ByteDance research reveals the cause of DeepSeek-V4 retrieval fluctuations
ByteDance's Seed team found that the accuracy of the DeepSeek-V4 series in long-context retrieval fluctuates periodically with the position of the target information in the input, and attributed the cause to its chunked KV Cache compression. In a needle-in-a-haystack test with 128K tokens and about 16,000 key-value pairs, the maximum accuracy gap between different positions for DeepSeek-V4-Flash-Base was 40.2 percentage points, and for DeepSeek-V4-Pro-Base it was 34.8 percentage points; the gap narrowed after post-training.