encode_values() accepted strings containing "\n" or "\r". ezdxf writes
1000-tag values verbatim, so the separator split the tag pair: the saved
DXF failed to reopen (DXFStructureError) and, because every undo and
transaction snapshot is also a DXF save, transaction_rollback broke after
a single such write. Both engines route through encode_values, so the
refusal (ValueError naming values[i]) now happens there, before either
backend touches the document. Only LF and CR split a DXF tag; tabs and
the other Unicode separators round-trip and stay allowed.
Tests: pure encoder refusal for \n, \r, \r\n; other control characters
still typed; ezdxf refuses-then-rollback-and-reopen round trip; COM fake
sees no SetXData / RegisteredApplications call.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
