- Never write to legacy/ — read-only, no exceptions
- Never write to docs/templates/ — read-only, use as reference only
- Only write to the active phase directory defined in CLAUDE.md "Aktiver Scope"
- docs/B_planning/decisions-log.md is always writable (append-only, never edit existing entries)
- Before any file write: verify target path is within allowed scope
- CLAUDE.md is only modified during phase transitions
- Never delete or rename existing discovery documents or decision entries