Complete recurrence editing and calendar preferences

README.md

@@ -65,10 +65,12 @@ and the user must sync before retrying. A calendar-owned task,
 `govoplan_calendar.sync_due_caldav_sources`, can run due sources in a worker or
 cron-style scheduler.
 
-This is not yet a full CalDAV network server. Scheduling inbox/outbox behavior,
-CalDAV server endpoints, UI credential management, and full user-facing
-recurrence editing remain follow-up work. The backend now includes a free/busy
-API primitive for scheduling and appointment modules.
+Calendar exposes collection and credential management, sync status/actions,
+durable per-user view preferences, recurrence expansion, detached occurrence
+overrides, instance/series editing, and a free/busy API primitive for scheduling
+and appointment modules. It is not yet a CalDAV network server: external clients
+cannot use GovOPlaN itself as their CalDAV endpoint, and scheduling inbox/outbox
+delivery remains owned by the scheduling and mail integration work.
 
 ## Development
 

docs/CALENDAR_INTEGRATION_CONCEPT.md

@@ -6,7 +6,7 @@
 
 - calendar collections
 - VEVENT storage and iCalendar import/export
-- event recurrence data, recurrence exceptions, and future recurrence expansion
+- event recurrence data, recurrence expansion, and recurrence exceptions
 - availability and free/busy semantics
 - resources such as rooms, shared equipment, and service desks
 - groupware calendar adapter boundaries, including CalDAV and Open-Xchange
@@ -22,7 +22,10 @@ The first standalone module provides:
 - normalized query fields: start, end, summary, location, all-day flag, status, transparency, classification, calendar ID, UID, recurrence ID, sequence, source, and ETag
 - iCalendar preservation: raw VEVENT properties, parameters, and generated `text/calendar` export
 - API endpoints for listing calendars, creating/updating/deleting events, importing iCalendar, and exporting event ICS
-- free/busy API primitive with recurrence expansion for scheduling and appointment conflict checks
+- bounded occurrence expansion with RRULE, RDATE, EXDATE, detached overrides,
+  instance/series editing, and free/busy reconciliation
+- durable per-user calendar view preferences exposed through the platform
+  Settings surface
 - calendar-owned CalDAV sync sources with credential references, scheduled due-sync metadata, full/incremental inbound sync, two-way PUT/DELETE writes, and ETag conflict handling
 - a Calendar-owned durable desired-state outbox for two-way CalDAV writes. Event
   state and the exact external resource snapshot commit atomically; workers use
@@ -30,7 +33,10 @@ The first standalone module provides:
   exponential retry, and semantic GET reconciliation after ambiguous outcomes
 - WebUI views: month, week, workweek, day, and continuous week-row scrolling
 
-The first implementation is not yet a full CalDAV network server. It is the internal calendar storage, sync, availability, and UI foundation on which Open-Xchange integration, richer recurrence editing, scheduling inbox/outbox behavior, and CalDAV server endpoints can be built.
+The implementation is not yet a full CalDAV network server. It is the internal
+calendar storage, recurrence, sync, availability, and UI foundation on which
+Open-Xchange integration, scheduling inbox/outbox behavior, and CalDAV server
+endpoints can be built.
 
 ## Outbound delivery operations
 
@@ -197,9 +203,6 @@ The connector boundary should hand calendar a configured profile and credentials
 
 ## Follow-Up Work
 
-- Full recurrence expansion for RRULE, RDATE, EXDATE, RECURRENCE-ID, overridden instances, and detached instances.
-- User-facing recurrence editing for RRULE, RDATE, EXDATE, RECURRENCE-ID, overridden instances, and detached instances.
-- UI management for CalDAV credentials, sync status, sync direction, and conflict resolution.
 - CalDAV server endpoints if GovOPlaN should expose calendars to external clients rather than only syncing remote collections.
 - Open-Xchange adapter that maps OX calendars, attendees, resources, recurrence, and free/busy to the internal calendar model.
 - Attendee RSVP workflow and mail/notification bridge.

src/govoplan_calendar/backend/db/models.py

@@ -94,6 +94,36 @@ class CalendarEvent(Base, TimestampMixin):
     calendar: Mapped[CalendarCollection] = relationship(back_populates="events")
 
 
+class CalendarViewPreference(Base, TimestampMixin):
+    __tablename__ = "calendar_view_preferences"
+    __table_args__ = (
+        UniqueConstraint(
+            "tenant_id",
+            "user_id",
+            name="uq_calendar_view_preferences_tenant_user",
+        ),
+    )
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=new_uuid)
+    tenant_id: Mapped[str] = mapped_column(
+        String(36),
+        nullable=False,
+        index=True,
+    )
+    user_id: Mapped[str] = mapped_column(
+        ForeignKey("access_users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    dim_weekends: Mapped[bool | None] = mapped_column(Boolean, nullable=True)
+    dim_off_hours: Mapped[bool | None] = mapped_column(Boolean, nullable=True)
+    workday_start_hour: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    workday_end_hour: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    continuous_virtualization: Mapped[bool | None] = mapped_column(Boolean, nullable=True)
+    continuous_overscan_weeks: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    alternate_continuous_months: Mapped[bool | None] = mapped_column(Boolean, nullable=True)
+
+
 class CalendarSyncSource(Base, TimestampMixin):
     __tablename__ = "calendar_sync_sources"
     __table_args__ = (
@@ -215,5 +245,6 @@ __all__ = [
     "CalendarOutboxOperation",
     "CalendarSyncCredential",
     "CalendarSyncSource",
+    "CalendarViewPreference",
     "new_uuid",
 ]

src/govoplan_calendar/backend/ews.py

@@ -0,0 +1,236 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Any
+
+from defusedxml import ElementTree as SafeElementTree
+
+
+EWS_SOAP_NS = "http://schemas.xmlsoap.org/soap/envelope/"
+EWS_MESSAGES_NS = (
+    "http://schemas.microsoft.com/exchange/services/2006/messages"
+)
+EWS_TYPES_NS = "http://schemas.microsoft.com/exchange/services/2006/types"
+
+
+class EwsAdapterError(ValueError):
+    """Raised when an EWS response cannot be translated safely."""
+
+
+def ews_find_item_body(
+    *,
+    start: datetime,
+    end: datetime,
+    mailbox: Any | None = None,
+) -> str:
+    start_text = normalize_datetime(start).isoformat().replace("+00:00", "Z")
+    end_text = normalize_datetime(end).isoformat().replace("+00:00", "Z")
+    mailbox_xml = ""
+    if mailbox:
+        mailbox_xml = (
+            "<t:Mailbox><t:EmailAddress>"
+            f"{xml_escape(str(mailbox))}"
+            "</t:EmailAddress></t:Mailbox>"
+        )
+    return f"""<?xml version="1.0" encoding="utf-8"?>
+<s:Envelope xmlns:s="{EWS_SOAP_NS}" xmlns:m="{EWS_MESSAGES_NS}" xmlns:t="{EWS_TYPES_NS}">
+  <s:Header>
+    <t:RequestServerVersion Version="Exchange2013_SP1" />
+  </s:Header>
+  <s:Body>
+    <m:FindItem Traversal="Shallow">
+      <m:ItemShape>
+        <t:BaseShape>AllProperties</t:BaseShape>
+      </m:ItemShape>
+      <m:CalendarView StartDate="{start_text}" EndDate="{end_text}" />
+      <m:ParentFolderIds>
+        <t:DistinguishedFolderId Id="calendar">{mailbox_xml}</t:DistinguishedFolderId>
+      </m:ParentFolderIds>
+    </m:FindItem>
+  </s:Body>
+</s:Envelope>"""
+
+
+def parse_ews_calendar_items(xml_text: str) -> list[dict[str, Any]]:
+    try:
+        root = SafeElementTree.fromstring(xml_text)
+    except SafeElementTree.ParseError as exc:
+        raise EwsAdapterError(f"Invalid EWS response XML: {exc}") from exc
+    items: list[dict[str, Any]] = []
+    for item in root.findall(f".//{{{EWS_TYPES_NS}}}CalendarItem"):
+        item_id = item.find(f"./{{{EWS_TYPES_NS}}}ItemId")
+        href = item_id.get("Id") if item_id is not None else None
+        if not href:
+            continue
+        change_key = (
+            item_id.get("ChangeKey") if item_id is not None else None
+        )
+        start = parse_ews_datetime(text_of(item, "Start"))
+        end_text = text_of(item, "End")
+        end = parse_ews_datetime(end_text) if end_text else start
+        uid = text_of(item, "UID") or href
+        subject = text_of(item, "Subject") or "(Untitled event)"
+        all_day = text_of(item, "IsAllDayEvent") == "true"
+        free_busy = text_of(item, "LegacyFreeBusyStatus") or "Busy"
+        sensitivity = text_of(item, "Sensitivity") or "Normal"
+        body = item.find(f"./{{{EWS_TYPES_NS}}}Body")
+        provider_payload = element_to_dict(item)
+        items.append(
+            {
+                "href": href,
+                "uid": uid,
+                "recurrence_id": (
+                    href
+                    if text_of(item, "CalendarItemType")
+                    in {"Occurrence", "Exception"}
+                    else None
+                ),
+                "sequence": int_or_default(
+                    text_of(item, "AppointmentSequenceNumber"),
+                    0,
+                ),
+                "summary": subject,
+                "description": body.text if body is not None else None,
+                "location": text_of(item, "Location"),
+                "status": (
+                    "CANCELLED"
+                    if text_of(item, "IsCancelled") == "true"
+                    else "CONFIRMED"
+                ),
+                "transparency": (
+                    "TRANSPARENT"
+                    if free_busy.lower() == "free"
+                    else "OPAQUE"
+                ),
+                "classification": (
+                    "PRIVATE"
+                    if sensitivity.lower() == "private"
+                    else "PUBLIC"
+                ),
+                "start_at": start,
+                "end_at": end,
+                "duration_seconds": int((end - start).total_seconds()),
+                "all_day": all_day,
+                "timezone": "UTC",
+                "organizer": ews_mailbox_record(
+                    item.find(
+                        f"./{{{EWS_TYPES_NS}}}Organizer/"
+                        f"{{{EWS_TYPES_NS}}}Mailbox"
+                    )
+                ),
+                "attendees": ews_attendees(item),
+                "categories": [
+                    category.text
+                    for category in item.findall(
+                        f"./{{{EWS_TYPES_NS}}}Categories/"
+                        f"{{{EWS_TYPES_NS}}}String"
+                    )
+                    if category.text
+                ],
+                "rrule": None,
+                "rdate": [],
+                "exdate": [],
+                "reminders": ews_reminders(item),
+                "attachments": [],
+                "related_to": [],
+                "etag": change_key,
+                "icalendar": {
+                    "component": "VEVENT",
+                    "schema_version": 1,
+                    "provider": "ews",
+                    "ews": provider_payload,
+                },
+                "metadata": {"ews": provider_payload},
+            }
+        )
+    return items
+
+
+def parse_ews_datetime(value: str | None) -> datetime:
+    if not value:
+        return datetime.now(timezone.utc)
+    return normalize_datetime(
+        datetime.fromisoformat(value.replace("Z", "+00:00"))
+    )
+
+
+def text_of(item: Any, name: str) -> str | None:
+    child = item.find(f"./{{{EWS_TYPES_NS}}}{name}")
+    return child.text if child is not None else None
+
+
+def ews_mailbox_record(mailbox: Any | None) -> dict[str, Any] | None:
+    if mailbox is None:
+        return None
+    return {
+        "name": text_of(mailbox, "Name") or "",
+        "email": text_of(mailbox, "EmailAddress") or "",
+        "routing_type": text_of(mailbox, "RoutingType") or "",
+    }
+
+
+def ews_attendees(item: Any) -> list[dict[str, Any]]:
+    attendees: list[dict[str, Any]] = []
+    for role, path in (
+        ("required", "RequiredAttendees"),
+        ("optional", "OptionalAttendees"),
+    ):
+        for attendee in item.findall(
+            f"./{{{EWS_TYPES_NS}}}{path}/"
+            f"{{{EWS_TYPES_NS}}}Attendee"
+        ):
+            mailbox = attendee.find(f"./{{{EWS_TYPES_NS}}}Mailbox")
+            record = ews_mailbox_record(mailbox) or {}
+            record["role"] = role
+            response = text_of(attendee, "ResponseType")
+            if response:
+                record["status"] = response
+            attendees.append(record)
+    return attendees
+
+
+def ews_reminders(item: Any) -> list[dict[str, Any]]:
+    if text_of(item, "ReminderIsSet") == "true":
+        minutes = int_or_default(
+            text_of(item, "ReminderMinutesBeforeStart"),
+            15,
+        )
+        return [{"action": "DISPLAY", "trigger_minutes_before": minutes}]
+    return []
+
+
+def element_to_dict(element: Any) -> dict[str, Any]:
+    tag = element.tag.rsplit("}", 1)[-1]
+    children = list(element)
+    result: dict[str, Any] = {"tag": tag}
+    if element.attrib:
+        result["attributes"] = dict(element.attrib)
+    if element.text and element.text.strip():
+        result["text"] = element.text.strip()
+    if children:
+        result["children"] = [
+            element_to_dict(child) for child in children
+        ]
+    return result
+
+
+def int_or_default(value: str | None, default: int) -> int:
+    try:
+        return int(value) if value is not None else default
+    except ValueError:
+        return default
+
+
+def xml_escape(value: str) -> str:
+    return (
+        value.replace("&", "&amp;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;")
+        .replace('"', "&quot;")
+    )
+
+
+def normalize_datetime(value: datetime) -> datetime:
+    if value.tzinfo is None:
+        return value.replace(tzinfo=timezone.utc)
+    return value.astimezone(timezone.utc)

src/govoplan_calendar/backend/graph.py

@@ -0,0 +1,157 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Any
+import uuid
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
+
+
+def graph_event_payload(item: dict[str, Any]) -> dict[str, Any]:
+    """Translate one Microsoft Graph event into the calendar event contract."""
+
+    start = graph_datetime(item.get("start"))
+    end = graph_datetime(item.get("end"))
+    all_day = bool(item.get("isAllDay"))
+    uid = str(
+        item.get("iCalUId")
+        or item.get("uid")
+        or item.get("id")
+        or uuid.uuid4()
+    )
+    return {
+        "uid": uid,
+        "recurrence_id": (
+            str(item.get("id"))
+            if item.get("type") == "occurrence"
+            else None
+        ),
+        "sequence": int(item.get("sequence") or 0),
+        "summary": str(item.get("subject") or "(Untitled event)"),
+        "description": graph_body_text(item),
+        "location": graph_location_text(item.get("location")),
+        "status": (
+            "CANCELLED" if item.get("isCancelled") else "CONFIRMED"
+        ),
+        "transparency": (
+            "TRANSPARENT"
+            if item.get("showAs") in {"free", "workingElsewhere"}
+            else "OPAQUE"
+        ),
+        "classification": (
+            "PRIVATE"
+            if item.get("sensitivity") == "private"
+            else "PUBLIC"
+        ),
+        "start_at": start,
+        "end_at": end,
+        "duration_seconds": int((end - start).total_seconds()),
+        "all_day": all_day,
+        "timezone": (
+            (item.get("start") or {}).get("timeZone")
+            if isinstance(item.get("start"), dict)
+            else None
+        )
+        or "UTC",
+        "organizer": graph_party(item.get("organizer")),
+        "attendees": [
+            graph_party(attendee)
+            for attendee in item.get("attendees") or []
+        ],
+        "categories": [
+            str(category) for category in item.get("categories") or []
+        ],
+        "rrule": (
+            item.get("recurrence")
+            if isinstance(item.get("recurrence"), dict)
+            else None
+        ),
+        "rdate": [],
+        "exdate": [],
+        "reminders": graph_reminders(item),
+        "attachments": [],
+        "related_to": [],
+        "etag": item.get("@odata.etag"),
+        "icalendar": {
+            "component": "VEVENT",
+            "schema_version": 1,
+            "provider": "graph",
+            "graph": item,
+        },
+        "metadata": {"graph": item},
+    }
+
+
+def graph_datetime(value: Any) -> datetime:
+    if not isinstance(value, dict) or not value.get("dateTime"):
+        return datetime.now(timezone.utc)
+    raw = str(value["dateTime"]).replace("Z", "+00:00")
+    parsed = datetime.fromisoformat(raw)
+    tz_name = str(value.get("timeZone") or "UTC")
+    if parsed.tzinfo is None:
+        try:
+            parsed = parsed.replace(tzinfo=ZoneInfo(tz_name))
+        except ZoneInfoNotFoundError:
+            parsed = parsed.replace(tzinfo=timezone.utc)
+    return normalize_datetime(parsed)
+
+
+def graph_body_text(item: dict[str, Any]) -> str | None:
+    body = item.get("body")
+    if isinstance(body, dict) and body.get("content"):
+        return str(body["content"])
+    return str(item.get("bodyPreview")) if item.get("bodyPreview") else None
+
+
+def graph_location_text(value: Any) -> str | None:
+    if isinstance(value, dict) and value.get("displayName"):
+        return str(value["displayName"])
+    return None
+
+
+def graph_party(value: Any) -> dict[str, Any]:
+    if not isinstance(value, dict):
+        return {}
+    email = (
+        value.get("emailAddress")
+        if isinstance(value.get("emailAddress"), dict)
+        else value
+    )
+    result = {
+        "name": (
+            str(email.get("name") or "")
+            if isinstance(email, dict)
+            else ""
+        ),
+        "email": (
+            str(email.get("address") or "")
+            if isinstance(email, dict)
+            else ""
+        ),
+    }
+    if value.get("type"):
+        result["role"] = value["type"]
+    if value.get("status"):
+        result["status"] = value["status"]
+    return result
+
+
+def graph_reminders(item: dict[str, Any]) -> list[dict[str, Any]]:
+    if (
+        item.get("isReminderOn")
+        and item.get("reminderMinutesBeforeStart") is not None
+    ):
+        return [
+            {
+                "action": "DISPLAY",
+                "trigger_minutes_before": int(
+                    item["reminderMinutesBeforeStart"]
+                ),
+            }
+        ]
+    return []
+
+
+def normalize_datetime(value: datetime) -> datetime:
+    if value.tzinfo is None:
+        return value.replace(tzinfo=timezone.utc)
+    return value.astimezone(timezone.utc)

src/govoplan_calendar/backend/ical.py

@@ -302,6 +302,30 @@ def recurrence_id_value(value: Any | None) -> str | None:
     return f"TZID={tzid}:{raw_value}" if tzid else raw_value
 
 
+def recurrence_id_datetime(value: str | None) -> datetime | None:
+    """Parse the canonical/raw RECURRENCE-ID forms stored by the module."""
+
+    if not value:
+        return None
+    raw_value = value
+    params: dict[str, Any] = {}
+    if value.startswith("TZID=") and ":" in value:
+        tzid, raw_value = value.removeprefix("TZID=").split(":", 1)
+        params["TZID"] = [tzid]
+    parsed = parse_ical_temporal(raw_value, params)
+    if parsed is not None:
+        return parsed
+    try:
+        return normalize_datetime(datetime.fromisoformat(raw_value))
+    except ValueError:
+        return None
+
+
+def normalized_recurrence_id(value: str | None) -> str | None:
+    parsed = recurrence_id_datetime(value)
+    return format_ical_datetime(parsed) if parsed is not None else value
+
+
 def recurrence_rule(value: Any | None) -> dict[str, Any] | None:
     if value is None:
         return None
@@ -653,13 +677,30 @@ def occurrence_overlaps(start_at: datetime, duration: timedelta, range_start: da
 def occurrence_payload(start_at: datetime, duration: timedelta, event: Any) -> dict[str, Any]:
     return {
         "uid": event.uid,
-        "recurrence_id": format_ical_datetime(start_at),
+        "recurrence_id": occurrence_recurrence_id(start_at, event),
         "start_at": start_at,
         "end_at": start_at + duration if duration else None,
         "all_day": event.all_day,
     }
 
 
+def occurrence_recurrence_id(start_at: datetime, event: Any) -> str:
+    start_at = normalize_datetime(start_at)
+    if event.all_day:
+        return start_at.strftime("%Y%m%d")
+    timezone_id = getattr(event, "timezone", None)
+    if timezone_id:
+        try:
+            local_start = start_at.astimezone(ZoneInfo(timezone_id))
+            return (
+                f"TZID={timezone_id}:"
+                f"{local_start.strftime('%Y%m%dT%H%M%S')}"
+            )
+        except ZoneInfoNotFoundError:
+            pass
+    return format_ical_datetime(start_at)
+
+
 def int_or_zero(value: str | None) -> int:
     try:
         return int(value or "0")

src/govoplan_calendar/backend/manifest.py

@@ -35,6 +35,7 @@ _calendar_table_retirement_provider = drop_table_retirement_provider(
     calendar_models.CalendarOutboxOperation,
     calendar_models.CalendarSyncCredential,
     calendar_models.CalendarSyncSource,
+    calendar_models.CalendarViewPreference,
     label="Calendar",
 )
 
@@ -127,6 +128,7 @@ def _tenant_summary(session, tenant_id: str) -> dict[str, int]:
         CalendarOutboxOperation,
         CalendarSyncCredential,
         CalendarSyncSource,
+        CalendarViewPreference,
     )
 
     return {
@@ -134,6 +136,7 @@ def _tenant_summary(session, tenant_id: str) -> dict[str, int]:
         "calendar_events": session.query(CalendarEvent).filter(CalendarEvent.tenant_id == tenant_id, CalendarEvent.deleted_at.is_(None)).count(),
         "calendar_sync_sources": session.query(CalendarSyncSource).filter(CalendarSyncSource.tenant_id == tenant_id, CalendarSyncSource.deleted_at.is_(None)).count(),
         "calendar_sync_credentials": session.query(CalendarSyncCredential).filter(CalendarSyncCredential.tenant_id == tenant_id, CalendarSyncCredential.deleted_at.is_(None)).count(),
+        "calendar_view_preferences": session.query(CalendarViewPreference).filter(CalendarViewPreference.tenant_id == tenant_id).count(),
         "calendar_outbox_pending": session.query(CalendarOutboxOperation)
         .filter(
             CalendarOutboxOperation.tenant_id == tenant_id,
@@ -213,6 +216,13 @@ manifest = ModuleManifest(
                 label="Upcoming events widget",
                 order=40,
             ),
+            ViewSurface(
+                id="calendar.settings.preferences",
+                module_id="calendar",
+                kind="section",
+                label="Calendar preferences",
+                order=45,
+            ),
         ),
     ),
     migration_spec=MigrationSpec(
@@ -230,6 +240,7 @@ manifest = ModuleManifest(
             calendar_models.CalendarOutboxOperation,
             calendar_models.CalendarSyncCredential,
             calendar_models.CalendarSyncSource,
+            calendar_models.CalendarViewPreference,
             label="Calendar",
         ),
     ),

src/govoplan_calendar/backend/migrations/dev_versions/b02c3d4e5f60_calendar_view_preferences.py

@@ -0,0 +1,28 @@
+"""Add durable per-user calendar view preferences on the development track.
+
+Revision ID: b02c3d4e5f60
+Revises: af1b2c3d4e5f
+Create Date: 2026-07-31 00:00:00.000000
+"""
+from __future__ import annotations
+
+from govoplan_calendar.backend.migrations.versions.b02c3d4e5f60_calendar_view_preferences import (
+    downgrade as _downgrade,
+)
+from govoplan_calendar.backend.migrations.versions.b02c3d4e5f60_calendar_view_preferences import (
+    upgrade as _upgrade,
+)
+
+
+revision = "b02c3d4e5f60"
+down_revision = "af1b2c3d4e5f"
+branch_labels = None
+depends_on = "4f2a9c8e7b6d"
+
+
+def upgrade() -> None:
+    _upgrade()
+
+
+def downgrade() -> None:
+    _downgrade()

src/govoplan_calendar/backend/migrations/versions/b02c3d4e5f60_calendar_view_preferences.py

@@ -0,0 +1,83 @@
+"""Add durable per-user calendar view preferences.
+
+Revision ID: b02c3d4e5f60
+Revises: af1b2c3d4e5f
+Create Date: 2026-07-31 00:00:00.000000
+"""
+from __future__ import annotations
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "b02c3d4e5f60"
+down_revision = "af1b2c3d4e5f"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "calendar_view_preferences",
+        sa.Column("id", sa.String(length=36), nullable=False),
+        sa.Column("tenant_id", sa.String(length=36), nullable=False),
+        sa.Column("user_id", sa.String(length=36), nullable=False),
+        sa.Column("dim_weekends", sa.Boolean(), nullable=True),
+        sa.Column("dim_off_hours", sa.Boolean(), nullable=True),
+        sa.Column("workday_start_hour", sa.Integer(), nullable=True),
+        sa.Column("workday_end_hour", sa.Integer(), nullable=True),
+        sa.Column("continuous_virtualization", sa.Boolean(), nullable=True),
+        sa.Column("continuous_overscan_weeks", sa.Integer(), nullable=True),
+        sa.Column("alternate_continuous_months", sa.Boolean(), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False),
+        sa.ForeignKeyConstraint(
+            ["tenant_id"],
+            ["core_scopes.id"],
+            name=op.f(
+                "fk_calendar_view_preferences_tenant_id_core_scopes"
+            ),
+            ondelete="CASCADE",
+        ),
+        sa.ForeignKeyConstraint(
+            ["user_id"],
+            ["access_users.id"],
+            name=op.f(
+                "fk_calendar_view_preferences_user_id_access_users"
+            ),
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint(
+            "id",
+            name=op.f("pk_calendar_view_preferences"),
+        ),
+        sa.UniqueConstraint(
+            "tenant_id",
+            "user_id",
+            name="uq_calendar_view_preferences_tenant_user",
+        ),
+    )
+    op.create_index(
+        op.f("ix_calendar_view_preferences_tenant_id"),
+        "calendar_view_preferences",
+        ["tenant_id"],
+        unique=False,
+    )
+    op.create_index(
+        op.f("ix_calendar_view_preferences_user_id"),
+        "calendar_view_preferences",
+        ["user_id"],
+        unique=False,
+    )
+
+
+def downgrade() -> None:
+    op.drop_index(
+        op.f("ix_calendar_view_preferences_user_id"),
+        table_name="calendar_view_preferences",
+    )
+    op.drop_index(
+        op.f("ix_calendar_view_preferences_tenant_id"),
+        table_name="calendar_view_preferences",
+    )
+    op.drop_table("calendar_view_preferences")

src/govoplan_calendar/backend/router.py

@@ -33,6 +33,8 @@ from govoplan_calendar.backend.schemas import (
     CalendarEventCreateRequest,
     CalendarEventDeltaResponse,
     CalendarEventListResponse,
+    CalendarEventOccurrenceDeleteRequest,
+    CalendarEventOccurrenceUpdateRequest,
     CalendarEventResponse,
     CalendarEventUpdateRequest,
     CalendarFreeBusyRequest,
@@ -49,6 +51,8 @@ from govoplan_calendar.backend.schemas import (
     CalendarSyncSourceSyncRequest,
     CalendarSyncSourceSyncResponse,
     CalendarSyncSourceUpdateRequest,
+    CalendarViewPreferencesResponse,
+    CalendarViewPreferencesUpdateRequest,
 )
 from govoplan_calendar.backend.outbox import (
     calendar_outbox_operation_response,
@@ -75,14 +79,17 @@ from govoplan_calendar.backend.service import (
     delete_caldav_source,
     delete_sync_source,
     delete_event,
+    delete_event_occurrence,
     discover_caldav_calendars,
     event_response,
+    get_calendar_view_preferences,
     get_event,
     import_ics_event,
     list_freebusy,
     list_caldav_sources,
     list_calendars,
     list_events,
+    list_event_occurrences,
     list_sync_sources,
     normalize_datetime,
     sync_due_sources,
@@ -93,6 +100,8 @@ from govoplan_calendar.backend.service import (
     update_caldav_source,
     update_sync_source,
     update_event,
+    update_event_occurrence,
+    update_calendar_view_preferences,
 )
 from govoplan_core.db.session import get_session
 
@@ -743,10 +752,39 @@ def api_list_events(
     calendar_id: str | None = None,
     start_at: datetime | None = Query(default=None),
     end_at: datetime | None = Query(default=None),
+    expand_recurring: bool = Query(default=False),
     principal: ApiPrincipal = Depends(get_api_principal),
     session: Session = Depends(get_session),
 ):
     _require_scope(principal, "calendar:event:read")
+    if expand_recurring:
+        if start_at is None or end_at is None:
+            raise HTTPException(
+                status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+                detail=(
+                    "start_at and end_at are required when expanding "
+                    "recurring events"
+                ),
+            )
+        try:
+            occurrences = list_event_occurrences(
+                session,
+                tenant_id=principal.tenant_id,
+                calendar_id=calendar_id,
+                start_at=start_at,
+                end_at=end_at,
+            )
+            return CalendarEventListResponse(
+                events=[
+                    CalendarEventResponse.model_validate(item)
+                    for item in occurrences
+                ]
+            )
+        except CalendarError as exc:
+            raise HTTPException(
+                status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+                detail=str(exc),
+            ) from exc
     events = list_events(session, tenant_id=principal.tenant_id, calendar_id=calendar_id, start_at=start_at, end_at=end_at)
     return CalendarEventListResponse(events=[_event_response(event) for event in events])
 
@@ -850,6 +888,70 @@ def api_update_event(
         raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_CONTENT, detail=str(exc)) from exc
 
 
+@router.patch(
+    "/events/{series_event_id}/occurrence",
+    response_model=CalendarEventResponse,
+)
+def api_update_event_occurrence(
+    series_event_id: str,
+    payload: CalendarEventOccurrenceUpdateRequest,
+    principal: ApiPrincipal = Depends(get_api_principal),
+    session: Session = Depends(get_session),
+):
+    _require_scope(principal, CALENDAR_EVENT_WRITE_SCOPE)
+    try:
+        event = update_event_occurrence(
+            session,
+            tenant_id=principal.tenant_id,
+            user_id=principal.user.id,
+            series_event_id=series_event_id,
+            payload=payload,
+        )
+        session.commit()
+        session.refresh(event)
+        return _event_response(event)
+    except CalendarError as exc:
+        session.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=str(exc),
+        ) from exc
+
+
+@router.delete(
+    "/events/{series_event_id}/occurrence",
+    response_model=CalendarEventResponse,
+)
+def api_delete_event_occurrence(
+    series_event_id: str,
+    payload: CalendarEventOccurrenceDeleteRequest,
+    principal: ApiPrincipal = Depends(get_api_principal),
+    session: Session = Depends(get_session),
+):
+    _require_any_scope(
+        principal,
+        "calendar:event:delete",
+        CALENDAR_EVENT_WRITE_SCOPE,
+    )
+    try:
+        event = delete_event_occurrence(
+            session,
+            tenant_id=principal.tenant_id,
+            user_id=principal.user.id,
+            series_event_id=series_event_id,
+            recurrence_id=payload.recurrence_id,
+        )
+        session.commit()
+        session.refresh(event)
+        return _event_response(event)
+    except CalendarError as exc:
+        session.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=str(exc),
+        ) from exc
+
+
 @router.delete("/events/{event_id}", status_code=status.HTTP_204_NO_CONTENT)
 def api_delete_event(
     event_id: str,
@@ -866,6 +968,51 @@ def api_delete_event(
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(exc)) from exc
 
 
+@router.get(
+    "/preferences/view",
+    response_model=CalendarViewPreferencesResponse,
+)
+def api_get_calendar_view_preferences(
+    principal: ApiPrincipal = Depends(get_api_principal),
+    session: Session = Depends(get_session),
+):
+    _require_scope(principal, "calendar:event:read")
+    return CalendarViewPreferencesResponse.model_validate(
+        get_calendar_view_preferences(
+            session,
+            tenant_id=principal.tenant_id,
+            user_id=principal.user.id,
+        )
+    )
+
+
+@router.patch(
+    "/preferences/view",
+    response_model=CalendarViewPreferencesResponse,
+)
+def api_update_calendar_view_preferences(
+    payload: CalendarViewPreferencesUpdateRequest,
+    principal: ApiPrincipal = Depends(get_api_principal),
+    session: Session = Depends(get_session),
+):
+    _require_scope(principal, "calendar:event:read")
+    try:
+        response = update_calendar_view_preferences(
+            session,
+            tenant_id=principal.tenant_id,
+            user_id=principal.user.id,
+            payload=payload,
+        )
+        session.commit()
+        return CalendarViewPreferencesResponse.model_validate(response)
+    except CalendarError as exc:
+        session.rollback()
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=str(exc),
+        ) from exc
+
+
 @router.post("/events/import-ics", response_model=CalendarEventResponse, status_code=status.HTTP_201_CREATED)
 def api_import_ics_event(
     payload: CalendarIcsImportRequest,

src/govoplan_calendar/backend/schemas.py

@@ -375,6 +375,16 @@ class CalendarEventUpdateRequest(BaseModel):
     metadata: dict[str, Any] | None = None
 
 
+class CalendarEventOccurrenceUpdateRequest(CalendarEventUpdateRequest):
+    recurrence_id: str = Field(min_length=1, max_length=255)
+
+
+class CalendarEventOccurrenceDeleteRequest(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    recurrence_id: str = Field(min_length=1, max_length=255)
+
+
 class CalendarEventResponse(BaseModel):
     id: str
     tenant_id: str
@@ -409,6 +419,10 @@ class CalendarEventResponse(BaseModel):
     created_at: datetime
     updated_at: datetime
     metadata: dict[str, Any] = Field(default_factory=dict)
+    instance_id: str | None = None
+    series_event_id: str | None = None
+    is_occurrence: bool = False
+    is_override: bool = False
 
 
 class CalendarEventListResponse(BaseModel):
@@ -423,6 +437,30 @@ class CalendarEventDeltaResponse(BaseModel):
     full: bool = False
 
 
+class CalendarViewPreferencesUpdateRequest(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    dim_weekends: bool | None = None
+    dim_off_hours: bool | None = None
+    workday_start_hour: int | None = Field(default=None, ge=0, le=23)
+    workday_end_hour: int | None = Field(default=None, ge=1, le=24)
+    continuous_virtualization: bool | None = None
+    continuous_overscan_weeks: int | None = Field(default=None, ge=2, le=20)
+    alternate_continuous_months: bool | None = None
+
+
+class CalendarViewPreferencesResponse(BaseModel):
+    dim_weekends: bool
+    dim_off_hours: bool
+    workday_start_hour: int
+    workday_end_hour: int
+    continuous_virtualization: bool
+    continuous_overscan_weeks: int
+    alternate_continuous_months: bool
+    overridden_fields: list[str] = Field(default_factory=list)
+    defaults: dict[str, bool | int] = Field(default_factory=dict)
+
+
 class CalendarFreeBusyRequest(BaseModel):
     model_config = ConfigDict(extra="forbid")
 

src/govoplan_calendar/backend/service.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import copy
 import json
 import posixpath
 import re
@@ -11,10 +12,8 @@ import urllib.request
 from dataclasses import dataclass, field
 from datetime import datetime, timedelta, timezone
 from typing import Any, Callable, Iterable
-from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
-from defusedxml import ElementTree as SafeElementTree
-from sqlalchemy import or_
+from sqlalchemy import func, or_
 from sqlalchemy.orm import Session
 
 from govoplan_core.security.outbound_http import (
@@ -35,8 +34,26 @@ from govoplan_core.security.credential_envelopes import (
 from govoplan_core.audit.logging import audit_event
 
 from govoplan_calendar.backend.caldav import CalDAVClient, CalDAVError, CalDAVNotFound, CalDAVObject, CalDAVReportResult, CalDAVSyncUnsupported, ensure_collection_url
-from govoplan_calendar.backend.db.models import CalendarCollection, CalendarEvent, CalendarSyncCredential, CalendarSyncSource
-from govoplan_calendar.backend.ical import expand_event_occurrences, parse_vevent, parse_vevents
+from govoplan_calendar.backend.db.models import (
+    CalendarCollection,
+    CalendarEvent,
+    CalendarSyncCredential,
+    CalendarSyncSource,
+    CalendarViewPreference,
+)
+from govoplan_calendar.backend.ews import (
+    EwsAdapterError,
+    ews_find_item_body,
+    parse_ews_calendar_items,
+)
+from govoplan_calendar.backend.graph import graph_event_payload
+from govoplan_calendar.backend.ical import (
+    expand_event_occurrences,
+    normalized_recurrence_id,
+    parse_vevent,
+    parse_vevents,
+    recurrence_id_datetime,
+)
 from govoplan_calendar.backend.runtime import get_registry
 from govoplan_calendar.backend.schemas import (
     CalendarCalDavDiscoveryRequest,
@@ -46,9 +63,11 @@ from govoplan_calendar.backend.schemas import (
     CalendarCollectionDeleteRequest,
     CalendarCollectionUpdateRequest,
     CalendarEventCreateRequest,
+    CalendarEventOccurrenceUpdateRequest,
     CalendarEventUpdateRequest,
     CalendarSyncSourceCreateRequest,
     CalendarSyncSourceUpdateRequest,
+    CalendarViewPreferencesUpdateRequest,
 )
 from govoplan_core.core.notifications import NotificationDispatchRequest, notification_dispatch_provider
 from govoplan_core.db.base import utcnow
@@ -67,14 +86,21 @@ CALDAV_DEFAULT_SYNC_INTERVAL_SECONDS = 900
 SYNC_SOURCE_KINDS = {"caldav", "ics", "webcal", "graph", "ews"}
 READ_ONLY_SYNC_SOURCE_KINDS = {"ics", "webcal", "graph", "ews"}
 GRAPH_DEFAULT_BASE_URL = "https://graph.microsoft.com/v1.0/"
-EWS_SOAP_NS = "http://schemas.xmlsoap.org/soap/envelope/"
-EWS_MESSAGES_NS = "http://schemas.microsoft.com/exchange/services/2006/messages"
-EWS_TYPES_NS = "http://schemas.microsoft.com/exchange/services/2006/types"
 CALENDAR_MODULE_ID = "calendar"
 CALENDAR_EVENTS_COLLECTION = "calendar.events"
 CALENDAR_EVENT_RESOURCE = "calendar_event"
 SOURCE_EVENT_CLEANUP_BATCH_SIZE = 500
 REMOTE_SYNC_MAX_ITEMS = 10_000
+MAX_OCCURRENCE_RANGE_DAYS = 400
+DEFAULT_CALENDAR_VIEW_PREFERENCES: dict[str, bool | int] = {
+    "dim_weekends": True,
+    "dim_off_hours": True,
+    "workday_start_hour": 6,
+    "workday_end_hour": 20,
+    "continuous_virtualization": True,
+    "continuous_overscan_weeks": 6,
+    "alternate_continuous_months": True,
+}
 
 
 def calendar_credential_context(
@@ -3027,89 +3053,6 @@ def sync_graph_source(
         raise
 
 
-def graph_event_payload(item: dict[str, Any]) -> dict[str, Any]:
-    start = graph_datetime(item.get("start"))
-    end = graph_datetime(item.get("end"))
-    all_day = bool(item.get("isAllDay"))
-    uid = str(item.get("iCalUId") or item.get("uid") or item.get("id") or uuid.uuid4())
-    return {
-        "uid": uid,
-        "recurrence_id": str(item.get("id")) if item.get("type") == "occurrence" else None,
-        "sequence": int(item.get("sequence") or 0),
-        "summary": str(item.get("subject") or "(Untitled event)"),
-        "description": graph_body_text(item),
-        "location": graph_location_text(item.get("location")),
-        "status": "CANCELLED" if item.get("isCancelled") else "CONFIRMED",
-        "transparency": "TRANSPARENT" if item.get("showAs") in {"free", "workingElsewhere"} else "OPAQUE",
-        "classification": "PRIVATE" if item.get("sensitivity") == "private" else "PUBLIC",
-        "start_at": start,
-        "end_at": end,
-        "duration_seconds": int((end - start).total_seconds()) if start and end else None,
-        "all_day": all_day,
-        "timezone": ((item.get("start") or {}).get("timeZone") if isinstance(item.get("start"), dict) else None) or "UTC",
-        "organizer": graph_party(item.get("organizer")),
-        "attendees": [graph_party(attendee) for attendee in item.get("attendees") or []],
-        "categories": [str(category) for category in item.get("categories") or []],
-        "rrule": item.get("recurrence") if isinstance(item.get("recurrence"), dict) else None,
-        "rdate": [],
-        "exdate": [],
-        "reminders": graph_reminders(item),
-        "attachments": [],
-        "related_to": [],
-        "etag": item.get("@odata.etag"),
-        "icalendar": {"component": "VEVENT", "schema_version": 1, "provider": "graph", "graph": item},
-        "metadata": {"graph": item},
-    }
-
-
-def graph_datetime(value: Any) -> datetime:
-    if not isinstance(value, dict) or not value.get("dateTime"):
-        return utcnow()
-    raw = str(value["dateTime"]).replace("Z", "+00:00")
-    parsed = datetime.fromisoformat(raw)
-    tz_name = str(value.get("timeZone") or "UTC")
-    if parsed.tzinfo is None:
-        try:
-            parsed = parsed.replace(tzinfo=ZoneInfo(tz_name))
-        except ZoneInfoNotFoundError:
-            parsed = parsed.replace(tzinfo=timezone.utc)
-    return normalize_datetime(parsed)
-
-
-def graph_body_text(item: dict[str, Any]) -> str | None:
-    body = item.get("body")
-    if isinstance(body, dict) and body.get("content"):
-        return str(body["content"])
-    return str(item.get("bodyPreview")) if item.get("bodyPreview") else None
-
-
-def graph_location_text(value: Any) -> str | None:
-    if isinstance(value, dict):
-        return str(value.get("displayName")) if value.get("displayName") else None
-    return None
-
-
-def graph_party(value: Any) -> dict[str, Any]:
-    if not isinstance(value, dict):
-        return {}
-    email = value.get("emailAddress") if isinstance(value.get("emailAddress"), dict) else value
-    result = {
-        "name": str(email.get("name") or "") if isinstance(email, dict) else "",
-        "email": str(email.get("address") or "") if isinstance(email, dict) else "",
-    }
-    if value.get("type"):
-        result["role"] = value["type"]
-    if value.get("status"):
-        result["status"] = value["status"]
-    return result
-
-
-def graph_reminders(item: dict[str, Any]) -> list[dict[str, Any]]:
-    if item.get("isReminderOn") and item.get("reminderMinutesBeforeStart") is not None:
-        return [{"action": "DISPLAY", "trigger_minutes_before": int(item["reminderMinutesBeforeStart"])}]
-    return []
-
-
 def sync_ews_source(
     session: Session,
     *,
@@ -3153,7 +3096,10 @@ def sync_ews_source(
                 mailbox=metadata.get("mailbox"),
             ),
         )
-        items = parse_ews_calendar_items(body)
+        try:
+            items = parse_ews_calendar_items(body)
+        except EwsAdapterError as exc:
+            raise CalendarError(str(exc)) from exc
         if len(items) > REMOTE_SYNC_MAX_ITEMS:
             raise CalendarError(
                 "Exchange Web Services sync exceeded the configured item limit."
@@ -3349,152 +3295,6 @@ def soft_delete_unseen_source_events(
     return count
 
 
-def ews_find_item_body(*, start: datetime, end: datetime, mailbox: Any | None = None) -> str:
-    start_text = normalize_datetime(start).isoformat().replace("+00:00", "Z")
-    end_text = normalize_datetime(end).isoformat().replace("+00:00", "Z")
-    mailbox_xml = ""
-    if mailbox:
-        mailbox_xml = f"<t:Mailbox><t:EmailAddress>{xml_escape(str(mailbox))}</t:EmailAddress></t:Mailbox>"
-    return f"""<?xml version="1.0" encoding="utf-8"?>
-<s:Envelope xmlns:s="{EWS_SOAP_NS}" xmlns:m="{EWS_MESSAGES_NS}" xmlns:t="{EWS_TYPES_NS}">
-  <s:Header>
-    <t:RequestServerVersion Version="Exchange2013_SP1" />
-  </s:Header>
-  <s:Body>
-    <m:FindItem Traversal="Shallow">
-      <m:ItemShape>
-        <t:BaseShape>AllProperties</t:BaseShape>
-      </m:ItemShape>
-      <m:CalendarView StartDate="{start_text}" EndDate="{end_text}" />
-      <m:ParentFolderIds>
-        <t:DistinguishedFolderId Id="calendar">{mailbox_xml}</t:DistinguishedFolderId>
-      </m:ParentFolderIds>
-    </m:FindItem>
-  </s:Body>
-</s:Envelope>"""
-
-
-def parse_ews_calendar_items(xml_text: str) -> list[dict[str, Any]]:
-    try:
-        root = SafeElementTree.fromstring(xml_text)
-    except SafeElementTree.ParseError as exc:
-        raise CalendarError(f"Invalid EWS response XML: {exc}") from exc
-    items: list[dict[str, Any]] = []
-    for item in root.findall(f".//{{{EWS_TYPES_NS}}}CalendarItem"):
-        item_id = item.find(f"./{{{EWS_TYPES_NS}}}ItemId")
-        href = item_id.get("Id") if item_id is not None else None
-        if not href:
-            continue
-        change_key = item_id.get("ChangeKey") if item_id is not None else None
-        start = parse_ews_datetime(text_of(item, "Start"))
-        end = parse_ews_datetime(text_of(item, "End")) if text_of(item, "End") else start
-        uid = text_of(item, "UID") or href
-        subject = text_of(item, "Subject") or "(Untitled event)"
-        all_day = text_of(item, "IsAllDayEvent") == "true"
-        free_busy = text_of(item, "LegacyFreeBusyStatus") or "Busy"
-        sensitivity = text_of(item, "Sensitivity") or "Normal"
-        body = item.find(f"./{{{EWS_TYPES_NS}}}Body")
-        provider_payload = element_to_dict(item)
-        items.append(
-            {
-                "href": href,
-                "uid": uid,
-                "recurrence_id": href if text_of(item, "CalendarItemType") in {"Occurrence", "Exception"} else None,
-                "sequence": int_or_default(text_of(item, "AppointmentSequenceNumber"), 0),
-                "summary": subject,
-                "description": body.text if body is not None else None,
-                "location": text_of(item, "Location"),
-                "status": "CANCELLED" if text_of(item, "IsCancelled") == "true" else "CONFIRMED",
-                "transparency": "TRANSPARENT" if free_busy.lower() == "free" else "OPAQUE",
-                "classification": "PRIVATE" if sensitivity.lower() == "private" else "PUBLIC",
-                "start_at": start,
-                "end_at": end,
-                "duration_seconds": int((end - start).total_seconds()) if start and end else None,
-                "all_day": all_day,
-                "timezone": "UTC",
-                "organizer": ews_mailbox_record(item.find(f"./{{{EWS_TYPES_NS}}}Organizer/{{{EWS_TYPES_NS}}}Mailbox")),
-                "attendees": ews_attendees(item),
-                "categories": [category.text for category in item.findall(f"./{{{EWS_TYPES_NS}}}Categories/{{{EWS_TYPES_NS}}}String") if category.text],
-                "rrule": None,
-                "rdate": [],
-                "exdate": [],
-                "reminders": ews_reminders(item),
-                "attachments": [],
-                "related_to": [],
-                "etag": change_key,
-                "icalendar": {"component": "VEVENT", "schema_version": 1, "provider": "ews", "ews": provider_payload},
-                "metadata": {"ews": provider_payload},
-            }
-        )
-    return items
-
-
-def parse_ews_datetime(value: str | None) -> datetime:
-    if not value:
-        return utcnow()
-    return normalize_datetime(datetime.fromisoformat(value.replace("Z", "+00:00")))
-
-
-def text_of(item: Any, name: str) -> str | None:
-    child = item.find(f"./{{{EWS_TYPES_NS}}}{name}")
-    return child.text if child is not None else None
-
-
-def ews_mailbox_record(mailbox: Any | None) -> dict[str, Any] | None:
-    if mailbox is None:
-        return None
-    return {
-        "name": text_of(mailbox, "Name") or "",
-        "email": text_of(mailbox, "EmailAddress") or "",
-        "routing_type": text_of(mailbox, "RoutingType") or "",
-    }
-
-
-def ews_attendees(item: Any) -> list[dict[str, Any]]:
-    attendees: list[dict[str, Any]] = []
-    for role, path in (("required", "RequiredAttendees"), ("optional", "OptionalAttendees")):
-        for attendee in item.findall(f"./{{{EWS_TYPES_NS}}}{path}/{{{EWS_TYPES_NS}}}Attendee"):
-            mailbox = attendee.find(f"./{{{EWS_TYPES_NS}}}Mailbox")
-            record = ews_mailbox_record(mailbox) or {}
-            record["role"] = role
-            response = text_of(attendee, "ResponseType")
-            if response:
-                record["status"] = response
-            attendees.append(record)
-    return attendees
-
-
-def ews_reminders(item: Any) -> list[dict[str, Any]]:
-    if text_of(item, "ReminderIsSet") == "true":
-        minutes = int_or_default(text_of(item, "ReminderMinutesBeforeStart"), 15)
-        return [{"action": "DISPLAY", "trigger_minutes_before": minutes}]
-    return []
-
-
-def element_to_dict(element: Any) -> dict[str, Any]:
-    tag = element.tag.rsplit("}", 1)[-1]
-    children = list(element)
-    result: dict[str, Any] = {"tag": tag}
-    if element.attrib:
-        result["attributes"] = dict(element.attrib)
-    if element.text and element.text.strip():
-        result["text"] = element.text.strip()
-    if children:
-        result["children"] = [element_to_dict(child) for child in children]
-    return result
-
-
-def int_or_default(value: str | None, default: int) -> int:
-    try:
-        return int(value) if value is not None else default
-    except ValueError:
-        return default
-
-
-def xml_escape(value: str) -> str:
-    return value.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;").replace('"', "&quot;")
-
-
 def sync_due_sources(
     session: Session,
     *,
@@ -3928,6 +3728,208 @@ def list_events(
     return query.order_by(CalendarEvent.start_at.asc(), CalendarEvent.summary.asc()).all()
 
 
+def list_event_occurrences(
+    session: Session,
+    *,
+    tenant_id: str,
+    start_at: datetime,
+    end_at: datetime,
+    calendar_id: str | None = None,
+) -> list[dict[str, Any]]:
+    """Return range-bounded events with recurring series fully reconciled."""
+
+    range_start = normalize_datetime(start_at)
+    range_end = normalize_datetime(end_at)
+    if range_end <= range_start:
+        raise CalendarError("Event range end must be after start")
+    if range_end - range_start > timedelta(days=MAX_OCCURRENCE_RANGE_DAYS):
+        raise CalendarError(
+            f"Expanded event ranges are limited to {MAX_OCCURRENCE_RANGE_DAYS} days"
+        )
+
+    base_query = session.query(CalendarEvent).filter(
+        CalendarEvent.tenant_id == tenant_id,
+        CalendarEvent.deleted_at.is_(None),
+    )
+    if calendar_id:
+        base_query = base_query.filter(CalendarEvent.calendar_id == calendar_id)
+
+    recurring_masters = (
+        base_query.filter(
+            CalendarEvent.recurrence_id.is_(None),
+            or_(
+                CalendarEvent.rrule.is_not(None),
+                func.json_array_length(CalendarEvent.rdate) > 0,
+            ),
+        )
+        .order_by(CalendarEvent.start_at.asc(), CalendarEvent.id.asc())
+        .all()
+    )
+    direct_events = (
+        base_query.filter(
+            or_(
+                CalendarEvent.end_at.is_(None),
+                CalendarEvent.end_at >= range_start,
+            ),
+            CalendarEvent.start_at <= range_end,
+        )
+        .order_by(CalendarEvent.start_at.asc(), CalendarEvent.id.asc())
+        .all()
+    )
+
+    series_keys = {
+        (event.calendar_id, event.uid) for event in recurring_masters
+    }
+    overrides: list[CalendarEvent] = []
+    if series_keys:
+        series_uids = {uid for _calendar_id, uid in series_keys}
+        overrides = [
+            event
+            for event in base_query.filter(
+                CalendarEvent.recurrence_id.is_not(None),
+                CalendarEvent.uid.in_(series_uids),
+            ).all()
+            if (event.calendar_id, event.uid) in series_keys
+        ]
+
+    overrides_by_series: dict[
+        tuple[str, str], dict[str, CalendarEvent]
+    ] = {}
+    for override in overrides:
+        recurrence_key = normalized_recurrence_id(override.recurrence_id)
+        if recurrence_key:
+            overrides_by_series.setdefault(
+                (override.calendar_id, override.uid), {}
+            )[recurrence_key] = override
+
+    results: list[dict[str, Any]] = []
+    consumed_event_ids: set[str] = set()
+    recurring_master_ids = {event.id for event in recurring_masters}
+    recurring_master_by_series = {
+        (event.calendar_id, event.uid): event for event in recurring_masters
+    }
+    for master in recurring_masters:
+        series_key = (master.calendar_id, master.uid)
+        series_overrides = overrides_by_series.get(series_key, {})
+        for occurrence in expand_event_occurrences(
+            master,
+            range_start,
+            range_end,
+        ):
+            occurrence_recurrence_id = str(
+                occurrence.get("recurrence_id") or ""
+            )
+            recurrence_key = normalized_recurrence_id(
+                occurrence_recurrence_id
+            )
+            override = (
+                series_overrides.get(recurrence_key)
+                if recurrence_key
+                else None
+            )
+            if override is not None:
+                consumed_event_ids.add(override.id)
+                if override.status.upper() == "CANCELLED":
+                    continue
+                if event_overlaps_range(
+                    override,
+                    range_start=range_start,
+                    range_end=range_end,
+                ):
+                    results.append(
+                        expanded_event_response(
+                            override,
+                            series_event_id=master.id,
+                            recurrence_id=(
+                                override.recurrence_id
+                                or occurrence_recurrence_id
+                            ),
+                            is_override=True,
+                        )
+                    )
+                continue
+            results.append(
+                expanded_event_response(
+                    master,
+                    series_event_id=master.id,
+                    recurrence_id=occurrence_recurrence_id,
+                    occurrence=occurrence,
+                )
+            )
+
+    for event in direct_events:
+        if event.id in recurring_master_ids or event.id in consumed_event_ids:
+            continue
+        series_event_id = None
+        is_override = False
+        if event.recurrence_id:
+            master = recurring_master_by_series.get(
+                (event.calendar_id, event.uid)
+            )
+            if master is not None:
+                series_event_id = master.id
+                is_override = True
+            if event.status.upper() == "CANCELLED":
+                continue
+        results.append(
+            expanded_event_response(
+                event,
+                series_event_id=series_event_id,
+                recurrence_id=normalized_recurrence_id(event.recurrence_id),
+                is_override=is_override,
+            )
+        )
+    return sorted(
+        results,
+        key=lambda item: (
+            item["start_at"],
+            item["calendar_id"],
+            item["summary"],
+            item["instance_id"],
+        ),
+    )
+
+
+def event_overlaps_range(
+    event: CalendarEvent,
+    *,
+    range_start: datetime,
+    range_end: datetime,
+) -> bool:
+    event_start = normalize_datetime(event.start_at)
+    event_end = (
+        normalize_datetime(event.end_at)
+        if event.end_at is not None
+        else event_start
+    )
+    return event_end >= range_start and event_start <= range_end
+
+
+def expanded_event_response(
+    event: CalendarEvent,
+    *,
+    series_event_id: str | None,
+    recurrence_id: str | None,
+    occurrence: dict[str, Any] | None = None,
+    is_override: bool = False,
+) -> dict[str, Any]:
+    payload = event_response(event)
+    if occurrence is not None:
+        payload["start_at"] = response_datetime(occurrence["start_at"])
+        payload["end_at"] = response_datetime(occurrence.get("end_at"))
+        payload["all_day"] = bool(occurrence.get("all_day"))
+    payload["recurrence_id"] = recurrence_id
+    payload["series_event_id"] = series_event_id
+    payload["is_occurrence"] = series_event_id is not None
+    payload["is_override"] = is_override
+    payload["instance_id"] = (
+        f"{series_event_id}:{recurrence_id}"
+        if series_event_id and recurrence_id
+        else event.id
+    )
+    return payload
+
+
 def list_freebusy(
     session: Session,
     *,
@@ -3940,40 +3942,49 @@ def list_freebusy(
     range_end = normalize_datetime(end_at)
     if range_end < range_start:
         raise CalendarError("Free/busy end must be after start")
-    query = session.query(CalendarEvent).filter(
-        CalendarEvent.tenant_id == tenant_id,
-        CalendarEvent.deleted_at.is_(None),
-        CalendarEvent.status != "CANCELLED",
-        CalendarEvent.transparency != "TRANSPARENT",
-    )
+    events: list[dict[str, Any]] = []
     if calendar_ids:
-        query = query.filter(CalendarEvent.calendar_id.in_(calendar_ids))
-    events = query.order_by(CalendarEvent.start_at.asc(), CalendarEvent.summary.asc()).all()
-    busy: list[dict[str, Any]] = []
-    for event in events:
-        if event.rrule or event.rdate:
-            for occurrence in expand_event_occurrences(event, range_start, range_end):
-                busy.append(freebusy_block(event, occurrence["start_at"], occurrence["end_at"], occurrence.get("recurrence_id")))
-            continue
-        event_start = normalize_datetime(event.start_at)
-        event_end = normalize_datetime(event.end_at) if event.end_at else event_start
-        if event_end >= range_start and event_start <= range_end:
-            busy.append(freebusy_block(event, event_start, event_end, event.recurrence_id))
-    return sorted(busy, key=lambda item: (item["start_at"], item["calendar_id"], item["uid"]))
-
-
-def freebusy_block(event: CalendarEvent, start_at: datetime, end_at: datetime | None, recurrence_id: str | None) -> dict[str, Any]:
-    return {
-        "calendar_id": event.calendar_id,
-        "event_id": event.id,
-        "uid": event.uid,
-        "recurrence_id": recurrence_id,
-        "start_at": response_datetime(start_at),
-        "end_at": response_datetime(end_at),
-        "all_day": event.all_day,
-        "transparency": event.transparency,
-        "status": event.status,
-    }
+        for calendar_id in dict.fromkeys(calendar_ids):
+            events.extend(
+                list_event_occurrences(
+                    session,
+                    tenant_id=tenant_id,
+                    calendar_id=calendar_id,
+                    start_at=range_start,
+                    end_at=range_end,
+                )
+            )
+    else:
+        events = list_event_occurrences(
+            session,
+            tenant_id=tenant_id,
+            start_at=range_start,
+            end_at=range_end,
+        )
+    busy = [
+        {
+            "calendar_id": event["calendar_id"],
+            "event_id": event["id"],
+            "uid": event["uid"],
+            "recurrence_id": event["recurrence_id"],
+            "start_at": event["start_at"],
+            "end_at": event["end_at"],
+            "all_day": event["all_day"],
+            "transparency": event["transparency"],
+            "status": event["status"],
+        }
+        for event in events
+        if event["status"].upper() != "CANCELLED"
+        and event["transparency"].upper() != "TRANSPARENT"
+    ]
+    return sorted(
+        busy,
+        key=lambda item: (
+            item["start_at"],
+            item["calendar_id"],
+            item["uid"],
+        ),
+    )
 
 
 def get_event(session: Session, *, tenant_id: str, event_id: str) -> CalendarEvent:
@@ -3987,6 +3998,78 @@ def get_event(session: Session, *, tenant_id: str, event_id: str) -> CalendarEve
     return event
 
 
+def get_calendar_view_preferences(
+    session: Session,
+    *,
+    tenant_id: str,
+    user_id: str,
+) -> dict[str, Any]:
+    preference = (
+        session.query(CalendarViewPreference)
+        .filter(
+            CalendarViewPreference.tenant_id == tenant_id,
+            CalendarViewPreference.user_id == user_id,
+        )
+        .first()
+    )
+    effective = dict(DEFAULT_CALENDAR_VIEW_PREFERENCES)
+    overridden_fields: list[str] = []
+    if preference is not None:
+        for field_name in DEFAULT_CALENDAR_VIEW_PREFERENCES:
+            value = getattr(preference, field_name)
+            if value is not None:
+                effective[field_name] = value
+                overridden_fields.append(field_name)
+    return {
+        **effective,
+        "overridden_fields": overridden_fields,
+        "defaults": dict(DEFAULT_CALENDAR_VIEW_PREFERENCES),
+    }
+
+
+def update_calendar_view_preferences(
+    session: Session,
+    *,
+    tenant_id: str,
+    user_id: str,
+    payload: CalendarViewPreferencesUpdateRequest,
+) -> dict[str, Any]:
+    preference = (
+        session.query(CalendarViewPreference)
+        .filter(
+            CalendarViewPreference.tenant_id == tenant_id,
+            CalendarViewPreference.user_id == user_id,
+        )
+        .first()
+    )
+    if preference is None:
+        preference = CalendarViewPreference(
+            tenant_id=tenant_id,
+            user_id=user_id,
+        )
+        session.add(preference)
+    for field_name in payload.model_fields_set:
+        setattr(preference, field_name, getattr(payload, field_name))
+
+    effective = dict(DEFAULT_CALENDAR_VIEW_PREFERENCES)
+    for field_name in DEFAULT_CALENDAR_VIEW_PREFERENCES:
+        value = getattr(preference, field_name)
+        if value is not None:
+            effective[field_name] = value
+    if int(effective["workday_end_hour"]) <= int(
+        effective["workday_start_hour"]
+    ):
+        raise CalendarError(
+            "Workday end hour must be after workday start hour"
+        )
+    session.flush()
+    return get_calendar_view_preferences(
+        session,
+        tenant_id=tenant_id,
+        user_id=user_id,
+    )
+
+
 def create_event(session: Session, *, tenant_id: str, user_id: str | None, payload: CalendarEventCreateRequest) -> CalendarEvent:
     default_calendar = None if payload.calendar_id else get_default_calendar(session, tenant_id=tenant_id)
     calendar_id = payload.calendar_id or (default_calendar.id if default_calendar else None)
@@ -4239,6 +4322,197 @@ def update_event(session: Session, *, tenant_id: str, user_id: str | None, event
     return event
 
 
+def update_event_occurrence(
+    session: Session,
+    *,
+    tenant_id: str,
+    user_id: str | None,
+    series_event_id: str,
+    payload: CalendarEventOccurrenceUpdateRequest,
+) -> CalendarEvent:
+    master = get_event(
+        session,
+        tenant_id=tenant_id,
+        event_id=series_event_id,
+    )
+    if master.recurrence_id is not None or not (master.rrule or master.rdate):
+        raise CalendarError("Calendar event is not a recurring series master")
+    occurrence = recurrence_occurrence(master, payload.recurrence_id)
+    recurrence_id = str(occurrence["recurrence_id"])
+    existing = find_event_override(
+        session,
+        tenant_id=tenant_id,
+        master=master,
+        recurrence_id=recurrence_id,
+    )
+    update_values = payload.model_dump(
+        exclude_unset=True,
+        exclude={"recurrence_id", "rrule", "rdate", "exdate"},
+    )
+    if (
+        "calendar_id" in update_values
+        and update_values["calendar_id"] != master.calendar_id
+    ):
+        raise CalendarError(
+            "A recurring occurrence cannot be moved to another calendar"
+        )
+    update_values.pop("calendar_id", None)
+    update_payload = CalendarEventUpdateRequest(**update_values)
+    if existing is not None:
+        return update_event(
+            session,
+            tenant_id=tenant_id,
+            user_id=user_id,
+            event_id=existing.id,
+            payload=update_payload,
+        )
+
+    source = active_sync_source_for_calendar(
+        session,
+        tenant_id=tenant_id,
+        calendar_id=master.calendar_id,
+        for_update=True,
+    )
+    assert_sync_mutation_allowed(source)
+    event = CalendarEvent(
+        tenant_id=tenant_id,
+        calendar_id=master.calendar_id,
+        uid=master.uid,
+        recurrence_id=recurrence_id,
+        sequence=max(0, int(master.sequence or 0)),
+        summary=master.summary,
+        description=master.description,
+        location=master.location,
+        status=master.status,
+        transparency=master.transparency,
+        classification=master.classification,
+        start_at=normalize_datetime(occurrence["start_at"]),
+        end_at=(
+            normalize_datetime(occurrence["end_at"])
+            if occurrence.get("end_at") is not None
+            else None
+        ),
+        duration_seconds=master.duration_seconds,
+        all_day=master.all_day,
+        timezone=master.timezone,
+        organizer=copy.deepcopy(master.organizer),
+        attendees=copy.deepcopy(master.attendees or []),
+        categories=copy.deepcopy(master.categories or []),
+        rrule=None,
+        rdate=[],
+        exdate=[],
+        reminders=copy.deepcopy(master.reminders or []),
+        attachments=copy.deepcopy(master.attachments or []),
+        related_to=copy.deepcopy(master.related_to or []),
+        source_kind=master.source_kind,
+        source_href=master.source_href,
+        etag=master.etag,
+        icalendar=copy.deepcopy(master.icalendar or {}),
+        raw_ics=None,
+        created_by_user_id=user_id,
+        updated_by_user_id=user_id,
+        metadata_=copy.deepcopy(master.metadata_ or {}),
+    )
+    _apply_event_update_values(
+        event,
+        user_id=user_id,
+        payload=update_payload,
+    )
+    validate_event_time(event)
+    session.add(event)
+    session.flush()
+    if should_push_event_to_caldav(source=source, event=event):
+        from govoplan_calendar.backend.outbox import enqueue_caldav_put
+
+        enqueue_caldav_put(session, source=source, event_model=event)
+    record_calendar_event_change(
+        session,
+        event=event,
+        operation="created",
+        user_id=user_id,
+    )
+    return event
+
+
+def delete_event_occurrence(
+    session: Session,
+    *,
+    tenant_id: str,
+    user_id: str | None,
+    series_event_id: str,
+    recurrence_id: str,
+) -> CalendarEvent:
+    return update_event_occurrence(
+        session,
+        tenant_id=tenant_id,
+        user_id=user_id,
+        series_event_id=series_event_id,
+        payload=CalendarEventOccurrenceUpdateRequest(
+            recurrence_id=recurrence_id,
+            status="CANCELLED",
+        ),
+    )
+
+
+def recurrence_occurrence(
+    master: CalendarEvent,
+    recurrence_id: str,
+) -> dict[str, Any]:
+    recurrence_start = recurrence_id_datetime(recurrence_id)
+    if recurrence_start is None:
+        raise CalendarError("Invalid recurrence_id")
+    recurrence_key = normalized_recurrence_id(recurrence_id)
+    candidates = expand_event_occurrences(
+        master,
+        recurrence_start - timedelta(seconds=1),
+        recurrence_start + timedelta(seconds=1),
+    )
+    occurrence = next(
+        (
+            item
+            for item in candidates
+            if normalized_recurrence_id(item.get("recurrence_id"))
+            == recurrence_key
+        ),
+        None,
+    )
+    if occurrence is None:
+        raise CalendarError(
+            "recurrence_id is not an occurrence in this event series"
+        )
+    return occurrence
+
+
+def find_event_override(
+    session: Session,
+    *,
+    tenant_id: str,
+    master: CalendarEvent,
+    recurrence_id: str,
+) -> CalendarEvent | None:
+    recurrence_key = normalized_recurrence_id(recurrence_id)
+    candidates = (
+        session.query(CalendarEvent)
+        .filter(
+            CalendarEvent.tenant_id == tenant_id,
+            CalendarEvent.calendar_id == master.calendar_id,
+            CalendarEvent.uid == master.uid,
+            CalendarEvent.recurrence_id.is_not(None),
+            CalendarEvent.deleted_at.is_(None),
+        )
+        .all()
+    )
+    return next(
+        (
+            event
+            for event in candidates
+            if normalized_recurrence_id(event.recurrence_id)
+            == recurrence_key
+        ),
+        None,
+    )
+
+
 def delete_event(session: Session, *, tenant_id: str, event_id: str, user_id: str | None = None) -> None:
     event_locator = (
         session.query(CalendarEvent.calendar_id)
@@ -4258,15 +4532,43 @@ def delete_event(session: Session, *, tenant_id: str, event_id: str, user_id: st
         for_update=True,
     )
     event = get_event(session, tenant_id=tenant_id, event_id=event_id)
-    previous = calendar_event_change_payload(event, prefix="previous_")
     assert_sync_mutation_allowed(source)
-    if should_push_event_to_caldav(source=source, event=event):
+    series_events = [event]
+    if event.recurrence_id is None and (event.rrule or event.rdate):
+        series_events = (
+            session.query(CalendarEvent)
+            .filter(
+                CalendarEvent.tenant_id == tenant_id,
+                CalendarEvent.calendar_id == event.calendar_id,
+                CalendarEvent.uid == event.uid,
+                CalendarEvent.deleted_at.is_(None),
+            )
+            .all()
+        )
+    previous_by_id = {
+        item.id: calendar_event_change_payload(
+            item,
+            prefix="previous_",
+        )
+        for item in series_events
+    }
+    push_delete = should_push_event_to_caldav(source=source, event=event)
+    deleted_at = utcnow()
+    for item in series_events:
+        item.deleted_at = deleted_at
+    session.flush()
+    if push_delete:
         from govoplan_calendar.backend.outbox import enqueue_caldav_delete
 
         enqueue_caldav_delete(session, source=source, event_model=event)
-    event.deleted_at = utcnow()
-    session.flush()
-    record_calendar_event_change(session, event=event, operation="deleted", user_id=user_id, previous=previous)
+    for item in series_events:
+        record_calendar_event_change(
+            session,
+            event=item,
+            operation="deleted",
+            user_id=user_id,
+            previous=previous_by_id[item.id],
+        )
 
 
 def active_sync_source_for_calendar(
@@ -4550,4 +4852,8 @@ def event_response(event: CalendarEvent) -> dict[str, Any]:
         "created_at": response_datetime(event.created_at),
         "updated_at": response_datetime(event.updated_at),
         "metadata": event.metadata_ or {},
+        "instance_id": event.id,
+        "series_event_id": None,
+        "is_occurrence": False,
+        "is_override": False,
     }

tests/test_provider_adapters.py

@@ -0,0 +1,113 @@
+from __future__ import annotations
+
+import unittest
+from datetime import datetime, timezone
+
+from govoplan_calendar.backend.ews import (
+    EwsAdapterError,
+    ews_find_item_body,
+    parse_ews_calendar_items,
+)
+from govoplan_calendar.backend.graph import graph_event_payload
+
+
+class ProviderAdapterTests(unittest.TestCase):
+    def test_graph_event_fixture_maps_provider_fields(self) -> None:
+        payload = graph_event_payload(
+            {
+                "id": "graph-event-1",
+                "iCalUId": "uid-1@example.test",
+                "@odata.etag": 'W/"etag-1"',
+                "type": "occurrence",
+                "subject": "Planning",
+                "body": {"content": "Agenda"},
+                "start": {
+                    "dateTime": "2026-07-08T09:00:00",
+                    "timeZone": "Europe/Berlin",
+                },
+                "end": {
+                    "dateTime": "2026-07-08T10:30:00",
+                    "timeZone": "Europe/Berlin",
+                },
+                "organizer": {
+                    "emailAddress": {
+                        "name": "Ada",
+                        "address": "ada@example.test",
+                    }
+                },
+                "attendees": [
+                    {
+                        "type": "required",
+                        "emailAddress": {
+                            "name": "Lin",
+                            "address": "lin@example.test",
+                        },
+                    }
+                ],
+                "isReminderOn": True,
+                "reminderMinutesBeforeStart": 15,
+            }
+        )
+
+        self.assertEqual(payload["uid"], "uid-1@example.test")
+        self.assertEqual(payload["recurrence_id"], "graph-event-1")
+        self.assertEqual(
+            payload["start_at"],
+            datetime(2026, 7, 8, 7, 0, tzinfo=timezone.utc),
+        )
+        self.assertEqual(payload["duration_seconds"], 5_400)
+        self.assertEqual(
+            payload["attendees"][0]["email"],
+            "lin@example.test",
+        )
+        self.assertEqual(
+            payload["reminders"][0]["trigger_minutes_before"],
+            15,
+        )
+
+    def test_ews_calendar_fixture_maps_item_and_escapes_mailbox(self) -> None:
+        response_xml = """<?xml version="1.0" encoding="utf-8"?>
+<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"
+  xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages"
+  xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types">
+  <s:Body><m:FindItemResponse><m:ResponseMessages>
+    <m:FindItemResponseMessage ResponseClass="Success"><m:RootFolder>
+      <t:Items><t:CalendarItem>
+        <t:ItemId Id="ews-event-1" ChangeKey="ews-etag-1" />
+        <t:Subject>EWS item</t:Subject>
+        <t:Start>2026-07-08T09:00:00Z</t:Start>
+        <t:End>2026-07-08T10:00:00Z</t:End>
+        <t:IsAllDayEvent>false</t:IsAllDayEvent>
+        <t:UID>ews-uid-1</t:UID>
+        <t:RequiredAttendees><t:Attendee><t:Mailbox>
+          <t:Name>Ada</t:Name>
+          <t:EmailAddress>ada@example.test</t:EmailAddress>
+        </t:Mailbox></t:Attendee></t:RequiredAttendees>
+      </t:CalendarItem></t:Items>
+    </m:RootFolder></m:FindItemResponseMessage>
+  </m:ResponseMessages></m:FindItemResponse></s:Body>
+</s:Envelope>"""
+
+        items = parse_ews_calendar_items(response_xml)
+
+        self.assertEqual(len(items), 1)
+        self.assertEqual(items[0]["href"], "ews-event-1")
+        self.assertEqual(items[0]["etag"], "ews-etag-1")
+        self.assertEqual(
+            items[0]["attendees"][0]["email"],
+            "ada@example.test",
+        )
+        request_body = ews_find_item_body(
+            start=datetime(2026, 7, 1, tzinfo=timezone.utc),
+            end=datetime(2026, 8, 1, tzinfo=timezone.utc),
+            mailbox='ops&"<@example.test',
+        )
+        self.assertIn("ops&amp;&quot;&lt;@example.test", request_body)
+
+    def test_ews_parser_rejects_invalid_xml(self) -> None:
+        with self.assertRaisesRegex(EwsAdapterError, "Invalid EWS"):
+            parse_ews_calendar_items("<not-closed>")
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_recurrence_preferences.py

@@ -0,0 +1,256 @@
+from __future__ import annotations
+
+import unittest
+from datetime import datetime, timezone
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from govoplan_access.backend.db import models as access_models  # noqa: F401
+from govoplan_calendar.backend.db.models import CalendarEvent
+from govoplan_calendar.backend.schemas import (
+    CalendarCollectionCreateRequest,
+    CalendarEventCreateRequest,
+    CalendarEventOccurrenceUpdateRequest,
+    CalendarViewPreferencesUpdateRequest,
+)
+from govoplan_calendar.backend.service import (
+    CalendarError,
+    create_calendar,
+    create_event,
+    delete_event,
+    delete_event_occurrence,
+    get_calendar_view_preferences,
+    list_event_occurrences,
+    list_freebusy,
+    update_calendar_view_preferences,
+    update_event_occurrence,
+)
+from govoplan_core.db.base import Base
+from govoplan_core.tenancy.scope import create_scope_tables
+from govoplan_tenancy.backend.db.models import Tenant
+
+
+class CalendarRecurrenceAndPreferenceTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self.engine = create_engine("sqlite:///:memory:")
+        create_scope_tables(self.engine)
+        Base.metadata.create_all(bind=self.engine)
+        self.Session = sessionmaker(bind=self.engine)
+        self.session = self.Session()
+        self.session.add(
+            Tenant(id="tenant-1", slug="tenant-1", name="Tenant")
+        )
+        self.calendar = create_calendar(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            payload=CalendarCollectionCreateRequest(name="Calendar"),
+        )
+        self.session.flush()
+
+    def tearDown(self) -> None:
+        self.session.close()
+        Base.metadata.drop_all(bind=self.engine)
+        self.engine.dispose()
+
+    def recurring_master(self) -> CalendarEvent:
+        return create_event(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            payload=CalendarEventCreateRequest(
+                calendar_id=self.calendar.id,
+                uid="series@example.test",
+                summary="Planning",
+                start_at=datetime(
+                    2026, 7, 8, 9, 0, tzinfo=timezone.utc
+                ),
+                end_at=datetime(
+                    2026, 7, 8, 10, 0, tzinfo=timezone.utc
+                ),
+                rrule={"FREQ": "WEEKLY", "COUNT": "3"},
+            ),
+        )
+
+    def test_occurrence_override_and_cancellation_reconcile_list_and_freebusy(
+        self,
+    ) -> None:
+        master = self.recurring_master()
+        override = update_event_occurrence(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            series_event_id=master.id,
+            payload=CalendarEventOccurrenceUpdateRequest(
+                recurrence_id="20260715T090000Z",
+                summary="Moved planning",
+                start_at=datetime(
+                    2026, 7, 15, 13, 0, tzinfo=timezone.utc
+                ),
+                end_at=datetime(
+                    2026, 7, 15, 14, 30, tzinfo=timezone.utc
+                ),
+            ),
+        )
+        cancelled = delete_event_occurrence(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            series_event_id=master.id,
+            recurrence_id="20260722T090000Z",
+        )
+        self.session.commit()
+
+        events = list_event_occurrences(
+            self.session,
+            tenant_id="tenant-1",
+            start_at=datetime(2026, 7, 1, tzinfo=timezone.utc),
+            end_at=datetime(2026, 7, 31, tzinfo=timezone.utc),
+        )
+        self.assertEqual(
+            [event["summary"] for event in events],
+            ["Planning", "Moved planning"],
+        )
+        self.assertEqual(events[1]["id"], override.id)
+        self.assertEqual(events[1]["series_event_id"], master.id)
+        self.assertTrue(events[1]["is_override"])
+        self.assertEqual(
+            events[1]["start_at"],
+            datetime(2026, 7, 15, 13, 0, tzinfo=timezone.utc),
+        )
+        self.assertEqual(cancelled.status, "CANCELLED")
+
+        busy = list_freebusy(
+            self.session,
+            tenant_id="tenant-1",
+            start_at=datetime(2026, 7, 1, tzinfo=timezone.utc),
+            end_at=datetime(2026, 7, 31, tzinfo=timezone.utc),
+        )
+        self.assertEqual(len(busy), 2)
+        self.assertEqual(
+            busy[1]["start_at"],
+            datetime(2026, 7, 15, 13, 0, tzinfo=timezone.utc),
+        )
+
+    def test_deleting_series_removes_its_overrides(self) -> None:
+        master = self.recurring_master()
+        update_event_occurrence(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            series_event_id=master.id,
+            payload=CalendarEventOccurrenceUpdateRequest(
+                recurrence_id="20260715T090000Z",
+                summary="Override",
+            ),
+        )
+
+        delete_event(
+            self.session,
+            tenant_id="tenant-1",
+            event_id=master.id,
+        )
+
+        active = (
+            self.session.query(CalendarEvent)
+            .filter(CalendarEvent.deleted_at.is_(None))
+            .count()
+        )
+        self.assertEqual(active, 0)
+
+    def test_all_day_occurrence_retains_date_recurrence_id(self) -> None:
+        master = create_event(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            payload=CalendarEventCreateRequest(
+                calendar_id=self.calendar.id,
+                uid="all-day-series@example.test",
+                summary="All-day planning",
+                start_at=datetime(
+                    2026, 7, 8, tzinfo=timezone.utc
+                ),
+                end_at=datetime(
+                    2026, 7, 9, tzinfo=timezone.utc
+                ),
+                all_day=True,
+                rrule={"FREQ": "WEEKLY", "COUNT": "2"},
+            ),
+        )
+
+        events = list_event_occurrences(
+            self.session,
+            tenant_id="tenant-1",
+            start_at=datetime(2026, 7, 1, tzinfo=timezone.utc),
+            end_at=datetime(2026, 7, 31, tzinfo=timezone.utc),
+        )
+        self.assertEqual(
+            [event["recurrence_id"] for event in events],
+            ["20260708", "20260715"],
+        )
+
+        override = update_event_occurrence(
+            self.session,
+            tenant_id="tenant-1",
+            user_id=None,
+            series_event_id=master.id,
+            payload=CalendarEventOccurrenceUpdateRequest(
+                recurrence_id=events[1]["recurrence_id"],
+                summary="Moved all-day planning",
+            ),
+        )
+        self.assertEqual(override.recurrence_id, "20260715")
+
+    def test_calendar_preferences_have_defaults_and_durable_user_overrides(
+        self,
+    ) -> None:
+        defaults = get_calendar_view_preferences(
+            self.session,
+            tenant_id="tenant-1",
+            user_id="user-1",
+        )
+        self.assertTrue(defaults["dim_weekends"])
+        self.assertEqual(defaults["overridden_fields"], [])
+
+        updated = update_calendar_view_preferences(
+            self.session,
+            tenant_id="tenant-1",
+            user_id="user-1",
+            payload=CalendarViewPreferencesUpdateRequest(
+                dim_weekends=False,
+                workday_start_hour=8,
+                workday_end_hour=18,
+            ),
+        )
+        self.session.commit()
+        reloaded = get_calendar_view_preferences(
+            self.session,
+            tenant_id="tenant-1",
+            user_id="user-1",
+        )
+
+        self.assertEqual(updated, reloaded)
+        self.assertFalse(reloaded["dim_weekends"])
+        self.assertEqual(reloaded["workday_start_hour"], 8)
+        self.assertEqual(reloaded["workday_end_hour"], 18)
+        self.assertEqual(
+            set(reloaded["overridden_fields"]),
+            {"dim_weekends", "workday_start_hour", "workday_end_hour"},
+        )
+
+    def test_calendar_preferences_reject_inverted_workday(self) -> None:
+        with self.assertRaisesRegex(CalendarError, "end hour"):
+            update_calendar_view_preferences(
+                self.session,
+                tenant_id="tenant-1",
+                user_id="user-1",
+                payload=CalendarViewPreferencesUpdateRequest(
+                    workday_start_hour=18,
+                    workday_end_hour=8,
+                ),
+            )
+
+
+if __name__ == "__main__":
+    unittest.main()

webui/src/api/calendar.ts

@@ -51,6 +51,10 @@ export type CalendarEvent = {
   created_at: string;
   updated_at: string;
   metadata?: Record<string, unknown> | null;
+  instance_id?: string | null;
+  series_event_id?: string | null;
+  is_occurrence?: boolean;
+  is_override?: boolean;
 };
 
 export type CalendarCollectionListResponse = { calendars: CalendarCollection[] };
@@ -243,6 +247,29 @@ export type CalendarEventCreatePayload = {
 };
 
 export type CalendarEventUpdatePayload = Partial<CalendarEventCreatePayload>;
+export type CalendarViewPreferences = {
+  dim_weekends: boolean;
+  dim_off_hours: boolean;
+  workday_start_hour: number;
+  workday_end_hour: number;
+  continuous_virtualization: boolean;
+  continuous_overscan_weeks: number;
+  alternate_continuous_months: boolean;
+  overridden_fields: string[];
+  defaults: Record<string, boolean | number>;
+};
+export type CalendarViewPreferencesUpdatePayload = Partial<
+  Pick<
+    CalendarViewPreferences,
+    | "dim_weekends"
+    | "dim_off_hours"
+    | "workday_start_hour"
+    | "workday_end_hour"
+    | "continuous_virtualization"
+    | "continuous_overscan_weeks"
+    | "alternate_continuous_months"
+  >
+>;
 
 export function listCalendars(settings: ApiSettings): Promise<CalendarCollectionListResponse> {
   return apiFetch<CalendarCollectionListResponse>(settings, "/api/v1/calendar/calendars");
@@ -320,12 +347,13 @@ export function syncCalDavSource(settings: ApiSettings, sourceId: string, payloa
 
 export function listCalendarEvents(
   settings: ApiSettings,
-  params: { calendar_id?: string; start_at?: string; end_at?: string } = {}
+  params: { calendar_id?: string; start_at?: string; end_at?: string; expand_recurring?: boolean } = {}
 ): Promise<CalendarEventListResponse> {
   const search = new URLSearchParams();
   if (params.calendar_id) search.set("calendar_id", params.calendar_id);
   if (params.start_at) search.set("start_at", params.start_at);
   if (params.end_at) search.set("end_at", params.end_at);
+  if (params.expand_recurring) search.set("expand_recurring", "true");
   const suffix = search.toString() ? `?${search.toString()}` : "";
   return apiFetch<CalendarEventListResponse>(settings, `/api/v1/calendar/events${suffix}`);
 }
@@ -344,6 +372,10 @@ export function listCalendarEventsDelta(
   return apiFetch<CalendarEventDeltaResponse>(settings, `/api/v1/calendar/events/delta${suffix}`);
 }
 
+export function getCalendarEvent(settings: ApiSettings, eventId: string): Promise<CalendarEvent> {
+  return apiFetch<CalendarEvent>(settings, `/api/v1/calendar/events/${eventId}`);
+}
+
 export function createCalendarEvent(settings: ApiSettings, payload: CalendarEventCreatePayload): Promise<CalendarEvent> {
   return apiFetch<CalendarEvent>(settings, "/api/v1/calendar/events", { method: "POST", body: JSON.stringify(payload) });
 }
@@ -355,3 +387,49 @@ export function updateCalendarEvent(settings: ApiSettings, eventId: string, payl
 export function deleteCalendarEvent(settings: ApiSettings, eventId: string): Promise<void> {
   return apiFetch<void>(settings, `/api/v1/calendar/events/${eventId}`, { method: "DELETE" });
 }
+
+export function updateCalendarEventOccurrence(
+  settings: ApiSettings,
+  seriesEventId: string,
+  recurrenceId: string,
+  payload: CalendarEventUpdatePayload
+): Promise<CalendarEvent> {
+  return apiFetch<CalendarEvent>(
+    settings,
+    `/api/v1/calendar/events/${seriesEventId}/occurrence`,
+    {
+      method: "PATCH",
+      body: JSON.stringify({ ...payload, recurrence_id: recurrenceId })
+    }
+  );
+}
+
+export function deleteCalendarEventOccurrence(
+  settings: ApiSettings,
+  seriesEventId: string,
+  recurrenceId: string
+): Promise<CalendarEvent> {
+  return apiFetch<CalendarEvent>(
+    settings,
+    `/api/v1/calendar/events/${seriesEventId}/occurrence`,
+    {
+      method: "DELETE",
+      body: JSON.stringify({ recurrence_id: recurrenceId })
+    }
+  );
+}
+
+export function getCalendarViewPreferences(settings: ApiSettings): Promise<CalendarViewPreferences> {
+  return apiFetch<CalendarViewPreferences>(settings, "/api/v1/calendar/preferences/view");
+}
+
+export function updateCalendarViewPreferences(
+  settings: ApiSettings,
+  payload: CalendarViewPreferencesUpdatePayload
+): Promise<CalendarViewPreferences> {
+  return apiFetch<CalendarViewPreferences>(
+    settings,
+    "/api/v1/calendar/preferences/view",
+    { method: "PATCH", body: JSON.stringify(payload) }
+  );
+}

webui/src/features/calendar/CalendarEventDialog.tsx

@@ -8,6 +8,7 @@ import {
   Button,
   DateField,
   Dialog,
+  SegmentedControl,
   TimeField,
   ToggleSwitch,
   useUnsavedDraftGuard,
@@ -30,6 +31,7 @@ import {
 } from "./calendarViewModel";
 
 type CalendarEventEndMode = "end" | "duration";
+type CalendarEventEditScope = "occurrence" | "series";
 type CalendarEventAdvancedPayload = Pick<
   CalendarEventCreatePayload,
   | "organizer"
@@ -49,25 +51,40 @@ export function CalendarEventDialog({
   calendars,
   defaultCalendarId,
   event,
+  editScope,
+  canChooseSeries,
+  seriesLoaded,
   focusDate,
   saving,
   canWrite,
   canDelete,
+  onEditScopeChange,
   onCancel,
   onSave,
   onDelete
-
-
-
-
-
-
-
-
-
-
-
-}: {calendars: CalendarCollection[];defaultCalendarId: string;event: CalendarEvent | null;focusDate: Date;saving: boolean;canWrite: boolean;canDelete: boolean;onCancel: () => void;onSave: (payload: CalendarEventCreatePayload, event: CalendarEvent | null) => Promise<boolean>;onDelete: (event: CalendarEvent) => Promise<void>;}) {
+}: {
+  calendars: CalendarCollection[];
+  defaultCalendarId: string;
+  event: CalendarEvent | null;
+  editScope: CalendarEventEditScope;
+  canChooseSeries: boolean;
+  seriesLoaded: boolean;
+  focusDate: Date;
+  saving: boolean;
+  canWrite: boolean;
+  canDelete: boolean;
+  onEditScopeChange: (scope: CalendarEventEditScope) => void;
+  onCancel: () => void;
+  onSave: (
+    payload: CalendarEventCreatePayload,
+    event: CalendarEvent | null,
+    editScope: CalendarEventEditScope
+  ) => Promise<boolean>;
+  onDelete: (
+    event: CalendarEvent,
+    editScope: CalendarEventEditScope
+  ) => Promise<void>;
+}) {
   const initialStart = event ? new Date(event.start_at) : focusDate;
   const initialEnd = event?.end_at ? new Date(event.end_at) : addHours(initialStart, 1);
   const initialAllDayEnd = event?.all_day && event.end_at ? addDays(startOfDay(initialEnd), -1) : initialEnd;
@@ -231,7 +248,7 @@ export function CalendarEventDialog({
       if (uid.trim()) payload.uid = uid.trim();
       if (recurrenceId.trim()) payload.recurrence_id = recurrenceId.trim();
     }
-    return onSave(payload, event);
+    return onSave(payload, event, editScope);
   }
 
   function submit(formEvent: FormEvent<HTMLFormElement>) {
@@ -245,7 +262,7 @@ export function CalendarEventDialog({
       setConfirmingDelete(true);
       return;
     }
-    void onDelete(event);
+    void onDelete(event, editScope);
   }
 
   return (
@@ -273,6 +290,24 @@ export function CalendarEventDialog({
       }>
 
       <form id={formId} className="calendar-dialog-form" onSubmit={submit}>
+        {canChooseSeries && (
+          <SegmentedControl
+            ariaLabel="Recurring event edit scope"
+            value={editScope}
+            onChange={onEditScopeChange}
+            width="fill"
+            size="equal"
+            disabled={saving}
+            options={[
+              { id: "occurrence", label: "This occurrence" },
+              {
+                id: "series",
+                label: seriesLoaded ? "Whole series" : "Loading series",
+                disabled: !seriesLoaded
+              }
+            ]}
+          />
+        )}
         {formError && <p className="calendar-form-error">{formError}</p>}
         <label>
           <span>i18n:govoplan-calendar.title.768e0c1c</span>
@@ -559,4 +594,3 @@ function eventUsesDuration(event: CalendarEvent): boolean {
 function isPlainObject(value: unknown): value is Record<string, unknown> {
   return typeof value === "object" && value !== null && !Array.isArray(value);
 }
-

webui/src/features/calendar/CalendarPage.tsx

@@ -26,14 +26,17 @@ import {
   createSyncSource,
   deleteCalendar,
   deleteCalendarEvent,
+  deleteCalendarEventOccurrence,
   discoverCalDavCalendars,
+  getCalendarEvent,
+  getCalendarViewPreferences,
   listCalendarEvents,
-  listCalendarEventsDelta,
   listCalendars,
   listSyncSources,
   syncSyncSource,
   updateCalendar,
   updateCalendarEvent,
+  updateCalendarEventOccurrence,
   updateSyncSource,
   type CalendarCalDavDiscoveryPayload,
   type CalendarCollection,
@@ -41,6 +44,7 @@ import {
   type CalendarEvent,
   type CalendarEventCreatePayload,
   type CalendarSyncSource,
+  type CalendarViewPreferences as CalendarViewPreferencesResponse,
   } from
 "../../api/calendar";
 import {
@@ -66,6 +70,7 @@ import {
   agendaDateLabel,
   agendaGroupsForDays,
   calendarEventColorStyle,
+  calendarEventInstanceId,
   continuousEventWindow,
   daysBetweenCount,
   daysForMode,
@@ -76,7 +81,6 @@ import {
   headingForMode,
   loadCalendarMode,
   loadCalendarViewPreferences,
-  mergeCalendarEventDelta,
   moveEventToDay,
   moveEventToTime,
   normalizeHexColor,
@@ -89,10 +93,19 @@ import {
   type CalendarDropTarget,
   type CalendarMode,
   type CalendarResizeEdge,
+  type CalendarViewPreferences,
   type ContinuousViewport,
 } from "./calendarViewModel";
 
-type EventDialogState = {kind: "create";} | {kind: "edit";event: CalendarEvent;};
+type EventEditScope = "occurrence" | "series";
+type EventDialogState =
+  | { kind: "create" }
+  | {
+      kind: "edit";
+      occurrence: CalendarEvent;
+      seriesEvent: CalendarEvent | null;
+      editScope: EventEditScope;
+    };
 const INITIAL_CONTINUOUS_WEEKS = { before: 4, after: 6 };
 
 const modeOptions: {id: CalendarMode;label: string;}[] = [
@@ -109,8 +122,6 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
   const [visibleCalendarIds, setVisibleCalendarIds] = useState<string[]>([]);
   const [eventCalendarId, setEventCalendarId] = useState("");
   const [events, setEvents] = useState<CalendarEvent[]>([]);
-  const eventsRef = useRef<CalendarEvent[]>([]);
-  const eventDeltaRef = useRef<{key: string;watermark: string | null;}>({ key: "", watermark: null });
   const eventRequestRef = useRef(0);
   const [mode, setMode] = useState<CalendarMode>(() => loadCalendarMode());
   const [focusDate, setFocusDate] = useState(() => startOfDay(new Date()));
@@ -132,7 +143,9 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
   const pendingContinuousScrollDayRef = useRef<Date | null>(null);
   const dragActionRef = useRef<CalendarDragAction | null>(null);
 
-  const viewPreferences = useMemo(() => loadCalendarViewPreferences(), []);
+  const [viewPreferences, setViewPreferences] = useState<CalendarViewPreferences>(
+    () => loadCalendarViewPreferences()
+  );
   const visibleCalendarIdSet = useMemo(() => new Set(visibleCalendarIds), [visibleCalendarIds]);
   const visibleEvents = useMemo(() => events.filter((event) => visibleCalendarIdSet.has(event.calendar_id)), [events, visibleCalendarIdSet]);
   const syncSourceByCalendarId = useMemo(() => new Map(syncSources.map((source) => [source.calendar_id, source])), [syncSources]);
@@ -152,6 +165,12 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
   const canManageCalendars = hasScope(auth, "calendar:calendar:write");
   const canDeleteCalendars = hasScope(auth, "calendar:calendar:admin");
   const heading = headingForMode(mode, focusDate, visibleRange);
+  const dialogEvent =
+    eventDialog?.kind === "edit"
+      ? eventDialog.editScope === "series"
+        ? eventDialog.seriesEvent
+        : eventDialog.occurrence
+      : null;
 
   useEffect(() => {
     void loadCalendars();
@@ -161,11 +180,35 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
     saveCalendarMode(mode);
   }, [mode]);
 
+  useEffect(() => {
+    let active = true;
+    const load = async () => {
+      try {
+        const preferences = await getCalendarViewPreferences(settings);
+        if (active) setViewPreferences(calendarViewPreferences(preferences));
+      } catch (err) {
+        if (active) setError(errorText(err));
+      }
+    };
+    const handlePreferenceChange = () => void load();
+    void load();
+    window.addEventListener(
+      "govoplan:calendar-preferences-changed",
+      handlePreferenceChange
+    );
+    return () => {
+      active = false;
+      window.removeEventListener(
+        "govoplan:calendar-preferences-changed",
+        handlePreferenceChange
+      );
+    };
+  }, [settings.apiBaseUrl, settings.apiKey, settings.accessToken]);
+
   useEffect(() => {
     if (calendars.length) {
       void loadEvents();
     } else {
-      eventsRef.current = [];
       setEvents([]);
     }
   }, [calendars.length, eventWindow.start.getTime(), eventWindow.end.getTime()]);
@@ -222,29 +265,17 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
     setError("");
     const start = eventWindow.start.toISOString();
     const end = eventWindow.end.toISOString();
-    const deltaKey = `${start}|${end}`;
     try {
-      let since = eventDeltaRef.current.key === deltaKey ? eventDeltaRef.current.watermark : null;
-      let nextEvents = eventDeltaRef.current.key === deltaKey ? eventsRef.current : [];
-      let response = null;
-      do {
-        response = await listCalendarEventsDelta(settings, {
-          start_at: start,
-          end_at: end,
-          since
-        });
-        nextEvents = mergeCalendarEventDelta(nextEvents, response);
-        since = response.watermark || null;
-      } while (response.has_more && response.watermark);
+      const response = await listCalendarEvents(settings, {
+        start_at: start,
+        end_at: end,
+        expand_recurring: true
+      });
       if (requestId !== eventRequestRef.current) return;
-      eventsRef.current = nextEvents;
-      eventDeltaRef.current = { key: deltaKey, watermark: since };
-      setEvents(nextEvents);
+      setEvents(response.events);
     } catch (err) {
       if (requestId !== eventRequestRef.current) return;
       setError(errorText(err));
-      eventsRef.current = [];
-      eventDeltaRef.current = { key: "", watermark: null };
       setEvents([]);
     } finally {
       if (requestId === eventRequestRef.current) setLoading(false);
@@ -352,7 +383,6 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
       if (calendars.length > 1 || payload.event_action === "move") {
         await loadEvents();
       } else {
-        eventsRef.current = [];
         setEvents([]);
       }
     } catch (err) {
@@ -469,15 +499,50 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
     window.requestAnimationFrame(() => updateContinuousViewport(node));
   }
 
+  function openEventEditor(event: CalendarEvent) {
+    const recurringOccurrence = Boolean(
+      event.is_occurrence &&
+      event.series_event_id &&
+      event.recurrence_id
+    );
+    setEventDialog({
+      kind: "edit",
+      occurrence: event,
+      seriesEvent: recurringOccurrence ? null : event,
+      editScope: recurringOccurrence ? "occurrence" : "series"
+    });
+    if (!recurringOccurrence || !event.series_event_id) return;
+    const instanceId = calendarEventInstanceId(event);
+    void getCalendarEvent(settings, event.series_event_id)
+      .then((seriesEvent) => {
+        setEventDialog((current) =>
+          current?.kind === "edit" &&
+          calendarEventInstanceId(current.occurrence) === instanceId
+            ? { ...current, seriesEvent }
+            : current
+        );
+      })
+      .catch((err) => setError(errorText(err)));
+  }
+
+  function setEventEditScope(scope: EventEditScope) {
+    setEventDialog((current) =>
+      current?.kind === "edit" &&
+      (scope === "occurrence" || current.seriesEvent)
+        ? { ...current, editScope: scope }
+        : current
+    );
+  }
+
   function beginEventDrag(dragEvent: ReactDragEvent<HTMLElement>, action: CalendarDragAction) {
     if (!canWrite) {
       dragEvent.preventDefault();
       return;
     }
     dragActionRef.current = action;
-    setDraggingEventId(action.event.id);
+    setDraggingEventId(calendarEventInstanceId(action.event));
     dragEvent.dataTransfer.effectAllowed = "move";
-    dragEvent.dataTransfer.setData("text/plain", action.event.id);
+    dragEvent.dataTransfer.setData("text/plain", calendarEventInstanceId(action.event));
   }
 
   function handleEventDragStart(dragEvent: ReactDragEvent<HTMLElement>, calendarEvent: CalendarEvent) {
@@ -553,11 +618,25 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
     setSaving(true);
     setError("");
     try {
-      await updateCalendarEvent(settings, calendarEvent.id, {
+      const payload = {
         start_at: next.startAt.toISOString(),
         end_at: next.endAt ? next.endAt.toISOString() : null,
         all_day: next.allDay
-      });
+      };
+      if (
+        calendarEvent.is_occurrence &&
+        calendarEvent.series_event_id &&
+        calendarEvent.recurrence_id
+      ) {
+        await updateCalendarEventOccurrence(
+          settings,
+          calendarEvent.series_event_id,
+          calendarEvent.recurrence_id,
+          payload
+        );
+      } else {
+        await updateCalendarEvent(settings, calendarEvent.id, payload);
+      }
       await loadEvents();
     } catch (err) {
       setError(errorText(err));
@@ -576,11 +655,29 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
     });
   }
 
-  async function handleSave(payload: CalendarEventCreatePayload, event: CalendarEvent | null): Promise<boolean> {
+  async function handleSave(
+    payload: CalendarEventCreatePayload,
+    event: CalendarEvent | null,
+    editScope: EventEditScope
+  ): Promise<boolean> {
     setSaving(true);
     setError("");
     try {
-      if (event) {
+      const currentDialog = eventDialog;
+      if (
+        event &&
+        currentDialog?.kind === "edit" &&
+        editScope === "occurrence" &&
+        currentDialog.occurrence.series_event_id &&
+        currentDialog.occurrence.recurrence_id
+      ) {
+        await updateCalendarEventOccurrence(
+          settings,
+          currentDialog.occurrence.series_event_id,
+          currentDialog.occurrence.recurrence_id,
+          payload
+        );
+      } else if (event) {
         await updateCalendarEvent(settings, event.id, payload);
       } else {
         await createCalendarEvent(settings, payload);
@@ -600,11 +697,28 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
     }
   }
 
-  async function handleDelete(event: CalendarEvent) {
+  async function handleDelete(
+    event: CalendarEvent,
+    editScope: EventEditScope
+  ) {
     setSaving(true);
     setError("");
     try {
-      await deleteCalendarEvent(settings, event.id);
+      const currentDialog = eventDialog;
+      if (
+        currentDialog?.kind === "edit" &&
+        editScope === "occurrence" &&
+        currentDialog.occurrence.series_event_id &&
+        currentDialog.occurrence.recurrence_id
+      ) {
+        await deleteCalendarEventOccurrence(
+          settings,
+          currentDialog.occurrence.series_event_id,
+          currentDialog.occurrence.recurrence_id
+        );
+      } else {
+        await deleteCalendarEvent(settings, event.id);
+      }
       setEventDialog(null);
       await loadEvents();
     } catch (err) {
@@ -690,15 +804,15 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
                 <h3>{agendaDateLabel(group.date)}</h3>
                 {group.events.map((event) =>
               <button
-                key={`${group.key}-${event.id}`}
+                key={`${group.key}-${calendarEventInstanceId(event)}`}
                 type="button"
-                className={["calendar-agenda-item", hoveredEventId === event.id ? "is-linked-hover" : ""].filter(Boolean).join(" ")}
+                className={["calendar-agenda-item", hoveredEventId === calendarEventInstanceId(event) ? "is-linked-hover" : ""].filter(Boolean).join(" ")}
                 style={calendarEventColorStyle(calendarColorById.get(event.calendar_id))}
-                onMouseEnter={() => setHoveredEventId(event.id)}
-                onMouseLeave={() => setHoveredEventId((current) => current === event.id ? "" : current)}
-                onFocus={() => setHoveredEventId(event.id)}
-                onBlur={() => setHoveredEventId((current) => current === event.id ? "" : current)}
-                onClick={() => setEventDialog({ kind: "edit", event })}>
+                onMouseEnter={() => setHoveredEventId(calendarEventInstanceId(event))}
+                onMouseLeave={() => setHoveredEventId((current) => current === calendarEventInstanceId(event) ? "" : current)}
+                onFocus={() => setHoveredEventId(calendarEventInstanceId(event))}
+                onBlur={() => setHoveredEventId((current) => current === calendarEventInstanceId(event) ? "" : current)}
+                onClick={() => openEventEditor(event)}>
 
                     <EventInlineLabel event={event} />
                   </button>
@@ -779,7 +893,7 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
                 hoveredEventId={hoveredEventId}
                 dropTarget={dropTarget}
                 viewport={continuousViewport}
-                onEventSelect={(event) => setEventDialog({ kind: "edit", event })}
+                onEventSelect={openEventEditor}
                 onEventHover={setHoveredEventId}
                 onEventDragStart={handleEventDragStart}
                 onEventDragEnd={handleEventDragEnd}
@@ -800,7 +914,7 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
               draggingEventId={draggingEventId}
               hoveredEventId={hoveredEventId}
               dropTarget={dropTarget}
-              onEventSelect={(event) => setEventDialog({ kind: "edit", event })}
+              onEventSelect={openEventEditor}
               onEventHover={setHoveredEventId}
               onEventDragStart={handleEventDragStart}
               onEventDragEnd={handleEventDragEnd}
@@ -819,7 +933,7 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
               draggingEventId={draggingEventId}
               hoveredEventId={hoveredEventId}
               dropTarget={dropTarget}
-              onEventSelect={(event) => setEventDialog({ kind: "edit", event })}
+              onEventSelect={openEventEditor}
               onEventHover={setHoveredEventId}
               onEventDragStart={handleEventDragStart}
               onEventResizeDragStart={handleEventResizeDragStart}
@@ -838,13 +952,28 @@ export default function CalendarPage({ settings, auth }: {settings: ApiSettings;
 
       {eventDialog && calendars.length > 0 &&
       <CalendarEventDialog
+        key={
+          eventDialog.kind === "edit"
+            ? `${calendarEventInstanceId(eventDialog.occurrence)}:${eventDialog.editScope}`
+            : "new-event"
+        }
         calendars={calendars}
         defaultCalendarId={targetCalendarId}
-        event={eventDialog.kind === "edit" ? eventDialog.event : null}
+        event={dialogEvent}
+        editScope={eventDialog.kind === "edit" ? eventDialog.editScope : "series"}
+        canChooseSeries={
+          eventDialog.kind === "edit" &&
+          Boolean(eventDialog.occurrence.is_occurrence)
+        }
+        seriesLoaded={
+          eventDialog.kind !== "edit" ||
+          eventDialog.seriesEvent !== null
+        }
         focusDate={focusDate}
         saving={saving}
         canWrite={canWrite}
         canDelete={canDelete}
+        onEditScopeChange={setEventEditScope}
         onCancel={() => setEventDialog(null)}
         onSave={handleSave}
         onDelete={handleDelete} />
@@ -887,3 +1016,17 @@ function compareCalendars(left: CalendarCollection, right: CalendarCollection):
   if (left.is_default !== right.is_default) return left.is_default ? -1 : 1;
   return left.name.localeCompare(right.name);
 }
+
+function calendarViewPreferences(
+  response: CalendarViewPreferencesResponse
+): CalendarViewPreferences {
+  return {
+    dimWeekends: response.dim_weekends,
+    dimOffHours: response.dim_off_hours,
+    workdayStartHour: response.workday_start_hour,
+    workdayEndHour: response.workday_end_hour,
+    continuousVirtualization: response.continuous_virtualization,
+    continuousOverscanWeeks: response.continuous_overscan_weeks,
+    alternateContinuousMonths: response.alternate_continuous_months
+  };
+}

webui/src/features/calendar/CalendarSettingsPanel.tsx

@@ -0,0 +1,241 @@
+import { useEffect, useMemo, useState } from "react";
+import { Save } from "lucide-react";
+import {
+  Button,
+  Card,
+  DismissibleAlert,
+  FormField,
+  ToggleSwitch,
+  type ApiSettings,
+  type AuthInfo
+} from "@govoplan/core-webui";
+import {
+  getCalendarViewPreferences,
+  updateCalendarViewPreferences,
+  type CalendarViewPreferences
+} from "../../api/calendar";
+
+type CalendarPreferenceDraft = Pick<
+  CalendarViewPreferences,
+  | "dim_weekends"
+  | "dim_off_hours"
+  | "workday_start_hour"
+  | "workday_end_hour"
+  | "continuous_virtualization"
+  | "continuous_overscan_weeks"
+  | "alternate_continuous_months"
+>;
+
+const FALLBACK_DRAFT: CalendarPreferenceDraft = {
+  dim_weekends: true,
+  dim_off_hours: true,
+  workday_start_hour: 6,
+  workday_end_hour: 20,
+  continuous_virtualization: true,
+  continuous_overscan_weeks: 6,
+  alternate_continuous_months: true
+};
+
+export default function CalendarSettingsPanel({
+  settings,
+  auth
+}: {
+  settings: ApiSettings;
+  auth: AuthInfo;
+}) {
+  const [loaded, setLoaded] = useState<CalendarPreferenceDraft | null>(null);
+  const [draft, setDraft] = useState<CalendarPreferenceDraft>(FALLBACK_DRAFT);
+  const [loading, setLoading] = useState(true);
+  const [saving, setSaving] = useState(false);
+  const [message, setMessage] = useState("");
+  const [tone, setTone] = useState<"success" | "warning">("success");
+  const dirty = useMemo(
+    () => loaded !== null && JSON.stringify(loaded) !== JSON.stringify(draft),
+    [draft, loaded]
+  );
+
+  useEffect(() => {
+    void loadPreferences();
+  }, [auth.user.id, settings.accessToken, settings.apiBaseUrl, settings.apiKey]);
+
+  async function loadPreferences() {
+    setLoading(true);
+    setMessage("");
+    try {
+      const response = await getCalendarViewPreferences(settings);
+      const next = preferenceDraft(response);
+      setLoaded(next);
+      setDraft(next);
+    } catch (error) {
+      setTone("warning");
+      setMessage(errorText(error));
+    } finally {
+      setLoading(false);
+    }
+  }
+
+  async function savePreferences() {
+    if (draft.workday_end_hour <= draft.workday_start_hour) {
+      setTone("warning");
+      setMessage("Workday end must be after workday start.");
+      return;
+    }
+    setSaving(true);
+    setMessage("");
+    try {
+      const response = await updateCalendarViewPreferences(settings, draft);
+      const next = preferenceDraft(response);
+      setLoaded(next);
+      setDraft(next);
+      setTone("success");
+      setMessage("Calendar preferences saved.");
+      window.dispatchEvent(
+        new CustomEvent("govoplan:calendar-preferences-changed")
+      );
+    } catch (error) {
+      setTone("warning");
+      setMessage(errorText(error));
+    } finally {
+      setSaving(false);
+    }
+  }
+
+  const disabled = loading || saving;
+  return (
+    <div className="dashboard-grid settings-dashboard-grid calendar-settings-panel">
+      <Card title="Calendar display">
+        <div className="form-grid">
+          <ToggleSwitch
+            label="Dim weekends"
+            help="Use a quieter background for Saturday and Sunday in week views."
+            checked={draft.dim_weekends}
+            disabled={disabled}
+            onChange={(dim_weekends) =>
+              setDraft((current) => ({ ...current, dim_weekends }))
+            }
+          />
+          <ToggleSwitch
+            label="Dim hours outside the workday"
+            checked={draft.dim_off_hours}
+            disabled={disabled}
+            onChange={(dim_off_hours) =>
+              setDraft((current) => ({ ...current, dim_off_hours }))
+            }
+          />
+          <div className="calendar-dialog-grid-two">
+            <FormField label="Workday starts">
+              <input
+                type="number"
+                min={0}
+                max={23}
+                value={draft.workday_start_hour}
+                disabled={disabled}
+                onChange={(event) =>
+                  setDraft((current) => ({
+                    ...current,
+                    workday_start_hour: Number(event.target.value)
+                  }))
+                }
+              />
+            </FormField>
+            <FormField label="Workday ends">
+              <input
+                type="number"
+                min={1}
+                max={24}
+                value={draft.workday_end_hour}
+                disabled={disabled}
+                onChange={(event) =>
+                  setDraft((current) => ({
+                    ...current,
+                    workday_end_hour: Number(event.target.value)
+                  }))
+                }
+              />
+            </FormField>
+          </div>
+        </div>
+      </Card>
+      <Card title="Continuous view">
+        <div className="form-grid">
+          <ToggleSwitch
+            label="Virtualize distant weeks"
+            help="Keep the continuous calendar responsive by rendering only nearby weeks."
+            checked={draft.continuous_virtualization}
+            disabled={disabled}
+            onChange={(continuous_virtualization) =>
+              setDraft((current) => ({
+                ...current,
+                continuous_virtualization
+              }))
+            }
+          />
+          <FormField
+            label="Overscan weeks"
+            help="Additional weeks rendered above and below the viewport."
+          >
+            <input
+              type="number"
+              min={2}
+              max={20}
+              value={draft.continuous_overscan_weeks}
+              disabled={disabled || !draft.continuous_virtualization}
+              onChange={(event) =>
+                setDraft((current) => ({
+                  ...current,
+                  continuous_overscan_weeks: Number(event.target.value)
+                }))
+              }
+            />
+          </FormField>
+          <ToggleSwitch
+            label="Alternate month backgrounds"
+            checked={draft.alternate_continuous_months}
+            disabled={disabled}
+            onChange={(alternate_continuous_months) =>
+              setDraft((current) => ({
+                ...current,
+                alternate_continuous_months
+              }))
+            }
+          />
+          <div className="button-row compact-actions">
+            <Button
+              type="button"
+              variant="primary"
+              disabled={disabled || !dirty}
+              onClick={() => void savePreferences()}
+            >
+              <Save size={16} /> {saving ? "Saving" : "Save preferences"}
+            </Button>
+          </div>
+          {message && (
+            <DismissibleAlert tone={tone} resetKey={message} floating>
+              {message}
+            </DismissibleAlert>
+          )}
+        </div>
+      </Card>
+    </div>
+  );
+}
+
+function preferenceDraft(
+  preferences: CalendarViewPreferences
+): CalendarPreferenceDraft {
+  return {
+    dim_weekends: preferences.dim_weekends,
+    dim_off_hours: preferences.dim_off_hours,
+    workday_start_hour: preferences.workday_start_hour,
+    workday_end_hour: preferences.workday_end_hour,
+    continuous_virtualization: preferences.continuous_virtualization,
+    continuous_overscan_weeks: preferences.continuous_overscan_weeks,
+    alternate_continuous_months: preferences.alternate_continuous_months
+  };
+}
+
+function errorText(error: unknown): string {
+  return error instanceof Error
+    ? error.message
+    : "Calendar preferences could not be loaded.";
+}

webui/src/features/calendar/CalendarViews.tsx

@@ -12,6 +12,7 @@ import {
   HOUR_ROW_HEIGHT,
   INITIAL_SCROLL_HOUR,
   calendarEventColorStyle,
+  calendarEventInstanceId,
   chunk,
   continuousVirtualWindow,
   dayKey,
@@ -185,12 +186,12 @@ export function CalendarWeekRows({
                 <div className="calendar-event-stack">
                   {dayEvents.slice(0, eventLimit).map((event) => (
                     <CalendarEventChip
-                      key={event.id}
+                      key={calendarEventInstanceId(event)}
                       event={event}
                       color={calendarColorById.get(event.calendar_id)}
                       canDrag={canWrite}
-                      dragging={draggingEventId === event.id}
-                      linkedHover={hoveredEventId === event.id}
+                      dragging={draggingEventId === calendarEventInstanceId(event)}
+                      linkedHover={hoveredEventId === calendarEventInstanceId(event)}
                       onSelect={onEventSelect}
                       onHover={onEventHover}
                       onDragStart={onEventDragStart}
@@ -350,13 +351,13 @@ export function CalendarTimeGrid({
             >
               {day.events.map((event) => (
                 <CalendarEventChip
-                  key={event.id}
+                  key={calendarEventInstanceId(event)}
                   event={event}
                   color={calendarColorById.get(event.calendar_id)}
                   compact
                   canDrag={canWrite}
-                  dragging={draggingEventId === event.id}
-                  linkedHover={hoveredEventId === event.id}
+                  dragging={draggingEventId === calendarEventInstanceId(event)}
+                  linkedHover={hoveredEventId === calendarEventInstanceId(event)}
                   onSelect={onEventSelect}
                   onHover={onEventHover}
                   onDragStart={onEventDragStart}
@@ -503,11 +504,11 @@ function TimedDayColumn({
       )}
       {layout.items.map((item) => (
         <div
-          key={item.event.id}
+          key={calendarEventInstanceId(item.event)}
           className={[
             "calendar-timed-event",
-            draggingEventId === item.event.id ? "is-dragging" : "",
-            hoveredEventId === item.event.id
+            draggingEventId === calendarEventInstanceId(item.event) ? "is-dragging" : "",
+            hoveredEventId === calendarEventInstanceId(item.event)
               ? "is-linked-hover"
               : "",
           ]
@@ -518,7 +519,7 @@ function TimedDayColumn({
             calendarColorById.get(item.event.calendar_id),
           )}
           draggable={canWrite}
-          onMouseEnter={() => onEventHover(item.event.id)}
+          onMouseEnter={() => onEventHover(calendarEventInstanceId(item.event))}
           onMouseLeave={() => onEventHover("")}
           onDragStart={
             canWrite
@@ -546,7 +547,7 @@ function TimedDayColumn({
             type="button"
             className="calendar-timed-event-content"
             onClick={() => onEventSelect(item.event)}
-            onFocus={() => onEventHover(item.event.id)}
+            onFocus={() => onEventHover(calendarEventInstanceId(item.event))}
             onBlur={() => onEventHover("")}
             title={i18nMessage(
               "i18n:govoplan-calendar.edit_value.fad75899",
@@ -629,9 +630,9 @@ function CalendarEventChip({
       style={calendarEventColorStyle(color)}
       draggable={canDrag}
       onClick={() => onSelect(event)}
-      onMouseEnter={onHover ? () => onHover(event.id) : undefined}
+      onMouseEnter={onHover ? () => onHover(calendarEventInstanceId(event)) : undefined}
       onMouseLeave={onHover ? () => onHover("") : undefined}
-      onFocus={onHover ? () => onHover(event.id) : undefined}
+      onFocus={onHover ? () => onHover(calendarEventInstanceId(event)) : undefined}
       onBlur={onHover ? () => onHover("") : undefined}
       onDragStart={
         canDrag && onDragStart

webui/src/features/calendar/UpcomingEventsWidget.tsx

@@ -32,10 +32,11 @@ export default function UpcomingEventsWidget({
     end.setDate(end.getDate() + daysAhead);
     const response = await listCalendarEvents(settings, {
       start_at: start.toISOString(),
-      end_at: end.toISOString()
+      end_at: end.toISOString(),
+      expand_recurring: true
     });
     return [...response.events]
-      .filter((event) => event.status !== "cancelled")
+      .filter((event) => event.status.toUpperCase() !== "CANCELLED")
       .sort(
         (left, right) =>
           new Date(left.start_at).getTime() - new Date(right.start_at).getTime()
@@ -57,7 +58,7 @@ export default function UpcomingEventsWidget({
       <DashboardWidgetList
         emptyText={`No events in the next ${daysAhead} days.`}
         items={(events ?? []).map((event) => ({
-          id: event.id,
+          id: event.instance_id || event.id,
           title: event.summary,
           detail:
             showLocation && event.location ? (

webui/src/features/calendar/calendarViewModel.ts

@@ -74,7 +74,7 @@ const MAX_TIMED_EVENT_COLUMNS = 3;
 const CALENDAR_MODE_STORAGE_KEY = "govoplan.calendar.mode";
 const CALENDAR_VIEW_PREFERENCES_STORAGE_KEY =
   "govoplan.calendar.viewPreferences";
-const DEFAULT_CALENDAR_VIEW_PREFERENCES: CalendarViewPreferences = {
+export const DEFAULT_CALENDAR_VIEW_PREFERENCES: CalendarViewPreferences = {
   dimWeekends: true,
   dimOffHours: true,
   workdayStartHour: 6,
@@ -84,6 +84,10 @@ const DEFAULT_CALENDAR_VIEW_PREFERENCES: CalendarViewPreferences = {
   alternateContinuousMonths: true,
 };
 
+export function calendarEventInstanceId(event: CalendarEvent): string {
+  return event.instance_id || event.id;
+}
+
 export function rangeForMode(
   mode: CalendarMode,
   focusDate: Date,
@@ -677,7 +681,7 @@ export function layoutTimedEventsForDay(
     }
     if (hidden.length > 0) {
       overflows.push({
-        key: `${dayKey(day)}-${hidden[0].event.id}-overflow`,
+        key: `${dayKey(day)}-${calendarEventInstanceId(hidden[0].event)}-overflow`,
         top: Math.min(...hidden.map((item) => item.top)),
         column: overflowColumn,
         columns: MAX_TIMED_EVENT_COLUMNS,

webui/src/module.ts

@@ -2,7 +2,8 @@ import { createElement, lazy } from "react";
 import type {
   CalendarPickerUiCapability,
   DashboardWidgetsUiCapability,
-  PlatformWebModule
+  PlatformWebModule,
+  SettingsSectionsUiCapability
 } from "@govoplan/core-webui";
 import "./styles/calendar.css";
 import { generatedTranslations } from "./i18n/generatedTranslations";
@@ -10,6 +11,9 @@ import CalendarPicker from "./features/calendar/CalendarPicker";
 import UpcomingEventsWidget from "./features/calendar/UpcomingEventsWidget";
 
 const CalendarPage = lazy(() => import("./features/calendar/CalendarPage"));
+const CalendarSettingsPanel = lazy(
+  () => import("./features/calendar/CalendarSettingsPanel")
+);
 
 const eventRead = ["calendar:event:read"];
 const translations = {
@@ -18,6 +22,20 @@ const translations = {
 };
 
 const calendarPicker: CalendarPickerUiCapability = { CalendarPicker };
+const calendarSettingsSections: SettingsSectionsUiCapability = {
+  sections: [
+    {
+      id: "calendar",
+      surfaceId: "calendar.settings.preferences",
+      label: "Calendar",
+      group: "ui",
+      order: 45,
+      anyOf: eventRead,
+      render: ({ settings, auth }) =>
+        createElement(CalendarSettingsPanel, { settings, auth })
+    }
+  ]
+};
 const calendarDashboardWidgets: DashboardWidgetsUiCapability = {
   widgets: [
     {
@@ -87,6 +105,13 @@ export const calendarModule: PlatformWebModule = {
       kind: "section",
       label: "Upcoming events widget",
       order: 40
+    },
+    {
+      id: "calendar.settings.preferences",
+      moduleId: "calendar",
+      kind: "section",
+      label: "Calendar preferences",
+      order: 45
     }
   ],
   navItems: [{ to: "/calendar", label: "i18n:govoplan-calendar.calendar.adab5090", iconName: "calendar", anyOf: eventRead, order: 55 }],
@@ -94,7 +119,8 @@ export const calendarModule: PlatformWebModule = {
   { path: "/calendar", anyOf: eventRead, order: 55, render: ({ settings, auth }) => createElement(CalendarPage, { settings, auth }) }],
   uiCapabilities: {
     "calendar.picker": calendarPicker,
-    "dashboard.widgets": calendarDashboardWidgets
+    "dashboard.widgets": calendarDashboardWidgets,
+    "settings.sections": calendarSettingsSections
   }
 
 };

webui/tsconfig.calendar-page-tests.json

@@ -23,13 +23,19 @@
       ],
       "react/jsx-runtime": [
         "../../govoplan-core/webui/node_modules/@types/react/jsx-runtime.d.ts"
+      ],
+      "react-router": [
+        "../../govoplan-core/webui/node_modules/react-router/dist/development/index.d.ts"
       ]
     }
   },
   "include": [
     "../../govoplan-core/webui/src/vite-env.d.ts",
+    "src/module.ts",
     "src/api/calendar.ts",
     "src/features/calendar/CalendarPage.tsx",
+    "src/features/calendar/CalendarSettingsPanel.tsx",
+    "src/features/calendar/UpcomingEventsWidget.tsx",
     "src/features/calendar/CalendarViews.tsx",
     "src/features/calendar/CalendarCollectionDialogs.tsx",
     "src/features/calendar/CalendarEventDialog.tsx",