Model Comparison
GPT-5.6 Terra vs Grok-4 HeavyWhich is better in 2026?
GPT-5.6 Terra significantly outperforms across most benchmarks.
Verdict: GPT-5.6 Terra vs Grok-4 Heavy — which is better?
GPT-5.6 Terra (by OpenAI) and Grok-4 Heavy (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-4 Heavy 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
Choose Grok-4 Heavy 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-4 Heavy 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
Both GPT-5.6 Terra and Grok-4 Heavy support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.6 Terra
Grok-4 Heavy
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-4 Heavy's release date is not specified.
We can confirm GPT-5.6 Terra's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.
Jul 9, 2026
1 weeks ago
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Knowledge Cutoff
When training data ends
GPT-5.6 Terra has a knowledge cutoff of 2026-02-16, while Grok-4 Heavy has a cutoff of 2024-12-31.
GPT-5.6 Terra has more recent training data (up to 2026-02-16), making it potentially better informed about events through that date compared to Grok-4 Heavy (2024-12-31).
Feb 2026
1.2 yr newerDec 2024
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-4 Heavy side-by-side, then vote on the output you prefer.
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FAQ
Common questions about GPT-5.6 Terra vs Grok-4 Heavy.