diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..67cddb2
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-05-27 - UI Blocking During Text Streaming
+**Learning:** During simulated text generation loops (like `setInterval` firing every 24ms), synchronous deterministic scoring and analysis functions that depend on the rapidly updating text state can bottleneck the main thread, leading to jittery render loops or missed frames.
+**Action:** Use React's `useDeferredValue` for rapidly updating text state before passing it into complex computations (like `analyzeText` or `scoreDeterministic` in `useMemo`). This allows React to process the updates asynchronously and interruptibly, maintaining UI responsiveness during simulated text streaming.
diff --git a/apps/quill/client/components/playground-view.tsx b/apps/quill/client/components/playground-view.tsx
index 511226b..1dc4700 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 +255,11 @@ export function PlaygroundView({
     };
   }, [output]);
 
-  const snapshot = useMemo(() => analyzeText(visibleOutput), [visibleOutput]);
+  // Defer the expensive analyzeText and scoreDeterministic calculations to a lower
+  // priority render cycle. This prevents them from blocking the main UI thread during
+  // rapid state updates like text streaming (which happens every 24ms).
+  const deferredOutput = useDeferredValue(visibleOutput);
+  const snapshot = useMemo(() => analyzeText(deferredOutput), [deferredOutput]);
   const { score, details } = useMemo(
     () =>
       guide