{
  "about": "Files and a patch in the *** Begin Patch envelope → the files afterwards (null: deleted), or the error the model is told (apply_patch's first format, OpenCode's). All or nothing.",
  "cases": [
    {
      "files": {
        "app.py": "def greet():\n    print('hi')\n"
      },
      "patch": "*** Begin Patch\n*** Update File: app.py\n@@ def greet():\n-    print('hi')\n+    print('hello')\n*** End Patch",
      "expect": {
        "files": {
          "app.py": "def greet():\n    print('hello')\n"
        }
      }
    },
    {
      "files": {},
      "patch": "*** Begin Patch\n*** Add File: new.txt\n+one\n+two\n*** End Patch",
      "expect": {
        "files": {
          "new.txt": "one\ntwo\n"
        }
      }
    },
    {
      "files": {
        "old.txt": "x\n"
      },
      "patch": "*** Begin Patch\n*** Delete File: old.txt\n*** End Patch",
      "expect": {
        "files": {
          "old.txt": null
        }
      }
    },
    {
      "files": {
        "a.txt": "1\n2\n3\n"
      },
      "patch": "*** Begin Patch\n*** Update File: a.txt\n*** Move to: b.txt\n 1\n-2\n+two\n 3\n*** End Patch",
      "expect": {
        "files": {
          "a.txt": null,
          "b.txt": "1\ntwo\n3\n"
        }
      }
    },
    {
      "files": {
        "a.txt": "1\n2\n3\n"
      },
      "patch": "*** Begin Patch\n*** Update File: a.txt\n 1\n-9\n+nine\n*** End Patch",
      "expect": {
        "error": "Failed to find expected lines in a.txt:\n1\n9"
      }
    },
    {
      "files": {
        "a.txt": "x\n"
      },
      "patch": "*** Begin Patch\n*** Add File: a.txt\n+y\n*** End Patch",
      "expect": {
        "error": "a.txt already exists; use Update File to change it."
      }
    },
    {
      "files": {},
      "patch": "no envelope at all",
      "expect": {
        "error": "Invalid patch format: missing Begin/End markers"
      }
    }
  ]
}