apps/server/src/core/ai-chat/ai-chat.prompt.spec.ts

@@ -303,6 +303,11 @@ describe('buildSystemPrompt page-changed note (#274)', () => {
     expect(prompt).toContain(NOTE_MARKER);
     expect(prompt).toContain('-old line');
     expect(prompt).toContain('+new line');
+    // Strengthened note (#274): instructs a fresh re-read via getPage and steers
+    // the agent toward small, targeted edits instead of a full-page overwrite.
+    expect(prompt).toContain('getPage');
+    expect(prompt.toLowerCase()).toContain('targeted');
+    expect(prompt).toContain('editPageText');
     // Inside the safety sandwich: the trailing SAFETY block follows the note.
     expect(prompt.lastIndexOf(SAFETY_MARKER)).toBeGreaterThan(
       prompt.indexOf(NOTE_MARKER),

apps/server/src/core/ai-chat/ai-chat.prompt.ts

@@ -85,11 +85,17 @@ const INTERRUPT_NOTE =
 const PAGE_CHANGED_NOTE =
   'NOTE: The user edited the open page AFTER your last response in this ' +
   'conversation, so any copy of that page you produced or remember from earlier ' +
-  'is now STALE. The unified diff below shows exactly what changed since you last ' +
-  'spoke (lines starting with "-" were removed, "+" were added) and is the source ' +
-  'of truth. Preserve the user\'s edits: build on the current page, do not revert ' +
-  'or overwrite their changes. If you need the full up-to-date page, re-read it ' +
-  'with the getPage tool before editing.';
+  'is now STALE and must not be reused. Before you edit the page, you MUST first ' +
+  're-read its current content with the getPage tool and base your work on that ' +
+  'live version — never on your earlier copy or on the transcript. The unified ' +
+  'diff below shows exactly what the user changed since you last spoke (lines ' +
+  'starting with "-" were removed, "+" were added) and is the source of truth. ' +
+  'Preserve every one of the user\'s edits: make the smallest change that ' +
+  'satisfies the request using the targeted edit tools (editPageText, patchNode, ' +
+  'insertNode, deleteNode) rather than replacing the whole page, and do not ' +
+  'revert, drop, or overwrite anything the user changed. If a full rewrite is ' +
+  'truly unavoidable, start from the current getPage content and carry over all ' +
+  'of the user\'s edits.';
 
 /**
  * Sanitize a value interpolated into a prompt XML-ish attribute (e.g.

apps/server/src/core/ai-chat/ai-chat.service.spec.ts

@@ -356,6 +356,32 @@ describe('flushAssistant', () => {
     expect(flushed.toolCalls).not.toBeNull();
     expect(flushed.metadata.error).toBe('boom');
   });
+
+  // #274 observability: the page-change diff the agent saw this turn is persisted
+  // to metadata.pageChanged when a non-empty diff was injected, and omitted when
+  // the diff is empty/whitespace or the arg is not supplied.
+  it('persists metadata.pageChanged when a non-empty diff was injected', () => {
+    const f = flushAssistant([], '', 'completed', {
+      pageChanged: { title: 'Doc', diff: '@@ -1 +1 @@\n-old\n+new' },
+    });
+    expect(f.metadata.pageChanged).toEqual({
+      title: 'Doc',
+      diff: '@@ -1 +1 @@\n-old\n+new',
+    });
+  });
+
+  it('omits metadata.pageChanged for an empty/whitespace diff or a missing arg', () => {
+    const whitespace = flushAssistant([], '', 'completed', {
+      pageChanged: { title: 'Doc', diff: '   \n  ' },
+    });
+    expect('pageChanged' in whitespace.metadata).toBe(false);
+
+    const nullArg = flushAssistant([], '', 'completed', { pageChanged: null });
+    expect('pageChanged' in nullArg.metadata).toBe(false);
+
+    const omitted = flushAssistant([], '', 'streaming');
+    expect('pageChanged' in omitted.metadata).toBe(false);
+  });
 });
 
 /**

apps/server/src/core/ai-chat/ai-chat.service.ts

@@ -685,7 +685,7 @@ export class AiChatService implements OnModuleInit {
     // no-op (guarded below) so the turn still streams to the user.
     let assistantId: string | undefined;
     try {
-      const seed = flushAssistant([], '', 'streaming');
+      const seed = flushAssistant([], '', 'streaming', { pageChanged });
       const seeded = await this.aiChatMessageRepo.insert({
         chatId,
         workspaceId: workspace.id,
@@ -720,7 +720,7 @@ export class AiChatService implements OnModuleInit {
         await this.aiChatMessageRepo.update(
           assistantId,
           workspace.id,
-          flushAssistant(capturedSteps, '', 'streaming'),
+          flushAssistant(capturedSteps, '', 'streaming', { pageChanged }),
           { onlyIfStreaming: true },
         );
       } catch (err) {
@@ -860,6 +860,7 @@ export class AiChatService implements OnModuleInit {
               // resolved from the admin-configured provider settings (in
               // closure scope here). Omitted/0 = no limit.
               maxContextTokens: resolved?.chatContextWindow,
+              pageChanged,
             }),
           );
           // Lifecycle: release the external MCP clients leased for this turn.
@@ -911,6 +912,7 @@ export class AiChatService implements OnModuleInit {
           await finalizeAssistant(
             flushAssistant(capturedSteps, inProgressText, 'error', {
               error: errorText,
+              pageChanged,
             }),
           );
           await closeExternalClients();
@@ -940,7 +942,9 @@ export class AiChatService implements OnModuleInit {
               `steps=${steps.length}`,
           );
           await finalizeAssistant(
-            flushAssistant(capturedSteps, inProgressText, 'aborted'),
+            flushAssistant(capturedSteps, inProgressText, 'aborted', {
+              pageChanged,
+            }),
           );
           await closeExternalClients();
           // Advance the page snapshot even on abort (#274): an agent edit that
@@ -1506,6 +1510,7 @@ export function flushAssistant(
     contextTokens?: number;
     maxContextTokens?: number;
     error?: string;
+    pageChanged?: { title: string; diff: string } | null;
   },
 ): AssistantFlush {
   const finished = capturedSteps ?? [];
@@ -1538,6 +1543,15 @@ export function flushAssistant(
   if (extra?.maxContextTokens)
     metadata.maxContextTokens = extra.maxContextTokens;
   if (extra?.error) metadata.error = extra.error;
+  // Persist the page-change diff the agent saw this turn (#274 observability),
+  // so history / the Markdown export can show what the user changed. Only when
+  // a non-empty diff was actually injected into the prompt this turn.
+  if (extra?.pageChanged && extra.pageChanged.diff?.trim().length) {
+    metadata.pageChanged = {
+      title: extra.pageChanged.title,
+      diff: extra.pageChanged.diff,
+    };
+  }
 
   return {
     content: stepsText + trailing,

apps/server/src/core/ai-chat/chat-markdown.util.spec.ts

@@ -269,6 +269,168 @@ describe('buildChatMarkdown (server) — structure', () => {
     expect(md).toContain('**⚠️ Error:** 401: Unauthorized');
   });
 
+  // #274 observability: an assistant row whose turn started with a user edit to
+  // the open page carries metadata.pageChanged = { title, diff }; the export
+  // renders the diff the agent saw, before the message body.
+  it('renders the persisted page-change diff block for an assistant row', () => {
+    const md = buildChatMarkdown({
+      title: 'T',
+      chatId: 'c',
+      rows: [
+        row({
+          role: 'assistant',
+          content: 'answer',
+          metadata: {
+            pageChanged: { title: 'Doc', diff: '@@ -1 +1 @@\n-old\n+new' },
+          } as never,
+        }),
+      ],
+    });
+    expect(md).toContain(
+      'The user edited this page before this turn; the diff the agent saw:',
+    );
+    expect(md).toContain('("Doc")');
+    expect(md).toContain('-old');
+    expect(md).toContain('+new');
+    // The diff sits before the message body (chronological: change, then reply).
+    expect(md.indexOf('-old')).toBeLessThan(md.indexOf('answer'));
+  });
+
+  it('does not render the page-change block when metadata.pageChanged is absent', () => {
+    const md = buildChatMarkdown({
+      title: 'T',
+      chatId: 'c',
+      rows: [row({ role: 'assistant', content: 'answer' })],
+    });
+    expect(md).not.toContain(
+      'The user edited this page before this turn; the diff the agent saw:',
+    );
+  });
+
+  // #288 F1/F2: an empty page title must render the BARE heading with no
+  // `("…")` suffix (the `pc.title ? … : …` false branch).
+  it('renders the page-change heading with no title suffix when title is empty', () => {
+    const md = buildChatMarkdown({
+      title: 'T',
+      chatId: 'c',
+      rows: [
+        row({
+          role: 'assistant',
+          content: 'answer',
+          metadata: {
+            pageChanged: { title: '', diff: '@@ -1 +1 @@\n-old\n+new' },
+          } as never,
+        }),
+      ],
+    });
+    // Bare heading, single line, no parenthesized title.
+    expect(md).toContain(
+      '> **📝 The user edited this page before this turn; the diff the agent saw:**',
+    );
+    expect(md).not.toContain('("');
+    expect(md).toContain('-old');
+  });
+
+  // #288 F1: the page title is UNTRUSTED cross-user data, so a title carrying a
+  // newline / backtick / `"` / `<`/`>` must be neutralized by escapeAttr before
+  // it is interpolated into the `> **…**` blockquote heading — otherwise it
+  // could break the blockquote onto multiple lines or inject markup/HTML into
+  // the downloaded .md. escapeAttr strips `<>"` and collapses whitespace runs to
+  // a single space, so `Ev"il\n> `x` <b>` becomes ``Evil `x` b``.
+  it('escapes an untrusted page title in the page-change heading', () => {
+    const md = buildChatMarkdown({
+      title: 'T',
+      chatId: 'c',
+      rows: [
+        row({
+          role: 'assistant',
+          content: 'answer',
+          metadata: {
+            pageChanged: {
+              title: 'Ev"il\n> `x` <b>',
+              diff: '@@ -1 +1 @@\n-old\n+new',
+            },
+          } as never,
+        }),
+      ],
+    });
+    // The heading stays a single blockquote line with the escaped title.
+    expect(md).toContain(
+      '> **📝 The user edited this page before this turn; the diff the agent saw: ("Evil `x` b")**',
+    );
+    // No raw attribute/markup breakers survived from the title.
+    expect(md).not.toContain('Ev"il');
+    expect(md).not.toContain('<b>');
+  });
+
+  // #288 review F1: escapeAttr ALONE is insufficient for this MARKDOWN sink —
+  // link/image syntax survives it. A cross-user title with `![x](url)` /
+  // `[phish](url)` must NOT become a working remote image or clickable link in
+  // the downloaded .md; markdownHeadingSafe backslash-escapes `[`/`]` so both are
+  // inert. (Non-vacuous: fails against the escapeAttr-only version, which left
+  // `](https://` intact.)
+  it('neutralizes markdown link/image syntax in an untrusted page title', () => {
+    const md = buildChatMarkdown({
+      title: 'T',
+      chatId: 'c',
+      rows: [
+        row({
+          role: 'assistant',
+          content: 'answer',
+          metadata: {
+            pageChanged: {
+              title:
+                '![x](https://attacker.example/t.png) and [click](https://phish.example)',
+              diff: '@@ -1 +1 @@\n-old\n+new',
+            },
+          } as never,
+        }),
+      ],
+    });
+    // No WORKING image/link syntax survives — the `[…]` sits escaped as `\[…\]`,
+    // so the unescaped `![x](` image and `[click](` link markers are gone. (We
+    // deliberately do NOT assert `not.toContain('](https://')`: after escaping the
+    // literal `\](https://` still contains `](https://` as a raw substring — that
+    // check would false-fail even though the link is inert.)
+    expect(md).not.toContain('![x](');
+    expect(md).not.toContain('[click](');
+    // The brackets are backslash-escaped, so `[text](url)`/`![text](url)` are inert.
+    expect(md).toContain('\\[');
+    expect(md).toContain('\\]');
+    // The heading stays a SINGLE blockquote line (no newline injected).
+    const headingLine = md
+      .split('\n')
+      .find((l) => l.includes('the diff the agent saw:'));
+    expect(headingLine).toBeDefined();
+    expect(headingLine).toContain('\\[x\\]');
+    expect(headingLine).toContain('\\[click\\]');
+  });
+
+  // #288 internal review Finding 2: a NON-empty title made up entirely of
+  // escapeAttr breakers (`<>"`) escapes to '' — the ternary must then fall to the
+  // BARE heading with NO `("…")` suffix. Locks the ternary-on-escaped-value
+  // behavior (distinct from the empty-string input test above).
+  it('renders the bare heading for a title that escapes to empty', () => {
+    const md = buildChatMarkdown({
+      title: 'T',
+      chatId: 'c',
+      rows: [
+        row({
+          role: 'assistant',
+          content: 'answer',
+          metadata: {
+            pageChanged: { title: '<>"', diff: '@@ -1 +1 @@\n-old\n+new' },
+          } as never,
+        }),
+      ],
+    });
+    expect(md).toContain(
+      '> **📝 The user edited this page before this turn; the diff the agent saw:**',
+    );
+    expect(md).not.toContain('("');
+    expect(md).toContain('-old');
+  });
+
   it('escapes embedded triple-backtick fences with a longer delimiter', () => {
     const md = buildChatMarkdown({
       title: 'T',

apps/server/src/core/ai-chat/chat-markdown.util.ts

@@ -15,6 +15,7 @@
  */
 
 import type { AiChatMessage } from '@docmost/db/types/entity.types';
+import { escapeAttr } from './ai-chat.prompt';
 
 /** Supported export label languages. Defaults to English. */
 export type ExportLang = 'en' | 'ru';
@@ -63,6 +64,7 @@ const LABELS: Record<
     tools: Record<string, string>;
     ranTool: (name: string) => string;
     stillGenerating: string;
+    pageEditedByUser: string;
   }
 > = {
   en: {
@@ -83,6 +85,8 @@ const LABELS: Record<
     ranTool: (name) => `Ran tool ${name}`,
     stillGenerating:
       'This message is still being generated — the export captured a partial, in-progress response.',
+    pageEditedByUser:
+      'The user edited this page before this turn; the diff the agent saw:',
   },
   ru: {
     untitled: 'Без названия',
@@ -102,9 +106,29 @@ const LABELS: Record<
     ranTool: (name) => `Выполнил инструмент ${name}`,
     stillGenerating:
       'Это сообщение всё ещё генерируется — экспорт захватил частичный, незавершённый ответ.',
+    pageEditedByUser:
+      'Пользователь изменил страницу перед этим ходом; дифф, который видел агент:',
   },
 };
 
+/**
+ * Make an untrusted title safe to interpolate into a Markdown blockquote
+ * HEADING. escapeAttr() neutralizes the XML/HTML breakers (`<` `>` `"`) and
+ * collapses whitespace for the PROMPT sink (`page="…"`), but this export sink is
+ * MARKDOWN — link/image syntax survives escapeAttr. So additionally backslash-
+ * escape `[` and `]`: that disables both `[text](url)` links and `![text](url)`
+ * images, so a cross-user title like `![x](http://evil)` or `[phish](http://evil)`
+ * cannot inject a remote (auto-loading) image or a clickable link into the
+ * downloaded .md disguised as a trusted system annotation. A bare `(url)` with no
+ * preceding `[]` is inert Markdown, so brackets are the only security-critical
+ * characters here. (We leave backticks to escapeAttr's whitespace pass — a title
+ * shown as inline code cannot escape the blockquote line or load a resource, so
+ * it is not a security concern for this sink.)
+ */
+function markdownHeadingSafe(title: string): string {
+  return escapeAttr(title).replace(/[[\]]/g, (m) => `\\${m}`);
+}
+
 /** True for AI SDK tool parts (static `tool-*` or `dynamic-tool`). */
 function isToolPart(type: string): boolean {
   return type.startsWith('tool-') || type === 'dynamic-tool';
@@ -208,6 +232,23 @@ function rowParts(row: AiChatMessage): ExportPart[] {
     : [{ type: 'text', text: row.content ?? '' }];
 }
 
+/** The persisted page-change diff the agent saw this turn (#274), when any. */
+function pageChangedOf(
+  row: AiChatMessage,
+): { title: string; diff: string } | undefined {
+  const meta = (row.metadata ?? {}) as {
+    pageChanged?: { title?: string; diff?: string };
+  };
+  const pc = meta.pageChanged;
+  if (pc && typeof pc.diff === 'string' && pc.diff.trim().length > 0) {
+    return {
+      title: typeof pc.title === 'string' ? pc.title : '',
+      diff: pc.diff,
+    };
+  }
+  return undefined;
+}
+
 /**
  * Serialize a chat to a Markdown string from its persisted rows. Source = DB
  * ONLY (no live client state). A row whose `status` is still 'streaming' is an
@@ -266,6 +307,26 @@ export function buildChatMarkdown(args: {
       blocks.push(`<!-- ${iso} -->`);
     }
 
+    // Page-change observability (#274): show the diff the agent saw at the start
+    // of this turn, before its response, so the export reflects the stale-page
+    // warning the model received.
+    const pc = pageChangedOf(row);
+    if (pc) {
+      // The page title is UNTRUSTED cross-user data (a collaborative page's title
+      // controllable by another user). escapeAttr() alone (the prompt sink) is
+      // INSUFFICIENT here: this is a MARKDOWN sink, so we neutralize link/image
+      // syntax too (backslash-escaping `[`/`]`) before interpolating it into this
+      // `> **…**` blockquote heading — otherwise `![x](url)` / `[phish](url)` would
+      // inject a remote image or clickable link into the downloaded .md. An
+      // all-`<>"` title escapes to empty and correctly falls to the bare heading.
+      // The diff body is already safe via fence(). (#288 review F1.)
+      const safeTitle = markdownHeadingSafe(pc.title);
+      const heading = safeTitle
+        ? `${L.pageEditedByUser} ("${safeTitle}")`
+        : L.pageEditedByUser;
+      blocks.push(`> **📝 ${heading}**\n\n${fence(pc.diff, 'diff')}`);
+    }
+
     blocks.push(...renderMessageParts(rowParts(row), lang));
 
     // A still-'streaming' row is an interrupted/in-progress turn captured by the