diff --git a/tools/structarmed/composer.json b/tools/structarmed/composer.json
index d148bae6..19a432a5 100644
--- a/tools/structarmed/composer.json
+++ b/tools/structarmed/composer.json
@@ -1,6 +1,6 @@
 {
     "require": {
-        "boundwize/structarmed": "^0.20.0"
+        "boundwize/structarmed": "^0.21.2"
     },
     "autoload": {
         "psr-4": {
diff --git a/tools/structarmed/src/Rule/InternalMustNotLeakIntoPublicSignatureRule.php b/tools/structarmed/src/Rule/InternalMustNotLeakIntoPublicSignatureRule.php
index 679fe1c8..c06b735d 100644
--- a/tools/structarmed/src/Rule/InternalMustNotLeakIntoPublicSignatureRule.php
+++ b/tools/structarmed/src/Rule/InternalMustNotLeakIntoPublicSignatureRule.php
@@ -5,10 +5,10 @@
 namespace Testo\Tools\StructArmed\Rule;
 
 use Boundwize\StructArmed\Analyser\ClassNode;
+use Boundwize\StructArmed\Analyser\ClassSignature;
 use Boundwize\StructArmed\Rule\MultipleRuleViolationInterface;
-use Boundwize\StructArmed\Rule\RuleInterface;
 use Boundwize\StructArmed\Rule\RuleViolation;
-use Testo\Tools\StructArmed\Support\ClassSignatures;
+use Boundwize\StructArmed\Rule\SignatureTypesAwareRuleInterface;
 
 /**
  * A class on the public surface must not name an internal type in its signature.
@@ -18,7 +18,7 @@
  * exempt: internal-to-internal coupling stays behind the package boundary (and any
  * cross-package leak is caught by [InternalIsUsableOnlyWithinItsPackageRule]).
  */
-final readonly class InternalMustNotLeakIntoPublicSignatureRule implements RuleInterface, MultipleRuleViolationInterface
+final readonly class InternalMustNotLeakIntoPublicSignatureRule implements SignatureTypesAwareRuleInterface, MultipleRuleViolationInterface
 {
     private const SEGMENT = '\\Internal\\';
 
@@ -43,20 +43,26 @@ public function evaluateAll(ClassNode $classNode): array
     {
         $violations = [];
 
-        foreach (ClassSignatures::publicTypes($classNode->file, $classNode->shortName()) as $type) {
-            if (! \str_contains($type, self::SEGMENT)) {
+        foreach ($classNode->signatures as $signature) {
+            // A privately promoted constructor param is a private property, not public surface.
+            if (! $signature->isExposed()
+                || ($signature->kind === ClassSignature::PARAM && $signature->isPromoted)
+                || ! \str_contains($signature->type, self::SEGMENT)
+            ) {
                 continue;
             }
 
             $violations[] = new RuleViolation(
                 message: \sprintf(
-                    '%s [%s] exposes internal type [%s] in its public signature',
+                    '%s [%s] exposes internal type [%s] in its public signature through %s [%s]',
                     $classNode->getType(),
                     $classNode->className,
-                    $type,
+                    $signature->type,
+                    $signature->kind,
+                    $signature->name,
                 ),
                 file: $classNode->file,
-                line: $classNode->line,
+                line: $signature->line,
                 className: $classNode->className,
                 layer: $classNode->layer,
             );
diff --git a/tools/structarmed/src/Support/ClassSignatures.php b/tools/structarmed/src/Support/ClassSignatures.php
deleted file mode 100644
index a5c01c4d..00000000
--- a/tools/structarmed/src/Support/ClassSignatures.php
+++ /dev/null
@@ -1,117 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Testo\Tools\StructArmed\Support;
-
-use PhpParser\Modifiers;
-use PhpParser\Node;
-use PhpParser\Node\IntersectionType;
-use PhpParser\Node\Name;
-use PhpParser\Node\NullableType;
-use PhpParser\Node\Stmt\ClassLike;
-use PhpParser\Node\UnionType;
-use PhpParser\NodeFinder;
-use PhpParser\NodeTraverser;
-use PhpParser\NodeVisitor\NameResolver;
-use PhpParser\ParserFactory;
-
-/**
- * Extracts the fully-qualified type names a class exposes on its public surface:
- * the parameter and return types of its public and protected methods, and the
- * types of its public and protected properties (promoted ones included).
- *
- * StructArmed's MethodNode records only counts (paramCount, hasReturnType), not
- * type names, so a signature-level rule has to read them from the AST. Names are
- * resolved to FQCN with NameResolver so callers can match against a namespace.
- * Parsed once per file and cached.
- */
-final class ClassSignatures
-{
-    /** @var array<string, array<string, list<string>>> file => short class name => FQ type names on its public surface */
-    private static array $cache = [];
-
-    /**
-     * @return list<string>
-     */
-    public static function publicTypes(string $file, string $shortName): array
-    {
-        return (self::$cache[$file] ??= self::parse($file))[$shortName] ?? [];
-    }
-
-    /**
-     * @return array<string, list<string>>
-     */
-    private static function parse(string $file): array
-    {
-        $code = @\file_get_contents($file);
-
-        if ($code === false) {
-            return [];
-        }
-
-        try {
-            $ast = (new ParserFactory())->createForNewestSupportedVersion()->parse($code) ?? [];
-
-            $traverser = new NodeTraverser(new NameResolver());
-            $ast = $traverser->traverse($ast);
-        } catch (\Throwable) {
-            return [];
-        }
-
-        $signatures = [];
-
-        foreach ((new NodeFinder())->findInstanceOf($ast, ClassLike::class) as $class) {
-            $name = $class->name?->toString();
-
-            if ($name === null) {
-                continue;
-            }
-
-            $types = [];
-
-            foreach ($class->getMethods() as $method) {
-                if ($method->isPrivate()) {
-                    continue;
-                }
-
-                foreach ($method->params as $param) {
-                    // A privately promoted constructor param is a private property, not surface.
-                    ($param->flags & Modifiers::PRIVATE) === 0 and self::collect($param->type, $types);
-                }
-
-                self::collect($method->returnType, $types);
-            }
-
-            foreach ($class->getProperties() as $property) {
-                $property->isPrivate() or self::collect($property->type, $types);
-            }
-
-            $signatures[$name] = \array_values(\array_unique($types));
-        }
-
-        return $signatures;
-    }
-
-    /**
-     * @param list<string> $types
-     */
-    private static function collect(?Node $type, array &$types): void
-    {
-        switch (true) {
-            case $type instanceof Name:
-                $types[] = $type->toString();
-                break;
-            case $type instanceof NullableType:
-                self::collect($type->type, $types);
-                break;
-            case $type instanceof UnionType:
-            case $type instanceof IntersectionType:
-                foreach ($type->types as $inner) {
-                    self::collect($inner, $types);
-                }
-                break;
-                // A plain Identifier (int, string, void, self, static, ...) carries no namespace: ignore.
-        }
-    }
-}