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Fable 5 and Mythos 5: What's the Difference?
6 min read ·
Claude Fable 5 and Claude Mythos 5 share the exact same capabilities, specs, and pricing — both run on a 1M-token context window, output up to 128K tokens, keep adaptive thinking always on, and cost $10 per million input tokens and $50 per million output tokens. The one meaningful difference is that Claude Mythos 5 omits the safety classifiers built into Claude Fable 5 and is offered only through Anthropic's limited-release Project Glasswing, while Fable 5 launched generally available.
What Fable 5 and Mythos 5 are
Claude Fable 5 and Claude Mythos 5 are two separate models that sit on top of one shared underlying capability base. They were introduced together on June 9, 2026, and from a raw-performance standpoint they behave the same way.
Claude Fable 5 (model ID claude-fable-5) is the version most developers heard about first. It launched generally available through the Claude API and major cloud platforms, with the same $10/$50 pricing and 1M-token context as its sibling.
Claude Mythos 5 (model ID claude-mythos-5) is the classifier-free, limited-release sibling. It is the successor to the earlier invitation-only Claude Mythos Preview, and access runs exclusively through Anthropic's Project Glasswing program for approved customers.
If you want the full picture on the generally available model, our companion guide on what Claude Fable 5 is walks through the specs in detail.
The key difference
The single defining difference between the two models is the presence of safety classifiers: Fable 5 has them, Mythos 5 does not. Everything else — pricing, context, output ceiling, thinking behavior — is identical.
In practice, that means Claude Fable 5 can return a stop_reason of "refusal" when its classifiers determine a request should be declined. Claude Mythos 5 ships without those classifiers, so it does not apply that same layer of automated request screening. The other distinction is access: Fable 5 was a general-availability release, while Mythos 5 is gated behind Project Glasswing.
| Attribute | Claude Fable 5 | Claude Mythos 5 |
|---|---|---|
| Model ID | claude-fable-5 | claude-mythos-5 |
| Safety classifiers | Yes | No |
| Availability | GA, now suspended | Project Glasswing only, now suspended |
| Pricing | $10/$50 | $10/$50 |
| Context | 1M | 1M |
You can read Anthropic's own introduction to the model line here:
Introducing Claude Fable 5 (Anthropic docs)
What Project Glasswing is
Project Glasswing is Anthropic's limited-release program through which Claude Mythos 5 is offered to approved customers only. It is not a public tier you can sign up for through the standard Claude API.
Glasswing is the successor framing for what used to be the invitation-only Claude Mythos Preview. Because Mythos 5 omits the safety classifiers present in Fable 5, restricting it to vetted, approved customers is how access is controlled.
For most builders, this means Mythos 5 is effectively out of reach: unless you have been approved into Glasswing, the model you would actually use is Fable 5 — or, with both suspended right now, one of the other Claude models.
Anthropic's program page for the initiative is here:
Both currently suspended
As of late June 2026, both Claude Fable 5 and Claude Mythos 5 are globally suspended — this is the most important practical fact about either model right now. The suspension is reported to be temporary, not a permanent ban.
According to reporting, both models were disabled around June 12, 2026, within roughly 72 hours of their June 9 launch, under a U.S. export-control directive that cited a jailbreak concern. The two models went down together, which is consistent with their shared capability base.
It is worth being precise about scope: this suspension applies to Fable 5 and Mythos 5 only. Opus 4.8, Sonnet 4.6, and Haiku 4.5 are unaffected and continue to operate normally.
For more on the access situation, see our breakdown of why Fable 5 is unavailable and the related question of whether Fable 5 is banned.
Independent coverage of the takedown is here:
Claude Fable 5 and Mythos 5 abruptly disabled (Malwarebytes)
Which one matters for you
For nearly every reader, the model that matters is Fable 5 rather than Mythos 5, because Mythos 5 access is restricted to Project Glasswing. Unless you are an approved Glasswing customer, you would never have been able to call claude-mythos-5 in the first place.
That said, both models are suspended right now, so neither is a practical choice today. The realistic decision is which currently available Claude model to build on while this situation develops.
If you are weighing your options, our roundup of the best Claude models in 2026 covers the unaffected models you can use today, including Opus 4.8, Sonnet 4.6, and Haiku 4.5.
Limitations and Tradeoffs
The biggest limitation is access: Mythos 5 is rare by design, gated behind Project Glasswing and offered only to approved customers. There is no public path to it.
On top of that, both models are suspended as of late June 2026, so this is very much a developing story. Details around the export-control directive and the reported jailbreak concern come from reporting, and the situation could change — the suspension is described as temporary, but no firm restoration date has been confirmed. Treat any plan that depends on Fable 5 or Mythos 5 as provisional until they return.
Related Guides
FAQ
What is the difference between Fable 5 and Mythos 5?
They share the same capabilities, specs, and pricing. The key difference is that Claude Fable 5 includes safety classifiers that can decline requests, while Claude Mythos 5 omits those classifiers. Fable 5 also launched generally available, whereas Mythos 5 is limited to Project Glasswing.
Is Fable 5 the same as Mythos 5?
No, but they are closely related. They are two distinct model IDs — claude-fable-5 and claude-mythos-5 — built on one shared capability base. Mythos 5 is the classifier-free, Glasswing-only sibling of Fable 5.
What is Project Glasswing?
Project Glasswing is Anthropic's limited-release program through which Claude Mythos 5 is offered to approved customers only. It is the successor to the earlier invitation-only Claude Mythos Preview and is not part of the standard public Claude API.
Is Mythos 5 suspended too?
Yes. According to reporting, both Fable 5 and Mythos 5 were globally suspended around June 12, 2026, under a U.S. export-control directive. The suspension is described as temporary, and Opus 4.8, Sonnet 4.6, and Haiku 4.5 are unaffected.
Which model can I actually use right now?
Neither Fable 5 nor Mythos 5 is usable while the suspension is in effect. For current work, use one of the unaffected Claude models — Opus 4.8, Sonnet 4.6, or Haiku 4.5 — until the situation is resolved.
Skills for this topic
Browse all skills →Frequently Asked Questions
What is the difference between Fable 5 and Mythos 5?
They share the same capabilities, specs, and pricing. The key difference is that Claude Fable 5 includes safety classifiers that can decline requests, while Claude Mythos 5 omits those classifiers. Fable 5 also launched generally available, whereas Mythos 5 is limited to Project Glasswing.
