diff --git a/b2/_internal/_cli/autocomplete_cache.py b/b2/_internal/_cli/autocomplete_cache.py
index bf18c475f..a398eefe9 100644
--- a/b2/_internal/_cli/autocomplete_cache.py
+++ b/b2/_internal/_cli/autocomplete_cache.py
@@ -122,6 +122,11 @@ def autocomplete_from_cache(
             return
 
     def _clean_parser(self, parser: argparse.ArgumentParser) -> None:
+        # Python 3.14 caches a validation formatter on parsers. The cached formatter can
+        # contain non-picklable color helpers (local lambdas), so drop it before pickling.
+        if hasattr(parser, '_cached_formatter'):
+            parser._cached_formatter = None
+
         parser.register('type', None, identity)
 
         def _get_deprecated_actions(actions):
diff --git a/changelog.d/+autocomplete-cache-py314.fixed.md b/changelog.d/+autocomplete-cache-py314.fixed.md
new file mode 100644
index 000000000..599e8b6a5
--- /dev/null
+++ b/changelog.d/+autocomplete-cache-py314.fixed.md
@@ -0,0 +1 @@
+Fixed autocomplete parser cache on Python 3.14.2+ by clearing argparse's cached validation formatter before pickling the parser. This avoids failures caused by non-picklable color formatting lambdas stored in the cached formatter.