Opus 5.5 system prompt hits 4,108 words, defying 'shorter prompt' narrative

Rajiv Shah's analysis shows Claude's system prompts keep growing: Opus 5.5 reaches 4,108 words, up 27% from Opus 5's 3,225, driven mainly by refusal guidance, contradicting the claim that stronger models need shorter prompts.

2026-09-23 ~ 2026-09-23 · 2 related posts

• Opus 5.5 System Prompt Grows to 4,108 Words, Up From Opus 5's 3,225 — rajistics · 2026-09-23
• Claude Opus system prompts keep growing: Opus 5.5 hits 4,108 words, mostly refusal guidance — rajistics · 2026-09-23