elsa-workflows/elsa-core · error · JsonException

Expected end of object.

Error message

Expected end of object.

What it means

PolymorphicDictionaryConverter.Read loops reader.Read() until EndObject to finish consuming the dictionary. If the stream ends (Read returns false) before the closing brace is seen, it throws JsonException("Expected end of object."). It signals unbalanced/unterminated JSON objects.

Solutions

1. Repair the truncated JSON (add the missing closing brace) or regenerate the payload.
2. Check for size limits on the storage or transport layer (column length, HTTP body limits) that clip the JSON.
3. Validate JSON completeness before deserializing.
4. Re-export the workflow or instance data from the source system.

Example fix

// before (truncated)
{ "key1": { "nested": 1 }, "key2": { "x": 2

// after
{ "key1": { "nested": 1 }, "key2": { "x": 2 } }

bool balanced = json.Count(c => c == '{') == json.Count(c => c == '}');
if (!balanced) throw new InvalidOperationException("JSON payload appears truncated (unbalanced braces)");

static bool IsCompleteJsonObject(string s) { try { using var d = JsonDocument.Parse(s); return d.RootElement.ValueKind == JsonValueKind.Object; } catch { return false; } }

try { var d = JsonSerializer.Deserialize<IDictionary<string, object>>(json); } catch (JsonException ex) when (ex.Message == "Expected end of object.") { log.LogError(ex, "Truncated dictionary JSON"); /* regenerate payload */ }

When it happens

Trigger: Deserializing a truncated JSON object — missing closing brace — where the while(reader.Read()) loop exhausts the buffer in PolymorphicDictionaryConverter.Read (src/modules/Elsa.Workflows.Core/Serialization/Converters/PolymorphicDictionaryConverter.cs:40).

Common situations: Cut-off HTTP response bodies; database blobs truncated by column size limits; log-export pipelines clipping long JSON strings.

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.

Related errors

• Cannot determine the element type of array
• Expected start of object.
• Failed to extract activity type property
• Failed to parse JsonDocument
• Runtime entity definition document

AI-assisted analysis of elsa-workflows/elsa-core@fe9217bdfa (2026-09-13). Data as JSON: /api/errors/51b8d11041cffd73. Report an issue: GitHub.

Appendix: source

Thrown at src/modules/Elsa.Workflows.Core/Serialization/Converters/PolymorphicDictionaryConverter.cs:40

    public override IDictionary<string, object> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if (reader.TokenType != JsonTokenType.StartObject)
            throw new JsonException("Expected start of object.");

        var dictionary = new Dictionary<string, object>();

        while (reader.Read())
        {
            if (reader.TokenType == JsonTokenType.EndObject)
                return dictionary;

            var key = reader.GetString()!;
            reader.Read();
            var value = _objectConverter.Read(ref reader, typeof(object), options)!;
            dictionary.Add(key, value);
        }

        throw new JsonException("Expected end of object.");
    }

    /// <inheritdoc />
    public override void Write(Utf8JsonWriter writer, IDictionary<string, object> value, JsonSerializerOptions options)
    {
        writer.WriteStartObject();

        foreach (var kvp in value)
        {
            writer.WritePropertyName(kvp.Key);
            _objectConverter.Write(writer, kvp.Value, options);
        }

        writer.WriteEndObject();
    }
}

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