Claude Code 2.1.300 cuts system prompt tokens by 58.5%, drops forced question-asking directive
ClaudeCodeLog · x · 2026-10-15
- Claude Code shipped v2.1.300 just 15 hours after 2.1.299; the ClaudeCodeLog tracker diffed the system prompt line by line.
- Prompt tokens dropped 19,045 (-58.5%) and prompt files fell from 24 to 11; the token mix shifted from 74.5%/25.5% (tools/system) to 70.0%/30.0%; bundle size grew 620.9 kB.
- Key behavioral change: the explicit "AskUserQuestion" directive is gone, replaced by a "claude-mermaid-runtime-begin" marker injected before the Harness block, suggesting a shift to runtime-wrapped instructions likely tied to Mermaid handling.
- CLI also removed the claude-checkpoint-index-H model entry (188→187 models). The changelog repo is public on GitHub.
Related event: Claude Code 2.1.300 Slashes System Prompt by 58.5%(2 posts)→
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