Model Comparison
GPT-5.6 Terra vs Grok-1.5Which is better in 2026?
GPT-5.6 Terra significantly outperforms across most benchmarks.
Verdict: GPT-5.6 Terra vs Grok-1.5 — which is better?
GPT-5.6 Terra (by OpenAI) and Grok-1.5 (by xAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.
GPT-5.6 Terra outperforms in 1 benchmarks (GPQA), while Grok-1.5 is better at 0 benchmarks. GPT-5.6 Terra significantly outperforms across most benchmarks.
Choose GPT-5.6 Terra if…
- you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
- you want the most recent training data — it shipped Jul 2026
Choose Grok-1.5 if…
- you are already invested in the xAI ecosystem
Performance Benchmarks
Comparative analysis across standard metrics
GPT-5.6 Terra outperforms in 1 benchmarks (GPQA), while Grok-1.5 is better at 0 benchmarks.
GPT-5.6 Terra significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
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
GPT-5.6 Terra supports multimodal inputs, whereas Grok-1.5 does not.
GPT-5.6 Terra can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.6 Terra
Grok-1.5
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 Grok-1.5 was released on 2024-03-28.
GPT-5.6 Terra is 28 months newer than Grok-1.5.
Jul 9, 2026
1 weeks ago
2.3yr newerMar 28, 2024
2.3 years ago
Knowledge Cutoff
When training data ends
GPT-5.6 Terra has a documented knowledge cutoff of 2026-02-16, while Grok-1.5'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 Grok-1.5's cutoff date.
Feb 2026
—
Outputs Comparison
Key Takeaways
No standout differentiators in the data we have for this pair.
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against GPT-5.6 Terra and Grok-1.5 side-by-side, then vote on the output you prefer.
| Feature | | |
|---|
FAQ
Common questions about GPT-5.6 Terra vs Grok-1.5.