GPT-5.1 vs GPT-5.1 Codex for coding
GPT-5.1 is the stronger coder of the two on benchmarks, but GPT-5.1 Codex can be the better pick when cost, speed, or context window matter more. Below: a side-by-side spec table and exactly when to pick each.
At a glance
| Spec | GPT-5.1 | GPT-5.1 Codex |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Released | Nov 2025 | Nov 2025 |
| SWE-bench Verified | 76% | 75% |
| HumanEval | 95% | 95% |
| MMLU | 89% | 88% |
| Context window | 400K | 400K |
| Max output | 128K | 128K |
| Input price (per 1M) | $1.25 | $1.25 |
| Output price (per 1M) | $10 | $10 |
| Price tier | Mid | Mid |
| Speed | Medium | Medium |
| Hosting | Closed/API | Closed/API |
| Modality | Multimodal (vision) | Text + Vision |
| Knowledge cutoff | Oct 2025 | Oct 2025 |
Pick GPT-5.1 if…
- It scores higher on SWE-bench Verified (76% vs 75%), the best proxy for real-world coding.
- It's tuned for default daily-driver coding agent with adaptive reasoning and warmer chat tone.
Pick GPT-5.1 Codex if…
- It's tuned for codex CLI and long-horizon coding agents; engineered for terminal-driven workflows.
GPT-5.1 vs GPT-5.1 Codex: which is better for coding?
GPT-5.1 is the stronger coder of the two on benchmarks, but GPT-5.1 Codex can be the better pick when cost, speed, or context window matter more. See the full spec table for SWE-bench, HumanEval, MMLU, context window, and pricing on both. Benchmarks are a directional signal, not a guarantee for your codebase — the most reliable test is running both on a real task you care about.
Compare these head-to-head with live data, or build a full stack around your pick — Flowpicker shows compatibility and monthly cost.
Open the live comparison →More comparisons
See the full model leaderboard ranked by SWE-bench, HumanEval, and MMLU.