How to set variables to context.extensions object when execute query?

Question

I need to send to a backend some additional variables, which are common to all queries and not directly related to the queries' schema. I've decided to use the context.extensions object to achieve this.

const { data } = await client.query({
  query: GET_BY_ID_QUERY,
  variables: { id: 111 },
  context: {
    extensions: {
      credentials: {
        securityHash: "a1b2c3d4",
      },
    },
  },
});

The problem is, when I specify my variables, the extensions object is ignored. I can only send it if I create a custom Apollo link, which sets the object to operation (comment 4).

Why is this work like this? Is there any explanation how to use the extensions object right? So far, I couldn't find any useful information.

const extensionLink = new ApolloLink((operation: Operation, forward) => {
  // 1. This context has the query's context extensions object with variables
  const ctx1 = operation.getContext();

  operation.setContext((oldCtx: any) => {
    // 2. The oldCtx also has the query's context extensions object with variables
    return {
      ...oldCtx,
      extensions: {
        ...oldCtx.extensions,
        ["random-value-1"]: Math.random(),
      },
    };
  });

  // 3. After the setContext execution the operation still doesn't contain the extensions object with variables

  // 4. Only when I assign extensions object, the Graphql send its variables to the backend
  operation.extensions = ctx1.extensions;
  operation.extensions["random-value-2"] = Math.random();

  return forward(operation);
});

Here is the demo repository: https://github.com/ivan-banha/apollo-graphql-extensions