Claude Fable 5 Released — A New Tier Above Opus

Anthropic announced Claude Fable 5 and Claude Mythos 5 on June 9 (local time). The announcement introduces a new Mythos-class tier sitting above Opus, which until now was the top of the lineup. Of the two, Fable 5 is the one regular users can start using right away.

01. Fable 5 is Mythos made generally available

The two are actually the same underlying model. Mythos 5 is the original with safeguards removed, offered only to Project Glasswing cybersecurity partners and select life-science researchers.

Fable 5 is that model with safeguards layered on top, released to the general public. The Mythos Preview that Anthropic called "too powerful to release" back in April has effectively come down to a generally available tier in just two months.

02. It reportedly tops nearly every benchmark

According to Anthropic's announcement, it set the best score on nearly every benchmark they tested. First place on Hebbia's finance benchmark and first on Cognition's FrontierCode were both cited in the release.

Among the case studies, Stripe reported that a migration across a 50-million-line Ruby codebase went from "months of engineering to days." On the vision side, the model reportedly beat Pokémon FireRed from screenshots alone, with no helper tooling.

Compared to Opus 4.8, Anthropic says it finishes the same tasks in fewer turns and 25–30% faster. That said, all of these numbers come from the announcement materials — how it actually feels is something to judge by trying it yourself.

03. It's included free with subscriptions until June 22

Subscription plan users can use Fable 5 at no extra cost from June 9 through June 22. It's already showing up in the /model picker in Claude Code.

Starting June 23, it requires usage credits separate from the subscription. With only a two-week free window, if you're planning to try it, this is the period to run your comparisons.

API pricing is $10 per million input tokens and $50 per million output tokens. That's 2x Opus 4.8, but less than half the price of Mythos Preview. The model ID is claude-fable-5, and it launched simultaneously on Amazon Bedrock, Vertex AI, and Microsoft Foundry.

04. Some prompts get answered by Opus 4.8 instead

The safeguard mechanism is unusual. Requests classified as cybersecurity attacks, bio/chemical risk areas, or attempts to distill the model into a third-party one are automatically answered by Opus 4.8 instead of Fable 5. Anthropic says this fallback affects less than 5% of all sessions.

One more thing: all traffic to Mythos-class models is retained for 30 days. Anthropic states it won't be used for anything beyond training and safety purposes, but if you handle sensitive data, it's worth knowing.

Sources: Anthropic — Claude Fable 5 and Claude Mythos 5, Claude API Docs

This post summarizes the official announcement. It is not sponsored by Anthropic in any form.

Original with full infographics and visual structure: https://jessinvestment.com/anthropic-launches-claude-fable-5-a-new-tier-above-opus/