diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e0ae2fe..c3149ebf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,7 +15,7 @@
 * Updated angel_configuration to 4.0.0 (6/8 test passed)
 * Updated angel_validate to 4.0.0 (6/7 test passed)
 * Updated json_god to 4.0.0 (13/13 test passed)
-* Updated angel_client to 3.0.0 (in progress)
+* Updated angel_client to 4.0.0 (6/13 test passed)
 * Updated angel_websocket to 3.0.0 (in progress)
 * Updated test to 3.0.0 (in progress)
 * Updated jael to 3.0.0 (in progress)
diff --git a/packages/client/example/main.dart b/packages/client/example/main.dart
index d237c4bb..2d058fa1 100644
--- a/packages/client/example/main.dart
+++ b/packages/client/example/main.dart
@@ -6,16 +6,16 @@ Future doSomething(Angel app) async {
       .service<String, Map<String, dynamic>>('api/users')
       .map(User.fromMap, User.toMap);
 
-  var users = await userService.index();
+  var users = await (userService.index() as FutureOr<List<User>>);
   print('Name: ${users.first.name}');
 }
 
 class User {
-  final String name;
+  final String? name;
 
   User({this.name});
 
-  static User fromMap(Map data) => User(name: data['name'] as String);
+  static User fromMap(Map data) => User(name: data['name'] as String?);
 
-  static Map<String, String> toMap(User user) => {'name': user.name};
+  static Map<String, String?> toMap(User user) => {'name': user.name};
 }
diff --git a/packages/client/lib/angel_client.dart b/packages/client/lib/angel_client.dart
index 9e4fb440..c7c40c0e 100644
--- a/packages/client/lib/angel_client.dart
+++ b/packages/client/lib/angel_client.dart
@@ -9,13 +9,13 @@ export 'package:angel_http_exception/angel_http_exception.dart';
 import 'package:meta/meta.dart';
 
 /// A function that configures an [Angel] client in some way.
-typedef FutureOr<void> AngelConfigurer(Angel app);
+typedef AngelConfigurer = FutureOr<void> Function(Angel app);
 
 /// A function that deserializes data received from the server.
 ///
 /// This is only really necessary in the browser, where `json_god`
 /// doesn't work.
-typedef T AngelDeserializer<T>(x);
+typedef AngelDeserializer<T> = T? Function(dynamic x);
 
 /// Represents an Angel server that we are querying.
 abstract class Angel extends http.BaseClient {
@@ -23,7 +23,7 @@ abstract class Angel extends http.BaseClient {
   /// that is automatically attached to every request sent.
   ///
   /// This is designed with `package:angel_auth` in mind.
-  String authToken;
+  String? authToken;
 
   /// The root URL at which the target server.
   final Uri baseUrl;
@@ -46,7 +46,7 @@ abstract class Angel extends http.BaseClient {
   ///
   /// The given [credentials] are sent to server as-is; the request body is sent as JSON.
   Future<AngelAuthResult> authenticate(
-      {@required String type,
+      {required String type,
       credentials,
       String authEndpoint = '/auth',
       @deprecated String reviveEndpoint = '/auth/token'});
@@ -85,57 +85,59 @@ abstract class Angel extends http.BaseClient {
   /// You can pass a custom [deserializer], which is typically necessary in cases where
   /// `dart:mirrors` does not exist.
   Service<Id, Data> service<Id, Data>(String path,
-      {@deprecated Type type, AngelDeserializer<Data> deserializer});
+      {@deprecated Type? type, AngelDeserializer<Data>? deserializer});
 
   //@override
   //Future<http.Response> delete(url, {Map<String, String> headers});
 
   @override
-  Future<http.Response> get(url, {Map<String, String> headers});
+  Future<http.Response> get(url, {Map<String, String>? headers});
 
   @override
-  Future<http.Response> head(url, {Map<String, String> headers});
+  Future<http.Response> head(url, {Map<String, String>? headers});
 
   @override
   Future<http.Response> patch(url,
-      {body, Map<String, String> headers, Encoding encoding});
+      {body, Map<String, String>? headers, Encoding? encoding});
 
   @override
   Future<http.Response> post(url,
-      {body, Map<String, String> headers, Encoding encoding});
+      {body, Map<String, String>? headers, Encoding? encoding});
 
   @override
   Future<http.Response> put(url,
-      {body, Map<String, String> headers, Encoding encoding});
+      {body, Map<String, String>? headers, Encoding? encoding});
 }
 
 /// Represents the result of authentication with an Angel server.
 class AngelAuthResult {
-  String _token;
+  String? _token;
   final Map<String, dynamic> data = {};
 
   /// The JSON Web token that was sent with this response.
-  String get token => _token;
+  String? get token => _token;
 
-  AngelAuthResult({String token, Map<String, dynamic> data = const {}}) {
+  AngelAuthResult({String? token, Map<String, dynamic> data = const {}}) {
     _token = token;
-    this.data.addAll(data ?? {});
+    this.data.addAll(data);
   }
 
   /// Attempts to deserialize a response from a [Map].
-  factory AngelAuthResult.fromMap(Map data) {
+  factory AngelAuthResult.fromMap(Map? data) {
     final result = AngelAuthResult();
 
-    if (data is Map && data.containsKey('token') && data['token'] is String)
+    if (data is Map && data.containsKey('token') && data['token'] is String) {
       result._token = data['token'].toString();
+    }
 
-    if (data is Map)
-      result.data.addAll((data['data'] as Map<String, dynamic>) ?? {});
+    if (data is Map) {
+      result.data.addAll((data['data'] as Map<String, dynamic>?) ?? {});
+    }
 
     if (result.token == null) {
       throw FormatException(
           'The required "token" field was not present in the given data.');
-    } else if (data['data'] is! Map) {
+    } else if (data!['data'] is! Map) {
       throw FormatException(
           'The required "data" field in the given data was not a map; instead, it was ${data['data']}.');
     }
@@ -145,7 +147,7 @@ class AngelAuthResult {
 
   /// Attempts to deserialize a response from a [String].
   factory AngelAuthResult.fromJson(String s) =>
-      AngelAuthResult.fromMap(json.decode(s) as Map);
+      AngelAuthResult.fromMap(json.decode(s) as Map?);
 
   /// Converts this instance into a JSON-friendly representation.
   Map<String, dynamic> toJson() {
@@ -179,22 +181,22 @@ abstract class Service<Id, Data> {
   Future close();
 
   /// Retrieves all resources.
-  Future<List<Data>> index([Map<String, dynamic> params]);
+  Future<List<Data>?> index([Map<String, dynamic>? params]);
 
   /// Retrieves the desired resource.
-  Future<Data> read(Id id, [Map<String, dynamic> params]);
+  Future<Data> read(Id id, [Map<String, dynamic>? params]);
 
   /// Creates a resource.
-  Future<Data> create(Data data, [Map<String, dynamic> params]);
+  Future<Data> create(Data data, [Map<String, dynamic>? params]);
 
   /// Modifies a resource.
-  Future<Data> modify(Id id, Data data, [Map<String, dynamic> params]);
+  Future<Data> modify(Id id, Data data, [Map<String, dynamic>? params]);
 
   /// Overwrites a resource.
-  Future<Data> update(Id id, Data data, [Map<String, dynamic> params]);
+  Future<Data> update(Id id, Data data, [Map<String, dynamic>? params]);
 
   /// Removes the given resource.
-  Future<Data> remove(Id id, [Map<String, dynamic> params]);
+  Future<Data> remove(Id id, [Map<String, dynamic>? params]);
 
   /// Creates a [Service] that wraps over this one, and maps input and output using two converter functions.
   ///
@@ -218,17 +220,17 @@ class _MappedService<Id, Data, U> extends Service<Id, U> {
   Future close() => Future.value();
 
   @override
-  Future<U> create(U data, [Map<String, dynamic> params]) {
+  Future<U> create(U data, [Map<String, dynamic>? params]) {
     return inner.create(decoder(data)).then(encoder);
   }
 
   @override
-  Future<List<U>> index([Map<String, dynamic> params]) {
-    return inner.index(params).then((l) => l.map(encoder).toList());
+  Future<List<U>> index([Map<String, dynamic>? params]) {
+    return inner.index(params).then((l) => l!.map(encoder).toList());
   }
 
   @override
-  Future<U> modify(Id id, U data, [Map<String, dynamic> params]) {
+  Future<U> modify(Id id, U data, [Map<String, dynamic>? params]) {
     return inner.modify(id, decoder(data), params).then(encoder);
   }
 
@@ -252,17 +254,17 @@ class _MappedService<Id, Data, U> extends Service<Id, U> {
   Stream<U> get onUpdated => inner.onUpdated.map(encoder);
 
   @override
-  Future<U> read(Id id, [Map<String, dynamic> params]) {
+  Future<U> read(Id id, [Map<String, dynamic>? params]) {
     return inner.read(id, params).then(encoder);
   }
 
   @override
-  Future<U> remove(Id id, [Map<String, dynamic> params]) {
+  Future<U> remove(Id id, [Map<String, dynamic>? params]) {
     return inner.remove(id, params).then(encoder);
   }
 
   @override
-  Future<U> update(Id id, U data, [Map<String, dynamic> params]) {
+  Future<U> update(Id id, U data, [Map<String, dynamic>? params]) {
     return inner.update(id, decoder(data), params).then(encoder);
   }
 }
@@ -275,9 +277,9 @@ class ServiceList<Id, Data> extends DelegatingList<Data> {
   /// A function used to compare the ID's two items for equality.
   ///
   /// Defaults to comparing the [idField] of `Map` instances.
-  Equality<Data> get equality => _equality;
+  Equality<Data>? get equality => _equality;
 
-  Equality<Data> _equality;
+  Equality<Data>? _equality;
 
   final Service<Id, Data> service;
 
@@ -285,15 +287,16 @@ class ServiceList<Id, Data> extends DelegatingList<Data> {
 
   final List<StreamSubscription> _subs = [];
 
-  ServiceList(this.service, {this.idField = 'id', Equality<Data> equality})
+  ServiceList(this.service, {this.idField = 'id', Equality<Data>? equality})
       : super([]) {
     _equality = equality;
-    _equality ??= EqualityBy<Data, Id>((map) {
-      if (map is Map)
-        return map[idField ?? 'id'] as Id;
-      else
+    _equality ??= EqualityBy<Data, Id?>((map) {
+      if (map is Map) {
+        return map[idField] as Id?;
+      } else {
         throw UnsupportedError(
             'ServiceList only knows how to find the id from a Map object. Provide a custom `Equality` in your call to the constructor.');
+      }
     });
     // Index
     _subs.add(service.onIndexed.where(_notNull).listen((data) {
@@ -310,15 +313,17 @@ class ServiceList<Id, Data> extends DelegatingList<Data> {
     }));
 
     // Modified/Updated
-    handleModified(Data item) {
+    void handleModified(Data item) {
       var indices = <int>[];
 
-      for (int i = 0; i < length; i++) {
-        if (_equality.equals(item, this[i])) indices.add(i);
+      for (var i = 0; i < length; i++) {
+        if (_equality!.equals(item, this[i])) indices.add(i);
       }
 
       if (indices.isNotEmpty) {
-        for (var i in indices) this[i] = item;
+        for (var i in indices) {
+          this[i] = item;
+        }
 
         _onChange.add(this);
       }
@@ -331,7 +336,7 @@ class ServiceList<Id, Data> extends DelegatingList<Data> {
 
     // Removed
     _subs.add(service.onRemoved.where(_notNull).listen((item) {
-      removeWhere((x) => _equality.equals(item, x));
+      removeWhere((x) => _equality!.equals(item, x));
       _onChange.add(this);
     }));
   }
diff --git a/packages/client/lib/base_angel_client.dart b/packages/client/lib/base_angel_client.dart
index 09403a7c..42c0e3b2 100644
--- a/packages/client/lib/base_angel_client.dart
+++ b/packages/client/lib/base_angel_client.dart
@@ -16,7 +16,7 @@ const Map<String, String> _writeHeaders = {
   'Content-Type': 'application/json'
 };
 
-Map<String, String> _buildQuery(Map<String, dynamic> params) {
+Map<String, String>? _buildQuery(Map<String, dynamic>? params) {
   return params?.map((k, v) => MapEntry(k, v.toString()));
 }
 
@@ -26,7 +26,7 @@ bool _invalid(http.Response response) =>
     response.statusCode >= 300;
 
 AngelHttpException failure(http.Response response,
-    {error, String message, StackTrace stack}) {
+    {error, String? message, StackTrace? stack}) {
   try {
     var v = json.decode(response.body);
 
@@ -52,7 +52,7 @@ abstract class BaseAngelClient extends Angel {
   final StreamController<AngelAuthResult> _onAuthenticated =
       StreamController<AngelAuthResult>();
   final List<Service> _services = [];
-  final http.BaseClient client;
+  final http.BaseClient? client;
 
   @override
   Stream<AngelAuthResult> get onAuthenticated => _onAuthenticated.stream;
@@ -61,7 +61,7 @@ abstract class BaseAngelClient extends Angel {
 
   @override
   Future<AngelAuthResult> authenticate(
-      {String type,
+      {String? type,
       credentials,
       String authEndpoint = '/auth',
       @deprecated String reviveEndpoint = '/auth/token'}) async {
@@ -92,14 +92,12 @@ abstract class BaseAngelClient extends Angel {
       //var v = json.decode(response.body);
       var v = jsonDecode(response.body);
 
-      if (v is! Map ||
-          !(v as Map).containsKey('data') ||
-          !(v as Map).containsKey('token')) {
+      if (v is! Map || !v.containsKey('data') || !v.containsKey('token')) {
         throw AngelHttpException.notAuthenticated(
             message: "Auth endpoint '$url' did not return a proper response.");
       }
 
-      var r = AngelAuthResult.fromMap(v as Map);
+      var r = AngelAuthResult.fromMap(v);
       _onAuthenticated.add(r);
       return r;
     } on AngelHttpException {
@@ -111,7 +109,7 @@ abstract class BaseAngelClient extends Angel {
 
   @override
   Future<void> close() async {
-    client.close();
+    client!.close();
     await _onAuthenticated.close();
     await Future.wait(_services.map((s) => s.close())).then((_) {
       _services.clear();
@@ -128,13 +126,13 @@ abstract class BaseAngelClient extends Angel {
     if (authToken?.isNotEmpty == true) {
       request.headers['authorization'] ??= 'Bearer $authToken';
     }
-    return client.send(request);
+    return client!.send(request);
   }
 
   /// Sends a non-streaming [Request] and returns a non-streaming [Response].
   Future<http.Response> sendUnstreamed(
-      String method, url, Map<String, String> headers,
-      [body, Encoding encoding]) async {
+      String method, url, Map<String, String>? headers,
+      [body, Encoding? encoding]) async {
     var request =
         http.Request(method, url is Uri ? url : Uri.parse(url.toString()));
 
@@ -160,12 +158,12 @@ abstract class BaseAngelClient extends Angel {
 
   @override
   Service<Id, Data> service<Id, Data>(String path,
-      {Type type, AngelDeserializer<Data> deserializer}) {
+      {Type? type, AngelDeserializer<Data>? deserializer}) {
     var url = baseUrl.replace(path: p.join(baseUrl.path, path));
     var s = BaseAngelService<Id, Data>(client, this, url,
         deserializer: deserializer);
     _services.add(s);
-    return s;
+    return s as Service<Id, Data>;
   }
 
   Uri _join(url) {
@@ -180,65 +178,65 @@ abstract class BaseAngelClient extends Angel {
   //}
 
   @override
-  Future<http.Response> get(url, {Map<String, String> headers}) async {
+  Future<http.Response> get(url, {Map<String, String>? headers}) async {
     return sendUnstreamed('GET', _join(url), headers);
   }
 
   @override
-  Future<http.Response> head(url, {Map<String, String> headers}) async {
+  Future<http.Response> head(url, {Map<String, String>? headers}) async {
     return sendUnstreamed('HEAD', _join(url), headers);
   }
 
   @override
   Future<http.Response> patch(url,
-      {body, Map<String, String> headers, Encoding encoding}) async {
+      {body, Map<String, String>? headers, Encoding? encoding}) async {
     return sendUnstreamed('PATCH', _join(url), headers, body, encoding);
   }
 
   @override
   Future<http.Response> post(url,
-      {body, Map<String, String> headers, Encoding encoding}) async {
+      {body, Map<String, String>? headers, Encoding? encoding}) async {
     return sendUnstreamed('POST', _join(url), headers, body, encoding);
   }
 
   @override
   Future<http.Response> put(url,
-      {body, Map<String, String> headers, Encoding encoding}) async {
+      {body, Map<String, String>? headers, Encoding? encoding}) async {
     return sendUnstreamed('PUT', _join(url), headers, body, encoding);
   }
 }
 
-class BaseAngelService<Id, Data> extends Service<Id, Data> {
+class BaseAngelService<Id, Data> extends Service<Id, Data?> {
   @override
   final BaseAngelClient app;
   final Uri baseUrl;
-  final http.BaseClient client;
-  final AngelDeserializer<Data> deserializer;
+  final http.BaseClient? client;
+  final AngelDeserializer<Data>? deserializer;
 
-  final StreamController<List<Data>> _onIndexed = StreamController();
-  final StreamController<Data> _onRead = StreamController(),
+  final StreamController<List<Data?>> _onIndexed = StreamController();
+  final StreamController<Data?> _onRead = StreamController(),
       _onCreated = StreamController(),
       _onModified = StreamController(),
       _onUpdated = StreamController(),
       _onRemoved = StreamController();
 
   @override
-  Stream<List<Data>> get onIndexed => _onIndexed.stream;
+  Stream<List<Data?>> get onIndexed => _onIndexed.stream;
 
   @override
-  Stream<Data> get onRead => _onRead.stream;
+  Stream<Data?> get onRead => _onRead.stream;
 
   @override
-  Stream<Data> get onCreated => _onCreated.stream;
+  Stream<Data?> get onCreated => _onCreated.stream;
 
   @override
-  Stream<Data> get onModified => _onModified.stream;
+  Stream<Data?> get onModified => _onModified.stream;
 
   @override
-  Stream<Data> get onUpdated => _onUpdated.stream;
+  Stream<Data?> get onUpdated => _onUpdated.stream;
 
   @override
-  Stream<Data> get onRemoved => _onRemoved.stream;
+  Stream<Data?> get onRemoved => _onRemoved.stream;
 
   @override
   Future close() async {
@@ -257,8 +255,8 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
   @deprecated
   String get basePath => baseUrl.toString();
 
-  Data deserialize(x) {
-    return deserializer != null ? deserializer(x) : x as Data;
+  Data? deserialize(x) {
+    return deserializer != null ? deserializer!(x) : x as Data?;
   }
 
   String makeBody(x) {
@@ -267,15 +265,15 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
   }
 
   Future<http.StreamedResponse> send(http.BaseRequest request) {
-    if (app.authToken != null && app.authToken.isNotEmpty) {
+    if (app.authToken != null && app.authToken!.isNotEmpty) {
       request.headers['Authorization'] = 'Bearer ${app.authToken}';
     }
 
-    return client.send(request);
+    return client!.send(request);
   }
 
   @override
-  Future<List<Data>> index([Map<String, dynamic> params]) async {
+  Future<List<Data?>?> index([Map<String, dynamic>? params]) async {
     var url = baseUrl.replace(queryParameters: _buildQuery(params));
     var response = await app.sendUnstreamed('GET', url, _readHeaders);
 
@@ -304,7 +302,7 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
   }
 
   @override
-  Future<Data> read(id, [Map<String, dynamic> params]) async {
+  Future<Data?> read(id, [Map<String, dynamic>? params]) async {
     var url = baseUrl.replace(
         path: p.join(baseUrl.path, id.toString()),
         queryParameters: _buildQuery(params));
@@ -313,54 +311,58 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
 
     try {
       if (_invalid(response)) {
-        if (_onRead.hasListener)
+        if (_onRead.hasListener) {
           _onRead.addError(failure(response));
-        else
+        } else {
           throw failure(response);
+        }
       }
 
       var r = deserialize(json.decode(response.body));
       _onRead.add(r);
       return r;
     } catch (e, st) {
-      if (_onRead.hasListener)
+      if (_onRead.hasListener) {
         _onRead.addError(e, st);
-      else
+      } else {
         throw failure(response, error: e, stack: st);
+      }
     }
 
     return null;
   }
 
   @override
-  Future<Data> create(data, [Map<String, dynamic> params]) async {
+  Future<Data?> create(data, [Map<String, dynamic>? params]) async {
     var url = baseUrl.replace(queryParameters: _buildQuery(params));
     var response =
         await app.sendUnstreamed('POST', url, _writeHeaders, makeBody(data));
 
     try {
       if (_invalid(response)) {
-        if (_onCreated.hasListener)
+        if (_onCreated.hasListener) {
           _onCreated.addError(failure(response));
-        else
+        } else {
           throw failure(response);
+        }
       }
 
       var r = deserialize(json.decode(response.body));
       _onCreated.add(r);
       return r;
     } catch (e, st) {
-      if (_onCreated.hasListener)
+      if (_onCreated.hasListener) {
         _onCreated.addError(e, st);
-      else
+      } else {
         throw failure(response, error: e, stack: st);
+      }
     }
 
     return null;
   }
 
   @override
-  Future<Data> modify(id, data, [Map<String, dynamic> params]) async {
+  Future<Data?> modify(id, data, [Map<String, dynamic>? params]) async {
     var url = baseUrl.replace(
         path: p.join(baseUrl.path, id.toString()),
         queryParameters: _buildQuery(params));
@@ -370,27 +372,29 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
 
     try {
       if (_invalid(response)) {
-        if (_onModified.hasListener)
+        if (_onModified.hasListener) {
           _onModified.addError(failure(response));
-        else
+        } else {
           throw failure(response);
+        }
       }
 
       var r = deserialize(json.decode(response.body));
       _onModified.add(r);
       return r;
     } catch (e, st) {
-      if (_onModified.hasListener)
+      if (_onModified.hasListener) {
         _onModified.addError(e, st);
-      else
+      } else {
         throw failure(response, error: e, stack: st);
+      }
     }
 
     return null;
   }
 
   @override
-  Future<Data> update(id, data, [Map<String, dynamic> params]) async {
+  Future<Data?> update(id, data, [Map<String, dynamic>? params]) async {
     var url = baseUrl.replace(
         path: p.join(baseUrl.path, id.toString()),
         queryParameters: _buildQuery(params));
@@ -400,27 +404,29 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
 
     try {
       if (_invalid(response)) {
-        if (_onUpdated.hasListener)
+        if (_onUpdated.hasListener) {
           _onUpdated.addError(failure(response));
-        else
+        } else {
           throw failure(response);
+        }
       }
 
       var r = deserialize(json.decode(response.body));
       _onUpdated.add(r);
       return r;
     } catch (e, st) {
-      if (_onUpdated.hasListener)
+      if (_onUpdated.hasListener) {
         _onUpdated.addError(e, st);
-      else
+      } else {
         throw failure(response, error: e, stack: st);
+      }
     }
 
     return null;
   }
 
   @override
-  Future<Data> remove(id, [Map<String, dynamic> params]) async {
+  Future<Data?> remove(id, [Map<String, dynamic>? params]) async {
     var url = baseUrl.replace(
         path: p.join(baseUrl.path, id.toString()),
         queryParameters: _buildQuery(params));
@@ -429,20 +435,22 @@ class BaseAngelService<Id, Data> extends Service<Id, Data> {
 
     try {
       if (_invalid(response)) {
-        if (_onRemoved.hasListener)
+        if (_onRemoved.hasListener) {
           _onRemoved.addError(failure(response));
-        else
+        } else {
           throw failure(response);
+        }
       }
 
       var r = deserialize(json.decode(response.body));
       _onRemoved.add(r);
       return r;
     } catch (e, st) {
-      if (_onRemoved.hasListener)
+      if (_onRemoved.hasListener) {
         _onRemoved.addError(e, st);
-      else
+      } else {
         throw failure(response, error: e, stack: st);
+      }
     }
 
     return null;
diff --git a/packages/client/lib/browser.dart b/packages/client/lib/browser.dart
index 5b25459a..0e9b0d1d 100644
--- a/packages/client/lib/browser.dart
+++ b/packages/client/lib/browser.dart
@@ -13,20 +13,21 @@ export 'angel_client.dart';
 
 /// Queries an Angel server via REST.
 class Rest extends BaseAngelClient {
-  Rest(String basePath) : super(new http.BrowserClient(), basePath);
+  Rest(String basePath) : super(http.BrowserClient(), basePath);
 
+  @override
   Future<AngelAuthResult> authenticate(
-      {String type,
+      {String? type,
       credentials,
       String authEndpoint = '/auth',
       @deprecated String reviveEndpoint = '/auth/token'}) async {
     if (type == null || type == 'token') {
       if (!window.localStorage.containsKey('token')) {
-        throw new Exception(
+        throw Exception(
             'Cannot revive token from localStorage - there is none.');
       }
 
-      var token = json.decode(window.localStorage['token']);
+      var token = json.decode(window.localStorage['token']!);
       credentials ??= {'token': token};
     }
 
@@ -39,33 +40,34 @@ class Rest extends BaseAngelClient {
 
   @override
   Stream<String> authenticateViaPopup(String url,
-      {String eventName = 'token', String errorMessage}) {
-    var ctrl = new StreamController<String>();
+      {String eventName = 'token', String? errorMessage}) {
+    var ctrl = StreamController<String>();
     var wnd = window.open(url, 'angel_client_auth_popup');
 
     Timer t;
-    StreamSubscription sub;
-    t = new Timer.periodic(new Duration(milliseconds: 500), (timer) {
+    StreamSubscription? sub;
+    t = Timer.periodic(Duration(milliseconds: 500), (timer) {
       if (!ctrl.isClosed) {
-        if (wnd.closed) {
-          ctrl.addError(new AngelHttpException.notAuthenticated(
+        if (wnd.closed!) {
+          ctrl.addError(AngelHttpException.notAuthenticated(
               message:
                   errorMessage ?? 'Authentication via popup window failed.'));
           ctrl.close();
           timer.cancel();
           sub?.cancel();
         }
-      } else
+      } else {
         timer.cancel();
+      }
     });
 
-    sub = window.on[eventName ?? 'token'].listen((Event ev) {
+    sub = window.on[eventName].listen((Event ev) {
       var e = ev as CustomEvent;
       if (!ctrl.isClosed) {
         ctrl.add(e.detail.toString());
         t.cancel();
         ctrl.close();
-        sub.cancel();
+        sub!.cancel();
       }
     });
 
diff --git a/packages/client/lib/flutter.dart b/packages/client/lib/flutter.dart
index 5e908fb5..3fecf32e 100644
--- a/packages/client/lib/flutter.dart
+++ b/packages/client/lib/flutter.dart
@@ -8,12 +8,12 @@ export 'angel_client.dart';
 
 /// Queries an Angel server via REST.
 class Rest extends BaseAngelClient {
-  Rest(String basePath) : super(new http.Client() as http.BaseClient, basePath);
+  Rest(String basePath) : super(http.Client() as http.BaseClient, basePath);
 
   @override
   Stream<String> authenticateViaPopup(String url,
       {String eventName = 'token'}) {
-    throw new UnimplementedError(
+    throw UnimplementedError(
         'Opening popup windows is not supported in the `flutter` client.');
   }
 }
diff --git a/packages/client/lib/io.dart b/packages/client/lib/io.dart
index 30a24901..99d296a5 100644
--- a/packages/client/lib/io.dart
+++ b/packages/client/lib/io.dart
@@ -17,11 +17,11 @@ class Rest extends BaseAngelClient {
 
   @override
   Service<Id, Data> service<Id, Data>(String path,
-      {Type type, AngelDeserializer deserializer}) {
+      {Type? type, AngelDeserializer? deserializer}) {
     var url = baseUrl.replace(path: p.join(baseUrl.path, path));
     var s = RestService<Id, Data>(client, this, url, type);
     _services.add(s);
-    return s;
+    return s as Service<Id, Data>;
   }
 
   @override
@@ -42,21 +42,21 @@ class Rest extends BaseAngelClient {
 
 /// Queries an Angel service via REST.
 class RestService<Id, Data> extends BaseAngelService<Id, Data> {
-  final Type type;
+  final Type? type;
 
-  RestService(http.BaseClient client, BaseAngelClient app, url, this.type)
+  RestService(http.BaseClient? client, BaseAngelClient app, url, this.type)
       : super(client, app, url);
 
   @override
-  Data deserialize(x) {
+  Data? deserialize(x) {
     print(x);
     if (type != null) {
       return x.runtimeType == type
-          ? x as Data
-          : god.deserializeDatum(x, outputType: type) as Data;
+          ? x as Data?
+          : god.deserializeDatum(x, outputType: type) as Data?;
     }
 
-    return x as Data;
+    return x as Data?;
   }
 
   @override
diff --git a/packages/client/pubspec.yaml b/packages/client/pubspec.yaml
index a8f3602e..5eb6c883 100644
--- a/packages/client/pubspec.yaml
+++ b/packages/client/pubspec.yaml
@@ -1,41 +1,45 @@
 name: angel_client
-version: 3.0.0
+version: 4.0.0
 description: Support for querying Angel servers in the browser, Flutter, and command-line.
 author: Tobe O <thosakwe@gmail.com>
 homepage: https://github.com/angel-dart/angel_client
 publish_to: none
 environment:
-  sdk: ">=2.10.0 <3.0.0"
+  sdk: '>=2.12.0 <3.0.0'
 dependencies:
   angel_http_exception:
     git: 
       url: https://github.com/dukefirehawk/angel.git
-      ref: sdk-2.12.x
+      ref: sdk-2.12.x_nnbd
       path: packages/http_exception
-  collection: ^1.0.0
-  http: ^0.13.0
+  collection: ^1.15.0
+  http: ^0.13.1
   json_god:
     git: 
       url: https://github.com/dukefirehawk/angel.git
-      ref: sdk-2.12.x
+      ref: sdk-2.12.x_nnbd
       path: packages/json_god
   #dart_json_mapper: ^1.7.0
-  meta: ^1.0.0
-  path: ^1.0.0
+  meta: ^1.3.0
+  path: ^1.8.0
 dev_dependencies:
   angel_framework:
     git: 
       url: https://github.com/dukefirehawk/angel.git
-      ref: sdk-2.12.x
+      ref: sdk-2.12.x_nnbd
       path: packages/framework
   angel_model:
     git: 
       url: https://github.com/dukefirehawk/angel.git
-      ref: sdk-2.12.x
+      ref: sdk-2.12.x_nnbd
       path: packages/model
-  async: ^2.0.0
-  build_runner: ^1.0.0
-  build_web_compilers: ^2.12.2
-  mock_request: ^1.0.0
+  async: ^2.5.0
+  build_runner: ^1.12.2
+  build_web_compilers: ^2.16.5
+  mock_request:
+    git: 
+      url: https://github.com/dukefirehawk/angel.git
+      ref: sdk-2.12.x_nnbd
+      path: packages/mock_request
   pedantic: ^1.11.0
-  test: ^1.16.5
+  test: ^1.16.8
diff --git a/packages/client/test/all_test.dart b/packages/client/test/all_test.dart
index acc8dc99..ad3e8128 100644
--- a/packages/client/test/all_test.dart
+++ b/packages/client/test/all_test.dart
@@ -9,75 +9,75 @@ void main() {
   test('sets method,body,headers,path', () async {
     await app.post(Uri.parse('/post'),
         headers: {'method': 'post'}, body: 'post');
-    expect(app.client.spec.method, 'POST');
-    expect(app.client.spec.path, '/post');
-    expect(app.client.spec.headers['method'], 'post');
-    expect(await read(app.client.spec.request.finalize()), 'post');
+    expect(app.client.spec!.method, 'POST');
+    expect(app.client.spec!.path, '/post');
+    expect(app.client.spec!.headers['method'], 'post');
+    expect(await read(app.client.spec!.request.finalize()), 'post');
   });
 
   group('service methods', () {
     test('index', () async {
       await todoService.index();
-      expect(app.client.spec.method, 'GET');
-      expect(app.client.spec.path, '/api/todos');
+      expect(app.client.spec!.method, 'GET');
+      expect(app.client.spec!.path, '/api/todos');
     });
 
     test('read', () async {
       await todoService.read('sleep');
-      expect(app.client.spec.method, 'GET');
-      expect(app.client.spec.path, '/api/todos/sleep');
+      expect(app.client.spec!.method, 'GET');
+      expect(app.client.spec!.path, '/api/todos/sleep');
     });
 
     test('create', () async {
       await todoService.create({});
-      expect(app.client.spec.method, 'POST');
-      expect(app.client.spec.headers['content-type'],
+      expect(app.client.spec!.method, 'POST');
+      expect(app.client.spec!.headers['content-type'],
           startsWith('application/json'));
-      expect(app.client.spec.path, '/api/todos');
-      expect(await read(app.client.spec.request.finalize()), '{}');
+      expect(app.client.spec!.path, '/api/todos');
+      expect(await read(app.client.spec!.request.finalize()), '{}');
     });
 
     test('modify', () async {
       await todoService.modify('sleep', {});
-      expect(app.client.spec.method, 'PATCH');
-      expect(app.client.spec.headers['content-type'],
+      expect(app.client.spec!.method, 'PATCH');
+      expect(app.client.spec!.headers['content-type'],
           startsWith('application/json'));
-      expect(app.client.spec.path, '/api/todos/sleep');
-      expect(await read(app.client.spec.request.finalize()), '{}');
+      expect(app.client.spec!.path, '/api/todos/sleep');
+      expect(await read(app.client.spec!.request.finalize()), '{}');
     });
 
     test('update', () async {
       await todoService.update('sleep', {});
-      expect(app.client.spec.method, 'POST');
-      expect(app.client.spec.headers['content-type'],
+      expect(app.client.spec!.method, 'POST');
+      expect(app.client.spec!.headers['content-type'],
           startsWith('application/json'));
-      expect(app.client.spec.path, '/api/todos/sleep');
-      expect(await read(app.client.spec.request.finalize()), '{}');
+      expect(app.client.spec!.path, '/api/todos/sleep');
+      expect(await read(app.client.spec!.request.finalize()), '{}');
     });
 
     test('remove', () async {
       await todoService.remove('sleep');
-      expect(app.client.spec.method, 'DELETE');
-      expect(app.client.spec.path, '/api/todos/sleep');
+      expect(app.client.spec!.method, 'DELETE');
+      expect(app.client.spec!.path, '/api/todos/sleep');
     });
   });
 
   group('authentication', () {
     test('no type defaults to token', () async {
       await app.authenticate(credentials: '<jwt>');
-      expect(app.client.spec.path, '/auth/token');
+      expect(app.client.spec!.path, '/auth/token');
     });
 
     test('sets type', () async {
       await app.authenticate(type: 'local');
-      expect(app.client.spec.path, '/auth/local');
+      expect(app.client.spec!.path, '/auth/local');
     });
 
     test('credentials send right body', () async {
       await app
           .authenticate(type: 'local', credentials: {'username': 'password'});
       expect(
-        await read(app.client.spec.request.finalize()),
+        await read(app.client.spec!.request.finalize()),
         json.encode({'username': 'password'}),
       );
     });
diff --git a/packages/client/test/common.dart b/packages/client/test/common.dart
index 8d7e2c90..638c389a 100644
--- a/packages/client/test/common.dart
+++ b/packages/client/test/common.dart
@@ -10,24 +10,25 @@ Future<String> read(Stream<List<int>> stream) =>
 
 class MockAngel extends BaseAngelClient {
   @override
-  final SpecClient client = new SpecClient();
+  final SpecClient client = SpecClient();
 
   MockAngel() : super(null, 'http://localhost:3000');
 
   @override
-  authenticateViaPopup(String url, {String eventName = 'token'}) {
-    throw new UnsupportedError('Nope');
+  Stream<String> authenticateViaPopup(String url,
+      {String eventName = 'token'}) {
+    throw UnsupportedError('Nope');
   }
 }
 
 class SpecClient extends http.BaseClient {
-  Spec _spec;
+  Spec? _spec;
 
-  Spec get spec => _spec;
+  Spec? get spec => _spec;
 
   @override
-  send(http.BaseRequest request) {
-    _spec = new Spec(request, request.method, request.url.path, request.headers,
+  Future<http.StreamedResponse> send(http.BaseRequest request) {
+    _spec = Spec(request, request.method, request.url.path, request.headers,
         request.contentLength);
     dynamic data = {'text': 'Clean your room!', 'completed': true};
 
@@ -40,8 +41,8 @@ class SpecClient extends http.BaseClient {
       data = [data];
     }
 
-    return new Future<http.StreamedResponse>.value(new http.StreamedResponse(
-      new Stream<List<int>>.fromIterable([utf8.encode(json.encode(data))]),
+    return Future<http.StreamedResponse>.value(http.StreamedResponse(
+      Stream<List<int>>.fromIterable([utf8.encode(json.encode(data))]),
       200,
       headers: {
         'content-type': 'application/json',
@@ -54,7 +55,7 @@ class Spec {
   final http.BaseRequest request;
   final String method, path;
   final Map<String, String> headers;
-  final int contentLength;
+  final int? contentLength;
 
   Spec(this.request, this.method, this.path, this.headers, this.contentLength);
 
diff --git a/packages/client/test/list_test.dart b/packages/client/test/list_test.dart
index ba632a9e..fc23429a 100644
--- a/packages/client/test/list_test.dart
+++ b/packages/client/test/list_test.dart
@@ -6,22 +6,22 @@ import 'package:angel_framework/http.dart' as s;
 import 'package:pedantic/pedantic.dart';
 import 'package:test/test.dart';
 
-main() {
-  HttpServer server;
-  c.Angel app;
-  c.ServiceList list;
-  StreamQueue queue;
+void main() {
+  late HttpServer server;
+  late c.Angel app;
+  late c.ServiceList list;
+  late StreamQueue queue;
 
   setUp(() async {
-    var serverApp = new s.Angel();
-    var http = new s.AngelHttp(serverApp);
-    serverApp.use('/api/todos', new s.MapService(autoIdAndDateFields: false));
+    var serverApp = s.Angel();
+    var http = s.AngelHttp(serverApp);
+    serverApp.use('/api/todos', s.MapService(autoIdAndDateFields: false));
 
     server = await http.startServer();
     var uri = 'http://${server.address.address}:${server.port}';
-    app = new c.Rest(uri);
-    list = new c.ServiceList(app.service('api/todos'));
-    queue = new StreamQueue(list.onChange);
+    app = c.Rest(uri);
+    list = c.ServiceList(app.service('api/todos'));
+    queue = StreamQueue(list.onChange);
   });
 
   tearDown(() async {
diff --git a/packages/client/test/shared.dart b/packages/client/test/shared.dart
index 11b6c660..479b02df 100644
--- a/packages/client/test/shared.dart
+++ b/packages/client/test/shared.dart
@@ -1,14 +1,14 @@
 import 'package:angel_model/angel_model.dart';
 
 class Postcard extends Model {
-  String location;
-  String message;
+  String? location;
+  String? message;
 
-  Postcard({String id, this.location, this.message}) {
+  Postcard({String? id, this.location, this.message}) {
     this.id = id;
   }
 
-  factory Postcard.fromJson(Map data) => new Postcard(
+  factory Postcard.fromJson(Map data) => Postcard(
       id: data['id'].toString(),
       location: data['location'].toString(),
       message: data['message'].toString());
diff --git a/packages/client/web/main.dart b/packages/client/web/main.dart
index 9e12ec08..498362e1 100644
--- a/packages/client/web/main.dart
+++ b/packages/client/web/main.dart
@@ -2,7 +2,7 @@ import 'dart:html';
 import 'package:angel_client/browser.dart';
 
 /// Dummy app to ensure client works with DDC.
-main() {
-  var app = new Rest(window.location.origin);
+void main() {
+  var app = Rest(window.location.origin);
   window.alert(app.baseUrl.toString());
 }