diff --git a/CHANGELOG.md b/CHANGELOG.md
index 524b90c..7b0dff5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   console commands `app:user:create` and `app:user:change-password`,
   and end-to-end functional + unit tests
   ([#2](https://github.com/itk-dev/ai-lib/issues/2)).
+- `Assistant` Doctrine entity with base fields (title, description,
+  language model, framework, tags as a JSON list), repository, and
+  migration. Organization linkage and the richer #14 scope
+  (system prompt, parameters, OpenWebUI mapping, versioning) are
+  deferred to follow-on PRs per ADR 005
+  ([#14](https://github.com/itk-dev/ai-lib/issues/14),
+  [#16](https://github.com/itk-dev/ai-lib/issues/16)).
 
 ### Changed
 
diff --git a/migrations/Version20260612120840.php b/migrations/Version20260612120840.php
new file mode 100644
index 0000000..aefeaef
--- /dev/null
+++ b/migrations/Version20260612120840.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Initial `assistant` table for the catalogue (#14).
+ */
+final class Version20260612120840 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Create the assistant table with base fields (title, description, languageModel, framework, tags).';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('CREATE TABLE assistant (id INT AUTO_INCREMENT NOT NULL, title VARCHAR(255) NOT NULL, description LONGTEXT NOT NULL, language_model VARCHAR(255) NOT NULL, framework VARCHAR(255) NOT NULL, tags JSON NOT NULL, PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('DROP TABLE assistant');
+    }
+}
diff --git a/src/Entity/Assistant.php b/src/Entity/Assistant.php
new file mode 100644
index 0000000..4322212
--- /dev/null
+++ b/src/Entity/Assistant.php
@@ -0,0 +1,134 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Entity;
+
+use App\Repository\AssistantRepository;
+use Doctrine\DBAL\Types\Types;
+use Doctrine\ORM\Mapping as ORM;
+
+#[ORM\Entity(repositoryClass: AssistantRepository::class)]
+#[ORM\Table(name: 'assistant')]
+class Assistant
+{
+    #[ORM\Id]
+    #[ORM\GeneratedValue]
+    #[ORM\Column]
+    private ?int $id = null;
+
+    #[ORM\Column(length: 255)]
+    private string $title;
+
+    #[ORM\Column(type: Types::TEXT)]
+    private string $description;
+
+    /**
+     * Captured at creation time from the creator's organisation (see
+     * ADR 005); stored on the assistant so an organisation switching
+     * its default later does not silently rewrite older catalogue
+     * rows.
+     */
+    #[ORM\Column(length: 255)]
+    private string $languageModel;
+
+    /**
+     * @see self::$languageModel for the snapshot rationale
+     */
+    #[ORM\Column(length: 255)]
+    private string $framework;
+
+    /**
+     * @var list<string>
+     */
+    #[ORM\Column(type: Types::JSON)]
+    private array $tags = [];
+
+    /**
+     * @param list<string> $tags
+     */
+    public function __construct(
+        string $title,
+        string $description,
+        string $languageModel,
+        string $framework,
+        array $tags = [],
+    ) {
+        $this->title = $title;
+        $this->description = $description;
+        $this->languageModel = $languageModel;
+        $this->framework = $framework;
+        $this->tags = array_values($tags);
+    }
+
+    public function getId(): ?int
+    {
+        return $this->id;
+    }
+
+    public function getTitle(): string
+    {
+        return $this->title;
+    }
+
+    public function setTitle(string $title): static
+    {
+        $this->title = $title;
+
+        return $this;
+    }
+
+    public function getDescription(): string
+    {
+        return $this->description;
+    }
+
+    public function setDescription(string $description): static
+    {
+        $this->description = $description;
+
+        return $this;
+    }
+
+    public function getLanguageModel(): string
+    {
+        return $this->languageModel;
+    }
+
+    public function setLanguageModel(string $languageModel): static
+    {
+        $this->languageModel = $languageModel;
+
+        return $this;
+    }
+
+    public function getFramework(): string
+    {
+        return $this->framework;
+    }
+
+    public function setFramework(string $framework): static
+    {
+        $this->framework = $framework;
+
+        return $this;
+    }
+
+    /**
+     * @return list<string>
+     */
+    public function getTags(): array
+    {
+        return $this->tags;
+    }
+
+    /**
+     * @param list<string> $tags
+     */
+    public function setTags(array $tags): static
+    {
+        $this->tags = array_values($tags);
+
+        return $this;
+    }
+}
diff --git a/src/Repository/AssistantRepository.php b/src/Repository/AssistantRepository.php
new file mode 100644
index 0000000..647939e
--- /dev/null
+++ b/src/Repository/AssistantRepository.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Repository;
+
+use App\Entity\Assistant;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @extends ServiceEntityRepository<Assistant>
+ */
+class AssistantRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, Assistant::class);
+    }
+}
diff --git a/tests/Entity/AssistantTest.php b/tests/Entity/AssistantTest.php
new file mode 100644
index 0000000..af48d2d
--- /dev/null
+++ b/tests/Entity/AssistantTest.php
@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Entity;
+
+use App\Entity\Assistant;
+use App\Repository\AssistantRepository;
+use App\Tests\Support\ResetsDatabaseSchemaTrait;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+
+/**
+ * Round-trips an Assistant through the entity manager so every getter
+ * and setter sees real persistence + hydration rather than in-memory
+ * object-graph wiring only.
+ */
+final class AssistantTest extends KernelTestCase
+{
+    use ResetsDatabaseSchemaTrait;
+
+    private EntityManagerInterface $em;
+    private AssistantRepository $repository;
+
+    protected function setUp(): void
+    {
+        self::bootKernel();
+        $container = self::getContainer();
+        self::resetSchema($container->get(EntityManagerInterface::class));
+
+        $this->em = $container->get(EntityManagerInterface::class);
+        $this->repository = $container->get(AssistantRepository::class);
+    }
+
+    public function testPersistsAndHydratesBaseFields(): void
+    {
+        $assistant = new Assistant(
+            title: 'Borgerservice-vejviser',
+            description: 'Hjælper sagsbehandlere med at finde den rigtige paragraf.',
+            languageModel: 'gpt-4o',
+            framework: 'openwebui',
+            tags: ['borgerservice', 'paragraf'],
+        );
+
+        $this->em->persist($assistant);
+        $this->em->flush();
+        $id = $assistant->getId();
+        self::assertNotNull($id);
+
+        $this->em->clear();
+        $reloaded = $this->repository->find($id);
+
+        self::assertInstanceOf(Assistant::class, $reloaded);
+        self::assertSame('Borgerservice-vejviser', $reloaded->getTitle());
+        self::assertSame('Hjælper sagsbehandlere med at finde den rigtige paragraf.', $reloaded->getDescription());
+        self::assertSame('gpt-4o', $reloaded->getLanguageModel());
+        self::assertSame('openwebui', $reloaded->getFramework());
+        self::assertSame(['borgerservice', 'paragraf'], $reloaded->getTags());
+    }
+
+    public function testSettersUpdatePersistedValues(): void
+    {
+        $assistant = new Assistant('original-title', 'original-desc', 'gpt-4o', 'openwebui');
+        $this->em->persist($assistant);
+        $this->em->flush();
+        $id = $assistant->getId();
+        self::assertNotNull($id);
+
+        $assistant
+            ->setTitle('new-title')
+            ->setDescription('new-desc')
+            ->setLanguageModel('claude-3.5-sonnet')
+            ->setFramework('custom-runtime')
+            ->setTags(['x', 'y']);
+        $this->em->flush();
+        $this->em->clear();
+
+        $reloaded = $this->repository->find($id);
+        self::assertInstanceOf(Assistant::class, $reloaded);
+        self::assertSame('new-title', $reloaded->getTitle());
+        self::assertSame('new-desc', $reloaded->getDescription());
+        self::assertSame('claude-3.5-sonnet', $reloaded->getLanguageModel());
+        self::assertSame('custom-runtime', $reloaded->getFramework());
+        self::assertSame(['x', 'y'], $reloaded->getTags());
+    }
+
+    public function testTagsDefaultToEmptyListAndAreReindexedOnSet(): void
+    {
+        $assistant = new Assistant('t', 'd', 'm', 'f');
+        self::assertSame([], $assistant->getTags());
+
+        // Setting with non-sequential keys must produce a clean list<string>
+        // — `array_values()` in setTags() guarantees JSON serialises as an
+        // array, not an object.
+        $assistant->setTags([3 => 'alpha', 7 => 'beta']);
+        self::assertSame(['alpha', 'beta'], $assistant->getTags());
+    }
+}