microsoft/semantic-kernel · error · ArgumentException

Unknown type

Error message

Unknown type {type}

What it means

Thrown by GetNetType's switch expression when a protobuf field type enum value is not one of the recognized TYPE_* cases (DOUBLE, FLOAT, INT64, ... BYTES, etc.). The default arm raises ArgumentException naming the unrecognized type token.

Solutions

1. Restrict the .proto operation payload to primitive scalar types the switch handles.
2. Avoid enum-typed, message-typed, or map fields in the gRPC operation contract used by this runner.
3. If you need an unsupported type, pass it as a string and handle conversion yourself.

Example fix

// before
// .proto field: repeated Item items = 1; (message type)
// after
// .proto field: string items_json = 1; (primitive)

// Inspect your .proto: only use scalar types this runner maps (TYPE_STRING, TYPE_INT32, ...).

try { /* invoke */ }
catch (ArgumentException ex) when (ex.Message.Contains("Unknown type")) {
    // a field type is unsupported; simplify the .proto
}

When it happens

Trigger: A FieldDescriptorProto.Type value outside the handled set — typically a newer protobuf type (e.g. enum-typed or message-typed fields that arrive as a Type enum the switch doesn't map) or a corrupt descriptor.

Common situations: Using complex message/enum/map fields in the .proto that the runner does not yet support; protobuf-schema features ahead of the supported set.

Related errors

• Impossible to create type for
• Impossible to find protobuf type name corresponding to
• No ' ' message type is found while resolving data contracts…
• Parsing of ' ' .proto document has failed. Details
• Failed to unpack payload into

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/160f8d9ce28f19d5. Report an issue: GitHub.

Appendix: source

Thrown at dotnet/src/Functions/Functions.Grpc/GrpcOperationRunner.cs:351

    private static Type GetNetType(string type) =>
        type switch
        {
            "TYPE_DOUBLE" => typeof(double),
            "TYPE_FLOAT" => typeof(float),
            "TYPE_INT64" => typeof(long),
            "TYPE_UINT64" => typeof(ulong),
            "TYPE_INT32" => typeof(int),
            "TYPE_FIXED64" => typeof(ulong),
            "TYPE_FIXED32" => typeof(uint),
            "TYPE_BOOL" => typeof(bool),
            "TYPE_STRING" => typeof(string),
            "TYPE_BYTES" => typeof(byte[]),
            "TYPE_UINT32" => typeof(uint),
            "TYPE_SFIXED32" => typeof(int),
            "TYPE_SFIXED64" => typeof(long),
            "TYPE_SINT32" => typeof(int),
            "TYPE_SINT64" => typeof(long),
            _ => throw new ArgumentException($"Unknown type {type}", nameof(type)),
        };
}

View on GitHub (pinned to c028a0c7dc)