Unity Editor HTTP Server

This package was designed and implemented through an AI-assisted development session using Claude (Anthropic). The architecture, all C# code, the OpenAPI spec, and the AI skill files were produced by the model from a conversational prompt, with a human reviewing and directing the work. No code was written by hand.

A Unity Editor package that exposes an HTTP API on localhost:8765, giving AI agents (and other tools) programmatic access to editor state, the TestRunner, the console log, and AssetDatabase — with no GUI interaction required.

Endpoints

Method	Path	Description
GET	/editor/status	Compilation state, play mode, Unity version, per-assembly compiler errors
POST	/assets/refresh	Trigger AssetDatabase.Refresh() after writing files to disk
GET	/assets/list	Enumerate project assets by type
GET	/tests/list	All discovered edit-mode test names
POST	/tests/run	Run tests with optional glob filter and minimal output mode
GET	/logs	Rolling console log buffer (last 500 entries)
POST	/logs/clear	Clear the log buffer
GET	/editor/screenshot	Capture the Game view as a PNG image
GET	/editor/selection	Currently selected objects in the Editor
GET	/swagger	Swagger UI
GET	/swagger/openapi.json	OpenAPI 3.0 spec

AI workflow

1. Write .cs files to Assets/
2. POST /assets/refresh
3. Poll GET /editor/status every 500ms until isCompiling == false
4. Check assemblies[*].compilerMessages for type == "Error" — fix and repeat if any
5. POST /tests/run {"minimal": true}
6. On failure: GET /logs?level=error for more context

Installation

In Unity's Package Manager, choose Add package from git URL and enter:

https://github.com/valarion/unity-editor-http-server.git

Or add to your project's Packages/manifest.json:

{
  "dependencies": {
    "com.devtools.unity-editor-http-server": "https://github.com/valarion/unity-editor-http-server.git"
  }
}

The server starts automatically when the Unity Editor opens (via [InitializeOnLoad]). Look for:

[TestHttpServer] Listening on http://localhost:8765/

in the Unity console.

Local development

To iterate on the package without pushing to git, point your Unity project at the local folder instead of the git URL. In Packages/manifest.json:

{
  "dependencies": {
    "com.devtools.unity-editor-http-server": "file:G:/unity-editor-http-server"
  }
}

Edit Editor/TestHttpServer.cs directly — Unity recompiles automatically on save. When satisfied, push to git and switch the manifest entry back to the git URL.

Adding custom endpoints

You can add endpoints from your own project without modifying the package. This is the recommended way to prototype new endpoints before contributing them upstream.

1. Create an Editor script in your project:

using UnityEditor;

[InitializeOnLoad]
public static class MyEndpoints
{
    static MyEndpoints()
    {
        TestHttpServer.RegisterEndpoint("GET", "/my/data", ctx =>
        {
            // Unity APIs must run on the main thread — use RunOnMainThread:
            var value = TestHttpServer.RunOnMainThread(() => MyService.GetValue());
            TestHttpServer.Respond(ctx, 200, $"{{\"value\":{TestHttpServer.JsonStr(value)}}}");
        });
    }
}

2. Test it:

curl http://localhost:8765/my/data

3. Contribute it upstream by opening a PR to this repository.

See Samples~/CustomEndpoints/CustomEndpointExample.cs for more examples including POST with a request body and main-thread dispatch.

Extension API reference

Member	Description
RegisterEndpoint(method, path, handler)	Register a custom route. Built-in routes take precedence.
RunOnMainThread(Action)	Dispatch work to Unity's main thread and block until done.
RunOnMainThread<T>(Func<T>)	Same, but returns a value.
Respond(ctx, status, body, contentType?)	Write an HTTP response.
JsonStr(string)	Escape and quote a string as a JSON literal, or "null".

Requirements

• Unity 2021.3 or newer
• com.unity.test-framework package (included by default in Unity projects)

AI skills

The skills/ directory contains ready-made integration files:

• skills/claude-skill.md — Drop into a Claude Code project's .claude/skills/ directory (or any skills directory). Teaches Claude how to use the API and when to invoke each endpoint.
• skills/mistral-skill.md — System prompt and function-calling schema for Mistral. Includes Python tool implementations mapping function names to HTTP calls.

Port

The default port is 8765. You can change it (and toggle auto-start) in Tools > HTTP Server > Settings. The port is persisted in EditorPrefs and survives recompiles. If the port is unavailable the server logs an error and stays inactive.

Notes

• Edit-mode tests only. PlayMode tests are not supported.
• The server is Editor-only and is stripped from builds.
• Compiler messages in /editor/status are populated by the CompilationPipeline.assemblyCompilationFinished event — they will be empty until Unity recompiles after the server starts. An empty compilerMessages array does not mean "no errors"; it means "no compile has happened yet."