Feature Request: autoCompactThreshold setting — auto-trigger /compact before context window is full

Problem

In multi-worker cowork setups (multiple Claude Code sessions working in parallel on the same repo), sessions regularly reach 100% context window. At that point, /compact itself fails — there is no context space left for the compaction operation to execute. This creates a hard deadlock requiring manual intervention to recover the session.

Requested Feature

Add an autoCompactThreshold setting to settings.json that automatically triggers compaction when the context window reaches a configurable percentage, while there is still enough space left for the compact operation to complete:

\\\json
{
"autoCompactThreshold": 0.75
}
\\\

A threshold of 0.75–0.80 would trigger compaction at 75–80% usage, leaving sufficient buffer for the compact operation itself.

Why Current Workarounds Don't Work

• Hooks (PreToolUse/PostToolUse): Hooks execute shell commands, but /compact is a user slash-command — it cannot be triggered programmatically from a hook.
• CronCreate / scheduled tasks: Same limitation — no programmatic access to slash-commands.
• Manual /compact: Works if the user notices and acts early enough, but in long autonomous sessions this is easy to miss.

Impact

• Affects all long-running autonomous sessions (agents, multi-worker setups)
• The 100% → deadlock pattern occurs daily in sessions with large codebases and extensive context (CLAUDE.md, multiple worktrees, parallel agents)
• No graceful recovery path exists once the deadlock is reached

Environment

• Claude Code version: 2.1.153
• Platform: macOS (darwin 25.5.0)
• Multi-worker setup: 4–5 parallel sessions per repo

🤖 Submitted via Claude Code