microsoft/aspire · error · InvalidOperationException

Bun apps cannot be debugged through the Node dev-server…

Error message

Bun apps cannot be debugged through the Node dev-server debug path. '{resource.Name}' is a BunAppResource; use AddBunApp, which wires its own Bun debug support.

What it means

The Node dev-server debug support extension only wires Node.js debug tooling. Bun has its own debugger wiring added via AddBunApp, so calling the Node debug path on a BunAppResource would attach an incompatible debugger. Aspire throws with guidance to use the Bun-specific API.

Solutions

Use AddBunApp for Bun workloads — it wires Bun's own debug support; do not call the Node debug extension.
In shared helpers, only call the Node debug extension when the resource is not BunAppResource/DenoAppResource.
Configure Bun's native inspector separately if a custom debug setup is needed.

Example fix

// before
builder.AddBunApp("app", "./app")
    .WithNodeDevServerDebugSupport();
// after
builder.AddBunApp("app", "./app"); // AddBunApp already wires Bun debug support

Defensive patterns

Strategy: type-guard

Validate before calling

if (resource is not BunAppResource)
    builder.WithNodeDevServerDebugSupport();

Type guard

bool SupportsNodeDevServerDebug(IResource r) => r is not BunAppResource and not DenoAppResource;

Try / catch

try { builder.WithNodeDevServerDebugSupport(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("BunAppResource"))
{
    // Bun debug support is already wired by AddBunApp; nothing to do
}

Prevention

In shared debug-setup helpers, branch on runtime type (Node vs Bun vs Deno).
Never apply Node-specific extensions to BunAppResource builders.
Let AddBunApp own Bun debug wiring.

When it happens

Trigger: Calling the Node dev-server debug extension (e.g. .WithNodeDevServerDebugSupport(...)) on a builder whose resource is a BunAppResource created with AddBunApp.

Common situations: Shared helper code applying uniform debug configuration to all JavaScript resources regardless of runtime; copy-pasted AppHost code where the resource changed from Node to Bun; generic loops attaching Node debug support to every resource.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/7b944410e549aaa0. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.JavaScript/JavaScriptHostingExtensions.cs:2871

    private static string GetJavaScriptPackageManagerLaunchConfigurationType(string packageManagerExecutable) => packageManagerExecutable switch
    {
        "bun" => "bun",
        "deno" => "deno",
        _ => "node",
    };

    [Experimental("ASPIREEXTENSION001", UrlFormat = "https://aka.ms/aspire/diagnostics/{0}")]
    internal static IResourceBuilder<T> WithVSCodeDebugging<T>(this IResourceBuilder<T> builder)
        where T : JavaScriptAppResource
    {
        ArgumentNullException.ThrowIfNull(builder);

        var resource = builder.Resource;
        var workingDirectory = Path.GetFullPath(resource.WorkingDirectory);

        if (resource is BunAppResource)
        {
            throw new InvalidOperationException(
                $"Bun apps cannot be debugged through the Node dev-server debug path. '{resource.Name}' is a {nameof(BunAppResource)}; use {nameof(AddBunApp)}, which wires its own Bun debug support.");
        }

        if (resource is DenoAppResource)
        {
            throw new InvalidOperationException(
                $"Deno apps cannot be debugged through the Node dev-server debug path. '{resource.Name}' is a {nameof(DenoAppResource)}; use {nameof(AddDenoApp)}, which wires its own Deno debug support.");
        }

        return builder.WithDebugSupport(
            mode =>
            {
                // Fall back to "npm" (the default for these frameworks) if no package manager annotation is present.
                var packageManager = "npm";
                if (resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out var pmAnnotation))
                {
                    packageManager = pmAnnotation.ExecutableName;
                }

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