Merge pull request 'Implement cancel-event feature (016)' (#38) from 016-cancel-event into master

- Convert Event and Rsvp from mutable POJOs to Java records
- Move all 8 exception classes to application.service.exception sub-package
- Add ArchUnit rule enforcing domain models must be records

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/.mvn/wrapper/maven-wrapper.properties

@@ -1,3 +1,3 @@
 wrapperVersion=3.3.4
 distributionType=only-script
-distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.13/apache-maven-3.9.13-bin.zip
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.14/apache-maven-3.9.14-bin.zip

backend/src/main/java/de/fete/adapter/in/web/EventController.java

@@ -8,18 +8,22 @@ import de.fete.adapter.in.web.model.CreateRsvpRequest;
 import de.fete.adapter.in.web.model.CreateRsvpResponse;
 import de.fete.adapter.in.web.model.GetAttendeesResponse;
 import de.fete.adapter.in.web.model.GetEventResponse;
-import de.fete.application.service.EventNotFoundException;
-import de.fete.application.service.InvalidTimezoneException;
+import de.fete.adapter.in.web.model.PatchEventRequest;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidTimezoneException;
 import de.fete.domain.model.CreateEventCommand;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.OrganizerToken;
 import de.fete.domain.model.Rsvp;
+import de.fete.domain.model.RsvpToken;
+import de.fete.domain.port.in.CancelRsvpUseCase;
 import de.fete.domain.port.in.CountAttendeesByEventUseCase;
 import de.fete.domain.port.in.CreateEventUseCase;
 import de.fete.domain.port.in.CreateRsvpUseCase;
 import de.fete.domain.port.in.GetAttendeesUseCase;
 import de.fete.domain.port.in.GetEventUseCase;
+import de.fete.domain.port.in.UpdateEventUseCase;
 import java.time.DateTimeException;
 import java.time.ZoneId;
 import java.util.List;
@@ -35,21 +39,27 @@ public class EventController implements EventsApi {
   private final CreateEventUseCase createEventUseCase;
   private final GetEventUseCase getEventUseCase;
   private final CreateRsvpUseCase createRsvpUseCase;
+  private final CancelRsvpUseCase cancelRsvpUseCase;
   private final CountAttendeesByEventUseCase countAttendeesByEventUseCase;
   private final GetAttendeesUseCase getAttendeesUseCase;
+  private final UpdateEventUseCase updateEventUseCase;
 
   /** Creates a new controller with the given use cases. */
   public EventController(
       CreateEventUseCase createEventUseCase,
       GetEventUseCase getEventUseCase,
       CreateRsvpUseCase createRsvpUseCase,
+      CancelRsvpUseCase cancelRsvpUseCase,
       CountAttendeesByEventUseCase countAttendeesByEventUseCase,
-      GetAttendeesUseCase getAttendeesUseCase) {
+      GetAttendeesUseCase getAttendeesUseCase,
+      UpdateEventUseCase updateEventUseCase) {
     this.createEventUseCase = createEventUseCase;
     this.getEventUseCase = getEventUseCase;
     this.createRsvpUseCase = createRsvpUseCase;
+    this.cancelRsvpUseCase = cancelRsvpUseCase;
     this.countAttendeesByEventUseCase = countAttendeesByEventUseCase;
     this.getAttendeesUseCase = getAttendeesUseCase;
+    this.updateEventUseCase = updateEventUseCase;
   }
 
   @Override
@@ -68,42 +78,55 @@ public class EventController implements EventsApi {
     Event event = createEventUseCase.createEvent(command);
 
     var response = new CreateEventResponse();
-    response.setEventToken(event.getEventToken().value());
-    response.setOrganizerToken(event.getOrganizerToken().value());
-    response.setTitle(event.getTitle());
-    response.setDateTime(event.getDateTime());
-    response.setTimezone(event.getTimezone().getId());
+    response.setEventToken(event.eventToken().value());
+    response.setOrganizerToken(event.organizerToken().value());
+    response.setTitle(event.title());
+    response.setDateTime(event.dateTime());
+    response.setTimezone(event.timezone().getId());
 
     return ResponseEntity.status(HttpStatus.CREATED).body(response);
   }
 
   @Override
-  public ResponseEntity<GetEventResponse> getEvent(UUID token) {
-    var eventToken = new de.fete.domain.model.EventToken(token);
-    Event event = getEventUseCase.getByEventToken(eventToken)
-        .orElseThrow(() -> new EventNotFoundException(token));
+  public ResponseEntity<GetEventResponse> getEvent(UUID eventToken) {
+    var evtToken = new EventToken(eventToken);
+    Event event = getEventUseCase.getByEventToken(evtToken)
+        .orElseThrow(() -> new EventNotFoundException(eventToken));
 
     var response = new GetEventResponse();
-    response.setEventToken(event.getEventToken().value());
-    response.setTitle(event.getTitle());
-    response.setDescription(event.getDescription());
-    response.setDateTime(event.getDateTime());
-    response.setTimezone(event.getTimezone().getId());
-    response.setLocation(event.getLocation());
+    response.setEventToken(event.eventToken().value());
+    response.setTitle(event.title());
+    response.setDescription(event.description());
+    response.setDateTime(event.dateTime());
+    response.setTimezone(event.timezone().getId());
+    response.setLocation(event.location());
     response.setAttendeeCount(
-        (int) countAttendeesByEventUseCase.countByEvent(eventToken));
+        (int) countAttendeesByEventUseCase.countByEvent(evtToken));
+    response.setCancelled(event.cancelled());
+    response.setCancellationReason(event.cancellationReason());
 
     return ResponseEntity.ok(response);
   }
 
+  @Override
+  public ResponseEntity<Void> patchEvent(
+      UUID eventToken, UUID organizerToken, PatchEventRequest request) {
+    updateEventUseCase.cancelEvent(
+        new EventToken(eventToken),
+        new OrganizerToken(organizerToken),
+        request.getCancelled(),
+        request.getCancellationReason());
+    return ResponseEntity.noContent().build();
+  }
+
   @Override
   public ResponseEntity<GetAttendeesResponse> getAttendees(
-      UUID token, UUID organizerToken) {
-    var eventToken = new EventToken(token);
+      UUID eventToken, UUID organizerToken) {
+    var evtToken = new EventToken(eventToken);
     var orgToken = new OrganizerToken(organizerToken);
 
     List<String> names = getAttendeesUseCase
-        .getAttendeeNames(eventToken, orgToken);
+        .getAttendeeNames(evtToken, orgToken);
 
     var attendees = names.stream()
         .map(name -> new Attendee().name(name))
@@ -117,17 +140,23 @@ public class EventController implements EventsApi {
 
   @Override
   public ResponseEntity<CreateRsvpResponse> createRsvp(
-      UUID token, CreateRsvpRequest createRsvpRequest) {
-    var eventToken = new EventToken(token);
-    Rsvp rsvp = createRsvpUseCase.createRsvp(eventToken, createRsvpRequest.getName());
+      UUID eventToken, CreateRsvpRequest createRsvpRequest) {
+    var evtToken = new EventToken(eventToken);
+    Rsvp rsvp = createRsvpUseCase.createRsvp(evtToken, createRsvpRequest.getName());
 
     var response = new CreateRsvpResponse();
-    response.setRsvpToken(rsvp.getRsvpToken().value());
-    response.setName(rsvp.getName());
+    response.setRsvpToken(rsvp.rsvpToken().value());
+    response.setName(rsvp.name());
 
     return ResponseEntity.status(HttpStatus.CREATED).body(response);
   }
 
+  @Override
+  public ResponseEntity<Void> cancelRsvp(UUID eventToken, UUID rsvpToken) {
+    cancelRsvpUseCase.cancelRsvp(new EventToken(eventToken), new RsvpToken(rsvpToken));
+    return ResponseEntity.noContent().build();
+  }
+
   private static ZoneId parseTimezone(String timezone) {
     try {
       return ZoneId.of(timezone);

backend/src/main/java/de/fete/adapter/in/web/GlobalExceptionHandler.java

@@ -1,11 +1,13 @@
 package de.fete.adapter.in.web;
 
-import de.fete.application.service.EventExpiredException;
-import de.fete.application.service.EventNotFoundException;
-import de.fete.application.service.ExpiryDateBeforeEventException;
-import de.fete.application.service.ExpiryDateInPastException;
-import de.fete.application.service.InvalidOrganizerTokenException;
-import de.fete.application.service.InvalidTimezoneException;
+import de.fete.application.service.exception.EventAlreadyCancelledException;
+import de.fete.application.service.exception.EventCancelledException;
+import de.fete.application.service.exception.EventExpiredException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.ExpiryDateBeforeEventException;
+import de.fete.application.service.exception.ExpiryDateInPastException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
+import de.fete.application.service.exception.InvalidTimezoneException;
 import java.net.URI;
 import java.util.List;
 import java.util.Map;
@@ -75,6 +77,32 @@ public class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
         .body(problemDetail);
   }
 
+  /** Handles attempt to cancel an already cancelled event. */
+  @ExceptionHandler(EventAlreadyCancelledException.class)
+  public ResponseEntity<ProblemDetail> handleEventAlreadyCancelled(
+      EventAlreadyCancelledException ex) {
+    ProblemDetail problemDetail = ProblemDetail.forStatusAndDetail(
+        HttpStatus.CONFLICT, ex.getMessage());
+    problemDetail.setTitle("Event Already Cancelled");
+    problemDetail.setType(URI.create("urn:problem-type:event-already-cancelled"));
+    return ResponseEntity.status(HttpStatus.CONFLICT)
+        .contentType(MediaType.APPLICATION_PROBLEM_JSON)
+        .body(problemDetail);
+  }
+
+  /** Handles RSVP on cancelled event. */
+  @ExceptionHandler(EventCancelledException.class)
+  public ResponseEntity<ProblemDetail> handleEventCancelled(
+      EventCancelledException ex) {
+    ProblemDetail problemDetail = ProblemDetail.forStatusAndDetail(
+        HttpStatus.CONFLICT, ex.getMessage());
+    problemDetail.setTitle("Event Cancelled");
+    problemDetail.setType(URI.create("urn:problem-type:event-cancelled"));
+    return ResponseEntity.status(HttpStatus.CONFLICT)
+        .contentType(MediaType.APPLICATION_PROBLEM_JSON)
+        .body(problemDetail);
+  }
+
   /** Handles RSVP on expired event. */
   @ExceptionHandler(EventExpiredException.class)
   public ResponseEntity<ProblemDetail> handleEventExpired(

backend/src/main/java/de/fete/adapter/in/web/SpaController.java

@@ -68,17 +68,17 @@ public class SpaController {
 
   /** Serves SPA HTML with event-specific meta-tags. */
   @GetMapping(
-      value = "/events/{token}",
+      value = "/events/{eventToken}",
       produces = MediaType.TEXT_HTML_VALUE
   )
   @ResponseBody
-  public String serveEventPage(@PathVariable String token,
+  public String serveEventPage(@PathVariable String eventToken,
       HttpServletRequest request) {
     if (htmlTemplate == null) {
       return "";
     }
     String baseUrl = getBaseUrl(request);
-    Map<String, String> meta = resolveEventMeta(token, baseUrl);
+    Map<String, String> meta = resolveEventMeta(eventToken, baseUrl);
     return htmlTemplate.replace(PLACEHOLDER, renderTags(meta));
   }
 
@@ -86,11 +86,11 @@ public class SpaController {
 
   private Map<String, String> buildEventMeta(Event event, String baseUrl) {
     var tags = new LinkedHashMap<String, String>();
-    String title = truncateTitle(event.getTitle());
+    String title = truncateTitle(event.title());
     String description = formatDescription(event);
     tags.put("og:title", title);
     tags.put("og:description", description);
-    tags.put("og:url", baseUrl + "/events/" + event.getEventToken().value());
+    tags.put("og:url", baseUrl + "/events/" + event.eventToken().value());
     tags.put("og:type", "website");
     tags.put("og:site_name", GENERIC_TITLE);
     tags.put("og:image", baseUrl + "/og-image.png");
@@ -138,16 +138,16 @@ public class SpaController {
   }
 
   private String formatDescription(Event event) {
-    ZonedDateTime zoned = event.getDateTime().atZoneSameInstant(event.getTimezone());
+    ZonedDateTime zoned = event.dateTime().atZoneSameInstant(event.timezone());
     var sb = new StringBuilder();
     sb.append("📅 ").append(zoned.format(DATE_FORMAT));
 
-    if (event.getLocation() != null && !event.getLocation().isBlank()) {
-      sb.append(" · 📍 ").append(event.getLocation());
+    if (event.location() != null && !event.location().isBlank()) {
+      sb.append(" · 📍 ").append(event.location());
     }
 
-    if (event.getDescription() != null && !event.getDescription().isBlank()) {
-      sb.append(" — ").append(event.getDescription());
+    if (event.description() != null && !event.description().isBlank()) {
+      sb.append(" — ").append(event.description());
     }
 
     String result = sb.toString();

backend/src/main/java/de/fete/adapter/out/persistence/EventJpaEntity.java

@@ -46,6 +46,12 @@ public class EventJpaEntity {
   @Column(name = "created_at", nullable = false)
   private OffsetDateTime createdAt;
 
+  @Column(name = "cancelled", nullable = false)
+  private boolean cancelled;
+
+  @Column(name = "cancellation_reason", length = 2000)
+  private String cancellationReason;
+
   /** Returns the internal database ID. */
   public Long getId() {
     return id;
@@ -145,4 +151,24 @@ public class EventJpaEntity {
   public void setCreatedAt(OffsetDateTime createdAt) {
     this.createdAt = createdAt;
   }
+
+  /** Returns whether the event is cancelled. */
+  public boolean isCancelled() {
+    return cancelled;
+  }
+
+  /** Sets the cancelled flag. */
+  public void setCancelled(boolean cancelled) {
+    this.cancelled = cancelled;
+  }
+
+  /** Returns the cancellation reason. */
+  public String getCancellationReason() {
+    return cancellationReason;
+  }
+
+  /** Sets the cancellation reason. */
+  public void setCancellationReason(String cancellationReason) {
+    this.cancellationReason = cancellationReason;
+  }
 }

backend/src/main/java/de/fete/adapter/out/persistence/EventPersistenceAdapter.java

@@ -38,31 +38,34 @@ public class EventPersistenceAdapter implements EventRepository {
 
   private EventJpaEntity toEntity(Event event) {
     var entity = new EventJpaEntity();
-    entity.setId(event.getId());
-    entity.setEventToken(event.getEventToken().value());
-    entity.setOrganizerToken(event.getOrganizerToken().value());
-    entity.setTitle(event.getTitle());
-    entity.setDescription(event.getDescription());
-    entity.setDateTime(event.getDateTime());
-    entity.setTimezone(event.getTimezone().getId());
-    entity.setLocation(event.getLocation());
-    entity.setExpiryDate(event.getExpiryDate());
-    entity.setCreatedAt(event.getCreatedAt());
+    entity.setId(event.id());
+    entity.setEventToken(event.eventToken().value());
+    entity.setOrganizerToken(event.organizerToken().value());
+    entity.setTitle(event.title());
+    entity.setDescription(event.description());
+    entity.setDateTime(event.dateTime());
+    entity.setTimezone(event.timezone().getId());
+    entity.setLocation(event.location());
+    entity.setExpiryDate(event.expiryDate());
+    entity.setCreatedAt(event.createdAt());
+    entity.setCancelled(event.cancelled());
+    entity.setCancellationReason(event.cancellationReason());
     return entity;
   }
 
   private Event toDomain(EventJpaEntity entity) {
-    var event = new Event();
-    event.setId(entity.getId());
-    event.setEventToken(new EventToken(entity.getEventToken()));
-    event.setOrganizerToken(new OrganizerToken(entity.getOrganizerToken()));
-    event.setTitle(entity.getTitle());
-    event.setDescription(entity.getDescription());
-    event.setDateTime(entity.getDateTime());
-    event.setTimezone(ZoneId.of(entity.getTimezone()));
-    event.setLocation(entity.getLocation());
-    event.setExpiryDate(entity.getExpiryDate());
-    event.setCreatedAt(entity.getCreatedAt());
-    return event;
+    return new Event(
+        entity.getId(),
+        new EventToken(entity.getEventToken()),
+        new OrganizerToken(entity.getOrganizerToken()),
+        entity.getTitle(),
+        entity.getDescription(),
+        entity.getDateTime(),
+        ZoneId.of(entity.getTimezone()),
+        entity.getLocation(),
+        entity.getExpiryDate(),
+        entity.getCreatedAt(),
+        entity.isCancelled(),
+        entity.getCancellationReason());
   }
 }

backend/src/main/java/de/fete/adapter/out/persistence/RsvpJpaRepository.java

@@ -14,4 +14,7 @@ public interface RsvpJpaRepository extends JpaRepository<RsvpJpaEntity, Long> {
 
   /** Finds all RSVPs for the given event, ordered by ID ascending. */
   java.util.List<RsvpJpaEntity> findAllByEventIdOrderByIdAsc(Long eventId);
+
+  /** Deletes an RSVP by event ID and RSVP token. Returns count of deleted rows. */
+  long deleteByEventIdAndRsvpToken(Long eventId, UUID rsvpToken);
 }

backend/src/main/java/de/fete/adapter/out/persistence/RsvpPersistenceAdapter.java

@@ -36,21 +36,25 @@ public class RsvpPersistenceAdapter implements RsvpRepository {
         .toList();
   }
 
+  @Override
+  public boolean deleteByEventIdAndRsvpToken(Long eventId, RsvpToken rsvpToken) {
+    return jpaRepository.deleteByEventIdAndRsvpToken(eventId, rsvpToken.value()) > 0;
+  }
+
   private RsvpJpaEntity toEntity(Rsvp rsvp) {
     var entity = new RsvpJpaEntity();
-    entity.setId(rsvp.getId());
-    entity.setRsvpToken(rsvp.getRsvpToken().value());
-    entity.setEventId(rsvp.getEventId());
-    entity.setName(rsvp.getName());
+    entity.setId(rsvp.id());
+    entity.setRsvpToken(rsvp.rsvpToken().value());
+    entity.setEventId(rsvp.eventId());
+    entity.setName(rsvp.name());
     return entity;
   }
 
   private Rsvp toDomain(RsvpJpaEntity entity) {
-    var rsvp = new Rsvp();
-    rsvp.setId(entity.getId());
-    rsvp.setRsvpToken(new RsvpToken(entity.getRsvpToken()));
-    rsvp.setEventId(entity.getEventId());
-    rsvp.setName(entity.getName());
-    return rsvp;
+    return new Rsvp(
+        entity.getId(),
+        new RsvpToken(entity.getRsvpToken()),
+        entity.getEventId(),
+        entity.getName());
   }
 }

backend/src/main/java/de/fete/application/service/EventService.java

@@ -1,21 +1,26 @@
 package de.fete.application.service;
 
+import de.fete.application.service.exception.EventAlreadyCancelledException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
 import de.fete.domain.model.CreateEventCommand;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.OrganizerToken;
 import de.fete.domain.port.in.CreateEventUseCase;
 import de.fete.domain.port.in.GetEventUseCase;
+import de.fete.domain.port.in.UpdateEventUseCase;
 import de.fete.domain.port.out.EventRepository;
 import java.time.Clock;
 import java.time.LocalDate;
 import java.time.OffsetDateTime;
 import java.util.Optional;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
 
 /** Application service implementing event creation and retrieval. */
 @Service
-public class EventService implements CreateEventUseCase, GetEventUseCase {
+public class EventService implements CreateEventUseCase, GetEventUseCase, UpdateEventUseCase {
 
   private static final int EXPIRY_DAYS_AFTER_EVENT = 7;
 
@@ -32,16 +37,19 @@ public class EventService implements CreateEventUseCase, GetEventUseCase {
   public Event createEvent(CreateEventCommand command) {
     LocalDate expiryDate = command.dateTime().toLocalDate().plusDays(EXPIRY_DAYS_AFTER_EVENT);
 
-    var event = new Event();
-    event.setEventToken(EventToken.generate());
-    event.setOrganizerToken(OrganizerToken.generate());
-    event.setTitle(command.title());
-    event.setDescription(command.description());
-    event.setDateTime(command.dateTime());
-    event.setTimezone(command.timezone());
-    event.setLocation(command.location());
-    event.setExpiryDate(expiryDate);
-    event.setCreatedAt(OffsetDateTime.now(clock));
+    var event = new Event(
+        null,
+        EventToken.generate(),
+        OrganizerToken.generate(),
+        command.title(),
+        command.description(),
+        command.dateTime(),
+        command.timezone(),
+        command.location(),
+        expiryDate,
+        OffsetDateTime.now(clock),
+        false,
+        null);
 
     return eventRepository.save(event);
   }
@@ -50,4 +58,27 @@ public class EventService implements CreateEventUseCase, GetEventUseCase {
   public Optional<Event> getByEventToken(EventToken eventToken) {
     return eventRepository.findByEventToken(eventToken);
   }
+
+  @Transactional
+  @Override
+  public void cancelEvent(
+      EventToken eventToken, OrganizerToken organizerToken,
+      Boolean cancelled, String reason) {
+    if (!Boolean.TRUE.equals(cancelled)) {
+      return;
+    }
+
+    Event event = eventRepository.findByEventToken(eventToken)
+        .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
+
+    if (!event.organizerToken().equals(organizerToken)) {
+      throw new InvalidOrganizerTokenException();
+    }
+
+    if (event.cancelled()) {
+      throw new EventAlreadyCancelledException(eventToken.value());
+    }
+
+    eventRepository.save(event.withCancellation(true, reason));
+  }
 }

backend/src/main/java/de/fete/application/service/RsvpService.java

@@ -1,15 +1,21 @@
 package de.fete.application.service;
 
+import de.fete.application.service.exception.EventCancelledException;
+import de.fete.application.service.exception.EventExpiredException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.OrganizerToken;
 import de.fete.domain.model.Rsvp;
 import de.fete.domain.model.RsvpToken;
+import de.fete.domain.port.in.CancelRsvpUseCase;
 import de.fete.domain.port.in.CountAttendeesByEventUseCase;
 import de.fete.domain.port.in.CreateRsvpUseCase;
 import de.fete.domain.port.in.GetAttendeesUseCase;
 import de.fete.domain.port.out.EventRepository;
 import de.fete.domain.port.out.RsvpRepository;
+import jakarta.transaction.Transactional;
 import java.time.Clock;
 import java.time.LocalDate;
 import java.util.List;
@@ -18,7 +24,8 @@ import org.springframework.stereotype.Service;
 /** Application service implementing RSVP operations. */
 @Service
 public class RsvpService
-    implements CreateRsvpUseCase, CountAttendeesByEventUseCase, GetAttendeesUseCase {
+    implements CreateRsvpUseCase, CancelRsvpUseCase, CountAttendeesByEventUseCase,
+    GetAttendeesUseCase {
 
   private final EventRepository eventRepository;
   private final RsvpRepository rsvpRepository;
@@ -39,23 +46,32 @@ public class RsvpService
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
 
-    if (!event.getExpiryDate().isAfter(LocalDate.now(clock))) {
+    if (event.cancelled()) {
+      throw new EventCancelledException(eventToken.value());
+    }
+
+    if (!event.expiryDate().isAfter(LocalDate.now(clock))) {
       throw new EventExpiredException(eventToken.value());
     }
 
-    var rsvp = new Rsvp();
-    rsvp.setRsvpToken(RsvpToken.generate());
-    rsvp.setEventId(event.getId());
-    rsvp.setName(name.strip());
+    var rsvp = new Rsvp(null, RsvpToken.generate(), event.id(), name.strip());
 
     return rsvpRepository.save(rsvp);
   }
 
+  @Override
+  @Transactional
+  public void cancelRsvp(EventToken eventToken, RsvpToken rsvpToken) {
+    eventRepository.findByEventToken(eventToken)
+        .ifPresent(event ->
+            rsvpRepository.deleteByEventIdAndRsvpToken(event.id(), rsvpToken));
+  }
+
   @Override
   public long countByEvent(EventToken eventToken) {
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
-    return rsvpRepository.countByEventId(event.getId());
+    return rsvpRepository.countByEventId(event.id());
   }
 
   @Override
@@ -63,12 +79,12 @@ public class RsvpService
     Event event = eventRepository.findByEventToken(eventToken)
         .orElseThrow(() -> new EventNotFoundException(eventToken.value()));
 
-    if (!event.getOrganizerToken().equals(organizerToken)) {
+    if (!event.organizerToken().equals(organizerToken)) {
       throw new InvalidOrganizerTokenException();
     }
 
-    return rsvpRepository.findByEventId(event.getId()).stream()
-        .map(Rsvp::getName)
+    return rsvpRepository.findByEventId(event.id()).stream()
+        .map(Rsvp::name)
         .toList();
   }
 }

backend/src/main/java/de/fete/application/service/exception/EventAlreadyCancelledException.java

@@ -0,0 +1,12 @@
+package de.fete.application.service.exception;
+
+import java.util.UUID;
+
+/** Thrown when attempting to cancel an event that is already cancelled. */
+public class EventAlreadyCancelledException extends RuntimeException {
+
+  /** Creates a new exception for the given event token. */
+  public EventAlreadyCancelledException(UUID eventToken) {
+    super("Event is already cancelled: " + eventToken);
+  }
+}

backend/src/main/java/de/fete/application/service/exception/EventCancelledException.java

@@ -0,0 +1,12 @@
+package de.fete.application.service.exception;
+
+import java.util.UUID;
+
+/** Thrown when an RSVP is attempted on a cancelled event. */
+public class EventCancelledException extends RuntimeException {
+
+  /** Creates a new exception for the given event token. */
+  public EventCancelledException(UUID eventToken) {
+    super("Event is cancelled: " + eventToken);
+  }
+}

backend/src/main/java/de/fete/application/service/exception/EventExpiredException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.util.UUID;
 

backend/src/main/java/de/fete/application/service/exception/EventNotFoundException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.util.UUID;
 

backend/src/main/java/de/fete/application/service/exception/ExpiryDateBeforeEventException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.time.LocalDate;
 import java.time.OffsetDateTime;

backend/src/main/java/de/fete/application/service/exception/ExpiryDateInPastException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 import java.time.LocalDate;
 

backend/src/main/java/de/fete/application/service/exception/InvalidOrganizerTokenException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 /** Thrown when an invalid organizer token is provided. */
 public class InvalidOrganizerTokenException extends RuntimeException {

backend/src/main/java/de/fete/application/service/exception/InvalidTimezoneException.java

@@ -1,4 +1,4 @@
-package de.fete.application.service;
+package de.fete.application.service.exception;
 
 /** Thrown when an invalid IANA timezone ID is provided. */
 public class InvalidTimezoneException extends RuntimeException {

backend/src/main/java/de/fete/application/service/exception/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Application-layer exceptions thrown by service use case implementations.
+ */
+package de.fete.application.service.exception;

backend/src/main/java/de/fete/domain/model/Event.java

@@ -5,116 +5,26 @@ import java.time.OffsetDateTime;
 import java.time.ZoneId;
 
 /** Domain entity representing an event. */
-public class Event {
+public record Event(
+    Long id,
+    EventToken eventToken,
+    OrganizerToken organizerToken,
+    String title,
+    String description,
+    OffsetDateTime dateTime,
+    ZoneId timezone,
+    String location,
+    LocalDate expiryDate,
+    OffsetDateTime createdAt,
+    boolean cancelled,
+    String cancellationReason
+) {
 
-  private Long id;
-  private EventToken eventToken;
-  private OrganizerToken organizerToken;
-  private String title;
-  private String description;
-  private OffsetDateTime dateTime;
-  private ZoneId timezone;
-  private String location;
-  private LocalDate expiryDate;
-  private OffsetDateTime createdAt;
-
-  /** Returns the internal database ID. */
-  public Long getId() {
-    return id;
-  }
-
-  /** Sets the internal database ID. */
-  public void setId(Long id) {
-    this.id = id;
-  }
-
-  /** Returns the public event token. */
-  public EventToken getEventToken() {
-    return eventToken;
-  }
-
-  /** Sets the public event token. */
-  public void setEventToken(EventToken eventToken) {
-    this.eventToken = eventToken;
-  }
-
-  /** Returns the secret organizer token. */
-  public OrganizerToken getOrganizerToken() {
-    return organizerToken;
-  }
-
-  /** Sets the secret organizer token. */
-  public void setOrganizerToken(OrganizerToken organizerToken) {
-    this.organizerToken = organizerToken;
-  }
-
-  /** Returns the event title. */
-  public String getTitle() {
-    return title;
-  }
-
-  /** Sets the event title. */
-  public void setTitle(String title) {
-    this.title = title;
-  }
-
-  /** Returns the event description. */
-  public String getDescription() {
-    return description;
-  }
-
-  /** Sets the event description. */
-  public void setDescription(String description) {
-    this.description = description;
-  }
-
-  /** Returns the event date and time with UTC offset. */
-  public OffsetDateTime getDateTime() {
-    return dateTime;
-  }
-
-  /** Sets the event date and time. */
-  public void setDateTime(OffsetDateTime dateTime) {
-    this.dateTime = dateTime;
-  }
-
-  /** Returns the IANA timezone. */
-  public ZoneId getTimezone() {
-    return timezone;
-  }
-
-  /** Sets the IANA timezone. */
-  public void setTimezone(ZoneId timezone) {
-    this.timezone = timezone;
-  }
-
-  /** Returns the event location. */
-  public String getLocation() {
-    return location;
-  }
-
-  /** Sets the event location. */
-  public void setLocation(String location) {
-    this.location = location;
-  }
-
-  /** Returns the expiry date after which event data is deleted. */
-  public LocalDate getExpiryDate() {
-    return expiryDate;
-  }
-
-  /** Sets the expiry date. */
-  public void setExpiryDate(LocalDate expiryDate) {
-    this.expiryDate = expiryDate;
-  }
-
-  /** Returns the creation timestamp. */
-  public OffsetDateTime getCreatedAt() {
-    return createdAt;
-  }
-
-  /** Sets the creation timestamp. */
-  public void setCreatedAt(OffsetDateTime createdAt) {
-    this.createdAt = createdAt;
+  /** Returns a copy of this event with cancellation applied. */
+  public Event withCancellation(boolean cancelled, String cancellationReason) {
+    return new Event(
+        id, eventToken, organizerToken, title, description,
+        dateTime, timezone, location, expiryDate, createdAt,
+        cancelled, cancellationReason);
   }
 }

backend/src/main/java/de/fete/domain/model/Rsvp.java

@@ -1,50 +1,9 @@
 package de.fete.domain.model;
 
 /** Domain entity representing an RSVP. */
-public class Rsvp {
-
-  private Long id;
-  private RsvpToken rsvpToken;
-  private Long eventId;
-  private String name;
-
-  /** Returns the internal database ID. */
-  public Long getId() {
-    return id;
-  }
-
-  /** Sets the internal database ID. */
-  public void setId(Long id) {
-    this.id = id;
-  }
-
-  /** Returns the RSVP token. */
-  public RsvpToken getRsvpToken() {
-    return rsvpToken;
-  }
-
-  /** Sets the RSVP token. */
-  public void setRsvpToken(RsvpToken rsvpToken) {
-    this.rsvpToken = rsvpToken;
-  }
-
-  /** Returns the event ID this RSVP belongs to. */
-  public Long getEventId() {
-    return eventId;
-  }
-
-  /** Sets the event ID. */
-  public void setEventId(Long eventId) {
-    this.eventId = eventId;
-  }
-
-  /** Returns the guest's display name. */
-  public String getName() {
-    return name;
-  }
-
-  /** Sets the guest's display name. */
-  public void setName(String name) {
-    this.name = name;
-  }
-}
+public record Rsvp(
+    Long id,
+    RsvpToken rsvpToken,
+    Long eventId,
+    String name
+) {}

backend/src/main/java/de/fete/domain/port/in/CancelRsvpUseCase.java

@@ -0,0 +1,11 @@
+package de.fete.domain.port.in;
+
+import de.fete.domain.model.EventToken;
+import de.fete.domain.model.RsvpToken;
+
+/** Inbound port for cancelling an RSVP. */
+public interface CancelRsvpUseCase {
+
+  /** Cancels the RSVP identified by the given tokens. Idempotent — no error if not found. */
+  void cancelRsvp(EventToken eventToken, RsvpToken rsvpToken);
+}

backend/src/main/java/de/fete/domain/port/in/UpdateEventUseCase.java

@@ -0,0 +1,13 @@
+package de.fete.domain.port.in;
+
+import de.fete.domain.model.EventToken;
+import de.fete.domain.model.OrganizerToken;
+
+/** Inbound port for updating an event. */
+public interface UpdateEventUseCase {
+
+  /** Cancels the event identified by the given token. */
+  void cancelEvent(
+      EventToken eventToken, OrganizerToken organizerToken,
+      Boolean cancelled, String reason);
+}

backend/src/main/java/de/fete/domain/port/out/RsvpRepository.java

@@ -1,6 +1,7 @@
 package de.fete.domain.port.out;
 
 import de.fete.domain.model.Rsvp;
+import de.fete.domain.model.RsvpToken;
 import java.util.List;
 
 /** Outbound port for persisting and querying RSVPs. */
@@ -14,4 +15,7 @@ public interface RsvpRepository {
 
   /** Finds all RSVPs for the given event, ordered by ID ascending. */
   List<Rsvp> findByEventId(Long eventId);
+
+  /** Deletes an RSVP by event ID and RSVP token. Returns true if a record was deleted. */
+  boolean deleteByEventIdAndRsvpToken(Long eventId, RsvpToken rsvpToken);
 }

backend/src/main/resources/db/changelog/004-add-cancellation-columns.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<databaseChangeLog
+    xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
+        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
+
+    <changeSet id="004-add-cancellation-columns" author="fete">
+        <addColumn tableName="events">
+            <column name="cancelled" type="BOOLEAN" defaultValueBoolean="false">
+                <constraints nullable="false"/>
+            </column>
+            <column name="cancellation_reason" type="VARCHAR(2000)"/>
+        </addColumn>
+    </changeSet>
+
+</databaseChangeLog>

backend/src/main/resources/db/changelog/db.changelog-master.xml

@@ -9,5 +9,6 @@
     <include file="db/changelog/001-create-events-table.xml"/>
     <include file="db/changelog/002-add-timezone-column.xml"/>
     <include file="db/changelog/003-create-rsvps-table.xml"/>
+    <include file="db/changelog/004-add-cancellation-columns.xml"/>
 
 </databaseChangeLog>

backend/src/main/resources/openapi/api.yaml

@@ -37,14 +37,46 @@ paths:
               schema:
                 $ref: "#/components/schemas/ValidationProblemDetail"
 
-  /events/{token}/rsvps:
+  /events/{eventToken}/rsvps/{rsvpToken}:
+    delete:
+      operationId: cancelRsvp
+      summary: Cancel RSVP
+      description: |
+        Permanently deletes an RSVP identified by the RSVP token.
+        Idempotent: returns 204 whether the RSVP existed or not.
+      tags:
+        - events
+      parameters:
+        - name: eventToken
+          in: path
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Event token (UUID)
+        - name: rsvpToken
+          in: path
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: RSVP token (UUID) identifying the attendance to cancel
+      responses:
+        "204":
+          description: >
+            RSVP successfully cancelled (or was already cancelled).
+            No response body.
+        "500":
+          description: Internal server error
+
+  /events/{eventToken}/rsvps:
     post:
       operationId: createRsvp
       summary: Submit an RSVP for an event
       tags:
         - events
       parameters:
-        - name: token
+        - name: eventToken
           in: path
           required: true
           schema:
@@ -83,14 +115,14 @@ paths:
               schema:
                 $ref: "#/components/schemas/ProblemDetail"
 
-  /events/{token}/attendees:
+  /events/{eventToken}/attendees:
     get:
       operationId: getAttendees
       summary: Get attendee list for an event (organizer only)
       tags:
         - events
       parameters:
-        - name: token
+        - name: eventToken
           in: path
           required: true
           schema:
@@ -124,14 +156,14 @@ paths:
               schema:
                 $ref: "#/components/schemas/ProblemDetail"
 
-  /events/{token}:
+  /events/{eventToken}:
     get:
       operationId: getEvent
       summary: Get public event details by token
       tags:
         - events
       parameters:
-        - name: token
+        - name: eventToken
           in: path
           required: true
           schema:
@@ -152,6 +184,58 @@ paths:
               schema:
                 $ref: "#/components/schemas/ProblemDetail"
 
+    patch:
+      operationId: patchEvent
+      summary: Update an event (currently cancel)
+      description: |
+        Partial update of an event resource. Currently the only supported operation
+        is cancellation (setting cancelled to true). Requires the organizer token.
+        Cancellation is irreversible.
+      tags:
+        - events
+      parameters:
+        - name: eventToken
+          in: path
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Public event token
+        - name: organizerToken
+          in: query
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Organizer token for authorization
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/PatchEventRequest"
+      responses:
+        "204":
+          description: Event updated successfully
+        "403":
+          description: Invalid organizer token
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+        "404":
+          description: Event not found
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+        "409":
+          description: Event is already cancelled
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+
 components:
   schemas:
     CreateEventRequest:
@@ -220,6 +304,7 @@ components:
         - dateTime
         - timezone
         - attendeeCount
+        - cancelled
       properties:
         eventToken:
           type: string
@@ -252,6 +337,31 @@ components:
           minimum: 0
           description: Number of confirmed attendees (attending=true)
           example: 12
+        cancelled:
+          type: boolean
+          description: Whether the event has been cancelled
+          example: false
+        cancellationReason:
+          type:
+            - string
+            - "null"
+          description: Reason for cancellation, if provided
+          example: null
+
+    PatchEventRequest:
+      type: object
+      required:
+        - cancelled
+      properties:
+        cancelled:
+          type: boolean
+          description: Set to true to cancel the event (irreversible)
+          example: true
+        cancellationReason:
+          type: string
+          maxLength: 2000
+          description: Optional cancellation reason
+          example: "Unfortunately the venue is no longer available."
 
     CreateRsvpRequest:
       type: object

backend/src/test/java/de/fete/HexagonalArchitectureTest.java

@@ -4,10 +4,14 @@ import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.classes;
 import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noClasses;
 import static com.tngtech.archunit.library.Architectures.onionArchitecture;
 
+import com.tngtech.archunit.core.domain.JavaClass;
 import com.tngtech.archunit.core.importer.ImportOption;
 import com.tngtech.archunit.junit.AnalyzeClasses;
 import com.tngtech.archunit.junit.ArchTest;
+import com.tngtech.archunit.lang.ArchCondition;
 import com.tngtech.archunit.lang.ArchRule;
+import com.tngtech.archunit.lang.ConditionEvents;
+import com.tngtech.archunit.lang.SimpleConditionEvent;
 
 @AnalyzeClasses(packages = "de.fete", importOptions = ImportOption.DoNotIncludeTests.class)
 class HexagonalArchitectureTest {
@@ -65,4 +69,24 @@ class HexagonalArchitectureTest {
   static final ArchRule webAdapterMustNotDependOnOutboundPorts = noClasses()
       .that().resideInAPackage("de.fete.adapter.in.web..")
       .should().dependOnClassesThat().resideInAPackage("de.fete.domain.port.out..");
+
+  @ArchTest
+  static final ArchRule domainModelsMustBeRecords = classes()
+      .that().resideInAPackage("de.fete.domain.model..")
+      .and().doNotHaveSimpleName("package-info")
+      .should(beRecords());
+
+  private static ArchCondition<JavaClass> beRecords() {
+    return new ArchCondition<>("be records") {
+      @Override
+      public void check(JavaClass javaClass,
+          ConditionEvents events) {
+        boolean isRecord = javaClass.reflect().isRecord();
+        if (!isRecord) {
+          events.add(SimpleConditionEvent.violated(javaClass,
+              javaClass.getFullName() + " is not a record"));
+        }
+      }
+    };
+  }
 }

backend/src/test/java/de/fete/adapter/in/web/EventControllerIntegrationTest.java

@@ -1,7 +1,9 @@
 package de.fete.adapter.in.web;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.delete;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.patch;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
@@ -20,6 +22,7 @@ import de.fete.adapter.out.persistence.RsvpJpaRepository;
 import java.time.LocalDate;
 import java.time.OffsetDateTime;
 import java.time.ZoneOffset;
+import java.util.Map;
 import java.util.UUID;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -374,6 +377,213 @@ class EventControllerIntegrationTest {
             "application/problem+json"));
   }
 
+  // --- Cancel RSVP tests ---
+
+  @Test
+  void cancelRsvpReturns204AndDeletesRow() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Cancel Event", null, "Europe/Berlin",
+        null, LocalDate.now().plusDays(30));
+    UUID rsvpToken = seedRsvpAndGetToken(event, "Departing Guest");
+
+    long countBefore = rsvpJpaRepository.count();
+
+    mockMvc.perform(delete("/api/events/" + event.getEventToken()
+            + "/rsvps/" + rsvpToken))
+        .andExpect(status().isNoContent());
+
+    assertThat(rsvpJpaRepository.count()).isEqualTo(countBefore - 1);
+    assertThat(rsvpJpaRepository.findByRsvpToken(rsvpToken)).isEmpty();
+  }
+
+  @Test
+  void cancelRsvpReturns204WhenAlreadyDeleted() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Idempotent Event", null, "Europe/Berlin",
+        null, LocalDate.now().plusDays(30));
+
+    mockMvc.perform(delete("/api/events/" + event.getEventToken()
+            + "/rsvps/" + UUID.randomUUID()))
+        .andExpect(status().isNoContent());
+  }
+
+  @Test
+  void cancelRsvpReturns204WhenEventNotFound() throws Exception {
+    mockMvc.perform(delete("/api/events/" + UUID.randomUUID()
+            + "/rsvps/" + UUID.randomUUID()))
+        .andExpect(status().isNoContent());
+  }
+
+  @Test
+  void attendeeCountDecreasesAfterCancelRsvp() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Count Cancel Event", null, "Europe/Berlin",
+        null, LocalDate.now().plusDays(30));
+    UUID rsvpToken = seedRsvpAndGetToken(event, "Leaving Guest");
+    seedRsvp(event, "Staying Guest");
+
+    mockMvc.perform(get("/api/events/" + event.getEventToken()))
+        .andExpect(jsonPath("$.attendeeCount").value(2));
+
+    mockMvc.perform(delete("/api/events/" + event.getEventToken()
+            + "/rsvps/" + rsvpToken))
+        .andExpect(status().isNoContent());
+
+    mockMvc.perform(get("/api/events/" + event.getEventToken()))
+        .andExpect(jsonPath("$.attendeeCount").value(1));
+  }
+
+  // --- Cancel Event tests ---
+
+  @Test
+  void cancelEventReturns204AndPersists() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Cancel Me", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    var body = Map.of(
+        "cancelled", true,
+        "cancellationReason", "Venue closed");
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + event.getOrganizerToken())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isNoContent());
+
+    EventJpaEntity persisted = jpaRepository
+        .findByEventToken(event.getEventToken()).orElseThrow();
+    assertThat(persisted.isCancelled()).isTrue();
+    assertThat(persisted.getCancellationReason()).isEqualTo("Venue closed");
+  }
+
+  @Test
+  void cancelEventWithoutReasonReturns204() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Cancel No Reason", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + event.getOrganizerToken())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isNoContent());
+
+    EventJpaEntity persisted = jpaRepository
+        .findByEventToken(event.getEventToken()).orElseThrow();
+    assertThat(persisted.isCancelled()).isTrue();
+    assertThat(persisted.getCancellationReason()).isNull();
+  }
+
+  @Test
+  void cancelEventWithWrongOrganizerTokenReturns403() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Wrong Token", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + UUID.randomUUID())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isForbidden())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:invalid-organizer-token"));
+
+    assertThat(jpaRepository.findByEventToken(event.getEventToken())
+        .orElseThrow().isCancelled()).isFalse();
+  }
+
+  @Test
+  void cancelEventNotFoundReturns404() throws Exception {
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + UUID.randomUUID()
+            + "?organizerToken=" + UUID.randomUUID())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isNotFound())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:event-not-found"));
+  }
+
+  @Test
+  void cancelAlreadyCancelledEventReturns409() throws Exception {
+    EventJpaEntity event = seedCancelledEvent("Already Cancelled");
+
+    var body = Map.of("cancelled", true);
+
+    mockMvc.perform(patch("/api/events/" + event.getEventToken()
+            + "?organizerToken=" + event.getOrganizerToken())
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(body)))
+        .andExpect(status().isConflict())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:event-already-cancelled"));
+  }
+
+  @Test
+  void getEventReturnsCancelledFields() throws Exception {
+    EventJpaEntity event = seedCancelledEvent("Weather Event");
+
+    mockMvc.perform(get("/api/events/" + event.getEventToken()))
+        .andExpect(status().isOk())
+        .andExpect(jsonPath("$.cancelled").value(true))
+        .andExpect(jsonPath("$.cancellationReason").value("Cancelled"));
+  }
+
+  @Test
+  void getEventReturnsNotCancelledByDefault() throws Exception {
+    EventJpaEntity event = seedEvent(
+        "Active Event", null, "Europe/Berlin", null, LocalDate.now().plusDays(30));
+
+    mockMvc.perform(get("/api/events/" + event.getEventToken()))
+        .andExpect(status().isOk())
+        .andExpect(jsonPath("$.cancelled").value(false))
+        .andExpect(jsonPath("$.cancellationReason").doesNotExist());
+  }
+
+  @Test
+  void createRsvpOnCancelledEventReturns409() throws Exception {
+    EventJpaEntity event = seedCancelledEvent("Cancelled RSVP");
+    long countBefore = rsvpJpaRepository.count();
+
+    var request = new CreateRsvpRequest().name("Late Guest");
+
+    mockMvc.perform(post("/api/events/" + event.getEventToken() + "/rsvps")
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(objectMapper.writeValueAsString(request)))
+        .andExpect(status().isConflict())
+        .andExpect(content().contentTypeCompatibleWith("application/problem+json"))
+        .andExpect(jsonPath("$.type").value("urn:problem-type:event-cancelled"));
+
+    assertThat(rsvpJpaRepository.count()).isEqualTo(countBefore);
+  }
+
+  private EventJpaEntity seedCancelledEvent(String title) {
+    var entity = new EventJpaEntity();
+    entity.setEventToken(UUID.randomUUID());
+    entity.setOrganizerToken(UUID.randomUUID());
+    entity.setTitle(title);
+    entity.setDateTime(OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)));
+    entity.setTimezone("Europe/Berlin");
+    entity.setExpiryDate(LocalDate.now().plusDays(30));
+    entity.setCreatedAt(OffsetDateTime.now());
+    entity.setCancelled(true);
+    entity.setCancellationReason("Cancelled");
+    return jpaRepository.save(entity);
+  }
+
+  private UUID seedRsvpAndGetToken(EventJpaEntity event, String name) {
+    var rsvp = new RsvpJpaEntity();
+    UUID token = UUID.randomUUID();
+    rsvp.setRsvpToken(token);
+    rsvp.setEventId(event.getId());
+    rsvp.setName(name);
+    rsvpJpaRepository.save(rsvp);
+    return token;
+  }
+
   private void seedRsvp(EventJpaEntity event, String name) {
     var rsvp = new RsvpJpaEntity();
     rsvp.setRsvpToken(UUID.randomUUID());

backend/src/test/java/de/fete/adapter/out/persistence/EventPersistenceAdapterIntegrationTest.java

@@ -42,7 +42,7 @@ class EventPersistenceAdapterIntegrationTest {
 
     eventRepository.deleteExpired();
 
-    assertThat(eventRepository.findByEventToken(saved.getEventToken())).isPresent();
+    assertThat(eventRepository.findByEventToken(saved.eventToken())).isPresent();
   }
 
   @Test
@@ -52,7 +52,7 @@ class EventPersistenceAdapterIntegrationTest {
 
     eventRepository.deleteExpired();
 
-    assertThat(eventRepository.findByEventToken(saved.getEventToken())).isPresent();
+    assertThat(eventRepository.findByEventToken(saved.eventToken())).isPresent();
   }
 
   @Test
@@ -66,16 +66,18 @@ class EventPersistenceAdapterIntegrationTest {
   }
 
   private Event buildEvent(String title, LocalDate expiryDate) {
-    var event = new Event();
-    event.setEventToken(EventToken.generate());
-    event.setOrganizerToken(OrganizerToken.generate());
-    event.setTitle(title);
-    event.setDescription("Test description");
-    event.setDateTime(OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)));
-    event.setTimezone(ZoneId.of("Europe/Berlin"));
-    event.setLocation("Test Location");
-    event.setExpiryDate(expiryDate);
-    event.setCreatedAt(OffsetDateTime.now());
-    return event;
+    return new Event(
+        null,
+        EventToken.generate(),
+        OrganizerToken.generate(),
+        title,
+        "Test description",
+        OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)),
+        ZoneId.of("Europe/Berlin"),
+        "Test Location",
+        expiryDate,
+        OffsetDateTime.now(),
+        false,
+        null);
   }
 }

backend/src/test/java/de/fete/adapter/out/persistence/EventPersistenceAdapterTest.java

@@ -30,8 +30,8 @@ class EventPersistenceAdapterTest {
 
     Event saved = eventRepository.save(event);
 
-    assertThat(saved.getId()).isNotNull();
-    assertThat(saved.getTitle()).isEqualTo("Test Event");
+    assertThat(saved.id()).isNotNull();
+    assertThat(saved.title()).isEqualTo("Test Event");
   }
 
   @Test
@@ -39,11 +39,11 @@ class EventPersistenceAdapterTest {
     Event event = buildEvent();
     Event saved = eventRepository.save(event);
 
-    Optional<Event> found = eventRepository.findByEventToken(saved.getEventToken());
+    Optional<Event> found = eventRepository.findByEventToken(saved.eventToken());
 
     assertThat(found).isPresent();
-    assertThat(found.get().getTitle()).isEqualTo("Test Event");
-    assertThat(found.get().getId()).isEqualTo(saved.getId());
+    assertThat(found.get().title()).isEqualTo("Test Event");
+    assertThat(found.get().id()).isEqualTo(saved.id());
   }
 
   @Test
@@ -61,42 +61,47 @@ class EventPersistenceAdapterTest {
     OffsetDateTime createdAt =
         OffsetDateTime.of(2026, 3, 4, 12, 0, 0, 0, ZoneOffset.UTC);
 
-    var event = new Event();
-    event.setEventToken(EventToken.generate());
-    event.setOrganizerToken(OrganizerToken.generate());
-    event.setTitle("Full Event");
-    event.setDescription("A detailed description");
-    event.setDateTime(dateTime);
-    event.setTimezone(ZoneId.of("Europe/Berlin"));
-    event.setLocation("Berlin, Germany");
-    event.setExpiryDate(expiryDate);
-    event.setCreatedAt(createdAt);
+    var event = new Event(
+        null,
+        EventToken.generate(),
+        OrganizerToken.generate(),
+        "Full Event",
+        "A detailed description",
+        dateTime,
+        ZoneId.of("Europe/Berlin"),
+        "Berlin, Germany",
+        expiryDate,
+        createdAt,
+        false,
+        null);
 
     Event saved = eventRepository.save(event);
-    Event found = eventRepository.findByEventToken(saved.getEventToken()).orElseThrow();
+    Event found = eventRepository.findByEventToken(saved.eventToken()).orElseThrow();
 
-    assertThat(found.getEventToken()).isEqualTo(event.getEventToken());
-    assertThat(found.getOrganizerToken()).isEqualTo(event.getOrganizerToken());
-    assertThat(found.getTitle()).isEqualTo("Full Event");
-    assertThat(found.getDescription()).isEqualTo("A detailed description");
-    assertThat(found.getDateTime().toInstant()).isEqualTo(dateTime.toInstant());
-    assertThat(found.getTimezone()).isEqualTo(ZoneId.of("Europe/Berlin"));
-    assertThat(found.getLocation()).isEqualTo("Berlin, Germany");
-    assertThat(found.getExpiryDate()).isEqualTo(expiryDate);
-    assertThat(found.getCreatedAt().toInstant()).isEqualTo(createdAt.toInstant());
+    assertThat(found.eventToken()).isEqualTo(event.eventToken());
+    assertThat(found.organizerToken()).isEqualTo(event.organizerToken());
+    assertThat(found.title()).isEqualTo("Full Event");
+    assertThat(found.description()).isEqualTo("A detailed description");
+    assertThat(found.dateTime().toInstant()).isEqualTo(dateTime.toInstant());
+    assertThat(found.timezone()).isEqualTo(ZoneId.of("Europe/Berlin"));
+    assertThat(found.location()).isEqualTo("Berlin, Germany");
+    assertThat(found.expiryDate()).isEqualTo(expiryDate);
+    assertThat(found.createdAt().toInstant()).isEqualTo(createdAt.toInstant());
   }
 
   private Event buildEvent() {
-    var event = new Event();
-    event.setEventToken(EventToken.generate());
-    event.setOrganizerToken(OrganizerToken.generate());
-    event.setTitle("Test Event");
-    event.setDescription("Test description");
-    event.setDateTime(OffsetDateTime.now().plusDays(7));
-    event.setTimezone(ZoneId.of("Europe/Berlin"));
-    event.setLocation("Somewhere");
-    event.setExpiryDate(LocalDate.now().plusDays(30));
-    event.setCreatedAt(OffsetDateTime.now());
-    return event;
+    return new Event(
+        null,
+        EventToken.generate(),
+        OrganizerToken.generate(),
+        "Test Event",
+        "Test description",
+        OffsetDateTime.now().plusDays(7),
+        ZoneId.of("Europe/Berlin"),
+        "Somewhere",
+        LocalDate.now().plusDays(30),
+        OffsetDateTime.now(),
+        false,
+        null);
   }
 }

backend/src/test/java/de/fete/application/service/EventServiceCancelTest.java

@@ -0,0 +1,133 @@
+package de.fete.application.service;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import de.fete.application.service.exception.EventAlreadyCancelledException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
+import de.fete.domain.model.Event;
+import de.fete.domain.model.EventToken;
+import de.fete.domain.model.OrganizerToken;
+import de.fete.domain.port.out.EventRepository;
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDate;
+import java.time.ZoneId;
+import java.util.Optional;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class EventServiceCancelTest {
+
+  private static final ZoneId ZONE = ZoneId.of("Europe/Berlin");
+  private static final Instant FIXED_INSTANT =
+      LocalDate.of(2026, 3, 5).atStartOfDay(ZONE).toInstant();
+  private static final Clock FIXED_CLOCK = Clock.fixed(FIXED_INSTANT, ZONE);
+
+  @Mock
+  private EventRepository eventRepository;
+
+  private EventService eventService;
+
+  @BeforeEach
+  void setUp() {
+    eventService = new EventService(eventRepository, FIXED_CLOCK);
+  }
+
+  @Test
+  void cancelEventDelegatesToDomainAndSaves() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+    var event = new Event(null, eventToken, organizerToken, null, null, null, null, null, null,
+        null, false, null);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+    when(eventRepository.save(any(Event.class)))
+        .thenAnswer(invocation -> invocation.getArgument(0));
+
+    eventService.cancelEvent(eventToken, organizerToken, true, "Venue unavailable");
+
+    ArgumentCaptor<Event> captor = ArgumentCaptor.forClass(Event.class);
+    verify(eventRepository).save(captor.capture());
+    assertThat(captor.getValue().cancelled()).isTrue();
+    assertThat(captor.getValue().cancellationReason()).isEqualTo("Venue unavailable");
+  }
+
+  @Test
+  void cancelEventWithNullReason() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+    var event = new Event(null, eventToken, organizerToken, null, null, null, null, null, null,
+        null, false, null);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+    when(eventRepository.save(any(Event.class)))
+        .thenAnswer(invocation -> invocation.getArgument(0));
+
+    eventService.cancelEvent(eventToken, organizerToken, true, null);
+
+    ArgumentCaptor<Event> captor = ArgumentCaptor.forClass(Event.class);
+    verify(eventRepository).save(captor.capture());
+    assertThat(captor.getValue().cancelled()).isTrue();
+    assertThat(captor.getValue().cancellationReason()).isNull();
+  }
+
+  @Test
+  void cancelEventThrows404WhenNotFound() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.empty());
+
+    assertThatThrownBy(() -> eventService.cancelEvent(eventToken, organizerToken, true, null))
+        .isInstanceOf(EventNotFoundException.class);
+
+    verify(eventRepository, never()).save(any());
+  }
+
+  @Test
+  void cancelEventThrows403WhenWrongOrganizerToken() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken correctToken = OrganizerToken.generate();
+    var event = new Event(null, eventToken, correctToken, null, null, null, null, null, null,
+        null, false, null);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+
+    final OrganizerToken wrongToken = OrganizerToken.generate();
+    assertThatThrownBy(() -> eventService.cancelEvent(eventToken, wrongToken, true, null))
+        .isInstanceOf(InvalidOrganizerTokenException.class);
+
+    verify(eventRepository, never()).save(any());
+  }
+
+  @Test
+  void cancelEventThrows409WhenAlreadyCancelled() {
+    EventToken eventToken = EventToken.generate();
+    OrganizerToken organizerToken = OrganizerToken.generate();
+    var event = new Event(null, eventToken, organizerToken, null, null, null, null, null, null,
+        null, true, null);
+
+    when(eventRepository.findByEventToken(eventToken))
+        .thenReturn(Optional.of(event));
+
+    assertThatThrownBy(() -> eventService.cancelEvent(eventToken, organizerToken, true, null))
+        .isInstanceOf(EventAlreadyCancelledException.class);
+
+    verify(eventRepository, never()).save(any());
+  }
+}

backend/src/test/java/de/fete/application/service/EventServiceTest.java

@@ -57,13 +57,13 @@ class EventServiceTest {
 
     Event result = eventService.createEvent(command);
 
-    assertThat(result.getTitle()).isEqualTo("Birthday Party");
-    assertThat(result.getDescription()).isEqualTo("Come celebrate!");
-    assertThat(result.getTimezone()).isEqualTo(ZONE);
-    assertThat(result.getLocation()).isEqualTo("Berlin");
-    assertThat(result.getEventToken()).isNotNull();
-    assertThat(result.getOrganizerToken()).isNotNull();
-    assertThat(result.getCreatedAt()).isEqualTo(OffsetDateTime.ofInstant(FIXED_INSTANT, ZONE));
+    assertThat(result.title()).isEqualTo("Birthday Party");
+    assertThat(result.description()).isEqualTo("Come celebrate!");
+    assertThat(result.timezone()).isEqualTo(ZONE);
+    assertThat(result.location()).isEqualTo("Berlin");
+    assertThat(result.eventToken()).isNotNull();
+    assertThat(result.organizerToken()).isNotNull();
+    assertThat(result.createdAt()).isEqualTo(OffsetDateTime.ofInstant(FIXED_INSTANT, ZONE));
   }
 
   @Test
@@ -80,7 +80,7 @@ class EventServiceTest {
 
     ArgumentCaptor<Event> captor = ArgumentCaptor.forClass(Event.class);
     verify(eventRepository, times(1)).save(captor.capture());
-    assertThat(captor.getValue().getTitle()).isEqualTo("Test");
+    assertThat(captor.getValue().title()).isEqualTo("Test");
   }
 
   @Test
@@ -96,7 +96,7 @@ class EventServiceTest {
 
     Event result = eventService.createEvent(command);
 
-    assertThat(result.getExpiryDate()).isEqualTo(eventDate.plusDays(7));
+    assertThat(result.expiryDate()).isEqualTo(eventDate.plusDays(7));
   }
 
   // --- GetEventUseCase tests (T004) ---
@@ -104,16 +104,15 @@ class EventServiceTest {
   @Test
   void getByEventTokenReturnsEvent() {
     EventToken token = EventToken.generate();
-    var event = new Event();
-    event.setEventToken(token);
-    event.setTitle("Found Event");
+    var event = new Event(null, token, null, "Found Event", null, null, null, null, null, null,
+        false, null);
     when(eventRepository.findByEventToken(token))
         .thenReturn(Optional.of(event));
 
     Optional<Event> result = eventService.getByEventToken(token);
 
     assertThat(result).isPresent();
-    assertThat(result.get().getTitle()).isEqualTo("Found Event");
+    assertThat(result.get().title()).isEqualTo("Found Event");
   }
 
   @Test
@@ -142,6 +141,6 @@ class EventServiceTest {
 
     Event result = eventService.createEvent(command);
 
-    assertThat(result.getTimezone()).isEqualTo(ZoneId.of("America/New_York"));
+    assertThat(result.timezone()).isEqualTo(ZoneId.of("America/New_York"));
   }
 }

backend/src/test/java/de/fete/application/service/RsvpServiceTest.java

@@ -6,6 +6,10 @@ import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import de.fete.application.service.exception.EventCancelledException;
+import de.fete.application.service.exception.EventExpiredException;
+import de.fete.application.service.exception.EventNotFoundException;
+import de.fete.application.service.exception.InvalidOrganizerTokenException;
 import de.fete.domain.model.Event;
 import de.fete.domain.model.EventToken;
 import de.fete.domain.model.OrganizerToken;
@@ -51,23 +55,23 @@ class RsvpServiceTest {
 
   @Test
   void createRsvpSucceedsForActiveEvent() {
-    Event event = buildActiveEvent();
-    EventToken token = event.getEventToken();
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
     when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
     when(rsvpRepository.save(any(Rsvp.class)))
         .thenAnswer(invocation -> invocation.getArgument(0));
 
     Rsvp result = rsvpService.createRsvp(token, "Max Mustermann");
 
-    assertThat(result.getName()).isEqualTo("Max Mustermann");
-    assertThat(result.getRsvpToken()).isNotNull();
-    assertThat(result.getEventId()).isEqualTo(event.getId());
+    assertThat(result.name()).isEqualTo("Max Mustermann");
+    assertThat(result.rsvpToken()).isNotNull();
+    assertThat(result.eventId()).isEqualTo(event.id());
   }
 
   @Test
   void createRsvpPersistsViaRepository() {
-    Event event = buildActiveEvent();
-    EventToken token = event.getEventToken();
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
     when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
     when(rsvpRepository.save(any(Rsvp.class)))
         .thenAnswer(invocation -> invocation.getArgument(0));
@@ -76,8 +80,8 @@ class RsvpServiceTest {
 
     ArgumentCaptor<Rsvp> captor = ArgumentCaptor.forClass(Rsvp.class);
     verify(rsvpRepository).save(captor.capture());
-    assertThat(captor.getValue().getName()).isEqualTo("Test Guest");
-    assertThat(captor.getValue().getEventId()).isEqualTo(event.getId());
+    assertThat(captor.getValue().name()).isEqualTo("Test Guest");
+    assertThat(captor.getValue().eventId()).isEqualTo(event.id());
   }
 
   @Test
@@ -91,22 +95,21 @@ class RsvpServiceTest {
 
   @Test
   void createRsvpTrimsName() {
-    Event event = buildActiveEvent();
-    EventToken token = event.getEventToken();
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
     when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
     when(rsvpRepository.save(any(Rsvp.class)))
         .thenAnswer(invocation -> invocation.getArgument(0));
 
     Rsvp result = rsvpService.createRsvp(token, "  Max  ");
 
-    assertThat(result.getName()).isEqualTo("Max");
+    assertThat(result.name()).isEqualTo("Max");
   }
 
   @Test
   void createRsvpThrowsWhenEventExpired() {
-    var event = buildActiveEvent();
-    event.setExpiryDate(TODAY.minusDays(1));
-    EventToken token = event.getEventToken();
+    Event event = buildActiveEvent(TODAY.minusDays(1));
+    EventToken token = event.eventToken();
     when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
 
     assertThatThrownBy(() -> rsvpService.createRsvp(token, "Late Guest"))
@@ -115,9 +118,8 @@ class RsvpServiceTest {
 
   @Test
   void createRsvpThrowsWhenEventExpiresToday() {
-    var event = buildActiveEvent();
-    event.setExpiryDate(TODAY);
-    EventToken token = event.getEventToken();
+    Event event = buildActiveEvent(TODAY);
+    EventToken token = event.eventToken();
     when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
 
     assertThatThrownBy(() -> rsvpService.createRsvp(token, "Late Guest"))
@@ -126,12 +128,12 @@ class RsvpServiceTest {
 
   @Test
   void getAttendeeNamesReturnsNamesInOrder() {
-    Event event = buildActiveEvent();
-    EventToken token = event.getEventToken();
-    OrganizerToken orgToken = event.getOrganizerToken();
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
+    OrganizerToken orgToken = event.organizerToken();
     when(eventRepository.findByEventToken(token))
         .thenReturn(Optional.of(event));
-    when(rsvpRepository.findByEventId(event.getId()))
+    when(rsvpRepository.findByEventId(event.id()))
         .thenReturn(List.of(
             buildRsvp(1L, "Alice"),
             buildRsvp(2L, "Bob"),
@@ -144,12 +146,12 @@ class RsvpServiceTest {
 
   @Test
   void getAttendeeNamesReturnsEmptyListWhenNoRsvps() {
-    Event event = buildActiveEvent();
-    EventToken token = event.getEventToken();
-    OrganizerToken orgToken = event.getOrganizerToken();
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
+    OrganizerToken orgToken = event.organizerToken();
     when(eventRepository.findByEventToken(token))
         .thenReturn(Optional.of(event));
-    when(rsvpRepository.findByEventId(event.getId()))
+    when(rsvpRepository.findByEventId(event.id()))
         .thenReturn(List.of());
 
     List<String> names = rsvpService.getAttendeeNames(token, orgToken);
@@ -171,8 +173,8 @@ class RsvpServiceTest {
 
   @Test
   void getAttendeeNamesThrowsWhenOrganizerTokenInvalid() {
-    Event event = buildActiveEvent();
-    EventToken token = event.getEventToken();
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
     OrganizerToken wrongToken = OrganizerToken.generate();
     when(eventRepository.findByEventToken(token))
         .thenReturn(Optional.of(event));
@@ -183,24 +185,57 @@ class RsvpServiceTest {
   }
 
   private Rsvp buildRsvp(Long id, String name) {
-    var rsvp = new Rsvp();
-    rsvp.setId(id);
-    rsvp.setRsvpToken(RsvpToken.generate());
-    rsvp.setEventId(1L);
-    rsvp.setName(name);
-    return rsvp;
+    return new Rsvp(id, RsvpToken.generate(), 1L, name);
   }
 
-  private Event buildActiveEvent() {
-    var event = new Event();
-    event.setId(1L);
-    event.setEventToken(EventToken.generate());
-    event.setOrganizerToken(OrganizerToken.generate());
-    event.setTitle("Test Event");
-    event.setDateTime(OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)));
-    event.setTimezone(ZONE);
-    event.setExpiryDate(TODAY.plusDays(30));
-    event.setCreatedAt(OffsetDateTime.now());
-    return event;
+  @Test
+  void cancelRsvpDeletesWhenEventAndRsvpExist() {
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
+    RsvpToken rsvpToken = RsvpToken.generate();
+    when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
+    when(rsvpRepository.deleteByEventIdAndRsvpToken(event.id(), rsvpToken)).thenReturn(true);
+
+    rsvpService.cancelRsvp(token, rsvpToken);
+
+    verify(rsvpRepository).deleteByEventIdAndRsvpToken(event.id(), rsvpToken);
+  }
+
+  @Test
+  void cancelRsvpSucceedsWhenRsvpNotFound() {
+    Event event = buildActiveEvent(TODAY.plusDays(30));
+    EventToken token = event.eventToken();
+    RsvpToken rsvpToken = RsvpToken.generate();
+    when(eventRepository.findByEventToken(token)).thenReturn(Optional.of(event));
+    when(rsvpRepository.deleteByEventIdAndRsvpToken(event.id(), rsvpToken)).thenReturn(false);
+
+    rsvpService.cancelRsvp(token, rsvpToken);
+
+    verify(rsvpRepository).deleteByEventIdAndRsvpToken(event.id(), rsvpToken);
+  }
+
+  @Test
+  void cancelRsvpSucceedsWhenEventNotFound() {
+    EventToken token = EventToken.generate();
+    RsvpToken rsvpToken = RsvpToken.generate();
+    when(eventRepository.findByEventToken(token)).thenReturn(Optional.empty());
+
+    rsvpService.cancelRsvp(token, rsvpToken);
+  }
+
+  private Event buildActiveEvent(LocalDate expiryDate) {
+    return new Event(
+        1L,
+        EventToken.generate(),
+        OrganizerToken.generate(),
+        "Test Event",
+        null,
+        OffsetDateTime.of(2026, 6, 15, 20, 0, 0, 0, ZoneOffset.ofHours(2)),
+        ZONE,
+        null,
+        expiryDate,
+        OffsetDateTime.now(),
+        false,
+        null);
   }
 }

frontend/e2e/cancel-event.spec.ts

@@ -0,0 +1,162 @@
+import { http, HttpResponse } from 'msw'
+import { test, expect } from './msw-setup'
+import type { StoredEvent } from '../src/composables/useEventStorage'
+
+const STORAGE_KEY = 'fete:events'
+
+const fullEvent = {
+  eventToken: 'a1b2c3d4-e5f6-7890-abcd-ef1234567890',
+  title: 'Summer BBQ',
+  description: 'Bring your own drinks!',
+  dateTime: '2026-03-15T20:00:00+01:00',
+  timezone: 'Europe/Berlin',
+  location: 'Central Park, NYC',
+  attendeeCount: 12,
+  cancelled: false,
+  cancellationReason: null,
+}
+
+const organizerToken = '550e8400-e29b-41d4-a716-446655440001'
+
+function seedEvents(events: StoredEvent[]): string {
+  return `window.localStorage.setItem('${STORAGE_KEY}', ${JSON.stringify(JSON.stringify(events))})`
+}
+
+function organizerSeed(): StoredEvent {
+  return {
+    eventToken: fullEvent.eventToken,
+    organizerToken,
+    title: fullEvent.title,
+    dateTime: fullEvent.dateTime,
+  }
+}
+
+test.describe('US1: Organizer cancels event with reason', () => {
+  test('organizer opens cancel bottom sheet, enters reason, confirms — event shows as cancelled on reload', async ({
+    page,
+    network,
+  }) => {
+    let cancelled = false
+    network.use(
+      http.get('*/api/events/:token', () => {
+        if (cancelled) {
+          return HttpResponse.json({
+            ...fullEvent,
+            cancelled: true,
+            cancellationReason: 'Venue closed',
+          })
+        }
+        return HttpResponse.json(fullEvent)
+      }),
+      http.patch('*/api/events/:token', ({ request }) => {
+        const url = new URL(request.url)
+        const token = url.searchParams.get('organizerToken')
+        if (token === organizerToken) {
+          cancelled = true
+          return new HttpResponse(null, { status: 204 })
+        }
+        return HttpResponse.json(
+          { type: 'urn:problem-type:invalid-organizer-token', title: 'Forbidden', status: 403 },
+          { status: 403 },
+        )
+      }),
+    )
+    await page.addInitScript(seedEvents([organizerSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Cancel button visible for organizer
+    const cancelBtn = page.getByRole('button', { name: /Cancel event/i })
+    await expect(cancelBtn).toBeVisible()
+
+    // Open cancel bottom sheet
+    await cancelBtn.click()
+
+    // Fill in reason
+    const reasonField = page.getByLabel(/reason/i)
+    await expect(reasonField).toBeVisible()
+    await reasonField.fill('Venue closed')
+
+    // Confirm cancellation
+    await page.getByRole('button', { name: /Confirm cancellation/i }).click()
+
+    // Event should show as cancelled
+    await expect(page.getByText(/This event has been cancelled/i)).toBeVisible()
+    await expect(page.getByText('Venue closed')).toBeVisible()
+
+    // Cancel button should be gone
+    await expect(cancelBtn).not.toBeVisible()
+  })
+})
+
+test.describe('US1: Organizer cancels event without reason', () => {
+  test('organizer cancels without reason — event shows as cancelled', async ({
+    page,
+    network,
+  }) => {
+    let cancelled = false
+    network.use(
+      http.get('*/api/events/:token', () => {
+        if (cancelled) {
+          return HttpResponse.json({
+            ...fullEvent,
+            cancelled: true,
+            cancellationReason: null,
+          })
+        }
+        return HttpResponse.json(fullEvent)
+      }),
+      http.patch('*/api/events/:token', ({ request }) => {
+        const url = new URL(request.url)
+        const token = url.searchParams.get('organizerToken')
+        if (token === organizerToken) {
+          cancelled = true
+          return new HttpResponse(null, { status: 204 })
+        }
+        return HttpResponse.json({}, { status: 403 })
+      }),
+    )
+    await page.addInitScript(seedEvents([organizerSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    await page.getByRole('button', { name: /Cancel event/i }).click()
+
+    // Don't fill in reason, just confirm
+    await page.getByRole('button', { name: /Confirm cancellation/i }).click()
+
+    // Event should show as cancelled without reason text
+    await expect(page.getByText(/This event has been cancelled/i)).toBeVisible()
+  })
+})
+
+test.describe('US1: Cancel API failure', () => {
+  test('cancel API fails — error displayed in bottom sheet, button re-enabled for retry', async ({
+    page,
+    network,
+  }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+      http.patch('*/api/events/:token', () => {
+        return HttpResponse.json(
+          {
+            type: 'about:blank',
+            title: 'Internal Server Error',
+            status: 500,
+            detail: 'Something went wrong',
+          },
+          { status: 500, headers: { 'Content-Type': 'application/problem+json' } },
+        )
+      }),
+    )
+    await page.addInitScript(seedEvents([organizerSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    await page.getByRole('button', { name: /Cancel event/i }).click()
+    await page.getByRole('button', { name: /Confirm cancellation/i }).click()
+
+    // Error message in bottom sheet
+    await expect(page.getByText(/Could not cancel event/i)).toBeVisible()
+
+    // Confirm button should be re-enabled
+    await expect(page.getByRole('button', { name: /Confirm cancellation/i })).toBeEnabled()
+  })
+})

frontend/e2e/cancel-rsvp.spec.ts

@@ -0,0 +1,276 @@
+import { http, HttpResponse } from 'msw'
+import { test, expect } from './msw-setup'
+import type { StoredEvent } from '../src/composables/useEventStorage'
+
+const STORAGE_KEY = 'fete:events'
+
+const fullEvent = {
+  eventToken: 'a1b2c3d4-e5f6-7890-abcd-ef1234567890',
+  title: 'Summer BBQ',
+  description: 'Bring your own drinks!',
+  dateTime: '2026-03-15T20:00:00+01:00',
+  timezone: 'Europe/Berlin',
+  location: 'Central Park, NYC',
+  attendeeCount: 12,
+}
+
+const rsvpToken = 'd4e5f6a7-b8c9-0123-4567-890abcdef012'
+
+function seedEvents(events: StoredEvent[]): string {
+  return `window.localStorage.setItem('${STORAGE_KEY}', ${JSON.stringify(JSON.stringify(events))})`
+}
+
+function rsvpSeed(): StoredEvent {
+  return {
+    eventToken: fullEvent.eventToken,
+    title: fullEvent.title,
+    dateTime: fullEvent.dateTime,
+    rsvpToken,
+    rsvpName: 'Anna',
+  }
+}
+
+test.describe('US1: Cancel RSVP from Event Detail View', () => {
+  test('status bar shows cancel affordance when RSVP\'d', async ({ page, network }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Status bar visible
+    const statusBar = page.getByRole('button', { name: /You're attending/ })
+    await expect(statusBar).toBeVisible()
+
+    // Cancel button hidden initially
+    await expect(page.getByRole('button', { name: 'Cancel attendance' })).not.toBeVisible()
+  })
+
+  test('tapping status bar reveals cancel button', async ({ page, network }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Tap status bar
+    await page.getByRole('button', { name: /You're attending/ }).click()
+
+    // Cancel button appears
+    await expect(page.getByRole('button', { name: 'Cancel attendance' })).toBeVisible()
+  })
+
+  test('confirm cancellation → localStorage cleared, count decremented, bar reset', async ({ page, network }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return new HttpResponse(null, { status: 204 })
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Expand → Cancel attendance → Confirm in dialog
+    await page.getByRole('button', { name: /You're attending/ }).click()
+    await page.locator('.rsvp-bar__cancel').click()
+
+    // Confirm dialog
+    await expect(page.getByText('Your attendance will be permanently cancelled.')).toBeVisible()
+    await page.getByRole('alertdialog').getByRole('button', { name: 'Cancel attendance' }).click()
+
+    // Bar resets to CTA state
+    await expect(page.getByRole('button', { name: "I'm attending" })).toBeVisible()
+    await expect(page.getByText("You're attending!")).not.toBeVisible()
+
+    // Attendee count decremented
+    await expect(page.getByText('11 going')).toBeVisible()
+
+    // localStorage cleared
+    const stored = await page.evaluate(() => {
+      const raw = localStorage.getItem('fete:events')
+      return raw ? JSON.parse(raw) : null
+    })
+    const event = stored?.find((e: StoredEvent) => e.eventToken === fullEvent.eventToken)
+    expect(event?.rsvpToken).toBeUndefined()
+    expect(event?.rsvpName).toBeUndefined()
+  })
+
+  test('server error → error message, state unchanged', async ({ page, network }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return HttpResponse.json({ error: 'fail' }, { status: 500 })
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Expand → Cancel → Confirm in dialog
+    await page.getByRole('button', { name: /You're attending/ }).click()
+    await page.locator('.rsvp-bar__cancel').click()
+    await page.getByRole('alertdialog').getByRole('button', { name: 'Cancel attendance' }).click()
+
+    // Error message
+    await expect(page.getByText('Could not cancel RSVP. Please try again.')).toBeVisible()
+
+    // Attendee count unchanged
+    await expect(page.getByText('12 going')).toBeVisible()
+  })
+
+  test('re-RSVP after cancel works', async ({ page, network }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return new HttpResponse(null, { status: 204 })
+      }),
+      http.post('*/api/events/:token/rsvps', () => {
+        return HttpResponse.json(
+          { rsvpToken: 'new-rsvp-token', name: 'Max' },
+          { status: 201 },
+        )
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Cancel first
+    await page.getByRole('button', { name: /You're attending/ }).click()
+    await page.locator('.rsvp-bar__cancel').click()
+    await page.getByRole('alertdialog').getByRole('button', { name: 'Cancel attendance' }).click()
+
+    // CTA should be back
+    await expect(page.getByRole('button', { name: "I'm attending" })).toBeVisible()
+
+    // Re-RSVP
+    await page.getByRole('button', { name: "I'm attending" }).click()
+    const dialog = page.getByRole('dialog', { name: 'RSVP' })
+    await dialog.getByLabel('Your name').fill('Max')
+    await dialog.getByRole('button', { name: 'Count me in' }).click()
+
+    // Status bar returns
+    await expect(page.getByText("You're attending!")).toBeVisible()
+  })
+})
+
+test.describe('US2: Auto-Cancel on Event List Removal', () => {
+  test('removal of RSVP\'d event shows attendance warning in dialog', async ({ page }) => {
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto('/')
+
+    await page.getByRole('button', { name: /Remove Summer BBQ/ }).click()
+
+    await expect(page.getByText('your attendance will be cancelled')).toBeVisible()
+  })
+
+  test('removal of non-RSVP\'d event shows standard dialog', async ({ page }) => {
+    const noRsvp: StoredEvent = {
+      eventToken: 'no-rsvp-token',
+      title: 'No RSVP Event',
+      dateTime: '2027-06-15T18:00:00Z',
+      organizerToken: 'org-123',
+    }
+    await page.addInitScript(seedEvents([noRsvp]))
+    await page.goto('/')
+
+    await page.getByRole('button', { name: /Remove No RSVP Event/ }).click()
+
+    await expect(page.getByText('This event will be removed from your list.')).toBeVisible()
+    await expect(page.getByText('attendance will be cancelled')).not.toBeVisible()
+  })
+
+  test('confirm removal → DELETE called → event removed from list', async ({ page, network }) => {
+    network.use(
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return new HttpResponse(null, { status: 204 })
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto('/')
+
+    await page.getByRole('button', { name: /Remove Summer BBQ/ }).click()
+    await page.getByRole('button', { name: 'Remove', exact: true }).click()
+
+    // Event gone
+    await expect(page.getByText('Summer BBQ')).not.toBeVisible()
+
+    // localStorage updated
+    const stored = await page.evaluate(() => {
+      const raw = localStorage.getItem('fete:events')
+      return raw ? JSON.parse(raw) : null
+    })
+    const found = stored?.find((e: StoredEvent) => e.eventToken === fullEvent.eventToken)
+    expect(found).toBeUndefined()
+  })
+
+  test('server error on DELETE → error message, event stays in list', async ({ page, network }) => {
+    network.use(
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return HttpResponse.json({ error: 'fail' }, { status: 500 })
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto('/')
+
+    await page.getByRole('button', { name: /Remove Summer BBQ/ }).click()
+    await page.getByRole('button', { name: 'Remove', exact: true }).click()
+
+    // Event still in list
+    await expect(page.getByText('Summer BBQ')).toBeVisible()
+  })
+
+  test('dismiss dialog → no changes', async ({ page }) => {
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto('/')
+
+    await page.getByRole('button', { name: /Remove Summer BBQ/ }).click()
+    await page.getByRole('button', { name: 'Cancel' }).click()
+
+    // Event still there
+    await expect(page.getByText('Summer BBQ')).toBeVisible()
+  })
+})
+
+test.describe('US3: Cancel RSVP with Stale/Invalid Token', () => {
+  test('cancel from detail view with stale token (404) → treated as success', async ({ page, network }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(fullEvent)),
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return HttpResponse.json({ error: 'not found' }, { status: 404 })
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto(`/events/${fullEvent.eventToken}`)
+
+    // Cancel flow
+    await page.getByRole('button', { name: /You're attending/ }).click()
+    await page.locator('.rsvp-bar__cancel').click()
+    await page.getByRole('alertdialog').getByRole('button', { name: 'Cancel attendance' }).click()
+
+    // Treated as success — CTA returns
+    await expect(page.getByRole('button', { name: "I'm attending" })).toBeVisible()
+
+    // localStorage cleaned
+    const stored = await page.evaluate(() => {
+      const raw = localStorage.getItem('fete:events')
+      return raw ? JSON.parse(raw) : null
+    })
+    const event = stored?.find((e: StoredEvent) => e.eventToken === fullEvent.eventToken)
+    expect(event?.rsvpToken).toBeUndefined()
+  })
+
+  test('event list removal with stale token (404) → treated as success', async ({ page, network }) => {
+    network.use(
+      http.delete('*/api/events/:token/rsvps/:rsvpToken', () => {
+        return HttpResponse.json({ error: 'not found' }, { status: 404 })
+      }),
+    )
+    await page.addInitScript(seedEvents([rsvpSeed()]))
+    await page.goto('/')
+
+    await page.getByRole('button', { name: /Remove Summer BBQ/ }).click()
+    await page.getByRole('button', { name: 'Remove', exact: true }).click()
+
+    // Event removed from list
+    await expect(page.getByText('Summer BBQ')).not.toBeVisible()
+  })
+})

frontend/e2e/cancelled-event-visitor.spec.ts

@@ -0,0 +1,74 @@
+import { http, HttpResponse } from 'msw'
+import { test, expect } from './msw-setup'
+
+const cancelledEventWithReason = {
+  eventToken: 'a1b2c3d4-e5f6-7890-abcd-ef1234567890',
+  title: 'Summer BBQ',
+  description: 'Bring your own drinks!',
+  dateTime: '2026-03-15T20:00:00+01:00',
+  timezone: 'Europe/Berlin',
+  location: 'Central Park, NYC',
+  attendeeCount: 12,
+  cancelled: true,
+  cancellationReason: 'Venue no longer available',
+}
+
+const cancelledEventWithoutReason = {
+  ...cancelledEventWithReason,
+  cancellationReason: null,
+}
+
+test.describe('US2: Visitor sees cancelled event with reason', () => {
+  test('visitor sees red banner with cancellation reason on cancelled event', async ({
+    page,
+    network,
+  }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(cancelledEventWithReason)),
+    )
+
+    await page.goto(`/events/${cancelledEventWithReason.eventToken}`)
+
+    await expect(page.getByText(/This event has been cancelled/i)).toBeVisible()
+    await expect(page.getByText('Venue no longer available')).toBeVisible()
+  })
+})
+
+test.describe('US2: Visitor sees cancelled event without reason', () => {
+  test('visitor sees red banner without reason when no reason was provided', async ({
+    page,
+    network,
+  }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(cancelledEventWithoutReason)),
+    )
+
+    await page.goto(`/events/${cancelledEventWithoutReason.eventToken}`)
+
+    await expect(page.getByText(/This event has been cancelled/i)).toBeVisible()
+    // No reason text shown
+    await expect(page.getByText('Venue no longer available')).not.toBeVisible()
+  })
+})
+
+test.describe('US2: RSVP buttons hidden on cancelled event', () => {
+  test('RSVP buttons hidden on cancelled event, other details remain visible', async ({
+    page,
+    network,
+  }) => {
+    network.use(
+      http.get('*/api/events/:token', () => HttpResponse.json(cancelledEventWithReason)),
+    )
+
+    await page.goto(`/events/${cancelledEventWithReason.eventToken}`)
+
+    // Event details are still visible
+    await expect(page.getByRole('heading', { name: 'Summer BBQ' })).toBeVisible()
+    await expect(page.getByText('Bring your own drinks!')).toBeVisible()
+    await expect(page.getByText('Central Park, NYC')).toBeVisible()
+    await expect(page.getByText('12 going')).toBeVisible()
+
+    // RSVP bar is NOT visible
+    await expect(page.getByRole('button', { name: "I'm attending" })).not.toBeVisible()
+  })
+})

frontend/package.json

@@ -38,17 +38,17 @@
     "@vue/tsconfig": "^0.9.0",
     "eslint": "^10.0.2",
     "eslint-config-prettier": "^10.1.8",
-    "eslint-plugin-oxlint": "~1.53.0",
+    "eslint-plugin-oxlint": "~1.55.0",
     "eslint-plugin-vue": "~10.8.0",
     "jiti": "^2.6.1",
     "jsdom": "^28.1.0",
     "msw": "^2.12.10",
     "npm-run-all2": "^8.0.4",
     "openapi-typescript": "^7.13.0",
-    "oxlint": "~1.53.0",
+    "oxlint": "~1.55.0",
     "prettier": "3.8.1",
     "typescript": "~5.9.3",
-    "vite": "^7.3.1",
+    "vite": "^8.0.0",
     "vite-plugin-vue-devtools": "^8.0.6",
     "vitest": "^4.0.18",
     "vue-tsc": "^3.2.5"

frontend/src/assets/main.css

@@ -18,6 +18,14 @@
   --color-card: #ffffff;
   --color-dark-base: #1B1730;
 
+  /* Danger / destructive actions */
+  --color-danger: #fca5a5;
+  --color-danger-bg: rgba(220, 38, 38, 0.15);
+  --color-danger-bg-hover: rgba(220, 38, 38, 0.25);
+  --color-danger-bg-strong: rgba(220, 38, 38, 0.2);
+  --color-danger-border: rgba(220, 38, 38, 0.3);
+  --color-danger-border-strong: rgba(220, 38, 38, 0.4);
+
   /* Glass system */
   --color-glass: rgba(255, 255, 255, 0.1);
   --color-glass-strong: rgba(255, 255, 255, 0.15);

frontend/src/components/EventList.vue

@@ -28,7 +28,7 @@
     <ConfirmDialog
       :open="!!pendingDeleteToken"
       title="Remove event?"
-      message="This event will be removed from your list."
+      :message="deleteDialogMessage"
       confirm-label="Remove"
       cancel-label="Cancel"
       @confirm="confirmDelete"
@@ -42,24 +42,62 @@ import { computed, ref } from 'vue'
 import { useEventStorage, isValidStoredEvent } from '../composables/useEventStorage'
 import { useEventGrouping } from '../composables/useEventGrouping'
 import { formatRelativeTime } from '../composables/useRelativeTime'
+import { api } from '../api/client'
 import EventCard from './EventCard.vue'
 import SectionHeader from './SectionHeader.vue'
 import DateSubheader from './DateSubheader.vue'
 import ConfirmDialog from './ConfirmDialog.vue'
 import type { StoredEvent } from '../composables/useEventStorage'
 
-const { getStoredEvents, removeEvent } = useEventStorage()
+const { getStoredEvents, getRsvp, removeEvent } = useEventStorage()
 
 const pendingDeleteToken = ref<string | null>(null)
+const deleteError = ref('')
+
+const deleteDialogMessage = computed(() => {
+  if (!pendingDeleteToken.value) return ''
+  const rsvp = getRsvp(pendingDeleteToken.value)
+  if (rsvp) {
+    return 'This event will be removed from your list and your attendance will be cancelled.'
+  }
+  return 'This event will be removed from your list.'
+})
 
 function requestDelete(eventToken: string) {
+  deleteError.value = ''
   pendingDeleteToken.value = eventToken
 }
 
-function confirmDelete() {
-  if (pendingDeleteToken.value) {
-    removeEvent(pendingDeleteToken.value)
+async function confirmDelete() {
+  if (!pendingDeleteToken.value) return
+
+  const eventToken = pendingDeleteToken.value
+  const rsvp = getRsvp(eventToken)
+
+  if (rsvp) {
+    try {
+      const { response } = await api.DELETE('/events/{eventToken}/rsvps/{rsvpToken}', {
+        params: {
+          path: {
+            eventToken: eventToken,
+            rsvpToken: rsvp.rsvpToken,
+          },
+        },
+      })
+
+      if (response.status !== 204 && response.status !== 404) {
+        deleteError.value = 'Could not cancel attendance. Please try again.'
+        pendingDeleteToken.value = null
+        return
       }
+    } catch {
+      deleteError.value = 'Could not cancel attendance. Please try again.'
+      pendingDeleteToken.value = null
+      return
+    }
+  }
+
+  removeEvent(eventToken)
   pendingDeleteToken.value = null
 }
 

frontend/src/components/RsvpBar.vue

@@ -2,9 +2,32 @@
   <div class="rsvp-bar">
     <div class="rsvp-bar__inner">
       <!-- Status state: already RSVPed -->
-      <div v-if="hasRsvp" class="rsvp-bar__status">
+      <div v-if="hasRsvp" class="rsvp-bar__status-wrapper">
+        <div
+          class="rsvp-bar__status"
+          role="button"
+          tabindex="0"
+          :aria-expanded="expanded"
+          aria-label="You're attending. Tap to show cancel option."
+          @click="expanded = !expanded"
+          @keydown.enter.prevent="expanded = !expanded"
+          @keydown.space.prevent="expanded = !expanded"
+          @keydown.escape="expanded = false"
+        >
           <span class="rsvp-bar__check" aria-hidden="true">✓</span>
           <span class="rsvp-bar__text">You're attending!</span>
+          <span class="rsvp-bar__chevron" :class="{ 'rsvp-bar__chevron--open': expanded }" aria-hidden="true">›</span>
+        </div>
+        <Transition name="rsvp-bar-cancel">
+          <button
+            v-if="expanded"
+            class="rsvp-bar__cancel"
+            type="button"
+            @click="$emit('cancel')"
+          >
+            Cancel attendance
+          </button>
+        </Transition>
       </div>
 
       <!-- CTA state: no RSVP yet -->
@@ -18,13 +41,37 @@
 </template>
 
 <script setup lang="ts">
-defineProps<{
+import { ref, watch } from 'vue'
+
+const props = defineProps<{
   hasRsvp?: boolean
 }>()
 
 defineEmits<{
   open: []
+  cancel: []
 }>()
+
+const expanded = ref(false)
+
+watch(() => props.hasRsvp, () => {
+  expanded.value = false
+})
+
+function onClickOutside(e: MouseEvent) {
+  const target = e.target as HTMLElement
+  if (!target.closest('.rsvp-bar__status-wrapper')) {
+    expanded.value = false
+  }
+}
+
+watch(expanded, (isExpanded) => {
+  if (isExpanded) {
+    document.addEventListener('click', onClickOutside, { capture: true })
+  } else {
+    document.removeEventListener('click', onClickOutside, { capture: true })
+  }
+})
 </script>
 
 <style scoped>
@@ -73,6 +120,12 @@ defineEmits<{
   cursor: pointer;
 }
 
+.rsvp-bar__status-wrapper {
+  display: flex;
+  flex-direction: column;
+  gap: var(--spacing-xs);
+}
+
 .rsvp-bar__status {
   display: flex;
   align-items: center;
@@ -88,6 +141,13 @@ defineEmits<{
   font-weight: 600;
   font-size: 0.95rem;
   color: var(--color-text-on-gradient);
+  cursor: pointer;
+  user-select: none;
+  -webkit-user-select: none;
+}
+
+.rsvp-bar__status:hover {
+  background: linear-gradient(135deg, var(--color-glass-hover) 0%, var(--color-glass-strong) 100%);
 }
 
 .rsvp-bar__check {
@@ -101,4 +161,49 @@ defineEmits<{
   text-overflow: ellipsis;
   white-space: nowrap;
 }
+
+.rsvp-bar__chevron {
+  font-size: 1.2rem;
+  font-weight: 700;
+  transition: transform 0.2s ease;
+  transform: rotate(0deg);
+  margin-left: auto;
+}
+
+.rsvp-bar__chevron--open {
+  transform: rotate(90deg);
+}
+
+.rsvp-bar__cancel {
+  display: block;
+  width: 100%;
+  padding: var(--spacing-sm) var(--spacing-lg);
+  border-radius: var(--radius-card);
+  font-family: inherit;
+  font-size: 0.9rem;
+  font-weight: 600;
+  color: #ef5350;
+  background: linear-gradient(135deg, var(--color-glass-strong) 0%, var(--color-glass-subtle) 100%);
+  border: 1px solid var(--color-glass-border);
+  backdrop-filter: blur(16px);
+  -webkit-backdrop-filter: blur(16px);
+  cursor: pointer;
+  text-align: center;
+  transition: background 0.15s ease;
+}
+
+.rsvp-bar__cancel:hover {
+  background: linear-gradient(135deg, var(--color-glass-hover) 0%, var(--color-glass-strong) 100%);
+}
+
+.rsvp-bar-cancel-enter-active,
+.rsvp-bar-cancel-leave-active {
+  transition: opacity 0.15s ease, transform 0.15s ease;
+}
+
+.rsvp-bar-cancel-enter-from,
+.rsvp-bar-cancel-leave-to {
+  opacity: 0;
+  transform: translateY(-4px);
+}
 </style>

frontend/src/composables/useEventStorage.ts

@@ -78,10 +78,20 @@ export function useEventStorage() {
     return undefined
   }
 
+  function removeRsvp(eventToken: string): void {
+    const events = readEvents()
+    const event = events.find((e) => e.eventToken === eventToken)
+    if (event) {
+      delete event.rsvpToken
+      delete event.rsvpName
+      writeEvents(events)
+    }
+  }
+
   function removeEvent(eventToken: string): void {
     const events = readEvents().filter((e) => e.eventToken !== eventToken)
     writeEvents(events)
   }
 
-  return { saveCreatedEvent, getStoredEvents, getOrganizerToken, saveRsvp, getRsvp, removeEvent }
+  return { saveCreatedEvent, getStoredEvents, getOrganizerToken, saveRsvp, getRsvp, removeRsvp, removeEvent }
 }

frontend/src/views/EventDetailView.vue

@@ -25,6 +25,12 @@
 
       <!-- Loaded state -->
       <div v-else-if="state === 'loaded' && event" class="detail__content">
+        <!-- Cancellation banner -->
+        <div v-if="event.cancelled" class="detail__cancelled-banner" role="alert">
+          <p class="detail__cancelled-banner-title">This event has been cancelled</p>
+          <p v-if="event.cancellationReason" class="detail__cancelled-banner-reason">{{ event.cancellationReason }}</p>
+        </div>
+
         <h1 class="detail__title">{{ event.title }}</h1>
 
         <dl class="detail__meta">
@@ -70,11 +76,63 @@
       </div>
     </div>
 
-    <!-- RSVP bar -->
+    <!-- Cancel event button (organizer only, not already cancelled) -->
+    <div v-if="state === 'loaded' && event && isOrganizer && !event.cancelled" class="detail__cancel-event">
+      <button class="detail__cancel-event-btn" type="button" @click="cancelSheetOpen = true">
+        Cancel event
+      </button>
+    </div>
+
+    <!-- Cancel event bottom sheet -->
+    <BottomSheet :open="cancelSheetOpen" label="Cancel event" @close="cancelSheetOpen = false">
+      <h2 class="sheet-title">Cancel event</h2>
+      <form class="cancel-form" @submit.prevent="handleCancelEvent" novalidate>
+        <div class="form-group">
+          <label class="cancel-form__label" for="cancel-reason">Reason (optional)</label>
+          <textarea
+            id="cancel-reason"
+            v-model.trim="cancelReasonInput"
+            class="form-field glass cancel-form__textarea"
+            placeholder="e.g. Venue no longer available"
+            maxlength="2000"
+            rows="3"
+            @input="cancelEventError = ''"
+          />
+          <span class="cancel-form__counter">{{ cancelReasonInput.length }} / 2000</span>
+        </div>
+        <button
+          class="cancel-form__confirm glass-inner"
+          type="submit"
+          :disabled="cancellingEvent"
+        >
+          {{ cancellingEvent ? 'Cancelling…' : 'Confirm cancellation' }}
+        </button>
+        <p v-if="cancelEventError" class="cancel-form__error" role="alert">{{ cancelEventError }}</p>
+      </form>
+    </BottomSheet>
+
+    <!-- Cancel RSVP error message -->
+    <div v-if="cancelError" class="detail__cancel-error" role="alert">
+      <p>{{ cancelError }}</p>
+    </div>
+
+    <!-- RSVP bar (hidden when cancelled) -->
     <RsvpBar
-      v-if="state === 'loaded' && event && !isOrganizer"
+      v-if="state === 'loaded' && event && !isOrganizer && !event.cancelled"
       :has-rsvp="!!rsvpName"
       @open="sheetOpen = true"
+      @cancel="confirmCancelOpen = true"
+    />
+
+    <!-- Cancel confirmation dialog -->
+    <ConfirmDialog
+      :open="confirmCancelOpen"
+      title="Cancel attendance?"
+      message="Your attendance will be permanently cancelled."
+      confirm-label="Cancel attendance"
+      cancel-label="Keep"
+      @confirm="handleCancelRsvp"
+      @cancel="confirmCancelOpen = false"
     />
 
     <!-- RSVP bottom sheet -->
@@ -113,6 +171,7 @@ import { api } from '@/api/client'
 import { useEventStorage } from '@/composables/useEventStorage'
 import AttendeeList from '@/components/AttendeeList.vue'
 import BottomSheet from '@/components/BottomSheet.vue'
+import ConfirmDialog from '@/components/ConfirmDialog.vue'
 import RsvpBar from '@/components/RsvpBar.vue'
 import type { components } from '@/api/schema'
 
@@ -120,7 +179,7 @@ type GetEventResponse = components['schemas']['GetEventResponse']
 type State = 'loading' | 'loaded' | 'not-found' | 'error'
 
 const route = useRoute()
-const { saveRsvp, getRsvp, getOrganizerToken } = useEventStorage()
+const { saveRsvp, getRsvp, removeRsvp, getOrganizerToken } = useEventStorage()
 
 const state = ref<State>('loading')
 const event = ref<GetEventResponse | null>(null)
@@ -132,9 +191,17 @@ const nameError = ref('')
 const submitError = ref('')
 const submitting = ref(false)
 const rsvpName = ref<string | undefined>(undefined)
+const confirmCancelOpen = ref(false)
+const cancelError = ref('')
 const isOrganizer = ref(false)
 const attendeeNames = ref<string[] | null>(null)
 
+// Cancel event state
+const cancelSheetOpen = ref(false)
+const cancelReasonInput = ref('')
+const cancelEventError = ref('')
+const cancellingEvent = ref(false)
+
 const formattedDateTime = computed(() => {
   if (!event.value) return ''
   const formatted = new Intl.DateTimeFormat(undefined, {
@@ -149,8 +216,8 @@ async function fetchEvent() {
   event.value = null
 
   try {
-    const { data, error, response } = await api.GET('/events/{token}', {
-      params: { path: { token: route.params.eventToken as string } },
+    const { data, error, response } = await api.GET('/events/{eventToken}', {
+      params: { path: { eventToken: route.params.eventToken as string } },
     })
 
     if (error) {
@@ -197,8 +264,8 @@ async function submitRsvp() {
   submitting.value = true
 
   try {
-    const { data, error } = await api.POST('/events/{token}/rsvps', {
-      params: { path: { token: route.params.eventToken as string } },
+    const { data, error } = await api.POST('/events/{eventToken}/rsvps', {
+      params: { path: { eventToken: route.params.eventToken as string } },
       body: { name: nameInput.value },
     })
 
@@ -228,11 +295,76 @@ async function submitRsvp() {
   }
 }
 
+async function handleCancelRsvp() {
+  confirmCancelOpen.value = false
+  cancelError.value = ''
+
+  const stored = getRsvp(route.params.eventToken as string)
+  if (!stored) return
+
+  try {
+    const { response } = await api.DELETE('/events/{eventToken}/rsvps/{rsvpToken}', {
+      params: {
+        path: {
+          eventToken: route.params.eventToken as string,
+          rsvpToken: stored.rsvpToken,
+        },
+      },
+    })
+
+    if (response.status === 204 || response.status === 404) {
+      removeRsvp(route.params.eventToken as string)
+      rsvpName.value = undefined
+      if (event.value) {
+        event.value.attendeeCount = Math.max(0, event.value.attendeeCount - 1)
+      }
+    } else {
+      cancelError.value = 'Could not cancel RSVP. Please try again.'
+    }
+  } catch {
+    cancelError.value = 'Could not cancel RSVP. Please try again.'
+  }
+}
+
+async function handleCancelEvent() {
+  cancelEventError.value = ''
+  cancellingEvent.value = true
+
+  const orgToken = getOrganizerToken(route.params.eventToken as string)
+  if (!orgToken) return
+
+  try {
+    const { error } = await api.PATCH('/events/{eventToken}', {
+      params: {
+        path: { eventToken: route.params.eventToken as string },
+        query: { organizerToken: orgToken },
+      },
+      body: {
+        cancelled: true,
+        cancellationReason: cancelReasonInput.value || undefined,
+      },
+    })
+
+    if (error) {
+      cancelEventError.value = 'Could not cancel event. Please try again.'
+      return
+    }
+
+    cancelSheetOpen.value = false
+    cancelReasonInput.value = ''
+    await fetchEvent()
+  } catch {
+    cancelEventError.value = 'Could not cancel event. Please try again.'
+  } finally {
+    cancellingEvent.value = false
+  }
+}
+
 async function fetchAttendees(eventToken: string, organizerToken: string) {
   try {
-    const { data, error } = await api.GET('/events/{token}/attendees', {
+    const { data, error } = await api.GET('/events/{eventToken}/attendees', {
       params: {
-        path: { token: eventToken },
+        path: { eventToken: eventToken },
         query: { organizerToken },
       },
     })
@@ -470,4 +602,105 @@ onMounted(fetchEvent)
   opacity: 0.6;
   cursor: not-allowed;
 }
+
+/* Cancellation banner */
+.detail__cancelled-banner {
+  padding: var(--spacing-md) var(--spacing-lg);
+  border-radius: var(--radius-card);
+  background: var(--color-danger-bg);
+  border: 1px solid var(--color-danger-border-strong);
+  text-align: center;
+}
+
+.detail__cancelled-banner-title {
+  font-weight: 700;
+  font-size: 0.95rem;
+  color: var(--color-danger);
+}
+
+.detail__cancelled-banner-reason {
+  margin-top: var(--spacing-xs);
+  font-size: 0.85rem;
+  color: var(--color-text-soft);
+  word-break: break-word;
+}
+
+/* Cancel event button */
+.detail__cancel-event {
+  position: fixed;
+  bottom: 0;
+  left: 0;
+  right: 0;
+  padding: var(--spacing-md) var(--content-padding);
+  padding-bottom: calc(var(--spacing-md) + env(safe-area-inset-bottom, 0px));
+  display: flex;
+  justify-content: center;
+  z-index: 10;
+}
+
+.detail__cancel-event-btn {
+  width: 100%;
+  max-width: var(--content-max-width);
+  padding: var(--spacing-md) var(--spacing-lg);
+  border-radius: var(--radius-button);
+  font-family: inherit;
+  font-size: 0.95rem;
+  font-weight: 600;
+  color: var(--color-danger);
+  background: var(--color-danger-bg);
+  border: 1px solid var(--color-danger-border);
+  cursor: pointer;
+  transition: background 0.15s ease;
+}
+
+.detail__cancel-event-btn:hover {
+  background: var(--color-danger-bg-hover);
+}
+
+/* Cancel event form (inside bottom sheet) */
+.cancel-form__textarea {
+  resize: vertical;
+  min-height: 4rem;
+  font-family: inherit;
+}
+
+.cancel-form__counter {
+  display: block;
+  text-align: right;
+  font-size: 0.75rem;
+  color: var(--color-text-muted);
+  margin-top: var(--spacing-xs);
+}
+
+.cancel-form__confirm {
+  display: block;
+  width: 100%;
+  margin-top: var(--spacing-md);
+  padding: var(--spacing-md) var(--spacing-lg);
+  border-radius: var(--radius-button);
+  font-family: inherit;
+  font-size: 1rem;
+  font-weight: 700;
+  color: var(--color-danger);
+  background: var(--color-danger-bg-strong);
+  border: 1px solid var(--color-danger-border);
+  cursor: pointer;
+  transition: background 0.15s ease;
+}
+
+.cancel-form__confirm:hover {
+  background: var(--color-danger-bg-hover);
+}
+
+.cancel-form__confirm:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+
+.cancel-form__error {
+  margin-top: var(--spacing-sm);
+  font-size: 0.85rem;
+  color: var(--color-danger);
+  text-align: center;
+}
 </style>

frontend/src/views/__tests__/EventCreateView.spec.ts

@@ -163,6 +163,7 @@ describe('EventCreateView', () => {
       getOrganizerToken: vi.fn(),
       saveRsvp: vi.fn(),
       getRsvp: vi.fn(),
+      removeRsvp: vi.fn(),
       removeEvent: vi.fn(),
     })
 

frontend/src/views/__tests__/EventDetailView.spec.ts

@@ -280,8 +280,8 @@ describe('EventDetailView', () => {
     await flushPromises()
 
     // Verify API call
-    expect(vi.mocked(api.POST)).toHaveBeenCalledWith('/events/{token}/rsvps', {
-      params: { path: { token: 'test-token' } },
+    expect(vi.mocked(api.POST)).toHaveBeenCalledWith('/events/{eventToken}/rsvps', {
+      params: { path: { eventToken: 'test-token' } },
       body: { name: 'Max' },
     })
 

specs/014-cancel-rsvp/checklists/requirements.md

@@ -0,0 +1,36 @@
+# Specification Quality Checklist: Cancel RSVP
+
+**Purpose**: Validate specification completeness and quality before proceeding to planning
+**Created**: 2026-03-09
+**Feature**: [spec.md](../spec.md)
+
+## Content Quality
+
+- [x] No implementation details (languages, frameworks, APIs)
+- [x] Focused on user value and business needs
+- [x] Written for non-technical stakeholders
+- [x] All mandatory sections completed
+
+## Requirement Completeness
+
+- [x] No [NEEDS CLARIFICATION] markers remain
+- [x] Requirements are testable and unambiguous
+- [x] Success criteria are measurable
+- [x] Success criteria are technology-agnostic (no implementation details)
+- [x] All acceptance scenarios are defined
+- [x] Edge cases are identified
+- [x] Scope is clearly bounded
+- [x] Dependencies and assumptions identified
+
+## Feature Readiness
+
+- [x] All functional requirements have clear acceptance criteria
+- [x] User scenarios cover primary flows
+- [x] Feature meets measurable outcomes defined in Success Criteria
+- [x] No implementation details leak into specification
+
+## Notes
+
+- All items pass. Spec is ready for `/speckit.clarify` or `/speckit.plan`.
+- The "Design Proposals" section is intentionally included as requested by the user — these are UX options, not implementation details.
+- One decision point remains: which design option (A, B, or C) for the cancel UI. This is deferred to discussion with the user rather than marked as [NEEDS CLARIFICATION] since the user explicitly requested proposals.

specs/014-cancel-rsvp/contracts/cancel-rsvp.yaml

@@ -0,0 +1,40 @@
+# Cancel RSVP — API Contract
+# This contract will be merged into backend/src/main/resources/openapi/api.yaml
+
+# Path: /events/{token}/rsvps/{rsvpToken}
+# Method: DELETE
+
+path:
+  /events/{token}/rsvps/{rsvpToken}:
+    delete:
+      summary: Cancel RSVP
+      description: |
+        Permanently deletes an RSVP identified by the RSVP token.
+        Idempotent: returns 204 whether the RSVP existed or not.
+      operationId: cancelRsvp
+      tags:
+        - Events
+      parameters:
+        - name: token
+          in: path
+          required: true
+          description: Event token (UUID)
+          schema:
+            type: string
+            format: uuid
+            example: "550e8400-e29b-41d4-a716-446655440000"
+        - name: rsvpToken
+          in: path
+          required: true
+          description: RSVP token (UUID) identifying the attendance to cancel
+          schema:
+            type: string
+            format: uuid
+            example: "7c9e6679-7425-40de-944b-e07fc1f90ae7"
+      responses:
+        "204":
+          description: >
+            RSVP successfully cancelled (or was already cancelled).
+            No response body.
+        "500":
+          description: Internal server error

specs/014-cancel-rsvp/data-model.md

@@ -0,0 +1,74 @@
+# Data Model: Cancel RSVP
+
+**Feature**: 014-cancel-rsvp | **Date**: 2026-03-09
+
+## Entities
+
+### RSVP (existing — no schema changes)
+
+| Field | Type | Constraints | Notes |
+|-------|------|-------------|-------|
+| id | BIGSERIAL | PK, auto-generated | Internal DB ID, never exposed |
+| rsvp_token | UUID | UNIQUE, NOT NULL | Bearer credential for the guest |
+| event_id | BIGINT | FK → events.id, NOT NULL | Links RSVP to event |
+| name | VARCHAR(100) | NOT NULL | Guest display name |
+
+**No migration needed.** The cancel feature only deletes existing rows — no new columns or tables.
+
+## State Transitions
+
+```
+┌──────────┐    POST /events/{token}/rsvps    ┌──────────┐
+│ No RSVP  │ ──────────────────────────────► │ Attending │
+│ (guest)  │ ◄────────────────────────────── │  (guest)  │
+└──────────┘  DELETE /events/{token}/rsvps/   └──────────┘
+                    {rsvpToken}
+```
+
+The transition is fully reversible: after cancellation, the guest can create a new RSVP (new token generated).
+
+## Client-Side Storage (localStorage)
+
+### StoredEvent (existing interface — no changes)
+
+```typescript
+interface StoredEvent {
+  eventToken: string      // always present
+  title: string           // always present
+  dateTime: string        // always present
+  organizerToken?: string // present if organizer
+  rsvpToken?: string      // present if RSVP'd — CLEARED on cancel
+  rsvpName?: string       // present if RSVP'd — CLEARED on cancel
+}
+```
+
+### Cancel Effects on localStorage
+
+| Action | rsvpToken | rsvpName | Event in list |
+|--------|-----------|----------|---------------|
+| Cancel from detail view | Removed | Removed | Kept |
+| Remove from event list | Removed | Removed | Removed |
+
+## Repository Changes
+
+### RsvpRepository (domain port)
+
+New method:
+
+```java
+/**
+ * Delete an RSVP by event ID and RSVP token.
+ * @return true if a record was deleted, false if not found
+ */
+boolean deleteByEventIdAndRsvpToken(Long eventId, RsvpToken rsvpToken);
+```
+
+### RsvpJpaRepository
+
+New method:
+
+```java
+long deleteByEventIdAndRsvpToken(Long eventId, UUID rsvpToken);
+```
+
+Returns count of deleted rows (0 or 1). Spring Data JPA auto-implements this derived query.

specs/014-cancel-rsvp/plan.md

@@ -0,0 +1,90 @@
+# Implementation Plan: Cancel RSVP
+
+**Branch**: `014-cancel-rsvp` | **Date**: 2026-03-09 | **Spec**: [spec.md](spec.md)
+**Input**: Feature specification from `/specs/014-cancel-rsvp/spec.md`
+
+## Summary
+
+Allow guests to cancel their RSVP either explicitly from the event detail view (tap-to-reveal pattern on the RSVP bar) or implicitly when removing an RSVP'd event from their event list. The backend provides an idempotent DELETE endpoint; the frontend handles confirmation, API call, localStorage cleanup, and UI state reset.
+
+## Technical Context
+
+**Language/Version**: Java 25 (backend), TypeScript 5.9 (frontend)
+**Primary Dependencies**: Spring Boot 3.5.x, Vue 3, Vue Router 5, openapi-fetch, openapi-typescript
+**Storage**: PostgreSQL (JPA via Spring Data, Liquibase migrations)
+**Testing**: JUnit + Mockito (backend unit), MockMvc + Testcontainers (backend integration), Vitest (frontend unit), Playwright + MSW (frontend E2E)
+**Target Platform**: Self-hosted PWA (web browser, mobile-first)
+**Project Type**: Web application (hexagonal backend + SPA frontend)
+**Performance Goals**: Cancel operation < 500ms server-side
+**Constraints**: Privacy by design (no analytics), token-based auth (no login), idempotent delete
+**Scale/Scope**: Single new endpoint, 3 modified frontend components, 1 new composable method
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+| Principle | Status | Notes |
+|-----------|--------|-------|
+| I. Privacy by Design | PASS | No new PII stored. Delete operation removes data. No analytics. |
+| II. Test-Driven Methodology | PASS | Plan includes TDD cycle: tests before implementation. E2E mandatory. |
+| III. API-First Development | PASS | OpenAPI spec updated first, types generated before implementation. |
+| IV. Simplicity & Quality | PASS | Minimal changes to existing code. No new abstractions. Idempotent delete is the simplest correct approach. |
+| V. Dependency Discipline | PASS | No new dependencies required. |
+| VI. Accessibility | PASS | Interactive elements will use semantic HTML, ARIA, keyboard navigation. Confirm dialog already accessible. |
+
+**Gate result**: ALL PASS — proceed to Phase 0.
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/014-cancel-rsvp/
+├── plan.md              # This file
+├── research.md          # Phase 0 output
+├── data-model.md        # Phase 1 output
+├── contracts/           # Phase 1 output
+│   └── cancel-rsvp.yaml # DELETE endpoint contract
+└── tasks.md             # Phase 2 output (by /speckit.tasks)
+```
+
+### Source Code (repository root)
+
+```text
+backend/
+├── src/main/java/de/fete/
+│   ├── domain/
+│   │   ├── model/Rsvp.java                          # existing (no changes)
+│   │   ├── model/RsvpToken.java                     # existing (no changes)
+│   │   └── port/
+│   │       ├── in/CancelRsvpUseCase.java            # NEW use case port
+│   │       └── out/RsvpRepository.java              # MODIFY (add deleteByRsvpToken)
+│   ├── application/service/RsvpService.java          # MODIFY (implement cancel)
+│   └── adapter/
+│       ├── in/web/EventController.java               # MODIFY (add DELETE handler)
+│       └── out/persistence/
+│           ├── RsvpJpaRepository.java                # MODIFY (add deleteByRsvpToken)
+│           └── RsvpPersistenceAdapter.java           # MODIFY (implement delete)
+├── src/main/resources/openapi/api.yaml               # MODIFY (add DELETE endpoint)
+└── src/test/java/de/fete/
+    ├── application/service/RsvpServiceTest.java      # MODIFY (add cancel tests)
+    └── adapter/in/web/EventControllerIntegrationTest.java  # MODIFY (add cancel tests)
+
+frontend/
+├── src/
+│   ├── api/schema.d.ts                               # REGENERATE (from updated OpenAPI)
+│   ├── components/
+│   │   ├── RsvpBar.vue                               # MODIFY (tap-to-reveal cancel)
+│   │   ├── EventList.vue                             # MODIFY (conditional dialog msg)
+│   │   └── ConfirmDialog.vue                         # existing (no changes)
+│   ├── composables/useEventStorage.ts                # MODIFY (add removeRsvp)
+│   └── views/EventDetailView.vue                     # MODIFY (add cancel logic)
+└── e2e/
+    └── cancel-rsvp.spec.ts                           # NEW (E2E tests)
+```
+
+**Structure Decision**: Follows existing hexagonal architecture. New use case port + implementation in existing service. Single new endpoint added to existing controller.
+
+## Complexity Tracking
+
+No constitution violations — table not needed.

specs/014-cancel-rsvp/quickstart.md

@@ -0,0 +1,57 @@
+# Quickstart: Cancel RSVP
+
+**Feature**: 014-cancel-rsvp | **Date**: 2026-03-09
+
+## Implementation Order
+
+1. **OpenAPI spec** — Add DELETE endpoint to `api.yaml`
+2. **Regenerate types** — Backend (Maven generate) + Frontend (`npm run generate:api`)
+3. **Backend TDD** — Write tests → implement repository → service → controller
+4. **Frontend composable** — Add `removeRsvp()` to `useEventStorage.ts`
+5. **Frontend US-1** — RsvpBar tap-to-reveal + EventDetailView cancel logic
+6. **Frontend US-2** — EventList conditional dialog + server-side cancel before removal
+7. **Frontend US-3** — Edge case handling (stale tokens treated as success)
+8. **E2E tests** — Playwright tests for all three user stories
+
+## Key Commands
+
+```bash
+# Backend
+cd backend && ./mvnw test                    # Run backend tests
+cd backend && ./mvnw verify                  # Full verify (checkstyle + tests)
+cd backend && ./mvnw spring-boot:run         # Run backend locally
+
+# Frontend
+cd frontend && npm run generate:api          # Regenerate types from OpenAPI
+cd frontend && npm run test:unit             # Run unit tests
+cd frontend && npx playwright test           # Run E2E tests
+cd frontend && npm run dev                   # Dev server
+
+# Both
+cd backend && ./mvnw test && cd ../frontend && npm run test:unit  # Quick check
+```
+
+## Key Files to Modify
+
+| File | Change |
+|------|--------|
+| `backend/src/main/resources/openapi/api.yaml` | Add DELETE `/events/{token}/rsvps/{rsvpToken}` |
+| `backend/.../port/in/CancelRsvpUseCase.java` | New use case interface |
+| `backend/.../port/out/RsvpRepository.java` | Add `deleteByEventIdAndRsvpToken()` |
+| `backend/.../RsvpJpaRepository.java` | Add derived delete query |
+| `backend/.../RsvpPersistenceAdapter.java` | Implement delete |
+| `backend/.../RsvpService.java` | Implement `CancelRsvpUseCase` |
+| `backend/.../EventController.java` | Add `cancelRsvp()` handler |
+| `frontend/src/composables/useEventStorage.ts` | Add `removeRsvp()` |
+| `frontend/src/components/RsvpBar.vue` | Tap-to-reveal cancel button |
+| `frontend/src/views/EventDetailView.vue` | Cancel logic + confirm dialog |
+| `frontend/src/components/EventList.vue` | Conditional dialog message + server cancel |
+| `frontend/e2e/cancel-rsvp.spec.ts` | E2E tests for all scenarios |
+
+## Gotchas
+
+- The JPA `deleteBy...` method requires `@Transactional` on the calling service method.
+- The `@Transactional` import must be `jakarta.transaction.Transactional` (not Spring's).
+- After updating OpenAPI spec, run `npm run generate:api` in frontend AND Maven generate-sources in backend.
+- The RsvpBar component currently has no click handler on the status state — this needs to be added carefully with proper accessibility (role, aria-expanded, keyboard support).
+- The EventList's `confirmDelete` currently calls `removeEvent()` synchronously — it needs to become async for the server call.

specs/014-cancel-rsvp/research.md

@@ -0,0 +1,82 @@
+# Research: Cancel RSVP
+
+**Feature**: 014-cancel-rsvp | **Date**: 2026-03-09
+
+## 1. Idempotent DELETE Semantics
+
+**Decision**: Return 204 No Content for both successful deletion and "already deleted" cases.
+
+**Rationale**: HTTP DELETE is defined as idempotent (RFC 9110 §9.3.5). Returning 204 regardless of whether the RSVP existed simplifies client logic — the client doesn't need to distinguish "deleted now" from "was already gone." This directly satisfies FR-002 and US-3.
+
+**Alternatives considered**:
+- Return 404 for "not found" RSVP: Violates idempotency expectations, forces client to handle two success paths.
+- Return 200 with body: Unnecessary — no useful information to return after deletion.
+
+## 2. Authorization Model for Delete
+
+**Decision**: DELETE requires both event token (path) and RSVP token (path). The RSVP token acts as a bearer credential — possession equals authorization.
+
+**Rationale**: Consistent with the existing privacy model. The RSVP token is a UUID v4 generated server-side, unguessable. No additional auth needed. The event token scopes the operation to prevent cross-event token collision (defense in depth).
+
+**Alternatives considered**:
+- RSVP token only: Sufficient in practice (UUIDs are globally unique) but loses the event context in the URL, making the API less RESTful.
+- Require organizer token: Would prevent guests from self-cancelling — contradicts the spec.
+
+## 3. Backend Delete Implementation Pattern
+
+**Decision**: Use `deleteByRsvpToken(UUID)` on the JPA repository. Return the count of deleted rows (0 or 1) to determine if a record was actually removed (needed for attendee count response).
+
+**Rationale**: Spring Data JPA supports `deleteBy...` derived queries returning `long` (count of deleted rows). This is a single query, no need to fetch-then-delete. The existing `findByRsvpToken()` method confirms the naming convention.
+
+**Alternatives considered**:
+- `findByRsvpToken()` then `delete(entity)`: Two queries instead of one. Unnecessary.
+- Native `@Query` DELETE: Overkill for a simple single-column delete.
+
+## 4. Backend Validation: Event Token Check
+
+**Decision**: Validate that the RSVP belongs to the specified event before deleting. If the RSVP token exists but belongs to a different event, return 404.
+
+**Rationale**: Defense in depth. Prevents accidental or malicious cross-event RSVP deletion via URL manipulation. The combined lookup (`findByEventIdAndRsvpToken`) is a single indexed query.
+
+**Alternatives considered**:
+- Skip event validation: Simpler but allows deleting RSVPs via wrong event URLs. Minor security concern but violates principle of least surprise.
+
+## 5. Frontend: Tap-to-Reveal Pattern for Cancel
+
+**Decision**: The "You're attending!" bar becomes tappable. Tapping reveals a slide-out "Cancel attendance" button. Tapping outside or pressing Escape collapses it. A subtle chevron/icon hints at interactivity.
+
+**Rationale**: Specified in the feature spec's design decision. Prevents accidental cancellation (two-step: reveal + confirm dialog). Keeps the default state clean and positive.
+
+**Alternatives considered**:
+- Always-visible cancel button: Too prominent, encourages cancellation over attendance.
+- Long-press to reveal: Not discoverable, no established mobile convention for this.
+- Swipe gesture: Already used for event list deletion — would create gesture ambiguity.
+
+## 6. Frontend: removeRsvp vs removeEvent in localStorage
+
+**Decision**: Add `removeRsvp(eventToken)` method to `useEventStorage.ts` that clears only `rsvpToken` and `rsvpName` from a stored event, keeping the event itself in the list.
+
+**Rationale**: Cancel from event detail view should NOT remove the event from the list — the guest may still want to see event details. Only the RSVP fields need clearing. The existing `removeEvent()` method is used for event list removal (US-2).
+
+**Alternatives considered**:
+- Reuse `removeEvent()` for both: Would remove the event from the list when cancelling from detail view — unexpected behavior.
+
+## 7. Frontend: Event List Removal with RSVP
+
+**Decision**: When removing an event that has an RSVP token, call DELETE on the server FIRST. On success (or 404), then remove from localStorage. On server error, show error and keep the event.
+
+**Rationale**: Server-first ensures data consistency (FR-007). If we removed from localStorage first and the server call failed, the RSVP would remain on the server with no way for the guest to cancel it.
+
+**Alternatives considered**:
+- Optimistic removal (remove from localStorage, fire-and-forget server call): Risks data inconsistency if server call fails.
+- Remove from localStorage first, retry server call: Complex retry logic, still risks inconsistency.
+
+## 8. Attendee Count After Cancellation
+
+**Decision**: After successful DELETE, decrement the local attendee count by 1 in the event detail view. Do not re-fetch the event.
+
+**Rationale**: Avoids an extra GET request. The count is deterministic — if the delete succeeded, exactly one attendee was removed. The same pattern is used for RSVP creation (increment by 1).
+
+**Alternatives considered**:
+- Re-fetch event data: Extra network request, slower UX, unnecessary.
+- Return updated count from DELETE endpoint: Adds response body to a 204 — semantically wrong.

specs/014-cancel-rsvp/spec.md

@@ -0,0 +1,114 @@
+# Feature Specification: Cancel RSVP
+
+**Feature Branch**: `014-cancel-rsvp`
+**Created**: 2026-03-09
+**Status**: Draft
+**Input**: User description: "A guest can cancel their attendance if they still have their RSVP token in localStorage. The event detail view should offer this functionality (design proposals needed). The RSVP is permanently deleted from the database by RSVP token. When a guest removes an entry from their event list, attendance is automatically cancelled. The confirmation dialog informs the guest about this behavior."
+
+## User Scenarios & Testing *(mandatory)*
+
+### User Story 1 - Cancel RSVP from Event Detail View (Priority: P1)
+
+A guest who previously RSVP'd to an event visits the event detail page. The sticky bottom bar shows their attendance status ("You're attending!"). The guest can cancel their attendance directly from this view. After cancellation, their RSVP is permanently removed from the server and from localStorage. The attendee count decreases by one, and the RSVP bar returns to the initial "I'm attending" call-to-action state, allowing the guest to re-RSVP if desired.
+
+**Why this priority**: This is the core feature — the explicit, intentional cancellation flow. It gives guests direct control over their attendance and is the primary interaction point.
+
+**Independent Test**: Can be fully tested by navigating to an event detail page as an RSVP'd guest, cancelling, and verifying the RSVP is deleted server-side and the UI resets.
+
+**Acceptance Scenarios**:
+
+1. **Given** a guest has an RSVP token stored in localStorage for an event, **When** they view the event detail page, **Then** they see a way to cancel their attendance alongside their attendance status.
+2. **Given** the guest initiates cancellation, **When** the system presents a confirmation prompt, **Then** the prompt clearly states that attendance will be permanently cancelled.
+3. **Given** the guest confirms cancellation, **When** the server successfully deletes the RSVP, **Then** the RSVP token and name are removed from localStorage, the attendee count decreases by one, and the RSVP bar returns to the initial call-to-action state.
+4. **Given** the guest confirms cancellation, **When** the server returns an error, **Then** the guest sees an error message and their attendance status remains unchanged.
+5. **Given** the guest cancels and the RSVP bar resets, **When** the guest taps the call-to-action, **Then** they can submit a new RSVP as normal.
+
+---
+
+### User Story 2 - Auto-Cancel on Event List Removal (Priority: P2)
+
+A guest removes an event from their personal event list (via delete button or swipe gesture on the event card). If the guest has an RSVP token for that event, the confirmation dialog informs them that removing the event will also cancel their attendance on the server. Upon confirmation, the RSVP is deleted from the server before the event is removed from localStorage.
+
+**Why this priority**: This ensures data consistency between client and server. Without it, a guest could believe they cancelled but their name would remain on the attendee list.
+
+**Independent Test**: Can be fully tested by adding an RSVP'd event to the list, removing it via the event list, and verifying the RSVP is deleted server-side.
+
+**Acceptance Scenarios**:
+
+1. **Given** a guest has an event in their list with an RSVP token, **When** they initiate removal (delete button or swipe), **Then** the confirmation dialog explicitly mentions that their attendance will also be cancelled.
+2. **Given** a guest has an event in their list without an RSVP token (organizer-only or link-only), **When** they initiate removal, **Then** the confirmation dialog does not mention attendance cancellation (existing behavior unchanged).
+3. **Given** the guest confirms removal of an RSVP'd event, **When** the server successfully deletes the RSVP, **Then** the event is removed from localStorage (including RSVP token) and disappears from the list.
+4. **Given** the guest confirms removal of an RSVP'd event, **When** the server fails to delete the RSVP, **Then** the guest sees an error message and the event remains in the list unchanged.
+5. **Given** the guest dismisses the confirmation dialog, **When** no action is taken, **Then** the event and RSVP remain unchanged.
+
+---
+
+### User Story 3 - Cancel RSVP with Expired/Invalid Token (Priority: P3)
+
+A guest attempts to cancel their RSVP, but the token is no longer valid on the server (e.g., the event was deleted, or the RSVP was already removed by another means). The system handles this gracefully.
+
+**Why this priority**: Edge case handling — less common but important for a smooth user experience.
+
+**Independent Test**: Can be tested by manipulating localStorage to contain a stale RSVP token and attempting cancellation.
+
+**Acceptance Scenarios**:
+
+1. **Given** a guest has a stale RSVP token in localStorage, **When** they attempt to cancel from the event detail view, **Then** the system treats a "not found" server response as a successful cancellation (the RSVP is already gone), cleans up localStorage, and resets the UI.
+2. **Given** a guest has a stale RSVP token in localStorage, **When** they remove the event from their list, **Then** the system treats a "not found" server response as success and removes the event from localStorage.
+
+---
+
+### Edge Cases
+
+- What happens when the guest has no internet connection during cancellation? → Show an error message; do not modify localStorage or UI state.
+- What happens if the event itself has been deleted? → The event detail view already handles the "not found" state. For list removal, treat the 404 as success and clean up localStorage.
+- What happens if multiple browser tabs are open? → localStorage changes propagate across tabs; the RSVP bar should reflect the current localStorage state on visibility/focus.
+
+## Requirements *(mandatory)*
+
+### Functional Requirements
+
+- **FR-001**: System MUST provide a cancellation endpoint that permanently deletes an RSVP record identified by event token and RSVP token.
+- **FR-002**: System MUST return a success response when the RSVP is deleted, including when the RSVP does not exist (idempotent delete).
+- **FR-003**: The event detail view MUST display a cancel option when the guest has an RSVP token in localStorage for the current event.
+- **FR-004**: The cancel option MUST require explicit confirmation before proceeding.
+- **FR-005**: After successful cancellation, the system MUST remove the RSVP token and RSVP name from localStorage for that event.
+- **FR-006**: After successful cancellation on the event detail view, the attendee count MUST decrease by one and the RSVP bar MUST return to its initial call-to-action state.
+- **FR-007**: When a guest removes an RSVP'd event from their event list, the system MUST attempt to delete the RSVP on the server before removing it from localStorage.
+- **FR-008**: The event list removal confirmation dialog MUST inform the guest that their attendance will be cancelled when an RSVP token is present.
+- **FR-009**: If the server returns an error (other than "not found") during cancellation, the system MUST show an error message and leave the local state unchanged.
+- **FR-010**: The cancellation endpoint MUST only delete the RSVP matching the provided RSVP token — no other RSVPs or event data may be affected.
+
+### Key Entities
+
+- **RSVP**: An attendance record linking a guest name to an event. Identified by a unique RSVP token (UUID). Existence indicates attendance; deletion indicates cancellation.
+- **Stored Event (client-side)**: A localStorage entry containing event metadata, and optionally an RSVP token and name if the guest has RSVP'd.
+
+## Success Criteria *(mandatory)*
+
+### Measurable Outcomes
+
+- **SC-001**: A guest can cancel their RSVP from the event detail view in under 5 seconds (two taps: cancel + confirm).
+- **SC-002**: After cancellation, the guest's name no longer appears in the attendee list when viewed by the organizer.
+- **SC-003**: Removing an RSVP'd event from the event list results in server-side RSVP deletion 100% of the time when the server is reachable.
+- **SC-004**: The confirmation dialog clearly communicates the consequence (attendance cancellation) — no guest should be surprised by the side effect.
+- **SC-005**: A guest can re-RSVP after cancellation without any issues.
+
+## Design Decision: Cancel UI on Event Detail View
+
+**Chosen**: Tap-to-Reveal Pattern
+
+The current RSVP bar (sticky bottom) shows "You're attending!" after an RSVP. The status bar becomes tappable. Tapping it reveals a slide-out or expand animation with a "Cancel attendance" button. Tapping outside collapses it back. A subtle visual hint (chevron or icon) indicates the bar is interactive.
+
+## Assumptions
+
+- The existing `findByRsvpToken()` repository method can be leveraged for the delete operation.
+- The RSVP token alone (combined with the event token in the URL) is sufficient authorization for deletion — consistent with the project's token-based privacy model.
+- The delete operation is idempotent: deleting an already-deleted RSVP returns success (not an error).
+- The event list confirmation dialog already exists and can be extended with conditional messaging.
+
+## Dependencies
+
+- **008-rsvp**: The RSVP creation flow and localStorage storage pattern (completed).
+- **007-view-event**: The event detail view and RSVP bar component (completed).
+- **009-list-events**: The event list with delete functionality (completed).

specs/014-cancel-rsvp/tasks.md

@@ -0,0 +1,206 @@
+# Tasks: Cancel RSVP
+
+**Input**: Design documents from `/specs/014-cancel-rsvp/`
+**Prerequisites**: plan.md (required), spec.md (required), research.md, data-model.md, contracts/
+
+**Tests**: Included — constitution mandates TDD (Red → Green → Refactor). E2E tests mandatory per principle II.
+
+**Organization**: Tasks are grouped by user story to enable independent implementation and testing of each story.
+
+## Format: `[ID] [P?] [Story] Description`
+
+- **[P]**: Can run in parallel (different files, no dependencies)
+- **[Story]**: Which user story this task belongs to (e.g., US1, US2, US3)
+- Include exact file paths in descriptions
+
+---
+
+## Phase 1: Setup (API Contract & Type Generation)
+
+**Purpose**: Define the DELETE endpoint contract and regenerate types for both backend and frontend.
+
+- [x] T001 Add DELETE `/events/{token}/rsvps/{rsvpToken}` endpoint to `backend/src/main/resources/openapi/api.yaml` per `specs/014-cancel-rsvp/contracts/cancel-rsvp.yaml` — operationId `cancelRsvp`, responses 204 (success/idempotent) and 500
+- [x] T002 Regenerate backend API interfaces from updated OpenAPI spec via `cd backend && ./mvnw generate-sources`
+- [x] T003 Regenerate frontend TypeScript types from updated OpenAPI spec via `cd frontend && npm run generate:api`
+
+---
+
+## Phase 2: Foundational (Backend Delete Infrastructure)
+
+**Purpose**: Backend repository and service layer for RSVP deletion — blocks all user stories.
+
+**⚠️ CRITICAL**: No user story work can begin until this phase is complete.
+
+### Tests (write FIRST, must FAIL before implementation)
+
+- [x] T004 [P] Write unit test for `cancelRsvp()` in `backend/src/test/java/de/fete/application/service/RsvpServiceTest.java` — test cases: successful delete (returns true), RSVP not found (returns false), event not found (returns false)
+- [x] T005 [P] Write integration test for `DELETE /api/events/{token}/rsvps/{rsvpToken}` in `backend/src/test/java/de/fete/adapter/in/web/EventControllerIntegrationTest.java` — test cases: 204 on successful delete, 204 on already-deleted RSVP (idempotent), 204 when event not found (idempotent), verify RSVP row actually removed from DB
+
+### Implementation
+
+- [x] T006 Create `CancelRsvpUseCase` interface in `backend/src/main/java/de/fete/domain/port/in/CancelRsvpUseCase.java` — single method `cancelRsvp(EventToken, RsvpToken)` returning void
+- [x] T007 Add `deleteByEventIdAndRsvpToken(Long eventId, RsvpToken rsvpToken)` to domain port `backend/src/main/java/de/fete/domain/port/out/RsvpRepository.java`
+- [x] T008 Add `deleteByEventIdAndRsvpToken(Long eventId, UUID rsvpToken)` derived delete query to `backend/src/main/java/de/fete/adapter/out/persistence/RsvpJpaRepository.java`
+- [x] T009 Implement `deleteByEventIdAndRsvpToken()` in `backend/src/main/java/de/fete/adapter/out/persistence/RsvpPersistenceAdapter.java` — delegate to JPA repository, return boolean (deleted count > 0)
+- [x] T010 Implement `CancelRsvpUseCase` in `backend/src/main/java/de/fete/application/service/RsvpService.java` — look up event by token, if found call repository delete, no error on not-found (idempotent). Add `@Transactional`
+- [x] T011 Implement `cancelRsvp()` handler in `backend/src/main/java/de/fete/adapter/in/web/EventController.java` — accept event token and RSVP token path params, call use case, return 204 No Content
+- [x] T012 Run `cd backend && ./mvnw verify` — all tests (existing + new) must pass
+
+**Checkpoint**: Backend DELETE endpoint functional and tested. Verify via integration tests.
+
+---
+
+## Phase 3: User Story 1 — Cancel RSVP from Event Detail View (Priority: P1) 🎯 MVP
+
+**Goal**: Guest can tap the "You're attending!" bar to reveal a cancel button, confirm cancellation, and have RSVP deleted server-side with UI reset.
+
+**Independent Test**: Navigate to event detail as RSVP'd guest → tap status bar → tap cancel → confirm → verify RSVP deleted, attendee count decremented, bar reset to CTA state. Then re-RSVP to verify flow works again.
+
+### Tests (write FIRST, must FAIL before implementation)
+
+- [x] T013 [US1] Write E2E test file `frontend/e2e/cancel-rsvp.spec.ts` — US1 scenarios: (1) status bar shows cancel affordance when RSVP'd, (2) tap reveals cancel button, (3) confirm cancellation → 204 → localStorage cleared + count decremented + bar reset, (4) server error → error message + state unchanged, (5) re-RSVP after cancel works
+
+### Implementation
+
+- [x] T014 [US1] Add `removeRsvp(eventToken: string)` method to `frontend/src/composables/useEventStorage.ts` — clears `rsvpToken` and `rsvpName` from the stored event without removing the event from the list
+- [x] T015 [US1] Modify `frontend/src/components/RsvpBar.vue` — make status state tappable with tap-to-reveal pattern: (1) add `expanded` state, (2) tapping "You're attending!" toggles expanded, (3) expanded state shows "Cancel attendance" button, (4) emit `cancel` event on button click, (5) collapse on outside click/Escape, (6) add subtle chevron icon hint, (7) ARIA: `role="button"`, `aria-expanded`, keyboard support (Enter/Space to toggle, Escape to collapse)
+- [x] T016 [US1] Add cancel RSVP logic to `frontend/src/views/EventDetailView.vue` — (1) handle `cancel` emit from RsvpBar, (2) show ConfirmDialog with message "Your attendance will be permanently cancelled.", (3) on confirm: call `api.DELETE('/events/{token}/rsvps/{rsvpToken}')`, (4) on 204: call `removeRsvp()`, decrement attendee count, reset RSVP state (`rsvpName = ''`), (5) on error: show error message "Could not cancel RSVP. Please try again.", (6) keep local state unchanged on error
+- [x] T017 [US1] Run frontend unit tests `cd frontend && npm run test:unit` and E2E tests `cd frontend && npx playwright test cancel-rsvp` — all must pass
+
+**Checkpoint**: US1 fully functional. Guest can cancel RSVP from event detail view and re-RSVP.
+
+---
+
+## Phase 4: User Story 2 — Auto-Cancel on Event List Removal (Priority: P2)
+
+**Goal**: When a guest removes an RSVP'd event from their event list, the confirmation dialog warns about attendance cancellation and the RSVP is deleted server-side before localStorage cleanup.
+
+**Independent Test**: Add RSVP'd event to list → initiate removal → verify dialog mentions attendance → confirm → verify server DELETE called → event removed from list. Also test: event without RSVP shows standard dialog (no mention of attendance).
+
+### Tests (write FIRST, must FAIL before implementation)
+
+- [x] T018 [US2] Add US2 E2E scenarios to `frontend/e2e/cancel-rsvp.spec.ts` — (1) removal of RSVP'd event shows "attendance will be cancelled" in dialog, (2) removal of non-RSVP'd event shows standard dialog (no attendance mention), (3) confirm removal → DELETE called → event removed from list, (4) server error on DELETE → error message + event stays in list, (5) dismiss dialog → no changes
+
+### Implementation
+
+- [x] T019 [US2] Modify `frontend/src/components/EventList.vue` — (1) detect if pending-delete event has RSVP token via `getRsvp(eventToken)`, (2) set conditional dialog message: with RSVP → "This event will be removed from your list and your attendance will be cancelled." / without RSVP → existing message, (3) make `confirmDelete()` async: if RSVP exists, call `api.DELETE('/events/{token}/rsvps/{rsvpToken}')` first, (4) on success or 404: proceed with `removeEvent()`, (5) on other error: show error message, abort removal
+- [x] T020 [US2] Import API client and `getRsvp` from `useEventStorage` in `frontend/src/components/EventList.vue` — ensure API client is available for server calls
+- [x] T021 [US2] Run E2E tests `cd frontend && npx playwright test cancel-rsvp` — all US1 + US2 scenarios must pass
+
+**Checkpoint**: US1 + US2 functional. Both cancel paths work independently.
+
+---
+
+## Phase 5: User Story 3 — Cancel RSVP with Expired/Invalid Token (Priority: P3)
+
+**Goal**: Gracefully handle stale RSVP tokens — treat "not found" server responses as successful cancellation.
+
+**Independent Test**: Set stale RSVP token in localStorage → attempt cancel from detail view → verify 404 treated as success → localStorage cleaned. Same for event list removal.
+
+### Tests (write FIRST, must FAIL before implementation)
+
+- [x] T022 [US3] Add US3 E2E scenarios to `frontend/e2e/cancel-rsvp.spec.ts` — (1) cancel from detail view with stale token (server 404) → treated as success, localStorage cleaned, UI reset, (2) event list removal with stale token (server 404) → treated as success, event removed
+
+### Implementation
+
+- [x] T023 (already implemented in T016 — 404 treated as success) [US3] Update cancel logic in `frontend/src/views/EventDetailView.vue` — treat 404 response from DELETE as success (RSVP already gone): clean up localStorage and reset UI same as 204
+- [x] T024 (already implemented in T019 — 404 treated as success) [US3] Update cancel logic in `frontend/src/components/EventList.vue` — treat 404 response from DELETE as success: proceed with `removeEvent()` (note: this may already be handled if T019 implemented "success or 404" correctly — verify and adjust if needed)
+- [x] T025 [US3] Run all E2E tests `cd frontend && npx playwright test cancel-rsvp` — all US1 + US2 + US3 scenarios must pass
+
+**Checkpoint**: All user stories functional. Edge cases handled gracefully.
+
+---
+
+## Phase 6: Polish & Cross-Cutting Concerns
+
+**Purpose**: Final verification and cleanup across all stories.
+
+- [x] T026 Run full backend verify `cd backend && ./mvnw verify` — checkstyle + all tests
+- [x] T027 Run full frontend test suite `cd frontend && npm run test:unit && npx playwright test` — all unit + E2E tests
+- [x] T028 Verify accessibility: RsvpBar cancel interaction is keyboard-navigable (Tab, Enter/Space, Escape), ARIA attributes correct, confirm dialog focus management works
+
+---
+
+## Dependencies & Execution Order
+
+### Phase Dependencies
+
+- **Setup (Phase 1)**: No dependencies — start immediately
+- **Foundational (Phase 2)**: Depends on Phase 1 (generated API interfaces needed)
+- **US1 (Phase 3)**: Depends on Phase 2 (backend endpoint must exist)
+- **US2 (Phase 4)**: Depends on Phase 2 (backend endpoint must exist). Independent of US1.
+- **US3 (Phase 5)**: Depends on US1 and US2 (refines their error handling)
+- **Polish (Phase 6)**: Depends on all stories complete
+
+### User Story Dependencies
+
+- **US1 (P1)**: Independent after Phase 2 — core cancel flow
+- **US2 (P2)**: Independent after Phase 2 — can be implemented in parallel with US1
+- **US3 (P3)**: Depends on US1 + US2 — refines error handling in both
+
+### Within Each User Story
+
+- Tests MUST be written and FAIL before implementation
+- Composable/model changes before component changes
+- Component changes before view integration
+- Story complete before moving to next priority
+
+### Parallel Opportunities
+
+- T004 + T005 (backend tests) can run in parallel
+- T006 + T007 (use case + repository port) can run in parallel
+- US1 and US2 can be implemented in parallel after Phase 2 (different files)
+- T026 + T027 (backend verify + frontend tests) can run in parallel
+
+---
+
+## Parallel Example: Phase 2 (Foundational)
+
+```bash
+# Write tests in parallel:
+Task T004: "Unit test for cancelRsvp in RsvpServiceTest.java"
+Task T005: "Integration test for DELETE endpoint in EventControllerIntegrationTest.java"
+
+# Then implement sequentially: T006 → T007 → T008 → T009 → T010 → T011 → T012
+```
+
+## Parallel Example: US1 + US2
+
+```bash
+# After Phase 2 completes, launch in parallel:
+# Stream A (US1): T013 → T014 → T015 → T016 → T017
+# Stream B (US2): T018 → T019 → T020 → T021
+```
+
+---
+
+## Implementation Strategy
+
+### MVP First (User Story 1 Only)
+
+1. Complete Phase 1: Setup (OpenAPI + type generation)
+2. Complete Phase 2: Foundational (backend DELETE endpoint)
+3. Complete Phase 3: User Story 1 (cancel from detail view)
+4. **STOP and VALIDATE**: Test cancel flow end-to-end
+5. Deploy/demo if ready
+
+### Incremental Delivery
+
+1. Setup + Foundational → Backend ready
+2. Add US1 → Cancel from detail view works → Deploy (MVP!)
+3. Add US2 → Auto-cancel on list removal → Deploy
+4. Add US3 → Stale token edge cases handled → Deploy
+5. Each story adds value without breaking previous stories
+
+---
+
+## Notes
+
+- [P] tasks = different files, no dependencies
+- [Story] label maps task to specific user story for traceability
+- Each user story should be independently completable and testable
+- Verify tests fail before implementing
+- Commit after each task or logical group
+- Stop at any checkpoint to validate story independently
+- Backend idempotent DELETE (204 always) simplifies all frontend error handling
+- The `@Transactional` annotation is required on the service method calling JPA `deleteBy...`

specs/016-cancel-event/checklists/requirements.md

@@ -0,0 +1,36 @@
+# Specification Quality Checklist: Cancel Event
+
+**Purpose**: Validate specification completeness and quality before proceeding to planning
+**Created**: 2026-03-12
+**Feature**: [spec.md](../spec.md)
+
+## Content Quality
+
+- [x] No implementation details (languages, frameworks, APIs)
+- [x] Focused on user value and business needs
+- [x] Written for non-technical stakeholders
+- [x] All mandatory sections completed
+
+## Requirement Completeness
+
+- [x] No [NEEDS CLARIFICATION] markers remain
+- [x] Requirements are testable and unambiguous
+- [x] Success criteria are measurable
+- [x] Success criteria are technology-agnostic (no implementation details)
+- [x] All acceptance scenarios are defined
+- [x] Edge cases are identified
+- [x] Scope is clearly bounded
+- [x] Dependencies and assumptions identified
+
+## Feature Readiness
+
+- [x] All functional requirements have clear acceptance criteria
+- [x] User scenarios cover primary flows
+- [x] Feature meets measurable outcomes defined in Success Criteria
+- [x] No implementation details leak into specification
+
+## Notes
+
+- All items pass. Spec is ready for `/speckit.clarify` or `/speckit.plan`.
+- Feature scope is deliberately tight: cancel + display. No notifications, no undo, no event-list changes.
+- Both user stories are P1 because they are two sides of the same coin (cancel action + display result).

specs/016-cancel-event/contracts/patch-event-endpoint.yaml

@@ -0,0 +1,78 @@
+# OpenAPI additions for Cancel Event feature
+# To be merged into backend/src/main/resources/openapi/api.yaml
+
+# PATCH method added to existing /events/{eventToken} path
+# Under paths./events/{eventToken}:
+
+# --- Add PATCH method to existing path ---
+# /events/{eventToken}:
+#   patch:
+#     operationId: patchEvent
+#     summary: Update an event (currently: cancel)
+#     description: |
+#       Partial update of an event resource. Currently the only supported operation
+#       is cancellation (setting cancelled to true). Requires the organizer token.
+#       Cancellation is irreversible.
+#     tags: [Events]
+#     parameters:
+#       - $ref: '#/components/parameters/EventToken'
+#     requestBody:
+#       required: true
+#       content:
+#         application/json:
+#           schema:
+#             $ref: '#/components/schemas/PatchEventRequest'
+#     responses:
+#       '204':
+#         description: Event updated successfully
+#       '403':
+#         description: Invalid organizer token
+#         content:
+#           application/json:
+#             schema:
+#               $ref: '#/components/schemas/ErrorResponse'
+#       '404':
+#         description: Event not found
+#         content:
+#           application/json:
+#             schema:
+#               $ref: '#/components/schemas/ErrorResponse'
+#       '409':
+#         description: Event is already cancelled
+#         content:
+#           application/json:
+#             schema:
+#               $ref: '#/components/schemas/ErrorResponse'
+
+# --- New schemas ---
+
+# PatchEventRequest:
+#   type: object
+#   required: [organizerToken, cancelled]
+#   properties:
+#     organizerToken:
+#       type: string
+#       format: uuid
+#       description: The organizer token proving ownership of the event
+#       example: "550e8400-e29b-41d4-a716-446655440001"
+#     cancelled:
+#       type: boolean
+#       description: Set to true to cancel the event (irreversible)
+#       example: true
+#     cancellationReason:
+#       type: string
+#       maxLength: 2000
+#       description: Optional cancellation reason
+#       example: "Unfortunately the venue is no longer available."
+
+# --- Extended schema: GetEventResponse ---
+# Add to existing GetEventResponse properties:
+#   cancelled:
+#     type: boolean
+#     description: Whether the event has been cancelled
+#     example: false
+#   cancellationReason:
+#     type: string
+#     nullable: true
+#     description: Reason for cancellation, if provided
+#     example: null

specs/016-cancel-event/data-model.md

@@ -0,0 +1,82 @@
+# Data Model: Cancel Event
+
+**Feature Branch**: `016-cancel-event` | **Date**: 2026-03-12
+
+## Entity Changes
+
+### Event (extended)
+
+Two new fields added to the existing Event entity:
+
+| Field              | Type           | Constraints                  | Description                                      |
+|--------------------|----------------|------------------------------|--------------------------------------------------|
+| cancelled          | boolean        | NOT NULL, DEFAULT false      | Whether the event has been cancelled              |
+| cancellationReason | String (2000)  | Nullable                     | Optional reason provided by organizer             |
+
+### State Transition
+
+```
+ACTIVE ──cancel()──► CANCELLED
+```
+
+- One-way transition only. No path from CANCELLED back to ACTIVE.
+- `cancel()` sets `cancelled = true` and optionally sets `cancellationReason`.
+- Once cancelled, the event remains visible but RSVP creation is blocked.
+
+### Validation Rules
+
+- `cancellationReason` max length: 2000 characters (matches description field).
+- `cancellationReason` is plain text only (no HTML/markdown).
+- `cancelled` can only transition from `false` to `true`, never back.
+- Existing RSVPs are preserved when an event is cancelled (no cascade).
+
+## Database Migration (Liquibase Changeset 004)
+
+```xml
+<changeSet id="004-add-cancellation-columns" author="fete">
+    <addColumn tableName="events">
+        <column name="cancelled" type="BOOLEAN" defaultValueBoolean="false">
+            <constraints nullable="false"/>
+        </column>
+        <column name="cancellation_reason" type="VARCHAR(2000)"/>
+    </addColumn>
+</changeSet>
+```
+
+## Domain Model Impact
+
+### Event.java (domain)
+
+Add fields:
+```java
+private boolean cancelled;
+private String cancellationReason;
+```
+
+Add method:
+```java
+public void cancel(String reason) {
+    if (this.cancelled) {
+        throw new EventAlreadyCancelledException();
+    }
+    this.cancelled = true;
+    this.cancellationReason = reason;
+}
+```
+
+### EventJpaEntity.java (persistence)
+
+Add columns:
+```java
+@Column(name = "cancelled", nullable = false)
+private boolean cancelled;
+
+@Column(name = "cancellation_reason", length = 2000)
+private String cancellationReason;
+```
+
+## RSVP Impact
+
+- `POST /events/{eventToken}/rsvps` must check `event.isCancelled()` before accepting.
+- If cancelled → return `409 Conflict`.
+- Existing RSVPs remain untouched — no delete, no status change.

specs/016-cancel-event/plan.md

@@ -0,0 +1,79 @@
+# Implementation Plan: Cancel Event
+
+**Branch**: `016-cancel-event` | **Date**: 2026-03-12 | **Spec**: [spec.md](spec.md)
+**Input**: Feature specification from `/specs/016-cancel-event/spec.md`
+
+## Summary
+
+Allow organizers to permanently cancel events via a bottom sheet UI. Cancelled events display a red banner to visitors and block new RSVPs. Implementation adds a `PATCH /events/{eventToken}` endpoint, extends the Event entity with `cancelled` and `cancellationReason` fields, and reuses the existing `BottomSheet.vue` component for the cancel interaction.
+
+## Technical Context
+
+**Language/Version**: Java 25 (backend), TypeScript 5.9 (frontend)
+**Primary Dependencies**: Spring Boot 3.5.x, Vue 3, Vue Router 5, openapi-fetch, openapi-typescript
+**Storage**: PostgreSQL (JPA via Spring Data, Liquibase migrations)
+**Testing**: JUnit (backend), Vitest (frontend unit), Playwright + MSW (frontend E2E)
+**Target Platform**: Self-hosted Linux server, mobile-first PWA
+**Project Type**: Web application (REST API + SPA)
+**Performance Goals**: N/A — simple state transition, no performance-critical path
+**Constraints**: Privacy by design (no analytics/tracking), WCAG AA, mobile-first
+**Scale/Scope**: Single new endpoint, 2 new DB columns, 1 view extension
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+| Principle | Status | Notes |
+|-----------|--------|-------|
+| I. Privacy by Design | PASS | No new data collection beyond organizer-provided reason. No analytics. |
+| II. Test-Driven Methodology | PASS | TDD enforced: tests before implementation, E2E mandatory for both user stories. |
+| III. API-First Development | PASS | OpenAPI spec updated first, types generated before implementation. `example:` fields included. |
+| IV. Simplicity & Quality | PASS | Minimal change: 2 columns, 1 endpoint, reuse existing BottomSheet. No over-engineering. |
+| V. Dependency Discipline | PASS | No new dependencies required. |
+| VI. Accessibility | PASS | Reuses accessible BottomSheet component. Banner uses semantic HTML + ARIA. |
+
+**Gate result: PASS** — no violations.
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/016-cancel-event/
+├── plan.md              # This file
+├── spec.md              # Feature specification
+├── research.md          # Phase 0 output — design decisions
+├── data-model.md        # Phase 1 output — entity changes
+├── quickstart.md        # Phase 1 output — implementation overview
+├── contracts/           # Phase 1 output — API contract additions
+│   └── patch-event-endpoint.yaml
+└── tasks.md             # Phase 2 output (/speckit.tasks command)
+```
+
+### Source Code (repository root)
+
+```text
+backend/
+├── src/main/java/de/fete/
+│   ├── domain/model/Event.java                          # + cancelled, cancellationReason, cancel()
+│   ├── application/service/EventService.java            # + CancelEventUseCase implementation
+│   ├── adapter/in/web/EventController.java              # + cancelEvent endpoint
+│   └── adapter/out/persistence/
+│       ├── EventJpaEntity.java                          # + cancelled, cancellation_reason columns
+│       └── EventPersistenceAdapter.java                 # + mapper updates
+├── src/main/resources/
+│   ├── openapi/api.yaml                                 # + cancel endpoint, request/response schemas
+│   └── db/changelog/004-add-cancellation-columns.xml    # New migration
+└── src/test/java/de/fete/                               # Unit + integration tests
+
+frontend/
+├── src/
+│   └── views/EventDetailView.vue                        # + cancel button, bottom sheet, banner
+└── e2e/                                                 # E2E tests for both user stories
+```
+
+**Structure Decision**: Web application (Option 2) — matches existing project layout with `backend/` and `frontend/` at repository root.
+
+## Complexity Tracking
+
+> No violations — table not applicable.

specs/016-cancel-event/quickstart.md

@@ -0,0 +1,48 @@
+# Quickstart: Cancel Event
+
+**Feature Branch**: `016-cancel-event`
+
+## What This Feature Does
+
+Adds the ability for an organizer to permanently cancel an event. Cancelled events display a red banner to visitors and block new RSVPs.
+
+## Implementation Scope
+
+### Backend
+1. **Liquibase migration** (003): Add `cancelled` (boolean) and `cancellation_reason` (varchar 2000) columns to `events` table.
+2. **Domain model**: Extend `Event.java` with `cancelled` and `cancellationReason` fields + `cancel()` method.
+3. **JPA entity**: Extend `EventJpaEntity.java` with matching columns and mapper updates.
+4. **OpenAPI spec**: Add `PATCH /events/{eventToken}` endpoint + extend `GetEventResponse` with cancellation fields.
+5. **Use case**: New `CancelEventUseCase` interface + implementation in `EventService`.
+6. **Controller**: Implement `cancelEvent` in `EventController`.
+7. **RSVP guard**: Add cancelled check to RSVP creation (return 409).
+
+### Frontend
+1. **Cancel bottom sheet**: Add cancel button (organizer-only) + bottom sheet with textarea and confirm button in `EventDetailView.vue`.
+2. **Cancellation banner**: Red banner at top of event detail when `cancelled === true`.
+3. **RSVP hiding**: Hide `RsvpBar` when event is cancelled.
+4. **API client**: Use generated types from updated OpenAPI spec.
+
+### Testing
+1. **Backend unit tests**: Cancel use case, RSVP rejection on cancelled events.
+2. **Backend integration tests**: Full cancel flow via API.
+3. **Frontend unit tests**: Cancel bottom sheet, banner display, RSVP hiding.
+4. **E2E tests**: Organizer cancels event, attendee sees cancelled event.
+
+## Key Files to Modify
+
+| File | Change |
+|------|--------|
+| `backend/src/main/resources/openapi/api.yaml` | New endpoint + schema extensions |
+| `backend/src/main/resources/db/changelog/` | New changeset 003 |
+| `backend/src/main/java/de/fete/domain/model/Event.java` | Add cancelled fields + cancel() |
+| `backend/src/main/java/de/fete/adapter/out/persistence/EventJpaEntity.java` | Add columns |
+| `backend/src/main/java/de/fete/application/service/EventService.java` | Implement cancel |
+| `backend/src/main/java/de/fete/adapter/in/web/EventController.java` | Implement endpoint |
+| `frontend/src/views/EventDetailView.vue` | Cancel button, bottom sheet, banner |
+
+## Prerequisites
+
+- Existing RSVP bottom sheet pattern (already implemented)
+- Organizer token stored in localStorage (already implemented)
+- `BottomSheet.vue` component (already exists)

specs/016-cancel-event/research.md

@@ -0,0 +1,87 @@
+# Research: Cancel Event
+
+**Feature Branch**: `016-cancel-event` | **Date**: 2026-03-12
+
+## Decision 1: API Endpoint Design
+
+**Decision**: Use `PATCH /events/{eventToken}` with organizer token and cancellation fields in request body.
+
+**Rationale**:
+- PATCH is standard REST for partial resource updates — cancellation is a state change on the event resource.
+- The event is not removed, so DELETE is not appropriate. The event remains visible with a cancellation banner.
+- The organizer token is sent in the request body to keep it out of URL/query strings and server access logs.
+- Request body: `{ "organizerToken": "uuid", "cancelled": true, "cancellationReason": "optional string" }`.
+- Response: `204 No Content` on success.
+- Error responses: `404` if event not found, `403` if organizer token is wrong, `409` if already cancelled.
+- Currently the only supported PATCH operation is cancellation. The endpoint validates that `cancelled` is `true` and rejects requests that attempt to set other fields.
+
+**Alternatives considered**:
+- `POST /events/{eventToken}/cancel` — rejected because a dedicated sub-resource endpoint is RPC-style, not RESTful. PATCH on the resource itself is the standard approach.
+- `DELETE /events/{eventToken}` — rejected because the event is not deleted, it remains visible with a cancellation banner.
+
+## Decision 2: Database Schema Extension
+
+**Decision**: Add two columns to the `events` table: `cancelled BOOLEAN NOT NULL DEFAULT FALSE` and `cancellation_reason VARCHAR(2000)`.
+
+**Rationale**:
+- Boolean flag is the simplest representation of the cancelled state.
+- 2000 chars matches the existing description field limit — consistent and generous.
+- DEFAULT FALSE ensures backward compatibility with existing rows.
+- A Liquibase changeset (003) adds both columns.
+
+**Alternatives considered**:
+- Enum status field (`ACTIVE`, `CANCELLED`) — rejected as over-engineering for a binary state with no other planned transitions.
+- Separate cancellation table — rejected as unnecessary complexity for two columns.
+
+## Decision 3: RSVP Blocking on Cancelled Events
+
+**Decision**: The RSVP creation endpoint (`POST /events/{eventToken}/rsvps`) checks the event's cancelled flag and returns `409 Conflict` if the event is cancelled.
+
+**Rationale**:
+- Server-side enforcement is required (FR-006) — frontend hiding the button is not sufficient.
+- 409 Conflict is semantically correct: the request conflicts with the current state of the resource.
+- Existing RSVPs are preserved (FR-007) — no cascade or cleanup needed.
+
+**Alternatives considered**:
+- 400 Bad Request — rejected because the request itself is well-formed; the conflict is with resource state.
+- 422 Unprocessable Entity — rejected because the issue is not validation but state conflict.
+
+## Decision 4: Frontend Cancel Bottom Sheet
+
+**Decision**: Reuse the existing `BottomSheet.vue` component. Add cancel-specific content (textarea + confirm button) directly in `EventDetailView.vue`, similar to how the RSVP form is embedded.
+
+**Rationale**:
+- The spec explicitly requires the bottom sheet pattern consistent with RSVP flow (FR-002).
+- `BottomSheet.vue` is already a generic, accessible, glassmorphism-styled container.
+- No need for a separate component — the cancel form is simple (textarea + button + error message).
+- Error handling follows the same pattern as RSVP: inline error in the sheet, button re-enabled.
+
+**Alternatives considered**:
+- Separate `CancelBottomSheet.vue` component — rejected as unnecessary extraction for a simple form.
+- ConfirmDialog instead of BottomSheet — rejected because spec explicitly requires bottom sheet.
+
+## Decision 5: Organizer Token Authorization
+
+**Decision**: The cancel endpoint receives the organizer token in the request body. The frontend retrieves it from localStorage via `useEventStorage.getOrganizerToken()`.
+
+**Rationale**:
+- Consistent with how organizer identity works throughout the app — token-based, no auth system.
+- The organizer token is already stored in localStorage when the event is created.
+- Body parameter keeps the token out of URL/query strings and server access logs.
+
+**Alternatives considered**:
+- Authorization header — rejected because there's no auth system; the organizer token is not a session token.
+- Query parameter — rejected to keep token out of server logs (same reason the attendee endpoint should eventually be migrated away from query params).
+
+## Decision 6: GetEventResponse Extension
+
+**Decision**: Add `cancelled: boolean` and `cancellationReason: string | null` to the `GetEventResponse` schema.
+
+**Rationale**:
+- The frontend needs to know whether an event is cancelled to show the banner and hide RSVP buttons.
+- Both fields are always returned (no separate endpoint needed).
+- `cancelled` defaults to `false` for existing events.
+
+**Alternatives considered**:
+- Separate endpoint for cancellation status — rejected as unnecessary network overhead.
+- Only return cancellation info for cancelled events — rejected because the frontend needs the boolean regardless to decide UI state.

specs/016-cancel-event/spec.md

@@ -0,0 +1,97 @@
+# Feature Specification: Cancel Event
+
+**Feature Branch**: `016-cancel-event`
+**Created**: 2026-03-12
+**Status**: Draft
+**Input**: User description: "As an organizer, I want to cancel an event so that attendees know the event will not take place"
+
+## User Scenarios & Testing *(mandatory)*
+
+### User Story 1 - Organizer Cancels an Event (Priority: P1)
+
+An organizer navigates to their event page (identified by having the organizer token). They decide to cancel the event. They tap a "Cancel Event" button, which opens a bottom sheet (visually similar to the attend/RSVP flow). The bottom sheet contains a text area for an optional cancellation reason and a confirm button. After confirming, the event is permanently marked as cancelled. This action is irreversible.
+
+**Why this priority**: This is the core action of the feature. Without it, nothing else matters.
+
+**Independent Test**: Can be fully tested by viewing the event with the organizer token, tapping cancel, optionally entering a reason, and confirming. The event's cancelled state persists on reload.
+
+**Acceptance Scenarios**:
+
+1. **Given** an active event viewed by someone who has the organizer token, **When** the organizer taps "Cancel Event", **Then** a bottom sheet opens with a text area and a confirm button.
+2. **Given** the cancel bottom sheet is open, **When** the organizer enters a cancellation reason and taps the confirm button, **Then** the event is marked as cancelled with the provided reason.
+3. **Given** the cancel bottom sheet is open, **When** the organizer taps confirm without entering a reason, **Then** the event is marked as cancelled without a reason.
+4. **Given** a cancelled event, **When** the organizer revisits the event page, **Then** the event remains cancelled (irreversible).
+5. **Given** the cancel bottom sheet is open, **When** the organizer taps confirm and the API call fails, **Then** an error message is displayed in the bottom sheet, the sheet remains open, and the confirm button is re-enabled for retry.
+
+---
+
+### User Story 2 - Attendee Sees Cancelled Event (Priority: P1)
+
+An attendee (or any visitor) opens the event detail page for a cancelled event. A prominent red banner is displayed at the top of the page, clearly communicating that the event has been cancelled. If the organizer provided a cancellation reason, it is shown within the banner. The RSVP buttons are hidden — no new RSVPs can be submitted.
+
+**Why this priority**: Equal to P1 because the cancellation must be visible to attendees for the feature to deliver value. Without this, cancelling has no effect from the attendee's perspective.
+
+**Independent Test**: Can be tested by viewing a cancelled event's detail page and verifying the banner appears, the reason is displayed (if provided), and RSVP buttons are hidden.
+
+**Acceptance Scenarios**:
+
+1. **Given** a cancelled event with a cancellation reason, **When** a visitor opens the event detail page, **Then** a prominent red banner is displayed showing that the event is cancelled along with the reason.
+2. **Given** a cancelled event without a cancellation reason, **When** a visitor opens the event detail page, **Then** a prominent red banner is displayed showing that the event is cancelled, without a reason text.
+3. **Given** a cancelled event, **When** a visitor opens the event detail page, **Then** the RSVP buttons are not visible.
+4. **Given** a cancelled event, **When** a visitor opens the event detail page, **Then** all other event details (title, date, location, description) remain visible.
+
+---
+
+### Edge Cases
+
+- What happens when the organizer tries to cancel an already cancelled event? The cancel button is not available on an already cancelled event.
+- What happens to existing RSVPs when an event is cancelled? They are preserved as-is but no new RSVPs can be submitted.
+- What happens when the event is both cancelled and expired? The auto-delete mechanism (feature 013) continues to apply normally — cancelled events are deleted on the same schedule as non-cancelled events.
+- What happens when the cancellation API call fails (network error, server error)? The bottom sheet remains open, a visible error message is displayed within the sheet, and the confirm button is re-enabled so the organizer can retry.
+- How are cancelled events displayed in the event list? Out of scope for this feature — the event list view is not affected.
+
+## Requirements *(mandatory)*
+
+### Functional Requirements
+
+- **FR-001**: System MUST allow the organizer to cancel an event via the organizer view.
+- **FR-002**: The cancellation interaction MUST use a bottom sheet pattern consistent with the existing RSVP/attend flow.
+- **FR-003**: The bottom sheet MUST contain a text area for an optional cancellation reason and a confirm button.
+- **FR-004**: Cancellation MUST be irreversible — once cancelled, there is no way to undo it.
+- **FR-005**: System MUST store a cancelled flag and an optional cancellation reason for the event.
+- **FR-006**: System MUST NOT allow new RSVPs for a cancelled event.
+- **FR-007**: System MUST preserve existing RSVPs when an event is cancelled.
+- **FR-008**: The event detail page MUST display a prominent red banner for cancelled events.
+- **FR-009**: The banner MUST include the cancellation reason when one was provided.
+- **FR-010**: The RSVP buttons MUST be hidden on a cancelled event's detail page.
+- **FR-011**: All other event information MUST remain visible on a cancelled event's detail page.
+- **FR-012**: The cancel button MUST NOT be shown on an already cancelled event.
+- **FR-013**: There MUST be no push notifications, emails, or any active notification mechanism for cancellations.
+- **FR-014**: If the cancellation API call fails, the bottom sheet MUST remain open, display an error message, and allow the organizer to retry.
+- **FR-015**: Changes to the event list view for cancelled events are explicitly OUT OF SCOPE for this feature.
+
+### Key Entities
+
+- **Event** (extended): Gains a cancelled state (boolean) and an optional cancellation reason (free text). An event can transition from active to cancelled, but not back.
+
+## Success Criteria *(mandatory)*
+
+### Measurable Outcomes
+
+- **SC-001**: Organizer can cancel an event in under 30 seconds (open bottom sheet, optionally type reason, confirm).
+- **SC-002**: 100% of visitors to a cancelled event's detail page see the cancellation banner without scrolling.
+- **SC-003**: 0% of cancelled events accept new RSVPs.
+- **SC-004**: Existing RSVPs are fully preserved after cancellation (no data loss).
+
+## Clarifications
+
+### Session 2026-03-12
+
+- Q: How should cancelled events appear in the event list view? → A: Out of scope for this feature — event list view is not affected.
+- Q: What should happen when the cancellation API call fails? → A: Error message displayed in the bottom sheet, sheet remains open, confirm button re-enabled for retry.
+
+## Assumptions
+
+- The bottom sheet component pattern already exists from the RSVP/attend flow and can be reused.
+- The cancellation reason has a maximum length of 2000 characters (consistent with the event description field).
+- The cancellation reason is plain text (no formatting or markup).

specs/016-cancel-event/tasks.md

@@ -0,0 +1,96 @@
+# Tasks: Cancel Event
+
+**Input**: Design documents from `/specs/016-cancel-event/`
+**Prerequisites**: plan.md, spec.md, research.md, data-model.md, contracts/patch-event-endpoint.yaml
+
+**Tests**: Included — constitution mandates TDD (tests before implementation) and E2E for every frontend user story.
+
+**Organization**: Tasks grouped by user story. Both stories are P1 but US2 depends on US1's backend work.
+
+## Format: `[ID] [P?] [Story] Description`
+
+- **[P]**: Can run in parallel (different files, no dependencies)
+- **[Story]**: Which user story this task belongs to (e.g., US1, US2)
+- Include exact file paths in descriptions
+
+---
+
+## Phase 1: Setup (Shared Infrastructure)
+
+**Purpose**: OpenAPI spec, database migration, and domain model changes that both user stories depend on.
+
+- [X] T001 Update OpenAPI spec with PATCH endpoint on `/events/{eventToken}` (organizerToken as query param), PatchEventRequest schema (`cancelled`, `cancellationReason`), and extend GetEventResponse with `cancelled`/`cancellationReason` fields in `backend/src/main/resources/openapi/api.yaml`
+- [X] T002 Add Liquibase changeset 004 adding `cancelled` (BOOLEAN NOT NULL DEFAULT FALSE) and `cancellation_reason` (VARCHAR 2000) columns to `events` table in `backend/src/main/resources/db/changelog/004-add-cancellation-columns.xml` and register it in `db.changelog-master.xml`
+- [X] T003 [P] Extend domain model `Event.java` with `cancelled`, `cancellationReason` fields and `cancel(String reason)` method (throws `EventAlreadyCancelledException`). Create `EventAlreadyCancelledException` in `backend/src/main/java/de/fete/domain/model/`. Domain model: `backend/src/main/java/de/fete/domain/model/Event.java`
+- [X] T004 [P] Extend JPA entity `EventJpaEntity.java` with `cancelled` and `cancellation_reason` columns and update mapper in `backend/src/main/java/de/fete/adapter/out/persistence/EventPersistenceAdapter.java`
+- [X] T005 Regenerate frontend TypeScript types from updated OpenAPI spec via `cd frontend && npm run generate:api`
+
+**Checkpoint**: Schema, migration, and domain model ready. Both user stories can now proceed.
+
+---
+
+## Phase 2: User Story 1 — Organizer Cancels an Event (Priority: P1) MVP
+
+**Goal**: Organizer can cancel an event via a bottom sheet with optional reason. Cancellation is irreversible and persists on reload.
+
+**Independent Test**: View event with organizer token, tap cancel, optionally enter reason, confirm. Event remains cancelled on reload.
+
+### Tests for User Story 1
+
+> **Write these tests FIRST — ensure they FAIL before implementation**
+
+- [X] ~~T006~~ Removed (EventTest.java unnecessary — cancel() tested via service/integration tests)
+- [X] T007 [P] [US1] Write unit test for cancel use case in EventService (delegates to domain, saves, 403/404/409 cases) in `backend/src/test/java/de/fete/application/service/EventServiceCancelTest.java`
+- [X] T008 [P] [US1] Write integration tests for `PATCH /events/{eventToken}` endpoint (204 success, 403 wrong token, 404 not found, 409 already cancelled) in `backend/src/test/java/de/fete/adapter/in/web/EventControllerIntegrationTest.java`
+- [X] T009 [P] [US1] Write E2E test: organizer opens cancel bottom sheet, enters reason, confirms — event shows as cancelled on reload in `frontend/e2e/cancel-event.spec.ts`
+- [X] T010 [P] [US1] Write E2E test: organizer cancels without reason — event shows as cancelled in `frontend/e2e/cancel-event.spec.ts`
+- [X] T011 [P] [US1] Write E2E test: cancel API fails — error displayed in bottom sheet, button re-enabled for retry in `frontend/e2e/cancel-event.spec.ts`
+
+### Implementation for User Story 1
+
+- [X] T012 [US1] Create `UpdateEventUseCase` interface in `backend/src/main/java/de/fete/domain/port/in/UpdateEventUseCase.java`
+- [X] T013 [US1] Implement cancel logic in `EventService.java` — load event, verify organizer token, call `event.cancel(reason)`, persist in `backend/src/main/java/de/fete/application/service/EventService.java`
+- [X] T014 [US1] Implement `patchEvent` endpoint in `EventController.java` — PATCH handler, query param organizerToken, request body binding, error mapping (403/404/409) in `backend/src/main/java/de/fete/adapter/in/web/EventController.java`
+- [X] T015 [US1] Add cancel button (visible only when organizer token exists and event not cancelled — covers FR-012) and cancel bottom sheet (textarea with 2000 char limit + confirm button + inline error) to `frontend/src/views/EventDetailView.vue`
+- [X] T016 [US1] Wire cancel bottom sheet confirm action to `PATCH /events/{eventToken}` API call via openapi-fetch, handle success (reload event data) and error (show inline message, re-enable button) in `frontend/src/views/EventDetailView.vue`
+
+**Checkpoint**: Organizer can cancel an event. All US1 acceptance scenarios pass.
+
+---
+
+## Phase 3: User Story 2 — Attendee Sees Cancelled Event (Priority: P1)
+
+**Goal**: Visitors see a prominent red cancellation banner on cancelled events. RSVP buttons are hidden. All other event details remain visible.
+
+**Independent Test**: View a cancelled event's detail page — banner visible (with reason if provided), RSVP buttons hidden, other details intact.
+
+### Tests for User Story 2
+
+> **Write these tests FIRST — ensure they FAIL before implementation**
+
+- [X] ~~T017~~ Removed (RsvpServiceCancelledTest unnecessary — covered by integration test)
+- [X] T018 [P] [US2] Write integration test for `POST /events/{eventToken}/rsvps` returning 409 when event is cancelled in `backend/src/test/java/de/fete/adapter/in/web/EventControllerIntegrationTest.java`
+- [X] T019 [P] [US2] Write E2E test: visitor sees red banner with cancellation reason on cancelled event in `frontend/e2e/cancelled-event-visitor.spec.ts`
+- [X] T020 [P] [US2] Write E2E test: visitor sees red banner without reason when no reason was provided in `frontend/e2e/cancelled-event-visitor.spec.ts`
+- [X] T021 [P] [US2] Write E2E test: RSVP buttons hidden on cancelled event, other details remain visible in `frontend/e2e/cancelled-event-visitor.spec.ts`
+
+### Implementation for User Story 2
+
+- [X] T022 [US2] Add cancelled-event guard to RSVP creation — check `event.isCancelled()`, return 409 Conflict in `backend/src/main/java/de/fete/application/service/RsvpService.java`
+- [X] T023 [US2] Add cancellation banner component/section (red, prominent, includes reason if present, WCAG AA contrast) to `frontend/src/views/EventDetailView.vue`
+- [X] T024 [US2] Hide RSVP buttons (`RsvpBar` or equivalent) when `event.cancelled === true` in `frontend/src/views/EventDetailView.vue`
+- [X] ~~T025~~ Merged into T015 (cancel button v-if already handles FR-012)
+
+**Checkpoint**: Both user stories fully functional. All acceptance scenarios pass.
+
+---
+
+## Phase 4: Polish & Cross-Cutting Concerns
+
+**Purpose**: Validation, edge cases, and final cleanup.
+
+- [X] T026 Verify cancellationReason max length (2000 chars) is enforced at API level (OpenAPI `maxLength`), domain level in `Event.java`, and UI level (textarea maxlength/counter)
+- [X] T027 Run full backend test suite (`cd backend && ./mvnw verify`) and fix any failures
+- [X] T028 Run full frontend test suite (`cd frontend && npm run test:unit`) and fix any failures
+- [X] T029 Run E2E tests (`cd frontend && npx playwright test`) and fix any failures
+- [X] T030 Run backend checkstyle (`cd backend && ./mvnw checkstyle:check`) and fix violations