From 38f4afb3174a065d74ca4adc5de58ecb52bd7d3c Mon Sep 17 00:00:00 2001
From: Eric Eastwood <erice@element.io>
Date: Wed, 4 Aug 2021 22:56:34 -0500
Subject: [PATCH 1/2] Mark all MSC2716 events as historical

---
 synapse/rest/client/v1/room.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 502a91758813..982f1341482f 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -458,6 +458,9 @@ async def on_POST(self, request, room_id):
                 "state_key": state_event["state_key"],
             }
 
+            # Mark all events as historical
+            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
+
             # Make the state events float off on their own
             fake_prev_event_id = "$" + random_string(43)
 
@@ -562,7 +565,10 @@ async def on_POST(self, request, room_id):
             "type": EventTypes.MSC2716_CHUNK,
             "sender": requester.user.to_string(),
             "room_id": room_id,
-            "content": {EventContentFields.MSC2716_CHUNK_ID: chunk_id_to_connect_to},
+            "content": {
+                EventContentFields.MSC2716_CHUNK_ID: chunk_id_to_connect_to,
+                EventContentFields.MSC2716_HISTORICAL: True,
+            },
             # Since the chunk event is put at the end of the chunk,
             # where the newest-in-time event is, copy the origin_server_ts from
             # the last event we're inserting
@@ -589,10 +595,6 @@ async def on_POST(self, request, room_id):
         for ev in events_to_create:
             assert_params_in_dict(ev, ["type", "origin_server_ts", "content", "sender"])
 
-            # Mark all events as historical
-            # This has important semantics within the Synapse internals to backfill properly
-            ev["content"][EventContentFields.MSC2716_HISTORICAL] = True
-
             event_dict = {
                 "type": ev["type"],
                 "origin_server_ts": ev["origin_server_ts"],
@@ -602,6 +604,9 @@ async def on_POST(self, request, room_id):
                 "prev_events": prev_event_ids.copy(),
             }
 
+            # Mark all events as historical
+            event_dict["content"][EventContentFields.MSC2716_HISTORICAL] = True
+
             event, context = await self.event_creation_handler.create_event(
                 await self._create_requester_for_user_id_from_app_service(
                     ev["sender"], requester.app_service

From 957623531db9fc9b61a7c1a4390980e81897c321 Mon Sep 17 00:00:00 2001
From: Eric Eastwood <erice@element.io>
Date: Wed, 4 Aug 2021 22:58:51 -0500
Subject: [PATCH 2/2] Add changelog

---
 changelog.d/10537.misc | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/10537.misc

diff --git a/changelog.d/10537.misc b/changelog.d/10537.misc
new file mode 100644
index 000000000000..c9e045300c3a
--- /dev/null
+++ b/changelog.d/10537.misc
@@ -0,0 +1 @@
+Mark all events stemming from the MSC2716 `/batch_send` endpoint as historical.