microsoft/aspire · error · JsonException

The configuration file

Error message

The configuration file '{0}' contains invalid JSON: {1}

What it means

When loading an Aspire CLI configuration file (aspire.config.json) via AspireConfigFile.Load, invalid JSON causes JsonSerializer.Deserialize to throw JsonException. The loader rethrows a JsonException with a formatted message including the file path and the underlying parser error, preserving path/line/position so users can find the syntax problem.

Solutions

1. Open the file named in the error at the reported line/position and fix the JSON syntax
2. Validate the file with a JSON linter or `jq . aspire.config.json`
3. Remove JSON comments and trailing commas, which are not allowed in strict JSON
4. Restore the file from version control and reapply changes carefully

Example fix

// before (aspire.config.json)
{ "channel": "stable", }
// after
{ "channel": "stable" }

try { using var doc = JsonDocument.Parse(File.ReadAllText("aspire.config.json")); }
catch (JsonException ex) { Console.Error.WriteLine($"aspire.config.json invalid: {ex.Message} at line {ex.LineNumber}"); }

try { var cfg = AspireConfigFile.Load(path); }
catch (JsonException ex) { Console.Error.WriteLine($"Fix {path}: {ex.Message} (line {ex.LineNumber})"); return 1; }

When it happens

Trigger: Calling `config` commands (or anything that reads aspire.config.json) when the file contains malformed JSON — trailing commas, unquoted keys, unclosed braces, or BOM/encoding problems.

Common situations: Hand-editing aspire.config.json and introducing a syntax error; a tool writing a partial file; copy-paste from documentation with comments (JSON does not allow comments).

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• The configuration file
• The configuration file
• The configuration file
• Failed to parse JSON output into type
• Integration assets file

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/87bcf63395fb9441. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Cli/Configuration/AspireConfigFile.cs:146

    /// <returns>The deserialized config, or <c>null</c> if the file does not exist.</returns>
    /// <exception cref="InvalidOperationException">Thrown when the file exists but contains invalid JSON.</exception>
    public static AspireConfigFile? Load(string directory)
    {
        var filePath = Path.Combine(directory, FileName);
        if (!File.Exists(filePath))
        {
            return null;
        }

        try
        {
            var json = File.ReadAllText(filePath);
            return JsonSerializer.Deserialize(json, JsonSourceGenerationContext.Default.AspireConfigFile)
                ?? new AspireConfigFile();
        }
        catch (JsonException ex)
        {
            throw new JsonException(
                string.Format(CultureInfo.CurrentCulture, ErrorStrings.InvalidJsonInConfigFile, filePath, ex.Message),
                ex.Path, ex.LineNumber, ex.BytePositionInLine, ex);
        }
    }

    /// <summary>
    /// Saves aspire.config.json to the specified directory.
    /// Uses relaxed JSON escaping so non-ASCII characters (CJK, etc.) are preserved as-is.
    /// </summary>
    public void Save(string directory)
    {
        Directory.CreateDirectory(directory);
        var filePath = Path.Combine(directory, FileName);
        var json = JsonSerializer.Serialize(this, JsonSourceGenerationContext.RelaxedEscaping.AspireConfigFile);
        File.WriteAllText(filePath, json);
    }

    /// <summary>

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