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abstract indexed · arXiv 2609.03430 · updated 2026-10-18

Random Attention: Rethinking KV Cache Eviction for Efficient Reasoning

First page of Random Attention: Rethinking KV Cache Eviction for Efficient Reasoning
From the original paper · arXiv 2609.03430Page 1. Select the image to read the PDF.

Random Attention replaces score-based KV cache eviction policies (such as H2O-style importance scoring) with uniform random eviction within each attention head, while always retaining the prompt, eliminating all per-token scoring computation. It costs nothing in memory or latency beyond the eviction itself and adds almost no implementation complexity, since the selection signal is removed entirely; quality is reported to match the best prior evictor on reasoning workloads. It can fail on workloads where the reasoning trace does not restate needed information or where redundancy across heads is insufficient, and on non-reasoning tasks or cache configurations where the prompt is not the dominant fragile component, since the findings are validated on reasoning traces with long chains of thought.

For solo builders

A possible application for this research area. Paper-specific feasibility still needs a full-paper review.

Long customer conversations exhaust memory or limit concurrent requests.

What you would change

Change only the attention cache policy, after checking model and runtime support.

Try the idea on your product

A proposed first test. Set your budget and success criteria before running it.

Change only the attention cache policy, after checking model and runtime support.

Compare against

The same model with its ordinary attention cache.

  1. Locate the paper's implementation and check its license, model support, data needs, and hardware requirements. Stop here if you cannot obtain the required artifacts.
  2. Save a small set of representative product tasks and expected outcomes. Keep evaluation tasks out of any training or tuning, and choose quality and cost limits before running.
  3. Run the baseline and the proposed change on identical inputs. Keep other settings fixed and repeat paired runs to expose variation.
  4. Save per-task outputs, failures, timings, and all usage costs. Review regressions before expanding the test.

What to measure

Peak cache memory, long-context answer quality, first-token latency, and requests completed.

When to keep it

Keep the change only if it meets your preselected quality and latency limits and improves the metric you care about after setup and operating costs. Otherwise retain the baseline. This is an exploration plan, not a validated recommendation.

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source-linked claims
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Why it was shortlisted

The technical change, research area, and reason it entered the archive.

recommendation
adopt
research area
KV cache
technical change
Random KV cache eviction preserving prompt tokens
published
2026-09-03

For a single-GPU or API-constrained team serving long reasoning outputs, removing the eviction scoring step is a strictly simpler mechanism that the paper shows preserves accuracy while delivering measurably higher throughput in a standard serving stack.

Central equations

Original equations, typeset for reading. Paperraft explanations connect the mechanism, its aim, and the evidence.

In the notation of §2, the entire method is

si={+∞,i≤ℓp(the prompt),ui∼Uniform⁡(0,1),otherwise,

equation (3) · §3 Random Attention · proposed method

We adopt the decode-phase framework of Cai et al. (2025) and Chang et al. (2026). The cache keeps a persistent budget of K pairs plus a buffer of the r≪K most recent pairs, which is never scored. Each decode step appends one pair, so the buffer fills every r steps and triggers an eviction: every candidate i in the candidate set 𝒞t, the cached positions outside the buffer, receives a real-valued score si from a policy-specific rule, which may depend on the whole cache and on the past queries, and the K highest-scoring candidates are kept,

𝒮t=top−⁡Ki∈𝒞t​si,

equation (2) · §2 Preliminaries · baseline

cross-head redundancy with a planted-fact probing experiment. A synthetic fact (e.g. Let zq = 4729; a fresh variable and value each time) is inserted into real model-generated MATH500 reasoning traces, with a question needing the value appended at the end. The fact is planted tokens before the question, so the cache is evicted times between the two (other distances in Appendix B); the question itself is always kept. What we control is which key-value heads keep the fact: a condition is a chosen set of heads in which the fact’s tokens are pinned, with the fact evicted from every other head and the standard per-head uniform eviction running on everything else. Two metrics measure what survives. Retrieval is the fraction of traces whose greedy decode reproduces the value at the question. Because retrieval falls to zero in the hardest conditions, a graded recall carries the comparison there:

R=∑i(LPi−LPidel)∑i(LPikept−LPidel),

equation (4) · §5 Why the Selection Signal Buys So Little · metric

equations from arXiv HTML · fetched 2026-09-25

Claims and evidence

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  1. claim 01Paperraft inference
    Read the brief interpretation

    Random Attention replaces score-based KV cache eviction policies (such as H2O-style importance scoring) with uniform random eviction within each attention head, while always retaining the prompt, eliminating all per-token scoring computation. It costs nothing in memory or latency beyond the eviction itself and adds almost no implementation complexity, since the selection signal is removed entirely; quality is reported to match the best prior evictor on reasoning workloads. It can fail on workloads where the reasoning trace does not restate needed information or where redundancy across heads is insufficient, and on non-reasoning tasks or cache configurations where the prompt is not the dominant fragile component, since the findings are validated on reasoning traces with long chains of thought.

    This is a Paperraft inference. It is not pinned to a verified PDF passage.

    Inspect the source
  2. claim 02Paperraft inference

    Serves 32-43% higher throughput than the strongest prior score-based evictor in vLLM while matching its accuracy across four models and six reasoning tasks.

    This is a Paperraft inference. It is not pinned to a verified PDF passage.

    Inspect the source

Exposure map

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quality

Still unknown

Which tasks improve, and which regress against the baseline?

compute and memory

Still unknown

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latency

Still unknown

Are startup time, typical response time, and slow requests measured separately?

operations

Still unknown

What must be monitored, maintained, and rolled back?

software compatibility

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Does the implementation support your model, runtime, and hardware?

security

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data and training

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reproducibility

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Continue the investigation

A reading guide for KV cache.

Editorial prompts, not findings from this paper or a validated test plan. Detailed analysis is still pending for the topics below.

What to inspect

Which tokens or cache entries are retained, compressed, or discarded? Look for tests of lost information.

Plan a fair comparison

Can you keep prompts and decoding settings fixed while measuring cache size, latency, and answer quality?

Questions for adoption

Does the evaluation cover long conversations and questions about information introduced early?

Read the paper with these questions

Inside the paper

Preview the first 3 pages of the original PDF. Click the stack to turn the page.

The downloadable skill includes SKILL.md and evidence.json, with recorded findings and unanswered checks. TRY-IT.md adds a product test plan and a blank results sheet.

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Provisional research brief updated 2026-10-18. Paperraft has not reproduced this experiment.

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