diff --git a/spec/integ/matrix-client-event-timeline.spec.ts b/spec/integ/matrix-client-event-timeline.spec.ts
index c7083db1968..49e472e76aa 100644
--- a/spec/integ/matrix-client-event-timeline.spec.ts
+++ b/spec/integ/matrix-client-event-timeline.spec.ts
@@ -29,6 +29,7 @@ import {
     PendingEventOrdering,
     RelationType,
     Room,
+    UNSIGNED_THREAD_ID_FIELD,
 } from "../../src/matrix";
 import { logger } from "../../src/logger";
 import { encodeParams, encodeUri, QueryDict, replaceParam } from "../../src/utils";
@@ -52,12 +53,16 @@ const withoutRoomId = (e: Partial<IEvent>): Partial<IEvent> => {
 /**
  * Our httpBackend only allows matching calls if we have the exact same query, in the exact same order
  * This method allows building queries with the exact same parameter order as the fetchRelations method in client
+ * @param client Matrix client to mock the request for
  * @param params query parameters
  */
-const buildRelationPaginationQuery = (params: QueryDict): string => {
+const buildRelationPaginationQuery = (client: MatrixClient, params: QueryDict): string => {
     if (Thread.hasServerSideFwdPaginationSupport === FeatureSupport.Experimental) {
         params = replaceParam("dir", "org.matrix.msc3715.dir", params);
     }
+    if (client.canSupport.get(Feature.RelationsRecursion) === ServerSupport.Unstable) {
+        params = replaceParam("recurse", "org.matrix.msc3981.recurse", params);
+    }
     return "?" + encodeParams(params).toString();
 };
 
@@ -179,6 +184,9 @@ const THREAD_REPLY = utils.mkEvent({
             event_id: THREAD_ROOT.event_id,
         },
     },
+    unsigned: {
+        [UNSIGNED_THREAD_ID_FIELD.name]: THREAD_ROOT.event_id,
+    },
     event: false,
 });
 
@@ -622,7 +630,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Backward, limit: 1 }),
+                        buildRelationPaginationQuery(client, { dir: Direction.Backward, limit: 1 }),
                 )
                 .respond(200, function () {
                     return {
@@ -1020,6 +1028,87 @@ describe("MatrixClient event timelines", function () {
             ]);
         });
 
+        it("should use recursive relations to paginate thread timelines", async function () {
+            function respondToThreads(
+                response = {
+                    chunk: [THREAD_ROOT],
+                    state: [],
+                    next_batch: null,
+                },
+            ): ExpectedHttpRequest {
+                const request = httpBackend.when(
+                    "GET",
+                    encodeUri("/_matrix/client/v1/rooms/$roomId/threads", {
+                        $roomId: roomId,
+                    }),
+                );
+                request.respond(200, response);
+                return request;
+            }
+
+            function respondToThread(
+                root: Partial<IEvent>,
+                replies: Partial<IEvent>[],
+                limit?: number,
+            ): ExpectedHttpRequest {
+                const request = httpBackend.when(
+                    "GET",
+                    "/_matrix/client/v1/rooms/!foo%3Abar/relations/" +
+                        encodeURIComponent(root.event_id!) +
+                        buildRelationPaginationQuery(client, {
+                            dir: Direction.Backward,
+                            limit: limit,
+                            recurse: true,
+                        }),
+                );
+                request.respond(200, function () {
+                    return {
+                        original_event: root,
+                        chunk: replies,
+                        // no next batch as this is the oldest end of the timeline
+                    };
+                });
+                return request;
+            }
+
+            function respondToEvent(event: Partial<IEvent> = THREAD_ROOT): ExpectedHttpRequest {
+                const request = httpBackend.when(
+                    "GET",
+                    encodeUri("/_matrix/client/r0/rooms/$roomId/event/$eventId", {
+                        $roomId: roomId,
+                        $eventId: event.event_id!,
+                    }),
+                );
+                request.respond(200, event);
+                return request;
+            }
+
+            // Setup
+            // @ts-ignore
+            client.clientOpts.threadSupport = true;
+            Thread.setServerSideSupport(FeatureSupport.Stable);
+            Thread.setServerSideListSupport(FeatureSupport.Stable);
+            Thread.setServerSideFwdPaginationSupport(FeatureSupport.Stable);
+            client.canSupport.set(Feature.RelationsRecursion, ServerSupport.Unstable);
+            const room = client.getRoom(roomId)!;
+            await room!.createThreadsTimelineSets();
+            respondToThreads();
+            respondToThreads();
+            respondToEvent();
+            respondToEvent();
+            respondToEvent();
+            respondToEvent();
+            respondToEvent();
+            respondToThread(THREAD_ROOT, [THREAD_REPLY], 1);
+            await flushHttp(room.fetchRoomThreads());
+            const thread = room.getThread(THREAD_ROOT.event_id!)!;
+            expect(thread).not.toBeNull();
+            respondToThread(THREAD_ROOT, [THREAD_REPLY], 1);
+            expect(thread.timelineSet.thread).toBe(thread);
+            expect(Thread.hasServerSideSupport).toBe(FeatureSupport.Stable);
+            await flushHttp(client.getLatestTimeline(thread.timelineSet));
+        });
+
         it("should create threads for thread roots discovered", function () {
             const room = client.getRoom(roomId)!;
             const timelineSet = room.getTimelineSets()[0];
@@ -1091,6 +1180,9 @@ describe("MatrixClient event timelines", function () {
                     event_id: THREAD_ROOT.event_id,
                 },
             },
+            unsigned: {
+                [UNSIGNED_THREAD_ID_FIELD.name]: THREAD_ROOT.event_id,
+            },
             event: true,
         });
         THREAD_REPLY2.localTimestamp += 1000;
@@ -1109,6 +1201,9 @@ describe("MatrixClient event timelines", function () {
                     event_id: THREAD_ROOT.event_id,
                 },
             },
+            unsigned: {
+                [UNSIGNED_THREAD_ID_FIELD.name]: THREAD_ROOT.event_id,
+            },
             event: true,
         });
         THREAD_REPLY3.localTimestamp += 2000;
@@ -1182,6 +1277,9 @@ describe("MatrixClient event timelines", function () {
                     event_id: THREAD_ROOT.event_id,
                 },
             },
+            unsigned: {
+                [UNSIGNED_THREAD_ID_FIELD.name]: THREAD_ROOT.event_id,
+            },
             event: true,
         });
         THREAD_REPLY2.localTimestamp += 1000;
@@ -1214,6 +1312,9 @@ describe("MatrixClient event timelines", function () {
                     event_id: THREAD_ROOT.event_id,
                 },
             },
+            unsigned: {
+                [UNSIGNED_THREAD_ID_FIELD.name]: THREAD_ROOT.event_id,
+            },
             event: true,
         });
         THREAD_REPLY3.localTimestamp += 3000;
@@ -1254,9 +1355,7 @@ describe("MatrixClient event timelines", function () {
                 "GET",
                 "/_matrix/client/v1/rooms/!foo%3Abar/relations/" +
                     encodeURIComponent(THREAD_ROOT_UPDATED.event_id!) +
-                    "/" +
-                    encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                    buildRelationPaginationQuery({
+                    buildRelationPaginationQuery(client, {
                         dir: Direction.Backward,
                         limit: 3,
                         recurse: true,
@@ -1904,7 +2003,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Backward, limit: 1 }),
+                        buildRelationPaginationQuery(client, { dir: Direction.Backward, limit: 1 }),
                 )
                 .respond(200, function () {
                     return {
@@ -1957,7 +2056,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({
+                        buildRelationPaginationQuery(client, {
                             dir: Direction.Backward,
                             from: "start_token",
                         }),
@@ -1974,7 +2073,7 @@ describe("MatrixClient event timelines", function () {
                         encodeURIComponent(THREAD_ROOT.event_id!) +
                         "/" +
                         encodeURIComponent(THREAD_RELATION_TYPE.name) +
-                        buildRelationPaginationQuery({ dir: Direction.Forward, from: "end_token" }),
+                        buildRelationPaginationQuery(client, { dir: Direction.Forward, from: "end_token" }),
                 )
                 .respond(200, function () {
                     return {
diff --git a/spec/unit/room.spec.ts b/spec/unit/room.spec.ts
index 2ed44dffd7b..4e2292810eb 100644
--- a/spec/unit/room.spec.ts
+++ b/spec/unit/room.spec.ts
@@ -42,6 +42,7 @@ import {
     RelationType,
     RoomEvent,
     RoomMember,
+    UNSIGNED_THREAD_ID_FIELD,
 } from "../../src";
 import { EventTimeline } from "../../src/models/event-timeline";
 import { NotificationCountType, Room } from "../../src/models/room";
@@ -133,6 +134,9 @@ describe("Room", function () {
                         "rel_type": "m.thread",
                     },
                 },
+                unsigned: {
+                    [UNSIGNED_THREAD_ID_FIELD.name]: root.getId(),
+                },
             },
             room.client,
         );
diff --git a/src/client.ts b/src/client.ts
index caca1a89a82..9bd8d7e7421 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -151,6 +151,7 @@ import {
     UNSTABLE_MSC3088_PURPOSE,
     UNSTABLE_MSC3089_TREE_SUBTYPE,
     MSC3912_RELATION_BASED_REDACTIONS_PROP,
+    UNSIGNED_THREAD_ID_FIELD,
 } from "./@types/event";
 import { IdServerUnbindResult, IImageInfo, Preset, Visibility } from "./@types/partials";
 import { EventMapper, eventMapperFor, MapperOpts } from "./event-mapper";
@@ -5750,18 +5751,19 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
                     throw new Error("could not get thread timeline: not a thread timeline");
                 }
 
+                const relType = recurse ? null : THREAD_RELATION_TYPE.name;
                 const thread = timelineSet.thread;
                 const resOlder: IRelationsResponse = await this.fetchRelations(
                     timelineSet.room.roomId,
                     thread.id,
-                    THREAD_RELATION_TYPE.name,
+                    relType,
                     null,
                     { dir: Direction.Backward, from: res.start, recurse: recurse || undefined },
                 );
                 const resNewer: IRelationsResponse = await this.fetchRelations(
                     timelineSet.room.roomId,
                     thread.id,
-                    THREAD_RELATION_TYPE.name,
+                    relType,
                     null,
                     { dir: Direction.Forward, from: res.end, recurse: recurse || undefined },
                 );
@@ -5774,6 +5776,10 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
                     ...resOlder.chunk.map(mapper),
                 ];
                 for (const event of events) {
+                    event.setUnsigned({
+                        ...event.getUnsigned(),
+                        [UNSIGNED_THREAD_ID_FIELD.name]: timelineSet.thread.id,
+                    });
                     await timelineSet.thread?.processEvent(event);
                 }
 
@@ -5805,21 +5811,20 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
                 // XXX: workaround for https://github.com/vector-im/element-meta/issues/150
 
                 const thread = timelineSet.thread;
+                const relType = recurse ? null : THREAD_RELATION_TYPE.name;
 
-                const resOlder = await this.fetchRelations(
-                    timelineSet.room.roomId,
-                    thread.id,
-                    THREAD_RELATION_TYPE.name,
-                    null,
-                    { dir: Direction.Backward, from: res.start, recurse: recurse || undefined },
-                );
+                const resOlder = await this.fetchRelations(timelineSet.room.roomId, thread.id, relType, null, {
+                    dir: Direction.Backward,
+                    from: res.start,
+                    recurse: recurse || undefined,
+                });
                 const eventsNewer: IEvent[] = [];
                 let nextBatch: Optional<string> = res.end;
                 while (nextBatch) {
                     const resNewer: IRelationsResponse = await this.fetchRelations(
                         timelineSet.room.roomId,
                         thread.id,
-                        THREAD_RELATION_TYPE.name,
+                        relType,
                         null,
                         { dir: Direction.Forward, from: nextBatch, recurse: recurse || undefined },
                     );
@@ -5835,6 +5840,12 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
                     ...resOlder.chunk.map(mapper),
                 ];
                 for (const event of events) {
+                    // Fallback to set unsigned thread id if the server doesn't support it
+                    // We know the thread id because we just requested this event via /relations
+                    event.setUnsigned({
+                        [UNSIGNED_THREAD_ID_FIELD.name]: timelineSet.thread.id,
+                        ...event.getUnsigned(),
+                    });
                     await timelineSet.thread?.processEvent(event);
                 }
 
@@ -5881,10 +5892,12 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         }
 
         let event;
+        const recurse = this.canSupport.get(Feature.RelationsRecursion) !== ServerSupport.Unsupported;
+        const relType = recurse ? null : THREAD_RELATION_TYPE.name;
         if (timelineSet.threadListType !== null) {
             const res = await this.createThreadListMessagesRequest(
                 timelineSet.room.roomId,
-                null,
+                relType,
                 1,
                 Direction.Backward,
                 timelineSet.threadListType,
@@ -5893,14 +5906,18 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             event = res.chunk?.[0];
         } else if (timelineSet.thread && Thread.hasServerSideSupport) {
             const recurse = this.canSupport.get(Feature.RelationsRecursion) !== ServerSupport.Unsupported;
-            const res = await this.fetchRelations(
-                timelineSet.room.roomId,
-                timelineSet.thread.id,
-                THREAD_RELATION_TYPE.name,
-                null,
-                { dir: Direction.Backward, limit: 1, recurse: recurse || undefined },
-            );
+            const res = await this.fetchRelations(timelineSet.room.roomId, timelineSet.thread.id, relType, null, {
+                dir: Direction.Backward,
+                limit: 1,
+                recurse: recurse || undefined,
+            });
             event = res.chunk?.[0];
+            // Fallback to set unsigned thread id if the server doesn't support it
+            // We know the thread id because we just requested this event via /relations
+            event.unsigned = {
+                [UNSIGNED_THREAD_ID_FIELD.name]: timelineSet.thread.id,
+                ...event.unsigned,
+            };
         } else {
             const messagesPath = utils.encodeUri("/rooms/$roomId/messages", {
                 $roomId: timelineSet.room.roomId,
@@ -6174,7 +6191,8 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
             }
 
             const recurse = this.canSupport.get(Feature.RelationsRecursion) !== ServerSupport.Unsupported;
-            promise = this.fetchRelations(eventTimeline.getRoomId() ?? "", thread.id, THREAD_RELATION_TYPE.name, null, {
+            const relType = recurse ? null : THREAD_RELATION_TYPE.name;
+            promise = this.fetchRelations(eventTimeline.getRoomId() ?? "", thread.id, relType, null, {
                 dir,
                 limit: opts.limit,
                 from: token ?? undefined,
@@ -6186,6 +6204,12 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
 
                     // Process latest events first
                     for (const event of matrixEvents.slice().reverse()) {
+                        // Fallback to set unsigned thread id if the server doesn't support it
+                        // We know the thread id because we just requested this event via /relations
+                        event.setUnsigned({
+                            [UNSIGNED_THREAD_ID_FIELD.name]: thread.id,
+                            ...event.getUnsigned(),
+                        });
                         await thread?.processEvent(event);
                         const sender = event.getSender()!;
                         if (!backwards || thread?.getEventReadUpTo(sender) === null) {