Scratchpad Patching: Decoupling Compute from Patch Size in Byte-Level Language Models

Hugging Face Daily Papers Papers

Summary

This paper introduces Scratchpad Patching, a technique for tokenizer-free language models that decouples compute from patch size by dynamically refreshing context within patches to reduce patch lag.

Tokenizer-free language models eliminate the tokenizer step of the language modeling pipeline by operating directly on bytes; patch-based variants further aggregate contiguous byte spans into patches for efficiency. However, the average patch size chosen at the model design stage governs a tight trade-off: larger patches reduce compute and KV-cache footprint, but degrade modeling quality. We trace this trade-off to patch lag: until a patch is fully observed, byte predictions within it must rely on a stale representation from the previous patch to preserve causality; this lag widens as patches grow larger. We introduce Scratchpad Patching (SP), which inserts transient scratchpads inside each patch to aggregate the bytes seen so far and refresh patch-level context for subsequent predictions. SP triggers scratchpads using next-byte prediction entropy, selectively allocating compute to information-dense regions and enabling post-hoc adjustment of inference-time compute. Across experiments on natural language and code, SP improves model quality at the same patch size; for example, even at 16 bytes per patch, SP-augmented models match or closely approach the byte-level baseline on downstream evaluations while using a 16times smaller KV cache over patches and 3-4times less inference compute.
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Paper page - Scratchpad Patching: Decoupling Compute from Patch Size in Byte-Level Language Models

Source: https://huggingface.co/papers/2605.09630

Abstract

Tokenizer-free language models using patch-based approaches face a trade-off between compute efficiency and modeling quality due to patch lag, which Scratchpad Patching addresses by dynamically refreshing context within patches based on prediction entropy.

Tokenizer-free language modelseliminate the tokenizer step of the language modeling pipeline by operating directly on bytes;patch-based variantsfurther aggregate contiguous byte spans into patches for efficiency. However, the average patch size chosen at the model design stage governs a tight trade-off: larger patches reduce compute and KV-cache footprint, but degrade modeling quality. We trace this trade-off topatch lag: until a patch is fully observed, byte predictions within it must rely on a stale representation from the previous patch to preserve causality; this lag widens as patches grow larger. We introduce Scratchpad Patching (SP), which inserts transientscratchpadsinside each patch to aggregate the bytes seen so far and refresh patch-level context for subsequent predictions. SP triggersscratchpadsusingnext-byte prediction entropy, selectively allocating compute to information-dense regions and enabling post-hoc adjustment of inference-time compute. Across experiments on natural language and code, SP improves model quality at the same patch size; for example, even at 16 bytes per patch, SP-augmented models match or closely approach the byte-level baseline on downstream evaluations while using a 16times smallerKV cacheover patches and 3-4times lessinference compute.

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