Revert "perf(chat): cap mobile memory with content-visibility on messages (#2391)"

This reverts commit 0bca81a.

Author: gary149

src/lib/actions/snapScrollToBottom.ts

@@ -96,27 +96,6 @@ export const snapScrollToBottom = (node: HTMLElement, dependency: MaybeScrollDep
 		}
 	};
 
-	const nextFrame = () =>
-		new Promise<void>((resolve) => {
-			if (typeof requestAnimationFrame === "function") requestAnimationFrame(() => resolve());
-			else resolve();
-		});
-
-	// content-visibility:auto messages start at their contain-intrinsic-size
-	// estimate, so a single scrollToBottom can land short of the true bottom: as
-	// the bottom messages scroll into view they render at full height and grow
-	// scrollHeight. Re-scroll across a few frames to converge, stopping early once
-	// we reach the bottom or the user takes over. Bounded so it can never loop
-	// indefinitely.
-	const scrollToBottomConverged = async (behavior: ScrollBehavior = "instant") => {
-		scrollToBottom(behavior);
-		for (let i = 0; i < 5; i++) {
-			await nextFrame();
-			if (isDetached || userScrolling || isAtBottom()) return;
-			scrollToBottom("instant");
-		}
-	};
-
 	const scheduleUserScrollEndCheck = () => {
 		userScrolling = true;
 		clearUserScrollTimeout();
@@ -197,16 +176,7 @@ export const snapScrollToBottom = (node: HTMLElement, dependency: MaybeScrollDep
 			clearUserScrollTimeout();
 
 			await tick();
-			const behavior = getScrollBehavior(newDependency);
-			// Conversation switch/load uses "instant" and renders content-visibility
-			// messages from their size estimate; converge to the real bottom. The
-			// "smooth" path (new user message) is handled by ChatWindow's spacer
-			// observer, so keep its single smooth scroll.
-			if (behavior === "instant") {
-				await scrollToBottomConverged(behavior);
-			} else {
-				scrollToBottom(behavior);
-			}
+			scrollToBottom(getScrollBehavior(newDependency));
 			return true;
 		}
 
@@ -314,7 +284,7 @@ export const snapScrollToBottom = (node: HTMLElement, dependency: MaybeScrollDep
 	if (dependency) {
 		void (async () => {
 			await tick();
-			await scrollToBottomConverged();
+			scrollToBottom();
 		})();
 	}
 

src/lib/components/chat/ChatMessage.svelte

@@ -374,7 +374,7 @@
 {#if message.from === "assistant"}
 	<div
 		bind:offsetWidth={messageWidth}
-		class="message-cv group relative -mb-4 flex w-fit max-w-full items-start justify-start gap-4 pb-4 leading-relaxed max-sm:mb-1 {message.routerMetadata &&
+		class="group relative -mb-4 flex w-fit max-w-full items-start justify-start gap-4 pb-4 leading-relaxed max-sm:mb-1 {message.routerMetadata &&
 		messageInfoWidth >= messageWidth
 			? 'mb-1'
 			: ''}"
@@ -552,7 +552,7 @@
 {/if}
 {#if message.from === "user"}
 	<div
-		class="message-cv group relative {alternatives.length > 1 && editMsdgId === null
+		class="group relative {alternatives.length > 1 && editMsdgId === null
 			? 'mb-7'
 			: ''} w-full items-start justify-start gap-4"
 		data-message-id={message.id}
@@ -686,25 +686,6 @@
 {/if}
 
 <style>
-	/* Long conversations render every message at once (no virtualization). On
-	   mobile WebKit each tab's renderer has a hard ~2 GB memory ceiling, and a
-	   few hundred messages worth of laid-out DOM + paint backing stores blows
-	   past it, so iOS Safari jetsam-kills the tab ("A problem repeatedly
-	   occurred"). content-visibility:auto lets the engine skip layout and paint
-	   for off-screen messages, keeping peak memory bounded. contain-intrinsic-size
-	   gives skipped messages a stable placeholder height so the scrollbar and
-	   scroll position stay sensible. content-visibility implies paint containment,
-	   which would clip the copy/retry/edit controls that sit just below each
-	   message (they overflow by up to ~44px); overflow-clip-margin extends the
-	   clip region so those controls keep painting. Browsers without
-	   content-visibility support simply ignore these rules (progressive
-	   enhancement). */
-	.message-cv {
-		content-visibility: auto;
-		contain-intrinsic-size: auto 200px;
-		overflow-clip-margin: 3rem;
-	}
-
 	@keyframes loading {
 		to {
 			stroke-dashoffset: 122.9;