Claude Mythos Preview vs GPT-5.6 Terra
Claude Mythos Preview shows notably better performance in the majority of benchmarks. GPT-5.6 Terra is 11.1x cheaper per token.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Mythos Preview outperforms in 3 benchmarks (GPQA, Graphwalks BFS >128k, SWE-Bench Pro), while GPT-5.6 Terra is better at 1 benchmark (BrowseComp). Claude Mythos Preview shows notably better performance in the majority of benchmarks.
On price, GPT-5.6 Terra is roughly 11.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current benchmark, pricing, and model metadata for 2026.
Choose Claude Mythos Preview
- you want the strongest raw capability — it leads on 3 of 4 shared benchmarks
Choose GPT-5.6 Terra
- cost matters — it's about 11.1x cheaper per token
At a glance
The differences that matter most.
Performance Benchmarks
Comparative analysis across standard metrics
Claude Mythos Preview outperforms in 3 benchmarks (GPQA, Graphwalks BFS >128k, SWE-Bench Pro), while GPT-5.6 Terra is better at 1 benchmark (BrowseComp).
Claude Mythos Preview shows notably better performance in the majority of benchmarks.
Arena Performance
Playground indexes and blind preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Mythos Preview ($25.00/1M tokens) is 12.5x more expensive than GPT-5.6 Terra ($2.00/1M tokens).
For output processing, Claude Mythos Preview ($125.00/1M tokens) is 10.4x more expensive than GPT-5.6 Terra ($12.00/1M tokens).
In conclusion, Claude Mythos Preview is more expensive than GPT-5.6 Terra.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Only GPT-5.6 Terra specifies input context (1,050,000 tokens). Only GPT-5.6 Terra specifies output context (128,000 tokens).
Input Capabilities
Supported data types and modalities
Both Claude Mythos Preview and GPT-5.6 Terra support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Mythos Preview
GPT-5.6 Terra
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
GPT-5.6 Terra was released on 2026-07-09, while Claude Mythos Preview's release date is not specified.
We can confirm GPT-5.6 Terra's release timeline, but cannot make a direct age comparison without Claude Mythos Preview's release date.
—
Jul 9, 2026
1 months ago
Knowledge Cutoff
When training data ends
GPT-5.6 Terra has a documented knowledge cutoff of 2026-02-16, while Claude Mythos Preview's cutoff date is not specified.
We can confirm GPT-5.6 Terra's training data extends to 2026-02-16, but cannot make a direct comparison without Claude Mythos Preview's cutoff date.
—
Feb 2026
Provider Availability
Claude Mythos Preview is available from Anthropic. GPT-5.6 Terra is available from OpenAI.
Claude Mythos Preview
GPT-5.6 Terra
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Mythos Preview and GPT-5.6 Terra side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Mythos Preview vs GPT-5.6 Terra.