fix(mobile): page native remote history until the reader sees an older turn

docs/architecture/peer-device-mode.md

@@ -125,6 +125,25 @@ records and responses from a device that is no longer rendered. Desktop
 `RelaySessionHistory` owns the subscription across initial loading, realtime
 delivery and older-page prefetch.
 
+Native mobile history keeps these record-page boundaries; a page is not a
+complete conversation turn. The initial replay and each older-history request
+reduce all received records before publishing one transcript projection. A turn
+split across pages may gain text or tools on a later read; that is normal and
+must preserve the existing reading position. Realtime updates remain incremental.
+
+The loading indicator covers the RPC and delivery to the reducer. Kotlin's
+buffered transport waits for downstream consumption before reporting caught-up
+or completing an older-page request; enqueueing records is not completion.
+Kotlin uses local history-start/ready events and HarmonyOS uses local replay
+callbacks to suppress intermediate projections. These are client-internal
+boundaries, not additions to the `read_stream` wire format. A failed multi-page
+read commits only the fully received pages and reports failure; a later retry
+continues from the durable record cursor. Session changes fence stale delivery.
+Native timelines retain visible message anchors on prepend, allow at most one
+automatic request per deliberate drag, and do not queue gestures made while
+loading. Layout, anchor correction and released-finger overscroll cannot request
+another page.
+
 Version skew is negotiated, not assumed. Hosts advertise `host_stream_v1` in
 their handshake `capabilities`; a controller that does not see it reports the
 host as too old instead of sending `read_stream`, and a host that receives the

src/apps/mobile/android/app/src/androidTest/kotlin/com/openbitfun/mobile/app/ChatMessageBubbleTest.kt

@@ -258,7 +258,6 @@ class ChatMessageBubbleTest {
         tools = emptyList(),
         blocks = blocks,
         streaming = streaming,
-        pending = false,
         typing = typing,
         showRetry = showRetry,
         error = null,

src/apps/mobile/android/app/src/androidTest/kotlin/com/openbitfun/mobile/app/ConversationViewTest.kt

@@ -25,6 +25,8 @@ import androidx.compose.ui.test.performClick
 import androidx.compose.ui.test.performTextReplacement
 import androidx.compose.ui.test.performTouchInput
 import androidx.compose.ui.test.swipeDown
+import androidx.compose.ui.test.performScrollToIndex
+import com.openbitfun.mobile.core.feature.session.HistoryLoadState
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import androidx.test.platform.app.InstrumentationRegistry
@@ -234,6 +236,38 @@ class ConversationViewTest {
             .assertDoesNotExist()
     }
 
+    @Test
+    fun historyPrependKeepsVisibleMessagesAndRepeatedDragsDoNotQueueRequests() {
+        val rows = mutableStateOf((0..5).map { assistantRow("history-$it", "history-$it") })
+        val loading = mutableStateOf(HistoryLoadState.IDLE)
+        var requests = 0
+        composeRule.setContent {
+            OpenBitFunTheme(dark = false) {
+                TimelineForTest(rows.value, hasMoreMessages = true, historyLoadState = loading.value,
+                    onLoadOlder = { requests++; loading.value = HistoryLoadState.LOADING })
+            }
+        }
+        val list = composeRule.onNodeWithTag(CONVERSATION_LIST_TEST_TAG)
+        repeat(3) { list.performTouchInput { swipeDown() }; composeRule.waitForIdle() }
+        composeRule.runOnIdle { assertEquals(1, requests) }
+        val before = composeRule.onNodeWithText("history-0").getUnclippedBoundsInRoot().top
+        composeRule.runOnIdle {
+            rows.value = (-12..-1).map { assistantRow("history-$it", "history-$it") } + rows.value
+            loading.value = HistoryLoadState.IDLE
+        }
+        composeRule.waitForIdle()
+        val after = composeRule.onNodeWithText("history-0").getUnclippedBoundsInRoot().top
+        assertTrue("Prepending moved the visible row from $before to $after", kotlin.math.abs((after - before).value) < 4)
+        composeRule.runOnIdle { assertEquals(1, requests) }
+        // Moving the list without a gesture must not fetch another page.
+        list.performScrollToIndex(0)
+        composeRule.waitForIdle()
+        composeRule.runOnIdle { assertEquals(1, requests) }
+        list.performTouchInput { swipeDown() }
+        composeRule.waitForIdle()
+        composeRule.runOnIdle { assertEquals(2, requests) }
+    }
+
     @Test
     fun withLoadOlderHeaderStreamingGrowthStaysOnTheRealTail() {
         val rows = mutableStateOf(
@@ -487,13 +521,16 @@ class ConversationViewTest {
         hasMoreMessages: Boolean = false,
         topInset: Dp = 0.dp,
         bottomInset: Dp = 0.dp,
+        historyLoadState: HistoryLoadState = HistoryLoadState.IDLE,
+        onLoadOlder: () -> Unit = {},
     ) {
         ConversationTimelineView(
             rows = rows,
             hasMoreMessages = hasMoreMessages,
             topInset = topInset,
             bottomInset = bottomInset,
-            onLoadOlder = {},
+            historyLoadState = historyLoadState,
+            onLoadOlder = onLoadOlder,
             enabled = true,
             onApproveTool = { _, _ -> },
             onRejectTool = { _, _ -> },
@@ -525,7 +562,6 @@ class ConversationViewTest {
         blocks = emptyList(),
         streaming = streaming,
         typing = false,
-        pending = false,
         showRetry = false,
         error = null,
         live = false,

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/chat/ChatMessageBubble.kt

@@ -13,7 +13,6 @@ import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
 import com.openbitfun.mobile.app.R
-import com.openbitfun.mobile.app.ui.chat.message.ChatCaption
 import com.openbitfun.mobile.app.ui.chat.message.ChatMessageRetryAction
 import com.openbitfun.mobile.app.ui.chat.message.ChatTypingDots
 import com.openbitfun.mobile.app.ui.chat.message.ChatUserMessageBubble
@@ -90,8 +89,8 @@ internal fun ChatMessageBubble(
             MessageImageGallery(images = row.images, userStyle = false)
         }
 
-        // Three mutually exclusive footnotes about delivery, in the order they
-        // can happen: nothing has arrived yet, sent but unacknowledged, refused.
+        // Two mutually exclusive footnotes about delivery: nothing has arrived
+        // yet, or the send was refused.
         when {
             row.showRetry -> ChatMessageRetryAction(
                 fromUser = fromUser,
@@ -101,7 +100,6 @@ internal fun ChatMessageBubble(
             )
 
             row.typing -> ChatTypingDots(Modifier)
-            row.pending -> ChatCaption(stringResource(R.string.chat_pending), error = false)
         }
     }
 }

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/chat/ComposerBar.kt

@@ -759,7 +759,7 @@ private fun AttachmentStrip(
     ) {
         items(images, key = { it.id }) { image ->
             Box(modifier = Modifier.size(64.dp)) {
-                val bitmap = remember(image.dataUrl) { decodeInlineImage(image.dataUrl) }
+                val bitmap = rememberInlineImage(image.dataUrl)
                 if (bitmap != null) {
                     Image(
                         bitmap = bitmap.asImageBitmap(),

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/chat/ConversationTimelineView.kt

@@ -26,6 +26,7 @@ import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.runtime.snapshotFlow
@@ -40,6 +41,7 @@ import com.openbitfun.mobile.app.R
 import com.openbitfun.mobile.core.feature.session.ConversationRow
 import com.openbitfun.mobile.core.feature.session.QuestionAnswer
 import com.openbitfun.mobile.core.feature.workspace.RemoteFileDownloadUiState
+import kotlinx.coroutines.flow.distinctUntilChanged
 
 /** Pure decisions for keeping a forward timeline at its visual tail. */
 internal object ConversationScrollPolicy {
@@ -65,6 +67,18 @@ internal object ConversationScrollPolicy {
         if (hasMoreMessages) rowCount else (rowCount - 1).coerceAtLeast(0)
 }
 
+/** One automatic page per deliberate drag; layout and bounce cannot re-arm it. */
+internal class HistoryPageArrivalTracker {
+    private var consumed = true
+    fun beginGesture() { consumed = false }
+    fun arrived(atStart: Boolean): Boolean {
+        if (!atStart || consumed) return false
+        consumed = true
+        return true
+    }
+    fun cancelArrival() { consumed = true }
+}
+
 /** Timeline renderer over feature-owned presentation rows; session routing stays above it. */
 @Composable
 internal fun ConversationTimelineView(
@@ -98,11 +112,12 @@ internal fun ConversationTimelineView(
     var stickToBottom by rememberSaveable { mutableStateOf(true) }
     val atBottom by remember(listState) { derivedStateOf { !listState.canScrollForward } }
 
+    val historyArrival = remember { HistoryPageArrivalTracker() }
     var userDragging by remember { mutableStateOf(false) }
     LaunchedEffect(listState.interactionSource) {
         listState.interactionSource.interactions.collect { interaction ->
             when (interaction) {
-                is DragInteraction.Start -> { userDragging = true; stickToBottom = false }
+                is DragInteraction.Start -> { historyArrival.beginGesture(); userDragging = true; stickToBottom = false }
                 is DragInteraction.Stop, is DragInteraction.Cancel -> userDragging = false
             }
         }
@@ -128,6 +143,31 @@ internal fun ConversationTimelineView(
         }
     }
 
+    // Reaching the start of the loaded transcript asks for the next page by
+    // itself; the header stays as the loading and retry state. Busy gestures
+    // are consumed so completion cannot silently queue another page.
+    val canRequestOlder by rememberUpdatedState(
+        enabled && hasMoreMessages && historyLoadState != HistoryLoadState.LOADING
+            && historyLoadState != HistoryLoadState.FAILED,
+    )
+    val requestOlder by rememberUpdatedState {
+        stickToBottom = false
+        onLoadOlder()
+    }
+    LaunchedEffect(listState, hasMoreMessages) {
+        // Index zero is the "load older messages" header, so seeing it is the
+        // reader standing at the start of what is loaded. Following the tail is
+        // excluded: a first page that does not fill the pane is at the start
+        // without the reader having gone there, and asking from there would
+        // fight the initial tail scroll.
+        snapshotFlow { userDragging && listState.firstVisibleItemIndex == 0 && !stickToBottom }
+            .distinctUntilChanged()
+            .collect { readerReachedStart ->
+                if (!historyArrival.arrived(readerReachedStart)) return@collect
+                if (canRequestOlder) requestOlder()
+            }
+    }
+
     Box(modifier = modifier) {
         LazyColumn(
             state = listState,
@@ -144,7 +184,7 @@ internal fun ConversationTimelineView(
                 item(key = "load-older-messages") {
                     Box(modifier = Modifier.fillMaxWidth(), contentAlignment = Alignment.Center) {
                         TextButton(
-                            onClick = { stickToBottom = false; onLoadOlder() },
+                            onClick = { historyArrival.cancelArrival(); stickToBottom = false; onLoadOlder() },
                             enabled = enabled && historyLoadState != HistoryLoadState.LOADING,
                             colors = ButtonDefaults.textButtonColors(contentColor = MaterialTheme.colorScheme.onSurfaceVariant),
                         ) {

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/chat/InlineImage.kt

@@ -22,3 +22,16 @@ internal fun decodeInlineImage(dataUrl: String): Bitmap? {
         BitmapFactory.decodeByteArray(bytes, 0, bytes.size)
     }.getOrNull()
 }
+
+/** Pure projection work belongs off the Compose/UI thread. Key changes cancel
+ * the old delivery, so a reused row cannot receive another message's bitmap. */
+@androidx.compose.runtime.Composable
+internal fun rememberInlineImage(dataUrl: String): Bitmap? {
+    val state = androidx.compose.runtime.produceState<Bitmap?>(null, dataUrl) {
+        value = null
+        value = kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Default) {
+            decodeInlineImage(dataUrl)
+        }
+    }
+    return state.value
+}

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/chat/message/ChatMessageChrome.kt

@@ -40,7 +40,7 @@ import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import com.openbitfun.mobile.app.R
-import com.openbitfun.mobile.app.ui.chat.decodeInlineImage
+import com.openbitfun.mobile.app.ui.chat.rememberInlineImage
 import com.openbitfun.mobile.app.ui.chat.tool.PillButton
 import com.openbitfun.mobile.core.feature.session.ConversationImage
 
@@ -198,7 +198,7 @@ internal fun MessageImageGallery(
 internal fun ChatAttachedImage(image: ConversationImage, userStyle: Boolean = false) {
     // Anything the relay did not carry inline shows as a name rather than a
     // broken frame; see [decodeInlineImage].
-    val bitmap = remember(image.dataUrl) { decodeInlineImage(image.dataUrl) }
+    val bitmap = rememberInlineImage(image.dataUrl)
     val imageSize = if (userStyle) 112.dp else 92.dp
     val shape = RoundedCornerShape(if (userStyle) 12.dp else 14.dp)
     if (bitmap != null) {

src/apps/mobile/android/app/src/main/kotlin/com/openbitfun/mobile/app/ui/remote/FilePreviewSurface.kt

@@ -229,10 +229,18 @@ internal fun FilePreviewSurface(
             }
 
             is RemoteFilePreviewUiState.Image -> {
-                val bitmap = remember(preview.bytes) {
-                    BitmapFactory.decodeByteArray(preview.bytes, 0, preview.bytes.size)
+                val decoded by androidx.compose.runtime.produceState<Pair<Boolean, android.graphics.Bitmap?>>(
+                    initialValue = false to null, key1 = preview.bytes,
+                ) {
+                    value = false to null
+                    value = true to kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Default) {
+                        BitmapFactory.decodeByteArray(preview.bytes, 0, preview.bytes.size)
+                    }
                 }
-                if (bitmap != null) {
+                val bitmap = decoded.second
+                if (!decoded.first) {
+                    CenteredState(spacing = 12, gutter = 32) { CircularProgressIndicator() }
+                } else if (bitmap != null) {
                     Image(
                         bitmap = bitmap.asImageBitmap(),
                         contentDescription = preview.name,

src/apps/mobile/android/app/src/main/res/values-zh/strings.xml

@@ -369,7 +369,6 @@
     <string name="chat_empty_title">还没有消息</string>
     <string name="chat_empty_hint">可以就这个工作区向智能体提问。</string>
     <string name="chat_empty_loading">正在加载对话…</string>
-    <string name="chat_pending">发送中…</string>
     <string name="chat_send_failed">发送失败，请检查连接后重试</string>
     <string name="chat_reply_interrupted">回复被中断。</string>
     <string name="chat_retry">重试</string>

src/apps/mobile/android/app/src/main/res/values/strings.xml

@@ -383,7 +383,6 @@
     <string name="chat_empty_title">No messages yet</string>
     <string name="chat_empty_hint">Ask the agent anything about this workspace.</string>
     <string name="chat_empty_loading">Loading conversation…</string>
-    <string name="chat_pending">Sending…</string>
     <string name="chat_send_failed">Send failed. Check the connection and retry.</string>
     <!-- The agent's reply started and stopped partway; the user's never left the device. -->
     <string name="chat_reply_interrupted">Reply interrupted.</string>

src/apps/mobile/android/app/src/test/kotlin/com/openbitfun/mobile/app/ui/chat/HistoryPageArrivalTrackerTest.kt

@@ -0,0 +1,23 @@
+package com.openbitfun.mobile.app.ui.chat
+
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class HistoryPageArrivalTrackerTest {
+    @Test fun layoutCannotRequestAndBounceCannotRearmTheSameGesture() {
+        val tracker = HistoryPageArrivalTracker()
+        assertFalse(tracker.arrived(true))
+        tracker.beginGesture()
+        assertFalse(tracker.arrived(false))
+        assertTrue(tracker.arrived(true))
+        repeat(10) {
+            assertFalse(tracker.arrived(false))
+            assertFalse(tracker.arrived(true))
+        }
+        tracker.beginGesture()
+        assertTrue(tracker.arrived(true))
+        tracker.cancelArrival()
+        assertFalse(tracker.arrived(true))
+    }
+}

src/apps/mobile/harmonyos/entry/src/main/ets/pages/components/ChatMessageBubble.ets

@@ -337,10 +337,11 @@ export struct ChatMessageBubble {
   }
 
   @Builder
-  SubagentGroup(entry: ConversationUiMessageItem, _path: string, activeScope: boolean = false) {
+  SubagentGroup(entry: ConversationUiMessageItem, path: string, activeScope: boolean = false) {
     SubagentTaskCard({
       interactionMailbox: this.interactionMailbox,
       title: this.subagentTitle(entry),
+      path: path,
       status: entry.tool?.status || (activeScope ? 'running' : 'completed'),
       items: entry.subItems || [],
       renderRevision: this.renderRevision,