diff --git a/.github/workflows/static.yml b/.github/workflows/static.yml
index 4f22379..9d5539c 100644
--- a/.github/workflows/static.yml
+++ b/.github/workflows/static.yml
@@ -8,7 +8,7 @@ on:
 jobs:
   codesniffer:
     name: PHP CodeSniffer
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
 
     steps:
       - name: Checkout code
@@ -24,7 +24,7 @@ jobs:
           update: true
 
       - name: Install Dependencies
-        uses: nick-invision/retry@v2
+        uses: nick-invision/retry@v3
         with:
           timeout_minutes: 5
           max_attempts: 5
@@ -51,7 +51,7 @@ jobs:
           update: true
 
       - name: Install Dependencies
-        uses: nick-invision/retry@v2
+        uses: nick-invision/retry@v3
         with:
           timeout_minutes: 5
           max_attempts: 5
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 5e2e15f..0183705 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -8,11 +8,11 @@ on:
 jobs:
   tests:
     name: PHP ${{ matrix.php }}
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-24.04
 
     strategy:
       matrix:
-        php: ['7.4', '8.0', '8.1', '8.2', '8.3']
+        php: ['7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
     steps:
       - name: Checkout Code
@@ -31,7 +31,7 @@ jobs:
         run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
 
       - name: Install Dependencies
-        uses: nick-invision/retry@v2
+        uses: nick-invision/retry@v3
         with:
           timeout_minutes: 5
           max_attempts: 5
diff --git a/composer.json b/composer.json
index cba6b96..658dce4 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,7 @@
         "guzzlehttp/psr7": "^2.4.3",
         "php-http/discovery": "^1.15.2",
         "phpunit/phpunit": "^9.6.3 || ^10.0.12",
-        "psalm/phar": "5.7.6",
+        "psalm/phar": "5.26.1",
         "psr/http-factory": "^1.0.1",
         "psr/http-message": "^1.0.1",
         "squizlabs/php_codesniffer": "3.7.2"
diff --git a/psalm-baseline.xml b/psalm-baseline.xml
new file mode 100644
index 0000000..253f2ed
--- /dev/null
+++ b/psalm-baseline.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="5.26.1@d747f6500b38ac4f7dfc5edbcae6e4b637d7add0">
+  <file src="src/Http/Unmarshaller.php">
+    <DocblockTypeContradiction>
+      <code><![CDATA[sprintf('application/cloudevents+%s', $type)]]></code>
+      <code><![CDATA[sprintf('application/cloudevents-batch+%s', $type)]]></code>
+    </DocblockTypeContradiction>
+  </file>
+</files>
diff --git a/psalm.xml.dist b/psalm.xml.dist
index db645bc..7ee17a8 100644
--- a/psalm.xml.dist
+++ b/psalm.xml.dist
@@ -5,6 +5,9 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    errorBaseline="psalm-baseline.xml"
+    findUnusedBaselineEntry="true"
+    findUnusedCode="false"
 >
     <projectFiles>
         <directory name="src" />
diff --git a/src/Exceptions/InvalidAttributeException.php b/src/Exceptions/InvalidAttributeException.php
index f8f9cac..65efd92 100644
--- a/src/Exceptions/InvalidAttributeException.php
+++ b/src/Exceptions/InvalidAttributeException.php
@@ -10,9 +10,9 @@
 class InvalidAttributeException extends Exception
 {
     public function __construct(
-        string $message = null,
+        ?string $message = null,
         int $code = 0,
-        Throwable $previous = null
+        ?Throwable $previous = null
     ) {
         parent::__construct($message ?? 'Invalid CloudEvent attribute.', $code, $previous);
     }
diff --git a/src/Exceptions/InvalidPayloadSyntaxException.php b/src/Exceptions/InvalidPayloadSyntaxException.php
index 970f1c8..9a7ed8f 100644
--- a/src/Exceptions/InvalidPayloadSyntaxException.php
+++ b/src/Exceptions/InvalidPayloadSyntaxException.php
@@ -10,9 +10,9 @@
 class InvalidPayloadSyntaxException extends Exception
 {
     public function __construct(
-        string $message = null,
+        ?string $message = null,
         int $code = 0,
-        Throwable $previous = null
+        ?Throwable $previous = null
     ) {
         parent::__construct($message ?? 'Invalid CloudEvent payload syntax.', $code, $previous);
     }
diff --git a/src/Exceptions/MissingAttributeException.php b/src/Exceptions/MissingAttributeException.php
index 7118561..43e8668 100644
--- a/src/Exceptions/MissingAttributeException.php
+++ b/src/Exceptions/MissingAttributeException.php
@@ -10,9 +10,9 @@
 class MissingAttributeException extends Exception
 {
     public function __construct(
-        string $message = null,
+        ?string $message = null,
         int $code = 0,
-        Throwable $previous = null
+        ?Throwable $previous = null
     ) {
         parent::__construct($message ?? 'Missing CloudEvent attribute.', $code, $previous);
     }
diff --git a/src/Exceptions/UnsupportedContentTypeException.php b/src/Exceptions/UnsupportedContentTypeException.php
index 0ed9493..bf8fd8c 100644
--- a/src/Exceptions/UnsupportedContentTypeException.php
+++ b/src/Exceptions/UnsupportedContentTypeException.php
@@ -10,9 +10,9 @@
 class UnsupportedContentTypeException extends Exception
 {
     public function __construct(
-        string $message = null,
+        ?string $message = null,
         int $code = 0,
-        Throwable $previous = null
+        ?Throwable $previous = null
     ) {
         parent::__construct($message ?? 'Unsupported CloudEvent content type.', $code, $previous);
     }
diff --git a/src/Exceptions/UnsupportedSpecVersionException.php b/src/Exceptions/UnsupportedSpecVersionException.php
index d6578d6..8525523 100644
--- a/src/Exceptions/UnsupportedSpecVersionException.php
+++ b/src/Exceptions/UnsupportedSpecVersionException.php
@@ -10,9 +10,9 @@
 class UnsupportedSpecVersionException extends Exception
 {
     public function __construct(
-        string $message = null,
+        ?string $message = null,
         int $code = 0,
-        Throwable $previous = null
+        ?Throwable $previous = null
     ) {
         parent::__construct($message ?? 'Unsupported CloudEvent spec version.', $code, $previous);
     }
diff --git a/src/Http/Marshaller.php b/src/Http/Marshaller.php
index 9aec3d3..48a077a 100644
--- a/src/Http/Marshaller.php
+++ b/src/Http/Marshaller.php
@@ -43,9 +43,9 @@ public function __construct(
     }
 
     public static function createJsonMarshaller(
-        RequestFactoryInterface $requestFactory = null,
-        ResponseFactoryInterface $responseFactory = null,
-        StreamFactoryInterface $streamFactory = null
+        ?RequestFactoryInterface $requestFactory = null,
+        ?ResponseFactoryInterface $responseFactory = null,
+        ?StreamFactoryInterface $streamFactory = null
     ): self {
         return new self(
             ['serializer' => JsonSerializer::create(), 'type' => 'json'],