diff --git a/crates/oxide_builtins/src/temporal.rs b/crates/oxide_builtins/src/temporal.rs
index e8b4b2e0..5152bd74 100644
--- a/crates/oxide_builtins/src/temporal.rs
+++ b/crates/oxide_builtins/src/temporal.rs
@@ -7862,6 +7862,17 @@ pub fn plain_month_day_to_json<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResu
     plain_month_day_default_string(vm, args)
 }
 
+/// `Temporal.PlainMonthDay.prototype.toLocaleString()`：locale/options 无引擎行为，
+/// 恒输出默认形串。
+pub fn plain_month_day_to_locale_string<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
+    plain_month_day_default_string(vm, args)
+}
+
+/// `Temporal.PlainMonthDay.prototype.valueOf()`：Temporal 对象无值表示，恒 TypeError。
+pub fn plain_month_day_value_of<H: VmHost>(vm: &mut H, _args: &[u8]) -> NativeResult {
+    NativeResult::Err(crate::error::create_type_error(vm, "Temporal.PlainMonthDay has no valueOf"))
+}
+
 /// PlainYearMonth 默认形串（`±YYYY-MM`），含 receiver 校验，不读 options。
 fn plain_year_month_default_string<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
     let ptr = native_try!(receiver_obj(vm, args));
@@ -7900,6 +7911,17 @@ pub fn plain_year_month_to_json<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeRes
     plain_year_month_default_string(vm, args)
 }
 
+/// `Temporal.PlainYearMonth.prototype.toLocaleString()`：locale/options 无引擎行为，
+/// 恒输出默认形串。
+pub fn plain_year_month_to_locale_string<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
+    plain_year_month_default_string(vm, args)
+}
+
+/// `Temporal.PlainYearMonth.prototype.valueOf()`：Temporal 对象无值表示，恒 TypeError。
+pub fn plain_year_month_value_of<H: VmHost>(vm: &mut H, _args: &[u8]) -> NativeResult {
+    NativeResult::Err(crate::error::create_type_error(vm, "Temporal.PlainYearMonth has no valueOf"))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/oxide_vm/src/bindings/bind_temporal.rs b/crates/oxide_vm/src/bindings/bind_temporal.rs
index 2636ec37..4eecd1b3 100644
--- a/crates/oxide_vm/src/bindings/bind_temporal.rs
+++ b/crates/oxide_vm/src/bindings/bind_temporal.rs
@@ -1005,6 +1005,16 @@ pub fn bind_temporal(core: &Arc<KernelCore>, session: &KernelSession, global: &m
                 oxide_builtins::temporal::plain_month_day_to_json::<crate::vm::Vm> as *const (),
                 0,
             ),
+            (
+                "toLocaleString",
+                oxide_builtins::temporal::plain_month_day_to_locale_string::<crate::vm::Vm> as *const (),
+                0,
+            ),
+            (
+                "valueOf",
+                oxide_builtins::temporal::plain_month_day_value_of::<crate::vm::Vm> as *const (),
+                0,
+            ),
         ],
     );
     bind_well_known_data_property(
@@ -1088,6 +1098,16 @@ pub fn bind_temporal(core: &Arc<KernelCore>, session: &KernelSession, global: &m
                 oxide_builtins::temporal::plain_year_month_to_json::<crate::vm::Vm> as *const (),
                 0,
             ),
+            (
+                "toLocaleString",
+                oxide_builtins::temporal::plain_year_month_to_locale_string::<crate::vm::Vm> as *const (),
+                0,
+            ),
+            (
+                "valueOf",
+                oxide_builtins::temporal::plain_year_month_value_of::<crate::vm::Vm> as *const (),
+                0,
+            ),
         ],
     );
     bind_well_known_data_property(
diff --git a/crates/oxide_vm/tests/builtins_temporal_tests.rs b/crates/oxide_vm/tests/builtins_temporal_tests.rs
index 9651db1d..450346fc 100644
--- a/crates/oxide_vm/tests/builtins_temporal_tests.rs
+++ b/crates/oxide_vm/tests/builtins_temporal_tests.rs
@@ -2797,3 +2797,32 @@ fn plain_month_day_and_year_month_branding() {
     .unwrap();
     assert_eq!(str_val(&vm, r), "TypeError|TypeError|TypeError|TypeError");
 }
+
+#[test]
+fn plain_month_day_and_year_month_to_locale_string_value_of_to_string_tag() {
+    let mut vm = Vm::new();
+    // toLocaleString 忽略 locale/options，恒默认形串；valueOf 恒 TypeError
+    // （`<` 走 ToPrimitive→valueOf 同抛）；toStringTag 经 Object.prototype.toString 读回。
+    let r = eval(
+        &mut vm,
+        "(() => {
+           const pmd = new Temporal.PlainMonthDay(5, 2);
+           const pym = new Temporal.PlainYearMonth(2021, 2);
+           const kind = (fn) => { try { fn(); return 'no'; } catch (e) { return e.constructor.name; } };
+           return [
+             pmd.toLocaleString('en-US', {calendar: 'iso8601'}),
+             pym.toLocaleString(),
+             kind(() => pmd.valueOf()),
+             kind(() => pym.valueOf()),
+             kind(() => pmd < pym),
+             Object.prototype.toString.call(pmd),
+             Object.prototype.toString.call(pym),
+           ].join('|');
+         })()",
+    )
+    .unwrap();
+    assert_eq!(
+        str_val(&vm, r),
+        "05-02|2021-02|TypeError|TypeError|TypeError|[object Temporal.PlainMonthDay]|[object Temporal.PlainYearMonth]"
+    );
+}