[BUG] autoCompact

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

• Previously, I was able to complete all four steps without compression.
• Now, compression occurs on the first step.
• Model used (Opus 4.5)

As it stands now, I can't get any work done.

What Should Happen?

If it compresses too early, the output quality will be poor and work will not progress. Stop compressing too early.

Error Messages/Logs

Steps to Reproduce

1. Start a new Claude Code session with claude-opus-4-5-20251101
2. Run /context to check initial token usage

• System prompt: ~2.9k tokens
• System tools: ~15.3k tokens
• Total: ~18k tokens consumed before any user interaction

1. Perform a multi-step coding task (e.g., reading files, editing, running builds)
2. Observe that auto-compact triggers much earlier than expected

## Expected Behavior

• Previously, could complete 4-step workflows without hitting context limits
• System overhead should be minimal to maximize usable context

## Actual Behavior

• Auto-compact triggers during the first step
• ~9% of context (18k/200k) consumed by system before starting work

## Environment

• Claude Code version: [バージョン入れる - claude --versionで確認]
• Model: claude-opus-4-5-20251101
• OS: WSL2 (Linux 5.10.16.3-microsoft-standard-WSL2)

バージョン確認：
claude --version

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.0.75

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_