Unity-MCP unity-version-split

Split a C# file into Unity 6.5+ and pre-Unity 6.5 variants. Use when a file needs different implementations for different Unity versions due to API changes (e.g., EntityId vs int, GetEntityId vs GetInstanceID).

install

source · Clone the upstream repo

git clone https://github.com/IvanMurzak/Unity-MCP

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/IvanMurzak/Unity-MCP "$T" && mkdir -p ~/.claude/skills && cp -r "$T/Unity-MCP-Plugin/.claude/skills/unity-version-split" ~/.claude/skills/ivanmurzak-unity-mcp-unity-version-split && rm -rf "$T"

manifest: Unity-MCP-Plugin/.claude/skills/unity-version-split/SKILL.md

source content

Unity Version Split

Split a C# source file into two variants: one for Unity 6.5+ (

UNITY_6000_5_OR_NEWER

) and one for older versions (pre-Unity 6.5).

When to Use

Unity 6.5 introduced breaking changes including:

```
EntityId
```
replaces
```
int
```
for instance IDs (
```
GetEntityId()
```
replaces
```
GetInstanceID()
```
)

EditorUtility.EntityIdToObject(EntityId)

replaces

EditorUtility.InstanceIDToObject(int)

Implicit
```
EntityId <-> int
```
conversions are marked
```
[Obsolete(..., true)]
```
(compile error)

When a file needs different code for these Unity versions, split it into two files following the project convention.

File Naming Convention

File	Purpose	Preprocessor Guard
`FileName.cs`	Unity 6.5+ (newer version)	`#if UNITY_6000_5_OR_NEWER`
`FileName.pre-Unity.6.5.cs`	Pre-Unity 6.5 (older version)	`#if !UNITY_6000_5_OR_NEWER`

For files that also have Editor/Runtime variants, combine the guards:

File	Guard
`FileName.Editor.cs`	`#if UNITY_EDITOR && UNITY_6000_5_OR_NEWER`
`FileName.Editor.pre-Unity.6.5.cs`	`#if UNITY_EDITOR && !UNITY_6000_5_OR_NEWER`
`FileName.Runtime.cs`	`#if !UNITY_EDITOR && UNITY_6000_5_OR_NEWER`
`FileName.Runtime.pre-Unity.6.5.cs`	`#if !UNITY_EDITOR && !UNITY_6000_5_OR_NEWER`

Step-by-Step Process

Step 1 — Read the Source File

Read

$ARGUMENTS

(the target file path). Identify which parts need version-specific code.

Step 2 — Identify the Split Points

Common differences between Unity 6.5+ and pre-6.5:

Unity 6.5+	Pre-Unity 6.5
`EntityId`	`int`
`EntityId.None`	`0`
`go.GetEntityId()`	`go.GetInstanceID()`
`EditorUtility.EntityIdToObject(entityId)`	`EditorUtility.InstanceIDToObject(instanceID)`
`ObjectRef.InstanceID` is `EntityId`	`ObjectRef.InstanceID` is `int?`

Step 3 — Create the Two Files

Update the original
```
.cs
```
file to contain only the Unity 6.5+ version:
- Set the preprocessor guard to include
```
UNITY_6000_5_OR_NEWER
```
- Use
```
EntityId
```
  ,
```
GetEntityId()
```
  , etc.
Create the
```
.pre-Unity.6.5.cs
```
file with the pre-6.5 version:
- Set the preprocessor guard to include
```
!UNITY_6000_5_OR_NEWER
```
- Use
```
int
```
  ,
```
GetInstanceID()
```
  , etc.

Both files must:

Start with
```
#nullable enable
```
Have the same copyright header as the original
Use the same namespace and class name (partial classes)
End with
```
#endif
```
matching the opening
```
#if
```

Step 4 — Refresh Assets

Run

assets-refresh

tool to let Unity generate

.meta

files and recompile.

IMPORTANT: Do NOT manually create

.meta

files. Unity auto-generates them after

assets-refresh

or any AssetDatabase.Refresh() call.

Step 5 — Verify

Check for compilation errors using

console-get-logs

tool.

Example

Given

GameObjectUtils.Runtime.cs

with

#if !UNITY_EDITOR

that uses both

EntityId

and

int

with

#if UNITY_6000_5_OR_NEWER

inside:

Before (single file with nested #if):

#if !UNITY_EDITOR
// ...
#if UNITY_6000_5_OR_NEWER
        public static GameObject? FindByInstanceID(EntityId instanceID) { ... }
#else
        public static GameObject? FindByInstanceID(int instanceID) { ... }
#endif
#endif

After (two clean files):

GameObjectUtils.Runtime.cs

#if !UNITY_EDITOR && UNITY_6000_5_OR_NEWER
// ...
        public static GameObject? FindByInstanceID(EntityId instanceID) { ... }
#endif

GameObjectUtils.Runtime.pre-Unity.6.5.cs

#if !UNITY_EDITOR && !UNITY_6000_5_OR_NEWER
// ...
        public static GameObject? FindByInstanceID(int instanceID) { ... }
#endif

Reference Files

Existing examples of this pattern in the codebase:

Runtime/Data/ObjectRef.cs

ObjectRef.pre-Unity.6.5.cs

Runtime/Data/GameObjectRef.cs

GameObjectRef.pre-Unity.6.5.cs

Runtime/Utils/GameObjectUtils.Editor.cs

GameObjectUtils.Editor.pre-Unity.6.5.cs

Tests/Editor/Tool/Assets/AssetsPrefabCreateTests.cs

AssetsPrefabCreateTests.pre-Unity.6.5.cs