diff --git a/psalm.xml b/psalm.xml
index bd44196..38edc2c 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/Config.php b/src/Config.php
index 69e7c29..e866fc8 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -29,6 +29,8 @@
 final class Config
 {
     /**
+     * @psalm-mutation-free
+     *
      * @param \Closure(Clock, self): Clock $mapClock
      * @param \Closure(Halt, self): Halt $mapHalt
      * @param \Closure(HttpTransport, self): HttpTransport $mapHttpTransport
@@ -60,6 +62,7 @@ private function __construct(
     ) {
     }
 
+    #[\NoDiscard]
     public static function new(): self
     {
         return new self(
@@ -97,6 +100,7 @@ public static function new(): self
      *
      * @param callable(self): self $map
      */
+    #[\NoDiscard]
     public function map(callable $map): self
     {
         /** @psalm-suppress ImpureFunctionCall */
@@ -106,6 +110,7 @@ public function map(callable $map): self
     /**
      * @psalm-mutation-free
      */
+    #[\NoDiscard]
     public function withClock(Clock $clock): self
     {
         return new self(
@@ -133,6 +138,7 @@ public function withClock(Clock $clock): self
      *
      * @param \Closure(Clock, self): Clock $map
      */
+    #[\NoDiscard]
     public function mapClock(\Closure $map): self
     {
         $previous = $this->mapClock;
@@ -163,6 +169,7 @@ public function mapClock(\Closure $map): self
     /**
      * @psalm-mutation-free
      */
+    #[\NoDiscard]
     public function haltProcessVia(Halt $halt): self
     {
         return new self(
@@ -190,6 +197,7 @@ public function haltProcessVia(Halt $halt): self
      *
      * @param \Closure(Halt, self): Halt $map
      */
+    #[\NoDiscard]
     public function mapHalt(\Closure $map): self
     {
         $previous = $this->mapHalt;
@@ -221,6 +229,7 @@ public function mapHalt(\Closure $map): self
     /**
      * @psalm-mutation-free
      */
+    #[\NoDiscard]
     public function withIO(IO $io): self
     {
         return new self(
@@ -246,6 +255,7 @@ public function withIO(IO $io): self
     /**
      * @psalm-mutation-free
      */
+    #[\NoDiscard]
     public function withEnvironmentPath(EnvironmentPath $path): self
     {
         return new self(
@@ -271,6 +281,7 @@ public function withEnvironmentPath(EnvironmentPath $path): self
     /**
      * @psalm-mutation-free
      */
+    #[\NoDiscard]
     public function useHttpTransport(HttpTransport $transport): self
     {
         return new self(
@@ -298,6 +309,7 @@ public function useHttpTransport(HttpTransport $transport): self
      *
      * @param \Closure(HttpTransport, self): HttpTransport $map
      */
+    #[\NoDiscard]
     public function mapHttpTransport(\Closure $map): self
     {
         $previous = $this->mapHttpTransport;
@@ -330,6 +342,7 @@ public function mapHttpTransport(\Closure $map): self
      *
      * @param \Closure(Url): AccessLayer\Connection $sql
      */
+    #[\NoDiscard]
     public function openSQLConnectionVia(\Closure $sql): self
     {
         return new self(
@@ -357,6 +370,7 @@ public function openSQLConnectionVia(\Closure $sql): self
      *
      * @param \Closure(AccessLayer\Connection, self): AccessLayer\Connection $map
      */
+    #[\NoDiscard]
     public function mapSQLConnection(\Closure $map): self
     {
         $previous = $this->mapSql;
@@ -389,6 +403,7 @@ public function mapSQLConnection(\Closure $map): self
      *
      * @param \Closure(Control\Server, self): Control\Server $map
      */
+    #[\NoDiscard]
     public function mapServerControl(\Closure $map): self
     {
         $previous = $this->mapServerControl;
@@ -421,6 +436,7 @@ public function mapServerControl(\Closure $map): self
      *
      * @param \Closure(Status\Server, self): Status\Server $map
      */
+    #[\NoDiscard]
     public function mapServerStatus(\Closure $map): self
     {
         $previous = $this->mapServerStatus;
@@ -453,6 +469,7 @@ public function mapServerStatus(\Closure $map): self
      *
      * @param \Closure(Watch, self): Watch $map
      */
+    #[\NoDiscard]
     public function mapFileWatch(\Closure $map): self
     {
         $previous = $this->mapFileWatch;
@@ -485,6 +502,7 @@ public function mapFileWatch(\Closure $map): self
      *
      * @param \Closure(Path, self): Attempt<Filesystem> $filesystem
      */
+    #[\NoDiscard]
     public function mountFilesystemVia(\Closure $filesystem): self
     {
         return new self(
@@ -512,6 +530,7 @@ public function mountFilesystemVia(\Closure $filesystem): self
      *
      * @param \Closure(Filesystem, self): Filesystem $map
      */
+    #[\NoDiscard]
     public function mapFilesystem(\Closure $map): self
     {
         $previous = $this->mapFilesystem;
@@ -542,6 +561,7 @@ public function mapFilesystem(\Closure $map): self
     /**
      * @psalm-mutation-free
      */
+    #[\NoDiscard]
     public function handleSignalsVia(Handler $handler): self
     {
         return new self(
@@ -567,6 +587,7 @@ public function handleSignalsVia(Handler $handler): self
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function clock(): Clock
     {
         return ($this->mapClock)($this->clock, $this);
@@ -577,6 +598,7 @@ public function clock(): Clock
      *
      * @return Attempt<Filesystem>
      */
+    #[\NoDiscard]
     public function filesystem(Path $path): Attempt
     {
         return ($this->filesystem)($path, $this)->map(
@@ -587,6 +609,7 @@ public function filesystem(Path $path): Attempt
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function io(): IO
     {
         return $this->io;
@@ -595,6 +618,7 @@ public function io(): IO
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function halt(): Halt
     {
         return ($this->mapHalt)($this->halt, $this);
@@ -603,6 +627,7 @@ public function halt(): Halt
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function environmentPath(): EnvironmentPath
     {
         return $this->path;
@@ -611,6 +636,7 @@ public function environmentPath(): EnvironmentPath
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function httpTransport(): HttpTransport
     {
         $transport = $this->httpTransport ?? Curl::of(
@@ -624,6 +650,7 @@ public function httpTransport(): HttpTransport
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function sql(Url $url): AccessLayer\Connection
     {
         return ($this->mapSql)(
@@ -635,6 +662,7 @@ public function sql(Url $url): AccessLayer\Connection
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function serverControl(Control\Server $server): Control\Server
     {
         return ($this->mapServerControl)($server, $this);
@@ -643,6 +671,7 @@ public function serverControl(Control\Server $server): Control\Server
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function serverStatus(Status\Server $server): Status\Server
     {
         return ($this->mapServerStatus)($server, $this);
@@ -651,6 +680,7 @@ public function serverStatus(Status\Server $server): Status\Server
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function fileWatch(Watch $watch): Watch
     {
         return ($this->mapFileWatch)($watch, $this);
@@ -659,6 +689,7 @@ public function fileWatch(Watch $watch): Watch
     /**
      * @internal
      */
+    #[\NoDiscard]
     public function signalsHandler(): Handler
     {
         return $this->signals;
diff --git a/src/Config/Logger.php b/src/Config/Logger.php
index 56dcdc2..fb7d2a4 100644
--- a/src/Config/Logger.php
+++ b/src/Config/Logger.php
@@ -14,6 +14,9 @@
 use Formal\AccessLayer\Connection;
 use Psr\Log\LoggerInterface;
 
+/**
+ * @psalm-immutable
+ */
 final class Logger
 {
     private function __construct(
@@ -21,6 +24,7 @@ private function __construct(
     ) {
     }
 
+    #[\NoDiscard]
     public function __invoke(Config $config): Config
     {
         return $config
@@ -55,6 +59,10 @@ public function __invoke(Config $config): Config
             ));
     }
 
+    /**
+     * @psalm-pure
+     */
+    #[\NoDiscard]
     public static function psr(LoggerInterface $logger): self
     {
         return new self($logger);
diff --git a/src/Config/Resilient.php b/src/Config/Resilient.php
index dd04ba6..3f44206 100644
--- a/src/Config/Resilient.php
+++ b/src/Config/Resilient.php
@@ -6,10 +6,14 @@
 use Innmind\OperatingSystem\Config;
 use Innmind\HttpTransport\ExponentialBackoff;
 
+/**
+ * @psalm-immutable
+ */
 enum Resilient
 {
     case instance;
 
+    #[\NoDiscard]
     public function __invoke(Config $config): Config
     {
         return $config
@@ -21,7 +25,10 @@ public function __invoke(Config $config): Config
 
     /**
      * This config helps retry certain _safe_ operations on remote systems
+     *
+     * @psalm-pure
      */
+    #[\NoDiscard]
     public static function new(): self
     {
         return self::instance;
diff --git a/src/CurrentProcess.php b/src/CurrentProcess.php
index eb3a433..e30d96c 100644
--- a/src/CurrentProcess.php
+++ b/src/CurrentProcess.php
@@ -29,6 +29,7 @@ private function __construct(Halt $halt, Handler $handler)
     /**
      * @internal
      */
+    #[\NoDiscard]
     public static function of(Halt $halt, Handler $handler): self
     {
         return new self($halt, $handler);
@@ -37,6 +38,7 @@ public static function of(Halt $halt, Handler $handler): self
     /**
      * @return Attempt<Pid>
      */
+    #[\NoDiscard]
     public function id(): Attempt
     {
         $pid = \getmypid();
@@ -48,6 +50,7 @@ public function id(): Attempt
         };
     }
 
+    #[\NoDiscard]
     public function signals(): Signals
     {
         return $this->signals ??= Signals::of($this->handler);
@@ -56,11 +59,13 @@ public function signals(): Signals
     /**
      * @return Attempt<SideEffect>
      */
+    #[\NoDiscard]
     public function halt(Period $period): Attempt
     {
         return ($this->halt)($period);
     }
 
+    #[\NoDiscard]
     public function memory(): Bytes
     {
         /** @psalm-suppress ArgumentTypeCoercion */
diff --git a/src/Factory.php b/src/Factory.php
index ee9cc5a..e67a1a9 100644
--- a/src/Factory.php
+++ b/src/Factory.php
@@ -5,6 +5,7 @@
 
 final class Factory
 {
+    #[\NoDiscard]
     public static function build(?Config $config = null): OperatingSystem
     {
         switch (\PHP_OS) {
diff --git a/src/Filesystem.php b/src/Filesystem.php
index 8426b11..4454165 100644
--- a/src/Filesystem.php
+++ b/src/Filesystem.php
@@ -41,6 +41,7 @@ private function __construct(Processes $processes, Config $config)
     /**
      * @internal
      */
+    #[\NoDiscard]
     public static function of(Processes $processes, Config $config): self
     {
         return new self($processes, $config);
@@ -49,6 +50,7 @@ public static function of(Processes $processes, Config $config): self
     /**
      * @return Attempt<Adapter>
      */
+    #[\NoDiscard]
     public function mount(Path $path): Attempt
     {
         /**
@@ -71,6 +73,7 @@ public function mount(Path $path): Attempt
             });
     }
 
+    #[\NoDiscard]
     public function contains(Path $path): bool
     {
         if (!\file_exists($path->toString())) {
@@ -87,6 +90,7 @@ public function contains(Path $path): bool
     /**
      * @return Maybe<mixed> Return the value returned by the file or nothing if the file doesn't exist
      */
+    #[\NoDiscard]
     public function require(Path $path): Maybe
     {
         $path = $path->toString();
@@ -104,6 +108,7 @@ public function require(Path $path): Maybe
         return Maybe::just(require $path);
     }
 
+    #[\NoDiscard]
     public function watch(Path $path): Ping
     {
         return ($this->watch)($path);
@@ -121,6 +126,7 @@ public function watch(Path $path): Ping
      *
      * @return Attempt<Content>
      */
+    #[\NoDiscard]
     public function temporary(Sequence $chunks): Attempt
     {
         return $this
diff --git a/src/OperatingSystem.php b/src/OperatingSystem.php
index a9ebd2a..e99877c 100644
--- a/src/OperatingSystem.php
+++ b/src/OperatingSystem.php
@@ -29,6 +29,7 @@ private function __construct(Config $config)
         $this->config = $config;
     }
 
+    #[\NoDiscard]
     public static function new(?Config $config = null): self
     {
         return new self($config ?? Config::new());
@@ -40,16 +41,19 @@ public static function new(?Config $config = null): self
      *
      * @param callable(Config): Config $map
      */
+    #[\NoDiscard]
     public function map(callable $map): self
     {
         return new self($map($this->config));
     }
 
+    #[\NoDiscard]
     public function clock(): Clock
     {
         return $this->config->clock();
     }
 
+    #[\NoDiscard]
     public function filesystem(): Filesystem
     {
         return $this->filesystem ??= Filesystem::of(
@@ -58,6 +62,7 @@ public function filesystem(): Filesystem
         );
     }
 
+    #[\NoDiscard]
     public function status(): ServerStatus
     {
         return $this->status ??= $this->config->serverStatus(
@@ -69,6 +74,7 @@ public function status(): ServerStatus
         );
     }
 
+    #[\NoDiscard]
     public function control(): ServerControl
     {
         return $this->control ??= $this->config->serverControl(
@@ -80,16 +86,19 @@ public function control(): ServerControl
         );
     }
 
+    #[\NoDiscard]
     public function ports(): Ports
     {
         return $this->ports ??= Ports::of($this->config);
     }
 
+    #[\NoDiscard]
     public function sockets(): Sockets
     {
         return $this->sockets ??= Sockets::of($this->config);
     }
 
+    #[\NoDiscard]
     public function remote(): Remote
     {
         return $this->remote ??= Remote::of(
@@ -98,6 +107,7 @@ public function remote(): Remote
         );
     }
 
+    #[\NoDiscard]
     public function process(): CurrentProcess
     {
         return $this->process ??= CurrentProcess::of(
diff --git a/src/Ports.php b/src/Ports.php
index 5794216..a938968 100644
--- a/src/Ports.php
+++ b/src/Ports.php
@@ -23,6 +23,7 @@ private function __construct(Config $config)
     /**
      * @internal
      */
+    #[\NoDiscard]
     public static function of(Config $config): self
     {
         return new self($config);
@@ -31,6 +32,7 @@ public static function of(Config $config): self
     /**
      * @return Attempt<Server>
      */
+    #[\NoDiscard]
     public function open(Transport $transport, IP $ip, Port $port): Attempt
     {
         return $this
diff --git a/src/Remote.php b/src/Remote.php
index e20ef77..fee3f57 100644
--- a/src/Remote.php
+++ b/src/Remote.php
@@ -35,11 +35,13 @@ private function __construct(Server $server, Config $config)
     /**
      * @internal
      */
+    #[\NoDiscard]
     public static function of(Server $server, Config $config): self
     {
         return new self($server, $config);
     }
 
+    #[\NoDiscard]
     public function ssh(Url $server): Server
     {
         $port = null;
@@ -61,6 +63,7 @@ public function ssh(Url $server): Server
     /**
      * @return Attempt<Client>
      */
+    #[\NoDiscard]
     public function socket(Transport $transport, Authority $authority): Attempt
     {
         return $this
@@ -71,11 +74,13 @@ public function socket(Transport $transport, Authority $authority): Attempt
             ->internet($transport, $authority);
     }
 
+    #[\NoDiscard]
     public function http(): HttpTransport
     {
         return $this->http ??= $this->config->httpTransport();
     }
 
+    #[\NoDiscard]
     public function sql(Url $server): Connection
     {
         return $this->config->sql($server);
diff --git a/src/Sockets.php b/src/Sockets.php
index a743622..abaadce 100644
--- a/src/Sockets.php
+++ b/src/Sockets.php
@@ -22,6 +22,7 @@ private function __construct(Config $config)
     /**
      * @internal
      */
+    #[\NoDiscard]
     public static function of(Config $config): self
     {
         return new self($config);
@@ -32,6 +33,7 @@ public static function of(Config $config): self
      *
      * @return Attempt<Server>
      */
+    #[\NoDiscard]
     public function open(Address $address): Attempt
     {
         return $this
@@ -47,6 +49,7 @@ public function open(Address $address): Attempt
      *
      * @return Attempt<Server>
      */
+    #[\NoDiscard]
     public function takeOver(Address $address): Attempt
     {
         return $this
@@ -60,6 +63,7 @@ public function takeOver(Address $address): Attempt
     /**
      * @return Attempt<Client>
      */
+    #[\NoDiscard]
     public function connectTo(Address $address): Attempt
     {
         return $this