Claude Code v2.1.90 Release: New Interactive Lessons, Performance Improvements, and Bug Fixes

New Features and Environment Variables

Claude Code v2.1.90 adds /powerup — interactive lessons with animated demos that teach Claude Code features. The release also introduces the CLAUDE_CODE_PLUGIN_KEEP_MARKETPLACE_ON_FAILURE environment variable, which keeps the existing marketplace cache when git pull fails, making it useful for offline environments. Additionally, .husky has been added to protected directories in acceptEdits mode.

Bug Fixes and UI Improvements

Several critical bugs have been addressed:

• Fixed an infinite loop where the rate-limit options dialog would repeatedly auto-open after hitting usage limits, eventually crashing sessions
• Fixed --resume causing a full prompt-cache miss on the first request for users with deferred tools, MCP servers, or custom agents (regression since v2.1.69)
• Fixed Edit/Write failing with "File content has changed" when PostToolUse format-on-save hooks rewrite files between consecutive edits
• Fixed PreToolUse hooks that emit JSON to stdout and exit with code 2 not correctly blocking tool calls
• Fixed collapsed search/read summary badge appearing multiple times in fullscreen scrollback when CLAUDE.md files auto-load during tool calls
• Fixed auto mode not respecting explicit user boundaries ("don't push", "wait for X before Y") even when actions would otherwise be allowed
• Fixed click-to-expand hover text being nearly invisible on light terminal themes
• Fixed UI crash when malformed tool input reached the permission dialog
• Fixed headers disappearing when scrolling /model, /config, and other selection screens

Security Hardening and Performance

PowerShell tool permission checks have been hardened with fixes for:

• Trailing & background job bypass
• -ErrorAction Break debugger hang
• Archive-extraction TOCTOU (Time-of-Check Time-of-Use) vulnerability
• Parse-fail fallback deny-rule degradation

Performance improvements include:

• Eliminated per-turn JSON.stringify of MCP tool schemas on cache-key lookup
• SSE transport now handles large streamed frames in linear time (was quadratic)
• SDK sessions with long conversations no longer slow down quadratically on transcript writes
• Improved /resume all-projects view loads project sessions in parallel, improving load times for users with many projects

Changes and Removals

The --resume picker no longer shows sessions created by claude -p or SDK invocations. Get-DnsClientCache and ipconfig /displaydns have been removed from auto-allow lists for DNS cache privacy reasons.