LFM2-24B-A2B-Cascadia-ternary3

ZTFlynn/LFM2-24B-A2B-Cascadia-ternary3

LiquidAI/LFM2-24B-A2B compressed to 15.37 GB with Cascadia — a spline manifold plus per-band lookup tables at 0.644 bytes per weight — and executable on CPU by a C runtime whose entire dependency list is libc, libm and libgomp.

Quality

32,704 paired tokens of FineWeb-Edu in 63 independent 512-token windows. Both models score identical tokens and are compared per token, which cuts the standard error 7.2x versus two independent means.

The window is the unit of inference, not the token: tokens inside one window share a context, and counting them as independent samples inflates the t-statistic several-fold. Resolving a difference of a few percent takes hundreds of windows.

The difference does not resolve. Stated precisely: this measurement bounds the perplexity change to within 4.5% and cannot distinguish it from zero — which is a limit on the evidence, not a proof that the cost is zero. Reconstruction fidelity below is measured directly and carries no such uncertainty.

Reconstruction fidelity

Perplexity measures how good a model is on a corpus, not how faithful a copy is, and the two disagree here: models compressed to identical reconstruction error differ by 16 percentage points of measured perplexity. Fidelity has no sampling uncertainty and no dependence on corpus domain, so it is measured directly and reported alongside.

By tensor class:

Experts are homogeneous, so a stride across them estimates the population; the figure above extrapolates each class from its sample to that class's full parameter count.

The tied embedding, the tensor whose error reaches the logits undamped, reconstructs at 0.0228.

Where the compression cost comes from

The cost is concentrated in one tensor. The tied embedding, which also serves as lm_head, is compressed by a single global codebook — no bands, no spline manifold, no exact outliers — while every linear tensor gets 32 bands, a spline, and 0.5% of its weights kept exact. Its error is the only error in the model that reaches the logits with nothing downstream to absorb it.

Measured on LFM2-350M, relative L2 reconstruction error:

At 27 entries the embedding is the worst-reconstructed tensor in the model. This package uses 81 entries for it, which costs about 6% in size and makes it the best-reconstructed tensor instead.

Usage

Executed by the Cascadia C runtime. This is a compressed package, not a transformers checkpoint.

git clone https://github.com/EntroMorphic/cassie && cd cassie
cmake -S src/c -B build -DCMAKE_BUILD_TYPE=Release && cmake --build build -j

huggingface-cli download ZTFlynn/LFM2-24B-A2B-Cascadia-ternary3 --local-dir ./pkg
./build/cascadia_generate ./pkg 512 --chat "Explain gradient descent."

Sampling is --temp / --top-k / --top-p / --seed; the default is greedy and seed-reproducible. Generation stops at <|im_end|>, so max_new is a ceiling.

This package is Mixture-of-Experts, which the CUDA backend does not execute yet; it runs on the C runtime above.

Python

from transformers import AutoModelForCausalLM
from cascadia import load_compressed

model = AutoModelForCausalLM.from_pretrained("LiquidAI/LFM2-24B-A2B", dtype="bfloat16")
model, stats = load_compressed(model, "./pkg", model_id="LiquidAI/LFM2-24B-A2B")

Sample output

Prompt: "How many eggs are in a baker's dozen?"

A **baker's dozen** is a term used to refer to **13 items**, rather than the usual 12. This tradition originated in medieval England, where bakers would add an extra egg (or sometimes more) to a dozen to ensure they didn't get fined for selling underweight bread.

So, the answer is:

**13 eggs** in a baker's dozen.

Greedy, generated to natural completion.

Package contents

Format specified in docs/package_format.md and machine-verified against every package.

How it works

A B-spline surface is fitted to each weight matrix to capture large-scale structure. Each weight is assigned to one of 32 bands by its spline value, and a k-means codebook is learned per band over the residuals. The top 0.5% of errors are kept exactly as f32. Codebook indices pack in base 3, five trits per byte, since 3⁵ = 243 fits a byte.

Reconstruction is W = spline(j,c) + codebook[band][index], evaluated inside the matvec so no dense weight matrix is ever built. Because the spline carries dynamic range, the residual tables need no per-block scale factors.

Limitations

• Runs under the Cascadia C runtime rather than transformers directly.
• The runtime executes ternary-3 packages; other presets convert but are not yet supported by the kernel.
• Batch-1 CPU inference, suited to edge and batch workloads.
• Greedy and sampled decoding; no beam search.

Acknowledgements

Deeply inspired by Magneato/deepseek-r1-qwen-7b-lutc, which demonstrated LUT-cascade compression of a 7B model at 5.45 bits per weight. The Guanaco LUT cascade — no-scale residuals, variable bit rate, and f32 outlier preservation — is the foundation this builds on. Cascadia adds a spline manifold for band selection and a Harmonic Collapse step that removes per-block scale factors entirely. Our thanks to Magneato for publishing both the approach and the weights that made it concrete.

Base model by Liquid AI, used under the LFM Open License.

Citation

@software{cascadia,
  title  = {Cascadia: Spline Manifold LUT Compression for Language Models},
  author = {Josserand-Austin, Tripp},
  year   = {2026},
  url    = {https://github.com/EntroMorphic/cassie}
}