I also retested the original LockRepro sample on 3 November 2026 in Xcode 27.2 (27B52). The sample still uses the Property List format, with project.pbxproj present and no project.xcproj. Xcode opened the project and displayed Build Settings. I clicked the project padlock, confirmed the dialog named LockRepro.xcodeproj, and clicked Unlock once. Xcode reported: “The file ‘project.xcproj’ could not be unlocked.” It said it could not find the file. This confirms both directions on the same Xcode version. For LockRepro (Property List), Unlock looked for the missing project.xcproj. For UnlockProbe (JSON), Unlock looked for the missing project.pbxproj. Both projects opened successfully before the Unlock action.

Follow-up (3 November 2026): I reproduced the project-level Unlock failure in Xcode 27.2 (27B52) with a fresh test project called UnlockProbe. Its .xcodeproj bundle contains the JSON project.xcproj and no project.pbxproj. Xcode opens it and displays Build Settings. To reproduce, select the project in the Project Navigator, open Build Settings, click the padlock at the far right of the editor breadcrumb bar, then click Unlock. Expected: Xcode uses the active JSON project definition when determining whether the project can be edited. Actual: Xcode says the project is locked because the file does not exist. After choosing Unlock, it reports that project.pbxproj could not be unlocked because it could not find the file. This is the reverse of my October reproduction: the traditional PBX-format project prompted for the missing JSON definition, while the fresh JSON-format project prompts for the missing PBX definition. The two tests suggest the editor’s Unlock action can look for a different project definition than the one Xcode opened.