diff --git a/.github/workflows/jar-and-R-ci.yaml b/.github/workflows/jar-and-R-ci.yaml
index 66283c20..5c3235ed 100644
--- a/.github/workflows/jar-and-R-ci.yaml
+++ b/.github/workflows/jar-and-R-ci.yaml
@@ -57,12 +57,29 @@ jobs:
       - name: Create pull request
         # https://github.com/actions/checkout/pull/1184
         run: |
-          git config user.name "github-actions[bot]"
-          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
-          mv java-r5rcore/build/libs/java-r5rcore-*.jar r-package/inst/jar/r5r.jar
-          git add r-package/inst/jar/r5r.jar
-          git commit -m "Rebuild JAR for commit ${GITHUB_SHA}"
-          git push
+          NEW_JAR="java-r5rcore/build/libs/java-r5rcore-*.jar"
+          TARGET_JAR="r-package/inst/jar/r5r.jar"
+        
+          new_sha=$(sha256sum $NEW_JAR | awk '{print $1}')
+          # ensure file exists and then compute sha
+          old_sha=$( [ -f "$TARGET_JAR" ] && sha256sum "$TARGET_JAR" | awk '{print $1}' || echo "" )
+          
+          echo "NEW: $new_sha"
+          echo "OLD: $old_sha"
+          
+          # Only push if sha different
+          if [ "$new_sha" != "$old_sha" ]; then
+            git config user.name "github-actions[bot]"
+            git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+        
+            echo "JAR changed — updating."
+            mv $NEW_JAR $TARGET_JAR
+            git add $TARGET_JAR
+            git commit -m "Rebuild JAR for commit ${GITHUB_SHA}"
+            git push
+          else
+            echo "JAR unchanged — skipping commit."
+          fi
 
   R-CMD-check:
     needs: build-jar
diff --git a/java-r5rcore/build.gradle b/java-r5rcore/build.gradle
index 8a749364..aa6051c9 100644
--- a/java-r5rcore/build.gradle
+++ b/java-r5rcore/build.gradle
@@ -2,6 +2,11 @@ plugins {
     id 'java'
 }
 
+tasks.withType(Jar).configureEach {
+    preserveFileTimestamps = false
+    reproducibleFileOrder = true
+}
+
 group 'org.ipea'
 version '1.1.0999-SNAPSHOT'
 
diff --git a/r-package/inst/jar/r5r.jar b/r-package/inst/jar/r5r.jar
index 407f6efb..b10e5058 100644
Binary files a/r-package/inst/jar/r5r.jar and b/r-package/inst/jar/r5r.jar differ