Astral-4B-Preview

Astral-4B is a specialized reasoning-focused language model developed as part of the Astral series, designed to deliver high-fidelity, step-by-step reasoning with configurable depth. Built upon the Qwen3-4b-thinking-2507 foundation, this variant has been fine-tuned on the nvidia/AceReason-1.1-SFT dataset to enhance logical coherence, problem-solving capability, and structured thinking.

This model is currently in preview and intended for research, evaluation, and development use. Feedback is encouraged to guide future iterations.

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Usage Instructions

To invoke the model correctly, include a reasoning-level indicator in the system prompt using the Reasoning-level: directive. The available levels are:

Level	Behavior
none	No reasoning trace generated, direct response only.
low	Minimal internal reasoning
medium	Creates a reasoning trace thats not too long nor too short
high	Second highest reasoning depth
ultra	Maximum depth reasoning

Note: The absence of a valid reasoning level will result in undefined behavior. Always specify one.

Example Prompt (ChatML Format):

<|im_start|>system
Reasoning-level: high
<|im_end|>
<|im_start|>user
What is the capital of France?
<|im_end|>
<|im_start|>assistant
<think>

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Important Notes

• This is a preview release. Performance may vary across edge cases or non-standard inputs.
• For production applications, please wait for the official release.

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