diff --git a/deps/v8/include/v8-version.h b/deps/v8/include/v8-version.h
index 4dd63447ed886e..491bdca61070fa 100644
--- a/deps/v8/include/v8-version.h
+++ b/deps/v8/include/v8-version.h
@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 10
 #define V8_MINOR_VERSION 7
 #define V8_BUILD_NUMBER 193
-#define V8_PATCH_LEVEL 13
+#define V8_PATCH_LEVEL 16
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
diff --git a/deps/v8/src/compiler/compilation-dependencies.cc b/deps/v8/src/compiler/compilation-dependencies.cc
index 761e6731f384af..c356f3b9ac452e 100644
--- a/deps/v8/src/compiler/compilation-dependencies.cc
+++ b/deps/v8/src/compiler/compilation-dependencies.cc
@@ -34,7 +34,8 @@ namespace compiler {
   V(Protector)                          \
   V(PrototypeProperty)                  \
   V(StableMap)                          \
-  V(Transition)
+  V(Transition)                         \
+  V(ObjectSlotValue)
 
 CompilationDependencies::CompilationDependencies(JSHeapBroker* broker,
                                                  Zone* zone)
@@ -868,6 +869,42 @@ class ProtectorDependency final : public CompilationDependency {
   const PropertyCellRef cell_;
 };
 
+// Check that an object slot will not change during compilation.
+class ObjectSlotValueDependency final : public CompilationDependency {
+ public:
+  explicit ObjectSlotValueDependency(const HeapObjectRef& object, int offset,
+                                     const ObjectRef& value)
+      : CompilationDependency(kObjectSlotValue),
+        object_(object.object()),
+        offset_(offset),
+        value_(value.object()) {}
+
+  bool IsValid() const override {
+    PtrComprCageBase cage_base = GetPtrComprCageBase(*object_);
+    Object current_value =
+        offset_ == HeapObject::kMapOffset
+            ? object_->map()
+            : TaggedField<Object>::Relaxed_Load(cage_base, *object_, offset_);
+    return *value_ == current_value;
+  }
+  void Install(PendingDependencies* deps) const override {}
+
+ private:
+  size_t Hash() const override {
+    return base::hash_combine(object_.address(), offset_, value_.address());
+  }
+
+  bool Equals(const CompilationDependency* that) const override {
+    const ObjectSlotValueDependency* const zat = that->AsObjectSlotValue();
+    return object_->address() == zat->object_->address() &&
+           offset_ == zat->offset_ && value_.address() == zat->value_.address();
+  }
+
+  Handle<HeapObject> object_;
+  int offset_;
+  Handle<Object> value_;
+};
+
 class ElementsKindDependency final : public CompilationDependency {
  public:
   ElementsKindDependency(const AllocationSiteRef& site, ElementsKind kind)
@@ -1120,6 +1157,12 @@ void CompilationDependencies::DependOnElementsKind(
   }
 }
 
+void CompilationDependencies::DependOnObjectSlotValue(
+    const HeapObjectRef& object, int offset, const ObjectRef& value) {
+  RecordDependency(
+      zone_->New<ObjectSlotValueDependency>(object, offset, value));
+}
+
 void CompilationDependencies::DependOnOwnConstantElement(
     const JSObjectRef& holder, uint32_t index, const ObjectRef& element) {
   RecordDependency(
diff --git a/deps/v8/src/compiler/compilation-dependencies.h b/deps/v8/src/compiler/compilation-dependencies.h
index 52c07ec819653c..b6799342d3a5bb 100644
--- a/deps/v8/src/compiler/compilation-dependencies.h
+++ b/deps/v8/src/compiler/compilation-dependencies.h
@@ -93,6 +93,10 @@ class V8_EXPORT_PRIVATE CompilationDependencies : public ZoneObject {
   // Record the assumption that {site}'s {ElementsKind} doesn't change.
   void DependOnElementsKind(const AllocationSiteRef& site);
 
+  // Check that an object slot will not change during compilation.
+  void DependOnObjectSlotValue(const HeapObjectRef& object, int offset,
+                               const ObjectRef& value);
+
   void DependOnOwnConstantElement(const JSObjectRef& holder, uint32_t index,
                                   const ObjectRef& element);
 
diff --git a/deps/v8/src/compiler/js-create-lowering.cc b/deps/v8/src/compiler/js-create-lowering.cc
index e4d590ed6962fe..4885a6c842248d 100644
--- a/deps/v8/src/compiler/js-create-lowering.cc
+++ b/deps/v8/src/compiler/js-create-lowering.cc
@@ -1673,6 +1673,10 @@ base::Optional<Node*> JSCreateLowering::TryAllocateFastLiteral(
 
   // Now that we hold the migration lock, get the current map.
   MapRef boilerplate_map = boilerplate.map();
+  // Protect against concurrent changes to the boilerplate object by checking
+  // for an identical value at the end of the compilation.
+  dependencies()->DependOnObjectSlotValue(boilerplate, HeapObject::kMapOffset,
+                                          boilerplate_map);
   {
     base::Optional<MapRef> current_boilerplate_map =
         boilerplate.map_direct_read();
@@ -1838,10 +1842,18 @@ base::Optional<Node*> JSCreateLowering::TryAllocateFastLiteralElements(
       boilerplate.elements(kRelaxedLoad);
   if (!maybe_boilerplate_elements.has_value()) return {};
   FixedArrayBaseRef boilerplate_elements = maybe_boilerplate_elements.value();
+  // Protect against concurrent changes to the boilerplate object by checking
+  // for an identical value at the end of the compilation.
+  dependencies()->DependOnObjectSlotValue(
+      boilerplate, JSObject::kElementsOffset, boilerplate_elements);
 
   // Empty or copy-on-write elements just store a constant.
   int const elements_length = boilerplate_elements.length();
   MapRef elements_map = boilerplate_elements.map();
+  // Protect against concurrent changes to the boilerplate object by checking
+  // for an identical value at the end of the compilation.
+  dependencies()->DependOnObjectSlotValue(boilerplate_elements,
+                                          HeapObject::kMapOffset, elements_map);
   if (boilerplate_elements.length() == 0 || elements_map.IsFixedCowArrayMap()) {
     if (allocation == AllocationType::kOld &&
         !boilerplate.IsElementsTenured(boilerplate_elements)) {
diff --git a/deps/v8/src/execution/isolate.cc b/deps/v8/src/execution/isolate.cc
index c6610b2fce8cd6..bbd6855bb3be48 100644
--- a/deps/v8/src/execution/isolate.cc
+++ b/deps/v8/src/execution/isolate.cc
@@ -2797,13 +2797,15 @@ bool PromiseHasUserDefinedRejectHandlerInternal(Isolate* isolate,
             Handle<PromiseCapability>::cast(promise_or_capability)->promise(),
             isolate);
       }
-      promise = Handle<JSPromise>::cast(promise_or_capability);
-      if (!reaction->reject_handler().IsUndefined(isolate)) {
-        Handle<JSReceiver> reject_handler(
-            JSReceiver::cast(reaction->reject_handler()), isolate);
-        if (PromiseIsRejectHandler(isolate, reject_handler)) return true;
+      if (promise_or_capability->IsJSPromise()) {
+        promise = Handle<JSPromise>::cast(promise_or_capability);
+        if (!reaction->reject_handler().IsUndefined(isolate)) {
+          Handle<JSReceiver> reject_handler(
+              JSReceiver::cast(reaction->reject_handler()), isolate);
+          if (PromiseIsRejectHandler(isolate, reject_handler)) return true;
+        }
+        if (isolate->PromiseHasUserDefinedRejectHandler(promise)) return true;
       }
-      if (isolate->PromiseHasUserDefinedRejectHandler(promise)) return true;
     }
     current = handle(reaction->next(), isolate);
   }
diff --git a/deps/v8/src/heap/concurrent-marking.cc b/deps/v8/src/heap/concurrent-marking.cc
index f9ee0dd8f7fc97..d15cb26bcd4850 100644
--- a/deps/v8/src/heap/concurrent-marking.cc
+++ b/deps/v8/src/heap/concurrent-marking.cc
@@ -65,21 +65,48 @@ class ConcurrentMarkingState final
 // Helper class for storing in-object slot addresses and values.
 class SlotSnapshot {
  public:
-  SlotSnapshot() : number_of_slots_(0) {}
+  SlotSnapshot()
+      : number_of_object_slots_(0), number_of_external_pointer_slots_(0) {}
   SlotSnapshot(const SlotSnapshot&) = delete;
   SlotSnapshot& operator=(const SlotSnapshot&) = delete;
-  int number_of_slots() const { return number_of_slots_; }
-  ObjectSlot slot(int i) const { return snapshot_[i].first; }
-  Object value(int i) const { return snapshot_[i].second; }
-  void clear() { number_of_slots_ = 0; }
+  int number_of_object_slots() const { return number_of_object_slots_; }
+  int number_of_external_pointer_slots() const {
+    return number_of_external_pointer_slots_;
+  }
+  ObjectSlot object_slot(int i) const { return object_snapshot_[i].first; }
+  Object object_value(int i) const { return object_snapshot_[i].second; }
+  ExternalPointerSlot external_pointer_slot(int i) const {
+    return external_pointer_snapshot_[i].first;
+  }
+  ExternalPointerTag external_pointer_tag(int i) const {
+    return external_pointer_snapshot_[i].second;
+  }
+  void clear() {
+    number_of_object_slots_ = 0;
+    number_of_external_pointer_slots_ = 0;
+  }
   void add(ObjectSlot slot, Object value) {
-    snapshot_[number_of_slots_++] = {slot, value};
+    DCHECK_LT(number_of_object_slots_, kMaxObjectSlots);
+    object_snapshot_[number_of_object_slots_++] = {slot, value};
+  }
+  void add(ExternalPointerSlot slot, ExternalPointerTag tag) {
+    DCHECK_LT(number_of_external_pointer_slots_, kMaxExternalPointerSlots);
+    external_pointer_snapshot_[number_of_external_pointer_slots_++] = {slot,
+                                                                       tag};
   }
 
  private:
-  static const int kMaxSnapshotSize = JSObject::kMaxInstanceSize / kTaggedSize;
-  int number_of_slots_;
-  std::pair<ObjectSlot, Object> snapshot_[kMaxSnapshotSize];
+  // Maximum number of pointer slots of objects we use snapshotting for.
+  // ConsStrings can have 3 (Map + Left + Right) pointers.
+  static constexpr int kMaxObjectSlots = 3;
+  // Maximum number of external pointer slots of objects we use snapshotting
+  // for. ExternalStrings can have 2 (resource + cached data) external pointers.
+  static constexpr int kMaxExternalPointerSlots = 2;
+  int number_of_object_slots_;
+  int number_of_external_pointer_slots_;
+  std::pair<ObjectSlot, Object> object_snapshot_[kMaxObjectSlots];
+  std::pair<ExternalPointerSlot, ExternalPointerTag>
+      external_pointer_snapshot_[kMaxExternalPointerSlots];
 };
 
 class ConcurrentMarkingVisitorUtility {
@@ -111,9 +138,9 @@ class ConcurrentMarkingVisitorUtility {
   template <typename Visitor>
   static void VisitPointersInSnapshot(Visitor* visitor, HeapObject host,
                                       const SlotSnapshot& snapshot) {
-    for (int i = 0; i < snapshot.number_of_slots(); i++) {
-      ObjectSlot slot = snapshot.slot(i);
-      Object object = snapshot.value(i);
+    for (int i = 0; i < snapshot.number_of_object_slots(); i++) {
+      ObjectSlot slot = snapshot.object_slot(i);
+      Object object = snapshot.object_value(i);
       DCHECK(!HasWeakHeapObjectTag(object));
       if (!object.IsHeapObject()) continue;
       HeapObject heap_object = HeapObject::cast(object);
@@ -126,6 +153,16 @@ class ConcurrentMarkingVisitorUtility {
     }
   }
 
+  template <typename Visitor>
+  static void VisitExternalPointersInSnapshot(Visitor* visitor, HeapObject host,
+                                              const SlotSnapshot& snapshot) {
+    for (int i = 0; i < snapshot.number_of_external_pointer_slots(); i++) {
+      ExternalPointerSlot slot = snapshot.external_pointer_slot(i);
+      ExternalPointerTag tag = snapshot.external_pointer_tag(i);
+      visitor->VisitExternalPointer(host, slot, tag);
+    }
+  }
+
   template <typename Visitor, typename T>
   static int VisitFullyWithSnapshot(Visitor* visitor, Map map, T object) {
     using TBodyDescriptor = typename T::BodyDescriptor;
@@ -136,6 +173,8 @@ class ConcurrentMarkingVisitorUtility {
     if (!visitor->ShouldVisit(object)) return 0;
     ConcurrentMarkingVisitorUtility::VisitPointersInSnapshot(visitor, object,
                                                              snapshot);
+    ConcurrentMarkingVisitorUtility::VisitExternalPointersInSnapshot(
+        visitor, object, snapshot);
     return size;
   }
 
@@ -182,6 +221,11 @@ class ConcurrentMarkingVisitorUtility {
       UNREACHABLE();
     }
 
+    void VisitExternalPointer(HeapObject host, ExternalPointerSlot slot,
+                              ExternalPointerTag tag) override {
+      slot_snapshot_->add(slot, tag);
+    }
+
     void VisitCodeTarget(Code host, RelocInfo* rinfo) final {
       // This should never happen, because snapshotting is performed only on
       // some String subclasses.
@@ -450,6 +494,16 @@ class ConcurrentMarkingVisitor final
     return SeqTwoByteString::SizeFor(object.length(kAcquireLoad));
   }
 
+  int VisitExternalOneByteString(Map map, ExternalOneByteString object) {
+    return ConcurrentMarkingVisitorUtility::VisitFullyWithSnapshot(this, map,
+                                                                   object);
+  }
+
+  int VisitExternalTwoByteString(Map map, ExternalTwoByteString object) {
+    return ConcurrentMarkingVisitorUtility::VisitFullyWithSnapshot(this, map,
+                                                                   object);
+  }
+
   // Implements ephemeron semantics: Marks value if key is already reachable.
   // Returns true if value was actually marked.
   bool ProcessEphemeron(HeapObject key, HeapObject value) {
diff --git a/deps/v8/src/objects/string.cc b/deps/v8/src/objects/string.cc
index e97fb996692fab..7060047d8eb55c 100644
--- a/deps/v8/src/objects/string.cc
+++ b/deps/v8/src/objects/string.cc
@@ -223,6 +223,14 @@ void String::MakeThin(IsolateT* isolate, String internalized) {
   Map target_map = ComputeThinStringMap(isolate, initial_shape,
                                         internalized.IsOneByteRepresentation());
   if (initial_shape.IsExternal()) {
+    // Notify GC about the layout change before the transition to avoid
+    // concurrent marking from observing any in-between state (e.g.
+    // ExternalString map where the resource external pointer is overwritten
+    // with a tagged pointer).
+    // ExternalString -> ThinString transitions can only happen on the
+    // main-thread.
+    isolate->AsIsolate()->heap()->NotifyObjectLayoutChange(
+        *this, no_gc, InvalidateRecordedSlots::kYes, ThinString::kSize);
     MigrateExternalString(isolate->AsIsolate(), *this, internalized);
   }
 
@@ -231,7 +239,11 @@ void String::MakeThin(IsolateT* isolate, String internalized) {
   // ThinString.
   ThinString thin = ThinString::unchecked_cast(*this);
   thin.set_actual(internalized);
-  set_map_safe_transition(target_map, kReleaseStore);
+  if (initial_shape.IsExternal()) {
+    set_map(target_map, kReleaseStore);
+  } else {
+    set_map_safe_transition(target_map, kReleaseStore);
+  }
 
   DCHECK_GE(old_size, ThinString::kSize);
   int size_delta = old_size - ThinString::kSize;