ui: reduce per-token render cost when streaming (#26053)

* performance harness - the empirical root Assisted-by: Claude Opus 4.8 * 210.36ms -> 2.67ms per streamed token Assisted-by: Claude Opus 4.8 * 11.58ms -> 0.62ms per streamed token Assisted-by: Claude Opus 4.8 * 22.02ms -> 3.33ms per streamed token Assisted-by: Claude Opus 4.8 * 3.07ms -> 1.36ms per streamed token at 40 messages Assisted-by: Claude Opus 4.8 --------- Co-authored-by: Zach Winter <dmtommy@icloud.com>
2026-07-24 22:09:46 +02:00
parent 96013c5112
commit 555881ebc8
18 changed files with 1037 additions and 35 deletions
@@ -90,8 +90,12 @@
 	</Collapsible.Trigger>

 	<Collapsible.Content>
-		<div class="p-3 pt-1">
-			{@render children()}
-		</div>
+		<!-- See CollapsibleContentBlock: bits-ui keeps closed content mounted, which
+		     makes a collapsed tool result re-render on every streamed token. -->
+		{#if open}
+			<div class="p-3 pt-1">
+				{@render children()}
+			</div>
+		{/if}
 	</Collapsible.Content>
 </Collapsible.Root>