diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 000000000..a2571cbb1
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,3 @@
+## 1.0.0-beta.8
+
+* Internal changes only.
diff --git a/bin/dart_sass_embedded.dart b/bin/dart_sass_embedded.dart
index d431ac14a..d073441db 100644
--- a/bin/dart_sass_embedded.dart
+++ b/bin/dart_sass_embedded.dart
@@ -39,13 +39,12 @@ void main(List<String> args) {
         request.style == InboundMessage_CompileRequest_OutputStyle.COMPRESSED
             ? sass.OutputStyle.compressed
             : sass.OutputStyle.expanded;
-    var color = request.alertColor ?? false;
-    var ascii = request.alertAscii ?? false;
-    var logger = Logger(dispatcher, request.id, color: color, ascii: ascii);
+    var logger = Logger(dispatcher, request.id,
+        color: request.alertColor, ascii: request.alertAscii);
 
     try {
       String result;
-      source_maps.SingleMapping sourceMap;
+      source_maps.SingleMapping? sourceMap;
       var sourceMapCallback = request.sourceMap
           ? (source_maps.SingleMapping map) => sourceMap = map
           : null;
@@ -61,7 +60,7 @@ void main(List<String> args) {
         case InboundMessage_CompileRequest_Input.string:
           var input = request.string;
           result = sass.compileString(input.source,
-              color: color,
+              color: request.alertColor,
               logger: logger,
               importers: importers,
               importer: _decodeImporter(dispatcher, request, input.importer),
@@ -75,7 +74,7 @@ void main(List<String> args) {
         case InboundMessage_CompileRequest_Input.path:
           try {
             result = sass.compile(request.path,
-                color: color,
+                color: request.alertColor,
                 logger: logger,
                 importers: importers,
                 functions: globalFunctions,
@@ -97,11 +96,13 @@ void main(List<String> args) {
       var success = OutboundMessage_CompileResponse_CompileSuccess()
         ..css = result;
       if (sourceMap != null) {
-        success.sourceMap = json.encode(sourceMap.toJson());
+        // dart-lang/language#1536
+        success.sourceMap = json.encode(sourceMap!.toJson());
       }
       return OutboundMessage_CompileResponse()..success = success;
     } on sass.SassException catch (error) {
-      var formatted = withGlyphs(() => error.toString(color: color),
+      var formatted = withGlyphs(
+          () => error.toString(color: request.alertColor),
           ascii: request.alertAscii);
       return OutboundMessage_CompileResponse()
         ..failure = (OutboundMessage_CompileResponse_CompileFailure()
@@ -114,7 +115,7 @@ void main(List<String> args) {
 }
 
 /// Converts [importer] into an [Importer].
-sass.Importer _decodeImporter(
+sass.Importer? _decodeImporter(
     Dispatcher dispatcher,
     InboundMessage_CompileRequest request,
     InboundMessage_CompileRequest_Importer importer) {
@@ -131,7 +132,4 @@ sass.Importer _decodeImporter(
     case InboundMessage_CompileRequest_Importer_Importer.notSet:
       return null;
   }
-
-  // dart-lang/sdk#38790
-  throw "Unknown Importer.importer $importer.";
 }
diff --git a/lib/src/dispatcher.dart b/lib/src/dispatcher.dart
index fcbd814bb..11e87c387 100644
--- a/lib/src/dispatcher.dart
+++ b/lib/src/dispatcher.dart
@@ -23,7 +23,7 @@ class Dispatcher {
   /// The completers are located at indexes in this list matching the request
   /// IDs. `null` elements indicate IDs whose requests have been responded to,
   /// and which are therefore free to re-use.
-  final _outstandingRequests = <Completer<GeneratedMessage>>[];
+  final _outstandingRequests = <Completer<GeneratedMessage>?>[];
 
   /// Creates a [Dispatcher] that sends and receives encoded protocol buffers
   /// over [channel].
@@ -47,7 +47,7 @@ class Dispatcher {
       // for new input.
       await Future.value();
 
-      InboundMessage message;
+      InboundMessage? message;
       try {
         try {
           message = InboundMessage.fromBuffer(binaryMessage);
@@ -182,7 +182,7 @@ class Dispatcher {
 
   /// Returns the id for [message] if it it's a request, or `null`
   /// otherwise.
-  int _inboundId(InboundMessage message) {
+  int? _inboundId(InboundMessage? message) {
     if (message == null) return null;
     switch (message.whichMessage()) {
       case InboundMessage_Message.compileRequest:
@@ -210,7 +210,7 @@ class Dispatcher {
         message.functionCallRequest.id = id;
         break;
       default:
-        return null;
+        break;
     }
   }
 }
diff --git a/lib/src/function_registry.dart b/lib/src/function_registry.dart
index 79b0cacce..1cfd69a05 100644
--- a/lib/src/function_registry.dart
+++ b/lib/src/function_registry.dart
@@ -29,5 +29,5 @@ class FunctionRegistry {
   /// Returns the compiler-side function associated with [id].
   ///
   /// If no such function exists, returns `null`.
-  sass.SassFunction operator [](int id) => _functionsById[id];
+  sass.SassFunction? operator [](int id) => _functionsById[id];
 }
diff --git a/lib/src/host_callable.dart b/lib/src/host_callable.dart
index e3990aaf7..bb567d419 100644
--- a/lib/src/host_callable.dart
+++ b/lib/src/host_callable.dart
@@ -23,7 +23,7 @@ import 'value.dart';
 /// Throws a [ProtocolError] if [signature] is invalid.
 sass.Callable hostCallable(Dispatcher dispatcher, FunctionRegistry functions,
     int compilationId, String signature,
-    {int id}) {
+    {int? id}) {
   var openParen = signature.indexOf('(');
   if (openParen == -1) {
     throw paramsError(
@@ -38,7 +38,7 @@ sass.Callable hostCallable(Dispatcher dispatcher, FunctionRegistry functions,
 
   var name = signature.substring(0, openParen);
   try {
-    return sass.Callable(
+    return sass.Callable.function(
         name, signature.substring(openParen + 1, signature.length - 1),
         (arguments) {
       var request = OutboundMessage_FunctionCallRequest()
@@ -66,9 +66,6 @@ sass.Callable hostCallable(Dispatcher dispatcher, FunctionRegistry functions,
           case InboundMessage_FunctionCallResponse_Result.notSet:
             throw mandatoryError('FunctionCallResponse.result');
         }
-
-        // dart-lang/sdk#38790
-        throw "Unknown FunctionCallResponse.result $response.";
       } on ProtocolError catch (error) {
         error.id = errorId;
         stderr.writeln("Host caused ${error.type.name.toLowerCase()} error: "
diff --git a/lib/src/importer.dart b/lib/src/importer.dart
index 4b6d9d4ec..7e871482c 100644
--- a/lib/src/importer.dart
+++ b/lib/src/importer.dart
@@ -4,7 +4,6 @@
 
 import 'dart:cli';
 
-import 'package:meta/meta.dart';
 import 'package:sass/sass.dart' as sass;
 
 import 'dispatcher.dart';
@@ -24,7 +23,7 @@ class Importer extends sass.Importer {
 
   Importer(this._dispatcher, this._compilationId, this._importerId);
 
-  Uri canonicalize(Uri url) {
+  Uri? canonicalize(Uri url) {
     return waitFor(() async {
       var response = await _dispatcher
           .sendCanonicalizeRequest(OutboundMessage_CanonicalizeRequest()
@@ -42,9 +41,6 @@ class Importer extends sass.Importer {
         case InboundMessage_CanonicalizeResponse_Result.notSet:
           return null;
       }
-
-      // dart-lang/sdk#38790
-      throw "Unknown CanonicalizeResponse.result $response.";
     }());
   }
 
@@ -70,11 +66,7 @@ class Importer extends sass.Importer {
 
         case InboundMessage_ImportResponse_Result.notSet:
           _sendAndThrow(mandatoryError("ImportResponse.result"));
-          break; // dart-lang/sdk#34048
       }
-
-      // dart-lang/sdk#38790
-      throw "Unknown ImporterResponse.result $response.";
     }());
   }
 
@@ -96,8 +88,7 @@ class Importer extends sass.Importer {
 
   /// Sends [error] to the remote endpoint, and also throws it so that the Sass
   /// compilation fails.
-  @alwaysThrows
-  void _sendAndThrow(ProtocolError error) {
+  Never _sendAndThrow(ProtocolError error) {
     _dispatcher.sendError(error);
     throw "Protocol error: ${error.message}";
   }
diff --git a/lib/src/logger.dart b/lib/src/logger.dart
index 06b82fb3f..566c0a2ab 100644
--- a/lib/src/logger.dart
+++ b/lib/src/logger.dart
@@ -47,9 +47,9 @@ class Logger implements sass.Logger {
   }
 
   void warn(String message,
-      {FileSpan span, Trace trace, bool deprecation = false}) {
+      {FileSpan? span, Trace? trace, bool deprecation = false}) {
     var formatted = withGlyphs(() {
-      var buffer = new StringBuffer();
+      var buffer = StringBuffer();
       if (_color) {
         buffer.write('\u001b[33m\u001b[1m');
         if (deprecation) buffer.write('Deprecation ');
diff --git a/lib/src/util/length_delimited_transformer.dart b/lib/src/util/length_delimited_transformer.dart
index aba63ab7f..20bc33c98 100644
--- a/lib/src/util/length_delimited_transformer.dart
+++ b/lib/src/util/length_delimited_transformer.dart
@@ -23,7 +23,7 @@ final StreamChannelTransformer<Uint8List, List<int>> lengthDelimited =
 final lengthDelimitedDecoder =
     StreamTransformer<List<int>, Uint8List>.fromBind((stream) {
   // The number of bits we've consumed so far to fill out [nextMessageLength].
-  int nextMessageLengthBits = 0;
+  var nextMessageLengthBits = 0;
 
   // The length of the next message, in bytes.
   //
@@ -31,16 +31,16 @@ final lengthDelimitedDecoder =
   // initialized.
   //
   // [varint]: https://developers.google.com/protocol-buffers/docs/encoding#varints
-  int nextMessageLength = 0;
+  var nextMessageLength = 0;
 
   // The buffer into which the packet data itself is written. Initialized once
   // [nextMessageLength] is known.
-  Uint8List buffer;
+  Uint8List? buffer;
 
   // The index of the next byte to write to [buffer]. Once this is equal to
   // [buffer.length] (or equivalently [nextMessageLength]), the full packet is
   // available.
-  int bufferIndex;
+  var bufferIndex = 0;
 
   // It seems a little silly to use a nested [StreamTransformer] here, but we
   // need the outer one to establish a closure context so we can share state
@@ -54,6 +54,8 @@ final lengthDelimitedDecoder =
     var i = 0;
 
     while (i < chunk.length) {
+      var buffer_ = buffer; // dart-lang/language#1536
+
       // We can be in one of two states here:
       //
       // * [buffer] is `null`, in which case we're adding data to
@@ -63,7 +65,7 @@ final lengthDelimitedDecoder =
       // * [buffer] is not `null`, in which case we're waiting for [buffer] to
       //   have [nextMessageLength] bytes in it before we send it to
       //   [queue.local.sink] and start waiting for the next message.
-      if (buffer == null) {
+      if (buffer_ == null) {
         var byte = chunk[i];
 
         // Varints encode data in the 7 lower bits of each byte, which we access
@@ -79,7 +81,7 @@ final lengthDelimitedDecoder =
 
         // Otherwise, [nextMessageLength] is now finalized and we can allocate
         // the data buffer.
-        buffer = Uint8List(nextMessageLength);
+        buffer_ = buffer = Uint8List(nextMessageLength);
         bufferIndex = 0;
       }
 
@@ -88,18 +90,17 @@ final lengthDelimitedDecoder =
       // message after the current one) or more than the chunk has available (if
       // the current message is split across multiple chunks).
       var bytesToWrite =
-          math.min(buffer.length - bufferIndex, chunk.length - i);
-      buffer.setRange(bufferIndex, bufferIndex + bytesToWrite, chunk, i);
+          math.min(buffer_.length - bufferIndex, chunk.length - i);
+      buffer_.setRange(bufferIndex, bufferIndex + bytesToWrite, chunk, i);
       i += bytesToWrite;
       bufferIndex += bytesToWrite;
       if (bufferIndex < nextMessageLength) return;
 
       // Once we've filled the buffer, emit it and reset our state.
-      sink.add(buffer);
+      sink.add(buffer_);
       nextMessageLength = 0;
       nextMessageLengthBits = 0;
       buffer = null;
-      bufferIndex = null;
     }
   }));
 });
diff --git a/lib/src/utils.dart b/lib/src/utils.dart
index a74e19a9c..dbd547c8a 100644
--- a/lib/src/utils.dart
+++ b/lib/src/utils.dart
@@ -2,7 +2,6 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import 'package:meta/meta.dart';
 import 'package:sass/sass.dart' as sass;
 import 'package:source_span/source_span.dart';
 import 'package:term_glyph/term_glyph.dart' as term_glyph;
@@ -66,7 +65,7 @@ String indent(String string, int indentation) =>
 
 /// Returns the result of running [callback] with the global ASCII config set
 /// to [ascii].
-T withGlyphs<T>(T callback(), {@required bool ascii}) {
+T withGlyphs<T>(T callback(), {required bool ascii}) {
   var currentConfig = term_glyph.ascii;
   term_glyph.ascii = ascii;
   var result = callback();
diff --git a/lib/src/value.dart b/lib/src/value.dart
index 065a2fcb8..6c286ecae 100644
--- a/lib/src/value.dart
+++ b/lib/src/value.dart
@@ -166,15 +166,10 @@ sass.Value deprotofyValue(Dispatcher dispatcher, FunctionRegistry functions,
         default:
           throw "Unknown Value.singleton ${value.singleton}";
       }
-      // dart-lang/sdk#39304
-      throw "Unreachable"; // ignore: dead_code
 
     case Value_Value.notSet:
       throw mandatoryError("Value.value");
   }
-
-  // dart-lang/sdk#38790
-  throw "Unknown Value.value $value.";
 }
 
 /// Converts [separator] to its Sass representation.
diff --git a/pubspec.yaml b/pubspec.yaml
index 7202a2605..28765ef44 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,11 @@
 name: sass_embedded
-version: 1.0.0-beta.7
+version: 1.0.0-dev
 description: An implementation of the Sass embedded protocol using Dart Sass.
 author: Sass Team
 homepage: https://github.com/sass/dart-sass-embedded
 
 environment:
-  sdk: '>=2.10.0 <3.0.0'
+  sdk: '>=2.12.0 <3.0.0'
 
 executables:
   dart-sass-embedded: dart_sass_embedded
@@ -13,8 +13,8 @@ executables:
 dependencies:
   async: ">=1.13.0 <3.0.0"
   meta: ^1.1.0
-  protobuf: ^1.0.0
-  sass: ^1.21.0
+  protobuf: ^2.0.0
+  sass: ^1.25.0
   source_maps: ^0.10.5
   source_span: ^1.1.0
   stack_trace: ^1.6.0
@@ -23,8 +23,8 @@ dependencies:
 
 dev_dependencies:
   cli_pkg: ^1.2.0
-  grinder: ^0.8.0
-  protoc_plugin: ^19.0.0
+  grinder: ^0.9.0
+  protoc_plugin: ^20.0.0
   path: ^1.6.0
   test: ^1.0.0
-  test_descriptor: ^1.0.0
+  test_descriptor: ^2.0.0
diff --git a/test/embedded_process.dart b/test/embedded_process.dart
index 9919992e7..75ca7897f 100644
--- a/test/embedded_process.dart
+++ b/test/embedded_process.dart
@@ -26,11 +26,11 @@ class EmbeddedProcess {
 
   /// A [StreamQueue] that emits each outbound protocol buffer from the process.
   StreamQueue<OutboundMessage> get outbound => _outbound;
-  StreamQueue<OutboundMessage> _outbound;
+  late StreamQueue<OutboundMessage> _outbound;
 
   /// A [StreamQueue] that emits each line of stderr from the process.
   StreamQueue<String> get stderr => _stderr;
-  StreamQueue<String> _stderr;
+  late StreamQueue<String> _stderr;
 
   /// A splitter that can emit new copies of [outbound].
   final StreamSplitter<OutboundMessage> _outboundSplitter;
@@ -49,7 +49,7 @@ class EmbeddedProcess {
   final _log = <String>[];
 
   /// Whether [_log] has been passed to [printOnFailure] yet.
-  bool _loggedOutput = false;
+  var _loggedOutput = false;
 
   /// Returns a [Future] which completes to the exit code of the process, once
   /// it completes.
@@ -60,8 +60,11 @@ class EmbeddedProcess {
 
   /// Completes to [_process]'s exit code if it's exited, otherwise completes to
   /// `null` immediately.
-  Future<int> get _exitCodeOrNull async =>
-      await exitCode.timeout(Duration.zero, onTimeout: () => null);
+  Future<int?> get _exitCodeOrNull async {
+    var exitCode =
+        await this.exitCode.timeout(Duration.zero, onTimeout: () => -1);
+    return exitCode == -1 ? null : exitCode;
+  }
 
   /// Starts a process.
   ///
@@ -73,8 +76,8 @@ class EmbeddedProcess {
   /// [stderr] will be printed to the console as they appear. This is only
   /// intended to be set temporarily to help when debugging test failures.
   static Future<EmbeddedProcess> start(
-      {String workingDirectory,
-      Map<String, String> environment,
+      {String? workingDirectory,
+      Map<String, String>? environment,
       bool includeParentEnvironment = true,
       bool runInShell = false,
       bool forwardOutput = false}) async {
diff --git a/test/function_test.dart b/test/function_test.dart
index fd5e3dd97..349352eae 100644
--- a/test/function_test.dart
+++ b/test/function_test.dart
@@ -14,7 +14,7 @@ final _true = Value()..singleton = Value_Singleton.TRUE;
 final _false = Value()..singleton = Value_Singleton.FALSE;
 final _null = Value()..singleton = Value_Singleton.NULL;
 
-EmbeddedProcess _process;
+late EmbeddedProcess _process;
 
 void main() {
   setUp(() async {
@@ -67,7 +67,7 @@ void main() {
 
   group("includes in FunctionCallRequest", () {
     var compilationId = 1234;
-    OutboundMessage_FunctionCallRequest request;
+    late OutboundMessage_FunctionCallRequest request;
     setUp(() async {
       _process.inbound.add(compileString("a {b: foo()}",
           id: compilationId, functions: ["foo()"]));
@@ -1232,7 +1232,7 @@ Future<String> _deprotofy(Value value, {bool inspect = false}) async {
 
   var success = await getCompileSuccess(await _process.outbound.next);
   expect(_process.kill(), completes);
-  return RegExp(r"  b: (.*);").firstMatch(success.css)[1];
+  return RegExp(r"  b: (.*);").firstMatch(success.css)![1]!;
 }
 
 /// Asserts that [value] causes a parameter error with a message matching
diff --git a/test/importer_test.dart b/test/importer_test.dart
index f60c7607b..42688095d 100644
--- a/test/importer_test.dart
+++ b/test/importer_test.dart
@@ -13,7 +13,7 @@ import 'embedded_process.dart';
 import 'utils.dart';
 
 void main() {
-  EmbeddedProcess process;
+  late EmbeddedProcess process;
   setUp(() async {
     process = await EmbeddedProcess.start();
   });
@@ -101,7 +101,7 @@ void main() {
     group("includes in CanonicalizeRequest", () {
       var compilationId = 1234;
       var importerId = 5679;
-      OutboundMessage_CanonicalizeRequest request;
+      late OutboundMessage_CanonicalizeRequest request;
       setUp(() async {
         process.inbound.add(compileString("@import 'other'",
             id: compilationId,
@@ -256,7 +256,7 @@ void main() {
     group("includes in ImportRequest", () {
       var compilationId = 1234;
       var importerId = 5678;
-      OutboundMessage_ImportRequest request;
+      late OutboundMessage_ImportRequest request;
       setUp(() async {
         process.inbound.add(compileString("@import 'other'",
             id: compilationId,
diff --git a/test/length_delimited_test.dart b/test/length_delimited_test.dart
index 1fc831821..38c247b8c 100644
--- a/test/length_delimited_test.dart
+++ b/test/length_delimited_test.dart
@@ -12,8 +12,8 @@ import 'package:test/test.dart';
 
 void main() {
   group("encoder", () {
-    Sink<List<int>> sink;
-    Stream<List<int>> stream;
+    late Sink<List<int>> sink;
+    late Stream<List<int>> stream;
     setUp(() {
       var controller = StreamController<List<int>>();
       sink = controller.sink;
@@ -52,8 +52,8 @@ void main() {
   });
 
   group("decoder", () {
-    Sink<List<int>> sink;
-    StreamQueue<Uint8List> queue;
+    late Sink<List<int>> sink;
+    late StreamQueue<Uint8List> queue;
     setUp(() {
       var controller = StreamController<List<int>>();
       sink = controller.sink;
diff --git a/test/protocol_test.dart b/test/protocol_test.dart
index dd839b573..9b3ab4835 100644
--- a/test/protocol_test.dart
+++ b/test/protocol_test.dart
@@ -13,7 +13,7 @@ import 'embedded_process.dart';
 import 'utils.dart';
 
 void main() {
-  EmbeddedProcess process;
+  late EmbeddedProcess process;
   setUp(() async {
     process = await EmbeddedProcess.start();
   });
@@ -119,7 +119,7 @@ void main() {
         process.outbound,
         emits(isSuccess("a { b: 3px; }", sourceMap: (map) {
           var mapping = source_maps.parse(map);
-          var span = mapping.spanFor(2, 5);
+          var span = mapping.spanFor(2, 5)!;
           expect(span.start.line, equals(0));
           expect(span.start.column, equals(3));
           expect(span.end, equals(span.start));
diff --git a/test/utils.dart b/test/utils.dart
index 6a2823248..e3fe8e087 100644
--- a/test/utils.dart
+++ b/test/utils.dart
@@ -13,16 +13,16 @@ import 'embedded_process.dart';
 /// Returns a [InboundMessage] that compiles the given plain CSS
 /// string.
 InboundMessage compileString(String css,
-    {int id,
-    bool alertColor,
-    bool alertAscii,
-    InboundMessage_Syntax syntax,
-    InboundMessage_CompileRequest_OutputStyle style,
-    String url,
-    bool sourceMap,
-    Iterable<InboundMessage_CompileRequest_Importer> importers,
-    InboundMessage_CompileRequest_Importer importer,
-    Iterable<String> functions}) {
+    {int? id,
+    bool? alertColor,
+    bool? alertAscii,
+    InboundMessage_Syntax? syntax,
+    InboundMessage_CompileRequest_OutputStyle? style,
+    String? url,
+    bool? sourceMap,
+    Iterable<InboundMessage_CompileRequest_Importer>? importers,
+    InboundMessage_CompileRequest_Importer? importer,
+    Iterable<String>? functions}) {
   var input = InboundMessage_CompileRequest_StringInput()..source = css;
   if (syntax != null) input.syntax = syntax;
   if (url != null) input.url = url;
diff --git a/tool/grind.dart b/tool/grind.dart
index 4cb59a20f..2247a2c55 100644
--- a/tool/grind.dart
+++ b/tool/grind.dart
@@ -10,7 +10,7 @@ import 'package:grinder/grinder.dart';
 import 'utils.dart';
 
 main(List<String> args) {
-  pkg.githubBearerToken.value = Platform.environment["GH_BEARER_TOKEN"];
+  pkg.githubBearerToken.fn = () => Platform.environment["GH_BEARER_TOKEN"]!;
 
   pkg.addGithubTasks();
   grind(args);
@@ -44,6 +44,6 @@ dart pub run protoc_plugin %*
       runOptions: RunOptions(environment: {
         "PATH": 'build' +
             (Platform.isWindows ? ";" : ":") +
-            Platform.environment["PATH"]
+            Platform.environment["PATH"]!
       }));
 }