diff --git a/examples/spec/async_iterators.js b/examples/spec/async_iterators.js
index 10be8dc..035c7f0 100644
--- a/examples/spec/async_iterators.js
+++ b/examples/spec/async_iterators.js
@@ -44,6 +44,11 @@ const dynamicAsyncIter = dynamicAsyncGen();
 test('AsyncGeneratorFunction constructs async generator function', Object.getPrototypeOf(dynamicAsyncGen), AsyncGeneratorFunction.prototype);
 test('AsyncGeneratorFunction instance uses function prototype', Object.getPrototypeOf(dynamicAsyncIter), dynamicAsyncGen.prototype);
 test('AsyncGeneratorFunction yielded value', (await dynamicAsyncIter.next()).value, 4);
+test(
+  'strict async generator function expression has own prototype',
+  Function('"use strict"; return (async function* () {}).hasOwnProperty("prototype");')(),
+  true
+);
 
 class CustomAsyncIterator extends AsyncIterator {
   constructor(values) {
diff --git a/include/object.h b/include/object.h
index a5b9303..067b4f0 100644
--- a/include/object.h
+++ b/include/object.h
@@ -71,11 +71,19 @@ typedef struct {
   uint32_t cap;
 } ant_private_table_t;
 
+typedef struct {
+  void *ptr;
+  uint32_t tag;
+} ant_native_entry_t;
+
 typedef struct {
   ant_extra_slot_t *extra_slots;
+  ant_native_entry_t *native_entries;
   ant_private_table_t private_table;
   ant_proxy_state_t *proxy_state;
   
+  uint8_t native_count;
+  uint8_t native_cap;
   uint8_t extra_count;
   uint8_t flags;
 } ant_object_sidecar_t;
@@ -101,11 +109,7 @@ typedef struct ant_object {
   
   void (*finalizer)(ant_t *, struct ant_object *);
   ant_value_t inobj[ANT_INOBJ_MAX_SLOTS];
-  
-  struct {
-    void *ptr;
-    uint32_t tag;
-  } native;
+  ant_native_entry_t native;
 
   union {
     struct { ant_value_t *data; uint32_t len; uint32_t cap; } array;
diff --git a/include/ptr.h b/include/ptr.h
index efd51fb..4fbf2ca 100644
--- a/include/ptr.h
+++ b/include/ptr.h
@@ -4,42 +4,90 @@
 #include "types.h"
 #include "internal.h" // IWYU pragma: keep
 
-static inline void js_set_native_ptr(ant_value_t obj, void *ptr) {
+static inline void *js_get_native(ant_value_t obj, uint32_t tag) {
   ant_object_t *o = js_obj_ptr(obj);
-  if (!o) return;
-  o->native.ptr = ptr;
-}
+  
+  if (!o || !tag) return NULL;
+  if (o->native.tag == tag) return o->native.ptr;
 
-static inline void *js_get_native_ptr(ant_value_t obj) {
-  ant_object_t *o = js_obj_ptr(obj);
-  return o ? o->native.ptr : NULL;
+  ant_object_sidecar_t *sidecar = ant_object_sidecar(o);
+  if (!sidecar) return NULL;
+  
+  for (uint8_t i = 0; i < sidecar->native_count; i++)
+    if (sidecar->native_entries[i].tag == tag) return sidecar->native_entries[i].ptr;
+
+  return NULL;
 }
 
-static inline void js_set_native_tag(ant_value_t obj, uint32_t tag) {
+static inline void js_clear_native(ant_value_t obj, uint32_t tag) {
   ant_object_t *o = js_obj_ptr(obj);
-  if (!o) return;
-  o->native.tag = tag;
+  if (!o || !tag) return;
+
+  ant_object_sidecar_t *sidecar = ant_object_sidecar(o);
+  if (o->native.tag == tag) {
+    if (sidecar && sidecar->native_count > 0) {
+      sidecar->native_count--;
+      o->native = sidecar->native_entries[sidecar->native_count];
+    } else {
+      o->native.ptr = NULL;
+      o->native.tag = 0;
+    }
+    return;
+  }
+
+  if (!sidecar) return;
+  for (uint8_t i = 0; i < sidecar->native_count; i++) {
+    if (sidecar->native_entries[i].tag != tag) continue;
+    sidecar->native_count--;
+    sidecar->native_entries[i] = sidecar->native_entries[sidecar->native_count];
+    return;
+  }
 }
 
 static inline void js_set_native(ant_value_t obj, void *ptr, uint32_t tag) {
   ant_object_t *o = js_obj_ptr(obj);
-  if (!o) return;
-  o->native.ptr = ptr;
-  o->native.tag = tag;
-}
+  if (!o || !tag) return;
+  
+  if (o->native.tag == 0 || o->native.tag == tag) {
+    o->native.ptr = ptr;
+    o->native.tag = tag;
+    return;
+  }
 
-static inline void js_clear_native(ant_value_t obj) {
-  js_set_native(obj, NULL, 0);
+  ant_object_sidecar_t *sidecar = ant_object_ensure_sidecar(o);
+  if (!sidecar) return;
+  
+  for (uint8_t i = 0; i < sidecar->native_count; i++) {
+    if (sidecar->native_entries[i].tag != tag) continue;
+    sidecar->native_entries[i].ptr = ptr;
+    return;
+  }
+
+  if (sidecar->native_count >= sidecar->native_cap) {
+    uint8_t next_cap = sidecar->native_cap ? (uint8_t)(sidecar->native_cap * 2) : 2;
+    ant_native_entry_t *next = realloc(sidecar->native_entries, next_cap * sizeof(*next));
+    
+    if (!next) return;
+    sidecar->native_entries = next;
+    sidecar->native_cap = next_cap;
+  }
+
+  sidecar->native_entries[sidecar->native_count++] = (ant_native_entry_t){ ptr, tag };
 }
 
-static inline uint32_t js_get_native_tag(ant_value_t obj) {
+static inline bool js_check_native_tag(ant_value_t obj, uint32_t tag) {
   ant_object_t *o = js_obj_ptr(obj);
-  return o ? o->native.tag : 0;
-}
+  
+  if (!o || !tag) return false;
+  if (o->native.tag == tag) return true;
 
+  ant_object_sidecar_t *sidecar = ant_object_sidecar(o);
+  if (!sidecar) return false;
+  
+  for (uint8_t i = 0; i < sidecar->native_count; i++)
+    if (sidecar->native_entries[i].tag == tag) return true;
 
-static inline bool js_check_native_tag(ant_value_t obj, uint32_t tag) {
-  return js_get_native_tag(obj) == tag;
+  return false;
 }
 
 #endif
diff --git a/src/ant.c b/src/ant.c
index fb9030c..2e384e4 100644
--- a/src/ant.c
+++ b/src/ant.c
@@ -2745,7 +2745,7 @@ typedef struct {
 
 static inline ant_arguments_state_t *js_arguments_state(ant_value_t obj) {
   if (!js_check_native_tag(obj, ANT_ARGUMENTS_NATIVE_TAG)) return NULL;
-  return (ant_arguments_state_t *)js_get_native_ptr(obj);
+  return (ant_arguments_state_t *)js_get_native(obj, ANT_ARGUMENTS_NATIVE_TAG);
 }
 
 static ant_value_t js_arguments_getter(ant_t *js, ant_value_t obj, const char *key, size_t key_len) {
@@ -2801,10 +2801,9 @@ static bool js_arguments_deleter(ant_t *js, ant_value_t obj, const char *key, si
 }
 
 static void js_arguments_finalizer(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != ANT_ARGUMENTS_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, ANT_ARGUMENTS_NATIVE_TAG));
+  js_clear_native(value, ANT_ARGUMENTS_NATIVE_TAG);
 }
 
 ant_value_t js_create_arguments_object(
@@ -2849,8 +2848,7 @@ ant_value_t js_create_arguments_object(
     state->frame_index = (int)(frame - js->vm->frames);
     state->mapped_count = (uint32_t)mapped_count;
     
-    js_set_native_ptr(arr, state);
-    js_set_native_tag(arr, ANT_ARGUMENTS_NATIVE_TAG);
+    js_set_native(arr, state, ANT_ARGUMENTS_NATIVE_TAG);
     js_set_finalizer(arr, js_arguments_finalizer);
     js_set_getter(arr, js_arguments_getter);
     js_set_setter(arr, js_arguments_setter);
diff --git a/src/gc/objects.c b/src/gc/objects.c
index 3801ee0..5200295 100644
--- a/src/gc/objects.c
+++ b/src/gc/objects.c
@@ -1,15 +1,18 @@
+#include "ptr.h"
+#include "sugar.h"
+#include "shapes.h"
+#include "runtime.h"
 #include "internal.h"
+
+#include "silver/engine.h"
+#include "modules/regex.h"
+#include "modules/generator.h"
+#include "modules/collections.h"
+
 #include "gc.h"
 #include "gc/objects.h"
 #include "gc/roots.h"
 #include "gc/modules.h"
-#include "sugar.h"
-#include "silver/engine.h"
-#include "shapes.h"
-#include "runtime.h"
-#include "modules/collections.h"
-#include "modules/generator.h"
-#include "modules/regex.h"
 
 #include <stdlib.h>
 #include <string.h>
@@ -245,8 +248,8 @@ static void gc_scan_obj(ant_t *js, ant_object_t *obj) {
   }
 
   if (obj->type_tag == T_MAP) {
-    map_entry_t **head = obj->native.tag == MAP_NATIVE_TAG 
-      ? (map_entry_t **)obj->native.ptr : NULL;
+    ant_value_t value = js_obj_from_ptr(obj);
+    map_entry_t **head = (map_entry_t **)js_get_native(value, MAP_NATIVE_TAG);
     if (head) {
     map_entry_t *e, *tmp;
     HASH_ITER(hh, *head, e, tmp) { 
@@ -256,8 +259,8 @@ static void gc_scan_obj(ant_t *js, ant_object_t *obj) {
   } 
   
   else if (obj->type_tag == T_WEAKMAP) {
-    weakmap_entry_t **head = obj->native.tag == WEAKMAP_NATIVE_TAG 
-      ? (weakmap_entry_t **)obj->native.ptr : NULL;
+    ant_value_t value = js_obj_from_ptr(obj);
+    weakmap_entry_t **head = (weakmap_entry_t **)js_get_native(value, WEAKMAP_NATIVE_TAG);
     if (head) {
     weakmap_entry_t *e, *tmp;
     HASH_ITER(hh, *head, e, tmp) {
@@ -267,8 +270,8 @@ static void gc_scan_obj(ant_t *js, ant_object_t *obj) {
   } 
   
   else if (obj->type_tag == T_SET) {
-    set_entry_t **head = obj->native.tag == SET_NATIVE_TAG 
-      ? (set_entry_t **)obj->native.ptr : NULL;
+    ant_value_t value = js_obj_from_ptr(obj);
+    set_entry_t **head = (set_entry_t **)js_get_native(value, SET_NATIVE_TAG);
     if (head) {
       set_entry_t *e, *tmp;
       HASH_ITER(hh, *head, e, tmp) { gc_mark_value(js, e->value); }
@@ -568,20 +571,6 @@ void gc_object_free(ant_t *js, ant_object_t *obj) {
     obj->shape = NULL;
   }
 
-  if (ant_object_has_sidecar(obj)) {
-    ant_object_sidecar_t *sidecar = ant_object_sidecar(obj);
-    free(sidecar->extra_slots);
-    free(sidecar->proxy_state);
-    free(sidecar->private_table.entries);
-    free(sidecar);
-    obj->extra_slots = NULL;
-  } 
-  
-  else if (obj->extra_slots) {
-    free(obj->extra_slots);
-    obj->extra_slots = NULL;
-  }
-
   if (obj->promise_state && obj->promise_state->gc_pending_rooted)
     gc_unroot_pending_promise(obj);
 
@@ -599,44 +588,67 @@ void gc_object_free(ant_t *js, ant_object_t *obj) {
 
   switch (obj->type_tag) {
     case T_MAP: {
-      map_entry_t **head = obj->native.tag == MAP_NATIVE_TAG ? (map_entry_t **)obj->native.ptr : NULL;
+      ant_value_t value = js_obj_from_ptr(obj);
+      map_entry_t **head = (map_entry_t **)js_get_native(value, MAP_NATIVE_TAG);
       if (head) {
         map_entry_t *e, *tmp;
         HASH_ITER(hh, *head, e, tmp) { HASH_DEL(*head, e); free(e->key); free(e); }
         free(head);
+        js_clear_native(value, MAP_NATIVE_TAG);
       }
       break;
     }
     case T_SET: {
-      set_entry_t **head = obj->native.tag == SET_NATIVE_TAG ? (set_entry_t **)obj->native.ptr : NULL;
+      ant_value_t value = js_obj_from_ptr(obj);
+      set_entry_t **head = (set_entry_t **)js_get_native(value, SET_NATIVE_TAG);
       if (head) {
         set_entry_t *e, *tmp;
         HASH_ITER(hh, *head, e, tmp) { HASH_DEL(*head, e); free(e->key); free(e); }
         free(head);
+        js_clear_native(value, SET_NATIVE_TAG);
       }
       break;
     }
     case T_WEAKMAP: {
-      weakmap_entry_t **head = obj->native.tag == WEAKMAP_NATIVE_TAG ? (weakmap_entry_t **)obj->native.ptr : NULL;
+      ant_value_t value = js_obj_from_ptr(obj);
+      weakmap_entry_t **head = (weakmap_entry_t **)js_get_native(value, WEAKMAP_NATIVE_TAG);
       if (head) {
         weakmap_entry_t *e, *tmp;
         HASH_ITER(hh, *head, e, tmp) { HASH_DEL(*head, e); free(e); }
         free(head);
+        js_clear_native(value, WEAKMAP_NATIVE_TAG);
       }
       break;
     }
     case T_WEAKSET: {
-      weakset_entry_t **head = obj->native.tag == WEAKSET_NATIVE_TAG ? (weakset_entry_t **)obj->native.ptr : NULL;
+      ant_value_t value = js_obj_from_ptr(obj);
+      weakset_entry_t **head = (weakset_entry_t **)js_get_native(value, WEAKSET_NATIVE_TAG);
       if (head) {
         weakset_entry_t *e, *tmp;
         HASH_ITER(hh, *head, e, tmp) { HASH_DEL(*head, e); free(e); }
         free(head);
+        js_clear_native(value, WEAKSET_NATIVE_TAG);
       }
       break;
     }
     default: break;
   }
 
+  if (ant_object_has_sidecar(obj)) {
+    ant_object_sidecar_t *sidecar = ant_object_sidecar(obj);
+    free(sidecar->extra_slots);
+    free(sidecar->native_entries);
+    free(sidecar->proxy_state);
+    free(sidecar->private_table.entries);
+    free(sidecar);
+    obj->extra_slots = NULL;
+  } 
+  
+  else if (obj->extra_slots) {
+    free(obj->extra_slots);
+    obj->extra_slots = NULL;
+  }
+
   free(obj->overflow_prop);
   obj->overflow_prop = NULL;
   free((void *)obj->exotic_ops);
diff --git a/src/modules/abort.c b/src/modules/abort.c
index 7fedcee..8795fd6 100644
--- a/src/modules/abort.c
+++ b/src/modules/abort.c
@@ -53,7 +53,7 @@ static inline unsigned int abort_array_len(UT_array *arr) {
 
 static abort_signal_data_t *get_signal_data(ant_value_t obj) {
   if (!js_check_native_tag(obj, ABORT_SIGNAL_NATIVE_TAG)) return NULL;
-  return (abort_signal_data_t *)js_get_native_ptr(obj);
+  return (abort_signal_data_t *)js_get_native(obj, ABORT_SIGNAL_NATIVE_TAG);
 }
 
 static abort_signal_data_t *get_signal_data_if_signal_object(ant_value_t obj) {
diff --git a/src/modules/blob.c b/src/modules/blob.c
index 7cccb58..d914a57 100644
--- a/src/modules/blob.c
+++ b/src/modules/blob.c
@@ -30,7 +30,7 @@ bool blob_is_blob(ant_t *js, ant_value_t obj) {
 
 blob_data_t *blob_get_data(ant_value_t obj) {
   if (!js_check_native_tag(obj, BLOB_NATIVE_TAG)) return NULL;
-  return (blob_data_t *)js_get_native_ptr(obj);
+  return (blob_data_t *)js_get_native(obj, BLOB_NATIVE_TAG);
 }
 
 static blob_data_t *blob_data_new(const uint8_t *data, size_t size, const char *type) {
@@ -152,11 +152,10 @@ static ant_value_t process_blob_parts(ant_t *js, byte_buf_t *buf, ant_value_t pa
 }
 
 static void blob_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != BLOB_NATIVE_TAG) return;
-  blob_data_t *bd = (blob_data_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  blob_data_t *bd = (blob_data_t *)js_get_native(value, BLOB_NATIVE_TAG);
   if (bd) { free(bd->data); free(bd->type); free(bd->name); free(bd); }
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, BLOB_NATIVE_TAG);
 }
 
 ant_value_t blob_create(ant_t *js, const uint8_t *data, size_t size, const char *type) {
diff --git a/src/modules/buffer.c b/src/modules/buffer.c
index 1a42e7e..3967105 100644
--- a/src/modules/buffer.c
+++ b/src/modules/buffer.c
@@ -57,7 +57,7 @@ static void ta_meta_free(void *ptr, size_t size) {
 ArrayBufferData *buffer_get_arraybuffer_data(ant_value_t value) {
   if (!is_object_type(value) || buffer_is_dataview(value)) return NULL;
   if (js_check_native_tag(value, BUFFER_ARRAYBUFFER_NATIVE_TAG))
-    return (ArrayBufferData *)js_get_native_ptr(value);
+    return (ArrayBufferData *)js_get_native(value, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   return NULL;
 }
 
@@ -66,32 +66,30 @@ TypedArrayData *buffer_get_typedarray_data(ant_value_t value) {
     return (TypedArrayData *)js_gettypedarray(value);
   if (!is_object_type(value)) return NULL;
   if (js_check_native_tag(value, BUFFER_TYPEDARRAY_NATIVE_TAG))
-    return (TypedArrayData *)js_get_native_ptr(value);
+    return (TypedArrayData *)js_get_native(value, BUFFER_TYPEDARRAY_NATIVE_TAG);
   return NULL;
 }
 
 DataViewData *buffer_get_dataview_data(ant_value_t value) {
   if (!is_object_type(value)) return NULL;
   if (js_check_native_tag(value, BUFFER_DATAVIEW_NATIVE_TAG))
-    return (DataViewData *)js_get_native_ptr(value);
+    return (DataViewData *)js_get_native(value, BUFFER_DATAVIEW_NATIVE_TAG);
   return NULL;
 }
 
 static void arraybuffer_finalize(ant_t *js, ant_object_t *obj) {
   ant_value_t value = js_obj_from_ptr(obj);
   if (!js_check_native_tag(value, BUFFER_ARRAYBUFFER_NATIVE_TAG)) return;
-  ArrayBufferData *data = (ArrayBufferData *)js_get_native_ptr(value);
-  js_set_native_ptr(value, NULL);
-  js_set_native_tag(value, 0);
+  ArrayBufferData *data = (ArrayBufferData *)js_get_native(value, BUFFER_ARRAYBUFFER_NATIVE_TAG);
+  js_clear_native(value, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   if (data) free_array_buffer_data(data);
 }
 
 static void typedarray_finalize(ant_t *js, ant_object_t *obj) {
   ant_value_t value = js_obj_from_ptr(obj);
   if (!js_check_native_tag(value, BUFFER_TYPEDARRAY_NATIVE_TAG)) return;
-  TypedArrayData *ta_data = (TypedArrayData *)js_get_native_ptr(value);
-  js_set_native_ptr(value, NULL);
-  js_set_native_tag(value, 0);
+  TypedArrayData *ta_data = (TypedArrayData *)js_get_native(value, BUFFER_TYPEDARRAY_NATIVE_TAG);
+  js_clear_native(value, BUFFER_TYPEDARRAY_NATIVE_TAG);
   if (!ta_data) return;
 
   if (ta_data->buffer) free_array_buffer_data(ta_data->buffer);
@@ -101,9 +99,8 @@ static void typedarray_finalize(ant_t *js, ant_object_t *obj) {
 static void dataview_finalize(ant_t *js, ant_object_t *obj) {
   ant_value_t value = js_obj_from_ptr(obj);
   if (!js_check_native_tag(value, BUFFER_DATAVIEW_NATIVE_TAG)) return;
-  DataViewData *dv_data = (DataViewData *)js_get_native_ptr(value);
-  js_set_native_ptr(value, NULL);
-  js_set_native_tag(value, 0);
+  DataViewData *dv_data = (DataViewData *)js_get_native(value, BUFFER_DATAVIEW_NATIVE_TAG);
+  js_clear_native(value, BUFFER_DATAVIEW_NATIVE_TAG);
   if (!dv_data) return;
 
   if (dv_data->buffer) free_array_buffer_data(dv_data->buffer);
@@ -386,8 +383,7 @@ static ant_value_t js_arraybuffer_constructor(ant_t *js, ant_value_t *args, int
   ant_value_t proto = js_get_ctor_proto(js, "ArrayBuffer", 11);
 
   if (is_special_object(proto)) js_set_proto_init(obj, proto);
-  js_set_native_ptr(obj, data);
-  js_set_native_tag(obj, BUFFER_ARRAYBUFFER_NATIVE_TAG);
+  js_set_native(obj, data, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   js_set(js, obj, "byteLength", js_mknum((double)length));
   js_set_finalizer(obj, arraybuffer_finalize);
 
@@ -420,8 +416,7 @@ static ant_value_t js_arraybuffer_slice(ant_t *js, ant_value_t *args, int nargs)
   ant_value_t proto = js_get_ctor_proto(js, "ArrayBuffer", 11);
 
   if (is_special_object(proto)) js_set_proto_init(new_obj, proto);
-  js_set_native_ptr(new_obj, new_data);
-  js_set_native_tag(new_obj, BUFFER_ARRAYBUFFER_NATIVE_TAG);
+  js_set_native(new_obj, new_data, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   js_set(js, new_obj, "byteLength", js_mknum((double)new_length));
   js_set_finalizer(new_obj, arraybuffer_finalize);
   
@@ -461,8 +456,7 @@ static ant_value_t js_arraybuffer_transfer(ant_t *js, ant_value_t *args, int nar
   ant_value_t proto = js_get_ctor_proto(js, "ArrayBuffer", 11);
 
   if (is_special_object(proto)) js_set_proto_init(new_obj, proto);
-  js_set_native_ptr(new_obj, new_data);
-  js_set_native_tag(new_obj, BUFFER_ARRAYBUFFER_NATIVE_TAG);
+  js_set_native(new_obj, new_data, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   js_set(js, new_obj, "byteLength", js_mknum((double)new_length));
   js_set_finalizer(new_obj, arraybuffer_finalize);
   
@@ -663,8 +657,7 @@ ant_value_t create_arraybuffer_obj(ant_t *js, ArrayBufferData *buffer) {
   ant_value_t ab_proto = js_get_ctor_proto(js, "ArrayBuffer", 11);
   if (is_special_object(ab_proto)) js_set_proto_init(ab_obj, ab_proto);
   
-  js_set_native_ptr(ab_obj, buffer);
-  js_set_native_tag(ab_obj, BUFFER_ARRAYBUFFER_NATIVE_TAG);
+  js_set_native(ab_obj, buffer, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   js_set(js, ab_obj, "byteLength", js_mknum((double)buffer->length));
   js_set_finalizer(ab_obj, arraybuffer_finalize);
   buffer->ref_count++;
@@ -691,8 +684,7 @@ ant_value_t create_typed_array_with_buffer(
   ant_value_t proto = js_get_ctor_proto(js, type_name, strlen(type_name));
   if (is_special_object(proto)) js_set_proto_init(obj, proto);
   
-  js_set_native_ptr(obj, ta_data);
-  js_set_native_tag(obj, BUFFER_TYPEDARRAY_NATIVE_TAG);
+  js_set_native(obj, ta_data, BUFFER_TYPEDARRAY_NATIVE_TAG);
   js_set(js, obj, "length", js_mknum((double)length));
   js_set(js, obj, "byteLength", js_mknum((double)(length * element_size)));
   js_set(js, obj, "byteOffset", js_mknum((double)byte_offset));
@@ -732,8 +724,7 @@ ant_value_t create_dataview_with_buffer(
   ant_value_t proto = js_get_ctor_proto(js, "DataView", 8);
   if (is_special_object(proto)) js_set_proto_init(obj, proto);
 
-  js_set_native_ptr(obj, dv_data);
-  js_set_native_tag(obj, BUFFER_DATAVIEW_NATIVE_TAG);
+  js_set_native(obj, dv_data, BUFFER_DATAVIEW_NATIVE_TAG);
   js_set_slot(obj, SLOT_BRAND, js_mknum(BRAND_DATAVIEW));
   js_mkprop_fast(js, obj, "buffer", 6, arraybuffer_obj);
   js_set_descriptor(js, obj, "buffer", 6, 0);
@@ -1435,8 +1426,7 @@ static ant_value_t js_dataview_constructor(ant_t *js, ant_value_t *args, int nar
   ant_value_t proto = js_get_ctor_proto(js, "DataView", 8);
   if (is_special_object(proto)) js_set_proto_init(obj, proto);
   
-  js_set_native_ptr(obj, dv_data);
-  js_set_native_tag(obj, BUFFER_DATAVIEW_NATIVE_TAG);
+  js_set_native(obj, dv_data, BUFFER_DATAVIEW_NATIVE_TAG);
   js_set_slot(obj, SLOT_BRAND, js_mknum(BRAND_DATAVIEW));
   js_mkprop_fast(js, obj, "buffer", 6, args[0]);
   js_set_descriptor(js, obj, "buffer", 6, 0);
@@ -2880,8 +2870,7 @@ static ant_value_t js_sharedarraybuffer_constructor(ant_t *js, ant_value_t *args
   ant_value_t proto = js_get_ctor_proto(js, "SharedArrayBuffer", 17);
 
   if (is_special_object(proto)) js_set_proto_init(obj, proto);
-  js_set_native_ptr(obj, data);
-  js_set_native_tag(obj, BUFFER_ARRAYBUFFER_NATIVE_TAG);
+  js_set_native(obj, data, BUFFER_ARRAYBUFFER_NATIVE_TAG);
   js_set(js, obj, "byteLength", js_mknum((double)length));
   js_set_finalizer(obj, arraybuffer_finalize);
   
diff --git a/src/modules/child_process.c b/src/modules/child_process.c
index 155bdf7..6f17b27 100644
--- a/src/modules/child_process.c
+++ b/src/modules/child_process.c
@@ -117,12 +117,12 @@ enum {
 
 static child_process_t *get_child_process(ant_value_t obj) {
   if (!js_check_native_tag(obj, CHILD_PROCESS_NATIVE_TAG)) return NULL;
-  return (child_process_t *)js_get_native_ptr(obj);
+  return (child_process_t *)js_get_native(obj, CHILD_PROCESS_NATIVE_TAG);
 }
 
 static child_stream_ctx_t *get_child_stream_ctx(ant_value_t obj) {
   if (!js_check_native_tag(obj, CHILD_STREAM_NATIVE_TAG)) return NULL;
-  return (child_stream_ctx_t *)js_get_native_ptr(obj);
+  return (child_stream_ctx_t *)js_get_native(obj, CHILD_STREAM_NATIVE_TAG);
 }
 static child_process_t *pending_children_tail = NULL;
 
diff --git a/src/modules/collections.c b/src/modules/collections.c
index 37296da..1e1005f 100644
--- a/src/modules/collections.c
+++ b/src/modules/collections.c
@@ -310,38 +310,38 @@ map_entry_t **get_map_from_obj(ant_value_t obj) {
   ant_object_t *ptr = js_obj_ptr(obj);
   if (!ptr || ptr->type_tag != T_MAP) return NULL;
   if (!js_check_native_tag(obj, MAP_NATIVE_TAG)) return NULL;
-  return (map_entry_t **)js_get_native_ptr(obj);
+  return (map_entry_t **)js_get_native(obj, MAP_NATIVE_TAG);
 }
 
 set_entry_t **get_set_from_obj(ant_value_t obj) {
   ant_object_t *ptr = js_obj_ptr(obj);
   if (!ptr || ptr->type_tag != T_SET) return NULL;
   if (!js_check_native_tag(obj, SET_NATIVE_TAG)) return NULL;
-  return (set_entry_t **)js_get_native_ptr(obj);
+  return (set_entry_t **)js_get_native(obj, SET_NATIVE_TAG);
 }
 
 static weakmap_entry_t **get_weakmap_from_obj(ant_value_t obj) {
   ant_object_t *ptr = js_obj_ptr(obj);
   if (!ptr || ptr->type_tag != T_WEAKMAP) return NULL;
   if (!js_check_native_tag(obj, WEAKMAP_NATIVE_TAG)) return NULL;
-  return (weakmap_entry_t **)js_get_native_ptr(obj);
+  return (weakmap_entry_t **)js_get_native(obj, WEAKMAP_NATIVE_TAG);
 }
 
 static weakset_entry_t **get_weakset_from_obj(ant_value_t obj) {
   ant_object_t *ptr = js_obj_ptr(obj);
   if (!ptr || ptr->type_tag != T_WEAKSET) return NULL;
   if (!js_check_native_tag(obj, WEAKSET_NATIVE_TAG)) return NULL;
-  return (weakset_entry_t **)js_get_native_ptr(obj);
+  return (weakset_entry_t **)js_get_native(obj, WEAKSET_NATIVE_TAG);
 }
 
 map_iterator_state_t *get_map_iter_state(ant_value_t obj) {
   if (!js_check_native_tag(obj, MAP_ITER_NATIVE_TAG)) return NULL;
-  return (map_iterator_state_t *)js_get_native_ptr(obj);
+  return (map_iterator_state_t *)js_get_native(obj, MAP_ITER_NATIVE_TAG);
 }
 
 set_iterator_state_t *get_set_iter_state(ant_value_t obj) {
   if (!js_check_native_tag(obj, SET_ITER_NATIVE_TAG)) return NULL;
-  return (set_iterator_state_t *)js_get_native_ptr(obj);
+  return (set_iterator_state_t *)js_get_native(obj, SET_ITER_NATIVE_TAG);
 }
 
 static ant_value_t map_set(ant_t *js, ant_value_t *args, int nargs) {
diff --git a/src/modules/crypto.c b/src/modules/crypto.c
index 62553ab..b05e0f9 100644
--- a/src/modules/crypto.c
+++ b/src/modules/crypto.c
@@ -223,7 +223,7 @@ static ant_value_t crypto_get_input_bytes(
 
 static ant_hash_state_t *crypto_get_hash_state(ant_value_t value) {
   if (!js_check_native_tag(value, CRYPTO_HASH_NATIVE_TAG)) return NULL;
-  ant_hash_state_t *state = (ant_hash_state_t *)js_get_native_ptr(value);
+  ant_hash_state_t *state = (ant_hash_state_t *)js_get_native(value, CRYPTO_HASH_NATIVE_TAG);
   return (state && state->ctx) ? state : NULL;
 }
 
diff --git a/src/modules/events.c b/src/modules/events.c
index 9a61bfc..842f8b3 100644
--- a/src/modules/events.c
+++ b/src/modules/events.c
@@ -42,7 +42,7 @@ enum {
 
 static event_data_t *get_event_data(ant_value_t obj) {
   if (!js_check_native_tag(obj, EVENT_NATIVE_TAG)) return NULL;
-  return (event_data_t *)js_get_native_ptr(obj);
+  return (event_data_t *)js_get_native(obj, EVENT_NATIVE_TAG);
 }
 
 static double get_timestamp_ms(void) {
@@ -169,7 +169,7 @@ static EventType **get_or_create_emitter_events(ant_t *js, ant_value_t this_obj)
     js_set_native(this_obj, events, EVENT_EMITTER_NATIVE_TAG);
     return events;
   }
-  return (EventType **)js_get_native_ptr(this_obj);
+  return (EventType **)js_get_native(this_obj, EVENT_EMITTER_NATIVE_TAG);
 }
 
 static EventType *find_or_create_global_event_type(ant_t *js, ant_value_t js_key) {
diff --git a/src/modules/fetch.c b/src/modules/fetch.c
index df0c987..b97fea6 100644
--- a/src/modules/fetch.c
+++ b/src/modules/fetch.c
@@ -658,7 +658,7 @@ static bool fetch_handle_data_url(fetch_request_t *req) {
 
 static ant_value_t fetch_upload_on_reject(ant_t *js, ant_value_t *args, int nargs) {
   fetch_request_t *req = js_check_native_tag(js->current_func, FETCH_REQUEST_NATIVE_TAG)
-    ? (fetch_request_t *)js_get_native_ptr(js->current_func)
+    ? (fetch_request_t *)js_get_native(js->current_func, FETCH_REQUEST_NATIVE_TAG)
     : NULL;
   ant_value_t reason = (nargs > 0) ? args[0] : js_mkundef();
 
@@ -678,7 +678,7 @@ static ant_value_t fetch_upload_on_reject(ant_t *js, ant_value_t *args, int narg
 static void fetch_upload_schedule_next_read(fetch_request_t *req);
 static ant_value_t fetch_upload_on_read(ant_t *js, ant_value_t *args, int nargs) {
   fetch_request_t *req = js_check_native_tag(js->current_func, FETCH_REQUEST_NATIVE_TAG)
-    ? (fetch_request_t *)js_get_native_ptr(js->current_func)
+    ? (fetch_request_t *)js_get_native(js->current_func, FETCH_REQUEST_NATIVE_TAG)
     : NULL;
   
   ant_value_t result = (nargs > 0) ? args[0] : js_mkundef();
@@ -839,7 +839,7 @@ static void fetch_start_http(fetch_request_t *req) {
 
 static ant_value_t fetch_abort_listener(ant_t *js, ant_value_t *args, int nargs) {
   fetch_request_t *req = js_check_native_tag(js->current_func, FETCH_REQUEST_NATIVE_TAG)
-    ? (fetch_request_t *)js_get_native_ptr(js->current_func)
+    ? (fetch_request_t *)js_get_native(js->current_func, FETCH_REQUEST_NATIVE_TAG)
     : NULL;
   ant_value_t signal = 0;
   ant_value_t reason = 0;
diff --git a/src/modules/ffi.c b/src/modules/ffi.c
index a3e23d0..8d91448 100644
--- a/src/modules/ffi.c
+++ b/src/modules/ffi.c
@@ -347,22 +347,22 @@ static ffi_marshaled_type_t ffi_infer_variadic_type(ant_value_t value) {
 
 static ffi_library_handle_t *ffi_library_data(ant_value_t value) {
   if (!js_check_native_tag(value, FFI_LIBRARY_NATIVE_TAG)) return NULL;
-  return (ffi_library_handle_t *)js_get_native_ptr(value);
+  return (ffi_library_handle_t *)js_get_native(value, FFI_LIBRARY_NATIVE_TAG);
 }
 
 static ffi_function_handle_t *ffi_function_data(ant_value_t value) {
   if (!js_check_native_tag(value, FFI_FUNCTION_NATIVE_TAG)) return NULL;
-  return (ffi_function_handle_t *)js_get_native_ptr(value);
+  return (ffi_function_handle_t *)js_get_native(value, FFI_FUNCTION_NATIVE_TAG);
 }
 
 static ffi_pointer_handle_t *ffi_pointer_data(ant_value_t value) {
   if (!js_check_native_tag(value, FFI_POINTER_NATIVE_TAG)) return NULL;
-  return (ffi_pointer_handle_t *)js_get_native_ptr(value);
+  return (ffi_pointer_handle_t *)js_get_native(value, FFI_POINTER_NATIVE_TAG);
 }
 
 static ffi_callback_handle_t *ffi_callback_data(ant_value_t value) {
   if (!js_check_native_tag(value, FFI_CALLBACK_NATIVE_TAG)) return NULL;
-  return (ffi_callback_handle_t *)js_get_native_ptr(value);
+  return (ffi_callback_handle_t *)js_get_native(value, FFI_CALLBACK_NATIVE_TAG);
 }
 
 static void ffi_library_close_handle(ffi_library_handle_t *library) {
@@ -470,8 +470,7 @@ static ant_value_t ffi_make_pointer(ant_t *js, ffi_pointer_region_t *region, siz
   if (region) region->ref_count++;
 
   if (g_ffi_pointer_proto) js_set_proto_init(obj, g_ffi_pointer_proto);
-  js_set_native_ptr(obj, handle);
-  js_set_native_tag(obj, FFI_POINTER_NATIVE_TAG);
+  js_set_native(obj, handle, FFI_POINTER_NATIVE_TAG);
   js_set_finalizer(obj, ffi_pointer_finalize);
 
   return obj;
@@ -773,8 +772,7 @@ static ant_value_t ffi_make_function(ant_t *js, ffi_library_handle_t *library, c
 
   if (g_ffi_function_proto) js_set_proto_init(obj, g_ffi_function_proto);
   js_set_slot(obj, SLOT_CFUNC, js_mkfun(ffi_function_call));
-  js_set_native_ptr(obj, handle);
-  js_set_native_tag(obj, FFI_FUNCTION_NATIVE_TAG);
+  js_set_native(obj, handle, FFI_FUNCTION_NATIVE_TAG);
   js_set_slot_wb(js, obj, SLOT_ENTRIES, library ? library->obj : js_mkundef());
   js_set_finalizer(obj, ffi_function_finalize);
 
@@ -784,56 +782,52 @@ static ant_value_t ffi_make_function(ant_t *js, ffi_library_handle_t *library, c
 
 void ffi_library_finalize(ant_t *js, ant_object_t *obj) {
   ffi_library_handle_t *library;
-  if (obj->native.tag != FFI_LIBRARY_NATIVE_TAG) return;
+  ant_value_t value = js_obj_from_ptr(obj);
   
-  library = (ffi_library_handle_t *)obj->native.ptr;
+  library = (ffi_library_handle_t *)js_get_native(value, FFI_LIBRARY_NATIVE_TAG);
   if (!library) return;
   
   ffi_library_close_handle(library);
   free(library->path);
   free(library);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, FFI_LIBRARY_NATIVE_TAG);
 }
 
 void ffi_function_finalize(ant_t *js, ant_object_t *obj) {
   ffi_function_handle_t *handle;
-  if (obj->native.tag != FFI_FUNCTION_NATIVE_TAG) return;
+  ant_value_t value = js_obj_from_ptr(obj);
   
-  handle = (ffi_function_handle_t *)obj->native.ptr;
+  handle = (ffi_function_handle_t *)js_get_native(value, FFI_FUNCTION_NATIVE_TAG);
   if (!handle) return;
   
   free(handle->symbol_name);
   ffi_signature_cleanup(&handle->signature);
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, FFI_FUNCTION_NATIVE_TAG);
 }
 
 void ffi_pointer_finalize(ant_t *js, ant_object_t *obj) {
   ffi_pointer_handle_t *handle;
-  if (obj->native.tag != FFI_POINTER_NATIVE_TAG) return;
+  ant_value_t value = js_obj_from_ptr(obj);
   
-  handle = (ffi_pointer_handle_t *)obj->native.ptr;
+  handle = (ffi_pointer_handle_t *)js_get_native(value, FFI_POINTER_NATIVE_TAG);
   if (!handle) return;
   
   ffi_pointer_close_handle(handle, false);
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, FFI_POINTER_NATIVE_TAG);
 }
 
 void ffi_callback_finalize(ant_t *js, ant_object_t *obj) {
   ffi_callback_handle_t *handle;
-  if (obj->native.tag != FFI_CALLBACK_NATIVE_TAG) return;
+  ant_value_t value = js_obj_from_ptr(obj);
   
-  handle = (ffi_callback_handle_t *)obj->native.ptr;
+  handle = (ffi_callback_handle_t *)js_get_native(value, FFI_CALLBACK_NATIVE_TAG);
   if (!handle) return;
   
   ffi_callback_close_handle(handle);
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, FFI_CALLBACK_NATIVE_TAG);
 }
 
 static bool ffi_callback_result_to_c(
@@ -1003,8 +997,7 @@ static ant_value_t ffi_dlopen(ant_t *js, ant_value_t *args, int nargs) {
   obj = js_mkobj(js);
   if (g_ffi_library_proto) js_set_proto_init(obj, g_ffi_library_proto);
   library->obj = obj;
-  js_set_native_ptr(obj, library);
-  js_set_native_tag(obj, FFI_LIBRARY_NATIVE_TAG);
+  js_set_native(obj, library, FFI_LIBRARY_NATIVE_TAG);
   js_set_finalizer(obj, ffi_library_finalize);
   return obj;
 }
@@ -1402,8 +1395,7 @@ static ant_value_t ffi_create_callback(ant_t *js, ant_value_t *args, int nargs)
   callback->owner_obj = obj;
   callback->owner_thread = pthread_self();
   callback->closed = false;
-  js_set_native_ptr(obj, callback);
-  js_set_native_tag(obj, FFI_CALLBACK_NATIVE_TAG);
+  js_set_native(obj, callback, FFI_CALLBACK_NATIVE_TAG);
   js_set_slot_wb(js, obj, SLOT_DATA, fn);
   js_set_finalizer(obj, ffi_callback_finalize);
   return obj;
diff --git a/src/modules/formdata.c b/src/modules/formdata.c
index 1048192..45eb575 100644
--- a/src/modules/formdata.c
+++ b/src/modules/formdata.c
@@ -71,7 +71,7 @@ static void fd_data_free(fd_data_t *d) {
 
 static fd_data_t *get_fd_data(ant_value_t obj) {
   if (!js_check_native_tag(obj, FORMDATA_NATIVE_TAG)) return NULL;
-  return (fd_data_t *)js_get_native_ptr(obj);
+  return (fd_data_t *)js_get_native(obj, FORMDATA_NATIVE_TAG);
 }
 
 // TODO: compact
@@ -84,11 +84,10 @@ static ant_value_t get_fd_values(ant_value_t obj) {
 }
 
 static void formdata_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != FORMDATA_NATIVE_TAG) return;
-  fd_data_t *d = (fd_data_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  fd_data_t *d = (fd_data_t *)js_get_native(value, FORMDATA_NATIVE_TAG);
   fd_data_free(d);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, FORMDATA_NATIVE_TAG);
 }
 
 static bool fd_append_str(fd_data_t *d, const char *name, const char *value) {
@@ -383,7 +382,7 @@ static ant_value_t formdata_iter_next(ant_t *js, ant_value_t *args, int nargs) {
   if (!js_check_native_tag(js->this_val, FORMDATA_ITER_NATIVE_TAG))
     return js_iter_result(js, false, js_mkundef());
 
-  fd_iter_t *st = (fd_iter_t *)js_get_native_ptr(js->this_val);
+  fd_iter_t *st = (fd_iter_t *)js_get_native(js->this_val, FORMDATA_ITER_NATIVE_TAG);
   ant_value_t fd_obj = js_get_slot(js->this_val, SLOT_DATA);
   fd_data_t *d = get_fd_data(fd_obj);
   if (!d) return js_iter_result(js, false, js_mkundef());
@@ -418,10 +417,9 @@ static ant_value_t formdata_iter_next(ant_t *js, ant_value_t *args, int nargs) {
 }
 
 static void formdata_iter_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != FORMDATA_ITER_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, FORMDATA_ITER_NATIVE_TAG));
+  js_clear_native(value, FORMDATA_ITER_NATIVE_TAG);
 }
 
 static ant_value_t make_formdata_iter(ant_t *js, ant_value_t fd_obj, int kind) {
diff --git a/src/modules/fs.c b/src/modules/fs.c
index 8b2c758..6e7a661 100644
--- a/src/modules/fs.c
+++ b/src/modules/fs.c
@@ -158,7 +158,7 @@ enum {
 
 static fs_watcher_t *fs_watcher_data(ant_value_t value) {
   if (!js_check_native_tag(value, FS_WATCHER_NATIVE_TAG)) return NULL;
-  return (fs_watcher_t *)js_get_native_ptr(value);
+  return (fs_watcher_t *)js_get_native(value, FS_WATCHER_NATIVE_TAG);
 }
 
 static void fs_add_active_watcher(fs_watcher_t *watcher) {
@@ -922,10 +922,10 @@ static ant_value_t js_fswatcher_ctor(ant_t *js, ant_value_t *args, int nargs) {
 
 static void fs_watcher_finalize(ant_t *js, ant_object_t *obj) {
   fs_watcher_t *watcher = NULL;
-  if (!obj) return;
+  ant_value_t value = js_obj_from_ptr(obj);
 
-  watcher = (fs_watcher_t *)obj->native.ptr;
-  obj->native.ptr = NULL;
+  watcher = (fs_watcher_t *)js_get_native(value, FS_WATCHER_NATIVE_TAG);
+  js_clear_native(value, FS_WATCHER_NATIVE_TAG);
   if (!watcher) return;
 
   watcher->finalized = true;
@@ -1083,8 +1083,7 @@ static ant_value_t fs_watcher_make_object(ant_t *js, fs_watcher_t *watcher) {
 
   obj = js_mkobj(js);
   js_set_proto_init(obj, g_fswatcher_proto);
-  js_set_native_ptr(obj, watcher);
-  js_set_native_tag(obj, FS_WATCHER_NATIVE_TAG);
+  js_set_native(obj, watcher, FS_WATCHER_NATIVE_TAG);
   js_set_finalizer(obj, fs_watcher_finalize);
   watcher->obj = obj;
   
@@ -1587,7 +1586,7 @@ static ant_value_t builtin_fs_filehandle_writeFile(ant_t *js, ant_value_t *args,
 static void fs_init_filehandle_proto(ant_t *js) {
   if (is_object_type(g_filehandle_proto)) return;
   g_filehandle_proto = js_mkobj(js);
-  js_set_native_tag(g_filehandle_proto, FS_FILEHANDLE_NATIVE_TAG);
+  js_set_native(g_filehandle_proto, NULL, FS_FILEHANDLE_NATIVE_TAG);
   js_set(js, g_filehandle_proto, "close", js_mkfun(builtin_fs_filehandle_close));
   js_set(js, g_filehandle_proto, "stat", js_mkfun(builtin_fs_filehandle_stat));
   js_set(js, g_filehandle_proto, "sync", js_mkfun(builtin_fs_filehandle_sync));
@@ -1601,7 +1600,7 @@ static ant_value_t fs_make_filehandle(ant_t *js, int fd) {
   fs_init_filehandle_proto(js);
   ant_value_t handle = js_mkobj(js);
   
-  js_set_native_tag(handle, FS_FILEHANDLE_NATIVE_TAG);
+  js_set_native(handle, NULL, FS_FILEHANDLE_NATIVE_TAG);
   js_set_proto_init(handle, g_filehandle_proto);
   js_set_slot(handle, SLOT_DATA, js_mknum((double)fd));
   js_set(js, handle, "fd", js_mknum((double)fd));
@@ -4335,7 +4334,7 @@ static ant_value_t builtin_fs_watch(ant_t *js, ant_value_t *args, int nargs) {
 
   rc = fs_watcher_start_event(watcher, path, opts.persistent, opts.recursive);
   if (rc != 0) {
-    js_set_native_ptr(watcher_obj, NULL);
+    js_clear_native(watcher_obj, FS_WATCHER_NATIVE_TAG);
     fs_watcher_free(watcher);
     return fs_watch_error(js, rc, path);
   }
diff --git a/src/modules/generator.c b/src/modules/generator.c
index baaee42..c583092 100644
--- a/src/modules/generator.c
+++ b/src/modules/generator.c
@@ -52,7 +52,7 @@ static ant_value_t generator_result(ant_t *js, bool done, ant_value_t value) {
 
 static generator_data_t *generator_data(ant_value_t gen) {
   if (!js_check_native_tag(gen, GENERATOR_NATIVE_TAG)) return NULL;
-  return (generator_data_t *)js_get_native_ptr(gen);
+  return (generator_data_t *)js_get_native(gen, GENERATOR_NATIVE_TAG);
 }
 
 static generator_state_t generator_state(ant_value_t gen) {
@@ -285,13 +285,12 @@ bool generator_resume_pending_request(ant_t *js, coroutine_t *coro, ant_value_t
 
 static void generator_finalize(ant_t *js, ant_object_t *obj) {
   ant_value_t gen = js_obj_from_ptr(obj);
-  generator_data_t *data = (generator_data_t *)js_get_native_ptr(gen);
+  generator_data_t *data = (generator_data_t *)js_get_native(gen, GENERATOR_NATIVE_TAG);
   
   if (!data) return;
   if (data->coro) generator_clear_coro(gen, data->coro);
   
-  js_set_native_ptr(gen, NULL);
-  js_set_native_tag(gen, 0);
+  js_set_native(gen, NULL, 0);
   
   generator_free_queue(data);
   free(data);
@@ -600,8 +599,7 @@ ant_value_t sv_call_generator_closure_dispatch(
   coroutine_hold(coro, CORO_HOLD_GENERATOR);
   coroutine_release(coro);
 
-  js_set_native_ptr(gen, data);
-  js_set_native_tag(gen, GENERATOR_NATIVE_TAG);
+  js_set_native(gen, data, GENERATOR_NATIVE_TAG);
   js_set_finalizer(gen, generator_finalize);
 
   ant_value_t instance_proto = js_get(js, callee_func, "prototype");
diff --git a/src/modules/headers.c b/src/modules/headers.c
index 70a5223..853b40a 100644
--- a/src/modules/headers.c
+++ b/src/modules/headers.c
@@ -71,7 +71,7 @@ static void list_free(hdr_list_t *l) {
 
 static hdr_list_t *get_list(ant_value_t obj) {
   if (!js_check_native_tag(obj, HEADERS_NATIVE_TAG)) return NULL;
-  return (hdr_list_t *)js_get_native_ptr(obj);
+  return (hdr_list_t *)js_get_native(obj, HEADERS_NATIVE_TAG);
 }
 
 static headers_guard_t get_guard(ant_value_t obj) {
@@ -480,7 +480,7 @@ static ant_value_t init_from_record(ant_t *js, hdr_list_t *l, ant_value_t obj) {
 
 bool advance_headers(ant_t *js, js_iter_t *it, ant_value_t *out) {
   if (!js_check_native_tag(it->iterator, HEADERS_ITER_NATIVE_TAG)) return false;
-  hdr_iter_t *st = (hdr_iter_t *)js_get_native_ptr(it->iterator);
+  hdr_iter_t *st = (hdr_iter_t *)js_get_native(it->iterator, HEADERS_ITER_NATIVE_TAG);
 
   size_t count = 0;
   sorted_pair_t *view = build_sorted_view(st->list, &count);
diff --git a/src/modules/iterator.c b/src/modules/iterator.c
index 8d06d61..92c493c 100644
--- a/src/modules/iterator.c
+++ b/src/modules/iterator.c
@@ -884,13 +884,14 @@ static ant_value_t async_terminal_finish_callback(ant_t *js, ant_value_t state,
 static void async_terminal_close_and_reject(ant_t *js, ant_value_t state, ant_value_t reason);
 
 static void async_terminal_state_finalize(ant_t *js, ant_object_t *obj) {
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, ASYNC_TERMINAL_STATE_TAG));
+  js_clear_native(value, ASYNC_TERMINAL_STATE_TAG);
 }
 
 static inline async_terminal_state_t *async_terminal_state(ant_value_t state) {
   if (!js_check_native_tag(state, ASYNC_TERMINAL_STATE_TAG)) return NULL;
-  return (async_terminal_state_t *)js_get_native_ptr(state);
+  return (async_terminal_state_t *)js_get_native(state, ASYNC_TERMINAL_STATE_TAG);
 }
 
 static inline int async_terminal_mode(ant_value_t state) {
@@ -1194,8 +1195,7 @@ static ant_value_t async_iter_terminal(ant_t *js, ant_value_t *args, int nargs,
   st->index = 0;
   st->has_acc = (mode == ASYNC_TERM_REDUCE && nargs > 1);
   
-  js_set_native_tag(state, ASYNC_TERMINAL_STATE_TAG);
-  js_set_native_ptr(state, st);
+  js_set_native(state, st, ASYNC_TERMINAL_STATE_TAG);
   js_set_finalizer(state, async_terminal_state_finalize);
 
   js_set_slot_wb(js, state, SLOT_DATA, iter);
diff --git a/src/modules/napi.c b/src/modules/napi.c
index 88d7e5a..b5a038e 100644
--- a/src/modules/napi.c
+++ b/src/modules/napi.c
@@ -483,7 +483,7 @@ static ant_value_t napi_callback_trampoline(ant_t *js, ant_value_t *args, int na
   ant_value_t current = js_getcurrentfunc(js);
   if (!js_check_native_tag(current, NAPI_CALLBACK_NATIVE_TAG)) return js_mkundef();
 
-  napi_callback_binding_t *binding = (napi_callback_binding_t *)js_get_native_ptr(current);
+  napi_callback_binding_t *binding = (napi_callback_binding_t *)js_get_native(current, NAPI_CALLBACK_NATIVE_TAG);
   if (!binding || !binding->cb) return js_mkundef();
 
   ant_napi_env_t *nenv = binding->env ? binding->env : napi_get_or_create_env(js);
diff --git a/src/modules/net.c b/src/modules/net.c
index 624396e..3186841 100644
--- a/src/modules/net.c
+++ b/src/modules/net.c
@@ -102,12 +102,12 @@ static ant_value_t net_not_implemented(ant_t *js, const char *what);
 
 static net_server_t *net_server_data(ant_value_t value) {
   if (!js_check_native_tag(value, NET_SERVER_NATIVE_TAG)) return NULL;
-  return (net_server_t *)js_get_native_ptr(value);
+  return (net_server_t *)js_get_native(value, NET_SERVER_NATIVE_TAG);
 }
 
 static net_socket_t *net_socket_data(ant_value_t value) {
   if (!js_check_native_tag(value, NET_SOCKET_NATIVE_TAG)) return NULL;
-  return (net_socket_t *)js_get_native_ptr(value);
+  return (net_socket_t *)js_get_native(value, NET_SOCKET_NATIVE_TAG);
 }
 
 static void net_add_active_server(net_server_t *server) {
@@ -357,8 +357,7 @@ static void net_socket_detach(net_socket_t *socket) {
 
   net_remove_active_socket(socket);
   if (is_object_type(socket->obj)) {
-    js_set_native_ptr(socket->obj, NULL);
-    js_set_native_tag(socket->obj, 0);
+    js_set_native(socket->obj, NULL, 0);
   }
   net_server_maybe_finish_close(socket->server);
   free(socket);
@@ -383,8 +382,7 @@ static net_socket_t *net_socket_create(ant_t *js, bool allow_half_open) {
   socket->encoding = js_mkundef();
   socket->allow_half_open = allow_half_open;
 
-  js_set_native_ptr(obj, socket);
-  js_set_native_tag(obj, NET_SOCKET_NATIVE_TAG);
+  js_set_native(obj, socket, NET_SOCKET_NATIVE_TAG);
   js_set(js, obj, "remoteAddress", js_mkundef());
   js_set(js, obj, "remotePort", js_mkundef());
   js_set(js, obj, "remoteFamily", js_mkundef());
@@ -431,8 +429,7 @@ static net_server_t *net_server_create(ant_t *js) {
     return NULL;
   }
 
-  js_set_native_ptr(obj, server);
-  js_set_native_tag(obj, NET_SERVER_NATIVE_TAG);
+  js_set_native(obj, server, NET_SERVER_NATIVE_TAG);
   net_server_sync_state(server);
   return server;
 }
diff --git a/src/modules/request.c b/src/modules/request.c
index 4db02a5..b58d666 100644
--- a/src/modules/request.c
+++ b/src/modules/request.c
@@ -32,7 +32,7 @@ enum { REQUEST_NATIVE_TAG = 0x52455153u }; // REQS
 
 static request_data_t *get_data(ant_value_t obj) {
   if (!js_check_native_tag(obj, REQUEST_NATIVE_TAG)) return NULL;
-  return (request_data_t *)js_get_native_ptr(obj);
+  return (request_data_t *)js_get_native(obj, REQUEST_NATIVE_TAG);
 }
 
 request_data_t *request_get_data(ant_value_t obj) {
diff --git a/src/modules/response.c b/src/modules/response.c
index ec1dcbe..bd90651 100644
--- a/src/modules/response.c
+++ b/src/modules/response.c
@@ -32,7 +32,7 @@ enum { RESPONSE_NATIVE_TAG = 0x52455350u }; // RESP
 
 static response_data_t *get_data(ant_value_t obj) {
   if (!js_check_native_tag(obj, RESPONSE_NATIVE_TAG)) return NULL;
-  return (response_data_t *)js_get_native_ptr(obj);
+  return (response_data_t *)js_get_native(obj, RESPONSE_NATIVE_TAG);
 }
 
 response_data_t *response_get_data(ant_value_t obj) {
diff --git a/src/modules/server.c b/src/modules/server.c
index 14a4245..cf1d3e0 100644
--- a/src/modules/server.c
+++ b/src/modules/server.c
@@ -37,6 +37,11 @@ typedef struct server_conn_state_s server_conn_state_t;
 
 static server_runtime_t *g_server = NULL;
 
+enum {
+  SERVER_REQUEST_NATIVE_TAG = 0x53524551u, // SREQ
+  SERVER_RUNTIME_NATIVE_TAG = 0x5352544du  // SRTM
+};
+
 typedef struct stop_waiter_s {
   ant_value_t promise;
   struct stop_waiter_s *next;
@@ -119,11 +124,11 @@ static inline void server_request_retain(server_request_t *req) {
 }
 
 static inline server_request_t *server_current_request(ant_t *js) {
-  return (server_request_t *)js_get_native_ptr(js->current_func);
+  return (server_request_t *)js_get_native(js->current_func, SERVER_REQUEST_NATIVE_TAG);
 }
 
 static inline server_runtime_t *server_current_runtime(ant_t *js) {
-  return (server_runtime_t *)js_get_native_ptr(js->current_func);
+  return (server_runtime_t *)js_get_native(js->current_func, SERVER_RUNTIME_NATIVE_TAG);
 }
 
 static ant_value_t server_mkreqfun(
@@ -132,7 +137,7 @@ static ant_value_t server_mkreqfun(
   server_request_t *req
 ) {
   ant_value_t func = js_heavy_mkfun(js, fn, js_mkundef());
-  js_set_native_ptr(func, req);
+  js_set_native(func, req, SERVER_REQUEST_NATIVE_TAG);
   return func;
 }
 
@@ -142,7 +147,7 @@ static ant_value_t server_mkruntimefun(
   server_runtime_t *server
 ) {
   ant_value_t func = js_heavy_mkfun(js, fn, js_mkundef());
-  js_set_native_ptr(func, server);
+  js_set_native(func, server, SERVER_RUNTIME_NATIVE_TAG);
   return func;
 }
 
diff --git a/src/modules/stream.c b/src/modules/stream.c
index 6459a5d..a8a1a6c 100644
--- a/src/modules/stream.c
+++ b/src/modules/stream.c
@@ -52,7 +52,7 @@ static inline void stream_set_end_callback(ant_t *js, ant_value_t stream_obj, an
 
 static stream_private_state_t *stream_private_state(ant_value_t stream_obj) {
   if (!stream_is_instance(stream_obj)) return NULL;
-  return (stream_private_state_t *)js_get_native_ptr(stream_obj);
+  return (stream_private_state_t *)js_get_native(stream_obj, STREAM_NATIVE_TAG);
 }
 
 static ant_value_t stream_require_this(ant_t *js, ant_value_t value, const char *label) {
@@ -118,7 +118,7 @@ static void stream_finalize(ant_t *js, ant_object_t *obj) {
   ant_value_t stream_obj = js_obj_from_ptr(obj);
   stream_private_state_t *priv = stream_private_state(stream_obj);
   if (!priv) return;
-  js_set_native_ptr(stream_obj, NULL);
+  js_clear_native(stream_obj, STREAM_NATIVE_TAG);
   if (priv->attached_state && priv->attached_state_finalize)
     priv->attached_state_finalize(js, stream_obj, priv->attached_state);
   free(priv);
@@ -347,9 +347,7 @@ static ant_value_t stream_make_base_object(ant_t *js, ant_value_t proto) {
   stream_private_state_t *priv = calloc(1, sizeof(*priv));
   
   if (is_object_type(proto)) js_set_proto_init(obj, proto);
-  js_set_native_tag(obj, STREAM_NATIVE_TAG);
-  
-  if (priv) js_set_native_ptr(obj, priv);
+  js_set_native(obj, priv, STREAM_NATIVE_TAG);
   js_set_slot(obj, SLOT_AUX, js_mkundef());
   js_set_finalizer(obj, stream_finalize);
   
@@ -1801,21 +1799,21 @@ ant_value_t stream_construct_writable(ant_t *js, ant_value_t base_proto, ant_val
 void stream_init_readable_object(ant_t *js, ant_value_t obj, ant_value_t options) {
   stream_init_constructors(js);
   if (!is_object_type(obj)) return;
-  js_set_native_tag(obj, STREAM_NATIVE_TAG);
+  js_set_native(obj, NULL, STREAM_NATIVE_TAG);
   stream_init_readable(js, obj, options);
 }
 
 void stream_init_writable_object(ant_t *js, ant_value_t obj, ant_value_t options) {
   stream_init_constructors(js);
   if (!is_object_type(obj)) return;
-  js_set_native_tag(obj, STREAM_NATIVE_TAG);
+  js_set_native(obj, NULL, STREAM_NATIVE_TAG);
   stream_init_writable(js, obj, options);
 }
 
 void stream_init_duplex_object(ant_t *js, ant_value_t obj, ant_value_t options) {
   stream_init_constructors(js);
   if (!is_object_type(obj)) return;
-  js_set_native_tag(obj, STREAM_NATIVE_TAG);
+  js_set_native(obj, NULL, STREAM_NATIVE_TAG);
   stream_init_readable(js, obj, options);
   stream_init_writable(js, obj, options);
 }
diff --git a/src/modules/string_decoder.c b/src/modules/string_decoder.c
index 861ee79..3d1fa70 100644
--- a/src/modules/string_decoder.c
+++ b/src/modules/string_decoder.c
@@ -35,15 +35,14 @@ enum { STRING_DECODER_NATIVE_TAG = 0x53444543u }; // SDEC
 
 static sd_state_t *sd_get_state(ant_value_t obj) {
   if (!js_check_native_tag(obj, STRING_DECODER_NATIVE_TAG)) return NULL;
-  return (sd_state_t *)js_get_native_ptr(obj);
+  return (sd_state_t *)js_get_native(obj, STRING_DECODER_NATIVE_TAG);
 }
 
 static void sd_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != STRING_DECODER_NATIVE_TAG) return;
-  sd_state_t *st = (sd_state_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  sd_state_t *st = (sd_state_t *)js_get_native(value, STRING_DECODER_NATIVE_TAG);
   if (st) { free(st->td); free(st); }
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, STRING_DECODER_NATIVE_TAG);
 }
 
 static int sd_parse_encoding(const char *s, size_t len) {
diff --git a/src/modules/textcodec.c b/src/modules/textcodec.c
index 026f29c..89229b5 100644
--- a/src/modules/textcodec.c
+++ b/src/modules/textcodec.c
@@ -30,14 +30,13 @@ td_state_t *td_state_new(td_encoding_t enc, bool fatal, bool ignore_bom) {
 
 static td_state_t *td_get_state(ant_value_t obj) {
   if (!js_check_native_tag(obj, TEXT_DECODER_NATIVE_TAG)) return NULL;
-  return (td_state_t *)js_get_native_ptr(obj);
+  return (td_state_t *)js_get_native(obj, TEXT_DECODER_NATIVE_TAG);
 }
 
 static void td_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != TEXT_DECODER_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, TEXT_DECODER_NATIVE_TAG));
+  js_clear_native(value, TEXT_DECODER_NATIVE_TAG);
 }
 
 static int resolve_encoding(const char *s, size_t len) {
diff --git a/src/modules/tls.c b/src/modules/tls.c
index d63aca4..9330923 100644
--- a/src/modules/tls.c
+++ b/src/modules/tls.c
@@ -41,7 +41,7 @@ static void tls_context_free(ant_tls_context_wrap_t *wrap) {
 
 static ant_tls_context_wrap_t *tls_context_data(ant_value_t value) {
   if (!js_check_native_tag(value, TLS_CONTEXT_NATIVE_TAG)) return NULL;
-  return (ant_tls_context_wrap_t *)js_get_native_ptr(value);
+  return (ant_tls_context_wrap_t *)js_get_native(value, TLS_CONTEXT_NATIVE_TAG);
 }
 
 static bool tls_value_bytes(
@@ -95,8 +95,7 @@ static ant_value_t js_tls_context_close(ant_t *js, ant_value_t *args, int nargs)
   if (!wrap) return js_getthis(js);
 
   tls_context_free(wrap);
-  js_set_native_ptr(wrap->obj, NULL);
-  js_set_native_tag(wrap->obj, 0);
+  js_set_native(wrap->obj, NULL, 0);
   return js_getthis(js);
 }
 
@@ -214,8 +213,7 @@ static ant_value_t js_tls_create_context(ant_t *js, ant_value_t *args, int nargs
   js_set_proto_init(obj, g_tls_context_proto);
   wrap->obj = obj;
   
-  js_set_native_ptr(obj, wrap);
-  js_set_native_tag(obj, TLS_CONTEXT_NATIVE_TAG);
+  js_set_native(obj, wrap, TLS_CONTEXT_NATIVE_TAG);
   
   return obj;
 }
diff --git a/src/modules/url.c b/src/modules/url.c
index e179ae7..30eed97 100644
--- a/src/modules/url.c
+++ b/src/modules/url.c
@@ -31,7 +31,7 @@ enum {
 
 url_state_t *url_get_state(ant_value_t obj) {
   if (!js_check_native_tag(obj, URL_NATIVE_TAG)) return NULL;
-  return (url_state_t *)js_get_native_ptr(obj);
+  return (url_state_t *)js_get_native(obj, URL_NATIVE_TAG);
 }
 
 bool usp_is_urlsearchparams(ant_t *js, ant_value_t obj) {
@@ -51,10 +51,9 @@ void url_free_state(url_state_t *s) {
 }
 
 static void url_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != URL_NATIVE_TAG) return;
-  url_free_state((url_state_t *)obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  url_free_state((url_state_t *)js_get_native(value, URL_NATIVE_TAG));
+  js_clear_native(value, URL_NATIVE_TAG);
 }
 
 static int default_port_for(const char *proto) {
diff --git a/src/modules/wasi.c b/src/modules/wasi.c
index ac3ff2e..ed5443b 100644
--- a/src/modules/wasi.c
+++ b/src/modules/wasi.c
@@ -224,7 +224,7 @@ static ant_value_t wasi_handle_proc_exit(wasm_module_inst_t inst) {
 static ant_value_t wasi_exported_func_call(ant_t *js, ant_value_t *args, int nargs) {
   if (!js_check_native_tag(js->current_func, WASI_FUNC_TAG))
     return js_mkerr(js, "Invalid WASI function");
-  wasi_func_env_t *env = (wasi_func_env_t *)js_get_native_ptr(js->current_func);
+  wasi_func_env_t *env = (wasi_func_env_t *)js_get_native(js->current_func, WASI_FUNC_TAG);
 
   uint32_t param_count = wasm_func_get_param_count(env->func, env->inst);
   uint32_t result_count = wasm_func_get_result_count(env->func, env->inst);
@@ -248,20 +248,19 @@ static ant_value_t wasi_exported_func_call(ant_t *js, ant_value_t *args, int nar
 }
 
 static void wasi_func_finalize(ant_t *js, ant_object_t *obj) {
-  if (obj->native.tag != WASI_FUNC_TAG) return;
-
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, WASI_FUNC_TAG));
+  js_clear_native(value, WASI_FUNC_TAG);
 }
 
 static void wasi_instance_finalize(ant_t *js, ant_object_t *obj) {
-  if (obj->native.tag != WASI_INSTANCE_TAG) return;
-  wasi_instance_handle_t *handle = (wasi_instance_handle_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  wasi_instance_handle_t *handle = (wasi_instance_handle_t *)js_get_native(value, WASI_INSTANCE_TAG);
 
   if (!handle) return;
   if (handle->exec_env) wasm_runtime_destroy_exec_env(handle->exec_env);
   if (handle->inst) wasm_runtime_deinstantiate(handle->inst);
+  js_clear_native(value, WASI_INSTANCE_TAG);
   if (handle->module) wasm_runtime_unload(handle->module);
 
   free(handle->binary);
@@ -340,8 +339,7 @@ static void wasi_bind_func_export(
   GC_ROOT_PIN(js, obj);
   
   js_set_slot(obj, SLOT_CFUNC, js_mkfun(wasi_exported_func_call));
-  js_set_native_ptr(obj, fenv);
-  js_set_native_tag(obj, WASI_FUNC_TAG);
+  js_set_native(obj, fenv, WASI_FUNC_TAG);
   js_set_slot_wb(js, obj, SLOT_ENTRIES, instance_obj);
   js_set_finalizer(obj, wasi_func_finalize);
   js_set(js, exports_obj, name, js_obj_to_func(obj));
@@ -441,8 +439,7 @@ ant_value_t wasi_instantiate(
   ant_value_t instance_obj = js_mkobj(js);
   ant_value_t exports_obj = js_mkobj(js);
 
-  js_set_native_ptr(instance_obj, handle);
-  js_set_native_tag(instance_obj, WASI_INSTANCE_TAG);
+  js_set_native(instance_obj, handle, WASI_INSTANCE_TAG);
   js_set_slot_wb(js, instance_obj, SLOT_CTOR, module_obj);
   js_set_finalizer(instance_obj, wasi_instance_finalize);
 
diff --git a/src/modules/wasm.c b/src/modules/wasm.c
index 2cbe360..8a41288 100644
--- a/src/modules/wasm.c
+++ b/src/modules/wasm.c
@@ -179,13 +179,13 @@ static wasm_valkind_t wasm_valkind_from_string(const char *name, size_t len, boo
 static wasm_module_handle_t *wasm_module_handle(ant_value_t value) {
   if (!js_check_brand(value, BRAND_WASM_MODULE)) return NULL;
   if (!js_check_native_tag(value, WASM_MODULE_NATIVE_TAG)) return NULL;
-  return (wasm_module_handle_t *)js_get_native_ptr(value);
+  return (wasm_module_handle_t *)js_get_native(value, WASM_MODULE_NATIVE_TAG);
 }
 
 static wasm_instance_handle_t *wasm_instance_handle(ant_value_t value) {
   if (!js_check_brand(value, BRAND_WASM_INSTANCE)) return NULL;
   if (!js_check_native_tag(value, WASM_INSTANCE_NATIVE_TAG)) return NULL;
-  return (wasm_instance_handle_t *)js_get_native_ptr(value);
+  return (wasm_instance_handle_t *)js_get_native(value, WASM_INSTANCE_NATIVE_TAG);
 }
 
 static wasm_extern_handle_t *wasm_extern_handle(ant_value_t value, wasm_extern_wrap_kind_t kind) {
@@ -196,7 +196,7 @@ static wasm_extern_handle_t *wasm_extern_handle(ant_value_t value, wasm_extern_w
   }
 
   if (!js_check_native_tag(value, WASM_EXTERN_NATIVE_TAG)) return NULL;
-  wasm_extern_handle_t *handle = (wasm_extern_handle_t *)js_get_native_ptr(value);
+  wasm_extern_handle_t *handle = (wasm_extern_handle_t *)js_get_native(value, WASM_EXTERN_NATIVE_TAG);
   return handle && handle->kind == kind ? handle : NULL;
 }
 
@@ -325,7 +325,7 @@ static bool js_value_to_wasm(ant_t *js, ant_value_t value, wasm_valkind_t kind,
       state = js_get_slot(value, SLOT_DATA);
       if (!is_object_type(state) || !js_check_native_tag(state, WASM_FUNC_STATE_TAG))
         return false;
-      handle = (wasm_func_handle_t *)js_get_native_ptr(state);
+      handle = (wasm_func_handle_t *)js_get_native(state, WASM_FUNC_STATE_TAG);
       if (!handle || !handle->func) return false;
       out->of.ref = wasm_func_as_ref(handle->func);
       return out->of.ref != NULL;
@@ -375,15 +375,14 @@ static ant_value_t wasm_wrap_module(ant_t *js, wasm_store_t *store, wasm_module_
 }
 
 static void wasm_module_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WASM_MODULE_NATIVE_TAG) return;
-  wasm_module_handle_t *handle = (wasm_module_handle_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  wasm_module_handle_t *handle = (wasm_module_handle_t *)js_get_native(value, WASM_MODULE_NATIVE_TAG);
   if (!handle) return;
   if (handle->module) wasm_module_delete(handle->module);
   if (handle->store) wasm_store_delete(handle->store);
   
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, WASM_MODULE_NATIVE_TAG);
 }
 
 static ant_value_t wasm_wrap_instance(ant_t *js, wasm_instance_handle_t *handle, ant_value_t module_ref) {
@@ -396,8 +395,8 @@ static ant_value_t wasm_wrap_instance(ant_t *js, wasm_instance_handle_t *handle,
 }
 
 static void wasm_instance_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WASM_INSTANCE_NATIVE_TAG) return;
-  wasm_instance_handle_t *handle = (wasm_instance_handle_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  wasm_instance_handle_t *handle = (wasm_instance_handle_t *)js_get_native(value, WASM_INSTANCE_NATIVE_TAG);
   if (!handle) return;
   for (size_t j = 0; j < handle->host_func_count; j++) 
     if (handle->host_funcs[j]) wasm_func_delete(handle->host_funcs[j]);
@@ -405,8 +404,7 @@ static void wasm_instance_finalize(ant_t *js, ant_object_t *obj) {
   free(handle->host_funcs);
   wasm_extern_vec_delete(&handle->exports);
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, WASM_INSTANCE_NATIVE_TAG);
 }
 
 static ant_value_t wasm_wrap_extern_object(ant_t *js, wasm_extern_wrap_kind_t kind, ant_value_t proto, int brand, wasm_store_t *store, bool own_handle, void *ptr, ant_value_t owner) {
@@ -433,8 +431,8 @@ static ant_value_t wasm_wrap_extern_object(ant_t *js, wasm_extern_wrap_kind_t ki
 }
 
 static void wasm_extern_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WASM_EXTERN_NATIVE_TAG) return;
-  wasm_extern_handle_t *handle = (wasm_extern_handle_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  wasm_extern_handle_t *handle = (wasm_extern_handle_t *)js_get_native(value, WASM_EXTERN_NATIVE_TAG);
   if (!handle) return;
 
   if (handle->own_handle) {
@@ -453,8 +451,7 @@ static void wasm_extern_finalize(ant_t *js, ant_object_t *obj) {
   }
 
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, WASM_EXTERN_NATIVE_TAG);
 }
 
 static ant_value_t js_wasm_exported_func_call(ant_t *js, ant_value_t *args, int nargs) {
@@ -465,7 +462,7 @@ static ant_value_t js_wasm_exported_func_call(ant_t *js, ant_value_t *args, int
   if (!is_object_type(state) || !js_check_native_tag(state, WASM_FUNC_STATE_TAG))
     return js_mkerr(js, "Invalid WebAssembly function");
 
-  handle = (wasm_func_handle_t *)js_get_native_ptr(state);
+  handle = (wasm_func_handle_t *)js_get_native(state, WASM_FUNC_STATE_TAG);
   func = handle ? handle->func : NULL;
   if (!func) return js_mkerr(js, "Invalid WebAssembly function");
 
@@ -531,15 +528,13 @@ static ant_value_t js_wasm_exported_func_call(ant_t *js, ant_value_t *args, int
 }
 
 static void wasm_func_state_finalize(ant_t *js, ant_object_t *obj) {
-  if (obj->native.tag != WASM_FUNC_STATE_TAG) return;
-
-  wasm_func_handle_t *handle = (wasm_func_handle_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  wasm_func_handle_t *handle = (wasm_func_handle_t *)js_get_native(value, WASM_FUNC_STATE_TAG);
   if (!handle) return;
 
   if (handle->own_func && handle->func) wasm_func_delete(handle->func);
   free(handle);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, WASM_FUNC_STATE_TAG);
 }
 
 static ant_value_t wasm_wrap_func(ant_t *js, wasm_func_t *func, ant_value_t owner, bool own_func) {
@@ -558,8 +553,7 @@ static ant_value_t wasm_wrap_func(ant_t *js, wasm_func_t *func, ant_value_t owne
   handle->own_func = own_func;
 
   state = js_mkobj(js);
-  js_set_native_ptr(state, handle);
-  js_set_native_tag(state, WASM_FUNC_STATE_TAG);
+  js_set_native(state, handle, WASM_FUNC_STATE_TAG);
   
   if (is_object_type(owner)) js_set_slot_wb(js, state, SLOT_ENTRIES, owner);
   js_set_finalizer(state, wasm_func_state_finalize);
@@ -1221,7 +1215,7 @@ static ant_value_t js_wasm_table_set(ant_t *js, ant_value_t *args, int nargs) {
     if (!is_object_type(state) || !js_check_native_tag(state, WASM_FUNC_STATE_TAG))
       return js_mkerr_typed(js, JS_ERR_TYPE, "WebAssembly.Table.set expects a WebAssembly function or null");
     
-    func_handle = (wasm_func_handle_t *)js_get_native_ptr(state);
+    func_handle = (wasm_func_handle_t *)js_get_native(state, WASM_FUNC_STATE_TAG);
     if (!func_handle || !func_handle->func)
       return js_mkerr_typed(js, JS_ERR_TYPE, "WebAssembly.Table.set expects a WebAssembly function or null");
     
diff --git a/src/modules/worker_threads.c b/src/modules/worker_threads.c
index 58ce686..b15c037 100644
--- a/src/modules/worker_threads.c
+++ b/src/modules/worker_threads.c
@@ -94,7 +94,7 @@ static void wt_init_env_store(ant_t *js, bool is_worker) {
 static ant_worker_thread_t *wt_get_worker(ant_t *js, ant_value_t this_obj) {
   if (!is_object_type(this_obj)) return NULL;
   if (!js_check_native_tag(this_obj, WORKER_NATIVE_TAG)) return NULL;
-  return (ant_worker_thread_t *)js_get_native_ptr(this_obj);
+  return (ant_worker_thread_t *)js_get_native(this_obj, WORKER_NATIVE_TAG);
 }
 
 static bool wt_is_message_port(ant_t *js, ant_value_t obj) {
diff --git a/src/modules/zlib.c b/src/modules/zlib.c
index 0fdbb4d..6d738f8 100644
--- a/src/modules/zlib.c
+++ b/src/modules/zlib.c
@@ -76,7 +76,7 @@ static ant_value_t pick_callback(ant_value_t *args, int nargs) {
 
 static zlib_stream_t *zlib_stream_ptr(ant_value_t obj) {
   if (!js_check_native_tag(obj, ZLIB_STREAM_TAG)) return NULL;
-  return (zlib_stream_t *)js_get_native_ptr(obj);
+  return (zlib_stream_t *)js_get_native(obj, ZLIB_STREAM_TAG);
 }
 
 static void zlib_add_active(zlib_stream_t *st) {
@@ -424,8 +424,7 @@ static ant_value_t zlib_create_stream(ant_t *js, zlib_kind_t kind) {
   ant_value_t obj = js_mkobj(js);
   if (is_object_type(g_transform_proto)) js_set_proto_init(obj, g_transform_proto);
 
-  js_set_native_ptr(obj, st);
-  js_set_native_tag(obj, ZLIB_STREAM_TAG);
+  js_set_native(obj, st, ZLIB_STREAM_TAG);
 
   js_set(js, obj, "readable", js_true);
   js_set(js, obj, "writable", js_true);
diff --git a/src/silver/ops/upvalues.h b/src/silver/ops/upvalues.h
index 9418e98..a1173c6 100644
--- a/src/silver/ops/upvalues.h
+++ b/src/silver/ops/upvalues.h
@@ -11,7 +11,6 @@ static inline ant_value_t sv_setup_function_prototype_with_parent(
 ) {
   ant_value_t proto_obj = mkobj(js, 0);
   if (is_err(proto_obj)) return proto_obj;
-  if (is_object_type(parent_proto)) js_set_proto_init(proto_obj, parent_proto);
 
   ant_value_t ctor_key = js_mkstr(js, "constructor", 11);
   if (is_err(ctor_key)) return ctor_key;
@@ -20,6 +19,8 @@ static inline ant_value_t sv_setup_function_prototype_with_parent(
   if (is_err(set_ctor)) return set_ctor;
   
   js_set_descriptor(js, proto_obj, "constructor", 11, JS_DESC_W | JS_DESC_C);
+  if (is_object_type(parent_proto)) js_set_proto_init(proto_obj, parent_proto);
+
   ant_value_t proto_key = js_mkstr(js, "prototype", 9);
   if (is_err(proto_key)) return proto_key;
   
diff --git a/src/streams/codec.c b/src/streams/codec.c
index 754bd8c..3e083dc 100644
--- a/src/streams/codec.c
+++ b/src/streams/codec.c
@@ -64,17 +64,15 @@ ant_value_t tds_stream_writable(ant_value_t obj) {
 }
 
 static void tes_state_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != TES_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, TES_NATIVE_TAG));
+  js_clear_native(value, TES_NATIVE_TAG);
 }
 
 static void tds_state_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != TDS_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, TDS_NATIVE_TAG));
+  js_clear_native(value, TDS_NATIVE_TAG);
 }
 
 static ant_value_t codec_transform_controller(ant_value_t *args, int nargs) {
@@ -87,7 +85,7 @@ static ant_value_t codec_flush_controller(ant_value_t *args, int nargs) {
 
 static ant_value_t tes_transform(ant_t *js, ant_value_t *args, int nargs) {
   tes_state_t *st = js_check_native_tag(js->current_func, TES_NATIVE_TAG)
-    ? (tes_state_t *)js_get_native_ptr(js->current_func)
+    ? (tes_state_t *)js_get_native(js->current_func, TES_NATIVE_TAG)
     : NULL;
   
   if (!st) return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid TextEncoderStream");
@@ -174,7 +172,7 @@ static ant_value_t tes_transform(ant_t *js, ant_value_t *args, int nargs) {
 
 static ant_value_t tes_flush(ant_t *js, ant_value_t *args, int nargs) {
   tes_state_t *st = js_check_native_tag(js->current_func, TES_NATIVE_TAG)
-    ? (tes_state_t *)js_get_native_ptr(js->current_func)
+    ? (tes_state_t *)js_get_native(js->current_func, TES_NATIVE_TAG)
     : NULL;
   
   if (!st) return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid TextEncoderStream");
@@ -242,13 +240,15 @@ static ant_value_t js_tes_ctor(ant_t *js, ant_value_t *args, int nargs) {
 
   if (is_err(ts_obj)) { free(st); return ts_obj; }
   js_set_slot(obj, SLOT_ENTRIES, ts_obj);
+  js_set_slot_wb(js, transform_fn, SLOT_ENTRIES, obj);
+  js_set_slot_wb(js, flush_fn, SLOT_ENTRIES, obj);
 
   return obj;
 }
 
 static ant_value_t tds_transform(ant_t *js, ant_value_t *args, int nargs) {
   td_state_t *st = js_check_native_tag(js->current_func, TDS_NATIVE_TAG)
-    ? (td_state_t *)js_get_native_ptr(js->current_func)
+    ? (td_state_t *)js_get_native(js->current_func, TDS_NATIVE_TAG)
     : NULL;
   
   if (!st) return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid TextDecoderStream");
@@ -277,7 +277,7 @@ static ant_value_t tds_transform(ant_t *js, ant_value_t *args, int nargs) {
 
 static ant_value_t tds_flush(ant_t *js, ant_value_t *args, int nargs) {
   td_state_t *st = js_check_native_tag(js->current_func, TDS_NATIVE_TAG)
-    ? (td_state_t *)js_get_native_ptr(js->current_func)
+    ? (td_state_t *)js_get_native(js->current_func, TDS_NATIVE_TAG)
     : NULL;
   
   if (!st) return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid TextDecoderStream");
@@ -298,7 +298,7 @@ static ant_value_t tds_flush(ant_t *js, ant_value_t *args, int nargs) {
 }
 
 static ant_value_t js_tds_get_encoding(ant_t *js, ant_value_t *args, int nargs) {
-  td_state_t *st = (td_state_t *)js_get_native_ptr(js->this_val);
+  td_state_t *st = (td_state_t *)js_get_native(js->this_val, TDS_NATIVE_TAG);
   if (!st) return js_mkstr(js, "utf-8", 5);
   switch (st->encoding) {
     case TD_ENC_UTF16LE: return js_mkstr(js, "utf-16le", 8);
@@ -310,12 +310,12 @@ static ant_value_t js_tds_get_encoding(ant_t *js, ant_value_t *args, int nargs)
 }
 
 static ant_value_t js_tds_get_fatal(ant_t *js, ant_value_t *args, int nargs) {
-  td_state_t *st = (td_state_t *)js_get_native_ptr(js->this_val);
+  td_state_t *st = (td_state_t *)js_get_native(js->this_val, TDS_NATIVE_TAG);
   return (st && st->fatal) ? js_true : js_false;
 }
 
 static ant_value_t js_tds_get_ignore_bom(ant_t *js, ant_value_t *args, int nargs) {
-  td_state_t *st = (td_state_t *)js_get_native_ptr(js->this_val);
+  td_state_t *st = (td_state_t *)js_get_native(js->this_val, TDS_NATIVE_TAG);
   return (st && st->ignore_bom) ? js_true : js_false;
 }
 
@@ -421,6 +421,8 @@ static ant_value_t js_tds_ctor(ant_t *js, ant_value_t *args, int nargs) {
 
   if (is_err(ts_obj)) { free(st); return ts_obj; }
   js_set_slot(obj, SLOT_ENTRIES, ts_obj);
+  js_set_slot_wb(js, transform_fn, SLOT_ENTRIES, obj);
+  js_set_slot_wb(js, flush_fn, SLOT_ENTRIES, obj);
 
   return obj;
 }
diff --git a/src/streams/compression.c b/src/streams/compression.c
index b00f074..5445903 100644
--- a/src/streams/compression.c
+++ b/src/streams/compression.c
@@ -87,31 +87,31 @@ ant_value_t ds_stream_writable(ant_value_t obj) {
 }
 
 static void zstate_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != CS_Z_NATIVE_TAG) return;
-  zstate_t *st = (zstate_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  zstate_t *st = (zstate_t *)js_get_native(value, CS_Z_NATIVE_TAG);
   if (!st) return;
   if (st->initialized) deflateEnd(&st->strm);
   free(st);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, CS_Z_NATIVE_TAG);
 }
 
 static void zstate_inflate_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != DS_Z_NATIVE_TAG) return;
-  zstate_t *st = (zstate_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  zstate_t *st = (zstate_t *)js_get_native(value, DS_Z_NATIVE_TAG);
   if (!st) return;
   if (st->initialized) inflateEnd(&st->strm);
   free(st);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, DS_Z_NATIVE_TAG);
 }
 
 static void brotli_state_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || (obj->native.tag != CS_BROTLI_NATIVE_TAG && obj->native.tag != DS_BROTLI_NATIVE_TAG)) return;
-  brotli_stream_state_t *st = (brotli_stream_state_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  uint32_t tag = js_check_native_tag(value, CS_BROTLI_NATIVE_TAG) 
+    ? CS_BROTLI_NATIVE_TAG 
+    : DS_BROTLI_NATIVE_TAG;
+  brotli_stream_state_t *st = (brotli_stream_state_t *)js_get_native(value, tag);
   brotli_stream_state_destroy(st);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, tag);
 }
 
 static ant_value_t enqueue_buffer(ant_t *js, ant_value_t ctrl_obj, const uint8_t *data, size_t len) {
@@ -127,9 +127,6 @@ static ant_value_t enqueue_buffer(ant_t *js, ant_value_t ctrl_obj, const uint8_t
 #define ZCHUNK_SIZE 16384
 
 static ant_value_t cs_transform(ant_t *js, ant_value_t *args, int nargs) {
-  uint32_t tag = js_get_native_tag(js->current_func);
-  zstate_t *st = (zstate_t *)js_get_native_ptr(js->current_func);
-  
   ant_value_t ctrl_obj = (nargs > 1) ? args[1] : js_mkundef();
   ant_value_t chunk = (nargs > 0) ? args[0] : js_mkundef();
   
@@ -141,12 +138,12 @@ static ant_value_t cs_transform(ant_t *js, ant_value_t *args, int nargs) {
 
   if (!input || input_len == 0) return js_mkundef();
 
-  if (tag == CS_BROTLI_NATIVE_TAG) {
-    brotli_stream_state_t *brotli_st = (brotli_stream_state_t *)js_get_native_ptr(js->current_func);
+  brotli_stream_state_t *brotli_st = (brotli_stream_state_t *)js_get_native(js->current_func, CS_BROTLI_NATIVE_TAG);
+  if (brotli_st)
     return brotli_stream_transform(js, brotli_st, ctrl_obj, input, input_len);
-  }
   
-  if (tag != CS_Z_NATIVE_TAG || !st) 
+  zstate_t *st = (zstate_t *)js_get_native(js->current_func, CS_Z_NATIVE_TAG);
+  if (!st) 
     return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid CompressionStream");
 
   st->strm.next_in = (Bytef *)input;
@@ -170,16 +167,14 @@ static ant_value_t cs_transform(ant_t *js, ant_value_t *args, int nargs) {
 }
 
 static ant_value_t cs_flush(ant_t *js, ant_value_t *args, int nargs) {
-  uint32_t tag = js_get_native_tag(js->current_func);
   ant_value_t ctrl_obj = (nargs > 0) ? args[0] : js_mkundef();
 
-  if (tag == CS_BROTLI_NATIVE_TAG) {
-    brotli_stream_state_t *brotli_st = (brotli_stream_state_t *)js_get_native_ptr(js->current_func);
+  brotli_stream_state_t *brotli_st = (brotli_stream_state_t *)js_get_native(js->current_func, CS_BROTLI_NATIVE_TAG);
+  if (brotli_st)
     return brotli_stream_flush(js, brotli_st, ctrl_obj);
-  }
   
-  zstate_t *st = (zstate_t *)js_get_native_ptr(js->current_func);
-  if (tag != CS_Z_NATIVE_TAG || !st) return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid CompressionStream");
+  zstate_t *st = (zstate_t *)js_get_native(js->current_func, CS_Z_NATIVE_TAG);
+  if (!st) return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid CompressionStream");
 
   st->strm.next_in = NULL;
   st->strm.avail_in = 0;
@@ -274,13 +269,13 @@ static ant_value_t js_cs_ctor(ant_t *js, ant_value_t *args, int nargs) {
     return ts_obj;
   }
   js_set_slot(obj, SLOT_ENTRIES, ts_obj);
+  js_set_slot_wb(js, transform_fn, SLOT_ENTRIES, obj);
+  js_set_slot_wb(js, flush_fn, SLOT_ENTRIES, obj);
 
   return obj;
 }
 
 static ant_value_t ds_transform(ant_t *js, ant_value_t *args, int nargs) {
-  uint32_t tag = js_get_native_tag(js->current_func);
-  zstate_t *st = (zstate_t *)js_get_native_ptr(js->current_func);
   ant_value_t ctrl_obj = (nargs > 1) ? args[1] : js_mkundef();
 
   ant_value_t chunk = (nargs > 0) ? args[0] : js_mkundef();
@@ -291,12 +286,12 @@ static ant_value_t ds_transform(ant_t *js, ant_value_t *args, int nargs) {
     return js_mkerr_typed(js, JS_ERR_TYPE, "The provided value is not of type '(ArrayBuffer or ArrayBufferView)'");
 
   if (!input || input_len == 0) return js_mkundef();
-  if (tag == DS_BROTLI_NATIVE_TAG) {
-    brotli_stream_state_t *brotli_st = (brotli_stream_state_t *)js_get_native_ptr(js->current_func);
+  brotli_stream_state_t *brotli_st = (brotli_stream_state_t *)js_get_native(js->current_func, DS_BROTLI_NATIVE_TAG);
+  if (brotli_st)
     return brotli_stream_transform(js, brotli_st, ctrl_obj, input, input_len);
-  }
   
-  if (tag != DS_Z_NATIVE_TAG || !st)
+  zstate_t *st = (zstate_t *)js_get_native(js->current_func, DS_Z_NATIVE_TAG);
+  if (!st)
     return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid DecompressionStream");
 
   st->strm.next_in = (Bytef *)input;
@@ -321,12 +316,10 @@ static ant_value_t ds_transform(ant_t *js, ant_value_t *args, int nargs) {
 }
 
 static ant_value_t ds_flush(ant_t *js, ant_value_t *args, int nargs) {
-  uint32_t tag = js_get_native_tag(js->current_func);
   ant_value_t ctrl_obj = (nargs > 0) ? args[0] : js_mkundef();
-  if (tag == DS_BROTLI_NATIVE_TAG) {
-    brotli_stream_state_t *st = (brotli_stream_state_t *)js_get_native_ptr(js->current_func);
+  brotli_stream_state_t *st = (brotli_stream_state_t *)js_get_native(js->current_func, DS_BROTLI_NATIVE_TAG);
+  if (st)
     return brotli_stream_flush(js, st, ctrl_obj);
-  }
   return js_mkundef();
 }
 
@@ -404,6 +397,8 @@ static ant_value_t js_ds_ctor(ant_t *js, ant_value_t *args, int nargs) {
   }
 
   js_set_slot(obj, SLOT_ENTRIES, ts_obj);
+  js_set_slot_wb(js, transform_fn, SLOT_ENTRIES, obj);
+  js_set_slot_wb(js, flush_fn, SLOT_ENTRIES, obj);
   return obj;
 }
 
diff --git a/src/streams/pipes.c b/src/streams/pipes.c
index 71f4094..6512282 100644
--- a/src/streams/pipes.c
+++ b/src/streams/pipes.c
@@ -52,15 +52,14 @@ static void pipes_chain_promise(
 }
 
 static void pipe_state_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != PIPE_STATE_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, PIPE_STATE_NATIVE_TAG));
+  js_clear_native(value, PIPE_STATE_NATIVE_TAG);
 }
 
 static pipe_state_t *pipe_get_state(ant_value_t state) {
   if (!js_check_native_tag(state, PIPE_STATE_NATIVE_TAG)) return NULL;
-  return (pipe_state_t *)js_get_native_ptr(state);
+  return (pipe_state_t *)js_get_native(state, PIPE_STATE_NATIVE_TAG);
 }
 
 static ant_value_t pipe_state_source(ant_value_t state) {
@@ -489,15 +488,14 @@ typedef struct {
 } tee_state_t;
 
 static void tee_state_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != TEE_STATE_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, TEE_STATE_NATIVE_TAG));
+  js_clear_native(value, TEE_STATE_NATIVE_TAG);
 }
 
 static tee_state_t *tee_get_state(ant_value_t state) {
   if (!js_check_native_tag(state, TEE_STATE_NATIVE_TAG)) return NULL;
-  return (tee_state_t *)js_get_native_ptr(state);
+  return (tee_state_t *)js_get_native(state, TEE_STATE_NATIVE_TAG);
 }
 
 static ant_value_t tee_state_reader(ant_value_t state) {
diff --git a/src/streams/readable.c b/src/streams/readable.c
index 15a5852..f9cb48a 100644
--- a/src/streams/readable.c
+++ b/src/streams/readable.c
@@ -51,29 +51,27 @@ bool rs_stream_unusable(ant_value_t stream_obj) {
 
 rs_stream_t *rs_get_stream(ant_value_t obj) {
   if (!js_check_native_tag(obj, RS_STREAM_NATIVE_TAG)) return NULL;
-  return (rs_stream_t *)js_get_native_ptr(obj);
+  return (rs_stream_t *)js_get_native(obj, RS_STREAM_NATIVE_TAG);
 }
 
 rs_controller_t *rs_get_controller(ant_value_t obj) {
   if (!js_check_native_tag(obj, RS_CONTROLLER_NATIVE_TAG)) return NULL;
-  return (rs_controller_t *)js_get_native_ptr(obj);
+  return (rs_controller_t *)js_get_native(obj, RS_CONTROLLER_NATIVE_TAG);
 }
 
 static void rs_stream_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != RS_STREAM_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, RS_STREAM_NATIVE_TAG));
+  js_clear_native(value, RS_STREAM_NATIVE_TAG);
 }
 
 static void rs_controller_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != RS_CONTROLLER_NATIVE_TAG) return;
-  rs_controller_t *ctrl = (rs_controller_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  rs_controller_t *ctrl = (rs_controller_t *)js_get_native(value, RS_CONTROLLER_NATIVE_TAG);
   if (!ctrl) return;
   free(ctrl->queue_sizes);
   free(ctrl);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, RS_CONTROLLER_NATIVE_TAG);
 }
 
 ant_value_t rs_stream_controller(ant_t *js, ant_value_t stream_obj) {
diff --git a/src/streams/transform.c b/src/streams/transform.c
index 7384179..9ada7eb 100644
--- a/src/streams/transform.c
+++ b/src/streams/transform.c
@@ -55,37 +55,33 @@ ant_value_t ts_stream_writable(ant_value_t ts_obj) {
 }
 
 static void ts_ws_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WS_STREAM_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, WS_STREAM_NATIVE_TAG));
+  js_clear_native(value, WS_STREAM_NATIVE_TAG);
 }
 
 static void ts_ws_ctrl_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WS_CONTROLLER_NATIVE_TAG) return;
-  ws_controller_t *ctrl = (ws_controller_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  ws_controller_t *ctrl = (ws_controller_t *)js_get_native(value, WS_CONTROLLER_NATIVE_TAG);
   if (!ctrl) return;
   free(ctrl->queue_sizes);
   free(ctrl);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, WS_CONTROLLER_NATIVE_TAG);
 }
 
 static void ts_rs_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != RS_STREAM_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, RS_STREAM_NATIVE_TAG));
+  js_clear_native(value, RS_STREAM_NATIVE_TAG);
 }
 
 static void ts_rs_ctrl_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != RS_CONTROLLER_NATIVE_TAG) return;
-  rs_controller_t *ctrl = (rs_controller_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  rs_controller_t *ctrl = (rs_controller_t *)js_get_native(value, RS_CONTROLLER_NATIVE_TAG);
   if (!ctrl) return;
   free(ctrl->queue_sizes);
   free(ctrl);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, RS_CONTROLLER_NATIVE_TAG);
 }
 
 static inline bool ts_get_backpressure(ant_value_t ts_obj) {
diff --git a/src/streams/writable.c b/src/streams/writable.c
index 2d069cc..4996d34 100644
--- a/src/streams/writable.c
+++ b/src/streams/writable.c
@@ -39,29 +39,27 @@ bool ws_is_controller(ant_value_t obj) {
 
 ws_stream_t *ws_get_stream(ant_value_t obj) {
   if (!js_check_native_tag(obj, WS_STREAM_NATIVE_TAG)) return NULL;
-  return (ws_stream_t *)js_get_native_ptr(obj);
+  return (ws_stream_t *)js_get_native(obj, WS_STREAM_NATIVE_TAG);
 }
 
 ws_controller_t *ws_get_controller(ant_value_t obj) {
   if (!js_check_native_tag(obj, WS_CONTROLLER_NATIVE_TAG)) return NULL;
-  return (ws_controller_t *)js_get_native_ptr(obj);
+  return (ws_controller_t *)js_get_native(obj, WS_CONTROLLER_NATIVE_TAG);
 }
 
 static void ws_stream_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WS_STREAM_NATIVE_TAG) return;
-  free(obj->native.ptr);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  ant_value_t value = js_obj_from_ptr(obj);
+  free(js_get_native(value, WS_STREAM_NATIVE_TAG));
+  js_clear_native(value, WS_STREAM_NATIVE_TAG);
 }
 
 static void ws_controller_finalize(ant_t *js, ant_object_t *obj) {
-  if (!obj || obj->native.tag != WS_CONTROLLER_NATIVE_TAG) return;
-  ws_controller_t *ctrl = (ws_controller_t *)obj->native.ptr;
+  ant_value_t value = js_obj_from_ptr(obj);
+  ws_controller_t *ctrl = (ws_controller_t *)js_get_native(value, WS_CONTROLLER_NATIVE_TAG);
   if (!ctrl) return;
   free(ctrl->queue_sizes);
   free(ctrl);
-  obj->native.ptr = NULL;
-  obj->native.tag = 0;
+  js_clear_native(value, WS_CONTROLLER_NATIVE_TAG);
 }
 
 ant_value_t ws_stream_controller(ant_value_t stream_obj) {