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Claude Code

Anthropic · CLI

Claude Code 2.1.187

2.1.186→2.1.187·June 23, 2026 at 5:07 PM UTC

Patch release adding background mode flags, an MCP tool idle timeout setting, and several prompt refinements while removing the Slackbot MCP tools.

Changelog

  • [new] Added --background / --bg flags to start Claude Code in background mode.
  • [removed] Removed the six Slackbot MCP tools (mcp__slackbot__*).

Models & prompts

  • Refined instructions around design system handling, neutral color and typeface choices, and avoiding common AI-generated design patterns.
  • Updated focus mode and plan mode guidance for clearer behavior when those modes are active.
  • Adjusted context management and ambient context handling to reduce unnecessary narration.
  • Tweaked task verification steps and rejection messaging for tool use.

Under the hood

  • Added CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT environment variable to control idle timeout for MCP tools.
  • Added CLAUDE_CHROME_CLASSIFIER_FLOOR environment variable.
  • Added several new Statsig feature gates related to client data caching, cowork Chrome auto mode, team memory, and startup announcements.
  • Removed three older feature gates (tengu_desktop_upsell_shown, tengu_fable5_launch_shown, tengu_slate_fern).

Upgrade notes

  • Projects relying on the removed Slackbot MCP tools will need to update their MCP configuration.
Older release← 2.1.186
All Claude Code releases →

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