diff --git a/composer.json b/composer.json
index 366f417..2e61259 100644
--- a/composer.json
+++ b/composer.json
@@ -16,15 +16,15 @@
   },
   "require": {
     "php": "^8.4.0",
-    "symfony/yaml": "^6 || ^7",
+    "symfony/yaml": "^7.4.12 || ^8.0.12",
     "devizzent/cebe-php-openapi": "^1.1.5"
   },
   "require-dev": {
-    "phpunit/phpunit": "^12.5.11",
-    "phpstan/phpstan": "^1.12.33",
+    "phpunit/phpunit": "^13.1.11",
+    "phpstan/phpstan": "^2.1.55",
     "squizlabs/php_codesniffer": "^4.0.1",
     "mikey179/vfsstream": "^v1.6.12",
-    "infection/infection": "^0.32.6"
+    "infection/infection": "^0.33.2"
   },
   "config": {
     "allow-plugins": {
diff --git a/src/CebeReader.php b/src/CebeReader.php
index 086f5a1..bb8dcb0 100644
--- a/src/CebeReader.php
+++ b/src/CebeReader.php
@@ -20,6 +20,7 @@ public function __construct(
         if (empty($this->supportedVersions)) {
             throw CannotSupport::noSupportedVersions();
         }
+        /** @phpstan-ignore-next-line this enforces the constructor type hint*/
         (fn (OpenAPIVersion ...$versions) => null)(...$this->supportedVersions);
     }
 
diff --git a/src/ValueObject/Valid/V30/Keywords.php b/src/ValueObject/Valid/V30/Keywords.php
index 27fc3e4..d80306a 100644
--- a/src/ValueObject/Valid/V30/Keywords.php
+++ b/src/ValueObject/Valid/V30/Keywords.php
@@ -135,7 +135,7 @@ public function __construct(
         }
     }
 
-    /** @return string[] */
+    /** @return list<string> */
     public function typesItCanBe(): array
     {
         $possibilities = [array_merge(
@@ -179,10 +179,6 @@ private function validateTypes(
         null|string|array $type,
         bool $nullable,
     ): array {
-        if (isset($this->types)) {
-            return $this->types;
-        }
-
         if (empty($type)) { // If type is unspecified, nullable has no effect
             return []; // So we can return immediately
         }
@@ -207,12 +203,12 @@ private function validateTypes(
             $result[] = Type::Null;
         }
 
-        return $result;
+        return array_values($result);
     }
 
     /**
      * @param list<Type> $types
-     * @param list<Value>|null $enum
+     * @param array<Value>|null $enum
      * @return non-empty-list<Value>
      */
     private function reviewEnum(
@@ -382,7 +378,7 @@ private function validateRequired(array | null $required): array
             $this->addWarning('required must not contain duplicates', Warning::INVALID);
         }
 
-        return $uniqueRequired;
+        return array_values($uniqueRequired);
     }
 
     /**
diff --git a/src/ValueObject/Valid/V30/OpenAPI.php b/src/ValueObject/Valid/V30/OpenAPI.php
index 7bd40c0..e7ea4ef 100644
--- a/src/ValueObject/Valid/V30/OpenAPI.php
+++ b/src/ValueObject/Valid/V30/OpenAPI.php
@@ -13,7 +13,7 @@
 final class OpenAPI extends Validated
 {
     /**
-     * @param array<int, Server> $servers
+     * @param list<Server> $servers
      * Optional, may be left empty.
      * If empty or unspecified, the array will contain the default Server.
      * The default Server has "url" === "/" and no "variables"
@@ -62,7 +62,7 @@ public static function fromPartial(Partial\OpenAPI $openAPI): self
 
     /**
      * @param Partial\Server[] $servers
-     * @return array<int,Server>
+     * @return list<Server>
      */
     private static function validateServers(
         Identifier $identifier,
@@ -93,7 +93,7 @@ private function reviewServers(array $servers): void
     }
 
     /**
-     * @param Server[] $servers
+     * @param list<Server> $servers
      * @param null|Partial\PathItem[] $pathItems
      * @return array<string,PathItem>
      */
diff --git a/src/ValueObject/Valid/V30/Operation.php b/src/ValueObject/Valid/V30/Operation.php
index b424f56..125189e 100644
--- a/src/ValueObject/Valid/V30/Operation.php
+++ b/src/ValueObject/Valid/V30/Operation.php
@@ -16,7 +16,7 @@
 final class Operation extends Validated
 {
     /**
-     * @param array<int,Server> $servers
+     * @param list<Server> $servers
      * Optional, may be left empty.
      * If empty or unspecified, the array will contain the Path level servers
      *
@@ -57,7 +57,7 @@ public function withoutServers(): Operation
     }
 
     /**
-     * @param Server[] $pathServers
+     * @param list<Server> $pathServers
      * @param Parameter[] $pathParameters
      */
     public static function fromPartial(
@@ -104,9 +104,9 @@ public static function fromPartial(
     }
 
     /**
-     * @param array<int,Server> $pathServers
+     * @param list<Server> $pathServers
      * @param Partial\Server[] $operationServers
-     * @return array<int,Server>>
+     * @return list<Server>
      */
     private static function validateServers(
         Identifier $identifier,
diff --git a/src/ValueObject/Valid/V30/PathItem.php b/src/ValueObject/Valid/V30/PathItem.php
index bbc504a..239f339 100644
--- a/src/ValueObject/Valid/V30/PathItem.php
+++ b/src/ValueObject/Valid/V30/PathItem.php
@@ -14,7 +14,7 @@
 final class PathItem extends Validated
 {
     /**
-     * @param array<int,Server> $servers
+     * @param list<Server> $servers
      *
      * @param  array<int,Parameter> $parameters
      * The list MUST NOT include duplicated parameters.
@@ -62,7 +62,7 @@ public function withoutServers(): PathItem
     }
 
     /**
-     * @param array<int,Server> $openAPIServers
+     * @param list<Server> $openAPIServers
      * If the pathItem does not contain servers, this will be used instead
      */
     public static function fromPartial(
@@ -168,7 +168,7 @@ public function getOperations(): array
     /**
      * @param array<int,Server> $openAPIServers
      * @param Partial\Server[] $pathServers
-     * @return array<int,Server>>
+     * @return list<Server>
      */
     private static function validateServers(
         Identifier $identifier,
@@ -176,7 +176,7 @@ private static function validateServers(
         array $pathServers
     ): array {
         if (empty($pathServers)) {
-            return $openAPIServers;
+            return array_values($openAPIServers);
         }
 
         return array_values(array_map(
@@ -249,7 +249,7 @@ private function reviewParameters(array $parameters): void
     }
 
     /**
-     * @param Server[] $servers
+     * @param list<Server> $servers
      * @param Parameter[] $parameters
      */
     private static function validateOperation(
diff --git a/src/ValueObject/Valid/V30/Schema.php b/src/ValueObject/Valid/V30/Schema.php
index f6a2b38..fbeb652 100644
--- a/src/ValueObject/Valid/V30/Schema.php
+++ b/src/ValueObject/Valid/V30/Schema.php
@@ -65,10 +65,10 @@ public function canBePrimitive(): bool
     public function typesItCanBe(): array
     {
         if ($this->value === true) {
-            return [
+            return array_values([
                 Type::Null->value,
                 ...Type::valuesForVersion(OpenAPIVersion::Version_3_0),
-            ];
+            ]);
         } elseif ($this->value === false) {
             return [];
         } else {
diff --git a/src/ValueObject/Valid/V30/ServerVariable.php b/src/ValueObject/Valid/V30/ServerVariable.php
index 91707d8..d70868b 100644
--- a/src/ValueObject/Valid/V30/ServerVariable.php
+++ b/src/ValueObject/Valid/V30/ServerVariable.php
@@ -51,6 +51,8 @@ public function __construct(
             }
         }
 
-        $this->enum = $serverVariable->enum;
+        $this->enum = isset($serverVariable->enum)
+            ? array_values($serverVariable->enum)
+            : null;
     }
 }
diff --git a/src/ValueObject/Valid/V31/Keywords.php b/src/ValueObject/Valid/V31/Keywords.php
index d1691c2..4cbefc9 100644
--- a/src/ValueObject/Valid/V31/Keywords.php
+++ b/src/ValueObject/Valid/V31/Keywords.php
@@ -125,7 +125,7 @@ public function __construct(
         }
     }
 
-    /** @return string[] */
+    /** @return list<string> */
     public function typesItCanBe(): array
     {
         $possibilities = [array_merge(
@@ -175,16 +175,16 @@ private function validateTypes(null|string|array $type): array
             $type = [$type];
         }
 
-        return array_map(
+        return array_values(array_map(
             fn($t) => Type::tryFromVersion(OpenAPIVersion::Version_3_1, $t)
                 ?? throw InvalidOpenAPI::invalidType($this->getIdentifier(), $t),
             $type,
-        );
+        ));
     }
 
     /**
      * @param list<Type> $types
-     * @param list<Value>|null $enum
+     * @param array<Value>|null $enum
      * @return non-empty-list<Value>|null
      */
     private function reviewEnum(
@@ -404,7 +404,7 @@ private function validateRequired(array | null $required): array
             $this->addWarning('required must not contain duplicates', Warning::INVALID);
         }
 
-        return $uniqueRequired;
+        return array_values($uniqueRequired);
     }
 
     /**
diff --git a/src/ValueObject/Valid/V31/OpenAPI.php b/src/ValueObject/Valid/V31/OpenAPI.php
index 30ba580..78268e5 100644
--- a/src/ValueObject/Valid/V31/OpenAPI.php
+++ b/src/ValueObject/Valid/V31/OpenAPI.php
@@ -13,7 +13,7 @@
 final class OpenAPI extends Validated
 {
     /**
-     * @param array<int, Server> $servers
+     * @param list<Server> $servers
      * Optional, may be left empty.
      * If empty or unspecified, the array will contain the default Server.
      * The default Server has "url" === "/" and no "variables"
@@ -62,7 +62,7 @@ public static function fromPartial(Partial\OpenAPI $openAPI): self
 
     /**
      * @param Partial\Server[] $servers
-     * @return array<int,Server>
+     * @return list<Server>
      */
     private static function validateServers(
         Identifier $identifier,
diff --git a/src/ValueObject/Valid/V31/Operation.php b/src/ValueObject/Valid/V31/Operation.php
index a733870..10020ac 100644
--- a/src/ValueObject/Valid/V31/Operation.php
+++ b/src/ValueObject/Valid/V31/Operation.php
@@ -16,7 +16,7 @@
 final class Operation extends Validated
 {
     /**
-     * @param array<int,Server> $servers
+     * @param list<Server> $servers
      * Optional, may be left empty.
      * If empty or unspecified, the array will contain the Path level servers
      *
@@ -106,7 +106,7 @@ public static function fromPartial(
     /**
      * @param array<int,Server> $pathServers
      * @param Partial\Server[] $operationServers
-     * @return array<int,Server>>
+     * @return list<Server>
      */
     private static function validateServers(
         Identifier $identifier,
@@ -114,7 +114,7 @@ private static function validateServers(
         array $operationServers
     ): array {
         if (empty($operationServers)) {
-            return $pathServers;
+            return array_values($pathServers);
         }
 
         $result = array_values(array_map(
diff --git a/src/ValueObject/Valid/V31/PathItem.php b/src/ValueObject/Valid/V31/PathItem.php
index e39e8db..e2d3f80 100644
--- a/src/ValueObject/Valid/V31/PathItem.php
+++ b/src/ValueObject/Valid/V31/PathItem.php
@@ -14,7 +14,7 @@
 final class PathItem extends Validated
 {
     /**
-     * @param array<int,Server> $servers
+     * @param list<Server> $servers
      *
      * @param  array<int,Parameter> $parameters
      * The list MUST NOT include duplicated parameters.
@@ -168,7 +168,7 @@ public function getOperations(): array
     /**
      * @param array<int,Server> $openAPIServers
      * @param Partial\Server[] $pathServers
-     * @return array<int,Server>>
+     * @return list<Server>
      */
     private static function validateServers(
         Identifier $identifier,
@@ -176,7 +176,7 @@ private static function validateServers(
         array $pathServers
     ): array {
         if (empty($pathServers)) {
-            return $openAPIServers;
+            return array_values($openAPIServers);
         }
 
         return array_values(array_map(
diff --git a/src/ValueObject/Valid/V31/Schema.php b/src/ValueObject/Valid/V31/Schema.php
index ccc41ab..06d150c 100644
--- a/src/ValueObject/Valid/V31/Schema.php
+++ b/src/ValueObject/Valid/V31/Schema.php
@@ -65,10 +65,10 @@ public function canBePrimitive(): bool
     public function typesItCanBe(): array
     {
         if ($this->value === true) {
-            return [
+            return array_values([
                 Type::Null->value,
                 ...Type::valuesForVersion(OpenAPIVersion::Version_3_0),
-            ];
+            ]);
         } elseif ($this->value === false) {
             return [];
         } else {
diff --git a/src/ValueObject/Valid/V31/ServerVariable.php b/src/ValueObject/Valid/V31/ServerVariable.php
index 424aa01..8bf3880 100644
--- a/src/ValueObject/Valid/V31/ServerVariable.php
+++ b/src/ValueObject/Valid/V31/ServerVariable.php
@@ -51,6 +51,6 @@ public function __construct(
             }
         }
 
-        $this->enum = $serverVariable->enum;
+        $this->enum = array_values($serverVariable->enum ?? []);
     }
 }