GPT-5.6 Sol Pro vs Grok 4.20
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for GPT-5.6 Sol Pro and Grok 4.20.
GPT-5.6 Sol Pro
GPT-5.6 Sol Pro is the same underlying model as [GPT-5.6 Sol](https://openrouter.ai/openai/gpt-5.6-sol), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. Learn more in OpenAI's docs: https://developers.openai.com/api/docs/guides/reasoning#reasoning-mode
Grok 4.20
Grok 4.20 is a reasoning model from xAI with industry-leading speed and agentic tool calling capabilities. It combines the lowest hallucination rate on the market with strict prompt adherance, delivering...
Technical Specifications
| Specification | GPT-5.6 Sol Pro | Grok 4.20 |
|---|---|---|
| Provider | OpenAI | xAI |
| Context Window | 1,050,000 tokens | 2,000,000 tokens |
| Agent Suitability | N/A | N/A |
| Time to First Token (TTFT) | N/A | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | beta | beta |
| API Available | Yes | Yes |
| Released Date | 2026-07-09 | 2026-03-31 |
API Pricing Comparison
Input Price per Million Tokens
GPT-5.6 Sol Pro
$5.00
Grok 4.20
$1.25
Output Price per Million Tokens
GPT-5.6 Sol Pro
$30.00
Grok 4.20
$2.50
Want to test both models live?
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
GPT-5.6 Sol Pro Quirks & Gotchas
No developer gotchas reported.
Grok 4.20 Quirks & Gotchas
No developer gotchas reported.