API Error 400 suggests non-existent /rewind command

Bug Report

Issue: When encountering an API Error 400 due to tool use concurrency issues, Claude Code displays this error message:

API Error: 400 due to tool use concurrency issues. Run /rewind to recover the conversation.

Problem: The /rewind command does not exist in Claude Code. Users cannot recover using the suggested command.

Expected behavior: Either:

1. The /rewind command should exist and work as suggested, or
2. The error message should suggest an actual recovery method that exists

Impact: Users are left confused when the error recovery instructions reference a non-existent command.

Environment: Claude Code CLI