Headless text_find_replace matched and wrote only dxf.text of an ATTRIB/ATTDEF, so on a multi-line attribute it reported replaced: 1 while block_get_attributes and block_explode still carried the old embedded MTEXT (and a needle on the second line was never found). The ATTRIB/ATTDEF branch now reads through _attrib_value and writes through _write_attrib_value, the same pair block_get_attributes / block_set_attributes use.
COM block_explode swallowed a failing GetAttributes() (attrs = ()), GetConstantAttributes() and Invisible, then exploded, deleted every ATTDEF placeholder and the reference and returned ok: True with no attribute text -- every value destroyed silently on a transient RPC_E_CALL_REJECTED. Those reads now happen before Explode() and propagate with nothing written; a failure after the explode deletes the members it added and the TEXTs written so far and leaves the reference in place (_undo_explode), so the drawing is never left half-burst under an exception. The fakes gain the members a live AcadBlockReference / AcadAttributeDefinition always expose (GetConstantAttributes, Constant, Invisible) instead of relying on the swallow.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
