diff --git a/.jules/bolt.md b/.jules/bolt.md
new file mode 100644
index 00000000..12a04e18
--- /dev/null
+++ b/.jules/bolt.md
@@ -0,0 +1,3 @@
+## 2026-06-25 - Content Hashing Optimization
+**Learning:** The default SHA-256 generation using `String.format("%02x", b)` in a loop is surprisingly slow for processing byte streams.
+**Action:** Use `java.util.HexFormat.of().formatHex(raw)` which is significantly faster and more memory efficient for converting bytes to hex string representations.
diff --git a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
index 9c595937..3cd4597b 100644
--- a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
+++ b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
@@ -121,12 +121,7 @@ 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();
+            return java.util.HexFormat.of().formatHex(raw);
         } catch (NoSuchAlgorithmException ex) {
             throw new IllegalStateException("SHA-256 digest unavailable", ex);
         } catch (IOException ex) {