Side by side
Standard-tier prices in effect today. The better value in each row is highlighted.
| Fact | Claude Mythos 5.1 | GPT-6 Astra |
|---|---|---|
| Price per 1M input tokens | $10 | $10 |
| Price per 1M output tokens | $50 | $50 |
| Cost of 10M input and 2M output tokens | $200 | $200 |
| Arena Text | Not measured | 1475 Elo (#18 of 39) |
| GPQA Diamond | Not measured | 95.8% (#1 of 37) |
| FrontierMath Tiers 1-3 (v2) | Not measured | 93.7% (#1 of 37) |
| SimpleQA Verified | Not measured | 75.6% (#1 of 34) |
| Provider | Anthropic | OpenAI |
| Release date | September 1, 2026 | September 3, 2026 |
| Access | API only | API only |
| Context window | Not reported | 1,050,000 tokens |
| Max output | Not reported | 128,000 tokens |
| Input | text, image | text, image |
| Output | text | text |
When to choose each
Claude Mythos 5.1
Best for
- Organisations already admitted to Anthropic’s limited-availability programme that need frontier capability at Fable 5.1 rates
Watch out for
- Limited availability: access is restricted to organisations vetted through Anthropic’s Glasswing programme, so it cannot be assumed available for a general evaluation
- Anthropic’s public model comparison table does not list a context window or maximum output for Mythos 5.1, so both are recorded as unknown here rather than inferred from Fable 5.1
GPT-6 Astra
Best for
- Frontier reasoning and agentic evaluations where deep-context retrieval accuracy is the binding constraint
- Workloads that can be kept under the long-context threshold, where the effective rate stays at $10 / $50
Watch out for
- Long-context billing is a cliff, not a taper: a request over the long-context threshold is rebilled in full at $20 per million input and $75 per million output, so a prompt that crosses it costs roughly double
- GPT-6 Astra is the first publicly released model OpenAI classifies as crossing the Critical cybersecurity threshold under its own Preparedness Framework, which carries additional deployment safeguards
- Vendor-reported benchmark figures come from OpenAI’s own launch material and its own harness; they are not independently reproduced here
Claude Mythos 5.1 vs GPT-6 Astra FAQ
Which is cheaper, Claude Mythos 5.1 or GPT-6 Astra?
Both cost $10 per 1M input tokens. For 10M input and 2M output tokens, Claude Mythos 5.1 costs $200 and GPT-6 Astra $200 at standard rates.
Related comparisons
Production evaluation
Choosing between Claude Mythos 5.1 and GPT-6 Astra?
Public benchmarks narrow the shortlist. We run both on your own tasks, data and cost limits, then build the routing and review controls to run the winner in production.
- A head-to-head evaluation on your real workload
- Routing between models by cost and difficulty