diff --git a/pkg/vm_service/CHANGELOG.md b/pkg/vm_service/CHANGELOG.md
index 5de2a68..727e2cd 100644
--- a/pkg/vm_service/CHANGELOG.md
+++ b/pkg/vm_service/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 9.1.0
+- Remove `required` keyword from most of the named parameters in the
+  constructors of the Dart API objects.
+
 ## 9.0.0
 - Update to version `3.58` of the spec.
 - Added optional `local` parameter to `lookupResolvedPackageUris` RPC.
diff --git a/pkg/vm_service/lib/src/vm_service.dart b/pkg/vm_service/lib/src/vm_service.dart
index 7d79815..1533b40 100644
--- a/pkg/vm_service/lib/src/vm_service.dart
+++ b/pkg/vm_service/lib/src/vm_service.dart
@@ -2845,8 +2845,8 @@
   int? dateLastServiceGC;
 
   AllocationProfile({
-    required this.members,
-    required this.memoryUsage,
+    this.members,
+    this.memoryUsage,
     this.dateLastAccumulatorReset,
     this.dateLastServiceGC,
   });
@@ -2906,8 +2906,8 @@
   dynamic value;
 
   BoundField({
-    required this.decl,
-    required this.value,
+    this.decl,
+    this.value,
   });
 
   BoundField._fromJson(Map<String, dynamic> json) {
@@ -2959,11 +2959,11 @@
   int? scopeEndTokenPos;
 
   BoundVariable({
-    required this.name,
-    required this.value,
-    required this.declarationTokenPos,
-    required this.scopeStartTokenPos,
-    required this.scopeEndTokenPos,
+    this.name,
+    this.value,
+    this.declarationTokenPos,
+    this.scopeStartTokenPos,
+    this.scopeEndTokenPos,
   });
 
   BoundVariable._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -3028,10 +3028,10 @@
   dynamic location;
 
   Breakpoint({
-    required this.breakpointNumber,
-    required this.enabled,
-    required this.resolved,
-    required this.location,
+    this.breakpointNumber,
+    this.enabled,
+    this.resolved,
+    this.location,
     required String id,
     this.isSyntheticAsyncContinuation,
   }) : super(
@@ -3096,8 +3096,8 @@
   List<InstanceRef>? typeParameters;
 
   ClassRef({
-    required this.name,
-    required this.library,
+    this.name,
+    this.library,
     required String id,
     this.location,
     this.typeParameters,
@@ -3209,15 +3209,15 @@
   List<ClassRef>? subclasses;
 
   Class({
-    required this.name,
-    required this.library,
-    required this.isAbstract,
-    required this.isConst,
-    required this.traceAllocations,
-    required this.interfaces,
-    required this.fields,
-    required this.functions,
-    required this.subclasses,
+    this.name,
+    this.library,
+    this.isAbstract,
+    this.isConst,
+    this.traceAllocations,
+    this.interfaces,
+    this.fields,
+    this.functions,
+    this.subclasses,
     required String id,
     this.location,
     this.typeParameters,
@@ -3321,11 +3321,11 @@
   int? instancesCurrent;
 
   ClassHeapStats({
-    required this.classRef,
-    required this.accumulatedSize,
-    required this.bytesCurrent,
-    required this.instancesAccumulated,
-    required this.instancesCurrent,
+    this.classRef,
+    this.accumulatedSize,
+    this.bytesCurrent,
+    this.instancesAccumulated,
+    this.instancesCurrent,
   });
 
   ClassHeapStats._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -3366,7 +3366,7 @@
   List<ClassRef>? classes;
 
   ClassList({
-    required this.classes,
+    this.classes,
   });
 
   ClassList._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -3403,8 +3403,8 @@
   /*CodeKind*/ String? kind;
 
   CodeRef({
-    required this.name,
-    required this.kind,
+    this.name,
+    this.kind,
     required String id,
   }) : super(
           id: id,
@@ -3448,8 +3448,8 @@
   /*CodeKind*/ String? kind;
 
   Code({
-    required this.name,
-    required this.kind,
+    this.name,
+    this.kind,
     required String id,
   }) : super(
           id: id,
@@ -3489,7 +3489,7 @@
   int? length;
 
   ContextRef({
-    required this.length,
+    this.length,
     required String id,
   }) : super(
           id: id,
@@ -3536,8 +3536,8 @@
   List<ContextElement>? variables;
 
   Context({
-    required this.length,
-    required this.variables,
+    this.length,
+    this.variables,
     required String id,
     this.parent,
   }) : super(
@@ -3585,7 +3585,7 @@
   dynamic value;
 
   ContextElement({
-    required this.value,
+    this.value,
   });
 
   ContextElement._fromJson(Map<String, dynamic> json) {
@@ -3637,8 +3637,8 @@
   int? pid;
 
   /// A list of functions seen in the relevant samples. These references can be
-  /// looked up using the indicies provided in a `CpuSample` `stack` to
-  /// determine which function was on the stack.
+  /// looked up using the indices provided in a `CpuSample` `stack` to determine
+  /// which function was on the stack.
   List<ProfileFunction>? functions;
 
   /// A list of samples collected in the range `[timeOriginMicros,
@@ -3646,15 +3646,15 @@
   List<CpuSample>? samples;
 
   CpuSamples({
-    required this.samplePeriod,
-    required this.maxStackDepth,
-    required this.sampleCount,
-    required this.timeSpan,
-    required this.timeOriginMicros,
-    required this.timeExtentMicros,
-    required this.pid,
-    required this.functions,
-    required this.samples,
+    this.samplePeriod,
+    this.maxStackDepth,
+    this.sampleCount,
+    this.timeSpan,
+    this.timeOriginMicros,
+    this.timeExtentMicros,
+    this.pid,
+    this.functions,
+    this.samples,
   });
 
   CpuSamples._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -3738,15 +3738,15 @@
   List<CpuSample>? samples;
 
   CpuSamplesEvent({
-    required this.samplePeriod,
-    required this.maxStackDepth,
-    required this.sampleCount,
-    required this.timeSpan,
-    required this.timeOriginMicros,
-    required this.timeExtentMicros,
-    required this.pid,
-    required this.functions,
-    required this.samples,
+    this.samplePeriod,
+    this.maxStackDepth,
+    this.sampleCount,
+    this.timeSpan,
+    this.timeOriginMicros,
+    this.timeExtentMicros,
+    this.pid,
+    this.functions,
+    this.samples,
   });
 
   CpuSamplesEvent._fromJson(Map<String, dynamic> json) {
@@ -3833,9 +3833,9 @@
   int? classId;
 
   CpuSample({
-    required this.tid,
-    required this.timestamp,
-    required this.stack,
+    this.tid,
+    this.timestamp,
+    this.stack,
     this.vmTag,
     this.userTag,
     this.truncated,
@@ -3885,8 +3885,8 @@
   String? message;
 
   ErrorRef({
-    required this.kind,
-    required this.message,
+    this.kind,
+    this.message,
     required String id,
   }) : super(
           id: id,
@@ -3942,8 +3942,8 @@
   InstanceRef? stacktrace;
 
   Error({
-    required this.kind,
-    required this.message,
+    this.kind,
+    this.message,
     required String id,
     this.exception,
     this.stacktrace,
@@ -4187,8 +4187,8 @@
   ByteData? data;
 
   Event({
-    required this.kind,
-    required this.timestamp,
+    this.kind,
+    this.timestamp,
     this.isolate,
     this.vm,
     this.breakpoint,
@@ -4347,12 +4347,12 @@
   SourceLocation? location;
 
   FieldRef({
-    required this.name,
-    required this.owner,
-    required this.declaredType,
-    required this.isConst,
-    required this.isFinal,
-    required this.isStatic,
+    this.name,
+    this.owner,
+    this.declaredType,
+    this.isConst,
+    this.isFinal,
+    this.isStatic,
     required String id,
     this.location,
   }) : super(
@@ -4444,12 +4444,12 @@
   dynamic staticValue;
 
   Field({
-    required this.name,
-    required this.owner,
-    required this.declaredType,
-    required this.isConst,
-    required this.isFinal,
-    required this.isStatic,
+    this.name,
+    this.owner,
+    this.declaredType,
+    this.isConst,
+    this.isFinal,
+    this.isStatic,
     required String id,
     this.location,
     this.staticValue,
@@ -4522,9 +4522,9 @@
   String? valueAsString;
 
   Flag({
-    required this.name,
-    required this.comment,
-    required this.modified,
+    this.name,
+    this.comment,
+    this.modified,
     this.valueAsString,
   });
 
@@ -4559,7 +4559,7 @@
   List<Flag>? flags;
 
   FlagList({
-    required this.flags,
+    this.flags,
   });
 
   FlagList._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -4605,7 +4605,7 @@
   /*FrameKind*/ String? kind;
 
   Frame({
-    required this.index,
+    this.index,
     this.function,
     this.code,
     this.location,
@@ -4684,11 +4684,11 @@
   SourceLocation? location;
 
   FuncRef({
-    required this.name,
-    required this.owner,
-    required this.isStatic,
-    required this.isConst,
-    required this.implicit,
+    this.name,
+    this.owner,
+    this.isStatic,
+    this.isConst,
+    this.implicit,
     required String id,
     this.location,
   }) : super(
@@ -4775,12 +4775,12 @@
   CodeRef? code;
 
   Func({
-    required this.name,
-    required this.owner,
-    required this.isStatic,
-    required this.isConst,
-    required this.implicit,
-    required this.signature,
+    this.name,
+    this.owner,
+    this.isStatic,
+    this.isConst,
+    this.implicit,
+    this.signature,
     required String id,
     this.location,
     this.code,
@@ -4980,9 +4980,9 @@
   String? debugName;
 
   InstanceRef({
-    required this.kind,
-    required this.identityHashCode,
-    required this.classRef,
+    this.kind,
+    this.identityHashCode,
+    this.classRef,
     required String id,
     this.valueAsString,
     this.valueAsStringIsTruncated,
@@ -5389,9 +5389,9 @@
   String? debugName;
 
   Instance({
-    required this.kind,
-    required this.identityHashCode,
-    required this.classRef,
+    this.kind,
+    this.identityHashCode,
+    this.classRef,
     required String id,
     this.valueAsString,
     this.valueAsStringIsTruncated,
@@ -5579,10 +5579,10 @@
   bool? isSystemIsolate;
 
   IsolateRef({
-    required this.id,
-    required this.number,
-    required this.name,
-    required this.isSystemIsolate,
+    this.id,
+    this.number,
+    this.name,
+    this.isSystemIsolate,
   });
 
   IsolateRef._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -5683,19 +5683,19 @@
   List<String>? extensionRPCs;
 
   Isolate({
-    required this.id,
-    required this.number,
-    required this.name,
-    required this.isSystemIsolate,
-    required this.isolateFlags,
-    required this.startTime,
-    required this.runnable,
-    required this.livePorts,
-    required this.pauseOnExit,
-    required this.pauseEvent,
-    required this.libraries,
-    required this.breakpoints,
-    required this.exceptionPauseMode,
+    this.id,
+    this.number,
+    this.name,
+    this.isSystemIsolate,
+    this.isolateFlags,
+    this.startTime,
+    this.runnable,
+    this.livePorts,
+    this.pauseOnExit,
+    this.pauseEvent,
+    this.libraries,
+    this.breakpoints,
+    this.exceptionPauseMode,
     this.rootLib,
     this.error,
     this.extensionRPCs,
@@ -5779,8 +5779,8 @@
   String? valueAsString;
 
   IsolateFlag({
-    required this.name,
-    required this.valueAsString,
+    this.name,
+    this.valueAsString,
   });
 
   IsolateFlag._fromJson(Map<String, dynamic> json) {
@@ -5821,10 +5821,10 @@
   bool? isSystemIsolateGroup;
 
   IsolateGroupRef({
-    required this.id,
-    required this.number,
-    required this.name,
-    required this.isSystemIsolateGroup,
+    this.id,
+    this.number,
+    this.name,
+    this.isSystemIsolateGroup,
   });
 
   IsolateGroupRef._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -5881,11 +5881,11 @@
   List<IsolateRef>? isolates;
 
   IsolateGroup({
-    required this.id,
-    required this.number,
-    required this.name,
-    required this.isSystemIsolateGroup,
-    required this.isolates,
+    this.id,
+    this.number,
+    this.name,
+    this.isSystemIsolateGroup,
+    this.isolates,
   });
 
   IsolateGroup._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -5933,7 +5933,7 @@
   List<InboundReference>? references;
 
   InboundReferences({
-    required this.references,
+    this.references,
   });
 
   InboundReferences._fromJson(Map<String, dynamic> json)
@@ -5979,7 +5979,7 @@
   FieldRef? parentField;
 
   InboundReference({
-    required this.source,
+    this.source,
     this.parentListIndex,
     this.parentField,
   });
@@ -6016,8 +6016,8 @@
   List<ObjRef>? instances;
 
   InstanceSet({
-    required this.totalCount,
-    required this.instances,
+    this.totalCount,
+    this.instances,
   });
 
   InstanceSet._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -6057,8 +6057,8 @@
   String? uri;
 
   LibraryRef({
-    required this.name,
-    required this.uri,
+    this.name,
+    this.uri,
     required String id,
   }) : super(
           id: id,
@@ -6122,14 +6122,14 @@
   List<ClassRef>? classes;
 
   Library({
-    required this.name,
-    required this.uri,
-    required this.debuggable,
-    required this.dependencies,
-    required this.scripts,
-    required this.variables,
-    required this.functions,
-    required this.classes,
+    this.name,
+    this.uri,
+    this.debuggable,
+    this.dependencies,
+    this.scripts,
+    this.variables,
+    this.functions,
+    this.classes,
     required String id,
   }) : super(
           id: id,
@@ -6208,10 +6208,10 @@
   List<String>? hides;
 
   LibraryDependency({
-    required this.isImport,
-    required this.isDeferred,
-    required this.prefix,
-    required this.target,
+    this.isImport,
+    this.isDeferred,
+    this.prefix,
+    this.target,
     this.shows,
     this.hides,
   });
@@ -6276,14 +6276,14 @@
   InstanceRef? stackTrace;
 
   LogRecord({
-    required this.message,
-    required this.time,
-    required this.level,
-    required this.sequenceNumber,
-    required this.loggerName,
-    required this.zone,
-    required this.error,
-    required this.stackTrace,
+    this.message,
+    this.time,
+    this.level,
+    this.sequenceNumber,
+    this.loggerName,
+    this.zone,
+    this.error,
+    this.stackTrace,
   });
 
   LogRecord._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -6336,8 +6336,8 @@
   dynamic value;
 
   MapAssociation({
-    required this.key,
-    required this.value,
+    this.key,
+    this.value,
   });
 
   MapAssociation._fromJson(Map<String, dynamic> json) {
@@ -6383,9 +6383,9 @@
   int? heapUsage;
 
   MemoryUsage({
-    required this.externalUsage,
-    required this.heapCapacity,
-    required this.heapUsage,
+    this.externalUsage,
+    this.heapCapacity,
+    this.heapUsage,
   });
 
   MemoryUsage._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -6443,10 +6443,10 @@
   SourceLocation? location;
 
   Message({
-    required this.index,
-    required this.name,
-    required this.messageObjectId,
-    required this.size,
+    this.index,
+    this.name,
+    this.messageObjectId,
+    this.size,
     this.handler,
     this.location,
   });
@@ -6495,7 +6495,7 @@
   String? name;
 
   NativeFunction({
-    required this.name,
+    this.name,
   });
 
   NativeFunction._fromJson(Map<String, dynamic> json) {
@@ -6523,7 +6523,7 @@
   String? valueAsString;
 
   NullValRef({
-    required this.valueAsString,
+    this.valueAsString,
   }) : super(
           id: 'instance/null',
           identityHashCode: 0,
@@ -6575,7 +6575,7 @@
   String? valueAsString;
 
   NullVal({
-    required this.valueAsString,
+    this.valueAsString,
   }) : super(
           id: 'instance/null',
           identityHashCode: 0,
@@ -6633,7 +6633,7 @@
   bool? fixedId;
 
   ObjRef({
-    required this.id,
+    this.id,
     this.fixedId,
   });
 
@@ -6702,7 +6702,7 @@
   int? size;
 
   Obj({
-    required this.id,
+    this.id,
     this.fixedId,
     this.classRef,
     this.size,
@@ -6761,8 +6761,8 @@
   bool? required;
 
   Parameter({
-    required this.parameterType,
-    required this.fixed,
+    this.parameterType,
+    this.fixed,
     this.name,
     this.required,
   });
@@ -6801,7 +6801,7 @@
   List<InstanceRef>? ports;
 
   PortList({
-    required this.ports,
+    this.ports,
   });
 
   PortList._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -6851,11 +6851,11 @@
   dynamic function;
 
   ProfileFunction({
-    required this.kind,
-    required this.inclusiveTicks,
-    required this.exclusiveTicks,
-    required this.resolvedUrl,
-    required this.function,
+    this.kind,
+    this.inclusiveTicks,
+    this.exclusiveTicks,
+    this.resolvedUrl,
+    this.function,
   });
 
   ProfileFunction._fromJson(Map<String, dynamic> json) {
@@ -6896,7 +6896,7 @@
   List<Protocol>? protocols;
 
   ProtocolList({
-    required this.protocols,
+    this.protocols,
   });
 
   ProtocolList._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -6936,9 +6936,9 @@
   int? minor;
 
   Protocol({
-    required this.protocolName,
-    required this.major,
-    required this.minor,
+    this.protocolName,
+    this.major,
+    this.minor,
   });
 
   Protocol._fromJson(Map<String, dynamic> json) {
@@ -6969,7 +6969,7 @@
   ProcessMemoryItem? root;
 
   ProcessMemoryUsage({
-    required this.root,
+    this.root,
   });
 
   ProcessMemoryUsage._fromJson(Map<String, dynamic> json)
@@ -7012,10 +7012,10 @@
   List<ProcessMemoryItem>? children;
 
   ProcessMemoryItem({
-    required this.name,
-    required this.description,
-    required this.size,
-    required this.children,
+    this.name,
+    this.description,
+    this.size,
+    this.children,
   });
 
   ProcessMemoryItem._fromJson(Map<String, dynamic> json) {
@@ -7052,7 +7052,7 @@
   bool? success;
 
   ReloadReport({
-    required this.success,
+    this.success,
   });
 
   ReloadReport._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7096,7 +7096,7 @@
   String? parentField;
 
   RetainingObject({
-    required this.value,
+    this.value,
     this.parentListIndex,
     this.parentMapKey,
     this.parentField,
@@ -7141,9 +7141,9 @@
   List<RetainingObject>? elements;
 
   RetainingPath({
-    required this.length,
-    required this.gcRootType,
-    required this.elements,
+    this.length,
+    this.gcRootType,
+    this.elements,
   });
 
   RetainingPath._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7216,8 +7216,8 @@
   String? valueAsString;
 
   Sentinel({
-    required this.kind,
-    required this.valueAsString,
+    this.kind,
+    this.valueAsString,
   });
 
   Sentinel._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7252,7 +7252,7 @@
   String? uri;
 
   ScriptRef({
-    required this.uri,
+    this.uri,
     required String id,
   }) : super(
           id: id,
@@ -7338,8 +7338,8 @@
   List<List<int>>? tokenPosTable;
 
   Script({
-    required this.uri,
-    required this.library,
+    this.uri,
+    this.library,
     required String id,
     this.lineOffset,
     this.columnOffset,
@@ -7424,7 +7424,7 @@
   List<ScriptRef>? scripts;
 
   ScriptList({
-    required this.scripts,
+    this.scripts,
   });
 
   ScriptList._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7476,8 +7476,8 @@
   int? column;
 
   SourceLocation({
-    required this.script,
-    required this.tokenPos,
+    this.script,
+    this.tokenPos,
     this.endTokenPos,
     this.line,
     this.column,
@@ -7533,8 +7533,8 @@
   List<ScriptRef>? scripts;
 
   SourceReport({
-    required this.ranges,
-    required this.scripts,
+    this.ranges,
+    this.scripts,
   });
 
   SourceReport._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7580,8 +7580,8 @@
   List<int>? misses;
 
   SourceReportCoverage({
-    required this.hits,
-    required this.misses,
+    this.hits,
+    this.misses,
   });
 
   SourceReportCoverage._fromJson(Map<String, dynamic> json) {
@@ -7648,10 +7648,10 @@
   SourceReportCoverage? branchCoverage;
 
   SourceReportRange({
-    required this.scriptIndex,
-    required this.startPos,
-    required this.endPos,
-    required this.compiled,
+    this.scriptIndex,
+    this.startPos,
+    this.endPos,
+    this.compiled,
     this.error,
     this.coverage,
     this.possibleBreakpoints,
@@ -7726,9 +7726,9 @@
   bool? truncated;
 
   Stack({
-    required this.frames,
-    required this.messages,
-    required this.truncated,
+    this.frames,
+    this.messages,
+    this.truncated,
     this.asyncCausalFrames,
     this.awaiterFrames,
   });
@@ -7814,9 +7814,9 @@
   int? timeExtentMicros;
 
   Timeline({
-    required this.traceEvents,
-    required this.timeOriginMicros,
-    required this.timeExtentMicros,
+    this.traceEvents,
+    this.timeOriginMicros,
+    this.timeExtentMicros,
   });
 
   Timeline._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7888,9 +7888,9 @@
   List<String>? recordedStreams;
 
   TimelineFlags({
-    required this.recorderName,
-    required this.availableStreams,
-    required this.recordedStreams,
+    this.recorderName,
+    this.availableStreams,
+    this.recordedStreams,
   });
 
   TimelineFlags._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7927,7 +7927,7 @@
   int? timestamp;
 
   Timestamp({
-    required this.timestamp,
+    this.timestamp,
   });
 
   Timestamp._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -7959,7 +7959,7 @@
   String? name;
 
   TypeArgumentsRef({
-    required this.name,
+    this.name,
     required String id,
   }) : super(
           id: id,
@@ -8006,8 +8006,8 @@
   List<InstanceRef>? types;
 
   TypeArguments({
-    required this.name,
-    required this.types,
+    this.name,
+    this.types,
     required String id,
   }) : super(
           id: id,
@@ -8058,9 +8058,9 @@
   TypeArgumentsRef? defaults;
 
   TypeParameters({
-    required this.names,
-    required this.bounds,
-    required this.defaults,
+    this.names,
+    this.bounds,
+    this.defaults,
   });
 
   TypeParameters._fromJson(Map<String, dynamic> json) {
@@ -8167,7 +8167,7 @@
   List<String?>? uris;
 
   UriList({
-    required this.uris,
+    this.uris,
   });
 
   UriList._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -8204,8 +8204,8 @@
   int? minor;
 
   Version({
-    required this.major,
-    required this.minor,
+    this.major,
+    this.minor,
   });
 
   Version._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -8239,7 +8239,7 @@
   String? name;
 
   VMRef({
-    required this.name,
+    this.name,
   });
 
   VMRef._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
@@ -8305,18 +8305,18 @@
   List<IsolateGroupRef>? systemIsolateGroups;
 
   VM({
-    required this.name,
-    required this.architectureBits,
-    required this.hostCPU,
-    required this.operatingSystem,
-    required this.targetCPU,
-    required this.version,
-    required this.pid,
-    required this.startTime,
-    required this.isolates,
-    required this.isolateGroups,
-    required this.systemIsolates,
-    required this.systemIsolateGroups,
+    this.name,
+    this.architectureBits,
+    this.hostCPU,
+    this.operatingSystem,
+    this.targetCPU,
+    this.version,
+    this.pid,
+    this.startTime,
+    this.isolates,
+    this.isolateGroups,
+    this.systemIsolates,
+    this.systemIsolateGroups,
   });
 
   VM._fromJson(Map<String, dynamic> json) : super._fromJson(json) {
diff --git a/pkg/vm_service/pubspec.yaml b/pkg/vm_service/pubspec.yaml
index 68572038..0f11496 100644
--- a/pkg/vm_service/pubspec.yaml
+++ b/pkg/vm_service/pubspec.yaml
@@ -1,5 +1,5 @@
 name: vm_service
-version: 9.0.0
+version: 9.1.0
 description: >-
   A library to communicate with a service implementing the Dart VM
   service protocol.
diff --git a/pkg/vm_service/tool/dart/generate_dart.dart b/pkg/vm_service/tool/dart/generate_dart.dart
index e15328c..ee8df6c 100644
--- a/pkg/vm_service/tool/dart/generate_dart.dart
+++ b/pkg/vm_service/tool/dart/generate_dart.dart
@@ -1829,13 +1829,10 @@
   }
 
   void generateNamedParameter(DartGenerator gen, {bool fromParent = false}) {
-    if (!optional) {
-      gen.write('required ');
-    }
     if (fromParent) {
       String? typeName =
           api.isEnumName(type.name) ? '/*${type.name}*/ String' : type.name;
-      gen.writeStatement('$typeName ${generatableName},');
+      gen.writeStatement('required $typeName ${generatableName},');
     } else {
       gen.writeStatement('this.${generatableName},');
     }