Claude Code v2.1.170 Release Notes

Claude Code v2.1.170 introduces Claude Fable 5, a groundbreaking Mythos-class model, and fixes session transcript saving issues.

June 9, 2026 • 10 min read • By ClaudeWorld

The Claude Code community has reason to celebrate with the release of v2.1.170, which brings one of the most significant upgrades in the platform’s history alongside important bug fixes for power users.

What’s New

Claude Fable 5: The New Mythos-Class Model

The headline feature of this release is the introduction of Claude Fable 5, Anthropic’s latest Mythos-class model that has been made safe for general use. This represents a major leap forward in AI capabilities, with Fable 5 exceeding the performance of any model previously made available to the Claude Code community.

Key highlights of Claude Fable 5:

  • Mythos-class architecture delivering unprecedented capabilities
  • Enhanced reasoning and problem-solving abilities
  • Improved code generation and debugging assistance
  • Maintained safety standards for production use

Session Transcript Fix

A critical bug affecting power users has been resolved in this release. Previously, sessions launched from VS Code’s integrated terminal or shells that inherited Claude Code environment variables would fail to save transcripts and wouldn’t appear when using the --resume flag. This issue has now been completely fixed, ensuring your session history is properly maintained regardless of how you launch Claude Code.

How to Update

To access Claude Fable 5 and benefit from the transcript fixes, update to version 2.1.170 using your preferred package manager:

# Update Claude Code to v2.1.170
pip install --upgrade claude-code

After updating, Claude Fable 5 will be available for use in your coding sessions.