From 0381ec7e538ecc5e17e1fae7b722240e3d033ad0 Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Fri, 17 Jul 2026 16:47:42 +0000
Subject: [PATCH] perf(web): avoid visit writes during thread streaming

Co-authored-by: Julius Marminge <juliusmarminge@users.noreply.github.com>
---
 apps/web/src/components/ChatView.tsx          | 27 +++----------------
 .../src/hooks/useMarkActiveThreadVisited.ts   | 17 ++++++++++++
 2 files changed, 21 insertions(+), 23 deletions(-)
 create mode 100644 apps/web/src/hooks/useMarkActiveThreadVisited.ts

diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index f5ea5bb1eba..439475bac90 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -93,7 +93,6 @@ import {
   togglePendingUserInputOptionSelection,
   type PendingUserInputDraftAnswer,
 } from "../pendingUserInput";
-import { useUiStateStore } from "../uiStateStore";
 import {
   buildPlanImplementationThreadTitle,
   buildPlanImplementationPrompt,
@@ -109,6 +108,7 @@ import {
   type Thread,
   type TurnDiffSummary,
 } from "../types";
+import { useMarkActiveThreadVisited } from "../hooks/useMarkActiveThreadVisited";
 import { useTheme } from "../hooks/useTheme";
 import { useTurnDiffSummaries } from "../hooks/useTurnDiffSummaries";
 import { isCommandPaletteOpen } from "../commandPaletteContext";
@@ -1036,9 +1036,9 @@ function ChatViewContent(props: ChatViewProps) {
   const composerDraftTarget: ScopedThreadRef | DraftId =
     routeKind === "server" ? routeThreadRef : props.draftId;
   const serverThread = useThread(routeKind === "server" ? routeThreadRef : null);
-  const markThreadVisited = useUiStateStore((store) => store.markThreadVisited);
-  const activeThreadLastVisitedAt = useUiStateStore((store) =>
-    routeKind === "server" ? store.threadLastVisitedAtById[routeThreadKey] : undefined,
+  useMarkActiveThreadVisited(
+    routeKind === "server" ? routeThreadKey : null,
+    serverThread?.latestTurn?.completedAt ?? null,
   );
   const settings = useEnvironmentSettings(environmentId);
   const setStickyComposerModelSelection = useComposerDraftStore(
@@ -1599,25 +1599,6 @@ function ChatViewContent(props: ChatViewProps) {
     [openOrReuseProjectDraftThread],
   );
 
-  useEffect(() => {
-    if (!serverThread?.id) return;
-    const threadUpdatedAt = Date.parse(serverThread.updatedAt);
-    if (Number.isNaN(threadUpdatedAt)) return;
-    const lastVisitedAt = activeThreadLastVisitedAt ? Date.parse(activeThreadLastVisitedAt) : NaN;
-    if (!Number.isNaN(lastVisitedAt) && lastVisitedAt >= threadUpdatedAt) return;
-
-    markThreadVisited(
-      scopedThreadKey(scopeThreadRef(serverThread.environmentId, serverThread.id)),
-      serverThread.updatedAt,
-    );
-  }, [
-    activeThreadLastVisitedAt,
-    markThreadVisited,
-    serverThread?.environmentId,
-    serverThread?.id,
-    serverThread?.updatedAt,
-  ]);
-
   const selectedProviderByThreadId = composerActiveProvider ?? null;
   const threadProvider =
     activeThread?.modelSelection.instanceId ??
diff --git a/apps/web/src/hooks/useMarkActiveThreadVisited.ts b/apps/web/src/hooks/useMarkActiveThreadVisited.ts
new file mode 100644
index 00000000000..408166c9636
--- /dev/null
+++ b/apps/web/src/hooks/useMarkActiveThreadVisited.ts
@@ -0,0 +1,17 @@
+import { useEffect } from "react";
+
+import { useUiStateStore } from "../uiStateStore";
+
+export function useMarkActiveThreadVisited(
+  threadKey: string | null,
+  latestTurnCompletedAt: string | null,
+): void {
+  const markThreadVisited = useUiStateStore((store) => store.markThreadVisited);
+
+  useEffect(() => {
+    if (threadKey === null || latestTurnCompletedAt === null) {
+      return;
+    }
+    markThreadVisited(threadKey, latestTurnCompletedAt);
+  }, [latestTurnCompletedAt, markThreadVisited, threadKey]);
+}