Nebula

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1. Introduction

Nebula is a 320M-parameter generalist Small Reasoning Model trained on 200B+ tokens, designed for edge AI and on-device deployment.

Nebula is designed to deliver an unusually strong balance of memory, general reasoning, math, and retrieval-friendly behavior for its size class, aiming to outperform many small models of a similar parameter range on non-code, industry-style benchmarks.

2. Reasoning style

Nebulaโ€™s reasoning traces use an intentionally compact style with dense, short, frequently non-verbal sentences, optimized for efficiency under limited model capacity.

Traces use the following stenographic notation integrated into special tokens:

Logical markers

Token Meaning Usage
โ†’ derivation / implication For very short causal/logical flow
โ†บ iterative return / refinement loop For backtracking, reconsidering priors, RAG re-querying
? uncertainty/questions to resolve Can be appended to short expressions/words, not only interrogatives
!/โ€ป insight/breakthroughs Emphatic mark for knowledge discovery
โ‰ˆ approximation/estimates For intermediary hypothesis / uncertain preliminary statements
โˆด therefore / final step Use sparingly to mark stable conclusions

Uncertainty

Token Meaning Usage
โ— high confidence well-supported empirical/theoretical ground; โ€œanchor points.โ€
โ— medium/partial confidence incomplete data; plausible but unverified links
โ—‹ low confidence speculation, missing context, weak inference chain
โš  bias/premise risk domain mismatch, cultural assumptions, language-switch artifacts
?maybe? soft speculation marks tentative ideas, branches that might collapse later

Verification process

Token Meaning Usage
โ˜ unverified hypothesis raw claim, no cross-check yet
โ˜‘ intermediate verification one source/argument supports it
โœ“ confirmed/validated multiple independent supports (โ—-level)

This reasoning format is designed to remain expressive while being lightweight enough for a small model.

3. Fine-Tuning/RL

Nebula has been successfully fine-tuned for a variety of tasks

Because Nebula is a reasoning-oriented model, it is expected to train well with reinforcement learning methods such as GRPO, both for verifiable tasks (with objective rewards) and for subjective tasks using an LLM-as-a-judge.

4. Benchmarks

Model MMLU
Nebula 40.0
SmolLM2-360M 35.8
Gemma 3 270M (IT) 26.5
Granite-4.0-H-350M 36.21
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