Unity Code MCP Server v0.5 Release Notes

Unity Code MCP Server 0.5 Release Changes

TL;DR

• UniTask is no longer required, simplifying installation and upgrades.
• play_unity_game is more reliable when Unity loses or regains focus, so agents can keep driving simulated input while working outside the Unity window.
• Tool execution is more robust, with main-thread-safe async handling and JSON dependencies supplied through Unity Package Manager.

The 0.5 release makes Unity Code MCP Server leaner to install and more dependable during long-running automation. The biggest gains are in gameplay testing: simulated actions now survive focus changes more reliably, clean up after themselves, and restore the project’s previous runtime state when a run finishes.

What’s New for You?

One less dependency to install

Unity Code MCP Server no longer requires UniTask. It now includes a focused async layer built on standard .NET tasks, reducing setup work and removing a package that projects only needed for the MCP server.

If your project uses UniTask elsewhere, you can keep it. If it was installed only for Unity Code MCP Server, you can remove it after upgrading.

Gameplay input that handles focus changes

AI agents often operate while the Unity window is not focused. In 0.5, play_unity_game accounts for those real-world workflows by re-enabling affected input devices and temporarily applying the runtime settings needed for dependable simulated actions.

Presses and holds are now more resilient when Unity loses focus or moves between focused and unfocused states. Each run also clears stale device state and releases simulated controls, preventing one gameplay command from leaking into the next.

For a practical look at this workflow, see how AI agents can playtest Unity games.

Safer, more predictable Editor execution

MCP tools are now marshalled onto Unity’s main thread. This reduces threading-related failures when agents work with scenes, assets, tests, and Play Mode operations.

The built-in task layer handles Editor updates, real-time delays, cancellation, exceptions, coroutines, and main-thread dispatch. That gives tool authors a standard .NET async model while respecting Unity’s execution constraints.

Better compatibility with Unity projects

JSON handling now uses Unity’s Newtonsoft Json package rather than bundled System.Text.Json assemblies. This reduces the chance of assembly conflicts in host projects and keeps schemas, prompts, resources, requests, responses, and tool arguments on a Unity-supported dependency.

Bundled skills have also moved under Skills~, so Unity does not unnecessarily import and compile their support files.

Breaking Changes and Migration

Most users can upgrade directly. Unity Input System 1.19.0 and Newtonsoft Json 3.2.2 are declared by the package and should be resolved automatically by Unity Package Manager.

Custom MCP tool authors need to update two APIs:

• Async tools: IToolAsync.ExecuteAsync now returns Task<ToolsCallResult> instead of UniTask<ToolsCallResult>.
• JSON values: Tool schemas and arguments now use Newtonsoft JToken instead of System.Text.Json.JsonElement. Import Newtonsoft.Json.Linq and follow the current repository examples.

After upgrading, test any custom tools and gameplay scenarios that depend on simulated input. Projects that installed UniTask solely for Unity Code MCP Server can remove it once no other code depends on the package.

Key Improvements

Gameplay automation

• Focus-resilient presses and holds across Unity focus changes.
• Automatic cleanup of queued actions, simulated inputs, and device state after every run.
• Restoration of the previous Editor pause state, time scale, background behavior, and Game View input routing.
• Expanded Play Mode regression coverage for repeated input, focus transitions, presses, holds, and cleanup.

Runtime and compatibility

• Standard task-based Editor async support without UniTask.
• Main-thread dispatch for more predictable Unity API access.
• Unity-managed Newtonsoft Json dependencies instead of bundled System.Text.Json assemblies.
• Cleaner package imports through the Skills~ directory.

Agent experience

• Shorter, clearer contracts for C# execution and gameplay simulation tools.
• Updated bundled skills for the current script-execution and Play Mode workflows.
• Refreshed README and custom-tool examples, including MCPorter CLI examples for direct tool calls.

Read the complete packaged notes and download the release from Unity Code MCP Server v0.5.12 on GitHub.