Who runs it
Anthropic. It names itself with the token Claude-User. Anthropic doesn't publish a full user agent string for it.
What it does
It supports Claude AI users. Anthropic says blocking it prevents the system from retrieving your content in response to a user query, which may reduce visibility in user-directed search.
Renders JavaScript
Not yet observed. Anthropic doesn't say whether Claude-User runs scripts, and this site hasn't recorded a verified visit yet.
How to verify it
Match the visiting address against Anthropic's published list, the same one that covers ClaudeBot and Claude-SearchBot.
robots.txt
Rules under User-agent: Claude-User apply to it. Anthropic says this lets site owners control which sites can be accessed through user-initiated requests, and documents no exception.
Questions
Does Claude-User follow robots.txt?
Anthropic says its machines honor robots.txt directives and documents no exception for user-initiated requests.