diff --git a/update.sh b/update.sh
new file mode 100644
index 00000000..30c99f2c
--- /dev/null
+++ b/update.sh
@@ -0,0 +1,156 @@
+#!/bin/bash
+
+set -e
+
+if [ "$#" -ne 2 ]; then
+    echo "Usage: $0 <child_project_path> <last_version_tag>"
+    exit 1
+fi
+
+CHILD_PATH="$1"
+LAST_TAG="$2"
+ROOT_PATH="$(pwd)"
+
+if [ ! -d "$CHILD_PATH" ]; then
+    echo "Child project path does not exist: $CHILD_PATH"
+    exit 1
+fi
+
+# 1. Get changed files
+CHANGED=$(git diff --name-status "$LAST_TAG" HEAD)
+
+# 2. Prepare lists
+ADDED_MODIFIED=()
+DELETED=()
+
+while IFS= read -r line; do
+    STATUS=$(echo "$line" | awk '{print $1}')
+    FILE=$(echo "$line" | awk '{print $2}')
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    if [[ "$STATUS" == "A" || "$STATUS" == "M" ]]; then
+        ADDED_MODIFIED+=("$FILE")
+    elif [[ "$STATUS" == "D" ]]; then
+        DELETED+=("$FILE")
+    fi
+done <<< "$CHANGED"
+
+# 3. Copy new/modified files
+for FILE in "${ADDED_MODIFIED[@]}"; do
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    DEST="$CHILD_PATH/$FILE"
+    mkdir -p "$(dirname "$DEST")"
+    cp "$FILE" "$DEST"
+    echo "Copied $FILE to $DEST"
+done
+
+# 4. Delete removed files
+for FILE in "${DELETED[@]}"; do
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    TARGET="$CHILD_PATH/$FILE"
+    if [ -f "$TARGET" ]; then
+        rm "$TARGET"
+        echo "Deleted $TARGET"
+    fi
+done
+
+# 5. Compare diffs and report
+# Get the latest tag for the 'to' version
+TO_TAG=$(git describe --tags --abbrev=0)
+REPORT_NAME="update_report_${LAST_TAG}_to_${TO_TAG}.txt"
+REPORT="$CHILD_PATH/$REPORT_NAME"
+> "$REPORT"
+
+for FILE in "${ADDED_MODIFIED[@]}"; do
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    if [ -f "$FILE" ] && [ -f "$CHILD_PATH/$FILE" ]; then
+        DIFF_MAIN=$(git diff "$LAST_TAG" HEAD -- "$FILE")
+        pushd "$CHILD_PATH" > /dev/null
+        DIFF_CHILD=$(git diff "$LAST_TAG" HEAD -- "$FILE" 2>/dev/null || true)
+        popd > /dev/null
+        if [ "$DIFF_MAIN" != "$DIFF_CHILD" ]; then
+            echo "$FILE" >> "$REPORT"
+        fi
+    fi
+done
+
+# Compare deleted files
+for FILE in "${DELETED[@]}"; do
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    if [ -f "$CHILD_PATH/$FILE" ]; then
+        git show "$LAST_TAG:$FILE" > /tmp/original_file 2>/dev/null || true
+        if [ -s /tmp/original_file ]; then
+            if ! diff -q /tmp/original_file "$CHILD_PATH/$FILE" > /dev/null; then
+                echo "$FILE" >> "$REPORT"
+            fi
+        else
+            echo "$FILE" >> "$REPORT"
+        fi
+        rm -f /tmp/original_file
+    fi
+done
+
+if [ -s "$REPORT" ]; then
+    echo "Update report created: $REPORT"
+    cat "$REPORT"
+else
+    echo "All files updated and verified. No mismatches found."
+    rm "$REPORT"
+fi
+
+# Update README.md in the child project
+README="$CHILD_PATH/README.md"
+VERSION_LINE="This is based on the core of Athenia version number $TO_TAG"
+if [ -f "$README" ]; then
+    if grep -q "This is based on the core of Athenia version number" "$README"; then
+        sed -i '' "s|This is based on the core of Athenia version number.*|$VERSION_LINE|" "$README"
+    else
+        echo "$VERSION_LINE" >> "$README"
+    fi
+else
+    echo "$VERSION_LINE" > "$README"
+fi
+
+# Git add all updated files not in the report
+pushd "$CHILD_PATH" > /dev/null
+if [ -f "$REPORT_NAME" ]; then
+    mapfile -t REPORTED < "$REPORT_NAME"
+else
+    REPORTED=()
+fi
+
+should_add() {
+    local file="$1"
+    for reported in "${REPORTED[@]}"; do
+        if [[ "$file" == "$reported" ]]; then
+            return 1
+        fi
+    done
+    return 0
+}
+
+for FILE in "${ADDED_MODIFIED[@]}"; do
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    should_add "$FILE" && git add "$FILE"
+done
+
+for FILE in "${DELETED[@]}"; do
+    if [[ "$FILE" == app/Providers/* || "$FILE" == UPGRADE*.md || "$FILE" == "update.sh" ]]; then
+        continue
+    fi
+    if [ ! -f "$FILE" ]; then
+        should_add "$FILE" && git rm --cached "$FILE" 2>/dev/null || true
+    fi
+done
+popd > /dev/null 
\ No newline at end of file