Removing wallet encryption z_exportwallet'd every private key in cleartext to
<datadir>/obsidiandecryptexport<ts>, re-imported it, and never deleted it — leaving a
full plaintext dump of every key on disk permanently. The decrypt flow now scrubs
(best-effort in-place zero-overwrite) and removes that file as soon as the
z_importwallet attempt resolves, on both the success and failure paths. Recovery, if
ever needed, remains the encrypted backup (wallet.dat.encrypted.bak), never this file.
Second fix in the wallet-hardening P0-A cluster (docs/wallet-hardening.md). Not
unit-testable (fs I/O in a deep worker lambda); build-clean, ctest 1/1.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>