diff --git a/runtime/docs/compiler/aot/entry_point_pragma.md b/runtime/docs/compiler/aot/entry_point_pragma.md
index 3694a98444b..fc68848a9d8 100644
--- a/runtime/docs/compiler/aot/entry_point_pragma.md
+++ b/runtime/docs/compiler/aot/entry_point_pragma.md
@@ -35,7 +35,7 @@ Any one of the following forms may be attached to a class:
 ```dart
 @pragma("vm:entry-point")
 @pragma("vm:entry-point", true/false)
-@pragma("vm:entry-point", !const bool.formEnvironment("dart.vm.product"))
+@pragma("vm:entry-point", !const bool.fromEnvironment("dart.vm.product"))
 class C { ... }
 ```
 
@@ -54,7 +54,7 @@ getters, setters and constructors):
 ```dart
 @pragma("vm:entry-point")
 @pragma("vm:entry-point", true/false)
-@pragma("vm:entry-point", !const bool.formEnvironment("dart.vm.product"))
+@pragma("vm:entry-point", !const bool.fromEnvironment("dart.vm.product"))
 @pragma("vm:entry-point", "get")
 @pragma("vm:entry-point", "call")
 void foo() { ... }
@@ -83,7 +83,7 @@ three forms may be attached to static fields.
 @pragma("vm:entry-point")
 @pragma("vm:entry-point", null)
 @pragma("vm:entry-point", true/false)
-@pragma("vm:entry-point", !const bool.formEnvironment("dart.vm.product"))
+@pragma("vm:entry-point", !const bool.fromEnvironment("dart.vm.product"))
 @pragma("vm:entry-point", "get"/"set")
 int foo;
 ```
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index a3e51a4bad6..181fd2b9059 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -1042,9 +1042,9 @@ abstract class VM extends ServiceObjectOwner implements M.VM {
       nativeZoneMemoryUsage = map['_nativeZoneMemoryUsage'];
     }
     pid = map['pid'];
-    mallocUsed = map['_mallocUsed'];
-    mallocCapacity = map['_mallocCapacity'];
-    mallocImplementation = map['_mallocImplementation'];
+    mallocUsed = map['_mallocUsed'] ?? -1;
+    mallocCapacity = map['_mallocCapacity'] ?? -1;
+    mallocImplementation = map['_mallocImplementation'] ?? 'unknown';
     embedder = map['_embedder'];
     currentMemory = map['_currentMemory'];
     maxRSS = map['_maxRSS'];
diff --git a/runtime/observatory/tests/service/developer_extension_test.dart b/runtime/observatory/tests/service/developer_extension_test.dart
index 9b18926ce0c..2983cf45da7 100644
--- a/runtime/observatory/tests/service/developer_extension_test.dart
+++ b/runtime/observatory/tests/service/developer_extension_test.dart
@@ -43,10 +43,15 @@ Future<ServiceExtensionResponse> Handler(String method, Map paremeters) {
 }
 
 void test() {
+  Expect.isFalse(extensionStreamHasListener);
+  postEvent('Disabled event', {'foo': 'bar'});
+
   registerExtension('ext..delay', Handler);
   debugger();
+  Expect.isTrue(extensionStreamHasListener);
   postEvent('ALPHA', {'cat': 'dog'});
   debugger();
+
   registerExtension('ext..error', Handler);
   registerExtension('ext..exception', Handler);
   registerExtension('ext..success', Handler);
@@ -56,7 +61,7 @@ void test() {
   } catch (e) {
     exceptionThrown = true;
   }
-  // This check is running in the target process so we can't used package:test.
+  // This check is running in the target process so we can't use package:test.
   Expect.isTrue(exceptionThrown);
 }
 
diff --git a/runtime/observatory_2/tests/service_2/developer_extension_test.dart b/runtime/observatory_2/tests/service_2/developer_extension_test.dart
index 61cab8ff4c2..e6df8972d20 100644
--- a/runtime/observatory_2/tests/service_2/developer_extension_test.dart
+++ b/runtime/observatory_2/tests/service_2/developer_extension_test.dart
@@ -55,7 +55,7 @@ void test() {
   } catch (e) {
     exceptionThrown = true;
   }
-  // This check is running in the target process so we can't used package:test.
+  // This check is running in the target process so we can't use package:test.
   Expect.isTrue(exceptionThrown);
 }
 
diff --git a/runtime/vm/compiler/frontend/kernel_to_il.cc b/runtime/vm/compiler/frontend/kernel_to_il.cc
index 905570f7aa7..a7699015535 100644
--- a/runtime/vm/compiler/frontend/kernel_to_il.cc
+++ b/runtime/vm/compiler/frontend/kernel_to_il.cc
@@ -952,6 +952,7 @@ bool FlowGraphBuilder::IsRecognizedMethodForFlowGraph(
     case MethodRecognizer::kReachabilityFence:
     case MethodRecognizer::kUtf8DecoderScan:
     case MethodRecognizer::kHas63BitSmis:
+    case MethodRecognizer::kExtensionStreamHasListener:
 #define CASE(method, slot) case MethodRecognizer::k##method:
       LOAD_NATIVE_FIELD(CASE)
       STORE_NATIVE_FIELD(CASE)
@@ -1488,6 +1489,17 @@ FlowGraph* FlowGraphBuilder::BuildGraphOfRecognizedMethod(
 #else
       body += Constant(Bool::False());
 #endif  // defined(ARCH_IS_64_BIT)
+    } break;
+    case MethodRecognizer::kExtensionStreamHasListener: {
+#ifdef PRODUCT
+      body += Constant(Bool::False());
+#else
+      body += LoadServiceExtensionStream();
+      body += RawLoadField(compiler::target::StreamInfo::enabled_offset());
+      // StreamInfo::enabled_ is a std::atomic<intptr_t>. This is effectively
+      // relaxed order access, which is acceptable for this use case.
+      body += IntToBool();
+#endif  // PRODUCT
     } break;
     case MethodRecognizer::kFfiAsExternalTypedDataInt8:
     case MethodRecognizer::kFfiAsExternalTypedDataInt16:
@@ -4077,6 +4089,14 @@ Fragment FlowGraphBuilder::LoadIsolate() {
   return body;
 }
 
+Fragment FlowGraphBuilder::LoadServiceExtensionStream() {
+  Fragment body;
+  body += LoadThread();
+  body +=
+      LoadUntagged(compiler::target::Thread::service_extension_stream_offset());
+  return body;
+}
+
 // TODO(http://dartbug.com/47487): Support unboxed output value.
 Fragment FlowGraphBuilder::BoolToInt() {
   // TODO(http://dartbug.com/36855) Build IfThenElseInstr, instead of letting
diff --git a/runtime/vm/compiler/frontend/kernel_to_il.h b/runtime/vm/compiler/frontend/kernel_to_il.h
index 2a92d6ae212..eeab45d479d 100644
--- a/runtime/vm/compiler/frontend/kernel_to_il.h
+++ b/runtime/vm/compiler/frontend/kernel_to_il.h
@@ -282,6 +282,9 @@ class FlowGraphBuilder : public BaseFlowGraphBuilder {
   // Loads the (untagged) isolate address.
   Fragment LoadIsolate();
 
+  // Loads the (untagged) service extension stream address.
+  Fragment LoadServiceExtensionStream();
+
   // Converts a true to 1 and false to 0.
   Fragment BoolToInt();
 
diff --git a/runtime/vm/compiler/recognized_methods_list.h b/runtime/vm/compiler/recognized_methods_list.h
index 7055a025d60..0331e006143 100644
--- a/runtime/vm/compiler/recognized_methods_list.h
+++ b/runtime/vm/compiler/recognized_methods_list.h
@@ -268,6 +268,7 @@ namespace dart {
   V(_RootZone, runUnary, RootZoneRunUnary, 0xb607f8bf)                         \
   V(_FutureListener, handleValue, FutureListenerHandleValue, 0x438115a8)       \
   V(::, has63BitSmis, Has63BitSmis, 0xf61b56f1)                                \
+  V(::, get:extensionStreamHasListener, ExtensionStreamHasListener, 0xfab46343)\
 
 // List of intrinsics:
 // (class-name, function-name, intrinsification method, fingerprint).
diff --git a/runtime/vm/compiler/runtime_api.h b/runtime/vm/compiler/runtime_api.h
index 41ad454c44f..f36cdc73647 100644
--- a/runtime/vm/compiler/runtime_api.h
+++ b/runtime/vm/compiler/runtime_api.h
@@ -1068,6 +1068,11 @@ class TimelineStream : public AllStatic {
   static word enabled_offset();
 };
 
+class StreamInfo : public AllStatic {
+ public:
+  static word enabled_offset();
+};
+
 class VMHandles : public AllStatic {
  public:
   static constexpr intptr_t kOffsetOfRawPtrInHandle = kWordSize;
@@ -1099,6 +1104,7 @@ class Thread : public AllStatic {
   static uword exit_through_runtime_call();
   static uword exit_through_ffi();
   static word dart_stream_offset();
+  static word service_extension_stream_offset();
   static word predefined_symbols_address_offset();
   static word optimize_entry_offset();
   static word deoptimize_entry_offset();
diff --git a/runtime/vm/compiler/runtime_offsets_extracted.h b/runtime/vm/compiler/runtime_offsets_extracted.h
index 04a65b3697a..49c7e2649fe 100644
--- a/runtime/vm/compiler/runtime_offsets_extracted.h
+++ b/runtime/vm/compiler/runtime_offsets_extracted.h
@@ -240,6 +240,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     8;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 4;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word String_hash_offset = 8;
 static constexpr dart::compiler::target::word String_length_offset = 4;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 4;
@@ -287,6 +288,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 796;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 820;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 224;
@@ -330,7 +333,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     788;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 40;
-static constexpr dart::compiler::target::word Thread_isolate_group_offset = 820;
+static constexpr dart::compiler::target::word Thread_isolate_group_offset = 824;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     64;
 static constexpr dart::compiler::target::word
@@ -832,6 +835,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -880,6 +884,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -924,7 +930,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1576;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -1427,6 +1433,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     8;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 4;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word String_hash_offset = 8;
 static constexpr dart::compiler::target::word String_length_offset = 4;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 4;
@@ -1474,6 +1481,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 764;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 788;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 224;
@@ -1517,7 +1526,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     756;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 40;
-static constexpr dart::compiler::target::word Thread_isolate_group_offset = 788;
+static constexpr dart::compiler::target::word Thread_isolate_group_offset = 792;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     64;
 static constexpr dart::compiler::target::word
@@ -2016,6 +2025,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -2064,6 +2074,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -2108,7 +2120,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1640;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -2613,6 +2625,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -2661,6 +2674,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -2705,7 +2720,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1576;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -3209,6 +3224,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -3257,6 +3273,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -3301,7 +3319,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1640;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -3805,6 +3823,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     8;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 4;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word String_hash_offset = 8;
 static constexpr dart::compiler::target::word String_length_offset = 4;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 4;
@@ -3852,6 +3871,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 836;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 860;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 224;
@@ -3895,7 +3916,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     828;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 40;
-static constexpr dart::compiler::target::word Thread_isolate_group_offset = 860;
+static constexpr dart::compiler::target::word Thread_isolate_group_offset = 864;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     64;
 static constexpr dart::compiler::target::word
@@ -4399,6 +4420,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -4447,6 +4469,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1648;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1688;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -4491,7 +4515,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1632;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1688;
+    1696;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -4991,6 +5015,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     8;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 4;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word String_hash_offset = 8;
 static constexpr dart::compiler::target::word String_length_offset = 4;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 4;
@@ -5038,6 +5063,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 796;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 820;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 224;
@@ -5081,7 +5108,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     788;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 40;
-static constexpr dart::compiler::target::word Thread_isolate_group_offset = 820;
+static constexpr dart::compiler::target::word Thread_isolate_group_offset = 824;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     64;
 static constexpr dart::compiler::target::word
@@ -5577,6 +5604,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -5625,6 +5653,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -5669,7 +5699,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1576;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -6166,6 +6196,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     8;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 4;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word String_hash_offset = 8;
 static constexpr dart::compiler::target::word String_length_offset = 4;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 4;
@@ -6213,6 +6244,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 764;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 788;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 224;
@@ -6256,7 +6289,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     756;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 40;
-static constexpr dart::compiler::target::word Thread_isolate_group_offset = 788;
+static constexpr dart::compiler::target::word Thread_isolate_group_offset = 792;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     64;
 static constexpr dart::compiler::target::word
@@ -6749,6 +6782,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -6797,6 +6831,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -6841,7 +6877,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1640;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -7340,6 +7376,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -7388,6 +7425,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -7432,7 +7471,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1576;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -7930,6 +7969,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -7978,6 +8018,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -8022,7 +8064,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1640;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -8520,6 +8562,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     8;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 4;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word String_hash_offset = 8;
 static constexpr dart::compiler::target::word String_length_offset = 4;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 4;
@@ -8567,6 +8610,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 836;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 860;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 224;
@@ -8610,7 +8655,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     828;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 40;
-static constexpr dart::compiler::target::word Thread_isolate_group_offset = 860;
+static constexpr dart::compiler::target::word Thread_isolate_group_offset = 864;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     64;
 static constexpr dart::compiler::target::word
@@ -9108,6 +9153,7 @@ static constexpr dart::compiler::target::word
 static constexpr dart::compiler::target::word StoreBufferBlock_pointers_offset =
     16;
 static constexpr dart::compiler::target::word StoreBufferBlock_top_offset = 8;
+static constexpr dart::compiler::target::word StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word String_hash_offset = 4;
 static constexpr dart::compiler::target::word String_length_offset = 8;
 static constexpr dart::compiler::target::word SubtypeTestCache_cache_offset = 8;
@@ -9156,6 +9202,8 @@ static constexpr dart::compiler::target::word
     Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     Thread_double_truncate_round_supported_offset = 1648;
+static constexpr dart::compiler::target::word
+    Thread_service_extension_stream_offset = 1688;
 static constexpr dart::compiler::target::word Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word Thread_optimize_stub_offset = 424;
@@ -9200,7 +9248,7 @@ static constexpr dart::compiler::target::word Thread_exit_through_ffi_offset =
     1632;
 static constexpr dart::compiler::target::word Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word Thread_isolate_group_offset =
-    1688;
+    1696;
 static constexpr dart::compiler::target::word Thread_field_table_values_offset =
     128;
 static constexpr dart::compiler::target::word
@@ -9735,6 +9783,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 8;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     4;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 4;
 static constexpr dart::compiler::target::word
@@ -9786,6 +9835,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 796;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 820;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -9831,7 +9882,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 788;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 40;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    820;
+    824;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 64;
 static constexpr dart::compiler::target::word
@@ -10401,6 +10452,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -10452,6 +10504,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -10497,7 +10551,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1576;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -11073,6 +11127,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -11124,6 +11179,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -11169,7 +11226,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1640;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -11742,6 +11799,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -11793,6 +11851,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -11838,7 +11898,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1576;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -12410,6 +12470,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -12461,6 +12522,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -12506,7 +12569,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1640;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -13079,6 +13142,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 8;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     4;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 4;
 static constexpr dart::compiler::target::word
@@ -13130,6 +13194,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 836;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 860;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -13175,7 +13241,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 828;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 40;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    860;
+    864;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 64;
 static constexpr dart::compiler::target::word
@@ -13747,6 +13813,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -13798,6 +13865,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1648;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1688;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -13843,7 +13912,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1632;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1688;
+    1696;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -14411,6 +14480,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 8;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     4;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 4;
 static constexpr dart::compiler::target::word
@@ -14462,6 +14532,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 796;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 820;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -14507,7 +14579,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 788;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 40;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    820;
+    824;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 64;
 static constexpr dart::compiler::target::word
@@ -15070,6 +15142,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -15121,6 +15194,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -15166,7 +15241,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1576;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -15735,6 +15810,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -15786,6 +15862,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -15831,7 +15909,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1640;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -16397,6 +16475,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -16448,6 +16527,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1592;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1632;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -16493,7 +16574,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1576;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1632;
+    1640;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -17058,6 +17139,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -17109,6 +17191,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1656;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1696;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -17154,7 +17238,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1640;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1696;
+    1704;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
@@ -17720,6 +17804,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 8;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     4;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 4;
 static constexpr dart::compiler::target::word
@@ -17771,6 +17856,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 44;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 836;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 860;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     312;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -17816,7 +17903,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 828;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 40;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    860;
+    864;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 64;
 static constexpr dart::compiler::target::word
@@ -18381,6 +18468,7 @@ static constexpr dart::compiler::target::word
     AOT_StoreBufferBlock_pointers_offset = 16;
 static constexpr dart::compiler::target::word AOT_StoreBufferBlock_top_offset =
     8;
+static constexpr dart::compiler::target::word AOT_StreamInfo_enabled_offset = 8;
 static constexpr dart::compiler::target::word AOT_String_hash_offset = 4;
 static constexpr dart::compiler::target::word AOT_String_length_offset = 8;
 static constexpr dart::compiler::target::word
@@ -18432,6 +18520,8 @@ static constexpr dart::compiler::target::word
     AOT_Thread_dispatch_table_array_offset = 88;
 static constexpr dart::compiler::target::word
     AOT_Thread_double_truncate_round_supported_offset = 1648;
+static constexpr dart::compiler::target::word
+    AOT_Thread_service_extension_stream_offset = 1688;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_entry_offset =
     600;
 static constexpr dart::compiler::target::word AOT_Thread_optimize_stub_offset =
@@ -18477,7 +18567,7 @@ static constexpr dart::compiler::target::word
     AOT_Thread_exit_through_ffi_offset = 1632;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_offset = 80;
 static constexpr dart::compiler::target::word AOT_Thread_isolate_group_offset =
-    1688;
+    1696;
 static constexpr dart::compiler::target::word
     AOT_Thread_field_table_values_offset = 128;
 static constexpr dart::compiler::target::word
diff --git a/runtime/vm/compiler/runtime_offsets_list.h b/runtime/vm/compiler/runtime_offsets_list.h
index 1e03be5f276..65982cf1f2c 100644
--- a/runtime/vm/compiler/runtime_offsets_list.h
+++ b/runtime/vm/compiler/runtime_offsets_list.h
@@ -186,6 +186,7 @@
   FIELD(SingleTargetCache, upper_limit_offset)                                 \
   FIELD(StoreBufferBlock, pointers_offset)                                     \
   FIELD(StoreBufferBlock, top_offset)                                          \
+  FIELD(StreamInfo, enabled_offset)                                            \
   FIELD(String, hash_offset)                                                   \
   FIELD(String, length_offset)                                                 \
   FIELD(SubtypeTestCache, cache_offset)                                        \
@@ -213,6 +214,7 @@
   FIELD(Thread, dart_stream_offset)                                            \
   FIELD(Thread, dispatch_table_array_offset)                                   \
   FIELD(Thread, double_truncate_round_supported_offset)                        \
+  FIELD(Thread, service_extension_stream_offset)                               \
   FIELD(Thread, optimize_entry_offset)                                         \
   FIELD(Thread, optimize_stub_offset)                                          \
   FIELD(Thread, deoptimize_entry_offset)                                       \
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 9162e8b0e75..1ae59b4e438 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -6,6 +6,7 @@
 
 #include <memory>
 
+#include "compiler/method_recognizer.h"
 #include "include/dart_api.h"
 #include "lib/stacktrace.h"
 #include "platform/assert.h"
@@ -8097,31 +8098,66 @@ void Function::SetIsOptimizable(bool value) const {
 }
 
 bool Function::ForceOptimize() const {
-  return IsFfiFromAddress() || IsFfiGetAddress() || IsFfiLoad() ||
-         IsFfiStore() || IsFfiTrampoline() || IsFfiAsExternalTypedData() ||
-         IsTypedDataViewFactory() || IsUtf8Scan() || IsGetNativeField() ||
-         IsFinalizerForceOptimized();
+  return RecognizedKindForceOptimize() || IsFfiTrampoline() ||
+         IsTypedDataViewFactory();
 }
 
-bool Function::IsFinalizerForceOptimized() const {
-  // Either because of unboxed/untagged data, or because we don't want the GC
-  // to trigger in between.
+bool Function::RecognizedKindForceOptimize() const {
   switch (recognized_kind()) {
+    // Uses unboxed/untagged data not supported in unoptimized.
     case MethodRecognizer::kFinalizerBase_getIsolateFinalizers:
     case MethodRecognizer::kFinalizerBase_setIsolate:
     case MethodRecognizer::kFinalizerBase_setIsolateFinalizers:
     case MethodRecognizer::kFinalizerEntry_getExternalSize:
-      // Unboxed/untagged representation not supported in unoptimized.
-      return true;
+    case MethodRecognizer::kExtensionStreamHasListener:
+    case MethodRecognizer::kFfiLoadInt8:
+    case MethodRecognizer::kFfiLoadInt16:
+    case MethodRecognizer::kFfiLoadInt32:
+    case MethodRecognizer::kFfiLoadInt64:
+    case MethodRecognizer::kFfiLoadUint8:
+    case MethodRecognizer::kFfiLoadUint16:
+    case MethodRecognizer::kFfiLoadUint32:
+    case MethodRecognizer::kFfiLoadUint64:
+    case MethodRecognizer::kFfiLoadFloat:
+    case MethodRecognizer::kFfiLoadFloatUnaligned:
+    case MethodRecognizer::kFfiLoadDouble:
+    case MethodRecognizer::kFfiLoadDoubleUnaligned:
+    case MethodRecognizer::kFfiLoadPointer:
+    case MethodRecognizer::kFfiStoreInt8:
+    case MethodRecognizer::kFfiStoreInt16:
+    case MethodRecognizer::kFfiStoreInt32:
+    case MethodRecognizer::kFfiStoreInt64:
+    case MethodRecognizer::kFfiStoreUint8:
+    case MethodRecognizer::kFfiStoreUint16:
+    case MethodRecognizer::kFfiStoreUint32:
+    case MethodRecognizer::kFfiStoreUint64:
+    case MethodRecognizer::kFfiStoreFloat:
+    case MethodRecognizer::kFfiStoreFloatUnaligned:
+    case MethodRecognizer::kFfiStoreDouble:
+    case MethodRecognizer::kFfiStoreDoubleUnaligned:
+    case MethodRecognizer::kFfiStorePointer:
+    case MethodRecognizer::kFfiFromAddress:
+    case MethodRecognizer::kFfiGetAddress:
+    case MethodRecognizer::kFfiAsExternalTypedDataInt8:
+    case MethodRecognizer::kFfiAsExternalTypedDataInt16:
+    case MethodRecognizer::kFfiAsExternalTypedDataInt32:
+    case MethodRecognizer::kFfiAsExternalTypedDataInt64:
+    case MethodRecognizer::kFfiAsExternalTypedDataUint8:
+    case MethodRecognizer::kFfiAsExternalTypedDataUint16:
+    case MethodRecognizer::kFfiAsExternalTypedDataUint32:
+    case MethodRecognizer::kFfiAsExternalTypedDataUint64:
+    case MethodRecognizer::kFfiAsExternalTypedDataFloat:
+    case MethodRecognizer::kFfiAsExternalTypedDataDouble:
+    case MethodRecognizer::kGetNativeField:
+    case MethodRecognizer::kUtf8DecoderScan:
+    // Prevent the GC from running so that the operation is atomic from
+    // a GC point of view. Always double check implementation in
+    // kernel_to_il.cc that no GC can happen in between the relevant IL
+    // instructions.
+    // TODO(https://dartbug.com/48527): Support inlining.
     case MethodRecognizer::kFinalizerBase_exchangeEntriesCollectedWithNull:
-      // Prevent the GC from running so that the operation is atomic from
-      // a GC point of view. Always double check implementation in
-      // kernel_to_il.cc that no GC can happen in between the relevant IL
-      // instructions.
-      // TODO(https://dartbug.com/48527): Support inlining.
-      return true;
+    // Both unboxed/untagged data and atomic-to-GC operation.
     case MethodRecognizer::kFinalizerEntry_allocate:
-      // Both of the above reasons.
       return true;
     default:
       return false;
@@ -14538,6 +14574,7 @@ void Library::CheckFunctionFingerprints() {
   all_libs.Add(&Library::ZoneHandle(Library::InternalLibrary()));
   all_libs.Add(&Library::ZoneHandle(Library::FfiLibrary()));
   all_libs.Add(&Library::ZoneHandle(Library::NativeWrappersLibrary()));
+  all_libs.Add(&Library::ZoneHandle(Library::DeveloperLibrary()));
   INTERNAL_LIB_INTRINSIC_LIST(CHECK_FINGERPRINTS_ASM_INTRINSIC);
   OTHER_RECOGNIZED_LIST(CHECK_FINGERPRINTS_OTHER);
   POLYMORPHIC_TARGET_LIST(CHECK_FINGERPRINTS);
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 7d9ffe061d3..3bd1912e2b2 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -3240,7 +3240,8 @@ class Function : public Object {
   // run.
   bool ForceOptimize() const;
 
-  bool IsFinalizerForceOptimized() const;
+  // Whether this function's |recognized_kind| requires optimization.
+  bool RecognizedKindForceOptimize() const;
 
   bool CanBeInlined() const;
 
@@ -3549,44 +3550,6 @@ class Function : public Object {
            UntaggedFunction::kFfiTrampoline;
   }
 
-  bool IsFfiLoad() const {
-    const auto kind = recognized_kind();
-    return MethodRecognizer::kFfiLoadInt8 <= kind &&
-           kind <= MethodRecognizer::kFfiLoadPointer;
-  }
-
-  bool IsFfiStore() const {
-    const auto kind = recognized_kind();
-    return MethodRecognizer::kFfiStoreInt8 <= kind &&
-           kind <= MethodRecognizer::kFfiStorePointer;
-  }
-
-  bool IsFfiFromAddress() const {
-    const auto kind = recognized_kind();
-    return kind == MethodRecognizer::kFfiFromAddress;
-  }
-
-  bool IsFfiGetAddress() const {
-    const auto kind = recognized_kind();
-    return kind == MethodRecognizer::kFfiGetAddress;
-  }
-
-  bool IsFfiAsExternalTypedData() const {
-    const auto kind = recognized_kind();
-    return MethodRecognizer::kFfiAsExternalTypedDataInt8 <= kind &&
-           kind <= MethodRecognizer::kFfiAsExternalTypedDataDouble;
-  }
-
-  bool IsGetNativeField() const {
-    const auto kind = recognized_kind();
-    return kind == MethodRecognizer::kGetNativeField;
-  }
-
-  bool IsUtf8Scan() const {
-    const auto kind = recognized_kind();
-    return kind == MethodRecognizer::kUtf8DecoderScan;
-  }
-
   // Recognise async functions like:
   //   user_func async {
   //     // ...
diff --git a/runtime/vm/service.h b/runtime/vm/service.h
index 6bf1e40ccbc..7dc4d4569b1 100644
--- a/runtime/vm/service.h
+++ b/runtime/vm/service.h
@@ -5,6 +5,8 @@
 #ifndef RUNTIME_VM_SERVICE_H_
 #define RUNTIME_VM_SERVICE_H_
 
+#include <atomic>
+
 #include "include/dart_tools_api.h"
 
 #include "vm/allocation.h"
@@ -73,17 +75,20 @@ class StreamInfo {
 
   const char* id() const { return id_; }
 
-  void set_enabled(bool value) { enabled_ = value; }
-  bool enabled() const { return enabled_; }
+  void set_enabled(bool value) { enabled_ = value ? 1 : 0; }
+  bool enabled() const { return !!enabled_; }
 
   void set_include_private_members(bool value) {
     include_private_members_ = value;
   }
   bool include_private_members() const { return include_private_members_; }
 
+  // This may get access by multiple threads, but relaxed access is ok.
+  static intptr_t enabled_offset() { return OFFSET_OF(StreamInfo, enabled_); }
+
  private:
   const char* id_;
-  bool enabled_;
+  std::atomic<intptr_t> enabled_;
   bool include_private_members_;
 };
 
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index e8ad780c06d..573e775d5a4 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -19,6 +19,7 @@
 #include "vm/os_thread.h"
 #include "vm/profiler.h"
 #include "vm/runtime_entry.h"
+#include "vm/service.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 #include "vm/thread_interrupter.h"
@@ -39,15 +40,15 @@ DECLARE_FLAG(bool, trace_service_verbose);
 
 Thread::~Thread() {
   // We should cleanly exit any isolate before destruction.
-  ASSERT(isolate_ == NULL);
-  ASSERT(store_buffer_block_ == NULL);
-  ASSERT(marking_stack_block_ == NULL);
+  ASSERT(isolate_ == nullptr);
+  ASSERT(store_buffer_block_ == nullptr);
+  ASSERT(marking_stack_block_ == nullptr);
   // There should be no top api scopes at this point.
-  ASSERT(api_top_scope() == NULL);
+  ASSERT(api_top_scope() == nullptr);
   // Delete the resusable api scope if there is one.
   if (api_reusable_scope_ != nullptr) {
     delete api_reusable_scope_;
-    api_reusable_scope_ = NULL;
+    api_reusable_scope_ = nullptr;
   }
 
   DO_IF_TSAN(delete tsan_utils_);
@@ -60,21 +61,21 @@ Thread::~Thread() {
 #define REUSABLE_HANDLE_SCOPE_INIT(object)
 #endif  // defined(DEBUG)
 
-#define REUSABLE_HANDLE_INITIALIZERS(object) object##_handle_(NULL),
+#define REUSABLE_HANDLE_INITIALIZERS(object) object##_handle_(nullptr),
 
 Thread::Thread(bool is_vm_isolate)
     : ThreadState(false),
       stack_limit_(0),
       write_barrier_mask_(UntaggedObject::kGenerationalBarrierMask),
       heap_base_(0),
-      isolate_(NULL),
-      dispatch_table_array_(NULL),
+      isolate_(nullptr),
+      dispatch_table_array_(nullptr),
       saved_stack_limit_(0),
       stack_overflow_flags_(0),
-      heap_(NULL),
+      heap_(nullptr),
       top_exit_frame_info_(0),
-      store_buffer_block_(NULL),
-      marking_stack_block_(NULL),
+      store_buffer_block_(nullptr),
+      marking_stack_block_(nullptr),
       vm_tag_(0),
       unboxed_int64_runtime_arg_(0),
       unboxed_double_runtime_arg_(0.0),
@@ -86,32 +87,37 @@ Thread::Thread(bool is_vm_isolate)
       safepoint_state_(0),
       ffi_callback_code_(GrowableObjectArray::null()),
       ffi_callback_stack_return_(TypedData::null()),
-      api_top_scope_(NULL),
+      api_top_scope_(nullptr),
       double_truncate_round_supported_(
           TargetCPUFeatures::double_truncate_round_supported() ? 1 : 0),
       tsan_utils_(DO_IF_TSAN(new TsanUtils()) DO_IF_NOT_TSAN(nullptr)),
       task_kind_(kUnknownTask),
-      dart_stream_(NULL),
+      dart_stream_(nullptr),
+      service_extension_stream_(nullptr),
       thread_lock_(),
-      api_reusable_scope_(NULL),
+      api_reusable_scope_(nullptr),
       no_callback_scope_depth_(0),
 #if defined(DEBUG)
       no_safepoint_scope_depth_(0),
 #endif
       reusable_handles_(),
       stack_overflow_count_(0),
-      hierarchy_info_(NULL),
-      type_usage_info_(NULL),
+      hierarchy_info_(nullptr),
+      type_usage_info_(nullptr),
       sticky_error_(Error::null()),
       REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_INITIALIZERS)
           REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_SCOPE_INIT)
 #if defined(USING_SAFE_STACK)
               saved_safestack_limit_(0),
 #endif
-      next_(NULL) {
+      next_(nullptr) {
 #if defined(SUPPORT_TIMELINE)
   dart_stream_ = Timeline::GetDartStream();
-  ASSERT(dart_stream_ != NULL);
+  ASSERT(dart_stream_ != nullptr);
+#endif
+#ifndef PRODUCT
+  service_extension_stream_ = &Service::extension_stream;
+  ASSERT(service_extension_stream_ != nullptr);
 #endif
 #define DEFAULT_INIT(type_name, member_name, init_expr, default_init_value)    \
   member_name = default_init_value;
@@ -276,8 +282,8 @@ bool Thread::EnterIsolate(Isolate* isolate, bool is_nested_reenter) {
 
   Thread* thread = isolate->ScheduleThread(kIsMutatorThread, is_nested_reenter,
                                            kBypassSafepoint);
-  if (thread != NULL) {
-    ASSERT(thread->store_buffer_block_ == NULL);
+  if (thread != nullptr) {
+    ASSERT(thread->store_buffer_block_ == nullptr);
     ASSERT(thread->isolate() == isolate);
     ASSERT(thread->isolate_group() == isolate->group());
     thread->FinishEntering(kMutatorTask);
@@ -316,7 +322,7 @@ bool Thread::EnterIsolateAsHelper(Isolate* isolate,
   const bool kIsNestedReenter = false;
   Thread* thread = isolate->ScheduleThread(kIsMutatorThread, kIsNestedReenter,
                                            bypass_safepoint);
-  if (thread != NULL) {
+  if (thread != nullptr) {
     ASSERT(!thread->IsMutatorThread());
     ASSERT(thread->isolate() == isolate);
     ASSERT(thread->isolate_group() == isolate->group());
@@ -336,7 +342,7 @@ void Thread::ExitIsolateAsHelper(bool bypass_safepoint) {
   thread->PrepareLeaving();
 
   Isolate* isolate = thread->isolate();
-  ASSERT(isolate != NULL);
+  ASSERT(isolate != nullptr);
   const bool kIsMutatorThread = false;
   const bool kIsNestedExit = false;
   isolate->UnscheduleThread(thread, kIsMutatorThread, kIsNestedExit,
@@ -348,7 +354,7 @@ bool Thread::EnterIsolateGroupAsHelper(IsolateGroup* isolate_group,
                                        bool bypass_safepoint) {
   ASSERT(kind != kMutatorTask);
   Thread* thread = isolate_group->ScheduleThread(bypass_safepoint);
-  if (thread != NULL) {
+  if (thread != nullptr) {
     ASSERT(!thread->IsMutatorThread());
     ASSERT(thread->isolate() == nullptr);
     ASSERT(thread->isolate_group() == isolate_group);
@@ -375,7 +381,7 @@ void Thread::ExitIsolateGroupAsHelper(bool bypass_safepoint) {
 void Thread::ReleaseStoreBuffer() {
   ASSERT(IsAtSafepoint());
   // Prevent scheduling another GC by ignoring the threshold.
-  ASSERT(store_buffer_block_ != NULL);
+  ASSERT(store_buffer_block_ != nullptr);
   StoreBufferRelease(StoreBuffer::kIgnoreThreshold);
   // Make sure to get an *empty* block; the isolate needs all entries
   // at GC time.
@@ -502,7 +508,7 @@ void Thread::StoreBufferAddObjectGC(ObjectPtr obj) {
 
 void Thread::StoreBufferRelease(StoreBuffer::ThresholdPolicy policy) {
   StoreBufferBlock* block = store_buffer_block_;
-  store_buffer_block_ = NULL;
+  store_buffer_block_ = nullptr;
   isolate_group()->store_buffer()->PushBlock(block, policy);
 }
 
@@ -536,7 +542,7 @@ void Thread::DeferredMarkingStackAddObject(ObjectPtr obj) {
 
 void Thread::MarkingStackRelease() {
   MarkingStackBlock* block = marking_stack_block_;
-  marking_stack_block_ = NULL;
+  marking_stack_block_ = nullptr;
   write_barrier_mask_ = UntaggedObject::kGenerationalBarrierMask;
   isolate_group()->marking_stack()->PushBlock(block);
 }
@@ -549,7 +555,7 @@ void Thread::MarkingStackAcquire() {
 
 void Thread::DeferredMarkingStackRelease() {
   MarkingStackBlock* block = deferred_marking_stack_block_;
-  deferred_marking_stack_block_ = NULL;
+  deferred_marking_stack_block_ = nullptr;
   isolate_group()->deferred_marking_stack()->PushBlock(block);
 }
 
@@ -591,9 +597,9 @@ void Thread::ClearReusableHandles() {
 
 void Thread::VisitObjectPointers(ObjectPointerVisitor* visitor,
                                  ValidationPolicy validation_policy) {
-  ASSERT(visitor != NULL);
+  ASSERT(visitor != nullptr);
 
-  if (zone() != NULL) {
+  if (zone() != nullptr) {
     zone()->VisitObjectPointers(visitor);
   }
 
@@ -610,7 +616,7 @@ void Thread::VisitObjectPointers(ObjectPointerVisitor* visitor,
 
   // Visit the api local scope as it has all the api local handles.
   ApiLocalScope* scope = api_top_scope_;
-  while (scope != NULL) {
+  while (scope != nullptr) {
     scope->local_handles()->VisitObjectPointers(visitor);
     scope = scope->previous();
   }
@@ -634,7 +640,7 @@ void Thread::VisitObjectPointers(ObjectPointerVisitor* visitor,
     StackFrameIterator frames_iterator(top_exit_frame_info(), validation_policy,
                                        this, cross_thread_policy);
     StackFrame* frame = frames_iterator.NextFrame();
-    while (frame != NULL) {
+    while (frame != nullptr) {
       frame->VisitObjectPointers(visitor);
       frame = frames_iterator.NextFrame();
     }
@@ -735,7 +741,7 @@ void Thread::RestoreWriteBarrierInvariant(RestoreWriteBarrierInvariantOp op) {
   RestoreWriteBarrierInvariantVisitor visitor(isolate_group(), this, op);
   ObjectStore* object_store = isolate_group()->object_store();
   bool scan_next_dart_frame = false;
-  for (StackFrame* frame = frames_iterator.NextFrame(); frame != NULL;
+  for (StackFrame* frame = frames_iterator.NextFrame(); frame != nullptr;
        frame = frames_iterator.NextFrame()) {
     if (frame->IsExitFrame()) {
       scan_next_dart_frame = true;
@@ -891,7 +897,7 @@ bool Thread::IsValidHandle(Dart_Handle object) const {
 
 bool Thread::IsValidLocalHandle(Dart_Handle object) const {
   ApiLocalScope* scope = api_top_scope_;
-  while (scope != NULL) {
+  while (scope != nullptr) {
     if (scope->local_handles()->IsValidHandle(object)) {
       return true;
     }
@@ -903,7 +909,7 @@ bool Thread::IsValidLocalHandle(Dart_Handle object) const {
 intptr_t Thread::CountLocalHandles() const {
   intptr_t total = 0;
   ApiLocalScope* scope = api_top_scope_;
-  while (scope != NULL) {
+  while (scope != nullptr) {
     total += scope->local_handles()->CountHandles();
     scope = scope->previous();
   }
@@ -913,7 +919,7 @@ intptr_t Thread::CountLocalHandles() const {
 int Thread::ZoneSizeInBytes() const {
   int total = 0;
   ApiLocalScope* scope = api_top_scope_;
-  while (scope != NULL) {
+  while (scope != nullptr) {
     total += scope->zone()->SizeInBytes();
     scope = scope->previous();
   }
@@ -923,12 +929,12 @@ int Thread::ZoneSizeInBytes() const {
 void Thread::EnterApiScope() {
   ASSERT(MayAllocateHandles());
   ApiLocalScope* new_scope = api_reusable_scope();
-  if (new_scope == NULL) {
+  if (new_scope == nullptr) {
     new_scope = new ApiLocalScope(api_top_scope(), top_exit_frame_info());
-    ASSERT(new_scope != NULL);
+    ASSERT(new_scope != nullptr);
   } else {
     new_scope->Reinit(this, api_top_scope(), top_exit_frame_info());
-    set_api_reusable_scope(NULL);
+    set_api_reusable_scope(nullptr);
   }
   set_api_top_scope(new_scope);  // New scope is now the top scope.
 }
@@ -938,7 +944,7 @@ void Thread::ExitApiScope() {
   ApiLocalScope* scope = api_top_scope();
   ApiLocalScope* reusable_scope = api_reusable_scope();
   set_api_top_scope(scope->previous());  // Reset top scope to previous.
-  if (reusable_scope == NULL) {
+  if (reusable_scope == nullptr) {
     scope->Reset(this);  // Reset the old scope which we just exited.
     set_api_reusable_scope(scope);
   } else {
@@ -951,7 +957,7 @@ void Thread::UnwindScopes(uword stack_marker) {
   // Unwind all scopes using the same stack_marker, i.e. all scopes allocated
   // under the same top_exit_frame_info.
   ApiLocalScope* scope = api_top_scope_;
-  while (scope != NULL && scope->stack_marker() != 0 &&
+  while (scope != nullptr && scope->stack_marker() != 0 &&
          scope->stack_marker() == stack_marker) {
     api_top_scope_ = scope->previous();
     delete scope;
@@ -975,7 +981,7 @@ void Thread::FinishEntering(TaskKind kind) {
   ASSERT(store_buffer_block_ == nullptr);
 
   task_kind_ = kind;
-  if (isolate_group()->marking_stack() != NULL) {
+  if (isolate_group()->marking_stack() != nullptr) {
     // Concurrent mark in progress. Enable barrier for this thread.
     MarkingStackAcquire();
     DeferredMarkingStackAcquire();
@@ -1004,17 +1010,17 @@ void Thread::PrepareLeaving() {
 
 DisableThreadInterruptsScope::DisableThreadInterruptsScope(Thread* thread)
     : StackResource(thread) {
-  if (thread != NULL) {
+  if (thread != nullptr) {
     OSThread* os_thread = thread->os_thread();
-    ASSERT(os_thread != NULL);
+    ASSERT(os_thread != nullptr);
     os_thread->DisableThreadInterrupts();
   }
 }
 
 DisableThreadInterruptsScope::~DisableThreadInterruptsScope() {
-  if (thread() != NULL) {
+  if (thread() != nullptr) {
     OSThread* os_thread = thread()->os_thread();
-    ASSERT(os_thread != NULL);
+    ASSERT(os_thread != nullptr);
     os_thread->EnableThreadInterrupts();
   }
 }
diff --git a/runtime/vm/thread.h b/runtime/vm/thread.h
index 15a7bd926b7..5918a360afb 100644
--- a/runtime/vm/thread.h
+++ b/runtime/vm/thread.h
@@ -58,6 +58,7 @@ class RuntimeEntry;
 class Smi;
 class StackResource;
 class StackTrace;
+class StreamInfo;
 class String;
 class TimelineStream;
 class TypeArguments;
@@ -512,6 +513,11 @@ class Thread : public ThreadState {
     return OFFSET_OF(Thread, dart_stream_);
   }
 
+  // Offset of the Dart VM Service Extension StreamInfo object.
+  static intptr_t service_extension_stream_offset() {
+    return OFFSET_OF(Thread, service_extension_stream_);
+  }
+
   // Is |this| executing Dart code?
   bool IsExecutingDartCode() const;
 
@@ -1173,6 +1179,7 @@ class Thread : public ThreadState {
 
   TaskKind task_kind_;
   TimelineStream* dart_stream_;
+  StreamInfo* service_extension_stream_;
   IsolateGroup* isolate_group_ = nullptr;
   mutable Monitor thread_lock_;
   ApiLocalScope* api_reusable_scope_;
diff --git a/sdk/lib/_internal/js_dev_runtime/patch/developer_patch.dart b/sdk/lib/_internal/js_dev_runtime/patch/developer_patch.dart
index 761bf6e7eff..c451d7fc366 100644
--- a/sdk/lib/_internal/js_dev_runtime/patch/developer_patch.dart
+++ b/sdk/lib/_internal/js_dev_runtime/patch/developer_patch.dart
@@ -11,7 +11,6 @@ import 'dart:async';
 import 'dart:convert' show json;
 import 'dart:isolate';
 
-var _issuedPostEventWarning = false;
 var _issuedRegisterExtensionWarning = false;
 final _developerSupportWarning = 'from dart:developer is only supported in '
     'build/run/test environments where the developer event method hooks have '
@@ -116,16 +115,11 @@ _invokeExtension(String methodName, String encodedJson) {
   });
 }
 
+@patch
+bool get extensionStreamHasListener => _debuggerAttached;
+
 @patch
 void _postEvent(String eventKind, String eventData) {
-  if (!_debuggerAttached) {
-    if (!_issuedPostEventWarning) {
-      var message = 'postEvent() $_developerSupportWarning';
-      JS('', 'console.warn(#)', message);
-      _issuedPostEventWarning = true;
-    }
-    return;
-  }
   // TODO(46377) Update this check when we have a documented API for DDC apps.
   if (JS<bool>('!', r'!!#.$emitDebugEvent', dart.global_)) {
     // See hooks assigned by package:dwds:
diff --git a/sdk/lib/_internal/js_runtime/lib/developer_patch.dart b/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
index feb0d485b37..54f7ca1b426 100644
--- a/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
@@ -47,6 +47,9 @@ _registerExtension(String method, ServiceExtensionHandler handler) {
   _extensions[method] = handler;
 }
 
+@patch
+bool get extensionStreamHasListener => false;
+
 @patch
 void _postEvent(String eventKind, String eventData) {
   // TODO.
diff --git a/sdk/lib/_internal/wasm/lib/developer.dart b/sdk/lib/_internal/wasm/lib/developer.dart
index ba930b33edc..32d3050e6f3 100644
--- a/sdk/lib/_internal/wasm/lib/developer.dart
+++ b/sdk/lib/_internal/wasm/lib/developer.dart
@@ -26,6 +26,9 @@ void log(String message,
     Object? error,
     StackTrace? stackTrace}) {}
 
+@patch
+bool get extensionStreamHasListener => false;
+
 @patch
 void _postEvent(String eventKind, String eventData) {}
 
diff --git a/sdk/lib/developer/developer.dart b/sdk/lib/developer/developer.dart
index e9df841ba85..2d8e15cfcd3 100644
--- a/sdk/lib/developer/developer.dart
+++ b/sdk/lib/developer/developer.dart
@@ -15,6 +15,7 @@
 /// {@category Core}
 library dart.developer;
 
+import "dart:_internal" show checkNotNullable;
 import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate' show Isolate, RawReceivePort, SendPort;
diff --git a/sdk/lib/developer/extension.dart b/sdk/lib/developer/extension.dart
index 184a00f956b..aa106744ced 100644
--- a/sdk/lib/developer/extension.dart
+++ b/sdk/lib/developer/extension.dart
@@ -27,7 +27,7 @@ class ServiceExtensionResponse {
         errorCode = null,
         errorDetail = null {
     // TODO: When NNBD is complete, delete the following line.
-    ArgumentError.checkNotNull(result, "result");
+    checkNotNullable(result, "result");
   }
 
   /// Creates an error response to a service protocol extension RPC.
@@ -42,7 +42,7 @@ class ServiceExtensionResponse {
         errorDetail = errorDetail {
     _validateErrorCode(errorCode);
     // TODO: When NNBD is complete, delete the following line.
-    ArgumentError.checkNotNull(errorDetail, "errorDetail");
+    checkNotNullable(errorDetail, "errorDetail");
   }
 
   /// Invalid method parameter(s) error code.
@@ -83,7 +83,7 @@ class ServiceExtensionResponse {
 
   static _validateErrorCode(int errorCode) {
     // TODO: When NNBD is complete, delete the following line.
-    ArgumentError.checkNotNull(errorCode, "errorCode");
+    checkNotNullable(errorCode, "errorCode");
     if (errorCode == invalidParams) return;
     if ((errorCode >= extensionErrorMin) && (errorCode <= extensionErrorMax)) {
       return;
@@ -129,7 +129,7 @@ typedef Future<ServiceExtensionResponse> ServiceExtensionHandler(
 /// must always include an 'isolateId' parameter with each RPC.
 void registerExtension(String method, ServiceExtensionHandler handler) {
   // TODO: When NNBD is complete, delete the following line.
-  ArgumentError.checkNotNull(method, 'method');
+  checkNotNullable(method, 'method');
   if (!method.startsWith('ext.')) {
     throw new ArgumentError.value(method, 'method', 'Must begin with ext.');
   }
@@ -137,16 +137,38 @@ void registerExtension(String method, ServiceExtensionHandler handler) {
     throw new ArgumentError('Extension already registered: $method');
   }
   // TODO: When NNBD is complete, delete the following line.
-  ArgumentError.checkNotNull(handler, 'handler');
+  checkNotNullable(handler, 'handler');
   _registerExtension(method, handler);
 }
 
-/// Post an event of [eventKind] with payload of [eventData] to the `Extension`
+/// Whether the "Extension" stream currently has at least one listener.
+///
+/// A client of the VM service can register as a listener
+/// on the extension stream using `listenStream` method.
+/// The extension stream has a listener while at least one such
+/// client has registered as a listener, and has not yet disconnected
+/// again.
+///
+/// Calling [postEvent] while the stream has listeners will attempt to
+/// deliver that event to all current listeners,
+/// although a listener can disconnect before the event is delivered.
+/// Calling [postEvent] when the stream has no listener means that
+/// no-one will receive the event, and the call is effectively a no-op.
+@pragma("vm:recognized", "other")
+@pragma("vm:prefer-inline")
+external bool get extensionStreamHasListener;
+
+/// Post an event of [eventKind] with payload of [eventData] to the "Extension"
 /// event stream.
+///
+/// If [extensionStreamHasListener] is false, this method is a no-op.
 void postEvent(String eventKind, Map eventData) {
+  if (!extensionStreamHasListener) {
+    return;
+  }
   // TODO: When NNBD is complete, delete the following two lines.
-  ArgumentError.checkNotNull(eventKind, 'eventKind');
-  ArgumentError.checkNotNull(eventData, 'eventData');
+  checkNotNullable(eventKind, 'eventKind');
+  checkNotNullable(eventData, 'eventData');
   String eventDataAsString = json.encode(eventData);
   _postEvent(eventKind, eventDataAsString);
 }
diff --git a/tests/dartdevc/developer_events_test.dart b/tests/dartdevc/developer_events_test.dart
index 907d801f993..22481f8f92b 100644
--- a/tests/dartdevc/developer_events_test.dart
+++ b/tests/dartdevc/developer_events_test.dart
@@ -122,17 +122,15 @@ void testWarningMessages() {
     var data0 = {'key0': 'value0'};
     postEvent('kind0', data0);
 
-    // A warning message was issued about calling `postEvent()` from
-    // dart:developer.
-    expect(consoleWarnLog.single.contains('postEvent() from dart:developer'),
-        true);
+    // Nothing is listening, so this was a no-op.
+    expect(consoleWarnLog.isEmpty, true);
 
     postEvent('kind0', data0);
     var data1 = {'key1': 'value1'};
     postEvent('kind1', data1);
 
-    // A warning is only issued on the first call of `postEvent()`.
-    expect(consoleWarnLog.length, 1);
+    // No warnings should be issued because postEvent is a no-op.
+    expect(consoleWarnLog.length, 0);
 
     consoleWarnLog.clear();
 
diff --git a/tests/dartdevc_2/developer_events_test.dart b/tests/dartdevc_2/developer_events_test.dart
index 8bc5ed877ba..d1851215d44 100644
--- a/tests/dartdevc_2/developer_events_test.dart
+++ b/tests/dartdevc_2/developer_events_test.dart
@@ -122,17 +122,15 @@ void testWarningMessages() {
     var data0 = {'key0': 'value0'};
     postEvent('kind0', data0);
 
-    // A warning message was issued about calling `postEvent()` from
-    // dart:developer.
-    expect(consoleWarnLog.single.contains('postEvent() from dart:developer'),
-        true);
+    // Nothing is listening, so this was a no-op.
+    expect(consoleWarnLog.isEmpty, true);
 
     postEvent('kind0', data0);
     var data1 = {'key1': 'value1'};
     postEvent('kind1', data1);
 
-    // A warning is only issued on the first call of `postEvent()`.
-    expect(consoleWarnLog.length, 1);
+    // No warnings should be issued because postEvent is a no-op.
+    expect(consoleWarnLog.length, 0);
 
     consoleWarnLog.clear();