diff --git a/backend/tools/xml_diagnostics.py b/backend/tools/xml_diagnostics.py
new file mode 100644
index 000000000..57b366588
--- /dev/null
+++ b/backend/tools/xml_diagnostics.py
@@ -0,0 +1,84 @@
+import sys
+from xml.sax.handler import ContentHandler  # nosec
+
+from defusedxml import ElementTree as ET
+from defusedxml.sax import make_parser
+
+
+class DiagnosticHandler(ContentHandler):
+    def __init__(self):
+        super().__init__()
+        self.line_number = 0
+        self.column_number = 0
+
+    def setDocumentLocator(self, locator):
+        self.locator = locator
+
+    def characters(self, content):
+        # Check for invalid XML characters
+        for char in content:
+            if ord(char) >= 0xFFFE or (ord(char) <= 0x1F and char not in "\n\r\t"):
+                print(
+                    f"Found invalid character '0x{ord(char):04x}' at line {self.locator.getLineNumber()}, column {self.locator.getColumnNumber()}"
+                )
+
+
+def diagnose_xml(filename):
+    print(f"Analyzing {filename}...")
+
+    # First, try to read the file in chunks to find encoding issues
+    try:
+        with open(filename, "rb") as f:
+            chunk_size = 8192
+            chunk_number = 0
+            while True:
+                chunk = f.read(chunk_size)
+                if not chunk:
+                    break
+                try:
+                    chunk.decode("utf-8")
+                except UnicodeDecodeError as e:
+                    byte_pos = chunk_number * chunk_size + e.start
+                    print(f"Found invalid UTF-8 sequence at byte position {byte_pos}")
+                    print(f"Problematic bytes: {chunk[e.start:e.end].decode('utf-8')}")
+                chunk_number += 1
+    except Exception as e:
+        print(f"Error reading file: {e}")
+        return
+
+    # Then try SAX parsing for detailed error reporting
+    parser = make_parser()
+    handler = DiagnosticHandler()
+    parser.setContentHandler(handler)
+
+    try:
+        parser.parse(filename)
+    except Exception as e:
+        print(f"SAX parsing error: {e}")
+
+    # Finally try ElementTree parsing
+    try:
+        ET.parse(filename)
+    except ET.ParseError as e:
+        print(f"ElementTree parsing error: {e}")
+
+        # Try to get context around the error
+        try:
+            with open(filename, "r", encoding="utf-8") as f:
+                lines = f.readlines()
+                line_num = e.position[0]
+                start = max(0, line_num - 2)
+                end = min(len(lines), line_num + 3)
+                print("\nContext around error:")
+                for i in range(start, end):
+                    prefix = "-> " if i + 1 == line_num else "   "
+                    print(f"{prefix}{i+1}: {lines[i].rstrip()}")
+        except Exception as context_error:
+            print(f"Could not get context: {context_error}")
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        print("Usage: python script.py <xml_file>")
+        sys.exit(1)
+    diagnose_xml(sys.argv[1])