In the Xcode Group Lab they state that Xcode 27 projects are compatible with Xcode 26 except for one project setting check box "Strictly Validate" You will also need to set the "Minimum Deployment" version to 26.0 or earlier. If you use an API not available in your minimum deployment version you will get an error. if #available(macOS 27.0, *) You cannot add an if available conditional check because macOS 27.0 is not defined when open the project in Xcode 26. My suggestion would be to comment out the API you would like to use with a note and use an older API. Then when Xcode 27 is released for submissions you can uncomment it and use an if available test.

In the Xcode Settings -> General you can set the Navigator Size to Small | Medium | Large

Menu File -> New -> Project produces the following for me Down Arrow x 2

I have a Claude Pro subscriptions and tried this with a Claude Agent and it worked just like in the video. But if I use the free OpenAI GPT-5 Chat then I don't get the links. There is a significant capability difference between an agent and just a plain chat. The agents have tools that make them much smarter and have access to your file system, but other than running an open source agent on your own hardware, you will need a subscription. I got an open source chat model running on my laptop last night using MLX. I have yet to get the OpenCode Agent working yet. Cheers.

The fix if you want to keep ENABLE_USER_SCRIPT_SANDBOXING enabled is to add the files as inputs and outputs. I use a script to set the build number in the build info plist file. I just need to set "${TARGET_BUILD_DIR}/${INFOPLIST_PATH}" as an output of the script build setting ENABLE_USER_SCRIPT_SANDBOXING was added in Xcode 14 but enabled in the update to recommend setting in Xcode 15 From the Xcode 14 Release Notes: You can now enable sandboxing for shell script build phases using the ENABLE_USER_SCRIPT_SANDBOXING build setting. Sandboxing blocks access to files inside the source root of the project as well as the Derived Data directory unless you list those files as inputs or outputs. When enabled, the build fails with a sandbox violation if a script phase attempts to read from or write to an undeclared dependency, preventing incorrect builds. Thanks to Daniel Jalket's Blog Post: Xcode Build Script Sandboxing - https://indiestack.com/2023/06/xcode-build-script-sandboxing/

From the WWDC Q&A (Apple) answered: Simply do not use a CloudKit container identifier when configuring the SwiftData stack. There is currently a bug with this, so please file a feedback report. I expect this will be fixed in the next Beta Release of Xcode.