- Ratchet state: atomic write via tmp + rename to prevent corruption on crash - Block header decode: replaced .unwrap() with proper error handling on untrusted network data (was a crash vector from malicious peers) - Shutdown channel: replaced .unwrap() with .ok_or_else() error propagation - Dead man's switch GPS: default changed to opt-out (auto_include_gps=false) - Alert signature verification: already covered by Phase 4 envelope checks Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>