diff --git a/crates/caldav/src/calendar/service.rs b/crates/caldav/src/calendar/service.rs
index a82c96a..aed3cb8 100644
--- a/crates/caldav/src/calendar/service.rs
+++ b/crates/caldav/src/calendar/service.rs
@@ -50,7 +50,7 @@ impl<C: CalendarStore, S: SubscriptionStore> ResourceService for CalendarResourc
     type Principal = User;
     type PrincipalUri = CalDavPrincipalUri;
 
-    const DAV_HEADER: &str = "1, 3, access-control, calendar-access";
+    const DAV_HEADER: &str = "1, 3, access-control, calendar-access, calendar-proxy";
 
     async fn get_resource(
         &self,
diff --git a/crates/caldav/src/principal/mod.rs b/crates/caldav/src/principal/mod.rs
index 5077a4d..ce9b35e 100644
--- a/crates/caldav/src/principal/mod.rs
+++ b/crates/caldav/src/principal/mod.rs
@@ -2,7 +2,7 @@ use crate::Error;
 use rustical_dav::extensions::CommonPropertiesExtension;
 use rustical_dav::privileges::UserPrivilegeSet;
 use rustical_dav::resource::{PrincipalUri, Resource, ResourceName};
-use rustical_dav::xml::{Resourcetype, ResourcetypeInner};
+use rustical_dav::xml::{Resourcetype, ResourcetypeInner, SupportedReportSet};
 use rustical_store::auth::User;
 
 mod service;
@@ -13,6 +13,7 @@ pub use prop::*;
 #[derive(Clone)]
 pub struct PrincipalResource {
     principal: User,
+    members: Vec<String>,
 }
 
 impl ResourceName for PrincipalResource {
@@ -32,6 +33,11 @@ impl Resource for PrincipalResource {
         Resourcetype(&[
             ResourcetypeInner(Some(rustical_dav::namespace::NS_DAV), "collection"),
             ResourcetypeInner(Some(rustical_dav::namespace::NS_DAV), "principal"),
+            // https://github.com/apple/ccs-calendarserver/blob/13c706b985fb728b9aab42dc0fef85aae21921c3/doc/Extensions/caldav-proxy.txt
+            ResourcetypeInner(
+                Some(rustical_dav::namespace::NS_CALENDARSERVER),
+                "calendar-proxy-write",
+            ),
         ])
     }
 
@@ -64,6 +70,14 @@ impl Resource for PrincipalResource {
                     PrincipalPropName::CalendarUserAddressSet => {
                         PrincipalProp::CalendarUserAddressSet(principal_url.into())
                     }
+                    PrincipalPropName::GroupMemberSet => {
+                        PrincipalProp::GroupMemberSet(GroupMemberSet(
+                            self.members
+                                .iter()
+                                .map(|principal| puri.principal_uri(principal).into())
+                                .collect(),
+                        ))
+                    }
                     PrincipalPropName::GroupMembership => {
                         PrincipalProp::GroupMembership(GroupMembership(
                             self.principal
@@ -79,6 +93,9 @@ impl Resource for PrincipalResource {
                             puri.principal_collection().into(),
                         ))
                     }
+                    PrincipalPropName::SupportedReportSet => {
+                        PrincipalProp::SupportedReportSet(SupportedReportSet::all())
+                    }
                 })
             }
             PrincipalPropWrapperName::Common(prop) => PrincipalPropWrapper::Common(
diff --git a/crates/caldav/src/principal/prop.rs b/crates/caldav/src/principal/prop.rs
index f62eb29..b46a3cb 100644
--- a/crates/caldav/src/principal/prop.rs
+++ b/crates/caldav/src/principal/prop.rs
@@ -1,6 +1,10 @@
-use rustical_dav::{extensions::CommonPropertiesProp, xml::HrefElement};
+use rustical_dav::{
+    extensions::CommonPropertiesProp,
+    xml::{HrefElement, SupportedReportSet},
+};
 use rustical_store::auth::user::PrincipalType;
 use rustical_xml::{EnumVariants, PropName, XmlDeserialize, XmlSerialize};
+use strum_macros::VariantArray;
 
 #[derive(XmlDeserialize, XmlSerialize, PartialEq, Clone, EnumVariants, PropName)]
 #[xml(unit_variants_ident = "PrincipalPropName")]
@@ -16,10 +20,14 @@ pub enum PrincipalProp {
     PrincipalUrl(HrefElement),
     #[xml(ns = "rustical_dav::namespace::NS_DAV")]
     GroupMembership(GroupMembership),
+    #[xml(ns = "rustical_dav::namespace::NS_DAV")]
+    GroupMemberSet(GroupMemberSet),
     #[xml(ns = "rustical_dav::namespace::NS_DAV", rename = b"alternate-URI-set")]
     AlternateUriSet,
     #[xml(ns = "rustical_dav::namespace::NS_DAV")]
     PrincipalCollectionSet(PrincipalCollectionSet),
+    #[xml(ns = "rustical_dav::namespace::NS_DAV", skip_deserializing)]
+    SupportedReportSet(SupportedReportSet<ReportMethod>),
 
     // CalDAV (RFC 4791)
     #[xml(ns = "rustical_dav::namespace::NS_CALDAV")]
@@ -39,5 +47,15 @@ pub struct CalendarHomeSet(#[xml(ty = "untagged", flatten)] pub(super) Vec<HrefE
 #[derive(XmlDeserialize, XmlSerialize, PartialEq, Clone)]
 pub struct GroupMembership(#[xml(ty = "untagged", flatten)] pub(super) Vec<HrefElement>);
 
+#[derive(XmlDeserialize, XmlSerialize, PartialEq, Clone)]
+pub struct GroupMemberSet(#[xml(ty = "untagged", flatten)] pub(super) Vec<HrefElement>);
+
 #[derive(XmlDeserialize, XmlSerialize, PartialEq, Clone)]
 pub struct PrincipalCollectionSet(#[xml(ty = "untagged")] pub(super) HrefElement);
+
+#[derive(XmlSerialize, PartialEq, Clone, VariantArray)]
+pub enum ReportMethod {
+    // We don't actually support principal-match
+    #[xml(ns = "rustical_dav::namespace::NS_DAV")]
+    PrincipalMatch,
+}
diff --git a/crates/caldav/src/principal/service.rs b/crates/caldav/src/principal/service.rs
index b24cbcf..e8b72ef 100644
--- a/crates/caldav/src/principal/service.rs
+++ b/crates/caldav/src/principal/service.rs
@@ -43,7 +43,7 @@ impl<AP: AuthenticationProvider, S: SubscriptionStore, CS: CalendarStore> Resour
     type Principal = User;
     type PrincipalUri = CalDavPrincipalUri;
 
-    const DAV_HEADER: &str = "1, 3, access-control, calendar-access";
+    const DAV_HEADER: &str = "1, 3, access-control, calendar-access, calendar-proxy";
 
     async fn get_resource(
         &self,
@@ -54,7 +54,10 @@ impl<AP: AuthenticationProvider, S: SubscriptionStore, CS: CalendarStore> Resour
             .get_principal(principal)
             .await?
             .ok_or(crate::Error::NotFound)?;
-        Ok(PrincipalResource { principal: user })
+        Ok(PrincipalResource {
+            members: self.auth_provider.list_members(&user.id).await?,
+            principal: user,
+        })
     }
 
     async fn get_members(