Google: Gemini 3.1 Pro Preview

google/gemini-3.1-pro-preview · GoogleDeclared and measured agree

Tokenizer lineage (measured): Gemini
Evidence confidence: High
Declared tokenizer tag: Gemini
Entered catalogue: 19 February 2026
Last tested: 3 September 2026
Measurement: Measured

Evidence

✓ exact tokenizer signature shared with 19 models

Compare with Google: Gemini 3.8 Flash

Download JSON Report a correction

Identity statement

Google: Gemini 3.1 Pro Preview is Google's model. Its measured tokenizer sits with the Gemini group, which is evidence that it builds on the Gemini tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against Google's authorship of the model itself.

Evidence stack

Signals of different kinds, weighed together

Signal	Result	Reference
Tokenizer signature	Exact match with 19 other models	tk_59ca250f
API surface	Identical contract to 2 other entries	api_16435537
Context and output	1,048,576 context · 65,536 max output	declared
Reasoning contract	Mandatory · efforts high, medium, low · default medium	declared
Serving providers observed	Google	measured 3 September 2026

Shares this fingerprint

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

Closest measured models

Agreement across the mutually clean test strings

Google: Gemini 3.7 Flashgoogle/gemini-3.7-flash50/50 · 100%Google: Gemma 3 4Bgoogle/gemma-3-4b-it50/50 · 100%Google: Gemma 3 12Bgoogle/gemma-3-12b-it50/50 · 100%Google: Gemma 3 27Bgoogle/gemma-3-27b-it50/50 · 100%Google: Gemini 2.5 Flash Litegoogle/gemini-2.5-flash-lite50/50 · 100%Google: Gemini 3.1 Flash Litegoogle/gemini-3.1-flash-lite50/50 · 100%

Click a row to open the full comparison.

The measured fingerprint

Marginal prompt-token cost of each test string, grouped by script

All 50 rows

English and whitespace

en-prose14

en-long16

spaces-203

spaces-604

tabs-203

newlines-203

mixed-ws9

Digits

digits-99

digits-1212

digits-3030

digits-sep12

float-long22

CJK

zh-common10

zh-long12

zh-rare25

ja-kana7

ja-kanji9

ko11

Other scripts

ru12

ar10

he13

hi8

th10

el13

Emoji

emoji-basic5

emoji-skin10

emoji-zwj-family7

emoji-zwj-x321

emoji-flags8

emoji-prof11

Rare Unicode

math26

boxdraw17

combining10

cjk-ext-b16

surrogates27

zalgo22

rtl-mix5

Code

py-code28

py-indent18

json28

html14

regex44

camel6

snake11

Repetition and encodings

rare-word-x525

repeat-tok21

base6434

hex16

url23

uuid36

An x marks a row excluded as corrupt (caching or provider interference detected during measurement). Overhead subtracted: 0 prompt tokens.

Declared record

What the catalogue claims about this model

Gemini 3.1 Pro Preview is Google’s frontier reasoning model, delivering enhanced software engineering performance, improved agentic reliability, and more efficient token usage across complex workflows. Building on the multimodal foundation...

Modalities: text+image+file+audio+video->text
Declared tokenizer: Gemini
Prompt price: $2.00 / M tokens
Completion price: $12.0 / M tokens

Supported parameters

include_reasoningmax_tokensreasoningreasoning_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

History

Every observation, kept as taken

19 February 2026Enters the OpenRouter catalogue declared as Gemini.
3 September 2026Fingerprinted in the YFarmX catalogue sweep · 50 of 50 strings measured clean.
3 September 2026YFarmX assessment: consistent with the Gemini family, high confidence.

Cite this page as the evidence record for Google: Gemini 3.1 Pro Preview: the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings.