Compaction fails: max_tokens must be greater than thinking.budget_tokens

Bug Description

Compaction fails with an API error when the context window gets large during a session. The only recovery option is /clear, which destroys all conversation context.

Error Message

Error during compaction: Error: API Error: 400
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "max_tokens must be greater than thinking.budget_tokens. Please consult our documentation at https://docs.claude.com/en/docs/build-with-claude/extended-thinking#max-tokens-and-context-window-size"
  }
}

Steps to Reproduce

1. Use Claude Code (Opus model) for an extended session with many file reads and edits
2. Context window grows large
3. Run /compact or automatic compaction triggers
4. Error occurs, compaction fails
5. Only option is /clear, losing all conversation context

Impact

• Loss of all conversation context mid-task
• Established decisions, reasoning, and tradeoffs from the session are lost
• Subsequent work in a cleared session produces inconsistent results because prior context is gone
• No graceful recovery path

Expected Behavior

Compaction should handle the max_tokens / thinking.budget_tokens relationship correctly and succeed, preserving conversation context.

Environment

• Model: claude-opus-4-6
• Platform: Windows (win32)