From b4f3ff626c8f9713dd9eba7810b8935313a5cec6 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Tue, 26 May 2026 05:26:56 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20Prevent=20main=20thread=20b?=
 =?UTF-8?q?locking=20during=20text=20streaming?=
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Implements `useDeferredValue` for rapidly updating text streaming to prevent UI thread blocking while running synchronous text analysis.

Co-authored-by: aloewright <3641844+aloewright@users.noreply.github.com>
---
 .jules/bolt.md                                   |  4 ++++
 apps/quill/client/components/playground-view.tsx | 11 +++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 .jules/bolt.md

diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..519dd032
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,4 @@
+
+## 2024-05-24 - Deferring State for Streaming Text Calculations
+**Learning:** When dealing with rapidly updating text streams (e.g., streaming LLM output character-by-character at intervals of ~24ms), running expensive synchronous computations (like text analysis/scoring) on the active stream value blocks the main UI thread and causes lag/stuttering.
+**Action:** Always use React's `useDeferredValue` to decouple the rapidly updating UI state from the state passed into expensive `useMemo` or synchronous operations. This allows React to prioritize rendering the stream while running the heavy calculations in the background.
diff --git a/apps/quill/client/components/playground-view.tsx b/apps/quill/client/components/playground-view.tsx
index 511226b4..b06a6c22 100644
--- a/apps/quill/client/components/playground-view.tsx
+++ b/apps/quill/client/components/playground-view.tsx
@@ -1,6 +1,6 @@
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { AnimatePresence, motion } from "framer-motion";
-import { useEffect, useMemo, useRef, useState } from "react";
+import { useDeferredValue, useEffect, useMemo, useRef, useState } from "react";
 import { USE_CASE_PRESETS } from "../../src/lib/presets";
 import { analyzeText, scoreDeterministic } from "../../src/lib/rubric";
 import type { Guide, UseCase } from "../../src/lib/types";
@@ -255,7 +255,14 @@ export function PlaygroundView({
     };
   }, [output]);
 
-  const snapshot = useMemo(() => analyzeText(visibleOutput), [visibleOutput]);
+  // Defer the rapidly updating text stream so that expensive analysis doesn't
+  // block the main thread.
+  const deferredVisibleOutput = useDeferredValue(visibleOutput);
+
+  const snapshot = useMemo(
+    () => analyzeText(deferredVisibleOutput),
+    [deferredVisibleOutput]
+  );
   const { score, details } = useMemo(
     () =>
       guide