GPT-5.1-Codex vs Step 5 Preview
Step 5 Preview leads GPT-5.1-Codex on coding, 61.1 to 15.3 on the Vibe Coding Index, and Step 5 Preview costs 3.7x less per output token ($2.70 vs $10.00 per million). Updated October 21, 2026; 6 benchmarks have a result for both.
GPT-5.1-Codex or Step 5 Preview: which to pick
Pick Step 5 Preview for coding: it scores 61.1 on the Vibe Coding Index against 15.3 for GPT-5.1-Codex.
GPT-5.1-Codex is neither cheaper nor larger in context, and leads no benchmark both models were measured on.
- Shared results
- 6
- GPT-5.1-Codex only
- 20
- Step 5 Preview only
- 55
- Like-for-like categories
- 4 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
Step 5 Preview
Step 5 Preview scores 61.1 against 15.3.
2 and 4 benchmarks behind the scores
Intelligence
AA Intelligence Index
Step 5 Preview
Step 5 Preview leads, 43.7 against 23.7.
Same board, both measured
Web design
Design Arena: websites
No call
Only GPT-5.1-Codex has a Design Arena: websites result, 1162.
Directional only
Long documents
Listed context window
Step 5 Preview
Step 5 Preview takes 1.05M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 5 Preview
GPT-5.1-Codex $0.0063, Step 5 Preview $0.0024 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only GPT-5.1-Codex has the number, $0.892.
Directional only
At a glance
- Coding index
- GPT-5.1-Codex 15.3 from 2 benchmarks, Step 5 Preview 61.1 from 4 benchmarks.
- Widest category
- Coding, 41.7 points apart on average over 3 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): GPT-5.1-Codex 13.1% against Step 5 Preview 70.4%, 57.3 points apart on a 0 to 100 scale.
- Output price
- GPT-5.1-Codex $10.00 against Step 5 Preview $2.70 per million output tokens, 3.7x apart.
- Context window
- GPT-5.1-Codex takes 400K tokens, Step 5 Preview 1.05M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | GPT-5.1-Codex | Bars | Step 5 Preview | Ties |
|---|---|---|---|---|
| Coding | 0 | 3 | ||
| Intelligence | 0 | 1 | ||
| Reasoning | 0 | 1 | ||
| General | 0 | 1 | ||
| All shared boards | 0 | 6 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index03
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| SWE-bench Verified | 66.0% | Not measured | Only GPT-5.1-Codex measured |
| LiveBench coding | Not measured | 85.6% | Only Step 5 Preview measured |
| LMArena WebDev | 1337 | 1567 | Step 5 Preview |
| LiveCodeBench (Vals AI) | 85.5% | Not measured | Only GPT-5.1-Codex measured |
| Terminal-Bench 4 (Vals AI) | Not measured | 31.8% | Only Step 5 Preview measured |
| Vibe Code Bench (Vals AI) | 13.1% | 70.4% | Step 5 Preview |
| Code migration (Vals AI) | Not measured | 39.0% | Only Step 5 Preview measured |
| IOI (Vals AI) | Not measured | 38.1% | Only Step 5 Preview measured |
| SWE-bench Multimodal (Vals AI) | Not measured | 40.8% | Only Step 5 Preview measured |
| LiveCodeBench (Artificial Analysis run) | 84.9% | Not measured | Only GPT-5.1-Codex measured |
| SciCode | Not measured | 58.9% | Only Step 5 Preview measured |
| Terminal-Bench Hard (Artificial Analysis run) | 34.8% | Not measured | Only GPT-5.1-Codex measured |
| Terminal-Bench | 57.8% | Not measured | Only GPT-5.1-Codex measured |
| ALE-Bench | 1244.9 | Not measured | Only GPT-5.1-Codex measured |
| LMArena Text: coding | Not measured | 1485 | Only Step 5 Preview measured |
| LMArena Text: software and IT | Not measured | 1473 | Only Step 5 Preview measured |
| LMArena WebDev: React | Not measured | 1583 | Only Step 5 Preview measured |
| LMArena WebDev: HTML | 1346 | 1556 | Step 5 Preview |
| LMArena WebDev: from an image | Not measured | 1550 | Only Step 5 Preview measured |
| Neither model has a result on the other 20 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| AA Intelligence Index | 23.7 | 43.7 | Step 5 Preview |
| Neither model has a result on the other 1 board here | |||
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index15 boards, none shared
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1018 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: agents building full-stack apps | 1086 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: agents building mobile apps | 1191 | Not measured | Only GPT-5.1-Codex measured |
| LiveBench research | Not measured | 72.8% | Only Step 5 Preview measured |
| LiveBench browser | Not measured | 24.0% | Only Step 5 Preview measured |
| LiveBench long agentic | Not measured | 27.5% | Only Step 5 Preview measured |
| SREBench (Vals AI) | Not measured | 0.4% | Only Step 5 Preview measured |
| Finance Agent (Vals AI) | Not measured | 50.7% | Only Step 5 Preview measured |
| Tax Agent Bench (Vals AI) | Not measured | 27.3% | Only Step 5 Preview measured |
| Legal Research Bench (Vals AI) | Not measured | 40.4% | Only Step 5 Preview measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 57.1% | Only Step 5 Preview measured |
| BioMysteryBench (Vals AI) | Not measured | 67.4% | Only Step 5 Preview measured |
| Terminal-Bench-Science (Vals AI) | Not measured | 2.9% | Only Step 5 Preview measured |
| Vals Science Index | Not measured | 29.6% | Only Step 5 Preview measured |
| τ²-Bench Telecom | 83.0% | Not measured | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 26 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench reasoning | Not measured | 83.8% | Only Step 5 Preview measured |
| MysteryMechanism (Vals AI) | Not measured | 18.5% | Only Step 5 Preview measured |
| GPQA Diamond (Artificial Analysis run) | 86.0% | Not measured | Only GPT-5.1-Codex measured |
| Humanity's Last Exam (Artificial Analysis run) | 25.7% | 46.5% | Step 5 Preview |
| LMArena Text: hard prompts | Not measured | 1461 | Only Step 5 Preview measured |
| LMArena Text: expert | Not measured | 1485 | Only Step 5 Preview measured |
| LMArena Text: hard prompts in English | Not measured | 1454 | Only Step 5 Preview measured |
| LMArena Vision: diagrams | Not measured | 1308 | Only Step 5 Preview measured |
| LMArena Vision: homework | Not measured | 1265 | Only Step 5 Preview measured |
| Neither model has a result on the other 13 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index5 boards, none shared
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| AA Math Index | 95.7 | Not measured | Only GPT-5.1-Codex measured |
| AIME 2025 (Artificial Analysis run) | 95.7% | Not measured | Only GPT-5.1-Codex measured |
| ProofBench | Not measured | 42.0% | Only Step 5 Preview measured |
| LMArena Text: math | Not measured | 1458 | Only Step 5 Preview measured |
| LMArena Text: mathematical work | Not measured | 1460 | Only Step 5 Preview measured |
| Neither model has a result on the other 8 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index5 boards, none shared
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| MMLU Pro (Artificial Analysis run) | 86.0% | Not measured | Only GPT-5.1-Codex measured |
| LMArena Text: science | Not measured | 1454 | Only Step 5 Preview measured |
| LMArena Text: medicine and healthcare | Not measured | 1439 | Only Step 5 Preview measured |
| LMArena Text: legal and government | Not measured | 1437 | Only Step 5 Preview measured |
| LMArena Text: business and finance | Not measured | 1435 | Only Step 5 Preview measured |
| Neither model has a result on the other 13 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| Design Arena: websites | 1162 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: UI components | 1237 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: game dev | 1138 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: data viz | 1213 | Not measured | Only GPT-5.1-Codex measured |
| Design Arena: all code categories | 1152 | Not measured | Only GPT-5.1-Codex measured |
| LiveBench design | Not measured | 76.9% | Only Step 5 Preview measured |
| Neither model has a result on the other 3 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| LiveBench data analysis | Not measured | 63.5% | Only Step 5 Preview measured |
| Public Benefits Bench (Vals AI) | Not measured | 58.1% | Only Step 5 Preview measured |
| IFBench | 70.0% | Not measured | Only GPT-5.1-Codex measured |
| Long context reasoning (AA-LCR) | 69.3% | 88.3% | Step 5 Preview |
| LMArena Text | Not measured | 1440 | Only Step 5 Preview measured |
| LMArena Text: instruction following | Not measured | 1438 | Only Step 5 Preview measured |
| LMArena Text: creative writing | Not measured | 1409 | Only Step 5 Preview measured |
| LMArena Vision | Not measured | 1265 | Only Step 5 Preview measured |
| LMArena Text: English | Not measured | 1447 | Only Step 5 Preview measured |
| LMArena Text: non-English | Not measured | 1428 | Only Step 5 Preview measured |
| LMArena Text: Chinese | Not measured | 1500 | Only Step 5 Preview measured |
| LMArena Text: Japanese | Not measured | 1383 | Only Step 5 Preview measured |
| LMArena Text: French | Not measured | 1438 | Only Step 5 Preview measured |
| LMArena Text: Spanish | Not measured | 1441 | Only Step 5 Preview measured |
| LMArena Text: Russian | Not measured | 1433 | Only Step 5 Preview measured |
| LMArena Text: multi-turn | Not measured | 1437 | Only Step 5 Preview measured |
| LMArena Text: longer queries | Not measured | 1449 | Only Step 5 Preview measured |
| LMArena Text: writing and language | Not measured | 1425 | Only Step 5 Preview measured |
| LMArena Text: entertainment and media | Not measured | 1412 | Only Step 5 Preview measured |
| LMArena Vision: English | Not measured | 1290 | Only Step 5 Preview measured |
| LMArena Vision: reading text | Not measured | 1282 | Only Step 5 Preview measured |
| Neither model has a result on the other 25 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | GPT-5.1-Codex | Step 5 Preview | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Step 5 Preview costs less
Repository review
50K input + 3K output tokens
Step 5 Preview costs less
Agent loop
200K input + 10K output tokens
Step 5 Preview costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | OpenAI GPT-5.1-Codex | StepFun Step 5 Preview |
|---|---|---|
| Maker | OpenAI | StepFun |
| Weights | No public weights listed | Open weights |
| Released | November 13, 2025 | October 8, 2026 |
| Context window | 400K | 1.05M |
| Input $/Mtok | $1.25 | $1.00 |
| Output $/Mtok | $10.00 | $2.70 |
| Coding index | 15.3 | 61.1 |
| Independent measurements behind it | 2 | 4 |
| Cost per solved task | $0.892 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.1-Codex better than Step 5 Preview for coding?
Pick Step 5 Preview for coding: it scores 61.1 on the Vibe Coding Index against 15.3 for GPT-5.1-Codex. GPT-5.1-Codex is neither cheaper nor larger in context, and leads no benchmark both models were measured on.
Which is cheaper, GPT-5.1-Codex or Step 5 Preview?
GPT-5.1-Codex costs $1.25 per million input tokens and $10.00 per million output tokens; Step 5 Preview costs $1.00 and $2.70. Cost per solved task is known for GPT-5.1-Codex only.
Which has the bigger context window, GPT-5.1-Codex or Step 5 Preview?
Step 5 Preview, with 1.05M tokens against 400K.
How many benchmarks is the GPT-5.1-Codex vs Step 5 Preview comparison based on?
6 benchmarks have a result for both models as of October 21, 2026. GPT-5.1-Codex's coding index rests on 2 independent benchmarks and Step 5 Preview's on 4. Where only one model has a result, the page says so instead of naming a winner.