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Bluebird 1.5 Base

Efficient language modelling with long-range memory

Model repository  ·  Apache 2.0  ·  Project Bluebird

742.5M parameters 32K context Mixed precision

Bluebird Highlights

  • Compact base language model: 742.5M parameters, a 24-layer decoder-only transformer, and a 32,768-token supported context window.
  • Hybrid long-range memory: local causal attention and compressed representations of previous 512-token chunks, combined through memory-augmented layers.
  • Grouped-query attention: 24 query heads and six key/value heads, with local attention over 2,048 tokens.
  • Pretraining: 23,000,514,560 recorded tokens from initial and continued pretraining.
  • Training environment: PyTorch mixed precision on eight Intel Gaudi 3 AI accelerators.

Model Overview

Bluebird 1.5 Base is a compact, decoder-only causal language model in the Project Bluebird family. With 742,528,520 parameters and a 32,768-token context window, it combines local causal attention with a compressed, chunked-memory mechanism for accessing information from earlier parts of a sequence.

The model is released as a base pretrained checkpoint, intended for language modelling, text completion, continued pretraining, domain adaptation, and downstream fine-tuning. It is not an instruction-tuned chat assistant.

Model specifications

Property Specification
Model tudor-iustin22/Bluebird-1.5-Base
Project Project Bluebird
Architecture Decoder-only transformer with local attention and chunked long-range memory
Parameters 742,528,520 (742.5M)
Transformer layers 24
Hidden size 1,536
Query attention heads 24
Key/value attention heads 6
Vocabulary size 65,536
Maximum sequence length 32,768 tokens
Local attention window 2,048 tokens
Memory chunk size 512 tokens
Learned summaries per chunk 4
Maximum memory summaries 256
Feed-forward activation SwiGLU
Normalisation RMSNorm
Positional embeddings Rotary position embeddings (RoPE)
Published checkpoint precision FP16
Training compute precision Mixed precision
Pretraining tokens recorded 23,000,514,560
Framework PyTorch
Intel Gaudi runtime device hpu
License Apache License 2.0

Architecture

Bluebird 1.5 uses a hybrid local-attention and chunked-memory architecture to provide a longer context window without applying full quadratic attention over the entire sequence.

  • Local causal attention processes the active token window.
  • Grouped-query attention (GQA) uses 24 query heads and six key/value heads.
  • Chunked memory compresses completed 512-token segments into learned memory representations.
  • Memory-augmented attention incorporates earlier compressed representations into the active token computation.
  • Learned gating integrates local attention and longer-range memory signals.

The 24-layer network includes 16 local-attention blocks and 8 memory-augmented blocks. Memory-augmented blocks are interleaved through the network at every third layer.

The context length specifies the supported input window; effective recall and reasoning quality depend on the input, task, and fine-tuning.

Quickstart

Bluebird 1.5 uses custom model code. Inspect the repository's Python files before using trust_remote_code=True.

Install the Intel Gaudi software stack and its compatible PyTorch build using the Intel Gaudi installation instructions. Then install the remaining dependencies in that environment:

python -m pip install transformers safetensors accelerate

Generate text on Intel Gaudi 3

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

model_id = "tudor-iustin22/Bluebird-1.5-Base"
device = torch.device("hpu")

tokenizer = AutoTokenizer.from_pretrained(
    model_id,
    trust_remote_code=True,
)

model = AutoModelForCausalLM.from_pretrained(
    model_id,
    trust_remote_code=True,
    torch_dtype=torch.bfloat16,
).to(device).eval()

prompt = "The future of efficient language models is"
inputs = tokenizer(prompt, return_tensors="pt").to(device)

with torch.inference_mode():
    generated = model.generate(
        **inputs,
        max_new_tokens=128,
        do_sample=False,
        use_cache=False,
        pad_token_id=tokenizer.pad_token_id,
        eos_token_id=tokenizer.eos_token_id,
    )

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

Base-model behaviour: The prompt is treated as text to continue. Chat templates and instruction-following behaviour require a separately fine-tuned variant.

PyTorch mixed precision on Intel Gaudi

Intel Gaudi supports mixed precision through PyTorch AMP. The following pattern uses BF16 autocast for operations supported by the Gaudi runtime, while other operations may remain at higher precision:

import torch

# Assumes `model`, `batch`, and `optimizer` have been initialized.
# Move both the model and batch to the HPU device first.
with torch.autocast(device_type="hpu", dtype=torch.bfloat16):
    outputs = model(**batch)
    loss = outputs.loss

optimizer.zero_grad(set_to_none=True)
loss.backward()
optimizer.step()

For distributed training across the eight accelerators, use the Intel Gaudi-enabled PyTorch installation with the HCCL distributed backend. Actual batch sizing, compilation settings, and optimizer configuration depend on the training objective and available sequence length.

See the Intel Gaudi PyTorch documentation for current runtime, distributed training, and mixed-precision guidance.

Training

Bluebird 1.5 Base's documented training-token count is 23,000,514,560 tokens, spanning initial and continued pretraining.

Intel Gaudi 3 compute configuration

Component Configuration
Accelerators 8 × Intel Gaudi 3 AI accelerators
Accelerator memory 128 GB HBM per device; 1,024 GB aggregate
CPU allocation 160 vCPUs
Host memory 1,792 GiB RAM
Local instance storage 25,600 GB
Deep learning framework PyTorch
Accelerator integration Intel Gaudi PyTorch / HPU
Compute precision Mixed precision
Supported mixed-precision mechanism PyTorch automatic mixed precision (AMP), including BF16 autocast
Multi-accelerator communication HCCL

Intel Gaudi 3 uses the PyTorch HPU device interface (torch.device("hpu")). Intel's separate general-purpose GPU products use the PyTorch xpu device interface. The correct backend for Gaudi 3 is hpu.

Training data

The model's documented corpus mixture includes the following datasets:

Dataset Approximate mixture share
FineWeb-Edu 60%
DCLM Baseline 25%
OpenWebMath 10%
Cosmopedia v2 5%

Dataset proportions are approximate. The distribution may include material subject to its own upstream dataset terms and usage restrictions.

Intended use

Bluebird 1.5 Base is suitable for:

  • Causal language modelling and text continuation.
  • Continued pretraining and domain-specific adaptation.
  • Supervised fine-tuning on downstream tasks.
  • Exploration of compact transformer architectures.
  • Research into chunked memory and long-context processing.
  • Model-efficiency and accelerator-performance studies.

Limitations

As a compact base model, Bluebird 1.5 may produce inaccurate, outdated, repetitive, biased, or unsafe text. A 32K-token input capacity does not guarantee perfect retrieval of earlier information. The base checkpoint has not been specifically aligned for conversational instruction following.

Evaluate model performance for each intended application and implement appropriate safeguards before production deployment. Do not use unverified generations as the sole basis for high-stakes decisions.

License and attribution

Project Bluebird — Copyright © 2026 Tudor Iustin.

Project Bluebird's original release materials are distributed under the Apache License, Version 2.0. Use, modification, redistribution, and commercial use are governed by that license, including applicable notice and attribution requirements.

This release is part of the Fabric 1.5-derived 0.7B model lineage. Copyright and license notices for pre-existing model code, weights, and other third-party material remain with their respective rights holders and must be preserved where required.

The repository should include the full Apache 2.0 license text in a separate LICENSE file and retain applicable upstream NOTICE information.

Read the Apache License, Version 2.0

Citation

@misc{bluebird15base2026,
  title        = {Bluebird 1.5 Base},
  author       = {Tudor Iustin},
  year         = {2026},
  publisher    = {Project Bluebird},
  howpublished = {Hugging Face model repository},
  url          = {https://huggingface.co/tudor-iustin22/Bluebird-1.5-Base}
}

PROJECT BLUEBIRD · Efficient language modelling. Open development.

© 2026 Tudor Iustin · Apache License 2.0

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