Qwen: Qwen3.5 Plus 2026-04-20

qwen/qwen3.5-plus-20260420 · Alibaba (Qwen)Declared and measured agree

Tokenizer lineage (measured): Qwen
Declared tokenizer tag: Qwen3
Entered catalogue: 27 April 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 Qwen: Qwen3.8 Max Prime

Report a correction

Identity statement

Qwen: Qwen3.5 Plus 2026-04-20 is Alibaba (Qwen)'s model. Its measured tokenizer sits with the Qwen group, which is evidence that it builds on the Qwen tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against Alibaba (Qwen)'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_181907f2
How its API is set up	Set up identically to 1 other listing, field for field	api_1584b07a
How much it can read and write	Reads up to 1,000,000 tokens at once, writes up to 65,536	its own listing
Whether it thinks before answering	Reasons when asked to	its own listing
Who served our requests	Alibaba	we measured it, 5 October 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

Nex AGI: Nex-N2-Mininex-agi/nex-n2-mini50/50 · 100%Qwen: Qwen3.7 Flashqwen/qwen3.7-flash50/50 · 100%Qwen: Qwen3.5-Flashqwen/qwen3.5-flash-02-2350/50 · 100%Qwen: Qwen3.5-9Bqwen/qwen3.5-9b50/50 · 100%Qwen: Qwen3.6 Flashqwen/qwen3.6-flash50/50 · 100%Qwen: Qwen3.5-27Bqwen/qwen3.5-27b50/50 · 100%

Click a row to open the full comparison.

The measured fingerprint

What each test string cost this model, in tokens

We sent Qwen: Qwen3.5 Plus 2026-04-20 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-long16

spaces-203

spaces-603

tabs-203

newlines-204

mixed-ws5

Digits

digits-99

digits-1212

digits-3030

digits-sep12

float-long22

CJK

zh-common9

zh-long10

zh-rare18

ja-kana7

ja-kanji10

ko13

Other scripts

ru12

ar10

he14

hi15

th8

el13

Emoji

emoji-basic9

emoji-skin30

emoji-zwj-family18

emoji-zwj-x354

emoji-flags24

emoji-prof29

Rare Unicode

math29

boxdraw28

combining5

cjk-ext-b13

surrogates40

zalgo36

rtl-mix6

Code

py-code26

py-indent18

json25

html16

regex44

camel5

snake6

Repetition and encodings

rare-word-x530

repeat-tok21

base6436

hex17

url19

uuid36

Overhead subtracted: 10 prompt tokens.

Declared record

What the catalogue claims about this model

Qwen3.5 Plus (April 2026) is a large-scale multimodal language model from Alibaba. It accepts text, image, and video input and produces text output, with a 1M token context window. This...

Modalities: text+image+video->text
Declared tokenizer: Qwen3
Prompt price: $0.30 / M tokens
Completion price: $1.80 / M tokens

Supported parameters

frequency_penaltyinclude_reasoninglogprobsmax_tokenspresence_penaltyreasoningresponse_formatseedstopstructured_outputstemperaturetool_choicetoolstop_ktop_logprobstop_p

defaults: {}

Catalogue entry

History

Every observation, kept as taken

27 April 2026Enters the OpenRouter catalogue declared as Qwen3.
5 October 2026Fingerprinted in the YFarmX catalogue sweep · 50 of 50 strings measured clean.
5 October 2026YFarmX assessment: consistent with the Qwen family, very high confidence.