DeepSeek V4's 1M Context Window: The Breaking Point

Deepseek V4's 1M context window: the breaking point

A Reddit user tested DeepSeek V4 on 45k, 180k, and 520k-token codebases and found 150k-250k tokens best for coding work. Past 300k tokens, line-number precision degraded; at 520k, outputs shifted toward architecture summaries and skipped implementation details.

Why it matters: A single Reddit post limits authority, but HKR-H/K/R all pass: it is a numbered first-person test with a concrete long-context failure pattern. The right band is featured, not 78+, because replication and model details are thin.