microsoft/semantic-kernel · error · NotSupportedException

The provided response modalities '{executionSettings.Modalit

Error message

The provided response modalities '{executionSettings.Modalities?.GetType()}' is not supported.

What it means

Terminal throw in the modalities mapper. After handling ChatResponseModalities enum, IEnumerable<string>, plain string, and JsonElement (string/array kinds), any other runtime type for executionSettings.Modalities is unsupported and its GetType() is reported. This catches mismatches like passing an int, a Dictionary, or a JsonElement of unexpected ValueKind (e.g. Object/Number).

Source

Thrown at dotnet/src/Connectors/Connectors.OpenAI/Core/ClientCore.ChatCompletion.cs:1176

            }
            throw new NotSupportedException($"The provided response modalities '{responseModalitiesString}' is not supported.");
        }

        if (executionSettings.Modalities is JsonElement responseModalitiesElement)
        {
            if (responseModalitiesElement.ValueKind == JsonValueKind.String &&
                Enum.TryParse<ChatResponseModalities>(responseModalitiesElement.GetString(), true, out var parsedResponseModalities))
            {
                return parsedResponseModalities;
            }

            if (responseModalitiesElement.ValueKind == JsonValueKind.Array)
            {
                var modalitiesEnumeration = JsonSerializer.Deserialize<IEnumerable<string>>(responseModalitiesElement.GetRawText())!;
                return ParseResponseModalitiesEnumerable(modalitiesEnumeration);
            }

            throw new NotSupportedException($"The provided response modalities '{executionSettings.Modalities?.GetType()}' is not supported.");
        }

        return ChatResponseModalities.Default;
    }

    /// <summary>
    /// Gets the audio options from the execution settings.
    /// </summary>
    /// <param name="executionSettings">The execution settings.</param>
    /// <returns>The audio options as a <see cref="ChatAudioOptions"/> object.</returns>
    /// <remarks>
    /// This method supports converting from various formats:
    /// <list type="bullet">
    /// <item><description>A <see cref="ChatAudioOptions"/> object</description></item>
    /// <item><description>A <see cref="JsonElement"/> containing the serialized audio options</description></item>
    /// <item><description>A <see cref="string"/> containing the JSON representation of the audio options</description></item>
    /// </list>
    /// </remarks>

View on GitHub (pinned to c028a0c7dc)

Solutions

Provide Modalities as a ChatResponseModalities enum, a string, an IEnumerable<string>, or a JsonElement that is a string or array.
Normalize the config value into one of those shapes before assigning.
If it is a JsonElement, ensure it is a string or array kind.

Example fix

// before
settings.Modalities = 1;
// after
settings.Modalities = ChatResponseModalities.Text;

Defensive patterns

Strategy: type-guard

Validate before calling

static bool IsSupportedModalities(object? o) => o is ChatResponseModalities or string or IEnumerable<string> or JsonElement;

Type guard

static bool IsSupportedModalities(object? o) => o is ChatResponseModalities or string or IEnumerable<string> or JsonElement;

Try / catch

try { await client.GetChatCompletionAsync(...); }
catch (NotSupportedException ex) when (ex.Message.Contains("response modalities")) { settings.Modalities = ChatResponseModalities.Default; }

Prevention

Coerce dynamic values to enum/string/array/JsonElement(string|array).
Ensure JSON deserializes Modalities as string or array, not object/number.

When it happens

Trigger: Setting Modalities to a non-supported type: an integer, a JObject/Dictionary, a JsonElement whose ValueKind is Object/Number/False, or a custom object.

Common situations: Deserializing settings where Modalities arrived as a JSON object or number; binding from dynamic config; cross-library interop that produces JsonNode instead of JsonElement.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/09160ea59dbe0c9c. Report an issue: GitHub.