Claude Fable 5.5: Release Date, Leaks and What Is Actually Confirmed

By Eoin Villarin, 2026-11-10

Claude Fable 5.5 has not been released. Here is every leak so far, from the Azure catalog entry to the hidden Mythos 5.5 label, what is confirmed, what is rumored and how developers should prepare.

Claude Fable 5.5 is the most searched Anthropic model of the month, but it has not been released. As of November 10, 2026, Anthropic has not announced it, has not published a model card or price, and its documentation still lists Claude Fable 5.1 as the newest Fable model. What exists are leaks: a cloud catalog entry, a pricing file that was removed a day later, code names spotted in partner tools and a "Mythos 5.5" label hidden in Anthropic's own website code. Here is everything that is confirmed, everything that is only rumored, and how developers and businesses should prepare.

What is Claude Fable?

Fable is the top commercial tier of Anthropic's Claude 5 family. It is the public, safeguarded version of Anthropic's Mythos-class models: it adds extra protections in high-risk areas such as cybersecurity and biology, and it can fall back to a smaller model when a request is classified as high-risk. Mythos is the restricted twin, offered only to vetted organizations through a trusted-access program. Opus, Sonnet and Haiku sit below Fable as faster and cheaper options.

The Claude 5 timeline so far

With Opus, Sonnet and Haiku already at 5.5, a Fable 5.5 is the obvious next step, which is why every leak gets so much attention. Anthropic said Fable 5.1 cut the cost of typical token-billed work by about 25% compared with Fable 5, and agent workloads by up to about 45%.

Claude Fable 5.5 leaks: the timeline

1. October 11: X user Chetaslua posted that "Claude Opus 5.5 is routing to a new model," suggesting some requests were answered by an unreleased model, possibly Fable 5.5.
2. October 13: A model ID, claude-fable-5-5, appeared in Microsoft's Azure catalog, reportedly marked "Generally available" in the East US 2 region. An automated update added it to the LiteLLM price list the same day.
3. October 14: LiteLLM removed the entry when Azure queries came back empty.
4. October 15: A leaker known as Lyra said partners had access to the model. The same day, a code name "claude-onigiri-eap" appeared briefly in Artificial Analysis's website with four effort levels, then disappeared within hours.
5. November 1: A "Mythos 5.5" label appeared six times in the hidden code of Anthropic's Mythos page, including an invisible headline and logo alt text. The visible page still showed Mythos 5.1.

Confirmed vs rumored

What specs and price will Fable 5.5 have?

Nobody outside Anthropic knows yet. The only numbers came from the removed LiteLLM entry: $10 per million input tokens, $50 per million output tokens, a 1M-token context window and up to 128K output tokens. Those are the same figures as Fable 5.1, so they were almost certainly copied over rather than real Fable 5.5 data. For comparison, Opus 5.5 costs $4 per million input tokens and $20 per million output tokens, and Anthropic says it performs at Fable 5.1's level on most tasks.

When will Claude Fable 5.5 be released?

There is no official date. Leakers expected a launch in late October, and that window passed. Some commentators connect the timing to Anthropic's IPO, since the company filed publicly on October 26 and its roadshow could start from November 10, but that link is speculation. If you want the background on the listing, I covered it in my post on the Anthropic IPO and the AI data center backlash.

How to check if Fable 5.5 is live

Do not trust screenshots. The fastest reliable check is Anthropic's own model list through the API:

curl https://api.anthropic.com/v1/models \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01"

If claude-fable-5-5 shows up in that list, it is real and available to your account. Anthropic's newsroom, model documentation and pricing page will also update on launch day.

How developers and businesses should prepare

1. Keep the model ID in one config value, not scattered through your code, so switching to a new model is a one-line change.
2. Build a small test set of 20 to 50 real prompts from your product, with the answers you expect, so you can compare a new model in minutes instead of guessing.
3. Track cost per task, not cost per token. A model that is more expensive per token but finishes a job in fewer steps can be cheaper overall.
4. Use the cheaper tier where it is enough. Opus 5.5 already covers most Fable 5.1 work at a lower price, so reserve Fable for the hardest tasks.
5. Plan a fallback. New models can be paused, rate-limited or restricted, as happened to Fable 5 in June, so keep a second model ready.

I build AI chatbots and automations for websites and online stores, with model fallbacks built in. See my AI chatbot and automation work, or read about the other rumored models this month: GPT-6.2 Astra and Gemini 4 Hydrogen.

Frequently asked questions

Is Claude Fable 5.5 out?

No. As of November 10, 2026, Anthropic has not announced or released Claude Fable 5.5. The newest Fable model is Claude Fable 5.1, released on September 1, 2026.

What is the Claude Fable 5.5 release date?

Anthropic has not given one. Leakers expected late October, which passed without a launch, so any date you see is a guess.

How much will Claude Fable 5.5 cost?

There is no official price. The only listed figures, $10 and $50 per million input and output tokens, came from a removed entry that copied Fable 5.1's pricing.

What is the difference between Claude Fable and Claude Mythos?

Fable is the public, safeguarded model with extra protections in high-risk areas. Mythos is the restricted version for vetted organizations, such as cybersecurity and research teams.

Is Claude Fable 5.5 better than Opus 5.5?

One leak claims it is, but there are no official benchmarks. Anthropic says Opus 5.5 already matches Fable 5.1 on most tasks at a lower price.

How can I tell if a Claude model is real?

Check Anthropic's newsroom, its model documentation or the models endpoint of the Claude API. Screenshots of catalogs and code labels are not proof of a release.

Sources

• Decrypt: Claude Fable 5.5, GPT 6.2 Astra could be right around the corner, leaks suggest
• TestingCatalog: Anthropic prepares to release Claude Fable 5.5
• 36Kr: Fable 5.5 spotted on Azure
• Wikipedia: Claude (language model)