diff --git a/apps/web/app/(dashboard)/_components/app-sidebar.tsx b/apps/web/app/(dashboard)/_components/app-sidebar.tsx
index 683cd9ad..bbcea35f 100644
--- a/apps/web/app/(dashboard)/_components/app-sidebar.tsx
+++ b/apps/web/app/(dashboard)/_components/app-sidebar.tsx
@@ -1,5 +1,6 @@
 "use client";
 
+import React from "react";
 import Link from "next/link";
 import { usePathname, useRouter } from "next/navigation";
 import {
@@ -77,7 +78,10 @@ export function AppSidebar() {
 
   const wsId = useWorkspaceId();
   const { data: inboxItems = [] } = useQuery(inboxListOptions(wsId));
-  const unreadCount = deduplicateInboxItems(inboxItems).filter((i) => !i.read).length;
+  const unreadCount = React.useMemo(
+    () => deduplicateInboxItems(inboxItems).filter((i) => !i.read).length,
+    [inboxItems],
+  );
 
   const logout = () => {
     router.push("/");
diff --git a/apps/web/core/index.ts b/apps/web/core/index.ts
index 26716d72..97d2430c 100644
--- a/apps/web/core/index.ts
+++ b/apps/web/core/index.ts
@@ -1,3 +1,3 @@
-export { createQueryClient, getQueryClient, setQueryClient } from "./query-client";
+export { createQueryClient } from "./query-client";
 export { QueryProvider } from "./provider";
 export { useWorkspaceId } from "./hooks";
diff --git a/apps/web/core/issues/mutations.ts b/apps/web/core/issues/mutations.ts
index 89d0ef5a..e05d17de 100644
--- a/apps/web/core/issues/mutations.ts
+++ b/apps/web/core/issues/mutations.ts
@@ -60,6 +60,9 @@ export function useUpdateIssue() {
       if (ctx?.prevDetail)
         qc.setQueryData(issueKeys.detail(wsId, ctx.id), ctx.prevDetail);
     },
+    onSettled: (_data, _err, vars) => {
+      qc.invalidateQueries({ queryKey: issueKeys.detail(wsId, vars.id) });
+    },
   });
 }
 
diff --git a/apps/web/core/issues/queries.ts b/apps/web/core/issues/queries.ts
index b848cb47..bdf50d03 100644
--- a/apps/web/core/issues/queries.ts
+++ b/apps/web/core/issues/queries.ts
@@ -12,6 +12,11 @@ export const issueKeys = {
     ["issues", "subscribers", issueId] as const,
 };
 
+/**
+ * CACHE SHAPE NOTE: The raw cache stores ListIssuesResponse ({ issues, total }),
+ * but `select` transforms it to Issue[] for consumers. Mutations and ws-updaters
+ * must use setQueryData<ListIssuesResponse>(...) — NOT setQueryData<Issue[]>.
+ */
 export function issueListOptions(wsId: string) {
   return queryOptions({
     queryKey: issueKeys.list(wsId),
diff --git a/apps/web/core/provider.tsx b/apps/web/core/provider.tsx
index 7723c771..41331d2e 100644
--- a/apps/web/core/provider.tsx
+++ b/apps/web/core/provider.tsx
@@ -3,15 +3,11 @@
 import { useState } from "react";
 import { QueryClientProvider } from "@tanstack/react-query";
 import { ReactQueryDevtools } from "@tanstack/react-query-devtools";
-import { createQueryClient, setQueryClient } from "./query-client";
+import { createQueryClient } from "./query-client";
 import type { ReactNode } from "react";
 
 export function QueryProvider({ children }: { children: ReactNode }) {
-  const [queryClient] = useState(() => {
-    const client = createQueryClient();
-    setQueryClient(client);
-    return client;
-  });
+  const [queryClient] = useState(createQueryClient);
   return (
     <QueryClientProvider client={queryClient}>
       {children}
diff --git a/apps/web/core/query-client.ts b/apps/web/core/query-client.ts
index b882845b..be5ebea0 100644
--- a/apps/web/core/query-client.ts
+++ b/apps/web/core/query-client.ts
@@ -1,7 +1,5 @@
 import { QueryClient } from "@tanstack/react-query";
 
-let _queryClient: QueryClient | null = null;
-
 export function createQueryClient(): QueryClient {
   return new QueryClient({
     defaultOptions: {
@@ -18,14 +16,3 @@ export function createQueryClient(): QueryClient {
     },
   });
 }
-
-/** Called by QueryProvider on mount to register the singleton. */
-export function setQueryClient(client: QueryClient) {
-  _queryClient = client;
-}
-
-/** Access QueryClient outside React tree (WS handlers, Zustand actions). */
-export function getQueryClient(): QueryClient {
-  if (!_queryClient) throw new Error("QueryClient not initialized");
-  return _queryClient;
-}
diff --git a/apps/web/features/editor/content-editor.tsx b/apps/web/features/editor/content-editor.tsx
index 85e040d2..3e125115 100644
--- a/apps/web/features/editor/content-editor.tsx
+++ b/apps/web/features/editor/content-editor.tsx
@@ -34,6 +34,7 @@ import {
 import { useEditor, EditorContent } from "@tiptap/react";
 import { cn } from "@/lib/utils";
 import type { UploadResult } from "@/shared/hooks/use-file-upload";
+import { useQueryClient } from "@tanstack/react-query";
 import { createEditorExtensions } from "./extensions";
 import { uploadAndInsertFile } from "./extensions/file-upload";
 import { preprocessMarkdown } from "./utils/preprocess";
@@ -94,6 +95,8 @@ const ContentEditor = forwardRef<ContentEditorRef, ContentEditorProps>(
     onBlurRef.current = onBlur;
     onUploadFileRef.current = onUploadFile;
 
+    const queryClient = useQueryClient();
+
     const editor = useEditor({
       immediatelyRender: false,
       editable,
@@ -102,6 +105,7 @@ const ContentEditor = forwardRef<ContentEditorRef, ContentEditorProps>(
       extensions: createEditorExtensions({
         editable,
         placeholder: placeholderText,
+        queryClient,
         onSubmitRef,
         onUploadFileRef,
       }),
diff --git a/apps/web/features/editor/extensions/index.ts b/apps/web/features/editor/extensions/index.ts
index c182dd8a..4052c6d5 100644
--- a/apps/web/features/editor/extensions/index.ts
+++ b/apps/web/features/editor/extensions/index.ts
@@ -76,6 +76,7 @@ const ImageExtension = Image.extend({
 export interface EditorExtensionsOptions {
   editable: boolean;
   placeholder?: string;
+  queryClient?: import("@tanstack/react-query").QueryClient;
   onSubmitRef?: RefObject<(() => void) | undefined>;
   onUploadFileRef?: RefObject<
     ((file: File) => Promise<UploadResult | null>) | undefined
@@ -107,7 +108,7 @@ export function createEditorExtensions(
     Markdown,
     BaseMentionExtension.configure({
       HTMLAttributes: { class: "mention" },
-      ...(editable ? { suggestion: createMentionSuggestion() } : {}),
+      ...(editable && options.queryClient ? { suggestion: createMentionSuggestion(options.queryClient) } : {}),
     }),
   ];
 
diff --git a/apps/web/features/editor/extensions/mention-suggestion.tsx b/apps/web/features/editor/extensions/mention-suggestion.tsx
index 4c15204a..1b9ed73e 100644
--- a/apps/web/features/editor/extensions/mention-suggestion.tsx
+++ b/apps/web/features/editor/extensions/mention-suggestion.tsx
@@ -10,8 +10,8 @@ import {
 } from "react";
 import { ReactRenderer } from "@tiptap/react";
 import { computePosition, offset, flip, shift } from "@floating-ui/dom";
+import type { QueryClient } from "@tanstack/react-query";
 import { useWorkspaceStore } from "@/features/workspace";
-import { getQueryClient } from "@core/query-client";
 import { issueKeys } from "@core/issues/queries";
 import { workspaceKeys } from "@core/workspace/queries";
 import type { Issue, ListIssuesResponse, MemberWithUser, Agent } from "@/shared/types";
@@ -213,18 +213,19 @@ function MentionRow({
 // Suggestion config factory
 // ---------------------------------------------------------------------------
 
-export function createMentionSuggestion(): Omit<
+export function createMentionSuggestion(qc: QueryClient): Omit<
   SuggestionOptions<MentionItem>,
   "editor"
 > {
   return {
     items: ({ query }) => {
       const wsId = useWorkspaceStore.getState().workspace?.id;
-      const members: MemberWithUser[] = wsId ? getQueryClient().getQueryData(workspaceKeys.members(wsId)) ?? [] : [];
-      const agents: Agent[] = wsId ? getQueryClient().getQueryData(workspaceKeys.agents(wsId)) ?? [] : [];
+      const members: MemberWithUser[] = wsId ? qc.getQueryData(workspaceKeys.members(wsId)) ?? [] : [];
+      const agents: Agent[] = wsId ? qc.getQueryData(workspaceKeys.agents(wsId)) ?? [] : [];
       const issues: Issue[] = wsId
-        ? getQueryClient().getQueryData<ListIssuesResponse>(issueKeys.list(wsId))?.issues ?? []
+        ? qc.getQueryData<ListIssuesResponse>(issueKeys.list(wsId))?.issues ?? []
         : [];
+
       const q = query.toLowerCase();
 
       // Show "All members" option when query is empty or matches "all"