feat(sharing): recipients can recolour a shared calendar (per-user, no rename)

A share recipient couldn't change anything on a shared calendar (update_calendar
is owner-only → 404), yet the clients still showed a colour picker for it.

Add a per-recipient colour: new nullable calendar_shares.color column (+ migration).
New PUT /calendars/{id}/color endpoint sets the calendar colour for the owner
(global) or, for a recipient, only their own share colour — never the name, so
recipients can recolour but not rename. The merge read and the calendar list now
prefer the recipient's share colour over the owner's (NULL = owner's colour).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/dav_util.py

@@ -0,0 +1,63 @@
+"""Shared helpers for CalDAV publishing of local calendars.
+
+Publishing is opt-in per calendar: a published calendar gets a secret
+``dav_token`` and is reachable as a two-way CalDAV collection at
+``/dav/{token}/``. ``dav_ctag`` changes on every event write so clients detect
+changes; each event carries an ``etag`` that changes on write. Rotating the
+token revokes existing subscriptions.
+"""
+
+from __future__ import annotations
+
+import os
+import secrets
+import uuid
+
+
+def new_token() -> str:
+    """A URL-safe, unguessable token used as the CalDAV collection path."""
+    return secrets.token_urlsafe(24)
+
+
+def new_tag() -> str:
+    """A fresh ctag/etag value."""
+    return uuid.uuid4().hex
+
+
+def bump_dav(cal, event=None) -> None:
+    """Mark a calendar (and optionally an event) as changed for CalDAV clients.
+
+    Safe to call unconditionally on every local-event write — it only refreshes
+    opaque change tags, so unpublished calendars are unaffected.
+    """
+    if cal is not None:
+        cal.dav_ctag = new_tag()
+    if event is not None:
+        event.etag = new_tag()
+
+
+def public_base(request) -> str:
+    """Public origin (scheme://host) as clients actually reach us.
+
+    Behind a reverse proxy (e.g. Nginx Proxy Manager) the app only sees
+    ``http://…:8080`` internally, so honour ``X-Forwarded-Proto/-Host`` and an
+    optional ``PUBLIC_BASE_URL`` override so published URLs are the real https
+    ones.
+    """
+    env = os.environ.get("PUBLIC_BASE_URL")
+    if env:
+        return env.rstrip("/")
+    h = request.headers
+    proto = (h.get("x-forwarded-proto") or request.url.scheme or "http").split(",")[0].strip()
+    host = (h.get("x-forwarded-host") or h.get("host") or request.url.netloc).split(",")[0].strip()
+    return f"{proto}://{host}"
+
+
+def caldav_url(request, token: str) -> str:
+    """Absolute per-calendar CalDAV collection URL (secret token, no login)."""
+    return f"{public_base(request)}/dav/{token}/"
+
+
+def caldav_login_url(request) -> str:
+    """Absolute discovery URL for username/password (Basic Auth) CalDAV access."""
+    return f"{public_base(request)}/caldav/"

backend/main.py

@@ -17,7 +17,7 @@ STATIC_CACHE = f"public, max-age={STATIC_MAX_AGE_SECONDS}, must-revalidate"
 sys.path.insert(0, str(Path(__file__).parent))
 
 from database import Base, engine
-from routers import auth_router, caldav_router, google_router, groups_router, homeassistant_router, ical_router, local_router, profile_router, settings_router, users_router
+from routers import auth_router, caldav_router, dav_router, google_router, groups_router, homeassistant_router, ical_router, local_router, profile_router, settings_router, users_router
 
 logging.basicConfig(level=logging.INFO)
 
@@ -225,6 +225,40 @@ def _migrate():
         except Exception:
             pass
 
+        # CalDAV publishing of local calendars (opt-in, secret token URL).
+        for col, ddl in (
+            ("caldav_published", "ALTER TABLE local_calendars ADD COLUMN caldav_published BOOLEAN DEFAULT 0"),
+            ("dav_token",        "ALTER TABLE local_calendars ADD COLUMN dav_token VARCHAR(64)"),
+            ("dav_ctag",         "ALTER TABLE local_calendars ADD COLUMN dav_ctag VARCHAR(32)"),
+        ):
+            try:
+                conn.execute(text(ddl))
+                conn.commit()
+                logging.info("Migration: added %s to local_calendars", col)
+            except Exception:
+                pass
+        try:
+            conn.execute(text("ALTER TABLE local_events ADD COLUMN etag VARCHAR(32)"))
+            conn.commit()
+            logging.info("Migration: added etag to local_events")
+        except Exception:
+            pass
+        # Per-recipient colour override for a shared calendar (NULL = owner's colour).
+        try:
+            conn.execute(text("ALTER TABLE calendar_shares ADD COLUMN color VARCHAR(16)"))
+            conn.commit()
+            logging.info("Migration: added color to calendar_shares")
+        except Exception:
+            pass
+
+        # Hide a user from sharing/group pickers (admin management still shows them).
+        try:
+            conn.execute(text("ALTER TABLE users ADD COLUMN directory_hidden BOOLEAN DEFAULT 0"))
+            conn.commit()
+            logging.info("Migration: added directory_hidden to users")
+        except Exception:
+            pass
+
 _migrate()
 
 app = FastAPI(title="Calendarr", docs_url=None, redoc_url=None)
@@ -272,6 +306,9 @@ app.include_router(groups_router.router, prefix="/api/groups", tags=["groups"])
 app.include_router(ical_router.router, prefix="/api/ical", tags=["ical"])
 app.include_router(google_router.router, prefix="/api/google", tags=["google"])
 app.include_router(homeassistant_router.router, prefix="/api/homeassistant", tags=["homeassistant"])
+# CalDAV publishing lives at root scope (no /api prefix) and must be registered
+# before the SPA catch-all so /dav/... isn't swallowed by the index fallback.
+app.include_router(dav_router.router, tags=["dav"])
 
 FRONTEND_DIR = Path(__file__).parent.parent / "frontend"
 app.mount("/static", StaticFiles(directory=str(FRONTEND_DIR)), name="static")

backend/models.py

@@ -17,6 +17,9 @@ class User(Base):
     avatar_filename = Column(String(255), nullable=True)
     totp_secret = Column(String(32), nullable=True)
     totp_enabled = Column(Boolean, default=False)
+    # When true, the user is hidden from sharing/group picker directories
+    # (/users/directory). Admin user management (/users/) still shows them.
+    directory_hidden = Column(Boolean, default=False, nullable=False)
 
     caldav_accounts = relationship(
         "CalDAVAccount", back_populates="user", cascade="all, delete-orphan"
@@ -114,6 +117,26 @@ class UserSettings(Base):
     user = relationship("User", back_populates="settings")
 
 
+class AppPassword(Base):
+    """Per-device app-specific password for CalDAV (Basic Auth).
+
+    Keeps MFA intact: accounts with 2FA can't use their normal password over
+    CalDAV (clients can't send a TOTP code), so they authenticate with one of
+    these revocable app passwords instead. Only the bcrypt hash is stored.
+    """
+
+    __tablename__ = "app_passwords"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    label = Column(String(100), nullable=False)
+    password_hash = Column(String(255), nullable=False)
+    created_at = Column(String(50), nullable=True)
+    last_used_at = Column(String(50), nullable=True)
+
+    user = relationship("User")
+
+
 class LocalCalendar(Base):
     __tablename__ = "local_calendars"
 
@@ -124,6 +147,12 @@ class LocalCalendar(Base):
     enabled = Column(Boolean, default=True)
     # Whether events of this calendar generate reminders/notifications on clients.
     reminders_enabled = Column(Boolean, default=True, nullable=False)
+    # CalDAV publishing (opt-in): expose this calendar as a two-way CalDAV
+    # collection reachable via a secret token URL. dav_ctag changes on every
+    # event write so clients detect changes; rotating the token revokes access.
+    caldav_published = Column(Boolean, default=False, nullable=False)
+    dav_token = Column(String(64), nullable=True, unique=True)
+    dav_ctag = Column(String(32), nullable=True)
 
     user = relationship("User", back_populates="local_calendars")
     events = relationship("LocalEvent", back_populates="calendar", cascade="all, delete-orphan")
@@ -152,6 +181,8 @@ class LocalEvent(Base):
     creator_name_external = Column(Text, nullable=True)
     # Private events are filtered for other group members per their visibility setting.
     is_private = Column(Boolean, default=False)
+    # CalDAV entity tag — changes on every write so CalDAV clients detect updates.
+    etag = Column(String(32), nullable=True)
 
     calendar = relationship("LocalCalendar", back_populates="events")
     creator = relationship("User")
@@ -276,6 +307,7 @@ class CalendarShare(Base):
     calendar_id = Column(Integer, ForeignKey("local_calendars.id"), nullable=False)
     user_id = Column(Integer, ForeignKey("users.id"), nullable=False)
     permission = Column(String(20), default="read")  # 'read' | 'read_write'
+    color = Column(String(16), nullable=True)  # recipient's own colour; NULL = owner's
     created_at = Column(String(50), nullable=True)  # ISO 8601
 
     calendar = relationship("LocalCalendar")

backend/permissions.py

@@ -97,8 +97,44 @@ def is_calendar_owner(db: Session, user: models.User, calendar_id: int) -> model
     return cal
 
 
+def co_member_group_visible_calendars(db: Session, user: models.User) -> list[models.LocalCalendar]:
+    """Calendars that co-members of the user's groups share into the group.
+
+    Each user designates ONE of their own calendars via
+    UserSettings.group_visible_calendar_id. This returns those calendars for
+    every co-member of any group the user belongs to (excluding the user's own).
+    The calendar must be owned by the designating member. Deduped (each calendar
+    appears once even across multiple shared groups).
+    """
+    my_group_ids = (
+        db.query(models.GroupMember.group_id)
+        .filter(models.GroupMember.user_id == user.id)
+    )
+    co_member_ids = (
+        db.query(models.GroupMember.user_id)
+        .filter(
+            models.GroupMember.group_id.in_(my_group_ids),
+            models.GroupMember.user_id != user.id,
+        )
+        .distinct()
+    )
+    return (
+        db.query(models.LocalCalendar)
+        .join(
+            models.UserSettings,
+            models.UserSettings.group_visible_calendar_id == models.LocalCalendar.id,
+        )
+        .filter(
+            models.UserSettings.user_id.in_(co_member_ids),
+            # the designating member must own the calendar they share
+            models.LocalCalendar.user_id == models.UserSettings.user_id,
+        )
+        .all()
+    )
+
+
 def readable_local_calendar_ids(db: Session, user: models.User) -> list[int]:
-    """All local calendar ids the user may read: own + shared + group calendars."""
+    """All local calendar ids the user may read: own + shared + group + co-member group-visible."""
     ids: set[int] = set()
 
     own = (
@@ -123,4 +159,7 @@ def readable_local_calendar_ids(db: Session, user: models.User) -> list[int]:
     )
     ids.update(r[0] for r in group_cals)
 
+    # Calendars co-members share into shared groups (group-visible).
+    ids.update(c.id for c in co_member_group_visible_calendars(db, user))
+
     return list(ids)

backend/routers/caldav_router.py

@@ -300,6 +300,7 @@ def get_events(
         end_dt = end_dt.replace(tzinfo=timezone.utc)
 
     all_events = []
+    sync_errors = []
     accounts = (
         db.query(models.CalDAVAccount)
         .filter(
@@ -333,6 +334,12 @@ def get_events(
                 logger.error(
                     "Error fetching calendar %s: %s", calendar.id, exc
                 )
+                sync_errors.append({
+                    "source": "caldav",
+                    "name": f"{account.username} – {calendar.name}",
+                    "calendar_id": calendar.id,
+                    "message": "Sync fehlgeschlagen",
+                })
 
     # ── Local calendar events (own + shared + group calendars) ─────────────
     readable_ids = permissions.readable_local_calendar_ids(db, current_user)
@@ -345,6 +352,21 @@ def get_events(
         .all()
     ) if readable_ids else []
     name_cache = {u.id: (u.display_name or u.username) for u in db.query(models.User).all()}
+    # A personal calendar shared WITH the current user is relabelled under the
+    # owner's name (so Guido's "Persönlich" reads as "Guido" for his mum) and
+    # flagged read_only unless the share grants write. Group calendars are
+    # excluded — they keep their own name and stay writable for members.
+    shares_by_cal = {
+        s.calendar_id: s
+        for s in db.query(models.CalendarShare).filter(
+            models.CalendarShare.user_id == current_user.id
+        )
+    }
+    group_cal_ids = {
+        r[0] for r in db.query(models.GroupCalendar.calendar_id).filter(
+            models.GroupCalendar.calendar_id.in_(readable_ids)
+        )
+    } if readable_ids else set()
     # Cache each owner's private-event visibility (one lookup per owner, not per event).
     vis_cache: dict = {}
 
@@ -354,6 +376,15 @@ def get_events(
         return vis_cache[uid]
 
     for local_cal in local_calendars:
+        # Decoration for a personal calendar shared with (not owned by) me.
+        is_shared_personal = (
+            local_cal.user_id != current_user.id
+            and local_cal.id not in group_cal_ids
+        )
+        share = shares_by_cal.get(local_cal.id) if is_shared_personal else None
+        shared_owner_name = name_cache.get(local_cal.user_id) if is_shared_personal else None
+        shared_read_only = is_shared_personal and (share.permission if share else None) != "read_write"
+        shared_color = share.color if share else None
         local_events = (
             db.query(models.LocalEvent)
             .filter(
@@ -384,6 +415,12 @@ def get_events(
             else:
                 built = [build_local_event_dict(ev, local_cal, rrule=None, creator=creator)]
             for b in built:
+                if shared_owner_name:
+                    b["calendar_name"] = shared_owner_name
+                if shared_read_only:
+                    b["read_only"] = True
+                if shared_color:
+                    b["calendarColor"] = shared_color
                 b = apply_event_privacy(
                     b, owner_id=owner_id, is_private=is_priv,
                     requester_id=current_user.id, visibility=visibility,
@@ -414,13 +451,18 @@ def get_events(
         .filter(models.GoogleAccount.user_id == current_user.id)
         .all()
     )
-    google_errors = []
     for g_acc in google_accounts:
         try:
-            all_events.extend(get_google_events(g_acc, start_dt, end_dt, db))
+            g_events, g_errors = get_google_events(g_acc, start_dt, end_dt, db)
+            all_events.extend(g_events)
+            sync_errors.extend(g_errors)
         except Exception as exc:
             logger.error("Error fetching Google Calendar for %s: %s", g_acc.email, exc)
-            google_errors.append({"email": g_acc.email})
+            sync_errors.append({
+                "source": "google",
+                "name": g_acc.email,
+                "message": "Sync fehlgeschlagen",
+            })
 
     # ── Home Assistant events ─────────────────────────────
     from routers.homeassistant_router import get_ha_events
@@ -431,11 +473,18 @@ def get_events(
     )
     for ha_acc in ha_accounts:
         try:
-            all_events.extend(get_ha_events(ha_acc, start_dt, end_dt, db))
+            ha_events, ha_errors = get_ha_events(ha_acc, start_dt, end_dt, db)
+            all_events.extend(ha_events)
+            sync_errors.extend(ha_errors)
         except Exception as exc:
             logger.error("Error fetching HA events for %s: %s", ha_acc.name, exc)
+            sync_errors.append({
+                "source": "homeassistant",
+                "name": ha_acc.name,
+                "message": "Sync fehlgeschlagen",
+            })
 
-    return {"events": all_events, "errors": google_errors}
+    return {"events": all_events, "errors": sync_errors}
 
 
 @router.post("/events")

backend/routers/dav_router.py

@@ -0,0 +1,491 @@
+"""Minimal two-way CalDAV server for published local calendars.
+
+Two ways to reach a published local calendar:
+
+1. Secret token URL (no login) — ``/dav/{token}/``.
+2. Username + password (HTTP Basic Auth) with principal discovery —
+   ``/caldav/`` advertises the user's calendar-home-set and lists every
+   published calendar as ``/caldav/{id}/``. This is what account-based clients
+   (Apple Calendar, DAVx5, Thunderbird) use when you enter server + credentials.
+
+Supported methods: OPTIONS, PROPFIND, REPORT (calendar-query / calendar-multiget),
+GET, PUT, DELETE. Change detection is ctag-based (CS:getctag on the collection +
+getetag per event), avoiding deletion tombstones.
+
+Reuses ``ical_io.build_ics`` / ``parse_ics``. Note: VALARM/reminders are not
+round-tripped (parse_ics ignores them).
+"""
+
+from __future__ import annotations
+
+import base64
+import uuid
+import xml.etree.ElementTree as ET
+from datetime import datetime, timezone
+from urllib.parse import quote, unquote
+from xml.sax.saxutils import escape as xml_escape
+
+from fastapi import APIRouter, Depends, Request
+from fastapi.responses import RedirectResponse, Response
+from sqlalchemy import func
+from sqlalchemy.orm import Session
+
+import dav_util
+import ical_io
+import models
+from auth import verify_password
+from database import get_db
+
+router = APIRouter()
+
+# XML namespaces used across WebDAV / CalDAV.
+NS_DAV = "DAV:"
+NS_CAL = "urn:ietf:params:xml:ns:caldav"
+NS_CS = "http://calendarserver.org/ns/"
+NS_ICAL = "http://apple.com/ns/ical/"
+
+_NS_DECL = (
+    'xmlns:D="DAV:" '
+    'xmlns:C="urn:ietf:params:xml:ns:caldav" '
+    'xmlns:CS="http://calendarserver.org/ns/" '
+    'xmlns:ICAL="http://apple.com/ns/ical/"'
+)
+
+_ALLOW = "OPTIONS, GET, HEAD, PUT, DELETE, PROPFIND, REPORT"
+_MULTISTATUS_CT = "application/xml; charset=utf-8"
+_LOGIN_HREF = "/caldav/"
+
+
+# ── Helpers ───────────────────────────────────────────────
+
+def _resolve(token: str, db: Session) -> models.LocalCalendar | None:
+    if not token:
+        return None
+    return (
+        db.query(models.LocalCalendar)
+        .filter(
+            models.LocalCalendar.dav_token == token,
+            models.LocalCalendar.caldav_published == True,  # noqa: E712
+        )
+        .first()
+    )
+
+
+def _basic_auth_user(request: Request, db: Session) -> models.User | None:
+    """Validate an HTTP Basic Authorization header against a Calendarr account.
+
+    Accepts an app-specific password (always) or the account password (only when
+    MFA is off — otherwise the account password would bypass 2FA, which CalDAV
+    clients can't satisfy).
+    """
+    hdr = request.headers.get("Authorization", "")
+    if not hdr.lower().startswith("basic "):
+        return None
+    try:
+        raw = base64.b64decode(hdr.split(" ", 1)[1]).decode("utf-8")
+    except Exception:
+        return None
+    username, sep, password = raw.partition(":")
+    if not sep:
+        return None
+    # Login names are stored lowercase; match case-insensitively like the web login.
+    user = (
+        db.query(models.User)
+        .filter(func.lower(models.User.username) == username.lower())
+        .first()
+    )
+    if not user:
+        return None
+
+    # 1) App-specific passwords — always allowed, MFA-safe.
+    for ap in db.query(models.AppPassword).filter(models.AppPassword.user_id == user.id).all():
+        try:
+            if verify_password(password, ap.password_hash):
+                ap.last_used_at = datetime.now(timezone.utc).isoformat()
+                db.commit()
+                return user
+        except Exception:
+            continue
+
+    # 2) Account password — only when 2FA is disabled.
+    if not user.totp_enabled:
+        try:
+            if verify_password(password, user.password_hash):
+                return user
+        except Exception:
+            return None
+    return None
+
+
+def _unauthorized() -> Response:
+    return Response(status_code=401, headers={"WWW-Authenticate": 'Basic realm="Calendarr CalDAV"'})
+
+
+def _published_calendars(user: models.User, db: Session) -> list[models.LocalCalendar]:
+    return (
+        db.query(models.LocalCalendar)
+        .filter(
+            models.LocalCalendar.user_id == user.id,
+            models.LocalCalendar.caldav_published == True,  # noqa: E712
+        )
+        .all()
+    )
+
+
+def _events(cal: models.LocalCalendar, db: Session) -> list[models.LocalEvent]:
+    return (
+        db.query(models.LocalEvent)
+        .filter(models.LocalEvent.calendar_id == cal.id)
+        .all()
+    )
+
+
+def _etag(ev: models.LocalEvent) -> str:
+    return ev.etag or "0"
+
+
+def _resource_name(ev: models.LocalEvent) -> str:
+    return f"{quote(ev.uid, safe='')}.ics"
+
+
+def _event_href(base: str, ev: models.LocalEvent) -> str:
+    return f"{base}{_resource_name(ev)}"
+
+
+def _name_cache(cal: models.LocalCalendar, db: Session) -> dict:
+    owner = db.query(models.User).filter(models.User.id == cal.user_id).first()
+    if owner:
+        return {owner.id: (owner.display_name or owner.username)}
+    return {}
+
+
+def _build_ics(cal: models.LocalCalendar, evs: list[models.LocalEvent], db: Session) -> str:
+    return ical_io.build_ics(cal, evs, name_cache=_name_cache(cal, db))
+
+
+# ── XML builders ──────────────────────────────────────────
+
+def _collection_propstat(cal: models.LocalCalendar, base: str, *,
+                         principal_href: str | None = None,
+                         home_href: str | None = None) -> str:
+    principal_href = principal_href or base
+    home_href = home_href or base
+    return f"""  <D:response>
+    <D:href>{base}</D:href>
+    <D:propstat>
+      <D:prop>
+        <D:resourcetype><D:collection/><C:calendar/></D:resourcetype>
+        <D:displayname>{xml_escape(cal.name or "")}</D:displayname>
+        <CS:getctag>{xml_escape(cal.dav_ctag or "0")}</CS:getctag>
+        <D:supported-report-set>
+          <D:supported-report><D:report><C:calendar-query/></D:report></D:supported-report>
+          <D:supported-report><D:report><C:calendar-multiget/></D:report></D:supported-report>
+        </D:supported-report-set>
+        <C:supported-calendar-component-set><C:comp name="VEVENT"/></C:supported-calendar-component-set>
+        <ICAL:calendar-color>{xml_escape(cal.color or "#34a853")}</ICAL:calendar-color>
+        <D:current-user-principal><D:href>{principal_href}</D:href></D:current-user-principal>
+        <D:principal-URL><D:href>{principal_href}</D:href></D:principal-URL>
+        <C:calendar-home-set><D:href>{home_href}</D:href></C:calendar-home-set>
+      </D:prop>
+      <D:status>HTTP/1.1 200 OK</D:status>
+    </D:propstat>
+  </D:response>"""
+
+
+def _principal_propstat(user: models.User) -> str:
+    href = _LOGIN_HREF
+    name = user.display_name or user.username
+    return f"""  <D:response>
+    <D:href>{href}</D:href>
+    <D:propstat>
+      <D:prop>
+        <D:resourcetype><D:collection/><D:principal/></D:resourcetype>
+        <D:displayname>{xml_escape(name)}</D:displayname>
+        <D:current-user-principal><D:href>{href}</D:href></D:current-user-principal>
+        <D:principal-URL><D:href>{href}</D:href></D:principal-URL>
+        <C:calendar-home-set><D:href>{href}</D:href></C:calendar-home-set>
+      </D:prop>
+      <D:status>HTTP/1.1 200 OK</D:status>
+    </D:propstat>
+  </D:response>"""
+
+
+def _event_propstat(base: str, ev: models.LocalEvent, *, with_data: bool = False,
+                    ics: str | None = None) -> str:
+    href = _event_href(base, ev)
+    data = ""
+    if with_data and ics is not None:
+        data = f"\n        <C:calendar-data>{xml_escape(ics)}</C:calendar-data>"
+    return f"""  <D:response>
+    <D:href>{href}</D:href>
+    <D:propstat>
+      <D:prop>
+        <D:resourcetype/>
+        <D:getetag>"{xml_escape(_etag(ev))}"</D:getetag>
+        <D:getcontenttype>text/calendar; charset=utf-8; component=VEVENT</D:getcontenttype>{data}
+      </D:prop>
+      <D:status>HTTP/1.1 200 OK</D:status>
+    </D:propstat>
+  </D:response>"""
+
+
+def _multistatus(body: str) -> Response:
+    xml = f'<?xml version="1.0" encoding="utf-8"?>\n<D:multistatus {_NS_DECL}>\n{body}\n</D:multistatus>'
+    return Response(content=xml, status_code=207, media_type=_MULTISTATUS_CT)
+
+
+# ── Method handlers (shared by token and Basic-Auth paths) ──
+
+def _handle_options() -> Response:
+    return Response(status_code=200, headers={
+        "DAV": "1, 2, 3, calendar-access",
+        "Allow": _ALLOW,
+    })
+
+
+def _find_event(cal: models.LocalCalendar, resource: str, db: Session) -> models.LocalEvent | None:
+    name = resource.rsplit("/", 1)[-1]
+    if name.endswith(".ics"):
+        name = name[:-4]
+    uid = unquote(name)
+    return (
+        db.query(models.LocalEvent)
+        .filter(
+            models.LocalEvent.calendar_id == cal.id,
+            models.LocalEvent.uid == uid,
+        )
+        .first()
+    )
+
+
+def _handle_propfind(cal: models.LocalCalendar, base: str, resource: str, depth: str,
+                     db: Session, *, principal_href: str | None = None,
+                     home_href: str | None = None) -> Response:
+    # PROPFIND on a single event resource.
+    if resource:
+        ev = _find_event(cal, resource, db)
+        if not ev:
+            return Response(status_code=404)
+        return _multistatus(_event_propstat(base, ev))
+
+    # Collection: always include collection props; Depth:1 adds each event.
+    parts = [_collection_propstat(cal, base, principal_href=principal_href, home_href=home_href)]
+    if depth != "0":
+        for ev in _events(cal, db):
+            parts.append(_event_propstat(base, ev))
+    return _multistatus("\n".join(parts))
+
+
+def _handle_report(cal: models.LocalCalendar, base: str, body: bytes, db: Session) -> Response:
+    report_type = None
+    hrefs: list[str] = []
+    if body:
+        try:
+            root = ET.fromstring(body)
+            report_type = root.tag.split("}")[-1]  # calendar-query | calendar-multiget
+            hrefs = [el.text for el in root.iter(f"{{{NS_DAV}}}href") if el.text]
+        except ET.ParseError:
+            pass
+
+    if report_type == "calendar-multiget" and hrefs:
+        wanted = {unquote(h.rstrip("/").rsplit("/", 1)[-1]) for h in hrefs}
+        evs = [ev for ev in _events(cal, db) if f"{ev.uid}.ics" in wanted]
+    else:
+        # calendar-query (or unknown) → return the whole calendar.
+        evs = _events(cal, db)
+
+    parts = []
+    for ev in evs:
+        ics = _build_ics(cal, [ev], db)
+        parts.append(_event_propstat(base, ev, with_data=True, ics=ics))
+    return _multistatus("\n".join(parts) if parts else "")
+
+
+def _handle_get(cal: models.LocalCalendar, resource: str, db: Session,
+                *, head: bool = False) -> Response:
+    ev = _find_event(cal, resource, db)
+    if not ev:
+        return Response(status_code=404)
+    ics = _build_ics(cal, [ev], db)
+    headers = {"ETag": f'"{_etag(ev)}"'}
+    return Response(
+        content=b"" if head else ics,
+        media_type="text/calendar; charset=utf-8",
+        headers=headers,
+    )
+
+
+def _handle_put(cal: models.LocalCalendar, resource: str, body: bytes, db: Session) -> Response:
+    try:
+        parsed = ical_io.parse_ics(body)
+    except ValueError:
+        return Response(status_code=400)
+    items = parsed.get("events") or []
+    if not items:
+        return Response(status_code=400)
+    item = items[0]
+
+    # Key by the VEVENT UID; fall back to the resource name.
+    uid = item.get("uid")
+    if not uid:
+        name = resource.rsplit("/", 1)[-1]
+        uid = unquote(name[:-4] if name.endswith(".ics") else name) or str(uuid.uuid4())
+
+    # Scope to THIS calendar — never touch another calendar's/user's event that
+    # happens to share the UID (local_events.uid is globally unique).
+    ev = (
+        db.query(models.LocalEvent)
+        .filter(
+            models.LocalEvent.calendar_id == cal.id,
+            models.LocalEvent.uid == uid,
+        )
+        .first()
+    )
+    created = ev is None
+    if created:
+        # If the UID already exists elsewhere, the global UNIQUE constraint would
+        # 500 on commit — reject cleanly with 409 instead.
+        if db.query(models.LocalEvent.id).filter(models.LocalEvent.uid == uid).first():
+            return Response(status_code=409)
+        ev = models.LocalEvent(calendar_id=cal.id, uid=uid, creator_id=cal.user_id)
+        db.add(ev)
+    ev.title = item.get("title") or "(ohne Titel)"
+    ev.start = item["start"]
+    ev.end = item["end"]
+    ev.all_day = item.get("all_day", False)
+    ev.location = item.get("location")
+    ev.description = item.get("description")
+    ev.rrule = item.get("rrule")
+    ev.exdate = item.get("exdate")
+    dav_util.bump_dav(cal, ev)
+    db.commit()
+    db.refresh(ev)
+    return Response(status_code=201 if created else 204, headers={"ETag": f'"{_etag(ev)}"'})
+
+
+def _handle_delete(cal: models.LocalCalendar, resource: str, db: Session) -> Response:
+    ev = _find_event(cal, resource, db)
+    if not ev:
+        return Response(status_code=404)
+    dav_util.bump_dav(cal)
+    db.delete(ev)
+    db.commit()
+    return Response(status_code=204)
+
+
+async def _dispatch_collection(request: Request, cal: models.LocalCalendar, base: str,
+                               resource: str, db: Session, *,
+                               principal_href: str | None = None,
+                               home_href: str | None = None) -> Response:
+    """Serve a single calendar collection; auth/ownership already checked."""
+    method = request.method.upper()
+    if method == "PROPFIND":
+        depth = request.headers.get("Depth", "0")
+        return _handle_propfind(cal, base, resource, depth, db,
+                                principal_href=principal_href, home_href=home_href)
+    if method == "REPORT":
+        return _handle_report(cal, base, await request.body(), db)
+    if method in ("GET", "HEAD"):
+        if not resource:
+            ics = _build_ics(cal, _events(cal, db), db)
+            return Response(content=ics, media_type="text/calendar; charset=utf-8")
+        return _handle_get(cal, resource, db, head=(method == "HEAD"))
+    if method == "PUT":
+        return _handle_put(cal, resource, await request.body(), db)
+    if method == "DELETE":
+        if not resource:
+            return Response(status_code=403)  # don't delete the collection itself
+        return _handle_delete(cal, resource, db)
+    return Response(status_code=405, headers={"Allow": _ALLOW})
+
+
+# ── Token path (no login): /dav/{token}/… ─────────────────
+
+async def _dispatch_token(request: Request, token: str, resource: str, db: Session) -> Response:
+    if request.method.upper() == "OPTIONS":
+        return _handle_options()
+    cal = _resolve(token, db)
+    if not cal:
+        return Response(status_code=404)
+    base = f"/dav/{token}/"
+    return await _dispatch_collection(request, cal, base, resource, db)
+
+
+_METHODS = ["OPTIONS", "GET", "HEAD", "PUT", "DELETE", "PROPFIND", "REPORT"]
+
+
+@router.api_route("/dav/{token}", methods=_METHODS, include_in_schema=False)
+async def dav_collection(token: str, request: Request, db: Session = Depends(get_db)):
+    return await _dispatch_token(request, token, "", db)
+
+
+@router.api_route("/dav/{token}/{resource:path}", methods=_METHODS, include_in_schema=False)
+async def dav_resource(token: str, resource: str, request: Request, db: Session = Depends(get_db)):
+    return await _dispatch_token(request, token, resource, db)
+
+
+# ── Basic-Auth path (username/password): /caldav/… ────────
+
+async def _dispatch_home(request: Request, db: Session) -> Response:
+    """Principal + calendar-home-set: lists the user's published calendars."""
+    if request.method.upper() == "OPTIONS":
+        return _handle_options()
+    user = _basic_auth_user(request, db)
+    if not user:
+        return _unauthorized()
+    if request.method.upper() != "PROPFIND":
+        return Response(status_code=405, headers={"Allow": _ALLOW})
+    depth = request.headers.get("Depth", "0")
+    parts = [_principal_propstat(user)]
+    if depth != "0":
+        for cal in _published_calendars(user, db):
+            parts.append(_collection_propstat(
+                cal, f"/caldav/{cal.id}/",
+                principal_href=_LOGIN_HREF, home_href=_LOGIN_HREF))
+    return _multistatus("\n".join(parts))
+
+
+async def _dispatch_auth_calendar(request: Request, cal_id: int, resource: str, db: Session) -> Response:
+    if request.method.upper() == "OPTIONS":
+        return _handle_options()
+    user = _basic_auth_user(request, db)
+    if not user:
+        return _unauthorized()
+    cal = (
+        db.query(models.LocalCalendar)
+        .filter(
+            models.LocalCalendar.id == cal_id,
+            models.LocalCalendar.user_id == user.id,
+            models.LocalCalendar.caldav_published == True,  # noqa: E712
+        )
+        .first()
+    )
+    if not cal:
+        return Response(status_code=404)
+    base = f"/caldav/{cal.id}/"
+    return await _dispatch_collection(request, cal, base, resource, db,
+                                      principal_href=_LOGIN_HREF, home_href=_LOGIN_HREF)
+
+
+@router.api_route("/.well-known/caldav", methods=["OPTIONS", "GET", "PROPFIND"], include_in_schema=False)
+async def wellknown_caldav(request: Request):
+    if request.method.upper() == "OPTIONS":
+        return _handle_options()
+    # Point discovery at the principal/home collection.
+    return RedirectResponse(url=_LOGIN_HREF, status_code=301)
+
+
+@router.api_route("/caldav", methods=_METHODS, include_in_schema=False)
+@router.api_route("/caldav/", methods=_METHODS, include_in_schema=False)
+async def caldav_home(request: Request, db: Session = Depends(get_db)):
+    return await _dispatch_home(request, db)
+
+
+@router.api_route("/caldav/{cal_id:int}", methods=_METHODS, include_in_schema=False)
+async def caldav_calendar(cal_id: int, request: Request, db: Session = Depends(get_db)):
+    return await _dispatch_auth_calendar(request, cal_id, "", db)
+
+
+@router.api_route("/caldav/{cal_id:int}/{resource:path}", methods=_METHODS, include_in_schema=False)
+async def caldav_calendar_resource(cal_id: int, resource: str, request: Request, db: Session = Depends(get_db)):
+    return await _dispatch_auth_calendar(request, cal_id, resource, db)

backend/routers/google_router.py

@@ -382,15 +382,35 @@ def update_calendar(
 
 # ── Events ───────────────────────────────────────────────
 
-def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt: datetime, db: Session) -> list:
+def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt: datetime, db: Session) -> tuple:
-    """Fetch events from all enabled Google calendars for an account."""
+    """Fetch events from all enabled Google calendars for an account.
+
+    Returns (events, errors) — errors is a list of
+    {"source": "google", "name": ..., "message": ...} dicts for any
+    calendar that failed to sync. Never includes raw exception text.
+    """
+    all_events = []
+    errors = []
     try:
         token = _refresh_access_token(account, db)
     except Exception as exc:
+        # A token failure aborts the whole account, but attribute it to each
+        # enabled calendar so clients can pin the error to a specific calendar
+        # (and preserve that calendar's cached events instead of wiping it).
         logger.error("Token refresh failed for Google account %s: %s", account.email, exc)
-        raise
+        for gcal in account.calendars:
+            if not gcal.enabled or gcal.sidebar_hidden:
+                continue
+            if _is_system_calendar(gcal.cal_id):
+                continue
+            errors.append({
+                "source": "google",
+                "name": f"{account.email} – {gcal.name}",
+                "calendar_id": gcal.id,
+                "message": "Sync fehlgeschlagen",
+            })
+        return all_events, errors
 
-    all_events = []
     for gcal in account.calendars:
         if not gcal.enabled or gcal.sidebar_hidden:
             continue
@@ -409,8 +429,14 @@ def get_google_events(account: models.GoogleAccount, start_dt: datetime, end_dt:
                 all_events.append(_parse_google_event(ev, gcal.id, gcal.name, gcal.color or "#4285f4"))
         except Exception as exc:
             logger.error("Error fetching events for calendar %s (%s): %s", gcal.name, gcal.cal_id, exc)
+            errors.append({
+                "source": "google",
+                "name": f"{account.email} – {gcal.name}",
+                "calendar_id": gcal.id,
+                "message": "Sync fehlgeschlagen",
+            })
 
-    return all_events
+    return all_events, errors
 
 
 class GoogleEventCreate(BaseModel):

backend/routers/groups_router.py

@@ -176,11 +176,22 @@ def _group_detail(db: Session, group: models.Group, current_user: models.User) -
     member_dicts = []
     for i, m in enumerate(members):
         u = db.query(models.User).filter(models.User.id == m.user_id).first()
+        # Whether this member actually shares a calendar into the group (owns a
+        # calendar designated as their group_visible). Lets clients hide phantom
+        # empty rows for members who share nothing.
+        s = db.query(models.UserSettings).filter(models.UserSettings.user_id == m.user_id).first()
+        shares_calendar = False
+        if s and s.group_visible_calendar_id is not None:
+            shares_calendar = db.query(models.LocalCalendar.id).filter(
+                models.LocalCalendar.id == s.group_visible_calendar_id,
+                models.LocalCalendar.user_id == m.user_id,
+            ).first() is not None
         member_dicts.append({
             "id": m.user_id,
             "display_name": (u.display_name or u.username) if u else None,
             "role": m.role,
             "color": m.color or MEMBER_PALETTE[i % len(MEMBER_PALETTE)],
+            "shares_calendar": shares_calendar,
         })
     gcal_id = _group_calendar_id(db, group.id)
     return {
@@ -317,17 +328,12 @@ def _first_name(name: Optional[str]) -> str:
 
 def _decorate_title(title: str, *, is_group: bool, creator: Optional[dict],
                     owner: Optional[dict], me_id: int) -> str:
-    """Server-side display title for the combined view so every client (web,
+    """Server-side display title for the combined view. The former owner/creator
-    iOS, Android) renders identically: another member's / creator's first name
+    first-name prefix ("Guido: …") was dropped: each member already has a
-    is prefixed. No icon glyph is embedded — group icons are semantic keys the
+    distinct colour, so the prefix was redundant noise. We still return a
-    clients render as native vector icons, and group-calendar events are
+    non-empty `display_title` (== raw title) so the clients' legacy fallback —
-    distinguished by their (group) colour. The raw `title` stays for editing."""
+    which rebuilds a prefix when `display_title` is empty — never kicks in.
-    if is_group:
+    `display_color` continues to carry the per-person colour."""
-        if creator and creator.get("id") is not None and creator.get("id") != me_id:
-            return f"{_first_name(creator.get('display_name'))}: {title}"
-        return title
-    if owner and owner.get("id") is not None and owner.get("id") != me_id:
-        return f"{_first_name(owner.get('display_name'))}: {title}"
     return title
 
 

backend/routers/homeassistant_router.py

@@ -313,13 +313,32 @@ def _parse_ha_event(ev: dict, cal_db_id: int, cal_name: str, cal_color: str) ->
     }
 
 
-def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_dt: datetime, db: Session) -> list:
+def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_dt: datetime, db: Session) -> tuple:
+    """Fetch events from all enabled HA calendars for an account.
+
+    Returns (events, errors) — errors is a list of
+    {"source": "homeassistant", "name": ..., "calendar_id": ..., "message": ...}
+    dicts for any calendar that failed to sync. Never includes raw exception text.
+    """
     all_events = []
+    errors = []
     try:
         token = _get_valid_token(account, db)
     except Exception as exc:
+        # A token failure aborts the whole account, but attribute it to each
+        # enabled calendar so clients can pin the error to a specific calendar
+        # (and preserve that calendar's cached events instead of wiping it).
         logger.error("HA token error for %s: %s", account.name, exc)
-        raise
+        for cal in account.calendars:
+            if not cal.enabled or cal.sidebar_hidden:
+                continue
+            errors.append({
+                "source": "homeassistant",
+                "name": f"{account.name} – {cal.name}",
+                "calendar_id": cal.id,
+                "message": "Sync fehlgeschlagen",
+            })
+        return all_events, errors
     for cal in account.calendars:
         if not cal.enabled or cal.sidebar_hidden:
             continue
@@ -330,7 +349,13 @@ def get_ha_events(account: models.HomeAssistantAccount, start_dt: datetime, end_
                 all_events.append(_parse_ha_event(ev, cal.id, cal.name, color))
         except Exception as exc:
             logger.error("HA event fetch error %s (%s): %s", cal.entity_id, account.name, exc)
-    return all_events
+            errors.append({
+                "source": "homeassistant",
+                "name": f"{account.name} – {cal.name}",
+                "calendar_id": cal.id,
+                "message": "Sync fehlgeschlagen",
+            })
+    return all_events, errors
 
 
 # ── Serialization ─────────────────────────────────────────

backend/routers/ical_router.py

@@ -1,6 +1,9 @@
+import ipaddress
 import logging
+import socket
 from datetime import datetime, timezone
 from typing import Optional
+from urllib.parse import urljoin, urlparse
 
 import requests as http_requests
 from fastapi import APIRouter, Depends, HTTPException
@@ -45,13 +48,67 @@ def _sub_dict(sub: models.ICalSubscription) -> dict:
     }
 
 
-def _fetch_ics(url: str) -> str:
+_MAX_ICS_BYTES = 5 * 1024 * 1024
-    """Download .ics content from a URL."""
+_MAX_REDIRECTS = 5
+
+
+def _host_is_public(host: str) -> bool:
+    """False if the host resolves to any private/loopback/link-local address."""
     try:
-        resp = http_requests.get(url, timeout=30, allow_redirects=True)
+        infos = socket.getaddrinfo(host, None)
+    except socket.gaierror:
+        return False
+    for info in infos:
+        try:
+            ip = ipaddress.ip_address(info[4][0])
+        except ValueError:
+            return False
+        if (ip.is_private or ip.is_loopback or ip.is_link_local
+                or ip.is_reserved or ip.is_multicast or ip.is_unspecified):
+            return False
+    return True
+
+
+def _validate_public_url(url: str) -> None:
+    parsed = urlparse(url)
+    if parsed.scheme not in ("http", "https"):
+        raise ValueError("Nur http(s)-URLs sind erlaubt.")
+    if not parsed.hostname:
+        raise ValueError("Ungültige URL.")
+    if not _host_is_public(parsed.hostname):
+        raise ValueError("Interne/private Adressen sind nicht erlaubt.")
+
+
+def _fetch_ics(url: str) -> str:
+    """Download .ics content, blocking SSRF to internal/private hosts.
+
+    Redirects are followed manually so every hop is re-validated (a public URL
+    can otherwise 30x-redirect into the internal network). Response size is
+    capped. (Residual risk: DNS rebinding between check and connect.)
+    """
+    if url.startswith("webcal://"):
+        url = "https://" + url[len("webcal://"):]
+    try:
+        for _ in range(_MAX_REDIRECTS + 1):
+            _validate_public_url(url)
+            resp = http_requests.get(url, timeout=30, allow_redirects=False, stream=True)
+            if resp.is_redirect and resp.headers.get("location"):
+                url = urljoin(url, resp.headers["location"])
+                resp.close()
+                continue
             resp.raise_for_status()
-        resp.encoding = 'utf-8'
+            resp.encoding = "utf-8"
-        return resp.text
+            chunks, total = [], 0
+            for chunk in resp.iter_content(8192, decode_unicode=True):
+                if not chunk:
+                    continue
+                chunks.append(chunk)
+                total += len(chunk)
+                if total > _MAX_ICS_BYTES:
+                    resp.close()
+                    raise ValueError("Datei zu groß (max. 5 MB).")
+            return "".join(chunks)
+        raise ValueError("Zu viele Weiterleitungen.")
     except http_requests.RequestException as e:
         raise ValueError(f"Fehler beim Abrufen der URL: {e}")
 

backend/routers/local_router.py

@@ -2,11 +2,12 @@ import uuid
 from datetime import datetime, timezone
 from typing import List, Optional
 
-from fastapi import APIRouter, Depends, Form, HTTPException, Query, UploadFile, File
+from fastapi import APIRouter, Depends, Form, HTTPException, Query, Request, UploadFile, File
 from fastapi.responses import Response
 from pydantic import BaseModel
 from sqlalchemy.orm import Session
 
+import dav_util
 import ical_io
 import models
 import permissions
@@ -31,6 +32,7 @@ class CalendarUpdate(BaseModel):
     color: Optional[str] = None
     enabled: Optional[bool] = None
     reminders_enabled: Optional[bool] = None
+    caldav_published: Optional[bool] = None
 
 
 class EventCreate(BaseModel):
@@ -67,16 +69,24 @@ class ShareCreate(BaseModel):
 
 
 def _cal_dict(cal: models.LocalCalendar, *, owned: bool = True,
-              shared_by: Optional[str] = None, permission: Optional[str] = None) -> dict:
+              shared_by: Optional[str] = None, permission: Optional[str] = None,
+              color_override: Optional[str] = None,
+              request: Optional[Request] = None) -> dict:
     d = {
         "id": cal.id,
         "name": cal.name,
-        "color": cal.color,
+        # A recipient's own colour for a shared calendar wins over the owner's.
+        "color": color_override or cal.color,
         "enabled": cal.enabled,
         "reminders_enabled": bool(cal.reminders_enabled),
+        "caldav_published": bool(cal.caldav_published),
         "type": "local",
         "owned": owned,
     }
+    # Only the owner may publish; expose the subscribe URLs only when active.
+    if owned and cal.caldav_published and cal.dav_token:
+        d["caldav_url"] = dav_util.caldav_url(request, cal.dav_token) if request else None
+        d["caldav_login_url"] = dav_util.caldav_login_url(request) if request else None
     if shared_by is not None:
         d["shared_by"] = shared_by
     if permission is not None:
@@ -92,6 +102,7 @@ def _event_dict(ev: models.LocalEvent, cal: models.LocalCalendar, db: Session) -
 
 @router.get("/calendars")
 def list_calendars(
+    request: Request,
     db: Session = Depends(get_db),
     current_user: models.User = Depends(get_current_user),
 ):
@@ -117,7 +128,7 @@ def list_calendars(
     )
     result = []
     for c in own:
-        d = _cal_dict(c, owned=True)
+        d = _cal_dict(c, owned=True, request=request)
         if c.id in group_cal_map:
             d["group"] = True
             d["shared_by"] = group_cal_map[c.id]  # group name, for labelling
@@ -141,6 +152,7 @@ def list_calendars(
             cal, owned=False,
             shared_by=(owner.display_name or owner.username) if owner else None,
             permission=share.permission,
+            color_override=share.color,
         )
         if cal.id in group_cal_map:
             d["group"] = True
@@ -158,6 +170,23 @@ def list_calendars(
         d = _cal_dict(cal, owned=False, shared_by=group_name, permission="read_write")
         d["group"] = True
         result.append(d)
+
+    # Calendars co-members share into shared groups (group_visible_calendar_id).
+    # Read-only, shown under the owner's name. Deduped against everything above
+    # so a calendar already shared directly / as a group calendar isn't doubled.
+    for cal in permissions.co_member_group_visible_calendars(db, current_user):
+        if cal.id in seen_ids:
+            continue
+        seen_ids.add(cal.id)
+        owner = db.query(models.User).filter(models.User.id == cal.user_id).first()
+        d = _cal_dict(
+            cal, owned=False,
+            shared_by=(owner.display_name or owner.username) if owner else None,
+            permission="read",
+            request=request,
+        )
+        d["group_shared"] = True
+        result.append(d)
     return result
 
 
@@ -182,6 +211,7 @@ def create_calendar(
 def update_calendar(
     calendar_id: int,
     data: CalendarUpdate,
+    request: Request,
     db: Session = Depends(get_db),
     current_user: models.User = Depends(get_current_user),
 ):
@@ -203,8 +233,74 @@ def update_calendar(
         cal.enabled = data.enabled
     if data.reminders_enabled is not None:
         cal.reminders_enabled = data.reminders_enabled
+    if data.caldav_published is not None:
+        cal.caldav_published = data.caldav_published
+        if data.caldav_published:
+            # First publish: mint a token + initial ctag so clients can sync.
+            if not cal.dav_token:
+                cal.dav_token = dav_util.new_token()
+            if not cal.dav_ctag:
+                cal.dav_ctag = dav_util.new_tag()
+        else:
+            # Unpublishing revokes access: drop the token so the URL 404s.
+            cal.dav_token = None
     db.commit()
-    return {"ok": True}
+    db.refresh(cal)
+    return _cal_dict(cal, owned=True, request=request)
+
+
+class CalendarColorUpdate(BaseModel):
+    color: str
+
+
+@router.put("/calendars/{calendar_id}/color")
+def set_calendar_color(
+    calendar_id: int,
+    data: CalendarColorUpdate,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    """Set a calendar's colour. The owner changes the calendar's colour for
+    everyone; a share recipient sets only their OWN per-user colour (stored on
+    the share) without touching the owner's. Recipients may recolour but never
+    rename a shared calendar."""
+    cal = permissions.accessible_local_calendar(db, current_user, calendar_id)
+    if cal.user_id == current_user.id:
+        cal.color = data.color
+    else:
+        share = permissions._share_for(db, calendar_id, current_user.id)
+        if share is None:
+            raise HTTPException(403, "Only the owner or a share recipient can set the colour")
+        share.color = data.color
+    db.commit()
+    return {"ok": True, "color": data.color}
+
+
+@router.post("/calendars/{calendar_id}/dav-token/rotate")
+def rotate_dav_token(
+    calendar_id: int,
+    request: Request,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    """Issue a fresh CalDAV token — the old subscribe URL stops working."""
+    cal = (
+        db.query(models.LocalCalendar)
+        .filter(
+            models.LocalCalendar.id == calendar_id,
+            models.LocalCalendar.user_id == current_user.id,
+        )
+        .first()
+    )
+    if not cal:
+        raise HTTPException(404, "Calendar not found")
+    if not cal.caldav_published:
+        raise HTTPException(422, "Calendar is not published")
+    cal.dav_token = dav_util.new_token()
+    cal.dav_ctag = dav_util.new_tag()
+    db.commit()
+    db.refresh(cal)
+    return _cal_dict(cal, owned=True, request=request)
 
 
 @router.delete("/calendars/{calendar_id}")
@@ -257,6 +353,7 @@ def create_event(
         creator_id=current_user.id,  # server-side, never from the client
     )
     db.add(ev)
+    dav_util.bump_dav(cal, ev)
     db.commit()
     db.refresh(ev)
     return _event_dict(ev, cal, db)
@@ -305,6 +402,7 @@ def update_event(
         ev.exdate = ",".join(dates)
     if data.reminders is not None:
         ev.reminders = ",".join(str(m) for m in data.reminders) if data.reminders else None
+    dav_util.bump_dav(ev.calendar, ev)
     db.commit()
     return {"ok": True}
 
@@ -316,6 +414,7 @@ def delete_event(
     current_user: models.User = Depends(get_current_user),
 ):
     ev = _writable_event(db, current_user, uid)
+    dav_util.bump_dav(ev.calendar)
     db.delete(ev)
     db.commit()
     return {"ok": True}
@@ -441,9 +540,12 @@ def _import_ics_into(cal: models.LocalCalendar, raw: bytes, db: Session) -> dict
             rrule=item.get("rrule"),
             exdate=item.get("exdate"),
             creator_name_external=item.get("organizer"),
+            etag=dav_util.new_tag(),
         )
         db.add(ev)
         imported += 1
+    if imported:
+        dav_util.bump_dav(cal)
     try:
         db.commit()
     except Exception as exc:

backend/routers/profile_router.py

@@ -1,6 +1,8 @@
 import io
 import re
 import base64
+import secrets
+from datetime import datetime, timezone
 from pathlib import Path
 from typing import Optional
 
@@ -32,6 +34,7 @@ class ProfileUpdate(BaseModel):
     email: Optional[str] = Field(default=None, max_length=120)
     display_name: Optional[str] = Field(default=None, max_length=80)
     username: Optional[str] = Field(default=None, max_length=50)  # login name (stored lowercase)
+    directory_hidden: Optional[bool] = None  # hide from sharing/group pickers
 
 
 def _strip_controls(s: str) -> str:
@@ -64,6 +67,7 @@ def get_profile(current_user: models.User = Depends(get_current_user)):
         "is_admin": current_user.is_admin,
         "has_avatar": current_user.avatar_filename is not None,
         "totp_enabled": current_user.totp_enabled,
+        "directory_hidden": bool(current_user.directory_hidden),
     }
 
 
@@ -107,11 +111,15 @@ def update_profile(
             if taken:
                 raise HTTPException(400, "Username already taken")
             current_user.username = new_login
+            if data.directory_hidden is not None:
+                current_user.directory_hidden = data.directory_hidden
             db.commit()
             # The JWT 'sub' is the login name — renaming it invalidates the old
             # token, so hand back a fresh one for the client to store.
             result["access_token"] = create_access_token({"sub": new_login})
             return result
+    if data.directory_hidden is not None:
+        current_user.directory_hidden = data.directory_hidden
     db.commit()
     return result
 
@@ -168,7 +176,11 @@ def get_avatar(current_user: models.User = Depends(get_current_user)):
 
 
 @router.get("/avatar/{user_id}")
-def get_user_avatar(user_id: int, db: Session = Depends(get_db)):
+def get_user_avatar(
+    user_id: int,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
     user = db.query(models.User).filter(models.User.id == user_id).first()
     if not user or not user.avatar_filename:
         raise HTTPException(404, "Kein Profilbild")
@@ -264,3 +276,74 @@ def disable_totp(
     current_user.totp_enabled = False
     db.commit()
     return {"ok": True}
+
+
+# ── App passwords (for CalDAV Basic Auth) ────────────────
+class AppPasswordCreate(BaseModel):
+    label: str = Field(default="CalDAV", max_length=100)
+
+
+def _app_pw_dict(ap: models.AppPassword) -> dict:
+    return {
+        "id": ap.id,
+        "label": ap.label,
+        "created_at": ap.created_at,
+        "last_used_at": ap.last_used_at,
+    }
+
+
+@router.get("/app-passwords")
+def list_app_passwords(
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    rows = (
+        db.query(models.AppPassword)
+        .filter(models.AppPassword.user_id == current_user.id)
+        .order_by(models.AppPassword.id.desc())
+        .all()
+    )
+    return [_app_pw_dict(r) for r in rows]
+
+
+@router.post("/app-passwords")
+def create_app_password(
+    data: AppPasswordCreate,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    # Show the plaintext exactly once; only the hash is stored.
+    password = secrets.token_urlsafe(18)
+    ap = models.AppPassword(
+        user_id=current_user.id,
+        label=(data.label or "CalDAV")[:100],
+        password_hash=get_password_hash(password),
+        created_at=datetime.now(timezone.utc).isoformat(),
+    )
+    db.add(ap)
+    db.commit()
+    db.refresh(ap)
+    out = _app_pw_dict(ap)
+    out["password"] = password
+    return out
+
+
+@router.delete("/app-passwords/{ap_id}")
+def delete_app_password(
+    ap_id: int,
+    db: Session = Depends(get_db),
+    current_user: models.User = Depends(get_current_user),
+):
+    ap = (
+        db.query(models.AppPassword)
+        .filter(
+            models.AppPassword.id == ap_id,
+            models.AppPassword.user_id == current_user.id,
+        )
+        .first()
+    )
+    if not ap:
+        raise HTTPException(404, "App password not found")
+    db.delete(ap)
+    db.commit()
+    return {"ok": True}

backend/routers/users_router.py

@@ -53,7 +53,10 @@ def user_directory(
     """
     users = (
         db.query(models.User)
-        .filter(models.User.id != current_user.id)
+        .filter(
+            models.User.id != current_user.id,
+            models.User.directory_hidden == False,  # noqa: E712 — hidden users opt out of pickers
+        )
         .order_by(models.User.username)
         .all()
     )

backend/tests/test_collaboration.py

@@ -409,3 +409,78 @@ def test_import_export_only_local(client):
     cal_id = _make_calendar(client, admin, "Privat")
     # Bob has no access -> 404 on export.
     assert client.get(f"/api/local/calendars/{cal_id}/export", headers=auth(b_tok)).status_code == 404
+
+
+# ── Group-visible calendars propagate to co-members' sidebars ─────────────
+
+def test_group_visible_propagates_to_member_sidebar(client):
+    admin = register_admin(client)
+    b_id, b_tok = create_user(client, admin, "bob")
+    client.post("/api/groups/", headers=auth(admin),
+                json={"name": "Team", "member_ids": [b_id]})
+
+    # Bob designates a calendar as group-visible; admin (co-member) should see it.
+    b_cal = _make_calendar(client, b_tok, "Bobs Kalender")
+    client.put("/api/settings/", headers=auth(b_tok), json={"group_visible_calendar_id": b_cal})
+    _make_event(client, b_tok, b_cal, "Bobs Termin")
+
+    cals = client.get("/api/local/calendars", headers=auth(admin)).json()
+    shared = [c for c in cals if c["id"] == b_cal]
+    assert len(shared) == 1, shared
+    assert shared[0]["owned"] is False
+    assert shared[0]["shared_by"] == "bob"
+    assert shared[0]["permission"] == "read"
+    assert shared[0].get("group_shared") is True
+
+    # Its events appear in the normal merged read, read-only.
+    events = client.get("/api/caldav/events", headers=auth(admin), params=RANGE).json()["events"]
+    bob_ev = [e for e in events if e["title"] == "Bobs Termin"]
+    assert bob_ev and bob_ev[0].get("read_only") is True
+
+
+def test_group_visible_absent_when_not_designated(client):
+    admin = register_admin(client)
+    b_id, b_tok = create_user(client, admin, "bob")
+    client.post("/api/groups/", headers=auth(admin),
+                json={"name": "Team", "member_ids": [b_id]})
+    b_cal = _make_calendar(client, b_tok, "Bobs Kalender")  # never designated
+    cals = client.get("/api/local/calendars", headers=auth(admin)).json()
+    assert not any(c["id"] == b_cal for c in cals)
+
+
+def test_group_visible_not_duplicated_with_direct_share(client):
+    admin = register_admin(client)
+    admin_id = client.get("/api/profile/", headers=auth(admin)).json()["id"]
+    b_id, b_tok = create_user(client, admin, "bob")
+    client.post("/api/groups/", headers=auth(admin),
+                json={"name": "Team", "member_ids": [b_id]})
+    b_cal = _make_calendar(client, b_tok, "Bobs Kalender")
+    client.put("/api/settings/", headers=auth(b_tok), json={"group_visible_calendar_id": b_cal})
+    # Also directly shared with admin (read_write) — must not double-list.
+    client.post(f"/api/local/calendars/{b_cal}/shares", headers=auth(b_tok),
+                json={"user_id": admin_id, "permission": "read_write"})
+    cals = client.get("/api/local/calendars", headers=auth(admin)).json()
+    matches = [c for c in cals if c["id"] == b_cal]
+    assert len(matches) == 1, matches
+    # The direct share wins (read_write, not flagged group_shared).
+    assert matches[0]["permission"] == "read_write"
+    assert matches[0].get("group_shared") is not True
+
+
+# ── Hidden profile (directory opt-out) ────────────────────────────────────
+
+def test_directory_hidden_excludes_from_picker_but_not_admin(client):
+    admin = register_admin(client)
+    b_id, b_tok = create_user(client, admin, "bob")
+
+    assert any(u["id"] == b_id for u in
+               client.get("/api/users/directory", headers=auth(admin)).json())
+
+    r = client.put("/api/profile/", headers=auth(b_tok), json={"directory_hidden": True})
+    assert r.status_code == 200, r.text
+
+    assert not any(u["id"] == b_id for u in
+                   client.get("/api/users/directory", headers=auth(admin)).json())
+    # Admin user management still lists the hidden user.
+    assert any(u["id"] == b_id for u in
+               client.get("/api/users/", headers=auth(admin)).json())

frontend/css/app.css

@@ -1462,6 +1462,22 @@ a { color: var(--primary); text-decoration: none; }
 .ct-dot { width: 9px; height: 9px; border-radius: 50%; display: inline-block; margin-right: 5px; vertical-align: middle; flex-shrink: 0; }
 .ct-empty { color: var(--text-3); font-size: 13px; padding: 16px 0; text-align: center; }
 .ct-toggle { cursor: pointer; }
+.ct-dav-toggle.on { color: var(--primary); }
+.ct-dav-row td { padding-top: 4px; padding-bottom: 12px; }
+.ct-dav-box { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
+.ct-dav-label { font-size: 12px; color: var(--text-3); }
+.ct-dav-url {
+  flex: 1; min-width: 220px; font-size: 12px; padding: 5px 8px;
+  border: 1px solid var(--border); border-radius: 6px;
+  background: var(--surface-2); color: var(--text-1);
+}
+.ct-dav-hint { font-size: 11px; color: var(--text-3); margin-top: 6px; max-width: 640px; }
+.app-pw-create { display: flex; gap: 8px; align-items: center; }
+.app-pw-create input { flex: 1; }
+.app-pw-new { margin: 8px 0; }
+.app-pw-item { display: flex; align-items: center; gap: 10px; padding: 6px 0; border-top: 1px solid var(--border); }
+.app-pw-name { font-weight: 500; }
+.app-pw-meta { font-size: 11px; color: var(--text-3); margin-left: auto; }
 .ct-eye, .ct-bell { opacity: .45; transition: opacity .15s; }
 .ct-eye[data-ct-visible="1"], .ct-bell[data-ct-on="1"] { opacity: 1; }
 .ct-eye:hover, .ct-bell:hover { opacity: 1; }
@@ -1986,12 +2002,21 @@ a { color: var(--primary); text-decoration: none; }
   border-radius: 10px;
 }
 .share-user-item {
+  display: flex; align-items: center; gap: 10px;
   padding: 10px 14px;
   cursor: pointer;
   border-bottom: 1px solid var(--border);
 }
 .share-user-item:last-child { border-bottom: none; }
 .share-user-item:hover { background: var(--bg-surface); }
+.share-user-item input[type=checkbox] { flex-shrink: 0; }
+/* "Shared with me" section header row inside the calendar-management table */
+.ct-section-row td {
+  padding-top: 14px; font-size: 12px; font-weight: 600;
+  color: var(--text-3); text-transform: uppercase; letter-spacing: .04em;
+}
+.checkbox-row { display: flex; align-items: center; gap: 8px; cursor: pointer; }
+.checkbox-row input[type=checkbox] { flex-shrink: 0; }
 /* .popup-creator styling moved into the .popup-row / #popup-creator rules above. */
 
 /* ── Groups ─────────────────────────────────────────────────── */
@@ -2123,6 +2148,8 @@ a { color: var(--primary); text-decoration: none; }
 /* Group emoji + icon picker */
 .group-emoji { flex: 0 0 auto; font-size: 16px; cursor: pointer; line-height: 1; }
 .cal-shared-flag { flex: 0 0 auto; font-size: 12px; opacity: .8; }
+/* Read-only (shared with me) indicator: a struck-through pencil. */
+.cal-readonly-flag { color: var(--text-3); opacity: .7; margin-left: 2px; }
 .group-icon-picker { display: flex; flex-wrap: wrap; gap: 6px; }
 .group-icon-opt {
   width: 38px; height: 38px;

frontend/index.html

@@ -716,6 +716,23 @@
           </div>
           <button class="btn btn-primary btn-sm" id="cfg-profile-save" data-i18n="save">Speichern</button>
 
+          <h4 class="panel-title" style="margin-top:24px" data-i18n="app_pw_title">App-Passwörter (CalDAV)</h4>
+          <p class="panel-desc" data-i18n="app_pw_desc">Eigene Passwörter für CalDAV-Clients. Bei aktivem 2FA nötig, da Apps keinen 2FA-Code eingeben können. Jederzeit widerrufbar.</p>
+          <div class="form-group app-pw-create">
+            <input type="text" id="app-pw-label" data-i18n-placeholder="app_pw_label_ph" placeholder="Name (z.B. iPhone)" maxlength="100" />
+            <button class="btn btn-primary btn-sm" id="app-pw-create-btn" data-i18n="app_pw_create">Erstellen</button>
+          </div>
+          <div id="app-pw-new" class="app-pw-new hidden">
+            <label data-i18n="app_pw_new_label">Neues App-Passwort (nur jetzt sichtbar):</label>
+            <div class="totp-secret-row">
+              <code id="app-pw-new-value"></code>
+              <button class="btn btn-ghost btn-sm" id="app-pw-copy" title="Kopieren">
+                <svg viewBox="0 0 24 24" fill="currentColor" width="16" height="16"><path d="M16 1H4c-1.1 0-2 .9-2 2v14h2V3h12V1zm3 4H8c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h11c1.1 0 2-.9 2-2V7c0-1.1-.9-2-2-2zm0 16H8V7h11v14z"/></svg>
+              </button>
+            </div>
+          </div>
+          <div id="app-pw-list"></div>
+
           <h4 class="panel-title" style="margin-top:24px" data-i18n="settings_privacy">Privatsphäre</h4>
           <p class="panel-desc" data-i18n="settings_private_visibility_desc">Wie private Termine für andere Gruppenmitglieder erscheinen</p>
           <div class="form-group">
@@ -725,6 +742,13 @@
               <option value="hidden" data-i18n="private_visibility_hidden">Ausblenden</option>
             </select>
           </div>
+          <div class="form-group">
+            <label class="checkbox-row">
+              <input type="checkbox" id="cfg-directory-hidden" />
+              <span data-i18n="settings_directory_hidden">Profil verbergen (nicht in Teilen-/Gruppen-Auswahl anzeigen)</span>
+            </label>
+            <p class="panel-desc" data-i18n="settings_directory_hidden_desc">Andere Nutzer können dich dann nicht auswählen, um Kalender zu teilen oder dich zu Gruppen hinzuzufügen. In der Admin-Benutzerverwaltung bleibst du sichtbar.</p>
+          </div>
 
           <h4 class="panel-title" style="margin-top:24px" data-i18n="settings_default_duration">Standard-Termindauer</h4>
           <div class="contrast-selector" id="cfg-event-duration">

frontend/js/app.js

@@ -192,8 +192,23 @@ boot();
 
 // ── Service Worker registration (PWA) ─────────────────────
 if ('serviceWorker' in navigator) {
+  // Auto-update: when a new service worker takes control, reload once so the
+  // page runs the fresh assets. Guarded so it never loops and never fires on
+  // the very first install (when there was no previous controller).
+  let refreshing = false;
+  const hadController = !!navigator.serviceWorker.controller;
+  navigator.serviceWorker.addEventListener('controllerchange', () => {
+    if (refreshing || !hadController) return;
+    refreshing = true;
+    window.location.reload();
+  });
+
   window.addEventListener('load', () => {
-    navigator.serviceWorker.register('/sw.js', { scope: '/' }).catch(err => {
+    navigator.serviceWorker.register('/sw.js', { scope: '/' }).then(reg => {
+      // Check for a new SW now and hourly, so long-open tabs pick up releases.
+      reg.update();
+      setInterval(() => reg.update(), 60 * 60 * 1000);
+    }).catch(err => {
       console.warn('SW registration failed:', err);
     });
   });

frontend/js/calendar.js

@@ -305,6 +305,28 @@ function setGroupColorOverride(groupId, key, hex) {
   try { localStorage.setItem('groupMemberColors', JSON.stringify(all)); } catch (e) { /* ignore */ }
 }
 
+// Per-device colour override for calendars shared WITH me. The calendar belongs
+// to someone else (server colour is theirs), so the recipient's chosen colour is
+// stored locally and re-applied on every fetch — keyed by local calendar id.
+function loadSharedCalColors() {
+  try { return JSON.parse(localStorage.getItem('sharedCalColors') || '{}'); } catch (e) { return {}; }
+}
+function sharedCalColorOverride(id) { return loadSharedCalColors()[String(id)] || null; }
+function setSharedCalColorOverride(id, hex) {
+  const all = loadSharedCalColors();
+  if (hex) all[String(id)] = hex; else delete all[String(id)];
+  try { localStorage.setItem('sharedCalColors', JSON.stringify(all)); } catch (e) { /* ignore */ }
+}
+function applySharedColorOverrides(events) {
+  const overrides = loadSharedCalColors();
+  if (!Object.keys(overrides).length) return;
+  events.forEach(ev => {
+    if (ev.source !== 'local') return;
+    const cid = String(ev.calendar_id).replace('local-', '');
+    if (overrides[cid]) ev.calendarColor = overrides[cid];
+  });
+}
+
 async function fetchAndRender(force = false, silent = false) {
   const { start, end } = getViewRange();
 
@@ -377,10 +399,13 @@ async function fetchAndRender(force = false, silent = false) {
     const resp = await api.get(`/caldav/events?start=${fetchStart.toISOString()}&end=${fetchEnd.toISOString()}`);
     const events = resp.events || resp;
     if (resp.errors && resp.errors.length) {
+      const sourceLabels = { caldav: 'CalDAV', homeassistant: 'Home Assistant', google: 'Google' };
       for (const err of resp.errors) {
-        showToast(`Google (${err.email}): Token abgelaufen – bitte Konto trennen und neu verbinden`, true);
+        const label = sourceLabels[err.source] || err.source || 'Kalender';
+        showToast(`${label} (${err.name}): ${err.message}`, true);
       }
     }
+    applySharedColorOverrides(events);
     eventCache.start  = fetchStart;
     eventCache.end    = fetchEnd;
     eventCache.events = events;
@@ -726,9 +751,13 @@ function renderCalendarList() {
       remove: { icon: TRASH, title: t('remove_cal') } });
   });
   state.localCalendars.filter(c => c.owned === false && !c.group).forEach(cal => {
+    const readOnly = cal.permission !== 'read_write';
+    // A shared calendar is shown to the recipient under the OWNER's name
+    // (e.g. Guido's "Persönlich" appears as "Guido"); the original calendar
+    // name stays in the sub-label so it's still identifiable.
     entries.push({ key: `local:${cal.id}`, source: 'local', dataId: `data-cal-id="${cal.id}"`,
-      name: cal.name, color: cal.color, enabled: cal.enabled,
+      name: cal.shared_by || cal.name, color: sharedCalColorOverride(cal.id) || cal.color, enabled: cal.enabled, readOnly,
-      sourceLabel: `${t('shared_with_me')} · ${cal.shared_by || ''}`, remove: null });
+      sourceLabel: `${t('shared_with_me')} · ${cal.name}${readOnly ? ' · ' + t('perm_read') : ''}`, remove: null });
   });
   // Group calendars (owned by the creator or reached via membership) — shown so
   // they can be toggled/recoloured. Owned group calendars can also be muted
@@ -787,6 +816,7 @@ function renderCalendarList() {
       ${e.isGroupCal ? `<span class="cal-shared-flag" title="${escHtml(e.sourceLabel)}">${groupIconSvg(e.groupIcon || 'people', 13)}</span>` : ''}
       ${e.groupVisible ? `<span class="cal-shared-flag cal-shared-flag-own" title="${t('group_visible_flag')}">${shareIconSvg(state.settings?.share_calendar_icon || 'share', 13)}</span>` : ''}
       <span class="cal-item-name" data-source="${e.source}">${escHtml(e.name)}</span>
+      ${e.readOnly ? `<span class="cal-shared-flag cal-readonly-flag" title="${t('perm_read')}"><svg viewBox="0 0 24 24" width="13" height="13" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M12 20h9"/><path d="M16.5 3.5a2.1 2.1 0 0 1 3 3L7 19l-4 1 1-4Z"/><line x1="3" y1="3" x2="21" y2="21"/></svg></span>` : ''}
       ${e.reminders ? `<button class="icon-btn mini-btn cal-item-bell ${e.remindersEnabled ? '' : 'off'}" data-source="${e.source}" ${e.dataId} title="${e.remindersEnabled ? t('calendar_reminders_on') : t('calendar_reminders_off')}">${e.remindersEnabled ? BELL : BELL_OFF}</button>` : ''}
       ${e.remove ? `<button class="icon-btn mini-btn cal-item-remove" data-source="${e.source}" ${e.dataId} title="${e.remove.title}">${e.remove.icon}</button>` : ''}
     </div>`
@@ -898,7 +928,16 @@ function renderCalendarList() {
       } else if (source === 'local') {
         const calId = parseInt(dot.dataset.calId);
         const cal = state.localCalendars.find(c => c.id === calId);
-        if (cal && cal.owned === false) { showToast(t('only_owner_color'), true); return; }
+        if (cal && cal.owned === false) {
+          // Shared calendar — belongs to someone else. Apply a per-device local
+          // colour (stored client-side) instead of a server PUT that would 403.
+          const picked = await openColorPicker(dot, sharedCalColorOverride(calId) || cal.color || '#34a853');
+          if (picked) {
+            setSharedCalColorOverride(calId, picked);
+            applyCalendarColor('local', calId, picked); // recolour cached events + re-render
+          }
+          return;
+        }
         const picked = await openColorPicker(dot, cal?.color || '#34a853');
         if (picked) {
           await api.put(`/local/calendars/${calId}`, { color: picked });
@@ -950,6 +989,12 @@ function renderCalendarList() {
       e.stopPropagation();
       const item = nameEl.closest('.cal-item');
       const source = nameEl.dataset.source;
+      // Can't rename a calendar shared with me — only the owner may. Renaming
+      // would just 403 on save, so don't even start editing.
+      if (source === 'local') {
+        const cal = state.localCalendars.find(c => c.id === parseInt(item?.dataset.calId));
+        if (cal && cal.owned === false) return;
+      }
       const currentName = nameEl.textContent;
       const input = document.createElement('input');
       input.type = 'text';
@@ -1575,8 +1620,10 @@ function populateCalendarSelect(selectedId) {
     });
   });
   // Local calendars. Group calendars are collected under a "Groups" optgroup
-  // (no emoji — a native <select> can't render the group icon SVG).
+  // (no emoji — a native <select> can't render the group icon SVG). Read-only
-  const localCals = state.localCalendars.filter(c => !c.sidebar_hidden);
+  // shared calendars are excluded — a save would only 403.
+  const localCals = state.localCalendars.filter(c =>
+    !c.sidebar_hidden && (c.owned !== false || c.permission === 'read_write'));
   const makeLocalOpt = cal => {
     const opt = document.createElement('option');
     opt.value = `local-${cal.id}`;
@@ -2674,31 +2721,42 @@ async function refreshShareModal(calendarId) {
     });
   });
 
-  // Store the directory (minus already-shared users) for the picker.
+  // Store the full directory + which users are already shared, so the picker
-  document.getElementById('modal-share').__users = users.filter(u => !sharedIds.has(u.id));
+  // can show a checkbox per user (checked = shared).
+  const modal = document.getElementById('modal-share');
+  modal.__users = users;
+  modal.__sharedIds = sharedIds;
   renderShareUserPicker();
 }
 
 function renderShareUserPicker() {
   const modal = document.getElementById('modal-share');
   const users = modal.__users || [];
+  const sharedIds = modal.__sharedIds || new Set();
   const q = (document.getElementById('share-user-search').value || '').toLowerCase();
   const filtered = users.filter(u => (u.display_name || '').toLowerCase().includes(q));
   const picker = document.getElementById('share-user-picker');
   picker.innerHTML = filtered.length
     ? filtered.map(u =>
-        `<div class="share-user-item" data-user-id="${u.id}">${escHtml(u.display_name || '')}</div>`
+        `<label class="share-user-item">
+          <input type="checkbox" class="share-user-cb" data-user-id="${u.id}" ${sharedIds.has(u.id) ? 'checked' : ''} />
+          <span>${escHtml(u.display_name || '')}</span>
+        </label>`
       ).join('')
     : `<span class="accounts-section-empty">${t('share_no_users')}</span>`;
-  picker.querySelectorAll('.share-user-item').forEach(el => {
+  picker.querySelectorAll('.share-user-cb').forEach(cb => {
-    el.addEventListener('click', async () => {
+    cb.addEventListener('change', async () => {
       const calId = parseInt(modal.dataset.calId);
-      const permission = document.getElementById('share-permission').value;
+      const userId = parseInt(cb.dataset.userId);
       try {
-        await api.post(`/local/calendars/${calId}/shares`,
+        if (cb.checked) {
-                       { user_id: parseInt(el.dataset.userId), permission });
+          const permission = document.getElementById('share-permission').value;
+          await api.post(`/local/calendars/${calId}/shares`, { user_id: userId, permission });
+        } else {
+          await api.delete(`/local/calendars/${calId}/shares/${userId}`);
+        }
         await refreshShareModal(calId);
-      } catch (e) { showToast(e.message, true); }
+      } catch (e) { showToast(e.message, true); cb.checked = !cb.checked; }
     });
   });
 }
@@ -2794,7 +2852,11 @@ function renderGroupMemberFilter() {
       <span class="cal-item-name">${escHtml(name)}</span>
     </div>`;
   };
-  const parts = (g.members || []).map(m => row(m.id, String(m.id), m.display_name || '—', m.color));
+  // Only members who actually share a calendar into the group get a toggle —
+  // otherwise we'd show phantom empty entries for members who share nothing.
+  const parts = (g.members || [])
+    .filter(m => m.shares_calendar)
+    .map(m => row(m.id, String(m.id), m.display_name || '—', m.color));
   parts.push(row('gc', 'gc', t('group_calendar'), g.group_calendar_color));
   items.innerHTML = parts.join('');
 
@@ -3109,7 +3171,10 @@ function openSettingsModal() {
   document.getElementById('cfg-login-name').value = pu.username || '';
   api.get('/profile/').then(p => {
     document.getElementById('cfg-email').value = p.email || '';
+    const dh = document.getElementById('cfg-directory-hidden');
+    if (dh) dh.checked = !!p.directory_hidden;
   }).catch(() => {});
+  initAppPasswords();
 
   // Set active contrast/hour-height/duration buttons
   [
@@ -3442,24 +3507,43 @@ function renderCalendarTable() {
 
   let rows = '';
 
-  // Local calendars
+  // Local calendars I own. Calendars shared WITH me (owned === false) are shown
+  // in a separate "shared with me" section further down.
   for (const cal of state.localCalendars) {
-    if (cal.group) continue;
+    if (cal.group || cal.owned === false) continue;
-    const owned = cal.owned !== false;
+    const pub = !!cal.caldav_published;
-    const canWrite = owned || cal.permission === 'read_write';
     rows += `<tr>
       <td>${dot(cal.color, '#34a853')}${escHtml(cal.name)}</td>
       <td class="ct-src">Lokal</td>
       <td>—</td>
-      <td>${owned ? rem('local', cal.id, cal.reminders_enabled !== false) : '—'}</td>
+      <td>${rem('local', cal.id, cal.reminders_enabled !== false)}</td>
       <td>
+        <button class="btn btn-ghost btn-sm" data-ct-share="${cal.id}">${t('share')}</button>
         <button class="btn btn-ghost btn-sm" data-ct-export="local" data-ct-id="${cal.id}" data-ct-name="${escHtml(cal.name)}">Export</button>
-        ${canWrite ? `<button class="btn btn-ghost btn-sm" data-ct-import="local" data-ct-id="${cal.id}">Import</button>` : ''}
+        <button class="btn btn-ghost btn-sm" data-ct-import="local" data-ct-id="${cal.id}">Import</button>
+        <button class="btn btn-ghost btn-sm ct-dav-toggle${pub ? ' on' : ''}" data-ct-dav-id="${cal.id}" data-ct-dav-on="${pub ? '1' : '0'}">${pub ? t('caldav_unpublish') : t('caldav_publish')}</button>
       </td>
       <td>—</td>
-      <td>${owned ? `<button class="icon-btn mini-btn" data-ct-del="local" data-ct-id="${cal.id}">${TRASH}</button>` : ''}</td>
+      <td><button class="icon-btn mini-btn" data-ct-del="local" data-ct-id="${cal.id}">${TRASH}</button></td>
     </tr>`;
     rowCount++;
+    if (owned && pub) {
+      rows += `<tr class="ct-dav-row"><td colspan="7">
+        <div class="ct-dav-box">
+          <span class="ct-dav-label">${t('caldav_published_url')}</span>
+          <input class="ct-dav-url" type="text" readonly value="${escHtml(cal.caldav_url || '')}">
+          <button class="btn btn-ghost btn-sm ct-dav-copy">${t('copy')}</button>
+          <button class="btn btn-ghost btn-sm ct-dav-rotate" data-ct-dav-id="${cal.id}">${t('caldav_token_rotate')}</button>
+        </div>
+        <div class="ct-dav-hint">${t('caldav_hint')}</div>
+        <div class="ct-dav-box">
+          <span class="ct-dav-label">${t('caldav_login_url')}</span>
+          <input class="ct-dav-url" type="text" readonly value="${escHtml(cal.caldav_login_url || '')}">
+          <button class="btn btn-ghost btn-sm ct-dav-copy">${t('copy')}</button>
+        </div>
+        <div class="ct-dav-hint">${t('caldav_login_hint')}</div>
+      </td></tr>`;
+    }
   }
 
   // iCal subscriptions
@@ -3539,6 +3623,22 @@ function renderCalendarTable() {
     }
   }
 
+  // Calendars shared WITH me (direct shares + group-shared) — read-only, no
+  // management actions since I don't own them. Shown under the owner's name.
+  const sharedWithMe = state.localCalendars.filter(c => c.owned === false && !c.group);
+  if (sharedWithMe.length) {
+    rows += `<tr class="ct-section-row"><td colspan="7">${t('shared_with_me')}</td></tr>`;
+    for (const cal of sharedWithMe) {
+      const readOnly = cal.permission !== 'read_write';
+      rows += `<tr>
+        <td>${dot(cal.color, '#34a853')}${escHtml(cal.shared_by || cal.name)}</td>
+        <td class="ct-src">${escHtml(cal.name)} <span class="cal-badge">${readOnly ? t('perm_read') : t('perm_read_write')}</span></td>
+        <td>—</td><td>—</td><td>—</td><td>—</td><td>—</td>
+      </tr>`;
+      rowCount++;
+    }
+  }
+
   if (!rowCount) {
     rows = `<tr><td colspan="7" class="ct-empty">Keine Kalender vorhanden</td></tr>`;
   }
@@ -3656,6 +3756,47 @@ function renderCalendarTable() {
     btn.addEventListener('click', () => triggerIcsImport(parseInt(btn.dataset.ctId)));
   });
 
+  // Share a calendar with specific users (person-to-person)
+  container.querySelectorAll('[data-ct-share]').forEach(btn => {
+    btn.addEventListener('click', () => openShareModal(parseInt(btn.dataset.ctShare)));
+  });
+
+  // CalDAV publishing
+  container.querySelectorAll('.ct-dav-toggle').forEach(btn => {
+    btn.addEventListener('click', async () => {
+      const id = parseInt(btn.dataset.ctDavId);
+      const newVal = btn.dataset.ctDavOn !== '1';
+      const cal = state.localCalendars.find(c => c.id === id);
+      if (!cal) return;
+      try {
+        const updated = await api.put(`/local/calendars/${id}`, { caldav_published: newVal });
+        cal.caldav_published = updated.caldav_published;
+        cal.caldav_url = updated.caldav_url;
+        renderCalendarTable();
+      } catch (e) { showToast(e.message, true); }
+    });
+  });
+  container.querySelectorAll('.ct-dav-copy').forEach(btn => {
+    btn.addEventListener('click', () => {
+      const input = btn.parentElement.querySelector('.ct-dav-url');
+      if (!input || !input.value) return;
+      navigator.clipboard.writeText(input.value).then(() => showToast(t('caldav_url_copied')));
+    });
+  });
+  container.querySelectorAll('.ct-dav-rotate').forEach(btn => {
+    btn.addEventListener('click', async () => {
+      const id = parseInt(btn.dataset.ctDavId);
+      const cal = state.localCalendars.find(c => c.id === id);
+      if (!cal || !confirm(t('caldav_rotate_confirm'))) return;
+      try {
+        const updated = await api.post(`/local/calendars/${id}/dav-token/rotate`);
+        cal.caldav_url = updated.caldav_url;
+        renderCalendarTable();
+        showToast(t('caldav_token_rotated'));
+      } catch (e) { showToast(e.message, true); }
+    });
+  });
+
   // Delete
   container.querySelectorAll('[data-ct-del]').forEach(btn => {
     btn.addEventListener('click', async () => {
@@ -3828,6 +3969,8 @@ function bindSettingsModal() {
     const body = { email: email || null };
     if (displayName) body.display_name = displayName;
     if (loginName && loginName.toLowerCase() !== (user.username || '')) body.username = loginName;
+    const dh = document.getElementById('cfg-directory-hidden');
+    if (dh) body.directory_hidden = dh.checked;
     try {
       const res = await api.put('/profile/', body);
       if (res && res.access_token) localStorage.setItem('token', res.access_token);
@@ -4091,6 +4234,55 @@ function bindProfileModal() {
   };
 }
 
+// ── App passwords (CalDAV) — lives in Settings → Profile ──
+function initAppPasswords() {
+  const appPwList = document.getElementById('app-pw-list');
+  if (!appPwList) return;
+  const newBox = document.getElementById('app-pw-new');
+  newBox.classList.add('hidden');
+  document.getElementById('app-pw-new-value').textContent = '';
+
+  const load = async () => {
+    try {
+      const rows = await api.get('/profile/app-passwords');
+      appPwList.innerHTML = rows.length
+        ? rows.map(r => `<div class="app-pw-item">
+            <span class="app-pw-name">${escHtml(r.label)}</span>
+            <span class="app-pw-meta">${r.last_used_at ? t('app_pw_last_used') + ' ' + new Date(r.last_used_at).toLocaleDateString() : t('app_pw_never_used')}</span>
+            <button class="btn btn-ghost btn-sm app-pw-del" data-id="${r.id}">${t('app_pw_revoke')}</button>
+          </div>`).join('')
+        : `<p class="text-muted">${t('app_pw_none')}</p>`;
+    } catch (e) { /* ignore */ }
+  };
+  load();
+
+  document.getElementById('app-pw-create-btn').onclick = async () => {
+    const label = document.getElementById('app-pw-label').value.trim() || 'CalDAV';
+    try {
+      const res = await api.post('/profile/app-passwords', { label });
+      document.getElementById('app-pw-new-value').textContent = res.password;
+      newBox.classList.remove('hidden');
+      document.getElementById('app-pw-label').value = '';
+      load();
+    } catch (e) { showToast(e.message, true); }
+  };
+
+  document.getElementById('app-pw-copy').onclick = () => {
+    const v = document.getElementById('app-pw-new-value').textContent;
+    if (v) navigator.clipboard.writeText(v).then(() => showToast(t('app_pw_copied')));
+  };
+
+  appPwList.onclick = async (e) => {
+    const btn = e.target.closest('.app-pw-del');
+    if (!btn) return;
+    if (!confirm(t('app_pw_revoke_confirm'))) return;
+    try {
+      await api.delete(`/profile/app-passwords/${btn.dataset.id}`);
+      load();
+    } catch (err) { showToast(err.message, true); }
+  };
+}
+
 function updateTopbarAvatar(hasAvatar) {
   const avatar = document.getElementById('user-avatar');
   if (hasAvatar) {

frontend/js/i18n.js

@@ -91,6 +91,8 @@ const translations = {
     settings_privacy: 'Privatsphäre',
     settings_private_visibility: 'Private Termine für Gruppenmitglieder',
     settings_private_visibility_desc: 'Wie private Termine für andere Gruppenmitglieder erscheinen',
+    settings_directory_hidden: 'Profil verbergen (nicht in Teilen-/Gruppen-Auswahl anzeigen)',
+    settings_directory_hidden_desc: 'Andere Nutzer können dich dann nicht auswählen, um Kalender zu teilen oder dich zu Gruppen hinzuzufügen. In der Admin-Benutzerverwaltung bleibst du sichtbar.',
     private_visibility_busy: 'Als „Beschäftigt“ anzeigen',
     private_visibility_hidden: 'Ausblenden',
     created_by: 'Erstellt von: {name}',
@@ -114,6 +116,28 @@ const translations = {
     reminders_calendar_off: 'Für diesen Kalender sind Benachrichtigungen deaktiviert – Erinnerungen werden nicht ausgeführt.',
     calendar_reminders_on: 'Benachrichtigungen aktiviert',
     calendar_reminders_off: 'Benachrichtigungen deaktiviert',
+    copy: 'Kopieren',
+    caldav_publish: 'CalDAV veröffentlichen',
+    caldav_unpublish: 'CalDAV deaktivieren',
+    caldav_published_url: 'CalDAV-URL (ohne Login):',
+    caldav_url_copied: 'CalDAV-URL kopiert',
+    caldav_token_rotate: 'Token neu generieren',
+    caldav_token_rotated: 'Neuer Token erzeugt – alte Abos müssen neu eingerichtet werden',
+    caldav_rotate_confirm: 'Neuen Token erzeugen? Die bisherige URL wird ungültig und bestehende Abos müssen mit der neuen URL neu eingerichtet werden.',
+    caldav_hint: 'Jeder mit dieser URL kann diesen Kalender abonnieren und bearbeiten – kein Login nötig. Über CalDAV-fähige Clients (Apple Kalender, Thunderbird, DAVx5) einbinden.',
+    caldav_login_url: 'CalDAV-URL (mit Login):',
+    caldav_login_hint: 'Alternativ im Client ein „CalDAV-Konto" mit dieser Server-URL sowie deinem Benutzernamen und App-Passwort hinzufügen – dann werden alle deine veröffentlichten Kalender gefunden.',
+    app_pw_title: 'App-Passwörter (CalDAV)',
+    app_pw_desc: 'Eigene Passwörter für CalDAV-Clients. Bei aktivem 2FA nötig, da Apps keinen 2FA-Code eingeben können. Jederzeit widerrufbar.',
+    app_pw_label_ph: 'Name (z.B. iPhone)',
+    app_pw_create: 'Erstellen',
+    app_pw_new_label: 'Neues App-Passwort (nur jetzt sichtbar):',
+    app_pw_last_used: 'zuletzt',
+    app_pw_never_used: 'noch nie genutzt',
+    app_pw_revoke: 'Widerrufen',
+    app_pw_none: 'Noch keine App-Passwörter.',
+    app_pw_copied: 'App-Passwort kopiert',
+    app_pw_revoke_confirm: 'Dieses App-Passwort widerrufen? Clients, die es nutzen, verlieren den Zugriff.',
     share: 'Teilen',
     import: 'Importieren',
     export: 'Exportieren',
@@ -384,6 +408,8 @@ const translations = {
     settings_privacy: 'Privacy',
     settings_private_visibility: 'Private events for group members',
     settings_private_visibility_desc: 'How your private events appear to other group members',
+    settings_directory_hidden: 'Hide my profile (don\'t show me in share/group pickers)',
+    settings_directory_hidden_desc: 'Other users then can\'t pick you to share calendars with or add you to groups. You remain visible in the admin user management.',
     private_visibility_busy: 'Show as "Busy"',
     private_visibility_hidden: 'Hide completely',
     created_by: 'Created by: {name}',
@@ -407,6 +433,28 @@ const translations = {
     reminders_calendar_off: 'Reminders are disabled for this calendar – they will not fire.',
     calendar_reminders_on: 'Reminders enabled',
     calendar_reminders_off: 'Reminders disabled',
+    copy: 'Copy',
+    caldav_publish: 'Publish via CalDAV',
+    caldav_unpublish: 'Unpublish CalDAV',
+    caldav_published_url: 'CalDAV URL (no login):',
+    caldav_url_copied: 'CalDAV URL copied',
+    caldav_token_rotate: 'Regenerate token',
+    caldav_token_rotated: 'New token generated – existing subscriptions must be re-added',
+    caldav_rotate_confirm: 'Generate a new token? The current URL will stop working and existing subscriptions must be re-added with the new URL.',
+    caldav_hint: 'Anyone with this URL can subscribe to and edit this calendar — no login required. Add it in a CalDAV-capable client (Apple Calendar, Thunderbird, DAVx5).',
+    caldav_login_url: 'CalDAV URL (with login):',
+    caldav_login_hint: 'Alternatively add a "CalDAV account" in your client using this server URL plus your username and app password — it will discover all your published calendars.',
+    app_pw_title: 'App passwords (CalDAV)',
+    app_pw_desc: "Dedicated passwords for CalDAV clients. Required when 2FA is on, since apps can't enter a 2FA code. Revocable anytime.",
+    app_pw_label_ph: 'Name (e.g. iPhone)',
+    app_pw_create: 'Create',
+    app_pw_new_label: 'New app password (shown only now):',
+    app_pw_last_used: 'last used',
+    app_pw_never_used: 'never used',
+    app_pw_revoke: 'Revoke',
+    app_pw_none: 'No app passwords yet.',
+    app_pw_copied: 'App password copied',
+    app_pw_revoke_confirm: 'Revoke this app password? Clients using it will lose access.',
     share: 'Share',
     import: 'Import',
     export: 'Export',

frontend/js/version.js

@@ -1,2 +1,2 @@
 // Increment APP_VERSION with every code change
-export const APP_VERSION = 'v62';
+export const APP_VERSION = 'v73';

frontend/sw.js

@@ -7,7 +7,7 @@
 // the entry HTML / version files). New releases take effect on the next
 // reload, no manual SW unregister required.
 
-const CACHE_VERSION  = 'calendarr-v23';
+const CACHE_VERSION  = 'calendarr-v24';
 const OFFLINE_SHELL  = ['/', '/index.html'];
 
 self.addEventListener('install', event => {