Prefect Server fails to bind in IPv6-only environments

[dopic]

1. Problem Description

The prefect server start command fails to initialize in a strict, single-stack IPv6-only environment (e.g., a modern AWS EKS cluster).

The server appears hard-coded to bind to 0.0.0.0 (IPv4) and does not provide a working mechanism to bind to the IPv6 unassigned address ([::]). This makes it impossible to self-host the server component in an IPv6-only Kubernetes pod, which has no IPv4 stack.

2. Steps to Reproduce

• Provision a Prefect Server (CRD) on a cluster that is 100% IPv6-only.
• Use the prefecthq/prefect:3.x image (e.g., 3.4.14).
• Attempt to run the server using the default prefect server start command.

3. Workaround Attempted

• Trying to force '::' or '[::]' causes the pod to crash with the error: Invalid host '[::]'. Please specify a valid hostname or IP address.

4. Additional Context

An interesting point is that when deploying the prefect-server helm chart, it works as expected in this same IPv6-only cluster.

[mitchnielsen]

Apologies for the delay here @dopic, and thanks for opening this. Getting started with addressing this in #232.