Claude Fable - Mythos 5.1 🧠 Models

Claude Fable - Mythos 5.1 is 💤 Quiet on Above the Fog’s AI hype radar: a hype score of 0 out of 100 on Sep 27, 2026, 19 points lower than 7 days before. Its attention is within the normal range across the monitored sources. Its last hype episode in the 30-day window ran from Sep 22 to Sep 22 (peak 30 on Sep 22).

Claude Fable 5.1 and Mythos 5.1 (Anthropic, Sep 1, 2026): the same frontier model with different safeguards; Mythos is trusted-access only.

First seen on Google Trends (search interest) · Sep 13 — the first monitored source to go above normal for it in the last 14 days.

Why this stage: within the normal range across monitored sources.

Stage

💤 Quiet — within the normal range across the monitored sources

Hype score

0 / 100 · −9.6 in 1 day · −18.9 in 7 days

In hype since

not in hype now

Peak, 30 days

85.5 on Sep 2, 2026

Category

🧠 Models

Made by

Anthropic

Part of

Claude

Official site

claude.ai

Sources above normal

0 of 24 scoring it (0 independent families)

Stories in 7 days

279

Share of voice

0.6% of the radar’s attention in 7 days

Where the attention comes from

“Normal” is the median of the source’s previous 14 normal days for this topic. A source is above normal when its value is at least 30% over that level and stands out from its usual day-to-day variation (z ≥ 2); the share is the part of the hype score that source explains. “× normal” is left blank when the normal level is 0.

Stories behind it

1. claude-fable-5-high enters the text Arena leaderboard at #8 — LMArena (leaderboard) (anthropic) · Sep 25 · score 36,462
2. THEY FUCKING COOKED YO! Opus 5.5 is a massive upgrade. — Reddit (r/ClaudeCode) · Sep 23 · score 1,454 · 187 comments
3. Claude 5.5 Sonnet is live and it’s roughly Opus 5.5 but cheaper www.anthropic.com/claude-sonne... — Bluesky · Sep 28 · score 145 · 14 comments
4. Claude Opus 5.5 Should Raise Your Ambitions — AI newsletters (RSS) (Zvi) · Sep 26 · score 118 · 27 comments
5. Ask HN: Do you think we'll ever have local models of Fable level? — Hacker News · Sep 23 · score 3 · 3 comments
6. Anthropic says Opus 5.5 matches Fable 5.1 “on most tasks” while costing about 40% less to run than Opus 5; Opus 5.5 costs $4/1M input and $20/1M output tokens — Techmeme (The Decoder) · Sep 22 · score 6 · 1 comment
7. Externe Benchmarks: Claude Opus 5.5 überholt Astra von OpenAI und Fable 5.1 Anthropics neues KI-Modell Opus 5.5 hat sich in einem unabhängigen KI-Benchmark an die Spitze gesetzt. Dafür sind die Koste… — Mastodon (fediverse) (social.heise.de) · Sep 25 · score 6 · 1 comment
8. Fable 5.1 costs twice as much as Opus 5, until your cache gets big enough — DEV Community (dev.to) (#ai) · Sep 28 · score 1 · 1 comment
9. Choosing a model through @Cursor in slack doesn't choose Fable 5.1 — Developer forums (Cursor, OpenAI, Hugging Face) (Cursor Forum) · Sep 25 · score 0 · 0 comments
10. Anthropic to include Fable 5 usage in Pro plans — Reddit (r/ClaudeAI) · Sep 24 · score 724 · 92 comments
11. Opus 5.5 is my favorite model ever, by far — Reddit (r/ClaudeAI) · Sep 26 · score 553 · 167 comments
12. Stupid question - if Opus 5.5 is better than Fable 5.1, why would we ever use Fable 5.1? — Reddit (r/ClaudeAI) · Sep 23 · score 512 · 137 comments

Themes

What its stories of the last 7 days are about: the 239 of them the Jev model kept as about the scene, by theme (a story can carry several themes):

• Models — 87% of its stories
• Agents — 28% of its stories
• Usage & adoption — 20% of its stories
• Companies & business — 7.5% of its stories
• Security & safety — 5.9% of its stories
• Protocols & infra — 2.5% of its stories

Related topics

Made by

Anthropic

Part of

Claude

Competes with

GPT-6 Astra, Gemini, Muse Spark

Mentioned with

Claude Code (78 stories), GPT-5.6 Sol - Terra - Luna (30 stories), LMArena (11 stories), TypeSafe AI (7 stories), AI in math (6 stories), Browser Use - browser agents (5 stories)

Hype score, last 30 days

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