perf(chat): release completed streaming parser history (#553)

- Keep only the active assistant response in streaming Markdown mode.\n- Remount completed responses in static mode to release incremental AST caches.\n- Preserve final Markdown, code rendering, and theme behavior.

CHANGELOG.md

@@ -51,6 +51,7 @@
 
 ### Performance
 
+- Release obsolete streamed Markdown parser history after each AI response completes, preventing chat memory from multiplying with every streamed chunk. (#544)
 - Use cached axis-aligned world positions for hit testing untransformed layer chains and add representative 500/2,000-node interaction profiles. (#527)
 - Coalesce writable-document autosaves that overlap an active `.fig` export while preserving a trailing save for newer edits. (#528)
 - Defer JSX generation and syntax highlighting until the Code panel is active, keeping large canvas selections responsive. (#500)

src/components/ChatPanel.vue

@@ -73,6 +73,13 @@ const failureMessage = computed(() => {
   }
 })
 const status = computed(() => chat.value?.status ?? 'ready')
+function isStreamingMessage(message: UIMessage, index: number): boolean {
+  return (
+    message.role === 'assistant' &&
+    index === messages.value.length - 1 &&
+    (status.value === 'submitted' || status.value === 'streaming')
+  )
+}
 const isThinking = computed(() => {
   const s = status.value
   if (s !== 'submitted' && s !== 'streaming') return false
@@ -254,7 +261,12 @@ function handleClearChat() {
 
           <!-- Messages -->
           <div v-else data-test-id="chat-messages" class="flex flex-col gap-3">
-            <ChatMessage v-for="msg in messages" :key="msg.id" :message="msg" />
+            <ChatMessage
+              v-for="(msg, index) in messages"
+              :key="msg.id"
+              :message="msg"
+              :streaming="isStreamingMessage(msg, index)"
+            />
 
             <!-- Thinking indicator: shown when AI is working but no visible activity -->
             <div v-if="isThinking" data-test-id="chat-typing-indicator" class="flex gap-2">

src/components/chat/ChatMessage.vue

@@ -15,9 +15,13 @@ import ImageAttachment from '@/components/chat/attachment/image/ImageAttachment.
 
 import type { UIDataTypes, UIMessage, UIMessagePart, UITools } from 'ai'
 
-const { message } = defineProps<{ message: UIMessage }>()
+const { message, streaming = false } = defineProps<{
+  message: UIMessage
+  streaming?: boolean
+}>()
 const { dialogs } = useI18n()
 const isDark = computed(() => resolvedAppTheme.value === 'dark')
+const markdownMode = computed(() => (streaming ? 'streaming' : 'static'))
 const imageAttachments = imageAttachmentsForMessage(message.id)
 
 type ToolPart = Extract<UIMessagePart<UIDataTypes, UITools>, { toolCallId: string }>
@@ -121,9 +125,12 @@ function partKey(part: UIMessagePart<UIDataTypes, UITools>, index: number): stri
             class="rounded-xl rounded-tl-md bg-hover px-3 py-2 text-xs leading-relaxed text-surface"
           >
             <Markdown
+              :key="markdownMode"
               :content="part.text"
               :is-dark="isDark"
               :mermaid="false"
+              :mode="markdownMode"
+              :data-chat-markdown-mode="markdownMode"
               class="chat-markdown [&_[data-stream-markdown=code]]:!bg-input"
             />
           </div>

tests/e2e/chat/panel.spec.ts

@@ -261,6 +261,16 @@ test('assistant responds', async () => {
   }
 })
 
+test('completed Markdown responses release streaming parser history', async () => {
+  await chatInput().fill('Show a code block')
+  await chatInput().press('Enter')
+
+  const markdown = page.locator('.chat-markdown').last()
+  await expect(markdown).toBeVisible()
+  await expect(markdown).toHaveAttribute('data-chat-markdown-mode', 'static')
+  await expect(markdown.locator('.shiki').first()).toBeVisible()
+})
+
 test('assistant code blocks follow the active theme with readable contrast', async () => {
   await chatInput().fill('Show a code block')
   await chatInput().press('Enter')