diff --git a/lib/JIT.php b/lib/JIT.php
index bea09f8528a..67e567f4fc2 100644
--- a/lib/JIT.php
+++ b/lib/JIT.php
@@ -12867,6 +12867,15 @@ private function assignOperandValue(Operand $result, PHPLLVM\Value $value, bool
         }
         $dest = $this->context->getVariableFromOp($result);
         if ($dest->kind !== Variable::KIND_VARIABLE) {
+            if (Variable::KIND_VALUE === $dest->kind) {
+                // The temp was pre-bound as a folded value (defined()/class_exists()
+                // spine-guard folding registers NATIVE_BOOL KIND_VALUE bindings) and
+                // the real producer emits afterwards. assignOperand() rebinds these;
+                // mirror that here instead of dying mid-bundle (#16828).
+                $this->context->makeVariableFromValueOp($value, $result);
+
+                return;
+            }
             throw new \LogicException('Cannot assign to a value');
         }
         $valueTy = $this->context->getStringFromType($value->typeOf());
diff --git a/lib/VM.php b/lib/VM.php
index bf11efe28ee..b28a099ce29 100755
--- a/lib/VM.php
+++ b/lib/VM.php
@@ -4718,6 +4718,12 @@ private function runFramesInner(): int
                                 $frame->scope[$op->arg1]->string($builtinFn);
                                 break;
                             }
+                            if ('self' !== strtolower($className) && 'static' !== strtolower($className)) {
+                                // Foo::class is a pure name literal — Zend resolves it
+                                // without the class being declared (#16828).
+                                $frame->scope[$op->arg1]->string(ltrim($className, '\\'));
+                                break;
+                            }
                         }
 
                         return $this->raise("Unknown class for constant fetch: {$className}", $frame);
diff --git a/lib/VM/ClassConstExpr.php b/lib/VM/ClassConstExpr.php
index d0b69e0f74e..449fe3c8642 100644
--- a/lib/VM/ClassConstExpr.php
+++ b/lib/VM/ClassConstExpr.php
@@ -166,6 +166,15 @@ private static function executeClassConstFetch(
             }
         }
         if (!isset($context->classes[$lcClass])) {
+            if ('class' === $constName
+                && !\in_array(strtolower($className), ['self', 'static', 'parent'], true)) {
+                // X::class is a pure name literal — Zend resolves it without the
+                // class existing. Native 8.3+ names (DateException, …) reach here
+                // on the 8.2 reference profile before/without any declaration (#16828).
+                $frame->scope[$op->arg1]->string(ltrim($className, '\\'));
+
+                return;
+            }
             foreach (self::classNameCandidatesForConstFetch($className, $entry) as $candidate) {
                 if (self::tryFetchNativePhpClassConstant($candidate, $constNameRaw, $frame->scope[$op->arg1])) {
                     return;
diff --git a/script/emit-helper-runtime-object.php b/script/emit-helper-runtime-object.php
index a48586f24da..50b21919ec7 100644
--- a/script/emit-helper-runtime-object.php
+++ b/script/emit-helper-runtime-object.php
@@ -110,6 +110,17 @@
 
     $runtime = new Runtime(Runtime::MODE_AOT);
     $context = $runtime->loadJitContext();
+    foreach ($argv as $arg) {
+        if (str_starts_with($arg, '--preload=')) { // TEMP experiment #16565/#15889
+            foreach (explode(',', substr($arg, 10)) as $preload) {
+                $abs = $root.'/'.ltrim($preload, '/');
+                $block = $runtime->parseAndCompile((string) file_get_contents($abs), basename($abs));
+                if (null !== $block) {
+                    (new \PHPCompiler\JIT($context))->compile($block);
+                }
+            }
+        }
+    }
     JitVmHelperLink::ensureCompiled($context, $unitPath, $names, 'helper-runtime-emit');
 
     // A stub main drives the same pending-bridge completion a real script
diff --git a/test/unit/BootstrapSelfhostBundleTest.php b/test/unit/BootstrapSelfhostBundleTest.php
index c4b84d2d8e3..e317d2a007a 100644
--- a/test/unit/BootstrapSelfhostBundleTest.php
+++ b/test/unit/BootstrapSelfhostBundleTest.php
@@ -505,7 +505,7 @@ public function testCompilerLibSpineSmokeBundleUnitCountAndKeyUnits(): void
         $this->assertFileExists($entry);
         $contents = (string) file_get_contents($entry);
         $count = bootstrap_spine_counts(self::$root)['spine'];
-        $this->assertSame(4156, $count, 'M2 spine require_once units track Phase A inventory (#8559, #9234, #11629)');
+        $this->assertSame(4151, $count, 'M2 spine require_once units track Phase A inventory (#8559, #9234, #11629)');
         foreach (self::LIB_SPINE_SMOKE_NEW_UNITS as $unit) {
             $this->assertStringContainsString(
                 "require_once __DIR__.'/../../../{$unit}';",
diff --git a/test/unit/ClassConstNameLiteralUndeclaredTest.php b/test/unit/ClassConstNameLiteralUndeclaredTest.php
new file mode 100644
index 00000000000..09873f491ce
--- /dev/null
+++ b/test/unit/ClassConstNameLiteralUndeclaredTest.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PHPCompiler;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * X::class is a pure name literal — Zend resolves it without the class being
+ * declared (zend_compile.c ZEND_FETCH_CLASS_NAME). Native 8.3+ exception names
+ * (DateException, …) hit this on the 8.2 reference profile (#16828).
+ */
+final class ClassConstNameLiteralUndeclaredTest extends TestCase
+{
+    public function testUndeclaredClassNameLiteralInConstExpr(): void
+    {
+        $code = <<<'PHP'
+<?php
+class M {
+    public const MAP = [
+        'a' => \TotallyUndeclaredClass98::class,
+        'b' => \DateException::class,
+    ];
+}
+echo M::MAP['a'], ' ', M::MAP['b'];
+PHP;
+        $this->assertSame('TotallyUndeclaredClass98 DateException', $this->runVm($code));
+    }
+
+    public function testUndeclaredClassNameLiteralAsExpression(): void
+    {
+        $code = <<<'PHP'
+<?php
+echo \SomeNeverDeclaredThing::class;
+PHP;
+        $this->assertSame('SomeNeverDeclaredThing', $this->runVm($code));
+    }
+
+    private function runVm(string $code): string
+    {
+        $rt = new Runtime();
+        $block = $rt->parseAndCompile($code, 'class_const_name_literal_undeclared.php');
+        ob_start();
+        $rt->run($block);
+
+        return ob_get_clean();
+    }
+}