Mistral: Mistral Small 4

mistralai/mistral-small-2603 · Mistral AIDeclared and measured agree

Tokenizer lineage (measured): Mistral
Declared tokenizer tag: Mistral
Entered catalogue: 16 March 2026
Last tested: 5 October 2026
Evidence confidence: Very high

Why very high: an exact fingerprint shared with 21 models and an identical API contract inside the same group: two signals of different kinds agree.

Evidence

✓ exact tokenizer signature shared with 21 models
✓ API-surface contract identical to a group member

Compare with Mistral: Mistral Medium 3.5

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Identity statement

Mistral: Mistral Small 4 is Mistral AI's model. Its measured tokenizer sits with the Mistral group, which is evidence that it builds on the Mistral tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against Mistral AI's authorship of the model itself.

What we checked

Four different kinds of evidence, and what each one showed

We checked	What we found	Where it came from
How it counts tokens	Counts every one of the 50 test strings exactly like 21 other models	tk_0da8a999
How its API is set up	Set up identically to 3 other listings, field for field	api_e77b232e
How much it can read and write	Reads up to 262,144 tokens at once, writes up to 209,715	its own listing
Whether it thinks before answering	Reasons when asked to, at high, none, high by default	its own listing
Who served our requests	Mistral	we measured it, 5 October 2026
Measured twice	The 5 October 2026 reading agreed with the 21 August 2026 reading on every one of the 50 strings clean in both: the tokenizer behind this name held.	50/50 agree

Shares this fingerprint

Exact signature first; template-boundary shifts of the same signature beneath

Closest measured models

Agreement across the mutually clean test strings

Mistral: Mistral Nemomistralai/mistral-nemo50/50 · 100%NVIDIA: Nemotron 3 Nano 30B A3Bnvidia/nemotron-3-nano-30b-a3b50/50 · 100%NVIDIA: Nemotron 3.5 Lightningnvidia/nemotron-3.5-lightning50/50 · 100%NVIDIA: Nemotron 3 Supernvidia/nemotron-3-super-120b-a12b50/50 · 100%Mistral: Mistral Small 3.2 24Bmistralai/mistral-small-3.2-24b-instruct50/50 · 100%Mistral: Ministral 3 3B 2512mistralai/ministral-3b-251250/50 · 100%

Click a row to open the full comparison.

The measured fingerprint

What each test string cost this model, in tokens

We sent Mistral: Mistral Small 4 fifty short pieces of text and recorded what each one cost it in tokens. The bars below are those costs. Two models built on the same tokenizer produce the same bars; a model built on a different one produces a different set, which is what makes this a fingerprint.

All 50 rows

English and whitespace

en-prose14

en-long18

spaces-203

spaces-603

tabs-204

newlines-207

mixed-ws7

Digits

digits-99

digits-1212

digits-3030

digits-sep12

float-long22

CJK

zh-common16

zh-long20

zh-rare20

ja-kana11

ja-kanji13

ko13

Other scripts

ru12

ar9

he10

hi14

th17

el13

Emoji

emoji-basic20

emoji-skin40

emoji-zwj-family19

emoji-zwj-x357

emoji-flags32

emoji-prof35

Rare Unicode

math33

boxdraw30

combining14

cjk-ext-b16

surrogates53

zalgo36

rtl-mix6

Code

py-code25

py-indent15

json25

html16

regex49

camel6

snake7

Repetition and encodings

rare-word-x536

repeat-tok41

base6439

hex19

url19

uuid36

Overhead subtracted: 15 prompt tokens.

Declared record

What the catalogue claims about this model

Mistral Small 4 is the next major release in the Mistral Small family, unifying the capabilities of several flagship Mistral models into a single system. It combines strong reasoning from...

Modalities: text+image->text
Declared tokenizer: Mistral
Prompt price: $0.15 / M tokens
Completion price: $0.60 / M tokens

Supported parameters

frequency_penaltyinclude_reasoningmax_tokenspresence_penaltyreasoningreasoning_effortresponse_formatseedstopstructured_outputstemperaturetool_choicetoolstop_p

defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}

Catalogue entry Weights on Hugging Face

History

Every observation, kept as taken

16 March 2026Enters the OpenRouter catalogue declared as Mistral.
21 August 2026Fingerprinted in the YFarmX catalogue sweep · 50 of 50 strings measured clean.
5 October 2026Fingerprinted again, to check the reading held · 50 of 50 strings measured clean.
5 October 2026YFarmX assessment: consistent with the Mistral family, very high confidence.