diff --git a/crates/oxide_emit/src/stmt/declaration/var.rs b/crates/oxide_emit/src/stmt/declaration/var.rs
index 74136f2..b901966 100644
--- a/crates/oxide_emit/src/stmt/declaration/var.rs
+++ b/crates/oxide_emit/src/stmt/declaration/var.rs
@@ -24,9 +24,11 @@ impl Emitter {
                 let val_reg = self.emit_expression(init, ctx)?;
                 self.emit_binding_pattern(&d.id, val_reg, decl.kind, is_const, ctx)?;
                 if let BindingPattern::BindingIdentifier(bi) = &d.id {
-                    if matches!(*init, Expression::ArrowFunctionExpression(_)) {
+                    if matches!(*init, Expression::ArrowFunctionExpression(_) | Expression::FunctionExpression(_)) {
                         if let Some(sub_mod) = ctx.nested.last_mut() {
-                            sub_mod.function_name = Some(bi.name.to_string());
+                            if sub_mod.function_name.is_none() {
+                                sub_mod.function_name = Some(bi.name.to_string());
+                            }
                         }
                     }
                 }
diff --git a/crates/oxide_test262/src/main.rs b/crates/oxide_test262/src/main.rs
index 106326c..28c192b 100644
--- a/crates/oxide_test262/src/main.rs
+++ b/crates/oxide_test262/src/main.rs
@@ -246,17 +246,6 @@ fn is_blacklisted_harness(name: &str) -> bool {
 }
 
 /// 生成 `Test262Error` 的 JS prelude（供测试脚本 `assert` 失败时抛出）。
-fn test262_error_prelude() -> &'static str {
-    r#"
-function Test262Error(message) {
-  this.message = message;
-  this.name = "Test262Error";
-}
-Test262Error.prototype = new Error();
-Test262Error.prototype.constructor = Test262Error;
-"#
-}
-
 /// 向拼接源码追加一段带注释标记的 harness 代码块。
 fn append_source_chunk(out: &mut String, name: &str, source: &str) {
     out.push_str("\n// ---- test262 harness: ");
@@ -282,7 +271,8 @@ fn build_harness_source(meta: &TestMeta, harness: &HarnessSources) -> Result<Str
     if meta.flags.iter().any(|f| f == "onlyStrict") {
         append_source_chunk(&mut source, "use strict", "\"use strict\";");
     }
-    append_source_chunk(&mut source, "Test262Error prelude", test262_error_prelude());
+    // Test262Error 由 sta.js 提供；此处不再重复定义（重复函数声明会引发
+    // 引擎 prototype 语义错乱，导致 assert.throws 的 constructor 比对失败）。
     append_source_chunk(
         &mut source,
         "sta.js",
diff --git a/crates/oxide_vm/src/dispatch/call.rs b/crates/oxide_vm/src/dispatch/call.rs
index c479487..6d203b8 100644
--- a/crates/oxide_vm/src/dispatch/call.rs
+++ b/crates/oxide_vm/src/dispatch/call.rs
@@ -102,6 +102,7 @@ impl Vm {
         let is_derived_constructor = sub.is_derived_constructor;
         let needs_home_object = sub.needs_home_object;
         let upvalue_captures = sub.upvalue_captures.clone();
+        let function_name = sub.function_name.clone();
         let result = self.create_function_object(
             sub_idx,
             is_arrow,
@@ -109,6 +110,11 @@ impl Vm {
             is_derived_constructor,
             needs_home_object,
         );
+        // 函数名推断：emit 端在变量声明/对象属性赋值点设置 function_name。
+        let func_obj = unsafe { &mut *result.as_js_object_ptr() };
+        let name_si = self.kernel_core.perm_interner().intern("name").0;
+        let name_val = function_name.as_deref().map(|n| self.new_string(n)).unwrap_or_else(|| self.new_string(""));
+        self.set_or_create_prop_value(func_obj, name_si, name_val);
         if !upvalue_captures.is_empty() {
             if let Some(current_cells) = self.cell_stack.last() {
                 let mut upvals = Box::new(Vec::with_capacity(upvalue_captures.len()));