diff --git a/CHANGES.md b/CHANGES.md
index fe076f2bce..43259f323c 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,19 @@
+Synapse 1.79.0rc2 (2023-03-13)
+==============================
+
+Bugfixes
+--------
+
+- Fix a bug introduced in Synapse 1.79.0rc1 where attempting to register a `on_remove_user_third_party_identifier` module API callback would be a no-op. ([\#15227](https://github.com/matrix-org/synapse/issues/15227))
+- Fix a rare bug introduced in Synapse 1.73 where events could remain unsent to other homeservers after a faster-join to a room. ([\#15248](https://github.com/matrix-org/synapse/issues/15248))
+
+
+Internal Changes
+----------------
+
+- Refactor `filter_events_for_server`. ([\#15240](https://github.com/matrix-org/synapse/issues/15240))
+
+
 Synapse 1.79.0rc1 (2023-03-07)
 ==============================
 
@@ -5,12 +21,12 @@ Features
 --------
 
 - Add two new Third Party Rules module API callbacks: [`on_add_user_third_party_identifier`](https://matrix-org.github.io/synapse/v1.79/modules/third_party_rules_callbacks.html#on_add_user_third_party_identifier) and [`on_remove_user_third_party_identifier`](https://matrix-org.github.io/synapse/v1.79/modules/third_party_rules_callbacks.html#on_remove_user_third_party_identifier). ([\#15044](https://github.com/matrix-org/synapse/issues/15044))
-- Experimental support for MSC3967 to not require UIA for setting up cross-signing on first use. ([\#15077](https://github.com/matrix-org/synapse/issues/15077))
+- Experimental support for [MSC3967](https://github.com/matrix-org/matrix-spec-proposals/pull/3967) to not require UIA for setting up cross-signing on first use. ([\#15077](https://github.com/matrix-org/synapse/issues/15077))
 - Add media information to the command line [user data export tool](https://matrix-org.github.io/synapse/v1.79/usage/administration/admin_faq.html#how-can-i-export-user-data). ([\#15107](https://github.com/matrix-org/synapse/issues/15107))
 - Add an [admin API](https://matrix-org.github.io/synapse/latest/usage/administration/admin_api/index.html) to delete a [specific event report](https://spec.matrix.org/v1.6/client-server-api/#reporting-content). ([\#15116](https://github.com/matrix-org/synapse/issues/15116))
 - Add support for knocking to workers. ([\#15133](https://github.com/matrix-org/synapse/issues/15133))
 - Allow use of the `/filter` Client-Server APIs on workers. ([\#15134](https://github.com/matrix-org/synapse/issues/15134))
-- Remove support for server-side aggregation of reactions. ([\#15172](https://github.com/matrix-org/synapse/issues/15172))
+- Update support for [MSC2677](https://github.com/matrix-org/matrix-spec-proposals/pull/2677): remove support for server-side aggregation of reactions. ([\#15172](https://github.com/matrix-org/synapse/issues/15172))
 - Stabilise support for [MSC3758](https://github.com/matrix-org/matrix-spec-proposals/pull/3758): `event_property_is` push condition. ([\#15185](https://github.com/matrix-org/synapse/issues/15185))
 
 
@@ -20,10 +36,8 @@ Bugfixes
 - Fix a bug introduced in Synapse 1.75 that caused experimental support for deleting account data to raise an internal server error while using an account data writer worker. ([\#14869](https://github.com/matrix-org/synapse/issues/14869))
 - Fix a long-standing bug where Synapse handled an unspecced field on push rules. ([\#15088](https://github.com/matrix-org/synapse/issues/15088))
 - Fix a long-standing bug where a URL preview would break if the discovered oEmbed failed to download. ([\#15092](https://github.com/matrix-org/synapse/issues/15092))
-- Remove the unspecced `room_alias` field from the [`/createRoom`](https://spec.matrix.org/v1.6/client-server-api/#post_matrixclientv3createroom) response. ([\#15093](https://github.com/matrix-org/synapse/issues/15093))
 - Fix a long-standing bug where an initial sync would not respond to changes to the list of ignored users if there was an initial sync cached. ([\#15163](https://github.com/matrix-org/synapse/issues/15163))
 - Add the `transaction_id` in the events included in many endpoints' responses. ([\#15174](https://github.com/matrix-org/synapse/issues/15174))
-- Fix `test_icu_word_boundary_punctuation` for Alpine acos installed ICU versions. ([\#15177](https://github.com/matrix-org/synapse/issues/15177))
 - Fix a bug introduced in Synapse 1.78.0 where requests to claim dehydrated devices would fail with a `405` error. ([\#15180](https://github.com/matrix-org/synapse/issues/15180))
 - Stop applying edits when bundling aggregations, per [MSC3925](https://github.com/matrix-org/matrix-spec-proposals/pull/3925). ([\#15193](https://github.com/matrix-org/synapse/issues/15193))
 - Fix a long-standing bug where the user directory search was not case-insensitive for accented characters. ([\#15143](https://github.com/matrix-org/synapse/issues/15143))
@@ -49,7 +63,11 @@ Improved Documentation
 Deprecations and Removals
 -------------------------
 
+- Deprecate the `on_threepid_bind` module callback, to be replaced by [`on_add_user_third_party_identifier`](https://matrix-org.github.io/synapse/v1.79/modules/third_party_rules_callbacks.html#on_add_user_third_party_identifier). See [upgrade notes](https://github.com/matrix-org/synapse/blob/release-v1.79/docs/upgrade.md#upgrading-to-v1790). ([\#15044](https://github.com/matrix-org/synapse/issues/15044))
+- Remove the unspecced `room_alias` field from the [`/createRoom`](https://spec.matrix.org/v1.6/client-server-api/#post_matrixclientv3createroom) response. ([\#15093](https://github.com/matrix-org/synapse/issues/15093))
+- Remove the unspecced `PUT` on the `/knock/{roomIdOrAlias}` endpoint. ([\#15189](https://github.com/matrix-org/synapse/issues/15189))
 - Remove the undocumented and unspecced `type` parameter to the `/thumbnail` endpoint. ([\#15137](https://github.com/matrix-org/synapse/issues/15137))
+- Remove unspecced and buggy `PUT` method on the unstable `/rooms/<room_id>/batch_send` endpoint. ([\#15199](https://github.com/matrix-org/synapse/issues/15199))
 
 
 Internal Changes
@@ -70,26 +88,26 @@ Internal Changes
 - Add a `get_next_txn` method to `StreamIdGenerator` to match `MultiWriterIdGenerator`. ([\#15191](https://github.com/matrix-org/synapse/issues/15191))
 - Combine `AbstractStreamIdTracker` and `AbstractStreamIdGenerator`. ([\#15192](https://github.com/matrix-org/synapse/issues/15192))
 - Automatically fix errors with `ruff`. ([\#15194](https://github.com/matrix-org/synapse/issues/15194))
-- Remove the unspecced `PUT` on the `/knock/{roomIdOrAlias}` endpoint. ([\#15189](https://github.com/matrix-org/synapse/issues/15189))
-- Remove unspecced and buggy `PUT` method on the unstable `/rooms/<room_id>/batch_send` endpoint. ([\#15199](https://github.com/matrix-org/synapse/issues/15199))
 - Refactor database transaction for query users' devices to reduce database pool contention. ([\#15215](https://github.com/matrix-org/synapse/issues/15215))
 - Correct `test_icu_word_boundary_punctuation` so that it passes with the ICU versions available in Alpine and macOS. ([\#15177](https://github.com/matrix-org/synapse/issues/15177))
-- <details><summary>Locked dependency updates</summary>
-    - Bump actions/checkout from 2 to 3. ([\#15155](https://github.com/matrix-org/synapse/issues/15155))
-    - Bump black from 22.12.0 to 23.1.0. ([\#15103](https://github.com/matrix-org/synapse/issues/15103))
-    - Bump dawidd6/action-download-artifact from 2.25.0 to 2.26.0. ([\#15152](https://github.com/matrix-org/synapse/issues/15152))
-    - Bump docker/login-action from 1 to 2. ([\#15154](https://github.com/matrix-org/synapse/issues/15154))
-    - Bump matrix-org/backend-meta from 1 to 2. ([\#15156](https://github.com/matrix-org/synapse/issues/15156))
-    - Bump ruff from 0.0.237 to 0.0.252. ([\#15159](https://github.com/matrix-org/synapse/issues/15159))
-    - Bump serde_json from 1.0.93 to 1.0.94. ([\#15214](https://github.com/matrix-org/synapse/issues/15214))
-    - Bump types-commonmark from 0.9.2.1 to 0.9.2.2. ([\#15209](https://github.com/matrix-org/synapse/issues/15209))
-    - Bump types-opentracing from 2.4.10.1 to 2.4.10.3. ([\#15158](https://github.com/matrix-org/synapse/issues/15158))
-    - Bump types-pillow from 9.4.0.13 to 9.4.0.17. ([\#15211](https://github.com/matrix-org/synapse/issues/15211))
-    - Bump types-psycopg2 from 2.9.21.4 to 2.9.21.8. ([\#15210](https://github.com/matrix-org/synapse/issues/15210))
-    - Bump types-pyopenssl from 22.1.0.2 to 23.0.0.4. ([\#15213](https://github.com/matrix-org/synapse/issues/15213))
-    - Bump types-setuptools from 67.3.0.1 to 67.4.0.3. ([\#15160](https://github.com/matrix-org/synapse/issues/15160))
-    - Bump types-setuptools from 67.4.0.3 to 67.5.0.0. ([\#15212](https://github.com/matrix-org/synapse/issues/15212))
-    - Bump typing-extensions from 4.4.0 to 4.5.0. ([\#15157](https://github.com/matrix-org/synapse/issues/15157))
+
+<details><summary>Locked dependency updates</summary>
+
+  - Bump actions/checkout from 2 to 3. ([\#15155](https://github.com/matrix-org/synapse/issues/15155))
+  - Bump black from 22.12.0 to 23.1.0. ([\#15103](https://github.com/matrix-org/synapse/issues/15103))
+  - Bump dawidd6/action-download-artifact from 2.25.0 to 2.26.0. ([\#15152](https://github.com/matrix-org/synapse/issues/15152))
+  - Bump docker/login-action from 1 to 2. ([\#15154](https://github.com/matrix-org/synapse/issues/15154))
+  - Bump matrix-org/backend-meta from 1 to 2. ([\#15156](https://github.com/matrix-org/synapse/issues/15156))
+  - Bump ruff from 0.0.237 to 0.0.252. ([\#15159](https://github.com/matrix-org/synapse/issues/15159))
+  - Bump serde_json from 1.0.93 to 1.0.94. ([\#15214](https://github.com/matrix-org/synapse/issues/15214))
+  - Bump types-commonmark from 0.9.2.1 to 0.9.2.2. ([\#15209](https://github.com/matrix-org/synapse/issues/15209))
+  - Bump types-opentracing from 2.4.10.1 to 2.4.10.3. ([\#15158](https://github.com/matrix-org/synapse/issues/15158))
+  - Bump types-pillow from 9.4.0.13 to 9.4.0.17. ([\#15211](https://github.com/matrix-org/synapse/issues/15211))
+  - Bump types-psycopg2 from 2.9.21.4 to 2.9.21.8. ([\#15210](https://github.com/matrix-org/synapse/issues/15210))
+  - Bump types-pyopenssl from 22.1.0.2 to 23.0.0.4. ([\#15213](https://github.com/matrix-org/synapse/issues/15213))
+  - Bump types-setuptools from 67.3.0.1 to 67.4.0.3. ([\#15160](https://github.com/matrix-org/synapse/issues/15160))
+  - Bump types-setuptools from 67.4.0.3 to 67.5.0.0. ([\#15212](https://github.com/matrix-org/synapse/issues/15212))
+  - Bump typing-extensions from 4.4.0 to 4.5.0. ([\#15157](https://github.com/matrix-org/synapse/issues/15157))
 </details>
 
 
diff --git a/debian/changelog b/debian/changelog
index 871c695f07..a91521f6b2 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+matrix-synapse-py3 (1.79.0~rc2) stable; urgency=medium
+
+  * New Synapse release 1.79.0rc2.
+
+ -- Synapse Packaging team <packages@matrix.org>  Mon, 13 Mar 2023 12:54:21 +0000
+
 matrix-synapse-py3 (1.79.0~rc1) stable; urgency=medium
 
   * New Synapse release 1.79.0rc1.
diff --git a/pyproject.toml b/pyproject.toml
index 90a1187416..dbdc3c4991 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -89,7 +89,7 @@ manifest-path = "rust/Cargo.toml"
 
 [tool.poetry]
 name = "matrix-synapse"
-version = "1.79.0rc1"
+version = "1.79.0rc2"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "Apache-2.0"
diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py
index 3e4d52c8d8..61d4530be7 100644
--- a/synapse/events/third_party_rules.py
+++ b/synapse/events/third_party_rules.py
@@ -247,6 +247,11 @@ class ThirdPartyEventRules:
                 on_add_user_third_party_identifier
             )
 
+        if on_remove_user_third_party_identifier is not None:
+            self._on_remove_user_third_party_identifier_callbacks.append(
+                on_remove_user_third_party_identifier
+            )
+
     async def check_event_allowed(
         self,
         event: EventBase,
diff --git a/synapse/federation/sender/per_destination_queue.py b/synapse/federation/sender/per_destination_queue.py
index ffc9d95ee7..31c5c2b7de 100644
--- a/synapse/federation/sender/per_destination_queue.py
+++ b/synapse/federation/sender/per_destination_queue.py
@@ -497,8 +497,8 @@ class PerDestinationQueue:
             #
             # Note: `catchup_pdus` will have exactly one PDU per room.
             for pdu in catchup_pdus:
-                # The PDU from the DB will be the last PDU in the room from
-                # *this server* that wasn't sent to the remote. However, other
+                # The PDU from the DB will be the newest PDU in the room from
+                # *this server* that we tried---but were unable---to send to the remote.
                 # servers may have sent lots of events since then, and we want
                 # to try and tell the remote only about the *latest* events in
                 # the room. This is so that it doesn't get inundated by events
@@ -516,6 +516,11 @@ class PerDestinationQueue:
                     # If the event is in the extremities, then great! We can just
                     # use that without having to do further checks.
                     room_catchup_pdus = [pdu]
+                elif await self._store.is_partial_state_room(pdu.room_id):
+                    # We can't be sure which events the destination should
+                    # see using only partial state. Avoid doing so, and just retry
+                    # sending our the newest PDU the remote is missing from us.
+                    room_catchup_pdus = [pdu]
                 else:
                     # If not, fetch the extremities and figure out which we can
                     # send.
@@ -547,6 +552,8 @@ class PerDestinationQueue:
                         self._server_name,
                         new_pdus,
                         redact=False,
+                        filter_out_erased_senders=True,
+                        filter_out_remote_partial_state_events=True,
                     )
 
                     # If we've filtered out all the extremities, fall back to
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 5f2057269d..80156ef343 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -392,7 +392,7 @@ class FederationHandler:
                 get_prev_content=False,
             )
 
-            # We set `check_history_visibility_only` as we might otherwise get false
+            # We unset `filter_out_erased_senders` as we might otherwise get false
             # positives from users having been erased.
             filtered_extremities = await filter_events_for_server(
                 self._storage_controllers,
@@ -400,7 +400,8 @@ class FederationHandler:
                 self.server_name,
                 events_to_check,
                 redact=False,
-                check_history_visibility_only=True,
+                filter_out_erased_senders=False,
+                filter_out_remote_partial_state_events=False,
             )
             if filtered_extremities:
                 extremities_to_request.append(bp.event_id)
@@ -1331,7 +1332,13 @@ class FederationHandler:
         )
 
         events = await filter_events_for_server(
-            self._storage_controllers, origin, self.server_name, events
+            self._storage_controllers,
+            origin,
+            self.server_name,
+            events,
+            redact=True,
+            filter_out_erased_senders=True,
+            filter_out_remote_partial_state_events=True,
         )
 
         return events
@@ -1362,7 +1369,13 @@ class FederationHandler:
         await self._event_auth_handler.assert_host_in_room(event.room_id, origin)
 
         events = await filter_events_for_server(
-            self._storage_controllers, origin, self.server_name, [event]
+            self._storage_controllers,
+            origin,
+            self.server_name,
+            [event],
+            redact=True,
+            filter_out_erased_senders=True,
+            filter_out_remote_partial_state_events=True,
         )
         event = events[0]
         return event
@@ -1390,7 +1403,13 @@ class FederationHandler:
         )
 
         missing_events = await filter_events_for_server(
-            self._storage_controllers, origin, self.server_name, missing_events
+            self._storage_controllers,
+            origin,
+            self.server_name,
+            missing_events,
+            redact=True,
+            filter_out_erased_senders=True,
+            filter_out_remote_partial_state_events=True,
         )
 
         return missing_events
diff --git a/synapse/visibility.py b/synapse/visibility.py
index e442de3173..468e22f8f6 100644
--- a/synapse/visibility.py
+++ b/synapse/visibility.py
@@ -14,7 +14,17 @@
 # limitations under the License.
 import logging
 from enum import Enum, auto
-from typing import Collection, Dict, FrozenSet, List, Optional, Tuple
+from typing import (
+    Collection,
+    Dict,
+    FrozenSet,
+    List,
+    Mapping,
+    Optional,
+    Sequence,
+    Set,
+    Tuple,
+)
 
 import attr
 from typing_extensions import Final
@@ -565,29 +575,43 @@ async def filter_events_for_server(
     storage: StorageControllers,
     target_server_name: str,
     local_server_name: str,
-    events: List[EventBase],
-    redact: bool = True,
-    check_history_visibility_only: bool = False,
+    events: Sequence[EventBase],
+    *,
+    redact: bool,
+    filter_out_erased_senders: bool,
+    filter_out_remote_partial_state_events: bool,
 ) -> List[EventBase]:
-    """Filter a list of events based on whether given server is allowed to
+    """Filter a list of events based on whether the target server is allowed to
     see them.
 
+    For a fully stated room, the target server is allowed to see an event E if:
+      - the state at E has world readable or shared history vis, OR
+      - the state at E says that the target server is in the room.
+
+    For a partially stated room, the target server is allowed to see E if:
+      - E was created by this homeserver, AND:
+          - the partial state at E has world readable or shared history vis, OR
+          - the partial state at E says that the target server is in the room.
+
+    TODO: state before or state after?
+
     Args:
         storage
-        server_name
+        target_server_name
+        local_server_name
         events
-        redact: Whether to return a redacted version of the event, or
-            to filter them out entirely.
-        check_history_visibility_only: Whether to only check the
-            history visibility, rather than things like if the sender has been
+        redact: Controls what to do with events which have been filtered out.
+            If True, include their redacted forms; if False, omit them entirely.
+        filter_out_erased_senders: If true, also filter out events whose sender has been
             erased. This is used e.g. during pagination to decide whether to
             backfill or not.
-
+        filter_out_remote_partial_state_events: If True, also filter out events in
+            partial state rooms created by other homeservers.
     Returns
         The filtered events.
     """
 
-    def is_sender_erased(event: EventBase, erased_senders: Dict[str, bool]) -> bool:
+    def is_sender_erased(event: EventBase, erased_senders: Mapping[str, bool]) -> bool:
         if erased_senders and erased_senders[event.sender]:
             logger.info("Sender of %s has been erased, redacting", event.event_id)
             return True
@@ -616,7 +640,7 @@ async def filter_events_for_server(
         # server has no users in the room: redact
         return False
 
-    if not check_history_visibility_only:
+    if filter_out_erased_senders:
         erased_senders = await storage.main.are_users_erased(e.sender for e in events)
     else:
         # We don't want to check whether users are erased, which is equivalent
@@ -631,15 +655,15 @@ async def filter_events_for_server(
     # otherwise a room could be fully joined after we retrieve those, which would then bypass
     # this check but would base the filtering on an outdated view of the membership events.
 
-    partial_state_invisible_events = set()
-    if not check_history_visibility_only:
+    partial_state_invisible_event_ids: Set[str] = set()
+    if filter_out_remote_partial_state_events:
         for e in events:
             sender_domain = get_domain_from_id(e.sender)
             if (
                 sender_domain != local_server_name
                 and await storage.main.is_partial_state_room(e.room_id)
             ):
-                partial_state_invisible_events.add(e)
+                partial_state_invisible_event_ids.add(e.event_id)
 
     # Let's check to see if all the events have a history visibility
     # of "shared" or "world_readable". If that's the case then we don't
@@ -658,17 +682,20 @@ async def filter_events_for_server(
         target_server_name,
     )
 
-    to_return = []
-    for e in events:
+    def include_event_in_output(e: EventBase) -> bool:
         erased = is_sender_erased(e, erased_senders)
         visible = check_event_is_visible(
             event_to_history_vis[e.event_id], event_to_memberships.get(e.event_id, {})
         )
 
-        if e in partial_state_invisible_events:
+        if e.event_id in partial_state_invisible_event_ids:
             visible = False
 
-        if visible and not erased:
+        return visible and not erased
+
+    to_return = []
+    for e in events:
+        if include_event_in_output(e):
             to_return.append(e)
         elif redact:
             to_return.append(prune_event(e))
diff --git a/tests/federation/test_federation_catch_up.py b/tests/federation/test_federation_catch_up.py
index 6381583c24..391ae51707 100644
--- a/tests/federation/test_federation_catch_up.py
+++ b/tests/federation/test_federation_catch_up.py
@@ -1,4 +1,5 @@
-from typing import Callable, List, Optional, Tuple
+from typing import Callable, Collection, List, Optional, Tuple
+from unittest import mock
 from unittest.mock import Mock
 
 from twisted.test.proto_helpers import MemoryReactor
@@ -500,3 +501,87 @@ class FederationCatchUpTestCases(FederatingHomeserverTestCase):
         self.assertEqual(len(sent_pdus), 1)
         self.assertEqual(sent_pdus[0].event_id, event_2.event_id)
         self.assertFalse(per_dest_queue._catching_up)
+
+    def test_catch_up_is_not_blocked_by_remote_event_in_partial_state_room(
+        self,
+    ) -> None:
+        """Detects (part of?) https://github.com/matrix-org/synapse/issues/15220."""
+        # ARRANGE:
+        # - a local user (u1)
+        # - a room which contains u1 and two remote users, @u2:host2 and @u3:other
+        # - events in that room such that
+        #   - history visibility is restricted
+        #   - u1 sent message events e1 and e2
+        #   - afterwards, u3 sent a remote event e3
+        # - catchup to begin for host2; last successfully sent event was e1
+        per_dest_queue, sent_pdus = self.make_fake_destination_queue()
+
+        self.register_user("u1", "you the one")
+        u1_token = self.login("u1", "you the one")
+        room = self.helper.create_room_as("u1", tok=u1_token)
+        self.helper.send_state(
+            room_id=room,
+            event_type="m.room.history_visibility",
+            body={"history_visibility": "joined"},
+            tok=u1_token,
+        )
+        self.get_success(
+            event_injection.inject_member_event(self.hs, room, "@u2:host2", "join")
+        )
+        self.get_success(
+            event_injection.inject_member_event(self.hs, room, "@u3:other", "join")
+        )
+
+        # create some events
+        event_id_1 = self.helper.send(room, "hello", tok=u1_token)["event_id"]
+        event_id_2 = self.helper.send(room, "world", tok=u1_token)["event_id"]
+        # pretend that u3 changes their displayname
+        event_id_3 = self.get_success(
+            event_injection.inject_member_event(self.hs, room, "@u3:other", "join")
+        ).event_id
+
+        # destination_rooms should already be populated, but let us pretend that we already
+        # sent (successfully) up to and including event id 1
+        event_1 = self.get_success(self.hs.get_datastores().main.get_event(event_id_1))
+        assert event_1.internal_metadata.stream_ordering is not None
+        self.get_success(
+            self.hs.get_datastores().main.set_destination_last_successful_stream_ordering(
+                "host2", event_1.internal_metadata.stream_ordering
+            )
+        )
+
+        # also fetch event 2 so we can compare its stream ordering to the sender's
+        # last_successful_stream_ordering later
+        event_2 = self.get_success(self.hs.get_datastores().main.get_event(event_id_2))
+
+        # Mock event 3 as having partial state
+        self.get_success(
+            event_injection.mark_event_as_partial_state(self.hs, event_id_3, room)
+        )
+
+        # Fail the test if we block on full state for event 3.
+        async def mock_await_full_state(event_ids: Collection[str]) -> None:
+            if event_id_3 in event_ids:
+                raise AssertionError("Tried to await full state for event_id_3")
+
+        # ACT
+        with mock.patch.object(
+            self.hs.get_storage_controllers().state._partial_state_events_tracker,
+            "await_full_state",
+            mock_await_full_state,
+        ):
+            self.get_success(per_dest_queue._catch_up_transmission_loop())
+
+        # ASSERT
+        # We should have:
+        # - not sent event 3: it's not ours, and the room is partial stated
+        # - fallen back to sending event 2: it's the most recent event in the room
+        #   we tried to send to host2
+        # - completed catch-up
+        self.assertEqual(len(sent_pdus), 1)
+        self.assertEqual(sent_pdus[0].event_id, event_id_2)
+        self.assertFalse(per_dest_queue._catching_up)
+        self.assertEqual(
+            per_dest_queue._last_successful_stream_ordering,
+            event_2.internal_metadata.stream_ordering,
+        )
diff --git a/tests/rest/client/test_third_party_rules.py b/tests/rest/client/test_third_party_rules.py
index 3b99513707..753ecc8d16 100644
--- a/tests/rest/client/test_third_party_rules.py
+++ b/tests/rest/client/test_third_party_rules.py
@@ -941,18 +941,16 @@ class ThirdPartyRulesTestCase(unittest.FederatingHomeserverTestCase):
         just before associating and removing a 3PID to/from an account.
         """
         # Pretend to be a Synapse module and register both callbacks as mocks.
-        third_party_rules = self.hs.get_third_party_event_rules()
         on_add_user_third_party_identifier_callback_mock = Mock(
             return_value=make_awaitable(None)
         )
         on_remove_user_third_party_identifier_callback_mock = Mock(
             return_value=make_awaitable(None)
         )
-        third_party_rules._on_threepid_bind_callbacks.append(
-            on_add_user_third_party_identifier_callback_mock
-        )
-        third_party_rules._on_threepid_bind_callbacks.append(
-            on_remove_user_third_party_identifier_callback_mock
+        third_party_rules = self.hs.get_third_party_event_rules()
+        third_party_rules.register_third_party_rules_callbacks(
+            on_add_user_third_party_identifier=on_add_user_third_party_identifier_callback_mock,
+            on_remove_user_third_party_identifier=on_remove_user_third_party_identifier_callback_mock,
         )
 
         # Register an admin user.
@@ -1008,12 +1006,12 @@ class ThirdPartyRulesTestCase(unittest.FederatingHomeserverTestCase):
         when a user is deactivated and their third-party ID associations are deleted.
         """
         # Pretend to be a Synapse module and register both callbacks as mocks.
-        third_party_rules = self.hs.get_third_party_event_rules()
         on_remove_user_third_party_identifier_callback_mock = Mock(
             return_value=make_awaitable(None)
         )
-        third_party_rules._on_threepid_bind_callbacks.append(
-            on_remove_user_third_party_identifier_callback_mock
+        third_party_rules = self.hs.get_third_party_event_rules()
+        third_party_rules.register_third_party_rules_callbacks(
+            on_remove_user_third_party_identifier=on_remove_user_third_party_identifier_callback_mock,
         )
 
         # Register an admin user.
@@ -1039,6 +1037,9 @@ class ThirdPartyRulesTestCase(unittest.FederatingHomeserverTestCase):
         )
         self.assertEqual(channel.code, 200, channel.json_body)
 
+        # Check that the mock was not called on the act of adding a third-party ID.
+        on_remove_user_third_party_identifier_callback_mock.assert_not_called()
+
         # Now deactivate the user.
         channel = self.make_request(
             "PUT",
diff --git a/tests/test_utils/event_injection.py b/tests/test_utils/event_injection.py
index a6330ed840..9679904c33 100644
--- a/tests/test_utils/event_injection.py
+++ b/tests/test_utils/event_injection.py
@@ -102,3 +102,34 @@ async def create_event(
     context = await unpersisted_context.persist(event)
 
     return event, context
+
+
+async def mark_event_as_partial_state(
+    hs: synapse.server.HomeServer,
+    event_id: str,
+    room_id: str,
+) -> None:
+    """
+    (Falsely) mark an event as having partial state.
+
+    Naughty, but occasionally useful when checking that partial state doesn't
+    block something from happening.
+
+    If the event already has partial state, this insert will fail (event_id is unique
+    in this table).
+    """
+    store = hs.get_datastores().main
+    await store.db_pool.simple_upsert(
+        table="partial_state_rooms",
+        keyvalues={"room_id": room_id},
+        values={},
+        insertion_values={"room_id": room_id},
+    )
+
+    await store.db_pool.simple_insert(
+        table="partial_state_events",
+        values={
+            "room_id": room_id,
+            "event_id": event_id,
+        },
+    )
diff --git a/tests/test_visibility.py b/tests/test_visibility.py
index 2801a950a8..9ed330f554 100644
--- a/tests/test_visibility.py
+++ b/tests/test_visibility.py
@@ -63,7 +63,13 @@ class FilterEventsForServerTestCase(unittest.HomeserverTestCase):
 
         filtered = self.get_success(
             filter_events_for_server(
-                self._storage_controllers, "test_server", "hs", events_to_filter
+                self._storage_controllers,
+                "test_server",
+                "hs",
+                events_to_filter,
+                redact=True,
+                filter_out_erased_senders=True,
+                filter_out_remote_partial_state_events=True,
             )
         )
 
@@ -85,7 +91,13 @@ class FilterEventsForServerTestCase(unittest.HomeserverTestCase):
         self.assertEqual(
             self.get_success(
                 filter_events_for_server(
-                    self._storage_controllers, "remote_hs", "hs", [outlier]
+                    self._storage_controllers,
+                    "remote_hs",
+                    "hs",
+                    [outlier],
+                    redact=True,
+                    filter_out_erased_senders=True,
+                    filter_out_remote_partial_state_events=True,
                 )
             ),
             [outlier],
@@ -96,7 +108,13 @@ class FilterEventsForServerTestCase(unittest.HomeserverTestCase):
 
         filtered = self.get_success(
             filter_events_for_server(
-                self._storage_controllers, "remote_hs", "local_hs", [outlier, evt]
+                self._storage_controllers,
+                "remote_hs",
+                "local_hs",
+                [outlier, evt],
+                redact=True,
+                filter_out_erased_senders=True,
+                filter_out_remote_partial_state_events=True,
             )
         )
         self.assertEqual(len(filtered), 2, f"expected 2 results, got: {filtered}")
@@ -108,7 +126,13 @@ class FilterEventsForServerTestCase(unittest.HomeserverTestCase):
         # be redacted)
         filtered = self.get_success(
             filter_events_for_server(
-                self._storage_controllers, "other_server", "local_hs", [outlier, evt]
+                self._storage_controllers,
+                "other_server",
+                "local_hs",
+                [outlier, evt],
+                redact=True,
+                filter_out_erased_senders=True,
+                filter_out_remote_partial_state_events=True,
             )
         )
         self.assertEqual(filtered[0], outlier)
@@ -143,7 +167,13 @@ class FilterEventsForServerTestCase(unittest.HomeserverTestCase):
         # ... and the filtering happens.
         filtered = self.get_success(
             filter_events_for_server(
-                self._storage_controllers, "test_server", "local_hs", events_to_filter
+                self._storage_controllers,
+                "test_server",
+                "local_hs",
+                events_to_filter,
+                redact=True,
+                filter_out_erased_senders=True,
+                filter_out_remote_partial_state_events=True,
             )
         )