System prompt size tripled after update to v2.1.101, causing 3x faster quota consumption

Summary

After updating Claude Code from v2.1.71 to v2.1.101, the base system prompt size tripled, causing usage quota to be consumed ~3x faster than before.

Evidence

Comparing cache_read_input_tokens from conversation JSONL files before and after the update:

| Version | Date | cache_read_input_tokens |
|---------|------|--------------------------|
| 2.1.71 | April 6, 2026 | ~54,000 |
| 2.1.101 | April 14, 2026 | ~163,000 |

This is consistent across multiple projects, confirming it's not caused by project-specific CLAUDE.md files or integrations.

Impact

• Each conversation turn now consumes ~2% of the hourly quota just from the base system prompt overhead
• Previously the same usage patterns would consume roughly 1/3 of that
• Affects all projects regardless of configuration

What was ruled out

• No active MCP integrations (Google Calendar, Gmail, etc. — all disconnected)
• No large CLAUDE.md files in global ~/.claude/ directory
• No enabled plugins injecting content
• Consistent across different projects

Environment

• OS: Windows 11
• Previous version: 2.1.71
• Current version: 2.1.101
• Model: claude-sonnet-4-6