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Bonsai 27B: On-Device Execution via 1-bit/Ternary Quantization

·2026.07.16 12:30

Key point

PrismML has released Bonsai 27B, a compressed version of the Qwen 27B model using 1-bit and ternary methods that can run even on smartphones.

Details

Bonsai 27B, released by PrismML, is a research output based on the Qwen 2.5-27B model that goes beyond the limitations of existing quantization methods by applying binary (1-bit) and ternary representations.

Existing mixed-precision quantization methods had to leave high-precision tensors in place to prevent quality degradation when going below 4-bit, but Bonsai succeeded in compressing key components such as embeddings, attention, and MLP projections end-to-end to low-bit.

Key Features and Performance:

  • Ultra-lightweight: The ternary model has a memory footprint of about 5.9 GB, and the binary model about 3.9 GB, making it runnable on smartphones like the iPhone 17 Pro Max or ordinary laptops.
  • Performance preservation: The reasoning, tool calling, and agentic workflow capabilities of the 27B-scale model are largely preserved even in the low-bit environment.
  • Practical approach: Unlike methods like BitNet that train in low-bit from scratch, Bonsai adopts an approach that converts already-validated pretrained models to low-bit, enhancing scalability.
  • License: All weights are released under the Apache 2.0 license.

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