We present Kathleen, a text classification architecture that operates directly on raw UTF-8 bytes using frequency-domain processing -- requiring no tokenizer, no attention mechanism, and under 470K parameters. Kathleen introduces several novel components: (1) RecurrentOscillatorBanks -- damped sinusoid convolutions with temporal memory for O(L) sequence processing; (2) an FFT-Rotate Wavetable Encoder that maps all 256 byte values using a single learnable vector (256 floats); (3) PhaseHarmonics -- a sinusoidal non-linearity with just 6 learnable phase parameters (+2.6% accuracy, <0.001% of model parameters); (4) Content-Dependent Reverb with Positional Decay Modulation -- a temporal memory mechanism whose decay rate is jointly conditioned on input content and a learned position-indexed bias vector; (5) Token-Level Module Sequencer with consonance and dissonance interference channels. Through iterative architecture evolution from an initial 733K-parameter baseline (Kathleen-Clean) to the current Kathleen-V9 (469K parameters), we demonstrate that pretraining can be entirely eliminated while improving accuracy. Kathleen-V9 achieves 88.5% +/- 0.2% on IMDB, 92.4% +/- 0.2% on AG News, and 85.8% +/- 0.5% on SST-2 (3-seed averages) -- matching or exceeding the pretrained baseline on all benchmarks with 36% fewer parameters. On SST-2, the improvement is +2.5% absolute over the pretrained predecessor. Kathleen processes sequences in O(L) time and memory.
Figures & tables
Encoder
Accuracy
Params (encoder)
nn.Embedding(256, 256)
83.1%
65,536
Fourier features ( K=32 )
82.3%
8,256
FFT-Rotate wavetable
83.7%
256
Table 1: Byte encoder comparison (IMDB, same architecture otherwise).
Dataset
Task
Train
Test
Classes
IMDB ( Maas et al., 2011 )
Sentiment
25,000
25,000
2
AG News ( Zhang et al., 2015 )
Topic
120,000
7,600
4
SST-2 ( Socher et al., 2013 )
Sentiment
67,349
872
2
Table 2: Benchmark datasets.
Model
IMDB
AG News
SST-2
Params
Pretrain
Pretrained Transformers (reference)
BERT-base ( Devlin et al., 2019 )
93.0
94.0
93.0
110M
Ext. corpus
DistilBERT ( Sanh et al., 2019 )
92.0
93.0
91.0
66M
Ext. corpus
Byte/char-level Transformers
CANINE-S ( Clark et al., 2022 )
—
—
85.8
132M
Ext. corpus
ByT5-Small ( Xue et al., 2022 )
—
—
∼ 92
300M
Ext. corpus
Table 3: Main classification results. All Kathleen variants operate on raw UTF-8 bytes with no tokenizer and no attention. V0 uses MLM pretraining; V9 uses no pretraining. All byte-level results report mean ± std over 3 seeds.
Dataset
seed=42
seed=123
seed=456
SST-2
86.4%
85.3%
85.6%
IMDB
88.8%
88.5%
88.2%
AG News
92.3%
92.2%
92.6%
Table 4: Individual seed results for Kathleen-V9 (no pretraining).
Model
L=1024
L=2048
L=4096
Transformer (byte)
82.1%
OOM
OOM
Kathleen (byte)
83.7%
84.4%
85.1%
Table 5: Accuracy vs. sequence length (IMDB). Transformer runs out of memory (OOM) beyond L=1024 bytes on a single T4 GPU.
Variant
IMDB
Δ
Full model
87.0%
—
− Adaptive Gate
84.8%
− 2.2%
− ConvLiteC
85.8%
− 1.2%
− PowerLawGate
87.0%
0.0%
− ResonanceCodebook
87.1%
+0.1%
Table 6: Tokenized Kathleen ablation (IMDB).
Variant
SST-2 (%)
Params
Δ
Full (all components)
84.4
1,823K
—
− PhaseHarmonics
81.8
1,364K
− 2.6
− HierarchicalKeys
82.7
1,293K
− 1.7
− PhaseShift
83.1
1,790K
− 1.3
− SDM Memory
83.4
1,823K
− 1.0
− Phantasy (560K params)
84.2
1,264K
− 0.2
Table 7: Component ablation of the predecessor model (SST-2, seed=42). Each row removes one component from the full model.
SST-2
IMDB
AG News
Model
Mean
Δ
Mean
Δ
Mean
Δ
V0 (733K, pretrain)
83.3%
—
88.6%
—
92.3%
—
V9 (469K, no pretrain)
85.8%
+2.5
88.5%
− 0.1
92.4%
+0.1
Table 8: V0 vs. V9 comparison (3-seed averages). V0 uses MLM pretraining; V9 uses no pretraining.
Context
PLG effect
Tokenized (word embeddings)
0.0%
Byte + nn.Embedding
0.0%
Byte + FFT-Rotate
+0.9%
Table 9: PowerLawGate effect depends on input representation.
Papers 1-2 of the Kathleen series showed that a byte-level, attention-free architecture built from a wavetable encoder and multi-scale reverberant state can match strong baselines on classification at ~450-700K parameters, without pretraining. We ask whether the same ingredients can generate. (1) Scaling: on byte-level language modeling (WikiText-103, raw UTF-8, no tokenizer), the reverberant model beats a parameter-matched transformer at every dataset scale measured (2-512 MB), e.g. 1.84 vs 2.04 bits/byte at 512 MB with ~0.5M parameters; the transformer needs more than 512 MB to match what the attention-free model learns from 32 MB. (2) Measurement: we introduce FORM DISTANCE, a non-parametric, gaming-resistant instrument for "reads like text": nine statistical axes of human text define a reference cloud, and five constructed fakes are all rejected. (3) Generation: decoding policy dominates architecture -- widening the sampler halves the same model's distance (3.17 to 1.52), and a retrieval-augmented decoding scheme takes the frozen model further (1.52 to 1.14) with no training step involved; the ablation attributes the gain to the sparse phrase dose itself, not the selection gate. The gain has a sharp boundary condition: the phrases must come from the model's own training corpus -- a 40x larger foreign library helps not at all, an effect the attention twin shares, consistent with in-context integration being a capability of scale. We also report four architectural additions that did not help, and a computed lexicon reaching 94% of a learned table's top-1 accuracy at one fifth of the parameters. Everything runs offline; all experiments are reproducible on a free Kaggle T4.
George Fountzoulas
Department of Computer Engineering & Informatics · Frederick University, Nicosia, Cyprus
Tokenizer-free language models remove the inductive bias of fixed tokenizers by modeling text directly as bytes, but the resulting longer sequences substantially increase computation and eliminate explicit text abstractions. We ask whether this additional computation can be useful, and whether standard Transformers can learn the abstractions that tokenization provides. We study these questions on Transformers without specialized tokenization-related architectures. With token-superposition training and hash embeddings, byte Transformers consistently outperform subword Transformers as model size scales. We further find that byte Transformers build local text abstractions as external tokenizers: a set of segmentation-like positions are used to collect local context representations, and restricting up to 25% of intermediate layers to these local representations preserves downstream performance. Finally, these learned structures induce highly non-uniform generation difficulty, with uncertainty concentrated near local structure boundaries; exploiting them for speculative decoding yields 3.4× more accepted tokens than in subword Transformers.
Jie Wang, Shiwei Luo, Qi Zhang +1
School of Computer Science, East China Normal University, Shanghai, China · School of Computer Science, Fudan University, Shanghai, China
Modern language models still rely on fixed, pre-defined subword tokenizations. Once a tokenizer is trained, the LM can only operate at this fixed level of granularity, which often leads to brittle and counterintuitive behaviors even in otherwise strong reasoning models. We introduce ByteFlow Net, a new hierarchical architecture that removes tokenizers entirely and instead enables models to learn their own segmentation of raw byte streams into semantically meaningful units. ByteFlow Net performs compression-driven segmentation based on the coding rate of latent representations, yielding adaptive boundaries \emph{while preserving a static computation graph via Top-K selection}. Unlike prior self-tokenizing methods that depend on brittle heuristics with human-designed inductive biases, ByteFlow Net adapts its internal representation granularity to the input itself. Experiments demonstrate that this compression-based chunking strategy yields substantial performance gains, with ByteFlow Net outperforming both BPE-based Transformers and previous byte-level architectures. These results suggest that end-to-end, tokenizer-free modeling is not only feasible but also more effective, opening a path toward more adaptive and information-grounded language models.
Chunyuan Deng, Sanket Lokegaonkar, Colin Lockard +3