Sky v2.0-6.5B — CREST Adaptive-Depth Language Model

Built by 0labs — Atharvsinh Jadav, Gujarat, India
One researcher. One GPU. Adaptive-depth LLMs.


What is This Model?

Sky v2.0-6.5B is a 6.47 billion parameter language model built on the CREST (Cognitively Recurrent Estimation of Step Termination) architecture — a proprietary adaptive-depth architecture developed by 0labs.

This is the K=2 variant of the full Sky v2.0-11B model. It retains the first two computational steps from the original four-step CREST architecture, preserving adaptive depth while being significantly lighter.

How CREST Works

In a standard transformer, every token gets the exact same computation — the word "the" gets the same processing as a critical step in a mathematical proof. CREST changes this.

Each transformer layer's Feed-Forward Network (FFN) is replaced with K independent MLPs and a learned halting gate. The model decides, per-token, per-layer, how many computational steps to take:

Easy token ("the", "is")     → 1 step  (fast, minimal computation)
Hard token (algorithm logic)  → 2 steps (deeper reasoning)

The halting gate is a learned sigmoid function that outputs a probability of stopping after each step. The final output is a weighted combination of all intermediate states.


Model Details

Property Value
Architecture CREST (0labs proprietary)
Total Parameters 6.47B
CREST Steps (K) 2
Hidden Dimension 2,560
Layers 32
Attention Heads 32
Context Window 32,768 tokens
Precision BFloat16
Vocabulary Size 248,320
Base Model Derived from Sky v2.0-11B (K=4)
License Apache 2.0

What's Included vs. the Full 11B

Feature Sky v2.0-11B Sky v2.0-6.5B (this model)
CREST Step 1 (base knowledge)
CREST Step 2 (verification)
CREST Step 3 (deep reasoning)
CREST Step 4 (complex logic)
Halting gates
Adaptive depth
Parameters 11.2B 6.47B

Steps 1 and 2 handle ~95% of all tokens in typical usage. This model retains the vast majority of the full model's capability at ~58% of the parameter count.


Quick Start

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained(
    "0labs-in/Sky-v2.0-6.5B",
    trust_remote_code=True,       # Required — CREST is a custom architecture
    torch_dtype=torch.bfloat16,
    device_map="auto",
)
tokenizer = AutoTokenizer.from_pretrained("0labs-in/Sky-v2.0-6.5B")

prompt = "Write a Python function to check if a number is prime."
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)

with torch.no_grad():
    outputs = model.generate(
        **inputs,
        max_new_tokens=512,
        temperature=0.7,
        top_p=0.9,
        do_sample=True,
    )

print(tokenizer.decode(outputs[0], skip_special_tokens=True))

Note: trust_remote_code=True is required because CREST uses custom modeling code (modeling_sky_crest.py, crest_block.py, configuration_sky_crest.py) that is included in this repository.


Hardware Requirements

Setup VRAM Required Works?
NVIDIA RTX 4090 (24GB) ~13GB BF16
NVIDIA RTX 3090 (24GB) ~13GB BF16
NVIDIA A100 (40/80GB) ~13GB BF16
AMD MI300X (192GB) ~13GB BF16
Apple M1/M2/M3 (16GB+) ~13GB ✅ (with MPS)
Google Colab Free (T4 15GB) ~13GB BF16 ⚠️ Tight
Load with load_in_4bit=True ~4GB ✅ Any GPU

For GPUs with less than 16GB VRAM, load in 4-bit:

model = AutoModelForCausalLM.from_pretrained(
    "0labs-in/Sky-v2.0-6.5B",
    trust_remote_code=True,
    load_in_4bit=True,
    device_map="auto",
)

Architecture: CREST in Detail

The CREST Block (replacing standard FFN)

Input from Attention
       ↓
   ┌──────────┐
   │   MLP₁   │  ← Step 1: Original pretrained knowledge
   └──────────┘
       ↓
   Halting Gate: "Is this token done?"
       │
       ├── If h₁ ≈ 1.0 → HALT (output = state₁)
       │
       ↓
   ┌──────────┐
   │   MLP₂   │  ← Step 2: Verification & deeper processing
   └──────────┘
       ↓
   Final output = p₁·state₁ + p₂·state₂

Key Properties

  • Independent parameters: MLP₁ and MLP₂ have completely separate weights, allowing specialization
  • Learned halting: The sigmoid gate learns which tokens need more computation
  • Residual gates: Scalar values controlling each step's contribution strength
  • Convex combination: Output probabilities always sum to 1.0

Model Family

Model Parameters CREST K Best For
Sky v2.0-11B 11.2B 4 Maximum capability
Sky v2.0-6.5B 6.47B 2 Balanced performance
Sky v2.0-11B-INT4 11.2B 4 Full CREST, memory-efficient
Sky v2.0-Lite 6.47B 2 Laptops & edge devices

Citation

@article{jadav2026crest,
  title={CREST: Cognitively Recurrent Estimation of Step Termination for Adaptive-Depth Language Modeling},
  author={Jadav, Atharvsinh},
  year={2026},
  url={https://huggingface.co/0labs-in/Sky-v2.0-11B}
}

About 0labs

0labs is an independent AI research lab founded by Atharvsinh Jadav in Gujarat, India. We build adaptive-depth LLMs that think harder on hard problems — trained on a single GPU.

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