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[Release] anthropics/claude-code v2.1.212: v2.1.212

By ashwin-antgithub
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Claude Code v2.1.212 introduces significant workflow improvements including session forking with background execution, enhanced safety limits on web searches and subagent spawning, and automatic background migration for long-running MCP tools. The release fixes critical issues with plan mode command execution, symlink handling, hook infrastructure, and cross-platform compatibility while improving prompt caching and inter-agent messaging efficiency.

Key Points

  • •Session forking now creates independent background sessions while maintaining current work context; `/subtask` replaces the old in-session subagent behavior
  • •New session-wide limits prevent runaway loops: 200 WebSearch calls (configurable via `CLAUDE_CODE_MAX_WEB_SEARCHES_PER_SESSION`) and 200 subagent spawns (configurable via `CLAUDE_CODE_MAX_SUBAGENTS_PER_SESSION`)
  • •MCP tools running longer than 2 minutes automatically move to background to keep sessions responsive; threshold configurable via `CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS`
  • •Session resumption now supports picker interface for past sessions including deleted ones, resumable as background sessions via `/resume`
  • •Fixed critical security issue: plan mode no longer auto-runs file-modifying Bash commands without permission prompts or SDK callbacks
  • •Resolved symlink vulnerability in worktree creation that could write files outside repository boundaries
  • •Windows compatibility improved: daemon now prefers PowerShell 7 when Group Policy blocks PowerShell 5.1
  • •Enhanced `/ultrareview` command with better branch fetching, PR reference support, and improved error messaging
  • •Reduced token usage in inter-agent messaging by eliminating `SendMessage` body duplication in replayed history
  • •Improved prompt caching now works behind LLM gateways and custom base URLs (Bedrock, Vertex, 1P)

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Artifacts (7)

WebSearch Limit Configurationbashconfig
CLAUDE_CODE_MAX_WEB_SEARCHES_PER_SESSION=200
Subagent Spawn Limit Configurationbashconfig
CLAUDE_CODE_MAX_SUBAGENTS_PER_SESSION=200
MCP Auto-Background Threshold Configurationbashconfig
CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS=120000
Auto-Mode Reset Commandcommand
claude auto-mode reset [--yes]
Session Fork Commandcommand
/fork
Session Resume Commandcommand
/resume
Subtask Commandcommand
/subtask