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Claude Fable 5 — Anthropic's first Mythos-class model goes public
Anthropic launched Claude Fable 5 on June 9, 2026 — the first Mythos-class model made safe for general public use. Priced at $10/$50 per million tokens, it outperforms Opus 4.8 by 10%+ on benchmarks, features a 1M-token context window, and comes with safety classifiers that fall back to Opus 4.8 for high-risk queries. A restricted sibling, Claude Mythos 5, goes to US government cyberdefenders only via Project Glasswing.
2026/6/10 · 22:35
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Claude Fable 5 is here — Anthropic's first Mythos-class model cleared for the public
Published: June 9, 2026 | Source: anthropic.com/news/claude-fable-5-mythos-5
Two months after Anthropic kept Mythos locked behind a government-only cybersecurity program, it has opened a version of that same engine to the public. Claude Fable 5, launched June 9, is the most powerful Claude model ever made generally available — the first in the company's "Mythos-class" tier, now fitted with safety classifiers for broad deployment.
What it is
Fable 5 runs on the same underlying model as Claude Mythos 5, but with safety classifiers that intercept requests in three high-risk areas: cybersecurity exploitation, biology/chemistry, and distillation. When triggered, the query is quietly rerouted to Claude Opus 4.8 — users get a capable response rather than a refusal. Anthropic says this fallback fires in fewer than 5% of sessions.
Mythos 5 itself, the unguarded sibling, remains restricted to "a small group of cyberdefenders and infrastructure providers" through Project Glasswing — a US government collaboration that began in April.
Key data points
- Pricing: $10 per million input tokens / $50 per million output tokens — roughly half the cost of the earlier Mythos Preview, twice the cost of Opus 4.8
- Context window: 1 million tokens
- Benchmark edge: More than 10% higher than Opus 4.8 on several capability benchmarks
- Stripe proof point: Fable 5 completed a codebase-wide migration of a 50-million-line Ruby codebase in one day; Stripe said it would have taken "a whole team over two months by hand"
- FrontierCode: Highest-scoring frontier model on Cognition's production-quality coding evaluation
Access window
| Period | Access |
|---|---|
| June 9 – June 22, 2026 | Included at no extra cost on Pro, Max, Team, and seat-based Enterprise plans |
| From June 23, 2026 | Shifts to usage-credit billing on those plans |
| Later (capacity TBD) | Anthropic intends to restore it as a standard subscription feature |
Why it matters now
Fable 5 lands days after Anthropic's confidential S-1 filing with the SEC and the close of its $65B Series H at a $965B post-money valuation. The company is racing OpenAI — which filed its own IPO paperwork on June 8 — to demonstrate that Mythos-level capability can be productized safely at scale. Fable 5 is both a product statement and an investor signal.
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