Problem Processing Request w/ graphql subscription on public api

Question

queries and mutations work fine, but whenever I try to create a subscription I get the error referenced above. which is odd, because when I try creating a subscription in graphi I get no issues. below is the relevant code:

```
      // Create a plain WebSocket connection to the external GraphQL server
      const externalWs = new ws("wss://backboard.railway.com/graphql/v2");

// When the connection opens, send the connection_init message.
      externalWs.on("open", () => {
        console.log("Opened connection to external GraphQL server");
        const connectionInitMsg = {
          type: "connection_init",
          payload: {},
        };
        externalWs.send(JSON.stringify(connectionInitMsg));
      });

// Listen for messages from the external GraphQL server.
      externalWs.on("message", (message: ws.RawData) => {
        let parsedMsg;
        try {
          parsedMsg = JSON.parse(message.toString());
        } catch (err) {
          console.error("Failed to parse message from external server", err);
          return;
        }

// When we receive a connection_ack, send the subscription request.
        if (parsedMsg.type === "connection_ack") {
          const subscriptionId = Math.random().toString(36).substring(2, 15);

const query = `
            subscription MyQuery($deploymentId: String!) {
              deploymentLogs(deploymentId: $deploymentId) {
                severity
                message
              }
            }
          `;

const subscribeMsg = {
            id: subscriptionId, // Use generated ID
            type: "subscribe",
            payload: {
              query: query,
              operationName: "MyQuery",
              variables: { deploymentId: data.deploymentId },
            },
          };

externalWs.send(JSON.stringify(subscribeMsg));
```