diff --git a/phpunit/src/FunctionTest.php b/phpunit/src/FunctionTest.php
index d04e7e4b..2209d56f 100644
--- a/phpunit/src/FunctionTest.php
+++ b/phpunit/src/FunctionTest.php
@@ -27,4 +27,14 @@ class FunctionTest extends \BaseTest
         $this->exec('Named argument `value` overwrites previous argument', 'native-call-named-overwrites-positional.php');
     }
 
+    public function testInternalCallUnknownNamedArgument()
+    {
+        $this->exec('Unknown named argument `foo`', 'internal-call-unknown-named-arg.php');
+    }
+
+    public function testInternalCallMissingRequiredNamedArgument()
+    {
+        $this->exec('Named argument `replace` is missing default value', 'internal-call-missing-required-named-arg.php');
+    }
+
 }
diff --git a/src/Php/Analysis/SsaBuilder.php b/src/Php/Analysis/SsaBuilder.php
index abf5bb23..46ea8a1c 100644
--- a/src/Php/Analysis/SsaBuilder.php
+++ b/src/Php/Analysis/SsaBuilder.php
@@ -206,8 +206,9 @@ class SsaBuilder
         private array $argInfoList = []
     ) {
         foreach ($this->argInfoList as $argInfo) {
-            $this->params[] = $argInfo->name;
-            $this->paramByRef[$argInfo->name] = $argInfo->byRef ?? false;
+            $paramName = $argInfo->phpName ?: $argInfo->name;
+            $this->params[] = $paramName;
+            $this->paramByRef[$paramName] = $argInfo->byRef ?? false;
         }
     }
 
diff --git a/src/Php/ArgInfo.php b/src/Php/ArgInfo.php
index 70902959..93843742 100644
--- a/src/Php/ArgInfo.php
+++ b/src/Php/ArgInfo.php
@@ -15,6 +15,7 @@ use PhpParser\NodeAbstract;
 class ArgInfo
 {
     public string $name;
+    public string $phpName = '';
     public string $type;
     public string $default = '';
     public ?ArrayInitPlan $arrayInitPlan = null;
diff --git a/src/Php/CompilerBase.php b/src/Php/CompilerBase.php
index 733299df..af79a610 100644
--- a/src/Php/CompilerBase.php
+++ b/src/Php/CompilerBase.php
@@ -1873,7 +1873,7 @@ class CompilerBase extends \PhpAot\Core\Translator
     {
         $argNameIndex = [];
         foreach ($functionDef->argInfoList as $k => $argInfo) {
-            $argNameIndex[$argInfo->name] = $k;
+            $argNameIndex[$argInfo->phpName ?: $this->unescapeVarName($argInfo->name)] = $k;
         }
         return $argNameIndex;
     }
@@ -2841,6 +2841,7 @@ class CompilerBase extends \PhpAot\Core\Translator
         if (!$ref) {
             return;
         }
+        $this->validateInternalNamedCallArgs($ref, $expr->args);
         $minArgs = $ref->getNumberOfRequiredParameters();
         $maxArgs = $ref->getNumberOfParameters();
         $actualArgCount = count($expr->args);
@@ -2852,6 +2853,77 @@ class CompilerBase extends \PhpAot\Core\Translator
         }
     }
 
+    protected function validateInternalNamedCallArgs(\ReflectionFunctionAbstract $ref, array $callArgs): void
+    {
+        $hasNamedArg = false;
+        $seenNamedArgs = [];
+        $providedArgIndexes = [];
+        $argNameIndex = [];
+        $requiredArgIndexes = [];
+        $variadicArgIndex = null;
+
+        foreach ($ref->getParameters() as $i => $param) {
+            $argNameIndex[$param->getName()] = $i;
+            if (!$param->isOptional() && !$param->isVariadic()) {
+                $requiredArgIndexes[$i] = $param->getName();
+            }
+            if ($param->isVariadic()) {
+                $variadicArgIndex = $i;
+            }
+        }
+
+        foreach ($callArgs as $i => $arg) {
+            if ($this->isPlaceholderExpr($arg)) {
+                continue;
+            }
+            if ($arg->name === null) {
+                if ($hasNamedArg) {
+                    $this->fatalError($arg, 'Cannot use positional argument after named argument');
+                }
+                $providedArgIndexes[$i] = true;
+                continue;
+            }
+            if (!$this->isIdExpr($arg->name)) {
+                $this->fatalError($arg, 'Named argument must be a string');
+            }
+
+            $argName = $arg->name->name;
+            if (isset($seenNamedArgs[$argName])) {
+                $this->fatalError($arg, "Duplicate named argument `{$argName}`");
+            }
+            if (!array_key_exists($argName, $argNameIndex)) {
+                if ($variadicArgIndex === null) {
+                    $this->fatalError($arg, "Unknown named argument `{$argName}`");
+                }
+                $seenNamedArgs[$argName] = true;
+                $hasNamedArg = true;
+                continue;
+            }
+
+            $argIndex = $argNameIndex[$argName];
+            if ($variadicArgIndex !== null && $argIndex === $variadicArgIndex) {
+                $seenNamedArgs[$argName] = true;
+                $hasNamedArg = true;
+                continue;
+            }
+            if (isset($providedArgIndexes[$argIndex])) {
+                $this->fatalError($arg, "Named argument `{$argName}` overwrites previous argument");
+            }
+
+            $seenNamedArgs[$argName] = true;
+            $providedArgIndexes[$argIndex] = true;
+            $hasNamedArg = true;
+        }
+
+        if ($hasNamedArg) {
+            foreach ($requiredArgIndexes as $index => $name) {
+                if (!isset($providedArgIndexes[$index])) {
+                    $this->fatalError($callArgs[array_key_last($callArgs)] ?? null, "Named argument `{$name}` is missing default value");
+                }
+            }
+        }
+    }
+
     protected function parseFuncCall(Expr\FuncCall $expr): string
     {
         if ($this->isVarExpr($expr->name)) {
@@ -2954,7 +3026,8 @@ class CompilerBase extends \PhpAot\Core\Translator
                                 break;
                             }
                         }
-                        $this->fatalError($errorNode ?? reset($callArgs), 'Named argument `' . $argInfo->name . '` is missing default value');
+                        $argName = $argInfo->phpName ?: $this->unescapeVarName($argInfo->name);
+                        $this->fatalError($errorNode ?? reset($callArgs), 'Named argument `' . $argName . '` is missing default value');
                     }
                     $args[$k] = new Node\Arg($argInfo->defaultValue);
                 }
@@ -3891,7 +3964,8 @@ class CompilerBase extends \PhpAot\Core\Translator
                 if ($this->isTypedObject($object)) {
                     $class = $this->getObjectType($object);
                     if ($class and $argInfo->class and !$this->isInheritedFrom($class, $argInfo->class)) {
-                        $this->fatalError($arg, "Argument `{$argInfo->name}` must be an instance of `{$argInfo->class}`, `{$class}` given");
+                        $argName = $argInfo->phpName ?: $this->unescapeVarName($argInfo->name);
+                        $this->fatalError($arg, "Argument `{$argName}` must be an instance of `{$argInfo->class}`, `{$class}` given");
                     }
                 }
             }
diff --git a/src/Php/Generator/ClosureGenerator.php b/src/Php/Generator/ClosureGenerator.php
index 9ee09f9a..401a9523 100644
--- a/src/Php/Generator/ClosureGenerator.php
+++ b/src/Php/Generator/ClosureGenerator.php
@@ -75,6 +75,7 @@ trait ClosureGenerator
                 $this->fatalError($expr, 'Closure cannot use reference parameter');
             }
             $var = $this->parseIdentifier($param->var);
+            $phpName = is_string($param->var->name) ? $param->var->name : $this->unescapeVarName($var);
             if ($param->variadic) {
                 $code .= $this->getIndent() . self::TYPE_ARRAY . ' ' . $var . ';' . PHP_EOL;
                 $code .= $this->getIndent() . 'for (uint32_t i = ' . $i . '; i < php::getCallArgNum(); i++) {' . PHP_EOL;
@@ -83,7 +84,7 @@ trait ClosureGenerator
                 $this->indentLevel--;
                 $code .= $this->getIndent() . '}' . PHP_EOL;
                 $this->addArgument($var, self::TYPE_ARRAY);
-                $code .= $this->genClosureParamTypeCheck($param, $var, $i, true);
+                $code .= $this->genClosureParamTypeCheck($param, $var, $phpName, $i, true);
                 continue;
             }
             $argExpr = $param->default === null
@@ -91,7 +92,7 @@ trait ClosureGenerator
                 : 'php::getCallArg(' . $i . ', ' . $this->parseParamDefaultValue($param->default) . ')';
             $code .= $this->getIndent() . 'auto ' . $var . ' = ' . $argExpr . ';' . PHP_EOL;
             $this->addArgument($var, self::TYPE_VAR);
-            $code .= $this->genClosureParamTypeCheck($param, $var, $i, false);
+            $code .= $this->genClosureParamTypeCheck($param, $var, $phpName, $i, false);
         }
 
         foreach ($uses as $i => $useItem) {
@@ -164,7 +165,7 @@ trait ClosureGenerator
         return $code;
     }
 
-    private function genClosureParamTypeCheck(Node\Param $param, string $var, int $index, bool $variadic): string
+    private function genClosureParamTypeCheck(Node\Param $param, string $var, string $phpName, int $index, bool $variadic): string
     {
         if (!$param->type instanceof NullableType && !$param->type instanceof UnionType && !$param->type instanceof IntersectionType) {
             return '';
@@ -177,6 +178,7 @@ trait ClosureGenerator
 
         $argInfo = new ArgInfo();
         $argInfo->name = $var;
+        $argInfo->phpName = $phpName;
         $argInfo->type = self::TYPE_VAR;
         $argInfo->variadic = $variadic;
         $argInfo->typeCheck = $typeInfo['check'];
diff --git a/src/Php/Generator/PropertyPromotion.php b/src/Php/Generator/PropertyPromotion.php
index 1ef954de..edea815e 100644
--- a/src/Php/Generator/PropertyPromotion.php
+++ b/src/Php/Generator/PropertyPromotion.php
@@ -15,7 +15,8 @@ trait PropertyPromotion
     protected function genPropertyPromotion(ArgInfo $argInfo): string
     {
         $code = '';
-        $code .= 'this_.setProperty(' . $this->genCharPtr($argInfo->name) . ', ' . $argInfo->name . ')';
+        $propertyName = $argInfo->phpName ?: $this->unescapeVarName($argInfo->name);
+        $code .= 'this_.setProperty(' . $this->genCharPtr($propertyName) . ', ' . $argInfo->name . ')';
         $code .= ";\n";
         return $code;
     }
diff --git a/src/Php/Generator/TypeCheckGenerator.php b/src/Php/Generator/TypeCheckGenerator.php
index 990ad37f..c0ee0699 100644
--- a/src/Php/Generator/TypeCheckGenerator.php
+++ b/src/Php/Generator/TypeCheckGenerator.php
@@ -265,7 +265,7 @@ trait TypeCheckGenerator
     protected function genUnionParamTypeErrorExpr(ArgInfo $argInfo, string $valueExpr, string $argNoExpr): string
     {
         $fnName = $this->getTypeCheckCallableName();
-        $paramName = $this->unescapeVarName($argInfo->name);
+        $paramName = $argInfo->phpName ?: $this->unescapeVarName($argInfo->name);
         return 'php::concat({'
             . 'php::Str(' . $this->genCharPtr($fnName . '(): Argument #', true) . '), '
             . 'php::toString(' . $argNoExpr . '), '
@@ -381,7 +381,7 @@ trait TypeCheckGenerator
 
     protected function genClosureParamTypeErrorExpr(ArgInfo $argInfo, string $valueExpr, string $argNoExpr): string
     {
-        $paramName = $this->unescapeVarName($argInfo->name);
+        $paramName = $argInfo->phpName ?: $this->unescapeVarName($argInfo->name);
         return 'php::concat({'
             . 'php::Str(' . $this->genCharPtr('{closure}(): Argument #', true) . '), '
             . 'php::toString(' . $argNoExpr . '), '
diff --git a/src/Php/Optimizer/FuncCallOptimizer.php b/src/Php/Optimizer/FuncCallOptimizer.php
index f0b9a08d..9a82847c 100644
--- a/src/Php/Optimizer/FuncCallOptimizer.php
+++ b/src/Php/Optimizer/FuncCallOptimizer.php
@@ -195,6 +195,12 @@ trait FuncCallOptimizer
 
     protected function parseFuncCallWithOptimizer(string $name, Node\Expr\FuncCall $expr): string|false
     {
+        foreach ($expr->args as $arg) {
+            if ($arg instanceof Node\Arg && $arg->name !== null) {
+                return false;
+            }
+        }
+
         $config = $this->getFuncCallConfig()[$name] ?? null;
         if ($config === null) {
             return false;
diff --git a/src/Php/Preprocessor.php b/src/Php/Preprocessor.php
index feff1478..13097bb8 100644
--- a/src/Php/Preprocessor.php
+++ b/src/Php/Preprocessor.php
@@ -249,21 +249,25 @@ class Preprocessor extends CompilerBase
         $last = array_key_last($params);
 
         foreach ($params as $i => $param) {
+            if (!is_string($param->var->name)) {
+                $this->fatalError($param, 'Parameter name must be a string');
+            }
+            $phpName = $param->var->name;
+            $name = $this->escapeVarName($phpName);
             // .stub 存根定义 C++ Native 函数，必须设置函数的参数类型
             if ($this->stubFile and !$param->type) {
-                throw new \RuntimeException('No type for ' . $this->parseIdentifier($param->var));
+                throw new \RuntimeException('No type for ' . $phpName);
             }
             // 构造方法属性定义语法（Constructor Property Promotion）
             if ($param->isPromoted()) {
                 if (!$this->classDef or !$this->methodDef or $this->methodDef->name !== '__construct') {
                     $this->fatalError($param, 'Promoted properties are not supported');
                 }
-                $name = $this->parseIdentifier($param->var);
                 $nullable = $param->type instanceof NullableType;
                 // Promoted property defaults belong to the constructor parameter,
                 // not to the property default table. The property itself must stay
                 // uninitialized until __construct assigns it.
-                $this->addClassProperty($name, $param->flags, $param->type, null, $nullable, $param);
+                $this->addClassProperty($phpName, $param->flags, $param->type, null, $nullable, $param);
             }
             if ($param->variadic) {
                 if ($i !== $last) {
@@ -272,13 +276,13 @@ class Preprocessor extends CompilerBase
                     $this->fatalError($param, 'Variadic parameters cannot be passed by reference');
                 }
             }
-            $name = $this->parseIdentifier($param->var);
             if ($this->method and $name === 'this_') {
                 $this->fatalError($param, 'Cannot use `$this` as parameter of class method');
             }
             $argInfo = new ArgInfo();
             $type = $this->parseParameterType($param, $argInfo, $name);
             $argInfo->name = $name;
+            $argInfo->phpName = $phpName;
             $argInfo->type = $type;
             $argInfo->byRef = $param->byRef;
             $argInfo->variadic = $param->variadic;
diff --git a/tests/aot/closure/closure-composite-type-check.phpt b/tests/aot/closure/closure-composite-type-check.phpt
new file mode 100644
index 00000000..457acac4
--- /dev/null
+++ b/tests/aot/closure/closure-composite-type-check.phpt
@@ -0,0 +1,82 @@
+--TEST--
+Closure composite type declarations use runtime type checks
+--ENV--
+USE_ZEND_ALLOC=0
+--FILE--
+<?php
+
+interface ClosureIA {}
+interface ClosureIB {}
+class ClosureBoth implements ClosureIA, ClosureIB {}
+class ClosureOnlyA implements ClosureIA {}
+
+function main(): void
+{
+    $nullable = function (?int $value) {
+        var_dump($value);
+    };
+    $nullable(null);
+
+    $union = function (int|string $union) {
+        var_dump($union);
+    };
+    $union("ok");
+
+    $variadic = function (int|string ...$values) {
+        var_dump($values);
+    };
+    $variadic(1, "two");
+
+    $intersection = function (ClosureIA&ClosureIB $value) {
+        var_dump(get_class($value));
+    };
+    $intersection(new ClosureBoth());
+
+    $returnUnion = function ($value): int|string {
+        return $value;
+    };
+    var_dump($returnUnion(42));
+
+    try {
+        $nullable("bad");
+    } catch (\TypeError $e) {
+        echo $e->getMessage(), "\n";
+    }
+    try {
+        $union([]);
+    } catch (\TypeError $e) {
+        echo $e->getMessage(), "\n";
+    }
+    try {
+        $variadic(1, []);
+    } catch (\TypeError $e) {
+        echo $e->getMessage(), "\n";
+    }
+    try {
+        $intersection(new ClosureOnlyA());
+    } catch (\TypeError $e) {
+        echo $e->getMessage(), "\n";
+    }
+    try {
+        $returnUnion([]);
+    } catch (\TypeError $e) {
+        echo $e->getMessage(), "\n";
+    }
+}
+?>
+--EXPECT--
+NULL
+string(2) "ok"
+array(2) {
+  [0]=>
+  int(1)
+  [1]=>
+  string(3) "two"
+}
+string(11) "ClosureBoth"
+int(42)
+{closure}(): Argument #1 ($value) must be of type ?int, string given
+{closure}(): Argument #1 ($union) must be of type int|string, array given
+{closure}(): Argument #2 ($values) must be of type int|string, array given
+{closure}(): Argument #1 ($value) must be of type ClosureIA&ClosureIB, object given
+{closure}(): Return value must be of type int|string, array given
diff --git a/tests/aot/closure/closure-param-defaults.phpt b/tests/aot/closure/closure-param-defaults.phpt
new file mode 100644
index 00000000..51eff8ec
--- /dev/null
+++ b/tests/aot/closure/closure-param-defaults.phpt
@@ -0,0 +1,41 @@
+--TEST--
+Closure parameters handle defaults and variadic arguments
+--ENV--
+USE_ZEND_ALLOC=0
+--FILE--
+<?php
+function main(): void
+{
+    $default = function ($value = 42) {
+        var_dump($value);
+    };
+    $default();
+
+    $variadic = function (...$values) {
+        var_dump($values);
+    };
+    $variadic(1, "two", null);
+
+    $required = function (?int $value) {
+        var_dump($value);
+    };
+    try {
+        $required();
+    } catch (\Throwable $e) {
+        var_dump(get_class($e));
+        var_dump($e->getMessage());
+    }
+}
+?>
+--EXPECT--
+int(42)
+array(3) {
+  [0]=>
+  int(1)
+  [1]=>
+  string(3) "two"
+  [2]=>
+  NULL
+}
+string(18) "ArgumentCountError"
+string(74) "Too few arguments to function {closure}(), 0 passed and exactly 1 expected"
diff --git a/tests/aot/functions/internal-named-args.phpt b/tests/aot/functions/internal-named-args.phpt
new file mode 100644
index 00000000..6d93c617
--- /dev/null
+++ b/tests/aot/functions/internal-named-args.phpt
@@ -0,0 +1,16 @@
+--TEST--
+Internal function named arguments are validated before optimization
+--FILE--
+<?php
+
+function main(): void
+{
+    var_dump(strlen(string: "abc"));
+    var_dump(str_replace(replace: "x", subject: "abc", search: "a"));
+    var_dump(substr(length: 2, string: "abcdef", offset: 3));
+}
+?>
+--EXPECT--
+int(3)
+string(3) "xbc"
+string(2) "de"
diff --git a/tests/aot/named_args/007.phpt b/tests/aot/named_args/007.phpt
new file mode 100644
index 00000000..705bdaff
--- /dev/null
+++ b/tests/aot/named_args/007.phpt
@@ -0,0 +1,37 @@
+--TEST--
+Named arguments and promoted properties with C++ reserved parameter names
+--FILE--
+<?php
+
+function reserved_params($union, $class = 2): array
+{
+    return [$union, $class];
+}
+
+class ReservedPromotion
+{
+    public function __construct(
+        public int $union,
+        public string $class = "default"
+    ) {
+    }
+}
+
+function main(): void
+{
+    var_dump(reserved_params(class: 20, union: 10));
+
+    $object = new ReservedPromotion(class: "named", union: 42);
+    var_dump($object->union);
+    var_dump($object->class);
+}
+?>
+--EXPECT--
+array(2) {
+  [0]=>
+  int(10)
+  [1]=>
+  int(20)
+}
+int(42)
+string(5) "named"
diff --git a/tests/aot/optimizations/reserved-param-ssa.phpt b/tests/aot/optimizations/reserved-param-ssa.phpt
new file mode 100644
index 00000000..15d0ac61
--- /dev/null
+++ b/tests/aot/optimizations/reserved-param-ssa.phpt
@@ -0,0 +1,21 @@
+--TEST--
+SSA optimizations handle parameters with C++ reserved names
+--FILE--
+<?php
+
+function sum_reserved(int $union, int $class): int
+{
+    $total = 0;
+    for ($i = 0; $i < $union; $i++) {
+        $total += $class;
+    }
+    return $total;
+}
+
+function main(): void
+{
+    var_dump(sum_reserved(union: 4, class: 3));
+}
+?>
+--EXPECT--
+int(12)