diff --git a/.horde.yml b/.horde.yml
index 03b65f7..a9eb566 100644
--- a/.horde.yml
+++ b/.horde.yml
@@ -26,6 +26,9 @@ dependencies:
     php: ^8.3
     composer:
       horde/http: '*'
+      psr/http-client: ^1.0
+      psr/http-factory: ^1.0
+      psr/http-message: ^2.0
   dev:
     composer:
       phpunit/phpunit: ^12
diff --git a/composer.json b/composer.json
index 1b438af..a3d55df 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,10 @@
     "repositories": [],
     "require": {
         "php": "^8.3",
-        "horde/http": "* || dev-FRAMEWORK_6_0"
+        "horde/http": "* || dev-FRAMEWORK_6_0",
+        "psr/http-client": "^1.0",
+        "psr/http-factory": "^1.0",
+        "psr/http-message": "^2.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^12",
@@ -44,5 +47,6 @@
         "branch-alias": {
             "dev-FRAMEWORK_6_0": "0.x-dev"
         }
-    }
-}
\ No newline at end of file
+    },
+    "minimum-stability": "dev"
+}
diff --git a/src/CreateReleaseParams.php b/src/CreateReleaseParams.php
new file mode 100644
index 0000000..47b4e58
--- /dev/null
+++ b/src/CreateReleaseParams.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Data transfer object for creating a GitHub release
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class CreateReleaseParams
+{
+    /**
+     * @param string $tagName The name of the tag (required)
+     * @param string $name The name of the release (optional)
+     * @param string $body Text describing the contents of the release (optional)
+     * @param bool $draft True to create a draft (unpublished) release (default: false)
+     * @param bool $prerelease True to identify the release as a prerelease (default: false)
+     * @param string $targetCommitish Specifies the commitish value for tag creation (optional)
+     */
+    public function __construct(
+        public readonly string $tagName,
+        public readonly string $name = '',
+        public readonly string $body = '',
+        public readonly bool $draft = false,
+        public readonly bool $prerelease = false,
+        public readonly string $targetCommitish = '',
+    ) {}
+
+    /**
+     * Convert to array for API request
+     *
+     * @return array<string, string|bool>
+     */
+    public function toArray(): array
+    {
+        $data = [
+            'tag_name' => $this->tagName,
+            'draft' => $this->draft,
+            'prerelease' => $this->prerelease,
+        ];
+
+        if ($this->name !== '') {
+            $data['name'] = $this->name;
+        }
+
+        if ($this->body !== '') {
+            $data['body'] = $this->body;
+        }
+
+        if ($this->targetCommitish !== '') {
+            $data['target_commitish'] = $this->targetCommitish;
+        }
+
+        return $data;
+    }
+}
diff --git a/src/CreateReleaseRequestFactory.php b/src/CreateReleaseRequestFactory.php
new file mode 100644
index 0000000..445f9be
--- /dev/null
+++ b/src/CreateReleaseRequestFactory.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\StreamFactoryInterface;
+
+/**
+ * Factory for creating requests to create a GitHub release
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class CreateReleaseRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly CreateReleaseParams $params,
+    ) {}
+
+    /**
+     * Create HTTP request to create a release
+     *
+     * @return RequestInterface
+     */
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/releases',
+            $this->repo->owner,
+            $this->repo->name,
+        );
+
+        $jsonBody = json_encode($this->params->toArray(), JSON_THROW_ON_ERROR);
+        $stream = $this->streamFactory->createStream($jsonBody);
+
+        $request = $this->requestFactory->createRequest('POST', $url);
+        $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+        $request = $request->withHeader('Content-Type', 'application/json');
+        $request = $request->withBody($stream);
+
+        return $request;
+    }
+}
diff --git a/src/GetReleaseByTagRequestFactory.php b/src/GetReleaseByTagRequestFactory.php
new file mode 100644
index 0000000..507033c
--- /dev/null
+++ b/src/GetReleaseByTagRequestFactory.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Factory for creating requests to get a GitHub release by tag
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class GetReleaseByTagRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly string $tag,
+    ) {}
+
+    /**
+     * Create HTTP request to get a release by tag
+     *
+     * @return RequestInterface
+     */
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/releases/tags/%s',
+            $this->repo->owner,
+            $this->repo->name,
+            rawurlencode($this->tag),
+        );
+
+        $request = $this->requestFactory->createRequest('GET', $url);
+        $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/GithubApiClient.php b/src/GithubApiClient.php
index c3c36b5..35d9411 100644
--- a/src/GithubApiClient.php
+++ b/src/GithubApiClient.php
@@ -653,6 +653,136 @@ public function createPullRequest(GithubRepository $repo, CreatePullRequestParam
         }
     }
 
+    /**
+     * Create a new release for a tag
+     *
+     * @param GithubRepository $repo The repository
+     * @param CreateReleaseParams $params The release parameters
+     * @return GithubRelease The created release
+     * @throws Exception
+     */
+    public function createRelease(GithubRepository $repo, CreateReleaseParams $params): GithubRelease
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for createRelease. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new CreateReleaseRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $repo,
+            $params
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 201) {
+            $data = json_decode((string) $response->getBody());
+            return GithubRelease::fromApiResponse($data);
+        } else {
+            throw new Exception($response->getStatusCode() . ' ' . $response->getReasonPhrase());
+        }
+    }
+
+    /**
+     * Get a release by tag name
+     *
+     * @param GithubRepository $repo The repository
+     * @param string $tag The tag name
+     * @return GithubRelease The release
+     * @throws Exception
+     */
+    public function getReleaseByTag(GithubRepository $repo, string $tag): GithubRelease
+    {
+        $requestFactory = new GetReleaseByTagRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $repo,
+            $tag
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            return GithubRelease::fromApiResponse($data);
+        } else {
+            throw new Exception($response->getStatusCode() . ' ' . $response->getReasonPhrase());
+        }
+    }
+
+    /**
+     * Update an existing release
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $releaseId The release ID
+     * @param UpdateReleaseParams $params The update parameters
+     * @return GithubRelease The updated release
+     * @throws Exception
+     */
+    public function updateRelease(GithubRepository $repo, int $releaseId, UpdateReleaseParams $params): GithubRelease
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for updateRelease. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new UpdateReleaseRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $repo,
+            $releaseId,
+            $params
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            return GithubRelease::fromApiResponse($data);
+        } else {
+            throw new Exception($response->getStatusCode() . ' ' . $response->getReasonPhrase());
+        }
+    }
+
+    /**
+     * Upload an asset to a release
+     *
+     * @param string $uploadUrl The upload URL from the release object
+     * @param string $filename The filename for the asset
+     * @param string $fileContent The file content
+     * @param string $contentType The MIME type (default: application/octet-stream)
+     * @return GithubReleaseAsset The uploaded asset
+     * @throws Exception
+     */
+    public function uploadReleaseAsset(string $uploadUrl, string $filename, string $fileContent, string $contentType = 'application/octet-stream'): GithubReleaseAsset
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for uploadReleaseAsset. Please provide it in the constructor.');
+        }
+
+        $stream = $this->streamFactory->createStream($fileContent);
+
+        $requestFactory = new UploadReleaseAssetRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $uploadUrl,
+            $filename,
+            $stream,
+            $contentType
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 201) {
+            $data = json_decode((string) $response->getBody());
+            return GithubReleaseAsset::fromApiResponse($data);
+        } else {
+            throw new Exception($response->getStatusCode() . ' ' . $response->getReasonPhrase());
+        }
+    }
+
     /**
      * @param array<mixed> $repos
      * @param string $json
diff --git a/src/GithubRelease.php b/src/GithubRelease.php
new file mode 100644
index 0000000..ab242e1
--- /dev/null
+++ b/src/GithubRelease.php
@@ -0,0 +1,89 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Stringable;
+
+/**
+ * Represents a GitHub Release
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class GithubRelease implements Stringable
+{
+    /**
+     * @param int $id Release ID
+     * @param string $tagName The name of the tag
+     * @param string $name Release name/title
+     * @param string $body Release notes (markdown)
+     * @param bool $draft Is draft release
+     * @param bool $prerelease Is prerelease
+     * @param string $createdAt Creation timestamp
+     * @param string $publishedAt Publication timestamp
+     * @param string $htmlUrl Web URL
+     * @param string $uploadUrl URL for uploading assets
+     * @param GithubUser $author Release author
+     * @param array<GithubReleaseAsset> $assets Release assets
+     */
+    public function __construct(
+        public readonly int $id,
+        public readonly string $tagName,
+        public readonly string $name,
+        public readonly string $body,
+        public readonly bool $draft,
+        public readonly bool $prerelease,
+        public readonly string $createdAt,
+        public readonly string $publishedAt,
+        public readonly string $htmlUrl,
+        public readonly string $uploadUrl,
+        public readonly GithubUser $author,
+        public readonly array $assets,
+    ) {}
+
+    public function __toString(): string
+    {
+        return $this->htmlUrl;
+    }
+
+    /**
+     * Create from GitHub API response
+     *
+     * @param object $data The API response data
+     * @return self
+     */
+    public static function fromApiResponse(object $data): self
+    {
+        $author = isset($data->author) ? GithubUser::fromApiResponse($data->author) : new GithubUser('', 0, '', '', '');
+
+        $assets = [];
+        if (isset($data->assets) && is_array($data->assets)) {
+            foreach ($data->assets as $assetData) {
+                $assets[] = GithubReleaseAsset::fromApiResponse($assetData);
+            }
+        }
+
+        return new self(
+            id: $data->id ?? 0,
+            tagName: $data->tag_name ?? '',
+            name: $data->name ?? '',
+            body: $data->body ?? '',
+            draft: $data->draft ?? false,
+            prerelease: $data->prerelease ?? false,
+            createdAt: $data->created_at ?? '',
+            publishedAt: $data->published_at ?? '',
+            htmlUrl: $data->html_url ?? '',
+            uploadUrl: $data->upload_url ?? '',
+            author: $author,
+            assets: $assets,
+        );
+    }
+}
diff --git a/src/GithubReleaseAsset.php b/src/GithubReleaseAsset.php
new file mode 100644
index 0000000..c069968
--- /dev/null
+++ b/src/GithubReleaseAsset.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Stringable;
+
+/**
+ * Represents a GitHub Release Asset (file attached to release)
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class GithubReleaseAsset implements Stringable
+{
+    public function __construct(
+        public readonly int $id,
+        public readonly string $name,
+        public readonly string $label,
+        public readonly string $contentType,
+        public readonly int $size,
+        public readonly int $downloadCount,
+        public readonly string $state,
+        public readonly string $browserDownloadUrl,
+        public readonly string $createdAt,
+        public readonly string $updatedAt,
+    ) {}
+
+    public function __toString(): string
+    {
+        return $this->browserDownloadUrl;
+    }
+
+    /**
+     * Create from GitHub API response
+     *
+     * @param object $data The API response data
+     * @return self
+     */
+    public static function fromApiResponse(object $data): self
+    {
+        return new self(
+            id: $data->id ?? 0,
+            name: $data->name ?? '',
+            label: $data->label ?? '',
+            contentType: $data->content_type ?? '',
+            size: $data->size ?? 0,
+            downloadCount: $data->download_count ?? 0,
+            state: $data->state ?? '',
+            browserDownloadUrl: $data->browser_download_url ?? '',
+            createdAt: $data->created_at ?? '',
+            updatedAt: $data->updated_at ?? '',
+        );
+    }
+}
diff --git a/src/UpdateReleaseParams.php b/src/UpdateReleaseParams.php
new file mode 100644
index 0000000..b088625
--- /dev/null
+++ b/src/UpdateReleaseParams.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Data transfer object for updating a GitHub release
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class UpdateReleaseParams
+{
+    public function __construct(
+        public readonly ?string $tagName = null,
+        public readonly ?string $name = null,
+        public readonly ?string $body = null,
+        public readonly ?bool $draft = null,
+        public readonly ?bool $prerelease = null,
+    ) {}
+
+    /**
+     * Convert to array for API request (only includes set fields)
+     *
+     * @return array<string, string|bool>
+     */
+    public function toArray(): array
+    {
+        $data = [];
+
+        if ($this->tagName !== null) {
+            $data['tag_name'] = $this->tagName;
+        }
+
+        if ($this->name !== null) {
+            $data['name'] = $this->name;
+        }
+
+        if ($this->body !== null) {
+            $data['body'] = $this->body;
+        }
+
+        if ($this->draft !== null) {
+            $data['draft'] = $this->draft;
+        }
+
+        if ($this->prerelease !== null) {
+            $data['prerelease'] = $this->prerelease;
+        }
+
+        return $data;
+    }
+
+    /**
+     * Check if any field is set
+     *
+     * @return bool
+     */
+    public function isEmpty(): bool
+    {
+        return $this->tagName === null
+            && $this->name === null
+            && $this->body === null
+            && $this->draft === null
+            && $this->prerelease === null;
+    }
+}
diff --git a/src/UpdateReleaseRequestFactory.php b/src/UpdateReleaseRequestFactory.php
new file mode 100644
index 0000000..e184006
--- /dev/null
+++ b/src/UpdateReleaseRequestFactory.php
@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\StreamFactoryInterface;
+
+/**
+ * Factory for creating requests to update a GitHub release
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class UpdateReleaseRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly int $releaseId,
+        private readonly UpdateReleaseParams $params,
+    ) {}
+
+    /**
+     * Create HTTP request to update a release
+     *
+     * @return RequestInterface
+     */
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/releases/%d',
+            $this->repo->owner,
+            $this->repo->name,
+            $this->releaseId,
+        );
+
+        $jsonBody = json_encode($this->params->toArray(), JSON_THROW_ON_ERROR);
+        $stream = $this->streamFactory->createStream($jsonBody);
+
+        $request = $this->requestFactory->createRequest('PATCH', $url);
+        $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+        $request = $request->withHeader('Content-Type', 'application/json');
+        $request = $request->withBody($stream);
+
+        return $request;
+    }
+}
diff --git a/src/UploadReleaseAssetRequestFactory.php b/src/UploadReleaseAssetRequestFactory.php
new file mode 100644
index 0000000..be1289b
--- /dev/null
+++ b/src/UploadReleaseAssetRequestFactory.php
@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\StreamInterface;
+
+/**
+ * Factory for creating requests to upload a release asset
+ *
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+class UploadReleaseAssetRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly string $uploadUrl,
+        private readonly string $filename,
+        private readonly StreamInterface $content,
+        private readonly string $contentType = 'application/octet-stream',
+    ) {}
+
+    /**
+     * Create HTTP request to upload a release asset
+     *
+     * @return RequestInterface
+     */
+    public function create(): RequestInterface
+    {
+        // Remove template parameters from upload_url
+        // GitHub returns: https://uploads.github.com/repos/:owner/:repo/releases/:id/assets{?name,label}
+        $url = preg_replace('/\{[^}]+\}/', '', $this->uploadUrl);
+
+        // Add filename as query parameter
+        $url .= '?name=' . rawurlencode($this->filename);
+
+        $request = $this->requestFactory->createRequest('POST', $url);
+        $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+        $request = $request->withHeader('Content-Type', $this->contentType);
+        $request = $request->withBody($this->content);
+
+        return $request;
+    }
+}
diff --git a/test/unit/CreateReleaseParamsTest.php b/test/unit/CreateReleaseParamsTest.php
new file mode 100644
index 0000000..ae7ea05
--- /dev/null
+++ b/test/unit/CreateReleaseParamsTest.php
@@ -0,0 +1,214 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+#[CoversClass(CreateReleaseParams::class)]
+class CreateReleaseParamsTest extends TestCase
+{
+    public function testMinimalConstruction(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0',
+        );
+
+        $this->assertSame('v1.0.0', $params->tagName);
+        $this->assertSame('', $params->name);
+        $this->assertSame('', $params->body);
+        $this->assertSame('', $params->targetCommitish);
+        $this->assertFalse($params->draft);
+        $this->assertFalse($params->prerelease);
+    }
+
+    public function testFullConstruction(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v2.0.0',
+            name: 'Release 2.0.0',
+            body: 'Major release with breaking changes',
+            targetCommitish: 'main',
+            draft: true,
+            prerelease: true,
+        );
+
+        $this->assertSame('v2.0.0', $params->tagName);
+        $this->assertSame('Release 2.0.0', $params->name);
+        $this->assertSame('Major release with breaking changes', $params->body);
+        $this->assertSame('main', $params->targetCommitish);
+        $this->assertTrue($params->draft);
+        $this->assertTrue($params->prerelease);
+    }
+
+    public function testToArrayMinimal(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0',
+        );
+
+        $array = $params->toArray();
+
+        $this->assertSame([
+            'tag_name' => 'v1.0.0',
+            'draft' => false,
+            'prerelease' => false,
+        ], $array);
+    }
+
+    public function testToArrayFull(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v2.0.0',
+            name: 'Release 2.0.0',
+            body: 'Major release',
+            targetCommitish: 'develop',
+            draft: true,
+            prerelease: false,
+        );
+
+        $array = $params->toArray();
+
+        // Order matches toArray() implementation
+        $this->assertArrayHasKey('tag_name', $array);
+        $this->assertArrayHasKey('draft', $array);
+        $this->assertArrayHasKey('prerelease', $array);
+        $this->assertArrayHasKey('name', $array);
+        $this->assertArrayHasKey('body', $array);
+        $this->assertArrayHasKey('target_commitish', $array);
+
+        $this->assertSame('v2.0.0', $array['tag_name']);
+        $this->assertSame('Release 2.0.0', $array['name']);
+        $this->assertSame('Major release', $array['body']);
+        $this->assertSame('develop', $array['target_commitish']);
+        $this->assertTrue($array['draft']);
+        $this->assertFalse($array['prerelease']);
+    }
+
+    public function testToArrayWithEmptyStrings(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0',
+            name: '',
+            body: '',
+        );
+
+        $array = $params->toArray();
+
+        // Empty strings should not be included
+        $this->assertSame([
+            'tag_name' => 'v1.0.0',
+            'draft' => false,
+            'prerelease' => false,
+        ], $array);
+    }
+
+    public function testToArrayWithOnlyName(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0',
+            name: 'Version 1.0.0',
+        );
+
+        $array = $params->toArray();
+
+        $this->assertArrayHasKey('tag_name', $array);
+        $this->assertArrayHasKey('draft', $array);
+        $this->assertArrayHasKey('prerelease', $array);
+        $this->assertArrayHasKey('name', $array);
+        $this->assertSame('v1.0.0', $array['tag_name']);
+        $this->assertSame('Version 1.0.0', $array['name']);
+        $this->assertFalse($array['draft']);
+        $this->assertFalse($array['prerelease']);
+    }
+
+    public function testToArrayWithOnlyBody(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0',
+            body: 'Release notes',
+        );
+
+        $array = $params->toArray();
+
+        $this->assertArrayHasKey('tag_name', $array);
+        $this->assertArrayHasKey('draft', $array);
+        $this->assertArrayHasKey('prerelease', $array);
+        $this->assertArrayHasKey('body', $array);
+        $this->assertSame('v1.0.0', $array['tag_name']);
+        $this->assertSame('Release notes', $array['body']);
+        $this->assertFalse($array['draft']);
+        $this->assertFalse($array['prerelease']);
+    }
+
+    public function testToArrayWithOnlyTargetCommitish(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0',
+            targetCommitish: 'abc123def',
+        );
+
+        $array = $params->toArray();
+
+        $this->assertArrayHasKey('tag_name', $array);
+        $this->assertArrayHasKey('draft', $array);
+        $this->assertArrayHasKey('prerelease', $array);
+        $this->assertArrayHasKey('target_commitish', $array);
+        $this->assertSame('v1.0.0', $array['tag_name']);
+        $this->assertSame('abc123def', $array['target_commitish']);
+        $this->assertFalse($array['draft']);
+        $this->assertFalse($array['prerelease']);
+    }
+
+    public function testDraftRelease(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0-rc1',
+            draft: true,
+        );
+
+        $array = $params->toArray();
+
+        $this->assertTrue($array['draft']);
+        $this->assertFalse($array['prerelease']);
+    }
+
+    public function testPrereleaseRelease(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0-beta.1',
+            prerelease: true,
+        );
+
+        $array = $params->toArray();
+
+        $this->assertFalse($array['draft']);
+        $this->assertTrue($array['prerelease']);
+    }
+
+    public function testDraftPrerelease(): void
+    {
+        $params = new CreateReleaseParams(
+            tagName: 'v1.0.0-alpha.1',
+            draft: true,
+            prerelease: true,
+        );
+
+        $array = $params->toArray();
+
+        $this->assertTrue($array['draft']);
+        $this->assertTrue($array['prerelease']);
+    }
+}
diff --git a/test/unit/GithubApiClientReleaseTest.php b/test/unit/GithubApiClientReleaseTest.php
new file mode 100644
index 0000000..147dc33
--- /dev/null
+++ b/test/unit/GithubApiClientReleaseTest.php
@@ -0,0 +1,457 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Exception;
+use Horde\GithubApiClient\CreateReleaseParams;
+use Horde\GithubApiClient\GithubApiClient;
+use Horde\GithubApiClient\GithubApiConfig;
+use Horde\GithubApiClient\GithubRelease;
+use Horde\GithubApiClient\GithubReleaseAsset;
+use Horde\GithubApiClient\GithubRepository;
+use Horde\GithubApiClient\UpdateReleaseParams;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Client\ClientInterface;
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\StreamFactoryInterface;
+use Psr\Http\Message\StreamInterface;
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+#[CoversClass(GithubApiClient::class)]
+class GithubApiClientReleaseTest extends TestCase
+{
+    public function testCreateReleaseSuccess(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $responseBodyContent = json_encode([
+            'id' => 123,
+            'tag_name' => 'v1.0.0',
+            'name' => 'Version 1.0.0',
+            'body' => 'Release notes',
+            'draft' => false,
+            'prerelease' => false,
+            'created_at' => '2026-01-01T10:00:00Z',
+            'published_at' => '2026-01-01T11:00:00Z',
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v1.0.0',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}',
+            'author' => [
+                'login' => 'octocat',
+                'id' => 1,
+                'avatar_url' => 'https://github.com/images/error/octocat_happy.gif',
+                'html_url' => 'https://github.com/octocat',
+            ],
+            'assets' => [],
+        ]);
+
+        $responseBody->method('__toString')->willReturn($responseBodyContent);
+        $response->method('getStatusCode')->willReturn(201);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+        $params = new CreateReleaseParams(tagName: 'v1.0.0', name: 'Version 1.0.0');
+
+        $release = $client->createRelease($repo, $params);
+
+        $this->assertInstanceOf(GithubRelease::class, $release);
+        $this->assertSame(123, $release->id);
+        $this->assertSame('v1.0.0', $release->tagName);
+        $this->assertSame('Version 1.0.0', $release->name);
+    }
+
+    public function testCreateReleaseThrowsExceptionWithoutStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+        $params = new CreateReleaseParams(tagName: 'v1.0.0');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for createRelease');
+
+        $client->createRelease($repo, $params);
+    }
+
+    public function testCreateReleaseThrowsOn422(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $response->method('getStatusCode')->willReturn(422);
+        $response->method('getReasonPhrase')->willReturn('Unprocessable Entity');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+        $params = new CreateReleaseParams(tagName: 'v1.0.0');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('422 Unprocessable Entity');
+
+        $client->createRelease($repo, $params);
+    }
+
+    public function testGetReleaseByTagSuccess(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBodyStream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+
+        $responseBodyContent = json_encode([
+            'id' => 456,
+            'tag_name' => 'v2.0.0',
+            'name' => 'Version 2.0.0',
+            'body' => 'Major release',
+            'draft' => false,
+            'prerelease' => false,
+            'created_at' => '2026-02-01T12:00:00Z',
+            'published_at' => '2026-02-01T13:00:00Z',
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v2.0.0',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/456/assets{?name,label}',
+            'author' => [
+                'login' => 'developer',
+                'id' => 99,
+                'avatar_url' => 'https://avatars.githubusercontent.com/u/99',
+                'html_url' => 'https://github.com/developer',
+            ],
+            'assets' => [
+                [
+                    'id' => 789,
+                    'name' => 'release.tar.gz',
+                    'label' => 'Source code',
+                    'content_type' => 'application/gzip',
+                    'size' => 2048,
+                    'download_count' => 100,
+                    'state' => 'uploaded',
+                    'browser_download_url' => 'https://github.com/releases/download/v2.0.0/release.tar.gz',
+                    'created_at' => '2026-02-01T12:30:00Z',
+                    'updated_at' => '2026-02-01T12:30:00Z',
+                ],
+            ],
+        ]);
+
+        $response->method('getStatusCode')->willReturn(200);
+        $responseBodyStream->method('__toString')->willReturn($responseBodyContent);
+        $response->method('getBody')->willReturn($responseBodyStream);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $release = $client->getReleaseByTag($repo, 'v2.0.0');
+
+        $this->assertInstanceOf(GithubRelease::class, $release);
+        $this->assertSame(456, $release->id);
+        $this->assertSame('v2.0.0', $release->tagName);
+        $this->assertCount(1, $release->assets);
+    }
+
+    public function testGetReleaseByTagThrowsOn404(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->getReleaseByTag($repo, 'nonexistent-tag');
+    }
+
+    public function testUpdateReleaseSuccess(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBodyStream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $responseBodyContent = json_encode([
+            'id' => 123,
+            'tag_name' => 'v1.0.1',
+            'name' => 'Version 1.0.1',
+            'body' => 'Updated release notes',
+            'draft' => false,
+            'prerelease' => false,
+            'created_at' => '2026-01-01T10:00:00Z',
+            'published_at' => '2026-01-01T12:00:00Z',
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v1.0.1',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}',
+            'author' => [
+                'login' => 'octocat',
+                'id' => 1,
+                'avatar_url' => 'https://github.com/images/error/octocat_happy.gif',
+                'html_url' => 'https://github.com/octocat',
+            ],
+            'assets' => [],
+        ]);
+
+        $response->method('getStatusCode')->willReturn(200);
+        $responseBodyStream->method('__toString')->willReturn($responseBodyContent);
+        $response->method('getBody')->willReturn($responseBodyStream);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+        $params = new UpdateReleaseParams(body: 'Updated release notes');
+
+        $release = $client->updateRelease($repo, 123, $params);
+
+        $this->assertInstanceOf(GithubRelease::class, $release);
+        $this->assertSame(123, $release->id);
+        $this->assertSame('Updated release notes', $release->body);
+    }
+
+    public function testUpdateReleaseThrowsExceptionWithoutStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+        $params = new UpdateReleaseParams(draft: false);
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for updateRelease');
+
+        $client->updateRelease($repo, 123, $params);
+    }
+
+    public function testUpdateReleaseThrowsOn404(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+        $params = new UpdateReleaseParams(name: 'Updated Name');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->updateRelease($repo, 99999, $params);
+    }
+
+    public function testUploadReleaseAssetSuccess(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBodyStream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $responseBodyContent = json_encode([
+            'id' => 999,
+            'name' => 'release.zip',
+            'label' => 'Release archive',
+            'content_type' => 'application/zip',
+            'size' => 4096,
+            'download_count' => 0,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v1.0.0/release.zip',
+            'created_at' => '2026-01-01T15:00:00Z',
+            'updated_at' => '2026-01-01T15:00:00Z',
+        ]);
+
+        $response->method('getStatusCode')->willReturn(201);
+        $responseBodyStream->method('__toString')->willReturn($responseBodyContent);
+        $response->method('getBody')->willReturn($responseBodyStream);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $uploadUrl = 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}';
+
+        $asset = $client->uploadReleaseAsset($uploadUrl, 'release.zip', 'fake-zip-content', 'application/zip');
+
+        $this->assertInstanceOf(GithubReleaseAsset::class, $asset);
+        $this->assertSame(999, $asset->id);
+        $this->assertSame('release.zip', $asset->name);
+        $this->assertSame('application/zip', $asset->contentType);
+    }
+
+    public function testUploadReleaseAssetThrowsExceptionWithoutStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $uploadUrl = 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}';
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for uploadReleaseAsset');
+
+        $client->uploadReleaseAsset($uploadUrl, 'file.txt', 'content');
+    }
+
+    public function testUploadReleaseAssetThrowsOn422(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $response->method('getStatusCode')->willReturn(422);
+        $response->method('getReasonPhrase')->willReturn('Unprocessable Entity');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $uploadUrl = 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}';
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('422 Unprocessable Entity');
+
+        $client->uploadReleaseAsset($uploadUrl, 'duplicate.zip', 'content');
+    }
+
+    public function testUploadReleaseAssetWithDefaultContentType(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'test-token');
+
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBodyStream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        $responseBodyContent = json_encode([
+            'id' => 888,
+            'name' => 'binary.bin',
+            'label' => '',
+            'content_type' => 'application/octet-stream',
+            'size' => 1024,
+            'download_count' => 0,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v1.0.0/binary.bin',
+            'created_at' => '2026-01-01T16:00:00Z',
+            'updated_at' => '2026-01-01T16:00:00Z',
+        ]);
+
+        $response->method('getStatusCode')->willReturn(201);
+        $responseBodyStream->method('__toString')->willReturn($responseBodyContent);
+        $response->method('getBody')->willReturn($responseBodyStream);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $uploadUrl = 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}';
+
+        // Test without specifying contentType (should default to application/octet-stream)
+        $asset = $client->uploadReleaseAsset($uploadUrl, 'binary.bin', 'binary-content');
+
+        $this->assertInstanceOf(GithubReleaseAsset::class, $asset);
+        $this->assertSame('application/octet-stream', $asset->contentType);
+    }
+}
diff --git a/test/unit/GithubReleaseAssetTest.php b/test/unit/GithubReleaseAssetTest.php
new file mode 100644
index 0000000..3cef412
--- /dev/null
+++ b/test/unit/GithubReleaseAssetTest.php
@@ -0,0 +1,234 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+#[CoversClass(GithubReleaseAsset::class)]
+class GithubReleaseAssetTest extends TestCase
+{
+    public function testConstruction(): void
+    {
+        $asset = new GithubReleaseAsset(
+            id: 123,
+            name: 'example.zip',
+            label: 'Example archive',
+            contentType: 'application/zip',
+            size: 2048,
+            downloadCount: 42,
+            state: 'uploaded',
+            browserDownloadUrl: 'https://github.com/releases/download/v1.0.0/example.zip',
+            createdAt: '2026-01-01T12:00:00Z',
+            updatedAt: '2026-01-01T12:30:00Z',
+        );
+
+        $this->assertSame(123, $asset->id);
+        $this->assertSame('example.zip', $asset->name);
+        $this->assertSame('Example archive', $asset->label);
+        $this->assertSame('application/zip', $asset->contentType);
+        $this->assertSame(2048, $asset->size);
+        $this->assertSame(42, $asset->downloadCount);
+        $this->assertSame('uploaded', $asset->state);
+        $this->assertSame('https://github.com/releases/download/v1.0.0/example.zip', $asset->browserDownloadUrl);
+        $this->assertSame('2026-01-01T12:00:00Z', $asset->createdAt);
+        $this->assertSame('2026-01-01T12:30:00Z', $asset->updatedAt);
+    }
+
+    public function testFromApiResponse(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 456,
+            'name' => 'release.tar.gz',
+            'label' => 'Source code',
+            'content_type' => 'application/gzip',
+            'size' => 4096,
+            'download_count' => 150,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v2.0.0/release.tar.gz',
+            'created_at' => '2026-02-01T10:00:00Z',
+            'updated_at' => '2026-02-01T10:05:00Z',
+        ]));
+
+        $asset = GithubReleaseAsset::fromApiResponse($data);
+
+        $this->assertSame(456, $asset->id);
+        $this->assertSame('release.tar.gz', $asset->name);
+        $this->assertSame('Source code', $asset->label);
+        $this->assertSame('application/gzip', $asset->contentType);
+        $this->assertSame(4096, $asset->size);
+        $this->assertSame(150, $asset->downloadCount);
+        $this->assertSame('uploaded', $asset->state);
+        $this->assertSame('https://github.com/releases/download/v2.0.0/release.tar.gz', $asset->browserDownloadUrl);
+        $this->assertSame('2026-02-01T10:00:00Z', $asset->createdAt);
+        $this->assertSame('2026-02-01T10:05:00Z', $asset->updatedAt);
+    }
+
+    public function testFromApiResponseWithEmptyLabel(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 789,
+            'name' => 'binary.exe',
+            'label' => '',
+            'content_type' => 'application/octet-stream',
+            'size' => 8192,
+            'download_count' => 0,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v1.0.0/binary.exe',
+            'created_at' => '2026-01-15T14:00:00Z',
+            'updated_at' => '2026-01-15T14:00:00Z',
+        ]));
+
+        $asset = GithubReleaseAsset::fromApiResponse($data);
+
+        $this->assertSame('', $asset->label);
+    }
+
+    public function testFromApiResponseZeroDownloads(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 111,
+            'name' => 'new-asset.dmg',
+            'label' => 'macOS installer',
+            'content_type' => 'application/x-apple-diskimage',
+            'size' => 16384,
+            'download_count' => 0,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v3.0.0/new-asset.dmg',
+            'created_at' => '2026-03-01T08:00:00Z',
+            'updated_at' => '2026-03-01T08:00:00Z',
+        ]));
+
+        $asset = GithubReleaseAsset::fromApiResponse($data);
+
+        $this->assertSame(0, $asset->downloadCount);
+    }
+
+    public function testFromApiResponseLargeFile(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 222,
+            'name' => 'large-file.iso',
+            'label' => 'Installation media',
+            'content_type' => 'application/x-iso9660-image',
+            'size' => 4294967296, // 4GB
+            'download_count' => 1000,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v5.0.0/large-file.iso',
+            'created_at' => '2026-02-15T00:00:00Z',
+            'updated_at' => '2026-02-15T01:00:00Z',
+        ]));
+
+        $asset = GithubReleaseAsset::fromApiResponse($data);
+
+        $this->assertSame(4294967296, $asset->size);
+    }
+
+    public function testFromApiResponseDifferentContentTypes(): void
+    {
+        $testCases = [
+            'application/zip',
+            'application/gzip',
+            'application/x-tar',
+            'application/octet-stream',
+            'application/x-apple-diskimage',
+            'application/vnd.debian.binary-package',
+            'application/x-rpm',
+        ];
+
+        foreach ($testCases as $index => $contentType) {
+            $data = json_decode(json_encode([
+                'id' => $index + 1,
+                'name' => "file-{$index}.bin",
+                'label' => "File {$index}",
+                'content_type' => $contentType,
+                'size' => 1024,
+                'download_count' => 10,
+                'state' => 'uploaded',
+                'browser_download_url' => "https://github.com/releases/download/v1.0.0/file-{$index}.bin",
+                'created_at' => '2026-01-01T00:00:00Z',
+                'updated_at' => '2026-01-01T00:00:00Z',
+            ]));
+
+            $asset = GithubReleaseAsset::fromApiResponse($data);
+
+            $this->assertSame($contentType, $asset->contentType);
+        }
+    }
+
+    public function testFromApiResponseDifferentStates(): void
+    {
+        $states = ['uploaded', 'open', 'starter'];
+
+        foreach ($states as $index => $state) {
+            $data = json_decode(json_encode([
+                'id' => $index + 100,
+                'name' => "asset-{$state}.bin",
+                'label' => "Asset in {$state} state",
+                'content_type' => 'application/octet-stream',
+                'size' => 512,
+                'download_count' => 5,
+                'state' => $state,
+                'browser_download_url' => "https://github.com/releases/download/v1.0.0/asset-{$state}.bin",
+                'created_at' => '2026-01-01T00:00:00Z',
+                'updated_at' => '2026-01-01T00:00:00Z',
+            ]));
+
+            $asset = GithubReleaseAsset::fromApiResponse($data);
+
+            $this->assertSame($state, $asset->state);
+        }
+    }
+
+    public function testFromApiResponseHighDownloadCount(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 999,
+            'name' => 'popular-asset.zip',
+            'label' => 'Very popular',
+            'content_type' => 'application/zip',
+            'size' => 1024,
+            'download_count' => 1000000,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v1.0.0/popular-asset.zip',
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-01T00:00:00Z',
+        ]));
+
+        $asset = GithubReleaseAsset::fromApiResponse($data);
+
+        $this->assertSame(1000000, $asset->downloadCount);
+    }
+
+    public function testFromApiResponseWithSpecialCharactersInName(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 333,
+            'name' => 'my-app-v1.0.0-alpha.1+build.123.tar.gz',
+            'label' => 'Special version naming',
+            'content_type' => 'application/gzip',
+            'size' => 2048,
+            'download_count' => 25,
+            'state' => 'uploaded',
+            'browser_download_url' => 'https://github.com/releases/download/v1.0.0-alpha.1/my-app-v1.0.0-alpha.1+build.123.tar.gz',
+            'created_at' => '2026-02-10T12:00:00Z',
+            'updated_at' => '2026-02-10T12:00:00Z',
+        ]));
+
+        $asset = GithubReleaseAsset::fromApiResponse($data);
+
+        $this->assertSame('my-app-v1.0.0-alpha.1+build.123.tar.gz', $asset->name);
+    }
+}
diff --git a/test/unit/GithubReleaseTest.php b/test/unit/GithubReleaseTest.php
new file mode 100644
index 0000000..44b4eab
--- /dev/null
+++ b/test/unit/GithubReleaseTest.php
@@ -0,0 +1,284 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+#[CoversClass(GithubRelease::class)]
+class GithubReleaseTest extends TestCase
+{
+    public function testConstruction(): void
+    {
+        $author = new GithubUser(
+            login: 'octocat',
+            id: 1,
+            avatarUrl: 'https://github.com/images/error/octocat_happy.gif',
+            htmlUrl: 'https://github.com/octocat',
+        );
+
+        $asset = new GithubReleaseAsset(
+            id: 1,
+            name: 'example.zip',
+            label: 'Example archive',
+            contentType: 'application/zip',
+            size: 1024,
+            downloadCount: 42,
+            state: 'uploaded',
+            browserDownloadUrl: 'https://github.com/releases/download/v1.0.0/example.zip',
+            createdAt: '2026-01-01T12:00:00Z',
+            updatedAt: '2026-01-01T12:00:00Z',
+        );
+
+        $release = new GithubRelease(
+            id: 123,
+            tagName: 'v1.0.0',
+            name: 'Version 1.0.0',
+            body: 'Release notes',
+            draft: false,
+            prerelease: false,
+            createdAt: '2026-01-01T10:00:00Z',
+            publishedAt: '2026-01-01T11:00:00Z',
+            htmlUrl: 'https://github.com/owner/repo/releases/tag/v1.0.0',
+            uploadUrl: 'https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}',
+            author: $author,
+            assets: [$asset],
+        );
+
+        $this->assertSame(123, $release->id);
+        $this->assertSame('v1.0.0', $release->tagName);
+        $this->assertSame('Version 1.0.0', $release->name);
+        $this->assertSame('Release notes', $release->body);
+        $this->assertFalse($release->draft);
+        $this->assertFalse($release->prerelease);
+        $this->assertSame('2026-01-01T10:00:00Z', $release->createdAt);
+        $this->assertSame('2026-01-01T11:00:00Z', $release->publishedAt);
+        $this->assertSame('https://github.com/owner/repo/releases/tag/v1.0.0', $release->htmlUrl);
+        $this->assertSame('https://uploads.github.com/repos/owner/repo/releases/123/assets{?name,label}', $release->uploadUrl);
+        $this->assertSame($author, $release->author);
+        $this->assertCount(1, $release->assets);
+        $this->assertSame($asset, $release->assets[0]);
+    }
+
+    public function testFromApiResponseComplete(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 456,
+            'tag_name' => 'v2.0.0',
+            'name' => 'Version 2.0.0',
+            'body' => 'Major release',
+            'draft' => true,
+            'prerelease' => false,
+            'created_at' => '2026-02-01T12:00:00Z',
+            'published_at' => '2026-02-01T13:00:00Z',
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v2.0.0',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/456/assets{?name,label}',
+            'author' => [
+                'login' => 'developer',
+                'id' => 99,
+                'avatar_url' => 'https://avatars.githubusercontent.com/u/99',
+                'html_url' => 'https://github.com/developer',
+            ],
+            'assets' => [
+                [
+                    'id' => 789,
+                    'name' => 'release.tar.gz',
+                    'label' => 'Source code',
+                    'content_type' => 'application/gzip',
+                    'size' => 2048,
+                    'download_count' => 100,
+                    'state' => 'uploaded',
+                    'browser_download_url' => 'https://github.com/releases/download/v2.0.0/release.tar.gz',
+                    'created_at' => '2026-02-01T12:30:00Z',
+                    'updated_at' => '2026-02-01T12:30:00Z',
+                ],
+            ],
+        ]));
+
+        $release = GithubRelease::fromApiResponse($data);
+
+        $this->assertSame(456, $release->id);
+        $this->assertSame('v2.0.0', $release->tagName);
+        $this->assertSame('Version 2.0.0', $release->name);
+        $this->assertSame('Major release', $release->body);
+        $this->assertTrue($release->draft);
+        $this->assertFalse($release->prerelease);
+        $this->assertSame('2026-02-01T12:00:00Z', $release->createdAt);
+        $this->assertSame('2026-02-01T13:00:00Z', $release->publishedAt);
+        $this->assertSame('https://github.com/owner/repo/releases/tag/v2.0.0', $release->htmlUrl);
+        $this->assertSame('https://uploads.github.com/repos/owner/repo/releases/456/assets{?name,label}', $release->uploadUrl);
+        $this->assertSame('developer', $release->author->login);
+        $this->assertCount(1, $release->assets);
+        $this->assertSame('release.tar.gz', $release->assets[0]->name);
+    }
+
+    public function testFromApiResponseMinimal(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 1,
+            'tag_name' => 'v0.1.0',
+            'name' => '',
+            'body' => '',
+            'draft' => false,
+            'prerelease' => true,
+            'created_at' => '2026-01-15T08:00:00Z',
+            'published_at' => null,
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v0.1.0',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/1/assets{?name,label}',
+            'author' => [
+                'login' => 'bot',
+                'id' => 1,
+                'avatar_url' => 'https://avatars.githubusercontent.com/u/1',
+                'html_url' => 'https://github.com/bot',
+            ],
+            'assets' => [],
+        ]));
+
+        $release = GithubRelease::fromApiResponse($data);
+
+        $this->assertSame(1, $release->id);
+        $this->assertSame('v0.1.0', $release->tagName);
+        $this->assertSame('', $release->name);
+        $this->assertSame('', $release->body);
+        $this->assertFalse($release->draft);
+        $this->assertTrue($release->prerelease);
+        $this->assertSame('2026-01-15T08:00:00Z', $release->createdAt);
+        $this->assertSame('', $release->publishedAt);
+        $this->assertCount(0, $release->assets);
+    }
+
+    public function testFromApiResponseWithMultipleAssets(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 999,
+            'tag_name' => 'v3.0.0',
+            'name' => 'Version 3.0.0',
+            'body' => 'Release with multiple assets',
+            'draft' => false,
+            'prerelease' => false,
+            'created_at' => '2026-03-01T00:00:00Z',
+            'published_at' => '2026-03-01T01:00:00Z',
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v3.0.0',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/999/assets{?name,label}',
+            'author' => [
+                'login' => 'maintainer',
+                'id' => 123,
+                'avatar_url' => 'https://avatars.githubusercontent.com/u/123',
+                'html_url' => 'https://github.com/maintainer',
+            ],
+            'assets' => [
+                [
+                    'id' => 1001,
+                    'name' => 'app.exe',
+                    'label' => 'Windows executable',
+                    'content_type' => 'application/octet-stream',
+                    'size' => 5120,
+                    'download_count' => 250,
+                    'state' => 'uploaded',
+                    'browser_download_url' => 'https://github.com/releases/download/v3.0.0/app.exe',
+                    'created_at' => '2026-03-01T00:30:00Z',
+                    'updated_at' => '2026-03-01T00:30:00Z',
+                ],
+                [
+                    'id' => 1002,
+                    'name' => 'app.dmg',
+                    'label' => 'macOS disk image',
+                    'content_type' => 'application/x-apple-diskimage',
+                    'size' => 10240,
+                    'download_count' => 180,
+                    'state' => 'uploaded',
+                    'browser_download_url' => 'https://github.com/releases/download/v3.0.0/app.dmg',
+                    'created_at' => '2026-03-01T00:35:00Z',
+                    'updated_at' => '2026-03-01T00:35:00Z',
+                ],
+                [
+                    'id' => 1003,
+                    'name' => 'app.tar.gz',
+                    'label' => 'Linux binary',
+                    'content_type' => 'application/gzip',
+                    'size' => 3072,
+                    'download_count' => 320,
+                    'state' => 'uploaded',
+                    'browser_download_url' => 'https://github.com/releases/download/v3.0.0/app.tar.gz',
+                    'created_at' => '2026-03-01T00:40:00Z',
+                    'updated_at' => '2026-03-01T00:40:00Z',
+                ],
+            ],
+        ]));
+
+        $release = GithubRelease::fromApiResponse($data);
+
+        $this->assertCount(3, $release->assets);
+        $this->assertSame('app.exe', $release->assets[0]->name);
+        $this->assertSame('app.dmg', $release->assets[1]->name);
+        $this->assertSame('app.tar.gz', $release->assets[2]->name);
+    }
+
+    public function testFromApiResponseDraftRelease(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 111,
+            'tag_name' => 'v1.0.0-rc1',
+            'name' => 'Release Candidate 1',
+            'body' => 'Testing before final release',
+            'draft' => true,
+            'prerelease' => true,
+            'created_at' => '2026-02-20T10:00:00Z',
+            'published_at' => null,
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v1.0.0-rc1',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/111/assets{?name,label}',
+            'author' => [
+                'login' => 'tester',
+                'id' => 50,
+                'avatar_url' => 'https://avatars.githubusercontent.com/u/50',
+                'html_url' => 'https://github.com/tester',
+            ],
+            'assets' => [],
+        ]));
+
+        $release = GithubRelease::fromApiResponse($data);
+
+        $this->assertTrue($release->draft);
+        $this->assertTrue($release->prerelease);
+        $this->assertSame('', $release->publishedAt);
+    }
+
+    public function testFromApiResponseWithNullPublishedAt(): void
+    {
+        $data = json_decode(json_encode([
+            'id' => 222,
+            'tag_name' => 'v1.5.0',
+            'name' => 'Unpublished',
+            'body' => 'Not yet published',
+            'draft' => true,
+            'prerelease' => false,
+            'created_at' => '2026-02-25T15:00:00Z',
+            'published_at' => null,
+            'html_url' => 'https://github.com/owner/repo/releases/tag/v1.5.0',
+            'upload_url' => 'https://uploads.github.com/repos/owner/repo/releases/222/assets{?name,label}',
+            'author' => [
+                'login' => 'author',
+                'id' => 10,
+                'avatar_url' => 'https://avatars.githubusercontent.com/u/10',
+                'html_url' => 'https://github.com/author',
+            ],
+            'assets' => [],
+        ]));
+
+        $release = GithubRelease::fromApiResponse($data);
+
+        $this->assertSame('', $release->publishedAt);
+    }
+}
diff --git a/test/unit/UpdateReleaseParamsTest.php b/test/unit/UpdateReleaseParamsTest.php
new file mode 100644
index 0000000..282da98
--- /dev/null
+++ b/test/unit/UpdateReleaseParamsTest.php
@@ -0,0 +1,218 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Copyright 2026 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file LICENSE for license information (LGPL). If you
+ * did not receive this file, see http://www.horde.org/licenses/lgpl21.
+ *
+ * @category Horde
+ * @package  GithubApiClient
+ * @license  http://www.horde.org/licenses/lgpl21 LGPL 2.1
+ */
+#[CoversClass(UpdateReleaseParams::class)]
+class UpdateReleaseParamsTest extends TestCase
+{
+    public function testEmptyConstruction(): void
+    {
+        $params = new UpdateReleaseParams();
+
+        $this->assertNull($params->tagName);
+        $this->assertNull($params->name);
+        $this->assertNull($params->body);
+        $this->assertNull($params->targetCommitish);
+        $this->assertNull($params->draft);
+        $this->assertNull($params->prerelease);
+    }
+
+    public function testFullConstruction(): void
+    {
+        $params = new UpdateReleaseParams(
+            tagName: 'v2.1.0',
+            name: 'Updated Release',
+            body: 'Updated release notes',
+            draft: false,
+            prerelease: true,
+        );
+
+        $this->assertSame('v2.1.0', $params->tagName);
+        $this->assertSame('Updated Release', $params->name);
+        $this->assertSame('Updated release notes', $params->body);
+        $this->assertFalse($params->draft);
+        $this->assertTrue($params->prerelease);
+    }
+
+    public function testIsEmptyWithNoParameters(): void
+    {
+        $params = new UpdateReleaseParams();
+
+        $this->assertTrue($params->isEmpty());
+    }
+
+    public function testIsEmptyWithTagName(): void
+    {
+        $params = new UpdateReleaseParams(tagName: 'v1.0.0');
+
+        $this->assertFalse($params->isEmpty());
+    }
+
+    public function testIsEmptyWithName(): void
+    {
+        $params = new UpdateReleaseParams(name: 'Release Name');
+
+        $this->assertFalse($params->isEmpty());
+    }
+
+    public function testIsEmptyWithBody(): void
+    {
+        $params = new UpdateReleaseParams(body: 'Release body');
+
+        $this->assertFalse($params->isEmpty());
+    }
+
+    public function testIsEmptyWithDraft(): void
+    {
+        $params = new UpdateReleaseParams(draft: true);
+
+        $this->assertFalse($params->isEmpty());
+    }
+
+    public function testIsEmptyWithPrerelease(): void
+    {
+        $params = new UpdateReleaseParams(prerelease: false);
+
+        $this->assertFalse($params->isEmpty());
+    }
+
+    public function testToArrayEmpty(): void
+    {
+        $params = new UpdateReleaseParams();
+
+        $array = $params->toArray();
+
+        $this->assertSame([], $array);
+    }
+
+    public function testToArrayWithTagName(): void
+    {
+        $params = new UpdateReleaseParams(tagName: 'v2.0.0');
+
+        $array = $params->toArray();
+
+        $this->assertSame(['tag_name' => 'v2.0.0'], $array);
+    }
+
+    public function testToArrayWithName(): void
+    {
+        $params = new UpdateReleaseParams(name: 'Version 2.0');
+
+        $array = $params->toArray();
+
+        $this->assertSame(['name' => 'Version 2.0'], $array);
+    }
+
+    public function testToArrayWithBody(): void
+    {
+        $params = new UpdateReleaseParams(body: 'New release notes');
+
+        $array = $params->toArray();
+
+        $this->assertSame(['body' => 'New release notes'], $array);
+    }
+
+    public function testToArrayWithDraftTrue(): void
+    {
+        $params = new UpdateReleaseParams(draft: true);
+
+        $array = $params->toArray();
+
+        $this->assertSame(['draft' => true], $array);
+    }
+
+    public function testToArrayWithDraftFalse(): void
+    {
+        $params = new UpdateReleaseParams(draft: false);
+
+        $array = $params->toArray();
+
+        $this->assertSame(['draft' => false], $array);
+    }
+
+    public function testToArrayWithPrereleaseFalse(): void
+    {
+        $params = new UpdateReleaseParams(prerelease: false);
+
+        $array = $params->toArray();
+
+        $this->assertSame(['prerelease' => false], $array);
+    }
+
+    public function testToArrayWithPrereleaseTrue(): void
+    {
+        $params = new UpdateReleaseParams(prerelease: true);
+
+        $array = $params->toArray();
+
+        $this->assertSame(['prerelease' => true], $array);
+    }
+
+    public function testToArrayFull(): void
+    {
+        $params = new UpdateReleaseParams(
+            tagName: 'v3.0.0',
+            name: 'Major Update',
+            body: 'Complete rewrite',
+            draft: false,
+            prerelease: false,
+        );
+
+        $array = $params->toArray();
+
+        $this->assertSame([
+            'tag_name' => 'v3.0.0',
+            'name' => 'Major Update',
+            'body' => 'Complete rewrite',
+            'draft' => false,
+            'prerelease' => false,
+        ], $array);
+    }
+
+    public function testToArrayWithEmptyStrings(): void
+    {
+        $params = new UpdateReleaseParams(
+            name: '',
+            body: '',
+        );
+
+        $array = $params->toArray();
+
+        // Empty strings should still be included for updates (to clear fields)
+        $this->assertSame([
+            'name' => '',
+            'body' => '',
+        ], $array);
+    }
+
+    public function testPublishDraftRelease(): void
+    {
+        $params = new UpdateReleaseParams(draft: false);
+
+        $this->assertFalse($params->isEmpty());
+        $this->assertSame(['draft' => false], $params->toArray());
+    }
+
+    public function testMarkAsPrerelease(): void
+    {
+        $params = new UpdateReleaseParams(prerelease: true);
+
+        $this->assertFalse($params->isEmpty());
+        $this->assertSame(['prerelease' => true], $params->toArray());
+    }
+}