Posts of videos drawn entirely in code pile up
Posts of animations drawn entirely in code, said to have been made with "Claude Fable 5.5," reportedly Anthropic's next model, piled up on X on Nov. 2. The account @notjazii, which shares rumors about new models, posted on the same day (8:47 p.m. Japan time) an animation it said was made in about an hour without external assets such as images or video. On the same day, @Haleeeemahh and @LuminaBench also posted similar examples and assessments. Some see this as a sign that the number of users with early access to Fable 5.5 has grown. Anthropic has not announced a model called "Fable 5.5," and it has not been confirmed through what route or with which model the posters made their work.
This is the second time such examples have spread. From Oct. 1 to 3, there was also a series of posts of videos said to have been made with Fable 5.5. A list collecting the examples on GitHub has 19 entries, including Marvel and DC heroes drawn in pure JavaScript only, a history of civilization depicted without video assets, and 13.8 billion years of the universe with visuals and music computed in code. The list's creator states that they confirmed the posts named Fable 5.5 and contained videos, but does not claim that Fable 5.5 has been officially released.
No way to verify from the outside which model made them
The means of verifying the posts are limited. In Anthropic's chat service and its AI coding tool Claude Code, users cannot see which model responded. According to Decrypt, a post on Oct. 11 said requests to Opus 5.5 were being routed to a new model, and a developer who made a 2D animation also showed the work while asking whether it was Fable 5.5. U.S.-based Emergent pointed out on Oct. 5 that impressive examples or answers about recent events alone cannot identify which model made them. According to Anthropic's documentation, each model name (ID) corresponds to a single fixed version, and updating the contents gives it a new name.
U.S.-based EvoLink, which compiled examples, also noted that while it confirmed the posts and videos, the model's identity and API availability are unconfirmed. In October, China's 36Kr (in an article by Xinzhiyuan) described an example of an online game with a map and characters made in about five hours and a 9-minute-38-second symphony with visuals made in about four hours, but noted that both were unverified claims on social media.
Post claims hidden model beat leader Opus 5.5 by 1.3 points
The figures circulating as clues to performance also come from a single post. U.S.-based Cognition, which develops AI for software development, released on Oct. 27 the results of "FrontierCode 2.0," an evaluation that has AI carry out real development work and scores whether the quality is good enough for people to adopt as is. Anthropic's Opus 5.5 led with 45.5%, followed by OpenAI's GPT-6 Astra at 42.8%. Scores are out of 100%, and each model was measured at its deepest reasoning setting.
On Oct. 27 (Oct. 28 Japan time), the newly created X account @tensorson posted that the evaluation data contained a hidden model, "Obsidian 3," which beat Opus 5.5 with 46.8%. Because it had been measured in an execution environment for Claude, the account speculated that it might be Fable 5.5. "Obsidian 3" does not appear in the table Cognition released. U.S.-based explainx pointed out that the 1.3-point gap with Opus 5.5 is within the range of variation that appears when the same model is measured again.
"Imminent release" speculation has kept missing since October
Speculation that Fable 5.5's release was near has continued since mid-October. On Oct. 13, "Fable 5.5" appeared as "generally available" in a list for Microsoft's Azure cloud, and the AI connection software LiteLLM automatically added an entry. However, the pricing and the length of text it could handle were the same as Fable 5.1's, and the entry disappeared the next day.
On Oct. 18 (Oct. 19 Japan time), the leak account @lyraxana relayed a rumor that a second prototype had been distributed to partners and would be released the following Tuesday or Wednesday, but no release followed. On Oct. 26, @notjazii also relayed, without citing a source, a rumor that large models including Fable 5.5 would be announced to coincide with Anthropic's IPO, but there was no announcement that week. On Nov. 1 (Nov. 2 Japan time), the name "Claude Mythos 5.5" was found in a hidden part of Anthropic's website. Mythos is a version with the same contents as Fable but different safety restrictions, offered only to researchers, and U.S.-based TestingCatalog has pointed to the possibility that the two will be released together.
- Anthropic releases Fable 5.1Official
- Anthropic announces Opus 5.5Official
- Videos said to be made with Fable 5.5 pile upRumor
- Fable 5.5 appears in Azure list, removed the next dayLeak
- Rumor that a prototype went to partners for release the following weekLeak
- "Fable 5.5" in a public commit to the software tool T3 CodeLeak
- Anthropic makes its S-1 publicOfficial
- Post claims hidden model "Obsidian 3" beat Opus 5.5Rumor
- "Claude Mythos 5.5" appears on official websiteLeak
- Code-only animation posts pile upRumor
Current Fable 5.1 costs 2.5 times as much as Opus 5.5
Fable 5.1, the highest-end model currently available, was released on Sept. 1 (Sept. 2 Japan time). Developer API pricing is $10 for input and $50 for output per million tokens, unchanged from the previous version, Fable 5. Opus 5.5, which Anthropic announced on Sept. 22, costs $4 for input and $20 for output, and the company says its performance is close to Fable 5.1 on most tasks. Fable 5.5's pricing, performance and release date have not been announced.
- Claude Fable 5.1
- Claude Opus 5.5
Overlaps with the IPO process
Anthropic made public on Oct. 26 its registration statement (S-1) for a listing on the Nasdaq. Revenue for January-June 2026 was $16.29 billion, about 14 times the $1.16 billion a year earlier. According to Decrypt, investor presentations (the roadshow) can begin as early as Nov. 10. The Wall Street Journal reported, citing people familiar with the matter, that the company is aiming to list in the week of Nov. 16. Some speculate that the timing of a new model announcement is tied to the IPO schedule, but Anthropic has not disclosed its model plans.
Competitors' moves also overlap. OpenAI released the low-cost "GPT-6.1 Terra" on Oct. 26 (Oct. 27 Japan time), the same day as the IPO filing. On Nov. 1, Decrypt reported that an unannounced "gpt-6.2-astra" had appeared in some users' Codex usage logs. OpenAI has not announced a 6.2 version.
