diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 0000000..fdc927f
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2024-06-27 - HexFormat Optimization
+**Learning:** Using `String.format("%02x", b)` in a loop for byte to hex conversion creates significant overhead due to excessive object allocations and parsing.
+**Action:** Always prefer `java.util.HexFormat.of().formatHex(raw)` introduced in Java 17 for byte array to hex string conversions, as it is highly optimized and avoids unnecessary object creation.
diff --git a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
index 9c59593..9dd4b0d 100644
--- a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
+++ b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
@@ -121,12 +121,10 @@ private String contentHash(MultipartFile file) {
             }
 
             byte[] raw = digest.digest();
-            StringBuilder hex = new StringBuilder(raw.length * 2);
-            for (byte b : raw) {
-                hex.append(String.format("%02x", b));
-            }
-
-            return hex.toString();
+            // ⚡ Bolt Optimization: Use java.util.HexFormat instead of
+            // String.format in loop to eliminate excessive object allocation
+            // overhead and significantly speed up hex string conversion.
+            return java.util.HexFormat.of().formatHex(raw);
         } catch (NoSuchAlgorithmException ex) {
             throw new IllegalStateException("SHA-256 digest unavailable", ex);
         } catch (IOException ex) {