apps/client/public/locales/en-US/translation.json

@@ -1382,5 +1382,8 @@
   "Applied": "Applied",
   "Suggestion applied": "Suggestion applied",
   "Failed to apply suggestion": "Failed to apply suggestion",
-  "The commented text changed since this suggestion was made; it was not applied.": "The commented text changed since this suggestion was made; it was not applied."
+  "The commented text changed since this suggestion was made; it was not applied.": "The commented text changed since this suggestion was made; it was not applied.",
+  "Dismiss": "Dismiss",
+  "Suggestion dismissed": "Suggestion dismissed",
+  "Failed to dismiss suggestion": "Failed to dismiss suggestion"
 }

apps/client/public/locales/ru-RU/translation.json

@@ -1245,5 +1245,8 @@
   "Applied": "Применено",
   "Suggestion applied": "Предложение применено",
   "Failed to apply suggestion": "Не удалось применить предложение",
-  "The commented text changed since this suggestion was made; it was not applied.": "Прокомментированный текст изменился после создания предложения; оно не было применено."
+  "The commented text changed since this suggestion was made; it was not applied.": "Прокомментированный текст изменился после создания предложения; оно не было применено.",
+  "Dismiss": "Не применять",
+  "Suggestion dismissed": "Предложение отклонено",
+  "Failed to dismiss suggestion": "Не удалось отклонить предложение"
 }

apps/client/src/features/comment/components/comment-list-item.test.tsx

@@ -8,6 +8,7 @@ import { IComment } from "@/features/comment/types/comment.types";
 // The comment mutation hooks reach out to react-query/network — stub them so the
 // component renders in isolation. We only assert the AI-badge rendering branch.
 const applyMutateAsync = vi.fn();
+const dismissMutateAsync = vi.fn();
 vi.mock("@/features/comment/queries/comment-query", () => ({
   useDeleteCommentMutation: () => ({ mutateAsync: vi.fn() }),
   useResolveCommentMutation: () => ({ mutateAsync: vi.fn() }),
@@ -16,6 +17,10 @@ vi.mock("@/features/comment/queries/comment-query", () => ({
     mutateAsync: applyMutateAsync,
     isPending: false,
   }),
+  useDismissSuggestionMutation: () => ({
+    mutateAsync: dismissMutateAsync,
+    isPending: false,
+  }),
 }));
 
 // CommentEditor pulls in the full TipTap editor stack; replace it with a stub.
@@ -24,7 +29,10 @@ vi.mock("@/features/comment/components/comment-editor", () => ({
 }));
 
 import CommentListItem from "./comment-list-item";
-import { canShowApply } from "@/features/comment/utils/suggestion";
+import {
+  canShowApply,
+  canShowDismiss,
+} from "@/features/comment/utils/suggestion";
 
 const baseComment = (over?: Partial<IComment>): IComment =>
   ({
@@ -38,14 +46,20 @@ const baseComment = (over?: Partial<IComment>): IComment =>
     ...over,
   }) as IComment;
 
-function renderItem(comment: IComment, canEdit = true) {
+function renderItem(
+  comment: IComment,
+  canEdit = true,
+  canComment = true,
+  userSpaceRole?: string,
+) {
   return render(
     <MantineProvider>
       <CommentListItem
         comment={comment}
         pageId="page-1"
-        canComment={true}
+        canComment={canComment}
         canEdit={canEdit}
+        userSpaceRole={userSpaceRole}
       />
     </MantineProvider>,
   );
@@ -159,6 +173,65 @@ describe("CommentListItem — suggested edit (#315)", () => {
   });
 });
 
+describe("CommentListItem — dismiss suggestion (#329)", () => {
+  const suggestion = (over?: Partial<IComment>): IComment =>
+    baseComment({
+      selection: "old wording here",
+      suggestedText: "new wording here",
+      ...over,
+    });
+
+  // A space admin (userSpaceRole="admin") satisfies the owner-or-admin gate
+  // regardless of who authored the comment; the tests below use it as the lever
+  // since the currentUser atom is unseeded (null) in this harness.
+  it("renders a Dismiss button alongside Apply when canEdit and canComment (owner/admin)", () => {
+    renderItem(suggestion(), true, true, "admin");
+    expect(screen.getByRole("button", { name: "Apply" })).toBeDefined();
+    expect(screen.getByRole("button", { name: "Dismiss" })).toBeDefined();
+  });
+
+  it("shows Dismiss but NOT Apply for an admin commenter who cannot edit", () => {
+    renderItem(suggestion(), false, true, "admin");
+    expect(screen.queryByRole("button", { name: "Apply" })).toBeNull();
+    expect(screen.getByRole("button", { name: "Dismiss" })).toBeDefined();
+  });
+
+  it("hides Dismiss when the viewer cannot comment", () => {
+    renderItem(suggestion(), false, false, "admin");
+    expect(screen.queryByRole("button", { name: "Dismiss" })).toBeNull();
+    expect(screen.queryByRole("button", { name: "Apply" })).toBeNull();
+  });
+
+  it("hides Dismiss for a non-owner non-admin even with canComment (#338 F5: mirrors server 403)", () => {
+    // canComment=true but NOT a space admin and NOT the comment owner (the
+    // currentUser atom is null while the comment is authored by user-1), so the
+    // server would 403 a dismiss — the button must not be shown at all.
+    renderItem(suggestion(), false, true, "member");
+    expect(screen.queryByRole("button", { name: "Dismiss" })).toBeNull();
+  });
+
+  it("hides Dismiss once the thread is resolved", () => {
+    renderItem(suggestion({ resolvedAt: new Date() }), true, true, "admin");
+    expect(screen.queryByRole("button", { name: "Dismiss" })).toBeNull();
+  });
+
+  it("hides Dismiss (shows the Applied badge) once applied", () => {
+    renderItem(suggestion({ suggestionAppliedAt: new Date() }), true, true, "admin");
+    expect(screen.queryByRole("button", { name: "Dismiss" })).toBeNull();
+    expect(screen.getByText("Applied")).toBeDefined();
+  });
+
+  it("calls the dismiss mutation when the Dismiss button is clicked", () => {
+    dismissMutateAsync.mockClear();
+    renderItem(suggestion(), true, true, "admin");
+    fireEvent.click(screen.getByRole("button", { name: "Dismiss" }));
+    expect(dismissMutateAsync).toHaveBeenCalledWith({
+      commentId: "c-1",
+      pageId: "page-1",
+    });
+  });
+});
+
 describe("canShowApply predicate", () => {
   const c = (over?: Partial<IComment>): IComment =>
     ({ suggestedText: "x", ...over }) as IComment;
@@ -184,3 +257,32 @@ describe("canShowApply predicate", () => {
     expect(canShowApply(c({ parentCommentId: "p" }), true)).toBe(false);
   });
 });
+
+describe("canShowDismiss predicate", () => {
+  const c = (over?: Partial<IComment>): IComment =>
+    ({ suggestedText: "x", ...over }) as IComment;
+
+  it("true when suggestion present, can comment, owner/admin, not applied/resolved, top-level", () => {
+    expect(canShowDismiss(c(), true, true)).toBe(true);
+  });
+  it("false without comment permission", () => {
+    expect(canShowDismiss(c(), false, true)).toBe(false);
+  });
+  it("false when not owner and not admin (#338 F5)", () => {
+    expect(canShowDismiss(c(), true, false)).toBe(false);
+  });
+  it("false when no suggestion", () => {
+    expect(canShowDismiss(c({ suggestedText: null }), true, true)).toBe(false);
+  });
+  it("false when already applied", () => {
+    expect(canShowDismiss(c({ suggestionAppliedAt: new Date() }), true, true)).toBe(
+      false,
+    );
+  });
+  it("false when resolved", () => {
+    expect(canShowDismiss(c({ resolvedAt: new Date() }), true, true)).toBe(false);
+  });
+  it("false for a reply comment", () => {
+    expect(canShowDismiss(c({ parentCommentId: "p" }), true, true)).toBe(false);
+  });
+});

apps/client/src/features/comment/components/comment-list-item.tsx

@@ -13,12 +13,14 @@ import { useHover } from "@mantine/hooks";
 import {
   useApplySuggestionMutation,
   useDeleteCommentMutation,
+  useDismissSuggestionMutation,
   useResolveCommentMutation,
   useUpdateCommentMutation,
 } from "@/features/comment/queries/comment-query";
 import { IComment } from "@/features/comment/types/comment.types";
 import {
   canShowApply,
+  canShowDismiss,
   computeSuggestionDiff,
 } from "@/features/comment/utils/suggestion";
 import { CustomAvatar } from "@/components/ui/custom-avatar.tsx";
@@ -54,6 +56,7 @@ function CommentListItem({
   const deleteCommentMutation = useDeleteCommentMutation(comment.pageId);
   const resolveCommentMutation = useResolveCommentMutation();
   const applySuggestionMutation = useApplySuggestionMutation();
+  const dismissSuggestionMutation = useDismissSuggestionMutation();
   const [currentUser] = useAtom(currentUserAtom);
   const createdAtAgo = useTimeAgo(comment.createdAt);
 
@@ -69,6 +72,12 @@ function CommentListItem({
     [comment.selection, comment.suggestedText],
   );
 
+  // Owner-or-space-admin gate (#338): mirrors the server authz for both the
+  // comment menu (edit/delete) and the suggestion Dismiss button, so we never
+  // render an action the server will 403.
+  const isOwnerOrAdmin =
+    currentUser?.user?.id === comment.creatorId || userSpaceRole === "admin";
+
   useEffect(() => {
     setContent(comment.content);
   }, [comment]);
@@ -130,6 +139,19 @@ function CommentListItem({
     }
   }
 
+  async function handleDismissSuggestion() {
+    try {
+      await dismissSuggestionMutation.mutateAsync({
+        commentId: comment.id,
+        pageId: comment.pageId,
+      });
+    } catch (error) {
+      // Idempotent races are reconciled to success in the mutation's onError;
+      // anything else surfaces there as a notification.
+      console.error("Failed to dismiss suggestion:", error);
+    }
+  }
+
   function handleCommentClick(comment: IComment) {
     const el = document.querySelector(
       `.comment-mark[data-comment-id="${comment.id}"]`,
@@ -205,7 +227,7 @@ function CommentListItem({
                 />
               )}
 
-              {(currentUser?.user?.id === comment.creatorId || userSpaceRole === 'admin') && (
+              {isOwnerOrAdmin && (
                 <CommentMenu
                   onEditComment={handleEditToggle}
                   onDeleteComment={handleDeleteComment}
@@ -286,18 +308,42 @@ function CommentListItem({
                 {t("Applied")}
               </Badge>
             ) : (
-              canShowApply(comment, canEdit) && (
-                <Button
-                  size="compact-xs"
-                  variant="light"
-                  color="green"
-                  mt={6}
-                  onClick={handleApplySuggestion}
-                  loading={applySuggestionMutation.isPending}
-                  disabled={applySuggestionMutation.isPending}
-                >
-                  {t("Apply")}
-                </Button>
+              (canShowApply(comment, canEdit) ||
+                canShowDismiss(comment, canComment, isOwnerOrAdmin)) && (
+                <Group gap="xs" mt={6}>
+                  {canShowApply(comment, canEdit) && (
+                    <Button
+                      size="compact-xs"
+                      variant="light"
+                      color="green"
+                      onClick={handleApplySuggestion}
+                      loading={applySuggestionMutation.isPending}
+                      disabled={
+                        applySuggestionMutation.isPending ||
+                        dismissSuggestionMutation.isPending
+                      }
+                    >
+                      {t("Apply")}
+                    </Button>
+                  )}
+                  {/* Dismiss ("Не применять", #329): removes the suggestion
+                      without changing the page text. Gated on canComment. */}
+                  {canShowDismiss(comment, canComment, isOwnerOrAdmin) && (
+                    <Button
+                      size="compact-xs"
+                      variant="subtle"
+                      color="gray"
+                      onClick={handleDismissSuggestion}
+                      loading={dismissSuggestionMutation.isPending}
+                      disabled={
+                        applySuggestionMutation.isPending ||
+                        dismissSuggestionMutation.isPending
+                      }
+                    >
+                      {t("Dismiss")}
+                    </Button>
+                  )}
+                </Group>
               )
             )}
           </Box>

apps/client/src/features/comment/queries/comment-query.suggestion-outcome.test.tsx

@@ -0,0 +1,279 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import React from "react";
+import { renderHook, waitFor } from "@testing-library/react";
+import {
+  QueryClient,
+  QueryClientProvider,
+  InfiniteData,
+} from "@tanstack/react-query";
+
+/**
+ * Coverage for the ephemeral-suggestion (#329) cache reconciliation in
+ * useApplySuggestionMutation / useDismissSuggestionMutation: the mutations act on
+ * the server `outcome` — 'deleted' drops the comment from the local list,
+ * 'resolved' relocates it (by stamping resolvedAt, which the tabs split on).
+ */
+
+vi.mock("@mantine/notifications", () => ({
+  notifications: { show: vi.fn() },
+}));
+
+vi.mock("@/features/comment/services/comment-service", () => ({
+  applySuggestion: vi.fn(),
+  dismissSuggestion: vi.fn(),
+  createComment: vi.fn(),
+  updateComment: vi.fn(),
+  deleteComment: vi.fn(),
+  resolveComment: vi.fn(),
+  getPageComments: vi.fn(),
+}));
+
+import { notifications } from "@mantine/notifications";
+import {
+  applySuggestion,
+  dismissSuggestion,
+} from "@/features/comment/services/comment-service";
+import {
+  useApplySuggestionMutation,
+  useDismissSuggestionMutation,
+  RQ_KEY,
+} from "@/features/comment/queries/comment-query";
+import { IComment } from "@/features/comment/types/comment.types";
+
+const PAGE_ID = "page-1";
+
+function seededClient(comment: IComment) {
+  const queryClient = new QueryClient({
+    defaultOptions: { mutations: { retry: false } },
+  });
+  const seed: InfiniteData<any> = {
+    pageParams: [undefined],
+    pages: [{ items: [comment], meta: { hasNextPage: false, nextCursor: null } }],
+  };
+  queryClient.setQueryData(RQ_KEY(PAGE_ID), seed);
+  const wrapper = ({ children }: { children: React.ReactNode }) => (
+    <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
+  );
+  return { queryClient, wrapper };
+}
+
+function items(queryClient: QueryClient): IComment[] {
+  const cache = queryClient.getQueryData(RQ_KEY(PAGE_ID)) as
+    | InfiniteData<any>
+    | undefined;
+  return cache?.pages.flatMap((p) => p.items) ?? [];
+}
+
+const comment = (over?: Partial<IComment>): IComment =>
+  ({
+    id: "c-1",
+    pageId: PAGE_ID,
+    content: "{}",
+    creatorId: "u-1",
+    workspaceId: "ws-1",
+    createdAt: new Date(),
+    suggestedText: "new",
+    ...over,
+  }) as IComment;
+
+describe("useApplySuggestionMutation — outcome handling (#329)", () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it("outcome=deleted → removes the comment from the list", async () => {
+    vi.mocked(applySuggestion).mockResolvedValue({
+      id: "c-1",
+      pageId: PAGE_ID,
+      outcome: "deleted",
+    } as any);
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useApplySuggestionMutation(), {
+      wrapper,
+    });
+    await result.current.mutateAsync({ commentId: "c-1", pageId: PAGE_ID });
+    await waitFor(() => expect(result.current.isSuccess).toBe(true));
+
+    expect(items(queryClient)).toHaveLength(0);
+  });
+
+  it("outcome=resolved → keeps the comment and stamps resolvedAt/applied fields", async () => {
+    const resolvedAt = new Date();
+    vi.mocked(applySuggestion).mockResolvedValue({
+      id: "c-1",
+      pageId: PAGE_ID,
+      outcome: "resolved",
+      resolvedAt,
+      resolvedById: "u-1",
+      resolvedBy: { id: "u-1", name: "A" },
+      suggestionAppliedAt: resolvedAt,
+      suggestionAppliedById: "u-1",
+    } as any);
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useApplySuggestionMutation(), {
+      wrapper,
+    });
+    await result.current.mutateAsync({ commentId: "c-1", pageId: PAGE_ID });
+    await waitFor(() => expect(result.current.isSuccess).toBe(true));
+
+    const list = items(queryClient);
+    expect(list).toHaveLength(1);
+    expect(list[0].resolvedAt).toBe(resolvedAt);
+    expect(list[0].suggestionAppliedAt).toBe(resolvedAt);
+  });
+});
+
+describe("useDismissSuggestionMutation — outcome handling (#329)", () => {
+  beforeEach(() => vi.clearAllMocks());
+
+  it("outcome=deleted → removes the comment from the list", async () => {
+    vi.mocked(dismissSuggestion).mockResolvedValue({
+      id: "c-1",
+      pageId: PAGE_ID,
+      outcome: "deleted",
+    } as any);
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useDismissSuggestionMutation(), {
+      wrapper,
+    });
+    await result.current.mutateAsync({ commentId: "c-1", pageId: PAGE_ID });
+    await waitFor(() => expect(result.current.isSuccess).toBe(true));
+
+    expect(items(queryClient)).toHaveLength(0);
+  });
+
+  it("outcome=resolved → keeps the comment and stamps resolvedAt", async () => {
+    const resolvedAt = new Date();
+    vi.mocked(dismissSuggestion).mockResolvedValue({
+      id: "c-1",
+      pageId: PAGE_ID,
+      outcome: "resolved",
+      resolvedAt,
+      resolvedById: "u-1",
+      resolvedBy: { id: "u-1", name: "A" },
+    } as any);
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useDismissSuggestionMutation(), {
+      wrapper,
+    });
+    await result.current.mutateAsync({ commentId: "c-1", pageId: PAGE_ID });
+    await waitFor(() => expect(result.current.isSuccess).toBe(true));
+
+    const list = items(queryClient);
+    expect(list).toHaveLength(1);
+    expect(list[0].resolvedAt).toBe(resolvedAt);
+  });
+
+  it("idempotent race (404) → treated as success, comment removed from the list", async () => {
+    vi.mocked(dismissSuggestion).mockRejectedValue({
+      response: { status: 404 },
+    });
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useDismissSuggestionMutation(), {
+      wrapper,
+    });
+    // mutateAsync rejects even though onError reconciles the cache; swallow it.
+    await result.current
+      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID })
+      .catch(() => undefined);
+    await waitFor(() => expect(result.current.isError).toBe(true));
+
+    expect(items(queryClient)).toHaveLength(0);
+    // #338 F3: the idempotent race must still fire the SUCCESS toast, not just
+    // silently drop the comment.
+    expect(notifications.show).toHaveBeenCalledWith({
+      message: "Suggestion dismissed",
+    });
+  });
+
+  it("dismiss 400 (thread still alive) → NOT a success, comment kept, no green toast (#338 F2)", async () => {
+    // 400 means the thread is alive (already resolved / a reply raced in).
+    // Narrowed onError: only 404 is a success-noop; 400 must surface a real error
+    // and keep the comment in the cache.
+    vi.mocked(dismissSuggestion).mockRejectedValue({
+      response: { status: 400 },
+    });
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useDismissSuggestionMutation(), {
+      wrapper,
+    });
+    await result.current
+      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID })
+      .catch(() => undefined);
+    await waitFor(() => expect(result.current.isError).toBe(true));
+
+    // Comment NOT dropped from the cache.
+    expect(items(queryClient)).toHaveLength(1);
+    // A real (red) error, never the success message.
+    expect(notifications.show).toHaveBeenCalledWith(
+      expect.objectContaining({ color: "red" }),
+    );
+    expect(notifications.show).not.toHaveBeenCalledWith({
+      message: "Suggestion dismissed",
+    });
+  });
+
+  it("APPLY idempotent race (404) → treated as success, comment removed from the list", async () => {
+    // After #329 an applied reply-less suggestion is hard-deleted, so a racing
+    // second apply hits 404 — must reconcile to success like dismiss, not a red
+    // error (restores the #315 apply idempotency).
+    vi.mocked(applySuggestion).mockRejectedValue({
+      response: { status: 404 },
+    });
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useApplySuggestionMutation(), {
+      wrapper,
+    });
+    await result.current
+      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID })
+      .catch(() => undefined);
+    await waitFor(() => expect(result.current.isError).toBe(true));
+
+    expect(items(queryClient)).toHaveLength(0);
+    // #338 F3: the idempotent race must still fire the SUCCESS toast.
+    expect(notifications.show).toHaveBeenCalledWith({
+      message: "Suggestion applied",
+    });
+  });
+
+  it("APPLY 400 (thread resolved, not applied) → NOT a success, comment kept, red error (#338 F2)", async () => {
+    // apply's only 400 is "Cannot apply … on a resolved comment thread" — the
+    // thread was resolved (often with discussion) but NOT applied. It must be a
+    // real error surfacing the server message, and must NOT drop the live thread.
+    vi.mocked(applySuggestion).mockRejectedValue({
+      response: {
+        status: 400,
+        data: {
+          message: "Cannot apply a suggested edit on a resolved comment thread",
+        },
+      },
+    });
+    const { queryClient, wrapper } = seededClient(comment());
+
+    const { result } = renderHook(() => useApplySuggestionMutation(), {
+      wrapper,
+    });
+    await result.current
+      .mutateAsync({ commentId: "c-1", pageId: PAGE_ID })
+      .catch(() => undefined);
+    await waitFor(() => expect(result.current.isError).toBe(true));
+
+    // The live thread is NOT dropped from the cache.
+    expect(items(queryClient)).toHaveLength(1);
+    // Surfaces the server's specific message as a red error, never a success.
+    expect(notifications.show).toHaveBeenCalledWith(
+      expect.objectContaining({
+        message: "Cannot apply a suggested edit on a resolved comment thread",
+        color: "red",
+      }),
+    );
+    expect(notifications.show).not.toHaveBeenCalledWith({
+      message: "Suggestion applied",
+    });
+  });
+});

apps/client/src/features/comment/queries/comment-query.ts

@@ -8,6 +8,7 @@ import {
   applySuggestion,
   createComment,
   deleteComment,
+  dismissSuggestion,
   getPageComments,
   resolveComment,
   updateComment,
@@ -16,6 +17,7 @@ import {
   ICommentParams,
   IComment,
   IResolveComment,
+  ISuggestionOutcome,
 } from "@/features/comment/types/comment.types";
 import { notifications } from "@mantine/notifications";
 import { IPagination } from "@/lib/types.ts";
@@ -177,40 +179,121 @@ function updateCommentInCache(
   };
 }
 
+function removeCommentFromCache(
+  cache: InfiniteData<IPagination<IComment>>,
+  commentId: string,
+): InfiniteData<IPagination<IComment>> {
+  return {
+    ...cache,
+    pages: cache.pages.map((page) => ({
+      ...page,
+      items: page.items.filter((comment) => comment.id !== commentId),
+    })),
+  };
+}
+
+// Reconcile the local comment cache with an ephemeral-suggestion outcome (#329)
+// returned by apply/dismiss: 'deleted' → drop the comment (it disappeared);
+// 'resolved' → the thread had replies and was resolved, so carry the resolved
+// state through (which relocates it to the resolved tab).
+function applySuggestionOutcomeToCache(
+  queryClient: ReturnType<typeof useQueryClient>,
+  pageId: string,
+  commentId: string,
+  data: ISuggestionOutcome,
+) {
+  const cache = queryClient.getQueryData(RQ_KEY(pageId)) as
+    | InfiniteData<IPagination<IComment>>
+    | undefined;
+  if (!cache) return;
+
+  if (data.outcome === "deleted") {
+    queryClient.setQueryData(RQ_KEY(pageId), removeCommentFromCache(cache, commentId));
+    return;
+  }
+
+  // 'resolved' (or an older server that omits outcome): reflect the resolved
+  // state and the applied stamps (apply sets them; dismiss leaves them null).
+  queryClient.setQueryData(
+    RQ_KEY(pageId),
+    updateCommentInCache(cache, commentId, (comment) => ({
+      ...comment,
+      suggestionAppliedAt: data.suggestionAppliedAt,
+      suggestionAppliedById: data.suggestionAppliedById,
+      resolvedAt: data.resolvedAt,
+      resolvedById: data.resolvedById,
+      resolvedBy: data.resolvedBy,
+    })),
+  );
+}
+
 export function useApplySuggestionMutation() {
   const queryClient = useQueryClient();
   const { t } = useTranslation();
 
-  return useMutation<IComment, any, { commentId: string; pageId: string }>({
+  return useMutation<
+    ISuggestionOutcome,
+    any,
+    { commentId: string; pageId: string }
+  >({
     // No optimistic update: apply can fail with 409 (the commented text drifted),
     // so we only mutate the cache once the server confirms.
     mutationFn: ({ commentId }) => applySuggestion(commentId),
     onSuccess: (data, variables) => {
-      const cache = queryClient.getQueryData(
-        RQ_KEY(variables.pageId),
-      ) as InfiniteData<IPagination<IComment>> | undefined;
-
-      if (cache) {
-        queryClient.setQueryData(
-          RQ_KEY(variables.pageId),
-          updateCommentInCache(cache, variables.commentId, (comment) => ({
-            ...comment,
-            suggestionAppliedAt: data.suggestionAppliedAt,
-            suggestionAppliedById: data.suggestionAppliedById,
-            // The server auto-resolves the thread on apply — carry that through.
-            resolvedAt: data.resolvedAt,
-            resolvedById: data.resolvedById,
-            resolvedBy: data.resolvedBy,
-          })),
-        );
-      }
+      // Ephemeral (#329): the server hard-deletes the applied suggestion when the
+      // thread has no replies ('deleted') or resolves it when it does ('resolved').
+      applySuggestionOutcomeToCache(
+        queryClient,
+        variables.pageId,
+        variables.commentId,
+        data,
+      );
 
       notifications.show({ message: t("Suggestion applied") });
     },
-    onError: (err: any) => {
+    onError: (err: any, variables) => {
+      const status = err?.response?.status;
+      // Idempotent race (double-click, or apply↔dismiss): after #329 an applied
+      // reply-less suggestion is hard-deleted, so a second/racing apply hits 404
+      // (already gone). ONLY 404 is a real success-noop — drop it from the cache
+      // and report success, the user's intent is already satisfied (restores the
+      // #315 apply idempotency the ephemeral delete would otherwise break).
+      //
+      // 400 is NOT success (#338 F2): apply's only 400 is "Cannot apply … on a
+      // resolved comment thread" — the thread was resolved (often WITH a live
+      // discussion) but the edit was NOT applied. Treating it as "Suggestion
+      // applied" is a false success that also drops a live thread from the cache.
+      // The #315 idempotent repeat does NOT produce 400 (childless → 404;
+      // with-replies → 200), so we never lose idempotency by excluding it here.
+      if (status === 404) {
+        const cache = queryClient.getQueryData(RQ_KEY(variables.pageId)) as
+          | InfiniteData<IPagination<IComment>>
+          | undefined;
+        if (cache) {
+          queryClient.setQueryData(
+            RQ_KEY(variables.pageId),
+            removeCommentFromCache(cache, variables.commentId),
+          );
+        }
+        notifications.show({ message: t("Suggestion applied") });
+        return;
+      }
+      // 400 => the thread was resolved and the edit could not be applied. Show a
+      // real error and KEEP the comment in the cache (it is still alive). Prefer
+      // the server's specific message when it carries one.
+      if (status === 400) {
+        const serverMsg = err?.response?.data?.message;
+        notifications.show({
+          message:
+            typeof serverMsg === "string" && serverMsg.length > 0
+              ? serverMsg
+              : t("Failed to apply suggestion"),
+          color: "red",
+        });
+        return;
+      }
       // 409 => the commented text changed since the suggestion was made. Surface
       // a specific message (with the current text) rather than a generic error.
-      const status = err?.response?.status;
       const currentText = err?.response?.data?.currentText;
       if (status === 409 && typeof currentText === "string") {
         const shortText =
@@ -234,6 +317,58 @@ export function useApplySuggestionMutation() {
   });
 }
 
+export function useDismissSuggestionMutation() {
+  const queryClient = useQueryClient();
+  const { t } = useTranslation();
+
+  return useMutation<
+    ISuggestionOutcome,
+    any,
+    { commentId: string; pageId: string }
+  >({
+    mutationFn: ({ commentId }) => dismissSuggestion(commentId),
+    onSuccess: (data, variables) => {
+      // Ephemeral (#329): dismiss hard-deletes the suggestion when the thread has
+      // no replies ('deleted') or resolves it when it does ('resolved').
+      applySuggestionOutcomeToCache(
+        queryClient,
+        variables.pageId,
+        variables.commentId,
+        data,
+      );
+
+      notifications.show({ message: t("Suggestion dismissed") });
+    },
+    onError: (err: any, variables) => {
+      // Idempotent race (double-click, or apply↔dismiss): the comment is already
+      // gone (404). ONLY 404 is a real success-noop — drop it from the cache and
+      // report success, the user's intent (make it disappear) is satisfied.
+      //
+      // 400 is NOT success (#338 F2): it means the thread is still ALIVE (already
+      // resolved, or a reply raced in), so treating it as "dismissed" would drop
+      // a live thread from the cache. Show a real error and keep the comment.
+      const status = err?.response?.status;
+      if (status === 404) {
+        const cache = queryClient.getQueryData(RQ_KEY(variables.pageId)) as
+          | InfiniteData<IPagination<IComment>>
+          | undefined;
+        if (cache) {
+          queryClient.setQueryData(
+            RQ_KEY(variables.pageId),
+            removeCommentFromCache(cache, variables.commentId),
+          );
+        }
+        notifications.show({ message: t("Suggestion dismissed") });
+        return;
+      }
+      notifications.show({
+        message: t("Failed to dismiss suggestion"),
+        color: "red",
+      });
+    },
+  });
+}
+
 export function useResolveCommentMutation() {
   const queryClient = useQueryClient();
   const { t } = useTranslation();

apps/client/src/features/comment/services/comment-service.ts

@@ -3,6 +3,7 @@ import {
   ICommentParams,
   IComment,
   IResolveComment,
+  ISuggestionOutcome,
 } from "@/features/comment/types/comment.types";
 import { IPagination } from "@/lib/types.ts";
 
@@ -18,13 +19,24 @@ export async function resolveComment(data: IResolveComment): Promise<IComment> {
   return req.data;
 }
 
-export async function applySuggestion(commentId: string): Promise<IComment> {
+export async function applySuggestion(
+  commentId: string,
+): Promise<ISuggestionOutcome> {
   // Mirrors resolveComment: let axios reject on non-2xx so the mutation can read
   // the 409 body (`{ message, currentText }`) off err.response.data.
   const req = await api.post("/comments/apply-suggestion", { commentId });
   return req.data.data ?? req.data;
 }
 
+export async function dismissSuggestion(
+  commentId: string,
+): Promise<ISuggestionOutcome> {
+  // Dismiss ("Не применять") a suggested edit (#329): the server hard-deletes
+  // the comment (or resolves it when it has replies) and returns the outcome.
+  const req = await api.post("/comments/dismiss-suggestion", { commentId });
+  return req.data.data ?? req.data;
+}
+
 export async function updateComment(
   data: Partial<IComment>,
 ): Promise<IComment> {

apps/client/src/features/comment/types/comment.types.ts

@@ -60,6 +60,15 @@ export interface IResolveComment {
   resolved: boolean;
 }
 
+// Result of applying or dismissing an ephemeral suggested edit (#329). The
+// server hard-deletes the comment (`deleted`) unless the thread has replies, in
+// which case it is resolved (`resolved`). The returned comment fields carry the
+// resolved-branch state; `outcome` tells the client which optimistic action to
+// take (drop the comment vs. move it to the resolved tab).
+export type ISuggestionOutcome = IComment & {
+  outcome?: "deleted" | "resolved";
+};
+
 export interface ICommentParams extends QueryParams {
   pageId: string;
 }

apps/client/src/features/comment/utils/suggestion.ts

@@ -115,3 +115,25 @@ export function computeSuggestionDiff(
 
   return { old: oldSegments, new: newSegments };
 }
+
+// Whether the suggested-edit (#329) "Не применять" (Dismiss) button should be
+// shown. Dismiss does NOT change the page text (so it needs only canComment, not
+// canEdit), BUT a childless dismiss IRREVERSIBLY hard-deletes the comment, so the
+// server gates it on comment-owner-OR-space-admin (#338 F5). The button must
+// mirror that authz or a non-owner non-admin sees a live Dismiss that always
+// 403s → red error. Hence isOwnerOrAdmin is required IN ADDITION to canComment.
+// Same not-applied/not-resolved/top-level conditions as Apply.
+export function canShowDismiss(
+  comment: IComment,
+  canComment?: boolean,
+  isOwnerOrAdmin?: boolean,
+): boolean {
+  return Boolean(
+    canComment &&
+      isOwnerOrAdmin &&
+      comment.suggestedText &&
+      !comment.suggestionAppliedAt &&
+      !comment.resolvedAt &&
+      !comment.parentCommentId,
+  );
+}

apps/server/src/collaboration/collaboration.handler.spec.ts

@@ -130,3 +130,59 @@ describe('CollaborationHandler.applyCommentSuggestion', () => {
     expect(value).toBe(42);
   });
 });
+
+describe('CollaborationHandler.deleteCommentMark', () => {
+  it('strips the comment mark for the given commentId (ephemeral suggestion #329)', async () => {
+    const doc = buildDocWithComment('Hello world', 'c1');
+    const { hocuspocus, connection } = fakeHocuspocus(doc);
+    const handler = new CollaborationHandler();
+    const handlers = handler.getHandlers(hocuspocus);
+
+    await handlers.deleteCommentMark('doc-1', { commentId: 'c1', user });
+
+    // The mark is gone; the text itself stays (deleting the anchor, not the run).
+    const xmlText = (
+      doc.getXmlFragment('default').get(0) as Y.XmlElement
+    ).get(0) as Y.XmlText;
+    expect(xmlText.toDelta()).toEqual([{ insert: 'Hello world' }]);
+    expect(connection.transact).toHaveBeenCalledTimes(1);
+    expect(connection.disconnect).toHaveBeenCalledTimes(1);
+  });
+
+  it('routes the removal through removeYjsMarkByAttribute with the right args', async () => {
+    const doc = buildDocWithComment('abc', 'c9');
+    const { hocuspocus } = fakeHocuspocus(doc);
+    const spy = jest.spyOn(yjsUtil, 'removeYjsMarkByAttribute');
+    const handler = new CollaborationHandler();
+    const handlers = handler.getHandlers(hocuspocus);
+
+    await handlers.deleteCommentMark('doc-1', { commentId: 'c9', user });
+
+    expect(spy).toHaveBeenCalledWith(
+      doc.getXmlFragment('default'),
+      'comment',
+      'commentId',
+      'c9',
+    );
+    spy.mockRestore();
+  });
+
+  it('leaves a different comment\'s mark intact', async () => {
+    const doc = buildDocWithComment('keep me', 'other');
+    const { hocuspocus } = fakeHocuspocus(doc);
+    const handler = new CollaborationHandler();
+    const handlers = handler.getHandlers(hocuspocus);
+
+    await handlers.deleteCommentMark('doc-1', { commentId: 'c1', user });
+
+    const xmlText = (
+      doc.getXmlFragment('default').get(0) as Y.XmlElement
+    ).get(0) as Y.XmlText;
+    expect(xmlText.toDelta()).toEqual([
+      {
+        insert: 'keep me',
+        attributes: { comment: { commentId: 'other', resolved: false } },
+      },
+    ]);
+  });
+});

apps/server/src/collaboration/collaboration.handler.ts

@@ -6,6 +6,7 @@ import {
   tiptapExtensions,
 } from './collaboration.util';
 import {
+  removeYjsMarkByAttribute,
   replaceYjsMarkedText,
   setYjsMark,
   updateYjsMarkAttribute,
@@ -78,6 +79,40 @@ export class CollaborationHandler {
           },
         );
       },
+      deleteCommentMark: async (
+        documentName: string,
+        payload: {
+          commentId: string;
+          user: User;
+        },
+      ) => {
+        const { commentId, user } = payload;
+        // Ephemeral suggestions (#329): when a suggestion-edit is dismissed or an
+        // applied one has no replies, the comment is hard-deleted and its inline
+        // anchor must vanish too. Mirror resolveCommentMark exactly, but instead
+        // of flipping the mark's `resolved` attribute we STRIP the `comment` mark
+        // entirely via removeYjsMarkByAttribute so no orphan highlight remains in
+        // the collaborative document.
+        //
+        // Routing this through collaboration.gateway's handleYjsEvent means the
+        // COLLAB_DISABLE_REDIS path invokes this handler directly (never a silent
+        // no-op) and a missing live instance is a hard error — the same guarantee
+        // applyCommentSuggestion/resolveCommentMark rely on.
+        await this.withYdocConnection(
+          hocuspocus,
+          documentName,
+          { user },
+          (doc) => {
+            const fragment = doc.getXmlFragment('default');
+            removeYjsMarkByAttribute(
+              fragment,
+              'comment',
+              'commentId',
+              commentId,
+            );
+          },
+        );
+      },
       applyCommentSuggestion: async (
         documentName: string,
         payload: {

apps/server/src/common/events/audit-events.ts

@@ -52,6 +52,7 @@ export const AuditEvent = {
   COMMENT_RESOLVED: 'comment.resolved',
   COMMENT_REOPENED: 'comment.reopened',
   COMMENT_SUGGESTION_APPLIED: 'comment.suggestion_applied',
+  COMMENT_SUGGESTION_DISMISSED: 'comment.suggestion_dismissed',
 
   // Page
   PAGE_CREATED: 'page.created',

apps/server/src/core/comment/comment.controller.spec.ts

@@ -1,4 +1,5 @@
 import {
+  BadRequestException,
   ForbiddenException,
   NotFoundException,
 } from '@nestjs/common';
@@ -117,3 +118,207 @@ describe('CommentController apply-suggestion authz', () => {
     expect(commentService.applySuggestion).not.toHaveBeenCalled();
   });
 });
+
+/**
+ * Authz-gate tests for the dismiss-suggestion route (#329). Dismissing a
+ * suggestion does NOT change the page text, so it authorizes with
+ * validateCanComment (NOT validateCanEdit) — a viewer allowed to comment but not
+ * edit can still dismiss. The gate MUST run BEFORE the service (which performs
+ * the delete/resolve + mark removal). These tests pin that boundary.
+ */
+describe('CommentController dismiss-suggestion authz', () => {
+  // isAdmin=false → ability.cannot(Manage, Settings) returns true (i.e. the user
+  // is NOT a space admin). Flip to true to model a space admin.
+  function makeController(isAdmin = false) {
+    const commentService = {
+      dismissSuggestion: jest.fn(async () => ({
+        id: 'c-1',
+        outcome: 'deleted',
+      })),
+    };
+    const commentRepo = { findById: jest.fn() };
+    const pageRepo = { findById: jest.fn() };
+    const spaceAbility = {
+      createForUser: jest.fn(async () => ({
+        cannot: jest.fn(() => !isAdmin),
+      })),
+    } as any;
+    const pageAccessService = {
+      validateCanComment: jest.fn(async () => undefined),
+      validateCanEdit: jest.fn(async () => undefined),
+    };
+    const wsService = {} as any;
+    const auditService = { log: jest.fn() };
+
+    const controller = new CommentController(
+      commentService as any,
+      commentRepo as any,
+      pageRepo as any,
+      spaceAbility,
+      pageAccessService as any,
+      wsService,
+      auditService as any,
+    );
+    return {
+      controller,
+      commentService,
+      commentRepo,
+      pageRepo,
+      pageAccessService,
+      spaceAbility,
+    };
+  }
+
+  const user: any = { id: 'u-1' };
+  const workspace: any = { id: 'ws-1' };
+  const provenance: any = undefined;
+  const dto: any = { commentId: 'c-1' };
+  // Owned by the acting user (u-1) unless a test overrides creatorId.
+  const comment = {
+    id: 'c-1',
+    pageId: 'p-1',
+    spaceId: 'sp-1',
+    creatorId: 'u-1',
+    suggestedText: 'new text',
+    selection: 'old text',
+  };
+  const page = { id: 'p-1', spaceId: 'sp-1', deletedAt: null };
+
+  it('authorizes with validateCanComment (NOT validateCanEdit) then calls the service', async () => {
+    const {
+      controller,
+      commentRepo,
+      pageRepo,
+      pageAccessService,
+      commentService,
+    } = makeController();
+    commentRepo.findById.mockResolvedValue(comment);
+    pageRepo.findById.mockResolvedValue(page);
+    const dismissed = { id: 'c-1', outcome: 'deleted' };
+    commentService.dismissSuggestion.mockResolvedValue(dismissed);
+
+    const result = await controller.dismissSuggestion(
+      dto,
+      user,
+      workspace,
+      provenance,
+    );
+
+    expect(pageAccessService.validateCanComment).toHaveBeenCalledWith(
+      page,
+      user,
+      workspace.id,
+    );
+    // Dismiss must NOT require edit access.
+    expect(pageAccessService.validateCanEdit).not.toHaveBeenCalled();
+    expect(commentService.dismissSuggestion).toHaveBeenCalledWith(
+      comment,
+      user,
+      provenance,
+    );
+    expect(result).toBe(dismissed);
+  });
+
+  it('validateCanComment throwing Forbidden rejects AND dismissSuggestion is never called', async () => {
+    const {
+      controller,
+      commentRepo,
+      pageRepo,
+      pageAccessService,
+      commentService,
+    } = makeController();
+    commentRepo.findById.mockResolvedValue(comment);
+    pageRepo.findById.mockResolvedValue(page);
+    pageAccessService.validateCanComment.mockRejectedValue(
+      new ForbiddenException('no comment access'),
+    );
+
+    await expect(
+      controller.dismissSuggestion(dto, user, workspace, provenance),
+    ).rejects.toBeInstanceOf(ForbiddenException);
+
+    expect(commentService.dismissSuggestion).not.toHaveBeenCalled();
+  });
+
+  it('missing comment: NotFound without authorizing or dismissing', async () => {
+    const { controller, commentRepo, pageRepo, pageAccessService, commentService } =
+      makeController();
+    commentRepo.findById.mockResolvedValue(null);
+
+    await expect(
+      controller.dismissSuggestion(dto, user, workspace, provenance),
+    ).rejects.toBeInstanceOf(NotFoundException);
+
+    expect(pageRepo.findById).not.toHaveBeenCalled();
+    expect(pageAccessService.validateCanComment).not.toHaveBeenCalled();
+    expect(commentService.dismissSuggestion).not.toHaveBeenCalled();
+  });
+
+  it('propagates a service BadRequest (e.g. already applied/resolved) unchanged', async () => {
+    const { controller, commentRepo, pageRepo, commentService } =
+      makeController();
+    commentRepo.findById.mockResolvedValue(comment);
+    pageRepo.findById.mockResolvedValue(page);
+    commentService.dismissSuggestion.mockRejectedValue(
+      new BadRequestException('already applied'),
+    );
+
+    await expect(
+      controller.dismissSuggestion(dto, user, workspace, provenance),
+    ).rejects.toBeInstanceOf(BadRequestException);
+  });
+
+  // --- #338 owner-or-space-admin gate (mirrors POST /comments/delete) --------
+  // A childless dismiss irreversibly hard-deletes the comment, so canComment is
+  // not enough: only the comment owner or a space admin may dismiss.
+
+  it('owner dismisses their own suggestion → allowed, no admin check needed', async () => {
+    const { controller, commentRepo, pageRepo, commentService, spaceAbility } =
+      makeController(false);
+    // comment.creatorId === user.id (owner).
+    commentRepo.findById.mockResolvedValue(comment);
+    pageRepo.findById.mockResolvedValue(page);
+
+    await controller.dismissSuggestion(dto, user, workspace, provenance);
+
+    // Owner short-circuits the admin lookup.
+    expect(spaceAbility.createForUser).not.toHaveBeenCalled();
+    expect(commentService.dismissSuggestion).toHaveBeenCalledWith(
+      comment,
+      user,
+      provenance,
+    );
+  });
+
+  it('non-owner non-admin → Forbidden AND the service is never called', async () => {
+    const { controller, commentRepo, pageRepo, commentService, spaceAbility } =
+      makeController(false); // NOT a space admin
+    commentRepo.findById.mockResolvedValue({
+      ...comment,
+      creatorId: 'someone-else',
+    });
+    pageRepo.findById.mockResolvedValue(page);
+
+    await expect(
+      controller.dismissSuggestion(dto, user, workspace, provenance),
+    ).rejects.toBeInstanceOf(ForbiddenException);
+
+    expect(spaceAbility.createForUser).toHaveBeenCalledWith(user, comment.spaceId);
+    expect(commentService.dismissSuggestion).not.toHaveBeenCalled();
+  });
+
+  it('non-owner space admin → allowed to dismiss another user’s suggestion', async () => {
+    const { controller, commentRepo, pageRepo, commentService, spaceAbility } =
+      makeController(true); // space admin
+    commentRepo.findById.mockResolvedValue({
+      ...comment,
+      creatorId: 'someone-else',
+    });
+    pageRepo.findById.mockResolvedValue(page);
+
+    await controller.dismissSuggestion(dto, user, workspace, provenance);
+
+    expect(spaceAbility.createForUser).toHaveBeenCalledWith(user, comment.spaceId);
+    expect(commentService.dismissSuggestion).toHaveBeenCalled();
+  });
+});

apps/server/src/core/comment/comment.controller.ts

@@ -15,6 +15,7 @@ import { CreateCommentDto } from './dto/create-comment.dto';
 import { UpdateCommentDto } from './dto/update-comment.dto';
 import { ResolveCommentDto } from './dto/resolve-comment.dto';
 import { ApplySuggestionDto } from './dto/apply-suggestion.dto';
+import { DismissSuggestionDto } from './dto/dismiss-suggestion.dto';
 import { PageIdDto, CommentIdDto } from './dto/comments.input';
 import { AuthUser } from '../../common/decorators/auth-user.decorator';
 import { AuthWorkspace } from '../../common/decorators/auth-workspace.decorator';
@@ -234,6 +235,59 @@ export class CommentController {
     return this.commentService.applySuggestion(comment, user, provenance);
   }
 
+  @HttpCode(HttpStatus.OK)
+  @Post('dismiss-suggestion')
+  async dismissSuggestion(
+    @Body() dto: DismissSuggestionDto,
+    @AuthUser() user: User,
+    @AuthWorkspace() workspace: Workspace,
+    @AuthProvenance() provenance: AuthProvenanceData,
+  ) {
+    const comment = await this.commentRepo.findById(dto.commentId, {
+      includeCreator: true,
+      includeResolvedBy: true,
+    });
+    if (!comment) {
+      throw new NotFoundException('Comment not found');
+    }
+
+    const page = await this.pageRepo.findById(comment.pageId);
+    if (!page || page.deletedAt) {
+      throw new NotFoundException('Page not found');
+    }
+
+    // Authorize BEFORE revealing any structural detail (metadata-disclosure
+    // hygiene, mirroring apply-suggestion). Dismissing a suggestion does NOT
+    // change the page text — it only removes/resolves the comment — so the
+    // page-level gate is comment access (canComment), NOT edit access. A viewer
+    // allowed to comment but not edit can still dismiss their own suggestion.
+    // The structural 400s (top-level / has-a-suggested-edit / not applied /
+    // not resolved) are re-checked by the service below.
+    await this.pageAccessService.validateCanComment(page, user, workspace.id);
+
+    // AUTHZ (#338): a childless dismiss IRREVERSIBLY hard-deletes the comment,
+    // so — beyond canComment — restrict it to the comment owner OR a space
+    // admin, exactly like POST /comments/delete. canComment alone is not enough:
+    // it would let any bystander commenter erase another user's suggestion for
+    // good. (apply-suggestion deliberately stays on canEdit: accepting an edit
+    // is the editor's semantics, not the suggestion author's.)
+    const isOwner = comment.creatorId === user.id;
+    if (!isOwner) {
+      const ability = await this.spaceAbility.createForUser(
+        user,
+        comment.spaceId,
+      );
+      // Space admin can dismiss any suggestion.
+      if (ability.cannot(SpaceCaslAction.Manage, SpaceCaslSubject.Settings)) {
+        throw new ForbiddenException(
+          'You can only dismiss your own suggestions',
+        );
+      }
+    }
+
+    return this.commentService.dismissSuggestion(comment, user, provenance);
+  }
+
   @HttpCode(HttpStatus.OK)
   @Post('delete')
   async delete(@Body() input: CommentIdDto, @AuthUser() user: User, @AuthWorkspace() workspace: Workspace) {

apps/server/src/core/comment/comment.service.apply-suggestion.spec.ts

@@ -13,17 +13,27 @@ import { AuditEvent, AuditResource } from '../../common/events/audit-events';
  *
  * The collaboration gateway verdict is the pivot of the whole flow, so each test
  * pins a specific { applied, currentText } and asserts the DB persistence,
- * auto-resolve, audit, ws broadcast, and error mapping that follow from it.
+ * settle (ephemeral delete vs. resolve), audit, ws broadcast, and error mapping
+ * that follow from it.
+ *
+ * Ephemeral rule (#329): once applied a suggestion DISAPPEARS (hard-delete +
+ * strip the inline anchor mark) UNLESS the thread has replies, in which case it
+ * is resolved to preserve the discussion. `hasChildren` selects the branch.
  */
 describe('CommentService — applySuggestion', () => {
   const UPDATED = { id: 'c-1', __updated: true } as any;
 
-  function makeService(verdict: unknown) {
+  function makeService(verdict: unknown, hasChildren = false, deletedRows = 1) {
     const commentRepo: any = {
       // Both the applied-stamp re-read and resolveComment's re-read go through
       // findById; return a recognizable enriched row.
       findById: jest.fn(async () => UPDATED),
       updateComment: jest.fn(async () => undefined),
+      hasChildren: jest.fn(async () => hasChildren),
+      deleteComment: jest.fn(async () => undefined),
+      // #338 F1: the childless ephemeral delete is atomic-conditional and
+      // returns the number of rows removed (1 = deleted, 0 = a reply raced in).
+      deleteCommentIfChildless: jest.fn(async () => deletedRows),
     };
     const pageRepo: any = {};
     const wsService: any = { emitCommentEvent: jest.fn() };
@@ -74,7 +84,9 @@ describe('CommentService — applySuggestion', () => {
       .map((c: any[]) => c[0])
       .find((patch: any) => 'suggestionAppliedAt' in patch);
 
-  it('applied=true → replaces text, persists applied stamps, auto-resolves, audits, returns updated', async () => {
+  // --- no replies → ephemeral delete branch -------------------------------
+
+  it('applied=true, no replies → replaces text, hard-deletes, strips the anchor mark, audits APPLIED, outcome=deleted', async () => {
     const { service, commentRepo, wsService, collaborationGateway, auditService } =
       makeService({ applied: true, currentText: 'new text' });
 
@@ -92,37 +104,34 @@ describe('CommentService — applySuggestion', () => {
       }),
     );
 
-    // Applied stamps persisted.
-    const patch = appliedPatch(commentRepo);
-    expect(patch.suggestionAppliedAt).toBeInstanceOf(Date);
-    expect(patch.suggestionAppliedById).toBe('user-1');
+    // Ephemeral: the redundant comment is hard-deleted (atomic-conditional) and
+    // its inline anchor mark removed via the deleteCommentMark collab event.
+    expect(commentRepo.deleteCommentIfChildless).toHaveBeenCalledWith('c-1');
+    expect(collaborationGateway.handleYjsEvent).toHaveBeenCalledWith(
+      'deleteCommentMark',
+      'page.page-1',
+      expect.objectContaining({ commentId: 'c-1', user: expect.any(Object) }),
+    );
+    // No applied stamps are written for a row about to be deleted.
+    expect(appliedPatch(commentRepo)).toBeUndefined();
 
-    // Auto-resolved: resolveComment writes a resolvedAt/resolvedById patch too.
-    const resolvePatch = commentRepo.updateComment.mock.calls
-      .map((c: any[]) => c[0])
-      .find((p: any) => 'resolvedAt' in p);
-    expect(resolvePatch.resolvedAt).toBeInstanceOf(Date);
-    expect(resolvePatch.resolvedById).toBe('user-1');
-
-    // Audit + broadcast + return.
+    // Broadcast a deletion, audit the (still-applied) suggestion, report outcome.
+    expect(wsService.emitCommentEvent).toHaveBeenCalledWith(
+      'space-1',
+      'page-1',
+      expect.objectContaining({ operation: 'commentDeleted', commentId: 'c-1' }),
+    );
     expect(auditService.log).toHaveBeenCalledWith(
       expect.objectContaining({
         event: AuditEvent.COMMENT_SUGGESTION_APPLIED,
         resourceType: AuditResource.COMMENT,
         resourceId: 'c-1',
-        spaceId: 'space-1',
-        metadata: { pageId: 'page-1' },
       }),
     );
-    expect(wsService.emitCommentEvent).toHaveBeenCalledWith(
-      'space-1',
-      'page-1',
-      expect.objectContaining({ operation: 'commentUpdated', comment: UPDATED }),
-    );
-    expect(result).toBe(UPDATED);
+    expect(result.outcome).toBe('deleted');
   });
 
-  it('applied=false but currentText === suggestedText → idempotent success (no 409)', async () => {
+  it('applied=false but currentText === suggestedText, no replies → idempotent delete (no 409)', async () => {
     const { service, commentRepo, auditService } = makeService({
       applied: false,
       currentText: 'new text',
@@ -130,15 +139,55 @@ describe('CommentService — applySuggestion', () => {
 
     const result = await service.applySuggestion(suggestionComment(), user());
 
-    // The stamps are still persisted (reconciling a crash between the doc
-    // mutation and the DB write) and the call succeeds.
+    expect(commentRepo.deleteCommentIfChildless).toHaveBeenCalledWith('c-1');
+    expect(auditService.log).toHaveBeenCalledTimes(1);
+    expect(result.outcome).toBe('deleted');
+  });
+
+  // --- has replies → resolve branch (discussion preserved) ----------------
+
+  it('applied=true, WITH replies → resolves (not delete), persists applied stamps, audits, outcome=resolved', async () => {
+    const { service, commentRepo, wsService, collaborationGateway, auditService } =
+      makeService({ applied: true, currentText: 'new text' }, true);
+
+    const result = await service.applySuggestion(suggestionComment(), user());
+
+    // Applied stamps persisted.
     const patch = appliedPatch(commentRepo);
     expect(patch.suggestionAppliedAt).toBeInstanceOf(Date);
     expect(patch.suggestionAppliedById).toBe('user-1');
-    expect(auditService.log).toHaveBeenCalledTimes(1);
-    expect(result).toBe(UPDATED);
+
+    // Auto-resolved (resolveComment writes the resolve patch + resolve mark).
+    const resolvePatch = commentRepo.updateComment.mock.calls
+      .map((c: any[]) => c[0])
+      .find((p: any) => 'resolvedAt' in p);
+    expect(resolvePatch.resolvedAt).toBeInstanceOf(Date);
+    expect(resolvePatch.resolvedById).toBe('user-1');
+
+    // NOT deleted; broadcast an update, not a deletion.
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
+    expect(collaborationGateway.handleYjsEvent).not.toHaveBeenCalledWith(
+      'deleteCommentMark',
+      expect.anything(),
+      expect.anything(),
+    );
+    expect(wsService.emitCommentEvent).toHaveBeenCalledWith(
+      'space-1',
+      'page-1',
+      expect.objectContaining({ operation: 'commentUpdated', comment: UPDATED }),
+    );
+
+    expect(auditService.log).toHaveBeenCalledWith(
+      expect.objectContaining({
+        event: AuditEvent.COMMENT_SUGGESTION_APPLIED,
+      }),
+    );
+    expect(result.id).toBe('c-1');
+    expect(result.outcome).toBe('resolved');
   });
 
+  // --- error / rejection branches -----------------------------------------
+
   it('applied=false and currentText differs → ConflictException with currentText in payload', async () => {
     const { service, commentRepo, auditService } = makeService({
       applied: false,
@@ -153,14 +202,14 @@ describe('CommentService — applySuggestion', () => {
     expect(err.getResponse()).toMatchObject({
       currentText: 'someone else edited this',
     });
-    // No persistence and no audit on a conflict.
-    expect(appliedPatch(commentRepo)).toBeUndefined();
+    // No delete and no audit on a conflict.
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
     expect(auditService.log).not.toHaveBeenCalled();
   });
 
-  it('already-applied AND already-resolved → idempotent success, no collab call, no re-resolve (#315 double-click)', async () => {
+  it('already-applied WITH replies → idempotent success, no re-apply, resolve branch', async () => {
     const { service, collaborationGateway, commentRepo, auditService } =
-      makeService({ applied: true, currentText: 'new text' });
+      makeService({ applied: true, currentText: 'new text' }, true);
 
     const result = await service.applySuggestion(
       suggestionComment({
@@ -171,17 +220,20 @@ describe('CommentService — applySuggestion', () => {
       user(),
     );
 
-    // Idempotent SUCCESS, not a 409. The suggestion is already applied, so the
-    // collaborative document is never touched again and nothing is re-stamped
-    // or re-resolved.
-    expect(result).toBe(UPDATED);
-    expect(collaborationGateway.handleYjsEvent).not.toHaveBeenCalled();
-    expect(commentRepo.updateComment).not.toHaveBeenCalled();
-    // Same success shape as the applied path (broadcast + audit).
+    // Idempotent SUCCESS. The suggestion is already applied, so the document is
+    // never re-mutated (no applyCommentSuggestion) and nothing is re-stamped.
+    expect(collaborationGateway.handleYjsEvent).not.toHaveBeenCalledWith(
+      'applyCommentSuggestion',
+      expect.anything(),
+      expect.anything(),
+    );
+    expect(appliedPatch(commentRepo)).toBeUndefined();
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
     expect(auditService.log).toHaveBeenCalledTimes(1);
+    expect(result.outcome).toBe('resolved');
   });
 
-  it('already-applied but NOT resolved (crash window) → idempotent success, self-heals resolve, no re-apply', async () => {
+  it('already-applied, no replies (double-click after a delete) → deletes idempotently', async () => {
     const { service, collaborationGateway, commentRepo } = makeService({
       applied: true,
       currentText: 'new text',
@@ -192,28 +244,43 @@ describe('CommentService — applySuggestion', () => {
       user(),
     );
 
-    expect(result).toBe(UPDATED);
-
-    // The suggestion is NOT re-applied to the document…
+    // No re-apply to the document; the childless applied comment is removed.
     expect(collaborationGateway.handleYjsEvent).not.toHaveBeenCalledWith(
       'applyCommentSuggestion',
       expect.anything(),
       expect.anything(),
     );
-    // …but the open thread is self-healed to resolved via resolveComment, which
-    // writes the resolve patch and updates the resolve mark.
+    expect(commentRepo.deleteCommentIfChildless).toHaveBeenCalledWith('c-1');
+    expect(result.outcome).toBe('deleted');
+  });
+
+  it('applied=true, no replies at read time but a reply races in (conditional delete → 0 rows) → resolves instead, no hard-delete, outcome=resolved (#338 F1)', async () => {
+    // The suggested text is already applied to the document, but between the
+    // hasChildren read and the atomic delete a reply landed. The parent must NOT
+    // be hard-deleted (cascade would destroy the reply); resolve the thread.
+    const { service, commentRepo, wsService, collaborationGateway } =
+      makeService({ applied: true, currentText: 'new text' }, false, 0);
+
+    const result = await service.applySuggestion(suggestionComment(), user());
+
+    expect(commentRepo.deleteCommentIfChildless).toHaveBeenCalledWith('c-1');
+    // No deletion broadcast — the row + the racing reply survive.
+    expect(wsService.emitCommentEvent).not.toHaveBeenCalledWith(
+      expect.anything(),
+      expect.anything(),
+      expect.objectContaining({ operation: 'commentDeleted' }),
+    );
+    // Fell back to resolving.
     const resolvePatch = commentRepo.updateComment.mock.calls
       .map((c: any[]) => c[0])
       .find((p: any) => 'resolvedAt' in p);
     expect(resolvePatch.resolvedAt).toBeInstanceOf(Date);
-    expect(resolvePatch.resolvedById).toBe('user-1');
     expect(collaborationGateway.handleYjsEvent).toHaveBeenCalledWith(
       'resolveCommentMark',
       'page.page-1',
       expect.objectContaining({ commentId: 'c-1', resolved: true }),
     );
-    // The applied stamps are NOT re-written (already stamped).
-    expect(appliedPatch(commentRepo)).toBeUndefined();
+    expect(result.outcome).toBe('resolved');
   });
 
   it('rejects a comment with no suggestedText', async () => {
@@ -238,8 +305,8 @@ describe('CommentService — applySuggestion', () => {
       service.applySuggestion(suggestionComment(), user()),
     ).rejects.toThrow(InternalServerErrorException);
 
-    // Nothing persisted, nothing audited.
-    expect(appliedPatch(commentRepo)).toBeUndefined();
+    // Nothing deleted, nothing audited.
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
     expect(auditService.log).not.toHaveBeenCalled();
   });
 });

apps/server/src/core/comment/comment.service.dismiss-suggestion.spec.ts

@@ -0,0 +1,229 @@
+import { BadRequestException } from '@nestjs/common';
+import { CommentService } from './comment.service';
+import { AuditEvent, AuditResource } from '../../common/events/audit-events';
+
+/**
+ * Coverage for CommentService.dismissSuggestion (#329). Dismiss ("Не применять")
+ * removes a suggested edit WITHOUT changing the page text: the comment
+ * disappears (hard-delete + strip the inline anchor mark) unless the thread has
+ * replies, in which case it is resolved to preserve the discussion.
+ *
+ * The permission gate (canComment, NOT canEdit) lives in the controller and is
+ * covered in comment.controller.spec.ts; here we pin the service's own state
+ * guards and the delete-vs-resolve fork.
+ */
+describe('CommentService — dismissSuggestion', () => {
+  const UPDATED = { id: 'c-1', __updated: true } as any;
+
+  function makeService(hasChildren = false, deletedRows = 1) {
+    const commentRepo: any = {
+      findById: jest.fn(async () => UPDATED),
+      updateComment: jest.fn(async () => undefined),
+      hasChildren: jest.fn(async () => hasChildren),
+      deleteComment: jest.fn(async () => undefined),
+      // #338 F1: the childless ephemeral delete is now atomic-conditional and
+      // returns the number of rows removed (1 = deleted, 0 = a reply raced in).
+      deleteCommentIfChildless: jest.fn(async () => deletedRows),
+    };
+    const pageRepo: any = {};
+    const wsService: any = { emitCommentEvent: jest.fn() };
+    const collaborationGateway: any = {
+      handleYjsEvent: jest.fn(async () => undefined),
+    };
+    const generalQueue: any = { add: jest.fn(() => Promise.resolve()) };
+    const notificationQueue: any = { add: jest.fn(async () => undefined) };
+    const auditService: any = { log: jest.fn() };
+
+    const service = new CommentService(
+      commentRepo,
+      pageRepo,
+      wsService,
+      collaborationGateway,
+      generalQueue,
+      notificationQueue,
+      auditService,
+    );
+
+    return { service, commentRepo, wsService, collaborationGateway, auditService };
+  }
+
+  const suggestionComment = (over?: Partial<any>): any => ({
+    id: 'c-1',
+    pageId: 'page-1',
+    spaceId: 'space-1',
+    workspaceId: 'ws-1',
+    creatorId: 'user-1',
+    parentCommentId: null,
+    selection: 'old text',
+    suggestedText: 'new text',
+    suggestionAppliedAt: null,
+    resolvedAt: null,
+    ...over,
+  });
+  const user = (over?: Partial<any>): any => ({ id: 'user-1', ...over });
+
+  it('no replies → hard-deletes, strips the anchor mark, does NOT touch page text, audits DISMISSED, outcome=deleted', async () => {
+    const { service, commentRepo, wsService, collaborationGateway, auditService } =
+      makeService(false);
+
+    const result = await service.dismissSuggestion(suggestionComment(), user());
+
+    // Never applies the suggestion to the document.
+    expect(collaborationGateway.handleYjsEvent).not.toHaveBeenCalledWith(
+      'applyCommentSuggestion',
+      expect.anything(),
+      expect.anything(),
+    );
+    // Hard-delete (atomic-conditional) + strip mark.
+    expect(commentRepo.deleteCommentIfChildless).toHaveBeenCalledWith('c-1');
+    expect(collaborationGateway.handleYjsEvent).toHaveBeenCalledWith(
+      'deleteCommentMark',
+      'page.page-1',
+      expect.objectContaining({ commentId: 'c-1', user: expect.any(Object) }),
+    );
+    expect(wsService.emitCommentEvent).toHaveBeenCalledWith(
+      'space-1',
+      'page-1',
+      expect.objectContaining({ operation: 'commentDeleted', commentId: 'c-1' }),
+    );
+    expect(auditService.log).toHaveBeenCalledWith(
+      expect.objectContaining({
+        event: AuditEvent.COMMENT_SUGGESTION_DISMISSED,
+        resourceType: AuditResource.COMMENT,
+        resourceId: 'c-1',
+      }),
+    );
+    expect(result.outcome).toBe('deleted');
+  });
+
+  it('no replies → if the anchor-mark removal FAILS, the row is NOT deleted and the error propagates (#329: no orphan anchor)', async () => {
+    const { service, commentRepo, wsService, collaborationGateway } =
+      makeService(false);
+    // Mark removal is FATAL and runs BEFORE the irreversible row delete: a collab
+    // failure (e.g. COLLAB_DISABLE_REDIS "no live instance") must abort the whole
+    // operation, leaving row + mark consistent — never a deleted row with an
+    // orphan anchor left in the document reporting success.
+    collaborationGateway.handleYjsEvent = jest.fn(async () => {
+      throw new Error('requires a live collaboration instance');
+    });
+
+    await expect(
+      service.dismissSuggestion(suggestionComment(), user()),
+    ).rejects.toThrow(/live collaboration/);
+
+    expect(commentRepo.deleteCommentIfChildless).not.toHaveBeenCalled();
+    expect(wsService.emitCommentEvent).not.toHaveBeenCalledWith(
+      expect.anything(),
+      expect.anything(),
+      expect.objectContaining({ operation: 'commentDeleted' }),
+    );
+  });
+
+  it('WITH replies → resolves (not delete), does NOT apply, audits DISMISSED, outcome=resolved', async () => {
+    const { service, commentRepo, wsService, collaborationGateway, auditService } =
+      makeService(true);
+
+    const result = await service.dismissSuggestion(suggestionComment(), user());
+
+    // Resolved via resolveComment (resolve patch + resolve mark), NOT deleted.
+    const resolvePatch = commentRepo.updateComment.mock.calls
+      .map((c: any[]) => c[0])
+      .find((p: any) => 'resolvedAt' in p);
+    expect(resolvePatch.resolvedAt).toBeInstanceOf(Date);
+    expect(resolvePatch.resolvedById).toBe('user-1');
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
+    expect(collaborationGateway.handleYjsEvent).toHaveBeenCalledWith(
+      'resolveCommentMark',
+      'page.page-1',
+      expect.objectContaining({ commentId: 'c-1', resolved: true }),
+    );
+    // No applied stamp — dismiss does not apply the edit.
+    const appliedPatch = commentRepo.updateComment.mock.calls
+      .map((c: any[]) => c[0])
+      .find((p: any) => 'suggestionAppliedAt' in p);
+    expect(appliedPatch).toBeUndefined();
+
+    expect(auditService.log).toHaveBeenCalledWith(
+      expect.objectContaining({
+        event: AuditEvent.COMMENT_SUGGESTION_DISMISSED,
+      }),
+    );
+    expect(result.outcome).toBe('resolved');
+  });
+
+  it('reply races in after the childless read (conditional delete → 0 rows) → resolves instead, does NOT hard-delete, reply survives, outcome=resolved (#338 F1)', async () => {
+    // hasChildren=false selects the ephemeral branch (the read saw no replies),
+    // but the atomic delete matches 0 rows because a reply landed in the window
+    // between that read and the delete. The parent must NOT be hard-deleted
+    // (a cascade would destroy the just-added reply); the thread is resolved.
+    const { service, commentRepo, wsService, collaborationGateway } =
+      makeService(false, 0);
+
+    const result = await service.dismissSuggestion(suggestionComment(), user());
+
+    // The conditional delete was attempted (and matched nothing).
+    expect(commentRepo.deleteCommentIfChildless).toHaveBeenCalledWith('c-1');
+    // No commentDeleted broadcast — the row (and the racing reply) survive.
+    expect(wsService.emitCommentEvent).not.toHaveBeenCalledWith(
+      expect.anything(),
+      expect.anything(),
+      expect.objectContaining({ operation: 'commentDeleted' }),
+    );
+    // Fell back to resolving the thread.
+    const resolvePatch = commentRepo.updateComment.mock.calls
+      .map((c: any[]) => c[0])
+      .find((p: any) => 'resolvedAt' in p);
+    expect(resolvePatch.resolvedAt).toBeInstanceOf(Date);
+    expect(resolvePatch.resolvedById).toBe('user-1');
+    expect(collaborationGateway.handleYjsEvent).toHaveBeenCalledWith(
+      'resolveCommentMark',
+      'page.page-1',
+      expect.objectContaining({ commentId: 'c-1', resolved: true }),
+    );
+    expect(result.outcome).toBe('resolved');
+  });
+
+  it('rejects a reply (non-top-level) comment', async () => {
+    const { service, commentRepo } = makeService();
+    await expect(
+      service.dismissSuggestion(
+        suggestionComment({ parentCommentId: 'parent-1' }),
+        user(),
+      ),
+    ).rejects.toThrow(BadRequestException);
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
+  });
+
+  it('rejects a comment without a suggested edit', async () => {
+    const { service, commentRepo } = makeService();
+    await expect(
+      service.dismissSuggestion(
+        suggestionComment({ suggestedText: null }),
+        user(),
+      ),
+    ).rejects.toThrow(BadRequestException);
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
+  });
+
+  it('rejects an already-applied suggestion', async () => {
+    const { service, commentRepo } = makeService();
+    await expect(
+      service.dismissSuggestion(
+        suggestionComment({ suggestionAppliedAt: new Date() }),
+        user(),
+      ),
+    ).rejects.toThrow(BadRequestException);
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
+  });
+
+  it('rejects an already-resolved thread', async () => {
+    const { service, commentRepo } = makeService();
+    await expect(
+      service.dismissSuggestion(
+        suggestionComment({ resolvedAt: new Date() }),
+        user(),
+      ),
+    ).rejects.toThrow(BadRequestException);
+    expect(commentRepo.deleteComment).not.toHaveBeenCalled();
+  });
+});

apps/server/src/core/comment/comment.service.ts

@@ -35,6 +35,12 @@ import {
   IAuditService,
 } from '../../integrations/audit/audit.service';
 
+// Ephemeral-suggestion settle result (#329): 'deleted' → the comment vanished
+// (hard-delete + anchor mark stripped); 'resolved' → the thread had replies and
+// was resolved instead. Returned to the client so it can pick the optimistic
+// cache action.
+export type SuggestionOutcome = 'deleted' | 'resolved';
+
 @Injectable()
 export class CommentService {
   private readonly logger = new Logger(CommentService.name);
@@ -362,7 +368,7 @@ export class CommentService {
     comment: Comment,
     user: User,
     provenance?: AuthProvenanceData,
-  ): Promise<Comment> {
+  ): Promise<Comment & { outcome: SuggestionOutcome }> {
     // Structural guards.
     if (comment.parentCommentId) {
       throw new BadRequestException(
@@ -449,42 +455,148 @@ export class CommentService {
   }
 
   /**
-   * Persist the applied stamps (idempotently), auto-resolve the thread and
-   * broadcast + audit the applied suggestion. Shared by the applied and the
+   * Dismiss ("Не применять") a suggested edit without touching the page text:
+   * the suggestion disappears. Ephemeral rule (#329) — a top-level suggestion
+   * comment is transient UI, so dismissing it hard-deletes the comment AND strips
+   * its inline anchor mark UNLESS the thread has replies, in which case the
+   * discussion is preserved by resolving it instead.
+   *
+   * Dismiss does NOT change the document text, so the controller authorizes it
+   * with canComment (NOT canEdit). This re-checks the comment's own state so the
+   * invariant holds regardless of caller.
+   */
+  async dismissSuggestion(
+    comment: Comment,
+    user: User,
+    provenance?: AuthProvenanceData,
+  ): Promise<Comment & { outcome: SuggestionOutcome }> {
+    // Structural guards (mirror applySuggestion).
+    if (comment.parentCommentId) {
+      throw new BadRequestException(
+        'Only a top-level comment can carry a suggested edit',
+      );
+    }
+    if (!comment.suggestedText) {
+      throw new BadRequestException(
+        'This comment has no suggested edit to dismiss',
+      );
+    }
+    // State guards: dismissing an already-applied or already-resolved thread is
+    // meaningless. On an apply↔dismiss race the loser sees the comment already
+    // gone (404 at the controller) or already resolved (this 400); the client
+    // treats both as "already resolved".
+    if (comment.suggestionAppliedAt) {
+      throw new BadRequestException(
+        'Cannot dismiss a suggested edit that was already applied',
+      );
+    }
+    if (comment.resolvedAt) {
+      throw new BadRequestException(
+        'Cannot dismiss a suggested edit on a resolved comment thread',
+      );
+    }
+
+    const hasChildren = await this.commentRepo.hasChildren(comment.id);
+
+    if (hasChildren) {
+      // Preserve the discussion: resolve (never delete) a thread with replies.
+      const updatedComment = await this.resolveComment(
+        comment,
+        true,
+        user,
+        provenance,
+      );
+      this.auditService.log({
+        event: AuditEvent.COMMENT_SUGGESTION_DISMISSED,
+        resourceType: AuditResource.COMMENT,
+        resourceId: comment.id,
+        spaceId: comment.spaceId,
+        metadata: { pageId: comment.pageId },
+      });
+      return { ...updatedComment, outcome: 'resolved' };
+    }
+
+    // Ephemeral: no replies → the suggestion vanishes entirely. The atomic
+    // conditional delete may still fall back to a resolve if a reply raced in
+    // (see deleteEphemeralSuggestion), so the outcome is whatever it settled on.
+    const settled = await this.deleteEphemeralSuggestion(comment, user, provenance);
+    this.auditService.log({
+      event: AuditEvent.COMMENT_SUGGESTION_DISMISSED,
+      resourceType: AuditResource.COMMENT,
+      resourceId: comment.id,
+      spaceId: comment.spaceId,
+      metadata: { pageId: comment.pageId },
+    });
+    return settled;
+  }
+
+  /**
+   * Persist the applied stamps (idempotently), then settle the suggestion under
+   * the ephemeral rule (#329): a suggestion whose thread has NO replies
+   * DISAPPEARS after apply (hard-delete + strip the inline anchor mark), since
+   * the suggested text is now in the document and a stand-alone resolved thread
+   * would only pile up an orphan anchor. A thread WITH replies is preserved by
+   * auto-resolving it (the historical behaviour). Shared by the applied and the
    * idempotent "already-applied" branches of applySuggestion.
+   *
+   * Returns the comment augmented with `outcome` so the client can pick the
+   * optimistic action ('deleted' → drop it, 'resolved' → move to the resolved
+   * tab).
    */
   private async finalizeAppliedSuggestion(
     comment: Comment,
     user: User,
     provenance?: AuthProvenanceData,
-  ): Promise<Comment> {
-    if (!comment.suggestionAppliedAt) {
-      await this.commentRepo.updateComment(
-        {
-          suggestionAppliedAt: new Date(),
-          suggestionAppliedById: user.id,
-        },
-        comment.id,
-      );
+  ): Promise<Comment & { outcome: SuggestionOutcome }> {
+    const hasChildren = await this.commentRepo.hasChildren(comment.id);
+
+    if (hasChildren) {
+      // Thread has replies → preserve the discussion: stamp applied + resolve.
+      if (!comment.suggestionAppliedAt) {
+        await this.commentRepo.updateComment(
+          {
+            suggestionAppliedAt: new Date(),
+            suggestionAppliedById: user.id,
+          },
+          comment.id,
+        );
+      }
+
+      // Auto-resolve the thread. resolveComment handles the resolve mark, its ws
+      // broadcast and the resolve notification. Stay defensive on re-entry.
+      if (!comment.resolvedAt) {
+        await this.resolveComment(comment, true, user, provenance);
+      }
+
+      const updatedComment = await this.commentRepo.findById(comment.id, {
+        includeCreator: true,
+        includeResolvedBy: true,
+      });
+
+      this.wsService.emitCommentEvent(comment.spaceId, comment.pageId, {
+        operation: 'commentUpdated',
+        pageId: comment.pageId,
+        comment: updatedComment,
+      });
+
+      this.auditService.log({
+        event: AuditEvent.COMMENT_SUGGESTION_APPLIED,
+        resourceType: AuditResource.COMMENT,
+        resourceId: comment.id,
+        spaceId: comment.spaceId,
+        metadata: { pageId: comment.pageId },
+      });
+
+      return { ...updatedComment, outcome: 'resolved' };
     }
 
-    // Auto-resolve the thread. resolveComment handles the resolve mark, its ws
-    // broadcast and the resolve notification. The guard above guarantees the
-    // thread was open when we entered, but stay defensive on re-entry.
-    if (!comment.resolvedAt) {
-      await this.resolveComment(comment, true, user, provenance);
-    }
-
-    const updatedComment = await this.commentRepo.findById(comment.id, {
-      includeCreator: true,
-      includeResolvedBy: true,
-    });
-
-    this.wsService.emitCommentEvent(comment.spaceId, comment.pageId, {
-      operation: 'commentUpdated',
-      pageId: comment.pageId,
-      comment: updatedComment,
-    });
+    // No replies → ephemeral: the suggested text is already in the document, so
+    // the comment is redundant. Hard-delete it and strip its inline anchor. We
+    // deliberately do NOT write the applied stamps first (the row is about to be
+    // deleted); the audit event still records that the suggestion was applied.
+    // The delete is atomic-conditional: if a reply raced in after the
+    // hasChildren read, it falls back to resolving instead (outcome 'resolved').
+    const settled = await this.deleteEphemeralSuggestion(comment, user, provenance);
 
     this.auditService.log({
       event: AuditEvent.COMMENT_SUGGESTION_APPLIED,
@@ -494,7 +606,86 @@ export class CommentService {
       metadata: { pageId: comment.pageId },
     });
 
-    return updatedComment;
+    return settled;
+  }
+
+  /**
+   * Settle an ephemeral suggestion whose thread looked childless: remove its
+   * inline `comment` anchor mark, then ATOMICALLY hard-delete the row only if it
+   * is still childless. Shared by the apply/dismiss no-replies branches (#329).
+   *
+   * ORDER MATTERS: the anchor mark is removed FIRST and FATALLY (mirrors
+   * applySuggestion, which mutates the doc before writing the DB). The row
+   * delete is irreversible, so if the mark removal fails — including the
+   * COLLAB_DISABLE_REDIS "no live instance" hard-error — we must NOT delete the
+   * row and report success, or the document is left with a permanent orphan
+   * anchor pointing at a comment that no longer exists (the exact data-integrity
+   * bug #329 targets). Let the exception propagate (→ 5xx); the operation is
+   * then repeatable with row + mark still consistent.
+   *
+   * RACE (#338 F4): the caller read `hasChildren` BEFORE the (slow) mark
+   * removal, so a reply can land in that window. `comments.parent_comment_id` is
+   * ON DELETE CASCADE, so an unconditional delete here would cascade-destroy the
+   * just-added reply forever. Instead we use `deleteCommentIfChildless`, which
+   * re-checks childlessness under a FOR UPDATE lock inside a transaction (a plain
+   * anti-join DELETE is NOT race-safe under READ COMMITTED — see the repo method
+   * docstring). If it removes the row (outcome 'deleted') we broadcast the
+   * deletion as before. If it removes 0 rows (a reply interleaved) we do NOT
+   * hard-delete — we resolve the thread instead (outcome 'resolved'), preserving
+   * the discussion and the new reply. The anchor mark is already gone by then, an
+   * accepted degradation: the thread lands in the resolved tab without its inline
+   * highlight — far better than losing a reply.
+   */
+  private async deleteEphemeralSuggestion(
+    comment: Comment,
+    user: User,
+    provenance?: AuthProvenanceData,
+  ): Promise<Comment & { outcome: SuggestionOutcome }> {
+    await this.deleteCommentMark(comment, user);
+
+    const deletedRows = await this.commentRepo.deleteCommentIfChildless(
+      comment.id,
+    );
+
+    if (deletedRows > 0) {
+      this.wsService.emitCommentEvent(comment.spaceId, comment.pageId, {
+        operation: 'commentDeleted',
+        pageId: comment.pageId,
+        commentId: comment.id,
+      });
+      return { ...comment, outcome: 'deleted' };
+    }
+
+    // A reply interleaved between the hasChildren read and this delete, so the
+    // conditional delete matched nothing. Preserve the discussion + the new
+    // reply by resolving the thread instead of hard-deleting it. resolveComment
+    // handles the resolve patch, its ws broadcast and the resolve notification;
+    // its collab call is best-effort, so the already-stripped mark is fine.
+    const resolvedComment = await this.resolveComment(
+      comment,
+      true,
+      user,
+      provenance,
+    );
+    return { ...resolvedComment, outcome: 'resolved' };
+  }
+
+  /**
+   * Remove the inline `comment` mark for a comment from the collaborative
+   * document. FATAL, NOT best-effort: unlike resolveComment (which keeps the row,
+   * so a failed mark update is recoverable), this is used before an irreversible
+   * hard-delete, so the mark removal MUST succeed or throw. Under
+   * COLLAB_DISABLE_REDIS the gateway invokes the deleteCommentMark handler
+   * directly (never a silent no-op) and a missing live instance surfaces as a
+   * thrown error, which we let propagate so the caller aborts before deleting.
+   */
+  private async deleteCommentMark(comment: Comment, user: User): Promise<void> {
+    const documentName = `page.${comment.pageId}`;
+    await this.collaborationGateway.handleYjsEvent(
+      'deleteCommentMark',
+      documentName,
+      { commentId: comment.id, user },
+    );
   }
 
   private async queueCommentNotification(

apps/server/src/core/comment/dto/dismiss-suggestion.dto.ts

@@ -0,0 +1,6 @@
+import { IsUUID } from 'class-validator';
+
+export class DismissSuggestionDto {
+  @IsUUID()
+  commentId: string;
+}

apps/server/src/database/repos/comment/comment.repo.ts

@@ -139,6 +139,65 @@ export class CommentRepo {
     await this.db.deleteFrom('comments').where('id', '=', commentId).execute();
   }
 
+  /**
+   * Delete an ephemeral suggestion row ONLY if it is still childless, returning
+   * the number of rows removed (0 or 1). Closes the data-loss race in
+   * dismiss/apply (#338 F4): the service reads `hasChildren`, then removes the
+   * anchor mark (a collab round-trip of tens-to-hundreds of ms), then calls this.
+   * `comments.parent_comment_id` is ON DELETE CASCADE, so a reply landing in that
+   * window would be cascade-destroyed by a blind delete.
+   *
+   * A single anti-join `DELETE … WHERE NOT EXISTS(child)` is NOT sufficient under
+   * READ COMMITTED: if a reply INSERT (holding FOR KEY SHARE on the parent, not
+   * yet committed) interleaves, the DELETE's snapshot does not see the
+   * uncommitted child, so `NOT EXISTS` is true and the parent qualifies; the
+   * DELETE then blocks on the child's key-share lock, and when it wakes the row
+   * was only LOCKED (not modified), so EvalPlanQual does NOT re-evaluate the
+   * predicate → the parent is deleted and the just-committed reply cascades away.
+   *
+   * So we do a lock-then-recheck in ONE transaction:
+   *  1. `SELECT id … FOR UPDATE` on the parent. FOR UPDATE conflicts with the
+   *     FOR KEY SHARE a concurrent reply INSERT takes on its parent (FK), so a
+   *     reply in the window serializes against us: it either commits before we
+   *     acquire the lock, or it must wait until this tx ends.
+   *  2. Re-read childlessness with a FRESH statement in the SAME tx. Under RC a
+   *     new statement gets a new snapshot, so a reply that committed while we
+   *     waited on the lock is now visible.
+   *  3. Delete only if still childless (return 1); otherwise return 0 so the
+   *     caller resolves the thread instead. The FOR UPDATE lock is held to
+   *     end-of-tx, so no new reply can insert between the re-check and the delete.
+   */
+  async deleteCommentIfChildless(commentId: string): Promise<number> {
+    return this.db.transaction().execute(async (trx) => {
+      const parent = await trx
+        .selectFrom('comments')
+        .select('id')
+        .where('id', '=', commentId)
+        .forUpdate()
+        .executeTakeFirst();
+
+      // Already gone (e.g. a racing delete won) → nothing to remove.
+      if (!parent) return 0;
+
+      const child = await trx
+        .selectFrom('comments')
+        .select('id')
+        .where('parentCommentId', '=', commentId)
+        .limit(1)
+        .executeTakeFirst();
+
+      // A reply exists (possibly one that just committed) → do NOT hard-delete;
+      // the cascade would destroy it. Caller falls back to resolving the thread.
+      if (child) return 0;
+
+      await trx
+        .deleteFrom('comments')
+        .where('id', '=', commentId)
+        .execute();
+      return 1;
+    });
+  }
+
   async hasChildren(commentId: string): Promise<boolean> {
     const result = await this.db
       .selectFrom('comments')

apps/server/test/integration/comment-delete-if-childless.int-spec.ts

@@ -0,0 +1,160 @@
+import { Kysely } from 'kysely';
+import { CommentRepo } from '../../src/database/repos/comment/comment.repo';
+import {
+  getTestDb,
+  destroyTestDb,
+  buildTestDb,
+  createWorkspace,
+  createSpace,
+  createPage,
+  createUser,
+  createComment,
+} from './db';
+
+/**
+ * Real-DB coverage for CommentRepo.deleteCommentIfChildless (#338 F4/F6).
+ *
+ * This is the guard that keeps an ephemeral-suggestion hard-delete from
+ * cascade-destroying a reply (`comments.parent_comment_id` is ON DELETE CASCADE).
+ * The unit tests MOCK this method to 0/1, so only an int-spec actually exercises
+ * the SQL — the FOR UPDATE lock-then-recheck transaction — against Postgres.
+ *
+ * The concurrency case is the whole point: a plain anti-join
+ * `DELETE … WHERE NOT EXISTS(child)` passes (a) and (b) but SILENTLY loses a
+ * reply that commits mid-operation under READ COMMITTED (EvalPlanQual does not
+ * re-check a merely-locked row). Test (c) reproduces exactly that interleaving
+ * and asserts the row + reply both survive.
+ */
+describe('CommentRepo.deleteCommentIfChildless [integration]', () => {
+  let db: Kysely<any>;
+  let repo: CommentRepo;
+  let workspaceId: string;
+  let spaceId: string;
+  let pageId: string;
+  let userId: string;
+
+  beforeAll(async () => {
+    db = getTestDb();
+    repo = new CommentRepo(db as any);
+    workspaceId = (await createWorkspace(db)).id;
+    spaceId = (await createSpace(db, workspaceId)).id;
+    pageId = (await createPage(db, { workspaceId, spaceId })).id;
+    userId = (await createUser(db, workspaceId)).id;
+  });
+
+  afterAll(async () => {
+    await destroyTestDb();
+  });
+
+  async function rowExists(id: string): Promise<boolean> {
+    const row = await db
+      .selectFrom('comments')
+      .select('id')
+      .where('id', '=', id)
+      .executeTakeFirst();
+    return Boolean(row);
+  }
+
+  function seedTopLevel() {
+    return createComment(db, {
+      workspaceId,
+      spaceId,
+      pageId,
+      creatorId: userId,
+      selection: 'old text',
+      suggestedText: 'new text',
+    });
+  }
+
+  function seedReply(parentId: string) {
+    return createComment(db, {
+      workspaceId,
+      spaceId,
+      pageId,
+      creatorId: userId,
+      parentCommentId: parentId,
+    });
+  }
+
+  it('(a) childless top-level → returns 1 and the row is gone', async () => {
+    const parent = await seedTopLevel();
+    expect(await rowExists(parent.id)).toBe(true);
+
+    const deleted = await repo.deleteCommentIfChildless(parent.id);
+
+    expect(deleted).toBe(1);
+    expect(await rowExists(parent.id)).toBe(false);
+  });
+
+  it('(b) top-level WITH a committed reply → returns 0, parent AND reply survive (gate blocks the cascade)', async () => {
+    const parent = await seedTopLevel();
+    const reply = await seedReply(parent.id);
+
+    const deleted = await repo.deleteCommentIfChildless(parent.id);
+
+    expect(deleted).toBe(0);
+    expect(await rowExists(parent.id)).toBe(true);
+    expect(await rowExists(reply.id)).toBe(true);
+  });
+
+  it('(c) reply COMMITS mid-operation (FOR UPDATE path) → returns 0, parent + reply survive; a blind anti-join would lose the reply', async () => {
+    const parent = await seedTopLevel();
+
+    // Second connection holds an open transaction that inserts a reply (taking
+    // FOR KEY SHARE on the parent via the FK) and does NOT commit until we open
+    // the gate — reproducing the "reply not yet committed" window.
+    const conn2 = buildTestDb();
+    let openGate!: () => void;
+    const gate = new Promise<void>((resolve) => {
+      openGate = resolve;
+    });
+    let replyId: string | undefined;
+
+    const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));
+
+    try {
+      const replyTx = conn2.transaction().execute(async (trx) => {
+        const row = await trx
+          .insertInto('comments')
+          .values({
+            workspaceId,
+            spaceId,
+            pageId,
+            creatorId: userId,
+            parentCommentId: parent.id,
+          })
+          .returning(['id'])
+          .executeTakeFirstOrThrow();
+        replyId = row.id as string;
+        // Hold the FOR KEY SHARE lock on the parent until the gate opens.
+        await gate;
+      });
+
+      // Let the reply INSERT acquire its lock before the delete starts.
+      await sleep(250);
+
+      // deleteCommentIfChildless does SELECT ... FOR UPDATE on the parent, which
+      // conflicts with the reply's FOR KEY SHARE, so it BLOCKS here.
+      const deletePromise = repo.deleteCommentIfChildless(parent.id);
+
+      // Give the delete time to reach (and block on) its FOR UPDATE, then let the
+      // reply commit. The delete then wakes, re-checks under the lock, sees the
+      // now-committed reply, and returns 0.
+      await sleep(250);
+      openGate();
+      await replyTx;
+
+      const deleted = await deletePromise;
+
+      expect(deleted).toBe(0);
+      expect(await rowExists(parent.id)).toBe(true);
+      expect(replyId).toBeDefined();
+      expect(await rowExists(replyId!)).toBe(true);
+    } finally {
+      // Always release the gate (in case an assertion threw before openGate) and
+      // close the extra connection so global-teardown can DROP the database.
+      openGate();
+      await conn2.destroy();
+    }
+  });
+});

apps/server/test/integration/db.ts

@@ -230,6 +230,40 @@ export async function createPage(
   return { id: row.id as string };
 }
 
+export async function createComment(
+  db: Kysely<any>,
+  args: {
+    workspaceId: string;
+    spaceId: string;
+    pageId: string;
+    creatorId?: string | null;
+    parentCommentId?: string | null;
+    content?: unknown;
+    selection?: string | null;
+    suggestedText?: string | null;
+    type?: string | null;
+  },
+): Promise<{ id: string }> {
+  const id = randomUUID();
+  const row = await db
+    .insertInto('comments')
+    .values({
+      id,
+      workspaceId: args.workspaceId,
+      spaceId: args.spaceId,
+      pageId: args.pageId,
+      creatorId: args.creatorId ?? null,
+      parentCommentId: args.parentCommentId ?? null,
+      content: (args.content ?? null) as any,
+      selection: args.selection ?? null,
+      suggestedText: args.suggestedText ?? null,
+      type: args.type ?? 'page',
+    })
+    .returning(['id'])
+    .executeTakeFirstOrThrow();
+  return { id: row.id as string };
+}
+
 export async function createRole(
   db: Kysely<any>,
   args: {