diff --git a/internal/mscs/msc2836/msc2836.go b/internal/mscs/msc2836/msc2836.go
index 0b227c8e6..cbf01c07d 100644
--- a/internal/mscs/msc2836/msc2836.go
+++ b/internal/mscs/msc2836/msc2836.go
@@ -44,6 +44,7 @@ type EventRelationshipRequest struct {
 	IncludeChildren *bool  `json:"include_children"`
 	Direction       string `json:"direction"`
 	Batch           string `json:"batch"`
+	AutoJoin        bool   `json:"auto_join"`
 }
 
 func (r *EventRelationshipRequest) applyDefaults() {
@@ -104,6 +105,13 @@ func Enable(base *setup.BaseDendrite, rsAPI roomserver.RoomserverInternalAPI, us
 	return nil
 }
 
+type reqCtx struct {
+	ctx    context.Context
+	rsAPI  roomserver.RoomserverInternalAPI
+	req    *EventRelationshipRequest
+	userID string
+}
+
 func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAPI) func(*http.Request, *userapi.Device) util.JSONResponse {
 	return func(req *http.Request, device *userapi.Device) util.JSONResponse {
 		var relation EventRelationshipRequest
@@ -118,9 +126,15 @@ func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAP
 		relation.applyDefaults()
 		var res EventRelationshipResponse
 		var returnEvents []*gomatrixserverlib.HeaderedEvent
+		rc := reqCtx{
+			ctx:    req.Context(),
+			req:    &relation,
+			userID: device.UserID,
+			rsAPI:  rsAPI,
+		}
 
 		// Can the user see (according to history visibility) event_id? If no, reject the request, else continue.
-		event := getEventIfVisible(req.Context(), rsAPI, relation.EventID, device.UserID)
+		event := rc.getEventIfVisible(relation.EventID)
 		if event == nil {
 			return util.JSONResponse{
 				Code: 403,
@@ -132,7 +146,7 @@ func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAP
 		returnEvents = append(returnEvents, event)
 
 		if *relation.IncludeParent {
-			if parentEvent := includeParent(req.Context(), rsAPI, event, device.UserID); parentEvent != nil {
+			if parentEvent := rc.includeParent(event); parentEvent != nil {
 				returnEvents = append(returnEvents, parentEvent)
 			}
 		}
@@ -140,7 +154,7 @@ func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAP
 		if *relation.IncludeChildren {
 			remaining := relation.Limit - len(returnEvents)
 			if remaining > 0 {
-				children, resErr := includeChildren(req.Context(), rsAPI, db, event.EventID(), remaining, *relation.RecentFirst, device.UserID)
+				children, resErr := rc.includeChildren(db, event.EventID(), remaining, *relation.RecentFirst)
 				if resErr != nil {
 					return *resErr
 				}
@@ -157,7 +171,7 @@ func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAP
 			}
 			var events []*gomatrixserverlib.HeaderedEvent
 			events, walkLimited = walkThread(
-				req.Context(), db, rsAPI, device.UserID, &relation, included, remaining,
+				req.Context(), db, &rc, included, remaining,
 			)
 			returnEvents = append(returnEvents, events...)
 		}
@@ -176,27 +190,27 @@ func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAP
 
 // If include_parent: true and there is a valid m.relationship field in the event,
 // retrieve the referenced event. Apply history visibility check to that event and if it passes, add it to the response array.
-func includeParent(ctx context.Context, rsAPI roomserver.RoomserverInternalAPI, event *gomatrixserverlib.HeaderedEvent, userID string) (parent *gomatrixserverlib.HeaderedEvent) {
+func (rc *reqCtx) includeParent(event *gomatrixserverlib.HeaderedEvent) (parent *gomatrixserverlib.HeaderedEvent) {
 	parentID, _, _ := parentChildEventIDs(event)
 	if parentID == "" {
 		return nil
 	}
-	return getEventIfVisible(ctx, rsAPI, parentID, userID)
+	return rc.getEventIfVisible(parentID)
 }
 
 // If include_children: true, lookup all events which have event_id as an m.relationship
 // Apply history visibility checks to all these events and add the ones which pass into the response array,
 // honouring the recent_first flag and the limit.
-func includeChildren(ctx context.Context, rsAPI roomserver.RoomserverInternalAPI, db Database, parentID string, limit int, recentFirst bool, userID string) ([]*gomatrixserverlib.HeaderedEvent, *util.JSONResponse) {
-	children, err := db.ChildrenForParent(ctx, parentID, constRelType, recentFirst)
+func (rc *reqCtx) includeChildren(db Database, parentID string, limit int, recentFirst bool) ([]*gomatrixserverlib.HeaderedEvent, *util.JSONResponse) {
+	children, err := db.ChildrenForParent(rc.ctx, parentID, constRelType, recentFirst)
 	if err != nil {
-		util.GetLogger(ctx).WithError(err).Error("failed to get ChildrenForParent")
+		util.GetLogger(rc.ctx).WithError(err).Error("failed to get ChildrenForParent")
 		resErr := jsonerror.InternalServerError()
 		return nil, &resErr
 	}
 	var childEvents []*gomatrixserverlib.HeaderedEvent
 	for _, child := range children {
-		childEvent := getEventIfVisible(ctx, rsAPI, child.EventID, userID)
+		childEvent := rc.getEventIfVisible(child.EventID)
 		if childEvent != nil {
 			childEvents = append(childEvents, childEvent)
 		}
@@ -211,16 +225,16 @@ func includeChildren(ctx context.Context, rsAPI roomserver.RoomserverInternalAPI
 // honouring the limit, max_depth and max_breadth values according to the following rules
 // nolint: unparam
 func walkThread(
-	ctx context.Context, db Database, rsAPI roomserver.RoomserverInternalAPI, userID string, req *EventRelationshipRequest, included map[string]bool, limit int,
+	ctx context.Context, db Database, rc *reqCtx, included map[string]bool, limit int,
 ) ([]*gomatrixserverlib.HeaderedEvent, bool) {
-	if req.Direction != "down" {
+	if rc.req.Direction != "down" {
 		util.GetLogger(ctx).Error("not implemented: direction=up")
 		return nil, false
 	}
 	var result []*gomatrixserverlib.HeaderedEvent
 	eventWalker := walker{
 		ctx: ctx,
-		req: req,
+		req: rc.req,
 		db:  db,
 		fn: func(wi *walkInfo) bool {
 			// If already processed event, skip.
@@ -234,7 +248,7 @@ func walkThread(
 			}
 
 			// Process the event.
-			event := getEventIfVisible(ctx, rsAPI, wi.EventID, userID)
+			event := rc.getEventIfVisible(wi.EventID)
 			if event != nil {
 				result = append(result, event)
 			}
@@ -242,24 +256,24 @@ func walkThread(
 			return false
 		},
 	}
-	limited, err := eventWalker.WalkFrom(req.EventID)
+	limited, err := eventWalker.WalkFrom(rc.req.EventID)
 	if err != nil {
-		util.GetLogger(ctx).WithError(err).Errorf("Failed to WalkFrom %s", req.EventID)
+		util.GetLogger(ctx).WithError(err).Errorf("Failed to WalkFrom %s", rc.req.EventID)
 	}
 	return result, limited
 }
 
-func getEventIfVisible(ctx context.Context, rsAPI roomserver.RoomserverInternalAPI, eventID, userID string) *gomatrixserverlib.HeaderedEvent {
+func (rc *reqCtx) getEventIfVisible(eventID string) *gomatrixserverlib.HeaderedEvent {
 	var queryEventsRes roomserver.QueryEventsByIDResponse
-	err := rsAPI.QueryEventsByID(ctx, &roomserver.QueryEventsByIDRequest{
+	err := rc.rsAPI.QueryEventsByID(rc.ctx, &roomserver.QueryEventsByIDRequest{
 		EventIDs: []string{eventID},
 	}, &queryEventsRes)
 	if err != nil {
-		util.GetLogger(ctx).WithError(err).Error("getEventIfVisible: failed to QueryEventsByID")
+		util.GetLogger(rc.ctx).WithError(err).Error("getEventIfVisible: failed to QueryEventsByID")
 		return nil
 	}
 	if len(queryEventsRes.Events) == 0 {
-		util.GetLogger(ctx).Infof("event does not exist")
+		util.GetLogger(rc.ctx).Infof("event does not exist")
 		return nil // event does not exist
 	}
 	event := queryEventsRes.Events[0]
@@ -268,19 +282,33 @@ func getEventIfVisible(ctx context.Context, rsAPI roomserver.RoomserverInternalA
 	// TODO: This does not honour history_visibility
 	// TODO: This does not honour m.room.create content
 	var queryMembershipRes roomserver.QueryMembershipForUserResponse
-	err = rsAPI.QueryMembershipForUser(ctx, &roomserver.QueryMembershipForUserRequest{
+	err = rc.rsAPI.QueryMembershipForUser(rc.ctx, &roomserver.QueryMembershipForUserRequest{
 		RoomID: event.RoomID(),
-		UserID: userID,
+		UserID: rc.userID,
 	}, &queryMembershipRes)
 	if err != nil {
-		util.GetLogger(ctx).WithError(err).Error("getEventIfVisible: failed to QueryMembershipForUser")
+		util.GetLogger(rc.ctx).WithError(err).Error("getEventIfVisible: failed to QueryMembershipForUser")
 		return nil
 	}
-	if !queryMembershipRes.IsInRoom {
-		util.GetLogger(ctx).Infof("user not in room")
-		return nil
+	if queryMembershipRes.IsInRoom {
+		return &event
 	}
-	return &event
+	if rc.req.AutoJoin {
+		var joinRes roomserver.PerformJoinResponse
+		rc.rsAPI.PerformJoin(rc.ctx, &roomserver.PerformJoinRequest{
+			UserID:        rc.userID,
+			Content:       map[string]interface{}{},
+			RoomIDOrAlias: event.RoomID(),
+			// TODO: Add server_names from linked room, currently this join will only work if the HS is already in the room
+		}, &joinRes)
+		if joinRes.Error != nil {
+			util.GetLogger(rc.ctx).WithError(joinRes.Error).WithField("room_id", event.RoomID()).Error("Failed to auto-join room")
+			return nil
+		}
+		return &event
+	}
+	util.GetLogger(rc.ctx).Infof("user not in room and auto_join disabled")
+	return nil
 }
 
 type walkInfo struct {
diff --git a/internal/mscs/msc2836/msc2836_test.go b/internal/mscs/msc2836/msc2836_test.go
index 17dd1d124..795ead6a6 100644
--- a/internal/mscs/msc2836/msc2836_test.go
+++ b/internal/mscs/msc2836/msc2836_test.go
@@ -353,6 +353,10 @@ func TestMSC2836(t *testing.T) {
 	})
 }
 
+// TODO: TestMSC2836TerminatesLoops (short and long)
+// TODO: TestMSC2836UnknownEventsSkipped
+// TODO: TestMSC2836SkipEventIfNotInRoom
+
 func runServer(t *testing.T, router *mux.Router) func() {
 	t.Helper()
 	externalServ := &http.Server{