Content scanner (Element Pro): scan timeline events for unsafe content (#7159)

* Simplify how event content with captions are displayed

The caption component will now be added in `TimelineItemEventContentView` instead of separately in each `TimelineItem__View` component

* Make sure `CoilMediaFetcher` methods to fetch media throw errors

We need to catch them later to check if the content scanner marked some thumbnails or medias as invalid/unsafe in `AsyncImage` instances

* Add a `ContentScannerService` that allows us to manually scan a list of medias in an event and then update and store the results

The results take the form of `ContentValidationValue`, stored in a `ContentValidationState` instance tied to the event

* Create `EventContentValidationCache` to keep the `ContentValidationStates` for events in a room

* Expose `EventContentValidationCache` to Compose using `LocalEventContentValidationState`

Also add a couple of helper functions to avoid having to manually remember the states

* Use the new components to display invalid content in the timeline items

* Add `blurhash` to most media items so we can use it while validating the thumbnails/medias

* Fix custom layout issues with screenshot and UI tests

* Also check the validation state for replied-to events in the composer

* Fix and add tests

* Handle unrecoverable content validation errors too: display a 'not found' UI

* Improve the performance of `EqualWidthColumn` for the single item case

* Update screenshots

---------

Co-authored-by: ElementBot <android@element.io>

features/contentscanner/api/src/main/kotlin/io/element/android/features/contentscanner/api/ContentScannerService.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.api
+
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.media.MediaSource
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+
+/**
+ * Service to perform security scans in the contents for a given event and media source.
+ *
+ * The default implementation (FOSS) always returns a valid state.
+ * This will only process media when a [ContentScanner] is provided when building the client in Pro.
+ */
+fun interface ContentScannerService {
+    fun scan(eventId: EventId, mediaSources: List<MediaSource>, contentValidationState: ContentValidationState)
+}

features/contentscanner/impl/build.gradle.kts

@@ -32,4 +32,5 @@ dependencies {
     testImplementation(libs.test.truth)
     testImplementation(libs.test.turbine)
     testImplementation(projects.libraries.matrix.test)
+    testImplementation(projects.tests.testutils)
 }

features/contentscanner/impl/src/main/kotlin/io/element/android/features/contentscanner/impl/DefaultContentScannerService.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl
+
+import io.element.android.features.contentscanner.api.ContentScannerService
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.media.MediaSource
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.launch
+import java.io.IOException
+
+/**
+ * Default implementation of [ContentScannerService] that uses a [ContentScanner] to scan media sources.
+ */
+class DefaultContentScannerService(
+    private val contentScanner: ContentScanner,
+    private val coroutineScope: CoroutineScope,
+    coroutineDispatchers: CoroutineDispatchers,
+) : ContentScannerService {
+    private val context = coroutineDispatchers.io.limitedParallelism(4)
+
+    override fun scan(eventId: EventId, mediaSources: List<MediaSource>, contentValidationState: ContentValidationState) {
+        for (mediaSource in mediaSources) {
+            val url = mediaSource.safeUrl
+            val currentState = contentValidationState.getCurrentMediaState(url)
+            if (currentState != ContentValidationValue.Unknown) continue
+            contentValidationState.update(url, ContentValidationValue.Loading)
+
+            coroutineScope.launch(context) {
+                contentScanner.scan(mediaSource)
+                    .onSuccess { isValid ->
+                        val contentValidationValue = if (isValid) ContentValidationValue.Valid else ContentValidationValue.Invalid
+                        contentValidationState.update(url, contentValidationValue)
+                    }
+                    .onFailure { exception ->
+                        if (exception is IOException) {
+                            // If it's an IO-related exception, we can retry later, so we don't store the error
+                            contentValidationState.update(url, ContentValidationValue.Unknown)
+                        } else {
+                            // For other exceptions, we cache the failure
+                            contentValidationState.update(url, ContentValidationValue.UnrecoverableError(exception))
+                        }
+                    }
+            }
+        }
+    }
+}

features/contentscanner/impl/src/main/kotlin/io/element/android/features/contentscanner/impl/DefaultEventContentValidationCache.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl
+
+import dev.zacsweers.metro.ContributesBinding
+import dev.zacsweers.metro.SingleIn
+import io.element.android.libraries.di.RoomScope
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.EventContentValidationCache
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NoopContentValidationState
+import timber.log.Timber
+import java.util.concurrent.ConcurrentHashMap
+
+@SingleIn(RoomScope::class)
+@ContributesBinding(RoomScope::class)
+class DefaultEventContentValidationCache(
+    private val contentScanner: ContentScanner?,
+) : EventContentValidationCache {
+    private val cache = ConcurrentHashMap<EventId, ContentValidationState>()
+
+    override operator fun get(eventId: EventId): ContentValidationState {
+        return cache.getOrPut(eventId) {
+            if (contentScanner != null) {
+                DefaultContentValidationState()
+            } else {
+                Timber.v("Content scanner is not available, returning NoopContentValidationState for eventId: $eventId")
+                NoopContentValidationState()
+            }
+        }
+    }
+}

features/contentscanner/impl/src/main/kotlin/io/element/android/features/contentscanner/impl/di/AlwaysValidContentScannerService.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl.di
+
+import io.element.android.features.contentscanner.api.ContentScannerService
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.media.MediaSource
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+
+/**
+ * Noop implementation of [ContentScannerService] that always returns success.
+ *
+ * This is used when the content scanner feature is not enabled or available.
+ */
+class AlwaysValidContentScannerService : ContentScannerService {
+    override fun scan(eventId: EventId, mediaSources: List<MediaSource>, contentValidationState: ContentValidationState) {
+        // Always return success for the noop implementation
+        for (mediaSource in mediaSources) {
+            val url = mediaSource.safeUrl
+            contentValidationState.update(url, ContentValidationValue.Valid)
+        }
+    }
+}

features/contentscanner/impl/src/main/kotlin/io/element/android/features/contentscanner/impl/di/ContentScannerModule.kt

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl.di
+
+import dev.zacsweers.metro.BindingContainer
+import dev.zacsweers.metro.ContributesTo
+import dev.zacsweers.metro.Provides
+import dev.zacsweers.metro.SingleIn
+import io.element.android.features.contentscanner.api.ContentScannerService
+import io.element.android.features.contentscanner.impl.DefaultContentScannerService
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.di.RoomScope
+import io.element.android.libraries.di.annotations.RoomCoroutineScope
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import kotlinx.coroutines.CoroutineScope
+
+@BindingContainer
+@ContributesTo(RoomScope::class)
+object ContentScannerModule {
+    @Provides
+    @SingleIn(RoomScope::class)
+    fun providesContentScannerService(
+        contentScanner: ContentScanner?,
+        @RoomCoroutineScope coroutineScope: CoroutineScope,
+        coroutineDispatchers: CoroutineDispatchers,
+    ): ContentScannerService {
+        return if (contentScanner != null) {
+            DefaultContentScannerService(
+                contentScanner = contentScanner,
+                coroutineScope = coroutineScope,
+                coroutineDispatchers = coroutineDispatchers,
+            )
+        } else {
+            AlwaysValidContentScannerService()
+        }
+    }
+}

features/contentscanner/impl/src/test/kotlin/io/element/android/features/contentscanner/impl/DefaultContentScannerServiceTest.kt

@@ -0,0 +1,217 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl
+
+import com.google.common.truth.Truth.assertThat
+import io.element.android.libraries.core.coroutine.CoroutineDispatchers
+import io.element.android.libraries.matrix.api.media.MediaSource
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import io.element.android.libraries.matrix.test.AN_EVENT_ID
+import io.element.android.libraries.matrix.test.media.aMediaSource
+import io.element.android.libraries.matrix.test.scanner.FakeContentScanner
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NoopContentValidationState
+import io.element.android.tests.testutils.lambda.lambdaRecorder
+import io.element.android.tests.testutils.lambda.value
+import io.element.android.tests.testutils.testCoroutineDispatchers
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runCurrent
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+import java.io.FileNotFoundException
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class DefaultContentScannerServiceTest {
+    @Test
+    fun `scan with no media sources returns valid`() = runTest {
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { Result.success(true) }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = DefaultContentValidationState()
+        createDefaultContentScannerService(
+            contentScanner = scanner,
+        ).scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = emptyList(),
+            contentValidationState = contentValidationState,
+        )
+
+        scanLambda.assertions().isNeverCalled()
+        assertThat(contentValidationState.getCurrentOverallState()).isEqualTo(ContentValidationValue.Valid)
+    }
+
+    @Test
+    fun `scan with single media source`() = runTest {
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { Result.success(false) }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = DefaultContentValidationState()
+
+        val mediaSource = aMediaSource("https://example.com/media.jpg")
+        createDefaultContentScannerService(
+            contentScanner = scanner,
+        ).scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSource),
+            contentValidationState = contentValidationState,
+        )
+
+        runCurrent()
+
+        scanLambda.assertions().isCalledOnce().with(value(mediaSource))
+        assertThat(contentValidationState.getCurrentOverallState()).isEqualTo(ContentValidationValue.Invalid)
+    }
+
+    @Test
+    fun `scan with several media sources`() = runTest {
+        val mediaSourceA = aMediaSource("https://example.com/mediaA.jpg")
+        val mediaSourceB = aMediaSource("https://example.com/mediaB.jpg")
+
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { source ->
+            when (source) {
+                mediaSourceA -> Result.success(true)
+                mediaSourceB -> Result.success(false)
+                else -> error("Unexpected media source: $source")
+            }
+        }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = DefaultContentValidationState()
+
+        createDefaultContentScannerService(
+            contentScanner = scanner,
+        ).scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSourceA, mediaSourceB),
+            contentValidationState = contentValidationState,
+        )
+
+        runCurrent()
+
+        scanLambda.assertions().isCalledExactly(2)
+        assertThat(contentValidationState.getMediaStateFlow(mediaSourceA.safeUrl).first()).isEqualTo(ContentValidationValue.Valid)
+        assertThat(contentValidationState.getMediaStateFlow(mediaSourceB.safeUrl).first()).isEqualTo(ContentValidationValue.Invalid)
+        assertThat(contentValidationState.overallStateFlow.first()).isEqualTo(ContentValidationValue.Invalid)
+    }
+
+    @Test
+    fun `scan won't be repeated for sources which are already being scanned`() = runTest {
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { Result.success(false) }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = DefaultContentValidationState()
+
+        val mediaSource = aMediaSource("https://example.com/media.jpg")
+        val service = createDefaultContentScannerService(
+            contentScanner = scanner,
+        )
+
+        // First scan attempt
+        service.scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSource),
+            contentValidationState = contentValidationState,
+        )
+
+        // Immediately after, a new scan attempt is made for the same media source
+        service.scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSource),
+            contentValidationState = contentValidationState,
+        )
+
+        runCurrent()
+
+        // The scan action was done just once, and the overall state is invalid as expected
+        scanLambda.assertions().isCalledOnce().with(value(mediaSource))
+        assertThat(contentValidationState.getCurrentOverallState()).isEqualTo(ContentValidationValue.Invalid)
+    }
+
+    @Test
+    fun `scan won't be repeated for sources which already have a cached value`() = runTest {
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { Result.success(false) }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = NoopContentValidationState(ContentValidationValue.Valid)
+
+        val mediaSource = aMediaSource("https://example.com/media.jpg")
+        val service = createDefaultContentScannerService(
+            contentScanner = scanner,
+        )
+
+        service.scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSource),
+            contentValidationState = contentValidationState,
+        )
+
+        runCurrent()
+
+        scanLambda.assertions().isNeverCalled()
+    }
+
+    @Test
+    fun `if a scan fails with a recoverable error, the content validation value will be back to Unknown`() = runTest {
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { Result.failure(FileNotFoundException("Some IO exception")) }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = DefaultContentValidationState()
+
+        val mediaSource = aMediaSource("https://example.com/media.jpg")
+        val service = createDefaultContentScannerService(
+            contentScanner = scanner,
+        )
+
+        service.scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSource),
+            contentValidationState = contentValidationState,
+        )
+
+        runCurrent()
+
+        scanLambda.assertions().isCalledOnce().with(value(mediaSource))
+        assertThat(contentValidationState.getCurrentMediaState(mediaSource.safeUrl)).isEqualTo(ContentValidationValue.Unknown)
+        assertThat(contentValidationState.getCurrentOverallState()).isEqualTo(ContentValidationValue.Unknown)
+    }
+
+    @Test
+    fun `if a scan fails with an unrecoverable error, the content validation value will be back to UnrecoverableError`() = runTest {
+        val error = OutOfMemoryError("BOOM")
+        val scanLambda = lambdaRecorder<MediaSource, Result<Boolean>> { Result.failure(error) }
+        val scanner = FakeContentScanner(scan = scanLambda)
+        val contentValidationState = DefaultContentValidationState()
+
+        val mediaSource = aMediaSource("https://example.com/media.jpg")
+        val service = createDefaultContentScannerService(
+            contentScanner = scanner,
+        )
+
+        service.scan(
+            eventId = AN_EVENT_ID,
+            mediaSources = listOf(mediaSource),
+            contentValidationState = contentValidationState,
+        )
+
+        runCurrent()
+
+        scanLambda.assertions().isCalledOnce().with(value(mediaSource))
+        assertThat(contentValidationState.getCurrentMediaState(mediaSource.safeUrl)).isEqualTo(ContentValidationValue.UnrecoverableError(error))
+        assertThat(contentValidationState.getCurrentOverallState()).isEqualTo(ContentValidationValue.UnrecoverableError(error))
+    }
+
+    private fun TestScope.createDefaultContentScannerService(
+        contentScanner: ContentScanner = FakeContentScanner(),
+        sessionCoroutineScope: CoroutineScope = backgroundScope,
+        coroutineDispatchers: CoroutineDispatchers = testCoroutineDispatchers(),
+    ): DefaultContentScannerService {
+        return DefaultContentScannerService(
+            contentScanner = contentScanner,
+            coroutineScope = sessionCoroutineScope,
+            coroutineDispatchers = coroutineDispatchers
+        )
+    }
+}

features/contentscanner/impl/src/test/kotlin/io/element/android/features/contentscanner/impl/DefaultEventContentValidationCacheTest.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl
+
+import com.google.common.truth.Truth.assertThat
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import io.element.android.libraries.matrix.test.AN_EVENT_ID
+import io.element.android.libraries.matrix.test.scanner.FakeContentScanner
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NoopContentValidationState
+import org.junit.Test
+
+class DefaultEventContentValidationCacheTest {
+    @Test
+    fun `get returns NoopContentValidationState when ContentScanner is null`() {
+        // Given
+        val contentScanner: ContentScanner? = null
+        val cache = DefaultEventContentValidationCache(contentScanner)
+
+        // When
+        val state = cache[AN_EVENT_ID]
+
+        // Then
+        assertThat(state).isInstanceOf(NoopContentValidationState::class.java)
+    }
+
+    @Test
+    fun `get returns an actual DefaultContentValidationState when ContentScanner is not null`() {
+        // Given
+        val contentScanner: ContentScanner? = FakeContentScanner()
+        val cache = DefaultEventContentValidationCache(contentScanner)
+
+        // When
+        val state = cache[AN_EVENT_ID]
+
+        // Then
+        assertThat(state).isInstanceOf(DefaultContentValidationState::class.java)
+    }
+}

features/contentscanner/impl/src/test/kotlin/io/element/android/features/contentscanner/impl/di/ContentScannerModuleTest.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.contentscanner.impl.di
+
+import com.google.common.truth.Truth.assertThat
+import io.element.android.features.contentscanner.impl.DefaultContentScannerService
+import io.element.android.libraries.matrix.api.scanner.ContentScanner
+import io.element.android.libraries.matrix.test.scanner.FakeContentScanner
+import io.element.android.tests.testutils.testCoroutineDispatchers
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+
+class ContentScannerModuleTest {
+    @Test
+    fun `ContentScannerModule provides NoopContentScannerService when ContentScanner is null`() = runTest {
+        // Given
+        val contentScanner: ContentScanner? = null
+        val sessionCoroutineScope = backgroundScope
+        val coroutineDispatchers = testCoroutineDispatchers()
+
+        // When
+        val contentScannerService = ContentScannerModule.providesContentScannerService(
+            contentScanner = contentScanner,
+            coroutineScope = sessionCoroutineScope,
+            coroutineDispatchers = coroutineDispatchers,
+        )
+
+        // Then
+        assertThat(contentScannerService).isInstanceOf(AlwaysValidContentScannerService::class.java)
+    }
+
+    @Test
+    fun `ContentScannerModule provides DefaultContentScannerService when ContentScanner is not null`() = runTest {
+        // Given
+        val contentScanner: ContentScanner? = FakeContentScanner()
+        val sessionCoroutineScope = backgroundScope
+        val coroutineDispatchers = testCoroutineDispatchers()
+
+        // When
+        val contentScannerService = ContentScannerModule.providesContentScannerService(
+            contentScanner = contentScanner,
+            coroutineScope = sessionCoroutineScope,
+            coroutineDispatchers = coroutineDispatchers,
+        )
+
+        // Then
+        assertThat(contentScannerService).isInstanceOf(DefaultContentScannerService::class.java)
+    }
+}

features/messages/impl/build.gradle.kts

@@ -62,6 +62,7 @@ dependencies {
     implementation(projects.libraries.uiUtils)
     implementation(projects.libraries.testtags)
     implementation(projects.features.networkmonitor.api)
+    implementation(projects.features.contentscanner.api)
     implementation(projects.services.analytics.compose)
     implementation(projects.services.appnavstate.api)
     implementation(projects.services.toolbox.api)

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/MessagesFlowNode.kt

@@ -57,6 +57,7 @@ import io.element.android.features.messages.impl.timeline.model.event.TimelineIt
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemLocationContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVideoContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVoiceContent
+import io.element.android.features.messages.impl.timeline.model.event.blurHash
 import io.element.android.features.messages.impl.timeline.model.event.duration
 import io.element.android.features.poll.api.create.CreatePollEntryPoint
 import io.element.android.features.poll.api.create.CreatePollMode
@@ -155,6 +156,7 @@ class MessagesFlowNode(
             val mediaSource: MediaSource,
             val thumbnailSource: MediaSource?,
             val canUseOverlay: Boolean,
+            val blurHash: String?,
         ) : NavTarget
 
         @Parcelize
@@ -377,6 +379,7 @@ class MessagesFlowNode(
                     mediaInfo = navTarget.mediaInfo,
                     mediaSource = navTarget.mediaSource,
                     thumbnailSource = navTarget.thumbnailSource,
+                    blurHash = navTarget.blurHash,
                 )
                 val callback = object : MediaViewerEntryPoint.Callback {
                     override fun onDone() {
@@ -828,6 +831,7 @@ class MessagesFlowNode(
                         mediaSource = galleryItem.mediaSource,
                         thumbnailSource = galleryItem.thumbnailSource,
                         type = galleryItem.type.toMediaViewerType(),
+                        blurHash = galleryItem.blurhash,
                     )
                 }.reversed()
                 NavTarget.GalleryViewer(
@@ -861,6 +865,7 @@ class MessagesFlowNode(
                         mediaSource = attachment.mediaSource,
                         thumbnailSource = attachment.thumbnailSource,
                         type = GalleryItemData.Type.File,
+                        blurHash = null,
                     )
                 }.reversed()
                 NavTarget.GalleryViewer(
@@ -920,6 +925,7 @@ class MessagesFlowNode(
             mediaSource = mediaSource,
             thumbnailSource = thumbnailSource,
             canUseOverlay = canUseOverlay,
+            blurHash = content.blurHash(),
         )
     }
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/MessagesNode.kt

@@ -66,6 +66,8 @@ import io.element.android.libraries.matrix.api.room.JoinedRoom
 import io.element.android.libraries.matrix.api.room.alias.matches
 import io.element.android.libraries.matrix.api.timeline.Timeline
 import io.element.android.libraries.matrix.api.timeline.item.TimelineItemDebugInfo
+import io.element.android.libraries.matrix.ui.media.contentvalidation.EventContentValidationCache
+import io.element.android.libraries.matrix.ui.media.contentvalidation.LocalEventContentValidationState
 import io.element.android.libraries.matrix.ui.model.getBestName
 import io.element.android.libraries.mediaplayer.api.MediaPlayer
 import io.element.android.libraries.ui.strings.CommonStrings
@@ -97,6 +99,7 @@ class MessagesNode(
     private val permalinkParser: PermalinkParser,
     private val knockRequestsBannerRenderer: KnockRequestsBannerRenderer,
     private val roomMemberModerationRenderer: RoomMemberModerationRenderer,
+    private val eventContentValidationCache: EventContentValidationCache,
 ) : Node(buildContext, plugins = plugins), MessagesNavigator {
     data class Inputs(
         val focusedEventId: EventId?,
@@ -261,6 +264,7 @@ class MessagesNode(
         val canUseOverlay = !isTalkbackActive() && !hasExternalKeyboard()
         CompositionLocalProvider(
             LocalTimelineItemPresenterFactories provides timelineItemPresenterFactories,
+            LocalEventContentValidationState provides eventContentValidationCache,
         ) {
             val state = presenter.present()
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/MessagesView.kt

@@ -123,6 +123,8 @@ import io.element.android.libraries.matrix.api.room.tombstone.SuccessorRoom
 import io.element.android.libraries.matrix.api.timeline.Timeline
 import io.element.android.libraries.matrix.api.timeline.item.event.LocalEventSendState
 import io.element.android.libraries.matrix.api.user.MatrixUser
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.LocalEventContentValidationState
 import io.element.android.libraries.textcomposer.model.TextEditorState
 import io.element.android.libraries.ui.strings.CommonStrings
 import io.element.android.wysiwyg.link.Link
@@ -148,6 +150,8 @@ fun MessagesView(
     forceJumpToBottomVisibility: Boolean = false,
     knockRequestsBannerView: @Composable () -> Unit,
 ) {
+    val eventContentValidationState = LocalEventContentValidationState.current
+
     OnLifecycleEvent { _, event ->
         state.voiceMessageComposerState.eventSink(VoiceMessageComposerEvent.LifecycleEvent(event))
     }
@@ -170,6 +174,9 @@ fun MessagesView(
 
     fun onContentClick(event: TimelineItem.Event) {
         Timber.v("onMessageClick= ${event.id}")
+        val eventId = event.eventId ?: return
+        if (eventContentValidationState[eventId].getCurrentOverallState() != ContentValidationValue.Valid) return
+
         val hideKeyboard = onEventContentClick(state.timelineState.isLive, event)
         if (hideKeyboard) {
             localView.hideKeyboard()

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/messagecomposer/MessageComposerPresenter.kt

@@ -31,6 +31,7 @@ import dev.zacsweers.metro.AssistedFactory
 import dev.zacsweers.metro.AssistedInject
 import im.vector.app.features.analytics.plan.Composer
 import im.vector.app.features.analytics.plan.Interaction
+import io.element.android.features.contentscanner.api.ContentScannerService
 import io.element.android.features.location.api.LocationService
 import io.element.android.features.messages.impl.MessagesNavigator
 import io.element.android.features.messages.impl.attachments.Attachment
@@ -61,8 +62,12 @@ import io.element.android.libraries.matrix.api.room.draft.ComposerDraftType
 import io.element.android.libraries.matrix.api.room.getDirectRoomMember
 import io.element.android.libraries.matrix.api.room.powerlevels.use
 import io.element.android.libraries.matrix.api.timeline.TimelineException
+import io.element.android.libraries.matrix.api.timeline.item.event.mediaSources
 import io.element.android.libraries.matrix.api.timeline.item.event.toEventOrTransactionId
+import io.element.android.libraries.matrix.ui.media.contentvalidation.EventContentValidationCache
 import io.element.android.libraries.matrix.ui.messages.reply.InReplyToDetails
+import io.element.android.libraries.matrix.ui.messages.reply.content
+import io.element.android.libraries.matrix.ui.messages.reply.eventId
 import io.element.android.libraries.matrix.ui.messages.reply.map
 import io.element.android.libraries.mediapickers.api.PickerProvider
 import io.element.android.libraries.mediaupload.api.MediaOptimizationConfigProvider
@@ -135,6 +140,8 @@ class MessageComposerPresenter(
     private val notificationConversationService: NotificationConversationService,
     private val slashCommandService: SlashCommandService,
     private val featureFlagService: FeatureFlagService,
+    private val contentScannerService: ContentScannerService,
+    private val contentValidationCache: EventContentValidationCache,
 ) : Presenter<MessageComposerState> {
     @AssistedFactory
     interface Factory {
@@ -848,6 +855,11 @@ class MessageComposerPresenter(
                 setText(newComposerMode.content, markdownTextEditorState, richTextEditorState, requestFocus = true)
             }
             else -> {
+                if (currentComposerMode is MessageComposerMode.Reply) {
+                    val mediaSources = currentComposerMode.replyToDetails.content()?.mediaSources() ?: return@launch
+                    val contentValidationState = contentValidationCache[currentComposerMode.replyToDetails.eventId()]
+                    contentScannerService.scan(currentComposerMode.replyToDetails.eventId(), mediaSources, contentValidationState)
+                }
                 // When coming from edit, just clear the composer as it'd be weird to reset a volatile draft in this scenario.
                 if (currentComposerMode.isEditing) {
                     setText("", markdownTextEditorState, richTextEditorState)

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/pinned/list/PinnedMessagesListView.kt

@@ -36,7 +36,6 @@ import io.element.android.features.messages.impl.timeline.components.event.Timel
 import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
 import io.element.android.features.messages.impl.timeline.model.TimelineItem
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemPollContent
-import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionEvent
 import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
 import io.element.android.features.poll.api.pollcontent.PollTitleView
 import io.element.android.libraries.designsystem.atomic.molecules.IconTitleSubtitleMolecule
@@ -290,9 +289,9 @@ private fun TimelineItemEventContentViewWrapper(
         )
     } else {
         TimelineItemEventContentView(
+            eventId = event.eventId,
             content = event.content,
-            hideMediaContent = timelineProtectionState.hideMediaContent(event.eventId, event.isMine),
-            onShowContentClick = { timelineProtectionState.eventSink(TimelineProtectionEvent.ShowContent(event.eventId)) },
+            timelineProtectionState = timelineProtectionState,
             onGalleryItemClick = onGalleryItemClick,
             onLinkClick = onLinkClick,
             onLinkLongClick = onLinkLongClick,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelineEvent.kt

@@ -13,7 +13,9 @@ import io.element.android.features.messages.impl.timeline.model.TimelineItem
 import io.element.android.libraries.matrix.api.core.EventId
 import io.element.android.libraries.matrix.api.core.RoomId
 import io.element.android.libraries.matrix.api.core.ThreadId
+import io.element.android.libraries.matrix.api.media.MediaSource
 import io.element.android.libraries.matrix.api.timeline.Timeline
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
 import kotlin.time.Duration
 
 sealed interface TimelineEvent {
@@ -61,4 +63,10 @@ sealed interface TimelineEvent {
     ) : TimelineItemPollEvent
 
     data object StopLiveLocationShare : TimelineItemEvent
+
+    data class ValidateMedia(
+        val eventId: EventId,
+        val mediaSources: List<MediaSource>,
+        val validationState: ContentValidationState
+    ) : TimelineItemEvent
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/TimelinePresenter.kt

@@ -35,6 +35,8 @@ import io.element.android.features.messages.impl.timeline.model.NewEventState
 import io.element.android.features.messages.impl.timeline.model.TimelineItem
 import io.element.android.features.messages.impl.timeline.model.virtual.TimelineItemReadMarkerModel
 import io.element.android.features.messages.impl.timeline.model.virtual.TimelineItemTypingNotificationModel
+import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionEvent
+import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
 import io.element.android.features.messages.impl.typing.TypingNotificationState
 import io.element.android.features.messages.impl.userEventPermissions
 import io.element.android.features.messages.impl.voicemessages.timeline.RedactedVoiceMessageManager
@@ -64,6 +66,7 @@ import io.element.android.services.analytics.api.finishLongRunningTransaction
 import io.element.android.services.analyticsproviders.api.AnalyticsUserData
 import kotlinx.collections.immutable.ImmutableList
 import kotlinx.collections.immutable.persistentListOf
+import kotlinx.collections.immutable.toImmutableList
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.combine
@@ -98,6 +101,7 @@ class TimelinePresenter(
     private val analyticsService: AnalyticsService,
     private val liveLocationShareManager: ActiveLiveLocationShareManager,
     private val markAsFullyRead: MarkAsFullyRead,
+    private val timelineProtectionPresenter: Presenter<TimelineProtectionState>,
 ) : Presenter<TimelineState> {
     private val tag = "TimelinePresenter"
 
@@ -157,6 +161,8 @@ class TimelinePresenter(
             value = featureFlagService.isFeatureEnabled(FeatureFlags.JumpToUnread)
         }
 
+        val timelineProtectionState = timelineProtectionPresenter.present()
+
         fun handleEvent(event: TimelineEvent) {
             when (event) {
                 is TimelineEvent.LoadMore -> {
@@ -252,6 +258,9 @@ class TimelinePresenter(
                         focusedEventId = event.focusedEvent,
                     )
                 }
+                is TimelineEvent.ValidateMedia -> {
+                    timelineProtectionState.eventSink(TimelineProtectionEvent.ValidateContent(event.eventId, event.mediaSources, event.validationState))
+                }
             }
         }
 
@@ -259,7 +268,7 @@ class TimelinePresenter(
             timelineItemsFactory.timelineItems
                 .onEach { newTimelineItems ->
                     timelineItemIndexer.process(newTimelineItems)
-                    timelineItems = newTimelineItems
+                    timelineItems = newTimelineItems.toImmutableList()
 
                     analyticsService.run {
                         finishLongRunningTransaction(DisplayFirstTimelineItems)

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/ContentPadding.kt

@@ -11,5 +11,6 @@ package io.element.android.features.messages.impl.timeline.components
 enum class ContentPadding {
     Textual,
     Media,
-    CaptionedMedia
+    CaptionedMedia,
+    InvalidContent,
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/MessageEventBubble.kt

@@ -19,7 +19,9 @@ import androidx.compose.foundation.layout.widthIn
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.ripple
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.drawWithCache
@@ -27,6 +29,8 @@ import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.BlendMode
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.Shape
+import androidx.compose.ui.graphics.drawOutline
+import androidx.compose.ui.graphics.drawscope.Stroke
 import androidx.compose.ui.graphics.layer.CompositingStrategy
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.LayoutDirection
@@ -62,6 +66,8 @@ fun MessageEventBubble(
     onClick: () -> Unit,
     onLongClick: () -> Unit,
     modifier: Modifier = Modifier,
+    customBackgroundColor: Color? = null,
+    borderColor: Color? = null,
     content: @Composable BoxScope.() -> Unit = {},
 ) {
     val clickableModifier = if (isTalkbackActive()) {
@@ -79,10 +85,12 @@ fun MessageEventBubble(
 
     val cutTopStart = state.cutTopStart
     // Ignore state.isHighlighted for now, we need a design decision on it.
-    val backgroundBubbleColor = MessageEventBubbleDefaults.backgroundBubbleColor(state.isMine)
+    val backgroundBubbleColor by rememberUpdatedState(customBackgroundColor ?: MessageEventBubbleDefaults.backgroundBubbleColor(state.isMine))
     val bubbleShape = remember(state) { MessageEventBubbleDefaults.shape(state.cutTopStart, state.groupPosition, state.isMine) }
     val radiusPx = (avatarRadius + SENDER_AVATAR_BORDER_WIDTH).toPx()
     val yOffsetPx = -(NEGATIVE_MARGIN_FOR_BUBBLE + avatarRadius).toPx()
+
+    val updatedBorderColor by rememberUpdatedState(borderColor)
     BoxWithConstraints(
         modifier = modifier
             .drawWithCache {
@@ -103,6 +111,9 @@ fun MessageEventBubble(
                         // Then draw the content on top of it
                         drawContent()
 
+                        // Draw border color, if any
+                        updatedBorderColor?.let { drawOutline(outline, it, style = Stroke(width = 1.dp.toPx())) }
+
                         // And then clip the top start corner if needed to make room for the avatar
                         if (cutTopStart) {
                             drawCircle(

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/TimelineItemContentScannerPreviews.kt

@@ -0,0 +1,320 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.messages.impl.timeline.components
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.remember
+import androidx.compose.ui.unit.dp
+import io.element.android.features.messages.impl.timeline.aTimelineItemEvent
+import io.element.android.features.messages.impl.timeline.components.event.ElementTimelineItemPreview
+import io.element.android.features.messages.impl.timeline.components.event.aGalleryItem
+import io.element.android.features.messages.impl.timeline.components.event.aTimelineItemGalleryContent
+import io.element.android.features.messages.impl.timeline.di.LocalTimelineItemPresenterFactories
+import io.element.android.features.messages.impl.timeline.di.aFakeTimelineItemPresenterFactories
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemAttachmentsContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemAudioContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemFileContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemImageContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemStickerContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemTextContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemVideoContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemVoiceContent
+import io.element.android.features.messages.impl.timeline.model.event.anAttachmentItem
+import io.element.android.libraries.designsystem.preview.ElementPreview
+import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.core.UserId
+import io.element.android.libraries.matrix.api.media.MediaSource
+import io.element.android.libraries.matrix.api.timeline.item.event.ImageMessageType
+import io.element.android.libraries.matrix.api.timeline.item.event.MessageContent
+import io.element.android.libraries.matrix.api.timeline.item.event.ProfileDetails
+import io.element.android.libraries.matrix.api.timeline.item.event.TextMessageType
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.InMemoryEventContentValidationCache
+import io.element.android.libraries.matrix.ui.media.contentvalidation.LocalEventContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NoopContentValidationState
+import io.element.android.libraries.matrix.ui.messages.reply.InReplyToDetails
+
+private val AN_EVENT_ID = EventId($$"$eventId")
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemImageViewScanningContentPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Loading)))
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        ATimelineItemEventRow(
+            event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemImageContent()),
+        )
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemStickerViewScanningContentPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Loading)))
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        ATimelineItemEventRow(
+            event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemStickerContent(aspectRatio = 1.5f)),
+        )
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemVideoViewScanningContentPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Loading)))
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        ATimelineItemEventRow(
+            event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemVideoContent()),
+        )
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemFileViewScanningContentPreview() {
+    ElementTimelineItemPreview {
+        val cache = remember {
+            InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Loading)))
+        }
+        CompositionLocalProvider(
+            LocalEventContentValidationState provides cache
+        ) {
+            ATimelineItemEventRow(event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemFileContent()))
+        }
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemAudioViewScanningContentPreview() {
+    ElementTimelineItemPreview {
+        val cache = remember {
+            InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Loading)))
+        }
+        CompositionLocalProvider(
+            LocalEventContentValidationState provides cache
+        ) {
+            ATimelineItemEventRow(event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemAudioContent()))
+        }
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemVoiceViewScanningContentPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Loading)))
+    }
+    ElementTimelineItemPreview {
+        CompositionLocalProvider(
+            LocalEventContentValidationState provides cache,
+            LocalTimelineItemPresenterFactories provides aFakeTimelineItemPresenterFactories(),
+        ) {
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemVoiceContent()),
+            )
+        }
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemScanningContentFailedPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Invalid)))
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+            ATimelineItemEventRow(event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemImageContent()))
+            ATimelineItemEventRow(event = aTimelineItemEvent(eventId = AN_EVENT_ID, content = aTimelineItemImageContent(caption = "A caption")))
+        }
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemScanningContentWithInvalidRepliesPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.Invalid)))
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(
+                    content = aTimelineItemTextContent(),
+                    inReplyTo = inReplyToInvalidContent(),
+                )
+            )
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(
+                    eventId = AN_EVENT_ID,
+                    content = aTimelineItemImageContent(),
+                    inReplyTo = inReplyToInvalidContent(),
+                )
+            )
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(
+                    eventId = AN_EVENT_ID,
+                    content = aTimelineItemImageContent(),
+                    inReplyTo = inReplyToTextContent(),
+                )
+            )
+        }
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemScanningContentWithRepliesFailedPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(
+            initial = mapOf(AN_EVENT_ID to NoopContentValidationState(ContentValidationValue.UnrecoverableError(IllegalStateException("BOOM"))))
+        )
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        Column(verticalArrangement = Arrangement.spacedBy(10.dp)) {
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(
+                    content = aTimelineItemTextContent(),
+                    inReplyTo = inReplyToInvalidContent(),
+                )
+            )
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(
+                    eventId = AN_EVENT_ID,
+                    content = aTimelineItemImageContent(),
+                    inReplyTo = inReplyToInvalidContent(),
+                )
+            )
+            ATimelineItemEventRow(
+                event = aTimelineItemEvent(
+                    eventId = AN_EVENT_ID,
+                    content = aTimelineItemImageContent(),
+                    inReplyTo = inReplyToTextContent(),
+                )
+            )
+        }
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemGalleryViewScanningContentFailedPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(
+            initial =
+                mapOf(
+                    AN_EVENT_ID to DefaultContentValidationState(mapOf(
+                        "invalid" to ContentValidationValue.Invalid,
+                        "error" to ContentValidationValue.UnrecoverableError(IllegalStateException("BOOM")),
+                        "" to ContentValidationValue.Valid
+                    ))
+                )
+        )
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        ATimelineItemEventRow(
+            event = aTimelineItemEvent(
+                eventId = AN_EVENT_ID,
+                content = aTimelineItemGalleryContent(
+                    items = listOf(
+                        aGalleryItem(),
+                        aGalleryItem(mediaSource = MediaSource("invalid", "{}")),
+                        aGalleryItem(),
+                        aGalleryItem(mediaSource = MediaSource("invalid", "{}")),
+                        aGalleryItem(mediaSource = MediaSource("error", "{}")),
+                        aGalleryItem(mediaSource = MediaSource("invalid", "{}")),
+                        aGalleryItem(),
+                    )
+                )
+            )
+        )
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun TimelineItemAttachmentsViewScanningContentFailedPreview() = ElementPreview {
+    val cache = remember {
+        InMemoryEventContentValidationCache(
+            initial =
+            mapOf(
+                AN_EVENT_ID to DefaultContentValidationState(mapOf(
+                    "invalid" to ContentValidationValue.Invalid,
+                    "error" to ContentValidationValue.UnrecoverableError(IllegalStateException("BOOM")),
+                    "" to ContentValidationValue.Valid
+                ))
+            )
+        )
+    }
+    CompositionLocalProvider(LocalEventContentValidationState provides cache) {
+        ATimelineItemEventRow(
+            event = aTimelineItemEvent(
+                eventId = AN_EVENT_ID,
+                content = aTimelineItemAttachmentsContent(
+                    attachments = listOf(
+                        anAttachmentItem(),
+                        anAttachmentItem(mediaSource = MediaSource("invalid", "{}")),
+                        anAttachmentItem(),
+                        anAttachmentItem(),
+                        anAttachmentItem(mediaSource = MediaSource("error", "{}")),
+                        anAttachmentItem(mediaSource = MediaSource("invalid", "{}")),
+                    )
+                )
+            )
+        )
+    }
+}
+
+private fun inReplyToInvalidContent(): InReplyToDetails.Ready = InReplyToDetails.Ready(
+    eventId = AN_EVENT_ID,
+    senderId = UserId("@sender:matrix.org"),
+    eventContent = MessageContent(
+        body = "A body",
+        inReplyTo = null,
+        isEdited = false,
+        threadInfo = null,
+        type = ImageMessageType(
+            filename = "A file",
+            caption = "A caption",
+            formattedCaption = null,
+            source = MediaSource("", ""),
+            info = null,
+        )
+    ),
+    textContent = "A text content",
+    senderProfile = ProfileDetails.Ready(displayName = "Sender", displayNameAmbiguous = false, avatarUrl = null)
+)
+
+private fun inReplyToTextContent(): InReplyToDetails.Ready = InReplyToDetails.Ready(
+    eventId = EventId($$"$text_eventId"),
+    senderId = UserId("@sender:matrix.org"),
+    eventContent = MessageContent(
+        body = "A body",
+        inReplyTo = null,
+        isEdited = false,
+        threadInfo = null,
+        type = TextMessageType(
+            body = "A body",
+            formatted = null,
+        )
+    ),
+    textContent = "A text content",
+    senderProfile = ProfileDetails.Ready(displayName = "Sender", displayNameAmbiguous = false, avatarUrl = null)
+)

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/TimelineItemEventRow.kt

@@ -33,9 +33,12 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
 import androidx.compose.runtime.movableContentOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
@@ -88,7 +91,6 @@ import io.element.android.features.messages.impl.timeline.model.event.TimelineIt
 import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemImageContent
 import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemTextContent
 import io.element.android.features.messages.impl.timeline.model.event.ensureActiveLiveLocation
-import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionEvent
 import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
 import io.element.android.features.messages.impl.timeline.protection.mustBeProtected
 import io.element.android.libraries.architecture.AsyncData
@@ -122,9 +124,13 @@ import io.element.android.libraries.matrix.api.timeline.item.event.TextMessageTy
 import io.element.android.libraries.matrix.api.timeline.item.event.getAvatarUrl
 import io.element.android.libraries.matrix.api.timeline.item.event.getDisambiguatedDisplayName
 import io.element.android.libraries.matrix.api.timeline.item.event.getDisplayName
+import io.element.android.libraries.matrix.api.timeline.item.event.mediaSources
 import io.element.android.libraries.matrix.api.user.MatrixUser
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectOverallState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.rememberEventContentValidationState
 import io.element.android.libraries.matrix.ui.messages.reply.InReplyToDetails
 import io.element.android.libraries.matrix.ui.messages.reply.InReplyToView
+import io.element.android.libraries.matrix.ui.messages.reply.content
 import io.element.android.libraries.matrix.ui.messages.reply.eventId
 import io.element.android.libraries.matrix.ui.messages.sender.SenderName
 import io.element.android.libraries.matrix.ui.messages.sender.SenderNameMode
@@ -176,12 +182,12 @@ fun TimelineItemEventRow(
         val onContentClick = onEventClick.takeUnless { event.isWholeContentClickable }
 
         TimelineItemEventContentView(
+            eventId = event.eventId,
             content = event.content,
-            hideMediaContent = timelineProtectionState.hideMediaContent(event.eventId),
+            timelineProtectionState = timelineProtectionState,
             onContentClick = onContentClick,
             onGalleryItemClick = onGalleryItemClick,
             onLongClick = onLongClick,
-            onShowContentClick = { timelineProtectionState.eventSink(TimelineProtectionEvent.ShowContent(event.eventId)) },
             onLinkClick = onLinkClick,
             onLinkLongClick = onLinkLongClick,
             eventSink = eventSink,
@@ -468,6 +474,23 @@ private fun TimelineItemEventRowContent(
             )
         }
 
+        val currentContentValidationState by rememberEventContentValidationState(eventId = event.eventId, needsValidation = event.content.isMedia)
+            .collectOverallState()
+        val needsInvalidContentCustomisations =
+            // Gallery events should not apply the custom bubble color, instead each item will apply some custom color if needed
+            event.content !is TimelineItemGalleryContent &&
+                event.content !is TimelineItemAttachmentsContent &&
+                currentContentValidationState.hasError() &&
+                event.content.isMedia
+
+        // If the event has a dangerous media content we need to set custom message bubble background and border colors
+        val themeColors = ElementTheme.colors
+        val (dangerousContentBubbleColor, borderColor) = remember(themeColors.isLight, needsInvalidContentCustomisations, event.content.type) {
+            val background = themeColors.bgCriticalSubtle.takeIf { needsInvalidContentCustomisations }
+            val border = themeColors.borderCriticalSubtle.takeIf { needsInvalidContentCustomisations }
+            background to border
+        }
+
         // Message bubble
         val bubbleState = BubbleState(
             groupPosition = event.groupPosition,
@@ -494,6 +517,8 @@ private fun TimelineItemEventRowContent(
             interactionSource = interactionSource,
             onClick = onContentClick,
             onLongClick = onLongClick,
+            customBackgroundColor = dangerousContentBubbleColor,
+            borderColor = borderColor,
         ) {
             MessageEventBubbleContent(
                 event = event,
@@ -747,6 +772,7 @@ private fun MessageEventBubbleContent(
             }
             ContentPadding.CaptionedMedia ->
                 Modifier.padding(start = 8.dp, end = 8.dp, top = topPadding, bottom = 8.dp)
+            ContentPadding.InvalidContent -> Modifier.padding(top = topPadding, bottom = 8.dp)
         }
 
         val threadDecoration = @Composable {
@@ -770,10 +796,13 @@ private fun MessageEventBubbleContent(
         }
 
         val inReplyTo = @Composable { inReplyTo: InReplyToDetails ->
+            val currentContentValidationState by rememberEventContentValidationState(eventId = inReplyTo.eventId(), eventContent = inReplyTo.content())
+                .collectOverallState()
             val topPadding = if (showThreadDecoration) 0.dp else 8.dp
+            val shape = RoundedCornerShape(6.dp)
             val inReplyToModifier = Modifier
                 .padding(top = topPadding, start = 8.dp, end = 8.dp)
-                .clip(RoundedCornerShape(6.dp))
+                .clip(shape)
 
             val talkbackCompatModifier = if (isTalkbackActive()) {
                 // Use z-index to make the replied to text being read after the message
@@ -782,14 +811,25 @@ private fun MessageEventBubbleContent(
             } else {
                 inReplyToModifier.clickable(onClick = inReplyToClick)
             }
+
+            val contentHasError = currentContentValidationState.hasError()
+            val borderColor = if (contentHasError) ElementTheme.colors.borderCriticalSubtle else ElementTheme.colors.separatorPrimary
+            val backgroundColor = if (contentHasError) ElementTheme.colors.bgCriticalSubtle else ElementTheme.colors.bgCanvasDefault
             Box(
                 modifier = talkbackCompatModifier
-                    .border(1.dp, ElementTheme.colors.separatorPrimary, RoundedCornerShape(6.dp))
-                    .background(ElementTheme.colors.bgCanvasDefault, RoundedCornerShape(6.dp))
+                    .border(1.dp, borderColor, shape)
+                    .background(backgroundColor, shape)
                     .padding(4.dp)
             ) {
+                val contentValidationState = rememberEventContentValidationState(eventId = inReplyTo.eventId(), eventContent = inReplyTo.content())
+                val updatedEventSink by rememberUpdatedState(eventSink)
+                LaunchedEffect(inReplyTo) {
+                    val mediaSources = inReplyTo.content()?.mediaSources() ?: return@LaunchedEffect
+                    updatedEventSink(TimelineEvent.ValidateMedia(inReplyTo.eventId(), mediaSources, contentValidationState))
+                }
                 InReplyToView(
                     inReplyTo = inReplyTo,
+                    contentValidationValue = currentContentValidationState,
                     hideImage = timelineProtectionState.hideMediaContent(inReplyTo.eventId()),
                 )
             }
@@ -809,30 +849,47 @@ private fun MessageEventBubbleContent(
         }
     }
 
-    val timestampPosition = when (val content = event.content) {
-        is TimelineItemImageContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Overlay
-        is TimelineItemVideoContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Overlay
-        is TimelineItemGalleryContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Below
-        is TimelineItemAttachmentsContent -> TimestampPosition.Below
-        is TimelineItemStickerContent -> TimestampPosition.Overlay
-        is TimelineItemLocationContent -> {
-            val content = content.ensureActiveLiveLocation()
-            val shouldHide = content.mode is TimelineItemLocationContent.Mode.Live &&
-                content.mode.isActive &&
-                content.mode.isOwnUser
-            if (shouldHide) TimestampPosition.Hidden else TimestampPosition.Overlay
+    val contentValidationState by rememberEventContentValidationState(eventId = event.eventId, needsValidation = event.content.isMedia).collectOverallState()
+    val needsInvalidContentLayout =
+        // Gallery events should not apply custom paddings or layout dispositions
+        event.content !is TimelineItemGalleryContent &&
+            event.content !is TimelineItemAttachmentsContent &&
+            contentValidationState.hasError()
+
+    val timestampPosition = if (needsInvalidContentLayout) {
+        // The invalid content view will be displayed in all these cases, independent of the event content
+        TimestampPosition.Aligned
+    } else {
+        when (val content = event.content) {
+            is TimelineItemImageContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Overlay
+            is TimelineItemVideoContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Overlay
+            is TimelineItemGalleryContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Below
+            is TimelineItemAttachmentsContent -> if (content.showCaption) TimestampPosition.Aligned else TimestampPosition.Below
+            is TimelineItemStickerContent -> TimestampPosition.Overlay
+            is TimelineItemLocationContent -> {
+                val content = content.ensureActiveLiveLocation()
+                val shouldHide = content.mode is TimelineItemLocationContent.Mode.Live &&
+                    content.mode.isActive &&
+                    content.mode.isOwnUser
+                if (shouldHide) TimestampPosition.Hidden else TimestampPosition.Overlay
+            }
+            is TimelineItemPollContent -> TimestampPosition.Below
+            else -> TimestampPosition.Default
         }
-        is TimelineItemPollContent -> TimestampPosition.Below
-        else -> TimestampPosition.Default
     }
-    val paddingBehaviour = when (event.content) {
-        is TimelineItemImageContent -> if (event.content.showCaption) ContentPadding.CaptionedMedia else ContentPadding.Media
-        is TimelineItemVideoContent -> if (event.content.showCaption) ContentPadding.CaptionedMedia else ContentPadding.Media
-        is TimelineItemGalleryContent -> ContentPadding.CaptionedMedia
-        is TimelineItemAttachmentsContent -> ContentPadding.CaptionedMedia
-        is TimelineItemStickerContent,
-        is TimelineItemLocationContent -> ContentPadding.Media
-        else -> ContentPadding.Textual
+
+    val paddingBehaviour = if (needsInvalidContentLayout) {
+        ContentPadding.InvalidContent
+    } else {
+        when (event.content) {
+            is TimelineItemImageContent -> if (event.content.showCaption) ContentPadding.CaptionedMedia else ContentPadding.Media
+            is TimelineItemVideoContent -> if (event.content.showCaption) ContentPadding.CaptionedMedia else ContentPadding.Media
+            is TimelineItemGalleryContent -> ContentPadding.CaptionedMedia
+            is TimelineItemAttachmentsContent -> ContentPadding.CaptionedMedia
+            is TimelineItemStickerContent,
+            is TimelineItemLocationContent -> ContentPadding.Media
+            else -> ContentPadding.Textual
+        }
     }
     CommonLayout(
         showThreadDecoration = timelineMode !is Timeline.Mode.Thread && event.threadInfo is TimelineItemThreadInfo.ThreadResponse,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/TimelineItemGroupedEventsRow.kt

@@ -28,7 +28,6 @@ import io.element.android.features.messages.impl.timeline.components.receipt.Rea
 import io.element.android.features.messages.impl.timeline.components.receipt.TimelineItemReadReceiptView
 import io.element.android.features.messages.impl.timeline.groups.isRedactedMessagesGroup
 import io.element.android.features.messages.impl.timeline.model.TimelineItem
-import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionEvent
 import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
 import io.element.android.features.messages.impl.timeline.protection.aTimelineProtectionState
 import io.element.android.libraries.designsystem.preview.ElementPreview
@@ -62,9 +61,9 @@ fun TimelineItemGroupedEventsRow(
     eventContentView: @Composable (TimelineItem.Event, Modifier, (ContentAvoidingLayoutData) -> Unit) -> Unit =
         { event, contentModifier, onContentLayoutChange ->
             TimelineItemEventContentView(
+                eventId = event.eventId,
                 content = event.content,
-                hideMediaContent = timelineProtectionState.hideMediaContent(event.eventId, event.isMine),
-                onShowContentClick = { timelineProtectionState.eventSink(TimelineProtectionEvent.ShowContent(event.eventId)) },
+                timelineProtectionState = timelineProtectionState,
                 onLinkClick = onLinkClick,
                 onLinkLongClick = onLinkLongClick,
                 eventSink = eventSink,
@@ -134,9 +133,9 @@ private fun TimelineItemGroupedEventsRowContent(
     eventContentView: @Composable (TimelineItem.Event, Modifier, (ContentAvoidingLayoutData) -> Unit) -> Unit =
         { event, contentModifier, onContentLayoutChange ->
             TimelineItemEventContentView(
+                eventId = event.eventId,
                 content = event.content,
-                hideMediaContent = timelineProtectionState.hideMediaContent(event.eventId, event.isMine),
-                onShowContentClick = { timelineProtectionState.eventSink(TimelineProtectionEvent.ShowContent(event.eventId)) },
+                timelineProtectionState = timelineProtectionState,
                 onLinkClick = onLinkClick,
                 onLinkLongClick = onLinkLongClick,
                 eventSink = eventSink,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/TimelineItemRow.kt

@@ -36,7 +36,6 @@ import io.element.android.features.messages.impl.timeline.model.event.TimelineIt
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemRtcNotificationContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemStateContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVoiceContent
-import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionEvent
 import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
 import io.element.android.libraries.designsystem.colors.gradientSubtleColors
 import io.element.android.libraries.designsystem.modifiers.onKeyboardContextMenuAction
@@ -77,9 +76,9 @@ internal fun TimelineItemRow(
     eventContentView: @Composable (TimelineItem.Event, Modifier, (ContentAvoidingLayoutData) -> Unit) -> Unit =
         { event, contentModifier, onContentLayoutChange ->
             TimelineItemEventContentView(
+                eventId = event.eventId,
                 content = event.content,
-                hideMediaContent = timelineProtectionState.hideMediaContent(event.eventId, event.isMine),
-                onShowContentClick = { timelineProtectionState.eventSink(TimelineProtectionEvent.ShowContent(event.eventId)) },
+                timelineProtectionState = timelineProtectionState,
                 onContentClick = { onContentClick(event) },
                 onGalleryItemClick = { index -> onGalleryItemClick(event, index) },
                 onLongClick = { onLongClick(event) },
@@ -119,6 +118,7 @@ internal fun TimelineItemRow(
                             onClick = { onContentClick(timelineItem) },
                             onReadReceiptsClick = onReadReceiptClick,
                             onLongClick = { onLongClick(timelineItem) },
+                            timelineProtectionState = timelineProtectionState,
                             eventSink = eventSink,
                         )
                     }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/TimelineItemStateEventRow.kt

@@ -31,6 +31,8 @@ import io.element.android.features.messages.impl.timeline.model.TimelineItem
 import io.element.android.features.messages.impl.timeline.model.TimelineItemGroupPosition
 import io.element.android.features.messages.impl.timeline.model.TimelineItemReadReceipts
 import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemStateEventContent
+import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
+import io.element.android.features.messages.impl.timeline.protection.aTimelineProtectionState
 import io.element.android.features.messages.impl.timeline.util.defaultTimelineContentPadding
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
@@ -43,6 +45,7 @@ fun TimelineItemStateEventRow(
     onClick: () -> Unit,
     onLongClick: () -> Unit,
     onReadReceiptsClick: (event: TimelineItem.Event) -> Unit,
+    timelineProtectionState: TimelineProtectionState,
     eventSink: (TimelineEvent.TimelineItemEvent) -> Unit,
     modifier: Modifier = Modifier
 ) {
@@ -67,11 +70,11 @@ fun TimelineItemStateEventRow(
                     .widthIn(max = 320.dp)
             ) {
                 TimelineItemEventContentView(
+                    eventId = event.eventId,
                     content = event.content,
                     onLinkClick = {},
                     onLinkLongClick = {},
-                    hideMediaContent = false,
-                    onShowContentClick = {},
+                    timelineProtectionState = timelineProtectionState,
                     eventSink = eventSink,
                     onContentClick = null,
                     onGalleryItemClick = {},
@@ -107,6 +110,7 @@ internal fun TimelineItemStateEventRowPreview() = ElementPreview {
         onClick = {},
         onLongClick = {},
         onReadReceiptsClick = {},
+        timelineProtectionState = aTimelineProtectionState(),
         eventSink = {}
     )
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemAttachmentView.kt

@@ -13,7 +13,6 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.runtime.Composable
@@ -25,8 +24,10 @@ import androidx.compose.ui.unit.dp
 import io.element.android.compound.theme.ElementTheme
 import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayout
 import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
+import io.element.android.libraries.designsystem.theme.components.CircularProgressIndicator
 import io.element.android.libraries.designsystem.theme.components.Icon
 import io.element.android.libraries.designsystem.theme.components.Text
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
 
 /**
  * package-private, you should only use TimelineItemFileView and TimelineItemAudioView.
@@ -38,9 +39,9 @@ fun TimelineItemAttachmentView(
     iconContentDescription: String?,
     filename: String,
     fileExtensionAndSize: String,
-    caption: String?,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationValue: ContentValidationValue = ContentValidationValue.Valid,
 ) {
     Column(
         modifier = modifier,
@@ -50,16 +51,9 @@ fun TimelineItemAttachmentView(
             iconContentDescription = iconContentDescription,
             filename = filename,
             fileExtensionAndSize = fileExtensionAndSize,
-            hasCaption = caption != null,
+            isLoading = !contentValidationValue.isValidated(),
             onContentLayoutChange = onContentLayoutChange,
         )
-        if (caption != null) {
-            TimelineItemAttachmentCaptionView(
-                modifier = Modifier.padding(top = 4.dp),
-                caption = caption,
-                onContentLayoutChange = onContentLayoutChange,
-            )
-        }
     }
 }
 
@@ -69,7 +63,7 @@ private fun TimelineItemAttachmentHeaderView(
     iconContentDescription: String?,
     filename: String,
     fileExtensionAndSize: String,
-    hasCaption: Boolean,
+    isLoading: Boolean,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
 ) {
@@ -86,12 +80,19 @@ private fun TimelineItemAttachmentHeaderView(
                 .background(ElementTheme.colors.bgCanvasDefault, RoundedCornerShape(4.dp)),
             contentAlignment = Alignment.Center,
         ) {
-            Icon(
-                imageVector = icon,
-                contentDescription = iconContentDescription,
-                tint = ElementTheme.colors.iconPrimary,
-                modifier = Modifier.size(24.dp),
-            )
+            if (isLoading) {
+                CircularProgressIndicator(
+                    modifier = Modifier.size(24.dp),
+                    color = ElementTheme.colors.iconPrimary,
+                )
+            } else {
+                Icon(
+                    imageVector = icon,
+                    contentDescription = iconContentDescription,
+                    tint = ElementTheme.colors.iconPrimary,
+                    modifier = Modifier.size(24.dp),
+                )
+            }
         }
         Column {
             Text(
@@ -107,32 +108,11 @@ private fun TimelineItemAttachmentHeaderView(
                 style = ElementTheme.typography.fontBodySmRegular,
                 maxLines = 1,
                 overflow = TextOverflow.Ellipsis,
-                onTextLayout = if (hasCaption) {
-                    {}
-                } else {
-                    ContentAvoidingLayout.measureLastTextLine(
-                        onContentLayoutChange = onContentLayoutChange,
-                        extraWidth = iconSize + spacing
-                    )
-                },
+                onTextLayout = ContentAvoidingLayout.measureLastTextLine(
+                    onContentLayoutChange = onContentLayoutChange,
+                    extraWidth = iconSize + spacing
+                ),
             )
         }
     }
 }
-
-@Composable
-private fun TimelineItemAttachmentCaptionView(
-    caption: String,
-    onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
-    modifier: Modifier = Modifier,
-) {
-    Text(
-        modifier = modifier,
-        text = caption,
-        color = ElementTheme.colors.textPrimary,
-        style = ElementTheme.typography.fontBodyLgRegular,
-        onTextLayout = ContentAvoidingLayout.measureLastTextLine(
-            onContentLayoutChange = onContentLayoutChange,
-        )
-    )
-}

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemAttachmentsContentProvider.kt

@@ -38,7 +38,6 @@ class TimelineItemAttachmentsContentProvider : PreviewParameterProvider<Timeline
             ),
             aTimelineItemAttachmentsContent(
                 body = "Files",
-                caption = "Files mixed with media",
                 attachments = listOf(
                     anAttachmentItem(
                         filename = "report.pdf",

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemAttachmentsListView.kt

@@ -7,31 +7,30 @@
 
 package io.element.android.features.messages.impl.timeline.components.event
 
-import android.text.SpannedString
 import androidx.compose.foundation.background
+import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.layout.widthIn
 import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.material3.LocalContentColor
-import androidx.compose.material3.LocalTextStyle
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.toMutableStateList
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.layout.ContentScale
-import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.tooling.preview.PreviewParameter
@@ -39,8 +38,6 @@ import androidx.compose.ui.unit.dp
 import coil3.compose.AsyncImage
 import io.element.android.compound.theme.ElementTheme
 import io.element.android.compound.tokens.generated.CompoundIcons
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayout
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
 import io.element.android.features.messages.impl.timeline.model.event.AttachmentItem
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemAttachmentsContent
 import io.element.android.libraries.core.mimetype.MimeTypes.isMimeTypeAudio
@@ -50,66 +47,124 @@ import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.designsystem.theme.components.HorizontalDivider
 import io.element.android.libraries.designsystem.theme.components.Icon
+import io.element.android.libraries.matrix.api.core.EventId
 import io.element.android.libraries.matrix.ui.media.MediaRequestData
-import io.element.android.libraries.textcomposer.ElementRichTextEditorStyle
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.InvalidContentView
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NotFoundContentView
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectMediaState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.rememberEventContentValidationState
 import io.element.android.libraries.ui.strings.CommonStrings
-import io.element.android.wysiwyg.compose.EditorStyledText
-import io.element.android.wysiwyg.link.Link
+import kotlin.math.max
 
 @Composable
 fun TimelineItemAttachmentsListView(
+    eventId: EventId?,
     content: TimelineItemAttachmentsContent,
     onGalleryItemClick: (Int) -> Unit,
-    onLinkClick: (Link) -> Unit,
-    onLinkLongClick: (Link) -> Unit,
-    onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
 ) {
-    Column(modifier = modifier) {
-        Column(
-            modifier = Modifier.fillMaxWidth(),
-        ) {
-            content.attachments.forEachIndexed { index, attachment ->
-                Column {
-                    if (index > 0) {
-                        HorizontalDivider(
-                            color = ElementTheme.colors.borderInteractiveSecondary,
+    val contentValidationState = rememberEventContentValidationState(
+        eventId = eventId,
+        needsValidation = content.isMedia,
+    )
+
+    Column(modifier = modifier.fillMaxWidth()) {
+        val validationStates = remember(content.attachments) {
+            buildList {
+                for (attachment in content.attachments) {
+                    add(validationStateForAttachment(attachment, contentValidationState))
+                }
+            }.toMutableStateList()
+        }
+        content.attachments.forEachIndexed { index, attachment ->
+            Column(modifier = Modifier.fillMaxWidth()) {
+                val thumbnailContentValidationState by contentValidationState.collectMediaState(attachment.thumbnailSource?.safeUrl)
+                val mediaContentValidationState by contentValidationState.collectMediaState(attachment.mediaSource.safeUrl)
+
+                val itemContentValidationState = remember(thumbnailContentValidationState, mediaContentValidationState) {
+                    validationStateForAttachment(attachment, contentValidationState)
+                }
+
+                LaunchedEffect(itemContentValidationState) {
+                    validationStates[index] = itemContentValidationState
+                }
+
+                val needsSeparator = index in 1..max(1, content.attachments.lastIndex)
+                val isPreviousItemInvalid = validationStates.getOrNull(index - 1)?.hasError() == true
+                if (needsSeparator && !itemContentValidationState.hasError() && !isPreviousItemInvalid) {
+                    HorizontalDivider(
+                        color = ElementTheme.colors.borderInteractiveSecondary,
+                    )
+                }
+
+                when (itemContentValidationState) {
+                    ContentValidationValue.Invalid -> {
+                        val shape = RoundedCornerShape(6.dp)
+                        InvalidContentView(
+                            modifier = Modifier
+                                .padding(vertical = 6.dp)
+                                .border(width = 1.dp, color = ElementTheme.colors.borderCriticalSubtle, shape = shape)
+                                .clip(shape),
+                            contentPadding = PaddingValues(horizontal = 12.dp, vertical = 4.dp),
                         )
                     }
-                    AttachmentListItem(
-                        attachment = attachment,
-                        onClick = { onGalleryItemClick(index) },
+                    is ContentValidationValue.UnrecoverableError -> {
+                        val shape = RoundedCornerShape(6.dp)
+                        NotFoundContentView(
+                            modifier = Modifier
+                                .padding(vertical = 6.dp)
+                                .border(width = 1.dp, color = ElementTheme.colors.borderCriticalSubtle, shape = shape)
+                                .clip(shape),
+                            contentPadding = PaddingValues(horizontal = 12.dp, vertical = 4.dp),
+                        )
+                    }
+                    ContentValidationValue.Loading -> {
+                        CircularProgressIndicator(modifier = Modifier.padding(8.dp).align(Alignment.CenterHorizontally))
+                    }
+                    ContentValidationValue.Valid -> {
+                        AttachmentListItem(
+                            attachment = attachment,
+                            onClick = { onGalleryItemClick(index) },
+                        )
+                    }
+                    else -> {
+                        // TODO handle cases where either the content hasn't started validation or it failed to do so
+                    }
+                }
+
+                if (index == content.attachments.lastIndex && content.showCaption && !itemContentValidationState.isInvalid()) {
+                    HorizontalDivider(
+                        color = ElementTheme.colors.borderInteractiveSecondary,
                     )
                 }
             }
         }
-        if (content.showCaption) {
-            HorizontalDivider(
-                color = ElementTheme.colors.borderInteractiveSecondary,
-            )
-            Spacer(modifier = Modifier.height(8.dp))
-            val caption = if (LocalInspectionMode.current) {
-                SpannedString(content.caption)
-            } else {
-                content.formattedCaption ?: SpannedString(content.caption)
-            }
-            CompositionLocalProvider(
-                LocalContentColor provides ElementTheme.colors.textPrimary,
-                LocalTextStyle provides ElementTheme.typography.fontBodyLgRegular
-            ) {
-                EditorStyledText(
-                    modifier = Modifier
-                        .padding(horizontal = 4.dp)
-                        .widthIn(min = 120.dp),
-                    text = caption,
-                    style = ElementRichTextEditorStyle.textStyle(),
-                    onLinkClickedListener = onLinkClick,
-                    onLinkLongClickedListener = onLinkLongClick,
-                    releaseOnDetach = false,
-                    onTextLayout = ContentAvoidingLayout.measureLegacyLastTextLine(onContentLayoutChange = onContentLayoutChange),
-                )
-            }
-        }
+    }
+}
+
+private fun validationStateForAttachment(
+    attachment: AttachmentItem,
+    contentValidationState: ContentValidationState,
+): ContentValidationValue {
+    val thumbnailValue = attachment.thumbnailSource?.safeUrl?.let { contentValidationState.getCurrentMediaState(it) } ?: ContentValidationValue.Unknown
+    val mediaValue = contentValidationState.getCurrentMediaState(attachment.mediaSource.safeUrl)
+    return validationStateForAttachment(thumbnailValue, mediaValue)
+}
+
+private fun validationStateForAttachment(
+    thumbnailValue: ContentValidationValue,
+    mediaValue: ContentValidationValue,
+): ContentValidationValue {
+    return if (thumbnailValue.isInvalid() || mediaValue.isInvalid()) {
+        ContentValidationValue.Invalid
+    } else if (thumbnailValue.hasUnrecoverableError() || mediaValue.hasUnrecoverableError()) {
+        listOf(thumbnailValue, mediaValue).first { it.hasUnrecoverableError() }
+    } else if (thumbnailValue.isLoading() || mediaValue.isLoading()) {
+        ContentValidationValue.Loading
+    } else {
+        mediaValue
     }
 }
 
@@ -213,10 +268,8 @@ internal fun TimelineItemAttachmentsListViewPreview(
     @PreviewParameter(TimelineItemAttachmentsContentProvider::class) content: TimelineItemAttachmentsContent
 ) = ElementPreview {
     TimelineItemAttachmentsListView(
+        eventId = EventId("\$eventId"),
         content = content,
         onGalleryItemClick = {},
-        onLinkClick = {},
-        onLinkLongClick = {},
-        onContentLayoutChange = {},
     )
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemAudioView.kt

@@ -16,21 +16,23 @@ import io.element.android.features.messages.impl.timeline.components.layout.Cont
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemAudioContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemAudioContentProvider
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
 
 @Composable
 fun TimelineItemAudioView(
     content: TimelineItemAudioContent,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationValue: ContentValidationValue = ContentValidationValue.Valid,
 ) {
     TimelineItemAttachmentView(
         icon = CompoundIcons.Audio(),
         iconContentDescription = null,
         filename = content.filename,
         fileExtensionAndSize = content.fileExtensionAndSize,
-        caption = content.caption,
         onContentLayoutChange = onContentLayoutChange,
         modifier = modifier,
+        contentValidationValue = contentValidationValue,
     )
 }
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemEventContentView.kt

@@ -8,9 +8,23 @@
 
 package io.element.android.features.messages.impl.timeline.components.event
 
+import android.text.SpannedString
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.LocalContentColor
+import androidx.compose.material3.LocalTextStyle
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalInspectionMode
+import androidx.compose.ui.unit.dp
+import io.element.android.compound.theme.ElementTheme
 import io.element.android.features.messages.impl.timeline.TimelineEvent
+import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayout
 import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
 import io.element.android.features.messages.impl.timeline.di.LocalTimelineItemPresenterFactories
 import io.element.android.features.messages.impl.timeline.di.rememberPresenter
@@ -32,132 +46,265 @@ import io.element.android.features.messages.impl.timeline.model.event.TimelineIt
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemUnknownContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVideoContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVoiceContent
+import io.element.android.features.messages.impl.timeline.model.event.captionOrNull
 import io.element.android.features.messages.impl.timeline.model.event.ensureActiveLiveLocation
+import io.element.android.features.messages.impl.timeline.model.event.formattedCaptionOrNull
+import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionEvent
+import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
 import io.element.android.libraries.architecture.Presenter
+import io.element.android.libraries.designsystem.components.EqualWidthColumn
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.InvalidContentView
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NotFoundContentView
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectOverallState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.rememberEventContentValidationState
+import io.element.android.libraries.textcomposer.ElementRichTextEditorStyle
 import io.element.android.libraries.voiceplayer.api.VoiceMessageState
+import io.element.android.wysiwyg.compose.EditorStyledText
 import io.element.android.wysiwyg.link.Link
 
 @Composable
 fun TimelineItemEventContentView(
+    eventId: EventId?,
     content: TimelineItemEventContent,
-    hideMediaContent: Boolean,
     onContentClick: (() -> Unit)?,
     onGalleryItemClick: ((Int) -> Unit),
+    timelineProtectionState: TimelineProtectionState,
     onLongClick: (() -> Unit)?,
-    onShowContentClick: () -> Unit,
     onLinkClick: (Link) -> Unit,
     onLinkLongClick: (Link) -> Unit,
     eventSink: (TimelineEvent.TimelineItemEvent) -> Unit,
     modifier: Modifier = Modifier,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit = {},
 ) {
-    val presenterFactories = LocalTimelineItemPresenterFactories.current
-    when (content) {
-        is TimelineItemEncryptedContent -> TimelineItemEncryptedView(
-            content = content,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier
-        )
-        is TimelineItemRedactedContent -> TimelineItemRedactedView(
-            content = content,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier
-        )
-        is TimelineItemTextBasedContent -> TimelineItemTextView(
-            content = content,
-            modifier = modifier,
-            onLinkClick = onLinkClick,
-            onLinkLongClick = onLinkLongClick,
-            onContentLayoutChange = onContentLayoutChange
-        )
-        is TimelineItemUnknownContent -> TimelineItemUnknownView(
-            content = content,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier
-        )
-        is TimelineItemLocationContent -> {
-            TimelineItemLocationView(
-                content = content.ensureActiveLiveLocation(),
-                onStopLiveLocationClick = { eventSink(TimelineEvent.StopLiveLocationShare) },
-                modifier = modifier
-            )
+    val hideMediaContent = remember(eventId, timelineProtectionState.protectionState) {
+        timelineProtectionState.hideMediaContent(eventId)
+    }
+
+    val onShowContentClick = remember(timelineProtectionState.eventSink) {
+        {
+            timelineProtectionState.eventSink(TimelineProtectionEvent.ShowContent(eventId))
         }
-        is TimelineItemImageContent -> TimelineItemImageView(
-            content = content,
-            hideMediaContent = hideMediaContent,
-            onContentClick = onContentClick,
-            onLongClick = onLongClick,
-            onShowContentClick = onShowContentClick,
-            onLinkClick = onLinkClick,
-            onLinkLongClick = onLinkLongClick,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier,
-        )
-        is TimelineItemGalleryContent -> TimelineItemGalleryView(
-            content = content,
-            onGalleryItemClick = { index -> onGalleryItemClick(index) },
-            onLongClick = onLongClick,
-            onLinkClick = onLinkClick,
-            onLinkLongClick = onLinkLongClick,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier,
-        )
-        is TimelineItemAttachmentsContent -> TimelineItemAttachmentsListView(
-            content = content,
-            onGalleryItemClick = { index -> onGalleryItemClick(index) },
-            onLinkClick = onLinkClick,
-            onLinkLongClick = onLinkLongClick,
-            onContentLayoutChange = {},
-            modifier = modifier,
-        )
-        is TimelineItemStickerContent -> TimelineItemStickerView(
-            content = content,
-            hideMediaContent = hideMediaContent,
-            onContentClick = onContentClick,
-            onLongClick = onLongClick,
-            onShowClick = onShowContentClick,
-            modifier = modifier,
-        )
-        is TimelineItemVideoContent -> TimelineItemVideoView(
-            content = content,
-            hideMediaContent = hideMediaContent,
-            onContentClick = onContentClick,
-            onLongClick = onLongClick,
-            onShowContentClick = onShowContentClick,
-            onLinkClick = onLinkClick,
-            onLinkLongClick = onLinkLongClick,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier
-        )
-        is TimelineItemFileContent -> TimelineItemFileView(
-            content = content,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier
-        )
-        is TimelineItemAudioContent -> TimelineItemAudioView(
-            content = content,
-            onContentLayoutChange = onContentLayoutChange,
-            modifier = modifier
-        )
-        is TimelineItemLegacyCallInviteContent -> TimelineItemLegacyCallInviteView(modifier = modifier)
-        is TimelineItemStateContent -> TimelineItemStateView(
-            content = content,
-            modifier = modifier
-        )
-        is TimelineItemPollContent -> TimelineItemPollView(
-            content = content,
-            eventSink = eventSink,
-            modifier = modifier,
-        )
-        is TimelineItemVoiceContent -> {
-            val presenter: Presenter<VoiceMessageState> = presenterFactories.rememberPresenter(content)
-            TimelineItemVoiceView(
-                state = presenter.present(),
-                content = content,
+    }
+
+    val contentValidationState = rememberEventContentValidationState(eventId = eventId, needsValidation = content.isMedia)
+    val overallValidationState by contentValidationState.collectOverallState()
+    val needsContentValidationPerItem = remember(content) { content is TimelineItemGalleryContent || content is TimelineItemAttachmentsContent }
+
+    if (eventId != null) {
+        ValidateMediaHelper(eventId, content, contentValidationState, eventSink)
+    }
+
+    val caption = content.captionOrNull()
+    val showCaption = caption != null && content !is TimelineItemStickerContent && content !is TimelineItemVoiceContent
+    // If a caption is added, it will be used to get the free space for the overlay, so we don't need to add onContentLayoutChange to the actual content
+    val calculatedOnContentLayoutChange = remember(onContentLayoutChange, showCaption) {
+        if (showCaption) {
+            {}
+        } else {
+            onContentLayoutChange
+        }
+    }
+
+    val displayInvalidContent = overallValidationState.isInvalid() && !needsContentValidationPerItem
+    val displayContentNotFound = overallValidationState.hasUnrecoverableError() && !needsContentValidationPerItem
+    EqualWidthColumn(modifier = modifier) {
+        if (displayInvalidContent) {
+            InvalidContentView(
+                contentPadding = PaddingValues(horizontal = 12.dp, vertical = 4.dp),
+                onTextLayout = ContentAvoidingLayout.measureLastTextLine(
+                    onContentLayoutChange = calculatedOnContentLayoutChange,
+                    // Icon + horizontal paddings
+                    extraWidth = 24.dp + 20.dp,
+                )
+            )
+        } else if (displayContentNotFound) {
+            NotFoundContentView(
+                contentPadding = PaddingValues(horizontal = 12.dp, vertical = 4.dp),
+                onTextLayout = ContentAvoidingLayout.measureLastTextLine(
+                    onContentLayoutChange = calculatedOnContentLayoutChange,
+                    // Icon + horizontal paddings
+                    extraWidth = 24.dp + 20.dp,
+                )
+            )
+        } else {
+            val presenterFactories = LocalTimelineItemPresenterFactories.current
+            when (content) {
+                is TimelineItemEncryptedContent -> TimelineItemEncryptedView(
+                    content = content,
+                    onContentLayoutChange = calculatedOnContentLayoutChange,
+                )
+                is TimelineItemRedactedContent -> TimelineItemRedactedView(
+                    content = content,
+                    onContentLayoutChange = calculatedOnContentLayoutChange,
+                )
+                is TimelineItemTextBasedContent -> TimelineItemTextView(
+                    content = content,
+                    onLinkClick = onLinkClick,
+                    onLinkLongClick = onLinkLongClick,
+                    onContentLayoutChange = calculatedOnContentLayoutChange,
+                )
+                is TimelineItemUnknownContent -> TimelineItemUnknownView(
+                    content = content,
+                    onContentLayoutChange = calculatedOnContentLayoutChange,
+                )
+                is TimelineItemLocationContent -> {
+                    TimelineItemLocationView(
+                        content = content.ensureActiveLiveLocation(),
+                        onStopLiveLocationClick = { eventSink(TimelineEvent.StopLiveLocationShare) },
+                    )
+                }
+                is TimelineItemImageContent -> {
+                    TimelineItemImageView(
+                        content = content,
+                        hideMediaContent = hideMediaContent,
+                        onContentClick = onContentClick,
+                        onLongClick = onLongClick,
+                        onShowContentClick = onShowContentClick,
+                        contentValidationState = contentValidationState,
+                    )
+                }
+                is TimelineItemStickerContent -> {
+                    TimelineItemStickerView(
+                        content = content,
+                        hideMediaContent = hideMediaContent,
+                        onContentClick = onContentClick,
+                        onLongClick = onLongClick,
+                        onShowClick = onShowContentClick,
+                        contentValidationState = contentValidationState,
+                    )
+                }
+                is TimelineItemVideoContent -> {
+                    TimelineItemVideoView(
+                        content = content,
+                        hideMediaContent = hideMediaContent,
+                        onContentClick = onContentClick,
+                        onLongClick = onLongClick,
+                        onShowContentClick = onShowContentClick,
+                        contentValidationState = contentValidationState,
+                    )
+                }
+                is TimelineItemGalleryContent -> TimelineItemGalleryView(
+                    eventId = eventId,
+                    content = content,
+                    onGalleryItemClick = { index -> onGalleryItemClick(index) },
+                    onLongClick = onLongClick,
+                )
+                is TimelineItemAttachmentsContent -> TimelineItemAttachmentsListView(
+                    eventId = eventId,
+                    content = content,
+                    onGalleryItemClick = { index -> onGalleryItemClick(index) },
+                )
+                is TimelineItemFileContent -> {
+                    TimelineItemFileView(
+                        content = content,
+                        onContentLayoutChange = calculatedOnContentLayoutChange,
+                        contentValidationValue = overallValidationState,
+                    )
+                }
+                is TimelineItemAudioContent -> {
+                    TimelineItemAudioView(
+                        content = content,
+                        onContentLayoutChange = calculatedOnContentLayoutChange,
+                        contentValidationValue = overallValidationState,
+                    )
+                }
+                is TimelineItemLegacyCallInviteContent -> TimelineItemLegacyCallInviteView()
+                is TimelineItemStateContent -> TimelineItemStateView(
+                    content = content,
+                )
+                is TimelineItemPollContent -> TimelineItemPollView(
+                    content = content,
+                    eventSink = eventSink,
+                )
+                is TimelineItemVoiceContent -> {
+                    val presenter: Presenter<VoiceMessageState> = presenterFactories.rememberPresenter(content)
+                    TimelineItemVoiceView(
+                        state = presenter.present(),
+                        content = content,
+                        onContentLayoutChange = calculatedOnContentLayoutChange,
+                        contentValidationValue = overallValidationState,
+                    )
+                }
+                is TimelineItemRtcNotificationContent -> error("This shouldn't be rendered as the content of a bubble")
+            }
+        }
+
+        if (showCaption) {
+            val padding = if (displayInvalidContent) {
+                PaddingValues(start = 12.dp, end = 12.dp, top = 4.dp, bottom = 0.dp)
+            } else {
+                when (content) {
+                    is TimelineItemImageContent,
+                    is TimelineItemVideoContent,
+                    is TimelineItemGalleryContent,
+                    is TimelineItemAttachmentsContent -> PaddingValues(start = 4.dp, end = 4.dp, top = 8.dp, bottom = 0.dp)
+                    else -> PaddingValues(horizontal = 12.dp, vertical = 8.dp)
+                }
+            }
+            CaptionView(
+                modifier = Modifier.padding(padding),
+                caption = caption,
+                formattedCaption = content.formattedCaptionOrNull(),
+                onLinkClick = onLinkClick,
+                onLinkLongClick = onLinkLongClick,
                 onContentLayoutChange = onContentLayoutChange,
-                modifier = modifier
             )
         }
-        is TimelineItemRtcNotificationContent -> error("This shouldn't be rendered as the content of a bubble")
+    }
+}
+
+@Composable
+private fun CaptionView(
+    caption: String,
+    formattedCaption: CharSequence?,
+    onLinkClick: (Link) -> Unit,
+    onLinkLongClick: (Link) -> Unit,
+    onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val caption = if (LocalInspectionMode.current) {
+        SpannedString(caption)
+    } else {
+        formattedCaption ?: SpannedString(caption)
+    }
+    CompositionLocalProvider(
+        LocalContentColor provides ElementTheme.colors.textPrimary,
+        LocalTextStyle provides ElementTheme.typography.fontBodyLgRegular
+    ) {
+        EditorStyledText(
+            modifier = modifier,
+            text = caption,
+            style = ElementRichTextEditorStyle.textStyle(),
+            onLinkClickedListener = onLinkClick,
+            onLinkLongClickedListener = onLinkLongClick,
+            releaseOnDetach = false,
+            onTextLayout = ContentAvoidingLayout.measureLegacyLastTextLine(onContentLayoutChange = onContentLayoutChange),
+        )
+    }
+}
+
+@Composable
+private fun ValidateMediaHelper(
+    eventId: EventId,
+    content: TimelineItemEventContent,
+    contentValidationState: ContentValidationState,
+    eventSink: (TimelineEvent.TimelineItemEvent) -> Unit,
+) {
+    val mediaSources = when (content) {
+        is TimelineItemImageContent -> listOfNotNull(content.thumbnailSource, content.mediaSource)
+        is TimelineItemStickerContent -> listOfNotNull(content.thumbnailSource, content.mediaSource)
+        is TimelineItemVideoContent -> listOfNotNull(content.thumbnailSource, content.mediaSource)
+        is TimelineItemFileContent -> listOfNotNull(content.thumbnailSource, content.mediaSource)
+        is TimelineItemAudioContent -> listOf(content.mediaSource)
+        is TimelineItemVoiceContent -> listOf(content.mediaSource)
+        is TimelineItemGalleryContent -> content.items.flatMap { listOfNotNull(it.thumbnailSource, it.mediaSource) }
+        is TimelineItemAttachmentsContent -> content.attachments.flatMap { listOfNotNull(it.thumbnailSource, it.mediaSource) }
+        else -> return
+    }
+    val updatedEventSink by rememberUpdatedState(eventSink)
+    LaunchedEffect(eventId, mediaSources) {
+        updatedEventSink(TimelineEvent.ValidateMedia(eventId, mediaSources, contentValidationState))
     }
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemFileView.kt

@@ -17,6 +17,7 @@ import io.element.android.features.messages.impl.timeline.components.layout.Cont
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemFileContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemFileContentProvider
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
 import io.element.android.libraries.ui.strings.CommonStrings
 
 /**
@@ -27,15 +28,16 @@ fun TimelineItemFileView(
     content: TimelineItemFileContent,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationValue: ContentValidationValue = ContentValidationValue.Valid,
 ) {
     TimelineItemAttachmentView(
         icon = CompoundIcons.Attachment(),
         iconContentDescription = stringResource(CommonStrings.common_file),
         filename = content.filename,
         fileExtensionAndSize = content.fileExtensionAndSize,
-        caption = content.caption,
         onContentLayoutChange = onContentLayoutChange,
         modifier = modifier,
+        contentValidationValue = contentValidationValue,
     )
 }
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemGalleryContentProvider.kt

@@ -116,6 +116,7 @@ fun aGalleryItem(
     width: Int = 400,
     height: Int = 300,
     duration: Duration = Duration.ZERO,
+    mediaSource: MediaSource = MediaSource(url = "", json = ""),
 ): GalleryItem {
     return GalleryItem(
         filename = filename,
@@ -125,7 +126,7 @@ fun aGalleryItem(
             GalleryItem.Type.File -> "application/pdf"
             GalleryItem.Type.Image -> "image/jpeg"
         },
-        mediaSource = MediaSource(url = "", json = ""),
+        mediaSource = mediaSource,
         thumbnailSource = null,
         width = width,
         height = height,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemGalleryView.kt

@@ -7,7 +7,6 @@
 
 package io.element.android.features.messages.impl.timeline.components.event
 
-import android.text.SpannedString
 import androidx.compose.foundation.background
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.layout.Arrangement
@@ -21,28 +20,24 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
-import androidx.compose.foundation.layout.widthIn
 import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.material3.LocalContentColor
-import androidx.compose.material3.LocalTextStyle
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.layout.ContentScale
-import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.dp
 import coil3.compose.AsyncImage
 import io.element.android.compound.theme.ElementTheme
 import io.element.android.compound.tokens.generated.CompoundIcons
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayout
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
 import io.element.android.features.messages.impl.timeline.model.event.GalleryItem
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemGalleryContent
 import io.element.android.libraries.designsystem.components.blurhash.blurHashBackground
@@ -50,10 +45,11 @@ import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.designsystem.theme.bgSubtleTertiary
 import io.element.android.libraries.designsystem.theme.components.Icon
-import io.element.android.libraries.textcomposer.ElementRichTextEditorStyle
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectMediaState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.rememberEventContentValidationState
 import io.element.android.libraries.ui.utils.time.formatShort
-import io.element.android.wysiwyg.compose.EditorStyledText
-import io.element.android.wysiwyg.link.Link
 import kotlinx.collections.immutable.ImmutableList
 
 private const val MAX_TILES = 5
@@ -67,12 +63,10 @@ private val THREE_IMAGE_ROW_HEIGHT = 85.dp
 
 @Composable
 fun TimelineItemGalleryView(
+    eventId: EventId?,
     content: TimelineItemGalleryContent,
     onGalleryItemClick: (Int) -> Unit,
     onLongClick: (() -> Unit)?,
-    onLinkClick: (Link) -> Unit,
-    onLinkLongClick: (Link) -> Unit,
-    onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
 ) {
     val totalItems = content.items.size
@@ -87,21 +81,25 @@ fun TimelineItemGalleryView(
             when (totalItems) {
                 0 -> Unit
                 1 -> SingleItemLayout(
+                    eventId = eventId,
                     item = content.items[0],
                     onClick = { onGalleryItemClick(0) },
                     onLongClick = onLongClick,
                 )
                 2 -> TwoItemLayout(
+                    eventId = eventId,
                     items = content.items,
                     onItemClick = onGalleryItemClick,
                     onLongClick = onLongClick,
                 )
                 3 -> ThreeItemLayout(
+                    eventId = eventId,
                     items = content.items,
                     onItemClick = onGalleryItemClick,
                     onLongClick = onLongClick,
                 )
                 else -> FourPlusItemLayout(
+                    eventId = eventId,
                     items = content.items,
                     showOverflow = showOverflow,
                     overflowCount = overflowCount,
@@ -110,40 +108,18 @@ fun TimelineItemGalleryView(
                 )
             }
         }
-        if (content.showCaption) {
-            Spacer(modifier = Modifier.height(8.dp))
-            val caption = if (LocalInspectionMode.current) {
-                SpannedString(content.caption)
-            } else {
-                content.formattedCaption ?: SpannedString(content.caption)
-            }
-            CompositionLocalProvider(
-                LocalContentColor provides ElementTheme.colors.textPrimary,
-                LocalTextStyle provides ElementTheme.typography.fontBodyLgRegular
-            ) {
-                EditorStyledText(
-                    modifier = Modifier
-                        .padding(horizontal = 4.dp)
-                        .widthIn(min = 120.dp),
-                    text = caption,
-                    style = ElementRichTextEditorStyle.textStyle(),
-                    onLinkClickedListener = onLinkClick,
-                    onLinkLongClickedListener = onLinkLongClick,
-                    releaseOnDetach = false,
-                    onTextLayout = ContentAvoidingLayout.measureLegacyLastTextLine(onContentLayoutChange = onContentLayoutChange),
-                )
-            }
-        }
     }
 }
 
 @Composable
 private fun SingleItemLayout(
+    eventId: EventId?,
     item: GalleryItem,
     onClick: () -> Unit,
     onLongClick: (() -> Unit)?,
 ) {
     GalleryItemCell(
+        eventId = eventId,
         item = item,
         isLast = false,
         remainingCount = 0,
@@ -157,6 +133,7 @@ private fun SingleItemLayout(
 
 @Composable
 private fun TwoItemLayout(
+    eventId: EventId?,
     items: ImmutableList<GalleryItem>,
     onItemClick: (Int) -> Unit,
     onLongClick: (() -> Unit)?,
@@ -167,6 +144,7 @@ private fun TwoItemLayout(
     ) {
         items.forEachIndexed { index, item ->
             GalleryItemCell(
+                eventId = eventId,
                 item = item,
                 isLast = false,
                 remainingCount = 0,
@@ -182,6 +160,7 @@ private fun TwoItemLayout(
 
 @Composable
 private fun ThreeItemLayout(
+    eventId: EventId?,
     items: ImmutableList<GalleryItem>,
     onItemClick: (Int) -> Unit,
     onLongClick: (() -> Unit)?,
@@ -191,6 +170,7 @@ private fun ThreeItemLayout(
         verticalArrangement = Arrangement.spacedBy(GRID_SPACING),
     ) {
         GalleryItemCell(
+            eventId = eventId,
             item = items[0],
             isLast = false,
             remainingCount = 0,
@@ -206,6 +186,7 @@ private fun ThreeItemLayout(
         ) {
             for (it in 1..2) {
                 GalleryItemCell(
+                    eventId = eventId,
                     item = items[it],
                     isLast = false,
                     remainingCount = 0,
@@ -222,6 +203,7 @@ private fun ThreeItemLayout(
 
 @Composable
 private fun FourPlusItemLayout(
+    eventId: EventId?,
     items: ImmutableList<GalleryItem>,
     showOverflow: Boolean,
     overflowCount: Int,
@@ -238,6 +220,7 @@ private fun FourPlusItemLayout(
         ) {
             for (it in 0..1) {
                 GalleryItemCell(
+                    eventId = eventId,
                     item = items[it],
                     isLast = false,
                     remainingCount = 0,
@@ -260,6 +243,7 @@ private fun FourPlusItemLayout(
                 if (itemIndex < items.size) {
                     val isOverflowItem = showOverflow && i == bottomRowItems - 1
                     GalleryItemCell(
+                        eventId = eventId,
                         item = items[itemIndex],
                         isLast = isOverflowItem,
                         remainingCount = if (isOverflowItem) overflowCount else 0,
@@ -277,6 +261,7 @@ private fun FourPlusItemLayout(
 
 @Composable
 private fun GalleryItemCell(
+    eventId: EventId?,
     item: GalleryItem,
     isLast: Boolean,
     remainingCount: Int,
@@ -284,6 +269,22 @@ private fun GalleryItemCell(
     onLongClick: (() -> Unit)?,
     modifier: Modifier = Modifier,
 ) {
+    val eventContentValidationState = rememberEventContentValidationState(eventId, needsValidation = true)
+    val thumbnailContentValidationState by eventContentValidationState.collectMediaState(item.thumbnailSource?.safeUrl)
+    val mediaContentValidationState by eventContentValidationState.collectMediaState(item.mediaSource.safeUrl)
+
+    val itemContentValidationState = remember(thumbnailContentValidationState, mediaContentValidationState) {
+        if (thumbnailContentValidationState.isInvalid() || mediaContentValidationState.isInvalid()) {
+            ContentValidationValue.Invalid
+        } else if (thumbnailContentValidationState.hasUnrecoverableError() || mediaContentValidationState.hasUnrecoverableError()) {
+            listOf(thumbnailContentValidationState, mediaContentValidationState).first { it is ContentValidationValue.UnrecoverableError }
+        } else if (thumbnailContentValidationState.isLoading() || mediaContentValidationState.isLoading()) {
+            ContentValidationValue.Loading
+        } else {
+            mediaContentValidationState
+        }
+    }
+
     Box(
         modifier = modifier
             .blurHashBackground(item.blurhash, alpha = 0.9f)
@@ -305,7 +306,20 @@ private fun GalleryItemCell(
             VideoOverlay(duration = item.duration)
         }
 
-        if (isLast && remainingCount > 0) {
+        if (itemContentValidationState.isLoading()) {
+            CircularProgressIndicator()
+        } else if (itemContentValidationState.hasError()) {
+            Box(
+                modifier = Modifier.fillMaxSize().background(ElementTheme.colors.bgCriticalSubtle)
+            ) {
+                Icon(
+                    modifier = Modifier.align(Alignment.Center),
+                    imageVector = CompoundIcons.Error(),
+                    tint = ElementTheme.colors.iconCriticalPrimary,
+                    contentDescription = null,
+                )
+            }
+        } else if (isLast && remainingCount > 0) {
             RemainingCountOverlay(count = remainingCount)
         }
     }
@@ -374,11 +388,9 @@ internal fun TimelineItemGalleryViewPreview(
     @PreviewParameter(TimelineItemGalleryContentProvider::class) content: TimelineItemGalleryContent,
 ) = ElementPreview {
     TimelineItemGalleryView(
+        eventId = null,
         content = content,
         onGalleryItemClick = {},
         onLongClick = {},
-        onLinkClick = {},
-        onLinkLongClick = {},
-        onContentLayoutChange = {},
     )
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemImageView.kt

@@ -8,20 +8,13 @@
 
 package io.element.android.features.messages.impl.timeline.components.event
 
-import android.text.SpannedString
 import androidx.compose.foundation.background
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
-import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.widthIn
+import androidx.compose.foundation.layout.wrapContentWidth
 import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.material3.LocalContentColor
-import androidx.compose.material3.LocalTextStyle
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -31,118 +24,97 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.layout.ContentScale
-import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.dp
 import coil3.compose.AsyncImage
-import coil3.compose.AsyncImagePainter
-import io.element.android.compound.theme.ElementTheme
 import io.element.android.features.messages.impl.timeline.aTimelineItemEvent
 import io.element.android.features.messages.impl.timeline.components.ATimelineItemEventRow
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayout
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
 import io.element.android.features.messages.impl.timeline.model.TimelineItemGroupPosition
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemImageContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemImageContentProvider
 import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemImageContent
 import io.element.android.features.messages.impl.timeline.protection.ProtectedView
 import io.element.android.features.messages.impl.timeline.protection.coerceRatioWhenHidingContent
+import io.element.android.features.messages.impl.timeline.util.handleAsyncImageStateChange
 import io.element.android.libraries.designsystem.components.blurhash.blurHashBackground
 import io.element.android.libraries.designsystem.modifiers.onKeyboardContextMenuAction
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
-import io.element.android.libraries.textcomposer.ElementRichTextEditorStyle
+import io.element.android.libraries.designsystem.theme.components.CircularProgressIndicator
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectOverallState
 import io.element.android.libraries.ui.strings.CommonStrings
 import io.element.android.libraries.ui.utils.a11y.isTalkbackActive
-import io.element.android.wysiwyg.compose.EditorStyledText
-import io.element.android.wysiwyg.link.Link
 
-private const val TALL_IMAGE_RATIO_DIVISOR = 3
 @Composable
 fun TimelineItemImageView(
     content: TimelineItemImageContent,
     hideMediaContent: Boolean,
     onContentClick: (() -> Unit)?,
     onLongClick: (() -> Unit)?,
-    onLinkClick: (Link) -> Unit,
-    onLinkLongClick: (Link) -> Unit,
     onShowContentClick: () -> Unit,
-    onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationState: ContentValidationState = remember { DefaultContentValidationState() },
 ) {
     val a11yLabel = stringResource(CommonStrings.common_image)
     val description = content.caption?.let { "$a11yLabel: $it" } ?: a11yLabel
-    Column(modifier = modifier) {
+    Column(modifier = modifier.wrapContentWidth(Alignment.CenterHorizontally)) {
         val containerModifier = if (content.showCaption) {
             Modifier.clip(RoundedCornerShape(10.dp))
         } else {
             Modifier
         }
+
+        val eventContentValidation by contentValidationState.collectOverallState()
+        val isContentBeingValidated = !eventContentValidation.isValidated()
         TimelineItemAspectRatioBox(
-            modifier = containerModifier.blurHashBackground(content.blurhash, alpha = 0.9f).align(Alignment.CenterHorizontally),
+            modifier = containerModifier
+                .blurHashBackground(content.blurhash, alpha = 0.9f)
+                .align(Alignment.CenterHorizontally),
             aspectRatio = coerceRatioWhenHidingContent(content.aspectRatio, hideMediaContent),
         ) {
-            ProtectedView(
-                hideContent = hideMediaContent,
-                onShowClick = onShowContentClick,
-            ) {
-                var isLoaded by remember { mutableStateOf(false) }
-                AsyncImage(
-                    modifier = Modifier
-                        .fillMaxWidth()
-                        .then(if (isLoaded) Modifier.background(Color.White) else Modifier)
-                        .then(
-                            if (!isTalkbackActive() && onContentClick != null) {
-                                Modifier
-                                    .combinedClickable(
-                                        onClick = onContentClick,
-                                        onLongClick = onLongClick,
-                                    )
-                                    .onKeyboardContextMenuAction(onLongClick)
-                            } else {
-                                Modifier
-                            }
-                        ),
-                    model = content.thumbnailMediaRequestData,
-                    contentScale = ContentScale.Crop,
-                    alignment = Alignment.Center,
-                    contentDescription = description,
-                    onState = { isLoaded = it is AsyncImagePainter.State.Success },
-                )
-            }
-        }
-
-        if (content.showCaption) {
-            Spacer(modifier = Modifier.height(8.dp))
-            val caption = if (LocalInspectionMode.current) {
-                SpannedString(content.caption)
+            if (isContentBeingValidated) {
+                CircularProgressIndicator(modifier = Modifier.align(Alignment.Center))
             } else {
-                content.formattedCaption ?: SpannedString(content.caption)
-            }
-            CompositionLocalProvider(
-                LocalContentColor provides ElementTheme.colors.textPrimary,
-                LocalTextStyle provides ElementTheme.typography.fontBodyLgRegular
-            ) {
-                val width = content.width ?: 0
-                val height = content.height ?: 0
-                // if image is narrow and tall use DEFAULT_ASPECT_RATIO
-                val aspectRatio = if (width < height / TALL_IMAGE_RATIO_DIVISOR) {
-                    DEFAULT_ASPECT_RATIO
-                } else {
-                    content.aspectRatio ?: DEFAULT_ASPECT_RATIO
+                ProtectedView(
+                    hideContent = hideMediaContent,
+                    onShowClick = onShowContentClick,
+                ) {
+                    var isLoaded by remember { mutableStateOf(false) }
+                    AsyncImage(
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .then(if (isLoaded) Modifier.background(Color.White) else Modifier)
+                            .then(
+                                if (!isTalkbackActive() && onContentClick != null) {
+                                    Modifier
+                                        .combinedClickable(
+                                            onClick = onContentClick,
+                                            onLongClick = onLongClick,
+                                        )
+                                        .onKeyboardContextMenuAction(onLongClick)
+                                } else {
+                                    Modifier
+                                }
+                            ),
+                        model = content.thumbnailMediaRequestData,
+                        contentScale = ContentScale.Crop,
+                        alignment = Alignment.Center,
+                        contentDescription = description,
+                        onState = { state ->
+                            val url = content.thumbnailMediaRequestData.source?.safeUrl
+                            if (url != null) {
+                                handleAsyncImageStateChange(
+                                    state = state,
+                                    onLoaded = { isLoaded = true },
+                                    updateContentValidationState = { contentValidationState.update(url, it) },
+                                )
+                            }
+                        },
+                    )
                 }
-                EditorStyledText(
-                    modifier = Modifier
-                        .padding(horizontal = 4.dp) // This is (12.dp - 8.dp) contentPadding from CommonLayout
-                        .widthIn(min = MIN_HEIGHT_IN_DP.dp * aspectRatio, max = MAX_HEIGHT_IN_DP.dp * aspectRatio),
-                    text = caption,
-                    style = ElementRichTextEditorStyle.textStyle(),
-                    onLinkClickedListener = onLinkClick,
-                    onLinkLongClickedListener = onLinkLongClick,
-                    releaseOnDetach = false,
-                    onTextLayout = ContentAvoidingLayout.measureLegacyLastTextLine(onContentLayoutChange = onContentLayoutChange),
-                )
             }
         }
     }
@@ -157,9 +129,6 @@ internal fun TimelineItemImageViewPreview(@PreviewParameter(TimelineItemImageCon
         onShowContentClick = {},
         onContentClick = {},
         onLongClick = {},
-        onLinkClick = {},
-        onLinkLongClick = {},
-        onContentLayoutChange = {},
     )
 }
 
@@ -172,43 +141,9 @@ internal fun TimelineItemImageViewHideMediaContentPreview() = ElementPreview {
         onShowContentClick = {},
         onContentClick = {},
         onLongClick = {},
-        onLinkClick = {},
-        onLinkLongClick = {},
-        onContentLayoutChange = {},
     )
 }
 
-@PreviewsDayNight
-@Composable
-internal fun TimelineImageWithCaptionRowPreview() = ElementPreview {
-    Column {
-        sequenceOf(false, true).forEach { isMine ->
-            ATimelineItemEventRow(
-                event = aTimelineItemEvent(
-                    isMine = isMine,
-                    content = aTimelineItemImageContent(
-                        filename = "image.jpg",
-                        caption = "A long caption that may wrap into several lines",
-                        aspectRatio = 2.5f,
-                    ),
-                    groupPosition = TimelineItemGroupPosition.Last,
-                ),
-            )
-        }
-        ATimelineItemEventRow(
-            event = aTimelineItemEvent(
-                isMine = false,
-                content = aTimelineItemImageContent(
-                    filename = "image.jpg",
-                    caption = "Image with null aspectRatio",
-                    aspectRatio = null,
-                ),
-                groupPosition = TimelineItemGroupPosition.Last,
-            ),
-        )
-    }
-}
-
 @PreviewsDayNight
 @Composable
 internal fun ATimelineItemEventRowPreview() = ElementPreview {
@@ -220,9 +155,9 @@ internal fun ATimelineItemEventRowPreview() = ElementPreview {
                     content = aTimelineItemImageContent(
                         filename = "image.jpg",
                         caption = "A long caption that may wrap into several lines",
-                        width = 80,
-                        height = 300,
-                        aspectRatio = 80f / 300f,
+                        width = 40,
+                        height = 20,
+                        aspectRatio = 40f / 20f,
                     ),
                     groupPosition = TimelineItemGroupPosition.Last,
                 ),
@@ -235,7 +170,7 @@ internal fun ATimelineItemEventRowPreview() = ElementPreview {
                     filename = "image.jpg",
                     caption = "Narrow image with null aspectRatio",
                     width = 80,
-                    height = 300,
+                    height = 150,
                     aspectRatio = null,
                 ),
                 groupPosition = TimelineItemGroupPosition.Last,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemStickerView.kt

@@ -12,6 +12,7 @@ import androidx.compose.foundation.background
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.wrapContentWidth
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -26,16 +27,20 @@ import androidx.compose.ui.semantics.contentDescription
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import coil3.compose.AsyncImage
-import coil3.compose.AsyncImagePainter
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemStickerContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemStickerContentProvider
 import io.element.android.features.messages.impl.timeline.protection.ProtectedView
 import io.element.android.features.messages.impl.timeline.protection.coerceRatioWhenHidingContent
+import io.element.android.features.messages.impl.timeline.util.handleAsyncImageStateChange
 import io.element.android.libraries.designsystem.components.blurhash.blurHashBackground
 import io.element.android.libraries.designsystem.modifiers.onKeyboardContextMenuAction
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.designsystem.theme.components.CircularProgressIndicator
 import io.element.android.libraries.matrix.ui.media.MediaRequestData
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectOverallState
 import io.element.android.libraries.ui.strings.CommonStrings
 
 private const val STICKER_SIZE_IN_DP = 128
@@ -48,10 +53,14 @@ fun TimelineItemStickerView(
     onLongClick: (() -> Unit)?,
     onShowClick: () -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationState: ContentValidationState = remember { DefaultContentValidationState() },
 ) {
     val description = content.bestDescription.takeIf { it.isNotEmpty() } ?: stringResource(CommonStrings.common_image)
+
+    val eventContentValidation by contentValidationState.collectOverallState()
+    val isContentBeingValidated = !eventContentValidation.isValidated()
     Column(
-        modifier = modifier.semantics { contentDescription = description },
+        modifier = modifier.semantics { contentDescription = description }.wrapContentWidth(Alignment.CenterHorizontally),
     ) {
         TimelineItemAspectRatioBox(
             modifier = Modifier.blurHashBackground(content.blurhash, alpha = 0.9f),
@@ -63,11 +72,12 @@ fun TimelineItemStickerView(
                 hideContent = hideMediaContent,
                 onShowClick = onShowClick,
             ) {
-                var isLoaded by remember { mutableStateOf(false) }
+                var isThumbnailLoaded by remember { mutableStateOf(false) }
+
                 AsyncImage(
                     modifier = Modifier
                         .fillMaxSize()
-                        .then(if (isLoaded) Modifier.background(Color.White) else Modifier)
+                        .then(if (isThumbnailLoaded) Modifier.background(Color.White) else Modifier)
                         .then(
                             if (onContentClick != null) {
                                 Modifier
@@ -91,9 +101,22 @@ fun TimelineItemStickerView(
                     contentScale = ContentScale.Crop,
                     alignment = Alignment.Center,
                     contentDescription = description,
-                    onState = { isLoaded = it is AsyncImagePainter.State.Success },
+                    onState = { state ->
+                        val url = content.preferredMediaSource?.safeUrl
+                        if (url != null) {
+                            handleAsyncImageStateChange(
+                                state = state,
+                                onLoaded = { isThumbnailLoaded = true },
+                                updateContentValidationState = { contentValidationState.update(url, it) },
+                            )
+                        }
+                    },
                 )
             }
+
+            if (isContentBeingValidated) {
+                CircularProgressIndicator(modifier = Modifier.align(Alignment.Center))
+            }
         }
     }
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemTextView.kt

@@ -30,6 +30,7 @@ import io.element.android.features.messages.impl.utils.containsOnlyEmojis
 import io.element.android.libraries.androidutils.text.LinkifyHelper
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.designsystem.utils.LocalUiTestMode
 import io.element.android.libraries.textcomposer.ElementRichTextEditorStyle
 import io.element.android.libraries.textcomposer.mentions.LocalMentionSpanUpdater
 import io.element.android.wysiwyg.compose.EditorStyledText
@@ -43,6 +44,9 @@ fun TimelineItemTextView(
     modifier: Modifier = Modifier,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit = {},
 ) {
+    // The View <-> Compose interop is not working well with Compose UI tests (it loops indefinitely), so we skip it in the UI test mode.
+    if (LocalUiTestMode.current) return
+
     val emojiOnly = content.formattedBody.toString() == content.body &&
         content.body.replace(" ", "").containsOnlyEmojis()
     val textStyle = when {

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemVideoView.kt

@@ -8,22 +8,17 @@
 
 package io.element.android.features.messages.impl.timeline.components.event
 
-import android.text.SpannedString
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.combinedClickable
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.widthIn
+import androidx.compose.foundation.layout.wrapContentWidth
 import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.material3.LocalContentColor
-import androidx.compose.material3.LocalTextStyle
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -34,26 +29,19 @@ import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.ColorFilter
 import androidx.compose.ui.layout.ContentScale
-import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.semantics.hideFromAccessibility
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.tooling.preview.PreviewParameter
 import androidx.compose.ui.unit.dp
 import coil3.compose.AsyncImage
-import coil3.compose.AsyncImagePainter
-import io.element.android.compound.theme.ElementTheme
 import io.element.android.compound.tokens.generated.CompoundIcons
-import io.element.android.features.messages.impl.timeline.aTimelineItemEvent
-import io.element.android.features.messages.impl.timeline.components.ATimelineItemEventRow
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayout
-import io.element.android.features.messages.impl.timeline.components.layout.ContentAvoidingLayoutData
-import io.element.android.features.messages.impl.timeline.model.TimelineItemGroupPosition
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVideoContent
 import io.element.android.features.messages.impl.timeline.model.event.TimelineItemVideoContentProvider
 import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemVideoContent
 import io.element.android.features.messages.impl.timeline.protection.ProtectedView
 import io.element.android.features.messages.impl.timeline.protection.coerceRatioWhenHidingContent
+import io.element.android.features.messages.impl.timeline.util.handleAsyncImageStateChange
 import io.element.android.libraries.designsystem.components.blurhash.blurHashBackground
 import io.element.android.libraries.designsystem.modifiers.onKeyboardContextMenuAction
 import io.element.android.libraries.designsystem.modifiers.roundedBackground
@@ -62,11 +50,11 @@ import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.matrix.ui.media.MAX_THUMBNAIL_HEIGHT
 import io.element.android.libraries.matrix.ui.media.MAX_THUMBNAIL_WIDTH
 import io.element.android.libraries.matrix.ui.media.MediaRequestData
-import io.element.android.libraries.textcomposer.ElementRichTextEditorStyle
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectOverallState
 import io.element.android.libraries.ui.strings.CommonStrings
 import io.element.android.libraries.ui.utils.a11y.isTalkbackActive
-import io.element.android.wysiwyg.compose.EditorStyledText
-import io.element.android.wysiwyg.link.Link
 
 @Composable
 fun TimelineItemVideoView(
@@ -75,15 +63,13 @@ fun TimelineItemVideoView(
     onContentClick: (() -> Unit)?,
     onLongClick: (() -> Unit)?,
     onShowContentClick: () -> Unit,
-    onLinkClick: (Link) -> Unit,
-    onLinkLongClick: (Link) -> Unit,
-    onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationState: ContentValidationState = remember { DefaultContentValidationState() },
 ) {
     val isTalkbackActive = isTalkbackActive()
     val a11yLabel = stringResource(CommonStrings.common_video)
     val description = content.caption?.let { "$a11yLabel: $it" } ?: a11yLabel
-    Column(modifier = modifier) {
+    Column(modifier = modifier.wrapContentWidth(Alignment.CenterHorizontally)) {
         val containerModifier = if (content.showCaption) {
             Modifier
                 .padding(top = 6.dp)
@@ -91,6 +77,9 @@ fun TimelineItemVideoView(
         } else {
             Modifier
         }
+
+        val eventContentValidation by contentValidationState.collectOverallState()
+        val isContentBeingValidated = !eventContentValidation.isValidated()
         TimelineItemAspectRatioBox(
             modifier = containerModifier.blurHashBackground(content.blurHash, alpha = 0.9f),
             aspectRatio = coerceRatioWhenHidingContent(content.aspectRatio, hideMediaContent),
@@ -127,48 +116,35 @@ fun TimelineItemVideoView(
                     contentScale = ContentScale.Crop,
                     alignment = Alignment.Center,
                     contentDescription = description,
-                    onState = { isLoaded = it is AsyncImagePainter.State.Success },
+                    onState = { state ->
+                        val url = content.thumbnailSource?.safeUrl
+                        if (url != null) {
+                            handleAsyncImageStateChange(
+                                state = state,
+                                onLoaded = { isLoaded = true },
+                                updateContentValidationState = { contentValidationState.update(url, it) },
+                            )
+                        }
+                    },
                 )
 
-                Box(
-                    modifier = Modifier.roundedBackground(),
-                    contentAlignment = Alignment.Center,
-                ) {
-                    Image(
-                        imageVector = CompoundIcons.PlaySolid(),
-                        contentDescription = stringResource(id = CommonStrings.a11y_play),
-                        colorFilter = ColorFilter.tint(Color.White),
-                        modifier = Modifier.semantics { hideFromAccessibility() }
-                    )
+                if (!isContentBeingValidated) {
+                    Box(
+                        modifier = Modifier.roundedBackground(),
+                        contentAlignment = Alignment.Center,
+                    ) {
+                        Image(
+                            imageVector = CompoundIcons.PlaySolid(),
+                            contentDescription = stringResource(id = CommonStrings.a11y_play),
+                            colorFilter = ColorFilter.tint(Color.White),
+                            modifier = Modifier.semantics { hideFromAccessibility() }
+                        )
+                    }
+                } else {
+                    CircularProgressIndicator()
                 }
             }
         }
-
-        if (content.showCaption) {
-            Spacer(modifier = Modifier.height(8.dp))
-            val caption = if (LocalInspectionMode.current) {
-                SpannedString(content.caption)
-            } else {
-                content.formattedCaption ?: SpannedString(content.caption)
-            }
-            CompositionLocalProvider(
-                LocalContentColor provides ElementTheme.colors.textPrimary,
-                LocalTextStyle provides ElementTheme.typography.fontBodyLgRegular,
-            ) {
-                val aspectRatio = content.aspectRatio ?: DEFAULT_ASPECT_RATIO
-                EditorStyledText(
-                    modifier = Modifier
-                        .padding(horizontal = 4.dp) // This is (12.dp - 8.dp) contentPadding from CommonLayout
-                        .widthIn(min = MIN_HEIGHT_IN_DP.dp * aspectRatio, max = MAX_HEIGHT_IN_DP.dp * aspectRatio),
-                    text = caption,
-                    onLinkClickedListener = onLinkClick,
-                    onLinkLongClickedListener = onLinkLongClick,
-                    style = ElementRichTextEditorStyle.textStyle(),
-                    releaseOnDetach = false,
-                    onTextLayout = ContentAvoidingLayout.measureLegacyLastTextLine(onContentLayoutChange = onContentLayoutChange),
-                )
-            }
-        }
     }
 }
 
@@ -181,9 +157,6 @@ internal fun TimelineItemVideoViewPreview(@PreviewParameter(TimelineItemVideoCon
         onShowContentClick = {},
         onContentClick = {},
         onLongClick = {},
-        onLinkClick = {},
-        onLinkLongClick = {},
-        onContentLayoutChange = {},
     )
 }
 
@@ -196,39 +169,5 @@ internal fun TimelineItemVideoViewHideMediaContentPreview() = ElementPreview {
         onShowContentClick = {},
         onContentClick = {},
         onLongClick = {},
-        onLinkClick = {},
-        onLinkLongClick = {},
-        onContentLayoutChange = {},
     )
 }
-
-@PreviewsDayNight
-@Composable
-internal fun TimelineVideoWithCaptionRowPreview() = ElementPreview {
-    Column {
-        sequenceOf(false, true).forEach { isMine ->
-            ATimelineItemEventRow(
-                event = aTimelineItemEvent(
-                    isMine = isMine,
-                    content = aTimelineItemVideoContent().copy(
-                        filename = "video.mp4",
-                        caption = "A long caption that may wrap into several lines",
-                        aspectRatio = 2.5f,
-                    ),
-                    groupPosition = TimelineItemGroupPosition.Last,
-                ),
-            )
-        }
-        ATimelineItemEventRow(
-            event = aTimelineItemEvent(
-                isMine = false,
-                content = aTimelineItemVideoContent().copy(
-                    filename = "video.mp4",
-                    caption = "Video with null aspect ratio",
-                    aspectRatio = null,
-                ),
-                groupPosition = TimelineItemGroupPosition.Last,
-            ),
-        )
-    }
-}

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/event/TimelineItemVoiceView.kt

@@ -51,6 +51,7 @@ import io.element.android.libraries.designsystem.theme.components.CircularProgre
 import io.element.android.libraries.designsystem.theme.components.Icon
 import io.element.android.libraries.designsystem.theme.components.IconButton
 import io.element.android.libraries.designsystem.theme.components.Text
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
 import io.element.android.libraries.ui.strings.CommonStrings
 import io.element.android.libraries.ui.utils.a11y.isTalkbackActive
 import io.element.android.libraries.voiceplayer.api.VoiceMessageEvent
@@ -64,6 +65,7 @@ fun TimelineItemVoiceView(
     content: TimelineItemVoiceContent,
     onContentLayoutChange: (ContentAvoidingLayoutData) -> Unit,
     modifier: Modifier = Modifier,
+    contentValidationValue: ContentValidationValue = ContentValidationValue.Valid,
 ) {
     fun playPause() {
         state.eventSink(VoiceMessageEvent.PlayPause)
@@ -103,12 +105,16 @@ fun TimelineItemVoiceView(
         verticalAlignment = Alignment.CenterVertically,
     ) {
         if (!isTalkbackActive()) {
-            when (state.buttonType) {
-                VoiceMessageState.ButtonType.Play -> PlayButton(onClick = ::playPause)
-                VoiceMessageState.ButtonType.Pause -> PauseButton(onClick = ::playPause)
-                VoiceMessageState.ButtonType.Downloading -> ProgressButton()
-                VoiceMessageState.ButtonType.Retry -> RetryButton(onClick = ::playPause)
-                VoiceMessageState.ButtonType.Disabled -> PlayButton(onClick = {}, enabled = false)
+            if (contentValidationValue.isValid()) {
+                when (state.buttonType) {
+                    VoiceMessageState.ButtonType.Play -> PlayButton(onClick = ::playPause)
+                    VoiceMessageState.ButtonType.Pause -> PauseButton(onClick = ::playPause)
+                    VoiceMessageState.ButtonType.Downloading -> ProgressButton()
+                    VoiceMessageState.ButtonType.Retry -> RetryButton(onClick = ::playPause)
+                    VoiceMessageState.ButtonType.Disabled -> PlayButton(onClick = {}, enabled = false)
+                }
+            } else {
+                ProgressButton(displayImmediately = true)
             }
         }
         Spacer(Modifier.width(8.dp))

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/components/layout/ContentAvoidingLayout.kt

@@ -9,6 +9,7 @@
 package io.element.android.features.messages.impl.timeline.components.layout
 
 import android.text.Layout
+import androidx.compose.foundation.layout.Column
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.MutableState
 import androidx.compose.runtime.mutableStateOf
@@ -23,6 +24,7 @@ import androidx.compose.ui.unit.DpOffset
 import androidx.compose.ui.unit.dp
 import io.element.android.libraries.core.data.tryOrNull
 import io.element.android.libraries.designsystem.text.roundToPx
+import io.element.android.libraries.designsystem.utils.LocalUiTestMode
 import io.element.android.wysiwyg.compose.EditorStyledText
 import kotlin.math.max
 import kotlin.math.min
@@ -41,6 +43,7 @@ import kotlin.math.roundToInt
  * @param shrinkContent Whether the content should be shrunk to fit the available width or not. Defaults to `false`.
  * @param content The 'content' component of the layout.
  */
+@Suppress("ContentSlotReused") // Since we added an exception for `LocalUiTestMode`, detekt thinks the layout can change in runtime: it won't
 @Composable
 fun ContentAvoidingLayout(
     overlay: @Composable () -> Unit,
@@ -52,6 +55,15 @@ fun ContentAvoidingLayout(
 ) {
     val scope = remember { ContentAvoidingLayoutScopeInstance() }
 
+    // Custom layouts don't seem to work well with Compose UI tests (they crash), so we use a Column instead when running in test mode.
+    if (LocalUiTestMode.current) {
+        Column {
+            scope.content()
+            overlay()
+        }
+        return
+    }
+
     Layout(
         modifier = modifier,
         content = {

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/event/TimelineItemAudioContentProvider.kt

@@ -19,8 +19,6 @@ open class TimelineItemAudioContentProvider : PreviewParameterProvider<TimelineI
             aTimelineItemAudioContent("A sound.mp3"),
             aTimelineItemAudioContent("A bigger name sound.mp3"),
             aTimelineItemAudioContent("An even bigger bigger bigger bigger bigger bigger bigger sound name which doesn't fit.mp3"),
-            aTimelineItemAudioContent(caption = "A caption"),
-            aTimelineItemAudioContent(caption = "An even bigger bigger bigger bigger bigger bigger bigger caption"),
         )
 }
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/event/TimelineItemEventContent.kt

@@ -15,6 +15,9 @@ import kotlin.time.Duration
 @Immutable
 sealed interface TimelineItemEventContent {
     val type: String
+
+    val isMedia: Boolean
+        get() = this is TimelineItemEventContentWithAttachment || this is TimelineItemGalleryContent || this is TimelineItemAttachmentsContent
 }
 
 interface TimelineItemEventMutableContent {
@@ -115,6 +118,13 @@ fun TimelineItemEventContent.captionOrNull(): String? = when (this) {
     else -> null
 }
 
+fun TimelineItemEventContent.formattedCaptionOrNull(): CharSequence? = when (this) {
+    is TimelineItemEventContentWithAttachment -> formattedCaption
+    is TimelineItemGalleryContent -> formattedCaption
+    is TimelineItemAttachmentsContent -> formattedCaption
+    else -> null
+}
+
 fun TimelineItemEventContentWithAttachment.duration(): Duration? {
     return when (this) {
         is TimelineItemAudioContent -> duration
@@ -123,3 +133,12 @@ fun TimelineItemEventContentWithAttachment.duration(): Duration? {
         else -> null
     }
 }
+
+fun TimelineItemEventContentWithAttachment.blurHash(): String? {
+    return when (this) {
+        is TimelineItemImageContent -> blurhash
+        is TimelineItemVideoContent -> blurHash
+        is TimelineItemStickerContent -> blurhash
+        else -> null
+    }
+}

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/event/TimelineItemEventContentProvider.kt

@@ -135,6 +135,7 @@ fun anAttachmentItem(
     fileSize: Long? = 1_000_000L,
     formattedFileSize: String = "1MB",
     mimeType: String? = null,
+    mediaSource: MediaSource = MediaSource(url = "", json = ""),
     thumbnailSource: MediaSource? = null,
     hasThumbnail: Boolean = false,
 ) = AttachmentItem(
@@ -143,7 +144,7 @@ fun anAttachmentItem(
         hasThumbnail -> "image/jpeg"
         else -> "application/$fileExtension"
     },
-    mediaSource = MediaSource(url = "", json = ""),
+    mediaSource = mediaSource,
     thumbnailSource = thumbnailSource ?: if (hasThumbnail) MediaSource(url = "", json = "") else null,
     fileSize = fileSize,
     formattedFileSize = formattedFileSize,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/event/TimelineItemFileContentProvider.kt

@@ -18,8 +18,6 @@ open class TimelineItemFileContentProvider : PreviewParameterProvider<TimelineIt
             aTimelineItemFileContent(),
             aTimelineItemFileContent("A bigger name file.pdf"),
             aTimelineItemFileContent("An even bigger bigger bigger bigger bigger bigger bigger file name which doesn't fit.pdf"),
-            aTimelineItemFileContent(caption = "A caption"),
-            aTimelineItemFileContent(caption = "An even bigger bigger bigger bigger bigger bigger bigger caption"),
         )
 }
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/event/TimelineItemVideoContentProvider.kt

@@ -20,6 +20,7 @@ open class TimelineItemVideoContentProvider : PreviewParameterProvider<TimelineI
             aTimelineItemVideoContent(),
             aTimelineItemVideoContent(aspectRatio = 1.0f),
             aTimelineItemVideoContent(aspectRatio = 1.5f),
+            aTimelineItemVideoContent(thumbnailMediaSource = MediaSource("https://example.com/thumbnail.jpg")),
             aTimelineItemVideoContent(blurhash = null),
         )
 }
@@ -27,17 +28,20 @@ open class TimelineItemVideoContentProvider : PreviewParameterProvider<TimelineI
 fun aTimelineItemVideoContent(
     aspectRatio: Float = 0.5f,
     blurhash: String? = A_BLUR_HASH,
+    caption: String? = null,
+    mediaSource: MediaSource = MediaSource(""),
+    thumbnailMediaSource: MediaSource? = null,
 ) = TimelineItemVideoContent(
     filename = "Video.mp4",
     fileSize = 14 * 1024 * 1024L,
-    caption = null,
+    caption = caption,
     formattedCaption = null,
     isEdited = false,
-    thumbnailSource = null,
+    thumbnailSource = thumbnailMediaSource,
     blurHash = blurhash,
     aspectRatio = aspectRatio,
     duration = 100.milliseconds,
-    mediaSource = MediaSource(""),
+    mediaSource = mediaSource,
     width = 150,
     height = 300,
     thumbnailWidth = 150,

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/protection/TimelineProtectionEvent.kt

@@ -9,7 +9,14 @@
 package io.element.android.features.messages.impl.timeline.protection
 
 import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.media.MediaSource
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
 
 sealed interface TimelineProtectionEvent {
     data class ShowContent(val eventId: EventId?) : TimelineProtectionEvent
+    data class ValidateContent(
+        val eventId: EventId,
+        val mediaSources: List<MediaSource>,
+        val validationState: ContentValidationState,
+    ) : TimelineProtectionEvent
 }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/protection/TimelineProtectionPresenter.kt

@@ -12,23 +12,28 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.mutableStateSetOf
 import androidx.compose.runtime.remember
 import dev.zacsweers.metro.Inject
+import dev.zacsweers.metro.SingleIn
+import io.element.android.features.contentscanner.api.ContentScannerService
 import io.element.android.libraries.architecture.Presenter
 import io.element.android.libraries.core.coroutine.mapState
+import io.element.android.libraries.di.RoomScope
 import io.element.android.libraries.matrix.api.core.EventId
 import io.element.android.libraries.matrix.api.media.MediaPreviewService
 import io.element.android.libraries.matrix.api.media.isPreviewEnabled
 import io.element.android.libraries.matrix.api.room.BaseRoom
 import kotlinx.collections.immutable.toImmutableSet
 
+@SingleIn(RoomScope::class)
 @Inject
 class TimelineProtectionPresenter(
     private val mediaPreviewService: MediaPreviewService,
     private val room: BaseRoom,
+    private val contentScannerService: ContentScannerService,
 ) : Presenter<TimelineProtectionState> {
-    private val allowedEvents = mutableStateOf<Set<EventId>>(setOf())
+    private val allowedEvents = mutableStateSetOf<EventId>()
 
     @Composable
     override fun present(): TimelineProtectionState {
@@ -36,13 +41,14 @@ class TimelineProtectionPresenter(
             mediaPreviewService.mediaPreviewConfigFlow.mapState { config -> config.mediaPreviewValue }
         }.collectAsState()
         val roomInfo = room.roomInfoFlow.collectAsState()
+
         val protectionState by remember {
             derivedStateOf {
                 val isPreviewEnabled = mediaPreviewValue.value.isPreviewEnabled(roomInfo.value.joinRule)
                 if (isPreviewEnabled) {
                     ProtectionState.RenderAll
                 } else {
-                    ProtectionState.RenderOnly(eventIds = allowedEvents.value.toImmutableSet())
+                    ProtectionState.RenderOnly(eventIds = allowedEvents.toImmutableSet())
                 }
             }
         }
@@ -50,7 +56,10 @@ class TimelineProtectionPresenter(
         fun handleEvent(event: TimelineProtectionEvent) {
             when (event) {
                 is TimelineProtectionEvent.ShowContent -> {
-                    allowedEvents.value = allowedEvents.value + setOfNotNull(event.eventId)
+                    allowedEvents += setOfNotNull(event.eventId)
+                }
+                is TimelineProtectionEvent.ValidateContent -> {
+                    contentScannerService.scan(event.eventId, event.mediaSources, event.validationState)
                 }
             }
         }

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/util/AsyncImageStateHandler.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.messages.impl.timeline.util
+
+import coil3.compose.AsyncImagePainter
+import io.element.android.libraries.matrix.api.exception.ClientException
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import okio.IOException
+
+fun handleAsyncImageStateChange(
+    state: AsyncImagePainter.State,
+    onLoaded: () -> Unit,
+    updateContentValidationState: ((ContentValidationValue) -> Unit)?,
+) {
+    if (state is AsyncImagePainter.State.Success) {
+        onLoaded()
+    }
+
+    val updatedContentValidationValue = when (state) {
+        is AsyncImagePainter.State.Empty -> ContentValidationValue.Unknown
+        is AsyncImagePainter.State.Loading -> ContentValidationValue.Loading
+        is AsyncImagePainter.State.Success -> ContentValidationValue.Valid
+        is AsyncImagePainter.State.Error -> {
+            when (val cause = state.result.throwable) {
+                is ClientException.ContentScanner if cause.reason.isDangerous() -> ContentValidationValue.Invalid
+                is IOException -> {
+                    // Use `Unknown` instead of `Invalid` to allow retrying the download later
+                    ContentValidationValue.Unknown
+                }
+                else -> ContentValidationValue.UnrecoverableError(cause)
+            }
+        }
+    }
+
+    updateContentValidationState?.invoke(updatedContentValidationValue)
+}

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/messagecomposer/MessageComposerPresenterSlashCommandTest.kt

@@ -37,6 +37,7 @@ import io.element.android.libraries.matrix.test.A_USER_ID
 import io.element.android.libraries.matrix.test.permalink.FakePermalinkBuilder
 import io.element.android.libraries.matrix.test.permalink.FakePermalinkParser
 import io.element.android.libraries.matrix.test.room.FakeJoinedRoom
+import io.element.android.libraries.matrix.ui.media.contentvalidation.InMemoryEventContentValidationCache
 import io.element.android.libraries.mediapickers.api.PickerProvider
 import io.element.android.libraries.mediapickers.test.FakePickerProvider
 import io.element.android.libraries.mediaupload.api.MediaOptimizationConfig
@@ -315,6 +316,8 @@ class MessageComposerPresenterSlashCommandTest {
         notificationConversationService = notificationConversationService,
         slashCommandService = slashCommandService,
         featureFlagService = featureFlagService,
+        contentScannerService = { _, _, _ -> },
+        contentValidationCache = InMemoryEventContentValidationCache(),
     ).apply {
         isTesting = true
         showTextFormatting = isRichTextEditorEnabled

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/messagecomposer/MessageComposerPresenterTest.kt

@@ -75,6 +75,7 @@ import io.element.android.libraries.matrix.test.room.aRoomInfo
 import io.element.android.libraries.matrix.test.room.aRoomMember
 import io.element.android.libraries.matrix.test.room.powerlevels.FakeRoomPermissions
 import io.element.android.libraries.matrix.test.timeline.FakeTimeline
+import io.element.android.libraries.matrix.ui.media.contentvalidation.InMemoryEventContentValidationCache
 import io.element.android.libraries.matrix.ui.messages.reply.InReplyToDetails
 import io.element.android.libraries.mediapickers.api.PickerProvider
 import io.element.android.libraries.mediapickers.test.FakePickerProvider
@@ -1649,6 +1650,8 @@ class MessageComposerPresenterTest : RobolectricTest() {
         notificationConversationService = notificationConversationService,
         slashCommandService = slashCommandService,
         featureFlagService = featureFlagService,
+        contentScannerService = { _, _, _ -> },
+        contentValidationCache = InMemoryEventContentValidationCache(),
     ).apply {
         isTesting = true
         showTextFormatting = isRichTextEditorEnabled

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/TimelinePresenterTest.kt

@@ -19,6 +19,8 @@ import io.element.android.features.messages.impl.timeline.components.MessageShie
 import io.element.android.features.messages.impl.timeline.components.aCriticalShield
 import io.element.android.features.messages.impl.timeline.model.NewEventState
 import io.element.android.features.messages.impl.timeline.model.TimelineItem
+import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
+import io.element.android.features.messages.impl.timeline.protection.aTimelineProtectionState
 import io.element.android.features.messages.impl.typing.aTypingNotificationState
 import io.element.android.features.messages.impl.voicemessages.timeline.FakeRedactedVoiceMessageManager
 import io.element.android.features.messages.impl.voicemessages.timeline.RedactedVoiceMessageManager
@@ -28,6 +30,7 @@ import io.element.android.features.poll.api.actions.SendPollResponseAction
 import io.element.android.features.poll.test.actions.FakeEndPollAction
 import io.element.android.features.poll.test.actions.FakeSendPollResponseAction
 import io.element.android.features.roomcall.api.aStandByCallState
+import io.element.android.libraries.architecture.Presenter
 import io.element.android.libraries.featureflag.api.FeatureFlags
 import io.element.android.libraries.featureflag.test.FakeFeatureFlagService
 import io.element.android.libraries.matrix.api.core.EventId
@@ -1585,6 +1588,7 @@ class TimelinePresenterTest {
         featureFlagService: FakeFeatureFlagService = FakeFeatureFlagService(),
         liveLocationShareManager: FakeActiveLiveLocationShareManager = FakeActiveLiveLocationShareManager(),
         markAsFullyRead: MarkAsFullyRead = FakeMarkAsFullyRead { _, _ -> },
+        timelineProtectionPresenter: Presenter<TimelineProtectionState> = { aTimelineProtectionState() },
     ): TimelinePresenter {
         return TimelinePresenter(
             timelineItemsFactoryCreator = aTimelineItemsFactoryCreator(),
@@ -1605,6 +1609,7 @@ class TimelinePresenterTest {
             analyticsService = FakeAnalyticsService(),
             liveLocationShareManager = liveLocationShareManager,
             markAsFullyRead = markAsFullyRead,
+            timelineProtectionPresenter = timelineProtectionPresenter,
         )
     }
 }

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/TimelineViewTest.kt

@@ -21,7 +21,7 @@ import androidx.compose.ui.test.v2.runAndroidComposeUiTest
 import io.element.android.features.messages.impl.timeline.components.MessageShieldData
 import io.element.android.features.messages.impl.timeline.components.aCriticalShield
 import io.element.android.features.messages.impl.timeline.model.TimelineItem
-import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemImageContent
+import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemTextContent
 import io.element.android.features.messages.impl.timeline.model.event.aTimelineItemUnknownContent
 import io.element.android.features.messages.impl.timeline.model.virtual.TimelineItemLoadingIndicatorModel
 import io.element.android.features.messages.impl.timeline.protection.TimelineProtectionState
@@ -67,7 +67,7 @@ class TimelineViewTest : RobolectricTest() {
         val eventsRecorder = EventsRecorder<TimelineEvent>()
         setTimelineView(
             state = aTimelineState(
-                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemImageContent())),
+                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemTextContent())),
                 eventSink = eventsRecorder,
             ),
         )
@@ -79,7 +79,7 @@ class TimelineViewTest : RobolectricTest() {
         val eventsRecorder = EventsRecorder<TimelineEvent>()
         setTimelineView(
             state = aTimelineState(
-                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemImageContent())),
+                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemTextContent())),
                 isLive = true,
                 eventSink = eventsRecorder,
             ),
@@ -98,7 +98,7 @@ class TimelineViewTest : RobolectricTest() {
         val eventsRecorder = EventsRecorder<TimelineEvent>()
         setTimelineView(
             state = aTimelineState(
-                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemImageContent())),
+                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemTextContent())),
                 isLive = false,
                 eventSink = eventsRecorder,
             ),
@@ -133,7 +133,7 @@ class TimelineViewTest : RobolectricTest() {
                 timelineItems = persistentListOf<TimelineItem>(
                     aTimelineItemEvent(
                         // Do not use a Text because EditorStyledText cannot be used in UI test.
-                        content = aTimelineItemImageContent(),
+                        content = aTimelineItemTextContent(),
                         messageShield = MessageShield.UnverifiedIdentity(true),
                     ),
                 ),
@@ -155,7 +155,7 @@ class TimelineViewTest : RobolectricTest() {
         val eventsRecorder = EventsRecorder<TimelineEvent>()
         setTimelineView(
             state = aTimelineState(
-                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemImageContent())),
+                timelineItems = persistentListOf(aTimelineItemEvent(content = aTimelineItemTextContent())),
                 isLive = false,
                 eventSink = eventsRecorder,
                 messageShield = aCriticalShield(),

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/protection/TimelineProtectionPresenterTest.kt

@@ -9,19 +9,28 @@
 package io.element.android.features.messages.impl.timeline.protection
 
 import com.google.common.truth.Truth.assertThat
+import io.element.android.features.contentscanner.api.ContentScannerService
+import io.element.android.libraries.matrix.api.core.EventId
 import io.element.android.libraries.matrix.api.media.MediaPreviewConfig
 import io.element.android.libraries.matrix.api.media.MediaPreviewService
 import io.element.android.libraries.matrix.api.media.MediaPreviewValue
+import io.element.android.libraries.matrix.api.media.MediaSource
 import io.element.android.libraries.matrix.api.room.BaseRoom
 import io.element.android.libraries.matrix.api.room.join.JoinRule
 import io.element.android.libraries.matrix.test.AN_EVENT_ID
 import io.element.android.libraries.matrix.test.media.FakeMediaPreviewService
 import io.element.android.libraries.matrix.test.room.FakeBaseRoom
 import io.element.android.libraries.matrix.test.room.aRoomInfo
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.DefaultContentValidationState
 import io.element.android.tests.testutils.WarmUpRule
+import io.element.android.tests.testutils.lambda.lambdaRecorder
 import io.element.android.tests.testutils.test
 import kotlinx.collections.immutable.persistentSetOf
+import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.test.runCurrent
 import kotlinx.coroutines.test.runTest
 import org.junit.Rule
 import org.junit.Test
@@ -87,11 +96,49 @@ class TimelineProtectionPresenterTest {
         }
     }
 
+    @OptIn(ExperimentalCoroutinesApi::class)
+    @Test
+    fun `present - validate media scans the media source`() = runTest {
+        val url = "https://example.com/media"
+
+        val mediaPreviewConfig = MediaPreviewConfig(mediaPreviewValue = MediaPreviewValue.Private, hideInviteAvatar = false)
+        val mediaPreviewService = FakeMediaPreviewService(mediaPreviewConfigFlow = MutableStateFlow(mediaPreviewConfig))
+        val room = FakeBaseRoom(initialRoomInfo = aRoomInfo(joinRule = JoinRule.Invite), roomCoroutineScope = backgroundScope)
+        val contentScannerService = lambdaRecorder { _: EventId, _: List<MediaSource>, state: ContentValidationState ->
+            state.update(url, ContentValidationValue.Valid)
+        }
+        val presenter = createPresenter(
+            mediaPreviewService = mediaPreviewService,
+            room = room,
+            contentScannerService = contentScannerService,
+        )
+        presenter.test {
+            val validationState = DefaultContentValidationState(initial = mapOf(url to ContentValidationValue.Unknown))
+            assertThat(validationState.getCurrentOverallState().isValid()).isFalse()
+
+            val initialState = awaitItem()
+            initialState.eventSink(
+                TimelineProtectionEvent.ValidateContent(
+                    eventId = AN_EVENT_ID,
+                    mediaSources = listOf(MediaSource(url)),
+                    validationState = validationState
+                )
+            )
+
+            runCurrent()
+
+            contentScannerService.assertions().isCalledOnce()
+            assertThat(validationState.getCurrentOverallState().isValid()).isTrue()
+        }
+    }
+
     private fun createPresenter(
         room: BaseRoom = FakeBaseRoom(),
         mediaPreviewService: MediaPreviewService = FakeMediaPreviewService(),
+        contentScannerService: ContentScannerService = ContentScannerService { _: EventId, _: List<MediaSource>, _: ContentValidationState -> },
     ) = TimelineProtectionPresenter(
         mediaPreviewService = mediaPreviewService,
         room = room,
+        contentScannerService = contentScannerService,
     )
 }

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/util/AsyncImageStateHandlerTest.kt

@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.messages.impl.timeline.util
+
+import androidx.compose.ui.graphics.painter.Painter
+import coil3.compose.AsyncImagePainter
+import coil3.request.ErrorResult
+import coil3.request.SuccessResult
+import io.element.android.libraries.matrix.api.exception.ClientException
+import io.element.android.libraries.matrix.api.exception.ContentScannerErrorReason
+import io.element.android.libraries.matrix.api.exception.ContentScannerErrorReason.MCS_MEDIA_NOT_CLEAN
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.tests.testutils.lambda.lambdaRecorder
+import io.element.android.tests.testutils.lambda.value
+import io.mockk.mockk
+import org.junit.Test
+import java.io.FileNotFoundException
+
+class AsyncImageStateHandlerTest {
+    @Test
+    fun `test Empty state sets the content validation state to Unknown`() {
+        val updateContentValidationState = lambdaRecorder<ContentValidationValue, Unit> {}
+        handleAsyncImageStateChange(
+            state = AsyncImagePainter.State.Empty,
+            onLoaded = {},
+            updateContentValidationState = updateContentValidationState,
+        )
+
+        updateContentValidationState.assertions().isCalledOnce().with(value(ContentValidationValue.Unknown))
+    }
+
+    @Test
+    fun `test Loading state sets the content validation state to Loading`() {
+        val updateContentValidationState = lambdaRecorder<ContentValidationValue, Unit> {}
+        handleAsyncImageStateChange(
+            state = AsyncImagePainter.State.Loading(null),
+            onLoaded = {},
+            updateContentValidationState = updateContentValidationState,
+        )
+
+        updateContentValidationState.assertions().isCalledOnce().with(value(ContentValidationValue.Loading))
+    }
+
+    @Test
+    fun `test Success state sets the content validation state to Valid and triggers onLoaded callback`() {
+        val updateContentValidationState = lambdaRecorder<ContentValidationValue, Unit> {}
+        val onLoaded = lambdaRecorder<Unit> {}
+        handleAsyncImageStateChange(
+            state = AsyncImagePainter.State.Success(mockk<Painter>(), SuccessResult(mockk(), mockk())),
+            onLoaded = onLoaded,
+            updateContentValidationState = updateContentValidationState,
+        )
+
+        onLoaded.assertions().isCalledOnce()
+        updateContentValidationState.assertions().isCalledOnce().with(value(ContentValidationValue.Valid))
+    }
+
+    @Test
+    fun `test Failure state sets the content validation state to Invalid if the error matches`() {
+        val updateContentValidationState = lambdaRecorder<ContentValidationValue, Unit> {}
+        val onLoaded = lambdaRecorder<Unit> {}
+        val mediaNotCleanError = ClientException.ContentScanner("dangerous", MCS_MEDIA_NOT_CLEAN)
+        val forbiddenMimeTypeError = ClientException.ContentScanner("dangerous", ContentScannerErrorReason.MCS_MIME_TYPE_FORBIDDEN)
+        handleAsyncImageStateChange(
+            state = AsyncImagePainter.State.Error(null, ErrorResult(null, mockk(), mediaNotCleanError)),
+            onLoaded = onLoaded,
+            updateContentValidationState = updateContentValidationState,
+        )
+
+        handleAsyncImageStateChange(
+            state = AsyncImagePainter.State.Error(null, ErrorResult(null, mockk(), forbiddenMimeTypeError)),
+            onLoaded = onLoaded,
+            updateContentValidationState = updateContentValidationState,
+        )
+
+        onLoaded.assertions().isNeverCalled()
+        updateContentValidationState.assertions()
+            .isCalledExactly(2)
+            .withSequence(
+                listOf(value(ContentValidationValue.Invalid)),
+                listOf(value(ContentValidationValue.Invalid))
+            )
+    }
+
+    @Test
+    fun `test Failure state sets the content validation state to Uknown if the error does not match a content scanner one`() {
+        val updateContentValidationState = lambdaRecorder<ContentValidationValue, Unit> {}
+        val onLoaded = lambdaRecorder<Unit> {}
+        val error = FileNotFoundException("File not found")
+        handleAsyncImageStateChange(
+            state = AsyncImagePainter.State.Error(null, ErrorResult(null, mockk(), error)),
+            onLoaded = onLoaded,
+            updateContentValidationState = updateContentValidationState,
+        )
+
+        onLoaded.assertions().isNeverCalled()
+        updateContentValidationState.assertions().isCalledOnce().with(value(ContentValidationValue.Unknown))
+    }
+}

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/components/EqualWidthColumn.kt

@@ -29,21 +29,32 @@ fun EqualWidthColumn(
 ) {
     SubcomposeLayout(modifier = modifier) { constraints ->
         val measurables = subcompose(0, content).map { it.measure(constraints) }
-        val maxWidth = measurables.maxOf { it.width }
-        val newConstraints = constraints.copy(minWidth = maxWidth)
-        val newMeasurables = if (measurables.all { it.width == maxWidth }) {
-            // Skip re-measuring if all children have the same width
-            measurables
+        if (measurables.isEmpty()) {
+            // No children, so just return a layout with 0 width and height
+            layout(0, 0) {}
+        } else if (measurables.size == 1) {
+            // No need to re-measure if there's only one child
+            val measurable = measurables.first()
+            layout(measurable.width, measurable.height) {
+                measurable.placeRelative(0, 0)
+            }
         } else {
-            // Re-measure with the largest width as the minWidth to have all children constrained to the same width
-            subcompose(1, content).map { it.measure(newConstraints) }
-        }
-        val totalHeight = (newMeasurables.sumOf { it.height } + spacing.toPx() * (newMeasurables.size - 1)).roundToInt()
-        layout(maxWidth, totalHeight) {
-            var yPosition = 0
-            newMeasurables.forEach { measurable ->
-                measurable.placeRelative(0, yPosition)
-                yPosition += measurable.height + spacing.roundToPx()
+            val maxWidth = measurables.maxOf { it.width }
+            val newConstraints = constraints.copy(minWidth = maxWidth)
+            val newMeasurables = if (measurables.all { it.width == maxWidth }) {
+                // Skip re-measuring if all children have the same width
+                measurables
+            } else {
+                // Re-measure with the largest width as the minWidth to have all children constrained to the same width
+                subcompose(1, content).map { it.measure(newConstraints) }
+            }
+            val totalHeight = (newMeasurables.sumOf { it.height } + spacing.toPx() * (newMeasurables.size - 1)).roundToInt()
+            layout(maxWidth, totalHeight) {
+                var yPosition = 0
+                newMeasurables.forEach { measurable ->
+                    measurable.placeRelative(0, yPosition)
+                    yPosition += measurable.height + spacing.roundToPx()
+                }
             }
         }
     }

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/item/event/EventContent.kt

@@ -124,3 +124,34 @@ data class CallNotifyContent(
 ) : EventContent
 
 data object UnknownContent : EventContent
+
+fun EventContent.isMediaContent(): Boolean {
+    return when (this) {
+        is MessageContent -> type is MessageTypeWithAttachment || type is GalleryMessageType
+        is StickerContent -> true
+        else -> false
+    }
+}
+
+fun EventContent.mediaSources(): List<MediaSource> {
+    return when (this) {
+        is MessageContent -> mediaSources()
+        is StickerContent -> listOfNotNull(source, info.thumbnailSource)
+        else -> emptyList()
+    }
+}
+
+fun MessageContent.mediaSources(): List<MediaSource> {
+    return when (val messageType = type) {
+        is MessageTypeWithAttachment -> when (messageType) {
+            is ImageMessageType -> listOfNotNull(messageType.source, messageType.info?.thumbnailSource)
+            is VideoMessageType -> listOfNotNull(messageType.source, messageType.info?.thumbnailSource)
+            is AudioMessageType -> listOf(messageType.source)
+            is VoiceMessageType -> listOf(messageType.source)
+            is FileMessageType -> listOfNotNull(messageType.source, messageType.info?.thumbnailSource)
+            else -> emptyList()
+        }
+        is GalleryMessageType -> messageType.items.flatMap { it.mediaSources() }
+        else -> emptyList()
+    }
+}

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/item/event/MessageType.kt

@@ -115,6 +115,14 @@ sealed interface GalleryItemType {
     data class Video(val content: VideoMessageType) : GalleryItemType
     data class File(val content: FileMessageType) : GalleryItemType
     data class Other(val itemType: String, val body: String) : GalleryItemType
+
+    fun mediaSources(): List<MediaSource> = when (this) {
+        is Image -> listOfNotNull(content.source, content.info?.thumbnailSource)
+        is Audio -> listOf(content.source)
+        is Video -> listOfNotNull(content.source, content.info?.thumbnailSource)
+        is File -> listOfNotNull(content.source, content.info?.thumbnailSource)
+        is Other -> emptyList()
+    }
 }
 
 data class OtherMessageType(

libraries/matrixmedia/impl/src/main/kotlin/io/element/android/libraries/matrix/ui/media/CoilMediaFetcher.kt

@@ -40,7 +40,7 @@ internal class CoilMediaFetcher(
                     onSuccess = { it },
                     onFailure = { error ->
                         if (error.isNetworkError()) {
-                            null
+                            throw error
                         } else {
                             fetchContent(mediaSource)
                         }
@@ -73,7 +73,7 @@ internal class CoilMediaFetcher(
             .onFailure {
                 Timber.e(it)
             }
-            .getOrNull()
+            .getOrThrow()
     }
 
     private suspend fun fetchContent(mediaSource: MediaSource): FetchResult? {
@@ -83,7 +83,7 @@ internal class CoilMediaFetcher(
             byteArray.asSourceResult()
         }.onFailure {
             Timber.e(it)
-        }.getOrNull()
+        }.getOrThrow()
     }
 
     private suspend fun fetchThumbnail(mediaSource: MediaSource, kind: MediaRequestData.Kind.Thumbnail): Result<FetchResult> {

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/ContentErrorView.kt

@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.BoxWithConstraints
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.material3.Icon
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.movableContentOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.text.rememberTextMeasurer
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import io.element.android.compound.theme.ElementTheme
+import io.element.android.compound.tokens.generated.CompoundIcons
+
+@Composable
+internal fun ContentErrorView(
+    title: String,
+    message: String,
+    modifier: Modifier = Modifier,
+    contentPadding: PaddingValues = PaddingValues.Zero,
+    onTextLayout: ((TextLayoutResult) -> Unit)? = null,
+) {
+    val updatedOnTextLayout by rememberUpdatedState(onTextLayout)
+    Row(
+        modifier = modifier
+            .background(color = ElementTheme.colors.bgCriticalSubtle)
+            .padding(contentPadding),
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+        verticalAlignment = Alignment.CenterVertically
+    ) {
+        Icon(
+            modifier = Modifier.size(24.dp),
+            imageVector = CompoundIcons.Error(),
+            contentDescription = null,
+            tint = ElementTheme.colors.iconCriticalPrimary
+        )
+        Column(Modifier.weight(1f)) {
+            Text(
+                text = title,
+                color = ElementTheme.colors.textCriticalPrimary,
+                style = ElementTheme.typography.fontBodyMdMedium,
+            )
+            val textMeasurer = rememberTextMeasurer()
+            val textContent = remember(message) {
+                movableContentOf(
+                    @Composable {
+                        Text(
+                            text = message,
+                            color = ElementTheme.colors.textSecondary,
+                            style = ElementTheme.typography.fontBodySmRegular,
+                        )
+                    }
+                )
+            }
+
+            // BoxWithConstraints is needed to be able to calculate the text layout in the current constraints, so we can pass it to the onTextLayout callback.
+            // However, this can't be used inside a SubComposeLayout (like the one in the text composer), so we only use it when the onTextLayout callback
+            // is provided.
+            if (updatedOnTextLayout != null) {
+                BoxWithConstraints(modifier = Modifier.fillMaxWidth()) {
+                    LaunchedEffect(message) {
+                        updatedOnTextLayout?.invoke(textMeasurer.measure(message, overflow = TextOverflow.Visible, constraints = constraints))
+                    }
+
+                    textContent()
+                }
+            } else {
+                textContent()
+            }
+        }
+    }
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/ContentValidationState.kt

@@ -0,0 +1,197 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.Immutable
+import androidx.compose.runtime.State
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.produceState
+import androidx.compose.runtime.remember
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.mapLatest
+import kotlinx.coroutines.flow.update
+
+/**
+ * Wrapper for the content validation state of an event.
+ *
+ * It can be used to check the overall validation state of the event, as well as the validation state of each media item in it.
+ */
+@Immutable
+interface ContentValidationState {
+    /**
+     * A flow that emits the overall validation state of the event, which is an aggregation of the different media values.
+     */
+    val overallStateFlow: Flow<ContentValidationValue>
+
+    /**
+     * Returns a flow that emits the validation state of a specific media item, identified by its URL.
+     */
+    fun getMediaStateFlow(url: String): Flow<ContentValidationValue>
+
+    /**
+     * Returns the current overall validation state of the event.
+     */
+    fun getCurrentOverallState(): ContentValidationValue
+
+    /**
+     * Returns the current validation state of a specific media item, identified by its URL.
+     */
+    fun getCurrentMediaState(url: String): ContentValidationValue
+
+    /**
+     * Updates the validation state of a specific media item, identified by its URL, with a new [ContentValidationValue].
+     */
+    fun update(url: String, newValue: ContentValidationValue)
+}
+
+/**
+ * A no-op implementation of [ContentValidationState] that always returns a fixed validation state.
+ * By default, this is [ContentValidationValue.Valid].
+ */
+@Immutable
+class NoopContentValidationState(
+    private val initial: ContentValidationValue = ContentValidationValue.Valid,
+) : ContentValidationState {
+    override val overallStateFlow: Flow<ContentValidationValue> = MutableStateFlow(initial)
+    override fun getMediaStateFlow(url: String): Flow<ContentValidationValue> = MutableStateFlow(initial)
+    override fun getCurrentOverallState(): ContentValidationValue = initial
+    override fun getCurrentMediaState(url: String): ContentValidationValue = initial
+    override fun update(url: String, newValue: ContentValidationValue) {}
+}
+
+/**
+ * A default implementation of [ContentValidationState] that tracks the validation state of media items in a mutable map.
+ * It calculates the overall validation state based on the individual media states.
+ */
+@Immutable
+class DefaultContentValidationState(
+    private val states: MutableStateFlow<Map<String, ContentValidationValue>>,
+) : ContentValidationState {
+    @OptIn(ExperimentalCoroutinesApi::class)
+    override val overallStateFlow: Flow<ContentValidationValue> = states
+        .mapLatest { states -> calculateOverallState(states) }
+        .distinctUntilChanged()
+
+    constructor() : this(states = MutableStateFlow(emptyMap()))
+
+    constructor(initial: Map<String, ContentValidationValue>) : this(states = MutableStateFlow(initial))
+
+    @OptIn(ExperimentalCoroutinesApi::class)
+    override fun getMediaStateFlow(url: String): Flow<ContentValidationValue> {
+        return states.map { states ->
+            states[url] ?: ContentValidationValue.Unknown
+        }.distinctUntilChanged()
+    }
+
+    override fun getCurrentOverallState(): ContentValidationValue {
+        return calculateOverallState(states.value)
+    }
+
+    override fun getCurrentMediaState(url: String): ContentValidationValue {
+        return states.value[url] ?: ContentValidationValue.Unknown
+    }
+
+    override fun update(url: String, newValue: ContentValidationValue) {
+        states.update { current ->
+            if (current[url]?.isValidated() == true && newValue.isLoading()) {
+                // If the current state is already validated and the new value is loading, we keep the current validated state
+                current
+            } else {
+                // Otherwise, we update the state for the given URL with the new value
+                current + (url to newValue)
+            }
+        }
+    }
+}
+
+private fun calculateOverallState(states: Map<String, ContentValidationValue>): ContentValidationValue {
+    return when {
+        states.values.any { it is ContentValidationValue.Invalid } -> ContentValidationValue.Invalid
+        states.values.any { it is ContentValidationValue.Loading } -> ContentValidationValue.Loading
+        states.values.any { it is ContentValidationValue.UnrecoverableError } -> states.values.first { it is ContentValidationValue.UnrecoverableError }
+        states.values.all { it is ContentValidationValue.Valid } -> ContentValidationValue.Valid
+        else -> ContentValidationValue.Unknown
+    }
+}
+
+/**
+ * Represents the validation state of a media item or an event.
+ */
+@Immutable
+sealed interface ContentValidationValue {
+    /** Indicates that the content is valid. */
+    data object Valid : ContentValidationValue
+
+    /** Indicates that the content is invalid/unsafe. */
+    data object Invalid : ContentValidationValue
+
+    /** Indicates that the content is currently being validated. */
+    data object Loading : ContentValidationValue
+
+    /** Indicates that an unrecoverable error occurred during validation, and it should not be retried. */
+    data class UnrecoverableError(val error: Throwable) : ContentValidationValue
+
+    /** Indicates that the validation state is unknown and should be checked. Recoverable errors are also represented with this. */
+    data object Unknown : ContentValidationValue
+
+    /**
+     * Returns true if the validation state is either [Valid], [Invalid], or [UnrecoverableError], meaning that the validation process has completed
+     * and a definitive result is available.
+     */
+    fun isValidated(): Boolean = when (this) {
+        is Valid -> true
+        is Invalid -> true
+        is Loading -> false
+        is UnrecoverableError -> true
+        is Unknown -> false
+    }
+
+    /** Returns true if the validation state is [Valid]. */
+    fun isValid(): Boolean = this is Valid
+
+    /** Returns true if the validation state is [Invalid]. */
+    fun isInvalid(): Boolean = this is Invalid
+
+    /** Returns true if the validation state is [Loading]. */
+    fun isLoading(): Boolean = this is Loading
+
+    /** Returns true if the validation state is [UnrecoverableError]. */
+    fun hasUnrecoverableError(): Boolean = this is UnrecoverableError
+
+    /** Returns true if the validation state is either [Invalid] or [UnrecoverableError]. */
+    fun hasError(): Boolean = this is Invalid || this is UnrecoverableError
+}
+
+/**
+ * Collects the overall validation state of the [ContentValidationState] as a [State] in a Composable context.
+ */
+@Composable
+fun ContentValidationState.collectOverallState(): State<ContentValidationValue> {
+    return produceState(getCurrentOverallState()) {
+        overallStateFlow.collect { value = it }
+    }
+}
+
+/**
+ * Collects the validation state of a specific media item, identified by its URL, as a [State] in a Composable context.
+ */
+@Composable
+fun ContentValidationState.collectMediaState(url: String?): State<ContentValidationValue> {
+    if (url == null) {
+        return remember { mutableStateOf(ContentValidationValue.Unknown) }
+    }
+
+    return produceState(getCurrentMediaState(url), key1 = url) {
+        getMediaStateFlow(url).collect { value = it }
+    }
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/EventContentValidationCache.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import io.element.android.libraries.matrix.api.core.EventId
+
+/**
+ * A cache that holds the validation state of event contents, based on their [EventId].
+ */
+interface EventContentValidationCache {
+    /**
+     * Returns the [ContentValidationState] for the given [eventId]. If none exists, it creates a new one with [ContentValidationValue.Unknown].
+     */
+    operator fun get(eventId: EventId): ContentValidationState
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/InMemoryEventContentValidationCache.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import io.element.android.libraries.matrix.api.core.EventId
+
+/**
+ * In-memory variant of [EventContentValidationCache] that holds the validation state of event contents, based on their [EventId].
+ *
+ * Note: this is intended to be used in tests.
+ */
+class InMemoryEventContentValidationCache(
+    initial: Map<EventId, ContentValidationState> = emptyMap(),
+) : EventContentValidationCache {
+    private val cache = initial.toMutableMap()
+
+    override operator fun get(eventId: EventId): ContentValidationState {
+        return cache[eventId] ?: DefaultContentValidationState()
+    }
+
+    fun put(eventId: EventId, state: ContentValidationState) {
+        cache[eventId] = state
+    }
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/InvalidContentView.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.unit.dp
+import io.element.android.libraries.designsystem.preview.ElementPreview
+import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.ui.strings.CommonStrings
+
+/**
+ * A view to display when the media content is invalid or dangerous.
+ */
+@Composable
+fun InvalidContentView(
+    modifier: Modifier = Modifier,
+    contentPadding: PaddingValues = PaddingValues.Zero,
+    onTextLayout: ((TextLayoutResult) -> Unit)? = null,
+) {
+    ContentErrorView(
+        title = stringResource(CommonStrings.content_scanner_unsafe_title),
+        message = stringResource(CommonStrings.content_scanner_unsafe_message),
+        modifier = modifier,
+        contentPadding = contentPadding,
+        onTextLayout = onTextLayout,
+    )
+}
+
+@PreviewsDayNight
+@Composable
+internal fun InvalidContentViewPreview() = ElementPreview {
+    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        InvalidContentView()
+    }
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/LocalEventContentValidationState.kt

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.staticCompositionLocalOf
+import io.element.android.libraries.matrix.api.core.EventId
+import io.element.android.libraries.matrix.api.timeline.item.event.EventContent
+import io.element.android.libraries.matrix.api.timeline.item.event.MessageContent
+import io.element.android.libraries.matrix.api.timeline.item.event.StickerContent
+import io.element.android.libraries.matrix.api.timeline.item.event.isMediaContent
+
+private val noopValue = NoopContentValidationState()
+
+/**
+ * A composition local that provides an [EventContentValidationCache] instance, so we can check if a given event content has been validated or not.
+ */
+val LocalEventContentValidationState = staticCompositionLocalOf<EventContentValidationCache> { NoopEventContentValidationCache() }
+
+/**
+ * A noop implementation of the [EventContentValidationCache] that immediately returns a successful validation state. This will be used in FOSS.
+ */
+class NoopEventContentValidationCache : EventContentValidationCache {
+    override operator fun get(eventId: EventId): ContentValidationState = noopValue
+}
+
+/**
+ * A helper to remember the validation state of an event content, based on its [EventId] and [EventContent], if known.
+ */
+@Composable
+fun rememberEventContentValidationState(eventId: EventId?, eventContent: EventContent?): ContentValidationState {
+    val needsValidation = remember(eventContent) {
+        when (eventContent) {
+            is MessageContent -> eventContent.isMediaContent()
+            is StickerContent -> true
+            // If the event content is not known or not a media content, we don't need to validate it.
+            else -> false
+        }
+    }
+
+    return rememberEventContentValidationState(eventId, needsValidation)
+}
+
+/**
+ * A helper to remember the validation state of an event content, based on its [EventId] and whether it needs validation or not.
+ */
+@Composable
+fun rememberEventContentValidationState(eventId: EventId?, needsValidation: Boolean): ContentValidationState {
+    if (!needsValidation) {
+        return noopValue
+    }
+
+    return rememberEventContentValidationStateInternal(eventId)
+}
+
+@Composable
+private fun rememberEventContentValidationStateInternal(eventId: EventId?): ContentValidationState {
+    val cache = LocalEventContentValidationState.current
+    return remember(eventId) {
+        if (eventId != null) {
+            cache[eventId]
+        } else {
+            noopValue
+        }
+    }
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/media/contentvalidation/NotFoundContentView.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.ui.media.contentvalidation
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.TextLayoutResult
+import androidx.compose.ui.unit.dp
+import io.element.android.libraries.designsystem.preview.ElementPreview
+import io.element.android.libraries.designsystem.preview.PreviewsDayNight
+import io.element.android.libraries.ui.strings.CommonStrings
+
+/**
+ * A view to display when the media content can't be fetched.
+ */
+@Composable
+fun NotFoundContentView(
+    modifier: Modifier = Modifier,
+    contentPadding: PaddingValues = PaddingValues.Zero,
+    onTextLayout: ((TextLayoutResult) -> Unit)? = null,
+) {
+    ContentErrorView(
+        title = stringResource(CommonStrings.content_scanner_not_found_title),
+        message = stringResource(CommonStrings.content_scanner_not_found),
+        modifier = modifier,
+        contentPadding = contentPadding,
+        onTextLayout = onTextLayout,
+    )
+}
+
+@PreviewsDayNight
+@Composable
+internal fun NotFoundContentViewPreview() = ElementPreview {
+    Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+        NotFoundContentView()
+    }
+}

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/messages/reply/InReplyToDetails.kt

@@ -40,6 +40,12 @@ fun InReplyToDetails.eventId() = when (this) {
     is InReplyToDetails.Error -> eventId
 }
 
+fun InReplyToDetails.content() = when (this) {
+    is InReplyToDetails.Ready -> eventContent
+    is InReplyToDetails.Loading -> null
+    is InReplyToDetails.Error -> null
+}
+
 fun InReplyTo.map(
     permalinkParser: PermalinkParser,
 ) = when (this) {

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/messages/reply/InReplyToView.kt

@@ -19,6 +19,7 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
@@ -44,6 +45,9 @@ import io.element.android.libraries.matrix.api.core.UserId
 import io.element.android.libraries.matrix.api.timeline.item.event.ProfileDetails
 import io.element.android.libraries.matrix.api.timeline.item.event.getDisambiguatedDisplayName
 import io.element.android.libraries.matrix.ui.components.AttachmentThumbnail
+import io.element.android.libraries.matrix.ui.media.contentvalidation.ContentValidationValue
+import io.element.android.libraries.matrix.ui.media.contentvalidation.InvalidContentView
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NotFoundContentView
 import io.element.android.libraries.matrix.ui.messages.sender.SenderName
 import io.element.android.libraries.matrix.ui.messages.sender.SenderNameMode
 import io.element.android.libraries.ui.strings.CommonStrings
@@ -55,18 +59,22 @@ import io.element.android.libraries.ui.strings.CommonStrings
 fun InReplyToView(
     inReplyTo: InReplyToDetails,
     hideImage: Boolean,
+    contentValidationValue: ContentValidationValue,
     modifier: Modifier = Modifier,
     maxLines: Int = 2,
 ) {
     when (inReplyTo) {
-        is InReplyToDetails.Ready -> {
-            ReplyToReadyContent(
+        is InReplyToDetails.Ready -> when (contentValidationValue) {
+            ContentValidationValue.Valid -> ReplyToReadyContent(
                 senderId = inReplyTo.senderId,
                 senderProfile = inReplyTo.senderProfile,
                 metadata = inReplyTo.metadata(hideImage),
                 maxLines = maxLines,
                 modifier = modifier,
             )
+            ContentValidationValue.Invalid -> ReplyToInvalidContent()
+            is ContentValidationValue.UnrecoverableError -> ReplyToNotFoundContent()
+            else -> ReplyToLoadingContent(modifier = modifier)
         }
         is InReplyToDetails.Error ->
             ReplyToErrorContent(data = inReplyTo, maxLines = maxLines, modifier = modifier)
@@ -86,7 +94,7 @@ private fun ReplyToReadyContent(
     val paddings = if (metadata is InReplyToMetadata.Thumbnail) {
         PaddingValues(end = 8.dp)
     } else {
-        PaddingValues(start = 8.dp, end = 8.dp)
+        PaddingValues(horizontal = 8.dp)
     }
     Row(
         modifier
@@ -213,11 +221,50 @@ private fun ReplyToContentText(
     }
 }
 
+@Composable
+private fun ReplyToInvalidContent(
+    modifier: Modifier = Modifier
+) {
+    InvalidContentView(
+        modifier = modifier,
+        contentPadding = PaddingValues(horizontal = 8.dp),
+        onTextLayout = null,
+    )
+}
+
+@Composable
+private fun ReplyToNotFoundContent(
+    modifier: Modifier = Modifier
+) {
+    NotFoundContentView(
+        modifier = modifier,
+        contentPadding = PaddingValues(horizontal = 8.dp),
+        onTextLayout = null,
+    )
+}
+
 @PreviewsDayNight
 @Composable
 internal fun InReplyToViewPreview(@PreviewParameter(provider = InReplyToDetailsProvider::class) inReplyTo: InReplyToDetails) = ElementPreview {
     InReplyToView(
         inReplyTo = inReplyTo,
         hideImage = false,
+        contentValidationValue = ContentValidationValue.Valid,
     )
 }
+
+@PreviewsDayNight
+@Composable
+internal fun ReplyToInvalidContentPreview() {
+    ElementPreview {
+        ReplyToInvalidContent(modifier = Modifier.padding(10.dp))
+    }
+}
+
+@PreviewsDayNight
+@Composable
+internal fun ReplyToNotFoundContentPreview() {
+    ElementPreview {
+        ReplyToNotFoundContent(modifier = Modifier.padding(10.dp))
+    }
+}

libraries/mediaviewer/api/src/main/kotlin/io/element/android/libraries/mediaviewer/api/GalleryItemData.kt

@@ -18,6 +18,7 @@ data class GalleryItemData(
     val mediaSource: MediaSource,
     val thumbnailSource: MediaSource?,
     val type: Type,
+    val blurHash: String?,
 ) : Parcelable {
     enum class Type {
         Image,

libraries/mediaviewer/api/src/main/kotlin/io/element/android/libraries/mediaviewer/api/MediaViewerEntryPoint.kt

@@ -42,6 +42,7 @@ interface MediaViewerEntryPoint : FeatureEntryPoint {
             val mediaInfo: MediaInfo,
             val mediaSource: MediaSource,
             val thumbnailSource: MediaSource?,
+            val blurHash: String?,
         ) : Params
 
         data class EventGallery(
@@ -55,6 +56,7 @@ interface MediaViewerEntryPoint : FeatureEntryPoint {
             val avatarInfo: AvatarInfo,
             val mediaSource: MediaSource,
             val thumbnailSource: MediaSource?,
+            val blurHash: String?,
         ) : Params
     }
 

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/DefaultMediaViewerEntryPoint.kt

@@ -27,6 +27,8 @@ class DefaultMediaViewerEntryPoint : MediaViewerEntryPoint {
             ),
             mediaSource = MediaSource(url = avatarUrl),
             thumbnailSource = null,
+            // Maybe add avatar blurhash if available?
+            blurHash = null,
         )
     }
 

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/datasource/EventItemFactory.kt

@@ -116,6 +116,7 @@ class EventItemFactory(
                                         ),
                                         mediaSource = c.source,
                                         thumbnailSource = c.info?.thumbnailSource,
+                                        blurHash = c.info?.blurhash,
                                     )
                                 }
                                 is GalleryItemType.Video -> {
@@ -136,6 +137,7 @@ class EventItemFactory(
                                         ),
                                         mediaSource = c.source,
                                         thumbnailSource = c.info?.thumbnailSource,
+                                        blurHash = c.info?.blurhash,
                                     )
                                 }
                                 is GalleryItemType.Audio -> {
@@ -242,6 +244,7 @@ class EventItemFactory(
                         ),
                         mediaSource = type.source,
                         thumbnailSource = type.info?.thumbnailSource,
+                        blurHash = type.info?.blurhash,
                     ))
                     is StickerMessageType -> listOf(MediaItem.Image(
                         id = currentTimelineItem.uniqueId,
@@ -264,6 +267,7 @@ class EventItemFactory(
                         ),
                         mediaSource = type.source,
                         thumbnailSource = type.info?.thumbnailSource,
+                        blurHash = type.info?.blurhash,
                     ))
                     is VideoMessageType -> listOf(MediaItem.Video(
                         id = currentTimelineItem.uniqueId,
@@ -286,6 +290,7 @@ class EventItemFactory(
                         ),
                         mediaSource = type.source,
                         thumbnailSource = type.info?.thumbnailSource,
+                        blurHash = type.info?.blurhash,
                     ))
                     is VoiceMessageType -> listOf(MediaItem.Voice(
                         id = currentTimelineItem.uniqueId,

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/gallery/root/MediaGalleryFlowNode.kt

@@ -34,6 +34,7 @@ import io.element.android.libraries.mediaviewer.api.MediaInfo
 import io.element.android.libraries.mediaviewer.api.MediaViewerEntryPoint
 import io.element.android.libraries.mediaviewer.impl.gallery.MediaGalleryNode
 import io.element.android.libraries.mediaviewer.impl.model.MediaItem
+import io.element.android.libraries.mediaviewer.impl.model.blurHash
 import io.element.android.libraries.mediaviewer.impl.model.eventId
 import io.element.android.libraries.mediaviewer.impl.model.mediaInfo
 import io.element.android.libraries.mediaviewer.impl.model.mediaSource
@@ -68,6 +69,7 @@ class MediaGalleryFlowNode(
             val mediaInfo: MediaInfo,
             val mediaSource: MediaSource,
             val thumbnailSource: MediaSource?,
+            val blurHash: String?,
         ) : NavTarget
     }
 
@@ -104,6 +106,7 @@ class MediaGalleryFlowNode(
                                 mediaInfo = item.mediaInfo(),
                                 mediaSource = item.mediaSource(),
                                 thumbnailSource = item.thumbnailSource(),
+                                blurHash = item.blurHash(),
                             )
                         )
                     }
@@ -134,6 +137,7 @@ class MediaGalleryFlowNode(
                         mediaInfo = navTarget.mediaInfo,
                         mediaSource = navTarget.mediaSource,
                         thumbnailSource = navTarget.thumbnailSource,
+                        blurHash = navTarget.blurHash,
                     ),
                     callback = callback,
                 )

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/gallery/ui/VideoItemView.kt

@@ -34,6 +34,7 @@ import coil3.compose.AsyncImage
 import coil3.compose.AsyncImagePainter
 import io.element.android.compound.theme.ElementTheme
 import io.element.android.compound.tokens.generated.CompoundIcons
+import io.element.android.libraries.designsystem.components.blurhash.blurHashBackground
 import io.element.android.libraries.designsystem.modifiers.onKeyboardContextMenuAction
 import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
@@ -51,6 +52,7 @@ fun VideoItemView(
 ) {
     Box(
         modifier = modifier
+            .blurHashBackground(blurHash = video.blurHash)
             .aspectRatio(1f)
             .combinedClickable(
                 onClick = onClick,

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/model/MediaItem.kt

@@ -35,6 +35,7 @@ sealed interface MediaItem {
         val mediaInfo: MediaInfo,
         val mediaSource: MediaSource,
         val thumbnailSource: MediaSource?,
+        val blurHash: String?,
     ) : Event {
         val thumbnailMediaRequestData: MediaRequestData
             get() = MediaRequestData(thumbnailSource ?: mediaSource, MediaRequestData.Kind.Thumbnail(100))
@@ -46,6 +47,7 @@ sealed interface MediaItem {
         val mediaInfo: MediaInfo,
         val mediaSource: MediaSource,
         val thumbnailSource: MediaSource?,
+        val blurHash: String?,
     ) : Event {
         val thumbnailMediaRequestData: MediaRequestData
             get() = MediaRequestData(thumbnailSource ?: mediaSource, MediaRequestData.Kind.Thumbnail(100))
@@ -124,3 +126,11 @@ fun MediaItem.Event.thumbnailSource(): MediaSource? {
         is MediaItem.Voice -> null
     }
 }
+
+fun MediaItem.Event.blurHash(): String? {
+    return when (this) {
+        is MediaItem.Image -> blurHash
+        is MediaItem.Video -> blurHash
+        else -> null
+    }
+}

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/model/MediaItemFactories.kt

@@ -34,6 +34,7 @@ fun aMediaItemImage(
         ),
         mediaSource = MediaSource(mediaSourceUrl),
         thumbnailSource = null,
+        blurHash = null,
     )
 }
 
@@ -50,6 +51,7 @@ fun aMediaItemVideo(
         ),
         mediaSource = mediaSource,
         thumbnailSource = null,
+        blurHash = null,
     )
 }
 

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/GalleryMediaGalleryDataSource.kt

@@ -63,6 +63,7 @@ class GalleryMediaGalleryDataSource(
                         mediaInfo = itemMediaInfo,
                         mediaSource = galleryItem.mediaSource,
                         thumbnailSource = galleryItem.thumbnailSource,
+                        blurHash = galleryItem.blurHash,
                     )
                     GalleryItemData.Type.Audio -> MediaItem.Audio(
                         id = id,
@@ -82,6 +83,7 @@ class GalleryMediaGalleryDataSource(
                         mediaInfo = itemMediaInfo,
                         mediaSource = galleryItem.mediaSource,
                         thumbnailSource = galleryItem.thumbnailSource,
+                        blurHash = galleryItem.blurHash,
                     )
                 }
                 mixedItems.add(mediaItem)

libraries/mediaviewer/impl/src/main/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/SingleMediaGalleryDataSource.kt

@@ -63,6 +63,7 @@ class SingleMediaGalleryDataSource(
                         ),
                         mediaSource = params.mediaSource,
                         thumbnailSource = params.thumbnailSource,
+                        blurHash = params.blurHash,
                     )
                 ),
                 fileItems = persistentListOf(),
@@ -79,6 +80,7 @@ fun MediaViewerEntryPoint.Params.RoomMedia.toMediaItem() = when {
             mediaInfo = mediaInfo,
             mediaSource = mediaSource,
             thumbnailSource = thumbnailSource,
+            blurHash = blurHash,
         )
     }
     mediaInfo.mimeType.isMimeTypeVideo() -> {
@@ -88,6 +90,7 @@ fun MediaViewerEntryPoint.Params.RoomMedia.toMediaItem() = when {
             mediaInfo = mediaInfo,
             mediaSource = mediaSource,
             thumbnailSource = thumbnailSource,
+            blurHash = blurHash,
         )
     }
     mediaInfo.mimeType.isMimeTypeAudio() -> {

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/DefaultMediaViewerEntryPointTest.kt

@@ -141,6 +141,7 @@ class DefaultMediaViewerEntryPointTest {
                 avatarInfo = AvatarInfo(filename = "avatar.png"),
                 mediaSource = MediaSource(url = "avatarUrl"),
                 thumbnailSource = null,
+                blurHash = null,
             )
         )
         assertThat(result.plugins).contains(callback)

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/datasource/EventItemFactoryTest.kt

@@ -226,6 +226,7 @@ class EventItemFactoryTest {
                 ),
                 mediaSource = MediaSource(""),
                 thumbnailSource = null,
+                blurHash = null,
             )
         )
     }
@@ -326,6 +327,7 @@ class EventItemFactoryTest {
                 ),
                 mediaSource = MediaSource(""),
                 thumbnailSource = null,
+                blurHash = null,
             )
         )
     }
@@ -437,6 +439,7 @@ class EventItemFactoryTest {
                 ),
                 mediaSource = MediaSource("image_url"),
                 thumbnailSource = MediaSource("thumbnail_url"),
+                blurHash = null,
             )
         )
     }
@@ -498,6 +501,7 @@ class EventItemFactoryTest {
                 ),
                 mediaSource = MediaSource("video_url"),
                 thumbnailSource = MediaSource("thumbnail_url"),
+                blurHash = null,
             )
         )
     }
@@ -744,6 +748,7 @@ class EventItemFactoryTest {
                 ),
                 mediaSource = MediaSource(""),
                 thumbnailSource = null,
+                blurHash = null,
             )
         )
     }

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/datasource/TimelineMediaGalleryDataSourceTest.kt

@@ -249,6 +249,7 @@ class TimelineMediaGalleryDataSourceTest {
                                 ),
                                 mediaSource = MediaSource("url"),
                                 thumbnailSource = MediaSource("url_thumbnail"),
+                                blurHash = A_BLUR_HASH,
                             )
                         ),
                         fileItems = persistentListOf()

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/GalleryMediaGalleryDataSourceTest.kt

@@ -91,6 +91,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("image_url"),
                     thumbnailSource = MediaSource("thumbnail_url"),
                     type = GalleryItemData.Type.Image,
+                    blurHash = null,
                 )
             ),
             galleryInfo = aGalleryInfo(),
@@ -104,6 +105,7 @@ class GalleryMediaGalleryDataSourceTest {
                 mediaInfo = expectedMediaInfo("image.jpg", MimeTypes.Jpeg),
                 mediaSource = MediaSource("image_url"),
                 thumbnailSource = MediaSource("thumbnail_url"),
+                blurHash = null,
             )
         )
     }
@@ -119,6 +121,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("video_url"),
                     thumbnailSource = MediaSource("thumbnail_url"),
                     type = GalleryItemData.Type.Video,
+                    blurHash = null,
                 )
             ),
             galleryInfo = aGalleryInfo(),
@@ -132,6 +135,7 @@ class GalleryMediaGalleryDataSourceTest {
                 mediaInfo = expectedMediaInfo("video.mp4", MimeTypes.Mp4),
                 mediaSource = MediaSource("video_url"),
                 thumbnailSource = MediaSource("thumbnail_url"),
+                blurHash = null,
             )
         )
     }
@@ -147,6 +151,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("audio_url"),
                     thumbnailSource = null,
                     type = GalleryItemData.Type.Audio,
+                    blurHash = null,
                 )
             ),
             galleryInfo = aGalleryInfo(),
@@ -174,6 +179,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("file_url"),
                     thumbnailSource = null,
                     type = GalleryItemData.Type.File,
+                    blurHash = null,
                 )
             ),
             galleryInfo = aGalleryInfo(),
@@ -201,6 +207,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("image_url"),
                     thumbnailSource = null,
                     type = GalleryItemData.Type.Image,
+                    blurHash = null,
                 )
             ),
             galleryInfo = aGalleryInfo(),
@@ -222,6 +229,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("image_url"),
                     thumbnailSource = null,
                     type = GalleryItemData.Type.Image,
+                    blurHash = null,
                 ),
                 GalleryItemData(
                     filename = "document.pdf",
@@ -229,6 +237,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("file_url"),
                     thumbnailSource = null,
                     type = GalleryItemData.Type.File,
+                    blurHash = null,
                 ),
                 GalleryItemData(
                     filename = "video.mp4",
@@ -236,6 +245,7 @@ class GalleryMediaGalleryDataSourceTest {
                     mediaSource = MediaSource("video_url"),
                     thumbnailSource = null,
                     type = GalleryItemData.Type.Video,
+                    blurHash = null,
                 ),
             ),
             galleryInfo = aGalleryInfo(),

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/MediaViewerPresenterTest.kt

@@ -114,6 +114,7 @@ class MediaViewerPresenterTest {
                 avatarInfo = AvatarInfo(filename = "avatar.png"),
                 mediaSource = aMediaSource(),
                 thumbnailSource = null,
+                blurHash = null,
             ),
             room = FakeJoinedRoom(
                 baseRoom = FakeBaseRoom(
@@ -983,4 +984,5 @@ internal fun createMediaViewerEntryPointParams(
     mediaInfo = TESTED_MEDIA_INFO,
     mediaSource = aMediaSource(),
     thumbnailSource = null,
+    blurHash = null,
 )

libraries/mediaviewer/impl/src/test/kotlin/io/element/android/libraries/mediaviewer/impl/viewer/SingleMediaGalleryDataSourceTest.kt

@@ -89,6 +89,7 @@ class SingleMediaGalleryDataSourceTest {
                     mediaInfo = params.mediaInfo,
                     mediaSource = params.mediaSource,
                     thumbnailSource = params.thumbnailSource,
+                    blurHash = null,
                 )
             }
         )
@@ -105,6 +106,7 @@ class SingleMediaGalleryDataSourceTest {
                     mediaInfo = params.mediaInfo,
                     mediaSource = params.mediaSource,
                     thumbnailSource = params.thumbnailSource,
+                    blurHash = null,
                 )
             }
         )
@@ -175,5 +177,6 @@ class SingleMediaGalleryDataSourceTest {
         mediaInfo = mediaInfo,
         mediaSource = aMediaSource(url = "aUrl"),
         thumbnailSource = aMediaSource(url = "aThumbnailUrl"),
+        blurHash = null,
     )
 }

libraries/textcomposer/impl/src/main/kotlin/io/element/android/libraries/textcomposer/ComposerModeView.kt

@@ -13,6 +13,7 @@ import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.interaction.MutableInteractionSource
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
@@ -20,6 +21,7 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.ripple
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
@@ -35,8 +37,11 @@ import io.element.android.libraries.designsystem.preview.ElementPreview
 import io.element.android.libraries.designsystem.preview.PreviewsDayNight
 import io.element.android.libraries.designsystem.theme.components.Icon
 import io.element.android.libraries.designsystem.theme.components.Text
+import io.element.android.libraries.matrix.ui.media.contentvalidation.collectOverallState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.rememberEventContentValidationState
 import io.element.android.libraries.matrix.ui.messages.reply.InReplyToDetails
 import io.element.android.libraries.matrix.ui.messages.reply.InReplyToView
+import io.element.android.libraries.matrix.ui.messages.reply.eventId
 import io.element.android.libraries.textcomposer.model.MessageComposerMode
 import io.element.android.libraries.ui.strings.CommonStrings
 
@@ -134,28 +139,44 @@ private fun ReplyToModeView(
     onResetComposerMode: () -> Unit,
     modifier: Modifier = Modifier,
 ) {
-    Row(
+    val shape = RoundedCornerShape(6.dp)
+    val contentValidationState = rememberEventContentValidationState(replyToDetails.eventId(), (replyToDetails as? InReplyToDetails.Ready)?.eventContent)
+    val currentValidationState by contentValidationState.collectOverallState()
+
+    val contentHasErrors = currentValidationState.hasError()
+
+    Box(
         modifier
-            .clip(RoundedCornerShape(6.dp))
-            .background(ElementTheme.colors.bgCanvasDefault)
-            .border(1.dp, ElementTheme.colors.separatorPrimary, RoundedCornerShape(6.dp))
+            .clip(shape)
+            .background(
+                color = if (contentHasErrors) ElementTheme.colors.bgCriticalSubtle else ElementTheme.colors.bgCanvasDefault,
+                shape = shape,
+            )
+            .border(
+                width = 1.dp,
+                color = if (contentHasErrors) ElementTheme.colors.borderCriticalSubtle else ElementTheme.colors.separatorPrimary,
+                shape = shape,
+            )
             .padding(4.dp)
     ) {
         // Larger density DPI and font scale means less space to display the content, so we limit it to 1 line to avoid overflow issues
         val currentDensity = LocalDensity.current
         val hasLowResolution = currentDensity.density * currentDensity.fontScale >= MAX_SCALING_VALUE
         val maxReplyContentLines = if (hasLowResolution) 1 else 2
+
         InReplyToView(
             inReplyTo = replyToDetails,
             hideImage = hideImage,
+            contentValidationValue = currentValidationState,
             maxLines = maxReplyContentLines,
-            modifier = Modifier.weight(1f),
+            modifier = Modifier.fillMaxWidth(),
         )
         Icon(
             imageVector = CompoundIcons.Close(),
             contentDescription = stringResource(CommonStrings.action_close),
-            tint = ElementTheme.colors.iconSecondary,
+            tint = if (contentHasErrors) ElementTheme.colors.iconCriticalPrimary else ElementTheme.colors.iconSecondary,
             modifier = Modifier
+                .align(Alignment.TopEnd)
                 .padding(end = 4.dp, top = 4.dp, start = 8.dp, bottom = 16.dp)
                 .size(16.dp)
                 .clickable(

tests/konsist/src/test/kotlin/io/element/android/tests/konsist/KonsistArchitectureTest.kt

@@ -34,6 +34,7 @@ class KonsistArchitectureTest {
             .classes()
             .withNameEndingWith("State")
             .withoutName(
+                "NoopContentValidationState",
                 "CameraPositionState",
                 "CustomSheetState",
             )

tests/konsist/src/test/kotlin/io/element/android/tests/konsist/KonsistPreviewTest.kt

@@ -145,7 +145,8 @@ class KonsistPreviewTest {
         "TextComposerVoiceNotEncryptedPreview",
         "TextComposerVoicePreview",
         "TextFieldDialogWithErrorPreview",
-        "TimelineImageWithCaptionRowPreview",
+        "TimelineItemAttachmentsViewScanningContentFailedPreview",
+        "TimelineItemAudioViewScanningContentPreview",
         "TimelineItemEventRowForDirectRoomPreview",
         "TimelineItemEventRowShieldPreview",
         "TimelineItemEventRowTimestampPreview",
@@ -155,13 +156,21 @@ class KonsistPreviewTest {
         "TimelineItemEventRowWithRRPreview",
         "TimelineItemEventRowWithReplyPreview",
         "TimelineItemEventRowWithThreadSummaryPreview",
+        "TimelineItemFileViewScanningContentPreview",
+        "TimelineItemGalleryViewScanningContentFailedPreview",
         "TimelineItemGroupedEventsRowContentCollapsePreview",
         "TimelineItemGroupedEventsRowContentExpandedPreview",
         "TimelineItemImageViewHideMediaContentPreview",
+        "TimelineItemImageViewScanningContentPreview",
         "TimelineItemRedactedMessagesGroupPreview",
+        "TimelineItemScanningContentFailedPreview",
+        "TimelineItemScanningContentWithInvalidRepliesPreview",
+        "TimelineItemScanningContentWithRepliesFailedPreview",
+        "TimelineItemStickerViewScanningContentPreview",
         "TimelineItemVideoViewHideMediaContentPreview",
+        "TimelineItemVideoViewScanningContentPreview",
+        "TimelineItemVoiceViewScanningContentPreview",
         "TimelineItemVoiceViewUnifiedPreview",
-        "TimelineVideoWithCaptionRowPreview",
         "TimelineViewMessageShieldPreview",
         "TimelineViewWithReadMarkerBothIndicatorsPreview",
         "TimelineViewWithReadMarkerJumpToUnreadIndicatorOnlyPreview",

tests/uitests/src/test/kotlin/base/ScreenshotTest.kt

@@ -26,6 +26,8 @@ import com.android.resources.Density.DEFAULT_DENSITY
 import com.android.resources.NightMode
 import com.android.resources.ScreenOrientation
 import io.element.android.compound.theme.ElementTheme
+import io.element.android.libraries.matrix.ui.media.contentvalidation.LocalEventContentValidationState
+import io.element.android.libraries.matrix.ui.media.contentvalidation.NoopEventContentValidationCache
 import sergio.sastre.composable.preview.scanner.android.AndroidPreviewInfo
 import sergio.sastre.composable.preview.scanner.core.preview.ComposablePreview
 import java.util.Locale
@@ -55,6 +57,7 @@ object ScreenshotTest {
                     setLocales(LocaleList(locale))
                     uiMode = preview.previewInfo.uiMode
                 },
+                LocalEventContentValidationState provides NoopEventContentValidationCache(),
             ) {
                 ElementTheme {
                     Box(

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.customreaction_EmojiItemWithPopup_Day_0_en.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:4746d11c30648f7c517b0880021e5a1dc6ed2819af6c800b081b0d842ac2c384
-size 5325
+oid sha256:c5572491b675a16724cd9e33ebb477c82edf285fa07d57ebef09c670fcaaddf1
+size 21285

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.customreaction_EmojiItemWithPopup_Night_0_en.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:eede6f990a7a1dbddee1cd9e722b30600160d475ad2ae72faebcb773f52aaa7b
-size 20793
+oid sha256:290a2be6838445739b0181006f9fea87337a85cfed3573c153e9f503c66624a6
+size 4994

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_ATimelineItemEventRow_Day_0_en.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:86eac241e9084cc830ff13d231908da2eb0dff246aa5cac64dddaac68a5d5f13
-size 295298
+oid sha256:ce15ca9f89274620728715e3448ce671e2253f4fed22a44035460e9a3709ca0b
+size 647404

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_ATimelineItemEventRow_Night_0_en.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:7076c9a44a433cd9eeca536365ae262d39b4ad99a8f854faadec272cb1b82031
-size 294992
+oid sha256:d0424685437a433b35b589668b409d55f26ab41bcae01af0121a54033c56a8c2
+size 646194

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineImageWithCaptionRow_Day_0_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:d6441c572f64d99bc119d649e5e6422fe516b9d097f310ccbd99a9ddded9609f
-size 612494

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineImageWithCaptionRow_Night_0_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:5a867dda82242d2b13bd4bc84a9f1c9b8b7b99c030e19a6cce39b2f828b517f3
-size 611488

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemAttachmentsListView_Day_1_en.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:aa4034a06aa6e8d24806b640d9c6604bf4cffc5ec5664d2b9b189e6c39850ce0
-size 42543
+oid sha256:9e8d673869b3fd1d6be2b95c79c8a12e94732f74f28b51a38e40c166a9eae4f6
+size 39466

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemAttachmentsListView_Night_1_en.png

@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:9b777363de123a6de81360e4ee9c5066c8953ac103c52349979e4c3fdca1e20c
-size 41699
+oid sha256:99672a8ee0d4d22f0d15a74d4e3c8923b762116ecd2e741fd09c184963737e11
+size 38609

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemAudioView_Day_3_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:c43d85e4658b9fb930ef76258479a876d5cde3b545bc4f4a76d86e4ef2d7a82f
-size 10773

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemAudioView_Day_4_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:c836c0a00fb5697138349028540d5e1cb4f1fddd2fd50d388cb5a1b55ccaa8f4
-size 21023

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemAudioView_Night_3_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:9fa672f2cb7dbf0fff171d507e66d1ed8494cbcd93b48bef1ee1b9b75d6717e7
-size 10499

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemAudioView_Night_4_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:5735813e0f9c40e5d861ba0c35ba73689ff7ee41224829289ce017746323922c
-size 20150

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemFileView_Day_3_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:10b79226a4eb5c67afc1fc8ace8c6fb49429a69b1e1518b622dcfd20bc2820ea
-size 10032

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemFileView_Day_4_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:085310083c4150fb70e48087881e529f17005df69cc01dd53807a06266f4f4bb
-size 20317

tests/uitests/src/test/snapshots/images/features.messages.impl.timeline.components.event_TimelineItemFileView_Night_3_en.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:4ef1884c4cac3debea52affbab071110a49b40cebfd38b316693085464fcc440
-size 9859