What is fault tolerance personal systems?

Fault tolerance personal systems is a concept in personal epistemology: A reliable agent works every time, not just when conditions are perfect.

Example: You built an agent that triggers a weekly review every Sunday morning. It works when you're home, rested, and have nothing planned. But on travel weekends, holidays, or after a bad night's sleep, the agent fails silently — you skip it without noticing. You don't have a reliability problem with the review itself. You have a reliability problem with the trigger-to-execution chain: the agent only fires under ideal conditions. Reliability optimization means redesigning the agent so it fires in degraded conditions too — a shorter version for travel, a voice-memo fallback for low energy, a Tuesday recovery protocol when Sunday breaks.

This concept is part of Phase 29 (Agent Optimization) in the How to Think curriculum, which builds the epistemic infrastructure for agent optimization.