diff --git a/drivers/place/visitor_mailer.cr b/drivers/place/visitor_mailer.cr
index 8ee9dd5017..6dbb3f8563 100644
--- a/drivers/place/visitor_mailer.cr
+++ b/drivers/place/visitor_mailer.cr
@@ -34,8 +34,10 @@ class Place::VisitorMailer < PlaceOS::Driver
     notify_induction_accepted_template: "induction_accepted",
     notify_induction_declined_template: "induction_declined",
     notify_original_host_template:      "notify_original_host",
-    # sent to all visitors when booking details change (date, time, location, etc.)
+    # sent to all visitors when details change (date, time, location, etc.):
+    # bookings (desk/resource) use booking_changed, calendar events (rooms) use event_changed
     booking_changed_template:           "booking_changed",
+    event_changed_template:             "event_changed",
     group_event_template:               "group_event",
     disable_qr_code:                    false,
     send_network_credentials:           false,
@@ -140,6 +142,7 @@ class Place::VisitorMailer < PlaceOS::Driver
   @notify_induction_declined_template : String = "induction_declined"
   @notify_original_host_template : String = "notify_original_host"
   @booking_changed_template : String = "booking_changed"
+  @event_changed_template : String = "event_changed"
   @group_event_template : String = "group_event"
   @determine_host_name_using : String = "calendar-driver"
   @send_network_credentials = false
@@ -171,6 +174,7 @@ class Place::VisitorMailer < PlaceOS::Driver
     @notify_induction_declined_template = setting?(String, :notify_induction_declined_template) || "induction_declined"
     @notify_original_host_template = setting?(String, :notify_original_host_template) || "notify_original_host"
     @booking_changed_template = setting?(String, :booking_changed_template) || "booking_changed"
+    @event_changed_template = setting?(String, :event_changed_template) || "event_changed"
     @group_event_template = setting?(String, :group_event_template) || "group_event"
     @disable_qr_code = setting?(Bool, :disable_qr_code) || false
     @determine_host_name_using = setting?(String, :determine_host_name_using) || "calendar-driver"
@@ -464,9 +468,11 @@ class Place::VisitorMailer < PlaceOS::Driver
     previous_host_email : String,
     new_host_email : String,
     event_title : String?,
-    event_start : Int64,
+    event_start : Int64?,
   )
-    local_start_time = Time.unix(event_start).in(@time_zone)
+    # A host can be reassigned via a metadata-only update that carries no event
+    # timing, so render the date/time only when a start time is available.
+    local_start_time = event_start.try { |timestamp| Time.unix(timestamp).in(@time_zone) }
 
     mailer.send_template(
       previous_host_email,
@@ -478,8 +484,8 @@ class Place::VisitorMailer < PlaceOS::Driver
         new_host_name:       get_host_name(new_host_email),
         building_name:       building_zone.display_name.presence || building_zone.name,
         event_title:         event_title,
-        event_date:          local_start_time.to_s(@date_format),
-        event_time:          local_start_time.to_s(@time_format),
+        event_date:          local_start_time.try(&.to_s(@date_format)),
+        event_time:          local_start_time.try(&.to_s(@time_format)),
       }
     )
   end
@@ -513,6 +519,16 @@ class Place::VisitorMailer < PlaceOS::Driver
       {name: "kiosk_url", description: "URL for the visitor kiosk"},
     ]
 
+    # Shared by the booking-changed and event-changed notifications, which carry
+    # the same data but render through separate templates.
+    changed_fields = common_fields + [
+      {name: "room_name", description: "Name of the room or area being visited"},
+      {name: "previous_event_date", description: "The original date before it was changed"},
+      {name: "previous_event_time", description: "The original time before it was changed"},
+      {name: "previous_room_name", description: "The original room or area name before it was moved"},
+      {name: "previous_building_name", description: "The original building name before it was moved"},
+    ]
+
     [
       TemplateFields.new(
         trigger: {"visitor_invited", @reminder_template},
@@ -574,14 +590,14 @@ class Place::VisitorMailer < PlaceOS::Driver
       TemplateFields.new(
         trigger: {"visitor_invited", @booking_changed_template},
         name: "Booking details changed notification",
-        description: "Notification sent to all visitors on a booking when details change (date, time, location, etc.)",
-        fields: common_fields + [
-          {name: "room_name", description: "Name of the room or area being visited"},
-          {name: "previous_event_date", description: "The original date of the booking before it was changed"},
-          {name: "previous_event_time", description: "The original time of the booking before it was changed"},
-          {name: "previous_room_name", description: "The original room or area name before the booking was moved"},
-          {name: "previous_building_name", description: "The original building name before the booking was moved"},
-        ]
+        description: "Notification sent to all visitors on a booking (desk/resource) when details change (date, time, etc.)",
+        fields: changed_fields
+      ),
+      TemplateFields.new(
+        trigger: {"visitor_invited", @event_changed_template},
+        name: "Event details changed notification",
+        description: "Notification sent to all visitors on a calendar event (room) when details change (date, time, location, etc.)",
+        fields: changed_fields
       ),
     ]
   end
@@ -595,6 +611,18 @@ class Place::VisitorMailer < PlaceOS::Driver
     # "checked_in") are ignored by default and don't trigger spurious emails.
     return unless details.action.in?("changed", "metadata_changed")
 
+    # Bookings auto-created from a calendar event (extension_data.parent_id set)
+    # are already covered by the event_changed flow (staff/event/changed), which
+    # resolves the room from the system. Skip them here so a single edit doesn't
+    # produce two notifications. Opt out with skip_event_linked_booking_email.
+    if @skip_event_linked_booking_email
+      parent_id = details.extension_data.try(&.["parent_id"]?).try(&.as_s?)
+      if parent_id && !parent_id.empty?
+        logger.debug { "skipping booking_changed email for booking #{details.id} as it is linked to event #{parent_id}" }
+        return
+      end
+    end
+
     # ensure the event is for this building
     if zones = details.zones
       check = [building_zone.id] + @parent_zone_ids
@@ -654,6 +682,7 @@ class Place::VisitorMailer < PlaceOS::Driver
 
     send_booking_changed_emails(
       guests,
+      @booking_changed_template,
       details.user_email,
       details.booking_start,
       details.title,
@@ -678,13 +707,6 @@ class Place::VisitorMailer < PlaceOS::Driver
     # only respond to updates, not creates or cancellations
     return unless details.action == "update"
 
-    # These fields may be missing from some payloads (e.g. cancelled events,
-    # metadata-only updates) so the model marks them nilable.
-    host = details.host
-    event_start = details.event_start
-    event_end = details.event_end
-    return unless host && event_start && event_end
-
     # ensure the event is for this building
     if zones = details.zones
       check = [building_zone.id] + @parent_zone_ids
@@ -695,20 +717,34 @@ class Place::VisitorMailer < PlaceOS::Driver
       end
     end
 
+    # The (new) host is required for every notification below.
+    host = details.host
+    return unless host
+
+    # event_start may be omitted from metadata-only update signals (e.g. an
+    # update_metadata that only touched ext_data). Look it up so the host
+    # notification and change emails always render a real date.
+    event_start = details.event_start || lookup_event_start(details.event_id, details.system_id)
+
     # --- Host change notification
-    if prev_host = details.previous_host_email
-      if prev_host.downcase != host.downcase
-        send_original_host_email(
-          @notify_original_host_template,
-          prev_host,
-          host,
-          details.title,
-          event_start,
-        )
-      end
+    # A host can be reassigned without any change to the event timing; the host
+    # email still renders (date/time blank only if the lookup also came up empty).
+    if (prev_host = details.previous_host_email) && prev_host.downcase != host.downcase
+      send_original_host_email(
+        @notify_original_host_template,
+        prev_host,
+        host,
+        details.title,
+        event_start,
+      )
     end
 
     # --- Date / time / location change notification
+    # These genuinely require the event timing to render the new schedule, so
+    # bail out when it is missing.
+    event_end = details.event_end
+    return unless event_start && event_end
+
     fields_changed = false
 
     # Date or time changed
@@ -726,23 +762,27 @@ class Place::VisitorMailer < PlaceOS::Driver
 
     return unless fields_changed
 
-    previous_building_name = building_zone.display_name.presence || building_zone.name
-    previous_room_name = @booking_space_name
-
-    if (prev_sys_id = details.previous_system_id) && prev_sys_id != details.system_id
-      # Use "unknown" as the fallback so a failed lookup surfaces in the email
-      # rather than silently showing the current room name.
-      previous_room_name = "unknown"
-      previous_room_name, previous_building_name = resolve_system_location_names(prev_sys_id, previous_room_name, previous_building_name)
-    end
-
     current_building_name = building_zone.display_name.presence || building_zone.name
     current_room_name = @booking_space_name
     current_room_name, current_building_name = resolve_system_location_names(details.system_id, current_room_name, current_building_name)
 
+    # Default the previous location to the current one; only override it when the
+    # room actually changed. This keeps date/time-only edits showing the same
+    # (unchanged) room in both the "previous" and "new" sections instead of the
+    # static @booking_space_name fallback.
+    previous_building_name = current_building_name
+    previous_room_name = current_room_name
+
+    if (prev_sys_id = details.previous_system_id) && prev_sys_id != details.system_id
+      # Use "unknown" as the room fallback so a failed lookup surfaces in the
+      # email rather than silently showing the current room name.
+      previous_room_name, previous_building_name = resolve_system_location_names(prev_sys_id, "unknown", current_building_name)
+    end
+
     guests = staff_api.event_guests(details.event_id, details.system_id, details.event_ical_uid).get.as_a
     send_booking_changed_emails(
       guests,
+      @event_changed_template,
       host,
       event_start,
       details.title,
@@ -767,6 +807,7 @@ class Place::VisitorMailer < PlaceOS::Driver
   # the booking flow, which has no system_id to resolve from).
   private def send_booking_changed_emails(
     guests : Array(JSON::Any),
+    template : String,
     host_email : String,
     event_start : Int64,
     event_title : String?,
@@ -796,7 +837,7 @@ class Place::VisitorMailer < PlaceOS::Driver
 
       mailer.send_template(
         visitor_email,
-        {"visitor_invited", @booking_changed_template},
+        {"visitor_invited", template},
         {
           visitor_email:          visitor_email,
           visitor_name:           visitor_name,
@@ -1037,6 +1078,16 @@ class Place::VisitorMailer < PlaceOS::Driver
     get_room_details(system_id, retries + 1)
   end
 
+  # Back-fills an event's start time from the staff API when a
+  # staff/event/changed signal omits it (e.g. metadata-only updates). Returns
+  # nil on failure so callers can still send without a date rather than crash.
+  protected def lookup_event_start(event_id : String, system_id : String) : Int64?
+    staff_api.get_event(event_id, system_id).get["event_start"]?.try(&.as_i64?)
+  rescue error
+    logger.warn(exception: error) { "failed to look up start time for event #{event_id}" }
+    nil
+  end
+
   protected def get_host_name(host_email)
     @determine_host_name_using == "staff-api-driver" ? get_host_name_from_staff_api_driver(host_email) : get_host_name_from_calendar_driver(host_email)
   end
diff --git a/drivers/place/visitor_mailer_spec.cr b/drivers/place/visitor_mailer_spec.cr
index 11517aa2bd..7e3ea8e7a9 100644
--- a/drivers/place/visitor_mailer_spec.cr
+++ b/drivers/place/visitor_mailer_spec.cr
@@ -227,6 +227,19 @@ class StaffAPIMock < DriverSpecs::MockDriver
       }
     end
   end
+
+  # Back-fills event_start when a staff/event/changed signal omits it.
+  # event_start/event_end are epoch integers, matching the real
+  # PlaceCalendar::Event serialisation (Time::EpochConverter).
+  def get_event(event_id : String, system_id : String? = nil, calendar : String? = nil)
+    case event_id
+    when "evt-no-start"
+      # Simulates an event the API can't supply a start time for.
+      {id: event_id, title: "No Start Event"}
+    else
+      {id: event_id, title: "Looked Up Event", event_start: 1_760_000_000_i64, event_end: 1_760_003_600_i64}
+    end
+  end
 end
 
 DriverSpecs.mock_driver "Place::VisitorMailer" do
@@ -678,7 +691,7 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   # Visitor should receive a booking_changed email
   system(:Mailer)[:send_count].should eq 10
   system(:Mailer)[:last_to].should eq "visitor@external.com"
-  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "event_changed"]
 
   args11 = system(:Mailer)[:last_args]
   args11["host_name"].should eq "Host User"
@@ -688,6 +701,14 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   # previous dates should be present
   args11["previous_event_date"].should_not be_nil
   args11["previous_event_time"].should_not be_nil
+  # The location did NOT change, so the "previous" room/building must mirror
+  # the (unchanged) current room — resolved from system_id — rather than the
+  # static @booking_space_name fallback.  Otherwise the email shows a bogus
+  # "moved from" room for a date/time-only edit.
+  args11["room_name"].should eq "Conference Room 1"
+  args11["building_name"].should eq "Main Building"
+  args11["previous_room_name"].should eq "Conference Room 1"
+  args11["previous_building_name"].should eq "Main Building"
 
   # ------------------------------------------------------------------
   # Test 12: event_changed with location change (system_id differs) —
@@ -713,7 +734,7 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
 
   system(:Mailer)[:send_count].should eq 11
   system(:Mailer)[:last_to].should eq "visitor@external.com"
-  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "event_changed"]
 
   args12 = system(:Mailer)[:last_args]
   args12["event_title"].should eq "Sprint Planning"
@@ -749,6 +770,72 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   args13["new_host_email"].should eq "new-organiser@example.com"
   args13["event_title"].should eq "Design Review"
 
+  # ------------------------------------------------------------------
+  # Test 13b: event_changed host change where the payload omits
+  #           event_end (a metadata-only reassignment).  The previous
+  #           host must STILL be notified — the host-change notification
+  #           does not depend on the event end time.
+  # ------------------------------------------------------------------
+
+  count_before_host_no_end = system(:Mailer)[:send_count].as_i
+
+  event_changed_host_no_end = {
+    action:         "update",
+    system_id:      "sys-room1",
+    event_id:       "evt-110",
+    event_ical_uid: "ical-110",
+    host:           "new-organiser2@example.com",
+    resource:       "room1@example.com",
+    title:          "Reassigned No End",
+    event_start:    now + 3600,
+    # no event_end
+    zones:               ["zone-building"],
+    previous_host_email: "old-organiser2@example.com",
+  }.to_json
+
+  publish("staff/event/changed", event_changed_host_no_end)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_host_no_end + 1
+  system(:Mailer)[:last_to].should eq "old-organiser2@example.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "notify_original_host"]
+
+  args13b = system(:Mailer)[:last_args]
+  args13b["previous_host_email"].should eq "old-organiser2@example.com"
+  args13b["new_host_email"].should eq "new-organiser2@example.com"
+  args13b["event_title"].should eq "Reassigned No End"
+  # event_start was present, so the date should still render
+  args13b["event_date"].raw.should_not be_nil
+
+  # ------------------------------------------------------------------
+  # Test 13c: event_changed host change where the payload omits BOTH
+  #           event_start and event_end (pure metadata reassignment).
+  #           The previous host must still be notified; the date/time
+  #           fields are simply left blank.
+  # ------------------------------------------------------------------
+
+  count_before_host_no_times = system(:Mailer)[:send_count].as_i
+
+  event_changed_host_no_times = {
+    action:         "update",
+    system_id:      "sys-room1",
+    event_id:       "evt-111",
+    event_ical_uid: "ical-111",
+    host:           "new-organiser3@example.com",
+    resource:       "room1@example.com",
+    title:          "Reassigned No Times",
+    # no event_start, no event_end
+    zones:               ["zone-building"],
+    previous_host_email: "old-organiser3@example.com",
+  }.to_json
+
+  publish("staff/event/changed", event_changed_host_no_times)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_host_no_times + 1
+  system(:Mailer)[:last_to].should eq "old-organiser3@example.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "notify_original_host"]
+
   # ------------------------------------------------------------------
   # Test 14: event_changed — action "create" is ignored (no previous
   #          values to compare)
@@ -771,7 +858,7 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   sleep 0.5
 
   # No email — create events have no previous state to diff against
-  system(:Mailer)[:send_count].should eq 12
+  system(:Mailer)[:send_count].should eq 14
 
   # ------------------------------------------------------------------
   # Test 15: event_changed — wrong zone is ignored
@@ -795,7 +882,7 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   publish("staff/event/changed", event_changed_wrong_zone)
   sleep 0.5
 
-  system(:Mailer)[:send_count].should eq 12
+  system(:Mailer)[:send_count].should eq 14
 
   # ------------------------------------------------------------------
   # Test 16: event_changed — no actual changes (previous == current)
@@ -820,7 +907,7 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   publish("staff/event/changed", event_changed_no_diff)
   sleep 0.5
 
-  system(:Mailer)[:send_count].should eq 12
+  system(:Mailer)[:send_count].should eq 14
 
   # ------------------------------------------------------------------
   # Test 17: event_changed with end-time-only change.
@@ -846,9 +933,9 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   publish("staff/event/changed", event_changed_end_only)
   sleep 1.5
 
-  system(:Mailer)[:send_count].should eq 13
+  system(:Mailer)[:send_count].should eq 15
   system(:Mailer)[:last_to].should eq "visitor@external.com"
-  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "event_changed"]
   system(:Mailer)[:last_args]["event_title"].should eq "End Time Only Event"
 
   # ------------------------------------------------------------------
@@ -874,9 +961,9 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   publish("staff/event/changed", event_changed_prev_location)
   sleep 1.5
 
-  system(:Mailer)[:send_count].should eq 14
+  system(:Mailer)[:send_count].should eq 16
   system(:Mailer)[:last_to].should eq "visitor@external.com"
-  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "event_changed"]
 
   args18 = system(:Mailer)[:last_args]
   args18["event_title"].should eq "Location Change Meeting"
@@ -1212,7 +1299,7 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
   # but only the visitor should receive the booking_changed email.
   system(:Mailer)[:send_count].should eq count_before_evt_host + 1
   system(:Mailer)[:last_to].should eq "visitor@external.com"
-  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "event_changed"]
 
   # ------------------------------------------------------------------
   # Test 29: send_booking_changed_emails (via booking_changed_event) —
@@ -1373,4 +1460,249 @@ DriverSpecs.mock_driver "Place::VisitorMailer" do
 
   system(:Mailer)[:send_count].should eq count_before_induction_decline + 1
   system(:Mailer)[:last_template].should eq ["visitor_invited", "custom_declined"]
+
+  # ------------------------------------------------------------------
+  # Test 33: event (room) changes and booking changes use SEPARATE
+  #          templates.  event_changed_event must use the
+  #          `event_changed_template`, while booking_changed_event keeps
+  #          the `booking_changed_template`.  Custom overrides confirm
+  #          both setting keys are wired up correctly.
+  # ------------------------------------------------------------------
+
+  settings({
+    timezone:                 "GMT",
+    booking_space_name:       "Client Floor",
+    invite_zone_tag:          "building",
+    booking_changed_template: "custom_booking_changed",
+    event_changed_template:   "custom_event_changed",
+  })
+  sleep 1.0
+
+  # --- event (room) based change uses the event_changed template
+  count_before_split_event = system(:Mailer)[:send_count].as_i
+
+  split_event_payload = {
+    action:               "update",
+    system_id:            "sys-room1",
+    event_id:             "evt-split",
+    event_ical_uid:       "ical-split",
+    host:                 "host@example.com",
+    resource:             "room1@example.com",
+    title:                "Split Event Change",
+    event_start:          now + 7200,
+    event_end:            now + 10800,
+    zones:                ["zone-building", "zone-room"],
+    previous_event_start: now + 3600,
+    previous_event_end:   now + 7200,
+  }.to_json
+
+  publish("staff/event/changed", split_event_payload)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_split_event + 1
+  system(:Mailer)[:last_to].should eq "visitor@external.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "custom_event_changed"]
+
+  # --- booking based change still uses the booking_changed template
+  count_before_split_booking = system(:Mailer)[:send_count].as_i
+
+  split_booking_payload = {
+    action:                 "changed",
+    id:                     900_i64,
+    booking_type:           "desk",
+    booking_start:          now + 7200,
+    booking_end:            now + 10800,
+    timezone:               "GMT",
+    resource_id:            "desk-1",
+    resource_ids:           ["desk-1"],
+    user_email:             "host@example.com",
+    title:                  "Split Booking Change",
+    zones:                  ["zone-building", "zone-room"],
+    previous_booking_start: now + 3600,
+    previous_booking_end:   now + 7200,
+  }.to_json
+
+  publish("staff/booking/changed", split_booking_payload)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_split_booking + 1
+  system(:Mailer)[:last_to].should eq "visitor@external.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "custom_booking_changed"]
+
+  # ==================================================================
+  # Issue 2 — de-duplicate event-linked booking notifications
+  # ==================================================================
+  #
+  # A calendar event with a room auto-creates a linked booking
+  # (extension_data.parent_id points to the event).  Editing the event
+  # fires staff/event/changed (handled by event_changed_event) AND the
+  # linked booking fires staff/booking/changed — so without de-duplication
+  # the visitor receives TWO change notifications.  booking_changed_event
+  # must skip event-linked bookings (same skip_event_linked_booking_email
+  # rule guest_event uses), letting the event_changed flow be the single
+  # source of truth.
+
+  settings({
+    timezone:           "GMT",
+    booking_space_name: "Client Floor",
+    invite_zone_tag:    "building",
+    # skip_event_linked_booking_email defaults to true
+  })
+  sleep 1.0
+
+  # ------------------------------------------------------------------
+  # Test 34: booking_changed for an event-linked booking is suppressed
+  # ------------------------------------------------------------------
+
+  count_before_linked_change = system(:Mailer)[:send_count].as_i
+
+  linked_booking_changed = {
+    action:                 "changed",
+    id:                     601_i64,
+    booking_type:           "visitor",
+    booking_start:          now + 7200,
+    booking_end:            now + 10800,
+    timezone:               "GMT",
+    resource_id:            "visitor@external.com",
+    resource_ids:           ["visitor@external.com"],
+    user_email:             "host@example.com",
+    title:                  "Linked Visit Changed",
+    zones:                  ["zone-building", "zone-room"],
+    previous_booking_start: now + 3600,
+    previous_booking_end:   now + 7200,
+    extension_data:         {parent_id: "event-evt-200"},
+  }.to_json
+
+  publish("staff/booking/changed", linked_booking_changed)
+  sleep 1.0
+
+  # Event-linked: the event_changed flow already notifies these visitors, so
+  # no booking_changed email should be sent.
+  system(:Mailer)[:send_count].should eq count_before_linked_change
+
+  # ------------------------------------------------------------------
+  # Test 35: standalone booking_changed (no parent_id) still notifies
+  # ------------------------------------------------------------------
+
+  count_before_standalone_change = system(:Mailer)[:send_count].as_i
+
+  standalone_booking_changed = {
+    action:                 "changed",
+    id:                     600_i64,
+    booking_type:           "visitor",
+    booking_start:          now + 7200,
+    booking_end:            now + 10800,
+    timezone:               "GMT",
+    resource_id:            "visitor@external.com",
+    resource_ids:           ["visitor@external.com"],
+    user_email:             "host@example.com",
+    title:                  "Standalone Visit Changed",
+    zones:                  ["zone-building", "zone-room"],
+    previous_booking_start: now + 3600,
+    previous_booking_end:   now + 7200,
+    # no extension_data / parent_id
+  }.to_json
+
+  publish("staff/booking/changed", standalone_booking_changed)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_standalone_change + 1
+  system(:Mailer)[:last_to].should eq "visitor@external.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+
+  # ------------------------------------------------------------------
+  # Test 36: opt-out (skip_event_linked_booking_email: false) restores
+  #          the booking_changed email even for event-linked bookings.
+  # ------------------------------------------------------------------
+
+  settings({
+    timezone:                        "GMT",
+    booking_space_name:              "Client Floor",
+    invite_zone_tag:                 "building",
+    skip_event_linked_booking_email: false,
+  })
+  sleep 1.0
+
+  count_before_optout_linked = system(:Mailer)[:send_count].as_i
+
+  publish("staff/booking/changed", linked_booking_changed)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_optout_linked + 1
+  system(:Mailer)[:last_to].should eq "visitor@external.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "booking_changed"]
+
+  # ==================================================================
+  # event_start back-fill
+  # ==================================================================
+  #
+  # Metadata-only staff/event/changed signals (e.g. update_metadata) omit
+  # the top-level event_start.  The host-change notification must still
+  # show a real date, so the driver looks the event up via the staff API.
+
+  settings({
+    timezone:           "GMT",
+    booking_space_name: "Client Floor",
+    invite_zone_tag:    "building",
+  })
+  sleep 1.0
+
+  # ------------------------------------------------------------------
+  # Test 37: event_start is looked up when omitted from the payload
+  # ------------------------------------------------------------------
+
+  count_before_lookup = system(:Mailer)[:send_count].as_i
+
+  event_changed_needs_lookup = {
+    action:         "update",
+    system_id:      "sys-room1",
+    event_id:       "evt-needs-lookup",
+    event_ical_uid: "ical-needs-lookup",
+    host:           "new-host-l@example.com",
+    resource:       "room1@example.com",
+    title:          "Needs Lookup",
+    # no event_start / event_end (metadata-only update)
+    zones:               ["zone-building"],
+    previous_host_email: "old-host-l@example.com",
+  }.to_json
+
+  publish("staff/event/changed", event_changed_needs_lookup)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_lookup + 1
+  system(:Mailer)[:last_to].should eq "old-host-l@example.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "notify_original_host"]
+
+  args37 = system(:Mailer)[:last_args]
+  # The payload carried no event_start, so a non-nil date proves it was
+  # back-filled from staff_api.get_event (epoch 1_760_000_000).
+  args37["event_date"].raw.should_not be_nil
+  args37["event_time"].raw.should_not be_nil
+
+  # ------------------------------------------------------------------
+  # Test 38: lookup that can't resolve a start time still notifies the
+  #          previous host (date/time simply left blank).
+  # ------------------------------------------------------------------
+
+  count_before_no_start = system(:Mailer)[:send_count].as_i
+
+  event_changed_no_start = {
+    action:              "update",
+    system_id:           "sys-room1",
+    event_id:            "evt-no-start",
+    event_ical_uid:      "ical-no-start",
+    host:                "new-host-n@example.com",
+    resource:            "room1@example.com",
+    title:               "No Start",
+    zones:               ["zone-building"],
+    previous_host_email: "old-host-n@example.com",
+  }.to_json
+
+  publish("staff/event/changed", event_changed_no_start)
+  sleep 1.5
+
+  system(:Mailer)[:send_count].should eq count_before_no_start + 1
+  system(:Mailer)[:last_to].should eq "old-host-n@example.com"
+  system(:Mailer)[:last_template].should eq ["visitor_invited", "notify_original_host"]
+  system(:Mailer)[:last_args]["event_date"].raw.should be_nil
 end
diff --git a/drivers/place/visitor_models.cr b/drivers/place/visitor_models.cr
index 6f60e2f01e..e098d56ec6 100644
--- a/drivers/place/visitor_models.cr
+++ b/drivers/place/visitor_models.cr
@@ -120,6 +120,10 @@ module Place
     property title : String?
     property zones : Array(String)?
 
+    # Present when the booking was auto-created from a calendar event;
+    # extension_data["parent_id"] holds the linked event id.
+    property extension_data : Hash(String, JSON::Any)?
+
     # Previous values — only present when action is "changed".
     # Add new previous_* fields here as more change notifications are introduced.
     property previous_booking_start : Int64?