Gemini 3 Flash Preview vs GPT-5.6 Luna
GPT-5.6 Luna leads Gemini 3 Flash Preview on coding, 58.0 to 43.7 on the Vibe Coding Index, and GPT-5.6 Luna costs 2.5x less per output token ($1.20 vs $3.00 per million). Updated October 22, 2026; 47 benchmarks have a result for both.
vs boards won of 47 shared, 2 tied
Gemini 3 Flash Preview or GPT-5.6 Luna: which to pick
Pick GPT-5.6 Luna for coding: it scores 58.0 on the Vibe Coding Index against 43.7 for Gemini 3 Flash Preview.
Pick Gemini 3 Flash Preview for work measured by WeirdML or SciCode, where it leads.
Model AGemini 3 Flash PreviewGoogle43.7/1002 independent benchmarks$0.37 per solved taskModel BGPT-5.6 LunaOpenAI58.0/1006 independent benchmarks$0.04 per solved task
- Shared results
- 47
- Gemini 3 Flash Preview only
- 24
- GPT-5.6 Luna only
- 72
- Like-for-like categories
- 8 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
GPT-5.6 Luna
GPT-5.6 Luna scores 58.0 against 43.7.
2 and 6 benchmarks behind the scores
Intelligence
AA Intelligence Index
GPT-5.6 Luna
GPT-5.6 Luna leads, 37.3 against 26.3.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only GPT-5.6 Luna has a AA Agentic Index result, 42.1.
Directional only
Reasoning
GPQA Diamond
GPT-5.6 Luna
GPT-5.6 Luna leads, 91.7% against 87.9%.
Same board, both measured
Math
AIME
No call
Only Gemini 3 Flash Preview has a AIME result, 95.6%.
Directional only
Knowledge
MMLU Pro
Gemini 3 Flash Preview
Gemini 3 Flash Preview leads, 88.6% against 86.0%.
Same board, both measured
Web design
Design Arena: websites
GPT-5.6 Luna
GPT-5.6 Luna leads, 1255 against 1196.
Same board, both measured
Long documents
Listed context window
GPT-5.6 Luna
GPT-5.6 Luna takes 1.05M tokens against 1.05M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5.6 Luna
Gemini 3 Flash Preview $0.0020, GPT-5.6 Luna $0.0008 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
GPT-5.6 Luna
Gemini 3 Flash Preview $0.37, GPT-5.6 Luna $0.04.
Published attempt cost and pass rate
At a glance
- Coding index
- Gemini 3 Flash Preview 43.7 from 2 benchmarks, GPT-5.6 Luna 58.0 from 6 benchmarks.
- Widest category
- Math, 30.6 points apart on average over 4 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): Gemini 3 Flash Preview 20.2% against GPT-5.6 Luna 77.1%, 56.9 points apart on a 0 to 100 scale.
- Output price
- Gemini 3 Flash Preview $3.00 against GPT-5.6 Luna $1.20 per million output tokens, 2.5x apart.
- Context window
- Gemini 3 Flash Preview takes 1.05M tokens, GPT-5.6 Luna 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 | Gemini 3 Flash Preview | Bars | GPT-5.6 Luna | Ties |
|---|---|---|---|---|
| Coding | 2 | 5 | 1 tie | |
| Intelligence | 0 | 1 | ||
| Agentic work | 1 | 5 | ||
| Reasoning | 3 | 7 | ||
| Math | 0 | 4 | ||
| Knowledge | 7 | 1 | ||
| Web design | 1 | 3 | ||
| General | 1 | 4 | 1 tie | |
| All shared boards | 15 | 30 | 2 ties |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index25
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| SWE-bench Verified | 75.8% | Not measured | Only Gemini 3 Flash Preview measured |
| LiveBench coding | Not measured | 73.6% | Only GPT-5.6 Luna measured |
| LMArena WebDev | Not measured | 1518 | Only GPT-5.6 Luna measured |
| AA Coding Index | Not measured | 71.4 | Only GPT-5.6 Luna measured |
| LiveCodeBench (Vals AI) | 85.6% | Not measured | Only Gemini 3 Flash Preview measured |
| SWE-bench Verified (Vals AI) | 75.0% | 93.0% | GPT-5.6 Luna |
| Terminal-Bench 4 (Vals AI) | Not measured | 11.6% | Only GPT-5.6 Luna measured |
| Vibe Code Bench (Vals AI) | 20.2% | 77.1% | GPT-5.6 Luna |
| Code migration (Vals AI) | 6.4% | 44.5% | GPT-5.6 Luna |
| ProgramBench (Vals AI) | 0.0% | 0.0% | Tie |
| IOI (Vals AI) | Not measured | 61.8% | Only GPT-5.6 Luna measured |
| Terminal-Bench 2.1 (Vals AI) | 53.9% | 79.0% | GPT-5.6 Luna |
| Vibe Code Bench 1-100 (Vals AI) | Not measured | 22.6% | Only GPT-5.6 Luna measured |
| SkillsBench (Vals AI) | Not measured | 60.5% | Only GPT-5.6 Luna measured |
| CyberBench (Vals AI) | Not measured | 73.6% | Only GPT-5.6 Luna measured |
| LiveCodeBench (Artificial Analysis run) | 90.8% | Not measured | Only Gemini 3 Flash Preview measured |
| SciCode | Not measured | 53.6% | Only GPT-5.6 Luna measured |
| Terminal-Bench Hard (Artificial Analysis run) | 38.6% | Not measured | Only Gemini 3 Flash Preview measured |
| Terminal-Bench | 64.3% | Not measured | Only Gemini 3 Flash Preview measured |
| FrontierCode | Not measured | 39.8% | Only GPT-5.6 Luna measured |
| GSO-Bench | 9.8% | Not measured | Only Gemini 3 Flash Preview measured |
| WeirdML | 61.6% | 60.9% | Gemini 3 Flash Preview |
| ALE-Bench | 1367.2 | 1667.4 | GPT-5.6 Luna |
| LMArena Text: coding | Not measured | 1466 | Only GPT-5.6 Luna measured |
| LMArena Text: software and IT | Not measured | 1463 | Only GPT-5.6 Luna measured |
| LMArena WebDev: React | Not measured | 1508 | Only GPT-5.6 Luna measured |
| LMArena WebDev: HTML | Not measured | 1520 | Only GPT-5.6 Luna measured |
| LMArena WebDev: from an image | Not measured | 1517 | Only GPT-5.6 Luna measured |
| SciCode | 12.7% | 6.2% | Gemini 3 Flash Preview |
| Neither model has a result on the other 10 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| AA Intelligence Index | 26.3 | 37.3 | GPT-5.6 Luna |
| Epoch Capabilities Index | Not measured | 156.5 | Only GPT-5.6 Luna measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index15
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| AA Agentic Index | Not measured | 42.1 | Only GPT-5.6 Luna measured |
| Design Arena: agents building web apps | 1111 | Not measured | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building full-stack apps | 1063 | Not measured | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building mobile apps | 1090 | Not measured | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building Android apps | 1051 | Not measured | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building Godot games | 1161 | Not measured | Only Gemini 3 Flash Preview measured |
| Design Arena: PowerPoint slides | 1036 | Not measured | Only Gemini 3 Flash Preview measured |
| LiveBench research | Not measured | 51.0% | Only GPT-5.6 Luna measured |
| LiveBench browser | Not measured | 68.0% | Only GPT-5.6 Luna measured |
| LiveBench long agentic | Not measured | 30.4% | Only GPT-5.6 Luna measured |
| SREBench (Vals AI) | Not measured | 1.5% | Only GPT-5.6 Luna measured |
| Finance Agent (Vals AI) | 42.5% | 55.0% | GPT-5.6 Luna |
| Tax Agent Bench (Vals AI) | 11.8% | 24.8% | GPT-5.6 Luna |
| Legal Research Bench (Vals AI) | 18.3% | 36.5% | GPT-5.6 Luna |
| Excel Modeling Benchmark (Vals AI) | 26.0% | 67.1% | GPT-5.6 Luna |
| BioMysteryBench (Vals AI) | Not measured | 61.5% | Only GPT-5.6 Luna measured |
| Terminal-Bench-Science (Vals AI) | Not measured | 0.0% | Only GPT-5.6 Luna measured |
| Vals Science Index | Not measured | 25.3% | Only GPT-5.6 Luna measured |
| τ²-Bench Telecom | 80.4% | Not measured | Only Gemini 3 Flash Preview measured |
| APEX-Agents | Not measured | 43.0% | Only GPT-5.6 Luna measured |
| BALROG | 48.1% | 45.6% | Gemini 3 Flash Preview |
| DeepResearch Bench | 49.8% | Not measured | Only Gemini 3 Flash Preview measured |
| Vending-Bench 2 | $3,635 | $4,095 | GPT-5.6 Luna |
| Neither model has a result on the other 18 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index37
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| GPQA Diamond | 87.9% | 91.7% | GPT-5.6 Luna |
| LiveBench reasoning | Not measured | 85.6% | Only GPT-5.6 Luna measured |
| MysteryMechanism (Vals AI) | Not measured | 14.4% | Only GPT-5.6 Luna measured |
| MMMU Pro (Vals AI) | 87.6% | 85.0% | Gemini 3 Flash Preview |
| GPQA Diamond (Artificial Analysis run) | 89.8% | 91.1% | GPT-5.6 Luna |
| Humanity's Last Exam (Artificial Analysis run) | 36.6% | 39.5% | GPT-5.6 Luna |
| GPQA Diamond (Epoch AI run) | 89.4% | 91.6% | GPT-5.6 Luna |
| ARC-AGI | 84.7% | 88.0% | GPT-5.6 Luna |
| ARC-AGI-2 | 33.6% | 59.5% | GPT-5.6 Luna |
| SimpleBench | 61.1% | 46.8% | Gemini 3 Flash Preview |
| Chess puzzles | 39.0% | 43.0% | GPT-5.6 Luna |
| Mystery game puzzles | 26.0% | 21.0% | Gemini 3 Flash Preview |
| VPCT | 72.6% | Not measured | Only Gemini 3 Flash Preview measured |
| LMArena Text: hard prompts | Not measured | 1451 | Only GPT-5.6 Luna measured |
| LMArena Text: expert | Not measured | 1478 | Only GPT-5.6 Luna measured |
| LMArena Text: hard prompts in English | Not measured | 1460 | Only GPT-5.6 Luna measured |
| LMArena Vision: diagrams | Not measured | 1273 | Only GPT-5.6 Luna measured |
| LMArena Vision: homework | Not measured | 1282 | Only GPT-5.6 Luna measured |
| Kagi LLM Benchmark | Not measured | 49.1% | Only GPT-5.6 Luna measured |
| Neither model has a result on the other 3 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| AIME | 95.6% | Not measured | Only Gemini 3 Flash Preview measured |
| MGSM (Vals AI) | 93.3% | Not measured | Only Gemini 3 Flash Preview measured |
| AA Math Index | 97.0 | Not measured | Only Gemini 3 Flash Preview measured |
| AIME 2025 (Artificial Analysis run) | 97.0% | Not measured | Only Gemini 3 Flash Preview measured |
| OTIS Mock AIME | 95.6% | 98.3% | GPT-5.6 Luna |
| FrontierMath, tiers 1 to 3 | 51.2% | 82.1% | GPT-5.6 Luna |
| FrontierMath, tier 4 | 17.1% | 61.0% | GPT-5.6 Luna |
| ProofBench | 15.0% | 60.0% | GPT-5.6 Luna |
| LMArena Text: math | Not measured | 1459 | Only GPT-5.6 Luna measured |
| LMArena Text: mathematical work | Not measured | 1470 | Only GPT-5.6 Luna measured |
| Neither model has a result on the other 3 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index71
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| MMLU Pro | 88.6% | 86.0% | Gemini 3 Flash Preview |
| LegalBench (Vals AI) | 86.9% | 84.0% | Gemini 3 Flash Preview |
| CaseLaw (Vals AI) | 55.8% | Not measured | Only Gemini 3 Flash Preview measured |
| CorpFin (Vals AI) | 66.4% | 64.2% | Gemini 3 Flash Preview |
| TaxEval (Vals AI) | 73.9% | 76.2% | GPT-5.6 Luna |
| MortgageTax (Vals AI) | 68.7% | 67.3% | Gemini 3 Flash Preview |
| MedQA (Vals AI) | 95.8% | Not measured | Only Gemini 3 Flash Preview measured |
| MedCode (Vals AI) | 55.9% | 42.4% | Gemini 3 Flash Preview |
| MMLU Pro (Artificial Analysis run) | 89.0% | Not measured | Only Gemini 3 Flash Preview measured |
| SimpleQA Verified | 66.8% | 41.0% | Gemini 3 Flash Preview |
| GeoBench | 88.0% | Not measured | Only Gemini 3 Flash Preview measured |
| LMArena Text: science | Not measured | 1433 | Only GPT-5.6 Luna measured |
| LMArena Text: medicine and healthcare | Not measured | 1399 | Only GPT-5.6 Luna measured |
| LMArena Text: legal and government | Not measured | 1446 | Only GPT-5.6 Luna measured |
| LMArena Text: business and finance | Not measured | 1439 | Only GPT-5.6 Luna measured |
| FACTS Benchmark Suite | 63.4% | 35.0% | Gemini 3 Flash Preview |
| Neither model has a result on the other 2 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index13
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| Design Arena: websites | 1196 | 1255 | GPT-5.6 Luna |
| Design Arena: UI components | Not measured | 1248 | Only GPT-5.6 Luna measured |
| Design Arena: game dev | 1166 | 1194 | GPT-5.6 Luna |
| Design Arena: data viz | Not measured | 1211 | Only GPT-5.6 Luna measured |
| Design Arena: 3D | 1183 | 1121 | Gemini 3 Flash Preview |
| Design Arena: all code categories | 1189 | 1231 | GPT-5.6 Luna |
| Design Arena: SVG | Not measured | 1194 | Only GPT-5.6 Luna measured |
| Design Arena: ASCII art | Not measured | 1142 | Only GPT-5.6 Luna measured |
| LiveBench design | Not measured | 76.0% | Only GPT-5.6 Luna measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index14
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | Leader |
|---|---|---|---|
| LiveBench data analysis | Not measured | 78.0% | Only GPT-5.6 Luna measured |
| Public Benefits Bench (Vals AI) | Not measured | 61.2% | Only GPT-5.6 Luna measured |
| SAGE (Vals AI) | 51.8% | 44.2% | Gemini 3 Flash Preview |
| MedScribe (Vals AI) | 69.9% | 84.4% | GPT-5.6 Luna |
| Vals Multimodal Index | 52.2% | 69.1% | GPT-5.6 Luna |
| IFBench | 78.0% | Not measured | Only Gemini 3 Flash Preview measured |
| Long context reasoning (AA-LCR) | 78.0% | 83.7% | GPT-5.6 Luna |
| DTBench | 89.1% | 89.1% | Tie |
| LMCA | 43.1% | 48.5% | GPT-5.6 Luna |
| Surface Evolver Bench | Not measured | 61.9% | Only GPT-5.6 Luna measured |
| Furniture assembly | Not measured | 42.5% | Only GPT-5.6 Luna measured |
| LMArena Text | Not measured | 1431 | Only GPT-5.6 Luna measured |
| LMArena Text: instruction following | Not measured | 1437 | Only GPT-5.6 Luna measured |
| LMArena Text: creative writing | Not measured | 1396 | Only GPT-5.6 Luna measured |
| LMArena Vision | Not measured | 1257 | Only GPT-5.6 Luna measured |
| LMArena Text: English | Not measured | 1441 | Only GPT-5.6 Luna measured |
| LMArena Text: non-English | Not measured | 1417 | Only GPT-5.6 Luna measured |
| LMArena Text: Chinese | Not measured | 1470 | Only GPT-5.6 Luna measured |
| LMArena Text: German | Not measured | 1455 | Only GPT-5.6 Luna measured |
| LMArena Text: Japanese | Not measured | 1415 | Only GPT-5.6 Luna measured |
| LMArena Text: Korean | Not measured | 1415 | Only GPT-5.6 Luna measured |
| LMArena Text: French | Not measured | 1458 | Only GPT-5.6 Luna measured |
| LMArena Text: Spanish | Not measured | 1446 | Only GPT-5.6 Luna measured |
| LMArena Text: Russian | Not measured | 1427 | Only GPT-5.6 Luna measured |
| LMArena Text: Polish | Not measured | 1405 | Only GPT-5.6 Luna measured |
| LMArena Text: multi-turn | Not measured | 1434 | Only GPT-5.6 Luna measured |
| LMArena Text: longer queries | Not measured | 1436 | Only GPT-5.6 Luna measured |
| LMArena Text: writing and language | Not measured | 1419 | Only GPT-5.6 Luna measured |
| LMArena Text: entertainment and media | Not measured | 1402 | Only GPT-5.6 Luna measured |
| LMArena Vision: English | Not measured | 1263 | Only GPT-5.6 Luna measured |
| LMArena Vision: Chinese | Not measured | 1294 | Only GPT-5.6 Luna measured |
| LMArena Vision: reading text | Not measured | 1264 | Only GPT-5.6 Luna measured |
| LMArena Vision: humor | Not measured | 1190 | Only GPT-5.6 Luna measured |
| LMArena Vision: creative writing | Not measured | 1257 | Only GPT-5.6 Luna measured |
| LMArena Document | Not measured | 1457 | Only GPT-5.6 Luna measured |
| Neither model has a result on the other 11 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3 Flash Preview | GPT-5.6 Luna | 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 Flash Preview$0.0020Fits in one request
GPT-5.6 Luna$0.0008Fits in one request
GPT-5.6 Luna costs less
Repository review
50K input + 3K output tokens
Gemini 3 Flash Preview$0.034Fits in one request
GPT-5.6 Luna$0.014Fits in one request
GPT-5.6 Luna costs less
Agent loop
200K input + 10K output tokens
Gemini 3 Flash Preview$0.130Fits in one request
GPT-5.6 Luna$0.052Fits in one request
GPT-5.6 Luna 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 Flash Preview | OpenAI GPT-5.6 Luna |
|---|---|---|
| Maker | OpenAI | |
| Weights | No public weights listed | No public weights listed |
| Released | December 17, 2025 | July 9, 2026 |
| Context window | 1.05M | 1.05M |
| Input $/Mtok | $0.50 | $0.20 |
| Output $/Mtok | $3.00 | $1.20 |
| Coding index | 43.7 | 58.0 |
| Independent measurements behind it | 2 | 6 |
| Cost per solved task | $0.37 | $0.04 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 3 Flash Preview better than GPT-5.6 Luna for coding?
Pick GPT-5.6 Luna for coding: it scores 58.0 on the Vibe Coding Index against 43.7 for Gemini 3 Flash Preview. Pick Gemini 3 Flash Preview for work measured by WeirdML or SciCode, where it leads.
Which is cheaper, Gemini 3 Flash Preview or GPT-5.6 Luna?
Gemini 3 Flash Preview costs $0.50 per million input tokens and $3.00 per million output tokens; GPT-5.6 Luna costs $0.20 and $1.20. Per solved SWE-bench Verified task, Gemini 3 Flash Preview costs $0.37 and GPT-5.6 Luna $0.04.
Which has the bigger context window, Gemini 3 Flash Preview or GPT-5.6 Luna?
GPT-5.6 Luna, with 1.05M tokens against 1.05M.
How many benchmarks is the Gemini 3 Flash Preview vs GPT-5.6 Luna comparison based on?
47 benchmarks have a result for both models as of October 22, 2026. Gemini 3 Flash Preview's coding index rests on 2 independent benchmarks and GPT-5.6 Luna's on 6. Where only one model has a result, the page says so instead of naming a winner.