Warn when the source text drops persisted segment boundaries

contributions/localizedStrings.json

@@ -101,6 +101,9 @@
       "%interlinearizer_boundaryControl_merge%": "Join these two segments",
       "%interlinearizer_boundaryControl_mergeAltHint%": "Join these two segments. Hold {key} and click between words to split.",
       "%interlinearizer_boundaryControl_split%": "Split segment here",
+      "%interlinearizer_segmentation_lostBoundaries%": "The source text changed, so {count} of your segment boundary changes no longer fit it and aren't applied.",
+      "%interlinearizer_segmentation_lostBoundaries_one%": "The source text changed, so one of your segment boundary changes no longer fits it and isn't applied.",
+      "%interlinearizer_segmentation_lostBoundaries_dismiss%": "Dismiss this warning",
       "%interlinearizer_phraseBox_glossLabel%": "Phrase gloss",
       "%interlinearizer_phraseBox_edit%": "Edit phrase",
       "%interlinearizer_phraseBox_unlink%": "Unlink phrase",

src/__tests__/components/InterlinearizerLoader.test.tsx

@@ -13,7 +13,9 @@ import { useGlossDispatch } from '../../components/AnalysisStore';
 import InterlinearizerLoader from '../../components/InterlinearizerLoader';
 import { RECENTER_FADE_MS } from '../../components/recenter-fade';
 import useInterlinearizerBookData from '../../hooks/useInterlinearizerBookData';
+import useLostBoundaryDismissal from '../../hooks/useLostBoundaryDismissal';
 import useOptimisticBooleanSetting from '../../hooks/useOptimisticBooleanSetting';
+import type { OpenableProject } from '../../hooks/useDraftProject';
 import { emptyAnalysis, emptyDraft } from '../../types/empty-factories';
 import { PT9_MANIFEST_TIMEOUT_MS } from '../../utils/pt9-manifest';
 import type { PhraseMode } from '../../types/phrase-mode';
@@ -33,6 +35,7 @@ import {
 import { mockKeyAsValueLocalizedStrings } from './test-helpers';
 
 jest.mock('../../hooks/useInterlinearizerBookData');
+jest.mock('../../hooks/useLostBoundaryDismissal');
 jest.mock('../../hooks/useOptimisticBooleanSetting');
 
 jest.mock('../../components/controls/ViewOptionsDropdown', () => ({
@@ -277,6 +280,15 @@ const STUB_IMPORT_PROJECT: MockProject = {
   pt9Import: { fileHashes: { 'Lexicon.xml': 'aaaa1111' }, importedAt: '2026-08-01T00:00:00Z' },
 };
 
+/**
+ * The project the stub picker's "Open project" button loads into the draft. Mutable so a test can
+ * choose the boundaries the opened project carries.
+ */
+let openableProjectForStub: OpenableProject = {
+  analysis: emptyAnalysis(),
+  analysisLanguages: ['en'],
+};
+
 jest.mock('../../components/modals/ProjectModals', () => ({
   __esModule: true,
   /**
@@ -293,6 +305,7 @@ jest.mock('../../components/modals/ProjectModals', () => ({
     activeProject,
     defaultAnalysisLanguage,
     hasUnsavedWork,
+    loadFromProject,
     onImportPt9,
     onOpenImport,
     openRequest,
@@ -304,7 +317,7 @@ jest.mock('../../components/modals/ProjectModals', () => ({
     defaultAnalysisLanguage?: string;
     hasUnsavedWork: boolean;
     getDraftSnapshot: () => DraftProject | undefined;
-    loadFromProject: (project: unknown) => void;
+    loadFromProject: (project: OpenableProject) => void;
     markSynced: () => void;
     onImportPt9: () => void;
     onOpenImport: (project: MockProject) => void;
@@ -366,6 +379,16 @@ jest.mock('../../components/modals/ProjectModals', () => ({
             >
               View info
             </button>
+            <button
+              type="button"
+              data-testid="select-modal-open-project"
+              onClick={() => {
+                loadFromProject(openableProjectForStub);
+                setModal('none');
+              }}
+            >
+              Open project
+            </button>
           </div>
         )}
         {modal === 'create' && (
@@ -535,13 +558,26 @@ function mockSettings(
   });
 }
 
+/**
+ * Stubs {@link useLostBoundaryDismissal} to report the given lost anchors as undismissed.
+ *
+ * @returns The dismiss callback the stub hands the banner, so the wiring can be asserted on.
+ */
+function mockLostBoundaries(undismissedLostBoundaries: readonly string[]): jest.Mock {
+  const onDismiss = jest.fn();
+  jest.mocked(useLostBoundaryDismissal).mockReturnValue({ undismissedLostBoundaries, onDismiss });
+  return onDismiss;
+}
+
 describe('InterlinearizerLoader', () => {
   beforeEach(() => {
     capturedInterlinearizerProps = undefined;
     capturedStoreProps = undefined;
     interlinearizerMountCount = 0;
+    openableProjectForStub = { analysis: emptyAnalysis(), analysisLanguages: ['en'] };
     mockBookData();
     mockOptimisticSetting();
+    mockLostBoundaries([]);
     // The loader's draft hook calls `interlinearizer.getDraft` on mount; default to a valid empty
     // draft so the editor renders. Individual tests override with mockResolvedValueOnce.
     mockSendCommand.mockResolvedValue(JSON.stringify(emptyDraft(testProjectId)));
@@ -1143,6 +1179,22 @@ describe('InterlinearizerLoader', () => {
       expect(screen.getByTestId('pt9-copy-button')).toBeInTheDocument();
     });
 
+    it('holds the banner back until the localized strings resolve', async () => {
+      mockImportCommands();
+      jest
+        .mocked(useLocalizedStrings)
+        .mockImplementation((keys: readonly string[]) => [
+          Object.fromEntries(keys.map((k) => [k, k])),
+          true,
+        ]);
+
+      await act(async () =>
+        renderLoader({ useWebViewState: makeWebViewState({ activeProject: STUB_IMPORT_PROJECT }) }),
+      );
+
+      expect(screen.queryByTestId('pt9-import-banner')).not.toBeInTheDocument();
+    });
+
     it('silences Save, Save As, and Wipe while an import is open', async () => {
       mockImportCommands();
       await renderImportView();
@@ -2541,6 +2593,115 @@ describe('InterlinearizerLoader', () => {
     });
   });
 
+  describe('lost segment boundaries', () => {
+    /**
+     * Renders the loader on a loaded book, parked on GEN unless a `scrRef` elsewhere asks for a
+     * cross-book swap.
+     */
+    async function renderOnLoadedBook(scrRef?: SerializedVerseRef): Promise<void> {
+      mockBookData({ book: GEN_1_1_BOOK });
+      await act(async () => {
+        renderLoader({ useWebViewScrollGroupScrRef: makeScrollGroupHook(scrRef) });
+      });
+    }
+
+    it('shows the banner when the hook reports an undismissed loss', async () => {
+      mockLostBoundaries(['GEN 1:9:0']);
+
+      await renderOnLoadedBook();
+
+      expect(screen.getByTestId('lost-boundaries-banner')).toBeInTheDocument();
+    });
+
+    it('does not show the banner when the hook reports no loss', async () => {
+      await renderOnLoadedBook();
+
+      expect(screen.queryByTestId('lost-boundaries-banner')).not.toBeInTheDocument();
+    });
+
+    it('holds the banner back until the localized strings resolve', async () => {
+      jest
+        .mocked(useLocalizedStrings)
+        .mockImplementation((keys: readonly string[]) => [
+          Object.fromEntries(keys.map((k) => [k, k])),
+          true,
+        ]);
+      mockLostBoundaries(['GEN 1:9:0']);
+
+      await renderOnLoadedBook();
+
+      expect(screen.queryByTestId('lost-boundaries-banner')).not.toBeInTheDocument();
+    });
+
+    it('holds the banner back during a cross-book swap', async () => {
+      // A swap is mid-flight when scrRef already names EXO but the loaded book is still GEN, whose
+      // anchors are the ones lost.
+      mockLostBoundaries(['GEN 1:9:0']);
+
+      await renderOnLoadedBook({ book: 'EXO', chapterNum: 1, verseNum: 1 });
+
+      expect(screen.queryByTestId('lost-boundaries-banner')).not.toBeInTheDocument();
+    });
+
+    it('interpolates the lost-anchor count into the banner text', async () => {
+      jest
+        .mocked(useLocalizedStrings)
+        .mockImplementation((keys: readonly string[]) => [
+          Object.fromEntries(
+            keys.map((k) => [
+              k,
+              k === '%interlinearizer_segmentation_lostBoundaries%' ? '{count} boundaries lost' : k,
+            ]),
+          ),
+          false,
+        ]);
+      mockLostBoundaries(['GEN 1:9:0', 'GEN 1:1:99']);
+
+      await renderOnLoadedBook();
+
+      expect(screen.getByTestId('lost-boundaries-banner')).toHaveTextContent('2 boundaries lost');
+    });
+
+    it('uses the singular string for a single lost anchor', async () => {
+      jest
+        .mocked(useLocalizedStrings)
+        .mockImplementation((keys: readonly string[]) => [
+          Object.fromEntries(
+            keys.map((k) => [
+              k,
+              k === '%interlinearizer_segmentation_lostBoundaries_one%' ? 'just the one' : k,
+            ]),
+          ),
+          false,
+        ]);
+      mockLostBoundaries(['GEN 1:9:0']);
+
+      await renderOnLoadedBook();
+
+      expect(screen.getByTestId('lost-boundaries-banner')).toHaveTextContent('just the one');
+    });
+
+    it('dismisses through the hook when the banner close button is clicked', async () => {
+      const onDismiss = mockLostBoundaries(['GEN 1:9:0']);
+      await renderOnLoadedBook();
+
+      await userEvent.click(screen.getByTestId('lost-boundaries-dismiss'));
+
+      expect(onDismiss).toHaveBeenCalledTimes(1);
+    });
+
+    it('leaves the draft untouched when the banner is dismissed', async () => {
+      mockLostBoundaries(['GEN 1:9:0']);
+      await renderOnLoadedBook();
+
+      await userEvent.click(screen.getByTestId('lost-boundaries-dismiss'));
+
+      // The banner is read-only: the anchors themselves stay for a source that reverts.
+      const saves = mockSendCommand.mock.calls.filter(([c]) => c === 'interlinearizer.saveDraft');
+      expect(saves).toHaveLength(0);
+    });
+  });
+
   describe('save command', () => {
     it('saves the draft analysis to the active project when Save is clicked with an active project', async () => {
       const draftAnalysis = emptyAnalysis();
@@ -3369,6 +3530,7 @@ describe('analysis store lifetime', () => {
     interlinearizerMountCount = 0;
     mockBookData();
     mockOptimisticSetting();
+    mockLostBoundaries([]);
     mockSendCommand.mockResolvedValue(JSON.stringify(emptyDraft(testProjectId)));
     jest
       .mocked(useData)