fix(errors): surface previously-silent async failures (DP1/DP4/DP6)

Several fire-and-forget promises failed silently:
- RoomInput slash-command exe() rejections reset the editor as if they
  succeeded; now caught and shown via an error toast.
- Favourite / low-priority room-tag toggles (setRoomTag/deleteRoomTag)
  swallowed rejections; now surfaced via the same error toast.
- Call-decline sendEvent(RTCDecline) was uncaught; now logged best-effort
  while the local UI still dismisses.

Adds a shared createErrorToast builder mirroring createDownloadToast.
/kick and /ban route through rateLimitedActions, whose to() helper
swallows non-429 errors, so those two can still resolve on failure — noted
in code; the top-level exe() catch covers everything that does reject.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/components/CallEmbedProvider.tsx

@@ -544,11 +544,16 @@ function IncomingCallListener({ callEmbed, joined }: IncomingCallListenerProps)
 
   const handleReject = useCallback(
     (room: Room, eventId: string) => {
+      // Best-effort: the local UI dismisses regardless (below), but a failed
+      // decline used to reject uncaught. Log it instead of surfacing — the caller
+      // will time the call out on their side even if our decline never lands.
       mx.sendEvent(room.roomId, EventType.RTCDecline, {
         'm.relates_to': {
           rel_type: RelationType.Reference,
           event_id: eventId,
         },
+      }).catch((err) => {
+        console.error('Failed to send call decline:', err);
       });
       setCallInfo(undefined);
     },

src/app/features/room-nav/RoomNavItem.tsx

@@ -26,7 +26,7 @@ import {
 } from 'folds';
 import { useFocusWithin, useHover } from 'react-aria';
 import FocusTrap from 'focus-trap-react';
-import { useAtom, useAtomValue } from 'jotai';
+import { useAtom, useAtomValue, useSetAtom } from 'jotai';
 import dayjs from 'dayjs';
 import isToday from 'dayjs/plugin/isToday';
 import isYesterday from 'dayjs/plugin/isYesterday';
@@ -68,6 +68,7 @@ import {
 import { useCallMembers, useCallSession } from '../../hooks/useCall';
 import { useCallEmbed, useCallStart } from '../../hooks/useCallEmbed';
 import { callChatAtom } from '../../state/callEmbed';
+import { createErrorToast, toastQueueAtom } from '../../state/toast';
 import { useCallPreferencesAtom } from '../../state/hooks/callPreferences';
 import { useAutoDiscoveryInfo } from '../../hooks/useAutoDiscoveryInfo';
 import { livekitSupport } from '../../hooks/useLivekitSupport';
@@ -324,6 +325,7 @@ const RoomNavItemMenu = forwardRef<HTMLDivElement, RoomNavItemMenuProps>(
     const canInvite = permissions.action('invite', mx.getSafeUserId());
     const openRoomSettings = useOpenRoomSettings();
     const space = useSpaceOptionally();
+    const setToast = useSetAtom(toastQueueAtom);
 
     const [invitePrompt, setInvitePrompt] = useState(false);
     const [muteMenuAnchor, setMuteMenuAnchor] = useState<RectCords>();
@@ -332,23 +334,31 @@ const RoomNavItemMenu = forwardRef<HTMLDivElement, RoomNavItemMenuProps>(
     const isFavorite = !!room.tags?.['m.favourite'];
     const isLowPriority = !!room.tags?.['m.lowpriority'];
 
+    // Surface a room-tag write failure instead of letting the toggle fail silently.
+    const notifyTagFailure = (err: unknown) => {
+      console.error('Failed to update room tag:', err);
+      setToast(
+        createErrorToast('Could not update this room. Please try again.', Icons.Warning, 'Failed'),
+      );
+    };
+
     const handleToggleFavorite = () => {
       if (isFavorite) {
-        mx.deleteRoomTag(room.roomId, 'm.favourite');
+        mx.deleteRoomTag(room.roomId, 'm.favourite').catch(notifyTagFailure);
       } else {
         // Favourite and low-priority are mutually exclusive.
-        if (isLowPriority) mx.deleteRoomTag(room.roomId, 'm.lowpriority');
-        mx.setRoomTag(room.roomId, 'm.favourite', { order: 0.5 });
+        if (isLowPriority) mx.deleteRoomTag(room.roomId, 'm.lowpriority').catch(notifyTagFailure);
+        mx.setRoomTag(room.roomId, 'm.favourite', { order: 0.5 }).catch(notifyTagFailure);
       }
       requestClose();
     };
 
     const handleToggleLowPriority = () => {
       if (isLowPriority) {
-        mx.deleteRoomTag(room.roomId, 'm.lowpriority');
+        mx.deleteRoomTag(room.roomId, 'm.lowpriority').catch(notifyTagFailure);
       } else {
-        if (isFavorite) mx.deleteRoomTag(room.roomId, 'm.favourite');
-        mx.setRoomTag(room.roomId, 'm.lowpriority', { order: 0.5 });
+        if (isFavorite) mx.deleteRoomTag(room.roomId, 'm.favourite').catch(notifyTagFailure);
+        mx.setRoomTag(room.roomId, 'm.lowpriority', { order: 0.5 }).catch(notifyTagFailure);
       }
       requestClose();
     };

src/app/features/room/RoomInput.tsx

@@ -136,6 +136,7 @@ import { ScheduleMessageModal } from './ScheduleMessageModal';
 import { ScheduledMessagesTray } from './ScheduledMessagesTray';
 import { DraftIndicator } from './DraftIndicator';
 import { scheduledMessagesAtom } from '../../state/scheduledMessages';
+import { createErrorToast, toastQueueAtom } from '../../state/toast';
 import { getThreadDraftKey } from '../../state/room/thread';
 
 const GifPicker = React.lazy(() =>
@@ -184,6 +185,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
     const [scheduleOpen, setScheduleOpen] = useState(false);
     const [scheduleContent, setScheduleContent] = useState<IContent | null>(null);
     const setScheduledMessages = useSetAtom(scheduledMessagesAtom);
+    const setToast = useSetAtom(toastQueueAtom);
 
     const alive = useAlive();
     // Scope drafts/replies/uploads by thread so a thread composer stays fully
@@ -539,7 +541,22 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
       } else if (commandName) {
         const commandContent = commands[commandName as Command];
         if (commandContent) {
-          commandContent.exe(plainText);
+          // Fire-and-forget by design (the editor resets immediately for UX), but
+          // surface a rejection instead of failing silently. NOTE: /kick and /ban
+          // route through rateLimitedActions (utils/matrix.ts), whose to() helper
+          // swallows non-429 errors, so those two commands can still resolve even
+          // when the underlying kick/ban failed — this catch only covers errors
+          // that actually reject out of exe().
+          commandContent.exe(plainText).catch((err) => {
+            console.error(`Failed to run /${commandName} command:`, err);
+            setToast(
+              createErrorToast(
+                `The /${commandName} command failed. Please try again.`,
+                Icons.Warning,
+                'Command failed',
+              ),
+            );
+          });
         }
         resetEditor(editor);
         resetEditorHistory(editor);
@@ -600,6 +617,7 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
       setReplyDraft,
       isMarkdown,
       commands,
+      setToast,
     ]);
 
     /**

src/app/hooks/useCommands.ts

@@ -291,7 +291,11 @@ export const useCommands = (mx: MatrixClient, room: Room): CommandRecord => {
             });
           }
 
-          rateLimitedActions(users, (id) => mx.kick(room.roomId, id, reason));
+          // NOTE: rateLimitedActions' to() helper (utils/matrix.ts) swallows every
+          // non-429 error, so a failed kick (e.g. insufficient power level) resolves
+          // silently here — the RoomInput exe() catch cannot surface it. Propagating
+          // would require refactoring rateLimitedActions' shared error handling.
+          await rateLimitedActions(users, (id) => mx.kick(room.roomId, id, reason));
         },
       },
       [Command.Ban]: {
@@ -313,7 +317,9 @@ export const useCommands = (mx: MatrixClient, room: Room): CommandRecord => {
             });
           }
 
-          rateLimitedActions(users, (id) => mx.ban(room.roomId, id, reason));
+          // See the /kick note: rateLimitedActions swallows non-429 errors, so a
+          // failed ban resolves silently and can't be surfaced by the exe() catch.
+          await rateLimitedActions(users, (id) => mx.ban(room.roomId, id, reason));
         },
       },
       [Command.UnBan]: {

src/app/state/toast.ts

@@ -27,6 +27,23 @@ export const createDownloadToast = (filename: string, iconSrc?: IconSrc): ToastN
   onClick: () => undefined,
 });
 
+// Build an error/system toast (e.g. a failed command or account action). Mirrors
+// createDownloadToast: folds-free (icon src passed in), empty roomId + no-op
+// onClick so a click only dismisses (never navigates to a room).
+export const createErrorToast = (
+  body: string,
+  iconSrc?: IconSrc,
+  displayName = 'Something went wrong',
+): ToastNotif => ({
+  id: `error-${Date.now()}-${Math.random().toString(36).slice(2, 8)}`,
+  displayName,
+  body,
+  roomName: '',
+  roomId: '',
+  iconSrc,
+  onClick: () => undefined,
+});
+
 const baseAtom = atom<ToastNotif[]>([]);
 
 // Write-only setter used in ClientNonUIFeatures