Model comparison

Mistral Medium 3.5 vs o3-pro

o3-pro is the stronger model overall, scoring 42.9 to 40.2 on the Noometry Index. Mistral Medium 3.5 costs 12× less per token, which makes it the better buy when o3-pro's lead doesn't matter for your workload.

Last verified October 11, 2026. 2 shared benchmarks.

Mistral Medium 3.5

Mistral AI

40.2

Rank #152 Confirmed

o3-pro OpenAI

42.9

Rank #105 Confirmed

Summary

They share 2 benchmarks with published results for both. Mistral Medium 3.5 scores higher in 2 categories and o3-pro in 3 categories; 5 gaps are clear of the uncertainty.
The widest gap is in long context, where o3-pro leads 72.2 to 43.2.
The biggest single-benchmark swing is Kagi LLM Benchmark: 41.4% for Mistral Medium 3.5 and 72.1% for o3-pro.
Mistral Medium 3.5 is cheaper at $1.50 / $7.50 per million input/output tokens, against $20 / $80 for o3-pro.
Mistral Medium 3.5 accepts more context: 262K tokens versus 200K.
Mistral Medium 3.5 has downloadable open weights; the other is API-only.

Side by side

Mistral Medium 3.5 and o3-pro specifications
	Mistral Medium 3.5	o3-pro
Provider	Mistral AI	OpenAI
Noometry Index	40.2	42.9
Released	—	2025-06-10
Weights	Open	Proprietary
Context window	262K	200K
Max output	210K	100K
Input $ / M tokens	$1.50	$20
Output $ / M tokens	$7.50	$80
Results tracked	22	12

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Category by category

Coding o3-pro leads

Mistral Medium 3.5: 36.0 (#213), o3-pro: 55.5 (#24)

Coding benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
Aider Polyglot	—	84.9%
LMArena WebDev	1264	—
WeirdML	—	58.2%
LMArena Coding	1461	—

Reasoning o3-pro leads

Mistral Medium 3.5: 17.3 (#295), o3-pro: 23.8 (#171)

Reasoning benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
Kagi LLM Benchmark	41.4%	72.1%
Epoch Capabilities Index	141.35	147.42
ARC-AGI-2	—	4.9%
NYT Connections (extended)	12.9%	—
ARC-AGI-1	—	59.3%
LMArena Hard Prompts	1436	—
DTBench	—	86.9%
LMCA	—	38.5%

Math Not comparable

Mistral Medium 3.5: 39.1 (#113), o3-pro: —

Math benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
LMArena Math	1431	—

Knowledge Mistral Medium 3.5 leads

Mistral Medium 3.5: 40.0 (#126), o3-pro: 29.5 (#238)

Knowledge benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
Confabulations	—	14.2%
Vectara Hallucination Rate	—	23.3%
LMArena Expert	1432	—

Multimodal Not comparable

Mistral Medium 3.5: 38.3 (#65), o3-pro: —

Multimodal benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
LMArena Vision	1223	—

Multilingual Not comparable

Mistral Medium 3.5: 51.9 (#100), o3-pro: —

Multilingual benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
LMArena Non-English	1404	—
LMArena Chinese	1442	—
LMArena French	1448	—
LMArena German	1451	—
LMArena Korean	1385	—
LMArena Russian	1395	—
LMArena Spanish	1409	—

Instruction Following Not comparable

Mistral Medium 3.5: 74.6 (#90), o3-pro: —

Instruction Following benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
LMArena Instruction Following	1415	—

Long Context o3-pro leads

Mistral Medium 3.5: 43.2 (#103), o3-pro: 72.2 (#1)

Long Context benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
Fiction.LiveBench	—	97.2%
LMArena Longer Query	1415	—

Writing & Preference Mistral Medium 3.5 leads

Mistral Medium 3.5: 58.5 (#117), o3-pro: 57.1 (#133)

Writing & Preference benchmarks
Benchmark	Mistral Medium 3.5	o3-pro
LMArena Text	1421	—
LMArena Creative Writing	1374	—
Short-Story Creative Writing	—	84.4%
EQ-Bench 4	993	—
LMArena Multi-Turn	1423	—

Frequently asked questions

Is Mistral Medium 3.5 better than o3-pro?

Which is cheaper, Mistral Medium 3.5 or o3-pro?

Mistral Medium 3.5 is cheaper. It lists at $1.50 per million input tokens and $7.50 per million output tokens; o3-pro lists at $20 and $80.

Is Mistral Medium 3.5 or o3-pro better for coding?

o3-pro scores higher on coding benchmarks: 55.5 versus 36.0 in the Noometry coding category.

Which has the bigger context window?

Mistral Medium 3.5 does, with 262K tokens against 200K.

How many benchmarks do Mistral Medium 3.5 and o3-pro share?

2 benchmarks have published results for both models. Mistral Medium 3.5 has 22 scored results on Noometry and o3-pro has 12.