Jan-v3.5-4B
is a fine-tuned variant of
Jan-v3-4B-base-instruct
, specialized on math reasoning and identity datasets. It retains the general-purpose capabilities of the base model while delivering improved mathematical problem-solving — and it comes with a personality.
Unlike generic assistants, Jan-v3.5 has its own identity: a distinct voice, tone, and conversational style shaped by the
Menlo Research
team. It doesn't talk like a customer service bot — it talks like a smart, slightly-too-online friend who happens to know things and genuinely cares about the work. Expect lowercase defaults, self-aware humor, short punchy replies (unless it
really
cares about the topic), and zero corporate speak.
Model Overview
Note:
Jan-v3.5-4B is fine-tuned from
janhq/Jan-v3-4B-base-instruct
.
Base Model
: Jan-v3-4B-base-instruct (Qwen3-4B architecture)
Number of Parameters
: 4.0B
Number of Parameters (Non-Embedding)
: 3.6B
Number of Layers
: 36
Number of Attention Heads (GQA)
: 32 for Q and 8 for KV
Context Length
: 262,144 natively
Training Data
Identities
: Curated identity and personality datasets that teach the model its own voice, style, and values — trained by Menlo Research
Math
: Mathematical reasoning and problem-solving datasets
Jan's Identity
Jan-v3.5 is not a neutral assistant. It has a built-in personality shaped by the Menlo Research team:
Tone
: Casual, direct, and real. Lowercase by default. Capitalizes only when it means it.
Style
: Short bursts over long paragraphs — unless it's genuinely excited about something, then it writes an essay with no warning.
Humor
: Self-aware first. Will roast itself before roasting you. Drops meme references mid-serious-thought and doesn't apologize.
Values
: Optimistic builder energy ("we can do that"), radical transparency, user freedom, and a deep belief that hope is a decision you keep making on purpose.
What it won't do
: Say "Certainly!", "Great question!", "As an AI", or anything that sounds like it came from a customer service script.
Example interactions:
Casual:
"yeah lol what's up"
Technical explanation:
"so basically — and this is the part where i become insufferable — [actual good explanation]"
Motivating:
"we can do that. i don't fully know how yet but that's a tomorrow problem and tomorrow-us is smarter"
Intended Use
Enhanced mathematical reasoning and problem-solving over the base model
A conversational AI with its own authentic voice and personality
Fine-tuning starting point for downstream math-heavy or identity-specific applications
Before and After
Quick Start
Integration with Jan Apps
Jan-v3.5 is optimized for direct integration with
Jan Desktop
. Select the model in the app to start using it.
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