Upstage: Solar Pro 4

upstage/solar-pro4 · UpstageTokenizer lineage measured

Tokenizer group (measured): Upstage
Entered catalogue: 10 August 2026
Last tested: 21 August 2026
Evidence confidence: Very high

Why very high: an exact fingerprint shared with 2 models and an identical API contract inside the same group: two signals of different kinds agree.

Evidence

✓ exact tokenizer signature shared with 2 models
✓ API-surface contract identical to a group member

Compare with Upstage: Solar Mini 4

Report a correction

Identity statement

Upstage: Solar Pro 4 is Upstage's model, and its measured tokenizer sits in Upstage's own signature group alongside its sibling models. No other maker's measured model shares it so far.

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 2 other models	tk_865d84ce
How its API is set up	Set up identically to 1 other listing, field for field	api_3eea2af4
How much it can read and write	Reads up to 524,288 tokens at once, writes up to 131,072	its own listing
Whether it thinks before answering	Reasons when asked to, at max, xhigh, high, medium, low, minimal, none, medium by default	its own listing
Who served our requests	Upstage	we measured it, 21 August 2026

Shares this fingerprint

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

Upstage: Solar Mini 4upstage/solar-mini4exact · 50/50 Upstage: Solar Pro 3upstage/solar-pro-3exact · 50/50

Closest measured models

Agreement across the mutually clean test strings

Upstage: Solar Pro 3upstage/solar-pro-350/50 · 100%Upstage: Solar Mini 4upstage/solar-mini450/50 · 100%Cohere: Command R (08-2024)cohere/command-r-08-202422/49 · 45%Cohere: Command R+ (08-2024)cohere/command-r-plus-08-202422/49 · 45%Cohere: Command R7B (12-2024)cohere/command-r7b-12-202422/50 · 44%Tencent: Hunyuan A13B Instructtencent/hunyuan-a13b-instruct22/50 · 44%

Click a row to open the full comparison.

The measured fingerprint

What each test string cost this model, in tokens

We sent Upstage: Solar Pro 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-long15

spaces-203

spaces-603

tabs-204

newlines-204

mixed-ws6

Digits

digits-99

digits-1212

digits-3030

digits-sep12

float-long22

CJK

zh-common12

zh-long17

zh-rare18

ja-kana8

ja-kanji10

ko7

Other scripts

ru14

ar12

he25

hi15

th14

el13

Emoji

emoji-basic10

emoji-skin15

emoji-zwj-family11

emoji-zwj-x333

emoji-flags16

emoji-prof19

Rare Unicode

math21

boxdraw26

combining9

cjk-ext-b16

surrogates37

zalgo35

rtl-mix10

Code

py-code25

py-indent15

json25

html17

regex41

camel5

snake6

Repetition and encodings

rare-word-x526

repeat-tok40

base6432

hex16

url19

uuid36

Overhead subtracted: 52 prompt tokens.

Declared record

What the catalogue claims about this model

Solar Pro 4 is Upstage's cost-efficient large language model, featuring a 524K context window. It is built for long-horizon tasks and agentic workflows, with strong capabilities in office productivity, document-intensive...

Modalities: text->text
Declared tokenizer: Other
Prompt price: $0.09 / M tokens
Completion price: $0.36 / M tokens

Supported parameters

frequency_penaltyinclude_reasoningmax_tokensparallel_tool_callspresence_penaltyreasoningreasoning_effortresponse_formatstructured_outputstemperaturetool_choicetoolstop_p

defaults: {}

Catalogue entry

History

Every observation, kept as taken

10 August 2026Enters the OpenRouter catalogue with no declared family.
21 August 2026Fingerprinted in the YFarmX catalogue sweep · 50 of 50 strings measured clean.
21 August 2026YFarmX assessment: consistent with the Upstage family, very high confidence.