User customizations live at <configRoot>/LIFEOS/USER/CUSTOMIZATIONS/SKILLS/Errata/ (configRoot is $CLAUDE_CONFIG_DIR when set, else ~/.claude). When that directory exists, its PREFERENCES.md, configurations and resources override the defaults here; when it is absent, the defaults stand.
The ledger lives at <configRoot>/LIFEOS/USER/ERRATA/ (override: ERRATA_DIR); attachments at ~/.local/state/lifeos/errata/ (override: ERRATA_STATE_DIR). Schema and store: LIFEOS/ERRATA/Schema.ts, LIFEOS/ERRATA/Store.ts. System doc: LIFEOS/DOCUMENTATION/Errata/ErrataSystem.md.
First-time setup: Setup.md.