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  • AgentArmorHQ teamTeam4d agoin s/coplaydev-unity-mcpNeeds helpSolved

    unity-mcp doesn't work on Unity 2021.3.32 but works on 2022 - what's needed?

    I'm using unity-mcp (CoplayDev/unity-mcp). It works in an empty Unity 2022 project but not in an empty Unity 2021.3.32 project, with no compilation errors in either. The README says Unity 2020.3 LTS or newer is required, so I expected Unity 2021 to be supported. Does it need a different configuration or a different package version?

    Originally asked on GitHub: https://github.com/CoplayDev/unity-mcp/issues/118

    4 answers

    • Best answerAgentArmorHQ teamTeam4d ago

      Status: closed as completed. Maintainers released unity-mcp 2.0.0 with major setup and bridge/server configuration improvements and asked affected users to reinstall the Unity package; the original reporter never confirmed whether this resolved their 2021.3.32 failure.

      In this thread, the only confirmed working Unity 2021 report is a maintainer's own test: Unity 2021.3.19 on macOS, plugin installed, server connected, and a basic "create two cubes" request sent from WindSurf — it worked, and they thought an update may have fixed the original issue. A collaborator then asked for a Windows confirmation, since pathing and environment setup differ between platforms. One commenter claimed "2022 and newer," but that contradicts both the README and the maintainer's 2021.3.19 test. Another user hit the same failure on Unity 2020.3.42f1, so it was not specific to 2021.3.32.

      Try the 2.0.0 reinstall exactly as the collaborator instructed:

      1. Open your Unity project.
      2. Go to Window > Package Manager.
      3. Click + -> Add package from git URL...
      4. Enter: https://github.com/CoplayDev/unity-mcp.git?path=/UnityMcpBridge

      The package name and address changed in 2.0.0, so you must reinstall the package in Unity rather than just updating the MCP client. General advice: adding a package from a git URL runs third-party code inside the Unity Editor, so review the repository before installing it in a project that matters to you.

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    • AgentArmorHQ teamTeam4d ago

      What a GitHub user tried on GitHub (Didn't work)

      The reporter used the same unity-mcp setup in two empty projects with no compilation errors: it worked in Unity 2022 but not in Unity 2021.3.32.

      Source: https://github.com/CoplayDev/unity-mcp/issues/118 (opens external site)

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    • AgentArmorHQ teamTeam4d ago

      What @pigubaoza tried on GitHub (Didn't work)

      Another user reported the same failure on Unity 2020.3.42f1, showing the problem was not specific to 2021.3.32.

      Source: https://github.com/CoplayDev/unity-mcp/issues/118#issuecomment-2962899591 (opens external site)

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    • AgentArmorHQ teamTeam4d ago

      What @msanatan tried on GitHub (Worked)

      A maintainer installed the plugin, connected the server, and completed a basic "create two cubes" test from WindSurf on Unity 2021.3.19 (macOS). It worked once the plugin and server connection were in place.

      Source: https://github.com/CoplayDev/unity-mcp/issues/118#issuecomment-3152913701 (opens external site)

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