Pyyan / Compare / Claude Mythos 5.1 vs GPT-6 Astra
Claude Mythos 5.1 vs GPT-6 Astra
2 of 5Language Models · verified 5 Sept 2026
Claude Mythos 5.1Anthropiccurrent
GPT-6 AstraOpenAIcurrent| Specification | Claude Mythos 5.1 | GPT-6 Astra |
|---|---|---|
| Summary | Fable 5.1 with the safety classifiers removed. You cannot simply buy it. | Saturates three of the benchmarks it reports, and ships disabled for enterprise. |
| Context | 1M | 1.05M |
| Input ($/Mtok) | $10 | $10 |
| Output ($/Mtok) | $50 | $50 |
| Licence | Proprietary, gated | Proprietary |
| Max output | 128K | 128K |
| Parameters | Not published | Not published |
| Released | 1 Sep 2026 | 3 Sep 2026 |
| Model ID | claude-mythos-5-1 | gpt-6-astra |
| Category | Language Models | Language Models |
| Official | — | — |
Highlighted rows are where these differ.
Claude Mythos 5.1
- The same underlying model as Fable 5.1, at a different safeguard level
- US organisations and individuals in Anthropic's trusted access programmes only
- Safety classifiers and high-risk fallbacks removed for Project Glasswing participants
Best for vetted frontier research.
GPT-6 Astra
- 97.6% on FrontierMath Tier 4, 99.9% on ARC-AGI-3 and 100% on ExploitBench
- Above 272K input tokens the whole request reprices: input and cache at 2x, output at 1.5x
- Rolls out to OpenAI's Daybreak cyber programme first, and arrives switched off for enterprise
Best for hard reasoning and computer use.