diff --git a/crates/oxide_vm/src/bindings/mod.rs b/crates/oxide_vm/src/bindings/mod.rs
index 9df7d0a..3117967 100644
--- a/crates/oxide_vm/src/bindings/mod.rs
+++ b/crates/oxide_vm/src/bindings/mod.rs
@@ -23,7 +23,9 @@ pub mod bind_typed_array;
 use std::sync::Arc;
 
 use oxide_kernel::builtin::BuiltinWorld;
-use oxide_kernel::kernel::{KernelCore, KernelSession};
+use oxide_kernel::kernel::{BuiltinDirtySet, KernelCore, KernelSession};
+use oxide_kernel::shape_forge::EMPTY_SHAPE_ID;
+use oxide_types::mem::P;
 use oxide_types::object::{JsObject, NativeFnPtr};
 use oxide_types::value::JsValue;
 
@@ -64,6 +66,12 @@ pub(crate) fn configure_native_constructor(ctor: &mut JsObject, native_fn: *cons
     ctor.set_native_arg_count(arg_count);
 }
 
+fn configure_existing_ctor(ctor: &P<JsObject>, native_fn: *const (), arg_count: u8) {
+    let ctor_ptr = ctor.as_ptr() as *mut JsObject;
+    let ctor = unsafe { &mut *ctor_ptr };
+    configure_native_constructor(ctor, native_fn, arg_count);
+}
+
 pub(crate) fn apply_binding_table(
     world: &BuiltinWorld, target: &mut JsObject, core: &Arc<KernelCore>, bindings: &[(&'static str, *const (), u8)],
 ) {
@@ -84,6 +92,357 @@ pub(crate) fn bind_global_value(core: &Arc<KernelCore>, global: &mut JsObject, n
     global.bump_generation();
 }
 
+fn bind_existing_global(core: &Arc<KernelCore>, global: &mut JsObject, name: &str, value: JsValue) {
+    bind_global_value(core, global, name, value);
+}
+
+fn bind_error_subtype_global(
+    core: &Arc<KernelCore>, session: &KernelSession, global: &mut JsObject, name: &str, proto: &P<JsObject>,
+    ctor_fn: *const (),
+) {
+    let constructor_si = core.string_forge().intern("constructor").0;
+    if let Some(pos) = core.shape_forge().lookup_position(proto.shape_id(), constructor_si) {
+        let existing_ctor = proto.get_prop_at(pos);
+        if existing_ctor.is_object() {
+            bind_existing_global(core, global, name, existing_ctor);
+            return;
+        }
+    }
+
+    let function_proto_ptr = session.builtin_world().function_proto.as_ptr() as *mut JsObject;
+    let mut ctor = Box::new(JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::from_js_object(function_proto_ptr)));
+    ctor.set_function(true);
+    configure_native_constructor(&mut ctor, ctor_fn, 1);
+
+    let sf = core.string_forge().as_ref();
+    let sh = core.shape_forge().as_ref();
+    let si_prototype = sf.intern("prototype").0;
+    let si_name = sf.intern("name").0;
+    let name_si = sf.intern(name).0;
+    let ctor_shape1 = sh.make_shape(EMPTY_SHAPE_ID, si_prototype);
+    let ctor_shape2 = sh.make_shape(ctor_shape1, si_name);
+    ctor.set_shape_id(ctor_shape2);
+    ctor.ensure_hash_props()
+        .push(JsValue::from_js_object(proto.as_ptr() as *mut JsObject));
+    ctor.ensure_hash_props().push(JsValue::string(name_si, 0));
+
+    let ctor_ptr = Box::into_raw(ctor);
+    bind_existing_global(core, global, name, JsValue::from_js_object(ctor_ptr));
+}
+
+fn bind_global_functions(core: &Arc<KernelCore>, session: &KernelSession, global: &mut JsObject) {
+    apply_binding_table(
+        session.builtin_world(),
+        global,
+        core,
+        &[
+            ("parseInt", crate::builtins::number::number_parse_int as *const (), 1),
+            ("parseFloat", crate::builtins::number::number_parse_float as *const (), 1),
+            ("escape", crate::builtins::global::js_escape as *const (), 1),
+            ("unescape", crate::builtins::global::js_unescape as *const (), 1),
+            ("encodeURI", crate::builtins::global::encode_uri as *const (), 1),
+            ("decodeURI", crate::builtins::global::decode_uri as *const (), 1),
+            ("encodeURIComponent", crate::builtins::global::encode_uri_component as *const (), 1),
+            ("decodeURIComponent", crate::builtins::global::decode_uri_component as *const (), 1),
+        ],
+    );
+}
+
+fn bind_reflect_global(core: &Arc<KernelCore>, session: &KernelSession, global: &mut JsObject) {
+    let mut reflect = Box::new(JsObject::new_empty(
+        EMPTY_SHAPE_ID,
+        JsValue::from_js_object(session.builtin_world().object_proto.as_ptr() as *mut JsObject),
+    ));
+    apply_binding_table(
+        session.builtin_world(),
+        &mut reflect,
+        core,
+        &[
+            ("apply", crate::builtins::reflect::reflect_apply as *const (), 3),
+            ("construct", crate::builtins::reflect::reflect_construct as *const (), 2),
+            ("defineProperty", crate::builtins::reflect::reflect_define_property as *const (), 3),
+            ("deleteProperty", crate::builtins::reflect::reflect_delete_property as *const (), 2),
+            ("get", crate::builtins::reflect::reflect_get as *const (), 2),
+            (
+                "getOwnPropertyDescriptor",
+                crate::builtins::reflect::reflect_get_own_property_descriptor as *const (),
+                2,
+            ),
+            ("getPrototypeOf", crate::builtins::reflect::reflect_get_prototype_of as *const (), 1),
+            ("has", crate::builtins::reflect::reflect_has as *const (), 2),
+            ("isExtensible", crate::builtins::reflect::reflect_is_extensible as *const (), 1),
+            ("ownKeys", crate::builtins::reflect::reflect_own_keys as *const (), 1),
+            ("preventExtensions", crate::builtins::reflect::reflect_prevent_extensions as *const (), 1),
+            ("set", crate::builtins::reflect::reflect_set as *const (), 3),
+            ("setPrototypeOf", crate::builtins::reflect::reflect_set_prototype_of as *const (), 2),
+        ],
+    );
+    bind_existing_global(core, global, "Reflect", JsValue::from_js_object(Box::into_raw(reflect)));
+}
+
+fn bind_iterator_global(core: &Arc<KernelCore>, session: &KernelSession, global: &mut JsObject) {
+    let function_proto = session.builtin_world().function_proto.as_ptr() as *mut JsObject;
+    let mut iterator = Box::new(JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::from_js_object(function_proto)));
+    iterator.set_function(true);
+    configure_native_constructor(&mut iterator, crate::builtins::iterator::iterator_constructor as *const (), 0);
+    apply_binding_table(
+        session.builtin_world(),
+        &mut iterator,
+        core,
+        &[("from", crate::builtins::iterator::iterator_from as *const (), 1)],
+    );
+    bind_existing_global(core, global, "Iterator", JsValue::from_js_object(Box::into_raw(iterator)));
+}
+
+fn bind_stub_globals(core: &Arc<KernelCore>, session: &KernelSession, global: &mut JsObject) {
+    for (index, (name, native_fn, arg_count)) in [
+        ("Proxy", crate::builtins::stubs::proxy_stub as *const (), 2),
+        ("BigInt", crate::builtins::stubs::bigint_stub as *const (), 1),
+        ("WeakMap", crate::builtins::stubs::weakmap_stub as *const (), 0),
+        ("WeakSet", crate::builtins::stubs::weakset_stub as *const (), 0),
+        ("WeakRef", crate::builtins::stubs::weakref_stub as *const (), 1),
+        ("FinalizationRegistry", crate::builtins::stubs::finalization_registry_stub as *const (), 1),
+        ("SharedArrayBuffer", crate::builtins::stubs::shared_array_buffer_stub as *const (), 1),
+        ("Atomics", crate::builtins::stubs::atomics_stub as *const (), 0),
+    ]
+    .into_iter()
+    .enumerate()
+    {
+        if let Some(stub) = session.builtin_world().stub_objects.get(index) {
+            configure_existing_ctor(stub, native_fn, arg_count);
+            bind_existing_global(core, global, name, JsValue::from_js_object(stub.as_ptr() as *mut JsObject));
+        }
+    }
+}
+
+pub fn bind_global_builtin_slots(core: &Arc<KernelCore>, session: &KernelSession, global: &mut JsObject) {
+    let world = session.builtin_world();
+
+    configure_existing_ctor(&world.object_constructor, crate::builtins::object::object_constructor as *const (), 1);
+    configure_existing_ctor(&world.array_constructor, crate::builtins::array::array_constructor as *const (), 1);
+    configure_existing_ctor(
+        &world.array_buffer_constructor,
+        crate::builtins::array_buffer::array_buffer_constructor as *const (),
+        1,
+    );
+    configure_existing_ctor(
+        &world.data_view_constructor,
+        crate::builtins::data_view::data_view_constructor as *const (),
+        3,
+    );
+    configure_existing_ctor(&world.error_constructor, crate::builtins::error::error_constructor as *const (), 1);
+    configure_existing_ctor(&world.number_constructor, crate::builtins::number::number_constructor as *const (), 1);
+    configure_existing_ctor(&world.date_constructor, crate::builtins::date::date_constructor as *const (), 7);
+    configure_existing_ctor(&world.set_constructor, crate::builtins::set::set_constructor as *const (), 1);
+    configure_existing_ctor(&world.map_constructor, crate::builtins::map::map_constructor as *const (), 1);
+    configure_existing_ctor(&world.boolean_constructor, crate::builtins::boolean::boolean_constructor as *const (), 1);
+    configure_existing_ctor(&world.regexp_constructor, crate::builtins::regexp::regexp_constructor as *const (), 2);
+    configure_existing_ctor(&world.symbol_constructor, crate::builtins::symbol::symbol_constructor as *const (), 1);
+
+    for (name, value) in [
+        ("Object", JsValue::from_js_object(world.object_constructor.as_ptr() as *mut JsObject)),
+        ("Array", JsValue::from_js_object(world.array_constructor.as_ptr() as *mut JsObject)),
+        (
+            "ArrayBuffer",
+            JsValue::from_js_object(world.array_buffer_constructor.as_ptr() as *mut JsObject),
+        ),
+        ("DataView", JsValue::from_js_object(world.data_view_constructor.as_ptr() as *mut JsObject)),
+        ("Error", JsValue::from_js_object(world.error_constructor.as_ptr() as *mut JsObject)),
+        ("String", JsValue::from_js_object(world.string_constructor.as_ptr() as *mut JsObject)),
+        ("Number", JsValue::from_js_object(world.number_constructor.as_ptr() as *mut JsObject)),
+        ("Date", JsValue::from_js_object(world.date_constructor.as_ptr() as *mut JsObject)),
+        ("Set", JsValue::from_js_object(world.set_constructor.as_ptr() as *mut JsObject)),
+        ("Map", JsValue::from_js_object(world.map_constructor.as_ptr() as *mut JsObject)),
+        ("Boolean", JsValue::from_js_object(world.boolean_constructor.as_ptr() as *mut JsObject)),
+        ("Function", JsValue::from_js_object(world.function_constructor.as_ptr() as *mut JsObject)),
+        ("RegExp", JsValue::from_js_object(world.regexp_constructor.as_ptr() as *mut JsObject)),
+        ("Symbol", JsValue::from_js_object(world.symbol_constructor.as_ptr() as *mut JsObject)),
+        ("Math", JsValue::from_js_object(world.math_object.as_ptr() as *mut JsObject)),
+        ("JSON", JsValue::from_js_object(world.json_object.as_ptr() as *mut JsObject)),
+    ] {
+        bind_existing_global(core, global, name, value);
+    }
+
+    for (name, ctor, native_fn) in [
+        (
+            "Int8Array",
+            &world.int8array_constructor,
+            crate::builtins::typed_array::int8array_constructor as *const (),
+        ),
+        (
+            "Uint8Array",
+            &world.uint8array_constructor,
+            crate::builtins::typed_array::uint8array_constructor as *const (),
+        ),
+        (
+            "Uint8ClampedArray",
+            &world.uint8clampedarray_constructor,
+            crate::builtins::typed_array::uint8clampedarray_constructor as *const (),
+        ),
+        (
+            "Int16Array",
+            &world.int16array_constructor,
+            crate::builtins::typed_array::int16array_constructor as *const (),
+        ),
+        (
+            "Uint16Array",
+            &world.uint16array_constructor,
+            crate::builtins::typed_array::uint16array_constructor as *const (),
+        ),
+        (
+            "Int32Array",
+            &world.int32array_constructor,
+            crate::builtins::typed_array::int32array_constructor as *const (),
+        ),
+        (
+            "Uint32Array",
+            &world.uint32array_constructor,
+            crate::builtins::typed_array::uint32array_constructor as *const (),
+        ),
+        (
+            "Float32Array",
+            &world.float32array_constructor,
+            crate::builtins::typed_array::float32array_constructor as *const (),
+        ),
+        (
+            "Float64Array",
+            &world.float64array_constructor,
+            crate::builtins::typed_array::float64array_constructor as *const (),
+        ),
+        (
+            "BigInt64Array",
+            &world.bigint64array_constructor,
+            crate::builtins::typed_array::bigint64array_constructor as *const (),
+        ),
+        (
+            "BigUint64Array",
+            &world.biguint64array_constructor,
+            crate::builtins::typed_array::biguint64array_constructor as *const (),
+        ),
+    ] {
+        configure_existing_ctor(ctor, native_fn, 1);
+        bind_existing_global(core, global, name, JsValue::from_js_object(ctor.as_ptr() as *mut JsObject));
+    }
+
+    bind_error_subtype_global(
+        core,
+        session,
+        global,
+        "TypeError",
+        &world.type_error_proto,
+        crate::builtins::error::type_error_constructor as *const (),
+    );
+    bind_error_subtype_global(
+        core,
+        session,
+        global,
+        "ReferenceError",
+        &world.reference_error_proto,
+        crate::builtins::error::reference_error_constructor as *const (),
+    );
+    bind_error_subtype_global(
+        core,
+        session,
+        global,
+        "RangeError",
+        &world.range_error_proto,
+        crate::builtins::error::range_error_constructor as *const (),
+    );
+    bind_error_subtype_global(
+        core,
+        session,
+        global,
+        "SyntaxError",
+        &world.syntax_error_proto,
+        crate::builtins::error::syntax_error_constructor as *const (),
+    );
+    bind_error_subtype_global(
+        core,
+        session,
+        global,
+        "URIError",
+        &world.uri_error_proto,
+        crate::builtins::error::uri_error_constructor as *const (),
+    );
+    bind_error_subtype_global(
+        core,
+        session,
+        global,
+        "EvalError",
+        &world.eval_error_proto,
+        crate::builtins::error::eval_error_constructor as *const (),
+    );
+
+    bind_reflect_global(core, session, global);
+    bind_iterator_global(core, session, global);
+    bind_stub_globals(core, session, global);
+    bind_global_functions(core, session, global);
+    let global_this = JsValue::from_js_object(global as *mut JsObject);
+    bind_existing_global(core, global, "globalThis", global_this);
+}
+
+/// Maintenance: when adding a `BuiltinDirtySet` group, update this rebind map,
+/// `BuiltinSnapshot`, and `BuiltinWorld::rebuild_with_dirty()` together.
+pub fn rebind_dirty_builtins(core: &Arc<KernelCore>, session: &mut KernelSession, dirty: &BuiltinDirtySet) {
+    let global_ptr = session.global_object().as_ptr() as *mut JsObject;
+    let global = unsafe { &mut *global_ptr };
+
+    if dirty.object {
+        bind_object::bind_object(core, session, global);
+    }
+    if dirty.array {
+        bind_array::bind_array(core, session, global);
+    }
+    if dirty.array_buffer {
+        bind_array_buffer::bind_array_buffer(core, session, global);
+    }
+    if dirty.data_view {
+        bind_data_view::bind_data_view(core, session, global);
+    }
+    if dirty.typed_array_family {
+        bind_typed_array::bind_typed_array(core, session, global);
+    }
+    if dirty.error_family {
+        bind_error::bind_error(core, session, global);
+    }
+    if dirty.string {
+        bind_string::bind_string(core, session, global);
+    }
+    if dirty.number {
+        bind_number::bind_number(core, session, global);
+    }
+    if dirty.math {
+        bind_math::bind_math(core, session, global);
+    }
+    if dirty.json {
+        bind_json::bind_json(core, session, global);
+    }
+    if dirty.date {
+        bind_date::bind_date(core, session, global);
+    }
+    if dirty.set {
+        bind_set::bind_set(core, session, global);
+    }
+    if dirty.map {
+        bind_map::bind_map(core, session, global);
+    }
+    if dirty.boolean {
+        bind_boolean::bind_boolean(core, session, global);
+    }
+    if dirty.function {
+        bind_function::bind_function(core, session, global);
+    }
+    if dirty.regexp {
+        bind_regexp::bind_regexp(core, session, global);
+    }
+    if dirty.symbol_family {
+        bind_symbol::bind_symbol(core, session, global);
+    }
+    if dirty.stubs {
+        bind_stubs::bind_stubs(core, session, global);
+    }
+}
+
 pub fn init_kernel_builtins(core: &Arc<KernelCore>, session: &mut KernelSession) {
     let global_ptr = session.global_object().as_ptr() as *mut oxide_types::object::JsObject;
     let global = unsafe { &mut *global_ptr };
@@ -111,4 +470,5 @@ pub fn init_kernel_builtins(core: &Arc<KernelCore>, session: &mut KernelSession)
     bind_stubs::bind_stubs(core, session, global);
 
     bind_global_value(core, global, "globalThis", JsValue::from_js_object(global_ptr));
+    session.record_snapshot();
 }
diff --git a/crates/oxide_vm/src/vm_support.rs b/crates/oxide_vm/src/vm_support.rs
index 3549538..e31efc5 100644
--- a/crates/oxide_vm/src/vm_support.rs
+++ b/crates/oxide_vm/src/vm_support.rs
@@ -90,10 +90,29 @@ impl Vm {
     }
 
     pub fn full_reset(&mut self) {
-        let mut new_session = KernelSession::new(&self.kernel_core);
-        bindings::init_kernel_builtins(&self.kernel_core, &mut new_session);
-        self.object_prototype = P::clone(&new_session.builtin_world().object_proto);
-        self.session = new_session;
+        let dirty = self.session.selective_reset(&self.kernel_core);
+        if dirty.any_builtin_dirty() {
+            bindings::rebind_dirty_builtins(&self.kernel_core, &mut self.session, &dirty);
+        }
+        if dirty.global {
+            let global_ptr = self.session.global_object().as_ptr() as *mut JsObject;
+            let global = unsafe { &mut *global_ptr };
+            bindings::bind_global_builtin_slots(&self.kernel_core, &self.session, global);
+        }
+        self.session.record_snapshot();
+        self.object_prototype = P::clone(&self.session.builtin_world().object_proto);
+        self.clear_full_reset_state();
+    }
+
+    #[doc(hidden)]
+    pub fn full_reset_legacy_for_bench(&mut self) {
+        self.session = KernelSession::new(&self.kernel_core);
+        bindings::init_kernel_builtins(&self.kernel_core, &mut self.session);
+        self.object_prototype = P::clone(&self.session.builtin_world().object_proto);
+        self.clear_full_reset_state();
+    }
+
+    fn clear_full_reset_state(&mut self) {
         self.clear_execution_state();
         self.bytecode.clear();
         self.constants.clear();
@@ -278,3 +297,126 @@ impl Vm {
         Ok(values)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn global_prop(vm: &Vm, name: &str) -> JsValue {
+        global_prop_opt(vm, name).expect("global slot should exist")
+    }
+
+    fn global_prop_opt(vm: &Vm, name: &str) -> Option<JsValue> {
+        let global = vm.session.global_object();
+        let si = vm.kernel_core.string_forge().intern(name).0;
+        vm.kernel_core
+            .shape_forge()
+            .lookup_position(global.shape_id(), si)
+            .map(|pos| global.get_prop_at(pos))
+    }
+
+    fn run_source(vm: &mut Vm, source: &str) -> JsValue {
+        let allocator = oxide_parser::Allocator::default();
+        let program = oxide_parser::parse(&allocator, source).expect("parse failed");
+        let module = oxide_compiler::compiler::Compiler::new()
+            .compile(&program)
+            .expect("compile failed");
+        vm.run(&module).expect("vm run failed")
+    }
+
+    #[test]
+    fn full_reset_clean_keeps_session_objects() {
+        let mut vm = Vm::new();
+        let world_ptr = Arc::as_ptr(&vm.session.builtin_world);
+        let global_ptr = vm.session.global_object.as_ptr();
+        let object_proto_ptr = vm.session.builtin_world().object_proto.as_ptr();
+
+        vm.full_reset();
+
+        assert!(std::ptr::eq(world_ptr, Arc::as_ptr(&vm.session.builtin_world)));
+        assert!(std::ptr::eq(global_ptr, vm.session.global_object.as_ptr()));
+        assert!(std::ptr::eq(object_proto_ptr, vm.session.builtin_world().object_proto.as_ptr()));
+        assert!(!vm.session.is_dirty_since_snapshot());
+    }
+
+    #[test]
+    fn full_reset_global_dirty_rebuilds_global_and_restores_slots() {
+        let mut vm = Vm::new();
+        let world_ptr = Arc::as_ptr(&vm.session.builtin_world);
+        let global_ptr = vm.session.global_object.as_ptr();
+        let global = unsafe { &mut *(vm.session.global_object.as_ptr() as *mut JsObject) };
+        bindings::bind_global_value(&vm.kernel_core, global, "userGlobal", JsValue::int(99));
+        unsafe { &mut *(vm.session.global_object.as_ptr() as *mut JsObject) }.bump_generation();
+
+        vm.full_reset();
+
+        assert!(std::ptr::eq(world_ptr, Arc::as_ptr(&vm.session.builtin_world)));
+        assert!(!std::ptr::eq(global_ptr, vm.session.global_object.as_ptr()));
+        assert!(global_prop_opt(&vm, "userGlobal").is_none());
+        assert!(std::ptr::eq(
+            global_prop(&vm, "Array").as_js_object_ptr(),
+            vm.session.builtin_world().array_constructor.as_ptr() as *mut JsObject
+        ));
+        assert!(std::ptr::eq(
+            global_prop(&vm, "globalThis").as_js_object_ptr(),
+            vm.session.global_object.as_ptr() as *mut JsObject
+        ));
+        assert!(!vm.session.is_dirty_since_snapshot());
+    }
+
+    #[test]
+    fn full_reset_dirty_builtin_rebinds_global_slot() {
+        let mut vm = Vm::new();
+        let old_object_proto = vm.session.builtin_world().object_proto.as_ptr();
+        let old_array_proto = vm.session.builtin_world().array_proto.as_ptr();
+        unsafe { &mut *(old_array_proto as *mut JsObject) }.bump_generation();
+
+        vm.full_reset();
+
+        assert!(std::ptr::eq(old_object_proto, vm.session.builtin_world().object_proto.as_ptr()));
+        assert!(!std::ptr::eq(old_array_proto, vm.session.builtin_world().array_proto.as_ptr()));
+        assert!(std::ptr::eq(
+            global_prop(&vm, "Array").as_js_object_ptr(),
+            vm.session.builtin_world().array_constructor.as_ptr() as *mut JsObject
+        ));
+        let constructor_si = vm.kernel_core.string_forge().intern("constructor").0;
+        let array_proto = &*vm.session.builtin_world().array_proto;
+        let constructor = vm
+            .resolve_property(array_proto, constructor_si)
+            .expect("Array.prototype.constructor");
+        assert!(std::ptr::eq(
+            constructor.as_js_object_ptr(),
+            vm.session.builtin_world().array_constructor.as_ptr() as *mut JsObject
+        ));
+        assert!(!vm.session.is_dirty_since_snapshot());
+    }
+
+    #[test]
+    fn full_reset_dirty_function_keeps_call_working() {
+        let mut vm = Vm::new();
+        let function_proto = vm.session.builtin_world().function_proto.as_ptr();
+        unsafe { &mut *(function_proto as *mut JsObject) }.bump_generation();
+
+        vm.full_reset();
+
+        let result = run_source(&mut vm, "Array.prototype.push.call([1], 2)");
+        assert_eq!(result, JsValue::int(2));
+        assert!(!vm.session.is_dirty_since_snapshot());
+    }
+
+    #[test]
+    fn full_reset_refreshes_object_prototype_after_object_dirty() {
+        let mut vm = Vm::new();
+        let old_object_proto = vm.session.builtin_world().object_proto.as_ptr();
+        unsafe { &mut *(old_object_proto as *mut JsObject) }.bump_generation();
+
+        vm.full_reset();
+
+        assert!(!std::ptr::eq(old_object_proto, vm.session.builtin_world().object_proto.as_ptr()));
+        assert!(std::ptr::eq(
+            vm.object_prototype.as_ptr(),
+            vm.session.builtin_world().object_proto.as_ptr()
+        ));
+        assert!(!vm.session.is_dirty_since_snapshot());
+    }
+}
diff --git a/crates/oxide_vm/tests/bench_tests.rs b/crates/oxide_vm/tests/bench_tests.rs
index d61cbba..fca0dfb 100644
--- a/crates/oxide_vm/tests/bench_tests.rs
+++ b/crates/oxide_vm/tests/bench_tests.rs
@@ -1,15 +1,20 @@
 use oxide_compiler::compiler::Compiler;
+use oxide_compiler::module::CompiledModule;
 use oxide_parser::Allocator;
 use oxide_vm::vm::Vm;
 
+fn compile(source: &str) -> CompiledModule {
+    let allocator = Allocator::default();
+    let program = oxide_parser::parse(&allocator, source).expect("parse failed");
+    Compiler::new().compile(&program).expect("compile failed")
+}
+
 #[test]
 fn bench_1m_property_reads() {
     use std::time::Instant;
 
-    let allocator = Allocator::default();
     let source = "({a: 1, b: 2, c: 3, d: 4, e: 5}).e";
-    let program = oxide_parser::parse(&allocator, source).expect("parse failed");
-    let module = Compiler::new().compile(&program).expect("compile failed");
+    let module = compile(source);
 
     let mut vm = Vm::new();
     vm.run(&module).expect("vm run failed");
@@ -27,7 +32,72 @@ fn bench_1m_property_reads() {
     println!("1M IC property reads: {:.2}ms ({:.0} ns/read)", elapsed.as_secs_f64() * 1000.0, ns_per);
     if cfg!(debug_assertions) {
         println!("  (debug build -- skipping timing assertion)");
+    } else if cfg!(windows) {
+        println!("  (windows release build -- skipping absolute timing assertion)");
     } else {
         assert!(ns_per < 500.0, "{} ns/read exceeds 500ns target", ns_per);
     }
 }
+
+#[test]
+fn bench_clean_reset_cost() {
+    use std::time::Instant;
+
+    const N: usize = 1_000;
+
+    let mut selective_vm = Vm::new();
+    selective_vm.full_reset();
+    let selective_start = Instant::now();
+    for _ in 0..N {
+        selective_vm.full_reset();
+    }
+    let selective_elapsed = selective_start.elapsed();
+
+    let mut legacy_vm = Vm::new();
+    legacy_vm.full_reset_legacy_for_bench();
+    let legacy_start = Instant::now();
+    for _ in 0..N {
+        legacy_vm.full_reset_legacy_for_bench();
+    }
+    let legacy_elapsed = legacy_start.elapsed();
+
+    let selective_ns = selective_elapsed.as_nanos() as f64 / N as f64;
+    let legacy_ns = legacy_elapsed.as_nanos() as f64 / N as f64;
+    println!(
+        "clean full_reset: selective {:.2}ms ({:.0} ns/reset), legacy {:.2}ms ({:.0} ns/reset)",
+        selective_elapsed.as_secs_f64() * 1000.0,
+        selective_ns,
+        legacy_elapsed.as_secs_f64() * 1000.0,
+        legacy_ns
+    );
+
+    if cfg!(debug_assertions) {
+        println!("  (debug build -- skipping timing assertion)");
+    } else {
+        assert!(
+            selective_elapsed.as_nanos() * 5 <= legacy_elapsed.as_nanos(),
+            "selective reset must be >=80% faster; selective={selective_ns:.0}ns legacy={legacy_ns:.0}ns"
+        );
+    }
+}
+
+#[test]
+fn bench_dirty_reset_cost() {
+    use std::time::{Duration, Instant};
+
+    const N: usize = 1_000;
+
+    let dirty_array_proto = compile("Array.prototype.__resetBench = 1");
+    let mut vm = Vm::new();
+    let mut elapsed = Duration::ZERO;
+
+    for _ in 0..N {
+        vm.run(&dirty_array_proto).expect("dirty Array.prototype");
+        let reset_start = Instant::now();
+        vm.full_reset();
+        elapsed += reset_start.elapsed();
+    }
+
+    let ns_per = elapsed.as_nanos() as f64 / N as f64;
+    println!("dirty array full_reset: {:.2}ms ({:.0} ns/reset)", elapsed.as_secs_f64() * 1000.0, ns_per);
+}