diff --git a/Vault/Package.swift b/Vault/Package.swift
index 690b6f04b..f3c529915 100644
--- a/Vault/Package.swift
+++ b/Vault/Package.swift
@@ -232,7 +232,7 @@ let package = Package(
         ),
         .testTarget(
             name: "VaultFeedTests",
-            dependencies: ["VaultFeed", "VaultCore", "FoundationExtensions", "TestHelpers"],
+            dependencies: ["VaultFeed", "VaultBackup", "VaultCore", "FoundationExtensions", "TestHelpers"],
             swiftSettings: swiftSettings,
             plugins: testTargetPlugins,
         ),
diff --git a/Vault/Tests/VaultFeedTests/Storage/BackupRoundTripTests.swift b/Vault/Tests/VaultFeedTests/Storage/BackupRoundTripTests.swift
new file mode 100644
index 000000000..a0a86b45c
--- /dev/null
+++ b/Vault/Tests/VaultFeedTests/Storage/BackupRoundTripTests.swift
@@ -0,0 +1,172 @@
+import Foundation
+import FoundationExtensions
+import PDFKit
+import SwiftData
+import Testing
+import VaultBackup
+import VaultCore
+import VaultExport
+import VaultKeygen
+@testable import VaultFeed
+
+/// End-to-end backup pipeline: seed store → export → encrypt → attach to
+/// PDF → serialize → detach → decrypt → import into a second store. The
+/// individual stages are unit-covered in VaultBackupTests; this proves
+/// the composition, and in particular that duress metadata (killphrase
+/// and search-passphrase digests, lock state, searchable level) survives
+/// the full trip (MANIFESTO C10).
+struct BackupRoundTripTests {
+    private let killDigester = KillphraseDigester(key: .zero())
+    private let searchDigester = SearchPassphraseDigester(key: .zero())
+
+    @Test
+    func pdfRoundTrip_merge_preservesDuressMetadata() async throws {
+        let source = try makeInMemoryStore()
+        let armedItem = anySecureNote(title: "armed").wrapInAnyVaultItem(
+            killphrase: killDigester.makeDigest(phrase: "kill me"),
+        )
+        let hiddenItem = anySecureNote(title: "hidden").wrapInAnyVaultItem(
+            visibility: .onlySearch,
+            searchableLevel: .onlyPassphrase,
+            searchPassphrase: searchDigester.makeDigest(phrase: "find me"),
+        )
+        let lockedItem = anySecureNote(title: "locked").wrapInAnyVaultItem(
+            lockState: .lockedWithNativeSecurity,
+        )
+        let tag = anyVaultItemTag()
+        try await source.importAndOverrideVault(payload: .init(
+            userDescription: "",
+            items: [armedItem, hiddenItem, lockedItem],
+            tags: [tag],
+        ))
+
+        let restored = try await roundTripThroughPDF(source: source)
+        let destination = try makeInMemoryStore()
+        try await destination.importAndMergeVault(payload: restored)
+
+        // Tags and item count survive.
+        let allItems = try await destination.retrieve(query: .init())
+        #expect(try await destination.retrieveTags().map(\.id) == [tag.id])
+
+        // Lock state and searchable level survive on the restored rows.
+        let restoredLocked = try #require(allItems.items.first(where: { $0.id == lockedItem.id }))
+        #expect(restoredLocked.metadata.lockState == .lockedWithNativeSecurity)
+
+        // The hidden item is reachable only through a matching digest.
+        let withoutMatcher = try await destination.retrieve(query: .init(filterText: "hidden"))
+        #expect(withoutMatcher.items.map(\.id).contains(hiddenItem.id) == false)
+        let withMatcher = try await destination.retrieve(
+            query: .init(filterText: "find me"),
+            searchPassphraseMatcher: searchDigester,
+        )
+        #expect(withMatcher.items.map(\.id).contains(hiddenItem.id))
+
+        // The killphrase still fires with the original phrase.
+        let didDelete = await destination.deleteItems(matchingKillphrase: "kill me", using: killDigester)
+        #expect(didDelete == true)
+        let afterKill = try await destination.retrieve(query: .init())
+        #expect(afterKill.items.map(\.id).contains(armedItem.id) == false)
+    }
+
+    @Test
+    func pdfRoundTrip_override_replacesExistingVault() async throws {
+        let source = try makeInMemoryStore()
+        let exportedItem = anySecureNote(title: "exported").wrapInAnyVaultItem()
+        try await source.importAndOverrideVault(payload: .init(
+            userDescription: "",
+            items: [exportedItem],
+            tags: [],
+        ))
+        let destination = try makeInMemoryStore()
+        let sacrificialItem = anySecureNote(title: "sacrificial").wrapInAnyVaultItem()
+        try await destination.importAndOverrideVault(payload: .init(
+            userDescription: "",
+            items: [sacrificialItem],
+            tags: [],
+        ))
+
+        let restored = try await roundTripThroughPDF(source: source)
+        try await destination.importAndOverrideVault(payload: restored)
+
+        let items = try await destination.retrieve(query: .init())
+        #expect(items.items.map(\.id) == [exportedItem.id])
+    }
+
+    @Test
+    func pdfRoundTrip_wrongKey_failsDecrypt() async throws {
+        let source = try makeInMemoryStore()
+        try await source.importAndOverrideVault(payload: .init(
+            userDescription: "",
+            items: [anySecureNote(title: "secret").wrapInAnyVaultItem()],
+            tags: [],
+        ))
+        let payload = try await source.exportVault(userDescription: "Backup")
+        let pdfData = try makePDFData(payload: payload, backupPassword: anyBackupPassword())
+
+        let pdf = try #require(PDFDocument(data: pdfData))
+        let encryptedVault = try VaultBackupPDFDetatcherImpl().detachEncryptedVault(fromPDF: pdf)
+        let wrongKey = try KeyData<32>(data: Data(repeating: 0xEE, count: 32))
+
+        #expect(throws: (any Error).self) {
+            try EncryptedVaultDecoderImpl().decryptAndDecode(key: wrongKey, encryptedVault: encryptedVault)
+        }
+    }
+}
+
+// MARK: - Helpers
+
+extension BackupRoundTripTests {
+    private func makeInMemoryStore() throws -> PersistedLocalVaultStore {
+        let container = try ModelContainer(
+            for: PersistedVaultItem.self, PersistedVaultTag.self,
+            configurations: .init(isStoredInMemoryOnly: true),
+        )
+        return PersistedLocalVaultStore(modelContainer: container)
+    }
+
+    /// Export → encrypt → PDF attach → `dataRepresentation()` →
+    /// `PDFDocument(data:)` → detach → decrypt. The serialize/reparse
+    /// step keeps the trip honest about PDF serialization.
+    private func roundTripThroughPDF(source: PersistedLocalVaultStore) async throws -> VaultApplicationPayload {
+        let backupPassword = anyBackupPassword()
+        let payload = try await source.exportVault(userDescription: "Backup")
+        let pdfData = try makePDFData(payload: payload, backupPassword: backupPassword)
+
+        let reparsedPDF = try #require(PDFDocument(data: pdfData))
+        let encryptedVault = try VaultBackupPDFDetatcherImpl().detachEncryptedVault(fromPDF: reparsedPDF)
+        return try EncryptedVaultDecoderImpl().decryptAndDecode(
+            key: backupPassword.key,
+            encryptedVault: encryptedVault,
+        )
+    }
+
+    private func makePDFData(
+        payload: VaultApplicationPayload,
+        backupPassword: DerivedEncryptionKey,
+    ) throws -> Data {
+        let clock = EpochClockMock(currentTime: 100)
+        let encryptedVault = try EncryptedVaultEncoder(clock: clock, backupPassword: backupPassword)
+            .encryptAndEncode(payload: payload)
+        let exportPayload = VaultExportPayload(
+            encryptedVault: encryptedVault,
+            userDescription: "Round-trip test backup",
+            created: clock.currentDate,
+        )
+        let generator = VaultBackupPDFGenerator(
+            size: A4DocumentSize(),
+            documentTitle: "Round Trip",
+            applicationName: "Vault",
+            authorName: "Vault",
+        )
+        let pdf = try generator.makePDF(payload: exportPayload)
+        return try #require(pdf.dataRepresentation())
+    }
+
+    private func anyBackupPassword() -> DerivedEncryptionKey {
+        DerivedEncryptionKey(
+            key: (try? KeyData<32>(data: Data(repeating: 0x45, count: 32))) ?? .zero(),
+            salt: Data.random(count: 16),
+            keyDervier: .testing,
+        )
+    }
+}