Grok 4.20 vs Mistral Medium 3.5
Grok 4.20 leads Mistral Medium 3.5 on coding, 33.3 to 25.5 on the Vibe Coding Index, and Grok 4.20 costs 3.0x less per output token ($2.50 vs $7.50 per million). Updated October 21, 2026; 36 benchmarks have a result for both.
Grok 4.20 or Mistral Medium 3.5: which to pick
Pick Grok 4.20 for coding: it scores 33.3 on the Vibe Coding Index against 25.5 for Mistral Medium 3.5, though on 2 benchmarks against 3.
Pick Mistral Medium 3.5 for work measured by Code migration (Vals AI) or Finance Agent (Vals AI), where it leads.
- Shared results
- 36
- Grok 4.20 only
- 18
- Mistral Medium 3.5 only
- 44
- 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
Grok 4.20
Grok 4.20 scores 33.3 against 25.5.
2 and 3 benchmarks behind the scores
Intelligence
AA Intelligence Index
Grok 4.20
Grok 4.20 leads, 25.7 against 14.2.
Same board, both measured
Agentic work
AA Agentic Index
No call
Only Mistral Medium 3.5 has a AA Agentic Index result, 7.0.
Directional only
Reasoning
GPQA Diamond
Grok 4.20
Grok 4.20 leads, 88.6% against 34.9%.
Same board, both measured
Math
AIME
No call
Only Grok 4.20 has a AIME result, 96.5%.
Directional only
Knowledge
MMLU Pro
Grok 4.20
Grok 4.20 leads, 86.3% against 75.3%.
Same board, both measured
Web design
Design Arena: websites
Grok 4.20
Grok 4.20 leads, 1229 against 1142.
Same board, both measured
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Grok 4.20
Grok 4.20 $0.0025, Mistral Medium 3.5 $0.0053 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
Grok 4.20
Grok 4.20 $0.72, Mistral Medium 3.5 $6.02.
Published attempt cost and pass rate
At a glance
- Coding index
- Grok 4.20 33.3 from 2 benchmarks, Mistral Medium 3.5 25.5 from 3 benchmarks.
- Widest category
- Reasoning, 30.3 points apart on average over 3 shared benchmarks.
- Widest single gap
- GPQA Diamond: Grok 4.20 88.6% against Mistral Medium 3.5 34.9%, 53.8 points apart on a 0 to 100 scale.
- Output price
- Grok 4.20 $2.50 against Mistral Medium 3.5 $7.50 per million output tokens, 3.0x apart.
- Context window
- Grok 4.20 takes 2M 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 | Grok 4.20 | Bars | Mistral Medium 3.5 | Ties |
|---|---|---|---|---|
| Coding | 4 | 1 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 3 | 2 | ||
| Reasoning | 3 | 0 | ||
| Knowledge | 5 | 1 | ||
| Web design | 8 | 0 | ||
| General | 5 | 2 | ||
| All shared boards | 30 | 6 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index41
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| LMArena WebDev | Not measured | 1264 | Only Mistral Medium 3.5 measured |
| AA Coding Index | Not measured | 46.9 | Only Mistral Medium 3.5 measured |
| LiveCodeBench (Vals AI) | 84.3% | Not measured | Only Grok 4.20 measured |
| SWE-bench Verified (Vals AI) | 72.2% | 66.4% | Grok 4.20 |
| Vibe Code Bench (Vals AI) | 4.1% | 2.9% | Grok 4.20 |
| Code migration (Vals AI) | 0.3% | 5.1% | Mistral Medium 3.5 |
| Terminal-Bench 2.1 (Vals AI) | 44.2% | 39.0% | Grok 4.20 |
| SciCode | Not measured | 40.2% | Only Mistral Medium 3.5 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | 33.3% | Grok 4.20 |
| Terminal-Bench | 57.3% | Not measured | Only Grok 4.20 measured |
| WeirdML | 52.3% | Not measured | Only Grok 4.20 measured |
| ALE-Bench | Not measured | 764.0 | Only Mistral Medium 3.5 measured |
| LMArena Text: coding | Not measured | 1460 | Only Mistral Medium 3.5 measured |
| LMArena Text: software and IT | Not measured | 1458 | Only Mistral Medium 3.5 measured |
| LMArena WebDev: React | Not measured | 1254 | Only Mistral Medium 3.5 measured |
| LMArena WebDev: HTML | Not measured | 1308 | Only Mistral Medium 3.5 measured |
| Neither model has a result on the other 22 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| AA Intelligence Index | 25.7 | 14.2 | Grok 4.20 |
| Epoch Capabilities Index | 152.1 | 141.4 | Grok 4.20 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index32
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| AA Agentic Index | Not measured | 7.0 | Only Mistral Medium 3.5 measured |
| Design Arena: agents building web apps | 1144 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building full-stack apps | 1054 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building mobile apps | 1090 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Android apps | 1052 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Godot games | 1089 | Not measured | Only Grok 4.20 measured |
| Design Arena: HTML slides | 1180 | Not measured | Only Grok 4.20 measured |
| Finance Agent (Vals AI) | 28.5% | 32.1% | Mistral Medium 3.5 |
| Tax Agent Bench (Vals AI) | 7.0% | 4.5% | Grok 4.20 |
| Legal Research Bench (Vals AI) | 13.9% | 9.1% | Grok 4.20 |
| Excel Modeling Benchmark (Vals AI) | 11.7% | 11.2% | Grok 4.20 |
| τ²-Bench Telecom | 93.0% | 94.2% | Mistral Medium 3.5 |
| Vending-Bench 2 | $4,663 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 26 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index30
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| GPQA Diamond | 88.6% | 34.9% | Grok 4.20 |
| MMMU Pro (Vals AI) | 83.5% | Not measured | Only Grok 4.20 measured |
| GPQA Diamond (Artificial Analysis run) | 91.1% | 74.8% | Grok 4.20 |
| Humanity's Last Exam (Artificial Analysis run) | 34.5% | 13.8% | Grok 4.20 |
| ARC-AGI | 89.5% | Not measured | Only Grok 4.20 measured |
| ARC-AGI-2 | 65.1% | Not measured | Only Grok 4.20 measured |
| LMArena Text: hard prompts | Not measured | 1436 | Only Mistral Medium 3.5 measured |
| LMArena Text: expert | Not measured | 1432 | Only Mistral Medium 3.5 measured |
| LMArena Text: hard prompts in English | Not measured | 1445 | Only Mistral Medium 3.5 measured |
| LMArena Vision: diagrams | Not measured | 1254 | Only Mistral Medium 3.5 measured |
| LMArena Vision: homework | Not measured | 1230 | Only Mistral Medium 3.5 measured |
| Neither model has a result on the other 10 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index4 boards, none shared
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| AIME | 96.5% | Not measured | Only Grok 4.20 measured |
| ProofBench | Not measured | 9.0% | Only Mistral Medium 3.5 measured |
| LMArena Text: math | Not measured | 1431 | Only Mistral Medium 3.5 measured |
| LMArena Text: mathematical work | Not measured | 1440 | Only Mistral Medium 3.5 measured |
| Neither model has a result on the other 9 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index51
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| MMLU Pro | 86.3% | 75.3% | Grok 4.20 |
| LegalBench (Vals AI) | 77.7% | Not measured | Only Grok 4.20 measured |
| CaseLaw (Vals AI) | 54.4% | 44.2% | Grok 4.20 |
| CorpFin (Vals AI) | 63.7% | 58.8% | Grok 4.20 |
| TaxEval (Vals AI) | 74.1% | 68.0% | Grok 4.20 |
| MortgageTax (Vals AI) | 45.4% | 28.9% | Grok 4.20 |
| MedQA (Vals AI) | 94.5% | Not measured | Only Grok 4.20 measured |
| MedCode (Vals AI) | 32.2% | 33.8% | Mistral Medium 3.5 |
| LMArena Text: science | Not measured | 1428 | Only Mistral Medium 3.5 measured |
| LMArena Text: medicine and healthcare | Not measured | 1409 | Only Mistral Medium 3.5 measured |
| LMArena Text: legal and government | Not measured | 1437 | Only Mistral Medium 3.5 measured |
| LMArena Text: business and finance | Not measured | 1426 | Only Mistral Medium 3.5 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 | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| Design Arena: websites | 1229 | 1142 | Grok 4.20 |
| Design Arena: UI components | 1199 | 1079 | Grok 4.20 |
| Design Arena: game dev | 1192 | 1079 | Grok 4.20 |
| Design Arena: data viz | 1217 | 1120 | Grok 4.20 |
| Design Arena: 3D | 1193 | 1061 | Grok 4.20 |
| Design Arena: all code categories | 1221 | 1121 | Grok 4.20 |
| Design Arena: SVG | 1164 | 950 | Grok 4.20 |
| Design Arena: ASCII art | 1174 | 1063 | Grok 4.20 |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index52
| Benchmark | Grok 4.20 | Mistral Medium 3.5 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 38.2% | 37.6% | Grok 4.20 |
| MedScribe (Vals AI) | 63.4% | 67.7% | Mistral Medium 3.5 |
| Vals Multimodal Index | 39.1% | 34.8% | Grok 4.20 |
| IFBench | 81.2% | 68.8% | Grok 4.20 |
| Long context reasoning (AA-LCR) | 69.0% | 69.3% | Mistral Medium 3.5 |
| DTBench | 90.1% | 75.5% | Grok 4.20 |
| LMCA | 38.7% | 26.1% | Grok 4.20 |
| CL-bench | 22.2% | Not measured | Only Grok 4.20 measured |
| Surface Evolver Bench | Not measured | 26.9% | Only Mistral Medium 3.5 measured |
| CL-bench Life | 11.9% | Not measured | Only Grok 4.20 measured |
| LMArena Text | Not measured | 1421 | Only Mistral Medium 3.5 measured |
| LMArena Text: instruction following | Not measured | 1415 | Only Mistral Medium 3.5 measured |
| LMArena Text: creative writing | Not measured | 1374 | Only Mistral Medium 3.5 measured |
| LMArena Vision | Not measured | 1222 | Only Mistral Medium 3.5 measured |
| LMArena Text: English | Not measured | 1433 | Only Mistral Medium 3.5 measured |
| LMArena Text: non-English | Not measured | 1404 | Only Mistral Medium 3.5 measured |
| LMArena Text: Chinese | Not measured | 1444 | Only Mistral Medium 3.5 measured |
| LMArena Text: German | Not measured | 1453 | Only Mistral Medium 3.5 measured |
| LMArena Text: Korean | Not measured | 1384 | Only Mistral Medium 3.5 measured |
| LMArena Text: French | Not measured | 1448 | Only Mistral Medium 3.5 measured |
| LMArena Text: Spanish | Not measured | 1411 | Only Mistral Medium 3.5 measured |
| LMArena Text: Russian | Not measured | 1395 | Only Mistral Medium 3.5 measured |
| LMArena Text: Polish | Not measured | 1430 | Only Mistral Medium 3.5 measured |
| LMArena Text: multi-turn | Not measured | 1423 | Only Mistral Medium 3.5 measured |
| LMArena Text: longer queries | Not measured | 1415 | Only Mistral Medium 3.5 measured |
| LMArena Text: writing and language | Not measured | 1384 | Only Mistral Medium 3.5 measured |
| LMArena Text: entertainment and media | Not measured | 1382 | Only Mistral Medium 3.5 measured |
| LMArena Vision: English | Not measured | 1240 | Only Mistral Medium 3.5 measured |
| LMArena Vision: Chinese | Not measured | 1244 | Only Mistral Medium 3.5 measured |
| LMArena Vision: reading text | Not measured | 1233 | Only Mistral Medium 3.5 measured |
| LMArena Vision: humor | Not measured | 1216 | Only Mistral Medium 3.5 measured |
| LMArena Vision: creative writing | Not measured | 1198 | Only Mistral Medium 3.5 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.20 | 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
Grok 4.20 costs less
Repository review
50K input + 3K output tokens
Grok 4.20 costs less
Agent loop
200K input + 10K output tokens
Grok 4.20 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 | SpaceXAI Grok 4.20 | Mistral Medium 3.5 |
|---|---|---|
| Maker | xAI | Mistral AI |
| Weights | No public weights listed | No public weights listed |
| Released | March 31, 2026 | April 30, 2026 |
| Context window | 2M | 262K |
| Input $/Mtok | $1.25 | $1.50 |
| Output $/Mtok | $2.50 | $7.50 |
| Coding index | 33.3 | 25.5 |
| Independent measurements behind it | 2 | 3 |
| Cost per solved task | $0.72 | $6.02 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.20 better than Mistral Medium 3.5 for coding?
Pick Grok 4.20 for coding: it scores 33.3 on the Vibe Coding Index against 25.5 for Mistral Medium 3.5, though on 2 benchmarks against 3. Pick Mistral Medium 3.5 for work measured by Code migration (Vals AI) or Finance Agent (Vals AI), where it leads.
Which is cheaper, Grok 4.20 or Mistral Medium 3.5?
Grok 4.20 costs $1.25 per million input tokens and $2.50 per million output tokens; Mistral Medium 3.5 costs $1.50 and $7.50. Per solved SWE-bench Verified task, Grok 4.20 costs $0.72 and Mistral Medium 3.5 $6.02.
Which has the bigger context window, Grok 4.20 or Mistral Medium 3.5?
Grok 4.20, with 2M tokens against 262K.
How many benchmarks is the Grok 4.20 vs Mistral Medium 3.5 comparison based on?
36 benchmarks have a result for both models as of October 21, 2026. Grok 4.20's coding index rests on 2 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.