '@bugsnag/core'
+
+interface ThrottlePlugin extends Plugin {
+  configSchema: {
+    [key: string]: {
+      defaultValue: () => unknown
+      message: string
+      validate: (value: unknown) => boolean
+    }
+  }
+}
+
+interface InternalClient extends Client {
+  _config: Config & { maxEvents: number }
+  _logger: Logger
+}
+
 /*
  * Throttles and dedupes events
  */
 
-const plugin: Plugin = {
+const plugin: ThrottlePlugin = {
   load: (client) => {
     // track sent events for each init of the plugin
     let n = 0
@@ -12,10 +28,8 @@ const plugin: Plugin = {
     // add onError hook
     client.addOnError((event) => {
       // have max events been sent already?
-      // @ts-expect-error _config is private API
-      if (n >= client._config.maxEvents) {
-        // @ts-expect-error _config is private API
-        client._logger.warn(`Cancelling event send due to maxEvents per session limit of ${client._config.maxEvents} being reached`)
+      if (n >= (client as InternalClient)._config.maxEvents) {
+        (client as InternalClient)._logger.warn(`Cancelling event send due to maxEvents per session limit of ${(client as InternalClient)._config.maxEvents} being reached`)
         return false
       }
       n++
@@ -23,7 +37,6 @@ const plugin: Plugin = {
 
     client.resetEventCount = () => { n = 0 }
   },
-  // @ts-expect-error _config is private API
   configSchema: {
     maxEvents: {
       defaultValue: () => 10,