I agree, the new inline comparison commit it not only unusable but dangerous. According to the Xcode 15 Release Notes the driving factor behind the change was a non-modal UI which lacks room for a side-by-side comparison. So they got rid of it. https://developer.apple.com/documentation/xcode-release-notes/xcode-15-release-notes

I am having the same issue with Claude Code. Authenticated in a new browser window using the magic code. Still does not work. Xcode 26.3 Intelligence Claude prompt error message: Your request could't be completed. Prompt stream failed: Agent has been closed. I have a Claude pro paid account which I purchased yesterday. It has yet to work at all with Xcode 26.3.

Claude is now working. I created a sample project on the Desktop. That was the problem. I moved the project into my developer folder. Now it works. Apparently, Claude is denied access to privacy-protected directories like the Desktop.