Claude 4 Fails Long-Context Retrieval, Suspected KV Compression Artifacts

teortaxesTex · x · 2026-08-01

A developer reported that the Claude 4 series has persistently failed at long-context string retrieval tasks since February. The model failed to find a 3-word substring, rationalizing that it needed one more word to succeed—which actually worked when given 4 words. The author speculates this curious behavior might stem from artifacts caused by token KV compression.

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