diff --git a/.babelrc b/.babelrc
index a541d8d01..6f4f54a93 100644
--- a/.babelrc
+++ b/.babelrc
@@ -1,11 +1,9 @@
 {
+    "sourceMaps": true,
     "presets": [
         ["@babel/preset-env", {
             "targets": {
-                "browsers": [
-                    "last 2 versions"
-                ],
-                "node": 12
+                "node": 10
             },
             "modules": "commonjs"
         }],
diff --git a/.buildkite/pipeline.yaml b/.buildkite/pipeline.yaml
index db885300a..4b2f319c8 100644
--- a/.buildkite/pipeline.yaml
+++ b/.buildkite/pipeline.yaml
@@ -1,11 +1,35 @@
 steps:
-  - label: ":eslint: Lint"
+  - label: ":eslint: JS Lint"
     command:
       - "yarn install"
-      - "yarn lint"
+      - "yarn lint:js"
     plugins:
       - docker#v3.0.1:
-          image: "node:10"
+          image: "node:12"
+
+  - label: ":tslint: TS Lint"
+    command:
+      - "yarn install"
+      - "yarn lint:ts"
+    plugins:
+      - docker#v3.0.1:
+          image: "node:12"
+
+  - label: ":typescript: Types Lint"
+    command:
+      - "yarn install"
+      - "yarn lint:types"
+    plugins:
+      - docker#v3.0.1:
+          image: "node:12"
+
+  - label: "🛠 Build"
+    command:
+      - "yarn install"
+      - "yarn build"
+    plugins:
+      - docker#v3.0.1:
+          image: "node:12"
 
   - label: ":jest: Tests"
     command:
@@ -13,7 +37,7 @@ steps:
       - "yarn test"
     plugins:
       - docker#v3.0.1:
-          image: "node:10"
+          image: "node:12"
 
   - label: "📃 Docs"
     command:
@@ -21,7 +45,7 @@ steps:
       - "yarn gendoc"
     plugins:
       - docker#v3.0.1:
-          image: "node:10"
+          image: "node:12"
 
   - wait
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 73e8a523c..27d834bb7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,61 @@
+Changes in [3.0.0](https://github.com/matrix-org/matrix-js-sdk/releases/tag/v3.0.0) (2020-01-13)
+================================================================================================
+[Full Changelog](https://github.com/matrix-org/matrix-js-sdk/compare/v3.0.0-rc.1...v3.0.0)
+
+ * No changes from rc.1
+
+Changes in [3.0.0-rc.1](https://github.com/matrix-org/matrix-js-sdk/releases/tag/v3.0.0-rc.1) (2020-01-06)
+==========================================================================================================
+[Full Changelog](https://github.com/matrix-org/matrix-js-sdk/compare/v2.4.6...v3.0.0-rc.1)
+
+BREAKING CHANGES
+================
+ * matrix-js-sdk no longer uses bluebird promises, so promises returned
+   by the js-sdk no longer support the done() method. Code that calls
+   done() on promises returned by the js-sdk will break and will need
+   to be updated to remove the done() call.
+
+All Changes
+===========
+ * Make displayName disambiguation more fuzzy especially against RTL/LTR
+   content
+   [\#1141](https://github.com/matrix-org/matrix-js-sdk/pull/1141)
+ * stop trying to resend event if we get M_TOO_LARGE
+   [\#1129](https://github.com/matrix-org/matrix-js-sdk/pull/1129)
+ * Fix creating a key backup with cross signing diabled
+   [\#1139](https://github.com/matrix-org/matrix-js-sdk/pull/1139)
+ * Use checkDeviceTrust with key backup
+   [\#1138](https://github.com/matrix-org/matrix-js-sdk/pull/1138)
+ * Add support for passthrough SSSS secrets
+   [\#1128](https://github.com/matrix-org/matrix-js-sdk/pull/1128)
+ * Add support for key backups using secret storage
+   [\#1118](https://github.com/matrix-org/matrix-js-sdk/pull/1118)
+ * Remove unused user verification event
+   [\#1117](https://github.com/matrix-org/matrix-js-sdk/pull/1117)
+ * Fix check for private keys
+   [\#1116](https://github.com/matrix-org/matrix-js-sdk/pull/1116)
+ * Restore watching mode for `start:watch`
+   [\#1115](https://github.com/matrix-org/matrix-js-sdk/pull/1115)
+ * Add secret storage bootstrap flow
+   [\#1079](https://github.com/matrix-org/matrix-js-sdk/pull/1079)
+ * Part 1 of many: Upgrade to babel@7 and TypeScript
+   [\#1112](https://github.com/matrix-org/matrix-js-sdk/pull/1112)
+ * Remove Bluebird: phase 2.5
+   [\#1100](https://github.com/matrix-org/matrix-js-sdk/pull/1100)
+ * Remove Bluebird: phase 3
+   [\#1088](https://github.com/matrix-org/matrix-js-sdk/pull/1088)
+ * ignore m.key.verification.done messages when we don't expect any more
+   messages
+   [\#1104](https://github.com/matrix-org/matrix-js-sdk/pull/1104)
+ * dont cancel on remote echo of own .request event
+   [\#1111](https://github.com/matrix-org/matrix-js-sdk/pull/1111)
+ * Refactor verification request code
+   [\#1109](https://github.com/matrix-org/matrix-js-sdk/pull/1109)
+ * Fix device list's cross-signing storage path
+   [\#1105](https://github.com/matrix-org/matrix-js-sdk/pull/1105)
+ * yarn upgrade
+   [\#1103](https://github.com/matrix-org/matrix-js-sdk/pull/1103)
+
 Changes in [2.4.6](https://github.com/matrix-org/matrix-js-sdk/releases/tag/v2.4.6) (2019-12-09)
 ================================================================================================
 [Full Changelog](https://github.com/matrix-org/matrix-js-sdk/compare/v2.4.6-rc.1...v2.4.6)
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index b4b7f67f1..d8ce41f99 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -36,8 +36,16 @@ minutes.
 Code style
 ~~~~~~~~~~
 
-The code-style for matrix-js-sdk is not formally documented, but contributors
-are encouraged to read the code style document for matrix-react-sdk
+The js-sdk aims to target TypeScript/ES6. All new files should be written in
+TypeScript and existing files should use ES6 principles where possible.
+
+Members should not be exported as a default export in general - it causes problems
+with the architecture of the SDK (index file becomes less clear) and could
+introduce naming problems (as default exports get aliased upon import). In
+general, avoid using `export default`.
+
+The remaining code-style for matrix-js-sdk is not formally documented, but
+contributors are encouraged to read the code style document for matrix-react-sdk
 (`<https://github.com/matrix-org/matrix-react-sdk/blob/master/code_style.md>`_)
 and follow the principles set out there.
 
diff --git a/README.md b/README.md
index f9f6029cb..c252447c4 100644
--- a/README.md
+++ b/README.md
@@ -9,12 +9,16 @@ Quickstart
 
 In a browser
 ------------
-Download either the full or minified version from
+Download the browser version from
 https://github.com/matrix-org/matrix-js-sdk/releases/latest and add that as a
 ``<script>`` to your page. There will be a global variable ``matrixcs``
 attached to ``window`` through which you can access the SDK. See below for how to
 include libolm to enable end-to-end-encryption.
 
+The browser bundle supports recent versions of browsers. Typically this is ES2015
+or `> 0.5%, last 2 versions, Firefox ESR, not dead` if using 
+[browserlists](https://github.com/browserslist/browserslist).
+
 Please check [the working browser example](examples/browser) for more information.
 
 In Node.js
@@ -22,13 +26,18 @@ In Node.js
 
 Ensure you have the latest LTS version of Node.js installed.
 
-Using `yarn` instead of `npm` is recommended. Please see the Yarn [install guide](https://yarnpkg.com/docs/install/) if you do not have it already.
+This SDK targets Node 10 for compatibility, which translates to ES6. If you're using
+a bundler like webpack you'll likely have to transpile dependencies, including this
+SDK, to match your target browsers.
+
+Using `yarn` instead of `npm` is recommended. Please see the Yarn [install guide](https://yarnpkg.com/docs/install/) 
+if you do not have it already.
 
 ``yarn add matrix-js-sdk``
 
 ```javascript
-  var sdk = require("matrix-js-sdk");
-  var client = sdk.createClient("https://matrix.org");
+  import * as sdk from "matrix-js-sdk";
+  const client = sdk.createClient("https://matrix.org");
   client.publicRooms(function(err, data) {
     console.log("Public Rooms: %s", JSON.stringify(data));
   });
@@ -59,7 +68,7 @@ client.once('sync', function(state, prevState, res) {
 To send a message:
 
 ```javascript
-var content = {
+const content = {
     "body": "message text",
     "msgtype": "m.text"
 };
@@ -191,10 +200,10 @@ This section provides some useful code snippets which demonstrate the
 core functionality of the SDK. These examples assume the SDK is setup like this:
 
 ```javascript
-   var sdk = require("matrix-js-sdk");
-   var myUserId = "@example:localhost";
-   var myAccessToken = "QGV4YW1wbGU6bG9jYWxob3N0.qPEvLuYfNBjxikiCjP";
-   var matrixClient = sdk.createClient({
+   import * as sdk from "matrix-js-sdk";
+   const myUserId = "@example:localhost";
+   const myAccessToken = "QGV4YW1wbGU6bG9jYWxob3N0.qPEvLuYfNBjxikiCjP";
+   const matrixClient = sdk.createClient({
        baseUrl: "http://localhost:8008",
        accessToken: myAccessToken,
        userId: myUserId
@@ -247,11 +256,11 @@ Output:
 
 ```javascript
    matrixClient.on("RoomState.members", function(event, state, member) {
-       var room = matrixClient.getRoom(state.roomId);
+       const room = matrixClient.getRoom(state.roomId);
        if (!room) {
            return;
        }
-       var memberList = state.getMembers();
+       const memberList = state.getMembers();
        console.log(room.name);
        console.log(Array(room.name.length + 1).join("="));  // underline
        for (var i = 0; i < memberList.length; i++) {
@@ -351,11 +360,6 @@ To build a browser version from scratch when developing::
  $ yarn build
 ```
 
-To constantly do builds when files are modified (using ``watchify``)::
-```
- $ yarn watch
-```
-
 To run tests (Jasmine)::
 ```
  $ yarn test
diff --git a/browser-index.js b/browser-index.js
deleted file mode 100644
index cc7e50fe8..000000000
--- a/browser-index.js
+++ /dev/null
@@ -1,35 +0,0 @@
-var matrixcs = require("./lib/matrix");
-const request = require('browser-request');
-const queryString = require('qs');
-
-matrixcs.request(function(opts, fn) {
-    // We manually fix the query string for browser-request because
-    // it doesn't correctly handle cases like ?via=one&via=two. Instead
-    // we mimic `request`'s query string interface to make it all work
-    // as expected.
-    // browser-request will happily take the constructed string as the
-    // query string without trying to modify it further.
-    opts.qs = queryString.stringify(opts.qs || {}, opts.qsStringifyOptions);
-    return request(opts, fn);
-});
-
-// just *accessing* indexedDB throws an exception in firefox with
-// indexeddb disabled.
-var indexedDB;
-try {
-    indexedDB = global.indexedDB;
-} catch(e) {}
-
-// if our browser (appears to) support indexeddb, use an indexeddb crypto store.
-if (indexedDB) {
-    matrixcs.setCryptoStoreFactory(
-        function() {
-            return new matrixcs.IndexedDBCryptoStore(
-                indexedDB, "matrix-js-sdk:crypto"
-            );
-        }
-    );
-}
-
-module.exports = matrixcs; // keep export for browserify package deps
-global.matrixcs = matrixcs;
diff --git a/examples/browser/browserTest.js b/examples/browser/browserTest.js
index 8f03b9c4b..2698877fd 100644
--- a/examples/browser/browserTest.js
+++ b/examples/browser/browserTest.js
@@ -1,4 +1,3 @@
-"use strict";
 console.log("Loading browser sdk");
 
 var client = matrixcs.createClient("http://matrix.org");
diff --git a/examples/node/app.js b/examples/node/app.js
index 688b2a070..46220a065 100644
--- a/examples/node/app.js
+++ b/examples/node/app.js
@@ -1,5 +1,3 @@
-"use strict";
-
 var myUserId = "@example:localhost";
 var myAccessToken = "QGV4YW1wbGU6bG9jYWxob3N0.qPEvLuYfNBjxikiCjP";
 var sdk = require("matrix-js-sdk");
diff --git a/examples/voip/browserTest.js b/examples/voip/browserTest.js
index a2f15888a..01f463421 100644
--- a/examples/voip/browserTest.js
+++ b/examples/voip/browserTest.js
@@ -1,4 +1,3 @@
-"use strict";
 console.log("Loading browser sdk");
 var BASE_URL = "https://matrix.org";
 var TOKEN = "accesstokengoeshere";
diff --git a/index.js b/index.js
deleted file mode 100644
index 35845b1f7..000000000
--- a/index.js
+++ /dev/null
@@ -1,6 +0,0 @@
-var matrixcs = require("./lib/matrix");
-matrixcs.request(require("request"));
-module.exports = matrixcs;
-
-var utils = require("./lib/utils");
-utils.runPolyfills();
diff --git a/package.json b/package.json
index 1da6adf08..2f5fc7604 100644
--- a/package.json
+++ b/package.json
@@ -1,21 +1,23 @@
 {
   "name": "matrix-js-sdk",
-  "version": "2.4.6",
+  "version": "3.0.0",
   "description": "Matrix Client-Server SDK for Javascript",
-  "main": "index.js",
   "scripts": {
-    "test:watch": "jest spec/ --coverage --testEnvironment node --watch",
-    "test": "jest spec/ --coverage --testEnvironment node",
-    "gendoc": "jsdoc -c jsdoc.json -P package.json",
-    "start": "yarn start:init && yarn start:watch",
-    "start:watch": "babel src -s -w --skip-initial-build -d lib --verbose --extensions \".ts,.js\"",
-    "start:init": "babel src -s -d lib --verbose --extensions \".ts,.js\"",
+    "start": "echo THIS IS FOR LEGACY PURPOSES ONLY. && babel src -w -s -d lib --verbose --extensions \".ts,.js\"",
+    "dist": "echo 'This is for the release script so it can make assets (browser bundle).' && yarn build",
     "clean": "rimraf lib dist",
-    "build": "babel src -s -d lib --verbose --extensions \".ts,.js\" && rimraf dist && mkdir dist && browserify -d browser-index.js | exorcist dist/browser-matrix.js.map > dist/browser-matrix.js && terser -c -m -o dist/browser-matrix.min.js --source-map \"content='dist/browser-matrix.js.map'\" dist/browser-matrix.js",
-    "dist": "yarn build",
-    "watch": "watchify -d browser-index.js -o 'exorcist dist/browser-matrix.js.map > dist/browser-matrix.js' -v",
-    "lint": "eslint --max-warnings 93 src spec",
-    "prepare": "yarn clean && yarn build && git rev-parse HEAD > git-revision.txt"
+    "build": "yarn clean && git rev-parse HEAD > git-revision.txt && yarn build:compile && yarn build:compile-browser && yarn build:minify-browser && yarn build:types",
+    "build:types": "tsc --emitDeclarationOnly",
+    "build:compile": "babel -d lib --verbose --extensions \".ts,.js\" src",
+    "build:compile-browser": "mkdirp dist && browserify -d src/browser-index.js -p [ tsify -p ./tsconfig.json ] -t [ babelify --sourceMaps=inline --presets [ @babel/preset-env @babel/preset-typescript ] ] | exorcist dist/browser-matrix.js.map > dist/browser-matrix.js",
+    "build:minify-browser": "terser dist/browser-matrix.js --compress --mangle --source-map --output dist/browser-matrix.min.js",
+    "gendoc": "jsdoc -c jsdoc.json -P package.json",
+    "lint": "yarn lint:types && yarn lint:ts && yarn lint:js",
+    "lint:js": "eslint --max-warnings 93 src spec",
+    "lint:types": "tsc --noEmit",
+    "lint:ts": "tslint --project ./tsconfig.json -t stylish",
+    "test": "jest spec/ --coverage --testEnvironment node",
+    "test:watch": "jest spec/ --coverage --testEnvironment node --watch"
   },
   "repository": {
     "type": "git",
@@ -24,28 +26,23 @@
   "keywords": [
     "matrix-org"
   ],
-  "browser": "browser-index.js",
+  "main": "./lib/index.js",
+  "typings": "./lib/index.d.ts",
+  "browser": "./lib/browser-index.js",
+  "matrix_src_main": "./src/index.ts",
+  "matrix_src_browser": "./src/browser-index.js",
   "author": "matrix.org",
   "license": "Apache-2.0",
   "files": [
-    ".babelrc",
-    ".eslintrc.js",
-    "spec/.eslintrc.js",
+    "lib",
+    "src",
+    "git-revision.txt",
     "CHANGELOG.md",
     "CONTRIBUTING.rst",
     "LICENSE",
     "README.md",
-    "RELEASING.md",
-    "examples",
-    "git-hooks",
-    "git-revision.txt",
-    "index.js",
-    "browser-index.js",
-    "lib",
     "package.json",
-    "release.sh",
-    "spec",
-    "src"
+    "release.sh"
   ],
   "dependencies": {
     "another-json": "^0.2.0",
@@ -69,11 +66,12 @@
     "@babel/preset-typescript": "^7.7.4",
     "@babel/register": "^7.7.4",
     "@babel/runtime": "^7.7.6",
+    "@types/node": "12",
     "babel-eslint": "^10.0.3",
     "babel-jest": "^24.9.0",
+    "babelify": "^10.0.0",
     "better-docs": "^1.4.7",
-    "browserify": "^16.2.3",
-    "browserify-shim": "^3.8.13",
+    "browserify": "^16.5.0",
     "eslint": "^5.12.0",
     "eslint-config-google": "^0.7.1",
     "eslint-plugin-babel": "^5.3.0",
@@ -84,15 +82,12 @@
     "matrix-mock-request": "^1.2.3",
     "olm": "https://packages.matrix.org/npm/olm/olm-3.1.4.tgz",
     "rimraf": "^3.0.0",
-    "source-map-support": "^0.5.13",
-    "sourceify": "^1.0.0",
-    "terser": "^4.3.8",
-    "typescript": "^3.7.3",
-    "watchify": "^3.11.1"
+    "terser": "^4.4.3",
+    "tsify": "^4.0.1",
+    "tslint": "^5.20.1",
+    "typescript": "^3.7.3"
   },
-  "browserify": {
-    "transform": [
-      "sourceify"
-    ]
+  "jest": {
+    "testEnvironment": "node"
   }
 }
diff --git a/release.sh b/release.sh
index 702e88cc3..7fe462c78 100755
--- a/release.sh
+++ b/release.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Script to perform a release of matrix-js-sdk.
+# Script to perform a release of matrix-js-sdk and downstream projects.
 #
 # Requires:
 #   github-changelog-generator; install via:
@@ -9,6 +9,8 @@
 #   hub; install via brew (macOS) or source/pre-compiled binaries (debian) (https://github.com/github/hub) - Tested on v2.2.9
 #   npm; typically installed by Node.js
 #   yarn; install via brew (macOS) or similar (https://yarnpkg.com/docs/install/)
+#
+# Note: this script is also used to release matrix-react-sdk and riot-web.
 
 set -e
 
diff --git a/spec/MockStorageApi.js b/spec/MockStorageApi.js
index 1063ad3db..d985fe0cf 100644
--- a/spec/MockStorageApi.js
+++ b/spec/MockStorageApi.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -18,7 +19,7 @@ limitations under the License.
  * A mock implementation of the webstorage api
  * @constructor
  */
-function MockStorageApi() {
+export function MockStorageApi() {
     this.data = {};
     this.keys = [];
     this.length = 0;
@@ -52,5 +53,3 @@ MockStorageApi.prototype = {
     },
 };
 
-/** */
-module.exports = MockStorageApi;
diff --git a/spec/TestClient.js b/spec/TestClient.js
index 1663847d2..29b443f4a 100644
--- a/spec/TestClient.js
+++ b/spec/TestClient.js
@@ -16,16 +16,16 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-"use strict";
-
 // load olm before the sdk if possible
 import './olm-loader';
 
-import sdk from '..';
-import testUtils from './test-utils';
 import MockHttpBackend from 'matrix-mock-request';
-import LocalStorageCryptoStore from '../lib/crypto/store/localStorage-crypto-store';
-import logger from '../lib/logger';
+import {LocalStorageCryptoStore} from '../src/crypto/store/localStorage-crypto-store';
+import {logger} from '../src/logger';
+import {WebStorageSessionStore} from "../src/store/session/webstorage";
+import {syncPromise} from "./test-utils";
+import {createClient} from "../src/matrix";
+import {MockStorageApi} from "./MockStorageApi";
 
 /**
  * Wrapper for a MockStorageApi, MockHttpBackend and MatrixClient
@@ -39,16 +39,16 @@ import logger from '../lib/logger';
  *     session store. If undefined, we will create a MockStorageApi.
  * @param {object} options additional options to pass to the client
  */
-export default function TestClient(
+export function TestClient(
     userId, deviceId, accessToken, sessionStoreBackend, options,
 ) {
     this.userId = userId;
     this.deviceId = deviceId;
 
     if (sessionStoreBackend === undefined) {
-        sessionStoreBackend = new testUtils.MockStorageApi();
+        sessionStoreBackend = new MockStorageApi();
     }
-    const sessionStore = new sdk.WebStorageSessionStore(sessionStoreBackend);
+    const sessionStore = new WebStorageSessionStore(sessionStoreBackend);
 
     this.httpBackend = new MockHttpBackend();
 
@@ -65,7 +65,7 @@ export default function TestClient(
         this.cryptoStore = new LocalStorageCryptoStore(sessionStoreBackend);
         options.cryptoStore = this.cryptoStore;
     }
-    this.client = sdk.createClient(options);
+    this.client = createClient(options);
 
     this.deviceKeys = null;
     this.oneTimeKeys = {};
@@ -97,7 +97,7 @@ TestClient.prototype.start = function() {
 
     return Promise.all([
         this.httpBackend.flushAllExpected(),
-        testUtils.syncPromise(this.client),
+        syncPromise(this.client),
     ]).then(() => {
         logger.log(this + ': started');
     });
@@ -225,7 +225,7 @@ TestClient.prototype.flushSync = function() {
     logger.log(`${this}: flushSync`);
     return Promise.all([
         this.httpBackend.flush('/sync', 1),
-        testUtils.syncPromise(this.client),
+        syncPromise(this.client),
     ]).then(() => {
         logger.log(`${this}: flushSync completed`);
     });
diff --git a/spec/integ/devicelist-integ-spec.js b/spec/integ/devicelist-integ-spec.js
index 52c906625..039d541ff 100644
--- a/spec/integ/devicelist-integ-spec.js
+++ b/spec/integ/devicelist-integ-spec.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,9 +16,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import TestClient from '../TestClient';
-import testUtils from '../test-utils';
-import logger from '../../lib/logger';
+import {TestClient} from '../TestClient';
+import * as testUtils from '../test-utils';
+import {logger} from '../../src/logger';
 
 const ROOM_ID = "!room:id";
 
diff --git a/spec/integ/matrix-client-crypto.spec.js b/spec/integ/matrix-client-crypto.spec.js
index 1e3471b64..8fe97ff21 100644
--- a/spec/integ/matrix-client-crypto.spec.js
+++ b/spec/integ/matrix-client-crypto.spec.js
@@ -2,6 +2,7 @@
 Copyright 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -24,17 +25,14 @@ limitations under the License.
  * See also `megolm.spec.js`.
  */
 
-"use strict";
-import 'source-map-support/register';
-
 // load olm before the sdk if possible
 import '../olm-loader';
 
-const sdk = require("../..");
-const utils = require("../../lib/utils");
-const testUtils = require("../test-utils");
-const TestClient = require('../TestClient').default;
-import logger from '../../lib/logger';
+import {logger} from '../../src/logger';
+import * as testUtils from "../test-utils";
+import * as utils from "../../src/utils";
+import {TestClient} from "../TestClient";
+import {CRYPTO_ENABLED} from "../../src/client";
 
 let aliTestClient;
 const roomId = "!room:localhost";
@@ -400,7 +398,7 @@ function firstSync(testClient) {
 
 
 describe("MatrixClient crypto", function() {
-    if (!sdk.CRYPTO_ENABLED) {
+    if (!CRYPTO_ENABLED) {
         return;
     }
 
diff --git a/spec/integ/matrix-client-event-emitter.spec.js b/spec/integ/matrix-client-event-emitter.spec.js
index 62381171e..b8f3b1868 100644
--- a/spec/integ/matrix-client-event-emitter.spec.js
+++ b/spec/integ/matrix-client-event-emitter.spec.js
@@ -1,24 +1,16 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const HttpBackend = require("matrix-mock-request");
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {TestClient} from "../TestClient";
 
 describe("MatrixClient events", function() {
-    const baseUrl = "http://localhost.or.something";
     let client;
     let httpBackend;
     const selfUserId = "@alice:localhost";
     const selfAccessToken = "aseukfgwef";
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
-        sdk.request(httpBackend.requestFn);
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: selfUserId,
-            accessToken: selfAccessToken,
-        });
+        const testClient = new TestClient(selfUserId, "DEVICE", selfAccessToken);
+        client = testClient.client;
+        httpBackend = testClient.httpBackend;
         httpBackend.when("GET", "/pushrules").respond(200, {});
         httpBackend.when("POST", "/filter").respond(200, { filter_id: "a filter id" });
     });
diff --git a/spec/integ/matrix-client-event-timeline.spec.js b/spec/integ/matrix-client-event-timeline.spec.js
index 7024e47c6..acaff0cee 100644
--- a/spec/integ/matrix-client-event-timeline.spec.js
+++ b/spec/integ/matrix-client-event-timeline.spec.js
@@ -1,12 +1,8 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const HttpBackend = require("matrix-mock-request");
-const utils = require("../test-utils");
-const EventTimeline = sdk.EventTimeline;
-import logger from '../../lib/logger';
+import * as utils from "../test-utils";
+import {EventTimeline} from "../../src/matrix";
+import {logger} from "../../src/logger";
+import {TestClient} from "../TestClient";
 
-const baseUrl = "http://localhost.or.something";
 const userId = "@alice:localhost";
 const userName = "Alice";
 const accessToken = "aseukfgwef";
@@ -103,8 +99,9 @@ describe("getEventTimeline support", function() {
     let client;
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
-        sdk.request(httpBackend.requestFn);
+        const testClient = new TestClient(userId, "DEVICE", accessToken);
+        client = testClient.client;
+        httpBackend = testClient.httpBackend;
     });
 
     afterEach(function() {
@@ -115,12 +112,6 @@ describe("getEventTimeline support", function() {
     });
 
     it("timeline support must be enabled to work", function() {
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            accessToken: accessToken,
-        });
-
         return startClient(httpBackend, client).then(function() {
             const room = client.getRoom(roomId);
             const timelineSet = room.getTimelineSets()[0];
@@ -131,12 +122,15 @@ describe("getEventTimeline support", function() {
     });
 
     it("timeline support works when enabled", function() {
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            accessToken: accessToken,
-            timelineSupport: true,
-        });
+        const testClient = new TestClient(
+            userId,
+            "DEVICE",
+            accessToken,
+            undefined,
+            {timelineSupport: true},
+        );
+        client = testClient.client;
+        httpBackend = testClient.httpBackend;
 
         return startClient(httpBackend, client).then(() => {
             const room = client.getRoom(roomId);
@@ -151,11 +145,7 @@ describe("getEventTimeline support", function() {
     it("scrollback should be able to scroll back to before a gappy /sync",
       function() {
         // need a client with timelineSupport disabled to make this work
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            accessToken: accessToken,
-        });
+
         let room;
 
         return startClient(httpBackend, client).then(function() {
@@ -223,15 +213,15 @@ describe("MatrixClient event timelines", function() {
     let httpBackend = null;
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
-        sdk.request(httpBackend.requestFn);
-
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            accessToken: accessToken,
-            timelineSupport: true,
-        });
+        const testClient = new TestClient(
+            userId,
+            "DEVICE",
+            accessToken,
+            undefined,
+            {timelineSupport: true},
+        );
+        client = testClient.client;
+        httpBackend = testClient.httpBackend;
 
         return startClient(httpBackend, client);
     });
diff --git a/spec/integ/matrix-client-methods.spec.js b/spec/integ/matrix-client-methods.spec.js
index 6b2a83df0..be241c912 100644
--- a/spec/integ/matrix-client-methods.spec.js
+++ b/spec/integ/matrix-client-methods.spec.js
@@ -1,39 +1,23 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const HttpBackend = require("matrix-mock-request");
-const publicGlobals = require("../../lib/matrix");
-const Room = publicGlobals.Room;
-const MemoryStore = publicGlobals.MemoryStore;
-const Filter = publicGlobals.Filter;
-const utils = require("../test-utils");
-const MockStorageApi = require("../MockStorageApi");
+import * as utils from "../test-utils";
+import {CRYPTO_ENABLED} from "../../src/client";
+import {Filter, MemoryStore, Room} from "../../src/matrix";
+import {TestClient} from "../TestClient";
 
 describe("MatrixClient", function() {
-    const baseUrl = "http://localhost.or.something";
     let client = null;
     let httpBackend = null;
     let store = null;
-    let sessionStore = null;
     const userId = "@alice:localhost";
     const accessToken = "aseukfgwef";
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
         store = new MemoryStore();
 
-        const mockStorage = new MockStorageApi();
-        sessionStore = new sdk.WebStorageSessionStore(mockStorage);
-
-        sdk.request(httpBackend.requestFn);
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            deviceId: "aliceDevice",
-            accessToken: accessToken,
+        const testClient = new TestClient(userId, "aliceDevice", accessToken, undefined, {
             store: store,
-            sessionStore: sessionStore,
         });
+        httpBackend = testClient.httpBackend;
+        client = testClient.client;
     });
 
     afterEach(function() {
@@ -303,7 +287,7 @@ describe("MatrixClient", function() {
 
 
     describe("downloadKeys", function() {
-        if (!sdk.CRYPTO_ENABLED) {
+        if (!CRYPTO_ENABLED) {
             return;
         }
 
diff --git a/spec/integ/matrix-client-opts.spec.js b/spec/integ/matrix-client-opts.spec.js
index f1a45effa..606674e4d 100644
--- a/spec/integ/matrix-client-opts.spec.js
+++ b/spec/integ/matrix-client-opts.spec.js
@@ -1,9 +1,8 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const MatrixClient = sdk.MatrixClient;
-const HttpBackend = require("matrix-mock-request");
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import HttpBackend from "matrix-mock-request";
+import {MatrixClient} from "../../src/matrix";
+import {MatrixScheduler} from "../../src/scheduler";
+import {MemoryStore} from "../../src/store/memory";
 
 describe("MatrixClient opts", function() {
     const baseUrl = "http://localhost.or.something";
@@ -71,7 +70,7 @@ describe("MatrixClient opts", function() {
                 baseUrl: baseUrl,
                 userId: userId,
                 accessToken: accessToken,
-                scheduler: new sdk.MatrixScheduler(),
+                scheduler: new MatrixScheduler(),
             });
         });
 
@@ -124,7 +123,7 @@ describe("MatrixClient opts", function() {
         beforeEach(function() {
             client = new MatrixClient({
                 request: httpBackend.requestFn,
-                store: new sdk.MemoryStore(),
+                store: new MemoryStore(),
                 baseUrl: baseUrl,
                 userId: userId,
                 accessToken: accessToken,
diff --git a/spec/integ/matrix-client-retrying.spec.js b/spec/integ/matrix-client-retrying.spec.js
index 949f153fc..fa13384c4 100644
--- a/spec/integ/matrix-client-retrying.spec.js
+++ b/spec/integ/matrix-client-retrying.spec.js
@@ -1,12 +1,9 @@
-"use strict";
-import 'source-map-support/register';
-
-const sdk = require("../..");
-const HttpBackend = require("matrix-mock-request");
-const EventStatus = sdk.EventStatus;
+import {EventStatus} from "../../src/matrix";
+import {MatrixScheduler} from "../../src/scheduler";
+import {Room} from "../../src/models/room";
+import {TestClient} from "../TestClient";
 
 describe("MatrixClient retrying", function() {
-    const baseUrl = "http://localhost.or.something";
     let client = null;
     let httpBackend = null;
     let scheduler;
@@ -16,16 +13,17 @@ describe("MatrixClient retrying", function() {
     let room;
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
-        sdk.request(httpBackend.requestFn);
-        scheduler = new sdk.MatrixScheduler();
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            accessToken: accessToken,
-            scheduler: scheduler,
-        });
-        room = new sdk.Room(roomId);
+        scheduler = new MatrixScheduler();
+        const testClient = new TestClient(
+            userId,
+            "DEVICE",
+            accessToken,
+            undefined,
+            {scheduler},
+        );
+        httpBackend = testClient.httpBackend;
+        client = testClient.client;
+        room = new Room(roomId);
         client.store.storeRoom(room);
     });
 
diff --git a/spec/integ/matrix-client-room-timeline.spec.js b/spec/integ/matrix-client-room-timeline.spec.js
index 20e0d8d84..b3de310a9 100644
--- a/spec/integ/matrix-client-room-timeline.spec.js
+++ b/spec/integ/matrix-client-room-timeline.spec.js
@@ -1,12 +1,9 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const EventStatus = sdk.EventStatus;
-const HttpBackend = require("matrix-mock-request");
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {EventStatus} from "../../src/models/event";
+import {TestClient} from "../TestClient";
+
 
 describe("MatrixClient room timelines", function() {
-    const baseUrl = "http://localhost.or.something";
     let client = null;
     let httpBackend = null;
     const userId = "@alice:localhost";
@@ -101,15 +98,17 @@ describe("MatrixClient room timelines", function() {
     }
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
-        sdk.request(httpBackend.requestFn);
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: userId,
-            accessToken: accessToken,
-            // these tests should work with or without timelineSupport
-            timelineSupport: true,
-        });
+        // these tests should work with or without timelineSupport
+        const testClient = new TestClient(
+            userId,
+            "DEVICE",
+            accessToken,
+            undefined,
+            {timelineSupport: true},
+        );
+        httpBackend = testClient.httpBackend;
+        client = testClient.client;
+
         setNextSyncData();
         httpBackend.when("GET", "/pushrules").respond(200, {});
         httpBackend.when("POST", "/filter").respond(200, { filter_id: "fid" });
diff --git a/spec/integ/matrix-client-syncing.spec.js b/spec/integ/matrix-client-syncing.spec.js
index 9e406ad50..adb6be965 100644
--- a/spec/integ/matrix-client-syncing.spec.js
+++ b/spec/integ/matrix-client-syncing.spec.js
@@ -1,13 +1,9 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const HttpBackend = require("matrix-mock-request");
-const utils = require("../test-utils");
-const MatrixEvent = sdk.MatrixEvent;
-const EventTimeline = sdk.EventTimeline;
+import {MatrixEvent} from "../../src/models/event";
+import {EventTimeline} from "../../src/models/event-timeline";
+import * as utils from "../test-utils";
+import {TestClient} from "../TestClient";
 
 describe("MatrixClient syncing", function() {
-    const baseUrl = "http://localhost.or.something";
     let client = null;
     let httpBackend = null;
     const selfUserId = "@alice:localhost";
@@ -20,13 +16,9 @@ describe("MatrixClient syncing", function() {
     const roomTwo = "!bar:localhost";
 
     beforeEach(function() {
-        httpBackend = new HttpBackend();
-        sdk.request(httpBackend.requestFn);
-        client = sdk.createClient({
-            baseUrl: baseUrl,
-            userId: selfUserId,
-            accessToken: selfAccessToken,
-        });
+        const testClient = new TestClient(selfUserId, "DEVICE", selfAccessToken);
+        httpBackend = testClient.httpBackend;
+        client = testClient.client;
         httpBackend.when("GET", "/pushrules").respond(200, {});
         httpBackend.when("POST", "/filter").respond(200, { filter_id: "a filter id" });
     });
diff --git a/spec/integ/megolm-integ.spec.js b/spec/integ/megolm-integ.spec.js
index 858568e94..0befd7a7c 100644
--- a/spec/integ/megolm-integ.spec.js
+++ b/spec/integ/megolm-integ.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,14 +15,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-"use strict";
-
-const anotherjson = require('another-json');
-
-const utils = require('../../lib/utils');
-const testUtils = require('../test-utils');
-const TestClient = require('../TestClient').default;
-import logger from '../../lib/logger';
+import anotherjson from "another-json";
+import * as utils from "../../src/utils";
+import * as testUtils from "../test-utils";
+import {TestClient} from "../TestClient";
+import {logger} from "../../src/logger";
 
 const ROOM_ID = "!room:id";
 
@@ -617,6 +615,9 @@ describe("megolm", function() {
             ).respond(200, {
                 event_id: '$event_id',
             });
+            aliceTestClient.httpBackend.when(
+                'PUT', '/sendToDevice/org.matrix.room_key.withheld/',
+            ).respond(200, {});
 
             return Promise.all([
                 aliceTestClient.client.sendTextMessage(ROOM_ID, 'test'),
@@ -714,6 +715,9 @@ describe("megolm", function() {
                     event_id: '$event_id',
                 };
             });
+            aliceTestClient.httpBackend.when(
+                'PUT', '/sendToDevice/org.matrix.room_key.withheld/',
+            ).respond(200, {});
 
             return Promise.all([
                 aliceTestClient.client.sendTextMessage(ROOM_ID, 'test2'),
diff --git a/spec/olm-loader.js b/spec/olm-loader.js
index 25ba6a5a5..b06ecdffc 100644
--- a/spec/olm-loader.js
+++ b/spec/olm-loader.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2017 Vector creations Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../lib/logger';
+import {logger} from '../src/logger';
 
 // try to load the olm library.
 try {
diff --git a/spec/test-utils.js b/spec/test-utils.js
index b18d10ae1..3ca1a5b9a 100644
--- a/spec/test-utils.js
+++ b/spec/test-utils.js
@@ -1,10 +1,8 @@
-"use strict";
 // load olm before the sdk if possible
 import './olm-loader';
 
-import logger from '../lib/logger';
-import sdk from '..';
-const MatrixEvent = sdk.MatrixEvent;
+import {logger} from '../src/logger';
+import {MatrixEvent} from "../src/models/event";
 
 /**
  * Return a promise that is resolved when the client next emits a
@@ -13,7 +11,7 @@ const MatrixEvent = sdk.MatrixEvent;
  * @param {Number=} count Number of syncs to wait for (default 1)
  * @return {Promise} Resolves once the client has emitted a SYNCING event
  */
-module.exports.syncPromise = function(client, count) {
+export function syncPromise(client, count) {
     if (count === undefined) {
         count = 1;
     }
@@ -24,7 +22,7 @@ module.exports.syncPromise = function(client, count) {
     const p = new Promise((resolve, reject) => {
         const cb = (state) => {
             logger.log(`${Date.now()} syncPromise(${count}): ${state}`);
-            if (state == 'SYNCING') {
+            if (state === 'SYNCING') {
                 resolve();
             } else {
                 client.once('sync', cb);
@@ -34,9 +32,9 @@ module.exports.syncPromise = function(client, count) {
     });
 
     return p.then(() => {
-        return module.exports.syncPromise(client, count-1);
+        return syncPromise(client, count-1);
     });
-};
+}
 
 /**
  * Create a spy for an object and automatically spy its methods.
@@ -44,7 +42,7 @@ module.exports.syncPromise = function(client, count) {
  * @param {string} name The name of the class
  * @return {Object} An instantiated object with spied methods/properties.
  */
-module.exports.mock = function(constr, name) {
+export function mock(constr, name) {
     // Based on
     // http://eclipsesource.com/blogs/2014/03/27/mocks-in-jasmine-tests/
     const HelperConstr = new Function(); // jshint ignore:line
@@ -65,7 +63,7 @@ module.exports.mock = function(constr, name) {
         }
     }
     return result;
-};
+}
 
 /**
  * Create an Event.
@@ -78,7 +76,7 @@ module.exports.mock = function(constr, name) {
  * @param {boolean} opts.event True to make a MatrixEvent.
  * @return {Object} a JSON object representing this event.
  */
-module.exports.mkEvent = function(opts) {
+export function mkEvent(opts) {
     if (!opts.type || !opts.content) {
         throw new Error("Missing .type or .content =>" + JSON.stringify(opts));
     }
@@ -97,14 +95,14 @@ module.exports.mkEvent = function(opts) {
         event.state_key = "";
     }
     return opts.event ? new MatrixEvent(event) : event;
-};
+}
 
 /**
  * Create an m.presence event.
  * @param {Object} opts Values for the presence.
  * @return {Object|MatrixEvent} The event
  */
-module.exports.mkPresence = function(opts) {
+export function mkPresence(opts) {
     if (!opts.user) {
         throw new Error("Missing user");
     }
@@ -120,7 +118,7 @@ module.exports.mkPresence = function(opts) {
         },
     };
     return opts.event ? new MatrixEvent(event) : event;
-};
+}
 
 /**
  * Create an m.room.member event.
@@ -135,7 +133,7 @@ module.exports.mkPresence = function(opts) {
  * @param {boolean} opts.event True to make a MatrixEvent.
  * @return {Object|MatrixEvent} The event
  */
-module.exports.mkMembership = function(opts) {
+export function mkMembership(opts) {
     opts.type = "m.room.member";
     if (!opts.skey) {
         opts.skey = opts.sender || opts.user;
@@ -152,8 +150,8 @@ module.exports.mkMembership = function(opts) {
     if (opts.url) {
         opts.content.avatar_url = opts.url;
     }
-    return module.exports.mkEvent(opts);
-};
+    return mkEvent(opts);
+}
 
 /**
  * Create an m.room.message event.
@@ -164,7 +162,7 @@ module.exports.mkMembership = function(opts) {
  * @param {boolean} opts.event True to make a MatrixEvent.
  * @return {Object|MatrixEvent} The event
  */
-module.exports.mkMessage = function(opts) {
+export function mkMessage(opts) {
     opts.type = "m.room.message";
     if (!opts.msg) {
         opts.msg = "Random->" + Math.random();
@@ -176,8 +174,8 @@ module.exports.mkMessage = function(opts) {
         msgtype: "m.text",
         body: opts.msg,
     };
-    return module.exports.mkEvent(opts);
-};
+    return mkEvent(opts);
+}
 
 
 /**
@@ -185,10 +183,10 @@ module.exports.mkMessage = function(opts) {
  *
  * @constructor
  */
-module.exports.MockStorageApi = function() {
+export function MockStorageApi() {
     this.data = {};
-};
-module.exports.MockStorageApi.prototype = {
+}
+MockStorageApi.prototype = {
     get length() {
         return Object.keys(this.data).length;
     },
@@ -213,7 +211,7 @@ module.exports.MockStorageApi.prototype = {
  * @param {MatrixEvent} event
  * @returns {Promise} promise which resolves (to `event`) when the event has been decrypted
  */
-module.exports.awaitDecryption = function(event) {
+export function awaitDecryption(event) {
     if (!event.isBeingDecrypted()) {
         return Promise.resolve(event);
     }
@@ -226,19 +224,19 @@ module.exports.awaitDecryption = function(event) {
             resolve(ev);
         });
     });
-};
+}
 
 
-const HttpResponse = module.exports.HttpResponse = function(
+export function HttpResponse(
     httpLookups, acceptKeepalives, ignoreUnhandledSync,
 ) {
     this.httpLookups = httpLookups;
     this.acceptKeepalives = acceptKeepalives === undefined ? true : acceptKeepalives;
     this.ignoreUnhandledSync = ignoreUnhandledSync;
     this.pendingLookup = null;
-};
+}
 
-HttpResponse.prototype.request = function HttpResponse(
+HttpResponse.prototype.request = function(
     cb, method, path, qp, data, prefix,
 ) {
     if (path === HttpResponse.KEEP_ALIVE_PATH && this.acceptKeepalives) {
@@ -351,7 +349,7 @@ HttpResponse.defaultResponses = function(userId) {
     ];
 };
 
-module.exports.setHttpResponses = function setHttpResponses(
+export function setHttpResponses(
     client, responses, acceptKeepalives, ignoreUnhandledSyncs,
 ) {
     const httpResponseObj = new HttpResponse(
@@ -367,4 +365,4 @@ module.exports.setHttpResponses = function setHttpResponses(
     client._http.authedRequestWithPrefix.mockImplementation(httpReq);
     client._http.requestWithPrefix.mockImplementation(httpReq);
     client._http.request.mockImplementation(httpReq);
-};
+}
diff --git a/spec/unit/autodiscovery.spec.js b/spec/unit/autodiscovery.spec.js
index 760c03adc..684186cd7 100644
--- a/spec/unit/autodiscovery.spec.js
+++ b/spec/unit/autodiscovery.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,15 +14,10 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
-
-import 'source-map-support/register';
-const sdk = require("../..");
-
-const AutoDiscovery = sdk.AutoDiscovery;
 
 import MockHttpBackend from "matrix-mock-request";
-
+import * as sdk from "../../src";
+import {AutoDiscovery} from "../../src/autodiscovery";
 
 describe("AutoDiscovery", function() {
     let httpBackend = null;
diff --git a/spec/unit/content-repo.spec.js b/spec/unit/content-repo.spec.js
index 70174fc77..b55055684 100644
--- a/spec/unit/content-repo.spec.js
+++ b/spec/unit/content-repo.spec.js
@@ -1,6 +1,4 @@
-"use strict";
-import 'source-map-support/register';
-const ContentRepo = require("../../lib/content-repo");
+import {getHttpUriForMxc, getIdenticonUri} from "../../src/content-repo";
 
 describe("ContentRepo", function() {
     const baseUrl = "https://my.home.server";
@@ -9,7 +7,7 @@ describe("ContentRepo", function() {
         it("should do nothing to HTTP URLs when allowing direct links", function() {
             const httpUrl = "http://example.com/image.jpeg";
             expect(
-                ContentRepo.getHttpUriForMxc(
+                getHttpUriForMxc(
                     baseUrl, httpUrl, undefined, undefined, undefined, true,
                 ),
             ).toEqual(httpUrl);
@@ -17,25 +15,25 @@ describe("ContentRepo", function() {
 
         it("should return the empty string HTTP URLs by default", function() {
             const httpUrl = "http://example.com/image.jpeg";
-            expect(ContentRepo.getHttpUriForMxc(baseUrl, httpUrl)).toEqual("");
+            expect(getHttpUriForMxc(baseUrl, httpUrl)).toEqual("");
         });
 
         it("should return a download URL if no width/height/resize are specified",
         function() {
             const mxcUri = "mxc://server.name/resourceid";
-            expect(ContentRepo.getHttpUriForMxc(baseUrl, mxcUri)).toEqual(
+            expect(getHttpUriForMxc(baseUrl, mxcUri)).toEqual(
                 baseUrl + "/_matrix/media/r0/download/server.name/resourceid",
             );
         });
 
         it("should return the empty string for null input", function() {
-            expect(ContentRepo.getHttpUriForMxc(null)).toEqual("");
+            expect(getHttpUriForMxc(null)).toEqual("");
         });
 
         it("should return a thumbnail URL if a width/height/resize is specified",
         function() {
             const mxcUri = "mxc://server.name/resourceid";
-            expect(ContentRepo.getHttpUriForMxc(baseUrl, mxcUri, 32, 64, "crop")).toEqual(
+            expect(getHttpUriForMxc(baseUrl, mxcUri, 32, 64, "crop")).toEqual(
                 baseUrl + "/_matrix/media/r0/thumbnail/server.name/resourceid" +
                 "?width=32&height=64&method=crop",
             );
@@ -44,7 +42,7 @@ describe("ContentRepo", function() {
         it("should put fragments from mxc:// URIs after any query parameters",
         function() {
             const mxcUri = "mxc://server.name/resourceid#automade";
-            expect(ContentRepo.getHttpUriForMxc(baseUrl, mxcUri, 32)).toEqual(
+            expect(getHttpUriForMxc(baseUrl, mxcUri, 32)).toEqual(
                 baseUrl + "/_matrix/media/r0/thumbnail/server.name/resourceid" +
                 "?width=32#automade",
             );
@@ -53,7 +51,7 @@ describe("ContentRepo", function() {
         it("should put fragments from mxc:// URIs at the end of the HTTP URI",
         function() {
             const mxcUri = "mxc://server.name/resourceid#automade";
-            expect(ContentRepo.getHttpUriForMxc(baseUrl, mxcUri)).toEqual(
+            expect(getHttpUriForMxc(baseUrl, mxcUri)).toEqual(
                 baseUrl + "/_matrix/media/r0/download/server.name/resourceid#automade",
             );
         });
@@ -61,25 +59,25 @@ describe("ContentRepo", function() {
 
     describe("getIdenticonUri", function() {
         it("should do nothing for null input", function() {
-            expect(ContentRepo.getIdenticonUri(null)).toEqual(null);
+            expect(getIdenticonUri(null)).toEqual(null);
         });
 
         it("should set w/h by default to 96", function() {
-            expect(ContentRepo.getIdenticonUri(baseUrl, "foobar")).toEqual(
+            expect(getIdenticonUri(baseUrl, "foobar")).toEqual(
                 baseUrl + "/_matrix/media/unstable/identicon/foobar" +
                 "?width=96&height=96",
             );
         });
 
         it("should be able to set custom w/h", function() {
-            expect(ContentRepo.getIdenticonUri(baseUrl, "foobar", 32, 64)).toEqual(
+            expect(getIdenticonUri(baseUrl, "foobar", 32, 64)).toEqual(
                 baseUrl + "/_matrix/media/unstable/identicon/foobar" +
                 "?width=32&height=64",
             );
         });
 
         it("should URL encode the identicon string", function() {
-            expect(ContentRepo.getIdenticonUri(baseUrl, "foo#bar", 32, 64)).toEqual(
+            expect(getIdenticonUri(baseUrl, "foo#bar", 32, 64)).toEqual(
                 baseUrl + "/_matrix/media/unstable/identicon/foo%23bar" +
                 "?width=32&height=64",
             );
diff --git a/spec/unit/crypto.spec.js b/spec/unit/crypto.spec.js
index c449d4624..9652f4b37 100644
--- a/spec/unit/crypto.spec.js
+++ b/spec/unit/crypto.spec.js
@@ -1,26 +1,20 @@
-import 'source-map-support/register';
-
 import '../olm-loader';
-
-import Crypto from '../../lib/crypto';
-
-import WebStorageSessionStore from '../../lib/store/session/webstorage';
-import MemoryCryptoStore from '../../lib/crypto/store/memory-crypto-store.js';
-import MockStorageApi from '../MockStorageApi';
-import TestClient from '../TestClient';
-import {MatrixEvent} from '../../lib/models/event';
-import Room from '../../lib/models/room';
-import olmlib from '../../lib/crypto/olmlib';
+import {Crypto} from "../../src/crypto";
+import {WebStorageSessionStore} from "../../src/store/session/webstorage";
+import {MemoryCryptoStore} from "../../src/crypto/store/memory-crypto-store";
+import {MockStorageApi} from "../MockStorageApi";
+import {TestClient} from "../TestClient";
+import {MatrixEvent} from "../../src/models/event";
+import {Room} from "../../src/models/room";
+import * as olmlib from "../../src/crypto/olmlib";
 import {sleep} from "../../src/utils";
-
-const EventEmitter = require("events").EventEmitter;
-
-const sdk = require("../..");
+import {EventEmitter} from "events";
+import {CRYPTO_ENABLED} from "../../src/client";
 
 const Olm = global.Olm;
 
 describe("Crypto", function() {
-    if (!sdk.CRYPTO_ENABLED) {
+    if (!CRYPTO_ENABLED) {
         return;
     }
 
diff --git a/spec/unit/crypto/DeviceList.spec.js b/spec/unit/crypto/DeviceList.spec.js
index 683187b78..1b92826e8 100644
--- a/spec/unit/crypto/DeviceList.spec.js
+++ b/spec/unit/crypto/DeviceList.spec.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018, 2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,10 +16,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import DeviceList from '../../../lib/crypto/DeviceList';
-import MemoryCryptoStore from '../../../lib/crypto/store/memory-crypto-store.js';
-import utils from '../../../lib/utils';
-import logger from '../../../lib/logger';
+import {logger} from "../../../src/logger";
+import * as utils from "../../../src/utils";
+import {MemoryCryptoStore} from "../../../src/crypto/store/memory-crypto-store";
+import {DeviceList} from "../../../src/crypto/DeviceList";
 
 const signedDeviceList = {
     "failures": {},
diff --git a/spec/unit/crypto/algorithms/megolm.spec.js b/spec/unit/crypto/algorithms/megolm.spec.js
index 88beac84f..e629385a0 100644
--- a/spec/unit/crypto/algorithms/megolm.spec.js
+++ b/spec/unit/crypto/algorithms/megolm.spec.js
@@ -1,15 +1,16 @@
 import '../../../olm-loader';
+import * as algorithms from "../../../../src/crypto/algorithms";
+import {MemoryCryptoStore} from "../../../../src/crypto/store/memory-crypto-store";
+import {MockStorageApi} from "../../../MockStorageApi";
+import * as testUtils from "../../../test-utils";
+import {OlmDevice} from "../../../../src/crypto/OlmDevice";
+import {Crypto} from "../../../../src/crypto";
+import {logger} from "../../../../src/logger";
+import {MatrixEvent} from "../../../../src/models/event";
+import {TestClient} from "../../../TestClient";
+import {Room} from "../../../../src/models/room";
+import * as olmlib from "../../../../src/crypto/olmlib";
 
-import sdk from '../../../..';
-import algorithms from '../../../../lib/crypto/algorithms';
-import MemoryCryptoStore from '../../../../lib/crypto/store/memory-crypto-store.js';
-import MockStorageApi from '../../../MockStorageApi';
-import testUtils from '../../../test-utils';
-import OlmDevice from '../../../../lib/crypto/OlmDevice';
-import Crypto from '../../../../lib/crypto';
-import logger from '../../../../lib/logger';
-
-const MatrixEvent = sdk.MatrixEvent;
 const MegolmDecryption = algorithms.DECRYPTION_CLASSES['m.megolm.v1.aes-sha2'];
 const MegolmEncryption = algorithms.ENCRYPTION_CLASSES['m.megolm.v1.aes-sha2'];
 
@@ -342,4 +343,346 @@ describe("MegolmDecryption", function() {
             expect(ct2.session_id).toEqual(ct1.session_id);
         });
     });
+
+    it("notifies devices that have been blocked", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient1 = (new TestClient(
+            "@bob:example.com", "bobdevice1",
+        )).client;
+        const bobClient2 = (new TestClient(
+            "@bob:example.com", "bobdevice2",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient1.initCrypto(),
+            bobClient2.initCrypto(),
+        ]);
+        const aliceDevice = aliceClient._crypto._olmDevice;
+        const bobDevice1 = bobClient1._crypto._olmDevice;
+        const bobDevice2 = bobClient2._crypto._olmDevice;
+
+        const encryptionCfg = {
+            "algorithm": "m.megolm.v1.aes-sha2",
+        };
+        const roomId = "!someroom";
+        const room = new Room(roomId, aliceClient, "@alice:example.com", {});
+        room.getEncryptionTargetMembers = async function() {
+            return [{userId: "@bob:example.com"}];
+        };
+        room.setBlacklistUnverifiedDevices(true);
+        aliceClient.store.storeRoom(room);
+        await aliceClient.setRoomEncryption(roomId, encryptionCfg);
+
+        const BOB_DEVICES = {
+            bobdevice1: {
+                user_id: "@bob:example.com",
+                device_id: "bobdevice1",
+                algorithms: [olmlib.OLM_ALGORITHM, olmlib.MEGOLM_ALGORITHM],
+                keys: {
+                    "ed25519:Dynabook": bobDevice1.deviceEd25519Key,
+                    "curve25519:Dynabook": bobDevice1.deviceCurve25519Key,
+                },
+                verified: 0,
+            },
+            bobdevice2: {
+                user_id: "@bob:example.com",
+                device_id: "bobdevice2",
+                algorithms: [olmlib.OLM_ALGORITHM, olmlib.MEGOLM_ALGORITHM],
+                keys: {
+                    "ed25519:Dynabook": bobDevice2.deviceEd25519Key,
+                    "curve25519:Dynabook": bobDevice2.deviceCurve25519Key,
+                },
+                verified: -1,
+            },
+        };
+
+        aliceClient._crypto._deviceList.storeDevicesForUser(
+            "@bob:example.com", BOB_DEVICES,
+        );
+        aliceClient._crypto._deviceList.downloadKeys = async function(userIds) {
+            return this._getDevicesFromStore(userIds);
+        };
+
+        let run = false;
+        aliceClient.sendToDevice = async (msgtype, contentMap) => {
+            run = true;
+            expect(msgtype).toBe("org.matrix.room_key.withheld");
+            delete contentMap["@bob:example.com"].bobdevice1.session_id;
+            delete contentMap["@bob:example.com"].bobdevice2.session_id;
+            expect(contentMap).toStrictEqual({
+                '@bob:example.com': {
+                    bobdevice1: {
+                        algorithm: "m.megolm.v1.aes-sha2",
+                        room_id: roomId,
+                        code: 'm.unverified',
+                        reason:
+                        'The sender has disabled encrypting to unverified devices.',
+                        sender_key: aliceDevice.deviceCurve25519Key,
+                    },
+                    bobdevice2: {
+                        algorithm: "m.megolm.v1.aes-sha2",
+                        room_id: roomId,
+                        code: 'm.blacklisted',
+                        reason: 'The sender has blocked you.',
+                        sender_key: aliceDevice.deviceCurve25519Key,
+                    },
+                },
+            });
+        };
+
+        const event = new MatrixEvent({
+            type: "m.room.message",
+            sender: "@alice:example.com",
+            room_id: roomId,
+            event_id: "$event",
+            content: {
+                msgtype: "m.text",
+                body: "secret",
+            },
+        });
+        await aliceClient._crypto.encryptEvent(event, room);
+
+        expect(run).toBe(true);
+
+        aliceClient.stopClient();
+        bobClient1.stopClient();
+        bobClient2.stopClient();
+    });
+
+    it("notifies devices when unable to create olm session", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const aliceDevice = aliceClient._crypto._olmDevice;
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const encryptionCfg = {
+            "algorithm": "m.megolm.v1.aes-sha2",
+        };
+        const roomId = "!someroom";
+        const aliceRoom = new Room(roomId, aliceClient, "@alice:example.com", {});
+        const bobRoom = new Room(roomId, bobClient, "@bob:example.com", {});
+        aliceClient.store.storeRoom(aliceRoom);
+        bobClient.store.storeRoom(bobRoom);
+        await aliceClient.setRoomEncryption(roomId, encryptionCfg);
+        await bobClient.setRoomEncryption(roomId, encryptionCfg);
+
+        aliceRoom.getEncryptionTargetMembers = async () => {
+            return [
+                {
+                    userId: "@alice:example.com",
+                    membership: "join",
+                },
+                {
+                    userId: "@bob:example.com",
+                    membership: "join",
+                },
+            ];
+        };
+        const BOB_DEVICES = {
+            bobdevice: {
+                user_id: "@bob:example.com",
+                device_id: "bobdevice",
+                algorithms: [olmlib.OLM_ALGORITHM, olmlib.MEGOLM_ALGORITHM],
+                keys: {
+                    "ed25519:bobdevice": bobDevice.deviceEd25519Key,
+                    "curve25519:bobdevice": bobDevice.deviceCurve25519Key,
+                },
+                known: true,
+                verified: 1,
+            },
+        };
+
+        aliceClient._crypto._deviceList.storeDevicesForUser(
+            "@bob:example.com", BOB_DEVICES,
+        );
+        aliceClient._crypto._deviceList.downloadKeys = async function(userIds) {
+            return this._getDevicesFromStore(userIds);
+        };
+
+        aliceClient.claimOneTimeKeys = async () => {
+            // Bob has no one-time keys
+            return {
+                one_time_keys: {},
+            };
+        };
+
+        let run = false;
+        aliceClient.sendToDevice = async (msgtype, contentMap) => {
+            run = true;
+            expect(msgtype).toBe("org.matrix.room_key.withheld");
+            expect(contentMap).toStrictEqual({
+                '@bob:example.com': {
+                    bobdevice: {
+                        algorithm: "m.megolm.v1.aes-sha2",
+                        code: 'm.no_olm',
+                        reason: 'Unable to establish a secure channel.',
+                        sender_key: aliceDevice.deviceCurve25519Key,
+                    },
+                },
+            });
+        };
+
+        const event = new MatrixEvent({
+            type: "m.room.message",
+            sender: "@alice:example.com",
+            room_id: roomId,
+            event_id: "$event",
+            content: {},
+        });
+        await aliceClient._crypto.encryptEvent(event, aliceRoom);
+
+        expect(run).toBe(true);
+    });
+
+    it("throws an error describing why it doesn't have a key", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const roomId = "!someroom";
+
+        aliceClient._crypto._onToDeviceEvent(new MatrixEvent({
+            type: "org.matrix.room_key.withheld",
+            sender: "@bob:example.com",
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                room_id: roomId,
+                session_id: "session_id",
+                sender_key: bobDevice.deviceCurve25519Key,
+                code: "m.blacklisted",
+                reason: "You have been blocked",
+            },
+        }));
+
+        await expect(aliceClient._crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id",
+            },
+        }))).rejects.toThrow("The sender has blocked you.");
+    });
+
+    it("throws an error describing the lack of an olm session", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const roomId = "!someroom";
+
+        const now = Date.now();
+
+        aliceClient._crypto._onToDeviceEvent(new MatrixEvent({
+            type: "org.matrix.room_key.withheld",
+            sender: "@bob:example.com",
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                room_id: roomId,
+                session_id: "session_id",
+                sender_key: bobDevice.deviceCurve25519Key,
+                code: "m.no_olm",
+                reason: "Unable to establish a secure channel.",
+            },
+        }));
+
+        await new Promise((resolve) => {
+            setTimeout(resolve, 100);
+        });
+
+        await expect(aliceClient._crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id",
+            },
+            origin_server_ts: now,
+        }))).rejects.toThrow("The sender was unable to establish a secure channel.");
+    });
+
+    it("throws an error to indicate a wedged olm session", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const roomId = "!someroom";
+
+        const now = Date.now();
+
+        // pretend we got an event that we can't decrypt
+        aliceClient._crypto._onToDeviceEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            content: {
+                msgtype: "m.bad.encrypted",
+                algorithm: "m.megolm.v1.aes-sha2",
+                session_id: "session_id",
+                sender_key: bobDevice.deviceCurve25519Key,
+            },
+        }));
+
+        await new Promise((resolve) => {
+            setTimeout(resolve, 100);
+        });
+
+        await expect(aliceClient._crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id",
+            },
+            origin_server_ts: now,
+        }))).rejects.toThrow("The secure channel with the sender was corrupted.");
+    });
 });
diff --git a/spec/unit/crypto/algorithms/olm.spec.js b/spec/unit/crypto/algorithms/olm.spec.js
index e701e2894..889115776 100644
--- a/spec/unit/crypto/algorithms/olm.spec.js
+++ b/spec/unit/crypto/algorithms/olm.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018,2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,14 +16,12 @@ limitations under the License.
 */
 
 import '../../../olm-loader';
-
-import MemoryCryptoStore from '../../../../lib/crypto/store/memory-crypto-store.js';
-import MockStorageApi from '../../../MockStorageApi';
-import logger from '../../../../lib/logger';
-
-import OlmDevice from '../../../../lib/crypto/OlmDevice';
-import olmlib from '../../../../lib/crypto/olmlib';
-import DeviceInfo from '../../../../lib/crypto/deviceinfo';
+import {MemoryCryptoStore} from "../../../../src/crypto/store/memory-crypto-store";
+import {MockStorageApi} from "../../../MockStorageApi";
+import {logger} from "../../../../src/logger";
+import {OlmDevice} from "../../../../src/crypto/OlmDevice";
+import * as olmlib from "../../../../src/crypto/olmlib";
+import {DeviceInfo} from "../../../../src/crypto/deviceinfo";
 
 function makeOlmDevice() {
     const mockStorage = new MockStorageApi();
diff --git a/spec/unit/crypto/backup.spec.js b/spec/unit/crypto/backup.spec.js
index f4d6a71cf..50c336325 100644
--- a/spec/unit/crypto/backup.spec.js
+++ b/spec/unit/crypto/backup.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,23 +16,20 @@ limitations under the License.
 */
 
 import '../../olm-loader';
-
-import sdk from '../../..';
-import algorithms from '../../../lib/crypto/algorithms';
-import WebStorageSessionStore from '../../../lib/store/session/webstorage';
-import MemoryCryptoStore from '../../../lib/crypto/store/memory-crypto-store.js';
-import MockStorageApi from '../../MockStorageApi';
-import testUtils from '../../test-utils';
-
-import OlmDevice from '../../../lib/crypto/OlmDevice';
-import Crypto from '../../../lib/crypto';
-import logger from '../../../lib/logger';
-import olmlib from '../../../lib/crypto/olmlib';
+import {logger} from "../../../src/logger";
+import * as olmlib from "../../../src/crypto/olmlib";
+import {MatrixClient} from "../../../src/client";
+import {MatrixEvent} from "../../../src/models/event";
+import * as algorithms from "../../../src/crypto/algorithms";
+import {WebStorageSessionStore} from "../../../src/store/session/webstorage";
+import {MemoryCryptoStore} from "../../../src/crypto/store/memory-crypto-store";
+import {MockStorageApi} from "../../MockStorageApi";
+import * as testUtils from "../../test-utils";
+import {OlmDevice} from "../../../src/crypto/OlmDevice";
+import {Crypto} from "../../../src/crypto";
 
 const Olm = global.Olm;
 
-const MatrixClient = sdk.MatrixClient;
-const MatrixEvent = sdk.MatrixEvent;
 const MegolmDecryption = algorithms.DECRYPTION_CLASSES['m.megolm.v1.aes-sha2'];
 
 const ROOM_ID = '!ROOM:ID';
diff --git a/spec/unit/crypto/cross-signing.spec.js b/spec/unit/crypto/cross-signing.spec.js
index a36c3bf70..23ee0ee1b 100644
--- a/spec/unit/crypto/cross-signing.spec.js
+++ b/spec/unit/crypto/cross-signing.spec.js
@@ -16,13 +16,9 @@ limitations under the License.
 */
 
 import '../../olm-loader';
-
 import anotherjson from 'another-json';
-
-import olmlib from '../../../lib/crypto/olmlib';
-
-import TestClient from '../../TestClient';
-
+import * as olmlib from "../../../src/crypto/olmlib";
+import {TestClient} from '../../TestClient';
 import {HttpResponse, setHttpResponses} from '../../test-utils';
 
 async function makeTestClient(userInfo, options, keys) {
diff --git a/spec/unit/crypto/secrets.spec.js b/spec/unit/crypto/secrets.spec.js
index 7c1195aae..254adf0c0 100644
--- a/spec/unit/crypto/secrets.spec.js
+++ b/spec/unit/crypto/secrets.spec.js
@@ -15,14 +15,11 @@ limitations under the License.
 */
 
 import '../../olm-loader';
-
-import { MatrixEvent } from '../../../lib/models/event';
-import { SECRET_STORAGE_ALGORITHM_V1 } from '../../../lib/crypto/SecretStorage';
-
-import olmlib from '../../../lib/crypto/olmlib';
-
-import TestClient from '../../TestClient';
-import { makeTestClients } from './verification/util';
+import * as olmlib from "../../../src/crypto/olmlib";
+import {SECRET_STORAGE_ALGORITHM_V1} from "../../../src/crypto/SecretStorage";
+import {MatrixEvent} from "../../../src/models/event";
+import {TestClient} from '../../TestClient';
+import {makeTestClients} from './verification/util';
 
 async function makeTestClient(userInfo, options) {
     const client = (new TestClient(
diff --git a/spec/unit/crypto/verification/qr_code.spec.js b/spec/unit/crypto/verification/qr_code.spec.js
index 3c92426b9..9f9a4c8bb 100644
--- a/spec/unit/crypto/verification/qr_code.spec.js
+++ b/spec/unit/crypto/verification/qr_code.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018-2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,17 +14,10 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-import logger from '../../../../lib/logger';
-
-try {
-    global.Olm = require('olm');
-} catch (e) {
-    logger.warn("unable to run device verification tests: libolm not available");
-}
-
-import DeviceInfo from '../../../../lib/crypto/deviceinfo';
-
-import {ShowQRCode, ScanQRCode} from '../../../../lib/crypto/verification/QRCode';
+import "../../../olm-loader";
+import {logger} from "../../../../src/logger";
+import {DeviceInfo} from "../../../../src/crypto/deviceinfo";
+import {ScanQRCode, ShowQRCode} from "../../../../src/crypto/verification/QRCode";
 
 const Olm = global.Olm;
 
diff --git a/spec/unit/crypto/verification/request.spec.js b/spec/unit/crypto/verification/request.spec.js
index 99ba0225b..be039824c 100644
--- a/spec/unit/crypto/verification/request.spec.js
+++ b/spec/unit/crypto/verification/request.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,22 +14,14 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-import logger from '../../../../lib/logger';
-
-try {
-    global.Olm = require('olm');
-} catch (e) {
-    logger.warn("unable to run device verification tests: libolm not available");
-}
-
-import {verificationMethods} from '../../../../lib/crypto';
-
-import SAS from '../../../../lib/crypto/verification/SAS';
+import "../../../olm-loader";
+import {verificationMethods} from "../../../../src/crypto";
+import {logger} from "../../../../src/logger";
+import {SAS} from "../../../../src/crypto/verification/SAS";
+import {makeTestClients} from './util';
 
 const Olm = global.Olm;
 
-import {makeTestClients} from './util';
-
 describe("verification request", function() {
     if (!global.Olm) {
         logger.warn('Not running device verification unit tests: libolm not present');
diff --git a/spec/unit/crypto/verification/sas.spec.js b/spec/unit/crypto/verification/sas.spec.js
index aa358dbf9..388737dd3 100644
--- a/spec/unit/crypto/verification/sas.spec.js
+++ b/spec/unit/crypto/verification/sas.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018-2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,29 +14,17 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-import logger from '../../../../lib/logger';
-
-try {
-    global.Olm = require('olm');
-} catch (e) {
-    logger.warn("unable to run device verification tests: libolm not available");
-}
-
-import olmlib from '../../../../lib/crypto/olmlib';
-
-import sdk from '../../../..';
-
-import {verificationMethods} from '../../../../lib/crypto';
-import DeviceInfo from '../../../../lib/crypto/deviceinfo';
-
-import SAS from '../../../../lib/crypto/verification/SAS';
+import "../../../olm-loader";
+import {makeTestClients} from './util';
+import {MatrixEvent} from "../../../../src/models/event";
+import {SAS} from "../../../../src/crypto/verification/SAS";
+import {DeviceInfo} from "../../../../src/crypto/deviceinfo";
+import {verificationMethods} from "../../../../src/crypto";
+import * as olmlib from "../../../../src/crypto/olmlib";
+import {logger} from "../../../../src/logger";
 
 const Olm = global.Olm;
 
-const MatrixEvent = sdk.MatrixEvent;
-
-import {makeTestClients} from './util';
-
 let ALICE_DEVICES;
 let BOB_DEVICES;
 
diff --git a/spec/unit/crypto/verification/util.js b/spec/unit/crypto/verification/util.js
index 53eb1b654..ea1cd81c9 100644
--- a/spec/unit/crypto/verification/util.js
+++ b/spec/unit/crypto/verification/util.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2019 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,10 +15,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import TestClient from '../../../TestClient';
-
-import sdk from '../../../..';
-const MatrixEvent = sdk.MatrixEvent;
+import {TestClient} from '../../../TestClient';
+import {MatrixEvent} from "../../../../src/models/event";
 
 export async function makeTestClients(userInfos, options) {
     const clients = [];
diff --git a/spec/unit/event-timeline.spec.js b/spec/unit/event-timeline.spec.js
index ab4ce9f38..bf5645d8d 100644
--- a/spec/unit/event-timeline.spec.js
+++ b/spec/unit/event-timeline.spec.js
@@ -1,12 +1,10 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const EventTimeline = sdk.EventTimeline;
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {EventTimeline} from "../../src/models/event-timeline";
+import {RoomState} from "../../src/models/room-state";
 
 function mockRoomStates(timeline) {
-    timeline._startState = utils.mock(sdk.RoomState, "startState");
-    timeline._endState = utils.mock(sdk.RoomState, "endState");
+    timeline._startState = utils.mock(RoomState, "startState");
+    timeline._endState = utils.mock(RoomState, "endState");
 }
 
 describe("EventTimeline", function() {
diff --git a/spec/unit/event.spec.js b/spec/unit/event.spec.js
index 225580d81..9b88e7ce9 100644
--- a/spec/unit/event.spec.js
+++ b/spec/unit/event.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2017 New Vector Ltd
+Copyright 2019 The Matrix.org Foundaction C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,10 +15,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import sdk from '../..';
-const MatrixEvent = sdk.MatrixEvent;
-
-import logger from '../../lib/logger';
+import {logger} from "../../src/logger";
+import {MatrixEvent} from "../../src/models/event";
 
 describe("MatrixEvent", () => {
     describe(".attemptDecryption", () => {
diff --git a/spec/unit/filter.spec.js b/spec/unit/filter.spec.js
index ed7722cf8..743296dd7 100644
--- a/spec/unit/filter.spec.js
+++ b/spec/unit/filter.spec.js
@@ -1,7 +1,4 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const Filter = sdk.Filter;
+import {Filter} from "../../src/filter";
 
 describe("Filter", function() {
     const filterId = "f1lt3ring15g00d4ursoul";
diff --git a/spec/unit/interactive-auth.spec.js b/spec/unit/interactive-auth.spec.js
index 0d706da30..46008b906 100644
--- a/spec/unit/interactive-auth.spec.js
+++ b/spec/unit/interactive-auth.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,15 +14,10 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
-import 'source-map-support/register';
-const sdk = require("../..");
-
-const InteractiveAuth = sdk.InteractiveAuth;
-const MatrixError = sdk.MatrixError;
-
-import logger from '../../lib/logger';
+import {logger} from "../../src/logger";
+import {InteractiveAuth} from "../../src/interactive-auth";
+import {MatrixError} from "../../src/http-api";
 
 // Trivial client object to test interactive auth
 // (we do not need TestClient here)
diff --git a/spec/unit/login.spec.js b/spec/unit/login.spec.js
index 0a294adc3..32d68f458 100644
--- a/spec/unit/login.spec.js
+++ b/spec/unit/login.spec.js
@@ -1,4 +1,4 @@
-import TestClient from '../TestClient';
+import {TestClient} from '../TestClient';
 
 describe('Login request', function() {
     let client;
diff --git a/spec/unit/matrix-client.spec.js b/spec/unit/matrix-client.spec.js
index c1726e174..fc4a4dc56 100644
--- a/spec/unit/matrix-client.spec.js
+++ b/spec/unit/matrix-client.spec.js
@@ -1,9 +1,6 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const MatrixClient = sdk.MatrixClient;
-
-import logger from '../../lib/logger';
+import {logger} from "../../src/logger";
+import {MatrixClient} from "../../src/client";
+import {Filter} from "../../src/filter";
 
 jest.useFakeTimers();
 
@@ -180,7 +177,7 @@ describe("MatrixClient", function() {
         httpLookups.push(SYNC_RESPONSE);
         const filterId = "ehfewf";
         store.getFilterIdByName.mockReturnValue(filterId);
-        const filter = new sdk.Filter(0, filterId);
+        const filter = new Filter(0, filterId);
         filter.setDefinition({"room": {"timeline": {"limit": 8}}});
         store.getFilter.mockReturnValue(filter);
         const syncPromise = new Promise((resolve, reject) => {
@@ -247,7 +244,7 @@ describe("MatrixClient", function() {
 
             const filterName = getFilterName(client.credentials.userId);
             client.store.setFilterIdByName(filterName, invalidFilterId);
-            const filter = new sdk.Filter(client.credentials.userId);
+            const filter = new Filter(client.credentials.userId);
 
             client.getOrCreateFilter(filterName, filter).then(function(filterId) {
                 expect(filterId).toEqual(FILTER_RESPONSE.data.filter_id);
diff --git a/spec/unit/pushprocessor.spec.js b/spec/unit/pushprocessor.spec.js
index 32580dec2..c1258f74d 100644
--- a/spec/unit/pushprocessor.spec.js
+++ b/spec/unit/pushprocessor.spec.js
@@ -1,7 +1,5 @@
-"use strict";
-import 'source-map-support/register';
-const PushProcessor = require("../../lib/pushprocessor");
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {PushProcessor} from "../../src/pushprocessor";
 
 describe('NotificationService', function() {
     const testUserId = "@ali:matrix.org";
diff --git a/spec/unit/realtime-callbacks.spec.js b/spec/unit/realtime-callbacks.spec.js
index 70510b26a..6ef6920d1 100644
--- a/spec/unit/realtime-callbacks.spec.js
+++ b/spec/unit/realtime-callbacks.spec.js
@@ -1,7 +1,4 @@
-"use strict";
-
-import 'source-map-support/register';
-const callbacks = require("../../src/realtime-callbacks");
+import * as callbacks from "../../src/realtime-callbacks";
 
 let wallTime = 1234567890;
 jest.useFakeTimers();
diff --git a/spec/unit/room-member.spec.js b/spec/unit/room-member.spec.js
index 9c7a8ee32..af0496c74 100644
--- a/spec/unit/room-member.spec.js
+++ b/spec/unit/room-member.spec.js
@@ -1,8 +1,5 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const RoomMember = sdk.RoomMember;
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {RoomMember} from "../../src/models/room-member";
 
 describe("RoomMember", function() {
     const roomId = "!foo:bar";
diff --git a/spec/unit/room-state.spec.js b/spec/unit/room-state.spec.js
index 87aedaf79..a950d63be 100644
--- a/spec/unit/room-state.spec.js
+++ b/spec/unit/room-state.spec.js
@@ -1,9 +1,6 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const RoomState = sdk.RoomState;
-const RoomMember = sdk.RoomMember;
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {RoomState} from "../../src/models/room-state";
+import {RoomMember} from "../../src/models/room-member";
 
 describe("RoomState", function() {
     const roomId = "!foo:bar";
diff --git a/spec/unit/room.spec.js b/spec/unit/room.spec.js
index 58cf2fd01..fa1c2c64e 100644
--- a/spec/unit/room.spec.js
+++ b/spec/unit/room.spec.js
@@ -1,12 +1,8 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const Room = sdk.Room;
-const RoomState = sdk.RoomState;
-const MatrixEvent = sdk.MatrixEvent;
-const EventStatus = sdk.EventStatus;
-const EventTimeline = sdk.EventTimeline;
-const utils = require("../test-utils");
+import * as utils from "../test-utils";
+import {EventStatus, MatrixEvent} from "../../src/models/event";
+import {EventTimeline} from "../../src/models/event-timeline";
+import {RoomState} from "../../src/models/room-state";
+import {Room} from "../../src/models/room";
 
 describe("Room", function() {
     const roomId = "!foo:bar";
@@ -20,9 +16,9 @@ describe("Room", function() {
         room = new Room(roomId);
         // mock RoomStates
         room.oldState = room.getLiveTimeline()._startState =
-            utils.mock(sdk.RoomState, "oldState");
+            utils.mock(RoomState, "oldState");
         room.currentState = room.getLiveTimeline()._endState =
-            utils.mock(sdk.RoomState, "currentState");
+            utils.mock(RoomState, "currentState");
     });
 
     describe("getAvatarUrl", function() {
diff --git a/spec/unit/scheduler.spec.js b/spec/unit/scheduler.spec.js
index d45e77bab..ffe9fa180 100644
--- a/spec/unit/scheduler.spec.js
+++ b/spec/unit/scheduler.spec.js
@@ -1,12 +1,10 @@
 // This file had a function whose name is all caps, which displeases eslint
 /* eslint new-cap: "off" */
 
-import 'source-map-support/register';
 import {defer} from '../../src/utils';
-const sdk = require("../..");
-const MatrixScheduler = sdk.MatrixScheduler;
-const MatrixError = sdk.MatrixError;
-const utils = require("../test-utils");
+import {MatrixError} from "../../src/http-api";
+import {MatrixScheduler} from "../../src/scheduler";
+import * as utils from "../test-utils";
 
 jest.useFakeTimers();
 
diff --git a/spec/unit/sync-accumulator.spec.js b/spec/unit/sync-accumulator.spec.js
index 6dfd76043..157ef4290 100644
--- a/spec/unit/sync-accumulator.spec.js
+++ b/spec/unit/sync-accumulator.spec.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2017 Vector Creations Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,11 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-"use strict";
-import 'source-map-support/register';
-import sdk from "../..";
-
-const SyncAccumulator = sdk.SyncAccumulator;
+import {SyncAccumulator} from "../../src/sync-accumulator";
 
 describe("SyncAccumulator", function() {
     let sa;
diff --git a/spec/unit/timeline-window.spec.js b/spec/unit/timeline-window.spec.js
index 2de036370..af873cc3d 100644
--- a/spec/unit/timeline-window.spec.js
+++ b/spec/unit/timeline-window.spec.js
@@ -1,11 +1,6 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const EventTimeline = sdk.EventTimeline;
-const TimelineWindow = sdk.TimelineWindow;
-const TimelineIndex = require("../../lib/timeline-window").TimelineIndex;
-
-const utils = require("../test-utils");
+import {EventTimeline} from "../../src/models/event-timeline";
+import {TimelineIndex, TimelineWindow} from "../../src/timeline-window";
+import * as utils from "../test-utils";
 
 const ROOM_ID = "roomId";
 const USER_ID = "userId";
diff --git a/spec/unit/user.spec.js b/spec/unit/user.spec.js
index 8cea9c03d..adef6e3c1 100644
--- a/spec/unit/user.spec.js
+++ b/spec/unit/user.spec.js
@@ -1,8 +1,5 @@
-"use strict";
-import 'source-map-support/register';
-const sdk = require("../..");
-const User = sdk.User;
-const utils = require("../test-utils");
+import {User} from "../../src/models/user";
+import * as utils from "../test-utils";
 
 describe("User", function() {
     const userId = "@alice:bar";
diff --git a/spec/unit/utils.spec.js b/spec/unit/utils.spec.js
index c52d00d2b..0b9f8ab93 100644
--- a/spec/unit/utils.spec.js
+++ b/spec/unit/utils.spec.js
@@ -1,6 +1,4 @@
-"use strict";
-import 'source-map-support/register';
-const utils = require("../../lib/utils");
+import * as utils from "../../src/utils";
 
 describe("utils", function() {
     describe("encodeParams", function() {
diff --git a/src/ReEmitter.js b/src/ReEmitter.js
index 4ddf3229a..84a856bb2 100644
--- a/src/ReEmitter.js
+++ b/src/ReEmitter.js
@@ -20,7 +20,7 @@ limitations under the License.
  * @module
  */
 
-export default class Reemitter {
+export class ReEmitter {
     constructor(target) {
         this.target = target;
 
diff --git a/src/autodiscovery.js b/src/autodiscovery.js
index 2258eabf4..fe689fd14 100644
--- a/src/autodiscovery.js
+++ b/src/autodiscovery.js
@@ -17,8 +17,8 @@ limitations under the License.
 
 /** @module auto-discovery */
 
-import logger from './logger';
-import { URL as NodeURL } from "url";
+import {logger} from './logger';
+import {URL as NodeURL} from "url";
 
 // Dev note: Auto discovery is part of the spec.
 // See: https://matrix.org/docs/spec/client_server/r0.4.0.html#server-discovery
diff --git a/src/base-apis.js b/src/base-apis.js
index 645ba6e23..576e32cdb 100644
--- a/src/base-apis.js
+++ b/src/base-apis.js
@@ -16,7 +16,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * This is an internal module. MatrixBaseApis is currently only meant to be used
@@ -25,17 +24,22 @@ limitations under the License.
  * @module base-apis
  */
 
-import { SERVICE_TYPES } from './service-types';
-import logger from './logger';
-
-const httpApi = require("./http-api");
-const utils = require("./utils");
-const PushProcessor = require("./pushprocessor");
+import {SERVICE_TYPES} from './service-types';
+import {logger} from './logger';
+import {PushProcessor} from "./pushprocessor";
+import * as utils from "./utils";
+import {
+    MatrixHttpApi,
+    PREFIX_IDENTITY_V1,
+    PREFIX_IDENTITY_V2,
+    PREFIX_R0,
+    PREFIX_UNSTABLE,
+} from "./http-api";
 
 function termsUrlForService(serviceType, baseUrl) {
     switch (serviceType) {
         case SERVICE_TYPES.IS:
-            return baseUrl + httpApi.PREFIX_IDENTITY_V2 + '/terms';
+            return baseUrl + PREFIX_IDENTITY_V2 + '/terms';
         case SERVICE_TYPES.IM:
             return baseUrl + '/_matrix/integrations/v1/terms';
         default:
@@ -83,7 +87,7 @@ function termsUrlForService(serviceType, baseUrl) {
  * @param {boolean} [opts.useAuthorizationHeader = false] Set to true to use
  * Authorization header instead of query param to send the access token to the server.
  */
-function MatrixBaseApis(opts) {
+export function MatrixBaseApis(opts) {
     utils.checkObjectHasKeys(opts, ["baseUrl", "request"]);
 
     this.baseUrl = opts.baseUrl;
@@ -95,13 +99,13 @@ function MatrixBaseApis(opts) {
         idBaseUrl: opts.idBaseUrl,
         accessToken: opts.accessToken,
         request: opts.request,
-        prefix: httpApi.PREFIX_R0,
+        prefix: PREFIX_R0,
         onlyData: true,
         extraParams: opts.queryParams,
         localTimeoutMs: opts.localTimeoutMs,
         useAuthorizationHeader: opts.useAuthorizationHeader,
     };
-    this._http = new httpApi.MatrixHttpApi(this, httpOpts);
+    this._http = new MatrixHttpApi(this, httpOpts);
 
     this._txnCtr = 0;
 }
@@ -369,7 +373,7 @@ MatrixBaseApis.prototype.getSsoLoginUrl = function(redirectUrl, loginType) {
     }
     return this._http.getUrl("/login/"+loginType+"/redirect", {
         "redirectUrl": redirectUrl,
-    }, httpApi.PREFIX_R0);
+    }, PREFIX_R0);
 };
 
 /**
@@ -447,7 +451,7 @@ MatrixBaseApis.prototype.getFallbackAuthUrl = function(loginType, authSessionId)
 
     return this._http.getUrl(path, {
         session: authSessionId,
-    }, httpApi.PREFIX_R0);
+    }, PREFIX_R0);
 };
 
 // Room operations
@@ -499,7 +503,7 @@ MatrixBaseApis.prototype.fetchRelations =
         });
     const response = await this._http.authedRequest(
         undefined, "GET", path, null, null, {
-            prefix: httpApi.PREFIX_UNSTABLE,
+            prefix: PREFIX_UNSTABLE,
         },
     );
     return response;
@@ -1377,7 +1381,7 @@ MatrixBaseApis.prototype.addThreePid = function(creds, bind, callback) {
 MatrixBaseApis.prototype.addThreePidOnly = async function(data) {
     const path = "/account/3pid/add";
     const prefix = await this.isVersionSupported("r0.6.0") ?
-        httpApi.PREFIX_R0 : httpApi.PREFIX_UNSTABLE;
+        PREFIX_R0 : PREFIX_UNSTABLE;
     return this._http.authedRequest(
         undefined, "POST", path, null, data, { prefix },
     );
@@ -1400,7 +1404,7 @@ MatrixBaseApis.prototype.addThreePidOnly = async function(data) {
 MatrixBaseApis.prototype.bindThreePid = async function(data) {
     const path = "/account/3pid/bind";
     const prefix = await this.isVersionSupported("r0.6.0") ?
-        httpApi.PREFIX_R0 : httpApi.PREFIX_UNSTABLE;
+        PREFIX_R0 : PREFIX_UNSTABLE;
     return this._http.authedRequest(
         undefined, "POST", path, null, data, { prefix },
     );
@@ -1425,7 +1429,7 @@ MatrixBaseApis.prototype.unbindThreePid = async function(medium, address) {
         id_server: this.getIdentityServerUrl(true),
     };
     const prefix = await this.isVersionSupported("r0.6.0") ?
-        httpApi.PREFIX_R0 : httpApi.PREFIX_UNSTABLE;
+        PREFIX_R0 : PREFIX_UNSTABLE;
     return this._http.authedRequest(
         undefined, "POST", path, null, data, { prefix },
     );
@@ -1722,7 +1726,7 @@ MatrixBaseApis.prototype.uploadKeySignatures = function(content) {
     return this._http.authedRequest(
         undefined, "POST", '/keys/signatures/upload', undefined,
         content, {
-            prefix: httpApi.PREFIX_UNSTABLE,
+            prefix: PREFIX_UNSTABLE,
         },
     );
 };
@@ -1815,7 +1819,7 @@ MatrixBaseApis.prototype.uploadDeviceSigningKeys = function(auth, keys) {
     const data = Object.assign({}, keys, {auth});
     return this._http.authedRequest(
         undefined, "POST", "/keys/device_signing/upload", undefined, data, {
-            prefix: httpApi.PREFIX_UNSTABLE,
+            prefix: PREFIX_UNSTABLE,
         },
     );
 };
@@ -1841,7 +1845,7 @@ MatrixBaseApis.prototype.registerWithIdentityServer = function(hsOpenIdToken) {
         throw new Error("No Identity Server base URL set");
     }
 
-    const uri = this.idBaseUrl + httpApi.PREFIX_IDENTITY_V2 + "/account/register";
+    const uri = this.idBaseUrl + PREFIX_IDENTITY_V2 + "/account/register";
     return this._http.requestOtherUrl(
         undefined, "POST", uri,
         null, hsOpenIdToken,
@@ -1890,7 +1894,7 @@ MatrixBaseApis.prototype.requestEmailToken = async function(
     try {
         const response = await this._http.idServerRequest(
             undefined, "POST", "/validate/email/requestToken",
-            params, httpApi.PREFIX_IDENTITY_V2, identityAccessToken,
+            params, PREFIX_IDENTITY_V2, identityAccessToken,
         );
         // TODO: Fold callback into above call once v1 path below is removed
         if (callback) callback(null, response);
@@ -1903,7 +1907,7 @@ MatrixBaseApis.prototype.requestEmailToken = async function(
             logger.warn("IS doesn't support v2, falling back to deprecated v1");
             return await this._http.idServerRequest(
                 callback, "POST", "/validate/email/requestToken",
-                params, httpApi.PREFIX_IDENTITY_V1,
+                params, PREFIX_IDENTITY_V1,
             );
         }
         if (callback) callback(err);
@@ -1958,7 +1962,7 @@ MatrixBaseApis.prototype.requestMsisdnToken = async function(
     try {
         const response = await this._http.idServerRequest(
             undefined, "POST", "/validate/msisdn/requestToken",
-            params, httpApi.PREFIX_IDENTITY_V2, identityAccessToken,
+            params, PREFIX_IDENTITY_V2, identityAccessToken,
         );
         // TODO: Fold callback into above call once v1 path below is removed
         if (callback) callback(null, response);
@@ -1971,7 +1975,7 @@ MatrixBaseApis.prototype.requestMsisdnToken = async function(
             logger.warn("IS doesn't support v2, falling back to deprecated v1");
             return await this._http.idServerRequest(
                 callback, "POST", "/validate/msisdn/requestToken",
-                params, httpApi.PREFIX_IDENTITY_V1,
+                params, PREFIX_IDENTITY_V1,
             );
         }
         if (callback) callback(err);
@@ -2013,7 +2017,7 @@ MatrixBaseApis.prototype.submitMsisdnToken = async function(
     try {
         return await this._http.idServerRequest(
             undefined, "POST", "/validate/msisdn/submitToken",
-            params, httpApi.PREFIX_IDENTITY_V2, identityAccessToken,
+            params, PREFIX_IDENTITY_V2, identityAccessToken,
         );
     } catch (err) {
         if (err.cors === "rejected" || err.httpStatus === 404) {
@@ -2023,7 +2027,7 @@ MatrixBaseApis.prototype.submitMsisdnToken = async function(
             logger.warn("IS doesn't support v2, falling back to deprecated v1");
             return await this._http.idServerRequest(
                 undefined, "POST", "/validate/msisdn/submitToken",
-                params, httpApi.PREFIX_IDENTITY_V1,
+                params, PREFIX_IDENTITY_V1,
             );
         }
         throw err;
@@ -2074,7 +2078,7 @@ MatrixBaseApis.prototype.submitMsisdnTokenOtherUrl = function(
 MatrixBaseApis.prototype.getIdentityHashDetails = function(identityAccessToken) {
     return this._http.idServerRequest(
         undefined, "GET", "/hash_details",
-        null, httpApi.PREFIX_IDENTITY_V2, identityAccessToken,
+        null, PREFIX_IDENTITY_V2, identityAccessToken,
     );
 };
 
@@ -2143,7 +2147,7 @@ MatrixBaseApis.prototype.identityHashedLookup = async function(
 
     const response = await this._http.idServerRequest(
         undefined, "POST", "/lookup",
-        params, httpApi.PREFIX_IDENTITY_V2, identityAccessToken,
+        params, PREFIX_IDENTITY_V2, identityAccessToken,
     );
 
     if (!response || !response['mappings']) return []; // no results
@@ -2223,7 +2227,7 @@ MatrixBaseApis.prototype.lookupThreePid = async function(
             logger.warn("IS doesn't support v2, falling back to deprecated v1");
             return await this._http.idServerRequest(
                 callback, "GET", "/lookup",
-                params, httpApi.PREFIX_IDENTITY_V1,
+                params, PREFIX_IDENTITY_V1,
             );
         }
         if (callback) callback(err, undefined);
@@ -2281,7 +2285,7 @@ MatrixBaseApis.prototype.bulkLookupThreePids = async function(
             logger.warn("IS doesn't support v2, falling back to deprecated v1");
             return await this._http.idServerRequest(
                 undefined, "POST", "/bulk_lookup", params,
-                httpApi.PREFIX_IDENTITY_V1, identityAccessToken,
+                PREFIX_IDENTITY_V1, identityAccessToken,
             );
         }
         throw err;
@@ -2304,7 +2308,7 @@ MatrixBaseApis.prototype.getIdentityAccount = function(
 ) {
     return this._http.idServerRequest(
         undefined, "GET", "/account",
-        undefined, httpApi.PREFIX_IDENTITY_V2, identityAccessToken,
+        undefined, PREFIX_IDENTITY_V2, identityAccessToken,
     );
 };
 
@@ -2432,7 +2436,3 @@ MatrixBaseApis.prototype.reportEvent = function(roomId, eventId, score, reason)
     return this._http.authedRequest(undefined, "POST", path, null, {score, reason});
 };
 
-/**
- * MatrixBaseApis object
- */
-module.exports = MatrixBaseApis;
diff --git a/src/browser-index.js b/src/browser-index.js
new file mode 100644
index 000000000..c1146ae13
--- /dev/null
+++ b/src/browser-index.js
@@ -0,0 +1,54 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import * as matrixcs from "./matrix";
+import request from "browser-request";
+import queryString from "qs";
+
+matrixcs.request(function(opts, fn) {
+    // We manually fix the query string for browser-request because
+    // it doesn't correctly handle cases like ?via=one&via=two. Instead
+    // we mimic `request`'s query string interface to make it all work
+    // as expected.
+    // browser-request will happily take the constructed string as the
+    // query string without trying to modify it further.
+    opts.qs = queryString.stringify(opts.qs || {}, opts.qsStringifyOptions);
+    return request(opts, fn);
+});
+
+// just *accessing* indexedDB throws an exception in firefox with
+// indexeddb disabled.
+let indexedDB;
+try {
+    indexedDB = global.indexedDB;
+} catch(e) {}
+
+// if our browser (appears to) support indexeddb, use an indexeddb crypto store.
+if (indexedDB) {
+    matrixcs.setCryptoStoreFactory(
+        function() {
+            return new matrixcs.IndexedDBCryptoStore(
+                indexedDB, "matrix-js-sdk:crypto",
+            );
+        },
+    );
+}
+
+// We export 3 things to make browserify happy as well as downstream projects.
+// It's awkward, but required.
+export * from "./matrix";
+export default matrixcs; // keep export for browserify package deps
+global.matrixcs = matrixcs;
diff --git a/src/client.js b/src/client.js
index df74f8a50..12671d27f 100644
--- a/src/client.js
+++ b/src/client.js
@@ -16,47 +16,41 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
-const PushProcessor = require('./pushprocessor');
-import {sleep} from './utils';
 
 /**
  * This is an internal module. See {@link MatrixClient} for the public class.
  * @module client
  */
-const EventEmitter = require("events").EventEmitter;
-const url = require('url');
 
-const httpApi = require("./http-api");
-const MatrixEvent = require("./models/event").MatrixEvent;
-const EventStatus = require("./models/event").EventStatus;
-const EventTimeline = require("./models/event-timeline");
-const SearchResult = require("./models/search-result");
-const StubStore = require("./store/stub");
-const webRtcCall = require("./webrtc/call");
-const utils = require("./utils");
-const contentRepo = require("./content-repo");
-const Filter = require("./filter");
-const SyncApi = require("./sync");
-const MatrixBaseApis = require("./base-apis");
-const MatrixError = httpApi.MatrixError;
-const ContentHelpers = require("./content-helpers");
-const olmlib = require("./crypto/olmlib");
-
-import ReEmitter from './ReEmitter';
-import RoomList from './crypto/RoomList';
-import logger from './logger';
-
-import Crypto from './crypto';
-import { isCryptoAvailable } from './crypto';
-import { decodeRecoveryKey } from './crypto/recoverykey';
-import { keyFromAuthData } from './crypto/key_passphrase';
-import { randomString } from './randomstring';
-import { encodeBase64, decodeBase64 } from '../lib/crypto/olmlib';
+import url from "url";
+import {EventEmitter} from "events";
+import {MatrixBaseApis} from "./base-apis";
+import {Filter} from "./filter";
+import {SyncApi} from "./sync";
+import {EventStatus, MatrixEvent} from "./models/event";
+import {EventTimeline} from "./models/event-timeline";
+import {SearchResult} from "./models/search-result";
+import {StubStore} from "./store/stub";
+import {createNewMatrixCall} from "./webrtc/call";
+import * as utils from './utils';
+import {sleep} from './utils';
+import {MatrixError, PREFIX_MEDIA_R0, PREFIX_UNSTABLE} from "./http-api";
+import {getHttpUriForMxc} from "./content-repo";
+import * as ContentHelpers from "./content-helpers";
+import * as olmlib from "./crypto/olmlib";
+import {ReEmitter} from './ReEmitter';
+import {RoomList} from './crypto/RoomList';
+import {logger} from './logger';
+import {Crypto, isCryptoAvailable} from './crypto';
+import {decodeRecoveryKey} from './crypto/recoverykey';
+import {keyFromAuthData} from './crypto/key_passphrase';
+import {randomString} from './randomstring';
+import {PushProcessor} from "./pushprocessor";
+import {encodeBase64, decodeBase64} from "./crypto/olmlib";
 
 const SCROLLBACK_DELAY_MS = 3000;
-const CRYPTO_ENABLED = isCryptoAvailable();
+export const CRYPTO_ENABLED = isCryptoAvailable();
 const CAPABILITIES_CACHE_MS = 21600000; // 6 hours - an arbitrary value
 
 function keysFromRecoverySession(sessions, decryptionKey, roomId) {
@@ -235,7 +229,7 @@ function keyFromRecoverySession(session, decryptionKey) {
  *   {DeviceTrustLevel} device_trust: The trust status of the device requesting
  *     the secret as returned by {@link module:client~MatrixClient#checkDeviceTrust}.
  */
-function MatrixClient(opts) {
+export function MatrixClient(opts) {
     opts.baseUrl = utils.ensureNoTrailingSlash(opts.baseUrl);
     opts.idBaseUrl = utils.ensureNoTrailingSlash(opts.idBaseUrl);
 
@@ -274,7 +268,7 @@ function MatrixClient(opts) {
 
     // try constructing a MatrixCall to see if we are running in an environment
     // which has WebRTC. If we are, listen for and handle m.call.* events.
-    const call = webRtcCall.createNewMatrixCall(this);
+    const call = createNewMatrixCall(this);
     this._supportsVoip = false;
     if (call) {
         setupCallEventHandler(this);
@@ -946,6 +940,35 @@ MatrixClient.prototype.getGlobalBlacklistUnverifiedDevices = function() {
     return this._crypto.getGlobalBlacklistUnverifiedDevices();
 };
 
+/**
+ * Set whether sendMessage in a room with unknown and unverified devices
+ * should throw an error and not send them message. This has 'Global' for
+ * symmetry with setGlobalBlacklistUnverifiedDevices but there is currently
+ * no room-level equivalent for this setting.
+ *
+ * This API is currently UNSTABLE and may change or be removed without notice.
+ *
+ * @param {boolean} value whether error on unknown devices
+ */
+MatrixClient.prototype.setGlobalErrorOnUnknownDevices = function(value) {
+    if (this._crypto === null) {
+        throw new Error("End-to-end encryption disabled");
+    }
+    this._crypto.setGlobalErrorOnUnknownDevices(value);
+};
+
+/**
+ * @return {boolean} whether to error on unknown devices
+ *
+ * This API is currently UNSTABLE and may change or be removed without notice.
+ */
+MatrixClient.prototype.getGlobalErrorOnUnknownDevices = function() {
+    if (this._crypto === null) {
+        throw new Error("End-to-end encryption disabled");
+    }
+    return this._crypto.getGlobalErrorOnUnknownDevices();
+};
+
 /**
  * Add methods that call the corresponding method in this._crypto
  *
@@ -1346,7 +1369,7 @@ MatrixClient.prototype.checkKeyBackup = function() {
 MatrixClient.prototype.getKeyBackupVersion = function() {
     return this._http.authedRequest(
         undefined, "GET", "/room_keys/version", undefined, undefined,
-        {prefix: httpApi.PREFIX_UNSTABLE},
+        {prefix: PREFIX_UNSTABLE},
     ).then((res) => {
         if (res.algorithm !== olmlib.MEGOLM_BACKUP_ALGORITHM) {
             const err = "Unknown backup algorithm: " + res.algorithm;
@@ -1505,14 +1528,20 @@ MatrixClient.prototype.createKeyBackupVersion = async function(info) {
     // favour of just signing with the cross-singing master key.
     await this._crypto._signObject(data.auth_data);
 
-    if (this._crypto._crossSigningInfo.getId()) {
+    if (
+        this._cryptoCallbacks.getCrossSigningKey &&
+        this._crypto._crossSigningInfo.getId()
+    ) {
         // now also sign the auth data with the cross-signing master key
+        // we check for the callback explicitly here because we still want to be able
+        // to create an un-cross-signed key backup if there is a cross-signing key but
+        // no callback supplied.
         await this._crypto._crossSigningInfo.signObject(data.auth_data, "master");
     }
 
     const res = await this._http.authedRequest(
         undefined, "POST", "/room_keys/version", undefined, data,
-        {prefix: httpApi.PREFIX_UNSTABLE},
+        {prefix: PREFIX_UNSTABLE},
     );
 
     // We could assume everything's okay and enable directly, but this ensures
@@ -1544,7 +1573,7 @@ MatrixClient.prototype.deleteKeyBackupVersion = function(version) {
 
     return this._http.authedRequest(
         undefined, "DELETE", path, undefined, undefined,
-        {prefix: httpApi.PREFIX_UNSTABLE},
+        {prefix: PREFIX_UNSTABLE},
     );
 };
 
@@ -1586,7 +1615,7 @@ MatrixClient.prototype.sendKeyBackup = function(roomId, sessionId, version, data
     const path = this._makeKeyBackupPath(roomId, sessionId, version);
     return this._http.authedRequest(
         undefined, "PUT", path.path, path.queryData, data,
-        {prefix: httpApi.PREFIX_UNSTABLE},
+        {prefix: PREFIX_UNSTABLE},
     );
 };
 
@@ -1720,7 +1749,7 @@ MatrixClient.prototype._restoreKeyBackup = function(
 
     return this._http.authedRequest(
         undefined, "GET", path.path, path.queryData, undefined,
-        {prefix: httpApi.PREFIX_UNSTABLE},
+        {prefix: PREFIX_UNSTABLE},
     ).then((res) => {
         if (res.rooms) {
             for (const [roomId, roomData] of Object.entries(res.rooms)) {
@@ -1728,7 +1757,7 @@ MatrixClient.prototype._restoreKeyBackup = function(
 
                 totalKeyCount += Object.keys(roomData.sessions).length;
                 const roomKeys = keysFromRecoverySession(
-                    roomData.sessions, decryption, roomId, roomKeys,
+                    roomData.sessions, decryption, roomId,
                 );
                 for (const k of roomKeys) {
                     k.room_id = roomId;
@@ -1770,7 +1799,7 @@ MatrixClient.prototype.deleteKeysFromBackup = function(roomId, sessionId, versio
     const path = this._makeKeyBackupPath(roomId, sessionId, version);
     return this._http.authedRequest(
         undefined, "DELETE", path.path, path.queryData, undefined,
-        {prefix: httpApi.PREFIX_UNSTABLE},
+        {prefix: PREFIX_UNSTABLE},
     );
 };
 
@@ -1806,7 +1835,7 @@ MatrixClient.prototype.getGroups = function() {
 MatrixClient.prototype.getMediaConfig = function(callback) {
     return this._http.authedRequest(
         callback, "GET", "/config", undefined, undefined, {
-            prefix: httpApi.PREFIX_MEDIA_R0,
+            prefix: PREFIX_MEDIA_R0,
         },
     );
 };
@@ -1913,6 +1942,25 @@ MatrixClient.prototype.getAccountData = function(eventType) {
     return this.store.getAccountData(eventType);
 };
 
+/**
+ * Get account data event of given type for the current user. This variant
+ * bypasses the local store and gets account data directly from the homeserver,
+ * which can be useful very early in startup before the initial sync.
+ * @param {string} eventType The event type
+ * @return {module:client.Promise} Resolves: The contents of the given account
+ * data event.
+ * @return {module:http-api.MatrixError} Rejects: with an error response.
+ */
+MatrixClient.prototype.getAccountDataFromServer = function(eventType) {
+    const path = utils.encodeUri("/user/$userId/account_data/$type", {
+        $userId: this.credentials.userId,
+        $type: eventType,
+    });
+    return this._http.authedRequest(
+        undefined, "GET", path, undefined,
+    );
+};
+
 /**
  * Gets the users that are ignored by this client
  * @returns {string[]} The array of users that are ignored (empty if none)
@@ -2743,7 +2791,7 @@ MatrixClient.prototype.getUrlPreview = function(url, ts, callback) {
             url: url,
             ts: ts,
         }, undefined, {
-            prefix: httpApi.PREFIX_MEDIA_R0,
+            prefix: PREFIX_MEDIA_R0,
         },
     ).then(function(response) {
         // TODO: expire cache occasionally
@@ -3193,7 +3241,7 @@ MatrixClient.prototype.setAvatarUrl = function(url, callback) {
  */
 MatrixClient.prototype.mxcUrlToHttp =
         function(mxcUrl, width, height, resizeMethod, allowDirectLinks) {
-    return contentRepo.getHttpUriForMxc(
+    return getHttpUriForMxc(
         this.baseUrl, mxcUrl, width, height, resizeMethod, allowDirectLinks,
     );
 };
@@ -4852,7 +4900,7 @@ function setupCallEventHandler(client) {
                 );
             }
 
-            call = webRtcCall.createNewMatrixCall(client, event.getRoomId(), {
+            call = createNewMatrixCall(client, event.getRoomId(), {
                 forceTURN: client._forceTURN,
             });
             if (!call) {
@@ -4952,7 +5000,7 @@ function setupCallEventHandler(client) {
                 // if not live, store the fact that the call has ended because
                 // we're probably getting events backwards so
                 // the hangup will come before the invite
-                call = webRtcCall.createNewMatrixCall(client, event.getRoomId());
+                call = createNewMatrixCall(client, event.getRoomId());
                 if (call) {
                     call.callId = content.call_id;
                     call._initWithHangup(event);
@@ -5052,11 +5100,6 @@ MatrixClient.prototype.generateClientSecret = function() {
     return randomString(32);
 };
 
-/** */
-module.exports.MatrixClient = MatrixClient;
-/** */
-module.exports.CRYPTO_ENABLED = CRYPTO_ENABLED;
-
 // MatrixClient Event JSDocs
 
 /**
diff --git a/src/content-helpers.js b/src/content-helpers.js
index a1afe1f71..c82f808c5 100644
--- a/src/content-helpers.js
+++ b/src/content-helpers.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,88 +14,86 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /** @module ContentHelpers */
-module.exports = {
-    /**
-     * Generates the content for a HTML Message event
-     * @param {string} body the plaintext body of the message
-     * @param {string} htmlBody the HTML representation of the message
-     * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
-     */
-    makeHtmlMessage: function(body, htmlBody) {
-        return {
-            msgtype: "m.text",
-            format: "org.matrix.custom.html",
-            body: body,
-            formatted_body: htmlBody,
-        };
-    },
 
-    /**
-     * Generates the content for a HTML Notice event
-     * @param {string} body the plaintext body of the notice
-     * @param {string} htmlBody the HTML representation of the notice
-     * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
-     */
-    makeHtmlNotice: function(body, htmlBody) {
-        return {
-            msgtype: "m.notice",
-            format: "org.matrix.custom.html",
-            body: body,
-            formatted_body: htmlBody,
-        };
-    },
+/**
+ * Generates the content for a HTML Message event
+ * @param {string} body the plaintext body of the message
+ * @param {string} htmlBody the HTML representation of the message
+ * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
+ */
+export function makeHtmlMessage(body, htmlBody) {
+    return {
+        msgtype: "m.text",
+        format: "org.matrix.custom.html",
+        body: body,
+        formatted_body: htmlBody,
+    };
+}
 
-    /**
-     * Generates the content for a HTML Emote event
-     * @param {string} body the plaintext body of the emote
-     * @param {string} htmlBody the HTML representation of the emote
-     * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
-     */
-    makeHtmlEmote: function(body, htmlBody) {
-        return {
-            msgtype: "m.emote",
-            format: "org.matrix.custom.html",
-            body: body,
-            formatted_body: htmlBody,
-        };
-    },
+/**
+ * Generates the content for a HTML Notice event
+ * @param {string} body the plaintext body of the notice
+ * @param {string} htmlBody the HTML representation of the notice
+ * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
+ */
+export function makeHtmlNotice(body, htmlBody) {
+    return {
+        msgtype: "m.notice",
+        format: "org.matrix.custom.html",
+        body: body,
+        formatted_body: htmlBody,
+    };
+}
 
-    /**
-     * Generates the content for a Plaintext Message event
-     * @param {string} body the plaintext body of the emote
-     * @returns {{msgtype: string, body: string}}
-     */
-    makeTextMessage: function(body) {
-        return {
-            msgtype: "m.text",
-            body: body,
-        };
-    },
+/**
+ * Generates the content for a HTML Emote event
+ * @param {string} body the plaintext body of the emote
+ * @param {string} htmlBody the HTML representation of the emote
+ * @returns {{msgtype: string, format: string, body: string, formatted_body: string}}
+ */
+export function makeHtmlEmote(body, htmlBody) {
+    return {
+        msgtype: "m.emote",
+        format: "org.matrix.custom.html",
+        body: body,
+        formatted_body: htmlBody,
+    };
+}
 
-    /**
-     * Generates the content for a Plaintext Notice event
-     * @param {string} body the plaintext body of the notice
-     * @returns {{msgtype: string, body: string}}
-     */
-    makeNotice: function(body) {
-        return {
-            msgtype: "m.notice",
-            body: body,
-        };
-    },
+/**
+ * Generates the content for a Plaintext Message event
+ * @param {string} body the plaintext body of the emote
+ * @returns {{msgtype: string, body: string}}
+ */
+export function makeTextMessage(body) {
+    return {
+        msgtype: "m.text",
+        body: body,
+    };
+}
 
-    /**
-     * Generates the content for a Plaintext Emote event
-     * @param {string} body the plaintext body of the emote
-     * @returns {{msgtype: string, body: string}}
-     */
-    makeEmoteMessage: function(body) {
-        return {
-            msgtype: "m.emote",
-            body: body,
-        };
-    },
-};
+/**
+ * Generates the content for a Plaintext Notice event
+ * @param {string} body the plaintext body of the notice
+ * @returns {{msgtype: string, body: string}}
+ */
+export function makeNotice(body) {
+    return {
+        msgtype: "m.notice",
+        body: body,
+    };
+}
+
+/**
+ * Generates the content for a Plaintext Emote event
+ * @param {string} body the plaintext body of the emote
+ * @returns {{msgtype: string, body: string}}
+ */
+export function makeEmoteMessage(body) {
+    return {
+        msgtype: "m.emote",
+        body: body,
+    };
+}
diff --git a/src/content-repo.js b/src/content-repo.js
index 9c0a3306b..4bc4ca688 100644
--- a/src/content-repo.js
+++ b/src/content-repo.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -16,95 +17,93 @@ limitations under the License.
 /**
  * @module content-repo
  */
-const utils = require("./utils");
 
-/** Content Repo utility functions */
-module.exports = {
-    /**
-     * Get the HTTP URL for an MXC URI.
-     * @param {string} baseUrl The base homeserver url which has a content repo.
-     * @param {string} mxc The mxc:// URI.
-     * @param {Number} width The desired width of the thumbnail.
-     * @param {Number} height The desired height of the thumbnail.
-     * @param {string} resizeMethod The thumbnail resize method to use, either
-     * "crop" or "scale".
-     * @param {Boolean} allowDirectLinks If true, return any non-mxc URLs
-     * directly. Fetching such URLs will leak information about the user to
-     * anyone they share a room with. If false, will return the emptry string
-     * for such URLs.
-     * @return {string} The complete URL to the content.
-     */
-    getHttpUriForMxc: function(baseUrl, mxc, width, height,
-                               resizeMethod, allowDirectLinks) {
-        if (typeof mxc !== "string" || !mxc) {
+import * as utils from "./utils";
+
+/**
+ * Get the HTTP URL for an MXC URI.
+ * @param {string} baseUrl The base homeserver url which has a content repo.
+ * @param {string} mxc The mxc:// URI.
+ * @param {Number} width The desired width of the thumbnail.
+ * @param {Number} height The desired height of the thumbnail.
+ * @param {string} resizeMethod The thumbnail resize method to use, either
+ * "crop" or "scale".
+ * @param {Boolean} allowDirectLinks If true, return any non-mxc URLs
+ * directly. Fetching such URLs will leak information about the user to
+ * anyone they share a room with. If false, will return the emptry string
+ * for such URLs.
+ * @return {string} The complete URL to the content.
+ */
+export function getHttpUriForMxc(baseUrl, mxc, width, height,
+                           resizeMethod, allowDirectLinks) {
+    if (typeof mxc !== "string" || !mxc) {
+        return '';
+    }
+    if (mxc.indexOf("mxc://") !== 0) {
+        if (allowDirectLinks) {
+            return mxc;
+        } else {
             return '';
         }
-        if (mxc.indexOf("mxc://") !== 0) {
-            if (allowDirectLinks) {
-                return mxc;
-            } else {
-                return '';
-            }
-        }
-        let serverAndMediaId = mxc.slice(6); // strips mxc://
-        let prefix = "/_matrix/media/r0/download/";
-        const params = {};
+    }
+    let serverAndMediaId = mxc.slice(6); // strips mxc://
+    let prefix = "/_matrix/media/r0/download/";
+    const params = {};
 
-        if (width) {
-            params.width = Math.round(width);
-        }
-        if (height) {
-            params.height = Math.round(height);
-        }
-        if (resizeMethod) {
-            params.method = resizeMethod;
-        }
-        if (utils.keys(params).length > 0) {
-            // these are thumbnailing params so they probably want the
-            // thumbnailing API...
-            prefix = "/_matrix/media/r0/thumbnail/";
-        }
+    if (width) {
+        params.width = Math.round(width);
+    }
+    if (height) {
+        params.height = Math.round(height);
+    }
+    if (resizeMethod) {
+        params.method = resizeMethod;
+    }
+    if (utils.keys(params).length > 0) {
+        // these are thumbnailing params so they probably want the
+        // thumbnailing API...
+        prefix = "/_matrix/media/r0/thumbnail/";
+    }
 
-        const fragmentOffset = serverAndMediaId.indexOf("#");
-        let fragment = "";
-        if (fragmentOffset >= 0) {
-            fragment = serverAndMediaId.substr(fragmentOffset);
-            serverAndMediaId = serverAndMediaId.substr(0, fragmentOffset);
-        }
-        return baseUrl + prefix + serverAndMediaId +
-            (utils.keys(params).length === 0 ? "" :
-            ("?" + utils.encodeParams(params))) + fragment;
-    },
+    const fragmentOffset = serverAndMediaId.indexOf("#");
+    let fragment = "";
+    if (fragmentOffset >= 0) {
+        fragment = serverAndMediaId.substr(fragmentOffset);
+        serverAndMediaId = serverAndMediaId.substr(0, fragmentOffset);
+    }
+    return baseUrl + prefix + serverAndMediaId +
+        (utils.keys(params).length === 0 ? "" :
+        ("?" + utils.encodeParams(params))) + fragment;
+}
 
-    /**
-     * Get an identicon URL from an arbitrary string.
-     * @param {string} baseUrl The base homeserver url which has a content repo.
-     * @param {string} identiconString The string to create an identicon for.
-     * @param {Number} width The desired width of the image in pixels. Default: 96.
-     * @param {Number} height The desired height of the image in pixels. Default: 96.
-     * @return {string} The complete URL to the identicon.
-     * @deprecated This is no longer in the specification.
-     */
-    getIdenticonUri: function(baseUrl, identiconString, width, height) {
-        if (!identiconString) {
-            return null;
-        }
-        if (!width) {
-            width = 96;
-        }
-        if (!height) {
-            height = 96;
-        }
-        const params = {
-            width: width,
-            height: height,
-        };
+/**
+ * Get an identicon URL from an arbitrary string.
+ * @param {string} baseUrl The base homeserver url which has a content repo.
+ * @param {string} identiconString The string to create an identicon for.
+ * @param {Number} width The desired width of the image in pixels. Default: 96.
+ * @param {Number} height The desired height of the image in pixels. Default: 96.
+ * @return {string} The complete URL to the identicon.
+ * @deprecated This is no longer in the specification.
+ */
+export function getIdenticonUri(baseUrl, identiconString, width, height) {
+    if (!identiconString) {
+        return null;
+    }
+    if (!width) {
+        width = 96;
+    }
+    if (!height) {
+        height = 96;
+    }
+    const params = {
+        width: width,
+        height: height,
+    };
 
-        const path = utils.encodeUri("/_matrix/media/unstable/identicon/$ident", {
-            $ident: identiconString,
-        });
-        return baseUrl + path +
-            (utils.keys(params).length === 0 ? "" :
-                ("?" + utils.encodeParams(params)));
-    },
-};
+    const path = utils.encodeUri("/_matrix/media/unstable/identicon/$ident", {
+        $ident: identiconString,
+    });
+    return baseUrl + path +
+        (utils.keys(params).length === 0 ? "" :
+            ("?" + utils.encodeParams(params)));
+}
diff --git a/src/crypto/CrossSigning.js b/src/crypto/CrossSigning.js
index 764f2c21e..b37fa6d43 100644
--- a/src/crypto/CrossSigning.js
+++ b/src/crypto/CrossSigning.js
@@ -20,9 +20,9 @@ limitations under the License.
  * @module crypto/CrossSigning
  */
 
-import {pkSign, pkVerify, encodeBase64, decodeBase64} from './olmlib';
+import {decodeBase64, encodeBase64, pkSign, pkVerify} from './olmlib';
 import {EventEmitter} from 'events';
-import logger from '../logger';
+import {logger} from '../logger';
 
 function publicKeyFromKeyInfo(keyInfo) {
     // `keys` is an object with { [`ed25519:${pubKey}`]: pubKey }
diff --git a/src/crypto/DeviceList.js b/src/crypto/DeviceList.js
index 7087bac43..073eb5282 100644
--- a/src/crypto/DeviceList.js
+++ b/src/crypto/DeviceList.js
@@ -15,7 +15,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module crypto/DeviceList
@@ -24,12 +23,11 @@ limitations under the License.
  */
 
 import {EventEmitter} from 'events';
-
-import logger from '../logger';
-import DeviceInfo from './deviceinfo';
+import {logger} from '../logger';
+import {DeviceInfo} from './deviceinfo';
 import {CrossSigningInfo} from './CrossSigning';
-import olmlib from './olmlib';
-import IndexedDBCryptoStore from './store/indexeddb-crypto-store';
+import * as olmlib from './olmlib';
+import {IndexedDBCryptoStore} from './store/indexeddb-crypto-store';
 import {defer, sleep} from '../utils';
 
 
@@ -63,7 +61,7 @@ const TRACKING_STATUS_UP_TO_DATE = 3;
 /**
  * @alias module:crypto/DeviceList
  */
-export default class DeviceList extends EventEmitter {
+export class DeviceList extends EventEmitter {
     constructor(baseApis, cryptoStore, olmDevice) {
         super();
 
diff --git a/src/crypto/OlmDevice.js b/src/crypto/OlmDevice.js
index b86b4f858..872f5aa93 100644
--- a/src/crypto/OlmDevice.js
+++ b/src/crypto/OlmDevice.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2016 OpenMarket Ltd
 Copyright 2017, 2019 New Vector Ltd
+Copyright 2019, 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,8 +16,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../logger';
-import IndexedDBCryptoStore from './store/indexeddb-crypto-store';
+import {logger} from '../logger';
+import {IndexedDBCryptoStore} from './store/indexeddb-crypto-store';
+import * as algorithms from './algorithms';
 
 // The maximum size of an event is 65K, and we base64 the content, so this is a
 // reasonable approximation to the biggest plaintext we can encrypt.
@@ -69,7 +71,7 @@ function checkPayloadLength(payloadString) {
  * @property {string} deviceCurve25519Key   Curve25519 key for the account
  * @property {string} deviceEd25519Key      Ed25519 key for the account
  */
-function OlmDevice(cryptoStore) {
+export function OlmDevice(cryptoStore) {
     this._cryptoStore = cryptoStore;
     this._pickleKey = "DEFAULT_KEY";
 
@@ -671,6 +673,18 @@ OlmDevice.prototype.matchesSession = async function(
     return matches;
 };
 
+OlmDevice.prototype.recordSessionProblem = async function(deviceKey, type, fixed) {
+    await this._cryptoStore.storeEndToEndSessionProblem(deviceKey, type, fixed);
+};
+
+OlmDevice.prototype.sessionMayHaveProblems = async function(deviceKey, timestamp) {
+    return await this._cryptoStore.getEndToEndSessionProblem(deviceKey, timestamp);
+};
+
+OlmDevice.prototype.filterOutNotifiedErrorDevices = async function(devices) {
+    return await this._cryptoStore.filterOutNotifiedErrorDevices(devices);
+};
+
 
 // Outbound group session
 // ======================
@@ -818,9 +832,9 @@ OlmDevice.prototype._getInboundGroupSession = function(
     roomId, senderKey, sessionId, txn, func,
 ) {
     this._cryptoStore.getEndToEndInboundGroupSession(
-        senderKey, sessionId, txn, (sessionData) => {
+        senderKey, sessionId, txn, (sessionData, withheld) => {
             if (sessionData === null) {
-                func(null);
+                func(null, null, withheld);
                 return;
             }
 
@@ -834,7 +848,7 @@ OlmDevice.prototype._getInboundGroupSession = function(
             }
 
             this._unpickleInboundGroupSession(sessionData, (session) => {
-                func(session, sessionData);
+                func(session, sessionData, withheld);
             });
         },
     );
@@ -859,7 +873,10 @@ OlmDevice.prototype.addInboundGroupSession = async function(
     exportFormat,
 ) {
     await this._cryptoStore.doTxn(
-        'readwrite', [IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS], (txn) => {
+        'readwrite', [
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS,
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD,
+        ], (txn) => {
             /* if we already have this session, consider updating it */
             this._getInboundGroupSession(
                 roomId, senderKey, sessionId, txn,
@@ -914,6 +931,60 @@ OlmDevice.prototype.addInboundGroupSession = async function(
     );
 };
 
+/**
+ * Record in the data store why an inbound group session was withheld.
+ *
+ * @param {string} roomId     room that the session belongs to
+ * @param {string} senderKey  base64-encoded curve25519 key of the sender
+ * @param {string} sessionId  session identifier
+ * @param {string} code       reason code
+ * @param {string} reason     human-readable version of `code`
+ */
+OlmDevice.prototype.addInboundGroupSessionWithheld = async function(
+    roomId, senderKey, sessionId, code, reason,
+) {
+    await this._cryptoStore.doTxn(
+        'readwrite', [IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD],
+        (txn) => {
+            this._cryptoStore.storeEndToEndInboundGroupSessionWithheld(
+                senderKey, sessionId,
+                {
+                    room_id: roomId,
+                    code: code,
+                    reason: reason,
+                },
+                txn,
+            );
+        },
+    );
+};
+
+export const WITHHELD_MESSAGES = {
+    "m.unverified": "The sender has disabled encrypting to unverified devices.",
+    "m.blacklisted": "The sender has blocked you.",
+    "m.unauthorised": "You are not authorised to read the message.",
+    "m.no_olm": "Unable to establish a secure channel.",
+};
+
+/**
+ * Calculate the message to use for the exception when a session key is withheld.
+ *
+ * @param {object} withheld  An object that describes why the key was withheld.
+ *
+ * @return {string} the message
+ *
+ * @private
+ */
+function _calculateWithheldMessage(withheld) {
+    if (withheld.code && withheld.code in WITHHELD_MESSAGES) {
+        return WITHHELD_MESSAGES[withheld.code];
+    } else if (withheld.reason) {
+        return withheld.reason;
+    } else {
+        return "decryption key withheld";
+    }
+}
+
 /**
  * Decrypt a received message with an inbound group session
  *
@@ -934,16 +1005,49 @@ OlmDevice.prototype.decryptGroupMessage = async function(
     roomId, senderKey, sessionId, body, eventId, timestamp,
 ) {
     let result;
+    // when the localstorage crypto store is used as an indexeddb backend,
+    // exceptions thrown from within the inner function are not passed through
+    // to the top level, so we store exceptions in a variable and raise them at
+    // the end
+    let error;
 
     await this._cryptoStore.doTxn(
-        'readwrite', [IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS], (txn) => {
+        'readwrite', [
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS,
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD,
+        ], (txn) => {
             this._getInboundGroupSession(
-                roomId, senderKey, sessionId, txn, (session, sessionData) => {
+                roomId, senderKey, sessionId, txn, (session, sessionData, withheld) => {
                     if (session === null) {
+                        if (withheld) {
+                            error = new algorithms.DecryptionError(
+                                "MEGOLM_UNKNOWN_INBOUND_SESSION_ID",
+                                _calculateWithheldMessage(withheld),
+                                {
+                                    session: senderKey + '|' + sessionId,
+                                },
+                            );
+                        }
                         result = null;
                         return;
                     }
-                    const res = session.decrypt(body);
+                    let res;
+                    try {
+                        res = session.decrypt(body);
+                    } catch (e) {
+                        if (e && e.message === 'OLM.UNKNOWN_MESSAGE_INDEX' && withheld) {
+                            error = new algorithms.DecryptionError(
+                                "MEGOLM_UNKNOWN_INBOUND_SESSION_ID",
+                                _calculateWithheldMessage(withheld),
+                                {
+                                    session: senderKey + '|' + sessionId,
+                                },
+                            );
+                        } else {
+                            error = e;
+                        }
+                        return;
+                    }
 
                     let plaintext = res.plaintext;
                     if (plaintext === undefined) {
@@ -965,10 +1069,11 @@ OlmDevice.prototype.decryptGroupMessage = async function(
                                 msgInfo.id !== eventId ||
                                 msgInfo.timestamp !== timestamp
                             ) {
-                                throw new Error(
+                                error = new Error(
                                     "Duplicate message index, possible replay attack: " +
                                     messageIndexKey,
                                 );
+                                return;
                             }
                         }
                         this._inboundGroupSessionMessageIndexes[messageIndexKey] = {
@@ -994,6 +1099,9 @@ OlmDevice.prototype.decryptGroupMessage = async function(
         },
     );
 
+    if (error) {
+        throw error;
+    }
     return result;
 };
 
@@ -1009,7 +1117,10 @@ OlmDevice.prototype.decryptGroupMessage = async function(
 OlmDevice.prototype.hasInboundSessionKeys = async function(roomId, senderKey, sessionId) {
     let result;
     await this._cryptoStore.doTxn(
-        'readonly', [IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS], (txn) => {
+        'readonly', [
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS,
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD,
+        ], (txn) => {
             this._cryptoStore.getEndToEndInboundGroupSession(
                 senderKey, sessionId, txn, (sessionData) => {
                     if (sessionData === null) {
@@ -1060,7 +1171,10 @@ OlmDevice.prototype.getInboundGroupSessionKey = async function(
 ) {
     let result;
     await this._cryptoStore.doTxn(
-        'readonly', [IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS], (txn) => {
+        'readonly', [
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS,
+            IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD,
+        ], (txn) => {
             this._getInboundGroupSession(
                 roomId, senderKey, sessionId, txn, (session, sessionData) => {
                     if (session === null) {
@@ -1139,6 +1253,3 @@ OlmDevice.prototype.verifySignature = function(
         util.ed25519_verify(key, message, signature);
     });
 };
-
-/** */
-module.exports = OlmDevice;
diff --git a/src/crypto/OutgoingRoomKeyRequestManager.js b/src/crypto/OutgoingRoomKeyRequestManager.js
index ef435e9c8..803791df4 100644
--- a/src/crypto/OutgoingRoomKeyRequestManager.js
+++ b/src/crypto/OutgoingRoomKeyRequestManager.js
@@ -14,8 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../logger';
-import utils from '../utils';
+import {logger} from '../logger';
+import * as utils from '../utils';
 
 /**
  * Internal module. Management of outgoing room key requests.
@@ -75,7 +75,7 @@ const ROOM_KEY_REQUEST_STATES = {
     CANCELLATION_PENDING_AND_WILL_RESEND: 3,
 };
 
-export default class OutgoingRoomKeyRequestManager {
+export class OutgoingRoomKeyRequestManager {
     constructor(baseApis, deviceId, cryptoStore) {
         this._baseApis = baseApis;
         this._deviceId = deviceId;
diff --git a/src/crypto/RoomList.js b/src/crypto/RoomList.js
index b8c87dd1f..6a3c6c22f 100644
--- a/src/crypto/RoomList.js
+++ b/src/crypto/RoomList.js
@@ -20,12 +20,12 @@ limitations under the License.
  * Manages the list of encrypted rooms
  */
 
-import IndexedDBCryptoStore from './store/indexeddb-crypto-store';
+import {IndexedDBCryptoStore} from './store/indexeddb-crypto-store';
 
 /**
  * @alias module:crypto/RoomList
  */
-export default class RoomList {
+export class RoomList {
     constructor(cryptoStore) {
         this._cryptoStore = cryptoStore;
 
diff --git a/src/crypto/SecretStorage.js b/src/crypto/SecretStorage.js
index 36aa59cf3..584c5c4c0 100644
--- a/src/crypto/SecretStorage.js
+++ b/src/crypto/SecretStorage.js
@@ -15,10 +15,10 @@ limitations under the License.
 */
 
 import {EventEmitter} from 'events';
-import logger from '../logger';
-import olmlib from './olmlib';
-import { randomString } from '../randomstring';
-import { pkVerify } from './olmlib';
+import {logger} from '../logger';
+import * as olmlib from './olmlib';
+import {pkVerify} from './olmlib';
+import {randomString} from '../randomstring';
 
 export const SECRET_STORAGE_ALGORITHM_V1 = "m.secret_storage.v1.curve25519-aes-sha2";
 
@@ -26,7 +26,7 @@ export const SECRET_STORAGE_ALGORITHM_V1 = "m.secret_storage.v1.curve25519-aes-s
  * Implements Secure Secret Storage and Sharing (MSC1946)
  * @module crypto/SecretStorage
  */
-export default class SecretStorage extends EventEmitter {
+export class SecretStorage extends EventEmitter {
     constructor(baseApis, cryptoCallbacks, crossSigningInfo) {
         super();
         this._baseApis = baseApis;
diff --git a/src/crypto/algorithms/base.js b/src/crypto/algorithms/base.js
index d5e38f477..115b35da9 100644
--- a/src/crypto/algorithms/base.js
+++ b/src/crypto/algorithms/base.js
@@ -50,7 +50,7 @@ export const DECRYPTION_CLASSES = {};
  * @param {string} params.roomId  The ID of the room we will be sending to
  * @param {object} params.config  The body of the m.room.encryption event
  */
-class EncryptionAlgorithm {
+export class EncryptionAlgorithm {
     constructor(params) {
         this._userId = params.userId;
         this._deviceId = params.deviceId;
@@ -84,7 +84,6 @@ class EncryptionAlgorithm {
      onRoomMembership(event, member, oldMembership) {
      }
 }
-export {EncryptionAlgorithm}; // https://github.com/jsdoc3/jsdoc/issues/1272
 
 /**
  * base type for decryption implementations
@@ -98,7 +97,7 @@ export {EncryptionAlgorithm}; // https://github.com/jsdoc3/jsdoc/issues/1272
  * @param {string=} params.roomId The ID of the room we will be receiving
  *     from. Null for to-device events.
  */
-class DecryptionAlgorithm {
+export class DecryptionAlgorithm {
     constructor(params) {
         this._userId = params.userId;
         this._crypto = params.crypto;
@@ -159,8 +158,17 @@ class DecryptionAlgorithm {
     shareKeysWithDevice(keyRequest) {
         throw new Error("shareKeysWithDevice not supported for this DecryptionAlgorithm");
     }
+
+    /**
+     * Retry decrypting all the events from a sender that haven't been
+     * decrypted yet.
+     *
+     * @param {string} senderKey the sender's key
+     */
+    async retryDecryptionFromSender(senderKey) {
+        // ignore by default
+    }
 }
-export {DecryptionAlgorithm}; // https://github.com/jsdoc3/jsdoc/issues/1272
 
 /**
  * Exception thrown when decryption fails
@@ -173,7 +181,7 @@ export {DecryptionAlgorithm}; // https://github.com/jsdoc3/jsdoc/issues/1272
  *
  * @extends Error
  */
-class DecryptionError extends Error {
+export class DecryptionError extends Error {
     constructor(code, msg, details) {
         super(msg);
         this.code = code;
@@ -181,7 +189,6 @@ class DecryptionError extends Error {
         this.detailedString = _detailedStringForDecryptionError(this, details);
     }
 }
-export {DecryptionError}; // https://github.com/jsdoc3/jsdoc/issues/1272
 
 function _detailedStringForDecryptionError(err, details) {
     let result = err.name + '[msg: ' + err.message;
diff --git a/src/crypto/algorithms/index.js b/src/crypto/algorithms/index.js
index ce64b3b11..0fb646cfe 100644
--- a/src/crypto/algorithms/index.js
+++ b/src/crypto/algorithms/index.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,28 +14,12 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module crypto/algorithms
  */
 
-const base = require("./base");
+import "./olm";
+import "./megolm";
 
-require("./olm");
-require("./megolm");
-
-/**
- * @see module:crypto/algorithms/base.ENCRYPTION_CLASSES
- */
-module.exports.ENCRYPTION_CLASSES = base.ENCRYPTION_CLASSES;
-
-/**
- * @see module:crypto/algorithms/base.DECRYPTION_CLASSES
- */
-module.exports.DECRYPTION_CLASSES = base.DECRYPTION_CLASSES;
-
-/**
- * @see module:crypto/algorithms/base.DecryptionError
- */
-module.exports.DecryptionError = base.DecryptionError;
+export * from "./base";
diff --git a/src/crypto/algorithms/megolm.js b/src/crypto/algorithms/megolm.js
index 8c60adf5c..ed085557a 100644
--- a/src/crypto/algorithms/megolm.js
+++ b/src/crypto/algorithms/megolm.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,7 +15,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * Defines m.olm encryption/decryption
@@ -22,11 +22,19 @@ limitations under the License.
  * @module crypto/algorithms/megolm
  */
 
-import logger from '../../logger';
+import {logger} from '../../logger';
+import * as utils from "../../utils";
+import {polyfillSuper} from "../../utils";
+import * as olmlib from "../olmlib";
+import {
+    DecryptionAlgorithm,
+    DecryptionError,
+    EncryptionAlgorithm,
+    registerAlgorithm,
+    UnknownDeviceError,
+} from "./base";
 
-const utils = require("../../utils");
-const olmlib = require("../olmlib");
-const base = require("./base");
+import {WITHHELD_MESSAGES} from '../OlmDevice';
 
 /**
  * @private
@@ -47,6 +55,7 @@ function OutboundSessionInfo(sessionId) {
     this.useCount = 0;
     this.creationTime = new Date().getTime();
     this.sharedWithDevices = {};
+    this.blockedDevicesNotified = {};
 }
 
 
@@ -84,6 +93,15 @@ OutboundSessionInfo.prototype.markSharedWithDevice = function(
     this.sharedWithDevices[userId][deviceId] = chainIndex;
 };
 
+OutboundSessionInfo.prototype.markNotifiedBlockedDevice = function(
+    userId, deviceId,
+) {
+    if (!this.blockedDevicesNotified[userId]) {
+        this.blockedDevicesNotified[userId] = {};
+    }
+    this.blockedDevicesNotified[userId][deviceId] = true;
+};
+
 /**
  * Determine if this session has been shared with devices which it shouldn't
  * have been.
@@ -128,13 +146,13 @@ OutboundSessionInfo.prototype.sharedWithTooManyDevices = function(
  * Megolm encryption implementation
  *
  * @constructor
- * @extends {module:crypto/algorithms/base.EncryptionAlgorithm}
+ * @extends {module:crypto/algorithms/EncryptionAlgorithm}
  *
  * @param {object} params parameters, as per
- *     {@link module:crypto/algorithms/base.EncryptionAlgorithm}
+ *     {@link module:crypto/algorithms/EncryptionAlgorithm}
  */
 function MegolmEncryption(params) {
-    base.EncryptionAlgorithm.call(this, params);
+    polyfillSuper(this, EncryptionAlgorithm, params);
 
     // the most recent attempt to set up a session. This is used to serialise
     // the session setups, so that we have a race-free view of which session we
@@ -160,17 +178,20 @@ function MegolmEncryption(params) {
         this._sessionRotationPeriodMsgs = params.config.rotation_period_msgs;
     }
 }
-utils.inherits(MegolmEncryption, base.EncryptionAlgorithm);
+utils.inherits(MegolmEncryption, EncryptionAlgorithm);
 
 /**
  * @private
  *
  * @param {Object} devicesInRoom The devices in this room, indexed by user ID
+ * @param {Object} blocked The devices that are blocked, indexed by user ID
  *
  * @return {module:client.Promise} Promise which resolves to the
  *    OutboundSessionInfo when setup is complete.
  */
-MegolmEncryption.prototype._ensureOutboundSession = function(devicesInRoom) {
+MegolmEncryption.prototype._ensureOutboundSession = async function(
+    devicesInRoom, blocked,
+) {
     const self = this;
 
     let session;
@@ -237,9 +258,50 @@ MegolmEncryption.prototype._ensureOutboundSession = function(devicesInRoom) {
             }
         }
 
-        return self._shareKeyWithDevices(
-            session, shareMap,
+        const errorDevices = [];
+
+        await self._shareKeyWithDevices(
+            session, shareMap, errorDevices,
         );
+
+        // are there any new blocked devices that we need to notify?
+        const blockedMap = {};
+        for (const userId in blocked) {
+            if (!blocked.hasOwnProperty(userId)) {
+                continue;
+            }
+
+            const userBlockedDevices = blocked[userId];
+
+            for (const deviceId in userBlockedDevices) {
+                if (!userBlockedDevices.hasOwnProperty(deviceId)) {
+                    continue;
+                }
+
+                if (
+                    !session.blockedDevicesNotified[userId] ||
+                        session.blockedDevicesNotified[userId][deviceId] === undefined
+                ) {
+                    blockedMap[userId] = blockedMap[userId] || [];
+                    blockedMap[userId].push(userBlockedDevices[deviceId]);
+                }
+            }
+        }
+
+
+        const filteredErrorDevices =
+              await self._olmDevice.filterOutNotifiedErrorDevices(errorDevices);
+        for (const {userId, deviceInfo} of filteredErrorDevices) {
+            blockedMap[userId] = blockedMap[userId] || [];
+            blockedMap[userId].push({
+                code: "m.no_olm",
+                reason: WITHHELD_MESSAGES["m.no_olm"],
+                deviceInfo,
+            });
+        }
+
+        // notify blocked devices that they're blocked
+        await self._notifyBlockedDevices(session, blockedMap);
     }
 
     // helper which returns the session prepared by prepareSession
@@ -287,6 +349,10 @@ MegolmEncryption.prototype._prepareNewSession = async function() {
 };
 
 /**
+ * Splits the user device map into multiple chunks to reduce the number of
+ * devices we encrypt to per API call. Also filters out devices we don't have
+ * a session with.
+ *
  * @private
  *
  * @param {module:crypto/algorithms/megolm.OutboundSessionInfo} session
@@ -299,12 +365,16 @@ MegolmEncryption.prototype._prepareNewSession = async function() {
  * @param {object<string, module:crypto/deviceinfo[]>} devicesByUser
  *    map from userid to list of devices
  *
+ * @param {array<object>} errorDevices
+ *    array that will be populated with the devices that can't get an
+ *    olm session for
+ *
  * @return {array<object<userid, deviceInfo>>}
  */
 MegolmEncryption.prototype._splitUserDeviceMap = function(
-    session, chainIndex, devicemap, devicesByUser,
+    session, chainIndex, devicemap, devicesByUser, errorDevices,
 ) {
-    const maxToDeviceMessagesPerRequest = 20;
+    const maxUsersPerRequest = 20;
 
     // use an array where the slices of a content map gets stored
     const mapSlices = [];
@@ -334,6 +404,8 @@ MegolmEncryption.prototype._splitUserDeviceMap = function(
                 // to claim a one-time-key for dead devices on every message.
                 session.markSharedWithDevice(userId, deviceId, chainIndex);
 
+                errorDevices.push({userId, deviceInfo});
+
                 // ensureOlmSessionsForUsers has already done the logging,
                 // so just skip it.
                 continue;
@@ -343,11 +415,6 @@ MegolmEncryption.prototype._splitUserDeviceMap = function(
                 "share keys with device " + userId + ":" + deviceId,
             );
 
-            if (entriesInCurrentSlice > maxToDeviceMessagesPerRequest) {
-                // the current slice is filled up. Start inserting into the next slice
-                entriesInCurrentSlice = 0;
-                currentSliceId++;
-            }
             if (!mapSlices[currentSliceId]) {
                 mapSlices[currentSliceId] = [];
             }
@@ -359,6 +426,61 @@ MegolmEncryption.prototype._splitUserDeviceMap = function(
 
             entriesInCurrentSlice++;
         }
+
+        // We do this in the per-user loop as we prefer that all messages to the
+        // same user end up in the same API call to make it easier for the
+        // server (e.g. only have to send one EDU if a remote user, etc). This
+        // does mean that if a user has many devices we may go over the desired
+        // limit, but its not a hard limit so that is fine.
+        if (entriesInCurrentSlice > maxUsersPerRequest) {
+            // the current slice is filled up. Start inserting into the next slice
+            entriesInCurrentSlice = 0;
+            currentSliceId++;
+        }
+    }
+    return mapSlices;
+};
+
+/**
+ * Splits the user device map into multiple chunks to reduce the number of
+ * devices we encrypt to per API call.
+ *
+ * @private
+ *
+ * @param {object} devicesByUser map from userid to list of devices
+ *
+ * @return {array<array<object>>} the blocked devices, split into chunks
+ */
+MegolmEncryption.prototype._splitBlockedDevices = function(devicesByUser) {
+    const maxUsersPerRequest = 20;
+
+    // use an array where the slices of a content map gets stored
+    let currentSlice = [];
+    const mapSlices = [currentSlice];
+
+    for (const userId of Object.keys(devicesByUser)) {
+        const userBlockedDevicesToShareWith = devicesByUser[userId];
+
+        for (const blockedInfo of userBlockedDevicesToShareWith) {
+            currentSlice.push({
+                userId: userId,
+                blockedInfo: blockedInfo,
+            });
+        }
+
+        // We do this in the per-user loop as we prefer that all messages to the
+        // same user end up in the same API call to make it easier for the
+        // server (e.g. only have to send one EDU if a remote user, etc). This
+        // does mean that if a user has many devices we may go over the desired
+        // limit, but its not a hard limit so that is fine.
+        if (currentSlice.length > maxUsersPerRequest) {
+            // the current slice is filled up. Start inserting into the next slice
+            currentSlice = [];
+            mapSlices.push(currentSlice);
+        }
+    }
+    if (currentSlice.length === 0) {
+        mapSlices.pop();
     }
     return mapSlices;
 };
@@ -381,15 +503,15 @@ MegolmEncryption.prototype._splitUserDeviceMap = function(
 MegolmEncryption.prototype._encryptAndSendKeysToDevices = function(
     session, chainIndex, userDeviceMap, payload,
 ) {
-    const encryptedContent = {
-        algorithm: olmlib.OLM_ALGORITHM,
-        sender_key: this._olmDevice.deviceCurve25519Key,
-        ciphertext: {},
-    };
     const contentMap = {};
 
     const promises = [];
     for (let i = 0; i < userDeviceMap.length; i++) {
+        const encryptedContent = {
+            algorithm: olmlib.OLM_ALGORITHM,
+            sender_key: this._olmDevice.deviceCurve25519Key,
+            ciphertext: {},
+        };
         const val = userDeviceMap[i];
         const userId = val.userId;
         const deviceInfo = val.deviceInfo;
@@ -427,6 +549,53 @@ MegolmEncryption.prototype._encryptAndSendKeysToDevices = function(
     });
 };
 
+/**
+ * @private
+ *
+ * @param {module:crypto/algorithms/megolm.OutboundSessionInfo} session
+ *
+ * @param {array<object>} userDeviceMap list of blocked devices to notify
+ *
+ * @param {object} payload fields to include in the notification payload
+ *
+ * @return {module:client.Promise} Promise which resolves once the notifications
+ *     for the given userDeviceMap is generated and has been sent.
+ */
+MegolmEncryption.prototype._sendBlockedNotificationsToDevices = async function(
+    session, userDeviceMap, payload,
+) {
+    const contentMap = {};
+
+    for (const val of userDeviceMap) {
+        const userId = val.userId;
+        const blockedInfo = val.blockedInfo;
+        const deviceInfo = blockedInfo.deviceInfo;
+        const deviceId = deviceInfo.deviceId;
+
+        const message = Object.assign({}, payload);
+        message.code = blockedInfo.code;
+        message.reason = blockedInfo.reason;
+        if (message.code === "m.no_olm") {
+            delete message.room_id;
+            delete message.session_id;
+        }
+
+        if (!contentMap[userId]) {
+            contentMap[userId] = {};
+        }
+        contentMap[userId][deviceId] = message;
+    }
+
+    await this._baseApis.sendToDevice("org.matrix.room_key.withheld", contentMap);
+
+    // store that we successfully uploaded the keys of the current slice
+    for (const userId of Object.keys(contentMap)) {
+        for (const deviceId of Object.keys(contentMap[userId])) {
+            session.markNotifiedBlockedDevice(userId, deviceId);
+        }
+    }
+};
+
 /**
  * Re-shares a megolm session key with devices if the key has already been
  * sent to them.
@@ -523,8 +692,14 @@ MegolmEncryption.prototype.reshareKeyWithDevice = async function(
  *
  * @param {object<string, module:crypto/deviceinfo[]>} devicesByUser
  *    map from userid to list of devices
+ *
+ * @param {array<object>} errorDevices
+ *    array that will be populated with the devices that we can't get an
+ *    olm session for
  */
-MegolmEncryption.prototype._shareKeyWithDevices = async function(session, devicesByUser) {
+MegolmEncryption.prototype._shareKeyWithDevices = async function(
+    session, devicesByUser, errorDevices,
+) {
     const key = this._olmDevice.getOutboundGroupSessionKey(session.sessionId);
     const payload = {
         type: "m.room_key",
@@ -542,7 +717,7 @@ MegolmEncryption.prototype._shareKeyWithDevices = async function(session, device
     );
 
     const userDeviceMaps = this._splitUserDeviceMap(
-        session, key.chain_index, devicemap, devicesByUser,
+        session, key.chain_index, devicemap, devicesByUser, errorDevices,
     );
 
     for (let i = 0; i < userDeviceMaps.length; i++) {
@@ -561,6 +736,42 @@ MegolmEncryption.prototype._shareKeyWithDevices = async function(session, device
     }
 };
 
+/**
+ * Notify blocked devices that they have been blocked.
+ *
+ * @param {module:crypto/algorithms/megolm.OutboundSessionInfo} session
+ *
+ * @param {object<string, object>} devicesByUser
+ *    map from userid to device ID to blocked data
+ */
+MegolmEncryption.prototype._notifyBlockedDevices = async function(
+    session, devicesByUser,
+) {
+    const payload = {
+        room_id: this._roomId,
+        session_id: session.sessionId,
+        algorithm: olmlib.MEGOLM_ALGORITHM,
+        sender_key: this._olmDevice.deviceCurve25519Key,
+    };
+
+    const userDeviceMaps = this._splitBlockedDevices(devicesByUser);
+
+    for (let i = 0; i < userDeviceMaps.length; i++) {
+        try {
+            await this._sendBlockedNotificationsToDevices(
+                session, userDeviceMaps[i], payload,
+            );
+            logger.log(`Completed blacklist notification for ${session.sessionId} `
+                + `in ${this._roomId} (slice ${i + 1}/${userDeviceMaps.length})`);
+        } catch (e) {
+            logger.log(`blacklist notification for ${session.sessionId} in `
+                + `${this._roomId} (slice ${i + 1}/${userDeviceMaps.length}) failed`);
+
+            throw e;
+        }
+    }
+};
+
 /**
  * @inheritdoc
  *
@@ -570,42 +781,43 @@ MegolmEncryption.prototype._shareKeyWithDevices = async function(session, device
  *
  * @return {module:client.Promise} Promise which resolves to the new event body
  */
-MegolmEncryption.prototype.encryptMessage = function(room, eventType, content) {
+MegolmEncryption.prototype.encryptMessage = async function(room, eventType, content) {
     const self = this;
     logger.log(`Starting to encrypt event for ${this._roomId}`);
 
-    return this._getDevicesInRoom(room).then(function(devicesInRoom) {
-        // check if any of these devices are not yet known to the user.
-        // if so, warn the user so they can verify or ignore.
+    const [devicesInRoom, blocked] = await this._getDevicesInRoom(room);
+
+    // check if any of these devices are not yet known to the user.
+    // if so, warn the user so they can verify or ignore.
+    if (this._crypto.getGlobalErrorOnUnknownDevices()) {
         self._checkForUnknownDevices(devicesInRoom);
+    }
 
-        return self._ensureOutboundSession(devicesInRoom);
-    }).then(function(session) {
-        const payloadJson = {
-            room_id: self._roomId,
-            type: eventType,
-            content: content,
-        };
+    const session = await self._ensureOutboundSession(devicesInRoom, blocked);
+    const payloadJson = {
+        room_id: self._roomId,
+        type: eventType,
+        content: content,
+    };
 
-        const ciphertext = self._olmDevice.encryptGroupMessage(
-            session.sessionId, JSON.stringify(payloadJson),
-        );
+    const ciphertext = self._olmDevice.encryptGroupMessage(
+        session.sessionId, JSON.stringify(payloadJson),
+    );
 
-        const encryptedContent = {
-            algorithm: olmlib.MEGOLM_ALGORITHM,
-            sender_key: self._olmDevice.deviceCurve25519Key,
-            ciphertext: ciphertext,
-            session_id: session.sessionId,
-             // Include our device ID so that recipients can send us a
-             // m.new_device message if they don't have our session key.
-             // XXX: Do we still need this now that m.new_device messages
-             // no longer exist since #483?
-            device_id: self._deviceId,
-        };
+    const encryptedContent = {
+        algorithm: olmlib.MEGOLM_ALGORITHM,
+        sender_key: self._olmDevice.deviceCurve25519Key,
+        ciphertext: ciphertext,
+        session_id: session.sessionId,
+        // Include our device ID so that recipients can send us a
+        // m.new_device message if they don't have our session key.
+        // XXX: Do we still need this now that m.new_device messages
+        // no longer exist since #483?
+        device_id: self._deviceId,
+    };
 
-        session.useCount++;
-        return encryptedContent;
-    });
+    session.useCount++;
+    return encryptedContent;
 };
 
 /**
@@ -643,7 +855,7 @@ MegolmEncryption.prototype._checkForUnknownDevices = function(devicesInRoom) {
 
     if (Object.keys(unknownDevices).length) {
         // it'd be kind to pass unknownDevices up to the user in this error
-        throw new base.UnknownDeviceError(
+        throw new UnknownDeviceError(
             "This room contains unknown devices which have not been verified. " +
             "We strongly recommend you verify them before continuing.", unknownDevices);
     }
@@ -654,8 +866,11 @@ MegolmEncryption.prototype._checkForUnknownDevices = function(devicesInRoom) {
  *
  * @param {module:models/room} room
  *
- * @return {module:client.Promise} Promise which resolves to a map
- *     from userId to deviceId to deviceInfo
+ * @return {module:client.Promise} Promise which resolves to an array whose
+ *     first element is a map from userId to deviceId to deviceInfo indicating
+ *     the devices that messages should be encrypted to, and whose second
+ *     element is a map from userId to deviceId to data indicating the devices
+ *     that are in the room but that have been blocked
  */
 MegolmEncryption.prototype._getDevicesInRoom = async function(room) {
     const members = await room.getEncryptionTargetMembers();
@@ -676,6 +891,7 @@ MegolmEncryption.prototype._getDevicesInRoom = async function(room) {
     // using all the device_lists changes and left fields.
     // See https://github.com/vector-im/riot-web/issues/2305 for details.
     const devices = await this._crypto.downloadKeys(roomMembers, false);
+    const blocked = {};
     // remove any blocked devices
     for (const userId in devices) {
         if (!devices.hasOwnProperty(userId)) {
@@ -690,26 +906,40 @@ MegolmEncryption.prototype._getDevicesInRoom = async function(room) {
 
             if (userDevices[deviceId].isBlocked() ||
                 (userDevices[deviceId].isUnverified() && isBlacklisting)
-               ) {
+            ) {
+                if (!blocked[userId]) {
+                    blocked[userId] = {};
+                }
+                const blockedInfo = userDevices[deviceId].isBlocked()
+                    ? {
+                        code: "m.blacklisted",
+                        reason: WITHHELD_MESSAGES["m.blacklisted"],
+                    }
+                    : {
+                        code: "m.unverified",
+                        reason: WITHHELD_MESSAGES["m.unverified"],
+                    };
+                blockedInfo.deviceInfo = userDevices[deviceId];
+                blocked[userId][deviceId] = blockedInfo;
                 delete userDevices[deviceId];
             }
         }
     }
 
-    return devices;
+    return [devices, blocked];
 };
 
 /**
  * Megolm decryption implementation
  *
  * @constructor
- * @extends {module:crypto/algorithms/base.DecryptionAlgorithm}
+ * @extends {module:crypto/algorithms/DecryptionAlgorithm}
  *
  * @param {object} params parameters, as per
- *     {@link module:crypto/algorithms/base.DecryptionAlgorithm}
+ *     {@link module:crypto/algorithms/DecryptionAlgorithm}
  */
 function MegolmDecryption(params) {
-    base.DecryptionAlgorithm.call(this, params);
+    polyfillSuper(this, DecryptionAlgorithm, params);
 
     // events which we couldn't decrypt due to unknown sessions / indexes: map from
     // senderKey|sessionId to Set of MatrixEvents
@@ -718,7 +948,12 @@ function MegolmDecryption(params) {
     // this gets stubbed out by the unit tests.
     this.olmlib = olmlib;
 }
-utils.inherits(MegolmDecryption, base.DecryptionAlgorithm);
+utils.inherits(MegolmDecryption, DecryptionAlgorithm);
+
+const PROBLEM_DESCRIPTIONS = {
+    no_olm: "The sender was unable to establish a secure channel.",
+    unknown: "The secure channel with the sender was corrupted.",
+};
 
 /**
  * @inheritdoc
@@ -736,7 +971,7 @@ MegolmDecryption.prototype.decryptEvent = async function(event) {
     if (!content.sender_key || !content.session_id ||
         !content.ciphertext
        ) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "MEGOLM_MISSING_FIELDS",
             "Missing fields in input",
         );
@@ -756,6 +991,11 @@ MegolmDecryption.prototype.decryptEvent = async function(event) {
             event.getId(), event.getTs(),
         );
     } catch (e) {
+        if (e.name === "DecryptionError") {
+            // re-throw decryption errors as-is
+            throw e;
+        }
+
         let errorCode = "OLM_DECRYPT_GROUP_MESSAGE_ERROR";
 
         if (e && e.message === 'OLM.UNKNOWN_MESSAGE_INDEX') {
@@ -764,7 +1004,7 @@ MegolmDecryption.prototype.decryptEvent = async function(event) {
             errorCode = 'OLM_UNKNOWN_MESSAGE_INDEX';
         }
 
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             errorCode,
             e ? e.toString() : "Unknown Error: Error is undefined", {
                 session: content.sender_key + '|' + content.session_id,
@@ -781,7 +1021,29 @@ MegolmDecryption.prototype.decryptEvent = async function(event) {
         // event is still in the pending list; if not, a retry will have been
         // scheduled, so we needn't send out the request here.)
         this._requestKeysForEvent(event);
-        throw new base.DecryptionError(
+
+        // See if there was a problem with the olm session at the time the
+        // event was sent.  Use a fuzz factor of 2 minutes.
+        const problem = await this._olmDevice.sessionMayHaveProblems(
+            content.sender_key, event.getTs() - 120000,
+        );
+        if (problem) {
+            let problemDescription = PROBLEM_DESCRIPTIONS[problem.type]
+                  || PROBLEM_DESCRIPTIONS.unknown;
+            if (problem.fixed) {
+                problemDescription +=
+                    " Trying to create a new secure channel and re-requesting the keys.";
+            }
+            throw new DecryptionError(
+                "MEGOLM_UNKNOWN_INBOUND_SESSION_ID",
+                problemDescription,
+                {
+                    session: content.sender_key + '|' + content.session_id,
+                },
+            );
+        }
+
+        throw new DecryptionError(
             "MEGOLM_UNKNOWN_INBOUND_SESSION_ID",
             "The sender's device has not sent us the keys for this message.",
             {
@@ -800,7 +1062,7 @@ MegolmDecryption.prototype.decryptEvent = async function(event) {
     // (this is somewhat redundant, since the megolm session is scoped to the
     // room, so neither the sender nor a MITM can lie about the room_id).
     if (payload.room_id !== event.getRoomId()) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "MEGOLM_BAD_ROOM",
             "Message intended for room " + payload.room_id,
         );
@@ -836,11 +1098,16 @@ MegolmDecryption.prototype._requestKeysForEvent = function(event) {
  */
 MegolmDecryption.prototype._addEventToPendingList = function(event) {
     const content = event.getWireContent();
-    const k = content.sender_key + "|" + content.session_id;
-    if (!this._pendingEvents[k]) {
-        this._pendingEvents[k] = new Set();
+    const senderKey = content.sender_key;
+    const sessionId = content.session_id;
+    if (!this._pendingEvents[senderKey]) {
+        this._pendingEvents[senderKey] = new Map();
     }
-    this._pendingEvents[k].add(event);
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    if (!senderPendingEvents.has(sessionId)) {
+        senderPendingEvents.set(sessionId, new Set());
+    }
+    senderPendingEvents.get(sessionId).add(event);
 };
 
 /**
@@ -852,14 +1119,20 @@ MegolmDecryption.prototype._addEventToPendingList = function(event) {
  */
 MegolmDecryption.prototype._removeEventFromPendingList = function(event) {
     const content = event.getWireContent();
-    const k = content.sender_key + "|" + content.session_id;
-    if (!this._pendingEvents[k]) {
+    const senderKey = content.sender_key;
+    const sessionId = content.session_id;
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    const pendingEvents = senderPendingEvents && senderPendingEvents.get(sessionId);
+    if (!pendingEvents) {
         return;
     }
 
-    this._pendingEvents[k].delete(event);
-    if (this._pendingEvents[k].size === 0) {
-        delete this._pendingEvents[k];
+    pendingEvents.delete(event);
+    if (pendingEvents.size === 0) {
+        senderPendingEvents.delete(senderKey);
+    }
+    if (senderPendingEvents.size === 0) {
+        delete this._pendingEvents[senderKey];
     }
 };
 
@@ -963,6 +1236,78 @@ MegolmDecryption.prototype.onRoomKeyEvent = function(event) {
     });
 };
 
+/**
+ * @inheritdoc
+ *
+ * @param {module:models/event.MatrixEvent} event key event
+ */
+MegolmDecryption.prototype.onRoomKeyWithheldEvent = async function(event) {
+    const content = event.getContent();
+    const senderKey = content.sender_key;
+
+    if (content.code === "m.no_olm") {
+        const sender = event.getSender();
+        // if the sender says that they haven't been able to establish an olm
+        // session, let's proactively establish one
+
+        // Note: after we record that the olm session has had a problem, we
+        // trigger retrying decryption for all the messages from the sender's
+        // key, so that we can update the error message to indicate the olm
+        // session problem.
+
+        if (await this._olmDevice.getSessionIdForDevice(senderKey)) {
+            // a session has already been established, so we don't need to
+            // create a new one.
+            await this._olmDevice.recordSessionProblem(senderKey, "no_olm", true);
+            this.retryDecryptionFromSender(senderKey);
+            return;
+        }
+        const device = this._crypto._deviceList.getDeviceByIdentityKey(
+            content.algorithm, senderKey,
+        );
+        if (!device) {
+            logger.info(
+                "Couldn't find device for identity key " + senderKey +
+                    ": not establishing session",
+            );
+            await this._olmDevice.recordSessionProblem(senderKey, "no_olm", false);
+            this.retryDecryptionFromSender(senderKey);
+            return;
+        }
+        await olmlib.ensureOlmSessionsForDevices(
+            this._olmDevice, this._baseApis, {[sender]: [device]}, false,
+        );
+        const encryptedContent = {
+            algorithm: olmlib.OLM_ALGORITHM,
+            sender_key: this._olmDevice.deviceCurve25519Key,
+            ciphertext: {},
+        };
+        await olmlib.encryptMessageForDevice(
+            encryptedContent.ciphertext,
+            this._userId,
+            this._deviceId,
+            this._olmDevice,
+            sender,
+            device,
+            {type: "m.dummy"},
+        );
+
+        await this._olmDevice.recordSessionProblem(senderKey, "no_olm", true);
+        this.retryDecryptionFromSender(senderKey);
+
+        await this._baseApis.sendToDevice("m.room.encrypted", {
+            [sender]: {
+                [device.deviceId]: encryptedContent,
+            },
+        });
+    } else {
+        await this._olmDevice.addInboundGroupSessionWithheld(
+            content.room_id, senderKey, content.session_id, content.code,
+            content.reason,
+        );
+    }
+};
+
 /**
  * @inheritdoc
  */
@@ -1106,13 +1451,20 @@ MegolmDecryption.prototype.importRoomKey = function(session) {
  * @return {Boolean} whether all messages were successfully decrypted
  */
 MegolmDecryption.prototype._retryDecryption = async function(senderKey, sessionId) {
-    const k = senderKey + "|" + sessionId;
-    const pending = this._pendingEvents[k];
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    if (!senderPendingEvents) {
+        return true;
+    }
+
+    const pending = senderPendingEvents.get(sessionId);
     if (!pending) {
         return true;
     }
 
-    delete this._pendingEvents[k];
+    pending.delete(sessionId);
+    if (pending.size === 0) {
+        this._pendingEvents[senderKey];
+    }
 
     await Promise.all([...pending].map(async (ev) => {
         try {
@@ -1122,9 +1474,34 @@ MegolmDecryption.prototype._retryDecryption = async function(senderKey, sessionI
         }
     }));
 
-    return !this._pendingEvents[k];
+    // ev.attemptDecryption will re-add to this._pendingEvents if an event
+    // couldn't be decrypted
+    return !((this._pendingEvents[senderKey] || {})[sessionId]);
 };
 
-base.registerAlgorithm(
+MegolmDecryption.prototype.retryDecryptionFromSender = async function(senderKey) {
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    logger.warn(senderPendingEvents);
+    if (!senderPendingEvents) {
+        return true;
+    }
+
+    delete this._pendingEvents[senderKey];
+
+    await Promise.all([...senderPendingEvents].map(async ([_sessionId, pending]) => {
+        await Promise.all([...pending].map(async (ev) => {
+            try {
+                logger.warn(ev.getId());
+                await ev.attemptDecryption(this._crypto);
+            } catch (e) {
+                // don't die if something goes wrong
+            }
+        }));
+    }));
+
+    return !this._pendingEvents[senderKey];
+};
+
+registerAlgorithm(
     olmlib.MEGOLM_ALGORITHM, MegolmEncryption, MegolmDecryption,
 );
diff --git a/src/crypto/algorithms/olm.js b/src/crypto/algorithms/olm.js
index 25fb21d94..3e2ad8123 100644
--- a/src/crypto/algorithms/olm.js
+++ b/src/crypto/algorithms/olm.js
@@ -13,36 +13,42 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * Defines m.olm encryption/decryption
  *
  * @module crypto/algorithms/olm
  */
-import logger from '../../logger';
-const utils = require("../../utils");
-const olmlib = require("../olmlib");
-const DeviceInfo = require("../deviceinfo");
-const DeviceVerification = DeviceInfo.DeviceVerification;
 
-const base = require("./base");
+import {logger} from '../../logger';
+import * as utils from "../../utils";
+import {polyfillSuper} from "../../utils";
+import * as olmlib from "../olmlib";
+import {DeviceInfo} from "../deviceinfo";
+import {
+    DecryptionAlgorithm,
+    DecryptionError,
+    EncryptionAlgorithm,
+    registerAlgorithm,
+} from "./base";
+
+const DeviceVerification = DeviceInfo.DeviceVerification;
 
 /**
  * Olm encryption implementation
  *
  * @constructor
- * @extends {module:crypto/algorithms/base.EncryptionAlgorithm}
+ * @extends {module:crypto/algorithms/EncryptionAlgorithm}
  *
  * @param {object} params parameters, as per
- *     {@link module:crypto/algorithms/base.EncryptionAlgorithm}
+ *     {@link module:crypto/algorithms/EncryptionAlgorithm}
  */
 function OlmEncryption(params) {
-    base.EncryptionAlgorithm.call(this, params);
+    polyfillSuper(this, EncryptionAlgorithm, params);
     this._sessionPrepared = false;
     this._prepPromise = null;
 }
-utils.inherits(OlmEncryption, base.EncryptionAlgorithm);
+utils.inherits(OlmEncryption, EncryptionAlgorithm);
 
 /**
  * @private
@@ -143,14 +149,14 @@ OlmEncryption.prototype.encryptMessage = async function(room, eventType, content
  * Olm decryption implementation
  *
  * @constructor
- * @extends {module:crypto/algorithms/base.DecryptionAlgorithm}
+ * @extends {module:crypto/algorithms/DecryptionAlgorithm}
  * @param {object} params parameters, as per
- *     {@link module:crypto/algorithms/base.DecryptionAlgorithm}
+ *     {@link module:crypto/algorithms/DecryptionAlgorithm}
  */
 function OlmDecryption(params) {
-    base.DecryptionAlgorithm.call(this, params);
+    polyfillSuper(this, DecryptionAlgorithm, params);
 }
-utils.inherits(OlmDecryption, base.DecryptionAlgorithm);
+utils.inherits(OlmDecryption, DecryptionAlgorithm);
 
 /**
  * @inheritdoc
@@ -168,14 +174,14 @@ OlmDecryption.prototype.decryptEvent = async function(event) {
     const ciphertext = content.ciphertext;
 
     if (!ciphertext) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_MISSING_CIPHERTEXT",
             "Missing ciphertext",
         );
     }
 
     if (!(this._olmDevice.deviceCurve25519Key in ciphertext)) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_NOT_INCLUDED_IN_RECIPIENTS",
             "Not included in recipients",
         );
@@ -186,7 +192,7 @@ OlmDecryption.prototype.decryptEvent = async function(event) {
     try {
         payloadString = await this._decryptMessage(deviceKey, message);
     } catch (e) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_BAD_ENCRYPTED_MESSAGE",
             "Bad Encrypted Message", {
                 sender: deviceKey,
@@ -200,14 +206,14 @@ OlmDecryption.prototype.decryptEvent = async function(event) {
     // check that we were the intended recipient, to avoid unknown-key attack
     // https://github.com/vector-im/vector-web/issues/2483
     if (payload.recipient != this._userId) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_BAD_RECIPIENT",
             "Message was intented for " + payload.recipient,
         );
     }
 
     if (payload.recipient_keys.ed25519 != this._olmDevice.deviceEd25519Key) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_BAD_RECIPIENT_KEY",
             "Message not intended for this device", {
                 intended: payload.recipient_keys.ed25519,
@@ -221,7 +227,7 @@ OlmDecryption.prototype.decryptEvent = async function(event) {
     // (this check is also provided via the sender's embedded ed25519 key,
     // which is checked elsewhere).
     if (payload.sender != event.getSender()) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_FORWARDED_MESSAGE",
             "Message forwarded from " + payload.sender, {
                 reported_sender: event.getSender(),
@@ -231,7 +237,7 @@ OlmDecryption.prototype.decryptEvent = async function(event) {
 
     // Olm events intended for a room have a room_id.
     if (payload.room_id !== event.getRoomId()) {
-        throw new base.DecryptionError(
+        throw new DecryptionError(
             "OLM_BAD_ROOM",
             "Message intended for room " + payload.room_id, {
                 reported_room: event.room_id,
@@ -334,4 +340,4 @@ OlmDecryption.prototype._decryptMessage = async function(
 };
 
 
-base.registerAlgorithm(olmlib.OLM_ALGORITHM, OlmEncryption, OlmDecryption);
+registerAlgorithm(olmlib.OLM_ALGORITHM, OlmEncryption, OlmDecryption);
diff --git a/src/crypto/deviceinfo.js b/src/crypto/deviceinfo.js
index 2dbb2393d..379d72c63 100644
--- a/src/crypto/deviceinfo.js
+++ b/src/crypto/deviceinfo.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,8 +14,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
-
 
 /**
  * @module crypto/deviceinfo
@@ -44,7 +43,7 @@ limitations under the License.
   *
   * @param {string} deviceId id of the device
   */
-function DeviceInfo(deviceId) {
+export function DeviceInfo(deviceId) {
     // you can't change the deviceId
     Object.defineProperty(this, 'deviceId', {
         enumerable: true,
@@ -167,5 +166,3 @@ DeviceInfo.DeviceVerification = {
 
 const DeviceVerification = DeviceInfo.DeviceVerification;
 
-/** */
-module.exports = DeviceInfo;
diff --git a/src/crypto/index.js b/src/crypto/index.js
index 749ea0726..fec8251eb 100644
--- a/src/crypto/index.js
+++ b/src/crypto/index.js
@@ -2,7 +2,7 @@
 Copyright 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2018-2019 New Vector Ltd
-Copyright 2019 The Matrix.org Foundation C.I.C.
+Copyright 2019-2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -16,44 +16,41 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module crypto
  */
 
-const anotherjson = require('another-json');
+import anotherjson from "another-json";
 import {EventEmitter} from 'events';
-import ReEmitter from '../ReEmitter';
-
-import logger from '../logger';
-const utils = require("../utils");
-const OlmDevice = require("./OlmDevice");
-const olmlib = require("./olmlib");
-const algorithms = require("./algorithms");
-const DeviceInfo = require("./deviceinfo");
-const DeviceVerification = DeviceInfo.DeviceVerification;
-const DeviceList = require('./DeviceList').default;
+import {ReEmitter} from '../ReEmitter';
+import {logger} from '../logger';
+import * as utils from "../utils";
+import {sleep} from "../utils";
+import {OlmDevice} from "./OlmDevice";
+import * as olmlib from "./olmlib";
+import {DeviceList} from "./DeviceList";
+import {DeviceInfo} from "./deviceinfo";
+import * as algorithms from "./algorithms";
 import {
     CrossSigningInfo,
-    UserTrustLevel,
-    DeviceTrustLevel,
     CrossSigningLevel,
+    DeviceTrustLevel,
+    UserTrustLevel,
 } from './CrossSigning';
-import SecretStorage, { SECRET_STORAGE_ALGORITHM_V1 } from './SecretStorage';
-
-import OutgoingRoomKeyRequestManager from './OutgoingRoomKeyRequestManager';
-import IndexedDBCryptoStore from './store/indexeddb-crypto-store';
-
-import {ShowQRCode, ScanQRCode} from './verification/QRCode';
-import SAS from './verification/SAS';
-import {sleep} from '../utils';
-import { keyFromPassphrase } from './key_passphrase';
-import { encodeRecoveryKey } from './recoverykey';
-
-import VerificationRequest from "./verification/request/VerificationRequest";
+import {SECRET_STORAGE_ALGORITHM_V1, SecretStorage} from './SecretStorage';
+import {OutgoingRoomKeyRequestManager} from './OutgoingRoomKeyRequestManager';
+import {IndexedDBCryptoStore} from './store/indexeddb-crypto-store';
+import {ScanQRCode, ShowQRCode} from './verification/QRCode';
+import {SAS} from './verification/SAS';
+import {keyFromPassphrase} from './key_passphrase';
+import {encodeRecoveryKey} from './recoverykey';
+import {VerificationRequest} from "./verification/request/VerificationRequest";
 import {InRoomChannel, InRoomRequests} from "./verification/request/InRoomChannel";
 import {ToDeviceChannel, ToDeviceRequests} from "./verification/request/ToDeviceChannel";
+import * as httpApi from "../http-api";
+
+const DeviceVerification = DeviceInfo.DeviceVerification;
 
 const defaultVerificationMethods = {
     [ScanQRCode.NAME]: ScanQRCode,
@@ -107,7 +104,7 @@ const KEY_BACKUP_KEYS_PER_REQUEST = 200;
  *    Each element can either be a string from MatrixClient.verificationMethods
  *    or a class that implements a verification method.
  */
-export default function Crypto(baseApis, sessionStore, userId, deviceId,
+export function Crypto(baseApis, sessionStore, userId, deviceId,
     clientStore, cryptoStore, roomList, verificationMethods) {
     this._onDeviceListUserCrossSigningUpdated =
         this._onDeviceListUserCrossSigningUpdated.bind(this);
@@ -176,6 +173,7 @@ export default function Crypto(baseApis, sessionStore, userId, deviceId,
     this._deviceKeys = {};
 
     this._globalBlacklistUnverifiedDevices = false;
+    this._globalErrorOnUnknownDevices = true;
 
     this._outgoingRoomKeyRequestManager = new OutgoingRoomKeyRequestManager(
          baseApis, this._deviceId, this._cryptoStore,
@@ -218,7 +216,7 @@ export default function Crypto(baseApis, sessionStore, userId, deviceId,
     );
 
     // Assuming no app-supplied callback, default to getting from SSSS.
-    if (!cryptoCallbacks.getCrossSigningKey) {
+    if (!cryptoCallbacks.getCrossSigningKey && cryptoCallbacks.getSecretStorageKey) {
         cryptoCallbacks.getCrossSigningKey = async (type) => {
             return CrossSigningInfo.getFromSecretStorage(type, this._secretStorage);
         };
@@ -418,6 +416,25 @@ Crypto.prototype.bootstrapSecretStorage = async function({
                 // Add an entry for the backup key in SSSS as a 'passthrough' key
                 // (ie. the secret is the key itself).
                 this._secretStorage.storePassthrough('m.megolm_backup.v1', newKeyId);
+
+                // if this key backup is trusted, sign it with the cross signing key
+                // so the key backup can be trusted via cross-signing.
+                const backupSigStatus = await this.checkKeyBackup(keyBackupInfo);
+                if (backupSigStatus.trustInfo.usable) {
+                    console.log("Adding cross signing signature to key backup");
+                    await this._crossSigningInfo.signObject(
+                        keyBackupInfo.auth_data, "master",
+                    );
+                    await this._baseApis._http.authedRequest(
+                        undefined, "PUT", "/room_keys/version/" + keyBackupInfo.version,
+                        undefined, keyBackupInfo,
+                        {prefix: httpApi.PREFIX_UNSTABLE},
+                    );
+                } else {
+                    console.log(
+                        "Key backup is NOT TRUSTED: NOT adding cross signing signature",
+                    );
+                }
             } else {
                 logger.log("Secret storage default key not found, creating new key");
                 const keyOptions = await createSecretStorageKey();
@@ -588,8 +605,8 @@ Crypto.prototype.resetCrossSigningKeys = async function(level, {
 
 /**
  * Run various follow-up actions after cross-signing keys have changed locally
- * (either by resetting the keys for the account or bye getting them from secret
- * storaoge), such as signing the current device, upgrading device
+ * (either by resetting the keys for the account or by getting them from secret
+ * storage), such as signing the current device, upgrading device
  * verifications, etc.
  */
 Crypto.prototype._afterCrossSigningLocalKeyChange = async function() {
@@ -1068,6 +1085,9 @@ Crypto.prototype.isKeyBackupTrusted = async function(backupInfo) {
         );
         if (device) {
             sigInfo.device = device;
+            sigInfo.deviceTrust = await this.checkDeviceTrust(
+                this._userId, sigInfo.deviceId,
+            );
             try {
                 await olmlib.verifySignature(
                     this._olmDevice,
@@ -1095,7 +1115,7 @@ Crypto.prototype.isKeyBackupTrusted = async function(backupInfo) {
     ret.usable = ret.sigs.some((s) => {
         return (
             s.valid && (
-                (s.device && s.device.isVerified()) ||
+                (s.device && s.deviceTrust.isVerified()) ||
                 (s.crossSigningId)
             )
         );
@@ -1183,6 +1203,29 @@ Crypto.prototype.getGlobalBlacklistUnverifiedDevices = function() {
     return this._globalBlacklistUnverifiedDevices;
 };
 
+/**
+ * Set whether sendMessage in a room with unknown and unverified devices
+ * should throw an error and not send them message. This has 'Global' for
+ * symmertry with setGlobalBlacklistUnverifiedDevices but there is currently
+ * no room-level equivalent for this setting.
+ *
+ * This API is currently UNSTABLE and may change or be removed without notice.
+ *
+ * @param {boolean} value whether error on unknown devices
+ */
+Crypto.prototype.setGlobalErrorOnUnknownDevices = function(value) {
+    this._globalErrorOnUnknownDevices = value;
+};
+
+/**
+ * @return {boolean} whether to error on unknown devices
+ *
+ * This API is currently UNSTABLE and may change or be removed without notice.
+ */
+Crypto.prototype.getGlobalErrorOnUnknownDevices = function() {
+    return this._globalErrorOnUnknownDevices;
+};
+
 /**
  * Upload the device keys to the homeserver.
  * @return {object} A promise that will resolve when the keys are uploaded.
@@ -2381,6 +2424,8 @@ Crypto.prototype._onToDeviceEvent = function(event) {
             this._secretStorage._onRequestReceived(event);
         } else if (event.getType() === "m.secret.send") {
             this._secretStorage._onSecretReceived(event);
+        } else if (event.getType() === "org.matrix.room_key.withheld") {
+            this._onRoomKeyWithheldEvent(event);
         } else if (event.getContent().transaction_id) {
             this._onKeyVerificationMessage(event);
         } else if (event.getContent().msgtype === "m.bad.encrypted") {
@@ -2420,6 +2465,42 @@ Crypto.prototype._onRoomKeyEvent = function(event) {
     alg.onRoomKeyEvent(event);
 };
 
+/**
+ * Handle a key withheld event
+ *
+ * @private
+ * @param {module:models/event.MatrixEvent} event key withheld event
+ */
+Crypto.prototype._onRoomKeyWithheldEvent = function(event) {
+    const content = event.getContent();
+
+    if ((content.code !== "m.no_olm" && (!content.room_id || !content.session_id))
+        || !content.algorithm || !content.sender_key) {
+        logger.error("key withheld event is missing fields");
+        return;
+    }
+
+    logger.info(
+        `Got room key withheld event from ${event.getSender()} (${content.sender_key}) `
+            + `for ${content.algorithm}/${content.room_id}/${content.session_id} `
+            + `with reason ${content.code} (${content.reason})`,
+    );
+
+    const alg = this._getRoomDecryptor(content.room_id, content.algorithm);
+    if (alg.onRoomKeyWithheldEvent) {
+        alg.onRoomKeyWithheldEvent(event);
+    }
+    if (!content.room_id) {
+        // retry decryption for all events sent by the sender_key.  This will
+        // update the events to show a message indicating that the olm session was
+        // wedged.
+        const roomDecryptors = this._getRoomDecryptors(content.algorithm);
+        for (const decryptor of roomDecryptors) {
+            decryptor.retryDecryptionFromSender(content.sender_key);
+        }
+    }
+};
+
 /**
  * Handle a general key verification event.
  *
@@ -2536,6 +2617,16 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
     const algorithm = content.algorithm;
     const deviceKey = content.sender_key;
 
+    // retry decryption for all events sent by the sender_key.  This will
+    // update the events to show a message indicating that the olm session was
+    // wedged.
+    const retryDecryption = () => {
+        const roomDecryptors = this._getRoomDecryptors(olmlib.MEGOLM_ALGORITHM);
+        for (const decryptor of roomDecryptors) {
+            decryptor.retryDecryptionFromSender(deviceKey);
+        }
+    };
+
     if (sender === undefined || deviceKey === undefined || deviceKey === undefined) {
         return;
     }
@@ -2549,6 +2640,8 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
             "New session already forced with device " + sender + ":" + deviceKey +
             " at " + lastNewSessionForced + ": not forcing another",
         );
+        await this._olmDevice.recordSessionProblem(deviceKey, "wedged", true);
+        retryDecryption();
         return;
     }
 
@@ -2562,6 +2655,8 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
             "Couldn't find device for identity key " + deviceKey +
             ": not re-establishing session",
         );
+        await this._olmDevice.recordSessionProblem(deviceKey, "wedged", false);
+        retryDecryption();
         return;
     }
     const devicesByUser = {};
@@ -2593,6 +2688,9 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
         {type: "m.dummy"},
     );
 
+    await this._olmDevice.recordSessionProblem(deviceKey, "wedged", true);
+    retryDecryption();
+
     await this._baseApis.sendToDevice("m.room.encrypted", {
         [sender]: {
             [device.deviceId]: encryptedContent,
@@ -2874,6 +2972,24 @@ Crypto.prototype._getRoomDecryptor = function(roomId, algorithm) {
 };
 
 
+/**
+ * Get all the room decryptors for a given encryption algorithm.
+ *
+ * @param {string} algorithm The encryption algorithm
+ *
+ * @return {array} An array of room decryptors
+ */
+Crypto.prototype._getRoomDecryptors = function(algorithm) {
+    const decryptors = [];
+    for (const d of Object.values(this._roomDecryptors)) {
+        if (algorithm in d) {
+            decryptors.push(d[algorithm]);
+        }
+    }
+    return decryptors;
+};
+
+
 /**
  * sign the given object with our ed25519 key
  *
diff --git a/src/crypto/key_passphrase.js b/src/crypto/key_passphrase.js
index 0291a6e07..3e8455472 100644
--- a/src/crypto/key_passphrase.js
+++ b/src/crypto/key_passphrase.js
@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { randomString } from '../randomstring';
+import {randomString} from '../randomstring';
 
 const DEFAULT_ITERATIONS = 500000;
 
diff --git a/src/crypto/olmlib.js b/src/crypto/olmlib.js
index e00431d93..b452f6d2c 100644
--- a/src/crypto/olmlib.js
+++ b/src/crypto/olmlib.js
@@ -22,25 +22,24 @@ limitations under the License.
  * Utilities common to olm encryption algorithms
  */
 
-const anotherjson = require('another-json');
-
-import logger from '../logger';
-const utils = require("../utils");
+import {logger} from '../logger';
+import * as utils from "../utils";
+import anotherjson from "another-json";
 
 /**
  * matrix algorithm tag for olm
  */
-module.exports.OLM_ALGORITHM = "m.olm.v1.curve25519-aes-sha2";
+export const OLM_ALGORITHM = "m.olm.v1.curve25519-aes-sha2";
 
 /**
  * matrix algorithm tag for megolm
  */
-module.exports.MEGOLM_ALGORITHM = "m.megolm.v1.aes-sha2";
+export const MEGOLM_ALGORITHM = "m.megolm.v1.aes-sha2";
 
 /**
  * matrix algorithm tag for megolm backups
  */
-module.exports.MEGOLM_BACKUP_ALGORITHM = "m.megolm_backup.v1.curve25519-aes-sha2";
+export const MEGOLM_BACKUP_ALGORITHM = "m.megolm_backup.v1.curve25519-aes-sha2";
 
 
 /**
@@ -59,7 +58,7 @@ module.exports.MEGOLM_BACKUP_ALGORITHM = "m.megolm_backup.v1.curve25519-aes-sha2
  * Returns a promise which resolves (to undefined) when the payload
  *    has been encrypted into `resultsObject`
  */
-module.exports.encryptMessageForDevice = async function(
+export async function encryptMessageForDevice(
     resultsObject,
     ourUserId, ourDeviceId, olmDevice, recipientUserId, recipientDevice,
     payloadFields,
@@ -112,7 +111,7 @@ module.exports.encryptMessageForDevice = async function(
     resultsObject[deviceKey] = await olmDevice.encryptMessage(
         deviceKey, sessionId, JSON.stringify(payload),
     );
-};
+}
 
 /**
  * Try to make sure we have established olm sessions for the given devices.
@@ -131,7 +130,7 @@ module.exports.encryptMessageForDevice = async function(
  *    an Object mapping from userId to deviceId to
  *    {@link module:crypto~OlmSessionResult}
  */
-module.exports.ensureOlmSessionsForDevices = async function(
+export async function ensureOlmSessionsForDevices(
     olmDevice, baseApis, devicesByUser, force,
 ) {
     const devicesWithoutSession = [
@@ -263,12 +262,12 @@ module.exports.ensureOlmSessionsForDevices = async function(
 
     await Promise.all(promises);
     return result;
-};
+}
 
 async function _verifyKeyAndStartSession(olmDevice, oneTimeKey, userId, deviceInfo) {
     const deviceId = deviceInfo.deviceId;
     try {
-        await _verifySignature(
+        await verifySignature(
             olmDevice, oneTimeKey, userId, deviceId,
             deviceInfo.getFingerprint(),
         );
@@ -314,7 +313,7 @@ async function _verifyKeyAndStartSession(olmDevice, oneTimeKey, userId, deviceIn
  * Returns a promise which resolves (to undefined) if the the signature is good,
  * or rejects with an Error if it is bad.
  */
-const _verifySignature = module.exports.verifySignature = async function(
+export async function verifySignature(
     olmDevice, obj, signingUserId, signingDeviceId, signingKey,
 ) {
     const signKeyId = "ed25519:" + signingDeviceId;
@@ -335,7 +334,7 @@ const _verifySignature = module.exports.verifySignature = async function(
     olmDevice.verifySignature(
         signingKey, json, signature,
     );
-};
+}
 
 /**
  * Sign a JSON object using public key cryptography
@@ -347,7 +346,7 @@ const _verifySignature = module.exports.verifySignature = async function(
  * @param {string} pubkey The public key (ignored if key is a seed)
  * @returns {string} the signature for the object
  */
-module.exports.pkSign = function(obj, key, userId, pubkey) {
+export function pkSign(obj, key, userId, pubkey) {
     let createdKey = false;
     if (key instanceof Uint8Array) {
         const keyObj = new global.Olm.PkSigning();
@@ -371,7 +370,7 @@ module.exports.pkSign = function(obj, key, userId, pubkey) {
             key.free();
         }
     }
-};
+}
 
 /**
  * Verify a signed JSON object
@@ -379,7 +378,7 @@ module.exports.pkSign = function(obj, key, userId, pubkey) {
  * @param {string} pubkey The public key to use to verify
  * @param {string} userId The user ID who signed the object
  */
-module.exports.pkVerify = function(obj, pubkey, userId) {
+export function pkVerify(obj, pubkey, userId) {
     const keyId = "ed25519:" + pubkey;
     if (!(obj.signatures && obj.signatures[userId] && obj.signatures[userId][keyId])) {
         throw new Error("No signature");
@@ -397,22 +396,22 @@ module.exports.pkVerify = function(obj, pubkey, userId) {
         if (unsigned) obj.unsigned = unsigned;
         util.free();
     }
-};
+}
 
 /**
  * Encode a typed array of uint8 as base64.
  * @param {Uint8Array} uint8Array The data to encode.
  * @return {string} The base64.
  */
-module.exports.encodeBase64 = function(uint8Array) {
+export function encodeBase64(uint8Array) {
     return Buffer.from(uint8Array).toString("base64");
-};
+}
 
 /**
  * Decode a base64 string to a typed array of uint8.
  * @param {string} base64 The base64 to decode.
  * @return {Uint8Array} The decoded data.
  */
-module.exports.decodeBase64 = function(base64) {
+export function decodeBase64(base64) {
     return Buffer.from(base64, "base64");
-};
+}
diff --git a/src/crypto/store/indexeddb-crypto-store-backend.js b/src/crypto/store/indexeddb-crypto-store-backend.js
index aeead378e..f42874720 100644
--- a/src/crypto/store/indexeddb-crypto-store-backend.js
+++ b/src/crypto/store/indexeddb-crypto-store-backend.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,10 +16,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../../logger';
-import utils from '../../utils';
+import {logger} from '../../logger';
+import * as utils from "../../utils";
 
-export const VERSION = 7;
+export const VERSION = 9;
 
 /**
  * Implementation of a CryptoStore which is backed by an existing
@@ -79,7 +80,7 @@ export class Backend {
                     `enqueueing key request for ${requestBody.room_id} / ` +
                         requestBody.session_id,
                 );
-                txn.oncomplete = () => { resolve(request); };
+                txn.oncomplete = () => {resolve(request);};
                 const store = txn.objectStore("outgoingRoomKeyRequests");
                 store.add(request);
             });
@@ -425,17 +426,107 @@ export class Backend {
         });
     }
 
+    async storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        const txn = this._db.transaction("session_problems", "readwrite");
+        const objectStore = txn.objectStore("session_problems");
+        objectStore.put({
+            deviceKey,
+            type,
+            fixed,
+            time: Date.now(),
+        });
+        return promiseifyTxn(txn);
+    }
+
+    async getEndToEndSessionProblem(deviceKey, timestamp) {
+        let result;
+        const txn = this._db.transaction("session_problems", "readwrite");
+        const objectStore = txn.objectStore("session_problems");
+        const index = objectStore.index("deviceKey");
+        const req = index.getAll(deviceKey);
+        req.onsuccess = (event) => {
+            const problems = req.result;
+            if (!problems.length) {
+                result = null;
+                return;
+            }
+            problems.sort((a, b) => {
+                return a.time - b.time;
+            });
+            const lastProblem = problems[problems.length - 1];
+            for (const problem of problems) {
+                if (problem.time > timestamp) {
+                    result = Object.assign({}, problem, {fixed: lastProblem.fixed});
+                    return;
+                }
+            }
+            if (lastProblem.fixed) {
+                result = null;
+            } else {
+                result = lastProblem;
+            }
+        };
+        await promiseifyTxn(txn);
+        return result;
+    }
+
+    // FIXME: we should probably prune this when devices get deleted
+    async filterOutNotifiedErrorDevices(devices) {
+        const txn = this._db.transaction("notified_error_devices", "readwrite");
+        const objectStore = txn.objectStore("notified_error_devices");
+
+        const ret = [];
+
+        await Promise.all(devices.map((device) => {
+            return new Promise((resolve) => {
+                const {userId, deviceInfo} = device;
+                const getReq = objectStore.get([userId, deviceInfo.deviceId]);
+                getReq.onsuccess = function() {
+                    if (!getReq.result) {
+                        objectStore.put({userId, deviceId: deviceInfo.deviceId});
+                        ret.push(device);
+                    }
+                    resolve();
+                };
+            });
+        }));
+
+        return ret;
+    }
+
     // Inbound group sessions
 
     getEndToEndInboundGroupSession(senderCurve25519Key, sessionId, txn, func) {
+        let session = false;
+        let withheld = false;
         const objectStore = txn.objectStore("inbound_group_sessions");
         const getReq = objectStore.get([senderCurve25519Key, sessionId]);
         getReq.onsuccess = function() {
             try {
                 if (getReq.result) {
-                    func(getReq.result.session);
+                    session = getReq.result.session;
                 } else {
-                    func(null);
+                    session = null;
+                }
+                if (withheld !== false) {
+                    func(session, withheld);
+                }
+            } catch (e) {
+                abortWithException(txn, e);
+            }
+        };
+
+        const withheldObjectStore = txn.objectStore("inbound_group_sessions_withheld");
+        const withheldGetReq = withheldObjectStore.get([senderCurve25519Key, sessionId]);
+        withheldGetReq.onsuccess = function() {
+            try {
+                if (withheldGetReq.result) {
+                    withheld = withheldGetReq.result.session;
+                } else {
+                    withheld = null;
+                }
+                if (session !== false) {
+                    func(session, withheld);
                 }
             } catch (e) {
                 abortWithException(txn, e);
@@ -499,6 +590,15 @@ export class Backend {
         });
     }
 
+    storeEndToEndInboundGroupSessionWithheld(
+        senderCurve25519Key, sessionId, sessionData, txn,
+    ) {
+        const objectStore = txn.objectStore("inbound_group_sessions_withheld");
+        objectStore.put({
+            senderCurve25519Key, sessionId, session: sessionData,
+        });
+    }
+
     getEndToEndDeviceData(txn, func) {
         const objectStore = txn.objectStore("device_data");
         const getReq = objectStore.get("-");
@@ -662,6 +762,21 @@ export function upgradeDatabase(db, oldVersion) {
             keyPath: ["senderCurve25519Key", "sessionId"],
         });
     }
+    if (oldVersion < 8) {
+        db.createObjectStore("inbound_group_sessions_withheld", {
+            keyPath: ["senderCurve25519Key", "sessionId"],
+        });
+    }
+    if (oldVersion < 9) {
+        const problemsStore = db.createObjectStore("session_problems", {
+            keyPath: ["deviceKey", "time"],
+        });
+        problemsStore.createIndex("deviceKey", "deviceKey");
+
+        db.createObjectStore("notified_error_devices", {
+            keyPath: ["userId", "deviceId"],
+        });
+    }
     // Expand as needed.
 }
 
diff --git a/src/crypto/store/indexeddb-crypto-store.js b/src/crypto/store/indexeddb-crypto-store.js
index 68c10aec1..fac67baf6 100644
--- a/src/crypto/store/indexeddb-crypto-store.js
+++ b/src/crypto/store/indexeddb-crypto-store.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,9 +16,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../../logger';
-import LocalStorageCryptoStore from './localStorage-crypto-store';
-import MemoryCryptoStore from './memory-crypto-store';
+import {logger} from '../../logger';
+import {LocalStorageCryptoStore} from './localStorage-crypto-store';
+import {MemoryCryptoStore} from './memory-crypto-store';
 import * as IndexedDBCryptoStoreBackend from './indexeddb-crypto-store-backend';
 import {InvalidCryptoStoreError} from '../../errors';
 import * as IndexedDBHelpers from "../../indexeddb-helpers";
@@ -34,7 +35,7 @@ import * as IndexedDBHelpers from "../../indexeddb-helpers";
  *
  * @implements {module:crypto/store/base~CryptoStore}
  */
-export default class IndexedDBCryptoStore {
+export class IndexedDBCryptoStore {
     /**
      * Create a new IndexedDBCryptoStore
      *
@@ -104,7 +105,10 @@ export default class IndexedDBCryptoStore {
             // we can fall back to a different backend.
             return backend.doTxn(
                 'readonly',
-                [IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS],
+                [
+                    IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS,
+                    IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD,
+                ],
                 (txn) => {
                     backend.getEndToEndInboundGroupSession('', '', txn, () => {});
                 }).then(() => {
@@ -405,6 +409,24 @@ export default class IndexedDBCryptoStore {
         });
     }
 
+    storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        return this._backendPromise.then(async (backend) => {
+            await backend.storeEndToEndSessionProblem(deviceKey, type, fixed);
+        });
+    }
+
+    getEndToEndSessionProblem(deviceKey, timestamp) {
+        return this._backendPromise.then(async (backend) => {
+            return await backend.getEndToEndSessionProblem(deviceKey, timestamp);
+        });
+    }
+
+    filterOutNotifiedErrorDevices(devices) {
+        return this._backendPromise.then(async (backend) => {
+            return await backend.filterOutNotifiedErrorDevices(devices);
+        });
+    }
+
     // Inbound group sessions
 
     /**
@@ -471,6 +493,16 @@ export default class IndexedDBCryptoStore {
         });
     }
 
+    storeEndToEndInboundGroupSessionWithheld(
+        senderCurve25519Key, sessionId, sessionData, txn,
+    ) {
+        this._backendPromise.then(backend => {
+            backend.storeEndToEndInboundGroupSessionWithheld(
+                senderCurve25519Key, sessionId, sessionData, txn,
+            );
+        });
+    }
+
     // End-to-end device tracking
 
     /**
@@ -607,6 +639,8 @@ export default class IndexedDBCryptoStore {
 IndexedDBCryptoStore.STORE_ACCOUNT = 'account';
 IndexedDBCryptoStore.STORE_SESSIONS = 'sessions';
 IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS = 'inbound_group_sessions';
+IndexedDBCryptoStore.STORE_INBOUND_GROUP_SESSIONS_WITHHELD
+    = 'inbound_group_sessions_withheld';
 IndexedDBCryptoStore.STORE_DEVICE_DATA = 'device_data';
 IndexedDBCryptoStore.STORE_ROOMS = 'rooms';
 IndexedDBCryptoStore.STORE_BACKUP = 'sessions_needing_backup';
diff --git a/src/crypto/store/localStorage-crypto-store.js b/src/crypto/store/localStorage-crypto-store.js
index 0f304fbb1..2e7d3cbd3 100644
--- a/src/crypto/store/localStorage-crypto-store.js
+++ b/src/crypto/store/localStorage-crypto-store.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2017, 2018 New Vector Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,8 +15,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../../logger';
-import MemoryCryptoStore from './memory-crypto-store';
+import {logger} from '../../logger';
+import {MemoryCryptoStore} from './memory-crypto-store';
 
 /**
  * Internal module. Partial localStorage backed storage for e2e.
@@ -30,8 +31,10 @@ import MemoryCryptoStore from './memory-crypto-store';
 const E2E_PREFIX = "crypto.";
 const KEY_END_TO_END_ACCOUNT = E2E_PREFIX + "account";
 const KEY_CROSS_SIGNING_KEYS = E2E_PREFIX + "cross_signing_keys";
+const KEY_NOTIFIED_ERROR_DEVICES = E2E_PREFIX + "notified_error_devices";
 const KEY_DEVICE_DATA = E2E_PREFIX + "device_data";
 const KEY_INBOUND_SESSION_PREFIX = E2E_PREFIX + "inboundgroupsessions/";
+const KEY_INBOUND_SESSION_WITHHELD_PREFIX = E2E_PREFIX + "inboundgroupsessions.withheld/";
 const KEY_ROOMS_PREFIX = E2E_PREFIX + "rooms/";
 const KEY_SESSIONS_NEEDING_BACKUP = E2E_PREFIX + "sessionsneedingbackup";
 
@@ -39,10 +42,18 @@ function keyEndToEndSessions(deviceKey) {
     return E2E_PREFIX + "sessions/" + deviceKey;
 }
 
+function keyEndToEndSessionProblems(deviceKey) {
+    return E2E_PREFIX + "session.problems/" + deviceKey;
+}
+
 function keyEndToEndInboundGroupSession(senderKey, sessionId) {
     return KEY_INBOUND_SESSION_PREFIX + senderKey + "/" + sessionId;
 }
 
+function keyEndToEndInboundGroupSessionWithheld(senderKey, sessionId) {
+    return KEY_INBOUND_SESSION_WITHHELD_PREFIX + senderKey + "/" + sessionId;
+}
+
 function keyEndToEndRoomsPrefix(roomId) {
     return KEY_ROOMS_PREFIX + roomId;
 }
@@ -50,7 +61,7 @@ function keyEndToEndRoomsPrefix(roomId) {
 /**
  * @implements {module:crypto/store/base~CryptoStore}
  */
-export default class LocalStorageCryptoStore extends MemoryCryptoStore {
+export class LocalStorageCryptoStore extends MemoryCryptoStore {
     constructor(webStore) {
         super();
         this.store = webStore;
@@ -122,13 +133,71 @@ export default class LocalStorageCryptoStore extends MemoryCryptoStore {
         );
     }
 
+    async storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        const key = keyEndToEndSessionProblems(deviceKey);
+        const problems = getJsonItem(this.store, key) || [];
+        problems.push({type, fixed, time: Date.now()});
+        problems.sort((a, b) => {
+            return a.time - b.time;
+        });
+        setJsonItem(this.store, key, problems);
+    }
+
+    async getEndToEndSessionProblem(deviceKey, timestamp) {
+        const key = keyEndToEndSessionProblems(deviceKey);
+        const problems = getJsonItem(this.store, key) || [];
+        if (!problems.length) {
+            return null;
+        }
+        const lastProblem = problems[problems.length - 1];
+        for (const problem of problems) {
+            if (problem.time > timestamp) {
+                return Object.assign({}, problem, {fixed: lastProblem.fixed});
+            }
+        }
+        if (lastProblem.fixed) {
+            return null;
+        } else {
+            return lastProblem;
+        }
+    }
+
+    async filterOutNotifiedErrorDevices(devices) {
+        const notifiedErrorDevices =
+              getJsonItem(this.store, KEY_NOTIFIED_ERROR_DEVICES) || {};
+        const ret = [];
+
+        for (const device of devices) {
+            const {userId, deviceInfo} = device;
+            if (userId in notifiedErrorDevices) {
+                if (!(deviceInfo.deviceId in notifiedErrorDevices[userId])) {
+                    ret.push(device);
+                    notifiedErrorDevices[userId][deviceInfo.deviceId] = true;
+                }
+            } else {
+                ret.push(device);
+                notifiedErrorDevices[userId] = {[deviceInfo.deviceId]: true };
+            }
+        }
+
+        setJsonItem(this.store, KEY_NOTIFIED_ERROR_DEVICES, notifiedErrorDevices);
+
+        return ret;
+    }
+
     // Inbound Group Sessions
 
     getEndToEndInboundGroupSession(senderCurve25519Key, sessionId, txn, func) {
-        func(getJsonItem(
-            this.store,
-            keyEndToEndInboundGroupSession(senderCurve25519Key, sessionId),
-        ));
+        func(
+            getJsonItem(
+                this.store,
+                keyEndToEndInboundGroupSession(senderCurve25519Key, sessionId),
+            ),
+            getJsonItem(
+                this.store,
+                keyEndToEndInboundGroupSessionWithheld(senderCurve25519Key, sessionId),
+            ),
+        );
     }
 
     getAllEndToEndInboundGroupSessions(txn, func) {
@@ -170,6 +239,16 @@ export default class LocalStorageCryptoStore extends MemoryCryptoStore {
         );
     }
 
+    storeEndToEndInboundGroupSessionWithheld(
+        senderCurve25519Key, sessionId, sessionData, txn,
+    ) {
+        setJsonItem(
+            this.store,
+            keyEndToEndInboundGroupSessionWithheld(senderCurve25519Key, sessionId),
+            sessionData,
+        );
+    }
+
     getEndToEndDeviceData(txn, func) {
         func(getJsonItem(
             this.store, KEY_DEVICE_DATA,
diff --git a/src/crypto/store/memory-crypto-store.js b/src/crypto/store/memory-crypto-store.js
index eca79f037..ee8e83700 100644
--- a/src/crypto/store/memory-crypto-store.js
+++ b/src/crypto/store/memory-crypto-store.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,8 +16,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../../logger';
-import utils from '../../utils';
+import {logger} from '../../logger';
+import * as utils from "../../utils";
 
 /**
  * Internal module. in-memory storage for e2e.
@@ -27,7 +28,7 @@ import utils from '../../utils';
 /**
  * @implements {module:crypto/store/base~CryptoStore}
  */
-export default class MemoryCryptoStore {
+export class MemoryCryptoStore {
     constructor() {
         this._outgoingRoomKeyRequests = [];
         this._account = null;
@@ -35,8 +36,13 @@ export default class MemoryCryptoStore {
 
         // Map of {devicekey -> {sessionId -> session pickle}}
         this._sessions = {};
+        // Map of {devicekey -> array of problems}
+        this._sessionProblems = {};
+        // Map of {userId -> deviceId -> true}
+        this._notifiedErrorDevices = {};
         // Map of {senderCurve25519Key+'/'+sessionId -> session data object}
         this._inboundGroupSessions = {};
+        this._inboundGroupSessionsWithheld = {};
         // Opaque device data object
         this._deviceData = null;
         // roomId -> Opaque roomInfo object
@@ -273,10 +279,61 @@ export default class MemoryCryptoStore {
         deviceSessions[sessionId] = sessionInfo;
     }
 
+    async storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        const problems = this._sessionProblems[deviceKey]
+              = this._sessionProblems[deviceKey] || [];
+        problems.push({type, fixed, time: Date.now()});
+        problems.sort((a, b) => {
+            return a.time - b.time;
+        });
+    }
+
+    async getEndToEndSessionProblem(deviceKey, timestamp) {
+        const problems = this._sessionProblems[deviceKey] || [];
+        if (!problems.length) {
+            return null;
+        }
+        const lastProblem = problems[problems.length - 1];
+        for (const problem of problems) {
+            if (problem.time > timestamp) {
+                return Object.assign({}, problem, {fixed: lastProblem.fixed});
+            }
+        }
+        if (lastProblem.fixed) {
+            return null;
+        } else {
+            return lastProblem;
+        }
+    }
+
+    async filterOutNotifiedErrorDevices(devices) {
+        const notifiedErrorDevices = this._notifiedErrorDevices;
+        const ret = [];
+
+        for (const device of devices) {
+            const {userId, deviceInfo} = device;
+            if (userId in notifiedErrorDevices) {
+                if (!(deviceInfo.deviceId in notifiedErrorDevices[userId])) {
+                    ret.push(device);
+                    notifiedErrorDevices[userId][deviceInfo.deviceId] = true;
+                }
+            } else {
+                ret.push(device);
+                notifiedErrorDevices[userId] = {[deviceInfo.deviceId]: true };
+            }
+        }
+
+        return ret;
+    }
+
     // Inbound Group Sessions
 
     getEndToEndInboundGroupSession(senderCurve25519Key, sessionId, txn, func) {
-        func(this._inboundGroupSessions[senderCurve25519Key+'/'+sessionId] || null);
+        const k = senderCurve25519Key+'/'+sessionId;
+        func(
+            this._inboundGroupSessions[k] || null,
+            this._inboundGroupSessionsWithheld[k] || null,
+        );
     }
 
     getAllEndToEndInboundGroupSessions(txn, func) {
@@ -306,6 +363,13 @@ export default class MemoryCryptoStore {
         this._inboundGroupSessions[senderCurve25519Key+'/'+sessionId] = sessionData;
     }
 
+    storeEndToEndInboundGroupSessionWithheld(
+        senderCurve25519Key, sessionId, sessionData, txn,
+    ) {
+        const k = senderCurve25519Key+'/'+sessionId;
+        this._inboundGroupSessionsWithheld[k] = sessionData;
+    }
+
     // Device Data
 
     getEndToEndDeviceData(txn, func) {
diff --git a/src/crypto/verification/Base.js b/src/crypto/verification/Base.js
index ab720fe6c..8d1475b51 100644
--- a/src/crypto/verification/Base.js
+++ b/src/crypto/verification/Base.js
@@ -21,13 +21,13 @@ limitations under the License.
 
 import {MatrixEvent} from '../../models/event';
 import {EventEmitter} from 'events';
-import logger from '../../logger';
-import DeviceInfo from '../deviceinfo';
+import {logger} from '../../logger';
+import {DeviceInfo} from '../deviceinfo';
 import {newTimeoutError} from "./Error";
 
 const timeoutException = new Error("Verification timed out");
 
-export default class VerificationBase extends EventEmitter {
+export class VerificationBase extends EventEmitter {
     /**
      * Base class for verification methods.
      *
diff --git a/src/crypto/verification/QRCode.js b/src/crypto/verification/QRCode.js
index d86e389b3..fe5830732 100644
--- a/src/crypto/verification/QRCode.js
+++ b/src/crypto/verification/QRCode.js
@@ -19,11 +19,11 @@ limitations under the License.
  * @module crypto/verification/QRCode
  */
 
-import Base from "./Base";
+import {VerificationBase as Base} from "./Base";
 import {
     errorFactory,
-    newUserCancelledError,
     newKeyMismatchError,
+    newUserCancelledError,
     newUserMismatchError,
 } from './Error';
 
diff --git a/src/crypto/verification/SAS.js b/src/crypto/verification/SAS.js
index cbca5fd35..f840b1abf 100644
--- a/src/crypto/verification/SAS.js
+++ b/src/crypto/verification/SAS.js
@@ -19,14 +19,14 @@ limitations under the License.
  * @module crypto/verification/SAS
  */
 
-import Base from "./Base";
+import {VerificationBase as Base} from "./Base";
 import anotherjson from 'another-json';
 import {
     errorFactory,
-    newUserCancelledError,
-    newUnknownMethodError,
-    newKeyMismatchError,
     newInvalidMessageError,
+    newKeyMismatchError,
+    newUnknownMethodError,
+    newUserCancelledError,
 } from './Error';
 
 const EVENTS = [
@@ -108,7 +108,7 @@ const emojiMapping = [
     ["✏️", "pencil"],     // 43
     ["📎", "paperclip"],  // 44
     ["✂️", "scissors"],    // 45
-    ["🔒", "padlock"],    // 46
+    ["🔒", "lock"],       // 46
     ["🔑", "key"],        // 47
     ["🔨", "hammer"],     // 48
     ["☎️", "telephone"],  // 49
@@ -185,7 +185,11 @@ function intersection(anArray, aSet) {
  * @alias module:crypto/verification/SAS
  * @extends {module:crypto/verification/Base}
  */
-export default class SAS extends Base {
+export class SAS extends Base {
+    static get NAME() {
+        return "m.sas.v1";
+    }
+
     get events() {
         return EVENTS;
     }
@@ -426,5 +430,3 @@ export default class SAS extends Base {
         });
     }
 }
-
-SAS.NAME = "m.sas.v1";
diff --git a/src/crypto/verification/request/InRoomChannel.js b/src/crypto/verification/request/InRoomChannel.js
index 157e30380..c6dde65ae 100644
--- a/src/crypto/verification/request/InRoomChannel.js
+++ b/src/crypto/verification/request/InRoomChannel.js
@@ -15,11 +15,13 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import VerificationRequest, {
+import {
+    VerificationRequest,
     REQUEST_TYPE,
     READY_TYPE,
     START_TYPE,
 } from "./VerificationRequest";
+
 const MESSAGE_TYPE = "m.room.message";
 const M_REFERENCE = "m.reference";
 const M_RELATES_TO = "m.relates_to";
diff --git a/src/crypto/verification/request/ToDeviceChannel.js b/src/crypto/verification/request/ToDeviceChannel.js
index 063a70b94..4956b594c 100644
--- a/src/crypto/verification/request/ToDeviceChannel.js
+++ b/src/crypto/verification/request/ToDeviceChannel.js
@@ -15,24 +15,19 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { randomString } from '../../../randomstring';
-import logger from '../../../logger';
-import VerificationRequest, {
+import {randomString} from '../../../randomstring';
+import {logger} from '../../../logger';
+import {
+    CANCEL_TYPE,
     PHASE_STARTED,
     PHASE_READY,
     REQUEST_TYPE,
     READY_TYPE,
     START_TYPE,
-    CANCEL_TYPE,
+    VerificationRequest,
 } from "./VerificationRequest";
-
-import {
-    newUnexpectedMessageError,
-    errorFromEvent,
-} from "../Error";
-
-const MatrixEvent = require("../../../models/event").MatrixEvent;
-
+import {errorFromEvent, newUnexpectedMessageError} from "../Error";
+import {MatrixEvent} from "../../../models/event";
 
 /**
  * A key verification channel that sends verification events over to_device messages.
diff --git a/src/crypto/verification/request/VerificationRequest.js b/src/crypto/verification/request/VerificationRequest.js
index 9d8b16c5f..f5456ddb8 100644
--- a/src/crypto/verification/request/VerificationRequest.js
+++ b/src/crypto/verification/request/VerificationRequest.js
@@ -15,13 +15,13 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../../../logger';
+import {logger} from '../../../logger';
 import {EventEmitter} from 'events';
 import {
-    newUnknownMethodError,
-    newUnexpectedMessageError,
-    errorFromEvent,
     errorFactory,
+    errorFromEvent,
+    newUnexpectedMessageError,
+    newUnknownMethodError,
 } from "../Error";
 
 // the recommended amount of time before a verification request
@@ -56,7 +56,7 @@ export const PHASE_DONE = 6;
  * send and receive verification events are put in `InRoomChannel` or `ToDeviceChannel`.
  * @event "change" whenever the state of the request object has changed.
  */
-export default class VerificationRequest extends EventEmitter {
+export class VerificationRequest extends EventEmitter {
     constructor(channel, verificationMethods, client) {
         super();
         this.channel = channel;
diff --git a/src/filter-component.js b/src/filter-component.js
index 38b1c8afd..7e8fd5244 100644
--- a/src/filter-component.js
+++ b/src/filter-component.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,7 +14,7 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module filter-component
  */
@@ -45,7 +46,7 @@ function _matches_wildcard(actual_value, filter_value) {
  * @constructor
  * @param {Object} filter_json the definition of this filter JSON, e.g. { 'contains_url': true }
  */
-function FilterComponent(filter_json) {
+export function FilterComponent(filter_json) {
     this.filter_json = filter_json;
 
     this.types = filter_json.types || null;
@@ -141,6 +142,3 @@ FilterComponent.prototype.filter = function(events) {
 FilterComponent.prototype.limit = function() {
     return this.filter_json.limit !== undefined ? this.filter_json.limit : 10;
 };
-
-/** The FilterComponent class */
-module.exports = FilterComponent;
diff --git a/src/filter.js b/src/filter.js
index a63fcee13..f8884b27b 100644
--- a/src/filter.js
+++ b/src/filter.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,12 +14,12 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module filter
  */
 
-const FilterComponent = require("./filter-component");
+import {FilterComponent} from "./filter-component";
 
 /**
  * @param {Object} obj
@@ -45,7 +46,7 @@ function setProp(obj, keyNesting, val) {
  * @prop {string} userId The user ID of the filter
  * @prop {?string} filterId The filter ID
  */
-function Filter(userId, filterId) {
+export function Filter(userId, filterId) {
     this.userId = userId;
     this.filterId = filterId;
     this.definition = {};
@@ -198,6 +199,3 @@ Filter.fromJson = function(userId, filterId, jsonObj) {
     filter.setDefinition(jsonObj);
     return filter;
 };
-
-/** The Filter class */
-module.exports = Filter;
diff --git a/src/http-api.js b/src/http-api.js
index 0d6aecd1d..927947432 100644
--- a/src/http-api.js
+++ b/src/http-api.js
@@ -14,20 +14,20 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * This is an internal module. See {@link MatrixHttpApi} for the public class.
  * @module http-api
  */
-const parseContentType = require('content-type').parse;
 
-const utils = require("./utils");
-import logger from './logger';
+import {parse as parseContentType} from "content-type";
+import * as utils from "./utils";
+import {logger} from './logger';
 
 // we use our own implementation of setTimeout, so that if we get suspended in
 // the middle of a /sync, we cancel the sync as soon as we awake, rather than
 // waiting for the delay to elapse.
-const callbacks = require("./realtime-callbacks");
+import * as callbacks from "./realtime-callbacks";
 
 /*
 TODO:
@@ -38,27 +38,27 @@ TODO:
 /**
  * A constant representing the URI path for release 0 of the Client-Server HTTP API.
  */
-module.exports.PREFIX_R0 = "/_matrix/client/r0";
+export const PREFIX_R0 = "/_matrix/client/r0";
 
 /**
  * A constant representing the URI path for as-yet unspecified Client-Server HTTP APIs.
  */
-module.exports.PREFIX_UNSTABLE = "/_matrix/client/unstable";
+export const PREFIX_UNSTABLE = "/_matrix/client/unstable";
 
 /**
  * URI path for v1 of the the identity API
  */
-module.exports.PREFIX_IDENTITY_V1 = "/_matrix/identity/api/v1";
+export const PREFIX_IDENTITY_V1 = "/_matrix/identity/api/v1";
 
 /**
  * URI path for the v2 identity API
  */
-module.exports.PREFIX_IDENTITY_V2 = "/_matrix/identity/v2";
+export const PREFIX_IDENTITY_V2 = "/_matrix/identity/v2";
 
 /**
  * URI path for the media repo API
  */
-module.exports.PREFIX_MEDIA_R0 = "/_matrix/media/r0";
+export const PREFIX_MEDIA_R0 = "/_matrix/media/r0";
 
 /**
  * Construct a MatrixHttpApi.
@@ -85,16 +85,16 @@ module.exports.PREFIX_MEDIA_R0 = "/_matrix/media/r0";
  * @param {boolean} [opts.useAuthorizationHeader = false] Set to true to use
  * Authorization header instead of query param to send the access token to the server.
  */
-module.exports.MatrixHttpApi = function MatrixHttpApi(event_emitter, opts) {
+export function MatrixHttpApi(event_emitter, opts) {
     utils.checkObjectHasKeys(opts, ["baseUrl", "request", "prefix"]);
     opts.onlyData = opts.onlyData || false;
     this.event_emitter = event_emitter;
     this.opts = opts;
     this.useAuthorizationHeader = Boolean(opts.useAuthorizationHeader);
     this.uploads = [];
-};
+}
 
-module.exports.MatrixHttpApi.prototype = {
+MatrixHttpApi.prototype = {
     /**
      * Sets the baase URL for the identity server
      * @param {string} url The new base url
@@ -698,7 +698,7 @@ module.exports.MatrixHttpApi.prototype = {
                     if (req && req.abort) {
                         req.abort();
                     }
-                    defer.reject(new module.exports.MatrixError({
+                    defer.reject(new MatrixError({
                         error: "Locally timed out waiting for a response",
                         errcode: "ORG.MATRIX.JSSDK_TIMEOUT",
                         timeout: localTimeoutMs,
@@ -836,7 +836,7 @@ function parseErrorResponse(response, body) {
     if (contentType) {
         if (contentType.type === 'application/json') {
             const jsonBody = typeof(body) === 'object' ? body : JSON.parse(body);
-            err = new module.exports.MatrixError(jsonBody);
+            err = new MatrixError(jsonBody);
         } else if (contentType.type === 'text/plain') {
             err = new Error(`Server returned ${httpStatus} error: ${body}`);
         }
@@ -891,13 +891,12 @@ function getResponseContentType(response) {
  * @prop {Object} data The raw Matrix error JSON used to construct this object.
  * @prop {integer} httpStatus The numeric HTTP status code given
  */
-module.exports.MatrixError = function MatrixError(errorJson) {
+export function MatrixError(errorJson) {
     errorJson = errorJson || {};
     this.errcode = errorJson.errcode;
     this.name = errorJson.errcode || "Unknown error code";
     this.message = errorJson.error || "Unknown message";
     this.data = errorJson;
-};
-module.exports.MatrixError.prototype = Object.create(Error.prototype);
-/** */
-module.exports.MatrixError.prototype.constructor = module.exports.MatrixError;
+}
+MatrixError.prototype = Object.create(Error.prototype);
+MatrixError.prototype.constructor = MatrixError;
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 000000000..229c4197e
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,24 @@
+/*
+Copyright 2019 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import * as matrixcs from "./matrix";
+import * as utils from "./utils";
+
+matrixcs.request(import("request"));
+utils.runPolyfills();
+
+export * from "./matrix";
+export default matrixcs;
diff --git a/src/indexeddb-worker.js b/src/indexeddb-worker.js
index aa6312e2f..b51d90afd 100644
--- a/src/indexeddb-worker.js
+++ b/src/indexeddb-worker.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2017 Vector Creations Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -20,5 +21,5 @@ limitations under the License.
  */
 
 /** The {@link module:indexeddb-store-worker~IndexedDBStoreWorker} class. */
-module.exports.IndexedDBStoreWorker = require("./store/indexeddb-store-worker.js");
+export {IndexedDBStoreWorker} from "./store/indexeddb-store-worker";
 
diff --git a/src/interactive-auth.js b/src/interactive-auth.js
index eb9d9dbaa..f4bf1bb18 100644
--- a/src/interactive-auth.js
+++ b/src/interactive-auth.js
@@ -15,13 +15,12 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /** @module interactive-auth */
-const url = require("url");
 
-const utils = require("./utils");
-import logger from './logger';
+import url from "url";
+import * as utils from "./utils";
+import {logger} from './logger';
 
 const EMAIL_STAGE_TYPE = "m.login.email.identity";
 const MSISDN_STAGE_TYPE = "m.login.msisdn";
@@ -103,7 +102,7 @@ const MSISDN_STAGE_TYPE = "m.login.msisdn";
  *     attemptAuth promise.
  *
  */
-function InteractiveAuth(opts) {
+export function InteractiveAuth(opts) {
     this._matrixClient = opts.matrixClient;
     this._data = opts.authData || {};
     this._requestCallback = opts.doRequest;
@@ -510,6 +509,3 @@ InteractiveAuth.prototype = {
     },
 };
 
-
-/** */
-module.exports = InteractiveAuth;
diff --git a/src/logger.js b/src/logger.js
index ee77c2918..b079dfd5f 100644
--- a/src/logger.js
+++ b/src/logger.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2018 André Jaenisch
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -17,7 +18,8 @@ limitations under the License.
 /**
  * @module logger
  */
-const log = require("loglevel");
+
+import log from "loglevel";
 
 // This is to demonstrate, that you can use any namespace you want.
 // Namespaces allow you to turn on/off the logging for specific parts of the
@@ -25,12 +27,12 @@ const log = require("loglevel");
 // An idea would be to control this via an environment variable (on Node.js).
 // See https://www.npmjs.com/package/debug to see how this could be implemented
 // Part of #332 is introducing a logging library in the first place.
-const DEFAULT_NAME_SPACE = "matrix";
-const logger = log.getLogger(DEFAULT_NAME_SPACE);
-logger.setLevel(log.levels.DEBUG);
+const DEFAULT_NAMESPACE = "matrix";
 
 /**
  * Drop-in replacement for <code>console</code> using {@link https://www.npmjs.com/package/loglevel|loglevel}.
  * Can be tailored down to specific use cases if needed.
-*/
-module.exports = logger;
+ */
+export const logger = log.getLogger(DEFAULT_NAMESPACE);
+logger.setLevel(log.levels.DEBUG);
+
diff --git a/src/matrix.js b/src/matrix.js
index 244b10f24..57d940ad4 100644
--- a/src/matrix.js
+++ b/src/matrix.js
@@ -15,129 +15,66 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
-/** The {@link module:ContentHelpers} object */
-module.exports.ContentHelpers = require("./content-helpers");
-/** The {@link module:models/event.MatrixEvent|MatrixEvent} class. */
-module.exports.MatrixEvent = require("./models/event").MatrixEvent;
-/** The {@link module:models/event.EventStatus|EventStatus} enum. */
-module.exports.EventStatus = require("./models/event").EventStatus;
-/** The {@link module:store/memory.MemoryStore|MemoryStore} class. */
-module.exports.MemoryStore = require("./store/memory").MemoryStore;
-/**
- * The {@link module:store/memory.MemoryStore|MemoryStore} class was previously
- * exported as `MatrixInMemoryStore`, so this is preserved for SDK consumers.
- * @deprecated Prefer `MemoryStore` going forward.
- */
-module.exports.MatrixInMemoryStore = module.exports.MemoryStore;
-/** The {@link module:store/indexeddb.IndexedDBStore|IndexedDBStore} class. */
-module.exports.IndexedDBStore = require("./store/indexeddb").IndexedDBStore;
-/** The {@link module:store/indexeddb.IndexedDBStoreBackend|IndexedDBStoreBackend} class. */
-module.exports.IndexedDBStoreBackend = require("./store/indexeddb").IndexedDBStoreBackend;
-/** The {@link module:sync-accumulator.SyncAccumulator|SyncAccumulator} class. */
-module.exports.SyncAccumulator = require("./sync-accumulator");
-/** The {@link module:http-api.MatrixHttpApi|MatrixHttpApi} class. */
-module.exports.MatrixHttpApi = require("./http-api").MatrixHttpApi;
-/** The {@link module:http-api.MatrixError|MatrixError} class. */
-module.exports.MatrixError = require("./http-api").MatrixError;
-/** The {@link module:errors.InvalidStoreError|InvalidStoreError} class. */
-module.exports.InvalidStoreError = require("./errors").InvalidStoreError;
-/** The {@link module:client.MatrixClient|MatrixClient} class. */
-module.exports.MatrixClient = require("./client").MatrixClient;
-/** The {@link module:models/room|Room} class. */
-module.exports.Room = require("./models/room");
-/** The {@link module:models/group|Group} class. */
-module.exports.Group = require("./models/group");
-/** The {@link module:models/event-timeline~EventTimeline} class. */
-module.exports.EventTimeline = require("./models/event-timeline");
-/** The {@link module:models/event-timeline-set~EventTimelineSet} class. */
-module.exports.EventTimelineSet = require("./models/event-timeline-set");
-/** The {@link module:models/room-member|RoomMember} class. */
-module.exports.RoomMember = require("./models/room-member");
-/** The {@link module:models/room-state~RoomState|RoomState} class. */
-module.exports.RoomState = require("./models/room-state");
-/** The {@link module:models/user~User|User} class. */
-module.exports.User = require("./models/user");
-/** The {@link module:scheduler~MatrixScheduler|MatrixScheduler} class. */
-module.exports.MatrixScheduler = require("./scheduler");
-/** The {@link module:store/session/webstorage~WebStorageSessionStore|
- * WebStorageSessionStore} class. <strong>Work in progress; unstable.</strong> */
-module.exports.WebStorageSessionStore = require("./store/session/webstorage");
-/** True if crypto libraries are being used on this client. */
-module.exports.CRYPTO_ENABLED = require("./client").CRYPTO_ENABLED;
-/** {@link module:content-repo|ContentRepo} utility functions. */
-module.exports.ContentRepo = require("./content-repo");
-/** The {@link module:filter~Filter|Filter} class. */
-module.exports.Filter = require("./filter");
-/** The {@link module:timeline-window~TimelineWindow} class. */
-module.exports.TimelineWindow = require("./timeline-window").TimelineWindow;
-/** The {@link module:interactive-auth} class. */
-module.exports.InteractiveAuth = require("./interactive-auth");
-/** The {@link module:auto-discovery|AutoDiscovery} class. */
-module.exports.AutoDiscovery = require("./autodiscovery").AutoDiscovery;
+import {MemoryCryptoStore} from "./crypto/store/memory-crypto-store";
+import {MemoryStore} from "./store/memory";
+import {MatrixScheduler} from "./scheduler";
+import {MatrixClient} from "./client";
 
-module.exports.SERVICE_TYPES = require('./service-types').SERVICE_TYPES;
-
-module.exports.MemoryCryptoStore =
-    require("./crypto/store/memory-crypto-store").default;
-module.exports.IndexedDBCryptoStore =
-    require("./crypto/store/indexeddb-crypto-store").default;
-
-/**
- * Create a new Matrix Call.
- * @function
- * @param {module:client.MatrixClient} client The MatrixClient instance to use.
- * @param {string} roomId The room the call is in.
- * @return {module:webrtc/call~MatrixCall} The Matrix call or null if the browser
- * does not support WebRTC.
- */
-module.exports.createNewMatrixCall = require("./webrtc/call").createNewMatrixCall;
-
-
-/**
- * Set a preferred audio output device to use for MatrixCalls
- * @function
- * @param {string=} deviceId the identifier for the device
- * undefined treated as unset
- */
-module.exports.setMatrixCallAudioOutput = require('./webrtc/call').setAudioOutput;
-/**
- * Set a preferred audio input device to use for MatrixCalls
- * @function
- * @param {string=} deviceId the identifier for the device
- * undefined treated as unset
- */
-module.exports.setMatrixCallAudioInput = require('./webrtc/call').setAudioInput;
-/**
- * Set a preferred video input device to use for MatrixCalls
- * @function
- * @param {string=} deviceId the identifier for the device
- * undefined treated as unset
- */
-module.exports.setMatrixCallVideoInput = require('./webrtc/call').setVideoInput;
+export * from "./client";
+export * from "./http-api";
+export * from "./autodiscovery";
+export * from "./sync-accumulator";
+export * from "./errors";
+export * from "./models/event";
+export * from "./models/room";
+export * from "./models/group";
+export * from "./models/event-timeline";
+export * from "./models/event-timeline-set";
+export * from "./models/room-member";
+export * from "./models/room-state";
+export * from "./models/user";
+export * from "./scheduler";
+export * from "./filter";
+export * from "./timeline-window";
+export * from "./interactive-auth";
+export * from "./service-types";
+export * from "./store/memory";
+export * from "./store/indexeddb";
+export * from "./store/session/webstorage";
+export * from "./crypto/store/memory-crypto-store";
+export * from "./crypto/store/indexeddb-crypto-store";
+export * from "./content-repo";
+export const ContentHelpers = import("./content-helpers");
+export {
+    createNewMatrixCall,
+    setAudioOutput as setMatrixCallAudioOutput,
+    setAudioInput as setMatrixCallAudioInput,
+    setVideoInput as setMatrixCallVideoInput,
+} from "./webrtc/call";
 
 
 // expose the underlying request object so different environments can use
 // different request libs (e.g. request or browser-request)
-let request;
+let requestInstance;
+
 /**
  * The function used to perform HTTP requests. Only use this if you want to
  * use a different HTTP library, e.g. Angular's <code>$http</code>. This should
  * be set prior to calling {@link createClient}.
  * @param {requestFunction} r The request function to use.
  */
-module.exports.request = function(r) {
-    request = r;
-};
+export function request(r) {
+    requestInstance = r;
+}
 
 /**
  * Return the currently-set request function.
  * @return {requestFunction} The current request function.
  */
-module.exports.getRequest = function() {
-    return request;
-};
+export function getRequest() {
+    return requestInstance;
+}
 
 /**
  * Apply wrapping code around the request function. The wrapper function is
@@ -145,15 +82,15 @@ module.exports.getRequest = function() {
  * previous value, along with the options and callback arguments.
  * @param {requestWrapperFunction} wrapper The wrapping function.
  */
-module.exports.wrapRequest = function(wrapper) {
-    const origRequest = request;
-    request = function(options, callback) {
+export function wrapRequest(wrapper) {
+    const origRequest = requestInstance;
+    requestInstance = function(options, callback) {
         return wrapper(origRequest, options, callback);
     };
-};
+}
 
 
-let cryptoStoreFactory = () => new module.exports.MemoryCryptoStore;
+let cryptoStoreFactory = () => new MemoryCryptoStore;
 
 /**
  * Configure a different factory to be used for creating crypto stores
@@ -161,9 +98,9 @@ let cryptoStoreFactory = () => new module.exports.MemoryCryptoStore;
  * @param {Function} fac  a function which will return a new
  *    {@link module:crypto.store.base~CryptoStore}.
  */
-module.exports.setCryptoStoreFactory = function(fac) {
+export function setCryptoStoreFactory(fac) {
     cryptoStoreFactory = fac;
-};
+}
 
 /**
  * Construct a Matrix Client. Similar to {@link module:client~MatrixClient}
@@ -188,20 +125,20 @@ module.exports.setCryptoStoreFactory = function(fac) {
  * @see {@link module:client~MatrixClient} for the full list of options for
  * <code>opts</code>.
  */
-module.exports.createClient = function(opts) {
+export function createClient(opts) {
     if (typeof opts === "string") {
         opts = {
             "baseUrl": opts,
         };
     }
-    opts.request = opts.request || request;
-    opts.store = opts.store || new module.exports.MemoryStore({
+    opts.request = opts.request || requestInstance;
+    opts.store = opts.store || new MemoryStore({
       localStorage: global.localStorage,
     });
-    opts.scheduler = opts.scheduler || new module.exports.MatrixScheduler();
+    opts.scheduler = opts.scheduler || new MatrixScheduler();
     opts.cryptoStore = opts.cryptoStore || cryptoStoreFactory();
-    return new module.exports.MatrixClient(opts);
-};
+    return new MatrixClient(opts);
+}
 
 /**
  * The request function interface for performing HTTP requests. This matches the
diff --git a/src/models/event-context.js b/src/models/event-context.js
index c2f298b99..5ffb103fe 100644
--- a/src/models/event-context.js
+++ b/src/models/event-context.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,7 +14,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module models/event-context
@@ -33,7 +33,7 @@ limitations under the License.
  *
  * @constructor
  */
-function EventContext(ourEvent) {
+export function EventContext(ourEvent) {
     this._timeline = [ourEvent];
     this._ourEventIndex = 0;
     this._paginateTokens = {b: null, f: null};
@@ -113,7 +113,3 @@ EventContext.prototype.addEvents = function(events, atStart) {
     }
 };
 
-/**
- * The EventContext class
- */
-module.exports = EventContext;
diff --git a/src/models/event-timeline-set.js b/src/models/event-timeline-set.js
index 1f250600b..948f6c778 100644
--- a/src/models/event-timeline-set.js
+++ b/src/models/event-timeline-set.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,16 +14,17 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module models/event-timeline-set
  */
-const EventEmitter = require("events").EventEmitter;
-const utils = require("../utils");
-const EventTimeline = require("./event-timeline");
+
+import {EventEmitter} from "events";
+import {EventTimeline} from "./event-timeline";
 import {EventStatus} from "./event";
-import logger from '../logger';
-import Relations from './relations';
+import * as utils from "../utils";
+import {logger} from '../logger';
+import {Relations} from './relations';
 
 // var DEBUG = false;
 const DEBUG = true;
@@ -71,7 +73,7 @@ if (DEBUG) {
  * via `getRelationsForEvent`.
  * This feature is currently unstable and the API may change without notice.
  */
-function EventTimelineSet(room, opts) {
+export function EventTimelineSet(room, opts) {
     this.room = room;
 
     this._timelineSupport = Boolean(opts.timelineSupport);
@@ -817,11 +819,6 @@ EventTimelineSet.prototype.aggregateRelations = function(event) {
     }
 };
 
-/**
- * The EventTimelineSet class.
- */
-module.exports = EventTimelineSet;
-
 /**
  * Fires whenever the timeline in a room is updated.
  * @event module:client~MatrixClient#"Room.timeline"
diff --git a/src/models/event-timeline.js b/src/models/event-timeline.js
index 63846cebd..20fee86a2 100644
--- a/src/models/event-timeline.js
+++ b/src/models/event-timeline.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016, 2017 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,13 +14,12 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module models/event-timeline
  */
 
-const RoomState = require("./room-state");
+import {RoomState} from "./room-state";
 
 /**
  * Construct a new EventTimeline
@@ -41,7 +41,7 @@ const RoomState = require("./room-state");
  * @param {EventTimelineSet} eventTimelineSet the set of timelines this is part of
  * @constructor
  */
-function EventTimeline(eventTimelineSet) {
+export function EventTimeline(eventTimelineSet) {
     this._eventTimelineSet = eventTimelineSet;
     this._roomId = eventTimelineSet.room ? eventTimelineSet.room.roomId : null;
     this._events = [];
@@ -396,8 +396,3 @@ EventTimeline.prototype.toString = function() {
     return this._name;
 };
 
-
-/**
- * The EventTimeline class
- */
-module.exports = EventTimeline;
diff --git a/src/models/event.js b/src/models/event.js
index 34af1ecfe..afa9e4cab 100644
--- a/src/models/event.js
+++ b/src/models/event.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,7 +14,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * This is an internal module. See {@link MatrixEvent} and {@link RoomEvent} for
@@ -22,15 +22,15 @@ limitations under the License.
  */
 
 import {EventEmitter} from 'events';
-import utils from '../utils.js';
-import logger from '../logger';
+import * as utils from '../utils.js';
+import {logger} from '../logger';
 
 /**
  * Enum for event statuses.
  * @readonly
  * @enum {string}
  */
-const EventStatus = {
+export const EventStatus = {
     /** The event was not sent and will no longer be retried. */
     NOT_SENT: "not_sent",
 
@@ -48,7 +48,6 @@ const EventStatus = {
     /** The event was cancelled before it was successfully sent. */
     CANCELLED: "cancelled",
 };
-module.exports.EventStatus = EventStatus;
 
 const interns = {};
 function intern(str) {
@@ -81,7 +80,7 @@ function intern(str) {
  * that getDirectionalContent() will return event.content and not event.prev_content.
  * Default: true. <strong>This property is experimental and may change.</strong>
  */
-module.exports.MatrixEvent = function MatrixEvent(
+export const MatrixEvent = function(
     event,
 ) {
     // intern the values of matrix events to force share strings and reduce the
@@ -162,10 +161,10 @@ module.exports.MatrixEvent = function MatrixEvent(
      */
     this.verificationRequest = null;
 };
-utils.inherits(module.exports.MatrixEvent, EventEmitter);
+utils.inherits(MatrixEvent, EventEmitter);
 
 
-utils.extend(module.exports.MatrixEvent.prototype, {
+utils.extend(MatrixEvent.prototype, {
 
     /**
      * Get the event_id for this event.
diff --git a/src/models/group.js b/src/models/group.js
index 9a4b9e989..74b86f53e 100644
--- a/src/models/group.js
+++ b/src/models/group.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2017 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -17,9 +18,9 @@ limitations under the License.
 /**
  * @module models/group
  */
-const EventEmitter = require("events").EventEmitter;
 
-const utils = require("../utils");
+import * as utils from "../utils";
+import {EventEmitter} from "events";
 
 /**
  * Construct a new Group.
@@ -34,7 +35,7 @@ const utils = require("../utils");
  *       to the group, if myMembership is 'invite'.
  * @prop {string} inviter.userId The user ID of the inviter
  */
-function Group(groupId) {
+export function Group(groupId) {
     this.groupId = groupId;
     this.name = null;
     this.avatarUrl = null;
@@ -70,8 +71,6 @@ Group.prototype.setInviter = function(inviter) {
     this.inviter = inviter;
 };
 
-module.exports = Group;
-
 /**
  * Fires whenever a group's profile information is updated.
  * This means the 'name' and 'avatarUrl' properties.
diff --git a/src/models/relations.js b/src/models/relations.js
index 81ead22de..fa0e2b85d 100644
--- a/src/models/relations.js
+++ b/src/models/relations.js
@@ -14,8 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import EventEmitter from 'events';
-import { EventStatus } from '../models/event';
+import {EventEmitter} from 'events';
+import {EventStatus} from '../models/event';
 
 /**
  * A container for relation events that supports easy access to common ways of
@@ -25,7 +25,7 @@ import { EventStatus } from '../models/event';
  * The typical way to get one of these containers is via
  * EventTimelineSet#getRelationsForEvent.
  */
-export default class Relations extends EventEmitter {
+export class Relations extends EventEmitter {
     /**
      * @param {String} relationType
      * The type of relation involved, such as "m.annotation", "m.reference",
diff --git a/src/models/room-member.js b/src/models/room-member.js
index d92267720..4dc973c79 100644
--- a/src/models/room-member.js
+++ b/src/models/room-member.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,14 +14,14 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module models/room-member
  */
-const EventEmitter = require("events").EventEmitter;
-const ContentRepo = require("../content-repo");
 
-const utils = require("../utils");
+import {EventEmitter} from "events";
+import {getHttpUriForMxc, getIdenticonUri} from "../content-repo";
+import * as utils from "../utils";
 
 /**
  * Construct a new room member.
@@ -45,7 +46,7 @@ const utils = require("../utils");
  * @prop {Object} events The events describing this RoomMember.
  * @prop {MatrixEvent} events.member The m.room.member event for this RoomMember.
  */
-function RoomMember(roomId, userId) {
+export function RoomMember(roomId, userId) {
     this.roomId = roomId;
     this.userId = userId;
     this.typing = false;
@@ -268,13 +269,13 @@ RoomMember.prototype.getAvatarUrl =
     if (!rawUrl && !allowDefault) {
         return null;
     }
-    const httpUrl = ContentRepo.getHttpUriForMxc(
+    const httpUrl = getHttpUriForMxc(
         baseUrl, rawUrl, width, height, resizeMethod, allowDirectLinks,
     );
     if (httpUrl) {
         return httpUrl;
     } else if (allowDefault) {
-        return ContentRepo.getIdenticonUri(
+        return getIdenticonUri(
             baseUrl, this.userId, width, height,
         );
     }
@@ -311,10 +312,18 @@ function calculateDisplayName(selfUserId, displayName, roomState) {
     // Next check if the name contains something that look like a mxid
     // If it does, it may be someone trying to impersonate someone else
     // Show full mxid in this case
-    // Also show mxid if there are other people with the same or similar
-    // displayname, after hidden character removal.
     let disambiguate = /@.+:.+/.test(displayName);
+
     if (!disambiguate) {
+        // Also show mxid if the display name contains any LTR/RTL characters as these
+        // make it very difficult for us to find similar *looking* display names
+        // E.g "Mark" could be cloned by writing "kraM" but in RTL.
+        disambiguate = /[\u200E\u200F\u202A-\u202F]/.test(displayName);
+    }
+
+    if (!disambiguate) {
+        // Also show mxid if there are other people with the same or similar
+        // displayname, after hidden character removal.
         const userIds = roomState.getUserIdsWithDisplayName(displayName);
         disambiguate = userIds.some((u) => u !== selfUserId);
     }
@@ -325,11 +334,6 @@ function calculateDisplayName(selfUserId, displayName, roomState) {
     return displayName;
 }
 
-/**
- * The RoomMember class.
- */
-module.exports = RoomMember;
-
 /**
  * Fires whenever any room member's name changes.
  * @event module:client~MatrixClient#"RoomMember.name"
diff --git a/src/models/room-state.js b/src/models/room-state.js
index cb1579f46..70590b465 100644
--- a/src/models/room-state.js
+++ b/src/models/room-state.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,15 +14,15 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module models/room-state
  */
-const EventEmitter = require("events").EventEmitter;
 
-const utils = require("../utils");
-const RoomMember = require("./room-member");
-import logger from '../logger';
+import {EventEmitter} from "events";
+import {RoomMember} from "./room-member";
+import {logger} from '../logger';
+import * as utils from "../utils";
 
 // possible statuses for out-of-band member loading
 const OOB_STATUS_NOTSTARTED = 1;
@@ -62,7 +63,7 @@ const OOB_STATUS_FINISHED = 3;
  * events dictionary, keyed on the event type and then the state_key value.
  * @prop {string} paginationToken The pagination token for this state.
  */
-function RoomState(roomId, oobMemberFlags = undefined) {
+export function RoomState(roomId, oobMemberFlags = undefined) {
     this.roomId = roomId;
     this.members = {
         // userId: RoomMember
@@ -714,11 +715,6 @@ RoomState.prototype.mayTriggerNotifOfType = function(notifLevelKey, userId) {
     return member.powerLevel >= notifLevel;
 };
 
-/**
- * The RoomState class.
- */
-module.exports = RoomState;
-
 
 function _updateThirdPartyTokenCache(roomState, memberEvent) {
     if (!memberEvent.getContent().third_party_invite) {
diff --git a/src/models/room-summary.js b/src/models/room-summary.js
index 7329c3e79..037fe2bd6 100644
--- a/src/models/room-summary.js
+++ b/src/models/room-summary.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,7 +14,7 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module models/room-summary
  */
@@ -31,12 +32,8 @@ limitations under the License.
  * @param {string[]} info.aliases The list of aliases for this room.
  * @param {Number} info.timestamp The timestamp for this room.
  */
-function RoomSummary(roomId, info) {
+export function RoomSummary(roomId, info) {
     this.roomId = roomId;
     this.info = info;
 }
 
-/**
- * The RoomSummary class.
- */
-module.exports = RoomSummary;
diff --git a/src/models/room.js b/src/models/room.js
index 8ef3b27b1..e362c4fc7 100644
--- a/src/models/room.js
+++ b/src/models/room.js
@@ -15,23 +15,21 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module models/room
  */
-const EventEmitter = require("events").EventEmitter;
 
-const EventStatus = require("./event").EventStatus;
-const RoomSummary = require("./room-summary");
-const RoomMember = require("./room-member");
-const MatrixEvent = require("./event").MatrixEvent;
-const utils = require("../utils");
-const ContentRepo = require("../content-repo");
-const EventTimeline = require("./event-timeline");
-const EventTimelineSet = require("./event-timeline-set");
-
-import logger from '../logger';
-import ReEmitter from '../ReEmitter';
+import {EventEmitter} from "events";
+import {EventTimelineSet} from "./event-timeline-set";
+import {EventTimeline} from "./event-timeline";
+import {getHttpUriForMxc, getIdenticonUri} from "../content-repo";
+import * as utils from "../utils";
+import {EventStatus, MatrixEvent} from "./event";
+import {RoomMember} from "./room-member";
+import {RoomSummary} from "./room-summary";
+import {logger} from '../logger';
+import {ReEmitter} from '../ReEmitter';
 
 // These constants are used as sane defaults when the homeserver doesn't support
 // the m.room_versions capability. In practice, KNOWN_SAFE_ROOM_VERSION should be
@@ -120,7 +118,7 @@ function synthesizeReceipt(userId, event, receiptType) {
  * @prop {*} storageToken A token which a data store can use to remember
  * the state of the room.
  */
-function Room(roomId, client, myUserId, opts) {
+export function Room(roomId, client, myUserId, opts) {
     opts = opts || {};
     opts.pendingEventOrdering = opts.pendingEventOrdering || "chronological";
 
@@ -813,11 +811,11 @@ Room.prototype.getAvatarUrl = function(baseUrl, width, height, resizeMethod,
 
     const mainUrl = roomAvatarEvent ? roomAvatarEvent.getContent().url : null;
     if (mainUrl) {
-        return ContentRepo.getHttpUriForMxc(
+        return getHttpUriForMxc(
             baseUrl, mainUrl, width, height, resizeMethod,
         );
     } else if (allowDefault) {
-        return ContentRepo.getIdenticonUri(
+        return getIdenticonUri(
             baseUrl, this.roomId, width, height,
         );
     }
@@ -1913,11 +1911,6 @@ function memberNamesToRoomName(names, count = (names.length + 1)) {
     }
 }
 
-/**
- * The Room class.
- */
-module.exports = Room;
-
 /**
  * Fires when an event we had previously received is redacted.
  *
diff --git a/src/models/search-result.js b/src/models/search-result.js
index bab76fa83..a8b50ea4b 100644
--- a/src/models/search-result.js
+++ b/src/models/search-result.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,14 +14,13 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module models/search-result
  */
 
-const EventContext = require("./event-context");
-const utils = require("../utils");
+import * as utils from "../utils";
+import {EventContext} from "./event-context";
 
 /**
  * Construct a new SearchResult
@@ -31,7 +31,7 @@ const utils = require("../utils");
  *
  * @constructor
  */
-function SearchResult(rank, eventContext) {
+export function SearchResult(rank, eventContext) {
     this.rank = rank;
     this.context = eventContext;
 }
@@ -59,8 +59,3 @@ SearchResult.fromJson = function(jsonObj, eventMapper) {
     return new SearchResult(jsonObj.rank, context);
 };
 
-
-/**
- * The SearchResult class
- */
-module.exports = SearchResult;
diff --git a/src/models/user.js b/src/models/user.js
index 5e6340f29..fe785586b 100644
--- a/src/models/user.js
+++ b/src/models/user.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,12 +14,13 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * @module models/user
  */
- const EventEmitter = require("events").EventEmitter;
- const utils = require("../utils");
+
+import * as utils from "../utils";
+import {EventEmitter} from "events";
 
 /**
  * Construct a new User. A User must have an ID and can optionally have extra
@@ -45,7 +47,7 @@ limitations under the License.
  * @prop {Object} events The events describing this user.
  * @prop {MatrixEvent} events.presence The m.presence event for this user.
  */
-function User(userId) {
+export function User(userId) {
     this.userId = userId;
     this.presence = "offline";
     this.presenceStatusMsg = null;
@@ -195,11 +197,6 @@ User.prototype._unstable_updateStatusMessage = function(event) {
     this.emit("User._unstable_statusMessage", this);
 };
 
-/**
- * The User class.
- */
-module.exports = User;
-
 /**
  * Fires whenever any user's lastPresenceTs changes,
  * ie. whenever any presence event is received for a user.
diff --git a/src/pushprocessor.js b/src/pushprocessor.js
index 3d0fc2db5..4c7338417 100644
--- a/src/pushprocessor.js
+++ b/src/pushprocessor.js
@@ -80,7 +80,7 @@ const DEFAULT_OVERRIDE_RULES = [
  * @constructor
  * @param {Object} client The Matrix client object to use
  */
-function PushProcessor(client) {
+export function PushProcessor(client) {
     const cachedGlobToRegex = {
         // $glob: RegExp,
     };
@@ -503,6 +503,4 @@ PushProcessor.rewriteDefaultRules = function(incomingRules) {
  * noise.
  */
 
-/** The PushProcessor class. */
-module.exports = PushProcessor;
 
diff --git a/src/realtime-callbacks.js b/src/realtime-callbacks.js
index 7a4401257..0d21e23fb 100644
--- a/src/realtime-callbacks.js
+++ b/src/realtime-callbacks.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -23,8 +24,7 @@ limitations under the License.
  * it will instead fire as soon as possible after resume.
  */
 
-"use strict";
-import logger from './logger';
+import {logger} from './logger';
 
 // we schedule a callback at least this often, to check if we've missed out on
 // some wall-clock time due to being suspended.
@@ -52,9 +52,9 @@ const debuglog = function() {};
  *
  * @internal
  */
-module.exports.setNow = function(f) {
+export function setNow(f) {
     _now = f || Date.now;
-};
+}
 let _now = Date.now;
 
 /**
@@ -67,7 +67,7 @@ let _now = Date.now;
  * @return {Number} an identifier for this callback, which may be passed into
  *                   clearTimeout later.
  */
-module.exports.setTimeout = function(func, delayMs) {
+export function setTimeout(func, delayMs) {
     delayMs = delayMs || 0;
     if (delayMs < 0) {
         delayMs = 0;
@@ -96,14 +96,14 @@ module.exports.setTimeout = function(func, delayMs) {
     _scheduleRealCallback();
 
     return key;
-};
+}
 
 /**
  * reimplementation of window.clearTimeout, which mirrors setTimeout
  *
  * @param {Number} key   result from an earlier setTimeout call
  */
-module.exports.clearTimeout = function(key) {
+export function clearTimeout(key) {
     if (_callbackList.length === 0) {
         return;
     }
@@ -122,7 +122,7 @@ module.exports.clearTimeout = function(key) {
     if (i === 0) {
         _scheduleRealCallback();
     }
-};
+}
 
 // use the real global.setTimeout to schedule a callback to _runCallbacks.
 function _scheduleRealCallback() {
diff --git a/src/scheduler.js b/src/scheduler.js
index 85ce50fd3..75e6f2ade 100644
--- a/src/scheduler.js
+++ b/src/scheduler.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,14 +14,14 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * This is an internal module which manages queuing, scheduling and retrying
  * of requests.
  * @module scheduler
  */
-const utils = require("./utils");
-import logger from './logger';
+import * as utils from "./utils";
+import {logger} from './logger';
 
 const DEBUG = false;  // set true to enable console logging.
 
@@ -36,7 +37,7 @@ const DEBUG = false;  // set true to enable console logging.
  * algorithm to apply when determining which events should be sent before the
  * given event. Defaults to {@link module:scheduler~MatrixScheduler.QUEUE_MESSAGES}.
  */
-function MatrixScheduler(retryAlgorithm, queueAlgorithm) {
+export function MatrixScheduler(retryAlgorithm, queueAlgorithm) {
     this.retryAlgorithm = retryAlgorithm || MatrixScheduler.RETRY_BACKOFF_RATELIMIT;
     this.queueAlgorithm = queueAlgorithm || MatrixScheduler.QUEUE_MESSAGES;
     this._queues = {
@@ -156,6 +157,11 @@ MatrixScheduler.RETRY_BACKOFF_RATELIMIT = function(event, attempts, err) {
         return -1;
     }
 
+    // if event that we are trying to send is too large in any way then retrying won't help
+    if (err.name === "M_TOO_LARGE") {
+        return -1;
+    }
+
     if (err.name === "M_LIMIT_EXCEEDED") {
         const waitTime = err.data.retry_after_ms;
         if (waitTime) {
@@ -318,7 +324,3 @@ function debuglog() {
  * @return {Promise} Resolved/rejected depending on the outcome of the request.
  */
 
-/**
- * The MatrixScheduler class.
- */
-module.exports = MatrixScheduler;
diff --git a/src/store/indexeddb-local-backend.js b/src/store/indexeddb-local-backend.js
index 587382eb8..0a5aa93f6 100644
--- a/src/store/indexeddb-local-backend.js
+++ b/src/store/indexeddb-local-backend.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,10 +16,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import SyncAccumulator from "../sync-accumulator";
-import utils from "../utils";
+import {SyncAccumulator} from "../sync-accumulator";
+import * as utils from "../utils";
 import * as IndexedDBHelpers from "../indexeddb-helpers";
-import logger from '../logger';
+import {logger} from '../logger';
 
 const VERSION = 3;
 
@@ -122,7 +123,7 @@ function reqAsCursorPromise(req) {
  * @param {string=} dbName Optional database name. The same name must be used
  * to open the same database.
  */
-const LocalIndexedDBStoreBackend = function LocalIndexedDBStoreBackend(
+export function LocalIndexedDBStoreBackend(
     indexedDBInterface, dbName,
 ) {
     this.indexedDB = indexedDBInterface;
@@ -131,7 +132,7 @@ const LocalIndexedDBStoreBackend = function LocalIndexedDBStoreBackend(
     this._disconnected = true;
     this._syncAccumulator = new SyncAccumulator();
     this._isNewlyCreated = false;
-};
+}
 
 LocalIndexedDBStoreBackend.exists = function(indexedDB, dbName) {
     dbName = "matrix-js-sdk:" + (dbName || "default");
@@ -572,5 +573,3 @@ LocalIndexedDBStoreBackend.prototype = {
         await txnAsPromise(txn);
     },
 };
-
-export default LocalIndexedDBStoreBackend;
diff --git a/src/store/indexeddb-remote-backend.js b/src/store/indexeddb-remote-backend.js
index e17014fb2..a00b16977 100644
--- a/src/store/indexeddb-remote-backend.js
+++ b/src/store/indexeddb-remote-backend.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,7 +16,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import logger from '../logger';
+import {logger} from '../logger';
 import {defer} from '../utils';
 
 /**
@@ -30,7 +31,7 @@ import {defer} from '../utils';
  * to open the same database.
  * @param {Object} workerApi The web worker compatible interface object
  */
-const RemoteIndexedDBStoreBackend = function RemoteIndexedDBStoreBackend(
+export function RemoteIndexedDBStoreBackend(
     workerScript, dbName, workerApi,
 ) {
     this._workerScript = workerScript;
@@ -45,7 +46,7 @@ const RemoteIndexedDBStoreBackend = function RemoteIndexedDBStoreBackend(
     // Once we start connecting, we keep the promise and re-use it
     // if we try to connect again
     this._startPromise = null;
-};
+}
 
 
 RemoteIndexedDBStoreBackend.prototype = {
@@ -194,5 +195,3 @@ RemoteIndexedDBStoreBackend.prototype = {
         }
     },
 };
-
-export default RemoteIndexedDBStoreBackend;
diff --git a/src/store/indexeddb-store-worker.js b/src/store/indexeddb-store-worker.js
index e652b9a4e..5c1971bb0 100644
--- a/src/store/indexeddb-store-worker.js
+++ b/src/store/indexeddb-store-worker.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,8 +16,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import LocalIndexedDBStoreBackend from "./indexeddb-local-backend.js";
-import logger from '../logger';
+import {LocalIndexedDBStoreBackend} from "./indexeddb-local-backend.js";
+import {logger} from '../logger';
 
 /**
  * This class lives in the webworker and drives a LocalIndexedDBStoreBackend
@@ -33,7 +34,7 @@ import logger from '../logger';
  * avoid a dependency on the whole js-sdk.
  *
  */
-class IndexedDBStoreWorker {
+export class IndexedDBStoreWorker {
     /**
      * @param {function} postMessage The web worker postMessage function that
      * should be used to communicate back to the main script.
@@ -143,5 +144,3 @@ class IndexedDBStoreWorker {
         });
     }
 }
-
-module.exports = IndexedDBStoreWorker;
diff --git a/src/store/indexeddb.js b/src/store/indexeddb.js
index c8eec104c..9cde4467d 100644
--- a/src/store/indexeddb.js
+++ b/src/store/indexeddb.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -18,13 +19,13 @@ limitations under the License.
 /* eslint-disable babel/no-invalid-this */
 
 import {MemoryStore} from "./memory";
-import utils from "../utils";
+import * as utils from "../utils";
 import {EventEmitter} from 'events';
-import LocalIndexedDBStoreBackend from "./indexeddb-local-backend.js";
-import RemoteIndexedDBStoreBackend from "./indexeddb-remote-backend.js";
-import User from "../models/user";
+import {LocalIndexedDBStoreBackend} from "./indexeddb-local-backend.js";
+import {RemoteIndexedDBStoreBackend} from "./indexeddb-remote-backend.js";
+import {User} from "../models/user";
 import {MatrixEvent} from "../models/event";
-import logger from '../logger';
+import {logger} from '../logger';
 
 /**
  * This is an internal module. See {@link IndexedDBStore} for the public class.
@@ -81,7 +82,7 @@ const WRITE_DELAY_MS = 1000 * 60 * 5; // once every 5 minutes
  * this API if you need to perform specific indexeddb actions like deleting the
  * database.
  */
-const IndexedDBStore = function IndexedDBStore(opts) {
+export function IndexedDBStore(opts) {
     MemoryStore.call(this, opts);
 
     if (!opts.indexedDB) {
@@ -111,7 +112,7 @@ const IndexedDBStore = function IndexedDBStore(opts) {
     this._userModifiedMap = {
         // user_id : timestamp
     };
-};
+}
 utils.inherits(IndexedDBStore, MemoryStore);
 utils.extend(IndexedDBStore.prototype, EventEmitter.prototype);
 
@@ -273,8 +274,6 @@ IndexedDBStore.prototype.storeClientOptions = degradable(function(options) {
     return this.backend.storeClientOptions(options);
 }, "storeClientOptions");
 
-module.exports.IndexedDBStore = IndexedDBStore;
-
 /**
  * All member functions of `IndexedDBStore` that access the backend use this wrapper to
  * watch for failures after initial store startup, including `QuotaExceededError` as
diff --git a/src/store/memory.js b/src/store/memory.js
index feeb56501..e420e05ac 100644
--- a/src/store/memory.js
+++ b/src/store/memory.js
@@ -2,6 +2,7 @@
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,13 +16,14 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * This is an internal module. See {@link MemoryStore} for the public class.
  * @module store/memory
  */
-const utils = require("../utils");
-const User = require("../models/user");
+
+import {User} from "../models/user";
+import * as utils from "../utils";
 
 /**
  * Construct a new in-memory data store for the Matrix Client.
@@ -30,7 +32,7 @@ const User = require("../models/user");
  * @param {LocalStorage} opts.localStorage The local storage instance to persist
  * some forms of data such as tokens. Rooms will NOT be stored.
  */
-module.exports.MemoryStore = function MemoryStore(opts) {
+export function MemoryStore(opts) {
     opts = opts || {};
     this.rooms = {
         // roomId: Room
@@ -55,9 +57,9 @@ module.exports.MemoryStore = function MemoryStore(opts) {
         // roomId: [member events]
     };
     this._clientOptions = {};
-};
+}
 
-module.exports.MemoryStore.prototype = {
+MemoryStore.prototype = {
 
     /**
      * Retrieve the token to stream from.
diff --git a/src/store/session/webstorage.js b/src/store/session/webstorage.js
index e379b2fae..0bdceb0e0 100644
--- a/src/store/session/webstorage.js
+++ b/src/store/session/webstorage.js
@@ -2,6 +2,7 @@
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 New Vector Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,14 +16,13 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /**
  * @module store/session/webstorage
  */
 
-const utils = require("../../utils");
-import logger from '../../logger';
+import * as utils from "../../utils";
+import {logger} from '../../logger';
 
 const DEBUG = false;  // set true to enable console logging.
 const E2E_PREFIX = "session.e2e.";
@@ -36,7 +36,7 @@ const E2E_PREFIX = "session.e2e.";
  * @throws if the supplied 'store' does not meet the Storage interface of the
  * WebStorage API.
  */
-function WebStorageSessionStore(webStore) {
+export function WebStorageSessionStore(webStore) {
     this.store = webStore;
     if (!utils.isFunction(webStore.getItem) ||
         !utils.isFunction(webStore.setItem) ||
@@ -261,6 +261,3 @@ function debuglog() {
         logger.log(...arguments);
     }
 }
-
-/** */
-module.exports = WebStorageSessionStore;
diff --git a/src/store/stub.js b/src/store/stub.js
index 2ab2256cd..f94e97393 100644
--- a/src/store/stub.js
+++ b/src/store/stub.js
@@ -2,6 +2,7 @@
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,7 +16,7 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * This is an internal module.
  * @module store/stub
@@ -25,7 +26,7 @@ limitations under the License.
  * Construct a stub store. This does no-ops on most store methods.
  * @constructor
  */
-function StubStore() {
+export function StubStore() {
     this.fromToken = null;
 }
 
@@ -289,6 +290,3 @@ StubStore.prototype = {
         return Promise.resolve();
     },
 };
-
-/** Stub Store class. */
-module.exports = StubStore;
diff --git a/src/sync-accumulator.js b/src/sync-accumulator.js
index 8d9b3b787..2f7ad30bf 100644
--- a/src/sync-accumulator.js
+++ b/src/sync-accumulator.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -20,9 +21,8 @@ limitations under the License.
  * @module sync-accumulator
  */
 
-import utils from "./utils";
-import logger from './logger';
-
+import {logger} from './logger';
+import {deepCopy} from "./utils";
 
 /**
  * The purpose of this class is to accumulate /sync responses such that a
@@ -34,7 +34,7 @@ import logger from './logger';
  * be loaded from disk and incremental syncs can be performed on the server,
  * rather than asking the server to do an initial sync on startup.
  */
-class SyncAccumulator {
+export class SyncAccumulator {
     /**
      * @param {Object} opts
      * @param {Number=} opts.maxTimelineEntries The ideal maximum number of
@@ -502,7 +502,7 @@ class SyncAccumulator {
                 // since we're going back in time, we need to use the previous
                 // state value else we'll break causality. We don't have the
                 // complete previous state event, so we need to create one.
-                const prevStateEvent = utils.deepCopy(timelineEvent);
+                const prevStateEvent = deepCopy(timelineEvent);
                 if (prevStateEvent.unsigned) {
                     if (prevStateEvent.unsigned.prev_content) {
                         prevStateEvent.content = prevStateEvent.unsigned.prev_content;
@@ -554,5 +554,3 @@ function setState(eventMap, event) {
     }
     eventMap[event.type][event.state_key] = event;
 }
-
-module.exports = SyncAccumulator;
diff --git a/src/sync.js b/src/sync.js
index e2f7c6295..a8946ef52 100644
--- a/src/sync.js
+++ b/src/sync.js
@@ -2,6 +2,7 @@
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 Vector Creations Ltd
 Copyright 2018 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,7 +16,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /*
  * TODO:
@@ -25,15 +25,15 @@ limitations under the License.
  * an alternative syncing API, we may want to have a proper syncing interface
  * for HTTP and WS at some point.
  */
-const User = require("./models/user");
-const Room = require("./models/room");
-const Group = require('./models/group');
-const utils = require("./utils");
-const Filter = require("./filter");
-const EventTimeline = require("./models/event-timeline");
-const PushProcessor = require("./pushprocessor");
-import logger from './logger';
 
+import {User} from "./models/user";
+import {Room} from "./models/room";
+import {Group} from "./models/group";
+import * as utils from "./utils";
+import {Filter} from "./filter";
+import {EventTimeline} from "./models/event-timeline";
+import {PushProcessor} from "./pushprocessor";
+import {logger} from './logger';
 import {InvalidStoreError} from './errors';
 
 const DEBUG = true;
@@ -78,7 +78,7 @@ function debuglog(...params) {
  * @param {Boolean=} opts.disablePresence True to perform syncing without automatically
  * updating presence.
  */
-function SyncApi(client, opts) {
+export function SyncApi(client, opts) {
     this.client = client;
     opts = opts || {};
     opts.initialSyncLimit = (
@@ -1699,5 +1699,3 @@ function createNewUser(client, userId) {
     return user;
 }
 
-/** */
-module.exports = SyncApi;
diff --git a/src/timeline-window.js b/src/timeline-window.js
index 03e515c62..c087600c8 100644
--- a/src/timeline-window.js
+++ b/src/timeline-window.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2016 OpenMarket Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -13,12 +14,11 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
 
 /** @module timeline-window */
 
-const EventTimeline = require("./models/event-timeline");
-import logger from './logger';
+import {EventTimeline} from './models/event-timeline';
+import {logger} from './logger';
 
 /**
  * @private
@@ -66,7 +66,7 @@ const DEFAULT_PAGINATE_LOOP_LIMIT = 5;
  *
  * @constructor
  */
-function TimelineWindow(client, timelineSet, opts) {
+export function TimelineWindow(client, timelineSet, opts) {
     opts = opts || {};
     this._client = client;
     this._timelineSet = timelineSet;
@@ -397,7 +397,7 @@ TimelineWindow.prototype.getEvents = function() {
  * @param {number} index
  * @private
  */
-function TimelineIndex(timeline, index) {
+export function TimelineIndex(timeline, index) {
     this.timeline = timeline;
 
     // the indexes are relative to BaseIndex, so could well be negative.
@@ -491,12 +491,3 @@ TimelineIndex.prototype.retreat = function(delta) {
     return this.advance(delta * -1) * -1;
 };
 
-/**
- * The TimelineWindow class.
- */
-module.exports.TimelineWindow = TimelineWindow;
-
-/**
- * The TimelineIndex class. exported here for unit testing.
- */
-module.exports.TimelineIndex = TimelineIndex;
diff --git a/src/utils.js b/src/utils.js
index e830a5daf..b0cb07311 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -14,13 +14,13 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * This is an internal module.
  * @module utils
  */
 
-const unhomoglyph = require('unhomoglyph');
+import unhomoglyph from 'unhomoglyph';
 
 /**
  * Encode a dictionary of query parameters.
@@ -28,7 +28,7 @@ const unhomoglyph = require('unhomoglyph');
  * {"foo": "bar", "baz": "taz"}
  * @return {string} The encoded string e.g. foo=bar&baz=taz
  */
-module.exports.encodeParams = function(params) {
+export function encodeParams(params) {
     let qs = "";
     for (const key in params) {
         if (!params.hasOwnProperty(key)) {
@@ -38,7 +38,7 @@ module.exports.encodeParams = function(params) {
                 encodeURIComponent(params[key]);
     }
     return qs.substring(1);
-};
+}
 
 /**
  * Encodes a URI according to a set of template variables. Variables will be
@@ -48,7 +48,7 @@ module.exports.encodeParams = function(params) {
  * variables with. E.g. { "$bar": "baz" }.
  * @return {string} The result of replacing all template variables e.g. '/foo/baz'.
  */
-module.exports.encodeUri = function(pathTemplate, variables) {
+export function encodeUri(pathTemplate, variables) {
     for (const key in variables) {
         if (!variables.hasOwnProperty(key)) {
             continue;
@@ -58,7 +58,7 @@ module.exports.encodeUri = function(pathTemplate, variables) {
         );
     }
     return pathTemplate;
-};
+}
 
 /**
  * Applies a map function to the given array.
@@ -67,13 +67,13 @@ module.exports.encodeUri = function(pathTemplate, variables) {
  * the array with the signature <code>fn(element){...}</code>
  * @return {Array} A new array with the results of the function.
  */
-module.exports.map = function(array, fn) {
+export function map(array, fn) {
     const results = new Array(array.length);
     for (let i = 0; i < array.length; i++) {
         results[i] = fn(array[i]);
     }
     return results;
-};
+}
 
 /**
  * Applies a filter function to the given array.
@@ -83,7 +83,7 @@ module.exports.map = function(array, fn) {
  * looks like <code>fn(element, index, array){...}</code>.
  * @return {Array} A new array with the results of the function.
  */
-module.exports.filter = function(array, fn) {
+export function filter(array, fn) {
     const results = [];
     for (let i = 0; i < array.length; i++) {
         if (fn(array[i], i, array)) {
@@ -91,14 +91,14 @@ module.exports.filter = function(array, fn) {
         }
     }
     return results;
-};
+}
 
 /**
  * Get the keys for an object. Same as <code>Object.keys()</code>.
  * @param {Object} obj The object to get the keys for.
  * @return {string[]} The keys of the object.
  */
-module.exports.keys = function(obj) {
+export function keys(obj) {
     const keys = [];
     for (const key in obj) {
         if (!obj.hasOwnProperty(key)) {
@@ -107,14 +107,14 @@ module.exports.keys = function(obj) {
         keys.push(key);
     }
     return keys;
-};
+}
 
 /**
  * Get the values for an object.
  * @param {Object} obj The object to get the values for.
  * @return {Array<*>} The values of the object.
  */
-module.exports.values = function(obj) {
+export function values(obj) {
     const values = [];
     for (const key in obj) {
         if (!obj.hasOwnProperty(key)) {
@@ -123,7 +123,7 @@ module.exports.values = function(obj) {
         values.push(obj[key]);
     }
     return values;
-};
+}
 
 /**
  * Invoke a function for each item in the array.
@@ -131,11 +131,11 @@ module.exports.values = function(obj) {
  * @param {Function} fn The function to invoke for each element. Has the
  * function signature <code>fn(element, index)</code>.
  */
-module.exports.forEach = function(array, fn) {
+export function forEach(array, fn) {
     for (let i = 0; i < array.length; i++) {
         fn(array[i], i);
     }
-};
+}
 
 /**
  * The findElement() method returns a value in the array, if an element in the array
@@ -148,7 +148,7 @@ module.exports.forEach = function(array, fn) {
  * @return {*} The first value in the array which returns <code>true</code> for
  * the given function.
  */
-module.exports.findElement = function(array, fn, reverse) {
+export function findElement(array, fn, reverse) {
     let i;
     if (reverse) {
         for (i = array.length - 1; i >= 0; i--) {
@@ -163,7 +163,7 @@ module.exports.findElement = function(array, fn, reverse) {
             }
         }
     }
-};
+}
 
 /**
  * The removeElement() method removes the first element in the array that
@@ -175,7 +175,7 @@ module.exports.findElement = function(array, fn, reverse) {
  * @param {boolean} reverse True to search in reverse order.
  * @return {boolean} True if an element was removed.
  */
-module.exports.removeElement = function(array, fn, reverse) {
+export function removeElement(array, fn, reverse) {
     let i;
     let removed;
     if (reverse) {
@@ -196,26 +196,26 @@ module.exports.removeElement = function(array, fn, reverse) {
         }
     }
     return false;
-};
+}
 
 /**
  * Checks if the given thing is a function.
  * @param {*} value The thing to check.
  * @return {boolean} True if it is a function.
  */
-module.exports.isFunction = function(value) {
+export function isFunction(value) {
     return Object.prototype.toString.call(value) == "[object Function]";
-};
+}
 
 /**
  * Checks if the given thing is an array.
  * @param {*} value The thing to check.
  * @return {boolean} True if it is an array.
  */
-module.exports.isArray = function(value) {
+export function isArray(value) {
     return Array.isArray ? Array.isArray(value) :
         Boolean(value && value.constructor === Array);
-};
+}
 
 /**
  * Checks that the given object has the specified keys.
@@ -223,13 +223,13 @@ module.exports.isArray = function(value) {
  * @param {string[]} keys The list of keys that 'obj' must have.
  * @throws If the object is missing keys.
  */
-module.exports.checkObjectHasKeys = function(obj, keys) {
+export function checkObjectHasKeys(obj, keys) {
     for (let i = 0; i < keys.length; i++) {
         if (!obj.hasOwnProperty(keys[i])) {
             throw new Error("Missing required key: " + keys[i]);
         }
     }
-};
+}
 
 /**
  * Checks that the given object has no extra keys other than the specified ones.
@@ -237,7 +237,7 @@ module.exports.checkObjectHasKeys = function(obj, keys) {
  * @param {string[]} allowedKeys The list of allowed key names.
  * @throws If there are extra keys.
  */
-module.exports.checkObjectHasNoAdditionalKeys = function(obj, allowedKeys) {
+export function checkObjectHasNoAdditionalKeys(obj, allowedKeys) {
     for (const key in obj) {
         if (!obj.hasOwnProperty(key)) {
             continue;
@@ -246,7 +246,7 @@ module.exports.checkObjectHasNoAdditionalKeys = function(obj, allowedKeys) {
             throw new Error("Unknown key: " + key);
         }
     }
-};
+}
 
 /**
  * Deep copy the given object. The object MUST NOT have circular references and
@@ -254,9 +254,9 @@ module.exports.checkObjectHasNoAdditionalKeys = function(obj, allowedKeys) {
  * @param {Object} obj The object to deep copy.
  * @return {Object} A copy of the object without any references to the original.
  */
-module.exports.deepCopy = function(obj) {
+export function deepCopy(obj) {
     return JSON.parse(JSON.stringify(obj));
-};
+}
 
 /**
  * Compare two objects for equality. The objects MUST NOT have circular references.
@@ -266,7 +266,7 @@ module.exports.deepCopy = function(obj) {
  *
  * @return {boolean} true if the two objects are equal
  */
-const deepCompare = module.exports.deepCompare = function(x, y) {
+export function deepCompare(x, y) {
     // Inspired by
     // http://stackoverflow.com/questions/1068834/object-comparison-in-javascript#1144249
 
@@ -342,7 +342,7 @@ const deepCompare = module.exports.deepCompare = function(x, y) {
     }
     /* jshint +W089 */
     return true;
-};
+}
 
 /**
  * Copy properties from one object to another.
@@ -357,7 +357,7 @@ const deepCompare = module.exports.deepCompare = function(x, y) {
  *
  * @return {Object} target
  */
-module.exports.extend = function() {
+export function extend() {
     const target = arguments[0] || {};
     for (let i = 1; i < arguments.length; i++) {
         const source = arguments[i];
@@ -366,12 +366,12 @@ module.exports.extend = function() {
         }
     }
     return target;
-};
+}
 
 /**
  * Run polyfills to add Array.map and Array.filter if they are missing.
  */
-module.exports.runPolyfills = function() {
+export function runPolyfills() {
     //                Array.prototype.filter
     // ========================================================
     // SOURCE:
@@ -562,7 +562,7 @@ module.exports.runPolyfills = function() {
         // 8. return undefined
       };
     }
-};
+}
 
 /**
  * Inherit the prototype methods from one constructor into another. This is a
@@ -572,56 +572,7 @@ module.exports.runPolyfills = function() {
  *     prototype.
  * @param {function} superCtor Constructor function to inherit prototype from.
  */
-module.exports.inherits = function(ctor, superCtor) {
-    // Add Object.create polyfill for IE8
-    // Source:
-    // https://developer.mozilla.org/en-US/docs/Web/JavaScript
-    // /Reference/Global_Objects/Object/create#Polyfill
-    if (typeof Object.create != 'function') {
-      // Production steps of ECMA-262, Edition 5, 15.2.3.5
-      // Reference: http://es5.github.io/#x15.2.3.5
-      Object.create = (function() {
-        // To save on memory, use a shared constructor
-        function Temp() {}
-
-        // make a safe reference to Object.prototype.hasOwnProperty
-        const hasOwn = Object.prototype.hasOwnProperty;
-
-        return function(O) {
-          // 1. If Type(O) is not Object or Null throw a TypeError exception.
-          if (typeof O != 'object') {
-            throw new TypeError('Object prototype may only be an Object or null');
-          }
-
-          // 2. Let obj be the result of creating a new object as if by the
-          //    expression new Object() where Object is the standard built-in
-          //    constructor with that name
-          // 3. Set the [[Prototype]] internal property of obj to O.
-          Temp.prototype = O;
-          const obj = new Temp();
-          Temp.prototype = null; // Let's not keep a stray reference to O...
-
-          // 4. If the argument Properties is present and not undefined, add
-          //    own properties to obj as if by calling the standard built-in
-          //    function Object.defineProperties with arguments obj and
-          //    Properties.
-          if (arguments.length > 1) {
-            // Object.defineProperties does ToObject on its first argument.
-            const Properties = Object(arguments[1]);
-            for (const prop in Properties) {
-              if (hasOwn.call(Properties, prop)) {
-                obj[prop] = Properties[prop];
-              }
-            }
-          }
-
-          // 5. Return obj
-          return obj;
-        };
-      })();
-    }
-    // END polyfill
-
+export function inherits(ctor, superCtor) {
     // Add util.inherits from Node.js
     // Source:
     // https://github.com/joyent/node/blob/master/lib/util.js
@@ -654,7 +605,27 @@ module.exports.inherits = function(ctor, superCtor) {
             configurable: true,
         },
     });
-};
+}
+
+/**
+ * Polyfills inheritance for prototypes by allowing different kinds of
+ * super types. Typically prototypes would use `SuperType.call(this, params)`
+ * though this doesn't always work in some environments - this function
+ * falls back to using `Object.assign()` to clone a constructed copy
+ * of the super type onto `thisArg`.
+ * @param {any} thisArg The child instance. Modified in place.
+ * @param {any} SuperType The type to act as a super instance
+ * @param {any} params Arguments to supply to the super type's constructor
+ */
+export function polyfillSuper(thisArg, SuperType, ...params) {
+    try {
+        SuperType.call(thisArg, ...params);
+    } catch (e) {
+        // fall back to Object.assign to just clone the thing
+        const fakeSuper = new SuperType(...params);
+        Object.assign(thisArg, fakeSuper);
+    }
+}
 
 /**
  * Returns whether the given value is a finite number without type-coercion
@@ -662,9 +633,9 @@ module.exports.inherits = function(ctor, superCtor) {
  * @param {*} value the value to test
  * @return {boolean} whether or not value is a finite number without type-coercion
  */
-module.exports.isNumber = function(value) {
+export function isNumber(value) {
     return typeof value === 'number' && isFinite(value);
-};
+}
 
 /**
  * Removes zero width chars, diacritics and whitespace from the string
@@ -672,17 +643,24 @@ module.exports.isNumber = function(value) {
  * @param {string} str the string to remove hidden characters from
  * @return {string} a string with the hidden characters removed
  */
-module.exports.removeHiddenChars = function(str) {
+export function removeHiddenChars(str) {
     return unhomoglyph(str.normalize('NFD').replace(removeHiddenCharsRegex, ''));
-};
-const removeHiddenCharsRegex = /[\u200B-\u200D\u0300-\u036f\uFEFF\s]/g;
+}
 
-function escapeRegExp(string) {
+// Regex matching bunch of unicode control characters and otherwise misleading/invisible characters.
+// Includes:
+// various width spaces U+2000 - U+200D
+// LTR and RTL marks U+200E and U+200F
+// LTR/RTL and other directional formatting marks U+202A - U+202F
+// Combining characters U+0300 - U+036F
+// Zero width no-break space (BOM) U+FEFF
+const removeHiddenCharsRegex = /[\u2000-\u200F\u202A-\u202F\u0300-\u036f\uFEFF\s]/g;
+
+export function escapeRegExp(string) {
     return string.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
 }
-module.exports.escapeRegExp = escapeRegExp;
 
-module.exports.globToRegexp = function(glob, extended) {
+export function globToRegexp(glob, extended) {
     extended = typeof(extended) === 'boolean' ? extended : true;
     // From
     // https://github.com/matrix-org/synapse/blob/abbee6b29be80a77e05730707602f3bbfc3f38cb/synapse/push/__init__.py#L132
@@ -699,27 +677,29 @@ module.exports.globToRegexp = function(glob, extended) {
         });
     }
     return pat;
-};
+}
 
-module.exports.ensureNoTrailingSlash = function(url) {
+export function ensureNoTrailingSlash(url) {
     if (url && url.endsWith("/")) {
         return url.substr(0, url.length - 1);
     } else {
         return url;
     }
-};
+}
 
 // Returns a promise which resolves with a given value after the given number of ms
-module.exports.sleep = (ms, value) => new Promise((resolve => {
-    setTimeout(resolve, ms, value);
-}));
+export function sleep(ms, value) {
+    return new Promise((resolve => {
+        setTimeout(resolve, ms, value);
+    }));
+}
 
-module.exports.isNullOrUndefined = function(val) {
+export function isNullOrUndefined(val) {
     return val === null || val === undefined;
-};
+}
 
 // Returns a Deferred
-module.exports.defer = () => {
+export function defer() {
     let resolve;
     let reject;
 
@@ -729,14 +709,14 @@ module.exports.defer = () => {
     });
 
     return {resolve, reject, promise};
-};
+}
 
-module.exports.promiseMapSeries = async (promises, fn) => {
+export async function promiseMapSeries(promises, fn) {
     for (const o of await promises) {
         await fn(await o);
     }
-};
+}
 
-module.exports.promiseTry = (fn) => {
+export function promiseTry(fn) {
     return new Promise((resolve) => resolve(fn()));
-};
+}
diff --git a/src/webrtc/call.js b/src/webrtc/call.js
index f5819c746..4128e98ed 100644
--- a/src/webrtc/call.js
+++ b/src/webrtc/call.js
@@ -1,6 +1,7 @@
 /*
 Copyright 2015, 2016 OpenMarket Ltd
 Copyright 2017 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -14,14 +15,16 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-"use strict";
+
 /**
  * This is an internal module. See {@link createNewMatrixCall} for the public API.
  * @module webrtc/call
  */
-const utils = require("../utils");
-const EventEmitter = require("events").EventEmitter;
-import logger from '../logger';
+
+import {logger} from '../logger';
+import {EventEmitter} from "events";
+import * as utils from "../utils";
+
 const DEBUG = true;  // set true to enable console logging.
 
 // events: hangup, error(err), replaced(call), state(state, oldState)
@@ -53,7 +56,7 @@ const DEBUG = true;  // set true to enable console logging.
  * @param {Array<Object>} opts.turnServers Optional. A list of TURN servers.
  * @param {MatrixClient} opts.client The Matrix Client instance to send events to.
  */
-function MatrixCall(opts) {
+export function MatrixCall(opts) {
     this.roomId = opts.roomId;
     this.client = opts.client;
     this.webRtc = opts.webRtc;
@@ -1304,9 +1307,6 @@ const forAllTracksOnStream = function(s, f) {
     forAllAudioTracksOnStream(s, f);
 };
 
-/** The MatrixCall class. */
-module.exports.MatrixCall = MatrixCall;
-
 let audioOutput;
 let audioInput;
 let videoInput;
@@ -1316,21 +1316,21 @@ let videoInput;
  * @param {string=} deviceId the identifier for the device
  * undefined treated as unset
  */
-module.exports.setAudioOutput = function(deviceId) { audioOutput = deviceId; };
+export function setAudioOutput(deviceId) { audioOutput = deviceId; }
 /**
  * Set an audio input device to use for MatrixCalls
  * @function
  * @param {string=} deviceId the identifier for the device
  * undefined treated as unset
  */
-module.exports.setAudioInput = function(deviceId) { audioInput = deviceId; };
+export function setAudioInput(deviceId) { audioInput = deviceId; }
 /**
  * Set a video input device to use for MatrixCalls
  * @function
  * @param {string=} deviceId the identifier for the device
  * undefined treated as unset
  */
-module.exports.setVideoInput = function(deviceId) { videoInput = deviceId; };
+export function setVideoInput(deviceId) { videoInput = deviceId; }
 
 /**
  * Create a new Matrix call for the browser.
@@ -1342,7 +1342,7 @@ module.exports.setVideoInput = function(deviceId) { videoInput = deviceId; };
  * since it's only possible to set this option on outbound calls.
  * @return {MatrixCall} the call or null if the browser doesn't support calling.
  */
-module.exports.createNewMatrixCall = function(client, roomId, options) {
+export function createNewMatrixCall(client, roomId, options) {
     const w = global.window;
     const doc = global.document;
     if (!w || !doc) {
@@ -1417,4 +1417,4 @@ module.exports.createNewMatrixCall = function(client, roomId, options) {
         forceTURN: client._forceTURN || optionsForceTURN,
     };
     return new MatrixCall(opts);
-};
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 000000000..e01a31f6c
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,19 @@
+{
+  "compilerOptions": {
+    "experimentalDecorators": true,
+    "emitDecoratorMetadata": true,
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "target": "es2016",
+    "noImplicitAny": false,
+    "sourceMap": true,
+    "outDir": "./lib",
+    "declaration": true,
+    "types": [
+      "node"
+    ]
+  },
+  "include": [
+    "./src/**/*.ts"
+  ]
+}
diff --git a/tslint.json b/tslint.json
new file mode 100644
index 000000000..fc234117f
--- /dev/null
+++ b/tslint.json
@@ -0,0 +1,72 @@
+{
+  "rules": {
+    "class-name": false,
+    "comment-format": [
+      true
+    ],
+    "curly": false,
+    "eofline": false,
+    "forin": false,
+    "indent": [
+      true,
+      "spaces"
+    ],
+    "label-position": true,
+    "max-line-length": false,
+    "member-access": false,
+    "member-ordering": [
+      true,
+      "static-after-instance",
+      "variables-before-functions"
+    ],
+    "no-arg": true,
+    "no-bitwise": false,
+    "no-console": false,
+    "no-construct": true,
+    "no-debugger": true,
+    "no-duplicate-variable": true,
+    "no-empty": false,
+    "no-eval": true,
+    "no-inferrable-types": true,
+    "no-shadowed-variable": true,
+    "no-string-literal": false,
+    "no-switch-case-fall-through": true,
+    "no-trailing-whitespace": true,
+    "no-unused-expression": true,
+    "no-use-before-declare": false,
+    "no-var-keyword": true,
+    "object-literal-sort-keys": false,
+    "one-line": [
+      true,
+      "check-open-brace",
+      "check-catch",
+      "check-else",
+      "check-whitespace"
+    ],
+    "quotemark": false,
+    "radix": true,
+    "semicolon": [
+      "always"
+    ],
+    "triple-equals": [],
+    "typedef-whitespace": [
+      true,
+      {
+        "call-signature": "nospace",
+        "index-signature": "nospace",
+        "parameter": "nospace",
+        "property-declaration": "nospace",
+        "variable-declaration": "nospace"
+      }
+    ],
+    "variable-name": false,
+    "whitespace": [
+      true,
+      "check-branch",
+      "check-decl",
+      "check-operator",
+      "check-separator",
+      "check-type"
+    ]
+  }
+}
diff --git a/yarn.lock b/yarn.lock
index 0d9724d0b..e32442213 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -992,6 +992,11 @@
   resolved "https://registry.yarnpkg.com/@types/json-schema/-/json-schema-7.0.3.tgz#bdfd69d61e464dcc81b25159c270d75a73c1a636"
   integrity sha512-Il2DtDVRGDcqjDtE+rF8iqg1CArehSK84HZJCT7AMITlyXRBpuPhqGLDQMowraqqu1coEaimg4ZOqggt6L6L+A==
 
+"@types/node@12":
+  version "12.12.17"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.12.17.tgz#191b71e7f4c325ee0fb23bc4a996477d92b8c39b"
+  integrity sha512-Is+l3mcHvs47sKy+afn2O1rV4ldZFU7W8101cNlOd+MRbjM4Onida8jSZnJdTe/0Pcf25g9BNIUsuugmE6puHA==
+
 "@types/stack-utils@^1.0.1":
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/@types/stack-utils/-/stack-utils-1.0.1.tgz#0a851d3bd96498fa25c33ab7278ed3bd65f06c3e"
@@ -1049,15 +1054,6 @@ abbrev@1:
   resolved "https://registry.yarnpkg.com/abbrev/-/abbrev-1.1.1.tgz#f8f2c887ad10bf67f634f005b6987fed3179aac8"
   integrity sha512-nne9/IiQ/hzIhY6pdDnbBtz7DjPTKrY00P/zvPSm5pOFkl6xuGrGnXn/VtTNNfNtAfZ9/1RtehkszU9qcTii0Q==
 
-accessory@~1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/accessory/-/accessory-1.1.0.tgz#7833e9839a32ded76d26021f36a41707a520f593"
-  integrity sha1-eDPpg5oy3tdtJgIfNqQXB6Ug9ZM=
-  dependencies:
-    ap "~0.2.0"
-    balanced-match "~0.2.0"
-    dot-parts "~1.0.0"
-
 acorn-globals@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/acorn-globals/-/acorn-globals-3.1.0.tgz#fd8270f71fbb4996b004fa880ee5d46573a731bf"
@@ -1107,7 +1103,7 @@ acorn@^4.0.4, acorn@~4.0.2:
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-4.0.13.tgz#105495ae5361d697bd195c825192e1ad7f253787"
   integrity sha1-EFSVrlNh1pe9GVyCUZLhrX8lN4c=
 
-acorn@^5.2.1, acorn@^5.5.3:
+acorn@^5.5.3:
   version "5.7.3"
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.7.3.tgz#67aa231bf8812974b85235a96771eb6bd07ea279"
   integrity sha512-T/zvzYRfbVojPWahDsE5evJdHb3oJoQfFbsrKM7w5Zcs++Tr257tia3BmMP8XYVjp1S9RZXQMh7gao96BlqZOw==
@@ -1141,11 +1137,6 @@ align-text@^0.1.1, align-text@^0.1.3:
     longest "^1.0.1"
     repeat-string "^1.5.2"
 
-amdefine@>=0.0.4:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/amdefine/-/amdefine-1.0.1.tgz#4a5282ac164729e93619bcfd3ad151f817ce91f5"
-  integrity sha1-SlKCrBZHKek2Gbz9OtFR+BfOkfU=
-
 another-json@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/another-json/-/another-json-0.2.0.tgz#b5f4019c973b6dd5c6506a2d93469cb6d32aeedc"
@@ -1178,6 +1169,11 @@ ansi-styles@^3.2.0, ansi-styles@^3.2.1:
   dependencies:
     color-convert "^1.9.0"
 
+any-promise@^1.3.0:
+  version "1.3.0"
+  resolved "https://registry.yarnpkg.com/any-promise/-/any-promise-1.3.0.tgz#abc6afeedcea52e809cdc0376aed3ce39635d17f"
+  integrity sha1-q8av7tzqUugJzcA3au0845Y10X8=
+
 anymatch@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/anymatch/-/anymatch-2.0.0.tgz#bcb24b4f37934d9aa7ac17b4adaf89e7c76ef2eb"
@@ -1186,11 +1182,6 @@ anymatch@^2.0.0:
     micromatch "^3.1.4"
     normalize-path "^2.1.1"
 
-ap@~0.2.0:
-  version "0.2.0"
-  resolved "https://registry.yarnpkg.com/ap/-/ap-0.2.0.tgz#ae0942600b29912f0d2b14ec60c45e8f330b6110"
-  integrity sha1-rglCYAspkS8NKxTsYMRejzMLYRA=
-
 aproba@^1.0.3:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/aproba/-/aproba-1.2.0.tgz#6802e6264efd18c790a1b0d517f0f2627bf2c94a"
@@ -1397,6 +1388,11 @@ babel-types@^6.26.0:
     lodash "^4.17.4"
     to-fast-properties "^1.0.3"
 
+babelify@^10.0.0:
+  version "10.0.0"
+  resolved "https://registry.yarnpkg.com/babelify/-/babelify-10.0.0.tgz#fe73b1a22583f06680d8d072e25a1e0d1d1d7fb5"
+  integrity sha512-X40FaxyH7t3X+JFAKvb1H9wooWKLRCi8pg3m8poqtdZaIng+bjzp9RvKQCvRjF9isHiPkXspbbXT/zwXLtwgwg==
+
 babylon@^6.18.0:
   version "6.18.0"
   resolved "https://registry.yarnpkg.com/babylon/-/babylon-6.18.0.tgz#af2f3b88fa6f5c1e4c634d1a0f8eac4f55b395e3"
@@ -1407,11 +1403,6 @@ balanced-match@^1.0.0:
   resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.0.tgz#89b4d199ab2bee49de164ea02b89ce462d71b767"
   integrity sha1-ibTRmasr7kneFk6gK4nORi1xt2c=
 
-balanced-match@~0.2.0:
-  version "0.2.1"
-  resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-0.2.1.tgz#7bc658b4bed61eee424ad74f75f5c3e2c4df3cc7"
-  integrity sha1-e8ZYtL7WHu5CStdPdfXD4sTfPMc=
-
 base-x@^3.0.2:
   version "3.0.7"
   resolved "https://registry.yarnpkg.com/base-x/-/base-x-3.0.7.tgz#1c5a7fafe8f66b4114063e8da102799d4e7c408f"
@@ -1574,17 +1565,6 @@ browserify-rsa@^4.0.0:
     bn.js "^4.1.0"
     randombytes "^2.0.1"
 
-browserify-shim@^3.8.13:
-  version "3.8.14"
-  resolved "https://registry.yarnpkg.com/browserify-shim/-/browserify-shim-3.8.14.tgz#bf1057026932d3253c75ef7dd714f3b877edec6b"
-  integrity sha1-vxBXAmky0yU8de991xTzuHft7Gs=
-  dependencies:
-    exposify "~0.5.0"
-    mothership "~0.2.0"
-    rename-function-calls "~0.1.0"
-    resolve "~0.6.1"
-    through "~2.3.4"
-
 browserify-sign@^4.0.0:
   version "4.0.4"
   resolved "https://registry.yarnpkg.com/browserify-sign/-/browserify-sign-4.0.4.tgz#aa4eb68e5d7b658baa6bf6a57e630cbd7a93d298"
@@ -1605,7 +1585,7 @@ browserify-zlib@~0.2.0:
   dependencies:
     pako "~1.0.5"
 
-browserify@^16.1.0, browserify@^16.2.3:
+browserify@^16.5.0:
   version "16.5.0"
   resolved "https://registry.yarnpkg.com/browserify/-/browserify-16.5.0.tgz#a1c2bc0431bec11fd29151941582e3f645ede881"
   integrity sha512-6bfI3cl76YLAnCZ75AGu/XPOsqUhRyc0F/olGIJeCxtfxF2HvPKEcmjU9M8oAPxl4uBY1U7Nry33Q6koV3f2iw==
@@ -1700,6 +1680,11 @@ buffer@^5.0.2:
     base64-js "^1.0.2"
     ieee754 "^1.1.4"
 
+builtin-modules@^1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/builtin-modules/-/builtin-modules-1.1.1.tgz#270f076c5a72c02f5b65a47df94c5fe3a278892f"
+  integrity sha1-Jw8HbFpywC9bZaR9+Uxf46J4iS8=
+
 builtin-status-codes@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/builtin-status-codes/-/builtin-status-codes-3.0.0.tgz#85982878e21b98e1c66425e03d0174788f569ee8"
@@ -1772,7 +1757,7 @@ center-align@^0.1.1:
     align-text "^0.1.3"
     lazy-cache "^1.0.3"
 
-chalk@^2.0.0, chalk@^2.0.1, chalk@^2.1.0, chalk@^2.4.2:
+chalk@^2.0.0, chalk@^2.0.1, chalk@^2.1.0, chalk@^2.3.0, chalk@^2.4.2:
   version "2.4.2"
   resolved "https://registry.yarnpkg.com/chalk/-/chalk-2.4.2.tgz#cd42541677a54333cf541a49108c1432b44c9424"
   integrity sha512-Mti+f9lpJNcwF4tWV8/OrTTtF1gZi+f8FqlyAdouralcFWFQWF2+NgCHShjkCb+IFBLq9buZwE1xckQU4peSuQ==
@@ -1793,7 +1778,7 @@ chardet@^0.7.0:
   resolved "https://registry.yarnpkg.com/chardet/-/chardet-0.7.0.tgz#90094849f0937f2eedc2425d0d28a9e5f0cbad9e"
   integrity sha512-mT8iDcrh03qDGRRmoA2hmBJnxpllMR+0/0qlzjqZES6NdiWDcZkCNAk4rPFZ9Q85r27unkiNNg8ZOiwZXBHwcA==
 
-chokidar@^2.1.1, chokidar@^2.1.8:
+chokidar@^2.1.8:
   version "2.1.8"
   resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-2.1.8.tgz#804b3a7b6a99358c3c5c61e71d8728f041cff917"
   integrity sha512-ZmZUazfOzf0Nve7duiCKD23PFSCs4JPoYyccjUFF3aQkQadqBhfzhjkwBH2mNOG9cTBwhamM37EIsIkZw3nRgg==
@@ -1924,7 +1909,7 @@ combined-stream@^1.0.6, combined-stream@~1.0.6:
   dependencies:
     delayed-stream "~1.0.0"
 
-commander@^2.19.0, commander@^2.20.0, commander@~2.20.3:
+commander@^2.12.1, commander@^2.19.0, commander@^2.20.0, commander@~2.20.3:
   version "2.20.3"
   resolved "https://registry.yarnpkg.com/commander/-/commander-2.20.3.tgz#fd485e84c03eb4881c20722ba48035e8531aeb33"
   integrity sha512-GpVkmM8vF2vQUkj2LvZmD35JxeJOLCwJ9cUkugyk2nuhbv3+mJvpLYYt+0+USMxE+oj+ey/lJEnhZw75x/OMcQ==
@@ -1989,7 +1974,7 @@ content-type@^1.0.2:
   resolved "https://registry.yarnpkg.com/content-type/-/content-type-1.0.4.tgz#e138cc75e040c727b1966fe5e5f8c9aee256fe3b"
   integrity sha512-hIP3EEPs8tB9AT1L+NUqtwOAps4mk2Zob89MWXMHjHWg9milF/j4osnnQLXBCBFBk/tvIG/tUc9mOUJiPBhPXA==
 
-convert-source-map@^1.1.0, convert-source-map@^1.1.3, convert-source-map@^1.4.0, convert-source-map@^1.7.0:
+convert-source-map@^1.1.0, convert-source-map@^1.4.0, convert-source-map@^1.7.0:
   version "1.7.0"
   resolved "https://registry.yarnpkg.com/convert-source-map/-/convert-source-map-1.7.0.tgz#17a2cb882d7f77d3490585e2ce6c524424a3a442"
   integrity sha512-4FJkXzKXEDB1snCFZlLP4gpC3JILicCpGbzG9f9G7tGqGCzETQ2hWPrcinA9oU4wtf2biUaEH5065UnMeR33oA==
@@ -2234,14 +2219,6 @@ detect-newline@^2.1.0:
   resolved "https://registry.yarnpkg.com/detect-newline/-/detect-newline-2.1.0.tgz#f41f1c10be4b00e87b5f13da680759f2c5bfd3e2"
   integrity sha1-9B8cEL5LAOh7XxPaaAdZ8sW/0+I=
 
-detective@^4.5.0:
-  version "4.7.1"
-  resolved "https://registry.yarnpkg.com/detective/-/detective-4.7.1.tgz#0eca7314338442febb6d65da54c10bb1c82b246e"
-  integrity sha512-H6PmeeUcZloWtdt4DAkFyzFL94arpHr3NOwwmVILFiy+9Qd4JTxxXrzfyGk/lmct2qVGBwTSwSXagqu2BxmWig==
-  dependencies:
-    acorn "^5.2.1"
-    defined "^1.0.0"
-
 detective@^5.0.2:
   version "5.2.0"
   resolved "https://registry.yarnpkg.com/detective/-/detective-5.2.0.tgz#feb2a77e85b904ecdea459ad897cc90a99bd2a7b"
@@ -2251,14 +2228,6 @@ detective@^5.0.2:
     defined "^1.0.0"
     minimist "^1.1.1"
 
-detective@~3.1.0:
-  version "3.1.0"
-  resolved "https://registry.yarnpkg.com/detective/-/detective-3.1.0.tgz#77782444ab752b88ca1be2e9d0a0395f1da25eed"
-  integrity sha1-d3gkRKt1K4jKG+Lp0KA5Xx2iXu0=
-  dependencies:
-    escodegen "~1.1.0"
-    esprima-fb "3001.1.0-dev-harmony-fb"
-
 diff-match-patch@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/diff-match-patch/-/diff-match-patch-1.0.4.tgz#6ac4b55237463761c4daf0dc603eb869124744b1"
@@ -2269,6 +2238,11 @@ diff-sequences@^24.9.0:
   resolved "https://registry.yarnpkg.com/diff-sequences/-/diff-sequences-24.9.0.tgz#5715d6244e2aa65f48bba0bc972db0b0b11e95b5"
   integrity sha512-Dj6Wk3tWyTE+Fo1rW8v0Xhwk80um6yFYKbuAxc9c3EZxIHFDYwbi34Uk42u1CdnIiVorvt4RmlSDjIPyzGC2ew==
 
+diff@^4.0.1:
+  version "4.0.1"
+  resolved "https://registry.yarnpkg.com/diff/-/diff-4.0.1.tgz#0c667cb467ebbb5cea7f14f135cc2dba7780a8ff"
+  integrity sha512-s2+XdvhPCOF01LRQBC8hf4vhbVmI2CGS5aZnxLJlT5FtdhPCDFq80q++zK2KlrVorVDdL5BOGZ/VfLrVtYNF+Q==
+
 diffie-hellman@^5.0.0:
   version "5.0.3"
   resolved "https://registry.yarnpkg.com/diffie-hellman/-/diffie-hellman-5.0.3.tgz#40e8ee98f55a2149607146921c63e1ae5f3d2875"
@@ -2302,11 +2276,6 @@ domexception@^1.0.1:
   dependencies:
     webidl-conversions "^4.0.2"
 
-dot-parts@~1.0.0:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/dot-parts/-/dot-parts-1.0.1.tgz#884bd7bcfc3082ffad2fe5db53e494d8f3e0743f"
-  integrity sha1-iEvXvPwwgv+tL+XbU+SU2PPgdD8=
-
 duplexer2@^0.1.2, duplexer2@~0.1.0, duplexer2@~0.1.2:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/duplexer2/-/duplexer2-0.1.4.tgz#8b12dab878c0d69e3e7891051662a32fc6bddcc1"
@@ -2357,7 +2326,7 @@ entities@~1.1.1:
   resolved "https://registry.yarnpkg.com/entities/-/entities-1.1.2.tgz#bdfa735299664dfafd34529ed4f8522a275fea56"
   integrity sha512-f2LZMYl1Fzu7YSBKg+RoROelpOaNrcGmE9AZubeDfrCEia483oW4MI4VyFd5VNHIgQ/7qm1I0wUHK1eJnn2y2w==
 
-error-ex@^1.3.1:
+error-ex@^1.2.0, error-ex@^1.3.1:
   version "1.3.2"
   resolved "https://registry.yarnpkg.com/error-ex/-/error-ex-1.3.2.tgz#b4ac40648107fdcdcfae242f428bea8a14d4f1bf"
   integrity sha512-7dFHNmqeFSEt2ZBsCriorKnn3Z2pj+fd9kmI6QoWw4//DL+icEBfc0U7qJCisqrTsKTjw4fNFy2pW9OqStD84g==
@@ -2402,7 +2371,7 @@ es-to-primitive@^1.2.1:
     is-date-object "^1.0.1"
     is-symbol "^1.0.2"
 
-escape-string-regexp@^1.0.3, escape-string-regexp@^1.0.5:
+escape-string-regexp@^1.0.5:
   version "1.0.5"
   resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-1.0.5.tgz#1b61c0562190a8dff6ae3bb2cf0200ca130b86d4"
   integrity sha1-G2HAViGQqN/2rjuyzwIAyhMLhtQ=
@@ -2424,17 +2393,6 @@ escodegen@^1.9.1:
   optionalDependencies:
     source-map "~0.6.1"
 
-escodegen@~1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/escodegen/-/escodegen-1.1.0.tgz#c663923f6e20aad48d0c0fa49f31c6d4f49360cf"
-  integrity sha1-xmOSP24gqtSNDA+knzHG1PSTYM8=
-  dependencies:
-    esprima "~1.0.4"
-    estraverse "~1.5.0"
-    esutils "~1.0.0"
-  optionalDependencies:
-    source-map "~0.1.30"
-
 eslint-config-google@^0.7.1:
   version "0.7.1"
   resolved "https://registry.yarnpkg.com/eslint-config-google/-/eslint-config-google-0.7.1.tgz#5598f8498e9e078420f34b80495b8d959f651fb2"
@@ -2538,11 +2496,6 @@ espree@^5.0.1:
     acorn-jsx "^5.0.0"
     eslint-visitor-keys "^1.0.0"
 
-esprima-fb@3001.1.0-dev-harmony-fb:
-  version "3001.1.0-dev-harmony-fb"
-  resolved "https://registry.yarnpkg.com/esprima-fb/-/esprima-fb-3001.0001.0000-dev-harmony-fb.tgz#b77d37abcd38ea0b77426bb8bc2922ce6b426411"
-  integrity sha1-t303q8046gt3Qmu4vCkizmtCZBE=
-
 esprima@^3.1.3:
   version "3.1.3"
   resolved "https://registry.yarnpkg.com/esprima/-/esprima-3.1.3.tgz#fdca51cee6133895e3c88d535ce49dbff62a4633"
@@ -2553,11 +2506,6 @@ esprima@^4.0.0, esprima@~4.0.0:
   resolved "https://registry.yarnpkg.com/esprima/-/esprima-4.0.1.tgz#13b04cdb3e6c5d19df91ab6987a8695619b0aa71"
   integrity sha512-eGuFFw7Upda+g4p+QHvnW0RyTX/SVeJBDM/gCtMARO0cLuT2HcEKnTPvhjV6aGeqrCB/sbNop0Kszm0jsaWU4A==
 
-esprima@~1.0.4:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/esprima/-/esprima-1.0.4.tgz#9f557e08fc3b4d26ece9dd34f8fbf476b62585ad"
-  integrity sha1-n1V+CPw7TSbs6d00+Pv0drYlha0=
-
 esquery@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/esquery/-/esquery-1.0.1.tgz#406c51658b1f5991a5f9b62b1dc25b00e3e5c708"
@@ -2577,21 +2525,11 @@ estraverse@^4.0.0, estraverse@^4.1.0, estraverse@^4.1.1, estraverse@^4.2.0:
   resolved "https://registry.yarnpkg.com/estraverse/-/estraverse-4.3.0.tgz#398ad3f3c5a24948be7725e83d11a7de28cdbd1d"
   integrity sha512-39nnKffWz8xN1BU/2c79n9nB9HDzo0niYUqx6xyqUnyoAnQyyWpOTdZEeiCch8BBu515t4wp9ZmgVfVhn9EBpw==
 
-estraverse@~1.5.0:
-  version "1.5.1"
-  resolved "https://registry.yarnpkg.com/estraverse/-/estraverse-1.5.1.tgz#867a3e8e58a9f84618afb6c2ddbcd916b7cbaf71"
-  integrity sha1-hno+jlip+EYYr7bC3bzZFrfLr3E=
-
 esutils@^2.0.2:
   version "2.0.3"
   resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.3.tgz#74d2eb4de0b8da1293711910d50775b9b710ef64"
   integrity sha512-kVscqXk4OCp68SZ0dkgEKVi6/8ij300KBWTJq32P/dYeWTSwK41WyTxalN1eRmA5Z9UU/LX9D7FWSmV9SAYx6g==
 
-esutils@~1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/esutils/-/esutils-1.0.0.tgz#8151d358e20c8acc7fb745e7472c0025fe496570"
-  integrity sha1-gVHTWOIMisx/t0XnRywAJf5JZXA=
-
 events@^2.0.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/events/-/events-2.1.0.tgz#2a9a1e18e6106e0e812aa9ebd4a819b3c29c0ba5"
@@ -2676,17 +2614,6 @@ expect@^24.9.0:
     jest-message-util "^24.9.0"
     jest-regex-util "^24.9.0"
 
-exposify@~0.5.0:
-  version "0.5.0"
-  resolved "https://registry.yarnpkg.com/exposify/-/exposify-0.5.0.tgz#f92d0094c265b3f553e1fa456a03a1883d1059cc"
-  integrity sha1-+S0AlMJls/VT4fpFagOhiD0QWcw=
-  dependencies:
-    globo "~1.1.0"
-    map-obj "~1.0.1"
-    replace-requires "~1.0.3"
-    through2 "~0.4.0"
-    transformify "~0.1.1"
-
 extend-shallow@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/extend-shallow/-/extend-shallow-2.0.1.tgz#51af7d614ad9a9f610ea1bafbb989d6b1c56890f"
@@ -2800,11 +2727,6 @@ find-cache-dir@^2.0.0:
     make-dir "^2.0.0"
     pkg-dir "^3.0.0"
 
-find-parent-dir@~0.3.0:
-  version "0.3.0"
-  resolved "https://registry.yarnpkg.com/find-parent-dir/-/find-parent-dir-0.3.0.tgz#33c44b429ab2b2f0646299c5f9f718f376ff8d54"
-  integrity sha1-M8RLQpqysvBkYpnF+fcY83b/jVQ=
-
 find-up@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/find-up/-/find-up-3.0.0.tgz#49169f1d7993430646da61ecc5ae355c21c97b73"
@@ -2960,15 +2882,6 @@ globals@^11.1.0, globals@^11.7.0:
   resolved "https://registry.yarnpkg.com/globals/-/globals-11.12.0.tgz#ab8795338868a0babd8525758018c2a7eb95c42e"
   integrity sha512-WOBp/EEGUiIsJSp7wcv/y6MO+lV9UoncWqxuFfm8eBwzWNgyfBd6Gz+IeKQ9jCmyhoH99g15M3T+QaVHFjizVA==
 
-globo@~1.1.0:
-  version "1.1.0"
-  resolved "https://registry.yarnpkg.com/globo/-/globo-1.1.0.tgz#0d26098955dea422eb2001b104898b0a101caaf3"
-  integrity sha1-DSYJiVXepCLrIAGxBImLChAcqvM=
-  dependencies:
-    accessory "~1.1.0"
-    is-defined "~1.0.0"
-    ternary "~1.0.0"
-
 graceful-fs@^4.1.11, graceful-fs@^4.1.15, graceful-fs@^4.1.2, graceful-fs@^4.1.9:
   version "4.2.3"
   resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.2.3.tgz#4a12ff1b60376ef09862c2093edd908328be8423"
@@ -3008,13 +2921,6 @@ has-flag@^3.0.0:
   resolved "https://registry.yarnpkg.com/has-flag/-/has-flag-3.0.0.tgz#b5d454dc2199ae225699f3467e5a07f3b955bafd"
   integrity sha1-tdRU3CGZriJWmfNGfloH87lVuv0=
 
-has-require@~1.2.1:
-  version "1.2.2"
-  resolved "https://registry.yarnpkg.com/has-require/-/has-require-1.2.2.tgz#921675ab130dbd9768fc8da8f1a8e242dfa41774"
-  integrity sha1-khZ1qxMNvZdo/I2o8ajiQt+kF3Q=
-  dependencies:
-    escape-string-regexp "^1.0.3"
-
 has-symbols@^1.0.0, has-symbols@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/has-symbols/-/has-symbols-1.0.1.tgz#9f5214758a44196c406d9bd76cebf81ec2dd31e8"
@@ -3335,11 +3241,6 @@ is-date-object@^1.0.1:
   resolved "https://registry.yarnpkg.com/is-date-object/-/is-date-object-1.0.1.tgz#9aa20eb6aeebbff77fbd33e74ca01b33581d3a16"
   integrity sha1-mqIOtq7rv/d/vTPnTKAbM1gdOhY=
 
-is-defined@~1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/is-defined/-/is-defined-1.0.0.tgz#1f07ca67d571f594c4b14415a45f7bef88f92bf5"
-  integrity sha1-HwfKZ9Vx9ZTEsUQVpF9774j5K/U=
-
 is-descriptor@^0.1.0:
   version "0.1.6"
   resolved "https://registry.yarnpkg.com/is-descriptor/-/is-descriptor-0.1.6.tgz#366d8240dde487ca51823b1ab9f07a10a78251ca"
@@ -3506,6 +3407,11 @@ is-typedarray@~1.0.0:
   resolved "https://registry.yarnpkg.com/is-typedarray/-/is-typedarray-1.0.0.tgz#e479c80858df0c1b11ddda6940f96011fcda4a9a"
   integrity sha1-5HnICFjfDBsR3dppQPlgEfzaSpo=
 
+is-utf8@^0.2.0:
+  version "0.2.1"
+  resolved "https://registry.yarnpkg.com/is-utf8/-/is-utf8-0.2.1.tgz#4b0da1442104d1b336340e80797e865cf39f7d72"
+  integrity sha1-Sw2hRCEE0bM2NA6AeX6GXPOffXI=
+
 is-weakmap@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/is-weakmap/-/is-weakmap-2.0.0.tgz#88bd0b8ec3a5724477637d58ed96cb00552593fd"
@@ -3526,11 +3432,6 @@ is-wsl@^1.1.0:
   resolved "https://registry.yarnpkg.com/is-wsl/-/is-wsl-1.1.0.tgz#1f16e4aa22b04d1336b66188a66af3c600c3a66d"
   integrity sha1-HxbkqiKwTRM2tmGIpmrzxgDDpm0=
 
-isarray@0.0.1:
-  version "0.0.1"
-  resolved "https://registry.yarnpkg.com/isarray/-/isarray-0.0.1.tgz#8a18acfca9a8f4177e09abfc6038939b05d1eedf"
-  integrity sha1-ihis/Kmo9Bd+Cav8YDiTmwXR7t8=
-
 isarray@1.0.0, isarray@~1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/isarray/-/isarray-1.0.0.tgz#bb935d48582cba168c06834957a54a3e07124f11"
@@ -3977,7 +3878,7 @@ js-stringify@^1.0.1:
   resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-4.0.0.tgz#19203fb59991df98e3a287050d4647cdeaf32499"
   integrity sha512-RdJUflcE3cUzKiMqQgsCu06FPu9UdIJO0beYbPhHN4k6apgJtifcoCtT9bcxOpYBtpD2kCM6Sbzg4CausW/PKQ==
 
-js-yaml@^3.13.0:
+js-yaml@^3.13.0, js-yaml@^3.13.1:
   version "3.13.1"
   resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.13.1.tgz#aff151b30bfdfa8e49e05da22e7415e9dfa37847"
   integrity sha512-YfbcO7jXDdyj0DGxYVSlSeQNHbD7XPWvrVWeVUujrQEoZzWJIRrCPoyk6kL6IAjAG2IolMK4T0hNUe0HOUs5Jw==
@@ -4293,11 +4194,6 @@ map-cache@^0.2.2:
   resolved "https://registry.yarnpkg.com/map-cache/-/map-cache-0.2.2.tgz#c32abd0bd6525d9b051645bb4f26ac5dc98a0dbf"
   integrity sha1-wyq9C9ZSXZsFFkW7TyasXcmKDb8=
 
-map-obj@~1.0.1:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/map-obj/-/map-obj-1.0.1.tgz#d933ceb9205d82bdcf4886f6742bdc2b4dea146d"
-  integrity sha1-2TPOuSBdgr3PSIb2dCvcK03qFG0=
-
 map-visit@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/map-visit/-/map-visit-1.0.0.tgz#ecdca8f13144e660f1b5bd41f12f3479d98dfb8f"
@@ -4493,13 +4389,6 @@ mold-source-map@~0.4.0:
     convert-source-map "^1.1.0"
     through "~2.2.7"
 
-mothership@~0.2.0:
-  version "0.2.0"
-  resolved "https://registry.yarnpkg.com/mothership/-/mothership-0.2.0.tgz#93d48a2fbc3e50e2a5fc8ed586f5bc44c65f9a99"
-  integrity sha1-k9SKL7w+UOKl/I7VhvW8RMZfmpk=
-  dependencies:
-    find-parent-dir "~0.3.0"
-
 ms@2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/ms/-/ms-2.0.0.tgz#5608aeadfc00be6c2901df5f9861788de0d597c8"
@@ -4711,11 +4600,6 @@ object-keys@^1.0.11, object-keys@^1.0.12, object-keys@^1.0.9, object-keys@^1.1.1
   resolved "https://registry.yarnpkg.com/object-keys/-/object-keys-1.1.1.tgz#1c47f272df277f3b1daf061677d9c82e2322c60e"
   integrity sha512-NuAESUOUMrlIXOfHKzD6bpPu3tYt3xvjNdRIQ+FeT0lNb4K8WR70CaDxhuNguS2XG+GjkyMwOzsN5ZktImfhLA==
 
-object-keys@~0.4.0:
-  version "0.4.0"
-  resolved "https://registry.yarnpkg.com/object-keys/-/object-keys-0.4.0.tgz#28a6aae7428dd2c3a92f3d95f21335dd204e0336"
-  integrity sha1-KKaq50KN0sOpLz2V8hM13SBOAzY=
-
 object-visit@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/object-visit/-/object-visit-1.0.1.tgz#f79c4493af0c5377b59fe39d395e41042dd045bb"
@@ -4819,13 +4703,6 @@ osenv@^0.1.4:
     os-homedir "^1.0.0"
     os-tmpdir "^1.0.0"
 
-outpipe@^1.1.0:
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/outpipe/-/outpipe-1.1.1.tgz#50cf8616365e87e031e29a5ec9339a3da4725fa2"
-  integrity sha1-UM+GFjZeh+Ax4ppeyTOaPaRyX6I=
-  dependencies:
-    shell-quote "^1.4.2"
-
 p-each-series@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/p-each-series/-/p-each-series-1.0.0.tgz#930f3d12dd1f50e7434457a22cd6f04ac6ad7f71"
@@ -4893,6 +4770,13 @@ parse-asn1@^5.0.0:
     pbkdf2 "^3.0.3"
     safe-buffer "^5.1.1"
 
+parse-json@^2.2.0:
+  version "2.2.0"
+  resolved "https://registry.yarnpkg.com/parse-json/-/parse-json-2.2.0.tgz#f480f40434ef80741f8469099f8dea18f55a4dc9"
+  integrity sha1-9ID0BDTvgHQfhGkJn43qGPVaTck=
+  dependencies:
+    error-ex "^1.2.0"
+
 parse-json@^4.0.0:
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/parse-json/-/parse-json-4.0.0.tgz#be35f5425be1f7f6c747184f98a788cb99477ee0"
@@ -4911,11 +4795,6 @@ pascalcase@^0.1.1:
   resolved "https://registry.yarnpkg.com/pascalcase/-/pascalcase-0.1.1.tgz#b363e55e8006ca6fe21784d2db22bd15d7917f14"
   integrity sha1-s2PlXoAGym/iF4TS2yK9FdeRfxQ=
 
-patch-text@~1.0.2:
-  version "1.0.2"
-  resolved "https://registry.yarnpkg.com/patch-text/-/patch-text-1.0.2.tgz#4bf36e65e51733d6e98f0cf62e09034daa0348ac"
-  integrity sha1-S/NuZeUXM9bpjwz2LgkDTaoDSKw=
-
 path-browserify@~0.0.0:
   version "0.0.1"
   resolved "https://registry.yarnpkg.com/path-browserify/-/path-browserify-0.0.1.tgz#e6c4ddd7ed3aa27c68a20cc4e50e1a4ee83bbc4a"
@@ -5348,26 +5227,6 @@ readable-stream@^3.0.6:
     string_decoder "^1.1.1"
     util-deprecate "^1.0.1"
 
-readable-stream@~1.0.17:
-  version "1.0.34"
-  resolved "https://registry.yarnpkg.com/readable-stream/-/readable-stream-1.0.34.tgz#125820e34bc842d2f2aaafafe4c2916ee32c157c"
-  integrity sha1-Elgg40vIQtLyqq+v5MKRbuMsFXw=
-  dependencies:
-    core-util-is "~1.0.0"
-    inherits "~2.0.1"
-    isarray "0.0.1"
-    string_decoder "~0.10.x"
-
-readable-stream@~1.1.9:
-  version "1.1.14"
-  resolved "https://registry.yarnpkg.com/readable-stream/-/readable-stream-1.1.14.tgz#7cf4c54ef648e3813084c636dd2079e166c081d9"
-  integrity sha1-fPTFTvZI44EwhMY23SB54WbAgdk=
-  dependencies:
-    core-util-is "~1.0.0"
-    inherits "~2.0.1"
-    isarray "0.0.1"
-    string_decoder "~0.10.x"
-
 readdirp@^2.2.1:
   version "2.2.1"
   resolved "https://registry.yarnpkg.com/readdirp/-/readdirp-2.2.1.tgz#0e87622a3325aa33e892285caf8b4e846529a525"
@@ -5465,13 +5324,6 @@ remove-trailing-separator@^1.0.1:
   resolved "https://registry.yarnpkg.com/remove-trailing-separator/-/remove-trailing-separator-1.1.0.tgz#c24bce2a283adad5bc3f58e0d48249b92379d8ef"
   integrity sha1-wkvOKig62tW8P1jg1IJJuSN52O8=
 
-rename-function-calls@~0.1.0:
-  version "0.1.1"
-  resolved "https://registry.yarnpkg.com/rename-function-calls/-/rename-function-calls-0.1.1.tgz#7f83369c007a3007f6abe3033ccf81686a108e01"
-  integrity sha1-f4M2nAB6MAf2q+MDPM+BaGoQjgE=
-  dependencies:
-    detective "~3.1.0"
-
 repeat-element@^1.1.2:
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/repeat-element/-/repeat-element-1.1.3.tgz#782e0d825c0c5a3bb39731f84efee6b742e6b1ce"
@@ -5482,16 +5334,6 @@ repeat-string@^1.5.2, repeat-string@^1.6.1:
   resolved "https://registry.yarnpkg.com/repeat-string/-/repeat-string-1.6.1.tgz#8dcae470e1c88abc2d600fff4a776286da75e637"
   integrity sha1-jcrkcOHIirwtYA//Sndihtp15jc=
 
-replace-requires@~1.0.3:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/replace-requires/-/replace-requires-1.0.4.tgz#014b7330b6b9e2557b71043b66fb02660c3bf667"
-  integrity sha1-AUtzMLa54lV7cQQ7ZvsCZgw79mc=
-  dependencies:
-    detective "^4.5.0"
-    has-require "~1.2.1"
-    patch-text "~1.0.2"
-    xtend "~4.0.0"
-
 request-promise-core@1.1.3:
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/request-promise-core/-/request-promise-core-1.1.3.tgz#e9a3c081b51380dfea677336061fea879a829ee9"
@@ -5585,11 +5427,6 @@ resolve@^1.1.4, resolve@^1.1.6, resolve@^1.10.0, resolve@^1.12.0, resolve@^1.3.2
   dependencies:
     path-parse "^1.0.6"
 
-resolve@~0.6.1:
-  version "0.6.3"
-  resolved "https://registry.yarnpkg.com/resolve/-/resolve-0.6.3.tgz#dd957982e7e736debdf53b58a4dd91754575dd46"
-  integrity sha1-3ZV5gufnNt699TtYpN2RdUV13UY=
-
 restore-cursor@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/restore-cursor/-/restore-cursor-2.0.0.tgz#9f7ee287f82fd326d4fd162923d62129eee0dfaf"
@@ -5760,7 +5597,7 @@ shebang-regex@^1.0.0:
   resolved "https://registry.yarnpkg.com/shebang-regex/-/shebang-regex-1.0.0.tgz#da42f49740c0b42db2ca9728571cb190c98efea3"
   integrity sha1-2kL0l0DAtC2yypcoVxyxkMmO/qM=
 
-shell-quote@^1.4.2, shell-quote@^1.6.1:
+shell-quote@^1.6.1:
   version "1.7.2"
   resolved "https://registry.yarnpkg.com/shell-quote/-/shell-quote-1.7.2.tgz#67a7d02c76c9da24f99d20808fcaded0e0e04be2"
   integrity sha512-mRz/m/JVscCrkMyPqHc/bczi3OQHkLTqXHEFu0zDhK/qfv3UcOA4SVmRCLmos4bhjr9ekVQubj/R7waKapmiQg==
@@ -5840,7 +5677,7 @@ source-map-resolve@^0.5.0:
     source-map-url "^0.4.0"
     urix "^0.1.0"
 
-source-map-support@^0.5.13, source-map-support@^0.5.16, source-map-support@^0.5.6, source-map-support@~0.5.12:
+source-map-support@^0.5.16, source-map-support@^0.5.6, source-map-support@~0.5.12:
   version "0.5.16"
   resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.16.tgz#0ae069e7fe3ba7538c64c98515e35339eac5a042"
   integrity sha512-efyLRJDr68D9hBBNIPWFjhpFzURh+KJykQwvMyW5UiZzYwoF6l4YMMDIJJEyFWxWCqfyxLzz6tSfUFR+kXXsVQ==
@@ -5863,21 +5700,6 @@ source-map@^0.6.0, source-map@^0.6.1, source-map@~0.6.0, source-map@~0.6.1:
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
   integrity sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==
 
-source-map@~0.1.30:
-  version "0.1.43"
-  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.1.43.tgz#c24bc146ca517c1471f5dacbe2571b2b7f9e3346"
-  integrity sha1-wkvBRspRfBRx9drL4lcbK3+eM0Y=
-  dependencies:
-    amdefine ">=0.0.4"
-
-sourceify@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/sourceify/-/sourceify-1.0.0.tgz#428da9a97fcbac6c250e03e58ea7aeb980c9e242"
-  integrity sha512-dA8NM9+02fcz693ou7x6hRaWbgWpfP+lAWsCPaOXR1z6HEyFBexRaQf9f/uRlTLNhenPo3knpj4hGf54RGoMjw==
-  dependencies:
-    convert-source-map "^1.1.3"
-    through2 "^2.0.0"
-
 spdx-correct@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/spdx-correct/-/spdx-correct-3.1.0.tgz#fb83e504445268f154b074e218c87c003cd31df4"
@@ -6040,11 +5862,6 @@ string_decoder@^1.1.1:
   dependencies:
     safe-buffer "~5.2.0"
 
-string_decoder@~0.10.x:
-  version "0.10.31"
-  resolved "https://registry.yarnpkg.com/string_decoder/-/string_decoder-0.10.31.tgz#62e203bc41766c6c28c9fc84301dab1c5310fa94"
-  integrity sha1-YuIDvEF2bGwoyfyEMB2rHFMQ+pQ=
-
 string_decoder@~1.1.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/string_decoder/-/string_decoder-1.1.1.tgz#9cf1611ba62685d7030ae9e4ba34149c3af03fc8"
@@ -6073,6 +5890,13 @@ strip-ansi@^5.0.0, strip-ansi@^5.1.0, strip-ansi@^5.2.0:
   dependencies:
     ansi-regex "^4.1.0"
 
+strip-bom@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/strip-bom/-/strip-bom-2.0.0.tgz#6219a85616520491f35788bdbf1447a99c7e6b0e"
+  integrity sha1-YhmoVhZSBJHzV4i9vxRHqZx+aw4=
+  dependencies:
+    is-utf8 "^0.2.0"
+
 strip-bom@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/strip-bom/-/strip-bom-3.0.0.tgz#2334c18e9c759f7bdd56fdef7e9ae3d588e68ed3"
@@ -6083,7 +5907,7 @@ strip-eof@^1.0.0:
   resolved "https://registry.yarnpkg.com/strip-eof/-/strip-eof-1.0.0.tgz#bb43ff5598a6eb05d89b59fcd129c983313606bf"
   integrity sha1-u0P/VZim6wXYm1n80SnJgzE2Br8=
 
-strip-json-comments@^2.0.1, strip-json-comments@~2.0.1:
+strip-json-comments@^2.0.0, strip-json-comments@^2.0.1, strip-json-comments@~2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-2.0.1.tgz#3c531942e908c2697c0ec344858c286c7ca0a60a"
   integrity sha1-PFMZQukIwml8DsNEhYwobHygpgo=
@@ -6154,15 +5978,10 @@ tar@^4:
     safe-buffer "^5.1.2"
     yallist "^3.0.3"
 
-ternary@~1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/ternary/-/ternary-1.0.0.tgz#45702725608c9499d46a9610e9b0e49ff26f789e"
-  integrity sha1-RXAnJWCMlJnUapYQ6bDkn/JveJ4=
-
-terser@^4.3.8:
-  version "4.4.2"
-  resolved "https://registry.yarnpkg.com/terser/-/terser-4.4.2.tgz#448fffad0245f4c8a277ce89788b458bfd7706e8"
-  integrity sha512-Uufrsvhj9O1ikwgITGsZ5EZS6qPokUOkCegS7fYOdGTv+OA90vndUbU6PEjr5ePqHfNUbGyMO7xyIZv2MhsALQ==
+terser@^4.4.3:
+  version "4.4.3"
+  resolved "https://registry.yarnpkg.com/terser/-/terser-4.4.3.tgz#401abc52b88869cf904412503b1eb7da093ae2f0"
+  integrity sha512-0ikKraVtRDKGzHrzkCv5rUNDzqlhmhowOBqC0XqUHFpW+vJ45+20/IFBcebwKfiS2Z9fJin6Eo+F1zLZsxi8RA==
   dependencies:
     commander "^2.20.0"
     source-map "~0.6.1"
@@ -6196,15 +6015,7 @@ through2@^2.0.0:
     readable-stream "~2.3.6"
     xtend "~4.0.1"
 
-through2@~0.4.0:
-  version "0.4.2"
-  resolved "https://registry.yarnpkg.com/through2/-/through2-0.4.2.tgz#dbf5866031151ec8352bb6c4db64a2292a840b9b"
-  integrity sha1-2/WGYDEVHsg1K7bE22SiKSqEC5s=
-  dependencies:
-    readable-stream "~1.0.17"
-    xtend "~2.1.1"
-
-"through@>=2.2.7 <3", through@^2.3.6, through@~2.3.4:
+"through@>=2.2.7 <3", through@^2.3.6:
   version "2.3.8"
   resolved "https://registry.yarnpkg.com/through/-/through-2.3.8.tgz#0dd4c9ffaabc357960b1b724115d7e0e86a2e1f5"
   integrity sha1-DdTJ/6q8NXlgsbckEV1+Doai4fU=
@@ -6301,23 +6112,64 @@ tr46@^1.0.1:
   dependencies:
     punycode "^2.1.0"
 
-transformify@~0.1.1:
-  version "0.1.2"
-  resolved "https://registry.yarnpkg.com/transformify/-/transformify-0.1.2.tgz#9a4f42a154433dd727b80575428a3c9e5489ebf1"
-  integrity sha1-mk9CoVRDPdcnuAV1Qoo8nlSJ6/E=
-  dependencies:
-    readable-stream "~1.1.9"
-
 ts-map@^1.0.3:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/ts-map/-/ts-map-1.0.3.tgz#1c4d218dec813d2103b7e04e4bcf348e1471c1ff"
   integrity sha512-vDWbsl26LIcPGmDpoVzjEP6+hvHZkBkLW7JpvwbCv/5IYPJlsbzCVXY3wsCeAxAUeTclNOUZxnLdGh3VBD/J6w==
 
-tslib@^1.8.1, tslib@^1.9.0:
+tsconfig@^5.0.3:
+  version "5.0.3"
+  resolved "https://registry.yarnpkg.com/tsconfig/-/tsconfig-5.0.3.tgz#5f4278e701800967a8fc383fd19648878f2a6e3a"
+  integrity sha1-X0J45wGACWeo/Dg/0ZZIh48qbjo=
+  dependencies:
+    any-promise "^1.3.0"
+    parse-json "^2.2.0"
+    strip-bom "^2.0.0"
+    strip-json-comments "^2.0.0"
+
+tsify@^4.0.1:
+  version "4.0.1"
+  resolved "https://registry.yarnpkg.com/tsify/-/tsify-4.0.1.tgz#b19b0ddf7f184368dbf65839293d2c5a6d48453d"
+  integrity sha512-ClznEI+pmwY5wmD0J7HCSVERwkD+l71ch3Dqyod2JuQLEsFaiNDI+vPjaGadsuVFVvmzgoI7HghrBtWsSmCDHQ==
+  dependencies:
+    convert-source-map "^1.1.0"
+    fs.realpath "^1.0.0"
+    object-assign "^4.1.0"
+    semver "^5.6.0"
+    through2 "^2.0.0"
+    tsconfig "^5.0.3"
+
+tslib@^1.8.0, tslib@^1.8.1, tslib@^1.9.0:
   version "1.10.0"
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.10.0.tgz#c3c19f95973fb0a62973fb09d90d961ee43e5c8a"
   integrity sha512-qOebF53frne81cf0S9B41ByenJ3/IuH8yJKngAX35CmiZySA0khhkovshKK+jGCaMnVomla7gVlIcc3EvKPbTQ==
 
+tslint@^5.20.1:
+  version "5.20.1"
+  resolved "https://registry.yarnpkg.com/tslint/-/tslint-5.20.1.tgz#e401e8aeda0152bc44dd07e614034f3f80c67b7d"
+  integrity sha512-EcMxhzCFt8k+/UP5r8waCf/lzmeSyVlqxqMEDQE7rWYiQky8KpIBz1JAoYXfROHrPZ1XXd43q8yQnULOLiBRQg==
+  dependencies:
+    "@babel/code-frame" "^7.0.0"
+    builtin-modules "^1.1.1"
+    chalk "^2.3.0"
+    commander "^2.12.1"
+    diff "^4.0.1"
+    glob "^7.1.1"
+    js-yaml "^3.13.1"
+    minimatch "^3.0.4"
+    mkdirp "^0.5.1"
+    resolve "^1.3.2"
+    semver "^5.3.0"
+    tslib "^1.8.0"
+    tsutils "^2.29.0"
+
+tsutils@^2.29.0:
+  version "2.29.0"
+  resolved "https://registry.yarnpkg.com/tsutils/-/tsutils-2.29.0.tgz#32b488501467acbedd4b85498673a0812aca0b99"
+  integrity sha512-g5JVHCIJwzfISaXpXE1qvNalca5Jwob6FjI4AoPlqMusJ6ftFE7IkkFoMhVLRgK+4Kx3gkzb8UZK5t5yTTvEmA==
+  dependencies:
+    tslib "^1.8.1"
+
 tsutils@^3.17.1:
   version "3.17.1"
   resolved "https://registry.yarnpkg.com/tsutils/-/tsutils-3.17.1.tgz#ed719917f11ca0dee586272b2ac49e015a2dd759"
@@ -6588,19 +6440,6 @@ walker@^1.0.7, walker@~1.0.5:
   dependencies:
     makeerror "1.0.x"
 
-watchify@^3.11.1:
-  version "3.11.1"
-  resolved "https://registry.yarnpkg.com/watchify/-/watchify-3.11.1.tgz#8e4665871fff1ef64c0430d1a2c9d084d9721881"
-  integrity sha512-WwnUClyFNRMB2NIiHgJU9RQPQNqVeFk7OmZaWf5dC5EnNa0Mgr7imBydbaJ7tGTuPM2hz1Cb4uiBvK9NVxMfog==
-  dependencies:
-    anymatch "^2.0.0"
-    browserify "^16.1.0"
-    chokidar "^2.1.1"
-    defined "^1.0.0"
-    outpipe "^1.1.0"
-    through2 "^2.0.0"
-    xtend "^4.0.0"
-
 webidl-conversions@^4.0.2:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/webidl-conversions/-/webidl-conversions-4.0.2.tgz#a855980b1f0b6b359ba1d5d9fb39ae941faa63ad"
@@ -6751,18 +6590,11 @@ xmlcreate@^2.0.0:
   resolved "https://registry.yarnpkg.com/xmlcreate/-/xmlcreate-2.0.1.tgz#2ec38bd7b708d213fd1a90e2431c4af9c09f6a52"
   integrity sha512-MjGsXhKG8YjTKrDCXseFo3ClbMGvUD4en29H2Cev1dv4P/chlpw6KdYmlCWDkhosBVKRDjM836+3e3pm1cBNJA==
 
-xtend@^4.0.0, xtend@^4.0.1, xtend@^4.0.2, xtend@~4.0.0, xtend@~4.0.1:
+xtend@^4.0.0, xtend@^4.0.1, xtend@^4.0.2, xtend@~4.0.1:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.2.tgz#bb72779f5fa465186b1f438f674fa347fdb5db54"
   integrity sha512-LKYU1iAXJXUgAXn9URjiu+MWhyUXHsvfp7mcuYm9dSUKK0/CjtrUwFAxD82/mCWbtLsGjFIad0wIsod4zrTAEQ==
 
-xtend@~2.1.1:
-  version "2.1.2"
-  resolved "https://registry.yarnpkg.com/xtend/-/xtend-2.1.2.tgz#6efecc2a4dad8e6962c4901b337ce7ba87b5d28b"
-  integrity sha1-bv7MKk2tjmlixJAbM3znuoe10os=
-  dependencies:
-    object-keys "~0.4.0"
-
 y18n@^4.0.0:
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/y18n/-/y18n-4.0.0.tgz#95ef94f85ecc81d007c264e190a120f0a3c8566b"