microsoft/aspire · error · DistributedApplicationException

The '--output-path [path]' option was not specified even…

Error message

The '--output-path [path]' option was not specified even though '--publisher manifest' argument was used.

What it means

The manifest publisher writes the distributed application model to a JSON manifest file and therefore requires an output path. PublishInternalAsync checks the configured OutputPath first and throws DistributedApplicationException if it is null, echoing the CLI option ('--output-path') that should have supplied it.

Solutions

1. Pass --output-path <path> when using --publisher manifest.
2. If invoking programmatically, set OutputPath in the publisher options before calling PublishAsync.
3. Check the config source (env vars/args) bound to OutputPath is actually present.

Example fix

// before
dotnet run --publisher manifest
// after
dotnet run --publisher manifest --output-path ./manifest.json

if (string.IsNullOrWhiteSpace(publisherOptions.OutputPath))
{
    throw new InvalidOperationException("--output-path is required with --publisher manifest.");
}

bool HasOutputPath(ManifestPublisherOptions? o) => !string.IsNullOrWhiteSpace(o?.OutputPath);

try
{
    await publisher.PublishAsync(model, ct);
}
catch (DistributedApplicationException ex) when (ex.Message.Contains("--output-path"))
{
    logger.LogError(ex, "Manifest publishing requires --output-path.");
}

When it happens

Trigger: Running the publisher in manifest mode ('--publisher manifest') via PublishAsync without setting --output-path, or invoking ManifestPublisher programmatically with an options object whose OutputPath is null.

Common situations: Forgetting the --output-path flag on 'aspire publish' / dotnet run --publisher manifest; configuration binding not populating OutputPath; calling the publisher API directly from tests or tooling without options.

Understand the failure class

Background: "--flag is required" and "must specify" CLI errors: how missing-required-flag validation works and how to fix it — this error's family across 20 libraries.

Related errors

• The '--output-path [path]' option was not specified even…
• Could not get directory name of output path
• Could not get the container image name for resource
• Downloaded Aspire skills package does not contain…
• Integration closure manifest file

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/4825d4316a1607ec. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/Publishing/ManifestPublisher.cs:33

                               IOptions<PublishingOptions> options,
                               DistributedApplicationExecutionContext executionContext) : IDistributedApplicationPublisher
{
    private readonly ILogger<ManifestPublisher> _logger = logger;
    private readonly IOptions<PublishingOptions> _options = options;
    private readonly DistributedApplicationExecutionContext _executionContext = executionContext;

    public Utf8JsonWriter? JsonWriter { get; set; }

    public async Task PublishAsync(DistributedApplicationModel model, CancellationToken cancellationToken)
    {
        await PublishInternalAsync(model, cancellationToken).ConfigureAwait(false);
    }

    protected virtual async Task PublishInternalAsync(DistributedApplicationModel model, CancellationToken cancellationToken)
    {
        if (_options.Value.OutputPath == null)
        {
            throw new DistributedApplicationException(
                "The '--output-path [path]' option was not specified even though '--publisher manifest' argument was used."
                );
        }

        if (!_options.Value.OutputPath.EndsWith(".json", StringComparison.Ordinal))
        {
            // If the manifest path ends with .json we assume that the output path was specified
            // as a filename. If not, we assume that the output path was specified as a directory
            // and append aspire-manifest.json to the path. This is so that we retain backwards
            // compatibility with AZD, but also support manifest publishing via the Aspire CLI
            // where the output path is a directory (since not all publishers use a manifest).
            _options.Value.OutputPath = Path.Combine(_options.Value.OutputPath, "aspire-manifest.json");
        }

        var parentDirectory = Directory.GetParent(_options.Value.OutputPath);
        if (!Directory.Exists(parentDirectory!.FullName))
        {
            // Create the directory if it does not exist

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