Improve thread partitioning for 2nd degree relations (#2165)

spec/integ/matrix-client-methods.spec.js

@@ -3,7 +3,6 @@ import { CRYPTO_ENABLED } from "../../src/client";
 import { MatrixEvent } from "../../src/models/event";
 import { Filter, MemoryStore, Room } from "../../src/matrix";
 import { TestClient } from "../TestClient";
-import { Thread } from "../../src/models/thread";
 
 describe("MatrixClient", function() {
     let client = null;
@@ -405,6 +404,11 @@ describe("MatrixClient", function() {
 
         it("copies pre-thread in-timeline vote events onto both timelines", function() {
             client.clientOpts = { experimentalThreadSupport: true };
+
+            const eventMessageInThread = buildEventMessageInThread();
+            const eventPollResponseReference = buildEventPollResponseReference();
+            const eventPollStartThreadRoot = buildEventPollStartThreadRoot();
+
             const events = [
                 eventMessageInThread,
                 eventPollResponseReference,
@@ -435,6 +439,11 @@ describe("MatrixClient", function() {
 
         it("copies pre-thread in-timeline reactions onto both timelines", function() {
             client.clientOpts = { experimentalThreadSupport: true };
+
+            const eventMessageInThread = buildEventMessageInThread();
+            const eventReaction = buildEventReaction();
+            const eventPollStartThreadRoot = buildEventPollStartThreadRoot();
+
             const events = [
                 eventMessageInThread,
                 eventReaction,
@@ -456,6 +465,11 @@ describe("MatrixClient", function() {
 
         it("copies post-thread in-timeline vote events onto both timelines", function() {
             client.clientOpts = { experimentalThreadSupport: true };
+
+            const eventPollResponseReference = buildEventPollResponseReference();
+            const eventMessageInThread = buildEventMessageInThread();
+            const eventPollStartThreadRoot = buildEventPollStartThreadRoot();
+
             const events = [
                 eventPollResponseReference,
                 eventMessageInThread,
@@ -475,119 +489,13 @@ describe("MatrixClient", function() {
             ]);
         });
 
-        it("copies post-thread in-thread vote events onto both timelines", function() {
-            client.clientOpts = { experimentalThreadSupport: true };
-
-            // Events for this test only, because we hack around with them
-            const eventMessageInThread2 = new MatrixEvent({
-                "age": 80098509,
-                "content": {
-                    "algorithm": "m.megolm.v1.aes-sha2",
-                    "ciphertext": "ENCRYPTEDSTUFF",
-                    "device_id": "XISFUZSKHH",
-                    "m.relates_to": {
-                        "event_id": "$AAA2ojbPmxb6x8ECetn45hmND6cRDcjgv-j-to9m7Vo",
-                        "m.in_reply_to": {
-                            "event_id": "$AAA2ojbPmxb6x8ECetn45hmND6cRDcjgv-j-to9m7Vo",
-                        },
-                        "rel_type": "io.element.thread",
-                    },
-                    "sender_key": "i3N3CtG/CD2bGB8rA9fW6adLYSDvlUhf2iuU73L65Vg",
-                    "session_id": "Ja11R/KG6ua0wdk8zAzognrxjio1Gm/RK2Gn6lFL804",
-                },
-                "event_id": "$AAAhKIGYowtBblVLkRimeIg8TcdjETnxhDPGfi6NpDg",
-                "origin_server_ts": 1643815466378,
-                "room_id": "!STrMRsukXHtqQdSeHa:matrix.org",
-                "sender": "@andybalaam-test1:matrix.org",
-                "type": "m.room.encrypted",
-                "unsigned": { "age": 80098509 },
-                "user_id": "@andybalaam-test1:matrix.org",
-            });
-
-            const eventPollStartThreadRoot2 = new MatrixEvent({
-                "age": 80108647,
-                "content": {
-                    "algorithm": "m.megolm.v1.aes-sha2",
-                    "ciphertext": "ENCRYPTEDSTUFF",
-                    "device_id": "XISFUZSKHH",
-                    "sender_key": "i3N3CtG/CD2bGB8rA9fW6adLYSDvlUhf2iuU73L65Vg",
-                    "session_id": "Ja11R/KG6ua0wdk8zAzognrxjio1Gm/RK2Gn6lFL804",
-                },
-                "event_id": "$AAA2ojbPmxb6x8ECetn45hmND6cRDcjgv-j-to9m7Vo",
-                "origin_server_ts": 1643815456240,
-                "room_id": "!STrMRsukXHtqQdSeHa:matrix.org",
-                "sender": "@andybalaam-test1:matrix.org",
-                "type": "m.room.encrypted",
-                "unsigned": { "age": 80108647 },
-                "user_id": "@andybalaam-test1:matrix.org",
-            });
-
-            const eventPollResponseReference2 = new MatrixEvent({
-                "age": 80098509,
-                "content": {
-                    "algorithm": "m.megolm.v1.aes-sha2",
-                    "ciphertext": "ENCRYPTEDSTUFF",
-                    "device_id": "XISFUZSKHH",
-                    "m.relates_to": {
-                        "event_id": "$AAA2ojbPmxb6x8ECetn45hmND6cRDcjgv-j-to9m7Vo",
-                        "rel_type": "m.reference",
-                    },
-                    "sender_key": "i3N3CtG/CD2bGB8rA9fW6adLYSDvlUhf2iuU73L65Vg",
-                    "session_id": "Ja11R/KG6ua0wdk8zAzognrxjio1Gm/RK2Gn6lFL804",
-                },
-                "event_id": "$AAAvpezvsF0cKgav3g8W-uEVS4WkDHgxbJZvL3uMR1g",
-                "origin_server_ts": 1643815458650,
-                "room_id": "!STrMRsukXHtqQdSeHa:matrix.org",
-                "sender": "@andybalaam-test1:matrix.org",
-                "type": "m.room.encrypted",
-                "unsigned": { "age": 80106237 },
-                "user_id": "@andybalaam-test1:matrix.org",
-            });
-
-            // When we react within a thread, sometimes the thread root
-            // has isThreadRelation === true, because thread is set on it,
-            // but threadId is not.
-            eventPollStartThreadRoot2.setThread(
-                new Thread(
-                    eventPollStartThreadRoot2,
-                    {
-                        client,
-                        room: new Room(),
-                    },
-                ),
-            );
-
-            const events = [
-                eventPollResponseReference2,
-                eventMessageInThread2,
-                eventPollStartThreadRoot2,
-            ];
-
-            const [timeline, threaded] = client.partitionThreadedEvents(events);
-
-            expect(timeline).toEqual([
-                eventPollResponseReference2,
-                // eventPollStartThreadRoot2,
-                // This is weird: by hacking the thread root to have an inconsistency
-                // between thread and threadId (which is what I have observed in the
-                // wild), we have persuaded the code that the thread root is actually
-                // within the thread, so it is not provided to the main timeline.
-                //
-                // This should go away when we fix this inconsistency.  When that
-                // happens, we should probably delete this test.
-            ]);
-
-            expect(threaded).toEqual([
-                withThreadId(
-                    eventPollResponseReference2, eventPollStartThreadRoot2.getId(),
-                ),
-                eventMessageInThread2,
-                eventPollStartThreadRoot2, // See note above for why this appears here.
-            ]);
-        });
-
         it("copies post-thread in-timeline reactions onto both timelines", function() {
             client.clientOpts = { experimentalThreadSupport: true };
+
+            const eventReaction = buildEventReaction();
+            const eventMessageInThread = buildEventMessageInThread();
+            const eventPollStartThreadRoot = buildEventPollStartThreadRoot();
+
             const events = [
                 eventReaction,
                 eventMessageInThread,
@@ -610,6 +518,19 @@ describe("MatrixClient", function() {
         it("sends room state events to the main timeline only", function() {
             client.clientOpts = { experimentalThreadSupport: true };
             // This is based on recording the events in a real room:
+
+            const eventMessageInThread = buildEventMessageInThread();
+            const eventPollResponseReference = buildEventPollResponseReference();
+            const eventPollStartThreadRoot = buildEventPollStartThreadRoot();
+            const eventRoomName = buildEventRoomName();
+            const eventEncryption = buildEventEncryption();
+            const eventGuestAccess = buildEventGuestAccess();
+            const eventHistoryVisibility = buildEventHistoryVisibility();
+            const eventJoinRules = buildEventJoinRules();
+            const eventPowerLevels = buildEventPowerLevels();
+            const eventMember = buildEventMember();
+            const eventCreate = buildEventCreate();
+
             const events = [
                 eventMessageInThread,
                 eventPollResponseReference,
@@ -655,7 +576,7 @@ function withThreadId(event, newThreadId) {
     return ret;
 }
 
-const eventMessageInThread = new MatrixEvent({
+const buildEventMessageInThread = () => new MatrixEvent({
     "age": 80098509,
     "content": {
         "algorithm": "m.megolm.v1.aes-sha2",
@@ -680,7 +601,7 @@ const eventMessageInThread = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventPollResponseReference = new MatrixEvent({
+const buildEventPollResponseReference = () => new MatrixEvent({
     "age": 80098509,
     "content": {
         "algorithm": "m.megolm.v1.aes-sha2",
@@ -702,7 +623,7 @@ const eventPollResponseReference = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventReaction = new MatrixEvent({
+const buildEventReaction = () => new MatrixEvent({
     "content": {
         "m.relates_to": {
             "event_id": "$VLS2ojbPmxb6x8ECetn45hmND6cRDcjgv-j-to9m7Vo",
@@ -721,7 +642,7 @@ const eventReaction = new MatrixEvent({
     "room_id": "!STrMRsukXHtqQdSeHa:matrix.org",
 });
 
-const eventPollStartThreadRoot = new MatrixEvent({
+const buildEventPollStartThreadRoot = () => new MatrixEvent({
     "age": 80108647,
     "content": {
         "algorithm": "m.megolm.v1.aes-sha2",
@@ -739,7 +660,7 @@ const eventPollStartThreadRoot = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventRoomName = new MatrixEvent({
+const buildEventRoomName = () => new MatrixEvent({
     "age": 80123249,
     "content": {
         "name": "1 poll, 1 vote, 1 thread",
@@ -754,7 +675,7 @@ const eventRoomName = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventEncryption = new MatrixEvent({
+const buildEventEncryption = () => new MatrixEvent({
     "age": 80123383,
     "content": {
         "algorithm": "m.megolm.v1.aes-sha2",
@@ -769,7 +690,7 @@ const eventEncryption = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventGuestAccess = new MatrixEvent({
+const buildEventGuestAccess = () => new MatrixEvent({
     "age": 80123473,
     "content": {
         "guest_access": "can_join",
@@ -784,7 +705,7 @@ const eventGuestAccess = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventHistoryVisibility = new MatrixEvent({
+const buildEventHistoryVisibility = () => new MatrixEvent({
     "age": 80123556,
     "content": {
         "history_visibility": "shared",
@@ -799,7 +720,7 @@ const eventHistoryVisibility = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventJoinRules = new MatrixEvent({
+const buildEventJoinRules = () => new MatrixEvent({
     "age": 80123696,
     "content": {
         "join_rule": "invite",
@@ -814,7 +735,7 @@ const eventJoinRules = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventPowerLevels = new MatrixEvent({
+const buildEventPowerLevels = () => new MatrixEvent({
     "age": 80124105,
     "content": {
         "ban": 50,
@@ -849,7 +770,7 @@ const eventPowerLevels = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventMember = new MatrixEvent({
+const buildEventMember = () => new MatrixEvent({
     "age": 80125279,
     "content": {
         "avatar_url": "mxc://matrix.org/aNtbVcFfwotudypZcHsIcPOc",
@@ -866,7 +787,7 @@ const eventMember = new MatrixEvent({
     "user_id": "@andybalaam-test1:matrix.org",
 });
 
-const eventCreate = new MatrixEvent({
+const buildEventCreate = () => new MatrixEvent({
     "age": 80126105,
     "content": {
         "creator": "@andybalaam-test1:matrix.org",

src/@types/event.ts

@@ -92,6 +92,7 @@ export enum EventType {
 export enum RelationType {
     Annotation = "m.annotation",
     Replace = "m.replace",
+    Reference = "m.reference",
     /**
      * Note, "io.element.thread" is hardcoded
      * Should be replaced with "m.thread" once MSC3440 lands

src/client.ts

@@ -3594,17 +3594,20 @@ export class MatrixClient extends EventEmitter {
             threadId = null;
         }
 
-        if (threadId && content["m.relates_to"]?.rel_type !== RelationType.Thread) {
+        // If we expect that an event is part of a thread but is missing the relation
+        // we need to add it manually, as well as the reply fallback
+        if (threadId && !content["m.relates_to"]?.rel_type) {
             content["m.relates_to"] = {
                 ...content["m.relates_to"],
                 "rel_type": RelationType.Thread,
                 "event_id": threadId,
             };
-
             const thread = this.getRoom(roomId)?.threads.get(threadId);
             if (thread) {
                 content["m.relates_to"]["m.in_reply_to"] = {
-                    "event_id": thread.replyToEvent.getId(),
+                    "event_id": thread.lastReply((ev: MatrixEvent) => {
+                        return ev.isThreadRelation && !ev.status;
+                    }),
                 };
             }
         }
@@ -3652,6 +3655,7 @@ export class MatrixClient extends EventEmitter {
         const thread = room?.threads.get(threadId);
         if (thread) {
             localEvent.setThread(thread);
+            localEvent.setThreadId(thread.id);
         }
 
         // if this is a relation or redaction of an event
@@ -9089,6 +9093,52 @@ export class MatrixClient extends EventEmitter {
         return threadRoots;
     }
 
+    private eventShouldLiveIn(event: MatrixEvent, room: Room, events: MatrixEvent[], roots: Set<string>): {
+        shouldLiveInRoom: boolean;
+        shouldLiveInThread: boolean;
+        threadId?: string;
+    } {
+        // A thread relation is always only shown in a thread
+        if (event.isThreadRelation) {
+            return {
+                shouldLiveInRoom: false,
+                shouldLiveInThread: true,
+                threadId: event.relationEventId,
+            };
+        }
+
+        const parentEventId = event.getAssociatedId();
+        const parentEvent = room?.findEventById(parentEventId) || events.find((mxEv: MatrixEvent) => (
+            mxEv.getId() === parentEventId
+        ));
+
+        // A reaction targetting the thread root needs to be routed to both the
+        // the main timeline and the associated thread
+        const targetingThreadRoot = parentEvent?.isThreadRoot || roots.has(event.relationEventId);
+        if (targetingThreadRoot) {
+            return {
+                shouldLiveInRoom: true,
+                shouldLiveInThread: true,
+                threadId: event.relationEventId,
+            };
+        }
+
+        // If the parent event also has an associated ID we want to re-run the
+        // computation for that parent event.
+        // In the case of the redaction of a reaction that targets a root event
+        // we want that redaction to be pushed to both timeline
+        if (parentEvent?.getAssociatedId()) {
+            return this.eventShouldLiveIn(parentEvent, room, events, roots);
+        } else {
+            // We've exhausted all scenarios, can safely assume that this event
+            // should live in the room timeline
+            return {
+                shouldLiveInRoom: true,
+                shouldLiveInThread: false,
+            };
+        }
+    }
+
     public partitionThreadedEvents(events: MatrixEvent[]): [MatrixEvent[], MatrixEvent[]] {
         // Indices to the events array, for readibility
         const ROOM = 0;
@@ -9097,35 +9147,22 @@ export class MatrixClient extends EventEmitter {
             const threadRoots = this.findThreadRoots(events);
             return events.reduce((memo, event: MatrixEvent) => {
                 const room = this.getRoom(event.getRoomId());
-                // An event should live in the thread timeline if
-                // - It's a reply in thread event
-                // - It's related to a reply in thread event
-                let shouldLiveInThreadTimeline = event.isThreadRelation;
-                if (!shouldLiveInThreadTimeline) {
-                    const parentEventId = event.parentEventId;
-                    const parentEvent = room?.findEventById(parentEventId) || events.find((mxEv: MatrixEvent) => {
-                        return mxEv.getId() === parentEventId;
-                    });
-                    const targetingThreadRoot = parentEvent?.isThreadRoot || threadRoots.has(event.relationEventId);
 
-                    if (targetingThreadRoot && !event.isThreadRelation && event.relationEventId) {
+                const {
-                        // If we refer to the thread root, we should be copied
+                    shouldLiveInRoom,
-                        // into the thread as well as the main timeline.
+                    shouldLiveInThread,
-                        // This happens for reactions, annotations, poll votes etc.
+                    threadId,
-                        const copiedEvent = event.toSnapshot();
+                } = this.eventShouldLiveIn(event, room, events, threadRoots);
 
-                        // The copied event is in this thread:
+                if (shouldLiveInRoom) {
-                        copiedEvent.setThreadId(parentEventId);
+                    memo[ROOM].push(event);
-                        memo[THREAD].push(copiedEvent);
-                    } else if (parentEvent?.isThreadRelation) {
-                        // If our parent is in a thread, we are in that
-                        // same thread too.  (E.g. if I reply within a thread.)
-                        shouldLiveInThreadTimeline = true;
-                        event.setThreadId(parentEvent.threadRootId);
                 }
+
+                if (shouldLiveInThread) {
+                    event.setThreadId(threadId);
+                    memo[THREAD].push(event);
                 }
-                const targetTimeline = shouldLiveInThreadTimeline ? THREAD : ROOM;
+
-                memo[targetTimeline].push(event);
                 return memo;
             }, [[], []]);
         } else {

src/models/event-timeline-set.ts

@@ -28,7 +28,6 @@ import { Room } from "./room";
 import { Filter } from "../filter";
 import { EventType, RelationType } from "../@types/event";
 import { RoomState } from "./room-state";
-import { Thread } from "./thread";
 
 // var DEBUG = false;
 const DEBUG = true;
@@ -159,17 +158,12 @@ export class EventTimelineSet extends EventEmitter {
      *
      * @throws If <code>opts.pendingEventOrdering</code> was not 'detached'
      */
-    public getPendingEvents(thread?: Thread): MatrixEvent[] {
+    public getPendingEvents(): MatrixEvent[] {
         if (!this.room || !this.displayPendingEvents) {
             return [];
         }
 
-        const pendingEvents = this.room.getPendingEvents(thread);
+        return this.room.getPendingEvents();
-        if (this.filter) {
-            return this.filter.filterRoomTimeline(pendingEvents);
-        } else {
-            return pendingEvents;
-        }
     }
     /**
      * Get the live timeline for this room.
@@ -756,7 +750,7 @@ export class EventTimelineSet extends EventEmitter {
      */
     public getRelationsForEvent(
         eventId: string,
-        relationType: RelationType,
+        relationType: RelationType | string,
         eventType: EventType | string,
     ): Relations | undefined {
         if (!this.unstableClientRelationAggregation) {
@@ -774,6 +768,17 @@ export class EventTimelineSet extends EventEmitter {
         return relationsWithRelType[eventType];
     }
 
+    public getAllRelationsEventForEvent(eventId: string): MatrixEvent[] {
+        const relationsForEvent = this.relations[eventId] || {};
+        const events = [];
+        for (const relationsRecord of Object.values(relationsForEvent)) {
+            for (const relations of Object.values(relationsRecord)) {
+                events.push(...relations.getRelations());
+            }
+        }
+        return events;
+    }
+
     /**
      * Set an event as the target event if any Relations exist for it already
      *

src/models/event.ts

@@ -512,8 +512,7 @@ export class MatrixEvent extends EventEmitter {
         if (relatesTo?.rel_type === RelationType.Thread) {
             return relatesTo.event_id;
         } else {
-            return this.threadId
+            return this.getThread()?.id || this.threadId;
-                || this.getThread()?.id;
         }
     }
 
@@ -537,10 +536,6 @@ export class MatrixEvent extends EventEmitter {
         return !!threadDetails || (this.getThread()?.id === this.getId());
     }
 
-    public get parentEventId(): string {
-        return this.replyEventId || this.relationEventId;
-    }
-
     public get replyEventId(): string {
         // We're prefer ev.getContent() over ev.getWireContent() to make sure
         // we grab the latest edit with potentially new relations. But we also
@@ -1427,7 +1422,9 @@ export class MatrixEvent extends EventEmitter {
      */
     public getAssociatedId(): string | undefined {
         const relation = this.getRelation();
-        if (relation) {
+        if (this.replyEventId) {
+            return this.replyEventId;
+        } else if (relation) {
             return relation.event_id;
         } else if (this.isRedaction()) {
             return this.event.redacts;
@@ -1561,6 +1558,7 @@ export class MatrixEvent extends EventEmitter {
      */
     public setThread(thread: Thread): void {
         this.thread = thread;
+        this.setThreadId(thread.id);
         this.reEmitter.reEmit(thread, [ThreadEvent.Ready, ThreadEvent.Update]);
     }
 

src/models/relations.ts

@@ -171,11 +171,11 @@ export class Relations extends EventEmitter {
      * @return {Array}
      * Relation events in insertion order.
      */
-    public getRelations() {
+    public getRelations(): MatrixEvent[] {
         return [...this.relations];
     }
 
-    private addAnnotationToAggregation(event: MatrixEvent) {
+    private addAnnotationToAggregation(event: MatrixEvent): void {
         const { key } = event.getRelation();
         if (!key) {
             return;
@@ -204,7 +204,7 @@ export class Relations extends EventEmitter {
         eventsFromSender.add(event);
     }
 
-    private removeAnnotationFromAggregation(event: MatrixEvent) {
+    private removeAnnotationFromAggregation(event: MatrixEvent): void {
         const { key } = event.getRelation();
         if (!key) {
             return;
@@ -240,7 +240,7 @@ export class Relations extends EventEmitter {
      * @param {MatrixEvent} redactedEvent
      * The original relation event that is about to be redacted.
      */
-    private onBeforeRedaction = async (redactedEvent: MatrixEvent) => {
+    private onBeforeRedaction = async (redactedEvent: MatrixEvent): Promise<void> => {
         if (!this.relations.has(redactedEvent)) {
             return;
         }

src/models/room.ts

@@ -512,16 +512,14 @@ export class Room extends EventEmitter {
      *
      * @throws If <code>opts.pendingEventOrdering</code> was not 'detached'
      */
-    public getPendingEvents(thread?: Thread): MatrixEvent[] {
+    public getPendingEvents(): MatrixEvent[] {
         if (this.opts.pendingEventOrdering !== PendingEventOrdering.Detached) {
             throw new Error(
                 "Cannot call getPendingEvents with pendingEventOrdering == " +
                 this.opts.pendingEventOrdering);
         }
 
-        return this.pendingEventList.filter(event => {
+        return this.pendingEventList;
-            return !thread || thread.id === event.threadRootId;
-        });
     }
 
     /**
@@ -1358,7 +1356,7 @@ export class Room extends EventEmitter {
         } else if (event.isThreadRoot) {
             return this.threads.get(event.getId());
         } else {
-            const parentEvent = this.findEventById(event.parentEventId);
+            const parentEvent = this.findEventById(event.getAssociatedId());
             return this.findThreadForEvent(parentEvent);
         }
     }
@@ -1396,21 +1394,15 @@ export class Room extends EventEmitter {
             }
         }
 
-        if (event.getUnsigned().transaction_id) {
-            const existingEvent = this.txnToEvent[event.getUnsigned().transaction_id];
-            if (existingEvent) {
-                // remote echo of an event we sent earlier
-                this.handleRemoteEcho(event, existingEvent);
-                return;
-            }
-        }
-
         this.emit(ThreadEvent.Update, thread);
     }
 
-    public createThread(rootEvent: MatrixEvent, events?: MatrixEvent[]): Thread | undefined {
+    public createThread(rootEvent: MatrixEvent, events: MatrixEvent[] = []): Thread | undefined {
+        const tl = this.getTimelineForEvent(rootEvent.getId());
+        const relatedEvents = tl?.getTimelineSet().getAllRelationsEventForEvent(rootEvent.getId()) ?? [];
+
         const thread = new Thread(rootEvent, {
-            initialEvents: events,
+            initialEvents: events.concat(relatedEvents),
             room: this,
             client: this.client,
         });
@@ -1564,8 +1556,7 @@ export class Room extends EventEmitter {
         EventTimeline.setEventMetadata(event, this.getLiveTimeline().getState(EventTimeline.FORWARDS), false);
 
         this.txnToEvent[txnId] = event;
-        const thread = this.findThreadForEvent(event);
+        if (this.opts.pendingEventOrdering === PendingEventOrdering.Detached) {
-        if (this.opts.pendingEventOrdering === PendingEventOrdering.Detached && !thread) {
             if (this.pendingEventList.some((e) => e.status === EventStatus.NOT_SENT)) {
                 logger.warn("Setting event as NOT_SENT due to messages in the same state");
                 event.setStatus(EventStatus.NOT_SENT);
@@ -1581,8 +1572,7 @@ export class Room extends EventEmitter {
 
             if (event.isRedaction()) {
                 const redactId = event.event.redacts;
-                let redactedEvent = this.pendingEventList &&
+                let redactedEvent = this.pendingEventList?.find(e => e.getId() === redactId);
-                    this.pendingEventList.find(e => e.getId() === redactId);
                 if (!redactedEvent) {
                     redactedEvent = this.findEventById(redactId);
                 }
@@ -1591,9 +1581,6 @@ export class Room extends EventEmitter {
                     this.emit("Room.redaction", event, this);
                 }
             }
-        } else {
-            if (thread) {
-                thread.addEvent(event, false);
         } else {
             for (let i = 0; i < this.timelineSets.length; i++) {
                 const timelineSet = this.timelineSets[i];
@@ -1608,7 +1595,6 @@ export class Room extends EventEmitter {
                 }
             }
         }
-        }
 
         this.emit("Room.localEchoUpdated", event, this, null, null);
     }
@@ -1666,7 +1652,9 @@ export class Room extends EventEmitter {
         const thread = this.findThreadForEvent(event);
         if (thread) {
             thread.timelineSet.aggregateRelations(event);
-        } else {
+        }
+
+        if (thread?.id === event.getAssociatedId() || !thread) {
             // TODO: We should consider whether this means it would be a better
             // design to lift the relations handling up to the room instead.
             for (let i = 0; i < this.timelineSets.length; i++) {
@@ -1682,6 +1670,10 @@ export class Room extends EventEmitter {
         }
     }
 
+    public getEventForTxnId(txnId: string): MatrixEvent {
+        return this.txnToEvent[txnId];
+    }
+
     /**
      * Deal with the echo of a message we sent.
      *
@@ -1696,7 +1688,7 @@ export class Room extends EventEmitter {
      * @fires module:client~MatrixClient#event:"Room.localEchoUpdated"
      * @private
      */
-    private handleRemoteEcho(remoteEvent: MatrixEvent, localEvent: MatrixEvent): void {
+    public handleRemoteEcho(remoteEvent: MatrixEvent, localEvent: MatrixEvent): void {
         const oldEventId = localEvent.getId();
         const newEventId = remoteEvent.getId();
         const oldStatus = localEvent.status;
@@ -1721,7 +1713,9 @@ export class Room extends EventEmitter {
         const thread = this.findThreadForEvent(remoteEvent);
         if (thread) {
             thread.timelineSet.handleRemoteEcho(localEvent, oldEventId, newEventId);
-        } else {
+        }
+
+        if (thread?.id === remoteEvent.getAssociatedId() || !thread) {
             for (let i = 0; i < this.timelineSets.length; i++) {
                 const timelineSet = this.timelineSets[i];
 
@@ -1791,7 +1785,8 @@ export class Room extends EventEmitter {
             const thread = this.findThreadForEvent(event);
             if (thread) {
                 thread.timelineSet.replaceEventId(oldEventId, newEventId);
-            } else {
+            }
+            if (thread?.id === event.getAssociatedId() || !thread) {
                 // if the event was already in the timeline (which will be the case if
                 // opts.pendingEventOrdering==chronological), we need to update the
                 // timeline map.

src/models/thread.ts

@@ -113,6 +113,27 @@ export class Thread extends TypedEventEmitter<ThreadEvent> {
         return this.room.getLiveTimeline().getState(EventTimeline.FORWARDS);
     }
 
+    private addEventToTimeline(event: MatrixEvent, toStartOfTimeline: boolean): void {
+        if (event.getUnsigned().transaction_id) {
+            const existingEvent = this.room.getEventForTxnId(event.getUnsigned().transaction_id);
+            if (existingEvent) {
+                // remote echo of an event we sent earlier
+                this.room.handleRemoteEcho(event, existingEvent);
+                return;
+            }
+        }
+
+        if (!this.findEventById(event.getId())) {
+            this.timelineSet.addEventToTimeline(
+                event,
+                this.liveTimeline,
+                toStartOfTimeline,
+                false,
+                this.roomState,
+            );
+        }
+    }
+
     /**
      * Add an event to the thread and updates
      * the tail/root references if needed
@@ -123,36 +144,20 @@ export class Thread extends TypedEventEmitter<ThreadEvent> {
         // Add all incoming events to the thread's timeline set when there's
         // no server support
         if (!this.hasServerSideSupport) {
-            if (this.timelineSet.findEventById(event.getId())) {
-                return;
-            }
-
             // all the relevant membership info to hydrate events with a sender
             // is held in the main room timeline
             // We want to fetch the room state from there and pass it down to this thread
             // timeline set to let it reconcile an event with its relevant RoomMember
 
             event.setThread(this);
-            this.timelineSet.addEventToTimeline(
+            this.addEventToTimeline(event, toStartOfTimeline);
-                event,
-                this.liveTimeline,
-                toStartOfTimeline,
-                false,
-                this.roomState,
-            );
 
             await this.client.decryptEventIfNeeded(event, {});
         }
 
         if (this.hasServerSideSupport && this.initialEventsFetched) {
-            if (event.localTimestamp > this.lastReply().localTimestamp && !this.findEventById(event.getId())) {
+            if (event.localTimestamp > this.lastReply().localTimestamp) {
-                this.timelineSet.addEventToTimeline(
+                this.addEventToTimeline(event, false);
-                    event,
-                    this.liveTimeline,
-                    false,
-                    false,
-                    this.roomState,
-                );
             }
         }
 

src/sync.ts

@@ -1727,7 +1727,7 @@ export class SyncApi {
     // extractRelatedEvents(event: MatrixEvent, events: MatrixEvent[], relatedEvents: MatrixEvent[] = []): MatrixEvent[] {
     //     relatedEvents.push(event);
 
-    //     const parentEventId = event.parentEventId;
+    //     const parentEventId = event.getAssociatedId();
     //     const parentEventIndex = events.findIndex(event => event.getId() === parentEventId);
 
     //     if (parentEventIndex > -1) {