Claude Code 2.1.181

• [new] Added --ax-screen-reader CLI flag and CLAUDE_AX_SCREEN_READER environment variable for screen reader support.
• [new] Added Slackbot MCP tools (mcp__slackbot__post_message, mcp__slackbot__reply, mcp__slackbot__react, mcp__slackbot__update_reply, mcp__slackbot__upload_file, mcp__slackbot__no_reply_needed).
• [new] Added CLAUDE_CODE_TERMINAL_MCP_TOOLS environment variable.
• [new] Added CLAUDE_CODE_BG_TASKS_REPORT_RUNNING and CLAUDE_CODE_POWERUP_ONBOARDING environment variables.
• [changed] Removed the assistantAutoBackgrounded field from SDK tool result types.
• [removed] Removed the nightly-2025-12-10 API beta header.

Models & prompts

• Updated system instructions to explicitly discourage spawning agents unless the user requests them by name or type, with guidance to handle multi-part tasks inline instead.
• Added and refined prompts for plan mode, focus mode, and context management, including clearer rules around read-only exploration, memory handling, and avoiding duplicate work across agents.
• Adjusted instructions around task tracking, interruption handling, and background agent notifications.

Under the hood

• Added environment variables CLAUDE_AX, CLAUDE_CLIENT, CLAUDE_CLIENT_PRESENCE_FILE, CLAUDE_CODE_ARTIFACTS_API_BASE_URL, CLAUDE_IN_SLACK_V2, and CLAUDE_REPL_VERBOSE.
• Removed the CLAUDE_CODE_TEAM_ONBOARDING environment variable.
• Added 21 new Statsig feature gates and removed 9, primarily around REPL execution, remote sending, mantle defaults, streaming timeouts, and powerup discovery.
• Added internal API routes for HTTP serving, SNI handling, and bulk security advisories.

Upgrade notes

No special upgrade steps required.