Claude Code Token Dropped by 80%? Opus 5 Surges by Another 72%

According to TrendWatch Beating Monitor, Claude Code team member Thariq posted that the team removed over 80% of the system prompt words, and the programming performance did not decline. System prompt words are the rules and environment instructions preloaded into Claude Code before each model call.

Qoder engineer Chen Cheng later captured the actual requests sent by Claude Code. He found that the significant slimming down occurred in Opus 4.8, not Opus 5. The system prompt words in Opus 4.7 were about 15,225 characters, reduced to 4,467 in 4.8, and then increased to 7,694 in Opus 5, 72% longer than 4.8.

The "80% Cut" itself is not wrong. Claude Code did compress several large sections of behavioral rules from 12,443 characters to 2,308, a reduction of about 81%. Most of the detailed rules such as "do not comment haphazardly" and "do not create unnecessary documents" were largely replaced by a single phrase, "refer to the existing code style."

However, after Opus 5 went live, Claude Code added two exclusive rules to it, mainly constraining it from repeated error explanations and frequent progress reporting. Fable 5 also has separate user communication rules.

Therefore, Claude Code did indeed delete a large number of general rules, but after new issues emerged in the new model, it will continue to add specific rules.