Mistral Medium 3 vs Step 3.5 Flash
Step 3.5 Flash leads Mistral Medium 3 on the Artificial Analysis Intelligence Index, 17.0 to 9.0, and Step 3.5 Flash costs 6.7x less per output token ($0.30 vs $2.00 per million). Updated October 22, 2026; 35 benchmarks have a result for both.
Mistral Medium 3 or Step 3.5 Flash: which to pick
Neither model has a coding score yet, so the two cannot be ranked on coding.
Pick Mistral Medium 3 for work measured by Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.
- Shared results
- 35
- Mistral Medium 3 only
- 22
- Step 3.5 Flash only
- 0
- Like-for-like categories
- 7 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
No call
Neither has a coding score yet.
One side not measured
Intelligence
AA Intelligence Index
Step 3.5 Flash
Step 3.5 Flash leads, 17.0 against 9.0.
Same board, both measured
Web design
Design Arena: websites
No call
Only Mistral Medium 3 has a Design Arena: websites result, 1079.
Directional only
Long documents
Listed context window
Step 3.5 Flash
Step 3.5 Flash takes 262K tokens against 131K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Step 3.5 Flash
Mistral Medium 3 $0.0014, Step 3.5 Flash $0.0003 per turn.
List prices
At a glance
- Coding index
- Mistral Medium 3 not benchmarked, Step 3.5 Flash not benchmarked.
- Widest category
- Agentic work, 70.2 points apart on average over 1 shared benchmark.
- Widest single gap
- τ²-Bench Telecom: Mistral Medium 3 24.3% against Step 3.5 Flash 94.4%, 70.2 points apart on a 0 to 100 scale.
- Output price
- Mistral Medium 3 $2.00 against Step 3.5 Flash $0.30 per million output tokens, 6.7x apart.
- Context window
- Mistral Medium 3 takes 131K tokens, Step 3.5 Flash 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 | Mistral Medium 3 | Bars | Step 3.5 Flash | Ties |
|---|---|---|---|---|
| Coding | 0 | 3 | ||
| Intelligence | 0 | 1 | ||
| Agentic work | 0 | 1 | ||
| Reasoning | 0 | 5 | ||
| Math | 0 | 2 | ||
| Knowledge | 0 | 4 | ||
| General | 0 | 19 | ||
| All shared boards | 0 | 35 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index03
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| LiveCodeBench (Artificial Analysis run) | 40.0% | Not measured | Only Mistral Medium 3 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 3.8% | 32.6% | Step 3.5 Flash |
| LMArena Text: coding | 1385 | 1436 | Step 3.5 Flash |
| LMArena Text: software and IT | 1385 | 1434 | Step 3.5 Flash |
| Neither model has a result on the other 35 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Intelligence Index | 9.0 | 17.0 | Step 3.5 Flash |
| Epoch Capabilities Index | 134.0 | Not measured | Only Mistral Medium 3 measured |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| τ²-Bench Telecom | 24.3% | 94.4% | Step 3.5 Flash |
| Neither model has a result on the other 40 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index05
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| GPQA Diamond (Artificial Analysis run) | 57.8% | 83.1% | Step 3.5 Flash |
| Humanity's Last Exam (Artificial Analysis run) | 4.1% | 24.5% | Step 3.5 Flash |
| LMArena Text: hard prompts | 1364 | 1411 | Step 3.5 Flash |
| LMArena Text: expert | 1342 | 1421 | Step 3.5 Flash |
| LMArena Text: hard prompts in English | 1374 | 1421 | Step 3.5 Flash |
| LMArena Vision: diagrams | 1155 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: homework | 1165 | Not measured | Only Mistral Medium 3 measured |
| Neither model has a result on the other 15 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| AA Math Index | 30.3 | Not measured | Only Mistral Medium 3 measured |
| AIME 2025 (Artificial Analysis run) | 30.3% | Not measured | Only Mistral Medium 3 measured |
| LMArena Text: math | 1353 | 1408 | Step 3.5 Flash |
| LMArena Text: mathematical work | 1354 | 1421 | Step 3.5 Flash |
| Neither model has a result on the other 9 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index04
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| MMLU Pro (Artificial Analysis run) | 76.0% | Not measured | Only Mistral Medium 3 measured |
| LMArena Text: science | 1381 | 1415 | Step 3.5 Flash |
| LMArena Text: medicine and healthcare | 1381 | 1408 | Step 3.5 Flash |
| LMArena Text: legal and government | 1384 | 1408 | Step 3.5 Flash |
| LMArena Text: business and finance | 1352 | 1394 | Step 3.5 Flash |
| 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 | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| Design Arena: websites | 1079 | Not measured | Only Mistral Medium 3 measured |
| Design Arena: UI components | 1022 | Not measured | Only Mistral Medium 3 measured |
| Design Arena: game dev | 1017 | Not measured | Only Mistral Medium 3 measured |
| Design Arena: data viz | 1034 | Not measured | Only Mistral Medium 3 measured |
| Design Arena: 3D | 1083 | Not measured | Only Mistral Medium 3 measured |
| Design Arena: all code categories | 1068 | Not measured | Only Mistral Medium 3 measured |
| Neither model has a result on the other 3 boards here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index019
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | Leader |
|---|---|---|---|
| IFBench | 39.3% | 66.5% | Step 3.5 Flash |
| Long context reasoning (AA-LCR) | 31.3% | 63.0% | Step 3.5 Flash |
| DTBench | 62.3% | Not measured | Only Mistral Medium 3 measured |
| LMArena Text | 1370 | 1403 | Step 3.5 Flash |
| LMArena Text: instruction following | 1338 | 1385 | Step 3.5 Flash |
| LMArena Text: creative writing | 1343 | 1357 | Step 3.5 Flash |
| LMArena Vision | 1157 | Not measured | Only Mistral Medium 3 measured |
| LMArena Text: English | 1385 | 1417 | Step 3.5 Flash |
| LMArena Text: non-English | 1353 | 1385 | Step 3.5 Flash |
| LMArena Text: Chinese | 1374 | 1446 | Step 3.5 Flash |
| LMArena Text: German | 1377 | 1405 | Step 3.5 Flash |
| LMArena Text: Japanese | 1316 | 1353 | Step 3.5 Flash |
| LMArena Text: Korean | 1304 | 1351 | Step 3.5 Flash |
| LMArena Text: French | 1368 | 1421 | Step 3.5 Flash |
| LMArena Text: Spanish | 1364 | 1419 | Step 3.5 Flash |
| LMArena Text: Russian | 1359 | 1385 | Step 3.5 Flash |
| LMArena Text: Polish | 1371 | 1389 | Step 3.5 Flash |
| LMArena Text: multi-turn | 1384 | 1404 | Step 3.5 Flash |
| LMArena Text: longer queries | 1360 | 1402 | Step 3.5 Flash |
| LMArena Text: writing and language | 1352 | 1372 | Step 3.5 Flash |
| LMArena Text: entertainment and media | 1335 | 1360 | Step 3.5 Flash |
| LMArena Vision: English | 1172 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: Chinese | 1161 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: reading text | 1154 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: humor | 1145 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: captioning | 1094 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: recognizing things | 1141 | Not measured | Only Mistral Medium 3 measured |
| LMArena Vision: creative writing | 1146 | Not measured | Only Mistral Medium 3 measured |
| Neither model has a result on the other 18 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Mistral Medium 3 | Step 3.5 Flash | 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 3.5 Flash costs less
Repository review
50K input + 3K output tokens
Step 3.5 Flash costs less
Agent loop
200K input + 10K output tokens
Step 3.5 Flash 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 | Mistral Medium 3 | StepFun Step 3.5 Flash |
|---|---|---|
| Maker | Mistral AI | StepFun |
| Weights | No public weights listed | Open weights |
| Released | May 7, 2025 | January 29, 2026 |
| Context window | 131K | 262K |
| Input $/Mtok | $0.40 | $0.10 |
| Output $/Mtok | $2.00 | $0.30 |
| Coding index | Not benchmarked | Not benchmarked |
| Independent measurements behind it | 0 | 0 |
| Cost per solved task | Not computable | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Mistral Medium 3 better than Step 3.5 Flash for coding?
Neither model has a coding score yet, so the two cannot be ranked on coding. Pick Mistral Medium 3 for work measured by Terminal-Bench Hard (Artificial Analysis run) or LMArena Text: coding, where it leads.
Which is cheaper, Mistral Medium 3 or Step 3.5 Flash?
Mistral Medium 3 costs $0.40 per million input tokens and $2.00 per million output tokens; Step 3.5 Flash costs $0.10 and $0.30. Cost per solved task is known for neither of them.
Which has the bigger context window, Mistral Medium 3 or Step 3.5 Flash?
Step 3.5 Flash, with 262K tokens against 131K.
How many benchmarks is the Mistral Medium 3 vs Step 3.5 Flash comparison based on?
35 benchmarks have a result for both models as of October 22, 2026. Mistral Medium 3's coding index rests on 0 independent benchmarks and Step 3.5 Flash's on 0. Where only one model has a result, the page says so instead of naming a winner.