diff --git a/assets/icons/lucide/key-round.svg b/assets/icons/lucide/key-round.svg
new file mode 100644
index 0000000..bc3350a
--- /dev/null
+++ b/assets/icons/lucide/key-round.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><g fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"><path d="M2.586 17.414A2 2 0 0 0 2 18.828V21a1 1 0 0 0 1 1h3a1 1 0 0 0 1-1v-1a1 1 0 0 1 1-1h1a1 1 0 0 0 1-1v-1a1 1 0 0 1 1-1h.172a2 2 0 0 0 1.414-.586l.814-.814a6.5 6.5 0 1 0-4-4z"/><circle cx="16.5" cy="7.5" r=".5" fill="currentColor"/></g></svg>
\ No newline at end of file
diff --git a/migrations/Version20260925120000.php b/migrations/Version20260925120000.php
new file mode 100644
index 0000000..7ad8aec
--- /dev/null
+++ b/migrations/Version20260925120000.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260925120000 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Adds the access codes for doors, the lift and the barrier';
+    }
+
+    public function up(Schema $schema): void
+    {
+        // No unique key: rotating a code means a second row for the same door, kept apart by
+        // valid_from. The index is on that, since every read orders by it.
+        $this->addSql('CREATE TABLE access_code (id INT AUTO_INCREMENT NOT NULL, label VARCHAR(50) NOT NULL, code VARCHAR(32) NOT NULL, valid_from DATE NOT NULL, description VARCHAR(255) DEFAULT NULL, visibility VARCHAR(20) NOT NULL, INDEX idx_access_code_valid_from (valid_from), PRIMARY KEY (id)) DEFAULT CHARACTER SET utf8mb4');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('DROP TABLE access_code');
+    }
+}
diff --git a/src/Controller/AccessCode/IndexController.php b/src/Controller/AccessCode/IndexController.php
new file mode 100644
index 0000000..6dc3f12
--- /dev/null
+++ b/src/Controller/AccessCode/IndexController.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller\AccessCode;
+
+use App\Controller\Traits\CurrentUserTrait;
+use App\Entity\AccessCode;
+use App\Repository\AccessCodeRepository;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+
+/**
+ * The quick look: what do I type at this door, right now.
+ *
+ * Read-only and deliberately thin -- one card per door with the code that works today, large
+ * enough to read on a phone held at arm's length in a badly lit lobby. Maintaining the codes
+ * happens in the table under /admin/access-codes, which is where the history, the dated-ahead
+ * codes and the buttons live.
+ *
+ * Nothing here is dated: a code that starts next week is not shown until it starts, and one that
+ * has been replaced is gone the day its successor takes over. Both would only be one more number
+ * on the screen for somebody to mistype.
+ */
+final class IndexController extends AbstractController
+{
+    use CurrentUserTrait;
+
+    public function __construct(private readonly AccessCodeRepository $codes)
+    {
+    }
+
+    #[Route('/access-codes', name: 'app_access_code', methods: ['GET'])]
+    public function index(): Response
+    {
+        $today = new \DateTimeImmutable('today');
+
+        return $this->render('access_code/index.html.twig', [
+            'codes' => $this->current($this->codes->findCurrentReadableBy($this->currentUser()->getRoles(), $today)),
+        ]);
+    }
+
+    /**
+     * One code per door: the newest of those already in force, which the repository puts first.
+     *
+     * A door only has more than one here because its code was rotated, and then the older rows
+     * are history -- readable in the admin table, not on the screen somebody is standing at a
+     * door with.
+     *
+     * @param list<AccessCode> $codes ordered by label, newest first within a label
+     *
+     * @return list<AccessCode>
+     */
+    private function current(array $codes): array
+    {
+        $current = [];
+
+        foreach ($codes as $code) {
+            $current[$code->getLabel()] ??= $code;
+        }
+
+        return array_values($current);
+    }
+}
diff --git a/src/Controller/Admin/AccessCode/CreateController.php b/src/Controller/Admin/AccessCode/CreateController.php
new file mode 100644
index 0000000..7182daf
--- /dev/null
+++ b/src/Controller/Admin/AccessCode/CreateController.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller\Admin\AccessCode;
+
+use App\Entity\AccessCode;
+use App\Enum\CodeVisibility;
+use App\Form\Admin\AccessCodeFormType;
+use App\Htmx\HxRedirectResponse;
+use App\Security\Role;
+use App\Service\AuditLogger;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+use Symfony\Component\Security\Http\Attribute\IsGranted;
+
+#[IsGranted(Role::ADMIN)]
+final class CreateController extends AbstractController
+{
+    public function __construct(
+        private readonly EntityManagerInterface $em,
+        private readonly AuditLogger $audit,
+    ) {
+    }
+
+    #[Route('/admin/access-codes/new', name: 'app_admin_access_code_new', methods: ['GET', 'POST'])]
+    public function index(Request $request): Response
+    {
+        // Prefilled with today: a code being entered is usually one that already works. Dating
+        // it forward is the deliberate act, and that is the one worth typing.
+        $code = new AccessCode('', '', new \DateTimeImmutable('today'), null, CodeVisibility::EVERYONE);
+        $form = $this->createForm(AccessCodeFormType::class, $code, [
+            'action' => $this->generateUrl('app_admin_access_code_new'),
+        ]);
+        $form->handleRequest($request);
+
+        if ($form->isSubmitted() && $form->isValid()) {
+            $this->em->persist($code);
+            $this->em->flush();
+
+            $this->audit->accessCodeCreated($code);
+            $this->addFlash('success', \sprintf('%s angelegt.', $code->getLabel()));
+
+            return new HxRedirectResponse($this->generateUrl('app_admin_access_code'));
+        }
+
+        return $this->render('admin/_modal_access_code.html.twig', [
+            'form' => $form,
+            'code' => $code,
+        ]);
+    }
+}
diff --git a/src/Controller/Admin/AccessCode/DeleteController.php b/src/Controller/Admin/AccessCode/DeleteController.php
new file mode 100644
index 0000000..bcc4506
--- /dev/null
+++ b/src/Controller/Admin/AccessCode/DeleteController.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller\Admin\AccessCode;
+
+use App\Controller\Traits\ConfirmedActionTrait;
+use App\Entity\AccessCode;
+use App\Htmx\HxRedirectResponse;
+use App\Security\Role;
+use App\Service\AuditLogger;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+use Symfony\Component\Security\Http\Attribute\IsGranted;
+
+/**
+ * Nothing refers to an access code, so there is nothing to refuse the deletion over -- only the
+ * confirmation, which is there because a deleted code is not recoverable from the screen that
+ * deleted it.
+ */
+#[IsGranted(Role::ADMIN)]
+final class DeleteController extends AbstractController
+{
+    use ConfirmedActionTrait;
+
+    public function __construct(
+        private readonly EntityManagerInterface $em,
+        private readonly AuditLogger $audit,
+    ) {
+    }
+
+    #[Route('/admin/access-codes/{id}/delete', name: 'app_admin_access_code_delete', methods: ['GET', 'POST'])]
+    public function index(Request $request, AccessCode $code): Response
+    {
+        if (!$request->isMethod(Request::METHOD_POST)) {
+            return $this->render('admin/_modal_access_code_delete.html.twig', [
+                'code' => $code,
+                'csrf_token_id' => 'delete-access-code-'.$code->getId(),
+            ]);
+        }
+
+        $this->denyUnlessCsrfValid($request, 'delete-access-code-'.$code->getId());
+
+        $this->audit->accessCodeDeleted((int) $code->getId(), $code->getLabel(), $code->getVisibility());
+
+        $label = $code->getLabel();
+        $this->em->remove($code);
+        $this->em->flush();
+
+        $this->addFlash('success', \sprintf('%s gelöscht.', $label));
+
+        return new HxRedirectResponse($this->generateUrl('app_admin_access_code'));
+    }
+}
diff --git a/src/Controller/Admin/AccessCode/EditController.php b/src/Controller/Admin/AccessCode/EditController.php
new file mode 100644
index 0000000..689b61e
--- /dev/null
+++ b/src/Controller/Admin/AccessCode/EditController.php
@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller\Admin\AccessCode;
+
+use App\Entity\AccessCode;
+use App\Form\Admin\AccessCodeFormType;
+use App\Htmx\HxRedirectResponse;
+use App\Security\Role;
+use App\Service\AuditLogger;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+use Symfony\Component\Security\Http\Attribute\IsGranted;
+
+#[IsGranted(Role::ADMIN)]
+final class EditController extends AbstractController
+{
+    public function __construct(
+        private readonly EntityManagerInterface $em,
+        private readonly AuditLogger $audit,
+    ) {
+    }
+
+    #[Route('/admin/access-codes/{id}/edit', name: 'app_admin_access_code_edit', methods: ['GET', 'POST'])]
+    public function index(Request $request, AccessCode $code): Response
+    {
+        // Read before the form binds, so the audit record can say that the code itself changed
+        // without saying what it was or what it became.
+        $previousCode = $code->getCode();
+        $previousVisibility = $code->getVisibility();
+
+        $form = $this->createForm(AccessCodeFormType::class, $code, [
+            'action' => $this->generateUrl('app_admin_access_code_edit', ['id' => $code->getId()]),
+        ]);
+        $form->handleRequest($request);
+
+        if ($form->isSubmitted() && $form->isValid()) {
+            $this->em->flush();
+
+            $this->audit->accessCodeUpdated($code, $previousCode !== $code->getCode(), $previousVisibility);
+            $this->addFlash('success', \sprintf('%s gespeichert.', $code->getLabel()));
+
+            return new HxRedirectResponse($this->generateUrl('app_admin_access_code'));
+        }
+
+        return $this->render('admin/_modal_access_code.html.twig', [
+            'form' => $form,
+            'code' => $code,
+        ]);
+    }
+}
diff --git a/src/Controller/Admin/AccessCode/IndexController.php b/src/Controller/Admin/AccessCode/IndexController.php
new file mode 100644
index 0000000..a915367
--- /dev/null
+++ b/src/Controller/Admin/AccessCode/IndexController.php
@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller\Admin\AccessCode;
+
+use App\Controller\Traits\CurrentUserTrait;
+use App\Entity\AccessCode;
+use App\Repository\AccessCodeRepository;
+use App\Security\Role;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+use Symfony\Component\Security\Http\Attribute\IsGranted;
+
+/**
+ * Maintaining the codes: every row there is, including the ones the quick look at /access-codes
+ * leaves out -- dated ahead, or replaced by a newer one.
+ *
+ * Which is which is a question about today rather than a stored flag, and it is answered here
+ * because it is a question about the whole list: a template cannot look back over its own rows.
+ */
+#[IsGranted(Role::ADMIN)]
+final class IndexController extends AbstractController
+{
+    use CurrentUserTrait;
+
+    public function __construct(private readonly AccessCodeRepository $codes)
+    {
+    }
+
+    #[Route('/admin/access-codes', name: 'app_admin_access_code', methods: ['GET'])]
+    public function index(): Response
+    {
+        $today = new \DateTimeImmutable('today');
+
+        return $this->render('admin/access_codes.html.twig', [
+            'rows' => $this->rows($this->codes->findReadableBy($this->currentUser()->getRoles()), $today),
+        ]);
+    }
+
+    /**
+     * One row per code, each told what it is in relation to the others for the same door.
+     *
+     * The repository hands them over grouped by label, newest first, so the current code of a
+     * door is the first one in its group that has come into force: everything above it is still
+     * to come, everything below it has been replaced. A door whose code has never been rotated
+     * has a group of one, which is the ordinary case and needs no special handling.
+     *
+     * @param list<AccessCode> $codes
+     *
+     * @return list<array{code: AccessCode, upcoming: bool, superseded: bool}>
+     */
+    private function rows(array $codes, \DateTimeImmutable $today): array
+    {
+        $rows = [];
+        $currentSeen = [];
+
+        foreach ($codes as $code) {
+            $upcoming = $code->isUpcoming($today);
+            $label = $code->getLabel();
+            $isCurrent = !$upcoming && !isset($currentSeen[$label]);
+
+            if ($isCurrent) {
+                $currentSeen[$label] = true;
+            }
+
+            $rows[] = [
+                'code' => $code,
+                'upcoming' => $upcoming,
+                'superseded' => !$upcoming && !$isCurrent,
+            ];
+        }
+
+        return $rows;
+    }
+}
diff --git a/src/Entity/AccessCode.php b/src/Entity/AccessCode.php
new file mode 100644
index 0000000..81e8874
--- /dev/null
+++ b/src/Entity/AccessCode.php
@@ -0,0 +1,131 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Entity;
+
+use App\Enum\CodeVisibility;
+use App\Repository\AccessCodeRepository;
+use Doctrine\ORM\Mapping as ORM;
+use Symfony\Component\Validator\Constraints as Assert;
+
+/**
+ * A code that opens something in the building: a door, the lift, the barrier.
+ *
+ * Stored in plain text, and that is the feature -- a code nobody can read opens nothing. What
+ * protects it is the firewall in front of the page and `visibility`, not the storage.
+ *
+ * Who a code is for is `visibility` and nothing else: it is the access decision and the caption
+ * at once. Anything about the audience that the two cases do not cover -- "nur donnerstags",
+ * "Reinigungsfirma" -- belongs in the description, which is prose and claims nothing.
+ *
+ * Nothing here is unique. The same door legitimately appears more than once, because rotating a
+ * code means adding the new one with a later `validFrom` while the old row is still the one that
+ * works; which of them is current is a question about today's date, answered when the list is
+ * built rather than by a flag somebody has to remember to clear.
+ */
+#[ORM\Entity(repositoryClass: AccessCodeRepository::class)]
+#[ORM\Index(name: 'idx_access_code_valid_from', columns: ['valid_from'])]
+class AccessCode
+{
+    #[ORM\Id]
+    #[ORM\GeneratedValue]
+    #[ORM\Column]
+    private ?int $id = null;
+
+    #[ORM\Column(length: 50)]
+    #[Assert\NotBlank]
+    #[Assert\Length(max: 50)]
+    private string $label;
+
+    #[ORM\Column(length: 32)]
+    #[Assert\NotBlank]
+    #[Assert\Length(max: 32)]
+    private string $code;
+
+    #[ORM\Column(type: 'date_immutable')]
+    #[Assert\NotNull]
+    private \DateTimeImmutable $validFrom;
+
+    #[ORM\Column(length: 255, nullable: true)]
+    #[Assert\Length(max: 255)]
+    private ?string $description = null;
+
+    #[ORM\Column(length: 20, enumType: CodeVisibility::class)]
+    private CodeVisibility $visibility = CodeVisibility::EVERYONE;
+
+    public function __construct(
+        string $label,
+        string $code,
+        \DateTimeImmutable $validFrom,
+        ?string $description = null,
+        CodeVisibility $visibility = CodeVisibility::EVERYONE,
+    ) {
+        $this->label = $label;
+        $this->code = $code;
+        $this->validFrom = $validFrom;
+        $this->description = $description;
+        $this->visibility = $visibility;
+    }
+
+    public function getId(): ?int
+    {
+        return $this->id;
+    }
+
+    public function getLabel(): string
+    {
+        return $this->label;
+    }
+
+    public function setLabel(string $label): void
+    {
+        $this->label = $label;
+    }
+
+    public function getCode(): string
+    {
+        return $this->code;
+    }
+
+    public function setCode(string $code): void
+    {
+        $this->code = $code;
+    }
+
+    public function getValidFrom(): \DateTimeImmutable
+    {
+        return $this->validFrom;
+    }
+
+    public function setValidFrom(\DateTimeImmutable $validFrom): void
+    {
+        $this->validFrom = $validFrom;
+    }
+
+    public function getDescription(): ?string
+    {
+        return $this->description;
+    }
+
+    public function setDescription(?string $description): void
+    {
+        $this->description = $description;
+    }
+
+    public function getVisibility(): CodeVisibility
+    {
+        return $this->visibility;
+    }
+
+    public function setVisibility(CodeVisibility $visibility): void
+    {
+        $this->visibility = $visibility;
+    }
+
+    /** Not yet in force: it is listed so nobody is surprised on the day it takes over. */
+    public function isUpcoming(\DateTimeImmutable $on): bool
+    {
+        return $this->validFrom > $on;
+    }
+}
diff --git a/src/Enum/CodeVisibility.php b/src/Enum/CodeVisibility.php
new file mode 100644
index 0000000..1209241
--- /dev/null
+++ b/src/Enum/CodeVisibility.php
@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enum;
+
+use App\Security\Role;
+
+/**
+ * Who may read an access code.
+ *
+ * Deliberately an enum with two cases rather than a boolean column: "admin only" is one policy
+ * among several plausible ones -- a code for the reception desk or for the cleaning company is
+ * the obvious next case -- and a third case here costs a case in the match below, where a third
+ * value of a boolean costs a migration.
+ *
+ * This is also what the list shows under "Für wen": the access decision and the caption are one
+ * value, so there is no second, prose field describing an audience that the filter does not
+ * actually enforce.
+ */
+enum CodeVisibility: string
+{
+    /** Every signed-in user, which in this application means everyone who works here. */
+    case EVERYONE = 'everyone';
+
+    /** Administrators only -- a code the whole staff has no business reading. */
+    case ADMIN = 'admin';
+
+    public function label(): string
+    {
+        return match ($this) {
+            self::EVERYONE => 'Alle Mitarbeitenden',
+            self::ADMIN => 'Administration',
+        };
+    }
+
+    /** Worth marking in the list: not everyone who can see the page can see this row. */
+    public function isRestricted(): bool
+    {
+        return self::EVERYONE !== $this;
+    }
+
+    /**
+     * The roles this application knows are the ones in Role::ELIGIBLE, so "everyone" needs no
+     * role of its own: reaching the page at all already required one.
+     *
+     * @param list<string> $roles
+     */
+    public function isReadableBy(array $roles): bool
+    {
+        return match ($this) {
+            self::EVERYONE => true,
+            self::ADMIN => \in_array(Role::ADMIN, $roles, true),
+        };
+    }
+
+    /**
+     * The cases somebody with these roles may read, for the repository to filter on.
+     *
+     * @param list<string> $roles
+     *
+     * @return list<self>
+     */
+    public static function readableBy(array $roles): array
+    {
+        return array_values(array_filter(
+            self::cases(),
+            static fn (self $visibility): bool => $visibility->isReadableBy($roles),
+        ));
+    }
+}
diff --git a/src/Form/Admin/AccessCodeFormType.php b/src/Form/Admin/AccessCodeFormType.php
new file mode 100644
index 0000000..f831be5
--- /dev/null
+++ b/src/Form/Admin/AccessCodeFormType.php
@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Form\Admin;
+
+use App\Entity\AccessCode;
+use App\Enum\CodeVisibility;
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\DateType;
+use Symfony\Component\Form\Extension\Core\Type\EnumType;
+use Symfony\Component\Form\Extension\Core\Type\TextareaType;
+use Symfony\Component\Form\Extension\Core\Type\TextType;
+use Symfony\Component\Form\FormBuilderInterface;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+/**
+ * An access code. Every field is editable, including the code itself -- correcting a typo in a
+ * code is an edit, while giving a door a new code is a new row with a later start date.
+ *
+ * The required text fields carry `empty_data => ''` for the reason ResourceGroupFormType's
+ * position does: their setters take a string, and a cleared field otherwise reaches them as null
+ * and fails with a TypeError before the NotBlank constraint ever gets to say so.
+ */
+final class AccessCodeFormType extends AbstractType
+{
+    public function buildForm(FormBuilderInterface $builder, array $options): void
+    {
+        $builder
+            ->add('label', TextType::class, [
+                'empty_data' => '',
+                'label' => 'Bezeichnung',
+            ])
+            ->add('description', TextareaType::class, [
+                'label' => 'Beschreibung',
+                'required' => false,
+                'attr' => ['rows' => 2],
+            ])
+            ->add('code', TextType::class, [
+                'empty_data' => '',
+                'label' => 'Code',
+            ])
+            ->add('validFrom', DateType::class, [
+                'label' => 'Gültig ab',
+                'widget' => 'single_text',
+            ])
+            ->add('visibility', EnumType::class, [
+                'label' => 'Für wen',
+                'class' => CodeVisibility::class,
+                'choice_label' => static fn (CodeVisibility $visibility): string => $visibility->label(),
+            ]);
+    }
+
+    public function configureOptions(OptionsResolver $resolver): void
+    {
+        $resolver->setDefaults([
+            'data_class' => AccessCode::class,
+        ]);
+    }
+}
diff --git a/src/Repository/AccessCodeRepository.php b/src/Repository/AccessCodeRepository.php
new file mode 100644
index 0000000..e023958
--- /dev/null
+++ b/src/Repository/AccessCodeRepository.php
@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Repository;
+
+use App\Entity\AccessCode;
+use App\Enum\CodeVisibility;
+use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
+use Doctrine\Persistence\ManagerRegistry;
+
+/**
+ * @extends ServiceEntityRepository<AccessCode>
+ */
+class AccessCodeRepository extends ServiceEntityRepository
+{
+    public function __construct(ManagerRegistry $registry)
+    {
+        parent::__construct($registry, AccessCode::class);
+    }
+
+    /**
+     * The code that opens each door today, for the quick-look list.
+     *
+     * Dated-ahead codes are left in the database and out of the query: a code that does not open
+     * anything yet is not an answer to "what do I type", and showing it beside one that does is
+     * how somebody ends up typing the wrong one. Ordered so that the first row per label is the
+     * one in force -- the caller only has to take it.
+     *
+     * @param list<string> $roles
+     *
+     * @return list<AccessCode>
+     */
+    public function findCurrentReadableBy(array $roles, \DateTimeImmutable $on): array
+    {
+        return $this->createQueryBuilder('c')
+            ->andWhere('c.visibility IN (:visibilities)')
+            ->andWhere('c.validFrom <= :on')
+            ->setParameter('visibilities', CodeVisibility::readableBy($roles))
+            ->setParameter('on', $on)
+            ->orderBy('c.label', 'ASC')
+            ->addOrderBy('c.validFrom', 'DESC')
+            ->addOrderBy('c.id', 'DESC')
+            ->getQuery()
+            ->getResult();
+    }
+
+    /**
+     * Everything the holder of these roles may read, grouped by door and newest code first.
+     *
+     * The restriction is applied here rather than in the template, so a code somebody may not
+     * read is never loaded into a response in the first place -- a hidden table row is still a
+     * published code.
+     *
+     * @param list<string> $roles
+     *
+     * @return list<AccessCode>
+     */
+    public function findReadableBy(array $roles): array
+    {
+        return $this->createQueryBuilder('c')
+            ->andWhere('c.visibility IN (:visibilities)')
+            ->setParameter('visibilities', CodeVisibility::readableBy($roles))
+            ->orderBy('c.label', 'ASC')
+            ->addOrderBy('c.validFrom', 'DESC')
+            ->addOrderBy('c.id', 'DESC')
+            ->getQuery()
+            ->getResult();
+    }
+}
diff --git a/src/Service/AuditLogger.php b/src/Service/AuditLogger.php
index 33fb9b8..6d098c5 100644
--- a/src/Service/AuditLogger.php
+++ b/src/Service/AuditLogger.php
@@ -4,11 +4,13 @@ declare(strict_types=1);
 
 namespace App\Service;
 
+use App\Entity\AccessCode;
 use App\Entity\Booking;
 use App\Entity\BookingSeries;
 use App\Entity\Resource;
 use App\Entity\ResourceGroup;
 use App\Entity\User;
+use App\Enum\CodeVisibility;
 use App\Enum\ResourceType;
 use App\Model\SeriesResult;
 use App\Model\TimeRange;
@@ -235,6 +237,49 @@ final readonly class AuditLogger
         ]);
     }
 
+    /**
+     * The code value itself is never logged, here or anywhere else.
+     *
+     * The audit trail is a file that whoever is investigating an incident reads, and a record of
+     * every door code ever set would turn it into a keyring -- one that outlives the codes, since
+     * the log is kept long after a code has been rotated away. What a record needs to answer is
+     * who changed which code and when, and that it can do while naming only the door.
+     */
+    public function accessCodeCreated(AccessCode $code): void
+    {
+        $this->logger->info('Access code created.', $this->accessCode($code));
+    }
+
+    /**
+     * @param bool           $codeChanged       whether the secret itself was replaced, as opposed
+     *                                          to a correction to the label or the date -- not
+     *                                          derivable later, since the value is never logged
+     * @param CodeVisibility $previousVisibility spelled out for the same reason as a resource's
+     *                                           `was_active`: widening a code from the
+     *                                           administrators to the whole staff is the one edit
+     *                                           here that changes who may read something
+     */
+    public function accessCodeUpdated(AccessCode $code, bool $codeChanged, CodeVisibility $previousVisibility): void
+    {
+        $this->logger->info('Access code updated.', $this->accessCode($code) + [
+            'code_changed' => $codeChanged,
+            'previous_visibility' => $previousVisibility->value,
+        ]);
+    }
+
+    /**
+     * Takes a snapshot rather than the entity, as the other deletions do: afterwards there is no
+     * id left to read.
+     */
+    public function accessCodeDeleted(int $id, string $label, CodeVisibility $visibility): void
+    {
+        $this->logger->info('Access code deleted.', [
+            'access_code' => $label,
+            'access_code_id' => $id,
+            'visibility' => $visibility->value,
+        ]);
+    }
+
     /**
      * @return array<string, mixed>
      */
@@ -275,6 +320,19 @@ final readonly class AuditLogger
         ];
     }
 
+    /**
+     * @return array<string, mixed>
+     */
+    private function accessCode(AccessCode $code): array
+    {
+        return [
+            'access_code' => $code->getLabel(),
+            'access_code_id' => $code->getId(),
+            'valid_from' => $code->getValidFrom()->format('Y-m-d'),
+            'visibility' => $code->getVisibility()->value,
+        ];
+    }
+
     /**
      * @return array<string, mixed>
      */
diff --git a/templates/access_code/index.html.twig b/templates/access_code/index.html.twig
new file mode 100644
index 0000000..674a272
--- /dev/null
+++ b/templates/access_code/index.html.twig
@@ -0,0 +1,59 @@
+{#
+    The quick look: what to type at a door, on the phone you are holding in front of it.
+
+    One card per door with the code in force today and nothing else -- no dates, no history, no
+    buttons. Maintaining the codes is admin/access_codes.html.twig, which is the table this page
+    used to be.
+
+    The card is sized for reading, not for fitting: the code is the largest thing on the screen,
+    in near-black on white and in a tabular font so 1 and 7 cannot be confused. One column on a
+    phone, more when there is room.
+#}
+{% extends 'layout.html.twig' %}
+
+{% block title %}Zugangscodes · E&P Platz{% endblock %}
+
+{% block content %}
+    <a class="text-sm text-gray-500 hover:text-gray-900" href="{{ path('app_dashboard') }}">← Übersicht</a>
+
+    <div class="flex flex-wrap items-baseline justify-between gap-2 pt-2">
+        <div>
+            <h1>Zugangscodes</h1>
+            <p class="subline">Türen, Aufzug etc.</p>
+        </div>
+        {% if is_granted('ROLE_ADMIN') %}
+            <a class="button button--small button--neutral" href="{{ path('app_admin_access_code') }}">Codes verwalten</a>
+        {% endif %}
+    </div>
+
+    {% if codes is empty %}
+        <p class="pt-8 text-sm text-gray-500">Zurzeit gilt kein Code.</p>
+    {% else %}
+        <div class="pt-8 grid gap-4 sm:grid-cols-2 lg:grid-cols-3">
+            {% for code in codes %}
+                <div class="flex flex-col rounded-md border border-gray-200 p-6" data-access-code>
+                    <div class="flex items-baseline justify-between gap-2">
+                        <span class="text-lg font-bold">{{ code.label }}</span>
+                        {% if code.visibility.isRestricted %}
+                            <span class="badge bg-gray-100 text-gray-600 shrink-0">{{ code.visibility.label }}</span>
+                        {% endif %}
+                    </div>
+
+                    {% if code.description %}
+                        <p class="pt-1 text-sm text-gray-500">{{ code.description }}</p>
+                    {% endif %}
+
+                    {# mt-auto, so the code sits at the bottom of the card and the codes of a row
+                       line up whether or not a door has a description -- grid stretches the cards
+                       of a row to the same height, and this spends the difference above the code
+                       rather than below it. Same device as the dashboard tiles.
+
+                       tracking-widest so a long code stays readable as digits rather than as a
+                       number, and break-all so it never overflows a narrow screen. #}
+                    <p class="mt-auto pt-4 font-mono text-4xl font-bold tracking-widest tabular-nums break-all text-gray-900"
+                       data-code>{{ code.code }}</p>
+                </div>
+            {% endfor %}
+        </div>
+    {% endif %}
+{% endblock %}
diff --git a/templates/admin/_modal_access_code.html.twig b/templates/admin/_modal_access_code.html.twig
new file mode 100644
index 0000000..57c1014
--- /dev/null
+++ b/templates/admin/_modal_access_code.html.twig
@@ -0,0 +1,37 @@
+{# Creating and editing an access code. See admin/_modal_resource.html.twig for how it closes. #}
+{% extends 'htmx_modal.html.twig' %}
+
+{% block title %}
+    {%- if code.id -%}
+        {{ code.label }} bearbeiten
+    {%- else -%}
+        Code hinzufügen
+    {%- endif -%}
+{% endblock %}
+
+{% block content %}
+    {{ form_start(form, { attr: {
+        'hx-post': form.vars.action,
+        'hx-target': '#htmx-modal',
+        'hx-swap': 'outerHTML',
+    } }) }}
+        {{ form_errors(form) }}
+
+        <div class="space-y-4">
+            {{ form_row(form.label) }}
+            {{ form_row(form.description) }}
+            {{ form_row(form.code) }}
+            {{ form_row(form.validFrom) }}
+            {{ form_row(form.visibility) }}
+        </div>
+
+        <div class="flex justify-end gap-2 pt-6">
+            <button type="button" class="button button--neutral" {{ stimulus_action('modal', 'close') }}>
+                Abbrechen
+            </button>
+            <button type="submit" class="button button--primary">
+                Speichern
+            </button>
+        </div>
+    {{ form_end(form) }}
+{% endblock %}
diff --git a/templates/admin/_modal_access_code_delete.html.twig b/templates/admin/_modal_access_code_delete.html.twig
new file mode 100644
index 0000000..0869971
--- /dev/null
+++ b/templates/admin/_modal_access_code_delete.html.twig
@@ -0,0 +1,12 @@
+{% extends 'htmx_confirmation_modal.html.twig' %}
+
+{% block title %}Code löschen?{% endblock %}
+
+{% block content %}
+    <p>
+        Der Code für <em>{{ code.label }}</em> (gültig ab
+        {{ code.validFrom|format_date(pattern: 'd.MM.y') }}) wird gelöscht.
+    </p>
+{% endblock %}
+
+{% block button_confirm %}Löschen{% endblock %}
diff --git a/templates/admin/access_codes.html.twig b/templates/admin/access_codes.html.twig
new file mode 100644
index 0000000..9ed73f2
--- /dev/null
+++ b/templates/admin/access_codes.html.twig
@@ -0,0 +1,82 @@
+{#
+    Maintaining the codes: every row there is, in a table, newest per door first.
+
+    The counterpart of access_code/index.html.twig, which shows one card per door with the code
+    that works today and nothing else. Everything the quick look leaves out is here -- rows the
+    controller marked `upcoming` or `superseded`, muted and labelled -- because this is the
+    screen on which a rotation is planned and checked.
+
+    „Für wen" is the visibility itself: it decides who is served the row and says so in the same
+    breath, so there is nothing to keep in step between the two.
+#}
+{% extends 'layout.html.twig' %}
+
+{% block title %}Zugangscodes verwalten · E&P Platz{% endblock %}
+
+{% block content %}
+    <a class="text-sm text-gray-500 hover:text-gray-900" href="{{ path('app_access_code') }}">← Zugangscodes</a>
+
+    <div class="flex flex-wrap items-baseline justify-between gap-2 pt-2">
+        <div>
+            <h1>Zugangscodes verwalten</h1>
+        </div>
+        <button type="button" class="button button--small button--primary"
+                hx-get="{{ path('app_admin_access_code_new') }}"
+                hx-target="body"
+                hx-swap="beforeend">Code hinzufügen</button>
+    </div>
+
+    {% if rows is empty %}
+        <p class="pt-8 text-sm text-gray-500">Noch nichts hinterlegt.</p>
+    {% else %}
+        <div class="pt-8 overflow-x-auto">
+            <table class="w-full text-left text-sm">
+                <thead class="border-b border-gray-200 text-gray-500">
+                    <tr>
+                        <th class="py-2 pr-4 font-semibold">Bezeichnung</th>
+                        <th class="py-2 pr-4 font-semibold">Beschreibung</th>
+                        <th class="py-2 pr-4 font-semibold">Code</th>
+                        <th class="py-2 pr-4 font-semibold">sichtbar für</th>
+                        <th class="py-2 pr-4 font-semibold">gültig ab</th>
+                        <th class="py-2 font-semibold"><span class="sr-only">Aktionen</span></th>
+                    </tr>
+                </thead>
+                <tbody class="divide-y divide-gray-200">
+                    {% for row in rows %}
+                        {% set muted = row.upcoming or row.superseded %}
+                        <tr data-access-code class="{{ muted ? 'text-gray-400' : '' }}">
+                            <td class="py-2 pr-4 font-semibold">{{ row.code.label }}</td>
+                            <td class="py-2 pr-4">{{ row.code.description }}</td>
+                            <td class="py-2 pr-4 font-mono">{{ row.code.code }}</td>
+                            <td class="py-2 pr-4">
+                                {% if row.code.visibility.isRestricted %}
+                                    <span class="badge bg-gray-100 text-gray-600">{{ row.code.visibility.label }}</span>
+                                {% else %}
+                                    {{ row.code.visibility.label }}
+                                {% endif %}
+                            </td>
+                            <td class="py-2 pr-4 whitespace-nowrap">
+                                {{ row.code.validFrom|format_date(pattern: 'd.MM.y') }}
+                                {% if row.upcoming %}
+                                    <span class="badge bg-amber-100 text-amber-800 ml-1">noch nicht gültig</span>
+                                {% elseif row.superseded %}
+                                    <span class="badge bg-gray-100 text-gray-600 ml-1">ersetzt</span>
+                                {% endif %}
+                            </td>
+                            <td class="py-2">
+                                <div class="flex justify-end gap-2">
+                                    <button type="button" class="button button--small button--neutral"
+                                            hx-get="{{ path('app_admin_access_code_edit', { id: row.code.id }) }}"
+                                            hx-target="body" hx-swap="beforeend">Bearbeiten</button>
+                                    <button type="button" class="button button--small button--neutral"
+                                            hx-get="{{ path('app_admin_access_code_delete', { id: row.code.id }) }}"
+                                            hx-target="body" hx-swap="beforeend">Löschen</button>
+                                </div>
+                            </td>
+                        </tr>
+                    {% endfor %}
+                </tbody>
+            </table>
+        </div>
+    {% endif %}
+{% endblock %}
diff --git a/templates/dashboard/index.html.twig b/templates/dashboard/index.html.twig
index e2d8aa6..9c696c2 100644
--- a/templates/dashboard/index.html.twig
+++ b/templates/dashboard/index.html.twig
@@ -49,6 +49,15 @@
             <p class="text-sm text-gray-500 pb-4">Alle Buchungen verwalten.</p>
         </a>
 
+        <a href="{{ path('app_access_code') }}"
+           class="group flex flex-col rounded-md border border-gray-200 p-6 hover:border-primary hover:bg-gray-50">
+            <div class="flex items-center gap-3 pb-2">
+                {{ ux_icon('lucide:key-round', { class: 'h-6 w-6 shrink-0 text-primary' }) }}
+                <span class="text-lg font-bold">Zugangscodes</span>
+            </div>
+            <p class="text-sm text-gray-500 pb-4">Codes für Türen, Aufzug und Schranke.</p>
+        </a>
+
         {#
             The header is deliberately not navigation, so the dashboard is the only place an
             admin screen can be reached from.
diff --git a/tests/Controller/AccessCodeControllerTest.php b/tests/Controller/AccessCodeControllerTest.php
new file mode 100644
index 0000000..907f1a3
--- /dev/null
+++ b/tests/Controller/AccessCodeControllerTest.php
@@ -0,0 +1,182 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Controller;
+
+use App\Entity\AccessCode;
+use App\Entity\User;
+use App\Enum\CodeVisibility;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\KernelBrowser;
+use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
+
+/**
+ * The quick look: one card per door with the code that works today.
+ *
+ * Most of what is asserted here is what the page does *not* show -- a code that is not in force
+ * is not an answer to "what do I type", and a code somebody may not read must not reach them at
+ * all. The full list is the admin table's job and is tested there.
+ */
+class AccessCodeControllerTest extends WebTestCase
+{
+    private KernelBrowser $client;
+    private EntityManagerInterface $em;
+
+    protected function setUp(): void
+    {
+        $this->client = self::createClient(server: ['HTTPS' => true]);
+        $this->client->disableReboot();
+        $this->em = self::getContainer()->get(EntityManagerInterface::class);
+        $this->em->getConnection()->beginTransaction();
+    }
+
+    protected function tearDown(): void
+    {
+        $this->em->getConnection()->rollBack();
+        parent::tearDown();
+    }
+
+    public function testItIsBehindTheFirewall(): void
+    {
+        $this->client->request('GET', '/access-codes');
+
+        self::assertResponseRedirects();
+    }
+
+    public function testAnEmployeeSeesACardPerDoor(): void
+    {
+        $this->code('Aufzug', '4711', description: 'Kabine im Erdgeschoss');
+        $this->code('Schranke', '1234');
+        $this->em->flush();
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+
+        $cards = $this->client->request('GET', '/access-codes')->filter('[data-access-code]');
+
+        self::assertResponseIsSuccessful();
+        self::assertCount(2, $cards);
+        self::assertStringContainsString('Aufzug', $cards->eq(0)->text());
+        self::assertStringContainsString('Kabine im Erdgeschoss', $cards->eq(0)->text());
+        self::assertSame('4711', $cards->eq(0)->filter('[data-code]')->text());
+        self::assertSame('1234', $cards->eq(1)->filter('[data-code]')->text());
+    }
+
+    /**
+     * The restriction is a filter on the query, not a hidden card: a code an employee may not
+     * read must not be in the response at all.
+     */
+    public function testAnAdminOnlyCodeIsNotSentToAnEmployee(): void
+    {
+        $this->code('Serverraum', '9999', visibility: CodeVisibility::ADMIN);
+        $this->em->flush();
+
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+        $crawler = $this->client->request('GET', '/access-codes');
+        self::assertCount(0, $crawler->filter('[data-access-code]'));
+        self::assertStringNotContainsString('9999', (string) $this->client->getResponse()->getContent());
+
+        $this->client->loginUser($this->user('chef@ep-reisen.de', ['ROLE_ADMIN']));
+        $card = $this->client->request('GET', '/access-codes')->filter('[data-access-code]');
+        self::assertCount(1, $card);
+        self::assertSame('9999', $card->filter('[data-code]')->text());
+        self::assertStringContainsString('Nur Verwaltung', $card->text());
+    }
+
+    /**
+     * Rotating a code. Only the one in force is shown: its predecessor is history, and its
+     * successor does not open anything yet -- both would only be another number to mistype.
+     */
+    public function testOnlyTheCodeInForceIsShown(): void
+    {
+        $this->code('Aufzug', 'OLD', validFrom: '-2 months');
+        $this->code('Aufzug', 'NOW', validFrom: '-1 day');
+        $this->code('Aufzug', 'NEXT', validFrom: '+1 month');
+        $this->em->flush();
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+
+        $cards = $this->client->request('GET', '/access-codes')->filter('[data-access-code]');
+
+        self::assertCount(1, $cards);
+        self::assertSame('NOW', $cards->filter('[data-code]')->text());
+        $body = (string) $this->client->getResponse()->getContent();
+        self::assertStringNotContainsString('OLD', $body);
+        self::assertStringNotContainsString('NEXT', $body);
+    }
+
+    /**
+     * A code that starts on a date starts that morning, not the day after.
+     */
+    public function testACodeStartingTodayIsInForce(): void
+    {
+        $this->code('Aufzug', '4711', validFrom: 'today');
+        $this->em->flush();
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+
+        $cards = $this->client->request('GET', '/access-codes')->filter('[data-access-code]');
+
+        self::assertCount(1, $cards);
+        self::assertSame('4711', $cards->filter('[data-code]')->text());
+    }
+
+    /**
+     * A door that only has a code for next week is simply not on the page yet.
+     */
+    public function testADoorWithNoCodeInForceIsAbsent(): void
+    {
+        $this->code('Schranke', 'SOON', validFrom: '+1 week');
+        $this->em->flush();
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+
+        $crawler = $this->client->request('GET', '/access-codes');
+
+        self::assertCount(0, $crawler->filter('[data-access-code]'));
+        self::assertStringContainsString('Zurzeit gilt kein Code', $crawler->filter('body')->text());
+    }
+
+    public function testOnlyAnAdminIsOfferedTheTable(): void
+    {
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+        self::assertCount(0, $this->client->request('GET', '/access-codes')->filter('a[href="/admin/access-codes"]'));
+
+        $this->client->loginUser($this->user('chef@ep-reisen.de', ['ROLE_ADMIN']));
+        self::assertCount(1, $this->client->request('GET', '/access-codes')->filter('a[href="/admin/access-codes"]'));
+    }
+
+    public function testTheDashboardLinksHereForEveryone(): void
+    {
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+
+        self::assertCount(1, $this->client->request('GET', '/')->filter('a[href="/access-codes"]'));
+    }
+
+    private function code(
+        string $label,
+        string $value,
+        string $validFrom = 'today',
+        ?string $description = null,
+        CodeVisibility $visibility = CodeVisibility::EVERYONE,
+    ): AccessCode {
+        $code = new AccessCode($label, $value, new \DateTimeImmutable($validFrom), $description, $visibility);
+        $this->em->persist($code);
+
+        return $code;
+    }
+
+    /**
+     * @param list<string> $roles
+     */
+    private function user(string $email, array $roles = ['ROLE_EMPLOYEE']): User
+    {
+        $existing = $this->em->getRepository(User::class)->findOneBy(['email' => $email]);
+        if (null !== $existing) {
+            return $existing;
+        }
+
+        $user = new User($email, 'Test');
+        $user->setRoles($roles);
+        $this->em->persist($user);
+        $this->em->flush();
+
+        return $user;
+    }
+}
diff --git a/tests/Controller/Admin/AccessCodeAdminControllerTest.php b/tests/Controller/Admin/AccessCodeAdminControllerTest.php
new file mode 100644
index 0000000..88b3bde
--- /dev/null
+++ b/tests/Controller/Admin/AccessCodeAdminControllerTest.php
@@ -0,0 +1,291 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Controller\Admin;
+
+use App\Entity\AccessCode;
+use App\Entity\User;
+use App\Enum\CodeVisibility;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\KernelBrowser;
+use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
+use Symfony\Component\HttpFoundation\Response;
+
+/**
+ * Maintaining the access codes: the table of everything there is, and the three writes.
+ *
+ * The quick look at /access-codes is the other half and is tested in AccessCodeControllerTest --
+ * what it shows is one card per door, what this shows is every row including the ones that page
+ * deliberately leaves out.
+ */
+class AccessCodeAdminControllerTest extends WebTestCase
+{
+    private KernelBrowser $client;
+    private EntityManagerInterface $em;
+
+    protected function setUp(): void
+    {
+        $this->client = self::createClient(server: ['HTTPS' => true]);
+        $this->client->disableReboot();
+        $this->em = self::getContainer()->get(EntityManagerInterface::class);
+        $this->em->getConnection()->beginTransaction();
+    }
+
+    protected function tearDown(): void
+    {
+        $this->em->getConnection()->rollBack();
+        parent::tearDown();
+    }
+
+    public function testAnEmployeeCannotReachIt(): void
+    {
+        $code = $this->code('Aufzug', '4711');
+        $this->client->loginUser($this->user('anna@ep-reisen.de'));
+
+        $this->client->request('GET', '/admin/access-codes');
+        self::assertResponseStatusCodeSame(Response::HTTP_FORBIDDEN);
+
+        $this->client->request('GET', '/admin/access-codes/new', server: ['HTTP_HX-Request' => 'true']);
+        self::assertResponseStatusCodeSame(Response::HTTP_FORBIDDEN);
+
+        $this->client->request('GET', \sprintf('/admin/access-codes/%d/edit', $code->getId()), server: ['HTTP_HX-Request' => 'true']);
+        self::assertResponseStatusCodeSame(Response::HTTP_FORBIDDEN);
+
+        $this->client->request('POST', \sprintf('/admin/access-codes/%d/delete', $code->getId()), ['_token' => 'whatever'], server: ['HTTP_HX-Request' => 'true']);
+        self::assertResponseStatusCodeSame(Response::HTTP_FORBIDDEN);
+        $this->em->clear();
+        self::assertNotNull($this->em->find(AccessCode::class, $code->getId()));
+    }
+
+    /**
+     * Every row, newest per door first, each marked with what it is today: the one in force
+     * carries no badge, its successor is „noch nicht gültig" and its predecessor „ersetzt".
+     */
+    public function testTheTableMarksUpcomingAndSupersededCodes(): void
+    {
+        $this->code('Aufzug', 'OLD', validFrom: '-2 months');
+        $this->code('Aufzug', 'NOW', validFrom: '-1 day');
+        $this->code('Aufzug', 'NEXT', validFrom: '+1 month');
+        $this->client->loginUser($this->admin());
+
+        $rows = $this->client->request('GET', '/admin/access-codes')->filter('[data-access-code]');
+
+        self::assertResponseIsSuccessful();
+        self::assertCount(3, $rows);
+        self::assertStringContainsString('NEXT', $rows->eq(0)->text());
+        self::assertStringContainsString('noch nicht gültig', $rows->eq(0)->text());
+        self::assertStringContainsString('NOW', $rows->eq(1)->text());
+        self::assertStringNotContainsString('ersetzt', $rows->eq(1)->text());
+        self::assertStringNotContainsString('noch nicht gültig', $rows->eq(1)->text());
+        self::assertStringContainsString('OLD', $rows->eq(2)->text());
+        self::assertStringContainsString('ersetzt', $rows->eq(2)->text());
+    }
+
+    /**
+     * A door whose code only starts next week has nothing in force -- and nothing may be marked
+     * as replaced, because nothing has replaced anything yet.
+     */
+    public function testACodeThatHasNotStartedYetSupersedesNothing(): void
+    {
+        $this->code('Schranke', 'SOON', validFrom: '+1 week');
+        $this->client->loginUser($this->admin());
+
+        $rows = $this->client->request('GET', '/admin/access-codes')->filter('[data-access-code]');
+
+        self::assertCount(1, $rows);
+        self::assertStringContainsString('noch nicht gültig', $rows->text());
+        self::assertStringNotContainsString('ersetzt', $rows->text());
+    }
+
+    public function testTheQuickLookOffersTheTableToAnAdmin(): void
+    {
+        $this->client->loginUser($this->admin());
+
+        $crawler = $this->client->request('GET', '/admin/access-codes');
+
+        self::assertCount(1, $crawler->filter('a[href="/access-codes"]'));
+    }
+
+    public function testCreatingACode(): void
+    {
+        $this->client->loginUser($this->admin());
+
+        $response = $this->submit('/admin/access-codes/new', 'access_code_form', [
+            'label' => 'Aufzug',
+            'description' => 'Kabine im Erdgeschoss',
+            'code' => '4711',
+            'validFrom' => '2026-10-01',
+            'visibility' => 'everyone',
+        ]);
+
+        self::assertSame('/admin/access-codes', $response->headers->get('HX-Redirect'));
+        $created = $this->em->getRepository(AccessCode::class)->findOneBy(['label' => 'Aufzug']);
+        self::assertNotNull($created);
+        self::assertSame('4711', $created->getCode());
+        self::assertSame('Kabine im Erdgeschoss', $created->getDescription());
+        self::assertSame('2026-10-01', $created->getValidFrom()->format('Y-m-d'));
+        self::assertSame(CodeVisibility::EVERYONE, $created->getVisibility());
+    }
+
+    /**
+     * The date is prefilled with today, because a code being entered usually already works.
+     */
+    public function testTheNewFormStartsToday(): void
+    {
+        $this->client->loginUser($this->admin());
+
+        $crawler = $this->client->request('GET', '/admin/access-codes/new', server: ['HTTP_HX-Request' => 'true']);
+
+        self::assertSame(date('Y-m-d'), $crawler->filter('#access_code_form_validFrom')->attr('value'));
+    }
+
+    public function testAMissingLabelIsRejected(): void
+    {
+        $this->client->loginUser($this->admin());
+
+        $response = $this->submit('/admin/access-codes/new', 'access_code_form', [
+            'label' => '',
+            'code' => '4711',
+            'validFrom' => '2026-10-01',
+            'visibility' => 'everyone',
+        ]);
+
+        self::assertSame(Response::HTTP_UNPROCESSABLE_ENTITY, $response->getStatusCode());
+        self::assertCount(0, $this->em->getRepository(AccessCode::class)->findAll());
+    }
+
+    public function testEditingACodeIncludingItsVisibility(): void
+    {
+        $code = $this->code('Serverraum', '4711');
+        $this->client->loginUser($this->admin());
+
+        $response = $this->submit(\sprintf('/admin/access-codes/%d/edit', $code->getId()), 'access_code_form', [
+            'label' => 'Serverraum',
+            'description' => '',
+            'code' => '9999',
+            'validFrom' => $code->getValidFrom()->format('Y-m-d'),
+            'visibility' => 'admin',
+        ]);
+
+        self::assertSame('/admin/access-codes', $response->headers->get('HX-Redirect'));
+        $code = $this->reload($code);
+        self::assertSame('9999', $code->getCode());
+        self::assertSame(CodeVisibility::ADMIN, $code->getVisibility());
+        self::assertNull($code->getDescription());
+    }
+
+    /**
+     * Two codes for the same door is the ordinary way to rotate one, so nothing may refuse it.
+     */
+    public function testASecondCodeForTheSameDoorIsAccepted(): void
+    {
+        $this->code('Aufzug', '4711');
+        $this->client->loginUser($this->admin());
+
+        $this->submit('/admin/access-codes/new', 'access_code_form', [
+            'label' => 'Aufzug',
+            'code' => '9999',
+            'validFrom' => '2026-12-01',
+            'visibility' => 'everyone',
+        ]);
+
+        self::assertCount(2, $this->em->getRepository(AccessCode::class)->findBy(['label' => 'Aufzug']));
+    }
+
+    public function testDeletingACode(): void
+    {
+        $code = $this->code('Aufzug', '4711');
+        $id = $code->getId();
+        $this->client->loginUser($this->admin());
+        $uri = \sprintf('/admin/access-codes/%d/delete', $id);
+
+        $this->client->request('POST', $uri, ['_token' => $this->confirmationToken($uri)], server: ['HTTP_HX-Request' => 'true']);
+
+        self::assertSame('/admin/access-codes', $this->client->getResponse()->headers->get('HX-Redirect'));
+        $this->em->clear();
+        self::assertNull($this->em->find(AccessCode::class, $id));
+    }
+
+    public function testDeletingACodeNeedsAValidToken(): void
+    {
+        $code = $this->code('Aufzug', '4711');
+        $this->client->loginUser($this->admin());
+
+        $this->client->request('POST', \sprintf('/admin/access-codes/%d/delete', $code->getId()), ['_token' => 'whatever'], server: ['HTTP_HX-Request' => 'true']);
+
+        self::assertResponseStatusCodeSame(Response::HTTP_FORBIDDEN);
+        $this->em->clear();
+        self::assertNotNull($this->em->find(AccessCode::class, $code->getId()));
+    }
+
+    /**
+     * Opens the modal, then posts the given fields with its CSRF token -- the round trip a
+     * browser makes.
+     *
+     * @param array<string, string> $fields
+     */
+    private function submit(string $uri, string $formName, array $fields): Response
+    {
+        $crawler = $this->client->request('GET', $uri, server: ['HTTP_HX-Request' => 'true']);
+        self::assertResponseIsSuccessful();
+
+        $fields['_token'] = $crawler->filter(\sprintf('#%s__token', $formName))->attr('value');
+        $this->client->request('POST', $uri, [$formName => $fields], server: ['HTTP_HX-Request' => 'true']);
+
+        return $this->client->getResponse();
+    }
+
+    private function confirmationToken(string $uri): string
+    {
+        $crawler = $this->client->request('GET', $uri, server: ['HTTP_HX-Request' => 'true']);
+        self::assertResponseIsSuccessful();
+
+        $vals = $crawler->filter('#htmx-confirmation-modal [hx-post]')->attr('hx-vals');
+
+        return json_decode((string) $vals, true, flags: \JSON_THROW_ON_ERROR)['_token'];
+    }
+
+    /**
+     * Each request resets the entity manager, so what a test holds is detached afterwards.
+     */
+    private function reload(AccessCode $code): AccessCode
+    {
+        $fresh = $this->em->find(AccessCode::class, $code->getId());
+        self::assertNotNull($fresh);
+
+        return $fresh;
+    }
+
+    private function code(string $label, string $value, string $validFrom = 'today'): AccessCode
+    {
+        $code = new AccessCode($label, $value, new \DateTimeImmutable($validFrom));
+        $this->em->persist($code);
+        $this->em->flush();
+
+        return $code;
+    }
+
+    private function admin(): User
+    {
+        return $this->user('chef@ep-reisen.de', ['ROLE_ADMIN']);
+    }
+
+    /**
+     * @param list<string> $roles
+     */
+    private function user(string $email, array $roles = ['ROLE_EMPLOYEE']): User
+    {
+        $existing = $this->em->getRepository(User::class)->findOneBy(['email' => $email]);
+        if (null !== $existing) {
+            return $existing;
+        }
+
+        $user = new User($email, 'Test');
+        $user->setRoles($roles);
+        $this->em->persist($user);
+        $this->em->flush();
+
+        return $user;
+    }
+}
diff --git a/tests/Service/AuditLoggerTest.php b/tests/Service/AuditLoggerTest.php
index 969ca79..500e940 100644
--- a/tests/Service/AuditLoggerTest.php
+++ b/tests/Service/AuditLoggerTest.php
@@ -4,11 +4,13 @@ declare(strict_types=1);
 
 namespace App\Tests\Service;
 
+use App\Entity\AccessCode;
 use App\Entity\Booking;
 use App\Entity\BookingSeries;
 use App\Entity\Resource;
 use App\Entity\ResourceGroup;
 use App\Entity\User;
+use App\Enum\CodeVisibility;
 use App\Enum\RecurrenceRule;
 use App\Enum\ResourceType;
 use App\Model\SeriesResult;
@@ -152,6 +154,32 @@ class AuditLoggerTest extends TestCase
         self::assertSame('holder@ep-reisen.de', $records[1]->context['account']);
     }
 
+    /**
+     * The one thing the trail must never carry. It is asserted rather than left to review,
+     * because a helpful "log what changed" added later would leak every door code in the
+     * building into a file that outlives the codes themselves.
+     */
+    public function testAnAccessCodeIsRecordedWithoutItsValue(): void
+    {
+        $code = new AccessCode('Aufzug', '4711', new \DateTimeImmutable('2026-10-01'));
+
+        $this->audit->accessCodeCreated($code);
+        $this->audit->accessCodeUpdated($code, true, CodeVisibility::ADMIN);
+        $this->audit->accessCodeDeleted(7, 'Aufzug', CodeVisibility::EVERYONE);
+
+        foreach ($this->handler->getRecords() as $record) {
+            self::assertStringNotContainsString('4711', json_encode($record->context, \JSON_THROW_ON_ERROR));
+        }
+
+        $records = $this->handler->getRecords();
+        self::assertSame('Aufzug', $records[0]->context['access_code']);
+        self::assertSame('2026-10-01', $records[0]->context['valid_from']);
+        self::assertSame('everyone', $records[0]->context['visibility']);
+        self::assertTrue($records[1]->context['code_changed']);
+        self::assertSame('admin', $records[1]->context['previous_visibility']);
+        self::assertSame(7, $records[2]->context['access_code_id']);
+    }
+
     private function record(): LogRecord
     {
         return $this->handler->getRecords()[0];