Merge pull request 'feat(comment): предложения правок агента + кнопка «Применить» (server-side atomic apply, #315)' (#318) from feat/315-comment-suggestions into develop

Reviewed-on: #318
2026-07-03 21:29:28 +03:00
parent b861266ff8 48c1ec46f7
commit 33d22ff164
41 changed files with 2714 additions and 51 deletions
@@ -1373,5 +1373,10 @@
  "Updated to the latest version": "Updated to the latest version",
  "This role is no longer in the catalog": "This role is no longer in the catalog",
  "This language is no longer available in the catalog": "This language is no longer available in the catalog",
-  "Connecting… (read-only)": "Connecting… (read-only)"
+  "Connecting… (read-only)": "Connecting… (read-only)",
+  "Apply": "Apply",
+  "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."
 }
@@ -1229,5 +1229,10 @@
  "Updated to the latest version": "Обновлено до последней версии",
  "This role is no longer in the catalog": "Эта роль больше не представлена в каталоге",
  "This language is no longer available in the catalog": "Этот язык больше не доступен в каталоге",
-  "Connecting… (read-only)": "Подключение… (только чтение)"
+  "Connecting… (read-only)": "Подключение… (только чтение)",
+  "Apply": "Применить",
+  "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."
 }
@@ -1,5 +1,5 @@
 import { describe, it, expect, vi } from "vitest";
-import { render, screen } from "@testing-library/react";
+import { render, screen, fireEvent } from "@testing-library/react";
 import { MantineProvider } from "@mantine/core";
 import { IComment } from "@/features/comment/types/comment.types";

@@ -7,10 +7,15 @@ 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();
 vi.mock("@/features/comment/queries/comment-query", () => ({
  useDeleteCommentMutation: () => ({ mutateAsync: vi.fn() }),
  useResolveCommentMutation: () => ({ mutateAsync: vi.fn() }),
  useUpdateCommentMutation: () => ({ mutateAsync: vi.fn() }),
+  useApplySuggestionMutation: () => ({
+    mutateAsync: applyMutateAsync,
+    isPending: false,
+  }),
 }));

 // CommentEditor pulls in the full TipTap editor stack; replace it with a stub.
@@ -19,6 +24,7 @@ vi.mock("@/features/comment/components/comment-editor", () => ({
 }));

 import CommentListItem from "./comment-list-item";
+import { canShowApply } from "@/features/comment/utils/suggestion";

 const baseComment = (over?: Partial<IComment>): IComment =>
  ({
@@ -32,10 +38,15 @@ const baseComment = (over?: Partial<IComment>): IComment =>
    ...over,
  }) as IComment;

-function renderItem(comment: IComment) {
+function renderItem(comment: IComment, canEdit = true) {
  return render(
    <MantineProvider>
-      <CommentListItem comment={comment} pageId="page-1" canComment={true} />
+      <CommentListItem
+        comment={comment}
+        pageId="page-1"
+        canComment={true}
+        canEdit={canEdit}
+      />
    </MantineProvider>,
  );
 }
@@ -87,3 +98,87 @@ describe("CommentListItem — agent avatar stack", () => {
  // are covered directly in agent-avatar-stack.test.tsx; this integration suite
  // only guards the insertion gate (agent → stack, user → no stack).
 });
+
+describe("CommentListItem — suggested edit (#315)", () => {
+  const suggestion = (over?: Partial<IComment>): IComment =>
+    baseComment({
+      selection: "old wording here",
+      suggestedText: "new wording here",
+      ...over,
+    });
+
+  it("renders the было→стало diff and an Apply button when canEdit and not applied/resolved", () => {
+    renderItem(suggestion(), true);
+    // Old text appears both as the selection quote and as the struck diff row.
+    expect(screen.getAllByText("old wording here").length).toBeGreaterThan(0);
+    expect(screen.getByText("new wording here")).toBeDefined();
+    // Apply button is present.
+    expect(screen.getByRole("button", { name: "Apply" })).toBeDefined();
+    // No Applied badge yet.
+    expect(screen.queryByText("Applied")).toBeNull();
+  });
+
+  it("hides the Apply button when canEdit is false", () => {
+    renderItem(suggestion(), false);
+    // Diff still renders...
+    expect(screen.getByText("new wording here")).toBeDefined();
+    // ...but no Apply button.
+    expect(screen.queryByRole("button", { name: "Apply" })).toBeNull();
+  });
+
+  it("shows an Applied badge (no Apply button) once suggestionAppliedAt is set", () => {
+    renderItem(suggestion({ suggestionAppliedAt: new Date() }), true);
+    expect(screen.getByText("Applied")).toBeDefined();
+    expect(screen.queryByRole("button", { name: "Apply" })).toBeNull();
+  });
+
+  it("hides the Apply button once the thread is resolved", () => {
+    renderItem(suggestion({ resolvedAt: new Date() }), true);
+    expect(screen.queryByRole("button", { name: "Apply" })).toBeNull();
+  });
+
+  it("calls the apply mutation when the Apply button is clicked", () => {
+    applyMutateAsync.mockClear();
+    renderItem(suggestion(), true);
+    fireEvent.click(screen.getByRole("button", { name: "Apply" }));
+    expect(applyMutateAsync).toHaveBeenCalledWith({
+      commentId: "c-1",
+      pageId: "page-1",
+    });
+  });
+
+  it("does not render the diff block for a reply (child) comment", () => {
+    renderItem(
+      suggestion({ parentCommentId: "c-0" }),
+      true,
+    );
+    expect(screen.queryByText("new wording here")).toBeNull();
+    expect(screen.queryByRole("button", { name: "Apply" })).toBeNull();
+  });
+});
+
+describe("canShowApply predicate", () => {
+  const c = (over?: Partial<IComment>): IComment =>
+    ({ suggestedText: "x", ...over }) as IComment;
+
+  it("true when suggestion present, editable, not applied/resolved, top-level", () => {
+    expect(canShowApply(c(), true)).toBe(true);
+  });
+  it("false without edit permission", () => {
+    expect(canShowApply(c(), false)).toBe(false);
+  });
+  it("false when no suggestion", () => {
+    expect(canShowApply(c({ suggestedText: null }), true)).toBe(false);
+  });
+  it("false when already applied", () => {
+    expect(canShowApply(c({ suggestionAppliedAt: new Date() }), true)).toBe(
+      false,
+    );
+  });
+  it("false when resolved", () => {
+    expect(canShowApply(c({ resolvedAt: new Date() }), true)).toBe(false);
+  });
+  it("false for a reply comment", () => {
+    expect(canShowApply(c({ parentCommentId: "p" }), true)).toBe(false);
+  });
+});
@@ -1,4 +1,4 @@
-import { Group, Text, Box } from "@mantine/core";
+import { Group, Text, Box, Badge, Button } from "@mantine/core";
 import { AgentAvatarStack } from "@/components/ui/agent-avatar-stack.tsx";
 import React, { useEffect, useRef, useState } from "react";
 import classes from "./comment.module.css";
@@ -11,11 +11,13 @@ import CommentMenu from "@/features/comment/components/comment-menu";
 import ResolveComment from "@/features/comment/components/resolve-comment";
 import { useHover } from "@mantine/hooks";
 import {
+  useApplySuggestionMutation,
  useDeleteCommentMutation,
  useResolveCommentMutation,
  useUpdateCommentMutation,
 } from "@/features/comment/queries/comment-query";
 import { IComment } from "@/features/comment/types/comment.types";
+import { canShowApply } from "@/features/comment/utils/suggestion";
 import { CustomAvatar } from "@/components/ui/custom-avatar.tsx";
 import { currentUserAtom } from "@/features/user/atoms/current-user-atom.ts";
 import { useTranslation } from "react-i18next";
@@ -24,6 +26,10 @@ interface CommentListItemProps {
  comment: IComment;
  pageId: string;
  canComment: boolean;
+  // Real page-edit permission (page.permissions.canEdit) — gates the suggestion
+  // "Apply" button. Distinct from `canComment`, which may be looser (viewers
+  // allowed to comment cannot apply edits).
+  canEdit?: boolean;
  userSpaceRole?: string;
 }

@@ -31,6 +37,7 @@ function CommentListItem({
  comment,
  pageId,
  canComment,
+  canEdit,
  userSpaceRole,
 }: CommentListItemProps) {
  const { t } = useTranslation();
@@ -43,6 +50,7 @@ function CommentListItem({
  const updateCommentMutation = useUpdateCommentMutation();
  const deleteCommentMutation = useDeleteCommentMutation(comment.pageId);
  const resolveCommentMutation = useResolveCommentMutation();
+  const applySuggestionMutation = useApplySuggestionMutation();
  const [currentUser] = useAtom(currentUserAtom);
  const createdAtAgo = useTimeAgo(comment.createdAt);

@@ -95,6 +103,18 @@ function CommentListItem({
    }
  }

+  async function handleApplySuggestion() {
+    try {
+      await applySuggestionMutation.mutateAsync({
+        commentId: comment.id,
+        pageId: comment.pageId,
+      });
+    } catch (error) {
+      // Errors surface via the mutation's onError notification (incl. 409).
+      console.error("Failed to apply suggestion:", error);
+    }
+  }
+
  function handleCommentClick(comment: IComment) {
    const el = document.querySelector(
      `.comment-mark[data-comment-id="${comment.id}"]`,
@@ -211,6 +231,47 @@ function CommentListItem({
          </Box>
        )}

+        {/* Suggested-edit (#315): "было → стало" diff for a top-level comment
+            carrying a suggestion. Old text struck-through/red, new text green. */}
+        {!comment.parentCommentId && comment.suggestedText && (
+          <Box className={classes.suggestionBlock}>
+            {comment.selection && (
+              <Text size="xs" className={classes.suggestionOld}>
+                {comment.selection}
+              </Text>
+            )}
+            <Text size="xs" className={classes.suggestionNew}>
+              {comment.suggestedText}
+            </Text>
+
+            {comment.suggestionAppliedAt ? (
+              <Badge
+                size="sm"
+                color="green"
+                variant="light"
+                mt={6}
+                aria-label={t("Applied")}
+              >
+                {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>
+              )
+            )}
+          </Box>
+        )}
+
        {!isEditing ? (
          <CommentEditor defaultContent={content} editable={false} />
        ) : (
@@ -49,8 +49,10 @@ function CommentListWithTabs({ onClose }: CommentListWithTabsProps) {
  const [isLoading, setIsLoading] = useState(false);
  const { data: space } = useGetSpaceBySlugQuery(page?.space?.slug);

+  const canEdit = page?.permissions?.canEdit ?? false;
+
  const canComment =
-    (page?.permissions?.canEdit ?? false) ||
+    canEdit ||
    (space?.settings?.comments?.allowViewerComments === true);

  // Separate active and resolved comments
@@ -137,6 +139,7 @@ function CommentListWithTabs({ onClose }: CommentListWithTabsProps) {
            comment={comment}
            pageId={page?.id}
            canComment={canComment}
+            canEdit={canEdit}
            userSpaceRole={space?.membership?.role}
          />
          <MemoizedChildComments
@@ -144,6 +147,7 @@ function CommentListWithTabs({ onClose }: CommentListWithTabsProps) {
            parentId={comment.id}
            pageId={page?.id}
            canComment={canComment}
+            canEdit={canEdit}
            userSpaceRole={space?.membership?.role}
          />
        </div>
@@ -160,7 +164,14 @@ function CommentListWithTabs({ onClose }: CommentListWithTabsProps) {
        )}
      </Paper>
    ),
-    [comments, handleAddReply, isLoading, space?.membership?.role, canComment],
+    [
+      comments,
+      handleAddReply,
+      isLoading,
+      space?.membership?.role,
+      canComment,
+      canEdit,
+    ],
  );

  if (isCommentsLoading) {
@@ -300,6 +311,7 @@ interface ChildCommentsProps {
  parentId: string;
  pageId: string;
  canComment: boolean;
+  canEdit?: boolean;
  userSpaceRole?: string;
 }
 const ChildComments = ({
@@ -307,6 +319,7 @@ const ChildComments = ({
  parentId,
  pageId,
  canComment,
+  canEdit,
  userSpaceRole,
 }: ChildCommentsProps) => {
  const getChildComments = useCallback(
@@ -325,6 +338,7 @@ const ChildComments = ({
            comment={childComment}
            pageId={pageId}
            canComment={canComment}
+            canEdit={canEdit}
            userSpaceRole={userSpaceRole}
          />
          <MemoizedChildComments
@@ -332,6 +346,7 @@ const ChildComments = ({
            parentId={childComment.id}
            pageId={pageId}
            canComment={canComment}
+            canEdit={canEdit}
            userSpaceRole={userSpaceRole}
          />
        </div>
@@ -21,6 +21,38 @@
    box-sizing: border-box;
 }

+/* Suggested-edit (#315) "было → стало" diff block. */
+.suggestionBlock {
+    margin-top: 8px;
+    margin-left: 6px;
+    padding: 6px;
+    border-radius: var(--mantine-radius-sm);
+    border: 1px solid var(--mantine-color-default-border);
+    overflow-wrap: break-word;
+    word-break: break-word;
+    max-width: 100%;
+    box-sizing: border-box;
+    display: flex;
+    flex-direction: column;
+    align-items: flex-start;
+}
+
+.suggestionOld {
+    text-decoration: line-through;
+    color: var(--mantine-color-red-7);
+    background: var(--mantine-color-red-light);
+    border-radius: 2px;
+    padding: 1px 3px;
+}
+
+.suggestionNew {
+    color: var(--mantine-color-green-9);
+    background: var(--mantine-color-green-light);
+    border-radius: 2px;
+    padding: 1px 3px;
+    margin-top: 4px;
+}
+
 .commentEditor {

    &[data-editable][data-surface="muted"] .ProseMirror:not(.focused) {
@@ -5,6 +5,7 @@ import {
  InfiniteData,
 } from "@tanstack/react-query";
 import {
+  applySuggestion,
  createComment,
  deleteComment,
  getPageComments,
@@ -176,6 +177,63 @@ function updateCommentInCache(
  };
 }

+export function useApplySuggestionMutation() {
+  const queryClient = useQueryClient();
+  const { t } = useTranslation();
+
+  return useMutation<IComment, 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,
+          })),
+        );
+      }
+
+      notifications.show({ message: t("Suggestion applied") });
+    },
+    onError: (err: any) => {
+      // 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 =
+          currentText.length > 80
+            ? `${currentText.slice(0, 80)}…`
+            : currentText;
+        notifications.show({
+          title: t(
+            "The commented text changed since this suggestion was made; it was not applied.",
+          ),
+          message: shortText,
+          color: "red",
+        });
+        return;
+      }
+      notifications.show({
+        message: t("Failed to apply suggestion"),
+        color: "red",
+      });
+    },
+  });
+}
+
 export function useResolveCommentMutation() {
  const queryClient = useQueryClient();
  const { t } = useTranslation();
@@ -18,6 +18,13 @@ export async function resolveComment(data: IResolveComment): Promise<IComment> {
  return req.data;
 }

+export async function applySuggestion(commentId: string): Promise<IComment> {
+  // 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 updateComment(
  data: Partial<IComment>,
 ): Promise<IComment> {
@@ -28,6 +28,13 @@ export interface IComment {
  createdSource?: string;
  aiChatId?: string | null;
  resolvedSource?: string | null;
+  // Suggested-edit (#315): when an agent proposes a replacement for the
+  // commented `selection`, `suggestedText` holds the "стало" text. Once a user
+  // applies it server-side the backend stamps `suggestionAppliedAt` /
+  // `suggestionAppliedById` and auto-resolves the thread.
+  suggestedText?: string | null;
+  suggestionAppliedAt?: Date | string | null;
+  suggestionAppliedById?: string | null;
  // Server-normalized "agent avatar stack" provenance (#300), present only when
  // createdSource === "agent": `agent` is the front identity, `launcher` the
  // human behind it (null for an external MCP agent).
@@ -0,0 +1,14 @@
+import { IComment } from "@/features/comment/types/comment.types";
+
+// Whether the suggested-edit (#315) "Apply" button should be shown for a
+// comment: it must carry a suggestion, not already be applied or resolved, be a
+// top-level comment, and the viewer must be able to edit the page.
+export function canShowApply(comment: IComment, canEdit?: boolean): boolean {
+  return Boolean(
+    canEdit &&
+      comment.suggestedText &&
+      !comment.suggestionAppliedAt &&
+      !comment.resolvedAt &&
+      !comment.parentCommentId,
+  );
+}
@@ -0,0 +1,60 @@
+import { CollaborationGateway } from './collaboration.gateway';
+import { CollaborationHandler } from './collaboration.handler';
+
+/**
+ * Focused test for the COLLAB_DISABLE_REDIS fallback in handleYjsEvent.
+ *
+ * With Redis disabled the gateway builds no RedisSyncExtension, so the old code
+ * (`return this.redisSync?.handleEvent(...)`) returned undefined and every
+ * doc-mutation event silently no-opped. The fallback must instead invoke the
+ * handler locally against the single hocuspocus instance and return its verdict.
+ *
+ * We construct the gateway with stub extensions and an EnvironmentService whose
+ * isCollabDisableRedis() returns true (redisSync stays null, real hocuspocus is
+ * still built), then spy getHandlers so no real direct connection is opened.
+ */
+
+const stubExtension = {} as any;
+
+function makeEnv() {
+  return {
+    getRedisUrl: () => 'redis://localhost:6379',
+    isCollabDisableRedis: () => true,
+  } as any;
+}
+
+describe('CollaborationGateway.handleYjsEvent (no-Redis fallback)', () => {
+  it('invokes the handler locally and returns its verdict instead of undefined', async () => {
+    const collabHandler = new CollaborationHandler();
+    const verdict = { applied: true, currentText: 'new' };
+    const fakeHandler = jest.fn().mockResolvedValue(verdict);
+    // Bypass the real direct-connection code path — assert dispatch only.
+    jest
+      .spyOn(collabHandler, 'getHandlers')
+      .mockReturnValue({ applyCommentSuggestion: fakeHandler } as any);
+
+    const gateway = new CollaborationGateway(
+      stubExtension,
+      stubExtension,
+      stubExtension,
+      makeEnv(),
+      collabHandler,
+    );
+
+    const payload = {
+      commentId: 'c1',
+      expectedText: 'old',
+      newText: 'new',
+      user: { id: 'u1' } as any,
+    };
+    const result = await gateway.handleYjsEvent(
+      'applyCommentSuggestion' as any,
+      'doc-1',
+      payload as any,
+    );
+
+    expect(fakeHandler).toHaveBeenCalledWith('doc-1', payload);
+    expect(result).toEqual(verdict);
+    expect(result).not.toBeUndefined();
+  });
+});
@@ -147,8 +147,41 @@ export class CollaborationGateway {
    eventName: TName,
    documentName: string,
    payload: Parameters<CollabEventHandlers[TName]>[1],
-  ) {
-    return this.redisSync?.handleEvent(eventName, documentName, payload);
+  ): ReturnType<CollabEventHandlers[TName]> {
+    if (this.redisSync) {
+      // Normal path: the Redis bridge routes the event to the instance that owns
+      // the document (local or another worker) and carries the handler's return
+      // value back to us (customEventComplete + replyId).
+      return this.redisSync.handleEvent(
+        eventName,
+        documentName,
+        payload,
+      ) as ReturnType<CollabEventHandlers[TName]>;
+    }
+
+    // COLLAB_DISABLE_REDIS: there is no cross-process bridge, so a single local
+    // hocuspocus instance owns every document. Invoke the handler directly
+    // against it instead of returning undefined — otherwise doc-mutation events
+    // (setCommentMark / resolveCommentMark / applyCommentSuggestion) would
+    // silently no-op and, for suggestions, the caller could never learn the
+    // verdict. openDirectConnection loads the doc via the persistence extension
+    // if it is not already in memory.
+    if (this.hocuspocus) {
+      const handlers = this.collabEventsService.getHandlers(this.hocuspocus);
+      const handler = handlers[eventName] as (
+        documentName: string,
+        payload: unknown,
+      ) => ReturnType<CollabEventHandlers[TName]>;
+      return handler(documentName, payload);
+    }
+
+    // Collaboration was never initialized (no live instance). Fail loudly rather
+    // than silently dropping a mutation; phase 4's caller maps this to a 5xx.
+    throw new Error(
+      `Cannot handle collaboration event "${String(
+        eventName,
+      )}": requires a live collaboration instance`,
+    );
  }

  openDirectConnection(documentName: string, context?: any) {
@@ -0,0 +1,132 @@
+import * as Y from 'yjs';
+import { CollaborationHandler } from './collaboration.handler';
+import * as yjsUtil from './yjs.util';
+import { User } from '@docmost/db/types/entity.types';
+
+/**
+ * Unit tests for the `applyCommentSuggestion` collab handler (phase 3 of #315).
+ *
+ * The handler runs `replaceYjsMarkedText` inside the owning instance's Y
+ * transaction and returns the verdict to the caller. We exercise it against a
+ * REAL in-memory Y.Doc carrying a marked comment run, driven through a FAKE
+ * hocuspocus whose openDirectConnection().transact(fn) simply runs fn(doc) —
+ * mirroring how the real hocuspocus DirectConnection invokes the callback with
+ * the shared document (it does not forward the callback's return value, which is
+ * exactly why withYdocConnection captures it via a closure).
+ */
+
+// Build a Y.Doc with a single paragraph whose text carries a `comment` mark for
+// the given commentId — the shape `replaceYjsMarkedText` walks in production.
+function buildDocWithComment(text: string, commentId: string) {
+  const doc = new Y.Doc();
+  const fragment = doc.getXmlFragment('default');
+  const paragraph = new Y.XmlElement('paragraph');
+  const xmlText = new Y.XmlText();
+  xmlText.insert(0, text);
+  xmlText.format(0, text.length, { comment: { commentId, resolved: false } });
+  paragraph.insert(0, [xmlText]);
+  fragment.insert(0, [paragraph]);
+  return doc;
+}
+
+// Fake hocuspocus exposing only what withYdocConnection needs: a direct
+// connection whose transact() runs the callback against `doc`.
+function fakeHocuspocus(doc: Y.Doc) {
+  const connection = {
+    transact: jest.fn(async (fn: (d: Y.Doc) => void) => {
+      fn(doc);
+    }),
+    disconnect: jest.fn(async () => {}),
+  };
+  const hocuspocus = {
+    openDirectConnection: jest.fn(async () => connection),
+  } as any;
+  return { hocuspocus, connection };
+}
+
+const user = { id: 'u1' } as unknown as User;
+
+describe('CollaborationHandler.applyCommentSuggestion', () => {
+  it('applies the replacement and returns the verdict when the marked text matches', async () => {
+    const doc = buildDocWithComment('Hello world', 'c1');
+    const { hocuspocus, connection } = fakeHocuspocus(doc);
+    const handler = new CollaborationHandler();
+    const handlers = handler.getHandlers(hocuspocus);
+
+    const result = await handlers.applyCommentSuggestion('doc-1', {
+      commentId: 'c1',
+      expectedText: 'Hello world',
+      newText: 'Goodbye world',
+      user,
+    });
+
+    expect(result).toEqual({ applied: true, currentText: 'Goodbye world' });
+    // The mutation ran inside the transaction and hit the real doc.
+    expect(connection.transact).toHaveBeenCalledTimes(1);
+    expect(connection.disconnect).toHaveBeenCalledTimes(1);
+    expect(doc.getXmlFragment('default').toString()).toContain(
+      'Goodbye world',
+    );
+  });
+
+  it('rejects (applied=false) and returns the current text when it changed', async () => {
+    const doc = buildDocWithComment('Hello world', 'c1');
+    const { hocuspocus } = fakeHocuspocus(doc);
+    const handler = new CollaborationHandler();
+    const handlers = handler.getHandlers(hocuspocus);
+
+    const result = await handlers.applyCommentSuggestion('doc-1', {
+      commentId: 'c1',
+      expectedText: 'Stale expected text',
+      newText: 'Goodbye world',
+      user,
+    });
+
+    expect(result).toEqual({ applied: false, currentText: 'Hello world' });
+    // Nothing was replaced.
+    expect(doc.getXmlFragment('default').toString()).toContain(
+      'Hello world',
+    );
+  });
+
+  it('forwards the exact args to replaceYjsMarkedText and returns its result', async () => {
+    const doc = buildDocWithComment('abc', 'c9');
+    const { hocuspocus } = fakeHocuspocus(doc);
+    const spy = jest
+      .spyOn(yjsUtil, 'replaceYjsMarkedText')
+      .mockReturnValue({ applied: true, currentText: 'xyz' });
+    const handler = new CollaborationHandler();
+    const handlers = handler.getHandlers(hocuspocus);
+
+    const result = await handlers.applyCommentSuggestion('doc-1', {
+      commentId: 'c9',
+      expectedText: 'abc',
+      newText: 'xyz',
+      user,
+    });
+
+    expect(spy).toHaveBeenCalledWith(
+      doc.getXmlFragment('default'),
+      'c9',
+      'abc',
+      'xyz',
+    );
+    expect(result).toEqual({ applied: true, currentText: 'xyz' });
+    spy.mockRestore();
+  });
+
+  it('withYdocConnection returns the callback result (transact does not forward it)', async () => {
+    const doc = new Y.Doc();
+    const { hocuspocus } = fakeHocuspocus(doc);
+    const handler = new CollaborationHandler();
+
+    const value = await handler.withYdocConnection(
+      hocuspocus,
+      'doc-1',
+      {},
+      () => 42,
+    );
+
+    expect(value).toBe(42);
+  });
+});
@@ -5,7 +5,12 @@ import {
  prosemirrorNodeToYElement,
  tiptapExtensions,
 } from './collaboration.util';
-import { setYjsMark, updateYjsMarkAttribute, YjsSelection } from './yjs.util';
+import {
+  replaceYjsMarkedText,
+  setYjsMark,
+  updateYjsMarkAttribute,
+  YjsSelection,
+} from './yjs.util';
 import * as Y from 'yjs';
 import { User } from '@docmost/db/types/entity.types';

@@ -73,6 +78,35 @@ export class CollaborationHandler {
          },
        );
      },
+      applyCommentSuggestion: async (
+        documentName: string,
+        payload: {
+          commentId: string;
+          expectedText: string;
+          newText: string;
+          user: User;
+        },
+      ): Promise<{ applied: boolean; currentText: string | null }> => {
+        const { commentId, expectedText, newText, user } = payload;
+        // Run the check-and-replace inside the owning instance's Y transaction so
+        // the delete+insert are atomic. The verdict from replaceYjsMarkedText is
+        // returned to the API-server caller (cross-process via the Redis bridge,
+        // or locally when Redis is disabled — see collaboration.gateway.ts).
+        return this.withYdocConnection(
+          hocuspocus,
+          documentName,
+          { user },
+          (doc) => {
+            const fragment = doc.getXmlFragment('default');
+            return replaceYjsMarkedText(
+              fragment,
+              commentId,
+              expectedText,
+              newText,
+            );
+          },
+        );
+      },
      updatePageContent: async (
        documentName: string,
        payload: {
@@ -115,18 +149,28 @@ export class CollaborationHandler {
    };
  }

-  async withYdocConnection(
+  async withYdocConnection<T>(
    hocuspocus: Hocuspocus,
    documentName: string,
    context: any = {},
-    fn: (doc: Document) => void,
-  ): Promise<void> {
+    // `fn` MUST be synchronous: hocuspocus `connection.transact(fn)` runs fn
+    // synchronously and does NOT await it, so any mutations after an `await`
+    // inside fn would execute OUTSIDE the Yjs transaction and lose atomicity.
+    fn: (doc: Document) => T,
+  ): Promise<T> {
    const connection = await hocuspocus.openDirectConnection(
      documentName,
      context,
    );
    try {
-      await connection.transact(fn);
+      // hocuspocus `connection.transact(fn)` invokes fn(document) but does NOT
+      // forward fn's return value, so we capture it in a closure and return it
+      // after the transaction (and its storeDocument hooks) resolve.
+      let result: T;
+      await connection.transact((doc) => {
+        result = fn(doc);
+      });
+      return result!;
    } finally {
      await connection.disconnect();
    }
@@ -10,6 +10,7 @@ import {
  setYjsMark,
  removeYjsMarkByAttribute,
  updateYjsMarkAttribute,
+  replaceYjsMarkedText,
  type YjsSelection,
 } from './yjs.util';

@@ -276,3 +277,256 @@ describe('updateYjsMarkAttribute', () => {
    expect(text.toDelta()).toEqual(before);
  });
 });
+
+describe('replaceYjsMarkedText', () => {
+  // Build a single-paragraph XmlText from runs. Insert the whole string as
+  // plain text FIRST, then format only the marked ranges — otherwise text
+  // inserted right after a marked run inherits its comment mark (Yjs carries
+  // formatting from the left insertion boundary).
+  function buildRuns(
+    runs: Array<{
+      text: string;
+      comment?: { commentId: string; resolved: boolean };
+    }>,
+  ): { fragment: Y.XmlFragment; text: Y.XmlText } {
+    const ydoc = new Y.Doc();
+    const fragment = ydoc.getXmlFragment('default');
+    const para = new Y.XmlElement('paragraph');
+    fragment.insert(0, [para]);
+    const text = new Y.XmlText();
+    para.insert(0, [text]);
+    text.insert(0, runs.map((r) => r.text).join(''));
+    let offset = 0;
+    for (const run of runs) {
+      if (run.comment) {
+        text.format(offset, run.text.length, { comment: run.comment });
+      }
+      offset += run.text.length;
+    }
+    return { fragment, text };
+  }
+
+  // Two paragraphs, each with its own XmlText, both marked with the same
+  // commentId — mirrors a suggestion anchor that got split across blocks.
+  function buildTwoParagraphs(
+    a: { text: string; comment?: { commentId: string; resolved: boolean } },
+    b: { text: string; comment?: { commentId: string; resolved: boolean } },
+  ): { fragment: Y.XmlFragment; textA: Y.XmlText; textB: Y.XmlText } {
+    const ydoc = new Y.Doc();
+    const fragment = ydoc.getXmlFragment('default');
+    const build = (seg: typeof a) => {
+      const para = new Y.XmlElement('paragraph');
+      const text = new Y.XmlText();
+      para.insert(0, [text]);
+      text.insert(0, seg.text);
+      if (seg.comment) {
+        text.format(0, seg.text.length, { comment: seg.comment });
+      }
+      return { para, text };
+    };
+    const pa = build(a);
+    const pb = build(b);
+    fragment.insert(0, [pa.para, pb.para]);
+    return { fragment, textA: pa.text, textB: pb.text };
+  }
+
+  it('happy path: replaces marked text with newText and keeps the comment mark', () => {
+    const { fragment, text } = buildRuns([
+      { text: 'Hello ' },
+      { text: 'world', comment: { commentId: 'c1', resolved: false } },
+      { text: '!' },
+    ]);
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'world', 'planet');
+
+    expect(result).toEqual({ applied: true, currentText: 'planet' });
+    // New text carries the SAME comment mark; surrounding text is untouched.
+    expect(text.toDelta()).toEqual([
+      { insert: 'Hello ' },
+      {
+        insert: 'planet',
+        attributes: { comment: { commentId: 'c1', resolved: false } },
+      },
+      { insert: '!' },
+    ]);
+  });
+
+  it('matches by commentId even when the mark is resolved', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'foo', comment: { commentId: 'c9', resolved: true } },
+    ]);
+
+    const result = replaceYjsMarkedText(fragment, 'c9', 'foo', 'bar');
+
+    expect(result).toEqual({ applied: true, currentText: 'bar' });
+    expect(text.toDelta()).toEqual([
+      {
+        insert: 'bar',
+        attributes: { comment: { commentId: 'c9', resolved: true } },
+      },
+    ]);
+  });
+
+  it('changed text: marked text differs from expected → no-op, doc unchanged', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'abc', comment: { commentId: 'c1', resolved: false } },
+    ]);
+    const before = text.toDelta();
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'expected', 'new');
+
+    expect(result).toEqual({ applied: false, currentText: 'abc' });
+    expect(text.toDelta()).toEqual(before);
+  });
+
+  // F1 regression: the marked doc text is TYPOGRAPHIC (smart quotes / em-dash)
+  // and expectedText equals that raw typographic text — as it now does, because
+  // the MCP client stores the RAW anchored substring (getAnchoredText) rather
+  // than the agent's ASCII input. The strict `joinedText !== expectedText`
+  // compare must therefore MATCH and the suggestion apply (not a spurious 409).
+  it('typographic marked text applies when expectedText is the raw typographic text', () => {
+    const marked = '“hello”—world';
+    const { fragment, text } = buildRuns([
+      { text: 'say ' },
+      { text: marked, comment: { commentId: 'c1', resolved: false } },
+      { text: '!' },
+    ]);
+
+    const result = replaceYjsMarkedText(fragment, 'c1', marked, 'bye');
+
+    expect(result).toEqual({ applied: true, currentText: 'bye' });
+    expect(text.toDelta()).toEqual([
+      { insert: 'say ' },
+      {
+        insert: 'bye',
+        attributes: { comment: { commentId: 'c1', resolved: false } },
+      },
+      { insert: '!' },
+    ]);
+  });
+
+  it('anchor deleted: no mark with that commentId → { applied: false, currentText: null }', () => {
+    const { fragment, text } = buildWithComments([
+      { text: 'abc', comment: { commentId: 'c1', resolved: false } },
+    ]);
+    const before = text.toDelta();
+
+    const result = replaceYjsMarkedText(fragment, 'missing', 'abc', 'new');
+
+    expect(result).toEqual({ applied: false, currentText: null });
+    expect(text.toDelta()).toEqual(before);
+  });
+
+  it('paragraph split: same commentId in two XmlText nodes → no-op, doc unchanged', () => {
+    const { fragment, textA, textB } = buildTwoParagraphs(
+      { text: 'Hello ', comment: { commentId: 'c1', resolved: false } },
+      { text: 'world', comment: { commentId: 'c1', resolved: false } },
+    );
+    const beforeA = textA.toDelta();
+    const beforeB = textB.toDelta();
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'Hello world', 'new');
+
+    expect(result).toEqual({ applied: false, currentText: 'Hello world' });
+    expect(textA.toDelta()).toEqual(beforeA);
+    expect(textB.toDelta()).toEqual(beforeB);
+  });
+
+  it('interleaved unmarked text: marked run not contiguous → no-op, doc unchanged', () => {
+    const { fragment, text } = buildRuns([
+      { text: 'abc', comment: { commentId: 'c1', resolved: false } },
+      { text: 'X' },
+      { text: 'def', comment: { commentId: 'c1', resolved: false } },
+    ]);
+    const before = text.toDelta();
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'abcdef', 'new');
+
+    // Joined marked text ("abcdef") is returned, but the run is not contiguous.
+    expect(result).toEqual({ applied: false, currentText: 'abcdef' });
+    expect(text.toDelta()).toEqual(before);
+  });
+
+  it('preserves surrounding text and merges adjacent marked segments on apply', () => {
+    // The marked run itself is split into two adjacent delta segments; they must
+    // be treated as one contiguous run and replaced as a whole.
+    const { fragment, text } = buildRuns([
+      { text: 'pre ' },
+      { text: 'ab', comment: { commentId: 'c1', resolved: false } },
+      { text: 'cd', comment: { commentId: 'c1', resolved: false } },
+      { text: ' post' },
+    ]);
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'abcd', 'Z');
+
+    expect(result).toEqual({ applied: true, currentText: 'Z' });
+    expect(text.toDelta()).toEqual([
+      { insert: 'pre ' },
+      {
+        insert: 'Z',
+        attributes: { comment: { commentId: 'c1', resolved: false } },
+      },
+      { insert: ' post' },
+    ]);
+  });
+
+  it('embed before the marked run: offset accounts for the embed unit → replaces the right text, embed intact', () => {
+    // "AB", then a Yjs embed (1 index unit), then marked "world". Before the
+    // fix the embed was skipped WITHOUT advancing offset, so the computed start
+    // for "world" was too low by 1 → delete/insert would have hit the embed/text
+    // instead of "world", mangling the embed. With the fix offset is correct.
+    const ydoc = new Y.Doc();
+    const fragment = ydoc.getXmlFragment('default');
+    const para = new Y.XmlElement('paragraph');
+    fragment.insert(0, [para]);
+    const text = new Y.XmlText();
+    para.insert(0, [text]);
+    text.insert(0, 'AB');
+    text.insertEmbed(2, { image: { src: 'x' } });
+    text.insert(3, 'world');
+    text.format(3, 'world'.length, {
+      comment: { commentId: 'c1', resolved: false },
+    });
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'world', 'planet');
+
+    expect(result).toEqual({ applied: true, currentText: 'planet' });
+    // "AB" untouched, embed still present and intact, "world" → "planet"
+    // carrying the SAME comment mark.
+    expect(text.toDelta()).toEqual([
+      { insert: 'AB' },
+      { insert: { image: { src: 'x' } } },
+      {
+        insert: 'planet',
+        attributes: { comment: { commentId: 'c1', resolved: false } },
+      },
+    ]);
+  });
+
+  it('embed inside the marked run: embed splits the run → non-contiguous → no-op, doc unchanged', () => {
+    // marked "abc", an embed, marked "def" — same commentId. The embed occupies
+    // one index unit between the two marked segments, so they are not contiguous
+    // → the guard rejects it and nothing is mutated (embed intact).
+    const ydoc = new Y.Doc();
+    const fragment = ydoc.getXmlFragment('default');
+    const para = new Y.XmlElement('paragraph');
+    fragment.insert(0, [para]);
+    const text = new Y.XmlText();
+    para.insert(0, [text]);
+    text.insert(0, 'abc');
+    text.insertEmbed(3, { image: { src: 'y' } });
+    text.insert(4, 'def');
+    text.format(0, 'abc'.length, {
+      comment: { commentId: 'c1', resolved: false },
+    });
+    text.format(4, 'def'.length, {
+      comment: { commentId: 'c1', resolved: false },
+    });
+    const before = text.toDelta();
+
+    const result = replaceYjsMarkedText(fragment, 'c1', 'abcdef', 'new');
+
+    expect(result).toEqual({ applied: false, currentText: 'abcdef' });
+    expect(text.toDelta()).toEqual(before);
+  });
+});
@@ -133,6 +133,137 @@ export function removeYjsMarkByAttribute(
  }
 }

+/**
+ * A single marked delta segment collected during the walk, together with the
+ * Y.XmlText node that owns it, the segment's start offset within that node,
+ * and the full `comment` mark attributes object (needed to re-attach the mark
+ * to the replacement text).
+ */
+type MarkedSegment = {
+  node: Y.XmlText;
+  offset: number;
+  length: number;
+  text: string;
+  markAttrs: Record<string, any>;
+};
+
+/**
+ * Atomically check-and-replace the text currently under a comment mark.
+ *
+ * Walks the fragment collecting every delta segment whose `comment` mark has the
+ * given commentId. The replacement is applied ONLY if the marked run is intact:
+ * it lives in a single Y.XmlText node, is contiguous (no unmarked text spliced
+ * into the middle), and its joined text still equals `expectedText`. On success
+ * the run is deleted and `newText` is inserted at the same offset carrying the
+ * SAME comment attributes, so the comment thread stays anchored to the new text.
+ *
+ * This mutates the passed fragment/text directly and does NOT open its own Y
+ * transaction — the caller is expected to wrap the call in connection.transact()
+ * so the delete+insert are atomic (mirrors updateYjsMarkAttribute's direct
+ * mutation style).
+ *
+ * @returns `{ applied: true, currentText: newText }` on replacement, otherwise
+ * `{ applied: false, currentText }` where currentText is the text currently
+ * under the mark (or null when the mark/anchor no longer exists).
+ */
+export function replaceYjsMarkedText(
+  fragment: Y.XmlFragment,
+  commentId: string,
+  expectedText: string,
+  newText: string,
+): { applied: boolean; currentText: string | null } {
+  // 1. Collect every marked segment in document order.
+  const segments: MarkedSegment[] = [];
+
+  const processItem = (item: any) => {
+    if (item instanceof Y.XmlText) {
+      const deltas = item.toDelta();
+      let offset = 0;
+
+      for (const delta of deltas) {
+        const insert = delta.insert;
+        // Non-string inserts (embeds) carry no text length we can splice on.
+        if (typeof insert !== 'string') {
+          // A Yjs embed occupies one unit in the index space used by delete/
+          // insert/format — advance offset so a marked segment after an embed
+          // gets the right position (and an embed inside a marked run creates a
+          // gap → the contiguity guard rejects it as a changed anchor).
+          offset += 1;
+          continue;
+        }
+        const length = insert.length;
+        const attributes = delta.attributes ?? {};
+        const markAttr = attributes['comment'];
+
+        if (markAttr && markAttr.commentId === commentId) {
+          segments.push({
+            node: item,
+            offset,
+            length,
+            text: insert,
+            markAttrs: markAttr,
+          });
+        }
+        offset += length;
+      }
+    } else if (item instanceof Y.XmlElement) {
+      for (let i = 0; i < item.length; i++) {
+        processItem(item.get(i));
+      }
+    }
+  };
+
+  for (let i = 0; i < fragment.length; i++) {
+    processItem(fragment.get(i));
+  }
+
+  const joinedText = segments.map((s) => s.text).join('');
+
+  // 2a. No segments — the mark/anchor was deleted.
+  if (segments.length === 0) {
+    return { applied: false, currentText: null };
+  }
+
+  // 2b. Segments span more than one Y.XmlText node (paragraph split by Enter,
+  // or the mark bled across blocks) — treat as changed.
+  const node = segments[0].node;
+  const sameNode = segments.every((s) => s.node === node);
+  if (!sameNode) {
+    return { applied: false, currentText: joinedText };
+  }
+
+  // 2c. Non-contiguous within the single node: unmarked text is spliced between
+  // the first and last marked segment. Since collected segments are in document
+  // order, contiguity holds iff each segment starts where the previous ended.
+  let contiguous = true;
+  for (let i = 1; i < segments.length; i++) {
+    if (segments[i].offset !== segments[i - 1].offset + segments[i - 1].length) {
+      contiguous = false;
+      break;
+    }
+  }
+  if (!contiguous) {
+    return { applied: false, currentText: joinedText };
+  }
+
+  // 2d. The text under the mark changed.
+  if (joinedText !== expectedText) {
+    return { applied: false, currentText: joinedText };
+  }
+
+  // 3. All guards passed: delete the marked run and re-insert newText with the
+  // same comment attributes at the same offset. Atomic within the caller's
+  // transaction.
+  const start = segments[0].offset;
+  const len = segments.reduce((sum, s) => sum + s.length, 0);
+  const markAttrs = segments[0].markAttrs;
+
+  node.delete(start, len);
+  node.insert(start, newText, { comment: markAttrs });
+
+  return { applied: true, currentText: newText };
+}
+
 /**
 * Updates a mark's attributes for all text that has the specified attribute value.
 * Useful for resolving/unresolving comments by commentId.
@@ -51,6 +51,7 @@ export const AuditEvent = {
  COMMENT_UPDATED: 'comment.updated',
  COMMENT_RESOLVED: 'comment.resolved',
  COMMENT_REOPENED: 'comment.reopened',
+  COMMENT_SUGGESTION_APPLIED: 'comment.suggestion_applied',

  // Page
  PAGE_CREATED: 'page.created',
@@ -518,6 +518,20 @@ describe('AiChatToolsService model-friendly input validation (#190)', () => {
    });
  });

+  it('createComment: accepts an optional suggestedText alongside a selection', async () => {
+    const tools = await buildTools();
+    const result = await inputSchemaOf(tools.createComment).validate({
+      pageId: '019efe44-0000-0000-0000-000000000000',
+      content: 'A remark',
+      selection: 'титановый проводник',
+      suggestedText: 'медный проводник',
+    });
+    expect(result.success).toBe(true);
+    expect(result.value).toMatchObject({
+      suggestedText: 'медный проводник',
+    });
+  });
+
  it('sharedTool-built tools (getOutline) also get the friendly message on a dropped pageId', async () => {
    const tools = await buildTools();
    const result = await inputSchemaOf(tools.getOutline).validate({});
@@ -450,8 +450,10 @@ export class AiChatToolsService {
          "new top-level comment REQUIRES a `selection`. Replies inherit the " +
          "parent's anchor and take no selection. If the call fails with a " +
          '"selection not found" error, retry with a corrected EXACT selection ' +
-          'copied verbatim from a single paragraph/block. Reversible via the ' +
-          'comment UI.',
+          'copied verbatim from a single paragraph/block. You may also attach a ' +
+          '`suggestedText` proposing a replacement for the `selection` (a human ' +
+          'applies it from the UI); when set, the `selection` must occur exactly ' +
+          'once in the page. Reversible via the comment UI.',
        inputSchema: modelFriendlyInput({
          pageId: z.string().describe('The id of the page to comment on.'),
          content: z.string().describe('The comment body as Markdown.'),
@@ -473,24 +475,57 @@ export class AiChatToolsService {
              'Optional id of a TOP-LEVEL comment to reply to (one level ' +
                'of replies only).',
            ),
+          suggestedText: z
+            .string()
+            .min(1)
+            .max(2000)
+            .optional()
+            .describe(
+              'Optional proposed replacement (PLAIN TEXT) for the `selection`, ' +
+                'applied by a human via the UI (never auto-applied). REQUIRES a ' +
+                '`selection`; NOT allowed on a reply. When set, the `selection` ' +
+                'must be UNIQUE in the page — expand it with surrounding context ' +
+                '(still <=250 chars) if it occurs more than once, or the call is ' +
+                'refused.',
+            ),
        }),
-        execute: async ({ pageId, content, selection, parentCommentId }) => {
-          // createComment(pageId, content, type, selection?, parentCommentId?).
-          // Top-level comments are inline and must carry a selection to anchor
-          // on; replies inherit the parent's anchor (no selection). Throwing
-          // here surfaces a tool error to the model (Vercel `ai` SDK) so the
-          // agent retries with a better selection — do not catch/suppress it.
+        execute: async ({
+          pageId,
+          content,
+          selection,
+          parentCommentId,
+          suggestedText,
+        }) => {
+          // createComment(pageId, content, type, selection?, parentCommentId?,
+          // suggestedText?). Top-level comments are inline and must carry a
+          // selection to anchor on; replies inherit the parent's anchor (no
+          // selection). Throwing here surfaces a tool error to the model (Vercel
+          // `ai` SDK) so the agent retries with a better selection — do not
+          // catch/suppress it.
          if (!parentCommentId && (!selection || !selection.trim())) {
            throw new Error(
              "createComment requires a 'selection' (exact text to anchor on) for a new top-level comment.",
            );
          }
+          if (suggestedText !== undefined) {
+            if (parentCommentId) {
+              throw new Error(
+                "createComment: 'suggestedText' cannot be attached to a reply; it applies only to a top-level inline comment.",
+              );
+            }
+            if (!selection || !selection.trim()) {
+              throw new Error(
+                "createComment: 'suggestedText' requires a 'selection' to anchor and rewrite.",
+              );
+            }
+          }
          const result = await client.createComment(
            pageId,
            content,
            'inline',
            selection,
            parentCommentId,
+            suggestedText,
          );
          const data = (result?.data ?? {}) as { id?: string };
          return { commentId: data.id, pageId };
@@ -177,6 +177,7 @@ export interface DocmostClientLike {
    type?: 'page' | 'inline',
    selection?: string,
    parentCommentId?: string,
+    suggestedText?: string,
  ): Promise<{ data: Record<string, unknown>; success: boolean }>;
  resolveComment(
    commentId: string,
@@ -0,0 +1,119 @@
+import {
+  ForbiddenException,
+  NotFoundException,
+} from '@nestjs/common';
+import { CommentController } from './comment.controller';
+
+/**
+ * Authz-gate tests for the apply-suggestion route. Applying a suggestion
+ * rewrites the page text, so the route MUST call
+ * pageAccessService.validateCanEdit BEFORE handing off to
+ * commentService.applySuggestion (which performs the document mutation + stamp).
+ * That ordering is a security boundary: an unauthorized user must never reach
+ * the mutation. These tests pin it against a fully mocked controller so any
+ * regression that drops the gate (or reorders it after the mutation) fails here.
+ */
+describe('CommentController apply-suggestion authz', () => {
+  function makeController() {
+    const commentService = {
+      applySuggestion: jest.fn(async () => ({ id: 'c-1', applied: true })),
+    };
+    const commentRepo = { findById: jest.fn() };
+    const pageRepo = { findById: jest.fn() };
+    const spaceAbility = {} as any;
+    const pageAccessService = {
+      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,
+    };
+  }
+
+  const user: any = { id: 'u-1' };
+  const workspace: any = { id: 'ws-1' };
+  const provenance: any = undefined;
+  const dto: any = { commentId: 'c-1' };
+
+  const comment = {
+    id: 'c-1',
+    pageId: 'p-1',
+    spaceId: 'sp-1',
+    suggestedText: 'new text',
+    selection: 'old text',
+  };
+  const page = { id: 'p-1', spaceId: 'sp-1', deletedAt: null };
+
+  it('validateCanEdit throwing Forbidden rejects AND applySuggestion is never called', async () => {
+    const { controller, commentRepo, pageRepo, pageAccessService, commentService } =
+      makeController();
+    commentRepo.findById.mockResolvedValue(comment);
+    pageRepo.findById.mockResolvedValue(page);
+    pageAccessService.validateCanEdit.mockRejectedValue(
+      new ForbiddenException('no edit access'),
+    );
+
+    await expect(
+      controller.applySuggestion(dto, user, workspace, provenance),
+    ).rejects.toBeInstanceOf(ForbiddenException);
+
+    // The security boundary: the mutation/stamp must NOT run for an
+    // unauthorized user.
+    expect(pageAccessService.validateCanEdit).toHaveBeenCalledWith(page, user);
+    expect(commentService.applySuggestion).not.toHaveBeenCalled();
+  });
+
+  it('happy path: validateCanEdit resolves → applySuggestion is called and its result returned', async () => {
+    const { controller, commentRepo, pageRepo, pageAccessService, commentService } =
+      makeController();
+    commentRepo.findById.mockResolvedValue(comment);
+    pageRepo.findById.mockResolvedValue(page);
+    const applied = { id: 'c-1', applied: true };
+    commentService.applySuggestion.mockResolvedValue(applied);
+
+    const result = await controller.applySuggestion(
+      dto,
+      user,
+      workspace,
+      provenance,
+    );
+
+    // Authorization ran before the mutation, then the service was invoked.
+    expect(pageAccessService.validateCanEdit).toHaveBeenCalledWith(page, user);
+    expect(commentService.applySuggestion).toHaveBeenCalledWith(
+      comment,
+      user,
+      provenance,
+    );
+    expect(result).toBe(applied);
+  });
+
+  it('missing comment: NotFound is thrown without authorizing or applying', async () => {
+    const { controller, commentRepo, pageRepo, pageAccessService, commentService } =
+      makeController();
+    commentRepo.findById.mockResolvedValue(null);
+
+    await expect(
+      controller.applySuggestion(dto, user, workspace, provenance),
+    ).rejects.toBeInstanceOf(NotFoundException);
+
+    expect(pageRepo.findById).not.toHaveBeenCalled();
+    expect(pageAccessService.validateCanEdit).not.toHaveBeenCalled();
+    expect(commentService.applySuggestion).not.toHaveBeenCalled();
+  });
+});
@@ -14,6 +14,7 @@ import { CommentService } from './comment.service';
 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 { PageIdDto, CommentIdDto } from './dto/comments.input';
 import { AuthUser } from '../../common/decorators/auth-user.decorator';
 import { AuthWorkspace } from '../../common/decorators/auth-workspace.decorator';
@@ -197,6 +198,42 @@ export class CommentController {
    return updated;
  }

+  @HttpCode(HttpStatus.OK)
+  @Post('apply-suggestion')
+  async applySuggestion(
+    @Body() dto: ApplySuggestionDto,
+    @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 about the comment
+    // (metadata-disclosure hygiene). Applying a suggestion rewrites the page
+    // text, so require edit access (NOT just comment access). Running this
+    // first means a cross-workspace user with a guessed comment UUID gets a
+    // uniform 403 regardless of the comment's type or suggestion state — it can
+    // never distinguish those before the access check. The structural 400s
+    // (top-level / has-a-suggested-edit) are re-checked by the service below.
+    await this.pageAccessService.validateCanEdit(page, user);
+
+    // The service re-validates the comment's state, returns idempotent success
+    // for an already-applied suggestion, and lets ConflictException (409, with
+    // currentText in the payload) propagate untouched.
+    return this.commentService.applySuggestion(comment, user, provenance);
+  }
+
  @HttpCode(HttpStatus.OK)
  @Post('delete')
  async delete(@Body() input: CommentIdDto, @AuthUser() user: User, @AuthWorkspace() workspace: Workspace) {
@@ -0,0 +1,245 @@
+import {
+  BadRequestException,
+  ConflictException,
+  InternalServerErrorException,
+} from '@nestjs/common';
+import { CommentService } from './comment.service';
+import { AuditEvent, AuditResource } from '../../common/events/audit-events';
+
+/**
+ * Focused coverage for CommentService.applySuggestion (comment.service.ts).
+ * The service is constructed directly with jest-mocked deps (the @InjectQueue
+ * tokens can't be resolved by Test.createTestingModule — see the sibling specs).
+ *
+ * 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.
+ */
+describe('CommentService — applySuggestion', () => {
+  const UPDATED = { id: 'c-1', __updated: true } as any;
+
+  function makeService(verdict: unknown) {
+    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),
+    };
+    const pageRepo: any = {};
+    const wsService: any = { emitCommentEvent: jest.fn() };
+    const collaborationGateway: any = {
+      handleYjsEvent: jest.fn(async () => verdict),
+    };
+    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 });
+
+  // Pull the updateComment patch that carries the applied stamps.
+  const appliedPatch = (commentRepo: any) =>
+    commentRepo.updateComment.mock.calls
+      .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 () => {
+    const { service, commentRepo, wsService, collaborationGateway, auditService } =
+      makeService({ applied: true, currentText: 'new text' });
+
+    const result = await service.applySuggestion(suggestionComment(), user());
+
+    // The atomic replace was requested against the exact marked text.
+    expect(collaborationGateway.handleYjsEvent).toHaveBeenCalledWith(
+      'applyCommentSuggestion',
+      'page.page-1',
+      expect.objectContaining({
+        commentId: 'c-1',
+        expectedText: 'old text',
+        newText: 'new text',
+        user: expect.objectContaining({ id: 'user-1' }),
+      }),
+    );
+
+    // Applied stamps persisted.
+    const patch = appliedPatch(commentRepo);
+    expect(patch.suggestionAppliedAt).toBeInstanceOf(Date);
+    expect(patch.suggestionAppliedById).toBe('user-1');
+
+    // 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.
+    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);
+  });
+
+  it('applied=false but currentText === suggestedText → idempotent success (no 409)', async () => {
+    const { service, commentRepo, auditService } = makeService({
+      applied: false,
+      currentText: 'new text',
+    });
+
+    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.
+    const patch = appliedPatch(commentRepo);
+    expect(patch.suggestionAppliedAt).toBeInstanceOf(Date);
+    expect(patch.suggestionAppliedById).toBe('user-1');
+    expect(auditService.log).toHaveBeenCalledTimes(1);
+    expect(result).toBe(UPDATED);
+  });
+
+  it('applied=false and currentText differs → ConflictException with currentText in payload', async () => {
+    const { service, commentRepo, auditService } = makeService({
+      applied: false,
+      currentText: 'someone else edited this',
+    });
+
+    const err = await service
+      .applySuggestion(suggestionComment(), user())
+      .catch((e) => e);
+
+    expect(err).toBeInstanceOf(ConflictException);
+    expect(err.getResponse()).toMatchObject({
+      currentText: 'someone else edited this',
+    });
+    // No persistence and no audit on a conflict.
+    expect(appliedPatch(commentRepo)).toBeUndefined();
+    expect(auditService.log).not.toHaveBeenCalled();
+  });
+
+  it('already-applied AND already-resolved → idempotent success, no collab call, no re-resolve (#315 double-click)', async () => {
+    const { service, collaborationGateway, commentRepo, auditService } =
+      makeService({ applied: true, currentText: 'new text' });
+
+    const result = await service.applySuggestion(
+      suggestionComment({
+        suggestionAppliedAt: new Date(),
+        resolvedAt: new Date(),
+        resolvedById: 'user-1',
+      }),
+      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).
+    expect(auditService.log).toHaveBeenCalledTimes(1);
+  });
+
+  it('already-applied but NOT resolved (crash window) → idempotent success, self-heals resolve, no re-apply', async () => {
+    const { service, collaborationGateway, commentRepo } = makeService({
+      applied: true,
+      currentText: 'new text',
+    });
+
+    const result = await service.applySuggestion(
+      suggestionComment({ suggestionAppliedAt: new Date(), resolvedAt: null }),
+      user(),
+    );
+
+    expect(result).toBe(UPDATED);
+
+    // The suggestion is NOT re-applied to the document…
+    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.
+    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();
+  });
+
+  it('rejects a comment with no suggestedText', async () => {
+    const { service, collaborationGateway } = makeService({
+      applied: true,
+      currentText: 'x',
+    });
+
+    await expect(
+      service.applySuggestion(
+        suggestionComment({ suggestedText: null }),
+        user(),
+      ),
+    ).rejects.toThrow(BadRequestException);
+    expect(collaborationGateway.handleYjsEvent).not.toHaveBeenCalled();
+  });
+
+  it('gateway returning undefined → hard error, not a silent success', async () => {
+    const { service, commentRepo, auditService } = makeService(undefined);
+
+    await expect(
+      service.applySuggestion(suggestionComment(), user()),
+    ).rejects.toThrow(InternalServerErrorException);
+
+    // Nothing persisted, nothing audited.
+    expect(appliedPatch(commentRepo)).toBeUndefined();
+    expect(auditService.log).not.toHaveBeenCalled();
+  });
+});
@@ -60,6 +60,7 @@ describe('CommentService — behavior', () => {
    };
    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,
@@ -68,14 +69,17 @@ describe('CommentService — behavior', () => {
      collaborationGateway,
      generalQueue,
      notificationQueue,
+      auditService,
    );

    return {
      service,
      commentRepo,
      wsService,
+      collaborationGateway,
      generalQueue,
      notificationQueue,
+      auditService,
    };
  }

@@ -181,6 +185,95 @@ describe('CommentService — behavior', () => {
    });
  });

+  describe('create — suggested edit validation & storage', () => {
+    it('rejects a suggestedText on a reply (not a top-level comment)', async () => {
+      const parentComment = {
+        id: 'parent-1',
+        pageId: 'page-1',
+        parentCommentId: null,
+      };
+      const { service, commentRepo } = makeService({ parentComment });
+
+      await expect(
+        service.create(
+          { page: page(), workspaceId: 'ws-1', user: user() },
+          {
+            content: JSON.stringify(docMentioning()),
+            parentCommentId: 'parent-1',
+            selection: 'hello world',
+            suggestedText: 'goodbye world',
+          } as any,
+        ),
+      ).rejects.toThrow(BadRequestException);
+
+      expect(commentRepo.insertComment).not.toHaveBeenCalled();
+    });
+
+    it('rejects a suggestedText without a selection', async () => {
+      const { service, commentRepo } = makeService();
+
+      await expect(
+        service.create(
+          { page: page(), workspaceId: 'ws-1', user: user() },
+          {
+            content: JSON.stringify(docMentioning()),
+            suggestedText: 'new text',
+          } as any,
+        ),
+      ).rejects.toThrow(BadRequestException);
+
+      expect(commentRepo.insertComment).not.toHaveBeenCalled();
+    });
+
+    it('rejects a suggestedText identical to the selection (no-op)', async () => {
+      const { service, commentRepo } = makeService();
+
+      await expect(
+        service.create(
+          { page: page(), workspaceId: 'ws-1', user: user() },
+          {
+            content: JSON.stringify(docMentioning()),
+            selection: 'same text',
+            // Only differs by surrounding whitespace → still a no-op after trim.
+            suggestedText: '  same text  ',
+          } as any,
+        ),
+      ).rejects.toThrow(BadRequestException);
+
+      expect(commentRepo.insertComment).not.toHaveBeenCalled();
+    });
+
+    it('stores a valid suggestedText (trimmed) on the inserted row', async () => {
+      const { service, commentRepo } = makeService();
+
+      await service.create(
+        { page: page(), workspaceId: 'ws-1', user: user() },
+        {
+          content: JSON.stringify(docMentioning()),
+          selection: 'old text',
+          type: 'inline',
+          suggestedText: '  new text  ',
+        } as any,
+      );
+
+      const insertArg = commentRepo.insertComment.mock.calls[0][0];
+      expect(insertArg.suggestedText).toBe('new text');
+      expect(insertArg.selection).toBe('old text');
+    });
+
+    it('leaves suggestedText null for an ordinary comment', async () => {
+      const { service, commentRepo } = makeService();
+
+      await service.create(
+        { page: page(), workspaceId: 'ws-1', user: user() },
+        { content: JSON.stringify(docMentioning()) } as any,
+      );
+
+      const insertArg = commentRepo.insertComment.mock.calls[0][0];
+      expect(insertArg.suggestedText).toBeNull();
+    });
+  });
+
  describe('resolveComment — provenance & resolve notifications', () => {
    it('stamps resolvedSource:"agent" when an agent resolves', async () => {
      const { service, commentRepo } = makeService();
@@ -61,6 +61,8 @@ describe('CommentService — broadcast carries the agent avatar stack', () => {
    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,
@@ -68,6 +70,7 @@ describe('CommentService — broadcast carries the agent avatar stack', () => {
      collaborationGateway,
      generalQueue,
      notificationQueue,
+      auditService,
    );

    return { service, commentRepo, wsService };
@@ -14,6 +14,7 @@ describe('CommentService', () => {
      {} as any, // collaborationGateway
      {} as any, // generalQueue
      {} as any, // notificationQueue
+      {} as any, // auditService
    );
  });

@@ -1,7 +1,10 @@
 import {
  BadRequestException,
+  ConflictException,
  ForbiddenException,
+  Inject,
  Injectable,
+  InternalServerErrorException,
  Logger,
  NotFoundException,
 } from '@nestjs/common';
@@ -26,6 +29,11 @@ import {
  AuthProvenanceData,
  agentSourceFields,
 } from '../../common/decorators/auth-provenance.decorator';
+import { AuditEvent, AuditResource } from '../../common/events/audit-events';
+import {
+  AUDIT_SERVICE,
+  IAuditService,
+} from '../../integrations/audit/audit.service';

@Injectable()
 export class CommentService {
@@ -40,6 +48,7 @@ export class CommentService {
    private generalQueue: Queue,
    @InjectQueue(QueueName.NOTIFICATION_QUEUE)
    private notificationQueue: Queue,
+    @Inject(AUDIT_SERVICE) private auditService: IAuditService,
  ) {}

  async findById(commentId: string) {
@@ -78,15 +87,58 @@ export class CommentService {
      }
    }

+    // Do NOT lossily truncate at 250: for a suggestion the client sends the RAW
+    // anchored document substring (the exact text under the comment mark) as the
+    // selection, which can be LONGER than the agent's <=250-char typed input
+    // (normalization collapses whitespace/typographic runs, so the raw span can
+    // exceed the normalized selection). Truncating it shorter than the mark span
+    // would break the apply-time equality check and make the suggestion
+    // un-appliable. Keep a generous 2000-char safety bound (matching
+    // suggestedText) so a legitimate anchored substring is never cut.
+    const selection = createCommentDto?.selection?.substring(0, 2000) ?? null;
+
+    // A suggested edit rewrites the exact text under an inline comment mark, so
+    // it is only meaningful on a top-level inline comment that carries a
+    // selection, and only if the suggestion actually changes that text.
+    let suggestedText: string | null = null;
+    if (
+      createCommentDto.suggestedText !== undefined &&
+      createCommentDto.suggestedText !== null
+    ) {
+      if (createCommentDto.parentCommentId) {
+        throw new BadRequestException(
+          'A suggested edit can only be attached to a top-level comment, not a reply',
+        );
+      }
+      if (!selection || selection.trim().length === 0) {
+        throw new BadRequestException(
+          'A suggested edit requires an inline comment with a non-empty text selection',
+        );
+      }
+      const trimmed = createCommentDto.suggestedText.trim();
+      if (trimmed.length === 0) {
+        throw new BadRequestException('A suggested edit cannot be empty');
+      }
+      // A no-op suggestion (identical to the selection) is meaningless and would
+      // make "apply" indistinguishable from "already applied".
+      if (trimmed === selection.trim()) {
+        throw new BadRequestException(
+          'A suggested edit must differ from the selected text',
+        );
+      }
+      suggestedText = trimmed;
+    }
+
    const inserted = await this.commentRepo.insertComment({
      pageId: page.id,
      content: commentContent,
-      selection: createCommentDto?.selection?.substring(0, 250) ?? null,
+      selection,
      type: createCommentDto.type ?? 'page',
      parentCommentId: createCommentDto?.parentCommentId,
      creatorId: user.id,
      workspaceId: workspaceId,
      spaceId: page.spaceId,
+      suggestedText,
      // Agent-edit provenance: the user stays creatorId; this only annotates the
      // source. Normal user requests leave the column default ('user').
      ...agentSourceFields(provenance, 'createdSource', 'aiChatId'),
@@ -299,6 +351,152 @@ export class CommentService {
    return updatedComment;
  }

+  /**
+   * Apply the suggested edit carried by a top-level inline comment: atomically
+   * replace the text under the comment mark in the collaborative document with
+   * the comment's suggestedText, then stamp the applied fields and auto-resolve
+   * the thread. The controller authorizes (validateCanEdit); this re-checks the
+   * comment's own state so the invariant holds regardless of caller.
+   */
+  async applySuggestion(
+    comment: Comment,
+    user: User,
+    provenance?: AuthProvenanceData,
+  ): Promise<Comment> {
+    // Structural guards.
+    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 apply');
+    }
+    // State guards. Order matters — the already-applied check precedes the
+    // resolved check because an applied comment is normally also resolved.
+    //
+    // Already applied → IDEMPOTENT SUCCESS (issue #315 DoD: double-click /
+    // two-user race → idempotent "already applied", NOT a 409). The suggestion
+    // is already in the document, so do NOT call the collab gateway again.
+    // finalizeAppliedSuggestion re-fetches/broadcasts the same success shape as
+    // the applied branch and, when the thread is still open (the rare "applied
+    // but not resolved" crash window), self-heals it via resolveComment.
+    if (comment.suggestionAppliedAt) {
+      return this.finalizeAppliedSuggestion(comment, user, provenance);
+    }
+    // Not-yet-applied on a resolved thread → reject. The client hides the apply
+    // button once a thread is resolved; this is the defensive server check.
+    if (comment.resolvedAt) {
+      throw new BadRequestException(
+        'Cannot apply a suggested edit on a resolved comment thread',
+      );
+    }
+
+    // Derive the document name the same way create()/resolveComment() do for
+    // the comment marks: `page.${pageId}`.
+    const documentName = `page.${comment.pageId}`;
+
+    let verdict: { applied: boolean; currentText: string | null } | undefined;
+    try {
+      verdict = await this.collaborationGateway.handleYjsEvent(
+        'applyCommentSuggestion',
+        documentName,
+        {
+          commentId: comment.id,
+          expectedText: comment.selection,
+          newText: comment.suggestedText,
+          user,
+        },
+      );
+    } catch (error) {
+      // A throwing gateway (or the phase-3 fallback failing) is a hard error —
+      // never silently succeed, the document may or may not have changed.
+      this.logger.error(
+        `Failed to apply suggested edit for comment ${comment.id}`,
+        error,
+      );
+      throw new InternalServerErrorException('Failed to apply the suggested edit');
+    }
+
+    if (!verdict) {
+      // Should not happen given the phase-3 fallback; treat as a hard error
+      // rather than assuming success.
+      throw new InternalServerErrorException('Failed to apply the suggested edit');
+    }
+
+    if (verdict.applied === true) {
+      return this.finalizeAppliedSuggestion(comment, user, provenance);
+    }
+
+    // Idempotent branch: the mutation didn't run now, but the text under the
+    // mark is ALREADY the suggested text (double-click, two-user race, or a
+    // crash between the doc mutation and the DB write). Reconcile the DB /
+    // resolved state and report success — do NOT 409.
+    if (
+      verdict.applied === false &&
+      verdict.currentText === comment.suggestedText
+    ) {
+      return this.finalizeAppliedSuggestion(comment, user, provenance);
+    }
+
+    // The commented text changed since the suggestion was made. Surface the
+    // current text so the client can tell the user what it is now.
+    throw new ConflictException({
+      message:
+        'The commented text changed since this suggestion was made; it was not applied.',
+      currentText: verdict.currentText,
+    });
+  }
+
+  /**
+   * Persist the applied stamps (idempotently), auto-resolve the thread and
+   * broadcast + audit the applied suggestion. Shared by the applied and the
+   * idempotent "already-applied" branches of applySuggestion.
+   */
+  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,
+      );
+    }
+
+    // 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,
+    });
+
+    this.auditService.log({
+      event: AuditEvent.COMMENT_SUGGESTION_APPLIED,
+      resourceType: AuditResource.COMMENT,
+      resourceId: comment.id,
+      spaceId: comment.spaceId,
+      metadata: { pageId: comment.pageId },
+    });
+
+    return updatedComment;
+  }
+
  private async queueCommentNotification(
    content: any,
    oldMentionIds: string[],
@@ -0,0 +1,6 @@
+import { IsUUID } from 'class-validator';
+
+export class ApplySuggestionDto {
+  @IsUUID()
+  commentId: string;
+}
@@ -1,4 +1,12 @@
-import { IsIn, IsJSON, IsObject, IsOptional, IsString, IsUUID } from 'class-validator';
+import {
+  IsIn,
+  IsJSON,
+  IsObject,
+  IsOptional,
+  IsString,
+  IsUUID,
+  MaxLength,
+} from 'class-validator';
 import { z } from 'zod';

 const yjsIdSchema = z.object({
@@ -25,8 +33,15 @@ export class CreateCommentDto {
  @IsJSON()
  content: any;

+  // The agent tool caps what it TYPES at 250 chars, but for a suggestion the
+  // client resolves and sends the RAW anchored document substring (the exact
+  // text under the mark), which can be longer once normalization is undone. Bound
+  // the stored value at 2000 (matching suggestedText) so a legitimate anchored
+  // substring is never rejected — the service used to lossily truncate at 250,
+  // which broke the apply-time equality check.
  @IsOptional()
  @IsString()
+  @MaxLength(2000)
  selection: string;

  @IsOptional()
@@ -43,4 +58,12 @@ export class CreateCommentDto {
    anchor: any;
    head: any;
  };
+
+  // Optional suggested replacement for the selected text (a "suggested edit").
+  // Only valid on a top-level inline comment that carries a non-empty selection;
+  // enforced in CommentService.create.
+  @IsOptional()
+  @IsString()
+  @MaxLength(2000)
+  suggestedText?: string;
 }
@@ -0,0 +1,26 @@
+import { type Kysely } from 'kysely';
+
+export async function up(db: Kysely<any>): Promise<void> {
+  // Agent comment suggestions (#315): a comment may carry a proposed replacement
+  // for its anchored `selection`, which a human applies via the comment UI.
+  await db.schema
+    .alterTable('comments')
+    // The proposed replacement text (plain text). NULL for ordinary comments.
+    .addColumn('suggested_text', 'text')
+    // When the suggestion was applied (NULL until applied).
+    .addColumn('suggestion_applied_at', 'timestamptz')
+    // Who applied it (NULL until applied).
+    .addColumn('suggestion_applied_by_id', 'uuid', (col) =>
+      col.references('users.id').onDelete('set null'),
+    )
+    .execute();
+}
+
+export async function down(db: Kysely<any>): Promise<void> {
+  await db.schema
+    .alterTable('comments')
+    .dropColumn('suggested_text')
+    .dropColumn('suggestion_applied_at')
+    .dropColumn('suggestion_applied_by_id')
+    .execute();
+}
@@ -173,6 +173,9 @@ export interface Comments {
  resolvedSource: string | null;
  selection: string | null;
  spaceId: string;
+  suggestedText: string | null;
+  suggestionAppliedAt: Timestamp | null;
+  suggestionAppliedById: string | null;
  type: string | null;
  updatedAt: Generated<Timestamp>;
  workspaceId: string;
@@ -17,7 +17,7 @@ import { withPageLock } from "./lib/page-lock.js";
 import { applyTextEdits, } from "./lib/json-edit.js";
 import { getCollabToken, performLogin } from "./lib/auth-utils.js";
 import { diffDocs, summarizeChange } from "./lib/diff.js";
-import { applyAnchorInDoc, canAnchorInDoc } from "./lib/comment-anchor.js";
+import { applyAnchorInDoc, canAnchorInDoc, countAnchorMatches, getAnchoredText, } from "./lib/comment-anchor.js";
 import { blockText, walk, getList, insertMarkerAfter, setCalloutRange, noteItem, mdToInlineNodes, commentsToFootnotes, canonicalizeFootnotes, insertInlineFootnote, } from "./lib/transforms.js";
 import vm from "node:vm";
 // Supported image types, kept as two lookup tables so both a local file
@@ -1912,9 +1912,21 @@ export class DocmostClient {
     * an orphan, unanchored comment behind. Replies (parentCommentId set) inherit
     * their parent's anchor: they take NO selection and are not anchored.
     */
-    async createComment(pageId, content, type = "page", selection, parentCommentId) {
+    async createComment(pageId, content, type = "page", selection, parentCommentId, suggestedText) {
        await this.ensureAuthenticated();
        const isReply = !!parentCommentId;
+        const hasSuggestion = suggestedText !== undefined && suggestedText !== null;
+        // Defense in depth mirroring the server DTO/service: a suggested edit rewrites
+        // the exact anchored text, so it is only meaningful on a top-level inline
+        // comment that carries a selection.
+        if (hasSuggestion) {
+            if (isReply) {
+                throw new Error("create_comment: a suggested edit (suggestedText) cannot be attached to a reply; it applies only to a top-level inline comment.");
+            }
+            if (!selection || !selection.trim()) {
+                throw new Error("create_comment: a suggested edit (suggestedText) requires a 'selection' to anchor and rewrite.");
+            }
+        }
        // Only top-level comments are inline-anchored, so they are stored as
        // "inline". Replies carry no inline selection, so they keep the historical
        // general ("page") type — both backward-compatible and semantically correct.
@@ -1924,6 +1936,16 @@ export class DocmostClient {
        if (!isReply && (!selection || !selection.trim())) {
            throw new Error("create_comment: an inline 'selection' (exact text to anchor on) is required for a top-level comment");
        }
+        // For a SUGGESTION, the value we store as the comment's `selection` must be
+        // the RAW document substring the mark lands on (typographic quotes/dashes,
+        // nbsp, collapsed whitespace), NOT the agent's ASCII input. The anchor is
+        // placed via normalization, so when the doc was auto-converted to
+        // typographic the raw substring differs from the agent input; apply-time
+        // compares the stored selection to the marked doc text STRICTLY, so storing
+        // the raw substring is what makes "Apply" succeed instead of a spurious 409.
+        // Captured in the pre-check below (which already reads the page) and used as
+        // payload.selection. Ordinary comments keep sending the raw agent selection.
+        let anchoredSelection = null;
        // For a top-level comment, fail BEFORE creating anything when the selection
        // is not present in the persisted document — this avoids leaving an orphan
        // comment + notification behind. A read failure (network) is non-fatal: the
@@ -1931,16 +1953,38 @@ export class DocmostClient {
        if (!isReply && selection) {
            try {
                const page = await this.getPageJson(pageId);
-                if (!canAnchorInDoc(page.content, selection)) {
+                if (hasSuggestion) {
+                    // A suggestion's anchor MUST be unambiguous: applying it rewrites the
+                    // exact anchored text, and ordinary anchoring silently takes the first
+                    // occurrence, so 0 matches -> not found and >=2 -> ambiguous, both
+                    // rejected BEFORE creating the comment.
+                    const matches = countAnchorMatches(page.content, selection);
+                    if (matches === 0) {
+                        throw new Error("create_comment: could not find the selection text in the page to anchor the comment. " +
+                            "Provide the EXACT contiguous text from a single paragraph/block (<=250 chars).");
+                    }
+                    if (matches >= 2) {
+                        throw new Error(`create_comment: the suggestion's selection is ambiguous — it occurs ${matches} times in the page. ` +
+                            "A suggested edit must anchor to a UNIQUE location; expand the selection with surrounding context " +
+                            "(still <=250 chars) so it appears exactly once.");
+                    }
+                    // Exactly one match: capture the RAW anchored substring to store as the
+                    // comment selection (so apply-time equality holds). If this returns
+                    // null despite countAnchorMatches===1 (shouldn't happen), fall back to
+                    // the raw agent selection below rather than crash.
+                    anchoredSelection = getAnchoredText(page.content, selection);
+                }
+                else if (!canAnchorInDoc(page.content, selection)) {
                    throw new Error("create_comment: could not find the selection text in the page to anchor the comment. " +
                        "Provide the EXACT contiguous text from a single paragraph/block (<=250 chars).");
                }
            }
            catch (e) {
-                // Rethrow our own "not found" error; swallow read/network errors so the
-                // live anchor step can still try (and enforce) the anchoring.
+                // Rethrow our own "not found"/"ambiguous" errors; swallow read/network
+                // errors so the live anchor step can still try (and enforce) anchoring.
                if (e instanceof Error &&
-                    e.message.startsWith("create_comment: could not find the selection")) {
+                    (e.message.startsWith("create_comment: could not find the selection") ||
+                        e.message.startsWith("create_comment: the suggestion's selection is ambiguous"))) {
                    throw e;
                }
                if (process.env.DEBUG) {
@@ -1958,10 +2002,19 @@ export class DocmostClient {
            content: JSON.stringify(jsonContent),
            type: effectiveType,
        };
+        // For a suggestion, store the RAW anchored substring (anchoredSelection) so
+        // the stored selection === the text under the mark === apply-time
+        // expectedText. Ordinary comments (and the null fallback) keep the raw
+        // agent selection — their selection is only display/anchor and never used
+        // by apply, so their behavior is unchanged.
        if (!isReply && selection)
-            payload.selection = selection;
+            payload.selection = anchoredSelection ?? selection;
        if (parentCommentId)
            payload.parentCommentId = parentCommentId;
+        // Only a top-level inline comment (with a selection) may carry a suggestion.
+        if (!isReply && selection && hasSuggestion) {
+            payload.suggestedText = suggestedText;
+        }
        const response = await this.client.post("/comments/create", payload);
        const comment = response.data.data || response.data;
        const markdown = comment.content
@@ -1988,15 +2041,34 @@ export class DocmostClient {
            throw new Error("create_comment: the server returned no comment id, so the comment could not be anchored");
        }
        let anchored = false;
+        // Set inside the transform when a suggestion's live anchor is ambiguous
+        // (>=2 occurrences), so the rollback path can surface the right error.
+        let ambiguousInLiveDoc = false;
        try {
            const collabToken = await this.getCollabTokenWithReauth();
            // Open the collab doc by the canonical UUID, never the slugId (#260). The
            // /comments/create REST call above keeps the agent-supplied id.
            const pageUuid = await this.resolvePageId(pageId);
-            const mutation = await mutatePageContent(pageUuid, collabToken, this.apiUrl, (liveDoc) => {
+            // Route through the mutatePage seam (not the free function) so this
+            // wrapper's uniqueness gate + rollback can be unit-tested without a live
+            // Hocuspocus collab socket.
+            const mutation = await this.mutatePage(pageUuid, collabToken, this.apiUrl, (liveDoc) => {
                const doc = liveDoc && liveDoc.type === "doc"
                    ? liveDoc
                    : { type: "doc", content: [] };
+                if (hasSuggestion) {
+                    // Authoritative uniqueness check against the LIVE document: a
+                    // suggestion must anchor to EXACTLY ONE occurrence, otherwise
+                    // "Apply" would rewrite the wrong/ambiguous text. If the live doc
+                    // no longer has exactly one occurrence (it changed since the
+                    // pre-check), abort so the just-created comment is rolled back
+                    // rather than mis-anchored to the first occurrence.
+                    const liveCount = countAnchorMatches(doc, selection);
+                    if (liveCount !== 1) {
+                        ambiguousInLiveDoc = liveCount >= 2;
+                        return null;
+                    }
+                }
                if (applyAnchorInDoc(doc, selection, newCommentId)) {
                    anchored = true;
                    return doc;
@@ -2014,10 +2086,13 @@ export class DocmostClient {
            throw e;
        }
        if (!anchored) {
-            // Mutation aborted because the selection was not found in the live
-            // document. Roll back the comment and surface a hard error.
+            // Mutation aborted because the selection was not found (or, for a
+            // suggestion, was ambiguous) in the live document. Roll back the comment
+            // and surface a hard error.
            await this.safeDeleteComment(newCommentId);
-            throw new Error("create_comment: failed to anchor the comment (selection not found in the live document); the comment was rolled back");
+            throw new Error(ambiguousInLiveDoc
+                ? "create_comment: the suggestion's selection is ambiguous in the live document (multiple occurrences); the comment was rolled back. Expand the selection with surrounding context so it is unique."
+                : "create_comment: failed to anchor the comment (selection not found in the live document); the comment was rolled back");
        }
        result.anchored = true;
        return result;
@@ -520,7 +520,10 @@ export function createDocmostMcpServer(config) {
            "A top-level comment REQUIRES an exact `selection`; if the selection " +
            "cannot be found in the page the call fails (no orphan comment is left). " +
            "Replies (parentCommentId set) inherit the parent's anchor and take no " +
-            "selection.",
+            "selection. You may also attach a `suggestedText` proposing a replacement " +
+            "for the `selection`; a human applies (or rejects) it from the UI. When " +
+            "`suggestedText` is set the `selection` MUST occur exactly once in the " +
+            "page — expand it with surrounding context if it is ambiguous.",
        inputSchema: {
            pageId: z.string().describe("ID of the page to comment on"),
            content: z.string().min(1).describe("Comment content in Markdown format"),
@@ -537,12 +540,30 @@ export function createDocmostMcpServer(config) {
                .string()
                .optional()
                .describe("Parent comment ID to create a reply (max 2 nesting levels)"),
+            suggestedText: z
+                .string()
+                .min(1)
+                .max(2000)
+                .optional()
+                .describe("Optional proposed replacement (PLAIN TEXT) for the `selection`, " +
+                "applied by a human via the UI (never auto-applied). REQUIRES a " +
+                "`selection`; NOT allowed on a reply. When set, the `selection` must " +
+                "be UNIQUE in the page — expand it with surrounding context (still " +
+                "<=250 chars) if it occurs more than once, or the call is refused."),
        },
-    }, async ({ pageId, content, selection, parentCommentId }) => {
+    }, async ({ pageId, content, selection, parentCommentId, suggestedText }) => {
        if (!parentCommentId && (!selection || !selection.trim())) {
            throw new Error("create_comment: a 'selection' (exact text to anchor on) is required for a top-level comment; omit it only when replying via parentCommentId.");
        }
-        const result = await docmostClient.createComment(pageId, content, "inline", selection, parentCommentId);
+        if (suggestedText !== undefined) {
+            if (parentCommentId) {
+                throw new Error("create_comment: 'suggestedText' cannot be attached to a reply; it applies only to a top-level inline comment.");
+            }
+            if (!selection || !selection.trim()) {
+                throw new Error("create_comment: 'suggestedText' requires a 'selection' to anchor and rewrite.");
+            }
+        }
+        const result = await docmostClient.createComment(pageId, content, "inline", selection, parentCommentId, suggestedText);
        return jsonContent(result);
    });
    // Tool: update_comment
@@ -148,6 +148,67 @@ export function findAnchorInBlock(blockContent, selection) {
    }
    return null;
 }
+/**
+ * Reconstruct the RAW text spanned by an AnchorMatch inside one block's
+ * `content` array. `startChild..endChild` are all text nodes (guaranteed by
+ * findAnchorInBlock, which only builds runs of `text` nodes), so concatenate
+ * each node's text slice: from `startOffset` on the first node, up to
+ * `endOffset` on the last, and the whole `.text` for any node fully inside the
+ * range. Mirrors spliceCommentMark's per-node slicing so the string returned
+ * here is EXACTLY the characters the comment mark will cover.
+ */
+function reconstructRawText(blockContent, match) {
+    const { startChild, startOffset, endChild, endOffset } = match;
+    let out = "";
+    for (let k = startChild; k <= endChild; k++) {
+        const n = blockContent[k];
+        const text = typeof n.text === "string" ? n.text : "";
+        const sliceStart = k === startChild ? startOffset : 0;
+        const sliceEnd = k === endChild ? endOffset : text.length;
+        out += text.slice(sliceStart, sliceEnd);
+    }
+    return out;
+}
+/**
+ * Return the RAW document substring that `selection` would anchor to — the exact
+ * characters the comment mark will cover — or `null` when the selection cannot
+ * be anchored anywhere in `doc`.
+ *
+ * This mirrors canAnchorInDoc / applyAnchorInDoc EXACTLY (same depth-first,
+ * document-order traversal and the same findAnchorInBlock match on the FIRST
+ * matching block), but instead of a boolean / an in-place mutation it
+ * reconstructs the raw text spanned by the matched range. Because
+ * findAnchorInBlock maps the normalized selection back to raw text-node
+ * positions, the returned string is the document's ORIGINAL characters (smart
+ * quotes, em-dashes, nbsp, collapsed whitespace) — NOT the normalized ASCII
+ * agent input.
+ *
+ * Callers store THIS as the comment's `selection` so the stored value equals the
+ * text actually under the mark, which is what the apply-suggestion equality
+ * check (replaceYjsMarkedText's `joinedText !== expectedText`) compares against.
+ * Without it a suggestion whose anchor only matched via normalization would be
+ * un-appliable (spurious 409).
+ */
+export function getAnchoredText(doc, selection) {
+    const visit = (node, depth) => {
+        if (depth > MAX_DEPTH || !node || typeof node !== "object")
+            return null;
+        if (!Array.isArray(node.content))
+            return null;
+        const match = findAnchorInBlock(node.content, selection);
+        if (match)
+            return reconstructRawText(node.content, match);
+        for (const child of node.content) {
+            if (child && typeof child === "object" && Array.isArray(child.content)) {
+                const found = visit(child, depth + 1);
+                if (found !== null)
+                    return found;
+            }
+        }
+        return null;
+    };
+    return visit(doc, 0);
+}
 /**
 * Depth-first, document-order check for whether `selection` can be anchored
 * anywhere in `doc`. At each node with an array `content`, first try to match
@@ -210,6 +271,77 @@ function spliceCommentMark(blockContent, match, commentId) {
    }
    blockContent.splice(startChild, endChild - startChild + 1, ...fragments);
 }
+/**
+ * Count how many times `selection` occurs across the whole document, using the
+ * same normalization and run-matching as findAnchorInBlock but WITHOUT stopping
+ * at the first hit: every non-overlapping occurrence within each block's text
+ * runs is counted and summed across all blocks (depth-first, the same traversal
+ * as canAnchorInDoc).
+ *
+ * This is the uniqueness gate for SUGGESTIONS: because applying a suggestion
+ * rewrites the exact anchored text, an ambiguous anchor (>1 occurrence) would
+ * silently edit the wrong place, so a suggestion is only allowed when this
+ * returns exactly 1. Ordinary comments keep first-occurrence anchoring and do
+ * not use this. (Note: counts OCCURRENCES, not just matching blocks, so two
+ * occurrences inside one block are correctly reported as 2.)
+ */
+export function countAnchorMatches(doc, selection) {
+    const normSel = normalizeForMatch(selection).norm.trim();
+    if (normSel.length === 0)
+        return 0;
+    // Count non-overlapping occurrences of the normalized selection within a
+    // single block's direct content, matching findAnchorInBlock's run building.
+    const countInBlock = (blockContent) => {
+        if (!Array.isArray(blockContent))
+            return 0;
+        let count = 0;
+        let i = 0;
+        while (i < blockContent.length) {
+            const node = blockContent[i];
+            if (!node || typeof node !== "object" || node.type !== "text") {
+                i++;
+                continue;
+            }
+            // Accumulate a maximal run of consecutive text nodes.
+            let rawRun = "";
+            let j = i;
+            while (j < blockContent.length) {
+                const n = blockContent[j];
+                if (!n || typeof n !== "object" || n.type !== "text")
+                    break;
+                rawRun += typeof n.text === "string" ? n.text : "";
+                j++;
+            }
+            const norm = normalizeForMatch(rawRun).norm;
+            // Count every non-overlapping occurrence in this run.
+            let from = 0;
+            for (;;) {
+                const idx = norm.indexOf(normSel, from);
+                if (idx === -1)
+                    break;
+                count++;
+                from = idx + normSel.length;
+            }
+            i = j > i ? j : i + 1;
+        }
+        return count;
+    };
+    let total = 0;
+    const visit = (node, depth) => {
+        if (depth > MAX_DEPTH || !node || typeof node !== "object")
+            return;
+        if (!Array.isArray(node.content))
+            return;
+        total += countInBlock(node.content);
+        for (const child of node.content) {
+            if (child && typeof child === "object" && Array.isArray(child.content)) {
+                visit(child, depth + 1);
+            }
+        }
+    };
+    visit(doc, 0);
+    return total;
+}
 /**
 * Depth-first (same order as canAnchorInDoc) over `doc`; on the FIRST block
 * whose content matches `selection`, splice the comment mark across the matched
@@ -70,6 +70,11 @@ export function filterComment(comment, markdownContent) {
        editedAt: comment.editedAt || null,
        resolvedAt: comment.resolvedAt || null,
        resolvedById: comment.resolvedById || null,
+        // Suggestion state: the proposed replacement text (if any) and, once a human
+        // applies it via the UI, when and by whom.
+        suggestedText: comment.suggestedText || null,
+        suggestionAppliedAt: comment.suggestionAppliedAt || null,
+        suggestionAppliedById: comment.suggestionAppliedById || null,
    };
 }
 export function filterSearchResult(result) {
@@ -56,7 +56,12 @@ import {
 } from "./lib/json-edit.js";
 import { getCollabToken, performLogin } from "./lib/auth-utils.js";
 import { diffDocs, summarizeChange } from "./lib/diff.js";
-import { applyAnchorInDoc, canAnchorInDoc } from "./lib/comment-anchor.js";
+import {
+  applyAnchorInDoc,
+  canAnchorInDoc,
+  countAnchorMatches,
+  getAnchoredText,
+} from "./lib/comment-anchor.js";
 import {
  blockText,
  walk,
@@ -2395,10 +2400,28 @@ export class DocmostClient {
    type: "page" | "inline" = "page",
    selection?: string,
    parentCommentId?: string,
+    suggestedText?: string,
  ) {
    await this.ensureAuthenticated();

    const isReply = !!parentCommentId;
+    const hasSuggestion =
+      suggestedText !== undefined && suggestedText !== null;
+    // Defense in depth mirroring the server DTO/service: a suggested edit rewrites
+    // the exact anchored text, so it is only meaningful on a top-level inline
+    // comment that carries a selection.
+    if (hasSuggestion) {
+      if (isReply) {
+        throw new Error(
+          "create_comment: a suggested edit (suggestedText) cannot be attached to a reply; it applies only to a top-level inline comment.",
+        );
+      }
+      if (!selection || !selection.trim()) {
+        throw new Error(
+          "create_comment: a suggested edit (suggestedText) requires a 'selection' to anchor and rewrite.",
+        );
+      }
+    }
    // Only top-level comments are inline-anchored, so they are stored as
    // "inline". Replies carry no inline selection, so they keep the historical
    // general ("page") type — both backward-compatible and semantically correct.
@@ -2411,6 +2434,17 @@ export class DocmostClient {
      );
    }

+    // For a SUGGESTION, the value we store as the comment's `selection` must be
+    // the RAW document substring the mark lands on (typographic quotes/dashes,
+    // nbsp, collapsed whitespace), NOT the agent's ASCII input. The anchor is
+    // placed via normalization, so when the doc was auto-converted to
+    // typographic the raw substring differs from the agent input; apply-time
+    // compares the stored selection to the marked doc text STRICTLY, so storing
+    // the raw substring is what makes "Apply" succeed instead of a spurious 409.
+    // Captured in the pre-check below (which already reads the page) and used as
+    // payload.selection. Ordinary comments keep sending the raw agent selection.
+    let anchoredSelection: string | null = null;
+
    // For a top-level comment, fail BEFORE creating anything when the selection
    // is not present in the persisted document — this avoids leaving an orphan
    // comment + notification behind. A read failure (network) is non-fatal: the
@@ -2418,18 +2452,45 @@ export class DocmostClient {
    if (!isReply && selection) {
      try {
        const page = await this.getPageJson(pageId);
-        if (!canAnchorInDoc(page.content, selection)) {
+        if (hasSuggestion) {
+          // A suggestion's anchor MUST be unambiguous: applying it rewrites the
+          // exact anchored text, and ordinary anchoring silently takes the first
+          // occurrence, so 0 matches -> not found and >=2 -> ambiguous, both
+          // rejected BEFORE creating the comment.
+          const matches = countAnchorMatches(page.content, selection);
+          if (matches === 0) {
+            throw new Error(
+              "create_comment: could not find the selection text in the page to anchor the comment. " +
+                "Provide the EXACT contiguous text from a single paragraph/block (<=250 chars).",
+            );
+          }
+          if (matches >= 2) {
+            throw new Error(
+              `create_comment: the suggestion's selection is ambiguous — it occurs ${matches} times in the page. ` +
+                "A suggested edit must anchor to a UNIQUE location; expand the selection with surrounding context " +
+                "(still <=250 chars) so it appears exactly once.",
+            );
+          }
+          // Exactly one match: capture the RAW anchored substring to store as the
+          // comment selection (so apply-time equality holds). If this returns
+          // null despite countAnchorMatches===1 (shouldn't happen), fall back to
+          // the raw agent selection below rather than crash.
+          anchoredSelection = getAnchoredText(page.content, selection);
+        } else if (!canAnchorInDoc(page.content, selection)) {
          throw new Error(
            "create_comment: could not find the selection text in the page to anchor the comment. " +
              "Provide the EXACT contiguous text from a single paragraph/block (<=250 chars).",
          );
        }
      } catch (e) {
-        // Rethrow our own "not found" error; swallow read/network errors so the
-        // live anchor step can still try (and enforce) the anchoring.
+        // Rethrow our own "not found"/"ambiguous" errors; swallow read/network
+        // errors so the live anchor step can still try (and enforce) anchoring.
        if (
          e instanceof Error &&
-          e.message.startsWith("create_comment: could not find the selection")
+          (e.message.startsWith("create_comment: could not find the selection") ||
+            e.message.startsWith(
+              "create_comment: the suggestion's selection is ambiguous",
+            ))
        ) {
          throw e;
        }
@@ -2452,8 +2513,18 @@ export class DocmostClient {
      content: JSON.stringify(jsonContent),
      type: effectiveType,
    };
-    if (!isReply && selection) payload.selection = selection;
+    // For a suggestion, store the RAW anchored substring (anchoredSelection) so
+    // the stored selection === the text under the mark === apply-time
+    // expectedText. Ordinary comments (and the null fallback) keep the raw
+    // agent selection — their selection is only display/anchor and never used
+    // by apply, so their behavior is unchanged.
+    if (!isReply && selection)
+      payload.selection = anchoredSelection ?? selection;
    if (parentCommentId) payload.parentCommentId = parentCommentId;
+    // Only a top-level inline comment (with a selection) may carry a suggestion.
+    if (!isReply && selection && hasSuggestion) {
+      payload.suggestedText = suggestedText;
+    }

    const response = await this.client.post("/comments/create", payload);
    const comment = response.data.data || response.data;
@@ -2485,12 +2556,18 @@ export class DocmostClient {
      );
    }
    let anchored = false;
+    // Set inside the transform when a suggestion's live anchor is ambiguous
+    // (>=2 occurrences), so the rollback path can surface the right error.
+    let ambiguousInLiveDoc = false;
    try {
      const collabToken = await this.getCollabTokenWithReauth();
      // Open the collab doc by the canonical UUID, never the slugId (#260). The
      // /comments/create REST call above keeps the agent-supplied id.
      const pageUuid = await this.resolvePageId(pageId);
-      const mutation = await mutatePageContent(
+      // Route through the mutatePage seam (not the free function) so this
+      // wrapper's uniqueness gate + rollback can be unit-tested without a live
+      // Hocuspocus collab socket.
+      const mutation = await this.mutatePage(
        pageUuid,
        collabToken,
        this.apiUrl,
@@ -2499,6 +2576,19 @@ export class DocmostClient {
            liveDoc && liveDoc.type === "doc"
              ? liveDoc
              : { type: "doc", content: [] };
+          if (hasSuggestion) {
+            // Authoritative uniqueness check against the LIVE document: a
+            // suggestion must anchor to EXACTLY ONE occurrence, otherwise
+            // "Apply" would rewrite the wrong/ambiguous text. If the live doc
+            // no longer has exactly one occurrence (it changed since the
+            // pre-check), abort so the just-created comment is rolled back
+            // rather than mis-anchored to the first occurrence.
+            const liveCount = countAnchorMatches(doc, selection as string);
+            if (liveCount !== 1) {
+              ambiguousInLiveDoc = liveCount >= 2;
+              return null;
+            }
+          }
          if (applyAnchorInDoc(doc, selection as string, newCommentId)) {
            anchored = true;
            return doc;
@@ -2517,11 +2607,14 @@ export class DocmostClient {
    }

    if (!anchored) {
-      // Mutation aborted because the selection was not found in the live
-      // document. Roll back the comment and surface a hard error.
+      // Mutation aborted because the selection was not found (or, for a
+      // suggestion, was ambiguous) in the live document. Roll back the comment
+      // and surface a hard error.
      await this.safeDeleteComment(newCommentId);
      throw new Error(
-        "create_comment: failed to anchor the comment (selection not found in the live document); the comment was rolled back",
+        ambiguousInLiveDoc
+          ? "create_comment: the suggestion's selection is ambiguous in the live document (multiple occurrences); the comment was rolled back. Expand the selection with surrounding context so it is unique."
+          : "create_comment: failed to anchor the comment (selection not found in the live document); the comment was rolled back",
      );
    }

@@ -722,7 +722,10 @@ server.registerTool(
      "A top-level comment REQUIRES an exact `selection`; if the selection " +
      "cannot be found in the page the call fails (no orphan comment is left). " +
      "Replies (parentCommentId set) inherit the parent's anchor and take no " +
-      "selection.",
+      "selection. You may also attach a `suggestedText` proposing a replacement " +
+      "for the `selection`; a human applies (or rejects) it from the UI. When " +
+      "`suggestedText` is set the `selection` MUST occur exactly once in the " +
+      "page — expand it with surrounding context if it is ambiguous.",
    inputSchema: {
      pageId: z.string().describe("ID of the page to comment on"),
      content: z.string().min(1).describe("Comment content in Markdown format"),
@@ -741,20 +744,45 @@ server.registerTool(
        .string()
        .optional()
        .describe("Parent comment ID to create a reply (max 2 nesting levels)"),
+      suggestedText: z
+        .string()
+        .min(1)
+        .max(2000)
+        .optional()
+        .describe(
+          "Optional proposed replacement (PLAIN TEXT) for the `selection`, " +
+            "applied by a human via the UI (never auto-applied). REQUIRES a " +
+            "`selection`; NOT allowed on a reply. When set, the `selection` must " +
+            "be UNIQUE in the page — expand it with surrounding context (still " +
+            "<=250 chars) if it occurs more than once, or the call is refused.",
+        ),
    },
  },
-  async ({ pageId, content, selection, parentCommentId }) => {
+  async ({ pageId, content, selection, parentCommentId, suggestedText }) => {
    if (!parentCommentId && (!selection || !selection.trim())) {
      throw new Error(
        "create_comment: a 'selection' (exact text to anchor on) is required for a top-level comment; omit it only when replying via parentCommentId.",
      );
    }
+    if (suggestedText !== undefined) {
+      if (parentCommentId) {
+        throw new Error(
+          "create_comment: 'suggestedText' cannot be attached to a reply; it applies only to a top-level inline comment.",
+        );
+      }
+      if (!selection || !selection.trim()) {
+        throw new Error(
+          "create_comment: 'suggestedText' requires a 'selection' to anchor and rewrite.",
+        );
+      }
+    }
    const result = await docmostClient.createComment(
      pageId,
      content,
      "inline",
      selection,
      parentCommentId,
+      suggestedText,
    );
    return jsonContent(result);
  },
@@ -171,6 +171,65 @@ export function findAnchorInBlock(
  return null;
 }

+/**
+ * Reconstruct the RAW text spanned by an AnchorMatch inside one block's
+ * `content` array. `startChild..endChild` are all text nodes (guaranteed by
+ * findAnchorInBlock, which only builds runs of `text` nodes), so concatenate
+ * each node's text slice: from `startOffset` on the first node, up to
+ * `endOffset` on the last, and the whole `.text` for any node fully inside the
+ * range. Mirrors spliceCommentMark's per-node slicing so the string returned
+ * here is EXACTLY the characters the comment mark will cover.
+ */
+function reconstructRawText(blockContent: any[], match: AnchorMatch): string {
+  const { startChild, startOffset, endChild, endOffset } = match;
+  let out = "";
+  for (let k = startChild; k <= endChild; k++) {
+    const n = blockContent[k];
+    const text: string = typeof n.text === "string" ? n.text : "";
+    const sliceStart = k === startChild ? startOffset : 0;
+    const sliceEnd = k === endChild ? endOffset : text.length;
+    out += text.slice(sliceStart, sliceEnd);
+  }
+  return out;
+}
+
+/**
+ * Return the RAW document substring that `selection` would anchor to — the exact
+ * characters the comment mark will cover — or `null` when the selection cannot
+ * be anchored anywhere in `doc`.
+ *
+ * This mirrors canAnchorInDoc / applyAnchorInDoc EXACTLY (same depth-first,
+ * document-order traversal and the same findAnchorInBlock match on the FIRST
+ * matching block), but instead of a boolean / an in-place mutation it
+ * reconstructs the raw text spanned by the matched range. Because
+ * findAnchorInBlock maps the normalized selection back to raw text-node
+ * positions, the returned string is the document's ORIGINAL characters (smart
+ * quotes, em-dashes, nbsp, collapsed whitespace) — NOT the normalized ASCII
+ * agent input.
+ *
+ * Callers store THIS as the comment's `selection` so the stored value equals the
+ * text actually under the mark, which is what the apply-suggestion equality
+ * check (replaceYjsMarkedText's `joinedText !== expectedText`) compares against.
+ * Without it a suggestion whose anchor only matched via normalization would be
+ * un-appliable (spurious 409).
+ */
+export function getAnchoredText(doc: any, selection: string): string | null {
+  const visit = (node: any, depth: number): string | null => {
+    if (depth > MAX_DEPTH || !node || typeof node !== "object") return null;
+    if (!Array.isArray(node.content)) return null;
+    const match = findAnchorInBlock(node.content, selection);
+    if (match) return reconstructRawText(node.content, match);
+    for (const child of node.content) {
+      if (child && typeof child === "object" && Array.isArray(child.content)) {
+        const found = visit(child, depth + 1);
+        if (found !== null) return found;
+      }
+    }
+    return null;
+  };
+  return visit(doc, 0);
+}
+
 /**
 * Depth-first, document-order check for whether `selection` can be anchored
 * anywhere in `doc`. At each node with an array `content`, first try to match
@@ -242,6 +301,74 @@ function spliceCommentMark(
  blockContent.splice(startChild, endChild - startChild + 1, ...fragments);
 }

+/**
+ * Count how many times `selection` occurs across the whole document, using the
+ * same normalization and run-matching as findAnchorInBlock but WITHOUT stopping
+ * at the first hit: every non-overlapping occurrence within each block's text
+ * runs is counted and summed across all blocks (depth-first, the same traversal
+ * as canAnchorInDoc).
+ *
+ * This is the uniqueness gate for SUGGESTIONS: because applying a suggestion
+ * rewrites the exact anchored text, an ambiguous anchor (>1 occurrence) would
+ * silently edit the wrong place, so a suggestion is only allowed when this
+ * returns exactly 1. Ordinary comments keep first-occurrence anchoring and do
+ * not use this. (Note: counts OCCURRENCES, not just matching blocks, so two
+ * occurrences inside one block are correctly reported as 2.)
+ */
+export function countAnchorMatches(doc: any, selection: string): number {
+  const normSel = normalizeForMatch(selection).norm.trim();
+  if (normSel.length === 0) return 0;
+
+  // Count non-overlapping occurrences of the normalized selection within a
+  // single block's direct content, matching findAnchorInBlock's run building.
+  const countInBlock = (blockContent: any[]): number => {
+    if (!Array.isArray(blockContent)) return 0;
+    let count = 0;
+    let i = 0;
+    while (i < blockContent.length) {
+      const node = blockContent[i];
+      if (!node || typeof node !== "object" || node.type !== "text") {
+        i++;
+        continue;
+      }
+      // Accumulate a maximal run of consecutive text nodes.
+      let rawRun = "";
+      let j = i;
+      while (j < blockContent.length) {
+        const n = blockContent[j];
+        if (!n || typeof n !== "object" || n.type !== "text") break;
+        rawRun += typeof n.text === "string" ? n.text : "";
+        j++;
+      }
+      const norm = normalizeForMatch(rawRun).norm;
+      // Count every non-overlapping occurrence in this run.
+      let from = 0;
+      for (;;) {
+        const idx = norm.indexOf(normSel, from);
+        if (idx === -1) break;
+        count++;
+        from = idx + normSel.length;
+      }
+      i = j > i ? j : i + 1;
+    }
+    return count;
+  };
+
+  let total = 0;
+  const visit = (node: any, depth: number): void => {
+    if (depth > MAX_DEPTH || !node || typeof node !== "object") return;
+    if (!Array.isArray(node.content)) return;
+    total += countInBlock(node.content);
+    for (const child of node.content) {
+      if (child && typeof child === "object" && Array.isArray(child.content)) {
+        visit(child, depth + 1);
+      }
+    }
+  };
+  visit(doc, 0);
+  return total;
+}
+
 /**
 * Depth-first (same order as canAnchorInDoc) over `doc`; on the FIRST block
 * whose content matches `selection`, splice the comment mark across the matched
@@ -75,6 +75,11 @@ export function filterComment(comment: any, markdownContent?: string) {
    editedAt: comment.editedAt || null,
    resolvedAt: comment.resolvedAt || null,
    resolvedById: comment.resolvedById || null,
+    // Suggestion state: the proposed replacement text (if any) and, once a human
+    // applies it via the UI, when and by whom.
+    suggestedText: comment.suggestedText || null,
+    suggestionAppliedAt: comment.suggestionAppliedAt || null,
+    suggestionAppliedById: comment.suggestionAppliedById || null,
  };
 }

@@ -229,3 +229,322 @@ test("a reply creates without selection or anchoring and is stored as type 'page
    "a reply must skip the pre-check/anchoring (no /pages/info read)",
  );
 });
+
+// -----------------------------------------------------------------------------
+// 4) suggestedText + a DUPLICATE selection is refused BEFORE creating anything:
+//    a suggestion must anchor to a unique location, so >=2 occurrences throws the
+//    ambiguity error (the /pages/info pre-check short-circuits before create).
+// -----------------------------------------------------------------------------
+test("suggestedText with an ambiguous selection is refused before creating", async () => {
+  let createCalls = 0;
+  let infoCalls = 0;
+
+  const { baseURL } = await spawn(async (req, res) => {
+    await readBody(req);
+    if (req.url === "/api/auth/login") {
+      sendJson(res, 200, { success: true }, {
+        "Set-Cookie": "authToken=t; Path=/; HttpOnly",
+      });
+      return;
+    }
+    if (req.url === "/api/pages/info") {
+      infoCalls++;
+      // "target" appears in two blocks -> ambiguous for a suggestion.
+      sendJson(res, 200, {
+        data: {
+          id: "page-1",
+          content: {
+            type: "doc",
+            content: [
+              { type: "paragraph", content: [{ type: "text", text: "first target here" }] },
+              { type: "paragraph", content: [{ type: "text", text: "second target here" }] },
+            ],
+          },
+        },
+      });
+      return;
+    }
+    if (req.url === "/api/comments/create") {
+      createCalls++;
+      sendJson(res, 200, { data: { id: "should-not-happen" } });
+      return;
+    }
+    sendJson(res, 404, { message: "not found" });
+  });
+
+  const client = new DocmostClient(baseURL, "user@example.com", "pw");
+
+  await assert.rejects(
+    () =>
+      client.createComment(
+        "page-1",
+        "body",
+        "inline",
+        "target",
+        undefined,
+        "TARGET",
+      ),
+    /ambiguous/i,
+    "an ambiguous suggestion selection must reject with the ambiguity error",
+  );
+  assert.ok(infoCalls >= 1, "the pre-check must read the page via /pages/info");
+  assert.equal(
+    createCalls,
+    0,
+    "/comments/create must NEVER be called for an ambiguous suggestion",
+  );
+});
+
+// -----------------------------------------------------------------------------
+// 5) suggestedText on a reply is refused immediately (before any HTTP).
+// -----------------------------------------------------------------------------
+test("suggestedText on a reply is rejected", async () => {
+  let anyCall = 0;
+  const { baseURL } = await spawn(async (req, res) => {
+    await readBody(req);
+    if (req.url === "/api/auth/login") {
+      sendJson(res, 200, { success: true }, {
+        "Set-Cookie": "authToken=t; Path=/; HttpOnly",
+      });
+      return;
+    }
+    anyCall++;
+    sendJson(res, 200, { data: { id: "x" } });
+  });
+
+  const client = new DocmostClient(baseURL, "user@example.com", "pw");
+
+  await assert.rejects(
+    () =>
+      client.createComment(
+        "page-1",
+        "body",
+        "inline",
+        undefined,
+        "parent-1",
+        "replacement",
+      ),
+    /reply/i,
+    "suggestedText on a reply must be rejected",
+  );
+  assert.equal(anyCall, 0, "no create/info call for a rejected reply suggestion");
+});
+
+// -----------------------------------------------------------------------------
+// 6) suggestedText without a selection is refused immediately.
+// -----------------------------------------------------------------------------
+test("suggestedText without a selection is rejected", async () => {
+  const { baseURL } = await spawn(async (req, res) => {
+    await readBody(req);
+    if (req.url === "/api/auth/login") {
+      sendJson(res, 200, { success: true }, {
+        "Set-Cookie": "authToken=t; Path=/; HttpOnly",
+      });
+      return;
+    }
+    sendJson(res, 200, { data: { id: "x" } });
+  });
+
+  const client = new DocmostClient(baseURL, "user@example.com", "pw");
+
+  await assert.rejects(
+    () =>
+      client.createComment(
+        "page-1",
+        "body",
+        "inline",
+        undefined,
+        undefined,
+        "replacement",
+      ),
+    /selection/i,
+    "suggestedText without a selection must be rejected",
+  );
+});
+
+// -----------------------------------------------------------------------------
+// 7) suggestedText + a UNIQUE selection succeeds: the pre-check passes, the
+//    create payload carries suggestedText, and the live anchoring step (stubbed
+//    via the mutatePage seam) writes the comment mark exactly once.
+// -----------------------------------------------------------------------------
+test("suggestedText with a unique selection succeeds and forwards the payload", async () => {
+  let createPayload = null;
+
+  const { baseURL } = await spawn(async (req, res) => {
+    const raw = await readBody(req);
+    if (req.url === "/api/auth/login") {
+      sendJson(res, 200, { success: true }, {
+        "Set-Cookie": "authToken=t; Path=/; HttpOnly",
+      });
+      return;
+    }
+    if (req.url === "/api/pages/info") {
+      // "brave" is unique in the page.
+      sendJson(res, 200, {
+        data: {
+          id: "11111111-1111-1111-1111-111111111111",
+          content: {
+            type: "doc",
+            content: [
+              { type: "paragraph", content: [{ type: "text", text: "Hello brave world" }] },
+            ],
+          },
+        },
+      });
+      return;
+    }
+    if (req.url === "/api/comments/create") {
+      createPayload = JSON.parse(raw);
+      sendJson(res, 200, {
+        data: {
+          id: "cmt-ok-1",
+          content: createPayload.content,
+          selection: createPayload.selection,
+          suggestedText: createPayload.suggestedText,
+          type: createPayload.type,
+        },
+      });
+      return;
+    }
+    sendJson(res, 404, { message: "not found" });
+  });
+
+  // Subclass to stub the collab write seam: no live Hocuspocus socket, but the
+  // wrapper's uniqueness gate + applyAnchorInDoc still run against `doc`.
+  class TestClient extends DocmostClient {
+    async getCollabTokenWithReauth() {
+      return "collab-token";
+    }
+    async resolvePageId(pageId) {
+      return "11111111-1111-1111-1111-111111111111";
+    }
+    async mutatePage(pageId, collabToken, apiUrl, transform) {
+      const doc = {
+        type: "doc",
+        content: [
+          { type: "paragraph", content: [{ type: "text", text: "Hello brave world" }] },
+        ],
+      };
+      const out = transform(doc);
+      return { doc: out, verify: { ok: true } };
+    }
+  }
+
+  const client = new TestClient(baseURL, "user@example.com", "pw");
+
+  const result = await client.createComment(
+    "11111111-1111-1111-1111-111111111111",
+    "please rename",
+    "inline",
+    "brave",
+    undefined,
+    "bold",
+  );
+
+  assert.equal(result.success, true, "a unique suggestion must resolve");
+  assert.equal(result.anchored, true, "the comment must be anchored");
+  assert.ok(createPayload, "/comments/create must have been called");
+  assert.equal(
+    createPayload.suggestedText,
+    "bold",
+    "the create payload must carry suggestedText for a top-level inline comment",
+  );
+  assert.equal(createPayload.selection, "brave");
+  assert.equal(result.data.suggestedText, "bold", "filterComment surfaces suggestedText");
+});
+
+// -----------------------------------------------------------------------------
+// 8) suggestedText where the DOC has TYPOGRAPHIC text and the agent selection is
+//    ASCII: the stored selection sent to /comments/create MUST be the doc's RAW
+//    typographic substring (what the mark covers), NOT the agent's ASCII input.
+//    This is the F1 contract that makes "Apply" succeed instead of a spurious
+//    409 (apply compares the stored selection to the marked doc text strictly).
+// -----------------------------------------------------------------------------
+test("suggestedText: the stored selection is the doc's RAW typographic substring, not the ASCII input", async () => {
+  let createPayload = null;
+
+  const { baseURL } = await spawn(async (req, res) => {
+    const raw = await readBody(req);
+    if (req.url === "/api/auth/login") {
+      sendJson(res, 200, { success: true }, {
+        "Set-Cookie": "authToken=t; Path=/; HttpOnly",
+      });
+      return;
+    }
+    if (req.url === "/api/pages/info") {
+      // The doc holds SMART quotes; the agent will select the ASCII form.
+      sendJson(res, 200, {
+        data: {
+          id: "22222222-2222-2222-2222-222222222222",
+          content: {
+            type: "doc",
+            content: [
+              {
+                type: "paragraph",
+                content: [{ type: "text", text: "he said “hello” loudly" }],
+              },
+            ],
+          },
+        },
+      });
+      return;
+    }
+    if (req.url === "/api/comments/create") {
+      createPayload = JSON.parse(raw);
+      sendJson(res, 200, {
+        data: {
+          id: "cmt-typo-1",
+          content: createPayload.content,
+          selection: createPayload.selection,
+          suggestedText: createPayload.suggestedText,
+          type: createPayload.type,
+        },
+      });
+      return;
+    }
+    sendJson(res, 404, { message: "not found" });
+  });
+
+  class TestClient extends DocmostClient {
+    async getCollabTokenWithReauth() {
+      return "collab-token";
+    }
+    async resolvePageId() {
+      return "22222222-2222-2222-2222-222222222222";
+    }
+    async mutatePage(pageId, collabToken, apiUrl, transform) {
+      const doc = {
+        type: "doc",
+        content: [
+          {
+            type: "paragraph",
+            content: [{ type: "text", text: "he said “hello” loudly" }],
+          },
+        ],
+      };
+      const out = transform(doc);
+      return { doc: out, verify: { ok: true } };
+    }
+  }
+
+  const client = new TestClient(baseURL, "user@example.com", "pw");
+
+  const result = await client.createComment(
+    "22222222-2222-2222-2222-222222222222",
+    "please change",
+    "inline",
+    '"hello"', // ASCII quotes — the doc has smart quotes
+    undefined,
+    "goodbye",
+  );
+
+  assert.equal(result.success, true);
+  assert.equal(result.anchored, true);
+  assert.ok(createPayload, "/comments/create must have been called");
+  assert.equal(
+    createPayload.selection,
+    "“hello”",
+    "the stored selection must be the doc's RAW typographic substring, not the ASCII input",
+  );
+  assert.equal(createPayload.suggestedText, "goodbye");
+});
@@ -6,6 +6,8 @@ import {
  findAnchorInBlock,
  canAnchorInDoc,
  applyAnchorInDoc,
+  countAnchorMatches,
+  getAnchoredText,
 } from "../../build/lib/comment-anchor.js";

 const COMMENT_ID = "cmt-123";
@@ -208,3 +210,101 @@ test("anchoring works inside a nested block (e.g. list item) via DFS recursion",
  assert.equal(marked.length, 1);
  assert.equal(marked[0].text, "target");
 });
+
+// ---------------------------------------------------------------------------
+// countAnchorMatches — the uniqueness gate for suggestions. Counts every
+// non-overlapping occurrence across the whole document (0 / 1 / N).
+// ---------------------------------------------------------------------------
+test("countAnchorMatches returns 0 when the selection is absent", () => {
+  const doc = paragraphDoc([{ type: "text", text: "hello world" }]);
+  assert.equal(countAnchorMatches(doc, "missing"), 0);
+});
+
+test("countAnchorMatches returns 1 for a unique selection", () => {
+  const doc = paragraphDoc([{ type: "text", text: "Hello brave world" }]);
+  assert.equal(countAnchorMatches(doc, "brave"), 1);
+});
+
+test("countAnchorMatches counts multiple occurrences within one block", () => {
+  const doc = paragraphDoc([{ type: "text", text: "ab ab ab" }]);
+  assert.equal(countAnchorMatches(doc, "ab"), 3);
+});
+
+test("countAnchorMatches sums occurrences across separate blocks", () => {
+  const doc = {
+    type: "doc",
+    content: [
+      { type: "paragraph", content: [{ type: "text", text: "first target here" }] },
+      { type: "paragraph", content: [{ type: "text", text: "second target here" }] },
+    ],
+  };
+  assert.equal(countAnchorMatches(doc, "target"), 2);
+});
+
+test("countAnchorMatches counts a match spanning adjacent text nodes as one", () => {
+  const doc = paragraphDoc([
+    { type: "text", text: "запуска ", marks: [{ type: "italic" }] },
+    { type: "text", text: "перед блоком", marks: [{ type: "italic" }] },
+  ]);
+  assert.equal(countAnchorMatches(doc, "запуска перед"), 1);
+});
+
+test("countAnchorMatches counts matches inside nested (recursed) blocks", () => {
+  const doc = {
+    type: "doc",
+    content: [
+      { type: "paragraph", content: [{ type: "text", text: "outer target" }] },
+      {
+        type: "bulletList",
+        content: [
+          {
+            type: "listItem",
+            content: [
+              { type: "paragraph", content: [{ type: "text", text: "nested target" }] },
+            ],
+          },
+        ],
+      },
+    ],
+  };
+  assert.equal(countAnchorMatches(doc, "target"), 2);
+});
+
+test("countAnchorMatches applies the same normalization as anchoring", () => {
+  // Smart quotes in the doc match ASCII quotes in the selection.
+  const doc = paragraphDoc([{ type: "text", text: "say “hi” now" }]);
+  assert.equal(countAnchorMatches(doc, '"hi"'), 1);
+});
+
+// -----------------------------------------------------------------------------
+// getAnchoredText: returns the RAW document substring the mark would cover (the
+// doc's original typographic characters), not the normalized ASCII selection.
+// This is what makes a suggestion's stored selection equal the apply-time
+// expectedText, so the strict equality in replaceYjsMarkedText holds.
+// -----------------------------------------------------------------------------
+test("getAnchoredText returns the RAW (typographic) doc substring for an ASCII selection", () => {
+  // Doc holds smart quotes; agent selection is the ASCII form.
+  const doc = paragraphDoc([{ type: "text", text: "he said “hello” loudly" }]);
+  assert.equal(getAnchoredText(doc, '"hello"'), "“hello”");
+});
+
+test("getAnchoredText undoes whitespace/dash normalization to the raw span", () => {
+  // Em-dash + nbsp in the doc; ASCII hyphen + single space in the selection.
+  const doc = paragraphDoc([{ type: "text", text: "a—b c" }]);
+  // selection "a-b c" (ascii dash) matches, raw substring keeps the em-dash+nbsp.
+  assert.equal(getAnchoredText(doc, "a-b c"), "a—b c");
+});
+
+test("getAnchoredText spans consecutive text nodes and returns their raw slices", () => {
+  const doc = paragraphDoc([
+    { type: "text", text: "Hello " },
+    { type: "text", text: "“brave”", marks: [{ type: "bold" }] },
+    { type: "text", text: " world" },
+  ]);
+  assert.equal(getAnchoredText(doc, '"brave" wor'), "“brave” wor");
+});
+
+test("getAnchoredText returns null when the selection does not anchor", () => {
+  const doc = paragraphDoc([{ type: "text", text: "hello world" }]);
+  assert.equal(getAnchoredText(doc, "not present"), null);
+});