diff --git a/tests/e2e/trip-editor/tripEditorErrorStateContracts.spec.ts b/tests/e2e/trip-editor/tripEditorErrorStateContracts.spec.ts
new file mode 100644
index 00000000..acf7bc46
--- /dev/null
+++ b/tests/e2e/trip-editor/tripEditorErrorStateContracts.spec.ts
@@ -0,0 +1,235 @@
+import { expect, test, type Locator, type Page, type Route } from '@playwright/test';
+import {
+  absoluteUrl,
+  editorApiPath,
+  editorPath,
+  expectMountedWorkspace,
+  loadEditorStateFixture,
+  signIn,
+  uniqueName
+} from './tripEditorTestUtils';
+
+type EditorState = Record<string, any>;
+
+test.describe.serial('Trip Editor Batch 3 error state contracts', () => {
+  test('mocked stale place save failure preserves draft and persisted state', async ({ page }) => {
+    await openEditor(page);
+    const initial = await loadEditorStateFixture(page) as EditorState;
+    const fixture = editablePlaceFixture(initial);
+    test.skip(!fixture, 'Configured Trip Editor fixture has no editable place for stale-save feedback coverage.');
+    if (!fixture) {
+      return;
+    }
+
+    await editPlace(page, fixture.place.id);
+    const form = page.locator('#trip-editor-place-form');
+    const draftName = uniqueName('PW failed place save draft');
+    await form.getByLabel('Name').fill(draftName);
+    await form.getByLabel('Address').fill('PW failed place save address');
+
+    const staleSave = await mockMutationFailure(page, 'PUT', `${editorApiPath}/places/${fixture.place.id}`, 404);
+    await page.getByRole('button', { name: 'Save Place' }).click();
+
+    await expect.poll(staleSave.requests).toBe(1);
+    await expect(page.getByRole('alert')).toContainText('Trip Editor place update returned 404');
+    await expectFailedStatus(page);
+    await expect(form.getByLabel('Name')).toHaveValue(draftName);
+    await expect(form.getByLabel('Address')).toHaveValue('PW failed place save address');
+    await expect(placeRow(page, fixture.place.id).locator('.trip-editor-place-row__name')).toHaveText(fixture.place.name);
+    await expectPersistedPlace(page, fixture.place.id, fixture.place.name, fixture.place.address);
+
+    await staleSave.unroute();
+    await page.getByRole('button', { name: 'Cancel' }).click();
+    await page.getByRole('dialog', { name: 'Discard changes?' }).getByRole('button', { name: 'Discard' }).click();
+    await expect(form).toHaveCount(0);
+    await expect(placeRow(page, fixture.place.id).locator('.trip-editor-place-row__name')).toHaveText(fixture.place.name);
+    await expectPersistedPlace(page, fixture.place.id, fixture.place.name, fixture.place.address);
+  });
+
+  test('mocked segment save failure preserves the separate segment draft path', async ({ page }) => {
+    await openEditor(page);
+    const initial = await loadEditorStateFixture(page) as EditorState;
+    const segment = editableSegment(initial);
+    test.skip(!segment, 'Configured Trip Editor fixture has no editable segment for failure feedback coverage.');
+    if (!segment) {
+      return;
+    }
+
+    await editSegment(page, segment.id);
+    const form = page.locator('#trip-editor-segment-form');
+    await form.getByLabel('Estimated distance km').fill('123.45');
+
+    const failure = await mockMutationFailure(page, 'PUT', `${editorApiPath}/segments/${segment.id}`, 500);
+    await page.getByRole('button', { name: 'Save Segment' }).click();
+
+    await expect.poll(failure.requests).toBe(1);
+    await expect(page.getByRole('alert')).toContainText('Trip Editor segment update returned 500');
+    await expectFailedStatus(page);
+    await expect(form.getByLabel('Estimated distance km')).toHaveValue('123.45');
+    await expectPersistedSegmentDistance(page, segment.id, segment.estimatedDistanceKm);
+
+    await failure.unroute();
+    await page.getByRole('button', { name: 'Cancel' }).click();
+    await page.getByRole('dialog', { name: 'Discard changes?' }).getByRole('button', { name: 'Discard' }).click();
+    await expect(form).toHaveCount(0);
+  });
+
+  test('delete confirmation appears first and mocked delete failure keeps row and editor state', async ({ page }) => {
+    await openEditor(page);
+    const initial = await loadEditorStateFixture(page) as EditorState;
+    const fixture = editablePlaceFixture(initial);
+    test.skip(!fixture, 'Configured Trip Editor fixture has no deletable place for delete failure coverage.');
+    if (!fixture) {
+      return;
+    }
+
+    await editPlace(page, fixture.place.id);
+    const form = page.locator('#trip-editor-place-form');
+    const failure = await mockMutationFailure(page, 'DELETE', `${editorApiPath}/places/${fixture.place.id}`, 500);
+
+    await page.getByRole('button', { name: 'Delete', exact: true }).click();
+    await expect(page.getByRole('dialog', { name: 'Delete place?' })).toBeVisible();
+    await expect.poll(failure.requests).toBe(0);
+    await page.getByRole('dialog', { name: 'Delete place?' }).getByRole('button', { name: 'Keep place' }).click();
+    await expect(page.getByRole('dialog', { name: 'Delete place?' })).toHaveCount(0);
+    await expect(form).toBeVisible();
+    await expect(placeRow(page, fixture.place.id)).toBeVisible();
+
+    await page.getByRole('button', { name: 'Delete', exact: true }).click();
+    await page.getByRole('dialog', { name: 'Delete place?' }).getByRole('button', { name: 'Delete' }).click();
+
+    await expect.poll(failure.requests).toBe(1);
+    await expect(page.getByRole('alert')).toContainText('Trip Editor place delete returned 500');
+    await expectFailedStatus(page);
+    await expect(form).toBeVisible();
+    await expect(placeRow(page, fixture.place.id)).toBeVisible();
+    await expectPersistedPlace(page, fixture.place.id, fixture.place.name, fixture.place.address);
+
+    await failure.unroute();
+  });
+
+  test('clean and dirty cancel paths leave persisted place state unchanged', async ({ page }) => {
+    await openEditor(page);
+    const initial = await loadEditorStateFixture(page) as EditorState;
+    const fixture = editablePlaceFixture(initial);
+    test.skip(!fixture, 'Configured Trip Editor fixture has no editable place for cancel-state coverage.');
+    if (!fixture) {
+      return;
+    }
+
+    await editPlace(page, fixture.place.id);
+    await page.getByRole('button', { name: 'Cancel' }).click();
+    await expect(page.getByRole('dialog', { name: 'Discard changes?' })).toHaveCount(0);
+    await expect(page.locator('#trip-editor-place-form')).toHaveCount(0);
+    await expectPersistedPlace(page, fixture.place.id, fixture.place.name, fixture.place.address);
+
+    await editPlace(page, fixture.place.id);
+    const form = page.locator('#trip-editor-place-form');
+    await form.getByLabel('Address').fill('PW dirty cancel draft address');
+    await page.getByRole('button', { name: 'Cancel' }).click();
+    const discard = page.getByRole('dialog', { name: 'Discard changes?' });
+    await expect(discard).toBeVisible();
+    await discard.getByRole('button', { name: 'Keep editing' }).click();
+    await expect(form.getByLabel('Address')).toHaveValue('PW dirty cancel draft address');
+    await expectPersistedPlace(page, fixture.place.id, fixture.place.name, fixture.place.address);
+
+    await page.getByRole('button', { name: 'Cancel' }).click();
+    await page.getByRole('dialog', { name: 'Discard changes?' }).getByRole('button', { name: 'Discard' }).click();
+    await expect(form).toHaveCount(0);
+    await expectPersistedPlace(page, fixture.place.id, fixture.place.name, fixture.place.address);
+  });
+});
+
+async function openEditor(page: Page): Promise<void> {
+  await signIn(page);
+  await page.goto(absoluteUrl(editorPath));
+  await expectMountedWorkspace(page);
+}
+
+async function editPlace(page: Page, placeId: string): Promise<void> {
+  await placeRow(page, placeId).getByRole('button', { name: 'Edit', exact: true }).click();
+  await expect(page.locator('#trip-editor-place-form')).toBeVisible();
+}
+
+async function editSegment(page: Page, segmentId: string): Promise<void> {
+  await segmentRow(page, segmentId).locator('.trip-editor-list-button').click();
+  await expect(page.locator('#trip-editor-segment-form')).toBeVisible();
+}
+
+async function mockMutationFailure(page: Page, method: string, path: string, status: number): Promise<{ requests: () => number; unroute: () => Promise<void> }> {
+  let count = 0;
+  const matcher = pathMatcher(path);
+  const handler = async (route: Route): Promise<void> => {
+    if (route.request().method() !== method) {
+      await route.fallback();
+      return;
+    }
+
+    count += 1;
+    await route.fulfill({
+      status,
+      contentType: 'application/problem+json',
+      body: JSON.stringify({ title: 'Injected Trip Editor failure', status })
+    });
+  };
+  await page.route(matcher, handler);
+  return {
+    requests: () => count,
+    unroute: async () => {
+      await page.unroute(matcher, handler);
+    }
+  };
+}
+
+async function expectFailedStatus(page: Page): Promise<void> {
+  const failedStatus = page.locator('.trip-editor-save-state').filter({ hasText: 'Save failed' }).first();
+  await expect(failedStatus).toBeVisible();
+  await expect(failedStatus).toHaveClass(/text-bg-danger.*trip-editor-save-state--danger/);
+}
+
+async function expectPersistedPlace(page: Page, placeId: string, name: string, address: string): Promise<void> {
+  const state = await loadEditorStateFixture(page) as EditorState;
+  expect(state.placesById[placeId].name).toBe(name);
+  expect(state.placesById[placeId].address).toBe(address);
+}
+
+async function expectPersistedSegmentDistance(page: Page, segmentId: string, distance: number | null): Promise<void> {
+  const state = await loadEditorStateFixture(page) as EditorState;
+  expect(state.segmentsById[segmentId].estimatedDistanceKm).toBe(distance);
+}
+
+function editablePlaceFixture(state: EditorState): { region: Record<string, any>; place: Record<string, any> } | null {
+  for (const regionId of state.regionOrder as string[]) {
+    const region = state.regionsById[regionId];
+    if (!region || region.isShadow) {
+      continue;
+    }
+
+    const placeId = (state.placeOrderByRegionId[regionId] as string[] | undefined)?.find(id => {
+      const place = state.placesById[id];
+      return place?.capabilities?.canEdit && place?.capabilities?.canDelete;
+    });
+    if (placeId) {
+      return { region, place: state.placesById[placeId] };
+    }
+  }
+
+  return null;
+}
+
+function editableSegment(state: EditorState): Record<string, any> | null {
+  const segmentId = (state.segmentOrder as string[]).find(id => state.segmentsById[id]?.capabilities?.canEdit && state.segmentsById[id]?.capabilities?.canDelete);
+  return segmentId ? state.segmentsById[segmentId] : null;
+}
+
+function placeRow(page: Page, placeId: string): Locator {
+  return page.locator(`[data-place-id="${placeId}"]`);
+}
+
+function segmentRow(page: Page, segmentId: string): Locator {
+  return page.locator(`[data-segment-id="${segmentId}"]`);
+}
+
+function pathMatcher(path: string): RegExp {
+  return new RegExp(`${path.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}/?$`, 'i');
+}