Claude Mythos 5.1 vs GPT-6 Astra
Claude Mythos 5.1 and GPT-6 Astra are closely matched at 45.2 and 60.4 on the LLM Stats Score. Claude Mythos 5.1 and GPT-6 Astra cost the same.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Mythos 5.1 and GPT-6 Astra are closely matched on the overall LLM Stats Score at 45.2 and 60.4.
In the 1 individual benchmarks reported for both models, Claude Mythos 5.1 wins 1; this is a narrower head-to-head signal than the composite indexes.
GPT-6 Astra also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Mythos 5.1
- you value its reported benchmark strengths — it wins 1 of 1 exact shared results
Choose GPT-6 Astra
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Sep 2026
At a glance
The differences that matter most.
Individual benchmarks
1 reported for Claude Mythos 5.1 · 22 for GPT-6 Astra
Claude Mythos 5.1 outperforms in 1 benchmarks (Terminal-Bench 4.0), while GPT-6 Astra is better at 0 benchmarks.
Claude Mythos 5.1 significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Mythos 5.1 ($10.00/1M tokens) costs the same as GPT-6 Astra ($10.00/1M tokens).
For output processing, Claude Mythos 5.1 ($50.00/1M tokens) costs the same as GPT-6 Astra ($50.00/1M tokens).
In conclusion, Claude Mythos 5.1 and GPT-6 Astra cost the same.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-6 Astra accepts 1,050,000 input tokens compared to Claude Mythos 5.1's 1,000,000 tokens. Both models can generate responses up to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Mythos 5.1 and GPT-6 Astra support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Mythos 5.1
GPT-6 Astra
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Mythos 5.1 was released on 2026-09-01, while GPT-6 Astra was released on 2026-09-04.
GPT-6 Astra is 0 month newer than Claude Mythos 5.1.
Sep 1, 2026
1 weeks ago
Sep 4, 2026
4 days ago
3d newerKnowledge Cutoff
When training data ends
GPT-6 Astra has a documented knowledge cutoff of 2026-04-30, while Claude Mythos 5.1's cutoff date is not specified.
We can confirm GPT-6 Astra's training data extends to 2026-04-30, but cannot make a direct comparison without Claude Mythos 5.1's cutoff date.
—
Apr 2026
Provider Availability
Claude Mythos 5.1 is available from Anthropic. GPT-6 Astra is available from OpenAI.
Claude Mythos 5.1
GPT-6 Astra
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Mythos 5.1 and GPT-6 Astra side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Mythos 5.1 vs GPT-6 Astra.