Byte seed team identifies deepseek's 'freakout' cause, highlights phase sensitivity in long context processing

On October 9, 2026, IT Home reported that the Byte Seed team submitted a paper to the arXiv preprint platform on September 30, 2026, discussing phase sensitivity caused by block KV cache compression. The study focused on DeepSeek-V4-Flash, DeepSeek-V4-Pro, and DeepSeek-V4.1-Flash, analyzing their performance with and without post-training. The team found that block KV cache compression reduces memory and attention costs for long-context inference but introduces a new positional coordinate called 'token phase,' which affects retrieval performance. They observed systematic asymmetry in retrieval, where information is easily accessible in one phase but not in another, leading to a potential 40 percentage point drop in accuracy across phases. This highlights a periodic weakness that may be masked by average benchmarks.