GPT-5.1 vs Mistral Medium 3.5

GPT-5.1 leads Mistral Medium 3.5 on coding, 40.4 to 25.5 on the Vibe Coding Index, and Mistral Medium 3.5 costs 1.3x less per output token ($7.50 vs $10.00 per million). Updated October 22, 2026; 68 benchmarks have a result for both.

Replace GPT-5.1 Replace Mistral Medium 3.5

GPT-5.1OpenAI

Coding: 40.4
Overall: 55.0
Output $/M: $10.00

Mistral Medium 3.5Mistral AI

Coding: 25.5
Overall: 37.3
Output $/M: $7.50

vs boards won of 68 shared, 1 tied

GPT-5.1 or Mistral Medium 3.5: which to pick

Pick GPT-5.1 for coding: it scores 40.4 on the Vibe Coding Index against 25.5 for Mistral Medium 3.5.

Pick Mistral Medium 3.5 for output tokens 1.3x cheaper ($7.50 vs $10.00 per million) and work measured by LMArena Text: coding or LMArena Text: software and IT, where it leads.

Model AGPT-5.1OpenAI40.4/1003 independent benchmarks$1.02 per solved task Model BMistral Medium 3.5Mistral AI25.5/1003 independent benchmarks$6.02 per solved task

683313

Shared results: 68
GPT-5.1 only: 33
Mistral Medium 3.5 only: 13
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-5.1
GPT-5.1 scores 40.4 against 25.5.
3 benchmarks behind each score
Intelligence
AA Intelligence Index
GPT-5.1
GPT-5.1 leads, 24.7 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
GPT-5.1
GPT-5.1 leads, 86.6% against 34.9%.
Same board, both measured
Math
AIME
No call
Only GPT-5.1 has a AIME result, 93.3%.
Directional only
Knowledge
MMLU Pro
GPT-5.1
GPT-5.1 leads, 86.4% against 75.3%.
Same board, both measured
Web design
Design Arena: websites
GPT-5.1
GPT-5.1 leads, 1187 against 1142.
Same board, both measured
Long documents
Listed context window
GPT-5.1
GPT-5.1 takes 400K tokens against 262K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mistral Medium 3.5
GPT-5.1 $0.0063, Mistral Medium 3.5 $0.0053 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
GPT-5.1
GPT-5.1 $1.02, Mistral Medium 3.5 $6.02.
Published attempt cost and pass rate

At a glance

Coding index: GPT-5.1 40.4 from 3 benchmarks, Mistral Medium 3.5 25.5 from 3 benchmarks.
Widest category: Reasoning, 12.6 points apart on average over 8 shared benchmarks.
Widest single gap: GPQA Diamond: GPT-5.1 86.6% against Mistral Medium 3.5 34.9%, 51.8 points apart on a 0 to 100 scale.
Output price: GPT-5.1 $10.00 against Mistral Medium 3.5 $7.50 per million output tokens, 1.3x apart.
Context window: GPT-5.1 takes 400K 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.

Boards won, where both have a result
Category	GPT-5.1	Mistral Medium 3.5	Ties
Coding	7	2
Intelligence	2	0
Agentic work	0	1
Reasoning	8	0
Math	2	0
Knowledge	10	0
Web design	7	0	1 tie
General	27	1
All shared boards	63	4	1 tie

CodingLike-for-likeSix of these boards feed the Vibe Coding Index72

Coding benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
SWE-bench Verified	66.0%	Not measured	Only GPT-5.1 measured
LMArena WebDev	1396	1264	GPT-5.1
AA Coding Index	49.4	46.9	GPT-5.1
LiveCodeBench (Vals AI)	86.5%	Not measured	Only GPT-5.1 measured
SWE-bench Verified (Vals AI)	69.8%	66.4%	GPT-5.1
Vibe Code Bench (Vals AI)	24.6%	2.9%	GPT-5.1
Code migration (Vals AI)	Not measured	5.1%	Only Mistral Medium 3.5 measured
Terminal-Bench 2.1 (Vals AI)	Not measured	39.0%	Only Mistral Medium 3.5 measured
LiveCodeBench (Artificial Analysis run)	86.8%	Not measured	Only GPT-5.1 measured
SciCode	Not measured	40.2%	Only Mistral Medium 3.5 measured
Terminal-Bench Hard (Artificial Analysis run)	45.5%	33.3%	GPT-5.1
Terminal-Bench	47.6%	Not measured	Only GPT-5.1 measured
GSO-Bench	13.7%	Not measured	Only GPT-5.1 measured
WeirdML	60.8%	Not measured	Only GPT-5.1 measured
ALE-Bench	Not measured	764.0	Only Mistral Medium 3.5 measured
LMArena Text: coding	1453	1460	Mistral Medium 3.5
LMArena Text: software and IT	1454	1458	Mistral Medium 3.5
LMArena WebDev: React	1307	1254	GPT-5.1
LMArena WebDev: HTML	1405	1308	GPT-5.1
LMArena WebDev: from an image	1421	Not measured	Only GPT-5.1 measured
Neither model has a result on the other 19 boards here

IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20

Intelligence benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
AA Intelligence Index	24.7	14.2	GPT-5.1
Epoch Capabilities Index	149.8	141.4	GPT-5.1

Agentic workLike-for-likePublic boards, shown as published, kept out of the index01

Agentic work benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
AA Agentic Index	Not measured	7.0	Only Mistral Medium 3.5 measured
Finance Agent (Vals AI)	Not measured	32.1%	Only Mistral Medium 3.5 measured
Tax Agent Bench (Vals AI)	Not measured	4.5%	Only Mistral Medium 3.5 measured
Legal Research Bench (Vals AI)	Not measured	9.1%	Only Mistral Medium 3.5 measured
Excel Modeling Benchmark (Vals AI)	Not measured	11.2%	Only Mistral Medium 3.5 measured
τ²-Bench Telecom	81.9%	94.2%	Mistral Medium 3.5
DeepResearch Bench	42.8%	Not measured	Only GPT-5.1 measured
Vending-Bench 2	$1,473	Not measured	Only GPT-5.1 measured
Neither model has a result on the other 33 boards here

ReasoningLike-for-likePublic boards, shown as published, kept out of the index80

Reasoning benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
GPQA Diamond	86.6%	34.9%	GPT-5.1
MMMU Pro (Vals AI)	83.2%	Not measured	Only GPT-5.1 measured
GPQA Diamond (Artificial Analysis run)	87.3%	74.8%	GPT-5.1
Humanity's Last Exam (Artificial Analysis run)	28.5%	13.8%	GPT-5.1
GPQA Diamond (Epoch AI run)	87.6%	Not measured	Only GPT-5.1 measured
ARC-AGI	72.8%	Not measured	Only GPT-5.1 measured
ARC-AGI-2	17.6%	Not measured	Only GPT-5.1 measured
SimpleBench	53.2%	Not measured	Only GPT-5.1 measured
Chess puzzles	42.0%	Not measured	Only GPT-5.1 measured
Mystery game puzzles	19.0%	Not measured	Only GPT-5.1 measured
VPCT	58.7%	Not measured	Only GPT-5.1 measured
LMArena Text: hard prompts	1457	1436	GPT-5.1
LMArena Text: expert	1470	1432	GPT-5.1
LMArena Text: hard prompts in English	1462	1445	GPT-5.1
LMArena Vision: diagrams	1264	1254	GPT-5.1
LMArena Vision: homework	1272	1230	GPT-5.1
Kagi LLM Benchmark	Not measured	41.4%	Only Mistral Medium 3.5 measured
Neither model has a result on the other 5 boards here

MathLike-for-likePublic boards, shown as published, kept out of the index20

Math benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
AIME	93.3%	Not measured	Only GPT-5.1 measured
MGSM (Vals AI)	93.0%	Not measured	Only GPT-5.1 measured
AA Math Index	94.0	Not measured	Only GPT-5.1 measured
AIME 2025 (Artificial Analysis run)	94.0%	Not measured	Only GPT-5.1 measured
OTIS Mock AIME	88.6%	Not measured	Only GPT-5.1 measured
ProofBench	Not measured	9.0%	Only Mistral Medium 3.5 measured
LMArena Text: math	1446	1431	GPT-5.1
LMArena Text: mathematical work	1449	1440	GPT-5.1
Neither model has a result on the other 5 boards here

KnowledgeLike-for-likePublic boards, shown as published, kept out of the index100

Knowledge benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
MMLU Pro	86.4%	75.3%	GPT-5.1
LegalBench (Vals AI)	85.7%	Not measured	Only GPT-5.1 measured
CaseLaw (Vals AI)	73.4%	44.2%	GPT-5.1
CorpFin (Vals AI)	63.8%	58.8%	GPT-5.1
TaxEval (Vals AI)	74.9%	68.0%	GPT-5.1
MortgageTax (Vals AI)	61.4%	28.9%	GPT-5.1
MedQA (Vals AI)	96.4%	Not measured	Only GPT-5.1 measured
MedCode (Vals AI)	52.7%	33.8%	GPT-5.1
MMLU Pro (Artificial Analysis run)	87.0%	Not measured	Only GPT-5.1 measured
SimpleQA Verified	48.0%	Not measured	Only GPT-5.1 measured
LMArena Text: science	1459	1428	GPT-5.1
LMArena Text: medicine and healthcare	1456	1409	GPT-5.1
LMArena Text: legal and government	1459	1437	GPT-5.1
LMArena Text: business and finance	1431	1426	GPT-5.1
FACTS Benchmark Suite	45.0%	Not measured	Only GPT-5.1 measured
Neither model has a result on the other 3 boards here

Web designLike-for-likePublic boards, shown as published, kept out of the index70

Web design benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
Design Arena: websites	1187	1142	GPT-5.1
Design Arena: UI components	1163	1076	GPT-5.1
Design Arena: game dev	1178	1079	GPT-5.1
Design Arena: data viz	1204	1120	GPT-5.1
Design Arena: 3D	1060	1060	Tie
Design Arena: all code categories	1170	1121	GPT-5.1
Design Arena: SVG	1149	949	GPT-5.1
Design Arena: ASCII art	1119	1062	GPT-5.1
Neither model has a result on the other 1 board here

GeneralLike-for-likePublic boards, shown as published, kept out of the index271

General benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	Mistral Medium 3.5	Leader
SAGE (Vals AI)	43.2%	37.6%	GPT-5.1
MedScribe (Vals AI)	88.1%	67.7%	GPT-5.1
Vals Multimodal Index	Not measured	34.8%	Only Mistral Medium 3.5 measured
IFBench	72.9%	68.8%	GPT-5.1
Long context reasoning (AA-LCR)	80.0%	69.3%	GPT-5.1
DTBench	90.1%	75.5%	GPT-5.1
LMCA	43.9%	26.1%	GPT-5.1
CL-bench	23.7%	Not measured	Only GPT-5.1 measured
Surface Evolver Bench	Not measured	26.9%	Only Mistral Medium 3.5 measured
CL-bench Life	17.3%	Not measured	Only GPT-5.1 measured
LMArena Text	1443	1421	GPT-5.1
LMArena Text: instruction following	1443	1415	GPT-5.1
LMArena Text: creative writing	1427	1374	GPT-5.1
LMArena Vision	1250	1222	GPT-5.1
LMArena Text: English	1451	1433	GPT-5.1
LMArena Text: non-English	1431	1404	GPT-5.1
LMArena Text: Chinese	1495	1444	GPT-5.1
LMArena Text: German	1438	1453	Mistral Medium 3.5
LMArena Text: Japanese	1453	Not measured	Only GPT-5.1 measured
LMArena Text: Korean	1401	1384	GPT-5.1
LMArena Text: French	1450	1448	GPT-5.1
LMArena Text: Spanish	1433	1411	GPT-5.1
LMArena Text: Russian	1435	1395	GPT-5.1
LMArena Text: Polish	1440	1430	GPT-5.1
LMArena Text: multi-turn	1450	1423	GPT-5.1
LMArena Text: longer queries	1448	1415	GPT-5.1
LMArena Text: writing and language	1428	1384	GPT-5.1
LMArena Text: entertainment and media	1415	1382	GPT-5.1
LMArena Vision: English	1252	1240	GPT-5.1
LMArena Vision: Chinese	1270	1244	GPT-5.1
LMArena Vision: reading text	1255	1233	GPT-5.1
LMArena Vision: humor	1263	1216	GPT-5.1
LMArena Vision: captioning	1252	Not measured	Only GPT-5.1 measured
LMArena Vision: recognizing things	1232	Not measured	Only GPT-5.1 measured
LMArena Vision: creative writing	1266	1198	GPT-5.1
LMArena Document	1403	Not measured	Only GPT-5.1 measured
Neither model has a result on the other 10 boards here

Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared

Image generation benchmarks for GPT-5.1 and Mistral Medium 3.5
Benchmark	GPT-5.1	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-5.1$0.0063Fits in one request

Mistral Medium 3.5$0.0053Fits in one request

Mistral Medium 3.5 costs less

Repository review

50K input + 3K output tokens

GPT-5.1$0.092Fits in one request

Mistral Medium 3.5$0.098Fits in one request

GPT-5.1 costs less

Agent loop

200K input + 10K output tokens

GPT-5.1$0.350Fits in one request

Mistral Medium 3.5$0.375Fits in one request

GPT-5.1 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.

Specifications of GPT-5.1 and Mistral Medium 3.5
Specification	OpenAI GPT-5.1	Mistral Medium 3.5
Maker	OpenAI	Mistral AI
Weights	No public weights listed	No public weights listed
Released	November 13, 2025	April 30, 2026
Context window	400K	262K
Input $/Mtok	$1.25	$1.50
Output $/Mtok	$10.00	$7.50
Coding index	40.4	25.5
Independent measurements behind it	3	3
Cost per solved task	$1.02	$6.02
Source	OpenRouter listing	OpenRouter listing

Questions

Is GPT-5.1 better than Mistral Medium 3.5 for coding?

Pick GPT-5.1 for coding: it scores 40.4 on the Vibe Coding Index against 25.5 for Mistral Medium 3.5. Pick Mistral Medium 3.5 for output tokens 1.3x cheaper ($7.50 vs $10.00 per million) and work measured by LMArena Text: coding or LMArena Text: software and IT, where it leads.

Which is cheaper, GPT-5.1 or Mistral Medium 3.5?

GPT-5.1 costs $1.25 per million input tokens and $10.00 per million output tokens; Mistral Medium 3.5 costs $1.50 and $7.50. Per solved SWE-bench Verified task, GPT-5.1 costs $1.02 and Mistral Medium 3.5 $6.02.

Which has the bigger context window, GPT-5.1 or Mistral Medium 3.5?

GPT-5.1, with 400K tokens against 262K.

How many benchmarks is the GPT-5.1 vs Mistral Medium 3.5 comparison based on?

68 benchmarks have a result for both models as of October 22, 2026. GPT-5.1's coding index rests on 3 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.

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GPT-5.1 or Mistral Medium 3.5: which to pick

Which one for your work

Coding

Intelligence

Agentic work

Reasoning

Math

Knowledge

Web design

Long documents

Everyday cost

Cost per solved task