Model comparison
GPT-5.1-Codex vs Step 5 Preview
Step 5 Preview is the stronger model overall, scoring 47.9 to 38.6 on the Noometry Index.
Last verified . 2 shared benchmarks.
StepFunSummary
- They share 2 benchmarks with published results for both. GPT-5.1-Codex scores higher in 0 categories and Step 5 Preview in 2 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in math, where Step 5 Preview leads 46.1 to 30.3.
- The biggest single-benchmark swing is ProofBench: 9% for GPT-5.1-Codex and 42% for Step 5 Preview.
- Step 5 Preview is cheaper at $1 / $2.70 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- Step 5 Preview accepts more context: 1.02M tokens versus 400K.
Side by side
| GPT-5.1-Codex | Step 5 Preview | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 38.6 | 47.9 |
| Released | 2025-11-12 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 1.02M |
| Max output | 128K | 66K |
| Input $ / M tokens | $1.25 | $1 |
| Output $ / M tokens | $10 | $2.70 |
| Results tracked | 6 | 18 |
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Category by category
Coding Step 5 Preview leads
GPT-5.1-Codex: 41.9 (#116), Step 5 Preview: 51.8 (#36)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1337 | 1564 |
| SWE-bench Verified (bash only) | 66% | — |
| SciCode | — | 58.9% |
| LMArena Coding | — | 1480 |
| ALE-Bench | 1,245 | — |
Agentic & Tool Use Not comparable
GPT-5.1-Codex: 38.0 (#33), Step 5 Preview: —
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 40.0 (#57)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| CritPt | — | 20.9% |
| LMArena Hard Prompts | — | 1465 |
Math Step 5 Preview leads
GPT-5.1-Codex: 30.3 (#235), Step 5 Preview: 46.1 (#72)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| ProofBench | 9% | 42% |
| LMArena Math | — | 1470 |
Knowledge Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 41.2 (#112)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena Expert | — | 1470 |
Multimodal Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 41.0 (#41)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena Vision | — | 1267 |
Multilingual Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 53.8 (#54)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena Non-English | — | 1432 |
| LMArena Chinese | — | 1519 |
| LMArena Russian | — | 1436 |
| LMArena Spanish | — | 1439 |
Instruction Following Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 76.0 (#50)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena Instruction Following | — | 1444 |
Long Context Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 44.5 (#64)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | — | 1455 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, Step 5 Preview: 62.8 (#71)
| Benchmark | GPT-5.1-Codex | Step 5 Preview |
|---|---|---|
| LMArena Text | — | 1442 |
| LMArena Creative Writing | — | 1410 |
| LMArena Multi-Turn | — | 1447 |
Frequently asked questions
Is GPT-5.1-Codex better than Step 5 Preview?
Step 5 Preview is the stronger model overall, scoring 47.9 to 38.6 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or Step 5 Preview?
Step 5 Preview is cheaper. It lists at $1 per million input tokens and $2.70 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is GPT-5.1-Codex or Step 5 Preview better for coding?
Step 5 Preview scores higher on coding benchmarks: 51.8 versus 41.9 in the Noometry coding category.
Which has the bigger context window?
Step 5 Preview does, with 1.02M tokens against 400K.
How many benchmarks do GPT-5.1-Codex and Step 5 Preview share?
2 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and Step 5 Preview has 18.