diff --git a/src/Changelog/CommitReleaseChangelogViaKeepAChangelog.php b/src/Changelog/CommitReleaseChangelogViaKeepAChangelog.php
index a5beb2ae..f25fb044 100644
--- a/src/Changelog/CommitReleaseChangelogViaKeepAChangelog.php
+++ b/src/Changelog/CommitReleaseChangelogViaKeepAChangelog.php
@@ -14,7 +14,7 @@
 use Psl\Type;
 use Psr\Log\LoggerInterface;
 
-final class CommitReleaseChangelogViaKeepAChangelog implements CommitReleaseChangelog
+final readonly class CommitReleaseChangelogViaKeepAChangelog implements CommitReleaseChangelog
 {
     private const CHANGELOG_FILE = 'CHANGELOG.md';
 
diff --git a/src/Git/FetchAndSetCurrentUserByReplacingCurrentOriginRemote.php b/src/Git/FetchAndSetCurrentUserByReplacingCurrentOriginRemote.php
index 23c51514..417d5b31 100644
--- a/src/Git/FetchAndSetCurrentUserByReplacingCurrentOriginRemote.php
+++ b/src/Git/FetchAndSetCurrentUserByReplacingCurrentOriginRemote.php
@@ -10,7 +10,7 @@
 use Psl\Shell;
 use Psr\Http\Message\UriInterface;
 
-final class FetchAndSetCurrentUserByReplacingCurrentOriginRemote implements Fetch
+final readonly class FetchAndSetCurrentUserByReplacingCurrentOriginRemote implements Fetch
 {
     public function __construct(private readonly EnvironmentVariables $variables)
     {
diff --git a/src/Git/Value/BranchName.php b/src/Git/Value/BranchName.php
index 5eec5c37..31f21ad2 100644
--- a/src/Git/Value/BranchName.php
+++ b/src/Git/Value/BranchName.php
@@ -9,15 +9,12 @@
 use Psl\Type;
 
 /** @psalm-immutable */
-final class BranchName
+final readonly class BranchName
 {
-    /** @psalm-var non-empty-string */
-    private string $name;
-
     /** @psalm-param non-empty-string $name */
-    private function __construct(string $name)
-    {
-        $this->name = $name;
+    private function __construct(
+        private readonly string $name,
+    ) {
     }
 
     /**
diff --git a/src/Git/Value/MergeTargetCandidateBranches.php b/src/Git/Value/MergeTargetCandidateBranches.php
index bc976a29..192d9ea4 100644
--- a/src/Git/Value/MergeTargetCandidateBranches.php
+++ b/src/Git/Value/MergeTargetCandidateBranches.php
@@ -13,7 +13,7 @@
 use function Psl\Vec\filter;
 use function Psl\Vec\reverse;
 
-final class MergeTargetCandidateBranches
+final readonly class MergeTargetCandidateBranches
 {
     /**
      * @param BranchName[] $sortedBranches branches that can be used for releases, sorted in ascending version number
@@ -25,9 +25,7 @@ private function __construct(private readonly array $sortedBranches)
 
     public static function fromAllBranches(BranchName ...$branches): self
     {
-        $mergeTargetBranches = filter($branches, static function (BranchName $branch): bool {
-            return $branch->isReleaseBranch();
-        });
+        $mergeTargetBranches = filter($branches, static fn (BranchName $branch): bool => $branch->isReleaseBranch());
 
         $mergeTargetBranches = Vec\sort($mergeTargetBranches, self::branchOrder(...));
 
diff --git a/src/Git/Value/SemVerVersion.php b/src/Git/Value/SemVerVersion.php
index d1032e69..0423aa44 100644
--- a/src/Git/Value/SemVerVersion.php
+++ b/src/Git/Value/SemVerVersion.php
@@ -8,7 +8,7 @@
 use Psl\Regex;
 
 /** @psalm-immutable */
-final class SemVerVersion
+final readonly class SemVerVersion
 {
     private function __construct(
         private readonly int $major,
diff --git a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Author.php b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Author.php
index 6fa0a932..550a2ef5 100644
--- a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Author.php
+++ b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Author.php
@@ -8,7 +8,7 @@
 use Psl\Type;
 use Psr\Http\Message\UriInterface;
 
-final class Author
+final readonly class Author
 {
     /** @psalm-param non-empty-string $name */
     private function __construct(
diff --git a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/IssueOrPullRequest.php b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/IssueOrPullRequest.php
index f1f05dc1..4e303202 100644
--- a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/IssueOrPullRequest.php
+++ b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/IssueOrPullRequest.php
@@ -10,7 +10,7 @@
 use Psr\Http\Message\UriInterface;
 
 /** @psalm-immutable */
-final class IssueOrPullRequest
+final readonly class IssueOrPullRequest
 {
     /**
      * @param array<int, Label> $labels
diff --git a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Label.php b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Label.php
index 4d416ca2..2fea1b11 100644
--- a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Label.php
+++ b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Label.php
@@ -11,7 +11,7 @@
 use Psr\Http\Message\UriInterface;
 
 /** @psalm-immutable */
-final class Label
+final readonly class Label
 {
     /**
      * @psalm-param non-empty-string $colour
diff --git a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Milestone.php b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Milestone.php
index 12ee574e..ec46bc43 100644
--- a/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Milestone.php
+++ b/src/Github/Api/GraphQL/Query/GetMilestoneChangelog/Response/Milestone.php
@@ -12,7 +12,7 @@
 use Psr\Http\Message\UriInterface;
 
 /** @psalm-immutable */
-final class Milestone
+final readonly class Milestone
 {
     /**
      * @param array<int, IssueOrPullRequest> $entries
@@ -101,8 +101,6 @@ public function url(): UriInterface
     /** @psalm-suppress ImpureFunctionCall the {@see \Psl\Iter\all()} API is conditionally pure */
     public function assertAllIssuesAreClosed(): void
     {
-        Psl\invariant(Iter\all($this->entries, static function (IssueOrPullRequest $entry): bool {
-            return $entry->closed();
-        }), 'Failed asserting that all milestone issues are closed.');
+        Psl\invariant(Iter\all($this->entries, static fn (IssueOrPullRequest $entry): bool => $entry->closed()), 'Failed asserting that all milestone issues are closed.');
     }
 }
diff --git a/src/Github/Api/GraphQL/Query/GetMilestoneFirst100IssuesAndPullRequests.php b/src/Github/Api/GraphQL/Query/GetMilestoneFirst100IssuesAndPullRequests.php
index 625db2cd..de6ec76a 100644
--- a/src/Github/Api/GraphQL/Query/GetMilestoneFirst100IssuesAndPullRequests.php
+++ b/src/Github/Api/GraphQL/Query/GetMilestoneFirst100IssuesAndPullRequests.php
@@ -9,7 +9,7 @@
 use Laminas\AutomaticReleases\Github\Value\RepositoryName;
 use Psl\Type;
 
-final class GetMilestoneFirst100IssuesAndPullRequests implements GetGithubMilestone
+final readonly class GetMilestoneFirst100IssuesAndPullRequests implements GetGithubMilestone
 {
     // @TODO this fetches ONLY the first 100 issues!!!
     private const QUERY = <<<'GRAPHQL'
diff --git a/src/Github/Api/GraphQL/RunGraphQLQuery.php b/src/Github/Api/GraphQL/RunGraphQLQuery.php
index d0edce88..71c1897b 100644
--- a/src/Github/Api/GraphQL/RunGraphQLQuery.php
+++ b/src/Github/Api/GraphQL/RunGraphQLQuery.php
@@ -12,7 +12,7 @@
 
 use function array_key_exists;
 
-final class RunGraphQLQuery implements RunQuery
+final readonly class RunGraphQLQuery implements RunQuery
 {
     private const ENDPOINT = 'https://api.github.com/graphql';
 
diff --git a/src/Github/Api/V3/CreateMilestoneThroughApiCall.php b/src/Github/Api/V3/CreateMilestoneThroughApiCall.php
index 66ecc72d..e4de0400 100644
--- a/src/Github/Api/V3/CreateMilestoneThroughApiCall.php
+++ b/src/Github/Api/V3/CreateMilestoneThroughApiCall.php
@@ -13,7 +13,7 @@
 use Psr\Http\Message\RequestFactoryInterface;
 use Psr\Log\LoggerInterface;
 
-final class CreateMilestoneThroughApiCall implements CreateMilestone
+final readonly class CreateMilestoneThroughApiCall implements CreateMilestone
 {
     private const API_ROOT = 'https://api.github.com/';
 
diff --git a/src/Github/Api/V3/CreatePullRequestThroughApiCall.php b/src/Github/Api/V3/CreatePullRequestThroughApiCall.php
index 0433c788..e0b51a38 100644
--- a/src/Github/Api/V3/CreatePullRequestThroughApiCall.php
+++ b/src/Github/Api/V3/CreatePullRequestThroughApiCall.php
@@ -12,7 +12,7 @@
 use Psr\Http\Client\ClientInterface;
 use Psr\Http\Message\RequestFactoryInterface;
 
-final class CreatePullRequestThroughApiCall implements CreatePullRequest
+final readonly class CreatePullRequestThroughApiCall implements CreatePullRequest
 {
     private const API_ROOT = 'https://api.github.com/';
 
diff --git a/src/Github/Api/V3/CreateReleaseThroughApiCall.php b/src/Github/Api/V3/CreateReleaseThroughApiCall.php
index a15eec28..128cdf8d 100644
--- a/src/Github/Api/V3/CreateReleaseThroughApiCall.php
+++ b/src/Github/Api/V3/CreateReleaseThroughApiCall.php
@@ -18,7 +18,7 @@
 use function Psl\Type\shape;
 use function sprintf;
 
-final class CreateReleaseThroughApiCall implements CreateRelease
+final readonly class CreateReleaseThroughApiCall implements CreateRelease
 {
     private const API_URI = 'https://api.github.com/repos/%s/%s/releases';
 
diff --git a/src/Github/Api/V3/SetDefaultBranchThroughApiCall.php b/src/Github/Api/V3/SetDefaultBranchThroughApiCall.php
index 2016862c..98accd43 100644
--- a/src/Github/Api/V3/SetDefaultBranchThroughApiCall.php
+++ b/src/Github/Api/V3/SetDefaultBranchThroughApiCall.php
@@ -12,7 +12,7 @@
 use Psr\Http\Client\ClientInterface;
 use Psr\Http\Message\RequestFactoryInterface;
 
-final class SetDefaultBranchThroughApiCall implements SetDefaultBranch
+final readonly class SetDefaultBranchThroughApiCall implements SetDefaultBranch
 {
     private const API_ROOT = 'https://api.github.com/';
 
diff --git a/src/Github/CreateReleaseTextThroughChangelog.php b/src/Github/CreateReleaseTextThroughChangelog.php
index 8bddf737..6c7b3e89 100644
--- a/src/Github/CreateReleaseTextThroughChangelog.php
+++ b/src/Github/CreateReleaseTextThroughChangelog.php
@@ -17,7 +17,7 @@
 
 use function preg_quote;
 
-final class CreateReleaseTextThroughChangelog implements CreateReleaseText
+final readonly class CreateReleaseTextThroughChangelog implements CreateReleaseText
 {
     private const TEMPLATE = <<<'MARKDOWN'
         ### Release Notes for %release%
diff --git a/src/Github/Event/Factory/LoadCurrentGithubEventFromGithubActionPath.php b/src/Github/Event/Factory/LoadCurrentGithubEventFromGithubActionPath.php
index e1fb6778..5217a4b8 100644
--- a/src/Github/Event/Factory/LoadCurrentGithubEventFromGithubActionPath.php
+++ b/src/Github/Event/Factory/LoadCurrentGithubEventFromGithubActionPath.php
@@ -9,7 +9,7 @@
 
 use function Psl\File\read;
 
-final class LoadCurrentGithubEventFromGithubActionPath implements LoadCurrentGithubEvent
+final readonly class LoadCurrentGithubEventFromGithubActionPath implements LoadCurrentGithubEvent
 {
     public function __construct(private readonly EnvironmentVariables $variables)
     {
diff --git a/src/Github/Event/MilestoneClosedEvent.php b/src/Github/Event/MilestoneClosedEvent.php
index 2a5cd475..5f4466a2 100644
--- a/src/Github/Event/MilestoneClosedEvent.php
+++ b/src/Github/Event/MilestoneClosedEvent.php
@@ -10,7 +10,7 @@
 use Psl\Type;
 
 /** @psalm-immutable */
-final class MilestoneClosedEvent
+final readonly class MilestoneClosedEvent
 {
     private function __construct(
         private readonly SemVerVersion $version,
diff --git a/src/Github/JwageGenerateChangelog.php b/src/Github/JwageGenerateChangelog.php
index c4bffe22..d5dd9b90 100644
--- a/src/Github/JwageGenerateChangelog.php
+++ b/src/Github/JwageGenerateChangelog.php
@@ -18,7 +18,7 @@
 use Psr\Http\Message\RequestFactoryInterface;
 use Symfony\Component\Console\Output\BufferedOutput;
 
-final class JwageGenerateChangelog implements GenerateChangelog
+final readonly class JwageGenerateChangelog implements GenerateChangelog
 {
     public function __construct(
         private readonly ChangelogGenerator $changelogGenerator,
diff --git a/src/Github/MergeMultipleReleaseNotes.php b/src/Github/MergeMultipleReleaseNotes.php
index 2ff895a9..da9ebecf 100644
--- a/src/Github/MergeMultipleReleaseNotes.php
+++ b/src/Github/MergeMultipleReleaseNotes.php
@@ -13,15 +13,12 @@
 use Psl\Type;
 use Psl\Vec;
 
-final class MergeMultipleReleaseNotes implements CreateReleaseText
+final readonly class MergeMultipleReleaseNotes implements CreateReleaseText
 {
-    /** @psalm-var non-empty-list<CreateReleaseText> */
-    private array $releaseTextGenerators;
-
     /** @psalm-param non-empty-list<CreateReleaseText> $releaseTextGenerators */
-    public function __construct(array $releaseTextGenerators)
-    {
-        $this->releaseTextGenerators = $releaseTextGenerators;
+    public function __construct(
+        private readonly array $releaseTextGenerators,
+    ) {
     }
 
     public function __invoke(
diff --git a/src/Github/Value/RepositoryName.php b/src/Github/Value/RepositoryName.php
index 68570397..1848d50d 100644
--- a/src/Github/Value/RepositoryName.php
+++ b/src/Github/Value/RepositoryName.php
@@ -14,22 +14,16 @@
 use function explode;
 
 /** @psalm-immutable */
-final class RepositoryName
+final readonly class RepositoryName
 {
-    /** @psalm-var non-empty-string */
-    private string $owner;
-
-    /** @psalm-var non-empty-string */
-    private string $name;
-
     /**
      * @psalm-param non-empty-string $owner
      * @psalm-param non-empty-string $name
      */
-    private function __construct(string $owner, string $name)
-    {
-        $this->owner = $owner;
-        $this->name  = $name;
+    private function __construct(
+        private readonly string $owner,
+        private readonly string $name,
+    ) {
     }
 
     /**
diff --git a/src/Gpg/SecretKeyId.php b/src/Gpg/SecretKeyId.php
index 3d381426..d234e2e4 100644
--- a/src/Gpg/SecretKeyId.php
+++ b/src/Gpg/SecretKeyId.php
@@ -9,15 +9,12 @@
 use Psl\Str;
 
 /** @psalm-immutable */
-final class SecretKeyId
+final readonly class SecretKeyId
 {
-    /** @psalm-var non-empty-string */
-    private string $id;
-
     /** @psalm-param non-empty-string $id */
-    private function __construct(string $id)
-    {
-        $this->id = $id;
+    private function __construct(
+        private readonly string $id,
+    ) {
     }
 
     /** @psalm-pure */
diff --git a/src/HttpClient/LoggingHttpClient.php b/src/HttpClient/LoggingHttpClient.php
index 017cdb1d..24e9687c 100644
--- a/src/HttpClient/LoggingHttpClient.php
+++ b/src/HttpClient/LoggingHttpClient.php
@@ -10,7 +10,7 @@
 use Psr\Log\LoggerInterface;
 
 /** @internal */
-final class LoggingHttpClient implements ClientInterface
+final readonly class LoggingHttpClient implements ClientInterface
 {
     public function __construct(private readonly ClientInterface $next, private readonly LoggerInterface $logger)
     {
diff --git a/test/unit/Environment/EnvironmentVariablesTest.php b/test/unit/Environment/EnvironmentVariablesTest.php
index 0245ed17..e4e5e4c0 100644
--- a/test/unit/Environment/EnvironmentVariablesTest.php
+++ b/test/unit/Environment/EnvironmentVariablesTest.php
@@ -38,7 +38,7 @@ protected function setUp(): void
 
         $this->originalValues = Dict\associate(self::RESET_ENVIRONMENT_VARIABLES, Dict\map(
             self::RESET_ENVIRONMENT_VARIABLES,
-            static fn (string $variable) => Env\get_var($variable),
+            static fn (string $variable): string|null => Env\get_var($variable),
         ));
     }