[BUG] Context auto-compaction re-enters plan mode without user request

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?

When context auto-compaction occurs during a session where plan mode was previously active (but the user had moved past it to other tasks), Claude re-enters plan mode after compaction completes. The user did not request plan mode — the post-compaction state restoration incorrectly resumed a stale planning context instead of the most recent activity.

This is especially disruptive because once re-entered, plan mode has no cancel/abort path (see #26520), so the user is trapped in a state they didn't initiate. The only escape is /clear, which destroys all session context.

What Should Happen?

Post-compaction state restoration should resume from the most recent user activity, not from an earlier plan mode state the user had already moved past. If the user completed a plan, persisted it, and moved on to other tasks, compaction should restore the session to those subsequent tasks — not re-enter plan mode.

Steps to Reproduce

1. Enter a session and begin work that involves plan mode.
2. Complete the plan. When ExitPlanMode is presented, instruct Claude to persist the plan file to disk and move on to other tasks instead of approving.
3. Continue working on other tasks (file writes, tool calls, etc.) until the context window fills.
4. Allow auto-compaction to trigger.
5. Observe: after compaction, Claude re-enters plan mode for the earlier plan rather than resuming the most recent task.
6. Attempting to exit plan mode without approving triggers the gridlock described in #26520.

Claude Model

Opus

Is this a regression?

Not sure

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Related: #26520 (ExitPlanMode lacks defer/abandon option). That issue covers the gridlock UX once stuck in plan mode. This issue is specifically about compaction incorrectly re-entering plan mode — a distinct root cause that amplifies the #26520 problem by putting users into the gridlock state without their consent.

Duplicate search performed: Searched "auto-compaction plan mode", "context compaction plan mode", "plan mode stuck", "ExitPlanMode", and "planning mode stuck". No existing issues cover the compaction-triggered re-entry scenario. Closest match is #26520 (gridlock UX) and #29371 (compaction aggressiveness near completion), but neither addresses compaction restoring stale plan mode state.

Claude Code version: 2.1.63