[BUG]

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?

Auto-compaction did not trigger when the conversation reached 100% context usage. The session continued to accept input but context was not compacted automatically. Manual /compact was required to continue.

What Should Happen?

Auto-compaction triggers automatically before or at 100% context, summarizing earlier conversation turns to free up context window space.

Error Messages/Logs

Steps to Reproduce

1. Start a long coding session
2. Allow context to reach 100% (visible in the status bar)
3. Send a new message

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.161 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

Description

Auto-compaction did not trigger when the conversation reached 100% context usage. The session continued to accept input but context was not compacted automatically. Manual /compact was required to continue.

Steps to Reproduce

1. Start a long coding session
2. Allow context to reach 100% (visible in the status bar)
3. Send a new message

Expected Behavior

Auto-compaction triggers automatically before or at 100% context, summarizing earlier conversation turns to free up context window space.

Actual Behavior

No compaction occurred. The session remained at 100% context. The next message was processed without compaction, leaving no room for tool call results and responses.

Environment

• Platform: macOS (darwin 25.5.0)
• Shell: zsh
• Model: claude-sonnet-4-6

Additional Context

The session was a multi-hour coding session involving many file reads, test runs, and code edits. The context meter showed 100% but the auto-compaction hook did not fire. After manually running /compact, the session continued normally.