From 96f559abbb37c0a8f313549d753fb693166b4917 Mon Sep 17 00:00:00 2001
From: Kohei <yamashita@0235.co.jp>
Date: Wed, 18 Feb 2026 22:17:46 +0900
Subject: [PATCH] feat: auto-scroll chat on new messages

Scroll to bottom when sending a message, and conditionally scroll on
received messages when the user is already near the latest messages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../android/feature/chat/ChatViewModel.kt        |  6 ++++++
 .../android/feature/chat/screen/ChatScreen.kt    | 16 ++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/ChatViewModel.kt b/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/ChatViewModel.kt
index 200f622a5..381a41c10 100644
--- a/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/ChatViewModel.kt
+++ b/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/ChatViewModel.kt
@@ -8,8 +8,10 @@ import io.picoclaw.android.core.domain.usecase.LoadMoreMessagesUseCase
 import io.picoclaw.android.core.domain.usecase.ObserveConnectionUseCase
 import io.picoclaw.android.core.domain.usecase.ObserveMessagesUseCase
 import io.picoclaw.android.core.domain.usecase.SendMessageUseCase
+import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asSharedFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
@@ -26,6 +28,9 @@ class ChatViewModel(
     private val _uiState = MutableStateFlow(ChatUiState())
     val uiState: StateFlow<ChatUiState> = _uiState.asStateFlow()
 
+    private val _scrollToBottom = MutableSharedFlow<Unit>(extraBufferCapacity = 1)
+    val scrollToBottom = _scrollToBottom.asSharedFlow()
+
     init {
         connectChat()
 
@@ -51,6 +56,7 @@ class ChatViewModel(
                 val state = _uiState.value
                 val text = state.inputText.trim()
                 if (text.isEmpty() && state.pendingImages.isEmpty()) return
+                _scrollToBottom.tryEmit(Unit)
                 _uiState.update { it.copy(inputText = "", pendingImages = emptyList()) }
                 viewModelScope.launch {
                     try {
diff --git a/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/screen/ChatScreen.kt b/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/screen/ChatScreen.kt
index f903d8e12..ae6003d09 100644
--- a/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/screen/ChatScreen.kt
+++ b/android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/screen/ChatScreen.kt
@@ -99,6 +99,22 @@ fun ChatScreen(
         if (shouldLoadMore) viewModel.onEvent(ChatEvent.OnLoadMore)
     }
 
+    LaunchedEffect(Unit) {
+        viewModel.scrollToBottom.collect {
+            listState.animateScrollToItem(0)
+        }
+    }
+
+    val isNearBottom by remember {
+        derivedStateOf { listState.firstVisibleItemIndex <= 3 }
+    }
+
+    LaunchedEffect(uiState.messages.size) {
+        if (isNearBottom) {
+            listState.animateScrollToItem(0)
+        }
+    }
+
     Scaffold(
         topBar = {
             TopAppBar(title = { Text("PicoClaw") })