Add delete_child command for prefab manage_contents action

MCPForUnity/Editor/Tools/Prefabs/ManagePrefabs.cs

@@ -905,6 +905,21 @@ private static (bool modified, ErrorResponse error) ApplyModificationsToPrefabOb
                 }
             }
 
+            // Delete child GameObjects (supports single string or array of paths/names)
+            JToken deleteChildToken = @params["deleteChild"] ?? @params["delete_child"];
+            if (deleteChildToken != null)
+            {
+                var deleteResult = RemoveChildren(deleteChildToken, targetGo, prefabRoot);
+                if (deleteResult.error != null)
+                {
+                    return (false, deleteResult.error);
+                }
+                if (deleteResult.removedCount > 0)
+                {
+                    modified = true;
+                }
+            }
+
             // Set properties on existing components
             JObject componentProperties = @params["componentProperties"] as JObject ?? @params["component_properties"] as JObject;
             if (componentProperties != null && componentProperties.Count > 0)
@@ -1132,6 +1147,47 @@ private static (bool created, ErrorResponse error) CreateSingleChildInPrefab(JTo
             return (true, null);
         }
 
+        /// <summary>
+        /// Removes child GameObjects from a prefab.
+        /// </summary>
+        private static (int removedCount, ErrorResponse error) RemoveChildren(JToken deleteChildToken, GameObject targetGo, GameObject prefabRoot)
+        {
+            int removedCount = 0;
+
+            // Normalize to array
+            JArray childrenToDelete;
+            if (deleteChildToken is JArray arr)
+            {
+                childrenToDelete = arr;
+            }
+            else
+            {
+                childrenToDelete = new JArray { deleteChildToken };
+            }
+
+            foreach (var childToken in childrenToDelete)
+            {
+                string childPath = childToken.Type == JTokenType.String ? childToken.ToString() : childToken["name"]?.ToString();
+                if (string.IsNullOrEmpty(childPath))
+                {
+                    return (removedCount, new ErrorResponse("'delete_child' must be a string or object with 'name' field."));
+                }
+
+                // Find the child to remove
+                Transform childToRemove = targetGo.transform.Find(childPath);
+                if (childToRemove == null)
+                {
+                    return (removedCount, new ErrorResponse($"Child '{childPath}' not found under '{targetGo.name}'."));
+                }
+
+                UnityEngine.Object.DestroyImmediate(childToRemove.gameObject);
+                removedCount++;
+                McpLog.Info($"[ManagePrefabs] Removed child '{childPath}' under '{targetGo.name}' in prefab.");
+            }
+
+            return (removedCount, null);
+        }
+
         #endregion
 
         #region Hierarchy Builder

Server/src/cli/commands/prefab.py

@@ -1,5 +1,6 @@
 """Prefab CLI commands."""
 
+import json
 import sys
 import click
 from typing import Optional, Any
@@ -246,3 +247,124 @@ def create(target: str, path: str, overwrite: bool, include_inactive: bool, unli
     click.echo(format_output(result, config.format))
     if result.get("success"):
         print_success(f"Created prefab: {path}")
+
+
+def _parse_vector3(value: str) -> list[float]:
+    """Parse 'x,y,z' string to list of floats."""
+    parts = value.split(",")
+    if len(parts) != 3:
+        raise click.BadParameter("Must be 'x,y,z' format")
+    return [float(p.strip()) for p in parts]
+
+
+def _parse_property(prop_str: str) -> tuple[str, str, Any]:
+    """Parse 'Component.prop=value' into (component, prop, value)."""
+    if "=" not in prop_str:
+        raise click.BadParameter("Must be 'Component.prop=value' format")
+    comp_prop, val_str = prop_str.split("=", 1)
+    if "." not in comp_prop:
+        raise click.BadParameter("Must be 'Component.prop=value' format")
+    component, prop = comp_prop.rsplit(".", 1)
+
+    val_str = val_str.strip()
+
+    # Parse booleans
+    if val_str.lower() == "true":
+        parsed_value: Any = True
+    elif val_str.lower() == "false":
+        parsed_value = False
+    # Parse numbers
+    elif "." in val_str:
+        try:
+            parsed_value = float(val_str)
+        except ValueError:
+            parsed_value = val_str
+    else:
+        try:
+            parsed_value = int(val_str)
+        except ValueError:
+            parsed_value = val_str
+
+    return component.strip(), prop.strip(), parsed_value
+
+
+@prefab.command("modify")
+@click.argument("path")
+@click.option("--target", "-t", help="Target object name/path within prefab (default: root)")
+@click.option("--position", "-p", help="New local position as 'x,y,z'")
+@click.option("--rotation", "-r", help="New local rotation as 'x,y,z'")
+@click.option("--scale", "-s", help="New local scale as 'x,y,z'")
+@click.option("--name", "-n", help="New name for target")
+@click.option("--tag", help="New tag")
+@click.option("--layer", help="New layer")
+@click.option("--active/--inactive", default=None, help="Set active state")
+@click.option("--parent", help="New parent object name/path")
+@click.option("--add-component", multiple=True, help="Component type to add (repeatable)")
+@click.option("--remove-component", multiple=True, help="Component type to remove (repeatable)")
+@click.option("--set-property", multiple=True, help="Property as 'Component.prop=value' (repeatable)")
+@click.option("--delete-child", multiple=True, help="Child name/path to remove (repeatable)")
+@click.option("--create-child", help="JSON object for child creation")
+@handle_unity_errors
+def modify(path: str, target: Optional[str], position: Optional[str], rotation: Optional[str],
+           scale: Optional[str], name: Optional[str], tag: Optional[str], layer: Optional[str],
+           active: Optional[bool], parent: Optional[str], add_component: tuple, remove_component: tuple,
+           set_property: tuple, delete_child: tuple, create_child: Optional[str]):
+    """Modify a prefab's contents (headless, no UI).
+
+    \b
+    Examples:
+        unity-mcp prefab modify "Assets/Prefabs/Player.prefab" --delete-child Child1
+        unity-mcp prefab modify "Assets/Prefabs/Player.prefab" --delete-child "Turret/Barrel" --delete-child Bullet
+        unity-mcp prefab modify "Assets/Prefabs/Player.prefab" --target Weapon --position "0,1,2"
+        unity-mcp prefab modify "Assets/Prefabs/Player.prefab" --set-property "Rigidbody.mass=5"
+        unity-mcp prefab modify "Assets/Prefabs/Player.prefab" --create-child '{"name":"Spawn","primitive_type":"Sphere"}'
+    """
+    config = get_config()
+
+    params: dict[str, Any] = {
+        "action": "modify_contents",
+        "prefabPath": path,
+    }
+
+    if target:
+        params["target"] = target
+    if position:
+        params["position"] = _parse_vector3(position)
+    if rotation:
+        params["rotation"] = _parse_vector3(rotation)
+    if scale:
+        params["scale"] = _parse_vector3(scale)
+    if name:
+        params["name"] = name
+    if tag:
+        params["tag"] = tag
+    if layer:
+        params["layer"] = layer
+    if active is not None:
+        params["setActive"] = active
+    if parent:
+        params["parent"] = parent
+    if add_component:
+        params["componentsToAdd"] = list(add_component)
+    if remove_component:
+        params["componentsToRemove"] = list(remove_component)
+    if set_property:
+        component_properties: dict[str, dict[str, Any]] = {}
+        for prop in set_property:
+            comp, name_p, val = _parse_property(prop)
+            if comp not in component_properties:
+                component_properties[comp] = {}
+            component_properties[comp][name_p] = val
+        params["componentProperties"] = component_properties
+    if delete_child:
+        params["deleteChild"] = list(delete_child)
+    if create_child:
+        try:
+            params["createChild"] = json.loads(create_child)
+        except json.JSONDecodeError as e:
+            raise click.BadParameter(f"Invalid JSON for --create-child: {e}")
+
+    result = run_command("manage_prefabs", params, config)
+    click.echo(format_output(result, config.format))
+    if result.get("success"):
+        print_success(f"Modified prefab: {path}")

Server/src/services/tools/manage_prefabs.py

@@ -29,6 +29,9 @@
         "(single object or array for batch creation in one save). "
         "Example: create_child=[{\"name\": \"Child1\", \"primitive_type\": \"Sphere\", \"position\": [1,0,0]}, "
         "{\"name\": \"Nested\", \"source_prefab_path\": \"Assets/Prefabs/Bullet.prefab\", \"position\": [0,2,0]}]. "
+        "Use delete_child parameter to remove child GameObjects from the prefab "
+        "(single name/path or array of paths for batch deletion. "
+        "Example: delete_child=[\"Child1\", \"Child2/Grandchild\"]). "
         "Use component_properties with modify_contents to set serialized fields on existing components "
         "(e.g. component_properties={\"Rigidbody\": {\"mass\": 5.0}, \"MyScript\": {\"health\": 100}}). "
         "Supports object references via {\"guid\": \"...\"}, {\"path\": \"Assets/...\"}, or {\"instanceID\": 123}. "
@@ -67,6 +70,7 @@ async def manage_prefabs(
     components_to_add: Annotated[list[str], "Component types to add in modify_contents."] | None = None,
     components_to_remove: Annotated[list[str], "Component types to remove in modify_contents."] | None = None,
     create_child: Annotated[dict[str, Any] | list[dict[str, Any]], "Create child GameObject(s) in the prefab. Single object or array of objects, each with: name (required), parent (optional, defaults to target), source_prefab_path (optional: asset path to instantiate as nested prefab, e.g. 'Assets/Prefabs/Bullet.prefab'), primitive_type (optional: Cube, Sphere, Capsule, Cylinder, Plane, Quad), position, rotation, scale, components_to_add, tag, layer, set_active. source_prefab_path and primitive_type are mutually exclusive."] | None = None,
+    delete_child: Annotated[str | list[str], "Child name(s) or path(s) to remove from the prefab. Supports single string or array for batch deletion (e.g. 'Child1' or ['Child1', 'Child1/Grandchild'])."] | None = None,
     component_properties: Annotated[dict[str, dict[str, Any]], "Set properties on existing components in modify_contents. Keys are component type names, values are dicts of property name to value. Example: {\"Rigidbody\": {\"mass\": 5.0}, \"MyScript\": {\"health\": 100}}. Supports object references via {\"guid\": \"...\"}, {\"path\": \"Assets/...\"}, or {\"instanceID\": 123}. For Sprite sub-assets: {\"guid\": \"...\", \"spriteName\": \"<name>\"}. Single-sprite textures auto-resolve."] | None = None,
 ) -> dict[str, Any]:
     # Back-compat: map 'name' → 'target' for create_from_gameobject (Unity accepts both)
@@ -185,6 +189,9 @@ def normalize_child_params(child: Any, index: int | None = None) -> tuple[dict |
                     return {"success": False, "message": err}
                 params["createChild"] = child_params
 
+        if delete_child is not None:
+            params["deleteChild"] = delete_child
+
         # Send command to Unity
         response = await send_with_unity_instance(
             async_send_command_with_retry, unity_instance, "manage_prefabs", params

Server/tests/test_cli.py

@@ -636,6 +636,115 @@ def test_prefab_create(self, runner, mock_unity_response):
             ])
             assert result.exit_code == 0
 
+    def test_prefab_modify_delete_child(self, runner, mock_unity_response):
+        """Test prefab modify delete-child command."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--delete-child", "Child1",
+                "--delete-child", "Turret/Barrel"
+            ])
+            assert result.exit_code == 0
+            # Verify the correct params were sent
+            call_args = mock_run.call_args[0]
+            assert call_args[0] == "manage_prefabs"
+            params = call_args[1]
+            assert params["action"] == "modify_contents"
+            assert params["deleteChild"] == ["Child1", "Turret/Barrel"]
+
+    def test_prefab_modify_transform(self, runner, mock_unity_response):
+        """Test prefab modify with transform options."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--target", "Weapon",
+                "--position", "1,2,3",
+                "--rotation", "45,0,90",
+                "--scale", "2,2,2"
+            ])
+            assert result.exit_code == 0
+            call_args = mock_run.call_args[0]
+            params = call_args[1]
+            assert params["target"] == "Weapon"
+            assert params["position"] == [1.0, 2.0, 3.0]
+            assert params["rotation"] == [45.0, 0.0, 90.0]
+            assert params["scale"] == [2.0, 2.0, 2.0]
+
+    def test_prefab_modify_set_property(self, runner, mock_unity_response):
+        """Test prefab modify set-property command."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--set-property", "Rigidbody.mass=5",
+                "--set-property", "Rigidbody.useGravity=false"
+            ])
+            assert result.exit_code == 0
+            call_args = mock_run.call_args[0]
+            params = call_args[1]
+            assert "componentProperties" in params
+            assert params["componentProperties"]["Rigidbody"]["mass"] == 5
+            assert params["componentProperties"]["Rigidbody"]["useGravity"] is False
+
+    def test_prefab_modify_set_property_float(self, runner, mock_unity_response):
+        """Test prefab modify set-property with float values."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--set-property", "Rigidbody.mass=5.5"
+            ])
+            assert result.exit_code == 0
+            call_args = mock_run.call_args[0]
+            params = call_args[1]
+            assert params["componentProperties"]["Rigidbody"]["mass"] == 5.5
+
+    def test_prefab_modify_components(self, runner, mock_unity_response):
+        """Test prefab modify add/remove components."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--add-component", "Rigidbody",
+                "--add-component", "BoxCollider",
+                "--remove-component", "SphereCollider"
+            ])
+            assert result.exit_code == 0
+            call_args = mock_run.call_args[0]
+            params = call_args[1]
+            assert params["componentsToAdd"] == ["Rigidbody", "BoxCollider"]
+            assert params["componentsToRemove"] == ["SphereCollider"]
+
+    def test_prefab_modify_create_child(self, runner, mock_unity_response):
+        """Test prefab modify create-child command."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--create-child", '{"name":"Spawn","primitive_type":"Sphere"}'
+            ])
+            assert result.exit_code == 0
+            call_args = mock_run.call_args[0]
+            params = call_args[1]
+            assert params["createChild"]["name"] == "Spawn"
+            assert params["createChild"]["primitive_type"] == "Sphere"
+
+    def test_prefab_modify_invalid_create_child_json(self, runner, mock_unity_response):
+        """Test prefab modify with invalid JSON for create-child."""
+        result = runner.invoke(cli, [
+            "prefab", "modify", "Assets/Prefabs/Player.prefab",
+            "--create-child", "not valid json"
+        ])
+        assert result.exit_code != 0
+
+    def test_prefab_modify_active_state(self, runner, mock_unity_response):
+        """Test prefab modify active/inactive flag."""
+        with patch("cli.commands.prefab.run_command", return_value=mock_unity_response) as mock_run:
+            result = runner.invoke(cli, [
+                "prefab", "modify", "Assets/Prefabs/Player.prefab",
+                "--inactive"
+            ])
+            assert result.exit_code == 0
+            call_args = mock_run.call_args[0]
+            params = call_args[1]
+            assert params["setActive"] is False
+
 
 # =============================================================================
 # Material Command Tests