diff --git a/audio_splitter/filename.py b/audio_splitter/filename.py
index 741be7b..dba71d6 100644
--- a/audio_splitter/filename.py
+++ b/audio_splitter/filename.py
@@ -41,7 +41,18 @@ def build_filename(track, idx, extension, args):
         clean_filename = apply_replacement(raw_filename,
                                            args.bad_chars,
                                            args.replacement_char)
-        clean_filename = cleanup_good_chars(clean_filename, args.replacement_char)
+        # Split off the file extension before cleanup so trailing
+        # replacement chars don't leak into the name portion.
+        name_part, _, ext_part = clean_filename.rpartition('.')
+        clean_filename = cleanup_good_chars(name_part, args.replacement_char)
+        # Strip leading/trailing separator characters (replacement char,
+        # hyphen, etc.) that may result from empty fields or bad-char
+        # sequences adjacent to template separators.
+        clean_filename = clean_filename.strip(f'{args.replacement_char}-')
+        # Fallback: if cleanup leaves an empty name, use the track number.
+        if not clean_filename:
+            clean_filename = f"{idx:02d}"
+        clean_filename = f"{clean_filename}.{ext_part}"
     else:
         clean_filename = raw_filename
         # Warn about unsafe characters.