diff --git a/psalm.xml b/psalm.xml
index 510148d..feccc34 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -14,4 +14,7 @@
             <directory name="vendor" />
         </ignoreFiles>
     </projectFiles>
+    <issueHandlers>
+        <UndefinedAttributeClass errorLevel="suppress" />
+    </issueHandlers>
 </psalm>
diff --git a/src/Manager.php b/src/Manager.php
index fee4b87..7774cf0 100644
--- a/src/Manager.php
+++ b/src/Manager.php
@@ -14,15 +14,18 @@ interface Manager
     /**
      * @return Maybe<Session>
      */
+    #[\NoDiscard]
     public function start(ServerRequest $request): Maybe;
 
     /**
      * @return Maybe<SideEffect>
      */
+    #[\NoDiscard]
     public function save(Session $session): Maybe;
 
     /**
      * @return Maybe<SideEffect>
      */
+    #[\NoDiscard]
     public function close(Session $session): Maybe;
 }
diff --git a/src/Manager/Native.php b/src/Manager/Native.php
index 57e15d1..b379af2 100644
--- a/src/Manager/Native.php
+++ b/src/Manager/Native.php
@@ -32,6 +32,7 @@ private function __construct(?Path $save = null)
         }
     }
 
+    #[\NoDiscard]
     public static function of(?Path $save = null): self
     {
         return new self($save);
diff --git a/src/Session.php b/src/Session.php
index e221d04..302a812 100644
--- a/src/Session.php
+++ b/src/Session.php
@@ -38,16 +38,19 @@ private function __construct(Id $id, Name $name, Map $values)
      *
      * @param Map<string, mixed> $values
      */
+    #[\NoDiscard]
     public static function of(Id $id, Name $name, Map $values): self
     {
         return new self($id, $name, $values);
     }
 
+    #[\NoDiscard]
     public function id(): Id
     {
         return $this->id;
     }
 
+    #[\NoDiscard]
     public function name(): Name
     {
         return $this->name;
@@ -58,6 +61,7 @@ public function name(): Name
      *
      * @throws LogicException
      */
+    #[\NoDiscard]
     public function get(string $key): mixed
     {
         return $this->maybe($key)->match(
@@ -69,16 +73,19 @@ public function get(string $key): mixed
     /**
      * @return Maybe<mixed>
      */
+    #[\NoDiscard]
     public function maybe(string $key): Maybe
     {
         return $this->values->get($key);
     }
 
+    #[\NoDiscard]
     public function contains(string $key): bool
     {
         return $this->values->contains($key);
     }
 
+    #[\NoDiscard]
     public function with(string $key, mixed $value): self
     {
         return new self(
@@ -95,6 +102,7 @@ public function with(string $key, mixed $value): self
      *
      * @return Map<string, mixed>
      */
+    #[\NoDiscard]
     public function values(): Map
     {
         return $this->values;
diff --git a/src/Session/Id.php b/src/Session/Id.php
index 9da2d6b..c3e6cfd 100644
--- a/src/Session/Id.php
+++ b/src/Session/Id.php
@@ -25,6 +25,7 @@ private function __construct(string $value)
      *
      * @return Maybe<self>
      */
+    #[\NoDiscard]
     public static function maybe(string $value): Maybe
     {
         return Maybe::just(Str::of($value))
@@ -32,6 +33,7 @@ public static function maybe(string $value): Maybe
             ->map(static fn($value) => new self($value->toString()));
     }
 
+    #[\NoDiscard]
     public function toString(): string
     {
         return $this->value;
diff --git a/src/Session/Name.php b/src/Session/Name.php
index 19b6569..4067c26 100644
--- a/src/Session/Name.php
+++ b/src/Session/Name.php
@@ -26,6 +26,7 @@ private function __construct(string $value)
      *
      * @return Maybe<self>
      */
+    #[\NoDiscard]
     public static function maybe(string $value): Maybe
     {
         return Maybe::just(Str::of($value))
@@ -33,6 +34,7 @@ public static function maybe(string $value): Maybe
             ->map(static fn($value) => new self($value->toString()));
     }
 
+    #[\NoDiscard]
     public function toString(): string
     {
         return $this->value;