Tools are often run without first ensuring the editor has updated the asset db and/or compiled

[strich]

Often code is changed and the LLM will request a console read back or try to run tests, but the editor hasn't first been told to refresh the asset db and recompile. It doesn't do this automatically because it doesn't have focus. All tool calls should ensure the editor has refreshed and the calls should survive a recompile.

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🔗 Similar Issues

Possible Duplicates

• Trigger Unity's script compilation? #305

Related Issues

• Reloading Unity editor with unity mcp. #143

👤 Suggested Assignees

• Kblack0610
• Doidel

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[dsarno]

Can you offer a repro case? There are only a few tools that change code (manage_script basically). And they reload domain reliably.

If you're talking about your IDE (Claude, cursor) making changes directly, that doesn't force a reload, but Unity will reload on next focus.

[strich]

I am indeed talking about using an external IDE. It's not viable to have to manually pull focus on the editor every time the AI wants to do something with it - Often the AI may be spending many minutes writing code, reading from the console and fixing bugs. Having to check back manually to pull focus then allow the read_console tool is frustrating and a time sink - That kind of tool call should happen in the background without my intervention.

A good solution here would be to provide an option in the editor window settings of the package to run AssetDatabase.Refresh() on every tool call. This is assuming tool calls survive recompilations?

[dsarno]

Yes, that's less a limitation of the mcp than the way IDEs work, but I agree it'd be nice to give the IDE a tool to reload domain when it wants to check its work. (This is how Coplay works). You would only want to call it on code changes because otherwise you don't need a recompile / domain reload.

[strich]

I disagree - it's not up to the IDE to tell unity things have changed. It's a failing of the MCP tools to ensure it's operating on the latest version of the assets. It would be silly to expect every IDE to somehow know it's working with a unity project and then also somehow know how to talk to the editor right?
Also you do want to call this on all tools all the time - calling assetdatabase.refesh() won't domain reload or recompile if no code has changed. It is a harmless call to make all the time

[dsarno]

Can't disagree with a well stated case. Thanks for pushing back.

Don't suppose you'd like to contribute a PR for it?

[strich]

The only thing I'm concerned about is whether you've made the tool calls durable over editor recompilations? I have no idea.

[dsarno]

Yes tools will retry if editor is compiling, then execute when editor is ready.

See e.g.: https://github.com/CoplayDev/unity-mcp/blob/main/MCPForUnity/Editor/Services/HttpBridgeReloadHandler.cs

And send_command_with_retry in https://github.com/CoplayDev/unity-mcp/blob/df906cb7477f9d9e4db04baa7b621284a9ba494e/Server/src/transport/legacy/unity_connection.py

[msanatan]

Yes tools will retry if editor is compiling, then execute when editor is ready.

See e.g.: https://github.com/CoplayDev/unity-mcp/blob/main/MCPForUnity/Editor/Services/HttpBridgeReloadHandler.cs

And send_command_with_retry in https://github.com/CoplayDev/unity-mcp/blob/df906cb7477f9d9e4db04baa7b621284a9ba494e/Server/src/transport/legacy/unity_connection.py

This is one of the dangers of having an asset reload tool with our current setup. When you do an asset DB refresh, Unity reloads the MCP plugin (not something we can control) and the reconnection happens. If the LLMs don't check state, it just tries again and gets stuck in a loop. This was tried before

[dsarno]

Agreed. This is too blunt a way to handle it. Most tools don't need a refresh. I'm going to try a more surgical approach.

[msanatan]

At least in my experience, tools and resources for testing don't work when the Unity editor isn't in focus, regardless of if I changed the state of the tests or not.

I'm not trying to discredit your problem @strich, but I think the solution is knowing how these tools work and ensuring we work with Unity in the correct way for each one.

At least from my experience with Coplay, there's a balance for users to be pulled back in focus and have LLMs do thing autonomously. You won't want it to be pulled in focus on every call.