dotnet/aspnetcore · error

Invalid payload for Invocation message.

Error message

Invalid payload for Invocation message.

What it means

Thrown by _createInvocationMessage when the decoded properties array has fewer than 5 elements. A valid Invocation is [MessageType.Invocation, headers, invocationId, target, arguments] (optionally plus streamIds), so five is the minimum. Hitting it means the server sent an Invocation frame missing required fields like target or arguments.

Source

Thrown at src/SignalR/clients/ts/signalr-protocol-msgpack/src/MessagePackHubProtocol.ts:190

        } as HubMessage;
    }

    private _createPingMessage(properties: any[]): HubMessage {
        // check minimum length to allow protocol to add items to the end of objects in future releases
        if (properties.length < 1) {
            throw new Error("Invalid payload for Ping message.");
        }

        return {
            // Ping messages have no headers.
            type: MessageType.Ping,
        } as HubMessage;
    }

    private _createInvocationMessage(headers: MessageHeaders, properties: any[]): InvocationMessage {
        // check minimum length to allow protocol to add items to the end of objects in future releases
        if (properties.length < 5) {
            throw new Error("Invalid payload for Invocation message.");
        }

        const invocationId = properties[2] as string;
        if (invocationId) {
            return {
                arguments: properties[4],
                headers,
                invocationId,
                streamIds: [],
                target: properties[3] as string,
                type: MessageType.Invocation,
            };
        } else {
            return {
                arguments: properties[4],
                headers,
                streamIds: [],
                target: properties[3],

View on GitHub (pinned to 294cab2f9b)

Solutions

1. Align SignalR client and server versions so the Invocation frame layout matches.
2. Inspect server-side logs for the hub method that triggered the malformed invocation.
3. Verify no middleware serializing/re-encoding the frame is in the path.
4. Catch and reconnect — a malformed Invocation cannot be recovered in place.

Example fix

// before
connection.on('Send', x => {}); // server sends short frame -> parseMessages throws

// after
try {
  // parseMessages called internally by the connection
} catch (e) {
  if (/Invocation message/.test(e.message)) {
    logger.log(LogLevel.Error, 'Malformed Invocation from server; reconnecting.');
    await connection.start();
  }
}

try {
  const messages = protocol.parseMessages(buffer, logger);
} catch (e) {
  if (/Invocation message/.test(e.message)) {
    logger.log(LogLevel.Error, 'Malformed Invocation frame; reconnecting.');
    await connection.start();
  } else throw e;
}

When it happens

Trigger: Server emits an Invocation frame with fewer than 5 slots (e.g. omitted arguments array); a partial/corrupted frame after splitting; protocol version mismatch where the server uses an older 4-element Invocation layout.

Common situations: Server/client version skew; a server-side hub method invocation serialized incorrectly due to a custom protocol/serializer; frame truncation on the wire.

Related errors

• Invalid payload for Completion message.
• Invalid payload for Close message.
• Invalid payload for Ping message.
• Invalid payload for StreamItem message.
• Invalid payload for Ack message.

AI-assisted analysis of dotnet/aspnetcore@294cab2f9b (2026-08-06). Data as JSON: /api/errors/b34b4e26d6466794. Report an issue: GitHub.