Claude Code 2.1.316 Adds Subagent Controls and Patches Security Flaws

Claude Code 2.1.316 shipped on October 31 with 34 fixes and new configuration options, including the CLAUDE_CODE_SUBAGENT_EFFORT variable, which lets subagents run at their own effort level instead of inheriting the session's level.

You can also use the CLAUDE_CODE_DISABLE_ULTRATHINK variable to turn off the ultrathink keyword, preventing accidental prompts from pushing effort to xhigh. In the VS Code extension, ultrathink now triggers xhigh effort and the rainbow effect to match the terminal.

Fast mode for Opus 4.8 was deprecated on October 30 and is scheduled for removal on November 30, 2026, after which requests will return an error without falling back to standard Opus 4.8.

The update patches a security issue in --restricted sessions where a Read allow rule covering paths outside working directories allowed file uploads. Another fix addresses orphaned shell commands on macOS and Linux that persisted when Claude Code exited independently. Team and Enterprise logins now apply server-managed settings without an approval prompt.

Earlier in the week, version 2.1.314 introduced permissions.blockWritesOutsideWorkingDirectories to reject Write and Edit paths outside working directories across all permission modes, while adding idle compaction for conversations exceeding 200K tokens in VS Code and the Desktop app's Code tab.