diff --git a/Cargo.lock b/Cargo.lock
index ebff378f..8bfb1e8c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1160,7 +1160,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_builtins"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "chrono",
  "fast-float",
@@ -1185,7 +1185,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_bytecode"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "num-bigint",
  "oxide_log",
@@ -1193,7 +1193,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_cfg"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_emit",
@@ -1204,7 +1204,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_cli"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "ansi_term",
  "bumpalo",
@@ -1225,7 +1225,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_code_cache"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "lru",
  "oxide_bytecode",
@@ -1234,7 +1234,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_compiler"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1253,7 +1253,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_dce"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1267,7 +1267,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_emit"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "num-bigint",
  "oxc_allocator",
@@ -1282,7 +1282,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_ir"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_log",
@@ -1291,7 +1291,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_kernel"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "bumpalo",
  "dashmap",
@@ -1306,7 +1306,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_liveness"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1318,7 +1318,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_log"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "tracing",
  "tracing-appender",
@@ -1327,7 +1327,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_parser"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxc_allocator",
  "oxc_ast",
@@ -1342,7 +1342,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_regalloc"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1358,7 +1358,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_runtime_api"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "num-bigint",
  "num-traits",
@@ -1370,7 +1370,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_test262"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "oxide_bytecode",
  "oxide_compiler",
@@ -1387,7 +1387,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_types"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "bumpalo",
  "hashbrown 0.14.5",
@@ -1399,7 +1399,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_vm"
-version = "0.8.49"
+version = "0.8.50"
 dependencies = [
  "bumpalo",
  "chrono",
diff --git a/Cargo.toml b/Cargo.toml
index 35f354d6..239521ac 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.8.49"
+version = "0.8.50"
 edition = "2021"
 license = "MIT"
 rust-version = "1.80"
diff --git a/crates/oxide_builtins/src/symbol.rs b/crates/oxide_builtins/src/symbol.rs
index 626ae43f..7033cea5 100644
--- a/crates/oxide_builtins/src/symbol.rs
+++ b/crates/oxide_builtins/src/symbol.rs
@@ -90,7 +90,7 @@ pub fn symbol_to_string<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
         Err(e) => return NativeResult::Err(e),
     };
     let idx = sym.as_symbol_index();
-    let desc = vm.symbol_description(idx).unwrap_or("").to_string();
+    let desc = vm.symbol_description(idx).unwrap_or_default();
     let result = format!("Symbol({})", desc);
     NativeResult::Ok(vm.new_string_owned(result))
 }
@@ -129,7 +129,7 @@ pub fn symbol_description_getter<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeRe
     };
     let idx = sym.as_symbol_index();
     match vm.symbol_description(idx) {
-        Some(desc) => NativeResult::Ok(vm.new_string_owned(desc.to_string())),
+        Some(desc) => NativeResult::Ok(vm.new_string_owned(desc)),
         None => NativeResult::Ok(JsValue::undefined()),
     }
 }
diff --git a/crates/oxide_kernel/src/kernel/core.rs b/crates/oxide_kernel/src/kernel/core.rs
index 9ee05d02..0bf2ccf1 100644
--- a/crates/oxide_kernel/src/kernel/core.rs
+++ b/crates/oxide_kernel/src/kernel/core.rs
@@ -4,7 +4,7 @@
 
 use std::num::NonZeroUsize;
 use std::path::PathBuf;
-use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicU32, AtomicUsize, Ordering};
 use std::sync::Arc;
 
 use crate::code_forge::CodeForge;
@@ -30,6 +30,10 @@ pub struct KernelCore {
     /// `Vm` 构造器增、`Drop for Vm` 减（恰好一次），供 sweep / kernel 重建 /
     /// kernel drop 处断言"无存活 VM"边界。
     active_vms: AtomicUsize,
+    /// realm 编号计数器：进程内单调递增，`alloc_realm_id` 取当前值后自增。
+    /// 首个 realm 编号为 0（与旧符号编码一致），至多 2^9 = 512 个 realm
+    /// （属性键符号空间 29 位减局部下标 20 位）。
+    realm_counter: AtomicU32,
 }
 
 impl KernelCore {
@@ -59,6 +63,7 @@ impl KernelCore {
             code_forge,
             prop_forge,
             active_vms: AtomicUsize::new(0),
+            realm_counter: AtomicU32::new(0),
         });
         kernel_info!("KernelCore initialized: max_cached_modules={}, min_pool={}", max_cached, min_pool);
         core
@@ -188,6 +193,15 @@ impl KernelCore {
     pub fn active_vms(&self) -> usize {
         self.active_vms.load(Ordering::Relaxed)
     }
+
+    /// 分配一个 realm 编号：取计数器当前值后自增，进程内单调递增。
+    ///
+    /// 首个 realm 编号为 0（与旧符号编码一致），供 `Realm` 构造时固化。
+    /// 编号空间至多 2^9 = 512（属性键符号空间约束），超出后回绕（debug 断言不触发，
+    /// 实际单进程 realm 数远小于该上界）。
+    pub fn alloc_realm_id(&self) -> u32 {
+        self.realm_counter.fetch_add(1, Ordering::Relaxed)
+    }
 }
 
 impl Drop for KernelCore {
diff --git a/crates/oxide_runtime_api/src/coercion.rs b/crates/oxide_runtime_api/src/coercion.rs
index d33d47c5..ab8223c8 100644
--- a/crates/oxide_runtime_api/src/coercion.rs
+++ b/crates/oxide_runtime_api/src/coercion.rs
@@ -986,7 +986,7 @@ fn string_to_bigint_full<H: VmHost>(host: &mut H, s: &str) -> Result<JsValue, St
 pub fn to_string_for_string_constructor<H: VmHost>(val: JsValue, host: &mut H) -> Result<String, String> {
     // 原始 Symbol：步骤 2a，SymbolDescriptiveString（不经 ToString）。
     if val.is_symbol() {
-        let desc = host.symbol_description(val.as_symbol_index()).unwrap_or("");
+        let desc = host.symbol_description(val.as_symbol_index()).unwrap_or_default();
         return Ok(format!("Symbol({desc})"));
     }
     // 步骤 3：ToString。装箱 Symbol 经 ToPrimitive 得 Symbol 本体，ToString 抛 TypeError。
diff --git a/crates/oxide_runtime_api/src/host.rs b/crates/oxide_runtime_api/src/host.rs
index 4fa8b473..f53ec614 100644
--- a/crates/oxide_runtime_api/src/host.rs
+++ b/crates/oxide_runtime_api/src/host.rs
@@ -258,9 +258,14 @@ pub trait VmHost {
     /// 动态编译脚本（`eval` 字符串模式）：按脚本模式编译，var/函数声明落全局对象。
     /// 编译或解析失败返回 `Err`，由调用方转为 `SyntaxError`。
     fn create_dynamic_script(&mut self, code: &str) -> Result<JsValue, String>;
+    /// 读取本 VM 所属 realm 的编号（符号身份 = (realm 编号, 局部下标) 的 realm 维度）。
+    ///
+    /// 供 `oxide_builtins` 侧构造 realm 感知符号键 / 符号值时取 realm 编号。
+    fn realm_id(&self) -> u32;
     /// `None` 表示无描述（`Symbol()`/`Symbol(undefined)`），`Some(desc)` 为字符串描述。
     fn symbol_intern(&mut self, desc: Option<String>) -> u32;
-    fn symbol_description(&self, idx: u32) -> Option<&str>;
+    /// 符号描述字符串（符号表入 realm 后数据在 `RefCell` 内，返回克隆串免临时 `Ref` 悬垂）。
+    fn symbol_description(&self, idx: u32) -> Option<String>;
     fn symbol_lookup_global(&self, key: &str) -> Option<u32>;
     fn symbol_register_global(&mut self, key: String, idx: u32);
     fn symbol_key_for_id(&self, idx: u32) -> Option<String>;
diff --git a/crates/oxide_types/src/private_key.rs b/crates/oxide_types/src/private_key.rs
index 93a1e1bc..dba16c35 100644
--- a/crates/oxide_types/src/private_key.rs
+++ b/crates/oxide_types/src/private_key.rs
@@ -173,5 +173,59 @@ pub const fn well_known_symbol_id_from_key(key: u32) -> Option<u32> {
     }
 }
 
+/// 符号键局部下标占用的位数（低 20 位）。
+///
+/// 每 realm 至多 2^20 个符号，充足；realm 编号占高位（属性键符号空间 29 位
+/// 减 20 位，至多 2^9 = 512 个 realm）。
+pub const SYMBOL_LOCAL_INDEX_BITS: u32 = 20;
+
+/// 符号键局部下标的位掩码（低 20 位）。
+pub const SYMBOL_LOCAL_INDEX_MASK: u32 = (1 << SYMBOL_LOCAL_INDEX_BITS) - 1;
+
+/// 把 (realm 编号, 全局下标) 编码为属性键。
+///
+/// 全局下标沿用现有口径（0..14 well-known、15 起用户符号）；编码时按现有口径
+/// 叠加 well-known 预留槽偏移（用户符号下标再加一次偏移），realm 编号前置到
+/// 高位。realm 编号为 0 时与旧编码（[`make_well_known_symbol_key`] /
+/// [`make_symbol_key`]）逐字节一致。
+///
+/// # 边界与前提
+/// - `realm_id < 2^9`（属性键符号空间 29 位减局部下标 20 位），`global_idx`
+///   的键偏移须落在 20 位内（每 realm 至多 2^20 个符号）。
+#[inline]
+pub const fn encode_symbol_key(realm_id: u32, global_idx: u32) -> u32 {
+    let offset = if global_idx < WELL_KNOWN_SYMBOL_COUNT {
+        global_idx
+    } else {
+        WELL_KNOWN_SYMBOL_COUNT + global_idx
+    };
+    SYMBOL_KEY_BASE | ((realm_id << SYMBOL_LOCAL_INDEX_BITS) | (offset & SYMBOL_LOCAL_INDEX_MASK))
+}
+
+/// 从属性键反解 realm 编号（与 [`encode_symbol_key`] 的 realm 维度互逆）。
+#[inline]
+pub const fn symbol_realm_id_from_key(key: u32) -> u32 {
+    (key - SYMBOL_KEY_BASE) >> SYMBOL_LOCAL_INDEX_BITS
+}
+
+/// 从属性键反解全局下标（与 [`encode_symbol_key`] 的下标维度互逆）。
+///
+/// 按现有口径反解：well-known 区间直取，用户区间减一次 well-known 预留槽偏移。
+#[inline]
+pub const fn symbol_local_index_from_key(key: u32) -> u32 {
+    let local = (key - SYMBOL_KEY_BASE) & SYMBOL_LOCAL_INDEX_MASK;
+    if local < WELL_KNOWN_SYMBOL_COUNT {
+        local
+    } else {
+        local - WELL_KNOWN_SYMBOL_COUNT
+    }
+}
+
+/// 把属性键反解为 (realm 编号, 全局下标)（与 [`encode_symbol_key`] 互逆）。
+#[inline]
+pub const fn decode_symbol_key(key: u32) -> (u32, u32) {
+    (symbol_realm_id_from_key(key), symbol_local_index_from_key(key))
+}
+
 #[cfg(test)]
 mod tests;
diff --git a/crates/oxide_types/src/private_key/tests.rs b/crates/oxide_types/src/private_key/tests.rs
index 5b04a384..305b79bd 100644
--- a/crates/oxide_types/src/private_key/tests.rs
+++ b/crates/oxide_types/src/private_key/tests.rs
@@ -74,3 +74,36 @@ fn int_key_roundtrip_max() {
     assert!(key < PRIVATE_NAME_BASE);
     assert_eq!(int_key_value(key), INT_KEY_COUNT - 1);
 }
+
+#[test]
+fn realm_zero_symbol_keys_match_legacy() {
+    // realm 编号为 0 时新编码与旧编码逐字节一致：well-known 与用户符号各取若干下标比对。
+    for id in 0..WELL_KNOWN_SYMBOL_COUNT {
+        assert_eq!(encode_symbol_key(0, id), make_well_known_symbol_key(id));
+    }
+    for idx in WELL_KNOWN_SYMBOL_COUNT..(WELL_KNOWN_SYMBOL_COUNT + 8) {
+        assert_eq!(encode_symbol_key(0, idx), make_symbol_key(idx));
+    }
+}
+
+#[test]
+fn symbol_key_realm_roundtrip() {
+    for realm in [0u32, 1, 7, 511] {
+        for idx in [0u32, 14, 15, 16, 1000] {
+            let key = encode_symbol_key(realm, idx);
+            assert!(is_symbol_key(key));
+            assert_eq!(decode_symbol_key(key), (realm, idx));
+            assert_eq!(symbol_realm_id_from_key(key), realm);
+            assert_eq!(symbol_local_index_from_key(key), idx);
+        }
+    }
+}
+
+#[test]
+fn symbol_key_realm_dimensions_distinct() {
+    // 同下标不同 realm 产生不同键；同 realm 不同下标产生不同键。
+    assert_ne!(encode_symbol_key(0, 15), encode_symbol_key(1, 15));
+    assert_ne!(encode_symbol_key(1, 15), encode_symbol_key(1, 16));
+    // 跨 realm 同名 well-known 符号也产生不同键。
+    assert_ne!(encode_symbol_key(0, WELL_KNOWN_SYMBOL_ITERATOR), encode_symbol_key(2, WELL_KNOWN_SYMBOL_ITERATOR));
+}
diff --git a/crates/oxide_types/src/value.rs b/crates/oxide_types/src/value.rs
index 8f1847d5..ed80e14a 100644
--- a/crates/oxide_types/src/value.rs
+++ b/crates/oxide_types/src/value.rs
@@ -364,6 +364,18 @@ impl JsValue {
         Self(make_tag(TAG_SYMBOL) | (index as u64))
     }
 
+    /// 构造 realm 感知 symbol 值（payload = (realm 编号 << 20) | 全局下标）。
+    ///
+    /// 全局下标沿用现有口径（0..14 well-known、15 起用户符号）。realm 编号为
+    /// 0 时与 [`symbol`](Self::symbol) 逐字节一致。
+    ///
+    /// # 边界与前提
+    /// - `realm_id < 2^12`（payload 32 位减局部下标 20 位），`local_index`
+    ///   须落在 20 位内（每 realm 至多 2^20 个符号）。
+    pub fn symbol_realm(realm_id: u32, local_index: u32) -> Self {
+        Self(make_tag(TAG_SYMBOL) | (((realm_id << 20) | (local_index & 0x000F_FFFF)) as u64))
+    }
+
     /// 是否为 symbol。
     pub fn is_symbol(&self) -> bool {
         is_nan_boxed(self.0) && get_tag(self.0) == TAG_SYMBOL
@@ -375,6 +387,19 @@ impl JsValue {
         (self.0 & INT_MASK) as u32
     }
 
+    /// 解出 symbol 的 realm 编号；调用方须先保证 [`is_symbol`](JsValue::is_symbol)。
+    pub fn as_symbol_realm_id(&self) -> u32 {
+        debug_assert!(self.is_symbol());
+        ((self.0 & INT_MASK) >> 20) as u32
+    }
+
+    /// 解出 symbol 的全局下标（0..14 well-known、15 起用户符号）；
+    /// 调用方须先保证 [`is_symbol`](JsValue::is_symbol)。
+    pub fn as_symbol_local_index(&self) -> u32 {
+        debug_assert!(self.is_symbol());
+        ((self.0 & INT_MASK) & 0x000F_FFFF) as u32
+    }
+
     /// 构造 BigInt 值（payload 为堆分配 `i128` 的 48 位指针）。
     ///
     /// 与 `JsString` 同机制：`i128` 本体存于 VM 管理的堆 box，这里携带指针。
diff --git a/crates/oxide_vm/src/realm.rs b/crates/oxide_vm/src/realm.rs
index 3bba844d..c7dbb604 100644
--- a/crates/oxide_vm/src/realm.rs
+++ b/crates/oxide_vm/src/realm.rs
@@ -19,7 +19,7 @@ use oxide_types::mem::P;
 use oxide_types::object::JsObject;
 
 use crate::session_gc::SessionGc;
-use crate::vm_state::GcState;
+use crate::vm_state::{GcState, SymbolState};
 
 /// 每 VM 的 realm 组合：内核会话（builtin world 与 global 对象）、
 /// session GC 簿记与 10 个内建原型槽。
@@ -30,8 +30,12 @@ use crate::vm_state::GcState;
 /// 透传。
 ///
 /// 字段顺序按原 `Vm` 声明顺序（session 先、10 个 P 字段次之、gc 最后），
-/// 保 Drop 相对顺序。
+/// 保 Drop 相对顺序。`realm_id` 是分配时固化的编号（无 Drop 关切）；
+/// `symbols` 是 per-realm 符号表（经 `RefCell` 内部可变性，与 session/gc 同型）。
 pub(crate) struct Realm {
+    /// realm 编号：构造时经 `KernelCore::alloc_realm_id` 分配，进程内单调递增，
+    /// 首个 realm 编号为 0（与旧符号编码一致）。符号身份 = (realm 编号, 局部下标)。
+    pub(crate) realm_id: u32,
     pub(crate) session: RefCell<KernelSession>,
     /// `%Object.prototype%`：session 的 Object 原型（global 的 `[[Prototype]]` 挂它）。
     pub(crate) object_prototype: RefCell<P<JsObject>>,
@@ -56,6 +60,9 @@ pub(crate) struct Realm {
     pub(crate) async_generator_function_proto: RefCell<P<JsObject>>,
     /// session 堆与 GC 簿记（对象/字符串/BigInt/cell 四表 + 水位与账目）。
     pub(crate) gc: RefCell<GcState>,
+    /// per-realm 符号表：well-known 名表 + 用户符号描述 + `Symbol.for` 全局注册表。
+    /// 只持 Rust `String` 与 `u32` 下标，无 GC 根，移入 realm 后 `Send` 性不变。
+    pub(crate) symbols: RefCell<SymbolState>,
 }
 
 impl Drop for Realm {
diff --git a/crates/oxide_vm/src/vm/gc_hooks.rs b/crates/oxide_vm/src/vm/gc_hooks.rs
index 31501cd7..3ae9956f 100644
--- a/crates/oxide_vm/src/vm/gc_hooks.rs
+++ b/crates/oxide_vm/src/vm/gc_hooks.rs
@@ -304,7 +304,7 @@ impl Vm {
 
     /// 全局 symbol 注册表中已注册的 key 数量。
     pub fn symbol_registry_len(&self) -> usize {
-        self.symbols.registry_len()
+        self.realm.symbols.borrow().registry_len()
     }
 
     /// inline cache 命中次数。
diff --git a/crates/oxide_vm/src/vm/mod.rs b/crates/oxide_vm/src/vm/mod.rs
index 885ee0d2..eac8279e 100644
--- a/crates/oxide_vm/src/vm/mod.rs
+++ b/crates/oxide_vm/src/vm/mod.rs
@@ -19,7 +19,7 @@ pub use crate::bindings::init_kernel_builtins;
 use crate::native::NativeFn;
 use crate::realm::Realm;
 use crate::vm_debug;
-use crate::vm_state::{IterState, ProfilingState, SampleState, SymbolState};
+use crate::vm_state::{IterState, ProfilingState, SampleState};
 use oxide_kernel::kernel::{KernelCore, KernelSession};
 use oxide_types::error::JsErrorKind;
 use oxide_types::object::{Cell, JsObject, JsString, NativeFnPtr};
@@ -341,8 +341,6 @@ pub struct Vm {
     /// 异步生成器 body `dispatch()` 的 AWAIT 让出信号：置 true 表示挂起在 await，
     /// 恢复方（异步生成器内嵌 dispatch 循环）据此快照挂起状态。
     pub(crate) async_gen_suspended: bool,
-    /// 分组保存 `Symbol` intern 状态。
-    pub(crate) symbols: SymbolState,
     /// 分组保存活跃的 for-in / for-of 迭代器状态。
     pub(crate) iters: IterState,
     /// 分组保存 inline cache 与指令计数器。
@@ -455,6 +453,11 @@ impl Vm {
         self.realm.session.borrow()
     }
 
+    /// 读取本 VM 所属 realm 的编号（符号身份 = (realm 编号, 局部下标) 的 realm 维度）。
+    pub fn realm_id(&self) -> u32 {
+        self.realm.realm_id
+    }
+
     /// 判定裸指针是否指向当前 session 的 `%Object.prototype%`。
     pub(crate) fn is_object_prototype(&self, ptr: *const JsObject) -> bool {
         let proto_ptr = self.realm.session.borrow().builtin_world().object_proto.as_ptr();
diff --git a/crates/oxide_vm/src/vm/vmhost.rs b/crates/oxide_vm/src/vm/vmhost.rs
index 9a06b6fb..bbd73f20 100644
--- a/crates/oxide_vm/src/vm/vmhost.rs
+++ b/crates/oxide_vm/src/vm/vmhost.rs
@@ -220,20 +220,23 @@ impl oxide_runtime_api::VmHost for Vm {
     fn create_dynamic_script(&mut self, code: &str) -> Result<JsValue, String> {
         self.create_dynamic_script(code)
     }
-    fn symbol_intern(&mut self, desc: Option<String>) -> u32 {
-        self.symbols.intern(desc)
+    fn realm_id(&self) -> u32 {
+        self.realm_id()
     }
-    fn symbol_description(&self, idx: u32) -> Option<&str> {
-        self.symbols.description(idx)
+    fn symbol_intern(&mut self, desc: Option<String>) -> u32 {
+        self.realm.symbols.borrow_mut().intern(desc)
+    }
+    fn symbol_description(&self, idx: u32) -> Option<String> {
+        self.realm.symbols.borrow().description(idx).map(|s| s.to_string())
     }
     fn symbol_lookup_global(&self, key: &str) -> Option<u32> {
-        self.symbols.lookup_global(key)
+        self.realm.symbols.borrow().lookup_global(key)
     }
     fn symbol_register_global(&mut self, key: String, idx: u32) {
-        self.symbols.register_global(key, idx)
+        self.realm.symbols.borrow_mut().register_global(key, idx)
     }
     fn symbol_key_for_id(&self, idx: u32) -> Option<String> {
-        self.symbols.key_for_id(idx)
+        self.realm.symbols.borrow().key_for_id(idx)
     }
     fn atomics_new_waiter_promise(&mut self) -> JsValue {
         self.atomics_new_waiter_promise()
diff --git a/crates/oxide_vm/src/vm_support.rs b/crates/oxide_vm/src/vm_support.rs
index 4b45a613..e4287a5c 100644
--- a/crates/oxide_vm/src/vm_support.rs
+++ b/crates/oxide_vm/src/vm_support.rs
@@ -58,6 +58,8 @@ impl Vm {
         let obj_proto = P::clone(&session.builtin_world().object_proto);
         // 提前缓存执行期字符串 GC 初始水位（构造后 config 不再变化）。
         let gc_threshold = core.config().session_gc_threshold;
+        // realm 编号在构造时分配并固化：首个 realm 编号为 0（与旧符号编码一致）。
+        let realm_id = core.alloc_realm_id();
         let mut vm = Self {
             regs: [JsValue::undefined(); 256],
             pc: 0,
@@ -66,6 +68,7 @@ impl Vm {
             frames: smallvec::SmallVec::new(),
             kernel_core: core,
             realm: Arc::new(Realm {
+                realm_id,
                 session: RefCell::new(session),
                 object_prototype: RefCell::new(obj_proto),
                 generator_proto: RefCell::new(P::new(JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::null()))),
@@ -92,6 +95,11 @@ impl Vm {
                     pending_forced_collect: false,
                     gc_pressure_mode: gc_pressure_mode_from_env(),
                 }),
+                symbols: RefCell::new(SymbolState {
+                    symbol_counter: 0,
+                    symbol_descriptions: Vec::new(),
+                    symbol_registry: std::collections::HashMap::new(),
+                }),
             }),
             length_si,
             length_perm_ptr,
@@ -153,11 +161,6 @@ impl Vm {
             async_gen_context: None,
             async_gen_dispatch: false,
             async_gen_suspended: false,
-            symbols: SymbolState {
-                symbol_counter: 0,
-                symbol_descriptions: Vec::new(),
-                symbol_registry: std::collections::HashMap::new(),
-            },
             iters: IterState {
                 for_in_iters: Vec::new(),
                 for_of_iters: Vec::new(),
@@ -205,6 +208,8 @@ impl Vm {
         let obj_proto = P::clone(&session.builtin_world().object_proto);
         // 提前缓存执行期字符串 GC 初始水位（构造后 config 不再变化）。
         let gc_threshold = core.config().session_gc_threshold;
+        // realm 编号在构造时分配并固化：首个 realm 编号为 0（与旧符号编码一致）。
+        let realm_id = core.alloc_realm_id();
         let mut vm = Self {
             regs: [JsValue::undefined(); 256],
             pc: 0,
@@ -213,6 +218,7 @@ impl Vm {
             frames: smallvec::SmallVec::new(),
             kernel_core: core,
             realm: Arc::new(Realm {
+                realm_id,
                 session: RefCell::new(session),
                 object_prototype: RefCell::new(obj_proto),
                 generator_proto: RefCell::new(P::new(JsObject::new_empty(EMPTY_SHAPE_ID, JsValue::null()))),
@@ -239,6 +245,11 @@ impl Vm {
                     pending_forced_collect: false,
                     gc_pressure_mode: gc_pressure_mode_from_env(),
                 }),
+                symbols: RefCell::new(SymbolState {
+                    symbol_counter: 0,
+                    symbol_descriptions: Vec::new(),
+                    symbol_registry: std::collections::HashMap::new(),
+                }),
             }),
             length_si,
             length_perm_ptr,
@@ -300,11 +311,6 @@ impl Vm {
             async_gen_context: None,
             async_gen_dispatch: false,
             async_gen_suspended: false,
-            symbols: SymbolState {
-                symbol_counter: 0,
-                symbol_descriptions: Vec::new(),
-                symbol_registry: std::collections::HashMap::new(),
-            },
             iters: IterState {
                 for_in_iters: Vec::new(),
                 for_of_iters: Vec::new(),
@@ -450,7 +456,7 @@ impl Vm {
         let threshold = self.realm.gc.borrow().gc_threshold_cached;
         self.realm.gc.borrow_mut().gc_watermark = threshold;
         self.realm.gc.borrow_mut().session_gc = crate::session_gc::SessionGc::new();
-        self.symbols.reset();
+        self.realm.symbols.borrow_mut().reset();
         self.root_reg_limit = 0;
         self.active_reg_limit = 0;
         // 步数上限覆盖随池回收清位：执行路径按请求必设覆盖（含 None），
diff --git a/crates/oxide_vm/src/vm_support/tests.rs b/crates/oxide_vm/src/vm_support/tests.rs
index 3710d009..3bc0c8ae 100644
--- a/crates/oxide_vm/src/vm_support/tests.rs
+++ b/crates/oxide_vm/src/vm_support/tests.rs
@@ -1108,13 +1108,13 @@ fn benign_run_does_not_falsely_dirty_builtins() {
 #[test]
 fn full_reset_clears_symbol_state() {
     let mut vm = Vm::new();
-    vm.symbols.intern(Some("shared".to_string()));
+    vm.realm.symbols.borrow_mut().intern(Some("shared".to_string()));
 
     vm.full_reset();
 
-    assert_eq!(vm.symbols.symbol_counter, 0);
-    assert!(vm.symbols.symbol_descriptions.is_empty());
-    assert!(vm.symbols.symbol_registry.is_empty());
+    assert_eq!(vm.realm.symbols.borrow().symbol_counter, 0);
+    assert!(vm.realm.symbols.borrow().symbol_descriptions.is_empty());
+    assert!(vm.realm.symbols.borrow().symbol_registry.is_empty());
 }
 
 /// 编译源文本为模块（供步数上限测试直接 `run` 并检查 `Result`）。