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Diagnostics:
  aws:lb:ListenerRule (stage-core-alb-i-radar-api-lr):
    error: 1 error occurred:
        * Error creating LB Listener Rule: ValidationError: A condition must be specified
        status code: 400, request id: cddc0d9c-6bc3-44fa-be55-1b733ae3bb60

  pulumi:pulumi:Stack (core-stage-core):
    error: update failed

trying to make a listener rule that forwards to a target group

for an internal load balancer with no domain

Here's the relevant doc <https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-listeners.html#listener-rules>
&gt; Listener rules
&gt; Each listener has a default rule, and you can optionally define additional rules. Each rule consists of a priority, one or more actions, and one or more conditions. You can add or edit rules at any time. For more information, see <https://docs.aws.amazon.com/elasticloadbalancing/latest/application/listener-update-rules.html#edit-rule|Edit a rule>.
You're trying to add listener rules so they have to have a condition. What you probably want is the default rule which is specified when you create the listener <https://www.pulumi.com/registry/packages/aws/api-docs/lb/listener/#forward-action>