read_console returns no entries for compilation errors (CS errors invisible to AI agents)

[johnkslg]

Description

read_console with types: ["error"] (or even types: ["all"]) returns zero entries when C# compilation errors exist. Compiler diagnostics (error CS####) are written to Editor.log and appear in the Unity Console UI, but are not returned by the read_console tool.

This means AI agents have no MCP-based way to detect compilation failures after editing scripts -- arguably the single most important feedback loop for code-editing agents.

Steps to Reproduce

1. Introduce a deliberate C# compilation error (e.g., call a method with wrong argument count)
2. Call refresh_unity with compile: "request", wait_for_ready: true
3. Wait 15 seconds for compilation to complete
4. Call read_console with action: "get", types: ["error"], count: 50
5. Result: Returns {"success": true} with zero entries
6. Call read_console with types: ["all"] -- still zero entries
7. Check Editor.log directly -- the error CS#### lines are there

Expected Behavior

read_console should return compilation errors (e.g., error CS1501: No overload for method 'Get' takes 3 arguments) as error-type entries.

Root Cause Analysis

Looking at the ReadConsole.cs source, it uses LogEntries.StartGettingEntries / GetEntryInternal / EndGettingEntries via reflection. This reads Unity's internal console log buffer.

The issue appears to be that when compilation fails, the domain reload does not complete, so:

• The LogEntries buffer may not contain the compiler diagnostics at all, or
• The entries exist but the MCP server (running in the editor domain) may be in a state where it can't read them properly

The InferTypeFromMessage method in ReadConsole.cs does have logic to detect "error CS" patterns, so the filtering logic is correct -- the entries simply aren't present in the LogEntries buffer.

Current Workaround

Read the Unity Editor.log file directly:

Get-Content "$env:LOCALAPPDATA\Unity\Editor\Editor.log" -Tail 300 | Select-String -Pattern "error CS\d{4}"

Suggested Fix

Consider using UnityEditor.Compilation.CompilationPipeline to capture compilation results separately. For example:

• CompilationPipeline.assemblyCompilationFinished event to capture per-assembly results
• Store compilation diagnostics in a separate buffer that read_console (or a new tool/resource) can query
• Alternatively, expose compilation status in the editor_state resource (the compilation field is currently always null)

Environment

• Unity MCP: v9.4.7
• Unity: 6 (6000.x)
• OS: Windows 10
• Client: Cursor IDE

[dsarno]

Are you sure you don't have something typed in console search? That filters out other console entries and it will be empty.

[johnkslg]

nope nothing typed in console search, errors are visible there

[dsarno]

Are you using HTTP mode or stdio? And only one unity instance open? Just wondering if it's querying something else, or you have a zombie server or something. This is definitely not a widespread error so the question is what's causing it on your system. Fairly good odds if you restarted computer it would go away.

[johnkslg]

ah i have two unity instances open... dont know which its querying, how does it decide?

[dsarno]

It defaults to whichever it talked to first, and should be smart about routing tool calls to the right one once it knows there are multiple.

[dsarno]

(But it can't read your mind so if all you say is "read console", it won't know which one so it'll just use the one it's already on probably)

[johnkslg]

I did try closing the second instance and restarting the mcp server and it still failed to find errors. It was able to find them by reading the console log directly, though, and other MCP commands worked. This is with just one instance