2026.7.1

Fixes

• COPY of large multipart-encrypted objects failed with InvalidTag (#104). _iter_multipart_plaintext decrypted each whole client part as a single AES-GCM seal, but a client part expands into multiple internal parts, each a sequence of independent frames. Any source whose parts held more than one frame (internal parts >8MB, e.g. ScyllaDB backups) failed to copy. The reader now walks internal parts → frames and decrypts one frame at a time, matching the GET path. Also bounds copy source-read peak memory to O(frame).