Claude Cowork grabs local DNS resolution on macOS which conflicts with secure web gateway aka ZTNA aka SASE products such as Cloudflare Warp which do similar. The work-around is to close Cowork, let Warp grab mDNSResponder's attention first, then restart Claude Desktop, or some similar special ordering sequence. It's annoying, but you could say that about everything having to do with MITM middleboxes.