Anthropic silently enrolled my Claude Code install in an A/B experiment, overrode my settings, and updated the CLI even with auto-updates disabled

Anthropic bypassed disabled auto-update settings to enroll Claude Code users in an A/B experiment. The CLI inserted an enrollment token into local configurations, attaching an x-cc-atis header to API requests that instructed Opus 4.8 to strip thinking text summaries from responses.