microsoft/aspire · error · TimeoutException

Build for resource ' ' timed out after .

Error message

Build for resource '{resource.Name}' timed out after {BuildTimeout:c}.

What it means

RunBuildAsync runs the MAUI build (dotnet build/run pipeline) with a per-resource build timeout (BuildTimeout). When the build process is killed because that timeout elapsed — not because the caller cancelled — the method kills the process and throws TimeoutException so the resource fails to start with a clear cause.

Solutions

Increase the build timeout configuration (BuildTimeout) to accommodate cold restore/workload installs.
Warm up the build by running dotnet build for the MAUI project once outside Aspire so subsequent queued builds are fast.
Re-run after transient network/NuGet slowness; pre-restore packages (dotnet restore) to reduce build time.
If cancellation is seen instead, check whether the caller token fired rather than the timeout CTS.

Example fix

// before
.WithBuildTimeout(TimeSpan.FromMinutes(5));
// after
.WithBuildTimeout(TimeSpan.FromMinutes(20)); // allow first-run workload restore

Defensive patterns

Strategy: retry

Validate before calling

// estimate: measure a cold build once
var sw = Stopwatch.StartNew(); RunDotnetBuild(); sw.Stop(); if (sw.Elapsed > configuredTimeout) raiseTimeout();

Try / catch

try { await startMauiResourceAsync(); } catch (TimeoutException ex) when (ex.Message.Contains("timed out after")) { /* raise BuildTimeout and retry the build once */ }

Prevention

Set a generous BuildTimeout that covers cold restore and workload installs
Warm the build cache (dotnet build) before running the AppHost
Pre-restore NuGet packages and workloads on CI images
Watch for slow networks during first-run package restore

When it happens

Trigger: The MAUI build (e.g. targeting iOS/Android/MacCatalyst workloads) takes longer than BuildTimeout; the timeout CancellationTokenSource fires during process.WaitForExitAsync while the caller token is still live (src/Aspire.Hosting.Maui/Lifecycle/MauiBuildQueueEventSubscriber.cs:235).

Common situations: First builds that restore workloads and NuGet packages (cold caches, slow networks); large MAUI solutions; slow CI machines or emulator-heavy targets; setting an aggressive custom BuildTimeout.

Understand the failure class

Background: Request timed out: what client-side request timeouts mean across libraries (Request timed out, TIMED_OUT, APITimeoutError) — this error's family across 39 libraries.

Timeouts: ETIMEDOUT, deadlines, and hung requests — what actually expires when a request times out.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/0ec05011b7673798. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.Maui/Lifecycle/MauiBuildQueueEventSubscriber.cs:235

        var token = timeoutCts.Token;

        using var process = new Process { StartInfo = psi };

        process.Start();

        // Pipe stdout/stderr to the resource logger so output is visible in the dashboard.
        var stdoutTask = PipeOutputAsync(process.StandardOutput, logger, LogLevel.Information, token);
        var stderrTask = PipeOutputAsync(process.StandardError, logger, LogLevel.Warning, token);

        try
        {
            await process.WaitForExitAsync(token).ConfigureAwait(false);
        }
        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
        {
            // The timeout CTS fired, not the caller's token — this is a build timeout.
            TryKillProcess(process, logger);
            throw new TimeoutException(
                $"Build for resource '{resource.Name}' timed out after {BuildTimeout:c}.");
        }
        catch (OperationCanceledException)
        {
            TryKillProcess(process, logger);
            throw;
        }
        finally
        {
            // Always drain remaining output — even on cancellation the process was killed
            // and the streams will reach EOF, so the tasks will complete promptly.
            await Task.WhenAll(stdoutTask, stderrTask).ConfigureAwait(false);
        }

        if (process.ExitCode != 0)
        {
            throw new InvalidOperationException(
                $"Build failed for resource '{resource.Name}' with exit code {process.ExitCode}.");

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