refactor: replace focusedIndex with activeChildId

- Replace focusedIndex integer with activeChildId string in messages schema
- Add migration to convert existing data and drop focused_index column
- Add  hooks for providers.updatedAt and messageParts.lastUpdatedAt
- Add file size column to files table
- Update message navigation to use child ID-based lookup
- Simplify delete logic by removing focusedIndex math
- Fix file delete endpoint filename ([id[ -> [id])

app/pages/agent/[id]/index.vue

@@ -30,7 +30,6 @@ const handleSubmit = async (message: BaseMessage, model: ModelWithProvider | nul
     }
 
     console.log("handleSubmit", message);
-    if (!message.content) return;
 
     pendingMessage.value = {
         id: '',
@@ -43,7 +42,7 @@ const handleSubmit = async (message: BaseMessage, model: ModelWithProvider | nul
         parentMessageId: null,
         children: [],
         generationId: null,
-        focusedIndex: null,
+        activeChildId: null,
         attachments: [],
         deleted: false,
         createdAt: new Date(),

app/pages/agent/[id]/topic/[topicId].vue

@@ -16,7 +16,7 @@ const { addShortcut } = useKeyboardShortcuts();
 const agent = getAgent(route.params.id as string);
 
 const topicId = computed(() => route.params.topicId as string);
-const { topic, sendMessage, startGeneration, regenerateMessage, patchMessageLocally } = await useChat(topicId);
+const { topic, sendMessage, startGeneration, regenerateMessage, patchMessageLocally, deleteMessagesFocusedDescendant } = await useChat(topicId);
 
 watch(() => topic.value?.name, (newTopicName) => {
     if (newTopicName !== undefined) {
@@ -61,12 +61,8 @@ const handleRegenerate = async (message: Message) => {
     }
 
     let messageId: string;
-    if (
-        (message.focusedIndex !== undefined && message.focusedIndex !== null)
-        && message.focusedIndex > 0
-        && message.children.length > 0
-    ) {
-        messageId = message.children[message.focusedIndex - 1]!.id;
+    if (message.activeChildId && message.children.length > 0) {
+        messageId = message.activeChildId;
     } else {
         messageId = message.id;
     }
@@ -98,9 +94,18 @@ const flatMessages = computed(() => {
 });
 
 const handleDelete = async (rootMessage: Message) => {
-    await $fetch(`/api/messages/${rootMessage.id}`, {
-        method: 'DELETE',
-    });
+    let messageId: string;
+    if (rootMessage.activeChildId && rootMessage.children.length > 0) {
+        messageId = rootMessage.activeChildId;
+    } else {
+        messageId = rootMessage.id;
+    }
+
+    const result = await deleteMessagesFocusedDescendant(messageId);
+    if (!result.ok) {
+        console.error('Failed to delete message:', result.error);
+        return;
+    }
 
     if (flatMessages.value.length === 0) {
         await navigateTo(`/agent/${route.params.id}`);
@@ -108,6 +113,20 @@ const handleDelete = async (rootMessage: Message) => {
     }
 }
 
+const handleResize = () => {
+    const el = chatPaneWrapper.value;
+    if (!el) return;
+
+    const atBottom = (el.scrollHeight - el.scrollTop - el.clientHeight) <= 80;
+    if (!atBottom) return;
+
+    nextTick().then(() => {
+        requestAnimationFrame(() => {
+            scrollToBottom('instant');
+        });
+    });
+}
+
 const activeGeneration = computed(() => {
     if (topic.value === null) return null;
     const generations = flatMessages.value.flatMap(message => message.generation);
@@ -155,8 +174,11 @@ addShortcut(['alt', '['], async (event) => {
 
     const lastMessage = topic.value?.messages?.at(-1);
     if (lastMessage && lastMessage.children.length > 0) {
-        const newIndex = Math.max(0, (lastMessage.focusedIndex || 0) - 1);
-        patchMessageLocally(lastMessage.id, { focusedIndex: newIndex });
+        const currentIdx = lastMessage.children.findIndex(c => c?.id === lastMessage.activeChildId);
+        const prevIdx = Math.max(0, currentIdx);
+        if (currentIdx > 0) {
+            patchMessageLocally(lastMessage.id, { activeChildId: lastMessage.children[prevIdx - 1]!.id });
+        }
     }
 })
 
@@ -165,10 +187,20 @@ addShortcut(['alt', ']'], async (event) => {
     event.stopPropagation();
 
     const lastMessage = topic.value?.messages?.at(-1);
-    const messageCount = lastMessage ? (lastMessage.deleted ? lastMessage.children.length : lastMessage.children.length + 1) : 0;
     if (lastMessage && lastMessage.children.length > 0) {
-        const newIndex = Math.min(messageCount - 1, (lastMessage.focusedIndex || 0) + 1);
-        patchMessageLocally(lastMessage.id, { focusedIndex: newIndex });
+        const currentIdx = lastMessage.children.findIndex(c => c?.id === lastMessage.activeChildId);
+        const maxIdx = lastMessage.deleted ? lastMessage.children.length - 1 : lastMessage.children.length;
+        const nextIdx = Math.min(maxIdx, currentIdx + 1);
+
+        if (lastMessage.deleted) {
+            patchMessageLocally(lastMessage.id, { activeChildId: lastMessage.children[nextIdx]?.id ?? null });
+        } else {
+            if (nextIdx === 0) {
+                patchMessageLocally(lastMessage.id, { activeChildId: null });
+            } else {
+                patchMessageLocally(lastMessage.id, { activeChildId: lastMessage.children[nextIdx - 1]?.id ?? null });
+            }
+        }
     }
 })
 
@@ -178,20 +210,32 @@ addShortcut(['ctrl', 'alt', 'arrowleft'], async (event) => {
         event.preventDefault();
         event.stopPropagation();
 
-        const newIndex = Math.max(0, (lastMessage.focusedIndex || 0) - 1);
-        patchMessageLocally(lastMessage.id, { focusedIndex: newIndex });
+        const currentIdx = lastMessage.children.findIndex(c => c?.id === lastMessage.activeChildId);
+        if (currentIdx > 0) {
+            patchMessageLocally(lastMessage.id, { activeChildId: lastMessage.children[currentIdx - 1]!.id });
+        }
     }
 })
 
 addShortcut(['ctrl', 'alt', 'arrowright'], async (event) => {
     const lastMessage = topic.value?.messages?.at(-1);
-    const messageCount = lastMessage ? (lastMessage.deleted ? lastMessage.children.length : lastMessage.children.length + 1) : 0;
     if (lastMessage && lastMessage.children.length > 0) {
         event.preventDefault();
         event.stopPropagation();
 
-        const newIndex = Math.min(messageCount - 1, (lastMessage.focusedIndex || 0) + 1);
-        patchMessageLocally(lastMessage.id, { focusedIndex: newIndex });
+        const currentIdx = lastMessage.children.findIndex(c => c?.id === lastMessage.activeChildId);
+        const maxIdx = lastMessage.deleted ? lastMessage.children.length - 1 : lastMessage.children.length;
+        const nextIdx = Math.min(maxIdx, currentIdx + 1);
+
+        if (lastMessage.deleted) {
+            patchMessageLocally(lastMessage.id, { activeChildId: lastMessage.children[nextIdx]?.id ?? null });
+        } else {
+            if (nextIdx === 0) {
+                patchMessageLocally(lastMessage.id, { activeChildId: null });
+            } else {
+                patchMessageLocally(lastMessage.id, { activeChildId: lastMessage.children[nextIdx - 1]?.id ?? null });
+            }
+        }
     }
 })
 
@@ -249,7 +293,8 @@ console.log("full page render took", Date.now() - rootStart);
                 <div class="sticky bottom-0 z-10 bg-[var(--bg-surface)] pb-4 w-full rounded-t-2xl">
                     <ChatInput v-model="inputValue" class="[view-transition-name:chat-prompt] duration-150 ease-in-out"
                         :loading="activeGeneration !== null" :agent="agent"
-                        :providers="providers?.filter(p => p.enabled)" @submit="submitMessage" @cancel="handleCancel" />
+                        :providers="providers?.filter(p => p.enabled)" @submit="submitMessage" @cancel="handleCancel"
+                        @resize="handleResize" />
                 </div>
             </div>
         </div>