diff --git a/crates/oxide_compiler/src/hash/class.rs b/crates/oxide_compiler/src/hash/class.rs
index 53659fff..6c2c30ad 100644
--- a/crates/oxide_compiler/src/hash/class.rs
+++ b/crates/oxide_compiler/src/hash/class.rs
@@ -19,9 +19,7 @@ pub(super) fn hash_class_element(element: &ClassElement, h: &mut rustc_hash::FxH
                 }
             }
             if let Some(body) = &method.value.body {
-                for stmt in &body.statements {
-                    statement::hash_statement(stmt, h, include_binding_names);
-                }
+                hash_function_body(body, h, include_binding_names);
             }
         }
         ClassElement::PropertyDefinition(prop) => {
diff --git a/crates/oxide_compiler/src/hash/expression.rs b/crates/oxide_compiler/src/hash/expression.rs
index 49706013..65d44949 100644
--- a/crates/oxide_compiler/src/hash/expression.rs
+++ b/crates/oxide_compiler/src/hash/expression.rs
@@ -88,9 +88,7 @@ pub(super) fn hash_expression(expr: &Expression, h: &mut rustc_hash::FxHasher, i
                     hash_binding_pattern(&param.pattern, h);
                 }
             }
-            for s in &arrow.body.statements {
-                statement::hash_statement(s, h, include_binding_names);
-            }
+            hash_function_body(&arrow.body, h, include_binding_names);
         }
         Expression::FunctionExpression(fe) => {
             (fe.params.items.len() as u32).hash(h);
@@ -103,9 +101,7 @@ pub(super) fn hash_expression(expr: &Expression, h: &mut rustc_hash::FxHasher, i
                 }
             }
             if let Some(body) = &fe.body {
-                for s in &body.statements {
-                    statement::hash_statement(s, h, include_binding_names);
-                }
+                hash_function_body(body, h, include_binding_names);
             }
         }
         Expression::ClassExpression(class) => {
diff --git a/crates/oxide_compiler/src/hash/mod.rs b/crates/oxide_compiler/src/hash/mod.rs
index ca36e5e9..e85b22cb 100644
--- a/crates/oxide_compiler/src/hash/mod.rs
+++ b/crates/oxide_compiler/src/hash/mod.rs
@@ -70,3 +70,18 @@ fn hash_binding_pattern(pattern: &BindingPattern, h: &mut rustc_hash::FxHasher)
         ident.name.as_str().hash(h);
     }
 }
+
+/// 函数体哈希：statements 之后追加 directives。
+///
+/// directives 决定函数体严格模式（`"use strict"` 等），不纳入 hash 时嵌套
+/// 函数/方法体 strict 标志随缓存键错配复用错误字节码（this 绑定语义漂移）。
+fn hash_function_body(
+    body: &oxide_parser::FunctionBody<'_>, h: &mut rustc_hash::FxHasher, include_binding_names: bool,
+) {
+    for stmt in &body.statements {
+        statement::hash_statement(stmt, h, include_binding_names);
+    }
+    for directive in &body.directives {
+        directive.directive.as_str().hash(h);
+    }
+}
diff --git a/crates/oxide_compiler/src/hash/statement.rs b/crates/oxide_compiler/src/hash/statement.rs
index 0fc3c69a..9c9976e0 100644
--- a/crates/oxide_compiler/src/hash/statement.rs
+++ b/crates/oxide_compiler/src/hash/statement.rs
@@ -208,9 +208,7 @@ fn hash_function_declaration(fd: &Function<'_>, h: &mut rustc_hash::FxHasher, in
         }
     }
     if let Some(body) = &fd.body {
-        for s in &body.statements {
-            hash_statement(s, h, include_binding_names);
-        }
+        hash_function_body(body, h, include_binding_names);
     }
 }
 
diff --git a/crates/oxide_compiler/tests/hash_collision_tests.rs b/crates/oxide_compiler/tests/hash_collision_tests.rs
index 84f2d2c7..3167e858 100644
--- a/crates/oxide_compiler/tests/hash_collision_tests.rs
+++ b/crates/oxide_compiler/tests/hash_collision_tests.rs
@@ -94,3 +94,39 @@ fn structural_hash_ignores_binding_names() {
     // 编译模块哈希纳入绑定名：改名的程序哈希不等。
     assert_ne!(compiled("function f(x){ return x }"), compiled("function f(y){ return y }"));
 }
+
+#[test]
+fn function_body_directives_distinguished() {
+    // 嵌套函数体 directives 决定其严格模式：不入 hash 时 strict 标志随缓存键错配。
+    assert_ne!(
+        compiled("function f(){ 'use strict'; return 1 }"),
+        compiled("function f(){ return 1 }"),
+        "function declaration body directive must be part of the hash"
+    );
+    assert_ne!(
+        compiled("var f = function(){ 'use strict'; return 1 }"),
+        compiled("var f = function(){ return 1 }"),
+        "function expression body directive must be part of the hash"
+    );
+    assert_ne!(
+        compiled("var f = () => { 'use strict'; return 1 }"),
+        compiled("var f = () => { return 1 }"),
+        "arrow function body directive must be part of the hash"
+    );
+    assert_ne!(
+        compiled("class A { m(){ 'use strict'; return 1 } }"),
+        compiled("class A { m(){ return 1 } }"),
+        "class method body directive must be part of the hash"
+    );
+    assert_ne!(
+        compiled("var o = { m(){ 'use strict'; return 1 } }"),
+        compiled("var o = { m(){ return 1 } }"),
+        "object literal method body directive must be part of the hash"
+    );
+    // 非 prologue 位置的字符串字面量是普通语句，不构成 directive，哈希不混同。
+    assert_eq!(
+        compiled("function f(){ 'not-a-directive'; return 1 }"),
+        compiled("function f(){ 'not-a-directive'; return 1 }"),
+        "identical sources must hash equally"
+    );
+}