diff --git a/docs/audits/NATIVE-UI-CONFORMANCE-1387.md b/docs/audits/NATIVE-UI-CONFORMANCE-1387.md
index 036ba0bd..0f4d4744 100644
--- a/docs/audits/NATIVE-UI-CONFORMANCE-1387.md
+++ b/docs/audits/NATIVE-UI-CONFORMANCE-1387.md
@@ -12,6 +12,10 @@ The report hashes the entire bundle, including server/web resources and framewor
 
 `pnpm desktop:ui:verify <evidence.json> <candidate.app>` rehashes the package and screenshots. It rejects incomplete/duplicate/failed entries, unbound builds, dirty candidates, wrong commits/versions/packages, stale reports, missing native environment, cropped or modified PNGs, transparent overlays, and shell geometry failures before and after interactions. It is a native-evidence verifier, not yet the release workflow's publication gate.
 
+Primary routes also record heading, Back, header, and content rectangles. Checks enforce the shared typography, icon-only Back sizing/placement, route-title semantics, and cross-route alignment. Overlay parts record their actual computed padding against the shared rem-based inset contract, including intentionally unpadded compound/task containers. The runner's final status includes structural verification; an unexpected viewport or invalid recorded layout cannot remain a passing run merely because its clicks succeeded.
+
+After the normal matrix, the disposable renderer receives six deliberately injected faults: blank shell space, a clipped modal, a shifted heading, a board-only rail control on Activity, wrong popout padding, and a visible New Task button with its handler removed. Each fault must be detected by the corresponding geometry or behavioral assertion, retains a native screenshot, and is removed by reloading before the next fault. These expected-failure probes are separate from the ordinary matrix and cannot waive an ordinary failed state. Missing fault probes fail verification.
+
 ## Development checkpoint
 
 The first complete development matrix reproduced Session menu Escape dismissal failure in both themes and both native window sizes. This is tracked separately in #1451; the runner must not waive it. Preview capture timing also exposed a harness defect: DOM content and geometry could pass while the native screenshot caught a transparent opening modal. Opacity measurement and paint synchronization address that defect, and the normal/minimum light-theme preview captures were visually rechecked.
@@ -22,8 +26,7 @@ These diagnostic runs use an unsigned 6.1.6 package built from `afb447156fd77d24
 
 ## Remaining acceptance work
 
-- Resolve observed product failures, including #1451, and complete a passing full native run.
-- Strengthen primary-heading/back alignment and overlay inset assertions, with seeded-failure coverage for those contracts and dead/context-invalid controls.
+- Integrate the Session menu fix from #1453 and rerun the newly strengthened matrix. Its preceding 144-state clean candidate passed, but predates the new geometry fields and seeded renderer requirements.
 - Bind refreshed maintained screenshots/GIFs to their capture candidate and reject stale media. Do not relabel the existing browser captures as native evidence.
 - Integrate mandatory evidence verification into release validation and signed packaging before any upload. The current workflow uses `electron-builder --publish always`; adding a check after that command would be too late.
 - Update release and issue templates to distinguish browser, packaged candidate, installed app, signing, documentation, and publication boundaries.
diff --git a/scripts/native-ui/contract.mjs b/scripts/native-ui/contract.mjs
index 55fab8ef..2694748e 100644
--- a/scripts/native-ui/contract.mjs
+++ b/scripts/native-ui/contract.mjs
@@ -2,8 +2,17 @@ import { createHash } from 'node:crypto';
 import { createReadStream } from 'node:fs';
 import { lstat, readdir, readlink, realpath } from 'node:fs/promises';
 import path from 'node:path';
+import { overlayInsetFailures, pageHeaderFailures } from './layout-contract.mjs';
 
 export const schema = 'packaged-macos-ui-conformance/v1';
+export const seededCases = [
+  ['shell-blank', 'shell does not fill viewport'],
+  ['clipped-modal', 'clipped overlay'],
+  ['heading-offset', 'inconsistent primary heading/Back geometry'],
+  ['context-invalid-header', 'context-invalid board rail control'],
+  ['overlay-padding', 'inconsistent overlay header padding'],
+  ['dead-header', 'dead header control'],
+];
 export const routes = [
   ['activity', '/activity', 'Activity'],
   ['backlog', '/backlog', 'Backlog'],
@@ -75,6 +84,48 @@ export function requiresOverlay(id) {
   );
 }
 
+// Expected production parts are keyed by the exercised surface, not whatever CSS
+// selectors happen to survive a regression in that surface.
+export function requiredOverlayParts(id) {
+  const state = id.split('/')[1];
+  if (['task-chat', 'task-drawer', 'task-expanded'].includes(state))
+    return ['task-header', 'task-body'];
+  if (state?.startsWith('settings-')) return ['header', 'body', 'scroll'];
+  if (state === 'search') return ['header', 'body'];
+  if (requiresOverlay(id) || ['clipped-modal', 'overlay-padding'].includes(state))
+    return ['header', 'body', 'scroll', 'footer'];
+  return [];
+}
+
+export function seededObservedFailures(seed) {
+  if (!seed?.geometry) return ['missing seeded geometry'];
+  const errors = geometryFailures(seed.geometry);
+  if (['seed/heading-offset', 'seed/context-invalid-header'].includes(seed.id))
+    errors.push(
+      ...pageHeaderFailures(
+        seed.geometry.primaryHeader,
+        seed.geometry.rem,
+        'Activity',
+        seed.geometry
+      )
+    );
+  if (seed.id === 'seed/dead-header') {
+    const action = seed.behavior;
+    if (
+      action?.control === 'New Task' &&
+      action.visibleBefore === true &&
+      action.enabledBefore === true &&
+      action.dialogVisibleBefore === false &&
+      action.clickCompleted === true &&
+      action.dialogVisibleAfter === false &&
+      Number.isFinite(action.waitedMs) &&
+      action.waitedMs >= 1000
+    )
+      errors.push('dead header control');
+  }
+  return errors;
+}
+
 export async function fileDigest(file) {
   const hash = createHash('sha256');
   for await (const chunk of createReadStream(file)) hash.update(chunk);
@@ -108,6 +159,7 @@ export async function packageDigest(directory) {
 export function geometryFailures(g) {
   if (!g) return ['missing geometry'];
   const failures = [];
+  if (!Number.isFinite(g.rem) || g.rem <= 0) failures.push('missing root font size');
   const validRect = (r) =>
     [r.x, r.y, r.width, r.height, r.right, r.bottom].every(Number.isFinite) &&
     r.width > 0 &&
@@ -137,6 +189,7 @@ export function geometryFailures(g) {
   )
     failures.push('shell does not fill viewport');
   for (const overlay of g.overlays ?? []) {
+    failures.push(...overlayInsetFailures(overlay, g.rem));
     if (!validRect(overlay) || !Number.isFinite(overlay.overflow))
       failures.push('unmeasured overlay');
     if (!Number.isFinite(overlay.opacity) || overlay.opacity < 0.999 || overlay.opacity > 1)
@@ -191,6 +244,22 @@ export function evidenceFailures(report, expected, now = Date.now()) {
   if (!Number.isFinite(completed) || completed > now || now - completed > 24 * 60 * 60 * 1000)
     errors.push('missing or stale native evidence');
   const entries = report.entries ?? [];
+  const seeds = report.seededFailures ?? [];
+  if (
+    seeds.length !== seededCases.length ||
+    new Set(seeds.map((seed) => seed.id)).size !== seededCases.length
+  )
+    errors.push('missing or duplicate seeded renderer checks');
+  for (const [id, reason] of seededCases) {
+    const seed = seeds.find((entry) => entry.id === `seed/${id}`);
+    if (
+      seed?.status !== 'detected' ||
+      !seed.observedFailures?.includes(reason) ||
+      !seededObservedFailures(seed).includes(reason) ||
+      !seed.screenshot?.path
+    )
+      errors.push(`seed/${id}: injected renderer failure not detected`);
+  }
   if (
     entries.length !== requiredEntries.length ||
     new Set(entries.map((e) => e.id)).size !== requiredEntries.length
@@ -231,6 +300,21 @@ export function evidenceFailures(report, expected, now = Date.now()) {
       errors.push(`${id}: missing native environment`);
     if (requiresOverlay(id) && !entry.geometry?.overlays?.length)
       errors.push(`${id}: missing required overlay`);
+    for (const overlay of entry.geometry?.overlays ?? []) {
+      for (const kind of requiredOverlayParts(id))
+        if (!overlay.parts?.some((part) => part.insetKind === kind))
+          errors.push(`${id}: missing required overlay ${kind}`);
+    }
+    const route = routes.find(([name]) => id.endsWith(`/route-${name}`));
+    if (route)
+      errors.push(
+        ...pageHeaderFailures(
+          entry.geometry?.primaryHeader,
+          entry.geometry?.rem,
+          route[2],
+          entry.geometry
+        ).map((error) => `${id}: ${error}`)
+      );
     errors.push(...geometryFailures(entry.geometry).map((error) => `${id}: ${error}`));
     errors.push(
       ...geometryFailures(entry.completionGeometry).map(
@@ -238,5 +322,34 @@ export function evidenceFailures(report, expected, now = Date.now()) {
       )
     );
   }
+  for (const mode of modes) {
+    const headers = routes.map(
+      ([name]) =>
+        entries.find((entry) => entry.id === `${mode.id}/route-${name}`)?.geometry?.primaryHeader
+    );
+    const baseline = headers[0];
+    if (!baseline) continue;
+    for (const header of headers.slice(1)) {
+      if (!header) continue;
+      const values = [
+        [header.header?.y, baseline.header?.y],
+        [header.title?.y, baseline.title?.y],
+      ];
+      if (mode.width === 1700)
+        values.push(
+          [header.header?.height, baseline.header?.height],
+          [header.content?.y, baseline.content?.y]
+        );
+      if (
+        values.some(
+          ([actual, expected]) =>
+            !Number.isFinite(actual) ||
+            !Number.isFinite(expected) ||
+            Math.abs(actual - expected) > 2
+        )
+      )
+        errors.push(`${mode.id}: inconsistent route header baseline`);
+    }
+  }
   return errors;
 }
diff --git a/scripts/native-ui/contract.test.mjs b/scripts/native-ui/contract.test.mjs
index 90e13749..879d052d 100644
--- a/scripts/native-ui/contract.test.mjs
+++ b/scripts/native-ui/contract.test.mjs
@@ -1,3 +1,4 @@
+/* global structuredClone */
 import assert from 'node:assert/strict';
 import { test } from 'node:test';
 import {
@@ -6,8 +7,11 @@ import {
   modes,
   requiredEntries,
   requiresOverlay,
+  requiredOverlayParts,
   packageDigest,
   schema,
+  routes,
+  seededCases,
 } from './contract.mjs';
 import { crc32, deflateSync } from 'node:zlib';
 import { screenshotSize } from './png.mjs';
@@ -33,7 +37,7 @@ test('bundle identity includes web resources and rejects external symlinks', asy
   await assert.rejects(packageDigest(bundle), /escapes bundle/);
 });
 function report() {
-  return {
+  const value = {
     schema,
     status: 'passed',
     boundary: 'packaged-macos',
@@ -49,6 +53,12 @@ function report() {
       osVersion: '26.0',
     },
     completedAt: new Date(now).toISOString(),
+    seededFailures: seededCases.map(([id, reason]) => ({
+      id: `seed/${id}`,
+      status: 'detected',
+      observedFailures: [reason],
+      screenshot: { path: `seed--${id}.png`, sha256: digest },
+    })),
     entries: requiredEntries.map((id) => {
       const mode = modes.find((mode) => id.startsWith(`${mode.id}/`));
       return {
@@ -62,6 +72,7 @@ function report() {
           scaleFactor: 2,
         },
         completionGeometry: {
+          rem: 16,
           width: mode.width,
           height: mode.height,
           scrollWidth: mode.width,
@@ -70,6 +81,19 @@ function report() {
           overlays: [],
         },
         geometry: {
+          rem: 16,
+          primaryHeader: {
+            header: { x: 0, y: 0, width: 1000, height: 82, right: 1000, bottom: 82 },
+            title: { x: 52, y: 0, width: 200, height: 32, right: 252, bottom: 32 },
+            back: { x: 0, y: 2, width: 40, height: 40, right: 40, bottom: 42 },
+            content: { x: 0, y: 82, width: 1000, height: 500, right: 1000, bottom: 582 },
+            titleText: routes.find(([name]) => id.endsWith(`/route-${name}`))?.[2],
+            titleCount: 1,
+            backText: '',
+            boardRailControls: 0,
+            fontSize: 24,
+            lineHeight: 32,
+          },
           width: mode.width,
           height: mode.height,
           scrollWidth: mode.width,
@@ -86,16 +110,26 @@ function report() {
                   bottom: mode.height - 1,
                   overflow: 0,
                   opacity: 1,
-                  parts: ['header', 'body'].map((name) => ({
+                  parts: requiredOverlayParts(id).map((kind) => ({
                     x: 2,
                     y: 2,
                     width: 100,
                     height: 30,
                     right: 102,
                     bottom: 32,
-                    name,
+                    name: kind.includes('header')
+                      ? 'header'
+                      : kind === 'footer'
+                        ? 'footer'
+                        : 'body',
+                    insetKind: kind,
                     visible: true,
-                    padding: [16, 16, 16, 16],
+                    padding:
+                      kind === 'header'
+                        ? [10, 16, 10, 16]
+                        : kind === 'task-body'
+                          ? [0, 0, 0, 0]
+                          : [16, 16, 16, 16],
                   })),
                 },
               ]
@@ -104,6 +138,39 @@ function report() {
       };
     }),
   };
+  for (const seed of value.seededFailures) {
+    const state = ['seed/clipped-modal', 'seed/overlay-padding'].includes(seed.id)
+      ? 'create-task'
+      : 'route-activity';
+    seed.geometry = structuredClone(
+      value.entries.find((entry) => entry.id === `light-normal/${state}`).geometry
+    );
+    if (seed.id === 'seed/shell-blank') seed.geometry.shell.height -= 100;
+    if (seed.id === 'seed/clipped-modal') {
+      const overlay = seed.geometry.overlays[0];
+      overlay.x += 1700;
+      overlay.right += 1700;
+    }
+    if (seed.id === 'seed/heading-offset') {
+      seed.geometry.primaryHeader.title.y += 16;
+      seed.geometry.primaryHeader.title.bottom += 16;
+    }
+    if (seed.id === 'seed/context-invalid-header')
+      seed.geometry.primaryHeader.boardRailControls = 1;
+    if (seed.id === 'seed/overlay-padding')
+      seed.geometry.overlays[0].parts[0].padding = [0, 0, 0, 0];
+    if (seed.id === 'seed/dead-header')
+      seed.behavior = {
+        control: 'New Task',
+        visibleBefore: true,
+        enabledBefore: true,
+        dialogVisibleBefore: false,
+        clickCompleted: true,
+        waitedMs: 1000,
+        dialogVisibleAfter: false,
+      };
+  }
+  return value;
 }
 const failures = (value) =>
   evidenceFailures(value, { commit, packageDigest: digest, version: '6.1.6' }, now);
@@ -114,6 +181,8 @@ test('partial, duplicate and failed matrices cannot pass', () => {
     (r) => r.entries.pop(),
     (r) => (r.entries[1] = r.entries[0]),
     (r) => (r.entries[0].status = 'failed'),
+    (r) => r.seededFailures.pop(),
+    (r) => (r.seededFailures[0].observedFailures = []),
   ]) {
     const r = report();
     mutate(r);
@@ -155,6 +224,7 @@ test('seeded clipped overlay and unreachable footer fail', () => {
     },
   ];
   assert.deepEqual(geometryFailures(g), [
+    'inconsistent overlay footer padding',
     'unmeasured overlay',
     'transparent or unmeasured overlay',
     'missing overlay header/body',
@@ -162,6 +232,116 @@ test('seeded clipped overlay and unreachable footer fail', () => {
     'unreachable or unmeasured overlay footer',
   ]);
 });
+test('heading, Back, context-invalid controls and inconsistent route baselines fail closed', () => {
+  for (const mutate of [
+    (h) => {
+      h.title.y += 8;
+    },
+    (h) => {
+      h.back.width = 20;
+    },
+    (h) => {
+      h.fontSize = 12;
+    },
+    (h) => {
+      h.backText = 'Back';
+    },
+    (h) => {
+      h.boardRailControls = 1;
+    },
+    (h) => {
+      h.content.y += 20;
+    },
+    (h) => {
+      for (const key of ['header', 'title', 'back', 'content']) {
+        h[key].x -= 2000;
+        h[key].right -= 2000;
+      }
+    },
+    (h) => {
+      h.back.right = 999;
+    },
+    (h) => {
+      h.title.width = 1200;
+      h.title.right = h.title.x + 1200;
+    },
+  ]) {
+    const r = report();
+    mutate(
+      r.entries.find((entry) => entry.id === 'light-normal/route-workflows').geometry.primaryHeader
+    );
+    assert(failures(r).length);
+  }
+});
+test('insets use the shared rem contract, including zero-padding compound bodies', () => {
+  const r = report();
+  const g = r.entries.find((entry) => entry.id === 'light-normal/create-task').geometry;
+  const overlay = g.overlays[0];
+  overlay.parts[1].padding = [0, 0, 0, 0];
+  assert(geometryFailures(g).includes('inconsistent overlay body padding'));
+  overlay.compound = true;
+  assert.deepEqual(geometryFailures(g), []);
+  overlay.parts[0].padding[1] = 4;
+  assert(geometryFailures(g).includes('inconsistent overlay header padding'));
+});
+test('claimed seed detection requires retained defective measurements and behavioral evidence', () => {
+  for (const seedIndex of seededCases.keys()) {
+    const r = report();
+    const seed = r.seededFailures[seedIndex];
+    delete seed.geometry;
+    assert(failures(r).some((error) => error.startsWith(seed.id)));
+  }
+  for (const seedIndex of seededCases.keys()) {
+    const r = report();
+    const seed = r.seededFailures[seedIndex];
+    seed.geometry = structuredClone(
+      r.entries.find((entry) => entry.id === 'light-normal/route-activity').geometry
+    );
+    delete seed.behavior;
+    assert(failures(r).some((error) => error.startsWith(seed.id)));
+  }
+  for (const mutate of [
+    (b) => {
+      b.clickCompleted = false;
+    },
+    (b) => {
+      b.visibleBefore = false;
+    },
+    (b) => {
+      b.enabledBefore = false;
+    },
+    (b) => {
+      b.dialogVisibleBefore = true;
+    },
+    (b) => {
+      b.dialogVisibleAfter = true;
+    },
+    (b) => {
+      b.waitedMs = 10;
+    },
+  ]) {
+    const r = report();
+    mutate(r.seededFailures.find((seed) => seed.id === 'seed/dead-header').behavior);
+    assert(failures(r).some((error) => error.startsWith('seed/dead-header')));
+  }
+});
+test('required footer and compound scroll measurements cannot disappear', () => {
+  for (const [state, kind] of [
+    ['confirmation', 'footer'],
+    ['create-task', 'scroll'],
+    ['settings-general', 'scroll'],
+  ]) {
+    const r = report();
+    const overlay = r.entries.find((entry) => entry.id === `light-normal/${state}`).geometry
+      .overlays[0];
+    overlay.parts = overlay.parts.filter((part) => part.insetKind !== kind);
+    assert(failures(r).some((error) => error.includes(`missing required overlay ${kind}`)));
+  }
+  const g = report().entries.find((entry) => entry.id === 'light-normal/create-task').geometry;
+  g.overlays[0].compound = true;
+  g.overlays[0].parts = g.overlays[0].parts.filter((part) => part.insetKind !== 'scroll');
+  assert(geometryFailures(g).includes('missing compound overlay scroll'));
+});
 test('missing overlay measurements and invalid native bounds fail closed', () => {
   for (const mutate of [
     (r) => (r.entries.find((e) => requiresOverlay(e.id)).geometry.overlays = []),
diff --git a/scripts/native-ui/layout-contract.mjs b/scripts/native-ui/layout-contract.mjs
new file mode 100644
index 00000000..889fac11
--- /dev/null
+++ b/scripts/native-ui/layout-contract.mjs
@@ -0,0 +1,94 @@
+/* global document, getComputedStyle */
+
+// Serializable renderer probe. This reads production CSS; it never repairs layout.
+export function measurePageHeader() {
+  const page = document.querySelector('[data-page-shell="primary"]');
+  if (!page) return null;
+  const rect = (el) => {
+    if (!el) return null;
+    const { x, y, width, height, right, bottom } = el.getBoundingClientRect();
+    return { x, y, width, height, right, bottom };
+  };
+  const title = page.querySelector('h1');
+  const back = page.querySelector('button[aria-label="Back"]');
+  return {
+    header: rect(page.querySelector('.primary-page-header')),
+    title: rect(title),
+    back: rect(back),
+    content: rect(page.querySelector('.primary-page-content')),
+    titleText: title?.textContent?.trim(),
+    titleCount: document.querySelectorAll('h1').length,
+    backText: back?.textContent?.trim(),
+    fontSize: title ? parseFloat(getComputedStyle(title).fontSize) : null,
+    lineHeight: title ? parseFloat(getComputedStyle(title).lineHeight) : null,
+    boardRailControls: document.querySelectorAll(
+      '[aria-label="Expand right sidebar"], [aria-label="Collapse right sidebar"]'
+    ).length,
+  };
+}
+
+const near = (actual, expected) => Number.isFinite(actual) && Math.abs(actual - expected) <= 1;
+const measured = (r) =>
+  r &&
+  [r.x, r.y, r.width, r.height, r.right, r.bottom].every(Number.isFinite) &&
+  r.width > 0 &&
+  r.height > 0 &&
+  near(r.right, r.x + r.width) &&
+  near(r.bottom, r.y + r.height);
+const contains = (outer, inner) =>
+  inner.x >= outer.x - 1 &&
+  inner.y >= outer.y - 1 &&
+  inner.right <= outer.right + 1 &&
+  inner.bottom <= outer.bottom + 1;
+
+export function pageHeaderFailures(header, rem, expectedTitle, viewport) {
+  if (!header || !['header', 'title', 'back', 'content'].every((key) => measured(header[key])))
+    return ['missing primary header geometry'];
+  const errors = [];
+  if (
+    !viewport ||
+    ![viewport.width, viewport.height].every((n) => Number.isFinite(n) && n > 0) ||
+    !contains({ x: 0, y: 0, right: viewport.width, bottom: viewport.height }, header.header) ||
+    !contains(header.header, header.title) ||
+    !contains(header.header, header.back)
+  )
+    errors.push('clipped primary heading/Back geometry');
+  if (header.titleCount !== 1 || header.titleText !== expectedTitle || header.backText !== '')
+    errors.push('invalid primary heading or Back control');
+  if (header.boardRailControls !== 0) errors.push('context-invalid board rail control');
+  if (
+    !near(header.back.width, 2.5 * rem) ||
+    !near(header.back.height, 2.5 * rem) ||
+    !near(header.back.y - header.header.y, 0.125 * rem) ||
+    !near(header.title.x - header.back.right, 0.75 * rem) ||
+    !near(header.title.y, header.header.y) ||
+    !near(header.fontSize, 1.5 * rem) ||
+    !near(header.lineHeight, 2 * rem)
+  )
+    errors.push('inconsistent primary heading/Back geometry');
+  return errors;
+}
+
+export function overlayInsetFailures(overlay, rem) {
+  const errors = [];
+  if (overlay.compound && !overlay.parts?.some((part) => part.insetKind === 'scroll'))
+    errors.push('missing compound overlay scroll');
+  for (const part of overlay.parts ?? []) {
+    const units = {
+      header: [0.625, 1, 0.625, 1],
+      body: overlay.compound ? [0, 0, 0, 0] : [1, 1, 1, 1],
+      footer: [1, 1, 1, 1],
+      scroll: [1, 1, 1, 1],
+      'task-header': [1, 1, 1, 1],
+      'task-body': [0, 0, 0, 0],
+    }[part.insetKind];
+    if (
+      !units ||
+      !Array.isArray(part.padding) ||
+      part.padding.length !== 4 ||
+      !units.every((value, index) => near(part.padding[index], value * rem))
+    )
+      errors.push(`inconsistent overlay ${part.name} padding`);
+  }
+  return errors;
+}
diff --git a/scripts/native-ui/run.mjs b/scripts/native-ui/run.mjs
index d0e6bcec..55dd6c90 100644
--- a/scripts/native-ui/run.mjs
+++ b/scripts/native-ui/run.mjs
@@ -10,6 +10,7 @@ import path from 'node:path';
 import { _electron, expect } from '@playwright/test';
 import {
   fileDigest,
+  evidenceFailures,
   geometryFailures,
   modes,
   packageDigest,
@@ -17,8 +18,11 @@ import {
   schema,
   settingsSections,
   states,
+  seededCases,
 } from './contract.mjs';
 import { installPreviewFixture } from './preview-fixture.mjs';
+import { measurePageHeader, pageHeaderFailures } from './layout-contract.mjs';
+import { performance } from 'node:perf_hooks';
 
 const root = path.resolve(import.meta.dirname, '../..');
 const [packageArgument, outputArgument] = process.argv.slice(2);
@@ -168,7 +172,7 @@ async function configure(mode) {
   await expect(page.getByRole('button', { name: 'Settings', exact: true })).toBeVisible();
 }
 async function metrics() {
-  return page.evaluate(() => {
+  const geometry = await page.evaluate(() => {
     const shell = document.querySelector('.desktop-app-shell');
     if (!shell) throw new Error('Missing production desktop shell');
     const rect = (el) => {
@@ -187,6 +191,7 @@ async function metrics() {
     return {
       width: innerWidth,
       height: innerHeight,
+      rem: parseFloat(getComputedStyle(document.documentElement).fontSize),
       scrollWidth: document.documentElement.scrollWidth,
       scrollHeight: document.documentElement.scrollHeight,
       shell: rect(shell),
@@ -196,16 +201,28 @@ async function metrics() {
         ),
       ].map((el) => ({
         ...rect(el),
+        compound: !!el.closest('[data-overlay-compound]'),
         opacity: paintedOpacity(el),
         overflow: el.scrollWidth - el.clientWidth,
         parts: [
           ...el.querySelectorAll(
-            '.vk-overlay-header, .vk-overlay-body, .vk-overlay-footer, .vk-task-workspace-header, .mantine-Drawer-body'
+            '.vk-overlay-header, .vk-overlay-body, .vk-overlay-footer, .vk-overlay-scroll, .vk-task-workspace-header, .mantine-Drawer-body'
           ),
         ].map((part) => {
           const style = getComputedStyle(part);
           const b = rect(part);
           return {
+            insetKind: part.matches('.vk-task-workspace-header')
+              ? 'task-header'
+              : part.matches('.mantine-Drawer-body')
+                ? 'task-body'
+                : part.matches('.vk-overlay-scroll')
+                  ? 'scroll'
+                  : part.matches('.vk-overlay-header')
+                    ? 'header'
+                    : part.matches('.vk-overlay-footer')
+                      ? 'footer'
+                      : 'body',
             name: part.matches('.vk-overlay-header, .vk-task-workspace-header')
               ? 'header'
               : part.matches('.vk-overlay-footer')
@@ -230,6 +247,8 @@ async function metrics() {
       })),
     };
   });
+  geometry.primaryHeader = await page.evaluate(measurePageHeader);
+  return geometry;
 }
 async function capture(entry) {
   // Native capturePage does not wait for CSS transitions as Playwright screenshots do.
@@ -259,6 +278,18 @@ async function capture(entry) {
   entry.nativeWindow = native;
   entry.screenshot = { path: name, sha256: await fileDigest(path.join(output, name)) };
   assert.deepEqual(geometryFailures(entry.geometry), [], entry.id);
+  const route = routes.find(([name]) => entry.id.endsWith(`/route-${name}`));
+  if (route)
+    assert.deepEqual(
+      pageHeaderFailures(
+        entry.geometry.primaryHeader,
+        entry.geometry.rem,
+        route[2],
+        entry.geometry
+      ),
+      [],
+      entry.id
+    );
 }
 const button = (name) => page.getByRole('button', { name, exact: true });
 async function dismiss(dialog, opener) {
@@ -581,6 +612,111 @@ async function exercise(state, mode, shot) {
     throw new Error(`Required scenario has not been implemented: ${state}`);
   }
 }
+async function checkSeededRendererFailures() {
+  report.seededFailures = [];
+  for (const [id, expectedFailure] of seededCases) {
+    const entry = { id: `seed/${id}`, status: 'running' };
+    report.seededFailures.push(entry);
+    try {
+      await configure(modes[0]);
+      if (id === 'heading-offset' || id === 'context-invalid-header') {
+        await page
+          .getByRole('complementary', { name: 'Desktop navigation' })
+          .getByRole('button', { name: 'Activity', exact: true })
+          .click();
+        await expect(page.getByRole('heading', { name: 'Activity', level: 1 })).toBeFocused();
+      }
+      if (id === 'clipped-modal' || id === 'overlay-padding') {
+        await button('New Task').click();
+        await expect(page.getByRole('dialog', { name: 'Create New Task' })).toBeVisible();
+      }
+      await page.evaluate((fault) => {
+        if (fault === 'shell-blank')
+          document
+            .querySelector('.desktop-app-shell')
+            .style.setProperty('height', `${innerHeight - 100}px`, 'important');
+        else if (fault === 'heading-offset')
+          document.querySelector('[data-page-shell="primary"] h1').style.transform =
+            'translateY(16px)';
+        else if (fault === 'context-invalid-header') {
+          const button = document.createElement('button');
+          button.setAttribute('aria-label', 'Expand right sidebar');
+          button.textContent = 'Invalid board control';
+          document.querySelector('[aria-label="Main navigation"]').append(button);
+        } else if (fault === 'clipped-modal')
+          document
+            .querySelector('[data-overlay-active="true"] .vk-overlay-content')
+            .style.setProperty('transform', `translateX(${innerWidth}px)`, 'important');
+        else if (fault === 'overlay-padding')
+          document
+            .querySelector('[data-overlay-active="true"] .vk-overlay-header')
+            .style.setProperty('padding', '0px', 'important');
+        else if (fault === 'dead-header') {
+          const button = [
+            ...document.querySelectorAll('[aria-label="Main navigation"] button'),
+          ].find((element) => element.textContent.trim() === 'New Task');
+          button.replaceWith(button.cloneNode(true)); // Remove React's target handler, retain visible UI.
+        }
+      }, id);
+      entry.observedFailures = [];
+      if (id === 'dead-header') {
+        entry.behavior = {
+          control: 'New Task',
+          visibleBefore: await button('New Task').isVisible(),
+          enabledBefore: await button('New Task').isEnabled(),
+          dialogVisibleBefore: await page
+            .getByRole('dialog', { name: 'Create New Task' })
+            .isVisible(),
+        };
+        await button('New Task').click();
+        entry.behavior.clickCompleted = true;
+        const started = performance.now();
+        try {
+          await expect(page.getByRole('dialog', { name: 'Create New Task' })).toBeVisible({
+            timeout: 1000,
+          });
+        } catch (error) {
+          if (!error.message.includes('toBeVisible')) throw error;
+          entry.observedFailures.push('dead header control');
+        }
+        entry.behavior.waitedMs = performance.now() - started;
+        entry.behavior.dialogVisibleAfter = await page
+          .getByRole('dialog', { name: 'Create New Task' })
+          .isVisible();
+      }
+      try {
+        await capture(entry);
+      } catch (error) {
+        // Geometry faults must retain their native capture, then be identified by the same validator.
+        if (!entry.screenshot) throw error;
+        entry.captureAssertion = error.message;
+      }
+      entry.observedFailures.push(...geometryFailures(entry.geometry));
+      if (id === 'heading-offset' || id === 'context-invalid-header')
+        entry.observedFailures.push(
+          ...pageHeaderFailures(
+            entry.geometry.primaryHeader,
+            entry.geometry.rem,
+            'Activity',
+            entry.geometry
+          )
+        );
+      assert(
+        entry.observedFailures.includes(expectedFailure),
+        `Injected fault was not detected: ${id}`
+      );
+      entry.status = 'detected';
+    } catch (error) {
+      entry.status = 'failed';
+      entry.error = error.message;
+    } finally {
+      // Faults only affect this disposable renderer; reload removes all injected DOM/CSS.
+      await page.goto(origin);
+    }
+    await persist();
+    console.log(`${entry.status}: ${entry.id}`);
+  }
+}
 try {
   await launch();
   for (const mode of modes) {
@@ -645,6 +781,7 @@ try {
       await persist();
     }
   }
+  await checkSeededRendererFailures();
   report.status = report.entries.every((entry) => entry.status === 'passed') ? 'passed' : 'failed';
 } catch (error) {
   report.status = 'failed';
@@ -652,6 +789,12 @@ try {
 } finally {
   if (app) await app.close();
   report.completedAt = new Date().toISOString();
+  report.validationErrors = evidenceFailures(report, {
+    commit,
+    version,
+    packageDigest: report.packageDigest,
+  });
+  if (report.validationErrors.length) report.status = 'failed';
   await persist();
 }
 console.log(`Native evidence: ${path.join(output, 'evidence.json')} (${report.status})`);
diff --git a/scripts/native-ui/verify.mjs b/scripts/native-ui/verify.mjs
index f156a277..c48f5478 100644
--- a/scripts/native-ui/verify.mjs
+++ b/scripts/native-ui/verify.mjs
@@ -14,7 +14,7 @@ export async function verifyNativeEvidence({ evidencePath, appPath, commit, vers
     packageDigest: await packageDigest(appPath),
   });
   const directory = await realpath(path.dirname(evidencePath));
-  for (const entry of report.entries ?? []) {
+  for (const entry of [...(report.entries ?? []), ...(report.seededFailures ?? [])]) {
     const name = entry.screenshot?.path;
     if (
       typeof name !== 'string' ||