The manage_prefabs tool with action: "create_from_gameobject" cannot locate GameObjects that have been set to inactive (SetActive(false)), even when those objects exist in the scene and can be found by other tools.

[HivemindOverlord]

Unity MCP Feature Request: Prefab Creation from Inactive GameObjects

Summary

The manage_prefabs tool with action: "create_from_gameobject" cannot locate GameObjects that have been set to inactive (SetActive(false)), even when those objects exist in the scene and can be found by other tools.

Environment

• Unity MCP (version unknown - whatever's current as of Jan 2025)
• Unity 6000.13f1
• Scene: MainMenu.unity

Steps to Reproduce

1. Create a GameObject successfully:

{
  "tool": "manage_gameobject",
  "params": {
    "action": "create",
    "name": "CoreStatsPanel",
    "parent": "MainMenuCanvas (1)",
    "components_to_add": ["UnityEngine.UI.Image", "XStellar.UI.Controllers.CoreStatsController"]
  }
}

✅ Result: GameObject created with instanceID -70128

2. Set the GameObject to inactive:

{
  "tool": "manage_gameobject",
  "params": {
    "action": "modify",
    "name": "CoreStatsPanel",
    "set_active": false
  }
}

✅ Result: GameObject set to activeSelf: false

3. Verify the object still exists (this works):

{
  "tool": "manage_gameobject",
  "params": {
    "action": "find",
    "search_method": "by_name",
    "search_term": "CoreStatsPanel",
    "search_inactive": true
  }
}

✅ Result: Found 1 GameObject with correct instanceID -70128, shows activeSelf: false

4. Attempt to create prefab (this fails):

{
  "tool": "manage_prefabs",
  "params": {
    "action": "create_from_gameobject",
    "target": "CoreStatsPanel",
    "prefab_path": "Assets/Prefabs/UI/CoreStats/CoreStatsPanel.prefab",
    "allow_overwrite": true
  }
}

❌ Result:

{
  "success": false,
  "code": "GameObject 'CoreStatsPanel' not found in the active scene.",
  "error": "GameObject 'CoreStatsPanel' not found in the active scene."
}

Workarounds Attempted (All Failed)

Attempt	Parameter Used	Result
Search by path	target: "MainMenuCanvas (1)/CoreStatsPanel"	Same error
Search inactive flag	search_inactive: true	Parameter not recognized/ignored
Use instance ID	target: "-70128"	Same error
Re-activate then create	set_active: true on modify	Modify command also couldn't find inactive object

Root Cause Analysis

The manage_prefabs tool appears to use a lookup method that only searches active GameObjects (likely GameObject.Find() or similar), whereas manage_gameobject with action: "find" has the search_inactive parameter that uses FindObjectsByType<T>(FindObjectsInactive.Include).

The prefab creation tool should support:

1. A search_inactive parameter like the find action has
2. Lookup by instanceID (which is unambiguous)
3. Or ideally, accepting the result object from a prior find call

Impact

This prevents a common workflow:

1. Build complex UI hierarchy in scene
2. Set panel to inactive (standard practice for UI panels)
3. Save as prefab
4. Delete scene instance

Users must either:

• Keep all objects active (clutters scene view, may cause runtime issues)
• Use a separate Editor script approach (defeats purpose of MCP)
• Manually create prefabs in Unity Editor

Suggested Fix

Add search_inactive parameter to manage_prefabs tool:

{
  "tool": "manage_prefabs",
  "params": {
    "action": "create_from_gameobject",
    "target": "CoreStatsPanel",
    "search_inactive": true,  // NEW PARAMETER
    "prefab_path": "Assets/Prefabs/UI/CoreStats/CoreStatsPanel.prefab"
  }
}

Or support instanceID targeting:

{
  "tool": "manage_prefabs",
  "params": {
    "action": "create_from_gameobject",
    "target_instance_id": -70128,  // Direct reference
    "prefab_path": "Assets/Prefabs/UI/CoreStats/CoreStatsPanel.prefab"
  }
}

Additional Context

The manage_gameobject tool with action: "modify" has the same limitation - it cannot modify inactive GameObjects even when you know their exact path or instanceID. This suggests the underlying GameObject lookup utility used across multiple tools needs the inactive search capability.

[HivemindOverlord]

formatted better w/ actual markdown