diff --git a/src/CreateIssueParams.php b/src/CreateIssueParams.php
new file mode 100644
index 0000000..3bfda52
--- /dev/null
+++ b/src/CreateIssueParams.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Data transfer object for creating an issue
+ *
+ * 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 CreateIssueParams
+{
+    /**
+     * @param string $title Issue title (required)
+     * @param string $body Issue body; emitted only when non-empty
+     * @param string[] $assignees Usernames to assign; emitted only when non-empty
+     * @param string[] $labels Label names; emitted only when non-empty
+     * @param int|null $milestone Milestone number to assign; emitted only when set
+     * @param string $type Issue type name; emitted only when non-empty
+     */
+    public function __construct(
+        public readonly string $title,
+        public readonly string $body = '',
+        public readonly array $assignees = [],
+        public readonly array $labels = [],
+        public readonly ?int $milestone = null,
+        public readonly string $type = ''
+    ) {}
+
+    /**
+     * Convert to array for API request body.
+     *
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        $data = ['title' => $this->title];
+
+        if ($this->body !== '') {
+            $data['body'] = $this->body;
+        }
+        if ($this->assignees !== []) {
+            $data['assignees'] = $this->assignees;
+        }
+        if ($this->labels !== []) {
+            $data['labels'] = $this->labels;
+        }
+        if ($this->milestone !== null) {
+            $data['milestone'] = $this->milestone;
+        }
+        if ($this->type !== '') {
+            $data['type'] = $this->type;
+        }
+
+        return $data;
+    }
+}
diff --git a/src/CreateIssueRequestFactory.php b/src/CreateIssueRequestFactory.php
new file mode 100644
index 0000000..5c58e83
--- /dev/null
+++ b/src/CreateIssueRequestFactory.php
@@ -0,0 +1,54 @@
+<?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 an issue
+ *
+ * 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 CreateIssueRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly CreateIssueParams $params
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/issues',
+            $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', $url);
+        if ($this->config->accessToken !== '') {
+            $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/CreateIssueTypeParams.php b/src/CreateIssueTypeParams.php
new file mode 100644
index 0000000..cac8478
--- /dev/null
+++ b/src/CreateIssueTypeParams.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Data transfer object for creating an organization-level issue type
+ *
+ * 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 CreateIssueTypeParams
+{
+    /**
+     * @param string $name Type name (required), e.g. "Bug"
+     * @param string $description Optional description; emitted only when non-empty
+     * @param string $color One of GitHub's enum colors (gray|blue|green|yellow|orange|red|pink|purple); emitted only when non-empty
+     * @param bool $isEnabled Whether the type is active in the org's UI (default: true)
+     */
+    public function __construct(
+        public readonly string $name,
+        public readonly string $description = '',
+        public readonly string $color = '',
+        public readonly bool $isEnabled = true
+    ) {}
+
+    /**
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        $data = [
+            'name' => $this->name,
+            'is_enabled' => $this->isEnabled,
+        ];
+
+        if ($this->description !== '') {
+            $data['description'] = $this->description;
+        }
+        if ($this->color !== '') {
+            $data['color'] = $this->color;
+        }
+
+        return $data;
+    }
+}
diff --git a/src/CreateIssueTypeRequestFactory.php b/src/CreateIssueTypeRequestFactory.php
new file mode 100644
index 0000000..dcd7f90
--- /dev/null
+++ b/src/CreateIssueTypeRequestFactory.php
@@ -0,0 +1,53 @@
+<?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 an organization-level issue type
+ *
+ * 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 CreateIssueTypeRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubOrganizationId $org,
+        private readonly CreateIssueTypeParams $params
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/orgs/%s/issue-types',
+            (string) $this->org
+        );
+
+        $jsonBody = json_encode($this->params->toArray(), JSON_THROW_ON_ERROR);
+        $stream = $this->streamFactory->createStream($jsonBody);
+
+        $request = $this->requestFactory->createRequest('POST', $url);
+        if ($this->config->accessToken !== '') {
+            $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/CreateMilestoneParams.php b/src/CreateMilestoneParams.php
new file mode 100644
index 0000000..7c1d026
--- /dev/null
+++ b/src/CreateMilestoneParams.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use DateTimeImmutable;
+
+/**
+ * Data transfer object for creating a milestone
+ *
+ * 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 CreateMilestoneParams
+{
+    /**
+     * @param string $title Milestone title (required)
+     * @param string $state 'open' (default) or 'closed'
+     * @param string $description Optional description; emitted only when non-empty
+     * @param DateTimeImmutable|null $dueOn Optional due date; emitted as ISO 8601 in due_on
+     */
+    public function __construct(
+        public readonly string $title,
+        public readonly string $state = 'open',
+        public readonly string $description = '',
+        public readonly ?DateTimeImmutable $dueOn = null
+    ) {}
+
+    /**
+     * Convert to array for API request body.
+     *
+     * @return array<string, string>
+     */
+    public function toArray(): array
+    {
+        $data = [
+            'title' => $this->title,
+            'state' => $this->state,
+        ];
+
+        if ($this->description !== '') {
+            $data['description'] = $this->description;
+        }
+        if ($this->dueOn !== null) {
+            $data['due_on'] = $this->dueOn->format(DATE_ATOM);
+        }
+
+        return $data;
+    }
+}
diff --git a/src/CreateMilestoneRequestFactory.php b/src/CreateMilestoneRequestFactory.php
new file mode 100644
index 0000000..22793ab
--- /dev/null
+++ b/src/CreateMilestoneRequestFactory.php
@@ -0,0 +1,54 @@
+<?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 milestone
+ *
+ * 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 CreateMilestoneRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly CreateMilestoneParams $params
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/milestones',
+            $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', $url);
+        if ($this->config->accessToken !== '') {
+            $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/DeleteIssueTypeRequestFactory.php b/src/DeleteIssueTypeRequestFactory.php
new file mode 100644
index 0000000..017e526
--- /dev/null
+++ b/src/DeleteIssueTypeRequestFactory.php
@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Factory for creating requests to delete an organization-level issue type
+ *
+ * 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 DeleteIssueTypeRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubOrganizationId $org,
+        private readonly int $issueTypeId
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/orgs/%s/issue-types/%d',
+            (string) $this->org,
+            $this->issueTypeId
+        );
+
+        $request = $this->requestFactory->createRequest('DELETE', $url);
+        if ($this->config->accessToken !== '') {
+            $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        }
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/DeleteMilestoneRequestFactory.php b/src/DeleteMilestoneRequestFactory.php
new file mode 100644
index 0000000..6c94f83
--- /dev/null
+++ b/src/DeleteMilestoneRequestFactory.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Factory for creating requests to delete a milestone
+ *
+ * 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 DeleteMilestoneRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly int $milestoneNumber
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/milestones/%d',
+            $this->repo->owner,
+            $this->repo->name,
+            $this->milestoneNumber
+        );
+
+        $request = $this->requestFactory->createRequest('DELETE', $url);
+        if ($this->config->accessToken !== '') {
+            $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        }
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/GetIssueRequestFactory.php b/src/GetIssueRequestFactory.php
new file mode 100644
index 0000000..b02fe25
--- /dev/null
+++ b/src/GetIssueRequestFactory.php
@@ -0,0 +1,48 @@
+<?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 single issue
+ *
+ * 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 GetIssueRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly int $issueNumber
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/issues/%d',
+            $this->repo->owner,
+            $this->repo->name,
+            $this->issueNumber
+        );
+
+        $request = $this->requestFactory->createRequest('GET', $url);
+        if ($this->config->accessToken !== '') {
+            $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        }
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/GetMilestoneRequestFactory.php b/src/GetMilestoneRequestFactory.php
new file mode 100644
index 0000000..09f9de5
--- /dev/null
+++ b/src/GetMilestoneRequestFactory.php
@@ -0,0 +1,48 @@
+<?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 single milestone
+ *
+ * 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 GetMilestoneRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly int $milestoneNumber
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/milestones/%d',
+            $this->repo->owner,
+            $this->repo->name,
+            $this->milestoneNumber
+        );
+
+        $request = $this->requestFactory->createRequest('GET', $url);
+        if ($this->config->accessToken !== '') {
+            $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 d238739..06e6abe 100644
--- a/src/GithubApiClient.php
+++ b/src/GithubApiClient.php
@@ -187,6 +187,527 @@ public function updatePullRequest(GithubRepository $repo, int $number, PullReque
         }
     }
 
+    /**
+     * List issues in a repository
+     *
+     * Returns both regular issues and pull requests (every PR is also an issue
+     * at the API level). Use `GithubIssue::$isPullRequest` to distinguish them.
+     *
+     * @param GithubRepository $repo The repository
+     * @param string $state 'open' (default), 'closed', or 'all'
+     * @param string $labels Comma-separated label names to filter by; empty for no filter
+     * @param string $milestone Milestone number, '*' (any), or 'none'; empty for no filter
+     * @param string $assignee Assignee login, '*' (any), or 'none'; empty for no filter
+     * @return GithubIssueList
+     * @throws Exception
+     */
+    public function listIssues(
+        GithubRepository $repo,
+        string $state = 'open',
+        string $labels = '',
+        string $milestone = '',
+        string $assignee = ''
+    ): GithubIssueList {
+        $requestFactory = new ListIssuesRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $repo,
+            $state,
+            $labels,
+            $milestone,
+            $assignee
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            $issueFactory = new GithubIssueFactory();
+            $issues = [];
+            if (is_array($data)) {
+                foreach ($data as $issueData) {
+                    if (is_object($issueData)) {
+                        $issues[] = $issueFactory->createFromApiResponse($issueData);
+                    }
+                }
+            }
+            return new GithubIssueList($issues);
+        } else {
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Get a single issue
+     *
+     * Works for both regular issues and pull requests — issues and PRs share
+     * a single counter per repo, so this returns whatever lives at #$number.
+     * Inspect `GithubIssue::$isPullRequest` to detect a PR.
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $number The issue (or PR) number
+     * @return GithubIssue
+     * @throws Exception
+     */
+    public function getIssue(GithubRepository $repo, int $number): GithubIssue
+    {
+        $requestFactory = new GetIssueRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $repo,
+            $number
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            $issueFactory = new GithubIssueFactory();
+            return $issueFactory->createFromApiResponse($data);
+        } else {
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Create a new issue
+     *
+     * @param GithubRepository $repo The repository
+     * @param CreateIssueParams $params The issue parameters
+     * @return GithubIssue The created issue
+     * @throws Exception
+     */
+    public function createIssue(GithubRepository $repo, CreateIssueParams $params): GithubIssue
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for createIssue. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new CreateIssueRequestFactory(
+            $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());
+            $issueFactory = new GithubIssueFactory();
+            return $issueFactory->createFromApiResponse($data);
+        } else {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Update an issue
+     *
+     * The IssueUpdate DTO distinguishes "leave alone" from "clear" — calling
+     * withMilestone(null) or withType(null) emits literal null in the request
+     * body, which is GitHub's signal to clear the current assignment.
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $number The issue (or PR) number
+     * @param IssueUpdate $update The update DTO
+     * @return GithubIssue The updated issue
+     * @throws Exception
+     */
+    public function updateIssue(GithubRepository $repo, int $number, IssueUpdate $update): GithubIssue
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for updateIssue. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new UpdateIssueRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $repo,
+            $number,
+            $update
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            $issueFactory = new GithubIssueFactory();
+            return $issueFactory->createFromApiResponse($data);
+        } else {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Close an issue (symmetric with closePullRequest)
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $number The issue number
+     * @return GithubIssue The closed issue
+     * @throws Exception
+     */
+    public function closeIssue(GithubRepository $repo, int $number): GithubIssue
+    {
+        return $this->updateIssue($repo, $number, (new IssueUpdate())->withState('closed'));
+    }
+
+    /**
+     * Reopen a closed issue (symmetric with reopenPullRequest)
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $number The issue number
+     * @return GithubIssue The reopened issue
+     * @throws Exception
+     */
+    public function reopenIssue(GithubRepository $repo, int $number): GithubIssue
+    {
+        return $this->updateIssue($repo, $number, (new IssueUpdate())->withState('open'));
+    }
+
+    /**
+     * List milestones in a repository
+     *
+     * @param GithubRepository $repo The repository
+     * @param string $state 'open' (default), 'closed', or 'all'
+     * @return GithubMilestoneList
+     * @throws Exception
+     */
+    public function listMilestones(GithubRepository $repo, string $state = 'open'): GithubMilestoneList
+    {
+        $requestFactory = new ListMilestonesRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $repo,
+            $state
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            $milestones = [];
+            if (is_array($data)) {
+                foreach ($data as $entry) {
+                    if (is_object($entry)) {
+                        $milestones[] = GithubMilestone::fromApiResponse($entry);
+                    }
+                }
+            }
+            return new GithubMilestoneList($milestones);
+        } else {
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Get a single milestone
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $milestoneNumber The milestone number
+     * @return GithubMilestone
+     * @throws Exception
+     */
+    public function getMilestone(GithubRepository $repo, int $milestoneNumber): GithubMilestone
+    {
+        $requestFactory = new GetMilestoneRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $repo,
+            $milestoneNumber
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            return GithubMilestone::fromApiResponse($data);
+        } else {
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Create a milestone
+     *
+     * @param GithubRepository $repo The repository
+     * @param CreateMilestoneParams $params Milestone parameters
+     * @return GithubMilestone The created milestone
+     * @throws Exception
+     */
+    public function createMilestone(GithubRepository $repo, CreateMilestoneParams $params): GithubMilestone
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for createMilestone. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new CreateMilestoneRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $repo,
+            $params
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 201) {
+            $data = json_decode((string) $response->getBody());
+            return GithubMilestone::fromApiResponse($data);
+        } else {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Update a milestone
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $milestoneNumber The milestone number
+     * @param UpdateMilestoneParams $params Update parameters
+     * @return GithubMilestone The updated milestone
+     * @throws Exception
+     */
+    public function updateMilestone(GithubRepository $repo, int $milestoneNumber, UpdateMilestoneParams $params): GithubMilestone
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for updateMilestone. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new UpdateMilestoneRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $repo,
+            $milestoneNumber,
+            $params
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            return GithubMilestone::fromApiResponse($data);
+        } else {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Delete a milestone
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $milestoneNumber The milestone number
+     * @return void
+     * @throws Exception
+     */
+    public function deleteMilestone(GithubRepository $repo, int $milestoneNumber): void
+    {
+        $requestFactory = new DeleteMilestoneRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $repo,
+            $milestoneNumber
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() !== 204) {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Assign a milestone to an issue (convenience wrapper for updateIssue)
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $issueNumber The issue (or PR) number
+     * @param int $milestoneNumber The milestone number to assign
+     * @return GithubIssue The updated issue
+     * @throws Exception
+     */
+    public function assignMilestone(GithubRepository $repo, int $issueNumber, int $milestoneNumber): GithubIssue
+    {
+        return $this->updateIssue($repo, $issueNumber, (new IssueUpdate())->withMilestone($milestoneNumber));
+    }
+
+    /**
+     * Clear the milestone on an issue (convenience wrapper for updateIssue)
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $issueNumber The issue (or PR) number
+     * @return GithubIssue The updated issue
+     * @throws Exception
+     */
+    public function unassignMilestone(GithubRepository $repo, int $issueNumber): GithubIssue
+    {
+        return $this->updateIssue($repo, $issueNumber, (new IssueUpdate())->withMilestone(null));
+    }
+
+    /**
+     * List organization-level issue types
+     *
+     * @param GithubOrganizationId $org The organization
+     * @return GithubIssueTypeList
+     * @throws Exception
+     */
+    public function listIssueTypes(GithubOrganizationId $org): GithubIssueTypeList
+    {
+        $requestFactory = new ListIssueTypesRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $org
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            $types = [];
+            if (is_array($data)) {
+                foreach ($data as $entry) {
+                    if (is_object($entry)) {
+                        $types[] = GithubIssueType::fromApiResponse($entry);
+                    }
+                }
+            }
+            return new GithubIssueTypeList($types);
+        } else {
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Create an organization-level issue type
+     *
+     * @param GithubOrganizationId $org The organization
+     * @param CreateIssueTypeParams $params The issue type parameters
+     * @return GithubIssueType The created issue type
+     * @throws Exception
+     */
+    public function createIssueType(GithubOrganizationId $org, CreateIssueTypeParams $params): GithubIssueType
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for createIssueType. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new CreateIssueTypeRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $org,
+            $params
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 201) {
+            $data = json_decode((string) $response->getBody());
+            return GithubIssueType::fromApiResponse($data);
+        } else {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Update an organization-level issue type
+     *
+     * GitHub uses PUT for this endpoint (not PATCH).
+     *
+     * @param GithubOrganizationId $org The organization
+     * @param int $issueTypeId The numeric id of the issue type
+     * @param UpdateIssueTypeParams $params Update parameters
+     * @return GithubIssueType The updated issue type
+     * @throws Exception
+     */
+    public function updateIssueType(GithubOrganizationId $org, int $issueTypeId, UpdateIssueTypeParams $params): GithubIssueType
+    {
+        if ($this->streamFactory === null) {
+            throw new Exception('StreamFactory is required for updateIssueType. Please provide it in the constructor.');
+        }
+
+        $requestFactory = new UpdateIssueTypeRequestFactory(
+            $this->requestFactory,
+            $this->streamFactory,
+            $this->config,
+            $org,
+            $issueTypeId,
+            $params
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() === 200) {
+            $data = json_decode((string) $response->getBody());
+            return GithubIssueType::fromApiResponse($data);
+        } else {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Delete an organization-level issue type
+     *
+     * @param GithubOrganizationId $org The organization
+     * @param int $issueTypeId The numeric id of the issue type
+     * @return void
+     * @throws Exception
+     */
+    public function deleteIssueType(GithubOrganizationId $org, int $issueTypeId): void
+    {
+        $requestFactory = new DeleteIssueTypeRequestFactory(
+            $this->requestFactory,
+            $this->config,
+            $org,
+            $issueTypeId
+        );
+        $request = $requestFactory->create();
+        $response = $this->httpClient->sendRequest($request);
+
+        if ($response->getStatusCode() !== 204) {
+            $this->maybeThrowAccessDenied($response);
+            throw new Exception($this->parseErrorResponse($response));
+        }
+    }
+
+    /**
+     * Assign an issue type to an issue (convenience wrapper for updateIssue)
+     *
+     * Type assignment is keyed by type name, not id, on the issue PATCH endpoint.
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $issueNumber The issue (or PR) number
+     * @param string $typeName The issue type name (e.g. "Bug")
+     * @return GithubIssue The updated issue
+     * @throws Exception
+     */
+    public function assignIssueType(GithubRepository $repo, int $issueNumber, string $typeName): GithubIssue
+    {
+        return $this->updateIssue($repo, $issueNumber, (new IssueUpdate())->withType($typeName));
+    }
+
+    /**
+     * Clear the issue type on an issue (convenience wrapper for updateIssue)
+     *
+     * @param GithubRepository $repo The repository
+     * @param int $issueNumber The issue (or PR) number
+     * @return GithubIssue The updated issue
+     * @throws Exception
+     */
+    public function unassignIssueType(GithubRepository $repo, int $issueNumber): GithubIssue
+    {
+        return $this->updateIssue($repo, $issueNumber, (new IssueUpdate())->withType(null));
+    }
+
     /**
      * List all comments on a pull request
      *
diff --git a/src/GithubIssue.php b/src/GithubIssue.php
new file mode 100644
index 0000000..7de49c8
--- /dev/null
+++ b/src/GithubIssue.php
@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Stringable;
+
+/**
+ * Represents a GitHub issue
+ *
+ * Note on the issue ↔ PR relationship: in a given repository, issues and pull
+ * requests share a single integer counter. Every PR is also an issue from the
+ * labels/comments/assignees/milestone perspective; the `isPullRequest` flag
+ * surfaces that overlap so callers can detect it without a second request.
+ *
+ * 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 GithubIssue implements Stringable
+{
+    /**
+     * @param GithubUser[] $assignees Users currently assigned (may be empty)
+     * @param GithubLabel[] $labels Labels currently attached (may be empty)
+     * @param array<string, mixed> $fieldValues Custom Issue Field values (from issue_field_values); empty array when none set
+     */
+    public function __construct(
+        public readonly int $id,
+        public readonly int $number,
+        public readonly string $title,
+        public readonly string $body,
+        public readonly string $state,
+        public readonly ?string $stateReason,
+        public readonly string $htmlUrl,
+        public readonly string $apiUrl,
+        public readonly GithubUser $author,
+        public readonly array $labels,
+        public readonly array $assignees,
+        public readonly ?GithubMilestone $milestone,
+        public readonly ?GithubIssueType $type,
+        public readonly int $comments,
+        public readonly string $createdAt,
+        public readonly string $updatedAt,
+        public readonly ?string $closedAt,
+        public readonly bool $isPullRequest,
+        public readonly array $fieldValues = [],
+        public readonly string $nodeId = '',
+    ) {}
+
+    public function __toString(): string
+    {
+        return sprintf('#%d %s', $this->number, $this->title);
+    }
+}
diff --git a/src/GithubIssueFactory.php b/src/GithubIssueFactory.php
new file mode 100644
index 0000000..bb07357
--- /dev/null
+++ b/src/GithubIssueFactory.php
@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Factory for creating GithubIssue objects from API responses
+ *
+ * Decoding here orchestrates the nested value objects (User, Label, Milestone,
+ * Type) via their own factories; missing fields fall back to null/empty cleanly.
+ *
+ * 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 GithubIssueFactory
+{
+    /**
+     * Create GithubIssue from GitHub API response
+     *
+     * @param object $data Decoded JSON issue object from API
+     * @return GithubIssue
+     */
+    public function createFromApiResponse(object $data): GithubIssue
+    {
+        $userFactory = new GithubUserFactory();
+        $labelFactory = new GithubLabelFactory();
+
+        $author = isset($data->user) && is_object($data->user)
+            ? $userFactory->createFromApiResponse($data->user)
+            : new GithubUser(login: '', id: 0, avatarUrl: '', htmlUrl: '');
+
+        $labels = [];
+        if (isset($data->labels) && is_array($data->labels)) {
+            foreach ($data->labels as $labelData) {
+                if (is_object($labelData)) {
+                    $labels[] = $labelFactory->createFromApiResponse($labelData);
+                }
+            }
+        }
+
+        $assignees = [];
+        if (isset($data->assignees) && is_array($data->assignees)) {
+            foreach ($data->assignees as $userData) {
+                if (is_object($userData)) {
+                    $assignees[] = $userFactory->createFromApiResponse($userData);
+                }
+            }
+        }
+
+        $milestone = null;
+        if (isset($data->milestone) && is_object($data->milestone)) {
+            $milestone = GithubMilestone::fromApiResponse($data->milestone);
+        }
+
+        $type = null;
+        if (isset($data->type) && is_object($data->type)) {
+            $type = GithubIssueType::fromApiResponse($data->type);
+        }
+
+        $fieldValues = $this->parseFieldValues($data);
+
+        return new GithubIssue(
+            id: $data->id ?? 0,
+            number: $data->number ?? 0,
+            title: $data->title ?? '',
+            body: $data->body ?? '',
+            state: $data->state ?? 'open',
+            stateReason: $data->state_reason ?? null,
+            htmlUrl: $data->html_url ?? '',
+            apiUrl: $data->url ?? '',
+            author: $author,
+            labels: $labels,
+            assignees: $assignees,
+            milestone: $milestone,
+            type: $type,
+            comments: $data->comments ?? 0,
+            createdAt: $data->created_at ?? '',
+            updatedAt: $data->updated_at ?? '',
+            closedAt: $data->closed_at ?? null,
+            isPullRequest: isset($data->pull_request),
+            fieldValues: $fieldValues,
+            nodeId: $data->node_id ?? '',
+        );
+    }
+
+    /**
+     * Parse the issue_field_values array into a name → value map.
+     *
+     * GitHub returns each entry as an object carrying a name and a value;
+     * we project the array into a flat map so callers don't have to walk
+     * nested objects. Write-side support for these values requires the
+     * GraphQL surface and is not in scope for this iteration.
+     *
+     * @param object $data Decoded JSON issue object
+     * @return array<string, mixed>
+     */
+    private function parseFieldValues(object $data): array
+    {
+        if (!isset($data->issue_field_values) || !is_array($data->issue_field_values)) {
+            return [];
+        }
+
+        $values = [];
+        foreach ($data->issue_field_values as $entry) {
+            if (!is_object($entry)) {
+                continue;
+            }
+            $name = $entry->name ?? '';
+            if ($name === '') {
+                continue;
+            }
+            $values[$name] = $entry->value ?? null;
+        }
+
+        return $values;
+    }
+}
diff --git a/src/GithubIssueList.php b/src/GithubIssueList.php
new file mode 100644
index 0000000..438a198
--- /dev/null
+++ b/src/GithubIssueList.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Countable;
+use Iterator;
+
+/**
+ * Collection of GitHub issues
+ *
+ * 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
+ * @implements Iterator<int, GithubIssue>
+ */
+class GithubIssueList implements Iterator, Countable
+{
+    private int $position = 0;
+
+    /**
+     * @param array<GithubIssue> $issues
+     */
+    public function __construct(
+        private readonly array $issues = []
+    ) {}
+
+    public function current(): GithubIssue
+    {
+        return $this->issues[$this->position];
+    }
+
+    public function key(): int
+    {
+        return $this->position;
+    }
+
+    public function next(): void
+    {
+        ++$this->position;
+    }
+
+    public function rewind(): void
+    {
+        $this->position = 0;
+    }
+
+    public function valid(): bool
+    {
+        return isset($this->issues[$this->position]);
+    }
+
+    public function count(): int
+    {
+        return count($this->issues);
+    }
+
+    /**
+     * @return array<GithubIssue>
+     */
+    public function toArray(): array
+    {
+        return $this->issues;
+    }
+}
diff --git a/src/GithubIssueType.php b/src/GithubIssueType.php
new file mode 100644
index 0000000..e59855a
--- /dev/null
+++ b/src/GithubIssueType.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Stringable;
+
+/**
+ * Represents a GitHub Issue Type (org-level taxonomy entry — Bug, Feature, Task, etc.)
+ *
+ * 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 GithubIssueType implements Stringable
+{
+    public function __construct(
+        public readonly int $id,
+        public readonly string $name,
+        public readonly ?string $description,
+        public readonly ?string $color,
+        public readonly bool $isEnabled,
+        public readonly string $createdAt,
+        public readonly string $updatedAt,
+        public readonly string $nodeId = '',
+    ) {}
+
+    public function __toString(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * Create from GitHub API response
+     *
+     * @param object $data Decoded JSON from API
+     * @return self
+     */
+    public static function fromApiResponse(object $data): self
+    {
+        return new self(
+            id: $data->id ?? 0,
+            name: $data->name ?? '',
+            description: $data->description ?? null,
+            color: $data->color ?? null,
+            isEnabled: $data->is_enabled ?? true,
+            createdAt: $data->created_at ?? '',
+            updatedAt: $data->updated_at ?? '',
+            nodeId: $data->node_id ?? '',
+        );
+    }
+}
diff --git a/src/GithubIssueTypeList.php b/src/GithubIssueTypeList.php
new file mode 100644
index 0000000..eba7ad5
--- /dev/null
+++ b/src/GithubIssueTypeList.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Countable;
+use Iterator;
+
+/**
+ * Collection of GitHub issue types
+ *
+ * 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
+ * @implements Iterator<int, GithubIssueType>
+ */
+class GithubIssueTypeList implements Iterator, Countable
+{
+    private int $position = 0;
+
+    /**
+     * @param array<GithubIssueType> $types
+     */
+    public function __construct(
+        private readonly array $types = []
+    ) {}
+
+    public function current(): GithubIssueType
+    {
+        return $this->types[$this->position];
+    }
+
+    public function key(): int
+    {
+        return $this->position;
+    }
+
+    public function next(): void
+    {
+        ++$this->position;
+    }
+
+    public function rewind(): void
+    {
+        $this->position = 0;
+    }
+
+    public function valid(): bool
+    {
+        return isset($this->types[$this->position]);
+    }
+
+    public function count(): int
+    {
+        return count($this->types);
+    }
+
+    /**
+     * @return array<GithubIssueType>
+     */
+    public function toArray(): array
+    {
+        return $this->types;
+    }
+}
diff --git a/src/GithubMilestone.php b/src/GithubMilestone.php
new file mode 100644
index 0000000..6e1c75d
--- /dev/null
+++ b/src/GithubMilestone.php
@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Stringable;
+
+/**
+ * Represents a GitHub repository milestone
+ *
+ * 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 GithubMilestone implements Stringable
+{
+    public function __construct(
+        public readonly int $id,
+        public readonly int $number,
+        public readonly string $title,
+        public readonly string $description,
+        public readonly string $state,
+        public readonly ?GithubUser $creator,
+        public readonly int $openIssues,
+        public readonly int $closedIssues,
+        public readonly string $htmlUrl,
+        public readonly string $createdAt,
+        public readonly string $updatedAt,
+        public readonly ?string $closedAt,
+        public readonly ?string $dueOn,
+        public readonly string $nodeId = '',
+    ) {}
+
+    public function __toString(): string
+    {
+        return $this->title;
+    }
+
+    /**
+     * Create from GitHub API response
+     *
+     * @param object $data Decoded JSON from API
+     * @return self
+     */
+    public static function fromApiResponse(object $data): self
+    {
+        $creator = null;
+        if (isset($data->creator) && is_object($data->creator)) {
+            $creator = GithubUser::fromApiResponse($data->creator);
+        }
+
+        return new self(
+            id: $data->id ?? 0,
+            number: $data->number ?? 0,
+            title: $data->title ?? '',
+            description: $data->description ?? '',
+            state: $data->state ?? 'open',
+            creator: $creator,
+            openIssues: $data->open_issues ?? 0,
+            closedIssues: $data->closed_issues ?? 0,
+            htmlUrl: $data->html_url ?? '',
+            createdAt: $data->created_at ?? '',
+            updatedAt: $data->updated_at ?? '',
+            closedAt: $data->closed_at ?? null,
+            dueOn: $data->due_on ?? null,
+            nodeId: $data->node_id ?? '',
+        );
+    }
+}
diff --git a/src/GithubMilestoneList.php b/src/GithubMilestoneList.php
new file mode 100644
index 0000000..4da6b08
--- /dev/null
+++ b/src/GithubMilestoneList.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Countable;
+use Iterator;
+
+/**
+ * Collection of GitHub milestones
+ *
+ * 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
+ * @implements Iterator<int, GithubMilestone>
+ */
+class GithubMilestoneList implements Iterator, Countable
+{
+    private int $position = 0;
+
+    /**
+     * @param array<GithubMilestone> $milestones
+     */
+    public function __construct(
+        private readonly array $milestones = []
+    ) {}
+
+    public function current(): GithubMilestone
+    {
+        return $this->milestones[$this->position];
+    }
+
+    public function key(): int
+    {
+        return $this->position;
+    }
+
+    public function next(): void
+    {
+        ++$this->position;
+    }
+
+    public function rewind(): void
+    {
+        $this->position = 0;
+    }
+
+    public function valid(): bool
+    {
+        return isset($this->milestones[$this->position]);
+    }
+
+    public function count(): int
+    {
+        return count($this->milestones);
+    }
+
+    /**
+     * @return array<GithubMilestone>
+     */
+    public function toArray(): array
+    {
+        return $this->milestones;
+    }
+}
diff --git a/src/IssueUpdate.php b/src/IssueUpdate.php
new file mode 100644
index 0000000..a776bfd
--- /dev/null
+++ b/src/IssueUpdate.php
@@ -0,0 +1,197 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Partial-update DTO for an issue.
+ *
+ * Uses a with*() builder + per-field "was-touched" flag so we can distinguish
+ * three states per field: untouched (omit from request body), set to a value
+ * (emit value), set to null (emit literal null). The last distinction matters
+ * because GitHub's `milestone` and `type` fields use null as the "clear current
+ * assignment" signal; emitting the key with null is meaningfully different
+ * from omitting it.
+ *
+ * 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 IssueUpdate
+{
+    private ?string $title = null;
+    private bool $titleSet = false;
+
+    private ?string $body = null;
+    private bool $bodySet = false;
+
+    private ?string $state = null;
+    private bool $stateSet = false;
+
+    private ?string $stateReason = null;
+    private bool $stateReasonSet = false;
+
+    /** @var string[] */
+    private array $labels = [];
+    private bool $labelsSet = false;
+
+    /** @var string[] */
+    private array $assignees = [];
+    private bool $assigneesSet = false;
+
+    private int|string|null $milestone = null;
+    private bool $milestoneSet = false;
+
+    private ?string $type = null;
+    private bool $typeSet = false;
+
+    public function withTitle(?string $title): self
+    {
+        $clone = clone $this;
+        $clone->title = $title;
+        $clone->titleSet = true;
+        return $clone;
+    }
+
+    public function withBody(?string $body): self
+    {
+        $clone = clone $this;
+        $clone->body = $body;
+        $clone->bodySet = true;
+        return $clone;
+    }
+
+    /**
+     * @param string $state 'open' or 'closed'
+     */
+    public function withState(string $state): self
+    {
+        $clone = clone $this;
+        $clone->state = $state;
+        $clone->stateSet = true;
+        return $clone;
+    }
+
+    /**
+     * @param string|null $reason 'completed', 'not_planned', 'reopened', or null to clear
+     */
+    public function withStateReason(?string $reason): self
+    {
+        $clone = clone $this;
+        $clone->stateReason = $reason;
+        $clone->stateReasonSet = true;
+        return $clone;
+    }
+
+    /**
+     * Replace the full set of labels. Pass [] to clear all labels.
+     *
+     * @param string[] $labels
+     */
+    public function withLabels(array $labels): self
+    {
+        $clone = clone $this;
+        $clone->labels = $labels;
+        $clone->labelsSet = true;
+        return $clone;
+    }
+
+    /**
+     * Replace the full set of assignees. Pass [] to clear all assignees.
+     *
+     * @param string[] $assignees Usernames
+     */
+    public function withAssignees(array $assignees): self
+    {
+        $clone = clone $this;
+        $clone->assignees = $assignees;
+        $clone->assigneesSet = true;
+        return $clone;
+    }
+
+    /**
+     * Assign or clear a milestone.
+     *
+     * @param int|null $milestoneNumber Milestone number to assign, or null to clear.
+     */
+    public function withMilestone(?int $milestoneNumber): self
+    {
+        $clone = clone $this;
+        $clone->milestone = $milestoneNumber;
+        $clone->milestoneSet = true;
+        return $clone;
+    }
+
+    /**
+     * Assign or clear an issue type.
+     *
+     * @param string|null $typeName Issue type name to assign, or null to clear.
+     */
+    public function withType(?string $typeName): self
+    {
+        $clone = clone $this;
+        $clone->type = $typeName;
+        $clone->typeSet = true;
+        return $clone;
+    }
+
+    /**
+     * Convert to array for API request body. Only emits keys that were
+     * explicitly touched via a with*() call; emits null for fields
+     * explicitly set to null (the GitHub "clear" signal).
+     *
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        $data = [];
+
+        if ($this->titleSet) {
+            $data['title'] = $this->title;
+        }
+        if ($this->bodySet) {
+            $data['body'] = $this->body;
+        }
+        if ($this->stateSet) {
+            $data['state'] = $this->state;
+        }
+        if ($this->stateReasonSet) {
+            $data['state_reason'] = $this->stateReason;
+        }
+        if ($this->labelsSet) {
+            $data['labels'] = $this->labels;
+        }
+        if ($this->assigneesSet) {
+            $data['assignees'] = $this->assignees;
+        }
+        if ($this->milestoneSet) {
+            $data['milestone'] = $this->milestone;
+        }
+        if ($this->typeSet) {
+            $data['type'] = $this->type;
+        }
+
+        return $data;
+    }
+
+    /**
+     * True when no with*() builder has been called yet.
+     */
+    public function isEmpty(): bool
+    {
+        return !$this->titleSet
+            && !$this->bodySet
+            && !$this->stateSet
+            && !$this->stateReasonSet
+            && !$this->labelsSet
+            && !$this->assigneesSet
+            && !$this->milestoneSet
+            && !$this->typeSet;
+    }
+}
diff --git a/src/ListIssueTypesRequestFactory.php b/src/ListIssueTypesRequestFactory.php
new file mode 100644
index 0000000..7002b64
--- /dev/null
+++ b/src/ListIssueTypesRequestFactory.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Factory for creating requests to list organization-level issue types
+ *
+ * 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 ListIssueTypesRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubOrganizationId $org
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/orgs/%s/issue-types',
+            (string) $this->org
+        );
+
+        $request = $this->requestFactory->createRequest('GET', $url);
+        if ($this->config->accessToken !== '') {
+            $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        }
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/ListIssuesRequestFactory.php b/src/ListIssuesRequestFactory.php
new file mode 100644
index 0000000..64fb49c
--- /dev/null
+++ b/src/ListIssuesRequestFactory.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Factory for creating requests to list issues in a repository
+ *
+ * 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 ListIssuesRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly string $state = 'open',
+        private readonly string $labels = '',
+        private readonly string $milestone = '',
+        private readonly string $assignee = ''
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $query = ['state' => $this->state];
+        if ($this->labels !== '') {
+            $query['labels'] = $this->labels;
+        }
+        if ($this->milestone !== '') {
+            $query['milestone'] = $this->milestone;
+        }
+        if ($this->assignee !== '') {
+            $query['assignee'] = $this->assignee;
+        }
+
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/issues?%s',
+            $this->repo->owner,
+            $this->repo->name,
+            http_build_query($query)
+        );
+
+        $request = $this->requestFactory->createRequest('GET', $url);
+        if ($this->config->accessToken !== '') {
+            $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        }
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/ListMilestonesRequestFactory.php b/src/ListMilestonesRequestFactory.php
new file mode 100644
index 0000000..e1b18b9
--- /dev/null
+++ b/src/ListMilestonesRequestFactory.php
@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Factory for creating requests to list repository milestones
+ *
+ * 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 ListMilestonesRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly string $state = 'open'
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/milestones?%s',
+            $this->repo->owner,
+            $this->repo->name,
+            http_build_query(['state' => $this->state])
+        );
+
+        $request = $this->requestFactory->createRequest('GET', $url);
+        if ($this->config->accessToken !== '') {
+            $request = $request->withHeader('Authorization', 'token ' . $this->config->accessToken);
+        }
+        $request = $request->withHeader('Accept', 'application/vnd.github.v3+json');
+
+        return $request;
+    }
+}
diff --git a/src/UpdateIssueRequestFactory.php b/src/UpdateIssueRequestFactory.php
new file mode 100644
index 0000000..c45f84a
--- /dev/null
+++ b/src/UpdateIssueRequestFactory.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\StreamFactoryInterface;
+
+/**
+ * Factory for creating requests to update an issue
+ *
+ * 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 UpdateIssueRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly int $issueNumber,
+        private readonly IssueUpdate $update
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/issues/%d',
+            $this->repo->owner,
+            $this->repo->name,
+            $this->issueNumber
+        );
+
+        $jsonBody = json_encode($this->update->toArray(), JSON_THROW_ON_ERROR);
+        $stream = $this->streamFactory->createStream($jsonBody);
+
+        $request = $this->requestFactory->createRequest('PATCH', $url);
+        if ($this->config->accessToken !== '') {
+            $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/UpdateIssueTypeParams.php b/src/UpdateIssueTypeParams.php
new file mode 100644
index 0000000..fad83c6
--- /dev/null
+++ b/src/UpdateIssueTypeParams.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+/**
+ * Data transfer object for updating an organization-level issue type.
+ *
+ * All fields optional. All-null toArray() returns [] so no-op updates are
+ * harmless.
+ *
+ * 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 UpdateIssueTypeParams
+{
+    public function __construct(
+        public readonly ?string $name = null,
+        public readonly ?string $description = null,
+        public readonly ?string $color = null,
+        public readonly ?bool $isEnabled = null
+    ) {}
+
+    /**
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        $data = [];
+
+        if ($this->name !== null) {
+            $data['name'] = $this->name;
+        }
+        if ($this->description !== null) {
+            $data['description'] = $this->description;
+        }
+        if ($this->color !== null) {
+            $data['color'] = $this->color;
+        }
+        if ($this->isEnabled !== null) {
+            $data['is_enabled'] = $this->isEnabled;
+        }
+
+        return $data;
+    }
+}
diff --git a/src/UpdateIssueTypeRequestFactory.php b/src/UpdateIssueTypeRequestFactory.php
new file mode 100644
index 0000000..31b068f
--- /dev/null
+++ b/src/UpdateIssueTypeRequestFactory.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 update an organization-level issue type.
+ *
+ * GitHub uses PUT (not PATCH) for issue-type updates, keyed by numeric id.
+ *
+ * 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 UpdateIssueTypeRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubOrganizationId $org,
+        private readonly int $issueTypeId,
+        private readonly UpdateIssueTypeParams $params
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/orgs/%s/issue-types/%d',
+            (string) $this->org,
+            $this->issueTypeId
+        );
+
+        $jsonBody = json_encode($this->params->toArray(), JSON_THROW_ON_ERROR);
+        $stream = $this->streamFactory->createStream($jsonBody);
+
+        $request = $this->requestFactory->createRequest('PUT', $url);
+        if ($this->config->accessToken !== '') {
+            $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/UpdateMilestoneParams.php b/src/UpdateMilestoneParams.php
new file mode 100644
index 0000000..1412ac5
--- /dev/null
+++ b/src/UpdateMilestoneParams.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient;
+
+use DateTimeImmutable;
+
+/**
+ * Data transfer object for updating a milestone.
+ *
+ * All fields optional. All-null toArray() returns [] so no-op updates are
+ * harmless.
+ *
+ * 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 UpdateMilestoneParams
+{
+    public function __construct(
+        public readonly ?string $title = null,
+        public readonly ?string $state = null,
+        public readonly ?string $description = null,
+        public readonly ?DateTimeImmutable $dueOn = null
+    ) {}
+
+    /**
+     * @return array<string, string>
+     */
+    public function toArray(): array
+    {
+        $data = [];
+
+        if ($this->title !== null) {
+            $data['title'] = $this->title;
+        }
+        if ($this->state !== null) {
+            $data['state'] = $this->state;
+        }
+        if ($this->description !== null) {
+            $data['description'] = $this->description;
+        }
+        if ($this->dueOn !== null) {
+            $data['due_on'] = $this->dueOn->format(DATE_ATOM);
+        }
+
+        return $data;
+    }
+}
diff --git a/src/UpdateMilestoneRequestFactory.php b/src/UpdateMilestoneRequestFactory.php
new file mode 100644
index 0000000..1723851
--- /dev/null
+++ b/src/UpdateMilestoneRequestFactory.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\StreamFactoryInterface;
+
+/**
+ * Factory for creating requests to update a milestone
+ *
+ * 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 UpdateMilestoneRequestFactory
+{
+    public function __construct(
+        private readonly RequestFactoryInterface $requestFactory,
+        private readonly StreamFactoryInterface $streamFactory,
+        private readonly GithubApiConfig $config,
+        private readonly GithubRepository $repo,
+        private readonly int $milestoneNumber,
+        private readonly UpdateMilestoneParams $params
+    ) {}
+
+    public function create(): RequestInterface
+    {
+        $url = sprintf(
+            'https://api.github.com/repos/%s/%s/milestones/%d',
+            $this->repo->owner,
+            $this->repo->name,
+            $this->milestoneNumber
+        );
+
+        $jsonBody = json_encode($this->params->toArray(), JSON_THROW_ON_ERROR);
+        $stream = $this->streamFactory->createStream($jsonBody);
+
+        $request = $this->requestFactory->createRequest('PATCH', $url);
+        if ($this->config->accessToken !== '') {
+            $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/test/unit/CreateIssueParamsTest.php b/test/unit/CreateIssueParamsTest.php
new file mode 100644
index 0000000..ad626cc
--- /dev/null
+++ b/test/unit/CreateIssueParamsTest.php
@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\CreateIssueParams;
+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(CreateIssueParams::class)]
+final class CreateIssueParamsTest extends TestCase
+{
+    public function testTitleOnly(): void
+    {
+        $params = new CreateIssueParams(title: 'Crash on launch');
+
+        $this->assertSame(['title' => 'Crash on launch'], $params->toArray());
+    }
+
+    public function testAllFields(): void
+    {
+        $params = new CreateIssueParams(
+            title: 'Crash',
+            body: 'Steps to reproduce',
+            assignees: ['alice', 'bob'],
+            labels: ['bug', 'urgent'],
+            milestone: 7,
+            type: 'Bug',
+        );
+
+        $this->assertSame(
+            [
+                'title' => 'Crash',
+                'body' => 'Steps to reproduce',
+                'assignees' => ['alice', 'bob'],
+                'labels' => ['bug', 'urgent'],
+                'milestone' => 7,
+                'type' => 'Bug',
+            ],
+            $params->toArray()
+        );
+    }
+
+    public function testOptionalsDropOutAtDefault(): void
+    {
+        $params = new CreateIssueParams(title: 't', body: '', assignees: [], labels: []);
+
+        $this->assertSame(['title' => 't'], $params->toArray());
+    }
+}
diff --git a/test/unit/CreateIssueTypeParamsTest.php b/test/unit/CreateIssueTypeParamsTest.php
new file mode 100644
index 0000000..3f3c011
--- /dev/null
+++ b/test/unit/CreateIssueTypeParamsTest.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\CreateIssueTypeParams;
+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(CreateIssueTypeParams::class)]
+final class CreateIssueTypeParamsTest extends TestCase
+{
+    public function testRequiredFieldsWithDefaults(): void
+    {
+        $params = new CreateIssueTypeParams(name: 'Bug');
+
+        $this->assertSame(['name' => 'Bug', 'is_enabled' => true], $params->toArray());
+    }
+
+    public function testIsEnabledFalseEmits(): void
+    {
+        $params = new CreateIssueTypeParams(name: 'Deprecated', isEnabled: false);
+
+        $array = $params->toArray();
+        $this->assertArrayHasKey('is_enabled', $array);
+        $this->assertFalse($array['is_enabled']);
+    }
+
+    public function testOptionalFieldsEmittedWhenSet(): void
+    {
+        $params = new CreateIssueTypeParams(
+            name: 'Bug',
+            description: 'A defect',
+            color: 'red',
+        );
+
+        $this->assertSame(
+            ['name' => 'Bug', 'is_enabled' => true, 'description' => 'A defect', 'color' => 'red'],
+            $params->toArray()
+        );
+    }
+
+    public function testSnakeCaseMapping(): void
+    {
+        $params = new CreateIssueTypeParams(name: 'x');
+        $array = $params->toArray();
+
+        $this->assertArrayHasKey('is_enabled', $array);
+        $this->assertArrayNotHasKey('isEnabled', $array);
+    }
+}
diff --git a/test/unit/CreateMilestoneParamsTest.php b/test/unit/CreateMilestoneParamsTest.php
new file mode 100644
index 0000000..9e10f4d
--- /dev/null
+++ b/test/unit/CreateMilestoneParamsTest.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use DateTimeImmutable;
+use Horde\GithubApiClient\CreateMilestoneParams;
+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(CreateMilestoneParams::class)]
+final class CreateMilestoneParamsTest extends TestCase
+{
+    public function testTitleOnly(): void
+    {
+        $params = new CreateMilestoneParams(title: 'v2');
+
+        $this->assertSame(['title' => 'v2', 'state' => 'open'], $params->toArray());
+    }
+
+    public function testDueOnEmittedAsIso8601(): void
+    {
+        $due = new DateTimeImmutable('2026-07-31T23:59:59+00:00');
+        $params = new CreateMilestoneParams(title: 'v2', dueOn: $due);
+
+        $this->assertSame('2026-07-31T23:59:59+00:00', $params->toArray()['due_on']);
+    }
+
+    public function testDescriptionEmittedWhenNonEmpty(): void
+    {
+        $params = new CreateMilestoneParams(title: 'v2', description: 'Major');
+
+        $this->assertSame(
+            ['title' => 'v2', 'state' => 'open', 'description' => 'Major'],
+            $params->toArray()
+        );
+    }
+}
diff --git a/test/unit/GithubApiClientIssueTest.php b/test/unit/GithubApiClientIssueTest.php
new file mode 100644
index 0000000..c50a654
--- /dev/null
+++ b/test/unit/GithubApiClientIssueTest.php
@@ -0,0 +1,339 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Exception;
+use Horde\GithubApiClient\CreateIssueParams;
+use Horde\GithubApiClient\GithubApiClient;
+use Horde\GithubApiClient\GithubApiConfig;
+use Horde\GithubApiClient\GithubIssue;
+use Horde\GithubApiClient\GithubIssueList;
+use Horde\GithubApiClient\GithubRepository;
+use Horde\GithubApiClient\IssueUpdate;
+use PHPUnit\Framework\Attributes\AllowMockObjectsWithoutExpectations;
+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)]
+#[AllowMockObjectsWithoutExpectations]
+final class GithubApiClientIssueTest extends TestCase
+{
+    /**
+     * @return array{ClientInterface, RequestFactoryInterface, StreamFactoryInterface, RequestInterface}
+     */
+    private function makeWriteMocks(): array
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        return [$httpClient, $requestFactory, $streamFactory, $request];
+    }
+
+    /**
+     * @return array{ClientInterface, RequestFactoryInterface, RequestInterface}
+     */
+    private function makeReadMocks(): array
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $request = $this->createMock(RequestInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+
+        return [$httpClient, $requestFactory, $request];
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    private function issueBody(int $number = 42, bool $isPr = false, ?string $state = 'open'): array
+    {
+        $body = [
+            'id' => $number * 100,
+            'number' => $number,
+            'title' => 'Issue ' . $number,
+            'body' => 'desc',
+            'state' => $state,
+            'state_reason' => null,
+            'html_url' => 'https://github.com/o/r/issues/' . $number,
+            'url' => 'https://api.github.com/repos/o/r/issues/' . $number,
+            'user' => ['login' => 'reporter', 'id' => 1, 'avatar_url' => '', 'html_url' => ''],
+            'labels' => [],
+            'assignees' => [],
+            'milestone' => null,
+            'type' => null,
+            'comments' => 0,
+            'created_at' => '2026-06-24T10:00:00Z',
+            'updated_at' => '2026-06-24T10:00:00Z',
+            'closed_at' => null,
+        ];
+        if ($isPr) {
+            $body['pull_request'] = ['url' => 'https://api.github.com/repos/o/r/pulls/' . $number];
+        }
+        return $body;
+    }
+
+    public function testListIssuesSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode([
+            $this->issueBody(1),
+            $this->issueBody(2, isPr: true),
+        ]));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $list = $client->listIssues($repo);
+
+        $this->assertInstanceOf(GithubIssueList::class, $list);
+        $this->assertCount(2, $list);
+        $array = $list->toArray();
+        $this->assertSame(1, $array[0]->number);
+        $this->assertFalse($array[0]->isPullRequest);
+        $this->assertTrue($array[1]->isPullRequest);
+    }
+
+    public function testListIssuesPassesFilters(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn('[]');
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $list = $client->listIssues($repo, state: 'closed', labels: 'bug,urgent', milestone: '7', assignee: 'alice');
+
+        $this->assertCount(0, $list);
+    }
+
+    public function testListIssuesThrowsOnNon200(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->listIssues($repo);
+    }
+
+    public function testGetIssueSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(42)));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->getIssue($repo, 42);
+
+        $this->assertInstanceOf(GithubIssue::class, $issue);
+        $this->assertSame(42, $issue->number);
+    }
+
+    public function testGetIssueDetectsPullRequest(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(7, isPr: true)));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->getIssue($repo, 7);
+
+        $this->assertTrue($issue->isPullRequest);
+    }
+
+    public function testGetIssueThrowsOn404(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->getIssue($repo, 9999);
+    }
+
+    public function testCreateIssueSuccess(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(42)));
+        $response->method('getStatusCode')->willReturn(201);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->createIssue($repo, new CreateIssueParams(title: 'Crash on launch'));
+
+        $this->assertSame(42, $issue->number);
+    }
+
+    public function testCreateIssueRequiresStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'tok');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for createIssue');
+
+        $client->createIssue($repo, new CreateIssueParams(title: 't'));
+    }
+
+    public function testUpdateIssueSuccess(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $body = $this->issueBody(42);
+        $body['title'] = 'New title';
+        $responseBody->method('__toString')->willReturn((string) json_encode($body));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->updateIssue($repo, 42, (new IssueUpdate())->withTitle('New title'));
+
+        $this->assertSame('New title', $issue->title);
+    }
+
+    public function testUpdateIssueRequiresStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'tok');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for updateIssue');
+
+        $client->updateIssue($repo, 42, new IssueUpdate());
+    }
+
+    public function testCloseIssueSendsClosedState(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(42, state: 'closed')));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->closeIssue($repo, 42);
+
+        $this->assertSame('closed', $issue->state);
+    }
+
+    public function testReopenIssueSendsOpenState(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(42, state: 'open')));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->reopenIssue($repo, 42);
+
+        $this->assertSame('open', $issue->state);
+    }
+}
diff --git a/test/unit/GithubApiClientIssueTypeTest.php b/test/unit/GithubApiClientIssueTypeTest.php
new file mode 100644
index 0000000..9c48302
--- /dev/null
+++ b/test/unit/GithubApiClientIssueTypeTest.php
@@ -0,0 +1,308 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Exception;
+use Horde\GithubApiClient\CreateIssueTypeParams;
+use Horde\GithubApiClient\GithubApiClient;
+use Horde\GithubApiClient\GithubApiConfig;
+use Horde\GithubApiClient\GithubIssueType;
+use Horde\GithubApiClient\GithubIssueTypeList;
+use Horde\GithubApiClient\GithubOrganizationId;
+use Horde\GithubApiClient\GithubRepository;
+use Horde\GithubApiClient\UpdateIssueTypeParams;
+use PHPUnit\Framework\Attributes\AllowMockObjectsWithoutExpectations;
+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)]
+#[AllowMockObjectsWithoutExpectations]
+final class GithubApiClientIssueTypeTest extends TestCase
+{
+    /**
+     * @return array{ClientInterface, RequestFactoryInterface, StreamFactoryInterface, RequestInterface}
+     */
+    private function makeWriteMocks(): array
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        return [$httpClient, $requestFactory, $streamFactory, $request];
+    }
+
+    /**
+     * @return array{ClientInterface, RequestFactoryInterface, RequestInterface}
+     */
+    private function makeReadMocks(): array
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $request = $this->createMock(RequestInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+
+        return [$httpClient, $requestFactory, $request];
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    private function typeBody(int $id = 9, string $name = 'Bug'): array
+    {
+        return [
+            'id' => $id,
+            'name' => $name,
+            'description' => 'A defect',
+            'color' => 'red',
+            'is_enabled' => true,
+            'created_at' => '',
+            'updated_at' => '',
+        ];
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    private function issueBody(int $number = 42, ?array $type = null): array
+    {
+        return [
+            'id' => 1,
+            'number' => $number,
+            'title' => 't',
+            'body' => '',
+            'state' => 'open',
+            'html_url' => '',
+            'url' => '',
+            'user' => ['login' => 'u', 'id' => 1, 'avatar_url' => '', 'html_url' => ''],
+            'labels' => [],
+            'assignees' => [],
+            'milestone' => null,
+            'type' => $type,
+            'comments' => 0,
+            'created_at' => '',
+            'updated_at' => '',
+            'closed_at' => null,
+        ];
+    }
+
+    public function testListIssueTypesSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn(
+            (string) json_encode([$this->typeBody(1, 'Bug'), $this->typeBody(2, 'Feature')])
+        );
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $org = new GithubOrganizationId('horde');
+
+        $list = $client->listIssueTypes($org);
+
+        $this->assertInstanceOf(GithubIssueTypeList::class, $list);
+        $this->assertCount(2, $list);
+        $array = $list->toArray();
+        $this->assertSame('Bug', $array[0]->name);
+        $this->assertSame('Feature', $array[1]->name);
+    }
+
+    public function testListIssueTypesThrowsOn404(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->listIssueTypes(new GithubOrganizationId('missing'));
+    }
+
+    public function testCreateIssueTypeSuccess(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->typeBody()));
+        $response->method('getStatusCode')->willReturn(201);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+
+        $type = $client->createIssueType(
+            new GithubOrganizationId('horde'),
+            new CreateIssueTypeParams(name: 'Bug')
+        );
+
+        $this->assertInstanceOf(GithubIssueType::class, $type);
+        $this->assertSame('Bug', $type->name);
+    }
+
+    public function testCreateIssueTypeRequiresStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'tok');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for createIssueType');
+
+        $client->createIssueType(new GithubOrganizationId('o'), new CreateIssueTypeParams(name: 'Bug'));
+    }
+
+    public function testUpdateIssueTypeSuccess(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $body = $this->typeBody();
+        $body['color'] = 'green';
+        $responseBody->method('__toString')->willReturn((string) json_encode($body));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+
+        $type = $client->updateIssueType(
+            new GithubOrganizationId('horde'),
+            9,
+            new UpdateIssueTypeParams(color: 'green')
+        );
+
+        $this->assertSame('green', $type->color);
+    }
+
+    public function testUpdateIssueTypeRequiresStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'tok');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for updateIssueType');
+
+        $client->updateIssueType(new GithubOrganizationId('o'), 9, new UpdateIssueTypeParams());
+    }
+
+    public function testDeleteIssueTypeSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(204);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+
+        $client->deleteIssueType(new GithubOrganizationId('horde'), 9);
+
+        $this->addToAssertionCount(1);
+    }
+
+    public function testDeleteIssueTypeThrowsOnNon204(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->deleteIssueType(new GithubOrganizationId('horde'), 9999);
+    }
+
+    public function testAssignIssueType(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode(
+            $this->issueBody(42, type: $this->typeBody(9, 'Bug'))
+        ));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->assignIssueType($repo, 42, 'Bug');
+
+        $this->assertNotNull($issue->type);
+        $this->assertSame('Bug', $issue->type->name);
+    }
+
+    public function testUnassignIssueType(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(42)));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->unassignIssueType($repo, 42);
+
+        $this->assertNull($issue->type);
+    }
+}
diff --git a/test/unit/GithubApiClientMilestoneTest.php b/test/unit/GithubApiClientMilestoneTest.php
new file mode 100644
index 0000000..fe17dd4
--- /dev/null
+++ b/test/unit/GithubApiClientMilestoneTest.php
@@ -0,0 +1,329 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Exception;
+use Horde\GithubApiClient\CreateMilestoneParams;
+use Horde\GithubApiClient\GithubApiClient;
+use Horde\GithubApiClient\GithubApiConfig;
+use Horde\GithubApiClient\GithubMilestone;
+use Horde\GithubApiClient\GithubMilestoneList;
+use Horde\GithubApiClient\GithubRepository;
+use Horde\GithubApiClient\UpdateMilestoneParams;
+use PHPUnit\Framework\Attributes\AllowMockObjectsWithoutExpectations;
+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)]
+#[AllowMockObjectsWithoutExpectations]
+final class GithubApiClientMilestoneTest extends TestCase
+{
+    /**
+     * @return array{ClientInterface, RequestFactoryInterface, StreamFactoryInterface, RequestInterface}
+     */
+    private function makeWriteMocks(): array
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $streamFactory = $this->createMock(StreamFactoryInterface::class);
+        $request = $this->createMock(RequestInterface::class);
+        $stream = $this->createMock(StreamInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+        $request->method('withBody')->willReturnSelf();
+        $streamFactory->method('createStream')->willReturn($stream);
+
+        return [$httpClient, $requestFactory, $streamFactory, $request];
+    }
+
+    /**
+     * @return array{ClientInterface, RequestFactoryInterface, RequestInterface}
+     */
+    private function makeReadMocks(): array
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $request = $this->createMock(RequestInterface::class);
+
+        $requestFactory->method('createRequest')->willReturn($request);
+        $request->method('withHeader')->willReturnSelf();
+
+        return [$httpClient, $requestFactory, $request];
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    private function milestoneBody(int $number = 3, string $title = 'v2'): array
+    {
+        return [
+            'id' => 10,
+            'number' => $number,
+            'title' => $title,
+            'description' => '',
+            'state' => 'open',
+            'creator' => null,
+            'open_issues' => 0,
+            'closed_issues' => 0,
+            'html_url' => '',
+            'created_at' => '',
+            'updated_at' => '',
+            'closed_at' => null,
+            'due_on' => null,
+        ];
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    private function issueBody(int $number = 42): array
+    {
+        return [
+            'id' => 1,
+            'number' => $number,
+            'title' => 't',
+            'body' => '',
+            'state' => 'open',
+            'html_url' => '',
+            'url' => '',
+            'user' => ['login' => 'u', 'id' => 1, 'avatar_url' => '', 'html_url' => ''],
+            'labels' => [],
+            'assignees' => [],
+            'milestone' => null,
+            'type' => null,
+            'comments' => 0,
+            'created_at' => '',
+            'updated_at' => '',
+            'closed_at' => null,
+        ];
+    }
+
+    public function testListMilestonesSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn(
+            (string) json_encode([$this->milestoneBody(1, 'v1'), $this->milestoneBody(2, 'v2')])
+        );
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $list = $client->listMilestones($repo);
+
+        $this->assertInstanceOf(GithubMilestoneList::class, $list);
+        $this->assertCount(2, $list);
+    }
+
+    public function testGetMilestoneSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->milestoneBody(3, 'v2')));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $milestone = $client->getMilestone($repo, 3);
+
+        $this->assertSame('v2', $milestone->title);
+    }
+
+    public function testGetMilestoneThrowsOn404(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->getMilestone($repo, 9999);
+    }
+
+    public function testCreateMilestoneSuccess(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->milestoneBody()));
+        $response->method('getStatusCode')->willReturn(201);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $milestone = $client->createMilestone($repo, new CreateMilestoneParams(title: 'v2'));
+
+        $this->assertInstanceOf(GithubMilestone::class, $milestone);
+    }
+
+    public function testCreateMilestoneRequiresStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'tok');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for createMilestone');
+
+        $client->createMilestone($repo, new CreateMilestoneParams(title: 'v2'));
+    }
+
+    public function testUpdateMilestoneSuccess(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $body = $this->milestoneBody();
+        $body['state'] = 'closed';
+        $responseBody->method('__toString')->willReturn((string) json_encode($body));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $milestone = $client->updateMilestone($repo, 3, new UpdateMilestoneParams(state: 'closed'));
+
+        $this->assertSame('closed', $milestone->state);
+    }
+
+    public function testUpdateMilestoneRequiresStreamFactory(): void
+    {
+        $httpClient = $this->createMock(ClientInterface::class);
+        $requestFactory = $this->createMock(RequestFactoryInterface::class);
+        $config = new GithubApiConfig(accessToken: 'tok');
+
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('StreamFactory is required for updateMilestone');
+
+        $client->updateMilestone($repo, 3, new UpdateMilestoneParams());
+    }
+
+    public function testDeleteMilestoneSuccess(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(204);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $client->deleteMilestone($repo, 3);
+
+        $this->addToAssertionCount(1);
+    }
+
+    public function testDeleteMilestoneThrowsOnNon204(): void
+    {
+        [$httpClient, $requestFactory] = $this->makeReadMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+        $response->method('getReasonPhrase')->willReturn('Not Found');
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('404 Not Found');
+
+        $client->deleteMilestone($repo, 9999);
+    }
+
+    public function testAssignMilestone(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $body = $this->issueBody(42);
+        $body['milestone'] = $this->milestoneBody(3, 'v2');
+        $responseBody->method('__toString')->willReturn((string) json_encode($body));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->assignMilestone($repo, 42, 3);
+
+        $this->assertNotNull($issue->milestone);
+        $this->assertSame('v2', $issue->milestone->title);
+    }
+
+    public function testUnassignMilestone(): void
+    {
+        [$httpClient, $requestFactory, $streamFactory] = $this->makeWriteMocks();
+        $response = $this->createMock(ResponseInterface::class);
+        $responseBody = $this->createMock(StreamInterface::class);
+
+        $responseBody->method('__toString')->willReturn((string) json_encode($this->issueBody(42)));
+        $response->method('getStatusCode')->willReturn(200);
+        $response->method('getBody')->willReturn($responseBody);
+        $httpClient->method('sendRequest')->willReturn($response);
+
+        $config = new GithubApiConfig(accessToken: 'tok');
+        $client = new GithubApiClient($httpClient, $requestFactory, $config, $streamFactory);
+        $repo = GithubRepository::fromFullName('owner/repo');
+
+        $issue = $client->unassignMilestone($repo, 42);
+
+        $this->assertNull($issue->milestone);
+    }
+}
diff --git a/test/unit/GithubIssueTest.php b/test/unit/GithubIssueTest.php
new file mode 100644
index 0000000..86c26d0
--- /dev/null
+++ b/test/unit/GithubIssueTest.php
@@ -0,0 +1,211 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\GithubIssueFactory;
+use Horde\GithubApiClient\GithubLabel;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use stdClass;
+
+/**
+ * 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(GithubIssueFactory::class)]
+final class GithubIssueTest extends TestCase
+{
+    private function user(string $login = 'octocat'): stdClass
+    {
+        $u = new stdClass();
+        $u->login = $login;
+        $u->id = 1;
+        $u->avatar_url = 'https://example/u.png';
+        $u->html_url = 'https://github.com/' . $login;
+        return $u;
+    }
+
+    public function testFromApiResponseRegularIssue(): void
+    {
+        $data = new stdClass();
+        $data->id = 999;
+        $data->number = 42;
+        $data->title = 'Crash on launch';
+        $data->body = 'Steps to reproduce…';
+        $data->state = 'open';
+        $data->state_reason = null;
+        $data->html_url = 'https://github.com/o/r/issues/42';
+        $data->url = 'https://api.github.com/repos/o/r/issues/42';
+        $data->user = $this->user('reporter');
+        $data->labels = [];
+        $data->assignees = [];
+        $data->milestone = null;
+        $data->type = null;
+        $data->comments = 3;
+        $data->created_at = '2026-06-24T10:00:00Z';
+        $data->updated_at = '2026-06-24T10:01:00Z';
+        $data->closed_at = null;
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertSame(42, $issue->number);
+        $this->assertSame('Crash on launch', $issue->title);
+        $this->assertSame('reporter', $issue->author->login);
+        $this->assertFalse($issue->isPullRequest);
+        $this->assertNull($issue->milestone);
+        $this->assertNull($issue->type);
+        $this->assertSame([], $issue->labels);
+        $this->assertSame([], $issue->assignees);
+        $this->assertSame([], $issue->fieldValues);
+    }
+
+    public function testFromApiResponseDetectsPullRequest(): void
+    {
+        $data = new stdClass();
+        $data->number = 7;
+        $data->title = 'PR title';
+        $data->body = '';
+        $data->state = 'open';
+        $data->html_url = '';
+        $data->url = '';
+        $data->user = $this->user();
+        $data->pull_request = new stdClass();
+        $data->pull_request->url = 'https://api.github.com/repos/o/r/pulls/7';
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertTrue($issue->isPullRequest);
+    }
+
+    public function testFromApiResponseDecodesNestedLabelsAndAssignees(): void
+    {
+        $label = new stdClass();
+        $label->name = 'bug';
+        $label->color = 'd73a4a';
+        $label->description = 'Something broken';
+
+        $data = new stdClass();
+        $data->number = 1;
+        $data->title = 't';
+        $data->body = '';
+        $data->state = 'open';
+        $data->html_url = '';
+        $data->url = '';
+        $data->user = $this->user();
+        $data->labels = [$label];
+        $data->assignees = [$this->user('alice'), $this->user('bob')];
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertCount(1, $issue->labels);
+        $this->assertInstanceOf(GithubLabel::class, $issue->labels[0]);
+        $this->assertSame('bug', $issue->labels[0]->name);
+        $this->assertCount(2, $issue->assignees);
+        $this->assertSame('alice', $issue->assignees[0]->login);
+        $this->assertSame('bob', $issue->assignees[1]->login);
+    }
+
+    public function testFromApiResponseDecodesMilestoneAndType(): void
+    {
+        $milestone = new stdClass();
+        $milestone->id = 1;
+        $milestone->number = 3;
+        $milestone->title = 'v2';
+        $milestone->state = 'open';
+        $milestone->description = '';
+        $milestone->open_issues = 5;
+        $milestone->closed_issues = 2;
+        $milestone->html_url = '';
+        $milestone->created_at = '';
+        $milestone->updated_at = '';
+
+        $type = new stdClass();
+        $type->id = 9;
+        $type->name = 'Bug';
+        $type->description = 'A bug';
+        $type->color = 'red';
+        $type->is_enabled = true;
+        $type->created_at = '';
+        $type->updated_at = '';
+
+        $data = new stdClass();
+        $data->number = 1;
+        $data->title = 't';
+        $data->body = '';
+        $data->state = 'open';
+        $data->html_url = '';
+        $data->url = '';
+        $data->user = $this->user();
+        $data->milestone = $milestone;
+        $data->type = $type;
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertNotNull($issue->milestone);
+        $this->assertSame('v2', $issue->milestone->title);
+        $this->assertNotNull($issue->type);
+        $this->assertSame('Bug', $issue->type->name);
+    }
+
+    public function testFromApiResponseParsesFieldValues(): void
+    {
+        $field1 = new stdClass();
+        $field1->name = 'Priority';
+        $field1->value = 'P1';
+        $field2 = new stdClass();
+        $field2->name = 'Severity';
+        $field2->value = 3;
+
+        $data = new stdClass();
+        $data->number = 1;
+        $data->title = 't';
+        $data->body = '';
+        $data->state = 'open';
+        $data->html_url = '';
+        $data->url = '';
+        $data->user = $this->user();
+        $data->issue_field_values = [$field1, $field2];
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertSame(['Priority' => 'P1', 'Severity' => 3], $issue->fieldValues);
+    }
+
+    public function testFromApiResponseHandlesMissingFieldsCleanly(): void
+    {
+        // Bare-minimum payload — every nullable falls back without throwing.
+        $data = new stdClass();
+        $data->number = 1;
+        $data->title = '';
+        $data->user = $this->user();
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertSame(1, $issue->number);
+        $this->assertSame('open', $issue->state);
+        $this->assertNull($issue->milestone);
+        $this->assertNull($issue->type);
+        $this->assertSame([], $issue->labels);
+        $this->assertFalse($issue->isPullRequest);
+    }
+
+    public function testStringableFormat(): void
+    {
+        $data = new stdClass();
+        $data->number = 42;
+        $data->title = 'Crash on launch';
+        $data->user = $this->user();
+
+        $issue = (new GithubIssueFactory())->createFromApiResponse($data);
+
+        $this->assertSame('#42 Crash on launch', (string) $issue);
+    }
+}
diff --git a/test/unit/GithubIssueTypeTest.php b/test/unit/GithubIssueTypeTest.php
new file mode 100644
index 0000000..e874933
--- /dev/null
+++ b/test/unit/GithubIssueTypeTest.php
@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\GithubIssueType;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use stdClass;
+
+/**
+ * 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(GithubIssueType::class)]
+final class GithubIssueTypeTest extends TestCase
+{
+    public function testFromApiResponseFull(): void
+    {
+        $data = new stdClass();
+        $data->id = 9;
+        $data->node_id = 'IT_kwAB';
+        $data->name = 'Bug';
+        $data->description = 'A defect';
+        $data->color = 'red';
+        $data->is_enabled = true;
+        $data->created_at = '2026-06-01T10:00:00Z';
+        $data->updated_at = '2026-06-20T10:00:00Z';
+
+        $type = GithubIssueType::fromApiResponse($data);
+
+        $this->assertSame(9, $type->id);
+        $this->assertSame('Bug', $type->name);
+        $this->assertSame('A defect', $type->description);
+        $this->assertSame('red', $type->color);
+        $this->assertTrue($type->isEnabled);
+        $this->assertSame('IT_kwAB', $type->nodeId);
+    }
+
+    public function testFromApiResponseNullableFields(): void
+    {
+        $data = new stdClass();
+        $data->id = 1;
+        $data->name = 'Task';
+        $data->description = null;
+        $data->color = null;
+        $data->is_enabled = false;
+        $data->created_at = '';
+        $data->updated_at = '';
+
+        $type = GithubIssueType::fromApiResponse($data);
+
+        $this->assertNull($type->description);
+        $this->assertNull($type->color);
+        $this->assertFalse($type->isEnabled);
+    }
+
+    public function testStringableReturnsName(): void
+    {
+        $data = new stdClass();
+        $data->id = 1;
+        $data->name = 'Feature';
+
+        $this->assertSame('Feature', (string) GithubIssueType::fromApiResponse($data));
+    }
+}
diff --git a/test/unit/GithubMilestoneTest.php b/test/unit/GithubMilestoneTest.php
new file mode 100644
index 0000000..f9ff75f
--- /dev/null
+++ b/test/unit/GithubMilestoneTest.php
@@ -0,0 +1,94 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\GithubMilestone;
+use Horde\GithubApiClient\GithubUser;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use stdClass;
+
+/**
+ * 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(GithubMilestone::class)]
+final class GithubMilestoneTest extends TestCase
+{
+    public function testFromApiResponseFull(): void
+    {
+        $creator = new stdClass();
+        $creator->login = 'pm';
+        $creator->id = 5;
+        $creator->avatar_url = '';
+        $creator->html_url = '';
+
+        $data = new stdClass();
+        $data->id = 10;
+        $data->number = 3;
+        $data->title = 'v2.0';
+        $data->description = 'Major release';
+        $data->state = 'open';
+        $data->creator = $creator;
+        $data->open_issues = 5;
+        $data->closed_issues = 2;
+        $data->html_url = 'https://github.com/o/r/milestone/3';
+        $data->created_at = '2026-06-01T10:00:00Z';
+        $data->updated_at = '2026-06-20T10:00:00Z';
+        $data->closed_at = null;
+        $data->due_on = '2026-07-31T23:59:59Z';
+
+        $milestone = GithubMilestone::fromApiResponse($data);
+
+        $this->assertSame(3, $milestone->number);
+        $this->assertSame('v2.0', $milestone->title);
+        $this->assertInstanceOf(GithubUser::class, $milestone->creator);
+        $this->assertSame('pm', $milestone->creator->login);
+        $this->assertSame(5, $milestone->openIssues);
+        $this->assertSame(2, $milestone->closedIssues);
+        $this->assertNull($milestone->closedAt);
+        $this->assertSame('2026-07-31T23:59:59Z', $milestone->dueOn);
+    }
+
+    public function testFromApiResponseHandlesNullCreatorAndDueOn(): void
+    {
+        $data = new stdClass();
+        $data->id = 1;
+        $data->number = 1;
+        $data->title = 'x';
+        $data->description = '';
+        $data->state = 'open';
+        $data->creator = null;
+        $data->open_issues = 0;
+        $data->closed_issues = 0;
+        $data->html_url = '';
+        $data->created_at = '';
+        $data->updated_at = '';
+        $data->closed_at = null;
+        $data->due_on = null;
+
+        $milestone = GithubMilestone::fromApiResponse($data);
+
+        $this->assertNull($milestone->creator);
+        $this->assertNull($milestone->dueOn);
+    }
+
+    public function testStringableReturnsTitle(): void
+    {
+        $data = new stdClass();
+        $data->number = 1;
+        $data->title = 'Sprint 23';
+
+        $milestone = GithubMilestone::fromApiResponse($data);
+
+        $this->assertSame('Sprint 23', (string) $milestone);
+    }
+}
diff --git a/test/unit/IssueUpdateTest.php b/test/unit/IssueUpdateTest.php
new file mode 100644
index 0000000..8b82ce7
--- /dev/null
+++ b/test/unit/IssueUpdateTest.php
@@ -0,0 +1,120 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\IssueUpdate;
+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(IssueUpdate::class)]
+final class IssueUpdateTest extends TestCase
+{
+    public function testFreshlyConstructedIsEmpty(): void
+    {
+        $update = new IssueUpdate();
+
+        $this->assertTrue($update->isEmpty());
+        $this->assertSame([], $update->toArray());
+    }
+
+    public function testUntouchedFieldsOmitted(): void
+    {
+        $update = (new IssueUpdate())->withTitle('hello');
+
+        $this->assertSame(['title' => 'hello'], $update->toArray());
+    }
+
+    public function testWithMilestoneNullEmitsLiteralNull(): void
+    {
+        // Critical for the "clear assignment" GitHub semantic.
+        $update = (new IssueUpdate())->withMilestone(null);
+
+        $array = $update->toArray();
+        $this->assertArrayHasKey('milestone', $array);
+        $this->assertNull($array['milestone']);
+    }
+
+    public function testWithTypeNullEmitsLiteralNull(): void
+    {
+        $update = (new IssueUpdate())->withType(null);
+
+        $array = $update->toArray();
+        $this->assertArrayHasKey('type', $array);
+        $this->assertNull($array['type']);
+    }
+
+    public function testWithMilestoneValueEmitsInteger(): void
+    {
+        $update = (new IssueUpdate())->withMilestone(7);
+
+        $this->assertSame(['milestone' => 7], $update->toArray());
+    }
+
+    public function testWithTypeValueEmitsString(): void
+    {
+        $update = (new IssueUpdate())->withType('Bug');
+
+        $this->assertSame(['type' => 'Bug'], $update->toArray());
+    }
+
+    public function testLastSetWins(): void
+    {
+        // Builder returns clones, so re-applying overrides cleanly.
+        $update = (new IssueUpdate())
+            ->withMilestone(7)
+            ->withMilestone(null);
+
+        $array = $update->toArray();
+        $this->assertArrayHasKey('milestone', $array);
+        $this->assertNull($array['milestone']);
+    }
+
+    public function testWithLabelsEmpty(): void
+    {
+        // [] is a valid value: clear all labels.
+        $update = (new IssueUpdate())->withLabels([]);
+
+        $this->assertSame(['labels' => []], $update->toArray());
+    }
+
+    public function testWithAssigneesEmpty(): void
+    {
+        $update = (new IssueUpdate())->withAssignees([]);
+
+        $this->assertSame(['assignees' => []], $update->toArray());
+    }
+
+    public function testWithStateAndReason(): void
+    {
+        $update = (new IssueUpdate())
+            ->withState('closed')
+            ->withStateReason('not_planned');
+
+        $this->assertSame(
+            ['state' => 'closed', 'state_reason' => 'not_planned'],
+            $update->toArray()
+        );
+    }
+
+    public function testBuilderReturnsClonesNotMutates(): void
+    {
+        $original = new IssueUpdate();
+        $modified = $original->withTitle('changed');
+
+        $this->assertTrue($original->isEmpty());
+        $this->assertFalse($modified->isEmpty());
+        $this->assertNotSame($original, $modified);
+    }
+}
diff --git a/test/unit/UpdateIssueTypeParamsTest.php b/test/unit/UpdateIssueTypeParamsTest.php
new file mode 100644
index 0000000..555c699
--- /dev/null
+++ b/test/unit/UpdateIssueTypeParamsTest.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use Horde\GithubApiClient\UpdateIssueTypeParams;
+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(UpdateIssueTypeParams::class)]
+final class UpdateIssueTypeParamsTest extends TestCase
+{
+    public function testAllNullReturnsEmpty(): void
+    {
+        $this->assertSame([], (new UpdateIssueTypeParams())->toArray());
+    }
+
+    public function testPartialUpdate(): void
+    {
+        $params = new UpdateIssueTypeParams(color: 'green');
+
+        $this->assertSame(['color' => 'green'], $params->toArray());
+    }
+
+    public function testIsEnabledFalseEmits(): void
+    {
+        // Setting isEnabled to false is meaningful — distinct from null/untouched.
+        $params = new UpdateIssueTypeParams(isEnabled: false);
+
+        $array = $params->toArray();
+        $this->assertArrayHasKey('is_enabled', $array);
+        $this->assertFalse($array['is_enabled']);
+    }
+}
diff --git a/test/unit/UpdateMilestoneParamsTest.php b/test/unit/UpdateMilestoneParamsTest.php
new file mode 100644
index 0000000..8b59347
--- /dev/null
+++ b/test/unit/UpdateMilestoneParamsTest.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Horde\GithubApiClient\Test\Unit;
+
+use DateTimeImmutable;
+use Horde\GithubApiClient\UpdateMilestoneParams;
+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(UpdateMilestoneParams::class)]
+final class UpdateMilestoneParamsTest extends TestCase
+{
+    public function testAllNullReturnsEmpty(): void
+    {
+        $this->assertSame([], (new UpdateMilestoneParams())->toArray());
+    }
+
+    public function testPartialUpdate(): void
+    {
+        $params = new UpdateMilestoneParams(state: 'closed');
+
+        $this->assertSame(['state' => 'closed'], $params->toArray());
+    }
+
+    public function testDueOnEmittedAsIso8601(): void
+    {
+        $due = new DateTimeImmutable('2026-07-31T23:59:59+00:00');
+        $params = new UpdateMilestoneParams(dueOn: $due);
+
+        $this->assertSame(['due_on' => '2026-07-31T23:59:59+00:00'], $params->toArray());
+    }
+}