Anthropic slashed Claude Code's prompt by 80% with no performance loss

Anthropic engineer Thariq Shihipar revealed the team removed over 80% of Claude Code's system prompt, shrinking it from 2,686 to 514 words, with no measurable drop in coding evaluations. The announcement garnered 4.3 million views in a week. Anthropic's audit found that contradictory instructions across the system prompt, CLAUDE.md, and skill definitions were making the model less reliable.