diff --git a/crates/oxide_builtins/src/array.rs b/crates/oxide_builtins/src/array.rs
index c22b09bd..e70b7ba5 100644
--- a/crates/oxide_builtins/src/array.rs
+++ b/crates/oxide_builtins/src/array.rs
@@ -619,7 +619,7 @@ fn array_from_set_length<H: VmHost>(vm: &mut H, a: *mut JsObject, is_array: bool
     let length_key = vm.new_string("length");
     let length_si = vm.property_key_si(length_key);
     let a_val = JsValue::from_js_object(a);
-    match vm.ordinary_set(a_obj, length_si, JsValue::int(len as i32), a_val) {
+    match vm.ordinary_set(a_obj, length_si, JsValue::int(len as i32), a_val, true) {
         Ok(()) => Ok(()),
         Err(err) => Err(from_engine_error(vm, &err)),
     }
@@ -731,7 +731,7 @@ pub fn array_slice<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     let a_val = JsValue::from_js_object(a_ptr);
     let length_key = vm.new_string("length");
     let length_si = vm.property_key_si(length_key);
-    if let Err(err) = vm.ordinary_set(unsafe { &mut *a_ptr }, length_si, js_array_index(out_idx), a_val) {
+    if let Err(err) = vm.ordinary_set(unsafe { &mut *a_ptr }, length_si, js_array_index(out_idx), a_val, true) {
         return NativeResult::Err(from_engine_error(vm, &err));
     }
     NativeResult::Ok(JsValue::from_js_object(a_ptr))
@@ -1843,7 +1843,7 @@ pub fn array_iterator_next<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
             }
             _ => element,
         };
-        if let Err(msg) = vm.ordinary_set(iter, index_si, JsValue::int(index + 1), this_val) {
+        if let Err(msg) = vm.ordinary_set(iter, index_si, JsValue::int(index + 1), this_val, true) {
             return NativeResult::Err(crate::error::create_from_text(vm, &msg));
         }
         return NativeResult::Ok(crate::iterator::make_iter_result(vm, value, false));
@@ -1876,7 +1876,7 @@ pub fn array_iterator_next<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
         }
         _ => element,
     };
-    if let Err(msg) = vm.ordinary_set(iter, index_si, JsValue::int(index + 1), this_val) {
+    if let Err(msg) = vm.ordinary_set(iter, index_si, JsValue::int(index + 1), this_val, true) {
         return NativeResult::Err(crate::error::create_from_text(vm, &msg));
     }
     NativeResult::Ok(crate::iterator::make_iter_result(vm, value, false))
diff --git a/crates/oxide_builtins/src/iterator.rs b/crates/oxide_builtins/src/iterator.rs
index 5ce94114..538cd30d 100644
--- a/crates/oxide_builtins/src/iterator.rs
+++ b/crates/oxide_builtins/src/iterator.rs
@@ -114,7 +114,7 @@ fn iterator_setter_ignore_proto_props<H: VmHost>(vm: &mut H, args: &[u8], key: u
             Err(err) => NativeResult::Err(crate::error::create_type_error(vm, &err)),
         }
     } else {
-        match vm.ordinary_set(this_obj, key, val, this_val) {
+        match vm.ordinary_set(this_obj, key, val, this_val, true) {
             Ok(()) => NativeResult::Ok(JsValue::undefined()),
             Err(err) => NativeResult::Err(crate::error::create_type_error(vm, &err)),
         }
diff --git a/crates/oxide_builtins/src/object.rs b/crates/oxide_builtins/src/object.rs
index 403ddf8d..6cc66a91 100644
--- a/crates/oxide_builtins/src/object.rs
+++ b/crates/oxide_builtins/src/object.rs
@@ -496,7 +496,7 @@ pub fn object_assign<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     for (si, val) in all_assignments {
         let promoted = vm.promote_if_needed_for_write_ptr(target_ptr, val);
         // Set(to, key, value, true)：receiver 为目标对象（目标同名 setter 的 this 指向 target）。
-        if let Err(err) = vm.ordinary_set(target, si, promoted, target_val) {
+        if let Err(err) = vm.ordinary_set(target, si, promoted, target_val, true) {
             return NativeResult::Err(crate::error::create_type_error(vm, &err));
         }
     }
@@ -1089,7 +1089,7 @@ pub fn object_from_entries<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
         // ToPropertyKey 语义建键：int/规范数字串/symbol 统一映射，避免数字键分裂。
         let si = vm.property_key_si(key_val);
         let promoted = vm.promote_if_needed_for_write_ptr(obj, value_val);
-        let _ = vm.ordinary_set(unsafe { &mut *obj }, si, promoted, target_val);
+        let _ = vm.ordinary_set(unsafe { &mut *obj }, si, promoted, target_val, true);
     }
     NativeResult::Ok(target_val)
 }
@@ -1483,7 +1483,7 @@ pub fn object_group_by<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
             let new_arr_val = JsValue::from_js_object(arr);
             let result_ref_mut = unsafe { &mut *result };
             let promoted = vm.promote_if_needed_for_write_ptr(result, new_arr_val);
-            let _ = vm.ordinary_set(result_ref_mut, key_si, promoted, result_val);
+            let _ = vm.ordinary_set(result_ref_mut, key_si, promoted, result_val, true);
             new_arr_val
         };
         // push element 到分组数组（写入前 promote，与 Array.prototype.push 同款）。
diff --git a/crates/oxide_builtins/src/reflect.rs b/crates/oxide_builtins/src/reflect.rs
index 4cf28edf..796667f4 100644
--- a/crates/oxide_builtins/src/reflect.rs
+++ b/crates/oxide_builtins/src/reflect.rs
@@ -222,7 +222,7 @@ pub fn reflect_set<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     if !target.is_extensible() && vm.get_own_property_slot(target, key_si).is_none() {
         return NativeResult::Ok(JsValue::bool(false));
     }
-    NativeResult::Ok(JsValue::bool(vm.ordinary_set(target, key_si, value, receiver).is_ok()))
+    NativeResult::Ok(JsValue::bool(vm.ordinary_set(target, key_si, value, receiver, true).is_ok()))
 }
 
 /// `Reflect.setPrototypeOf(target, proto)`：设置 prototype（对象或 null）。
diff --git a/crates/oxide_runtime_api/src/lib.rs b/crates/oxide_runtime_api/src/lib.rs
index c7c7bd78..3e6fa973 100644
--- a/crates/oxide_runtime_api/src/lib.rs
+++ b/crates/oxide_runtime_api/src/lib.rs
@@ -151,8 +151,10 @@ pub trait VmHost {
 
     // 属性访问
     fn ordinary_get(&mut self, obj: &JsObject, prop_name_si: u32, receiver: JsValue) -> Result<JsValue, String>;
+    /// `strict` 为写方严格模式：写失败时严格抛错，sloppy 静默 no-op。内置调用方
+    /// 一律传 true（内置写语义恒抛错，与调用上下文模式无关）。
     fn ordinary_set(
-        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue,
+        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, strict: bool,
     ) -> Result<(), String>;
 
     // 属性定义
diff --git a/crates/oxide_vm/src/dispatch/member.rs b/crates/oxide_vm/src/dispatch/member.rs
index a85b5ddd..1c8f19c5 100644
--- a/crates/oxide_vm/src/dispatch/member.rs
+++ b/crates/oxide_vm/src/dispatch/member.rs
@@ -160,7 +160,7 @@ impl Vm {
         let prop_val = self.ordinary_get(obj, prop_name_si, receiver)?;
         let n = self.coerce_number_bounded(prop_val)?;
         let new_val = JsValue::float(n + 1.0);
-        self.ordinary_set(obj, prop_name_si, new_val, receiver)?;
+        self.ordinary_set(obj, prop_name_si, new_val, receiver, self.current_strict())?;
         self.regs[b] = new_val;
         Ok(())
     }
@@ -176,7 +176,7 @@ impl Vm {
         let prop_val = self.ordinary_get(obj, prop_name_si, receiver)?;
         let n = self.coerce_number_bounded(prop_val)?;
         let new_val = JsValue::float(n - 1.0);
-        self.ordinary_set(obj, prop_name_si, new_val, receiver)?;
+        self.ordinary_set(obj, prop_name_si, new_val, receiver, self.current_strict())?;
         self.regs[b] = new_val;
         Ok(())
     }
diff --git a/crates/oxide_vm/src/dispatch/property.rs b/crates/oxide_vm/src/dispatch/property.rs
index 486a46f3..7a9202a2 100644
--- a/crates/oxide_vm/src/dispatch/property.rs
+++ b/crates/oxide_vm/src/dispatch/property.rs
@@ -435,7 +435,7 @@ impl Vm {
         }
 
         if obj.has_prop_meta() {
-            self.ordinary_set_dispatch(obj, prop_name_si, value, receiver)?;
+            self.ordinary_set_dispatch(obj, prop_name_si, value, receiver, self.current_strict())?;
             return Ok(());
         }
 
@@ -451,10 +451,10 @@ impl Vm {
             // 写新属性（shape 转换）：数组 length / 整数索引键仍走完整
             // ordinary_set_dispatch 语义，其余走 CreateDataProperty 快路径。
             if self.named_prop_create_needs_ordinary_set(obj, prop_name_si) {
-                self.ordinary_set_dispatch(obj, prop_name_si, value, receiver)?;
+                self.ordinary_set_dispatch(obj, prop_name_si, value, receiver, self.current_strict())?;
                 return Ok(());
             }
-            self.create_named_prop_fast(obj, prop_name_si, value, receiver, ic_pc, true)?;
+            self.create_named_prop_fast(obj, prop_name_si, value, receiver, ic_pc, true, self.current_strict())?;
         }
 
         Ok(())
@@ -496,7 +496,7 @@ impl Vm {
         }
         let value = self.promote_if_needed_for_write_ptr(obj_ptr, self.regs[a]);
         let obj = unsafe { &mut *obj_ptr };
-        self.ordinary_set_dispatch(obj, prop_name_si, value, self.regs[rd])?;
+        self.ordinary_set_dispatch(obj, prop_name_si, value, self.regs[rd], self.current_strict())?;
         Ok(())
     }
 
@@ -593,7 +593,7 @@ impl Vm {
         }
         let value = self.promote_if_needed_for_write_ptr(obj_ptr, self.regs[b]);
         let obj = unsafe { &mut *obj_ptr };
-        self.ordinary_set_dispatch(obj, prop_name_si, value, self.regs[rd])?;
+        self.ordinary_set_dispatch(obj, prop_name_si, value, self.regs[rd], self.current_strict())?;
         Ok(())
     }
 
@@ -616,7 +616,7 @@ impl Vm {
         // 直写绕过冻结语义。
         if obj.has_prop_meta() {
             let si = make_int_key(idx);
-            return self.ordinary_set_dispatch(obj, si, value, self.regs[rd]);
+            return self.ordinary_set_dispatch(obj, si, value, self.regs[rd], self.current_strict());
         }
         // 无 meta 快路径：不可扩展对象禁止新增元素（越界下标）；已有元素直写不受限
         // （无 meta 即默认可写）。
diff --git a/crates/oxide_vm/src/session_gc.rs b/crates/oxide_vm/src/session_gc.rs
index 4f6775fd..256d7d3e 100644
--- a/crates/oxide_vm/src/session_gc.rs
+++ b/crates/oxide_vm/src/session_gc.rs
@@ -1012,6 +1012,7 @@ mod tests {
             saved_new_target: JsValue::from_js_object(child_session),
             callee: JsValue::from_js_object(child_session),
             construct_result_reg: None,
+            strict: false,
             constructed_this: Some(JsValue::from_js_object(child_session)),
             is_derived_constructor: false,
             super_called: false,
diff --git a/crates/oxide_vm/src/suspended.rs b/crates/oxide_vm/src/suspended.rs
index 62564e35..d950607c 100644
--- a/crates/oxide_vm/src/suspended.rs
+++ b/crates/oxide_vm/src/suspended.rs
@@ -289,6 +289,7 @@ impl SuspendedFrame {
                 constructed_this: f.constructed_this.map(&mut rewrite),
                 is_derived_constructor: f.is_derived_constructor,
                 super_called: f.super_called,
+                strict: f.strict,
                 continuation: f.continuation,
             }),
             spill_stack: self.spill_stack.iter().copied().map(&mut rewrite).collect(),
@@ -365,6 +366,7 @@ mod tests {
             constructed_this: Some(tag),
             is_derived_constructor: false,
             super_called: false,
+            strict: false,
             continuation: FrameContinuation::None,
         }
     }
diff --git a/crates/oxide_vm/src/vm.rs b/crates/oxide_vm/src/vm.rs
index 084e4276..1bbeb54a 100644
--- a/crates/oxide_vm/src/vm.rs
+++ b/crates/oxide_vm/src/vm.rs
@@ -220,6 +220,9 @@ pub struct CallFrame {
     /// 旧方案——多层继承时中间 derived 帧由 SUPER_CALL 以构造 this 压入，
     /// regs[254] 恒非 undefined，值判定三重失效。
     pub super_called: bool,
+    /// 本帧函数的严格模式标志（来源：模块编译产物 `is_strict`）。
+    /// 属性写失败时据此分派：严格模式抛 TypeError，sloppy 静默 no-op。
+    pub strict: bool,
     pub continuation: FrameContinuation,
 }
 
@@ -372,6 +375,11 @@ pub(crate) struct InlineSyncState {
     pub(crate) spill_stack: Vec<JsValue>,
     pub(crate) cell_stack: Vec<Vec<*mut Cell>>,
     pub(crate) inline_callee: Option<JsValue>,
+    /// inline 目标函数的严格模式标志（内联执行期间写路径的 strict/sloppy 判定
+    /// 来源；嵌套内联时随本快照保存/恢复）。
+    pub(crate) inline_strict: bool,
+    /// inline 起始时 `frames.len()` 基线（嵌套内联时随本快照保存/恢复）。
+    pub(crate) inline_frames_base: usize,
     pub(crate) inline_args_base: u32,
     pub(crate) inline_args_count: u16,
     pub(crate) accessor_frame_target_reg: Option<u8>,
@@ -474,6 +482,16 @@ pub struct Vm {
     /// frames 为空（inline 隔离状态）时由此取闭包 upvalues。嵌套 inline 由
     /// InlineSyncState 保存/恢复。
     pub(crate) inline_callee: Option<JsValue>,
+    /// inline 目标函数的严格模式标志（与 `inline_callee` 同生命周期，
+    /// InlineSyncState 保存/恢复）：内联执行期间帧表被隔离，写路径的
+    /// strict/sloppy 判定取此值而非帧标志。
+    pub(crate) inline_strict: bool,
+    /// inline 起始时 `frames.len()` 基线（随 InlineSyncState 保存/恢复）：
+    /// 内联执行中新压的帧（CALL/accessor）越过该基线，其严格性归帧栈顶。
+    pub(crate) inline_frames_base: usize,
+    /// 本次 run 顶层脚本的严格模式标志（`module.is_strict`，run 时填充）：
+    /// 无帧且无 inline（顶层脚本赋值）时写路径的 strict/sloppy 判定来源。
+    pub(crate) top_level_strict: bool,
     /// inline 同步调用寄存器窗口缓冲池：`save_inline_state` 取出复用、
     /// `restore_inline_state` 归还。热回调循环内 save/restore 反复使用同一块
     /// 缓冲，只在嵌套（池已被外层取走）时新分配。
@@ -1327,6 +1345,27 @@ impl Vm {
         .max(1)
     }
 
+    /// 当前执行上下文的严格模式标志：属性写失败路径据此分派（严格抛
+    /// TypeError，sloppy 静默 no-op）。
+    ///
+    /// # 边界与前提
+    /// - inline 执行期间帧表可能非空（调用方帧隔离在外），须以
+    ///   `inline_frames_base` 为基线区分"inline 前已有帧"与"inline 内新压帧"
+    ///   （CALL/accessor 帧严格性归目标函数，最内层执行上下文即帧栈顶）。
+    /// - 无帧且无 inline 时为顶层脚本执行，取 `top_level_strict`。
+    pub(crate) fn current_strict(&self) -> bool {
+        if self.inline_callee.is_some() {
+            if self.frames.len() > self.inline_frames_base {
+                return self.frames.last().unwrap().strict;
+            }
+            return self.inline_strict;
+        }
+        if let Some(frame) = self.frames.last() {
+            return frame.strict;
+        }
+        self.top_level_strict
+    }
+
     #[expect(clippy::too_many_arguments)]
     pub(crate) fn push_bytecode_frame(
         &mut self, callee: JsValue, this_value: JsValue, args: FrameArgs, construct_result_reg: Option<u8>,
@@ -1436,6 +1475,7 @@ impl Vm {
             constructed_this,
             is_derived_constructor: obj.is_derived_constructor(),
             super_called: false,
+            strict: sub_is_strict,
             continuation,
         });
 
@@ -2207,9 +2247,9 @@ impl oxide_runtime_api::VmHost for Vm {
         self.ordinary_get(obj, prop_name_si, receiver)
     }
     fn ordinary_set(
-        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue,
+        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, strict: bool,
     ) -> Result<(), String> {
-        self.ordinary_set(obj, prop_name_si, val, receiver)
+        self.ordinary_set(obj, prop_name_si, val, receiver, strict)
     }
     fn define_data_property(
         &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, attributes: PropAttributes,
@@ -2528,6 +2568,7 @@ mod tests {
             saved_new_target: JsValue::undefined(),
             callee: JsValue::undefined(),
             construct_result_reg: None,
+            strict: false,
             constructed_this: None,
             is_derived_constructor: false,
             super_called: false,
@@ -2682,7 +2723,7 @@ mod tests {
 
         let x_si = vm.kernel_core.perm_interner().intern("x").0;
         let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
-        vm.ordinary_set(obj, x_si, JsValue::int(9), obj_val).expect("setter");
+        vm.ordinary_set(obj, x_si, JsValue::int(9), obj_val, true).expect("setter");
 
         let marker_si = vm.kernel_core.perm_interner().intern("marker").0;
         let obj = unsafe { &*obj_val.as_js_object_ptr() };
@@ -2720,7 +2761,7 @@ mod tests {
 
         let x_si = vm.kernel_core.perm_interner().intern("x").0;
         let child = unsafe { &mut *child_val.as_js_object_ptr() };
-        vm.ordinary_set(child, x_si, JsValue::int(12), child_val).expect("setter");
+        vm.ordinary_set(child, x_si, JsValue::int(12), child_val, true).expect("setter");
 
         let marker_si = vm.kernel_core.perm_interner().intern("marker").0;
         let child = unsafe { &*child_val.as_js_object_ptr() };
@@ -2744,7 +2785,7 @@ mod tests {
 
         let x_si = vm.kernel_core.perm_interner().intern("x").0;
         let child = unsafe { &mut *child_val.as_js_object_ptr() };
-        vm.ordinary_set(child, x_si, JsValue::int(15), child_val).expect("setter");
+        vm.ordinary_set(child, x_si, JsValue::int(15), child_val, true).expect("setter");
 
         let marker_si = vm.kernel_core.perm_interner().intern("marker").0;
         let child = unsafe { &*child_val.as_js_object_ptr() };
@@ -2761,7 +2802,7 @@ mod tests {
         let obj = unsafe { &mut *obj_val.as_js_object_ptr() };
         assert!(!obj.has_prop_meta());
         assert_eq!(vm.ordinary_get(obj, x_si, obj_val).expect("get"), JsValue::int(1));
-        vm.ordinary_set(obj, x_si, JsValue::int(2), obj_val).expect("set");
+        vm.ordinary_set(obj, x_si, JsValue::int(2), obj_val, true).expect("set");
         assert_eq!(vm.ordinary_get(obj, x_si, obj_val).expect("get"), JsValue::int(2));
     }
 
diff --git a/crates/oxide_vm/src/vm_props.rs b/crates/oxide_vm/src/vm_props.rs
index bc230ba2..4b163e71 100644
--- a/crates/oxide_vm/src/vm_props.rs
+++ b/crates/oxide_vm/src/vm_props.rs
@@ -152,22 +152,25 @@ impl Vm {
         None
     }
 
+    /// `strict` 为写方（执行赋值的那个函数/脚本）的严格模式：写失败时严格抛
+    /// TypeError，sloppy 静默 no-op（ECMA-262 OrdinarySetOwnProperty 失败分支）。
     pub(crate) fn ordinary_set(
-        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue,
+        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, strict: bool,
     ) -> Result<(), String> {
         let val = self.promote_if_needed_for_write_ptr(obj as *mut JsObject, val);
-        self.ordinary_set_inner(obj, prop_name_si, val, receiver, false)
+        self.ordinary_set_inner(obj, prop_name_si, val, receiver, false, strict)
     }
 
     /// 分发期入口：调用方（dispatch_set_prop 等）已对值做过 promote。
     pub(crate) fn ordinary_set_dispatch(
-        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue,
+        &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, strict: bool,
     ) -> Result<(), String> {
-        self.ordinary_set_inner(obj, prop_name_si, val, receiver, true)
+        self.ordinary_set_inner(obj, prop_name_si, val, receiver, true, strict)
     }
 
     fn ordinary_set_inner(
         &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, use_frame_push: bool,
+        strict: bool,
     ) -> Result<(), String> {
         vm_trace!(
             "ordinary_set_inner: shape={} prop_si={} frame_push={}",
@@ -180,7 +183,15 @@ impl Vm {
         if obj.is_typed_array_obj() {
             if let Some(index) = self.array_index_from_property_key(prop_name_si) {
                 if !std::ptr::eq(receiver.as_js_object_ptr(), obj as *mut JsObject) {
-                    return self.set_to_receiver(obj, prop_name_si, val, receiver, index as usize, use_frame_push);
+                    return self.set_to_receiver(
+                        obj,
+                        prop_name_si,
+                        val,
+                        receiver,
+                        index as usize,
+                        use_frame_push,
+                        strict,
+                    );
                 }
                 return oxide_builtins::typed_array::typed_array_element_set(self, obj, index, val);
             }
@@ -190,8 +201,8 @@ impl Vm {
         // prop_count/迭代/内置方法看到的长度不一致。
         let length_si = self.length_si;
         if obj.is_array() && prop_name_si == length_si {
-            // 冻结数组的 length 属性不可写（writable=false），赋值直接失败。
-            // sloppy/strict 差异未实现，与其它只读属性写一致统一抛 TypeError。
+            // 冻结数组的 length 属性不可写（writable=false），赋值直接失败；
+            // 两模式统一抛 TypeError（length 冻结检查的 strict/sloppy 差异不在本路径范围）。
             if obj.is_frozen() {
                 return self.raise_type_error("Cannot assign to read only property 'length'");
             }
@@ -215,12 +226,12 @@ impl Vm {
             let old_logical = obj.logical_len() as usize;
             let old_count = obj.array_prop_count as usize;
             // ArraySetLength：增长（newLen > oldLen）要求对象可扩展，不可扩展时
-            // 整个赋值失败且不修改（sloppy 静默失败；VM 未实现 strict 标志）。
+            // 整个赋值失败且不修改（length 失败两模式均静默 no-op，不抛）。
             if raw_new_len > old_logical && !obj.is_extensible() {
                 return Ok(());
             }
             // ArraySetLength：收缩时若 [newLen, oldLen) 内存在不可配置元素，整个收缩
-            // 失败且不做任何修改（sloppy 赋值静默失败；VM 未实现 strict 标志，统一按 no-op）。
+            // 失败且不做任何修改（length 失败两模式均静默 no-op，不抛）。
             if raw_new_len < old_logical {
                 for idx in raw_new_len..old_count {
                     if let Some(meta) = obj.prop_meta_at(idx) {
@@ -256,12 +267,20 @@ impl Vm {
             if let Some(meta) = obj.prop_meta_at(pos) {
                 if meta.is_accessor {
                     if meta.set.is_undefined() {
-                        return self.raise_type_error("property has no setter");
+                        // 无 setter：严格抛错，sloppy 静默 no-op。
+                        if strict {
+                            return self.raise_type_error("property has no setter");
+                        }
+                        return Ok(());
                     }
                     return self.call_or_push_setter(meta.set, receiver, val, use_frame_push);
                 }
                 if !meta.attributes.writable() {
-                    return self.raise_type_error("cannot assign to read-only property");
+                    // 只读数据属性：严格抛错，sloppy 静默 no-op。
+                    if strict {
+                        return self.raise_type_error("cannot assign to read-only property");
+                    }
+                    return Ok(());
                 }
             }
             // pos 是存储索引（get_own_property_slot 对数组已加元素区偏移）。
@@ -272,19 +291,30 @@ impl Vm {
         if let Some(meta) = self.inherited_property_meta(obj, prop_name_si) {
             if meta.is_accessor {
                 if meta.set.is_undefined() {
-                    return self.raise_type_error("property has no setter");
+                    // 继承无 setter：严格抛错，sloppy 静默 no-op。
+                    if strict {
+                        return self.raise_type_error("property has no setter");
+                    }
+                    return Ok(());
                 }
                 return self.call_or_push_setter(meta.set, receiver, val, use_frame_push);
             }
             if !meta.attributes.writable() {
-                return self.raise_type_error("cannot assign to read-only property");
+                // 继承只读数据属性：严格抛错，sloppy 静默 no-op（不遮蔽）。
+                if strict {
+                    return self.raise_type_error("cannot assign to read-only property");
+                }
+                return Ok(());
             }
         }
 
         // 新属性（自身与原型链均无同名）：须对象可扩展（OrdinarySet 的 extensible
-        // 检查），不可扩展时赋值失败。
+        // 检查），不可扩展时赋值失败（严格抛错，sloppy 静默 no-op）。
         if !obj.is_extensible() {
-            return self.raise_type_error("object is not extensible");
+            if strict {
+                return self.raise_type_error("object is not extensible");
+            }
+            return Ok(());
         }
         self.set_or_create_prop_value(obj, prop_name_si, val);
         Ok(())
@@ -293,9 +323,10 @@ impl Vm {
     /// TypedArray 整数索引在 `receiver` ≠ TA 时的 [[Set]] 语义：越界或非对象
     /// receiver 直接返回 true（不写、不 ToNumber）；界内对象 receiver 走普通 set
     /// 把属性落到 receiver 自身。
+    #[allow(clippy::too_many_arguments)]
     fn set_to_receiver(
         &mut self, ta_obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, index: usize,
-        use_frame_push: bool,
+        use_frame_push: bool, strict: bool,
     ) -> Result<(), String> {
         let Some((_, length)) = oxide_builtins::typed_array::typed_array_integer_index(self, ta_obj, prop_name_si)
         else {
@@ -310,7 +341,7 @@ impl Vm {
         }
         let promoted = self.promote_if_needed_for_write_ptr(receiver_ptr, val);
         let receiver_obj = unsafe { &mut *receiver_ptr };
-        self.ordinary_set_inner(receiver_obj, prop_name_si, promoted, receiver, use_frame_push)
+        self.ordinary_set_inner(receiver_obj, prop_name_si, promoted, receiver, use_frame_push, strict)
     }
 
     pub(crate) fn call_or_push_setter(
@@ -430,8 +461,10 @@ impl Vm {
     ) -> Result<(), String> {
         ic_trace!("set_member_prop: shape_id={} prop_name_si={}", obj.shape_id(), prop_name_si);
         let val = self.promote_if_needed_for_write_ptr(obj as *mut JsObject, val);
+        // 写方即当前执行函数（赋值语义），strict/sloppy 判定取当前上下文。
+        let strict = self.current_strict();
         if obj.has_prop_meta() {
-            self.ordinary_set(obj, prop_name_si, val, receiver)?;
+            self.ordinary_set(obj, prop_name_si, val, receiver, strict)?;
             return Ok(());
         }
         if crate::ic_helper::ic_set_hit_own(obj, &self.bytecode, ext_pc, val) {
@@ -445,9 +478,9 @@ impl Vm {
         } else if self.named_prop_create_needs_ordinary_set(obj, prop_name_si) {
             // 数组 length / 整数索引键写新属性：分流回 ordinary_set（ArraySetLength /
             // 元素区写），与 dispatch_ic_set_prop 对称，防快路径建影子槽破坏数组语义。
-            self.ordinary_set(obj, prop_name_si, val, receiver)?;
+            self.ordinary_set(obj, prop_name_si, val, receiver, strict)?;
         } else {
-            self.create_named_prop_fast(obj, prop_name_si, val, receiver, ext_pc, false)?;
+            self.create_named_prop_fast(obj, prop_name_si, val, receiver, ext_pc, false, strict)?;
         }
         Ok(())
     }
@@ -459,26 +492,40 @@ impl Vm {
     /// - 调用方已确认属性不存在于 shape 链（lookup_position miss）。
     /// - 数组 length / 数组与 TA 整数索引键不进入本路径（调用方先分流到 ordinary_set）。
     /// - `use_frame_push` 与 ordinary_set* 入口一致（member 写 false / IC_SET 分发 true）。
+    /// - `strict` 为写方的严格模式：原型链只读/无 setter/不可扩展时严格抛错、sloppy 静默 no-op。
+    #[allow(clippy::too_many_arguments)]
     pub(crate) fn create_named_prop_fast(
         &mut self, obj: &mut JsObject, prop_name_si: u32, val: JsValue, receiver: JsValue, ext_pc: usize,
-        use_frame_push: bool,
+        use_frame_push: bool, strict: bool,
     ) -> Result<(), String> {
         // 原型链同名 accessor 须触发 setter、只读 data 须报错（与 ordinary_set 一致），
         // 命中时不得创建 own 属性（规范 [[Set]] shadow 语义）。
         if let Some(meta) = self.inherited_property_meta(obj, prop_name_si) {
             if meta.is_accessor {
                 if meta.set.is_undefined() {
-                    return self.raise_type_error("property has no setter");
+                    // 继承无 setter：严格抛错，sloppy 静默 no-op。
+                    if strict {
+                        return self.raise_type_error("property has no setter");
+                    }
+                    return Ok(());
                 }
                 return self.call_or_push_setter(meta.set, receiver, val, use_frame_push);
             }
             if !meta.attributes.writable() {
-                return self.raise_type_error("cannot assign to read-only property");
+                // 继承只读数据属性：严格抛错，sloppy 静默 no-op（不遮蔽）。
+                if strict {
+                    return self.raise_type_error("cannot assign to read-only property");
+                }
+                return Ok(());
             }
         }
         // 新属性创建要求对象可扩展（规范 extensible 检查在原型链 setter/只读判定之后）。
         if !obj.is_extensible() {
-            return self.raise_type_error("object is not extensible");
+            // 不可扩展：严格抛错，sloppy 静默 no-op。
+            if strict {
+                return self.raise_type_error("object is not extensible");
+            }
+            return Ok(());
         }
         // 新 shape 槽位 = 追加前命名属性数（与 push_prop 的追加位置一致）。
         let slot = obj.prop_vec_len() as u32;
diff --git a/crates/oxide_vm/src/vm_runtime.rs b/crates/oxide_vm/src/vm_runtime.rs
index 446f9177..50591aab 100644
--- a/crates/oxide_vm/src/vm_runtime.rs
+++ b/crates/oxide_vm/src/vm_runtime.rs
@@ -100,6 +100,12 @@ macro_rules! inline_save_field {
     ($recv:ident, $window_regs:ident, inline_callee, opt_copy) => {
         $recv.inline_callee
     };
+    ($recv:ident, $window_regs:ident, inline_strict, copy) => {
+        $recv.inline_strict
+    };
+    ($recv:ident, $window_regs:ident, inline_frames_base, copy) => {
+        $recv.inline_frames_base
+    };
     ($recv:ident, $window_regs:ident, inline_args_base, copy) => {
         $recv.inline_args_base
     };
@@ -183,6 +189,12 @@ macro_rules! inline_restore_field {
     ($recv:ident, $saved:ident, inline_callee, opt_copy) => {
         $recv.inline_callee = $saved.inline_callee
     };
+    ($recv:ident, $saved:ident, inline_strict, copy) => {
+        $recv.inline_strict = $saved.inline_strict
+    };
+    ($recv:ident, $saved:ident, inline_frames_base, copy) => {
+        $recv.inline_frames_base = $saved.inline_frames_base
+    };
     ($recv:ident, $saved:ident, inline_args_base, copy) => {
         $recv.inline_args_base = $saved.inline_args_base
     };
@@ -228,6 +240,8 @@ macro_rules! inline_core_fields {
             (spill_stack, move_field),            // V M
             (cell_stack, move_field),             // V M
             (inline_callee, opt_copy),            // V M
+            (inline_strict, copy),                // M
+            (inline_frames_base, copy),           // M
             (inline_args_base, copy),             // M
             (inline_args_count, copy),            // M
             (accessor_frame_target_reg, copy),    // M
@@ -382,6 +396,11 @@ impl Vm {
         self.root_reg_limit = self.active_reg_limit;
         self.cell_stack.push(Vec::with_capacity(sub.cells_needed as usize));
         self.inline_callee = Some(callee);
+        // inline 无 CallFrame：目标函数严格模式单独记录，内联执行期间的写路径
+        // strict/sloppy 判定据此分派（嵌套内联时外层值由 InlineSyncState 恢复）。
+        self.inline_strict = sub.is_strict;
+        // 帧基线快照：内联期间新压的帧（CALL/accessor）越过基线，其严格性归帧栈顶。
+        self.inline_frames_base = self.frames.len();
         // inline 同步调用无 CallFrame：完整实参写入 spill 栈实参区，供 CREATE_ARGUMENTS 读取。
         self.inline_args_base = self.spill_stack.len() as u32;
         self.spill_stack.extend_from_slice(args);
@@ -486,6 +505,8 @@ impl Vm {
         self.cell_stack.push(Vec::new());
         self.sub_modules = Arc::new(collect_flat_modules(module));
         self.immutables_cache = (0..self.sub_modules.len()).map(|_| OnceLock::new()).collect();
+        // 顶层脚本严格模式：无帧且无 inline 时写路径的 strict/sloppy 判定来源。
+        self.top_level_strict = module.is_strict;
         self.bytecode = Arc::clone(&module.bytecode);
         self.activate_immutables(0, &module.constants);
         self.root_reg_limit = module.n_registers.max(1);
diff --git a/crates/oxide_vm/src/vm_support.rs b/crates/oxide_vm/src/vm_support.rs
index dcc29b73..5cc049eb 100644
--- a/crates/oxide_vm/src/vm_support.rs
+++ b/crates/oxide_vm/src/vm_support.rs
@@ -75,6 +75,9 @@ impl Vm {
             inline_args_count: 0,
             accessor_frame_target_reg: None,
             inline_callee: None,
+            inline_strict: false,
+            inline_frames_base: 0,
+            top_level_strict: false,
             inline_reg_pool: None,
             generator_suspended: None,
             delegated_iterator: None,
@@ -184,6 +187,9 @@ impl Vm {
             inline_args_count: 0,
             accessor_frame_target_reg: None,
             inline_callee: None,
+            inline_strict: false,
+            inline_frames_base: 0,
+            top_level_strict: false,
             inline_reg_pool: None,
             generator_suspended: None,
             delegated_iterator: None,
diff --git a/crates/oxide_vm/tests/builtins_object_tests.rs b/crates/oxide_vm/tests/builtins_object_tests.rs
index 9750106c..5d2c05ac 100644
--- a/crates/oxide_vm/tests/builtins_object_tests.rs
+++ b/crates/oxide_vm/tests/builtins_object_tests.rs
@@ -124,8 +124,8 @@ fn object_define_property_rejects_mixed_descriptor() {
 }
 
 #[test]
-fn object_define_property_non_writable_assignment_throws() {
-    let err = match eval("var o={}; Object.defineProperty(o,'x',{value:1}); o.x=2") {
+fn object_define_property_non_writable_assignment_throws_in_strict() {
+    let err = match eval("var o={}; Object.defineProperty(o,'x',{value:1}); (function(){'use strict'; o.x=2})()") {
         Ok(_) => panic!("expected assignment to fail"),
         Err(err) => err,
     };
diff --git a/crates/oxide_vm/tests/member_write_ic_tests.rs b/crates/oxide_vm/tests/member_write_ic_tests.rs
index 2f6f4d19..391613ba 100644
--- a/crates/oxide_vm/tests/member_write_ic_tests.rs
+++ b/crates/oxide_vm/tests/member_write_ic_tests.rs
@@ -90,16 +90,18 @@ fn proto_setter_called_both_write_paths() {
     assert_eq!(r, "2:0", "setter 被调 2 次（IC_SET 与 member 各 1），o 无 own 属性");
 }
 
-/// 原型只读 data：两条写路径都按 ordinary_set 抛 TypeError。
+/// 严格模式原型只读 data：两条写路径都按 ordinary_set 抛 TypeError。
 #[test]
-fn readonly_inherited_data_raises() {
+fn readonly_inherited_data_raises_in_strict() {
     let (r, _hits, _misses) = run_once(
         r#"var p = {};
            Object.defineProperty(p, 'x', { value: 1, writable: false });
            var o = Object.create(p);
            var msg = '';
-           try { o.x = 5; } catch (e) { msg = e.message; }
-           try { o.x += 1; } catch (e) { msg += '|' + e.message; }
+           (function() { 'use strict';
+             try { o.x = 5; } catch (e) { msg = e.message; }
+             try { o.x += 1; } catch (e) { msg += '|' + e.message; }
+           })();
            msg"#,
     );
     assert_eq!(
@@ -108,6 +110,21 @@ fn readonly_inherited_data_raises() {
     );
 }
 
+/// sloppy 原型只读 data：两条写路径都静默 no-op（值不变、不抛）。
+#[test]
+fn readonly_inherited_data_silently_fails_in_sloppy() {
+    let (r, _hits, _misses) = run_once(
+        r#"var p = {};
+           Object.defineProperty(p, 'x', { value: 1, writable: false });
+           var o = Object.create(p);
+           var threw = false;
+           try { o.x = 5; } catch (e) { threw = true; }
+           try { o.x += 1; } catch (e) { threw = true; }
+           threw + ':' + o.x + ':' + o.hasOwnProperty('x')"#,
+    );
+    assert_eq!(r, "false:1:false", "sloppy 只读继承属性写静默失败，值保持 1，不创建 own 属性");
+}
+
 /// 写新属性（shape 转换）：快路径建 shape + 写回，循环内同 shape 写全命中。
 #[test]
 fn write_new_prop_then_hit() {
diff --git a/crates/oxide_vm/tests/property_array_fastpath_tests.rs b/crates/oxide_vm/tests/property_array_fastpath_tests.rs
index 9f1eb042..e0ddf119 100644
--- a/crates/oxide_vm/tests/property_array_fastpath_tests.rs
+++ b/crates/oxide_vm/tests/property_array_fastpath_tests.rs
@@ -89,16 +89,26 @@ fn accessor_getter_and_setter_still_trigger() {
     );
 }
 
-// 非写属性（writable:false）写入：fast path 不命中，走完整协议抛 TypeError。
+// 非写属性（writable:false）写入（严格模式）：fast path 不命中，走完整协议抛 TypeError。
 #[test]
-fn non_writable_index_write_throws() {
+fn non_writable_index_write_throws_in_strict() {
     let r = eval_str(
-        "var a=[1,2,3]; Object.defineProperty(a,0,{writable:false,value:1}); try { a[0]=9; 'no' } catch(e) { e instanceof TypeError ? 'throws' : 'wrong' }"
+        "var a=[1,2,3]; Object.defineProperty(a,0,{writable:false,value:1}); var r='no'; (function(){'use strict'; try { a[0]=9; } catch(e) { r = (e instanceof TypeError ? 'throws' : 'wrong'); } })(); r"
     )
     .unwrap();
     assert_eq!(r, "throws", "expected TypeError, got {r:?}");
 }
 
+// 非写属性（writable:false）写入（sloppy）：静默 no-op，值不变。
+#[test]
+fn non_writable_index_write_silently_fails_in_sloppy() {
+    let r = eval_str(
+        "var a=[1,2,3]; Object.defineProperty(a,0,{writable:false,value:1}); try { a[0]=9; 'no' } catch(e) { 'threw' }; a[0]"
+    )
+    .unwrap();
+    assert_eq!(r, "1", "sloppy 只读元素写应静默 no-op，值保持 1，实际 {r:?}");
+}
+
 // 非规范数字串（前导零）不映射整数键，走字符串键慢路径（不命中 fast path）。
 #[test]
 fn non_canonical_index_string_uses_slow_path() {
diff --git a/crates/oxide_vm/tests/property_write_protection_tests.rs b/crates/oxide_vm/tests/property_write_protection_tests.rs
index a595bd6d..185b80a5 100644
--- a/crates/oxide_vm/tests/property_write_protection_tests.rs
+++ b/crates/oxide_vm/tests/property_write_protection_tests.rs
@@ -33,17 +33,30 @@ fn assert_err_contains(result: Result<JsValue, String>, expected: &str) {
     }
 }
 
-// ── 向不可写自身属性赋值抛 TypeError ──
+// ── 严格模式向不可写自身属性赋值抛 TypeError ──
 #[test]
-fn assign_to_non_writable_throws() {
+fn assign_to_non_writable_throws_in_strict() {
     let result = eval_many(&[
         "var obj = {}",
         "Object.defineProperty(obj, 'x', {value: 1, writable: false})",
-        "obj.x = 2",
+        "(function() { 'use strict'; obj.x = 2 })()",
     ]);
     assert_err_contains(result, "read-only");
 }
 
+// ── sloppy 向不可写自身属性赋值静默失败（值不变、不抛） ──
+#[test]
+fn assign_to_non_writable_silently_fails_in_sloppy() {
+    let r = eval_many(&[
+        "var obj = {}",
+        "Object.defineProperty(obj, 'x', {value: 1, writable: false})",
+        "obj.x = 2",
+        "obj.x",
+    ])
+    .unwrap();
+    assert!(r.is_int() && r.as_int() == 1, "sloppy 只读属性写应静默 no-op，值保持 1，实际 {:?}", r);
+}
+
 // ── 向可写自身属性赋值成功 ──
 #[test]
 fn assign_to_writable_succeeds() {
@@ -57,46 +70,87 @@ fn assign_to_writable_succeeds() {
     assert!(r.is_int() && r.as_int() == 2, "assign to writable should set value to 2, got {:?}", r);
 }
 
-// ── 向原型上不可写的继承属性赋值抛错 ──
+// ── 严格模式向原型上不可写的继承属性赋值抛错 ──
 #[test]
-fn assign_to_inherited_non_writable_throws() {
+fn assign_to_inherited_non_writable_throws_in_strict() {
     let result = eval_many(&[
         "var proto = {}",
         "Object.defineProperty(proto, 'x', {value: 1, writable: false, enumerable: true, configurable: true})",
         "var child = Object.create(proto)",
-        "child.x = 2",
+        "(function() { 'use strict'; child.x = 2 })()",
     ]);
     assert_err_contains(result, "read-only");
 }
 
-// ── 原型属性不可写但子对象无自有属性时，赋值会在子对象上创建自有属性
-// ponytail: spec allows shadowing when proto prop is configurable; engine doesn't yet.
-// 引擎对不可写原型属性正确抛错；完整遮蔽作为后续工作。
+// ── 继承只读数据属性：sloppy 赋值静默失败，不创建自有属性（不遮蔽） ──
 #[test]
-fn assign_non_writable_proto_configurable_prop_throws() {
+fn assign_to_inherited_non_writable_silently_fails_in_sloppy() {
+    let (_vm, r) = eval_keep_vm(
+        &[
+            "var proto = {}",
+            "Object.defineProperty(proto, 'x', {value: 1, writable: false, enumerable: true, configurable: true})",
+            "var child = Object.create(proto)",
+            "child.x = 99",
+            "[child.x, child.hasOwnProperty('x')]",
+        ]
+        .join("; "),
+    )
+    .unwrap();
+    let arr = unsafe { &*r.as_js_object_ptr() };
+    assert!(
+        arr.get_prop_at(0).is_int() && arr.get_prop_at(0).as_int() == 1,
+        "sloppy 写只读继承属性应静默 no-op，值保持 1"
+    );
+    assert!(
+        arr.get_prop_at(1).is_bool() && !arr.get_prop_at(1).as_bool(),
+        "静默失败不得在子对象上创建自有属性"
+    );
+}
+
+// ── 严格模式：原型只读可配置属性赋值抛错（不可写数据属性不可遮蔽） ──
+#[test]
+fn assign_non_writable_proto_configurable_prop_throws_in_strict() {
     let result = eval_many(&[
         "var proto = {}",
         "Object.defineProperty(proto, 'x', {value: 1, writable: false, enumerable: true, configurable: true})",
         "var child = Object.create(proto)",
-        "child.x = 99",
+        "(function() { 'use strict'; child.x = 99 })()",
     ]);
     assert_err_contains(result, "read-only");
 }
 
-// ── Object.freeze 后写已有属性抛 TypeError ──
+// ── 严格模式 Object.freeze 后写已有属性抛 TypeError ──
 #[test]
-fn frozen_write_existing_prop_throws() {
-    let result = eval_many(&["var o = Object.freeze({a: 1})", "o.a = 2"]);
+fn frozen_write_existing_prop_throws_in_strict() {
+    let result = eval_many(&["var o = Object.freeze({a: 1})", "(function() { 'use strict'; o.a = 2 })()"]);
     assert_err_contains(result, "read-only");
 }
 
-// ── Object.freeze 后写新属性抛 TypeError ──
+// ── sloppy Object.freeze 后写已有属性静默失败 ──
 #[test]
-fn frozen_write_new_prop_throws() {
-    let result = eval_many(&["var o = Object.freeze({a: 1})", "o.b = 2"]);
+fn frozen_write_existing_prop_silently_fails_in_sloppy() {
+    let r = eval_many(&["var o = Object.freeze({a: 1})", "o.a = 2", "o.a"]).unwrap();
+    assert!(r.is_int() && r.as_int() == 1, "sloppy 冻结对象写应静默 no-op，值保持 1，实际 {:?}", r);
+}
+
+// ── 严格模式 Object.freeze 后写新属性抛 TypeError ──
+#[test]
+fn frozen_write_new_prop_throws_in_strict() {
+    let result = eval_many(&["var o = Object.freeze({a: 1})", "(function() { 'use strict'; o.b = 2 })()"]);
     assert_err_contains(result, "not extensible");
 }
 
+// ── sloppy Object.freeze 后写新属性静默失败（属性不创建） ──
+#[test]
+fn frozen_write_new_prop_silently_fails_in_sloppy() {
+    let r = eval_many(&["var o = Object.freeze({a: 1})", "o.b = 2", "o.b === undefined"]).unwrap();
+    assert!(
+        r.is_bool() && r.as_bool(),
+        "sloppy 冻结对象写新属性应静默 no-op，属性不创建，实际 {:?}",
+        r
+    );
+}
+
 // ── Object.freeze 后 defineProperty 抛 TypeError ──
 #[test]
 fn frozen_define_property_throws() {
@@ -104,13 +158,14 @@ fn frozen_define_property_throws() {
     assert_err_contains(result, "not extensible");
 }
 
-// ── Object.seal 后写新属性抛错、删属性返回 false、改值生效 ──
+// ── 严格模式 Object.seal 后写新属性抛错、删属性返回 false、改值生效 ──
 #[test]
 fn sealed_semantics() {
     let (_vm, r) = eval_keep_vm(
         &[
             "var o = Object.seal({a: 1})",
-            "var new_throws = false; try { o.b = 2 } catch (e) { new_throws = true }",
+            "var new_throws = false",
+            "(function() { 'use strict'; try { o.b = 2 } catch (e) { new_throws = true } })()",
             "var del = delete o.a",
             "o.a = 5",
             "[new_throws, del, o.a, o.hasOwnProperty('a')]",
@@ -121,30 +176,30 @@ fn sealed_semantics() {
     let arr = unsafe { &*r.as_js_object_ptr() };
     assert!(
         arr.get_prop_at(0).is_bool() && arr.get_prop_at(0).as_bool(),
-        "new prop write should throw"
+        "strict new prop write should throw"
     );
     assert!(arr.get_prop_at(1).is_bool() && !arr.get_prop_at(1).as_bool(), "delete should be false");
     assert!(arr.get_prop_at(2).is_int() && arr.get_prop_at(2).as_int() == 5, "value write should work");
     assert!(arr.get_prop_at(3).is_bool() && arr.get_prop_at(3).as_bool(), "prop should remain own");
 }
 
-// ── Object.preventExtensions 后新属性不生效（sloppy 抛错），已有属性可写 ──
+// ── Object.preventExtensions 后新属性写静默失效（sloppy），已有属性可写 ──
 #[test]
 fn prevent_extensions_semantics() {
     let (_vm, r) = eval_keep_vm(
         &[
             "var o = Object.preventExtensions({a: 1})",
-            "var new_throws = false; try { o.b = 3 } catch (e) { new_throws = true }",
+            "var new_threw = false; try { o.b = 3 } catch (e) { new_threw = true }",
             "o.a = 2",
-            "[new_throws, o.a, o.b === undefined]",
+            "[new_threw, o.a, o.b === undefined]",
         ]
         .join("; "),
     )
     .unwrap();
     let arr = unsafe { &*r.as_js_object_ptr() };
     assert!(
-        arr.get_prop_at(0).is_bool() && arr.get_prop_at(0).as_bool(),
-        "new prop write should throw"
+        arr.get_prop_at(0).is_bool() && !arr.get_prop_at(0).as_bool(),
+        "sloppy new prop write should silently fail"
     );
     assert!(
         arr.get_prop_at(1).is_int() && arr.get_prop_at(1).as_int() == 2,
@@ -153,15 +208,15 @@ fn prevent_extensions_semantics() {
     assert!(arr.get_prop_at(2).is_bool() && arr.get_prop_at(2).as_bool(), "new prop should be absent");
 }
 
-// ── Object.freeze 数组：元素写与 length 收缩均被拦截 ──
+// ── 严格模式 Object.freeze 数组：元素写与 length 收缩均抛错 ──
 #[test]
-fn frozen_array_write_and_length_throws() {
+fn frozen_array_write_and_length_throws_in_strict() {
     let (_vm, r) = eval_keep_vm(
         &[
             "var a = Object.freeze([1, 2])",
             "var e1 = false, e2 = false",
-            "try { a[0] = 9 } catch (e) { e1 = true }",
-            "try { a.length = 0 } catch (e) { e2 = true }",
+            "(function() { 'use strict'; try { a[0] = 9 } catch (e) { e1 = true } })()",
+            "(function() { 'use strict'; try { a.length = 0 } catch (e) { e2 = true } })()",
             "[e1, e2, a[0], a.length, Object.getOwnPropertyDescriptor(a, '0').writable]",
         ]
         .join("; "),
@@ -178,6 +233,27 @@ fn frozen_array_write_and_length_throws() {
     );
 }
 
+// ── sloppy Object.freeze 数组：元素写静默失败（length 冻结检查仍抛错） ──
+#[test]
+fn frozen_array_element_write_silently_fails_in_sloppy() {
+    let (_vm, r) = eval_keep_vm(
+        &[
+            "var a = Object.freeze([1, 2])",
+            "var e1 = false",
+            "try { a[0] = 9 } catch (e) { e1 = true }",
+            "[e1, a[0]]",
+        ]
+        .join("; "),
+    )
+    .unwrap();
+    let arr = unsafe { &*r.as_js_object_ptr() };
+    assert!(
+        arr.get_prop_at(0).is_bool() && !arr.get_prop_at(0).as_bool(),
+        "sloppy 冻结数组元素写应静默 no-op"
+    );
+    assert!(arr.get_prop_at(1).is_int() && arr.get_prop_at(1).as_int() == 1, "element value unchanged");
+}
+
 // ── isFrozen/isSealed：手动 defineProperty 全部冻结（未调 freeze）也应判 true ──
 #[test]
 fn is_frozen_manual_define_props() {
@@ -212,19 +288,40 @@ fn reflect_ops_on_frozen_return_false() {
     }
 }
 
-// ── freeze/seal 后 IC 直写路径失效：循环写仍被拦截 ──
+// ── 严格模式 freeze 后 IC 直写路径失效：循环写仍被拦截 ──
 #[test]
-fn frozen_ic_path_still_blocks_write() {
+fn frozen_ic_path_still_blocks_write_in_strict() {
     let r = eval_many(&[
         "var o = Object.freeze({a: 1})",
         "var threw = false",
-        "for (var i = 0; i < 3; i++) { try { o.a = i } catch (e) { threw = true } }",
+        "(function() { 'use strict'; for (var i = 0; i < 3; i++) { try { o.a = i } catch (e) { threw = true } } })()",
         "threw",
     ])
     .unwrap();
     assert!(r.is_bool() && r.as_bool(), "IC path should still throw on frozen write");
 }
 
+// ── sloppy freeze 后循环写静默失效（值不变、不抛） ──
+#[test]
+fn frozen_ic_path_silently_fails_in_sloppy() {
+    let (_vm, r) = eval_keep_vm(
+        &[
+            "var o = Object.freeze({a: 1})",
+            "var threw = false",
+            "for (var i = 0; i < 3; i++) { try { o.a = i } catch (e) { threw = true } }",
+            "[threw, o.a]",
+        ]
+        .join("; "),
+    )
+    .unwrap();
+    let arr = unsafe { &*r.as_js_object_ptr() };
+    assert!(
+        arr.get_prop_at(0).is_bool() && !arr.get_prop_at(0).as_bool(),
+        "sloppy frozen write should silently fail"
+    );
+    assert!(arr.get_prop_at(1).is_int() && arr.get_prop_at(1).as_int() == 1, "value unchanged");
+}
+
 // ── sealed 对象 IC 路径：已有属性写正常 ──
 #[test]
 fn sealed_ic_path_allows_existing_write() {
diff --git a/crates/oxide_vm/tests/sloppy_assignment_silent_tests.rs b/crates/oxide_vm/tests/sloppy_assignment_silent_tests.rs
new file mode 100644
index 00000000..0326f1a8
--- /dev/null
+++ b/crates/oxide_vm/tests/sloppy_assignment_silent_tests.rs
@@ -0,0 +1,196 @@
+//! sloppy 模式赋值静默失败语义测试：ordinary_set 失败分支（自身/继承只读数据、
+//! 无 setter 访问器、不可扩展新属性）在 sloppy 静默 no-op，严格模式抛 TypeError。
+//! 覆盖脚本顶层（`top_level_strict`）、函数级（帧 `strict`）与内联内置回调
+//! （forEach 等，`inline_strict` + 帧基线）三种执行上下文。
+
+use oxide_compiler::compiler::Compiler;
+use oxide_types::value::JsValue;
+use oxide_vm::vm::Vm;
+
+fn eval(source: &str) -> Result<JsValue, String> {
+    let allocator = oxide_parser::Allocator::default();
+    let program = oxide_parser::parse(&allocator, source).map_err(|e| format!("Parse error: {:?}", e))?;
+    let module = Compiler::new().compile(&program).map_err(|e| format!("Compile error: {}", e))?;
+    let mut vm = Vm::new();
+    vm.run(&module)
+}
+
+fn eval_many(lines: &[&str]) -> Result<JsValue, String> {
+    eval(&lines.join("; "))
+}
+
+fn assert_err_contains(result: Result<JsValue, String>, expected: &str) {
+    match result {
+        Ok(_) => panic!("expected error containing '{}', got Ok", expected),
+        Err(e) => assert!(e.contains(expected), "expected error containing '{}', got: {}", expected, e),
+    }
+}
+
+/// 求值并把结果按字符串提取（`JsValue` Display 不携带字符串内容）。
+fn eval_str(source: &str) -> String {
+    let allocator = oxide_parser::Allocator::default();
+    let program = oxide_parser::parse(&allocator, source).expect("parse");
+    let module = Compiler::new().compile(&program).expect("compile");
+    let mut vm = Vm::new();
+    let result = vm.run(&module).expect("run");
+    vm.lookup_str(result).unwrap_or_else(|| format!("{result}"))
+}
+
+// ── sloppy 脚本顶层：无 setter 访问器赋值静默 no-op（值不变、不抛） ──
+#[test]
+fn sloppy_script_top_level_accessor_no_setter_silently_fails() {
+    let r = eval_many(&["var o = { get h() { return 1 } }", "o.h = 2", "o.h"]).unwrap();
+    assert!(
+        r.is_int() && r.as_int() == 1,
+        "sloppy 无 setter 访问器写应静默 no-op，值保持 1，实际 {:?}",
+        r
+    );
+}
+
+// ── 严格脚本（顶层指令）：无 setter 访问器赋值抛 TypeError ──
+#[test]
+fn strict_script_top_level_accessor_no_setter_throws() {
+    let result = eval("'use strict'; var o = { get h() { return 1 } }; o.h = 2");
+    assert_err_contains(result, "no setter");
+}
+
+// ── sloppy 脚本顶层：只读自身属性赋值静默失败 ──
+#[test]
+fn sloppy_script_top_level_readonly_silently_fails() {
+    let r = eval("var o = {}; Object.defineProperty(o, 'x', {value: 1, writable: false}); o.x = 2; o.x").unwrap();
+    assert!(r.is_int() && r.as_int() == 1, "sloppy 只读属性写应静默 no-op，值保持 1，实际 {:?}", r);
+}
+
+// ── 严格脚本（顶层指令）：只读自身属性赋值抛 TypeError ──
+#[test]
+fn strict_script_top_level_readonly_throws() {
+    let result = eval("'use strict'; var o = {}; Object.defineProperty(o, 'x', {value: 1, writable: false}); o.x = 2");
+    assert_err_contains(result, "read-only");
+}
+
+// ── sloppy 函数级（非严格函数）：不可扩展对象写新属性静默失败 ──
+#[test]
+fn sloppy_function_write_new_prop_on_non_extensible_silently_fails() {
+    let r = eval_many(&[
+        "var o = Object.preventExtensions({})",
+        "function w() { o.n = 3 }",
+        "w()",
+        "o.n === undefined",
+    ])
+    .unwrap();
+    assert!(
+        r.is_bool() && r.as_bool(),
+        "sloppy 函数写不可扩展对象新属性应静默 no-op，属性不创建，实际 {:?}",
+        r
+    );
+}
+
+// ── 严格函数：不可扩展对象写新属性抛 TypeError ──
+#[test]
+fn strict_function_write_new_prop_on_non_extensible_throws() {
+    let result = eval_many(&["var o = Object.preventExtensions({})", "(function() { 'use strict'; o.n = 3 })()"]);
+    assert_err_contains(result, "not extensible");
+}
+
+// ── 继承只读数据属性：sloppy 赋值静默失败且不创建自有属性 ──
+#[test]
+fn sloppy_inherited_readonly_silently_fails_without_shadow() {
+    let s = eval_str(
+        "var p = {}; Object.defineProperty(p, 'x', {value: 1, writable: false, configurable: true}); \
+         var c = Object.create(p); c.x = 9; c.x + ':' + c.hasOwnProperty('x')",
+    );
+    assert_eq!(s, "1:false", "sloppy 只读继承属性写应静默 no-op，值保持 1 且不遮蔽");
+}
+
+// ── 内联回调（forEach）：sloppy 顶层 + sloppy 回调，只读属性写静默失败 ──
+#[test]
+fn sloppy_inline_callback_write_to_readonly_silently_fails() {
+    let r = eval_many(&[
+        "var o = {}",
+        "Object.defineProperty(o, 'p', {value: 0, writable: false, configurable: true})",
+        "[1].forEach(function() { o.p = 1 })",
+        "o.p",
+    ])
+    .unwrap();
+    assert!(r.is_int() && r.as_int() == 0, "sloppy 内联回调内只读属性写应静默 no-op，实际 {:?}", r);
+}
+
+// ── 内联回调：严格函数上下文（回调继承严格），只读属性写抛 TypeError ──
+#[test]
+fn strict_inline_callback_write_to_readonly_throws() {
+    let r = eval_many(&[
+        "var o = {}",
+        "Object.defineProperty(o, 'p', {value: 0, writable: false, configurable: true})",
+        "var threw = false",
+        "(function() { 'use strict'; [1].forEach(function() { try { o.p = 1 } catch (e) { threw = true } }) })()",
+        "threw",
+    ])
+    .unwrap();
+    assert!(r.is_bool() && r.as_bool(), "严格内联回调内只读属性写应抛 TypeError，实际 {:?}", r);
+}
+
+// ── 嵌套内联：sloppy 回调内调用严格动态函数，写只读属性抛 TypeError
+//    （严格性随内联快照逐层保存/恢复，内层取内层目标） ──
+#[test]
+fn nested_inline_strict_target_write_throws() {
+    let r = eval_many(&[
+        "var o = {}",
+        "Object.defineProperty(o, 'p', {value: 0, writable: false, configurable: true})",
+        "var strictWrite = new Function('o', \"'use strict'; o.p = 1\")",
+        "var threw = false",
+        "[1].forEach(function() { try { strictWrite(o) } catch (e) { threw = true } })",
+        "threw",
+    ])
+    .unwrap();
+    assert!(
+        r.is_bool() && r.as_bool(),
+        "嵌套内联中严格目标函数的只读属性写应抛 TypeError，实际 {:?}",
+        r
+    );
+}
+
+// ── 嵌套内联反向：严格回调内调用 sloppy 动态函数，写只读属性静默失败 ──
+#[test]
+fn nested_inline_sloppy_target_write_silently_fails() {
+    let r = eval_many(&[
+        "var o = {}",
+        "Object.defineProperty(o, 'p', {value: 0, writable: false, configurable: true})",
+        "var sloppyWrite = new Function('o', 'o.p = 1')",
+        "(function() { 'use strict'; [1].forEach(function() { sloppyWrite(o) }) })()",
+        "o.p",
+    ])
+    .unwrap();
+    assert!(
+        r.is_int() && r.as_int() == 0,
+        "嵌套内联中 sloppy 目标函数的只读属性写应静默 no-op，实际 {:?}",
+        r
+    );
+}
+
+// ── 链式赋值中间对象只读（冻结）：sloppy 对中间对象写新属性静默失败 ──
+#[test]
+fn sloppy_chained_write_through_readonly_middle_silently_fails() {
+    let s = eval_str(
+        "var holder = Object.freeze({}); var o = { b: holder }; o.b.c = 1; \
+         Object.keys(o.b).length + ':' + (o.b.c === undefined)",
+    );
+    assert_eq!(s, "0:true", "sloppy 链式中间冻结对象写新属性应静默 no-op，c 不创建");
+}
+
+// ── 链式赋值中间对象只读（冻结）：严格模式抛 TypeError ──
+#[test]
+fn strict_chained_write_through_readonly_middle_throws() {
+    let result = eval_many(&[
+        "var holder = Object.freeze({})",
+        "var o = { b: holder }",
+        "(function() { 'use strict'; o.b.c = 1 })()",
+    ]);
+    assert_err_contains(result, "not extensible");
+}
+
+// ── 顶层脚本 sloppy 赋值只读全局属性（undefined）不抛错 ──
+#[test]
+fn sloppy_top_level_assign_to_readonly_global_no_throw() {
+    let r = eval_many(&["undefined = 1", "typeof undefined"]).unwrap();
+    assert!(r.is_string(), "sloppy 顶层对只读全局属性赋值不得抛错，实际 {:?}", r);
+}