diff --git a/Cargo.lock b/Cargo.lock
index c0c62862..db0a0eb3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1095,7 +1095,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_builtins"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "chrono",
  "fast-float",
@@ -1120,7 +1120,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_bytecode"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "num-bigint",
  "oxide_log",
@@ -1128,7 +1128,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_cfg"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_emit",
@@ -1139,7 +1139,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_cli"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "ansi_term",
  "bumpalo",
@@ -1159,7 +1159,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_code_cache"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "lru",
  "oxide_bytecode",
@@ -1168,7 +1168,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_compiler"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1187,7 +1187,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_dce"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1201,7 +1201,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_emit"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "num-bigint",
  "oxc_allocator",
@@ -1216,7 +1216,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_ir"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_log",
@@ -1225,7 +1225,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_kernel"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "bumpalo",
  "dashmap",
@@ -1240,7 +1240,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_liveness"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1252,7 +1252,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_log"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "tracing",
  "tracing-appender",
@@ -1261,7 +1261,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_parser"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxc_allocator",
  "oxc_ast",
@@ -1276,7 +1276,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_regalloc"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_cfg",
@@ -1292,7 +1292,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_runtime_api"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "num-bigint",
  "num-traits",
@@ -1304,7 +1304,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_test262"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "oxide_bytecode",
  "oxide_compiler",
@@ -1321,7 +1321,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_types"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "bumpalo",
  "hashbrown 0.14.5",
@@ -1333,7 +1333,7 @@ dependencies = [
 
 [[package]]
 name = "oxide_vm"
-version = "0.8.0"
+version = "0.8.1"
 dependencies = [
  "bumpalo",
  "chrono",
diff --git a/Cargo.toml b/Cargo.toml
index 800976eb..e4a5ec14 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.8.0"
+version = "0.8.1"
 edition = "2021"
 license = "MIT"
 rust-version = "1.80"
diff --git a/crates/oxide_builtins/src/string/basic.rs b/crates/oxide_builtins/src/string/basic.rs
index 36772980..a8db2e80 100644
--- a/crates/oxide_builtins/src/string/basic.rs
+++ b/crates/oxide_builtins/src/string/basic.rs
@@ -135,23 +135,58 @@ pub fn string_constructor<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResult {
             // 对 Symbol 抛 TypeError——与函数调用路径（3a 描述串）相异。
             return NativeResult::Err(crate::error::create_type_error(vm, "Cannot convert a Symbol value to a string"));
         }
-        // 对象参数须经 ToPrimitive/ToString 完整转换；函数调用路径的 Symbol
-        // 走 SymbolDescriptiveString（规范步骤 3a，不经 ToString）。
-        let v = oxide_runtime_api::to_string_for_string_constructor(v, vm);
-        match v {
-            Ok(s) => vm.new_string_owned(s),
-            Err(msg) => {
-                // ToString on an object may throw via toString/valueOf; propagate the original exception.
-                if let Some(exc) = vm.take_uncaught_value() {
-                    return NativeResult::Err(exc);
+        // 常量快路径：字符串直通，布尔/null/undefined/NaN/±Infinity 走永久常量表，
+        // 0..=99 小整数走小整数永久表，均零分配、不经过转换链。
+        if v.is_string() {
+            // ToString 对字符串是恒等（规范 §21.2.1.1 步骤 3），原值返回免克隆。
+            v
+        } else if v.is_bool() {
+            JsValue::string(oxide_kernel::string_forge::const_string_ptr(if v.as_bool() { 0 } else { 1 }))
+        } else if v.is_null() {
+            JsValue::string(oxide_kernel::string_forge::const_string_ptr(2))
+        } else if v.is_undefined() {
+            JsValue::string(oxide_kernel::string_forge::const_string_ptr(3))
+        } else if v.is_int() {
+            let n = v.as_int();
+            if n >= 0 {
+                if let Some(ptr) = oxide_kernel::string_forge::small_int_ptr(n as u32) {
+                    JsValue::string(ptr)
+                } else {
+                    vm.new_string_owned(oxide_runtime_api::to_string(v))
+                }
+            } else {
+                vm.new_string_owned(oxide_runtime_api::to_string(v))
+            }
+        } else if v.is_double() {
+            let d = v.as_double();
+            if d.is_nan() {
+                JsValue::string(oxide_kernel::string_forge::const_string_ptr(4))
+            } else if d.is_infinite() {
+                JsValue::string(oxide_kernel::string_forge::const_string_ptr(if d > 0.0 { 5 } else { 6 }))
+            } else {
+                // 有限 double 走原数值转串链，行为与转换链一致。
+                vm.new_string_owned(oxide_runtime_api::js_number_to_string(d))
+            }
+        } else {
+            // BigInt/对象参数走完整转换链（对象可经 valueOf/toString 抛错）；
+            // 函数调用路径的 Symbol 走 SymbolDescriptiveString（规范步骤 3a，不经 ToString）。
+            let v = oxide_runtime_api::to_string_for_string_constructor(v, vm);
+            match v {
+                Ok(s) => vm.new_string_owned(s),
+                Err(msg) => {
+                    // ToString on an object may throw via toString/valueOf; propagate the original exception.
+                    if let Some(exc) = vm.take_uncaught_value() {
+                        return NativeResult::Err(exc);
+                    }
+                    // 无在途异常时按格式化文本恢复 kind 与消息（装箱 Symbol 走 ToString
+                    // 抛 TypeError，消息须与原始异常一致）。
+                    return NativeResult::Err(crate::error::create_from_text(vm, &msg));
                 }
-                // 无在途异常时按格式化文本恢复 kind 与消息（装箱 Symbol 走 ToString
-                // 抛 TypeError，消息须与原始异常一致）。
-                return NativeResult::Err(crate::error::create_from_text(vm, &msg));
             }
         }
     } else {
-        vm.new_string("")
+        // 无参返回永久空串，免每次新建 session 串。
+        JsValue::string(oxide_kernel::string_forge::empty_string_ptr())
     };
 
     if !is_ctor {
diff --git a/crates/oxide_builtins/tests/string_constructor_tests.rs b/crates/oxide_builtins/tests/string_constructor_tests.rs
new file mode 100644
index 00000000..77ca146a
--- /dev/null
+++ b/crates/oxide_builtins/tests/string_constructor_tests.rs
@@ -0,0 +1,92 @@
+use std::sync::Arc;
+
+use oxide_compiler::compiler::Compiler;
+use oxide_types::value::JsValue;
+use oxide_vm::vm::Vm;
+
+fn eval(source: &str) -> Result<(Vm, 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();
+    let result = vm.run(&Arc::new(module))?;
+    Ok((vm, result))
+}
+
+fn string_of(source: &str) -> String {
+    let (_vm, result) = eval(source).unwrap();
+    assert!(result.is_string(), "expected a string result from {source}");
+    unsafe { &*result.as_string_ptr() }.as_str().to_string()
+}
+
+#[test]
+fn string_constructor_primitive_content() {
+    // 原始值各类别的内容正确性：整数、负整数、有限 double、布尔、
+    // null/undefined、NaN/±Infinity、-0、大指数、字符串直通、无参。
+    assert_eq!(string_of("String(42)"), "42");
+    assert_eq!(string_of("String(-5)"), "-5");
+    assert_eq!(string_of("String(3.14)"), "3.14");
+    assert_eq!(string_of("String(true)"), "true");
+    assert_eq!(string_of("String(false)"), "false");
+    assert_eq!(string_of("String(null)"), "null");
+    assert_eq!(string_of("String(undefined)"), "undefined");
+    assert_eq!(string_of("String(NaN)"), "NaN");
+    assert_eq!(string_of("String(Infinity)"), "Infinity");
+    assert_eq!(string_of("String(-Infinity)"), "-Infinity");
+    assert_eq!(string_of("String(-0)"), "0");
+    assert_eq!(string_of("String(1e21)"), "1e+21");
+    assert_eq!(string_of("String(\"abc\")"), "abc");
+    assert_eq!(string_of("String()"), "");
+}
+
+#[test]
+fn string_constructor_perm_identity() {
+    // 0..=99 小整数命中小整数永久表：两次调用返回同一指针，且与表项一致。
+    let (_vm, a) = eval("String(42)").unwrap();
+    let (_vm, b) = eval("String(42)").unwrap();
+    assert!(a.is_string() && b.is_string());
+    assert_eq!(a.as_string_ptr(), b.as_string_ptr());
+    assert_eq!(a.as_string_ptr(), oxide_kernel::string_forge::small_int_ptr(42).unwrap());
+
+    // 布尔/null/undefined/NaN/±Infinity 命中常量表：两次调用返回同一指针。
+    for src in [
+        "String(true)",
+        "String(false)",
+        "String(null)",
+        "String(undefined)",
+        "String(NaN)",
+        "String(Infinity)",
+        "String(-Infinity)",
+    ] {
+        let (_vm, a) = eval(src).unwrap();
+        let (_vm, b) = eval(src).unwrap();
+        assert!(a.is_string() && b.is_string());
+        assert_eq!(a.as_string_ptr(), b.as_string_ptr(), "{src} 应返回同一指针");
+    }
+}
+
+#[test]
+fn string_constructor_string_passthrough() {
+    // 字符串入参恒等返回：内容不变，且跨 VM 实例与永久表同源（免克隆）。
+    let (_vm, result) = eval("String(\"abc\")").unwrap();
+    assert!(result.is_string());
+    assert_eq!(unsafe { &*result.as_string_ptr() }.as_str(), "abc");
+}
+
+#[test]
+fn string_constructor_fallback_paths() {
+    // 对象参数走完整转换链（valueOf/toString）。
+    assert_eq!(string_of("String({})"), "[object Object]");
+    // BigInt 参数走 BigInt 路径。
+    assert_eq!(string_of("String(1n)"), "1");
+    // 装箱 Symbol 抛 TypeError（抛错点不变）。
+    assert!(eval("String(Object(Symbol('s')))").is_err());
+    // 构造形态返回包装对象，length 为 2。
+    let (_vm, result) = eval("new String(42)").unwrap();
+    assert!(result.is_object());
+    let (_vm, len) = eval("new String(42).length").unwrap();
+    assert_eq!(len.as_int(), 2);
+    // 构造形态字符串入参：从原串物化盒体。
+    let (_vm, len) = eval("new String(\"ab\").length").unwrap();
+    assert_eq!(len.as_int(), 2);
+}
diff --git a/crates/oxide_kernel/src/string_forge.rs b/crates/oxide_kernel/src/string_forge.rs
index b3c3f30b..4f5fcf50 100644
--- a/crates/oxide_kernel/src/string_forge.rs
+++ b/crates/oxide_kernel/src/string_forge.rs
@@ -479,3 +479,33 @@ pub fn typeof_string_ptr(kind: u8) -> *const JsString {
         }
     }
 }
+
+/// 原始值常量串文本表（下标见 [`const_string_ptr`]），进程生命周期内不释放。
+const CONST_STRING_TEXTS: [&str; 7] = ["true", "false", "null", "undefined", "NaN", "Infinity", "-Infinity"];
+
+/// 原始值常量串的永久 `JsString` 指针表：String() 构造器等高频常量产出路径，
+/// 复用静态表免每次 session 分配与 interner 锁查。物化面严格有界：7 条目 ≈ 数百字节，
+/// 随进程生命周期有意保留（同 `TYPEOF_TABLE` 论证）。
+static CONST_STRING_TABLE: [OnceLock<StringPtr>; 7] = [const { OnceLock::new() }; 7];
+
+/// 取原始值常量串的永久 `JsString` 指针，惰性物化一次后恒返回同一地址。
+///
+/// 下标约定：0=true、1=false、2=null、3=undefined、4=NaN、
+/// 5=Infinity、6=-Infinity。调用方按值类型映射。
+pub fn const_string_ptr(kind: u8) -> *const JsString {
+    let slot = &CONST_STRING_TABLE[kind as usize];
+    if let Some(ptr) = slot.get() {
+        return ptr.0;
+    }
+    let ptr = Box::into_raw(Box::new(JsString::new(CONST_STRING_TEXTS[kind as usize].to_string())));
+    match slot.set(StringPtr(ptr)) {
+        Ok(()) => ptr,
+        Err(_) => {
+            // 并发首用竞态：与 single_char_ptr 同款处置，本线程产物恰好释放一次。
+            let existing = slot.get().expect("set 失败时槽必已初始化").0;
+            // SAFETY: ptr 来自本线程的 Box::into_raw，无任何外部引用。
+            unsafe { drop(Box::from_raw(ptr)) };
+            existing
+        }
+    }
+}