Anthropic briefly names Claude Mythos 5.5

The top of Anthropic's own Claude Mythos page read Claude Mythos 5.5 on the 1st of November 2026, ArtificialWatch reported. Anthropic has not announced any model by that name.

By the next day the page header read Claude Mythos 5.1 again. Daily Agentic checked the page on the 2nd of November and found no mention of 5.5.

What the page showed

ArtificialWatch said it read the page code at about 15:30 UTC on the 1st of November. The name Claude Mythos 5.5 appeared six times, all in the header and logo text.

Everything below the header still described Mythos 5.1, the site said. That includes the price and who can use it.

Then the name was gone

At 17:30 UTC the header read Claude Mythos 5.1 again, ArtificialWatch said. An X user noticed the change two minutes earlier.

Anthropic has not commented on the page or on any new Mythos model.

What Mythos is

Mythos is Anthropic's strongest AI model family for cyber defence and biology research. Only checked groups can use it, through Anthropic's access programs.

Mythos 5.1 came out on the 1st of September 2026, Anthropic's page says. It costs 10 dollars per million input tokens, the word pieces AI reads.

Below we break down the timing

The name was seen at 15:30 UTC and gone by 17:30 UTC. That gives a window of about two hours, by our arithmetic.

Output for Mythos 5.1 costs 50 dollars per million tokens. That is five times the input price.

What is confirmed and what is not

The page header did show the name, ArtificialWatch said. A release date, a price and who could use Mythos 5.5 are all unknown.

Key facts

Anthropic's Mythos page header read Claude Mythos 5.5 on the 1st of November 2026.

The name was removed about two hours later, ArtificialWatch said.

The page now shows Claude Mythos 5.1.

Anthropic has not announced Mythos 5.5.