[Jacob Viau (jviau)]

Summary

Updates func start local host binding and makes the bind address configurable.

Changes in src/Cli/func/Actions/HostActions/StartHostAction.cs (and src/Cli/func/Common/HostStartSettings.cs):

• Default binding: both the HTTP path (Setup()) and the HTTPS path (Kestrel Listen) bind to the IPv4 loopback address (127.0.0.1 / IPAddress.Loopback).
• New opt-in --address flag: lets you specify the local IP address to bind to. When unset it defaults to 127.0.0.1.
• New local.settings.json setting: Host.LocalHttpAddress provides the same override via config.
• Precedence: --address flag → Host.LocalHttpAddress → 127.0.0.1.

The address is resolved once via a shared ResolveBindAddress() helper that validates the value and throws a clear CliException on invalid input. It feeds both binding paths (the listen URI is built through an IPEndPoint so IPv6 values are bracketed correctly). BaseUri and displayed function URLs remain localhost, so normal local development output is unchanged.

Notes

• Default behavior is localhost-only; broadening the bind address is strictly opt-in.
• No change to IPv6 defaults.
• Existing localhost-based workflows and tests (which connect via http://localhost:{port}) are unaffected.
• NetworkHelpers and unrelated build assets are untouched.

Validation

• dotnet build of src/Cli/func succeeds with 0 warnings / 0 errors.
• 4 new unit tests in StartHostActionTests.cs cover the default, the --address override, the config-supplied value, and invalid-input handling — all pass.

[Shyju Krishnankutty (kshyju)]

1. Release notes entry missing?

2. My agent review flagged this. Is this something we should mention in the "breaking change" docs?:

The 0.0.0.0 → 127.0.0.1 default change breaks a common workflow: running func start in a container and reaching it from the host via a mapped port (docker run -p 7071:7071, Compose, etc.). Docker forwards host traffic to the container's eth0, not loopback, so a loopback-only bind refuses those connections — a confusing "connection refused" on a port that's clearly mapped. Same for container-to-container and WSL2 → Windows host. This worked before with no flags; now it requires --address 0.0.0.0.