diff --git a/docs/release-control/v6/internal/subsystems/frontend-primitives.md b/docs/release-control/v6/internal/subsystems/frontend-primitives.md
index dd225b090f..0bf42b1a70 100644
--- a/docs/release-control/v6/internal/subsystems/frontend-primitives.md
+++ b/docs/release-control/v6/internal/subsystems/frontend-primitives.md
@@ -88,6 +88,17 @@ API context; late responses cannot repopulate old evidence. Disposal aborts
 reads and removes subscriptions. This uses the existing query lifecycle, without
 new inventory polling or a remount cache.
 
+Successful HTTP responses still need a readable backup envelope, collections
+and consumed row fields. Invalid JSON, missing data and malformed rows produce
+a source-local unavailable state with fixed format guidance, never raw response
+content, a fabricated empty inventory or a page-level rendering failure that
+hides another source. No invalid rows are silently dropped, no completion flags
+are coerced, and only a validated response clears the warning. Explicitly nil
+PVE collections remain compatible with the existing Go encoding.
+`proxmoxBackupInventory.test.ts`, mounted backup-table controls and
+`browser-tests/backup-inventory-format.cjs` verify these boundaries and isolated
+keyboard/touch recovery, not native backup or released availability.
+
 Verification: mounted `ProxmoxBackupsTable.test.tsx` covers source pending,
 partial/both-source failure, isolated retry, fulfilled empty counts, 401/403,
 organisation replacement, late response and disposal. Production component,
diff --git a/docs/release-control/v6/internal/subsystems/storage-recovery.md b/docs/release-control/v6/internal/subsystems/storage-recovery.md
index 0d7f50f36c..3711fff084 100644
--- a/docs/release-control/v6/internal/subsystems/storage-recovery.md
+++ b/docs/release-control/v6/internal/subsystems/storage-recovery.md
@@ -41,6 +41,17 @@ disposal. `browser-tests/backup-inventory.cjs` uses production components,
 API adapters, router and CSS in Chromium/WebKit with synthetic HTTP responses;
 these controls are not native backup, permission, thaw or release acceptance.
 
+An HTTP success alone does not establish readable recovery evidence. The client
+validates the data envelope, source collections and consumed row fields before
+publishing that inventory. Malformed or undecodable responses invalidate that
+source atomically, not a silently truncated list or confirmed empty inventory.
+PVE's explicitly nil Go collections remain valid empty observations; absent
+fields are not nil collections. Optional unknown facts and additional fields
+retain their existing meaning, and completion flags are never coerced.
+`proxmoxBackupInventory.test.ts`, the mounted backup-table tests and
+`browser-tests/backup-inventory-format.cjs` cover this response boundary, source
+isolation and recovery without extending native protection or thaw claims.
+
 ### Backup identity, phone storage and History consent composition
 
 The Proxmox Coverage last-backup pointer selects completed PBS snapshots or PVE
diff --git a/docs/release-control/v6/internal/subsystems/unified-resources.md b/docs/release-control/v6/internal/subsystems/unified-resources.md
index 19287752f7..98e6481a30 100644
--- a/docs/release-control/v6/internal/subsystems/unified-resources.md
+++ b/docs/release-control/v6/internal/subsystems/unified-resources.md
@@ -35,6 +35,13 @@ count lifecycle; `browser-tests/backup-inventory.cjs` verifies production rows
 and source notices on desktop/phone. This changes no resource identity, native
 provider assessment or permission policy.
 
+The backup inventory count also remains unavailable when an HTTP200 response
+fails the client backup-envelope/row validation; transport success is not an
+observed zero. A malformed source cannot remove independently readable canonical
+server health or the other source's artifacts. Fixed diagnostics expose no
+response body. The inventory parser, mounted table and
+`browser-tests/backup-inventory-format.cjs` exercise that combined boundary.
+
 ### Guest disk freshness presentation
 
 Existing workload disk evidence retains its source reason through the row,
diff --git a/frontend-modern/browser-tests/backup-inventory-format.cjs b/frontend-modern/browser-tests/backup-inventory-format.cjs
new file mode 100644
index 0000000000..1d0fce2be9
--- /dev/null
+++ b/frontend-modern/browser-tests/backup-inventory-format.cjs
@@ -0,0 +1,278 @@
+// Production backup readers/table/router/CSS, synthetic HTTP only.
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+const crypto = require('node:crypto');
+const { chromium, webkit } = require('playwright');
+const phase = 'final';
+const root = '/workspace/frontend-modern';
+const output = `/workspace/tmp/backup-format-${phase}`;
+const sha256 = (file) => crypto.createHash('sha256').update(fs.readFileSync(file)).digest('hex');
+const emptyPVE = { data: { backupTasks: [], storageBackups: [], guestSnapshots: [] } };
+const emptyPBS = { data: { backups: [] } };
+const archive = {
+  id: 'archive-112',
+  instance: 'pve-a',
+  node: 'pve-a',
+  storage: 'local',
+  type: 'ct',
+  vmid: 112,
+  time: '2026-10-03T01:00:00Z',
+  format: 'zst',
+  volid: 'local:backup/vzdump-lxc-112.tar.zst',
+};
+const snapshot = {
+  id: 'pbs-main/main/ct/112/2026-10-03T02:00:00Z',
+  instance: 'pbs-main',
+  datastore: 'main',
+  backupType: 'ct',
+  vmid: '112',
+  backupTime: '2026-10-03T02:00:00Z',
+  files: ['index.json.blob'],
+};
+const pvePayload = { data: { ...emptyPVE.data, storageBackups: [archive] } };
+const pbsPayload = { data: { backups: [snapshot] } };
+
+(async () => {
+  fs.mkdirSync(output, { recursive: true });
+  process.chdir(root);
+  const playwrightVersion = require('playwright/package.json').version;
+  assert.equal(
+    playwrightVersion,
+    JSON.parse(fs.readFileSync('/workspace/tests/integration/package-lock.json')).packages[
+      'node_modules/@playwright/test'
+    ].version,
+  );
+  const { createServer } = await import(path.join(root, 'node_modules/vite/dist/node/index.js'));
+  const server = await createServer({
+    cacheDir: path.join(output, 'vite-cache'),
+    server: { host: '127.0.0.1', port: 5298, strictPort: true },
+  });
+  const observations = [];
+  let browser;
+  try {
+    await server.listen();
+    for (const [name, engine, phone] of [
+      ['chromium-desktop', chromium, false],
+      ['webkit-phone', webkit, true],
+    ]) {
+      browser = await engine.launch(
+        engine === chromium
+          ? { headless: true, channel: 'chromium', args: ['--no-sandbox'] }
+          : { headless: true },
+      );
+      const viewport = phone ? { width: 390, height: 844 } : { width: 1365, height: 900 };
+      const page = await browser.newPage({
+        viewport,
+        isMobile: phone,
+        hasTouch: phone,
+        locale: 'en-GB',
+        timezoneId: 'UTC',
+      });
+      page.setDefaultTimeout(20000);
+      await page.clock.setFixedTime(new Date('2026-10-03T12:00:00Z'));
+      const errors = [],
+        requests = [],
+        offOrigin = [],
+        screenshots = [],
+        checks = [];
+      page.on('pageerror', (error) => errors.push(error.message));
+      const sources = { pve: emptyPVE, pbs: {} };
+      let retryGate;
+      await page.route('**/*', async (route) => {
+        const request = route.request();
+        const url = new URL(request.url());
+        if (url.origin !== 'http://127.0.0.1:5298') {
+          offOrigin.push(url.origin);
+          return route.abort();
+        }
+        if (!url.pathname.startsWith('/api/')) return route.continue();
+        requests.push({ path: url.pathname, method: request.method() });
+        const key =
+          url.pathname === '/api/backups/pbs'
+            ? 'pbs'
+            : url.pathname === '/api/backups/pve'
+              ? 'pve'
+              : null;
+        const payload = key ? sources[key] : { data: [], policy: {}, meta: {} };
+        if (key === 'pbs' && retryGate) await retryGate;
+        await route.fulfill({
+          status: 200,
+          contentType: 'application/json',
+          body: JSON.stringify(payload),
+        });
+      });
+      const rows = () => page.locator('[data-proxmox-backup-row="recoverable"]');
+      const notice = (source) =>
+        page.getByRole('status').filter({
+          hasText: `${source} backup inventory is unavailable`,
+        });
+      const load = async () => {
+        await page.goto('http://127.0.0.1:5298/browser-tests/backup-inventory.html?view=date', {
+          waitUntil: 'domcontentloaded',
+        });
+        if (phone) await page.evaluate(() => document.documentElement.classList.add('dark'));
+      };
+      const capture = async (suffix) => {
+        await page.evaluate(() =>
+          Promise.all(
+            document
+              .getAnimations()
+              .filter((animation) => animation.effect?.getTiming().iterations !== Infinity)
+              .map((animation) => animation.finished.catch(() => undefined)),
+          ),
+        );
+        const file = path.join(output, `${name}-${suffix}.png`);
+        await page.screenshot({ path: file, fullPage: true });
+        screenshots.push({ path: path.relative('/workspace', file), sha256: sha256(file) });
+      };
+
+      await load();
+      if (phase === 'baseline') {
+        await page.getByText('No backups yet', { exact: true }).waitFor();
+        assert.equal(await notice('PBS').count(), 0);
+        checks.push('HTTP200 missing PBS data is incorrectly shown as No backups yet');
+      } else {
+        await notice('PBS').waitFor();
+        await page.getByText('Backup inventory is incomplete', { exact: true }).waitFor();
+        assert.equal(await page.getByText('No backups yet', { exact: true }).count(), 0);
+        await page.getByText(/The response format is invalid/).waitFor();
+        if (!phone) await page.locator('[title="PBS backup inventory is unavailable"]').waitFor();
+        checks.push(
+          'HTTP200 missing data remains incomplete with a fixed format explanation, not empty/zero',
+        );
+      }
+      await capture('missing-data');
+
+      sources.pve = pvePayload;
+      sources.pbs = { data: { backups: {} }, message: 'SYNTHETIC_PRIVATE_BODY_DO_NOT_DISPLAY' };
+      await load();
+      if (phase === 'baseline') {
+        await page.getByRole('alert').filter({ hasText: 'Backup view failed' }).waitFor();
+        assert.equal(await rows().count(), 0);
+        checks.push(
+          'HTTP200 non-array PBS inventory removes independently readable PVE evidence at ErrorBoundary',
+        );
+      } else {
+        await notice('PBS').waitFor();
+        await rows().first().waitFor();
+        assert.equal(await rows().count(), 1);
+        assert.match(await rows().first().innerText(), /PVE file/);
+        assert.equal(await page.getByRole('alert').count(), 0);
+        assert.equal(await page.getByText('SYNTHETIC_PRIVATE_BODY_DO_NOT_DISPLAY').count(), 0);
+        checks.push(
+          'Malformed PBS is source-local; readable PVE remains and raw response content is not displayed',
+        );
+      }
+      await capture('pbs-invalid');
+
+      sources.pbs = pbsPayload;
+      sources.pve = { data: { ...emptyPVE.data, backupTasks: {} } };
+      await load();
+      if (phase === 'baseline') {
+        await page.getByRole('alert').filter({ hasText: 'Backup view failed' }).waitFor();
+        assert.equal(await rows().count(), 0);
+        checks.push(
+          'HTTP200 non-array PVE tasks removes independently readable PBS evidence at ErrorBoundary',
+        );
+      } else {
+        await notice('PVE').waitFor();
+        await rows().first().waitFor();
+        assert.equal(await rows().count(), 1);
+        await rows().first().getByText('PBS', { exact: true }).waitFor();
+        await rows().first().getByText('Snapshot', { exact: true }).waitFor();
+        assert.equal(await page.getByRole('alert').count(), 0);
+        checks.push('Malformed PVE is source-local and independent PBS evidence remains usable');
+      }
+      await capture('pve-invalid');
+
+      if (phase === 'final') {
+        sources.pve = pvePayload;
+        sources.pbs = { data: { backups: [{ ...snapshot, inProgress: 'true' }] } };
+        await load();
+        await notice('PBS').waitFor();
+        await rows().first().waitFor();
+        assert.equal(
+          await rows().count(),
+          1,
+          'a mistyped completion flag must not become recovery evidence',
+        );
+        const before = requests.filter((r) => r.path === '/api/backups/pve').length;
+        sources.pbs = pbsPayload;
+        let release;
+        retryGate = new Promise((resolve) => (release = resolve));
+        const retry = page.getByRole('button', { name: 'Retry PBS inventory', exact: true });
+        if (phone) await retry.tap();
+        else {
+          await retry.focus();
+          await page.keyboard.press('Enter');
+        }
+        assert.equal(await retry.isDisabled(), true);
+        await notice('PBS').waitFor();
+        assert.equal(await rows().count(), 1);
+        release();
+        await page.waitForFunction(
+          () => document.querySelectorAll('[data-proxmox-backup-row="recoverable"]').length === 2,
+        );
+        retryGate = null;
+        assert.equal(await notice('PBS').count(), 0);
+        assert.equal(requests.filter((r) => r.path === '/api/backups/pve').length, before);
+        await capture('recovered');
+        checks.push(
+          'Mistyped incomplete flag is rejected; warning persists through keyboard/touch isolated retry until valid recovery',
+        );
+
+        sources.pve = { data: { backupTasks: null, storageBackups: null, guestSnapshots: null } };
+        sources.pbs = emptyPBS;
+        await load();
+        await page.getByText('No backups yet', { exact: true }).waitFor();
+        assert.equal(await page.getByRole('status').filter({ hasText: 'inventory' }).count(), 0);
+        checks.push('Explicit Go nil PVE collections remain a valid empty observation');
+      }
+      const overflow = await page.evaluate(
+        () => document.documentElement.scrollWidth > window.innerWidth + 1,
+      );
+      assert.equal(overflow, false);
+      assert.deepEqual(errors, []);
+      assert.deepEqual(offOrigin, []);
+      assert(requests.every((r) => r.method === 'GET'));
+      observations.push({
+        name,
+        browserVersion: browser.version(),
+        viewport,
+        checks,
+        requests,
+        errors,
+        offOrigin,
+        overflow,
+        screenshots,
+      });
+      await browser.close();
+      browser = null;
+    }
+    const runtime = [
+      'src/features/proxmox/ProxmoxBackupsTable.tsx',
+      'src/features/proxmox/proxmoxBackupInventory.ts',
+    ].filter((p) => fs.existsSync(path.join(root, p)));
+    fs.writeFileSync(
+      path.join(output, 'result.json'),
+      JSON.stringify(
+        {
+          phase,
+          playwrightVersion,
+          runtimeSha256: Object.fromEntries(runtime.map((p) => [p, sha256(path.join(root, p))])),
+          observations,
+        },
+        null,
+        2,
+      ) + '\n',
+    );
+    console.log(`${phase}: ${observations.length} browser contexts passed; receipts at ${output}`);
+  } finally {
+    if (browser) await browser.close();
+    await server.close();
+  }
+})().catch((error) => {
+  console.error(error);
+  process.exitCode = 1;
+});
diff --git a/frontend-modern/browser-verification/78c9d8427bdfa307.json b/frontend-modern/browser-verification/78c9d8427bdfa307.json
new file mode 100644
index 0000000000..099102e7a1
--- /dev/null
+++ b/frontend-modern/browser-verification/78c9d8427bdfa307.json
@@ -0,0 +1,53 @@
+{
+  "version": 1,
+  "base_sha": "f5925942f49b088689695678b98e703af9ead9ef",
+  "verified_at": "2026-10-03T21:03:10.375831Z",
+  "result": "passed",
+  "changed_paths": [
+    "frontend-modern/src/features/proxmox/ProxmoxBackupsTable.tsx",
+    "frontend-modern/src/features/proxmox/proxmoxBackupInventory.ts"
+  ],
+  "content_sha256": {
+    "frontend-modern/src/features/proxmox/ProxmoxBackupsTable.tsx": "8e1113c7c9e263d284c86e4c3373381b3d71f6a0161897d9dcc782ce225478d5",
+    "frontend-modern/src/features/proxmox/proxmoxBackupInventory.ts": "deccbf62dcdbafd447cca0f33b516bf98fddb8c726515a30b85b614d26a37095"
+  },
+  "routes": [
+    "/browser-tests/backup-inventory.html?view=date"
+  ],
+  "viewports": [
+    {
+      "width": 1365,
+      "height": 900
+    },
+    {
+      "width": 390,
+      "height": 844
+    }
+  ],
+  "states": [
+    "HTTP200 missing PBS envelope stays incomplete, never no-backups/zero",
+    "Malformed PBS/PVE collections preserve independent source and server health without a rendering failure",
+    "Mistyped incomplete flags are unavailable, not completed restore points",
+    "Explicit Go nil PVE collections remain valid empty observations"
+  ],
+  "interactions": [
+    "Desktop Enter and phone touch isolated retry keep warnings and independent rows while pending, clear only after validated success",
+    "Eight settled final screenshots and two baseline screenshots opened and inspected; light desktop/dark phone warnings and rows readable, no page overflow"
+  ],
+  "playwright_version": "1.56.1",
+  "browser_versions": [
+    {
+      "engine": "chromium-desktop",
+      "version": "141.0.7390.37"
+    },
+    {
+      "engine": "webkit-phone",
+      "version": "26.0"
+    }
+  ],
+  "dependency_snapshot": "8aaf02a3db8e1c245174d04d132398d1716a69525064975470ff738d168abb82",
+  "limitations": [
+    "Synthetic source responses through production table/router/API/CSS, not native provider collection, permission, restore, QGA/thaw or installed/released acceptance.",
+    "Production/embed build is separately source-proved; no new route, polling, source cache or authority."
+  ]
+}
diff --git a/frontend-modern/src/features/proxmox/ProxmoxBackupsTable.tsx b/frontend-modern/src/features/proxmox/ProxmoxBackupsTable.tsx
index e3d51a93b9..c0bf4513ea 100644
--- a/frontend-modern/src/features/proxmox/ProxmoxBackupsTable.tsx
+++ b/frontend-modern/src/features/proxmox/ProxmoxBackupsTable.tsx
@@ -29,9 +29,7 @@ import type {
   GuestSnapshot,
   PBSBackup,
   PBSBackupsPayload,
-  PBSBackupsResponse,
   PVEBackupsPayload,
-  PVEBackupsResponse,
   StorageBackup,
 } from '@/types/api';
 import type { Resource } from '@/types/resource';
@@ -70,6 +68,12 @@ import { ProxmoxBackupsCoverageStrip } from './ProxmoxBackupsCoverageStrip';
 import { ProxmoxBackupServersTable } from './ProxmoxBackupServersTable';
 import { ProxmoxCoverageTable } from './ProxmoxCoverageTable';
 import { ProxmoxRecoverableTable } from './ProxmoxRecoverableTable';
+import {
+  BackupInventoryFormatError,
+  parsePBSBackupInventory,
+  parsePVEBackupInventory,
+  readBackupInventoryJSON,
+} from './proxmoxBackupInventory';
 
 // One backups surface, two operator views: a chronological recoverable-artifact
 // feed for "what ran when", and a guest coverage table for "what is protected".
@@ -97,8 +101,7 @@ async function fetchPVEBackups(signal: AbortSignal): Promise<PVEBackupsPayload>
       status: response.status,
     });
   }
-  const payload = (await response.json()) as PVEBackupsResponse;
-  return payload?.data ?? EMPTY_PVE_BACKUPS;
+  return parsePVEBackupInventory(await readBackupInventoryJSON(response));
 }
 
 async function fetchPBSBackups(signal: AbortSignal): Promise<PBSBackupsPayload> {
@@ -108,8 +111,7 @@ async function fetchPBSBackups(signal: AbortSignal): Promise<PBSBackupsPayload>
       status: response.status,
     });
   }
-  const payload = (await response.json()) as PBSBackupsResponse;
-  return payload?.data ?? EMPTY_PBS_BACKUPS;
+  return parsePBSBackupInventory(await readBackupInventoryJSON(response));
 }
 
 export const ProxmoxBackupsTable: Component<{
@@ -702,6 +704,11 @@ export const ProxmoxBackupsTable: Component<{
                   <span>
                     {label} backup inventory is {query.error() ? 'unavailable' : 'loading'}. Counts
                     are incomplete. {getAPIReadAccessErrorMessage(query.error())}
+                    <Show when={query.error() instanceof BackupInventoryFormatError}>
+                      {' '}
+                      The response format is invalid. Missing restore points do not mean no backups
+                      exist.
+                    </Show>
                   </span>
                   <Show when={query.error()}>
                     <button
diff --git a/frontend-modern/src/features/proxmox/__tests__/ProxmoxBackupsTable.test.tsx b/frontend-modern/src/features/proxmox/__tests__/ProxmoxBackupsTable.test.tsx
index a1b06924c8..72df095cc2 100644
--- a/frontend-modern/src/features/proxmox/__tests__/ProxmoxBackupsTable.test.tsx
+++ b/frontend-modern/src/features/proxmox/__tests__/ProxmoxBackupsTable.test.tsx
@@ -735,6 +735,79 @@ describe('independent Proxmox backup inventory reads', () => {
     window.history.replaceState({}, '', '/proxmox/backups/date');
     apiFetchJSONMock.mockResolvedValue({ data: [], policy: {}, meta: {} });
   });
+
+  it.each(['pve', 'pbs'] as const)(
+    'keeps malformed HTTP200 %s responses source-local and recovers with an isolated retry',
+    async (source) => {
+      const bad = source === 'pbs' ? { data: { backups: [null] } } : { data: {} };
+      let response = Promise.resolve(jsonResponse(bad));
+      apiFetchMock.mockImplementation((url) =>
+        url.endsWith(`/${source}`)
+          ? response
+          : Promise.resolve(jsonResponse(source === 'pve' ? pbsPayload : readPvePayload)),
+      );
+      mountBackupReadState();
+      await screen.findByText(/The response format is invalid/);
+      await waitFor(() => expect(recoverableRows()).toHaveLength(1));
+      expect(screen.queryByText('No backups yet')).not.toBeInTheDocument();
+      expect(screen.queryByRole('alert')).not.toBeInTheDocument();
+      if (source === 'pbs') expect(serverTable()).toHaveTextContent('Unavailable');
+      const pending = deferred<Response>();
+      response = pending.promise;
+      const retry = screen.getByRole('button', { name: `Retry ${source.toUpperCase()} inventory` });
+      fireEvent.click(retry);
+      expect(retry).toBeDisabled();
+      expect(screen.getByText(/The response format is invalid/)).toBeInTheDocument();
+      expect(recoverableRows()).toHaveLength(1);
+      pending.resolve(jsonResponse(source === 'pbs' ? pbsPayload : readPvePayload));
+      await waitFor(() => expect(recoverableRows()).toHaveLength(2));
+      expect(screen.queryByText(/The response format is invalid/)).not.toBeInTheDocument();
+      expect(sourceCalls(source === 'pbs' ? 'pve' : 'pbs')).toHaveLength(1);
+    },
+  );
+
+  it('does not infer empty PBS inventory from a missing data envelope', async () => {
+    apiFetchMock.mockImplementation((url) =>
+      Promise.resolve(jsonResponse(url.endsWith('/pbs') ? {} : emptyPVE)),
+    );
+    mountBackupReadState();
+    await screen.findByText('Backup inventory is incomplete');
+    expect(screen.queryByText('No backups yet')).not.toBeInTheDocument();
+    expect(serverTable()).toHaveTextContent('Unavailable');
+  });
+
+  it('keeps undecodable successful bodies out of user-facing diagnostics', async () => {
+    apiFetchMock.mockImplementation((url) =>
+      Promise.resolve(
+        url.endsWith('/pbs')
+          ? new Response('SYNTHETIC_PRIVATE_BODY_DO_NOT_DISPLAY', { status: 200 })
+          : jsonResponse(readPvePayload),
+      ),
+    );
+    mountBackupReadState();
+    await screen.findByText(/The response format is invalid/);
+    await waitFor(() => expect(recoverableRows()).toHaveLength(1));
+    expect(document.body).not.toHaveTextContent('SYNTHETIC_PRIVATE_BODY_DO_NOT_DISPLAY');
+  });
+
+  it('accepts Go nil PVE collections as explicitly observed empty inventory', async () => {
+    apiFetchMock.mockImplementation((url) =>
+      Promise.resolve(
+        jsonResponse(
+          url.endsWith('/pbs')
+            ? emptyPBS
+            : { data: { backupTasks: null, storageBackups: null, guestSnapshots: null } },
+        ),
+      ),
+    );
+    mountBackupReadState();
+    await screen.findByText('No backups yet');
+    expect(screen.queryByText(/inventory is unavailable/)).not.toBeInTheDocument();
+    expect(
+      within(serverTable() as HTMLElement).getByText('0', { exact: true }),
+    ).toBeInTheDocument();
+  });
+
   it('does not present an unread PBS inventory as empty or a measured zero', async () => {
     const pending = deferred<Response>();
     apiFetchMock.mockImplementation((url) =>
diff --git a/frontend-modern/src/features/proxmox/__tests__/proxmoxBackupInventory.test.ts b/frontend-modern/src/features/proxmox/__tests__/proxmoxBackupInventory.test.ts
new file mode 100644
index 0000000000..fceb21e9cb
--- /dev/null
+++ b/frontend-modern/src/features/proxmox/__tests__/proxmoxBackupInventory.test.ts
@@ -0,0 +1,153 @@
+import { describe, expect, it } from 'vitest';
+import {
+  BackupInventoryFormatError,
+  parsePBSBackupInventory,
+  parsePVEBackupInventory,
+  readBackupInventoryJSON,
+} from '../proxmoxBackupInventory';
+
+const task = { id: 'task-112', vmid: 112, type: 'ct', status: 'OK', startTime: '' };
+const archive = { id: 'archive-112', vmid: 112, type: 'ct', time: '' };
+const snapshot = { id: 'snapshot-112', vmid: 112, type: 'ct', time: '' };
+const pbs = { id: 'pbs-112', vmid: '112', backupType: 'ct', backupTime: '', files: [] };
+const pveData = { backupTasks: [task], storageBackups: [archive], guestSnapshots: [snapshot] };
+const pbsData = { backups: [pbs] };
+
+describe('backup inventory response boundary', () => {
+  it('keeps observed rows, missing optional facts and future fields without coercion', () => {
+    const data = {
+      ...pveData,
+      storageBackups: [{ ...archive, inProgress: true, futureField: { enabled: true } }],
+    };
+    const result = parsePVEBackupInventory({ data });
+    expect(result).toEqual(data);
+    expect(result.storageBackups).toBe(data.storageBackups);
+    expect(result.storageBackups[0].size).toBeUndefined();
+    expect(parsePBSBackupInventory({ data: pbsData })).toEqual(pbsData);
+  });
+
+  it('accepts empty arrays and explicitly nil PVE collections, not missing collections', () => {
+    const empty = { backupTasks: [], storageBackups: [], guestSnapshots: [] };
+    expect(parsePVEBackupInventory({ data: empty })).toEqual(empty);
+    expect(
+      parsePVEBackupInventory({
+        data: { backupTasks: null, storageBackups: null, guestSnapshots: null },
+      }),
+    ).toEqual(empty);
+    expect(parsePBSBackupInventory({ data: { backups: [] } })).toEqual({ backups: [] });
+    expect(() => parsePBSBackupInventory({ data: { backups: null } })).toThrow(
+      BackupInventoryFormatError,
+    );
+  });
+
+  it.each([undefined, null, false, 'response', [], {}, { data: null }, { data: [] }, { data: {} }])(
+    'rejects a missing or invalid envelope: %j',
+    (payload) => {
+      expect(() => parsePVEBackupInventory(payload)).toThrow(BackupInventoryFormatError);
+      expect(() => parsePBSBackupInventory(payload)).toThrow(BackupInventoryFormatError);
+    },
+  );
+
+  it.each(['backupTasks', 'storageBackups', 'guestSnapshots'] as const)(
+    'rejects missing, scalar, object and invalid %s rows without silently dropping them',
+    (key) => {
+      for (const value of [undefined, false, '', {}, [null], ['row'], [pveData[key][0], {}]]) {
+        expect(() => parsePVEBackupInventory({ data: { ...pveData, [key]: value } })).toThrow(
+          BackupInventoryFormatError,
+        );
+      }
+    },
+  );
+
+  it.each([undefined, false, '', {}, [null], ['row'], [pbs, {}]])(
+    'rejects a malformed PBS collection or row: %j',
+    (backups) => {
+      expect(() => parsePBSBackupInventory({ data: { backups } })).toThrow(
+        BackupInventoryFormatError,
+      );
+    },
+  );
+
+  it.each([
+    ['id', ''],
+    ['vmid', 112],
+    ['backupType', {}],
+    ['backupTime', null],
+    ['files', undefined],
+    ['files', null],
+    ['files', {}],
+    ['files', [42]],
+    ['instance', {}],
+    ['datastore', []],
+    ['namespace', 1],
+    ['size', '1000'],
+    ['size', -1],
+    ['size', Number.NaN],
+    ['protected', 'false'],
+    ['verified', 1],
+    ['inProgress', 'true'],
+    ['writeActivityObserved', {}],
+    ['writeActive', null],
+  ])(
+    'rejects mistyped PBS %s without inventing an identity or completion state',
+    (field, value) => {
+      expect(() =>
+        parsePBSBackupInventory({ data: { backups: [{ ...pbs, [field as string]: value }] } }),
+      ).toThrow(BackupInventoryFormatError);
+    },
+  );
+
+  it.each([
+    ['backupTasks', task, 'status', {}],
+    ['backupTasks', task, 'startTime', null],
+    ['backupTasks', task, 'endTime', 1],
+    ['backupTasks', task, 'error', []],
+    ['storageBackups', archive, 'id', ' '],
+    ['storageBackups', archive, 'vmid', '112'],
+    ['storageBackups', archive, 'vmid', 1.5],
+    ['storageBackups', archive, 'vmid', -1],
+    ['storageBackups', archive, 'time', {}],
+    ['storageBackups', archive, 'type', null],
+    ['storageBackups', archive, 'node', {}],
+    ['storageBackups', archive, 'instance', 1],
+    ['storageBackups', archive, 'storage', []],
+    ['storageBackups', archive, 'format', {}],
+    ['storageBackups', archive, 'volid', []],
+    ['storageBackups', archive, 'size', Number.POSITIVE_INFINITY],
+    ['storageBackups', archive, 'protected', 'false'],
+    ['storageBackups', archive, 'verified', 1],
+    ['storageBackups', archive, 'isPBS', 'false'],
+    ['storageBackups', archive, 'inProgress', 'true'],
+    ['guestSnapshots', snapshot, 'name', {}],
+    ['guestSnapshots', snapshot, 'description', []],
+    ['guestSnapshots', snapshot, 'sizeBytes', -1],
+  ] as const)('rejects mistyped PVE %s.%s', (key, row, field, value) => {
+    expect(() =>
+      parsePVEBackupInventory({ data: { ...pveData, [key]: [{ ...row, [field]: value }] } }),
+    ).toThrow(BackupInventoryFormatError);
+  });
+
+  it('preserves valid zero values, host identifiers and boolean completion facts', () => {
+    const row = {
+      ...pbs,
+      vmid: '',
+      backupType: 'host',
+      namespace: '',
+      size: 0,
+      protected: false,
+      verified: false,
+      inProgress: true,
+      writeActivityObserved: true,
+      writeActive: false,
+    };
+    expect(parsePBSBackupInventory({ data: { backups: [row] } }).backups[0]).toEqual(row);
+  });
+
+  it('replaces JSON decoding errors with fixed copy that contains no response content', async () => {
+    const response = new Response('SYNTHETIC_PRIVATE_BODY_DO_NOT_DISPLAY');
+    await expect(readBackupInventoryJSON(response)).rejects.toEqual(
+      new BackupInventoryFormatError(),
+    );
+    await expect(readBackupInventoryJSON(new Response('null'))).resolves.toBeNull();
+  });
+});
diff --git a/frontend-modern/src/features/proxmox/proxmoxBackupInventory.ts b/frontend-modern/src/features/proxmox/proxmoxBackupInventory.ts
new file mode 100644
index 0000000000..485bae6d0e
--- /dev/null
+++ b/frontend-modern/src/features/proxmox/proxmoxBackupInventory.ts
@@ -0,0 +1,131 @@
+import type {
+  BackupTask,
+  GuestSnapshot,
+  PBSBackup,
+  PBSBackupsPayload,
+  PVEBackupsPayload,
+  StorageBackup,
+} from '@/types/api';
+
+export class BackupInventoryFormatError extends Error {
+  constructor() {
+    // Never include response bodies, provider identifiers or JSON parser text.
+    super('The response format is invalid. Missing restore points do not mean no backups exist.');
+    this.name = 'BackupInventoryFormatError';
+  }
+}
+
+type FieldCheck = (value: unknown) => boolean;
+type RowShape = Readonly<Record<string, FieldCheck>>;
+const isRecord = (value: unknown): value is Record<string, unknown> =>
+  value !== null && typeof value === 'object' && !Array.isArray(value);
+const isString: FieldCheck = (value) => typeof value === 'string';
+const isID: FieldCheck = (value) => typeof value === 'string' && value.trim().length > 0;
+const isBoolean: FieldCheck = (value) => typeof value === 'boolean';
+const isNonnegativeNumber: FieldCheck = (value) =>
+  typeof value === 'number' && Number.isFinite(value) && value >= 0;
+const isGuestID: FieldCheck = (value) => isNonnegativeNumber(value) && Number.isSafeInteger(value);
+const optional =
+  (check: FieldCheck): FieldCheck =>
+  (value) =>
+    value === undefined || check(value);
+const isFiles: FieldCheck = (value) => Array.isArray(value) && value.every(isString);
+
+// Validate what the recovery model consumes, without guessing missing identity,
+// coercing completion flags, silently dropping bad rows or rejecting extra fields.
+// Optional display fields retain the model's existing unknown/fallback behaviour.
+const pveGuestShape: RowShape = {
+  id: isID,
+  vmid: isGuestID,
+  type: isString,
+  node: optional(isString),
+  instance: optional(isString),
+};
+const taskShape: RowShape = {
+  ...pveGuestShape,
+  status: isString,
+  startTime: isString,
+  endTime: optional(isString),
+  error: optional(isString),
+};
+const archiveShape: RowShape = {
+  ...pveGuestShape,
+  time: isString,
+  storage: optional(isString),
+  format: optional(isString),
+  volid: optional(isString),
+  size: optional(isNonnegativeNumber),
+  protected: optional(isBoolean),
+  isPBS: optional(isBoolean),
+  verified: optional(isBoolean),
+  inProgress: optional(isBoolean),
+};
+const snapshotShape: RowShape = {
+  ...pveGuestShape,
+  time: isString,
+  name: optional(isString),
+  description: optional(isString),
+  sizeBytes: optional(isNonnegativeNumber),
+};
+const pbsShape: RowShape = {
+  id: isID,
+  vmid: isString,
+  backupType: isString,
+  backupTime: isString,
+  files: isFiles,
+  instance: optional(isString),
+  datastore: optional(isString),
+  namespace: optional(isString),
+  size: optional(isNonnegativeNumber),
+  protected: optional(isBoolean),
+  verified: optional(isBoolean),
+  inProgress: optional(isBoolean),
+  writeActivityObserved: optional(isBoolean),
+  writeActive: optional(isBoolean),
+};
+
+function inventoryData(payload: unknown): Record<string, unknown> {
+  if (!isRecord(payload) || !isRecord(payload.data)) throw new BackupInventoryFormatError();
+  return payload.data;
+}
+
+function collection<T>(
+  data: Record<string, unknown>,
+  key: string,
+  shape: RowShape,
+  allowNil = false,
+): T[] {
+  const value = data[key];
+  // The PVE handler can encode its empty Go slices as null. A missing field
+  // is not that observation. PBS normalizes both its list and files to arrays.
+  if (allowNil && value === null) return [];
+  const fields = Object.entries(shape);
+  if (
+    !Array.isArray(value) ||
+    !value.every((row) => isRecord(row) && fields.every(([field, check]) => check(row[field])))
+  ) {
+    throw new BackupInventoryFormatError();
+  }
+  return value as T[];
+}
+
+export function parsePVEBackupInventory(payload: unknown): PVEBackupsPayload {
+  const data = inventoryData(payload);
+  return {
+    backupTasks: collection<BackupTask>(data, 'backupTasks', taskShape, true),
+    storageBackups: collection<StorageBackup>(data, 'storageBackups', archiveShape, true),
+    guestSnapshots: collection<GuestSnapshot>(data, 'guestSnapshots', snapshotShape, true),
+  };
+}
+
+export function parsePBSBackupInventory(payload: unknown): PBSBackupsPayload {
+  return { backups: collection<PBSBackup>(inventoryData(payload), 'backups', pbsShape) };
+}
+
+export async function readBackupInventoryJSON(response: Response): Promise<unknown> {
+  try {
+    return await response.json();
+  } catch {
+    throw new BackupInventoryFormatError();
+  }
+}