diff --git a/packages/celest/lib/src/runtime/sse/sse_handler.dart b/packages/celest/lib/src/runtime/sse/sse_handler.dart
index 48181a86..167d2b95 100644
--- a/packages/celest/lib/src/runtime/sse/sse_handler.dart
+++ b/packages/celest/lib/src/runtime/sse/sse_handler.dart
@@ -5,6 +5,7 @@ library;
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 
 import 'package:async/async.dart';
 import 'package:celest_core/_internal.dart';
@@ -205,6 +206,9 @@ final class _SseHandler {
     });
   }
 
+  static final _jsonUtf8Decoder =
+      utf8.decoder.fuse(json.decoder).cast<Uint8List, Object?>();
+
   Future<Response> _handleIncomingMessage(Request request) async {
     final clientId = request.url.queryParameters['sseClientId'];
     if (clientId == null) {
@@ -222,11 +226,7 @@ final class _SseHandler {
       request.url.queryParameters['messageId'] ?? '0',
     );
     try {
-      final message = await request
-          .read()
-          .transform(utf8.decoder)
-          .transform(json.decoder)
-          .single;
+      final message = await request.read().transform(_jsonUtf8Decoder).first;
       connection._handleIncoming(messageId, message);
       return Response(HttpStatus.accepted);
     } on Object catch (e, st) {
diff --git a/packages/celest/lib/src/runtime/targets.dart b/packages/celest/lib/src/runtime/targets.dart
index 1e3d74ab..9e31951f 100644
--- a/packages/celest/lib/src/runtime/targets.dart
+++ b/packages/celest/lib/src/runtime/targets.dart
@@ -79,7 +79,7 @@ abstract base class CloudEventSourceTarget extends CloudFunctionTarget {
           StreamChannelTransformer(
             StreamTransformer.fromHandlers(
               handleData: (data, sink) {
-                sink.add(JsonUtf8.decodeMap(data));
+                sink.add(JsonUtf8.decodeAny(data));
               },
             ),
             StreamSinkTransformer.fromHandlers(
diff --git a/packages/celest_core/lib/src/base/base_protocol.dart b/packages/celest_core/lib/src/base/base_protocol.dart
index 96c3cabe..8434454c 100644
--- a/packages/celest_core/lib/src/base/base_protocol.dart
+++ b/packages/celest_core/lib/src/base/base_protocol.dart
@@ -55,7 +55,7 @@ mixin BaseProtocol {
     };
   }
 
-  Stream<Map<String, Object?>> connect(
+  Stream<Object?> connect(
     String path, {
     required Map<String, Object?> payload,
   }) {
@@ -84,10 +84,10 @@ mixin BaseProtocol {
       );
     }
     final json = jsonDecode(response.body) as Map<String, Object?>;
-    final error = json['error'] as Map<String, Object?>?;
+    final error = json['@error'] as Map<String, Object?>?;
     throw createError(
-      error?['message'] as String?,
-      details: switch (error?['details']) {
+      error?['message'] as String? ?? json['message'] as String?,
+      details: switch (json['details']) {
         null => null,
         final Object details => JsonValue(details),
       },
diff --git a/packages/celest_core/lib/src/events/event_channel.dart b/packages/celest_core/lib/src/events/event_channel.dart
index 5d0b2aa8..33b797ac 100644
--- a/packages/celest_core/lib/src/events/event_channel.dart
+++ b/packages/celest_core/lib/src/events/event_channel.dart
@@ -4,7 +4,7 @@ import 'package:celest_core/src/events/event_channel.vm.dart'
 import 'package:http/http.dart' as http;
 import 'package:stream_channel/stream_channel.dart';
 
-abstract class EventChannel with StreamChannelMixin<Map<String, Object?>> {
+abstract class EventChannel with StreamChannelMixin<Object?> {
   EventChannel();
   factory EventChannel.connect(
     Uri uri, {
diff --git a/packages/celest_core/lib/src/events/event_channel.vm.dart b/packages/celest_core/lib/src/events/event_channel.vm.dart
index 21e665cc..9b0f1492 100644
--- a/packages/celest_core/lib/src/events/event_channel.vm.dart
+++ b/packages/celest_core/lib/src/events/event_channel.vm.dart
@@ -31,8 +31,7 @@ final class EventChannelPlatform extends EventChannel {
   }
 
   final WebSocketChannel _ws;
-  late final StreamSink<Map<String, Object?>> _wsSink =
-      _ws.sink.rejectErrors().transform(
+  late final StreamSink<Object?> _wsSink = _ws.sink.rejectErrors().transform(
     StreamSinkTransformer.fromHandlers(
       handleData: (data, sink) {
         sink.add(jsonEncode(data));
@@ -41,10 +40,10 @@ final class EventChannelPlatform extends EventChannel {
   );
 
   @override
-  Stream<Map<String, Object?>> get stream => _ws.stream.map(JsonUtf8.decodeMap);
+  Stream<Object?> get stream => _ws.stream.map(JsonUtf8.decodeAny);
 
   @override
-  StreamSink<Map<String, Object?>> get sink => _wsSink;
+  StreamSink<Object?> get sink => _wsSink;
 
   @override
   void close() {
diff --git a/packages/celest_core/lib/src/events/event_channel.web.dart b/packages/celest_core/lib/src/events/event_channel.web.dart
index db7fccd6..8c323302 100644
--- a/packages/celest_core/lib/src/events/event_channel.web.dart
+++ b/packages/celest_core/lib/src/events/event_channel.web.dart
@@ -5,8 +5,7 @@ import 'package:celest_core/src/events/event_channel.dart';
 import 'package:http/http.dart' as http;
 import 'package:stream_channel/stream_channel.dart';
 
-final class EventChannelPlatform
-    extends DelegatingStreamChannel<Map<String, Object?>>
+final class EventChannelPlatform extends DelegatingStreamChannel<Object?>
     implements EventChannel {
   EventChannelPlatform._(super._inner);
 
@@ -16,7 +15,7 @@ final class EventChannelPlatform
     http.Client? httpClient,
   }) {
     final sseClient = SseClient(serverUri: uri, httpClient: httpClient);
-    final completer = StreamChannelCompleter<Map<String, Object?>>();
+    final completer = StreamChannelCompleter<Object?>();
     sseClient.onConnected
         .then((_) => completer.setChannel(sseClient))
         .onError<Object>((e, st) {
diff --git a/packages/celest_core/lib/src/events/sse/sse_client.dart b/packages/celest_core/lib/src/events/sse/sse_client.dart
index be925f1c..89da6f7d 100644
--- a/packages/celest_core/lib/src/events/sse/sse_client.dart
+++ b/packages/celest_core/lib/src/events/sse/sse_client.dart
@@ -7,7 +7,7 @@ import 'package:stream_channel/stream_channel.dart';
 /// {@template celest.runtime.sse_client}
 /// A Server-Sent Events (SSE) client.
 /// {@endtemplate}
-abstract class SseClient with StreamChannelMixin<Map<String, Object?>> {
+abstract class SseClient with StreamChannelMixin<Object?> {
   /// Creates a new [SseClient] connected to the server at [serverUri].
   factory SseClient({
     required Uri serverUri,
diff --git a/packages/celest_core/lib/src/events/sse/sse_client.web.dart b/packages/celest_core/lib/src/events/sse/sse_client.web.dart
index daa95e10..5801a01a 100644
--- a/packages/celest_core/lib/src/events/sse/sse_client.web.dart
+++ b/packages/celest_core/lib/src/events/sse/sse_client.web.dart
@@ -56,18 +56,16 @@ final class SseClientPlatform extends SseClient {
 
   var _lastMessageId = -1;
 
-  late final StreamController<Map<String, Object?>> _incomingController =
+  late final StreamController<Object?> _incomingController =
       StreamController(onCancel: close);
 
   @override
-  Stream<Map<String, Object?>> get stream => _incomingController.stream;
+  Stream<Object?> get stream => _incomingController.stream;
 
-  late final StreamController<Map<String, Object?>> _outgoingController =
-      StreamController();
+  late final StreamController<Object?> _outgoingController = StreamController();
 
   @override
-  late final StreamSink<Map<String, Object?>> sink =
-      _outgoingController.sink.transform(
+  late final StreamSink<Object?> sink = _outgoingController.sink.transform(
     StreamSinkTransformer.fromHandlers(
       handleError: (error, stackTrace, sink) {
         _closeWithError(error, stackTrace);
@@ -118,9 +116,6 @@ final class SseClientPlatform extends SseClient {
     _logger.finest('Message event: $data');
     try {
       final message = jsonDecode(data);
-      if (message is! Map<String, Object?>) {
-        throw FormatException('Expected a Map, got ${message.runtimeType}');
-      }
       _incomingController.add(message);
     } on Object catch (e, st) {
       _logger.severe('Invalid message: $data', e, st);
@@ -131,7 +126,7 @@ final class SseClientPlatform extends SseClient {
     }
   }
 
-  Future<void> _onOutgoingMessage(Map<String, Object?> message) async {
+  Future<void> _onOutgoingMessage(Object? message) async {
     final uri = serverUri.replace(
       queryParameters: {
         ...serverUri.queryParametersAll,
diff --git a/packages/celest_core/lib/src/util/json.dart b/packages/celest_core/lib/src/util/json.dart
index ebe947c3..8b20d018 100644
--- a/packages/celest_core/lib/src/util/json.dart
+++ b/packages/celest_core/lib/src/util/json.dart
@@ -27,6 +27,23 @@ extension JsonUtf8 on Object {
     );
   }
 
+  /// Decodes a JSON map [body] from a `List<int>` or [String].
+  static Object? decodeAny(Object? body) {
+    return switch (body) {
+      List<int>() => body.isEmpty ? const {} : decode(body),
+      String() => body.isEmpty
+          ? const {}
+          : () {
+              try {
+                return jsonDecode(body);
+              } on Object {
+                return body;
+              }
+            }(),
+      _ => body,
+    };
+  }
+
   /// Decodes a JSON map [body] from a `List<int>` or [String].
   static Map<String, Object?> decodeMap(Object? body) {
     Object? decoded;
@@ -36,7 +53,11 @@ extension JsonUtf8 on Object {
         decoded = decode(body);
       case String():
         if (body.isEmpty) return const {};
-        decoded = jsonDecode(body);
+        try {
+          decoded = jsonDecode(body);
+        } on Object {
+          decoded = body;
+        }
       default:
         decoded = body;
     }