# Fourier Magnitude KV Cache Quantization > Source: > Published: 2026-08-23 10:51:15+00:00 It looks like you’ve pushed the exploration quite a bit further: My short version is: **I think the correction is substantive, but I do not think it removes the interesting signal. It narrows it into something more testable.** What I would carry forward from the current state is less: Fourier / phase is uniquely special selective layers are redundant early decode anchors give a sub-int8 recipe and more: the exact K representation being quantized matters a lot, and low-bit perturbation of the K that is actually stored/reused after normalization + RoPE can be genuinely fragile. I would probably make that tensor/locus distinction the organizing boundary from here. For current Transformers Gemma 3, the K path is essentially: ``` hidden state ↓ k_proj ↓ k_norm ↓ RoPE ↓ past_key_values.update(K, V, ...) ↓ attention ``` You can see that ordering directly in the [Gemma 3 implementation in Transformers](https://github.com/huggingface/transformers/blob/v5.15.0/src/transformers/models/gemma3/modular_gemma3.py). That means a hook on `k_proj` is testing a different object from the post-KNorm/post-RoPE K entering the cache. Once I separated those, the picture became much easier to interpret. My default route from here would be: ``` intervention/storage locus ↓ storage-only mechanism ↓ teacher-forced distributional validation ↓ better K quantizer geometry ↓ joint K/V rate accounting ↓ only then packed bytes / kernels / serving claims ``` The part I found most convincing is that the effect still survives a **post-forward storage-only control**: keeping the forward that creates a K state completely full precision, then demoting only the persistent cached copy, can still alter later logits and later generation. So there does seem to be a real cache-reuse phenomenon left after the retractions. What seems to survive the selective-layer correctionIf I were choosing the next path by goal, I would use something like this: ``` If the goal is to understand the mechanism: corrected storage-only teacher-forced KL/NLL ↓ locate which older prompt regions / K states matter ↓ test whether sensitivity tracks age, content, attention, or quantizer error If the goal is a practical low-bit cache: stop increasing the FP window for now ↓ improve K quantizer geometry ↓ compare against a strong int8 / KIVI-like baseline ↓ reintroduce a residual only if it buys a real rate-quality improvement If the goal is a deployable codec: first get a fidelity-successful K/V policy ↓ define an actual packed representation ↓ count metadata and real bytes ↓ then measure latency / throughput / context scaling ``` So, from my side, I would not read the corrections as the exploration collapsing. The interesting part seems to have **narrowed from a fairly broad Fourier/anchor story into a cleaner question about K representation, cache locus, and future error propagation**. That is a smaller claim, but it also looks much easier to falsify, compare against existing KV methods, and turn into a reproducible next experiment.