From ebcd8ec926c2026e07fd8fac82a044bbed0f27db Mon Sep 17 00:00:00 2001
From: Jared Vititoe <jjvititoe1@gmail.com>
Date: Thu, 2 Jul 2026 14:30:33 -0400
Subject: [PATCH] feat(ux): forward to multiple rooms + live bookmark previews
 (P6-3)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Forward: checkbox multi-select room picker + "Send to N rooms" batch send
(Promise.allSettled). Full success auto-closes; partial failure keeps the dialog
open with a "Forwarded to X/N — failed: …" summary and prunes the selection to
only the failures (retry won't duplicate to already-sent rooms). Content builder
extracted to a unit-tested forwardContent.ts (edit-forwarding, reply-strip,
undecryptable-refused; 4 tests).

Bookmarks: BookmarksPanel resolves each saved message's live event (useRoomEvent)
so previews reflect edits and show a deleted indicator for redactions; the stored
snapshot stays as the fallback while loading, on fetch failure, or after leaving
the room. Stored bookmark shape unchanged.

Gates: tsc/eslint/prettier clean, build OK, 665 tests. Reviewed (dup-resend on
retry + Checkbox readOnly fixed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 LOTUS_BUGS.md                                 |   1 +
 LOTUS_FEATURES.md                             |   8 +
 LOTUS_TODO.md                                 |   8 +-
 src/app/features/bookmarks/BookmarksPanel.tsx |  72 +++++-
 .../room/message/ForwardMessageDialog.tsx     | 233 ++++++++++--------
 .../room/message/forwardContent.test.ts       | 138 +++++++++++
 .../features/room/message/forwardContent.ts   |  39 +++
 7 files changed, 391 insertions(+), 108 deletions(-)
 create mode 100644 src/app/features/room/message/forwardContent.test.ts
 create mode 100644 src/app/features/room/message/forwardContent.ts

diff --git a/LOTUS_BUGS.md b/LOTUS_BUGS.md
index 9e1f146df..8f68d695a 100644
--- a/LOTUS_BUGS.md
+++ b/LOTUS_BUGS.md
@@ -44,6 +44,7 @@ Implemented and gate-green; confirm each per `LOTUS_TESTING.md`, then delete the
 | P3-4 | Accessibility compliance pass (collapsed-msg SR sender, form/overlay labels, typing announce, focus-return, `?` help, jsx-a11y CI gate) | `message/*`, `RoomViewTyping`, `features/shortcuts/*`, `eslint.config.mjs` | LOTUS_TESTING §P — axe-core + VoiceOver/NVDA on the golden path                                                                                                                           |
 | P6-1 | Desktop Linux parity (no-sleep in calls, launcher badge), autostart toggle, tray Do-Not-Disturb                                         | `native/power.rs`, `lib.rs`, `useTauriDnd`, `General.tsx`                  | Linux desktop: no display sleep during a call; tray DND silences notifications; launch-on-login persists; Unity badge (Ubuntu); DND toggle polarity                                       |
 | P6-2 | EC deafen/screenshare-audio-mute via `io.lotus.set_deafen` (retires the `<audio>.muted` iframe hack)                                    | fork `lotusDeafen.ts`, cinny `CallControl.ts`                              | AFTER publish+pin-bump: deafen silences remote audio + survives a reconnect / new screenshare / late joiner (the cases the DOM hack failed); screenshare-audio-mute toggles independently |
+| P6-3 | Forward-to-multiple-rooms (multi-select + partial-failure summary) + live bookmark previews (edits/redactions, snapshot fallback)       | `ForwardMessageDialog.tsx`+`forwardContent.ts`, `BookmarksPanel.tsx`       | forward one msg to 3 rooms (incl. 1 you cannot post to = partial summary); bookmark then edit shows edited; redact shows deleted; leave room shows snapshot                               |
 
 **Verified working in live testing (2026-06):** A2, B1–B4, C1, C3, D (mic/camera/deafen/screenshare/fullscreen/more-menu/PiP). Denoise quality in D is still poor — tracked under the denoise project, not a regression.
 
diff --git a/LOTUS_FEATURES.md b/LOTUS_FEATURES.md
index f97f68339..1eac843e6 100644
--- a/LOTUS_FEATURES.md
+++ b/LOTUS_FEATURES.md
@@ -905,6 +905,14 @@ Hook: `src/app/hooks/useUserNotes.ts`
 
 ## UX & Composer
 
+### Forward to Multiple Rooms (P6-3)
+
+The Forward Message dialog is a checkbox multi-select: pick any number of rooms (search + select persist across queries) and **"Send to N rooms"** forwards in one batch (`Promise.allSettled`). Full success auto-closes; a partial failure keeps the dialog open with a "Forwarded to X/N — failed: …" summary. The forwarded content (latest edit via `m.new_content`, reply-quote stripped, undecryptable refused) is built by the shared, unit-tested `forwardContent.ts`.
+
+### Live Bookmark Previews (P6-3)
+
+`BookmarksPanel` resolves each saved message's **live event** (`useRoomEvent`) so previews reflect **edits** and show a **deleted** indicator for redactions, instead of the save-time snapshot. The stored snapshot (`previewText`) remains the fallback while loading, on fetch failure, or when you've **left the room**.
+
 ### Message Length Counter
 
 A character count indicator is shown in the composer when `charCount > 0`. The counter resets to zero when switching rooms.
diff --git a/LOTUS_TODO.md b/LOTUS_TODO.md
index 70aa9c70c..4af28ded9 100644
--- a/LOTUS_TODO.md
+++ b/LOTUS_TODO.md
@@ -541,7 +541,13 @@ Replace cinny's fragile iframe-`contentDocument` reaches with proper `io.lotus.*
 - Retire the `useCallSpeakers` DOM-scrape fallback once `io.lotus.call_state` is verified.
   Fork commits are local (coordinator); publishing needs the user's npm token.
 
-### [ ] P6-3 · Web UX wins (from the audit ADD list)
+### [~] P6-3 · Web UX wins - DONE (2026-07): forward multi-select + live bookmark previews
+
+**Shipped:** Forward Message multi-select (checkbox rooms + "Send to N", batch `Promise.allSettled` with partial-failure summary; content builder extracted to tested `forwardContent.ts`). Live bookmark previews (`BookmarksPanel` renders the live event via `useRoomEvent` - edits + redactions - snapshot as fallback / left-room). Both `lotus`, gate-green (665 tests).
+
+_Original scope:_
+
+### [ ] P6-3-orig · Web UX wins (from the audit ADD list)
 
 - **Forward to multiple rooms** — multi-select (checkbox + "Send to N") in `ForwardMessageDialog` (currently one room per open, capped at 60).
 - **Live bookmark previews** — `BookmarksPanel` shows a stale snapshot captured at save time; resolve live from the event when cached (edits/redactions), fall back to the snapshot.
diff --git a/src/app/features/bookmarks/BookmarksPanel.tsx b/src/app/features/bookmarks/BookmarksPanel.tsx
index f0ff23bc3..05b56c11e 100644
--- a/src/app/features/bookmarks/BookmarksPanel.tsx
+++ b/src/app/features/bookmarks/BookmarksPanel.tsx
@@ -1,4 +1,5 @@
-import React, { ChangeEvent, useCallback, useEffect, useState } from 'react';
+import React, { ChangeEvent, ReactNode, useCallback, useEffect, useState } from 'react';
+import { Room } from 'matrix-js-sdk';
 import {
   Avatar,
   Box,
@@ -16,6 +17,8 @@ import {
 import classNames from 'classnames';
 import { useBookmarks, Bookmark } from '../../hooks/useBookmarks';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
+import { useRoomEvent } from '../../hooks/useRoomEvent';
+import { MessageDeletedContent } from '../../components/message/content/FallbackContent';
 import { useRoomNavigate } from '../../hooks/useRoomNavigate';
 import { useMediaAuthentication } from '../../hooks/useMediaAuthentication';
 import { RoomAvatar } from '../../components/room-avatar';
@@ -42,9 +45,11 @@ type BookmarkItemProps = {
   bookmark: Bookmark;
   onJump: (roomId: string, eventId: string) => void;
   onRemove: (eventId: string) => void;
+  // Optional live-rendered preview node; falls back to the stored snapshot when absent.
+  preview?: ReactNode;
 };
 
-function BookmarkItem({ bookmark, onJump, onRemove }: BookmarkItemProps) {
+function BookmarkItem({ bookmark, onJump, onRemove, preview }: BookmarkItemProps) {
   const mx = useMatrixClient();
   const useAuthentication = useMediaAuthentication();
   const room = mx.getRoom(bookmark.roomId) ?? undefined;
@@ -104,18 +109,50 @@ function BookmarkItem({ bookmark, onJump, onRemove }: BookmarkItemProps) {
         style={{ justifyContent: 'flex-start', height: 'unset', padding: config.space.S200 }}
       >
         <Text className={css.BookmarkPreview} size="T200" priority="400">
-          {bookmark.previewText || '(no preview)'}
+          {preview ?? (bookmark.previewText || '(no preview)')}
         </Text>
       </Button>
     </Box>
   );
 }
 
+type LiveBookmarkItemProps = BookmarkItemProps & { room: Room };
+
+// Renders the same layout as BookmarkItem, but resolves the message body live so
+// edits (m.replace, applied by useRoomEvent) and redactions are reflected. The
+// stored snapshot (previewText) remains the fallback for loading/failed/empty states.
+function LiveBookmarkItem({ room, bookmark, onJump, onRemove }: LiveBookmarkItemProps) {
+  const liveEvent = useRoomEvent(room, bookmark.eventId, () =>
+    room.findEventById(bookmark.eventId),
+  );
+
+  const snapshot = bookmark.previewText || '(no preview)';
+  let preview: ReactNode = snapshot;
+
+  // undefined (loading) and null (fetch failed / not found) both keep the snapshot.
+  if (liveEvent) {
+    if (liveEvent.isRedacted()) {
+      preview = (
+        <MessageDeletedContent
+          reason={liveEvent.getUnsigned().redacted_because?.content?.reason as string | undefined}
+        />
+      );
+    } else {
+      // body is already the edited text since useRoomEvent applied m.replace.
+      const { body } = liveEvent.getContent();
+      preview = typeof body === 'string' && body ? body : snapshot;
+    }
+  }
+
+  return <BookmarkItem bookmark={bookmark} onJump={onJump} onRemove={onRemove} preview={preview} />;
+}
+
 type BookmarksPanelProps = {
   onClose: () => void;
 };
 
 export function BookmarksPanel({ onClose }: BookmarksPanelProps) {
+  const mx = useMatrixClient();
   const { bookmarks, removeBookmark } = useBookmarks();
   const { navigateRoom } = useRoomNavigate();
   const [filter, setFilter] = useState('');
@@ -228,14 +265,27 @@ export function BookmarksPanel({ onClose }: BookmarksPanelProps) {
             </Box>
           ) : (
             <Box className={css.BookmarksContent} direction="Column" gap="200">
-              {filtered.map((bk) => (
-                <BookmarkItem
-                  key={bk.eventId}
-                  bookmark={bk}
-                  onJump={handleJump}
-                  onRemove={removeBookmark}
-                />
-              ))}
+              {filtered.map((bk) => {
+                // Live render when the room is joined (useRoomEvent needs a non-null Room);
+                // otherwise fall back to the stored snapshot for rooms we've left.
+                const room = mx.getRoom(bk.roomId);
+                return room ? (
+                  <LiveBookmarkItem
+                    key={bk.eventId}
+                    room={room}
+                    bookmark={bk}
+                    onJump={handleJump}
+                    onRemove={removeBookmark}
+                  />
+                ) : (
+                  <BookmarkItem
+                    key={bk.eventId}
+                    bookmark={bk}
+                    onJump={handleJump}
+                    onRemove={removeBookmark}
+                  />
+                );
+              })}
             </Box>
           )}
         </Scroll>
diff --git a/src/app/features/room/message/ForwardMessageDialog.tsx b/src/app/features/room/message/ForwardMessageDialog.tsx
index b2a4d84a8..3845bf1a5 100644
--- a/src/app/features/room/message/ForwardMessageDialog.tsx
+++ b/src/app/features/room/message/ForwardMessageDialog.tsx
@@ -3,6 +3,8 @@ import FocusTrap from 'focus-trap-react';
 import {
   Avatar,
   Box,
+  Button,
+  Checkbox,
   color,
   config,
   Header,
@@ -29,16 +31,17 @@ import { mDirectAtom } from '../../../state/mDirectList';
 import { useMediaAuthentication } from '../../../hooks/useMediaAuthentication';
 import { mxcUrlToHttp } from '../../../utils/matrix';
 import { RoomAvatar, RoomIcon } from '../../../components/room-avatar';
-import { getEditedEvent, trimReplyFromBody, trimReplyFromFormattedBody } from '../../../utils/room';
+import { buildForwardContent } from './forwardContent';
 
 type RoomRowProps = {
   room: Room;
   dm: boolean;
   useAuthentication: boolean;
-  onClick: () => void;
+  selected: boolean;
+  onToggle: () => void;
   sending: boolean;
 };
-function RoomRow({ room, dm, useAuthentication, onClick, sending }: RoomRowProps) {
+function RoomRow({ room, dm, useAuthentication, selected, onToggle, sending }: RoomRowProps) {
   const mx = useMatrixClient();
   const avatarMxc = room.getMxcAvatarUrl();
   const avatarUrl = avatarMxc
@@ -49,8 +52,20 @@ function RoomRow({ room, dm, useAuthentication, onClick, sending }: RoomRowProps
     <MenuItem
       size="300"
       radii="300"
-      onClick={onClick}
+      onClick={onToggle}
       disabled={sending}
+      after={
+        <Checkbox
+          checked={selected}
+          readOnly
+          variant="Primary"
+          disabled={sending}
+          onClick={(evt) => {
+            evt.stopPropagation();
+            onToggle();
+          }}
+        />
+      }
       before={
         <Avatar size="200" radii="300">
           <RoomAvatar
@@ -93,6 +108,21 @@ export function ForwardMessageDialog({ mEvent, onClose }: Props) {
   const [sending, setSending] = useState(false);
   const [sentTo, setSentTo] = useState<string | null>(null);
   const [error, setError] = useState<string | null>(null);
+  // Selection persists across query changes: a room selected then filtered out
+  // of the rendered slice stays selected.
+  const [selectedRoomIds, setSelectedRoomIds] = useState<Set<string>>(new Set());
+
+  const toggleRoom = useCallback((roomId: string) => {
+    setSelectedRoomIds((prev) => {
+      const next = new Set(prev);
+      if (next.has(roomId)) {
+        next.delete(roomId);
+      } else {
+        next.add(roomId);
+      }
+      return next;
+    });
+  }, []);
 
   const allRooms = useMemo(
     () =>
@@ -109,63 +139,52 @@ export function ForwardMessageDialog({ mEvent, onClose }: Props) {
     return allRooms.filter((r) => r.name.toLowerCase().includes(q));
   }, [allRooms, query]);
 
-  /**
-   * Build the content to forward:
-   * - undecryptable events are refused (would forward `m.bad.encrypted` junk)
-   * - edited messages forward the LATEST edit (`m.new_content`), not the
-   *   original pre-edit body
-   * - reply fallbacks (`> <@user> …` quote + `<mx-reply>` block) are stripped
-   *   along with the `m.relates_to` reply/thread relation, so the forwarded
-   *   message stands alone in the target room
-   */
-  const buildForwardContent = useCallback((): Record<string, unknown> | undefined => {
-    if (mEvent.isDecryptionFailure()) return undefined;
+  const sendToSelected = useCallback(async () => {
+    if (sending || selectedRoomIds.size === 0) return;
+    const fwdContent = buildForwardContent(mx, mEvent);
+    if (!fwdContent) {
+      setError('This message could not be decrypted, so it cannot be forwarded.');
+      return;
+    }
+    setSending(true);
+    setError(null);
 
-    let content = { ...mEvent.getContent() };
+    const ids = [...selectedRoomIds];
+    const results = await Promise.allSettled(
+      // threadId-aware overload (P3-8): explicit null = send to the main timeline.
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      ids.map((id) => mx.sendEvent(id, null, mEvent.getType() as any, fwdContent)),
+    );
 
-    const eventId = mEvent.getId();
-    const room = mx.getRoom(mEvent.getRoomId());
-    if (eventId && room) {
-      const editedEvent = getEditedEvent(eventId, mEvent, room.getUnfilteredTimelineSet());
-      const newContent = editedEvent?.getContent()['m.new_content'];
-      if (newContent && typeof newContent === 'object') {
-        content = { ...(newContent as Record<string, unknown>) };
+    const failedIds: string[] = [];
+    const failedNames: string[] = [];
+    results.forEach((result, i) => {
+      if (result.status === 'rejected') {
+        failedIds.push(ids[i]);
+        failedNames.push(mx.getRoom(ids[i])?.name ?? ids[i]);
       }
+    });
+
+    const total = ids.length;
+    const failed = failedNames.length;
+    const succeeded = total - failed;
+
+    if (failed === 0) {
+      setSentTo(`Forwarded to ${total} ${total === 1 ? 'room' : 'rooms'}`);
+      setTimeout(onClose, 1400);
+      return;
     }
 
-    delete content['m.relates_to'];
-    if (typeof content.body === 'string') {
-      content.body = trimReplyFromBody(content.body);
+    setSending(false);
+    // Prune to only the failures so a retry doesn't re-send to rooms that
+    // already succeeded (duplicate messages).
+    setSelectedRoomIds(new Set(failedIds));
+    if (succeeded === 0) {
+      setError('Failed to forward. Try again.');
+      return;
     }
-    if (typeof content.formatted_body === 'string') {
-      content.formatted_body = trimReplyFromFormattedBody(content.formatted_body);
-    }
-    return content;
-  }, [mx, mEvent]);
-
-  const forward = useCallback(
-    async (room: Room) => {
-      if (sending) return;
-      const fwdContent = buildForwardContent();
-      if (!fwdContent) {
-        setError('This message could not be decrypted, so it cannot be forwarded.');
-        return;
-      }
-      setSending(true);
-      setError(null);
-      try {
-        // threadId-aware overload (P3-8): explicit null = send to the main timeline.
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        await mx.sendEvent(room.roomId, null, mEvent.getType() as any, fwdContent);
-        setSentTo(room.name);
-        setTimeout(onClose, 1400);
-      } catch {
-        setSending(false);
-        setError(`Failed to forward to ${room.name}. Try again.`);
-      }
-    },
-    [mx, mEvent, onClose, sending, buildForwardContent],
-  );
+    setError(`Forwarded to ${succeeded}/${total}. Failed: ${failedNames.join(', ')}.`);
+  }, [mx, mEvent, onClose, sending, selectedRoomIds]);
 
   return (
     <Overlay open backdrop={<OverlayBackdrop />}>
@@ -237,50 +256,72 @@ export function ForwardMessageDialog({ mEvent, onClose }: Props) {
                 gap="300"
                 style={{ padding: config.space.S400 }}
               >
-                <Text size="T300">✓ Forwarded to {sentTo}</Text>
+                <Text size="T300">✓ {sentTo}</Text>
               </Box>
             ) : (
-              <Box grow="Yes" style={{ minHeight: 0, position: 'relative' }}>
-                <Scroll size="300" hideTrack visibility="Hover">
-                  <Box direction="Column" gap="100" style={{ padding: config.space.S200 }}>
-                    {filtered.slice(0, 60).map((room) => (
-                      <RoomRow
-                        key={room.roomId}
-                        room={room}
-                        dm={directs.has(room.roomId)}
-                        useAuthentication={useAuthentication}
-                        onClick={() => forward(room)}
-                        sending={sending}
-                      />
-                    ))}
-                    {filtered.length === 0 && (
-                      <Box
-                        alignItems="Center"
-                        justifyContent="Center"
-                        style={{ padding: config.space.S400 }}
-                      >
-                        <Text size="T300" priority="300">
-                          No rooms found
-                        </Text>
-                      </Box>
-                    )}
-                  </Box>
-                </Scroll>
-                {sending && (
-                  <Box
-                    alignItems="Center"
-                    justifyContent="Center"
-                    style={{
-                      position: 'absolute',
-                      inset: 0,
-                      background: 'rgba(0,0,0,0.35)',
-                      borderRadius: config.radii.R500,
-                    }}
+              <>
+                <Box grow="Yes" style={{ minHeight: 0, position: 'relative' }}>
+                  <Scroll size="300" hideTrack visibility="Hover">
+                    <Box direction="Column" gap="100" style={{ padding: config.space.S200 }}>
+                      {filtered.slice(0, 60).map((room) => (
+                        <RoomRow
+                          key={room.roomId}
+                          room={room}
+                          dm={directs.has(room.roomId)}
+                          useAuthentication={useAuthentication}
+                          selected={selectedRoomIds.has(room.roomId)}
+                          onToggle={() => toggleRoom(room.roomId)}
+                          sending={sending}
+                        />
+                      ))}
+                      {filtered.length === 0 && (
+                        <Box
+                          alignItems="Center"
+                          justifyContent="Center"
+                          style={{ padding: config.space.S400 }}
+                        >
+                          <Text size="T300" priority="300">
+                            No rooms found
+                          </Text>
+                        </Box>
+                      )}
+                    </Box>
+                  </Scroll>
+                  {sending && (
+                    <Box
+                      alignItems="Center"
+                      justifyContent="Center"
+                      style={{
+                        position: 'absolute',
+                        inset: 0,
+                        background: 'rgba(0,0,0,0.35)',
+                        borderRadius: config.radii.R500,
+                      }}
+                    >
+                      <Spinner variant="Secondary" size="400" />
+                    </Box>
+                  )}
+                </Box>
+                <Line size="300" />
+                <Box
+                  shrink="No"
+                  direction="Column"
+                  style={{ padding: `${config.space.S200} ${config.space.S400}` }}
+                >
+                  <Button
+                    variant="Primary"
+                    size="400"
+                    radii="400"
+                    disabled={selectedRoomIds.size === 0 || sending}
+                    before={sending && <Spinner variant="Primary" fill="Solid" size="200" />}
+                    onClick={sendToSelected}
                   >
-                    <Spinner variant="Secondary" size="400" />
-                  </Box>
-                )}
-              </Box>
+                    <Text size="B400">
+                      Send to {selectedRoomIds.size} {selectedRoomIds.size === 1 ? 'room' : 'rooms'}
+                    </Text>
+                  </Button>
+                </Box>
+              </>
             )}
           </Modal>
         </FocusTrap>
diff --git a/src/app/features/room/message/forwardContent.test.ts b/src/app/features/room/message/forwardContent.test.ts
new file mode 100644
index 000000000..3044b0fcc
--- /dev/null
+++ b/src/app/features/room/message/forwardContent.test.ts
@@ -0,0 +1,138 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { MatrixClient, MatrixEvent } from 'matrix-js-sdk';
+import { buildForwardContent } from './forwardContent';
+
+// Pure content builder buildForwardContent: refuses undecryptable events, forwards
+// the latest edit (`m.new_content`), and strips reply fallbacks + `m.relates_to`.
+// MatrixClient / MatrixEvent are mocked minimally. getEditedEvent reads edits off
+// `timelineSet.relations.getChildEventsForEvent(...).getRelations()`, so the base
+// client returns no child edits and the edit test injects one.
+
+const SENDER = '@me:example.org';
+
+type EventOptions = {
+  content?: Record<string, unknown>;
+  type?: string;
+  id?: string;
+  roomId?: string;
+  decryptionFailure?: boolean;
+  ts?: number;
+};
+
+const makeEvent = (options: EventOptions = {}): MatrixEvent => {
+  const {
+    content = {},
+    type = 'm.room.message',
+    id = '$evt:example.org',
+    roomId = '!room:example.org',
+    decryptionFailure = false,
+    ts = 0,
+  } = options;
+
+  return {
+    getContent: () => content,
+    getType: () => type,
+    getId: () => id,
+    getRoomId: () => roomId,
+    getSender: () => SENDER,
+    getTs: () => ts,
+    isDecryptionFailure: () => decryptionFailure,
+  } as unknown as MatrixEvent;
+};
+
+// Base client: the timeline reports no `m.replace` edits, so the original content
+// is forwarded unchanged.
+const makeClient = (): MatrixClient =>
+  ({
+    getRoom: () => ({
+      getUnfilteredTimelineSet: () => ({
+        relations: {
+          getChildEventsForEvent: () => null,
+        },
+      }),
+    }),
+  }) as unknown as MatrixClient;
+
+test('plain text forwards the body and strips m.relates_to', () => {
+  const mx = makeClient();
+  const mEvent = makeEvent({
+    content: {
+      msgtype: 'm.text',
+      body: 'hello world',
+      'm.relates_to': { rel_type: 'm.thread', event_id: '$root:example.org' },
+    },
+  });
+
+  const content = buildForwardContent(mx, mEvent);
+
+  assert.ok(content);
+  assert.equal(content.body, 'hello world');
+  assert.equal(content.msgtype, 'm.text');
+  assert.equal(content['m.relates_to'], undefined);
+});
+
+test('reply quote is stripped from body and formatted_body', () => {
+  const mx = makeClient();
+  const mEvent = makeEvent({
+    content: {
+      msgtype: 'm.text',
+      body: '> <@alice:example.org> original\n\nmy reply',
+      format: 'org.matrix.custom.html',
+      formatted_body: '<mx-reply><blockquote>original</blockquote></mx-reply>my reply',
+      'm.relates_to': { 'm.in_reply_to': { event_id: '$root:example.org' } },
+    },
+  });
+
+  const content = buildForwardContent(mx, mEvent);
+
+  assert.ok(content);
+  assert.equal(content.body, 'my reply');
+  assert.equal(content.formatted_body, 'my reply');
+  assert.equal(content['m.relates_to'], undefined);
+});
+
+test('decryption failure returns undefined', () => {
+  const mx = makeClient();
+  const mEvent = makeEvent({
+    content: { msgtype: 'm.bad.encrypted' },
+    decryptionFailure: true,
+  });
+
+  assert.equal(buildForwardContent(mx, mEvent), undefined);
+});
+
+test('edited message forwards m.new_content', () => {
+  const mEvent = makeEvent({
+    content: {
+      msgtype: 'm.text',
+      body: 'original body',
+      'm.relates_to': { rel_type: 'm.thread', event_id: '$root:example.org' },
+    },
+  });
+
+  // The latest `m.replace` edit carries the new content under `m.new_content`.
+  const editEvent = makeEvent({
+    content: { 'm.new_content': { msgtype: 'm.text', body: 'edited body' } },
+    ts: 100,
+  });
+  const mx = {
+    getRoom: () => ({
+      getUnfilteredTimelineSet: () => ({
+        relations: {
+          getChildEventsForEvent: () => ({
+            getRelations: () => [editEvent],
+          }),
+        },
+      }),
+    }),
+  } as unknown as MatrixClient;
+
+  const content = buildForwardContent(mx, mEvent);
+
+  assert.ok(content);
+  assert.equal(content.body, 'edited body');
+  assert.equal(content.msgtype, 'm.text');
+  assert.equal(content['m.new_content'], undefined);
+  assert.equal(content['m.relates_to'], undefined);
+});
diff --git a/src/app/features/room/message/forwardContent.ts b/src/app/features/room/message/forwardContent.ts
new file mode 100644
index 000000000..7cdf78e71
--- /dev/null
+++ b/src/app/features/room/message/forwardContent.ts
@@ -0,0 +1,39 @@
+import { MatrixClient, MatrixEvent } from 'matrix-js-sdk';
+import { getEditedEvent, trimReplyFromBody, trimReplyFromFormattedBody } from '../../../utils/room';
+
+/**
+ * Build the content to forward:
+ * - undecryptable events are refused (would forward `m.bad.encrypted` junk)
+ * - edited messages forward the LATEST edit (`m.new_content`), not the
+ *   original pre-edit body
+ * - reply fallbacks (`> <@user> …` quote + `<mx-reply>` block) are stripped
+ *   along with the `m.relates_to` reply/thread relation, so the forwarded
+ *   message stands alone in the target room
+ */
+export function buildForwardContent(
+  mx: MatrixClient,
+  mEvent: MatrixEvent,
+): Record<string, unknown> | undefined {
+  if (mEvent.isDecryptionFailure()) return undefined;
+
+  let content = { ...mEvent.getContent() };
+
+  const eventId = mEvent.getId();
+  const room = mx.getRoom(mEvent.getRoomId());
+  if (eventId && room) {
+    const editedEvent = getEditedEvent(eventId, mEvent, room.getUnfilteredTimelineSet());
+    const newContent = editedEvent?.getContent()['m.new_content'];
+    if (newContent && typeof newContent === 'object') {
+      content = { ...(newContent as Record<string, unknown>) };
+    }
+  }
+
+  delete content['m.relates_to'];
+  if (typeof content.body === 'string') {
+    content.body = trimReplyFromBody(content.body);
+  }
+  if (typeof content.formatted_body === 'string') {
+    content.formatted_body = trimReplyFromFormattedBody(content.formatted_body);
+  }
+  return content;
+}