Claude Mythos 5.1 vs GPT-5.6 Luna
Claude Mythos 5.1 and GPT-5.6 Luna are closely matched at 45.1 and 45.1 on the LLM Stats Score. GPT-5.6 Luna is 44.4x cheaper per token.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Mythos 5.1 and GPT-5.6 Luna are closely matched on the overall LLM Stats Score at 45.1 and 45.1.
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.
On price, GPT-5.6 Luna is roughly 44.4x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.6 Luna 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
- your work emphasizes agents — it leads those capability indexes
- you value its reported benchmark strengths — it wins 1 of 1 exact shared results
- you want the most recent training data — it shipped Sep 2026
Choose GPT-5.6 Luna
- cost matters — it's about 44.4x cheaper per token
- you process long inputs — it offers a 1,050,000 token context window
At a glance
The differences that matter most.
Individual benchmarks
1 reported for Claude Mythos 5.1 · 45 for GPT-5.6 Luna
Claude Mythos 5.1 outperforms in 1 benchmarks (Terminal-Bench 4.0), while GPT-5.6 Luna 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) is 50.0x more expensive than GPT-5.6 Luna ($0.20/1M tokens).
For output processing, Claude Mythos 5.1 ($50.00/1M tokens) is 41.7x more expensive than GPT-5.6 Luna ($1.20/1M tokens).
In conclusion, Claude Mythos 5.1 is more expensive than GPT-5.6 Luna.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.6 Luna 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-5.6 Luna support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Mythos 5.1
GPT-5.6 Luna
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-5.6 Luna was released on 2026-07-09.
Claude Mythos 5.1 is 2 months newer than GPT-5.6 Luna.
Sep 1, 2026
2 weeks ago
1mo newerJul 9, 2026
2 months ago
Knowledge Cutoff
When training data ends
GPT-5.6 Luna has a documented knowledge cutoff of 2026-02-16, while Claude Mythos 5.1's cutoff date is not specified.
We can confirm GPT-5.6 Luna's training data extends to 2026-02-16, but cannot make a direct comparison without Claude Mythos 5.1's cutoff date.
—
Feb 2026
Provider Availability
Claude Mythos 5.1 is available from Anthropic. GPT-5.6 Luna is available from OpenAI.
Claude Mythos 5.1
GPT-5.6 Luna
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Mythos 5.1 and GPT-5.6 Luna side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Mythos 5.1 vs GPT-5.6 Luna.