SelKV: Selective KV Cache Merging with Per-Token Merge-or-Drop and Attention Compensation

• URL: http://arxiv.org/abs/2607.16213v1
• Date: Tue, 19 May 2026 17:44:56 GMT
• Title: SelKV: Selective KV Cache Merging with Per-Token Merge-or-Drop and Attention Compensation
• Abstract summary: Large Language Models generate text autoregressively, relying on a key-value (KV) cache whose memory footprint grows linearly with context length.<n>Recent compression methods mitigate this cost via token merging.<n>We propose a training-free, dual-component framework for KV cache compression that addresses these limitations.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Large Language Models (LLMs) generate text autoregressively, relying on a key-value (KV) cache whose memory footprint grows linearly with context length, creating a major bottleneck. Recent compression methods mitigate this cost via token merging; however, these approaches often rely on indiscriminate aggregation, which degrades representations and introduces attention sag, a mismatch where merged tokens receive the same softmax mass as individual tokens despite encoding multiple inputs. We propose a training-free, dual-component framework for KV cache compression that addresses these limitations. First, a soft cosine gate adaptively modulates merging decisions based on value-vector similarity, suppressing or discarding dissimilar tokens to preserve semantic fidelity. Second, we introduce an attention-ratio compensation mechanism that applies a decoding-time logit bias derived from prefill attention statistics, correcting the softmax imbalance induced by merging. Evaluated on LongBench (16 English datasets) while retaining only 25% of the KV cache, our framework achieves strong compressed performance against representative one-shot baselines. It is especially robust on the evaluated grouped-query attention (GQA) models, maintaining nearlossless generation quality. Furthermore, the method outperforms the full-cache baseline on complex multi-document QA tasks and delivers a 3.3x decoding speedup at 100k tokens.

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