New 'server.allowedHosts' config does not allow the value 'true'

[st11x]

Astro Info

Astro                    v5.4.1
Node                     v22.4.1
System                   Linux (x64)
Package Manager          pnpm
Output                   static
Adapter                  none
Integrations             none

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

I created a new project using pnpm create astro@latest with the basic, minimal starter template. Then I changed the astro.config.mjs to:

// @ts-check
import { defineConfig } from "astro/config";

// https://astro.build/config
export default defineConfig({
    server: {
        allowedHosts: true,
    },
});

Now even astro info fails with

> foo@0.0.1 astro /app/projects/astro
> astro info

[config] Astro found issue(s) with your configuration:

! server.allowedHosts: Did not match union.
  > Expected type { 0: string } |
  > Received [ true ]

and starting the dev server fails with

dev-1  |
dev-1  | > foo@0.0.1 dev /app/projects/astro
dev-1  | > astro dev --host
dev-1  |
dev-1  | [config] Astro found issue(s) with your configuration:
dev-1  |
dev-1  | ! server.allowedHosts: Did not match union.
dev-1  |   > Expected type { 0: string } |
dev-1  |   > Received [ true ]
dev-1  |

The workaround is to use the --allowed-hosts CLI parameter.

What's the expected result?

The astro info and astro dev commands should not error out. According to Vite's documentation as linked in the release notes, you are allowed to specify the boolean value true.

Link to Minimal Reproducible Example

https://zzmivbmxlngithub-dieg--4321--31ca1d38.local-corp.webcontainer.io

Participation

• I am willing to submit a pull request for this issue.