The rumored Claude Fable 5.5 and Mythos 5.5 didn’t ship. Fable 5.2 and Mythos 5.2 did

What shipped on November 9

On November 9, 2026, Anthropic released Claude Fable 5.2 and Claude Mythos 5.2. The announcement has no 5.5 in it. Nor do the models overview, the API pricing, the deprecations page or Claude Code’s changelog, whose version 2.1.321 “Added Claude Fable 5.2 (claude-fable-5-2), now the default Fable model.”

Model	Status on November 9	Who can use it	API price per million tokens
Claude Mythos 5.2	Out since November 9	Only “vetted cyberdefenders and life scientists”	$8 in, $40 out
Claude Fable 5.2	Out since November 9	The API; Max and Ultra, up to half the weekly limit; Team premium seats; Enterprise; Pro with usage credits, and included through November 16	$8 in, $40 out
Claude Fable 5.1	Still available	The same plans as Fable 5.2	$10 in, $50 out
Claude Opus 5.5	Out since September 22	The API and every paid plan	$4 in, $20 out
Claude Mythos 5.5	Not announced	Not announced	Not announced
Claude Fable 5.5	Not announced	Not announced	Not announced

Our launch memo has the rest: the plans, this week’s offer for Pro, the benchmarks and how to switch in Claude Code. This memo keeps the record of what was rumored, and how it turned out.

What the rumors got right, and wrong

• Right: a newer Fable was close. “Some new Claude models have recently entered early testing. A newer Fable checkpoint + new Opus,” @legit_api wrote on October 29. A new Fable shipped 11 days later. No new Opus has.
• Right: Mythos and Fable move together. Anthropic released Fable 5 and Mythos 5 together on June 9, Fable 5.1 and Mythos 5.1 together on September 1, and 5.2 of each together on November 9. People who read a new Mythos number as a new Fable had that part right.
• Wrong: the name. The leaks that gave a version said 5.5. Bettors hedged: Polymarket’s market was titled “Next Fable Model (5.2+) released by…?”
• Wrong: the price row. The LiteLLM row for a Fable 5.5 showed $10 in and $50 out. Fable 5.2 costs $8 and $40.
• Wrong: every date. Six guesses are in the table below, and none of them was November 9.

What people saw on Anthropic’s page

At 15:31 UTC on November 1, 2026, TestingCatalog posted: “A hidden Claude Mythos 5.5 mention has been spotted on the official Anthropic website.” @chetaslua then wrote that “Mythos 5.5” was in the page’s HTML six times, as a “hidden h1 + logo alt text,” adding: “The visible text still says 5.1.” @AiBattle_ added that an October 23 archive copy didn’t have it.

We read Anthropic’s Mythos page and the Internet Archive’s copies ourselves:

When (UTC)	The page’s hidden title	“Mythos 5.5” in the HTML
October 23, 02:24	Claude Claude Mythos 5	0 times
October 31, 21:49	Claude Claude Mythos 5.5	6 times
November 1, 20:05	Claude Mythos 5.1	0 times
Live page, November 2, 00:06	Claude Mythos 5.1	0 times
Live page, November 4, 06:00	Claude Mythos 5.1	0 times
Live page, November 9, after the launch	Claude Mythos 5.2	0 times

So the reports were right that the name was there, and it was gone within a day of being noticed. Between the October 31 and November 1 copies, the only change is that title, in those same six places. After the launch on November 9 the title read Claude Mythos 5.2, and the page’s newest announcement was “Introducing Claude Mythos 5.2.”

Three things limit what the 5.5 tells you:

• Visitors didn’t see that title. The logo is an image that reads “Claude Mythos,” with no number, in the four copies from October 23 to November 2. TestingCatalog’s screenshot shows “Claude Mythos 5.5” as a large headline, which we couldn’t reproduce from any of them.
• The field has been wrong before. On October 23 it said Mythos 5, seven weeks after Mythos 5.1 came out. The same title on Anthropic’s Fable page read “Claude Claude Fable 5” when we checked on November 4, and reads “Claude Fable 5.2” now.
• Anthropic hasn’t explained it. We found no comment on why the name went in or came out.

Our reading, not Anthropic’s: someone was editing the page ahead of a Mythos launch, and the number either changed or was a mistake. That doesn’t rule out a 5.5 later. It does mean the hidden title was never a date, a price or an announcement.

What Anthropic said before the launch

Nothing about either name. When we checked on November 4, the models overview listed Fable 5.1 as the current Fable, the pricing and deprecations pages had no 5.5 of either model, the platform release notes, the apps release notes and Anthropic’s newsroom named neither, and Claude Code’s model guide said “the fable alias resolves to Fable 5.1.” Five days later every one of those pages except the apps release notes had Fable 5.2 on it, and still no 5.5.

A Mythos number mattered to people who will never get Mythos because of what Anthropic says about the two lines. “Claude Fable 5.2 and Claude Mythos 5.2 are the same underlying model,” its Mythos page says now, as it said of 5.1 before.

Two other things Anthropic has said got folded into the rumors. It wrote that “an unreleased, internal research model” built working exploits (our memo), and its IPO filing says it “chose to delay pre-training a new frontier base model for more than a month” (our memo). It named neither model, it hasn’t tied either to a 5.5, and the 5.2 announcement mentions neither.

What was rumored

Everything here is someone’s report, not Anthropic’s word.

• Testing. Besides @legit_api’s post, TestingCatalog said on November 1 that “multiple reports suggest” A/B tests with selected users, and that the comparisons “remain anecdotal, with no public benchmarks.” When BitsMinds went through the first wave in early October, the screenshots still showed the 5.1 label, and the same kind of clip had been credited to Opus 5.5 a day earlier.
• Azure. On October 13, LiteLLM’s price sync added a row for azure_ai/claude-fable-5-5 at $10 in and $50 out, pointing to Azure’s East US 2 model list. The next day its maintainers removed it because it “prices a model that Azure does not list,” and requests returned a 404. MLflow’s catalog still carried the row on November 9, with the same numbers as Fable 5.1’s, and had no row for Fable 5.2. TestingCatalog had cautioned that “most of those values appear to have been carried over from Fable 5.1.” Polymarket’s small market on the debut price had 36% on $50 or more for output when we read it on November 4. It has since resolved, with “$50+” at 0%.
• Partners. “Partners got access to the upcoming Claude Fable 5.5,” @lyraxana wrote on October 15, with nothing attached.
• A new Opus. Besides @legit_api’s post, TestingCatalog’s October 17 piece lists early-access codenames found in Cognition’s Devin CLI, and it treats matching them to models as uncertain. Polymarket’s market on the “Next Claude Opus (5.6+)” had 54% by November 30 and 90% by December 31 when we read it on November 9, with about $18,000 traded.

The dates were the weakest part:

Said on	By	The claim	Outcome
October 1	@imjustnewatai	“expected to release next week… I’m hearing of a Tuesday release”	Passed
October 15	Andrew Curran, as quoted by OrcaRouter; we didn’t read the original	“may actually arrive today,” or “could get pushed to next week”	Passed
October 15	@lyraxana	“I assume next week”	Passed
October 17	TestingCatalog	“Anthropic prepares to release Claude Fable 5.5 next week”	Passed
November 1	TestingCatalog	“could point to a launch as early as next week”	Passed; 5.2 came the Monday after
November 1	@chetaslua	“i think tuesday can be launch day”	Passed

Tuesday was the easy guess. Fable 5, Fable 5.1 and Opus 5.5 all launched on a Tuesday, though Sonnet 5.5 came on a Monday and Haiku 5.5 on a Wednesday. As BitsMinds put it, “Someone with no information at all would also say Tuesday.” Fable 5.2 came on a Monday.

The early-testing reports held up better than the dates. BitsMinds notes that @synthwavedd reported a Fable successor in testing on August 18, and Fable 5.1 shipped 14 days later; this time the gap from @legit_api’s post was 11 days. The bettors weren’t sure either. When we read Polymarket on November 4, it had the next Fable at 14% by November 6, 36% by November 10, 46% by November 12, 80% by November 30 and 95% by December 31, with about $1.3 million traded. So five days before the launch, the market gave it roughly one chance in three of arriving by November 10.

What to do now

1. Stop waiting for a 5.5. The new Fable is out, and nothing says another is close. Our launch memo covers what Fable 5.2 costs on each plan. If you’re on Pro, the included week ends November 16, 2026 at 11:59 pm PT.
2. Know what your Claude Code setting did. We wrote here on November 4 that a new Fable could reach you without a choice, and it did. Version 2.1.321 “Changed saved Fable 5.1 model picks to move to fable: on Pro and Max plans at once, on Team and Enterprise plans once your organization allows it; use /model claude-fable-5-1 to switch back.”
3. On the API, nothing moved by itself. The deprecations page lists claude-fable-5-1 as Active, with retirement “Not sooner than September 1, 2027.” Test Fable 5.2 against your own work before you switch.
4. If you do security or life sciences work, apply. The Mythos page says “Security teams can apply for advanced cyber capabilities on Claude Mythos 5.2, Claude Opus 5.5, Claude Sonnet 5.5, Claude Mythos 5.1, and future models through the Cyber Verification Program,” whose help article explains the tiers. Life sciences researchers have their own program.
5. Treat the next version rumor the same way. On November 9 the launch showed up where a launch does: a post in Anthropic’s newsroom, a row in the models overview and a price on the pricing page. Until those change, a screenshot is a screenshot.

If you use Claude Code through Enjoy

Enjoy runs Claude Code on your Claude plan and asks Claude Code for its current models each time you open the settings, so Fable 5.2 appears there without an Enjoy update, once your Claude Code is on 2.1.321 or later. If it’s missing, update Claude Code. If Fable uses up your limit faster, you can switch the conversation to another agent, such as Codex, and it gets the messages it missed. Enjoy doesn’t add usage to a Claude plan, and it can’t give you a model your account doesn’t have, Mythos included.

What Anthropic hasn’t said

• Whether a Fable 5.5 or Mythos 5.5 exists, or ever did under that name.
• Why “Mythos 5.5” went onto the Mythos page, and why it came off.
• Whether the stronger model people said they were served in October was Fable 5.2.
• Whether a new Opus is coming.

We’ll update this memo if Anthropic says more about a 5.5.