Gemini 3.1 Flash Lite Preview vs GPT-5.1-Codex
Updated October 21, 2026. 11 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.
Decision reading
Pick GPT-5.1-Codex for coding: it scores 50.5 on the Vibe Coding Index against 8.1 for Gemini 3.1 Flash Lite Preview.
Pick Gemini 3.1 Flash Lite Preview when output tokens cost 6.7x less, or when a solved task costs $0.18 against $0.892.
- Shared results
- 11
- Gemini 3.1 Flash Lite Preview only
- 66
- GPT-5.1-Codex only
- 15
- Like-for-like categories
- 3 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 8.1.
1 and 2 benchmarks behind the scores
Intelligence
AA Intelligence Index
GPT-5.1-Codex
GPT-5.1-Codex leads, 23.7 against 15.6.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Gemini 3.1 Flash Lite Preview has a AA Agentic Index result, 1.6.
Directional only
Reasoning
GPQA Diamond
No call
Only Gemini 3.1 Flash Lite Preview has a GPQA Diamond result, 81.1%.
Directional only
Math
AIME
No call
Only Gemini 3.1 Flash Lite Preview has a AIME result, 83.3%.
Directional only
Knowledge
MMLU Pro
No call
Only Gemini 3.1 Flash Lite Preview has a MMLU Pro result, 86.2%.
Directional only
Web design
Design Arena: websites
GPT-5.1-Codex
GPT-5.1-Codex leads, 1162 against 1083.
Same board, both measured
Long documents
Listed context window
Gemini 3.1 Flash Lite Preview
Gemini 3.1 Flash Lite Preview takes 1.05M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 3.1 Flash Lite Preview
Gemini 3.1 Flash Lite Preview $0.0010, GPT-5.1-Codex $0.0063 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Gemini 3.1 Flash Lite Preview
Gemini 3.1 Flash Lite Preview $0.18, GPT-5.1-Codex $0.892.
Published attempt cost and pass rate
At a glance
- Coding index
- Gemini 3.1 Flash Lite Preview 8.1 from 1 benchmark, GPT-5.1-Codex 50.5 from 2 benchmarks.
- Widest category
- Web design, 15.1 points apart on average over 5 shared benchmarks.
- Widest single gap
- Design Arena: data viz: Gemini 3.1 Flash Lite Preview 1045 against GPT-5.1-Codex 1213, 21.0 points apart on a 0 to 100 scale.
- Output price
- Gemini 3.1 Flash Lite Preview $1.50 against GPT-5.1-Codex $10.00 per million output tokens, 6.7x apart.
- Context window
- Gemini 3.1 Flash Lite 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 Flash Lite Preview | Bars | GPT-5.1-Codex | Ties |
|---|---|---|---|---|
| Coding | 0 | 5 | ||
| Intelligence | 0 | 1 | ||
| Web design | 0 | 5 | ||
| All shared boards | 0 | 11 |
CodingLike-for-likeFour of these boards feed the Vibe Coding Index05
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 66.0% | Only GPT-5.1-Codex measured |
| LMArena WebDev | 1257 | 1337 | GPT-5.1-Codex |
| AA Coding Index | 34.7 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LiveCodeBench (Vals AI) | 80.1% | 85.5% | GPT-5.1-Codex |
| SWE-bench Verified (Vals AI) | 62.8% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Vibe Code Bench (Vals AI) | 0.0% | 13.1% | GPT-5.1-Codex |
| Code migration (Vals AI) | 4.6% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Terminal-Bench 2.1 (Vals AI) | 34.1% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LiveCodeBench (Artificial Analysis run) | Not measured | 84.9% | Only GPT-5.1-Codex measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 34.8% | Only GPT-5.1-Codex measured |
| Terminal-Bench | Not measured | 57.8% | Only GPT-5.1-Codex measured |
| ALE-Bench | 797.7 | 1244.9 | GPT-5.1-Codex |
| LMArena Text: coding | 1400 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: software and IT | 1413 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena WebDev: React | 1245 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena WebDev: HTML | 1276 | 1346 | GPT-5.1-Codex |
| LMArena WebDev: from an image | 1336 | Not measured | Only Gemini 3.1 Flash Lite 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 | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| AA Intelligence Index | 15.6 | 23.7 | GPT-5.1-Codex |
| Neither model has a result on the other 1 board here | |||
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| AA Agentic Index | 1.6 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Design Arena: agents building web apps | Not measured | 1018 | Only GPT-5.1-Codex measured |
| Design Arena: agents building full-stack apps | Not measured | 1086 | Only GPT-5.1-Codex measured |
| Design Arena: agents building mobile apps | Not measured | 1191 | Only GPT-5.1-Codex measured |
| Finance Agent (Vals AI) | 30.0% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Tax Agent Bench (Vals AI) | 3.1% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Legal Research Bench (Vals AI) | 3.4% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Excel Modeling Benchmark (Vals AI) | 8.6% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| τ²-Bench Telecom | Not measured | 83.0% | Only GPT-5.1-Codex measured |
| Neither model has a result on the other 30 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| GPQA Diamond | 81.1% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| MMMU Pro (Vals AI) | 82.5% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 86.0% | Only GPT-5.1-Codex measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 25.7% | Only GPT-5.1-Codex measured |
| LMArena Text: hard prompts | 1407 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: expert | 1398 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: hard prompts in English | 1403 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: diagrams | 1242 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: homework | 1271 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Neither model has a result on the other 12 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index5 boards, none shared
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| AIME | 83.3% | Not measured | Only Gemini 3.1 Flash Lite 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 |
| LMArena Text: math | 1428 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: mathematical work | 1417 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Neither model has a result on the other 8 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| MMLU Pro | 86.2% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LegalBench (Vals AI) | 83.8% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| CaseLaw (Vals AI) | 55.0% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| CorpFin (Vals AI) | 59.4% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| TaxEval (Vals AI) | 71.8% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| MortgageTax (Vals AI) | 68.0% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| MedCode (Vals AI) | 47.6% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| MMLU Pro (Artificial Analysis run) | Not measured | 86.0% | Only GPT-5.1-Codex measured |
| LMArena Text: science | 1425 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: medicine and healthcare | 1428 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: legal and government | 1418 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: business and finance | 1389 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Neither model has a result on the other 5 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index05
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| Design Arena: websites | 1083 | 1162 | GPT-5.1-Codex |
| Design Arena: UI components | 1071 | 1237 | GPT-5.1-Codex |
| Design Arena: game dev | 1029 | 1138 | GPT-5.1-Codex |
| Design Arena: data viz | 1045 | 1213 | GPT-5.1-Codex |
| Design Arena: 3D | 1048 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Design Arena: all code categories | 1072 | 1153 | GPT-5.1-Codex |
| Design Arena: SVG | 1052 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Design Arena: ASCII art | 1166 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Neither model has a result on the other 1 board here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index30 boards, none shared
| Benchmark | Gemini 3.1 Flash Lite Preview | GPT-5.1-Codex | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 49.5% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| MedScribe (Vals AI) | 63.9% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Vals Multimodal Index | 41.4% | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| IFBench | Not measured | 70.0% | Only GPT-5.1-Codex measured |
| Long context reasoning (AA-LCR) | Not measured | 69.3% | Only GPT-5.1-Codex measured |
| LMArena Text | 1416 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: instruction following | 1377 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: creative writing | 1401 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision | 1240 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: English | 1414 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: non-English | 1410 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: Chinese | 1460 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: German | 1430 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: Japanese | 1413 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: Korean | 1392 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: French | 1424 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: Spanish | 1421 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: Russian | 1420 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: Polish | 1443 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: multi-turn | 1417 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: longer queries | 1394 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: writing and language | 1408 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Text: entertainment and media | 1386 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: English | 1232 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: Chinese | 1278 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: reading text | 1246 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: humor | 1266 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: captioning | 1259 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: recognizing things | 1308 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| LMArena Vision: creative writing | 1248 | Not measured | Only Gemini 3.1 Flash Lite Preview measured |
| Neither model has a result on the other 16 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3.1 Flash Lite 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 Flash Lite Preview costs less
Repository review
50K input + 3K output tokens
Gemini 3.1 Flash Lite Preview costs less
Agent loop
200K input + 10K output tokens
Gemini 3.1 Flash Lite 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 | Google Gemini 3.1 Flash Lite Preview | OpenAI GPT-5.1-Codex |
|---|---|---|
| Maker | OpenAI | |
| Weights | No public weights listed | No public weights listed |
| Released | March 3, 2026 | November 13, 2025 |
| Context window | 1.05M | 400K |
| Input $/Mtok | $0.25 | $1.25 |
| Output $/Mtok | $1.50 | $10.00 |
| Coding index | 8.1 | 50.5 |
| Independent measurements behind it | 1 | 2 |
| Cost per solved task | $0.18 | $0.892 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 3.1 Flash Lite 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 8.1 for Gemini 3.1 Flash Lite Preview. Pick Gemini 3.1 Flash Lite Preview when output tokens cost 6.7x less, or when a solved task costs $0.18 against $0.892.
Which is cheaper, Gemini 3.1 Flash Lite Preview or GPT-5.1-Codex?
Gemini 3.1 Flash Lite Preview costs $0.25 per million input tokens and $1.50 per million output tokens; GPT-5.1-Codex costs $1.25 and $10.00. Per solved SWE-bench Verified task, Gemini 3.1 Flash Lite Preview costs $0.18 and GPT-5.1-Codex $0.892.
Which has the bigger context window, Gemini 3.1 Flash Lite Preview or GPT-5.1-Codex?
Gemini 3.1 Flash Lite Preview, with 1.05M tokens against 400K.
How many benchmarks is the Gemini 3.1 Flash Lite Preview vs GPT-5.1-Codex comparison based on?
11 benchmarks have a result for both models as of October 21, 2026. Gemini 3.1 Flash Lite 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.