Claude Fable 5.2 ranks first overall in independent tests (174 vs 169), but not on science
Anthropic released it on 9 November 2026. Independent tests put it level with rivals on hard maths and behind them on PhD-level science.
ARC-AGI-3: interactive puzzle games
Best ARC Prize score on the semi-private set. Standard harness vs a lab's own harness.
What this measures: Hundreds of small turn-based games with no instructions: the AI has to explore, work out the rules and win in as few moves as possible. Every game was beaten by human testers; 100% means matching a typical first-time human player's efficiency on every game.
- ARC's standard harness
- Lab's own harness (provider adapter)
- Reference level
The harness matters on interactive tasks: every model tested both ways scored far higher when it could keep its own hidden reasoning between moves (e.g. GPT-6 Astra 62.7% → 99.9%, Claude Fable 5.2 81.2% → 97.7%). Dates are model release dates. ARC-AGI-3 costs are per run, not per task. ARC Prize 2026 competition results are due on 4 December 2026.
Show data table and sources
| Series | Date | Model | Value |
|---|---|---|---|
| ARC's standard harness | 25 Mar 2026 | Best frontier AI at launch | 0.5% |
| ARC's standard harness | 1 Jun 2026 | Claude Opus 4.8 (high) | 1.5% |
| ARC's standard harness | 9 Jul 2026 | GPT-5.6 Sol (max) | 7.8% |
| ARC's standard harness | 24 Jul 2026 | Claude Opus 5 (high) | 30% |
| ARC's standard harness | 2 Sept 2026 | GPT-6 Astra (max) | 63% |
| ARC's standard harness | 2 Sept 2026 | Gemini 3.8 Flash | 10% |
| ARC's standard harness | 28 Sept 2026 | Claude Sonnet 5.5 | 24% |
| ARC's standard harness | 29 Sept 2026 | GPT-6.1 Sol | 53% |
| ARC's standard harness | 30 Sept 2026 | Gemini 4 Argon | 50% |
| ARC's standard harness | 9 Nov 2026 | Claude Fable 5.2 | 81% |
| Lab's own harness (provider adapter) | 2 Sept 2026 | Gemini 3.8 Flash + adapter | 35% |
| Lab's own harness (provider adapter) | 3 Sept 2026 | GPT-6 Astra + OpenAI adapter | 100% |
| Lab's own harness (provider adapter) | 28 Sept 2026 | Claude Sonnet 5.5 + adapter | 72% |
| Lab's own harness (provider adapter) | 29 Sept 2026 | GPT-6.1 Sol + adapter | 96% |
| Lab's own harness (provider adapter) | 30 Sept 2026 | Gemini 4 Argon + adapter | 98% |
| Lab's own harness (provider adapter) | 9 Nov 2026 | Claude Fable 5.2 + adapter | 98% |
| Reference | Typical first-time human player (100%) | 100% |
- ARC-AGI Leaderboard (ARC Prize)
- ARC Prize leaderboard data (evaluations.json) (ARC Prize)
- ARC-AGI-3 launch (ARC Prize)
- GPT-6 Astra results (ARC Prize)
- OpenAI's GPT-6 Astra on ARC-AGI-3 (ARC Prize Foundation)
FrontierMath: hard math problems solved
Best score on Epoch AI's FrontierMath (corrected v2 set), plotted at each model's release date.
What this measures: Hundreds of unpublished problems written by mathematicians. Tiers 1–3 are advanced; Tier 4 is research-level. Answers are checked automatically.
- Tiers 1–3 (advanced)
- Tier 4 (research-level)
Tier 4 (research-level), Saturated: Epoch AI considers Tier 4 saturated: GPT-6 Astra solved the last problem no model had solved (September 2026), and GPT-6.1 Sol scores 100%. Now watch: FrontierMath Erdős (68 genuinely open problems).
Epoch AI re-ran older models on the corrected v2 problem set (June 2026), so early points come from those re-runs. OpenAI funded FrontierMath and has access to many problems; Epoch keeps a held-out set. Answers are checked automatically. These are not proofs of open problems.
Show data table and sources
| Series | Date | Label | Value |
|---|---|---|---|
| Tiers 1–3 (advanced) | 17 Dec 2024 | o1 (high) | 15% |
| Tiers 1–3 (advanced) | 31 Jan 2025 | o3-mini (high) | 19% |
| Tiers 1–3 (advanced) | 16 Apr 2025 | o4-mini (high) | 36% |
| Tiers 1–3 (advanced) | 7 Aug 2025 | GPT-5 (high) | 55% |
| Tiers 1–3 (advanced) | 11 Dec 2025 | GPT-5.2 Pro | 74% |
| Tiers 1–3 (advanced) | 5 Mar 2026 | GPT-5.4 Pro | 83% |
| Tiers 1–3 (advanced) | 23 Apr 2026 | GPT-5.5 Pro | 88% |
| Tiers 1–3 (advanced) | 9 Jul 2026 | GPT-5.6 Sol | 89% |
| Tiers 1–3 (advanced) | 1 Sept 2026 | Claude Fable 5.1 | 90% |
| Tiers 1–3 (advanced) | 3 Sept 2026 | GPT-6 Astra | 94% |
| Tiers 1–3 (advanced) | 9 Nov 2026 | Claude Fable 5.2 (max) | 95% |
| Tier 4 (research-level) | 16 Apr 2025 | o4-mini | 4.9% |
| Tier 4 (research-level) | 7 Aug 2025 | GPT-5 | 22% |
| Tier 4 (research-level) | 11 Dec 2025 | GPT-5.2 Pro | 46% |
| Tier 4 (research-level) | 5 Mar 2026 | GPT-5.4 Pro | 59% |
| Tier 4 (research-level) | 23 Apr 2026 | GPT-5.5 Pro | 78% |
| Tier 4 (research-level) | 9 Jun 2026 | Claude Fable 5 | 90% |
| Tier 4 (research-level) | 3 Sept 2026 | GPT-6 Astra | 98% |
| Tier 4 (research-level) | 29 Sept 2026 | GPT-6.1 Sol (max) | 100% |
| Tier 4 (research-level) | 9 Nov 2026 | Claude Fable 5.2 (max) | 100% |
- Epoch AI benchmark data (CSV export) (Epoch AI)
- FrontierMath Tier 4 benchmark page (Epoch AI)
Anthropic released Claude Fable 5.2 on 9 November 2026. It now tops Epoch AI’s Capabilities Index, which combines more than 50 tests into one score: 174.2, against 169.2 for GPT-6 Astra.
Its biggest lead is on ARC-AGI-3, a set of puzzle games that come with no instructions. With ARC Prize’s standard harness (the software wrapped around a model while it’s tested), Fable 5.2 scored 81.2%, up from GPT-6 Astra’s 62.7%. On FrontierMath Tiers 1–3, hard maths problems run by Epoch, it scored 95.1%. That is ahead of the previous best of 93.7%, but inside the margin of error. It tied GPT-6.1 Sol at 100% on the research-level Tier 4.
It does not lead everywhere. On GPQA Diamond, a set of PhD-level science questions, it scored 93.9%, below Gemini 4 Argon’s 96.4%. On ARC-AGI-2, a set of visual puzzles, it came third with 93.8%, behind GPT-6 Astra (95.0%) and GPT-6.1 Sol (94.2%).
Fable 5.2 costs $8 per million input tokens and $40 per million output tokens (a token is a short piece of a word), less than Fable 5.1. Anthropic says it is the same underlying model as Claude Mythos 5.2. Fable adds cyber and biology safeguards; Mythos is limited to vetted organisations.
What it means
The overall lead has moved to Anthropic, but only just, and not on every task: Google’s and OpenAI’s models still score higher on science questions and visual puzzles. The launch-day index score rests on 10 tests and may shift. Fable 5.2 is also cheaper than the version it replaces.
Caveats
- The index score is from launch day and rests on 10 tests so far, with a range of 170.1 to 178.8. Expect it to move as Epoch runs more.
- More reasoning did not always help. On ARC-AGI-3, Fable 5.2 scored 81.2% at “XHigh” effort and 65.7% at “Max”.
- With each lab’s own harness on ARC-AGI-3, GPT-6 Astra still leads: 99.9% against 97.7%.
- Anthropic’s launch numbers use its own setup and are not comparable with the independent scores here. Its 73.2% on Humanity’s Last Exam was graded by another Claude model; the best independent score on that test is 54.8% (GPT-6 Astra).
- Several leaderboards had not listed Fable 5.2 on launch day, including LMArena, MirrorCode and OSWorld.