fix(messages): merge stale-sender-profile fallback into #32's uid-shape guard

Two independent fixes for the same raw-uid-leak bug landed in parallel:
upstream added groupSenderLabel() to catch uid-shaped names by regex
(covers a still-present member whose display_name IS the uid); the local
change instead resolved a left-group sender's real name via a standalone
getUserProfile() lookup (covers a member no longer in memberByUserId at
all). Neither alone covers both paths. groupSenderLabel now takes multiple
candidates in priority order -- member-list name first, then the fetched
stale-sender name, falling through to the placeholder only when neither
resolves to something that isn't uid-shaped -- so a left member with a
resolvable profile still shows their real name instead of the placeholder,
while the still-present-but-nameless case is unaffected.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/features/messages/ConversationView.tsx

@@ -1,6 +1,6 @@
 import { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react';
 
-import { useQuery } from '@tanstack/react-query';
+import { useQueries, useQuery } from '@tanstack/react-query';
 import { Link, useNavigate, useOutletContext, useParams } from 'react-router-dom';
 import type { StoredMessage } from 'tinode-sdk';
 import { Drafty } from 'tinode-sdk';
@@ -542,6 +542,38 @@ export function ConversationView() {
     enabled: isGroup,
   });
   const memberByUserId = useMemo(() => new Map((membersQuery.data || []).map((m) => [m.user_id, m])), [membersQuery.data]);
+  // `memberByUserId` only ever holds CURRENT members (`getAllGroupMembers`) -- a historical message
+  // from someone who has since left/been removed has no entry there, and used to fall all the way
+  // back to the raw `msg.from` uid string in the bubble (confirmed live, 2026-09-20: a real message
+  // from a member who then left the group rendered as "usrp77kUAkgqpU" instead of "systest02").
+  // Fetching each such uid's standalone profile (same `getUserProfile`/`['user-profile', id]` P2P
+  // already uses above) recovers a real display name/avatar in the common case; `retry:false` and a
+  // swallowed error mean a stranger this account has no visibility into (403, same as the already-
+  // documented `usrW9ijv236hHA` case) just falls back to the uid exactly as before -- never worse.
+  const staleSenderIds = useMemo(() => {
+    if (!isGroup) return [] as string[];
+    const ids = new Set<string>();
+    for (const msg of messages) {
+      if (msg.from && !memberByUserId.has(msg.from)) ids.add(msg.from);
+    }
+    return Array.from(ids);
+  }, [isGroup, messages, memberByUserId]);
+  const staleSenderQueries = useQueries({
+    queries: staleSenderIds.map((uid) => ({
+      queryKey: ['user-profile', uid],
+      queryFn: () => getUserProfile(uid),
+      staleTime: Infinity,
+      retry: false,
+    })),
+  });
+  const staleSenderById = useMemo(() => {
+    const map = new Map<string, { display_name: string; avatar_file_id?: string }>();
+    staleSenderIds.forEach((uid, i) => {
+      const data = staleSenderQueries[i]?.data;
+      if (data) map.set(uid, data);
+    });
+    return map;
+  }, [staleSenderIds, staleSenderQueries]);
   const myMember = myUserId ? memberByUserId.get(myUserId) : undefined;
   const isGroupAdmin = myMember?.role === 'owner' || myMember?.role === 'admin';
   const groupSublineParts = [
@@ -569,7 +601,9 @@ export function ConversationView() {
   // second, divergent resolution path.
   const quotedSenderLabel = (fromUserId: string | undefined) => {
     if (myUserId && fromUserId === myUserId) return '我';
-    if (isGroup && fromUserId) return groupSenderLabel(memberByUserId.get(fromUserId)?.display_name);
+    if (isGroup && fromUserId) {
+      return groupSenderLabel(memberByUserId.get(fromUserId)?.display_name, staleSenderById.get(fromUserId)?.display_name);
+    }
     return peerName;
   };
 
@@ -944,8 +978,13 @@ export function ConversationView() {
         {loadingOlder ? <div className="py-2 text-center text-xs text-text-tertiary-4">加载中…</div> : null}
         {messages.map((msg) => {
           const sender = isGroup && msg.from ? memberByUserId.get(msg.from) : undefined;
+          const staleSender = isGroup && msg.from && !sender ? staleSenderById.get(msg.from) : undefined;
           const mine = !!myUserId && msg.from === myUserId;
-          const rowAvatarFileId = mine ? myAvatarFileId : isGroup ? sender?.avatar_file_id : peerAvatarFileId;
+          const rowAvatarFileId = mine
+            ? myAvatarFileId
+            : isGroup
+              ? sender?.avatar_file_id || staleSender?.avatar_file_id
+              : peerAvatarFileId;
           return (
             <MessageRow
               key={msg.seq}
@@ -954,7 +993,7 @@ export function ConversationView() {
               mine={mine}
               isGroup={isGroup}
               peerName={peerName}
-              senderName={sender?.display_name}
+              senderName={sender?.display_name || staleSender?.display_name}
               senderRole={sender?.role}
               avatarFileId={rowAvatarFileId}
               selectMode={selectMode}

web/src/lib/messages/sender-name.ts

@@ -14,9 +14,19 @@ const UID_SHAPE = /^usr[A-Za-z0-9_-]+$/;
 
 export const UNKNOWN_SENDER_LABEL = '未知用户';
 
-export function groupSenderLabel(senderName: string | undefined): string {
-  const name = senderName?.trim();
-  if (name && !UID_SHAPE.test(name)) return name;
+/**
+ * Accepts multiple name candidates in priority order (e.g. the current member list's
+ * `display_name`, then a standalone profile lookup for a sender who has since left the group)
+ * and returns the first one that isn't uid-shaped. A left-group member's own profile can
+ * usually still be resolved by id and is a real name worth showing instead of the placeholder;
+ * a still-present member whose `display_name` IS the uid (the second bug path above) has no
+ * better candidate to fall back to and correctly lands on the placeholder either way.
+ */
+export function groupSenderLabel(...candidates: Array<string | undefined>): string {
+  for (const candidate of candidates) {
+    const name = candidate?.trim();
+    if (name && !UID_SHAPE.test(name)) return name;
+  }
   // No usable name -- never show the raw uid even when it IS available; it's not a user-facing name.
   return UNKNOWN_SENDER_LABEL;
 }