GPT-5.1-Codex-Max 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-5.1-Codex-Max and Grok 4.20.
GPT-5.1-Codex-Max
GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic...
Grok 4.20
Grok 4.20 is xAI's most advanced reasoning model, combining powerful analytical capabilities with unique real-time integration to the X (formerly Twitter) platform data stream. This live data access allows Grok 4.20 to answer queries with up-to-the-minute context, making it invaluable for financial analysis, current events research, and real-time market monitoring. Exceptionally strong in physics, advanced mathematics, and code synthesis, it operates with a 2-million-token context window and is priced at $1.25/MTok for input — delivering frontier-tier reasoning at a highly competitive cost for developers building intelligent agents and analytical tools.
Technical Specifications
| Specification | GPT-5.1-Codex-Max | Grok 4.20 |
|---|---|---|
| Provider | OpenAI | xAI |
| Context Window | 400,000 tokens | 2,000,000 tokens |
| Agent Suitability | N/A | 90/100 |
| Time to First Token (TTFT) | N/A | 350 ms |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2025-12-04 | 2026-05-05 |
API Pricing Comparison
Input Price per Million Tokens
GPT-5.1-Codex-Max
$1.25
Grok 4.20
$1.25
Output Price per Million Tokens
GPT-5.1-Codex-Max
$10.00
Grok 4.20
$2.50
Want to test both models live?
Run side-by-side prompt prompts in our dynamic Sandbox. Check execution speeds, latency metrics, and compute actual costs in real-time.
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-5.1-Codex-Max Quirks & Gotchas
No developer gotchas reported.
Grok 4.20 Quirks & Gotchas
- ▸Real-time X data access — unparalleled for current events / financial analysis
- ▸Tool calling API is still maturing — test thoroughly for production agentic use