Capability-Gated Model Fallback

Fable 5's safeguard architecture: classifiers detect cyber / bio-chem / distillation queries and route the response to a less-capable model (Opus 4.8) instead of refusing — 'fallback, not refusal'; >95% of sessions never trigger; conservative tuning, robust to 1,000+ hours of jailbreak testing; a new point on the safeguard spectrum for capabilities past a risk threshold