TypeError: null is not an object (evaluating 'T.effortLevel') - sessions interrupted on every prompt

Bug Description

New Claude Code sessions get interrupted on every prompt with the message:

⎿  Interrupted · What should Claude do instead?

This happens immediately after typing any prompt (even just "hi"). Existing sessions continue to work, but no new sessions can be started.

Debug Log Errors

[ERROR] TypeError: TypeError: null is not an object (evaluating 'T.effortLevel')
    at JEA (/$bunfs/root/claude:1780:3906)
    at aK (/$bunfs/root/claude:2142:4153)
    at processTicksAndRejections (native:7:39)

[ERROR] Error: Error: 1: 1 
    at H57 (/$bunfs/root/claude:1025:4019)
    at async B57 (/$bunfs/root/claude:1025:1623)

[ERROR] Error: NON-FATAL: Lock acquisition failed for ~/.local/share/claude/versions/2.0.76 (expected in multi-process scenarios)

The effortLevel error appears multiple times during session initialization.

Troubleshooting Attempted

• Removed ~/.claude/plugins/marketplaces/claude-plugins-official (was corrupted)
• Backed up and removed project session data (~/.claude/projects/...)
• Backed up and removed ~/.claude.json
• Killed stale Claude processes

None of these resolved the issue.

Environment

• Claude Code version: 2.0.76
• OS: macOS (Darwin 24.6.0)
• Plan: Claude Team
• Model: Opus 4.5

Steps to Reproduce

1. Have an existing Claude session running
2. Open a new terminal
3. Run claude or claude --debug
4. Type any prompt
5. Observe immediate interruption

Expected Behavior

New sessions should accept prompts and respond normally.

Actual Behavior

Every prompt is immediately interrupted with "What should Claude do instead?"