diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..14deda2
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-24 - [Defer Expensive Synchronous Work During Fake Streaming]
+**Learning:** Fake text streaming with `setInterval` at rapid intervals (e.g. 24ms) can severely block the main thread if expensive synchronous computations (like text analysis/scoring) depend directly on the streaming state.
+**Action:** Always wrap rapidly changing state in `useDeferredValue` before feeding it into expensive `useMemo` hooks to keep the UI thread unblocked.
diff --git a/apps/quill/client/components/playground-view.tsx b/apps/quill/client/components/playground-view.tsx
index 511226b..cd8a787 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 +255,12 @@ export function PlaygroundView({
     };
   }, [output]);
 
-  const snapshot = useMemo(() => analyzeText(visibleOutput), [visibleOutput]);
+  const deferredVisibleOutput = useDeferredValue(visibleOutput);
+
+  const snapshot = useMemo(
+    () => analyzeText(deferredVisibleOutput),
+    [deferredVisibleOutput]
+  );
   const { score, details } = useMemo(
     () =>
       guide