diff --git a/CHANGELOG.md b/CHANGELOG.md
index b09eb3465a..0ce439e587 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@ All notable changes to elephc, a PHP-to-native compiler written in Rust.
 Releases are listed newest first.
 
 ## [Unreleased]
+- Fixed a transposed x86_64 heap magic stamped by several throwable emitters (issue #482): objects created through the runtime-raised `ValueError`/`TypeError`/`LogicException`/`Error` paths, JSON throw errors, and some SPL/hash/static-property paths carried a header magic the refcount helpers do not recognize, silently opting them out of reference counting on linux-x86_64. Every kind-word stamp now goes through one shared, tested helper (`x86_64_heap_kind_word`), and a repository lint test keeps the hand-typed transposed literal from coming back.
 - Removed the legacy direct AST → ASM backend completely. EIR is now the only
   codegen implementation path.
 - Int-backed enum `from()` / `tryFrom()` now accept a dynamically-typed (`mixed`) argument (issue #449): a `foreach` value over a heterogeneous array, an untyped parameter, etc. are coerced on their runtime type before the enum lookup — integer/numeric-string resolve (or throw `ValueError`), float truncates, bool/null coerce, and array/object/resource/closure throw `TypeError` naming the given type. Previously any `mixed` argument was rejected at compile time. Target-aware on every supported backend.
diff --git a/src/codegen/lower_inst/builtins/math.rs b/src/codegen/lower_inst/builtins/math.rs
index 2e6c4f8d9a..3078d7e9f6 100644
--- a/src/codegen/lower_inst/builtins/math.rs
+++ b/src/codegen/lower_inst/builtins/math.rs
@@ -652,7 +652,7 @@ fn emit_throw_value_error_x86_64(
     ctx.emitter.instruction("sub rsp, 16");                                     // keep the nested heap allocation call 16-byte aligned
     ctx.emitter.instruction("mov rax, 32");                                     // request Throwable payload storage for the clamp ValueError
     ctx.emitter.instruction("call __rt_heap_alloc");                            // allocate the ValueError object payload
-    ctx.emitter.instruction("mov r10, 0x4548504c00000006");                     // materialize the x86_64 object heap-kind header
+    ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");                    // stamp the allocation header as a runtime object
     ctx.emitter.instruction("mov r10, QWORD PTR [rip + _spl_value_error_class_id]"); // load ValueError's runtime class id for this program
     ctx.emitter.instruction("mov QWORD PTR [rax], r10");                        // store the ValueError class id in the Throwable header
diff --git a/src/codegen/lower_inst/enums.rs b/src/codegen/lower_inst/enums.rs
index 1ad4740788..7d8dbe3989 100644
--- a/src/codegen/lower_inst/enums.rs
+++ b/src/codegen/lower_inst/enums.rs
@@ -437,7 +437,7 @@ fn emit_throw_value_error_from_string_result_aarch64(ctx: &mut FunctionContext<'
 fn emit_throw_value_error_from_string_result_x86_64(ctx: &mut FunctionContext<'_>) {
     abi::emit_load_int_immediate(ctx.emitter, "rax", 32);
     abi::emit_call_label(ctx.emitter, "__rt_heap_alloc");
-    ctx.emitter.instruction("mov r10, 0x4548504c00000006");                     // x86_64 heap-kind word: HE LP magic + kind 6 object
+    ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");                    // stamp allocation as a runtime object
     abi::emit_load_symbol_to_reg(ctx.emitter, "r10", "_spl_value_error_class_id", 0);
     ctx.emitter.instruction("mov QWORD PTR [rax], r10");                        // store ValueError class id at object header
@@ -681,7 +681,7 @@ fn emit_throw_type_error_from_string_result(ctx: &mut FunctionContext<'_>) {
         Arch::X86_64 => {
             abi::emit_load_int_immediate(ctx.emitter, "rax", 32);
             abi::emit_call_label(ctx.emitter, "__rt_heap_alloc");
-            ctx.emitter.instruction("mov r10, 0x4548504c00000006");             // x86_64 heap-kind word: HELP magic + kind 6 object
+            ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
             ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");            // stamp allocation as a runtime object
             abi::emit_load_symbol_to_reg(ctx.emitter, "r10", "_spl_type_error_class_id", 0);
             ctx.emitter.instruction("mov QWORD PTR [rax], r10");                // store TypeError class id at object header
@@ -726,7 +726,7 @@ fn emit_throw_enum_from_type_error_x86_64(
 ) {
     abi::emit_load_int_immediate(ctx.emitter, "rax", 32);
     abi::emit_call_label(ctx.emitter, "__rt_heap_alloc");
-    ctx.emitter.instruction("mov r10, 0x4548504c00000006");                     // x86_64 heap-kind word: HELP magic + kind 6 object
+    ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");                    // stamp allocation as a runtime object
     abi::emit_load_symbol_to_reg(ctx.emitter, "r10", "_spl_type_error_class_id", 0);
     ctx.emitter.instruction("mov QWORD PTR [rax], r10");                        // store TypeError class id at object header
diff --git a/src/codegen/lower_inst/objects.rs b/src/codegen/lower_inst/objects.rs
index 49cf6fff96..17b2e293b8 100644
--- a/src/codegen/lower_inst/objects.rs
+++ b/src/codegen/lower_inst/objects.rs
@@ -708,7 +708,7 @@ fn emit_throw_iterator_iterator_downcast_logic_exception(ctx: &mut FunctionConte
             ctx.emitter.instruction("sub rsp, 16");                             // keep the nested heap allocation call aligned
             ctx.emitter.instruction("mov rax, 32");                             // request Throwable payload storage
             abi::emit_call_label(ctx.emitter, "__rt_heap_alloc");
-            ctx.emitter.instruction("mov r10, 0x4548504c00000006");             // materialize the x86_64 object heap kind word
+            ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
             ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");            // stamp allocation as a runtime object
             ctx.emitter.instruction("mov r10, QWORD PTR [rip + _spl_logic_exception_class_id]"); // load LogicException's runtime class id
             ctx.emitter.instruction("mov QWORD PTR [rax], r10");                // store the class id at object header
@@ -5034,7 +5034,7 @@ fn emit_uninitialized_typed_property_fatal(
             ctx.emitter.instruction("sub rsp, 16");                                // keep the nested heap allocation call 16-byte aligned
             ctx.emitter.instruction("mov rax, 32");                                // request Throwable payload storage
             ctx.emitter.instruction("call __rt_heap_alloc");                       // allocate the Error object payload
-            ctx.emitter.instruction("mov r10, 0x4548504c00000006");              // x86_64 heap-kind word: HE LP magic + kind 6 object
+            ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
             ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");               // stamp allocation as a runtime object
             abi::emit_load_symbol_to_reg(ctx.emitter, "r10", "_spl_error_class_id", 0); // load Error's runtime class id for this program
             ctx.emitter.instruction("mov QWORD PTR [rax], r10");                   // store class id at the object header
diff --git a/src/codegen/lower_inst/static_properties.rs b/src/codegen/lower_inst/static_properties.rs
index f62a893a1e..70de1c5670 100644
--- a/src/codegen/lower_inst/static_properties.rs
+++ b/src/codegen/lower_inst/static_properties.rs
@@ -752,7 +752,7 @@ fn emit_uninitialized_static_property_fatal(
             ctx.emitter.instruction("sub rsp, 16");                                // keep the nested heap allocation call 16-byte aligned
             ctx.emitter.instruction("mov rax, 32");                                // request Throwable payload storage
             ctx.emitter.instruction("call __rt_heap_alloc");                       // allocate the Error object payload
-            ctx.emitter.instruction("mov r10, 0x4548504c00000006");              // x86_64 heap-kind word: HE LP magic + kind 6 object
+            ctx.emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
             ctx.emitter.instruction("mov QWORD PTR [rax - 8], r10");               // stamp allocation as a runtime object
             abi::emit_load_symbol_to_reg(ctx.emitter, "r10", "_spl_error_class_id", 0); // load Error's runtime class id for this program
             ctx.emitter.instruction("mov QWORD PTR [rax], r10");                   // store class id at the object header
diff --git a/src/codegen_support/hash_crypto.rs b/src/codegen_support/hash_crypto.rs
index 0c0f2b5004..93d2ba7c93 100644
--- a/src/codegen_support/hash_crypto.rs
+++ b/src/codegen_support/hash_crypto.rs
@@ -112,7 +112,7 @@ fn emit_throw_value_error_x86_64(emitter: &mut Emitter, message_symbol: &str, me
     emitter.instruction("sub rsp, 16"); // keep the nested heap allocation call 16-byte aligned
     emitter.instruction("mov rax, 32"); // request Throwable payload storage
     emitter.instruction("call __rt_heap_alloc"); // allocate the ValueError object payload
-    emitter.instruction("mov r10, 0x4548504c00000006"); // x86_64 heap-kind word: HE LP magic + kind 6 object
+    emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     emitter.instruction("mov QWORD PTR [rax - 8], r10"); // stamp allocation as a runtime object
     abi::emit_load_symbol_to_reg(emitter, "r10", "_spl_value_error_class_id", 0); // load ValueError's runtime class id for this program
     emitter.instruction("mov QWORD PTR [rax], r10"); // store class id at the object header
diff --git a/src/codegen_support/runtime/arrays/value_error.rs b/src/codegen_support/runtime/arrays/value_error.rs
index 30b40ea716..0bcd50c271 100644
--- a/src/codegen_support/runtime/arrays/value_error.rs
+++ b/src/codegen_support/runtime/arrays/value_error.rs
@@ -53,7 +53,7 @@ pub(super) fn emit_throw_value_error_x86_64(
     emitter.instruction("sub rsp, 16");                                         // keep the nested heap allocation call 16-byte aligned
     emitter.instruction("mov rax, 32");                                         // request Throwable payload storage
     emitter.instruction("call __rt_heap_alloc");                                // allocate the ValueError object payload
-    emitter.instruction("mov r10, 0x4548504c00000006");                         // x86_64 heap-kind word: HE LP magic + kind 6 object
+    emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     emitter.instruction("mov QWORD PTR [rax - 8], r10");                        // stamp allocation as a runtime object
     abi::emit_load_symbol_to_reg(emitter, "r10", "_spl_value_error_class_id", 0); // load ValueError's runtime class id for this program
     emitter.instruction("mov QWORD PTR [rax], r10");                            // store class id at the object header
diff --git a/src/codegen_support/runtime/spl/doubly_linked_list.rs b/src/codegen_support/runtime/spl/doubly_linked_list.rs
index 56ef9777d8..b6bcf5585f 100644
--- a/src/codegen_support/runtime/spl/doubly_linked_list.rs
+++ b/src/codegen_support/runtime/spl/doubly_linked_list.rs
@@ -2525,7 +2525,7 @@ fn emit_throw_exception_x86_64(
     emitter.instruction("sub rsp, 16");                                         // keep the nested heap allocation call 16-byte aligned
     emitter.instruction("mov rax, 32");                                         // request Throwable payload storage
     emitter.instruction("call __rt_heap_alloc");                                // allocate the exception object payload
-    emitter.instruction("mov r10, 0x4548504c00000006");                         // x86_64 heap-kind word: HE LP magic + kind 6 object
+    emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     emitter.instruction("mov QWORD PTR [rax - 8], r10");                        // stamp allocation as a runtime object
     abi::emit_load_symbol_to_reg(emitter, "r10", class_id_symbol, 0);           // load the exception class id for this program
     emitter.instruction("mov QWORD PTR [rax], r10");                            // store class id at object header
diff --git a/src/codegen_support/runtime/spl/fixed_array.rs b/src/codegen_support/runtime/spl/fixed_array.rs
index c3db05f1ff..8caff31105 100644
--- a/src/codegen_support/runtime/spl/fixed_array.rs
+++ b/src/codegen_support/runtime/spl/fixed_array.rs
@@ -1447,7 +1447,7 @@ fn emit_throw_exception_x86_64(
     emitter.instruction("sub rsp, 16");                                         // keep the nested heap allocation call 16-byte aligned
     emitter.instruction("mov rax, 32");                                         // request Throwable payload storage
     emitter.instruction("call __rt_heap_alloc");                                // allocate the exception object payload
-    emitter.instruction("mov r10, 0x4548504c00000006");                         // x86_64 heap-kind word: HE LP magic + kind 6 object
+    emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     emitter.instruction("mov QWORD PTR [rax - 8], r10");                        // stamp allocation as a runtime object
     abi::emit_load_symbol_to_reg(emitter, "r10", class_id_symbol, 0);           // load the exception class id for this program
     emitter.instruction("mov QWORD PTR [rax], r10");                            // store class id at object header
diff --git a/src/codegen_support/runtime/system/json_throw_error.rs b/src/codegen_support/runtime/system/json_throw_error.rs
index 3cc87e97a5..1e470e0c38 100644
--- a/src/codegen_support/runtime/system/json_throw_error.rs
+++ b/src/codegen_support/runtime/system/json_throw_error.rs
@@ -161,7 +161,7 @@ fn emit_json_throw_error_linux_x86_64(emitter: &mut Emitter) {
 
     emitter.instruction("mov rax, 32");                                         // size = class_id (8) + message ptr/len (16) + code (8)
     emitter.instruction("call __rt_heap_alloc");                                // allocate the JsonException payload (rax = payload ptr)
-    emitter.instruction("mov r10, 0x4548504c00000006");                         // x86_64 heap-kind word: HE LP magic + kind 6 (object)
+    emitter.instruction(&format!("mov r10, 0x{:x}", crate::codegen_support::sentinels::x86_64_heap_kind_word(6))); // stamp the canonical x86_64 heap-kind word (magic + kind 6 throwable)
     emitter.instruction("mov QWORD PTR [rax - 8], r10");                        // tag the allocation as an object in the uniform header
 
     abi::emit_load_symbol_to_reg(emitter, "r10", "_json_exception_class_id", 0); // load JsonException's runtime class id (-1 when absent)
diff --git a/src/codegen_support/sentinels.rs b/src/codegen_support/sentinels.rs
index 309e7247c9..0682eaf511 100644
--- a/src/codegen_support/sentinels.rs
+++ b/src/codegen_support/sentinels.rs
@@ -147,6 +147,21 @@ pub(crate) fn emit_tagged_scalar_to_int_null_as_zero(emitter: &mut Emitter) {
     }
 }
 
+
+/// High 32 bits of the x86_64 uniform heap-header kind word (`"ELPH"` in ASCII bytes
+/// `0x45 0x4C 0x50 0x48`). Every x86_64 allocation is stamped with this marker; the
+/// refcount and free helpers ignore pointers whose header does not carry it, so an
+/// emitter that stamps a different value silently opts its objects out of refcounting.
+pub(crate) const X86_64_HEAP_MAGIC_HI32: u64 = 0x454C5048;
+
+/// Builds the full x86_64 heap-header kind word for `kind`: the heap magic in the high
+/// word and the uniform heap-kind tag in the low byte. Emitters must use this instead of
+/// a hand-typed literal — a transposed magic assembles fine but makes every refcount
+/// operation on the stamped object a silent no-op (issue #482).
+pub(crate) fn x86_64_heap_kind_word(kind: u8) -> u64 {
+    (X86_64_HEAP_MAGIC_HI32 << 32) | kind as u64
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -167,4 +182,42 @@ mod tests {
         );
         assert_eq!(UNINITIALIZED_TYPED_PROPERTY_SENTINEL, i64::MAX - 2);
     }
+
+    /// Verifies the x86_64 heap kind word carries the canonical magic ("ELPH") in the
+    /// high word and the kind tag in the low byte — guarding against the transposed
+    /// literal that no-ops refcounting (issue #482).
+    #[test]
+    fn test_x86_64_heap_kind_word_layout() {
+        assert_eq!(x86_64_heap_kind_word(6), 0x454C_5048_0000_0006);
+        assert_eq!(x86_64_heap_kind_word(4), 0x454C_5048_0000_0004);
+        assert_ne!(x86_64_heap_kind_word(6) >> 32, 0x4548_504C, "transposed magic");
+    }
+
+    /// Repo lint: no emitter may hand-type the transposed heap magic again — every
+    /// stamped kind word must come from `x86_64_heap_kind_word` (issue #482).
+    #[test]
+    fn test_no_transposed_heap_magic_in_source() {
+        fn scan(dir: &std::path::Path, hits: &mut Vec<String>) {
+            for entry in std::fs::read_dir(dir).expect("readable src dir") {
+                let path = entry.expect("dir entry").path();
+                if path.is_dir() {
+                    scan(&path, hits);
+                } else if path.extension().is_some_and(|e| e == "rs") {
+                    let body = std::fs::read_to_string(&path).expect("readable source");
+                    // Needle built at runtime so this test file never matches itself.
+                    let needle = ["0x4548", "504c"].concat();
+                    if body.to_lowercase().contains(&needle) {
+                        hits.push(path.display().to_string());
+                    }
+                }
+            }
+        }
+        let src = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("src");
+        let mut hits = Vec::new();
+        scan(&src, &mut hits);
+        assert!(
+            hits.is_empty(),
+            "transposed x86_64 heap magic found in: {hits:?}"
+        );
+    }
 }