GPT-5.6 Luna vs Mistral Medium 3.5
GPT-5.6 Luna leads Mistral Medium 3.5 on coding, 58.0 to 25.5 on the Vibe Coding Index, and GPT-5.6 Luna costs 6.3x less per output token ($1.20 vs $7.50 per million). Updated October 22, 2026; 77 benchmarks have a result for both.
GPT-5.6 Luna or Mistral Medium 3.5: which to pick
Pick GPT-5.6 Luna for coding: it scores 58.0 on the Vibe Coding Index against 25.5 for Mistral Medium 3.5.
Pick Mistral Medium 3.5 for work measured by LMArena Text: medicine and healthcare or LMArena Text: Polish, where it leads.
- Shared results
- 77
- GPT-5.6 Luna only
- 42
- Mistral Medium 3.5 only
- 4
- 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 25.5.
6 and 3 benchmarks behind the scores
Intelligence
AA Intelligence Index
GPT-5.6 Luna
GPT-5.6 Luna leads, 37.3 against 14.2.
Same board, both measured
Agentic work
AA Agentic Index
GPT-5.6 Luna
GPT-5.6 Luna leads, 42.1 against 7.0.
Same board, both measured
Reasoning
GPQA Diamond
GPT-5.6 Luna
GPT-5.6 Luna leads, 91.7% against 34.9%.
Same board, both measured
Knowledge
MMLU Pro
GPT-5.6 Luna
GPT-5.6 Luna leads, 86.0% against 75.3%.
Same board, both measured
Web design
Design Arena: websites
GPT-5.6 Luna
GPT-5.6 Luna leads, 1255 against 1142.
Same board, both measured
Long documents
Listed context window
GPT-5.6 Luna
GPT-5.6 Luna takes 1.05M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5.6 Luna
GPT-5.6 Luna $0.0008, Mistral Medium 3.5 $0.0053 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
GPT-5.6 Luna
GPT-5.6 Luna $0.04, Mistral Medium 3.5 $6.02.
Published attempt cost and pass rate
At a glance
- Coding index
- GPT-5.6 Luna 58.0 from 6 benchmarks, Mistral Medium 3.5 25.5 from 3 benchmarks.
- Widest category
- Agentic work, 32.3 points apart on average over 5 shared benchmarks.
- Widest single gap
- Vibe Code Bench (Vals AI): GPT-5.6 Luna 77.1% against Mistral Medium 3.5 2.9%, 74.2 points apart on a 0 to 100 scale.
- Output price
- GPT-5.6 Luna $1.20 against Mistral Medium 3.5 $7.50 per million output tokens, 6.3x apart.
- Context window
- GPT-5.6 Luna takes 1.05M tokens, Mistral Medium 3.5 262K.
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-5.6 Luna | Bars | Mistral Medium 3.5 | Ties |
|---|---|---|---|---|
| Coding | 12 | 0 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 5 | 0 | ||
| Reasoning | 9 | 0 | ||
| Math | 3 | 0 | ||
| Knowledge | 8 | 1 | ||
| Web design | 8 | 0 | ||
| General | 27 | 2 | ||
| All shared boards | 74 | 3 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index120
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| LiveBench coding | 73.6% | Not measured | Only GPT-5.6 Luna measured |
| LMArena WebDev | 1518 | 1264 | GPT-5.6 Luna |
| AA Coding Index | 71.4 | 46.9 | GPT-5.6 Luna |
| SWE-bench Verified (Vals AI) | 93.0% | 66.4% | GPT-5.6 Luna |
| Terminal-Bench 4 (Vals AI) | 11.6% | Not measured | Only GPT-5.6 Luna measured |
| Vibe Code Bench (Vals AI) | 77.1% | 2.9% | GPT-5.6 Luna |
| Code migration (Vals AI) | 44.5% | 5.1% | GPT-5.6 Luna |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only GPT-5.6 Luna measured |
| IOI (Vals AI) | 61.8% | Not measured | Only GPT-5.6 Luna measured |
| Terminal-Bench 2.1 (Vals AI) | 79.0% | 39.0% | GPT-5.6 Luna |
| Vibe Code Bench 1-100 (Vals AI) | 22.6% | Not measured | Only GPT-5.6 Luna measured |
| SkillsBench (Vals AI) | 60.5% | Not measured | Only GPT-5.6 Luna measured |
| CyberBench (Vals AI) | 73.6% | Not measured | Only GPT-5.6 Luna measured |
| SciCode | 53.6% | 40.2% | GPT-5.6 Luna |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 33.3% | Only Mistral Medium 3.5 measured |
| FrontierCode | 39.8% | Not measured | Only GPT-5.6 Luna measured |
| WeirdML | 60.9% | Not measured | Only GPT-5.6 Luna measured |
| ALE-Bench | 1667.4 | 764.0 | GPT-5.6 Luna |
| LMArena Text: coding | 1466 | 1460 | GPT-5.6 Luna |
| LMArena Text: software and IT | 1463 | 1458 | GPT-5.6 Luna |
| LMArena WebDev: React | 1508 | 1254 | GPT-5.6 Luna |
| LMArena WebDev: HTML | 1520 | 1308 | GPT-5.6 Luna |
| LMArena WebDev: from an image | 1517 | Not measured | Only GPT-5.6 Luna measured |
| SciCode | 6.2% | Not measured | Only GPT-5.6 Luna measured |
| Neither model has a result on the other 15 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 37.3 | 14.2 | GPT-5.6 Luna |
| Epoch Capabilities Index | 156.5 | 141.4 | GPT-5.6 Luna |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| AA Agentic Index | 42.1 | 7.0 | GPT-5.6 Luna |
| LiveBench research | 51.0% | Not measured | Only GPT-5.6 Luna measured |
| LiveBench browser | 68.0% | Not measured | Only GPT-5.6 Luna measured |
| LiveBench long agentic | 30.4% | Not measured | Only GPT-5.6 Luna measured |
| SREBench (Vals AI) | 1.5% | Not measured | Only GPT-5.6 Luna measured |
| Finance Agent (Vals AI) | 55.0% | 32.1% | GPT-5.6 Luna |
| Tax Agent Bench (Vals AI) | 24.8% | 4.5% | GPT-5.6 Luna |
| Legal Research Bench (Vals AI) | 36.5% | 9.1% | GPT-5.6 Luna |
| Excel Modeling Benchmark (Vals AI) | 67.1% | 11.2% | GPT-5.6 Luna |
| BioMysteryBench (Vals AI) | 61.5% | Not measured | Only GPT-5.6 Luna measured |
| Terminal-Bench-Science (Vals AI) | 0.0% | Not measured | Only GPT-5.6 Luna measured |
| Vals Science Index | 25.3% | Not measured | Only GPT-5.6 Luna measured |
| τ²-Bench Telecom | Not measured | 94.2% | Only Mistral Medium 3.5 measured |
| APEX-Agents | 43.0% | Not measured | Only GPT-5.6 Luna measured |
| BALROG | 45.6% | Not measured | Only GPT-5.6 Luna measured |
| Vending-Bench 2 | $4,095 | Not measured | Only GPT-5.6 Luna measured |
| Neither model has a result on the other 25 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index90
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| GPQA Diamond | 91.7% | 34.9% | GPT-5.6 Luna |
| LiveBench reasoning | 85.6% | Not measured | Only GPT-5.6 Luna measured |
| MysteryMechanism (Vals AI) | 14.4% | Not measured | Only GPT-5.6 Luna measured |
| MMMU Pro (Vals AI) | 85.0% | Not measured | Only GPT-5.6 Luna measured |
| GPQA Diamond (Artificial Analysis run) | 91.1% | 74.8% | GPT-5.6 Luna |
| Humanity's Last Exam (Artificial Analysis run) | 39.5% | 13.8% | GPT-5.6 Luna |
| GPQA Diamond (Epoch AI run) | 91.6% | Not measured | Only GPT-5.6 Luna measured |
| ARC-AGI | 88.0% | Not measured | Only GPT-5.6 Luna measured |
| ARC-AGI-2 | 59.5% | Not measured | Only GPT-5.6 Luna measured |
| SimpleBench | 46.8% | Not measured | Only GPT-5.6 Luna measured |
| Chess puzzles | 43.0% | Not measured | Only GPT-5.6 Luna measured |
| Mystery game puzzles | 21.0% | Not measured | Only GPT-5.6 Luna measured |
| LMArena Text: hard prompts | 1451 | 1436 | GPT-5.6 Luna |
| LMArena Text: expert | 1478 | 1432 | GPT-5.6 Luna |
| LMArena Text: hard prompts in English | 1460 | 1445 | GPT-5.6 Luna |
| LMArena Vision: diagrams | 1273 | 1254 | GPT-5.6 Luna |
| LMArena Vision: homework | 1282 | 1230 | GPT-5.6 Luna |
| Kagi LLM Benchmark | 49.1% | 41.4% | GPT-5.6 Luna |
| Neither model has a result on the other 4 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| OTIS Mock AIME | 98.3% | Not measured | Only GPT-5.6 Luna measured |
| FrontierMath, tiers 1 to 3 | 82.1% | Not measured | Only GPT-5.6 Luna measured |
| FrontierMath, tier 4 | 61.0% | Not measured | Only GPT-5.6 Luna measured |
| ProofBench | 60.0% | 9.0% | GPT-5.6 Luna |
| LMArena Text: math | 1459 | 1431 | GPT-5.6 Luna |
| LMArena Text: mathematical work | 1470 | 1440 | GPT-5.6 Luna |
| Neither model has a result on the other 7 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index81
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| MMLU Pro | 86.0% | 75.3% | GPT-5.6 Luna |
| LegalBench (Vals AI) | 84.0% | Not measured | Only GPT-5.6 Luna measured |
| CaseLaw (Vals AI) | Not measured | 44.2% | Only Mistral Medium 3.5 measured |
| CorpFin (Vals AI) | 64.2% | 58.8% | GPT-5.6 Luna |
| TaxEval (Vals AI) | 76.2% | 68.0% | GPT-5.6 Luna |
| MortgageTax (Vals AI) | 67.3% | 28.9% | GPT-5.6 Luna |
| MedCode (Vals AI) | 42.4% | 33.8% | GPT-5.6 Luna |
| SimpleQA Verified | 41.0% | Not measured | Only GPT-5.6 Luna measured |
| LMArena Text: science | 1433 | 1428 | GPT-5.6 Luna |
| LMArena Text: medicine and healthcare | 1399 | 1409 | Mistral Medium 3.5 |
| LMArena Text: legal and government | 1446 | 1437 | GPT-5.6 Luna |
| LMArena Text: business and finance | 1439 | 1426 | GPT-5.6 Luna |
| FACTS Benchmark Suite | 35.0% | Not measured | Only GPT-5.6 Luna measured |
| Neither model has a result on the other 5 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index80
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1255 | 1142 | GPT-5.6 Luna |
| Design Arena: UI components | 1248 | 1076 | GPT-5.6 Luna |
| Design Arena: game dev | 1194 | 1079 | GPT-5.6 Luna |
| Design Arena: data viz | 1211 | 1120 | GPT-5.6 Luna |
| Design Arena: 3D | 1121 | 1060 | GPT-5.6 Luna |
| Design Arena: all code categories | 1231 | 1121 | GPT-5.6 Luna |
| Design Arena: SVG | 1194 | 949 | GPT-5.6 Luna |
| Design Arena: ASCII art | 1142 | 1062 | GPT-5.6 Luna |
| LiveBench design | 76.0% | Not measured | Only GPT-5.6 Luna measured |
GeneralLike-for-likePublic boards, shown as published, kept out of the index272
| Benchmark | GPT-5.6 Luna | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| LiveBench data analysis | 78.0% | Not measured | Only GPT-5.6 Luna measured |
| Public Benefits Bench (Vals AI) | 61.2% | Not measured | Only GPT-5.6 Luna measured |
| SAGE (Vals AI) | 44.2% | 37.6% | GPT-5.6 Luna |
| MedScribe (Vals AI) | 84.4% | 67.7% | GPT-5.6 Luna |
| Vals Multimodal Index | 69.1% | 34.8% | GPT-5.6 Luna |
| IFBench | Not measured | 68.8% | Only Mistral Medium 3.5 measured |
| Long context reasoning (AA-LCR) | 83.7% | 69.3% | GPT-5.6 Luna |
| DTBench | 89.1% | 75.5% | GPT-5.6 Luna |
| LMCA | 48.5% | 26.1% | GPT-5.6 Luna |
| Surface Evolver Bench | 61.9% | 26.9% | GPT-5.6 Luna |
| Furniture assembly | 42.5% | Not measured | Only GPT-5.6 Luna measured |
| LMArena Text | 1431 | 1421 | GPT-5.6 Luna |
| LMArena Text: instruction following | 1437 | 1415 | GPT-5.6 Luna |
| LMArena Text: creative writing | 1396 | 1374 | GPT-5.6 Luna |
| LMArena Vision | 1257 | 1222 | GPT-5.6 Luna |
| LMArena Text: English | 1441 | 1433 | GPT-5.6 Luna |
| LMArena Text: non-English | 1417 | 1404 | GPT-5.6 Luna |
| LMArena Text: Chinese | 1470 | 1444 | GPT-5.6 Luna |
| LMArena Text: German | 1455 | 1453 | GPT-5.6 Luna |
| LMArena Text: Japanese | 1415 | Not measured | Only GPT-5.6 Luna measured |
| LMArena Text: Korean | 1415 | 1384 | GPT-5.6 Luna |
| LMArena Text: French | 1458 | 1448 | GPT-5.6 Luna |
| LMArena Text: Spanish | 1446 | 1411 | GPT-5.6 Luna |
| LMArena Text: Russian | 1427 | 1395 | GPT-5.6 Luna |
| LMArena Text: Polish | 1405 | 1430 | Mistral Medium 3.5 |
| LMArena Text: multi-turn | 1434 | 1423 | GPT-5.6 Luna |
| LMArena Text: longer queries | 1436 | 1415 | GPT-5.6 Luna |
| LMArena Text: writing and language | 1419 | 1384 | GPT-5.6 Luna |
| LMArena Text: entertainment and media | 1402 | 1382 | GPT-5.6 Luna |
| LMArena Vision: English | 1263 | 1240 | GPT-5.6 Luna |
| LMArena Vision: Chinese | 1294 | 1244 | GPT-5.6 Luna |
| LMArena Vision: reading text | 1264 | 1233 | GPT-5.6 Luna |
| LMArena Vision: humor | 1190 | 1216 | Mistral Medium 3.5 |
| LMArena Vision: creative writing | 1257 | 1198 | GPT-5.6 Luna |
| LMArena Document | 1457 | Not measured | 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 | GPT-5.6 Luna | Mistral Medium 3.5 | 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
GPT-5.6 Luna costs less
Repository review
50K input + 3K output tokens
GPT-5.6 Luna costs less
Agent loop
200K input + 10K output tokens
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 | OpenAI GPT-5.6 Luna | Mistral Medium 3.5 |
|---|---|---|
| Maker | OpenAI | Mistral AI |
| Weights | No public weights listed | No public weights listed |
| Released | July 9, 2026 | April 30, 2026 |
| Context window | 1.05M | 262K |
| Input $/Mtok | $0.20 | $1.50 |
| Output $/Mtok | $1.20 | $7.50 |
| Coding index | 58.0 | 25.5 |
| Independent measurements behind it | 6 | 3 |
| Cost per solved task | $0.04 | $6.02 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5.6 Luna better than Mistral Medium 3.5 for coding?
Pick GPT-5.6 Luna for coding: it scores 58.0 on the Vibe Coding Index against 25.5 for Mistral Medium 3.5. Pick Mistral Medium 3.5 for work measured by LMArena Text: medicine and healthcare or LMArena Text: Polish, where it leads.
Which is cheaper, GPT-5.6 Luna or Mistral Medium 3.5?
GPT-5.6 Luna costs $0.20 per million input tokens and $1.20 per million output tokens; Mistral Medium 3.5 costs $1.50 and $7.50. Per solved SWE-bench Verified task, GPT-5.6 Luna costs $0.04 and Mistral Medium 3.5 $6.02.
Which has the bigger context window, GPT-5.6 Luna or Mistral Medium 3.5?
GPT-5.6 Luna, with 1.05M tokens against 262K.
How many benchmarks is the GPT-5.6 Luna vs Mistral Medium 3.5 comparison based on?
77 benchmarks have a result for both models as of October 22, 2026. GPT-5.6 Luna's coding index rests on 6 independent benchmarks and Mistral Medium 3.5's on 3. Where only one model has a result, the page says so instead of naming a winner.