diff --git a/app/src/test/kotlin/org/libremail/data/attachment/AttachmentUriGrantsTest.kt b/app/src/test/kotlin/org/libremail/data/attachment/AttachmentUriGrantsTest.kt
index b9ff6f3..e99ee50 100644
--- a/app/src/test/kotlin/org/libremail/data/attachment/AttachmentUriGrantsTest.kt
+++ b/app/src/test/kotlin/org/libremail/data/attachment/AttachmentUriGrantsTest.kt
@@ -1,14 +1,33 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 package org.libremail.data.attachment
 
+import android.content.ContentResolver
+import android.content.Context
+import android.content.Intent
+import android.net.Uri
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.mockkStatic
+import io.mockk.unmockkAll
+import io.mockk.verify
+import kotlinx.coroutines.test.runTest
+import org.junit.After
 import org.junit.Test
+import org.libremail.data.local.dao.DraftDao
+import org.libremail.data.local.dao.OutboxDao
+import org.libremail.data.local.entity.DraftEntity
+import org.libremail.data.local.entity.OutboxEntity
 import kotlin.test.assertEquals
 
 /**
  * The release decision that [AttachmentUriGrants] runs after a draft/outbox row is deleted: a picked
  * URI's persistable grant is released only when no *remaining* draft or outbox row still references
- * it. The Android release call itself (`releasePersistableUriPermission`) is a thin wrapper; the
- * decision here is the part worth pinning.
+ * it. The pure [unreferencedUris] decision is pinned first; the instance-method tests then wire that
+ * decision to the DAOs and the (mocked) content resolver, covering the empty-set short-circuit, the
+ * still-referenced guard against drafts and outbox rows alike, and the swallowed SecurityException
+ * from releasing a grant the app never actually held.
  */
 class AttachmentUriGrantsTest {
 
@@ -47,4 +66,95 @@ class AttachmentUriGrantsTest {
             unreferencedUris(candidates = listOf("content://a"), referenced = setOf("content://a")),
         )
     }
+
+    // --- releaseUnreferenced: wiring the decision to the DAOs and the content resolver --------------
+
+    private val draftDao = mockk<DraftDao>()
+    private val outboxDao = mockk<OutboxDao>()
+    private val resolver = mockk<ContentResolver>(relaxed = true)
+    private val context = mockk<Context>()
+    private val grants = AttachmentUriGrants(context, draftDao, outboxDao)
+
+    @After
+    fun tearDown() = unmockkAll()
+
+    private fun draft(vararg uris: String) = DraftEntity(
+        id = "draft-${uris.joinToString()}",
+        accountId = "a",
+        toAddresses = "",
+        ccAddresses = "",
+        subject = "",
+        body = "",
+        updatedAt = 0L,
+        attachments = attachmentsJson(*uris),
+    )
+
+    private fun outbox(vararg uris: String) = OutboxEntity(
+        id = "outbox-${uris.joinToString()}",
+        accountId = "a",
+        toAddresses = "",
+        ccAddresses = "",
+        subject = "",
+        body = "",
+        createdAt = 0L,
+        attachments = attachmentsJson(*uris),
+    )
+
+    private fun attachmentsJson(vararg uris: String): String =
+        if (uris.isEmpty()) "" else uris.joinToString(",", "[", "]") { """{"uri":"$it","name":"n"}""" }
+
+    private fun stubResolver() {
+        mockkStatic(Uri::class)
+        every { Uri.parse(any()) } returns mockk(relaxed = true)
+        every { context.contentResolver } returns resolver
+    }
+
+    @Test
+    fun `releaseUnreferenced short-circuits on an empty uri set without querying the daos`() = runTest {
+        grants.releaseUnreferenced(emptyList())
+
+        coVerify(exactly = 0) { draftDao.getAll() }
+        coVerify(exactly = 0) { outboxDao.getAll() }
+    }
+
+    @Test
+    fun `releaseUnreferenced releases only the uris no remaining draft or outbox row references`() = runTest {
+        stubResolver()
+        // "content://shared" is still attached to a live draft; "content://gone" is referenced by nobody.
+        coEvery { draftDao.getAll() } returns listOf(draft("content://shared"))
+        coEvery { outboxDao.getAll() } returns emptyList()
+
+        grants.releaseUnreferenced(listOf("content://gone", "content://shared"))
+
+        // The still-referenced uri is kept (never parsed for release); only the orphan is released.
+        verify(exactly = 1) { Uri.parse("content://gone") }
+        verify(exactly = 0) { Uri.parse("content://shared") }
+        verify(exactly = 1) {
+            resolver.releasePersistableUriPermission(any(), eq(Intent.FLAG_GRANT_READ_URI_PERMISSION))
+        }
+    }
+
+    @Test
+    fun `releaseUnreferenced keeps a uri still referenced by a queued outbox row`() = runTest {
+        stubResolver()
+        coEvery { draftDao.getAll() } returns emptyList()
+        coEvery { outboxDao.getAll() } returns listOf(outbox("content://queued"))
+
+        grants.releaseUnreferenced(listOf("content://queued"))
+
+        verify(exactly = 0) { resolver.releasePersistableUriPermission(any(), any()) }
+    }
+
+    @Test
+    fun `releaseUnreferenced swallows the SecurityException from releasing a grant it never held`() = runTest {
+        stubResolver()
+        coEvery { draftDao.getAll() } returns emptyList()
+        coEvery { outboxDao.getAll() } returns emptyList()
+        every { resolver.releasePersistableUriPermission(any(), any()) } throws SecurityException("no grant held")
+
+        // Releasing a never-persisted uri throws SecurityException inside runCatching; it must not escape.
+        grants.releaseUnreferenced(listOf("content://never-held"))
+
+        verify { resolver.releasePersistableUriPermission(any(), any()) }
+    }
 }
diff --git a/app/src/test/kotlin/org/libremail/data/security/CredentialStoreTest.kt b/app/src/test/kotlin/org/libremail/data/security/CredentialStoreTest.kt
new file mode 100644
index 0000000..9ed451e
--- /dev/null
+++ b/app/src/test/kotlin/org/libremail/data/security/CredentialStoreTest.kt
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.data.security
+
+import io.mockk.Runs
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.every
+import io.mockk.just
+import io.mockk.mockk
+import io.mockk.slot
+import io.mockk.verify
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+import org.libremail.data.local.dao.CredentialDao
+import org.libremail.data.local.entity.CredentialEntity
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+
+/**
+ * [CredentialStore] wraps a single encrypted-secret row per account: it encrypts on the way in,
+ * decrypts on the way out, and reports a missing row as `null`. The Keystore crypto is mocked so the
+ * store's own read/modify/write and null-handling are what these pin — the AES-GCM round-trip itself
+ * is [KeystoreCrypto]'s concern and is device-bound.
+ */
+class CredentialStoreTest {
+
+    private val crypto = mockk<KeystoreCrypto>()
+    private val dao = mockk<CredentialDao>()
+    private val store = CredentialStore(crypto, dao)
+
+    @Test
+    fun `saveSecret encrypts the secret and upserts it under the account id`() = runTest {
+        every { crypto.encrypt("token") } returns "cipher(token)"
+        val saved = slot<CredentialEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        store.saveSecret("acct", "token")
+
+        assertEquals("acct", saved.captured.accountId)
+        assertEquals("cipher(token)", saved.captured.encryptedSecret)
+    }
+
+    @Test
+    fun `loadSecret decrypts the stored ciphertext`() = runTest {
+        coEvery { dao.getById("acct") } returns CredentialEntity("acct", "cipher(token)")
+        every { crypto.decrypt("cipher(token)") } returns "token"
+
+        assertEquals("token", store.loadSecret("acct"))
+    }
+
+    @Test
+    fun `loadSecret returns null when the account has no stored secret`() = runTest {
+        coEvery { dao.getById("acct") } returns null
+
+        assertNull(store.loadSecret("acct"))
+        // With no row there is nothing to decrypt.
+        verify(exactly = 0) { crypto.decrypt(any()) }
+    }
+
+    @Test
+    fun `delete removes the account's secret row`() = runTest {
+        coEvery { dao.deleteById("acct") } just Runs
+
+        store.delete("acct")
+
+        coVerify { dao.deleteById("acct") }
+    }
+}
diff --git a/app/src/test/kotlin/org/libremail/data/security/EncryptedCacheGuardTest.kt b/app/src/test/kotlin/org/libremail/data/security/EncryptedCacheGuardTest.kt
new file mode 100644
index 0000000..3e5cd3c
--- /dev/null
+++ b/app/src/test/kotlin/org/libremail/data/security/EncryptedCacheGuardTest.kt
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package org.libremail.data.security
+
+import io.mockk.every
+import io.mockk.mockk
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+import org.libremail.data.settings.AppSettings
+import org.libremail.data.settings.SettingsRepository
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+/**
+ * [EncryptedCacheGuard.isCacheLocked] is the pure truth table `appLock && encryptCache && !unlocked`:
+ * only when app-lock AND the encrypted cache are both on AND the passphrase session has not been
+ * unlocked would opening the Room DB block on authentication, so background work must defer. Every
+ * other combination is safe to proceed. Both collaborators are DataStore/in-memory only, so this is a
+ * clean JVM test.
+ */
+class EncryptedCacheGuardTest {
+
+    private val settingsRepository = mockk<SettingsRepository>()
+    private val session = mockk<PassphraseSession>()
+
+    private suspend fun cacheLocked(appLock: Boolean, encryptCache: Boolean, unlocked: Boolean): Boolean {
+        every { settingsRepository.settings } returns
+            flowOf(AppSettings(appLock = appLock, encryptCache = encryptCache))
+        every { session.isUnlocked() } returns unlocked
+        return EncryptedCacheGuard(settingsRepository, session).isCacheLocked()
+    }
+
+    @Test
+    fun `locked only when app-lock and encrypted cache are on and the session is not unlocked`() = runTest {
+        assertTrue(cacheLocked(appLock = true, encryptCache = true, unlocked = false))
+    }
+
+    @Test
+    fun `not locked once the passphrase session is unlocked`() = runTest {
+        assertFalse(cacheLocked(appLock = true, encryptCache = true, unlocked = true))
+    }
+
+    @Test
+    fun `not locked when the cache is not encrypted`() = runTest {
+        assertFalse(cacheLocked(appLock = true, encryptCache = false, unlocked = false))
+    }
+
+    @Test
+    fun `not locked when app-lock is off`() = runTest {
+        assertFalse(cacheLocked(appLock = false, encryptCache = true, unlocked = false))
+    }
+
+    @Test
+    fun `not locked when neither app-lock nor encrypted cache is on`() = runTest {
+        assertFalse(cacheLocked(appLock = false, encryptCache = false, unlocked = true))
+    }
+}
diff --git a/app/src/test/kotlin/org/libremail/data/settings/AccountSettingsRepositoryTest.kt b/app/src/test/kotlin/org/libremail/data/settings/AccountSettingsRepositoryTest.kt
index 4a9a08d..d43d281 100644
--- a/app/src/test/kotlin/org/libremail/data/settings/AccountSettingsRepositoryTest.kt
+++ b/app/src/test/kotlin/org/libremail/data/settings/AccountSettingsRepositoryTest.kt
@@ -1,17 +1,22 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 package org.libremail.data.settings
 
+import app.cash.turbine.test
 import io.mockk.Runs
 import io.mockk.coEvery
 import io.mockk.coVerify
+import io.mockk.every
 import io.mockk.just
 import io.mockk.mockk
 import io.mockk.slot
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.test.runTest
 import org.junit.Test
 import org.libremail.data.local.dao.AccountSettingsDao
 import org.libremail.data.local.entity.AccountSettingsEntity
 import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
 import kotlin.test.assertTrue
 
 class AccountSettingsRepositoryTest {
@@ -65,4 +70,101 @@ class AccountSettingsRepositoryTest {
 
         coVerify(exactly = 0) { dao.upsert(any()) }
     }
+
+    @Test
+    fun `observe maps the stored row to the domain model`() = runTest {
+        every { dao.observe("acct") } returns flowOf(
+            AccountSettingsEntity("acct", signature = "sig", signatureEnabled = false, notificationsEnabled = true),
+        )
+
+        repository.observe("acct").test {
+            val settings = awaitItem()
+            assertEquals("sig", settings.signature)
+            assertFalse(settings.signatureEnabled)
+            assertTrue(settings.notificationsEnabled)
+            awaitComplete()
+        }
+    }
+
+    @Test
+    fun `observe emits defaults for an account with no stored row`() = runTest {
+        every { dao.observe("acct") } returns flowOf(null)
+
+        repository.observe("acct").test {
+            val settings = awaitItem()
+            assertEquals("acct", settings.accountId)
+            assertEquals("", settings.signature)
+            assertTrue(settings.signatureEnabled)
+            awaitComplete()
+        }
+    }
+
+    @Test
+    fun `setSignatureEnabled reads, modifies, and writes the row`() = runTest {
+        coEvery { dao.get("acct") } returns
+            AccountSettingsEntity("acct", signature = "keep", signatureEnabled = true, notificationsEnabled = true)
+        val saved = slot<AccountSettingsEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.setSignatureEnabled("acct", false)
+
+        assertFalse(saved.captured.signatureEnabled)
+        // Untouched fields are preserved.
+        assertEquals("keep", saved.captured.signature)
+    }
+
+    @Test
+    fun `setNotificationsEnabled reads, modifies, and writes the row`() = runTest {
+        coEvery { dao.get("acct") } returns AccountSettingsEntity("acct", notificationsEnabled = true)
+        val saved = slot<AccountSettingsEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.setNotificationsEnabled("acct", false)
+
+        assertFalse(saved.captured.notificationsEnabled)
+    }
+
+    @Test
+    fun `setRetentionCount clamps a negative override to zero`() = runTest {
+        coEvery { dao.get("acct") } returns AccountSettingsEntity("acct")
+        val saved = slot<AccountSettingsEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.setRetentionCount("acct", -5)
+
+        assertEquals(0, saved.captured.retentionCount)
+    }
+
+    @Test
+    fun `setRetentionCount preserves null as inherit-the-global-default`() = runTest {
+        coEvery { dao.get("acct") } returns AccountSettingsEntity("acct", retentionCount = 10)
+        val saved = slot<AccountSettingsEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.setRetentionCount("acct", null)
+
+        assertNull(saved.captured.retentionCount)
+    }
+
+    @Test
+    fun `setRetentionMonths clamps a negative override to zero`() = runTest {
+        coEvery { dao.get("acct") } returns AccountSettingsEntity("acct")
+        val saved = slot<AccountSettingsEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.setRetentionMonths("acct", -3)
+
+        assertEquals(0, saved.captured.retentionMonths)
+    }
+
+    @Test
+    fun `setRetentionMonths keeps a positive override as given`() = runTest {
+        coEvery { dao.get("acct") } returns AccountSettingsEntity("acct")
+        val saved = slot<AccountSettingsEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.setRetentionMonths("acct", 6)
+
+        assertEquals(6, saved.captured.retentionMonths)
+    }
 }
diff --git a/app/src/test/kotlin/org/libremail/data/settings/SignatureRepositoryTest.kt b/app/src/test/kotlin/org/libremail/data/settings/SignatureRepositoryTest.kt
index b38c0df..3430e18 100644
--- a/app/src/test/kotlin/org/libremail/data/settings/SignatureRepositoryTest.kt
+++ b/app/src/test/kotlin/org/libremail/data/settings/SignatureRepositoryTest.kt
@@ -1,17 +1,22 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 package org.libremail.data.settings
 
+import app.cash.turbine.test
 import io.mockk.Runs
 import io.mockk.coEvery
 import io.mockk.coVerify
+import io.mockk.every
 import io.mockk.just
 import io.mockk.mockk
 import io.mockk.slot
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.test.runTest
 import org.junit.Test
 import org.libremail.data.local.dao.SignatureDao
 import org.libremail.data.local.entity.SignatureEntity
+import kotlin.test.assertEquals
 import kotlin.test.assertFalse
+import kotlin.test.assertNull
 import kotlin.test.assertTrue
 
 class SignatureRepositoryTest {
@@ -71,4 +76,75 @@ class SignatureRepositoryTest {
         repository.setDefault("acct", "s1")
         coVerify { dao.setDefault("acct", "s1") }
     }
+
+    @Test
+    fun `observeForAccount maps entity rows to domain signatures`() = runTest {
+        every { dao.observeForAccount("acct") } returns flowOf(
+            listOf(entity("s1", isDefault = true), entity("s2", isDefault = false)),
+        )
+
+        repository.observeForAccount("acct").test {
+            val signatures = awaitItem()
+            assertEquals(listOf("s1", "s2"), signatures.map { it.id })
+            assertEquals("acct", signatures.first().accountId)
+            assertTrue(signatures.first().isDefault)
+            awaitComplete()
+        }
+    }
+
+    @Test
+    fun `get maps the stored row to a domain signature`() = runTest {
+        coEvery { dao.getById("s1") } returns entity("s1", isDefault = true)
+
+        val signature = repository.get("s1")
+
+        assertEquals("s1", signature?.id)
+        assertEquals("<p>x</p>", signature?.html)
+        assertTrue(signature?.isDefault == true)
+    }
+
+    @Test
+    fun `get returns null for an unknown id`() = runTest {
+        coEvery { dao.getById("missing") } returns null
+
+        assertNull(repository.get("missing"))
+    }
+
+    @Test
+    fun `getDefault returns the account's default signature`() = runTest {
+        coEvery { dao.getDefault("acct") } returns entity("s1", isDefault = true)
+
+        assertEquals("s1", repository.getDefault("acct")?.id)
+    }
+
+    @Test
+    fun `getDefault returns null when the account has no default`() = runTest {
+        coEvery { dao.getDefault("acct") } returns null
+
+        assertNull(repository.getDefault("acct"))
+    }
+
+    @Test
+    fun `update rewrites the name and html of an existing signature`() = runTest {
+        coEvery { dao.getById("s1") } returns entity("s1", isDefault = true)
+        val saved = slot<SignatureEntity>()
+        coEvery { dao.upsert(capture(saved)) } just Runs
+
+        repository.update("s1", "Renamed", "<p>new</p>")
+
+        assertEquals("Renamed", saved.captured.name)
+        assertEquals("<p>new</p>", saved.captured.contentHtml)
+        // Editing a signature leaves its default flag and account untouched.
+        assertTrue(saved.captured.isDefault)
+        assertEquals("acct", saved.captured.accountId)
+    }
+
+    @Test
+    fun `update is a no-op for an unknown id`() = runTest {
+        coEvery { dao.getById("missing") } returns null
+
+        repository.update("missing", "X", "<p>y</p>")
+
+        coVerify(exactly = 0) { dao.upsert(any()) }
+    }
 }
diff --git a/app/src/test/kotlin/org/libremail/data/sync/SyncSchedulerTest.kt b/app/src/test/kotlin/org/libremail/data/sync/SyncSchedulerTest.kt
index 81d267c..35da23f 100644
--- a/app/src/test/kotlin/org/libremail/data/sync/SyncSchedulerTest.kt
+++ b/app/src/test/kotlin/org/libremail/data/sync/SyncSchedulerTest.kt
@@ -66,6 +66,19 @@ class SyncSchedulerTest {
         }
     }
 
+    @Test
+    fun `periodic report purge is enqueued with UPDATE so upgrades re-apply its schedule`() {
+        scheduler.schedulePeriodicReportPurge()
+
+        verify {
+            workManager.enqueueUniquePeriodicWork(
+                "libremail_periodic_report_purge",
+                ExistingPeriodicWorkPolicy.UPDATE,
+                any<PeriodicWorkRequest>(),
+            )
+        }
+    }
+
     // The one-shot kicks are a separate concern from #96 and keep their existing policies: syncNow and
     // pruneNow REPLACE for a clean immediate attempt; backfillNow KEEPs an in-flight all-account run.
 
diff --git a/app/src/test/kotlin/org/libremail/mail/SmtpSenderTest.kt b/app/src/test/kotlin/org/libremail/mail/SmtpSenderTest.kt
index 6eaeb81..e9ba07c 100644
--- a/app/src/test/kotlin/org/libremail/mail/SmtpSenderTest.kt
+++ b/app/src/test/kotlin/org/libremail/mail/SmtpSenderTest.kt
@@ -15,6 +15,7 @@ import org.libremail.domain.model.OutgoingMessage
 import org.libremail.domain.model.SmtpParams
 import java.io.File
 import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
 import kotlin.test.assertFalse
 import kotlin.test.assertNull
 import kotlin.test.assertTrue
@@ -288,4 +289,96 @@ class SmtpSenderTest {
         // Jakarta Mail strips the Bcc header before transmission, so it must not appear on the wire.
         received.forEach { assertNull(it.getHeader("Bcc")) }
     }
+
+    @Test
+    fun `send copies cc recipients on the wire`() = runTest {
+        sender.send(
+            params = params(),
+            from = "sender@example.org",
+            message = OutgoingMessage(
+                accountId = "x",
+                to = "bob@example.org",
+                cc = "carol@example.org",
+                subject = "With CC",
+                body = "Hello cc.",
+            ),
+        )
+
+        // To + Cc are both in the envelope, so GreenMail delivers two copies; Cc stays on the wire.
+        greenMail.waitForIncomingEmail(2)
+        val received = greenMail.receivedMessages
+        assertEquals(2, received.size)
+        assertTrue(GreenMailUtil.getWholeMessage(received[0]).contains("carol@example.org"), "missing Cc header")
+    }
+
+    @Test
+    fun `an inline image plus a regular attachment nests a related body inside mixed`() = runTest {
+        val image = File.createTempFile("libremail-inline", ".png").apply { writeText("PNGDATA") }
+        val doc = File.createTempFile("libremail-doc", ".txt").apply { writeText("attached doc") }
+
+        sender.send(
+            params = params(),
+            from = "sender@example.org",
+            message = OutgoingMessage(
+                accountId = "x",
+                to = "bob@example.org",
+                subject = "Inline + file",
+                body = "See image and file",
+                bodyHtml = "<p>See <img src=\"cid:logo@libremail\"></p>",
+            ),
+            attachments = listOf(
+                SendableAttachment(image, contentId = "logo@libremail", isInline = true),
+                SendableAttachment(doc),
+            ),
+        )
+
+        greenMail.waitForIncomingEmail(1)
+        val received = greenMail.receivedMessages.single()
+        // A regular attachment makes the top level multipart/mixed; the inline image wraps the body in
+        // a multipart/related nested as the first mixed part (the `bodyPart` inline branch).
+        assertTrue(received.contentType.contains("multipart/mixed", ignoreCase = true), received.contentType)
+        val raw = GreenMailUtil.getWholeMessage(received)
+        assertTrue(raw.contains("multipart/related", ignoreCase = true), "inline body must be wrapped in related")
+        assertTrue(raw.contains("<logo@libremail>"), "inline part must carry a matching Content-ID")
+        assertTrue(raw.contains(doc.name), "regular attachment must be present")
+        image.delete()
+        doc.delete()
+    }
+
+    @Test
+    fun `send fails and delivers nothing when a required STARTTLS upgrade is unavailable`() = runTest {
+        // The plain GreenMail server does not advertise STARTTLS; with a strict (required) STARTTLS
+        // policy the client refuses to fall back to plaintext, so send throws and nothing is delivered.
+        // Exercises the STARTTLS + XOAUTH2 branches of the property builder and the connect error path.
+        assertFailsWith<Exception> {
+            sender.send(
+                params = params(security = MailSecurity.STARTTLS, useXoauth2 = true),
+                from = "sender@example.org",
+                message = OutgoingMessage(accountId = "x", to = "bob@example.org", subject = "No TLS", body = "x"),
+            )
+        }
+        assertTrue(greenMail.receivedMessages.isEmpty())
+    }
+
+    @Test
+    fun `send fails when implicit TLS cannot be negotiated`() = runTest {
+        // Driving the implicit-TLS (SSL_TLS) path at the plain SMTP port makes the handshake fail, so
+        // send throws — covering the ssl.enable branch of the property builder and the connect error path.
+        assertFailsWith<Exception> {
+            sender.send(
+                params = params(security = MailSecurity.SSL_TLS),
+                from = "sender@example.org",
+                message = OutgoingMessage(accountId = "x", to = "bob@example.org", subject = "No TLS", body = "x"),
+            )
+        }
+    }
+
+    private fun params(security: MailSecurity = MailSecurity.NONE, useXoauth2: Boolean = false) = SmtpParams(
+        host = "127.0.0.1",
+        port = greenMail.smtp.port,
+        security = security,
+        username = "sender@example.org",
+        secret = "secret",
+        useXoauth2 = useXoauth2,
+    )
 }
diff --git a/app/src/test/kotlin/org/libremail/ui/lock/AppLockViewModelTest.kt b/app/src/test/kotlin/org/libremail/ui/lock/AppLockViewModelTest.kt
index 49f16fd..36890cf 100644
--- a/app/src/test/kotlin/org/libremail/ui/lock/AppLockViewModelTest.kt
+++ b/app/src/test/kotlin/org/libremail/ui/lock/AppLockViewModelTest.kt
@@ -17,6 +17,7 @@ import io.mockk.mockkObject
 import io.mockk.mockkStatic
 import io.mockk.unmockkAll
 import io.mockk.verify
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.flowOf
@@ -40,9 +41,12 @@ import org.libremail.data.settings.AppSettings
 import org.libremail.data.settings.SettingsRepository
 import org.libremail.data.sync.SyncScheduler
 import org.libremail.restart.ProcessRestarter
+import java.util.concurrent.ExecutionException
 import java.util.concurrent.TimeoutException
 import kotlin.test.assertEquals
 import kotlin.test.assertIs
+import kotlin.test.assertNotEquals
+import kotlin.test.assertTrue
 
 /**
  * Wiring guard for #101: the app-lock gate must be an INJECTED, application-scoped dependency so its
@@ -172,6 +176,103 @@ class AppLockViewModelTest {
         verify { processRestarter.restart() }
     }
 
+    @Test
+    fun `recovery still restarts when the re-sync enqueue fails to persist`() = runTest(dispatcher) {
+        val (future, syncScheduler) = enqueueingScheduler()
+        every { future.get(any(), any()) } throws ExecutionException(IllegalStateException("insert failed"))
+        val processRestarter = mockk<ProcessRestarter>(relaxed = true)
+        val vm = clearOnForegroundViewModel(syncScheduler = syncScheduler, processRestarter = processRestarter)
+
+        vm.onForeground()
+        advanceUntilIdle()
+
+        // A failed enqueue is swallowed like a timeout: recovery restarts anyway.
+        verify { future.get(any(), any()) }
+        verify { processRestarter.restart() }
+    }
+
+    @Test
+    fun `recovery still restarts when awaiting the re-sync enqueue is interrupted`() = runTest(dispatcher) {
+        val (future, syncScheduler) = enqueueingScheduler()
+        every { future.get(any(), any()) } throws InterruptedException("interrupted")
+        val processRestarter = mockk<ProcessRestarter>(relaxed = true)
+        val vm = clearOnForegroundViewModel(syncScheduler = syncScheduler, processRestarter = processRestarter)
+
+        vm.onForeground()
+        // The recovery runs inline on this (unconfined) thread and re-sets its interrupt flag; capture and
+        // clear it immediately so it can neither disrupt the scheduler nor leak into a later test.
+        val reInterrupted = Thread.interrupted()
+        advanceUntilIdle()
+
+        // An interrupt while awaiting the enqueue is swallowed (flag preserved) and recovery restarts anyway.
+        assertTrue(reInterrupted)
+        verify { future.get(any(), any()) }
+        verify { processRestarter.restart() }
+    }
+
+    @Test
+    fun `onAuthenticated rethrows a cancellation while unwrapping and never wipes the cache`() = runTest(dispatcher) {
+        stubLog()
+        val session = mockk<PassphraseSession>(relaxed = true)
+        every { session.isUnlocked() } returns false
+        val databaseKeyStore = mockk<DatabaseKeyStore>(relaxed = true)
+        coEvery { databaseKeyStore.hasAuthSealedPassphrase() } returns true
+        coEvery { databaseKeyStore.unlockWithAuth() } throws CancellationException("scope cancelled")
+        val databaseKeyCipher = mockk<DatabaseKeyCipher>(relaxed = true)
+        every { databaseKeyCipher.hasKey() } returns true
+        val processRestarter = mockk<ProcessRestarter>(relaxed = true)
+        val vm = viewModel(
+            gate = mockk(relaxed = true),
+            session = session,
+            databaseKeyStore = databaseKeyStore,
+            databaseKeyCipher = databaseKeyCipher,
+            processRestarter = processRestarter,
+        )
+
+        vm.onAuthenticated()
+        advanceUntilIdle()
+
+        // A cancellation is rethrown, never mapped to UNRECOVERABLE, so the cache is not wiped/restarted.
+        coVerify { databaseKeyStore.unlockWithAuth() }
+        coVerify(exactly = 0) { databaseKeyStore.setClearPending() }
+        verify(exactly = 0) { processRestarter.restart() }
+    }
+
+    @Test
+    fun `each lock emission carries a distinct nonce so a repeat lock still updates the UI`() = runTest(dispatcher) {
+        val vm = viewModel(gate = mockk(relaxed = true))
+
+        vm.onAuthError("boom")
+        val first = assertIs<AppLockUiState.Locked>(vm.uiState.value).nonce
+        vm.onAuthError("boom")
+        val second = assertIs<AppLockUiState.Locked>(vm.uiState.value).nonce
+
+        // StateFlow conflates equal values; the bumped nonce guarantees the repeated lock still emits.
+        assertNotEquals(first, second)
+    }
+
+    @Test
+    fun `onBackground covers the app content when app-lock is on and the app was showing`() = runTest(dispatcher) {
+        mockkStatic(SystemClock::class)
+        every { SystemClock.elapsedRealtime() } returns 2_000L
+        val gate = mockk<AppLockGate>(relaxed = true)
+        every { gate.state } returns LockState.UNLOCKED
+        val session = mockk<PassphraseSession>(relaxed = true)
+        every { session.isUnlocked() } returns true
+        val vm = viewModel(gate = gate, session = session, appLock = true)
+
+        // Reach the Unlocked state (app content showing) via a warm re-auth...
+        vm.onAuthenticated()
+        advanceUntilIdle()
+        assertIs<AppLockUiState.Unlocked>(vm.uiState.value)
+
+        // ...then backgrounding must immediately cover it so nothing sensitive lands in the recents snapshot.
+        vm.onBackground()
+
+        assertIs<AppLockUiState.Checking>(vm.uiState.value)
+        verify { gate.onBackground(2_000L) }
+    }
+
     // --- onForeground: LockAction dispatch (issue #100) ------------------------------------------
 
     @Test
diff --git a/app/src/test/kotlin/org/libremail/ui/reporting/StartupReportViewModelTest.kt b/app/src/test/kotlin/org/libremail/ui/reporting/StartupReportViewModelTest.kt
index 83f6901..3b74045 100644
--- a/app/src/test/kotlin/org/libremail/ui/reporting/StartupReportViewModelTest.kt
+++ b/app/src/test/kotlin/org/libremail/ui/reporting/StartupReportViewModelTest.kt
@@ -163,4 +163,16 @@ class StartupReportViewModelTest {
         assertNull(vm.pendingCrash.value)
         assertNull(store.find("c"))
     }
+
+    @Test
+    fun `the injected constructor gates the crash age against the real system clock`() = runTest(dispatcher) {
+        val store = store()
+        // Created against the real wall clock so the injected `now = System.currentTimeMillis` gate
+        // (exercised only via the @Inject constructor, not the test's fixed-clock one) sees it as fresh.
+        store.save(crash("c", createdAt = System.currentTimeMillis()))
+        val vm = StartupReportViewModel(store)
+        subscribe(vm)
+
+        assertEquals("c", vm.pendingCrash.value?.id)
+    }
 }