Gemini 3.1 Pro Preview vs GPT-5.1-Codex
Updated October 21, 2026. 21 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
vs boards won of 21 shared
Decision reading
Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 35.3 for Gemini 3.1 Pro Preview.
Pick Gemini 3.1 Pro Preview when the context window is larger, 1.05M against 400K tokens, or when what matters is LMArena WebDev or LiveCodeBench (Vals AI), where it leads.
Model AGemini 3.1 Pro PreviewGoogle35.3/1001 independent benchmark$0.99 per solved taskModel BGPT-5.1-CodexOpenAI50.5/1002 independent benchmarks$0.892 per solved task
- Shared results
- 21
- Gemini 3.1 Pro Preview only
- 110
- GPT-5.1-Codex only
- 5
- Like-for-like categories
- 6 of 9
Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.
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, four public coding benchmarks
GPT-5.1-Codex
GPT-5.1-Codex scores 50.5 against 35.3.
1 and 2 benchmarks behind the scores
Intelligence
AA Intelligence Index
Gemini 3.1 Pro Preview
Gemini 3.1 Pro Preview leads, 29.7 against 23.7.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Gemini 3.1 Pro Preview has a AA Agentic Index result, 8.2.
Directional only
Reasoning
GPQA Diamond
No call
Only Gemini 3.1 Pro Preview has a GPQA Diamond result, 95.5%.
Directional only
Math
AIME
No call
Only Gemini 3.1 Pro Preview has a AIME result, 98.1%.
Directional only
Knowledge
MMLU Pro
No call
Only Gemini 3.1 Pro Preview has a MMLU Pro result, 91.0%.
Directional only
Web design
Design Arena: websites
Gemini 3.1 Pro Preview
Gemini 3.1 Pro Preview leads, 1234 against 1162.
Same board, both measured
Long documents
Listed context window
Gemini 3.1 Pro Preview
Gemini 3.1 Pro Preview takes 1.05M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5.1-Codex
Gemini 3.1 Pro Preview $0.0080, GPT-5.1-Codex $0.0063 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
GPT-5.1-Codex
Gemini 3.1 Pro Preview $0.99, GPT-5.1-Codex $0.892.
Published attempt cost and pass rate
At a glance
- Coding index
- Gemini 3.1 Pro Preview 35.3 from 1 benchmark, GPT-5.1-Codex 50.5 from 2 benchmarks.
- Widest category
- Coding, 15.1 points apart on average over 7 shared benchmarks.
- Widest single gap
- LMArena WebDev: HTML: Gemini 3.1 Pro Preview 1490 against GPT-5.1-Codex 1346, 23.9 points apart on a 0 to 100 scale.
- Output price
- Gemini 3.1 Pro Preview $12.00 against GPT-5.1-Codex $10.00 per million output tokens, 1.2x apart.
- Context window
- Gemini 3.1 Pro Preview takes 1.05M tokens, GPT-5.1-Codex 400K.
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 | Gemini 3.1 Pro Preview | Bars | GPT-5.1-Codex | Ties |
|---|---|---|---|---|
| Coding | 6 | 1 | ||
| Intelligence | 1 | 0 | ||
| Agentic work | 2 | 2 | ||
| Reasoning | 2 | 0 | ||
| Web design | 3 | 2 | ||
| General | 2 | 0 | ||
| All shared boards | 16 | 5 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index61
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 66.0% | Only GPT-5.1-Codex measured |
| LMArena WebDev | 1447 | 1337 | Gemini 3.1 Pro Preview |
| AA Coding Index | 68.8 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LiveCodeBench (Vals AI) | 88.5% | 85.5% | Gemini 3.1 Pro Preview |
| SWE-bench Verified (Vals AI) | 78.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Terminal-Bench 4 (Vals AI) | 2.5% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Vibe Code Bench (Vals AI) | 32.0% | 13.1% | Gemini 3.1 Pro Preview |
| Code migration (Vals AI) | 17.3% | Not measured | Only Gemini 3.1 Pro Preview measured |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| IOI (Vals AI) | 51.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Terminal-Bench 2.1 (Vals AI) | 70.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Vibe Code Bench 1-100 (Vals AI) | 6.7% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LiveCodeBench (Artificial Analysis run) | Not measured | 84.9% | Only GPT-5.1-Codex measured |
| SciCode | 58.7% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Terminal-Bench Hard (Artificial Analysis run) | 53.8% | 34.8% | Gemini 3.1 Pro Preview |
| Terminal-Bench | 80.2% | 57.8% | Gemini 3.1 Pro Preview |
| GSO-Bench | 22.6% | Not measured | Only Gemini 3.1 Pro Preview measured |
| WeirdML | 72.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MirrorCode | 8.9% | Not measured | Only Gemini 3.1 Pro Preview measured |
| ALE-Bench | 1160.6 | 1244.9 | GPT-5.1-Codex |
| LMArena Text: coding | 1484 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: software and IT | 1487 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena WebDev: React | 1438 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena WebDev: HTML | 1490 | 1346 | Gemini 3.1 Pro Preview |
| LMArena WebDev: from an image | 1481 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 13 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| AA Intelligence Index | 29.7 | 23.7 | Gemini 3.1 Pro Preview |
| Neither model has a result on the other 1 board here | |||
Agentic workLike-for-likePublic boards, shown as published, kept out of the index22
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| AA Agentic Index | 8.2 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: agents building web apps | 1125 | 1018 | Gemini 3.1 Pro Preview |
| Design Arena: agents building full-stack apps | 1068 | 1086 | GPT-5.1-Codex |
| Design Arena: agents building mobile apps | 1094 | 1191 | GPT-5.1-Codex |
| Design Arena: agents building Android apps | 1055 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: agents building Godot games | 1236 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: agents building games | 1114 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: HTML slides | 1153 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: PowerPoint slides | 1064 | Not measured | Only Gemini 3.1 Pro Preview measured |
| SREBench (Vals AI) | 0.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Finance Agent (Vals AI) | 43.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Tax Agent Bench (Vals AI) | 9.3% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Legal Research Bench (Vals AI) | 20.7% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Excel Modeling Benchmark (Vals AI) | 52.6% | Not measured | Only Gemini 3.1 Pro Preview measured |
| BioMysteryBench (Vals AI) | 60.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Terminal-Bench-Science (Vals AI) | 1.4% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Vals Science Index | 27.4% | Not measured | Only Gemini 3.1 Pro Preview measured |
| τ²-Bench Telecom | 95.6% | 83.0% | Gemini 3.1 Pro Preview |
| APEX-Agents | 35.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| METR time horizons | 77.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| BALROG | 57.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| DeepResearch Bench | 47.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| PostTrainBench | 22.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Vending-Bench 2 | $911 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 15 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| GPQA Diamond | 95.5% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MysteryMechanism (Vals AI) | 20.7% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MMMU Pro (Vals AI) | 88.2% | Not measured | Only Gemini 3.1 Pro Preview measured |
| GPQA Diamond (Artificial Analysis run) | 94.1% | 86.0% | Gemini 3.1 Pro Preview |
| Humanity's Last Exam (Artificial Analysis run) | 47.0% | 25.7% | Gemini 3.1 Pro Preview |
| GPQA Diamond (Epoch AI run) | 94.4% | Not measured | Only Gemini 3.1 Pro Preview measured |
| ARC-AGI | 98.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| ARC-AGI-2 | 77.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| SimpleBench | 79.6% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Chess puzzles | 51.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Mystery game puzzles | 34.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| EBR-bench | 14.3% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: hard prompts | 1485 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: expert | 1483 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: hard prompts in English | 1480 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: diagrams | 1311 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: homework | 1316 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 4 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| AIME | 98.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| AA Math Index | Not measured | 95.7 | Only GPT-5.1-Codex measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 95.7% | Only GPT-5.1-Codex measured |
| OTIS Mock AIME | 95.6% | Not measured | Only Gemini 3.1 Pro Preview measured |
| FrontierMath, tiers 1 to 3 | 59.6% | Not measured | Only Gemini 3.1 Pro Preview measured |
| FrontierMath, tier 4 | 26.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| ProofBench | 26.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: math | 1486 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: mathematical work | 1478 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 4 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index14 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| MMLU Pro | 91.0% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LegalBench (Vals AI) | 87.4% | Not measured | Only Gemini 3.1 Pro Preview measured |
| CaseLaw (Vals AI) | 64.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| CorpFin (Vals AI) | 64.5% | Not measured | Only Gemini 3.1 Pro Preview measured |
| TaxEval (Vals AI) | 72.9% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MortgageTax (Vals AI) | 69.4% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MedQA (Vals AI) | 96.4% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MedCode (Vals AI) | 59.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MMLU Pro (Artificial Analysis run) | Not measured | 86.0% | Only GPT-5.1-Codex measured |
| SimpleQA Verified | 73.5% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: science | 1497 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: medicine and healthcare | 1486 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: legal and government | 1487 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: business and finance | 1459 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 3 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index32
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| Design Arena: websites | 1234 | 1162 | Gemini 3.1 Pro Preview |
| Design Arena: UI components | 1226 | 1237 | GPT-5.1-Codex |
| Design Arena: game dev | 1203 | 1138 | Gemini 3.1 Pro Preview |
| Design Arena: data viz | 1209 | 1213 | GPT-5.1-Codex |
| Design Arena: 3D | 1234 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: all code categories | 1231 | 1153 | Gemini 3.1 Pro Preview |
| Design Arena: SVG | 1285 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Design Arena: ASCII art | 1270 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| Public Benefits Bench (Vals AI) | 53.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| SAGE (Vals AI) | 48.7% | Not measured | Only Gemini 3.1 Pro Preview measured |
| MedScribe (Vals AI) | 76.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Vals Multimodal Index | 56.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| IFBench | 77.1% | 70.0% | Gemini 3.1 Pro Preview |
| Long context reasoning (AA-LCR) | 82.0% | 69.3% | Gemini 3.1 Pro Preview |
| DTBench | 97.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMCA | 53.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| CL-bench | 20.8% | Not measured | Only Gemini 3.1 Pro Preview measured |
| Furniture assembly | 26.7% | Not measured | Only Gemini 3.1 Pro Preview measured |
| ExploitBench | 26.1% | Not measured | Only Gemini 3.1 Pro Preview measured |
| CL-bench Life | 16.9% | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text | 1480 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: instruction following | 1466 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: creative writing | 1482 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision | 1296 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: English | 1478 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: non-English | 1476 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: Chinese | 1527 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: German | 1490 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: Japanese | 1491 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: Korean | 1455 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: French | 1487 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: Spanish | 1481 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: Russian | 1497 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: Polish | 1498 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: multi-turn | 1487 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: longer queries | 1482 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: writing and language | 1481 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Text: entertainment and media | 1465 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: English | 1287 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: Chinese | 1364 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: reading text | 1304 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: humor | 1322 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: captioning | 1345 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: recognizing things | 1330 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Vision: creative writing | 1324 | Not measured | Only Gemini 3.1 Pro Preview measured |
| LMArena Document | 1444 | Not measured | Only Gemini 3.1 Pro Preview measured |
| Neither model has a result on the other 8 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.1-Codex | 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
Gemini 3.1 Pro Preview$0.0080Fits in one request
GPT-5.1-Codex$0.0063Fits in one request
GPT-5.1-Codex costs less
Repository review
50K input + 3K output tokens
Gemini 3.1 Pro Preview$0.136Fits in one request
GPT-5.1-Codex$0.092Fits in one request
GPT-5.1-Codex costs less
Agent loop
200K input + 10K output tokens
Gemini 3.1 Pro Preview$0.520Fits in one request
GPT-5.1-Codex$0.350Fits in one request
GPT-5.1-Codex 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 | Google Gemini 3.1 Pro Preview | OpenAI GPT-5.1-Codex |
|---|---|---|
| Maker | OpenAI | |
| Weights | No public weights listed | No public weights listed |
| Released | February 19, 2026 | November 13, 2025 |
| Context window | 1.05M | 400K |
| Input $/Mtok | $2.00 | $1.25 |
| Output $/Mtok | $12.00 | $10.00 |
| Coding index | 35.3 | 50.5 |
| Independent measurements behind it | 1 | 2 |
| Cost per solved task | $0.99 | $0.892 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 3.1 Pro Preview better than GPT-5.1-Codex for coding?
Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 35.3 for Gemini 3.1 Pro Preview. Pick Gemini 3.1 Pro Preview when the context window is larger, 1.05M against 400K tokens, or when what matters is LMArena WebDev or LiveCodeBench (Vals AI), where it leads.
Which is cheaper, Gemini 3.1 Pro Preview or GPT-5.1-Codex?
Gemini 3.1 Pro Preview costs $2.00 per million input tokens and $12.00 per million output tokens; GPT-5.1-Codex costs $1.25 and $10.00. Per solved SWE-bench Verified task, Gemini 3.1 Pro Preview costs $0.99 and GPT-5.1-Codex $0.892.
Which has the bigger context window, Gemini 3.1 Pro Preview or GPT-5.1-Codex?
Gemini 3.1 Pro Preview, with 1.05M tokens against 400K.
How many benchmarks is the Gemini 3.1 Pro Preview vs GPT-5.1-Codex comparison based on?
21 benchmarks have a result for both models as of October 21, 2026. Gemini 3.1 Pro Preview's coding index rests on 1 independent benchmark and GPT-5.1-Codex's on 2. Where only one model has a result, the page says so instead of naming a winner.