Dev: better-auth/client/plugins fails to resolve when auth is enabled (the better-auth/client alias matches it as a prefix) #565

Description

With auth enabled, void dev aliases better-auth/client (and /react, /vue, /svelte, /solid) to absolute file paths. A string alias in Vite also matches subpaths, so better-auth/client/plugins, where Better Auth's client plugins such as adminClient() live, is rewritten to …/better-auth/dist/client/index.mjs/plugins, which doesn't exist. Any app that passes a Better Auth client plugin to createAuthClient breaks in dev. void build is not affected, because the alias is only added for serve.

Steps to reproduce

1. Enable auth in void.config.ts: auth: { providers: ['email'] }.

2. Add better-auth as a dependency (the same version Void uses).

3. Create a client with a plugin and import it from a page:

   // src/lib/auth-client.ts
   import { adminClient } from 'better-auth/client/plugins';
   import { createAuthClient } from 'void/client';
   
   export const authClient = createAuthClient({
     basePath: '/api/auth',
     plugins: [adminClient()],
   });

4. Run void dev and open that page.

Actual behavior

• Client: Pre-transform error: Failed to resolve import "better-auth/client/plugins" from "src/lib/auth-client.ts". Does the file exist?
• SSR: the page returns 500 with Error: No such module "workers/runner-worker/file:/…/better-auth/dist/client/plugins/index.mjs".

Expected behavior

better-auth/client/plugins resolves to better-auth/dist/client/plugins/index.mjs, as it does in void build and in Node.

Cause

packages/void/src/plugin-routing.ts (main @ 6ba3dbcc3a, lines 616–622):

const betterAuthSubpaths = ['client', 'react', 'vue', 'svelte', 'solid'];
const resolvedAliases = betterAuthSubpaths.flatMap((sub) => {
  try {
    return [{ find: `better-auth/${sub}`, replacement: resolveFile(`better-auth/${sub}`) }];
  } catch {
    return [];
  }
});

A string find matches the exact id and any id that starts with find + '/', replacing the prefix. resolveFile('better-auth/client') is …/dist/client/index.mjs, so better-auth/client/plugins becomes …/dist/client/index.mjs/plugins.

Possible fix

Anchor the patterns so they only match the exact specifier, and pre-resolve client/plugins too if it should avoid the lazy-discovery reload the comment mentions:

const betterAuthSubpaths = ['client', 'client/plugins', 'react', 'vue', 'svelte', 'solid'];
// …
return [{ find: new RegExp(`^better-auth/${sub}$`), replacement: resolveFile(`better-auth/${sub}`) }];

Workaround

A plugin listed after voidPlugin() adds an exact-match alias. Aliases from a later plugin's config hook are tried first, so this one wins:

// vite.config.ts
import { createRequire } from 'node:module';
import type { Plugin } from 'vite-plus';

const require = createRequire(import.meta.url);

function betterAuthClientPlugins(): Plugin {
  return {
    name: 'better-auth-client-plugins',
    config: () => ({
      resolve: {
        alias: [
          {
            find: /^better-auth\/client\/plugins$/,
            replacement: require.resolve('better-auth/client/plugins'),
          },
        ],
      },
    }),
  };
}

// plugins: [voidPlugin(), voidReact(), betterAuthClientPlugins()]

Related

#554 edits the same block (adds authConfigEnvironmentConfig to the returned config) but keeps the prefix aliases.

Environment

• void 1.2.1 (also on 1.1.12), better-auth 1.7.11
• vite-plus 1.3.0, Node 22.23.3, macOS 26.6