Claude Fable 5 briefly put a Mythos-class model in everyone's hands

Anthropic shipped Claude Fable 5 on June 9 — the first Mythos-class model to go generally available before the access suspension noted above. The Mythos Preview and Glasswing entries further down this chapter were the gated version of this capability; Fable 5 is the public release. It and Claude Mythos 5 are the same underlying model — the split is safety, not power. Fable 5 ships with classifiers that route cybersecurity, biology/chemistry, and model-distillation prompts to Opus 4.8 instead of answering them directly, while Mythos 5 has those safeguards lifted and stays restricted to vetted Project Glasswing partners and the US government. The classifiers are tuned conservatively — they trigger in under 5% of sessions and will sometimes catch harmless requests.

The benchmarks are a clear step over the current reasoning tier. SWE-Bench Pro hits 80.3%, up from Opus 4.8's 69.2% and well past GPT-5.5's 58.6%. USAMO 2026 lands at 97.6%, and GDPval-AA reaches 1932 against Opus 4.8's 1890 and GPT-5.5's 1769. The one that closes a standing gap: Terminal-Bench 2.0 at 82.0% — essentially level with GPT-5.5's 82.7% on the same benchmark, erasing the long autonomous-loop advantage that's defined the Opus-vs-GPT split all spring. It's also the first model past 90% on Hex's analytical benchmark, and it scored 91 on Every's senior-engineer eval.

Pricing is $10 / $50 per million tokens — double Opus 4.8, but less than half what Mythos Preview cost — with a 90% prompt-caching discount and the same 1M-input / 128K-output context window as the Opus line. At launch, it was live on the Claude API (claude-fable-5), Claude Code, Amazon Bedrock, Google Cloud Vertex AI, and Microsoft Foundry, with GitHub Copilot and Harvey supporting it from day one. Pro, Max, Team, and seat-based Enterprise plans received free launch-period access through June 22.

Practical read: this is the entry the Mythos Preview and Glasswing sections below were pointing at — the capability that shipped to defenders first is now on the public API, minus the offensive-security edge. With broad access restored, it is the new top of the stack for everyday reasoning and agentic coding, and the Terminal-Bench parity is the quietly important bit: you no longer pay a long-loop penalty for staying on the reasoning tier, so one model covers both review-grade reasoning and hour-long shell runs instead of switching between Opus and GPT-5.5 by workload. The asterisk is cost — at 2× Opus 4.8 you'll want Fable on the hard tasks and a cheaper tier on the rest. And the launch timing — a more-powerful public model days after Anthropic warned that AI is getting too dangerous to ship unguarded — is the whole story of the safety split in a single release. Worth watching how often that sub-5% classifier rate trips on legitimate security work.