Claude Fable/Mythos 5.2 Leak Wave Spreads, Unverified and Likely Fabricated

Claude Fable 5.2 launched on November 10, and official benchmark comparison tables shared by multiple users (markk, accourtt, MoneyAd3945, etc.) show the new model leading Opus 5.5, GPT-6 Astra, and Gemini 4 Carbon on nearly all of roughly 12-13 evaluations, with major gains over the previous Fable 5.1.

Confirmed

• On the agentic coding benchmark FrontierCode 2.0: Fable 5.2 scores 49.1%, versus 32.4% for Fable 5.1, 45.5% for Opus 5.5, and 42.8% for GPT-6 Astra, ranking first
• FrontierSWE v2 reaches 69.9%
• Robotics scores jump from 27.6% to 64.9%
• minchoi notes Fable 5.2 costs roughly half as much as Opus
• The benchmark table spans comparisons across Fable 5.1, Opus 5.5, GPT-6 Astra, and Gemini 4 Carbon

Why it matters

• FrontierCode 2.0 measures whether a model's code changes would be merged by open-source project maintainers, making it an agentic coding metric close to real-world engineering ability; Fable 5.2 topping it at half the cost is directly relevant to anyone invested in coding automation
• Benchmark data shared by multiple independent accounts corroborate each other, suggesting wide circulation, but all are reposts of the official table, with no deeper independent evaluation yet

2026-11-10 ~ 2026-11-10 · 21 related posts

Full story(16 episodes)→

• Episode 1: Claude Fable/Mythos 5.2 Leak Wave Spreads, Unverified and Likely Fabricated(2026-11-10, 21 posts)
• Episode 2: Anthropic Launches Claude Fable 5.2 and Mythos 5.2: Faster, Cheaper, Frontier-Focused(2026-11-10, 82 posts)
• Episode 3: Anthropic's 1000-Agent Swarm Formalizes Fermat's Last Theorem in 30 Hours(2026-11-10, 23 posts)
• Episode 4: Shumer Reviews Fable 5.2: Smartest Model Ever, But Heavy Guardrails(2026-11-10, 3 posts)
• Episode 5: Anthropic offers Claude Pro users free limited trial of Fable 5.2(2026-11-10, 2 posts)
• Episode 6: Claude Fable 5.2 Tops LiveBench but Cost Concerns Emerge(2026-11-10, 3 posts)
• Episode 7: Fable 5.2 Wins Praise for Open-Ended Tasks(2026-11-10, 2 posts)
• Episode 8: Claude Fable 5.2 Lands on Perplexity, Sets WANDR Benchmark Record(2026-11-10, 3 posts)
• Episode 9: Claude Fable 5.2 Sets New Record on ARC-AGI-3(2026-11-10, 2 posts)
• Episode 10: Over 90% of merged changes in Anthropic's core codebase now written by Claude(2026-11-10, 2 posts)
• Episode 11: Claude Fable 5.2 Tops Artificial Analysis Intelligence Index at 65, but Per-Task Cost Draws Skepticism(2026-11-10, 12 posts)
• Episode 12: METR Files Confirm Fable 5.2 Is "Model 3"; Stronger Unreleased Model May Exist(2026-11-10, 4 posts)
• Episode 13: Hands-on with Claude Fable 5.2: 30% faster, API 20% cheaper, 55% fewer blocks(2026-11-10, 2 posts)
• Episode 14: Fable 5.2 Not Yet Available in Claude Code(2026-11-10, 2 posts)
• Episode 15: Claude Fable 5.2 Sets ECI Record of 174, Topping GPT-6 Astra(2026-11-10, 4 posts)
• Episode 16: Claude Fable 5.2 Tops WebDev Arena While Getting Faster and Cheaper(2026-11-10, 2 posts)

• [source] Claude Fable 5.2 spotted rolling out on Anthropic API — kimmonismus · 2026-11-10
• Claude Fable & Mythos 5.2 reportedly rolling out, API tracker shows claude-fable-5-2 — Scobleizer · 2026-11-10
• Anthropic rolls out Claude Fable 5.2 and Mythos 5.2 — 141_1337 · 2026-11-10
• Leak claims Anthropic to launch Claude Fable 5.2 and Mythos 5.2 at lower prices — testingcatalog · 2026-11-10
• Reddit post claims 'Fable and Mythos 5.2' released — a Claude model family that doesn't exist — Your_mortal_enemy · 2026-11-10
• Fable 5.2 benchmarks leak: 49.1% FrontierCode, robotics jumps to 64.9%, 89.3% computer use — ChrisGPT · 2026-11-10
• Viral Screenshot Shows 'Fable 5.2' and Opus 5.5 in Claude Code — Likely a Fake — YashasGunderia · 2026-11-10
• Claude Fable 5.2 lands: beats Opus 5.5 and GPT-6 across agent benchmarks — accourtt · 2026-11-10
• Leak: Claude Fable 5.2 launching today, model already being deployed — mark_k · 2026-11-10
• Claude Fable 5.2 benchmark dump: sweeps 12 evals, robotics jumps to 64.9% — mark_k · 2026-11-10
• Fable 5.2 released: sweeps agentic coding, cybersecurity and robotics benchmarks — Money_Ad_3945 · 2026-11-10
• Fable 5.2 tops FrontierCode 2.0 at 49.1%, matching Opus Max at half the cost — minchoi · 2026-11-10
• Claude Fable 5.2 benchmark chart shows 74.6% on agentic scientific research, big leap over 5.1 — Dr_Singularity · 2026-11-10
• [source] Thread origin: Claude reportedly ships Fable 5.2 and Mythos 5.2 at half Opus 5.5's cost — FinanceYF5 · 2026-11-10
• Leak: Fable/Mythos 5.2 externally safety-tested by AISI, FrontierDesign and METR — FinanceYF5 · 2026-11-10
• Leaked Fable 5.2 eval table: tops 9 of 13 benchmarks, RLI hits 41.3% — FinanceYF5 · 2026-11-10
• Rumor: Claude launches Fable 5.2 and Mythos 5.2, Xhigh tier beats Opus 5.5 at half the cost — FinanceYF5 · 2026-11-10
• [source] Unverified claim: Anthropic launches 'Fable/Mythos 5.2', $8/M tokens, Fermat proof — xiaohu · 2026-11-10
• Rumor: Claude Fable 5.2 and Mythos 5.2 released with 10 agent showcases — FinanceYF5 · 2026-11-10
• Unverified: Fable 5.2 controls real robots untrained on those tasks — FinanceYF5 · 2026-11-10
• Unverified: Claude designed a working voice assistant from one prompt — FinanceYF5 · 2026-11-10