Merge pull request #129 from ulsklyc/feat/multi-assignment

feat: multi-person assignment for tasks and calendar events (v0.48.0)

CHANGELOG.md

@@ -7,6 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.48.0] - 2026-05-06
+
+### Added
+- **Multi-person assignment**: tasks and calendar events can now be assigned to multiple family members simultaneously. A new `task_assignments` / `event_assignments` join table (migration v32) stores the assignments; existing single-user data is migrated automatically.
+- **Avatar stack**: task cards, Kanban cards, and the calendar agenda view display stacked avatars for all assigned users (up to 3 visible, then a `+N` overflow badge).
+- **Shared UserMultiSelect component** (`public/components/user-multi-select.js`): checkbox-based dropdown used in both the task modal and the calendar event modal; replaces the previous single-user `<select>`.
+- **`assigned_to` filter extended**: `GET /api/v1/tasks?assigned_to=<id>` and `GET /api/v1/calendar?assigned_to=<id>` now match any task/event where the user appears in the assignments list.
+
+### Changed
+- API response for tasks and calendar events now includes `assigned_users: [{id, display_name, color}]` array alongside the legacy `assigned_to` / `assigned_name` / `assigned_color` fields.
+- Recurring task completion copies all multi-person assignments to the new recurring instance.
+
 ## [0.47.5] - 2026-05-06
 
 ### Changed

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "oikos",
-  "version": "0.47.4",
+  "version": "0.48.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "oikos",
-      "version": "0.47.4",
+      "version": "0.48.0",
       "license": "MIT",
       "dependencies": {
         "bcrypt": "^6.0.0",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "oikos",
-  "version": "0.47.5",
+  "version": "0.48.0",
   "description": "Self-hosted family planner - calendar, tasks, shopping, meal planning, budget and more. Private, open-source, no subscription.",
   "main": "server/index.js",
   "type": "module",
@@ -13,6 +13,7 @@
     "setup": "node --import dotenv/config setup.js",
     "test:db": "node --experimental-sqlite test-db.js",
     "test:dashboard": "node --experimental-sqlite test-dashboard.js",
+    "test:multi-assignment": "node --experimental-sqlite test-multi-assignment.js",
     "test:tasks": "node --experimental-sqlite test-tasks.js",
     "test:shopping": "node --experimental-sqlite test-shopping.js",
     "test:meals": "node --experimental-sqlite test-meals.js",
@@ -29,7 +30,7 @@
     "test:backup-scheduler": "node --experimental-sqlite test-backup-scheduler.js",
     "test:caldav": "node --experimental-sqlite test-caldav-sync.js",
     "test:carddav": "node --experimental-sqlite test-carddav.js",
-    "test": "node --experimental-sqlite test-db.js && node --experimental-sqlite test-dashboard.js && node --experimental-sqlite test-tasks.js && node --experimental-sqlite test-shopping.js && node --experimental-sqlite test-meals.js && node --experimental-sqlite test-calendar.js && node --experimental-sqlite test-notes-contacts-budget.js && npm run test:ux-utils && npm run test:modal-utils && npm run test:reminders && npm run test:api && npm run test:ics-parser && npm run test:ics-sub && npm run test:setup && npm run test:kitchen-tabs && npm run test:backup-scheduler && npm run test:caldav && npm run test:carddav"
+    "test": "node --experimental-sqlite test-db.js && node --experimental-sqlite test-dashboard.js && node --experimental-sqlite test-tasks.js && node --experimental-sqlite test-multi-assignment.js && node --experimental-sqlite test-shopping.js && node --experimental-sqlite test-meals.js && node --experimental-sqlite test-calendar.js && node --experimental-sqlite test-notes-contacts-budget.js && npm run test:ux-utils && npm run test:modal-utils && npm run test:reminders && npm run test:api && npm run test:ics-parser && npm run test:ics-sub && npm run test:setup && npm run test:kitchen-tabs && npm run test:backup-scheduler && npm run test:caldav && npm run test:carddav"
   },
   "dependencies": {
     "bcrypt": "^6.0.0",

public/components/user-multi-select.js

@@ -0,0 +1,124 @@
+/**
+ * Modul: User Multi-Select
+ * Zweck: Wiederverwendbare Mehrfachauswahl-Komponente für Benutzer (Tasks & Kalender)
+ * Abhängigkeiten: public/utils/html.js, public/i18n.js
+ */
+
+import { esc } from '/utils/html.js';
+import { t } from '/i18n.js';
+
+/**
+ * Rendert einen Avatar-Stack für mehrere zugewiesene Benutzer.
+ * @param {Array<{id, display_name, color}>} users
+ * @param {object} opts
+ * @param {number} [opts.size=28]      Avatar-Größe in px
+ * @param {number} [opts.maxVisible=3] Maximale Avatare vor "+N"-Anzeige
+ * @returns {string} HTML-String
+ */
+export function renderAvatarStack(users, { size = 28, maxVisible = 3 } = {}) {
+  if (!users?.length) return '';
+  const visible = users.slice(0, maxVisible);
+  const overflow = users.length - visible.length;
+  const fs = Math.round(size * 0.4);
+  const avatars = visible.map((u) => {
+    const initials = (u.display_name ?? '')
+      .split(' ')
+      .map((w) => w[0] ?? '')
+      .join('')
+      .toUpperCase()
+      .slice(0, 2);
+    return `<span class="avatar-stack__item"
+      style="width:${size}px;height:${size}px;font-size:${fs}px;background-color:${esc(u.color ?? '#8E8E93')}"
+      title="${esc(u.display_name ?? '')}">
+      ${esc(initials)}
+    </span>`;
+  });
+  if (overflow > 0) {
+    avatars.push(`<span class="avatar-stack__item avatar-stack__overflow"
+      style="width:${size}px;height:${size}px;font-size:${fs}px"
+      title="${overflow} ${t('userMultiSelect.moreUsers')}">+${overflow}</span>`);
+  }
+  return `<span class="avatar-stack">${avatars.join('')}</span>`;
+}
+
+/**
+ * Rendert das Multi-Select-Widget als Dropdown-Checkbox-Liste.
+ * @param {Array<{id, display_name, avatar_color}>} allUsers  Alle verfügbaren Benutzer
+ * @param {number[]} selectedIds                               Bereits ausgewählte IDs
+ * @param {string}   inputName                                 Name-Attribut des Widgets
+ * @param {string}   labelKey                                  i18n-Schlüssel für das Label
+ * @returns {string} HTML-String
+ */
+export function renderUserMultiSelect(allUsers, selectedIds, inputName, labelKey) {
+  const selectedSet = new Set(selectedIds ?? []);
+  const items = allUsers.map((u) => {
+    const checked = selectedSet.has(u.id) ? 'checked' : '';
+    const initials = (u.display_name ?? '')
+      .split(' ')
+      .map((w) => w[0] ?? '')
+      .join('')
+      .toUpperCase()
+      .slice(0, 2);
+    return `
+      <label class="user-ms__option">
+        <input type="checkbox" class="user-ms__checkbox" value="${u.id}" ${checked}
+               data-ms-input="${esc(inputName)}">
+        <span class="user-ms__avatar" style="background-color:${esc(u.avatar_color ?? '#8E8E93')}">
+          ${esc(initials)}
+        </span>
+        <span class="user-ms__name">${esc(u.display_name)}</span>
+      </label>`;
+  });
+
+  const noneLabel = t('userMultiSelect.nobody');
+  return `
+    <div class="user-ms" data-ms-name="${esc(inputName)}">
+      <label class="label">${t(labelKey)}</label>
+      <div class="user-ms__options">
+        <label class="user-ms__option">
+          <input type="checkbox" class="user-ms__checkbox user-ms__none" value=""
+                 data-ms-input="${esc(inputName)}" ${selectedSet.size === 0 ? 'checked' : ''}>
+          <span class="user-ms__avatar user-ms__avatar--none">–</span>
+          <span class="user-ms__name">${noneLabel}</span>
+        </label>
+        ${items.join('')}
+      </div>
+    </div>`;
+}
+
+/**
+ * Liest die ausgewählten User-IDs aus einem gerenderten Multi-Select-Widget.
+ * @param {Element} container  DOM-Element, das das Widget enthält
+ * @param {string}  inputName  Name-Attribut des Widgets
+ * @returns {number[]}
+ */
+export function getSelectedUserIds(container, inputName) {
+  const checkboxes = container.querySelectorAll(
+    `[data-ms-input="${CSS.escape(inputName)}"]:not(.user-ms__none):checked`
+  );
+  return Array.from(checkboxes).map((cb) => Number(cb.value)).filter(Boolean);
+}
+
+/**
+ * Bindet die Checkbox-Logik:
+ * - "Niemand" deselektiert alle anderen
+ * - Andere Auswahl deselektiert "Niemand"
+ * @param {Element} container
+ * @param {string}  inputName
+ */
+export function bindUserMultiSelect(container, inputName) {
+  const widget = container.querySelector(`.user-ms[data-ms-name="${CSS.escape(inputName)}"]`);
+  if (!widget) return;
+
+  widget.addEventListener('change', (e) => {
+    const cb = e.target;
+    if (!cb.matches('.user-ms__checkbox')) return;
+
+    if (cb.classList.contains('user-ms__none') && cb.checked) {
+      widget.querySelectorAll('.user-ms__checkbox:not(.user-ms__none)').forEach((c) => { c.checked = false; });
+    } else if (!cb.classList.contains('user-ms__none') && cb.checked) {
+      const none = widget.querySelector('.user-ms__none');
+      if (none) none.checked = false;
+    }
+  });
+}

public/index.html

@@ -44,6 +44,7 @@
   <link rel="stylesheet" href="/styles/glass.css" />
   <link rel="stylesheet" href="/styles/sub-tabs.css" />
   <link rel="stylesheet" href="/styles/kitchen-tabs.css" />
+  <link rel="stylesheet" href="/styles/user-multi-select.css" />
   <link rel="stylesheet" href="/styles/login.css" />
 
   <!-- Lucide Icons (lokal, v0.469.0) -->

public/locales/de.json

@@ -1293,5 +1293,9 @@
     "dropzoneTitle": "Datei hier ablegen oder klicken",
     "dropzoneHint": "Ziehe eine Datei in diesen Bereich oder nutze die Dateiauswahl.",
     "selectedFileLabel": "Ausgewählt: {{name}}"
+  },
+  "userMultiSelect": {
+    "nobody": "- Niemand -",
+    "moreUsers": "weitere"
   }
 }

public/pages/calendar.js

@@ -11,6 +11,7 @@ import { stagger } from '/utils/ux.js';
 import { t, formatDate as formatPreferredDate, formatTime, dateInputPlaceholder, formatDateInput, parseDateInput, isDateInputValid, formatTimeInput, parseTimeInput, timeInputPlaceholder } from '/i18n.js';
 import { esc, fmtLocation } from '/utils/html.js';
 import { refresh as refreshReminders } from '/reminders.js';
+import { renderUserMultiSelect, getSelectedUserIds, bindUserMultiSelect, renderAvatarStack } from '/components/user-multi-select.js';
 
 // --------------------------------------------------------
 // Konstanten
@@ -1032,11 +1033,8 @@ function renderAgendaEvent(ev) {
     : formatTime(ev.start_datetime)
       + (ev.end_datetime ? ` – ${formatTime(ev.end_datetime)} ${t('calendar.timeSuffix')}`.trimEnd() : ` ${t('calendar.timeSuffix')}`.trimEnd());
 
-  const initials = ev.assigned_name
-    ? ev.assigned_name.split(' ').map((w) => w[0]).join('').toUpperCase().slice(0, 2)
-    : '';
-
   const displayColor = ev.cal_color || ev.color;
+  const assignedUsers = ev.assigned_users ?? [];
   return `
     <div class="agenda-event" data-id="${ev.id}">
       <div class="agenda-event__color" style="background-color:${esc(displayColor)};"></div>
@@ -1046,11 +1044,7 @@ function renderAgendaEvent(ev) {
           <span>${timeStr}</span>
           ${ev.location ? `<span>📍 ${esc(fmtLocation(ev.location))}</span>` : ''}
           ${ev.cal_name ? `<span class="event-cal-label" style="--cal-color:${esc(displayColor)}">${esc(ev.cal_name)}</span>` : ''}
-          ${ev.assigned_name ? `
+          ${assignedUsers.length ? `<span class="agenda-event__assigned">${renderAvatarStack(assignedUsers, { size: 20, maxVisible: 3 })}</span>` : ''}
-            <span class="agenda-event__assigned">
-              <span class="agenda-event__avatar" style="background-color:${esc(ev.assigned_color || '#8E8E93')}">${initials}</span>
-              ${esc(ev.assigned_name)}
-            </span>` : ''}
         </div>
       </div>
     </div>
@@ -1328,6 +1322,7 @@ function openEventModal({ mode, event = null, date = null, reminder = null }) {
     onSave(panel) {
       // RRULE-Events binden
       bindRRuleEvents(panel, 'event');
+      bindUserMultiSelect(panel, 'cal_assigned');
 
       const selectedColor = isEdit ? (event?.color || EVENT_COLORS[0]) : EVENT_COLORS[0];
 
@@ -1573,12 +1568,9 @@ function buildEventModalContent({ mode, event, date, reminder = null }) {
       </div>
     </div>`).join('');
 
-  const userOpts = [
+  const selectedUserIds = isEdit
-    `<option value="">${t('calendar.assignedNobody')}</option>`,
+    ? (event.assigned_users?.map((u) => u.id) ?? (event.assigned_to ? [event.assigned_to] : []))
-    ...state.users.map((u) =>
+    : [];
-      `<option value="${u.id}" ${isEdit && event.assigned_to === u.id ? 'selected' : ''}>${esc(u.display_name)}</option>`
-    ),
-  ].join('');
 
   return `
     <div class="event-title-picker">
@@ -1660,8 +1652,7 @@ function buildEventModalContent({ mode, event, date, reminder = null }) {
     </div>
 
     <div class="form-group">
-      <label class="form-label" for="modal-assigned">${t('calendar.assignedLabel')}</label>
+      ${renderUserMultiSelect(state.users, selectedUserIds, 'cal_assigned', 'calendar.assignedLabel')}
-      <select class="form-input" id="modal-assigned">${userOpts}</select>
     </div>
 
     <div class="form-group">
@@ -1738,7 +1729,7 @@ async function saveEvent(overlay, mode, eventId, existingReminder = null, attach
   const color   = overlay.querySelector('.color-swatch--active')?.dataset.color || EVENT_COLORS[0];
   const icon    = eventIconName(overlay.querySelector('#modal-icon')?.value);
   const location    = overlay.querySelector('#modal-location').value.trim() || null;
-  const assigned_to = overlay.querySelector('#modal-assigned').value || null;
+  const assigned_to = getSelectedUserIds(overlay, 'cal_assigned');
   const description = overlay.querySelector('#modal-description').value.trim() || null;
 
   let start_datetime, end_datetime;
@@ -1815,7 +1806,7 @@ async function saveEvent(overlay, mode, eventId, existingReminder = null, attach
     const body = {
       title, description, start_datetime, end_datetime,
       all_day: allday ? 1 : 0,
-      location, color, icon, assigned_to: assigned_to ? parseInt(assigned_to, 10) : null,
+      location, color, icon, assigned_to,
       recurrence_rule: rrule.recurrence_rule,
       attachment_name: attachmentPayload.name,
       attachment_mime: attachmentPayload.mime,

public/pages/tasks.js

@@ -11,6 +11,7 @@ import { stagger, vibrate } from '/utils/ux.js';
 import { t, formatDate, formatTime, dateInputPlaceholder, formatDateInput, parseDateInput, isDateInputValid, formatTimeInput, parseTimeInput, timeInputPlaceholder } from '/i18n.js';
 import { esc } from '/utils/html.js';
 import { refresh as refreshReminders } from '/reminders.js';
+import { renderUserMultiSelect, getSelectedUserIds, bindUserMultiSelect, renderAvatarStack } from '/components/user-multi-select.js';
 
 // --------------------------------------------------------
 // Konstanten
@@ -203,11 +204,7 @@ function renderTaskCard(task, opts = {}) {
           </div>
         </div>
 
-        ${task.assigned_color ? `
+        ${renderAvatarStack(task.assigned_users ?? [], { size: 28 })}
-          <div class="task-avatar" style="background-color:${esc(task.assigned_color)}"
-               title="${esc(task.assigned_name)}">
-            ${esc(initials(task.assigned_name ?? ''))}
-          </div>` : ''}
 
         <button class="btn btn--ghost btn--icon btn--icon-sm" data-action="edit-task" data-id="${task.id}"
                 aria-label="${t('tasks.editButton')}">
@@ -305,9 +302,7 @@ function renderTaskGroups(tasks, groupMode) {
 function renderModalContent({ task = null, users = [], reminder = null } = {}) {
   const isEdit = !!task;
 
-  const userOptions = users.map((u) =>
+  const selectedIds = task?.assigned_users?.map((u) => u.id) ?? (task?.assigned_to ? [task.assigned_to] : []);
-    `<option value="${u.id}" ${task?.assigned_to === u.id ? 'selected' : ''}>${esc(u.display_name)}</option>`
-  ).join('');
 
   const catLabels = CATEGORY_LABELS();
   const categoryOptions = CATEGORIES.map((c) =>
@@ -374,11 +369,7 @@ function renderModalContent({ task = null, users = [], reminder = null } = {}) {
       </div>
 
       <div class="form-group" style="margin-top:var(--space-4)">
-        <label class="label" for="task-assigned">${t('tasks.assignedLabel')}</label>
+        ${renderUserMultiSelect(users, selectedIds, 'task_assigned', 'tasks.assignedLabel')}
-        <select class="input" id="task-assigned" name="assigned_to">
-          <option value="">${t('tasks.assignedNobody')}</option>
-          ${userOptions}
-        </select>
       </div>
 
       ${isEdit ? `
@@ -553,6 +544,7 @@ function openTaskModal({ task = null, users = [], reminder = null } = {}, contai
       panel.querySelector('.modal-panel__body')?.classList.add('modal-panel__body--tasks-fit');
       // RRULE-Events binden
       bindRRuleEvents(document, 'task');
+      bindUserMultiSelect(panel, 'task_assigned');
 
       // Blur-Validierung für required-Felder aktivieren
       wireBlurValidation(panel);
@@ -629,7 +621,7 @@ async function handleFormSubmit(e, container) {
     priority:        form.priority.value,
     category:        form.category.value,
     due_date:        dueDate || null,
-    assigned_to:     form.assigned_to.value ? Number(form.assigned_to.value) : null,
+    assigned_to:     getSelectedUserIds(form, 'task_assigned'),
     is_recurring:    rrule.is_recurring ? 1 : 0,
     recurrence_rule: rrule.recurrence_rule,
   };
@@ -773,11 +765,7 @@ function renderKanbanCard(task) {
         ${due ? `<span class="due-date ${due.cls}"><i data-lucide="clock" class="icon-xs" aria-hidden="true"></i> ${due.label}</span>` : ''}
       </div>
       <div class="kanban-card__footer">
-        ${task.assigned_color ? `
+        ${renderAvatarStack(task.assigned_users ?? [], { size: 22 }) || '<span></span>'}
-          <div class="task-avatar" style="background-color:${task.assigned_color};width:22px;height:22px;font-size:9px"
-               title="${esc(task.assigned_name ?? '')}">
-            ${initials(task.assigned_name ?? '')}
-          </div>` : '<span></span>'}
         <button class="kanban-card__status-btn" type="button"
                 data-next-status="${next}" title="${nextLabel}" aria-label="${nextLabel}">
           <i data-lucide="${icon}" aria-hidden="true"></i>

public/styles/user-multi-select.css

@@ -0,0 +1,102 @@
+/* ------------------------------------------------------------------ */
+/* Avatar-Stack (Mehrfach-Zuweisung Anzeige)                           */
+/* ------------------------------------------------------------------ */
+
+.avatar-stack {
+  display: inline-flex;
+  align-items: center;
+  flex-direction: row-reverse;
+}
+
+.avatar-stack__item {
+  border-radius: var(--radius-full);
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  font-weight: var(--font-weight-bold);
+  color: var(--color-text-on-accent);
+  border: 2px solid var(--color-surface);
+  flex-shrink: 0;
+  margin-left: -6px;
+}
+
+.avatar-stack__item:last-child {
+  margin-left: 0;
+}
+
+.avatar-stack__overflow {
+  background-color: var(--color-text-secondary);
+}
+
+/* ------------------------------------------------------------------ */
+/* User Multi-Select Widget                                             */
+/* ------------------------------------------------------------------ */
+
+.user-ms {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-1);
+}
+
+.user-ms__options {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-1);
+  max-height: 180px;
+  overflow-y: auto;
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-md);
+  padding: var(--space-1);
+  background: var(--color-surface);
+}
+
+.user-ms__option {
+  display: flex;
+  align-items: center;
+  gap: var(--space-2);
+  padding: var(--space-1) var(--space-2);
+  border-radius: var(--radius-sm);
+  cursor: pointer;
+  transition: background var(--transition-fast);
+  user-select: none;
+}
+
+.user-ms__option:hover {
+  background: var(--color-surface-alt);
+}
+
+.user-ms__checkbox {
+  accent-color: var(--color-accent);
+  width: 16px;
+  height: 16px;
+  flex-shrink: 0;
+  cursor: pointer;
+}
+
+.user-ms__avatar {
+  width: 26px;
+  height: 26px;
+  border-radius: var(--radius-full);
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  font-size: var(--text-xs);
+  font-weight: var(--font-weight-bold);
+  color: var(--color-text-on-accent);
+  flex-shrink: 0;
+}
+
+.user-ms__avatar--none {
+  background-color: var(--color-border);
+  color: var(--color-text-secondary);
+}
+
+.user-ms__name {
+  font-size: var(--text-sm);
+  color: var(--color-text-primary);
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}

server/db-schema-test.js

@@ -252,6 +252,17 @@ const MIGRATIONS_SQL = {
     CREATE INDEX IF NOT EXISTS idx_birthdays_calendar_ref ON birthdays(calendar_event_id);
     CREATE INDEX IF NOT EXISTS idx_api_tokens_hash      ON api_tokens(token_hash);
     CREATE INDEX IF NOT EXISTS idx_api_tokens_created_by ON api_tokens(created_by);
+
+    CREATE TABLE IF NOT EXISTS task_assignments (
+      task_id  INTEGER NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
+      user_id  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      PRIMARY KEY (task_id, user_id)
+    );
+    CREATE TABLE IF NOT EXISTS event_assignments (
+      event_id INTEGER NOT NULL REFERENCES calendar_events(id) ON DELETE CASCADE,
+      user_id  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      PRIMARY KEY (event_id, user_id)
+    );
   `,
   2: `
     CREATE TABLE IF NOT EXISTS sync_config (

server/db.js

@@ -1189,6 +1189,26 @@ const MIGRATIONS = [
       ALTER TABLE birthdays ADD COLUMN reminder_custom_unit TEXT;
     `,
   },
+  {
+    version: 32,
+    description: 'Multi-person assignment for tasks and calendar events',
+    up: `
+      CREATE TABLE IF NOT EXISTS task_assignments (
+        task_id  INTEGER NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
+        user_id  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+        PRIMARY KEY (task_id, user_id)
+      );
+      CREATE TABLE IF NOT EXISTS event_assignments (
+        event_id INTEGER NOT NULL REFERENCES calendar_events(id) ON DELETE CASCADE,
+        user_id  INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+        PRIMARY KEY (event_id, user_id)
+      );
+      INSERT OR IGNORE INTO task_assignments (task_id, user_id)
+        SELECT id, assigned_to FROM tasks WHERE assigned_to IS NOT NULL;
+      INSERT OR IGNORE INTO event_assignments (event_id, user_id)
+        SELECT id, assigned_to FROM calendar_events WHERE assigned_to IS NOT NULL;
+    `,
+  },
 ];
 
 /**

server/routes/calendar.js

@@ -94,10 +94,33 @@ function attachmentDataUrl(event) {
   return `data:${event.attachment_mime};base64,${event.attachment_data}`;
 }
 
+const ASSIGNED_USERS_SQL = `(
+  SELECT json_group_array(json_object(
+    'id', u.id, 'display_name', u.display_name, 'color', u.avatar_color
+  ))
+  FROM event_assignments ea JOIN users u ON u.id = ea.user_id
+  WHERE ea.event_id = e.id
+) AS assigned_users_json`;
+
+function parseAssignedTo(val) {
+  if (Array.isArray(val)) return val.map(Number).filter(Boolean);
+  if (val !== null && val !== undefined && val !== '') return [Number(val)].filter(Boolean);
+  return [];
+}
+
+function setEventAssignments(d, eventId, userIds) {
+  d.prepare('DELETE FROM event_assignments WHERE event_id = ?').run(eventId);
+  const ins = d.prepare('INSERT OR IGNORE INTO event_assignments (event_id, user_id) VALUES (?, ?)');
+  for (const uid of userIds) ins.run(eventId, uid);
+}
+
 function serializeEvent(event) {
   if (!event) return event;
+  const assigned_users = event.assigned_users_json ? JSON.parse(event.assigned_users_json) : [];
+  const { assigned_users_json, ...rest } = event;
   return {
-    ...event,
+    ...rest,
+    assigned_users,
     attachment_data: attachmentDataUrl(event),
   };
 }
@@ -207,7 +230,8 @@ router.get('/', (req, res) => {
              u_assigned.avatar_color AS assigned_color,
              u_created.display_name  AS creator_name,
              ec.name  AS cal_name,
-             ec.color AS cal_color
+             ec.color AS cal_color,
+             ${ASSIGNED_USERS_SQL}
       FROM calendar_events e
       LEFT JOIN users u_assigned ON u_assigned.id = e.assigned_to
       LEFT JOIN users u_created  ON u_created.id  = e.created_by
@@ -229,7 +253,7 @@ router.get('/', (req, res) => {
     const params = [to, from, to, getUserId(req)];
 
     if (req.query.assigned_to) {
-      sql += ' AND e.assigned_to = ?';
+      sql += ' AND EXISTS (SELECT 1 FROM event_assignments ea WHERE ea.event_id = e.id AND ea.user_id = ?)';
       params.push(parseInt(req.query.assigned_to, 10));
     }
 
@@ -267,7 +291,8 @@ router.get('/upcoming', (req, res) => {
              u_assigned.display_name AS assigned_name,
              u_assigned.avatar_color AS assigned_color,
              ec.name  AS cal_name,
-             ec.color AS cal_color
+             ec.color AS cal_color,
+             ${ASSIGNED_USERS_SQL}
       FROM calendar_events e
       LEFT JOIN users u_assigned ON u_assigned.id = e.assigned_to
       LEFT JOIN external_calendars ec ON ec.id = e.calendar_ref_id
@@ -580,7 +605,8 @@ router.get('/:id', (req, res) => {
       SELECT e.*,
              u_assigned.display_name AS assigned_name,
              u_assigned.avatar_color AS assigned_color,
-             u_created.display_name  AS creator_name
+             u_created.display_name  AS creator_name,
+             ${ASSIGNED_USERS_SQL}
       FROM calendar_events e
       LEFT JOIN users u_assigned ON u_assigned.id = e.assigned_to
       LEFT JOIN users u_created  ON u_created.id  = e.created_by
@@ -628,43 +654,45 @@ router.post('/', (req, res) => {
     if (errors.length) return res.status(400).json({ error: errors.join(' '), code: 400 });
     if (!vIcon) return res.status(400).json({ error: 'icon: invalid calendar event icon.', code: 400 });
 
-    const { all_day = 0, assigned_to = null } = req.body;
+    const { all_day = 0 } = req.body;
-
+    const userIds  = parseAssignedTo(req.body.assigned_to);
-    if (assigned_to) {
+    const firstUid = userIds[0] ?? null;
-      const user = db.get().prepare('SELECT id FROM users WHERE id = ?').get(assigned_to);
-      if (!user) return res.status(400).json({ error: 'assigned_to: Benutzer nicht gefunden', code: 400 });
-    }
 
     const attachment = req.body.attachment_data ? parseAttachment(req.body.attachment_data) : { mime: null, size: null, data: null };
 
-    const result = db.get().prepare(`
+    const eventId = db.get().transaction(() => {
-      INSERT INTO calendar_events
+      const result = db.get().prepare(`
-        (title, description, start_datetime, end_datetime, all_day,
+        INSERT INTO calendar_events
-         location, color, icon, assigned_to, created_by, recurrence_rule,
+          (title, description, start_datetime, end_datetime, all_day,
-         attachment_name, attachment_mime, attachment_size, attachment_data)
+           location, color, icon, assigned_to, created_by, recurrence_rule,
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+           attachment_name, attachment_mime, attachment_size, attachment_data)
-    `).run(
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-      vTitle.value, vDesc.value,
+      `).run(
-      vStart.value, vEnd.value,
+        vTitle.value, vDesc.value,
-      all_day ? 1 : 0, vLoc.value,
+        vStart.value, vEnd.value,
-      vColor.value, vIcon, assigned_to || null,
+        all_day ? 1 : 0, vLoc.value,
-      userId, vRrule.value,
+        vColor.value, vIcon, firstUid,
-      req.body.attachment_name || null,
+        userId, vRrule.value,
-      attachment.mime,
+        req.body.attachment_name || null,
-      attachment.size,
+        attachment.mime,
-      attachment.data
+        attachment.size,
-    );
+        attachment.data
+      );
+      setEventAssignments(db.get(), result.lastInsertRowid, userIds);
+      return result.lastInsertRowid;
+    })();
 
     const event = db.get().prepare(`
       SELECT e.*,
              u_assigned.display_name AS assigned_name,
              u_assigned.avatar_color AS assigned_color,
-             u_created.display_name  AS creator_name
+             u_created.display_name  AS creator_name,
+             ${ASSIGNED_USERS_SQL}
       FROM calendar_events e
       LEFT JOIN users u_assigned ON u_assigned.id = e.assigned_to
       LEFT JOIN users u_created  ON u_created.id  = e.created_by
       WHERE e.id = ?
-    `).get(result.lastInsertRowid);
+    `).get(eventId);
 
     res.status(201).json({ data: serializeEvent(event) });
   } catch (err) {
@@ -707,53 +735,63 @@ router.put('/:id', (req, res) => {
 
     const {
       title, description, start_datetime, end_datetime,
-      all_day, location, color: colorVal, assigned_to, recurrence_rule, attachment_name,
+      all_day, location, color: colorVal, recurrence_rule, attachment_name,
     } = req.body;
 
+    const userIds  = req.body.assigned_to !== undefined
+      ? parseAssignedTo(req.body.assigned_to)
+      : db.get().prepare('SELECT user_id FROM event_assignments WHERE event_id = ?')
+          .all(id).map((r) => r.user_id);
+    const firstUid = userIds[0] ?? null;
+
     const userModified = event.external_source !== 'local' ? 1 : event.user_modified;
 
-    db.get().prepare(`
+    db.get().transaction(() => {
-      UPDATE calendar_events
+      db.get().prepare(`
-      SET title           = COALESCE(?, title),
+        UPDATE calendar_events
-          description     = ?,
+        SET title           = COALESCE(?, title),
-          start_datetime  = COALESCE(?, start_datetime),
+            description     = ?,
-          end_datetime    = ?,
+            start_datetime  = COALESCE(?, start_datetime),
-          all_day         = COALESCE(?, all_day),
+            end_datetime    = ?,
-          location        = ?,
+            all_day         = COALESCE(?, all_day),
-          color           = COALESCE(?, color),
+            location        = ?,
-          icon            = COALESCE(?, icon),
+            color           = COALESCE(?, color),
-          assigned_to     = ?,
+            icon            = COALESCE(?, icon),
-          recurrence_rule = ?,
+            assigned_to     = ?,
-          attachment_name = ?,
+            recurrence_rule = ?,
-          attachment_mime  = ?,
+            attachment_name = ?,
-          attachment_size  = ?,
+            attachment_mime  = ?,
-          attachment_data  = ?,
+            attachment_size  = ?,
-          user_modified   = ?
+            attachment_data  = ?,
-      WHERE id = ?
+            user_modified   = ?
-    `).run(
+        WHERE id = ?
-      title?.trim()  ?? null,
+      `).run(
-      description !== undefined ? (description || null) : event.description,
+        title?.trim()  ?? null,
-      start_datetime ?? null,
+        description !== undefined ? (description || null) : event.description,
-      end_datetime !== undefined ? (end_datetime || null) : event.end_datetime,
+        start_datetime ?? null,
-      all_day !== undefined ? (all_day ? 1 : 0) : null,
+        end_datetime !== undefined ? (end_datetime || null) : event.end_datetime,
-      location !== undefined ? (location || null) : event.location,
+        all_day !== undefined ? (all_day ? 1 : 0) : null,
-      colorVal ?? null,
+        location !== undefined ? (location || null) : event.location,
-      req.body.icon !== undefined ? vIcon : null,
+        colorVal ?? null,
-      assigned_to !== undefined ? (assigned_to || null) : event.assigned_to,
+        req.body.icon !== undefined ? vIcon : null,
-      recurrence_rule !== undefined ? (recurrence_rule || null) : event.recurrence_rule,
+        firstUid !== undefined ? firstUid : event.assigned_to,
-      attachment_name !== undefined ? (attachment_name || null) : event.attachment_name,
+        recurrence_rule !== undefined ? (recurrence_rule || null) : event.recurrence_rule,
-      attachment.mime,
+        attachment_name !== undefined ? (attachment_name || null) : event.attachment_name,
-      attachment.size,
+        attachment.mime,
-      attachment.data,
+        attachment.size,
-      userModified,
+        attachment.data,
-      id
+        userModified,
-    );
+        id
+      );
+      setEventAssignments(db.get(), id, userIds);
+    })();
 
     const updated = db.get().prepare(`
       SELECT e.*,
              u_assigned.display_name AS assigned_name,
              u_assigned.avatar_color AS assigned_color,
-             u_created.display_name  AS creator_name
+             u_created.display_name  AS creator_name,
+             ${ASSIGNED_USERS_SQL}
       FROM calendar_events e
       LEFT JOIN users u_assigned ON u_assigned.id = e.assigned_to
       LEFT JOIN users u_created  ON u_created.id  = e.created_by

server/routes/tasks.js

@@ -27,15 +27,42 @@ const VALID_CATEGORIES = ['household', 'school', 'shopping', 'repair',
 // Hilfsfunktionen
 // --------------------------------------------------------
 
+const ASSIGNED_USERS_SQL = `(
+  SELECT json_group_array(json_object(
+    'id', u.id, 'display_name', u.display_name, 'color', u.avatar_color
+  ))
+  FROM task_assignments ta JOIN users u ON u.id = ta.user_id
+  WHERE ta.task_id = t.id
+) AS assigned_users_json`;
+
+function addAssignedUsers(task) {
+  task.assigned_users = task.assigned_users_json ? JSON.parse(task.assigned_users_json) : [];
+  delete task.assigned_users_json;
+  return task;
+}
+
+function parseAssignedTo(val) {
+  if (Array.isArray(val)) return val.map(Number).filter(Boolean);
+  if (val !== null && val !== undefined && val !== '') return [Number(val)].filter(Boolean);
+  return [];
+}
+
+function setAssignments(d, taskId, userIds) {
+  d.prepare('DELETE FROM task_assignments WHERE task_id = ?').run(taskId);
+  const ins = d.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)');
+  for (const uid of userIds) ins.run(taskId, uid);
+}
+
 /** Alle Subtasks einer Aufgabe laden (eine Ebene tief). */
 function loadSubtasks(taskId) {
   return db.get().prepare(`
-    SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color
+    SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color,
+      ${ASSIGNED_USERS_SQL}
     FROM tasks t
     LEFT JOIN users u ON t.assigned_to = u.id
     WHERE t.parent_task_id = ?
     ORDER BY t.created_at ASC
-  `).all(taskId);
+  `).all(taskId).map(addAssignedUsers);
 }
 
 /** Fortschritt der Subtasks berechnen (erledigte / gesamt). */
@@ -79,6 +106,7 @@ router.get('/', (req, res) => {
         t.*,
         u.display_name AS assigned_name,
         u.avatar_color AS assigned_color,
+        ${ASSIGNED_USERS_SQL},
         (SELECT COUNT(*) FROM tasks s WHERE s.parent_task_id = t.id)                           AS subtask_total,
         (SELECT COUNT(*) FROM tasks s WHERE s.parent_task_id = t.id AND s.status = 'done')     AS subtask_done
       FROM tasks t
@@ -89,7 +117,10 @@ router.get('/', (req, res) => {
 
     if (status)      { sql += ' AND t.status = ?';      params.push(status); }
     if (priority)    { sql += ' AND t.priority = ?';    params.push(priority); }
-    if (assigned_to) { sql += ' AND t.assigned_to = ?'; params.push(Number(assigned_to)); }
+    if (assigned_to) {
+      sql += ' AND EXISTS (SELECT 1 FROM task_assignments ta WHERE ta.task_id = t.id AND ta.user_id = ?)';
+      params.push(Number(assigned_to));
+    }
     if (category)    { sql += ' AND t.category = ?';    params.push(category); }
 
     sql += `
@@ -101,7 +132,7 @@ router.get('/', (req, res) => {
         t.created_at DESC
     `;
 
-    res.json({ data: db.get().prepare(sql).all(...params) });
+    res.json({ data: db.get().prepare(sql).all(...params).map(addAssignedUsers) });
   } catch (err) {
     log.error('GET / error:', err);
     res.status(500).json({ error: 'Internal server error.', code: 500 });
@@ -116,7 +147,8 @@ router.get('/', (req, res) => {
 router.get('/:id', (req, res) => {
   try {
     const task = db.get().prepare(`
-      SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color
+      SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color,
+        ${ASSIGNED_USERS_SQL}
       FROM tasks t
       LEFT JOIN users u ON t.assigned_to = u.id
       WHERE t.id = ? AND t.parent_task_id IS NULL
@@ -124,6 +156,7 @@ router.get('/:id', (req, res) => {
 
     if (!task) return res.status(404).json({ error: 'Task not found.', code: 404 });
 
+    addAssignedUsers(task);
     task.subtasks = loadSubtasks(task.id);
     res.json({ data: task });
   } catch (err) {
@@ -151,12 +184,14 @@ router.post('/', (req, res) => {
       priority        = 'none',
       due_date        = null,
       due_time        = null,
-      assigned_to     = null,
       parent_task_id  = null,
       is_recurring    = 0,
       recurrence_rule = null,
     } = req.body;
 
+    const userIds  = parseAssignedTo(req.body.assigned_to);
+    const firstUid = userIds[0] ?? null;
+
     // Tiefe begrenzen: Subtasks dürfen keine eigenen Subtasks haben (max. 2 Ebenen)
     if (parent_task_id) {
       const parent = db.get().prepare('SELECT parent_task_id FROM tasks WHERE id = ?')
@@ -166,24 +201,29 @@ router.post('/', (req, res) => {
         return res.status(400).json({ error: 'Maximal 2 Verschachtelungsebenen erlaubt.', code: 400 });
     }
 
-    const result = db.get().prepare(`
+    const taskId = db.get().transaction(() => {
-      INSERT INTO tasks
+      const result = db.get().prepare(`
-        (title, description, category, priority, due_date, due_time,
+        INSERT INTO tasks
-         assigned_to, created_by, parent_task_id, is_recurring, recurrence_rule)
+          (title, description, category, priority, due_date, due_time,
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+           assigned_to, created_by, parent_task_id, is_recurring, recurrence_rule)
-    `).run(
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-      title.trim(), description, category, priority,
+      `).run(
-      due_date, due_time, assigned_to, req.session.userId, parent_task_id,
+        title.trim(), description, category, priority,
-      is_recurring ? 1 : 0, recurrence_rule
+        due_date, due_time, firstUid, req.session.userId, parent_task_id,
-    );
+        is_recurring ? 1 : 0, recurrence_rule
+      );
+      setAssignments(db.get(), result.lastInsertRowid, userIds);
+      return result.lastInsertRowid;
+    })();
 
     const task = db.get().prepare(`
-      SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color
+      SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color,
+        ${ASSIGNED_USERS_SQL}
       FROM tasks t LEFT JOIN users u ON t.assigned_to = u.id
       WHERE t.id = ?
-    `).get(result.lastInsertRowid);
+    `).get(taskId);
 
-    res.status(201).json({ data: task });
+    res.status(201).json({ data: addAssignedUsers(task) });
   } catch (err) {
     log.error('POST / error:', err);
     res.status(500).json({ error: 'Internal server error.', code: 500 });
@@ -213,26 +253,36 @@ router.put('/:id', (req, res) => {
       status          = task.status,
       due_date        = task.due_date,
       due_time        = task.due_time,
-      assigned_to     = task.assigned_to,
       is_recurring    = task.is_recurring,
       recurrence_rule = task.recurrence_rule,
     } = req.body;
 
-    db.get().prepare(`
+    const userIds  = req.body.assigned_to !== undefined
-      UPDATE tasks SET
+      ? parseAssignedTo(req.body.assigned_to)
-        title = ?, description = ?, category = ?, priority = ?,
+      : db.get().prepare('SELECT user_id FROM task_assignments WHERE task_id = ?')
-        status = ?, due_date = ?, due_time = ?, assigned_to = ?,
+          .all(task.id).map((r) => r.user_id);
-        is_recurring = ?, recurrence_rule = ?
+    const firstUid = userIds[0] ?? null;
-      WHERE id = ?
+
-    `).run(title.trim(), description, category, priority,
+    db.get().transaction(() => {
-           status, due_date, due_time, assigned_to,
+      db.get().prepare(`
-           is_recurring ? 1 : 0, recurrence_rule, req.params.id);
+        UPDATE tasks SET
+          title = ?, description = ?, category = ?, priority = ?,
+          status = ?, due_date = ?, due_time = ?, assigned_to = ?,
+          is_recurring = ?, recurrence_rule = ?
+        WHERE id = ?
+      `).run(title.trim(), description, category, priority,
+             status, due_date, due_time, firstUid,
+             is_recurring ? 1 : 0, recurrence_rule, req.params.id);
+      setAssignments(db.get(), task.id, userIds);
+    })();
 
     const updated = db.get().prepare(`
-      SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color
+      SELECT t.*, u.display_name AS assigned_name, u.avatar_color AS assigned_color,
+        ${ASSIGNED_USERS_SQL}
       FROM tasks t LEFT JOIN users u ON t.assigned_to = u.id
       WHERE t.id = ?
     `).get(req.params.id);
+    addAssignedUsers(updated);
     updated.subtasks = loadSubtasks(updated.id);
 
     res.json({ data: updated });
@@ -266,15 +316,21 @@ router.patch('/:id/status', (req, res) => {
       if (task?.is_recurring && task.recurrence_rule && !task.parent_task_id) {
         const nextDate = nextOccurrence(task.due_date, task.recurrence_rule);
         if (nextDate) {
-          db.get().prepare(`
+          const existingAssignments = db.get()
-            INSERT INTO tasks (title, description, category, priority, status,
+            .prepare('SELECT user_id FROM task_assignments WHERE task_id = ?')
-              due_date, due_time, assigned_to, created_by, is_recurring, recurrence_rule)
+            .all(task.id).map((r) => r.user_id);
-            VALUES (?, ?, ?, ?, 'open', ?, ?, ?, ?, 1, ?)
+          db.get().transaction(() => {
-          `).run(
+            const newTask = db.get().prepare(`
-            task.title, task.description, task.category, task.priority,
+              INSERT INTO tasks (title, description, category, priority, status,
-            nextDate, task.due_time, task.assigned_to, task.created_by,
+                due_date, due_time, assigned_to, created_by, is_recurring, recurrence_rule)
-            task.recurrence_rule
+              VALUES (?, ?, ?, ?, 'open', ?, ?, ?, ?, 1, ?)
-          );
+            `).run(
+              task.title, task.description, task.category, task.priority,
+              nextDate, task.due_time, task.assigned_to, task.created_by,
+              task.recurrence_rule
+            );
+            setAssignments(db.get(), newTask.lastInsertRowid, existingAssignments);
+          })();
         }
       }
     }

test-multi-assignment.js

@@ -0,0 +1,166 @@
+/**
+ * Modul: Multi-Assignment-Test
+ * Zweck: Validiert Multi-Personen-Zuweisung für Tasks und Kalendereinträge
+ * Ausführen: node --experimental-sqlite test-multi-assignment.js
+ */
+
+import { DatabaseSync } from 'node:sqlite';
+import { MIGRATIONS_SQL } from './server/db-schema-test.js';
+
+let passed = 0;
+let failed = 0;
+
+function test(name, fn) {
+  try { fn(); console.log(`  ✓ ${name}`); passed++; }
+  catch (err) { console.error(`  ✗ ${name}: ${err.message}`); failed++; }
+}
+function assert(cond, msg) { if (!cond) throw new Error(msg || 'Assertion fehlgeschlagen'); }
+
+const db = new DatabaseSync(':memory:');
+db.exec('PRAGMA foreign_keys = ON;');
+db.exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
+  version INTEGER PRIMARY KEY, description TEXT NOT NULL,
+  applied_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+);`);
+db.exec(MIGRATIONS_SQL[1]);
+
+// Testdaten
+const u1 = db.prepare(`INSERT INTO users (username, display_name, password_hash, avatar_color, role)
+  VALUES ('anna', 'Anna', 'x', '#007AFF', 'admin')`).run();
+const u2 = db.prepare(`INSERT INTO users (username, display_name, password_hash, avatar_color)
+  VALUES ('max', 'Max', 'x', '#34C759')`).run();
+const u3 = db.prepare(`INSERT INTO users (username, display_name, password_hash, avatar_color)
+  VALUES ('lisa', 'Lisa', 'x', '#FF9500')`).run();
+const uid1 = u1.lastInsertRowid;
+const uid2 = u2.lastInsertRowid;
+const uid3 = u3.lastInsertRowid;
+
+console.log('\n[Multi-Assignment-Test] Tasks\n');
+
+let taskId1, taskId2;
+
+test('Task mit einem Zugewiesenen erstellen', () => {
+  const r = db.prepare(`INSERT INTO tasks (title, category, priority, status, assigned_to, created_by)
+    VALUES ('Aufgabe 1', 'misc', 'low', 'open', ?, ?)`).run(uid1, uid1);
+  taskId1 = r.lastInsertRowid;
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId1, uid1);
+  assert(taskId1 > 0, 'ID muss > 0 sein');
+});
+
+test('Zweiten Benutzer zur gleichen Aufgabe hinzufügen', () => {
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId1, uid2);
+  const rows = db.prepare('SELECT user_id FROM task_assignments WHERE task_id = ?').all(taskId1);
+  assert(rows.length === 2, `Erwartet 2 Assignments, erhalten ${rows.length}`);
+});
+
+test('Dritten Benutzer zur Aufgabe hinzufügen', () => {
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId1, uid3);
+  const rows = db.prepare('SELECT user_id FROM task_assignments WHERE task_id = ?').all(taskId1);
+  assert(rows.length === 3, `Erwartet 3 Assignments, erhalten ${rows.length}`);
+});
+
+test('Duplicate-Assignment wird ignoriert (PRIMARY KEY)', () => {
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId1, uid1);
+  const rows = db.prepare('SELECT user_id FROM task_assignments WHERE task_id = ?').all(taskId1);
+  assert(rows.length === 3, `Erwartet weiterhin 3, erhalten ${rows.length}`);
+});
+
+test('JSON-Aggregation der zugewiesenen User', () => {
+  const row = db.prepare(`
+    SELECT json_group_array(json_object('id', u.id, 'display_name', u.display_name, 'color', u.avatar_color))
+           AS assigned_users_json
+    FROM task_assignments ta JOIN users u ON u.id = ta.user_id
+    WHERE ta.task_id = ?
+  `).get(taskId1);
+  const users = JSON.parse(row.assigned_users_json);
+  assert(users.length === 3, `Erwartet 3 User-Objekte, erhalten ${users.length}`);
+  assert(users.every((u) => u.id && u.display_name && u.color), 'Alle Felder müssen vorhanden sein');
+});
+
+test('Filter per EXISTS: Aufgaben für Benutzer 2 finden', () => {
+  const r2 = db.prepare(`INSERT INTO tasks (title, category, priority, status, assigned_to, created_by)
+    VALUES ('Aufgabe 2', 'misc', 'low', 'open', ?, ?)`).run(uid2, uid1);
+  taskId2 = r2.lastInsertRowid;
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId2, uid2);
+
+  const rows = db.prepare(`
+    SELECT t.id FROM tasks t
+    WHERE EXISTS (SELECT 1 FROM task_assignments ta WHERE ta.task_id = t.id AND ta.user_id = ?)
+  `).all(uid2);
+  assert(rows.length === 2, `uid2 sollte in 2 Tasks sein, erhalten ${rows.length}`);
+});
+
+test('Filter: Aufgaben nur für Benutzer 3', () => {
+  const rows = db.prepare(`
+    SELECT t.id FROM tasks t
+    WHERE EXISTS (SELECT 1 FROM task_assignments ta WHERE ta.task_id = t.id AND ta.user_id = ?)
+  `).all(uid3);
+  assert(rows.length === 1, `uid3 sollte in 1 Task sein, erhalten ${rows.length}`);
+  assert(rows[0].id === taskId1, 'Falsche Task-ID gefunden');
+});
+
+test('Assignments ersetzen (DELETE + INSERT)', () => {
+  db.prepare('DELETE FROM task_assignments WHERE task_id = ?').run(taskId1);
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId1, uid3);
+  const rows = db.prepare('SELECT user_id FROM task_assignments WHERE task_id = ?').all(taskId1);
+  assert(rows.length === 1, `Nach Ersetzen soll 1 Assignment sein, erhalten ${rows.length}`);
+  assert(rows[0].user_id === uid3, 'Falscher User nach Ersetzen');
+});
+
+test('CASCADE: Assignments werden beim Task-Löschen mitgelöscht', () => {
+  db.prepare('DELETE FROM tasks WHERE id = ?').run(taskId1);
+  const rows = db.prepare('SELECT * FROM task_assignments WHERE task_id = ?').all(taskId1);
+  assert(rows.length === 0, `Assignments sollen gelöscht sein, erhalten ${rows.length}`);
+});
+
+test('CASCADE: Assignments werden beim User-Löschen entfernt', () => {
+  db.prepare('INSERT OR IGNORE INTO task_assignments (task_id, user_id) VALUES (?, ?)').run(taskId2, uid3);
+  db.prepare('DELETE FROM users WHERE id = ?').run(uid3);
+  const rows = db.prepare('SELECT * FROM task_assignments WHERE user_id = ?').all(uid3);
+  assert(rows.length === 0, 'user_id-Referenz soll entfernt sein');
+});
+
+console.log('\n[Multi-Assignment-Test] Kalendereinträge\n');
+
+let eventId1;
+
+const tomorrow = new Date(Date.now() + 86400000).toISOString().slice(0, 10);
+
+test('Event mit zwei Zugewiesenen erstellen', () => {
+  const r = db.prepare(`INSERT INTO calendar_events
+    (title, start_datetime, all_day, color, icon, assigned_to, created_by, external_source)
+    VALUES ('Termin', ?, 0, '#007AFF', 'calendar', ?, ?, 'local')`).run(`${tomorrow}T10:00`, uid1, uid1);
+  eventId1 = r.lastInsertRowid;
+  db.prepare('INSERT OR IGNORE INTO event_assignments (event_id, user_id) VALUES (?, ?)').run(eventId1, uid1);
+  db.prepare('INSERT OR IGNORE INTO event_assignments (event_id, user_id) VALUES (?, ?)').run(eventId1, uid2);
+  const rows = db.prepare('SELECT user_id FROM event_assignments WHERE event_id = ?').all(eventId1);
+  assert(rows.length === 2, `Erwartet 2 Event-Assignments, erhalten ${rows.length}`);
+});
+
+test('Event-Assignments JSON-Aggregation', () => {
+  const row = db.prepare(`
+    SELECT json_group_array(json_object('id', u.id, 'display_name', u.display_name, 'color', u.avatar_color))
+           AS assigned_users_json
+    FROM event_assignments ea JOIN users u ON u.id = ea.user_id
+    WHERE ea.event_id = ?
+  `).get(eventId1);
+  const users = JSON.parse(row.assigned_users_json);
+  assert(users.length === 2, `Erwartet 2, erhalten ${users.length}`);
+});
+
+test('EXISTS-Filter für Events', () => {
+  const rows = db.prepare(`
+    SELECT e.id FROM calendar_events e
+    WHERE EXISTS (SELECT 1 FROM event_assignments ea WHERE ea.event_id = e.id AND ea.user_id = ?)
+  `).all(uid2);
+  assert(rows.length === 1, `uid2 soll in 1 Event sein, erhalten ${rows.length}`);
+});
+
+test('CASCADE: Event-Assignments beim Event-Löschen entfernt', () => {
+  db.prepare('DELETE FROM calendar_events WHERE id = ?').run(eventId1);
+  const rows = db.prepare('SELECT * FROM event_assignments WHERE event_id = ?').all(eventId1);
+  assert(rows.length === 0, `Event-Assignments sollen gelöscht sein, erhalten ${rows.length}`);
+});
+
+console.log(`\n[Multi-Assignment-Test] Ergebnis: ${passed} bestanden, ${failed} fehlgeschlagen\n`);
+if (failed > 0) process.exit(1);