diff --git a/docs/search-chrome-behaviour.md b/docs/search-chrome-behaviour.md
index 556e84ba35..50c2103639 100644
--- a/docs/search-chrome-behaviour.md
+++ b/docs/search-chrome-behaviour.md
@@ -46,7 +46,10 @@ This repo uses one shared search experience across the global shell, dashboard r
     the top bar is hidden; section anchors use `--document-anchor-offset`, published from the live collapse-row height
     plus that sticky header when the shared bar is away, instead of a fixed `scroll-mt`. Observe the shared header
     from the viewer; never edit it for this. The in-column section index card is `lg+` only — phones use the header
-    disclosure and section sheet.
+    disclosure and section sheet. Exactly one element may own `id="document-overview"` (the DocumentViewer overview
+    landing wrapper); `DocumentClinicalSummary` must not reuse that id. The phone sheet lists only present sections —
+    omit `source-images` when `visualCount === 0`, and do not require a "Tables and diagrams" sheet row in smoke for
+    the empty-images lithium demo doc.
 23. Safari's status bar, collapsing address bar, and pixels outside `window.innerHeight` are native browser/system controls. Do not use negative safe-area overscan, a fixed app root, synthetic document padding, or an opaque viewport slab to make CSS appear to own those pixels. Acceptance is no contrasting **app-owned** band around the native controls, with a matching opaque root canvas. Use the labelled physical-device matrix in [phone-chrome-physical-acceptance.md](phone-chrome-physical-acceptance.md).
 
 ## Results band (`SearchResultsHeaderBand`)
diff --git a/tests/document-clinical-summary.dom.test.tsx b/tests/document-clinical-summary.dom.test.tsx
index b7b54064b7..4839c4d230 100644
--- a/tests/document-clinical-summary.dom.test.tsx
+++ b/tests/document-clinical-summary.dom.test.tsx
@@ -78,4 +78,15 @@ describe("DocumentClinicalSummary", () => {
     expect(screen.getByText("A structured clinical summary has not been indexed for this document yet.")).toBeVisible();
     expect(screen.queryByText("Source-backed")).not.toBeInTheDocument();
   });
+
+  it("does not claim the document-overview section id", () => {
+    // DocumentViewer owns id="document-overview" on the overview landing wrapper.
+    // A second claim here duplicates the id and fails Production UI DOM integrity.
+    const { container } = render(
+      <DocumentClinicalSummary document={document} pageHref={(page) => `?page=${page}`} onPageChange={vi.fn()} />,
+    );
+
+    expect(container.querySelector("#document-overview")).toBeNull();
+    expect(screen.getByTestId("document-clinical-summary")).not.toHaveAttribute("id", "document-overview");
+  });
 });
diff --git a/tests/document-section-nav-contract.test.ts b/tests/document-section-nav-contract.test.ts
new file mode 100644
index 0000000000..c6031f75e5
--- /dev/null
+++ b/tests/document-section-nav-contract.test.ts
@@ -0,0 +1,67 @@
+import { readFileSync } from "node:fs";
+
+import { describe, expect, it } from "vitest";
+
+/**
+ * Cheap wiring contract for document section navigation.
+ *
+ * Production UI on PR #1311 failed twice for the same class of drift:
+ * 1. `DocumentClinicalSummary` and the DocumentViewer overview wrapper both
+ *    claimed `id="document-overview"`, so `expectDomIntegrity` failed.
+ * 2. ui-smoke still drove the retired in-flow "Document viewer sections" nav
+ *    and required a "Tables and diagrams" sheet row for the lithium demo doc,
+ *    which omits that row when `visualCount === 0`.
+ *
+ * Chromium proof stays in `tests/ui-smoke.spec.ts`; this file keeps the cheap
+ * suite honest about the ownership and selectors that proof depends on.
+ */
+
+const read = (relativePath: string) => readFileSync(new URL(`../${relativePath}`, import.meta.url), "utf8");
+
+const documentViewerSource = read("src/components/DocumentViewer.tsx");
+const clinicalSummarySource = read("src/components/document-viewer/document-clinical-summary.tsx");
+const sectionIndexSource = read("src/components/document-viewer/section-index.ts");
+const sectionNavSource = read("src/components/document-viewer/section-nav.tsx");
+const uiSmokeSource = read("tests/ui-smoke.spec.ts");
+const lithiumDemoSource = read("src/lib/demo-data.ts");
+
+describe("document section navigation ownership", () => {
+  it("keeps a single document-overview section id owner", () => {
+    // The overview landing wrapper is the scroll target. A second id on the
+    // clinical summary card duplicates the DOM id and fails ui-smoke integrity.
+    expect(documentViewerSource).toContain("id={documentOverviewSectionId}");
+    expect(clinicalSummarySource).not.toMatch(/\bid=["']document-overview["']/);
+    expect(clinicalSummarySource).not.toContain("id={documentOverviewSectionId}");
+    expect(clinicalSummarySource).toContain('data-testid="document-clinical-summary"');
+  });
+
+  it("exposes phone section navigation through the title sheet, not an in-flow nav row", () => {
+    expect(documentViewerSource).toContain('data-testid="document-section-trigger"');
+    expect(sectionNavSource).toContain('testId="document-section-sheet"');
+    expect(documentViewerSource).not.toMatch(/Document viewer sections/);
+    expect(sectionNavSource).not.toMatch(/Document viewer sections/);
+  });
+
+  it("omits Tables and diagrams from the index when a ready document has no visuals", () => {
+    // The lithium demo document used by ui-smoke has image_count: 0.
+    // Requiring that label in the phone sheet will red Production UI again.
+    expect(sectionIndexSource).toContain("input.visualCount > 0");
+    expect(lithiumDemoSource).toMatch(/id:\s*"11111111-1111-4111-8111-111111111111"[\s\S]*?image_count:\s*0/);
+  });
+
+  it("keeps document-viewer ui-smoke on the current phone section chrome", () => {
+    const documentViewerSmoke = uiSmokeSource.slice(
+      uiSmokeSource.indexOf('test("document viewer puts the PDF preview first'),
+      uiSmokeSource.indexOf('test("answer glass header overlays main'),
+    );
+
+    expect(documentViewerSmoke).toContain('getByTestId("document-section-trigger")');
+    expect(documentViewerSmoke).toContain('getByTestId("document-section-sheet")');
+    expect(documentViewerSmoke).not.toMatch(
+      /getByRole\(\s*["']navigation["']\s*,\s*\{\s*name:\s*["']Document viewer sections["']/,
+    );
+    // Demo docs without visuals omit Images from the sheet; open via summary.
+    expect(documentViewerSmoke).toContain("openImagesDisclosure");
+    expect(documentViewerSmoke).toContain('images.locator("summary")');
+  });
+});