WebsocketsApi logical id with invoke local

I use the API Gateway websockets and need to pass the connection url to my lambdas.

The WS resource is defined by having the event on a lambda (ts syntax):

events: [
      websocket: {
        route: 'render',

I then reference it in the custom section to create a variable with the right id.

custom: {
    apiGatewayEndpoint: {

This works well with serverless deploy, but when I try to invoke local any function, I get an error:

Could not resolve "apiGatewayEndpoint" environment variable: Unsupported environment variable format: {
    'Fn::Sub': 'https://${WebsocketsApi}.execute-api.${AWS::Region}.amazonaws.com/alexdb'

What could be a way to have a fully dynamic serverless config file? I would like to avoid having to add local .env files with the ids for my dev stacks.