Claude Fable 5.5 rumored for next week: 'partners already have it,' and 'I built this with it' demos pile up

Talk that Anthropic's next top model, Claude Fable 5.5, will ship next week is spreading fast on X. Anthropic has not confirmed a release or a date.

It started with an Oct 15 post from leaker Lyra (@lyraxana): "Partners got access to the upcoming Claude Fable 5.5. No info on any release date this time but I assume next week." It passed 1,100 likes. Around the same time, per TestingCatalog, Fable 5.5 briefly appeared in Microsoft Azure's model catalog with specs that looked copied from Fable 5.1, and a new codename, "claude-onigiri-eap," showed up in Artificial Analysis's frontend before being pulled hours later.

"Made with Fable 5.5" demos keep coming: an SVG of a bike riding a pelican (2,200 likes), a math-driven music visualization and a Blender-coded 3D animation. Posters say they hit the new model through "grey testing" in Claude Code, where requests were routed away from Opus 5.5, but there is no way to confirm it was actually Fable 5.5.

Posts also claim OpenAI will answer. One listing "Fable 5.5, GPT 6.1 Astra, Grok 4.8" for the next few weeks got 1,200 likes. But OpenAI said on Sept 28 it would not release GPT-6.1 Astra because it "didn't quite meet the bar" on safety, and it has not announced a replacement since.