Model comparison
GPT-5.1-Codex vs GPT-6.1 Sol
GPT-6.1 Sol is the stronger model overall, scoring 65.6 to 38.6 on the Noometry Index.
Last verified . 2 shared benchmarks.
Summary
- They share 2 benchmarks with published results for both. GPT-5.1-Codex scores higher in 0 categories and GPT-6.1 Sol in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-6.1 Sol leads 93.7 to 30.3.
- The biggest single-benchmark swing is ProofBench: 9% for GPT-5.1-Codex and 99% for GPT-6.1 Sol.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $2 / $10 for GPT-6.1 Sol.
- GPT-6.1 Sol accepts more context: 1.05M tokens versus 400K.
Side by side
| GPT-5.1-Codex | GPT-6.1 Sol | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.6 | 65.6 |
| Released | 2025-11-12 | 2026-09-29 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 1.05M |
| Max output | 128K | 128K |
| Input $ / M tokens | $1.25 | $2 |
| Output $ / M tokens | $10 | $10 |
| Results tracked | 6 | 34 |
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Category by category
Coding GPT-6.1 Sol leads
GPT-5.1-Codex: 41.9 (#116), GPT-6.1 Sol: 63.2 (#8)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| LMArena WebDev | 1337 | 1755 |
| DeepSWE | — | 75.2% |
| FrontierCode | — | 50.2% |
| SWE-bench Verified (bash only) | 66% | — |
| SciCode | — | 55.8% |
| LMArena Coding | — | 1487 |
| ALE-Bench | 1,245 | — |
Agentic & Tool Use GPT-6.1 Sol leads
GPT-5.1-Codex: 38.0 (#33), GPT-6.1 Sol: 39.6 (#26)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| APEX-Agents | — | 60% |
| GDP.pdf | — | 32% |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 81.9 (#2)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| ARC-AGI-2 | — | 94.2% |
| NYT Connections (extended) | — | 95.5% |
| ARC-AGI-1 | — | 98.5% |
| CritPt | — | 31.7% |
| Chess Puzzles | — | 61% |
| EBR-Bench | — | 54.3% |
| LMArena Hard Prompts | — | 1466 |
| Mystery Game Puzzles | — | 80% |
| Epoch Capabilities Index | — | 166.09 |
Math GPT-6.1 Sol leads
GPT-5.1-Codex: 30.3 (#235), GPT-6.1 Sol: 93.7 (#1)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| ProofBench | 9% | 99% |
| FrontierMath (Tiers 1-3) | — | 93.7% |
| FrontierMath Tier 4 | — | 100% |
| OTIS Mock AIME 2024-2025 | — | 100% |
| LMArena Math | — | 1464 |
Knowledge Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 71.8 (#4)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| GPQA Diamond | — | 95.4% |
| SimpleQA Verified | — | 73.9% |
| LMArena Expert | — | 1502 |
Multimodal Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 52.7 (#5)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| LMArena Vision | — | 1288 |
| Furniture Assembly | — | 80% |
Multilingual Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 54.3 (#46)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| LMArena Non-English | — | 1438 |
| LMArena Chinese | — | 1477 |
| LMArena Russian | — | 1455 |
Instruction Following Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 77.0 (#29)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| LMArena Instruction Following | — | 1468 |
Long Context Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 44.9 (#54)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| LMArena Longer Query | — | 1465 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, GPT-6.1 Sol: 63.6 (#63)
| Benchmark | GPT-5.1-Codex | GPT-6.1 Sol |
|---|---|---|
| LMArena Text | — | 1447 |
| LMArena Creative Writing | — | 1432 |
| LMArena Multi-Turn | — | 1449 |
Frequently asked questions
Is GPT-5.1-Codex better than GPT-6.1 Sol?
GPT-6.1 Sol is the stronger model overall, scoring 65.6 to 38.6 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or GPT-6.1 Sol?
GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-6.1 Sol lists at $2 and $10.
Is GPT-5.1-Codex or GPT-6.1 Sol better for coding?
GPT-6.1 Sol scores higher on coding benchmarks: 63.2 versus 41.9 in the Noometry coding category.
Which has the bigger context window?
GPT-6.1 Sol does, with 1.05M tokens against 400K.
How many benchmarks do GPT-5.1-Codex and GPT-6.1 Sol share?
2 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-6.1 Sol has 34.