diff --git a/Neos.Flow/Classes/Http/ContentStream.php b/Neos.Flow/Classes/Http/ContentStream.php
index b502c8da61..2f3b333d20 100644
--- a/Neos.Flow/Classes/Http/ContentStream.php
+++ b/Neos.Flow/Classes/Http/ContentStream.php
@@ -69,7 +69,7 @@ public static function fromContents(string $contents): self
      *
      * @return void
      */
-    public function close()
+    public function close(): void
     {
         if (!$this->resource) {
             return;
@@ -119,7 +119,7 @@ public function replace($stream, $mode = 'r')
      *
      * @return int|null Returns the size in bytes if known, or null if unknown.
      */
-    public function getSize()
+    public function getSize(): ?int
     {
         if (!$this->isValidResource($this->resource)) {
             return null;
@@ -136,7 +136,7 @@ public function getSize()
      * @return int Position of the file pointer
      * @throws \RuntimeException on error.
      */
-    public function tell()
+    public function tell(): int
     {
         $this->ensureResourceOpen();
 
@@ -153,7 +153,7 @@ public function tell()
      *
      * @return bool
      */
-    public function eof()
+    public function eof(): bool
     {
         if (!$this->isValidResource($this->resource)) {
             return true;
@@ -167,7 +167,7 @@ public function eof()
      *
      * @return bool
      */
-    public function isSeekable()
+    public function isSeekable(): bool
     {
         if (!$this->isValidResource($this->resource)) {
             return false;
@@ -188,10 +188,9 @@ public function isSeekable()
      *     PHP $whence values for `fseek()`.  SEEK_SET: Set position equal to
      *     offset bytes SEEK_CUR: Set position to current location plus offset
      *     SEEK_END: Set position to end-of-stream plus offset.
-     * @return bool
      * @throws \RuntimeException on failure.
      */
-    public function seek($offset, $whence = SEEK_SET)
+    public function seek($offset, $whence = SEEK_SET): void
     {
         $this->ensureResourceOpen();
 
@@ -205,7 +204,7 @@ public function seek($offset, $whence = SEEK_SET)
             throw new \RuntimeException('Error seeking within stream', 1453892231);
         }
 
-        return true;
+        return;
     }
 
     /**
@@ -218,9 +217,9 @@ public function seek($offset, $whence = SEEK_SET)
      * @link http://www.php.net/manual/en/function.fseek.php
      * @throws \RuntimeException on failure.
      */
-    public function rewind()
+    public function rewind(): void
     {
-        return $this->seek(0);
+        $this->seek(0);
     }
 
     /**
@@ -228,7 +227,7 @@ public function rewind()
      *
      * @return bool
      */
-    public function isWritable()
+    public function isWritable(): bool
     {
         if (!$this->isValidResource($this->resource)) {
             return false;
@@ -253,7 +252,7 @@ public function isWritable()
      * @return int Returns the number of bytes written to the stream.
      * @throws \RuntimeException on failure.
      */
-    public function write($string)
+    public function write($string): int
     {
         if (!$this->isWritable()) {
             throw new \RuntimeException('Stream is not writable', 1453892241);
@@ -273,7 +272,7 @@ public function write($string)
      *
      * @return bool
      */
-    public function isReadable()
+    public function isReadable(): bool
     {
         if (!$this->isValidResource($this->resource)) {
             return false;
@@ -295,7 +294,7 @@ public function isReadable()
      *     if no bytes are available.
      * @throws \RuntimeException if an error occurs.
      */
-    public function read($length)
+    public function read($length): string
     {
         $this->ensureResourceReadable();
 
@@ -315,7 +314,7 @@ public function read($length)
      * @throws \RuntimeException if unable to read or an error occurs while
      *     reading.
      */
-    public function getContents()
+    public function getContents(): string
     {
         $this->ensureResourceReadable();
 
@@ -334,12 +333,12 @@ public function getContents()
      * stream_get_meta_data() function.
      *
      * @link http://php.net/manual/en/function.stream-get-meta-data.php
-     * @param string $key Specific metadata to retrieve.
+     * @param string|null $key Specific metadata to retrieve.
      * @return array|mixed|null Returns an associative array if no key is
      *     provided. Returns a specific key value if a key is provided and the
      *     value is found, or null if the key is not found.
      */
-    public function getMetadata($key = null)
+    public function getMetadata(?string $key = null)
     {
         if ($key === null) {
             return stream_get_meta_data($this->resource);
@@ -395,7 +394,7 @@ protected function isValidResource($resource)
      * @see http://php.net/manual/en/language.oop5.magic.php#object.tostring
      * @return string
      */
-    public function __toString()
+    public function __toString(): string
     {
         if (!$this->isReadable()) {
             return '';
diff --git a/Neos.Flow/Classes/Http/UploadedFile.php b/Neos.Flow/Classes/Http/UploadedFile.php
index 90d9139dff..e97b9fa6ca 100644
--- a/Neos.Flow/Classes/Http/UploadedFile.php
+++ b/Neos.Flow/Classes/Http/UploadedFile.php
@@ -127,7 +127,7 @@ public function isMoved()
      * @throws RuntimeException if the upload was not successful.
      * @api PSR-7
      */
-    public function getStream()
+    public function getStream(): StreamInterface
     {
         $this->throwExceptionIfNotAccessible();
 
@@ -172,7 +172,7 @@ public function getStream()
      *     the second or subsequent call to the method.
      * @api PSR-7
      */
-    public function moveTo($targetPath)
+    public function moveTo($targetPath): void
     {
         $this->throwExceptionIfNotAccessible();
 
@@ -203,7 +203,7 @@ public function moveTo($targetPath)
      * @return int|null The file size in bytes or null if unknown.
      * @api PSR-7
      */
-    public function getSize()
+    public function getSize(): ?int
     {
         return $this->size;
     }
@@ -223,7 +223,7 @@ public function getSize()
      * @return int One of PHP's UPLOAD_ERR_XXX constants.
      * @api PSR-7
      */
-    public function getError()
+    public function getError(): int
     {
         return $this->error;
     }
@@ -242,7 +242,7 @@ public function getError()
      *     was provided.
      * @api PSR-7
      */
-    public function getClientFilename()
+    public function getClientFilename(): ?string
     {
         return $this->clientFilename;
     }
@@ -259,7 +259,7 @@ public function getClientFilename()
      *
      * @api PSR-7
      */
-    public function getClientMediaType()
+    public function getClientMediaType(): ?string
     {
         return $this->clientMediaType;
     }
diff --git a/Neos.Flow/Classes/ObjectManagement/ObjectManager.php b/Neos.Flow/Classes/ObjectManagement/ObjectManager.php
index 6a03f2c458..2c6d8dc859 100644
--- a/Neos.Flow/Classes/ObjectManagement/ObjectManager.php
+++ b/Neos.Flow/Classes/ObjectManagement/ObjectManager.php
@@ -164,7 +164,7 @@ public function isRegistered($objectName): bool
      * @param string $objectName
      * @return bool
      */
-    public function has($objectName): bool
+    public function has(string $objectName): bool
     {
         return $this->isRegistered($objectName);
     }
@@ -200,7 +200,7 @@ public function registerShutdownObject($object, $shutdownLifecycleMethodName): v
      * @throws InvalidConfigurationTypeException
      * @api
      */
-    public function get($objectName, ...$constructorArguments): object
+    public function get(string $objectName, ...$constructorArguments): object
     {
         if (!empty($constructorArguments) && isset($this->objects[$objectName]) && $this->objects[$objectName][self::KEY_SCOPE] !== ObjectConfiguration::SCOPE_PROTOTYPE) {
             throw new \InvalidArgumentException('You cannot provide constructor arguments for singleton objects via get(). If you need to pass arguments to the constructor, define them in the Objects.yaml configuration.', 1298049934);
diff --git a/Neos.Flow/Classes/ObjectManagement/ObjectManagerInterface.php b/Neos.Flow/Classes/ObjectManagement/ObjectManagerInterface.php
index c3ce693c72..a5d4695486 100644
--- a/Neos.Flow/Classes/ObjectManagement/ObjectManagerInterface.php
+++ b/Neos.Flow/Classes/ObjectManagement/ObjectManagerInterface.php
@@ -50,7 +50,7 @@ public function getContext();
      * @return T The object instance
      * @api
      */
-    public function get($objectName, ...$constructorArguments);
+    public function get(string $objectName, ...$constructorArguments);
 
     /**
      * This is the PSR-11 ContainerInterface equivalent to `isRegistered`.
@@ -59,7 +59,7 @@ public function get($objectName, ...$constructorArguments);
      * @return bool
      * @see isRegistered
      */
-    public function has($objectName);
+    public function has(string $objectName): bool;
 
     /**
      * Returns true if an object with the given name has already
diff --git a/Neos.Flow/Tests/Unit/Validation/Validator/FileSizeValidatorTest.php b/Neos.Flow/Tests/Unit/Validation/Validator/FileSizeValidatorTest.php
index 63022859ea..5798d64351 100644
--- a/Neos.Flow/Tests/Unit/Validation/Validator/FileSizeValidatorTest.php
+++ b/Neos.Flow/Tests/Unit/Validation/Validator/FileSizeValidatorTest.php
@@ -38,7 +38,7 @@ protected function createResourceMetaDataInterfaceMock(int $filesize): ResourceM
         return $mock;
     }
 
-    protected function createUploadedFileInterfaceMock(string $filesize): UploadedFileInterface
+    protected function createUploadedFileInterfaceMock(int $filesize): UploadedFileInterface
     {
         $mock = $this->createMock(UploadedFileInterface::class);
         $mock->expects($this->once())->method('getSize')->willReturn($filesize);
diff --git a/Neos.Flow/composer.json b/Neos.Flow/composer.json
index 1f3ada347a..55462e8017 100644
--- a/Neos.Flow/composer.json
+++ b/Neos.Flow/composer.json
@@ -31,9 +31,9 @@
 
         "neos/composer-plugin": "^2.0",
 
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^2.0",
         "psr/http-factory": "^1.0",
-        "psr/container": "^1.0",
+        "psr/container": "^2.0",
         "psr/log": "^2.0 || ^3.0",
         "psr/http-server-middleware": "^1.0",
         "psr/http-server-handler": "^1.0",
diff --git a/Neos.Http.Factories/composer.json b/Neos.Http.Factories/composer.json
index 0b700ddd6a..8504929892 100644
--- a/Neos.Http.Factories/composer.json
+++ b/Neos.Http.Factories/composer.json
@@ -8,7 +8,7 @@
     ],
     "require": {
         "php": "^8.2",
-        "psr/http-factory": "^1.0",
+        "psr/http-factory": "^2.0",
         "guzzlehttp/psr7": "^1.8.4 || ^2.1.1"
     },
     "autoload": {
diff --git a/composer.json b/composer.json
index 9bf75ac0c7..20b1011a6a 100644
--- a/composer.json
+++ b/composer.json
@@ -28,9 +28,9 @@
         "ext-xml": "*",
         "ext-xmlreader": "*",
         "neos/composer-plugin": "^2.0",
-        "psr/http-message": "^1.0",
+        "psr/http-message": "^2.0",
         "psr/http-factory": "^1.0",
-        "psr/container": "^1.0",
+        "psr/container": "^2.0",
         "psr/http-server-middleware": "^1.0",
         "psr/http-server-handler": "^1.0",
         "psr/http-client": "^1.0",